JPS6050391B2 - Method for preparing coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preparing a coating composition that provides a cured film having excellent scratch resistance and coating adhesion.

The surface of plastic molded products is easily scratched, and transparent plastic molded products, such as sunglass lenses, prescription glasses lenses, meter covers, goggles, etc., have the disadvantage that scratches can cause them to become cloudy.

In order to eliminate these drawbacks, various methods have been proposed for forming a silicone resin coating film on the surface of the molded product.
Coating compositions are disclosed in Japanese Patent Laid-Open No. 53-10299-Gin, etc. In addition, hydrolyzed condensates of alkyltrialkoxysilanes are used as coating silicone resins for plastic molded products; for example, in U.S. Pat. It shows how things are made. Useful coating compositions are obtained by dissolving this solid alkyltrialkoxysilane hydrolytic condensate in an organic solvent. Particularly when using a hydrolyzed condensate of solid alkyltrialkoxysilane,
The presence of water in the coating liquid is necessary and must be added deliberately. Furthermore, the procedure for preparing the coating solution is important; if water is added at the end after preparing the coating solution, a long heat-aging time is required, and if the coating is applied immediately after preparation, the desired physical properties of the coating film may not be obtained. I can't do it. As mentioned above, even if the coating composition is the same, depending on the preparation method, the desired physical properties of the coating film may not be maximized. The present inventors have studied this point and found that the coating composition can stably exhibit the best physical properties of the coating film in a short period of time, such as scratch resistance, solvent resistance, and coating film properties. The present invention was achieved by discovering a method for preparing a coating composition with excellent adhesion. 7 That is, the present invention provides solid and solvent-soluble compounds of the general formula RSi(OR').

(R, R″ are C1-C4 aliphatic hydrocarbon groups) Hydrolyzed condensate of alkyltrialkoxysilane 20
~35 parts by weight (B) 0.05 to 3 parts by weight of curing catalyst (C) 5 to 35 parts by weight of acetic acid (D) 2 to 11 parts by weight of water (E) For preparing a coating composition containing alcohol as an essential component This method of preparing a coating composition is characterized in that the hydrolyzed condensate is first dissolved in alcohol containing 7 to 35% by weight of water.

R of the alkyltrialkoxysilane represented by the general formula RSi(0R'')3 is a C1 to C4 aliphatic hydrocarbon group,
Examples include methyl, ethyl, propyl, butyl, vinyl, allyl, etc., or R'' is a C1 to C4 aliphatic hydrocarbon group, and examples include methyl, ethyl, propyl, butyl, etc.
Typical alkyltrialkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, and the like.

The hydrolyzed condensate of a solid, solvent-soluble alkyltrialkoxysilane used in the present invention is prepared by adding water and a small amount of acid to an alkyltrialkoxysilane, as shown in U.S. Pat. No. 3,389,114. 50-80
The hydrolyzed condensate obtained by heating for 1 to 1 hour at a temperature of °C is distilled to force out the by-product alcohol and excess water, and then heated using an efficient instantaneous evaporator such as a thin film evaporator. The remaining alcohol and water are expelled in an evaporator, resulting in a solid and solvent-soluble alkyltrialcohol containing virtually no solvent or water! A hydrolyzed condensate of disilane is obtained.

The finally obtained solid and alcohol-soluble hydrolyzed condensate of alkyltrialkoxysilane is dissolved in deuterated chloroform, and the R. The ratio (molar ratio) of 15OH is R:0H=1:0.05 to 3, and 50%3
(% by weight) An ethanol solution having a solution viscosity of 10 to 60 centipoise (Bruckfield viscosity 200C), preferably 20 to 40 centipoise, is suitable for the present invention. A coating composition is prepared by dissolving a solid hydrolyzed tetrahydrolyzed condensate of alkyltrialkoxysilane in alcohol containing water, adding a curing catalyst and acetic acid, and mixing well.

At this time, if necessary, use low boiling point, medium boiling point, high boiling point solvents, anionic or nonionic surfactants, fluorine-containing or silicone-containing surfactants, ultraviolet absorbers, colorants, etc. It can also be added. The viscosity of the final coating composition is preferably 5 to 20 centipoise (Burckfield viscometer, 20°C), preferably 10 to 15 centipoise.
Adjust to centipoise. The amount of the alkyltrialkoxysilane hydrolyzed condensate in 10 parts by weight of the coating composition is 20 to 35 parts by weight. The alcohol for dissolving the hydrolysis condensate of solid alkyltrialkoxysilane is a C1 to C4 alcohol, preferably ethyl alcohol. The coating composition of the present invention is characterized by containing acetic acid, and the amount of acetic acid added is 5 to 35 parts by weight.

Acetic acid is an essential component when applying and curing the present coating composition onto a plastic molded product, and serves to improve the adhesion between the cured coating and the substrate, as well as prolonging the pot life of the coating solution. Examples of curing catalysts used include organic carboxylic acids, alkali metal salts of naphthenic acid, trialkylamines such as trimethylamine and triethylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, trimethylbenzylammonium hydroxide, and triethylbenzyl. Ammonium hydroxide such as ammonium hydroxide, linear amidine such as guwanidine, rings such as 1,8-diazabicyclo(5,4,0)undecene-7,1,5-diazabicyclo(4,3,0)nonene-5, etc. Examples include the formula amidine.

Strongly basic amines whose aqueous solution has a pH of 11 or higher are preferred. It can also be used as a weak acid salt of these strongly basic amines. Examples of weak acids include carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, and chloroacetic acid, polybasic acids such as fumaric acid, maleic acid, and tartaric acid, benzoic acid, and butanolic acid. Examples include aromatic carboxylic acids such as phenol, thioacetic acid, and the like. The amount of curing catalyst is 0.05 to 3 parts by weight per 20 to 35 parts by weight of the hydrolyzed condensate of alkyltrialkoxysilane.
Parts by weight.

If the amount of curing catalyst is too small, there will be no catalytic effect, and if it is too large, the catalyst will bleed onto the surface, which will actually worsen the adhesion of the coating film. In preparing a coating composition by dissolving a solid alkyltrialkoxysilane hydrolysis condensate, the solid alkyltrialkoxysilane hydrolysis condensate is dissolved in alcohol containing 7 to 35% by weight of water. According to the method of the present invention, in which a curing catalyst, acetic acid, and other additives are added to this solution, the best physical properties of the coating film can be obtained even if the coating composition is coated immediately after preparation, and the prepared coating composition is stable. There is.
1. A method for dissolving a solid hydrolyzed condensate of alkyltrialkoxysilane other than the method of the present invention includes, for example, dissolving a solid hydrolyzed condensate of alkyltrialkoxysilane in anhydrous alcohol, and then adding water, a curing catalyst, and acetic acid. Examples include a method in which a hydrolyzed condensate of a solid alkyltrialkoxysilane is dissolved in an organic solvent containing a curing catalyst and acetic acid, and then water is added. The composition requires time to ripen, the stability of the coating composition is poor, and the physical properties of the coating film vary even after aging, which is undesirable. The amount of water in the coating composition is preferably 2 to 11 parts by weight, and this amount can be adjusted by adjusting the water content of the hydrous alcohol that dissolves the hydrolysis condensate of solid alkyltrialkoxysilane.

That is, the water content in the alcohol for dissolving the alkyltrialkoxysilane hydrolysis condensate is 7 to 35% by weight.
The presence of water in the coating composition is important; if it is less than 2 parts by weight, the curing catalyst after coating and curing will have insufficient scratch resistance, poor solvent resistance, and poor adhesion of the coating film. On the other hand, if there is too much water, the coating film tends to whiten when coated. Further, there arises a problem that the hydrolyzed condensate of solid alkyltrialkoxysilane cannot be dissolved in alcohol.
The water in the hydrous alcohol must have a specific resistance of about 1 Cf'ΩG or more obtained by distillation or ion exchange. The prepared coating composition is applied to a surface-washed plastic molded article and cured by heating to form a cured film.

As the base resin, resins with poor surface scratch resistance are useful, and methyl methacrylate resins with excellent transparency, weather resistance, and optical properties are particularly useful. Other polycarbonate,
Polystyrene, acrylonitrile styrene copolymer resin,
Methyl methacrylate styrene copolymer resin, polydiethylene glycol bisallyl carbonate, transparent ABS resin, rubber reinforced methacrylic resin, cellulose acetate,
It can be applied to transparent plastics such as cellulose propionate, cellulose acetate butyrate, and polyvinyl chloride, as well as opaque plastics such as ABS resin and high impact polystyrene. Coating methods include dipping, spraying, flow coating, and spin coating.

The applied plastic is heated and cured. The higher the heating temperature, the faster the curing speed, but it is limited by the heat deformation temperature of the molded product. The curing temperature varies depending on the base resin, but is usually 50 to 140°C, preferably 60 to 140°C.
Perform at 120°C. The coating composition obtained by the present invention can be used for optical lenses such as transparent plastic sunglass lenses, prescription eyeglass lenses, and camera finder lenses, covers for various instruments, window glasses for automobiles, trains, and aircraft, and plastic mirrors. Useful for products such as

The present invention will be explained below with reference to Examples.

In addition, parts in the examples are based on weight unless otherwise specified. Example 1 Preparation of solid alkyltrialkoxysilane hydrolysis condensate) Methyltriethoxysilane 534y (3 mol) and water 1629 (9 mol) were placed in a reactor equipped with a reflux condenser.
Add 0.5 cc of 0.1N hydrochloric acid, mix well, and heat to 80°C.
After heating under reflux for 4 hours, the initially heterogeneous layer became a clear homogeneous layer.

Next, 5-ethanol (containing a portion of water) was removed by distillation, and the solution was concentrated to obtain a solution with a solid content of 50%, which was further aged for two phases under reflux. The solvent was evaporated in a thin film evaporator for a short time of less than 1 minute to obtain a hydrolyzed condensate of solvent-soluble methyltriethoxydisilane in the form of solid flakes. CH
The ratio of 3 to 0H was 1:0.2. Preparation reagent for coating composition: 1st grade ethanol (contains 0.2% moisture) 27
and 3 parts of deionized water to prepare 10% aqueous ethanol.

Three solid flakes of methyltriethoxysilane hydrolyzed condensate were added to this and were completely dissolved in about 1 hour with vigorous stirring to prepare a 50% solution. The solution viscosity was measured with a Breckfield viscometer and was 35 centipoise at 20°C. Separately, reagents: 23 parts of primary ethanol, 0.45 parts of a curing catalyst consisting of a phenol salt of 1,8-diazabicyclo(5.4.0) undecene-7, 0.1 part of an anionic surfactant having a fluorine carbide chain, and reagents. 17 parts of primary glacial acetic acid were added in this order and mixed well to prepare a catalyst solution. The above 50% solution and catalyst solution were mixed to prepare a coating composition containing 30% methyltriethoxysilane hydrolyzed condensate flakes and 3% water. The solution viscosity was measured with a Bruckfield viscometer and was 12 centipoise at 20°C. Coating The surface of a 2 mm thick sheet made of methyl methacrylic resin was thoroughly washed, immersed in the coating composition, and gently pulled up at a pulling speed of 13 cm/min.

It was directly placed in a hot air dryer and cured at 90°C for 5 hours. A meniscus type lens-shaped molded product made of methacrylic resin was coated under the same conditions. The resulting coating composition was colorless and transparent. The coating film was 6μ. Evaluation of coated products To evaluate the scratch resistance of coated plastic molded product surfaces, ASTM D-1044, also DlO
Measured according to O3.

Weared wheel CS-10F' load 5 by taper abrasion tester
00y1 wear count! The surface of the sheet was scratched under conditions of 100 cycles, and the haze (%) was measured using a haze meter. To measure the adhesion of the coating film to the base resin, ASTM D-3359, cross-cut method (B method) was used, and the evaluation was 0 (no peeling) to 5 (severe peeling) 3 out of 6.
I went to the stage display. To measure solvent resistance, acetone was poured into the concave surface of the coated lens, the whole was placed in a shear tray, and the time until the paint film peeled off was measured. The results are shown in Table 1.

4 Examples 2 to 3 Instead of the 10% aqueous ethanol used to dissolve the solid alkyltrialkoxysilane hydrolysis condensate in Example 1, 20% (Example 2) and 27% (Example 3) were used. A coating composition was prepared in the same manner as in Example 1, except that one part of aqueous ethanol was used.

At this time, the water content in the coating composition was 6% (Example 2) and 8% (Example 3), respectively. The methacrylic resin was coated in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 1 In Example 1, 3 parts of the reagent 1st grade ethanol were added to the ethanol for dissolving the hydrolyzed condensate of solid alkyltrialkoxysilane, 3 parts of the reagent 1st grade ethanol (A) and deionized water were added to the ethanol for dissolving the curing catalyst. A coating composition was prepared as in Example 1 except that 3 parts of 13% aqueous ethanol were used.

At this time, the amount of water in the coating composition was 3%. Next, a methacrylic resin molded article was coated one day after preparing the coating composition, and the results are shown in Table 1.
Comparative Example 2 Except for Example 1, in which 1st class ethanol 3 reagents were used as the ethanol for dissolving the hydrolyzed condensate of solid alkyltrialkoxysilane, and 1st class ethanol 2 reagents were used as the ethanol for dissolving the curing catalyst. The same thing as in Example 1 was done.

3 parts of deionized water was added to the final coating solution to prepare the coating solution, and one day after the coating solution was prepared, it was coated on a methacrylic resin molded article. The results are shown in Table 1.

Example 4 A lens-shaped molded product obtained by injection molding with polycarbonate resin was degreased and washed, then coated with α-aminopropyltriethoxysilane as an undercoating agent by a dipping method, and cured at 130°C in a two-powder open environment. did.

Next, 13α/
The sample was gently pulled up at a pulling speed of 10 minutes, and after removing the solvent in an open environment at 70°C for 10 minutes, the temperature was raised to 130°C and cured for 4 hours.

The results are shown in Table 1.

Comparative Example 3 In Example 1, deionized water was not added, and the reagent primary ethanol (9) parts was used instead of 10% aqueous ethanol (9) parts as ethanol for dissolving the hydrolysis condensate of solid alkyltrialkoxysilane. Example 1 except that part) was used.
I did the same thing.

The results are shown in Table 1.

Comparative Example 4 A scratch resistance test was conducted on a powder coated sheet made of methacrylic resin using a taper abrasion tester, and the results are shown in Table 1.

, 3 Comparative Example 5 A scratch resistance test was conducted on the polycarbonate resin powder coated sheet using a taper abrasion tester, and the results are shown in Table 1.

Compared to the case where water was not added to the methyl methacrylic resin and polycarbonate resin of Comparative Examples 4 and 5, and the coating liquid of Comparative Example 3, in Examples 1 to 4 in which water was added, the haze after taper abrasion, ? Excellent film adhesion and acetone resistance.

Claims (1)

[Scope of Claims] 1(A) solid and solvent soluble having the general formula RSi(OR'
)_3 (R, R' are aliphatic hydrocarbon groups of C_1 to C_4) 20 to 35 parts by weight of hydrolyzed condensate of alkyltrialkoxysilane (B) 0.05 to 3 parts by weight of curing catalyst (C) In preparing a coating composition containing 5 to 35 parts by weight of acetic acid (D), 2 to 11 parts by weight of water (E) and alcohol, the hydrolyzed condensate is first dissolved in alcohol containing 7 to 35% by weight of water. A method for preparing a coating composition, characterized in that: