JPH0317861B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a low-temperature curing resin composition for coating that completely cures even at temperatures of about 100°C. Currently, solvent-type aminoacrylic resin paints are widely used as top coats for metals such as automobiles and home appliances. This aminoacrylic resin paint is a mixture of a melamine resin such as butylated melamine in an organic solvent solution of an acrylic resin having hydroxyl groups, and is generally painted by baking at a temperature of 140°C to 160°C for 20 to 30 minutes. I'm going. However, baking operations at such high temperatures are industrially disadvantageous in terms of productivity and workability. In addition, a method of adding an acid catalyst such as P-toluenesulfonic acid to enable curing even at low temperatures has been put into practical use, but in addition to shortening the pot life, it also has the disadvantage of causing rust on metals. There is. The present invention solves the conventional problems as described above. The coating resin composition of the present invention contains a hydroxyl group-containing monomer (a ₁ ) 10 to 40% by weight of mono(2-hydroxyethyl (meth)acrylate) acid phosphate or mono(2-hydroxypropyl (meth)acrylate) acid. Dophosphate ( _a2 )
An amino resin (B) is blended into an organic solvent solution of a copolymer (A) having a composition of 0.01 to 2% by weight and 60 to 90% by weight of an acrylic monomer or styrene monomer (a ₃ ), and the following: It has excellent effects such as (1) Baking temperature of 140 to 160℃, which was previously considered necessary.
can be lowered to about 100℃, and even if the baking temperature is lowered in this way, the gelation fraction remains
Virtually complete curing of 95-96% can be achieved. (2) Long pot life. The composition of the present invention is heated at 40°C.
Since the reactivity is slow below, it can be stored for a long time even if melamine resin is added. (3) It has excellent metal adhesion and rust prevention effect, and also has excellent coating performance such as hardness, gloss, Erichsen value, bending resistance, and boiling water resistance. In the present invention, the hydroxyl group-containing monomer (a ₁ ),
A composition consisting of mono(2-hydroxyethyl (meth)acrylate) acid phosphate or mono(2-hydroxypropyl (meth)acrylate) acid phosphate (a ₂ ) and an acrylic monomer or styrenic monomer (a ₃ ) A copolymer (A) having the following is used. Examples of the hydroxyl group-containing monomer (a ₁ ) include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, and 3-hydroxypropyl acrylate.
Hydroxypropyl methacrylate, 2-hydroxy-3-chloropropyl acrylate, acryloyloxyethyl hydrogen phthalate, β-hydroxyethyl-β-acryloyloxyethyl phthalate, 1,4-butylene glycol monoacrylate, N-methylol acrylamide, hydroxy Examples include styrene, allyl alcohol, methalyl alcohol, isopropenyl alcohol, and 1-butenyl alcohol. Among these, the first four are particularly suitable. Hydroxyl group-containing monomer (a ₁ ) in copolymer (A)
The proportion of is selected from the range of 10 to 40% by weight. If the amount is less than 10% by weight, curing performance will be insufficient, while if the amount exceeds 40% by weight, the crosslinking density will increase too much, resulting in poor flexibility of the coating film. This may cause a decrease in elasticity, bending resistance, and impact resistance. In addition, mono(2-hydroxyethyl (meth)acrylate) acid phosphate or mono(2-hydroxypropyl (meth)acrylate) acid phosphate (a ₂ ) in the copolymer (A)
The proportion of
It is difficult to obtain curing properties at temperatures around ℃, and on the other hand, if the temperature is too high, gelation tends to occur during copolymer production.
Furthermore, storage stability becomes poor when mixed with amino resin. Examples of the acrylic monomer or styrene monomer (a ₃ ) include acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate. Examples include methacrylates such as methacrylates, styrene monomers such as styrene, α-methylstyrene, and vinyltoluene. The proportion of the acrylic monomer or styrene monomer (a ₃ ) in the copolymer (A) is selected from the range of 60 to 90% by weight, and this monomer component becomes the main chain of the copolymer, and the proportion is 60% by weight. Even if it is less than 90% by weight or more than 90% by weight, the physical properties of the coating will be unbalanced. This (a ₃ ) component is usually used in a suitable combination of a hard component and a soft component, thereby obtaining a copolymer having desired weather resistance, gloss, flexibility, strength, etc. In addition to the above components (a ₁ ), (a ₂ ), and (a ₃ ),
Vinyl esters such as vinyl acetate and vinyl versatate; unsaturated monocarboxylic acids such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, acrylic acid, methacrylic acid, and crotonic acid; unsaturated acids such as maleic acid, fumaric acid, and itaconic acid. The dicarboxylic acid or its partial ester, complete ester/anhydride, glycidyl acrylate, glycidyl methacrylate, vinyl ether, etc. may be included. The above copolymer (A) is used in the form of an organic solvent solution. Examples of organic solvents include benzene, xylene, n
- Hydrocarbons such as hexane, esters such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, acetone, methyl ethyl ketone,
Ketones such as methyl isopropyl ketone, methyl isopropyl ketone, cyclohexanone, alcohols such as methanol, ethanol, isopropanol, butanol, cyclohexanol, ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, halogenated hydrocarbons, etc. These can be used alone or in combination of two or more. Amino resin (B) is added to the organic solvent solution of copolymer (A).
is blended. The amino resin (B) is an initial reaction product of one or more amino compounds such as melamine, acetognamine, benzoguanamine, urea, etc. and formaldehyde or other aldehyde, or this is treated with alcohol, epoxy compound, or other compound. Say something that has changed. In particular, partially or completely etherified products of methylolmelamine, such as methylated methylolmelamine, butylated methylolmelamine, and isobutylated methylolmelamine, are highly practical. The blending ratio of the copolymer (A) and the amino resin (B) is not particularly limited and can be varied widely depending on the purpose and use.
For the purpose of curing, the weight ratio of (A) and (B) is 99:1 ~
50:50; conversely, for the purpose of modifying amino resin (B) with copolymer (A), the weight ratio of (A) and (B) should be 1:99 or more.
It can be 50:50. However, copolymer (A)
The combination of blending 10 to 50 parts by weight of amino resin (B) with 100 parts by weight is the most practical. Pigments, dyes, fillers, anti-sag agents, antifoaming agents, dispersants, etc. are further added to the composition obtained by blending the amino resin (B) with the organic solvent solution of the copolymer (A), as necessary. be able to. The coating resin composition of the present invention has a long pot life, so it can be stored for a long time even if the above components (A) and (B) are mixed together. However, it is recommended to mix (A) and (B) before use. However, there is no difference. The coating resin composition of the present invention is particularly preferred as a type of coating that is baked at a temperature of about 100°C.
Of course, there is no problem with baking at high temperatures. Next, the coating resin composition of the present invention will be further explained with reference to examples. Hereinafter, "parts" and "%" are expressed on a weight basis. Example 1 37 parts of styrene, 23 parts of methyl methacrylate, 2
- 20 parts of ethylhexyl acrylate, 20 parts of 2-hydroxyethyl methacrylate, and 1.2 parts of mono(2-hydroxyethyl methacrylate) acid phosphate were mixed with a benzoyl peroxide catalyst in a mixed solvent of toluene and butyl acetate in a ratio of 1:1 by weight. Solid content 50.5%, viscosity at 25℃
An acrylic polymer solution of 2100 cps was obtained. Add n-butylated melamine resin solution (Yuban, manufactured by Mitsui Toatsu Chemical Co., Ltd.) to the above acrylic polymer solution.
20SE-60) so that the weight ratio of acrylic polymer/n-butylated melamine was 100/25,
The pot life and hardenability (gel fraction) when baked at various temperatures were investigated. In addition, various physical properties of the coating film were measured for adhesion. The results are shown in Tables 1 and 2. Control example 1 Mono(2-hydroxyethyl methacrylate)
Polymerization and blending of nr-butylated melamine were carried out in the same manner as in Example 1, except that the use of acid phosphate was omitted. The results are shown in Tables 1 and 2. Control Example 2 The composition of Control Example 1 was further blended with 1% P-toluenesulfonic acid based on the acrylic polymer solution. The results are shown in Tables 1 and 2.

[Table] As is clear from the table above, conventional acrylic
Control example 1, which is a melamine formulation, requires baking at 140℃ for 30 minutes to reach the target hardening speed (gelation fraction 95-96%).
does not reach. Furthermore, Comparative Example 2, which is a formulation containing P-toluenesulfonic acid, has a major drawback in that although the curing speed is fast, the pot life is short.

[Table] As is clear from the table above, the conventional formulation, Control Example 1, had significantly poor coating film properties when baked at 100°C for 30 minutes, and it was not until baked at 140°C for 30 minutes that practical coating film properties were achieved. come to have it. Also, in Comparative Example 2, which also has a conventional formulation, metal coating is impossible due to the occurrence of rust. On the other hand, it can be seen that the formulation of Example 1 has even better physical properties of the coating film than that of Comparative Example 1, which was baked at 140° C. for 30 minutes. Control example 3-4 Mono(2-hydroxyethyl methacrylate)
Polymerization was carried out in the same manner as in Example 1, except that the amount of acid phosphate used was 2.5 parts (Comparative Example 3) and 4 parts (Comparative Example 4), but the resulting reaction solution was slightly cloudy. The degree of cloudiness was more significant in Control Example 4. Further, when n-butylated melamine resin liquid was added to these reaction solutions in the same manner as in Example 1, the pot life was 5 days (Control Example 3) and 3 days (Control Example 4),
It was shorter than Example 1. The curability was almost the same as in Example 1. The physical properties of the coating film were inferior to those of Example 1 in terms of appearance (initial gloss, sharpness). Control Example 5 40 parts of methyl methacrylate, 15 parts of n-butyl acrylate, 30 parts of ethyl methacrylate, 10 parts of pyridine salt of mono(2-hydroxyethyl methacrylate) acid phosphate, 5 parts of methacrylic acid, cyclohexane and ethylene glycol monobutyl ether at 80 °C using azobisisobutyronitrile catalyst in a 1:1 mixed solvent by weight of
By reacting for 10 hours, an acrylic polymer solution with a resin content of 51.5% was obtained. Add 1.5 parts of dimethylethanolamine to 100 parts of this solution, and then add nn-
Butylated melamine resin liquid to acrylic polymer/n
-The weight ratio of butylated melamine was 100/25. This composition showed favorable coating film properties under the baking conditions of 140°C x 30 minutes, but under the baking conditions of 100°C x 30 minutes, it showed poor adhesion, boiling water resistance, and salt spray resistance as shown in Example 1. The physical properties were significantly inferior to that of . Metal adhesion Bonded steel plate 100/100 Mild steel plate 100/100 Tin plate 0/100 Boiling water resistance Appearance/Gloss retention rate
× (blistering, blistering) Adhesion × Salt spray resistance × (blistering) Example 2 Methyl methacrylate 40% n-butyl methacrylate 12% n-butyl acrylate 25.6% 2-hydroxyethyl acrylate 22% Mono (2 -Hydroxyethyl methacrylate) acid phosphate 0.4%, solid content 51.0%, viscosity 3300 cps at 25°C, isobutylated melamine resin solution (Mitsui Toatsu Chemical Co., Ltd.) Yuban 60) manufactured by the company was blended so that the weight ratio of acrylic polymer/isobutylated melamine was 100/25, and the pot life and curing properties when baked at various temperatures were examined. Control Example 6 An experiment was conducted in the same manner as in Example 2 except that a copolymer lacking only the mono(2-hydroxyethyl acrylate) acid phosphate component was used. Example 3 Solids content: 52.2%, viscosity at 25°C: 7200 cps, with the following composition: vinyl toluene 30% ethyl methacrylate 23% ethyl acrylate 30% 2-hydroxyethyl acrylate 14% mono(2-hydroxypropyl acrylate) acid phosphate 3% Acrylic polymer butyl acetate/
Add 50 parts of toluene mixed solvent solution, 35 parts of titanium oxide (TITONE SR-1 manufactured by Sakai Chemical Industry Co., Ltd.), 20 parts of toluene, and 10 parts of methyl ethyl ketone to form a 1 mm
Add 100 parts of glass beads of the same diameter and shake for 30 minutes.
Further, 50 parts of the above polymer solution was added and shaken for 5 minutes to form a paint. This white enamel was coated with methylated melamine resin liquid (Nikalatsuku MS for baking paint manufactured by Sanwa Chemical Co., Ltd.).
-11) was blended so that the weight ratio of acrylic polymer/methylated melamine was 100/30, and the pot life and curing properties when baked at various temperatures were investigated. Control example 7 Mono(2-hydroxypropyl acrylate)
The experiment was carried out as in Example 3 except that a copolymer lacking only the acid phosphate component was used. Example 4 Solid content 49.7% with the following composition: styrene 20%, n-butyl methacrylate 35%, n-butyl acrylate 14.2%, 2-hydroxypropyl methacrylate 30%, mono(2-hydroxyethyl methacrylate) acid phosphite 0.8%, 25°C. Acrylic polymer butyl acetate with a viscosity of 1800 cps/
A urea-melamine-formaldehyde initial reaction product was blended into a methyl ethyl ketone mixed solvent solution so that the ratio of both resins was 100/30 by weight, and the pot life and curing properties were examined. Control example 8 Mono(2-hydroxyethyl methacrylate)
The experiment was carried out in the same manner as in Example 4, except that a copolymer lacking only the acid phosphite component was used. The results of Examples 2 to 4 and Control Examples 6 to 8 are shown in Table 3.

【table】

Claims (1)

[Scope of Claims] 1 Hydroxyl group-containing monomer (a ₁ ) 10 to 40% by weight Mono(2-hydroxyethyl (meth)acrylate) acid phosphate or mono(2-hydroxypropyl (meth)acrylate) acid phosphate ( _a2 ) 0.01 to 2% by weight of an acrylic monomer or styrene monomer ( _a3 ) 60 to 90% by weight of an organic solvent solution of a copolymer (A) mixed with an amino resin (B). Resin composition for coating. 2. The composition according to claim 1, wherein the content of component ( _a2 ) is 0.05 to 1.8% by weight.