JPH0953043A - One-component cold-curing urethane coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a one-component cold-curing urethane coating compsn. which gives a coating film excellent in weatherability, flexibility, etc., by combining a specific main component with a curative component comprising a specific blocked polyisocyanate. SOLUTION: This compsn. contains a polyhydroxyl compd. having a number- average mol.wt. of 300-60,000, a hydroxyl value of 10-500mgKOH/g, and an acid value of 0-200mgKOH/g as the main component and, as the curative component, a blocked isocyanate which is prepd. by reacting a diisocyanate compd. or a diisocyanate compd. mixture with a polyhydroxyl compd. having an average hydroxyl functionality of 4-100 and then blocking 50-100% of isocyanate groups of the resulting polyisocyanate (having an average isocyanate functionality of 4-20, an isocyanate group content of 5-20wt.%, a number-average mol.wt. of 1,200-10,000, and a viscosity of 2,000-200,000mPa.s/25 deg.C) with a thermally dissociable blocking agent and which has an isocyanate functionality of 4-20, an isocyanate group content of 2-15wt.%, and a number-average mol.wt. of 1,500-15,000.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-pack type urethane-based coating composition using a non-yellowing type block polyisocyanate, which has excellent low-temperature curability, weather resistance and the like, and is used for automobile coatings and architectural coatings. Is useful as

[0002]

2. Description of the Related Art Non-yellowing type polyisocyanates and blocked polyisocyanates have good weather resistance. For example, when they are used as a curing agent for urethane-based paints, the resulting coating films have chemical resistance and flexibility. Due to its excellent physical properties, it is extremely useful for coating metals, plastics, etc. in the fields of paints for automobiles, paints for construction, pre-coated metals, paints for cans, etc.

Further, in order to obtain polyisocyanate, a modifying agent such as polyol is used in addition to diisocyanate depending on the use. For example, in Japanese Patent Publication No. 6-70120, the number of carbon atoms is 2 to 30 in order to impart more flexibility.
Having a number average molecular weight of 400 to 1,500 and a hydroxyl group average number of functional groups of 2 to 3 in one molecule, in JP-A-3-40048, a number average molecular weight of 500 to 1,5.
00 polycaprolactone diol and / or triol are used as modifiers.

Further, in order to improve the drying property, for example, in JP-A-48-1099, a hydroxyl group-containing acrylic copolymer is reacted with a polyisocyanate. Further, in order to improve the sagging resistance to the vertical surface, JP-A-57-102918 proposes that the molecular weight, the hydroxyl value, the hydroxyl group / isocyanate equivalent ratio and the like have specific values.

Further, since polyurethane resin paints are generally two-component, it is extremely inconvenient to use them. That is, a normal urethane 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. Once mixed, the coating gels in a short time and cannot be used. The current situation. This is the line of pre-coat metal and post-coat etc. including anti-corrosion steel plate by spray coating, dipping coating, roll coating, electrodeposition coating etc. performed on automobiles, home appliances, office equipment, metal products in construction etc., plastic molded products etc. It is extremely difficult to automate the coating field or the field of using an adhesive containing polyisocyanate, an adhesiveness-imparting agent, or a sealing agent.

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 remarkably reduced. Conventionally, in order to improve the above-mentioned drawbacks, it has been proposed to use a blocked polyisocyanate in which all active isocyanate groups are blocked with a blocking agent. Although this blocked polyisocyanate does not react with the polyol at room temperature, it has the property of dissociating the blocking agent at high temperature and regenerating an active isocyanate group to react with the polyol to cause a cross-linking reaction. be able to.

However, the above crosslinking reaction requires a high baking temperature such as 150 to 200 ° C.
A high baking temperature not only increases energy costs, but also increases air pollution that accompanies it. I am using tools, but sometimes special jigs cannot be used.

[0008] Therefore, a one-part polyurethane coating composition having a low temperature curability is particularly desired, and several proposals for imparting a low temperature curability have been made. A curing accelerator is usually used in the one-component polyurethane coating composition, and many proposals therefor are made. Japanese Patent Publication Sho 44-18
877, JP-A-53-138434, JP-A-56-
No. 84714 and JP-A-57-8217 disclose specific organotin compounds, and JP-A No. 62-199609 discloses lead compounds and inorganic zinc compounds in JP-A-2-1991.
In Japanese Patent No. 12, gazette, an organotin compound and cobalt, nickel,
A combination of zinc compounds has been proposed. However, the low-temperature curability may not be sufficiently imparted only by these curing accelerators.

There are also many proposals regarding blocking agents. In JP-A-60-149572, alkyl acetoacetate is disclosed, in JP-A-6-287269, a combination of an oxime compound and an active methylene compound is disclosed, and JP-A-7-
Japanese Patent Laid-Open No. 7-216051 proposes a combined use of a triazole-based compound and a pyrazole-based compound in JP-A-304843, and a pyrazoline-based compound in JP-A-7-216051.

Most of the conventional proposals for imparting low temperature curability have been related to a curing accelerator and a blocking agent, but in JP-A-6-293878, the isocyanate group of polyisocyanate having an isocyanurate skeleton is disclosed. Although a low-temperature curability is imparted by polyfunctionalizing the above, further low-temperature curability is desired. Thus, there is a strong demand for low-temperature curable one-component polyurethane coating compositions, and further improvement in low-temperature curing performance is required.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a one-pack type urethane coating composition which overcomes the above problems and is excellent in low temperature curing property, weather resistance and the like. .

[0012]

Means for Solving the Problems The inventors of the present invention have surprisingly studied the above-mentioned problems, and as a result, surprisingly, 4-10
Obtained from a functional specific polyhydric hydroxy compound and a specific diisocyanate, by using a blocked polyisocyanate obtained by blocking the isocyanate group of a specific polyisocyanate with a specific heat-dissociable blocking agent, the above problems can be solved. Heading out, the present invention was completed.

That is, the present invention is as follows. A urethane coating composition comprising at least the following components (a) and (b): (A) As a main component, a number average molecular weight of 300 to 60,0
00, a polyhydric hydroxyl group-containing compound having a resin component hydroxyl value of 10 to 500 mgKOH / g and an acid value of 0 to 200 mgKOH / g. (B) As a curing agent component, an aliphatic or alicyclic diisocyanate alone or in a mixture and an average number of hydroxyl functional groups of 4 to
A polyisocyanate obtained by reacting 10 polyvalent hydroxy compounds and then substantially removing unreacted monomers, wherein (1) average number of isocyanate functional groups; 4 to 20 (2) isocyanate concentration; 5 to 20% by weight ( 3) Number average molecular weight; 1,200 to 10,000 (4) Viscosity; 2,000 to 200,000 mPa.s. s
/ 25 ° C (5) Isocyanate cyclic trimer concentration; 50% by weight of the isocyanate group of the polyisocyanate of 10% by weight or less
To 100% is blocked with at least one thermal dissociative blocking agent selected from alkylphenol-based, oxime-based, acid amide-based and active methylene-based compounds, and (1) average blocked isocyanate functional group number: 4 to 20 (2) Blocked isocyanate concentration; 2 to 15% by weight (3) Number average molecular weight; 1,500 to 15,000 blocked polyisocyanate. The coating composition as described above, wherein the polyisocyanate has an allophanate bond. The coating composition as described above or above, wherein the polyhydric hydroxy compound is a propylene oxide adduct polyether polyol and / or polyester.

The diisocyanate used in the present invention is aliphatic or alicyclic. Aromatic isocyanates can also be used, but weather resistance and the like are required, and they cannot be said to have sufficient effects in the field. The aliphatic diisocyanate preferably has 4 to 30 carbon atoms, and the alicyclic diisocyanate preferably has 8 to 30 carbon atoms.
For example, tetramethylene-1,4-diisocyanate,
Pentamethylene-1,5-diisocyanate, hexamethylene diisocyanate (hereinafter referred to as HMDI),
2,2,4-trimethyl-hexamethylene-1,6-diisocyanate, lysine diisocyanate, isophorone diisocyanate (hereinafter referred to as IPDI), 1,3-
Bis (isocyanatomethyl) -cyclohexane, 4,
4'-dicyclohexyl methane diisocyanate etc. can be mentioned. Among them, HMDI and IPDI are preferable from the viewpoint of weather resistance and industrial availability. The above diisocyanates may be used alone or in combination.

The polyhydroxy compound used in the present invention has an average number of hydroxyl functional groups of 4 to 10, preferably 5 to 8.
It is. The average number of hydroxyl functional groups is the number of hydroxyl groups statistically possessed by one molecule of the polyvalent hydroxy compound, and the number average molecular weight of the polyvalent hydroxy compound and the polyvalent hydroxy compound 1
It is calculated by the following general formula (1) from the total number of hydroxyl groups contained in parts by weight (hereinafter referred to as hydroxyl group concentration).

[0016]

[Equation 1]

Specific examples of such polyhydroxy compounds include, for example, diglycerin, ditrimethylolpropane,
Pentaerythritol, dipentaerythritol, etc., for example, sugar alcohol compounds such as erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, rhamnitol, for example, arabinose, ribose, xylose, glucose. , Monooses such as mannose, galactose, fructose, sorbose, rhamnose, fucose, and ribodeose; disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, melibiose; There are sugars such as tetrasaccharides such as stachyose.

Further, in addition to the polyhydroxy compound,
There are also polyether polyols, polyester polyols, epoxy polyols, and the like, which use the polyhydric hydroxy compound as a raw material. As the polyether polyols, in the polyhydric hydroxy compound alone or in a mixture,
For example, using hydroxides such as lithium, sodium and potassium, alcoholates and strongly basic catalysts such as alkylamines, ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide,
Polyether polyols obtained by adding alkylene oxides such as styrene oxide alone or in a mixture, further polyether polyols obtained by reacting a polyfunctional compound such as ethylenediamine with alkylene oxide, and these polyethers So-called polymer polyols and the like, which are obtained by polymerizing acrylamide or the like with the medium as a medium, are included.

British Patent 994890 describes a polyisocyanate obtained from a polyether polyol and a diisocyanate. Block polyisocyanate using the same and low temperature curability of a one-pack coating composition using the same. Is neither described nor suggested. Examples of the polyester polyols include succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, and other dicarboxylic acids alone or in a mixture. And a polyester polyol resin obtained by a condensation reaction of ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylol propane, a polyhydric alcohol selected from the group such as glycerin, alone or in a mixture, and, for example, Examples thereof include polycaprolactone polyols obtained by ring-opening polymerization addition of ε-caprolactone to a polyhydric alcohol.

Examples of the epoxy resins include 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, polyvalent carboxylic acid. Ester type, aminoglycidyl type,
Epoxy resins such as halogenated type and resorcinol type are exemplified.

Among these polyols, the above-mentioned polyether polyols and polyester polyols are preferable, the polyether polyols are more preferable, and the polyether polyol to which propylene oxide is added is particularly preferable. Further, these polyols may be used alone or in combination of two or more, and may be modified with urethane or the like.

The number average molecular weight is preferably 500 to 5,000, more preferably 600 to 3,000. When reacting a polyvalent hydroxy compound and diisocyanate,
Isocyanate group / hydroxyl group equivalent ratio is 2/1 to 30/1
Is preferred. If it is less than 2/1, the viscosity of the reaction liquid after the reaction will be high, and the equipment investment for industrial production will be large, and if it exceeds 30/1, the productivity will be reduced. Preferably it is 5/1 to 20/1. The polyhydric hydroxy compound and the diisocyanate may be mixed before the temperature of the reaction liquid is raised, or the diisocyanate may be charged into the reactor first, and after reaching the predetermined temperature, the polyhydric hydroxy compound may be added all at once or in portions. Is also good.

A solvent may be used in the above reaction. In that case, a solvent inert to the isocyanate groups should be used. The reaction temperature is 60 to 200 ° C, preferably 130 to 180 ° C. If the temperature is lower than 60 ° C, the reaction rate is slow and the increase in the average number of functional groups of isocyanate, which is presumed to be due to the allophanatization reaction, is unlikely to occur. If it exceeds 200 ° C, an undesirable side reaction such as coloring of the obtained polyol occurs.

Although the reaction time depends on the reaction temperature, it is 1
~ 8 hours, preferably 2-6 hours. A catalyst may be used in the reaction. As the catalyst, those having a basic property are generally preferable, and examples thereof include tetraalkylammonium hydroxide and quaternary amine compounds such as weak organic acid salts such as acetic acid and capric acid, for example, trioctylamine and 1,4-. Tertiary amine compounds such as diazabicyclo (2,2,2) octane, 1,8-diazabicyclo (5,4,0) undecene-7,1,5-diazabicyclo (4,3,0) nonene-5, for example, It is also effective to use acetylacetone metal salts such as zinc and the like, and catalysts that promote allophanate formation reaction such as weak organic metal salts such as zinc, tin, lead and iron.

The catalyst concentration is usually selected from the range of 10 ppm to 1.0% based on the isocyanate compound.
At least some of the urethane bonds present in the reaction solution are converted to allophanate bonds. The conversion of urethane bond to allophanate bond is 10% or more, preferably 20% or more. If the above value is less than 10%, it is difficult to increase the average number of functional groups in the isocyanate, and the viscosity of the polyisocyanate may be too high.

The yield is generally 20% by weight or more and 70% by weight or less. Unreacted diisocyanate and solvent are removed to obtain the polyisocyanate used in the present invention.
Unreacted diisocyanate not removed is 5% by weight or less,
It is preferably 1% by weight or less. The average number of isocyanate functional groups of polyisocyanate referred to in the present invention is the number of isocyanate functional groups statistically possessed by one molecule of polyisocyanate, and the number average molecular weight of polyisocyanate and all isocyanate functional groups contained in 1 part by weight of polyisocyanate. Parts by weight (hereinafter referred to as isocyanate concentration)
It can be calculated from the following general formula (2).

[0027]

[Equation 2]

The polyisocyanate obtained has an average isocyanate functionality of 4.0 to 20, preferably 5 to 14. When the value is less than 4.0, the curability is insufficient when used in a coating composition, and when it exceeds 20, the surface property of the coating film may be adversely affected. As a conventionally disclosed polyisocyanate having a high average isocyanate functional group number, Japanese Patent Application Laid-Open No. 2-132116 describes a specific polyisocyanate structure. From the structure, the number of isocyanate groups per molecule of polyisocyanate is 3 to 6. However, these polyisocyanates having the above value of 4 or more are inferior in durability because they contain an aromatic isocyanate.

The polyisocyanate used in the present invention has an isocyanate concentration of 5 to 20% by weight. If it is less than 5% by weight, a sufficient crosslink density cannot be obtained and it cannot be used. Also 2
If it exceeds 0% by weight, the crosslinking density becomes too high to use. The polyisocyanate used in the present invention has a number average molecular weight of 1,200 to 10,000. Number average molecular weight 1,
If it is less than 200, the crosslinking density becomes too high,
If it exceeds 000, the appearance of the coating film deteriorates.

The viscosity of polyisocyanate is 2,000 to
200,000 mPa · s / 25 ° C, preferably 5,0
It is 00-100,000 mPa * s / 25 degreeC. Two
If it is less than 000 mPa · s / 25 ° C, sagging will occur during coating on a vertical surface, and 200,000 mPa · s / 25 ° C.
If it exceeds, the appearance of the coating film deteriorates, which is not preferable. The present inventors have previously proposed a urethane-based coating composition using a polyisocyanate having an isocyanurate structure having an isocyanate average functional number of 4.5 to 10 and a blocked polyisocyanate in JP-A-6-293878. The present invention is a coating composition using a blocked polyisocyanate having a limited isocyanate cyclic trimer concentration,
Surprisingly, it has been found that the low temperature curability of the coating composition of the present invention is further improved.

The concentration of the isocyanate cyclic trimer is 10% by weight or less. If it exceeds 10% by weight, there is a limit to the low temperature curability. This concentration is indicated by the area percentage of the isocyanate cyclic trimer peak obtained by gel permeation chromatography using tetrahydrofuran as the carrier and refractive index as the detector.

Examples of the heat dissociative blocking agent for blocking the isocyanate group of polyisocyanate include alcohol type, alkylphenol type, phenol type, active methylene, mercaptan type, acid amide type, acid imide type, imidazole type, urea type, Oxime-based, amine-based,
There are imide compounds and pyrazole compounds. Specific examples of such blocking agents are shown below. (1) Methanol, ethanol, 2-propanol, n
-Butanol, sec-butanol, 2-ethyl-1-
Alcohols such as hexanol, 2-methoxyethanol, 2-ethoxyethanol and 2-butoxyethanol; (2) Alkylphenols; mono- and dialkylphenols having an alkyl group having 4 or more carbon atoms as a substituent, such as, for example, , N-propylphenol,
i-propylphenol, n-butylphenol, se
c-butylphenol, t-butylphenol, n-hexylphenol, 2-ethylhexylphenol, n
-Monoalkylphenols such as octylphenol and n-nonylphenol, di-n-propylphenol,
Diisopropylphenol, isopropylcresol,
Di-n-butylphenol, di-t-butylphenol, di-sec-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, di-
Dialkylphenols such as n-nonylphenol (3) Phenol type; phenol, cresol, ethylphenol, styrenated phenol, hydroxybenzoic acid ester, etc. (4) Active methylene type; dimethyl malonate, diethyl malonate, methyl acetoacetate , Ethyl acetoacetate, acetylacetone, etc. (5) mercaptan type; butyl mercaptan, dodecyl mercaptan etc., (6) acid amide type; acetanilide, acetic acid amide, ε-
Caprolactam, δ-valerolactam, γ-butyrolactam, etc. (7) Acid imide type; succinimide, maleic acid imide, etc. (8) Imidazole type; Imidazole, 2-methylimidazole, etc. (9) Urea type; urea, Thiourea, ethyleneurea, etc. (10) oxime type; formaldoxime, acetoaldoxime, acetoxime, methylethylketoxime, cyclohexanone oxime, etc. (11) amine type; diphenylamine, aniline, carbazole, di-n-propylamine, Diisopropylamine, isopropylethylamine, etc. (12) Imine type; Ethyleneimine, Polyethyleneimine, etc. (13) Bisulfite; Sodium bisulfite, etc. (14) Pyrazole type; Pyrazole, 3-methylpyrazole, 3,5-dimethyl Pilazo Etc..

The heat dissociative blocking agent used in the present invention is at least one selected from alkylphenol type, oxime type, acid amide type and active methylene type. Particularly preferred are nonylphenol, t-butylphenol, acetoxime, methylethylketoxime, ε-caprolactam, ethyl acetoacetate, and dialkyl malonate, and two or more species such as oxime-based and active methylene-based compounds and two active methylene-based compounds are used. You may mix.

The heat dissociative blocking agent preferably blocks 50 to 100% of the isocyanate groups of the polyisocyanate. Polyisocyanates capped less than 50% of course do not have the paint storability that blocked polyisocyanates must possess. The blocking reaction between the polyisocyanate and the blocking agent can be carried out regardless of the presence or absence of the solvent.
When a solvent is used, it is necessary to use a solvent inert to isocyanate groups.

In the blocking reaction, organic metal salts such as tin, zinc and lead, tertiary amine compounds and alkali metal alcoholates such as sodium may be used as catalysts. The reaction can be generally carried out at -20 to 150 ° C, preferably 30 to 100 ° C. At temperatures above 150 ° C, side reactions may occur, while-
If the temperature is lower than 20 ° C, the reaction rate becomes slow, which is disadvantageous.

The thus obtained block polyisocyanate used in the present invention has (1) average number of blocked isocyanate functional groups; 4 to 20, (2) blocked isocyanate group concentration; 2 to 15% by weight, (3) number average Molecular weight: 1,500 to 15,000.

It was surprising that the curability of a coating composition using a blocked polyisocyanate having a specific number of blocked isocyanate functional groups as described above is lowered in temperature. The average number of blocked isocyanate functional groups of the blocked polyisocyanate is the number of blocked isocyanate functional groups which one molecule of the blocked polyisocyanate statistically has, and the number average molecular weight of the blocked polyisocyanate and the block contained in 1 part by weight of the blocked polyisocyanate. It is calculated by the following general formula (3) from the total number of isocyanate functional groups (hereinafter, referred to as blocked isocyanate concentration) including the isocyanate group.

[0038]

(Equation 3)

Examples of the polyvalent hydroxyl group-containing compound used as the component (a) in the present invention include aliphatic hydrocarbon polyols, polyether polyols, polyester polyols, epoxy resins, fluorine polyols and acrylic polyols. Etc. Specific examples of the aliphatic hydrocarbon polyols include, for example, end-hydroxylated polybutadiene and hydrogenated products thereof. Further, as the polyether polyols, for example, polyether polyols obtained by adding a single or mixture of polyhydric alcohols such as glycerin and propylene glycol, ethylene oxide, alkylene oxides such as propylene oxide, Polytetramethylene glycols, further, ethylenediamine to alkylene oxide, polyether polyols obtained by reacting a polyfunctional compound such as ethanolamines, and obtained by polymerizing acrylamide or the like using these polyethers as a medium, So-called polymer polyols and the like are included.

Examples of the polyester polyols include succinic acid, adipic acid, sebacic acid, dimer acid,
Dibasic acids selected from the group of carboxylic acids such as maleic anhydride, phthalic anhydride, isophthalic acid, and terephthalic acid, alone or in combination, with ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, glycerin, etc. Polyester polyol resins obtained by a condensation reaction with a polyhydric alcohol selected from the group consisting of a polyhydric alcohol and a polycaprolactone obtained by, for example, ring-opening polymerization of ε-caprolactone with a polyhydric alcohol. Examples thereof include polyols.

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, polyvalent carboxylic acid. Ester type, aminoglycidyl type,
Examples thereof include halogenated type and resorcin type epoxy resins, and resins obtained by modifying these epoxy resins with amino compounds, polyamide compounds and the like.

Fluorine polyols are, for example, JP-A-57-34107 and JP-A-61-275311.
There are copolymers such as fluoroolefins, cyclohexyl vinyl ethers, hydroxyalkyl vinyl ethers, monocarboxylic acid vinyl esters, etc., which are disclosed in the publications and the like. As acrylic polyols, 1 per molecule
Polymerizable monomers having one or more active hydrogens, for example, acrylic acid esters having active hydrogens such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and 2-hydroxybutyl acrylate, methacrylic acid- Methacrylic acid esters having active hydrogen such as 2-hydroxydiethyl, 2-hydroxypropyl methacrylate, and 2-hydroxybutyl methacrylate, or acrylic acid monoesters or methacrylic acid monoesters of glycerin, trimethylolpropane acrylic A single or mixture selected from the group of (meth) acrylic acid esters having polyvalent active hydrogen such as acid monoesters or methacrylic acid monoesters, and other monomers copolymerizable therewith, for example, methyl acrylate. , Ethyl acrylate, acryl Acid isopropyl acrylate -n-
Butyl, acrylic acid esters such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, -n-butyl methacrylate, isobutyl methacrylate, -n-hexyl methacrylate, cyclohexyl methacrylate, methacryl Methacrylic acid esters such as lauryl acid and glycidyl methacrylate, and, if necessary, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid, acrylamide, N-methylol acrylamide, diacetone acrylamide and the like. Examples thereof include those obtained by copolymerizing a saturated amide and a single or a mixture selected from the group of other polymerizable monomers such as styrene, vinyltoluene, vinyl acetate and acrylonitrile.

Further, it is also possible to use an acrylic polyol resin obtained by copolymerizing a polymerizable UV-stable monomer exemplified in JP-A-1-261409 and JP-A-3-6273. is there. The polyvalent hydroxyl group-containing compound used in the present invention has a hydroxyl value of 10 to 500 mg KOH.
/ G, acid value 0 to 200 mg KOH / g, number average molecular weight 3
It is from 00 to 60,000, and acrylic polyol, polyester polyol and epoxy polyol are particularly preferably used.

When the hydroxyl value is less than 10, a coating film having a low cross-linking density is formed and preferable mechanical properties of the coating film cannot be obtained, and when it exceeds 500, a coating film lacking flexibility is insufficient. Formed, which is not preferable. If the number average molecular weight is out of the above range, a good coating cannot be formed. The polyvalent hydroxyl group-containing compound preferably has a low acid value of 20 m.
It is preferably gKOH / g or less.

In the present invention, the equivalent ratio of the blocked isocyanate group in the blocked polyisocyanate as the component (b) to the hydroxyl group in the polyvalent hydroxyl group-containing compound as the component (a) is the required coating amount. Although it is determined by the physical properties of the film, it is usually 10/1 to 1/10, preferably 5/1 to 1/5. In the present invention, a melamine resin can be used together. As a melamine resin,
Hexamethoxymethylol melamine, methyl butylated melamine, butylated melamine and the like are exemplified.

Various solvents and additives may be used depending on the use and purpose. As the solvent, 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 and cellosolve acetate, alcohols such as butanol and isopropyl alcohol according to the purpose and use. These solvents may be used alone or in combination of two or more.

If desired, a curing accelerator such as
Organic metal compounds such as tin, zinc and lead such as carboxylic acids, antioxidants such as hindered phenols, ultraviolet absorbers such as benzotriazole and benzophenone, pigments such as titanium oxide, carbon black, indigo, quinacridone and pearl Mica and the like, metal powder pigments such as aluminum, and rheology control agents such as hydroxyethyl cellulose and urea compounds may be added.

The coating composition thus prepared is applied as a primer or an upper intermediate coating to a material such as a steel plate, a surface-treated steel plate and other metals and plastics by roll coating, curtain flow coating, spray coating, electrodeposition coating or the like. It is useful for imparting cosmetic properties, weather resistance, acid resistance, rust resistance, chipping resistance, etc. to pre-coated metal including rust-proof steel plate, automobile coating and the like.

[0049]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. All percentages are by weight and all parts are by weight. The evaluation was performed according to the following. [Measurement of number average molecular weight] The number average molecular weight is measured by gel permeation chromatograph (hereinafter referred to as G
It is a number average molecular weight based on polystyrene by measurement (referred to as PC). [Isocyanate Cyclic Trimer Concentration] The concentration of the peak of the molecular weight corresponding to the diisocyanate cyclic trimer (for example, 504 in the case of HMDI) obtained by the GPC measurement was expressed as the area percentage. [Measurement of allophanate binding concentration] FT-N of JEOL
MR "FX90Q" was used, acetone-d6 was used as the solvent, and as a result of H-NMR measurement, the peak integrated value of the allophanate bond and the urethane bond was expressed by allophanate bond / (allophanate bond + urethane bond). 9
Above is A, less than 0.9 0.1 or more is B, less than 0.1 is C
Indicated by . [Viscosity measurement] The viscosity was measured at 25 ° C. using an Emila type rotational viscometer. [Gel Fraction] The value of the undissolved part weight when the cured coating film was immersed in acetone at 20 ° C. for 24 hours with respect to the weight before immersion was calculated. When less than 80% was ×, when 80% or more and less than 90% was ◯,
90% or more is represented by ⊚.

When the main component was an epoxy polyol, methanol was used as the solvent.

[0051]

[Production Example 1] A 4-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blow-in tube, and a dropping funnel was filled with a nitrogen atmosphere, and HMDI was 600 parts. Charged with 169 parts of an electrified product name "ADEKA NEW POLYOL WR-474", number average molecular weight 475) (isocyanate group / hydroxyl group equivalent ratio 5/1), and the temperature inside the reactor was 120 ° C under stirring.
Hold for 5 hours. The temperature of the reaction solution was lowered, and unreacted HMDI was removed using a thin film evaporator. It was confirmed that the polyisocyanate used in the present invention was produced by measuring the molecular weight of the reaction product by GPC and measuring the isocyanate concentration by titration.

The polyisocyanate obtained had a viscosity at 25 ° C. of 20,000 mPa · s, an isocyanate content of 13.2% and a number average molecular weight of 1,690.
The average number of functional groups of isocyanate was 5.3, and the concentration of isocyanate cyclic trimer was 1.7%. The allophanate bond concentration of this polyisocyanate was B.

[0053]

[Production Examples 2 to 8 and Reference Production Examples 1 and 2] Using the same apparatus as in Production Example 1, the reaction was carried out under the reaction conditions shown in Table 1, and unreacted HMDI was removed in the same manner as in Production Example 1. . Table 1 shows the physical properties of polyisocyanate.

[0054]

[Reference Production Example 3] HMDI;
600 parts and 11 parts of 1,3-butanediol were charged, and the temperature inside the reactor was maintained at 80 ° C. for 2 hours under a nitrogen atmosphere and with stirring. After that, the temperature inside the reactor was maintained at 60 ° C., an isocyanurate-forming reaction catalyst tetramethylammonium capryate was added, and when the yield reached 28%, phosphoric acid was added to stop the reaction. After filtering the reaction solution, unreacted HMDI was removed using a thin film evaporator. Table 1 shows the physical properties of the obtained polyisocyanate having an isocyanurate structure.
Shown in

[0055]

[Reference Production Example 4] HMDI;
Polyester polyol "Plaxel 303" (trade name of Daicel Chemical Industries) 30 which is 600 parts and a trihydric alcohol 30
Was charged, and the temperature inside the reactor was adjusted to 9 with stirring under a nitrogen atmosphere.
Hold at 0 ° C for 1 hour. After that, the temperature inside the reactor is 60 ° C.
Then, the isocyanurate-forming reaction catalyst tetramethylammonium capryate was added, and when the yield reached 54%, phosphoric acid was added to stop the reaction. After filtering the reaction solution, unreacted HMDI was removed using a thin film evaporator.
Table 1 shows the physical properties of the obtained polyisocyanate having an isocyanurate structure.

[0056]

[Production Example 9] (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 filled with a nitrogen atmosphere,
100 parts of the polyisocyanate obtained in Preparation Example 1 and 30 parts of methyl isobutyl ketone were charged, and methyl ethyl ketoxime was added dropwise until the characteristic absorption of isocyanate in the infrared spectrum disappeared so that the reaction temperature did not exceed 50 ° C. A 80% min blocked polyisocyanate solution was obtained.

The blocked polyisocyanate thus obtained had an average number of blocked isocyanate functional groups of 5.3, a blocked isocyanate group concentration of 10.4% by weight and a number average molecular weight of 2,150.

[0058]

Production Examples 10 to 16 (Production of Block Polyisocyanate) A blocked polyisocyanate solution having a solid content of 80% was obtained in the same manner as in Production Example 9 except that the polyisocyanates obtained in Production Examples 2 to 8 were used. Table 3 shows the properties of the obtained blocked polyisocyanate.

[0059]

[Reference Production Examples 5 to 8] (Production of Block Polyisocyanate) The same procedure as in Production Example 9 was repeated except that the polyisocyanates obtained in Reference Production Examples 1 to 4 were used to prepare a blocked polyisocyanate solution having a solid content of 80%. Obtained. Table 3 shows the properties of the obtained blocked polyisocyanate.

[0060]

Example 1 Blocked polyisocyanate and acrylic polyol obtained in Production Example 9 (trade name Acrydic A-801 manufactured by Dainippon Ink, resin content hydroxyl value 100 mgK
OH / g, number average molecular weight 9000, resin acid value 1.5m
gKOH / g) was added so that the equivalent ratio of blocked isocyanate / hydroxyl group would be 1.0, and 0.5% of dibutyltin dilaurate was added to the coating resin component, and ethyl acetate / toluene / acetic acid as a thinner was added to this. A mixture of butyl / xylene / propylene glycol monomethyl ether acetate in a weight ratio of 30/30/20/15/5 was added, and the temperature was adjusted to 20 seconds / 20 ° C. with Ford cup # 4.

The obtained coating solution is spray-coated,
After setting the room temperature for 1 minute, baking was performed for 30 minutes in an oven maintained at 120 ° C. Table 4 shows the obtained measurement results of physical properties of the coating film.

[0062]

Examples 2 to 8 The same procedure as in Example 1 was carried out except that the blocked polyisocyanate obtained in Production Examples 10 to 16 was used. Table 4 shows the obtained measurement results of physical properties of the coating film.

[0063]

[Comparative Examples 1 and 2] The same procedure as in Example 1 was carried out except that the results shown in Table 4 were used. The results obtained are shown in Table 4.

[0064]

[Production Example 17] (Production of epoxy polyol) A 4-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube, and a dropping funnel was placed in a nitrogen atmosphere,
Bisphenol A type epoxy resin (Asahi Ciba brand name AE
R6071, 100 parts of epoxy equivalent 460) and 82 parts of methyl isobutyl ketone were charged, the reactor internal temperature was set to 90 ° C., and then 23 parts of diethanolamine was added dropwise over 30 minutes while maintaining the reaction temperature at 90 ° C. 30 minutes after the end of dropping,
The reaction temperature was raised to 120 ° C. and kept for 1 hour. An epoxy polyol solution having a resin solid content of 60% and a resin content of hydroxyl group of 400 mgKOH / g was obtained.

[0065]

Example 9 The epoxy polyol of Production Example 17 and the blocked polyisocyanate of Production Example 9 were blended so that the equivalent ratio of blocked isocyanate / hydroxyl group would be 0.5, and coating was performed with an applicator. After setting at room temperature for 30 minutes, baking was performed for 30 minutes in an oven maintained at 120 ° C. The results obtained are shown in Table 4.

[0066]

Examples 10 to 16 The same procedure as in Example 9 was carried out except that the results shown in Table 4 were used. The results obtained are shown in Table 4.

[0067]

Comparative Examples 3 and 4 Example 9 was repeated except that the blocked polyisocyanate obtained in Reference Production Examples 7 and 8 was used. The results are shown in Table 4.

[0068]

[Table 1]

[0069]

[Table 2]

[0070]

[Table 3]

[0071]

[Table 4]

[0072]

The coating composition of the present invention is excellent in low temperature curability, compatibility and weather resistance as compared with the conventional non-yellowing one-pack type polyurethane coating composed mainly of a polyol and a blocked polyisocyanate. It is possible to obtain film physical properties, and it is used as a top coat paint for automobiles, anti-chipping paint, paint for automobile parts, pre-coated metal / rust-preventing steel plates for metal products such as home appliances and office equipment, paint for building materials, paint for plastics, It exhibits excellent performance as an adhesive, an adhesiveness-imparting agent, a sealing agent, and an electrodeposition paint.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C08G 18/80 NFM C08G 18/80 NFM

Claims (3)

[Claims] 1. A urethane coating composition comprising at least the following components (a) and (b): (A) As a main component, a number average molecular weight of 300 to 60,0
00, a polyhydric hydroxyl group-containing compound having a resin component hydroxyl value of 10 to 500 mgKOH / g and an acid value of 0 to 200 mgKOH / g. (B) As a curing agent component, an aliphatic or alicyclic diisocyanate alone or in a mixture and an average number of hydroxyl functional groups of 4 to
A polyisocyanate obtained by reacting 10 polyvalent hydroxy compounds and then substantially removing unreacted monomers, wherein (1) average number of isocyanate functional groups; 4 to 20 (2) isocyanate concentration; 5 to 20% by weight ( 3) Number average molecular weight; 1,200 to 10,000 (4) Viscosity; 2,000 to 200,000 mPa.s. s
/ 25 ° C (5) Isocyanate cyclic trimer concentration; 50% by weight of the isocyanate group of the polyisocyanate of 10% by weight or less
To 100% is blocked with at least one thermal dissociative blocking agent selected from alkylphenol-based, oxime-based, acid amide-based and active methylene-based compounds, and (1) average blocked isocyanate functional group number: 4 to 20 (2) Blocked isocyanate concentration; 2 to 15% by weight (3) Number average molecular weight; 1,500 to 15,000 blocked polyisocyanate. 2. The coating composition according to claim 1, wherein the polyisocyanate has an allophanate bond. 3. The coating composition according to claim 1, wherein the polyhydric hydroxy compound is a propylene oxide adduct polyether polyol and / or polyester.