JPH11100477A - Hardening resin composition using michael reaction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hardening resin composition for high-solid coating materials cured by Michael reaction. SOLUTION: This composition utilizes an acrylic copolymer dissolved in a non-polar solvent as a stabilizer, and utilizes a non-aqueous dispersion (addreviated as NAD in the following) of fine particles of an acrylic copolymer insoluble in the solvent but stably dispersing in the stabilizer solution. The acrylic copolymer of the stabilizer contains 25 to 40 wt.% of an acrylic monomer containing an active methylene group, and 35 to 60 wt.% of a >=6C alkyl (meth) acrylate. The composition comprises this NAD and a rolyfunctional α,β-unsaturated carbonyl compound as a curing agent and a catalyst for promoting the Michael reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION The present invention relates to a curable resin composition and a paint utilizing a Michael addition reaction (hereinafter referred to as "Michael reaction").

The Michael reaction in which an active methylene group (donor) adds to a polarized double bond (acceptor) such as an α, β-unsaturated carbonyl is well known in the field of organic chemistry.

Since the Michael reaction is an addition reaction, it does not produce a reaction by-product, and the new bond (crosslink bond) is a chemically stable carbon-carbon bond. Attempts to do so have been made for a long time. See, for example, U.S. Pat. No. 4,408,018.

One type of paint utilizing the Michael reaction as a curing mechanism is a copolymer of an active methylene group-containing acrylic monomer such as 2-acetoacetoxyethyl (meth) acrylate and a plurality of α, β-unsaturated monomers. There is a solvent type paint in which a compound or resin containing a carbonyl group is combined with a catalyst.

[0005] In recent years, for the purpose of reducing the volatilization of VOCs in the atmosphere, it has been demanded that the solvent type paint be made high solid. One of the techniques for this is a method using a non-aqueous dispersion (NAD). NAD is composed of a solution of a stabilizer resin dissolved in a non-polar solvent (hydrophobic solvent) and fine particles of a dispersion resin which is insoluble in this solvent but is stably dispersed in the solution of the stabilizer resin. Due to the presence of dispersed resin particles, NAD
Indicates structural viscosity, and the apparent viscosity decreases as the shear stress increases. For this reason, it is possible to increase the maximum solid content at which spray coating is possible while preventing sagging from the object to be coated.

Therefore, it is desired to apply the NAD technology to make the above-mentioned Michael-curable solvent-type paint high solid.

DISCLOSURE OF THE INVENTION The stabilizer resin of NAD must be soluble in a non-polar solvent, whereas the dispersing resin must be insoluble in the solvent. For this reason, the dispersion resin can contain a large amount of a hydrophilic (high SP value) monomer, but the stabilizer resin cannot contain a large amount of a hydrophilic monomer and must be mainly composed of a hydrophobic monomer. For this reason, a large amount of the active methylene group-containing acrylic monomer, which is a hydrophilic monomer, cannot be copolymerized with the stabilizer resin, and the limit is at most 20%.

[0008] When the content of active methylene monomer in the NAD stabilizer resin is low, satisfactory curability is not exhibited even when the dispersed resin particles contain a high content of active methylene monomer. I found it unbearable.

Therefore, the present invention provides (a) 25 to 40% by weight of an active methylene group-containing acrylic monomer dissolved in a nonpolar solvent, and (ii) an alkyl group having 6 carbon atoms.
35 to 60% by weight of the above alkyl (meth) acrylate, (iii) 0 to 0 of ethylenically unsaturated monomers other than the above.
A non-aqueous dispersion of an acrylic copolymer solution having a monomer composition of 40% by weight and acrylic copolymer fine particles insoluble in the solvent but stably dispersed in the acrylic copolymer solution; (b A) a curable resin composition comprising: a compound having a plurality of α, β-unsaturated carbonyl groups; and (c) a catalyst for promoting a Michael reaction.

The compositions of the present invention have better curing reactivity and a higher solids content than the corresponding homogeneous solution-type compositions at the same overall active methylene monomer content.

Detailed Discussion As is well known, NAD forms a dispersion stabilizer resin solution by solution polymerization in a non-polar solvent, in which the polymerization of monomers constituting the dispersion resin insoluble in the solvent is carried out. able to make.

Examples of the non-polar solvent include aliphatic hydrocarbons such as hexane, octane, isooctane, decane, nonane, dodecane, isododecane, cyclohexane, methylcyclohexane, cycloheptane, methylcycloheptane, and decalin. , Toluene, xylene, ethylbenzene, tetralin, etc.
And petroleum-based mixed solvents such as Isopar E, G, H,
L, M, V (all manufactured by Exxon), naphtisol L,
M and H (all manufactured by Nippon Oil Co., Ltd.), Cielsol A and B, Loose, House (all manufactured by Shell), Solvesso 100,
150, 1500 (all manufactured by Esso), Swazole 10
00, 1500 (all manufactured by Kyodo Sekiyu) and Tox Solvent (manufactured by Shoei Chemical) can be used.

In the present invention, the stabilizer resin solution is prepared by solution polymerization of a mixture of the following monomers in a non-polar solvent by a conventional method.

(I) Acrylic monomer having an active methylene group: Examples of the monomer having an active methylene group include 2-
Acetoacetoxyethyl (meth) acrylate, 2-ethoxymalonyloxyethyl (meth) acrylate, 2
-Cyanoacetoxyethyl (meth) acrylate, N-
(2-cyanoacetoxyethyl) acrylamide, N-
(2-propionylacetoxybutyl) acrylamide, N- (4-acetoacetoxymethylbenzyl) acrylamide, N- (2-acetoacetylaminoethyl)
Acrylamide and the like.

The acrylic monomer having an active methylene group preferably accounts for 25 to 40%, especially 30% or more, of the monomer mixture.

(Ii) Long-chain alkyl (having 6 or more carbon atoms) (meth) acrylate: hexyl (meth) acrylate, 2
-Ethylhexyl (meth) acrylate, octyl (meth) acrylate, tridecyl (meth) acrylate,
Lauryl (meth) acrylate, stearyl (meth) acrylate and the like.

As described above, since the active methylene group-containing monomer (i) is hydrophilic, if it contains a large amount of the monomer, the stabilizer resin will not be sufficiently hydrophobic. Therefore, it is necessary to copolymerize these monomers in order to impart sufficient hydrophobicity to the stabilizer resin. 2-Ethylhexyl (meth) acrylate and lauryl (meth) acrylate are preferred.

The proportion of these monomers in the monomer mixture should be determined according to the degree and proportion of hydrophobicity of the monomers chosen, but is generally from 35 to 60%, in particular about 50%.
%.

(Iii) Although not essential for the stabilizer resin, an ethylenically unsaturated monomer other than the above monomers may be contained as a copolymerization component.

Examples include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-
Short-chain alkyl (meth) acrylates such as butyl (meth) acrylate, isobutyl (meth) acrylate, and t-butyl (meth) acrylate; acrylonitrile, glycidyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, and styrene And acrylic and non-acrylic monomers such as vinyl toluene, α-methylstyrene and vinyl acetate. Styrene and methyl methacrylate are preferred.
The proportion of these monomers ranges from 0 to 40%.

The dispersed resin dispersed as particles in the stabilizer resin solution must be hydrophilic, as opposed to the stabilizer resin. Examples of monomers that impart hydrophilicity include hydroxyethyl methacrylate (HEMA), hydroxyethyl acrylate (HEA), 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, and 4-hydroxypropyl acrylate.
Hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, N-methylol acrylamide, HE
Ring-opening adducts of MA and caprolactone (Placcel-FM series manufactured by Daicel Chemical Industries, Ltd.) and ring-opening adducts of HEA and caprolactone (Placcel-FA series manufactured by Daicel Chemical Industries, Ltd.) are included. The ratio is 2
It is in the range of 0 to 50%.

Resins dispersed as particles include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t- butyl (meth) lower alkyl (C ₄ or less) such as acrylates include acrylate or methacrylate in a proportion of 50-80%.

Other monomers such as styrene, acrylonitrile, glycidyl (meth) acrylate, and an active methylene-containing acrylic monomer may be contained in a proportion of 20% or less.

It is advantageous that the NAD contains a large amount of the dispersed resin which is a particle component unless the stability is impaired. Therefore N
The solids weight ratio of the dispersion resin to the stabilizer resin in AD is 2: 1.
１ ： 1: 3, particularly preferably 1: 1. Within this range, high solidification of the paint and rheological control are compatible.

The composition of the present invention is cross-linked and cured by a Michael reaction using NAD as a donor and a compound having a plurality of α, β-unsaturated carbonyl groups as an acceptor. The curing agent used for this purpose is a polyhydric alcohol (meth) acrylate. Specifically, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycerol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate Acrylate, dipentaerythritol hexa (meth) acrylate, and the like. In this case, the amount of the curing agent is active methylene /
The equivalent ratio of α, β-unsaturated carbonyl is 2/1 to 1/2,
Preferably it is 1.5 / 1 to 1 / 1.5.

A base catalyst is used in the curing reaction utilizing the Michael reaction. When a strong base catalyst such as an alkali metal hydroxide, an alcoholate, a carbonate or a quaternary ammonium base is used, the reaction proceeds even at room temperature. Therefore, these catalysts must be mixed with other components immediately before use. Japanese Unexamined Patent Publication (Kokai) No. 7-173262 of the present applicant discloses a curing system based on the Michael reaction in which both storage stability and curability are compatible. This system uses as catalyst a combination of an onium salt that does not itself promote the Michael reaction, for example, tetrabutylammonium bromide and an epoxy compound. In the present invention, this technique may also be applied to obtain a one-part thermosetting composition. In that case, glycidyl (meta)
If an epoxy group-containing monomer such as acrylate is copolymerized, it is not necessary to add an epoxy compound as an independent component. A 5-membered ring carbonate may be used instead of the epoxy compound. Japanese Patent Application Laid-Open No. 8-2836 of the present applicant
See No. 27.

The curable resin composition of the present invention is useful as a vehicle for paints. The paint may be a clear paint containing no pigment or a colored paint containing a conventional pigment. Since the composition is based on NAD, it can be made into a high solid.On the other hand, the apparent viscosity at the time of coating is low due to structural viscosity, but after adhering to the object to be coated, the apparent viscosity rises and the thick coating causes sagging. Does not occur. Further, it can be applied from room temperature drying to baking drying by selecting a catalyst.

Hereinafter, the present invention will be illustrated by Production Examples, Examples and Comparative Examples. In these, "part" and "%"
Is based on weight.

Preparation Example 1 of Stabilizer Solution In a reaction vessel equipped with a stirrer, thermometer, nitrogen introduction pipe, and cooling pipe, 30.0 parts of Toxsorbent (a petroleum-based mixed solvent manufactured by Shoei Chemical Co., Ltd.) was charged under a stream of nitrogen gas. The temperature was raised to 120 ° C. Into this, 7.5 parts of styrene (ST), 25.0 parts of 2-ethylhexyl methacrylate (EHMA),
Acetoacetoxyethyl methacrylate (AAEM) 1
A mixture of 7.5 parts, 1.0 part of Kayaester O (t-butylperoxy 2-ethylhexanoate manufactured by Nippon Kayaku) and 1.0 part of toxsorbent was added dropwise over 3 hours, and the mixture was added for 1 hour. After maintaining the temperature, 0.25 parts of Kayaester O,
2.33 parts of Toxsorbent was added dropwise over 30 minutes, and the temperature was maintained at the same temperature for 1.5 hours, followed by cooling to obtain stabilizer solution A. Nonvolatile content 59.4%, viscosity Z-Z1 ″,
Mn = 7292, Mw = 19052, Mw / Mn = 2.
61

Preparation Examples 2 to 4 In the same manner as in Preparation Example 1 except that the monomer mixture shown in Table 1 was used, stabilizer solutions B to D were obtained. However, in Production Example 3, the polymerization temperature was 130 ° C.

[0031]

[Table 1]

NAD Production Example 5 A reaction vessel equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a cooling tube was charged with 253.74 parts of the stabilizer solution and heated to 120 ° C. A mixed solution of 31.0 parts of MMA, 19.0 parts of 2-hydroxyethyl methacrylate (HEMA) and 1.0 part of Kayaester O was dropped therein over 2 hours, and kept at the same temperature for 2 hours. Kayaester O 0.
25 parts were added and maintained at the same temperature for 2 hours. After cooling, the mixture was diluted with 33.33 parts of Toxsorbent, NAD having a nonvolatile content of 60.7%, a viscosity of 10,400 CPS and a particle diameter of 0.408 μm.
(I) was obtained.

Production Examples 6 to 8 In place of the stabilizer solution and the monomer mixture shown in Table 2,
NADs (II) to (IV) were obtained in the same manner as in Production Example 5. However, NAD (IV) is for a comparative example.

[0034]

[Table 2]

Examples 1 to 3 and Comparative Example 1 NAD (I) to (IV), ADP-6 (trade name of dipentaerythritol hexaacrylate), propenyl ether propylene carbonate (PEPC), and tetrabutylammonium bromide (TBABr) and
The clear coating was prepared by blending with the blending shown in Table 3.

Comparative Example 2 AAEM 30.0 parts, HEMA 9.2 parts, styrene 4
15. 0.0 part, n-butyl acrylate (n-BA)
A monomer mixture consisting of 8 parts and 4.0 parts of MMA was copolymerized by a solution polymerization method to prepare a varnish having a nonvolatile content of 60%. 179.7 parts of this varnish, APP-6 14.5
Parts, 4.77 parts of PEPC and 0.974 parts of TBABr were mixed to prepare a clear paint.

Curability test (No. 1): NAD
The clear paints of Examples 1 to 3 containing (I) to (III) were applied to a tin plate using a No. 30 bar coater, baked at 160 ° C. for 20 minutes, and the pencil hardness was measured. The pencil hardness was B for Examples 1 and 2, and HB for Example 3.

Curability test (part 2): The paints of Example 1, Comparative Examples 1 and 2 were applied to a tin plate in the same manner as above, and
After baking for 20 minutes at each of the temperatures shown in Table 1 and extracting with an acetone solvent for 3 hours using a Soxhlet extractor,
After drying for a time, the gel fraction was determined by the following equation.

Gel fraction (%) = 100 × (weight of film after extraction) / (weight of film before extraction)

[0040]

[Table 3]

As a result, the paints of Examples 1 to 3 in which the NAD stabilizer resin contained 25% or more of the active methylene monomer were as follows:
The paint of Comparative Example 1 in which the amount of active methylene monomer in the stabilizer resin is 20% and the amount of active methylene monomer in the particles is 40%, and the amount of active methylene monomer is 30%
It can be seen that the curability is superior to that of Comparative Example 2 of the homogeneous solution type.

Claims (6)

[Claims] 1. An active methylene group-containing acrylic monomer (a) dissolved in a nonpolar solvent (a)
(Ii) alkyl (meth) having 6 or more carbon atoms in the alkyl group
(Iii) other ethylenically unsaturated monomers 0 to 40
(B) a non-aqueous dispersion of an acrylic copolymer solution having a monomer composition of wt.% And acrylic copolymer fine particles insoluble in the solvent but stably dispersed in the acrylic copolymer solution; A curable resin composition comprising: a compound having a plurality of α, β-unsaturated carbonyl groups; and (c) a catalyst for promoting a Michael reaction. 2. The method according to claim 1, wherein the fine particles of the acrylic copolymer have an alkyl (meth) acrylate having 4 or less carbon atoms in the alkyl group.
0 to 80% by weight, acrylic monomer having hydroxyl group 20
The curable resin composition according to claim 1, which has a monomer composition of 0 to 50% by weight and 0 to 20% by weight of another ethylenically unsaturated monomer containing an active methylene group-containing acrylic monomer. 3. The curable resin composition according to claim 1, wherein the weight ratio of the solid content of the acrylic copolymer solution and the fine particles of the acrylic copolymer in the non-aqueous dispersion is from 3: 1 to 1: 2. 4. The curable resin composition according to claim 1, wherein said catalyst is a strong base, and said composition is a two-part, room temperature curable type. 5. A catalyst comprising a quaternary ammonium salt, a quaternary phosphonium salt or a tertiary sulfonium salt which does not have a catalytic activity in the Michael reaction by itself, an epoxy compound or a tertiary sulfonium salt.
The curable composition according to any one of claims 1 to 3, wherein the composition is a combination with a membered ring carbonate compound, and the composition is a one-part thermosetting type. 6. A paint containing the curable resin according to claim 1 as a vehicle.