Natural Rubber vs Natural Rubber Latex PSA's , do they differ ?

FEB 26FEB 26 thth20172017

NaturalNatural RubberRubber PSAPSAV/sV/sNatyralNatyral Rubber LatexRubber Latex basedbasedPSAPSADo they differ ?Do they differ ?

NaturalNatural RubberRubber PSAPSAV/sV/sNatyralNatyral Rubber LatexRubber Latex basedbasedPSAPSADo they differ ?Do they differ ?

The purpose of publishing this Article is tostudy the behavior and also to compare theperformance ofNatural Rubber based PSA’sV/sNatural Rubber Latex Based PSA ,Do they differ in performance ?

2/26/2017 2

The purpose of publishing this Article is tostudy the behavior and also to compare theperformance ofNatural Rubber based PSA’sV/sNatural Rubber Latex Based PSA ,Do they differ in performance ?

Let me address to a general question in any bodies mindLet me address to a general question in any bodies mind

Water Borne Adhesives And Coatings

Natural Rubber Latex based adhesives , can they offer the same ,amount of Adhesion, water resistance ,Heat Resistance, holdingpower , and service life ?can they overcome The Mechanical Stability Problems ?

Can they replace Natural Rubber Solvent Based PSA ?

The answer is YesYes2/26/2017 3

Let me address to a general question in any bodies mindLet me address to a general question in any bodies mind

Water Borne Adhesives And Coatings

Natural Rubber Latex based adhesives , can they offer the same ,amount of Adhesion, water resistance ,Heat Resistance, holdingpower , and service life ?can they overcome The Mechanical Stability Problems ?

Can they replace Natural Rubber Solvent Based PSA ?

The answer is YesYes

NowNowLet us see how the Rubber Based PSA’s are manufacturedLet us see how the Rubber Based PSA’s are manufactured

ChemicalFormula

ofNaturalRubber

We see that this is a very long chain molecule with a lot ofWe see that this is a very long chain molecule with a lot ofunsaturation or double bonds in it .unsaturation or double bonds in it .

Available in two forms

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Emulsion/ LatexEmulsion/ Latex Dry Rubber Base

Available in two forms

Difference Between Rubber and LatexDifference Between Rubber and Latex

Rubber and latex are both elastomers in which dimensions canbe changed largely when stressed, and which can be returned totheir original dimensions after the stress is removed. They fallinto the category of polymeric materials. Latex items and rubberitems can be distinguished by the method of production. Inaddition, latex and rubber can be differentiated from each other,because latex is the raw material for rubber. So, latex should beidentified first.

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Difference Between Rubber and LatexDifference Between Rubber and Latex

Rubber and latex are both elastomers in which dimensions canbe changed largely when stressed, and which can be returned totheir original dimensions after the stress is removed. They fallinto the category of polymeric materials. Latex items and rubberitems can be distinguished by the method of production. Inaddition, latex and rubber can be differentiated from each other,because latex is the raw material for rubber. So, latex should beidentified first.

LatexLatex

Latex is defined as a stable colloidal dispersion of a polymericsubstance in an aqueous medium. The most common latex is thesap, obtained from the Heveabrasiliensis tree. In latex, there aretwo systems, namely a dispersion medium and a dispersed phase.In latex, rubber particles are suspended in the aqueous medium.Rubber molecules are present as chains in the structure, andthere is free space in between chains.latex, is mixed with compounding agents (i.e. additives added toimprove the properties of latex).Generally, latex is used to make thin films

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LatexLatex

Latex is defined as a stable colloidal dispersion of a polymericsubstance in an aqueous medium. The most common latex is thesap, obtained from the Heveabrasiliensis tree. In latex, there aretwo systems, namely a dispersion medium and a dispersed phase.In latex, rubber particles are suspended in the aqueous medium.Rubber molecules are present as chains in the structure, andthere is free space in between chains.latex, is mixed with compounding agents (i.e. additives added toimprove the properties of latex).Generally, latex is used to make thin films

RubberRubberRubber is obtained from latex, which is tapped from trees. Themost common tree that is used to produce rubber isHeveabrasiliensis.The molecular structure of natural rubber is cis-1, 4-polyisoprene.Tapped latex is first diluted and then it is coagulated using anacid. After that, this coagulated latex is compressed in rollers, toremove water. The products are raw rubber sheets. These sheetsare taken to produce rubber items. Rubber sheets are mixed withcompounding agents, to impart the desired properties of the finalproduct.Both latex and rubber are water proof.

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RubberRubberRubber is obtained from latex, which is tapped from trees. Themost common tree that is used to produce rubber isHeveabrasiliensis.The molecular structure of natural rubber is cis-1, 4-polyisoprene.Tapped latex is first diluted and then it is coagulated using anacid. After that, this coagulated latex is compressed in rollers, toremove water. The products are raw rubber sheets. These sheetsare taken to produce rubber items. Rubber sheets are mixed withcompounding agents, to impart the desired properties of the finalproduct.Both latex and rubber are water proof.

At this moment let us study how Dry RubberBase PSA’s are Manufactured

Let’s have a look at the Rubber molecule yet again

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We see that this is a veryWe see that this is a verylong chain molecule withlong chain molecule witha lot of unsaturation ora lot of unsaturation ordouble bonds in it .double bonds in it .Hence it needs to beHence it needs to beprocessed to break theprocessed to break thelong chainlong chain

Dry Rubber Adhesive ManufacturingDry Rubber Adhesive ManufacturingProcess Flow ChartProcess Flow Chart

This is DryThis is DryNatural RubberNatural Rubber

Masticated onMasticated onTwo Roll MillTwo Roll MillFor about 30For about 30--

40 minutes40 minutes

NaturalNaturalRubber LatexRubber Latex

filteredfilteredpurified andpurified andcoagulatedcoagulated

Water andWater andrubberrubber

separatedseparated

Rubber sheetsRubber sheetsare then driedare then dried

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Masticated onMasticated onTwo Roll MillTwo Roll MillFor about 30For about 30--

40 minutes40 minutes

At this stageAt this stageResins+ A/O +Resins+ A/O +

PlasticizerPlasticizerAdded toAdded toRubberRubber

For about 40For about 40minutesminutes

The mixture isThe mixture ischarged to a sigmacharged to a sigmamixer and solventmixer and solventToluene is addedToluene is addedgradually withgradually with

continuous mixingcontinuous mixingFor about 3For about 3--4 hours4 hours

ReadyReadyAdhesive isAdhesive is

stored instored inbarrelsbarrelsBeforeBefore

CoatingCoating

Rubber MasticationRubber MasticationMastication, the process by which the viscosity of natural rubber is reduced to asuitable level, is an important step in the mixing process. Rubber polymers suchas Natural Rubber (NR) require mastication to reduce their viscosity/elasticityand to even out variations between different polymer lots. This process can besimulated by a torque rheometer.Compounds with curing agents are tested for minimum viscosity, the onset ofscorching and for the rate of cure.These tests allow the assessment of the initial flow properties of the sample: thetorque peak caused by the high resistance of polymer being sheared while stillcold. Then one can evaluate the process of mastication.The figure below combines the two mastication test runs for an easycomparison:Mastication of a natural rubber (“NR“) just under the influence of shear andtemperature;Mastication as above but with the additional influence of a chemical additivecalled “Renacit 7“ added to the polymer at a level of 0.5 %. This accelerates thebreakdown of the molecular structure and greatly reduces the mixing energy.

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Rubber MasticationRubber MasticationMastication, the process by which the viscosity of natural rubber is reduced to asuitable level, is an important step in the mixing process. Rubber polymers suchas Natural Rubber (NR) require mastication to reduce their viscosity/elasticityand to even out variations between different polymer lots. This process can besimulated by a torque rheometer.Compounds with curing agents are tested for minimum viscosity, the onset ofscorching and for the rate of cure.These tests allow the assessment of the initial flow properties of the sample: thetorque peak caused by the high resistance of polymer being sheared while stillcold. Then one can evaluate the process of mastication.The figure below combines the two mastication test runs for an easycomparison:Mastication of a natural rubber (“NR“) just under the influence of shear andtemperature;Mastication as above but with the additional influence of a chemical additivecalled “Renacit 7“ added to the polymer at a level of 0.5 %. This accelerates thebreakdown of the molecular structure and greatly reduces the mixing energy.

Mastication and softening are usually carried out in batches. The operation isdone either in large enclosed mixing machines or on rubber mills. Thepreeminent example of an enclosed machine is the Banbury (registeredtrademark) mixer, consisting of heavy steel counter rotating paddles in anhourglass-shaped chamber, holding up to one-half ton of rubber. Rubber millshave two large horizontally opposed, closely spaced steel cylinders, up to 3metres (10 feet) long, that are rotated slowly in opposite directions and atsomewhat different speeds. Rubber is sheared and softened in the gapbetween the paddles and wall of the Banbury mixer and in the gap betweenthe two cylinders in the roll mill.

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Mastication and softening are usually carried out in batches. The operation isdone either in large enclosed mixing machines or on rubber mills. Thepreeminent example of an enclosed machine is the Banbury (registeredtrademark) mixer, consisting of heavy steel counter rotating paddles in anhourglass-shaped chamber, holding up to one-half ton of rubber. Rubber millshave two large horizontally opposed, closely spaced steel cylinders, up to 3metres (10 feet) long, that are rotated slowly in opposite directions and atsomewhat different speeds. Rubber is sheared and softened in the gapbetween the paddles and wall of the Banbury mixer and in the gap betweenthe two cylinders in the roll mill.

Mastication is an important step in the manufacture of rubber compounds. Itdecreases the viscosity of rubber, promotes good dispersion of fillers andchemicals, and increases compound plasticity. In this paper the authorssummarize the present knowledge about mastication of rubber and peptizingagents and present the recent work carried out in their laboratories on thesetopics. It is demonstrated that peptizing agents act in the mechanochemical andthermoxidative breakdown of elastomers as radical acceptors at lowtemperatures and as oxidation catalysts at high temperatures.

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Mastication is an important step in the manufacture of rubber compounds. Itdecreases the viscosity of rubber, promotes good dispersion of fillers andchemicals, and increases compound plasticity. In this paper the authorssummarize the present knowledge about mastication of rubber and peptizingagents and present the recent work carried out in their laboratories on thesetopics. It is demonstrated that peptizing agents act in the mechanochemical andthermoxidative breakdown of elastomers as radical acceptors at lowtemperatures and as oxidation catalysts at high temperatures.

Rubber Mixing MillThe basic design and construction of the mills has been subjected to continuousimprovements which have permitted them to keep pace with the day to day needsof the industry.

Available in sizes varying from 6"x16" to 26"x84" for compounding, warming,sheeting of various grades and types of rubber and other material.In the category of Mill also available in different sizes are Refiners, Crackers,Grinders, Rubber Breakers Mills and Asbestos Shelters.

Salient features include chilled cast iron rolls, frames, caps, journal boxes in highgrade casting, gear of cast iron or casting and MS steel fabricated as per dulyrequirements special alloy leaded bronze bushing suitable to take heavyseparating forces and to give longer wear life, gravity/forced or flood lubricatingsystems rolls suitable for steam heating/water cooling, positive pull back fail safesystem for emergency stop. Special accessories include strip cutters, stockdividing guides, stock blanders etc

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Rubber Mixing MillThe basic design and construction of the mills has been subjected to continuousimprovements which have permitted them to keep pace with the day to day needsof the industry.

Available in sizes varying from 6"x16" to 26"x84" for compounding, warming,sheeting of various grades and types of rubber and other material.In the category of Mill also available in different sizes are Refiners, Crackers,Grinders, Rubber Breakers Mills and Asbestos Shelters.

Salient features include chilled cast iron rolls, frames, caps, journal boxes in highgrade casting, gear of cast iron or casting and MS steel fabricated as per dulyrequirements special alloy leaded bronze bushing suitable to take heavyseparating forces and to give longer wear life, gravity/forced or flood lubricatingsystems rolls suitable for steam heating/water cooling, positive pull back fail safesystem for emergency stop. Special accessories include strip cutters, stockdividing guides, stock blanders etc

Specification of Rubber Mixing MillSize of Roll Capacity Kgs. R.P.M.of Motor Friction Ratio Electric6” x 13”8” x 18”10” x 24”12” x 30”14” x 36”16” x 42”18” x 48”22” x 60”24” x 78”26” x 84”

3 / 67 / 1015 / 2020 / 3030 / 4550 / 6075 / 9090 / 110130 / 150160 / 180

29232121191715121210

1 : 1 . 151 : 1 . 151 : 1 . 181 : 1 . 181 : 1 . 181 : 1 . 181 : 1 . 181 : 1 . 181 : 1 . 181 : 1 . 18

7.5102030406075120175225

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Specification of Rubber Mixing MillSize of Roll Capacity Kgs. R.P.M.of Motor Friction Ratio Electric6” x 13”8” x 18”10” x 24”12” x 30”14” x 36”16” x 42”18” x 48”22” x 60”24” x 78”26” x 84”

3 / 67 / 1015 / 2020 / 3030 / 4550 / 6075 / 9090 / 110130 / 150160 / 180

29232121191715121210

1 : 1 . 151 : 1 . 151 : 1 . 181 : 1 . 181 : 1 . 181 : 1 . 181 : 1 . 181 : 1 . 181 : 1 . 181 : 1 . 18

7.5102030406075120175225

Rubber Dispersion KneadersUnderstanding the needs of plastics & rubber processingindustry and developing fully indigenous solution to cater tothese needs has always been the prime target. When the needwas felt for a mixer capable of : hard mixing from processcompounding view point, We developed Dispersion Kneader.Dispersion Mixer can be employed in a wide range ofmaterial mixing, ranging from low viscosity adhesives tohigh viscosity rubber. Internal Mixer series to a highlydeveloped range of Dispersion Kneaders for rubber and otherpolymers with high productivity and consistently goodmixing with minimum electricity consumption.

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Rubber Dispersion KneadersUnderstanding the needs of plastics & rubber processingindustry and developing fully indigenous solution to cater tothese needs has always been the prime target. When the needwas felt for a mixer capable of : hard mixing from processcompounding view point, We developed Dispersion Kneader.Dispersion Mixer can be employed in a wide range ofmaterial mixing, ranging from low viscosity adhesives tohigh viscosity rubber. Internal Mixer series to a highlydeveloped range of Dispersion Kneaders for rubber and otherpolymers with high productivity and consistently goodmixing with minimum electricity consumption.

Model Main TotalWeight Working Rotor Tilt Tilt Tilt Air

MotorH.P. Comp.HP Cap.

AppCap.Ltrs. R.P.M. Method Angle Motor H.P.

5 ltrs.

15 ltrs.

25 ltrs.

35 ltrs.

55 ltrs.

75 ltrs.

110 ltrs.

125 ltrs.

7.5

25

40

60

75/100

100/125

125/150

150/175

8

30

45

75

125

225

170

265

5

15

25

35

55

110

75

125

33.28

33.28

33.28

33.28

33.28

33.28

33.28

33.28

Pneumatic

Screw

Screw

Screw

Screw

Screw

Screw

Screw

120

110

110

110

110

110

110

110

-

1.5

2

2

3

5

7.5

7.5

2

2

2

2

5

7.5

10

12.5

1 Ton

3 ,,

5 ,,

6 ,,

7 ,,

8 ,,

8 ,,

13 ,,

2/26/2017 16

Model Main TotalWeight Working Rotor Tilt Tilt Tilt Air

MotorH.P. Comp.HP Cap.

AppCap.Ltrs. R.P.M. Method Angle Motor H.P.

5 ltrs.

15 ltrs.

25 ltrs.

35 ltrs.

55 ltrs.

75 ltrs.

110 ltrs.

125 ltrs.

7.5

25

40

60

75/100

100/125

125/150

150/175

8

30

45

75

125

225

170

265

5

15

25

35

55

110

75

125

33.28

33.28

33.28

33.28

33.28

33.28

33.28

33.28

Pneumatic

Screw

Screw

Screw

Screw

Screw

Screw

Screw

120

110

110

110

110

110

110

110

-

1.5

2

2

3

5

7.5

7.5

2

2

2

2

5

7.5

10

12.5

1 Ton

3 ,,

5 ,,

6 ,,

7 ,,

8 ,,

8 ,,

13 ,,

Sigma mixer (kneader) to produce uniform mixing and kneadingheavier viscosity materials. The Sigma mixture is suitable formany applications like mixing, etc.

The sigma mixer have application to produce highly viscousmaterials like different kinds of adhesives, etc.

2/26/2017 17

The Electrical Load required for Solvent dissolvedThe Electrical Load required for Solvent dissolvedNatural Rubber AdhesiveNatural Rubber Adhesive

Mastication onRubber MillConnected Load :15 HP = 11.25KwMastication Time: 30 minutesRubber Quantity :12 kgs

Mixing of Resins /A/O , other raw mat.on Rubber MillConnected Load : 15HP = 11.25 KwMixing Time : 90minutesTotal Quantity : 24kgs

Mixing of Dry Rubbercompound withSolvent TolueneConnected Load : 35HP = 26.25 KwMixing Time : 240minutesTotal SolutionQuantity : 48 kgs

18

Mastication onRubber MillConnected Load :15 HP = 11.25KwMastication Time: 30 minutesRubber Quantity :12 kgs

Mixing of Resins /A/O , other raw mat.on Rubber MillConnected Load : 15HP = 11.25 KwMixing Time : 90minutesTotal Quantity : 24kgs

Mixing of Dry Rubbercompound withSolvent TolueneConnected Load : 35HP = 26.25 KwMixing Time : 240minutesTotal SolutionQuantity : 48 kgs

26-02-2017

This means that

The Electrical Energy consumption ofRubber Mill : 11.25 kw x 120 minutes = 11.25 kw X 2 hrs =22.5 UnitsSigma Mixer : 26.25 X 240 minutes = 26.25X 4 hrs = 105unitsTotal Electrical Units = 127.5 , for 24 kgs of dry adhesive

= 5.31 units / kg = INR 37.18 / Kg

19

This means that

The Electrical Energy consumption ofRubber Mill : 11.25 kw x 120 minutes = 11.25 kw X 2 hrs =22.5 UnitsSigma Mixer : 26.25 X 240 minutes = 26.25X 4 hrs = 105unitsTotal Electrical Units = 127.5 , for 24 kgs of dry adhesive

= 5.31 units / kg = INR 37.18 / Kg

26-02-2017

This means

The Man Power cost ofOn Rubber Mill : 1+1 person x 120 minutes = 2 men X 2 hrs =2 X ( (10000/25 = 400 / day/person = 50/hr/person x2= INR100 / 24 kg of adhesive = INR 4.00 / kg )

On Sigma Mixer : 1 person X 240 minutes = 1 manX 4 hrs =1 X ( (10000/25 = 400 / day/person = 50/hr/person x1X 4 hrs =INR 200 / 24 kg of adhesive = INR 8.00 / kg )Total Manpower cost = 300 , for 24 kgs of dry adhesive

= INR 12.50 / Kg

20

This means

The Man Power cost ofOn Rubber Mill : 1+1 person x 120 minutes = 2 men X 2 hrs =2 X ( (10000/25 = 400 / day/person = 50/hr/person x2= INR100 / 24 kg of adhesive = INR 4.00 / kg )

On Sigma Mixer : 1 person X 240 minutes = 1 manX 4 hrs =1 X ( (10000/25 = 400 / day/person = 50/hr/person x1X 4 hrs =INR 200 / 24 kg of adhesive = INR 8.00 / kg )Total Manpower cost = 300 , for 24 kgs of dry adhesive

= INR 12.50 / Kg

26-02-2017

At this moment let us study how LatexRubber Base PSA’s are Manufactured

Let’s have a look at the Rubber molecule yet again

2/26/2017 21

We see that this is a very longWe see that this is a very longchain molecule with a lot ofchain molecule with a lot ofunsaturation or double bonds in itunsaturation or double bonds in it..But it is available in a emulsionBut it is available in a emulsionformform

Latex Rubber Adhesive ManufacturingLatex Rubber Adhesive ManufacturingProcess Flow ChartProcess Flow Chart

NaturalNaturalRubber LatexRubber Latex

Purified andPurified andprocessed byprocessed byCentrifugalCentrifugal

methodmethod

At this stageAt this stageResinsResins

emulsions +emulsions +and otherand other

Raw MaterialsRaw Materialsin emulsionin emulsion

formformAnd Mixed inAnd Mixed in

a simplea simpleagitator for 30agitator for 30

minutesminutes

2/26/2017 22

At this stageAt this stageResinsResins

emulsions +emulsions +and otherand other

Raw MaterialsRaw Materialsin emulsionin emulsion

formformAnd Mixed inAnd Mixed in

a simplea simpleagitator for 30agitator for 30

minutesminutes

ReadyReadyAdhesive isAdhesive is

stored instored inbarrelsbarrelsBeforeBefore

CoatingCoating

Structure of Natural Rubber particle

IntroductionIntroductionBased on the reactions of NR latex towards various chemical treatments "andphysical techniques the following structure has been proposed for the structureof natural rubber particle.

2/26/2017 23

The principal phospholipids of the NR latex are of the lecithin typeand they are strongly adsorbed on to the surfaces of the rubberparticles. They are thought to be intermediaries by which theproteins are anchored on to the rubber particles. The adhesionbetween the proteins and the adsorbed lecithin has been accountedfor the fact that at the pH of fresh latex the lipid layer carries aslight overall positive charge, whereas the proteins, being on thealkaline side of their iso electric point are negatively charged, sothat ionic interaction between the two layers is possible(Blackley, 1966).

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The principal phospholipids of the NR latex are of the lecithin typeand they are strongly adsorbed on to the surfaces of the rubberparticles. They are thought to be intermediaries by which theproteins are anchored on to the rubber particles. The adhesionbetween the proteins and the adsorbed lecithin has been accountedfor the fact that at the pH of fresh latex the lipid layer carries aslight overall positive charge, whereas the proteins, being on thealkaline side of their iso electric point are negatively charged, sothat ionic interaction between the two layers is possible(Blackley, 1966).

Chemical composition of fresh NR LatexBeing a natural product the composition of NR latex would varydepending on various factors such as clone, season, soil conditions,fertilizer application techniques and tapping frequencies etc. Assuch it is not possible to give an exact composition for the NRlatex. However a typical composition can always be suggested asgiven below; % by weight of latexDry rubber content 30-35Proteinous substances 1-1.5Lipids 1-2.5Sugars 1Inorganic ions 1Water 60-65

2/26/2017 25

Chemical composition of fresh NR LatexBeing a natural product the composition of NR latex would varydepending on various factors such as clone, season, soil conditions,fertilizer application techniques and tapping frequencies etc. Assuch it is not possible to give an exact composition for the NRlatex. However a typical composition can always be suggested asgiven below; % by weight of latexDry rubber content 30-35Proteinous substances 1-1.5Lipids 1-2.5Sugars 1Inorganic ions 1Water 60-65

All these non-rubber substances are distributed between threeprincipal phases. The average percentage of each of these threephases is given below:% by weight of latexRubber phase 35Aqueous phase 55Lutoid phase 10Lutoid phase can only be seen in fresh NR latex since the lutoidparticles which constitute the lutoid phase are very sensitive tovarious factors such as dilution, ammoniation and heat. Lutoidparticles are slightly larger than the rubber particles and areirregular in shape. Chemically, they appear to be mainly water. Inaddition to that they contain various other substances such ascarotenoids, acids, mineral salts, proteins and even rubber particles.The boundary of a lutoid particle is a semipermeable membraneand hence they are osmotically sensitive.2/26/2017 26

All these non-rubber substances are distributed between threeprincipal phases. The average percentage of each of these threephases is given below:% by weight of latexRubber phase 35Aqueous phase 55Lutoid phase 10Lutoid phase can only be seen in fresh NR latex since the lutoidparticles which constitute the lutoid phase are very sensitive tovarious factors such as dilution, ammoniation and heat. Lutoidparticles are slightly larger than the rubber particles and areirregular in shape. Chemically, they appear to be mainly water. Inaddition to that they contain various other substances such ascarotenoids, acids, mineral salts, proteins and even rubber particles.The boundary of a lutoid particle is a semipermeable membraneand hence they are osmotically sensitive.

Preservation of NR latexPreservation of NR latex is normally achieved by adding up to1.0%(w/w on the aqueous phase) of ammonia. Ammonia being agood biocide has several advantages; it• controls the proliferation of bacteria• neutralises the free acids formed in the latex• helps in the precipitation of heavy metals such as Mg• hydrolyses the interfacial proteins and phospholipids, therebymaking the latex more stable.

The hydrolysis of phospholipids has been found to occur morerapidly than that of the proteins, and as a consequence, by thetime the latex reaches the latex reception point of the industrialuser, the phospholipids of ammoniated and concentrated latexhave been converted to fatty-acid soaps (Blackley, 1966).2/26/2017 27

Preservation of NR latexPreservation of NR latex is normally achieved by adding up to1.0%(w/w on the aqueous phase) of ammonia. Ammonia being agood biocide has several advantages; it• controls the proliferation of bacteria• neutralises the free acids formed in the latex• helps in the precipitation of heavy metals such as Mg• hydrolyses the interfacial proteins and phospholipids, therebymaking the latex more stable.

The hydrolysis of phospholipids has been found to occur morerapidly than that of the proteins, and as a consequence, by thetime the latex reaches the latex reception point of the industrialuser, the phospholipids of ammoniated and concentrated latexhave been converted to fatty-acid soaps (Blackley, 1966).

Among other products, much of the proteins remainunhydrolysed. The interfacial film at this stage consists of asoap/protein mixture, and the composition of this interfacialfilm changes as the latex ages.

Colloidal instability of latices:The simplest type of colloid system is a dispersion of one phasein a second phase, in which the disperse phase is in a state ofdispersion such that at least one dimension is in the rangebetween lnm and lOOOnm. Colloids are generally classifiedlyophobic (there is no tendency for the disperse phase to mix withthe dispersion 11 medium) or lyophillic (there is a strongtendency for the disperse phase to mix with the dispersionmedium). The most important property of a lyophobic colloid isits colloid stability. Rubber latices are examples of lyophobiccolloids.2/26/2017 28

Among other products, much of the proteins remainunhydrolysed. The interfacial film at this stage consists of asoap/protein mixture, and the composition of this interfacialfilm changes as the latex ages.

Colloidal instability of latices:The simplest type of colloid system is a dispersion of one phasein a second phase, in which the disperse phase is in a state ofdispersion such that at least one dimension is in the rangebetween lnm and lOOOnm. Colloids are generally classifiedlyophobic (there is no tendency for the disperse phase to mix withthe dispersion 11 medium) or lyophillic (there is a strongtendency for the disperse phase to mix with the dispersionmedium). The most important property of a lyophobic colloid isits colloid stability. Rubber latices are examples of lyophobiccolloids.

The factors which determine the colloid stability of a rubber latexare essentially those which determine the colloid stability of anylyophobic colloid.In latices, as in colloidal dispersions in general, frequentencounters between particles occur due to Brownianmovement,to gravity (creaming and sedimentation), and to convection.Whether such encounters results in permanent contact, or whetherthe particles rebound and remain free, is determined by the forceswhich are operative between the particles. If the attractive forces,which are assumed to be of London Van der Waals type, arelarger than the repulsive forces, interaction between two or moreparticles may first cohere to give a loose aggregate and thensubsequently to give a little larger particle.

2/26/2017 29

The factors which determine the colloid stability of a rubber latexare essentially those which determine the colloid stability of anylyophobic colloid.In latices, as in colloidal dispersions in general, frequentencounters between particles occur due to Brownianmovement,to gravity (creaming and sedimentation), and to convection.Whether such encounters results in permanent contact, or whetherthe particles rebound and remain free, is determined by the forceswhich are operative between the particles. If the attractive forces,which are assumed to be of London Van der Waals type, arelarger than the repulsive forces, interaction between two or moreparticles may first cohere to give a loose aggregate and thensubsequently to give a little larger particle.

Nature of stability of lyophobic colloids A lyophobic colloid issaid to be stable if it persists as a colloidal dispersion overa period of time. However, all lyophobic colloids arethermodynamically unstable because of their high interfacial freeenergy which is a result of the high ratio of interfacial area tovolume of the disperse phase. Aggregation or the flocculation ofthe dispersed particles, which brings about a reduction of theinterfacial area and free energy is therefore thermodynamicallyfavorable. As mentioned earlier the stability/flocculation behaviorof a lyophobic colloid is governed by the various attractive andrepulsive forces between the particles. Amongst the possiblebasic interparticle forces involved in colloidal systems of alltypes, the following can be considered as the important forceswhich are operative between the rubber particles in NR latex;

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Nature of stability of lyophobic colloids A lyophobic colloid issaid to be stable if it persists as a colloidal dispersion overa period of time. However, all lyophobic colloids arethermodynamically unstable because of their high interfacial freeenergy which is a result of the high ratio of interfacial area tovolume of the disperse phase. Aggregation or the flocculation ofthe dispersed particles, which brings about a reduction of theinterfacial area and free energy is therefore thermodynamicallyfavorable. As mentioned earlier the stability/flocculation behaviorof a lyophobic colloid is governed by the various attractive andrepulsive forces between the particles. Amongst the possiblebasic interparticle forces involved in colloidal systems of alltypes, the following can be considered as the important forceswhich are operative between the rubber particles in NR latex;

Centrifuged Latex of 60% of Dry Rubber Content(CENEX)Processing of natural rubber latex into high quality latexconcentrate of 60% dry rubber content is done throughcentrifugation. Centrifuging involves the separation ofpreserved field latex into two fractions, one containing theconcentrated latex of more than 60% dry rubber and the othercontaining 4-6% dry rubber. Centrifuged latex is todayavailable commercially in two different verities with highammonia (min.0.7% of ammonia) and low ammonia (max.0.3% of ammonia). The former is preserved solely withammonia and later contains one or more preservatives besidesammonia.

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Centrifuged Latex of 60% of Dry Rubber Content(CENEX)Processing of natural rubber latex into high quality latexconcentrate of 60% dry rubber content is done throughcentrifugation. Centrifuging involves the separation ofpreserved field latex into two fractions, one containing theconcentrated latex of more than 60% dry rubber and the othercontaining 4-6% dry rubber. Centrifuged latex is todayavailable commercially in two different verities with highammonia (min.0.7% of ammonia) and low ammonia (max.0.3% of ammonia). The former is preserved solely withammonia and later contains one or more preservatives besidesammonia.

LA latex has several advantages which include better quality,lower cost of production by way of savings in preservatives,acid and low cost of effluent treatment.

Grades and applicationsHigh Ammonia (HA) -Foam products, dipped goods, adhesives,elastic thread, household and industrial gloves, balloons, rubberbands and finger caps.

Low Ammonia (LATZ) - Preferred for all applications when deammonia is necessary for product manufacture. Requirementfor centrifuged natural rubber latex is given in the table.

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LA latex has several advantages which include better quality,lower cost of production by way of savings in preservatives,acid and low cost of effluent treatment.

Grades and applicationsHigh Ammonia (HA) -Foam products, dipped goods, adhesives,elastic thread, household and industrial gloves, balloons, rubberbands and finger caps.

Low Ammonia (LATZ) - Preferred for all applications when deammonia is necessary for product manufacture. Requirementfor centrifuged natural rubber latex is given in the table.

HenceWe can see thatThere is practically No differenceNo difference in the DryAdhesive FilmObtainedBy coated Natural Rubber Solvent dissolved PSAOrNatural Rubber Latex based PSA

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HenceWe can see thatThere is practically No differenceNo difference in the DryAdhesive FilmObtainedBy coated Natural Rubber Solvent dissolved PSAOrNatural Rubber Latex based PSA

TheThe ease in handling latex based ( water borne )ease in handling latex based ( water borne )

Easy to cleaningEasy to cleaning

Require Much lesser time for cleaningRequire Much lesser time for cleaning

Fast change over'sFast change over's

The ease in handling gravureThe ease in handling gravureOrOrKiss coating with Myer barKiss coating with Myer bar

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TheThe ease in handling latex based ( water borne )ease in handling latex based ( water borne )

Easy to cleaningEasy to cleaning

Require Much lesser time for cleaningRequire Much lesser time for cleaning

Fast change over'sFast change over's

The key advantages to using waterborneThe key advantages to using waterborne adhesives

they posses good resistance to heat and abrasionProvide excellent adhesionLow toxicity and flammability due to low VOC levelsHelp reducing air emissionthese coatings cost less than solvent-borne coatingsless coating is required to cover the same surface areaThe pot life of waterborne products is relatively longand unused coatings can be preserved in a sealed container forfuture useThe coating machine components can be cleaned easily withwater or water-based solutions and do not require any solvent.

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The key advantages to using waterborneThe key advantages to using waterborne adhesives

they posses good resistance to heat and abrasionProvide excellent adhesionLow toxicity and flammability due to low VOC levelsHelp reducing air emissionthese coatings cost less than solvent-borne coatingsless coating is required to cover the same surface areaThe pot life of waterborne products is relatively longand unused coatings can be preserved in a sealed container forfuture useThe coating machine components can be cleaned easily withwater or water-based solutions and do not require any solvent.

How the Coating Process of Solvent Borne and Water Borne isHow the Coating Process of Solvent Borne and Water Borne isdifferentdifferent

Let us first look at the ways , of coating solventcoating solvent borne

The coating processcoating process largely depends upon the

The ViscosityThe solids contentThe rheologyAndThe loading of ingredients other than the main polymerThe particle sizeThe solvent evaporation temp

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How the Coating Process of Solvent Borne and Water Borne isHow the Coating Process of Solvent Borne and Water Borne isdifferentdifferent

Let us first look at the ways , of coating solventcoating solvent borne

The coating processcoating process largely depends upon the

The ViscosityThe solids contentThe rheologyAndThe loading of ingredients other than the main polymerThe particle sizeThe solvent evaporation temp

The coating process alsocoating process also depends upon the

The coat weight , either wet or dry the type of substrate , like paper, film, fabric, or foil etc. the type of solvent associated with the adhesive

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However the most popular methods employed forcoatingcoating waterwater borne are

Gravure CoatingGravure Coating

A schematic design is displayed here

Its most suitable for lower coatingweights ( 0.3 to 4.0 gsm ) , such asPrimer coating , release coating ,printing etc.Coating weight across the width andlength is precisely controlled.The coat weight depends on theCoating solids content , viscosity ,solvent evaporation rate , and thegravure cell structure or size.

Drying TunnelDrying Tunnel

Coated webCoated web

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A schematic design is displayed here

Its most suitable for lower coatingweights ( 0.3 to 4.0 gsm ) , such asPrimer coating , release coating ,printing etc.Coating weight across the width andlength is precisely controlled.The coat weight depends on theCoating solids content , viscosity ,solvent evaporation rate , and thegravure cell structure or size.

Adhesive TrayAdhesive Tray

Doctor’s bladeDoctor’s blade

Web to beWeb to becoatedcoated

Gravure RollerGravure Roller


The AdvantagesThe Advantages

1. Its most suitable for lower coatingweights ( 0.3 to 4.0 gsm )

2. Coating weight across the widthand length is precisely controlled.

3. Faster speeds4. Relatively quick changeovers5. Easy to operate

Drying TunnelDrying Tunnel

Coated webCoated web

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1. Its most suitable for lower coatingweights ( 0.3 to 4.0 gsm )

2. Coating weight across the widthand length is precisely controlled.

3. Faster speeds4. Relatively quick changeovers5. Easy to operate Adhesive TrayAdhesive Tray

Doctor’s bladeDoctor’s blade

Web to beWeb to becoatedcoated

Gravure RollerGravure Roller


The disadvantagesThe disadvantages1. Max coat wt possible is 10-12 gsm2. The liquid coating level in the tray has to be monitored and maintained3. In case of very fast drying solvents , chances of premature drying of the

coating in the gravure cells is possible , that could be a cause of concern ,4. Coat wt variation / no coating etc can cause rejection due to above.5. One has to take at most care while handing , low coat wt , coatings ,

especially like silicone coating . A silicone coating batch may contain just 1to 3 % solids , and the rest all is solvent.

6. The film of paper generates a lot of static electricity , while passing overrubber rollers / Idler rollers. The static eliminators have to play a verycrucial role here .

7. A smallest static discharge here can lead to a major fire , because , thehighly inflammable solvents are just across , in the coating tray.

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The disadvantagesThe disadvantages1. Max coat wt possible is 10-12 gsm2. The liquid coating level in the tray has to be monitored and maintained3. In case of very fast drying solvents , chances of premature drying of the

coating in the gravure cells is possible , that could be a cause of concern ,4. Coat wt variation / no coating etc can cause rejection due to above.5. One has to take at most care while handing , low coat wt , coatings ,

especially like silicone coating . A silicone coating batch may contain just 1to 3 % solids , and the rest all is solvent.

6. The film of paper generates a lot of static electricity , while passing overrubber rollers / Idler rollers. The static eliminators have to play a verycrucial role here .

7. A smallest static discharge here can lead to a major fire , because , thehighly inflammable solvents are just across , in the coating tray.

However the most popular methods employed forcoating solventcoating solvent borne are

Comma CoatingComma CoatingThis method is most suitablehigher coating weights.

The coating weight across thewidth can be controlled with in 2grams variation

The coat weight depends on theThe gap set between theThe metering and the applicatorroller,Coating solids content , viscosity, solvent evaporation rate .

Applicator roll

Metering roll

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Comma CoatingComma CoatingThis method is most suitablehigher coating weights.


The coat weight depends on theThe gap set between theThe metering and the applicatorroller,Coating solids content , viscosity, solvent evaporation rate .

Comma CoatingComma Coating


1. This method is most suitablehigher coating weights.

2. The coating weight acrossthe width can be controlledwith in 2 grams variation

Applicator roll

Metering roll

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Comma CoatingComma Coating




Comma CoatingComma CoatingThe DisadvantagesThe Disadvantages

1. The coating nip has to be precisely controlled.2. Any foreign particle , dry adhesive can cause a problem

like snapping of web .this is because the web is passingbetween a very narrow gap created between applicator andmetering roll.

3. Dry adhesive particles towards the web edges can cause ,web snaps and high wastage.

4. Any leakage of adhesive from the chick plates at the edgescan cause uneven coating problems.

5. Higher change over timing6. Higher cost of cleaning , due to the consumption of

solvents

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Comma CoatingComma CoatingThe DisadvantagesThe Disadvantages

1. The coating nip has to be precisely controlled.2. Any foreign particle , dry adhesive can cause a problem

like snapping of web .this is because the web is passingbetween a very narrow gap created between applicator andmetering roll.

3. Dry adhesive particles towards the web edges can cause ,web snaps and high wastage.

4. Any leakage of adhesive from the chick plates at the edgescan cause uneven coating problems.

5. Higher change over timing6. Higher cost of cleaning , due to the consumption of

solvents

Reverse Roller coatingReverse Roller coatingThis method is also mostsuitable higher coating weights.


The coat weight depends on theThe gap set between theThe metering and the applicatorroller, Coating solids content ,viscosity , solvent evaporationrate .

Applicatorroll

Metering roll

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Reverse Roller coatingReverse Roller coatingThis method is also mostsuitable higher coating weights.


The coat weight depends on theThe gap set between theThe metering and the applicatorroller, Coating solids content ,viscosity , solvent evaporationrate .

Reverse Roller coatingReverse Roller coatingThe AdvantagesThe Advantages



3. Relatively quick changeoverscompared to comma coating

Applicatorroll

Metering roll

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Reverse Roller coatingReverse Roller coatingThe AdvantagesThe Advantages



3. Relatively quick changeoverscompared to comma coating

Reverse Roller coatingReverse Roller coatingThe DisadvantagesThe Disadvantages

1. The coating nip has to be precisely controlled.2. Dry adhesive particles towards the web edges can cause ,

web snaps and high wastage.3. Any leakage of adhesive from the chick plates at the edges

can cause uneven coating problems.4. Higher change over timing5. Higher cost of cleaning , due to the consumption of solvents

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Reverse Roller coatingReverse Roller coatingThe DisadvantagesThe Disadvantages

1. The coating nip has to be precisely controlled.2. Dry adhesive particles towards the web edges can cause ,

web snaps and high wastage.3. Any leakage of adhesive from the chick plates at the edges

can cause uneven coating problems.4. Higher change over timing5. Higher cost of cleaning , due to the consumption of solvents


Floating Knife coating

This method isgenerally used for nonadhesive coatings

Backup rolls

Floating Knife

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This method isgenerally used for nonadhesive coatings

Backup rolls


Floating Knife coatingFloating Knife coating

The Advantages

1. This is the mosteasy method to coat

2. Generally used forFabric based web

3. Fast changeovers4. No snaps5. Low wastage

Backup rolls

Floating Knife

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Floating Knife coatingFloating Knife coating

The Advantages

1. This is the mosteasy method to coat

2. Generally used forFabric based web

3. Fast changeovers4. No snaps5. Low wastage

Backup rolls



Disadvantages

1. Suitable only forhigh coat weights

2. Suitable forstronger webs likefabrics

Backup rolls

Floating Knife

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Disadvantages

1. Suitable only forhigh coat weights

2. Suitable forstronger webs likefabrics

Backup rolls

Natural Rubber LatexEmulsion

Adhesive coated film afterAdhesive coated film afterdrying do not Contain anydrying do not Contain anySurfactantsSurfactantsOr hydrophilic ingredientsOr hydrophilic ingredients

Natural RubberSolvent DissolvedAdhesive


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Dry Natural Rubber SB AdhesiveAdhesiveFilmFilm ( coated on PET FilmPET Film )

Dry WB Acrylic Adhesive FilmAdhesive Film( coated on PET FilmPET Film )




On exposure to water or high Humidity



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On exposure to water or high Humidity

Dry WB Acrylic Adhesive FilmAdhesive Film( coated on PET FilmPET Film )Relatively no Swelling

Dry Natural Rubber SB AdhesiveAdhesiveFilmFilm ( coated on PET FilmPET Film )Relatively no Swelling





The Physical Properties like

TackTackPeel AdhesionPeel AdhesionShear strengthShear strength

The test Results for all the above properties remain thesame , and even the after ageing results also are similar

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The Physical Properties like

TackTackPeel AdhesionPeel AdhesionShear strengthShear strength

The test Results for all the above properties remain thesame , and even the after ageing results also are similar

ConclusionConclusion

This exercise was essential to understand , as to how the ,

Natural Rubber Latex based Adhesives filmsandthe Natural Rubber Solvent dissolved adhesivesare formed and do they Differ in performance ?

The Answer is

There is NO DifferenceThere is NO Difference

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ConclusionConclusion

This exercise was essential to understand , as to how the ,

Natural Rubber Latex based Adhesives filmsandthe Natural Rubber Solvent dissolved adhesivesare formed and do they Differ in performance ?

The Answer is

There is NO DifferenceThere is NO Difference

ThankThankYouYou

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00 91 75882882045426-02-2017

Technology

Natural Rubber vs Natural Rubber Latex PSA's , do they differ ?