JP2009155371A - Paint composition and method of forming coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paint composition capable of forming a coating film excellent in all of abrasion flaw resistance, acid-proofness and finish appearance. <P>SOLUTION: This paint composition contains an acrylic resin A obtained by copolymerizing (a) 10-60 mass% of secondary hydroxyl group containing (meth)acrylate having a hydroxyl alkyl group with a secondary hydroxyl group bonded to a carbon atom in an alkyl chain in a position of the 8-th position or more distant therefrom counted from a (meth)acryloyloxy group, and having the hydroxyl alkyl group with 10C-25C alkyl chain, (b) 5-75 mass% of hydroxyl group containing (meth)acrylate other than the (a), and (c) 10-75 mass% of copolymerizable unsaturated monomer other than the (a) and (b), and having 100-200 mg-KOH/g of hydroxyl value, 2,000-50,000 of weight-averaged molecular weight, and 15-100 mg-KOH/g of hydroxyl value derived from the (a), and a polyisocyanate compound B. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coating composition excellent in scratch resistance, acid resistance and finished appearance.

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

  Conventionally, a melamine cross-linking coating material has been widely used as the coating material for the object. The melamine cross-linking paint is a paint containing a hydroxyl group-containing resin and a melamine resin as a cross-linking agent, has a high cross-linking density at the time of heat curing, and is excellent in coating film performance such as scratch resistance and finish. However, this paint has a problem that the melamine cross-linking 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.

  JP-A-3-278868 discloses a hydroxyl group-containing (meth) acrylate ester having a specific structure including a secondary hydroxyl group in a 3-coat / 2-bake coating method as a method for forming a coating film having excellent scratch resistance and the like. Also disclosed is a method of forming a coating film using a second clear coat paint comprising an acrylic copolymer (and an alkyl etherified melamine resin) containing as a constituent component. However, this coating film formation method is insufficient in both scratch resistance and finished appearance.

Japanese Patent Laid-Open No. 6-220397 JP-A-3-278868

  An object of the present invention is to provide a coating composition capable of forming a cured coating film excellent in any of scratch resistance, acid resistance and finished appearance.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors are characterized mainly in that the secondary hydroxyl group is a long-chain hydroxyalkyl group located at a certain distance or more from the polymer main chain. The inventors have found that the above object can be achieved by a coating composition containing a secondary hydroxyl group-containing acrylic resin and a polyisocyanate compound, and have completed the present invention.

  That is, in the present invention, the secondary (a) hydroxyl group is bonded to the carbon atom in the alkyl chain at the 8th position or more from the (meth) acryloyloxy group side, and the alkyl chain has 10 to 25 carbon atoms. Secondary hydroxyl group-containing (meth) acrylic acid ester having a hydroxyalkyl group of 10 to 60% by mass, (b) hydroxyl group-containing (meth) acrylic acid ester other than (a) 5 to 50% by mass, and (c) ( an acrylic resin obtained by copolymerizing 10 to 75% by mass of other copolymerizable unsaturated monomers other than a) and (b), having a hydroxyl value of 100 to 200 mgKOH / g, a weight average molecular weight of 2000 to 50000, A coating composition containing an acrylic resin (A) having a hydroxyl value of 15 to 100 mg KOH / g derived from (a) and a polyisocyanate compound (B) is provided.

  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 characterized by coating the coating composition described above.

  Secondary hydroxyl groups are generally less reactive than primary hydroxyl groups and are therefore advantageous for improving the finished appearance of the coating film, improving interlayer adhesion, etc., but the coating film obtained by reacting with a crosslinking agent The coating film performance such as scratch resistance is reduced. In the coating composition of the present invention, the secondary hydroxyl group of the acrylic resin is located at a certain distance or more away from the polymer main chain, so that the reactivity can be improved and the curability is lowered by the secondary hydroxyl group. Can be suppressed. Moreover, since a long-chain hydroxyalkyl group is introduced, it is possible to reduce the polarity of the resin and impart flexibility to the cured coating film.

  Furthermore, urethane cross-linking by reaction of a hydroxyl group-containing acrylic resin and a polyisocyanate compound is excellent in acid hydrolysis resistance and mechanical properties.

  From the above, according to the coating composition of the present invention, it is possible to produce an effect that a cured coating film having excellent scratch resistance, acid resistance and finished appearance can be formed.

  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.

In the coating composition of the present invention, (a) the secondary hydroxyl group is bonded to the carbon atom in the alkyl chain at the 8th position or more from the (meth) acryloyloxy group side, and the alkyl chain has 10 carbon atoms. Secondary hydroxyl group-containing (meth) acrylic acid ester having a hydroxyalkyl group of ˜25 to 10 to 60% by mass, hydroxyl group-containing (meth) acrylate ester other than (b) (a) to 5 to 50% by mass, and (c ) Acrylic resin having a hydroxyl value and a weight average molecular weight in a specific range obtained by copolymerizing 10 to 75% by mass of at least one other copolymerizable vinyl monomer other than (a) and (b). A coating composition comprising (A) and a polyisocyanate compound (B).
Acrylic resin (A)
In the acrylic resin (A), (a) the secondary hydroxyl group is bonded to the carbon atom in the alkyl chain at the 8th position or more from the (meth) acryloyloxy group side, and the alkyl chain has 10 to 10 carbon atoms. Secondary hydroxyl group-containing (meth) acrylic acid ester having a hydroxyalkyl group of 25 to 10% by mass, (b) hydroxyl group-containing (meth) acrylic acid ester other than (a) 5 to 50% by mass, and (c) Obtained by copolymerizing 10 to 75% by mass of other copolymerizable unsaturated monomers other than (a) and (b), hydroxyl value 100 to 200 mgKOH / g, weight average molecular weight 2000 to 50000, derived from (a) Is an acrylic resin having a hydroxyl value of 15 to 100 mgKOH / g.

The hydroxyl group of the acrylic resin (A) acts as a functional group when reacting with the curing agent (B).
The acrylic resin (A) is a secondary hydroxyl group-containing (meth) acrylic acid ester (a), a hydroxyl group-containing (meth) acrylic acid ester other than (a) (b), and a copolymer other than (a) and (b). It can be produced by copolymerizing other possible unsaturated monomers (c) by conventional methods.

In the present specification, “(meth) acrylate” means “acrylate or methacrylate”. “(Meth) acrylic acid” means “acrylic acid or methacrylic acid”. “(Meth) acryloyl” means “acryloyl or methacryloyl”.
The secondary hydroxyl group-containing (meth) acrylic acid ester (a) has a secondary hydroxyl group bonded to a carbon atom in the alkyl chain at the 8th position or more from the (meth) acryloyloxy group side, It is a compound having a secondary hydroxyl group which is a hydroxyalkyl group having 10 to 25 carbon atoms and one (meth) acryloyloxy group.

  As the secondary hydroxyl group-containing (meth) acrylic acid ester (a), for example, (meth) acrylic acid ester of 12-hydroxystearyl alcohol (18 carbon atoms), 10-hydroxylauryl alcohol (10 carbon atoms) ( (Meth) acrylic acid ester, 10-hydroxymyristyl alcohol (14 carbon atoms) (meth) acrylic acid ester, 10-hydroxycetyl alcohol (16 carbon atoms) (meth) acrylic acid ester, 16-hydroxyoctyldodecanol (Meth) acrylic acid ester having 20 carbon atoms, (meth) acrylic acid ester having 18-hydroxybehenyl alcohol (22 carbon atoms), and the like.

  Among these, (meth) acrylic acid ester of 12-hydroxystearyl alcohol is particularly preferable from the viewpoint of availability.

  The monomer (a) can be used alone or in combination of two or more.

  The carbon number of the alkyl chain of the hydroxyalkyl group of the secondary hydroxyl group-containing (meth) acrylic acid ester (a) is 10 to 25, and from the viewpoint of scratch resistance and stain resistance of the resulting coating film, it is 12 to 20 It is preferable that it is 12-18.

  Secondary hydroxyl group of secondary hydroxyl group-containing (meth) acrylic acid ester (a) is bonded to a carbon atom in the alkyl chain at the 8th position or more from the (meth) acryloyloxy group side, and is scratch-resistant. From the viewpoint of sex, it is preferably 10th or more, more preferably 12th or more.

  When the alkyl chain is a branched alkyl chain, the carbon atom bonded to the (meth) acryloyloxy group and the carbon atom bonded to the secondary hydroxyl group are counted in counting the position of the carbon atom bonded to the secondary hydroxyl group. It shall be counted according to the shortest alkyl chain to be connected (the route), and when it has two or more secondary hydroxyl groups, it shall refer to the secondary hydroxyl group bonded to the carbon atom closest to the (meth) acryloyloxy group And

  The alkyl chain of the hydroxyalkyl group of the secondary hydroxyl group-containing (meth) acrylic acid ester (a) is preferably linear from the viewpoint of scratch resistance.

  The secondary hydroxyl group-containing (meth) acrylic acid ester (a) preferably has one secondary hydroxyl group from the viewpoint of scratch resistance of the resulting coating film.

  The secondary hydroxyl group-containing (meth) acrylic acid ester (a) in which the secondary hydroxyl group is bonded to a specific position as described above has, for example, 10 to 25 carbon atoms, and one primary hydroxyl group and at least 1 Each having a secondary hydroxyl group, and the secondary hydroxyl group is an alcohol bonded to a carbon atom in the alkyl chain at a position 8 or more from the carbon atom to which the primary hydroxyl group is bonded, (meth) acrylic acid, and / Or (meth) acrylic acid derivatives (for example, esters) can be obtained by an esterification reaction.

  In the above reaction, it is necessary to selectively react the primary hydroxyl group of the alcohol with (meth) acrylic acid and / or a (meth) acrylic acid derivative. Usually, the reaction product is a by-product such as a diester. In addition, the yield of the desired secondary hydroxyl group-containing (meth) acrylic acid ester (a) can be improved by selecting the reaction conditions such as the reaction catalyst. .

  In addition, although it is preferable that there are few by-products and unreacted substances other than the target secondary hydroxyl group containing (meth) acrylic acid ester (a) as much as possible, synthesis | combination of acrylic resin (A) remains a mixture, without isolate | separating. Can be used.

  As the catalyst for the above reaction, a known acid catalyst, base catalyst, activated carbon and the like can be used. Examples of the acid catalyst include Bronsted acids such as sulfuric acid, p-toluenesulfonic acid, phosphoric acid; titanium tetraisopropoxide, dibutyltin oxide, dioctyltin oxide, dibutyltin laurate, dioctyltin laurate, stannous chloride, stannic chloride Examples thereof include metal Lewis acids such as tin and zirconium tetrabutoxide. Examples of the base catalyst include basic compounds such as triethylamine, sodium methoxide, and sodium hydroxide.

  Examples of suitable catalysts include lipases, especially immobilized lipases.

  When an ester synthesis reaction is carried out using an immobilized lipase, formation of a diester and a secondary monoester can be suppressed, and the desired secondary hydroxyl group-containing (meth) acrylic acid ester ( a) can be selectively synthesized.

  Examples of lipase-derived organisms include yeasts such as Candida antaractica and Candida rugosa, fungi such as Aspergilus niger, Penicillium camembert, Rhizopus japonics, Rhizopus niveus and Rhizopus oryzae, bacteria such as Burkholderia cepacia, Burkholderia glumae, Pseudomonas Examples thereof include animals such as pancreas and rat liver, and plants such as rice bran.

  When lipase is immobilized, examples of the carrier include resin beads such as polystyrene and acrylic resin, inorganic carriers such as diatomaceous earth, porous glass beads, porous silica, and zeolite. The immobilization can be performed by a known method.

  Hydroxyl group-containing (meth) acrylic acid ester (b) is a hydroxyl group-containing (meth) acrylic acid ester other than (a), and each group contains one hydroxyl group and an unsaturated bond ((meth) acryloyloxy group). It is a compound having a number.

  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, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate etc. can be mentioned.

  In addition, as a monoesterified product of the polyhydric alcohol and acrylic acid or methacrylic acid, a compound obtained by ring-opening polymerization of ε-caprolactone to a hydroxyl group-containing (meth) acrylic ester, for example, “Placcel FA-1” "Plaxel FA-2", "Plaxel FA-3", "Plaxel FA-4", "Plaxel FA-5", "Plaxel FM-1", "Plaxel FM-2", "Plaxel FM-3", “Placcel FM-4”, “Placcel FM-5” (all of which are manufactured by Daicel Chemical Industries, Ltd., trade names) and the like can be mentioned.

  Among the above, the hydroxyl group-containing (meth) acrylic acid ester (b-1) having a hydroxyalkyl group having 4 to 10 carbon atoms can be suitably used from the viewpoint of improving the scratch resistance of the coating film. By using (b-1) as a constituent component, it is possible to increase the cross-linking density of the resulting coating film, so that the effect of improving the scratch resistance of the coating film can be obtained. When (b-1) is used as a constituent component, the blending ratio is 3 to 50% by mass, particularly 10 to 40% by mass, based on the total amount of (a), (b) and (c). Preferably there is.

  Examples of the hydroxyl group-containing (meth) acrylic acid ester having a hydroxyalkyl group having 4 or more carbon atoms include monoesterified products of acrylic acid or methacrylic acid and dihydric alcohols having 4 to 10 carbon atoms, acrylic acid or methacrylic acid. And a compound obtained by ring-opening polymerization of ε-caprolactone to a monoesterified product of a dihydric alcohol having 2 to 10 carbon atoms.

Specific examples of the monoesterified product of acrylic acid or methacrylic acid and a dihydric alcohol having 4 to 10 carbon atoms include 4-hydroxybutyl (meth) acrylate among those described above.

  Specific examples of the compound obtained by ring-opening polymerization of ε-caprolactone to a monoesterified product of acrylic acid or methacrylic acid and a dihydric alcohol having 2 to 10 carbon atoms include “Placcel FA-2”, “ Plaxel FM-3 "(all of which are trade names, manufactured by Daicel Chemical Industries, Ltd.).

  The unsaturated monomer (c) is a secondary hydroxyl group-containing (meth) acrylic acid ester (a) and other copolymerizable unsaturated monomer other than the hydroxyl group-containing (meth) acrylic acid ester (b) other than (a). Specifically, it is a compound having one polymerizable unsaturated bond in one molecule. Specific examples of the unsaturated monomer (c) are listed in the following (1) to (8).

(1) Acid group-containing monomer The acid group-containing monomer is a compound having one acid group and one polymerizable unsaturated bond in one molecule. Examples of the monomer include carboxyl group-containing monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid and maleic anhydride; sulfonic acid group-containing monomers such as vinyl sulfonic acid and sulfoethyl (meth) acrylate; 2 Acidic phosphoric acid such as-(meth) acryloyloxyethyl acid phosphate, 2- (meth) acryloyloxypropyl acid phosphate, 2- (meth) acryloyloxy-3-chloropropyl acid phosphate, 2-methacryloyloxyethylphenyl phosphate Examples include ester monomers.
The acid group-containing monomer can also act as an internal catalyst when the component (A) undergoes a crosslinking reaction with the crosslinking agent.

(2) Monoesterification product of acrylic acid or methacrylic acid and monohydric alcohol having 1 to 20 carbon atoms Specifically, methyl (meth) acrylate, ethyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n -Butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isomyristyl (meth) acrylate, isostearyl acrylate (Osaka Organic) Chemical Industry, trade name), cyclohexyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, adamantyl (meth) acrylate, 3,5-dimethyl Adamantyl (meth) acrylate, 3-tetracyclododecyl methacrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, 4-methylcyclohexylmethyl (meth) acrylate, 4-ethylcyclohexylmethyl (meth) acrylate, 4-methoxycyclohexyl Examples thereof include methyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclododecyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, and the like.

  Among the above, unsaturated monomers having a bridged alicyclic hydrocarbon group having 10 to 20 carbon atoms and / or unsaturated monomers having an alicyclic hydrocarbon group having 3 to 12 carbon atoms (c-2- 1) can be suitably used from the viewpoint of improving the stain resistance of the coating film. By using the monomer (c-2-1) as a constituent component, the Tg of the resulting resin is increased and the polarity is decreased. Therefore, the finish is improved by smoothing the surface, and the water resistance and stain resistance are improved. The effect of can be obtained. Typical examples of the bridged alicyclic hydrocarbon group having 10 to 20 carbon atoms include isobornyl group, tricyclodecanyl group and adamantyl group.

  Specific examples of the unsaturated monomer having a bridged alicyclic hydrocarbon group having 10 to 20 carbon atoms include, for example, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, adamantyl ( Examples include meth) acrylate, 3,5-dimethyladamantyl (meth) acrylate, and 3-tetracyclododecyl methacrylate.

  Specific examples of the unsaturated monomer having an alicyclic hydrocarbon group having 3 to 12 carbon atoms include, for example, cyclohexyl (meth) acrylate, 4-methylcyclohexylmethyl (meth) acrylate, 4-ethyl among those described above. Examples include cyclohexylmethyl (meth) acrylate, 4-methoxycyclohexylmethyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclododecyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, and the like. be able to.

  Moreover, among the above, the unsaturated monomer (c-2-2) 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 the monomer (c-2-2) as a constituent component, the Tg and polarity of the resulting resin are reduced, so that the improvement in scratch resistance of the coating film by imparting flexibility and the finish by smoothing the surface. An improvement effect can be obtained. In addition, since it has a branched structure, a decrease in the Tg of the coating film can be suppressed as compared with a case where a 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.

  Specific examples of the unsaturated monomer having a branched hydrocarbon structure having 8 or more carbon atoms include, for example, 2-ethylhexyl acrylate, isooctyl (meth) acrylate, isomyristyl (meth) acrylate, Examples include stearyl acrylate (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.).

  When the monomer (c-2-2) is used as a constituent component, the blending ratio is 3 to 50% by weight, particularly 10 to 40% by weight, based on the total amount of (a), (b) and (c). It is preferable to be within the range.

(3) alkoxysilyl group-containing unsaturated monomer For example, vinyltrimethoxysilane, vinyltriethoxysilane, acryloxyethyltrimethoxysilane, methacryloxyethyltrimethoxysilane, acryloxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, Examples thereof include acryloxypropyltriethoxysilane, methacryloxypropyltriethoxysilane, and vinyltris (β-methoxyethoxy) silane. Among these, preferable alkoxysilyl group-containing unsaturated monomers include vinyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like.

  By using an alkoxysilyl group-containing unsaturated monomer as a constituent component, in addition to the crosslinking bond between a hydroxyl group and an isocyanate group, a condensation reaction between alkoxysilyl groups and a crosslinking bond due to a reaction between an alkoxysilyl group and a hydroxyl group can be generated. . Thereby, since the crosslinking density of the obtained coating film improves, the effect of an improvement in acid resistance and stain resistance can be obtained.

  When an alkoxysilyl group-containing unsaturated monomer is used as a constituent component, the blending ratio is 3 to 50% by weight, particularly 5 to 35% by weight, based on the total amount of (a), (b) and (c). Is preferred.

(4) Aromatic vinyl monomer Specific examples include styrene, α-methylstyrene, vinyltoluene and the like.

  By using an aromatic vinyl monomer as a constituent, the Tg of the resulting resin is increased, and a hydrophobic coating film with a high refractive index can be obtained. The effect of improving water resistance and acid resistance can be obtained.

  When the aromatic vinyl monomer is used as a constituent component, the blending ratio is 3 to 50% by weight, particularly 5 to 40% by weight based on the total amount of (a), (b) and (c). Preferably there is.

(5) Glycidyl group-containing vinyl monomer The glycidyl group-containing vinyl monomer is a compound having one glycidyl group and one polymerizable unsaturated bond in one molecule. Specific examples thereof include glycidyl acrylate and glycidyl methacrylate. be able to.

(6) Polymerizable unsaturated bond-containing amide compounds For example, acrylic acid amide, methacrylic acid amide, dimethylacrylamide, N, N-dimethylpropylacrylamide, N-butoxymethylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, And diacetone acrylamide.

(7) Other vinyl compounds For example, vinyl acetate, vinyl propionate, vinyl chloride, versatic acid vinyl ester and the like can be mentioned. Examples of the versatic acid vinyl ester include “Veoba 9” and “Veoba 10” (trade names, manufactured by Japan Epoxy Resin Co., Ltd.), which are commercially available products.

(8) Polymerizable unsaturated bond-containing nitrile compound Examples include acrylonitrile and methacrylonitrile.
As an unsaturated monomer (c), the monomer shown by said (1)-(8) can be used by 1 type, or in combination of 2 or more types.

  Other secondary hydroxyl group-containing (meth) acrylic acid esters (a), hydroxyl group-containing (meth) acrylic acid esters other than (a) (b), and other copolymerizable unsaturations other than (a) and (b) The acrylic resin (A) can be synthesized by copolymerizing a monomer mixture composed of the monomer (c).

  The copolymerization method for copolymerizing the monomer mixture to obtain the acrylic resin (A) is not particularly limited, and a copolymerization method known per se can be used. Thus, a solution polymerization method in which polymerization is carried out 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 alone or in combination of two or more. However, since the acrylic resin used in the coating material has a high hydroxyl value, it has a high boiling point from the viewpoint of the solubility of the resin. It is preferable to use a system solvent. In addition, aromatic solvents having higher boiling points can be suitably used in combination.

  Examples of the polymerization initiator that can be used in the copolymerization of the acrylic resin (A) include 2,2′-azobisisobutyronitrile, benzoyl peroxide, di-t-butyl peroxide, and di-t-amyl peroxide. , T-butyl peroctoate, 2,2′-azobis (2-methylbutyronitrile) and the like radical polymerization initiators known per se.

  The hydroxyl value of the acrylic resin (A) is 100 to 200 mgKOH / g, preferably about 110 to 170 mgKOH / g, and more preferably about 130 to 160 mgKOH / g. When the hydroxyl value is less than 100 mgKOH / g, the scratch resistance of the coating film obtained from the coating composition of the present invention may be insufficient. On the other hand, when it exceeds 200 mgKOH / g, the water resistance of the coating film decreases. There is a case.

  In particular, the hydroxyl value derived from the monomer (a) is 15 to 100 mgKOH / g, preferably about 30 to 80 mgKOH / g, and more preferably about 40 to 70 mgKOH / g. When the hydroxyl value derived from the monomer (a) is less than 15 mgKOH / g, the scratch resistance of the coating film obtained from the coating composition of the present invention may be insufficient, while when it exceeds 100 mgKOH / g, it is resistant to contamination. May decrease.

  The weight average molecular weight of the acrylic resin (A) is about 2000 to 50000, preferably about 3000 to 25000, and more preferably about 4000 to 15000, from the viewpoint of excellent acid resistance and smoothness of the coating surface.

  In this specification, the weight average molecular weight of resin was measured on the basis of standard polystyrene by gel permeation chromatograph (GPC). Measurements in the following production examples and the like are as follows: “HLC8120GPC” (trade name, manufactured by Tosoh Corporation) as a GPC device, “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL” Using “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name), mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 cc / min, detector: RI It was.

  The glass transition temperature of the acrylic resin (A) is preferably about −40 to 30 ° C., more preferably about −30 to 10 ° C., from the viewpoint of the hardness of the obtained coating film and the smoothness of the coating surface. .

  In this specification, the glass transition temperature is a value measured by DSC (Differential Scanning Calorimeter) at a heating rate of 10 ° C./min based on JISK7121 (Plastic transition temperature measurement method). The measurement in the following production examples, etc., uses “SSC5200” (trade name, manufactured by Seiko Denshi Kogyo Co., Ltd.) as a DSC. I did it.

  Secondary hydroxyl group-containing (meth) acrylic acid ester (a), hydroxyl group-containing (meth) acrylic acid ester (b) other than (a), and other copolymerizable unsaturated monomers other than (a) and (b) The blending ratio of (c) is such that the monomer (a) is about 10 to 60% by mass, preferably about 15 to 55% by mass, more preferably about 20 to 50% by mass, based on the total monomer amount. b) is about 5 to 50% by mass, preferably about 7 to 30% by mass, more preferably about 10 to 28% by mass, and other unsaturated monomer (c) is about 10 to 75% by mass, preferably It is about 15-65 mass%, More preferably, it is about 20-60 mass%.

When the amount of the monomer (a) is less than 10% by mass, the resulting coating film may have insufficient scratch resistance, and when it exceeds 60% by mass, the coating film may have insufficient acid resistance. is there. When the amount of the monomer (b) is less than 5% by mass, the resulting coating film may have insufficient scratch resistance, and when it exceeds 50% by mass, the finished appearance of the coating film may be insufficient. is there.
Polyisocyanate compound (B)
The polyisocyanate compound (B) is a crosslinking agent of the present coating composition, and is a compound having two or more isocyanate groups in one molecule. Examples of the polyisocyanate compound (B) include those known for polyurethane production, such as aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of these polyisocyanates. be able to.

  Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3- Aliphatic diisocyanates such as butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, such as lysine ester triisocyanate, 1,4,8- Triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2 5,7 and aliphatic triisocyanates such as trimethyl-1,8-diisocyanato-5-isocyanatomethyl octane and the like.

  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-bis (isocyanatomethyl) cyclohexane, 1,4-bis (Isocyanatomethyl) cycloaliphatic diisocyanates such as cyclohexane, norbornane diisocyanate, for example 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanate Natocyclohexane, 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-isocyanatopropyl) -bicyclo ( 2.1) -Heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, and other alicyclic triisocyanates And so on.

  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 an aromatic aliphatic diisocyanate such as a mixture thereof, for example, an araliphatic triisocyanate such as 1,3,5-triisocyanatomethylbenzene And so on.

  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, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene and other aromatic triisocyanates such as 4,4'-diphenylmethane-2,2 ', 5 5'-te Or the like can be mentioned aromatic tetracarboxylic isocyanates such as La isocyanate.

  Examples of the polyisocyanate derivative include various derivatives such as dimer, trimer, biuret, allophanate, carbodiimide, uretdione, uretoimine, isocyanurate, and iminooxadiazinedione of the above-described polyisocyanate compound.

These polyisocyanates can be used alone or in combination of two or more. Among these polyisocyanates, aliphatic diisocyanates, alicyclic diisocyanates and derivatives thereof are preferable from the viewpoint of excellent weather resistance of the cured coating film, and hexamethylene diisocyanate (HDI), hexamethylene diisocyanate derivatives, isophorone diisocyanate (IPDI). And derivatives of isophorone diisocyanate are more preferred.
Further, as the polyisocyanate compound, a blocked polyisocyanate compound which is a compound obtained by blocking an isocyanate group of a polyisocyanate compound having two or more free isocyanate groups in one molecule with a blocking agent can also be used.

  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 such blocking agents 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 Ethers such as propylene glycol 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: Dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone Which active methylene series; mercaptans such as butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, ethylthiophenol; Acid amides such as amides, acetic acid amides, stearic acid amides, benzamides; imides such as succinic acid imides, phthalic acid imides, maleic acid imides; Amines such as butylamine, dibutylamine and butylphenylamine; imidazo such as imidazole and 2-ethylimidazole Pyrazoles such as 3,5-dimethylpyrazole; Ureas such as urea, thiourea, ethylene urea, ethylene thiourea and diphenyl urea; Carbamate esters such as phenyl N-phenylcarbamate; Ethyleneimine and propyleneimine Examples thereof include blocking agents such as imine series; sulfite series such as sodium bisulfite 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 give.

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

  In the coating composition of the present invention, the equivalent ratio (NCO / OH) of the hydroxyl group in the acrylic resin (A) and the isocyanate group in the polyisocyanate compound (B) is excellent in the curability and coating stability of the composition. Therefore, it is preferably about 0.5 to 2.0, and more preferably about 0.8 to 1.5.

The amount of the acrylic resin (A) and the polyisocyanate compound (B) in the coating composition of the present invention is an acrylic resin (A) and a non-volatile component based on the total solid content of the component (A) and the component (B). It is suitable that A) is in the range of 40 to 80% by mass, preferably 45 to 70% by mass, and the polyisocyanate compound (B) is in the range of 20 to 60% by mass, preferably 30 to 55% by mass.
Other Components Known pigments such as color pigments, extender pigments, glitter pigments, and rust preventive pigments can be blended in the coating composition of the present invention as necessary.

  Examples of the coloring pigment include titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, selenium pigment, Examples include perylene pigments. Examples of extender pigments include talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, silica, and alumina white. Examples of the bright pigment include aluminum powder, mica powder, and mica powder coated with titanium oxide.

  Various resins such as an acrylic resin, a polyester resin, an alkyd resin, a silicon resin, and a fluororesin can be added to the coating composition of the present invention as necessary. It is also possible to use a small amount of a crosslinking agent such as a melamine resin or a blocked polyisocyanate compound. Furthermore, if necessary, general paint additives such as a curing catalyst, an ultraviolet absorber, a light stabilizer, an antioxidant, a surface conditioner, and an antifoaming agent can be blended.

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

  These compounds described above as the curing catalyst may be used alone or as a mixture of two or more. The amount of the curing catalyst varies depending on the type thereof, but is usually 0 to 5 parts by mass, preferably about 0.1 to 4 parts by mass with respect to 100 parts by mass of the total solids of the component (A) and the component (B). .

  Known ultraviolet absorbers can be used, and examples thereof include ultraviolet absorbers such as benzotriazole absorbers, triazine absorbers, salicylic acid derivative absorbers, and benzophenone absorbers. By blending the ultraviolet absorber, the weather resistance, yellowing resistance and the like of the coating film can be improved.

  As content in the coating composition of a ultraviolet absorber, it is about 0-10 mass parts normally with respect to 100 mass parts of resin solid content total measurement. Moreover, it is preferable that content of a ultraviolet absorber is about 0.2-5 mass parts, and it is more preferable that it is about 0.3-2 mass parts.

  A conventionally well-known thing can be used as a light stabilizer, For example, a hindered amine light stabilizer can be mention | raise | lifted. By blending a light stabilizer, the weather resistance, yellowing resistance and the like of the coating film can be improved.

  As content in the coating composition of a light stabilizer, it is about 0-10 mass parts normally with respect to 100 mass parts of resin solid content total measurement. Further, the content of the light stabilizer is preferably about 0.2 to 5 parts by mass, and more preferably about 0.3 to 2 parts by mass.

Although the form of the coating composition of the present invention is not particularly limited, it is usually used as an organic solvent type coating composition. As the organic solvent used in this case, various organic solvents for paints such as aromatic or aliphatic hydrocarbon solvents; alcohol solvents; ester solvents; ketone solvents; ether solvents and the like can be used. As the organic solvent to be used, those used at the preparation of the component (A), the component (B) and the like may be used as they are, or may be added as appropriate.
Preparation method of coating composition The coating composition of the present invention comprises an acrylic resin (A), a polyisocyanate compound (B), and a curing catalyst, a pigment, various resins, an ultraviolet absorber, a light stabilizer, used as necessary, An organic solvent or the like can be prepared by mixing by a known method.

  When the isocyanate group of the polyisocyanate compound which is the component (B) is not blocked, the coating composition of the present invention has an acrylic resin (A) and a polyisocyanate compound (B) because of storage stability. Are two-component paints separated from each other, and it is preferable to mix the two before use.

  The solid content concentration of the coating composition of the present invention is preferably about 30 to 70% by mass, and more preferably about 40 to 60% by mass.

Coating Method The coating composition of the present invention can be suitably used in various coating methods shown below.

Examples of the object to be coated include bodies such as automobiles and motorcycles, or parts thereof. Further, cold rolled steel sheets, galvanized steel sheets, zinc alloy plated steel sheets, stainless steel sheets, tin plated steel sheets, etc., metal base materials such as aluminum plates and aluminum alloy plates; various plastic base materials, etc. May be.

  Moreover, as a to-be-coated article, the metal surface of the said vehicle body, components, and a metal base material may be subjected to chemical conversion treatment such as phosphate treatment, chromate treatment, and complex oxide treatment. Furthermore, as the object to be coated, an undercoat film and / or an intermediate coat film such as various electrodeposition paints may be formed on the vehicle body, metal base material, or the like.

Coating and curing method The coating method of the coating composition of the present invention is not particularly limited. For example, a wet coating film is formed by a coating method such as air spray coating, airless spray coating, rotary atomization coating, or curtain coat coating. be able to. In air spray coating, airless spray coating, and rotary atomization coating, electrostatic application may be performed as necessary. Of these, air spray coating and rotary atomization coating are particularly preferred. In general, the coating film thickness is preferably about 10 to 50 μm as the cured film thickness.

  In the case of air spray coating, airless spray coating, and rotary atomization coating, 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.

  The wet coating film is cured by heating. Heating can be performed by a known heating means. For example, a drying furnace such as a hot air furnace, an electric furnace, or an infrared induction heating furnace can be applied.

  The heating temperature is usually about 100 to 180 ° C, preferably about 120 to 160 ° C. The heating time is usually in the range of about 5 to 60 minutes.

Multilayer coating film forming method According to the coating composition of the present invention, a coating film having excellent coating performance such as scratch resistance, acid resistance, and finished appearance can be formed. In the coating film forming method to be used, it is preferably used as a clear coating composition for forming a top clear coat.

  Therefore, the multilayer coating film forming method of the present invention is a coating film forming method in which at least one colored base coat and at least one clear coat are sequentially formed on an object to be coated, and the uppermost clear coat is applied. The coating composition of the present invention is used as the coating composition to be formed.

  As an object to which the multilayer coating film forming method of the present invention is applied, an automobile body and its parts are particularly preferable.

  More specifically, examples of the method for forming a multilayer coating film include a method of using the coating composition of the present invention for forming a top clear coat in the multilayer coating film forming method of the following methods a to c. Can do.

  Method a: A method of forming a top coat multilayer coating film in which a colored base coat and a top clear coat are sequentially formed on an object to be coated.

  Method b: A method of forming a top coat multilayer coating film in which a colored base coat, a clear coat, and a top clear coat are sequentially formed on an object to be coated.

  Method c: A three-coating multi-layer coating film forming method in which a first colored base coat, a second colored base coat, and a top clear coat are sequentially formed on an object to be coated.

  Each top coat film forming step of these methods a, b and c will be described in detail.

  In each method, as a method for applying the colored base coating composition and the clear coating composition, a coating method such as airless spray, air spray, or rotary atomization coating can be employed. In these coating methods, electrostatic application may be performed as necessary.

In the method a, as the coating composition for forming the colored base coat, a known colored coating composition can be used.
As the colored base coating composition, it is preferable to use a coating composition that is used when painting an automobile body or the like.

  The colored base coating composition is an organic solvent-type or aqueous coating composition containing a base resin, a crosslinking agent, a colored pigment, a metallic pigment, a light interference pigment, an extender pigment and the like.

  As the base resin, for example, at least one of acrylic resin, vinyl resin, polyester resin, alkyd resin, urethane resin, and the like can be used. The base resin has, for example, a crosslinkable functional group such as a hydroxyl group, an epoxy group, a carboxyl group, or an alkoxysilyl group. As the crosslinking agent, for example, at least one of alkyl etherified melamine resin, urea resin, guanamine resin, polyisocyanate compound, blocked polyisocyanate compound, epoxy compound, carboxyl group-containing compound and the like can be used. The base resin and the crosslinking agent are preferably used in a proportion of 50 to 90% by weight of the base resin and 50 to 10% by weight of the crosslinking agent based on the total amount of both components.

  In method a, the colored base coating composition is applied to an object to be coated so that the cured film thickness is about 10 to 50 μm. The coated base coating composition is cured by heating at about 100-180 ° C., preferably about 120-160 ° C. for about 10-40 minutes, or left at room temperature for several minutes without curing after coating, or about 40 Preheat at ~ 100 ° C for about 1-20 minutes.

  Next, as a paint for forming a top clear coat, the clear paint composition of the present invention is applied so that the film thickness is about 10 to 70 μm in terms of the cured film thickness, and is heated to cure the multilayer coating film Can be formed. Heating is about 100 to 180 ° C., preferably about 120 to 160 ° C., and preferably about 10 to 40 minutes.

  In the above-mentioned two-coat system, the base paint composition is applied and the clear paint composition is applied without being heated and cured, and when these two-layer coating films are cured simultaneously, the two-coat one-bake system is used. When the composition is applied and cured by heating, and then the clear coating composition is applied and the clear coating film is cured, the 2-coat 2-bake method is used.

  As the colored base coating composition in method b, the same colored base coating composition as described in the section of method a can be used. Further, the first clear paint composition for forming the clear coat may be a paint for forming a transparent coating film, for example, a paint composition that does not contain most or all of the pigment in the above-mentioned known colored base paint composition. Things can be used. And the coating composition of this invention is used as a 2nd clear coating composition which forms a top clear coat. In addition, as the first clear paint composition, the clear coat and the top clear coat formed from the clear paint composition of the present invention may be formed using the clear paint composition of the present invention.

  In method b, in the same manner as in method a, the colored base coating composition is applied to the object to be coated and heat-cured, or left to stand at room temperature for several minutes or preheated without being cured, and then the colored base coating composition is coated. The first clear coating composition is applied onto the film so that the film thickness is about 10 to 50 μm as a cured film thickness, and is about 100 to 180 ° C., preferably about 120 to 160 ° C., for about 10 to 40 minutes. Heat to cure or leave or preheat at room temperature for several minutes without curing.

  Next, as the second clear paint composition, the paint composition of the present invention is applied so that the film thickness is about 10 to 50 μm as a cured film thickness, and heated to form a cured multilayer coating film. can do. The heating conditions are the same as in method a.

  Without applying and curing the base coating composition, the first clear coating composition is applied, the second clear coating composition is applied without curing, and the three-layer coating film is simultaneously cured. In this case, the 3 coat 1 bake method is used. When the first clear paint composition is applied without applying the base paint composition and heat-curing, these coating films are simultaneously heat-cured, and the second clear paint composition is applied and cured. Is a 3-coat 2-bake system. In addition, when a base coating composition is applied and heated and cured, a first clear coating composition is applied, this is cured, a second clear coating composition is applied, and this is cured, a 3 coat 3 bake system It is.

  In the method c, as the first colored base coating composition, the same colored base coating composition as described in the method a can be used.

  In the method c, in the same manner as in the method a, the first colored base coating composition is applied to the object to be coated and heat-cured, or left to stand for several minutes at room temperature without being cured or pre-heated. On the colored base coating film, the second colored base coating composition is applied so that the film thickness is about 10 to 50 μm as a cured film thickness, and about 100 to 180 ° C., preferably about 120 to 160 ° C. Heat for 10 to 40 minutes to cure, or leave or preheat at room temperature for several minutes without curing.

  Next, as a coating composition for forming the top clear coat, the coating composition of the present invention is applied so that the film thickness is about 10 to 50 μm in terms of the cured film thickness, and heated to form a cured multilayer coating. A film can be formed. The heating conditions are the same as in method a.

  Without applying the first base coating composition and curing by heating, the second base coating composition is applied, and without being cured, the clear coating composition is applied, and these three-layer coating films are simultaneously cured. In this case, the 3-coat 1-bake method is used. In addition, when the first base coating composition is applied and heated and cured, the second base coating composition is applied, the clear coating composition is applied without curing, and these coating films are simultaneously cured. This is a 3-coat 2-bake method. When the first base coating composition is applied and heat-cured, the second base coating composition is applied, this is cured, and the clear coating composition is applied and cured. It is.

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 and production examples 1 to 5 of secondary hydroxyl group-containing (meth) acrylic acid ester (a)
A four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and an air introduction tube was charged with 0.5 part of p-methoxyphenol and the amount (parts by mass) of alcohol and monomer shown in Table 1. Then, it heated to 40 degreeC using the water bath, ventilating air in a liquid, and 50 parts of Novozyme435 (Novozyx lipase immobilization lipase) was added. After adding Novozyme 435, the mixture was reacted at 40 ° C. for 24 hours. A light brown transparent liquid from which Novozyme 435 was removed using a filter paper was concentrated under reduced pressure at 50 ° C. until the content of secondary hydroxyl group-containing (meth) acrylic acid ester (a) was 90% as confirmed by gas chromatography. No. of the reaction product containing wax-like secondary hydroxyl group-containing (meth) acrylic acid ester (a) by cooling to room temperature. 1-4 were obtained. Moreover, when the content rate of secondary hydroxyl group containing (meth) acrylic acid ester (a) was less than 90%, it corrected by adding each raw material monomer in a table | surface.

  The secondary hydroxyl group-containing (meth) acrylic acid ester (a ′) No. 1 in Production Example 5 was used. 1 is a monomer for synthesizing an acrylic resin for a comparative example.

Production Examples 6-9
A four-necked flask equipped with a temperature controller, an air introduction tube, and a stirrer was charged with 1.0 part of alcohol and monomer in an amount (parts by mass) shown in Table 2, and 1.0 part of dibutyltin oxide and 5.0 parts of methoquinone. . Then, it was made to react for 14 hours, keeping at 100-120 degreeC, stirring under air ventilation from an air introduction pipe | tube. Meanwhile, the reaction was carried out while removing alcohol produced by the transesterification reaction (ethanol in Production Examples 6, 8 and 9 and methanol in Production Example 7). After the reaction, the reactor was depressurized and the reaction product was distilled off until the content of the secondary hydroxyl group-containing (meth) acrylic acid ester (a) was 80% as confirmed by gas chromatography. No. of the reaction product containing secondary hydroxyl group-containing (meth) acrylic acid ester (a). 5-8 were obtained. Moreover, when the content rate of secondary hydroxyl-containing (meth) acrylic acid ester (a) was less than 80%, it corrected by adding each raw material monomer in a table | surface.

Production Examples of Acrylic Resin (A) Production Examples 10 to 28
A four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was charged with 310 parts of Swazol 1000 (trade name, manufactured by Cosmo Oil Co., Ltd., hydrocarbon solvent) and heated to 125 ° C under a nitrogen atmosphere. The mixture of the monomer and the polymerization initiator in the amount (parts by mass) shown in Table 3 below was added dropwise over 4 hours. Next, after aging for 30 minutes while flowing nitrogen gas at 125 ° C., a mixture of 320 parts of Swazol 1000 and 5 parts of 2,2′-azobisisobutyronitrile was added dropwise over 1 hour. By aging for time, each acrylic resin (A) No. 1 to 14 solutions were obtained. Each of the obtained acrylic resins (A) No. The special values of the solutions 1 to 14 are shown together in Table 3 below.

  In addition, acrylic resin (A ') No. of manufacture examples 24-28. 1 to 5 are acrylic resins for comparative examples. The resulting acrylic resin (A ′) No. The special values of the solutions 1 to 5 are also shown in Table 3 below.

Production Examples 1-15 and Comparative Examples 1-5 of Coating Composition
Each acrylic resin (A) No. obtained by the said manufacture examples 10-28. 1-14, each acrylic resin (A ′) No. 1 to 5 and the raw materials listed in Table 4 below, each coating composition No. 1-20 were obtained. In addition, the mixing | blending of each coating composition shown in Table 4 is solid content mass ratio of each component. In addition, the coating composition No. 16-20 are paints for comparative examples.

  In Table 4, (* 1) to (* 4) have the following meanings.

  (* 1) N-3300: manufactured by Sumika Bayer Urethane Co., Ltd., hexamethylene diisocyanate, solid content 100%, NCO content 21.8%.

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

  (* 3) HALS292: Ciba Geigy, light stabilizer.

(* 4) BYK-300: trade name, manufactured by Big Chemie, surface conditioner Each coating composition No. obtained in Examples 1 to 15 and Comparative Examples 1 to 5 above. Nos. 1 to 20 are ford cups #No. 4 was adjusted to a viscosity of 25 seconds at 20 ° C.

Preparation of test plate Each coating composition No. 1 to 20 were used to prepare test plates as follows.

  Electron GT-10 (trade name, thermosetting epoxy resin-based cationic electrodeposition paint, manufactured by Kansai Paint Co., Ltd.) having a thickness of 20 μm is formed on a 0.8 mm thick dull steel sheet subjected to zinc phosphate conversion treatment. Electrodeposited and heated at 170 ° C. for 30 minutes to cure, and on the electrodeposited surface, Amirac TP-65-2 (Kansai Paint Co., Ltd., trade name, polyester / melamine resin-based automotive intermediate coating) was applied. Air spray coating was performed to a film thickness of 35 μm, and the film was cured by heating 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 base coat paint, black paint color) is applied on the intermediate coating surface to 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 No. Each test plate was obtained by coating 1 to 20 to a film thickness of 35 μm, allowing to stand at room temperature for 10 minutes, and then heating at 140 ° C. for 20 minutes to cure both coating films together. Each of the obtained test plates was allowed to stand at room temperature for 7 days and then subjected to the following coating film performance test.

In addition, in the contamination resistance test, ELECRON GT-10 (trade name, manufactured by Kansai Paint Co., Ltd., thermosetting epoxy resin-based cationic battery) was formed on a 0.8 mm-thick dull steel sheet subjected to zinc phosphate conversion treatment. Electrodeposition coating to a film thickness of 20 μm, heated at 170 ° C. for 30 minutes to cure, and then Amirac TP-65-2 (manufactured by Kansai Paint Co., Ltd., trade name, polyester / melamine resin system) Automotive coating, white coating color) was applied by air spraying to a film thickness of 35 μm and heated and cured at 140 ° C. for 30 minutes as a coating, and each coating composition No. Each white test plate obtained by coating 1 to 20 to a film thickness of 35 μm, allowing to stand at room temperature for 10 minutes, and heating and curing at 140 ° C. for 20 minutes was used. Similarly, each test plate was allowed to stand at room temperature for 7 days and then subjected to a stain resistance test.
Results of performance test : Scratch resistance: 20 degree specular reflectance of test plate after car washer was washed 15 times with car wash machine under 20 ° C condition with test plate affixed to roof with water resistant tape made by Nichiban (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 wash machine, “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 using a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., surface roughness profile 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.

  Contamination resistance: Each test plate was tested for 600 hours under the conditions of JIS K5400 in a sunshine weatherometer (manufactured by Suga Test Instruments Co., Ltd., accelerated rust resistance tester). 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 equation.

ΔL = (L value before stain resistance test) − (L value after stain resistance test)
The L value was measured using CR400 manufactured by Konica Minolta (tristimulus value direct-reading color meter D65 light source 2 ° visual field diffuse illumination vertical light reception (d / 0)). The L value is a value based on the CIE 1976 L ^* a ^* b ^* color system.

  A: ΔL <0.2, O: 0.2 ≦ ΔL <0.5, OΔ: 0.5 ≦ ΔL <1, Δ: 1 ≦ ΔL <2, X: 2 ≦ ΔL.

  Finishability (20 ° gloss): The 20-degree specular reflectance (20 ° gloss value) of each test plate was measured using HG-268 (manufactured by Handy Gloss Meter Suga Test Instruments Co., Ltd.).

  The performance test results are also shown in Table 4.

Claims (7)

  (A) a hydroxyalkyl group in which the secondary hydroxyl group is bonded to the carbon atom in the alkyl chain at the 8th position or more from the (meth) acryloyloxy group side, and the alkyl chain has 10 to 25 carbon atoms. Secondary hydroxyl group-containing (meth) acrylic acid ester having 10-60 mass%, (b) hydroxyl group-containing (meth) acrylic acid ester other than (a) 5-50 mass%, and (c) (a) and (b) Acrylic resin obtained by copolymerizing 10 to 75% by mass of other unsaturated monomers that can be copolymerized, except that the hydroxyl value is 100 to 200 mg KOH / g, the weight average molecular weight is 2000 to 50000, and the hydroxyl group is derived from (a). The coating composition containing the acrylic resin (A) and polyisocyanate compound (B) which are 15-100 mgKOH / g.   (C) An unsaturated monomer having an alicyclic hydrocarbon group having 3 to 12 carbon atoms is contained as a copolymerization component as another copolymerizable unsaturated monomer other than (a) and (b). The coating composition according to 1.   (C) As another copolymerizable unsaturated monomer other than (a) and (b), an unsaturated monomer having a bridged alicyclic hydrocarbon group having 10 to 20 carbon atoms is contained as a copolymerization component. The coating composition according to claim 1 or 2.   (C) An unsaturated monomer having a hydrocarbon group having 8 or more carbon atoms having a branched structure as a copolymerizable component as another copolymerizable unsaturated monomer other than (a) and (b). The coating composition according to any one of 1 to 3.   (C) As another copolymerizable unsaturated monomer other than (a) and (b), an alkoxysilyl group-containing unsaturated monomer is contained as a copolymerization component. Paint composition.   The coating composition of any one of Claims 1-5 containing aliphatic diisocyanate and these derivatives as a polyisocyanate compound (B).   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 an object to be coated. A method for forming a multilayer coating film, comprising coating the coating composition according to claim 1.