JP4901180B2 - Aqueous block polyisocyanate composition and aqueous coating composition containing the same - Google Patents

Description

  The present invention is an aqueous block polyisocyanate composition and an aqueous coating composition using the same as a curing agent.

The present invention relates to an aqueous block polyisocyanate composition and an aqueous coating composition using the same as a curing agent.
In recent years, water-based paints have attracted attention from the viewpoints of the global environment, safety, and hygiene. It has come to be used for industrial coatings such as for building cans and coil coatings from building exteriors. Furthermore, there are many proposals regarding a one-component paint for automobiles that require high quality such as weather resistance, chemical resistance, and impact resistance (Patent Documents 1, 2, and 3). Many of the curing agents used here are alkyl etherified melamine resins alone. A coating film formed using a melamine resin such as an alkyl etherified melamine resin as a curing agent has excellent physical properties such as hardness and adhesion, but lacks flexibility such as impact resistance.

In addition, the coatings obtained from urethane-based paints that crosslink with urethane bonds formed by isocyanate groups and hydroxyl groups have very good impact resistance, wear resistance, chemical resistance, and stain resistance. Further, by using non-yellowing polyisocyanate made from aliphatic / alicyclic diisocyanate as an isocyanate component, weather resistance is further improved, and its demand is increasing.
Accordingly, the development of water-based urethane paints that crosslink with urethane bonds has been actively conducted. When a one-component property such as a paint for lines is required, the isocyanate group of a polyisocyanate that is a curing agent is usually blocked with a blocking agent and used as a blocked polyisocyanate.

  For example, a technology using a surfactant for making a block polyisocyanate aqueous (Patent Document 4), a polyethylene oxide containing a higher fatty acid having 7 to 26 carbon atoms, Technology that uses sodium bisulfite as the blocking agent for the isocyanate group of polyisocyanate (Patent Document 5), reacting polyisocyanate with specific polyoxyethylene, which is a hydrophilic group, to prevent elution of hydrophilic components, A technique (Patent Document 6) for making it aqueous by using it is disclosed.

Technology for making aqueous block of polyisocyanate having heat-resistant isocyanurate structure (Patent Documents 7 and 8), adding polyoxyethylene group to part of polyisocyanate, and further adding polyethylene glycol, ethylene oxide and propylene oxide A technique of mixing a water-soluble polymer compound such as a copolymer (Patent Document 9), a technique of imparting hydrophilicity with a hydroxycarboxylic acid (Patent Document 10), and the like are disclosed.
The resin solid content of the above aqueous block polyisocyanate is low, and not only the coating composition is restricted but also the transportation cost is heavy when considering the problem of high solids coating.

JP-A-56-157358 JP 63-175079 A JP 63-193968 A JP 52-59657 A JP-A-56-151753 JP-A-61 31422 Japanese Patent Laid-Open No. 62-151419 JP-A-2-3465 Japanese Patent Laid-Open No. 62-151419 JP-A-2-3465

  An object of the present invention is to provide an aqueous block polyisocyanate composition having a high resin solid content and a low viscosity, and an aqueous coating composition containing the same.

As a result of intensive studies to solve the above problems, the present inventors have found that this can be achieved with a specific aqueous block polyisocyanate composition and an aqueous coating composition using the same, and have reached the present invention.
That is, the present invention is as follows.
1. An aqueous block polyisocyanate composition characterized by satisfying all of the following conditions.
1) The precursor is a polyisocyanate having an average number of isocyanate groups of 4.0 to 20 derived from at least one aliphatic / alicyclic diisocyanate monomer and a divalent to hexavalent alcohol compound, and has a hydrophilic group. 50 to 95% by weight of blocked polyisocyanate.
2) 1 to 49% by mass of organic solvent.
3) Water is 1 to 49% by mass.
2. 1. An aqueous block polyisocyanate composition in which the aliphatic / alicyclic diisocyanate monomer is hexamethylene diisocyanate.
3 . An aqueous coating composition comprising the aqueous blocked polyisocyanate composition according to 1 or 2 .

  The present invention is an aqueous block polyisocyanate composition having a high resin solid content and a low viscosity, and an aqueous coating composition containing the same, and can exhibit excellent performance as an aqueous intermediate coating, particularly as an automotive intermediate coating.

The present invention will be specifically described below.
The aliphatic / alicyclic diisocyanate monomer means an aliphatic diisocyanate monomer and an alicyclic diisocyanate monomer.
The aliphatic diisocyanate monomer used in the present invention is preferably one having 4 to 30 carbon atoms, such as tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, hexamethylene diisocyanate (hereinafter referred to as HDI). Examples include 2,2,4-trimethylhexamethylene-1,6-diisocyanate and lysine diisocyanate.

As the alicyclic diisocyanate monomer used in the present invention, those having 8 to 30 carbon atoms are preferable, and isophorone diisocyanate (hereinafter referred to as IPDI), 1,3-bis (isocyanatomethyl) -cyclohexane, 4,4′-dicyclohexylmethane. There are diisocyanates.
Among these, HDI is preferable from the viewpoint of weather resistance and industrial availability, and two or more kinds can be used in combination.

The diisocyanate monomer is derived to obtain a polyisocyanate that is a precursor of the aqueous block polyisocyanate used in the present invention.
The polyisocyanate can include, for example, biuret bonds, urea bonds, isocyanurate bonds, uretdione bonds, urethane bonds, allophanate bonds, oxadiazine trione bonds, and the like. Two or more bonds can also be included.
A polyisocyanate having a biuret bond is obtained by reacting a so-called biuretizing agent such as water, t-butanol and urea with a diisocyanate monomer at a molar ratio of the biuretizing agent / isocyanate group of the diisocyanate monomer at about 1/2 to about 1/100. Thereafter, the diisocyanate monomer can be removed and purified. With respect to these techniques, for example, JP-A-53-106797, JP-A-55-11452, JP-A-59-95259 are disclosed.

  The polyisocyanate having an isocyanurate bond can be obtained by carrying out a cyclic trimerization reaction with a catalyst or the like, for example, stopping the reaction when the conversion rate is about 5 to about 80% by mass, and removing and purifying the diisocyanate monomer. In this case, a monovalent to hexavalent alcohol compound can be used in combination. With regard to these techniques, for example, JP-A-55-38380, JP-A-57-78460, JP-A-57-47321, JP-A-61-111371, JP-A-64-33115. No. 2, JP-A-2-250872, and JP-A-6-3129969.

The polyisocyanate having a urethane bond, for example, has a molar ratio of a hydroxyl group of the alcohol compound / isocyanate group of the diisocyanate monomer to about 1/100 to about 1/100 of the divalent to hexavalent alcohol compound such as trimethylolpropane and the diisocyanate monomer. After the reaction, the diisocyanate monomer can be removed and purified.
The diisocyanate monomer concentration in the obtained polyisocyanate is 3% by mass or less, preferably 1% by mass or less. If it exceeds 3% by mass, curability may be lowered. Two or more of these polyisocyanates can be mixed and used.
The average number of isocyanate groups in the polyisocyanate is preferably 4.0 to 20, and if it is less than 4.0, the curability of the finally obtained aqueous block polyisocyanate composition and the flexibility of the obtained coating film are lowered. If it exceeds 20, the reactivity after partial curing of the resulting aqueous block polyisocyanate composition may be reduced.

  The hydrophilic group that can be used in the present invention is an anionic group or a nonionic group. Examples of the anionic group include a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group. Nonionic groups include, for example, polyethylene glycol type and polyhydric alcohol type. In addition, a compound having an active hydrogen group is used to introduce a hydrophilic group into the aqueous blocked polyisocyanate. The active hydrogen group is a functional group that reacts with an isocyanate group, and examples thereof include a hydroxyl group, a mercapto group, and a carboxylic acid group. As a compound having both an anionic group and an active hydrogen group, there is an oxyacid having both a hydroxyl group and a carboxylic acid group. Examples include glycolic acid, lactic acid, tartaric acid, citric acid, oxybutyric acid, oxyvaleric acid, hydroxypivalic acid, dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, polycaprolactone having a carboxylic acid group, hydroxyl group and sulfone For example, there is isethionic acid having both acid groups. Examples include mercaptoacetic acid, which is a mercaptocarboxylic acid having both an active hydrogen group and a mercapto group and a carboxylic acid group. Examples of the compound having both a nonionic group and an active hydrogen group include polyethylene oxide. Polyethylene oxide is obtained, for example, by adding ethylene oxide to monoalcohol such as methanol, ethanol, or butanol, and may contain propylene oxide.

The active hydrogen group is preferably a hydroxyl group, and the hydrophilic group is preferably a carboxylic acid group, and dimethylolpropionic acid, dimethylolbutanoic acid, and polycaprolactone having a carboxylic acid group are preferred.
The blocking agent that can be used in the present invention is a compound having one active hydrogen group in the molecule, and examples thereof include alcohols, alkylphenols, phenols, active methylenes, mercaptans, acid amides, and acid imides. , Imidazole, urea, oxime, amine, imide, and pyrazole compounds. Examples of more specific blocking agents are shown below.

(1) Alcohols such as methanol, ethanol, 2-propanol, 1-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, and 2-butoxyethanol.
(2) Alkylphenol-based mono- and dialkylphenols having an alkyl group having 4 or more carbon atoms as a substituent, such as 1-propylphenol, iso-propylphenol, 1-butylphenol, sec-butylphenol, t-butylphenol Monoalkylphenols such as 1-hexylphenol, 2-ethylhexylphenol, N-octylphenol, nonylphenol, di-1-propylphenol, diisopropylphenol, isopropylcresol, di-1-butylphenol, di-t-butylphenol, di-sec -Dialkylphenols such as butylphenol, di-1-octylphenol, di-2-ethylhexylphenol, and di-1-nonylphenol.

(3) Phenol type: phenol, cresol, ethylphenol, styrenated phenol, hydroxybenzoic acid ester and the like.
(4) Active methylene type: dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone and the like.
(5) Mercaptan type; butyl mercaptan, dodecyl mercaptan, and the like.
(6) Acid amide type; acetanilide, acetic acid amide, ε-caprolactam, ∂-valerolactam, 7-butyrolactam and the like.

(7) Acid imide type; succinimide, maleic imide and the like.
(8) Imidazole series; imidazole, 2-methylimidazole and the like.
(9) Urea type; urea, thiourea, ethylene urea, and the like.
(10) Oxime series: formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime and the like.
(11) Amine-based: diphenylamine, aniline, carbazole, di-N-propylamine, diisopropylamine, isopropylethylamine and the like.
(12) Imine type; ethyleneimine, polyethyleneimine and the like.
(13) Pyrazole type; pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole and the like.
There is.

A preferred blocking agent is at least one selected from alcohols, oximes, acid amides, active methylenes, and pyrazoles.
The anionic group which is a hydrophilic group that can be used in the present invention is preferably neutralized with an organic amine. This neutralization imparts water dispersibility and water solubility to the block polyisocyanate.

Examples of the specific organic amine compound include, for example, ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, C1-C20 linear, branched 1, 2 or tertiary amines such as dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine and ethylenediamine, cyclic amines such as morpholine, N-alkylmorpholine and pyridine , Monoisopropanolamine, methylethanolamine, methylisopropanolamine, dimethylethanolamine, diisopropanolamine, diethanolamine, triethanol Min, diethylethanolamine, a hydroxyl group-containing amines such as triethanolamine and the like.

Using the raw materials detailed above, an aqueous block polyisocyanate that can be used in the present invention can be derived. One example of the manufacturing method will be described in detail. First, the polyisocyanate and the blocking agent are reacted. This reaction can be performed with or without an organic solvent. When using an organic solvent, it is necessary to use an organic solvent inert to the isocyanate group. Examples of the organic solvent include ketone solvents such as acetone and methyl ethyl ketone, and ester solvents such as ethyl acetate.
The blocked polyisocyanate in which the isocyanate group as an intermediate is partially blocked with a blocking agent often has a high viscosity. In this case, it is preferable to lower the viscosity using an organic solvent and proceed to the next step.

In the blocking reaction, organometallic salts such as tin, zinc and lead, tertiary amine compounds, alkali metal alcoholates such as sodium, and the like may be used as catalysts.
The reaction can generally be carried out at −20 to 150 ° C., preferably 30 to 100 ° C. If the temperature exceeds 150 ° C., a side reaction may occur, and if it is less than −20 ° C., the reaction rate decreases, which is disadvantageous.
It is preferred to react 40 to 90% of the isocyanate groups of the polyisocyanate with a blocking agent. If it is less than 40%, the blocked isocyanate group concentration is lowered, and when blending a paint, a large amount may be required, which is not preferable. If it exceeds 90%, the carboxyl group introduction amount described later decreases, and the water dispersibility and water solubility of the aqueous block polyisocyanate decrease, which is not preferable.

  The residual isocyanate group of the partially blocked polyisocyanate thus obtained is reacted with a compound having both active hydrogen groups and hydrophilic groups. The reaction temperature of this reaction and the reaction conditions such as the catalyst can be performed in the same manner as in the blocking reaction. When an isocyanate group remains after the reaction, it is preferable to add a blocking agent or the like to eliminate the isocyanate group. When an isocyanate group remains, it is subject to limitations such as additives described later.

  The carboxyl group added to the block polyisocyanate is neutralized with an organic amine compound. These organic amine compounds are used in the range of 0.5 to 1.5 equivalents relative to the carboxyl group. If it is less than 0.5, the water dispersibility and water solubility of the water-based blocked polyisocyanate may decrease. If it exceeds 1.5, the pH of the water-based block polyisocyanate solution becomes high, and the paint using this The stability of the may decrease. The acid value of the aqueous block polyisocyanate thus obtained is 10 to 70 mgKOH / g.

If necessary, a nonionic hydrophilic group such as polyethylene glycol can also be introduced. Further, nonionic, anionic, cationic and amphoteric surfactants can be added depending on the purpose such as improvement of water dispersibility. Specific examples of the surfactant include nonionic compounds such as polyethylene glycol and polyhydric alcohol fatty acid esters, fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, sulfosuccinates, alkyl phosphates, and the like, alkyls There are surfactants such as amine salts, cationic systems such as alkylbetaines, carboxylic acid amine salts, sulfonic acid amine salts, and sulfate ester salts.
Thereafter, water is added. After adding water, in some cases, the organic solvent used in the reaction can be removed. The organic solvent is usually removed under reduced pressure. When the organic solvent used for the reaction is removed, the organic solvent is added after the removal.

The aqueous block polyisocyanate produced as described above contains an organic solvent and water as a medium. The organic solvent is preferably 1 to 49% by mass, the water is 1 to 49% by mass, more preferably the organic solvent is 5 to 35% by mass, and the water is 15 to 45% by mass. The solvent is 5 to 25% by mass, and the water is 25 to 45% by mass. The aqueous block polyisocyanate resin solid content in the aqueous block polyisocyanate composition is preferably 50 to 95% by mass, more preferably 60 to 90% by mass. If it is 50% by mass or less, the solid content of the aqueous coating composition using the same may decrease, and the coating workability may decrease. If it exceeds 95% by mass, the viscosity will increase, Workability may be reduced.
It was surprising that the aqueous blocked polyisocyanate composition contained a specific concentration of the organic solvent, so that the aqueous blocked polyisocyanate could achieve a low viscosity while having a high concentration.

  Examples of the specific organic solvent include 1-methylpyrrolidone, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether, Methyl ethyl ketone, acetone, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, ethanol, methanol, iso-propanol, 1-propanol, iso-butanol, 1-butanol, 2-ethylhexanol, cyclohexanol, ethylene glycol, diethylene glycol, triethylene glycol , Propylene glycol, dipropylene glycol, 1 Examples include 4-butanediol, 1,3-butanediol, ethyl acetate, isopropyl acetate, butyl acetate, toluene, xylene, pentane, iso-pentane, hexane, iso-hexane, cyclohexane, solvent naphtha, mineral spirit, etc. Two or more kinds can be used in combination. As a preferable organic solvent, those having a solubility in water of 5% by mass or more are preferable, and when an organic solvent having a solubility in water of less than 5% by mass is used, the viscosity of the aqueous block polyisocyanate composition is increased, and workability is improved. May decrease. Moreover, the thing whose boiling point is 100 degreeC or more is preferable, and when the organic solvent whose boiling point is less than 100 degreeC is used, volatilization of the organic solvent will become quick at the time of coating-film formation, and it may affect the coating-film surface appearance.

The pH of the aqueous blocked polyisocyanate composition thus obtained is preferably 7.0 to 8.5, more preferably 7.0 to 8.0.
The aqueous coating composition of the present invention is formed using the aqueous block polyisocyanate composition and the polyol thus obtained as main components.
Examples of these polyols include acrylic polyol, polyester polyol, polyether polyol, aliphatic hydrocarbon polyol, epoxy polyol, and fluorine polyol.

Examples of the acrylic polyol include acrylic acid esters having active hydrogen such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate, or glycerol monoester or methacrylic acid. Monoester, trimethylolpropane acrylic acid monoester or methacrylic acid monoester alone or in mixture and methyl acrylate, ethyl acrylate, isopropyl acrylate, 1-butyl acrylate, acrylate-2- Acrylic esters such as ethylhexyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, methacrylic acid-4 Methacrylic acid ester having active hydrogen such as hydroxybutyl, or methacrylic acid such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, 1-butyl methacrylate, isobutyl methacrylate, 1-hexyl methacrylate, lauryl methacrylate Using alone or a mixture selected from the group of esters, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid, unsaturated amides such as acrylamide, N-methylol acrylamide and diacetone acrylamide, and methacrylic acid Acyl obtained by polymerization in the presence or absence of a single or mixture selected from the group of other polymerizable monomers such as glycidyl acid, styrene, vinyl toluene, vinyl acetate, acrylonitrile, dibutyl fumarate Le polyols. As the polymerization method, it can be produced by emulsion polymerization, suspension polymerization, dispersion polymerization, or solution polymerization. In emulsion polymerization, it can also be polymerized stepwise.

  As the polyester polyol, for example, a single selected from the group of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc. Or a mixture and low molecular weight polyols and diols include, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,2-propanediol, 1,5-pentanediol, 2-methyl-2, 3-butanediol, 1,6-hex Diol, 1,2-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethylhexanediol, 1,2- There are octanediol, 1,2-decanediol, 2,2,4-trimethylpentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, etc. The triols include, for example, glycerin and trimethylolpropane, and the tetraols include, for example, a polyhydric alcohol selected from the group of diglycerin, dimethylolpropane, pentaerythritol and the like alone or in a mixture. Polyester polyols obtained by condensation reactions and, for example, low molecular weight polyols Polycaprolactones such as obtained by ring-opening polymerization of ε- caprolactone hydroxyl group.

  As the polyether polyol, ethylene oxide, propylene oxide, butylene is used by using a strongly basic catalyst such as hydroxide, alcoholate, alkylamine, etc., for example, a hydroxide such as lithium, sodium, and potassium, or a mixture of polyvalent hydroxy compounds. Polyether polyols obtained by adding an alkylene oxide such as oxide, cyclohexene oxide, and styrene oxide alone or in a mixture, polyether polyols obtained by reacting an alkylene oxide with a polyfunctional compound such as ethylenediamine, and So-called polymer polyols obtained by polymerizing acrylamide or the like using these polyethers as a medium are included.

Examples of the polyvalent hydroxy compound (1) include diglycerin, ditrimethylolpropane, pentaerythritol, and dipentaerythritol.
(2) Sugar alcohol compounds such as erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, and rhamnitol.
(3) Monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, ribodesose.
(4) Disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, melibiose.
(5) Trisaccharides such as raffinose, gentianose, and meletitose.
(6) For example, tetrasaccharides such as stachyose.
and so on.

Examples of the aliphatic hydrocarbon polyol include terminal hydroxylated polybutadiene and hydrogenated products thereof.
Examples of the epoxy polyol include bisphenol-type epoxy resins modified with amine or amino alcohol.
Examples of the fluorine polyol include a resin composed of a monomer copolymerizable with fluorinated ethylene.
The polyol must be emulsified, dispersed or dissolved in water. Therefore, the carboxyl group, sulfone group, etc. contained in the polyol can be neutralized.

  Examples of neutralizing agents for neutralizing carboxyl groups and sulfone groups include ammonia and water-soluble amino compounds such as monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, propylamine, dipropylamine, and isopropylamine. , Diisopropylamine, triethanolamine, butylamine, dibutylamine, 2-ethylhexylamine, ethylenediamine, propylenediamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, morpholine and the like can be used. Preferably, tertiary amines such as triethylamine and dimethylethanolamine are preferable.

The hydroxyl group per resin component of the polyol is preferably from 30 to 300 mgKOH / g, and the acid value is preferably from 20 to 100 mgKOH / g.
Preferred polyols are acrylic polyols and polyester polyols.
The mixing ratio of the aqueous blocked polyisocyanate composition of the present invention and the above polyol is such that the equivalent ratio of the blocked isocyanate group of the aqueous blocked polyisocyanate to the hydroxyl group of the polyol is in the range of 0.3 to 1.5, if necessary. Selected.
If necessary, a resin such as a melamine curing agent and a urethane dispersion can be used in combination with the coating composition of the present invention.

  As said melamine type hardening | curing agent, it is an alkyl etherified melamine resin, for example. As its production method, for example, urea, melamine, benzoguanamine, glycoluril and the like are added with formaldehyde in alcohol under alkaline conditions to perform methylolation, and then at least a part of the methylol group is alkyletherified. Examples of the alkyl group include methyl, ethyl, propyl, butyl, ethyl cellosolve, and butyl cellosolve, and two or more kinds may be used. Preferred are methyl, ethyl, propyl and butyl. It may have an imino group.

When the melamine curing agent is used, the mixing mass ratio of the water-based block polyisocyanate composition of the present invention and the melamine curing agent is from 10/1 to 1/10, preferably from 5/1 to 1/5. When the ratio is less than 1/10, the flexibility of the coating film may be lowered. If it exceeds 10/1, it is difficult to achieve, for example, an improvement in coating film hardness, which is the purpose of adding a melamine curing agent.
The present invention can contain an acidic compound and a basic compound as a curing accelerator. In particular, when a melamine curing agent is used in combination, the addition of an acidic compound is effective.

Specific examples of the acidic compound include, for example, acetic acid, lactic acid, succinic acid, oxalic acid, maleic acid, decanedicarboxylic acid and the like as carboxylic acids, and examples of the sulfonic acids include paratoluenesulfonic acid and dodecylbenzenesulfone. Acid, dinonylnaphthalenedisulfonic acid, etc., and phosphate esters include, for example, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, dilauryl phosphate, monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monooctyl phosphate, etc. Acid phosphate esters such as diethyl phosphite, dibutyl phosphite, dioctyl phosphite, dilauryl phosphite, monoethyl phosphite, monobutyl phosphite Aito, mono octyl phosphite, there is such as thing lauryl phosphite.

These acidic compounds can be reacted with amine compounds to improve storage stability. Examples of the amine compound include alkylamines such as ethylamine, diethylamine, triethylamine, 1-butylamine and di-1-butylamine, and alkanolamines such as ethanolamine, diethanolamine and triethanolamine.
Specific examples of the basic compound include amine compounds such as triethylamine and 1,4-diazabicyclooctane, dibutyltin dilaurate, and zinc naphthenate metal carboxylate.

The addition amount of a hardening accelerator is 0.1-10 mass% with respect to the coating resin component mix | blended, Preferably it is 0.1-5 mass%.
If necessary, an antioxidant, an ultraviolet absorber, a pigment, for example, a metal powder pigment such as aluminum, an inorganic pigment such as titanium oxide or carbon black, a rheology control agent, a leveling agent, a solvent, etc. may be added. .
Examples of the substrate to be coated of the aqueous coating composition thus prepared include metals, plastics, and inorganic substrates.

In addition, it is useful as a coating for new car skins, exterior paints, paints for plastic parts such as bumpers, paints for repairing automobiles, organic coatings such as precoat metals, etc. .
Examples of the coating method include bell coating, spray coating, roll coating, shower coating, and immersion coating.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.
In addition, all% was shown by the mass%. Evaluation was performed according to the following.
(Measurement of number average molecular weight)
The number average molecular weight is a polystyrene-based number average molecular weight measured by gel permeation chromatography (hereinafter referred to as GPC) using the following apparatus.
Apparatus: Tosoh Corp .: HLC-8120 (trade name)
Column: manufactured by Tosoh Corporation: TSK GEL SuperH1000 (trade name) x 1
TSK GEL SuperH2000 (trade name) x 1
TSK GEL SuperH3000 (trade name) x 1 Carrier: Tetrahydrofuran Detection method: Differential refractometer

(Calculation of the average number of isocyanate groups)
The average number of isocyanate groups was determined by the following formula.
(Polyisocyanate number average molecular weight × isocyanate group concentration × 0.01) / 42
Isocyanate group concentration is mass%
(Viscosity measurement)
The viscosity was measured using the following apparatus.
Apparatus: Thermo Haake, Leo Stress RS1
Sensor: Cone & Plate C20 / 2 Ti
Condition: 6 rpm / 25 ° C
A measured viscosity of less than 250 Pa · s is represented by “O”, 250 to 350 Pa · s is represented by Δ, and 350 Pa · s or more is represented by “x”.

(Impact resistance test)
Evaluation was carried out at 20 ° C. using a DuPont impact resistance tester. Place a steel plate with a 50 μm-thickness coating film cured at 150 ° C. for 30 minutes on a cradle, place a striker (radius 6.35 mm), and drop a 500 g load from a height of 20 cm and 10 cm And the state of the coating film was observed. X when the coating film shows abnormalities such as cracks and cracks due to falling from 10 cm, and ○ when the film shows abnormalities such as cracks and cracks when dropped from 20 cm The case where no abnormalities such as cracks and cracks were observed in the coating film even when dropped from the case was marked with ◎.

[Production Example 1] (Production of polyisocyanate)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was placed in a nitrogen atmosphere, and 600 parts of HDI, polycaprolactone-based polyester polyol “Placcel 303” (Daicel Chemical) Trade name: Number average molecular weight 300) 30 parts were charged, and the temperature inside the reactor was maintained at 90 ° C. for 1 hour under stirring to carry out a urethanization reaction. Thereafter, the temperature in the reactor was set to 60 ° C., the isocyanurate-forming catalyst tetramethylammonium capriate was added, and when the yield reached 48%, phosphoric acid was added to stop the reaction. After filtering the reaction solution, the diisocyanate monomer was removed with a thin film evaporator.
The resulting polyisocyanate had a viscosity at 25 ° C. of 9500 mPa · s, an isocyanate group concentration of 19.2 mass%, a diisocyanate monomer concentration of 0.1 mass%, a number average molecular weight of 1100, and an isocyanate group average number of 5.1. It was.

[Production Example 2] (Production of polyisocyanate)
A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen blowing tube was placed in a nitrogen atmosphere, 100 parts of HDI was charged, and the temperature in the reactor was kept at 60 ° C. with stirring. Then, 0.1 part of isocyanurate-forming catalyst tetramethylammonium acetate (2-butanol 5.0 mass% solution) was added, and when the yield reached 24 mass%, phosphoric acid (85 mass% aqueous solution). The reaction was stopped by adding 14 parts. Thereafter, the mixture was further heated at 100 ° C. for 1 hour, cooled to room temperature, the reaction solution was filtered to remove insoluble matters, and then the monomer diisocyanate was removed with a thin-film distiller.
The resulting polyisocyanate had a viscosity at 25 ° C. of 1600 mPa · s, an isocyanate group concentration of 23.0% by mass, a diisocyanate monomer concentration of 0.1% by mass, a number average molecular weight of 585, and an average number of isocyanate groups of 3.2. It was.

[Example 1] (Production of aqueous block polyisocyanate composition)
A 4-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel is placed in a nitrogen atmosphere, and 100 parts of polyisocyanate obtained in Production Example 1 and 70 parts of methyl ethyl ketone are charged and mixed. Methyl ethyl ketoxime (28 parts) is added dropwise so that the reaction solution temperature does not exceed 60 ° C., and the mixture is stirred for 30 minutes after completion of the addition. Then, after adding 0.0049 parts of dibutyltin dilaurate, 35 parts of a diol “Placcel 205BA” (trade name number average molecular weight 510 of Daicel Chemical) having one carboxyl group is added, and the isocyanate group is detected by infrared spectroscopy. The mixture is stirred at 80 ° C. for 120 minutes until it disappears. Next, 6 parts of N, N-dimethylethanolamine is added for neutralization, and then 60 parts of ion exchange water and 12 parts of dipropylene glycol monomethyl ether are added. Thereafter, by distilling off methyl ethyl ketone at 60 ° C. under reduced pressure, the resin solid content was 70% by mass, dipropylene glycol monomethyl ether 5% by mass, water 25% by mass, pH 8.0, blocked isocyanate group concentration per resin. An 8.0% aqueous blocked polyisocyanate composition was obtained. The viscosity of this aqueous block polyisocyanate composition was ◯.

[Examples 2 to 4, Comparative Example 3 ] (Production of aqueous block polyisocyanate composition)
It carried out like Example 1 except using each ingredient shown in Table 1. The results are shown in Table 1.
[Comparative Example 1] (Production of aqueous block polyisocyanate and composition thereof)
A 4-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel is placed in a nitrogen atmosphere, and 100 parts of polyisocyanate obtained in Production Example 1 and 70 parts of methyl ethyl ketone are charged and mixed. Methyl ethyl ketoxime (28 parts) is added dropwise so that the reaction solution temperature does not exceed 60 ° C., and the mixture is stirred for 30 minutes after completion of the addition. Then, after adding 0.0049 parts of dibutyltin dilaurate, 35 parts of a diol “Placcel 205BA” (trade name number average molecular weight 510 of Daicel Chemical) having one carboxyl group is added, and the isocyanate group is detected by infrared spectroscopy. The mixture is stirred at 80 ° C. for 120 minutes until it disappears. Next, 6 parts of N, N-dimethylethanolamine is added for neutralization, and 72 parts of ion-exchanged water is further added. Thereafter, methyl ethyl ketone was distilled off at 60 ° C. under reduced pressure to obtain an aqueous blocked polyisocyanate having a resin solid content of 70% by mass, water of 30% by mass, pH 8.0, and blocked isocyanate group concentration of 8.0% per resin. A composition was obtained. The viscosity of this aqueous block polyisocyanate composition was x.

[Comparative Example 2] (Production of aqueous block polyisocyanate composition)
It carried out like Example 1 except using each ingredient shown in Table 1. The results are shown in Table 1.
[Example 6] (Preparation and evaluation of aqueous coating composition)
Aqueous polyester polyol “SETAL 6306 SS-60” (trade name of AKZO, resin hydroxyl group concentration 2.7% by mass, resin acid value 43 mg KOH / g) 100 parts of dimethylaminoethanol neutralized product, aqueous block polyisocyanate composition of Example 1 100 parts of the product was mixed, and ion-exchanged water was added to prepare a solid content of 20% by mass. This coating solution was applied with an applicator and baked at 150 ° C. for 30 minutes. The impact resistance test was ◎.

[Examples 7 to 9, Comparative Example 5 ] (Preparation and Evaluation of Aqueous Coating Composition)
It carried out like Example 6 except using the water-based block polyisocyanate composition shown in Table 2. The results are shown in Table 2.
[Comparative Example 4 ] (Preparation and evaluation of aqueous coating composition)
Aqueous polyester polyol "SETAL 6306 SS-60" (trade name of AKZO, resin hydroxyl group concentration 2.7% by mass, resin acid value 43 mg KOH / g) 100 parts of dimethylaminoethanol neutralized product, melamine "Cymel 327" (Mitsui Cytec Co., Ltd.) (Trade name) 100 parts were mixed, and ion-exchanged water was added to prepare a solid content of 20% by mass. This coating solution was applied with an applicator and baked at 150 ° C. for 30 minutes. The impact resistance test was x.

  The aqueous coating composition containing the water-based blocked polyisocyanate composition of the present invention is used for top intermediate coating and undercoating, such as coatings for new vehicle outer panels, coatings for exterior parts of buildings, coatings for plastic parts such as bumpers, automotive repair coatings, and precoat metals. It is suitably used in the field of organic coating materials such as.

Claims (3)

An aqueous block polyisocyanate composition characterized by satisfying all of the following conditions.
1) The precursor is a polyisocyanate having an average number of isocyanate groups of 4.0 to 20 derived from at least one aliphatic / alicyclic diisocyanate monomer and a divalent to hexavalent alcohol compound, and has a hydrophilic group. 50 to 95% by weight of blocked polyisocyanate.
2) 1 to 49% by mass of organic solvent.
3) Water is 1 to 49% by mass.   The aqueous block polyisocyanate composition according to claim 1, wherein the aliphatic / alicyclic diisocyanate monomer is hexamethylene diisocyanate. An aqueous coating composition comprising the aqueous blocked polyisocyanate composition according to claim 1 or 2 .