JPS633666B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for surface treatment of synthetic resin molded articles. More specifically, by applying a primer paint to the surface of a polycarbonate resin molded product before applying a top coat of surface-curing silicone resin, the paint film has excellent adhesion, is colorless and transparent, and has excellent scratch resistance, hot water resistance, weather resistance, and The present invention relates to a surface treatment method that can improve solvent resistance. In general, plastics are used for a variety of purposes because they have excellent properties such as easy moldability, light weight, impact resistance, and ease of processing.However, compared to other materials, plastics have a lower surface hardness, are easily scratched, and are resistant to solvents. The biggest drawback is that the product value tends to drop. In order to solve these drawbacks, the present inventors previously proposed applying a partially hydrolyzed condensate of alkyltrialkoxysilane to the surface of a plastic molded article and curing it (Japanese Patent Publication No. 37828/1983). However, if the plastic is polycarbonate resin, sufficient adhesion of the coating film cannot be obtained.
Therefore, it has been proposed to use a primer to further improve the adhesion of the coating film. The present inventors previously proposed the use of, for example, a partially hydrolyzed condensate of phenyltrialkoxysilane and alkyltrialkoxysilane (Japanese Patent Application No. 124897/1989) as a primer, but these primers The drawback is that the curing speed is extremely slow. Therefore, the present inventors researched an even better primer in order to improve these drawbacks, and as a result, we found that the coating film has a fast curing speed, excellent coating adhesion, is colorless and transparent, and has scratch resistance, hot water resistance, and weather resistance. We have discovered a method for surface treatment of polycarbonate resin with excellent properties and solvent resistance. That is, the present invention provides a surface treatment method in which a primer is applied to the surface of a polycarbonate resin molded article, heat treated, and then a paint mainly composed of a partially hydrolyzed condensate of alkyltrialkoxysilane is applied and cured. As (A) (a) General formula C ₆ H ₅ Si (OR ¹ ) ₃ (However, R ¹ has a carbon number of 1
1 mol of phenyl alkoxysilane represented by the general formula R ² Si(OR ³ ) ₃ (wherein R ² and R ³ are alkyl groups having 1 to 4 carbon atoms) Partially hydrolyzed condensate of silicon compound consisting of 0 to 10 moles of alkoxysilane
100 parts by weight (B) General formula R ⁴ COOH (R ⁴ is H or carbon number 1
Solvent (C) containing at _least ^the same mole of carboxylic acid represented by ^the following alkyl group (alkyl group ^of R ⁶ is an alkyl group having 1 to 4 carbon atoms) Aminoalkyltrialkoxysilane 50
The present invention relates to a method for surface treatment of polycarbonate resin molded articles, characterized in that a mixture comprising 100 parts by weight is used. Examples of the polycarbonate resin molded product serving as the base material in the present invention include polycarbonate resin molded products made from aromatic polycarbonates such as those obtained from bisphenol A and phosgene, aliphatic polycarbonates such as diethylene glycol bisallyl carbonate, and the like. . The primer component phenyltrialkoxysilane (A) (a) used in the present invention has the general formula C ₆ H ₅ Si
(OR ¹ ) ₃ , where R ¹ is methyl, ethyl,
Examples include _C1 - _C4 alkyl groups such as propyl and butyl. A typical phenyltrialkoxysilane is phenyltriethoxysilane. The alkyltrialkoxysilane (A) (b) that can be co-condensed with phenyltrialkoxysilane (A) (a) is represented by the general formula R ² Si (OR ³ ) ₃ , where R ² and R ³ are methyl, Methyltriethoxysilane is exemplified as a typical alkyltrialkoxysilane having a _C1 to _C4 alkyl group such as ethyl, propyl, butyl. The aminoalkyltrialkoxysilane (C) as a co-condensing agent is represented by the general formula R ⁵ Si (OR ⁶ ) ₃ ,
^R5 is an aminoalkyl group, exemplified by -( _CH2 ) _a - _NH2 or -( _CH2 ) _b -NH-( _CH2 ) _c - _NH2 ,
Preferably, a, b, and c in the formula are 2 or 3, and R ⁶ is a C ₁ to _{C 4} alkyl group such as methyl, ethyl, propyl, butyl, and a typical aminoalkyltrialkoxysilane is γ. -aminopropyltriethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and the like. The ratio of phenyltrialkoxysilane to alkyltrialkoxysilane in the partially hydrolyzed condensate of silicon compound as component (A) as a primer is 0 to 10 mol of alkyltrialkoxysilane to 1 mol of phenyltrialkoxysilane. , preferably 0 to 1 mol. The initial adhesion of the coating film to polycarbonate resin is excellent when the alkyltrialkoxysilane is in the range of 0 to 10 moles, but the adhesion when immersed in hot water is poor when the alkyltrialkoxysilane is 0 to 1 mole, that is, an excess of phenyltrialkoxysilane. is better. As described in Japanese Patent Publication No. 15079/1983, the partial hydrolysis condensate of the silicon compound (A) above is
Initial hydration obtained by adding water and a small amount of acid to phenyltrialkoxysilane alone or a mixture of phenyltrialkoxysilane and alkyltrialkoxysilane, and heating the mixture under reflux at a temperature of 50 to 80°C for about 1 to 10 hours. It is a decomposition condensation product. When used as a primer, after concentrating the initial hydrolysis condensate, alcohol such as methanol, ethanol, propanol, butanol, formic acid, acetic acid,
Carboxylic acids such as propionic acid, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate, ethyl lactate and butyl acetate, ether solvents such as methyl cellosolve and ethyl cellosolve, and one or more other solvents. The solution is diluted using the above method, and a surfactant, an ultraviolet absorber, a dye, etc. are added as necessary. (Hereinafter, this will be referred to as liquid (A)). Component (B) as a primer, that is, a solvent containing carboxylic acid, contains at least an equimolar amount of formic acid, acetic acid,
Carboxylic acids such as propionic acid, butyric acid, and valeric acid are diluted with alcohol, ketone, ester, and ether solvents. To use as a primer, mix this component with the above solution (A). (hereinafter referred to as (B)
liquid). The final primer is prepared by mixing component (C), ie, aminoalkyltrialkoxysilane, with the solution (B). Here, as the aminoalkyltrialkoxysilane, γ-aminopropyltriethoxysilane or N-β-aminoethyl-γ
The use of -aminopropyltrimethoxysilane is preferred. At this time, if you mix component (C) directly into solution (A), the solution will immediately gel and solidify, so be sure to mix component (B) with solution (A) before mixing component (C). This must be done after it has been made into a liquid. The solid content in the primer solution is about 1 to 40% by weight, preferably about 2 to 30% by weight, and is adjusted by the amount of the solvent (B) added. Primer application methods include dipping, spraying, flow coating, and
The primer is applied by spin coating or the like, and then dried and cured by heat treatment. The heat treatment conditions should be below the heat distortion temperature of polycarbonate resin, usually 60℃ to 130℃.
Heat curing is performed at ℃ for 5 minutes to 12 hours. Preferably, heat curing is performed at 80 to 90°C for 10 minutes to 2 hours. As for the degree of curing, good adhesion can be obtained if the primer layer is cured to such an extent that the primer layer does not peel off when the top coat is applied. If the primer layer is cured too much, the adhesion between the top coat and the primer layer will decrease, so it is necessary to select an appropriate range for the curing of the primer. The coating thickness of the primer can be freely selected depending on the purpose, but it is preferably about 0.1 to 10 μm. Next, as the top coating according to the present invention, a coating mainly composed of a partially hydrolyzed condensate of alkyltrialkoxysilane is used. Here, as the alkyltrialkoxysilane, those represented by the general formula R ⁷ Si(OR ⁸ ) ₃ are preferably used, and R ⁷ and R ⁸ in the formula are C ₁ such as methyl, ethyl, propyl, butyl, etc.
~ _C4 alkyl groups are preferred, with methyltriethoxysilane being a typical example. As described in US Pat. No. 3,389,114, it is a partially hydrolyzed condensate obtained by adding water and a small amount of acid and heating the mixture at a temperature of 50 to 80°C for 1 to 10 hours. For the purpose of improving the hardness of the coating film, tetraalkoxysilane may be mixed with alkyltrialkoxysilane and co-hydrolyzed. Further, a hydrolyzate of tetraalkoxysilane can be mixed with a hydrolyzate of alkyltrialkoxysilane for use. The concentrated alkyltrialkoxysilane partial hydrolysis condensate can be mixed with alcohols such as methanol, ethanol, propanol, and butanol, carboxylic acids such as formic acid, acetic acid, and propionic acid, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ethyl acetate, and ethyl lactate. , ester solvents such as butyl acetate, ether solvents such as methyl cellosolve, ethyl cellosolve, and other solvents.
A top coat is prepared by diluting the solution to a specific level or more, and then adding a curing catalyst, a surfactant, and if necessary, an ultraviolet absorber, a dye, and other additives. Curing catalysts added for the purpose of accelerating the curing of the coating film include quaternary ammonium hydroxide such as tetraethylammonium hydroxide and trimethylbenzyl hydroxide;
Alkali metal salts of inorganic acids such as sodium phosphate and sodium borate; alkali metal salts of organic carboxylic acids such as sodium acetate, sodium oleate and sodium naphthenate; tetrasodium salt of ethylenediaminetetraacetate acid (EDTA); Triethylamine, 1,8-diazabicyclo (5,4,
0) Examples include organic amines such as undecene 7, cyclic amidines, or salts thereof. The solid content in the top coat is about 1 to 40% by weight, preferably about 10 to 30% by weight. The present invention is achieved by applying this top coat paint to a polycarbonate resin molded product etc. that has been coated and cured with the primer by a method such as a dipping method, a spray method, a flow coating method, or a spin coating method, and then drying and curing by heating. . The film thickness of the top coat varies depending on the application of the coated material, but is usually 1 to 20 microns. The usual heat curing conditions are 50 to 140°C for 15 minutes to 12 hours, preferably 80 to 130°C for 2 to 5 hours. Polycarbonate resin molded products obtained by the present invention have excellent coating film adhesion, scratch resistance, hot water resistance, weather resistance, and solvent resistance, so they can be used in automobiles, trains, etc.
Aircraft window glass, building window glass, ski goggles, sunglass lenses, protective eyewear lenses,
Useful for preventing scratches on prescription eyeglass lenses and optical equipment lenses. The present invention will be explained below with reference to Examples. Example 1 720 g (3 moles) of phenyltriethoxysilane and 160 g (9 moles) of water were placed in a reactor equipped with a reflux condenser.
1 c.c. of 0.1N hydrochloric acid was added, mixed well, and heated under reflux for 4 hours until the liquid, which was initially a non-uniform layer, became a uniform layer. Next, ethanol was removed by distillation and the mixture was concentrated to obtain a solid product of a partially hydrolyzed condensate of phenyltriethoxysilane. Partially hydrolyzed condensate of phenyltriethoxysilane (solid) 20 parts (hereinafter referred to as parts by weight)
was dissolved in 58 parts of n-butanol, and further 10 parts of acetic acid was added. This was cooled to below 20° C., and while stirring, 10 parts of γ-aminopropyltriethoxysilane was gradually added thereto, and further 2 parts of ice were added and mixed well to prepare a primer solution. The viscosity of the primer solution was measured with a Bruckfield viscometer and was 10 centipoise at 20°C. Next, a top coat was prepared as follows. 356 g (2 moles) of methyltriethoxysilane, 108 g (6 moles) of water, and 1 c.c. of 0.1N hydrochloric acid were thoroughly mixed and heated under reflux for 4 hours. Next, ethanol was removed by distillation to obtain a partially hydrolyzed condensate of methyltriethoxysilane. 30 parts of partially hydrolyzed condensate of methyltriethoxysilane, 50 parts of industrial ethanol, 20 parts of acetic acid, 10% of tetraethylammonium hydroxide
A top coat was prepared by thoroughly mixing 3 parts of an aqueous solution and 0.5 part of a surfactant. A 100 x 100 x 2 mm polycarbonate resin sheet was washed and dried, immersed in the primer solution, and pulled up at a pulling speed of 20 cm/min without vibration. It was immediately placed in a hot air dryer and heated at 90°C for 2 hours. The primer-coated sheet was then dipped into the top coat and pulled up at a pulling speed of 20 cm/min without vibration. Immediately put it in a hot air dryer.
It was heated at 90° C. for 5 hours to obtain a polycarbonate sheet having a surface hardened film. This coating sheet was evaluated by the following method. The results are shown in Table 1. (1) Measurement of scratch resistance Scratches were made on the surface of the coating sheet using a Taber Mamo tester (manufactured by Yasuda Seiki) under the conditions of a wear wheel CS-10F with a load of 500 g and 100 cycles. Next, the total light transmittance and scattered light were measured using a haze meter (manufactured by Suga Test Instruments KK), and the scratch resistance was expressed as haze (%) = scattered light/total light transmittance x 100. (2) Initial adhesion Cross-cut sheet tester (manufactured by Toyo Seiki)
Place it on the surface and fix it, apply a load of 200g with a single-edged razor, and make 11 vertical and horizontal cuts at 1mm intervals to create a crosshatch. A cellophane adhesive tape was pasted on the crosshatch, and the tape was strongly pulled in a direction perpendicular to the sheet to observe the peeling state of the paint film. It is expressed as the number of squares remaining (numerator) out of 100 crosshatch squares (denominator). (3) Hot water resistance After immersing the previous coating sheet in hot water at 100°C or 60°C, the same thing as the initial adhesion test was performed, and the adhesion was expressed as the time at which the adhesion started to decrease. (4) Weather resistance test A weather resistance test was conducted using a sunshine in-type weather meter, the same as the initial adhesion test, and the weather meter irradiation time at which adhesion began to deteriorate was expressed. (5) Solvent resistance Acetone is placed on the sheet to the extent that it does not flow, and the time required for the paint film to blister or peel is indicated. If the acetone evaporates and becomes low, add more acetone. Example 2 In Example 1, phenyltriethoxysilane
The same procedure as in Example 1 was carried out except that 960 g (4 moles) of phenyltriethoxysilane and 178 g (1 mole) of methyltriethoxysilane were used instead of 720 g (3 moles). The results are shown in Table 1. Example 3 In Example 1, phenyltriethoxysilane
The same procedure as in Example 1 was carried out except that 240 g (1 mol) of phenyltriethoxysilane and 356 g (2 mol) of methyltriethoxysilane were used instead of 720 g (3 mol). The results are shown in Table 1. Example 4 Phenyltriethoxysilane (4 mol) and methyltriethoxysilane (1 mol) used in Example 2
Dissolve 5 parts (hereinafter referred to as parts by weight) of a partially hydrolyzed condensate (solid) consisting of in 80 parts of n-butanol, further add 10 parts of acetic acid, and further add 5 parts of γ-aminopropyltriethoxysilane and mix well. A primer solution was prepared. This was applied in the same manner as in Example 1, and immediately placed in a hot air dryer and heated at 80°C for 10 minutes. Next, the primer-coated sheet was prepared in Example 1.
A top coat was applied in the same manner as above and cured by heating. The results are shown in Table 1. Example 5 N-β-(aminoethyl)-γ was used instead of γ-aminopropyltriethoxysilane used in Example 4.
The same procedure as in Example 4 was carried out except that -aminopropyltrimethoxysilane was used. The results are shown in Table 1. Example 6 The same procedure as in Example 4 was carried out except that a polydiethylene glycol bisallyl carbonate plate was used in place of the polycarbonate sheet used in Example 4. The results are shown in Table 1. Comparative Example 1 Various tests were conducted on the original polycarbonate as it was. The results are shown in Table 1. Comparative Example 2 The same top coat as in Example was applied to a polycarbonate sheet without using a primer, and then heated and cured in the same manner. The results are shown in Table 1. Comparative Example 3 The same procedure as in Example 1 was carried out except that γ-aminopropyltriethoxysilane was applied instead of the primer paint of Example 1. The results are shown in Table 1.

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Claims (1)

[Scope of Claims] 1. Surface treatment of a polycarbonate resin molded product, in which a primer is applied to the surface of the polycarbonate resin molded product, heated, and then a paint mainly composed of a partial hydrolyzate of alkyltrialkoxysilane is applied and cured. In the method, the primer (A) (a) has the general formula C ₆ H ₅ Si(OR ¹ ) ₃ (wherein R ¹ has a carbon number of 1).
1 mol of phenyltrialkoxysilane represented by the general formula R ² Si (OR ³ ) ₃ (wherein R ² and R ³ are alkyl groups having 1 to 4 carbon atoms) Partially hydrolyzed condensate of silicon compound consisting of 0 to 10 moles of trialkoxysilane
100 parts by weight (B) General formula R ⁴ COOH (R ⁴ is H or carbon number 1
Solvent (C) containing at _least ^the same mole of carboxylic acid represented by ^the following alkyl group (alkyl group ^of R ⁶ is an alkyl group having 1 to 4 carbon atoms) Aminoalkyltrialkoxysilane 50
A method for surface treatment of polycarbonate resin molded articles, characterized by using a mixture comprising ~100 parts by weight.