JP2007023208A - Aqueous blocked polyisocyanate composition and water-borne composition containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous blocked polyisocyanate composition which can achieve high coating film curability and excellent flexibility, and to provide a water-borne coating composition containing the same. <P>SOLUTION: This aqueous blocked polyisocyanate is characterized by being derived from at least the following (1) to (4) components. (1) A polyisocyanate derived from at least one aliphatic or alicyclic diisocyanate monomer and satisfying the following conditions (a) to (c). (a) The concentration of the diisocyanate monomer : ≤3 mass%. (b) The viscosity at 25°C : 50 to 2,000,000 mPa s. (c) The average number of the isocyanate groups : 4.0 to 20. (2) A carboxy group-having diol having a number-average mol.wt. of <200. (3) A blocking agent. (4) An organic amine compound. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a water-based block polyisocyanate composition and a water-based coating composition using the same as a curing agent, which can form a coating film having particularly high hardness and excellent flexibility.

  In recent years, water-based paints have attracted attention from the viewpoints of the global environment, safety, hygiene, and the like, and have come to be used in industrial paints such as food cans and coil coatings from architectural 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 or alicyclic diisocyanate as an isocyanate component, the 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.

  As an aqueous technology for block polyisocyanate, for example, a technology (Patent Document 4) using a surfactant for making block polyisocyanate aqueous, polyethylene oxide containing a higher fatty acid having 7 to 26 carbon atoms, And technology that uses sodium bisulfite as a 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, high-speed stirring group, etc. (Patent Document 6), making a water-resistant polyisocyanate block having a heat-resistant isocyanurate structure (Patent Documents 7 and 8), a polyoxyethylene group in a part of the polyisocyanate In addition, polyethylene glycol, ethylene oxide and propylene Side copolymer of a water-soluble polymer compound mixed technology (Patent Document 9), such as a technique for imparting hydrophilicity (Patent Document 10) are disclosed in above literature by hydroxy acids.

However, in recent years, further improvement in the flexibility of the coating film has been desired. In particular, in automobiles and the like, when pebbles, rock salt, and the like collide at low temperatures in winter and the like, the coating film absorbs the impact energy to improve the function of protecting the automobile.
It is also important to ensure the hardness of the coating film in order to ensure sharpness, and the coating film hardness obtained from the aqueous block polyisocyanate composition to which hydrophilicity is added only with nonionic groups may be lowered. (Patent Documents 11 and 12).

JP-A-56-157358 JP 63-175079 A JP 63-193968 A JP-A 52-59657 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 Japanese Patent Laid-Open No. 10-231347 Japanese Patent Application Laid-Open No. 11-100500

  An object of the present invention is to provide a water-based block polyisocyanate composition having a high coating film hardness and capable of achieving excellent flexibility 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 the above problems can be solved with a specific aqueous block polyisocyanate composition and an aqueous coating composition using the same, and have reached the present invention. did.
That is, the present invention is as follows.
1. An aqueous block polyisocyanate composition derived from at least the following components 1) to 4):
1) The following conditions a. Derived from at least one of aliphatic and alicyclic diisocyanate monomers ~ C. Polyisocyanate satisfying all of the above.
a. Diisocyanate monomer concentration: 3% by mass or less b. Viscosity at 25 ° C. is 50 to 2,000,000 mPa · s.
c. Isocyanate group average number of 4.0 to 20
2) Diol having a carboxyl group having a number average molecular weight of less than 200 3) Blocking agent 4) Organic amine compound 1. the aliphatic or alicyclic diisocyanate monomer comprises hexamethylene diisocyanate; The aqueous block polyisocyanate composition described.
3. 1. The ratio of (diol having a carboxyl group) / (diol having a polyisocyanate and a carboxyl group) is 5 to 50% by mass. Or 2. The aqueous block polyisocyanate composition described.
4.1. ~ 3. An aqueous coating composition comprising the aqueous block polyisocyanate composition according to any one of the above.

  The present invention is a water-based block polyisocyanate composition having a high coating film hardness and capable of achieving excellent flexibility and an aqueous coating composition containing the same, and has excellent performance as an aqueous intermediate coating, particularly an automotive intermediate coating. Can demonstrate.

The present invention will be specifically described below.
As the aliphatic diisocyanate that can be used in the present invention, those having 4 to 30 carbon atoms are preferable. For example, tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, hexamethylene diisocyanate (hereinafter referred to as HDI). 2), 2,2,4-trimethyl-hexamethylene-1,6-diisocyanate, lysine diisocyanate, and the like.
As the alicyclic diisocyanate 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 diisocyanate. and so on.
Among these, HDI is preferable from the viewpoint of weather resistance and industrial availability, and two or more kinds can be used in combination.

By inducing the diisocyanate monomer, a polyisocyanate that is a precursor of the aqueous block polyisocyanate composition of the present invention is obtained.
The polyisocyanate can include, for example, a biuret bond, a urea bond, an isocyanurate bond, a uretdione bond, a urethane bond, an allophanate bond, an oxadiazine trione bond, 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 or 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 is obtained by, for example, performing a cyclic trimerization reaction with a catalyst or the like, 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, 1 to 6 valent alcohol compounds 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 is, for example, a molar ratio of a hydroxyl group of the alcohol compound to the isocyanate group of the diisocyanate monomer is about 1/2 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 viscosity of the polyisocyanate used in the present invention at 25 ° C. is 50 to 2,000,000 mPa.s. s. When the viscosity is less than 50 mPa · s, the statistical average number of isocyanate groups contained in one molecule of polyisocyanate (hereinafter referred to as the average number of isocyanate groups) may decrease as a result. The viscosity of the aqueous block polyisocyanate composition to be obtained also increases, and the appearance of the coating film using the composition may deteriorate.
The average number of isocyanate groups in the polyisocyanate is 4.0 to 20, preferably 4.5 to 10. If it is less than 4.0, the curability of the finally obtained water-based block polyisocyanate composition and the flexibility of the obtained coating film may be lowered. If it exceeds 20, the water-based block polyisocyanate obtained is obtained. The reactivity after partial curing of the composition may decrease.

Next, the diol having a carboxyl group used in the present invention will be described in detail.
The number average molecular weight of the diol having a carboxyl group used in the present invention is less than 200. When it exceeds 200, the hardness of the coating film obtained from the aqueous block polyisocyanate composition obtained by using this decreases. Specific examples thereof include dimethylolpropionic acid and dimethylolbutanoic acid. Coating film obtained by using, as a curing agent, an aqueous block polyisocyanate composition which is derived from a diol having a specific isocyanate group average number of polyisocyanates which is a precursor of an aqueous block polyisocyanate composition and a carboxyl group having a specific molecular weight as described above. In addition to flexibility, it was surprising that high film hardness can be achieved.
The blocking agent that can be used in the present invention is described in detail below. The blocking agent is a low molecular weight compound having active hydrogen that reacts with the isocyanate group of the polyisocyanate. The isocyanate group reacted with the blocking agent does not react with the hydroxyl group of the polyol at room temperature, but reacts by heating.

The blocking agent that can be used in the present invention is a compound having one active hydrogen in the molecule, for example, alcohol, alkylphenol, phenol, active methylene, mercaptan, acid amide, and acid imide. 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, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, etc. (2) alkylphenols Mono- and dialkylphenols having an alkyl group having 4 or more carbon atoms as a substituent, such as n-propylphenol, i-propylphenol, n-butylphenol, sec-butylphenol, t-butylphenol, n-hexylphenol; Monoalkylphenols such as 2-ethylhexylphenol, n-octylphenol, n-nonylphenol, di-n-propylphenol, diisopropylphenol, isopropylcresol, di-n-butylphenol Nord, di -t- butylphenol, di -sec- butylphenol, di -n- octylphenol, di-2-ethylhexyl phenol, di alkylphenols di -n- nonylphenol

(3) Phenol type; phenol, cresol, ethyl phenol, styrenated phenol, hydroxybenzoic acid ester, etc. (4) Active methylene type; dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, etc. (5) Mercaptan series; Butyl mercaptan, dodecyl mercaptan, etc. (6) Acid amide series; Acetanilide, acetate amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam etc. (7) Acid imide series; Succinimide, maleic imide etc 8) Imidazole series; imidazole, 2-methylimidazole, etc. (9) Urea series; Urea, thiourea, ethylene urea, etc. (10) Oxime series; (11) Amine series; diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine, isopropylethylamine etc. (12) imine series; ethyleneimine, polyethyleneimine etc. (13) pyrazole series; pyrazole, 3-methylpyrazole 3,5-dimethylpyrazole and the like.
A preferred blocking agent is at least one selected from alcohols, oximes, acid amides, active methylenes, and pyrazoles.

Next, the organic amine compound that can be used in the present invention will be described in detail. The organic amine compound neutralizes the carboxyl group of the aqueous block polyisocyanate composition, imparts water dispersibility and water solubility to the aqueous block polyisocyanate composition, and contains ionic nitrogen in the molecule.
Examples of specific organic amine compounds include, for example, ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, and dibutylamine. C 1-20 linear, branched 1, 2 or tertiary amines such as trimethylamine, triethylamine, triisopropylamine, tributylamine, ethylenediamine, cyclic amines such as morpholine, N-alkylmorpholine, pyridine, mono Isopropanolamine, methylethanolamine, methylisopropanolamine, dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine Diethylethanolamine, a hydroxyl group-containing amines such as triethanolamine and the like.

The aqueous block polyisocyanate composition of the present invention can be derived using the raw materials detailed above. One example will be described in detail. First, the polyisocyanate and the blocking agent are reacted. This reaction can be performed with or without a solvent. When using a solvent, it is necessary to use a solvent inert to the isocyanate group. Examples of the solvent include ketone solvents such as acetone and methyl ethyl ketone, and ester solvents such as ethyl acetate.
When these solvents are finally removed, the boiling point of the solvent is preferably lower than that of water.
A blocked polyisocyanate in which an 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 a 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. On the other hand, if the temperature is lower than −20 ° C., the reaction rate decreases, which is disadvantageous.
It is preferable to react 50 to 90% of the isocyanate groups of the polyisocyanate with a blocking agent. If it is less than 50%, it will be easily gelled by the subsequent reaction with a diol having a carboxyl group, and the concentration of blocked isocyanate groups will decrease, which may be necessary in a large amount, and 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 composition decrease, which is not preferable. The average number of unblocked isocyanate groups of one molecule of the partially blocked polyisocyanate thus obtained is preferably 1.5 to 3.0. If it is less than 1.5, a diol having a carboxyl group that does not react with an isocyanate group remains, and the water resistance of the coating film formed thereby may be lowered. If it exceeds 3.0, gelation may occur during the reaction with a diol having a carboxyl group.

The thus obtained blocked polyisocyanate leaving an isocyanate group that has not reacted with the blocking agent is reacted with a diol having a carboxyl group.
When the polyisocyanate and the diol having a carboxyl group are reacted, the mass ratio of (diol having a carboxyl group) / (diol having a polyisocyanate and a carboxyl group) is 5 to 50% by mass, preferably 5 to 25% by mass. %, More preferably 5 to 10% by mass. If it is less than 5% by mass, the hydrophilicity of the resulting water-based block polyisocyanate composition may decrease, and if it exceeds 50% by mass, the water resistance of the coating film may decrease.

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 block polyisocyanate composition may be reduced, and if it exceeds 1.5, the pH of the water-based block polyisocyanate composition solution becomes high. In some cases, the stability of the paint using the resin may decrease.
The acid value of the aqueous block polyisocyanate composition thus obtained is 10 to 50 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. The water-based block polyisocyanate composition itself often has a high viscosity, and water becomes a medium of the water-based block polyisocyanate composition and can reduce the viscosity.
After adding water, the organic solvent used for the reaction is preferably removed. The organic solvent is usually removed under reduced pressure. Depending on the situation, the organic solvent can be left or added.

The aqueous block polyisocyanate composition produced as described above contains water as a medium and an organic solvent depending on the situation, and the concentration of the aqueous block polyisocyanate composition is preferably 30 to 90% by mass, more preferably 60 to 90% by mass. If it is 30% 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 90% by mass, the viscosity increases, Workability may be reduced.
The aqueous block polyisocyanate composition thus obtained preferably has a pH of 7.0 to 8.5, more preferably 7.0 to 8.0.
An aqueous coating composition is formed with the aqueous block polyisocyanate composition and the polyol thus obtained as the main components.

The polyol used in the present invention is dissolved or dispersed in a medium mainly containing water. Examples of these polyols include acrylic polyols, polyester polyols, polyether polyols, aliphatic hydrocarbon polyols, epoxy polyols, fluorine polyols, and chlorinated polyols.
Examples of polyester polyols, polyether polyols, and acrylic polyols include the aforementioned polyols.
Examples of the aliphatic hydrocarbon polyols include terminal hydroxylated polybutadiene and hydrogenated products thereof.

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, acrylic acid-n-butyl, acrylic acid-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, methacrylate-n-butyl, isobutyl methacrylate, methacrylate-n-hexyl, lauryl methacrylate A single or mixture selected from the group of esters, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, unsaturated amides such as acrylamide, N-methylol acrylamide, diacetone acrylamide, and methacrylic acid Acrylates obtained by polymerization in the presence or absence of a single or mixture selected from the group of other polymerizable monomers such as glycidyl, styrene, vinyl toluene, vinyl acetate, acrylonitrile, dibutyl fumarate and the like. Polyols.
As the polymerization method, emulsion polymerization, suspension polymerization, dispersion polymerization, and solution polymerization can be used. 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 with a mixture,
Examples of low molecular weight polyols and diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, and 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-hexanediol, 1,2-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl- Hexanediol, 1,2-octanediol, 1,2-decandioe 2,2,4-trimethylpentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, and the triols include, for example, glycerin, Examples of tetraols include polyester polyols obtained by a condensation reaction with a polyhydric alcohol selected from the group of diglycerin, dimethylolpropane, pentaerythritol and the like, and low molecular weight, for example. Examples thereof include polycaprolactones obtained by ring-opening polymerization of ε-caprolactone to the hydroxyl group of a polyol.

  Polyether polyols include, for example, ethylene oxide, propylene oxide, a single or mixture of polyvalent hydroxy compounds, using, for example, hydroxides such as lithium, sodium and potassium, strong basic catalysts such as alcoholates and alkylamines. Polyether polyols obtained by adding a single or mixture of alkylene oxides such as butylene oxide, cyclohexene oxide, and styrene oxide, polyether polyols obtained by reacting 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 include (1) diglycerin, ditrimethylolpropane, pentaerythritol, dipentaerythritol, etc. (2) e.g. erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, Sugar alcohol compounds such as rhamnitol (3) monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, ribodesource,
(4) Disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, melibiose,
(5) For example, trisaccharides such as raffinose, gentianose, and meletitose (6) There are tetrasaccharides such as stachyose.

The polyol is preferably 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. Preferable examples are triethylamine and dimethylethanolamine which are tertiary absorbing amines.
The hydroxyl group per resin content of the polyol is preferably 30 to 300 mgKOH / g, and the acid value is preferably 20 to 100 mgKOH / g.
Preferred polyols are acrylic polyols and polyester polyols.
The mixing ratio of the water-based blocked polyisocyanate composition and the above polyol is selected as necessary so that the equivalent ratio of the blocked isocyanate group of the water-based block polyisocyanate composition to the hydroxyl group of the polyol is in the range of 0.3 to 1.5. Is done.

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 using a melamine type hardening | curing agent, the mixing mass ratio of the water-system block polyisocyanate composition of this invention and a melamine type hardening | curing agent is 10/1 to 1/10, Preferably it is 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, decane carboxylic acid and the like as carboxylic acids, and as sulfonic acids, for example, paratoluenesulfonic acid and dodecylbenzene. Examples of phosphoric acid esters include dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, dilauryl phosphate, monoethyl phosphate, monoethyl phosphate, monobutyl phosphate, and monooctyl phosphate. Acid phosphates such as phosphates 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, n-butylamine and di-n-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%.
Moreover, you may add antioxidant, a ultraviolet absorber, a pigment, metal powder pigments, such as aluminum, inorganic pigments, such as a titanium oxide and carbon black, a rheology control agent, a leveling agent, and a solvent as needed.
The water-based paint composition prepared in this way is applied to metals such as automobiles, plastics, building materials, etc. by methods such as bell painting, spray painting, roll painting, shower painting, immersion painting, etc. It is useful as a paint for new car skins, exterior paint for buildings, paint for plastic parts such as bumpers, paint for repairing automobiles, paint for organic coatings such as pre-coated metal, etc.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.
All% means 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 using the following apparatus.
Equipment: Tosoh Corporation HLC-802A
Column: Tosoh Corporation G1000HXL x 1
G2000HXL 〃
G3000HXL 〃
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
The unit of the isocyanate group concentration is%.
(Viscosity measurement)
It measured at 25 degreeC using the E-type rotational viscometer (VISICONIC ED type | mold by Tokimec).
(Gel fraction)
When the cured coating film was immersed in acetone at 20 ° C. for 24 hours, the value of the undissolved partial mass with respect to the cured coating film mass before immersion was calculated. Less than 60% was x, 60% or more, and less than 80% was Δ, 80 % Or more is represented by ○.

(Shock resistance test)
Evaluation was performed at 20 ° C. using a DuPont impact resistance tester. Place on a cradle with a 50μm thick coating cured at 150 ° C for 30 minutes, place a striker (radius 6.35mm) and drop a 500g load from a height of 20cm. The state of the coating film was observed. The case where an abnormality such as a crack was observed on the coating film was marked as x, and the case where no abnormality was found was marked as ◯.
(Coating hardness)
The König hardness of a 50 μm-thickness coating film coated on a glass plate and cured at 150 ° C. for 30 minutes was measured at 20 ° C. with a pendulum type hardness meter manufactured by BYK Chemie. A coating hardness of less than 50 was indicated as x, and 50 or more was indicated as ◯.

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

[Production Example 2] (Production of polyisocyanate composition)
The same procedure as in Production Example 1 was carried out except that the polycaprolactone-based polyester polyol “Placcel 303” was 60 parts and the yield was 63%. The resulting polyisocyanate had a viscosity at 25 ° C. of 31000 mPa · s, an isocyanate content of 17.5% by mass, a diisocyanate monomer concentration of 0.1% by mass, a number average molecular weight of 1820, and an average number of isocyanate groups of 7.6. It was.
[Production Example 3] (Production of polyisocyanate composition)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel is placed in a nitrogen atmosphere, 600 parts of HDI (hexamethylene diisocyanate) is charged, and the temperature in the reactor is 70 ° C. with stirring. Retained. Isocyanuration catalyst tetramethylammonium capriate was added, and when the yield reached 40%, phosphoric acid was added to stop the reaction. After the reaction solution was filtered, unreacted HDI was removed using a thin film evaporator. The resulting polyisocyanate had a viscosity at 25 ° C. of 2700 mPa · s, an isocyanate content of 21.7% by mass, a diisocyanate monomer concentration of 0.1% by mass, a number average molecular weight of 660, and an average number of isocyanate groups of 3.4. It was.

[Example 1] (Production of aqueous block polyisocyanate composition)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was placed in a nitrogen atmosphere, and 100 parts of polyisocyanate obtained in Production Example 1, 50 parts of methyl ethyl ketone, N-methylpyrrolidone 14 Charge and mix the parts. Methyl ethyl ketoxime (32 parts) is added dropwise so that the reaction temperature does not exceed 60 ° C., and maintained for 30 minutes after the addition. Then, after adding 0.0042 parts of dibutyltin dilaurate, 9 parts of dimethylolpropionic acid (diol having one carboxyl group, molecular weight 134) is added. This solution is held at 80 ° C. for 120 minutes. Further, 6 parts of N, N, -dimethylethanolamine and 51 parts of ion-exchanged water are added. Thereafter, by distilling off methyl ethyl ketone at 60 ° C. under reduced pressure, an aqueous block polyisocyanate having a solid content of 70%, N-methylpyrrolidone of 7%, water of 23%, and a blocked isocyanate group concentration of 10.5% per resin. A composition was obtained.

[Examples 2 to 3] (Production of aqueous block polyisocyanate composition)
The procedure was the same as in Example 1 except that it was shown in Table 1. The results are shown in Table 1.
[Comparative Examples 1 and 2] (Production of aqueous block polyisocyanate composition)
The procedure was the same as in Example 1 except that it was shown in Table 1. The results are shown in Table 1.
[Comparative Example 3] (Production of aqueous block polyisocyanate composition)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was placed in a nitrogen atmosphere, and 100 parts of polyisocyanate obtained in Production Example 1, methoxypolyethylene glycol (molecular weight 600, Japanese fats and oils) (Trademark "Uniox M600") and 19 parts of N-methylpyrrolidone are charged and mixed. The temperature was maintained at 80 ° C. for 7 hours. The temperature inside the reactor was lowered to 50 ° C., 38 parts of methyl ethyl ketoxime was added dropwise, and it was confirmed that characteristic absorption of isocyanate groups by infrared spectrum disappeared. An aqueous block polyisocyanate composition having a solid content of 80% and a blocked isocyanate group concentration of 11.7% per resin was obtained.

[Example 4] Preparation and evaluation of aqueous coating composition Water-based polyester polyol (trade name of AKZO, SETAL 6306 SS-60 (resin hydroxyl group concentration: 2.7% by mass, resin acid value: 43 mg KOH / g) 100 parts of diethyl ethanol The neutralized amine product and 100 parts of the aqueous block polyisocyanate composition of Example 1 were mixed, and ion-exchanged water was added to adjust the solid content to 20%. This coating solution was applied with an applicator and baked at 150 ° C. for 30 minutes, the gel fraction was ◯, the coating film hardness was ◯, and the impact resistance was ◯.
[Examples 5 to 6] Preparation and evaluation of aqueous coating composition The same procedures as in Example 4 were performed except for the compositions shown in Table 2. The results are shown in Table 2.
[Comparative Examples 4 to 6] Preparation and evaluation of water-based coating composition The same procedures as in Example 4 were conducted except the conditions shown in Table 2. The results are shown in Table 2.

  The water-based block polyisocyanate composition of the present invention and the aqueous coating composition using the same as a curing agent are used for building coatings and industrial products such as food cans and coil coatings. Furthermore, it can be suitably used in the field of automotive one-component paints that require high quality such as weather resistance, chemical resistance, and impact resistance.

Claims (4)

An aqueous block polyisocyanate composition derived from at least the following components 1) to 4):
1) The following conditions a. Derived from at least one of aliphatic or alicyclic diisocyanate monomers ~ C. Polyisocyanate satisfying all of the above.
a. Diisocyanate monomer concentration: 3% by mass or less b. Viscosity at 25 ° C. is 50 to 2,000,000 mPa · s.
c. Isocyanate group average number of 4.0 to 20
2) Diol having a carboxyl group having a number average molecular weight of less than 200 3) Blocking agent 4) Organic amine compound   The aqueous block polyisocyanate composition according to claim 1, wherein the aliphatic or alicyclic diisocyanate monomer comprises hexamethylene diisocyanate.   The aqueous block polyisocyanate composition according to claim 1 or 2, wherein a ratio of (diol having a carboxyl group) / (diol having a polyisocyanate and a carboxyl group) is 5 to 50% by mass.   The water-based coating composition containing the water-system block polyisocyanate composition in any one of Claims 1-3.