JPH0717768B2 - Surface treatment method for thermoplastic resin molding - Google Patents

Description

The present invention relates to a surface treatment method for a thermoplastic resin molded body. More specifically, the present invention relates to a surface treatment method for a thermoplastic resin molded body such as polycarbonate, which can effectively impart excellent light resistance and weather resistance.

[Conventional technology]

Thermoplastic resins such as polyolefins, polyvinyl chloride, styrene resins, polycarbonates, thermoplastic polyesters and polyamides are widely used in many fields as films and various molded products.

When these thermoplastic resins are exposed to sunlight, their energy, especially the high energy of ultraviolet rays, causes structural changes such as the formation of quinone and double bonds, the breaking of the main chain, the formation of crosslinked structures and the formation of oxides. Cause
It has the drawback of causing cracking, lowering of strength, and deterioration such as coloring, and therefore light resistance and weather resistance are important problems especially when used outdoors.

Therefore, conventionally, by adding an ultraviolet absorber to the thermoplastic resin during the polymerization step or kneading,
A method of imparting light resistance and weather resistance is taken. However, in such an addition method, since the ultraviolet absorber is dispersed in the entire resin, it is necessary to add a large amount, and there is a problem that the effect is not sufficiently exhibited for the added amount.

Therefore, in order to solve such a problem, a method of treating the surface of the thermoplastic resin molded body with a solution in which an ultraviolet absorber is dissolved in an organic solvent has been attempted. In this method, it is important to select a solvent that can sufficiently impregnate the surface layer of the ultraviolet absorber without roughening the surface of the molded article, for example, in the surface treatment of the polycarbonate molded article, As the solvent, a method using a mixed solvent of an aliphatic lower halogenated hydrocarbon and an aliphatic lower alcohol or a halogen-substituted aliphatic lower alcohol (Japanese Patent Publication No. 53-7945) or a mixture of an acrylic ester and a hydroxy ether Method using a solvent (JP-A-55)
No. 145740) has been proposed.

However, in the former method, since a solvent containing halogen is used as the solvent, the surface of the molded article is swollen so that it is necessary to control the contact time in a short time. The impregnation amount is small, and there are drawbacks such as insufficient light resistance and weather resistance. Further, in the latter method, although such a drawback has been improved to some extent, it is not yet fully satisfactory.

[Problems to be solved by the invention]

The present invention overcomes the drawbacks of the conventional surface treatment method for thermoplastic resin moldings and sufficiently impregnates this surface layer with an ultraviolet absorber without mildly acting and roughening the surface of the moldings. It is an object of the present invention to provide a surface treatment method capable of imparting excellent light resistance and weather resistance to the thermoplastic resin molded article.

[Means for Solving the Problems] As a result of intensive studies conducted by the present inventors to achieve the above-mentioned object, an ultraviolet absorber-containing liquid containing a specific mixed solvent was used to form a thermoplastic resin molded article. By treating the surface,
It has been found that this object can be achieved, and the present invention has been completed based on this finding.

That is, the present invention, the surface of the thermoplastic resin molded product, a cyclic ether 10 to 50 wt% and a poor solvent for the thermoplastic resin 90 to 95 wt% treated with a solution containing an ultraviolet absorber as a solvent The present invention provides a method for surface-treating a thermoplastic resin molded body, characterized by:

Hereinafter, the present invention will be described in detail.

The thermoplastic resin molding used in the method of the present invention,
For example, polycarbonate, thermoplastic polyester, styrene resin, polyolefin, polyamide, polyphenylene sulfide, polyphenylene ether, methacrylic acid ester polymer, polyvinyl chloride and the like can be mentioned. Examples of the thermoplastic polyester include polyethylene terephthalate and polybutylene terephthalate, and examples of the styrene resin include polystyrene, rubber-modified polystyrene, and sterene-maleic anhydride copolymer. Further, as the polyolefin, for example, polyethylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-hexene copolymer, ethylene-octene-1 copolymer, polypropylene, propylene-ethylene copolymer,
Examples include propylene-butene-1 copolymer, polybutene-1, poly-4-methylpentene-1 and the like.

These thermoplastic resin moldings may be obtained by any molding method such as injection molding, extrusion molding, hollow molding, compression molding, vacuum molding, transfer molding, and the shape thereof is not particularly limited. Not,
Although any shape can be used, it is particularly preferable to apply the method of the present invention to a polycarbonate molded body.

The ultraviolet absorber used in the method of the present invention can be roughly classified into an ultraviolet absorber in a narrow sense and a light resistance stabilizer. UV rays
It has a wavelength of 10 to 400 mμ and is slightly shorter than visible light, but about 10 to 290 mμ of this ultraviolet light is absorbed in the upper atmosphere, and the problem is in the range of 290 to 400 mμ. And this light energy is extremely large. A UV absorber in a narrow sense absorbs this high-energy UV light, converts it to harmless energy, and re-irradiates it to improve the light resistance and weather resistance of the plastic.

On the other hand, the light resistance stabilizer itself hardly absorbs ultraviolet rays, but improves the light resistance and weather resistance of plastics by efficiently capturing active free radicals generated by ultraviolet rays.

Examples of the ultraviolet absorber in a narrow sense include 2-hydroxy-
4-methoxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-stearyloxybenzophenone, 2-hydroxy-4-dodecyloxy. Benzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-4- (2-hydroxy-methacryloxy) propoxybenzophenone, 2-hydroxy-4-methoxy-4'-methylbenzophenone, 2-hydroxy-4.
-Benzyloxybenzophenone, 2-hydroxy-5
-Monohydroxybenzophenone type such as chlorobenzophenone, 2,4-dihydroxybenzophenone, 2,2'-
Dihydroxybenzophenone, 2,2'-dihydroxy-
4-methoxybenzophenone, 2,2'-dihydroxy-
4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4-n-octoxybenzophenone and other dihydroxybenzophenones, o-benzoylbenzoic acid, 2,
Other benzophenone compounds such as 2 ', 4,4'-tetrahydroxybenzophenone, 2- (2'-hydroxy-5'
-Methylphenyl) benzotriazole, 2- (2'-
Hydroxy-5'-teat-butylphenyl) benzotriazole, 2- (2'-hydroxy-5'-tert-butylphenyl) -5-chlorobenzotriazole, 2-
(2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2-
(2'-Hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-
3 ', 5'-ditert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3', 5'-
Di-pentylphenyl) benzotriazole, 2-
(2'-Hydroxy-4'-octoxyphenyl) benzotriazole, 2- (2'-hydroxy-5'-cyclohexylphenyl) benzotriazole, 2- (2 '
-Hydroxy-3 ', 5'-dimethylphenyl) benzotriazole, 2- (2'-hydroxy-3'-methyl-
Benzotriazoles such as 5'-tert-butylphenyl) benzotriazole, phenyl salicylates, 4
Salicylates such as -tert-butylphenyl salicylate, 4-octylphenyl salicylate, bisphenol A-di-salicylate, resorcinol-monobenzoate, 2,4-di-tert-butylphenyl-3 ', 5'
Benzoate such as di-tert-butyl-4-hydroxybenzoate, ethyl 2-cyano-3,3-diphenylacrylate, cyanoacrylate such as 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, α
-Cyano-β-methyl-β- (p-methoxyphenyl)
Crotonic acid derivatives such as methyl crotonate, N- (2-
Ethylphenyl) -N '-(2-ethoxy-5-tert-
Examples include oxalic acid anilide derivatives such as butylphenyl) oxalic acid diamide and malonic acid esters.

On the other hand, examples of the light resistance stabilizer include [2,2'-thiobis (4-tert-octylphenolato)]-n-butylamine.nickel (II) and [2,2'-thiobis (4-tert-
Octylphenolato)]-triethano-lumian nickel (II), [2,2'-thiobis (4-tert-octylphenolato)]-cyclohexyl-diethanolamine nickel (II), [2,2'-thiobis ( 4-tert-octylphenolato)]-2-ethylhexylamine nickel (II), nickel complex such as nickel salt of bis (3,5-di-tert-butyl-4-hydroxybenzylphosphoric acid) monoethyl ester System, hindered amines such as 4-benzyloxy-2,2,6,6-tetramethylpiperidine, bis (2,2,6,6-tetramethyl-4-piperidine) sebacate, and the like.

These ultraviolet absorbers may be used alone or in combination of two or more, and among these, benzophenone type and salicylate type are particularly preferable.

In the method of the present invention, the solvent used in the liquid containing these ultraviolet absorbers is a mixed liquid of a cyclic ether and a poor solvent for the thermoplastic resin, and examples of the cyclic ether include tetrahydrofuran, 1,4-dioxane, and 2 -Methyltetrahydrofuran, tetrahydropyran, propylene oxide, trioxane and the like can be mentioned, of which tetrahydrofuran and 1,4-dioxane are preferable.

On the other hand, examples of the poor solvent include lower alcohols having 1 to 5 carbon atoms, dihydric alcohols such as ethylene glycol, propylene glycol and butylene glycol, and trihydric alcohols such as glycerin.

The ratio of the cyclic ether to the poor solvent is 1 on a weight basis.
It is selected in the range of 0:90 to 50:50. When the cyclic ether is less than 10% by weight with respect to the mixed solvent with the poor solvent, the ultraviolet absorber does not sufficiently impregnate the surface layer of the molded body, and thus desired light resistance and weather resistance cannot be obtained, while 90% by weight. If it exceeds%, the surface of the molded body is excessively dissolved and becomes rough, which is not preferable. A suitable ratio of the cyclic ether and the poor solvent varies depending on the type of the resin of the thermoplastic resin molding used,
For example, when using a polycarbonate molded body, it is preferable to select it in the range of 20:80 to 30:70 on a weight basis.

The preferred content of the ultraviolet absorbent in the ultraviolet absorbent-containing liquid used in the method of the present invention, depending on the type of the resin of the thermoplastic resin molding used, usually 100 parts by weight of the mixed solvent, It is desirable to contain the ultraviolet absorber in a proportion of 0.1 to 5% by weight, preferably 0.5 to 2% by weight. The ultraviolet absorbent-containing liquid thus prepared may be in the form of a uniform solution in which the ultraviolet absorbent is completely dissolved, or may be a dispersion liquid in which fine particles are uniformly dispersed. In order to effectively impregnate the surface layer with the ultraviolet absorber, the solution form is preferable.

In the method of the present invention, the surface of the thermoplastic resin molded body,
The treatment is carried out with the above-mentioned ultraviolet absorbent-containing liquid, and as the treatment method, a method of immersing the molded body in the ultraviolet absorbent-containing liquid, or a method of pouring the ultraviolet absorbent-containing liquid on the surface of the molded body, spraying And a roller coating method, among which the dipping method is preferable.

When this dipping method is adopted, a suitable dipping time varies depending on the type of resin and the type of solvent of the molded product, for example, when a polycarbonate molded product is used and a mixed solvent of tetrahydrofuran and ethylene glycol is used as a solvent. Is at room temperature for 10 seconds to 10 minutes, preferably about 0.5 to 3 minutes.

In this way, after subjecting to a dipping treatment and the like, a drying treatment is carried out.This drying treatment may be carried out by any of a vacuum drying method and a heat drying method, but in the case of a polycarbonate molded body, It is preferable to dry at a temperature of 90 to 100 ° C for 5 to 10 minutes.

By performing such a surface treatment, the surface layer of the molded article is sufficiently impregnated with the ultraviolet absorber without roughening the surface of the thermoplastic resin article, and the molded article is provided with light resistance and weather resistance. It

〔Example〕

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A square plate (thickness: 3 mm, length: 2 mm, width: 60 mm) of a polycarbonate resin [Taflon A3000, manufactured by Idemitsu Petrochemical Co., Ltd.] was mixed with a mixed solvent of tetrahydrofuran and ethylene glycol (25 parts by weight of tetrahydrofuran, ethylene glycol: 75). (Parts by weight), as a UV absorber, 2-hydroxy-4
After soaking in a liquid containing an ultraviolet absorber containing 1.0 part by weight of -n-octoxybenzophenone for 1 minute 30 seconds, 90
It was dried by heating in an oven at ℃ for 5 minutes.

Measure the absorbance to check the impregnated amount of UV absorber,
In addition, YI was measured to determine weather resistance (referred to as YIa). Next, with a sunshine weather meter,
YI was measured after 420 hours of exposure (YIb). The weather resistance was evaluated using the difference in YI before and after exposure as ΔYI (YIa-YIb). The results are shown in the attached table.

Examples 2-8, Comparative Examples 1-6 In Example 1, it carried out like Example 1 except having changed the solvent system, the kind and concentration of the ultraviolet absorber, and the immersion time, and evaluated the weather resistance. . The results are shown in the attached table. In Comparative Example 1, the surface was whitened and the weather resistance could not be measured.

[Effect of the invention] The surface treatment method of the thermoplastic resin molded body of the present invention is a method of treating the surface of the molded body with an ultraviolet absorbent-containing liquid using a specific mixed solvent, and roughening the surface. Since it is possible to sufficiently impregnate the surface layer with the ultraviolet absorber without using the ultraviolet absorber, compared with the conventional method of adding the ultraviolet absorber during the polymerization step or kneading of the thermoplastic resin, the amount of the ultraviolet absorber is smaller, It is possible to effectively impart light resistance and weather resistance to the body.

Claims (3)

[Claims] 1. A surface of a thermoplastic resin molding is provided with 10 to 50% by weight of a cyclic ether and a poor solvent of 90 to 95 for the thermoplastic resin.
A method for treating a surface of a thermoplastic resin molded article, which comprises treating with a liquid containing an ultraviolet absorber using a mixed solution with a weight% as a solvent. 2. The surface treatment method according to claim 1, wherein the thermoplastic resin is polycarbonate. 3. The surface treatment method according to claim 1, wherein the ultraviolet absorber-containing liquid contains 0.1 to 5 parts by weight of the ultraviolet absorber with respect to 100 parts by weight of the solvent.