JPS60149572A - Block polyisocyanate compound and thermosetting coating composition containing same as component - Google Patents

Abstract

NEW MATERIAL:A polyisocyanate, blocked with an alkyl acetoacetate, and expressed by formula I (R1 is 1-6C alkyl; R2 is expressed by formula II or III). EXAMPLE:Polyisocyanurate of hexamethylene diisocyanate blocked with methyl acetoacetate. USE:A raw material for one-pack type polyurethane resin coating materials, capable of improving workability and backing temperature, etc. of two-pack type polyurethane serin coating materials, having improved weather resistance, yellowing resistance and low temperature curability, and applicable to materials affected easily by heat, e.g. plastics. PREPARATION:A polyisocyanete compound of hexamethylene diisocyanate is reacted with a compound expressed by formula IV to give the compound expressed by formula I . A one-pack type polyurethane thermosetting coating composition obtained by incorporating the above-mentioned compound with a polyhydric hydroxy compound is a coating material curable by baking at a temperature as low as about 120 deg.C to give coating films having improved physical properties and weather resistance thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel block polyisocyanate and a thermosetting coating composition using the same, and more specifically, to a two-component polyurethane having excellent weather resistance and a low baking temperature. The present invention relates to a block polyisocyanate that can provide a resin coating, and a two-component polyurethane thermosetting coating composition using the same.

Traditionally, polyurethane resin paints have very good abrasion resistance,
In addition to having chemical resistance and stain resistance, polyurethane resin paints using polyisocyanates derived from aliphatic compounds, especially hexamethylene diinocyanate, have even better weather resistance, and demand for them is on the rise. .

However, since polyurethane resin paints are generally two-component, they are extremely inconvenient to use.

That is, ordinary urethane paints consist of two components, a polyol component and a polyisocyanate, and it is necessary to store them separately and mix the two components at the time of painting. Furthermore, the current situation is that paints mixed with -tan become gelled within several hours to several days and become unusable. This makes it extremely difficult to perform automatic painting in fields where line painting is performed, such as automobiles or low-voltage painting.

Furthermore, since it is necessary to thoroughly clean the coating machine and coating tank after the work is completed, the work efficiency is significantly reduced. Conventionally, in order to improve the above-mentioned drawbacks, it has been proposed to use blocked polyisocyanates in which all of the active isocyanate groups are blocked with active basis hydrogen-containing compounds (blocking agents). This blocked polyisocyanate does not react with polyols at room temperature, but at relatively high temperatures the blocking agent is dissociated and active incyanate groups are regenerated, reacting with polyols and causing a crosslinking reaction, so the above-mentioned drawbacks can be overcome. can be improved. Therefore, many blocking agents have been investigated, and typical blocking agents include phenol and methyl ethyl ketoxime.

However, blocked polyisocyanates using these blocking agents generally require a high baking temperature of 150° C. or higher. Requiring high temperatures for baking in this manner not only causes a large energy loss, but also becomes a fatal drawback when coating materials that are sensitive to heat, such as plastics, which are in particular demand these days.

Therefore, in the field of polyurethane resin paints, there has long been a demand for blocked isocyanates that can provide two-component polyurethane resin paints that have excellent weather resistance and a low baking temperature.

As a result of extensive research to meet these demands, the present inventors have discovered that the purpose can be achieved by using a specific polyisocyanate as the incyanate and appropriately selecting a blocking agent. Based on this finding, we have completed the present invention.

That is, the present invention is a residue represented by the general formula [wherein R is an alkyl group having 1 to 6 carbon atoms, and R2 is the general formula (however, R1 has the same meaning as above] or the general formula ] A two-component polyurethane thermosetting coating composition comprising a polyisocyphnate blocked with an acetoacetic acetate alkyl ester represented by the formula (1), a polyincyanate represented by the general formula (1), and a polyhydric hydroxyl compound. It provides:

The polyisocyanate blocked with acetoacetic acid alkyl ester represented by the general formula (1) can be prepared by a known method, for example, the method described in JP-A-57-834560! polyisocyanurate compounds of hexamethylene diisocyanate derived from nitrogen and the general formula cH
It is produced by reaction with acetoacetic acid alkyl ester represented by 3-co-cH2-cooR1 (wherein R1 is an alkyl group having 1 to 6 carbon atoms).

At this time, it is important to use an excess of acetoacetate to complete the reaction with respect to the isocyanate group in the polyisocyanurate compound of hexamethylene diisocyanate. It is desirable to use a suitable solvent that does not react with incyanate groups such as ester, ketone, and aromatic hydrocarbon groups. The reaction temperature is 110℃ or less, especially 60-9
A range of 5°C is preferred and it is also possible to use a catalyst such as zinc acetylacetonate to accelerate the reaction. The reaction generally takes 2 to 20 hours to complete.

The two-component polyurethane thermosetting coating composition obtained by blending the block polyisocyanate and the polyhydric hydroxyl compound obtained in this way has excellent coating film properties and weather resistance, and is cured by low-temperature baking at about 120°C. It makes an excellent paint. In this composition, the molar ratio of the blocked incyanate groups in the blocked polyisocyanate to the hydroxyl groups in the polyhydric hydroxyl compound is 0.4° to 1.
．． A range of 2 is preferred.

The polyhydric hydroxyl compound is a compound having at least two hydroxyl groups in one molecule, and examples thereof include aliphatic hydrocarbon polyols, polyether polyols, polyester polyols, epoxy resins, and acrylic resins. Examples include polyols.

Specific examples of aliphatic hydrocarbon polyols include:
Examples include terminal hydroxyl-terminated polybutadiene and its hydrogenated products, and examples of the polyether polyols include polyhydric alcohols such as glycerin and propylene glycol, or mixtures thereof, and alkylene oxides such as ethylene oxide and propylene oxide. Polyether polyols and polytetramethylene glycols obtained either singly or in combination; polyether polyols obtained by reacting alkylene oxide with polyfunctional compounds such as ethylenediamine and ethanolamine; and these polyethers. These include so-called polymer polyols obtained by polymerizing acrylamide and the like using acrylamide as a medium.

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

In addition, examples of epoxy resins include novolak type,
β-methylepicro type, cyclic oxirane type, glycidyl ether type, glycol ether type, glycol ether type, epoxidized type of aliphatic unsaturated compound, epoxidized fatty acid ester type, polyvalent carboxylic acid ester type, amiclicidyl type, halogenated type , epoxy resins such as resorcinol type can be used.

Ushida acrylic polyols are obtained by copolymerizing a polymerizable monomer having one or more active hydrogens in one molecule and other monomers that can be copolymerized therewith. Examples of such substances include acrylic acid esters having active hydrogen such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate, and 2-hydroxymethacrylic acid. Methacrylic acid esters with active hydrogen such as methyl, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, or acrylic monoester of glycerin or monoestenopetrimethylol methacrylate. Acrylic acid monoester or methacrylic acid monoester of propane alone or in a mixture selected from the group, metinope acrylate, ethyl acrylate, isoglobil acrylate, n-butyl acrylate,
Acrylic acid esters such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate,
methane (IJ) such as lauryl methacrylate; and unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, acrylamide, N-methylol acrylamide, and diacetone acrylamide. and other polymerizable monomers such as glycidyl methacrylate, styrene, vinyltoluene, vinyl acetate, acrylonitrile, etc., alone or in the absence of a mixture thereof. Examples include acrylic polyol resins obtained by

Particularly preferred among these polyhydroxyl compounds are acrylic polyols.

In addition, in the composition of the present invention, when mixing both components, a suitable solvent such as benzene, toluene,
Hydrocarbons such as quinoa, cyclohexane, mineral spirits, naphtha, acetone, methyl ethyl ketone,
Ketones such as methyl isobutyl ketone, ethyl acetate,
Depending on the purpose and use, it can be used by appropriately selecting from the group of esters such as n-butyl acetate and cellosolve acetate. These solvents may be used alone or
They may be used in combination.

Furthermore, depending on the purpose and use, various additives used in the technical field such as catalysts, pigments, leveling agents, antioxidants, plasticizers, and surfactants may be mixed and used.

The thermosetting coating composition of the present invention has weather resistance and yellowing resistance comparable to conventional two-component polyurethane resin paints using highly anticipated aliphatic polyisocyanates, as well as excellent low-temperature curability. As a liquid-type polyurethane paint, it can be applied to a wide range of materials such as metal, plastic, rubber, leather, concrete, and wood.

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

Production example Hexamethylene diisocyanate 500 parts by weight, 1.3
2 parts by weight of -butanediol and 200 parts by weight of ethylene glycol monomethyl ether acetate as a solvent were mixed, 1 part by weight of sodium methoxide as a catalyst and 5 parts by weight of phenol were added, and the mixture was heated at 90° C. for 3 hours. After filtering off sodium methoxide from the resulting reaction solution, excess hexamethylene diisocyanate and the solvent were removed using a thin film evaporator. A polyisocyanurate of hexamethylene diinocyanate having a viscosity at 25° C. of 2800 Cp1 and an NCO content of 21.3% by weight was obtained as a bottom liquid.

Example 1 70 parts by weight of methyl acetoacetate and an equivalent mixture of xylene/ethylene glycol monoethyl ether acetate 21,
Dissolve 0.2 parts by weight of zinc acetylacetonate in a mixture with 7 parts by weight and keep at 90°C while stirring, and add 100 parts by weight of the polyisocyanurate of hexamethylene diisocyanate obtained in the production example to xylene/ethylene glycol monoethyl ether. A solution of 20 parts by weight of an acetate equivalent mixture was added dropwise over 2 hours. After that 90
As a result of continuing the reaction while keeping the temperature at ~95°C and following the decrease in diisocyanate groups in the infrared absorption spectrum,
The incyanate group disappeared 7 hours after the completion of the dropwise addition.

The obtained reaction product was a pale yellow transparent liquid with a nonvolatile content of 755% by weight and a viscosity of 680 cp at 25°C.

Example 2 69 parts by weight of ethyl acetoacetate, 26 parts by weight of ethyl acetate,
A mixed solution of 3 parts by weight of zinc acetylacetonate was heated to 80°C.
A solution prepared by dissolving 100 parts by weight of polyin cyanurate of hexamethylene diisocyanate obtained in Production Example in 26 parts by weight of ethyl acetate was dropped into the solution over 2 hours. Thereafter, the reaction was continued while keeping the temperature at 80° C. and tracking the decrease in isocyanate groups using an infrared absorption spectrum, and as a result, the NCO groups disappeared 12 hours after the completion of the dropwise addition.

The obtained reaction product was a pale yellow transparent liquid with a nonvolatile content of 74.8% by weight and a viscosity at 25°C of 510 cp.

Example 3.4 Using Acridic A-801 (Dainippon Ink ■ acrylic polyol resin) as a polyhydric hydroxyl compound, the block incyanate obtained in Examples 1 and 2 and A-
801 so that NeoloH = 1.0, and to this, ethyl acetate/toluene/butyl acetate/xylene/ethylene glycol monoethyl ether acetate (weight ratio = 30/30/20/1515) was added as a thinner.
) in a Ford cup #4 for 20 seconds (
25° C.) to obtain a one-component thermosetting coating composition of the present invention.

This was coated with an air spray gun to a dry film thickness of 50 μm, and heated at 120° C. for 30 minutes to cure. The performance of the resulting coating film is shown in the table below.

Claims (1)

[Scope of Claims] 1 General formula [In the formula, R1 is an alkyl group having 1 to 6 carbon atoms, R2 is a general formula (however, R1 has the same meaning as above) or a general formula (however, Ro is the same as above) A polyisocyanate blocked with an acetoacetic acid alkyl ester having the same meaning. 2. The polyisocyanate according to claim 1, wherein R1 in general formula (I) is a methyl group or an ethyl group. 3 general formula/C0CI(. A two-component polyurethane thermosetting coating composition comprising a polyisocyanate blocked with an acetoacetic acetate alkyl ester represented by the following formula and a polyhydric hydroxyl compound. 5. The composition according to claim 3, wherein R1 in formula (1) is a methyl group or an ethyl group. 5. The composition according to claim 3, wherein the polyhydric hydroxyl compound is an acrylic polyol.