2K Clear Coat Coating Composition

Abstract

The present invention provides a two-component clear coat coating composition comprising: (A) a first resin having at least one primary hydroxyl group in an amount of 10% to 70% by mass, preferably 20% to 50% by mass; (B) a second resin comprising a resin (B-1) having at least one primary hydroxyl group and / or a resin (B-2) having at least one secondary hydroxyl group in an amount of 2% to 40% by mass, preferably 5% to 25% by mass; and (C) a crosslinking agent comprising at least one polyisocyanate and at least one amino resin, wherein the mass percentages of components (A) and (B) are based on the total mass of the coating composition, and the mass ratio between components (A) and (B) is in the range of 6:1 to 1:2, preferably 4:1 to 1:1. The present invention also provides an article coated with the coating composition of the present invention, and the article preferably has a metal substrate.

Description

Technical Field

[0001] The present invention relates to a coating composition, and more particularly to a 2K clear coat coating composition used in the automotive field.

Background Art

[0002] The clear coat provides both decoration and protection to automobiles as a top coat. Therefore, excellent appearance, scratch resistance, and sufficient hardness are simultaneously required. Furthermore, for environmental protection purposes, the coating composition forming the clear coat is required to have low VOC, that is, a high solid content. Taking China as an example, in the low VOC regulation, it is required that the usable VOC value of the 2K coating composition is less than 420 g / L, which is almost equal to the usable solid content being at least 57% by mass. However, low VOC or high solid content results in a high viscosity of the coating composition, and it is difficult to obtain a good appearance by applying a coating composition having a high viscosity, not to mention special requirements from OEM manufacturers.

[0003] On the other hand, in order to improve the scratch resistance of the clear coat layer, nano-silica particles may be added to the coating composition, or Si-OR groups may be grafted onto the resin or crosslinking agent component of the coating composition. However, this often has a negative impact on the appearance of the clear coat layer, especially in wet-on-wet processing.

[0004] CN105612227A discloses a coating composition comprising a main agent containing a polyisocyanate compound and a curing agent, wherein the main agent contains a hydroxy-containing acrylic resin having a relatively low glass transition temperature and a hydroxy-containing acrylic resin having a relatively high glass transition temperature. The coating composition has excellent scratch resistance, hardness, appearance, and adhesion to a plastic substrate, and forms a coating film having resistance to a composition containing a UV absorber. However, the coating film of CN105612227A is only suitable for a plastic substrate and is not suitable for a metal substrate under a high baking temperature (e.g., over 100 °C).

[0005] US7,423,077B2 discloses a coating material comprising (A) at least one hydroxyl-containing (meth)acrylate (co)polymer, (B) at least one carbamate-functional compound and a hydroxyl-functional compound, (C) at least one amino resin, and (D) at least one triazine compound. The amino resin and the triazine compound are used as crosslinking agents, and alcohol is released during the polycondensation reaction, causing strong shrinkage and internal stress after cooling. As a result, it has an adverse effect on the appearance of the clear coat layer, especially in a wet-on-wet process.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, there is still a need to provide a coating composition that simultaneously has a high solids content and a low viscosity, and from which a clear coat layer that can be obtained or is obtainable exhibits good appearance, scratch resistance, and sufficient hardness, and is particularly applicable to a metal substrate under a high baking temperature (e.g., above 100°C).

Means for Solving the Problems

[0008] In one embodiment, the present invention relates to the following components, (A) 10% to 70% by mass, and preferably 20% to 50% by mass, of a first resin having at least one primary hydroxyl group, (B) 2% to 40% by mass, and preferably 5% to 25% by mass, of a second resin containing a resin (B-1) having at least one primary hydroxyl group and / or a resin (B-2) having at least one secondary hydroxyl group, and (C) A crosslinking agent containing at least one polyisocyanate and at least one amino resin A 2K clear coat coating composition comprising The mass percentages of components (A) and (B) are based on the total mass of the coating composition, and the mass ratio between components (A) and (B) is in the range of 6:1 to 1:2, and preferably 4:1 to 1:1. A 2K clear coat coating composition is provided.

[0009] In another embodiment, the present invention provides an article coated with the coating composition of the present invention, and the article preferably has a metal substrate.

[0010] Surprisingly, the coating composition of the present invention simultaneously has a low VOC and a low viscosity, and the clear coat layer that can be obtained or is obtainable from the composition exhibits good appearance, scratch resistance, and sufficient hardness, and is particularly applicable to a metal substrate under a high baking temperature (e.g., above 100°C).

Modes for Carrying Out the Invention

[0011] The present invention will be described in detail below. It should be understood that the present invention can be embodied in many different ways and is not to be construed as limited to the embodiments described herein.

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

[0013] As used herein, the articles "a" and "an" refer to one or more (i.e., at least one) of the grammatical objects of the article or component.

[0014] As used herein, the terms "comprise", "comprising", etc. are used interchangeably with "contain", "containing", etc., and are interpreted non-limitingly and in an open-ended manner. That is, for example, additional components or elements can be present. "Consists of", "consists essentially of", or synonymous expressions can be included within "comprise" or synonyms.

[0015] Unless otherwise specified, all percentages (%) are "mass percentages", and parts represent parts by mass.

[0016] In the present invention, "(meth)acrylate" means acrylate and methacrylate, "(meth)acrylic" 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 value is measured in accordance with DIN EN ISO 2114 (date: June 2002).

[0018] In the present invention, the hydroxyl value (OHV) is measured in accordance with DIN 53240-2 (date: November 2007).

[0019] In the present invention, the solid content was measured in accordance with DIN EN ISO 3251 (date: June 2008).

[0020] In the present invention, the mass average molecular weight is measured in accordance with DIN 55672-1 (date: August 2007).

[0021] In the present invention, the glass transition temperature of the copolymer is a numerical value calculated using the following formula: 1 / Tg (K) = Σ(mi / Tgi) Tg (°C) = Tg (K) - 273 Tg: Glass transition temperature of the copolymer mi: MoI fraction of monomer component i Tgi: Glass transition temperature (K) of the homopolymer of monomer component i.

[0022] Furthermore, the glass transition temperature (K) of the homopolymer of monomer component i is based on the values obtained from POLYMER HANDBOOK, 4th Edition, edited by J. Brandrup, E. H. Immergut, E. A. Grulke (1999). For the homopolymers of monomers not described in this literature, the glass transition temperature can be determined by synthesizing a homopolymer of the monomer with a mass average molecular weight of approximately 50,000 and measuring the glass transition temperature by differential scanning calorimetry.

[0023] The first resin The first resin has at least one primary hydroxyl group and a Tg (glass transition temperature) in the range of -80°C to 0°C, preferably -60°C to -10°C, more preferably -50°C to -20°C, such as -40°C and -30°C.

[0024] The first resin has a hydroxyl value (OH value) in the range of 100 to 240 mgKOH / g, preferably 150 to 200 mgKOH / g, such as 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, and 230 mgKOH / g.

[0025] The first resin has a mass average molecular weight in the range of 2,000 to 10,000, preferably 4,000 to 8,000, such as 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, and 9,000.

[0026] In a preferred embodiment of the present invention, the first resin is an acrylic resin containing at least one primary hydroxyl group in the molecule.

[0027] The acrylic resin containing at least one primary hydroxyl group can be synthesized by copolymerizing a primary hydroxyl group-containing acrylic monomer and other copolymerizable monomers by a conventional method, such as radical polymerization.

[0028] Examples of the primary hydroxyl group-containing acrylic monomer include C1 to C 10and preferably a hydroxylalkyl (meth)acrylate having a C2-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, 4-hydroxybutyl (meth)acrylate, 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 monomer can be used alone or in combination of two or more monomers.

[0029] Preferably, the primary hydroxyl-containing acrylic monomer is at least one selected from the group consisting of 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, or a combination thereof, more preferably at least one selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0030] 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 (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, N-methylolacrylamide butyl ether. Other copolymerizable monomers can be used alone or in combination of two or more monomers.

[0031] 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, (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.

[0032] The first resin contains units derived from acrylic monomers in an amount of at least 60% by mass, preferably at least 70% by mass, and more preferably at least 80% by mass, such as 60% by mass, 65% by mass, 70% by mass, 75% by mass, 80% by mass, 85% by mass, 90% by mass, and 95% by mass, etc., and these mass percentages are based on the total mass of the first resin. The acrylic monomers include any acrylic monomer having at least one primary hydroxyl group and other copolymerizable monomers.

[0033] In a preferred embodiment of the present invention, the first resin contains units derived from acrylic monomers in an amount of 60% to 95% by mass, such as 70% to 90% by mass, and 75% to 85% by mass, etc., and these mass percentages are based on the total mass of the first resin.

[0034] The first resin contains units derived from primary hydroxyl group-containing acrylic monomers in an amount of 30% to 50% by mass, and preferably 35% to 45% by mass, such as 40% by mass, and these mass percentages are based on the total mass of the first resin.

[0035] The first resin contains units derived from 50% to 70% by mass, preferably 55% to 65% by mass, for example 60% by mass, of other copolymerizable monomers, and these mass percentages are based on the total mass of the first resin.

[0036] The two-component coating composition contains 10% to 70% by mass, preferably 20% to 50% by mass, for example 10% by mass, 20% by mass, 30% by mass, 40% by mass, 50% by mass, 60% by mass, and 70% by mass, etc., of the first resin, and these mass percentages are based on the total mass of the coating composition.

[0037] Preferably, the first resin has an acid value in the range of 0 to 30 KOH / mg / g, for example 5 KOH / mg / g, 10 KOH / mg / g, 15 KOH / mg / g, etc.

[0038] The first resin can be produced by a conventional method, for example, radical polymerization. Examples of radical polymerization initiators include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethyl-valeronitrile, 4,4'-azobis-4-cyanovaleric acid, 1-azobis-1-cyclohexanecarbonitrile, dimethyl-2,2'-azobisisobutyrate, etc., 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-bis(t-butylperoxy)octane, t-butyl hydroperoxide, diisopropylbenzene hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide (DTBP), t-butyl cumyl peroxide, isobutyl peroxide, lauroyl peroxide, benzoyl peroxide, diisopropyl peroxydicarbonate, tertiary butyl peroxy-2-ethylhexanoate (TBPEH), t-butyl peroxyneodecanoate, t-butyl peroxylaurate, t-butyl peroxybenzoate, t-butyl peroxyisopropyl carbonate, etc. One of these radical polymerization initiators can be used alone or in combination of two or more kinds.

[0039] The amount of the radical polymerization initiator is not particularly limited, but 0.01% by mass to 20% by mass is preferable with respect to the total mass of the radically polymerizable monomer.

[0040] Examples of suitable organic solvents that can be used in the production of the first resin include aliphatic hydrocarbon solvents such as cyclohexane, ethylcyclohexane, etc., aromatic hydrocarbon solvents such as toluene, xylene, ethylbenzene, aromatic naphtha, etc., ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, etc., ester solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, 3-methoxybutyl acetate, bis(2-ethylhexyl) adipate, etc., ether solvents such as dibutyl ether, tetrahydrofuran, 1,4-dioxane, 1,3,5-trioxane, etc., and nitrogen-containing solvents such as acetonitrile, valeronitrile, N,N-dimethyl-formamide, N,N-diethylformamide, etc. The organic solvent can be a single type or a mixed solvent containing two or more types.

[0041] The method of adding the organic solvent and the radical polymerization initiator when producing the first resin is arbitrary, but from the viewpoint of controlling the polymerization heat and the reaction heat, a method of introducing the organic solvent into the reactor and then dropping the radically polymerizable monomer or its organic solution from the dropping tank while stirring is preferred.

[0042] The polymerization temperature of 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, for example, at temperatures 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, and 190°C.

[0043] The second resin The second resin is at least one selected from a resin (B-1) having at least one primary hydroxyl group and a Tg in the range of 0°C to 30°C and a resin (B-2) having at least one secondary hydroxyl group and a Tg of at least 20°C.

[0044] In one embodiment of the present invention, the second resin is a resin (B-1) having at least one primary hydroxyl group and a Tg in the range of 0°C to 30°C, preferably 5°C to 20°C, such as 10°C, 15°C, and 25°C.

[0045] The resin (B-1) has a hydroxyl value in the range of 100 to 240 mgKOH / g, preferably 150 to 200 mgKOH / g, such as 110 mgKOH / g, 120 mgKOH / g, 130 mgKOH / g, 140 mgKOH / g, 150 mgKOH / g, 160 mgKOH / g, 170 mgKOH / g, 180 mgKOH / g, 190 mgKOH / g, 200 mgKOH / g, 210 mgKOH / g, 220 mgKOH / g, and 230 mgKOH / g.

[0046] The resin (B-1) has a mass average molecular weight in the range of 2,000 to 10,000, preferably 3,000 to 7,000, such as 3,000, 3,500, 4,000, 4,500, 5,000, 5,500, 6,500, 7,000, 7,500, 8,000, 8,500, and 9,000.

[0047] In a preferred embodiment of the present invention, the resin (B-1) is an acrylic resin containing at least one primary hydroxyl group in the molecule.

[0048] The resin (B-1) contains monomer units derived from a primary hydroxylalkyl (meth)acrylate having a C1 to C 10 and preferably a C2 to C6 alkyl group.

[0049] The acrylic resin containing at least one primary hydroxyl group can be synthesized by copolymerizing a primary hydroxyl group-containing acrylic monomer and other copolymerizable monomers by a conventional method, such as radical polymerization.

[0050] Examples of primary hydroxyl group-containing acrylic monomers include hydroxylalkyl (meth) acrylates having an alkyl group with 1 to 10 carbon atoms, preferably 2 to 6 carbon atoms, 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 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 group-containing acrylic monomers can be used alone or in combination of two or more monomers.

[0051] Preferably, the primary hydroxyl-containing acrylic monomer is 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, or a combination thereof, more preferably at least one selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0052] Examples of other copolymerizable monomers include C1-C 20 -alkyl (meth)acrylate, preferably C1-C 10- Alkyl (meth)acrylate, 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, 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, N-methylolacrylamide butyl ether are included. Other copolymerizable monomers can be used alone or in combination of two or more monomers.

[0053] 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, (meth) acrylic acid, 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, and styrene.

[0054] Resin (B-1) contains units derived from at least 60% by mass, and preferably at least 70% by mass, such as 75% by mass, 80% by mass, 85% by mass, 90% by mass, and 95% by mass, etc. of acrylic monomers, and these mass percentages are based on the total mass of resin (B-1). The acrylic monomers include any primary hydroxyl-containing acrylic monomer and other copolymerizable monomers.

[0055] In a preferred embodiment of the present invention, resin (B-1) contains units derived from 60% to 95% by mass, such as 65% to 75% by mass, of acrylic monomers, and these mass percentages are based on the total mass of resin (B-1).

[0056] Resin (B-1) contains units derived from 30% to 50% by mass, and preferably 35% to 45% by mass, such as 40% by mass, of primary hydroxyl-containing acrylic monomers, and these mass percentages are based on the total mass of resin (B-1).

[0057] Resin (B-1) contains units derived from 50% to 70% by mass, and preferably 55% to 65% by mass, for example 60% by mass, of other copolymerizable monomers, and these mass percentages are based on the total mass of resin (B-1).

[0058] In another embodiment of the present invention, the second resin is a resin (B-2) having at least one secondary hydroxyl group and a glass transition temperature (Tg) in the range of at least 20°C, preferably at least 25°C and more preferably at least 30°C, for example, 20°C to 150°C, preferably 25°C to 100°C, more preferably 30°C to 50°C, such as 35°C, 40°C, 45°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 110°C, 120°C, 130°C and 140°C. Resin (B-2) has a hydroxyl value in the range of 100 to 200 mgKOH / g, preferably 130 to 170 mgKOH / g, for example 100 mgKOH / g, 120 mgKOH / g, 130 mgKOH / g, 140 mgKOH / g, 150 mgKOH / g, 160 mgKOH / g, 170 mgKOH / g, 180 mgKOH / g, 190 mgKOH / g and 200 mgKOH / g.

[0059] Resin (B-2) has a mass average molecular weight in the range of 2,000 to 10,000, preferably 3,000 to 7,000, for example 3,000, 3,500, 4,000, 4,500, 5,000, 5,500, 6,500, 7,000, 7,500, 8,000, 8,500 and 9,000.

[0060] In a preferred embodiment of the present invention, resin (B-2) is an acrylic resin containing at least one secondary hydroxyl group in the molecule.

[0061] Resin (B-2) contains monomer units derived from hydroxylalkyl (meth)acrylates having C1 to C 10 and preferably C2 to C6 alkyl groups.

[0062] An acrylic resin containing at least one secondary hydroxyl group can be synthesized by copolymerizing a secondary hydroxyl group-containing acrylic monomer and other copolymerizable monomers in a conventional manner, for example, by radical polymerization.

[0063] Examples of the secondary hydroxyl group-containing acrylic monomer include hydroxylalkyl (meth)acrylates having an alkyl group in the range of 2 to 10 carbon atoms, preferably in the range of 2 to 6 carbon atoms, 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-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, 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 group-containing acrylic monomer can be used alone or in combination of two or more monomers.

[0064] 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), and more preferably 2-hydroxypropyl methacrylate (2-HPMA).

[0065] Examples of other copolymerizable monomers include C1-C 20 -alkyl (meth)acrylate, 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 (CHMA), 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, N-methylolacrylamide butyl ether are included. Other copolymerizable monomers can be used alone or in combination of two or more monomers.

[0066] 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, (meth) acrylic acid, 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 and styrene.

[0067] Resin (B-2) contains units derived from acrylic monomers in an amount of at least 70% by mass, preferably at least 80% by mass and more preferably at least 90% by mass, such as 75% by mass, 80% by mass, 85% by mass, 90% by mass and 95% by mass, etc., and these mass percentages are based on the total mass of resin (B-2). The acrylic monomers include any secondary hydroxyl-containing acrylic monomer and other copolymerizable monomers.

[0068] In a preferred embodiment of the present invention, resin (B-2) contains units derived from acrylic monomers in an amount of 85% to 95% by mass based on the total mass of resin (B-2).

[0069] Resin (B-2) contains units derived from secondary hydroxyl-containing acrylic monomers in an amount of 30% to 50% by mass and preferably 35% to 45% by mass, such as 40% by mass, and these mass percentages are based on the total mass of resin (B-2).

[0070] Resin (B-2) contains units derived from 50% to 70% by mass, preferably 55% to 65% by mass, for example 60% by mass of other copolymerizable monomers, and these mass percentages are based on the total mass of resin (B-2).

[0071] The coating composition contains 2% to 40% by mass, preferably 5% to 25% by mass, for example 5% by mass, 10% by mass, 15% by mass, 20% by mass, 25% by mass, 30% by mass, 35% by mass, etc. of a second resin, and these mass percentages are based on the total mass of the coating composition.

[0072] Preferably, the second resin has an acid value in the range of 0 to 30 KOH / mg, for example 5 KOH / mg / g, 10 KOH / mg / g, 15 KOH / mg / g, etc.

[0073] The mass ratio between the first resin and the second resin in the coating composition is in the range of 6:1 to 1:2, preferably 4:1 to 1:1, for example 2:1, 3:1, 4:1, 5:1, etc.

[0074] The second resin can be produced by conventional methods, for example, by radical polymerization, and the method for preparing the first resin can also be applied to the second resin.

[0075] Crosslinking agent In the present invention, the crosslinking agent contains at least one polyisocyanate and at least one amino resin.

[0076] A polyisocyanate having at least two, preferably at least three isocyanate groups can be used as the crosslinking agent in the coating composition of the present invention, and a polyisocyanate of one kind or a combination of two or more kinds can be used.

[0077] 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'-biphenylene diisocyanate, methylene bis(phenyl isocyanate), lysine methyl ester diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 2-isocyanatoethyl-2,6-diisocyanatohexanoate, 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, oligomer or polymeric isocyanates of these compounds, or mixtures thereof are included.

[0078] In a preferred embodiment, the polyisocyanate is an aliphatic polyisocyanate such as Covestro's Desmodur N100, N75, N3200, N3400, N3600, Desmodur 3390 and Desmodur Z4470.

[0079] In a preferred embodiment, the polyisocyanate is an oligomeric isocyanate compound such as an isocyanate dimer, an isocyanate trimer, etc.

[0080] In a particular embodiment, the polyisocyanate is a trimer of HDI, such as Desmodur 3390 from Covestro.

[0081] The molar ratio between the NCO groups in the polyisocyanate and the hydroxyl groups of both the first resin and the second resin ranges from 1.6:1 to 0.7:1 and preferably from 1.35:1 to 1.05:1.

[0082] The amino resin is a condensation product of an aldehyde, particularly formaldehyde, with, for example, urea, melamine, guanamine, and benzoguanamine. The amino resin contains alcohol groups, preferably methylol groups, which are generally partially or preferably completely etherified with an alcohol. In particular, a melamine-formaldehyde resin etherified with a lower alcohol, particularly methanol or butanol, is used. Very particularly preferably, a melamine-formaldehyde resin etherified with a lower alcohol, particularly methanol and / or ethanol and / or butanol, is used as the crosslinking agent.

[0083] In this context, it is possible to use any amino resin suitable for a transparent topcoat or clearcoat material, or a mixture of such resins. Particularly suitable are conventional amino resins in which the methylol group and / or the methoxymethyl group have been defunctionalized by a carbamate group or an allophanate group.

[0084] This type of crosslinking agent is described in U.S. Patent No. 4,710,542A, EP0245700B1, and the paper by B. Singh and Coworkers, "Carbamylmethylated Melamines, Novel Crosslinkers for the Coatings Industry," Advanced Organic Coatings Science and Technology Series, Vol. 13, pp. 193 - 207, 1991. For melamine resins, see also Rompp Lexikon Lacke und Druckfarben, 1988, pp. 374 and 375, "Melamine resins," and the book "Lackadditive" [Coating Additives], by Johan Bieleman, 1988, pp. 242 - 250, section "Melamine - resin - crosslinking systems."

[0085] Preferably, the crosslinking agent contains at least 60% by mass, preferably at least 70% by mass, and more preferably at least 80% by mass of melamine resin based on the total mass of the crosslinking agent containing melamine resin and amino resin.

[0086] 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, Resimene® and Maprenal® MF from Solutia.

[0087] Suitable examples of relatively low molecular weight, highly etherified melamine resins containing free imino groups include Cymel® 325 and 327 (methanol-etherified), Cymel 202 and 203 (mixture of methanol- and butanol-etherified), and 1158 (butanol-etherified) from Cytec; Luwipal® 062 (methanol-etherified), 018 (butanol-etherified), and 014 (butanol-etherified, relatively high viscosity) from BASF Aktiengesellschaft; Maprenal® MF927 and 3950 (methanol-etherified), VMF3611 and 3615 (butanol-etherified), and 580 (isobutanol-etherified) from Solutia; Resimene® 717 and 718 (methanol-etherified), 750 and 5901 (butanol-etherified), and MB9539; and Setamine® US138 and US146 (butanol-etherified) from Akzo Resins.

[0088] Examples of suitable relatively low molecular weight, partially etherified melamine resins include Luwipal® 012, 016, 015, 010 from BASF Aktiengesellschaft; Maprenal® MF590 and 600 from Solutia; and Setamine® US132 and 134 from Akzo Resins.

[0089] The amount of amino resin is in the range of 1% to 30% by mass, preferably 5% to 15% by mass, for example 3% by mass, 8% by mass, 10% by mass, 12% by mass, 16% by mass, 18% by mass, 20% by mass, and 25% by mass, etc., and these mass percentages are based on the total mass of the coating composition.

[0090] In a preferred embodiment according to the present invention, the 2K coating composition comprises: (A) a first resin having at least one primary hydroxyl group and a Tg in the range of -50°C to -20°C; (B) a second resin having at least one primary hydroxyl group and a Tg temperature in the range of 5°C to 20°C; and (C) a crosslinking agent comprising at least one polyisocyanate and at least one amino resin.

[0091] In a specific embodiment according to the present invention, the 2K coating composition comprises: (A) an acrylic resin having at least one primary hydroxyl group and a Tg in the range of -50°C to -20°C; (B) an acrylic resin having a primary hydroxyl group and a Tg in the range of 5°C to 20°C; and (C) a crosslinking agent comprising an aliphatic polyisocyanate and a melamine resin.

[0092] In another specific embodiment according to the present invention, the 2K coating composition comprises: (A) an acrylic resin having at least one primary hydroxyl group, a Tg in the range of -50°C to -20°C, and a mass average molecular weight in the range of 4,000 to 8,000; (B) an acrylic resin having at least one primary hydroxyl group, a Tg in the range of 5°C to 20°C, and a mass average molecular weight in the range of 3,000 to 7,000; and (C) a crosslinking agent comprising an aliphatic polyisocyanate and a melamine resin.

[0093] In a preferred embodiment according to the present invention, the 2K coating composition comprises: (A) a first resin having at least one primary hydroxyl group and a Tg in the range of -50°C to -20°C; (B) a second resin having at least one secondary hydroxyl group and a Tg in the range of 30°C to 50°C; and (C) a crosslinking agent comprising a polyisocyanate and an amino resin.

[0094] In a specific embodiment according to the present invention, the 2K coating composition comprises: (A) an acrylic resin having at least one primary hydroxyl group and a Tg in the range of -50°C to -20°C; (B) an acrylic resin having at least one secondary hydroxyl group and a Tg in the range of 30°C to 50°C; and (C) a crosslinking agent comprising an aliphatic polyisocyanate and a melamine resin.

[0095] In another specific embodiment according to the present invention, the 2K coating composition comprises: (A) an acrylic resin having at least one primary hydroxyl group, a Tg in the range of -50°C to -20°C, and a mass average molecular weight in the range of 4,000 to 8,000; (B) an acrylic resin having at least one secondary hydroxyl group, a Tg in the range of 30°C to 50°C, and a mass average molecular weight in the range of 3,000 to 7,000; and (C) a crosslinking agent comprising an aliphatic polyisocyanate and a melamine resin.

[0096] If necessary, various additives can be added, such as leveling agents, sagging inhibitors, defoamers, light stabilizers, UV absorbers, colorants, antioxidants, surfactants, surface modifiers, curing reaction catalysts, antistatic agents, fragrances, water scavengers, and rheology modifiers, such as polyethylene wax, polyamide wax, internally crosslinked resin fine particles, etc.

[0097] The coating composition of the present invention can be used as a clear coat or as a color paint added with dyes, pigments, etc.

[0098] The application of the coating composition of the present invention is carried out using any method in the prior art, such as air spraying, electrostatic air spraying, roll coating, flow coating, dipping, brushing, bar coating, or applicator, etc. And in the present invention, spray coating is preferred.

[0099] 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 dried coating film is preferably in the range of 10 μm to 150 μm, and more preferably in the range of 30 μm to 60 μm.

[0100] Furthermore, examples of the substrate to which the coating composition of the present invention is applied include both inorganic materials and organic materials, such as metals, wood, glass, cloth, plastics, foams, elastomers, paper, ceramics, concrete, gypsum board, etc., and metal substrates are preferred. Whether or not these substrate materials are pretreated does not matter.

[0101] Examples of the coated articles that can be obtained or can be obtained include metal products, structural materials, wooden products, plastic products, rubber products, paper products, ceramic products, glass products, etc., and more specifically, automobiles and automobile parts (for example, bodies, bumpers, spoilers, mirrors, wheels, interior decorative parts, etc., these are 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, airplanes, furniture, musical instruments, household electrical appliances, building materials, containers, office supplies, sports goods, toys, etc., and metal products are preferred.

[0102] Embodiment Specific preferred embodiments are given in the following detailed description, but those skilled in the art should understand that these embodiments are merely illustrative and that the present invention can be implemented in alternative ways.

[0103] Embodiment 1 The following components, (A) 10% to 70% by mass, and preferably 20% to 50% by mass, of a first resin having at least one primary hydroxyl group, (B) A second resin containing 2% to 40% by mass, and preferably 5% to 25% by mass, of a resin (B-1) having at least one primary hydroxyl group and / or a resin (B-2) having at least one secondary hydroxyl group, and A crosslinking agent containing at least one polyisocyanate and at least one amino resin A two-component clear coat coating composition containing The mass percentages of components (A) and (B) are based on the total mass of the coating composition, and the mass ratio between components (A) and (B) is in the range of 6:1 to 1:2, and preferably 4:1 to 1:1 Two-component clear coat coating composition

[0104] Embodiment 2 The coating composition according to Embodiment 1, wherein the first resin has a Tg of -80°C to 0°C, preferably -80°C to -10°C, and more preferably -40°C to -20°C

[0105] Embodiment 3 The coating composition according to any one of Embodiments 1 to 2, wherein the first resin has a hydroxyl value in the range of 100 to 240 mgKOH / g, and preferably 150 to 200 mgKOH / g

[0106] Embodiment 4 The coating composition according to any one of Embodiments 1 to 3, wherein the first resin has a mass average molecular weight in the range of 2,000 to 10,000, and preferably 4,000 to 8,000

[0107] Embodiment 5 The first resin is at least one acrylic resin, and preferably a hydroxylalkyl (meth) acrylate resin having a C1 to C 10 And preferably a hydroxylalkyl (meth) acrylate resin having a C2 to C6 alkyl group, the coating composition according to any one of Embodiments 1 to 4

[0108] Embodiment 6 The coating composition according to any one of Embodiments 1 to 5, wherein the resin (B-1) has a Tg in the range of 0°C to 30°C, and preferably 5°C to 20°C

[0109] Embodiment 7 The coating composition according to any one of Embodiments 1 to 6, wherein the resin (B-1) has a hydroxyl value in the range of 100 to 240 mgKOH / g, and preferably in the range of 150 to 200 mgKOH / g.

[0110] Embodiment 8 The coating composition according to any one of Embodiments 1 to 7, wherein the resin (B-1) has a mass average molecular weight in the range of 2,000 to 10,000, and preferably in the range of 3,000 to 7,000.

[0111] Embodiment 9 The resin (B-1) is at least one acrylic resin, and preferably a hydroxylalkyl (meth)acrylate resin having a C1 to C 10 and preferably a C2 to C6 alkyl group, and the coating composition according to any one of Embodiments 1 to 8.

[0112] Embodiment 10 The coating composition according to any one of Embodiments 1 to 5, wherein the resin (B-2) has a Tg of at least 20°C, and preferably at least 30°C.

[0113] Embodiment 11 The coating composition according to any one of Embodiments 1 to 10, wherein the resin (B-2) has a hydroxyl value in the range of 100 to 200 mgKOH / g, and preferably in the range of 130 to 170 mgKOH / g.

[0114] Embodiment 12 The coating composition according to any one of Embodiments 1 or 11, wherein the resin (B-2) has a mass average molecular weight in the range of 2,000 to 10,000, preferably in the range of 3,000 to 7,000.

[0115] Embodiment 13 The resin (B-2) is at least one acrylic resin, and preferably a C2 to C 10The coating composition according to any one of Embodiments 1 to 12, which is a hydroxylalkyl (meth)acrylate resin having a C2-C6 alkyl group, preferably.

[0116] Embodiment 14 The coating composition according to any one of Embodiments 1 to 13, wherein the molar ratio between the NCO groups in the polyisocyanate and the hydroxyl groups of both the first resin and the second resin is in the range of 1.6:1 to 0.7:1, and preferably 1.35:1 to 1.05:1.

[0117] Embodiment 15 The coating composition according to any one of Embodiments 1 to 14, wherein the amount of the amino resin is in the range of 1% by mass to 30% by mass, preferably 5% by mass to 15% by mass, based on the total mass of the coating composition.

[0118] Embodiment 16 The coating composition according to any one of Embodiments 1 to 15, wherein the amino resin is a melamine resin.

[0119] Embodiment 17 The coating composition according to any one of Embodiments 1 to 16, wherein the coating composition further contains a hydroxyl-containing polyester resin.

[0120] Embodiment 18 An article, preferably having a metal substrate, coated with the coating composition according to any one of Embodiments 1 to 17.

Examples

[0121] Hereinafter, the present invention will be more practically described by exemplary examples, but the present invention is not limited by these exemplary examples at all.

[0122] The performance of the coating film obtained using the coating composition of the present invention was measured by the method shown below.

[0123] Performance Test of Clear Coat (1) Appearance The appearance of the dried and cured clear coat was evaluated by the surface texture measured by the BYK Wave Scan Dual. The surface texture was a mixture of various textures ranging from very fine to very coarse. The BYK Wave Scan Dual measured the surface texture at different scale levels distinguished into six categories identified by wavelengths (Du, Wa, Wb, Wc, Wd, We). Based on these measurement data, Lw and Sw were calculated by the device and indicated the appearance level of the coating. The lower the Lw and Sw values, the better the appearance performance. Generally, good appearance performance is defined as Lw < 5 and simultaneously Sw < 20.

[0124] (2) Scratch Resistance The scratch resistance was evaluated by the gloss retention rate at 20° after dry scratching. Dry scratching was created with a clock meter attached with PERSI abrasive paper (grain size: 10 microns). During the test, 15 reciprocations were repeated. The gloss before and after dry scratching at 20° was compared. The higher the gloss retention rate, the better the scratch resistance. The 20° gloss retention rate of the conventional polyurethane 2K clear coat was about 40% measured by the above method.

[0125] (3) Hardness The hardness of the coating was evaluated by pencil hardness in accordance with GB / T standard 6739-2006.

[0126] (4) VOC VOC was evaluated based on the measurement of the solid content in accordance with the methods described in GB / T38597 / 2020, GB / T1725-2007 and GB / T23985-2009. The solid content was measured by the following process: 1 g of the sample was weighed into an aluminum pan with a diameter of 75 mm and baked at 105 °C for 1 hour. The calculation of VOC was performed according to the formula listed below. For all of the samples of the present invention and the comparative samples cited in the present invention, the density ρ of the measured coating sample was 0.97 g / mL. ρ(VOC)=(100 - NV)×ρ×10 ρ(VOC) = Calculated value of sample VOC, g / L NV = Solids content of sample, expressed as mass fraction (%) ρ = Density of the coating sample measured at 23°C, g / mL.

[0127] The polyacrylate in the following preparation examples was prepared according to the monomer composition and mass ratio shown in Table 1.

[0128] Material Setalux (registered trademark) 91756 VS - 60 YA is a sag control agent of Allnex. Cymel (registered trademark) 327 is an amino resin crosslinking agent of Allnex. Luwipal (registered trademark) 018 is an amino resin crosslinking agent of BASF. Cycat (registered trademark) 4045 is a catalyst of Allnex. BYK355 is a leveling agent of BYK Chemie. Disperbyk161 is a leveling agent of BYK Chemie. BYK325 is a leveling agent of BYK Chemie. BYK315 is a leveling agent of BYK Chemie. Disparlon (registered trademark) OX - 883HF is an antifoaming agent of King Industries. Tinuvin (registered trademark) 5248 is a light stabilizer of BASF.

[0129] Preparation Example 1 A stainless steel reactor equipped with a reflux condenser and an N2 inlet was charged with 27.9 parts by mass of a mixture of solvent naphtha 160 / 180 (SN) and caprolactone, and this initial charge was heated to 140 °C. Then, over 4.75 hours, an initiator solution (5.1 parts by mass of tertiary butyl peroxy-2-ethylhexanoate (TBPEH) in 3.7 parts by mass of solvent naphtha 160 / 180 (SN)) was metered in at a uniform rate with stirring. A monomer mixture containing 6.4 parts by mass of styrene (St), 30.1 parts by mass of 2-ethylhexyl acrylate (EHA), and 23.1 parts by mass of 2-hydroxyethyl acrylate (2-HEA) was metered in at a uniform rate with stirring over 4 hours. Then, the reaction mixture was heated to 160 °C and held for 4 hours. Next, the reaction mixture was cooled to 60 °C and diluted by the addition of 5.4 parts by mass of solvent naphtha 160 / 180 (SN). The solid content of the resulting polyacrylate solution was 65% by mass. The resulting polyacrylate (i.e., the low Tg resin-1 in Table 1) had a mass average molecular weight (M W ) of 6,500 g / mol, an OH value of 175 mgKOH / g, and a Tg of -30 °C.

[0130] Preparation Example 2 A stainless steel reactor equipped with a reflux condenser and an N2 inlet was charged with 27.9 parts by mass of a mixture of solvent naphtha 160 / 180 (SN) and caprolactone, and this initial charge was heated to 140 °C. Then, over 4.75 hours, an initiator solution (5.1 parts by mass of tertiary butyl peroxy-2-ethylhexanoate (TBPEH) in 1.9 parts by mass of solvent naphtha 160 / 180 (SN)) was metered in at a uniform rate with stirring. A monomer mixture containing 6.4 parts by mass of styrene (St), 30.1 parts by mass of 2-ethylhexyl acrylate (EHA), and 23.1 parts by mass of 2-hydroxyethyl acrylate (2-HEA) was metered in at a uniform rate over 4 hours with stirring. Then, the reaction mixture was heated to 160 °C and held for 4 hours. Next, the reaction mixture was cooled to 60 °C and diluted by the addition of 5.4 parts by mass of solvent naphtha 160 / 180 (SN). The solid content of the resulting polyacrylate solution was 65% by mass. The resulting polyacrylate (i.e., the low Tg resin-2 in Table 1) had a mass average molecular weight (M W ) of 13,000 g / mol, an OH value of 175 mg KOH / g, and a Tg of -30 °C.

[0131] Preparation Example 3 A stainless steel reactor equipped with a reflux condenser and an N2 inlet was charged with 27.9 parts by mass of solvent naphtha 160 / 180 (SN), and this initial charge was heated to 140 °C. Then, over 4.75 hours, an initiator solution (5.1 parts by mass of tertiary butyl peroxy-2-ethylhexanoate (TBPEH) in 3.7 parts by mass of solvent naphtha 160 / 180 (SN)) was metered in at a uniform rate with stirring. A monomer mixture containing 15.2 parts by mass of styrene (St), 19.6 parts by mass of n-butyl acrylate (nBA), and 23.7 parts by mass of 2-hydroxyethyl methacrylate (2-HEMA) was metered in at a uniform rate with stirring over 4 hours. Then, the reaction mixture was heated to 160 °C and held for 4 hours. Next, the reaction mixture was cooled to 60 °C and diluted by the addition of 5.4 parts by mass of solvent naphtha 160 / 180 (SN). The solid content of the resulting polyacrylate solution was 60% by mass. The resulting polyacrylate (i.e., the Tg resin in Table 1) had a mass average molecular weight (M W ) of 5,700 g / mol, an OH value of 175 mg KOH / g, and a Tg of 12 °C.

[0132] Preparation Example 4 A stainless steel reactor equipped with a reflux condenser and an N2 inlet was charged with 28 parts by mass of solvent naphtha 160 / 180 (SN), and this initial charge was heated to 160 °C. Then, over 4.75 hours, an initiator solution (0.9 part by mass of di-tert-butyl peroxide (DTBP) in 3.4 parts by mass of solvent naphtha 160 / 180 (SN)) was metered in at a uniform rate with stirring. A monomer mixture containing 13.9 parts by mass of styrene (St), 23.6 parts by mass of 2-hydroxyethyl acrylate (2-HEA), 6.7 parts by mass of n-butyl acrylate (nBA), 11.4 parts by mass of cyclohexyl methacrylate (CHMA), and 1.4 parts by mass of acrylic acid (AA) was metered in at a uniform rate with stirring over 4 hours. Then, the reaction mixture was held for 4 hours. Next, the reaction mixture was cooled to 60 °C and diluted by the addition of 16.9 parts by mass of butyl acetate (BA). The solid content of the resulting polyacrylate solution was 60% by mass. The resulting polyacrylate (i.e., high Tg resin-1 in Table 1) had a mass average molecular weight (M W ) of 6000 g / mol, an OH value of 167 mg KOH / g, and a Tg of 32 °C.

[0133] Preparation Example 5 28 parts by mass of solvent naphtha 160 / 180 (SN) was charged into a stainless steel reactor equipped with a reflux condenser and an N2 inlet, and this initial charge was heated to 150 °C. Then, over 4.75 hours, an initiator solution (0.9 part by mass of di-tert-butyl peroxide (DTBP) in 3.4 parts by mass of solvent naphtha 160 / 180 (SN)) was metered in at a uniform rate with stirring. A monomer mixture containing 5.1 parts by mass of styrene (St), 20.3 parts by mass of 2-hydroxypropyl methacrylate (2-HPMA), 7.7 parts by mass of n-butyl methacrylate (nBMA), 17.2 parts by mass of t-butyl acrylate (tBA), and 0.4 part by mass of acrylic acid (AA) was metered in at a uniform rate with stirring over 4 hours. Then, the reaction mixture was held for 4 hours. Next, the reaction mixture was cooled to 60 °C and diluted by the addition of 16.9 parts by mass of butyl acetate (BA). The solid content of the resulting polyacrylate solution (i.e., the high Tg resin-2 in Table 1) was 53% by mass. The resulting polyacrylate (i.e., the high Tg resin-2 in Table 1) had a mass average molecular weight (M W ) of 5,500 g / mol, an OH value of 150 mg KOH / g, and a Tg of 40 °C.

[0134]

Table 1

[0135] Preparation of 2K clear coat composition Table 2 describes the composition of Component I for the 2K clear coat composition. All the components listed in the table were subsequently mixed to obtain Component I. To obtain Component II, Desmodur 3390 (Covestro) was diluted to 80% by mass in a mixture of solvent naphtha and butyl acetate (mass ratio 1:1). The molar ratio of NCO of Component II to the total OH of Component I was 1.2:1.

[0136]

Table 2

[0137] Preparation of the Dried and Cured Film Component I and Component II of each 2K clear coat composition were mixed, and the mixture was stirred uniformly. The mixture was sprayed onto a steel plate and baked at 140 °C for 20 minutes.

[0138] The evaluation of the clear coat film was carried out on a multilayer coating including a black aqueous base coat material (Colorbrite) commercially available from BASF Shanghai Coating Ltd. The black base coat was selected because it allows for optimal observation of the appearance changes in the multi-coat coating system.

[0139]

Table 3

[0140] From Table 3, it can be seen that only the examples of the present invention showed both a high solid content (i.e., low VOC) and a low viscosity at the same time. Also, the obtained clear coat layer showed good appearance, scratch resistance, and sufficient hardness, while the comparative examples showed one or more drawbacks.

[0141] 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 considered as illustrative only. Accordingly, the present invention is intended to cover modifications and variations that come within the scope of the appended claims and their equivalents.

Claims

1. The following components, (A) 10% to 70% by mass, preferably 20% to 50% by mass, of a first resin having at least one primary hydroxyl group, (B) 2% to 40% by mass, preferably 5% to 25% by mass, of a second resin containing a resin (B-1) having at least one primary hydroxyl group and / or a resin (B-2) having at least one secondary hydroxyl group, and (C) A crosslinking agent containing at least one polyisocyanate and at least one amino resin A two-component clear coat coating composition comprising, wherein the mass percentages of components (A) and (B) are based on the total mass of the coating composition, and the mass ratio between components (A) and (B) is in the range of 6:1 to 1:2, preferably 4:1 to 1:

1. A two-component clear coat coating composition.

2. The coating composition according to claim 1, wherein the first resin has a Tg of -80°C to 0°C, preferably -80°C to -10°C, and more preferably -40°C to -20°C.

3. The coating composition according to claim 1 or 2, wherein the first resin has a hydroxyl value in the range of 100 to 240 mgKOH / g, and preferably 150 to 200 mgKOH / g.

4. The coating composition according to claim 1 or 2, wherein the first resin has a mass average molecular weight in the range of 2,000 to 10,000, and preferably 4,000 to 8,000.

5. The first resin is at least one acrylic resin, and preferably C １ to C １０ and preferably C ２ to C ６ The coating composition according to claim 1 or 2, which is a hydroxylalkyl (meth)acrylate resin having an alkyl group.

6. The coating composition according to claim 1 or 2, wherein the resin (B-1) has a Tg in the range of 0°C to 30°C, preferably 5°C to 20°C.

7. The coating composition according to claim 1 or 2, wherein the resin (B-1) has a hydroxyl value in the range of 100 to 240 mgKOH / g, and preferably 150 to 200 mgKOH / g.

8. The coating composition according to claim 1 or 2, wherein the resin (B-1) has a mass average molecular weight in the range of 2,000 to 10,000, preferably 3,000 to 7,000.

9. The resin (B-1) is at least one acrylic resin, and preferably C １ -C １０ and preferably C ２ -C ６ The coating composition according to claim 1 or 2, which is a hydroxylalkyl (meth)acrylate resin having an alkyl group.

10. The coating composition according to claim 1 or 2, wherein the resin (B-2) has a Tg of at least 20°C, preferably at least 30°C.

11. The coating composition according to claim 1 or 2, wherein the resin (B-2) has a hydroxyl value in the range of 100 to 200 mgKOH / g and preferably in the range of 130 to 170 mgKOH / g.

12. The coating composition according to claim 1 or 2, wherein the resin (B-2) has a mass average molecular weight in the range of 2,000 to 10,000, preferably in the range of 3,000 to 7,000.

13. The resin (B-2) is at least one acrylic resin, and preferably C ２ -C １０ and preferably C ２ -C ６ The coating composition according to claim 1 or 2, which is a hydroxylalkyl (meth)acrylate resin having an alkyl group.

14. The coating composition according to claim 1 or 2, wherein the molar ratio between the NCO groups in the polyisocyanate and the hydroxyl groups of both the first resin and the second resin is in the range of 1.6:1 to 0.7:1 and preferably in the range of 1.35:1 to 1.05:

1.

15. The coating composition according to claim 1 or 2, wherein the amount of the amino resin is in the range of 1% by mass to 30% by mass, preferably in the range of 5% by mass to 15% by mass, based on the total mass of the coating composition.

16. The coating composition according to claim 1 or 2, wherein the amino resin is a melamine resin.

17. The coating composition according to claim 1 or 2, further comprising a hydroxyl-containing polyester resin.

18. An article coated with the coating composition according to claim 1 or 2, preferably having a metal substrate.

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