Silicone Surface-Active Agents

By Donna Perry

Dow Corning Corporation

Dow Corning Silicone Solutions As the pioneer of silicon-based technology Dow Corning has been improving customersrsquo products and profitability for more than 60 years With a full range of product and application solutions reliable supply world-class manufacturing and global reach Dow Corning can meet virtually any silicone-related need through our total solution offering and technology leadership For more information call +1-989-496-6000

Dow Corning (wwwdowcorningcom) provides performance-enhancing solutions to serve the diverse needs of more than 25000 customers worldwide A global leader in technology and innovation offering more than 7000 products and services Dow Corning is equally owned by The Dow Chemical Company and Corning Incorporated More than half of Dow Corning sales are outside the United States

Dow Corning Silicone Solutions As the pioneer of silicon-based technology Dow Corning has been improving customersrsquo products and profitability for more than 60 years With a full range of product and application solutions reliable supply world-class manufacturing and global reach Dow Corning can meet virtually any silicone-related need through our total solution offering and technology leadership For more information call +1-989-496-6000

Dow Corning (wwwdowcorningcom) provides performance-enhancing solutions to serve the diverse needs of more than 25000 customers worldwide A global leader in technology and innovation offering more than 7000 products and services Dow Corning is equally owned by The Dow Chemical Company and Corning Incorporated More than half of Dow Corning sales are outside the United States

Silicone Surface-Active Agents

by Donna Perry Dow Corning Corporation

Introduction Surface-active agents are chemicals that reduce the surface energy of a material to which they are added by absorption at the airliquid interface The increasing popularity of waterborne coatings presents a continuing challenge for formulators There is the need to formulate more environmentally acceptable products to comply with government regulations on VOCs to reduce flammability and to generally reduce the hazard profile of coating systems

In comparison with solvent-borne systems waterborne coatings exhibit a much higher surface tension This results from water having a surface tension of 724 mNm As a result waterborne coatings exhibit poor substrate wetting capabilities when compared to solvent-based equivalents The high surface tension of water is due to its polarity and the cohesive hydrogen bonding between the water molecules

Additives or surface-active agents such as silicone polyethers are used to modify the surface properties of watershyborne coatings to achieve the desired flow levelling and wetting performance Silicone polyethers have traditionally been used in the coating area for surface modification but along with these types of materials Dow Corning has introshyduced novel functionalities to broaden applications and improve surfactant performance

This paper covers the traditional performance attributes of the silicone polyether additive class while also introducing novel carbinol functional materials and their differences

Surface Tension Effects in Waterborne Coatings Surface tension can be considered in various ways but perhaps best as a result of the forces of attraction existing between the molecules of a liquid It is measured by the force per unit length acting in the surface at right angles to an element of any line drawn in the surface (mNm)

Wetting is the effect of displacing one fluid from the substrate surface by another liquid In general the liquid must have the same or a lower surface tension than the substrate otherwise no wetting will be achieved This will produce a positive spreading coefficient and lead to a good coating This can be best expressed in equation (1) By addition of the correct additive the surface tension of the coating can be modified to improve substrate wetting The additive acts by lowering the surface tension of the coating enabling it to wet-out over the substrate

Levelling is the process of eliminating the surface irregularities of a continuous liquid film under the influence of the liquidrsquos surface tension Levelling is an important step in obtaining a smooth and uniform film Concentration and surface

tension gradients in coatings are the main causes of poor levelling which develop as the coating dries due to variations in drying rates Addition of the appropriate additive will modify the surface tension For instance a silicone additive will migrate to the liquidair interface giving an even surface tension across the film during the drying process thus reducing surface tension gradients

Wetting and levelling are therefore totally different processes Though the surface tension of the coating plays an important role in both processes the effects of surface tension on spreading is opposite to that observed in levelling

Substrate wetting can be subdivided into two distinct categories ldquospreading wettingrdquo and ldquoadhesion wettingrdquo Spreading wetting is necessary for even coverage of applied films in particular for the low-surface-energy substrates of many plastics

Adhesion wetting is defined in equation (2) It is important for example in printing processes in which it is undesirable for the applied ink to spread across a surface and then merge with other colors

Spreading wetting S(Spreading coeff) = - GSpreading A = γ Substrate - γ SubstrateLiquid - γ Liquid = γ Liquid (cos θ - 1) (1)

When γ SubstrateLiquid gt 0 spreading will occur spontaneously

Adhesion wetting WA(Work of adhesion) = - G Adhesion A = γ Substrate + γ Liquid - γ SubstrateLiquid = γ Liquid (cos θ +1) (2)

(γ (gamma) = Surface tension) (θ (theta) = Contact angle)

Figure 1 Molecular structure of a rake-type silicone surfactant

CH3

CH3

(CH3)

3 ndash Si ndash O ndash( Si ndash O )

x-( Si ndash O )

yndash Si ndash (CH

3)

3

CH3

(CH2)

3

(OCH2CH

2)

nOR

Figure 3 Molecular structure of a trisiloxane surfactant

CH3

(CH3)

3 ndash Si ndash O ndash Si ndash O - Si ndash (CH

3)

3

(CH2)

3

(OCH2CH

2)

nOR

Figure 2 Molecular structure of an ABA-type siloxane surfactant

CH3

CH3

CH3

RO (CH2CH

2O)

n (CH

2)

3ndash Si ndash O ndash( Si ndash O )

xndash Si ndash (CH

2)

3(OCH

2CH

2)

n OR

CH3

CH3

CH3

Silicones as Surface-Active Agents Of the various surface-active chemistries currently available this paper will mainly concentrate on a class of materials called silicone polyethers and the introduction of novel carbinol materials based on similar structures This family of copolymers is used to provide multifunctional benefits in waterborne systems The main uses of silicone polyethers in inks and coatings include de-foaming de-aerating improved substrate wetting and level-ling and enhanced slip properties12 The three most common molecular structures for silicone surfactants are rake-type copolymers ABA copolymers and trisiloxane surfactants These are illustrated in Figures 1 2 and 3

respectively and the performance of these structures will be described in two types of coatings

Silicones are highly surface active due ttheir low surface tension caused by the large number of methyl groups and due to the small intermolecular attractions between the siloxane hydrophobes The siloxane backbone of the molecule is highly flexible which allows for maximum orientation of the attached groups at interfaces

Silicone polyethers are non-ionic and have both a hydrophilic part (low-molecular-weight polymer of ethylene oxide or propylene oxide or both) and a hydrophobic part (the methylated siloxane moiety) The new carbinolshyfunctional materials also incorporate

o

a hydrophilic species on them and function under the same principles in which the traditional silicone polyethers do The polyether groups are either ethylene oxide or propylene oxide and are attached to a side chain of the siloxane backbone through a hydroshysilylation or condensation process They can form a rake-like comb structure or linear structure Silicone polyethers are stable up to 320-256degF (160-180degC) There is a great degree of flexibility in designing these types of polymers A very wide variety of co-polymers is possible when the two chemistries are combined

They can be varied by molecular weight molecular structure (pendantlinear) and the composition of the polyether chain (EOPO) and the ratio of siloxane to polyether The molecular weight influences the rate of migration to the interface The increased molecular weight of a polymer typically leads to an increased viscosity but may also give greater substantivity to surfaces and improved shine level Other variables include absence or presence of functionshyality or end groups on the polyether fragments

Depending on the ratio of ethylene oxide to propylene oxide these molecules can be water soluble dispersible or insolushyble obviously for efficient wetting these surfactants need to have good solubility in solution As surfactants they have the ability to produce and stabilize foam depending on their structure Conversely if their solubility parameters are low they behave as anti-foaming agents

The different structures affect how the molecules can pack at an interface With pendant types in aqueous media the silicone backbone aligns itself with the interface leaving the polyalkylene oxide groups projecting into the water Linear types form a very flattened ldquoWrdquo alignment where the central silicone

portion of the molecule aligns with the interface and the terminal groups are in the aqueous phase The amounts to be added vary between 001 and 05 of the total formulation

This paper will now discuss the behavior of silicone polyethers along with comparisons to silicones with novel carbinol functionalities in water together with some studies in coating formulashytions The results are compared with other additives that are currently used in coatings

Silicone Polyethers as Wetting Agents In this study the three different siloxane surfactants described above were evaluated in aqueous solution in a water-based printing ink and in a water-based polyester coating in comparison with fluorosurfactants and acetylenic glycols which are also used as wetting agents To achieve good wetting and a positive spreading coefficient the surface tension of the coating must be lower than the critical surface tension of the substrate

Water has a typical surface tension of 72 mNm and as can be seen from Table I all the surfactants tested reduced the surface tension of the system and as a result the aqueous medium wetted more efficiently For the silicone surfacshytants the best results were achieved with product A a low-molecular-weight material Trisiloxane A gave a very low figure that was improved by the fluoroshysurfactant

The critical micelle concentration (CMC) is the required level of product to initiate the formation of micelles in the bulk of a liquid Up to this point the surfactant added to the water migrated to the liquidair interface to form a film that reduced the surface tension The low CMC for A showed its high packing efficiency at the interface in the much lower level required in comparison to the other products

Table I Equilibrium surface tension with a Kruumlss K10T tensiometer and a platinum Wilhelmy plate additive concentrations 01

Surfactant Equilibrium Surface Tension (nMm) CMC ()

Trisiloxane A 205 0008

ABA Siloxane B 290 0025

Rake Siloxane C 299 0018

Fluorosurfactant

Ethoxylated Acetylenic Diol

175

253

0030

0050

In this context it is important to understand the difference between equilibrium and dynamic surface tension For an equilibrium surface tension measurement a platinum plate is immersed in a test solution and then slowly withdrawn The force required to remove the plate from the solution is a measure of the surface tension of that liquid

Dynamic surface tension can be measured by an instrument that bubbles air through the test liquid at an increasshying rate during which the maximum pressure that is required to form a bubble is measured As the bubble rate increases from 1 bubble per second to 10 the time to create the new interface (liquidair) decreases This is effectively measuring how quickly the surfactant lowers the surface tension

The dynamic method is more represenshytative of the coating application for example spraying Under these circumshystances it is important to know how quickly a surfactant can migrate to newly formed interfaces An ideal surface-active agent would provide excellent surface tension reduction under both equilibrium and dynamic conditions

Figure 4 shows dynamic surface tension results for the above materials at 01 in water Trisiloxane A gives better performance than the other silicone polyethers but does not give the very low values achieved by either the fluorosurfactants or ethoxylated acetylenic glycols However it must be remembered that dynamic surface tension represents only one aspect of the total phenomenon

MM

Figure 4 Dynamic surface tension maximum bubble pressure (Kruumlss BP1) 01 in water

DDITIVE

DDITIVE

DDITIVE

amp3URFACTANT

THOXYLATED CETYLENIC$IOL

UBBLEampREQUENCY(ERTZ

Figure 5 Contact angle measurement

Figure 6 Contact angle measurement with a VCA 2000 video contact angle equipment additive concentration at 01 in water

ONTROL

DDITIVE

ONTACTNGLE

DDITIVE

THOXYLATED CETYLENIC$IOL

DDITIVE

amp3URFACTANT

3URFACENERGYOF3UBSTRATEMM

In practice not only the conditions at the airliquid interface are of interest but also the conditions at the liquidsubstrate interface In general the smaller the contact angle produced by a system the better the substrate wetting The equipment used to measure the contact angle theta (θ) was a VCA 2000 instrument that automatically dispensed a minute droplet of the liquid to be measured and then photographed the droplet after a set period or could be programmed to take a number of photographs and measure correspondshying contact angles after regular time intervals This technique enabled the monitoring of droplets spreading on non-porous surfaces

When θ is greater than 90 degrees as in Figure 5 then beading or non-wetting is occurring as is shown by water on a plastic surface such as high-density polyethylene If θ is less than 90

degrees as shown in Figure 5 then wetting is occurring the smaller the angle the better the wetting process Spontaneous wetting occurs when θ=0 the droplet immediately spreading to

form a very thin continuous film on the substrate with effectively no contact angle capable of being determined

Figure 6 shows the behavior of the same surfactants on a range of low-energy substrates such as polyethylene and polypropylene For wetting it has been shown that the most efficient silicone

and allow for very efficient packing at interfaces For critical low-energy substrates only the trisiloxane surfactant A allows perfect (spontaneous) wetting and excellent spreading

polyether is trisiloxane A which has three Si atoms with pendant ethylene oxide The low molecular weight and size give greater mobility in solution

Extending this performance behavior now into practical life applications the effects of these surfactants in a water-based flexographic ink formulation are shown in Figure 7 The addition of siloxane surfactant A shows excellent substrate wetting performance on plastic foil followed by the fluorosurfactant The siloxane surfactants B and C which have a different structure and a higher molecular weight do not improve the wetting behavior It can be seen that the acetylenic glycol has only a small impacton the wetting behavior

Any surfactant molecule has the potential to generate foam that is undesirable in many applications Figure 8 shows the density measurements after a high shear stir test which give an indication of air entrapment in the ink The siloxane

Figure 7 Flexographic printing ink additive concentration 05 wettingappearance performance after application on plastic foil (surface energy 34 mNm) by draw down 12 micron rated on a scale from 1ndash5

ETTING

ANCE7

PPEAR

ONTROL 4RISILOXANE 2AKE CETYLENIC amp3URFACTANT LYCOL

2ATINGFROM13EXCELLENT

Figure 8 Flexographic printing ink additive concentration 05 density measurement after dissolver stirring test (5 minutes at 2800 rpm) as a measure of rate of foam development

$ENSITYINGCM

ONTROL 2AKE 4RISILOXANE CETYLENIC amp3URFACTANT LYCOL

$ENSITYWITHOUTSTIRRINGGCM

Table II Contact angle data

Sample Water Contact Angle

Acrylic Binder 43

Binder with 1 ABA 34

Binder with 1 Novel ABA lt15

Binder with 1 Novel Resin lt15

surfactant C (rake) acts only as a lowshy to-moderate foam enhancer compared to the fluorosurfactant What is also interesting is that siloxane surfactant B the silicone product with the highest molecular weight is performing as a de-aerator

Silicones as Slip Additives Slip represents the lubrication of a dry coating surface Given that the function of a coating is often to protect the underlying surface from damage while maintaining a satisfactory appearance it is clear that the coating itself must be capable of resisting mechanical damage This is where slip is important It is often referred to as mar resistance rather than abrasion resistance In the latter the bulk mechanical properties of the film are important in addition to the surface lubricity

Slip additives must reduce friction at the coating surface A thin layer of a material with low inter-molecular forces is capable of achieving this The slip additive should be sufficiently compatible with the coating before application to avoid separation After application it should not cause fisheyes or other defects associated with non- wetting of the additive by the coating However there has to be some degree of incompatibility to drive the additive to the surface of the coating film during drying

Silicone polyethers are important as slip agents due to their structure The ratio of the EOPO segments has to be carefully controlled to achieve the required compatibility balance Too low a polyether content may lead to the de-wetting defects already mentioned On the other hand high polyether content can render the copolymer too soluble with no driving force to get it to the coating surface during drying

Figure 9 Effect of molecular weight on slip performance of silicone-polyether copolymers in water-reducible polyester stoving paint (A low molecular weight B high molecular weight)

3LIPNGLE

ONTROL 4RISILOXANE 2AKE

As previously described for wetting the architecture of the copolymer has a profound effect on its behavior as a slip additive Optimized structures have been identified by designed experimentation to give the desired combination of compatibility and slip performance Compatibility is particularly important in clear coatings where gloss reduction or haze is not acceptable

Figure 9 shows slip angle results for silicone-polyether copolymers A and B in water-reducible stoving paint The main difference between the copolymers is overall molecular weight Both products contain pendant polyether groups It can be seen that trisiloxane A has almost no impact on slip This is believed to be due to the very short nature of its silicone chains A minimum amount of dimethylsiloxy units is required to give noticeable changes in slip This requirement is met in rake structure B which shows an improved slip

Novel Carbinol Function Silicones in Comparison to Traditional SPEs in Architectural Coatings The purpose of looking at new functionshyalities was to determine if we could improve hydrophilicity beyond what we were seeing in the traditional silicone polyethers that would lend themselves to more easy-clean surface development

In this study two novel carbinol functionality materials were compared to a traditional silicone polyether of similar degree of polymerization (Dp) and its performance toward dirt release in an architectural binder Each sample was doped into an acrylic-based binder by weight of resin and surface appearance and properties were characterized With the incorporation of the novel carbinol functionality the data shows an increase in the hydrophilicity of the coating as compared to the traditional SPE (Table II) This yields what was seen as an

Table V Dirt release characteristics after outdoor aging

Dirt Release Properties after 1008

Sample Hours Weathering

SG 30 Neat -

SG 30 with 1 ABA 0

SG 30 with 1 Novel ABA +

SG 30 with 1 Novel Resin ++

LOSS

ASE

4XANE

RISILO

4XANE

RISILOEL

WITHOV

EL

WITHOV

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

Figure 10 Mar resistance as a function of gloss

)NITIAL 2UBS

ampORMULATION

Table III Dirt-release characteristics through simple spray method

Sample Dirt Release Properties

Binder 0

Binder with 1 ABA +

Binder with 1 Novel ABA ++

Binder with 1 Novel Resin ++

Table IV Dirt pickup and pencil hardness

Pencil Formulation Dirt Pickup Hardness

Binder 0 3B

Binder with 1 ABA - 45B

Binder with 1 Novel ABA

Binder with 1 Novel Resin

-

-

45B

4B

though with the addition of the tradishytional ABA materials there was a slight improvement over the baseline but not as great as the unaged samples The novel ABA materials still showed significant improvement while the resinous materials showed excellent dirt-release characteristics (Table V)

Novel Carbinol Functional Silicones in Comparison with Traditional SPEs in Overprint Varnish Applications A baseline formulation for a general-purpose overprint varnish was obtained by Johnson Polymers The formulation was run with and without the Aerosol OT-75 noting no differences in the wet-out performance and was omitted for all the runs with the addition of the additives The appearance and wet-out of the OPV were not affected by the incorporation of the siloxane additive either standard or with the novel functionality

Samples were coated onto Lentea charts and run for 250 cycles on a Sutherland rub tester with gloss being documented prior and after rubs to determine each formulationrsquos resistance to mar The initial point to be noted was an increase in the initial gloss with siloxane incorporation excluding the standard ABA and the BYK material bench-marked against Enhancement was higher in those containing the novel functionality There was also better mar resistance overall with all these samples versus the baseline material

increase in the dirt-release ability of the coating through simple water spraying This increase in hydrophilicity was seen in both the ABA-structured materials as well as resinous-based siloxanes

After a simple draw down and cure time the coatings were dusted with a layer of dirt and sprayed with water to note the dirt-releasing properties With the addition of the ABA silicone polyether structure there was an enhancement of the dirt-release properties but this enhancement was even greater in those samples incorporating the new carbinol functionality (Table III) One thing to be noted is that the addition of the silicone surfactants either with the new carbinol material or the traditional polyethers does cause a slight softening of the coating itself which actually correlates into an initial dirt pickup that is slightly enhanced over the neat acrylic binder (Table IV)

Durability of this hydrophilicity is a known deficiency given the current additives function by migrating to the surface and can often wash away over an extended time with exposure to the environment After subjecting the coatings to external weathering exposure for 1008 hours the dirt-release performance decreased The neat SG 30 sample no longer released dirt as easily

shy

Oamp

Figure 11 Coefficient of friction data on OPV samples

ASE

4RISILOXANE

4RISILOXANE

ampORMULATION WITHOVEL

3TATICOamp +INETICOamp

WITHOVEL

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

modified to improve substrate wetting In particular the trisiloxane structure gives the best equilibrium surface tension reduction and excellent wetting to plastic surfaces and other low-energy substrates This material has the greatest capacity for lowering the liquidsolid interfacial tension The higher-molecularweight siloxane surfactants with rake and linear structures give moderate wetting However materials of these types can be used to provide other benefits for instance mar resistance slip and de-aeration The incorporation of a resinous material with functionality can also yield a higher substantivity in a coating that is likely desired when a coating is being exposed to long-term weathering effects The addition of novel functionalities in place of the linear polyethers also can enhance the properties of the silicone polyether materials research is being done to fine-tune these functionalities to the most appropriate applications

shy

shy

Coefficient of friction data (CoF) indicates that the mar resistance improvements were not due to increasing the slip of the surface By industry standards the slip change that was documented is within error This indicates a possibility for applications such as floor varnish where mar resistance needs to be increased with no effect on the CoF or slipperiness of the surface The CoF data demonshystrates that the additive is not residing on the surface but possibly allowing the PE wax to better orientate at the surface and yield higher mar resistance

In looking at the surface tension data of the materials used in this study there is actually very little difference that would

indicate this is the reason why the material performs this way

Work continues to optimize the strucshytures and find application in which they can be utilized

Conclusions Silicone-based surfactants offer many benefits in waterborne coatings By the addition of the correct silicone surfactant the coating surface tension can be

shy

Table VI Surface energy of standard and modified siloxanes

Surface Energy at 1 (Dynescm)

Trisiloxane 201

Trisiloxane with Novel 212

ABA 246

ABA with Novel 238

Resin not soluble

Resin with Novel 264

References 1 Schlachter I and Feldmann-Krane Georg Silicone Surfactants Surfactants Sci Ser 1998 74 p 201-239

2 Scholz W Verkroniek 10 13 1995

How to Contact Us Dow Corning has sales offices manufacshyturing sites and science and technology laboratories around the globe Telephone numbers of locations near you are available on the World Wide Web at wwwdowcorningcom or by calling one of our primary locations listed below

Your Global Connection Americas +1 989 496 6000

Europe +49 0611 237 342

Asia +86 21 62882626

LIMITED WARRANTY INFORMATION ndash PLEASE READ CAREFULLY

The information contained herein is offered in good faith and is believed to be accurate However because conditions and methods of use of our products are beyond our control this information should not be used in substitution for customerrsquos tests to ensure that Dow Corningrsquos products are safe effective and fully satisfactory for the intended end use Suggestions of use shall not be taken as inducements to infringe any patent

Dow Corningrsquos sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted

DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY

DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES

Dow Corning is a registered trademark of Dow Corning Corporation

We help you invent the future is a trademark of Dow Corning Corporation

copy2005 Dow Corning Corporation All rights reserved

shy

Printed in USA AGP7561 Form No 26-1365-01

Figure 1 Molecular structure of a rake-type silicone surfactant

CH3

CH3

(CH3)

3 ndash Si ndash O ndash( Si ndash O )

x-( Si ndash O )

yndash Si ndash (CH

3)

3

CH3

(CH2)

3

(OCH2CH

2)

nOR

Figure 3 Molecular structure of a trisiloxane surfactant

CH3

(CH3)

3 ndash Si ndash O ndash Si ndash O - Si ndash (CH

3)

3

(CH2)

3

(OCH2CH

2)

nOR

Figure 2 Molecular structure of an ABA-type siloxane surfactant

CH3

CH3

CH3

RO (CH2CH

2O)

n (CH

2)

3ndash Si ndash O ndash( Si ndash O )

xndash Si ndash (CH

2)

3(OCH

2CH

2)

n OR

CH3

CH3

CH3

Silicones as Surface-Active Agents Of the various surface-active chemistries currently available this paper will mainly concentrate on a class of materials called silicone polyethers and the introduction of novel carbinol materials based on similar structures This family of copolymers is used to provide multifunctional benefits in waterborne systems The main uses of silicone polyethers in inks and coatings include de-foaming de-aerating improved substrate wetting and level-ling and enhanced slip properties12 The three most common molecular structures for silicone surfactants are rake-type copolymers ABA copolymers and trisiloxane surfactants These are illustrated in Figures 1 2 and 3

respectively and the performance of these structures will be described in two types of coatings

Silicones are highly surface active due ttheir low surface tension caused by the large number of methyl groups and due to the small intermolecular attractions between the siloxane hydrophobes The siloxane backbone of the molecule is highly flexible which allows for maximum orientation of the attached groups at interfaces

Silicone polyethers are non-ionic and have both a hydrophilic part (low-molecular-weight polymer of ethylene oxide or propylene oxide or both) and a hydrophobic part (the methylated siloxane moiety) The new carbinolshyfunctional materials also incorporate

o

a hydrophilic species on them and function under the same principles in which the traditional silicone polyethers do The polyether groups are either ethylene oxide or propylene oxide and are attached to a side chain of the siloxane backbone through a hydroshysilylation or condensation process They can form a rake-like comb structure or linear structure Silicone polyethers are stable up to 320-256degF (160-180degC) There is a great degree of flexibility in designing these types of polymers A very wide variety of co-polymers is possible when the two chemistries are combined

They can be varied by molecular weight molecular structure (pendantlinear) and the composition of the polyether chain (EOPO) and the ratio of siloxane to polyether The molecular weight influences the rate of migration to the interface The increased molecular weight of a polymer typically leads to an increased viscosity but may also give greater substantivity to surfaces and improved shine level Other variables include absence or presence of functionshyality or end groups on the polyether fragments

Depending on the ratio of ethylene oxide to propylene oxide these molecules can be water soluble dispersible or insolushyble obviously for efficient wetting these surfactants need to have good solubility in solution As surfactants they have the ability to produce and stabilize foam depending on their structure Conversely if their solubility parameters are low they behave as anti-foaming agents

The different structures affect how the molecules can pack at an interface With pendant types in aqueous media the silicone backbone aligns itself with the interface leaving the polyalkylene oxide groups projecting into the water Linear types form a very flattened ldquoWrdquo alignment where the central silicone

portion of the molecule aligns with the interface and the terminal groups are in the aqueous phase The amounts to be added vary between 001 and 05 of the total formulation

This paper will now discuss the behavior of silicone polyethers along with comparisons to silicones with novel carbinol functionalities in water together with some studies in coating formulashytions The results are compared with other additives that are currently used in coatings

Silicone Polyethers as Wetting Agents In this study the three different siloxane surfactants described above were evaluated in aqueous solution in a water-based printing ink and in a water-based polyester coating in comparison with fluorosurfactants and acetylenic glycols which are also used as wetting agents To achieve good wetting and a positive spreading coefficient the surface tension of the coating must be lower than the critical surface tension of the substrate

Water has a typical surface tension of 72 mNm and as can be seen from Table I all the surfactants tested reduced the surface tension of the system and as a result the aqueous medium wetted more efficiently For the silicone surfacshytants the best results were achieved with product A a low-molecular-weight material Trisiloxane A gave a very low figure that was improved by the fluoroshysurfactant

The critical micelle concentration (CMC) is the required level of product to initiate the formation of micelles in the bulk of a liquid Up to this point the surfactant added to the water migrated to the liquidair interface to form a film that reduced the surface tension The low CMC for A showed its high packing efficiency at the interface in the much lower level required in comparison to the other products

Table I Equilibrium surface tension with a Kruumlss K10T tensiometer and a platinum Wilhelmy plate additive concentrations 01

Surfactant Equilibrium Surface Tension (nMm) CMC ()

Trisiloxane A 205 0008

ABA Siloxane B 290 0025

Rake Siloxane C 299 0018

Fluorosurfactant

Ethoxylated Acetylenic Diol

175

253

0030

0050

In this context it is important to understand the difference between equilibrium and dynamic surface tension For an equilibrium surface tension measurement a platinum plate is immersed in a test solution and then slowly withdrawn The force required to remove the plate from the solution is a measure of the surface tension of that liquid

Dynamic surface tension can be measured by an instrument that bubbles air through the test liquid at an increasshying rate during which the maximum pressure that is required to form a bubble is measured As the bubble rate increases from 1 bubble per second to 10 the time to create the new interface (liquidair) decreases This is effectively measuring how quickly the surfactant lowers the surface tension

The dynamic method is more represenshytative of the coating application for example spraying Under these circumshystances it is important to know how quickly a surfactant can migrate to newly formed interfaces An ideal surface-active agent would provide excellent surface tension reduction under both equilibrium and dynamic conditions

Figure 4 shows dynamic surface tension results for the above materials at 01 in water Trisiloxane A gives better performance than the other silicone polyethers but does not give the very low values achieved by either the fluorosurfactants or ethoxylated acetylenic glycols However it must be remembered that dynamic surface tension represents only one aspect of the total phenomenon

MM

Figure 4 Dynamic surface tension maximum bubble pressure (Kruumlss BP1) 01 in water

DDITIVE

DDITIVE

DDITIVE

amp3URFACTANT

THOXYLATED CETYLENIC$IOL

UBBLEampREQUENCY(ERTZ

Figure 5 Contact angle measurement

Figure 6 Contact angle measurement with a VCA 2000 video contact angle equipment additive concentration at 01 in water

ONTROL

DDITIVE

ONTACTNGLE

DDITIVE

THOXYLATED CETYLENIC$IOL

DDITIVE

amp3URFACTANT

3URFACENERGYOF3UBSTRATEMM

In practice not only the conditions at the airliquid interface are of interest but also the conditions at the liquidsubstrate interface In general the smaller the contact angle produced by a system the better the substrate wetting The equipment used to measure the contact angle theta (θ) was a VCA 2000 instrument that automatically dispensed a minute droplet of the liquid to be measured and then photographed the droplet after a set period or could be programmed to take a number of photographs and measure correspondshying contact angles after regular time intervals This technique enabled the monitoring of droplets spreading on non-porous surfaces

When θ is greater than 90 degrees as in Figure 5 then beading or non-wetting is occurring as is shown by water on a plastic surface such as high-density polyethylene If θ is less than 90

degrees as shown in Figure 5 then wetting is occurring the smaller the angle the better the wetting process Spontaneous wetting occurs when θ=0 the droplet immediately spreading to

form a very thin continuous film on the substrate with effectively no contact angle capable of being determined

Figure 6 shows the behavior of the same surfactants on a range of low-energy substrates such as polyethylene and polypropylene For wetting it has been shown that the most efficient silicone

and allow for very efficient packing at interfaces For critical low-energy substrates only the trisiloxane surfactant A allows perfect (spontaneous) wetting and excellent spreading

polyether is trisiloxane A which has three Si atoms with pendant ethylene oxide The low molecular weight and size give greater mobility in solution

Extending this performance behavior now into practical life applications the effects of these surfactants in a water-based flexographic ink formulation are shown in Figure 7 The addition of siloxane surfactant A shows excellent substrate wetting performance on plastic foil followed by the fluorosurfactant The siloxane surfactants B and C which have a different structure and a higher molecular weight do not improve the wetting behavior It can be seen that the acetylenic glycol has only a small impacton the wetting behavior

Any surfactant molecule has the potential to generate foam that is undesirable in many applications Figure 8 shows the density measurements after a high shear stir test which give an indication of air entrapment in the ink The siloxane

Figure 7 Flexographic printing ink additive concentration 05 wettingappearance performance after application on plastic foil (surface energy 34 mNm) by draw down 12 micron rated on a scale from 1ndash5

ETTING

ANCE7

PPEAR

ONTROL 4RISILOXANE 2AKE CETYLENIC amp3URFACTANT LYCOL

2ATINGFROM13EXCELLENT

Figure 8 Flexographic printing ink additive concentration 05 density measurement after dissolver stirring test (5 minutes at 2800 rpm) as a measure of rate of foam development

$ENSITYINGCM

ONTROL 2AKE 4RISILOXANE CETYLENIC amp3URFACTANT LYCOL

$ENSITYWITHOUTSTIRRINGGCM

Table II Contact angle data

Sample Water Contact Angle

Acrylic Binder 43

Binder with 1 ABA 34

Binder with 1 Novel ABA lt15

Binder with 1 Novel Resin lt15

surfactant C (rake) acts only as a lowshy to-moderate foam enhancer compared to the fluorosurfactant What is also interesting is that siloxane surfactant B the silicone product with the highest molecular weight is performing as a de-aerator

Silicones as Slip Additives Slip represents the lubrication of a dry coating surface Given that the function of a coating is often to protect the underlying surface from damage while maintaining a satisfactory appearance it is clear that the coating itself must be capable of resisting mechanical damage This is where slip is important It is often referred to as mar resistance rather than abrasion resistance In the latter the bulk mechanical properties of the film are important in addition to the surface lubricity

Slip additives must reduce friction at the coating surface A thin layer of a material with low inter-molecular forces is capable of achieving this The slip additive should be sufficiently compatible with the coating before application to avoid separation After application it should not cause fisheyes or other defects associated with non- wetting of the additive by the coating However there has to be some degree of incompatibility to drive the additive to the surface of the coating film during drying

Silicone polyethers are important as slip agents due to their structure The ratio of the EOPO segments has to be carefully controlled to achieve the required compatibility balance Too low a polyether content may lead to the de-wetting defects already mentioned On the other hand high polyether content can render the copolymer too soluble with no driving force to get it to the coating surface during drying

Figure 9 Effect of molecular weight on slip performance of silicone-polyether copolymers in water-reducible polyester stoving paint (A low molecular weight B high molecular weight)

3LIPNGLE

ONTROL 4RISILOXANE 2AKE

As previously described for wetting the architecture of the copolymer has a profound effect on its behavior as a slip additive Optimized structures have been identified by designed experimentation to give the desired combination of compatibility and slip performance Compatibility is particularly important in clear coatings where gloss reduction or haze is not acceptable

Figure 9 shows slip angle results for silicone-polyether copolymers A and B in water-reducible stoving paint The main difference between the copolymers is overall molecular weight Both products contain pendant polyether groups It can be seen that trisiloxane A has almost no impact on slip This is believed to be due to the very short nature of its silicone chains A minimum amount of dimethylsiloxy units is required to give noticeable changes in slip This requirement is met in rake structure B which shows an improved slip

Novel Carbinol Function Silicones in Comparison to Traditional SPEs in Architectural Coatings The purpose of looking at new functionshyalities was to determine if we could improve hydrophilicity beyond what we were seeing in the traditional silicone polyethers that would lend themselves to more easy-clean surface development

In this study two novel carbinol functionality materials were compared to a traditional silicone polyether of similar degree of polymerization (Dp) and its performance toward dirt release in an architectural binder Each sample was doped into an acrylic-based binder by weight of resin and surface appearance and properties were characterized With the incorporation of the novel carbinol functionality the data shows an increase in the hydrophilicity of the coating as compared to the traditional SPE (Table II) This yields what was seen as an

Table V Dirt release characteristics after outdoor aging

Dirt Release Properties after 1008

Sample Hours Weathering

SG 30 Neat -

SG 30 with 1 ABA 0

SG 30 with 1 Novel ABA +

SG 30 with 1 Novel Resin ++

LOSS

ASE

4XANE

RISILO

4XANE

RISILOEL

WITHOV

EL

WITHOV

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

Figure 10 Mar resistance as a function of gloss

)NITIAL 2UBS

ampORMULATION

Table III Dirt-release characteristics through simple spray method

Sample Dirt Release Properties

Binder 0

Binder with 1 ABA +

Binder with 1 Novel ABA ++

Binder with 1 Novel Resin ++

Table IV Dirt pickup and pencil hardness

Pencil Formulation Dirt Pickup Hardness

Binder 0 3B

Binder with 1 ABA - 45B

Binder with 1 Novel ABA

Binder with 1 Novel Resin

-

-

45B

4B

though with the addition of the tradishytional ABA materials there was a slight improvement over the baseline but not as great as the unaged samples The novel ABA materials still showed significant improvement while the resinous materials showed excellent dirt-release characteristics (Table V)

Novel Carbinol Functional Silicones in Comparison with Traditional SPEs in Overprint Varnish Applications A baseline formulation for a general-purpose overprint varnish was obtained by Johnson Polymers The formulation was run with and without the Aerosol OT-75 noting no differences in the wet-out performance and was omitted for all the runs with the addition of the additives The appearance and wet-out of the OPV were not affected by the incorporation of the siloxane additive either standard or with the novel functionality

Samples were coated onto Lentea charts and run for 250 cycles on a Sutherland rub tester with gloss being documented prior and after rubs to determine each formulationrsquos resistance to mar The initial point to be noted was an increase in the initial gloss with siloxane incorporation excluding the standard ABA and the BYK material bench-marked against Enhancement was higher in those containing the novel functionality There was also better mar resistance overall with all these samples versus the baseline material

increase in the dirt-release ability of the coating through simple water spraying This increase in hydrophilicity was seen in both the ABA-structured materials as well as resinous-based siloxanes

After a simple draw down and cure time the coatings were dusted with a layer of dirt and sprayed with water to note the dirt-releasing properties With the addition of the ABA silicone polyether structure there was an enhancement of the dirt-release properties but this enhancement was even greater in those samples incorporating the new carbinol functionality (Table III) One thing to be noted is that the addition of the silicone surfactants either with the new carbinol material or the traditional polyethers does cause a slight softening of the coating itself which actually correlates into an initial dirt pickup that is slightly enhanced over the neat acrylic binder (Table IV)

Durability of this hydrophilicity is a known deficiency given the current additives function by migrating to the surface and can often wash away over an extended time with exposure to the environment After subjecting the coatings to external weathering exposure for 1008 hours the dirt-release performance decreased The neat SG 30 sample no longer released dirt as easily

shy

Oamp

Figure 11 Coefficient of friction data on OPV samples

ASE

4RISILOXANE

4RISILOXANE

ampORMULATION WITHOVEL

3TATICOamp +INETICOamp

WITHOVEL

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

modified to improve substrate wetting In particular the trisiloxane structure gives the best equilibrium surface tension reduction and excellent wetting to plastic surfaces and other low-energy substrates This material has the greatest capacity for lowering the liquidsolid interfacial tension The higher-molecularweight siloxane surfactants with rake and linear structures give moderate wetting However materials of these types can be used to provide other benefits for instance mar resistance slip and de-aeration The incorporation of a resinous material with functionality can also yield a higher substantivity in a coating that is likely desired when a coating is being exposed to long-term weathering effects The addition of novel functionalities in place of the linear polyethers also can enhance the properties of the silicone polyether materials research is being done to fine-tune these functionalities to the most appropriate applications

shy

shy

Coefficient of friction data (CoF) indicates that the mar resistance improvements were not due to increasing the slip of the surface By industry standards the slip change that was documented is within error This indicates a possibility for applications such as floor varnish where mar resistance needs to be increased with no effect on the CoF or slipperiness of the surface The CoF data demonshystrates that the additive is not residing on the surface but possibly allowing the PE wax to better orientate at the surface and yield higher mar resistance

In looking at the surface tension data of the materials used in this study there is actually very little difference that would

indicate this is the reason why the material performs this way

Work continues to optimize the strucshytures and find application in which they can be utilized

Conclusions Silicone-based surfactants offer many benefits in waterborne coatings By the addition of the correct silicone surfactant the coating surface tension can be

shy

Table VI Surface energy of standard and modified siloxanes

Surface Energy at 1 (Dynescm)

Trisiloxane 201

Trisiloxane with Novel 212

ABA 246

ABA with Novel 238

Resin not soluble

Resin with Novel 264

References 1 Schlachter I and Feldmann-Krane Georg Silicone Surfactants Surfactants Sci Ser 1998 74 p 201-239

2 Scholz W Verkroniek 10 13 1995

How to Contact Us Dow Corning has sales offices manufacshyturing sites and science and technology laboratories around the globe Telephone numbers of locations near you are available on the World Wide Web at wwwdowcorningcom or by calling one of our primary locations listed below

Your Global Connection Americas +1 989 496 6000

Europe +49 0611 237 342

Asia +86 21 62882626

LIMITED WARRANTY INFORMATION ndash PLEASE READ CAREFULLY

The information contained herein is offered in good faith and is believed to be accurate However because conditions and methods of use of our products are beyond our control this information should not be used in substitution for customerrsquos tests to ensure that Dow Corningrsquos products are safe effective and fully satisfactory for the intended end use Suggestions of use shall not be taken as inducements to infringe any patent

Dow Corningrsquos sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted

DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY

DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES

Dow Corning is a registered trademark of Dow Corning Corporation

We help you invent the future is a trademark of Dow Corning Corporation

copy2005 Dow Corning Corporation All rights reserved

shy

Printed in USA AGP7561 Form No 26-1365-01

portion of the molecule aligns with the interface and the terminal groups are in the aqueous phase The amounts to be added vary between 001 and 05 of the total formulation

This paper will now discuss the behavior of silicone polyethers along with comparisons to silicones with novel carbinol functionalities in water together with some studies in coating formulashytions The results are compared with other additives that are currently used in coatings

Silicone Polyethers as Wetting Agents In this study the three different siloxane surfactants described above were evaluated in aqueous solution in a water-based printing ink and in a water-based polyester coating in comparison with fluorosurfactants and acetylenic glycols which are also used as wetting agents To achieve good wetting and a positive spreading coefficient the surface tension of the coating must be lower than the critical surface tension of the substrate

Water has a typical surface tension of 72 mNm and as can be seen from Table I all the surfactants tested reduced the surface tension of the system and as a result the aqueous medium wetted more efficiently For the silicone surfacshytants the best results were achieved with product A a low-molecular-weight material Trisiloxane A gave a very low figure that was improved by the fluoroshysurfactant

The critical micelle concentration (CMC) is the required level of product to initiate the formation of micelles in the bulk of a liquid Up to this point the surfactant added to the water migrated to the liquidair interface to form a film that reduced the surface tension The low CMC for A showed its high packing efficiency at the interface in the much lower level required in comparison to the other products

Table I Equilibrium surface tension with a Kruumlss K10T tensiometer and a platinum Wilhelmy plate additive concentrations 01

Surfactant Equilibrium Surface Tension (nMm) CMC ()

Trisiloxane A 205 0008

ABA Siloxane B 290 0025

Rake Siloxane C 299 0018

Fluorosurfactant

Ethoxylated Acetylenic Diol

175

253

0030

0050

In this context it is important to understand the difference between equilibrium and dynamic surface tension For an equilibrium surface tension measurement a platinum plate is immersed in a test solution and then slowly withdrawn The force required to remove the plate from the solution is a measure of the surface tension of that liquid

Dynamic surface tension can be measured by an instrument that bubbles air through the test liquid at an increasshying rate during which the maximum pressure that is required to form a bubble is measured As the bubble rate increases from 1 bubble per second to 10 the time to create the new interface (liquidair) decreases This is effectively measuring how quickly the surfactant lowers the surface tension

The dynamic method is more represenshytative of the coating application for example spraying Under these circumshystances it is important to know how quickly a surfactant can migrate to newly formed interfaces An ideal surface-active agent would provide excellent surface tension reduction under both equilibrium and dynamic conditions

Figure 4 shows dynamic surface tension results for the above materials at 01 in water Trisiloxane A gives better performance than the other silicone polyethers but does not give the very low values achieved by either the fluorosurfactants or ethoxylated acetylenic glycols However it must be remembered that dynamic surface tension represents only one aspect of the total phenomenon

MM

Figure 4 Dynamic surface tension maximum bubble pressure (Kruumlss BP1) 01 in water

DDITIVE

DDITIVE

DDITIVE

amp3URFACTANT

THOXYLATED CETYLENIC$IOL

UBBLEampREQUENCY(ERTZ

Figure 5 Contact angle measurement

Figure 6 Contact angle measurement with a VCA 2000 video contact angle equipment additive concentration at 01 in water

ONTROL

DDITIVE

ONTACTNGLE

DDITIVE

THOXYLATED CETYLENIC$IOL

DDITIVE

amp3URFACTANT

3URFACENERGYOF3UBSTRATEMM

In practice not only the conditions at the airliquid interface are of interest but also the conditions at the liquidsubstrate interface In general the smaller the contact angle produced by a system the better the substrate wetting The equipment used to measure the contact angle theta (θ) was a VCA 2000 instrument that automatically dispensed a minute droplet of the liquid to be measured and then photographed the droplet after a set period or could be programmed to take a number of photographs and measure correspondshying contact angles after regular time intervals This technique enabled the monitoring of droplets spreading on non-porous surfaces

When θ is greater than 90 degrees as in Figure 5 then beading or non-wetting is occurring as is shown by water on a plastic surface such as high-density polyethylene If θ is less than 90

degrees as shown in Figure 5 then wetting is occurring the smaller the angle the better the wetting process Spontaneous wetting occurs when θ=0 the droplet immediately spreading to

form a very thin continuous film on the substrate with effectively no contact angle capable of being determined

Figure 6 shows the behavior of the same surfactants on a range of low-energy substrates such as polyethylene and polypropylene For wetting it has been shown that the most efficient silicone

and allow for very efficient packing at interfaces For critical low-energy substrates only the trisiloxane surfactant A allows perfect (spontaneous) wetting and excellent spreading

polyether is trisiloxane A which has three Si atoms with pendant ethylene oxide The low molecular weight and size give greater mobility in solution

Extending this performance behavior now into practical life applications the effects of these surfactants in a water-based flexographic ink formulation are shown in Figure 7 The addition of siloxane surfactant A shows excellent substrate wetting performance on plastic foil followed by the fluorosurfactant The siloxane surfactants B and C which have a different structure and a higher molecular weight do not improve the wetting behavior It can be seen that the acetylenic glycol has only a small impacton the wetting behavior

Any surfactant molecule has the potential to generate foam that is undesirable in many applications Figure 8 shows the density measurements after a high shear stir test which give an indication of air entrapment in the ink The siloxane

Figure 7 Flexographic printing ink additive concentration 05 wettingappearance performance after application on plastic foil (surface energy 34 mNm) by draw down 12 micron rated on a scale from 1ndash5

ETTING

ANCE7

PPEAR

ONTROL 4RISILOXANE 2AKE CETYLENIC amp3URFACTANT LYCOL

2ATINGFROM13EXCELLENT

Figure 8 Flexographic printing ink additive concentration 05 density measurement after dissolver stirring test (5 minutes at 2800 rpm) as a measure of rate of foam development

$ENSITYINGCM

ONTROL 2AKE 4RISILOXANE CETYLENIC amp3URFACTANT LYCOL

$ENSITYWITHOUTSTIRRINGGCM

Table II Contact angle data

Sample Water Contact Angle

Acrylic Binder 43

Binder with 1 ABA 34

Binder with 1 Novel ABA lt15

Binder with 1 Novel Resin lt15

surfactant C (rake) acts only as a lowshy to-moderate foam enhancer compared to the fluorosurfactant What is also interesting is that siloxane surfactant B the silicone product with the highest molecular weight is performing as a de-aerator

Silicones as Slip Additives Slip represents the lubrication of a dry coating surface Given that the function of a coating is often to protect the underlying surface from damage while maintaining a satisfactory appearance it is clear that the coating itself must be capable of resisting mechanical damage This is where slip is important It is often referred to as mar resistance rather than abrasion resistance In the latter the bulk mechanical properties of the film are important in addition to the surface lubricity

Slip additives must reduce friction at the coating surface A thin layer of a material with low inter-molecular forces is capable of achieving this The slip additive should be sufficiently compatible with the coating before application to avoid separation After application it should not cause fisheyes or other defects associated with non- wetting of the additive by the coating However there has to be some degree of incompatibility to drive the additive to the surface of the coating film during drying

Silicone polyethers are important as slip agents due to their structure The ratio of the EOPO segments has to be carefully controlled to achieve the required compatibility balance Too low a polyether content may lead to the de-wetting defects already mentioned On the other hand high polyether content can render the copolymer too soluble with no driving force to get it to the coating surface during drying

Figure 9 Effect of molecular weight on slip performance of silicone-polyether copolymers in water-reducible polyester stoving paint (A low molecular weight B high molecular weight)

3LIPNGLE

ONTROL 4RISILOXANE 2AKE

As previously described for wetting the architecture of the copolymer has a profound effect on its behavior as a slip additive Optimized structures have been identified by designed experimentation to give the desired combination of compatibility and slip performance Compatibility is particularly important in clear coatings where gloss reduction or haze is not acceptable

Figure 9 shows slip angle results for silicone-polyether copolymers A and B in water-reducible stoving paint The main difference between the copolymers is overall molecular weight Both products contain pendant polyether groups It can be seen that trisiloxane A has almost no impact on slip This is believed to be due to the very short nature of its silicone chains A minimum amount of dimethylsiloxy units is required to give noticeable changes in slip This requirement is met in rake structure B which shows an improved slip

Novel Carbinol Function Silicones in Comparison to Traditional SPEs in Architectural Coatings The purpose of looking at new functionshyalities was to determine if we could improve hydrophilicity beyond what we were seeing in the traditional silicone polyethers that would lend themselves to more easy-clean surface development

In this study two novel carbinol functionality materials were compared to a traditional silicone polyether of similar degree of polymerization (Dp) and its performance toward dirt release in an architectural binder Each sample was doped into an acrylic-based binder by weight of resin and surface appearance and properties were characterized With the incorporation of the novel carbinol functionality the data shows an increase in the hydrophilicity of the coating as compared to the traditional SPE (Table II) This yields what was seen as an

Table V Dirt release characteristics after outdoor aging

Dirt Release Properties after 1008

Sample Hours Weathering

SG 30 Neat -

SG 30 with 1 ABA 0

SG 30 with 1 Novel ABA +

SG 30 with 1 Novel Resin ++

LOSS

ASE

4XANE

RISILO

4XANE

RISILOEL

WITHOV

EL

WITHOV

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

Figure 10 Mar resistance as a function of gloss

)NITIAL 2UBS

ampORMULATION

Table III Dirt-release characteristics through simple spray method

Sample Dirt Release Properties

Binder 0

Binder with 1 ABA +

Binder with 1 Novel ABA ++

Binder with 1 Novel Resin ++

Table IV Dirt pickup and pencil hardness

Pencil Formulation Dirt Pickup Hardness

Binder 0 3B

Binder with 1 ABA - 45B

Binder with 1 Novel ABA

Binder with 1 Novel Resin

-

-

45B

4B

though with the addition of the tradishytional ABA materials there was a slight improvement over the baseline but not as great as the unaged samples The novel ABA materials still showed significant improvement while the resinous materials showed excellent dirt-release characteristics (Table V)

Novel Carbinol Functional Silicones in Comparison with Traditional SPEs in Overprint Varnish Applications A baseline formulation for a general-purpose overprint varnish was obtained by Johnson Polymers The formulation was run with and without the Aerosol OT-75 noting no differences in the wet-out performance and was omitted for all the runs with the addition of the additives The appearance and wet-out of the OPV were not affected by the incorporation of the siloxane additive either standard or with the novel functionality

Samples were coated onto Lentea charts and run for 250 cycles on a Sutherland rub tester with gloss being documented prior and after rubs to determine each formulationrsquos resistance to mar The initial point to be noted was an increase in the initial gloss with siloxane incorporation excluding the standard ABA and the BYK material bench-marked against Enhancement was higher in those containing the novel functionality There was also better mar resistance overall with all these samples versus the baseline material

increase in the dirt-release ability of the coating through simple water spraying This increase in hydrophilicity was seen in both the ABA-structured materials as well as resinous-based siloxanes

After a simple draw down and cure time the coatings were dusted with a layer of dirt and sprayed with water to note the dirt-releasing properties With the addition of the ABA silicone polyether structure there was an enhancement of the dirt-release properties but this enhancement was even greater in those samples incorporating the new carbinol functionality (Table III) One thing to be noted is that the addition of the silicone surfactants either with the new carbinol material or the traditional polyethers does cause a slight softening of the coating itself which actually correlates into an initial dirt pickup that is slightly enhanced over the neat acrylic binder (Table IV)

Durability of this hydrophilicity is a known deficiency given the current additives function by migrating to the surface and can often wash away over an extended time with exposure to the environment After subjecting the coatings to external weathering exposure for 1008 hours the dirt-release performance decreased The neat SG 30 sample no longer released dirt as easily

shy

Oamp

Figure 11 Coefficient of friction data on OPV samples

ASE

4RISILOXANE

4RISILOXANE

ampORMULATION WITHOVEL

3TATICOamp +INETICOamp

WITHOVEL

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

modified to improve substrate wetting In particular the trisiloxane structure gives the best equilibrium surface tension reduction and excellent wetting to plastic surfaces and other low-energy substrates This material has the greatest capacity for lowering the liquidsolid interfacial tension The higher-molecularweight siloxane surfactants with rake and linear structures give moderate wetting However materials of these types can be used to provide other benefits for instance mar resistance slip and de-aeration The incorporation of a resinous material with functionality can also yield a higher substantivity in a coating that is likely desired when a coating is being exposed to long-term weathering effects The addition of novel functionalities in place of the linear polyethers also can enhance the properties of the silicone polyether materials research is being done to fine-tune these functionalities to the most appropriate applications

shy

shy

Coefficient of friction data (CoF) indicates that the mar resistance improvements were not due to increasing the slip of the surface By industry standards the slip change that was documented is within error This indicates a possibility for applications such as floor varnish where mar resistance needs to be increased with no effect on the CoF or slipperiness of the surface The CoF data demonshystrates that the additive is not residing on the surface but possibly allowing the PE wax to better orientate at the surface and yield higher mar resistance

In looking at the surface tension data of the materials used in this study there is actually very little difference that would

indicate this is the reason why the material performs this way

Work continues to optimize the strucshytures and find application in which they can be utilized

Conclusions Silicone-based surfactants offer many benefits in waterborne coatings By the addition of the correct silicone surfactant the coating surface tension can be

shy

Table VI Surface energy of standard and modified siloxanes

Surface Energy at 1 (Dynescm)

Trisiloxane 201

Trisiloxane with Novel 212

ABA 246

ABA with Novel 238

Resin not soluble

Resin with Novel 264

References 1 Schlachter I and Feldmann-Krane Georg Silicone Surfactants Surfactants Sci Ser 1998 74 p 201-239

2 Scholz W Verkroniek 10 13 1995

How to Contact Us Dow Corning has sales offices manufacshyturing sites and science and technology laboratories around the globe Telephone numbers of locations near you are available on the World Wide Web at wwwdowcorningcom or by calling one of our primary locations listed below

Your Global Connection Americas +1 989 496 6000

Europe +49 0611 237 342

Asia +86 21 62882626

LIMITED WARRANTY INFORMATION ndash PLEASE READ CAREFULLY

The information contained herein is offered in good faith and is believed to be accurate However because conditions and methods of use of our products are beyond our control this information should not be used in substitution for customerrsquos tests to ensure that Dow Corningrsquos products are safe effective and fully satisfactory for the intended end use Suggestions of use shall not be taken as inducements to infringe any patent

Dow Corningrsquos sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted

DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY

DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES

Dow Corning is a registered trademark of Dow Corning Corporation

We help you invent the future is a trademark of Dow Corning Corporation

copy2005 Dow Corning Corporation All rights reserved

shy

Printed in USA AGP7561 Form No 26-1365-01

Figure 5 Contact angle measurement

Figure 6 Contact angle measurement with a VCA 2000 video contact angle equipment additive concentration at 01 in water

ONTROL

DDITIVE

ONTACTNGLE

DDITIVE

THOXYLATED CETYLENIC$IOL

DDITIVE

amp3URFACTANT

3URFACENERGYOF3UBSTRATEMM

In practice not only the conditions at the airliquid interface are of interest but also the conditions at the liquidsubstrate interface In general the smaller the contact angle produced by a system the better the substrate wetting The equipment used to measure the contact angle theta (θ) was a VCA 2000 instrument that automatically dispensed a minute droplet of the liquid to be measured and then photographed the droplet after a set period or could be programmed to take a number of photographs and measure correspondshying contact angles after regular time intervals This technique enabled the monitoring of droplets spreading on non-porous surfaces

When θ is greater than 90 degrees as in Figure 5 then beading or non-wetting is occurring as is shown by water on a plastic surface such as high-density polyethylene If θ is less than 90

degrees as shown in Figure 5 then wetting is occurring the smaller the angle the better the wetting process Spontaneous wetting occurs when θ=0 the droplet immediately spreading to

form a very thin continuous film on the substrate with effectively no contact angle capable of being determined

Figure 6 shows the behavior of the same surfactants on a range of low-energy substrates such as polyethylene and polypropylene For wetting it has been shown that the most efficient silicone

and allow for very efficient packing at interfaces For critical low-energy substrates only the trisiloxane surfactant A allows perfect (spontaneous) wetting and excellent spreading

polyether is trisiloxane A which has three Si atoms with pendant ethylene oxide The low molecular weight and size give greater mobility in solution

Extending this performance behavior now into practical life applications the effects of these surfactants in a water-based flexographic ink formulation are shown in Figure 7 The addition of siloxane surfactant A shows excellent substrate wetting performance on plastic foil followed by the fluorosurfactant The siloxane surfactants B and C which have a different structure and a higher molecular weight do not improve the wetting behavior It can be seen that the acetylenic glycol has only a small impacton the wetting behavior

Any surfactant molecule has the potential to generate foam that is undesirable in many applications Figure 8 shows the density measurements after a high shear stir test which give an indication of air entrapment in the ink The siloxane

Figure 7 Flexographic printing ink additive concentration 05 wettingappearance performance after application on plastic foil (surface energy 34 mNm) by draw down 12 micron rated on a scale from 1ndash5

ETTING

ANCE7

PPEAR

ONTROL 4RISILOXANE 2AKE CETYLENIC amp3URFACTANT LYCOL

2ATINGFROM13EXCELLENT

Figure 8 Flexographic printing ink additive concentration 05 density measurement after dissolver stirring test (5 minutes at 2800 rpm) as a measure of rate of foam development

$ENSITYINGCM

ONTROL 2AKE 4RISILOXANE CETYLENIC amp3URFACTANT LYCOL

$ENSITYWITHOUTSTIRRINGGCM

Table II Contact angle data

Sample Water Contact Angle

Acrylic Binder 43

Binder with 1 ABA 34

Binder with 1 Novel ABA lt15

Binder with 1 Novel Resin lt15

surfactant C (rake) acts only as a lowshy to-moderate foam enhancer compared to the fluorosurfactant What is also interesting is that siloxane surfactant B the silicone product with the highest molecular weight is performing as a de-aerator

Silicones as Slip Additives Slip represents the lubrication of a dry coating surface Given that the function of a coating is often to protect the underlying surface from damage while maintaining a satisfactory appearance it is clear that the coating itself must be capable of resisting mechanical damage This is where slip is important It is often referred to as mar resistance rather than abrasion resistance In the latter the bulk mechanical properties of the film are important in addition to the surface lubricity

Slip additives must reduce friction at the coating surface A thin layer of a material with low inter-molecular forces is capable of achieving this The slip additive should be sufficiently compatible with the coating before application to avoid separation After application it should not cause fisheyes or other defects associated with non- wetting of the additive by the coating However there has to be some degree of incompatibility to drive the additive to the surface of the coating film during drying

Silicone polyethers are important as slip agents due to their structure The ratio of the EOPO segments has to be carefully controlled to achieve the required compatibility balance Too low a polyether content may lead to the de-wetting defects already mentioned On the other hand high polyether content can render the copolymer too soluble with no driving force to get it to the coating surface during drying

Figure 9 Effect of molecular weight on slip performance of silicone-polyether copolymers in water-reducible polyester stoving paint (A low molecular weight B high molecular weight)

3LIPNGLE

ONTROL 4RISILOXANE 2AKE

As previously described for wetting the architecture of the copolymer has a profound effect on its behavior as a slip additive Optimized structures have been identified by designed experimentation to give the desired combination of compatibility and slip performance Compatibility is particularly important in clear coatings where gloss reduction or haze is not acceptable

Figure 9 shows slip angle results for silicone-polyether copolymers A and B in water-reducible stoving paint The main difference between the copolymers is overall molecular weight Both products contain pendant polyether groups It can be seen that trisiloxane A has almost no impact on slip This is believed to be due to the very short nature of its silicone chains A minimum amount of dimethylsiloxy units is required to give noticeable changes in slip This requirement is met in rake structure B which shows an improved slip

Novel Carbinol Function Silicones in Comparison to Traditional SPEs in Architectural Coatings The purpose of looking at new functionshyalities was to determine if we could improve hydrophilicity beyond what we were seeing in the traditional silicone polyethers that would lend themselves to more easy-clean surface development

In this study two novel carbinol functionality materials were compared to a traditional silicone polyether of similar degree of polymerization (Dp) and its performance toward dirt release in an architectural binder Each sample was doped into an acrylic-based binder by weight of resin and surface appearance and properties were characterized With the incorporation of the novel carbinol functionality the data shows an increase in the hydrophilicity of the coating as compared to the traditional SPE (Table II) This yields what was seen as an

Table V Dirt release characteristics after outdoor aging

Dirt Release Properties after 1008

Sample Hours Weathering

SG 30 Neat -

SG 30 with 1 ABA 0

SG 30 with 1 Novel ABA +

SG 30 with 1 Novel Resin ++

LOSS

ASE

4XANE

RISILO

4XANE

RISILOEL

WITHOV

EL

WITHOV

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

Figure 10 Mar resistance as a function of gloss

)NITIAL 2UBS

ampORMULATION

Table III Dirt-release characteristics through simple spray method

Sample Dirt Release Properties

Binder 0

Binder with 1 ABA +

Binder with 1 Novel ABA ++

Binder with 1 Novel Resin ++

Table IV Dirt pickup and pencil hardness

Pencil Formulation Dirt Pickup Hardness

Binder 0 3B

Binder with 1 ABA - 45B

Binder with 1 Novel ABA

Binder with 1 Novel Resin

-

-

45B

4B

though with the addition of the tradishytional ABA materials there was a slight improvement over the baseline but not as great as the unaged samples The novel ABA materials still showed significant improvement while the resinous materials showed excellent dirt-release characteristics (Table V)

Novel Carbinol Functional Silicones in Comparison with Traditional SPEs in Overprint Varnish Applications A baseline formulation for a general-purpose overprint varnish was obtained by Johnson Polymers The formulation was run with and without the Aerosol OT-75 noting no differences in the wet-out performance and was omitted for all the runs with the addition of the additives The appearance and wet-out of the OPV were not affected by the incorporation of the siloxane additive either standard or with the novel functionality

Samples were coated onto Lentea charts and run for 250 cycles on a Sutherland rub tester with gloss being documented prior and after rubs to determine each formulationrsquos resistance to mar The initial point to be noted was an increase in the initial gloss with siloxane incorporation excluding the standard ABA and the BYK material bench-marked against Enhancement was higher in those containing the novel functionality There was also better mar resistance overall with all these samples versus the baseline material

increase in the dirt-release ability of the coating through simple water spraying This increase in hydrophilicity was seen in both the ABA-structured materials as well as resinous-based siloxanes

After a simple draw down and cure time the coatings were dusted with a layer of dirt and sprayed with water to note the dirt-releasing properties With the addition of the ABA silicone polyether structure there was an enhancement of the dirt-release properties but this enhancement was even greater in those samples incorporating the new carbinol functionality (Table III) One thing to be noted is that the addition of the silicone surfactants either with the new carbinol material or the traditional polyethers does cause a slight softening of the coating itself which actually correlates into an initial dirt pickup that is slightly enhanced over the neat acrylic binder (Table IV)

Durability of this hydrophilicity is a known deficiency given the current additives function by migrating to the surface and can often wash away over an extended time with exposure to the environment After subjecting the coatings to external weathering exposure for 1008 hours the dirt-release performance decreased The neat SG 30 sample no longer released dirt as easily

shy

Oamp

Figure 11 Coefficient of friction data on OPV samples

ASE

4RISILOXANE

4RISILOXANE

ampORMULATION WITHOVEL

3TATICOamp +INETICOamp

WITHOVEL

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

modified to improve substrate wetting In particular the trisiloxane structure gives the best equilibrium surface tension reduction and excellent wetting to plastic surfaces and other low-energy substrates This material has the greatest capacity for lowering the liquidsolid interfacial tension The higher-molecularweight siloxane surfactants with rake and linear structures give moderate wetting However materials of these types can be used to provide other benefits for instance mar resistance slip and de-aeration The incorporation of a resinous material with functionality can also yield a higher substantivity in a coating that is likely desired when a coating is being exposed to long-term weathering effects The addition of novel functionalities in place of the linear polyethers also can enhance the properties of the silicone polyether materials research is being done to fine-tune these functionalities to the most appropriate applications

shy

shy

Coefficient of friction data (CoF) indicates that the mar resistance improvements were not due to increasing the slip of the surface By industry standards the slip change that was documented is within error This indicates a possibility for applications such as floor varnish where mar resistance needs to be increased with no effect on the CoF or slipperiness of the surface The CoF data demonshystrates that the additive is not residing on the surface but possibly allowing the PE wax to better orientate at the surface and yield higher mar resistance

In looking at the surface tension data of the materials used in this study there is actually very little difference that would

indicate this is the reason why the material performs this way

Work continues to optimize the strucshytures and find application in which they can be utilized

Conclusions Silicone-based surfactants offer many benefits in waterborne coatings By the addition of the correct silicone surfactant the coating surface tension can be

shy

Table VI Surface energy of standard and modified siloxanes

Surface Energy at 1 (Dynescm)

Trisiloxane 201

Trisiloxane with Novel 212

ABA 246

ABA with Novel 238

Resin not soluble

Resin with Novel 264

References 1 Schlachter I and Feldmann-Krane Georg Silicone Surfactants Surfactants Sci Ser 1998 74 p 201-239

2 Scholz W Verkroniek 10 13 1995

How to Contact Us Dow Corning has sales offices manufacshyturing sites and science and technology laboratories around the globe Telephone numbers of locations near you are available on the World Wide Web at wwwdowcorningcom or by calling one of our primary locations listed below

Your Global Connection Americas +1 989 496 6000

Europe +49 0611 237 342

Asia +86 21 62882626

LIMITED WARRANTY INFORMATION ndash PLEASE READ CAREFULLY

The information contained herein is offered in good faith and is believed to be accurate However because conditions and methods of use of our products are beyond our control this information should not be used in substitution for customerrsquos tests to ensure that Dow Corningrsquos products are safe effective and fully satisfactory for the intended end use Suggestions of use shall not be taken as inducements to infringe any patent

Dow Corningrsquos sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted

DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY

DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES

Dow Corning is a registered trademark of Dow Corning Corporation

We help you invent the future is a trademark of Dow Corning Corporation

copy2005 Dow Corning Corporation All rights reserved

shy

Printed in USA AGP7561 Form No 26-1365-01

Table II Contact angle data

Sample Water Contact Angle

Acrylic Binder 43

Binder with 1 ABA 34

Binder with 1 Novel ABA lt15

Binder with 1 Novel Resin lt15

surfactant C (rake) acts only as a lowshy to-moderate foam enhancer compared to the fluorosurfactant What is also interesting is that siloxane surfactant B the silicone product with the highest molecular weight is performing as a de-aerator

Silicones as Slip Additives Slip represents the lubrication of a dry coating surface Given that the function of a coating is often to protect the underlying surface from damage while maintaining a satisfactory appearance it is clear that the coating itself must be capable of resisting mechanical damage This is where slip is important It is often referred to as mar resistance rather than abrasion resistance In the latter the bulk mechanical properties of the film are important in addition to the surface lubricity

Slip additives must reduce friction at the coating surface A thin layer of a material with low inter-molecular forces is capable of achieving this The slip additive should be sufficiently compatible with the coating before application to avoid separation After application it should not cause fisheyes or other defects associated with non- wetting of the additive by the coating However there has to be some degree of incompatibility to drive the additive to the surface of the coating film during drying

Silicone polyethers are important as slip agents due to their structure The ratio of the EOPO segments has to be carefully controlled to achieve the required compatibility balance Too low a polyether content may lead to the de-wetting defects already mentioned On the other hand high polyether content can render the copolymer too soluble with no driving force to get it to the coating surface during drying

Figure 9 Effect of molecular weight on slip performance of silicone-polyether copolymers in water-reducible polyester stoving paint (A low molecular weight B high molecular weight)

3LIPNGLE

ONTROL 4RISILOXANE 2AKE

As previously described for wetting the architecture of the copolymer has a profound effect on its behavior as a slip additive Optimized structures have been identified by designed experimentation to give the desired combination of compatibility and slip performance Compatibility is particularly important in clear coatings where gloss reduction or haze is not acceptable

Figure 9 shows slip angle results for silicone-polyether copolymers A and B in water-reducible stoving paint The main difference between the copolymers is overall molecular weight Both products contain pendant polyether groups It can be seen that trisiloxane A has almost no impact on slip This is believed to be due to the very short nature of its silicone chains A minimum amount of dimethylsiloxy units is required to give noticeable changes in slip This requirement is met in rake structure B which shows an improved slip

Novel Carbinol Function Silicones in Comparison to Traditional SPEs in Architectural Coatings The purpose of looking at new functionshyalities was to determine if we could improve hydrophilicity beyond what we were seeing in the traditional silicone polyethers that would lend themselves to more easy-clean surface development

In this study two novel carbinol functionality materials were compared to a traditional silicone polyether of similar degree of polymerization (Dp) and its performance toward dirt release in an architectural binder Each sample was doped into an acrylic-based binder by weight of resin and surface appearance and properties were characterized With the incorporation of the novel carbinol functionality the data shows an increase in the hydrophilicity of the coating as compared to the traditional SPE (Table II) This yields what was seen as an

Table V Dirt release characteristics after outdoor aging

Dirt Release Properties after 1008

Sample Hours Weathering

SG 30 Neat -

SG 30 with 1 ABA 0

SG 30 with 1 Novel ABA +

SG 30 with 1 Novel Resin ++

LOSS

ASE

4XANE

RISILO

4XANE

RISILOEL

WITHOV

EL

WITHOV

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

Figure 10 Mar resistance as a function of gloss

)NITIAL 2UBS

ampORMULATION

Table III Dirt-release characteristics through simple spray method

Sample Dirt Release Properties

Binder 0

Binder with 1 ABA +

Binder with 1 Novel ABA ++

Binder with 1 Novel Resin ++

Table IV Dirt pickup and pencil hardness

Pencil Formulation Dirt Pickup Hardness

Binder 0 3B

Binder with 1 ABA - 45B

Binder with 1 Novel ABA

Binder with 1 Novel Resin

-

-

45B

4B

though with the addition of the tradishytional ABA materials there was a slight improvement over the baseline but not as great as the unaged samples The novel ABA materials still showed significant improvement while the resinous materials showed excellent dirt-release characteristics (Table V)

Novel Carbinol Functional Silicones in Comparison with Traditional SPEs in Overprint Varnish Applications A baseline formulation for a general-purpose overprint varnish was obtained by Johnson Polymers The formulation was run with and without the Aerosol OT-75 noting no differences in the wet-out performance and was omitted for all the runs with the addition of the additives The appearance and wet-out of the OPV were not affected by the incorporation of the siloxane additive either standard or with the novel functionality

Samples were coated onto Lentea charts and run for 250 cycles on a Sutherland rub tester with gloss being documented prior and after rubs to determine each formulationrsquos resistance to mar The initial point to be noted was an increase in the initial gloss with siloxane incorporation excluding the standard ABA and the BYK material bench-marked against Enhancement was higher in those containing the novel functionality There was also better mar resistance overall with all these samples versus the baseline material

increase in the dirt-release ability of the coating through simple water spraying This increase in hydrophilicity was seen in both the ABA-structured materials as well as resinous-based siloxanes

After a simple draw down and cure time the coatings were dusted with a layer of dirt and sprayed with water to note the dirt-releasing properties With the addition of the ABA silicone polyether structure there was an enhancement of the dirt-release properties but this enhancement was even greater in those samples incorporating the new carbinol functionality (Table III) One thing to be noted is that the addition of the silicone surfactants either with the new carbinol material or the traditional polyethers does cause a slight softening of the coating itself which actually correlates into an initial dirt pickup that is slightly enhanced over the neat acrylic binder (Table IV)

Durability of this hydrophilicity is a known deficiency given the current additives function by migrating to the surface and can often wash away over an extended time with exposure to the environment After subjecting the coatings to external weathering exposure for 1008 hours the dirt-release performance decreased The neat SG 30 sample no longer released dirt as easily

shy

Oamp

Figure 11 Coefficient of friction data on OPV samples

ASE

4RISILOXANE

4RISILOXANE

ampORMULATION WITHOVEL

3TATICOamp +INETICOamp

WITHOVEL

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

modified to improve substrate wetting In particular the trisiloxane structure gives the best equilibrium surface tension reduction and excellent wetting to plastic surfaces and other low-energy substrates This material has the greatest capacity for lowering the liquidsolid interfacial tension The higher-molecularweight siloxane surfactants with rake and linear structures give moderate wetting However materials of these types can be used to provide other benefits for instance mar resistance slip and de-aeration The incorporation of a resinous material with functionality can also yield a higher substantivity in a coating that is likely desired when a coating is being exposed to long-term weathering effects The addition of novel functionalities in place of the linear polyethers also can enhance the properties of the silicone polyether materials research is being done to fine-tune these functionalities to the most appropriate applications

shy

shy

Coefficient of friction data (CoF) indicates that the mar resistance improvements were not due to increasing the slip of the surface By industry standards the slip change that was documented is within error This indicates a possibility for applications such as floor varnish where mar resistance needs to be increased with no effect on the CoF or slipperiness of the surface The CoF data demonshystrates that the additive is not residing on the surface but possibly allowing the PE wax to better orientate at the surface and yield higher mar resistance

In looking at the surface tension data of the materials used in this study there is actually very little difference that would

indicate this is the reason why the material performs this way

Work continues to optimize the strucshytures and find application in which they can be utilized

Conclusions Silicone-based surfactants offer many benefits in waterborne coatings By the addition of the correct silicone surfactant the coating surface tension can be

shy

Table VI Surface energy of standard and modified siloxanes

Surface Energy at 1 (Dynescm)

Trisiloxane 201

Trisiloxane with Novel 212

ABA 246

ABA with Novel 238

Resin not soluble

Resin with Novel 264

References 1 Schlachter I and Feldmann-Krane Georg Silicone Surfactants Surfactants Sci Ser 1998 74 p 201-239

2 Scholz W Verkroniek 10 13 1995

How to Contact Us Dow Corning has sales offices manufacshyturing sites and science and technology laboratories around the globe Telephone numbers of locations near you are available on the World Wide Web at wwwdowcorningcom or by calling one of our primary locations listed below

Your Global Connection Americas +1 989 496 6000

Europe +49 0611 237 342

Asia +86 21 62882626

LIMITED WARRANTY INFORMATION ndash PLEASE READ CAREFULLY

The information contained herein is offered in good faith and is believed to be accurate However because conditions and methods of use of our products are beyond our control this information should not be used in substitution for customerrsquos tests to ensure that Dow Corningrsquos products are safe effective and fully satisfactory for the intended end use Suggestions of use shall not be taken as inducements to infringe any patent

Dow Corningrsquos sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted

DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY

DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES

Dow Corning is a registered trademark of Dow Corning Corporation

We help you invent the future is a trademark of Dow Corning Corporation

copy2005 Dow Corning Corporation All rights reserved

shy

Printed in USA AGP7561 Form No 26-1365-01

Table V Dirt release characteristics after outdoor aging

Dirt Release Properties after 1008

Sample Hours Weathering

SG 30 Neat -

SG 30 with 1 ABA 0

SG 30 with 1 Novel ABA +

SG 30 with 1 Novel Resin ++

LOSS

ASE

4XANE

RISILO

4XANE

RISILOEL

WITHOV

EL

WITHOV

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

Figure 10 Mar resistance as a function of gloss

)NITIAL 2UBS

ampORMULATION

Table III Dirt-release characteristics through simple spray method

Sample Dirt Release Properties

Binder 0

Binder with 1 ABA +

Binder with 1 Novel ABA ++

Binder with 1 Novel Resin ++

Table IV Dirt pickup and pencil hardness

Pencil Formulation Dirt Pickup Hardness

Binder 0 3B

Binder with 1 ABA - 45B

Binder with 1 Novel ABA

Binder with 1 Novel Resin

-

-

45B

4B

though with the addition of the tradishytional ABA materials there was a slight improvement over the baseline but not as great as the unaged samples The novel ABA materials still showed significant improvement while the resinous materials showed excellent dirt-release characteristics (Table V)

Novel Carbinol Functional Silicones in Comparison with Traditional SPEs in Overprint Varnish Applications A baseline formulation for a general-purpose overprint varnish was obtained by Johnson Polymers The formulation was run with and without the Aerosol OT-75 noting no differences in the wet-out performance and was omitted for all the runs with the addition of the additives The appearance and wet-out of the OPV were not affected by the incorporation of the siloxane additive either standard or with the novel functionality

Samples were coated onto Lentea charts and run for 250 cycles on a Sutherland rub tester with gloss being documented prior and after rubs to determine each formulationrsquos resistance to mar The initial point to be noted was an increase in the initial gloss with siloxane incorporation excluding the standard ABA and the BYK material bench-marked against Enhancement was higher in those containing the novel functionality There was also better mar resistance overall with all these samples versus the baseline material

increase in the dirt-release ability of the coating through simple water spraying This increase in hydrophilicity was seen in both the ABA-structured materials as well as resinous-based siloxanes

After a simple draw down and cure time the coatings were dusted with a layer of dirt and sprayed with water to note the dirt-releasing properties With the addition of the ABA silicone polyether structure there was an enhancement of the dirt-release properties but this enhancement was even greater in those samples incorporating the new carbinol functionality (Table III) One thing to be noted is that the addition of the silicone surfactants either with the new carbinol material or the traditional polyethers does cause a slight softening of the coating itself which actually correlates into an initial dirt pickup that is slightly enhanced over the neat acrylic binder (Table IV)

Durability of this hydrophilicity is a known deficiency given the current additives function by migrating to the surface and can often wash away over an extended time with exposure to the environment After subjecting the coatings to external weathering exposure for 1008 hours the dirt-release performance decreased The neat SG 30 sample no longer released dirt as easily

shy

Oamp

Figure 11 Coefficient of friction data on OPV samples

ASE

4RISILOXANE

4RISILOXANE

ampORMULATION WITHOVEL

3TATICOamp +INETICOamp

WITHOVEL

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

modified to improve substrate wetting In particular the trisiloxane structure gives the best equilibrium surface tension reduction and excellent wetting to plastic surfaces and other low-energy substrates This material has the greatest capacity for lowering the liquidsolid interfacial tension The higher-molecularweight siloxane surfactants with rake and linear structures give moderate wetting However materials of these types can be used to provide other benefits for instance mar resistance slip and de-aeration The incorporation of a resinous material with functionality can also yield a higher substantivity in a coating that is likely desired when a coating is being exposed to long-term weathering effects The addition of novel functionalities in place of the linear polyethers also can enhance the properties of the silicone polyether materials research is being done to fine-tune these functionalities to the most appropriate applications

shy

shy

Coefficient of friction data (CoF) indicates that the mar resistance improvements were not due to increasing the slip of the surface By industry standards the slip change that was documented is within error This indicates a possibility for applications such as floor varnish where mar resistance needs to be increased with no effect on the CoF or slipperiness of the surface The CoF data demonshystrates that the additive is not residing on the surface but possibly allowing the PE wax to better orientate at the surface and yield higher mar resistance

In looking at the surface tension data of the materials used in this study there is actually very little difference that would

indicate this is the reason why the material performs this way

Work continues to optimize the strucshytures and find application in which they can be utilized

Conclusions Silicone-based surfactants offer many benefits in waterborne coatings By the addition of the correct silicone surfactant the coating surface tension can be

shy

Table VI Surface energy of standard and modified siloxanes

Surface Energy at 1 (Dynescm)

Trisiloxane 201

Trisiloxane with Novel 212

ABA 246

ABA with Novel 238

Resin not soluble

Resin with Novel 264

References 1 Schlachter I and Feldmann-Krane Georg Silicone Surfactants Surfactants Sci Ser 1998 74 p 201-239

2 Scholz W Verkroniek 10 13 1995

How to Contact Us Dow Corning has sales offices manufacshyturing sites and science and technology laboratories around the globe Telephone numbers of locations near you are available on the World Wide Web at wwwdowcorningcom or by calling one of our primary locations listed below

Your Global Connection Americas +1 989 496 6000

Europe +49 0611 237 342

Asia +86 21 62882626

LIMITED WARRANTY INFORMATION ndash PLEASE READ CAREFULLY

The information contained herein is offered in good faith and is believed to be accurate However because conditions and methods of use of our products are beyond our control this information should not be used in substitution for customerrsquos tests to ensure that Dow Corningrsquos products are safe effective and fully satisfactory for the intended end use Suggestions of use shall not be taken as inducements to infringe any patent

Dow Corningrsquos sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted

DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY

DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES

Dow Corning is a registered trademark of Dow Corning Corporation

We help you invent the future is a trademark of Dow Corning Corporation

copy2005 Dow Corning Corporation All rights reserved

shy

Printed in USA AGP7561 Form No 26-1365-01

Oamp

Figure 11 Coefficient of friction data on OPV samples

ASE

4RISILOXANE

4RISILOXANE

ampORMULATION WITHOVEL

3TATICOamp +INETICOamp

WITHOVEL

2ESIN

WITHOVEL

OMPETITOR

3AMPLE

modified to improve substrate wetting In particular the trisiloxane structure gives the best equilibrium surface tension reduction and excellent wetting to plastic surfaces and other low-energy substrates This material has the greatest capacity for lowering the liquidsolid interfacial tension The higher-molecularweight siloxane surfactants with rake and linear structures give moderate wetting However materials of these types can be used to provide other benefits for instance mar resistance slip and de-aeration The incorporation of a resinous material with functionality can also yield a higher substantivity in a coating that is likely desired when a coating is being exposed to long-term weathering effects The addition of novel functionalities in place of the linear polyethers also can enhance the properties of the silicone polyether materials research is being done to fine-tune these functionalities to the most appropriate applications

shy

shy

Coefficient of friction data (CoF) indicates that the mar resistance improvements were not due to increasing the slip of the surface By industry standards the slip change that was documented is within error This indicates a possibility for applications such as floor varnish where mar resistance needs to be increased with no effect on the CoF or slipperiness of the surface The CoF data demonshystrates that the additive is not residing on the surface but possibly allowing the PE wax to better orientate at the surface and yield higher mar resistance

In looking at the surface tension data of the materials used in this study there is actually very little difference that would

indicate this is the reason why the material performs this way

Work continues to optimize the strucshytures and find application in which they can be utilized

Conclusions Silicone-based surfactants offer many benefits in waterborne coatings By the addition of the correct silicone surfactant the coating surface tension can be

shy

Table VI Surface energy of standard and modified siloxanes

Surface Energy at 1 (Dynescm)

Trisiloxane 201

Trisiloxane with Novel 212

ABA 246

ABA with Novel 238

Resin not soluble

Resin with Novel 264

References 1 Schlachter I and Feldmann-Krane Georg Silicone Surfactants Surfactants Sci Ser 1998 74 p 201-239

2 Scholz W Verkroniek 10 13 1995

How to Contact Us Dow Corning has sales offices manufacshyturing sites and science and technology laboratories around the globe Telephone numbers of locations near you are available on the World Wide Web at wwwdowcorningcom or by calling one of our primary locations listed below

Your Global Connection Americas +1 989 496 6000

Europe +49 0611 237 342

Asia +86 21 62882626

LIMITED WARRANTY INFORMATION ndash PLEASE READ CAREFULLY

The information contained herein is offered in good faith and is believed to be accurate However because conditions and methods of use of our products are beyond our control this information should not be used in substitution for customerrsquos tests to ensure that Dow Corningrsquos products are safe effective and fully satisfactory for the intended end use Suggestions of use shall not be taken as inducements to infringe any patent

Dow Corningrsquos sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted

DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY

DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES

Dow Corning is a registered trademark of Dow Corning Corporation

We help you invent the future is a trademark of Dow Corning Corporation

copy2005 Dow Corning Corporation All rights reserved

shy

Printed in USA AGP7561 Form No 26-1365-01

References 1 Schlachter I and Feldmann-Krane Georg Silicone Surfactants Surfactants Sci Ser 1998 74 p 201-239

2 Scholz W Verkroniek 10 13 1995

How to Contact Us Dow Corning has sales offices manufacshyturing sites and science and technology laboratories around the globe Telephone numbers of locations near you are available on the World Wide Web at wwwdowcorningcom or by calling one of our primary locations listed below

Your Global Connection Americas +1 989 496 6000

Europe +49 0611 237 342

Asia +86 21 62882626

LIMITED WARRANTY INFORMATION ndash PLEASE READ CAREFULLY

The information contained herein is offered in good faith and is believed to be accurate However because conditions and methods of use of our products are beyond our control this information should not be used in substitution for customerrsquos tests to ensure that Dow Corningrsquos products are safe effective and fully satisfactory for the intended end use Suggestions of use shall not be taken as inducements to infringe any patent

Dow Corningrsquos sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted

DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY

DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES

Dow Corning is a registered trademark of Dow Corning Corporation

We help you invent the future is a trademark of Dow Corning Corporation

copy2005 Dow Corning Corporation All rights reserved

shy

Printed in USA AGP7561 Form No 26-1365-01

How to Contact Us Dow Corning has sales offices manufacshyturing sites and science and technology laboratories around the globe Telephone numbers of locations near you are available on the World Wide Web at wwwdowcorningcom or by calling one of our primary locations listed below

Your Global Connection Americas +1 989 496 6000

Europe +49 0611 237 342

Asia +86 21 62882626

LIMITED WARRANTY INFORMATION ndash PLEASE READ CAREFULLY

The information contained herein is offered in good faith and is believed to be accurate However because conditions and methods of use of our products are beyond our control this information should not be used in substitution for customerrsquos tests to ensure that Dow Corningrsquos products are safe effective and fully satisfactory for the intended end use Suggestions of use shall not be taken as inducements to infringe any patent

Dow Corningrsquos sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted

DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY

DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES

Dow Corning is a registered trademark of Dow Corning Corporation

We help you invent the future is a trademark of Dow Corning Corporation

copy2005 Dow Corning Corporation All rights reserved

shy

Printed in USA AGP7561 Form No 26-1365-01