JPS6030712B2 - coating composition - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating composition that provides a cured film with excellent scratch resistance and good adhesion. Plastics have features such as impact resistance, easy moldability, and light weight, and are used for various purposes, but they have the disadvantage that the surface of plastic molded products is easily scratched. In order to improve the scratch resistance of plastic surfaces, a cured film of organopolysiloxane resin is formed on the surface of plastic molded products. It is known to use hydrolyzed condensates of alkyltrialkoxysilanes as curable organopolysiloxanes. Add water to the alkyltrialkoxysilane and add a certain amount of acid.
Hydrolysis is performed to obtain a solution of a hydrolyzed condensate of alkyltrialkoxysilane. It is common practice to add a curing catalyst, a surfactant, and other necessary additives to this solution to prepare a coating liquid. As another method,
The solution of the hydrolyzed condensate of alkyltrialkoxysilane obtained by hydrolytic condensation is concentrated to remove the created alcohol, excess water and acid, and then the remaining volatile components are removed using an evaporator to form a solvent-soluble solid. A coating solution can also be prepared by obtaining a hydrolyzed condensate of alkyltrialkoxysilane and redissolving it in a solvent.
Solid hydrolyzed condensates of alkyltrialkoxysilanes have better storage stability than the solution type. It has characteristics such as easy transportation. On the other hand, they have low curing reactivity, and even if they are simply dissolved in a solvent and a suitable curing catalyst is used, the resulting cured film has poor scratch resistance and poor adhesion compared to solution-type alkyltrialkoxysilanes. As a result of intensive research by the present inventors to eliminate these drawbacks, the present inventors have developed a coating composition that maintains the advantages of hydrolyzed condensates of solid alkyltrialkoxysilanes and has excellent scratch resistance and paint film adhesion. This discovery led to the present invention. That is, the present invention is a solid and alcohol-soluble hydrolyzed condensate of alkyltrialkoxysilane represented by the general formula RSi(OR')3 (R, R' are C, to C4 aliphatic hydrocarbon groups). and the ratio (molar ratio) of R and OH of the terminal group is 1:0.05 to 3.
parts by weight,

[B} A mixture consisting of 0.05 to 3 parts by weight of a strongly basic organic amine and/or its weak acid salt, 2 to 14 parts by weight of water, dish acetic acid, and an organic solvent whose main components are alcohol. is 6 to 20 centipoise (2 pi○)
It is a coating composition. R of the alkyltrialkoxysilane represented by the general formula RSi(OR')3 is a C, to C4 aliphatic hydrocarbon group,
Examples include methyl, ethyl, propyl, butyl, vinyl, allyl, etc., and R' is a C, to C4 aliphatic hydrocarbon group,
Examples include methyl, ethyl, propyl, butyl, etc., and typical alkyltrialkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, etc. The hydrolyzed condensate of a solid, alcohol-soluble alkyltrialkoxysilane used in the present invention is prepared by adding water and a certain amount of acid to an alkyltrialkoxysilane, as shown in US Pat. No. 3,9114. 50-80
It is a hydrolyzed condensate obtained by boiling for 1 to 1 hour at a temperature of °C, which is distilled to remove the alcohol and excess water, and then evaporated in an efficient instantaneous evaporator such as a thin film evaporator. By expelling the alcohol and water, a solid hydrolyzed condensate of alkyltrialkoxysilane which is substantially solvent- and water-free and solvent-soluble is obtained. The ratio of R and OH (molar ratio) obtained from NMR by dissolving the final hydrolyzed condensate of a solid and alcohol-soluble alkyltrialkoxysilane in deuterated chloroform is R:OH = 1:0.05 ~ 3, and the solution viscosity of the 50% (wt%) ethanol solution is 10 to 60 centipoise (Brookfield viscosity 20 qo), preferably 20
~40 centipoise is suitable for this invention. A coating composition is prepared by dissolving a solid hydrolyzed condensate of alkyltrialkoxysilane in alcohol, adding acetic acid, water, and a curing catalyst 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 (Bruckfield viscometer, 2 pi 0), preferably 10 to 15 centipoise.
Prepare to centiboise. The alkyltrialkoxysilane hydrolysis condensate in 100 parts by weight of the coating composition is 20 to 4 parts by weight. The alcohol used in the present invention is a C. to C4 alcohol, preferably ethyl alcohol. Alcohols having different boiling points may be mixed and used to adjust the evaporation rate of the coating liquid. Further, other solvents having different boiling points may be added. The coating liquid of the present invention is characterized by containing acetic acid, and this acetic acid increases the pot life of the coating liquid. Further, it is added for the purpose of improving the adhesion of the coating film, and its amount can be appropriately selected depending on the coating conditions and curing conditions. Examples of organic amines used as curing catalysts include trialkylamines such as trimethylamine and triethylamine, quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, trimethylbenzylammonium hydroxide, and triethylbenzylammonium hydroxide. linear amidines such as de, guanidine, 1,8-diazabicyclo(5,4,0) undecene-7,1,6-diazabicyclo(4,3,0)/
Examples include cyclic amidines such as Nene-5. Strongly basic amines whose aqueous solution speckles are above 112 mm are preferred. It can also be used as a chloride salt of these strongly basic amines. Examples of weak acids include formic acid, acetic acid, propionic acid, butyric acid, cyanobic acid, hexanoic acid, hebutanoic acid, octanoic acid, carboxylic acids such as chloroacetic acid, fumaric acid, maleic acid,
Examples include polybasic acids such as tartaric acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, phenol, and thioacetic acid. The amount of curing catalyst is 0.05 to 3 parts by weight based on 20 to 4 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 adhesion of the coating film will deteriorate. The amount of water in the coating liquid was 2014 parts by weight. The presence of water in the coating liquid is important, and either there is no water in the coating ink liquid, or if the amount of water is less than 2 parts by weight, the cured film after curing by pyo may have insufficient scratch resistance and solvent resistance. The properties are poor, and the adhesion of the paint film is also poor. On the other hand, if there is too much water, the coating film tends to whiten during coating, the viscosity of the coating solution increases quickly, and problems such as shortening of the so-called pot line occur. As for the quality of the water to be added, it is necessary to use water of a quality that has a resistivity of 1 or more as determined by distillation or ion exchange method. Tap water containing a large amount of iron ions and other ions cannot provide good physical properties. The prepared coating liquid is applied to a plastic molded product whose surface has been cleaned and cured by heating to form a cured film. As the base resin, it is useful to use methyl methacrylate resin, which is a resin with poor surface scratch resistance and has particularly excellent transparency, weather resistance, and optical properties. Other polycarbonate, polystyrene, acrylonitrile styrene copolymer resin, methyl methacrylate styrene copolymer resin, polydiethylene glycol bisallyl carbonate, transparent ABG
Transparent plastics such as resin, rubber-reinforced methacrylic resin, cellulose acetate, cellulose acetate propionate, cellulose propionate, cellulose acetate butyrate, polyvinyl chloride, and unsaturated plastics such as ABS resin and high impact polystyrene. Can be applied. Coating methods include dipping, spraying, flow coating, and spin coating. The applied plastics are heat cured. The higher the heating temperature, the faster the curing speed, but it is limited by the heat distortion temperature of the molded product. The curing temperature varies depending on the base resin, but is usually 50-140 pm, preferably 80-140 pm.
The coating composition of the present invention can be applied to transparent plastic sunglass lenses, prescription eyeglass lenses, optical lenses such as camera finder lenses, covers for various instruments, automobile, train, and aviation window glasses, and plastics. Useful for products such as mirrors. The present invention will be explained below with reference to Examples. Note that parts in the examples are based on weight unless otherwise specified. Example 1 Preparation of solid alkyltrialkoxysilane hydrolysis condensate In a reactor equipped with a reflux condenser, 5 parts (3 moles) of methyltriethoxysilane and 162 parts (9 moles) of water were added.
, 0.5 cc of 0.1N hydrochloric acid was added, mixed well, and heated under reflux at 80° C. for 4 hours. The liquid, which was initially a non-uniform layer, became a transparent uniform layer. Next, the ethyl alcohol (containing some water) was removed by distillation and concentrated to obtain a solution with a solid content of 50%, which was further aged under reflux for 2 hours. This was subjected to solvent evaporation using a thin film evaporator in a short period of less than 1 minute to obtain a hydrolyzed condensate of solvent-soluble methyltriethoxysilane in the form of solid flakes. The solid hydrolyzed condensate of methyltriethoxycin obtained here was dissolved in deuterated chloroform and dissolved in NMR, and the ratio of C and OH obtained from NMR was 1:0.2. Preparation of Coating Solution 27 parts of reagent primary ethanol (water content 0.2%) and 3 parts of deionized water were mixed to prepare 10% water-containing ethanol. Three parts of solid flakes of methyltriethoxysilane hydrolyzed condensate were added to the mixture and dissolved completely in about 40 minutes while shaking vigorously to prepare a 50% solution. The viscosity of the melt solution was measured with a Flookfield viscometer and was 35 centipoise at 20:00. Separately, the reagents are 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 1 reagent. grade glacial acetic acid 17
parts were added in this order and mixed well to prepare a catalyst solution. A coating solution containing 3 parts of flakes of a hydrolyzed condensate of methyltriethoxysilane obtained by mixing the above 50% solution and catalyst solution and 3 parts of water was prepared. The solution viscosity was measured with a Bruckfield viscometer and was 12 centipoise at 2 pi. The surface of a sheet made of coating methyl methacrylic resin and having a thickness of 2 mm was thoroughly washed, immersed in the coating liquid, and gently pulled up at a pulling speed of 13 min/min. It was directly placed in a hot air dryer and cured at 9 pm for 5 hours. A methacrylic resin final varnish staple lens molded product was coated under the same conditions. The obtained coated molded product was colorless and transparent. The coating film was 6 degrees thick. Evaluation method: To evaluate the scratch resistance of the coated plastic molded product surface, ASTM D-]044, also DIO
It was measured in accordance with 03. S-1 valence load 500 subjected to wear by taper abrasion tester
In the evening, the surface of the sheet was scratched under conditions of 100 wear cycles and the haze (%) was measured using a haze meter. A to measure the adhesion of the coating film to the base resin
0(
The test was performed on a 6-level scale from 5 (no peeling) to 5 (severe peeling).
To measure solvent resistance, acetone was poured into the coated concave surface, the whole was placed in a Petri dish, and the time until the coating peeled off was measured. The results are shown in Table 1. Examples 2 to 3 Instead of the 10% ethanol solution used to dissolve the solid alkyltrialkoxysilane hydrolysis condensate in Example 1, 20% (Example 2) and 27% A coating liquid was prepared in the same manner as in Example 1 except that each of the three hydrous ethanol bases in Example 3 was used. At this time, the water content in the coating liquid 10 was 6 parts (Example 2) and 8 parts (Example 3), respectively. The methacrylic resin was coated in the same manner as in Example 1, and the results are shown in Table 1. Example 4 In place of the 10% hydrated ethyl alcohol used to dissolve the solid alkyltrialkoxysilane hydrolysis condensate in Example 1, 27% hydrated ethanol was used to dissolve the curing catalyst, etc. Instead of the 23 parts of 1st grade ethanol used as a reagent, 2 parts of 17% hydrated ethanol consisting of 1 part of 1st grade reagent and 4 parts of deionized water was used, making the total amount of water in 100 parts of the coating solution 12 parts. The same procedure as in Example 1 was performed except for this. The methacrylic resin was coated in the same manner as in Example 1, and the results are shown in Table 1. Example 5 In Example 1, the ethanol for dissolving the hydrolysis condensate of a solid alkyltrialkoxysilane was mixed with 3 parts of primary ethanol as a reagent, and the ethanol for dissolving the curing catalyst was mixed with 2 parts of primary ethanol and 3 parts of deionized water. A coating solution was prepared in the same manner as in Example 1, except that 13% bottle water ethanol consisting of 1.5% was used. At this time, the amount of water in 100 parts of the coating liquid was 3 parts.
Next, a coating solution was prepared on the methacrylic resin molded product, and one week later, the coating was applied, and the results are shown in Table 1. Example 6 In Example 1, reagent 1 was added to ethanol for dissolving the hydrolyzed product of solid alkyltrialkoxysilane.
The same procedure as in Example 1 was carried out, except that 3 parts of grade 1 ethanol was used and 2 parts of grade 1 ethanol was used as the reagent for dissolving the curing catalyst. A coating solution was prepared by adding 3 parts of deionized water to the final coating solution, and one month after the preparation, it was cornered into a methacrylic resin molded article. The results are shown in Table 1. Example 7 After degreasing and polishing a lens-shaped molded product injection-molded with polycarbonate resin, y-aminopropyltriethoxysilane was applied as an undercoat agent by a dipping method.
Cured in the open for 20 minutes at qo. Next, the coating solution used in Example 4 was immersed in the solution for 13 minutes.
The sample was gently pulled up at a pulling rate of 1.5 min, and the solvent was removed in an oven at 70 qo for 1 q, and then the temperature was raised to 130 qo and cured for 4 hours. The results are shown in Table 1. Comparative Example 1 Same as Example 1, except that three bases of reagent grade 1 ethanol were used instead of three bases of 10% aqueous ethanol as the ethanol for dissolving the hydrolyzed product of solid alkyltrialkoxysilane in Example 1. I did the same thing. The results are shown in Table 1. Comparative Example 2 An uncoated methacrylic resin sheet was subjected to an abrasion resistance test using a Taber abrasion tester, and the results are shown in Table 1. Comparative Example 3 An uncoated polycarbonate resin sheet was subjected to a scratch resistance test using a taper abrasion tester, and the results are shown in Table 1. Table 1 Common conditions: 3 parts of solids in the coating liquid (methyltriethoxysilane hydrolyzed condensate) PMMA: Polymethyl methacrylate PC: Polycarbonate When dihydrate was not added to the coating liquid of the comparative example (
Compared to Comparative Example 1), Examples 1 to 7 in which the compound was added were superior in haze after Taber abrasion, coating film adhesion, and acetone resistance. Moreover, in Examples 5 and 6, one week or one day after preparing the coating solution.
It is shown that the properties of the coating film are good when the coating is performed after a maturing time of several months.

Claims (1)

[Scope of Claims] 1 (A) solid and alcohol-soluble with the general formula RSi
A hydrolyzed condensate of alkyltrialkoxysilane represented by (OR')_3 (R, R' are aliphatic hydrocarbon groups of C_1 to C_4), and the ratio (molar ratio) of R and OH of the terminal group
1:0.05-3, the hydrolyzed condensate 20-40
Part by weight (B) 0.05 to 3 parts by weight of a strongly basic organic amine and/or its weak acid salt (C) 2 to 14 parts by weight of water (D) A mixture consisting of an organic solvent containing acetic acid and alcohol as main components, A coating composition wherein the mixture has a viscosity of 5 to 20 centipoise.