MXPA00011525A - Coating containing hydroxy containing acrylosilane polymer to improve mar and acid etch resistance - Google Patents

Abstract

A coating composition particularly useful as a clear coating used over a pigmented base coat that has improved resistance to marring and to acid etching when exposed to natural weathering conditions containing 40-70%by weight of film forming binder and 30-60%by weight of a volatile liquid carrier for the binder;wherein the binder contains (a) 50-90%by weight, based on the weight of the binder, of an acrylosilane polymer of polymerized monomers from the following group:an alkyl methacrylate, an alkyl acrylate, each having 1-12 carbon atoms in the alkyl group, cycloaliphatic alkyl methacrylate, cycloaliphatic alkyl acrylate, styrene or any mixture of these monomers;hydroxy containing monomers from the following group:hydroxy alkyl methacrylate, hydroxy alkyl acrylate each having 1-4 carbon atoms in the alkyl group, or any mixtures of these monomers;and a mono-ethylenically unsaturated silane monomer;and the polymer having a weight average molecular weight of 1,000-15,000 determined by gel permeation chromatography. (b) 10-50%by weight, based on the weight of the binder of an organic polyisocyanate;and wherein the ratio of isocyanate groups of the organic polyisocyanate to hydroxy groups of the acrylosilane polymer is about 0.4:1 to 1.3:1.

Description

COATING CONTAINING HYDROXY, WHICH CONTAINS A POLYMER OF ACRYLOSILA OR TO IMPROVE THE RESISTANCE TO USUAL WEAR AND RESISTANCE TO THE ATTACK OF THE ACIDS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is directed to coating compositions, in particular to a clear coating composition used as a clear coating on a color coating or base coat of a motor vehicle having improved resistance to the usual wear and tear of acids. 2. Description of the Previous Technique Acid rain and other air pollutants have caused problems of water staining and the acid attack of the finishes used on cars and trucks. The selection finish that is currently used on the exterior of automobiles and trucks is a clear coating / color coating finish in which a clear Ref.124768 coating is applied over a color coating or clear coating which is pigmented to provide protection to the color coating and improve the appearance of the overall finish such as brightness and clarity or sharpness of the image. Another problem is the usual wear resistance of the clear coating. Finishing damage can be caused by mechanical washing procedures used in a typical commercial car wash or by other mechanical damage to the finish. A number of clear coatings containing acrylosilane polymers have been used as clear coatings as shown in Hazan et al., U.S. Pat. No. 5,066,698 issued November 19, 1991, Nordstrom et al., U.S. Pat. No. 5,532,027 issued July 2, 1996 and Lewin et al., U.S. Pat. No. 5,684,084 issued November 4, 1997. However, none of the compositions shown in the above patents have the necessary combination of properties that include the costs that are desirable for an automotive OEM clear coating composition (original equipment manufacture). . There is a need for clear OEM coating compositions that will form finishes that are resistant to acid attack and water stains caused by acid rain and that are resistant to the usual damage.

Brief Description of the Invention A coating composition containing 40-70% by weight of a film-forming binder ^ 30-60% by weight of a volatile liquid carrier for the binder; wherein the binder contains a. 50-90% by weight, based on the weight of the binder, of an acrylosilane polymer of the polymerized monomers of the following group; an alkyl methacrylate, an alkyl acrylate, each having 1-12 carbon atoms in the alkyl group, the cycloaliphatic alkyl methacrylate, the cycloaliphatic alkyl acrylate, the styrene or any mixture of these monomers; the hydroxy-containing monomers of the following group: hydroxyalkyl methacrylate, hydroxyalkyl acrylate each having 1-4 carbon atoms in the alkyl group, or any mixtures of these monomers; and a monoethylenically unsaturated silane monomer, and the polymer having a weight average molecular weight of 1,000-15,000 determined by gel permeation chromatography; b. 10-50% by weight, based on the weight of the binder, of an organic polyisocyanate; and wherein the ratio or proportion of the isocyanate groups of the organic polyisocyanate to the hydroxy groups of the acrylosilane polymer is from 0.4: 1 to 1.3: 1.

Detailed description of the invention The coating composition of this invention is generally used as a clear coating composition which is applied over a base coat which is a pigmented coating composition. The clear coating / color coating finishes are conventionally used on the exterior of automobiles and trucks. The coating composition of this invention forms a clear finish, has improved resistance against usual wear, improved resistance against attack by acids, and improved resistance against the formation of water spots. For a typical car or truck body, metal foil or plastic is used or a composite material can be used. If the steel is used, it is first treated with an oxidation-proof, inorganic compound, such as zinc or iron phosphate and then a primer coating is applied by electrodeposition. Typically, these electrodeposition primers are epoxy modified resins crosslinked with a polyisocyanate and are applied by a;? cathodic electrodeposition process. Optionally, a primer can be applied onto the primer electrodeposited usually by spraying to provide a better appearance and / or improved adhesion of the base coat to the primer. Then a pigmented basecoat or a color coating is applied. A typical color coating comprises a pigment which may include metallic flake pigments such as aluminum flake or flake-flake pigments, a film-forming binder the which may be a polyurethane, an acrylourethane, an acrylic polymer or a silane polymer, and contains a crosslinking agent such as an aminoplast, typically, an alkylated formaldehyde melamine crosslinking agent or a polyisocyanate. The base coat may be carried by a solvent or by water and may be in the form of a dispersion or a solution. A clear coating or topcoat is then applied to the color coating or basecoat before the basecoat is fully cured or hardened and the basecoat and clearcoat are then fully cured in the usual manner by baking at 100-150 °. C for 15-45 minutes. The base coat and clear coat preferably have a dry coating thickness of 2.5-75 microns and 25-100 microns, respectively. The clear coating composition of this invention contains 40-70% by weight of a film-forming binder and 30-60% of a volatile organic liquid carrier which is usually a solvent for the binder and volatilizes at 35 ° C and above this value. The clear coating can also be in a dispersion form. The film-forming binder of the clear coating composition contains 50-90% by weight of an acrylosilane polymer having reactive hydroxyl and silane groups and 10-50% by weight of an organic polyisocyanate crosslinking agent. The acrylosilane polymer comprises polymerized n-silane containing monomers of alkyl methacrylates, alkyl acrylate, each having 1-12 carbon atoms in the alkyl groups, cycloaliphatic alkyl methacrylate, cycloaliphatic alkyl acrylate, styrene or mixtures of any of the previous monomers. The polymer contains polymerized hydroxy which contains monomers such as hydroxy alkyl methacrylate, hydroxy alkyl acrylate each having 1-4 carbon atoms in the alkyl group or a mixture of these monomers and contains polymerized ethylenically monounsaturated silane monomers . The acrylosilane polymer has a weight average molecular weight of 1,000-15,000. All molecular weights described herein are determined by gel permeation chromatography (GPC). Preferred acrylosilane polymers contain 35-75% by weight of the polymerized alkyl or styrene alkyl acrylate or styrene monomers or mixtures thereof, 20-40% by weight of polymerized hydroxy alkyl acrylate or methacrylate monomers or mixtures thereof and 5-25% by weight of the ethylenically monounsaturated silane monomer. A preferred acrylosilane polymer is the product of the polymerization of 35-75% by weight of the non-silane monomers of an alkyl methacrylate, an alkyl acrylate having each of 1-8 carbon atoms in the alkyl group, styrene or mixtures of styrene of these monomers; 20-40% by weight of the hydroxy alkyl methacrylate having 1-4 carbon atoms in the alkyl group; and 5-25% by weight of a monomer containing silane, ethylenically monounsaturated.

Typically the useful ethylenically unsaturated silane-containing monomers are alkyl acrylates, alkyl methacrylates wherein the alkyl groups have 1-12 carbon atoms such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylate butyl, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, lauryl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, nonyl acrylate, and lauryl acrylate. Alkyl cycloaliphatic alkyl acrylates and methacrylates, for example, such as cyclohexyl methacrylate, cyclohexyl acrylate, trimethylcyclohexyl methacrylate, trimethylcyclohexyl acrylate, isobutyl methacrylate, t-butyl cyclohexyl acrylate, methacrylate t -butyl cyclohexyl, isobornyl methacrylate, isobornyl acrylate and the like. The aryl acrylate and the aryl methacrylates can also be used, for example, such as benzyl acrylate and benzyl methacrylate. Mixtures of two or more of the monomers mentioned above are useful in the formulation of the polymer with the desired characteristics.

In addition to the alkyl acrylates or methacrylates, other polymerizable monomers which do not contain silane, in amounts of up to 50% by weight of the polymer, can be used in a silane polymer for the purpose of achieving the desired physical properties such as hardness, appearance, and resistance to habitual wear. Examples of such other monomers are styrene, methyl styrene, acrylamide, acrylonitrile, and methacrylonitrile. Styrene can be used in the range of 0-50% by weight. The hydroxy-functional monomers can be incorporated into the silane polymer to produce a polymer having a hydroxy number of 20 to 200. Typically, the useful hydroxy-functional monomers are hydroxy alkyl acrylates and methacrylates such as methacrylate. of hydroxy ethyl, hydroxy propyl methacrylate, hydroxy butyl methacrylates, hydroxy isobutyl methacrylate, hydroxy ethyl acrylate, hydroxy propyl acrylate, and hydroxy butyl acrylate. Typical commercial hydroxy-functional monomers may contain up to 1% acrylic or methacrylic acid. During polymerization, the acid may cause side reactions involving the silane monomers that extend or expand the molecular weight distribution of the acrylic polymer which will have detrimental effects on the solids content of the paint, the stability of the paint and still cause the gelation during the preparation of the copolymer. Preferably, the acid content of these hydroxy monomers should be limited to about 0.1%. A suitable silane-containing monomer useful in the formation of an acrylosilane polymer is a silane having the following structural formula: wherein R is either CH3, CH3CH2, CH30, or CH3CH20; R1 and R2 are CH3 or CH3CH2; R3 is either H, CH3, or CH3CH2; and n is 0 or a positive integer from 1 to 10. Preferably, R is CH30 or CH3CH20 and n is 1. Typical examples of such silanes are acrylate alkoxy silanes, such as gamma acryloxypropyltrimethoxy silane and methacrylate alkoxy silanes, such as gamma-methacryloxypropyltrimethoxy silane or gamma trimethoxy silyl propyl methacrylate, and gamma-methacryloxypropyltris (2-methoxyethoxy) silane. Other suitable silane monomers have the following structural formula: wherein R, R1 and R2 are as described above and n is a positive integer from 1 to 10. Examples of such silanes are vinylalkoxy silanes, such as vinyltrimethoxy silane, vinyltriethoxy silane, and vinyltris (2-methoxyethoxy) silane . Other monomers containing silane, useful, are acyloxysilanes, including acrylate, silanes, methacrylate, silanes, and vinylacetoxy silanes, such as vinylmethyl diacetoxy silane, acrylatepropyltriacetoxy silane, and methacrylatepropylthiacetoxy silane. Mixtures of the silane-containing monomers mentioned above are also suitable. Consistent with the aforementioned components of the acrylosilane polymer, the following are an example of an acrylosilane polymer useful in the coating composition of this invention which contains the following constituents: 15-30% by weight styrene, 30-50% by weight weight of isobutyl methacrylate, 15-30% by weight of hydroxyethyl methacrylate, and 15-30% by weight of methacryloxypropyl trimethoxy silane.

Typical polymerization catalysts used to form the acrylosilane polymer are the azo-type catalysts such as azo-bis-isobutyronitrile, acetate catalysts such as t-butyl peracetate, di-t-butyl peroxide, t-butyl perbenzoate. -butyl, and t-butyl peroctoate. Typical solvents that can be used to polymerize the monomers and to form the coating composition are ketones such as methyl amyl ketone, isobutyl ketone, methyl ethyl ketone, aromatic hydrocarbon solvents such as toluene, xylene, aromatic solvent "Solvesso" 100, ethers, esters, alcohols, acetates and mixtures of the above. The coating composition may contain from 1-20% by weight of a polyester resin which is the esterification product of an aliphatic dicarboxylic acid, a polyol having at least three reactive hydroxyl groups, a diol, a cyclic anhydride and a cyclic alcohol and having a number average molecular weight of 500-4,000. A preferred polyester resin is the esterification product of adipic acid, trimethylol propane, hexandiol, hexahydrophthalic anhydride and dicyclohexanedimethanol.

Also, the coating composition may contain from 1-20% by weight of an acrylic resin with hydroxy function (without the functionality of the silane). The coating composition also contains an organic polyisocyanate crosslinking agent. Any of the adducts with aromatic, aliphatic, cycloaliphatic, isocyanate, trifunctional and isocyanate isocyanate, conventional, polyol and diisocyanate functions can be used. Typically, the useful diisocyanates are hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-bisphenylene diisocyanate, toluene diisocyanate, biscyclohexyl diisocyanate, tetramethylene xylene diisocyanate, ethyl ethylene diisocyanate, 2,3-dimethyl ethylene diisocyanate, 1-methyltrimethylene diisocyanate, 1,3-dicyclopentylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,3-phenylene diisocyanate, 1,3-diisocyanate, naphthalene, bis- (4-isocyanatocyclohexyl) -methane, and 4,4'-diisocyanatodiphenyl ether. Typical trifunctional isocyanates that may be used are triphenylmethane triisocyanate, 1,3-benzene triisocyanate, and 2,4,6-toluene triisocyanate. The trimers of the diisocyanates can also be used. These trimers may be biurets or isocyanurates. The examples are sold under the registered names of "Desmodur" N3300 or "Tolonate" HDT. These trimers also contain higher oligomers such as pentamers, heptamers, etc., which are; generated during the process of preparing these trimers. A useful isocyanurate is the isocyanurate of isophorone diisocyanate. The isocyanate-functional adducts which are formed from an organic polyisocyanate and a polyol can be used. Any of the polyisocyanates mentioned above can be used with a polyol to form an adduct. Polyols such as trimethylol alkanes similar to trimethyl propane or ethane can be used. A useful adduct is the product of the reaction of tetramethylxylidene diisocyanate and trimethylolpropane and is sold under the trade name "Cythane" 3160. Curing or hardening catalysts are generally used in the coating composition in amounts of 0.1-5. % by weight, based on the weight of the binder, for the catalysis of the crosslinking between the silane portions and the hydroxy portions of the acrylosilane polymer with the isocyanate portions of the polyisocyanate. A mixture of a blocked sulphonic acid catalyst and an alkyl or aryl acid phosphate catalyst such as butyl acid phosphate or phenylic acid phosphate is preferred. Typical blocked acid catalysts are dodecyl benzene sulphonic acid blocked with an amine such as amino methyl propanol. The blocked toluene sulphonic acid can also be used. In a two component composition where component A contains the acrylosilane polymerThe blocked acid catalyst is added to this component and the acid phosphate catalyst is added to the component B which contains the crosslinking agent of the polyisocyanate. Just before application, components A and B are mixed together and applied: usually by spraying or electrostatic spraying. Other catalysts can be used and include dibutyl tin dilaurate, dibutyl tin diacetate, dibutyl tin dichloride, dibutyl tin dibromide, tenyl boron, tetraisopropyl titanate, triethanolamine titanate chelate, dioxide dibutyl tin, dibutyl tin dioctoate, tin octoate, aluminum titanate, aluminum chelates, zirconium chelate, and other such catalysts or mixtures thereof known to those skilled in the art. Tertiary amines and acids or combinations thereof are also useful for catalyzing the silane bond. Other silane curing catalysts are described in U.S. Pat. No. 4,923,945, column 15 to column 17, incorporated herein by reference. To improve the environmental resistance of the clear coating, the ultraviolet light stabilizers or a combination of the ultraviolet light stabilizers can be added to the clear coating composition in the amount of 0.1-10% by weight, based on the weight of the binder. Such stabilizers include the absorbed, filtered, ultraviolet light absorbers and light stabilizers of specified hindered amines. An antioxidant may also be added, in the amount of 0.1-5% by weight, based on the weight of the binder. Typical ultraviolet light stabilizers that are useful include benzophenones, triazoles, triazines, benzoates, hindered amines and mixtures thereof. Specific examples of ultraviolet light stabilizers are described in U.S. Pat. No. 4,591,533, the complete descion of which is incorporated herein for reference. For its good durability, a mixture of "Tinuvin" 1130, "Tinuvin" 384 and "Tinuvin" 123 (hindered amine), all commercially available from Ciba-Geigy, is preferred. The clear coating composition may also include other additives of conventional formulation such as flow control agents, for example, such as Resiflow® S (polybutyl acrylate), BYK® 320 and 325 (high molecular weight polyacrylates); and agents for the control of rheology; such as smoky silica. The conventional solvents and diluents described above are used to disperse and / or dilute the aforementioned polymers of the clear coating composition. Typical base coatings used in combination with the clear coating composition comprise as the film-forming binder a polyurethane, an acrylourethane, a silane resin, an acrylic resin and a crosslinking agent such as a polyisocyanate or a melamine resin rented. The base coat can be a solution transported by water or a solution or dispersion based on a solvent. The basecoat contains pigments such as those conventionally used, including metallic flake pigments such as aluminum flakes.

Both the base coat and the clear coat are applied by conventional techniques such as spraying, electrostatic spraying, submersion, brush application, and flow coating. The following examples illustrate the invention. All parts and percentages are on a weight basis unless otherwise indicated. Molecular weights are determined by GPC (Gel Permeation Chromatography) using polymethyl methacrylate as the standard.

EXAMPLE 1 A polymeric solution of acrylosilane was prepared by copolymerization in the presence of a mixture of butanol / Solvesso Aromatic Solvent 2/1 of 134 parts by weight of styrene (S), 134 parts by weight of hydroxyethyl methacrylate (HEMA), 134 parts by weight. weight of methacryloxypropyl trimethoxy silane (MAPTS) and 268 parts by weight of isobutyl methacrylate (IBMA) in the presence of 53.6 parts by weight of Vazo®674. The resulting polymer solution had a solids content of 67% and a viscosity of X-Y on the Gardner Holdt scale measured at 25 ° C. The polymer composition is 20% S / 20% HEMA / 20% MAPTS / 40% IBMA and has an average molecular weight of 4800.

A coating composition was formulated by mixing together the following ingredients: Portion A Parts by Weight Acrylosilane Polymer Solution (Prepared previously) 80. 0 Amine Light Stabilizers 4. 3 Stored and UV (HALS) 19.7% Tinuvin® 11301, 16.7% Tinuvin® 3841, 4.1% Tinuvin® 1231 and 14.7% Tinuvin® 0791 in 44.8% Solvent Solvent Solvent 100) "Resiflow" S2 (50% Solids one agent of 0.2 control of the polybutyl acrylate flow in Solvesso Aromatic Solvent 100) Solution of the Dodecylbenzene Sulphonic Acid (at 33.3% solids in methanol and blocked with amino methyl propanol) Aromatic solvent Solvesso 100 10. 0 3-Ethoxy Propionate of Ethyl 12. 0 Portion B Solution of Hexa Diisocyanate Trimer24. 0 methylene (at 72% solids Desmodur® 33003 in a 50/35/15 mixture by weight of n-butanol and aromatic hydrocarbon solvent) Total 131. 8 Sources of the above constituents are: 1. Product of Ciba Specialty Chemical Company 2. Product of King Industries Inc. 3. Product of Bayer Corp. 4. Product of E. I. du Pont de Nemours and Company Portion A is loaded into a mixing vessel and mixed and then Portion B is added and mixed to form the coating composition containing 76% by weight of the acrylosilane polymer by weight and 24% by weight of the isocyanate. The coating composition was reduced to a spray viscosity of 35 seconds measured on a # 2 Fisher apparatus with ethyl 3-ethoxy propionate. The steel panels electrically coated with a conventional primer were spray-coated with an acrylic melamine basecoat modified with water-borne polyester, black and after 10 minutes of waiting it was pre-baked for 10 minutes at 83 ° C and then the The clear coating composition prepared above was sprayed to provide a 0.00508 cm (2 mil) film when cured and then the panels were baked at 120 ° C for 30 minutes to form a clear base coat / coating that has a higher gloss of 80 on a 20 ° brightness meter and a hardness of 12 knoop units measured with a Tukon Hardness Machine.

EXAMPLE 2 A polymer solution (B) of acrylosilane was prepared by copolymerizing 108 parts of a monomer / initiator mixture (20 parts of styrene, 30 parts of hydroxyethyl methacrylate, 10 parts of gamma-methacryloxypropyl trimethoxy silane, 28 parts of isobutyl methacrylate, 12 parts of ethylhexyl acrylate, 8 parts of Vazo® 67) in 60 parts of a 2/1 reflux mixture of 100 / n-butanol aromatic solvent. The resulting resin solution was 66% solids, had a Gardner-Holt viscosity of X +, and a MW of 5100 as determined by CPG. A coating composition was formulated by mixing the following ingredients: Portion To Parts in Weight Acrylosilane polymer B 100,. 0 UV / HALS solution (described in Ex. 1) 5. . 4 Resifluow S 0. , 3 Solution of Dodecylbenzene Sulphonic Acid 1. , 7 (described in Ex. 1) Aromatic Solvent 100 12.5 Ethyl 3-Ethoxy Propionate 15.0 Portion B Desmodur® 3300 solution (72% solids 37.5 described in Ex. 1) Phenyl acid phosphate Albright® PA-75 0.6 Total 173.0 A clear coating was prepared and sprayed on a black water-borne base coat, in the same manner as described in Example 1. The base coat / clear coat was baked at 1305 for 30 minutes. The results of the test are shown in the Table I.

Comparative Example 3 This example illustrates a clear two-component urethane coating that does not contain silane with good resistance to acid attack but poor resistance to usual wear. An acrylic polymer solution with function of; hydroxyl (C) was prepared by copolymerizing 104 parts of a monomer / initiator mixture (25 parts of styrene, 32 parts of hydroxyethyl acrylate, 43 parts of n-butyl methacrylate, 4 parts of Vazo® 67) in 60 parts of a reflux mixture 9/1 aromatic solvent 100 / n-butyl acetate solvent. The resulting resin solution was 66% solids, had a Gardner-Holt viscosity of Y-, and a MW of 5300 as determined by CPG. A clear coating was prepared by mixing 2.6 parts of Portion A (bottom) with 1 part of Portion B (bottom): Portion To Parts in Weight Acrylic polymer C (described above) 100, 0 UV / HALS solution (see Example 1) 1. 2 Xylene solution 50% Resifluow S 0. 4 75% solution of phenyl or 0 phenyl phosphate. , 5 in butanol n-butanol 10.0 Aromatic Solvent 100 20.1 3-Ethoxy Ethyl Propionate 13.4 Portion B Desmodur® 3300 39.4 Solution 3 of Desmodur® 4470 39.2 Aromatic Solvent 100 2.2 Butyl Acetate 7.7 Ethyl 3-Ethoxy Propionate 6.0 Xylene 5.5 A clear coating was sprayed onto a: waterborne basecoat, black, in the same manner as described in Example 1. E.L basecoat / clearcoat was baked at 130 ° C for 30 minutes. The test results are shown in the Table I.

Comparative Example 4 This example illustrates a clear coating of 2K urethane which does not contain silane with good wear resistance but poor resistance to attack by the acid. A clear coating was prepared by combining 2. (5 parts of Portion A (bottom) with 1 part of Portion B (bottom).

Portion To Parts in Weight Acrylic Polymer C (described in Example 3) 100.0 UV / HALS Solution (described in Example 1) 7.3 50% Xylene Solution of Resifluow S 0.4 Butyl Benzyl Phthalate 6.0 75% solution of 0.1 phenyl phosphate in butanol n-butanol 10.0 3-Ethoxy Ethyl Propionate 18.3 Portion B Desmodur® 3300 72.0 n-butanol 14.0 Xylene 10.0 Aromatic Solvent 100 4.0 A clear coating was prepared and sprayed on a water-borne, black base coat, in the same manner as described in Example 1.

The basecoat / clearcoat was baked at 130 ° C for 30 minutes. The results of the test are shown in Table I.

Table I Note 1 Lowest temperature (° C) where the acid attack occurs on the test in the gradual furnace Note 2 Damage generated on the Benchtop Car Wash (5 = good, 10 = poor).

Test Methods Acid Attack Resistance Panels, which have a clear, cured coating on the black base coatings, are placed over a gradual temperature furnace with a surface temperature ranging from 45 to 85 ° C. The panels were stained (200 microliters) with an acid solution of pH 1 along the gradient. After 30 minutes of exposure, the stains are removed by washing with deionized water.

Resistance to Habitual Wear A Benchstop car wash machine is used to inflict damage on the cured panels with the clear coating on the black basecoat. The method is described in the GM 9707P Standard Specification Test of General Motors Engineering.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following

Claims (11)

1. A coating composition comprising 40-70% by weight of a film-forming binder and 30-60% by weight of a volatile liquid carrier for the binder; characterized in that the binder consists essentially of: a. 50-90% by weight, based on the weight of the binder, of an acrylosilane polymer consisting essentially of the polymerized monomers of the following group; an ethylenically monounsaturated silane monomer; monomers selected from the group consisting of an alkyl methacrylate, an alkyl acrylate, each having 1-12 carbon atoms in the alkyl group, cycloaliphatic alkyl methacrylate, the cycloaliphatic alkyl acrylate, the styrene or any mixture of these monomers; the hydroxy-containing monomers selected from the group consisting of hydroxyalkyl methacrylate, hydroxyalkyl acrylate each having 1-4 carbon atoms in the alkyl group or any mixtures of these monomers; and the polymer having a weight average molecular weight of 1,000-15,000 determined by gel permeation chromatography; b. 10-50% by weight, based on the weight of the binder of an organic polyisocyanate; and wherein the ratio or proportion of the isocyanate groups of the organic polyisocyanate to the hydroxy groups of the acrylosilane polymer is from 0.4: 1 to 1.3: 1.

2. The coating composition according to claim 1, characterized in that the ethylenically monounsaturated silane monomer has the following structural formula: wherein: R is selected from the group consisting of CH3, CH3CH2, CH30, or CH3CH20; R1 and R2 are individually selected from the group consisting of CH3, or CH3CH2; and R3 is selected from the group consisting of H, CH3, or CH3CH2 and n is 0 or a positive integer from 1 to 10.

3. The coating composition according to claim 2, characterized in that the silane monomer is selected from the group consisting; of gamma trimethoxy silyl propyl methacrylate and gamma trimethoxy silyl propyl acrylate.

. The coating composition according to claim 2, characterized in that the acrylosilane polymer consists essentially of 35-75% by weight, based on the weight of the acrylosilane polymer, of the polymerized monomers selected from the group consisting of alkyl acrylates. , alkyl methacrylates having each 1-8 carbon atoms in the alkyl and styrene group, 20-40% by weight, based on the weight of the acrylosilane polymer, of the polymerized monomers selected from the group consisting of methacrylates. hydroxy alkyl and hydroxy alkyl acrylates each having 1-4 carbon atoms in the alkyl groups and 5-25% by weight of the ethylenically monounsaturated silane monomer.

5. The coating composition according to claim 4, characterized in that the organic polyisocyanate is the trimer of the hexamethylene diisocyanate or the trimer of the isophorone diisocyanate.

6. The coating composition according to claim 5, characterized in that it contains 0.1-5% by weight, based on the weight of the binder, of a mixture of the catalysts of a blocked sulfonic acid catalyst and the acid phosphate of aryl or alkyl .

7. The coating composition according to claim 6, characterized in that the blocked acid catalyst is a blocked dodecyl benzene sulphonic acid and the aryl acid phosphate is the phenyl acid phosphate.

8. The coating composition according to claim 2, characterized in that it contains about 1-10% by weight, based on the weight of the binder, of ultraviolet light absorbers.

9. The coating composition of; according to claim 2, characterized in that the acrylosilane polymer consists essentially; of 35-75% by weight, based on the weight of the polymer of; acrylosilane, of the polymerized monomers selected from the group consisting of alkyl acrylates, alkyl methacrylates each having 1-4 carbon atoms in the alkyl and styrene group, 20-40% by weight, based on the weight of the polymer of acrylosilane, of the polymerized monomers selected from the group consisting of hydroxy alkyl methacrylates and hydroxy alkyl ds acrylates each having 1-4 carbon atoms in the alkyl groups and 5-25% by weight of the ethylenically monounsaturated silane monomer and the organic polyisocyanate is the trimer of hexamethylene diisocyanate or the trimer of isophorone diisocyanate and the coating composition contains 0.1 - 5% by weight, based on the weight of the binder, of a mixture of catalysts of a sulphonic acid catalyst blocked and aryl or alkyl acid phosphate.

10. A two-component coating composition, characterized in that it comprises: Component A of an acrylosilane polymer consisting essentially of 35-75% by weight, based on the weight of the acrylosilane polymer, of the polymerized monomers selected from the group consisting of of alkyl acrylates, alkyl methacrylates each having 1-4 carbon atoms in the alkyl and styrene group, 20-40% by weight, based on the weight of the acrylosilane polymer, of the polymerized monomers selected from the group consisting of of hydroxy alkyl methacrylates and hydroxy alkyl acrylates each having 1-4 carbon atoms in the alkyl groups and 5-25% by weight, of the ethylenically monounsaturated silane monomer and containing 0.1-2% by weight, based on in the weight of component A, of "a blocked dodecylbenzene sulphonic acid and Component B consists of an organic polyisocyanate of the trimer of hexamethylene diisocyanate or the trimer of isophorone diisocyanate and containing 0.1-2% by weight, based on the weight of Component B, of an aryl acid phosphate catalyst; wherein the components A and B are completely mixed together to form a coating composition before application.

11. A substrate, characterized in that it has a base coat layer of a composition of; coating pigmented and coated on the top with the coating composition in accordance with claim 1. ACRYLOSILAN POLYMER TO IMPROVE THE RESISTANCE TO USUAL WEAR AND RESISTANCE TO THE ATTACK OF THE ACIDS SUMMARY OF THE INVENTION The present invention relates to a coating composition particularly useful as a clear coating used on a pigmented base coat having improved resistance to usual wear and an improved resistance to attack by the acid when exposed to environmental conditions. , which contains 40-70% by weight of a film-forming binder and 30-60% by weight of a volatile liquid carrier for the binder; wherein the binder contains: (a) 50-90% by weight, based on the weight of the binder, of an acrylosilane polymer of the polymerized monomers of the following group; an alkyl methacrylate, an alkyl acrylate, each having 1-12 carbon atoms in the alkyl group, cycloaliphatic alkyl methacrylate, the cycloaliphatic alkyl acrylate, the styrene - or any mixture of these monomers; the hydroxy-containing monomers of the following group: hydroxyalkyl methacrylate, hydroxyalkyl acrylate each having 1-4 carbon atoms in the alkyl group or any mixtures of these monomers; and an ethylenically monounsaturated silane monomer, and the polymer having a weight average molecular weight of 1,000-15,000 determined by gel permeation chromatography. (b) 10-50% by weight, based on the weight of the binder of an organic polyisocyanate; and wherein the ratio or proportion of the isocyanate groups of the organic polyisocyanate to the hydroxy groups of the acrylosilane polymer is from 0.4: 1 to 1.3: 1.