2K clear coat coating composition and its uses

Abstract

The present invention provides (A) C1 to C 10 (B) a first resin having at least one primary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having C2 to C6 alkyl groups; 10 A 2K clearcoat coating composition is provided, comprising (C) a second resin having at least one secondary hydroxyl group selected from hydroxyl alkyl (meth)acrylate resins having an alkyl group, and component I comprising at least one amino resin; and (D) component II comprising a crosslinker comprising at least one polyisocyanate, wherein the first resin has a hydroxyl number in the range of 100 to 250 mg KOH / g and a weight average molecular weight in the range of 3,000 to 15,000, and the second resin has a hydroxyl number in the range of 150 to 500 mg KOH / g and a weight average molecular weight in the range of 500 to 2,500. The present invention also provides an article coated with the coating composition of the present invention.

Description

[Technical Field]

[0001] The present invention relates to a 2K clearcoat coating composition for use on automobiles. [Background technology]

[0002] Clearcoats, which act as topcoats to both decorate and protect automobiles, must simultaneously exhibit high initial gloss, good appearance, and sufficient hardness. To meet these performance requirements, clearcoats must be highly crosslinked through the baking process. Currently, solvent-borne 2K clearcoats generally require baking at temperatures above 140°C for at least 30 minutes to ensure sufficient crosslinking. With the social trend toward reducing carbon emissions, lowering baking temperatures can result in significant energy savings, so baking temperatures must be reduced as much as possible.

[0003] Furthermore, for environmental reasons, coating compositions that form clear coats are required to have low VOC or high solids content. However, low VOC or high solids content leads to high viscosity of the coating composition, which makes it difficult to apply a high viscosity coating composition to obtain a good appearance, as well as special requirements from OEM manufacturers.

[0004] WO 2009 / 024351 A1 discloses a coating composition containing: (A) a hydroxyl group-containing resin having a hydroxyl value of 80 to 220 mg KOH / g, a glass transition temperature of −50°C or higher but lower than 0°C, and 25 to 55 mass% of 4-hydroxybutyl (meth)acrylate monomer units; (B) a hydroxyl group-containing resin having a hydroxyl value of 0 to 220 mg KOH / g and a glass transition temperature of 0 to 50°C; and (C) a crosslinking agent containing a polyisocyanate compound. The coating composition of this invention is applied as a top coat coating in an uncrosslinked state and baked at 140°C for 30 minutes to prepare a sample. In this invention, a relatively high baking temperature is required to crosslink the top coat coating.

[0005] CN109476933A discloses a two-layer coating system comprising a first layer comprising a water-borne coating composition and a second layer comprising a solvent-borne coating composition, wherein a catalyst in the water-borne coating composition catalyzes the crosslinking reaction of the solvent-borne coating composition but not the water-borne coating composition, and a catalyst in the solvent-borne coating composition catalyzes the crosslinking reaction of the aqueous coating composition but not the solvent-borne coating composition, and the solvent-borne coating composition and the aqueous coating composition can be cured within 20 minutes at a temperature of 80°C to 120°C. Although the coating composition of this invention can be cured at a relatively low temperature, the two-layer coating system is complicated and requires the use of two different catalysts. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2009 / 024351A1 [Patent Document 2] CN109476933A Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, there remains a need to provide a coating composition that simultaneously has high solids and low viscosity, such that the resulting or obtainable clear coat layer exhibits high initial gloss, good appearance, and sufficient hardness even when baked at low temperatures. [Means for solving the problem]

[0008] In one aspect, the present invention provides a method for producing a pharmaceutical composition comprising: (A) C1~C 10 a first resin having at least one primary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; (B) C2~C10 a second resin having at least one secondary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; and (C) at least one amino resin Component I comprising: (D) at least one polyisocyanate Ingredient II containing a 2K clear coat coating composition comprising: Here, the first resin has a hydroxyl number in the range of 100 to 250 mgKOH / g and a mass average molecular weight in the range of 3,000 to 15,000, and the second resin has a hydroxyl number in the range of 150 to 500 mgKOH / g and a mass average molecular weight in the range of 500 to 2,500.

[0009] In another aspect, the present invention provides an article coated with the coating composition of the present invention.

[0010] It has been surprisingly found that the coating compositions of the present invention simultaneously have low VOC and low viscosity, and furthermore, the coating compositions of the present invention are compatible with low baking temperatures such as 110° C. The clear coat layer obtained or obtainable exhibits high initial gloss, good appearance and sufficient hardness even when baked at lower temperatures. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in detail. It should be understood that the present invention may be embodied in many different ways and should not be construed as limited to the embodiments set forth herein.

[0012] Unless otherwise defined, all technical and scientific terms used herein have the meaning commonly understood by one of ordinary skill in the art to which this invention belongs. As used herein, the following terms have the following meanings unless otherwise defined:

[0013] The articles "a" and "an" are used herein to refer to one or to more than one (ie, to at least one) of the grammatical object of the article or component.

[0014] As used herein, the terms "comprise," "comprises," and the like are used interchangeably with "contain," "include," and the like, and are to be interpreted in an open and non-limiting manner. That is, for example, additional components or elements may be present. Expressions such as "consisting of" or "consisting essentially of" or similar terms can be subsumed within "comprise" or similar terms.

[0015] Unless otherwise specified, all percentages (%) are "% by mass" and parts refer to parts by mass, and "%" and "% by mass" are used interchangeably in the text.

[0016] In the present invention, "(meth)acrylate" means acrylate and methacrylate, "(meth)acrylic acid" means acrylic acid and methacrylic acid, "(meth)acrylamide" means acrylamide and methacrylamide, "acrylic resin" includes acrylic resin and methacrylic resin, and "acrylic monomer" includes acrylic monomer and methacrylic monomer.

[0017] In the present invention, the acid number (AV) is determined in accordance with DIN EN ISO 2114 (date: June 2002), the hydroxyl number (OH number or OHV) is determined in accordance with DIN 53240-2 (date: November 2007), the solids content is determined in accordance with DIN EN ISO 3251 (date: June 2008) and the weight average molecular weight is determined in accordance with DIN 55672-1 (date: August 2007).

[0018] In the present invention, the glass transition temperature of the copolymer is a value calculated by the following formula: 1 / Tg(K)=Σ(mi / Tgi) Tg(℃)=Tg(K)-273 Tg: Glass transition temperature of the copolymer mi: mole fraction of monomer component i Tgi: Glass transition temperature (K) of the homopolymer of monomer component i.

[0019] Furthermore, the glass transition temperature (K) of the homopolymer of monomer component i is based on the value obtained from POLYMER HANDBOOK, 4th Edition, edited by J. Brandrup, Eh Immergut, and E.A. Grulke (1999). For homopolymers of monomers not listed herein, the glass transition temperature can be determined by synthesizing a homopolymer of the monomer having a weight average molecular weight of about 50,000 and measuring the glass transition temperature by differential scanning calorimetry.

[0020] First Resin The first resin has at least one primary hydroxyl group. Preferably, the first resin has at least 60 mol%, e.g., at least 70 mol%, at least 80 mol%, at least 90 mol%, and 100 mol% primary hydroxyl groups based on the total hydroxyl groups of the first resin.

[0021] The first resin has a Tg (glass transition temperature) in the range of 10°C to 80°C, preferably 10°C to 60°C, and more preferably 12°C to 45°C, for example, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, etc.

[0022] The first resin has a hydroxyl number in the range of 100 to 250 mgKOH / g, preferably 120 to 185 mgKOH / g, for example, 110 mgKOH / g, 120 mgKOH / g, 130 mgKOH / g, 140 mgKOH / g, 160 mgKOH / g, 170 mgKOH / g, 180 mgKOH / g, 190 mgKOH / g, 210 mgKOH / g, 220 mgKOH / g, 230 mgKOH / g, 240 mgKOH / g, etc.

[0023] The first resin has a mass average molecular weight in the range of 3,000 to 15,000, preferably 3,500 to 12,000, such as 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, or 14,000.

[0024] In one preferred embodiment of the present invention, the first resin is an acrylic resin containing at least one primary hydroxyl group in the molecule.

[0025] The acrylic resin containing at least one primary hydroxyl group can be synthesized by copolymerizing a primary hydroxyl group-containing acrylic monomer with another copolymerizable monomer by a conventional method such as radical polymerization.

[0026] Examples of primary hydroxyl-containing acrylic monomers include C1-C 10, preferably hydroxylalkyl(meth)acrylates having a C2 to C6 alkyl group, for example, 2-hydroxyethyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 5-hydroxypentyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 7-hydroxyheptyl(meth)acrylate, 8-hydroxyoctyl(meth)acrylate, 7-methyl-8-hydroxyoctyl(meth)acrylate, 2-methyl-8-hydroxyoctyl(meth)acrylate, 9-hydroxynonyl(meth)acrylate, and ethylene oxide and / or propylene oxide adducts of 2-hydroxyethyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate or 4-hydroxybutyl(meth)acrylate, preferably 2-hydroxyethyl(meth)acrylate. acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 7-hydroxyheptyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 7-methyl-8-hydroxyoctyl (meth)acrylate, 2-methyl-8-hydroxyoctyl (meth)acrylate, 9-hydroxynonyl (meth)acrylate, or a combination thereof, more preferably 2-hydroxyethyl acrylate (2-HEA), 2-hydroxyethyl methacrylate (2-HEMA), 3-hydroxypropyl acrylate (3-HPA), 3-hydroxypropyl methacrylate (3-HPMA), 4-hydroxybutyl acrylate (4-HBA), and 4-hydroxybutyl methacrylate (4-HBMA). The primary hydroxyl-containing acrylic monomers can be used alone or in combination of two or more.

[0027] Examples of other copolymerizable monomers include C1-C 20 - alkyl (meth)acrylates, preferably C1-C 10alkyl(meth)acrylates, such as methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, tert-butyl(meth)acrylate, amyl(meth)acrylate, hexyl(meth)acrylate, cyclohexyl(meth)acrylate, n-octyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, nonyl(meth)acrylate, lauryl(meth)acrylate, isobornyl(meth)acrylate, stearyl(meth)acrylate, cyclohexyl methacrylate (CHMA); Styrene, (meth)acrylic acid, maleic acid, caprolactone, maleic anhydride, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, aminoalkyl (meth)acrylate, (meth)acrylamide or its derivatives, such as N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, N-methylolacrylamide, N-methylolacrylamide methyl ether, and N-methylolacrylamide butyl ether. Other copolymerizable monomers can be used alone or in combination of two or more, and can be reacted with the primary hydroxyl group-containing acrylic monomer during polymerization.

[0028] Preferably, the other copolymerizable monomer is methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, The acrylate, (meth)acrylic acid, caprolactone, styrene or a combination thereof, preferably at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylic acid, caprolactone and styrene.

[0029] The first resin comprises at least 60% by weight, preferably at least 70% by weight, more preferably at least 80% by weight, such as 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc., of units derived from acrylic monomers, based on the total weight of the first resin. The acrylic monomers include any acrylic monomers having at least one primary hydroxyl group and other copolymerizable acrylic monomers.

[0030] In a preferred embodiment of the present invention, the first resin contains 60% to 90% by mass, for example 65% to 85% by mass, or 70% to 80% by mass, of units derived from acrylic monomers, based on the total mass of the first resin.

[0031] The first resin comprises 20% by mass to 50% by mass, preferably 25% by mass to 45% by mass, for example 30% by mass, 35% by mass, 40% by mass, etc. of units derived from primary hydroxyl-containing acrylic monomers, based on the total mass of the first resin.

[0032] The first resin contains 50% by mass to 80% by mass, preferably 55% by mass to 75% by mass, for example 60% by mass, 65% by mass, 70% by mass, etc. of units derived from other copolymerizable monomers, based on the total mass of the first resin.

[0033] Preferably, the first resin has an acid value in the range of 0 to 20 KOH / mg / g, preferably 2 to 20 KOH / mg / g, such as 5 KOH / mg / g, 10 KOH / mg / g, 15 KOH / mg / g, etc.

[0034] The 2K coating composition comprises 10% to 70% by weight, preferably 20% to 50% by weight, of the first resin, based on the total weight of the coating composition, for example 10%, 20%, 30%, 40%, 50%, 60%, 70% by weight, etc.

[0035] The first resin can be produced by a conventional method such as radical polymerization. Examples of radical polymerization initiators include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 4,4'-azobis-4-cyanovaleric acid, 1-azobis-1-cyclohexanecarbonitrile, and dimethyl-2,2'-azobisisobutyrate, and organic peroxides such as methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,5,5-trimethylhexanone peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)-cyclohexane, 2,2- Examples of the radical polymerization initiator include bis(t-butylperoxy)octane, t-butyl hydroperoxide, diisopropylbenzene hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide (DTBP), t-butylcumyl peroxide, isobutyl peroxide, lauroyl peroxide, benzoyl peroxide, diisopropyl peroxydicarbonate, tertiary butyl peroxy-2-ethylhexanoate (TBPEH), t-butyl peroxy neodecanoate, t-butyl peroxy laurate, t-butyl peroxy benzoate, and t-butyl peroxy isopropyl carbonate. These radical polymerization initiators may be used alone or in combination of two or more.

[0036] The amount of the radical polymerization initiator is not particularly limited, but is preferably 0.01% by mass to 20% by mass based on the total mass of the radically polymerizable monomers.

[0037] Examples of suitable organic solvents that can be used in producing the first resin include aliphatic hydrocarbon-based solvents such as cyclohexane and ethylcyclohexane, aromatic hydrocarbon-based solvents such as toluene, xylene, ethylbenzene, and aromatic naphtha, ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone, ester-based solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, 3-methoxybutyl acetate, and bis(2-ethylhexyl)adipate, ether-based solvents such as dibutyl ether, tetrahydrofuran, 1,4-dioxane, and 1,3,5-trioxane, and nitrogen-containing solvents such as acetonitrile, valeronitrile, N,N-dimethylformamide, and N,N-diethylformamide. The organic solvent may be a single type or a mixed solvent containing two or more types.

[0038] When producing the first resin, any method may be used to add the organic solvent and the radical polymerization initiator. However, from the viewpoint of controlling the heat of polymerization and the heat of reaction, a method in which an organic solvent is introduced into a reactor and the radical polymerizable monomer or an organic solution thereof is dropped from a dropping tank while stirring is preferred.

[0039] The polymerization temperature for the above polymerization reaction varies depending on the type of radical polymerization initiator, but is preferably in the range of 50°C to 200°C, more preferably 100°C to 160°C, such as 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, or 190°C.

[0040] Second Resin There is no specific definition regarding the Tg of the second resin. In one embodiment of the present invention, the second resin has a Tg in the range of -50°C to 150°C, for example, -40°C, -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, etc.

[0041] The second resin has a hydroxyl number in the range of 150 to 500 mgKOH / g, preferably 200 to 300 mgKOH / g, for example, 150 mgKOH / g, 200 mgKOH / g, 250 mgKOH / g, 300 mgKOH / g, 350 mgKOH / g, 400 mgKOH / g, 450 mgKOH / g, etc.

[0042] The mass average molecular weight of the second resin is less than 3,000, preferably in the range of 500 to 2,500, for example, 1,000, 1,500, or 2,000.

[0043] In one preferred embodiment of the present invention, the second resin is an acrylic resin containing at least one secondary hydroxyl group in the molecule.

[0044] The second resin is C2 to C 10 Preferably, the copolymer contains monomer units derived from a hydroxylalkyl (meth)acrylate having a C2 to C6 alkyl group.

[0045] The acrylic resin having at least one secondary hydroxyl group can be synthesized by copolymerizing a secondary hydroxyl-containing acrylic monomer, any primary hydroxyl-containing acrylic monomer, and other copolymerizable monomers by a conventional method such as radical polymerization.

[0046] Examples of secondary hydroxyl-containing acrylic monomers include hydroxylalkyl (meth)acrylates having alkyl groups with a carbon number ranging from 2 to 10, preferably from 2 to 6, such as 1-hydroxyethyl (meth)acrylate, 1- or 2-hydroxypropyl (meth)acrylate, 1-, 2- or 3-hydroxybutyl (meth)acrylate, 1-, 2-, 3- or 4-hydroxypentyl (meth)acrylate, 1-, 2-, 3-, 4- or 5-hydroxyhexyl (meth)acrylate, 1-, 2-, 3-, 4-, 5- or 6 ... Examples of the secondary hydroxyl-containing acrylic monomer include hydroxyheptyl (meth)acrylate, 1-, 2-, 3-, 4-, 5-, 6-, or 7-hydroxyoctyl (meth)acrylate, and ethylene oxide and / or propylene oxide adducts of 1-hydroxyethyl (meth)acrylate, 1- or 2-hydroxypropyl (meth)acrylate, and 1-, 2-, or 3-hydroxybutyl (meth)acrylate, preferably 1-hydroxyethyl (meth)acrylate, 1- or 2-hydroxypropyl (meth)acrylate, and 1-, 2-, or 3-hydroxybutyl methacrylate. The secondary hydroxyl-containing acrylic monomer may be used alone or in combination of two or more.

[0047] Preferably, the secondary hydroxyl-containing acrylic monomer is at least one selected from the group consisting of 1-hydroxyethyl acrylate (1-HEA), 1-hydroxyethyl methacrylate (1-HEMA), 1- or 2-hydroxypropyl acrylate (1- or 2-HPA), 1- or 2-hydroxypropyl methacrylate (1- or 2-HPMA), 1-, 2- or 3-hydroxybutyl acrylate (1-, 2- or 3-HBA) and 1-, 2- or 3-hydroxybutyl methacrylate (1-, 2- or 3-HBMA), more preferably 2-hydroxypropyl methacrylate (2-HPMA).

[0048] Examples of primary hydroxyl-containing acrylic monomers include C1-C 10hydroxyalkyl (meth)acrylates, preferably having a C2 to C6 alkyl group, such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 7-hydroxyheptyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 7-methyl-8-hydroxyoctyl (meth)acrylate, 2-methyl-8-hydroxyoctyl (meth)acrylate, 9-hydroxynonyl (meth)acrylate, and ethylene oxide and / or propylene oxide adducts of 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, preferably 2-hydroxyethyl (meth)acrylate. acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 7-hydroxyheptyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 7-methyl-8-hydroxyoctyl (meth)acrylate, 2-methyl-8-hydroxyoctyl (meth)acrylate, 9-hydroxynonyl (meth)acrylate, or a combination thereof, more preferably 2-hydroxyethyl acrylate (2-HEA), 2-hydroxyethyl methacrylate (2-HEMA), 3-hydroxypropyl acrylate (3-HPA), 3-hydroxypropyl methacrylate (3-HPMA), 4-hydroxybutyl acrylate (4-HBA), and 4-hydroxybutyl methacrylate (4-HBMA). The primary hydroxyl-containing acrylic monomers can be used alone or in combination of two or more.

[0049] Examples of other copolymerizable monomers include C1-C 20 - alkyl (meth)acrylates, preferably C1-C 10- alkyl (meth)acrylates, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl methacrylate (C HMA); styrene; (meth)acrylic acid; maleic acid; maleic anhydride; N,N-dimethylaminoethyl (meth)acrylate; N,N-diethylaminoethyl (meth)acrylate; N,N-dimethylaminopropyl (meth)acrylate; aminoalkyl (meth)acrylate; (meth)acrylamide or its derivatives, such as N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, N-methylolacrylamide, N-methylolacrylamide methyl ether, and N-methylolacrylamide butyl ether. Other copolymerizable monomers can be used alone or in combination and can be reacted with the hydroxyl group-containing acrylic monomer during polymerization.

[0050] Preferably, the other copolymerizable monomer is at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, (meth)acrylic acid, styrene, or a combination thereof, preferably methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylic acid, and styrene.

[0051] The second resin comprises at least 70%, preferably at least 80%, more preferably at least 90%, such as 75%, 80%, 85%, 90%, 95%, etc., by weight of units derived from acrylic monomers, based on the total weight of the second resin, including all hydroxyl-containing acrylic monomers and other copolymerizable acrylic monomers.

[0052] In a preferred embodiment of the present invention, the second resin contains 85% by mass to 95% by mass of units derived from acrylic monomers, based on the total mass of the second resin.

[0053] The second resin comprises 30% to 70% by mass, preferably 40% to 60% by mass, for example 50% by mass, of units derived from a hydroxyl-containing acrylic monomer, preferably a secondary hydroxyl-containing acrylic monomer, based on the total mass of the second resin.

[0054] The second resin contains 30% to 70% by mass, and preferably 40% to 60% by mass, of units derived from other copolymerizable monomers, based on the total mass of the second resin.

[0055] In one embodiment, the second resin is a resin having at least one secondary hydroxyl group and at least one primary hydroxyl group, wherein the molar ratio of the secondary hydroxyl groups to the primary hydroxyl groups in the second resin is in the range of 2:1 to 10:1, preferably 3:1 to 5:1, such as 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, and 9:1.

[0056] Preferably, the second resin has an acid value in the range of 0 to 30 KOH / mg, such as 5 KOH / mg / g, 10 KOH / mg / g, or 15 KOH / mg / g.

[0057] The coating composition comprises 2% to 20% by mass, preferably 5% to 15% by mass, such as 5%, 10%, 15%, 20% by mass, etc. of the second resin based on the total mass of the coating composition.

[0058] The mass ratio of the first resin to the second resin in the coating composition is in the range of 2:1 to 10:1, preferably 3:1 to 5:1, such as 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, etc.

[0059] The second resin can be produced by a conventional method such as radical polymerization, and the method for preparing the first resin can also be applied to the second resin.

[0060] Preferably, the sum of the first resin and the second resin is in the range of 40% by mass to 80% by mass, based on the total mass of the coating composition, such as 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 55%, 60%, 65%, 70%, and 75% by mass.

[0061] Amino Resin Amino resins are condensation products of aldehydes, particularly formaldehyde, with, for example, urea, melamine, guanamine, or benzoguanamine. Amino resins contain alcohol groups, preferably methylol groups, which are generally partially or preferably completely etherified with alcohol. In particular, melamine-formaldehyde resins etherified with lower alcohols, particularly methanol or butanol, are used. It is highly preferred to use melamine-formaldehyde resins etherified with lower alcohols, particularly methanol and / or ethanol and / or butanol, as crosslinking agents.

[0062] In this context, any amino resin suitable for transparent topcoat or clearcoat materials, or a mixture of such resins, can be used, particularly preferred are conventional amino resins in which the methylol and / or methoxymethyl groups have been defunctionalized with carbamate or allophanate groups.

[0063] A preferred amino resin is melamine resin as a crosslinker. Crosslinkers of this type are described in U.S. Pat. No. 4,710,542 A and EP 0,245 700 B1, and also in the article by B. Singh and Coworkers, "Carbamylmethylated Melamine, a New Crosslinker for the Coatings Industry," Advanced Organic Coatings Science and Technology Series, Vol. 13, pp. 193-207, 1991. For more information on melamine resins, see Rompp Lexikon Lacke und Druckfarben, pp. 374 and 375, "Melamine Resins," and Johan Bieleman, "Lackadditive" [Coating Additives], pp. 242-250, 1988, section "Melamine-Resin-Crosslinking Systems."

[0064] Melamine resins are well known to those skilled in the art and are supplied as commercial products by many companies. Examples of suitable low molecular weight fully etherified melamine resins include Cymel® 301 and 303 from Cytec, Luwipal® 066 from BASF Aktiengesellschaft, and Resimene® and Maprenal® MF from Solutia.

[0065] Suitable examples of relatively low molecular weight, highly etherified melamine resins containing free imino groups include Cymel® 325 and 327 (etherified with methanol), Cymel® 202 and 203 (mixtures etherified with methanol and butanol) and 1158 (etherified with butanol) from Cytec, Luwipal® 062 (etherified with methanol), 018 (etherified with butanol) and 014 (etherified with butanol, relatively high viscosity) from BASF Aktiengesellschaft, Maprenal® MF 927 and 3950 (etherified with methanol), VMF 3611 and 3615 (etherified with butanol) and 580 (etherified with isobutanol), Resimene® 717 and 718 (etherified with methanol), and 750 and 5901 (etherified with butanol), and also MB 9539 from Solutia, and Akzo and Setamine® US 138 and US 146 (etherified with butanol) from Resins.

[0066] Examples of suitable relatively low molecular weight partially etherified melamine resins include Luwipal® 012, 016, 015, 018 and 010 from BASF Aktiengesellschaft, Maprenal® MF 590 and 600 from Solutia, and Setamine® US 132 and 134 from Akzo Resins.

[0067] The amount of amino resin is in the range of 1% by weight to 30% by weight, preferably 5% by weight to 15% by weight, such as 3%, 8%, 10%, 12%, 16%, 18%, 20%, and 25% by weight, based on the total weight of the coating composition.

[0068] Polyisocyanate As the crosslinking agent in the coating composition of the present invention, a polyisocyanate having at least two, preferably at least three, isocyanate groups per molecule can be used, and one or more types can be used in combination.

[0069] Examples of polyisocyanates having at least two isocyanate groups per molecule include aliphatic, cycloaliphatic, araliphatic and / or aromatic isocyanates, such as 1,4-tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexane-1,6-diisocyanate, methylcyclohexyl-diisocyanate, p-phenylene diisocyanate, biphenyl diisocyanate, tolylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, methylenebis(phenylisocyanate), lysine methyl ester diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 2-isocyanatoethyl-2,6-diisocyanatohexanoate, and the like. cyclohexane 1,4-diisocyanate, 1,4- and / or 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), cyclohexane 1,4-diisocyanate, 1-methylcyclohexane 2,4- and / or 2,6-diisocyanate and / or dicyclohexylmethane 4,4'-, 2,4'- and 2,2'-diisocyanate, diphenylmethane 2,2'-, 2,4'- and / or 4,4'-diisocyanate (MDI), polymeric MDI, naphthylene 1,5-diisocyanate (NDI), tolylene 2,4- and / or 2,6-diisocyanate (TDI), 3,3'-dimethyldiphenyl diisocyanate, 1,2-diphenylethane diisocyanate and / or phenylene diisocyanate, biuret, isocyanurate, oligomeric or polymeric isocyanates of these compounds, or mixtures thereof.

[0070] In a preferred embodiment, the polyisocyanate is an aliphatic polyisocyanate, such as Desmodur N100, N75, N3200, N3400, N3600, Desmodur 3390, and Desmodur Z4470 from Covestro. In a preferred embodiment, the polyisocyanate is an oligomeric isocyanate compound, such as an isocyanate dimer or an isocyanate trimer. In a particular embodiment, the polyisocyanate is a trimer of HDI, such as Desmodur 3390 from Covestro.

[0071] The molar ratio of NCO groups in the polyisocyanate to hydroxyl groups in both the first and second resins ranges from 0.7:1 to 1.6:1, preferably from 1.1:1 to 1.3:1.

[0072] In one particular embodiment according to the present invention, the 2K clear coat coating composition comprises (A) 15% by mass to 75% by mass, preferably 25% by mass to 60% by mass of C1 to C 10 a first resin having at least one primary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; (B) 2% by mass to 25% by mass, preferably 5% by mass to 15% by mass of C2 to C 10 a second resin having at least one secondary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; and (C) at least one amino resin Component I comprising: (D) at least one polyisocyanate Ingredient II containing Including, Here, the first resin has a Tg of 10°C to 80°C, a hydroxyl number in the range of 100 to 190 mgKOH / g, and a weight average molecular weight in the range of 3,000 to 15,000, the second resin has a hydroxyl number in the range of 150 to 500 mgKOH / g and a weight average molecular weight in the range of 500 to 2,500, and the total weight percent of the first resin and the second resin is in the range of 40% to 80% by weight based on the total weight of the coating composition.

[0073] In another particular embodiment according to the present invention, the 2K clear coat coating composition comprises (A) 15% by mass to 75% by mass, preferably 25% by mass to 60% by mass of C1 to C 10 a first resin having at least one primary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; (B) 2% by mass to 25% by mass, preferably 5% by mass to 15% by mass of C2 to C 10 a second resin having at least one secondary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; and (C) at least one amino resin Component I comprising: (D) at least one polyisocyanate Ingredient II containing Including, Here, the first resin has a Tg of 10°C to 80°C, a hydroxyl number in the range of 120 to 140 mgKOH / g, and a weight average molecular weight in the range of 10,000 to 15,000, the second resin has a hydroxyl number in the range of 150 to 500 mgKOH / g and a weight average molecular weight in the range of 500 to 2,500, and the total weight percent of the first resin and the second resin is in the range of 40% to 80% by weight based on the total weight of the coating composition.

[0074] In another particular embodiment according to the present invention, the 2K clear coat coating composition comprises (A) 15% by mass to 75% by mass, preferably 25% by mass to 60% by mass of C1 to C 10a first resin having at least one primary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; (B) 2% by mass to 25% by mass, preferably 5% by mass to 15% by mass of C2 to C 10 a second resin having at least one secondary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; and (C) at least one amino resin Component I comprising: (D) at least one polyisocyanate Ingredient II containing Including, Here, the first resin has a Tg of 10°C to 80°C, a hydroxyl number in the range of 140 to 190 mgKOH / g, and a weight average molecular weight in the range of 10,000 to 15,000, the second resin has a hydroxyl number in the range of 150 to 500 mgKOH / g and a weight average molecular weight in the range of 500 to 2,500, and the total weight percent of the first resin and the second resin is in the range of 40% to 80% by weight based on the total weight of the coating composition.

[0075] In another particular embodiment according to the present invention, the 2K clear coat coating composition comprises (A) 15% by mass to 75% by mass, preferably 25% by mass to 60% by mass of C1 to C 10 a first resin having at least one primary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; (B) 2% by mass to 25% by mass, preferably 5% by mass to 15% by mass of C2 to C 10 a second resin having at least one secondary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; and (C) at least one amino resin Component I comprising: (D) at least one polyisocyanate Ingredient II containing Including, Here, the first resin has a Tg of 10°C to 80°C, a hydroxyl number in the range of 190 to 250 mgKOH / g, and a weight average molecular weight in the range of 3,000 to 5,000, the second resin has a hydroxyl number in the range of 150 to 500 mgKOH / g and a weight average molecular weight in the range of 500 to 2,500, and the total weight percent of the first resin and the second resin is in the range of 40% to 80% by weight based on the total weight of the coating composition.

[0076] In another particular embodiment according to the present invention, the 2K clear coat coating composition comprises (A) 15% by mass to 75% by mass, preferably 25% by mass to 60% by mass of C1 to C 10 a first resin having at least one primary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; (B) 2% by mass to 25% by mass, preferably 5% by mass to 15% by mass of C2 to C 10 a second resin having at least one secondary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; and (C) at least one amino resin Component I comprising: (D) at least one polyisocyanate Ingredient II containing Including, Here, the first resin has a Tg of 10°C to 80°C, a hydroxyl number in the range of 190 to 250 mgKOH / g, and a weight average molecular weight in the range of 5,000 to 10,000, the second resin has a hydroxyl number in the range of 150 to 500 mgKOH / g and a weight average molecular weight in the range of 500 to 2,500, and the total weight percent of the first resin and the second resin is in the range of 40% to 80% by weight based on the total weight of the coating composition.

[0077] If necessary, various additives may be added, such as a leveling agent, a slack adjusting agent, an antifoaming agent, a light stabilizer, an ultraviolet absorber, a colorant, an antioxidant, a surfactant, a surface conditioner, a curing reaction catalyst, an antistatic agent, a fragrance, a dewatering agent, and a rheology control agent, such as polyethylene wax, polyamide wax, and internally crosslinked resin fine particles.

[0078] The coating composition of the present invention can be used as a clear coat or as a color paint by adding dyes, pigments, etc.

[0079] The coating composition of the present invention can be applied by any method known in the art, such as air spraying, electrostatic air spraying, roll coating, flow coating, or dipping, or by brushing, bar coating, or applicator, etc. Spray coating is preferred in the present invention.

[0080] The thickness of the coating film obtained by applying the coating composition of the present invention is not particularly limited, but the thickness of the coating film after drying is preferably in the range of 10 μm to 150 μm, more preferably 30 μm to 60 μm.

[0081] Furthermore, examples of substrates to which the coating composition of the present invention can be applied include both inorganic and organic materials such as metal, wood, glass, fabric, plastic, foam, elastomer, paper, ceramics, concrete, gypsum board, etc. Metal substrates are preferred. These substrate materials can be used with or without pretreatment.

[0082] Examples of coated articles that have been obtained or can be obtained include metal products, structural materials, wood products, plastic products, rubber products, paper products, ceramic products, glass products, etc., and more specifically include automobiles and automobile parts (for example, bodies, bumpers, spoilers, mirrors, wheels, interior decoration parts, etc. made of various materials), metal plates such as steel plates, bicycles, bicycle parts, materials used for roads (for example, guardrails, traffic signs, sound insulation walls, etc.), materials used for tunnels (for example, side wall panels, etc.), ships, railway vehicles, aircraft, furniture, musical instruments, household electrical appliances, building materials, containers, office supplies, sporting goods, toys, etc., with metal products being preferred.

[0083] Embodiment Although the following detailed description provides certain preferred embodiments, those skilled in the art should understand that these embodiments are merely exemplary and that the invention may be practiced in alternative ways.

[0084] Embodiment 1 (A) C1~C 10 a first resin having at least one primary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; (B) C2~C 10 a second resin having at least one secondary hydroxyl group, preferably selected from hydroxyl alkyl (meth)acrylate resins having a C2 to C6 alkyl group; and (C) at least one amino resin Component I comprising: (D) at least one polyisocyanate Ingredient II containing 1. A 2K clear coat coating composition comprising: A coating composition, wherein the first resin has a hydroxyl number in the range of 100 to 250 mgKOH / g and a weight average molecular weight in the range of 3,000 to 15,000, and the second resin has a hydroxyl number in the range of 150 to 500 mgKOH / g and a weight average molecular weight in the range of 500 to 2,500.

[0085] Embodiment 2 2. The coating composition of embodiment 1, wherein the first resin has a Tg in the range of 10°C to 80°C, preferably 10°C to 45°C.

[0086] Embodiment 3 3. The coating composition of embodiment 1 or 2, wherein the first resin has an acid number in the range of 0 to 20, preferably 2 to 20.

[0087] Embodiment 4 4. The coating composition of any one of embodiments 1 to 3, wherein the first resin has a weight average molecular weight in the range of 3,500 to 12,000.

[0088] Embodiment 5 5. The coating composition of any one of the preceding claims, wherein the first resin has a hydroxyl number in the range of 190 to 250 mg KOH / g and a weight average molecular weight in the range of 3,000 to 10,000.

[0089] Embodiment 6 5. The coating composition of any one of the preceding claims, wherein the first resin has a hydroxyl number in the range of 100 to 190 mg KOH / g and a weight average molecular weight in the range of 3,000 to 15,000.

[0090] Embodiment 7 7. The coating composition of any one of the preceding embodiments, wherein the second resin has a hydroxyl number in the range of 200 to 300 mg KOH / g.

[0091] Embodiment 8 8. The coating composition of any one of the preceding embodiments, wherein the second resin further comprises at least one primary hydroxyl group.

[0092] Embodiment 9 9. The coating composition of embodiment 8, wherein the molar ratio of secondary hydroxyl groups to primary hydroxyl groups in the second resin ranges from 2:1 to 10:1, preferably from 3:1 to 5:1.

[0093] Embodiment 10 10. The coating composition of any one of the preceding embodiments, wherein the molar ratio of NCO groups of component (D) to the total hydroxyl groups of components (A) and (B) ranges from 0.7:1 to 1.6:1, preferably from 1.1:1 to 1.3:1.

[0094] Embodiment 11 11. The coating composition of any one of embodiments 1 to 10, wherein the weight percentage of component (A) is in the range of 15% to 75%, preferably 25% to 60%, the weight percentage of component (B) is in the range of 2% to 25%, preferably 5% to 15%, and the combined weight percentage of components (A) and (B) is in the range of 40% to 80%, preferably 44% to 60%, based on the total weight of the coating composition.

[0095] Embodiment 12 12. The coating composition of any one of the preceding embodiments, wherein the weight percentage of the amino resin ranges from 1% to 30%, preferably from 5% to 15%, based on the total weight of the coating composition.

[0096] Embodiment 13 13. The coating composition of any one of the preceding embodiments, wherein the amino resin is a melamine resin.

[0097] Embodiment 14 14. An article coated with the coating composition of any one of embodiments 1 to 13. [Example]

[0098] The present invention will be explained more practically below with reference to illustrative examples, but the present invention is not limited to these illustrative examples in any way.

[0099] The performance of the coating film obtained using the coating composition of the present invention was measured by the following method.

[0100] Clear Coat Performance Testing

[0101] (1)Tukon hardness The hardness of the coating was evaluated using a Wilson Tukon 1102 tester according to ASTM D1474 Tukon hardness.

[0102] (2) Appearance The appearance of the dried and cured clearcoat was evaluated by measuring its surface texture using a BYK Wavescan Dual. Surface textures range from very fine to very fine. The BYK Wavescan Dual measured the surface texture at different scale levels, distinguished into six categories identified by wavelength (Du, Wa, Wb, Wc, Wd, and We). Based on these measurement data, the instrument calculated Lw, Sw, and DOI, which indicate the appearance level of the coating. Lower Lw and Sw and higher DOI values ​​indicate better appearance performance. Lw is primarily defined by the clearcoat layer, while Sw and DOI are defined not only by the clearcoat layer but also by the substrate and basecoat. Good appearance performance is typically defined by simultaneously meeting Lw < 5 and Sw < 15.

[0103] (3) Gloss The gloss of the coating surface was measured at an angle of 20° using a BYK Haze Gloss Meter according to the method of DIN 67530. Automotive coatings are a type of high gloss coating, and a high gloss is more suitable for the end use.

[0104] (4) VOCs VOC was evaluated based on solid content measurement according to the methods described in GB / T 38597 / 2020, GB / T 1725-2007, and GB / T 23985-2009. The solid content was measured by the following process: 1 g of sample was placed in an aluminum pan with a diameter of 75 mm and baked at 105°C for 1 hour. The VOC was calculated according to the following formula: For all of the inventive and comparative samples listed in this invention, the measured coating sample density ρ was 0.97 g / mL. ρ(VOC)=(100-NV)×ρ×10 (where ρ(VOC) = calculated VOC of sample, g / L; NV = solid content of the sample, mass fraction (%) ρ = density of the coated sample measured at 23 °C, g / mL).

[0105] material Setalux® 91756 VS-60 YA is a sagging inhibitor from Allnex; Cymel® 202 is an amino resin crosslinker from Allnex; Cycat® 4045 is a catalyst from Allnex; Disperbyk® 110 is a leveling agent from BYK Chemie, BYK® 325N, a leveling agent from BYK Chemie, BYK® 315N, a leveling agent from BYK Chemie, BYK® 355N, a leveling agent from BYK Chemie, BYK® ES 80 is a conductive additive from BYK Chemie, Disparlon® OX-883HF is a defoamer from King Industries Tinuvin® 5248 is a light stabilizer from BASF, Desmodur 3390 is a polyisocyanate crosslinker from Covestro.

[0106] According to the monomer compositions and mass ratios shown in Table 1, the first resins in the following preparation examples were prepared.

[0107] [Table 1]

[0108] Preparation example of first resin 1 A stainless steel reactor equipped with a reflux condenser and a N2 inlet was charged with 25.492 parts by weight of solvent naphtha 160 / 180 (SN). This initial charge was heated to 160 °C while maintaining a pressure of 1.5 bar. Over a period of 4.5 hours, an initiator solution (6 parts by weight of di-tert-butyl peroxide (DTBP) in 1.42 parts by weight of solvent naphtha 160 / 180 (SN)) was then metered in uniformly with stirring. Over a period of 4 hours, a monomer mixture containing 24.4 parts by weight of styrene (ST), 20 parts by weight of cyclohexyl methacrylate (CHMA), 5.8 parts by weight of n-butyl acrylate (n-BA), 19.8 parts by weight of n-butyl methacrylate (n-BMA), and 29 parts by weight of 2-hydroxyethyl acrylate (2-HEA) was metered in uniformly with stirring. The reaction mixture was then held at 150° C. and 1.5 bar pressure for 1.5 hours, after which the reaction mixture was cooled to 80° C. and diluted with 0.913 parts by weight of solvent naphtha 160 / 180 (SN) and 7 parts by weight of N-butyl acrylate (BA).

[0109] Preparation Examples of First Resin 2 to First Resin 9 As shown in Table 1, preparation examples of first resin 2 to first resin 9 were similar to first resin 1 except for the monomer composition.

[0110] The characteristics of the first resin prepared are shown in Table 2.

[0111] [Table 2]

[0112] Preparation example of second resin A stainless steel reactor equipped with a reflux condenser and a N2 inlet was charged with 27 parts by weight of solvent naphtha 160 / 180 (SN), and this initial charge was heated to 160°C while maintaining the pressure at 2.5 bar. Then, over a period of 4.75 hours, an initiator solution (1 part by weight of [di-tert-butyl peroxide (DTBP)] in 2.02 parts by weight of solvent naphtha 160 / 180 (SN)) was metered in at a uniform rate with stirring. A monomer mixture containing 5 parts by weight of n-butyl methacrylate (n-BMA), 22 parts by weight of 2-ethylhexyl methacrylate (EHMA), 8 parts by weight of cyclohexyl methacrylate (CHMA), 12 parts by weight of styrene (ST), 42 parts by weight of 2-hydroxypropyl methacrylate (2-HPMA), 10 parts by weight of 4-hydroxybutyl acrylate (4-HBA), and 1 part by weight of acrylic acid (AA) was metered in at a uniform rate over 4 hours while stirring. The reaction mixture was then held at 110°C and atmospheric pressure for 1.5 hours. The reaction mixture was then cooled to 80°C and diluted with 26.85 parts by weight of the solvent naphtha 160 / 180 (SN). The solids content of the resulting polyacrylate solution was 65% by weight.

[0113] Preparation of 2K Clearcoat Coating Composition Table 3 lists the composition of component I for a 2K clear coat composition. All components listed in the table are subsequently mixed to obtain component I. To obtain component II, Desmodur 3390 (from Covestro) was diluted to 80% by weight with a mixture of solvent naphtha and butyl acetate (1:1 by weight ratio). The molar ratio of NCO in component II to the total OH in component I is 1.2:1.

[0114] [Table 3]

[0115] Preparation of dried and cured films Components I and II of each 2K coating composition were mixed, the mixture was stirred uniformly, and then sprayed onto a steel plate and baked at 110°C for 20 minutes. The coating composition of Comparative Example 2 was cured by using only polyisocyanate Desmodur 3390 in Component II without using amino resin Cymel® 202. The coating composition of Comparative Example 3 contained only component I without component II, so the coating composition was cured using only amino resin Cymel® 202 in Component I.

[0116] Comparative Example 4 Comparative Example 4 was a 2K clearcoat commercially available from BASF (trademark: ProGloss) that was sprayed onto a steel panel and baked for 20 minutes at 140° C. ProGloss used the same type of resin as Component B in the coating composition of the present invention, but used a different resin than Component A in the coating composition of the present invention.

[0117] Comparative Example 5 Comparative Example 5 is the same as Comparative Example 4 except that the firing temperature is 110°C.

[0118] The clearcoat film evaluation was performed on multi-layer coatings containing a black (or white) waterborne basecoat made from commercially available black (or white) waterborne basecoat materials from BASF Shanghai Coatings Co., Ltd. The black and white basecoats were chosen because these two basecoats are basic and widely available. The results are shown in Table 4.

[0119] [Table 4]

[0120] As can be seen from Table 4, the inventive examples simultaneously exhibit high solids (i.e., low VOC) and low viscosity, and the resulting clear coat layers exhibit high initial gloss, good appearance, and sufficient hardness, while the comparative examples exhibit one or more drawbacks.

[0121] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. The embodiments and examples are intended to be exemplary only. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.

Claims

1. (A) C １ ~C １０ , preferably C ２ ~C ６ a first resin having at least one primary hydroxyl group selected from hydroxyl alkyl (meth)acrylate resins having an alkyl group; (B) C ２ ~C １０ , preferably C ２ ~C ６ a second resin having at least one secondary hydroxyl group selected from hydroxyl alkyl (meth)acrylate resins having an alkyl group; and (C) at least one amino resin Component I comprising: (D) a crosslinking agent comprising at least one polyisocyanate Component II comprising 1. A 2K clear coat coating composition comprising:

1. A coating composition comprising: a first resin having a hydroxyl number in the range of 100 to 250 mg KOH / g and a weight average molecular weight in the range of 3,000 to 15,000; and a second resin having a hydroxyl number in the range of 150 to 500 mg KOH / g and a weight average molecular weight in the range of 500 to 2,500.

2. 2. The coating composition of claim 1, wherein the first resin has a Tg in the range of 10°C to 80°C, preferably 10°C to 45°C.

3. 3. The coating composition of claim 1 or 2, wherein the first resin has an acid number in the range of 0 to 20, preferably 2 to 20.

4. 3. The coating composition according to claim 1, wherein the first resin has a weight average molecular weight in the range of 3,500 to 12,000.

5. 3. The coating composition of claim 1, wherein the first resin has a hydroxyl number in the range of 190 to 250 mg KOH / g and a weight average molecular weight in the range of 3,000 to 10,000.

6. 3. The coating composition of claim 1, wherein the first resin has a hydroxyl number in the range of 100 to 190 mg KOH / g and a weight average molecular weight in the range of 3,000 to 15,000.

7. 3. The coating composition of claim 1, wherein the second resin has a hydroxyl number in the range of 200 to 300 mg KOH / g.

8. The coating composition of claim 1 or 2, wherein the second resin further comprises at least one primary hydroxyl group.

9. 9. The coating composition of claim 8, wherein the molar ratio of secondary hydroxyl groups to primary hydroxyl groups in the second resin ranges from 2:1 to 10:1, preferably from 3:1 to 5:

1.

10. 3. The coating composition of claim 1, wherein the molar ratio of NCO groups of component (D) to the total hydroxyl groups of components (A) and (B) is in the range of 0.7:1 to 1.6:1, preferably 1.1:1 to 1.3:

1.

11. 3. The coating composition according to claim 1 or 2, wherein the weight percentage of component (A) is in the range of 15% to 75%, preferably 25% to 60%, the weight percentage of component (B) is in the range of 2% to 25%, preferably 5% to 15%, and the combined weight percentage of components (A) and (B) is in the range of 40% to 80%, preferably 44% to 60%, based on the total weight of the coating composition.

12. 3. The coating composition according to claim 1 or 2, wherein the weight percentage of the amino resin ranges from 1% to 30%, preferably from 5% to 15%, based on the total weight of the coating composition.

13. 3. The coating composition according to claim 1, wherein the amino resin is a melamine resin.

14. An article coated with the coating composition of claim 1 or 2.

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