JPH07258598A - Blocked polyisocyanate and composition for one-pack coating material of good storage stability - Google Patents

Abstract

PURPOSE:To obtain a blocked polyisocyanate composition useful for obtaining a one-pack polyurethane resin coating material excellent in low-temperature curability and storage stability by selecting a blocked polyisocyanate composition containing a specified amount of a free monofunctional active hydrogen compound and having specified properties. CONSTITUTION:A blocked polyisocyanate composition which is liquid at 25 deg.C and is a blocked polyisocyanate desirably at least partially consisting of structural units derived from hexamethylene diisocyanate (e.g. a polyisocyanate blocked with methyl ethyl ketoxime), wherein 0.15-3.0 equivalents, per equivalent of the blocked NCO groups, of a free monofunctional active hydrogen compound (e.g. methyl ethyl ketoxime) is contained. This composition is mixed with a polyol (e.g. acrylic polyol) having a hydroxyl value of the resin component of 10-300mgKOH/g to obtain a one-pack solution-type coating composition.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel urethane thermosetting coating composition.

[0002]

2. Description of the Related Art Conventionally, polyurethane resin paints have very excellent abrasion resistance, chemical resistance and stain resistance, and their demand tends to increase. However, since polyurethane resin paints are generally two-part, it is extremely inconvenient to use them. That is, an ordinary polyurethane resin coating consists of two components, a polyol and a polyisocyanate, and it is necessary to store them separately and mix them at the time of coating. In addition, under the present circumstances, once mixed, the coating material gels in a short time and cannot be used. This makes it extremely difficult to perform automatic painting in the field of line painting such as automobiles or weak electric painting. In addition, since isocyanate reacts easily with water, it cannot be used in water-based paints such as electrodeposition paints. Further, since it is necessary to sufficiently wash the coating machine and the coating tank at the end of the work, the work efficiency is significantly reduced. In order to improve the above-mentioned drawbacks, it has been proposed to use a blocked isocyanate in which all active isocyanate groups are blocked with a blocking agent. This blocked isocyanate does not easily react with the polyol at room temperature, but at high temperature, the blocking agent is dissociated, the active isocyanate group is regenerated, and the blocked isocyanate reacts with the polyol to cause a crosslinking reaction, so that the above-mentioned drawbacks can be improved.

However, the reaction between the blocked isocyanate and the polyol gradually proceeds at room temperature, but the blocking agent dissociates to react with the isocyanate and the polyol, the viscosity of the coating increases, and finally the gelation occurs and the flow becomes poor. , Can not be used. This storage stability was less of an issue for those requiring high baking temperatures for the crosslinking reaction. However, recent research on blocking agents, catalysts, etc. has developed a system in which the crosslinking reaction proceeds at a low baking temperature, and the storage stability becomes worse as the crosslinking reaction proceeds at lower temperatures, which is a major drawback as a one-component paint. Was there.

Therefore, in the field of polyurethane resin coatings, for example, upper intermediate coatings for automobiles, chipping-resistant coatings, electrodeposition coatings,
Low cross-linking temperature and storage stability in pre-coated metal / rust-proof steel plates for automobile parts, metal products such as home appliances and office equipment, paints for building materials, paints for plastics, adhesives, adhesives, sealing agents, etc. There has been a demand for the emergence of a one-component polyurethane resin coating material excellent in heat resistance.

Usually, the blocked isocyanate has an isocyanate group: active hydrogen of the blocking agent = 1: 1.01-
It is mixed and synthesized at a ratio of 1: 1.1. That is, the blocked isocyanate contains 0.01 to 0.1 equivalent of free blocking agent per equivalent of blocked isocyanate. However, this is because the blocking is completed, and the amount added is too small to improve the storage stability, and the expected effect cannot be obtained.

Further, JP-A-5-310884 discloses that an equivalent of blocked isocyanate is 0.1 to 0.1.
A solid block polyisocyanate composition containing 1.0 equivalent of a free blocking agent and a method of using the same in a powder coating are disclosed. However, the disadvantages of the powder coating are poor appearance and high curing temperature. There is no description or suggestion regarding the solution type one-pack coating composition according to the present invention and its excellent storage stability capable of solving the above problems.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a coating composition having excellent storage stability in a solution type one-component coating composition which uses a blocked polyisocyanate as a curing agent and is cured at a low temperature.

[0008]

Means for Solving the Problems As a result of intensive investigations by the present inventors, by containing a specific substance in the paint, the storage stability of the paint using the same was significantly improved and the present invention was achieved. It was. That is, the present invention is characterized in that it is liquid at 25 ° C. and contains 0.15 to 3.0 equivalents of free monofunctional active hydrogen-containing compound per equivalent of blocked isocyanate. Is an isocyanate composition.

The blocked polyisocyanate is the above-mentioned blocked polyisocyanate composition having at least part of a unit derived from hexamethylene diisocyanate as a constituent unit. Resin component hydroxyl value 10-300 mg
Solution type characterized in that KOH / g polyol and blocked polyisocyanate are the main components and that 0.15 to 3.0 equivalents of free monofunctional active hydrogen-containing compound are contained per equivalent of blocked isocyanate. It is a one-pack coating composition.

The purpose of the above-mentioned solution type one-pack coating composition is that the blocked polyisocyanate has at least a part of a unit derived from hexamethylene diisocyanate as a constitutional unit. The blocked polyisocyanate in the present invention is obtained by a known reaction between polyisocyanate and a blocking agent. As the polyisocyanate, for example, isocyanurate-modified polyisocyanate, buret-modified polyisocyanate,
Urethane modified polyisocyanate and diisocyanate,
There are triisocyanate and the like. Preferred is isocyanurate-modified polyisocyanate, which is excellent in weather resistance and heat resistance. When synthesizing an isocyanurate-modified polyisocyanate, for example, JP-A-57-47321, JP-A-61-111371, and Japanese Patent Application No. 5-24152.
It may be modified with a hydroxyl compound as described in No. Examples of the hydroxyl compound used for modification include methanol, ethanol, isopropanol, monohydroxyl compounds such as phenol, ethylene glycol, propylene glycol, 1,3-butanediol, pentanediol, hexanediol, cyclohexanediol, neopentyl glycol, 2,2,4-
Dihydroxyl compounds such as trimethyl 1,3-pentanediol, low molecular weight polyhydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol, aliphatic hydrocarbon polyols, polyether polyols,
There are high molecular weight polyhydric alcohols such as polyester polyols and epoxy resins. These may be used alone or in combination of two or more.

These polyisocyanates are derived from aliphatic, cycloaliphatic or aromatic diisocyanates. As the aliphatic diisocyanate, those having 4 to 30 carbon atoms,
Alicyclic and aromatic diisocyanates have 8 to 3 carbon atoms.
0 is preferable, for example, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate (hereinafter referred to as HMDI), 2,2,4-trimethyl-1,6-
Hexamethylene diisocyanate, lysine diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, hereinafter referred to as IPDI), 1,3-bis (isocyanatomethyl) -cyclohexane, 4,4′-dicyclohexylmethane Examples thereof include diisocyanate, tolylene diisocyanate (hereinafter referred to as TDI), 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate and xylylene diisocyanate. Above all,
HMDI is preferable from the viewpoint of weather resistance and industrial availability. These may be used alone or in combination.

Examples of the blocking agent in the present invention include alcohol type, phenol type, active methylene type, mercaptan type, acid amide type, acid imide type, imidazole type, urea type, oxime type, amine type, imide type compounds,
There are pyridine compounds and the like, and these may be used alone or in combination. Examples of more specific blocking agents are shown below.

Alcohols such as methanol, ethanol, propanol, butanol, 2 ethylhexanol, methyl cellosolve, butyl cellosolve, methyl carbitol, benzyl alcohol, cyclohexanol, etc., and phenols such as phenol, cresol, ethylphenol, butylphenol, nonylphenol. , Dinonylphenol, styrenated phenol, hydroxybenzoic acid ester, etc., as active methylene type, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, etc., mercaptan type, butyl mercaptan, dodecyl mercaptan, etc., acid Examples of amide-based compounds include acetanilide, acetic amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, and the like. As a system, succinimide,
Maleic imide, imidazole-based, imidazole, 2-methylimidazole, urea-based, urea, thiourea, ethylene urea, etc., oxime-based, formaldoxime, acetoaldoxime, acetoxime, methylethylketoxime, cyclohexanone oxime, etc. Examples of amines include diphenylamine, aniline, and carbazole; examples of imines include ethyleneimine and polyethyleneimine; examples of bisulfites include sodium bisulfite; and examples of pyridines include 2-hydroxypyridine, 2-hydroxyquinoline.

Of these, oxime type, active methylene type and phenol type are preferable, and acetoxime and methyl ethyl ketoxime are particularly preferable. The reaction between the polyisocyanate and the blocking agent can be carried out with or without the presence of a solvent. In the blocking reaction, an organic metal salt of tin, zinc, lead or the like, a tertiary amine or the like may be used as a catalyst.

The reaction can be generally carried out at -20 to 150 ° C, preferably 0 to 100 ° C. 100
If the temperature is higher than 0 ° C, a side reaction may occur. On the other hand, if the temperature is too low, the reaction rate becomes slow, which is disadvantageous. The monofunctional active hydrogen-containing compound in the present invention is basically the same kind of compound as the blocking agent, and all the blocking agents shown above are applicable.

What is required of the monofunctional active hydrogen-containing compound is to prevent the presence of free isocyanate groups during storage and reduce the probability of reaction with the polyol, and to prevent the reaction between the isocyanate groups and polyol during baking and curing. Since it does not hinder, a compound having the same system as the blocking agent of the blocked polyisocyanate is desirable as the monofunctional active hydrogen-containing compound, and it has a low boiling point and rapidly goes out of the system by baking. . The boiling point is preferably 250 ° C. or lower at atmospheric pressure, more preferably 200 ° C. or lower. That is, the preferred monofunctional active hydrogen-containing compound is
They are alcohol-based, mercaptan-based, imidazole-based, oxime-based, imine-based, and pyridine-based compounds having the above boiling points. Particularly preferred are alcohol-based and oxime-based compounds.

For example, in a block polyisocyanate containing an oxime-based compound as a blocking agent, acetoxime and methylethylketoxime are most preferred as the monofunctional active hydrogen-containing compound, and other oximes such as cyclohexanone oxime, ethanol, propanol, and the like.
Alcohols such as butanol and butyl cellosolve are also preferable.

The monofunctional active hydrogen-containing compound is added in an amount of 0.15 to 3.0 equivalents, preferably 0.2 to 2.0 equivalents per equivalent of blocked isocyanate. 0.1
If it is less than 5 equivalents, the effect of improving storage stability is poor, and if it exceeds 3.0 equivalents, it becomes difficult to quickly go out of the system at the time of baking, resulting in insufficient curing, and the thinner composition is restricted, resulting in poor coating appearance. Have an adverse effect.

When a monofunctional active hydrogen-containing compound different from the blocking agent is added to the blocked polyisocyanate, it is preferably added after the reaction of the polyisocyanate and the blocking agent. Further, the monofunctional active hydrogen-containing compound may be added to the polyol or may be added at the time of blending the polyol and the blocked polyisocyanate. The monofunctional active hydrogen-containing compound may be used alone or in combination of two or more kinds.

The blocked polyisocyanate composition of the present invention contains a suitable solvent, if necessary. Examples of the solvent include hydrocarbons such as benzene, toluene, xylene, cyclohexane, mineral spirit, and naphtha, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, esters such as ethyl acetate, -n-butyl acetate, and cellosolve acetate. Etc.

The blocked polyisocyanate composition of the present invention may be liquid and fluid at 25 ° C., and preferably has a viscosity at 25 ° C. of 100,000.
cps or less, further preferably 50,000 cps or less, and more preferably 10,000 cps or less. In order to make a block-type polyisocyanate composition that is solid at room temperature into a solution-type paint, it is necessary to stir or heat for a long time to mix it with the polyol, which is not preferable.

The polyol in the present invention is a compound having at least two hydroxyl groups in one molecule, for example, aliphatic hydrocarbon polyols, polyether polyols, polyester polyols, epoxy resins, fluorine polyols and Examples thereof include acrylic polyols. Specific examples of the aliphatic hydrocarbon polyols include:
Examples thereof include terminal hydroxylated polybutadiene and hydrogenated products thereof. Examples of the polyether polyols include polyether polyols obtained by adding alkylene oxides such as ethylene oxide and propylene oxide to a single or mixture of polyhydric alcohols such as glycerin and propylene glycol, and a polytetraol. Polyethylene polyols obtained by reacting methylene glycols and alkylene oxides with polyfunctional compounds such as ethylenediamine and ethanolamine, and so-called polymer polyols obtained by polymerizing acrylamide and the like using these polyethers as a medium. Etc. are included.

As the polyester polyols, for example, a dibasic acid alone selected from the group of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid and terephthalic acid. Or a polyester polyol resin obtained by a condensation reaction of a mixture and a polyhydric alcohol selected from the group of ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, glycerin, etc., alone or in a mixture, and, for example, ε- Examples thereof include polycaprolactones obtained by ring-opening polymerization of caprolactone using a polyhydric alcohol.

The epoxy resins include, for example, novolac type, β-methyl epichloro type, cyclic oxirane type, glycidyl ether type, glycol ether type, epoxy type of aliphatic unsaturated compound, epoxidized fatty acid ester type,
Examples thereof include polycarboxylic acid ester type, aminoglycidyl type, halogenated type, resorcin type epoxy resins and the like, and resins obtained by modifying these epoxy resins with amino compounds, polyamide compounds and the like.

Examples of the fluorinated polyols are, for example, JP-A-57-34107 and JP-A-61-275311.
There are copolymers of fluoroolefin, cyclohexyl vinyl ether, hydroxyalkyl vinyl ether, monocarboxylic acid vinyl ester and the like disclosed in Japanese Patent Publication No. Acrylic polyols are obtained by copolymerizing a polymerizable monomer having one or more active hydrogens in one molecule with another monomer copolymerizable with the polymerizable monomer.
For example, acrylic acid esters having active hydrogen such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate,
Methacrylic acid esters having active hydrogen such as 2-hydroxydiethyl methacrylate, 2-hydroxypropyl methacrylate, and 2-hydroxybutyl methacrylate, or acrylic acid monoesters or methacrylic acid monoesters of glycerin, trimethylolpropane A single or a mixture selected from the group of (meth) acrylic acid esters having polyvalent active hydrogen such as acrylic acid monoesters or methacrylic acid monoesters, and methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic Acrylic acid esters such as acid-n-butyl, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacrylic acid-n Hexyl, cyclohexyl methacrylate, lauryl methacrylate, methacrylic acid esters such as glycidyl methacrylate, and if necessary, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamide, N-methylol acrylamide, It is obtained by copolymerizing an unsaturated amide such as diacetone acrylamide and a single or a mixture selected from the group of other polymerizable monomers such as styrene, vinyltoluene, vinyl acetate and acrylonitrile.

Further, polymerizable UV-stable monomers such as 4- (meth) acryloyloxy-2,2,6, which are exemplified in JP-A-1-261409, JP-A-3-6273 and the like. 6-tetramethylpiperidine, 4-
(Meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine,
An acrylic polyol resin obtained by copolymerizing 2-hydroxy-4- (3-methacryloxy-2-hydroxypropoxy) benzophenone or the like can also be used.

Particularly preferable among these polyols are the above-mentioned acrylic polyols. The polyol of the present invention has a resin component hydroxyl value of 10 to 300 mg KO.
H / g. When the hydroxyl value of the resin component is less than 10 mgKOH / g, the crosslinking density of urethane due to the reaction with the isocyanate component is reduced and the function of the urethane bond cannot be exhibited, and when the hydroxyl value of the resin component exceeds 300 mgKOH / g, On the contrary, the crosslink density increases, the mechanical properties of the coating film deteriorate, and in some cases, the hydroxyl group and the isocyanate group do not completely react, which is not preferable.

The equivalence ratio of the blocked isocyanate group in the blocked polyisocyanate to the hydroxyl group in the polyol in the present invention is determined by the required physical properties of the coating film. A melamine resin can also be used together. As the melamine resin, hexamethoxymethylol melamine,
Examples include methyl butylated melamine and butylated melamine.

In the composition of the present invention, the following raw materials commonly used in the art can be used. For example, quinacridone-based, azo-based, phthalocyanine-based organic pigments, titanium oxide, barium sulfate, calcium carbonate,
Inorganic pigments such as silica, other, carbon-based pigments, metal foil pigments, rust-preventive pigments, hindered amine-based, benzotriazole-based, benzophenone-based UV absorbers, hindered phenol-based, phosphorus-based, sulfur-based, Additives such as hydrazine-based antioxidants, tin-based, zinc-based, amine-based urethane formation (blocking agent dissociation) catalysts, leveling agents, rheology control agents, pigment dispersants, etc. If necessary, suitable solvents when mixing the components, for example, benzene, toluene, xylene, cyclohexane, mineral spirits, hydrocarbons such as naphtha, acetone, methyl ethyl ketone, ketones such as methyl isobutyl ketone,
It can be appropriately selected and used from the group of esters such as ethyl acetate, -n-butyl acetate, cellosolve acetate, etc. according to the purpose and application. These solvents may be used alone or in combination of two or more.

The solution type one-pack coating composition of the present invention is premised to be cured at a low temperature.
For example, the gel fraction when baked at 130 ° C. for 30 minutes (pass time) is 80% or more. The gel fraction is a value of the undissolved part weight when the cured coating film is immersed in acetone at 20 ° C. for 24 hours, before the immersion.

[0031]

EXAMPLES All "parts" in the examples are by weight.
The evaluation was performed according to the following. (Storage stability) A liquid whose coating solid content was adjusted to 50% with a thinner was stored at 50 ° C., and the number of days until gelation was examined,
Less than 21 days is represented by x, 21 days or more and less than 28 days is represented by O, and 28 days or more is represented by ⊚. (Curability) The value (gel fraction) of the undissolved part weight of a cured coating film baked at 130 ° C. for 30 minutes (pass time) before being immersed in acetone at 20 ° C. for 24 hours was calculated and calculated as 80 Less than% is x, 80% or more and less than 90% is good, 90
% Or more is represented by ◎.

The curability was evaluated twice, on the day when the paint was compounded (without storage) and after storage at 50 ° C. for 14 days. The sample which was gelled before 14 days was also coated with an applicator to evaluate the curability. (Coating film haze) It is applied to a transparent glass plate having a thickness of 1 mm,
Film thickness 50 baked at 130 ° C for 30 minutes (pass time)
The coating film of μ was measured by a direct reading haze computer HGM-2DP of Suga Test Instruments Co., Ltd. Less than 0.5 is ○, 0.5
The above is represented by x. (Coating gloss) Coated on white tile, 30 at 130 ℃
The coating film having a film thickness of 50 μm which was baked for minutes (pass time) was measured at 60 ° by a digital automatic colorimeter of Suga Test Instruments Co., Ltd. A value of 95 or more is represented by O, and a value of less than 95 is represented by X.

(Production Example 1) (Production of Block Polyisocyanate) An HMDI-based isocyanurate-modified polyisocyanate “Duranate MF” was placed in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser tube, a nitrogen blowing tube, and a dropping funnel.
-90X "(trade name of Asahi Kasei, NCO content 16.
4%, solid content 90%) 100 parts and xylene 72 parts are charged, and the inside of the flask is made a nitrogen atmosphere. Reaction temperature is 50 ℃
35 parts of methyl ethyl ketoxime was added dropwise so as not to exceed the limit, and it was confirmed that the characteristic absorption of isocyanate in the infrared spectrum had disappeared, and a blocked polyisocyanate solution with a solid content of 60% was obtained. The free monofunctional active hydrogen-containing compound (methylethylketoxime) in this blocked polyisocyanate solution is 0.03 equivalent per equivalent of blocked isocyanate (hereinafter, this ratio is referred to as an equivalent ratio). The viscosity at 25 ° C is 300 cps. Further, the viscosities at 25 ° C. of the solid content of 75% and the solid content of 85% obtained by changing the addition amount of xylene by the same method were 2000 cps and 50,000 cps, respectively.

(Production Example 2) (Production of Block Polyisocyanate) 100 parts of HMDI-based isocyanurate-modified polyisocyanate “Duranate TPA-100” (trade name of Asahi Kasei Kogyo Co., Ltd., NCO content 23.5%) was used, and methyl ethyl ketoxime was used. The amount of xylene added is 50
Parts and 98 parts, except that it was carried out in the same manner as in Production Example 1 to obtain a blocked polyisocyanate solution having a solid content of 60% and an equivalent ratio of 0.03.

(Production Example 3) (Production of Block Polyisocyanate) HMDI-based bullet modified polyisocyanate "Duranate 24A-100" (trade name of Asahi Kasei Kogyo, NCO
Content 23.5%) 100 parts, except that the addition amounts of methyl ethyl ketoxime and xylene were changed to 50 parts and 98 parts, respectively, the same procedure as in Production Example 1 was carried out to obtain a block having a solid content of 60% and an equivalent ratio of 0.03. A polyisocyanate solution was obtained.

(Production Example 4) (Production of Block Polyisocyanate) IPDI-based isocyanurate-modified polyisocyanate "IPDI-T1890" (Huls trade name, NCO
(17.0% content) and 100 parts of methyl ethyl ketoxime and xylene were added in amounts of 36 parts and 89 parts, respectively, and the same procedure as in Production Example 1 was repeated to obtain a block having a solid content of 60% and an equivalent ratio of 0.03. A polyisocyanate solution was obtained.

(Production Example 5) (Production of Block Polyisocyanate) TDI-based urethane-modified polyisocyanate "Coronate L" (trade name of Nippon Polyurethane Industry, NCO content 1
3.2%, solid content 75%) 100 parts, and added methyl ethyl ketoxime and xylene at 28 parts,
Solid content of 60
%, And an equivalent ratio of 0.03 was obtained as a blocked polyisocyanate solution.

(Production Example 6) (Production of Block Polyisocyanate) A four-necked flask equipped with a stirrer, a thermometer, a reflux cooling tube, a nitrogen blowing tube, and a dropping funnel was placed in a nitrogen atmosphere and H 2
MDI-based isocyanurate-modified polyisocyanate "Duranate TPA-100" (trade name of Asahi Kasei Kogyo, N
CO content 23.5%) 100 parts, xylene 113 parts, and zinc 2-ethylhexanoate 0.1 parts are put in an oil bath to make 9
Heat to 0 ° C. 75 parts of ethyl acetoacetate is added dropwise thereto and reacted with stirring. After the dropping was completed, the reaction was performed for 12 hours. It was confirmed by infrared spectrum that the absorption of isocyanate groups had disappeared, and a blocked polyisocyanate solution having a solid content of 60% and an equivalent ratio of 0.03 was obtained.

(Production Example 7) (Production of Block Polyisocyanate) A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser tube, a nitrogen blowing tube, and a dropping funnel was placed in a nitrogen atmosphere, and H
MDI-based isocyanurate-modified polyisocyanate "Duranate TPA-100" (trade name of Asahi Kasei Kogyo, N
100 parts of CO content (23.5%) and 99 parts of xylene are added and heated to 50 ° C. in an oil bath, 56 parts of 2-hydroxypyridine are added dropwise and the reaction is carried out with stirring. After the dropping was completed, the reaction was carried out for 8 hours. It was confirmed by infrared spectrum that the absorption of isocyanate groups had disappeared, and a blocked polyisocyanate solution having a solid content of 60% and an equivalent ratio of 0.05 was obtained.

[0040]

Example 1 The amount of methyl ethyl ketoxime added was 51
Parts and xylene were added in the same manner as in Production Example 1 except that the addition amount was changed to 56 parts to obtain a blocked polyisocyanate solution having a solid content of 60% and an equivalent ratio of 0.5.

[0041]

Example 2 The blocked polyisocyanate obtained in Production Example 1 (latent isocyanate content per resin: 13.
2%, solid content 60%, equivalent ratio 0.03) 100 parts and acrylic polyol (Dainippon Ink's trade name Acrydike A-801, resin content hydroxyl value 100 mgKOH / g, solid content 50%) 212 parts, methyl ethyl ketoxime 2 ．
0 parts, and an organometallic catalyst (trade name Sca manufactured by Sankyo Machine Synthesis
3.3 parts (t2K, solid content 50%). The equivalent ratio of this coating solution is 0.15. To this, a mixture of ethyl acetate / toluene / butyl acetate / xylene / propylene glycol monomethyl ether acetate (weight ratio = 30/30/20/15/5) was added as a thinner, and a Ford cup # 4 was used for coating film test. The temperature was adjusted to 20 seconds / 20 ° C. For storage stability test, the solid content is 5
It adjusted to 0% and the storage stability test was done. The coating solution for measuring the physical properties of the coating film was applied with an air spray gun so that the dry film thickness would be 50 μm, and baked in an oven maintained at 130 ° C. for 30 minutes. Table 2 shows the obtained storage stability test results and curability measurement results. The equivalent ratio in the table is the equivalent ratio of free monofunctional active hydrogen-containing compound / blocked isocyanate group. The coating film haze and coating film gloss were both good.

[0042]

[Examples 3 to 13 and Comparative Examples 1 to 7] Coating compositions were prepared according to the formulations shown in Table 1, and storage stability tests and coating film physical properties were measured in the same manner as in Example 2. The results are shown in Table 2. Incidentally, the coating film haze,
The coating film gloss was both good.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

INDUSTRIAL APPLICABILITY The composition of the present invention can achieve both low-temperature curability and storage stability as compared with a conventional solution type one-component polyurethane paint mainly composed of a polyol and a blocked isocyanate. Intermediate coating, chipping-resistant coating, electrodeposition coating, coating for automobile parts, precoat metal for metal products such as home appliances and office equipment, rust-proof steel plate, coating for building materials, coating for plastics, adhesives, adhesion promoters Excellent performance as a sealing agent, etc.

Claims (4)

[Claims] 1. 0.15 to 3.0 per equivalent of blocked isocyanate which is liquid at 25 ° C.
A blocked polyisocyanate composition containing an equivalent amount of a free monofunctional active hydrogen-containing compound. 2. The block polyisocyanate composition according to claim 1, wherein the block polyisocyanate has at least part of a unit derived from hexamethylene diisocyanate as a constituent unit. 3. A resin component having a hydroxyl value of 10 to 300 mg KOH
/ G of polyol, blocked polyisocyanate as a main component, per blocked isocyanate equivalent,
A solution type one-pack coating composition comprising 0.15 to 3.0 equivalents of a free monofunctional active hydrogen-containing compound. 4. The solution type one-pack coating composition according to claim 3, wherein the blocked polyisocyanate has at least part of a unit derived from hexamethylene diisocyanate as a constituent unit.