BRPI0620613A2 - multilayer coating system - Google Patents

Abstract

MULTIPLE LAYER COATING SYSTEM. The invention relates to a multilayer coating system comprising: - at least one layer a) comprising a coating composition a) comprising at least one isocyanate-functional compound and at least one thiol-functional compound and - at least one layer b) comprising an aqueous coating composition b), wherein at least one layer a) and at least one layer b) have at least one layer boundary in common and wherein the coating composition b) comprises at least 17 mmoles / kg, calculated on the weight of the coating composition b), of a catalyst for the reaction of adding at least one thiol-functional compound and at least one isocyanate-functional compound.

Description

Descriptive Report of the Invention Patent for "MULTIPLE LAYER COATING SYSTEM".

The invention relates to a multilayer coating system comprising at least one layer a) comprising a coating composition a) comprising at least one isocyanate-functional compound and at least one thiol-functional compound and at least one layer b) comprising an aqueous coating composition b), wherein at least one layer a) and at least one layer b) have at least one layer boundary in common. The invention also relates to a process for preparing the multilayer coating system and a part kit for preparing a base coating composition.

United States Patent US 5,578,346 describes multi-layer composite coatings which comprise (a) a first coat which is substantially free of isocyanate functionality and which comprises a curing or drying film-forming composition and a catalyst for the reaction of isocyanate groups and active hydrogen groups; and (b) a second coating which is applied to the surface of the first coating and which comprises an active hydrogen compound and a polyisocyanate. Examples where the first coating comprises dibutyl tin dilaurate and the second coating is based on a polyol and a polyisocyanate are described.

International patent application WO 0192362 describes a photoactivatable coating composition comprising a photopolymer base and a base-catalyzed curable or polymerizable organic material comprising at least one polyisocyanate and at least one compound containing at least one group. thiol. The photoactivatable coating composition may be a transparent coating composition which must be applied over a base coating composition. The photo-activable coating composition has a long service life and exhibits rapid cure upon irradiation with visible and ultraviolet light. The known photo-activable coating composition eventually also cures in shadow areas, i.e. those areas of a coated substrate which are not exposed to ultraviolet or visible light.

A shortcoming of known multilayer coating systems is that the cure rate of the topcoats of known systems is not always as fast as desired. Fast curing of the photoactivatable coating composition according to WO 0192362 is obtained only when irradiating with visible and / or ultraviolet light, although the cure rate in shadow areas is somewhat slow and subject to further refinement.

The present invention seeks to alleviate the above mentioned shortcomings of known multilayer coating systems. More particularly, the coating composition comprising at least one isocyanate-functional compound and at least one thiol-functional compound should be readily curable in shadow areas or even without any visible and / or ultraviolet light irradiation. Fast cure capacity should not be obtained at the expense of the life of the composition. Further, if the coating composition comprising at least one isocyanate-functional compound and at least one thiol-functional compound is a transparent composition, it is desirable that application of the transparent composition lead only to minimal or no strike-in effect. on an underlying base coat layer.

It has now been found that these objectives can be achieved with a multilayer coating system comprising:

- at least one layer a) comprising a coating composition a) comprising at least one isocyanate-functional compound and at least one thiol-functional compound and

- at least one layer b) comprising an aqueous coating composition b), wherein at least one layer a) and at least one layer b) have at least one layer boundary in common and wherein the coating composition b ) comprises at least 17 mmol / kg, calculated on the weight of coating composition (b), of a catalyst for the addition reaction of at least one thiolfunctional compound and at least one isocyanatefunctional compound.

In the multilayer coating system according to the invention, the coating composition a) comprising at least one isocyanate-functional compound and at least one thiol-functional compound also cures rapidly in shaded areas or even without any irradiation with visible and / or ultraviolet light. Since no additional components, such as a catalyst, need to be added to coating composition a), the shelf life of coating composition a) is not diminished. Thus, rapid cure ability is not obtained at the expense of the life of the composition. Further, application of a clear coating composition of coating composition (a) leads to minimal or no strike-in effect on an underlying base coat produced from an aqueous base coating composition. B).

The invention also relates to a method of increasing cure speed in a multilayer coating system. The method comprises applying a transparent coating composition (a) comprising at least one isocyanate-functional compound and; at least one thiol-functional compound above a base coat b) prepared from an aqueous-based coating composition b) comprising at least 17 nmoles / kg calculated on the weight of the coating composition b ) of a catalyst for the addition reaction of at least one thiol-functional compound and at least one isocyanate-functional compound.

Isocyanate-functional compounds suitable for use in the coating composition (a) are isocyanate-functional compounds comprising at least one isocyanate group. Alternatively, the isocyanate-functional compound in the coating composition a) is a polyisocyanate, such as an aliphatic, cycloaliphatic or aromatic di-, tri- or tetraisocyanate. Examples of diisocyanates include 1,2-propylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, 2,3-butylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 2,2,4-trimethylhexylene diisocyanate, dodecamethylene, ω, ω'-dipropylether diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, 4-methyl-1,3-diisocyanatocyclohexane, trans-vinylidene diisocyanate, dicyclohexyl methane ^^ - diisocyanate (Desmodur® W), toluene diisocyanate, 1,3-bis (isocyanatomethyl) benzene, xylene diisocyanate, α, α, α ', α'- diisocyanate tetramethyl xylylene (TMXDI®), 1,5-dimethyl-2,4-bis (2-isocyanatoethyl) benzene, 1,3,5-triethyl-2,4-bis (isocyanatomethyl) benzene, 4,4'-diisocyanato- diphenyl, S'-dichloro-4'-diisocyanate-diphenyl, 3,3'-diphenyl-4,4'-diisocyanate-diphenyl, S'-dimethoxy-N'-diisocyanate-diphenyl, 4,4'-diisocyanate-diphenyl 1 methane, 3,3'-dimethyl-4,4'-diisocyanato diphenylmethane and diisocyanatonaphthalene. Examples of triisocyanates include 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 1,8-diisocyanate-4- (isocyanatomethyl) octane and lysine triisocyanate. Polyisocyanate adducts and oligomers, for example, biurets, isocyanurates, allophanates, urethydes, urethanes and mixtures thereof are also included. Examples of such oligomers and adducts are the 2-molecule adduct of a diisocyanate, for example hexamethylene diisocyanate or isophorone diisocyanate, to a diol such as ethylene glycol, the 3-molecule adduct of hexamethylene diisocyanate to 1 water molecule (available under the Bayer trademark Desmodur N), the 1-molecule trimethylol propane adduct to 3 toluene diisocyanate molecules (available under the Bayer trademark Desmodur L), the 1-trimethylol adduct molecule propane for 3 isophorone diisocyanate molecules, the adduct of 1 pentaerythritol molecule for 4 molecules of toluene diisocyanate, the 3 mol adduct of ma.aa ^ -tetramethyl xylene diisocyanate for 1 mole trimethylol propane, the trimer 1,6-diisocyanatohexane isocyanurate, isophorone diisocyanate isocyanurate trimer, 1,6-diisocyanatohexane uretdion dimer, 1,6-diisocyanatohexane biuret, 1,6-diisocyanatohexane allophanate and mixtures thereof. In addition, (co) polymers of isocyanate-functional monomers, such as α, α'-dimethyl-m-isopropenyl benzyl isocyanate, are suitable for use.

The polyisocyanate may comprise hydrophilic groups, for example covalently bonded hydrophilic polyether moieties which facilitate the formation of aqueous dispersions.

Thiol functional compounds which may be suitably used in the coating composition a) include dodecyl mercaptan, mercapto ethanol, 1,3-propanedithiol, 1,6-hexanedithiol, methylthioglycolate, 2-mercaptoacetic acid, mercapto-succinic acid and cysteine. Also suitable are esters of a thiol-functional carboxylic acid with a polyol, such as esters of 2-mercaptoacetic acid, 3-mercaptopropionic acid, 2-mercaptopropionic acid, 11-mercaptoundecanoic acid and mercapto-succinic acid. Examples of such esters include pentaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tetrakis (2-mercaptoacetate), trimethylol propane tris (3-mercaptopropionate), trimethylol propane tris (2-mercaptopropionate) and trimethylol propane tris (2-mercaptoate). Another example of such a compound consists of a hyperbranched polyol core based on an initiating polyol, for example trimethylol propane and dimethylol propionic acid, which is subsequently esterified with 3-mercaptopropionic acid and isononanoic acid. Such compounds are described in European patent application EP 0448224 A and International patent application WO 9317060.

Products of the addition of H2S to epoxy functional compounds also provide thiol functional compounds. Such compounds may have a structure of the following formula Tt (O-CHR-CH2 -O) nCH2CHXHCH2YHlm, with T being a valiant organic moiety m, where m is an integer between 1 and 25, R being hydrogen or methyl, η being an integer between 0 and 30, X and Y being oxygen or sulfur, as long as XeY is not equal. An example of such a compound is commercially available from Cogis under the trademark Capcure® 3/800.

Other syntheses for preparing compounds comprising thiol-functional groups involve: reacting an aryl or alkyl halide with NaHS to introduce a pendant mercapto group into the alkyl and aryl compounds, respectively; reacting a Grignard reagent with sulfur to introduce a pendant mercapto group into the structure; the reaction of a polymercaptan with a polyolefin according to a nucleophilic reaction, an electrophilic reaction or a radical reaction; the disulfide reaction.

Good results have so far been obtained with pentaerythritol tetrakis (3-mercapto propionate), trimethylolpropane tris (3-mercaptopropionate) and Capcure 3/800 as thiol-functional compounds.

In another embodiment of the invention, the thiol group of thio-functional compound in coating composition a) may be covalently attached to a resin. Such resins include thiol-functional polyurethane resins, thiol-functional polyester resins, thiol-functional polyaddition polymer resins, thiol-functional polyether resins, thiol-functional polyamide resins, thiol-functional polyurea resins and mixtures thereof. . Thiol-functional resins may be prepared by reacting H2S with an epoxy group or a resin containing unsaturated carbon-carbon bond, the reaction between a hydroxyl-functional resin and a thiol-functional acid and by the reaction of an isocyanate-functional polymer and a thiol-functional alcohol or a di- or polymercapto compound.

A thiol-functional polyurethane resin may be the reaction product of a mono-, di-, tri- or tetrafunctional thiol compound with an isocyanate-terminated polyurethane and preferably is the reaction product of a mono-, di-, tri- or tetrafunctional thiol compound and preferably is the reaction product of a diisocyanate and (a) diol-functional compound (s). Suitable thiol-functional polyurethane resins are first obtainable by preparing an isocyanate-functional polyurethane from diols, diisocyanates and optionally building blocks containing groups which facilitate the stabilization of the resin in an aqueous dispersion, followed by reaction of the isocyanate-functional polyurethane with a polyfunctional thiol in a base-catalyzed addition reaction. Other thiol-functional polyurethane resins are known and described, for example, in German patent publication DE 2642071 A and European patent application EP 0794204 A.

The thiol functional resin may be a polyester prepared from (a) at least one polycarboxylic acid or reactive derivatives thereof, (b) at least one polyol and (c) at least one thiol functional carboxylic acid. The polyesters preferably have a branched structure. Branched polyesters may conventionally be obtained by condensing polycarboxylic acids or reactive derivatives thereof, such as the corresponding anhydrides or lower alkyl esters, with poly alcohols, when at least one of the reagents has a functionality of at least 3.

Examples of suitable polycarboxylic acids or reactive derivatives thereof are tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyl hexahydrophthalic acid, methyl hexahydrophthalic anhydride, dimethylcyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, 5-tert-butyl isophthalic acid, trimellitic anhydride, maleic acid, maleic anhydride, fumaric acid, succinic anhydride, dodecenyl succinic anhydride, glutamic acid succinate, 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-propylene glycol, 1,3-propylene glycol, 2-methylpropane-1,3-diol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propane diol, cyclohexane-1,4-dimethylol, neopentyl glycol monoester and hydroxypivalic acid, hydrogenated Bisphenol A, 1,5-pentane diol, 3-methyl pentane diol, 1,6-hexane diol, 2,2,4-trimethyl 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, thiosalicylic acid, mercapto-succinic 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 acids and C6 -C18 monoalcohols are used. Examples of 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, isoartic acid, stearic acid hydroxy stearic acid, benzoic acid, 4-tert acid. benzoic butyl and mixtures thereof. Examples of C 1 -C 6 mono alcohols include cyclohexanol, 2-ethylhexanol, stearyl alcohol and 4-tert. butyl cyclohexanol.

In addition to thiol groups, thiol-functional polyester prepared from the above components may also comprise hydroxyl groups. If hydroxyl groups are present, the ratio of thiol groups to hydroxyl groups is suitably in the range of 90:10 to 10:90, preferably 75:25 to 25:75.

The thiol functional resin may be a thiol functional polyaddition polymer, for example a poly (meth) acrylate. Such poly (meth) acrylate is derived from hydroxyl-functional (meth) acrylic monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and other ethylenically unsaturated polymerizable monomers as described above for the preparation of the same. polyaddition polymer. The thiol group is introduced by esterifying the (part of) hydroxyl groups of the acrylate copolymer with one or more of the thiol-functional carboxylic acids described above.

Alternatively, glycidyl methacrylate is introduced into the polymer to prepare epoxy-functional poly (meth) acrylate. The epoxy groups are then reacted with suitable thiol-functional carboxylic acids as mentioned above. Alternatively, thiol group may be introduced by reaction of an isocyanate-functional polyacrylate with a thiol-functional alcohol, for example, mercapto ethanol. The polyaddition polymer is prepared by conventional methods as described above, for example by slowly adding appropriate monomers to a solution of a suitable polymerization initiator such as an azo or peroxy initiator.

The coating composition a) in the multilayer system according to the present invention may be a water bringing composition, a solvent bearing 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. Suitably, the theoretical content of organic volatiles (VOC) in coating composition a) is less than 450 g / l or less than 350 g / l or even less than 250 g / l. Alternatively, coating composition a) may be an aqueous powder coating dispersion wherein the thiol-functional compound is a resin having a Tg above 20 ° C. The coating composition may also be a powder coating composition or a hot melt coating composition.

In one embodiment, the coating composition a) comprises a combination of pentaerythritol tetrakis (3-mercapto propionate) and a thiol-functional polyester. It is preferred that the thiol-functional polyester additionally comprises hydroxyl groups.

As mentioned above, in the multilayer system according to the invention, the coating composition a) cures rapidly even without any visible and / or ultraviolet light irradiation. However, it may be desirable to further increase the cure rate by visible and / or ultraviolet light irradiation. Accordingly, in one embodiment of the invention, the coating composition a) comprises a photolatent base. Suitable photolysing bases include N-substituted 4- (o-nitrophenyl) dihydropyridines, optionally substituted by alkyl ether and / or alkyl ester groups and quaternary organo-boron photoinitiators. Examples of N-substituted 4- (o-nitrophenyl) dihydropyridines are N-methyl nifedipine, N-butyl nifedipine, N-butyl 2,6-dimethyl 4- (2-nitrophenyl) 1,4-dihydropyridine acid diethyl ester 3, 5-dicarboxylic acid and a nifedipine according to the formula: i.e. diethyl ester N-methyl 2,6-dimethyl 4- (4,5-dimethoxy-2-nitrophenyl) 1,4-dihydropyridine 3,5-dicarboxylic acid . Examples of quaternary organo-boron photoinitiators are disclosed in GB 2307473 A1 such as:

Thus, optimal results were obtained with a photolatent base belonging to the group of α-amino acetophenones. Examples of α-amino acetophenones which may be used in photoactivatable coating compositions according to the present invention are: 4- (methylthiobenzoyl) -1-methyl-1-morpholinethane (Irgacure® 907 ex Ciba Specialty Chemicals) and ( 4-morpholinobenzoyl) -1-benzyl-1-dimethylamino propane (Irgacure® 369 ex Ciba Specialty Chemicals) disclosed in EP 0898202 A. Preferred is an α-amino acetophenone according to the following formula:

<formula> formula see original document page 11 </formula>

The photolatent base may be used in an amount of 0.01 to 10 wt% on the curable solid material of the coating composition a), preferably 0.05 to 5 wt%, more preferably 0.05 to 3 wt. % by weight.

If the coating composition a) comprises a tolerant base, it is radiation curable upon application and optionally solvent evaporation. Curing by UV light irradiation is particularly suitable. IR / UV irradiation combinations are also suitable. Radiation sources which can be used are those common to UV, such as high and medium pressure mercury lamps. In order to avoid any risk involved in the handling of very short wavelength UV light (UVB and / or UVC light), preference is given, especially for use in automotive catering shops, to fluorescent lamps. which produce the least harmful UVA light. Alternatively, it is also possible to use UV lamps equipped with a filter which does not allow the transmission of UVB and UVC radiation.

When a photolatent base is used in coating composition a), a sensitizer may optionally be included in coating composition a).

Suitable sensitizers are thioxanthones such as isopropyl thioxantone according to the following formula:

<formula> formula see original document page 12 </formula>

(Quantacure® ITX ex G. Lakes), oxazines and rhodamines. Colorless surfaces can be obtained with benzophenone and derivatives thereof. Examples of suitable benzophenone derivatives are:

<formula> formula see original document page 12 </formula>

wherein R1, R2 and R3 may be the same or different and mean CH3 or H (Speedcure® BEM ex Lambson),

<formula> formula see original document page 12 </formula> <formula> formula see original document page 13 </formula>

wherein R1, F2 and R3 may be the same or different and mean CH3 or H (Esacure® TZT ex Lamberti).

The sensitizer may be present in an amount of 0.1 to 5 wt% on the curable solid material in the coating composition a), preferably 0.5 to 2.5 wt%.

In addition to the isocyanate-functional compound and the thiol-functional compound as described above, other compounds may be present in coating composition a). Such compounds may be major binder and / or reactive diluents, optionally comprising reactive groups which may be cross-linked with the aforementioned functional compounds. Examples include hydroxyl functional binders, for example, polyester polyols, polyether polyols, polyacrylate polyols, polyurethane polyols, cellulose acetobutyrate, hydroxyl functional epoxy resins, alkyls and dendrimeric polyols as described in the application. International patent WO 9317060. Also, hydroxyl-functional oligomers and monomers, such as castor oil and trimethylol propane, may be present.

The coating composition a) may also comprise latent hydroxyl-functional compounds, such as compounds comprising bicyclic orthoester or spiro-orthoester groups. Such compounds and their use are described in WO 9731073.

Finally, ketone resins, asparagylic acid esters, and latent or non-latent amino-functional compounds such as oxazolidines, ketimines, aldimines, diimines, secondary amines and polyamines may be present. These and other compounds are known to those skilled in the art and are mentioned inter alia in US 5214086.

The ratio of isocyanate-functional to thiol-functional groups in the coating composition a) is suitably between 0.5: 1 and 3: 1, preferably 0.8: 1 to 2: 1.

Coating composition a) may further comprise other ingredients, additives or auxiliaries commonly used in coating compositions such as pigments, dyes, emulsifiers (surfactants), pigment dispersing aids, leveling agents, wetting agents anti-crater agents, anti-foaming agents, anti-sinking agents, thermal stabilizers, light stabilizers, UV absorbers, antioxidants and fillers.

If hydroxyl-functional compounds are present in coating composition a), the composition preferably comprises one or 1.1 more catalysts for crosslinking isocyanate groups with hydroxyl groups. Examples thereof include Sn based catalysts, such as dibutyl tin dilaurate, dibutyl tin diacetate and tin octoate. Also, basic catalysts are suitable.

As mentioned above, the aqueous coating composition b) comprises at least 17 mmol / kg, calculated on the weight of the coating composition b), of a catalyst for the addition reaction of at least one thiolfunctional compound and at least one isocyanate-functional compound of the coating composition a). Such amount of catalyst causes a measurable increase in the rate of drying of the coating composition (a) when applied to a surface of a coating layer prepared from the coating composition (b). The actual amount of catalyst employed in the coating composition (b) still depends on the specific catalyst activity of the individual catalyst, the equivalent weight of the catalyst, the proportion of the other components in the coating composition (b), the type of isocyanate compound. function and the required cure rate of the coating composition (a). Therefore, the most suitable amount of catalyst in the coating composition b) may vary over very wide ranges. Generally, the amount of catalyst in the coating composition (b) is in the range of 17 millimoles to 10 moles of catalyst per kg of coating composition or 35 millimoles to 9 moles per kg or 50 millimoles to 8 moles per kg or 200 millimoles. at 7 moles per kg.

Suitable catalysts in the aqueous coating composition b) are all compounds capable of accelerating the addition reaction of thiol-functional compounds and isocyanate-functional compounds.

Generally, suitable catalysts are basic catalysts. Examples are inorganic basic compounds such as hydroxides and basic metal oxides. Lithium, sodium, potassium, calcium and magnesium hydroxides may be explicitly mentioned.

Quaternary ammonium hydroxides, such as tetraethylammonium hydroxide, may also be used as a catalyst in the coating composition b).

In addition, amines are suitable catalysts in coating composition b).

Suitable primary amines are, for example, isopropyl amine, butyl amine, ethanol amine, 3-amino-1-propanol, 1-amino-2-propanol, 2-amino-2-methyl-1-propanol or 2-amino-2. -methyl-1,3-propane diol. Secondary amines that may be used are, for example, morpholine, diethyl amine, dibutyl amine, N-methyl ethanol amine, diethanol amine and diisopropanol amine. Also suitable are diamines and polyamines, such as the products of the addition of epoxides and ammonia or the products of the addition of primary, secondary or tertiary epoxides and amines.

Tertiary amines are a particularly suitable class of basic catalysts. Examples of suitable tertiary amines include trimethyl amine, triethyl amine, triisopropyl amine, triisopropanol amine, N, N-dimethyl ethanol amine, dimethyl isopropyl amine, Δ, β-diethyl ethanol amine, 1-dimethyl amino-2-propanol, 3-dimethyl amino-1-propanol, 2-dimethyl amino-2-methyl-1-propanol, N-methyl diethanol amine, triethanol amine, N-ethyl diethanol amine, N-butyl diethanol amine, Ν, Ν-dibutyl ethanol amine, and N-ethyl morpholine. N, N-dimethyl ethanol amine is a preferred catalyst in coating composition b).

Also suitable are 1,4-diazabicyclo [2.2.2] octane, 1,8-diazabicyclo [5.4.0] undec-7-eno, 1,5-diazabicyl [4.3.0] non-5-eno, guanidine, guanine , guanosine, melamine and mixtures and derivatives thereof.

The amine catalyst in coating composition b) may also be an amine-functional, film-forming polymer or resin, such as a 2- (dimethylamino) ethyl (meth) acrylate (co) polymer.

When the catalyst in coating composition b) is a base, it is preferred that the base be present as such as compared to being present in blocked or neutralized form.

The catalyst in the coating composition b) may alternatively be a metal compound with an organic binder wherein the metal is 1.1 a metal from Groups 3 to 13 of the Periodic Table. Preferably the metal is a transition metal. More preferably, the metal is a Group 4 metal from the Periodic Table.

Metal compounds comprise metal salts and / or complexes of organic compounds. Organic compounds are groups having 2 to 40 carbon atoms, optionally comprising atoms such as O, N and S. Metal salts comprise anions selected from the carboxylate groups. Examples thereof include propionate, butyrate, pentanoate, 2-ethyl hexanoate, naphthenate, oxalate, malonate, succinate, glutamate and adipate. Metal complexes comprise binders selected from the group of beta-diketones, alkyl acetoacetates, alcoholates and combinations thereof. Examples thereof include acetyl acetone (2,4-pentanedione), 2,4-heptanedione, 6-methyl-2,4-heptadione, 2,4-octanedione, propoxide, isopropoxide and butoxide. Preferably, the metal compound is a metal complex.

Examples of metals include aluminum, titanium, zirconium and hafnium. Examples of metal complexes include 2,4-pentanedione complex aluminum (K-KAT® XC5218 ex King Industries), aluminum triacetyl acetonate, zirconium tetraacetyl acetonate, zirconium tetrabutoxide (Tyzor® NBZ ex Dupont), titanium tetrabutoxide (Tyzor® TBT ex Dupont), zirconium complex with 6-methyl-2,4-heptadione, K-KAT® XC6212 ex King Industries, aluminum triisopropoxide and titanium diisopropoxide bis-2,4 (pentadionate) ( Tyzor® AA ex DuPont).

Still other suitable classes of catalysts in coating composition b) are cocatalysts comprising a phosphine and a Michael acceptor, as described in International patent application WO 0168736. When such cocatalysts are used, it is possible that both co-catalyst components, i.e. phosphine and Michael's acceptor, are present in coating composition b). Alternatively, it is also possible to include only one of the components in the coating composition (b) and to include the other component in the coating composition (a). Thus, when coating composition b) comprises a Michael acceptor, coating composition a) may comprise a phosphine. It is also possible to include phosphine in the coating composition (b) and to include the Michael acceptor in the coating composition (a).

Phosphine employed as one of the cocatalysts is a compound according to formula Z (PR2) n, where η is an integer from 1 to 6, R is independently selected from an aryl group or a group (ci - clo) alkyl which may be linear or branched and may or may not contain one or more heteroatoms, such as oxygen atoms and halogen atoms, provided that oxygen heteroatoms are not directly attached to each other. a phosphorus atom. Preferably R is an alkyl or aryl group, more preferably the alkyl group has 1 to 15 carbon atoms and the aryl group has 6 to 15 carbon atoms.

Where η = 1, Z is a group according to R. Such compounds are hereinafter referred to as monophosphines. Examples of monophosphines include triphenyl phosphine and trioctyl phosphine.

In the case where η ≥ 2, Z is selected from an arylene group, a group (cyclo) alq (en) ila which may be linear or branched and may or may not contain heteroatoms such as oxygen, phosphorus, nitrogen as long as oxygen and nitrogen heteroatoms are not directly attached to a phosphorus atom and / or selected groups of carboxyl, anhydride, cycloalkyl, aryl or may be a single bond. Such compounds are hereinafter referred to as polyphosphines. Examples of polyphosphines include bis (2-diphenylphosphinoethyl) phenylphosphine, 1,4-bis (diphenylphosphino) butane, bis (diphenylphosphino) methane, 1,3-bis (diphenylphosphino) propane, 1,5-bis (diphenylphosphino) pentane, trans - 1,2-bis (diphenylphosphine) ethylene, cis-1,2-bis (diphenylphosphine) ethylene, (R) - (+) - 2,2'-bis (diphenylphosphine) -1,1'-binaphthyl, tetrafenylbiphosphine, tris 2- (diphenylphosphino) (ethyl) phosphine, 1,1-bis (diphenylphosphino) ethylene, 1,1,1-tris (diphenylphosphinomethyl) ethane, 2,3-bis (diphenylphosphino) maleic anhydride, 1,2-bis ( diphenylphosphino) benzene, 1,2-bis (pentafluorophenyl) (phosphino) ethane, (2R, 3R) - (-) - 2,3-bis (diphenylphosphino) bicyclo [2.2.1] hept-5-ene and ethylene bis (2-methoxyphenyl) (phenylphosphine). Preferred are polyphosphines wherein Z is a straight or branched alkylene group having 1 to 8 M carbon atoms optionally comprising a phosphorus atom and R is an aryl group. Most preferred phosphines are 1,4-bis (diphenylphosphino) butane or triphenylphosphine.

The Michael acceptor preferably comprises one or more olefinically unsaturated groups, the olefinically unsaturated group comprising at least one electron extraction functionality attached to an unsaturated bond carbon atom. The olefinically unsaturated bond may be a double or triple bond. Generally, the Michael acceptor has a structure according to the following formula I:

wherein at least one of R1, R2, R3 and R4 comprises an electron extraction functionality attached to an unsaturated bond carbon atom and m is an integer from 1 to 6.

Examples of electron extraction functionalities include carbonyl, carboxyl, ester, thiocarbonyl, thiocarboxyl, thioesters, sulfoxide, sulfonyl, sulfo, phosphate, phosphite, phosphonite, phosphinite, nitro, nitrile and amide.

Where m is one, at least one of R1, R2, R3 and / or R4 comprises the electron extraction functionality and the electron extraction functionality may be attached to a hydrogen, alkyl, cycloalkyl, linear or branched alkenyl, cycloalkenyl, alkynyl, cycloalkynyl and aryl which may be optionally substituted by various other functionalities such as carboxylic acid or hydroxide. If they do not comprise an electron extraction functionality, R1, R2, R3 and / or R4 may be independently selected from a hydrogen atom, alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl and straight or branched aryl which may be optionally substituted by various functionalities such as carboxylic acid or hydroxide. R1 and R3 or R2 and R4 may also form a ring comprising one or more electron extraction features.

Where m is 2 to 6, R 1 is selected from a single bond, an electron extraction functionality and a polyvalent group derived from a hydrocarbon compound optionally comprising heteroatoms such as -O-, -S-, -Si and -P-, such as amide, urea and ester groups and / or one or more electron extraction features. The hydrocarbon compound may be an alkane, cycloalkane, alkene, cycloalkene, alkyne, cycloalcino, substituted or unsubstituted arene or combinations thereof. The polyvalent group is preferably derived from a polyalcohol. Examples of such polyalcohols include trimethylol propane, trimethylol ethane, glycerol, 1,2,6-hexanotriol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methylpropane-1,3-diol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propane diol, cyclohexane-1,4-dimethylol, neopentyl glycol monoester and hydroxypivalic acid, hydrogenated Bisphenol A, 1,5-pentanediol, 3-methyl -pentanediol, 1,6-hexanediol, 2,2,4-trimethyl pentane-1,3-diol, dimethylol propionic acid, pentaerythritol, dimethylethyl propane and dipentaerythritol. Alternatively, R3 may also form a ring with R1 comprising one or more electron extraction features.

Examples of Michael acceptors are isobornyl acrylate, isooctyl acrylate, 2,2'-methylene bis (6-butyl 4-methyl phenol) monoacrylate, phenoxyethyl acrylate, lauryl acrylate, dicyclopentadiene acrylate, N-butyl maleimide, benzyl acrylate, trimethylol triacrylate, maleic anhydride, a trifunctional isophorone diisocyanate adduct for 2-hydroxyethyl maleimide, diethyl maleate, methoxypropyl citraconimide, diethylbenzylidene malonate or an α, β-unsaturated aldehyde, for example cinnamaldehyde or citral. Examples of preferred Michael acceptors are trimethylol propane triacrylate, Irganox 3052 or N-butyl maleimide.

In one embodiment of the multilayer coating system, the coating composition b) consists essentially of the above described catalyst and water as a liquid carrier. In this case, layer (b) of the multilayer coating system consists essentially of the catalyst described above after evaporation of water.

In another embodiment, coating composition b) also 1.1 comprises a film forming binder. The film-forming binder in the coating composition (b) may be any resin commonly used in aqueous coating compositions, such as a polyaddition polymer, polyurethane, polyester, polyether, polyamide, polyurethane, polyurethane-polyester, polyurethane. polyether, cellulose-based binders, such as cellulose acetobutyrate, and / or hybrid resins. Such resins may be present in the aqueous coating composition b) as a solution in the aqueous carrier medium or as a dispersion in the aqueous carrier medium.

Suitable polyaddition polymer resins may include ethylene unsaturated (co) polymers. The polyaddition polymer may be prepared by conventional free-radical radical polymerization methods. Alternatively, advanced polymerization techniques such as group transfer polymerization (GTP), atom transfer radical polymerization (ATRP) and reversible addition fragmentation chain transfer polymerization (RAFT) 1 also may be used for the preparation of polyaddition polymer resins.

The polyaddition polymer may be an acrylic polyol derived from hydroxy-functional acrylic monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, other acrylic monomers such as acid (meth). ) acrylic, methyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, optionally in combination with a vinyl derivative such as styrene and the like or mixtures thereof, the terms (meth) acrylate and (meth) acid ) acrylic referring to methacrylate and acrylate as well as methacrylic acid and acrylic acid respectively.

In one embodiment, the resin in coating composition b) is an aqueous dispersion of an addition polymer. The aqueous dispersion may be mixed with a metallic pigment such as aluminum or a pigment such as coated metal-oxide so that coatings of a metallic appearance can be obtained.

The addition polymer is suitably a copolymer prepared in 2 or more steps by emulsion polymerization and obtained by first-stage copolymerization of 60-95 parts by weight calculated on 100 parts by weight of the polymer. addition of a monomer A mixture consisting of 65-100 mol% of a (cyclo) alkyl (meth) acrylate, of which the (cyclo) alkyl group contains 4-12 carbon atoms and 0-40 mol% of a di (cyclo) alkyl maleate and / or a di (cyclo) alkyl fumarate, of which (cyclo) alkyl groups contain 4-12 carbon atoms and 0-35 mol% of a copolymerizable monoethylenically unsaturated monomer and by copolymerization , in subsequent steps, of 5-40 parts by weight (calculated on 100 parts by weight of the addition polymer) of a mixture of 10-60 mol% (meth) acrylic acid monomer B, with the carboxylic acid groups derived from the (meth) acrylic acid being at least partially ionized. Preferably, the addition polymer is derived by copolymerizing 80-90 parts by weight of the monomer mixture A and 10-20 parts by weight of the monomer B mixture, both amounts being calculated on 100 parts by weight of the monomer polymer. addition. By emulsion polymerization is meant herein the polymerization of a water-unsaturated ethylenically unsaturated monomer in the presence of a water-soluble or water-insoluble initiator and using 0.1-9% by weight calculated on the monomer of an emulsifier.

Examples of (cyclo) alkyl (meth) acrylates suitable for use in the monomer A mixture and having a (cyclo) alkyl group of 4-12 carbon atoms may be mentioned butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate , 2-ethylhexyl methacrylate, octyl acrylate, octyl methacrylate, isobornyl acrylate, isobornyl methacrylate, dodecyl acrylate, dodecyl methacrylate, cyclohexyl acrylate and cyclohexyl methacrylate. It is preferred that the monomer A mixture contains 70-95, more particularly 80-95 mol% of the aforementioned (cyclo) alkyl (meth) acrylate. Examples of (cyclo) alkyl maleates and / or fumarates having 4-12 carbon atoms suitable for use in the monomer A mixture may include: dibutyl maleate, dibutyl fumarate, 2-ethylhexyl maleate, 2- ethylhexyl, octyl maleate, isobornyl maleate, dodecyl maleate and cyclohexyl maleate.

As monoethylenically unsaturated monomer compounds, of which up to 35 and preferably 5-20 mol% may be used in the monomer A mixture, the following may be mentioned: alkyl (meth) acrylates having less than 4 C atoms in the group alkyl such as methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate; alkyl maleates and fumarates having less than 4 C atoms in alkyl groups such as dimethyl maleate, diethyl maleate, diethyl fumarate and dipropyl maleate; (meth) acrylates having ether groups such as 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 3-methoxypropyl acrylate; hydroxyalkyl (meth) acrylates, for example 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, p-hydroxycyclohexyl acrylate, p hydroxycyclohexyl methacrylate, hydroxypolyethylene glycol (meth) acrylates, hydroxypolypropylene glycol (meth) acrylates and the corresponding alkoxy derivatives thereof; epoxy (meth) acrylates such as glycidyl acrylate, glycidyl methacrylate; monovillin aromatic hydrocarbons, such as styrene, vinyl toluene, α-methyl styrene, vinyl naphthalene; also acrylamide and methacrylamide, acrylonitrile, methacrylonitrile, N-methylol acrylamide, N-methylol methacrylamide; N-alkyl (meth) acrylamides, such as N-isopropyl acrylamide, N-isopropyl methacrylamide, N-t-butyl acrylamide, N-t-octyl acrylamide, N, N-dimethyl aminoethyl methacrylate, N, β-diethyl aminoethyl methacrylate; monomers such as vinyl chloride, vinyl acetate, vinyl propionate and monomers containing one or more urea or urethane groups such as, for example, the reaction product of 1 mol isocyanatoethyl methacrylate and 1 mol butylamine, 1 mol of benzylamine, 1 mol of butanol, 1 mol of 2-ethylhexanol and 1 mol of methanol, respectively. Mixtures of these compounds may also be used. Since, in the first step, a non-crosslinked polymer can be formed, the monomers in the monomer A mixture do not contain any groups which react with each other.

Examples of monoethylenically unsaturated compounds which may be used in the monomer B mixture in addition to (meth) acrylic acid may be mentioned: aromatic mohninyl hydrocarbons such as styrene, vinyl toluene, α-methyl styrene and vinyl naphthalene; nitriles, such as acrylonitrile, methacrylonitrile; acrylic or methacrylic esters such as methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, p-hydroxycyclohexyl acrylate, 2-ethylhexyl acrylate, 2-methoxyethyl methacrylate, 2-ethyloxy methacrylate, 3-methoxypropyl acrylate; hydroxypolyethylene glycol (meth) acrylates, hydroxypolypropylene glycol (meth) acrylates and the corresponding alkoxy derivatives thereof; ethylenically unsaturated monocarboxylic acids such as crotonic acid and itaconic acid and compounds such as vinyl chloride, vinyl acetate, vinyl propionate, vinyl pyrrolidone, acrylamide, methacrylamide, N-alkyl (meth) acrylamides such as N-isopropyl acrylamide, Nt-butyl acrylamide, Nt-octyl acrylamide. Mixtures of such compounds may also be used. It is preferred that the monomer B mixture contains 15-50, more particularly 20-40 mol% (meth) acrylic acid and 50-85, more particularly 60-80 mol% of a different copolymerizable ethylenically unsaturated monomer. Copolymerization of the monomer B mixture will generally provide a copolymer having an acid number of 30-450 and preferably 60-350 and a hydroxyl number of 0- 450 and preferably 60-300. The acid number and hydroxyl number are expressed in mg of KOH per g of copolymer. Optionally, different monomer mixtures A and / or B may be used successively.

The emulsifiers used are preferably made in emulsion polymerization are of an anionic or nonionic nature. Examples of anionic emulsifiers include: Potassium laurate, potassium stearate, potassium oleate, sodium decyl sulfate, sodium dodecyl sulfate and sodium rosinate. Examples of nonionic emulsifiers include: linear and branched alkyl and alkylaryl polyethylene glycol and polypropylene glycol ethers and thioethers, alkyl phenoxypoly (ethyleneoxy) ethanols, such as the 1 mol nonyl phenol adduct for 5-12 moles of ethylene oxide or the sulfate ammonium salt of this pipeline. Also, in emulsion polymerization, conventional radical initiators may be used in usual amounts. Examples of suitable radical initiators include: ammonium per sulfate, sodium per sulfate, potassium per sulfate, bis (2-ethylhexyl) peroxydicarbonate, di-n-butyl peroxydicarbonate, perpivalate t-butyl acid, t-butyl hydroperoxide, cumene hydroperoxide, dibenzoyl peroxide, dilauroyl peroxide, 2,2'-azobisisobutyronitrile and 2,2'-azobis-2-methylbutyronitrile. As suitable reducing agents which may be used in combination with, for example, a hydroperoxide may be mentioned: ascorbic acid, sodium sulphoxylate formaldehyde, thiosulphates, bisulphates, hydrosulphates, amines water soluble, such as diethylene triamine, triethylene tetraamine, tetraethylene pentamine, β, β-dimethyl ethanolamine, β, β-diethyl ethanolamine and reduction salts such as cobalt sulfate, iron, nickel and copper. Optionally, a chain length regulator, for example n-octyl mercaptan, do-decyl mercaptan, 3-mercaptopropionic acid may also be used.

Copolymerization of monomeric mixtures is generally performed at atmospheric pressure at a temperature of 40-100 sC, preferably 60-90 9C, in an atmosphere of an inert gas such as nitrogen. Optionally, however, copolymerization may also be performed at elevated pressure and at a temperature of 40-100 ° C or higher.

Carboxylic acid groups derived from acrylic acid and / or methacrylic acid are at least 40-100% ionized by the addition of 0.5-1.5, preferably 0.8-1.3 equivalents of one ionizing agent per equivalent. of carboxylic acid group. Suitable ionizing agents for carboxylic acid may include ammonia and amines such as β, β-dimethyl ethanolamine, β, β-diethyl ethanolamine, triethyl amine and morpholine. It is preferred that ionization of the carboxylic acid groups be carried out after polymerization.

The coating composition b) may optionally comprise at least one second resin. This second resin is not identical to the resin already present in composition b) and may be selected from the same group of polyaddition, polyester, polyurethane, polyether resins or a mixture thereof.

Suitable polyurethanes may generally be prepared from polyisocyanates and polyols, as known to those skilled in the art.

Examples thereof include Neorez R970 (formerly NeoResins) and Daotan VTW 2275 (formerly Vianova Resins). Also included in the definition of polyurethanes are polyurethane hybrids, such as polyurethane acrylate hybrids. Examples thereof include Neopac E115 (formerly NeoResins) and Daotan VTW 6460 (formerly Vianova Resins).

Preferably the polyurethane is a polyurethane polyurea. More preferably, the polyurethane polyurea comprises:

(i) at least 200 millimoles per 100 g of chemically incorporated carbon group solids --0 - C0--0 — and

ii) a combined total of up to 320 millimoles per 100 g solids of chemically incorporated urethane groups -NH - CO - O — and chemically incorporated urea groups --NH - CO - NH-.

Such polyurethane polyurea dispersions are known from DE 39 36 794.

Preferably, the polyurethane polyurea comprises at least 250 millimoles per 100 g of solids content of chemically incorporated -O-CO-O — carbonate groups and a combined total of 200 to 300 micro-equivalents per 100 g. solids, urethane groups -NH-CO-O — and urea groups --NH - CO - NH--.

Polyurethane polyurea can be prepared in a known manner by reaction:

(a) organic polyisocyanates which do not contain hydrophilic groups or groups convertible to hydrophilic groups having

(b) relatively high molecular weight organic polyhydroxyl compounds which do not have hydrophilic groups or groups convertible to hydrophilic groups;

c) optionally low molecular weight compositions containing at least two isocyanate-reactive groups, but no hydrophilic groups or groups capable of conversion to hydrophilic groups,

d) optionally nonionic hydrophilic initiating components containing at least one isocyanate group or at least one isocyanate-reactive group; and

(e) optionally, initiation components containing at least one ionic group or at least one group capable of conversion to an ionic group, as well as at least one isocyanate-reactive hydrogen atom;

provided that the qualities of the nonionic groups and ionic groups present in components d) and e) are sufficient to ensure the dispersibility of polyurethane polyureas in water.

The reaction between isocyanate groups and hydroxyl groups results in urethane groups, while any urea groups present in the reaction products are formed of amine-functional initiation components and / or the reaction between isocyanate groups and dispersion water, which It is always possible during the preparation of aqueous polyurethane dispersions.

The polyisocyanate component a) includes any polyisocyanate known from polyurethane chemistry. Such polyisocyanates generally have a molecular weight of 112 to 1,000, preferably 140 to 400. Suitable polyisocyanates are those which correspond to the formula Q (NCO) n, where Q represents an organic group obtained by removal of the isocyanate groups from an organic polyisocyanate having a molecular weight of 112 to 1,000, preferably 140 to 400 and n means a number of 2 to 4, preferably 2 or 3 and more preferably 2. In the above formula, Q preferably represents a aliphatic divalent hydrocarbon group having 4 to 18 carbon atoms, a divalent cycloaliphatic hydrocarbon group having 5 to 15 carbon atoms, a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms or an araliphatic hydrocarbon group having 7 to 15 carbon atoms. Examples of suitable polyisocyanates include tetramethylene diisocyanate, dodecamethylene 1,6-diisocyanatohexane diisocyanate (HDI), undecane 2,2,4-trimethylhexane diisocyanate, lysine ester diisocyanate, cyclohexane diisocyanate -1,3- and -1,4-diisocyanate, 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl cyclohexane (IPDI) and 4,4'-diisocyanate dicyclohexylmethane. Also suitable are aromatic diisocyanates, such as 2,4-diisocyanate toluene and / or 2,6-diisocyanate toluene, 4,4'-diisocyanate diphenyl methane and 1,4-diisocyanate isopropyl benzene. HDI, IPDI and mixtures of these diisocyanates are particularly Preferred.

Component b) includes organic polyhydroxyl compounds having a molecular weight of from 300 to 5,000, preferably from 500 to 3,000 and containing at least 50 wt%, preferably more than 70 wt%, polyhydroxy polycarbonates. Polyhydroxy polycarbonates are carbonic acid esters obtained by reacting carbonic acid derivatives, for example diphenyl carbonate or phosgene, with diols. Examples of such diols include ethylene glycol, propane-1,2- and 1,3-diol, butane-1,4- and -1,3-diol, hexane-1,6-diol, octane-1,8-diol. diol, neopentyl glycol, 1,4-bishydroxymethyl cyclohexane, 2-methylpropane-1,3-diol, 2,2,4-trimethylpentane-1,3-diol, diethylene glycol, tri- and tetraethylene glycol, dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, Bisphenol A and tetrabrom Bisphenol A. The diol component preferably contains from 40 to 100% by weight of a hexane diol, preferably hexane-1,6-diol and / or hexane diol derivatives preferably containing ether or ester groups in addition to terminal OH groups, for example, products obtained by reacting 1 mol of hexane diol with ≥ 1 mol, preferably 1 to 2 caprolactone according to DE 17 70 245 or products obtained by self-etherification of hexane diol to form dihexylene or trihexylene glycol according to DE 15 70 540. Polyether polycarbonate diols are described in FIG. The costs in DE 37 17 060 are also very suitable.

The hydroxy polycarbonates should be substantially linear, although they may, if desired, be slightly branched by incorporating polyfunctional components, in particular low molecular weight polyols such as glycerol, trimethylol propane, hexane-1,2, 6-triol, butane-1,2,4-triol, trimethylol propane, pentaerythritol, quinitol, mannitol and sorbitol, methyl glycoside and 1,4,3,6-dianhydrohexitols.

In addition to polyhydroxy polycarbonates, the initiating component

b) may contain other known polyhydroxyl compounds having the previously mentioned molecular weights, e.g.

(b1) dihydroxy polyesters obtained from dicarboxylic acids such as succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, italic acid, isophthalic acid, terephthalic acid, and diols such as ethylene glycol, propane 1,2-diol, propane-1,3-diol, diethylene glycol, butane-1,4-diol, hexane-1,6-diol, octane-1,8-diol, neopentyl glycol, 2-methyl propane -1,3-diol and the various isomeric bishydroxymethyl cyclohexanes;

b2) polylactones, such as ε-caprolactone polymers initiated with the above-mentioned dihydric alcohols; and

b3) polyethers, for example the polymers or copolymers of tetrahydrofuran, styrene oxide, propylene oxide, ethylene oxide, butylene oxides or epichlorohydrin initiated with different initiator molecules such as water, the above mentioned diols or amines containing 2 NH bonds, in particular propylene oxide polymers and copolymers and optionally ethylene oxide. Ethylene oxide may be used as a portion of the amount of ether molecules as long as the resulting polyether diol does not contain more than 10% by weight of ethylene oxide units. It is preferred to use polyether diols which were obtained without the addition of ethylene oxide, especially those based on propylene oxide and tetrahydrofuran only.

Optionally used initiator components c) are known low molecular weight compounds which have a molecular weight below 300, contain hydroxyl and / or amino groups and are at least difunctional in isocyanate addition reactions. Compounds which are difunctional in isocyanate addition reactions (chain extenders), compounds which are at least trifunctional in isocyanate addition reactions (crosslinking agents) and mixtures of such compounds may be used as initiation components c). Examples of such compounds include low molecular weight polyhydric alcohols, such as ethylene glycol, propane-1,2- and -1,3-diol, butane-1,4- and-1,3-diol, hexane-1,6- diol, octane-1,8-diol, neopentyl glycol, 1,4-bishydroxymethyl cyclohexane, 2-methylpropane-1,3-diol, 2,2,4-trimethyl pentane-1,3-diol, glycerol trimethylol propane, trimethylol ethane, isomeric hexane triols and pentaerythritol; low molecular weight diamines such as ethylene diamine, 1,2- and 1,3-diaminopropane, 1,3-, 1,4- and 1,6-diaminohexane, 1,3-diamino-2,2- dimethyl propane, isophorone diamine, 4,4'-diaminodicyclohexyl methane, 4,4-diamino-3,3'-dimethylcyclohexyl methane, 1,4-bis- (2-amino-prop-2-yl) -cyclohexane, hydrazine, hydrazide and mixtures of such diamines and hydrazines; functional upper polyamines such as diethylene triamine, triethylene tetramine, dipropylene triamine and tripropylene tetramine; hydrogenated products of the addition of acrylonitrile to aliphatic or cycloaliphatic diamines, preferably those obtained by the addition of an acrylonitrile group to a diamine molecule, for example hexamethylene propylene triamine, tetramethylene propylene triamine, isophorone propylene triamine or 1 3- or 1,3-cyclohexane propylene triamine and mixtures of such polyamines.

D) Hydrophilic initiation components are compounds containing ethylene oxide units incorporated within polyether chains, specifically:

d1) diisocyanates and / or compositions which contain isocyanate-reactive hydrogen atoms and are difunctional in isocyanate polyaddition reactions, diisocyanates and compositions also containing polyether side chains containing ethylene oxide units and

d2) monoisocyanates and / or compositions which are monofunctional in isocyanate polyaddition reactions and contain an isocyanate-reactive hydrogen atom, monoisocyanates and compositions also containing terminal polyether chains containing ethylene oxide units and

d3) mixtures of d1) and d2).

The preparation of such hydrophilic initiation components is performed by methods analogous to those described in US 3920598, US 3905929, US 4190566 and US 4237264.

The compounds used as the initiating component e) have at least one isocyanate-reactive group and at least one (potentially) ionic group. They include the tertiary amino groups containing alcohols, hydroxy carboxylic acids 1.1, hydroxy sulfonic acids, amino carboxylic acids, and amino sulfonic acids disclosed in US 3479310. Instead of those starting compounds containing potentially ionic groups, the derivatives of corresponding salt types thereof may be used, that is, ionic groups formed by quaternizing or neutralizing the potentially ionic groups. Examples of suitable quaternizing and neutralizing agents for converting potentially ionic groups to ionic groups are also given in US 3479310. When potentially ionic initiating components are used, at least partial conversion of potentially ionic groups to ionic groups is carried out by quaternization or neutralization after or during preparation of the polyurethane polyureas.

Preferred e) initiation components include 2,2-bis- (hydroxymethyl) -alkane monocarboxylic acids having a total of 5 to 8 carbon atoms and / or salts thereof obtained by partial or complete neutralization with organic amines or NH 3 . 2,2-Dimethyl propionic acid (2,2-bishydroxymethyl propionic acid) and / or salts thereof are particularly preferred for use as the initiating component e).

Preparation of the polyurethanes from the starting components a) to e) is carried out in a known manner at one or more stages by using the reagents in proportions such that the equivalent proportion of isocyanate groups present in the starting components for isocyclic groups. Reactive compounds present in the initiation components are from 0.8: 1 to 2: 1, preferably 0.95: 1 to 1.5: 1 and more preferably 0.95: 1 to 1.2: 1.

Component d) is used in such an amount that the polyurethane polyurea contains 0 to 30 wt%, preferably 1 to 20 wt%, of ethylene oxide units incorporated into terminal or side polyether chains.

The amount of component e) and the degree of neutralization required to form ionic groups is calculated to ensure that the finally obtained polyurethane contains 0 to 120, preferably 1 to 80 millimoles, of organic groups per 100 g of solids. The total amount of ethylene oxide units and ionic groups should be sufficient to ensure the availability of polyurethane polyureas in water.

The reaction of the initiation components a) to e) may be carried out in one or more stages, optionally in the presence of a water miscible isocyanate-inert solvent, so that the reaction products are obtained as a solution in such a solvent. In this context, the term "solution" denotes a true solution or a water in oil emulsion which may be formed if, for example, individual initiating components are used in the form of aqueous solutions. Examples of suitable solvents include acetone, methyl ethyl ketone, N-methyl pyrrolidone and any mixtures of such solvents. Such solvents are generally used in such amounts that the reaction products of initiating components a) to e) are obtained as a solution having a non-volatile content of 10 to 70% by weight.

When the preparation of polyurethane polyureas is carried out as a single stage reaction, the isocyanate-reactive group initiation components are preferably mixed together and then reacted with the isocyanate group initiation components. This reaction is preferably carried out initially in the absence of solvents at temperatures of 50 to 150 ° C, optionally in the presence of known catalysts. The viscosity of the mixture increases during the course of the reaction and one of the aforementioned solvents is therefore gradually added to the mixture. The polyurethane content of the organic solution is finally adjusted to a concentration of 10 to 70 wt%, in particular 15 to 55 wt%.

When a two-stage process is employed, an isocyanate prepolymer is preferably first solvent-free prepared at about 50 to 150Â ° C from excessive amounts of isocyanate-containing initiation components and hydroxyl-containing initiation components. NCO / OH equivalent ratio of 1.1: 1 to 3.5: 1, preferably 1.2: 1 to 2.5: 1, with or without a solvent and such isopropanol prepolymer. 1.1 cyanate is then captured in a solvent if no solvent has been used up to this stage. The obtained solution is then further reacted with chain extenders or cross-linking agents (c) which are optionally used in the form of aqueous solutions and are preferably initiation components of the above type containing primary amino groups and / or secondary. The amount of initiation components c) used in the second stage is calculated to ensure that the equivalent proportion of all initiation components used in the first and second stages conforms to previously established conditions.

The end products of both variations (single stage and two stage) are solutions of the reaction products in the solvent mentioned above having a solids content within the ranges indicated above.

If any potentially ionic groups are present, their conversion at least partially to ionic groups by quaternization or neutralization is performed prior to the addition of the dispersion water. If the initiator component e) contains carboxyl groups which is preferred, in particular dimethylol propionic acid, the neutralizing agents used are preferably tertiary amines such as triethylamine, tri-n-butylamine, Ν, Ν, Ν trimethyl cyclohexylamine, N-methyl morpholine, N-methyl piperazine, N, N-dimethyl ethanolamine, N-methyl piperidine and triethanolamine. For neutralization of carboxyl groups it is also preferred to use ammonia under the conditions set out in EP 0269972 A.

After addition of water as a solvent or dispersion medium, at least the major proportion of the auxiliary solvent used is optionally removed by distillation. Water is used in an amount which is sufficient to provide a product with a solids content of 10 to 60 wt%, preferably 20 to 45 wt%.

Polyurethane polyureas may also be prepared by other methods known in the art, for example, using hydrazine chain extenders or diamines in a locked form, i.e. in the form of the corresponding azines or ketimines, as appropriate. disclosed in US 4269748 and US 4829122.

Alternatively, the so-called prepolymer blending process may be used. In this process, an NCO prepolymer is initially prepared as described above and, after at least partially conversion of any potentially ionic groups present in ionic groups, the prepolymer is mixed with water to form an emulsion. The prepolymer NCO groups are then maintained in reaction in the aqueous phase by the addition of amine-functional chain extenders or c) crosslinking agents and / or by reaction with water.

An example of such a polyurethane polyurea dispersion is Bahyhydrol VPLS 2952 ex Bayer. Polyurethane blends may be used.

The coating composition b) optionally comprises a curing agent capable of chemical reaction with the functional groups present in the coating composition b). Examples of such functional groups are hydroxyl groups. Examples of suitable curing agents capable of chemical reaction are the polyisocyanates described above. In this case, the coating composition b) is at least partially curable by chemical reaction.

A minimum degree of crosslinking in layer b) may be beneficial to the performance of the multilayer coating system, in particular in view of improved adhesion between layer a) and layer b). Therefore, in a preferred embodiment, the coating composition (b) is a coating composition which dries essentially by physical drying, that is, by evaporation of water and to a minimum degree by crosslinking.

When the coating composition b) dries essentially by crosslinking, the mobility and / or availability of the catalyst in at least one boundary layer of layer a) and layer b) of the multilayer system according to the invention may be insufficient for effectively cure the coating composition a) in layer a). Accordingly, it is preferred that the coating composition (b) is not the coating composition comprising a polyisocyanate and a thiol-functional compound.

Coating layer b) is preferably a base coating layer for effect and / or color prepared from an aqueous based coating composition. Such a base coating composition usually comprises pigments that impart effect and / or color. Effect and / or color pigments are well known in the art. Aluminum particles and mica particles may be specifically mentioned.

As mentioned above, coating composition b) is an aqueous coating composition. This means that the volatile vehicle liquid is mainly water. However, coating composition b) may also comprise minimal amounts of organic solvents which are compatible with aqueous coating compositions. Suitable organic solvents may include alcohols containing an ether group, such as butoxyethanol, 1-methoxypropanol-2,1-ethoxypropanol-2,1-propoxypropanol-2,1-butoxypropanol-2 and 1 isobutoxy-propanol-2; alcohols, such as methanol and hexanol; and diols, such as ethylene glycol and diethylene glycol.

The invention also relates to a kit of parts for the preparation of an aqueous based coating composition comprising a toner module comprising at least one resin and at least one effect and / or color pigment, optionally a connector module comprising at least at least one resin compatible with the toner module resin and an essentially resin and pigment free reducing module, wherein one of the modules comprises an effective amount of a catalyst for the addition reaction of a thiol-functional compound and a compound. isocyanate-functional. Preferably, the effective amount of a catalyst for the addition reaction of a thiol-functional compound and an isocyanate-functional compound is comprised in the connector module or the reducing module. The catalyst is present in a non-neutralized form when the catalyst is a base catalyst.

For the production of the multilayer coating system of the invention, coating compositions a) and b) may be applied one after the other without intermediate drying, the so-called "wet-on-wet" application. Alternatively, there may be an intermediate drying step. Coating compositions a) and b) may be applied in random order and may be a filler composition, a primer composition, a base coating composition, a transparent coating composition and / or a higher coating composition.

Accordingly, the invention also relates to a process for preparing a multilayer coating system comprising the steps of:

(i) applying a layer b) of an aqueous coating composition b) comprising at least 17 mmol / kg, calculated on the weight of the coating composition b), of a catalyst for the addition reaction of a non-functional compound and an isocyanate-functional compound to a substrate,

(ii) prior to or subsequent to the application of layer b), application of a layer a) of a coating composition a) comprising at least one isocyanate-functional compound and at least one thiol-functional compound such that the layer a) and layer b) have at least one layer boundary in common and

(iii) curing the layer a) at room temperature or elevated temperature, optionally supported by UV and / or visible light irradiation.

In one embodiment, the coating composition (b) is first applied to an optionally coated substrate and subsequently the coating composition (a) is applied over the coating composition (b) to obtain the multiple coating system. layers according to the invention.

Application on a substrate may be via any method known to those skilled in the art, for example via rolling, spraying, brushing, flow coating, dipping and roller coating. Preferably at least one of the coating compositions a) and b) as described above is applied by spraying. The 1.1 coating composition a) and the coating composition b) may also be sprayable coating compositions.

The coating compositions according to the present invention may be applied to any substrate, the substrate may be, for example, metal, for example iron, steel and aluminum, plastic, wood, glass, synthetic material, paper, leather or another coating layer, such as a primer or filler layer.

Curing temperatures are generally between 0 and 80 ° C or between 20 and 60 ° C.

A specific application of the coating system is as a transparent coating / base coating system as is often used in automotive and transport coating. In such a case, the coating composition b) may be an aqueous based coating composition and the coating composition a) may be a transparent coating composition. The coating system and process is especially useful in the catering industry, in particular car repair and repair shops. The coating system and process are also applicable in the automotive industry and for finishing large transportation vehicles such as trucks, buses, trains and airplanes and parts thereof. Examples

Raw materials used:

Sikkens Autowave®: Commercially available modular water-based coating system from Akzo Nobel

Car refinishes

577, 504, 098, Commercially Available Modules from Sikkens

888EC, 888YA Autowave by Akzo Nobel Car Refinishes

WB Activator: Akzo Nobel Car Refinishes Aqueous Commercially Available Reducer Tolonate HDT LV: Rhodia Polyisocyanate

Sanduvor 3206: Clariant Light Stabilizer

Byk 306: Byk Chemie Wetting Additive

DMEA: N, N-Dimethyl Ethanolamine

Preparation of a polyol polyester 1:

A polyester polyol was prepared from the following components:

Hexahydrophthalic anhydride 13.30 kg

Trimethylolpropane 16.80 kg

Isononic acid 6.18 kg

Dimethylol cyclohexane 0.33 kg

85% aqueous phosphoric acid solution 0,04 kg

The components were placed in a stainless steel reactor equipped with a stirrer, a packed column, a condenser, oil heating, temperature controls, a vacuum tubing and a nitrogen inlet. The reaction mixture was heated under a stream of nitrogen. The temperature of the mixture was gradually raised to 240 ° C. The reaction water was distilled at such a rate that the temperature at the top of the packed column did not exceed 103 ° C. Finally, a vacuum of 200 mbar was applied while maintaining the nitrogen stream and the reaction was performed at 240 ° C for one hour until an acid value below 5 mg KOH / g was obtained. The hydroxyl value of the polyol polyester was 269 mg KOH / g. The polyol polyester had an Mn of 1,114 and an Mw of 2146 as measured by gel permeation chromatography using polystyrene as standard. The reaction product was finally cooled to 130 ° C and diluted with n-butyl acetate to provide a polyol polyol solution having a solids content of 77%.

Preparation of a thiol-functional polyester:

In a glass lined reactor equipped with an agitator, a columnless distillation environment, a condenser, oil heating, temperature controls, vacuum and a nitrogen inlet were charged 19.76 kg of the polyol polyester solution 1 described. above. Butyl acetate was distilled at 150 ° C at 70 mbar.

3.87 g of 3-mercaptopropionic acid was added at atmospheric pressure. The esterification reaction was performed at 150 ° C under 1.1 vacuum (maintaining nitrogen flow) until an acid value of approximately 25 mg KOH / g was reached. A second 1.93 kg portion of 3-mercaptopropionic acid was added. Esterification was continued to an acid value of approximately 30 mg KOH / g. 10 g of methane sulfonic acid was added and esterification was continued until no further reaction water was collected. 4.98 kg of n-butyl acetate was added and distilled at 150 ° C at 10 mbar. The reaction mixture was cooled to 130 ° C and diluted with 4.98 kg of n-butyl acetate. The product was cooled to 50-60 ° C and filtered over a 10 micron filter cloth. A thiol-functional polyester was obtained with a solids content of 80.0%, an acid value of 10 mg KOH / g, an SH value of 146 mg KOH / g and a hydroxyl value of 61 mg KOH / g, all based on solids content. The thiol-functional polyester had an Mn of 1,126 and an Mw of 2,297 as measured by gel permeation chromatography using polystyrene as a standard.

Preparation of a coating composition a) comprising an isocyanate-functional compound and thiol-functional compounds:

A sprayable clear coating composition having a molar ratio of isocyanate-reactive groups to isocyanate groups of 100 to 150 was prepared by mixing the following components: pentaerythritol tetrakis (3-mercapto propionate) 250 g

Thiol-functional polyester solution as prepared above 579 g

N-Butyl Acetate 616 g

Sanduvor 3206 24 g

Byk 306 11g

10 wt.% Solution of dibutyl tin dilaurate in acetone 20 g 1: 1 n-butyl / xylene acetate

ToIonatoHDTLV 1,000 g

Α-Amino Acetophenone Photolytic Base 10 g

Preparation of a comparative aqueous ba) coating composition:

A white base coating composition bringing physically drying sprayable water was prepared by mixing the following components:

AW 098 (toner module) 900 g

WB activator (reducer module) 100 g

Preparation of a comparative aqueous coating composition:

A green base coating composition bringing physically drying sprayable water was prepared by mixing the following components:

577 (toner module) 900 g

WB activator (reducer module) 100 g

Preparation of a comparative aqueous by) coating composition:

A red base coating composition bringing physically drying sprayable water was prepared by mixing the following components:

504 (toner module) 900 g

WB activator (reducer module) 100 g

Preparation of a comparative aqueous (b) coating composition:

A silver metal base coating composition bringing physically drying sprayable water was prepared by mixing the following components:

888EC (toner module) 900 g WB Activator (reduction module) 10 g

Preparation of a comparative aqueous coating composition bz):

A golden metal base coat composition bringing physically drying sprayable water was prepared by mixing the following components:

888YA (toner module) 900 g

WB activator (reducer module) 100 g

Comparative multi-layer coating systems A and E were prepared by applying and drying base coat layers of comparative coating compositions ba) to b) to primed aluminum panels as prescribed in the Autowave technical documentation. . The dry layer thickness of the base coatings was about 15 to 40 μm.

Subsequently, the sprayable clear coating composition a) as described above was applied by spraying onto the base coating layers. The applied transparent coatings had a dry layer thickness of about 50 to 80 μιτι. The clear coatings were allowed to dry at room temperature (20-24 ° C).

Preparation of an aqueous b1) coating composition according to the invention:

A white base coating composition bringing physically drying sprayable water was prepared by mixing the

following components:

<table> table see original document page 40 </column> </row> <table>

Preparation of an aqueous b2) coating composition according to the invention:

A green base coating composition bringing physically drying sprayable water was prepared by mixing the following components: 577 (toner module) 900 g

WB activator (reducer module) 90 g

DMEA 10g

Preparation of an aqueous b3) coating composition according to the invention:

A red base coating composition bringing physically drying sprayable water was prepared by mixing the

following components:

504 (toner module) 900 g

WB activator (reducer module) 90 g

DMEA 10g

Preparation of an aqueous b4) coating composition according to the invention:

A silver metal base coating composition bringing physically drying sprayable water was prepared by mixing the following components:

888EC (toner module) 900 g

WB activator (reducer module) 90 g

DMEA 10g

Preparation of an aqueous b5) coating composition according to the invention:

A golden metal base coat composition bringing physically drying sprayable water was prepared by mixing the following components:

888YA (toner module) 900 g

WB activator (reducer module) 90 g

DMEA 10g

Coating compositions b1) to b5) according to the invention contain 1% by weight, calculated on the weight of the total composition, of α, β-dimethyl ethanolamine (DMEA) as a basic catalyst. This corresponds to 112 mmoles / kg of basic catalyst, calculated on the weight of coating composition b). Multilayer coating systems 1 to 5 according to the invention have been prepared by applying and drying base coatings from coating compositions b1) to%) to primed aluminum panels as prescribed in Autowave technical documentation. The dry layer thickness of the base coatings was about 15 to 40 μιτι.

Subsequently, the sprayable clear coating composition a) as described above was applied by spraying onto the base coating layers. The applied transparent coatings had a dry layer thickness of about 50 to 80 μιη. The clear coatings were allowed to dry at room temperature (20-24 ° C) in a laboratory under normal illumination, ie without UV radiation.

Drying of the transparent coatings was determined manually. The clear coating was considered dry without dust when slight rubbing with the thumb hardly left a mark. A tuft of padding, dropped on the paint, could be blown. The transparent coating was considered to be dry by hand when the firm thumb push disappeared after 1-2 minutes.

The results are summarized in Table 1:

<table> table see original document page 42 </column> </row> <table> <table> table see original document page 43 </column> </row> <table>

From Table 1, it can be inferred that the addition of a basic catalyst to the coating composition b) leads to an increased drying rate of the coating composition a) comprising an isocyanate-functional compound and thiol-functional compounds applied. above a coating composition layer b). In the multilayer coating systems 1 to 5 according to the invention, the drying times of the transparent coatings were shorter than the drying times of the transparent coatings in the corresponding comparative multilayer coating systems AeE.

This indicates an increase in cure rate also when the transparent coating is not irradiated with UV radiation. The multilayer coating systems according to the invention also have other desirable properties such as low strike-in, good hardness, flexibility, scratch resistance, high gloss and good resistance to organic solvents. and water.

Claims (19)

A multilayer coating system comprising: - at least one layer a) comprising a coating composition a) comprising at least one isocyanate-functional compound and at least one thiol-functional compound and - at least one layer b) comprising an aqueous coating composition b), - at least one layer a) and at least one layer b) having at least one common layer boundary, characterized in that the coating composition b) -1,1 comprises at least 17 mmol / kg, calculated on the weight of coating composition (b), of a catalyst for the addition reaction of at least one thiol-functional compound and at least one isocyanate-functional compound. Multilayer coating system according to claim 1, characterized in that the coating composition a) comprises pentaerythritol tetrakis (3-mercapto propionate). Multilayer coating system according to claim 1 or 2, characterized in that the coating composition a) comprises a thiol-functional polyester. Multilayer coating system according to claim 3, characterized in that the thiol-functional polyester further comprises hydroxyl groups. Multilayer coating system according to any one of the preceding claims, characterized in that the coating composition a) comprises pentaerythritol tetrakis (3-mercapto propionate) and a thiol-functional polyester. Multilayer coating system according to any one of the preceding claims, characterized in that the coating composition a) comprises a photolatent base. Multilayer coating system according to claim 6, characterized in that the photolatent base is an α-amino acetophenone. Multilayer coating system according to any of the preceding claims, characterized in that layer a) is a transparent coating layer. Multilayer coating system according to any one of the preceding claims, characterized in that the catalyst for the addition reaction of at least one thiol-functional compound and the at least one isocyanate-functional compound in the composition. coating b) is a tertiary amine. Multilayer coating system according to claim 9, characterized in that the tertiary amine is N1N-dimethyl ethanolamine. Multilayer coating system according to any one of claims 1 to 8, characterized in that the catalyst for the addition reaction of at least one thiolfunctional compound and at least one isocyanatefunctional compound in the composition. coating b) is a metal compound with an organic binder wherein the metal is a metal of Groups 3 to 13 of the Periodic Table. Multilayer coating system according to any one of claims 1 to 8, characterized in that the catalyst for the addition reaction of at least one thiolfunctional compound and at least one isocyanatefunctional compound in the composition. coating b) is a cocatalyst comprising a phosphine component and a Michael acceptor component. A multilayer coating system comprising: - at least one layer a) comprising a coating composition a) comprising at least one isocyanate-functional compound and at least one thiol-functional compound and - at least one layer b) comprising an aqueous coating composition b), - at least one layer a) and at least one layer b) having at least one common layer boundary, characterized in that the coating composition b) comprises an effective amount of at least one component of a cocatalyst comprising a phosphine component and a Michael acceptor component and the other of the phosphine component and the Michael acceptor is present in the coating composition a). Multilayer coating system according to any one of the preceding claims, characterized in that layer a) is a base coating layer which confers color and / or effect. Multilayer coating system according to any one of the preceding claims, characterized in that the coating composition b) comprises a curing agent capable of chemical reaction with functional groups present in the coating composition b). A process for preparing a multilayer coating system comprising the steps of: i. applying a layer b) of an aqueous coating composition b) comprising at least 17 mmol / kg, calculated on the weight of the coating composition b), of a catalyst for the addition reaction of a compound thiol-functional and an isocyanate-functional compound to a substrate, ii. prior to or subsequent to the application of layer b) applying a layer a) of a coating composition a) comprising at least one isocyanate-functional compound and at least one thiol-functional compound such that layer a) and layer b) have at least one layer boundary in common and iii. curing the layer a) at room temperature or elevated temperature, optionally supported by UV and / or visible light radiation. Process according to claim 16, characterized in that it is implemented for the finishing or restoration of automobiles, large transport vehicles or parts thereof. A method of increasing the drying rate in a multilayer coating system comprising applying a transparent coating composition (a) comprising at least one isocyanate-functional compound and at least one above thiol-functional compound. of a base coat layer b) prepared from an aqueous base coat composition b) comprising at least 17 mmol / kg, calculated on the weight of the coating composition b), of a catalyst for the reaction of adding at least one thiol-functional compound and at least one isocyanate-functional compound. A kit of parts for the preparation of an aqueous based coating composition comprising: (i) a toner model comprising at least one resin and at least one color and / or effect imparting pigment; (ii) optionally the modulus. connector comprising at least one resin compatible with the toner module resin and (iii) a reduction module essentially free of resins and pigments, wherein at least one of the reducing module and the connector module comprises an effective amount of a catalyst for the addition reaction of a thiol-functional compound and an isocyanate-functional compound and wherein said catalyst is present in non-neutralized form when the catalyst is a base catalyst.