JP2006022216A - Polyesterpolyol and thermosetting aqueous coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosetting aqueous coating composition which has a wide range of coating workability and can form a coating film excellent in finishing properties such as the smoothness of the coated surface and a metallic feeling, and a coating film-forming method. <P>SOLUTION: A polyesterpolyol is obtained by reacting (a-1) a polyhydric alcohol, (a-2) a polycarboxylic acid and/or a polycarboxylic anhydride, and (a-3) a monoepoxide compound having a long-chain hydrocarbon group. The thermosetting aqueous coating composition uses the polyesterpolyol, and the coating film-forming method uses the coating composition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention uses a novel polyester polyol, an aqueous coating composition comprising the polyester polyol, which can form a coating film having excellent finish properties such as metallic feeling and smoothness of the coating surface, and the aqueous coating composition. The present invention relates to a coating film forming method.

  In the paint field, reduction of the amount of organic solvent used is an important issue from the viewpoint of environmental conservation and resource saving. In recent years, in order to reduce the amount of organic solvent in the paint, the development of water-based paint and high solid differentiation has been promoted.

  As water-based paints in the field of automotive paints, for example, thermosetting water-based paints containing polyvalent carboxylic acid resin, amino resin, linear low-molecular polyester diol and benzoin as main components are known (for example, see Patent Document 1). However, the solid content concentration is low, and the smoothness of the coating film is not sufficient.

  Among automotive paints, top coats are required to have excellent appearance quality, and when metallic paints are used, the scale-like glitter pigments such as aluminum in the metallic base paints should be well oriented. Therefore, it is required to obtain a coating film appearance excellent in finish properties such as metallic feeling.

  As an aqueous metallic base paint used for such metallic coating, for example, it is possible to maximize the flip-flop effect of the metallic pigment and to have a metallic feeling, characterized in that it contains crosslinked polymer fine particles in the aqueous base paint. A base coat composition that forms an excellent coating film has been proposed (see, for example, Patent Document 2). However, the composition has a defect that coating film defects such as sagging and unevenness are likely to occur due to changes in coating conditions, particularly humidity.

  In addition, in the coating method of 2 coats and 1 bake, for example, as a paint used for aqueous metallic base coating, a specific long chain monomer such as stearyl acrylate or stearyl methacrylate is added to an aqueous dispersion containing polymer fine particles. A method for forming a coating film using a copolymerized aqueous dispersion has also been proposed (for example, see Patent Document 3), but there are problems such as insufficient coating workability, smoothness, and finished properties such as a metallic feeling. is there.

JP-A-4-93374 Japanese Patent Publication No. 3-14869 JP 2001-104878 A

  An object of the present invention is to provide a thermosetting aqueous coating composition and a method for forming a coating film that can form a coating film having a wide range of coating workability and excellent finish such as coating surface smoothness and metallic feeling. It is to be.

  The present inventors have now developed a polyester polyol having a specific monomer composition, and can achieve the above-described object by a thermosetting aqueous coating composition using the polyester polyol and a coating film forming method using the same. The present inventors have found that this can be done and have completed the present invention.

  Thus, the present invention provides (a-1) a polyhydric alcohol, (a-2) a polyvalent carboxylic acid and / or a polyvalent carboxylic acid anhydride, and (a-3) a monoepoxide compound having a long-chain hydrocarbon group. A polyester polyol having a hydroxyl value in the range of 30 to 350 mgKOH / g, an acid value in the range of 10 to 100 mgKOH / g, and a number average molecular weight in the range of 300 to 3,000, obtained by reacting Is.

  The present invention also provides a thermosetting aqueous coating composition comprising (A) the above-described polyester polyol, (B) water-dispersible polymer particles, and (C) a crosslinking agent. .

  The present invention further provides a method for forming a multilayer coating film using the above-mentioned thermosetting aqueous coating composition.

  The thermosetting water-based paint composition of the present invention forms a coating film with extremely excellent finish, and can be used to form a highly solid paint, particularly when used as an aqueous metallic base coat paint. In addition, it is possible to obtain a coating film having excellent finish such as metallic feeling. In addition, the thermosetting aqueous coating composition of the present invention has an effect that the appropriate width of the coating operation with respect to fluctuations in temperature and humidity is wider than that of a conventional aqueous coating.

  Hereinafter, the polyester polyol, the thermosetting aqueous coating composition, and the multilayer coating film forming method of the present invention will be described in more detail.

Polyester polyol The polyester polyol (A) of the present invention comprises (a-1) a polyhydric alcohol, (a-2) a polyvalent carboxylic acid and / or a polyvalent carboxylic acid anhydride, and (a-3) a long-chain hydrocarbon. It is a polyester polyol obtained by reacting a monoepoxide compound having a group.

  The method for synthesizing the polyester polyol (A) is not particularly limited, and can be performed according to an ordinary method. For example, each of the above components (a-1) to (a-3) is about It can synthesize | combine by heating at 90-250 degreeC for about 5 to 10 hours, and performing esterification reaction of an epoxy group and a carboxyl group, and esterification reaction of a hydroxyl group and a carboxyl group. Each of the above reaction components (a-1) to (a-3) may be added and reacted at once, or after reacting components (a-1) and (a-2), component (a- You may make it react in the multistep which makes 3) react. In that case, known esterification catalysts such as dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, tetraisopropyl titanate can be used as the catalyst. .

  Moreover, with respect to the polyester polyol (A), for example, at least one compound selected from, for example, a polyvalent carboxylic acid and / or a polyvalent carboxylic acid anhydride is reacted with a hydroxyl group of the polyester polyol (A). Further, an acid group can be further introduced. As such a polyvalent carboxylic acid and a polyvalent carboxylic acid anhydride, the same as the component (a-2) can be used.

  The polyhydric alcohol (a-1) is a compound having two or more hydroxyl groups in one molecule. For example, ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,5 -Pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,5-pentanediol, 2,2,4-trimethyl- 1,3-pentanediol, 1,6-hexanediol, 1, -Glycols such as hexanediol, 1,4-hexanediol, 2,5-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol, and hydroxypivalic acid neopentyl glycol ester, and the like Polylactone diols obtained by adding lactones such as ε-caprolactone to the glycols, polyester diols such as bis (hydroxyethyl) terephthalate, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecanedi Methanol, hydrogenated bisphenol A, hydrogenated bisphenol F, spiroglycol, dihydroxymethyltricyclodecane, glycerin, trimethylolpropane, trimethylolethane, diglycerin, triglycerin, 1,2 , 6-hexanetriol, pentaerythritol, dipentaerythritol, dipentaerythritol, sorbitol, mannitol and the like can be mentioned, and these can be used alone or in combination of two or more.

  The (a-2) component polyvalent carboxylic 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, sebacin Acid, 2,4-diethylglutaric acid, naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, het acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic Acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, tetrahydrophthalic acid, hexahydrotrimellitic acid, methylhexahydrophthalic acid These can be used alone or in combination of two or more. Can be used together.

  The (a-2) component polycarboxylic acid anhydride is a compound having one or more acid anhydride groups in one molecule, and examples thereof include the above polyhydric carboxylic acid anhydrides. Here, it is assumed that one acid anhydride group is divalent or bifunctional.

  The monoepoxide compound (a-3) having a long-chain hydrocarbon group is a monoepoxide compound having a chain or cyclic hydrocarbon group having 4 or more carbon atoms, preferably 6 to 20 carbon atoms, and the monoepoxide compound Specific examples of (a-3) include pivalic acid glycidyl ester, hexanoic acid glycidyl ester, cyclohexanecarboxylic acid glycidyl ester, 2-ethylhexanoic acid glycidyl ester, isononanoic acid glycidyl ester, decanoic acid glycidyl ester, and undecane. Acid glycidyl ester, lauric acid glycidyl ester, myristic acid glycidyl ester, palmitic acid glycidyl ester, stearic acid glycidyl ester, Cardura E10P (manufactured by Japan Epoxy Resin, Neodecanoic acid monoglycidyl ester) Any glycidyl ester; glycidyl ethers such as butyl glycidyl ether, phenyl glycidyl ether, decyl glycidyl ether; and α-olefin monoepoxides such as styrene oxide and AOEX24 (a mixture of α-olefin monoepoxides manufactured by Daicel Chemical Industries) .

  The hydrocarbon group having 4 or more carbon atoms may have, for example, a substituent such as a hydroxyl group. Specifically, as a monoepoxide compound having a hydrocarbon group having such a substituent, for example, 1,2-epoxyoctanol, hydroxyoctyl glycidyl ether, and the like.

  These monoepoxide compounds (a-3) having a long-chain hydrocarbon group can be used alone or in combination of two or more.

The polyester polyol (A) generally has a number average molecular weight in the range of 300 to 3,000, preferably 400 to 1,800, generally an acid value in the range of 10 to 100 mgKOH / g, preferably 20 to 95 mgKOH / g, And generally having a hydroxyl value in the range of 30 to 350 mg KOH / g, preferably 50 to 300 mg KOH / g. When the number average molecular weight of the component (A) is greater than 3,000, it is difficult to achieve high solid differentiation of the paint, and when the hydroxyl value is less than 30 mgKOH / g, the curability tends to be insufficient.
In the present specification, the “number average molecular weight” is a value measured by gel permeation chromatography and determined in terms of polystyrene.

  The use ratio of the components (a-1), (a-2) and (a-3) is selected so that the number average molecular weight, acid value and hydroxyl value of the resulting polyester polyol (A) are in the above-described ranges. Is done.

  At that time, it is preferable to use a bifunctional or trifunctional alcohol as the component (a-1) and a bifunctional or trifunctional carboxylic acid anhydride as the component (a-2).

  Furthermore, from the viewpoints of wettability, compatibility and the like, it is preferable to use a monoepoxide compound having a hydrocarbon group having 6 to 20 carbon atoms as the component (a-3), particularly 6 to 20 carbon atoms. A glycidyl ester compound having a hydrocarbon group is preferred.

  The polyester polyol (A) is usually dissolved or dispersed in an aqueous medium containing a basic compound in an amount of 0.3 to 1.2 equivalents, preferably 0.5 to 1.0 equivalents based on the resin acid value. An aqueous resin composition can be adjusted. Examples of the basic compound include inorganic basic compounds such as alkali metal hydroxides and aqueous ammonia; methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, isopropylamine, diisopropylamine, diethylenetriamine, triethylene Examples of amine compounds include tetramine, monoethanolamine, diethanolamine, 2-amino-2-methylpropanol, morpholine, N-methylmorpholine, N-ethylmorpholine, piperazine, dimethylethanolamine, diethylethanolamine, and dimethyldodecylamine. it can. Of these, triethylamine, dimethylethanolamine, and diethylethanolamine are particularly preferable.

Thermosetting aqueous coating composition The thermosetting aqueous coating composition of the present invention comprises the polyester polyol (A), water-dispersible polymer particles (B) and a crosslinking agent (C).

Water dispersible polymer particles (B)
The water-dispersible polymer particles (B) of the thermosetting aqueous coating composition of the present invention are not particularly limited, and those usually used in aqueous coating compositions can be used in the same manner. Examples include water-dispersed products such as acrylic resins, polyester resins (including alkyd resins), epoxy resins, and urethane resins, all of which have a hydroxyl group, a carboxyl group, or the like in the molecular structure. More preferred.

  Among these, the water-dispersible acrylic polymer particles (B-1) and the water-dispersible urethane polymer particles (B-2) described below are particularly preferable, and are optimal for use as an aqueous base coat paint.

Water dispersible acrylic polymer particles (B-1)
Water-dispersible acrylic polymer particles obtained by emulsion polymerization of a vinyl monomer using a radical polymerization initiator in the presence of a dispersion stabilizer such as a surfactant.

  The water-dispersible acrylic polymer particles (B-1) may have any structure of a normal structure or a multilayer structure such as a core / shell structure. Moreover, any type of an intraparticle non-crosslinked type or an intraparticle crosslinked type may be used. In the core / shell structure, for example, the core part and the shell part can be of a crosslinked type or an uncrosslinked type, for example, the core part is an intraparticle crosslinked type and the shell part is an intraparticle uncrosslinked type.

  The vinyl monomer to be emulsion polymerized is preferably selected from a carboxyl group-containing vinyl monomer (M-1), a hydroxyl group-containing vinyl monomer (M-2), and other vinyl monomers (M-3). A method of using a small amount of a polyvinyl compound (M-4) having two or more saturated bonds in one molecule, and a small amount of each of a vinyl monomer having a glycidyl group and a carboxyl group-containing vinyl monomer (M-1) in one molecule Intraparticle crosslinked water-dispersible acrylic polymer particles can be obtained by the combined use method, the hydroxyl group-containing vinyl monomer (M-2) and the vinyl monomer having an isocyanate group in one molecule in small amounts. .

  Specifically, the water-dispersible acrylic polymer particles (B-1) having a core / shell structure include, for example, a vinyl monomer component containing no or little carboxyl group-containing vinyl monomer (M-1) at first. It can be obtained by emulsion polymerization and then emulsion polymerization by adding a vinyl monomer component containing a large amount of carboxyl group-containing vinyl monomer (M-1).

  Specifically, the water-dispersible acrylic polymer particles (B-1) having a core / crosslinking core / shell structure are, for example, a small amount of a polyvinyl compound (M-4) and a carboxyl group-containing vinyl monomer ( Obtained by emulsion polymerization of a vinyl monomer component containing no or little M-1), and then emulsion polymerization by adding a vinyl monomer component containing a large amount of carboxyl group-containing vinyl monomer (M-1). Can do.

  The bond between the core part and the shell part is, for example, a polymerizable unsaturated bond introduced via a hydrolyzable functional group or silanol group provided on the surface of the core part, or an allyl remaining on the surface of the core part ( The polymerization can be carried out by copolymerizing a polymerizable unsaturated bond derived from (meth) acrylate with a vinyl monomer component containing a carboxyl group-containing vinyl monomer (M-1) (a shell portion is formed).

  The carboxyl group-containing vinyl monomer (M-1) includes a compound having one or more carboxyl groups and one polymerizable unsaturated bond in one molecule, such as acrylic acid, methacrylic acid, crotonic acid, Examples include maleic acid and itaconic acid. Furthermore, acid anhydrides and half-esterified monocarboxylic acids of these compounds are included in the monomer (M-1) in the present specification.

  The hydroxyl group-containing vinyl monomer (M-2) includes a compound having one hydroxyl group and one polymerizable unsaturated bond in one molecule, and this hydroxyl group can act as a functional group that reacts with a crosslinking agent. . As the monomer (M-2), specifically, a monoesterified product of acrylic acid or methacrylic acid and a dihydric alcohol having 2 to 10 carbon atoms is suitable, for example, 2-hydroxyethyl acrylate, 2 -Hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate and the like.

  Other vinyl monomers (M-3) include monomers other than the above-mentioned monomers (M-1) and (M-2) and having one polymerizable unsaturated bond in one molecule. Specific examples thereof are listed in the following (1) to (8).

  (1) Monoesterified product of acrylic acid or methacrylic acid and monohydric alcohol having 1 to 20 carbon atoms: for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate, and the like.

  (2) Aromatic vinyl monomers: For example, styrene, α-methylstyrene, vinyltoluene and the like.

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

  (4) Nitrogen-containing alkyl (C1-20) acrylate: for example, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate and the like.

  (5) Polymerizable unsaturated bond-containing amide compounds: for example, acrylic acid amide, methacrylic acid amide, dimethylacrylamide, N, N-dimethylpropylacrylamide, N-butoxymethylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide , Diacetone acrylamide and the like.

  (6) Vinyl compound: For example, vinyl acetate, vinyl propionate, vinyl chloride and the like.

  (7) Polymerizable unsaturated bond-containing nitrile compounds: for example, acrylonitrile, methacrylonitrile and the like.

  (8) Diene compounds: for example, butadiene, isoprene and the like.

  These other vinyl monomers (M-3) can be used alone or in combination of two or more.

  Examples of the polyvinyl compound (M-4) include ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, allyl methacrylate, and allyl acrylate. , Divinylbenzene, trimethylolpropane triacrylate and the like, and the diene compound is not included here.

  On the other hand, examples of the dispersion stabilizer used in the emulsion polymerization include an anionic emulsifier, a nonionic emulsifier, and an amphoteric ion emulsifier. Specifically, examples of the anionic emulsifier include fatty acids, alkyl sulfate esters, alkylbenzene sulfonates, and alkyl phosphates. Examples of nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene derivatives, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl amines, alkyl alkanolamides, and the like. . Examples of the zwitterionic emulsifier include alkylbedine.

  The concentration of these emulsifiers is suitably within the range of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the solid content weight of the water-dispersible acrylic polymer particles.

  Examples of the radical polymerization initiator include ammonium persulfate and 4,4′-azobis (4-cyanobutanoic acid). The amount of the initiator used is the solid content weight of the water-dispersible acrylic polymer particles. In general, the range of 0.01 to 10% by weight, preferably 0.1 to 5% by weight is suitable.

  The reaction temperature during emulsion polymerization is usually 60 to 90 ° C., and the reaction time can be about 5 to 10 hours.

  The obtained water-dispersible acrylic polymer particles (B-1) are generally hydroxyl groups in the range of 1 to 100 mgKOH / g, preferably 5 to 80 mgKOH / g, from the viewpoint of water resistance and curability of the resulting coating film. It is preferable to have a valence. In addition, the water-dispersible acrylic polymer particles (B-1) are generally in the range of 1 to 100 mgKOH / g, preferably 5 to 80 mgKOH / g, from the viewpoint of water resistance and curability of the resulting coating film. It preferably has an acid value. Furthermore, the water-dispersible acrylic polymer particles (B-1) can generally have a particle size in the range of 10 to 1000 nm, preferably 20 to 500 nm.

The water-dispersible acrylic polymer particles (B-1) are preferably neutralized with a basic compound.
As a neutralizing agent for the water-dispersible acrylic polymer particles (B-1), ammonia or a water-soluble amino compound such as monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, propylamine, dipropylamine, Isopropylamine, diisopropylamine, triethanolamine, butylamine, dibutylamine, 2-ethylhexylamine, ethylenediamine, propylenediamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, 2-amino-2-methylpropanol, diethanolamine, morpholine, etc. Can be preferably used.

Water dispersible urethane polymer particles (B-2)
Water-dispersible urethane polymer particles (B-2) are commonly used in the field of paints for the purpose of improving coating film properties such as stress relaxation effects. For example, when used in automobile applications, It is effective in improving the damage resistance (referred to as chipping resistance) of the coating film due to the stone splash while the film is running, and in improving the adhesion.

  Water-dispersible urethane polymer particles (B-2) are prepared by dispersing an active hydrogen-containing compound, a compound having active hydrogen and a hydrophilic group in the molecule, and a urethane polymer obtained by reacting an organic polyisocyanate compound in water. Or it can obtain by melt | dissolving.

  Examples of the active hydrogen-containing compound include high-molecular polyols, low-molecular polyols, and polyamines (for example, those described in JP-A-3-9951).

  As the polymer polyol, polyether polyol, polyester polyol and polycarbonate polyol are preferable. The polymer polyol may have an OH group equivalent within a range of usually 200 to 3000, preferably 250 to 2000. As the low molecular weight polyol, 1,4-butanediol, 3-methylpentanediol, pentaerythritol and trimethylolpropane are preferable. As the polyamine, hexamethylenediamine, isophoronediamine, N-hydroxyethylethylenediamine, and 4,4'-diaminodicyclohexylmethane are preferable.

  The compound having an active hydrogen and a hydrophilic group in the molecule is preferably a compound containing an active hydrogen and an anion group or an anion-forming group. For example, dihydroxycarboxylic acid (α, α-dimethylolpropionic acid, α, α- Dimethylolbutyric acid etc.), dihydroxysulfonic acid compounds [3- (2,3-dihydroxypropoxy) -1-propanesulfonic acid sodium salt etc.], diaminocarboxylic acids (eg diaminobenzoic acid etc.) and the like are neutralized Examples of the basic compound for the purpose include organic bases (for example, triethylamine, trimethylamine, etc.) and inorganic bases (for example, sodium hydroxide, potassium hydroxide, etc.).

  Examples of the organic polyisocyanate compound include isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI), 2,4 and / or 2,6-tolylene diisocyanate ( TDI), 4,4′-diphenylmethane diisocyanate (MDI), α, α, α ′, α′-tetramethylxylylene diisocyanate (TMXDI) and the like.

  In producing the urethane polymer, the reaction of an active hydrogen-containing compound, a compound having active hydrogen and a hydrophilic group in the molecule, and an organic polyisocyanate compound is a one-shot method in which each component is reacted at one time, or, for example, After reacting part of an active hydrogen-containing compound (for example, a polymer polyol), a compound having an active hydrogen and a hydrophilic group in the molecule, and an organic polyisocyanate compound to produce an isocyanate-terminated prepolymer, It can be carried out by any of multistage methods in which the remainder is reacted.

  Said reaction can be normally performed at 40-140 degreeC, Preferably it is 60-120 degreeC. The reaction may be carried out in an organic solvent inert to isocyanate (acetone, toluene, dimethylformamide, etc.), and the organic solvent may be added either during or after the reaction.

  Water-dispersible urethane polymer particles (B-2) are obtained by neutralizing a urethane polymer having a hydrophilic group obtained as described above with a basic compound to form an anionic group, and then dispersing or dispersing in water. It can be obtained by dissolving.

  In addition, when the urethane polymer is dispersed or dissolved in water, an anionic and / or nonionic surfactant can be used in combination as necessary.

Cross-linking agent (C)
The crosslinking agent (C) of the thermosetting aqueous coating composition of the present invention is not particularly limited, and examples thereof include a blocked polyisocyanate curing agent (c ₁ ) and a water-dispersible blocked polyisocyanate curing described below. An agent (c ₂ ), a melamine resin (c ₃ ) and the like can be suitably used.

The blocked polyisocyanate curing agent (c ₁ ) is obtained by blocking an isocyanate group of a polyisocyanate compound having two or more free isocyanate groups in one molecule with a blocking agent.

  Examples of the polyisocyanate compound include aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate; burette type adducts of these aliphatic polyisocyanates, isocyanurate ring addition Isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4- (or-2,6-) diisocyanate, 1,3- (or 1,4-) di (isocyanatomethyl) Cycloaliphatic diisocyanates such as cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate; Bullet type adduct of alicyclic diisocyanate, isocyanurate ring adduct; xylylene diisocyanate, tetramethylxylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), 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 diisocyanate compounds such as' -dimethyl-4,4'-biphenylene diisocyanate, bis (4-isocyanatophenyl) sulfone, isopropylidenebis (4-phenylisocyanate); and these Burelet type adduct of isocyanate, isocyanurate cycloadduct; hydrogenated MDI, and derivatives of hydrogenated MDI; triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanate It has three or more isocyanate groups in one molecule such as natobenzene, 2,4,6-triisocyanatotoluene, 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate. Polyisocyanates; burette type adducts and isocyanurate cycloadducts of these polyisocyanates; ethylene glycol, propylene glycol, 1,4-butylene glycol, dimethylolpropionic acid, polyalkylene glycol, trimethylolpropane, hexanetriol, etc. Isocyanate to the hydroxyl group of Examples thereof include urethanated adducts obtained by reacting polyisocyanate compounds in an excess amount of nate groups; burette type adducts, isocyanurate ring adducts, and the like of these urethanized adducts.

Further, the blocking agent blocks free isocyanate groups in these polyisocyanate compounds. For example, when heated to 100 ° C. or higher, preferably 130 ° C. or higher, the blocking agent dissociates to form free isocyanate groups. It can be regenerated and easily reacted with hydroxyl groups. 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, γ -Lactams such as butyrolactam and 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 monobutyl 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 Alcohol system such as methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime, etc. Oxime system;
Malonic acid dialkyl esters such as dimethyl malonate, diethyl malonate, diisopropyl malonate, di-n-butyl malonate, diethyl methylmalonate, benzylmethyl malonate, diphenyl malonate, methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate Active methylenes such as acetoacetate such as n-propyl acetoacetate, benzyl acetoacetate and phenylacetoacetate, phenylacetoacetate, and acetylacetone; Mercaptans such as phenol, methylthiophenol, ethylthiophenol; acetanilide, acetanisidide, acetolide, acrylamide, methacrylamide, acetic acid amide Acid amides such as stearamide, benzamide; imides such as succinimide, phthalimide, maleic imide; diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine Amines such as butylphenylamine; imidazoles such as imidazole and 2-ethylimidazole; pyrazoles such as 3,5-dimethylpyrazole; ureas such as urea, thiourea, ethyleneurea, ethylenethiourea and diphenylurea; N -Blocking agents such as carbamate esters such as phenyl phenyl carbamate; imines such as ethylene imine and propylene imine; and sulfites such as sodium bisulfite and potassium bisulfite. That.

In order to reduce the amount of organic solvent in paints (lower VOC), it is better to reduce the amount of organic solvent from the cross-linking agent (C). A blocked polyisocyanate curing agent (c ₂ ) obtained by imparting water dispersibility to the agent (c ₁ ) can be used.

In the blocked polyisocyanate curing agent (c ₂ ) imparted with water dispersibility, for example, the isocyanate group of the polyisocyanate compound is blocked with a blocking agent and hydroxy monocarboxylic acids, and the carboxyl group introduced by the hydroxy monocarboxylic acids is added. Blocked polyisocyanate compounds imparted with water dispersibility by neutralization are included.

As the polyisocyanate compound, polyisocyanate compounds similar to those exemplified in the blocked polyisocyanate curing agent (c ₁ ) can be used, and in particular, hexamethylene diisocyanate (HMDI), hexamethylene diisocyanate (HMDI). ) Derivatives, isophorone diisocyanate (IPDI), isophorone diisocyanate (IPDI) derivatives, hydrogenated MDI and hydrogenated MDI derivatives.

The water-dispersible blocked polyisocyanate curing agent (c ₂ ) can be produced, for example, by blocking an isocyanate group of a polyisocyanate compound with a blocking agent and reacting with a hydroxymonocarboxylic acid. In this case, the polyisocyanate compound is reacted so that at least one isocyanate group is added to the hydroxyl group of the hydroxymonocarboxylic acid.

As the blocking agent, the same blocking agent as exemplified in the blocked polyisocyanate curing agent (c ₁ ) can be used. Examples of hydroxy monocarboxylic acids include 2-hydroxyacetic acid, 3-hydroxypropanoic acid, 12-hydroxy-9-octadecanoic acid (ricinoleic acid), 3-hydroxy-2,2-dimethylpropanoic acid (hydroxypivalic acid). ), 2,2-dimethylolpropionic acid (DMPA) and the like, among which 3-hydroxy-2,2-dimethylpropanoic acid (hydroxypivalic acid) is preferable. The reaction can be carried out in a solvent that is not reactive with an isocyanate group, for example, a ketone such as acetone or methyl ethyl ketone, an ester such as ethyl acetate, or a solvent such as N-methylpyrrolidone (NMP).

Specific examples of the melamine resin (c ₃ ) include di-, tree, tetra-, penta-, hexa-methylol melamine and alkyl etherified products thereof (for example, methyl, ethyl, propyl, isopropyl, Butyl, isobutyl, 2-ethylhexyl alcohol, etc.) and their condensates, etc., and as commercial products, for example, Cymel series such as Cymel 254 manufactured by Nippon Cytec Industries, Inc .; manufactured by Mitsui Chemicals, Inc. Uban series such as Uban 20SB can be used.
When melamine resin (c ₃ ) is used as a curing agent, sulfonic acids such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and salts with these amines should be used as catalysts. Can do.

  The thermosetting aqueous coating composition of the present invention is prepared by, for example, dissolving or dispersing the polyester polyol as the component (A) in an aqueous medium containing a neutralizing base to produce an aqueous varnish, and then adding a crosslinking agent as the component (C). Furthermore, it can adjust by adding and disperse | distributing the water-dispersible polymer particle of (B) component. In that case, the neutralization base can be normally used within the range in which the pH of the thermosetting aqueous coating composition is 7-9.

  The blending amounts of the polyester polyol (A), the water-dispersible polymer particles (B) and the crosslinking agent (C) in the thermosetting aqueous coating composition of the present invention are not strictly limited, and the coating composition In general, the polyester polyol (A) is 5 to 5 in terms of non-volatile content based on 100 parts by weight of the resin solid content in the thermosetting aqueous coating composition. 50 wt%, preferably in the range of 10-40 wt%, water dispersible polymer particles (B) in the range of 20-80 wt%, preferably in the range of 25-70 wt%, and the crosslinker (C) in the range of 15 It can be in the range of -65% by weight, preferably 20-50% by weight.

  In addition to the above-described components (A) to (C), the thermosetting aqueous coating composition of the present invention can further contain other resins as necessary. Examples of such a resin include an acrylic resin, a polyester resin, a urethane-modified polyester resin, and an epoxy resin. Among them, the acrylic resin and the polyester resin described below are preferable.

What is synthesize | combined by copolymerizing an acrylic resin radically polymerizable monomer according to a conventional method by solution polymerization can be used suitably. As an organic solvent that can be used for solution polymerization, for example, a hydrophilic organic solvent such as a propylene glycol type or a dipropylene glycol type is preferable. From the viewpoint of water dispersibility, the acrylic resin preferably has an acid group such as a carboxyl group.

As the radical polymerizable monomer, conventionally known monomers can be used, and for example, a hydroxyl group-containing radical polymerizable monomer, a carboxyl group-containing radical polymerizable monomer, and other radical polymerizable monomers can be used.
Examples of the hydroxyl group-containing radical polymerizable monomer include 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, and ε-caprolactone-modified tetrahydrofur. Furyl (meth) acrylate, ε-caprolactone-modified hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-hydroxy- Examples thereof include 3-butoxypropyl (meth) acrylate and monohydroxyethyl (meth) acrylate phthalate.

  Examples of the carboxyl group-containing radical polymerizable monomer include acrylic acid and methacrylic acid.

  Examples of other radical polymerizable monomers include styrene, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and cyclohexyl (meth) acrylate. , Cyclohexenyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) ) Acrylate, Aronix M110 (Toagosei), N-methylol (meth) acrylamide, N-butoxy (meth) acrylamide, acryloylmorpholine, Methylaminoethyl (meth) acrylate, N- vinyl-2-pyrrolidone, .gamma. acrylate etc. b propyl trimethoxysilane can be exemplified.

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

  The acrylic resin generally has a weight average molecular weight in the range of 1,000 to 200,000, preferably 2,000 to 100,000. The acrylic resin generally has a hydroxyl value in the range of 10 to 250 mg KOH / g, preferably in the range of 30 to 150 mg KOH / g and generally an acid value in the range of 10 to 100 mg KOH / g, preferably 20 to 60 mg KOH / g. it can.

Polyester resin A polyester that can be synthesized by a known method by esterifying a polybasic acid and a polyhydric alcohol, which does not contain a monoepoxide compound other than the polyester polyol (A) of the present invention. Resin.

  A 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, hexahydrophthalic acid Examples thereof include acid, hetic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, and anhydrides thereof, and polyhydric alcohol is a compound having two or more hydroxyl groups in one molecule. Examples thereof include ethylene glycol, propylene glycol, butylene glycol, hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol.

  In addition, as the polyester resin, sesame oil fatty acid, coconut oil fatty acid, safflower oil fatty acid, soybean oil fatty acid, sesame oil fatty acid, eno oil fatty acid, hemp oil fatty acid, toll oil fatty acid, dehydrated castor oil fatty acid, etc. (half) A fatty acid-modified polyester resin modified with a dry oil fatty acid or the like can also be used. In general, the amount of modification with these fatty acids is preferably 30% by weight or less in terms of oil length. Further, a product obtained by partially reacting a monobasic acid such as benzoic acid may be used. Further, for example, in order to introduce an acid group into a polyester resin, after the esterification reaction of the polybasic acid and the polyhydric alcohol, a polybasic acid such as trimellitic acid or trimellitic anhydride and an anhydride thereof are further added. It can also be reacted.

  The polyester resin generally has a weight average molecular weight in the range of 1,000 to 200,000, preferably 2,000 to 50,000. Also, the polyester resin generally has a hydroxyl value in the range of 10 to 250 mg KOH / g, preferably 30 to 150 mg KOH / g and generally an acid value in the range of 10 to 100 mg KOH / g, preferably 20 to 60 mg KOH / g. it can.

  The thermosetting aqueous coating composition of the present invention usually contains pigments, curing catalysts, ultraviolet absorbers, light stabilizers, surface conditioners, deterioration inhibitors, anti-settling agents, anti-settling agents, etc., as necessary. The paint additive can be contained.

  Examples of the 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, and perylene. Colored pigments such as pigments; extender pigments such as talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, silica, and alumina white; bright pigments such as mica powder coated with aluminum powder, mica powder, and titanium oxide Etc.

  When the thermosetting aqueous coating composition of the present invention is used as an aqueous base coat coating for metallic specifications, a bright pigment and, if necessary, a coloring pigment can be added. When used as an intermediate coating, extender pigments such as barium sulfate, calcium carbonate, and clay can be used in combination with the color pigment. The pigment can be made from a portion of the resin described above to make a pigment paste, which can be added to the remaining aqueous varnish along with other ingredients. In preparing the pigment paste, conventional additives such as an antifoaming agent, a dispersing agent, and a surface conditioner can be appropriately used as necessary.

  The blending amount of the pigment is generally 1 to 250 parts by weight, particularly 3 to 150 parts by weight per 100 parts by weight of the total solid content of the resin component.

Moreover, a curing catalyst can also be blended, and examples of the curing catalyst include organic metal-based, acid-based and base-based compounds.
Examples of organometallic compounds include tetraisopropyl titanate, tetrabutyl titanate, lithium acetate, acetylacetone iron (III), zinc 2-ethylhexanoate, copper acetate, vanadium trichloride, tin octylate, dibutyltin diacetate, dibutyl Tin dioctoate, dibutyltin dilaurate, dibutyltin dimaleate, tetrabutyltin, dibutyltin oxide, tetra-n-butyl-1,3-diacetyloxydistanoxane, tetra-n-propyl-1,3-diacetyloxydistanoxane, Examples thereof include metal catalysts such as tetra-n-butyl-1,3-dilauryloxydistanoxane, and in particular, organotin compounds such as tin octylate, dibutyltin diacetate, dibutyltin dilaurate, and distanoxanes. Preferably, further, low temperature firing If the put is required, dibutyltin diacetate is preferably used.

  Examples of the acid compounds include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, butylphosphoric acid, octylphosphoric acid, and the like. Japanese products are also preferably used.

  Examples of the base compound include trimethylamine, triethylamine, dimethylcyclohexylamine, N-tetramethylhexane-1,6-diamine, N-pentamethyldiethylenetriamine, 2-methyl-1,4-diazabicyclo [2,2,2]. ] Compounds such as octane can be mentioned.

  These compounds described above as the curing catalyst can be used alone or in combination of two or more. The amount of the curing catalyst to be used varies depending on the kind thereof, but usually about 0.05 to 5 parts by weight is suitable for 100 parts by weight of the total solid content of the resin component.

  As the ultraviolet absorber, those known per se can be used, and examples thereof include a benzotriazole-based absorbent, a triazine-based absorbent, a salicylic acid derivative-based absorbent, and a benzophenone-based absorbent.

  When the ultraviolet absorber is contained, the content in the coating composition is usually 0.1 to 10 parts by weight, particularly 0.2 to 5 parts by weight, more particularly 100 parts by weight of the total amount of resin solids. The range of 0.3 to 2 parts by weight is preferable from the viewpoints of weather resistance, yellowing resistance and the like.

  As the light stabilizer, those known per se can be used, and examples thereof include hindered amine light stabilizers.

  When the light stabilizer is contained, the content in the coating composition is usually 0.1 to 10 parts by weight, particularly 0.2 to 5 parts by weight, more particularly 100 parts by weight of the total resin solid content. The range of 0.3 to 2 parts by weight is preferable in terms of weather resistance and yellowing resistance.

Coating Film Forming Method The coating object to which the thermosetting aqueous coating composition of the present invention can be applied is not particularly limited, but for example, car bodies of various vehicles such as automobiles, motorcycles and containers are preferable. In addition, cold rolled steel sheets, galvanized steel sheets, zinc alloy plated steel sheets, stainless steel sheets, tin plated steel sheets, etc. forming metal bodies; metal substrates such as aluminum plates and aluminum alloy plates; various plastic materials, etc. Good.

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

  The coating method of the thermosetting aqueous coating composition of the present invention is not particularly limited, and examples thereof include air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, and the like. A wet coating film can be formed. These coating methods may be electrostatically applied as necessary. Among these, an air spray coating method, an electrostatic coating method, and the like are particularly preferable. The coating amount of the coating composition is usually preferably an amount of about 10 to 70 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 composition 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 an organic solvent and / or water so that the viscosity is within a range of about 15 to 60 seconds at 20 ° C.

  The wet coating film is cured by applying a thermosetting water-based coating composition to an object to be coated and then 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 used. The heating temperature is usually 80 to 180 ° C, preferably 100 to 160 ° C. The heating time is not particularly limited, but can usually be about 20 to 40 minutes.

  The thermosetting water-based coating composition of the present invention can be suitably used as an automotive paint, and in particular, can be more suitably used as a topcoat base coat paint.

  When used as a topcoat base coat, for example, the thermosetting water-based paint composition of the present invention is applied to an object that has been subjected to electrodeposition coating and / or intermediate coating, and the coating film is cured. Instead, by applying a clear coat paint on the uncured coating film and simultaneously curing the base coat and the clear coat, a multilayer coating film can be formed by the 2-coat 1-bake method.

  Further, an intermediate coating is applied on the object to be coated, and the thermosetting aqueous coating composition of the present invention is applied as a colored topcoat base coating without curing the coating, and the coating is further cured. It is also possible to form a coating film by applying a clear coat paint on it and curing the three-layer coating film simultaneously.

  As the intermediate coating used in the above, a conventionally known thermosetting intermediate coating can be used. Specifically, for example, an amino acid is added to a base resin such as an alkyd resin, a polyester resin, an acrylic resin, or a urethane resin. A coating material obtained by appropriately combining a curing agent such as a resin, a polyisocyanate compound, or a block polyisocyanate compound with a reactive functional group contained in the base resin can be used. As said polyisocyanate compound and block polyisocyanate compound, the same thing as described about the said crosslinking agent (C) can be used, for example. The intermediate coating is preferably a high solid type with a small amount of organic solvent used from the viewpoint of environmental problems, resource saving, and the like, and an aqueous coating or powder coating can also be used.

  As the clear coat paint used in the above, a conventionally known thermosetting clear coat paint can be used. Specifically, for example, alkyd resin, polyester resin, acrylic resin, silicon resin, fluororesin, urethane It is formed by appropriately combining a curing agent such as amino resin, polyisocyanate compound, block polyisocyanate compound, polycarboxylic acid or anhydride thereof, and reactive silane compound with a reactive functional group contained in the base resin, on a base resin such as a resin. Organic solvent diluted paint can be used. As said polyisocyanate compound and block polyisocyanate compound, the same thing as described about the said crosslinking agent (C) can be used, for example. The clear coat paint is preferably a high solid type with a small amount of organic solvent used from the viewpoints of environmental problems, resource saving, and the like, and an aqueous paint or a powder paint can also be used.

  In particular, an acrylic resin / melamine resin system, an acrylic resin / polyisocyanate curing agent system, an acrylic resin / block polyisocyanate curing agent system, or an acid group-containing resin / epoxy group-containing resin system can be suitably used.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited only to these examples. “Part” and “%” are both based on weight, and the film thickness of the coating film is based on the cured coating film.
(Example)
Production example of polyester polyol (A)

  A reactor equipped with a stirrer, reflux condenser, water separator and thermometer was charged with 273 parts of trimethylolpropane and 308 parts of hexahydrophthalic anhydride, and reacted at 100 ° C. for 2 hours. Then, 490 parts of Cardura E10P (manufactured by Japan Epoxy Resin Co., Ltd., neodecanoic acid monoglycidyl ester) was added and reacted at 120 ° C for 3 hours. Thereafter, 308 parts of hexahydrophthalic anhydride was added and reacted at 120 ° C. for 3 hours to obtain a polyester polyol 1 having a hydroxyl value of 160 mgKOH / g, an acid value of 80 mgKOH / g, and a number average molecular weight of 700.

  A reactor equipped with a stirrer, reflux condenser, water separator and thermometer was charged with 273 parts of trimethylolpropane, 160 parts of succinic anhydride, 58 parts of adipic acid and 490 parts of Cardura E10P for 4 hours at 100 to 230 ° C. Reacted. Thereafter, 192 parts of trimellitic anhydride was added and reacted at 180 ° C. for 1 hour to obtain polyester polyol 2 having a hydroxyl value of 234 mgKOH / g, an acid value of 94 mgKOH / g and a number average molecular weight of 600.

  In a reactor equipped with a stirrer, a reflux condenser, a water separator and a thermometer, 236 parts of 1,6-hexanediol and 308 parts of hexahydrophthalic anhydride were charged and reacted at 100 ° C. for 2 hours. Thereafter, 318.5 parts of Cardura E10P was added and reacted at 120 ° C. for 3 hours to obtain Polyester Polyol 3 having a hydroxyl value of 215 mgKOH / g, an acid value of 45 mgKOH / g, and a number average molecular weight of 440.

A reactor equipped with a stirrer, a reflux condenser, a water separator and a thermometer was charged with 273 parts of trimethylolpropane and 924 parts of hexahydrophthalic anhydride and reacted at 100 ° C. for 2 hours. Thereafter, 980 parts of Cardura E10P was added and reacted at 120 ° C. for 3 hours to obtain a polyester polyol 4 having a hydroxyl value of 103 mgKOH / g, an acid value of 51 mgKOH / g and a number average molecular weight of 1100.
(Comparative Example 1)
In a reactor equipped with a stirrer, reflux condenser, water separator and thermometer, 79.2 parts trimethylolpropane, 134.5 parts 1,6-hexanediol, 246.4 parts hexahydrophthalic anhydride, 35 adipic acid 35 Part and 68.6 parts of Cardura E10P were heated between 160 ° C. and 230 ° C. over 3 hours and then reacted at 230 ° C. for 4 hours. Subsequently, in order to add a carboxyl group to the obtained reaction product, 46.1 parts of trimellitic anhydride was further added and reacted at 180 ° C. for 1 hour to have a hydroxyl value of 59 mgKOH / g and an acid value of 40 mgKOH / g. Polyester polyol 5 having a number average molecular weight of 3150 was obtained.

Production example of water-dispersible polymer particles (B) (Production Example 1)
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device was charged with 145 parts of deionized water and 1.2 parts of Newcol 562SF (Note 1), stirred and mixed in a nitrogen stream, and heated to 80 ° C. Warm up. Subsequently, 1% of the total amount of the following monomer emulsion 1 and 5.2 parts of a 3% aqueous solution of ammonium persulfate were introduced into the reaction vessel and maintained at 80 ° C. for 15 minutes. Then, the remaining monomer emulsion 1 was dripped in reaction container over 3 hours, and it age | cure | ripened for 1 hour after completion | finish of dripping. Thereafter, the following monomer emulsion 2 was added dropwise over 2 hours and aged for 1 hour, and then 89 parts of a 1.5% N, N-dimethyl-2-hydroxyethylamine aqueous solution was gradually added to the reaction vessel up to 30 ° C. The mixture was cooled and discharged while being filtered through a 100 mesh nylon cloth, and water-dispersible acrylic polymer particles 6 having an average particle diameter of 100 nm, an acid value of 30.7 mgKOH / g and a hydroxyl value of 22.1 mgKOH / g (solid content 25.2). %).
(Note 1) Newcol 562SF; manufactured by Nippon Emulsifier Co., Ltd., trade name, ammonium polyoxyethylene alkylbenzenesulfonate, active ingredient 60%.

  Monomer emulsion 1: 94.3 parts of deionized water, 17 parts of methyl methacrylate, 80 parts of n-butyl acrylate, 3 parts of allyl methacrylate and 1.2 parts of Newcol 562SF were mixed and stirred to obtain monomer emulsion 1.

  Monomer emulsion 2: 39 parts of deionized water, 15.4 parts of methyl methacrylate, 2.9 parts of n-butyl acrylate, 5.9 parts of hydroxyethyl acrylate, 5.1 parts of methacrylic acid and 0.5 part of Newcol 562SF are mixed and stirred. Thus, a monomer emulsion 2 was obtained.

Production Example of Crosslinking Agent (C) (Production Example 2)
49 parts of hexamethylene diisocyanate was added dropwise to 51 parts of methyl ethyl ketone oxime at 40 to 60 ° C., followed by heating at 80 ° C. for 1 hour to obtain a blocked polyisocyanate curing agent solution 7.
(Production Example 3)
A reactor equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a dropping pump, and the like was added to Sumidur N-3300 (manufactured by Sumika Bayer Urethane Co., Ltd., isocyanurate structure-containing polyisocyanate, number average molecular weight of about 600, isocyanate content of 21. 6%) 605 parts, diethyl malonate 413 parts, and ethyl acetate 181 parts were blended, 7.0 parts of a 28% sodium hydroxide methanol solution was added under a nitrogen stream, and the mixture was kept at 60 ° C. for 12 hours. Thereafter, when the NCO value was measured, the isocyanate content was 0.2%. 99 parts of ethyl acetate was added thereto to obtain a resin solution. 505 parts of this resin solution was taken out into another similar reactor, 450 parts of propylene glycol monopropyl ether was added, and the temperature was raised to 90 ° C. Under reduced pressure, the solvent was distilled off and removed over 2 hours while maintaining the temperature of the system at 80 to 90 ° C. to obtain 624 parts of a blocked polyisocyanate curing agent solution. The removal solvent simple trap contained 42 parts of ethanol. The resulting blocked polyisocyanate curing agent solution was diluted with propylene glycol monopropyl ether to obtain blocked polyisocyanate curing agent solution 8 having a solid content of 80%. The number average molecular weight of the blocked polyisocyanate curing agent was about 3,500.

Manufacture of thermosetting water-based paint composition (water-based topcoat base coat)

To 20 parts of the polyester polyol 1 obtained in Example 1, 43.8 parts of Cymel 325 (Mitsui Cytec Co., Ltd., methyl / butyl mixed etherified melamine resin, solid content 80%) and water obtained in Production Example 1 were stirred. 178.6 parts of dispersible acrylic polymer particles 6 (solid content 25.2%) were added. Thereafter, an aluminum paste GX180A (aluminum flake paste, manufactured by Asahi Kasei Co., Ltd.) in an amount of 20 parts as an aluminum pigment is added with mixing and dispersed, and further dimethylethanolamine and deionized water are added to adjust the pH to 8. 0, Ford Cup No. The viscosity was 40 seconds at 20 ° C. as measured by 4 to obtain an aqueous topcoat base coat paint 1.

  In Example 5, except that the polyester polyol 1 was changed to the polyester polyol 2 obtained in Example 2, it was adjusted in the same manner as in Example 5 to obtain an aqueous topcoat base coating material 2.

  In Example 5, except that the polyester polyol 1 was changed to the polyester polyol 3 obtained in Example 3, it was adjusted in the same manner as in Example 5 to obtain an aqueous topcoat base coating material 3.

  An aqueous topcoat base coat paint 4 was obtained in the same manner as in Example 5 except that the polyester polyol 1 obtained in Example 5 was changed to the polyester polyol 4 obtained in Example 4.

  In Example 5, Cymel 325 was changed from 43.8 parts to 31.3 parts, and 25 parts of Superflex 410 (Daiichi Kogyo Seiyaku Co., Ltd., trade name, aqueous polycarbonate urethane resin, solid content 40%) Except for the addition, adjustment was carried out in the same manner as in Example 5 to obtain an aqueous topcoat base coat paint 5.

  An aqueous topcoat base coating material 6 was obtained in the same manner as in Example 5 except that the polyester polyol 1 was changed from 20 parts to 10 parts in Example 5 and further 25 parts of Superflex 410 was added.

  In Example 5, water-dispersible acrylic polymer particles 6 were prepared in the same manner as in Example 5 except that 178.6 parts to 138.9 parts were added and 25 parts of Superflex 410 were added. A paint 7 was obtained.

In Example 5, the polyester polyol 1 was changed from 20 parts to 10 parts, and Cymel 325 was changed from 43.8 parts to 31.3 parts, and the blocked polyisocyanate curing agent solution 8 obtained in Production Example 3 (containing solid content) 80%) Except that 12.5 parts and 25 parts of Superflex 410 were added, adjustment was made in the same manner as in Example 5 to obtain an aqueous topcoat base coat paint 8.
(Comparative Example 2)
An aqueous topcoat basecoat paint 9 was obtained in the same manner as in Example 5 except that the polyester polyol 1 in Example 5 was changed to the polyester polyol 5 obtained in Comparative Example 1.
Preparation of test plate 1
For the aqueous topcoat base coat paints 1 to 9 obtained in Examples 5 to 12 and Comparative Example 2, test plates were prepared as follows.
(Coating material) The thickness of ELECRON 9600 (manufactured by Kansai Paint Co., Ltd., trade name, thermosetting epoxy resin-based cationic electrodeposition coating) on a 0.8 mm-thick dull steel plate subjected to zinc phosphate chemical conversion treatment Electrodeposited to a thickness of 20 μm, heated at 170 ° C. for 30 minutes to cure, and then coated with Amirac TP-65-2 (trade name, amino-alkyd automotive intermediate coating) manufactured by Kansai Paint Co., Ltd. Air spray coating was performed to a thickness of 35 μm, and heat curing was performed at 140 ° C. for 30 minutes to obtain a coating object.

Using the rotary electrostatic coating machine, the water-based topcoat basecoat paints 1 to 9 produced in the above-mentioned examples and comparative examples were applied to the object to be coated with a discharge amount of 300 cc, a rotational speed of 25,000 rpm, and a shaping air pressure of 1.5 kg / The coating was applied to a film thickness of 15 μm at a cm ² , a gun distance of 30 cm, a conveyor speed of 5 m / min, a booth temperature and humidity of 25 ° C./75%, allowed to stand for 2 minutes, and then preheated at 80 ° C. for 3 minutes. Next, Magcron TC-71 (trade name, acrylic / melamine resin solvent-type clear coating) manufactured by Kansai Paint Co., Ltd. was applied to the uncured coating surface. 4 was used to add Swazol 1000 (manufactured by Cosmo Oil Co., Ltd., petroleum aromatic hydrocarbon solvent) to adjust the viscosity to 30 seconds at a coating temperature of 20 ° C., and using a minibell rotary electrostatic coating machine, Painted to a film thickness of 40μm at a discharge rate of 200cc, a rotational speed of 40,000rpm, a shaping air pressure of 1kg / cm ² , a gun distance of 30cm, a conveyor speed of 4.2m / min, a booth temperature and humidity of 25 ° C / 75%. After leaving for 7 minutes, the test plate was produced by heating at 140 ° C. for 30 minutes to cure both coating films simultaneously.
Performance test result 1
Table 1 shows the performance test results of the test plate and the water-based topcoat base coating materials 1 to 9 formed as described above. Test methods and evaluation methods are as follows.

Smoothness of coating film: The appearance of the test plate was visually evaluated.
○: Smoothness, gloss, and sharpness are all good △: Smoothness, gloss, and sharpness are slightly inferior ×: Any of smoothness, gloss, and sharpness is remarkably inferior IV value : IV value measured using a laser-type metallic feeling measuring device (Alcope LMR-200 (manufactured by Kansai Paint)). IV is the whiteness of the metallic coating film, and the more the metallic pigment is uniformly oriented in parallel to the coating surface, the more white it is, the better the metallic feel, and the higher the IV value, the more white it is.

  Metallic unevenness: The degree of metallic unevenness of the test plate was visually evaluated. A: Almost no metallic unevenness is observed, Δ: A little metallic unevenness is observed, and X: Many metallic unevennesses are recognized.

  Paint solid content: About 2 g of paint was sampled into an aluminum foil cup having a diameter of about 5 cm, and the solid content weight concentration (%) was measured (solid content measurement condition: measured after drying at 110 ° C. for 1 hour).

Preparation of test plate 2
Regarding the aqueous topcoat base coat obtained in Example 5 and Comparative Example 2, two types of test plates were prepared according to the description of Example 13 and Comparative Example 3 below.
(Coating material) The thickness of ELECRON 9600 (manufactured by Kansai Paint Co., Ltd., trade name, thermosetting epoxy resin-based cationic electrodeposition coating) on a 0.8 mm-thick dull steel plate subjected to zinc phosphate chemical conversion treatment An object to be coated was formed by electrodeposition coating so as to have a thickness of 20 μm and heating at 170 ° C. for 30 minutes to form an electrodeposition coating film.

WP-300T (polyester resin / polyisocyanate curing agent aqueous intermediate coating, manufactured by Kansai Paint Co., Ltd.) was applied on the object to be coated to a thickness of 35 μm. After standing for 2 minutes and preheating at 80 ° C. for 5 minutes, the aqueous topcoat basecoat paint 1 produced in Example 5 on the uncured coating film was rotated at a discharge rate of 300 cc using a rotary electrostatic coating machine. Several 25,000 rpm, shaping air pressure 1.5 kg / cm ² , gun distance 30 cm, conveyor speed 5 m / min, booth temperature and humidity 25 ° C./75%, coated to a film thickness of 15 μm, and left for 2 minutes And preheating at 80 ° C. for 3 minutes.
Next, Magycron TC-71 (trade name, acrylic / melamine resin solvent-type clear clear paint manufactured by Kansai Paint Co., Ltd.) was applied to the uncured aqueous topcoat base coat film. 4 is used to adjust the viscosity to 30 seconds at a paint temperature of 20 ° C. with the addition of Swazol 1000, using a minibell-type rotary electrostatic coating machine, with a discharge amount of 200 cc, a rotational speed of 40,000 rpm, and a shaping air pressure 1kg / cm ² , gun distance 30cm, conveyor speed 4.2m / min, booth temperature and humidity 25 ° C / 75%, coated to a film thickness of 40µm, left for 7 minutes, then heated at 140 ° C for 30 minutes A test plate was prepared by simultaneously curing the three-layer coating film.
(Comparative Example 3)
A test plate was produced in the same manner as in Example 13 except that the aqueous topcoat basecoat paint 1 in Example 13 was changed to the aqueous topcoat basecoat paint 9 obtained in Comparative Example 2.
Performance test result 2
Table 2 shows the performance test results of the test plates produced as described above. The test method and the evaluation method were tested and evaluated in the same manner as the method shown in the performance test result 1.

Claims (10)

(A-1) obtained by reacting a polyhydric alcohol, (a-2) a polycarboxylic acid and / or a polycarboxylic acid anhydride, and (a-3) a monoepoxide compound having a long-chain hydrocarbon group. Polyester polyol having a hydroxyl value in the range of 30 to 350 mg KOH / g, an acid value in the range of 10 to 100 mg KOH / g, and a number average molecular weight in the range of 300 to 3,000. The polyester polyol according to claim 1, wherein the component (a-1) is a bifunctional or trifunctional alcohol, and the component (a-2) is a bifunctional or trifunctional carboxylic acid anhydride. . (A) A thermosetting aqueous coating composition comprising the polyester polyol according to claim 1, (B) water-dispersible polymer particles, and (C) a crosslinking agent. The water-dispersible polymer particles (B) are water-dispersible acrylic polymer particles (B-1) having an acid value in the range of 1 to 100 mgKOH / g and a hydroxyl value in the range of 1 to 100 mgKOH / g. Item 4. The thermosetting aqueous coating composition according to Item 3. The thermosetting aqueous coating composition according to claim 3 or 4, wherein the crosslinking agent (C) is a melamine resin and / or a block polyisocyanate compound. Based on 100 parts by weight of resin solid content in the thermosetting aqueous coating composition, 5 to 50 parts by weight of (A) component, 20 to 80 parts by weight of (B) component and (C) component as non-volatile content The thermosetting aqueous coating composition according to any one of claims 3 to 5, which is contained in an amount of 15 to 65 parts by weight. The thermosetting water-based paint composition according to any one of claims 3 to 6 is applied as a base coat paint to an object to be coated, and further a clear coat paint is applied onto the uncured base coat coated surface. And a clear coat is simultaneously cured. An intermediate coating is applied to the object to be coated, and the thermosetting aqueous coating composition according to any one of claims 3 to 6 is applied as a base coat coating on the uncured intermediate coating surface. A method for forming a multi-layer coating film, comprising: applying a clear coat paint on the uncured base coat coated surface and simultaneously curing three layers of the intermediate coat, base coat and clear coat. 9. The clear coat paint is an acrylic resin / melamine resin system, an acrylic resin / polyisocyanate curing agent system, an acrylic resin / block polyisocyanate curing agent system, or an acid group-containing resin / epoxy group-containing resin system paint. A method for forming a multilayer coating film. An article coated by the method according to any one of claims 7-9.