GB2176197A - Vapor permeation curable coatings comprising polymercaptan resins and multi-isocyanate curing agents - Google Patents

Abstract

A method for curing a film of a coating composition under vapor permeation curable conditions comprises exposing a coating composition to a vaporous tertiary amine catalyst. The coating composition can be in the form of an atomizate which is concurrently generated and mixed with a vaporous tertiary amine catalyst followed by application to a substrate, or can be an applied film of the coating composition which is exposed to the vaporous tertiary amine catalyst. The coating composition comprises a polymercapto-compound and a multi-isocyanate curing agent. The coating composition can be formulated to contain very high solids content (e.g. in excess of 70% and on up to 100% non-volatile solids). Alternatively, the coating composition comprises a polyol and a multi-isocyanate curing agent and the curing is effected in the presence of a thio-urethane compound formed by the reaction of a mercaptan compound and an isocyanate compound.

Description

SPECIFICATION Vapor permeation curable coatings comprising polymercaptan resins and multi-isocyanate curing agents The present invention relatesto vapor permeation curable coatings and more particularly to the synthesis and utilization of polymercapto resinstherefor.

Vapor permeation curable coatings traditionally are a class of coatings formulated from aromatic hydroxylfunctional polymers and multi-isocyanate cross-linking agents wherein an applied film thereof is cured by exposure to a vaporous tertiary amine catalyst. In orderto contain and handlethevaporoustertiaryamine catalyst economically and safely, curing chambers were developed. Curing chambers typically are substantially empty boxes through which a conveyor bearing the coated substrate passes and in which the vaporous tertiary amine, normally borne by an inert gas carrier, contacts such coated substrate. The use of aromatic hydroxy-functional polymers is recommended if a stable one-packsystem is required. If two-packformulations are acceptable, then use of aliphatic hydroxyl-functional resins can be made.Multi-isocyanatecrosslinking agents in traditional vapor permeation curable coatings contain at least some aromatic isocyanate groups in orderfor practical cure rates to be achieved.

Such traditional vapor permeation curable coatings requirements have been altered to a degree bythe vaporous amine catalyst spray method disclosed by Blegen in application U.S.S.N. 06/615,135,filed May30, 1984. Such vaporous catalyst spray method relies on the concurrent generation of an atomizate of a coating composition and a carrier gas bearing a catalytic amountof a vaporous tertiary amine catalyst. Such generated atomizate and vaporous catalytic amine-bearing carrier gas flow are admixed and directed onto a substrate to form a film thereof. Curing is rapid and use of a curing chamber is not required. Moreover, all aliphatic isocyanate curing agents can be utilized in such spray process. Hydroxyl groups on the resin, however, still are required.

One drawback to the requirement of aromatic hydroxyl groups on the resin is the inherent limitationwhich such aromaticity provides in formulating high solids coatings. The same is true of the requirement of aromaticity in the multi-isocyanate cross-linking agent. Such non-volatile solids content restriction even applies two the vaporous amine catalyst spray method described above.

The present invention solves many of the limitations which have been placed on chamber cured vapor permeation curable coatings. The method for curing a film of a coating composition in accordance with the present invention comprises exposing said coating composition as an atomizate or as an applied film to a vaporous tertiary-amine catalyst. The coating composition comprises a polymercapto-compound and a multi-isocyanate curing agent. As an applied film, the coating composition is cured by exposure of an applied film of said coating composition to a vaporous tertiary amine catalyst in a curing chamber. Alternatively, an atomizate of said coating composition can be generated and admixed with a vaporous tertiary amine catalyst, which mixture then is applied to a substrate and cured.

Another embodiment ofthe present invention involves the coating composition comprising a hydroxylfunctional compound, a polymercapto-compound, and a multi-isocyanate curing agent. The curing agent may be an all aliphtic isocyanate curing agent and the polymercapto-compound can be a reactive diluent present in small proportions for catalyzing or enhancing the cure ofthe polyol resin and the aliphatic isocyanatecuring agent.

Advantages of the present invention include the abilityto formulate high solids coating compositions containing upwards to 100% non-volatile solids content. Another advantage is the ability to utilize all aliphatic isocyanate-containing curing agents and still achieve rapid cure in a curing chamber. Another advantage is the unusual high gloss which polymercapto-containing vapor permeation cured coatings possess when cured in a curing chamber. These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein.

The use of polymercapto-functional monomers, oligomers, or polymers in vapor permeation curable coatings retains the advantageous properties achieved in the use of aromatic hydroxyl-functional compounds including the ability to formulate single package systems which are storage stableforseveral hours on upto several days, but which formulations rapidly cure at room temperature by exposure to vaporous tertiary amine catalysts. Several unique benefits additionally are achieved by the use of such resinous or nonresinousthiols. One ofthese benefits is the ability to formulate very high solids coatings ranging on upto 100% non-volatile solids.Such higher solids content, in part, is due to the freedom which the use ofthiols permits in reducing aromatic content of both the resin and the curing agent. That is, aromaticity adjacentthe mercapto groups is not required for storage stability norforcurabilityofthecoating composition. Also, aromaticity is not required ofthe curing agent in orderforroom temperature rapid cure to be achieved in the presence of vaporoustertiary amine catalysts. It will be appreciated that aromaticity was quite desirable in coating compositions when conventional chamber cure techniques were employed. Another benefit in the ability to formulate coating compositions diminished in aromatic groups isthe abilityto increasetheflex- ibility ofthe cured coating composition.This is true since it is difficult to arrive at a very flexible system with high elongation since aromatic groups tend to impart stearic hindrance to the polymer resulting in increased brittleness. Of course, traditional vapor permeation curable coating compositions contained at least somme aromatic curing agent in order four rapid cure to be achieved and contained aromatic hydroxyl functionality on the resin in orderto retain benefits of increased pot life ofthe coating composition. The use ofpolymercapto resins in accordancewith the precepts ofthe present invention provides greaterflexibility informulating vapor permeation curable coatings.

Monomers, oligomers, and polymers containing pendant mercaptan orthiol groups are commercially available or can be readily synthesized For example, mercaptan groups can be attached to the oligomeror polymer by esterification of free hydroxyl groups on the polymer,for example, a polyester, a polyacrylate, a polyether, orthe like with a mercaptan-terminated acid, such as 3-mercapto propionic acid orthiosalicylic acid. Similarly, an epoxy-functional resin can be reacted with a mercaptan-terminated acid under acidiccon- ditionsfor enhancing the preferential reaction of the carboxylic acid group with the epoxy group.Mercaptan groups can be introduced intothe oligomerorpolymeradditionally by reacting pendant primary orsec- ondaryamine grnups with a mercaptan-terminated acid or by reacting the free-isocyanate groups on an isocyanate-terminated oligomer or polymer with a mercaptan4erminated acid ester having at least two pen dant mercaptan groups. Further reaction schemes for introducing the mercaptan groups into an oligomeror polymer include conducting a Michael addition reaction of a polymercaptan with a polyolefin. Afurther synthesis scheme involvesthe reaction of an aryl or alkyl halide with NaSH for introducing a pendant mercaptan group into the alkyl oraryl compound.Itis possible even to react a Grignard reagent with sulfurfor introducing a pendant mercaptan group into the structure. In fact, a disulfide can be reduced (e.g. zincor other catalyst under acid conditions) to produce a mercaptan-functional monomer which may be used as a reactive diluent in vapor permeation cure coatings. Mercaptan groups can be introduced into the oligomer or polymer by numerous other methods which are well known in the art. The mercaptan groups are pendantly attached to the oligomer orpolymer. For purposes ofthis application, pendant mercaptan groups include terminal mercaptan groups. By pendantly attached is meant that such mercaptan groups are attached to the polymer chain orto a pendant side chain of the polymer or oligomer.The resinous material containing pendant mercaptan groups should be at least difunctional for cross-linking with the curing agent, though higher degrees offunctionality may be used additionally. Mono-functional mercaptan-containing resinous materials may be used as a reactive diluent, as further elaborated on below.

Various polymercaptans suitable for synthesizing the mercapto-functional resinous materials for usein forming the coating compositions ofthe present invention include, for example, 1,4-butane dithiol, 2,3- dimercapto propanol, toluene-3,4-dithiol, and alpha,alpha'-dimercapto-p-xylene. Other suitable active mer captan compounds include thiosalicylic acid, mercapto acetic acid, mercapto propionic acid, 2-mercapto ethanol, dodecane dithiol, didodecane dithiol, dithiol phenol, di-para-chlorothiophenol, dimercapto benzothiazole, 3,4-dimercapto toluene, allyl mercaptan, 1,6 hexane dithiol, 1 ,2-ethane dithiol, benzyl mercaptan, 1-octane thiol, p-thiocresol, 2,3,5,6-tetrafl u orothio ph enol, cyclohexyl mercaptan, methylthioglycolate, mercapto pyridines, dithioeryth ritrol, 6-ethoxy-2-mercaptobenzothiazol, and the like. Further useful mercaptans can be found in various catalogs of commercially-available mercaptans.

Virtually any oligomer, polymer, or resinous compound can be modified to contain pendant mercaptan-or thiol groups. Representative resinous materials containing mercaptan groups can be derived from,for example, epoxy and epoxy-modified diglycidyl ethers of bisphenol A structures, variousaliphatic polyethylene or polypropylene glycol (diglycidyl ether) adducts, and glycidyl ethers of phenolic resins. Other useful poly mers containing pendant mercaptan groups include polyamide resins,forexample, condensation products ofdimerized fatty acids coreacted with difunctional amine, such as ethylene diamine, followed by reaction with 3-mercapto propionic acid orthe like.A variety of acrylic resins and vinyl resins can be readily envisioned for modification in accordance with the precepts ofthe present invention additionally.

In this regard, is should be understood that virtually any conventional hydroxl-containing monomer, oli- gomer, or polymer previously proposed for use in vapor permeation curable coatings can be suitablymodi- fiend to contain pendant mercaptan groups for use in formulating coating compositions in accordance with the present invention. For exam ple, esterification (or transesterification) of such polyols with a mercaptanterminated acid is but onetechnique which can be readily envisioned for use in modifying such priorvapor permeation curable materials for use in formulating the coating compositions of the present invention.While not exhaustive, the following discussion discloses priorvapor permeation curable coating composition which can be suitably modified. U.S. Pat. No.3,409,579 discloses a binder composition of a phenol-aldehyde resin (including resole, novolac, and resitole),which preferably is a benzylicetherora polyether phenol resin.

U.S. Pat. No. 3,676,392 discloses a resin composition in an organic solvent composed of a polyether phenol or a methylol-terminated phenolic (resole) resin. U. S. Pat. No.3,429,848 discloses a composition likethatin U.S. Pat. No.3,409,579 with the addition of a silanethereto.

U.S. Pat. No. 3,789,O44disclosesa polyepoxide resin capped with hydroxybenzoicacid. U.S. Pat. No.

3,822,226 discloses a curable composition of a phenol reacted with an unsaturated material selected from unsaturated fatty acids, oils, fatty acid esters, butadiene homopolymers, butadiene copolymers, alcohols and acids. U.S. Pat. No.3,836,491 discloses a similar hydroxy-functional polymer (e.g. polyester, acrylic, polyether, etc.) capped with hydroxybenzoic acid. British Pat 1,369,351 discloses a hydroxy or epoxy compound which has been capped with diphenolic acid. British Pat. 1,351,881 modifies a polyhydroxy, polyepoxy, or polycarboxyl resin with the reaction product of a phyenol and an aldehyde.

U.S. Pat. No.2,967,117 discloses a polyhydroxy polyester while U.S. Pat. No.4,267,239 reacts an alkyd resin with para-hydroxybenzoic acid. U.S. Pat. No.4,298,658 proposes an alkyd resin modified with 2,6-dimethylolp-cresol.

U.S. Pats. Nos. 4,343,839,4,365,039, and 4,374,167 disclose polyester resin coatings especially adapted for flexible substrates. U.S. Pat. No.4,374,181 discloses resins especially adapted for application to reaction injection molded (RIM) urethane parts. U.S. Pat. No.4,331,782 discloses a hydroxybenzoicacid-epoxy adduct. U.S. Rat. No.4,343,924 proposes a stabilized phenol-functional condensation productofa phenolaldehyde reaction product. U.S. Pat. No.4,366,193 proposes the use of 1 ,2-dihydroxybenzene or derivatives thereof in vapor permeation curable coatings. U.S. Pat. No.4,368,222 discloses the uniqueness of utilizing vapor permeation curable coatings on surface-porous substrates offibrous-reinforced molding compounds (e.g. SMC). Finally, U.S. Pat.No.4,396,647 discloses the use of 2,3',4-trihydroxy diphenyl.

It will be appreciated that the foregoing aromatic-hydroxyl polymers or resins as well as many other resins suitably can be modified to contain mercaptan groups for use in formulating coating compositions in accordance with the precepts ofthe present invention.

Finally, the mercapto resinous materials of the present invention can be utilized for formulating coating compositions ideally suited forthe vaporous amine catalystspray method of Blegen, cited above. Such vaporous amine catalyst spray method comprises the concurrent generation of an atomizate of the coating composition and vaporous tertiary amine, which flows are admixed and applied to a substrate. The increased non-volatile solids content of coating compositions formulated with mercapto resinous materials even can permit the spray application of pigmented coatings containing in excess of 80% non-volatile solids.In this regard, the coating compositions may contain reactive orvolatile solventforformulating the coating compositions, for viscosity control for application (e.g. spraying orthe like) or for other purposes as is necessary desirable, or convenient in conventional fashion.

Multi-isocyanate cross-linking agents cross link with the mercaptan orthiol groups ofthe resulting adductcapped polymer underthe influence of a vaporous tertiary amine to cure the coating. Aromatic isocyanates may be preferred in orderto obtain reasonable pot life and the desired rapid reaction in the presence ofthe vaporous tertiary amine catalysts at room temperature. For high performance coatings, initial color as well as the discoloration dueto sunlight can be minimized by including at least a moderate level ofaliphaticiso- cyanate in the curing agent. Of course, polymeric isocyanates areemployed in order to reduce toxic vapors of isocyanate monomers.Further, alcohol-modified and other modified isocyanate compositions (e.g.thiocya- nates) find utility in the invention. Multi-isocyanates (i.e. polyisocyanates) preferablywill have from about 2-4 isocyanate groups per molecule for use in the coating composition ofthe present invention.Suitable multiisocyanates for use in the present invention include, for example, hexamethylene diisocyanate, 4,4'-toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymethyl polyphenyl isocyanate (Polymeric MDI or PAPI), m- and p-phenylene diisocyanates, bitolylene diisocyanate, triphenylmethane triisocyanate, tris-(4isocyanatophenyl) thiophosphate, cyclohexane diisocyanate (CHDI), bis-(isocyanatomethyl) cyclohexane (HsXDl), dicyclohexylmethane diisocyanate (H12MDl), trimethylhexane, dilsocyanate, dimer acid dilsocy- anate (DDI), dicyclohexylmethane diisocyanate, and dimethyl derivatives thereof, trimethyl hexamethylene diisocyanate, lysine diisocyanate and its methyl ester, isophorone diisocyanate, methyl cyclohexane diisocy anate, 1,5-napthalene diisocyanate, triphenyl methanetriisocyanate, xylylene diisocyanate and methyl and hydrogenated derivatives thereof, polymethylene polyphenyl isocyanate, chlorophenylene-2,4- diisocy- anate, and the like and mixyures thereof. Aromatic and aliphatic polyisocyanate dimers, trimers, oligomers, polymers (including biuret and isocyanurate derivatives), and isocyanate functional prepolymers often are available as preformed packages and such packages are suitable for ue in the present invention also.

The ratio of mercaptan groups from the mercapto resinous materials to the isocyanate equivalents ofthe multi-isocyanate cross-linking agents preferably should be greaterthan about 1:1 and can range on upto about 1:2. The precise intended application of the coating composition often will dictate this ratio or isocyanate index.

As noted above, a solvent orvehicle may be included as part ofthe coating composition. Volatile organic solvents may include ketones and esters for minimizing viscosity, though some aromatic solvent may be necessary and typically is part ofthe volatiles contained in commercial isocyanate polymers. Representative volatile organic solvents include, for example, methyl ethyl ketone, acetone, methyl isobutyl ketone, ethylene glycol monoethyl ether acetate (sold underthe trademark Cellosolve acetate), and the like. Organic solvents commercially utilized in polyisocyanate polymers include, for example, toluene, xylene, and the like.It should be noted that the effective non-volatile solids content of the coating composition can be increased by incorporation of a relatively low or non-volatile (high boiling) ester plasticizer which is retained for the most part in the cured film. Such suitable ester plasticizers include, for example, dibutyl phthalate, di(2-ethylhexyl) phthalate (DOP), and the like. The porportion of ester plasticizershould not exceed about 5-10% by weight, otherwise loss of mar resistance can occur.

The coating composition additionally can contain opacifying pigments and inert extenders such as, for example, titanium dioxide, zinc oxide, clays such as kaolinite clays, silica, talc, carbon or graphite (e.g. for conductive coatings), and the like. Additionally, the coating compositions can contain tinctorial pigments, corrosion-inhibiting pigments, and a variety of agents typically found in coating compositions. Such additi onal additives include, for example, surfactants, flow or leveling agents, pigment dispersants, and the like.

As to the performance requirements which are met by the coating composition, it should be noted thatthe coating composition, polymercapto resin and isocyanate cross-linking agent, can have a minimum pot life of at least 4 hours in an open pot and generallythe coating can be formulated to have a pot life which exceeds 8 hours and can range upto 18 hours or more. Such long pot life meansthat refilling the pot atthe plantduring shifts generaliy is not required.Moreover, the pot life ofthe coating composition in a closed containercan exceed one month depending upon formulation of the coating composition.-Afterstorage ofthecoating composition, the stored composition can be cutto application viscositywith suitable solvent(if required) and such composition retains all ofthe excellent performance characteristics which it initially possessed.

The vaporous amine catalyst will be atertiary amine include,for example, tertiary amines containing sub stituents such as alkyl, alkanol,aryl, aryl, cycloaliphatic, and mixtures thereof. Additionally, heterocyclictertiary amines may be suitable for use in the invention also.Representativetertiary amines include,forexample, triethyl amine, dimethyl ethyl amine, trimethyl amine, tributyl amine, dimethyl benzyl amine, dimethyl cyclo hexyl amine, dimethyi ethanol amine, diethyl ethanol amine,triethanol amine,pyridine,4-phenylpropyl pyridine, 2,4,6-collidine, quinoline, sioquinoline, N-ethyl morpholine, triethylene diamine, and the like and mixturesthereof. Additionally, it is conceivableto use amine oxides and quaternary ammonium amines depending uponthe practicality of providing such amines in the vaporous phase. A myriad of proprietary tertiary amine catalysts cu rrentyl are available and should function in the process additionally.It should be noted that the catalytic activity ofthe tertiary amine catalysts may be enhanced by the addition oaf complex salts to the coating composition as reported in the bulletin, "The Activation of IPDI by Various Accelerator Systems", Veba-Chemie AG, Gelsenkkirchen-Buer,West Germany. Thus the addition offerric, manganic, and aluminium salts to the liquid coating composition maybe implemented as an embodiment of the present invention.

While the proportion ofvaporous aminecatalystmay range on up to 6% or more, percentages of lessthan 1 volume-percenttypicaIlywill suffice, e.g. between about 0.25 and 1% by volume. Is should be cautioned that higher levels of amine catalyst are not recommended where airorsources of molecular oxygen are presentas exposive mixtures may result. The tertiaryamine catalyst is in vaporous form in a carrier gas which may be inert,such as nitrogen or carbon dioxid, or may be in air, or mixturestherof.Itwill be appreciated that depending upon the carrier gas and the particulartertiary amine catalyst of choice, certain minimum tem peratures and pressures of of the atomizing gas stream must be maintained in orderto ensure that the amine catalyst remains vaporous and does not condense in any lines. Additionally, the proportion of amine and carrier gas maybe altered depending upon whether a conventional curing chamber is utilizedorwhetherthe Blegen vaporous amine catalyst spray method is employed. In this regard,the preferred curing chambers for use with the coating compositions ofthe present invention are disclosed in U.S.Pats. Nos. 4,491,610 and 4,492,041 it must be recognized, however, that other curing chambers may be utilized, e.g. as disclosed in U.S. Pats. No. 3,851,402 and 3,931,684.

Upon exposure to vaporous tertiary amine catalyst, the mercaptan groups ofthe resinous material and isocyanate groups of the curing agent reactto form a cured network of carbamothioate groups (carbamothiolicacid ester groups). The reaction is rapid at room temperature enabling handling of cured parts in a shorttime following catalystcure, e.g. often as shortas 1-5 minutes. Such rapid curing retention ofthe coating compositions of the present invention is a decided benefit. In this regard, it will be appreciated that such rapid cure also takes placewhetherthe curing agent is all aliphatic, all aromatic, or a mixture of aliphatic and aromatic isocyanates.

In this regard, the use of a minor proportion of mono- or poly-functional mercaptan compounds as a reactive diluent (e.g. upto 20 weight percent) can markedly enhance the reaction between a polyol and aliphatic isocyanate groups of a curing agent undervapor permeation cure conditions. Of a positive benefit in using the mercaptan compounds to enhance the polyolisocyanate reaction, is the retention of performance propertieswhich the polyol and curing agentexhibitwithoutthe addition of the mercaptan compounds and even improvement of performance properties on occasion.Besides the in situ formation ofcarbamothioate groups which appearto be catalytic in nature with respect to the polyol/polyisocyanate reaction, preformed carbamothioate groups (preformed reaction productofa mercapto compound and an isocyanate compound) can be incorporated into the coating composition and a similar catalytic effect observed. The use-of a preformed compound may not provide the degree of improvement in cure response as is seen when such groupsare formed in situ during the cure ofthe coating composition. Thus, this aspect oftheinvention comprises the coating composition being cured in the presence of a compound containing one or more of the following moeities.

The compound from which such moiety is derived in this preformed embodiment of the invention can be represented as follows:

where R1 and R2 each is a monovalentorganic radical which desirably is an alkyl or an aryl group.

- As the data will demonstrate,the preformed embodiment ofthe invention does not appearto function to the same degree when an aliphatic isocyanate and an aliphatic polyol comprises the coating composition.

Some aromaticity, then, should be presentforthe preformed embodiment ofthe invention and preferably such aromaticity is derived from the aromatic isocyanate component ofthe coating composition. In the in situ preferred embodiment of the invention, however, the film properties and reaction occurring with the mer- captan compound appears to provide a stronger catalytic or promoting effect in the hydroxyl/isocyanate reaction so that aromaticity is not as an important factor as in the preformed embodiment. Nevertheless, some aromaticity is preferred in the coating composition for both embodiments of the invention.

Avariety of substrates can be coated with the coating compositions of the present invention. Substrates include metal, such as,forexample, iron, steel, aluminium, copper, galvanized steel, zinc, and the like. Additi- onally, the coating composition can be applied to wood, fiberboard, RIM, SMC, vinly, acrylic, other polymeric or plastic material, paper, and the like. Since the coating compositions can be cured at room temperature, thermal damageto thermally-sensitive substrates is not a limitation on use of the coating compositions ofthe present invention. Further, with the ability to use the Blegen vaporous amine catalyst spray method,the flexibility in use of the coating compositions of the present invention is enhanced even further.

The following examples show howthe present invention can be practiced bust should not be construed as limiting. In this application, all percentages and proportions ofthe coating compositions are by weight and all percentages and proportions of the vaporous tertiary amine catlayst are by volume, unless otherwise expressly indicated. Also, all units are in the metric system andall citations referred to herein are expressly incorporated by reference.

Examples Example 1 The nature of VPC cure response of mercaptan groups was evaluated and compared to aliphatic hydroxyl groups on molecules which are structurally identical butfortheir containing -SH or aliphatic -OH groups.

Viscosity and survey performance tests were conducted on the following-compositions.

TABLE 1 Coating (gm.) Ingredient Ethylene Glycol 18.6 -- -- -- -- -1,2-Ethanedithiol -- 18.4 -- -- -- - Butanediol -- -- 27.0 -- -- -1,4-Butanedithiol -- -- -- 12.2 -- - Hexanediol -- -- -- -- 35.4 -1,6-Hexanedithiol -- -- -- -- -- 15.0 Curing Agent) 69.3 46.2 69.3 23.1 69.3 23.1 MlBKSolventl2) 20.0 0 20.0 0 0 Wt-%Solids -- 92.9 -- 93.5 -- 94.0 (1) Desmodur N-3390 is an aliphatic isocyanate of hexamethylene diisocyanate (NCO content 20%, 90% solids in butyl acetate, equivalent weight of 210, Mobay Chemical Corporation, Pittsburgh, Pa.) (2) MIBKis methyl isobutyl ketone.

Each of the coating compositions were exposed to 0.9 vol-% triethylamine catalyst (TEA) in a curing chamber and evaluated with the following results.

TABLE 2A Swardr') MEK/2) Coating Viscosity (cups) Cure Time Hardness Rub Initial 4hr 24hr 48hr 72hr (sect RT(3) HTr4) RT HT 1 100 -- -- Separated 600(5) 18,16 14,20 100+ 1004 2 35 40 60 90 140 60 14,14 14,14 18 17 3 100 Semi- Gel 600(5) 6,8 6,8 15 100 4 125 15 15 25 40 60 6,8 6,8 9 8 5 Settled Gelled 600(5) ---(6)--- ---(7)--6 30 30 40 65 95 60 2,4 4,4 6 6 (1) Plate glass is defined as 100 for Sward Hardness; two readings per panel were taken.

(2) Methyl ethyl ketone (MEK) wetted rag rubbed over one area of cured film with moderate thumb pressure until glass substrate is visible.

(3) RT: Sample allowed to stand for 3 days at room temperature priorto testing.

(4) HT: Samples held at 160 C for 5 minutes aftervaporous amine catalyst exposure;then allowed to stand for3 days at room temperature prior to testing.

(5) Coating not cured after 600 sec. curetime.

(6) Reading could not be taken because the film bunched.

(7) Reading not possibie because film puddled.

TABLE 2B Solvent resistance (1) Coating H20 5% Na OH 10% H2SO4 Xylene RT HT RT HT RT HT RT HT 1 Pass Pass Fail Pass Fail Pass Pass Pass 2 Pass Pass -Pass Pass Pass Pass Pass Pass 3 Pass Pass Fail Fail Fail Pass Pass Pass 4 Pass Pass Fail Fail Pass Pass Pass Pass 5 Pass Pass Fail Fail Fail Pass Pass Pass 6 Pass Pass Pass Fail Pass Pass Pass Pass (1)The indicated solvent in a pool on the coating is placed under a watch glass for24 hours atambientindoor temperature and then the solvent resistance of the coating judged.

The above-tabulated results demonstrate the excellent combination of stability (as determined by the viscosity data) and rapid cure response. In fact, aliphatic hydroxyl groups cured only after two days, whereas the mercaptan groups were cured within a minute or so.

Example 2 Avariety of isocyanate curing agents were evaluated with glycol dimer captopropionate (GDP) inthe following coating compositions.

TABLE 3 Coating (g) Ingredient 1 2 3 4 5 6 7 8 9 GDP 24.4 18.3 12.2 12.8 12.2 61.0 18.3 21.0 24.4 Curing Agent(') 46.2 60.3 49.8 46.2 11.1 67.3 57.8 46.2 41.6 MIBK 5.0 -- 12.0 5.0 -- -- 5.0 3.0 5.0 Cellosolve(2) -- 13.0 -- -- -- -- -- -- - Acetate Wt-%Solids 87.3 58.4 56.9 74.2 100 100 72.5 89.2 93.0 (1) Coating 1-Curing agent was KL5-2444 aliphatic isocyanurate of hexamethylene diisocyanate (NCO content 20%, 90% solids in Cellosolve acetate, equivalent weight of 210, Mobay Chemical Corporation) Coating2-Curing agentwas Mondur HC, an approximately tetrafunctional reaction product of hexamethylene diisocyanate and toluene diisccyanate (11.5% NCO content, equivalent weight of 365, 60% solids in Cellosolve acetate/xylene, MobayChemical Corporation) Coating 3-Curing agent was trimethylolpropane-mα,α,α;',α'-metramethylxylene diisocyanate adduct Coating 4-Curing agent was Takenate D-120-N trimethylolpropane adduct of hydrogenated xylene diisocyanate (NCO content 11.0%, 75% solids in ethyl acetate,Takeda Chemical Industries) Coating 5-Cu ring agentwas methane diisocyanate Coating 6-Curing agent was meta-α,α,α',α'-tetramethylxylene diisocyanate (American Cyanamid Company) Coating 7-Curing agent was Desmodur Z-4370 isocyanurate of isophorone diisocyanate (NCO content ca.

12%, equivalent weight 350, 70% solids in ethylene glycol acetate/xylene (1:1), Mobay Chemical Corporation) Coating 8-Curing agentwas Desmodur N-3390 of Example 1 - Coating 9-Curing agent was Desmodur KL5-2550 aliphatic polyisocyanate (1 ,6-hexamethylene diisocyanate, Mobay Chemical Corporation) Cellosolve acetate is ethylene glycol monoethyl ether acetate (Union Carbide Corporation.

Each of the coatings was cured by exposure to 0.9 vol.-% triethylamine catalyst (except coatings 2 which was exposed to 0.5 vol.-% TEA) in a curing chamber and subjected to the survey performance tests described in Example 1.

TABLE 4A Sward(1) MEK(2) Coating Viscosity (cps) Cure Time Hardness Rub Initial 4hr 24hr 48hr 72hr (sec) RT(3) HTI4) RT HT 1 85 90 125 185 310 60 8,10 52,40 95 90 2 140 150 215 270 315 60 38,46 64,68 100+ 100+ 3 135 135 135 140 150 120 8,8 12,16 63 73 4 150 180 325 560 780 120 10,12 14,14 100+ 100+ LikeWater 240 34,38 72,68 2 2 6 15 20 20 15 25 60 38,32 76,66 9 3 7 105 115 115 125 155 60 60,60 52,48 100 100 8 -- -- Gelled -- -- 180 2,4 6,6 28 85 9 9 110 545 Gelled -- -- 60 6,8 4,4 35 18 TABLE 4B Solvent resistance Coating H20 5%NaOH 10% H2S04 Xylene RT HT RT HT RT HT RT HT 1 Pass Pass Pass Pass Fail Fail Pass Pass 2 Pass Pass Fail Fail Pass Pass Pass Pass 3 Pass Pass Fail Pass Pass Pass Pass Pass 4 Pass Pass Pass Fail Pass Pass Pass Pass 5 Pass Pass Fail Pass Pass Pass Pass Pass 6 Pass Pass Pass Pass Pass Pass Pass Pass 7 Pass Pass Fail Fail Pass Pass Pass Pass 8 Pass Pass Fail Fail Pass Pass Pass Pass 9 Pass Pass Fail Fail Fail Fail Pass Pass Again, the excellent stability (pot life) of coatingsformulated with mercaptan reactants in combination with good cure response is demonstrated. Also, these coatings possessed a very high solids contentwhich contributes to their uniqueness. Offurther note is the ability to utilize all-alipahtic multi-isocyanatecuring agents in formulating VPC coatings.

Example 3 In this series of tests, trimethylolpropane tris (3-mercaptopropionate), hereinafterTMP-3MP, served as the mercaptan-functional compound which was evaluated with a variety of curing agents as in Example 2.

TABLE 5 Coating (gm.) Ingredient 1 2 3 4 5 6 TMP-3MP 20.7 20.7 27.6 20.7 0.2 20.7 Curing Agent 44.4 60.3 46.2 20.8 33.6 11.1 MIBK -- -- -- 2.0 -- - CellosiveAcetate 3.0 13.0 10.0 -- -- - Wt-%Solids 69.5 60.5 82.6 94.3 100 100 "Coating 1-Curing agent was Mondur CB-60 aromatic polyisocyanate (NCO equivalent of 10.0to 1,0, Mobay Chemical Corporation).

Coating2-Curing agent was MondurHC of Example 2.

Coating 3-Curing agent was KL5-2444 of Example 2.

Coating 4-Curing agent was KL5-2550 of Example2/ Coating 5-Curing agent was meta-tetramethyl xylene diisocyanate of Example 2.

Coating 6-Curing agent was methane diisocyanate of Example 2.

Each of the coatings was cured by exposureto triethyl amine catalyst, 0.5 vol.-%forCoatings 1 and 2 and 0.9 vol.-% for all other coatings, in a curing chamber and subjected to the survey performance tests described above.

TABLE 6A Sward(1) MEK(2) Coating Viscosity (cups) Cure Time Hardness Rub Initial 4hr 24hr 48hr 72hr sec RTr31 HT(4) RT HT 1 150 140 195 -- 260 60 56,60 80,84 100+ 100+ 2 135 145 295 570 1186 60 62,60 62,64 100+ 100+ 3 Gelled -- -- -- -- 60 14,18 48,52 100+ 100+ 4 110 5800 Gelled -- -- 60 18,20 24,34 100+ 100+ 5 60 55 60 80 95 60 34,38 64,58 37 18 6 LikeWater -- -- -- -- 240 38,40 58,58 22 20 TABLE 6B Solvent resistance Coating H2O 5%NaOH 10%H2SO4 Xylene RT HT RT HT RT HT RT HT 1 Pass Pass Fail Pass Pass Pass Pass Pass 2 Pass Pass Fail Fail Fail Fail Pass Pass 3 Pass Pass Pass Pass Pass Pass Pass Pass 4 Pass Pass Pass Pass Pass Pass Pass Pass 5 Pass Pass Fail Pass Pass Pass Pass Pass The above-tabulated results once again establish the unique combination of properties exhibited by the inventive coatings: stability, good cure response,and the abilityto utilize aliphatic isocyanatecuring agents.

The performance ofthese coatings tends to match the performance of the coating tested in Example 2, even though a tri-functional mercaptan was used in this example compared to a di-functional mercaptan in Example 2. In this regard, compare Coatings 2 of Examples 2 and 3, Coating 3 of Example 3 and Coating 1 of Example2, Coating 4 of Example 3 and Coating 9 of Example 2, Coating 5 of Example 3 and Coating 6 of Example 2,and Coating 6 of Example3 and Coating 5 of Example 2. The most noticeable performance improvement in the coatings of Example 3 are in MEK RubsforCoatings4,5, and 6.

Example 4 The mercaptan-functional compounds evaluated were dimercaptodiethyl ether (DMDE), pentaerythritol tetra(3-mercaptopropionate) (PT-3MP), and dipentaerythritol hexa(3-mercaptopropionate) (DPH-3MP).

TABLE 7 Coating (gm) Ingredient r 2 3 4 5 DMDE 7.2 10.8 -- -- - PT-3MP -- -- 18.8 25.2 - DPH-3MP -- -- -- -- 14.2 Curing Agent 23.1 60.3 60.3 46.2 11.1 MIBK 10.0 -- -- 10.0 - CellosolveAcetate -- 7.0 15.0 - - Wt.-%Solids 69.4 60.2 58.4 82.1 100 "Coatings 1 and 4-Curing agentwas KL-5-2444 of Example 2.

Coatings 2 and 3-Curing agentwas Mondur HC of Example 2.

Coating 5-Curing agentwas methane diisocyanate of Example 2.

Coatings 1,4, and 5 were cured by exposureto 0.9 vol.-%triethylamiune catalyst in a curing chamberwhile Coatings 2 and 3 were cured by exposureto 0.5vol.-% ofthe same catalyst. The following survey performance test results were recorded.

TABLE 8A Solvent resistance (1) Sward MEK Coating Viscosity (cps) Cure Time Hardness Rub Initial 4hr 24hr 48hr 72hr (secJ RTr3) HT(4) RT HT 1 Gelled -- -- -- -- 60 12,14 62,64 95 100 2 110 220 1212.5 3200 8300 60 54,48 66,68 100+ 100+ 3 130 155 620 2975 Semi- 60 48,44 70,60 100+ 100+ Gel 4 130 Gelledin5minutes 60 34,30 72,66 100+ 100+ 5 MilkyGelied -- -- -- 300 12,12 10,10 50 50 (lowviscosity) TABLE 8B Solvent resistance (1) Coating H20 5% NaOH 10% H2S04 Xylene RT HT RT HT RT HT RT HT 1 Pass Pass Pass Pass Fail Fail Pass Pass 2 Pass Pass Fail Fail Pass Pass Pass Pass 3 Pass Pass Fail Fail Pass Pass Pass Pass 4 Pass Pass Pass Pass Pass Pass Pass Pass 5 Pass Pass Fail Pass Pass Pass Pass Pass Again, the uniqueness ofthe inventive coatings is demonstrated. The use of aliphatic or mixed aliphatic aromatic curing agents for Coatings 1 and 2 or Coatings 3 and 4 does not appear to alter performance significantly. The same can be said of the results of Coating 1 (Example 2), Coating 3 (Example 3), and Coating 4 (Example4) which used the same curing agent but a difunctional mercaptan (Example 2), atrifunctional mercaptan (Example 3), and a tetrafunctional mercaptan (Example4).

Example5 The following mercaptan functional compoundswere evaluated: polyethylene glycol di(3- mercaptopropionate) (MW of about 776, PEG 776-M), polyethylene glycol di(3-mercaptopropionate) (MW of about326, PEG 326-M), Rucoflex S-1028-210 (a difunctional polyester, OH no. of about 210, Ruco Chemical Co., Hicksville, N.Y.) capped with 3-mercaptopropionic acid (R-3MP), polypropylene glycol (DOW P1200, MW of about 1200, Dow Chemical Company, Midland, Michigan) capped with 3-mercaptopropionic acid (PG-3MP), Tone M-100 homopolymer (polycaprolactone monoacrylate homopolymer, MW of about 344, Union Carbide Corporation, Danbury, Connecticut) capped with 3-mercaptopropionic acid (T100-3MP), and Tone 200 (difunc tional polycaprolactone, OH no. of 215, Union Carbide Corporation, Danbury, Connecticut) capped with 3-mercaptopropionic acid (T200-3MP).

TABLE 9 Coating (gm.) Ingredient 1 2 3 4 5 6 PEG 776-M 38.2 -- -- -- -- - PEG 326-M -- 32.6 -- -- -- - R-3MP -- -- 72.8 -- -- - PG-3MP -- -- -- 56.5 -- - T100-3MP -- -- -- -- 41.5 - T200-3MP -- -- -- -- -- 34.9 Curing Agent* 23.1 46.2 46.2 23.1 23.1 23.1 MIBK -- 5.0 20.0 5.0 10.0 5.0 Wt.-%Solids 96.3 88.5 81.3 88.9 82.4 87.3 Desmondur N-3390 curing agent of Example 1.

Each of the coatings was cured by exposure to 0.9 vol-% triethylamine catalyst in a curing chamber except for Coating 1 which air dried in one minute. The following survey performance test results were recorded. 25 TABLE 10A Sward(1) MEK(2) Coating Viscosity(cps) Cure Time Hardness Rub lnitial 4hr -24hr 48hr 72hr (sec) RT(3) HTr4) RT HT 1 Exothermed and Gelled -- 8,6 8,8 2 3 2 90 90 135 -- -- 60 6,4 4,4 40 32 3 135 140 240 -- -- 60 24 2,4 30 16 4 150 Semi-Gelled -- -- 60 2,4 2,2 5 5 5 120 145 175 190 210 60 2,0 0,0 6 7 6 120 120 235 328 530 60 4,4 4,4 16 21 TABLE 10B Solvent Resistance Coating H20 5%NaOH 10% H2S04 Xylene RT HT RT HT RT HT RT HT 1 Fail Fail Fail Fail Fail Fail Pass Fail 2 Pass Pass Fail Fail Fail Fail Pass Pass 3 Pass Pass Fail Fail Pass Pass Pass Pass 4 Pass Pass Fail Fail Fail Fail Fail Fail 5 Pass Pass Fail Fail Fail Fail Pass Pass 6 Pass Pass Pass Fail Fail Fail Pass Pass With respectto Coatings 1 and 2,the lower molecularweight polyether (Coating 2) had a longer pot life, superior MEK resistance, and superior solvent resistance than the higher molecular weight polyether (Coating 1). With respect to Coatings 3 and 4, the Rucoflex-based system (Coating 3) yielded better pot life, solvent resistance,and MEK rub resistance compared to the polypropylene glycol-based system (Coating 4).The performance of both polycaprolactone-based systems (Coatings 3 and 4) were about equivalent.

Example 6 Several additional mercaptan-functional resins were synthesized from the ingredientsetforth below.

TABLE 11 Resin (moles) Ingredient 34 37 52 43 DN AdipicAcid 2 -- 3.5 2 - Neopentyl Glycol 1 -- -- -- - lso-PhthalicAcid 1 -- -- -- - Cardura E(1) 1 - -- -- - Trimethylol Propane 2 -- 1 1 - AcrylicAcid -- 1.0 -- -- - Isobutyl Acrylate -- 2.08 -- -- - 1,3-Butylene Glycol -- -- 3.2 - - PropyleneGlycol -- -- -- 1.64 - N-3390t2) -- -- -- -- 1.0 3-Mercaptopropionic Excess -- Excess - - Acid 2-Mercaptoethanol -- Excess -- -- Excess ThiosalicylicAcid -- -- -- 2 - (1) Cardura E is a glycidyl ester for Versatic 911 acid which is reported to be a mixture of aliphatic mostly tertiary acids with 9-11 carbon atoms (Cardura and Versatic being trademarks of Shell Chemical Company, NewYork, New York), (2) DesmodurN-3390 of Example 1.

Coatingswere compounded from the above-tabulated resins as follows: TABLE 12 Coating (gm) Ingredient 234 237 252 243 2DN Resin 34 41.9 -- -- -- - Resin 37 -- 105.5 -- -- - Resin 52 -- -- 48.8 -- - Resin 43 -- -- -- 48.8 - Resin DN -- -- -- -- 44.9 Curing Agent" 40.2 23.1 23.1 23.1 23.1 MIBK -- -- 21.0 10.0 - CellosolveAcetate 17.0 -- -- -- - N-Methyl Pyrrolidone -- -- -- -- 27.0 Wt.-%Solids 59.6 49.9 74.3 66.4 53.7 Coating 234-Curing agent was Mondur HC of Example 2.

Coatings 237,252,243, and 2DN-Curing agent was Desmodur N-3390 of Example 1.

Coating 234 was cured by exposure of 0.5 vol.-%triethylene catalyst while all other coatings were exposed to 0.9 vol.-% of catalyst. The following survey performance test results were recorded.

TABLE 13A Sward MEK/21 Coating Viscosity(cps) Cure Time Hardness Rub Initial 4hr 24hr 48hr 72hr (sec) RTr3J HT14 RT HT 234 145 180 760 340 400 60 76,68 74,74 65 100+ 237 60 Gelledin5 60 43,46 62,54 10 17 minutes 25 135 285 890 Gelled -- 60 4,2 4,2 8 0 243 130 8050 Gelled -- -- 60 28,30 44,36 42 37 2DN 135 135 200 245 330 180 18,22 34,32 11 19 TABLE 13B Solvent resistance (1) Coating H20 5% NaOH 10% H2S04 Xylene RT HT RT HT RT HT RT HT 234 Pass Pass Fail Fail Pass Pass Pass Pass 237 Fail Pass Fail Fail Pass Pass Fail Fail 252 Pass Pass Fail Fail Fail Fail Pass Pass 243 Pass Pass Fail Fail Pass Pass Pass Pass 2DN Pass Pass Fail Pass Fail Fail Pass Pass Coating 234 clearly provided the best performance as the above-tabulated results reveal. Coating 237 lacked pot life and possessed only fair solvent resistance, yet provided fairly good Sward Hardness. Coating 252was a bit soft, but may be improved by the addition of aromatic structure to the resin backbone. Coating 243 which contained aromatic mercaptan groups performed admirably but for its short potlife. Finally, coating 2DN possessed good properties but for some sensitivity to MEK rub resistance.

Example 7 In this example, GDP of Example 2 was used as a reactive diluent along with aromatic hydroxyl-functional resins in order to ascertain whether cure speed with aliphatic isocyanates could be improved. The following polyol resins were evaluated.

Polyol 274: Tone M-1 00 homopolymer of Example5 capped with p-hydroxy benzoic acid.

Polyester Polyol: Aromatic hydroxyl-terminated polyester of Example 1 of U.S. Pat. No.4,374,167.

Acrylic Polyol: Butyl acrylate (4 moles), butyl methacrylate (4 moles), styrene (1 mole), 2-ethyl hexylacrylate (2 moles), gycidyl methacrylate (2 moles), diphenolic acid (2 moles, second stage reaction).

Coatings were formulated from these polyol resins, Desmodur N-3390 curing agent of Example 1, and varying amounts of GDP. Curing conditions (0.9 vol.-% TEA catalyst) as described above were again utilized with the following results being recorded.

TABLE 14 Polyol 274 0% GDP 5% GDP 10% GDP 20% GDP Test RT HT RT HT RT HT RT HT Cure (sec) 300 300 240 240 180- 180 180 180 Sward Hardness 4,4 6,4 4,4 6,6 4,4 4,6 2,2 2,2 MEKRubs 9 5 10 13 13 13 7 9 Solvents: H2O Pass Pass Pass Pass Pass Pass Pass Pass 5% NaOH Fail Fail Fail Fail Fail Fail Fail Fail 10% H2S04 Pass Pass Pass Pass Pass Pass Pass Pass Xylene Pass Pass Pass Pass Pass Pass Pass Pass TABLE 15 Polyester Polyol 0%GDP 5% GOP 10%GDP 20% GDP Test RT HT RT HT RT HT RT HT Cure (sec) 240 240 180 180 180 180 120 120 Sward Hardness 56,60 54,52 66,58 54,58 56,58 54,54 62,62 58,52 MEKRubs 29 15 48 22 49 27 39 28 Solvents:: H2O Pass Pass Pass Pass Pass Pass Pass Pass 5% NaOH Pass Pass Pass Pass Pass Pass Pass Pass 10% H2OSO4 Pass Fail Pass Fail Pass Fail Pass Pass Xyiene Pass Pass Pass Pass Pass Pass Pass Pass TABLE 16 Acrylic Polyol 0% GDP 5% GDP 10% GDP 20% GDP Test RT HT RT HT RT HT RT HT Cure (sec) 180 180 180 180 180 180 120 120 Sward Hardness 44,48 86,82 56,52 92,84 48,52 86,82 36,32 74,66 MEKRubs 39 30 44 32 35 37 31 45 Solvents: H2O Pass Pass Pass Pass Pass Pass Pass Pass 5% NaOH Pass Pass Fail -Fail Fail Pass Fail Pass 10%H2OSO4 Pass Pass Fail Pass Fail Fail Fail Pass Xylene Pass Pass Pass Pass Pass Pass Pass Pass The above-tabulated results demonstrate that cure speed of aliphatic isocyanate/polyol coatings can be increased bythe addition of a mercaptan compound while maintaining, if not improving, performance.

Example8 Duplicate pigmented formulations were compounded for long-term QUV evaluation as follows: TABLE 17 Resin (g) Ingredient 78E 79B GDP 36.6 36.6 TiO2(1) 38.5 38.5 Curing Agent(2) 69.3 69.3 MIBK 20.0 20.0 FC-430 Surfactant(3) 8 drops 8 drops Viscosity 55 cps 55 cps Solids(wt.-%) 83.6 83.6 (1) RCL-6 titanium dioxide pigment (SCM Corporation, Baltimore, Md), preformed pigment grind (Hegman 7) with GDP (122.0g GDPand 128.49 RCL-6) (2) Desmodur N-3390 of Example 1 (3) FC-430 surfactant is a non-ionicfluorocarbon used at 25% in MEK(Minnesota Mining and Manufacturing Company) The coatings were applied to RIM substrates by the Blegen vaporous catalyst spray method described above (0.25 vol.-% dimethylethanol amine catalyst).Both coatings displayed excellent cure response and good gloss.

The following optical measurements (Hunter Color Difference readings) were recorded.

TABLE 18 Resin 78E Resin 79B Weathering L a b L a b (hours) Initial 94.7 -0.7 +1.2 94.4 -0.8 +0.5 200 94.2 -0.5 +2.0 93.7 -0.6 +1.3 300 93.9 -0.4 +2.3 93 -0.5 +1.3 500 94.2 -0.8 +2.3 93.3 -0.8 +1.5 Thus, the anti-yellowing behavior ofthese coatings is demonstrated.

Example 9 Coating 9 of Example 2 and Coating 234 of Example 6 were tested and found to possess elongations of 166% and 4.5%, respectively (atfailure of coating on the substrate). The same coatings, however, possessed average tensile strengths of 115.5 kg/cm2 (1643 psi) and 151.2 kg/cm2 (2151 psi), respectively.

Example 10 A preformed carbamothioate co-catalyst, 4423-195, was made from trimethylolpropanetris(3mercaptopropionate) (TMP-3MP, 142.9 g), phenyl isocyanate (119 g), methyl isobutyl ketone solvent (112 g), and Amberlyst A-21 catalyst beads (acidic ion exchange resin, 5 g) by holding this mixture for 8 hours following by removal of the catalyst beads by filtration. No appreciable residual mercaptan or isocyanatewere detected.

Coating compositions were formulated without the co-catalyst and with 5% by weight of the co-catalyst.

Each sample was applied by the Blegen catalyst spray method described above using 0.6 vol-% dimethyletha- nol amine catalyst. The coatings formulations were made at an isocyanate index (NCO :OH molar ratio) of 1:1 and cut to application viscosity of 60 cps with M I BK solvent. Cure response data are set forth below.

TABLE 19 Formulation No. (wt. Parts) Ingredient* 4423-196-1 4423-197-2 4423-197-3 4423-197-4 PolyesterPolyol 50.3 50.3 DESMODURHL 40.2 - 40.2 DESMOPHEN 800 - - 19.5 19.5 DESMODUR N3390 - 21.6 - 21.6 MIBK 25.0 20.0 21.0 20.0 Polyester Polyol of Example 7 DESMODUR HLis DESMODUR HC (Example 2) but with butyl acetate solvent DESMOPHEN 800 polyesterpolyol, 100% n.v. solids, OH no.290, MobayChemical Co.

DESMODUR N3390, See Example 1.

TABLE 20 Tack Free Time (min.) TackFree Time (min.) Formulation 5wt-% No. Control Co-Catalyst 4423-196-1 5 Immediate 4423-197-2 100 3 4423-197-3 5 Immediate 4423-197-4 < 100 6 This data unquestionably demonstrates the efficacy of the co-catalyst in promoting the hydroxyl/isocyanate reaction, Example 11 Preformed mercapto/isocyanate or mercapto/thiocyanate compounds were evaluated for their effect in promoting the hydroxyl/isocyanate curing reaction. Thefollowing reactants were used to make the preformed compounds evaluated in this example.

TABLE 21 CompoundNo. Mercapto Reactant Isocyanate Reactant 4541-85-1 Methyl 3-mercaptopropionate Phenylthiocyanate 4541-85-2 Methyl 3-mercaptopropionate Butyl isocyanate 4541-85-3 Methyl 3-mercaptopropionate Butyl thiocyanate 4541-85-4 Methyl 3-mercaptopropionate Phenyl isocyanate The foregoing compounds were dissolved in methyl isobutyl ketone (MIBK) solvent at 10% solids. These compounds (co-catalysts) were tested at 1 % and 5% byweight levels.

The various compositions tested were applied bythe Blegen vaporous amine spray method of U.S. Pat. No.

4,517,222 using vaporous dimethylethanol amine (DMEOLA) at 0,7 vol-%. Duplicate samples were cured at ambient indoor room temperature orwere subjected to a 5 minute bake at about 121.1 'C (250'F). The data reported to the left oftheslash are forthe ambienttemperature samples whilethedata to the right oftheslash areforthe post-cure baked samples. Data lacking a slash areforthe ambienttemperature samples only. The coating composition formulation and the results recorded are set forth below.

TABLE 22 Formulation No.

Test* Data 4541-86-1 4541-86-2 4541-86-3 4541-86-5 4541-86-6 4541-86-8 4541-86-9 4541-86-11 4541-80-12 Co-Catalyst None 4591-85-1 4591-85-1 4941-85-2 4541-85-2 4541-85-3 4541-85-3 4541-85-4 4541-85-4 Pot Life (cps) Init. 50 50 50 50 50 50 50 50 50 4 Hr 65 75 85 65 90 145 gel 75 90 24 Hr 115 110 125 105 130 gel gel 130 130 48 Hr 360 225 220 225 195 gel gel 350 235 72 Hr gel gel gel gel gel gel gel gel gel Formulation (g) VIC 5033 50.3 50.3 50.33 50.3 50.3 50.3 50.3 50.3 50.3 Mondur HC 36.5 36.5 36.5 36.5 36.5 36.5 36.5 36.5 36.5 MIBK 27.0 22 0 22 0 22 0 22 0 Co-Catalyst - 5.4 27 5.4 27 5.4 27 5.4 27 Tack Free 5/yes 1/yes 1/yes 3/yes 3/yes 2/yes 4/yes 4/yes (min) MEK Rubs 1 Hr 15/45 22/55 20/46 37/56 38/60 65/143 32/55 36/58 24 Hr 40/78 40/74 53/73 70/111 147/327 140/231 135/210 72 Hr 147/157 155/171 156/180 173/200 175/200 137/348 265/+500 +500/500 *VIC 5033 is a phenolic acrylic polyol, equivalent wt 504, 69.9% n.v. solids, OH no. 111, Ashland Chemical Company, VIC is a registered trademark MONDUR HC-see Example 2 MIBK is methyl isobutyl ketone MEK Rubs is methyl ethyl ketone double rubs.

TABLE 23 Formulation No.

Test* Data 4541-88-1 4541-88-2 4541-88-3 4541-88-5 4541-88-6 4541-88-8 4541-88-9 4541-88-11 4541-88-12 Pot Life (cps) Init 30 30 30 30 30 30 30 30 30 4 Hr 425 475 500 450 435 460 450 450 475 24 Hr gel gel gel gel gel gel gel gel gel 48 Hr gel gel gel gel gel gel gel gel gel 72 Hr gel gel gel gel gel gel gel gel gel Formulation (g) K-flux 148 23.9 23.9 23.9 23.9 23.9 23.9 23.9 23.9 23.9 Mondur HC 36.5 36.5 36.5 36.5 36.5 36.5 36.5 36.5 36.5 MIBK 24 19 19 19 0 19 0 19 0 Co-Catalyst 5 5 5 24 5 24 5 24 Tack Free 10/yes 10/yes 8/yes 10/yes 10/yes 8/yes 8/yes 6/yes 6/yes (min) MEK Rubs 1 Hr 8/15 15/35 14/39 21/69 26/38 19/57 35/67 40/45 35/89 24 Hr 40/36 40/45 32/42 37/43 39/48 40/45 35/67 40/45 37/112 72 Hr 206/127 195/210 135/145 206/255 200/197 230/212 202/217 197/190 175/202 *K-Flex 148 is a flexible polyester polyol, 100% n.v. solids, OH No. 235, King Industries.

Table 24 Formulation No.

Test* Data 4541-89-1 4541-89-2 4541-89-3 4541-89-5 4541-89-6 4541-89-8 4541-89-9 4541-89-11 4541-89-12 Co-catalyst None 4541-85-1 4541-85-1 4541-85-2 4541-85-2 4541-85-3 4541-85-3 4541-85-4 4541-85-4 Pot Life (cps) Init. 70 70 70 70 70 70 70 70 70 4 Hr - - - - - - - - 24 Hr 115 105 110 120 120 115 120 110 115 48 Hr 150 140 150 gel gel gel 175 160 150 72 Hr - - - - - - - - Formulation (g) VIC 5033 40.1 40.1 40.1 40.1 40.1 40.1 40.1 40.1 40.1 Des N3390 21.6 21.6 2.16 2.16 2.16 2.16 2.16 2.16 2.16 MIBK 24 19 0 19 19 0 19 0 Co-Catalyst - 5 24 5 24 5 24 5 24 Tack Free 90/yes 90/yes 90/yes 90/yes 90/yes 90/yes 90/yes 90/yes 90/yes (min) MEK Rubs 1 Hr /11 /12 /15 /17 /13 /18 /20 /15 /17 24 Hr 47/55 52/51 55/55 44/52 49/57 50/55 55/60 50/55 50/58 72 Hr 120/189 111/202 117/197 110/189 109/195 110/185 120/205 135/185 102/185 *Desmodur N3390-see Example 1 These results demonstrate that the preformed thiourethane co-catalyst is effective in improving the cure of the polyol/polyisocyanate coating composition. The 4541-85-4 co-catalyst appeared to be the most effective of the compounds evaluated, though all of the compounds were effective in promoting the cure.

Claims (21)

1. Method for curing afilm of a coating composition which comprises exposing said coating composition as an atomizate which then is applied to a substrate or as an applied film on a substrate to a vaporoustertiary amine catalyst, said coating composition comprising a polymercapto compound and a multi-isocyanate curing agent.

2. The method of claim f wherein said coating composition is dispersed in a fugitive organic solvent.

3. The method of claim 1 wherein said polymercapto compound is monomer, oligomer, or polymer.

4. The method of claim 1 wherein the molar ratio of mercapto groups is isocyanatew groups in said coating composition is between about 1 and 1:2

5. The method of claim 1 wherein said coating composition also contains a particulatefiller.

6. The method of claim 1 wherein said polymercapto compound is selected from orthe mercapto groups thereon are derived from 1,4-butane dithiol, 2,3-dimercapto propanol, toluene-3,4-dithiol, alpha,alpha' dimercapto-p-xylene thiosalicylic acid, mercapto acetic acid, 2-mercapto ethanol, monododecane dithiol, didodecane dithiol, dithiol phenol, di-para-chlorothiophenol, dimercapto benzothiazole, 3,4-dimercapto toluene, alkyl mercaptan, 1,6 hexane dithiol, benzyl mercaptan, 1-octane thiol, p-th iocresol, 23,5,6- tetrafluorothiophenol, cyclohexyl mercaptan, methylthioglycolate, mercapto pyridines, dithioerythritrol, 6- ethoxy-2-mercaptobenzothiazol, and mixtures thereof.

7. The method of claim 1 wherein the coating composition is cured by exposure of an applied film thereof to a vaporous tertiary amine catalyst.

8. The method of claim 1 wherein an atomizate of said coating compositionn concurrently generated with a vaporous tertiary amine catalyst are admixed, said mixture applied to a substrate, and said coating composition cured.

9. The method of cliam 1 wherein said curing agent is selected from an aliphatic multi-isocyanate curing agent, an aromatic multi-isocyanate curing agent, and mixtures thereof.

10. A coating composition rapidly curable at room temperature in the presence ofvaporous tertiaryamine catalyst comprising a polymercapto compound and a multi-isocyanate curing agent.

11. The composition of claim 10 wherein said coating composition additionally comprises a fugitive organic solvent.

12. The composition of claim 10 wherein said polymercapto compound is selected from a monomer, oligomer, or polymer.

13. The coating composition of claim 10wherein said polymercapto compound is selected from oris derived from an ingredient selected from 1,4-butane dithiol, 2,3-dimercapto propanol,toluene-3,4-dithiol, alpha,alpha'-dimercapto-p-xylene thiosalicylic acid, mercapto acetic acid, 2-mercapto ethanol, monododecane dithiol, didodecane dithiol, dithiol phenol, di-para-chlorothiophenol, dimercapto benzothiazole, 3,4 dimercapto toluene, allyl mercaptan, 1;;6 hexane dithiol, benzyl mercaptan, 1-octane thiol, p-thi6crnsol, 2,3,5,6-tetrafluorothiophenol, cyclohexyl mercaptan, methyithioglycolate, mercapto pyridines, dithioerythrit- rol, 6-ethoxy-2-mercaptobenzothiazol, and mixtures thereof.

14. The coating composition of claim 10 wherein said multi-isocyanate curing agent is selected from an aliphatic multi-isocyanate curing agent, an aromatic multi-isocyanate curing agent, and mixtures thereof.

15. In a method for curing the film of a coating composition which comprises exposing said coating composition as an atomizatewhich then is applied to a substrate or as an applied film on a substrate to a vaporous tertiary amine catalyst, said coating composition comprising a polyol and a multi-isocyanate curing agent, the improvement which comprises said coating composition being cured in the presence of a thiourethane compound formed by the reaction of a mercaptan compound and an isocyanate compound.

16. The method of claim 1 5wherein said coating composition additionally comprises a mercapto compound which forms said thio-urethane compound in situ during the curing of said coating composition.

17. The method of claim 15 wherein said thio-urethane compound is pre-formed and added to said coating composition.

18. The method of claim 15 wherein said thio-urethane compound is represented bythefollowing structure:

where R1 and R2 each is a monovalent organic radical which dirably is an alkyl or an arylgroup.

19. The method of claim 16 wherein said mercapto compound is a monomercapto compound, a polymercapto compound, or mixtures thereof.

20. The method of claim 15whererein said multi-isocyanate curing agent is an aromatic multi-isocyanate, an aliphatic multi-isocyanate, and mixtures thereof; and said polyol is selected from an aromatic polyol, or mixtures of an aliphatic polyol and an aromaticpolyol.

21. A method of curing a film of a coating composition according to Claim 1 and substantially as described in any ofthe examples herein.