Technical Paper

34 European Coatings JOURNAL 05 l 2015 www.european-coatings.com

EC Award winning paper

R. Brinkhuis, J. Schutyser, F. Thys, E. De Wolf, T. Buser, J. Kalis, N. Mangnus, F. Van Wijk

A new low VOC, isocyanate- and tin-free coating system is built on a novel blocked catalyst and kinetic control additive package used in conjunction with Michael Addition chemistry. Pot life and drying time can be effectively decoupled, combining fast cure with an extended pot life. Comparisons with standard 2K systems are presented.

Contact:Dr Fred van WijkNuplex Resinsfred.vanwijk@nuplex.comT +31 164 276 593

Taming the Michael Addition reactionUltra-fast drying, low VOC, isocyanate-free technology for 2K coatings

Driven by changes in HSE legislation, competition on paint application costs and coating performance, to-day’s paint technology continues to develop in the

direction of higher solids, lower curing temperatures and faster painting processes. Meeting these combined re-quirements is very challenging and encounters the limits of versatility of presently available cure chemistries. Mi-chael Addition chemistry [1] offers a perspective for mak-ing steps beyond those limits. Michael Addition (MA) has been explored before for coat-ing applications [2], although it has never established itself as a mainstream cure technology yet, most likely because it is too reactive. The key components of a MA system are electron deficient C=C double bonds (e.g. an acryloyl, the acceptor), acidic C-H bonds (as present in acetoacetate and malonate moieties, the donor), and a base catalyst yield-ing a nucleophilic carbanion that can add to the double bond. A carbon-carbon link is formed between the two moieties. The second proton of the donor species is avail-able for reaction with similar reactivity (Figure 1).Relevant features derived from the characteristics of MA chemistry include: » The need for a base strong enough to abstract a proton from the donor species. The pKa of an acetoacetate C-H is around 10.7, for a malonate it is even higher (>13). » The absence of acidic species that will deactivate the catalyst. » The very high reactivity of the carbanions formed, especially when using malonate species as the donor. In catalysed paint formulations it is easy to create condi-tions under which a MA reaction between malonate and acryloyl species can essentially be completed within minutes. In this instance, both malonate and acryloyl may coexist in the uncatalysed paint and pre-sent good shelf stability. » The nature of the carbon-carbon links formed; not lead-ing to weak spots in durability. » Michael addition technology opens a window to using non-polar, low equivalent weight crosslinking com-ponents that can lead to very low solvent demand formulations capable of creating high crosslink density polymer networks.

The options of MA chemistry were expanded by focusing on ways to control the inherent reactivity of a malonate-acryloyl system by using its high reactivity potential, whilst creating both a long potlife and a workable open time as described below. Combined with specially developed res-ins, the obtained benefits are so profound that it may be recognised as a new type of curing technology, finding use in many different markets and applications. Hereinaf-ter, this new chemistry is refered to as ‘Acure’.

Figure 1: The Michael Addition reaction between malonate and acryloyl

Figure 2: Blocked catalyst formation and activation; HA presents a proton donor

Figure 3: Conver-sion of acrylic dou-ble bonds (FT-IR, 809 cm-1) showing the effect of CO2 expulsion (Figure 2b); green line: without 1,2,4-tria-zole, blue line: 1 eq 1,2,4-triazole / mol cat (50 µeq/g)

a)

b)

35www.european-coatings.com 05 l 2015 European Coatings JOURNAL

Technical PaperEC Award winning paper

Controlling pot life and drying

Very high reactivity cannot easily be combined with a good pot life. However, a solution was found in the reversible blocking of a strong base catalyst with a di-alkylcarbonate as depicted in Figure 2a. Strong bases will form alkyl carbonate anions with a basicity low enough to not initiate the MA reaction. These carbonates are in-herently unstable, and through protonated species will form an equilibrium with free CO2 and alcohol (Figure 2b).After mixing in a container (with a relatively low surface/volume ratio), there is no fast CO2 release and long pot lives are observed (vide infra). Upon applying the paint however, large surface areas will be created facilitating easy escape of solvent and especially CO2. This shifts the equilibria, followed by rapid de-blocking of the basic species which triggers the full reactivity potential of the malonate acryloyl system. This de-blocking process will be accelerated when HA becomes more acidic, shifting equilibrium 2b to the right (Figure 3). The net result is the combination of a very long pot life with very fast drying. Workable pot lives of at least four hours are easily ob-tained, and if needed can be formulated to be counted in days. At the same time it can be observed that tack free times down to 10 minutes after application, and phase 4 (scratch free) drying recorder times not much longer. Fig-ure 4 shows the different pot life / drying speed balance for Acure versus isocyanate based systems.The effect of adding alcohols to Acure paints is shifting the equilibrium of Figure 2b to the left, extending the pot life without significantly affecting dry times. When following the acryloyl conversion upon application with FTIR (809 cm-1), it is observed that conversion can

Results at a glance

Two-component urethane topcoats are well established in coatings applications. There is a need, however, for systems with increased productivity coupled with environmental and health and safety friendliness. This paper outlines the launch of a new, low VOC, isocyanate and tin free, breakthrough tech-nology which meets these needs.

The system is built on a novel blocked catalyst and kinetic control additive package used in conjunction with Michael Addition chemistry. Prototype paint formulae highlight the low VOC capability (<250 g/l) of this very fast drying 2K system (10 to 50 minutes, ambient) and the unique decoupling of dry time and pot life (>5 hours), expected to trigger new paint and process solutions.

The chemistry of the system and comparative re-sults versus other topcoats are presented. The results show that the system has significant potential to displace existing two component topcoats in Marine and Protective and Industrial OEM market applica-tions, without compromise.

easily reach values above 80 % in the first 10 minutes. This indicates not only a rapid physical dry state of the film but also a very rapid crosslink density development with the associated beneficial early coating performance of both chemical and mechanical robustness. The poten-tial reactivity may also be used at temperatures below ambient: dry times of less than an hour have been ob-served at application temperatures as low as 15  ºC. In terms of its practical use, this system may be used as a 2K coating with both reactive components (malonate polymer and acryloyl oligomer) premixed and the cata-lyst being added as an activator.

Complications arising from very fast cure

Paint systems with drying times this short may bring complications not normally recognized for ‘slow’ systems. Firstly, such drying times become competitive with the ability of the solvents to escape from the film. Under am-bient curing conditions the glass transition temperature

Figure 4: Gener-alised picture of potlife – drying balance. Blue area: the ‘world’ of OH and NH isocy-anate curing; red area: the field of operation for Acure based paints.

Figure 5: Effect of blocking the cata-lyst and adding an excess (relative to catalyst) of kinetic control additives on the conversion of acrylic double bonds (FT-IR, 809 cm-1) by Michael addition. Cat conc.: 40 μeq/g resin solids for all curves, unless noted otherwise.

Technical PaperEC Award winning paper

36 European Coatings JOURNAL 05 l 2015 www.european-coatings.com

(Tg) of the wet coating rises due to solvent release and reaction. When the Tg reaches room temperature (RT) the system will vitrify: both solvent diffusion and chemical reactivity become severely retarded. If such vitrification in the surface of the coating, becoming tack free, oc-curs much earlier than in the deeper layers, some solvent may be retained in those deeper layers which cannot then easily escape through this closed surface. I.e. fur-ther solvent release will be significantly slowed down. The upside to this picture is that solvents are excellent plasticizers. This means that the crosslink conversion is able to rise further while the reaction is not yet impeded by a high Tg and it is then easier to reach full conversion before vitrification. However, an excess of entrapped sol-vent may cause the Tg in deeper layers to remain lower in which case a lower pendulum hardness may be ob-served. Kiil modelled the competition between chemical reaction and solvent escape [3].

Secondly, ultrafast drying may lead to reduced appear-ance as a very narrow time window for levelling re-mains. One may see such fast drying systems struggle with releasing entrapped air and picking up overspray. Under some conditions, a rapid surface cure on top of a still mobile sublayer can even give rise to wrinkling phenomena, furthermore telegraphing defects are more likely to occur.It is clear that combining a very fast dry profile with very good pot life is not a guarantee for an application profile without significant complications. The challenge addressed was how to save the fast dry time profiles, and simultane-ously mitigate the problems described above. The solution is presented below with the use of special kinetic control additives to create an induction period in the crosslink reac-tion, and so create a tuneable ‘open time’ window.

Creating a controlled ‘open time’The concept used revolves around the presence of HA species in the formulation that can add to the acryloyl acceptors by a Michael addition after deprotonation, but differing from malonate in that:a. HA is significantly more acidic than the malonate C-H; i.e. the base will deprotonate HA much more readily than malonate, postponing the fast addition of malonate onto acryloyl.b. The conjugate anion (A-) has a significantly lower reac-tivity towards the acryloyl: the consumption of these spe-cies by the MA reaction is slow, i.e. already low concentra-tions of HA will have a significant effect on early kinetics. c. Ideally, the generated HA-acryloyl adduct does not sig-nificantly increase viscosity of the paint. This implies that HA is preferably a low molecular weight, mono-function-al component; guaranteeing the wet layer’s ability to wet, level, de-gas, pick-up overspray, etc.Various components have been identified which meet the profile above, these are based either on carbon or nitrogen acids: some examples are listed in Table 1. Each

Figure 6: Reactivity control of Acure chemistry. MA: Michael Addition. Reaction (1): potlife control. Reaction (2): open time control. Reactions (3): crosslinking. Both malonate hydrogens react with acryloyl

Structure Name pKa (in water)

Ethylacetoacetate 10.7

Succinimide 9.5

1H-benzotriazole 8.5

1,2,4-triazole 10.2

Malonate 13

Table 1: Suitable kinetic control additives; pKa’s from [4]

1)

2)

3)

www.eurocoat-expo.com

ContaCt to EXHIBIt

Cyril LadetShow Director+33 (0)1 77 92 96 84cladet@infopro-digital.com

The best offer in coating, raw materials and equipment!

An event co-organised by:

International Exhibition & Congressfor the paint, printing ink, varnish, glue and adhesive industries

5 , 6 , 7 April P a r i s E x p o

Porte de Versailles

F r a n c e

RAW MATERIALSRESINSPIGMENTS

MINERAL DILUENTSADJUVANTSSOLVENTS

BIOBASED PRODUCTS

PRODUCTION AND APPLICATION MATERIALS

DISPERSERS

CONTROL AND MEASURINGMIXERS

SHREDDERS

CHEMICAL PACKAGINGCODING AND LABELLING

LABORATORY MATERIALSCOLORIMETRY

PACKAGINGTRAINING AND TEACHINGSURFACE TREATMENTS

MATERIALS HANDLING

PRODUCTION ENGINEERING

NEW DATES

EC 2016 Pub 210X297 EN partenaire.indd 1 25/02/15 16:59

Technical PaperEC Award winning paper

38 European Coatings JOURNAL 05 l 2015 www.european-coatings.com

of these components differs slightly in terms of specific impact on the application performance. Combined with the blocked catalyst, warranting a long pot life, an in-duction (open) time is created; its length is tuneable by the amount of additive used. Only then a very strong acceleration of the reaction occurs once the more acidic HA species are consumed, still reaching high conversion. The net result is a sigmoidal kinetics profile (Figures 5, 7). Along with the amount of catalyst and alcohol co-sol-vents controlling the reaction rate, a formulation toolbox is available for easy optimisation of Acure paints to meet specific application performance demands.

Curing is rapid after tuneable open timeA beneficial consequence of using a relatively acidic spe-cies HA is that reaction b in Figure 2 will shift to the right,

“Acure” paint 30" DIN4-23 °C 1000 gMalonate polyester A 132.2 gSuccinimide mod. polyester B 182.0 g1,2,4-triazole 4.5 gAcrylate based pigment paste 535.9 gPaint additives 7.0 gn-propanol 62.5 gButyl acetate 52.4 gBlocked catalyst 23.5 gVOC 245 g/lSolids by weight 80.3 %PVC 16.3 %Catalyst 0.05 meq/g solid resinSuccinimide / catalyst 1.0 eq/eq1,2,4-triazole / catalyst 3.0 eq/eqAcrylate / malonate-H 0.95

Table 2: The Acure paint composition

Acure Aspar-tate

4 % OH-NCO A

4 % OH-NCO B

4% OH-NCO C

Spray viscosity (Din4) 30 24 20 20 25SC at appl.visc. (g/l) 81 83  71 72 76 NCO wt% on solids - 29.0 17.4 17.4 22.0NCO : OH, NH - 1.05 1.1 1.1 1.05Cure temperature (°C) RT RT RT 60 80DOI 91 93 94 94 94Haze (HU) 11 10 10 21 16Gloss 60° (GU) 90 93 95 95 97Foam limit (mm) > 240 > 240 > 160 ~100 ~110Haze * (HU) 34 314 63 78 32Gloss retention 60° * (%) 100 89 99 100 98PH Persoz 2 hours 108 194 - 45 125 1 day 169 234 138 137 154 7 days 189 248 218 207 206Reverse impact9 mm Crock (mar): > 105 > 105 20 4 > 105

60° gloss retention (%) 75 49 42 49 49 60° GR after 7 days RT (%) 79 51 44 53 62* 24 hrs 120°C

Table 3: Appearance and mechanical properties directly after application and after ageing (DFT: 45 + 4 µm on Q-panel)

increasing the concentration of weak acid (A-) and in par-ticular CO2. The latter will now diffuse out of the paint lay-er more readily. Because of its low reactivity (compared to malonate) the higher concentration of A- does not neutralize the positive effect of the ‘newly created’ open time. However, if all HA is consumed and CO2 mostly ex-pelled then the maximum concentration of fast react-ing anionic species is present in the paint. The malonate then becomes deprotonated and the full potential of the ultra-fast Michael addition is released as if there never was a blocked catalyst (Figure 5). Acure chemistry can then be summarized as in Figure 6, where a tetrabutyl ammonium cation counters the blocked base with suc-cinimide as example kinetic control additive (HA).Note that the paint components controlling the reactions 1 and 2 in Figure 6 are different species, allowing both the pot life and open time to be tuned independently, while accepting only a limited compromise in drying time. Simultaneously, very significant advantages in pendulum hardness development and appearance are obtained (Figures 7 and 8). For layer thicknesses above 40 µm it was observed that both 1,2,4-triazole and suc-cinimide are needed for optimum results.

Good durability and excellent adhesion on most substrates

In general, accelerated weathering tests on white pig-mented topcoats yield results that are very comparable to high quality (4  % OH) urethane coatings (tested in UV-B, Xenon [5]) even though it was that found various commonly used UV absorbers are incompatible with the Acure technology. HALS could be used with the usual beneficial effects, however. Gloss retention after two years of Florida exposure was at least on par with high end WB 2K, HS and MS 2K urethane references [5]. Adhesion studies of Acure top coatings were carried out over many different types of commercially available primers used in a wide field of end use applications in-cluding general industry, ACE and protective coatings. The different epoxy primer types that were tested included new build, holding, fast-cure, surface tolerant, low tem-perature cure and zinc rich types. Good to excellent ad-hesion was found on more than 80 % of these primers, which can be explained by chemical bond formation be-tween remaining free amine groups on the substrate and acryloyl groups from the Acure paint. Obtaining chemical adhesion with Acure paints on substrates not containing NH-moieties can be more difficult. However, it was found that the presence of 1,2,4-triazole, apart from its function as kinetic control additive, also helps as an adhesion pro-moting agent on some metallic substrates. Well-known [6] metal pre-treatment methods with silanes also exhibited excellent adhesion with Acure top coats. Alternatively, known alkoxysilane adhesion promoters can be used in combination with Acure, if added shortly before use.

Comparing Acure technology with isocyanate-containing systems

Comparative data obtained from various TiO2-white paint formulations is shown below; one Acure and four high solids isocyanate containing systems. All paint formula-

39www.european-coatings.com 05 l 2015 European Coatings JOURNAL

Technical PaperEC Award winning paper

tions were optimised for best performance as a high gloss industrial top coat. All reference paint components used are commercially available. 4 % OH-NCO paint A is a “state-of-the-art” very fast RT drying top coat system, paints B and C are intended for elevated temperature curing (B: 60 °C, C: 80 °C). All paints have identical pigment to binder ra-tios. The Acure paint composition is given in Table 2 and is based on DTMPTA (di-trimethylolpropane tetra acrylate) as acryloyl acceptor. The malonate functional resin A is a specially designed polyester resin with a number aver-age molecular weight of about 1780 Da and a malonate equivalent weight of 350 g/mol solid resin. The resin is at 85 % solids in butyl acetate and has a viscosity of 5-10 Pa.s. The malonate functional resin B is the same resin; however modified with 1.4 % succinimide on solids. The emphasis was on leveraging the control of the cure chemistry in systems with relatively high concentrations of functional groups. Consequently, Acure coatings with very high crosslink densities (XLD) of typically 2.5 - 3 mmol/cc are obtained, as derived from DMTA measurements [5]. These XLDs are higher by a factor of around 3 relative to high end, e.g. 4 % OH – isocyanate or aspartate based sys-tems, even when using high isocyanate levels (see Table 3 for comparing the isocyanate levels used in this study). For Acure the XLD is amongst others, tuned by the acry-loyl – malonate hydrogen ratio, see Figure 9, showing the resistance to MEK dramatically improve when A/M > 0.9. Surprisingly, it was observed that yellowing in the dark of Acure coatings depended also on the A/M ratio. In order to avoid this, the A/M ratio should also be > 0.9, in which case it may even out-perform isocyanate based systems.

High level of appearance and physical properties

The appearance of all coatings in this comparative test was good. Focussing on the differences, it was noted that the aspartate coating deteriorated significantly with time when exposed to 24 hrs 120 °C. An advantage of Acure chemistry is its relative insensitivity of appearance as a function of the applied layer thickness. Unlike OH-isocyanate-containing systems there are no foam generating reactions with water or solvent popping phenomena and subsequent pin-holing risk. In the lab Acure paints have been applied at over 240 µm DFT that still exhibit very good appearance. Table 3 further shows mechanical test results, again only focussing on differences between the tested systems. All tested coatings had excellent flexibility (as tested with the conical mandrel). Hardness development for the various coatings is remarkably different. Note that paints B and C were cured at the recommended elevated temperature (30 min 60 °C and 80 °C respectively). Yet, the early hardness cannot always compete with Acure and aspartate. The su-perior mar (scratch) resistance is consistent with the high crosslink density present in the Acure coating.Resistance to various chemicals is equal to or better than the references for Acure coatings. Resistance to acid etch, was found to out-perform the reference coatings.Finally, Table 4 shows the comparative potlife – drying bal-ance for these paints at room temperature. Paint Acure II dif-fered from Acure I only in that the former contains half the amount of succinimide and 20 % more catalyst compared

Figure 7: Pendulum hardness develop-ment of an Acure coating formulated for 30 min tackfree at room tempera-ture (red line) and a typical 4 % OH- NCO coating dried for 30 min at 60 °C (blue line)

Figure 8: Influence of catalyst addi-tives succinimide and 1,2,4-triazole on Acure appear-ance (shortwave) at 60 µm

chemistry you can trust

Hardeners for Epoxy Systems

Polyamides

Polyaminoamides

Polyamide/polyamine Adducts

Aliphatic/Cycloaliphatic Amines

Mannich Bases

Waterborne Epoxy Systems

Hot Melt Polyamides

Formulated Epoxy Resins

Via Crear, 15 Loc. Mazzantica 37050 Oppeano (VERONA) ItalyT: +39 045 6985000 - contact@ddchem.it

www.ddchem.itECS: Visit us at stand 555 in hall 7

Technical PaperEC Award winning paper

40 European Coatings JOURNAL 05 l 2015 www.european-coatings.com

to the latter to match the cure speed of the aspartate paint. Note the very long pot lives for both Acure paints.

VOC, health and safetyAcure paints consist of malonate functional polyesters and acryloyl functional oligomers, both of which are compounds of low polarity with no appreciable hydrogen bonding. Consequently, the intrinsic viscosity of the paint is significantly lower than when using hydroxyl function-al binders. The Acure paint of Table 2 contained about 245 g/l VOC; no effort was made to optimise for low VOC.Acure is base catalysed; it does not require an organo-tin or any other organometallic catalyst, nor does it re-lease formaldehydes. Depending on the type of selected acryloyl oligomers the paint can be formulated without skin sensitising compounds; e.g. di-trimethylol propane tetraacrylate (DTMPTA). If this is not a requirement more cost effective alternatives are available (e.g. TMPTA).

Summarising Acure performance and outlook

Acure, based on Michael addition chemistry, extended with the kinetic toolbox developed and put to work with dedicated malonate polyesters, has yielded an impres-sive combination of attractive performance parameters. These innovations are expected to form the basis for a next generation of novel high performance coatings ca-pable of providing significant improvements in applica-tion cost efficiency. Key features and benefits include: » very fast drying, with fast crosslink density develop-ment, and a very long pot life

» application at ambient temperatures, or even below » very low solvent content (VOC < 250 g/l) » excellent appearance » thick layer application (> 150 µm) possible » very good chemical resistance » very good mar resistance » excellent flexibility » good outdoor durability » isocyanate, formaldehyde and organotin-free cure

chemistryAs such, Acure presents a system that can combine many premium characteristics through an unprecedented control over the cure kinetics. Of course, being a base catalysed system, it also encounters some inherent limi-tations, especially in terms of sensitivity to acidic com-ponents that may interact with the catalyst system. Care must be taken when selecting additives in order to avoid those that can potentially cause acid contaminations, e.g. dispersants, rheology control agents, etc. With a proper choice of additives, complications can be avoided. As an alternative to acidic rheology additives, Acure compat-ible malonated polyesters equipped with urea nanocrys-tal based rheology agents (SCA’s) have been made, pro-viding thixotropy. Cure inhibition complications can also arise when applying Acure paints onto substrates con-taining mobile acid species, such as WB base coatings used in automotive applications. In this paper, the first observations based on a limited set of malonated binders are presented. Considerable room to decrease the viscosity of the binders and develop low-er VOC Acure paints is expected. Likewise variations in e.g. polarity, malonate equivalent weight, or resin Tg and the nearly unlimited variations in paint formulation will further add to the potential for Acure in a broad range of application fields. E.g. it has already been shown that ‘quasi 1K’ paint systems (pot lives extending over days) are possible whilst still retaining the cure speed by in-creasing the amount of alcohols.

RefeRenCeS [1] Michael, A. (1887). "Über die Addition von Natriumacetessig- und

Natriummalonsäureäthern zu den Aethern ungesättigter Säuren". Journal für Praktische Chemie 35: 349–356.

[2] A. Noomen, Progress in Organic Coatings, 32 (1997), 137-142[3] S. Kiil, J. Coat.Technol.Res., 7 (5), (2010), 569-586. [4] http://www2.lsdiv.harvard.edu/pdf/evans_pKa_table.pdf[5] R. Brinkhuis, J. Schutyser, F. Thys, E. De Wolf, M. Bosma, M.

Gessner, T. Buser, J. Kalis, N. Mangnus, A. Bastiaenen, ‘New, ultra-fast drying, low VOC, isocyanate free technology for 2K coating systems’, Proc. Eur. Coatings Conf, Nuremberg, April 2015, in print.

[6] T.S.N. Sankara Narayanan, Rev. Adv. Mater. Sci. 9 (2005), 130 – 177

ACKnOwledGemenTSThe autors wish to express their gratitude for their contributions to this work to: Mrs A. Bastiaenen, Mrs M. Thannhauser, Mrs L. Taylor, Mr M. Gessner, Mr P. Dolphijn, Mr Dr M Bosma, Mr Dr. J. Akkerman, and Mr Dr. D. Mestach.

With our VAE dispersion you can formulate paints with these benefits:

• Low odor and emissions for cleaner air

• Meet a variety of labelling requirements

• Meet performance needs

• Makes consumers happy for years to come

everywhere today, tomorrow today, tomorrow today, tomorrow today, tomorrow and for years and for years to come

Paints do more than just cover walls with color. They bring

light and life into the spaces where your customers live light and life into the spaces where your customers live

and work. Paint emissions shouldn’t impact the pursuit of

living a healthier, happier life. Our VAE dispersions reduce living a healthier, happier life. Our VAE dispersions reduce

the impact paints have on indoor air quality the impact paints have on indoor air quality so everyone

can breathe a little easiercan breathe a little easier.

Connect to Us:Your Celanese representative

Email Mowilith.info@celanese.com

Call +49 69 45009 2162

LEARN MORE AT CELANESE.COM/BETTERAIR

bettereverywhere

today, tomorrow today, tomorrow and for years today, tomorrow today, tomorrow and for years

air,betterbetterbetterbetter

and for years today, tomorrow today, tomorrow and for years

air,air,air, today, tomorrowair, today, tomorrow

betterbetterbetterbetterbetterbetterair,

RT curing “Acure” I

“Acure” II Aspartate 4 %

OH-NCO A4 %

OH-NCO A

4 % OH-NCO

ADust dry hh:mm 0:35 0:14 0:15 0:55 1:20 4:20Tack free hh:mm 0:40 0:18 0:25 3:30 5:35 > 7:00 Pot life DIN53211 hh:mm 20:00 16:00 0:26 1:25 2:05 1:50

Table 4: Comparing potlife – drying balance at room temperature

Figure 9: Hard-ness (DFT 65 µm) after one day at RT (blue), yellowing after 24 hr 120 °C (red) and resist-ance to 4 min. MEK exposure on a scale of 1 (bad) to 5 (no visible damage)