JPH1025434A - Weatherable powder coating resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder coating resin composition which highly absorbs ultraviolet and can impart long-lasting weatherability to a coating film. SOLUTION: The composition comprises: an ultraviolet-absorbing copolymer obtained by polymerizing an ultraviolet-absorbing vinyl monomer based on benzotriazole with an unsaturated monomer copolymerizable therewith; and a resin for a powder coating. The copolymer has a content of units derived from the vinyl monomer of 0.1-70wt.% and a weight-average mol.wt. of 2,000-100,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a weather-resistant powder coating resin composition.

In the field of resin coatings such as coatings for automobiles, it is essential to improve the weather resistance. For this purpose, benzophenones, benzotriazoles, phenyl benzoates, phenyl salicylates are required. Various ultraviolet absorbers, such as those, are blended and used. However, in applications where a film is inevitably formed at a high temperature, such as a powder coating, when a conventionally available low molecular weight ultraviolet absorber is used, the ultraviolet absorber is significantly volatilized. In addition, there are problems that the weather resistance of the coating film cannot be sufficiently improved, the yield of the ultraviolet absorbent is low, and the working environment is contaminated. On the other hand, an attempt to solve the problems of the conventional low-molecular-weight ultraviolet absorber by blending a high-molecular-weight ultraviolet absorber has been reported in Japanese Patent Publication No. 2-5 / 1995.
No. 0142 and the like. However, since the method disclosed in the above publication uses a polymer whose ultraviolet absorbing group is composed of benzophenone, the absorption wavelength range is narrow and the performance as an ultraviolet absorber is inferior, so that the coating film has sufficient weather resistance. At present, it cannot be given.

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have succeeded in obtaining a novel powder coating composition, and have now completed the present invention. Was. That is, the present invention is a copolymer obtained by polymerizing a benzotriazole-based UV-absorbing vinyl monomer and an unsaturated monomer copolymerizable with the monomer, wherein the copolymer has a UV-absorbing property in a copolymer composition. 0.1 to 70 of vinyl monomer
% By weight and a weight average molecular weight of 2,000 to 100
The present invention relates to a weather-resistant powder coating resin composition containing a UV-absorbing polymer of 000 and a resin for powder coating. In the powder resin composition of the present invention, even when the thermosetting treatment is performed at a high temperature, the ultraviolet absorbent does not volatilize from the coating film. For this reason,
There is no need to contaminate the working environment, and there is no need to incorporate more ultraviolet absorbers into the paint than is necessary in the past. Further, inconveniences such as a reduction in the effect of absorbing ultraviolet light with the passage of time in an actual use situation are eliminated, so that a long-term weather resistance can be imparted to the coating film.

BEST MODE FOR CARRYING OUT THE INVENTION In the powder coating composition of the present invention, a UV-absorbing copolymer used as an active ingredient is a benzotriazole-based UV-absorbing vinyl monomer and an unsaturated monomer copolymerizable with the monomer. It can be produced by copolymerizing with a monomer. The benzotriazole-based UV-absorbing vinyl monomer is not particularly limited as long as it has at least one benzotriazole-based UV-absorbing group and at least one vinyl group in the molecule, and conventionally known ones can be widely used. As such a compound, for example, the following general formula (1)

Embedded image [Wherein, X represents a hydrogen atom or a chlorine atom. R ¹ represents a hydrogen atom, a methyl group or a tertiary alkyl group having 4 to 8 carbon atoms. R ² represents a linear or branched alkylene group having 2 to 10 carbon atoms. R ³ represents a hydrogen atom or a methyl group. n represents 0 or 1. A compound represented by the general formula (2)

Embedded image Wherein R ¹ and R ³ are the same as above. A compound represented by the general formula (3)

Embedded image Wherein R ¹ , R ² and R ³ are the same as above. R ⁴ is -C ₂ H ₄
— Or —CH ₂ CH (OH) CH ₂ —. And the like. In the general formula (1), the tertiary alkyl group having 4 to 8 carbon atoms represented by R ¹ includes a tert-butyl group and a tert-butyl group.
Examples include a pentyl group, a tert-hexyl group, a tert-heptyl group, a tert-octyl group, and a ditert-octyl group. Examples of the linear or branched alkylene group having 2 to 10 carbon atoms represented by R ² include an ethylene group, a trimethylene group, a propylene group, a tetramethylene group, a 1,1-dimethyltetramethylene group, and a butylene group. Octamethylene group, octylene group, decamethylene group, decylene group and the like. Among these, an ethylene group and a propylene group are preferred. In the general formulas (2) and (3), the tertiary alkyl group having 4 to 8 carbon atoms represented by R ¹ includes a tertiary alkyl group having 4 to 8 carbon atoms represented by R ¹ in the general formula (1). And the same as the tertiary alkyl group. Also,
In the general formulas (2) and (3), the linear or branched alkylene group having 2 to 10 carbon atoms represented by R ² is represented by R ¹ in the general formula (1). The same thing as a linear or branched C2-C10 alkylene group can be mentioned. Specific examples of the compound represented by the general formula (1) include, for example, 2- [2′-
Hydroxy-5 '-(methacryloyloxy) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5'-(methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(2-methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(2-acryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5 '-(2-methacryloyloxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2-
[2'-hydroxy-3'-methyl-5 '-(8-acryloyloxyoctyl) phenyl] -2H-benzotriazole and the like. Specific examples of the compound represented by the general formula (2) include, for example, 2- [2′-
Hydroxy-5'-tert-butyl-3 '-(methacrylamidomethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-di-tert-
Octyl-3 '-(methacrylamidomethyl) phenyl] -2H-benzotriazole. Specific examples of the compound represented by the general formula (3) include:
For example, 2- [2'-hydroxy-3'-tert-butyl-5'-2- (2-methacryloyloxyethoxycarbonyl) ethylphenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'- tert-butyl-5'-2- (3-methacryloyloxy-2-hydroxypropoxycarbonyl) ethylphenyl] -2H
-Benzotriazole and the like. Among the benzotriazole-based UV-absorbing monomers, the compound represented by the general formula (1) can be particularly preferably used. In addition, the benzotriazole-based UV-absorbing monomer may be used alone or in combination of two or more. The content of the benzotriazole-based UV-absorbing monomer in the UV-absorbing copolymer of the present invention is usually 0 considering the compatibility of the obtained UV-absorbing polymer and the powder coating resin containing the same. 0.1 to 70% by weight, preferably 10 to 70% by weight
It is 50% by weight. As the polymerizable unsaturated monomer copolymerizable with the benzotriazole-based UV-absorbing vinyl monomer, conventionally known ones can be used, for example, methacrylic acid,
Methacrylic acid such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, n-lauryl methacrylate and its alkyl esters, acrylic acid, ethyl acrylate, n-acrylic acid
Acrylic acid such as butyl and n-octyl acrylate and its alkyl ester, 1-hexene, 1-octene, 1
Α-olefins such as decene, vinyl acetate, styrene,
2-hydroxyethyl methacrylate, acrylamide,
Examples thereof include vinyl chloride. These polymerizable unsaturated monomers are used alone or in combination of two or more. Further, in addition to the unsaturated monomer, by using an unsaturated monomer having a reactive functional group capable of participating in the chemical reaction of the resin for powder coating thermally cured, the coating film is formed after thermal curing. The ultraviolet-absorbing polymer unit can be introduced into the resin chain by chemical bonding, and the hardness of the coating film can be improved at the same time. Examples of the unsaturated monomer having such a reactive functional group include glycidyl methacrylate,
Glycidyl acrylate, α-methyl glycidyl methacrylate, unsaturated monomer having a glycidyl group such as α-methyl glycidyl acrylate, acrylic acid, methacrylic acid,
Maleic anhydride, unsaturated monomers having a carboxyl group such as itaconic acid, 2-hydroxyethyl methacrylate,
Examples thereof include unsaturated monomers having a hydroxyl group such as 2-hydroxyethyl acrylate, methylol methacrylamide, and methylol acrylamide. These unsaturated monomers can also be used alone or in combination of two or more. The ultraviolet absorbing copolymer in the present invention can be synthesized by a conventional method, for example, according to conventionally known various polymerization methods such as a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, and a bulk polymerization method. In the present invention, among the ultraviolet-absorbing copolymers obtained above, the weight-average molecular weight is usually from 2,000 to 1,
0000, preferably 5000 to 50000. When the weight average molecular weight is less than 2,000, there is a risk of volatilization in the course of the thermosetting treatment. On the other hand, when the weight average molecular weight exceeds 100,000, the compatibility with the coating resin may be insufficient, and neither is preferable. . In the weatherable powder coating resin composition of the present invention, the resin for powder coating used in combination with the ultraviolet absorbing copolymer is not particularly limited, and any resin used in the coating field can be used. However, for example, acrylic resin, epoxy resin, polyester resin, melamine resin, urethane resin and the like can be preferably used. In the composition of the present invention, the blending ratio of the ultraviolet-absorbing copolymer and the resin for powder coating is not particularly limited and can be appropriately selected from a wide range. In consideration of preventing a decrease in physical properties such as mechanical strength and hardness, the UV-absorbing copolymer is usually about 0.2 to 20% by weight, preferably 1 to 10% by weight, based on 100% by weight of the powder coating resin. % May be blended. The composition of the present invention may contain general additives for powder coatings in addition to the essential components of the ultraviolet absorbing copolymer and the resin for powder coatings.
Specific examples of the additives include, for example, pigments, oxidation stabilizers, fillers, viscosity modifiers, antiblocking agents, antistatic agents, rust inhibitors, other common ultraviolet absorbers, and the like. . The composition of the present invention can be produced by mixing a predetermined amount of the UV-absorbing copolymer, which is an essential component, with a resin for a powder coating, and, if necessary, other additives according to a usual method. For example, a method of pulverizing each component and then dry-mixing with a Henschel mixer, a super mixer, a tumbler or the like, a method of melting and mixing with a Banbury mixer or the like, and then pulverizing the components can be mentioned. The substrate to which the composition of the present invention can be applied is not particularly limited, and may be a metal, a synthetic resin,
Any of ceramics and wood may be used, for example,
Preferred are metals such as iron, aluminum, zinc, and tin, alloys of at least two of these, ceramics such as glass, and synthetic resins such as polyurethane, epoxy resin, polyester resin, nylon, polyethylene, and polypropylene.

EXAMPLES The present invention will be specifically described below with reference to Synthesis Examples, Examples and Comparative Examples. In the following, “parts” and “%” are “parts by weight” and “% by weight”, respectively.
Means Synthesis Example 1 Synthesis of UV-absorbing polymer A 70 parts of methyl methacrylate, 2- [2′-hydroxy-5 ′-(2-methacryloyloxyethyl) phenyl] -2H-benzotriazole 30 as a UV-absorbing monomer A mixture consisting of 2.8 parts of azoisobutyronitrile and 2.8 parts of azoisobutyronitrile was gradually added dropwise to 100 parts of butyl acetate heated to 120 ° C., and then kept at the same temperature for 4 hours. Then, the solvent was volatilized from the obtained reaction product at 160 ° C. under a reduced pressure of 50 torr to obtain an ultraviolet absorbing polymer having a weight average molecular weight of 10,500. Synthesis Example 2 Synthesis of ultraviolet absorbing polymer B 54 parts of methyl methacrylate, 13 parts of 2-ethylhexyl acrylate, 3 parts of glycidyl methacrylate, and 2- [2′-hydroxy-5 ′-( 2-
1. methacryloyloxyethyl) phenyl] -2H-benzotriazole 30 parts and azoisobutyronitrile
The mixture consisting of 8 parts was gradually dropped into 100 parts of butyl acetate heated to 120 ° C., and then kept at the same temperature for 4 hours. Subsequently, the solvent was volatilized from the obtained reaction product at 160 ° C. under a reduced pressure of 50 torr to obtain an ultraviolet absorbing polymer having a weight average molecular weight of 10300. Synthesis Example 3 Synthesis of UV-absorbing polymer C 54 parts of methyl methacrylate, 13 parts of 2-ethylhexyl acrylate, 3 parts of 2-hydroxyethyl methacrylate,
2- [2'-hydroxy-
5 '-(2-methacryloyloxyethyl) phenyl]
A mixture composed of 30 parts of -2H-benzotriazole and 2.8 parts of azoisobutyronitrile was gradually dropped into 100 parts of butyl acetate heated to 120 ° C, and then kept at the same temperature for 4 hours. Then, at 160 ° C., 50 torr
Under reduced pressure, the solvent was evaporated from the obtained reaction product to obtain an ultraviolet absorbing polymer having a weight average molecular weight of 9600. Synthesis Example 4 Synthesis of ultraviolet absorbing polymer D 54 parts of methyl methacrylate, 13 parts of butyl acrylate,
3 parts of 2-hydroxyethyl methacrylate, 2- [2′-hydroxy-3′-tert) as an ultraviolet absorbing monomer
-Butyl-5'-2- (3-methacryloyloxy-2
-Hydroxypropoxycarbonyl) ethylphenyl]
A mixture composed of 30 parts of -2H-benzotriazole and 2.8 parts of azoisobutyronitrile was gradually dropped into 100 parts of butyl acetate heated to 120 ° C, and then kept at the same temperature for 4 hours. Then, at 160 ° C., 50 torr
Under reduced pressure, the solvent was volatilized from the obtained reaction product to obtain an ultraviolet absorbing polymer having a weight average molecular weight of 10200. Synthesis Example 5 Synthesis of Acrylic Resin A mixture consisting of 55 parts of methyl methacrylate, 10 parts of styrene, 30 parts of glycidyl methacrylate, 15 parts of butyl acrylate, and 0.6 part of azoisobutyronitrile was added to 11 parts of
After gradually dropping into 100 parts of toluene heated to 0 ° C., the temperature was maintained for another 4 hours. Then, the solvent was volatilized from the obtained reaction product at 160 ° C. under a reduced pressure of 50 torr to obtain an acrylic resin having a glass transition temperature of 80 ° C. Example 1 Epoxy powder coating (trade name: Epotote YD-019,
To 100 parts of Toto Kasei Co., Ltd., 3.3 parts of the ultraviolet absorbing polymer A obtained in Synthesis Example 1 and 4 parts of dicyandiamide were blended, melt-kneaded at a temperature of 90 ° C. with a hot roll, and cooled. Then, the mixture was finely pulverized with a pulverizer and collected through a 150-mesh sieve to obtain a powder coating of the present invention. Comparative Example 1 As a heat-resistant ultraviolet absorber, 2- [2′-hydroxy-5 ′-(tert-octyl) phenyl] -2H— instead of 3.3 parts of the ultraviolet absorbing polymer A obtained in Synthesis Example 1 was used. A powder coating was produced in the same manner as in Example 1, except that 2 parts of benzotriazole was added. 100 parts of the paints obtained in Example 1 and Comparative Example 1 were mixed with tetrahydrofuran 20
After dissolving in 0 parts, it was coated on a glass plate having a thickness of about 100 μm so that the dry film thickness became about 10 μm, and dried at room temperature.
Next, in order to examine the stability of the ultraviolet absorber contained in the dried coating film during thermal curing, the glass plate on which the coating film was formed was placed in a heating furnace at 160 ° C., and the maximum absorption wavelength (implemented every 10 minutes) was measured. 339 nm in the case of Example 1 and 34 in the case of Comparative Example 1.
1 nm) was measured. Table 1 shows the results.

[Table 1] From Table 1, it can be seen that while the low molecular weight ultraviolet absorber incorporated into the coating film according to the prior art is mostly volatilized during the heat curing treatment, the ultraviolet absorbing polymer of the present invention also volatilizes during the heat curing treatment. It can be seen that the ultraviolet absorbing ability is maintained without performing the process. Example 2 3.3 parts of the ultraviolet absorbing polymer B obtained in Synthesis Example 2 and 24 parts of decanedicarboxylic acid were blended with 100 parts of the acrylic resin obtained in Synthesis Example 5, and the same operation as in Example 1 was carried out. Thus, the powder coating of the present invention was produced. Comparative Example 2 As a heat-resistant ultraviolet absorber, 2- [2′-hydroxy-3 ′, 5′-di (te) was used in place of the ultraviolet absorbing polymer B.
rt-butyl) phenyl] -benzotriazole (2 parts) was blended and the same procedure as in Example 1 was carried out to produce a powder coating. The paints obtained in Example 2 and Comparative Example 2 were electrodeposited on a zinc phosphate chemical conversion treated steel sheet so as to have a dry film thickness of about 20 μm, and then cured by heating at 180 ° C. for 30 minutes. Manufactured. These test plates were subjected to an acceleration test using a sunshine weather meter, and the glossiness of the coating film before and after the acceleration test was measured at 60 ° to determine the gloss retention (%).
The results of the accelerated test are shown in Table 2. Example 3 Main agent of polyester powder coating (trade name: ER-810)
5, Unitika Ltd.) was mixed with 100 parts of 3.3 parts of the ultraviolet absorbing polymer C obtained in Synthesis Example 3 and 6 parts of triglycidyl isocyanate (curing agent), and then operated in the same manner as in Example 1. Thus, a powder coating of the present invention was produced. Comparative Example 3 As a heat-resistant UV absorber, 2- [2′-hydroxy-5′- was used instead of the UV-absorbing polymer C obtained in Synthesis Example 3.
(Tert-octyl) phenyl] -benzotriazole (2 parts) was blended and the same operation as in Example 1 was carried out to produce a powder coating. Example 4 Main agent of polyester powder coating (trade name: ER-810)
5, 100 parts of Unitika Ltd.) were mixed with 3.3 parts of the ultraviolet absorbing polymer D obtained in Synthesis Example 4 and 6 parts of triglycidyl isocyanate (curing agent), and then operated in the same manner as in Example 1. Thus, a powder coating of the present invention was produced. The powder coatings produced in Example 3, Comparative Example 3 and Example 4 were electrodeposited on a zinc phosphate chemical conversion treated steel sheet so as to have a dry film thickness of about 20 μm, and then heated at 200 ° C. for 30 minutes. It was cured to obtain a test plate. These test plates were subjected to an accelerated test using a sunshine weather meter, and the paint film before and after the accelerated test was tested.
゜ The gloss was measured, and the gloss retention (%) was determined. The results of the accelerated test are also shown in Table 2.

[Table 2]

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Claims (1)

[Claims] 1. A copolymer obtained by polymerizing a benzotriazole-based UV-absorbing vinyl monomer and an unsaturated monomer copolymerizable with the monomer, wherein the copolymer has a copolymer composition and the UV-absorbing vinyl monomer. 0.1 to 70% by weight of monomer
Containing and having a weight average molecular weight of 2,000 to 100,000
A weatherable powder coating resin composition comprising an ultraviolet absorbent polymer and a resin for powder coating.