JP5946356B2 - Coating composition and coating film forming method - Google Patents

Description

  The present invention relates to a coating composition capable of obtaining a coating film having excellent scratch resistance, acid resistance and stain resistance, and having excellent finished appearance and repairability.

  A paint to be applied to an object such as an automobile body is required to have excellent coating film performance such as scratch resistance, acid resistance, stain resistance, and finished appearance.

  Conventionally, a melamine cross-linking coating material has been widely used as the coating material for the object. The melamine crosslinking paint is a paint containing a hydroxyl group-containing resin and a melamine resin as a crosslinking agent. However, the melamine crosslinked coating has a problem that the melamine crosslinked bond is easily hydrolyzed by acid rain, and the acid resistance of the coating film is poor.

  Japanese Patent Application Laid-Open No. 6-220397 discloses a two-component urethane cross-linking coating composition comprising a hydroxyl group-containing acrylic resin, a hydroxyl group-containing oligoester and an isocyanate prepolymer. This paint is excellent in acid resistance of the coating film because urethane crosslinks are hardly hydrolyzed. However, the scratch resistance of the coating film is insufficient.

  Japanese Patent Application Laid-Open No. 2000-136332 includes an organic material characterized by containing a thermosetting resin composition and colloidal silica having a solid content of less than 3 to 10 parts by weight per 100 parts by weight of resin solids of the resin composition. Solvent-based thermosetting coating compositions are disclosed. This paint has excellent scratch resistance because of its high surface hardness due to the effect of colloidal silica. However, when a melamine resin is used as a cross-linking agent, the coating film has insufficient acid resistance and is repaired. Sex was insufficient.

  In WO 2006/28130, a hydroxyl group-containing resin and an aliphatic polyisocyanate compound containing a alicyclic hydrocarbon group-containing polymerizable unsaturated monomer, a hydroxyl group-containing polymerizable unsaturated monomer, and the like as copolymerization components are disclosed. A coating composition containing is disclosed. This paint is excellent in scratch resistance and acid resistance of the coating film, but there are cases where the stain resistance and repair resistance of the coating film are insufficient.

Japanese Patent Laid-Open No. 6-220397 JP 2000-136332 A WO2006 / 28130

  An object of the present invention is to provide a coating composition that is excellent in scratch resistance, acid resistance, and stain resistance, and that can provide a coating film that is excellent in both finished appearance and repairability.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a hydroxyl group-containing acrylic having a hydroxyl group polymerizable unsaturated monomer, a specific alicyclic hydrocarbon group-containing polymerizable unsaturated monomer, or the like as a copolymerization component. It has been found that the above object can be achieved by a polyisocyanate compound comprising an aliphatic diisocyanate containing a resin and a specific multimeric component, and a polysiloxane-modified silica particle, and the present invention has been completed. .

That is, the present invention provides a coating composition shown in the following section:
Item 1. (A) (a) 25-50 mass% of a hydroxyl group-containing polymerizable unsaturated monomer, (b) 5-30 mass% of an alicyclic hydrocarbon group-containing polymerizable unsaturated monomer having 6-20 carbon atoms, and (c) other. A hydroxyl group-containing acrylic resin which is a copolymer of monomer components consisting of 20 to 70% by mass of a polymerizable unsaturated monomer of
(B) Based on the total amount of the polyisocyanate compound, the isocyanurate trimer content is 30 to 70% by mass, the uretdione dimer content is 3 to 30% by mass, and other trimer-containing multimers are contained. A coating composition comprising a polyisocyanate compound comprising an aliphatic diisocyanate in an amount of 0 to 67% by mass and (C) polysiloxane-modified silica particles having an average primary particle size of 1 to 40 nm.

  Item 2. (B) an alicyclic hydrocarbon group-containing polymerizable unsaturated monomer having 6 to 20 carbon atoms is cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) Item 2. The coating composition according to Item 1, which is at least one selected from the group consisting of acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, and tricyclodecanyl (meth) acrylate.

  Item 3. Item 3. The coating composition according to Item 1 or 2, wherein the hydroxyl group-containing acrylic resin (A) has a weight average molecular weight in the range of 5,000 to 30,000.

  Item 4. Item 4. The coating composition according to any one of Items 1 to 3, wherein the polysiloxane of the polysiloxane-modified silica particles (C) is an organic-modified polysiloxane.

  Item 5. Item 4. The coating composition according to any one of Items 1 to 3, wherein the polysiloxane of the polysiloxane-modified silica particles (C) is polydimethylsiloxane and / or polydiphenylsiloxane.

  Item 6. Any one of Items 1 to 5 wherein the equivalent ratio (NCO / OH) of the isocyanate group in the polyisocyanate compound (B) and the hydroxyl group in the hydroxyl group-containing acrylic resin (A) is in the range of 0.8 to 1.5. The coating composition according to claim 1.

  Item 7. The mixing ratio of the hydroxyl group-containing acrylic resin (A), the polyisocyanate compound (B) and the polysiloxane-modified silica particles (C) is based on the total amount of the hydroxyl group-containing acrylic resin (A) and the polyisocyanate compound (B). The acrylic resin (A) is in the range of 55 to 80% by mass, the polyisocyanate compound (B) is in the range of 20 to 45% by mass, and the polysiloxane-modified silica particles (C) are 0.1 to 10% by mass. Item 7. The coating composition according to any one of Items 1 to 6, which is within a range of%.

  Item 8. Item 8. The coating composition according to any one of Items 1 to 7, wherein the coating film to be formed has a glass transition temperature (Tg) in the range of 70 to 110 ° C.

  Moreover, this invention provides the articles | goods containing the coating film obtained by coating the said coating composition.

  The present invention also relates to a method of forming a multilayer coating film by coating at least one layer of a colored base coat paint and at least one layer of a clear coat paint on an object to be coated. The present invention provides a method for forming a multilayer coating film comprising coating the coating composition described above.

  The coating composition of the present invention is excellent in scratch resistance by containing polysiloxane-modified silica, and has a high hardness coating film by having many alicyclic hydrocarbon structures in which the acrylic resin is hard. Therefore, it is considered that a coating film excellent in repairability and stain resistance can be obtained.

  Polysiloxane-modified silica is a particle having a structure coated with an organic layer of polysiloxane, unlike silica particles that are not coated with a particle surface typified by general colloidal silica. From the effect, the reaction between the reactive functional group remaining on the surface of the silica particles and the acrylic resin or polyisocyanate compound as the binder component, and further, the reactive functional group of other silica particles is suppressed. Compared to the case where unmodified silica particles are used, the silica particles are stable both in the coating composition and in the formed coating film and are considered to be uniformly distributed in the coating film. It is done.

  As a result, the properties of the silica particles are uniformly imparted in the matrix structure of the binder component, so that the mechanical properties of the coating film can be dramatically improved. It is thought that a coating film is obtained.

In particular, since the polyisocyanate compound as a crosslinking agent component has a relatively large amount of uretdione dimer component having a low molecular weight in the quantitative constitution of the multimer component, The flowability is improved, and a coating film having an excellent finished appearance can be obtained.
In addition, since it also contains an isocyanurate trimer, it is excellent in curability and the crosslinking density is improved, so that a coating film excellent in scratch resistance can be obtained.

  Furthermore, since the crosslinked structure becomes a urethane crosslinked structure excellent in resistance to hydrolysis by acid, a coating film excellent in acid resistance can be obtained.

  As described above, according to the coating composition of the present invention, there is an effect that it is possible to obtain a coating film which is excellent in scratch resistance, acid resistance and stain resistance, and which is excellent in both finished appearance and repairability. Can do.

  Hereinafter, the coating composition of the present invention (hereinafter sometimes referred to as “the present coating”) and the method for forming a multilayer coating film will be described in detail.

  The coating composition of the present invention includes a specific hydroxyl group-containing acrylic resin (A) having a hydroxyl group-polymerizable unsaturated monomer and an alicyclic hydrocarbon group-containing polymerizable unsaturated monomer as a copolymerization component, and a specific multimeric component. It is a coating composition characterized by containing the polyisocyanate compound (B) which consists of aliphatic diisocyanate which has the following quantitative structure, and the polysiloxane modified silica particle (C) which has the average primary particle diameter of a specific range.

Hydroxyl group-containing acrylic resin (A)
The hydroxyl group-containing acrylic resin (A) comprises (a) a hydroxyl group-containing polymerizable unsaturated monomer, (b) a C 6-20 alicyclic hydrocarbon group-containing polymerizable unsaturated monomer, and (c) other polymerizable groups. It can be produced by copolymerizing a monomer component composed of a saturated monomer by a conventional method.

  The hydroxyl group-containing polymerizable unsaturated monomer (a) is a compound having one hydroxyl group and one unsaturated bond in one molecule, and this hydroxyl group is a functional group that mainly reacts with the polyisocyanate compound (B) as a crosslinking agent. It acts as. As the monomer, specifically, monoesterified products of acrylic acid or methacrylic acid and a dihydric alcohol having 2 to 10 carbon atoms are suitable. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl Examples thereof include hydroxyalkyl (meth) acrylates such as (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Furthermore, examples of the monomer include a ring-opening polymerization adduct of the hydroxyalkyl (meth) acrylate and a lactone such as ε-caprolactone. Specifically, for example, “Plaxel FA-1”, “Plaxel FA-2”, “Plaxel FA-3”, “Plaxel FA-4”, “Plaxel FA-5”, “Plaxel FM-1”, “ “Placcel FM-2”, “Placcel FM-3”, “Placcel FM-4”, “Placcel FM-5” (all are trade names, manufactured by Daicel Chemical Industries, Ltd.) and the like.

  As the hydroxyl group-containing polymerizable unsaturated monomer (a), the finished appearance of the resulting coating film can be improved by reducing the reactivity between the polyisocyanate compound as a crosslinking agent and the acrylic resin (A). From the above, it is preferable to contain a polymerizable unsaturated monomer (a1) having a secondary hydroxyl group.

  Examples of the polymerizable unsaturated monomer (a1) having a secondary hydroxyl group include unsaturated monomers such as 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxybutyl (meth) acrylate ( A polymerizable unsaturated monomer having a secondary hydroxyl group having 2 to 8, preferably 2 to 4 and more preferably 2 to 3 carbon atoms in the alkyl group in the ester part of a1) can be mentioned. In particular, 2-hydroxypropyl (meth) acrylate can be preferably used. When the carbon number of the alkyl group is 5 or more, the finished appearance of the coating film may be deteriorated, and the pot life of the coating composition may be decreased. These can be used alone or in combination of two or more.

  The blending ratio of the polymerizable unsaturated monomer (a1) having a secondary hydroxyl group is preferably 25 to 50% by mass, more preferably 25 to 45% by mass, and still more preferably 25 based on the total amount of the monomer components. It is in the range of ˜40% by mass.

  Moreover, the polymerizable unsaturated monomer (a2) which has both a cyclohexyl ring and a hydroxyl group can also be used suitably from a viewpoint of improving abrasion resistance, without reducing the acid resistance of a coating film. Specific examples include CHDMMA (manufactured by Nippon Kasei Co., Ltd., 1,4-cyclohexanedimethanol monoacrylate).

  As the unsaturated monomer (a2), for example, a polyester oligomer having a hydroxycyclohexyl group or a methylolcyclohexyl group at both ends of the molecule, and a (equimolar) reaction product of a diisocyanate compound and a hydroxyl group-containing (meth) acrylate are reacted. The resulting macromonomer can also be used. Examples of the polyester oligomer include flexo reds 148 and flexo reds 188 (both trade names, manufactured by King Industries, USA).

  The acrylic resin having both a cyclohexyl ring and a hydroxyl group obtained by using the polymerizable unsaturated monomer (a2) having both a cyclohexyl ring and a hydroxyl group as a copolymerization component is, for example, an acrylic resin having a hydroxyl group and a cyclohexyl ring. An acid anhydride having an acid (for example, hexahydrophthalic anhydride) is subjected to an addition reaction, and a compound having both an epoxy group and a hydroxyl group (for example, glycidol) is added to the carboxylic acid produced by the addition reaction by an acid / epoxy reaction. It can also be obtained by a method such as addition reaction to form a terminal hydroxyl group.

  The mixing ratio of the hydroxyl group-containing polymerizable unsaturated monomer (a) is 25 to 50% by mass, particularly 25 to 45% by mass, more particularly 25 to 40% by mass, based on the total amount of the monomer components. It is preferable.

  When the blending ratio of the hydroxyl group-containing polymerizable unsaturated monomer (a) is less than 25% by mass, the cured coating film may be insufficiently cross-linked and the scratch resistance may be insufficient. On the other hand, if it exceeds 50% by mass, the compatibility with the monomer components other than the unsaturated monomer (a) (unsaturated monomer (b) or unsaturated monomer (c)) and copolymerization reactivity are reduced, and further obtained. When the compatibility with the other component (polyisocyanate compound (B) or polysiloxane-modified silica particles (C)) of the hydroxyl group-containing acrylic resin (A) is reduced, the finished appearance of the resulting coating film may be reduced. is there.

  In the present specification, “(meth) acrylate” means “acrylate or methacrylate”.

  The alicyclic hydrocarbon group-containing polymerizable unsaturated monomer (b) is a polymerizable unsaturated monomer containing an alicyclic hydrocarbon group having 6 to 20 carbon atoms.

  Since the unsaturated monomer (b) is used as a copolymerization component, the glass transition temperature of the hydroxyl group-containing acrylic resin (A) increases and the polarity decreases. And, the effect of improving the stain resistance and water resistance of the obtained coating film can be obtained.

  Typical examples of the alicyclic hydrocarbon group having 6 to 20 carbon atoms include a cyclohexyl group, a cyclooctyl group, a cyclododecyl group, an isobornyl group, an adamantyl group, and a tricyclodecanyl group.

  Specific examples of the alicyclic hydrocarbon group-containing polymerizable unsaturated monomer (b) include, for example, cyclohexyl (meth) acrylate, methylcyclohexylmethyl (meth) acrylate (for example, 4-methylcyclohexylmethyl (meth) acrylate), Ethylcyclohexylmethyl (meth) acrylate (for example, 4-ethylcyclohexylmethyl (meth) acrylate), methoxycyclohexylmethyl (meth) acrylate (for example, 4-methoxycyclohexylmethyl (meth) acrylate), tert-butylcyclohexyl (meth) acrylate , Cyclooctyl (meth) acrylate, cycloalkyl (meth) acrylate such as cyclododecyl (meth) acrylate; isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate Examples thereof include polymerizable unsaturated monomers having a bridged alicyclic hydrocarbon group such as relate, adamantyl (meth) acrylate, 3,5-dimethyladamantyl (meth) acrylate, and 3-tetracyclododecyl (meth) acrylate. Preferred examples include cyclohexyl (meth) acrylate and isobornyl (meth) acrylate.

  The blending ratio of the alicyclic hydrocarbon group-containing polymerizable unsaturated monomer (b) is 5 to 30% by mass, particularly 10 to 30% by mass, more particularly 10 to 25% by mass, based on the total amount of the monomer components. It is preferable to be within the range.

  When the blending ratio of the alicyclic hydrocarbon group-containing polymerizable unsaturated monomer (b) is less than 5% by mass, the hardness of the cured coating film may be insufficient and the stain resistance may be insufficient. is there. On the other hand, when it exceeds 30 mass%, the hardness of the cured coating film becomes too high, and the finished appearance of the coating film may be deteriorated.

  The other polymerizable unsaturated monomer (c) is one unsaturated per molecule other than the hydroxyl group-containing polymerizable unsaturated monomer (a) and the alicyclic hydrocarbon group-containing polymerizable unsaturated monomer (b). Specific examples of these compounds are shown below in (1) to (8).

  (1) Acid group-containing polymerizable unsaturated monomer: a compound having one or more acid groups and one unsaturated bond in a molecule, for example, (meth) acrylic acid, crotonic acid, itaconic acid, malein Carboxyl group-containing polymerizable unsaturated monomers such as acid and maleic anhydride; sulfonic acid group-containing polymerizable unsaturated monomers such as vinyl sulfonic acid and sulfoethyl (meth) acrylate; 2- (meth) acryloyloxyethyl acid phosphate; Examples include 2- (meth) acryloyloxypropyl acid phosphate, 2- (meth) acryloyloxy-3-chloropropyl acid phosphate, and acidic phosphate ester polymerizable unsaturated monomers such as 2-methacryloyloxyethylphenyl phosphate. be able to. These can be used alone or in combination of two or more. The acid group-containing polymerizable unsaturated monomer can also act as an internal catalyst when the (A) component is a crosslinking agent and the (B) component is a crosslinking agent, and the amount used is a hydroxyl group-containing acrylic resin. Based on the total amount of monomer components constituting (A), it is preferably used in the range of 0 to 5% by mass, particularly 0.1 to 3% by mass.

  (2) Monoesterified product of acrylic acid or methacrylic acid and C1-C20 monohydric alcohol: for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) Acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isomyristyl (meth) acrylate, isostearyl acrylate (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.) ), Lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, and the like.

  Moreover, among the above, the polymerizable unsaturated monomer (c2-1) which has a C8 or more hydrocarbon group which has a branched structure can be used conveniently from a viewpoint of improving the abrasion resistance of a coating film. By using a polymerizable unsaturated monomer (c2-1) as a constituent monomer component, a soft structure is partially introduced into the resulting acrylic resin (A), and the polarity of the resin is lowered, so that flexibility is achieved. It is possible to obtain the effect of improving the scratch resistance of the coating film by the application and the finishing property by smoothing the surface. In addition, since it has a branched structure, it suppresses a decrease in the glass transition temperature of the coating film as compared with a case where a polymerizable unsaturated monomer having a linear hydrocarbon group having 8 or more carbon atoms is used as a constituent component. Therefore, it is advantageous from the viewpoint of improving acid resistance.

  As specific examples of the polymerizable unsaturated monomer having a hydrocarbon group having 8 or more carbon atoms having a branched structure, among those described above, for example, 2-ethylhexyl acrylate, isooctyl (meth) acrylate, isomyristyl (meth) acrylate, An example is isostearyl acrylate (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.).

  When the polymerizable unsaturated monomer (c2-1) is used as a constituent component, the blending ratio is preferably 3 to 40% by mass, particularly 10 to 30% by mass, based on the total amount of the monomer components. .

  (3) Alkoxysilyl group-containing polymerizable unsaturated monomer: for example, vinyltrimethoxysilane, vinyltriethoxysilane, acryloxyethyltrimethoxysilane, methacryloxyethyltrimethoxysilane, acryloxypropyltrimethoxysilane, methacryloxypropyltri Methoxysilane, acryloxypropyltriethoxysilane, methacryloxypropyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, and the like. Among these, preferred alkoxysilyl group-containing polymerizable unsaturated monomers include vinyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like.

  By using an alkoxysilyl group-containing polymerizable unsaturated monomer as a constituent component, in addition to the crosslinking bond between a hydroxyl group and an isocyanate group, a condensation reaction between alkoxylyl groups and a crosslinking bond between the alkoxysilyl group and the hydroxyl group are generated. be able to. Thereby, since the crosslinking density of the obtained coating film is improved, the effect of improving the scratch resistance, acid resistance and stain resistance can be obtained.

  When an alkoxysilyl group-containing polymerizable unsaturated monomer is used as a constituent component, the blending ratio is preferably 1 to 20% by mass, particularly preferably 1 to 10% by mass, based on the total amount of monomer components.

  (4) Aromatic polymerizable unsaturated monomer: For example, styrene, α-methylstyrene, vinyltoluene and the like.

  By using an aromatic polymerizable unsaturated monomer as a constituent component, the Tg of the resulting resin is increased, and a hydrophobic coating film with a high refractive index can be obtained. The effects of improving the appearance, improving water resistance and acid resistance can be obtained. Accordingly, the other polymerizable unsaturated monomer (c) is preferably one containing (4) an aromatic polymerizable unsaturated monomer such as styrene.

  When an aromatic polymerizable unsaturated monomer is used as a constituent component, the blending ratio is preferably 3 to 50% by mass, particularly 5 to 40% by mass, based on the total amount of monomer components.

  (5) Glycidyl group-containing polymerizable unsaturated monomer: A compound having one glycidyl group and one unsaturated bond in one molecule, specifically, glycidyl acrylate, glycidyl methacrylate, and the like.

  (6) Nitrogen-containing polymerizable unsaturated monomers: for example, acrylamide, methacrylamide, dimethylacrylamide, N, N-dimethylpropylacrylamide, N-butoxymethylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetoneacrylamide, N, N-dimethylaminoethyl (meth) acrylate, vinylpyridine, vinylimidazole and the like.

  (7) Other vinyl compounds: For example, vinyl acetate, vinyl propionate, vinyl chloride, versatic acid vinyl ester Veova 9, Veova 10 (Japan Epoxy Resin) and the like.

  (8) Unsaturated bond-containing nitrile compounds: for example, acrylonitrile, methacrylonitrile and the like.

  These other polymerizable unsaturated monomers (c) can be used alone or in combination of two or more.

  A hydroxyl group-containing acrylic resin (A) can be obtained by copolymerizing the monomer mixture comprising the polymerizable unsaturated monomers (a), (b) and (c).

  The copolymerization method for obtaining the hydroxyl group-containing acrylic resin (A) by copolymerizing the monomer mixture is not particularly limited, and a known copolymerization method can be used. Among them, a solution polymerization method in which polymerization is performed in the presence of a polymerization initiator can be preferably used.

  Examples of the organic solvent used in the solution polymerization method include aromatic solvents such as toluene, xylene, and swazole 1000 (trade name, high-boiling petroleum solvent) manufactured by Cosmo Oil; ethyl acetate, 3-methoxybutyl Ester solvents such as acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, propyl propionate, butyl propionate, ethoxy ethyl propionate, etc. Can be mentioned.

  These organic solvents can be used singly or in combination of two or more, but it is preferable to use a high boiling ester solvent or ketone solvent from the viewpoint of the solubility of the acrylic resin. In addition, aromatic solvents having higher boiling points can be suitably used in combination.

  Examples of the polymerization initiator that can be used for copolymerization of the hydroxyl group-containing acrylic resin (A) include 2,2′-azobisisobutyronitrile, benzoyl peroxide, di-tert-butyl peroxide, and di-tert-amyl. Mention may be made of radical polymerization initiators known per se, such as peroxide, tert-butyl peroctoate, 2,2′-azobis (2-methylbutyronitrile).

  The hydroxyl value of the hydroxyl group-containing acrylic resin (A) is preferably 120 to 200 mgKOH / g, more preferably 130 to 200 mgKOH / g, and still more preferably 140 to 200 mgKOH / g, from the viewpoint of both scratch resistance and water resistance. Is within the range.

  The weight average molecular weight of the hydroxyl group-containing acrylic resin is preferably in the range of 5000 to 30000, more preferably 5000 to 20000, and still more preferably 10,000 to 20000. By reducing the weight average molecular weight to 5000 or more, it is possible to suppress deterioration of the coating performance such as acid resistance, and by setting it to 30000 or less, it is possible to suppress the deterioration of the finished appearance accompanying the decrease in the smoothness of the coating film. Therefore, it is preferable.

  In addition, in this specification, a weight average molecular weight is the value computed on the basis of the molecular weight of standard polystyrene from the chromatogram measured by the gel permeation chromatograph. As the gel permeation chromatograph, “HLC8120GPC” (manufactured by Tosoh Corporation) was used. As the columns, four columns of “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name) were used, Mobile phase: Tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 cc / min, detector: RI

  The glass transition temperature of the hydroxyl group-containing acrylic resin (A) is preferably in the range of -30 ° C to 30 ° C, particularly -20 ° C to 20 ° C. When the glass transition temperature is less than −30 ° C., the coating film hardness may be insufficient, and when it exceeds 30 ° C., the coating surface smoothness and crack resistance may be deteriorated.

  The hydroxyl group-containing acrylic resin (A) includes so-called urethane-modified acrylic resins.

  A hydroxyl-containing acrylic resin (A) can be used individually or in combination of 2 or more types.

  In the coating composition of the present invention, as the base resin, a resin other than the hydroxyl group-containing acrylic resin (A) can be used together as necessary. Accordingly, the coating composition of the present invention includes those containing a resin other than the hydroxyl group-containing acrylic resin (A) as the base resin. Specifically, for example, a polyester resin, a polyether resin, a polyurethane resin, and the like can be given, and preferable examples include a hydroxyl group-containing polyester resin and a hydroxyl group-containing polyurethane resin.

  The hydroxyl group-containing polyester resin can be produced by an ordinary method, for example, by an esterification reaction of a polybasic acid and a polyhydric alcohol. The polybasic acid is a compound having two or more carboxyl groups in one molecule. For example, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexa Examples include hydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic acid, and anhydrides thereof. The polyhydric alcohol has two or more hydroxyl groups in one molecule. For example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-diethyl-1,3 -Propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, hydroxy Diols such as neopentyl glycol phosphate, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethylpentanediol, hydrogenated bisphenol A, etc. , And trivalent or higher polyol components such as trimethylolpropane, trimethylolethane, glycerin, pentaerythritol, and the like, and 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylol Examples thereof include hydroxycarboxylic acids such as pentanoic acid, 2,2-dimethylolhexanoic acid, and 2,2-dimethyloloctanoic acid.

  Also, by reacting mono-epoxy compounds such as α-olefin epoxides such as propylene oxide and butylene oxide, Cardura E10 (product name, glycidyl ester of synthetic hyperbranched saturated fatty acid) and the like with acids, A compound may be introduced into the polyester resin.

  When introducing a carboxyl group into a polyester resin, for example, it can be introduced by adding an acid anhydride to a hydroxyl group-containing polyester and half-esterifying it.

  The hydroxyl value of the hydroxyl group-containing polyester resin is preferably in the range of 100 to 200 mgKOH / g, and more preferably in the range of 120 to 180 mgKOH / g. The weight average molecular weight of the hydroxyl group-containing polyester resin is preferably in the range of 2500 to 40000, more preferably in the range of 5000 to 30000.

  Examples of the hydroxyl group-containing polyurethane resin include a hydroxyl group-containing polyurethane resin obtained by reacting a polyol and a polyisocyanate.

  Examples of the polyol include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol and hexamethylene glycol, and trihydric alcohols such as trimethylolpropane, glycerin and pentaerythritol as low molecular weight substances. Can do. Examples of the high molecular weight material include polyether polyol, polyester polyol, acrylic polyol, and epoxy polyol. Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Examples of the polyester polyol include alcohols such as the divalent alcohols, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol, and dibasic acids such as adipic acid, azelaic acid, and sebacic acid. Lactone-based ring-opening polymer polyol such as polycaprolactone, polycarbonate diol, and the like. Moreover, for example, carboxyl group-containing polyols such as 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid can also be used.

  Examples of the polyisocyanate to be reacted with the above polyol include aliphatic polyisocyanate compounds such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate; and burette type addition of these polyisocyanates. Product, isocyanurate cycloadduct; isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4- (or-2,6-) diisocyanate, 1,3- (or 1,4-) Alicyclic diisocyanates such as di (isocyanatomethyl) cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate And burette type adducts, isocyanurate cycloadducts of these polyisocyanates; xylylene diisocyanate, metaxylylene diisocyanate, tetramethyl xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1, 5-naphthalene diisocyanate, 1,4-naphthalene diisocyanate, 4,4-toluidine diisocyanate, 4,4′-diphenyl ether diisocyanate, (m- or p-) phenylene diisocyanate, 4,4′-biphenylene diisocyanate, 3,3′- Aromatic dii such as dimethyl-4,4′-biphenylene diisocyanate, bis (4-isocyanatophenyl) sulfone, isopropylidenebis (4-phenylisocyanate) Cyanate compounds; and burette-type adducts of these polyisocyanates, isocyanurate cycloadducts; triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2, Polyisocyanate compounds having three or more isocyanate groups in one molecule such as 4,6-triisocyanatotoluene, 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate; and these And polyisocyanate burette type adducts, isocyanurate ring adducts, and the like.

  The hydroxyl value of the hydroxyl group-containing polyurethane resin is preferably in the range of 80 to 200 mgKOH / g, more preferably in the range of 100 to 180 mgKOH / g. The weight average molecular weight of the hydroxyl group-containing polyurethane resin is preferably in the range of 2500 to 40000, more preferably in the range of 5000 to 30000. The glass transition temperature of the hydroxyl group-containing polyurethane resin is preferably in the range of −40 ° C. to 85 ° C., more preferably in the range of −30 ° C. to 80 ° C.

  When a resin other than the above hydroxyl group-containing acrylic resin (A) (more specifically, a polyester resin, a polyether resin, a polyurethane resin, etc.) is used in combination, the resin other than the hydroxyl group-containing acrylic resin (A) contains a hydroxyl group. Preferably it is 100 mass% or less with respect to solid content total amount of an acrylic resin (A), More preferably, it exists in the range of 10-50 mass%.

Polyisocyanate compound (B)
The polyisocyanate compound (B) of the coating composition of the present invention comprises an aliphatic diisocyanate, and the aliphatic diisocyanate is a diisocyanate compound having an aliphatic alkyl chain in the structure of the diisocyanate compound. The aliphatic alkyl chain preferably has 4 to 30 carbon atoms, particularly 4 to 20 carbon atoms, more preferably 4 to 10 carbon atoms. In the present invention, the polyisocyanate compound (B) includes an isocyanurate trimer and a uretdione dimer. The aliphatic diisocyanate may further contain other trimer or higher multimers. In the present invention, “the polyisocyanate compound (B) is composed of an aliphatic diisocyanate” means that the polyisocyanate compound (B) is produced using an aliphatic diisocyanate as a raw material, and more specifically, For example, it shows that a polyisocyanate compound (B) is obtained by multimerization (dimerization, trimerization, etc.) of aliphatic diisocyanate.

  Specific examples of the aliphatic diisocyanate include trimethylene diisocyanate, tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, and 1,2-butylene. Examples include diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,2,4-trimethyl-hexamethylene-1,6-diisocyanate, 2,6-diisocyanatomethylcaproate, lysine diisocyanate, and the like. Can do. Among these, hexamethylene diisocyanate (hereinafter referred to as HMDI) can be particularly preferably used because of scratch resistance and industrial availability.

  The isocyanurate trimer, which is one of the constituent components of the polyisocyanate compound, is a polyisocyanate having an isocyanurate group consisting of three diisocyanate monomer molecules.

  In the polyisocyanate compound, the content of the isocyanurate trimer is 30 to 70% by mass, preferably 40 to 70% by mass, more preferably 50 to 70% by mass, based on the total amount of the polyisocyanate compound (B). It is. If it is less than 30% by mass, the viscosity of the polyisocyanate compound (composition) may increase or the crosslinkability may decrease. On the other hand, when it exceeds 70% by mass, the viscosity increases and the finished appearance may be deteriorated.

  When the isocyanurate group-containing polyisocyanate is derived from a diisocyanate monomer, it can be usually performed using an isocyanurate-forming catalyst. As a specific isocyanuration catalyst, for example, a catalyst having basicity is generally preferable. 1) Tetraalkylammonium hydroxide such as tetramethylammonium and tetraethylammonium, and weak organic acid salts such as acetic acid and capric acid, and 2) Hydroxyalkylammonium hydroxides such as trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, triethylhydroxyethylammonium and the like, organic weak acid salts such as acetic acid and capric acid, Metal salts of alkyl carboxylic acids such as acids such as tin, zinc, lead, sodium and potassium, 4) metal alcoholates such as sodium and potassium, 5) hexame Aminosilyl group-containing compounds such Rujishirazan, 6) Mannich bases, 7) there is a combination such as the tertiary amines and epoxy compounds.

  Of the above, 1), 2), and 3) are particularly preferable from the viewpoint of reaction selectivity (isocyanuration). The aminosilyl group-containing compound may undergo side reactions such as uretdione formation and biuret group-containing polyisocyanate formation depending on the use conditions.

  An isocyanurate group-containing polyisocyanate can be obtained using the catalyst. The resulting isocyanurate group-containing polyisocyanate contains multimers such as pentamers and heptamers in addition to trimers. The conversion rate of the isocyanurate conversion reaction (mass ratio of the polyisocyanate produced by the isocyanurate conversion reaction) for obtaining the predetermined isocyanurate trimer concentration range is preferably 20% or less, more preferably 15% or less. . If it exceeds 20%, it may be difficult to achieve the predetermined isocyanurate trimer concentration, which is a constituent requirement, and the finished appearance of the resulting coating film may be insufficient.

  In the isocyanurate-forming reaction, polyisocyanates other than isocyanurate group-containing polyisocyanates such as uretdione group-containing polyisocyanate may be generated at the same time. The uretdione dimer concentration produced by the isocyanuration reaction is preferably 2% by mass or less, more preferably 1% by mass or less based on the polyisocyanate produced by the isocyanuration reaction.

  The uretdione dimer, which is one of the components of the polyisocyanate compound, is a polyisocyanate having a uretdione group, which is composed of two diisocyanate monomer molecules.

  In the polyisocyanate compound, the content of the uretdione dimer is 3 to 30% by mass based on the total amount of the polyisocyanate compound (B) from the viewpoint of the curability of the coating composition and the finished appearance of the resulting coating film. The content is preferably 5 to 25% by mass, more preferably 8 to 20% by mass. If it is less than 3% by mass, the viscosity of the polyisocyanate compound (composition) may increase, or the finished appearance of the resulting coating film may decrease. Moreover, when it exceeds 30 mass%, the sclerosis | hardenability of a coating composition may fall.

  A uretdione dimer can be obtained using a uretdione-forming catalyst. Specific examples of the uretdione conversion catalyst include trialkylphosphine such as tri-phosphine, trialkylphosphine such as tri-n-butylphosphine and tri-n-octylphosphine, and tris (dialkyl) such as tris- (dimethylamino) -phosphine. And cycloalkyl phosphines such as amino) phosphine and cyclohexyl-di-n-hexylphosphine. These compounds can also be allophanatization catalysts. Many of these compounds also promote the isocyanuration reaction at the same time, producing isocyanurate group-containing polyisocyanates in addition to uretdione group-containing polyisocyanates.

  Moreover, it can also obtain by heating, without using the above catalysts. The yield of uretdione group-containing polyisocyanate that can be obtained by heating was low, and it was not efficient as a means for obtaining uretdione group-containing polyisocyanate.

  However, it has been found that the amount of diisocyanate monomer liberated during storage of the uretdione group-containing polyisocyanate obtained by heating alone without using a catalyst has been found to be remarkably low.

  The uretdione group is easily decomposed by heating, and therefore, it has been considered that the diisocyanate monomer is liberated by storage from the uretdione group-containing polyisocyanate.

  For the above reasons, the uretdione group-containing polyisocyanate, which is one of the components of the polyisocyanate compound, is preferably produced by heating.

  The polyisocyanate compound preferably does not contain biuret type polyisocyanate.

  The above-described isocyanurate reaction and uretdione reaction can be performed sequentially or in parallel. Preferably, it is preferable to precede the isocyanuration reaction, and then perform the uretdioneation reaction. The isocyanuration reaction is preferably performed by using a catalyst and the uretdioneation reaction can be simplified by heat.

  After these reactions are completed, the unreacted diisocyanate monomer is removed by a thin film evaporator, extraction or the like.

  The polyisocyanate compound preferably contains no unreacted diisocyanate monomer, and the residual diisocyanate monomer concentration is preferably 1% by mass or less, more preferably 0.5% by mass or less.

  In the present invention, the aliphatic diisocyanate constituting the polyisocyanate compound (B) may further contain other trimer or higher multimer in addition to isocyanurate trimer and uretdione dimer.

  The other trimer or higher multimer is not particularly limited, and per se known multimers can be widely used, and examples thereof include uretdione trimer.

  A polyisocyanate compound (B) can be used individually or in combination of 2 or more types.

  In the polyisocyanate compound, the viscosity at 25 ° C. is preferably 100 to 3000 mPa · s, more preferably 200 to 2000 mPa · s, and still more preferably 200 to 1000 mPa · s. If it is less than 100 mPa · s, the curability of the coating composition of the present invention may be lowered. Moreover, when it exceeds 3000 mPa · s, the finished appearance of the obtained coating film may be deteriorated.

  In the polyisocyanate compound (B), the content of the isocyanurate trimer is 30 to 70% by mass, preferably 40 to 70% by mass, more preferably 50 to 70% by mass, based on the total amount of the polyisocyanate compound. The content of uretdione dimer is 3 to 30% by mass, preferably 5 to 25% by mass, more preferably 8 to 20% by mass, and the content of other trimer or higher multimer is 0 to 67%. It is in the range of mass%, preferably 5-55 mass%, more preferably 10-42 mass%.

  Moreover, in the said polyisocyanate compound, it can also be used as a blocked polyisocyanate compound which is a compound which blocked the free isocyanate group with the blocking agent.

  The blocking agent blocks free isocyanate groups. When the blocked polyisocyanate compound is heated to, for example, 100 ° C. or higher, preferably 130 ° C. or higher, the isocyanate group is regenerated and can easily react with the hydroxyl group. Examples of the blocking agent include phenols such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and hydroxybenzoic acid methyl; ε-caprolactam, δ-valerolactam, lactams such as γ-butyrolactam, β-propiolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, lauryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono Butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, pro Ethers such as lenglycol monomethyl ether and methoxymethanol; benzyl alcohol; glycolic acid; glycolic acid esters such as methyl glycolate, ethyl glycolate and butyl glycolate; lactic acid esters such as lactic acid, methyl lactate, ethyl lactate and butyl lactate; Alcohols such as methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; oximes such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime System: Active methylene system such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone ; Mercaptans such as butyl mercaptan, tert-butyl mercaptan, hexyl mercaptan, tert-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, ethylthiophenol; Acid amides such as stearamide, benzamide; imides such as succinimide, phthalimide, maleic imide; diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, di Amines such as butylamine and butylphenylamine; Imidazoles such as imidazole and 2-ethylimidazole; 3,5- Pyrazoles such as methylpyrazole; ureas such as urea, thiourea, ethyleneurea, ethylenethiourea, diphenylurea; carbamates such as phenyl N-phenylcarbamate; imines such as ethyleneimine and propyleneimine; bisulfite Examples of the blocking agent include sulfites such as soda and potassium bisulfite.

  When blocking (reacting the blocking agent), a solvent can be added as necessary. As the solvent used for the blocking reaction, those not reactive to isocyanate groups are preferable. For example, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and solvents such as N-methylpyrrolidone (NMP). Can be mentioned.

  In addition, if necessary, for example, an aliphatic polyisocyanate, an alicyclic polyisocyanate, an araliphatic polyisocyanate, an aromatic polyisocyanate, and these polyisocyanates other than the polyisocyanate compound (B) comprising the above aliphatic polyisocyanate. Derivatives and the like can also be used together. Accordingly, the coating composition according to the present invention includes an aliphatic polyisocyanate, an alicyclic polyisocyanate, an araliphatic polyisocyanate, an aromatic polyisocyanate, and these other than the polyisocyanate compound (B) comprising the above aliphatic polyisocyanate. It may contain a polyisocyanate derivative or the like.

  Examples of the aliphatic polyisocyanate other than the polyisocyanate compound (B) comprising an aliphatic polyisocyanate include lysine ester triisocyanate, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, Aliphatic triisocyanates such as 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane Etc.

  Examples of the alicyclic polyisocyanate include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: Isophorone diisocyanate), 4,4′-methylenebis (cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,3- or 1,4-bis (isocyanatomethyl) cyclohexane ( Common name: hydrogenated xylylene diisocyanate) or mixtures thereof, alicyclic diisocyanates such as norbornane diisocyanate, for example, 1,3,5-triisocyanatocyclohexane, 1,3, -Trimethylisocyanatocyclohexane, 2- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 2- (3-isocyanatopropyl) -2,6 -Di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 3- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 5 -(2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl -3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatotop Pyr) -bicyclo (2.2.1) -heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, etc. Alicyclic triisocyanate and the like.

  Examples of the araliphatic polyisocyanate include 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω, ω′-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis ( 1-isocyanato-1-methylethyl) benzene (common name: tetramethylxylylene diisocyanate) or a mixture thereof, for example, an araliphatic triisocyanate such as 1,3,5-triisocyanatomethylbenzene Etc.

  Examples of the aromatic polyisocyanate include m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4′- or 4,4′-diphenylmethane diisocyanate or a mixture thereof. 2,4- or 2,6-tolylene diisocyanate or mixtures thereof, aromatic diisocyanates such as 4,4′-toluidine diisocyanate, 4,4′-diphenyl ether diisocyanate, for example, triphenylmethane-4,4 ′, 4 '' '-Triisocyanate, aromatic triisocyanate such as 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, for example, 4,4'-diphenylmethane-2,2', 5 , 5'-Tetri It can be mentioned aromatic tetracarboxylic isocyanates such as cyanate.

  Examples of the polyisocyanate derivative include dimer, trimer, biuret, allophanate, carbodiimide, uretdione, uretoimine, isocyanurate, oxadiazine trione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric). MDI) and crude TDI.

  These polyisocyanate compounds that can be used as necessary may be used alone or in combination of two or more.

Polysiloxane-modified silica particles (C)
The polysiloxane-modified silica particles (C) are silica particles having a structure in which the particle surface is modified with a polysiloxane chain.

  As silica particles, for example, powder silica and colloidal silica can be used. The silica particles may be any shape such as spherical, hollow, porous, rod-like, plate-like, fiber-like, and indefinite shape, with the spherical one being preferred.

  As the silica particles, it is preferable to use colloidal silica in which fine silica particles are dispersed in water or an organic solvent. When colloidal silica is used, it is preferably used in the state of a dispersion. As the colloidal silica dispersion, the medium is preferably an organic solvent. Examples of the organic solvent include methanol, isopropyl alcohol, ethylene glycol, butanol, ethylene glycol monopropyl ether, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, dimethylformamide and the like. Also, a mixed solvent using two or more of these in combination, or a mixed solvent using a water-soluble organic solvent and water in combination can be used. Among these organic solvents, methanol, isopropyl alcohol, methyl ethyl ketone, and xylene are preferable from the viewpoint of easy modification reaction on the surface of the silica particles.

  Examples of the method for modifying the surface of the silica particles with polysiloxane chains include, for example, a method in which an alkoxysilane having a polysiloxane chain is used for modification by a dealcoholization reaction with silanol on the surface of the silica particles, and an alkoxysilane having a polysiloxane chain. Hydrolysis in the presence of water to generate silanol groups, followed by a dehydration condensation reaction between the silanol groups and the silanol groups on the silica particle surface, alcohol having a polysiloxane chain and silanols on the silica particle surface Examples thereof include a method of modifying by a dehydration condensation reaction with a group.

  As another method of modifying the silica particle surface with a polysiloxane chain, an alkoxysilane having a reactive group (generally referred to as a silane coupling agent; hereinafter referred to as “compound (C1)”) is described above. A method of reacting a compound (C2) having a polysiloxane chain with a functional group capable of forming a chemical bond by reacting with the reactive group after dehydration or dealcoholization condensation reaction on the surface of silica particles in the same manner as above Further, the compound (C1) is reacted in advance with a compound (C2) having a functional group capable of forming a chemical bond by reacting with the reactive group of the compound (C1) and a polysiloxane chain, to obtain a polysiloxane. A method of reacting this compound with silica particles after obtaining an alkoxysilane compound having a chain can also be mentioned.

  As a reactive group which the said compound (C1) has, an epoxy group, an amino group, a mercapto group, an isocyanate group etc. can be mentioned, for example. Specific examples of the compound (C1) include, for example, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, Compounds having an epoxy group such as 3-glycidoxypropyltriethoxysilane; N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane and other compounds having an amino group; 3-mercaptopropylmethyldimethoxysilane, 3 -Mercaptopropyltrimethoxysilane, etc. Compounds having a script group; 3- isocyanatopropyltriethoxysilane isocyanate groups, and the like compounds having a.

  The functional group that the compound (C2) has is selected depending on the reactive group that the compound (C1) has. When the reactive group that the compound (C1) has is an epoxy group, the functional group that the compound (C2) has is preferably a carboxyl group. When the reactive group included in the compound (C1) is an amino group, the functional group included in the compound (C2) is preferably an epoxy group. Furthermore, when the reactive group that the compound (C1) has is a mercapto group, the functional group that the compound (C2) has is preferably an isocyanate group, and when the reactive group that the compound (C1) has is an isocyanate group, The functional group of the compound (C2) is preferably a hydroxyl group or a mercapto group. The compound (C2) preferably has a functional group at one end of the polysiloxane chain.

  Among the above combinations, the case where the reactive group of the compound (C1) is an isocyanate group and the functional group of the compound (C2) is a hydroxyl group is particularly preferable because the reaction is easy.

  Examples of the compound that forms the polysiloxane chain of the compound (C2) include polydimethylsiloxane and polydiphenylsiloxane. In addition, the organic groups bonded to the silicon atom of these polysiloxanes may be all the same or different.

  When the reactive group which the said compound (C1) has is an isocyanate group, and the functional group which the said compound (C2) has is a hydroxyl group, the usage-amount of the said compound (C1) is based on 1 mol of said compounds (C2). As for it, it is preferable to set it as 0.5-1.1, and it is especially preferable to set it as 0.9-1.0 mol by the point which does not leave an unreacted compound (C1).

  In the above case, the reaction between the compound (C1) and the compound (C2) can be carried out without a solvent or with a solvent. However, the use of a solvent improves the fluidity of the reaction solution. Is preferable. Examples of the solvent include ester solvents such as ethyl acetate, butyl acetate and propylene glycol monomethyl ether acetate; ether solvents such as diisopropyl ether, dimethoxyethane and diethylene glycol dimethyl ether; halogen solvents such as dichloromethane and dichloroethane; toluene, xylene and the like. Aromatic solvents; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; aprotic polar solvents such as dimethylformamide and dimethyl sulfoxide. Among these, ester solvents; ketone solvents; ether solvents are preferable.

  Moreover, in order to promote reaction with the said compound (C1) and compound (C2), it is preferable to make it react in presence of a urethanization catalyst. Examples of the urethanization catalyst include amine catalysts such as pyridine, pyrrole, triethylamine, diethylamine and dibutylamine; phosphine catalysts such as triphenylphosphine and triethylphosphine; dibutyltin dilaurate, octyltin trilaurate, octyltin diacetate, dibutyltin diacetate Examples thereof include organic tin compounds such as acetate and tin octylate; organometallic compounds such as zinc octylate and the like. Moreover, it is preferable to use an organic tin compound and amines together because the urethanization reaction proceeds smoothly.

  As a modifier for obtaining polysiloxane-modified silica particles, a compound having a polysiloxane chain represented by the following general formula (polysiloxane) can be given as a suitable compound.

(R ¹ _x R ² _3-x SiR ³ ) _y R ⁵ (1)
In the above general formula, x = 0 to 2, particularly 0, y = 1 to 10, preferably 2 to 5, R ¹ is a monovalent organic group having 1 to 18 carbon atoms, particularly 1 to 3 carbon atoms, R ² Is a hydroxyl group; a linear, branched or cyclic alkoxy group having 1 to 6 carbon atoms, particularly 1 to 2 carbon atoms; a halogen atom, particularly chlorine; or; a carboxylic acid having 1 to 4 carbon atoms, preferably 2 carbon atoms. A hydrolyzable group consisting of a group; R ³ is oxygen or; preferably a linear or branched alkylene group having 1 to 8 carbon atoms; an alkylene ether; an alkylene thioether; preferably ethylene oxide, propylene oxide or butylene oxide or these Alkylene polyethers based on mixtures; alkylene polyethers; alkylene polyesters; or; in addition to ester groups and / or ether groups, urethane groups and / or Or a divalent organic group comprising an organic aliphatic, aromatic or araliphatic group having a urea group, and R ⁵ has a number average molecular weight of 300 to 5,000, The alkyl substituent is an organic group composed of polydialkylsiloxane having 1 to 8 carbon atoms.

  Silica particles modified with the compound having a polysiloxane chain (polysiloxane) are coated with the compound (modifier), and the functional reactive group remaining on the surface of the silica particles is sterically hindered by other functional groups. Since the reactivity is suppressed, the silica particles are extremely stable both in the coating composition and in the formed coating film, and are uniformly distributed in the coating film. The compound (modifier) is covalently bonded to the surface of the silica particles.

  The compound (modifier) has at least one anchor group or two or more anchor groups that react with the surface of the silica particles and polysiloxane.

  Furthermore, the anchor group having bonding properties may be incorporated at the end of the polysiloxane and may be present in one side chain of the polysiloxane.

  Among the compounds having a polysiloxane chain represented by the above general formula (1) (polysiloxane), more preferred compounds include compounds represented by the following general formula (2).

^{_{R 1 x R 2 3-x}} Si-R 3 -R 4 (2)
Here, R ⁴ is a monovalent organic group having a number average molecular weight of 300 to 5,000 and comprising a polydialkylsiloxane having an alkyl substituent of a silicon atom having 1 to 8 carbon atoms.

The compound represented by the above formula (2) (modifier) is a linear group having a head group reactive to the surface of the silica particles, a bonded intermediate unit (R ³ ), and a polydialkylsiloxane (R ⁴ ) end group. It is a compound having a structure.

The compound is covalently bonded to the surface of the silica particle through at least one, preferably 2 or more, and more preferably three covalent bonds. Further, the compound contains a spacer component (polydialkylsiloxane (R ⁴ )) that cannot react with the surface of the silica particles and is also inert to the components (A) and (B).

  The amount of modification of the polysiloxane chain with respect to the solid content mass of the silica particles is preferably 0.1 to 80 mass% with respect to the total solid content of the silica particles, and is 0.1 from the viewpoint of efficiently modifying the coating film surface. -40 mass% is preferable.

  The average primary particle diameter of the polysiloxane-modified silica particles (C) is preferably 1 to 100 nm, more preferably 1 to 50 nm, and even more preferably 1 to 40 nm.

In the present invention, the average primary particle size is a particle size (D ₅₀ ) at which the integrated particle size distribution from the small particle size side becomes 50% in the volume-based particle size distribution.

  The volume-based particle size distribution is measured by the laser diffraction / scattering method. In the present invention, the volume-based particle size distribution of the polysiloxane-modified silica particles (C) was measured using a laser diffraction / scattering particle size distribution measuring device “Microtrack NT3300” (trade name, manufactured by Nikkiso Co., Ltd.). At that time, the sample concentration was adjusted to be within a predetermined transmittance range set in the apparatus.

  In the coating composition of the present invention, the equivalent ratio (NCO) of the isocyanate group in the polyisocyanate compound (B) and the hydroxyl group in the hydroxyl group-containing acrylic resin (A) from the viewpoints of the curability and scratch resistance of the coating film. / OH) is preferably in the range of 0.8 to 1.5, more preferably 0.8 to 1.2, and even more preferably 0.80 to 1.15.

  The amount of the hydroxyl group-containing acrylic resin (A), polyisocyanate compound (B) and polysiloxane-modified silica particles (C) in the coating composition of the present invention is based on the total amount of the component (A) and the component (B). As the nonvolatile content, the hydroxyl group-containing acrylic resin (A) is 55 to 80% by mass, preferably 60 to 75% by mass, and the polyisocyanate compound (B) is 20 to 45% by mass, preferably 25 to 40% by mass, poly It is suitable that the siloxane-modified silica particles (C) are in the range of 0.1 to 10% by mass, preferably 0.2 to 5% by mass, and more preferably 0.3 to 3% by mass.

  With the coating composition of the present invention, the glass transition temperature (Tg) of the coating film to be formed is excellent in scratch resistance, acid resistance and stain resistance, and further, a coating film having excellent finished appearance and repairability is obtained. From the viewpoint that can be achieved, it is preferably in the range of 70 to 110 ° C, more preferably 70 to 100 ° C.

  In the present invention, the glass transition temperature (Tg) of the coating film is a value determined by dynamic viscoelasticity measurement.

  The dynamic viscoelasticity was measured under conditions of a temperature rising rate of 3 ° C./min, a temperature range of 20 to 200 ° C., and a frequency of 11 Hz. The glass transition temperature (Tg ° C.) of the coating film is a temperature at which the value of tan δ shows a maximum value in this measurement. As the dynamic viscoelasticity measuring device, FT Leospectra DVE-V4 (manufactured by Rheology, trade name, dynamic viscoelasticity measuring device) was used.

Other components This coating material is a coating composition containing the hydroxyl group-containing acrylic resin (A), the polyisocyanate compound (B) and the polysiloxane-modified silica (C) as essential components, and usually contains an organic solvent, If necessary, other additives such as other curing catalysts, pigments, pigment dispersants, leveling agents, rheology control agents, UV absorbers, light stabilizers, plasticizers, etc., which are usually used in the field of paints. Can do.

  Examples of the curing catalyst include tin octylate, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dioctyltin diacetate, dibutyltin dilaurate, dibutyltin oxide, and dioctyl. Examples thereof include organometallic catalysts such as tin oxide and lead 2-ethylhexanoate, and tertiary amines.

  These compounds described above as the curing catalyst can be used alone or in combination of two or more. Although the amount of the curing catalyst varies depending on the type, it is usually 0 to 5% by mass, preferably about 0.1 to 4% by mass, based on the total solid content of the component (A), component (B) and component (C). It is.

  As the pigment, it can be used without particular limitation, for example, titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, Colored pigments such as isoindoline pigments, selenium pigments, perylene pigments; body pigments such as talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, silica, alumina white; aluminum powder, mica powder, titanium oxide Examples thereof include metallic pigments such as coated mica powder.

  These pigments described above can be used alone or in combination of two or more. The pigment content varies depending on the type, but is usually 0 to 200% by mass, preferably about 1 to 100% by mass, based on the total solid content of the components (A), (B) and (C). .

  Moreover, although content of a coloring pigment changes with the kinds, it is 0-150 mass% normally with respect to the solid content total amount of (A) component, (B) component, and (C) component, Preferably it is 1-100 mass%. Degree.

  As the ultraviolet absorber, conventionally known ones can be used, and examples thereof include ultraviolet absorbers such as benzotriazole-based absorbent, triazine-based absorbent, salicylic acid-based absorbent, and benzophenone-based absorbent.

  The content of the UV absorber in the coating composition is usually in the range of 0 to 10% by mass, particularly 0.2 to 5% by mass, more particularly 0.3 to 2% by mass, based on the total amount of resin solids. It is preferable from the viewpoint of weather resistance and yellowing resistance.

  A conventionally well-known thing can be used as a light stabilizer, For example, a hindered amine light stabilizer can be mention | raise | lifted.

  The content of the light stabilizer in the coating composition is usually in the range of 0 to 10% by mass, particularly 0.2 to 5% by mass, more particularly 0.3 to 2% by mass, based on the total solid content of the resin. It is preferable from the viewpoint of weather resistance and yellowing resistance.

  When the isocyanate group of the polyisocyanate compound as the component (B) is not blocked, the coating composition of the present invention has a hydroxyl group-containing acrylic resin (A) and a polysiloxane modified from the viewpoint of storage stability. It is preferable to use a two-component paint in which silica (C) and polyisocyanate compound (B) are separated, and it is preferable to use a mixture of both before use.

Coating method of coating composition The coating material to which the present coating is applied is not particularly limited. For example, steel sheets such as cold-rolled steel sheets, galvanized steel sheets, zinc alloy-plated steel sheets, stainless steel sheets, and tin-plated steel sheets Metal substrates such as aluminum plates and aluminum alloy plates; various plastic materials are preferred. Further, it may be a vehicle body such as an automobile, a two-wheeled vehicle, a container or the like formed of the metal base material or a plastic material.

  Moreover, as a to-be-coated object, surface treatments, such as a phosphate process, a chromate process, complex oxide process, may be given to the metal surface of the said metal base material or a vehicle body. Furthermore, as an object to be coated, an undercoating film and / or an intermediate coating film such as various electrodeposition paints may be formed on the metal base material, the vehicle body or the like.

  The coating method of the paint is not particularly limited, and for example, the wet coating film can be formed by a coating method such as air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, or the like. In these coating methods, electrostatic application may be performed as necessary. Of these, air spray coating is particularly preferred. In general, the coating amount of the paint is preferably set to an amount of about 10 to 50 μm as a cured film thickness.

  When air spray coating, airless spray coating, and rotary atomization coating are performed, the viscosity of the coating is adjusted to a viscosity range suitable for the coating, usually Ford Cup #No. In a 4-viscosity meter, it is preferable to adjust appropriately using a solvent such as an organic solvent so that the viscosity is within a range of about 15 to 60 seconds at 20 ° C.

  Curing of the wet coating film formed by applying the coating material to the object to be coated is performed by heating, and the heating can be performed by a known heating means, such as a hot air furnace, an electric furnace, an infrared induction heating furnace, etc. The drying oven can be applied. The heating temperature is suitably in the range of 60 to 180 ° C, preferably 90 to 150 ° C. The heating time is not particularly limited, but is preferably in the range of 15 to 30 minutes.

  This paint is excellent in scratch resistance, acid resistance and stain resistance, and can obtain a coating film excellent in both finished appearance and repairability. it can. This paint can be particularly suitably used as an automobile paint.

Multi-layer coating film forming method As a top clear coat paint, as a multi-layer coating film forming method in which this paint is applied,
A method for forming a multi-layer coating film by coating at least one layer of a colored base coat paint and at least one layer of a clear coat paint on a substrate to be coated, wherein the paint composition of the present invention is used as the uppermost clear coat paint. An example is a method for forming a multilayer coating film characterized by coating an object.

  Specifically, for example, a solvent-type or water-based base coat paint is applied on an object to which electrodeposition coating and / or intermediate coating has been applied, and the coating film is not cured, as needed. In order to promote the volatilization of the solvent in the base coat paint, for example, after preheating at 40 to 90 ° C. for about 3 to 30 minutes, the paint is applied as a clear coat paint on the uncured base coat film. Thereafter, there can be mentioned a method of forming a multi-layer coating film of a 2-coat 1-bake method in which the base coat and the clear coat are cured together.

  Further, it can also be suitably used as a top clear coat paint in the top coat of the 3-coat 2-bake method or the 3-coat 1-bake method.

  As the base coat paint used in the above, a conventionally known normal thermosetting base coat paint can be used. Specifically, for example, a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin type, or the like. In addition, a coating material obtained by appropriately combining a curing agent such as an amino resin, a polyisocyanate compound, or a block polyisocyanate compound with a reactive functional group contained in the base resin can be used.

  The base coat paint is preferably a high solid type with a small amount of organic solvent used from the viewpoints of environmental problems and resource saving, and water paint or powder paint can also be used.

  In the method of forming a multi-layer coating film, when two or more clear coats are applied, in addition to the present paint, a conventionally known thermosetting clear coat paint such as an acrylic / melamine resin system may be used as the clear coat paint. it can.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples. In the following, “part” and “%” are both based on mass, and the film thickness of the coating film is based on the cured coating film.

Production Examples of Hydroxyl-Containing Acrylic Resins Production Examples 1-15
31 parts of ethoxyethyl propionate was charged into a four-necked flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet, and the temperature was raised to 155 ° C. under nitrogen gas flow. After reaching 155 ° C., the nitrogen gas flow was stopped, and a monomer mixture composed of a monomer and a polymerization initiator shown in Table 1 below was added dropwise over 4 hours. Next, after aging for 2 hours while aeration of nitrogen gas at 155 ° C., the mixture was cooled to 100 ° C. and diluted with 32.5 parts of butyl acetate (7.5 parts only in Production Example 10) to obtain 60% solid content. The hydroxyl group-containing acrylic resins (A-1) to (A-15) were obtained. The mass solid content concentration (%) and the resin property value of the obtained hydroxyl group-containing acrylic resin are shown in Table 1 below.

The glass transition temperature (° C.) in Table 1 was calculated by the following formula.
1 / Tg (K) = (W1 / T1) + (W2 / T2) +
Tg (° C.) = Tg (K) -273
In each formula, W1, W2,... Represent the respective mass fractions of the monomers used for copolymerization, and T1, T2,... Represent the Tg (K) of the homopolymer of each monomer. T1, T2,... Are values according to Polymer Handbook (Second Edition, edited by J. Brandup, E. H. Immergut).

  In addition, the glass transition temperature of the hydroxyl-containing acrylic resin which has a monomer which is not described in the said literature (data) as a monomer component is a value measured by Seiko Electronics Industry DSC220U (differential scanning calorimeter). For measurement, a predetermined amount of 50 mg of sample is weighed on a dedicated sample pan, dried at 130 ° C. for 3 hours, then heated in an inert gas from −50 ° C. to 150 ° C. at a speed of 10 ° C./min, This was carried out by reading the temperature at the inflection point of the obtained heat quantity change curve.

  In addition, hydroxyl-containing acrylic resin (A-13)-(A-15) is resin for a comparative example.

Production Examples 1-17 and Comparative Examples 1-8 of Coating Composition
Using the hydroxyl group-containing acrylic resin obtained in the above Production Examples 1 to 15 and the raw materials shown in Table 2 below, the mixture shown in Table 2 below is stirred and mixed using a blade-type stirrer to form a paint. Each coating composition was obtained. In addition, the mixing | blending of the coating composition shown in Table 2 is solid content mass ratio of each component.

  (* 1) to (* 12) in Table 2 have the following meanings, respectively.

  (* 1) Polyisocyanate compound A: Sumidur N-3300 manufactured by Sumika Bayer Urethane Co., Ltd. The composition ratio of polyisocyanate compound consisting of hexamethylene diisocyanate and multimers is 53% for isocyanurate trimers and 47% for multimers other than trimers. Solid content 100%, NCO content 21.8%.

  (* 2) Polyisocyanate compound B: Duranate TLA-100 manufactured by Asahi Kasei Chemicals Corporation. The composition ratio of the polyisocyanate compound consisting of hexamethylene diisocyanate and multimers is 63% for isocyanurate trimers, 12% for uretdione dimers, and 25% for multimers other than trimers. Solid content 100%, NCO content 21.8%.

  (* 3) 1: 1 mixture (mass ratio) of polyisocyanate compound C: Duranate TLA-100 (manufactured by Asahi Kasei Chemicals Corporation) and Desmodur N-3400 (manufactured by Sumika Bayer Urethane Co., Ltd.) . The composition ratio of the polyisocyanate compound consisting of hexamethylene diisocyanate and the multimer is 45% for the isocyanurate trimer, 25% for the uretdione dimer, and 30% for the multimer other than the trimer. Solid content 100%, NCO content 21.8%.

  (* 4) Polyisocyanate compound D: Desmodur N-3400 manufactured by Sumika Bayer Urethane Co., Ltd. The composition ratio of polyisocyanate compound consisting of hexamethylene diisocyanate and multimer is 27% for isocyanurate trimer, 37% for uretdione dimer, and 36% for multimers other than trimer. Solid content 100%, NCO content 21.8%.

  (* 5) Takenate D160N: Takeda Pharmaceutical Company Limited, trade name, hexamethylene diisoisocyanate and trimethylolpropane adduct, solid content 75%, NCO content 12.6%.

  (* 6) NANOBYK-3650: manufactured by BYK, trade name, linear alkyl group-modified polydimethylsiloxane-modified silica particle dispersion, low polarity, average particle size 20 nm, solid content concentration 31% (silica particle concentration 25%).

  (* 7) NANOBYK-3651: manufactured by BYK, trade name, branched alkyl group-modified polydimethylsiloxane-modified silica particle dispersion, high polarity, average particle diameter 20 nm, solid content concentration 34%. (Silica particle concentration 20%).

  (* 8) NANOBYK-3652: manufactured by BYK, trade name, linear alkyl group-modified polydimethylsiloxane-modified silica particle dispersion, medium polarity, average particle size 20 nm, solid content concentration 31% (silica particle concentration 25%).

  (* 9) NANOBYK-3610: manufactured by BYK, trade name, alkyl group-modified polysiloxane-modified alumina particle dispersion, low polarity, average particle size 20 nm, solid content concentration 37% (alumina particle concentration 30%).

  (* 10) Sno-Tex XBA-ST: manufactured by Nissan Chemical Industries, Ltd., trade name, colloidal silica having a high molecular weight by a siloxane bond (no polysiloxane structure) in an organic solvent (xylene / butanol) In which the surface has hydroxyl groups, the shape is true spherical, and the particle size is 10 to 20 nm. Solid content concentration 30%.

  (* 11) UV1164: UV absorber manufactured by Ciba Geigy.

  (* 12) HALS292: Hindered amine light stabilizer manufactured by Ciba Geigy.

  Each coating composition No. obtained in Examples 1 to 17 and Comparative Examples 1 to 8 was used. Nos. 1 to 25 are ford cups #No. 4 was adjusted to a viscosity of 25 seconds at 20 ° C.

Preparation of test plates Each of the coating composition Nos. 1 to 17 obtained in Examples 1 to 17 and Comparative Examples 1 to 8 was used. A test plate was prepared as follows for each of those having a viscosity adjusted to 1 to 25.

  Electron GT-10 (trade name, thermosetting epoxy resin-based cationic electrodeposition paint manufactured by Kansai Paint Co., Ltd.) has a thickness of 20 μm on a 0.8 mm-thick dull steel sheet subjected to zinc phosphate conversion treatment. Electrodeposited as above, cured by heating at 170 ° C. for 30 minutes, and then coated with Amirac TP-65-2 (trade name, polyester / melamine resin-based automotive intermediate coating) manufactured by Kansai Paint Co., Ltd. with a film thickness of 35 μm Air spray coating was performed, and the mixture was heated and cured at 140 ° C. for 30 minutes. A water-based metallic base coat WBC713T # 202 (manufactured by Kansai Paint Co., Ltd., acrylic / melamine resin-based automotive top coat paint, black paint color) is applied to the coating film so as to have a film thickness of 15 μm and left at room temperature for 5 minutes. Then, after preheating at 80 ° C. for 10 minutes, each coating composition prepared and adjusted in viscosity in the above Examples and Comparative Examples was applied on the uncured coating film so as to have a film thickness of 35 μm. And then left at 10 ° C. for 10 minutes and then heated at 140 ° C. for 20 minutes to cure both coatings together to obtain a test plate. Each of the obtained test plates was allowed to stand at room temperature for 7 days, and then the following coating film performance test was performed.

Performance test results Scratch resistance: 20 degree specular reflectivity of test plate after car washer was washed 15 times with car wash machine at 20 ° C under condition of 20 ° C car with test plate affixed to roof with Nichiban water resistant tape (20 ° gloss value) was measured and evaluated by the gloss retention (%) relative to the 20 ° gloss value before the test. The higher the gloss retention, the better the scratch resistance. As the car washer, “PO20 FWRC” manufactured by Yasui Industry Co., Ltd. was used.

  Acid resistance: 0.4 cc of 40% sulfuric acid was dropped on the coating film of each test plate, heated for 15 minutes on a hot plate heated to 60 ° C., and then the test plate was washed with water. The etching depth (μm) of the sulfuric acid dropping portion was cut off with a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., surface roughness shape measuring machine “Surfcom 570A”) with a cutoff of 0.8 mm (scanning speed 0.3 mm / sec, The acid resistance was evaluated by measurement under the condition of 5000 times magnification. The smaller the etching depth, the better the acid resistance.

Finished appearance (gloss): The 20-degree specular reflectance (20 ° gloss value) of the test plate was measured and evaluated.
As a guide, if the 20 ° gloss value is 86 or more, the finished appearance (gloss) is good.

Repairability: The test plate was sanded (polished) with # 2000 sandpaper until the 20 ° gloss value (G1) was 0.5 or less, then applied with a compound, and a weight of 500 g was applied to the test plate. The 20 ° gloss value (G2) after reciprocal polishing was measured. Repairability was evaluated based on the value of ΔG (G2-G1).
The larger the value of ΔG, the better the repairability (polishing repairability).

Contamination resistance: After each test coating plate was tested for 600 hours in a sunshine weatherometer (manufactured by Suga Test Instruments Co., Ltd., accelerated weathering tester), each test coating plate was contaminated with a mixture of mud, carbon black, mineral oil and clay. The substance was adhered to the nell and rubbed lightly on the surface of each test plate. This was left for 24 hours in a constant temperature and humidity chamber at 20 ° C. and 75% RH, and then the coated surface was washed with running water, and the degree of contamination of the coated film was evaluated according to the following criteria based on the lightness difference (ΔL) of the coated plate. The smaller the ΔL value, the better the stain resistance. ΔL was determined by the following formula:
ΔL = (L value before stain resistance test) − (L value after stain resistance test)
The L value was measured using CR-200 (color difference meter manufactured by Minolta Camera Co.).
A: ΔL <0.2, O: 0.2 ≦ ΔL <1, Δ: 1 ≦ ΔL <2, X: 2 ≦ ΔL.

  In the contamination resistance test, Eleclon GT-10 (trade name, thermosetting epoxy resin-based cationic battery, manufactured by Kansai Paint Co., Ltd.) was applied on a 0.8 mm-thick dull steel plate subjected to zinc phosphate conversion treatment. Electrodeposition coating to a film thickness of 20 μm, and cured by heating at 170 ° C. for 30 minutes, and then amylak TP-65-2 (trade name, polyester / melamine resin system, manufactured by Kansai Paint Co., Ltd.) Each of the above-mentioned Examples and Comparative Examples was prepared and viscosity-adjusted on a coating film that was air-sprayed to a film thickness of 35 μm and cured by heating at 140 ° C. for 30 minutes. The test plate obtained by coating the coating composition so as to have a film thickness of 35 μm, allowing it to stand at room temperature for 10 minutes, and heating and curing at 140 ° C. for 20 minutes was used in the same manner. 7 at room temperature The soil resistance test was conducted after standing for a day.

Comprehensive evaluation: In the field of paints applied to automobile bodies and the like to which the present invention belongs, it is desired that they have excellent scratch resistance, acid resistance and stain resistance, as well as excellent finished appearance and repairability. Therefore, a comprehensive evaluation was performed based on the following criteria:
A: The gloss retention (%) in the scratch resistance test is 85 or more, the etching depth (μm) in the acid resistance test is 0.6 or less, and the 20 ° gloss value in the finished appearance test (gloss) is 85. That is the above, ΔG in the repairability test is 45 or more, and the contamination resistance is ◎;
○: Gloss retention (%) in scratch resistance test is 85 or more, etching depth (μm) in acid resistance test is 0.6 or less, and 20 ° gloss value in finished appearance test (gloss) is 85 Or more, ΔG in the repairability test is 45 or more, and the contamination resistance is ○;
Δ: Gloss retention (%) in scratch resistance test is 85 or more, etching depth (μm) in acid resistance test is 0.6 or less, and 20 ° gloss value in finished appearance test (gloss) is 85 Or more, ΔG in the repairability test is 45 or more, and the stain resistance is Δ;
X: The gloss retention (%) in the scratch resistance test is less than 85, the etching depth (μm) in the acid resistance test is larger than 0.6, or the 20 ° gloss value in the finished appearance test (gloss) Is less than 85, ΔG in repairability test is less than 45, or stain resistance is x;
The performance test results are also shown in Table 2.

Claims (10)

(A) (a) 25-50 mass% of a hydroxyl group-containing polymerizable unsaturated monomer, (b) 5-30 mass% of an alicyclic hydrocarbon group-containing polymerizable unsaturated monomer having 6-20 carbon atoms, and (c) other. A hydroxyl group-containing acrylic resin which is a copolymer of monomer components consisting of 20 to 70% by mass of a polymerizable unsaturated monomer of
(B) Based on the total amount of the polyisocyanate compound, the isocyanurate trimer content is 30 to 70% by mass, the uretdione dimer content is 3 to 30% by mass, and other trimer-containing multimers are contained. the amount is 0-67 wt%, the coating composition, characterized in that the polyisocyanate compound is a multimer of an aliphatic diisocyanate and (C) having an average primary particle size contains a polysiloxane-modified silica particles 1~40nm .   (B) an alicyclic hydrocarbon group-containing polymerizable unsaturated monomer having 6 to 20 carbon atoms is cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) The coating composition according to claim 1, which is at least one selected from the group consisting of acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate and tricyclodecanyl (meth) acrylate.   The coating composition according to claim 1 or 2, wherein the hydroxyl group-containing acrylic resin (A) has a weight average molecular weight in the range of 5000 to 30000.   The coating composition according to any one of claims 1 to 3, wherein the polysiloxane of the polysiloxane-modified silica particles (C) is an organic-modified polysiloxane.   The coating composition according to any one of claims 1 to 3, wherein the polysiloxane of the polysiloxane-modified silica particles (C) is polydimethylsiloxane and / or polydiphenylsiloxane.   The equivalent ratio (NCO / OH) of the isocyanate group in the polyisocyanate compound (B) and the hydroxyl group in the hydroxyl group-containing acrylic resin (A) is in the range of 0.8 to 1.5. The coating composition according to any one of the above.   The mixing ratio of the hydroxyl group-containing acrylic resin (A), the polyisocyanate compound (B) and the polysiloxane-modified silica particles (C) is based on the total amount of the hydroxyl group-containing acrylic resin (A) and the polyisocyanate compound (B). The acrylic resin (A) is in the range of 55 to 80% by mass, the polyisocyanate compound (B) is in the range of 20 to 45% by mass, and the polysiloxane-modified silica particles (C) are 0.1 to 10% by mass. The coating composition according to any one of claims 1 to 6, which is in a range of%.   The coating composition according to any one of claims 1 to 7, wherein the coating film to be formed has a glass transition temperature (Tg) in the range of 70 to 110 ° C.   An article comprising a coating film obtained by coating the coating composition according to any one of claims 1 to 8.   A method for forming a multilayer coating film by coating at least one layer of a colored base coat paint and at least one layer of a clear coat paint on an object to be coated, wherein the clear coat paint is the uppermost layer. A method for forming a multilayer coating film, comprising coating the coating composition according to any one of the above.