JPH0136507B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating composition capable of forming a coating film with high adhesion on the surface of molded products such as plastics and metals with excellent scratch resistance and abrasion resistance and good dyeability. In general, plastic molded products and metal molded products such as aluminum and zinc have drawbacks such as being easily scratched and easily worn due to their low surface hardness. In order to improve these problems, a method of forming a coating film of a curable substance on the surface of the molded article as described above has been carried out, and various coating compositions have been proposed for forming the coating film. For example, JP-A-53-78273, JP-A-48-55884
No. 4,027,073 discloses a coating composition comprising an alkyltrialkoxysilane or a mixture thereof with a tetraalkoxysilane or colloidal silica. however,
Although the coating film obtained by hydrolyzing and curing these coating compositions by heating has excellent scratch resistance, it has poor adhesion to the surface of the molded product or poor flexibility of the coating film itself. peels off and cracks in hot water. Therefore, a method of providing an undercoat layer (amino acrylate type) when coating with such a coating composition has been disclosed (Japanese Patent Application Laid-Open No. 138476-1983).
However, although this method improves adhesion, the resulting coated film lacks smoothness, making it difficult to uniformly dye it with, for example, a disperse dye. On the other hand, coating compositions containing epoxy group-containing organoalkoxysilanes and epoxy resins have excellent adhesion and dyeing properties, but have low surface hardness, and in order to increase this, a curing agent and a crosslinking agent are mixed in the coating composition. When this value is increased, the dyeability and adhesion, which were originally good, become poor. Therefore, the present inventors conducted extensive research in order to develop a coating composition that can form a coating film with excellent scratch resistance, wear resistance, and stainability on the surface of plastic molded products with high adhesion. The inventors have discovered that a coating film obtained from a coating composition containing a specific disilane compound containing a spiran structure as a constituent component satisfies all of these properties, and has completed the present invention. That is, the present invention is based on the general formula A disilane compound represented by the formula (where k is 2 or 3, R ¹ and R ² are the same or different alkyl groups,
R ³ and R ⁴ are the same or different alkyl groups,
and m is 0 or 1). The greatest feature of the present invention is that, as mentioned above, while conventional coating compositions have only a monosilane compound as a constituent component,
The point is that a disilane compound containing a spiran structure is used. Since this disilane compound has 4 to 6 alkoxy groups at both ends per molecule, the coating film formed by the polycondensation reaction of its hydrolyzate has a high crosslinking density and high surface hardness. It is thought that it has excellent scratch resistance, abrasion resistance, and solvent resistance. Also, Si
Since the structure has a structure in which the functional groups between Si have a certain distance, it stains well with the molded product, and the coating film itself is elastic and has excellent flexibility, so the molded product does not expand due to heat. Can handle shrinkage and exhibits excellent adhesion. Furthermore, it has good dyeability with disperse dyes and can be easily dyed using ordinary dyeing methods. Hereinafter, the coating composition of the present invention will be explained in detail. In the disilane compound represented by the above general formula (1), R ¹ and R ² are alkyl groups including the same or different alkoxyalkyl groups, and have 1 to 6 carbon atoms, especially 1 to 3 carbon atoms, or Carbon number 1
An alkoxyalkyl group consisting of an alkyl group having 1 to 6 carbon atoms, especially 1 to 3 carbon atoms, bonded with 1 to 3 alkoxy groups is preferred. Specifically, methyl group, ethyl group, propyl group, methoxyethyl group, etc. are common. Further, R ³ and R ⁴ are the same or different alkyl groups, and have 1 to 4 carbon atoms.
Preferably. Specific examples include methyl group, ethyl group, and propyl group. These disilane compounds represented by general formula (1) are
It can be synthesized by various conventionally known methods. For example, the general formula

[Formula] (In the formula, R is -CH=CH ₂ or -CH ₂ -CH=
CH ₂ ) under a platinum catalyst.

[Formula] and/or

[Formula] (R ¹ to R ⁴ and l and m in the formula are the same as above)
It can be synthesized by addition reaction of an alkoxysilane represented by Or instead of alkoxysilane,

[Formula] and/or

The chlorosilane represented by the formula is subjected to an addition reaction, and then
Alkoxylation may be performed with an alcohol represented by R ¹ OH or R ² OH. (In the above formula, R ¹ to R ⁴ and l and m are the same as above) The above reaction conditions are not particularly limited, but generally at normal pressure and a temperature of -20 to 160°C,
If necessary, the above reaction may be carried out in a polar nonaqueous solvent such as benzene, toluene, dimethyl ether, or the like.
Further, it is preferable to use platinum black as the platinum catalyst since a colorless and transparent product can be obtained. In the coating composition containing the disilane compound of the present invention, it is preferable to hydrolyze the disilane compound prior to coating the molded article, and use the disilane compound in a hydrolyzed or partially polycondensed form. Doing so will produce desirable effects. Hydrolysis of the disilane compound may be carried out by adding and stirring a weakly acidic aqueous solution containing an inorganic acid such as hydrochloric acid or sulfuric acid or an organic acid such as formic acid or acetic acid. However, polycondensation may proceed excessively due to heat generated by hydrolysis, resulting in solidification of the reaction solution and shortening of the life of the prepared coating composition. Therefore, the disilane compound is mixed in an appropriate solvent, preferably at a concentration of 30% by weight or less when converted to a state in which the disilane compound is completely hydrolyzed and polycondensed (hereinafter referred to as the "converted concentration"). After that, it is desirable to gradually hydrolyze it. In addition, in order to ensure that the hydrolysis reaction and the subsequent partial polycondensation reaction proceed, and to obtain reproducible and stable coating film performance, it is desirable to leave the reaction solution to mature. Approximately 1 to 2 days is appropriate. The coating composition of the present invention may contain alcohol, alkoxy alcohol, unreacted water, or solvent produced by the above-mentioned hydrolysis during use, but after hydrolysis, the above-mentioned components are removed by heating and/or under reduced pressure. The solvent can also be replaced by removal by distillation and subsequent addition of a suitable solvent. The final concentration of the coating composition is preferably 10 to 40% by weight; if it is less than this, it will be difficult to obtain sufficient scratch resistance and abrasion resistance for the coated film that is formed, and if it is more than this, the viscosity will increase. , it becomes difficult to apply the coating uniformly to the surface to be coated. Suitable solvents for replacing the solvent include those having 1 to 4 carbon atoms;
lower alcohols such as methanol, ethanol, propanol, and butanol; lower carboxylic acids or alkyl esters thereof such as acetic acid and methyl acetate; ethers such as cellosolve; ketones such as acetone and acetylacetone; halogenated hydrocarbons such as methylene chloride ; One or more aromatic hydrocarbons such as benzene and toluene. As explained above, the coating composition containing the disilane compound represented by the general formula (1) as a component can form a coating film with excellent properties. The present invention also provides a coating composition that can improve the surface hardness of the resulting coat film by adding a specific compound to the compound. That is, the present invention is based on the general formula A disilane compound represented by (wherein k is 2 or 3, R ¹ and R ² are the same or different alkyl groups,
R ³ and R ⁴ are the same or different alkyl groups, l and m are 0 or 1), and the general formula ^An organoalkoxysilane compound represented ^by So, n
is 0 or 1, R ⁷ is an alkyl group), a tetraalkoxysilane compound represented by the general formula Si(OR ⁸ ) ₄ ...(3) (wherein R ⁸ is an alkyl group), colloidal silica,
This is a coating composition containing as a constituent component at least one additive selected from an epoxy compound and a melamine derivative. Among the above additives, the organoalkoxysilane compound represented by the general formula (2) is generally used, especially those in which R ⁶ has 1 to 4 carbon atoms and R ⁷ has 1 to 4 carbon atoms. Specifically, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, phenyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, Vinyltrismethoxyethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-
Mercaptopropyltrimethoxysilane, β-
Examples include (3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-aminopropyltriethoxysilane. Further, the tetraalkoxysilane compound represented by the general formula (3) is generally used when R ⁸ has 1 to 4 carbon atoms. Specific examples include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. It is recommended that the alkoxysilane compounds represented by the above general formulas (2) and (3) be used after being hydrolyzed in the same manner as disilane compounds (in this case, it is also possible to hydrolyze without a solvent). be done. For example, the alkoxysilane compound may be hydrolyzed and then added to the disilane compound hydrolyzate solution, or may be hydrolyzed simultaneously with the disilane compound. As colloidal silica, fine silica powder having a particle size of 1 to 100 μm, which is produced by various conventionally known methods, can be used as it is or in the form of a colloidal solution obtained by dispersing it in a polar solvent. For the composition of the present invention, a colloidal solution prepared by dispersing the colloidal silica in a polar solvent, for example, water or an alcoholic solvent such as isopropanol, is preferably adjusted to be slightly acidic. Examples of the epoxy compound include polyolefin epoxy resins, alicyclic epoxy resins, epoxy novolac resins, and polyglycidyl ethers of polyhydric alcohols, which are manufactured by various conventionally known methods. Melamine derivatives are prepared by conventionally known methods, such as mixtures of commercially available alkyl etherified methylolmelamines such as hexamethoxymethylmelamine with nitrified cotton, or precondensates with polyhydric alcohols such as 1,4-butanediol. and can be used. The total amount of the above additives is preferably in the range of 10 to 900 parts by weight based on 100 parts by weight of the disilane compound in terms of converted concentration ratio. In order to lower the curing temperature and shorten the curing time, the coating composition of the present invention uses known compounds as curing catalysts, such as hydrochloric acid, sulfuric acid, acetic acid/sodium acetate mixture, tin chloride, perchloric acid, and perchloric acid. It is preferable to use perchlorates such as ammonium, metal acetylacetonates such as aluminum acetylacetonate, metal naphthenates, p-toluenesulfonic acid, benzoic acid, alkali metal phosphates, sodium thiocyanate, and the like. The amount used is preferably 0.01 to 5 percent by weight based on the amount converted into a completely polycondensed state of the polycondensable components in the coating composition (hereinafter referred to as converted amount). Of course, the use of a curing catalyst is not essential. Furthermore, a silicone-based or fluorine-based surfactant may be added to the coating composition of the present invention for the purpose of further improving the smoothness of the coated film. In addition, various other additives such as ultraviolet absorbers, antioxidants, dyes and pigments, and organic carboxylic acids such as formic acid and acetic acid as gelling inhibitors can also be used. In the present invention, the object to be coated is not particularly limited. Generally, molded products with low surface hardness and poor scratch resistance and abrasion resistance, especially plastic molded products, are mainly targeted. For example, polyunsaturated esters such as polymethyl methacrylate, polymethacrylate, polyethylene terephthalate, polyacrylate, polymethyl acrylate; polystyrene; polyvinyl chloride; epoxy resin; polyamide; polycarbonate; polyacrylic such as polydiethylene glycol bisallyl carbonate. Carbonates include polymers such as cellulose acetate plastics, and molded products made of copolymers of monomers forming these polymers or copolymers of the monomers and other monomers.
In particular, the coating composition of the present invention can be used for plastic molded articles with excellent transparency made of polymers such as polymethacrylic esters, polyacrylic esters, polycarbonates, and polyacrylic carbonates. The resulting coating film is highly transparent and has a good appearance, so it is particularly effective in that it does not lose its optical properties. Since the condition of the surface of a plastic molded article greatly affects the properties of the coated film obtained, it is preferable to clean the surface by degreasing and washing with a solvent or the like. In addition, when the adhesion of the coating composition of the present invention is insufficient depending on the plastic fabric, for example, polycarbonates,
For plastic molded products such as styrene-based polymers, known methods such as reagent treatment with an aqueous sodium hydroxide solution, potassium dichromate/sulfuric acid solution, discharge treatment with plasma, etc., or primer coating can be applied to the plastic molded product and the coating film. It is effective to improve the adhesion of It is further preferred that the discharge-treated surface dissolves the layer modified by the treatment with a solvent that does not substantially dissolve the plastic. The method of applying the coating composition of the present invention to the surface of a plastic molded article can be used without particular limitation. For example, a method of immersing a molded article in a solution of a coating composition, a method of applying the solution by spraying, brushing, roller, etc. are generally employed. After coating, the coating film is cured by air-drying in dry air or air and usually heat-treated to form a coating film. The heating temperature varies depending on the molded product, but is preferably 50°C or higher, preferably 70°C or higher, or a temperature at which the molded product does not undergo thermal change, generally 150°C or higher. The curing time is approximately 1 hour at a heating temperature of 130°C, and approximately 2 to 4 hours at a heating temperature of 70°C to 80°C. The coat film formed by curing can have a thickness of about 0.1 μm to 50 μm, but a thickness of 1 μm to 20 μm is particularly suitable. The coating film thus formed from the coating composition of the present invention has excellent surface properties such as scratch resistance, abrasion resistance, dyeability, hot water resistance, and heat resistance. Examples are shown below to specifically explain the present invention, but the present invention is not limited to these Examples. Note that the performance evaluation of the coat film was carried out by the following method. (1) Adhesion test Place a cutter knife with a sharp tip on the sample surface.
After 100 squares of mm x 1 mm were attached, commercially available cellophane tape was attached and the number of squares remaining when quickly peeled off was measured. (2) Scratch resistance test #0000 in a scratch resistance tester manufactured by Fukuda Kikai Kogyo Co., Ltd.
After attaching steel wool and reciprocating the surface of the test piece 10 times under a load of 1 kg, the degree of damage to the surface was visually observed. The condition was evaluated on a five-grade scale from A to E with E as the condition. (3) Heat resistance test Leave in an air oven set at 130°C for 3 hours, and visually observe the appearance of the coated film.
If the coat film had no cracks, peeling, blistering, whitening, etc. and had a good appearance, it was rated as ○, and if it was poor, it was rated as ×. (4) Hot water resistance test The coated film was left in boiling water (80°C warm water was used for polymethyl methacrylate) for 2 hours, and the appearance of the coated film was visually observed. If the coat film had no peeling, blistering, cracking, whitening, etc. and had a good appearance, it was rated ○, and if it was poor, it was rated ×. (5) Dyeability test A dyeing bath in which 0.5 parts by weight of disperse dye (manufactured by Nippon Kayaku Co., Ltd.; Kayalon-Polyester, Brown AF) was dispersed and dissolved in 100 parts by weight of water was maintained at 80°C and dyed for 10 minutes. A is a case where the staining is as good as or better than that of polydiethylene glycol bisallyl carbonate, which has good stainability, and C is a case where it is not stained to the same level or worse than polymethyl methacrylate, which has a poor stainability. Evaluation was made on a 3-grade scale from ~C. Example 1 A commercially available polymethyl methacrylate plate was used as a plastic molded product. First, it was washed with methanol and thoroughly air-dried to a clear state.
It was immersed in a coating composition having the composition shown in the table, thoroughly air-dried at room temperature, and then heated at 80° C. for 3 hours to cure it, to obtain a coated film. The coating composition is prepared by mixing and dissolving the equivalent amounts of the compositions shown in Table 1 in isopropyl alcohol as a solvent so that the concentration is 25% by weight, and then 0.05% of the equivalent amount required for hydrolysis of the alkoxy group in the above composition. Normalized hydrochloric acid was added at room temperature, the mixture was left to age for one day, and then sodium acetate/acetic acid (1/10 weight ratio) was added as a curing catalyst in an amount of 2% by weight based on the converted amount. The colloidal silica is OSCAL manufactured by Catalysts & Chemicals Co., Ltd.
(Product name: _SiO2 30% by weight, particle size 10~
20 mμ, solvent isopropyl alcohol) was used. Table 1 also shows the evaluation results of the coating films obtained from each coating solution. In either case, the coating film thickness was about 5 to 10 microns.

[Table] Example 2 A polyethylene glycol bisallyl carbonate plate produced by cast polymerization was used as a plastic molded article. First, as a pretreatment, the plate was washed with acetone and thoroughly air-dried to form a clear film, and then immersed in a 5% NaOH aqueous solution for 5 minutes.
It was thoroughly washed with water and air-dried again. The above-treated plate-like bodies were immersed in coating compositions prepared in exactly the same manner as Nos. 1 to 12 of Example 1 except that no curing catalyst was added, and then thoroughly air-dried at room temperature and heated at 130°C. It was heated and cured for 1 hour to obtain a coated film.
Table 2 shows the evaluation results of the coated films obtained from each coating composition. In either case, the coating film thickness was about 5 to 10 microns.

【table】

[Table] Example 3 Copolymer of 2,2'-bis[4-(2-methacryloxy)-ethoxy-3,5-dibromophenyl]-propane and styrene produced from plastic molded products by cast polymerization (hereinafter referred to as TB-styrene copolymer) with a TB/styrene weight ratio of 2/
A plate-like body consisting of 3 was used. First, as a pretreatment, the plate was washed with acetone and thoroughly air-dried to a clear state, and then treated with an argon/oxygen mixed gas (flow rate: 30ml/min/10ml/
min) under the conditions of a pressure of 0.7 Torr, an output of 200 W, and a processing time of 1 minute, and then washed using an ultrasonic cleaner using acetone as a solvent for 5 minutes, and air-dried again.
The above-treated plate-shaped bodies were coated in the same manner as in Nos. 1 to 12 of Example 2 to obtain coated films. Table 3 shows the evaluation results of the coated films obtained from each coating composition. In either case, the coating film thickness was about 5 to 10 microns.

【table】

[Table] Example 4 In No. 5 of Example 1,

For coatings in which the same amount of polyethylene glycol diglycidyl ether (Epolite 200E, manufactured by Kyoeisha Yushi Co., Ltd.) or a precondensate consisting of 50 parts by weight of hexamethoxymethylmelamine and 50 parts by weight of 1,4-butanediol is added instead of [Formula]. The composition is manufactured by cast polymerization. A plate of polydiethylene glycol bisallyl carbonate and TB/styrene copolymer was pretreated and coated in the same manner as in Example 3 to obtain a coated film. In either case, the adhesion of the coating film (100/100), scratch resistance (A),
Heat resistance (○), hot water resistance (○), and dyeability (A) were good. Example 5 A plate of polyethylene glycol bisallyl carbonate produced by cast polymerization and a TB/styrene copolymer was pretreated in the same manner as in Example 3, and prepared in the same manner as in Example 1. After immersing the coating composition in the various compositions shown in Table 4, it was thoroughly air-dried at room temperature, and then heated to 130°C for 1 hour.
A coated film was obtained by heating and curing for a period of time. Coating films of polyethylene glycol bisallyl carbonate and TB/styrene copolymer showed similar coating film performance for each coating solution. The evaluation results are shown in Table 4 along with the coating liquid composition.

[Table] Example 6 After washing an aluminum plate with acetone and air drying it to a clear state, it was coated by immersing it in coating solution No. 5 of Table 1, and after thoroughly air drying at room temperature,
It was heat cured at 130°C for 1 hour. The obtained coat film had good adhesion (100/100), scratch resistance (A), heat resistance (◯), and hot water resistance (◯).

Claims (1)

[Claims] 1. General formula A disilane compound represented by (where k is 2 or 3, R ¹ and R ² are the same or different alkyl groups, R ³ and R ⁴ are the same or different alkyl groups,
1 and m are 0 or 1). 2 General formula A disilane compound represented by (where k is 2 or 3, R ¹ and R ² are the same or different alkyl groups, R ³ and R ⁴ are the same or different alkyl groups,
l and m are 0 or 1) and the general formula An ^{organoalkoxysilane} compound represented ^by group, n is 0 or 1, R ⁷ is an alkyl group), general formula Si
(OR ⁸ ) A coating composition comprising a tetraalkoxysilane compound represented by ₄ (where R ⁸ is an alkyl group), at least one additive selected from colloidal silica, epoxy compounds, and melamine derivatives. thing.