Title of Invention	COATING COMPOSITION BASED ON THIOL-NCO CURING
Abstract	Coating composition comprising one or more polythiols and one or more polyisocyanates and a latent base catalyst which is activatable by moisture, wherein the equivalence ratio NCO : SH is between 1 :2 and 2:1. The latent catalyst is selected from the group of oxazolidine, aldimine, ketimine, and enamine. The latent catalyst is present in an amount of up to 20% relative to the weight of the curable material. The composition further comprises one or more photoinitiators in an amount of up to 4% relative to the weight of the curable material.

Title of Invention

COATING COMPOSITION BASED ON THIOL-NCO CURING

Abstract

Coating composition comprising one or more polythiols and one or more polyisocyanates and a latent base catalyst which is activatable by moisture, wherein the equivalence ratio NCO : SH is between 1 :2 and 2:1. The latent catalyst is selected from the group of oxazolidine, aldimine, ketimine, and enamine. The latent catalyst is present in an amount of up to 20% relative to the weight of the curable material. The composition further comprises one or more photoinitiators in an amount of up to 4% relative to the weight of the curable material.

Full Text	The present invention relates, to a coating composition comprising one or more polythiols. one or more polyisocyanates. and a deactivated base catalyst. Coating compositions based on polythiols and polyisocyanates are catalyzed by base catalysts. To prevent premature cross-linking, the base catalysts can be blocked or deactivated. WO 01/92362 discloses compositions based on thiol- isocyanate cross- linking using a photoiatent base. To cure such coatings, the freshh' applied layers need to be irradiated with actinic radiation of the right wavelengths. Hence, such coalings are less useful when large surfaces are to be coated, such as garage floors and the like. Moreover, some spots of the surface may be more difficult to irradiate. The curing speed on such shadow spots is low. The object of the invention is to provide a coating composition which has a long pot life but a fast curing speed over the complete substrate, including shadow spots. The object of the invention is achieved with a coating composition comprising one or more polythiols, one or more polyisocyanates, and a deactivated base catalyst which is activatable by moisture. The equivalence ratio NCO : SH, the number of NCO groups relative to the number of SH groups, is between 1 :2 and 2:1. Moisture activatable base compounds, such as oxazolidines. are generally reactive with isocyanate groups. For this reason, such compounds are used as crosslinkers for polyisocyanates. Surprisingly, it was found that in thiol- isocyanate crosslinking systems these compounds are not bound by the isocyanate groups on a substantial scale but rather function as a catalyst for the thiol-isocyanate crosslinking under the influence of moisture. Oxarolldines are su.table compounds reacting with moisture to form a base which is able to catalyze SH-NCO reactions. Suitable oxazolidines are for oxample carbonato-bis-N-ethyl-2-isopropyl-1,3-oxazolidina, commercially available as Incozol® LV, 2-(3-heptyl)-N-butyt-1,3-oxazolane, commercially available as Incozol® 2, and urethane bis-oxazolidines, such as those which are commercially available as Hardener OZ. Other suitable latent base compounds are for example enamines, ketimines, and aldimines. The latent catalyst can be present in an amount of, e.g., up to 20% relative to the weight of the curable material, e.g. 0.01 - 6%, such as 3.5 - 5%. In a further embodiment, the coating composition may further comprise one or more photoinitiators, forming radicals under the influence of light. Surprisingly, it was found that drying was accelerated considerably, about 2-20 times, even in pigmented systems applied in thick layers. This effect particularly occurred when using oxazoiidine as a catalyst The photoinitiator can for example be present in an amount of 0.01 - 2.0% relative to the weight of the curable material, e.g, in an amount of 0.1 to 1.0%. Suitable photoinitiators are for example ethyl 4-(dimethylamino)benzoate (Speedcure® EPD), 2-(dimethylamino)ethyl benzoate (Speedcure® DMB), 4- benzoyl-4'-methyldiphenyl sulphide (Speedcure® BMS), 2-ethylhexyl-4- dimethylaminobenzoate (Speedcure® EHA); 1,3,5-trimethylbenzoyl diphcnylphosphine oxide (Speedcuro® TPO), all available from Lambson. A photoinitiator for use in visible daylight is for instance bis (4-cylcopentadien-1- yl)-bis [2,6-difluoro-3-(1H-pyrrol-yl)-phenyl]titanium (Irgacure® 784, Ciba Specialty). Other suitablo photoinitiators include ketones, such as methyl ethyl ketone, 2,3-butanedione, 1-hydroxy cyclohexyl phenyl ketone, 2-hydroxy-2- methyl-1 -phenyl propan-1-one, and aromatic ketones, e.g., acetophenone, benzophenone, 4-arninobenzo-phenone, 4,4'-diaminobenzophenone, 4,4'- bis(dimethylamino) benzophenone, valero-phenone, hexanophenone, o- methoxybenzophenone, a-phenylbutyrophenone, -γ-phenylbutyrophenone, p- morpholinopropiophenone, dibenzosuberone, 4-morpholinobenzophenone, 4- methoxyacetophenone, p-diacetylbenzene, 1,3,5-triacetylbenzene; benzoin compounds, e.g., benzoin, benzoin methyl ether and benzoin ethyl ether, 4- morpholinodeoxybenzoin; quinone and anthrone compounds, e.g., hydroquinone, anthraquinone, napthoquinone, acenaphthenequinone, and 3- methyl-1,3-diazo-1,9-benzanthrorie; phenolic compounds, e.g., 2,4-dinitro- phenol; phosphine compounds such as triphenyl-phosphine and tri-o- tolyphosphine; azo compounds, e.g., azoblslsobutyronitrile; thloxanthone compounds including for example 2,4-dlethoxythioxanthone, isopropylthtoxanthone (Speedcure® ITX), 1-chloro-4-propoxythioxanlhone (Speedcure® CPTX); and 2-chlorothioxanthone; and various other compounds, e.g., benzll, benzaldehyde, 1-naphthaldehyde, α-totralone, 2- acetylphenanthrene, 3-acetylphenanthrene, 9-acetyl-phenanthrene, 10- thioxanthenone, 3-acetylindole, 9-fluorenone, 1-indanone, 9-xanthenono, 9- thioxanthenone, 7-H-benz[de]anthracen-7-one, 1-acetonaphthone and 2- acetonaphthone. Alternatively, the photoinitiator can be a phosphine oxide compound, such as 2,4,6-trimethyl benzoykjiphenyl phosphine oxide (Lucirin® TPO, available from BASF) or acyl phosphine oxide compounds, such as mono- bis- or tiisacyl phosphine oxide or mixtures thereof. An example of a bisacylphosphine oxide photoinitiator is bis(2,4,6-trimethylbenzoyl)-phenyl- phosphine oxide (Irgacure® 819, availablo from Ciba Specialty Chemicals) or bls(2,6-dimethoxy-benzoyl)-2,4,4-trimethyl pentyl phosphino oxide (DMBAPO, Irgacure® 403, available from Ciba Specialty Chemicals). Mixtures of different photoinitiators may be used. Alternatively, or additionally, one or more phototatent bases can be used, e.g., the photolatent bases as disclosed in WO 94728075 and EP-A 0 882 072. Suitable photolatent bases include N-substituted 4-(o-nitrophenyl) dihydropy- ndines, optionally substituted with alkyl ether and/or alkyl ester groups, and quaternary organo-boron photoinitiators. An example of an N-substituted 4-(o- nitrophenyl) dihydropyrldino is N-mothyl nifedipine (Macromolecules 1998, 31, 4798), N-butyl nifedipine, N-butyl 2,6-dimethyl 4-(2-nitrophenyl) 1,4-dihydropy- ridine 3,5-dlcarboxylic acid diethyl ester, and a nifedipine according to the following formula i.e., N-methyl 2,6-dimethyl 4-(4,5-dimethoxy-2-nitrophenyl) 1,4-dihydropyridine 3,5-dicarboxylic acid diethyl ester. Examples of quaternary organo-boron photoinitiators are disclosed in GB-A-2 307 473, such as A further suitable alternative is a photolatent base belonging to the group of a- amino acetophenones. Examples of α-amino acetophonones which can bo used are 4-(methytthiobenzoyl)-1-rnethyl-1-rnorpholinoethane (Irgacure® 907 ex Ciba Specialty Chemicals), (4-moipholinobenzoyl)-1-benzyl-1-dimethylamino propane (Irgacure® 369 ex Ciba Specialty Chemicals) or an a-amino acetophenone according to the following formula Furthermore, it was found that for these light-accelerated moisture curing systems, the pot life could be increased considerably by the addition of an inorganic acid (such as nitric acid), even when small amounts, e.g., 0.005 - 0.05 wt.%, were used. The addition of small amounts of acid hardly influences the cure time. Suitable polythiols can be prepared by reacting hydroxyl group-containing compounds with thiol group-containing acids, such as 3-mercaptopropionic acid, 2-mercaptopropionic acid, thio-sallcylic acid, mercaptosuccinic acid, mercaptoacetic acid, or cysteine. Examplos of suitable hydroxyl group- containing compounds are diols, triols, and tetraols, such as 1,4-butane diol, 1,6-hexane diol, 2,2-dimethyl-1 ,3-propane diol, 2-ethyi-2-propyl-1,3-propane diol, 1,2-, 1,3-, and 1,4-cyclohexane diols, and the corresponding cyclohexane dimethanol, 1,1,1-trimothylo) propane, 1,2,3-trimethylol propane, and pentaerythritol. Examples of compounds prepared according to such a method include pontaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tetrakis (2-mercaptoacetate), trimeth/ol propane tris (3-mercaptopnopionate), trimethytol propane tris (2-mwcaptoproptanate), and trimethytol propane trts (2- mercaptoacetate). Good results have been obtained with thmethylol propane tris (3-mercapto propionate) and pentaerythritol tetrakis (3-mercapto propionate). A further example of a compound prepared according to such a method consists of a hyperbranched polyol core based on a starter polyol, e.g., trimethytol propane, and dimethylol propionic acid. This polyol is subsequently esterified with 3-mercaptopropionic acid and isononanoic acid. Those methods are described in EP-A 0 448 224 and WO 93717060. Other syntheses to prepare compounds comprising poiythiols involve: the reaction of an aryl or alkyl halide with NaHS to introduce a pendant thiol group into the a;kyl and aryl compounds, respectively; tho reaction of a Grignard reagent with sulphur to introduce a pendant thiol group into the structure; the reaction of a polymercaptan with a polyolefin according to a Michael addition reaction, a nucleophilic reaction, an electrophilic reaction or a radical reaction; the reaction of a thiol-functional alcohol and an isocyanate-functional compound, and the reduction of disulphidos. The polythiol may for example have one or more hydroxy! groups and have a structure according to the following formula: T[(C3HeO)nCH2CHOHCH2SH]3, with T being a triol such as trimethylol propane or glycerol. An example of such a compound is commercially available from Henkel under the trademark Henkel Capcure® 3/800. Alternatively, the polythiol can for instance be a resin having a polyester resin, polyurethane resin, polyacrylate resin, or polyether resin as backbone. These isocyanate-reactive compounds may also comprise hydroxyl groups. The polythiol may for instance be a polyester prepared from (a) at least one polycarboxylic add or reactive derivatives thereof, (b) at least one polyol, and (c) at least one thiol-functional carboxylic acid. The polyesters preferably possess a branched structure. Branched polyesters are conventionally obtained through condensation of polycarboxylic acids or reactive derivatives thereof, such as the corresponding anhydrides or lower alkyl esters, with polyalcohols, when at least one of the reactants has a functionality of at least 3. Examples of suitable polycarboxylic acids or reactive derivatives thereof are tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthaltc acid, hexahydroph:halic anhydride, methyl hexahydrophthalic acid, methyl hexahy- drophthalic anhydride, dimethytayclohexane dlcarboxylate, 1,4-cyclohexano dicarboxylic acid, 1,3-cyciohexane dicarboxylic acid, phthalic acid, phthalic anhydride, isophthaltc acid, terephthaiic acid, 5-tert. butyl isophthalic acid, trimellitic anhydride, maleic acid, maleic anhydride, fumaric acid, succinic acid, succinic anhydride, dodecenyl succinic anhydride, dimethyl succinate, glutaric acid, adipic acid, dimethyl adipate, azelaic acid, and mixtures thereof. Examples of suitable polyols include trimethylol propane, trimethylol ethane, glycerol, 1,2,6-hexanetriol, ethylene glycol, 1,2-propyleno glycol, 1,3-propylene glycol, 2- methylpropane-1,3-diol, neoperttyl glycol, 2-butyl-2-ethyl-1,3-propano diol, cyclohexane-1,4-dimethylol, the monoester of neopentyl glycol and hydroxy- pivalic acid, hydrogenated Bisphenol A, 1,5-pentane diol, 3-methyl-pentane diol, 1,6-hexane diol, 2,2,4-trimethyt pentane-1,3-diol, dimethylol propionic acid, pentaerythritol, di-trimethylol propane, dipentaerythritol, and mixtures thereof. Examples of suitable thiol-functional organic acids include 3-mercaptopropionic acid, 2-mercaptopropionic acid, thio-salicylic acid, mercaptosuccinic acid, mercaptoacetic acid, cysteine, and mixtures thereof. Optionally, monocarboxylic acids and monoalcohols may be used in the preparation of the polyesters. Preferably, C4-C18 monocarboxylic adds and C6-C18 monoalcohols aro used. Examplos of the C4-C18 monocarboxylic acids include pivalic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, 2-ethylhexanoic acid, isononanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, isostearic acid, stearic acid, hydroxystearic acid, benzoic acid, 4-tert. butyl benzoic acid, and mixtures thereof. Examples of the C6-C18 monoalcohols include cyclohexanol, 2-ethylhexanol, stearyl alcohol, and 4-tert butyl cyclohexanol. Alternatively, the polythiol may be a thiol-functional polyacrylate. Such polyacrylate can be derived from (meth)acrylic monomers such as (meth)acrylic acid, methyl (meth)acrylate, butyl (meth)acrylate, a vinyl derivative such as styrene, and optionally hydroxy-functional acrylic monomers, such as hydroxy ethyl (meth)acrylate, hydroxy propyl (meth)acrylate hydroxy butyl (moth)acrylate and the like, or mixtures thereof, with the terms (meth)acrylate and (moth)acrylic acid referring to both methacrylate and acrylate and methacrylic acid and acrylic acid, respoctivoty. Tho thiol group is introduced by the reaction product of dimethyl-m-isopropenyl benzyl isocyanate and mercapto ethanol. Alternatively, glyctdyl methacrylate is introduced into the polymer to prepare an epoxy-functional polyacryate. The epoxy groups are then reacted with suitable thiol-functional organic acids such as mentioned above. The polyacrylate is prepared by conventional methods, for instance, by the slow addition of appropriate monomers to a solution of an appropriate polymerization initiator, such as an azo or peroxy initiator. Also included in the coating compositions of the invention may be di-, tri-, or higher thiol-functional diluents such as ethane dithtal or bls-beta-mercapto-ethyl sulphide. Preference is given to the use of higher-molecular weight thiol- functional compounds, which may be obtained by reaction of a polythiol- funotional compound with a polyisocyanate. Suitable organic polyisocyanates include polyfunctional, preferably free polyisocyanates, with an average NCO functionality of 2.5 to 5, and may be (cyclo)aliphatic, araliphatic or aromatic in nature. The organic polyisocyanate may be blocked. The polyisocyanate may include biuret, urethane, uretdione, and isocyanurate derivatives. Examples of these organic polyisocyanates include 1,6-diisocyanatohexane, Isophororte diisocyanate, 2,4-toluene diiso- cyanate, 2,6-toluene diisocyanate, diphenyl mothane-diisocyanato, 4,4'- bis(isocyanato-cydohexyl) methane, 1,4-diisocyanatobutane, 1,5-diisocyanato- 2,2-dimethyl pentane, 2,2,4-tr1methyl-1,6-diisocyanatohexane, 1,10-difeocyana- todecane, 4,4-diisocyanato-cyclohexane, 2,4-hexahydrotoluene diisocyanate, 2,6-hexahydrotoluene diisocyanate, norbomane diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1-isocyanato-3-(isocyanato methyl)-1- methyt cyclohexane, m-ot,a-a',a'-tetramethyl xylylene diisocyanate, the above- mentioned derivatives thereof, and mixtures thereof. Normally, these products are liquid at ambient temperature and commercially available in a wide range. Particularly suitable isocyanate curing agents are triisocyanates and adducts. Examples thereof are 1 ,B-diisocyanatc-4-{lsocyanatomethyl) octane, the adduct of 3 moles of toluene diisocyanate to 1 mole of trimethyld propane, the isocyanurate trimer of 1,6-diisocyanatohexane, the isocyanurate trimer of isophororte diisocyanate, the uretdione dimer of 1,6-diisocyanatohexane, the biuret trimer of 1,6-diisocyanatohexane, the adduct of 3 moles of m-a.a-a'.u'- tetramethyl xylene diisocyanate to 1 mole of trimethyloi propane, and mixtures thereof. Preferred are cyclic trimers (isocyanurates) and uretdiones of 1,6- hexane diisocyanate and isophorone diisocyanate. Usually these compounds contain small quantities of their higher homoiogues. Optionally, a hydroxyl-functional compound comprising at least two hydroxyl- functional groups may bo presont In the curablo material. Tho hydroxyl- functional compound comprising at least two hydroxyl-functional groups may be selected from polyester polyols, potyether pofyols, polyacrylate polyols, polyurethane polyols, cellulose acetobutyrate, hydroxyl-functional epoxy resins, alkyds, and dendrimeric polyols such as described in WO 93/17060. Also, hydroxyl-functional oligomers and monomers, such as castor oil and tnmethyiol propane, may be included. A suitable polyol is an acrytate polyol, such as for example Seta lux® 1157 available from Nuplex. The polyisocyanate can be mixed with the porythiols by any suitable technique. However, simply stirring usually is sufficient Sometimes it can be useful to dlluto the polyisocyanate somewhat with an organic solvent such as ethyl acetate or 1-methoxy-2-propyl acetate to reduce Its viscosity. The pot life of the coating composition at ambient temperature usually is more than a quarter of an hour, e.g. more than half an hour, up to about 5 hours or even longer, depending on the catalysts used and their amounts and whether or not blocking acids are used. The composition according to the present invention can be a solvent borne composition or a solvent-free composition. Since the composition may be composed of liquid oligomers, it is especially suitable for use as a high-solids composition or a solvent-free composition. The coating composition can also be used in powder coating compositions and hot melt coatings compositions. Preferably, the theoretical volatile organic content (VOC) in tho composition is less than about 450 g/l, more preferably less than about 350 g/l, most preferably less than about 250 g/l, or even less than 100 g/l. The coating compositions may further comprise other ingredients, additives or auxiliaries, such as pigments, dyes, emulsifiers (surfactants), pigment dispersion aids, photosensitizes, levelling agents, anti-cratering agents, antifoaming agents, antisagging agents, heat stabilisers, UV absorbers, antioxidants, and fillers. The coating composition of the present invention can be applied to any substrate. The substrate may be, for example, metal, plastic, wood, glass, ceramic, or somo other coating layer. The other coating layer may be comprised of the coating composition of the current invention or it may bo a different coating composition. The coating compositions of the current invention show particular utility as a floor coating, e.g. on concrete floors or as a coating or repair coating, e.g. as a primer or as a dear coat, for vehicles, such as cars, trains, air planes or the like. The coating compositions can be applied by conventional means such as by spray gun, brush, or roller, spraying being preferred. Curing temperatures are generally between 0 and 100°C, e.g., between 0 and 30°C. The invention is further illustrated by the following examples. In these examples the compositions listed below are available as indicated. The following test methods were used: Pot life - The time during which the system could be brush-applied after mixing the components; Drying time - The coating composition was applied on a glass plate with a draw bar. The layer thickness was 125 µm, the temperature was 20° C. Drying was tested by means of a BK Drying Recorder. The results can be classified as follows: Phase 1: the line traced by the pin doses up again ("open time"); Phase 2: the pin traces a straight line in the paint which does not close up again ("tack-free time"); Phase 3: the pin traces a scratchy line ("dust free"); Phase 4: the pin does not leave a scratch ("scratch-free time"). Viscosity measured using a Rheometer (Rheolab MC1, spindle: Z2 DIN); after 15 minutes resting, the viscosity was measured over 1 minute with a speed of 150 rotations per minute. This program was repeated several times. Example 1 A two-component coating composition was prepared. The first component comprised pentaerythritol 3-mercaptopropionate and 40% butyl acetate. The second component comprised a polyisocyanate (Tolonate® HDT LV) and 6% oxazolidine (Hardener OZ). The components were stoichiometrically mixed before application. The Phase-4 cure time was 60 minutes (at 85% RH), the viscosity in the can at that time was: 0.13 Pa.s. The pot life was 3 hours. Example 2 A two-component coating composition was prepared. The first component comprised pentaerythritol 3-mercaptopropionate and 40% butyl acetate. The second component comprised a polytsocyanate (Tolonate® HDT LV) and 6% oxazolidirte (Incozol® 2). The components were stolchiometrically mixed before application. The Phase-4 cure time was: 20 minutes (at 85% RH), the viscosity at that time was: 0.25 Pas. Example 3 A two-component coating composition was prepared. The first componont comprised pentaerythritol 3-mercaptoproplonaie and 40% butyl acetate. The second component comprised a polyisocyanate (Tolonate® HDT LV) and 6% oxazolidine (Incozol® LV). The components were stoichiornetrically mixed before application. The Phase-4 cure time was: 80 minutes (at 85% RH), the viscosity at that time was: 0.10 Pa.s. Example 4 To the formulation in Example 1,1% Speedcure® BMS was added. The sample was applied on a panel and the panel was irradiated with a UV-A lamp at 20 cm (UVAHAND-250, 35 mW/cm2). The Phase-4 cure time was reduced to 10 minutes. The pot life was not affected by the addition of Speedcure® BMS and remained 3 h. Example 5 To the formulation in Example 1, 1% Speedcure® BMS, 10% TiO2 (Tipure® R902-38), and 1% organic black (Colour Black FW2) wore added. Tho sample was applied on a panel and the panel was irradiated with the UV-A lamp at 20 cm. The Phase-4 cure time was reduced to 20 minutes. Example 6 To the formulation in Example 1,1% Irgacure® 784 was added. The sample was applied on a panel and the panel was irradiated with a 1000 W construction lamp at 50 cm. The Phase-4 cure time was reduced to 3 minutes. The pot life was not affected by the addition of Irgacure® 784. Example 7 To the formulation in Example 4, 0.03% HNO3 was added. The sample was applied on a panel and the panel was irradiated with the UV-A lamp at 20 cm. The Phaso-4 cure time remained 10 minutes. The pot life was doubled. Example 8 A solvent free, two-component coating composition was prepared. The first component comprised pentaecythrttol 3-mercaptopropionate and 1% Speedcure® BMS. The second component comprised a polyisocyanate (Totonate® HDT LV) and 2% oxazolidine (Incozol® LV). The sample was appiied on a panel and the panel was irradiated with the UV-A lamp at 20 cm. The Phase-4 cure time was 20 minutes (at 60% RH). The pot life was 45 minutes. Example 9 A two-component coating composition was prepared. Tho first component comprised pentaerythritol 3-mercaptopropionate and 40% butyl acetate. The second componont comprised a polyisocyanate (Dosmodur® E14, Bayer) and 6% oxazolidine (Hardener OZ). The components were stoichiometrically mixed before application. The Phase-4 cure time was 1.5 h (60% RH), the potlife was 2 h. Example 10 A two-component coating composition was prepared. The first component comprised pentaerythritol 3-mercaptopropionate and 40% butyl acetate. The second component comprised a polyisocyanate (Desmodur® DN) and 6% oxazolidine (Hardener OZ). The components were stoichiometrically mixed before application. The Phase-4 care time was 1.5 h (60% RH), the pot life was 2 h. Exampio 11 A two-component coating composition was prepared. The first component comprised pentaerythritol 3-mercaptopropionate and 40% butyl acetate. The socond component comprised a polyisocyanate (Totonate® HDT LV) and 6% ketimine (Vestamin® A139). The components were stoichiometrically mixed before application. The Phase-4 cure time was 2.0 h (60% RH), the pot life was 2 h. Comparative example 1 A two-component coating composition was prepared. The first component comprised pentaorythritol 3-mercaptopropionato, 15% butyl acetate, and 0.25% triphenylphospine. The second component comprised a polyisocyanate (Totonate® HDT LV) and 2% acrylate (Actilane®411). The components were stoichiometncally mixed before application. The Phase-4 cure time was: 1.5 h (at 20*C and 85% RV), the pot life was 30 minutes. Comparative example 2 A two-component coating composition was prepared. The first component comprised pentaerythritol 3-mercaptopropionate, 15% butyl acetate, and 0.05% Ancamine® k54 (Air Products). The second component comprised a polyisocyanate (Tolonate® HDT LV, Rhodia). The components were stoichiometrically mixed before application. The Phase-4 cure time was: 3.0 h (at 20°C and 85% RV), the pot life was 20 minutes. Example 12 A three-component floor coating was prepared including a thiol component A, an isocyanate component B and a catalyst component C. Component A comprised 83 wt.% pentaerythrttol tetra (3-mercaptopropionate), 16,5 wt% TiO2 (Tipuro® R 902) and about 0,5 wt% of a silicone based defoamer (Byk® A- 525). A pigment paste is also added to component A, in any desired amount If a black pigment paste is used, the paste should contain, per 1 parts by weight (pbw) of carbon black (Farbruss FW2), 20 pbw of pentaerythritol tetra (3- mercaptopropionate), 0,2 pbw of Byk® A-525 defoamer, and 0,04 pbw of methyl-di-ethanolamine to neutralize the acidity. Component B comprises 100 % of the isocyanurate of hexamethylene diisocyanate (Tolonate® HDT-LV2). Component C comprises 120 pbw sand, 15 pbw quartz sand and 1 - 4 wt.% of Incozol® 2. Components A and B were mixed in a ratio A : B = 48 : 52 and applied on a concrete substrate. Subsequently, the sand component C was sprinkled over the freshly applied layer to catalyze the NCO-SH cross-linking. A second layer of components A + B is applied after the sand has been sprinkled over the first layer. Example 13 A two-component clear coat was prepared. The first component comprised pentaerythritol3-mercaptopropionate, 0.8 wt.% (on total weight of solid binder) Speedcure® BMS, 14.6 wt.% (on total weight of solid binder) butyl acetate and an additive for reducing the surface tension (Byk® 306). The second component comprised a polyisocyanate (Tolonate® HDT LV), 7.7% (on total solid binder) xylene and 5.2% (on total solid binder) oxazolidine (Hardener OZ, Bayer). The components were stoichiometrically mixed before application. The pot life was 20 minutes, The sample was used to apply a clearcoat (approx. 60 µm) on panels with a blue (Halcyon Blue M.2c) solvent based basecoat (Autobase® Plus of Akzp Nobel Car Reflnishes). After 3 minutes flash-off, these panels were irradiated with UV-A light from 4 TL-10R tubes (Philips lightning: 11-13 mW/cm2). The through cure time of the clearcoat was 14 minutes (at 45% RH). The through cure time of these panels without UV (shadow-cure) was approximately 90 minutes (at 45% RH). Example 14 Example 13 was repeated, while 4% (on weight) oxazolidine was added to the solvent borne basecoat After drying of the basecoat, the two component composition of example 1 was used to apply a clearcoat of 60 µm on this basecoat. After flash-off the panel was irradiated by UV-A light. The through cure was accelerated from 14 to 9 minutes. Example 15 A two component UV-primer was made with a pigment volume concentration PVC of 30. The first component comprised pentaerythritol 3- mercaptopropionate, isobutyl acetate, 0,3 wt.% (on total weight of solid binder) Disperbyk® 110, 52,8 wt.% (on.total weight of solid binder) Zeeospheres® W- 210 (available from 3M), Aerosil® R 972 (available from Degussa) and 35,9 wt.% (on total weight of solid binder) ASP 600 (available from Engelhard corp.). These solid materials were milled in the pentaerythritol 3-mercaptbpropionate and isobutyl acetate with the help of a dissolver to 20 urn. At the end, 0,7 wt.% (on total weight of solid binder) of Byk® 306 was added. The second component comprised a polyisocyanate (Tolonate® HDT LV), xylene, 5,6 wt.% (on total weight of solid binder) of oxazolidine (Hardener OZ, Bayer) and 0,7 wt.% (on total weight of solid binder) of Speedcure® BMS. The components were mixed (the equivalence ratio SH:NCO = 100:125) before application. The pot life was approximately 20 minutes. The coating composition was applied on tlnplate with a draw bar. The (dry) layer thickness was 110-120 µm. After 3 minutes flash-off, these panels were irradiated with UV-A light. The through cure time of the primer was 15 minutes (at 45% RH). The coating was good sandable in 60 minutes. The through cure time of these panels without UV (shadow-cure) was approximately 60 minutes (at 45% RH). After 3 hours sanding was reasonable. We Claim: 1. Coating composition comprising: i) a curable material comprising one or more polythiols and one or more polyisocyanates wherein the equivalence ratio NCO : SH is between 1:2 and 2:1; and, ii) a latent base catalyst which is activatable by moisture. 2. The coating composition as claimed in claim 1, wherein the latent catalyst is selected from the group of oxazolidine, aldimine, ketimine, and enamine. 3. The coating composition as claimed in claim 1 or 2, wherein the latent catalyst is present in an amount of up to 20% relative to the weight of the curable material, e.g., 0.01 to 10 wt% or 0.9 to 6 wt.%. 4. The coating composition as claimed in any of the preceding claims, wherein the composition further comprises one or more photoinitiators. 5. The coating composition as claimed in claim 4, wherein the photoinitiator is present in an amount of up to 4% relative to the weight of the curable material, preferably between 0.001 - 1.2wt.%. 6. The coating composition as claimed in any one of the preceding claims, wherein the composition comprises a combination of oxazolidine and a photoinitiator. 7. The coating composition as claimed in to claim 6, wherein the composition comprises from 0.01 to 6% oxazolidone and from 0.01 to 2% photoinitator, relative to the weight of the curable material. 8. The coating composition as claimed in any one of the preceding claims, wherein the composition comprises an inorganic acid, e.g., nitric acid. 9. A thiol-isocyanate cross-linking system comprising the combination of oxazolidine and a photoinitiator as claimed in claim 6, wherein the photoinitiator forms radicals under the influence of light and the oxazolidine is used as a moisture-activatable catalyst. 10. The coating composition as claimed in claims 1 - 8, wherein the coating composition is used as a car repair primer or a car repair clear coat or a coating for concrete floors. Coating composition comprising one or more polythiols and one or more polyisocyanates and a latent base catalyst which is activatable by moisture, wherein the equivalence ratio NCO : SH is between 1 :2 and 2:1. The latent catalyst is selected from the group of oxazolidine, aldimine, ketimine, and enamine. The latent catalyst is present in an amount of up to 20% relative to the weight of the curable material. The composition further comprises one or more photoinitiators in an amount of up to 4% relative to the weight of the curable material.

Full Text

The present invention relates, to a coating composition comprising one or more
polythiols. one or more polyisocyanates. and a deactivated base catalyst.
Coating compositions based on polythiols and polyisocyanates are catalyzed by base
catalysts. To prevent premature cross-linking, the base catalysts can be blocked or
deactivated. WO 01/92362 discloses compositions based on thiol- isocyanate cross-
linking using a photoiatent base. To cure such coatings, the freshh' applied layers need to
be irradiated with actinic radiation of the right wavelengths. Hence, such coalings are less
useful when large surfaces are to be coated, such as garage floors and the like. Moreover,
some spots of the surface may be more difficult to irradiate. The curing speed on such
shadow spots is low.
The object of the invention is to provide a coating composition which has a long pot life
but a fast curing speed over the complete substrate, including shadow spots.
The object of the invention is achieved with a coating composition comprising one or
more polythiols, one or more polyisocyanates, and a deactivated base catalyst which is
activatable by moisture. The equivalence ratio NCO : SH, the number of NCO groups
relative to the number of SH groups, is between 1 :2 and 2:1.
Moisture activatable base compounds, such as oxazolidines. are generally reactive with
isocyanate groups. For this reason, such compounds are used as crosslinkers for
polyisocyanates. Surprisingly, it was found that in thiol- isocyanate crosslinking systems
these compounds are not bound by the isocyanate groups on a substantial scale but rather
function as a catalyst for the thiol-isocyanate crosslinking under the influence of
moisture.

Oxarolldines are su.table compounds reacting with moisture to form a base
which is able to catalyze SH-NCO reactions. Suitable oxazolidines are for
oxample carbonato-bis-N-ethyl-2-isopropyl-1,3-oxazolidina, commercially
available as Incozol® LV, 2-(3-heptyl)-N-butyt-1,3-oxazolane, commercially
available as Incozol® 2, and urethane bis-oxazolidines, such as those which are
commercially available as Hardener OZ. Other suitable latent base compounds
are for example enamines, ketimines, and aldimines.
The latent catalyst can be present in an amount of, e.g., up to 20% relative to
the weight of the curable material, e.g. 0.01 - 6%, such as 3.5 - 5%.
In a further embodiment, the coating composition may further comprise one or
more photoinitiators, forming radicals under the influence of light. Surprisingly, it
was found that drying was accelerated considerably, about 2-20 times, even
in pigmented systems applied in thick layers. This effect particularly occurred
when using oxazoiidine as a catalyst The photoinitiator can for example be
present in an amount of 0.01 - 2.0% relative to the weight of the curable
material, e.g, in an amount of 0.1 to 1.0%.
Suitable photoinitiators are for example ethyl 4-(dimethylamino)benzoate
(Speedcure® EPD), 2-(dimethylamino)ethyl benzoate (Speedcure® DMB), 4-
benzoyl-4'-methyldiphenyl sulphide (Speedcure® BMS), 2-ethylhexyl-4-
dimethylaminobenzoate (Speedcure® EHA); 1,3,5-trimethylbenzoyl
diphcnylphosphine oxide (Speedcuro® TPO), all available from Lambson. A
photoinitiator for use in visible daylight is for instance bis (4-cylcopentadien-1-
yl)-bis [2,6-difluoro-3-(1H-pyrrol-yl)-phenyl]titanium (Irgacure® 784, Ciba
Specialty). Other suitablo photoinitiators include ketones, such as methyl ethyl
ketone, 2,3-butanedione, 1-hydroxy cyclohexyl phenyl ketone, 2-hydroxy-2-
methyl-1 -phenyl propan-1-one, and aromatic ketones, e.g., acetophenone,
benzophenone, 4-arninobenzo-phenone, 4,4'-diaminobenzophenone, 4,4'-
bis(dimethylamino) benzophenone, valero-phenone, hexanophenone, o-
methoxybenzophenone, a-phenylbutyrophenone, -γ-phenylbutyrophenone, p-

morpholinopropiophenone, dibenzosuberone, 4-morpholinobenzophenone, 4-
methoxyacetophenone, p-diacetylbenzene, 1,3,5-triacetylbenzene; benzoin
compounds, e.g., benzoin, benzoin methyl ether and benzoin ethyl ether, 4-
morpholinodeoxybenzoin; quinone and anthrone compounds, e.g.,
hydroquinone, anthraquinone, napthoquinone, acenaphthenequinone, and 3-
methyl-1,3-diazo-1,9-benzanthrorie; phenolic compounds, e.g., 2,4-dinitro-
phenol; phosphine compounds such as triphenyl-phosphine and tri-o-
tolyphosphine; azo compounds, e.g., azoblslsobutyronitrile; thloxanthone
compounds including for example 2,4-dlethoxythioxanthone,
isopropylthtoxanthone (Speedcure® ITX), 1-chloro-4-propoxythioxanlhone
(Speedcure® CPTX); and 2-chlorothioxanthone; and various other compounds,
e.g., benzll, benzaldehyde, 1-naphthaldehyde, α-totralone, 2-
acetylphenanthrene, 3-acetylphenanthrene, 9-acetyl-phenanthrene, 10-
thioxanthenone, 3-acetylindole, 9-fluorenone, 1-indanone, 9-xanthenono, 9-
thioxanthenone, 7-H-benz[de]anthracen-7-one, 1-acetonaphthone and 2-
acetonaphthone. Alternatively, the photoinitiator can be a phosphine oxide
compound, such as 2,4,6-trimethyl benzoykjiphenyl phosphine oxide (Lucirin®
TPO, available from BASF) or acyl phosphine oxide compounds, such as mono-
bis- or tiisacyl phosphine oxide or mixtures thereof. An example of a
bisacylphosphine oxide photoinitiator is bis(2,4,6-trimethylbenzoyl)-phenyl-
phosphine oxide (Irgacure® 819, availablo from Ciba Specialty Chemicals) or
bls(2,6-dimethoxy-benzoyl)-2,4,4-trimethyl pentyl phosphino oxide (DMBAPO,
Irgacure® 403, available from Ciba Specialty Chemicals). Mixtures of different
photoinitiators may be used.
Alternatively, or additionally, one or more phototatent bases can be used, e.g.,
the photolatent bases as disclosed in WO 94728075 and EP-A 0 882 072.
Suitable photolatent bases include N-substituted 4-(o-nitrophenyl) dihydropy-
ndines, optionally substituted with alkyl ether and/or alkyl ester groups, and
quaternary organo-boron photoinitiators. An example of an N-substituted 4-(o-
nitrophenyl) dihydropyrldino is N-mothyl nifedipine (Macromolecules 1998, 31,
4798), N-butyl nifedipine, N-butyl 2,6-dimethyl 4-(2-nitrophenyl) 1,4-dihydropy-

ridine 3,5-dlcarboxylic acid diethyl ester, and a nifedipine according to the
following formula

i.e., N-methyl 2,6-dimethyl 4-(4,5-dimethoxy-2-nitrophenyl) 1,4-dihydropyridine
3,5-dicarboxylic acid diethyl ester. Examples of quaternary organo-boron
photoinitiators are disclosed in GB-A-2 307 473, such as

A further suitable alternative is a photolatent base belonging to the group of a-
amino acetophenones. Examples of α-amino acetophonones which can bo
used are 4-(methytthiobenzoyl)-1-rnethyl-1-rnorpholinoethane (Irgacure® 907 ex
Ciba Specialty Chemicals), (4-moipholinobenzoyl)-1-benzyl-1-dimethylamino
propane (Irgacure® 369 ex Ciba Specialty Chemicals) or an a-amino
acetophenone according to the following formula

Furthermore, it was found that for these light-accelerated moisture curing
systems, the pot life could be increased considerably by the addition of an
inorganic acid (such as nitric acid), even when small amounts, e.g., 0.005 -
0.05 wt.%, were used. The addition of small amounts of acid hardly influences
the cure time.

Suitable polythiols can be prepared by reacting hydroxyl group-containing
compounds with thiol group-containing acids, such as 3-mercaptopropionic
acid, 2-mercaptopropionic acid, thio-sallcylic acid, mercaptosuccinic acid,
mercaptoacetic acid, or cysteine. Examplos of suitable hydroxyl group-
containing compounds are diols, triols, and tetraols, such as 1,4-butane diol,
1,6-hexane diol, 2,2-dimethyl-1 ,3-propane diol, 2-ethyi-2-propyl-1,3-propane
diol, 1,2-, 1,3-, and 1,4-cyclohexane diols, and the corresponding cyclohexane
dimethanol, 1,1,1-trimothylo) propane, 1,2,3-trimethylol propane, and
pentaerythritol. Examples of compounds prepared according to such a method
include pontaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tetrakis
(2-mercaptoacetate), trimeth/ol propane tris (3-mercaptopnopionate),
trimethytol propane tris (2-mwcaptoproptanate), and trimethytol propane trts (2-
mercaptoacetate). Good results have been obtained with thmethylol propane
tris (3-mercapto propionate) and pentaerythritol tetrakis (3-mercapto
propionate). A further example of a compound prepared according to such a
method consists of a hyperbranched polyol core based on a starter polyol, e.g.,
trimethytol propane, and dimethylol propionic acid. This polyol is subsequently
esterified with 3-mercaptopropionic acid and isononanoic acid. Those methods
are described in EP-A 0 448 224 and WO 93717060.
Other syntheses to prepare compounds comprising poiythiols involve:
the reaction of an aryl or alkyl halide with NaHS to introduce a pendant thiol
group into the a;kyl and aryl compounds, respectively;
tho reaction of a Grignard reagent with sulphur to introduce a pendant thiol
group into the structure;
the reaction of a polymercaptan with a polyolefin according to a Michael
addition reaction, a nucleophilic reaction, an electrophilic reaction or a
radical reaction;
the reaction of a thiol-functional alcohol and an isocyanate-functional
compound, and
the reduction of disulphidos.

The polythiol may for example have one or more hydroxy! groups and have a
structure according to the following formula: T[(C3HeO)nCH2CHOHCH2SH]3,
with T being a triol such as trimethylol propane or glycerol. An example of such
a compound is commercially available from Henkel under the trademark Henkel
Capcure® 3/800.
Alternatively, the polythiol can for instance be a resin having a polyester resin,
polyurethane resin, polyacrylate resin, or polyether resin as backbone. These
isocyanate-reactive compounds may also comprise hydroxyl groups.
The polythiol may for instance be a polyester prepared from (a) at least one
polycarboxylic add or reactive derivatives thereof, (b) at least one polyol, and
(c) at least one thiol-functional carboxylic acid. The polyesters preferably
possess a branched structure. Branched polyesters are conventionally obtained
through condensation of polycarboxylic acids or reactive derivatives thereof,
such as the corresponding anhydrides or lower alkyl esters, with polyalcohols,
when at least one of the reactants has a functionality of at least 3. Examples of
suitable polycarboxylic acids or reactive derivatives thereof are
tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthaltc acid,
hexahydroph:halic anhydride, methyl hexahydrophthalic acid, methyl hexahy-
drophthalic anhydride, dimethytayclohexane dlcarboxylate, 1,4-cyclohexano
dicarboxylic acid, 1,3-cyciohexane dicarboxylic acid, phthalic acid, phthalic
anhydride, isophthaltc acid, terephthaiic acid, 5-tert. butyl isophthalic acid,
trimellitic anhydride, maleic acid, maleic anhydride, fumaric acid, succinic acid,
succinic anhydride, dodecenyl succinic anhydride, dimethyl succinate, glutaric
acid, adipic acid, dimethyl adipate, azelaic acid, and mixtures thereof. Examples
of suitable polyols include trimethylol propane, trimethylol ethane, glycerol,
1,2,6-hexanetriol, ethylene glycol, 1,2-propyleno glycol, 1,3-propylene glycol, 2-
methylpropane-1,3-diol, neoperttyl glycol, 2-butyl-2-ethyl-1,3-propano diol,
cyclohexane-1,4-dimethylol, the monoester of neopentyl glycol and hydroxy-
pivalic acid, hydrogenated Bisphenol A, 1,5-pentane diol, 3-methyl-pentane diol,

1,6-hexane diol, 2,2,4-trimethyt pentane-1,3-diol, dimethylol propionic acid,
pentaerythritol, di-trimethylol propane, dipentaerythritol, and mixtures thereof.
Examples of suitable thiol-functional organic acids include 3-mercaptopropionic
acid, 2-mercaptopropionic acid, thio-salicylic acid, mercaptosuccinic acid,
mercaptoacetic acid, cysteine, and mixtures thereof. Optionally, monocarboxylic
acids and monoalcohols may be used in the preparation of the polyesters.
Preferably, C4-C18 monocarboxylic adds and C6-C18 monoalcohols aro used.
Examplos of the C4-C18 monocarboxylic acids include pivalic acid, hexanoic
acid, heptanoic acid, octanoic acid, nonanoic acid, 2-ethylhexanoic acid,
isononanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid,
isostearic acid, stearic acid, hydroxystearic acid, benzoic acid, 4-tert. butyl
benzoic acid, and mixtures thereof. Examples of the C6-C18 monoalcohols
include cyclohexanol, 2-ethylhexanol, stearyl alcohol, and 4-tert butyl
cyclohexanol.
Alternatively, the polythiol may be a thiol-functional polyacrylate. Such
polyacrylate can be derived from (meth)acrylic monomers such as (meth)acrylic
acid, methyl (meth)acrylate, butyl (meth)acrylate, a vinyl derivative such as
styrene, and optionally hydroxy-functional acrylic monomers, such as hydroxy
ethyl (meth)acrylate, hydroxy propyl (meth)acrylate hydroxy butyl
(moth)acrylate and the like, or mixtures thereof, with the terms (meth)acrylate
and (moth)acrylic acid referring to both methacrylate and acrylate and
methacrylic acid and acrylic acid, respoctivoty. Tho thiol group is introduced by
the reaction product of dimethyl-m-isopropenyl benzyl isocyanate and mercapto
ethanol. Alternatively, glyctdyl methacrylate is introduced into the polymer to
prepare an epoxy-functional polyacryate. The epoxy groups are then reacted
with suitable thiol-functional organic acids such as mentioned above. The
polyacrylate is prepared by conventional methods, for instance, by the slow
addition of appropriate monomers to a solution of an appropriate polymerization
initiator, such as an azo or peroxy initiator.

Also included in the coating compositions of the invention may be di-, tri-, or
higher thiol-functional diluents such as ethane dithtal or bls-beta-mercapto-ethyl
sulphide. Preference is given to the use of higher-molecular weight thiol-
functional compounds, which may be obtained by reaction of a polythiol-
funotional compound with a polyisocyanate.
Suitable organic polyisocyanates include polyfunctional, preferably free
polyisocyanates, with an average NCO functionality of 2.5 to 5, and may be
(cyclo)aliphatic, araliphatic or aromatic in nature. The organic polyisocyanate
may be blocked. The polyisocyanate may include biuret, urethane, uretdione,
and isocyanurate derivatives. Examples of these organic polyisocyanates
include 1,6-diisocyanatohexane, Isophororte diisocyanate, 2,4-toluene diiso-
cyanate, 2,6-toluene diisocyanate, diphenyl mothane-diisocyanato, 4,4'-
bis(isocyanato-cydohexyl) methane, 1,4-diisocyanatobutane, 1,5-diisocyanato-
2,2-dimethyl pentane, 2,2,4-tr1methyl-1,6-diisocyanatohexane, 1,10-difeocyana-
todecane, 4,4-diisocyanato-cyclohexane, 2,4-hexahydrotoluene diisocyanate,
2,6-hexahydrotoluene diisocyanate, norbomane diisocyanate, 1,3-xylylene
diisocyanate, 1,4-xylylene diisocyanate, 1-isocyanato-3-(isocyanato methyl)-1-
methyt cyclohexane, m-ot,a-a',a'-tetramethyl xylylene diisocyanate, the above-
mentioned derivatives thereof, and mixtures thereof. Normally, these products
are liquid at ambient temperature and commercially available in a wide range.
Particularly suitable isocyanate curing agents are triisocyanates and adducts.
Examples thereof are 1 ,B-diisocyanatc-4-{lsocyanatomethyl) octane, the adduct
of 3 moles of toluene diisocyanate to 1 mole of trimethyld propane, the
isocyanurate trimer of 1,6-diisocyanatohexane, the isocyanurate trimer of
isophororte diisocyanate, the uretdione dimer of 1,6-diisocyanatohexane, the
biuret trimer of 1,6-diisocyanatohexane, the adduct of 3 moles of m-a.a-a'.u'-
tetramethyl xylene diisocyanate to 1 mole of trimethyloi propane, and mixtures
thereof. Preferred are cyclic trimers (isocyanurates) and uretdiones of 1,6-
hexane diisocyanate and isophorone diisocyanate. Usually these compounds
contain small quantities of their higher homoiogues.

Optionally, a hydroxyl-functional compound comprising at least two hydroxyl-
functional groups may bo presont In the curablo material. Tho hydroxyl-
functional compound comprising at least two hydroxyl-functional groups may be
selected from polyester polyols, potyether pofyols, polyacrylate polyols,
polyurethane polyols, cellulose acetobutyrate, hydroxyl-functional epoxy resins,
alkyds, and dendrimeric polyols such as described in WO 93/17060. Also,
hydroxyl-functional oligomers and monomers, such as castor oil and tnmethyiol
propane, may be included. A suitable polyol is an acrytate polyol, such as for
example Seta lux® 1157 available from Nuplex.
The polyisocyanate can be mixed with the porythiols by any suitable technique.
However, simply stirring usually is sufficient Sometimes it can be useful to
dlluto the polyisocyanate somewhat with an organic solvent such as ethyl
acetate or 1-methoxy-2-propyl acetate to reduce Its viscosity.
The pot life of the coating composition at ambient temperature usually is more
than a quarter of an hour, e.g. more than half an hour, up to about 5 hours or
even longer, depending on the catalysts used and their amounts and whether or
not blocking acids are used.
The composition according to the present invention can be a solvent borne
composition or a solvent-free composition. Since the composition may be
composed of liquid oligomers, it is especially suitable for use as a high-solids
composition or a solvent-free composition. The coating composition can also be
used in powder coating compositions and hot melt coatings compositions.
Preferably, the theoretical volatile organic content (VOC) in tho composition is
less than about 450 g/l, more preferably less than about 350 g/l, most preferably
less than about 250 g/l, or even less than 100 g/l.
The coating compositions may further comprise other ingredients, additives or
auxiliaries, such as pigments, dyes, emulsifiers (surfactants), pigment

dispersion aids, photosensitizes, levelling agents, anti-cratering agents,
antifoaming agents, antisagging agents, heat stabilisers, UV absorbers,
antioxidants, and fillers.
The coating composition of the present invention can be applied to any
substrate. The substrate may be, for example, metal, plastic, wood, glass,
ceramic, or somo other coating layer. The other coating layer may be comprised
of the coating composition of the current invention or it may bo a different
coating composition. The coating compositions of the current invention show
particular utility as a floor coating, e.g. on concrete floors or as a coating or
repair coating, e.g. as a primer or as a dear coat, for vehicles, such as cars,
trains, air planes or the like.
The coating compositions can be applied by conventional means such as by
spray gun, brush, or roller, spraying being preferred. Curing temperatures are
generally between 0 and 100°C, e.g., between 0 and 30°C.
The invention is further illustrated by the following examples. In these examples
the compositions listed below are available as indicated.

The following test methods were used:
Pot life - The time during which the system could be brush-applied
after mixing the components;
Drying time - The coating composition was applied on a glass plate with
a draw bar. The layer thickness was 125 µm, the
temperature was 20° C. Drying was tested by means of a
BK Drying Recorder. The results can be classified as
follows:
Phase 1: the line traced by the pin doses up again
("open time");
Phase 2: the pin traces a straight line in the paint which
does not close up again ("tack-free time");
Phase 3: the pin traces a scratchy line ("dust free");
Phase 4: the pin does not leave a scratch ("scratch-free
time").
Viscosity measured using a Rheometer (Rheolab MC1, spindle: Z2
DIN); after 15 minutes resting, the viscosity was measured
over 1 minute with a speed of 150 rotations per minute.
This program was repeated several times.
Example 1
A two-component coating composition was prepared. The first component
comprised pentaerythritol 3-mercaptopropionate and 40% butyl acetate. The
second component comprised a polyisocyanate (Tolonate® HDT LV) and 6%
oxazolidine (Hardener OZ).
The components were stoichiometrically mixed before application. The Phase-4
cure time was 60 minutes (at 85% RH), the viscosity in the can at that time was:
0.13 Pa.s. The pot life was 3 hours.

Example 2
A two-component coating composition was prepared. The first component
comprised pentaerythritol 3-mercaptopropionate and 40% butyl acetate. The
second component comprised a polytsocyanate (Tolonate® HDT LV) and 6%
oxazolidirte (Incozol® 2).
The components were stolchiometrically mixed before application. The Phase-4
cure time was: 20 minutes (at 85% RH), the viscosity at that time was: 0.25
Pas.
Example 3
A two-component coating composition was prepared. The first componont
comprised pentaerythritol 3-mercaptoproplonaie and 40% butyl acetate. The
second component comprised a polyisocyanate (Tolonate® HDT LV) and 6%
oxazolidine (Incozol® LV).
The components were stoichiornetrically mixed before application. The Phase-4
cure time was: 80 minutes (at 85% RH), the viscosity at that time was: 0.10
Pa.s.
Example 4
To the formulation in Example 1,1% Speedcure® BMS was added. The sample
was applied on a panel and the panel was irradiated with a UV-A lamp at 20 cm
(UVAHAND-250, 35 mW/cm2). The Phase-4 cure time was reduced to 10
minutes. The pot life was not affected by the addition of Speedcure® BMS and
remained 3 h.

Example 5
To the formulation in Example 1, 1% Speedcure® BMS, 10% TiO2 (Tipure®
R902-38), and 1% organic black (Colour Black FW2) wore added. Tho sample
was applied on a panel and the panel was irradiated with the UV-A lamp at 20
cm. The Phase-4 cure time was reduced to 20 minutes.
Example 6
To the formulation in Example 1,1% Irgacure® 784 was added. The sample
was applied on a panel and the panel was irradiated with a 1000 W construction
lamp at 50 cm. The Phase-4 cure time was reduced to 3 minutes. The pot life
was not affected by the addition of Irgacure® 784.
Example 7
To the formulation in Example 4, 0.03% HNO3 was added. The sample was
applied on a panel and the panel was irradiated with the UV-A lamp at 20 cm.
The Phaso-4 cure time remained 10 minutes. The pot life was doubled.
Example 8
A solvent free, two-component coating composition was prepared. The first
component comprised pentaecythrttol 3-mercaptopropionate and 1%
Speedcure® BMS. The second component comprised a polyisocyanate
(Totonate® HDT LV) and 2% oxazolidine (Incozol® LV). The sample was appiied
on a panel and the panel was irradiated with the UV-A lamp at 20 cm. The
Phase-4 cure time was 20 minutes (at 60% RH). The pot life was 45 minutes.

Example 9
A two-component coating composition was prepared. Tho first component
comprised pentaerythritol 3-mercaptopropionate and 40% butyl acetate. The
second componont comprised a polyisocyanate (Dosmodur® E14, Bayer) and
6% oxazolidine (Hardener OZ).
The components were stoichiometrically mixed before application. The Phase-4
cure time was 1.5 h (60% RH), the potlife was 2 h.
Example 10
A two-component coating composition was prepared. The first component
comprised pentaerythritol 3-mercaptopropionate and 40% butyl acetate. The
second component comprised a polyisocyanate (Desmodur® DN) and 6%
oxazolidine (Hardener OZ).
The components were stoichiometrically mixed before application. The Phase-4
care time was 1.5 h (60% RH), the pot life was 2 h.
Exampio 11
A two-component coating composition was prepared. The first component
comprised pentaerythritol 3-mercaptopropionate and 40% butyl acetate. The
socond component comprised a polyisocyanate (Totonate® HDT LV) and 6%
ketimine (Vestamin® A139).
The components were stoichiometrically mixed before application. The Phase-4
cure time was 2.0 h (60% RH), the pot life was 2 h.

Comparative example 1
A two-component coating composition was prepared. The first component
comprised pentaorythritol 3-mercaptopropionato, 15% butyl acetate, and 0.25%
triphenylphospine. The second component comprised a polyisocyanate
(Totonate® HDT LV) and 2% acrylate (Actilane®411).
The components were stoichiometncally mixed before application. The Phase-4
cure time was: 1.5 h (at 20*C and 85% RV), the pot life was 30 minutes.
Comparative example 2
A two-component coating composition was prepared. The first component
comprised pentaerythritol 3-mercaptopropionate, 15% butyl acetate, and 0.05%
Ancamine® k54 (Air Products). The second component comprised a
polyisocyanate (Tolonate® HDT LV, Rhodia).
The components were stoichiometrically mixed before application. The Phase-4
cure time was: 3.0 h (at 20°C and 85% RV), the pot life was 20 minutes.
Example 12
A three-component floor coating was prepared including a thiol component A,
an isocyanate component B and a catalyst component C. Component A
comprised 83 wt.% pentaerythrttol tetra (3-mercaptopropionate), 16,5 wt%
TiO2 (Tipuro® R 902) and about 0,5 wt% of a silicone based defoamer (Byk® A-
525). A pigment paste is also added to component A, in any desired amount If
a black pigment paste is used, the paste should contain, per 1 parts by weight
(pbw) of carbon black (Farbruss FW2), 20 pbw of pentaerythritol tetra (3-
mercaptopropionate), 0,2 pbw of Byk® A-525 defoamer, and 0,04 pbw of
methyl-di-ethanolamine to neutralize the acidity. Component B comprises 100
% of the isocyanurate of hexamethylene diisocyanate (Tolonate® HDT-LV2).

Component C comprises 120 pbw sand, 15 pbw quartz sand and 1 - 4 wt.% of
Incozol® 2.
Components A and B were mixed in a ratio A : B = 48 : 52 and applied on a
concrete substrate. Subsequently, the sand component C was sprinkled over
the freshly applied layer to catalyze the NCO-SH cross-linking. A second layer
of components A + B is applied after the sand has been sprinkled over the first
layer.
Example 13
A two-component clear coat was prepared. The first component comprised
pentaerythritol3-mercaptopropionate, 0.8 wt.% (on total weight of solid binder)
Speedcure® BMS, 14.6 wt.% (on total weight of solid binder) butyl acetate and
an additive for reducing the surface tension (Byk® 306).
The second component comprised a polyisocyanate (Tolonate® HDT LV), 7.7%
(on total solid binder) xylene and 5.2% (on total solid binder) oxazolidine
(Hardener OZ, Bayer).
The components were stoichiometrically mixed before application. The pot life
was 20 minutes, The sample was used to apply a clearcoat (approx. 60 µm) on
panels with a blue (Halcyon Blue M.2c) solvent based basecoat (Autobase®
Plus of Akzp Nobel Car Reflnishes). After 3 minutes flash-off, these panels were
irradiated with UV-A light from 4 TL-10R tubes (Philips lightning: 11-13
mW/cm2). The through cure time of the clearcoat was 14 minutes (at 45% RH).
The through cure time of these panels without UV (shadow-cure) was
approximately 90 minutes (at 45% RH).

Example 14
Example 13 was repeated, while 4% (on weight) oxazolidine was added to the
solvent borne basecoat After drying of the basecoat, the two component
composition of example 1 was used to apply a clearcoat of 60 µm on this
basecoat. After flash-off the panel was irradiated by UV-A light. The through
cure was accelerated from 14 to 9 minutes.
Example 15
A two component UV-primer was made with a pigment volume concentration
PVC of 30. The first component comprised pentaerythritol 3-
mercaptopropionate, isobutyl acetate, 0,3 wt.% (on total weight of solid binder)
Disperbyk® 110, 52,8 wt.% (on.total weight of solid binder) Zeeospheres® W-
210 (available from 3M), Aerosil® R 972 (available from Degussa) and 35,9
wt.% (on total weight of solid binder) ASP 600 (available from Engelhard corp.).
These solid materials were milled in the pentaerythritol 3-mercaptbpropionate
and isobutyl acetate with the help of a dissolver to 20 urn. At the end, 0,7 wt.%
(on total weight of solid binder) of Byk® 306 was added.
The second component comprised a polyisocyanate (Tolonate® HDT LV),
xylene, 5,6 wt.% (on total weight of solid binder) of oxazolidine (Hardener OZ,
Bayer) and 0,7 wt.% (on total weight of solid binder) of Speedcure® BMS.
The components were mixed (the equivalence ratio SH:NCO = 100:125) before
application. The pot life was approximately 20 minutes. The coating composition
was applied on tlnplate with a draw bar. The (dry) layer thickness was 110-120
µm. After 3 minutes flash-off, these panels were irradiated with UV-A light. The
through cure time of the primer was 15 minutes (at 45% RH). The coating was
good sandable in 60 minutes. The through cure time of these panels without UV
(shadow-cure) was approximately 60 minutes (at 45% RH). After 3 hours
sanding was reasonable.

We Claim:
1. Coating composition comprising:
i) a curable material comprising one or more polythiols and one or more
polyisocyanates wherein the equivalence ratio NCO : SH is between 1:2 and 2:1; and,
ii) a latent base catalyst which is activatable by moisture.
2. The coating composition as claimed in claim 1, wherein the latent catalyst is
selected from the group of oxazolidine, aldimine, ketimine, and enamine.
3. The coating composition as claimed in claim 1 or 2, wherein the latent catalyst is
present in an amount of up to 20% relative to the weight of the curable material, e.g., 0.01
to 10 wt% or 0.9 to 6 wt.%.
4. The coating composition as claimed in any of the preceding claims, wherein the
composition further comprises one or more photoinitiators.
5. The coating composition as claimed in claim 4, wherein the photoinitiator is
present in an amount of up to 4% relative to the weight of the curable material, preferably
between 0.001 - 1.2wt.%.
6. The coating composition as claimed in any one of the preceding claims, wherein
the composition comprises a combination of oxazolidine and a photoinitiator.
7. The coating composition as claimed in to claim 6, wherein the composition
comprises from 0.01 to 6% oxazolidone and from 0.01 to 2% photoinitator, relative to the
weight of the curable material.
8. The coating composition as claimed in any one of the preceding claims, wherein
the composition comprises an inorganic acid, e.g., nitric acid.

9. A thiol-isocyanate cross-linking system comprising the combination of
oxazolidine and a photoinitiator as claimed in claim 6, wherein the photoinitiator forms
radicals under the influence of light and the oxazolidine is used as a moisture-activatable
catalyst.
10. The coating composition as claimed in claims 1 - 8, wherein the coating
composition is used as a car repair primer or a car repair clear coat or a coating for
concrete floors.

Coating composition comprising one or more polythiols and one or more polyisocyanates
and a latent base catalyst which is activatable by moisture, wherein the equivalence ratio
NCO : SH is between 1 :2 and 2:1. The latent catalyst is selected from the group of
oxazolidine, aldimine, ketimine, and enamine. The latent catalyst is present in an amount
of up to 20% relative to the weight of the curable material. The composition further
comprises one or more photoinitiators in an amount of up to 4% relative to the weight of
the curable material.

COATING COMPOSITION BASED ON THIOL-NCO CURING

Documents:

Inventors:

PCT Conventions: