JPH0317862B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin composition for coating that has excellent pigment dispersibility and is completely cured even at temperatures of about 100°C. Currently, aminoacrylic resin paints are widely used as top coats for metals such as automobiles and home appliances. Aminoacrylic resin paints are made by blending pigments and melamine resins such as butylated melamine into an organic solvent solution of acrylic resins having hydroxyl groups, but poor pigment dispersibility has become a practical problem. Also, this paint generally has a temperature of 140℃ to 160℃.
Painting is usually done by baking at a high temperature for 20 to 30 minutes, but baking at such high temperatures is industrially disadvantageous in terms of productivity and workability. Therefore, P-
A method of adding an acid catalyst such as toluenesulfonic acid has also been put into practical use, but in addition to shortening the pot life, it also has the disadvantage of rusting on metals. The present invention solves the conventional problems as described above. The curable resin composition for coating 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 phosphate ( _A2 ) 0.01-2% by weight Acrylic monomer or styrene monomer ( _A3 ) 60-90% by weight Pigment (B) in an organic solvent solution of copolymer (A) and amino resin (C), and has the following excellent effects. (1) Pigment dispersibility is extremely excellent, reducing the time required for uniform mixing regardless of the type of pigment, and once dispersion, uniformity can be maintained for a long time, even when mixed color pigments are used. No color separation occurs during wrapping tests or overcoating. (2) 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. (3) 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. (4) It has excellent metal adhesion and rust prevention effect, and also has excellent coating performance such as hardness, gloss, Erichsen value, bending resistance, boiling water resistance, and salt spray 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, Examples include hydroxystyrene, 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 is selected from the range of 0.01 to 2% by weight, especially 0.05 to 1.8% by weight. If the proportion is too small, pigment dispersibility, low temperature curing properties, and other effects cannot be obtained.
On the other hand, if it is too large, gelation tends to occur during copolymer production, and storage stability when mixed with an amino resin deteriorates. 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, ethyl methacrylate, propyl methacrylate, butyl methacrylate; −
Examples include methacrylates such as ethylhexyl methacrylate, 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. It may also contain dicarboxylic acids or their partial esters, complete esters/anhydrides, vinyl ethers, etc. 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. Among these organic strength agents, hydrocarbons, esters, ketones, etc. are particularly desirable, and when using alcoholic solvents such as alcohol, mono-, di-, or triethylene glycol monoalkyl ether, hydrocarbons, It is preferable to use it in combination with esters, ketones, etc. A pigment (B) and an amino resin (C) are blended into the organic solvent solution of the copolymer (A). Pigments (B) include white pigments such as titanium oxide, calcium carbonate, talc, lithopone, barium sulfate, calcium sulfate, alumina, and clay, black pigments such as carbon black, blue pigments such as phthalocyanine blue, navy blue, and ultramarine, and lake. yellow,
A wide variety of pigments are used, including yellow pigments such as yellow lead, orca yellow, and Hansa yellow, red pigments such as red pigment and lake red, orange pigments such as chrome vermilion, and green pigments such as phthalocyanine green and chromium oxide. In addition, when two or more of these pigments are mixed, pigments such as titanium oxide/carbon black, titanium oxide/cyanine blue, titanium oxide/red iron oxide, etc. can also be used. The blending ratio of copolymer (A) and pigment (B) is not particularly limited, but 2 to 300 parts of pigment (B) is added to 100 parts by weight of copolymer (A).
In practical terms, it is particularly desirable to incorporate it in parts by weight. The amino resin (C) is an initial reaction product of one or more amino compounds such as melamine, acetoguanamine, benzoguanamine, urea, etc. and formaldehyde or other aldehyde, or it is combined with alcohol, epoxy compound, or other compound. It refers to something that has been denatured. 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 (C) is not particularly limited and can be varied widely depending on the purpose and application. A combination containing 10 to 50 parts by weight of C) is particularly practical. The composition containing the pigment (B) and amino resin (C) in an organic solvent solution of the copolymer (A) may be further added with known plasticizers, anti-sagging agents, antifoaming agents, dispersants, etc. as necessary. Additives can be added. The curable resin composition for painting of the present invention has a long pot life, so it can be stored for a long time even if the above components (A), (B), and (C) are mixed together. There is no problem in mixing them. The curable resin composition for painting of the present invention is particularly preferred as a coating for low-temperature baking, but even when it is baked at a higher temperature, it can be baked in a shorter time than in the past, leading to improved productivity. Next, the curable resin composition for coating of the present invention will be further explained by giving examples. Hereinafter, "parts" and "%" are expressed on a weight basis. Example 1 30 parts of styrene, 30 parts of methyl methacrylate, n
-18.8 parts of butyl hair acrylate, 20 parts of 2-hydroxyethyl acrylate and mono(2-hydroxyethyl acrylate) acid phosphate
1.2 parts of toluene and butyl acetate in a ratio of 1:1 by weight
By reacting for 10 hours at a temperature of 100 to 110℃ using a benzoyl peroxide catalyst in a mixed solvent of
An acrylic polymer solution was obtained. To 100 parts of this polymer solution, 30 parts of titanium oxide (TITONE SR-1 manufactured by Sakai Chemical Industry Co., Ltd.) and 15 parts of toluene were added, and 150 parts of each 1 mm glass beads were added.
and dispersed with a paint agitator for 1 hour. (White enamel) Also add 5 parts of carbon black to 100 parts of this polymer solution.
15 parts of toluene and 150 parts of glass beads with a diameter of 1 mm were added, followed by dispersion in a paint agitator for 1 hour. (Black enamel) Separately, 10 parts of cyanine blue and 15 parts of toluene were added to 100 parts of the above resin solution, and 150 parts of glass beads with a diameter of 1 mm were added, followed by dispersion for 1 hour using a paint agitator. (Blue enamel) Next, 10 parts of the above black enamel, 30 parts of white enamel, and 20 parts of toluene were mixed and stirred with a disper.
(Black/white mixed color enamel) 10 parts of the above blue enamel, 30 parts of white enamel and 20 parts of toluene were mixed and stirred with a disper.
(Blue/white mixed color enamel) N-butylated melamine resin liquid (Yuban 20SE-60 manufactured by Mitsui Toatsu Chemical Co., Ltd.) was added to each of the above enamels at a weight ratio of acrylic polymer/n-butylated melamine of 100/25. It was blended so that Table 1 shows the results of examining pigment dispersibility using the paints of each color thus obtained. Table 2 shows the results of examining the pot life of white enamels and the hardening properties (gelling fraction) when baked at various temperatures. Furthermore, Table 3 shows the results of measuring the adhesion and various physical properties of the coating film for white enamel. Control example 1 Mono(2-hydroxyethyl methacrylate)
Polymerization was carried out in the same manner as in Example 1, except that only the use of acid phosphate was omitted, and the pigment and n-butylated melamine were blended. The results are shown in Tables 1 and 2.
It is shown in Table and Table 3.

[Table] As is clear from the above table, the conventional formulation, Control Example 1, has insufficient pigment dispersibility, especially for black pigments, blue pigments, and mixed color pigments; however, the formulation of Example 1 It can be seen that excellent pigment dispersibility is exhibited regardless of the type of pigment and whether or not the colors are mixed. (Note) Dispersion time is determined by measuring the change in particle size of carbon black over time with a tube gauge, and determining the maximum particle size.
It is expressed as the time required to become 20μ or less. Gloss was determined by measuring 60° specular reflection using a VG-103 reversal meter manufactured by Nippon Denshoku Industries. The rubbing test consists of 30 parts of white enamel, 10 parts of black or blue enamel, and 20 parts of toluene in a disper.
After dispersing for a minute, it was poured onto a tin plate, and 60 seconds later, the painted surface was lightly rubbed with a finger to compare the color with the static painted surface. To check for color separation by overcoating, pour the mixed paint used in the rubbing test onto a tin plate, and after 60 seconds, apply another layer over a portion of the tin plate to see the difference in color between the first and second coats. compared. Storage stability is determined by adding toluene to the resulting paint to dilute it to a food cup viscosity of 13 seconds, and then leaving it in a 200ml wide-mouthed glass bottle for 24 hours.The total paint height is A.
It is expressed as a ratio of the precipitated pigment height B (cm) to (cm). Storage stability = B/A x 100 (%)

[Table] Note that Control Example 2 in Table 2 above and Table 3 below is a composition in which P-toluenesulfonic acid was further added to the composition of Control Example 1 in an amount of 1% based on the acrylic polymer solution. 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. On the other hand, the formulation of Example 1 has an excellent effect in that complete hardening can be achieved even under baking conditions of about 100°C, despite the long pot life.

[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. Example 2 Methyl methacrylate 40% n-butyl methacrylate 12% n-butyl acrylate 25.6% 2-hydroxyethyl acrylate 22% Mono(2-hydroxyethyl methacrylate)
A pigment was added in the same manner as in Example 1 to a solution of an acrylic polymer in a toluene/butyl acetate (1/1) mixed solvent solution having a composition of 0.4% acid phosphate, a solid content of 51.0%, and a viscosity of 3300 cps at 25°C. to prepare enamel of each color,
The n-butylated melamine resin liquid used in Example 1 was blended with these so that the weight ratio of acrylic polymer/methylated melamine was 100/25 to improve pigment dispersibility.
The pot life and hardenability when baked at various temperatures were examined. Control Example 3 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 Vinyltoluene 30% Ethyl methacrylate 23% Ethyl acrylate 30% 2-hydroxyethyl acrylate 14% Mono(2-hydroxypropyl acrylate)
Butyl acetate is an acrylic polymer with a solid content of 52.2% and a viscosity of 7200 cps at 25°C, with a composition of 3% acid phosphate.
Various enamels were prepared by adding pigments to the toluene mixed solvent solution in the same manner as in Example 1, and methylated melamine resin liquid (Nikalatsuk MS-11 for baking paints manufactured by Sanwa Chemical Co., Ltd.) was added to the acrylic polymer/methyl enamel. The pigment dispersibility, pot life, and hardenability when baked at various temperatures were examined by blending melamine in a weight ratio of 100/30. Control example 4 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-hydroxypropyl methacrylate) acid phosphite 0.8%, 25°C. Acrylic polymer butyl acetate with a viscosity of 1800 cps/
Pigments were added to the methyl ethyl ketone mixed solvent solution in the same manner as in Example 1 to prepare various enamels, and the urea-melamine-formaldehyde initial reaction product was blended with these so that the resin ratio of both was 100/30 by weight. , pigment dispersibility, pot life and curing properties were investigated. Control Example 5 An experiment was carried out in the same manner as in Example 4, except that a copolymer lacking only the mono(2-hydroxypropyl methacrylate) acid phosphite component was used. The results of Examples 2 to 4 and Control Examples 3 to 5 are shown in Table 4 for pigment dispersibility, and Table 5 for pot life and curability.

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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 Pigment ₍ B ₎ and amino resin ( A curable resin composition for painting comprising C). 2. Claim 1, wherein the blending amounts of (B) and (C) are 2 to 300 parts by weight of (B) and 10 to 50 parts by weight of (C) per 100 parts by weight of (A) in terms of solid content ratio. Compositions as described.