JP2004346294A - Low solvent type coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosetting coating composition using less amount of an organic solvent in the coating, excellent in appearance of the obtained coated film, such as smoothness, clear reflectance, transparency, etc., physical properties such as hardness, scratch resistance, etc., chemical properties such as solvent resistance, acid rain resistance, etc., and weather resistance, and further usable suitably in various uses as a low solvent type coating having a good storing stability, and provide further a clear coating for top coating of an automobile outer plate consisting of the thermosetting coating composition. <P>SOLUTION: This low solvent-type coating contains at least (a) a polymer having &ge;2 epoxy groups in a molecule on average, (b) a curing agent and (c) an organic solvent, and the curing agent (b) is an aliphatic tricarboxylic acid. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  TECHNICAL FIELD The present invention relates to a coating material used by dissolving a curable composition comprising a polymer having an epoxy group and a tricarboxylic acid in an organic solvent.

In recent years, the development of new coating materials for metal products such as the body surface of automobiles and aluminum wheels has caused a large amount of organic solvents to evaporate during the coating and baking processes of paint, causing pollution and contaminating the global environment. There is a problem.
Conventionally, acrylic melamine-based organic solvent-based paints are generally widely used on the outer surface of the body of automobiles, etc., but the solid content concentration is low because the paint uses a low-solids-type melamine resin as a crosslinking agent. , The number of processing steps is increasing. Further, if a thick film is to be obtained at one time, sagging of the coating occurs, and the coating is performed in several steps, so that there is a problem that the number of coating steps is increased.
Such a low solid type paint uses a large amount of an organic solvent. Therefore, a low solvent type paint having an organic solvent of 65% by mass or less is desired from an environmental point of view and further for simplifying a treatment process. Usually, paints having a solvent content of 50% by mass or less are called high solid paints and are used as environmentally friendly paints.

Due to rising environmental awareness in the field of paints, development of such high solid type paints, water-based paints, and powder paints has been actively conducted. Further, such development trends are being actively pursued in the automobile industry.
Among them, as an automotive top coat, various cross-linking forms using an addition reaction of an epoxy group and a carboxyl group have been proposed, but the use is required to have a remarkably high appearance quality, an improvement in surface gloss, and an improvement in surface smoothness. In addition, there is a demand for improved appearance, improved appearance such as high weather resistance, and improved film thickness for simplification of processing steps.
However, none of the conventional high solid type top coat paints satisfy these performances and storage stability. Further, there is a problem that high-quality gloss and smoothness cannot be obtained with a powder paint type paint or a water-based paint.

For example, Patent Document 1 discloses a composition comprising a low molecular weight polyepoxide, a polyfunctional curing agent synthesized by reacting a cyclic acid anhydride with a diester polyol comprising an epoxy group-containing acrylic polymer, an aliphatic dicarboxylic acid and a polyol. However, if an amine catalyst is not used in combination, hardness, acid resistance and solvent resistance are insufficient, and sufficient coating film performance cannot be obtained. As a result, the storage stability becomes insufficient due to the addition of the amine catalyst, and a high solid type top coat paint satisfying the above performance cannot be obtained.
On the other hand, a curable composition comprising an epoxy group-containing compound and a carboxyl group-containing compound has been used for powder coatings and the like. There are various combinations, but in the case of a powder coating or a water-dispersed slurry coating, the glycidyl group-containing acrylic resin is used because the resulting coating has excellent appearance, weather resistance, and stain resistance. And dibasic acids are preferably used.

The powder coating is usually manufactured by melt-kneading a resin, a curing agent, an additive, and the like at a temperature equal to or lower than the melting point of the curing agent, and then pulverizing the mixture. However, the melting point of these dibasic acids is high, usually at or above 130 ° C. Therefore, there is a problem that the temperature at which the paint melts is close to the temperature at which crosslinking starts, and the crosslinking reaction occurs almost simultaneously with the dissolution of the curing agent, and a sufficiently smooth coating film cannot be obtained.
Since these powder coatings contain almost no organic solvent, their expectations as environmentally friendly coatings are increasing, and they are already used in home appliances, road and building materials, automobile parts, water supply materials, steel furniture, etc. It has also begun to be used in some of the top coats of automobiles.
However, in the case of powder coatings, it is necessary to renew coating equipment when replacing with solvent-based coatings, and there are many problems to be solved, such as dust and bumps in the recycling use of coatings.
On the other hand, polybasic acid compounds having two or more carboxyl groups, such as adipic acid, sebacic acid, decanedicarboxylic acid, trimellitic acid, etc., are generally used as curing agents for low solvent type coatings such as high solid type coatings. There is a problem that the solubility in an organic solvent which is commonly used is low, and the solids concentration cannot be increased when blended with the glycidyl group-containing acrylic copolymer. Low-molecular-weight dicarboxylic acids having high solubility are not used for general purposes because they sublimate during curing and baking.

JP-A-01-165670

  The object of the present invention is to use a small amount of an organic solvent in a coating material, and to obtain a coating film having a smoothness, sharpness, appearance such as transparency, hardness, physical strength such as scratch resistance, solvent resistance, and the like. A thermosetting coating composition which is excellent in chemical properties such as acid rain resistance, and weather resistance, and which can be suitably used for various applications as a low solvent type coating having good storage stability, and further, the thermosetting coating composition It is an object of the present invention to provide a clear coating material for an automobile outer panel top coat.

  The present inventors have found that, by using an aliphatic tricarboxylic acid as a curing agent for a polymer having an average of two or more epoxy groups in a molecule, the solubility in an organic solvent is higher than other polycarboxylic acids. From this, it is possible to obtain a thermosetting low-solvent type paint, and when the paint system is applied to a top coat of an automobile outer panel, it has been found that the paint has high appearance, high quality, and excellent storage stability of the paint. The invention has been completed.

［但し、ｐ，ｒ，ｓは０〜８の整数、ｑは１〜９の整数、１≦ｐ＋ｑ＋ｒ＋ｓ≦９であって、ｒ＜ｓまたは（ｒ＝ｓかつｐ≦ｑ）である。］ That is, the present invention is as follows.
(1) At least a polymer (a) having an average of two or more epoxy groups in a molecule, a curing agent (b), and an organic solvent (c), wherein the curing agent (b) is an aliphatic tricarboxylic acid. A low-solvent type paint characterized by the following.
(2) The low solvent paint according to the above (1), wherein the concentration of the organic solvent (c) in the paint is 15 to 65% by mass.
(3) The low solvent type paint according to the above (1) or (2), wherein the curing agent (b) is an aliphatic tricarboxylic acid represented by the formula (1).

[However, p, r, and s are integers of 0-8, q is an integer of 1-9, 1 ≦ p + q + r + s ≦ 9, and r <s or (r = s and p ≦ q). ]

(4) The low solvent type paint according to the above (3), wherein the curing agent (b) is an aliphatic tricarboxylic acid wherein p + q + r + s = 3 in the formula (1).
(5) The low solvent according to the above (4), wherein the curing agent (b) is an aliphatic tricarboxylic acid wherein p = 1, q = 2 and r = s = 0 in the formula (1). Mold paint.
(6) a compound in which the organic solvent (c) has one or more groups selected from a ketone group, a hydroxyl group, an ether group and an ester group in the same molecule and / or a ketone group in the same molecule An organic solvent containing a compound having two or more groups selected from a hydroxyl group, an ether group and an ester group, wherein the proportion of the compound in the organic solvent is 1 to 100% by mass. The low solvent type paint according to any one of the above (1) to (5).

(7) The low solvent type paint according to any one of (1) to (6), wherein the polymer (a) having an average of two or more epoxy groups in the molecule is an epoxy group-containing acrylic resin polymer.
(8) The low solvent according to (7), wherein the epoxy group-containing acrylic resin polymer has an epoxy equivalent of 200 to 5,000 and a number average molecular weight in terms of styrene of 1,000 to 50,000. Mold paint.
(9) A low-solvent paint comprising an antioxidant added to the low-solvent paint according to any one of (1) to (8) in an amount of 10 mass ppm to 10 mass%.
(10) For a low solvent type paint, comprising a polymer (a) having an average of two or more epoxy groups in a molecule and a curing agent (b), wherein the curing agent is an aliphatic tricarboxylic acid. Curable composition.
(11) A clear paint for a top coat of an automobile outer panel, comprising the low-solvent paint according to any one of (1) to (9).

  The paint of the present invention has excellent compatibility and reactivity, good storage stability, and further excellent coatability. The coating film obtained by using the paint has an appearance such as smoothness, clarity, and transparency, hardness, impact resistance, bending resistance, physical strength such as scratch resistance, solvent resistance, and acid rain resistance. Excellent in chemical properties such as properties and weather resistance.

Hereinafter, the present invention will be described in detail.
The low solvent type paint of the present invention comprises at least a polymer (a) having an average of two or more epoxy groups in a molecule, a curing agent (b) composed of an aliphatic tricarboxylic acid, and (c) an organic solvent. First, the polymer (a) having an average of two or more epoxy groups in a molecule used in the present invention will be described.
The epoxy group in the present invention is a bonding group having an epoxy structure (a three-membered ring structure composed of carbon-oxygen-carbon), and the carbon-carbon portion may be a part of a linear or branched hydrocarbon structure. It may be a part of a hydrocarbon structure forming a cyclic structure such as a five-membered ring or a six-membered ring. Further, a halogen such as fluorine, chlorine or bromine, or a functional group such as a hydroxyl group or a nitrile group may be bonded to these hydrocarbon structures. Further, an alkyl group such as a methyl group, a halogen, or the like may be bonded to a carbon atom forming the epoxy structure. These epoxy groups include a glycidyl group and a bonding group represented by the following formula (2). In particular, a glycidyl group is desirable because it is industrially produced from allyl alcohol or epichlorohydrin and is easily available.

（式中、Ｒ₁ 及びＲ₂ は炭素数１〜１２の炭化水素基を、ｍは０〜３の整数表す。）

(In the formula, R ₁ and R ₂ represent a hydrocarbon group having 1 to 12 carbon atoms, and m represents an integer of 0 to _3. )

  The polymer (a) having an average of two or more epoxy groups in a molecule used in the present invention includes, for example, a polymer having a polyester skeleton, a polymer having a polyamide skeleton, a poly (meth) acrylate, and a polyvinyl acetate. System, vinyl acetate-acrylic system, vinyl acetate-mixed trialkyl acetate vinyl ester system, ethylene vinyl acetate system, silicone system, polybutadiene system, styrene butadiene system, NBR system, polyvinyl chloride system, chlorinated polypropylene system, polyethylene system, Examples include polymers such as polystyrene, vinylidene chloride, polystyrene- (meth) acrylate, and styrene-maleic anhydride, and silicone-modified acrylic, fluorine-acryl, acrylic silicon, and epoxy-acryl. Modified polymer, crosslinkable resin, core / shell type resin, etc. Included, it can be used alone or in combination of two or more thereof. Among them, epoxy group-containing acrylic resins such as poly (meth) acrylate, vinyl acetate-acryl, polystyrene- (meth) acrylate, silicone-modified acrylic, fluorine-acryl, acrylic silicon, and epoxy-acryl. Coalescing can be suitably used. (Meth) acrylate expressed in the present invention means acrylate or methacrylate.

The polymer (a) is a polymer of one or more polymerizable monomers having an epoxy group, or one or two or more polymerizable monomers having an epoxy group and has no epoxy group. It is a copolymer of one or more polymerizable monomers. As the polymerizable monomer having an epoxy group, for example, a compound having a glycidyl group or a methylglycidyl group represented by the following formula (3) can be particularly preferably used.

Examples of the polymerizable monomer having an epoxy group include glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 2,3-epoxycyclohexyl (meth) acrylate, and 3,4-epoxycyclohexyl (meth). Examples include (meth) acrylates such as acrylates, glycidyl ether and methyl glycidyl ether of allyl alcohol, N-glycidyl acrylamide, and glycidyl vinyl sulfonate. One or more of these monomers can be used. Among them, glycidyl methacrylate is easily available on an industrial scale, and a glycidyl group-containing (meth) acrylic resin, which is a copolymer using the glycidyl methacrylate, provides a cured product having improved durability such as weather resistance and abrasion resistance. Excellent and particularly preferred when the curable composition of the present invention is used for paint applications.
The polymerizable monomer having an epoxy group is preferably used in the range of 5 to 70% by mass of the total polymerizable monomer.

  Examples of the polymerizable monomer having no epoxy group, which can be copolymerized with the polymerizable monomer having an epoxy group, include (meth) acrylates, (meth) acrylamide-based monomers, and vinyl cyanides. No. Examples of the (meth) acrylate include alkyl (meth) acrylates having 1 to 18 carbon atoms in an alkyl group, hydroxyalkyl (meth) acrylates having 1 to 18 carbon atoms in a hydroxyalkyl group, and ethylene. (Poly) oxyethylene (meth) acrylate having 1 to 100 oxide groups, (poly) oxypropylene (meth) acrylate having 1 to 100 propylene oxide groups, and 1 to 100 ethylene oxide groups (Poly) oxyethylene di (meth) acrylate. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n- (meth) acrylate. Butyl, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, ( Octyl (meth) acrylate, 2-ethyloctyl (meth) acrylate, benzyl (meth) acrylate, dodecyl (meth) acrylate, phenyl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate And the like. Specific examples of the hydroxyalkyl (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and (meth) acrylic acid 2 -Hydroxycyclohexyl, hydroxydodecyl (meth) acrylate and the like.

  Specific examples of (poly) oxyethylene (meth) acrylate include ethylene glycol (meth) acrylate, ethylene glycol methoxy (meth) acrylate, diethylene glycol (meth) acrylate, diethylene glycol methoxy (meth) acrylate, (meth) Examples thereof include tetraethylene glycol acrylate and tetraethylene glycol methoxy (meth) acrylate. Specific examples of (poly) oxylopylene (meth) acrylate include propylene glycol (meth) acrylate, propylene glycol methoxy (meth) acrylate, dipropylene glycol (meth) acrylate, and dipropylene glycol methoxy (meth) acrylate. , Tetrapropylene glycol (meth) acrylate, tetrapropylene glycol methoxy (meth) acrylate, and the like.

Specific examples of (poly) oxyethylene di (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene di (meth) acrylate. Ethylene glycol and the like.
Examples of the (meth) acrylamide-based monomer include (meth) acrylamide, N-methylol (meth) acrylamide, and N-butoxymethyl (meth) acrylamide. Examples of the vinyl cyanide include (meth) acrylonitrile and the like. There is.
Further, as the polymerizable monomer having no epoxy group, an ethylenically unsaturated carboxylic acid monomer may be used. Examples include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, maleic anhydride, and half-esters of itaconic acid, fumaric acid, and maleic acid.
Further, an ethylenically unsaturated monomer having a cationic group may be used. Examples thereof include dimethylaminoethyl (meth) acrylate and its salts, diethylaminoethyl (meth) acrylate and its salts, dimethylaminopropyl (meth) acrylate and its salts, dimethylaminomethyl (meth) acrylamide and its salts, Examples thereof include dimethylaminoethyl (meth) acrylamide and a salt thereof, dimethylaminopropyl (meth) acrylamide and a salt thereof, and vinyl pyridine.

  Specific examples of the polymerizable monomer having no epoxy group other than the above, for example, ethylene, propylene, olefins such as isobutylene, dienes such as butadiene, vinyl chloride, haloolefins such as vinylidene chloride, vinyl acetate, Vinyl carboxylate esters such as vinyl propionate, vinyl n-butyrate, vinyl benzoate, vinyl pt-butyl benzoate, vinyl pivalate, vinyl 2-ethylhexanoate, mixed trialkyl vinyl acetate and vinyl laurate; Carboxylic acid isopropenyl esters such as isopropenyl acetate and isopropenyl propionate; vinyl ethers such as ethyl vinyl ether, isobutyl vinyl ether and cyclohexyl vinyl ether; aromatic vinyl compounds such as styrene, α-methylstyrene and vinyl toluene; Esters such as dialkyl acrylates and dialkyl itaconates; allyl esters such as allyl acetate and allyl benzoate; allyl ethers such as allyl ethyl ether and allyl phenyl ether; and γ- (meth) acryloxypropyltrimethoxysilane , Vinylmethyldiethoxysilane, vinylmethyldimethoxysilane, vinyldimethylethoxysilane, vinyldimethylmethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4- (meth) acryloyloxy-2,2,6,6-tetramethyl Piperidine, 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, perfluoromethyl (meth) acrylate, perfluoropropyl (meth) acrylate, perfluoropropylmethyl (Meth) acrylate, vinylpyrrolidone, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxypropyl methacrylate, methylpropanesulfonic acrylamide, divinyl Examples thereof include benzene, vinyl oxazoline, lauryl vinyl ether, halogen-containing vinyl monomers, silicon-containing vinyl monomers, isocyanate group-containing vinyl monomers, and copolymerizable polyester resins having an unsaturated bond. One or more of these monomers can be used.

In the present invention, a copolymer containing methyl methacrylate and glycidyl methacrylate as main components, a copolymer containing methyl methacrylate, glycidyl methacrylate, and styrene as main components, further, methyl methacrylate, glycidyl methacrylate Glycidyl group-containing acrylic resin polymers, such as butyl (meth) acrylate and styrene copolymers, are excellent in durability such as weather resistance and abrasion resistance, and are used in the coatings field, especially in low solvent. When it is used in the field of mold paints, it can be particularly preferably used.
In the production of the curable composition of the present invention, the production method of the resin may be any method, but usually, a polymerizable monomer having an epoxy group, a polymerizable monomer having no epoxy group, an initiator, and Polymerization is carried out using a reducing agent or the like as appropriate. Any of radical polymerization, anionic polymerization, cationic polymerization and the like may be used, but radical polymerization is preferable, and it is obtained by bulk polymerization, solution polymerization, suspension polymerization or the like.
The molecular weight of the polymer (a) having an average of two or more epoxy groups in the molecule of the present invention is 1 in terms of styrene in terms of styrene in terms of film properties such as acid resistance and solvent resistance of the film. It is preferably at least 000, and more preferably at most 50,000 from the viewpoint of the viscosity of the paint after dilution in a solvent. It is more preferably from 1,000 to 10,000, particularly preferably from 1,500 to 8,000.

Further, the epoxy equivalent of the polymer (a) is preferably in the range of 200 to 5,000 g / equivalent, more preferably in the range of 200 to 1,500 g / equivalent, and more preferably in the range of 250 to 1,000 g, from the viewpoint of the adhesion of the coating film. / Equivalent range is particularly preferred.
The average number of epoxy groups contained in the polymer (a) can be obtained by dividing the above-mentioned number average molecular weight by the above-mentioned epoxy equivalent.
Further, the melt index of the polymer (a) is preferably 10 g / 10 min or more from the viewpoint of the viscosity of the coating material after dilution with a solvent, and from the viewpoint of the film properties such as acid resistance and solvent resistance of the coating film. It is preferably at most 200 g / 10 min, more preferably at 15 to 150 g / 10 min, particularly preferably at 20 to 100 g / 10 min.
As the polymer (a) having an average of two or more epoxy groups in a molecule used in the present invention (hereinafter sometimes simply referred to as polymer (a)), other than the above, for example, the above-mentioned epoxy group A compound having an epoxy group via an ester bond, a compound having an epoxy group derived from amines or isocyanuric acid directly bonded to a nitrogen atom, an alicyclic epoxy group-containing compound, etc. And a polymer (a) derived therefrom.

  Examples of the epoxy compound having the glycidyl group via an ether bond include, for example, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, butanediol diglycidyl ether, pentanediol diglycidyl ether, neopentyl glycol diglycidyl ether, hexanediol Diglycidyl ether, cyclopentanediol diglycidyl ether, cyclohexanediol diglycidyl ether, cyclohexane dimethanol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, diethylene glycol diglycidyl ether, trimethylolpropane triglycidyl Ether, pentaerythritol triglycidyl ether, Diglycidyl ether derived from droquinone, diglycidyl ether derived from resorcinol, diglycidyl ether derived from catechol, diglycidyl ether derived from bisphenol A, diglycidyl ether derived from bisphenol F, bisphenol AD Derived from diglycidyl ether, derived from bisphenol S, derived from 4,4'-dihydroxybiphenyl, derived from 3,3 ', 5,5'-tetramethyldihydroxybiphenyl Diglycidyl ether, glycidyl ether compound derived from phenol novolak resin, glycidyl compound derived from cresol novolak resin, and halides and oligomers thereof And the like. Among these, diglycidyl ether derived from bisphenol A is generally used as a “bisphenol A type epoxy resin” in a liquid or solid state depending on the molecular weight, and is the most widely used compound and is easily available. And can be suitably used as the polymer (a) component of the present invention.

Examples of the compound having a glycidyl group via an ester bond include diglycidyl phthalate, diglycidyl maleate, diglycidyl terephthalate, diglycidyl isophthalate, diglycidyl naphthalenedicarboxylate, diglycidyl biphenyldicarboxylate, diglycidyl succinate, diglycidyl fumarate, and glutaric acid. Acid glycidyl, diglycidyl adipate, diglycidyl suberate, diglycidyl sebacate, diglycidyl decanedicarboxylate, diglycidyl cyclohexanedicarboxylate, triglycidyl trimellitate, glycidyl esters derived from dimer acid, and halides and oligomers thereof. Can be
Examples of the compound having a glycidyl group bonded to a nitrogen atom include triglycidyl isocyanurate, tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, diglycidylaniline, diglycidyltoluidine, tetraglycidyl metaxylenediamine, tetraglycidylhexamethylenediamine, and tetraglycidyl. Examples include bisaminomethylcyclohexane, glycidyl compounds derived from hydantoin compounds, and halides and oligomers thereof.

Examples of the alicyclic epoxy compound include bis (3,4-epoxycyclohexyl) adipate, bis (3,4-epoxycyclohexyl) terephthalate, 3,4-epoxycyclohexyl-3,4-epoxycyclohexanecarboxylate, 4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis (3,4-epoxycyclohexylmethyl) oxalate, bis (3,4-epoxy-6-methylcyclohexyl) adipate, bis (3,4-epoxycyclohexyl) Methyl) pimelate, vinylcyclohexenedioxide and the like.
Further, the polymer (a) has an epoxy group such as a glycidyl group in a terminal, a side chain or a branched chain, and has a number average molecular weight in terms of styrene of preferably from 1,000 to 50,000, more preferably from 1,000 to 50,000. 10,000 is more preferable, and 1,500 to 8,000 is particularly preferable.
The epoxy equivalent of the polymer (a) is preferably in the range of 200 to 5,000 g / equivalent, more preferably in the range of 200 to 1,500 g / equivalent, and particularly preferably in the range of 250 to 1,000 g / equivalent.
The epoxy group-containing polymer (a) of the present invention may be a polymer derived from using the above epoxy compound alone or as a mixture of two or more, depending on various applications and desired physical properties.

  The curing agent (b) of the present invention means a compound that can react with an epoxy group to form a crosslinked structure. The curing agent (b) used in the present invention is an aliphatic tricarboxylic acid and means a compound in which three carboxyl groups are bonded to a linear or branched hydrocarbon. As the linear one, 1,2,3-propanetricarboxylic acid, 1,2,3-butanetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,3-pentanetricarboxylic acid, 1,2 1,4-pentanetricarboxylic acid, 1,2,5-pentanetricarboxylic acid, 1,3,4-pentanetricarboxylic acid, 1,3,5-pentanetricarboxylic acid, 2,3,4-pentanetricarboxylic acid, 1,2 1,5-hexanetricarboxylic acid, 1,1,6-hexanetricarboxylic acid, 1,3,5-hexanetricarboxylic acid, 1,2,6-hexanetricarboxylic acid, 1,3,3-hexanetricarboxylic acid, 1,2 1,4-hexanetricarboxylic acid, 2,4,4-hexanetricarboxylic acid, 1,4,5-hexanetricarboxylic acid, 1,3,4-hexanetricarboxylic acid, 3,6-hexanetricarboxylic acid, 2,3,5-hexanetricarboxylic acid, 1,4,8-octanetricarboxylic acid, 1,5,10-nonanetricarboxylic acid, 1,6,12-dodecanetricarboxylic acid, 7,13-tridecanetricarboxylic acid and the like, as branched-chain ones, are 2-carboxymethyl-1,3-propanedicarboxylic acid, 3-carboxymethyl-1,5-pentanedicarboxylic acid, 3-carboxyethyl-1 , 5-pentanedicarboxylic acid, 3-carboxyethyl-1,6-hexanedicarboxylic acid, and the like. Among them, an aliphatic tricarboxylic acid represented by the following formula (1) is preferable.

［但し、ｐ，ｒ，ｓは０〜８の整数、ｑは１〜９の整数、１≦ｐ＋ｑ＋ｒ＋ｓ≦９であって、かつｒ＜ｓまたは（ｒ＝ｓかつｐ≦ｑ）］

[However, p, r, and s are integers of 0 to 8, q is an integer of 1 to 9, 1 ≦ p + q + r + s ≦ 9, and r <s or (r = s and p ≦ q)]

  Examples of the water-soluble aliphatic tricarboxylic acid represented by the above formula (1) include 1,2,4-butanetricarboxylic acid, 1,2,4-pentanetricarboxylic acid, 1,2,5-pentanetricarboxylic acid, 1,3,4-pentanetricarboxylic acid, 1,3,5-pentanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3,5-hexanetricarboxylic acid, 1,2,6-hexanetricarboxylic acid, 1,2,4-hexanetricarboxylic acid, 1,4,5-hexanetricarboxylic acid, 1,3,4-hexanetricarboxylic acid, 1,3,6-hexanetricarboxylic acid, 2,3,5-hexanetricarboxylic acid, Examples thereof include 1,4,8-octanetricarboxylic acid, 1,5,10-nonanetricarboxylic acid, and 1,6,12-dodecanetricarboxylic acid. Among them, 1,2,5-, 1,3,5-, 1,2,6-, 1,2,4-, 1,4,5-, 1,3,4-, and 1,3, 6-hexanetricarboxylic acid is preferred because of its high thermal stability. In particular, 1,3,6-hexanetricarboxylic acid has a melting point of about 110 ° C., and has excellent physical properties such as excellent curing characteristics, as well as being easily available industrially as described below. Is most preferred.

In the present invention, the above-mentioned aliphatic tricarboxylic acids may be used alone or in combination of two or more.
The method for producing the aliphatic tricarboxylic acid used in the present invention is not particularly limited. 1,3,6-hexanetricarboxylic acid is, for example, trimerizing acrylonitrile industrially produced on a large scale, or converting a trinitrile compound obtained at the time of producing adiponitrile by electrolytic dimerization of acrylonitrile into sulfuric acid or the like. It can be easily obtained by hydrolysis using an alkali such as an acid or caustic soda.
Further, in the present invention, a curing agent other than the aliphatic tricarboxylic acid, such as a carboxyl group-containing compound, an acid anhydride, or a curing agent for a general epoxy resin capable of forming a crosslinked structure by reacting with an epoxy group other than these. One or more of these may be used in combination with an aliphatic tricarboxylic acid depending on various uses.

The carboxyl group-containing compound that can be used as a curing agent other than the aliphatic tricarboxylic acid is a compound having two or more carboxyl groups in a molecule, and cannot be said unconditionally depending on the ratio of using the curing agent, As long as it has solubility in a solvent, it can be suitably used, and particularly, aliphatic, aromatic, alicyclic polyvalent carboxylic acids and the like can be suitably used.
Examples of the aliphatic polycarboxylic acid include glutaric acid, adipic acid, suberic acid, sebacic acid, azelaic acid, decanedicarboxylic acid, hexadecanedicarboxylic acid, eicosandicarboxylic acid and tetraicosandicarboxylic acid, and acrylic acid and methacrylic acid. Copolymer, polyester, polyamide and the like.
Examples of the aromatic polycarboxylic acid include isophthalic acid, phthalic acid, trimellitic acid, and 1,3,5-benzenetricarboxylic acid. Further, examples of the alicyclic polycarboxylic acid include hexahydrophthalic acid, tetrahydrophthalic acid, 1,4-cyclohexanedicarboxylic acid, and 1,2,3,4-cyclobutanetetracarboxylic acid.

Examples of the acid anhydride include anhydrides of the above-mentioned aliphatic, aromatic, and alicyclic polycarboxylic acids, and anhydrides of these polycarboxylic acids and monovalent carboxylic acids.
Further, as a general epoxy resin curing agent capable of forming a crosslinked structure by reacting with the above-mentioned epoxy group, dicyandiamides, dihydrazides, imidazoles, polyhydrates and the like can be mentioned. In addition, triazines such as tris (alkoxycarbonylamino) triazine, polycarboxylic acids containing an organosilyl group, acrylic resins having two or more carboxyl groups in a molecule, and resins such as polyester resins are also other than aliphatic tricarboxylic acids. Can be used as a curing agent.
The content of the aliphatic tricarboxylic acid in the total amount of the curing agent (b) used in the present invention is 0.1 to 100% by mass. It is preferably from 1 to 100% by mass, particularly preferably from 10 to 100% by mass, most preferably from 50 to 100% by mass. When the content of the aliphatic tricarboxylic acid is 0.1% by mass or less, the curing rate tends to decrease, and the mechanical properties of the obtained cured product tend to decrease.

The aliphatic tricarboxylic acid used in the low solvent type paint of the present invention depends on the case where it is used in combination with another curing agent. The groups can be used in 0.01 to 5 equivalents. In particular, in order to remarkably express the curability of the aliphatic tricarboxylic acid and obtain a cured product having improved mechanical properties with improved crosslink density, 0.1 to 3.0 equivalents are preferable, and 0.3 to 2 equivalents are preferable. 0.0 equivalent is more preferred, and 0.5 to 1.5 equivalent is particularly preferred.
In general, a curable composition comprising an epoxy compound and a carboxyl group-containing compound has a carboxyl group to an epoxy group in an equivalent ratio of 1, or a composition ratio in the vicinity thereof, and the equivalent ratio largely deviates from 1. In such a case, the gel fraction of the cured product tends to decrease. In the low solvent type paint of the present invention, even when the equivalence ratio deviates greatly from 1, a sufficient gel fraction is exhibited by curing for a short time.

In the present invention, when the polymer (a) having an average of two or more epoxy groups in the molecule has a hydroxyl group and / or a carboxyl group, at least one functional group capable of reacting with the hydroxyl group or the carboxyl group An auxiliary cross-linking agent having the following or a modifier can be added. These include blocked isocyanates, alkylated melamine formaldehyde resins, alkylated glycoluril resins, hydantoin epoxides, triglycidyl isocyanurate, aliphatic glycidyl ethers, aliphatic glycidyl esters, cycloaliphatic epoxides, hydrogenated bisphenol A and epichloro Includes epoxy resins derived from hydrin, oxazolines, 2- and 4-functional β-hydroxyalkylamides, and the like.
In addition, the low solvent type paint of the present invention includes a compound having one epoxy group in the molecule, an acrylic resin having one carboxyl group and / or one or more hydroxyl groups, a polyester resin, or other. And a compound such as a resin that is liquid at room temperature can also be added.

The organic solvent (c) of the present invention will be described.
The organic solvent (c) used in the low solvent type paint of the present invention means an organic solvent capable of dissolving both the polymer (a) having an average of two or more epoxy groups and the curing agent (b). .
The organic solvent (c) used in the present invention is a compound having one or two or more groups selected from a ketone group, a hydroxyl group, an ether group and an ester group in one molecule and / or Organic compound containing a compound having two or more groups selected from a ketone group, a hydroxyl group, an ether group and an ester group, wherein the proportion of the compound in the organic solvent is 1 to 100% by mass. preferable.
Specific examples of the compound having a ketone group include acetone, methyl acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, methyl-n-amyl ketone, diethyl ketone, diisobutyl ketone, and acetone oil. , Acetonylacetone, diacetone alcohol, mesityl oxide, holon, isophorone, acetophenone, and the like. Preferred are acetone, methyl acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, diethyl ketone, diacetone alcohol, mesityl oxide, and acetonylacetone. Examples of the compound having a ketone group include those having a linear, branched, cyclic, aliphatic, aromatic, saturated, unsaturated structure, or the like.
Among compounds having a ketone group, the solubility of the curing agent (b) decreases as the number of carbon atoms increases. Therefore, the number of carbon atoms is preferably 8 or less, more preferably 7 or less, and particularly preferably 6 carbon atoms. It is a compound having the following ketone group.

Next, as the compound having a hydroxyl group, specifically, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-amyl alcohol, isoamino alcohol, tert-butyl alcohol, 2-methyl-1-butanol , Secondary amyl alcohol, 3-pentanol, n-hexanol, methyl amyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, 2-octanol, 2-ethylhexanol, 3,5,5 -Trimethylhexanol, nonanol, n-decanol, undecanol, n-dodecanol, trimethylnonyl alcohol, tetradecanol, cyclohexanol, 2-methylcyclohexanol, furfuryl alcohol, tetrahydrofur Lil alcohol, alpha-terpineol, benzyl alcohol, monoacetin, diacetin, triacetin, fusel oils, and the like can be suitably used.
Examples of the compound having a hydroxyl group include those having a linear, branched, cyclic, aliphatic, aromatic, saturated, unsaturated structure, or the like.
Among the compounds having a hydroxyl group, the solubility of the curing agent (b) decreases as the number of carbon atoms increases, so that the number of carbon atoms is preferably 8 or less, more preferably 7 or less, and particularly preferably 6 or less. It is a compound having a hydroxyl group.

Further, polyhydric alcohols and derivatives thereof can also be preferably used. Specifically, ethylene glycol, methyl cellosolve, methyl cellosolve acetate, ethyl cellosolve, diethyl cellosolve, cellosolve acetate, ethylene glycol isopropyl ether, butyl cellosolve, dibutyl cellosolve, butyl cellosolve acetate, ethylene glycol isoamyl ether, hexyl cellosolve, methoxy methoxy ethanol, ethylene Glycol monoacetate, ethylene glycol diacetate, monoglycol formate, digitsan glycol, diethylene glycol, methyl carbitol, ethyl carbitol, carbitol acetate, diethylene glycol methyl ether, diethyl carbitol, diethylene glycol acetate, triethylene glycol monomethyl ether, propylene glycol Coal, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, 1-butoxyethoxypropanol, propylene glycol monoacetate, propylene glycol formate diester, propylene glycol acetate diester, 1-methoxy-2-propanol acetate, 1- Ethoxy-2-propanol acetate, propylene glycol-n-propyl ether, propylene glycol isopropyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, trimethylene glycol, butanediol, hexylene glycol, octylene Glycol, glyceryl monoacetate, etc. It is. These polyhydric alcohols and derivatives of polyhydric alcohols are those derived from polyhydric alcohols in addition to those having two or more hydroxyl groups in the same molecule and having hydroxyl, ether, and ester groups in the same molecule. Those having one kind or two or more kinds at the same time are also included.
The above-mentioned polyhydric alcohol and its derivative preferably have a small ratio of the number of carbon atoms to the total of each group. That is, from the viewpoint of the solubility of the curing agent (c), the number of carbon atoms is preferably 5 or less, more preferably 4 or less, and particularly preferably 3 or less.

Next, specific examples of the compound having an ether group include ethyl ether, isopropyl ether, n-butyl ether, hexyl ether, 1,2-propylene oxide, dioxolan, tetrahydrofuran, 4-methyldioxolan, 1,4-dioxane, and dimethyldioxane. , Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monobutyl ether, ethylene glycol mono-n-hexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethyl butyl ether, ethylene glycol dibutyl ether , Diethylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol Monobutylether, diethylene glycol dibutyl ether, diethylene glycol mono -n- hexyl ether, ethoxy triglycol, monopropylene glycol methyl ether, dipropylene glycol methyl ether, tripropylene glycol methyl ether, terpene ether, or the like can be suitably used.
The compound having an ether group preferably has a small ratio of the number of carbon atoms to the total of the ether group and other groups. That is, from the viewpoint of the solubility of the curing agent (c), the number of carbon atoms is preferably 5 or less, more preferably 4 or less, and particularly preferably 3 or less.

Next, regarding the compound having an ester group, specifically, methyl formate, ethyl formate, propyl formate, butyl formate, isoamyl formate, glycol formate, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, isobutyl acetate, -Amyl, isoamyl acetate, 3-methoxybutyl acetate, methyl amyl acetate, 2-ethyl amyl acetate, 2-ethylhexyl acetate, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, methyl acetoacetate, ethyl acetoacetate, ethylene glycol monomethyl ether acetate, acetic acid It can be suitably used in ethylene glycol monoethyl ether, methyl propionate, ethyl propionate, butyl propionate, isoamyl propionate, methyl lactate, ethyl lactate, butyl lactate, and the like. More preferred are ester compounds, which are compounds having one or more ether groups and hydroxyl groups in the same molecule.
The boiling point of the organic solvent (c) is preferably in the range of 20 to 250C, more preferably in the range of 25 to 200C, in any of the compounds having a ketone group, a hydroxyl group, an ether group and an ester group. Particularly preferably, it is 30 to 180 ° C. When the boiling point of these organic solvents is in the range of 20 to 250 ° C., the coating is dried too quickly, and no clogging of nozzles occurs in spray coating or unevenness of the coating film surface does not occur. If the temperature is too high, the drying temperature of the coating film will not be too high, and the coating film will not be discolored during baking, or the coating film will not be dried sufficiently and no solvent will remain in the coating film after baking.

The organic solvent (c) of the present invention may be used alone or in combination of two or more. Further, the total content of the compound having a ketone group, a hydroxyl group, an ether group and / or an ester group in the organic solvent used in the present invention may be a polymer (a) having an average of two or more epoxy groups and a curing agent (b). The solubility is preferably 1 to 100% by mass, more preferably 5 to 100% by mass, still more preferably 30 to 100% by mass, and particularly preferably 40 to 100% by mass.
As the organic solvent (c) of the present invention, one or more other organic solvents can be used in combination as long as the effects of the present invention are not impaired. For example, amides such as N, N'-dimethylformamide, formamide, and acetamide; hydrocarbons such as toluene, xylene, ethylbenzene, cyclohexane, and n-hexane; and halogenated hydrocarbons such as methylene chloride and ethyl chloride. Isopropyl chloride, chlorobenzene, dichlorobenzene and the like. These organic solvents are not limited to those listed above. The above-mentioned amides, hydrocarbons, and halogenated hydrocarbons are added to adjust the drying property of the paint, or to adjust or improve the viscosity, fluidity, handling property, paintability, etc. of the paint. Can be added in the range of 0 to 70% by mass of the total content of the organic solvent. When the amount exceeds 70% by mass in the organic solvent, the solubility of the curing agent (b) is reduced, so that a uniform paint cannot be obtained or the curing agent (b) precipitates during storage of the paint. .

The solvent concentration of the organic solvent (c) in the coating composition of the present invention is preferably in the range of 15 to 65% by mass. It is more preferably in the range of 20 to 60% by mass, and particularly preferably in the range of 25 to 55% by mass. When the concentration of the organic solvent (c) in the coating material is less than 15% by mass, the solubility of the polymer (a) having an average of two or more epoxy groups in the molecule and the curing agent (b) becomes poor, and the coating material becomes poor. It is not preferable because it becomes uneven. When the concentration of the organic solvent exceeds 65% by mass in the coating, the concentration of the solid content is low, so that the number of treatment steps becomes large. Further, if a thick film is to be obtained at one time, sagging of the coating occurs, and the coating is performed in several steps, so that there is a problem that the number of coating steps is increased.
Further, a reactive diluent is blended with the polymer (a), the curing agent (b), and the organic solvent (c) of the present invention in a range that does not hinder the effects of the present invention, and the solid content concentration is adjusted, or It can also be used for the purpose of adjusting the viscosity of the paint, controlling the crosslinkability, and the like. Specific examples of the reactive diluent include butyl glycidyl ether allyl glycidyl ether, 2-ethylhexyl glycidyl ether, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, p-sec-butylphenyl glycidyl ether, glycidyl methacrylate, and tertiary carboxylic acid. Acid glycidyl ester, etc., can be used preferably.

In the present invention, it is preferable to use an antioxidant.
The antioxidant used in the present invention has a function of suppressing the yellowing of the coating film due to heat when the low-solvent coating material of the present invention is applied to an object to be coated and then baked and cured. Things. Examples of antioxidants (heat stabilizers) include hindered phenol-based, phosphorus-based, lactone-based, vitamin E-based, and sulfur-based ones. Specific examples include Irganox 1010, Irganox 1222, Irganox 259, Irganox 565, Irganox 1520L, Irganox PS800FL, Irgafoss P-EPQ, Irgafoss 38 (all commercially available from Ciba Specialty Chemicals). .
The addition rate of the antioxidant is preferably 10% by mass to 10% by mass with respect to the low solvent type paint. More preferably, it is 100 mass ppm to 8 mass%, particularly preferably 1000 mass ppm to 5 mass%. If the addition rate is less than 10 ppm by mass, a sufficient antioxidant effect cannot be obtained, and yellowing of the coating film occurs during baking and curing of the coating film, which is not preferable. If the addition ratio exceeds 10% by mass, the coloring of the coating film due to the coloring of the antioxidant itself is not preferred. Further, since the addition ratio of the antioxidant is too high, the physical properties of the coating film are deteriorated, which is not preferable.

  Furthermore, the low solvent type paint of the present invention may be used in combination with additives usually used in paints and the like according to various applications, such as dispersants, dispersing aids, curing accelerators (curing catalysts), fillers and reinforcing agents, and pigments. If necessary, agents capable of preventing deterioration of the coating due to ultraviolet rays, such as a release agent, a flow control agent, a plasticizer, and an ultraviolet absorber, and a water-proofing agent can be added. Examples of dispersants include alkali metal salts, amine salts and ammonium salts of polycarboxylic acids, polyvinyl alcohol, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene alcohol ether, and polyoxyethylene. Sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, sorbitan fatty acid ester, glycerin sorbitan fatty acid ester, alkali metal salt of alkyl sulfonic acid, sodium pyrophosphate, sodium hexametaphosphate and the like. % By mass.

  Examples of the curing accelerator include imidazoles such as 2-ethyl-4-methylimidazole, 2-methylimidazole, 1-benzyl-2-methylimidazole, dimethylcyclohexylamine, benzyldimethylamine, and tris (diaminomethyl) phenol. Tertiary amines, diazabicycloalkenes such as 1,8-diazabicyclo [5.4.0] undecene-7 and salts thereof, zinc octylate, alkyl titanate compounds, tin octylate, monoalkylstannic acid, etc. Organometallic compounds such as tin compounds, aluminum acetylacetone complexes; organophosphorus compounds such as triphenylphosphine and triphenyl phosphite; boron trifluoride; boron trifluoride diethyl ether complex; boron trifluoride piperidine complex; Phenylborate Boron compounds, zinc halides, metal halides such as stannic chloride, quaternary ammonium compounds, alkali metal alcoholates such as sodium alcoholate of 2,4-dihydroxy-3-hydroxymethylpentane, anacardic acid and Examples thereof include salts thereof, cardol, cardanol, phenol, nonylphenol, phenols such as cresol, and blocked strong acid catalysts.

Examples of fillers and reinforcing agents include coal tar, bitumen, woven fabric, glass fiber, asbestos fiber, boron fiber, carbon fiber, aramid fiber, mineral silicate, mica, quartz powder, aluminum hydroxide, bentonite, kaolin, and silicate aerogel. And metal powders such as aluminum powder and iron powder.
Pigments include azo pigments, copper phthalocyanine pigments, basic dye lakes, acid dye lakes, mordant dye pigments, construction dye pigments, quinacridone pigments, dioxazine pigments, carbon black, chromate salts, ferrocyanes , Titanium oxide, mica powder, pearlite, selenium sulfide compound, silicate, carbonate such as calcium carbonate, phosphate, metal powder, etc., coloring pigments, barium sulfate, barium carbonate, gypsum, alumina white, clay, silica , Talc, calcium silicate, magnesium carbonate and the like. Silica may be added as a gloss modifier for the coating.

Examples of the release agent and the flow control agent include silicone, aerosil, colloidal hydrous aluminum silicate, wax, paraffin emulsion, stearate such as calcium stearate, calcium carbonate, and talc.
Further, as a plasticizer, pine oil, low-viscosity liquid polymer, rubbery substance, tar, polysulfide, urethane prepolymer, polyol, diethyl phthalate, dibutyl phthalate, polymer of epichlorohydrin, dioctyl phthalate, dioctyl adipate, tricresyl phosphate And the like.
Examples of the ultraviolet absorber include benzotriazole-based, triazine-based, benzophenone-based, benzoate-based, and hindered amine-based light stabilizers such as tinuvin (Tinuvin, commercially available from Ciba Specialty Chemicals). For example, Tinuvin 144, Tinuvin 234, Tinuvin 900, Tinuvin P, Tinuvin 329, Tinuvin 1577, Tinuvin 120 (all are commercially available from Ciba Specialty Chemicals), and the like.
Examples of the waterproofing agent include formalin, hexamine, melamine resin, urea resin, glyoxal and the like.

  Further, a dryer such as cobalt naphthenate, an anti-skinning agent such as methoxyphenol and cyclohexane oxime, a thickening agent such as highly polymerized linseed oil, organic bentonite and silica, an anti-side agent such as benzoin, Modaflow (manufactured by Monsanto Co.) ), Resiflow (Worlee), Acronal (Acronal, BASF), etc., antimony trioxide, bromo compounds, flame retardants such as aluminum hydroxide, dyes, waxes, antioxidants (antioxidants). Oxidizing agents), light stabilizers, radical scavengers, heat stabilizers, defoamers such as polyglycols, fatty acid esters, phosphate esters, silicone oils, degassing agents (degassing agents), acrylic oligomers, funnel oils, Leveling agents such as dicyandiamide and urea, spreading agents, coloring agents, and dioxide Tongue, viscosity adjuster, pH adjuster, preservative, emulsifier, surfactant, wetting agent, film forming aid, rust inhibitor, surface conditioner, matting agent, biocide, biocide, bactericide, flow Spreading aids, neutralizers, amines, water retention agents, auxiliaries, epoxy resins, bismuth compounds, fine powdered silica, calcined gypsum, imidazoline compounds, crosslinked resin fine particles, polyester resin powder coatings, thermal latent cationic polymerization Initiators, hydrotalcite compounds, and other various additives can be added. One or two or more of these additives can be arbitrarily applied in an application amount that does not impair the effects of the present invention. The method for blending these additives is not particularly limited, and a conventional blending method can be applied.

  The method for producing the low-solvent paint of the present invention is not particularly limited, but is a method of dissolving the polymer (a) in the organic solvent (c), adding the curing agent (b) in a solid state, and using it after dissolution. Alternatively, a method in which the curing agent (b) is dissolved in an organic solvent (c), and then the polymer (a) is added and dissolved to form a coating material. Further, the polymer (a) and the curing agent (b) are separately prepared. A method in which a solution dissolved in the organic solvent (c) is prepared in advance to form a coating material, and the like. The timing of adding the curing agent (b) to the polymer (a) is not limited at all, and it may be blended in advance, stored until use, and used for painting, or blended immediately before use. Is also good. Further, the apparatus for dissolving the polymer (a) and the curing agent (b) with the organic solvent (c) is not limited at all, and a stirring dissolution method using a stirring tank, kneading using a three-roll mill or the like is used. Dissolution and mixing can be performed using a known method such as a dissolution method.

When applying the low solvent type paint of the present invention, a commonly used coating method such as roll coating, curtain flow coating, spray coating, electrostatic coating and the like are used, and there is no particular limitation.
The low solvent type coating material of the present invention can be cured by heat, ultraviolet light, energy such as electron beam, and, for example, when cured by heating, the curing reaction is usually performed in the range of 150 to 250 ° C. A coating film having good physical properties can be obtained within a practical curing time range even at a low curing temperature range recently desired. Although the curing time depends on the composition, it is usually in the range of 20 minutes to 200 hours, but the curing can be performed for 20 minutes or less.
The thickness of the coating film obtained by the low solvent type paint of the present invention is usually in the range of 1 to 1000 μm, preferably in the range of 1 to 500 μm, more preferably in the range of 1 to 200 μm.

The low solvent type paint of the present invention is used as a molding compound, a semiconductor encapsulant, an insulating paint, an electric insulating material such as a laminate, a matrix resin of a composite material, an adhesive, a sealing agent, a coating agent, a paint, etc. Although it can be suitably used, it can be particularly preferably used as an organic solvent type paint.
The coating film obtained using the low solvent type paint of the present invention has smoothness, sharpness, appearance such as transparency, hardness, impact resistance, bending resistance, physical strength such as scratch resistance, resistance to scratches and the like. Excellent in chemical properties such as solvent resistance and acid rain resistance, and weather resistance, etc., and as a protective material for metals, concrete precursors, wood, plastic materials, etc., home appliances, electric equipment, automobile parts, automobile outer panels, ships It can be suitably applied to steel furniture, water supply materials, cans, road / construction / construction materials, and the like. In particular, it can be preferably used as a clear coating film containing no pigment component, for example, for vending machines, road materials, aluminum wheels, top coats for automobiles and the like.

Next, a clear coating material for a top coat of an outer panel for an automobile in which the low solvent type coating material of the present invention is preferably used will be described. The form of the coating film formed by the clear coating for top coat is not particularly limited, and includes a multi-layer coating film in which a colored base coat film and one or more clear top coat films are sequentially formed. be able to.
As a specific example, for example, a method of forming a clear top coat film with a low solvent type paint of the present invention after forming a base coat film with a thermosetting colored paint on a substrate, or a thermosetting colored paint on a substrate After forming a base coat film and a thermosetting clear coat film of a melamine type or an acid-epoxy type, a method of forming a clear top coat film with a low solvent type paint of the present invention and the like can be given.

Specific examples of the above thermosetting coloring paint include, for example, acrylic resin-amino resin system, alkyd resin-amino resin system, polyester resin-amino resin system, acrylic resin-polyisocyanate system, alkyd resin-polyisocyanate system, A coating composition in which a coloring pigment is blended with a known resin composition such as a polyester resin-polyisocyanate-based resin, an epoxy-based acrylic resin-a carboxylic acid-based acrylic resin, and the like can be given.
As the form of the above-mentioned thermosetting colored paint, any form such as an organic solvent type, a high solid type, an aqueous solution type and a water dispersion type can be used. However, from the viewpoint of suppressing the amount of solvent discharged at the time of forming the coating film, it is preferable to form the base coat film with a water-containing thermosetting coloring paint.
After forming the above base coat film, a clear top coat film may be formed using a clear paint for a top coat which is a low solvent type paint of the present invention, but as a clear intermediate film, a melamine type or an acid-epoxy is used. The clear top coat film of the present invention may be formed after applying and curing a type thermosetting clear coat paint.
[Examples and Comparative Examples]

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
The methods for measuring various physical properties used in Examples and Comparative Examples are as follows. (1) Number average molecular weight It was determined from a polystyrene standard calibration curve using gel permeation chromatography. As a measurement sample, each sample (dried product) was dissolved in tetrahydrofuran to have a concentration of about 0.1% by mass.
(Used equipment)
・ GPC equipment: HLC-8120GPC manufactured by Tosoh Corporation
-Column: TSKgel GMH _HR- N manufactured by Tosoh Corporation
Shodex GPC KF-801 Showa Denko KK
TSKgel G-1000H _XL x 2 Tosoh Corporation
・ Column temperature: 40 ° C
・ Developing liquid: tetrahydrofuran ・ Developing liquid flow rate: 1.0 ml / min

(2) Epoxy equivalent 0.1-1.0 g of the sample (dried product) was precisely weighed in a 100 ml Erlenmeyer flask, and a stirrer was put therein. Subsequently, about 50 ml of n-propyl alcohol, about 4 ml of benzyl alcohol, and about 3 ml of 0.04% bromthymol blue indicator were added, and a reflux condenser was attached, and the mixture was refluxed with stirring on a stirrer equipped with a hot plate. Further, 3.0 g of potassium iodide dissolved in 10 ml of water was added under reflux (to be blue). Titration was performed with 1N or 0.2N hydrochloric acid under reflux, and the end point was when the yellow color was maintained for 30 seconds, and the epoxy equivalent was determined by the following formula.
Epoxy equivalent (g / eq) = sample weight (g) × 1000 / (normality of hydrochloric acid (N) × titration (ml))

(3) Solubility Add a curing agent while stirring the solvent at 25 ° C., and stir for 3 hours. The epoxy group-containing polymer was added in several portions while keeping the state capable of stirring. When the solution generates heat, the dissolving tank is water-cooled within a range not exceeding 30 ° C. and stirred for 3 hours. Thereafter, the coating was allowed to stand, and the paint was visually evaluated. A mark where the insoluble matter was precipitated visually was marked with a cross, a mark where a small amount of insoluble matter was observed was marked with a mark, a cloudy or scattered thing was marked with a circle, and a homogeneously dissolved matter was marked with a double mark.
(4) Coatability The paint was applied to a SPCC (JIS standard, general cold-rolled) steel plate (manufactured by Testpiece Co., Ltd.) with a spray gun, and those that could not be sprayed continuously during coating were marked with a cross, A mark with a large amount of liquid droplets visually observed on the coated surface was marked with △, a mark with liquid droplets partially observed on the coated surface was marked with ○, and a mark with a uniform coated surface was marked with ◎.

(5) Smoothness and gloss of the coating film The surface of the coating film was evaluated with the naked eye.る も の indicates that the gloss was slightly inferior, and ◎ indicates that both the smoothness and the gloss were good.
(6) Erichsen value The coated plate was placed in a constant temperature and humidity room (20 ° C., 75% RH) for 1 hour, and then the coating was attached to an Erichsen tester (Toyo Seiki Seisakusho) with the coating facing outward, about 10 mm. Is extruded at a specified distance from the back surface of the test plate at a speed of about 0.1 mm per second so that the speed is as uniform as possible. Immediately after extrusion, the protruding portion of the coating film was visually inspected for cracks or peeling, and expressed by the maximum mm number when there was no abnormality in the coating film.

(7) Pencil hardness The pencil hardness was measured according to the tester method for the pencil scratch value of JIS K5400.
(8) Adhesion The adhered state of the coating film was visually observed by a grid tape method according to JIS K5400. Actually, 100 squares of about 1 mm × 1 mm were prepared with a cutter knife for the coating film, and the evaluation result was “number of squares not peeled off by tape / 100 squares”.

(9) Color difference A paint is applied on a white board and baked under two conditions of 140 ° C. for 30 minutes and 160 ° C. for 30 minutes. The color difference was measured using a color difference meter CR-200b (manufactured by Minolta Co., Ltd.) with the coating amount adjusted such that the thickness of the coating film after baking became about 70 μm. ΔE was determined from the L value, a value, and b value obtained by baking at 140 ° C. and 160 ° C. according to the following equation.
ΔE = [(ΔL) ² + (Δa) ² + (Δb) ² ] ^1/2
(In the formula, the ΔL value represents the difference between the lightness index L values before and after the coating process, and the Δa value and the Δb value represent the difference between the chromaticness index a value and the b value before and after the coating process, respectively.)
Lightness index L value: 100 (white) <L value <0 (black)
Chromanetics index a value: + (red) ← 0 →-(green)
Chromanetics index b value: + (yellow) ← 0 →-(blue)

[Production of epoxy group-containing acrylic resin polymer]
[Production Example 1]
Of a monomer and a polymerization initiator comprising 20 parts by weight of methyl methacrylate, 10 parts by weight of n-butyl acrylate, 55 parts by weight of glycidyl methacrylate, 15 parts by weight of styrene, and 8.4 parts by weight of azobisisobutyronitrile The mixture was dropped into 100 parts by weight of toluene at 110 ° C. over about 30 minutes, and polymerization was carried out for 5 hours from the end of dropping while maintaining the internal temperature at 110 ° C. The solvent was removed from the resulting solution under reduced pressure to obtain an epoxy group-containing polymer A having a number average molecular weight of 3,610 and an epoxy equivalent of 243 g / equivalent.
[Production Examples 2 to 9]
Polymerization was carried out in the same manner as in Production Example 1 to obtain epoxy group-containing polymers B to I. The polymerization composition and the polymerization result are shown in Tables 1 and 2.

[Preparation, coating and evaluation of paint]
[Example 1]
1000 g of acetone was put into a 3 L dissolution tank equipped with a cooling jacket, and 230 g of 1,3,6-hexanetricarboxylic acid was added while stirring the acetone with a propeller-type stirring blade, followed by stirring for 3 hours.
Next, while stirring, 770 g of the epoxy group-containing polymer A of Production Example 1 was added at a rate within a range that can be stirred, and the mixture was further stirred for 3 hours to dissolve the polymer. Water was circulated through the cooling jacket so that the solution temperature did not exceed 30 ° C. during dissolution.
The obtained paint was applied with a spray gun so that the thickness of the coating film after baking on an SPCC steel sheet was about 70 μm. The obtained substrate was baked at 140 ° C. for 30 minutes. In Example 1, the solubility of 1,3,6-hexanetricarboxylic acid in the solvent was ◎, and the coatability, the smoothness and the gloss of the obtained coating film were also ◎.

[Examples 2 to 26, Comparative Examples 1 to 9]
Production, coating, and evaluation of paints were performed in the same manner as in Example 1 using the composition shown in Tables 3 to 10. The results are shown in Tables 3 to 10.
In Examples 2 and 3, the solubility of 1,3,6-hexanetricarboxylic acid in a solvent was good, and the coatability, the smoothness and gloss of the obtained coating film were also good.
When the solvent concentration in Example 4 was 13% by mass, the solubility of 1,3,6-hexanetricarboxylic acid was slightly poor, and the smoothness was insufficient.
In Example 5, when the solvent concentration was 67% by mass, the solid content of the paint was slightly too low, and the flow of the applied paint was slightly uneven.
Comparative Examples 1 to 3 are examples in which decanedicarboxylic acid was used, but the solubility was poor and a uniform paint could not be obtained.
In Examples 6, 7, 8 and 9, good results were obtained in solubility, coatability, Erichsen and adhesion.

In Comparative Example 4, since the molecular weight of the polymer was close to the epoxy equivalent, the number of epoxy groups in the polymer was less than 2, and a sufficient crosslink density could not be obtained, resulting in insufficient Erichsen or adhesiveness.
In Example 10, since the epoxy equivalent and the molecular weight were large, the TC amount was small, and the solubility was good.
In Example 11, a coating film having a high pencil hardness was obtained because the molecular weight of the polymer was high. In Example 12, the crosslinking density was high due to the small epoxy equivalent, and the pencil hardness of the coating film was high.
Comparative Example 5 is an example in which decanedicarboxylic acid was blended, but the smoothness and gloss were insufficient due to poor solubility of decanedicarboxylic acid.

In Examples 13 to 19, examples are given in which the type and amount of the solvent are changed. 1,3,6-hexanetricarboxylic acid has sufficient solubility in various solvents.
In Example 20, a coating film having a high pencil hardness was obtained because the molecular weight of the polymer was high.
In Comparative Examples 6 to 8, decanedicarboxylic acid is compared with the same solvent. However, the solubility in the solvent is extremely low, so that the crosslink density cannot be sufficiently obtained, and the Erichsen or adhesiveness is insufficient.
Although the solvent concentration was increased to 65% by mass in Comparative Example 9, decanedicarboxylic acid could not be completely dissolved, and a uniform coating could not be obtained.
Examples 21 to 24 show examples of the addition of an antioxidant. The addition of an antioxidant has a remarkable effect of improving the yellowing of the coating film after baking. Examples 25 and 26 show examples in which the amount of the antioxidant added was changed.

[Example 27]
The paint of Example 7 was left at 40 ° C. for 2 weeks, coated, and baked at 140 ° C. for 30 minutes. As a result, the coating properties ◎, the smoothness and gloss ◎, the pencil hardness 2H, the Erichsen 8 mm, the adhesiveness 100/100, and the same results as the evaluation results before storing the paint were obtained.
[Example 28]
The coating of Example 7 was baked at 140 ° C. for 30 minutes, using a weatherometer XENOTEST 1200 CPS (manufactured by Heraeus) under the conditions of black panel 63 ° C., 60 W · m ² , rainfall conditions for 250 hours. Xenon arc irradiation was performed. As a result of measuring the gloss (gloss) at 60 ° of the surface of the baked coating film before and after the above test, the retention was 90% or more of the gloss before the test, and excellent weather resistance was obtained.

[Example 29]
Epco primer no. 1000BF2 (registered trademark, manufactured by NOF Corporation) was applied to a dry film thickness (the film thickness was measured with a micrometer) of 20 μm, and then baked at 160 ° C. for 20 minutes.
Subsequently, an intermediate coating (“Lugabake AM” manufactured by Kansai Paint Co., Ltd., trade name, polyester resin / melamine resin-based coating, gray color) is applied to a dry film thickness of 30 μm, and heat-cured at 140 ° C. for 30 minutes. did.
A metallic paint ("TWX-402" manufactured by Kansai Paint Co., Ltd., trade name, acrylic resin / melamine resin paint) is applied to the obtained thermosetting coating surface to a dry film thickness of 18 µm and left at room temperature for 3 minutes. The paint described in Example 2 was applied as a clear paint for an automobile top coat by a spray gun to the uncured coated surface after the coating, and baked at 140 ° C. for 30 minutes. The dry film thickness of the top clear coat film was about 40 μm (determined by the film thickness difference between the case where the top clear coat film was applied and the case where the top clear coat film was cured only with the metallic paint). The coatability, the smoothness and gloss of the obtained coating film were also good (（). The pencil hardness was 2H, Erichsen was 8 mm, and the adhesiveness evaluation was 100/100, which was excellent.

[Example 30]
Example 29 was carried out in the same manner as in Example 29 except that the paint described in Example 7 was used as a clear paint for an automobile top coat. The dry film thickness was about 20 μm for the base coat and about 40 μm for the top clear coat film. The coatability, the smoothness and gloss of the obtained coating film were also good (（). The pencil hardness was 2H, Erichsen was 8 mm, and the adhesiveness evaluation was 100/100, which was excellent.
[Comparative Example 10]
Example 29 was carried out in the same manner as in Example 29 except that the paint described in Comparative Example 1 was used as a clear paint for an automobile top coat. The dry film thickness was about 20 μm for the base coat and about 40 μm for the top clear coat film. The smoothness and gloss of the obtained coating film were poor (x), the pencil hardness was B, the Erichsen was 2 mm, and the adhesiveness evaluation was an insufficient value of 33/100.

  The low solvent type paint of the present invention can be used as a protective material for metals, concrete precursors, wood, plastic materials, etc., as home appliances, electric appliances, automobile parts, automobile outer panels, ships, steel furniture, water supply materials, cans, roads. -Applicable to construction and civil engineering materials. In particular, it can be preferably used as a clear coating film containing no pigment component, for example, for vending machines, road materials, aluminum wheels, top coats for automobiles and the like.

Claims (11)

  At least a polymer (a) having an average of two or more epoxy groups in a molecule, a curing agent (b), and an organic solvent (c), and the curing agent (b) is an aliphatic tricarboxylic acid. Characteristic low solvent type paint.   The low solvent type paint according to claim 1, wherein the concentration of the organic solvent (c) in the paint is 15 to 65% by mass. The low solvent type paint according to claim 1 or 2, wherein the curing agent (b) is an aliphatic tricarboxylic acid represented by the formula (1).

[However, p, r, and s are integers of 0-8, q is an integer of 1-9, 1 ≦ p + q + r + s ≦ 9, and r <s or (r = s and p ≦ q). ]   The low solvent type paint according to claim 3, wherein the curing agent (b) is an aliphatic tricarboxylic acid in which p + q + r + s = 3 in the formula (1).   The low solvent type paint according to claim 4, wherein the curing agent (b) is an aliphatic tricarboxylic acid in which p = 1, q = 2, and r = s = 0 in the formula (1).   A compound in which the organic solvent (c) has one or two or more groups selected from a ketone group, a hydroxyl group, an ether group and an ester group in the same molecule and / or a ketone group, a hydroxyl group, 2. An organic solvent containing a compound having two or more kinds of groups selected from an ether group and an ester group, wherein the proportion of the compound in the organic solvent is 1 to 100% by mass. 6. The low solvent type paint according to any one of items 1 to 5.   The low solvent type paint according to any one of claims 1 to 6, wherein the polymer (a) having an average of two or more epoxy groups in a molecule is an epoxy group-containing acrylic resin polymer.   The low solvent type paint according to claim 7, wherein the epoxy group-containing acrylic resin polymer has an epoxy equivalent of 200 to 5,000 and a number average molecular weight in terms of styrene of 1,000 to 50,000.   A low-solvent paint comprising an antioxidant added to the low-solvent paint according to any one of claims 1 to 10 in an amount of 10 mass ppm to 10 mass%.   A curable composition for a low solvent type paint, comprising a polymer (a) having an average of two or more epoxy groups in a molecule and a curing agent (b), wherein the curing agent is an aliphatic tricarboxylic acid. object.   A clear coating material for a top coat of an automobile outer panel, comprising the low solvent type coating material according to claim 1.