JPH0118944B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an aromatic polycarbonate molded article having a coating film with excellent surface properties such as surface hardness. More specifically, a primer layer made of a thermoplastic acrylic polymer is formed on the surface of an aromatic polycarbonate molded article, and then a protective film made of cured organopolysiloxane is formed on this primer layer. The present invention relates to a method for producing an aromatic polycarbonate molded article. Aromatic polycarbonate has various features such as being transparent, lightweight, excellent mechanical properties, and easy to process, so it is being used as a structural component material to replace glass by taking advantage of these inherent features. As is well known, it is also used for various other purposes. However, compared to metals and glass, they are inferior in various surface properties such as surface hardness, abrasion resistance, scratch resistance, and solvent resistance, which limits their use. There is a strong demand for improving raw materials. In order to improve the surface properties of aromatic polycarbonate molded articles, various attempts have been made to apply paint to the surface of the molded article to form a protective coating. For example, a thermosetting melamine resin paint is applied and a protective film is formed by heat curing, a polyfunctional acrylic compound is applied and a protective film is formed by UV curing, and a carbon fan is applied. Many methods have been proposed, such as forming a protective film with organopolysiloxane that is cured by applying a hydrolysis product of a silane compound. However, the protective films obtained by these methods
There are problems with adhesion to the polycarbonate base material and durability of the coating film. Although the cured organopolysiloxane layer provides excellent surface properties, it has poor adhesion to the polycarbonate substrate. To improve this, various methods have been proposed for pre-treating the polycarbonate substrate. Paints containing thermoplastic acrylic polymers (for example, JP-A-52
-138565 publication, U.S. Patent No. 4224378),
There is also a method using a paint containing a thermosetting acrylic polymer (for example, US Pat. No. 3,707,397) or a paint containing a bisphenol type epoxy resin (for example, JP-A-55-40743). Are known. On the other hand, it is well known that a layer made of cured organopolysiloxane is more suitable as a coating film with excellent surface properties, and there are many proposals for coatings that provide such cured organopolysiloxane. However, when carbon functional silane compounds are used, severe curing conditions are required, making it difficult to obtain a coating film that satisfies high surface properties, and is particularly fatal in terms of poor weather resistance. On the other hand, when a silicone functional silane compound is used, it can be cured under milder conditions and the resulting coating film has excellent weather resistance, making it more practical. However, cured organopolysiloxanes obtained from silicone functional silane-based compounds usually have poor adhesion. A combination of various requirements must be considered, such as the selection of compounds, the selection of pretreatment materials, and the selection of solvents to be used. The present invention produces a cured organopolymer with particularly excellent surface properties by applying a top coat containing a curable organopolysiloxane to an aromatic polycarbonate molded product on which a primer layer made of a thermoplastic acrylic polymer is formed. The present invention relates to a method of forming a film made of siloxane. As mentioned earlier, in order to form a cured organopolysiloxane layer with excellent surface properties, it is important to select the curable organopolysiloxane that makes up the top coat, as well as the silane compound that is its precursor. In addition, cracks are likely to occur in the coating film when curable organopolysiloxane is heated to form a film made of cured organopolysiloxane, so the selection of curing conditions and curing operations must be carefully selected. Control is also an important requirement. The present invention solves these problems by forming a coating film consisting of a cured organopolysiloxane layer with excellent surface properties on the surface of a polycarbonate molded product without causing cracks in the coating film. provide a method to do so. That is, in the present invention, a primer layer made of a thermoplastic acrylic polymer is formed on the surface of an aromatic polycarbonate molded article, and then (a) 100 parts by weight of alkyltrialkoxysilane, dialkyldialkoxy 100 parts by weight of a curable organopolysiloxane obtained by cohydrolyzing a silane functional silane compound mixture consisting of 10 to 20 parts by weight of silane and 5 to 20 parts by weight of tetraalkoxysilane, and (b) 0.5 to 0.5 parts by weight of polyvinyl butyral resin. A coating film with excellent surface properties, which is obtained by applying a top coat obtained by dissolving 10 parts by weight of 10 parts by weight in a solvent, removing the solvent, and then heating to form a protective film containing hardened organopolysiloxane. This is a method for manufacturing a polycarbonate molded article having the following steps. In this way, even if polyvinyl butyral resin is blended into the top coat, the surface properties and adhesion of the cured organopolysiloxane protective film are not impaired at all, and the protective film (top coat layer) is free from cracks. Modifying the coating film of polyvinyl butyral resin is of great significance in that it can prevent this from occurring and also enables stable curing of the curable organopolysiloxane. The curable organopolysiloxane contained in the top coat used in the method of the present invention contains an alkyltrialkoxysilane as a main component and a silane functional silane compound mixture consisting of a dialkyldialkoxysilane and a tetraalkoxysilane. It refers _to a reaction product obtained by hydrolysis ^, and more ^{specifically , it} has the following formula ^: dialkyldialkoxysilane ^10-
20 parts by weight, preferably 12 to 15 parts by weight, (2) Alkyltrialkoxysilane 100 represented by the general formula R ¹ Si(OR ³ ) ₃ (wherein R ¹ and R ³ are the same as above)
and (3) a silicon functional comprising 5 to 20 parts by weight, preferably 10 to 15 parts by weight, of a tetraalkoxysilane represented by the general formula Si(OR ³ ) ₄ (wherein R ³ is the same as above) Refers to the co-hydrolysis reaction product of a mixture of silane compounds. The curable organopolysiloxane contained in the top coat used in the method of the present invention must be a reaction product obtained by cohydrolyzing a mixture of three silicone functional silane compounds as described above. For example, when a mixture of products obtained by hydrolyzing three silicone functional silane compounds individually is used as a curable organopolysiloxane, craters appear in the final coating. Furthermore, JP-A-49-14535 discloses a mixed composition containing a hydrolyzed product of hydrolyzed tetraalkoxysilane and alkyltrialkoxysilane, and a hydrolyzed dialkyldialkoxysilane as a coating composition. discloses and teaches that the dialkyldialkoxysilane should be hydrolyzed with any of the other components. However, when the coating composition obtained here is applied on the primer layer and heat-cured to form a protective film made of hardened organopolysiloxane, the coating composition cannot be coated in a long-term weather resistance test or heat test. It became clear that there were defects in durability, such as cracks occurring in the membrane. On the other hand, when a top coat containing a curable organopolysiloxane obtained by the above-mentioned cohydrolysis used in the present invention is used, the resulting protective film has a good balance between hardness and toughness, and is resistant to weathering. It has excellent properties such as heat resistance and heat resistance, and the adhesion of the protective film is also extremely good. In the present invention, the mixing ratio of the three types of silicon functional silane compounds is critical in the sense that it significantly influences the properties of the cured organopolysiloxane layer, that is, the top coat layer. That is, alkyltrialkoxysilane
Based on 100 parts by weight, if the amount of dialkyldialkoxysilane is less than 10 parts by weight, the coating film will lack durability and cracks will easily occur, and in some cases, a hardened film may be formed by heating. Cracks occur when the product is washed, which seriously impairs the appearance of the product, and on the other hand,
If it exceeds 20 parts by weight, there is no risk of cracking, but it will cause a significant decrease in surface hardness. Furthermore, if the amount of tetraalkoxysilane blended is less than 5 parts by weight based on 100 parts by weight of alkyltrialkoxysilane, the cured state of the coating film may be insufficient and the desired surface properties may not be achieved, or the acrylic It requires curing at a high enough temperature to cause deterioration of the polymer primer layer, while if it exceeds 20 parts by weight, the coating film will lack durability and will be prone to cracking. Co-hydrolysis of the above-mentioned silicon functional silane compound mixture may be carried out according to a known method, for example, by adding a desired amount of water in a solvent mainly containing a lower alcohol in the presence of a small amount of an acidic catalyst. Let the reaction take place. The curable organopolysiloxane obtained by cohydrolysis is a combination of alcohols, acetate,
It is prepared as a top coat by dissolving it in various solvents such as methyl ethyl ketone, ethylene glycol monoalkyl ether, toluene, and benzene. Alcohols and ethylene glycol monoalkyl ethers are preferable when considering the attack of solvents on the polycarbonate substrate. Furthermore, when the top coat is stored for a long period of time, the curable organopolysiloxane deteriorates due to an alkoxy group exchange reaction and the final coating becomes difficult. In order to avoid inconveniences such as adversely affecting the properties of the film, lower alcohols having 4 or less carbon atoms are more preferably used. The concentration of the curable organopolysiloxane in the top coat is preferably adjusted to be in the range of 30 to 60% by weight. The three types of silicon functional silane compounds used in the present invention are dialkyldialkoxysilanes such as dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldipropoxysilane, dimethyldiptoxysilane, diethyldimethoxysilane, and diethyldimethoxysilane. Ethoxysilane, diethyldiptoxysilane, dipropyldimethoxysilane, dipropyldiethoxysilane,
Examples include dipropyldiptoxysilane. Examples of alkyltrialkoxysilane include methyltrimethoxysilane, methyltriethoxysilane,
Examples include ethyltrimethoxysilane, propyltrimethoxysilane, and propyltriethoxysilane. Examples of the tetraalkoxysilane include tetramethoxysilane and tetraethoxysilane. The polyvinyl butyral resin that is blended into the top coat to modify the coating performance together with the above-mentioned curable organopolysiloxane may be any ordinary polyvinyl butyral resin sold on the market, and its blending amount is as follows. The amount may be selected within the range of 0.5 to 10 parts by weight per 100 parts by weight of the silicon functional silane compound mixture. The top coat thus prepared may contain known curing catalysts, surfactants, and other additives, if desired. The method of the present invention is specifically carried out according to the following operations. That is, a primer paint containing a thermoplastic acrylic polymer is applied to the surface of an aromatic polycarbonate molded product, air-dried for several minutes, and then heated and dried at a temperature of 70 to 110°C to form a product made of the acrylic polymer. Form a primer layer. Application of the primer paint is carried out using any known means such as dipping, spraying, and roll coating. Next, on the primer layer formed on the polycarbonate molded article, a top coat paint containing the curable organopolysiloxane of the present invention as described in detail above is applied.
Heating is performed at a temperature of ~130°C for a period of 30 minutes to 4 hours to form a cured organopolysiloxane layer. The top coat paint is applied by any known means such as dipping, spraying or roll coating. Thermoplastic acrylic polymers used to form the primer layer include homopolymers or copolymers derived from alkyl acrylates and alkyl methacrylates. When the top coat layer requires high surface properties, specifically abrasion resistance and surface hardness, even if a conventionally widely used thermoplastic acrylic polymer with a molecular weight of around 30,000 is used as the primer layer, the requirements will not be met. Not fulfilled. In order to satisfy such requirements, a copolymer of methacrylic acid alkyl ester and acrylic acid alkyl ester is required, and the copolymer composition is 70 to 90% by weight of methacrylic acid alkyl ester and 30 to 10% by weight of acrylic acid alkyl ester. % by weight, preferably each 80
A copolymer consisting of ~85% by weight and 15~20% by weight and having a high molecular weight of 50,000 or more, preferably 100,000 or more is preferably used. In particular, a copolymer of methyl methacrylate and butyl acrylate is suitable. These thermoplastic acrylic polymers are dissolved in a suitable solvent to prepare a primer coating, but solvents that corrode the polycarbonate molded article substrate are not preferred. When using the above-mentioned high molecular weight acrylic copolymer, ethylene glycol monoalkyl ether is preferably used as a solvent in consideration of its solubility and erodibility of the polycarbonate substrate. The concentration of acrylic polymer in primer paint is 10
A range of 30% by weight is suitable. The primer paint may contain an ultraviolet absorber, if desired. As the ultraviolet absorber, known compounds such as benzotriazole, benzophenone, and benzoate compounds are used. When a high degree of weather resistance is required, the ultraviolet absorber should be used in an amount of 10% by weight or more based on the acrylic polymer. The primer layer in the method of the present invention may be formed by laminating a thin film of thermoplastic acrylic polymer onto a polycarbonate molded article. The aromatic polycarbonate molded article to which the method of the present invention is applied is a sheet made of a polycarbonate resin obtained by polymerizing aromatic dihydric phenols, typically bisphenol A, and a carbonate precursor by a known method. Refers to molded products obtained by molding into other shapes. The thus obtained composite polycarbonate molded product has excellent surface properties, including excellent abrasion resistance and chemical resistance, high surface hardness, and good adhesion to the polycarbonate base of the protective film. It exhibits excellent durability, with no cracks occurring in the top coat layer and no deterioration in the adhesion between the protective film and the polycarbonate even after long-term outdoor use. The method of the present invention will be explained in more detail below using Examples and Comparative Examples. Parts and percentages are by weight unless otherwise specified. The performance test method shown in the examples is as follows. (1) Appearance Judgment was made visually. Judgment criteria: 〇...Good △...Cracks occur in the paint film ×...The paint film peels off naturally. (2) Steel wool test Apply #〇〇〇〇 steel wool to the paint surface while lightly pressing it back and forth 15 times. The degree of scratches on the surface of the coating film after that was determined according to the following criteria, and the abrasion resistance was evaluated. A'...No damage. A...There is almost no damage. B: Scratches occur, but the gloss is maintained. C: There are countless scratches and the luster is lost. (3) Adhesion Add 100 goblets (1 mm ² ) to the paint film, adhere tightly with cellophane tape, and then peel off sharply at right angles. At this time, the number of stitches that remained without peeling was expressed against the total number of stitches of 100, and the adhesiveness was evaluated. (4) Heat resistance test The sample was heat-treated for a predetermined time in a hot air circulation constant temperature bath at 100°C, and various performances were then evaluated. Reference example: 100 parts of methyltrimethoxysilane, 20 parts of tetramethoxysilane, 10 parts of dimethyldimethoxysilane
parts, 125 parts of isopropyl alcohol and glacial acetic acid
25 parts were mixed and cooled on ice to maintain the liquid temperature at 5°C. A hydrolysis reaction was carried out while dropping 62 parts of 0.01N hydrochloric acid into this cold solution. Since the reaction generated heat, the dropping rate was adjusted so that the liquid temperature did not exceed 30°C. After the entire amount was added, stirring was continued for an additional 4 hours at room temperature. Next, anhydrous sodium acetate was added to the reaction product solution.
0.6 parts, 6 parts of pure water and isopropyl alcohol
55 parts of the mixture was added and stirring continued for an additional 3 hours. 0.2 part of a fluorine-based surfactant (manufactured by Sumitomo 3M, trade name "FC-430") was added to the obtained reaction product liquid, and the mixture was further stirred for 12 hours. The product liquid thus obtained is aged for one week at room temperature and used as a top coat. Example 410 parts of methyl methacrylate, butyl acrylate
90 parts, ethylene glycol monoethyl ether
500 parts of azobisisobutyronitrile and 1.5 parts of azobisisobutyronitrile were charged into a four-necked flask with a capacity of 3 equipped with a reflux, a stirrer, and a thermometer, and heated to 80 to 85 parts under a nitrogen atmosphere.
The mixture was heated to ℃ and stirred. After 3 hours, add 1.0 part of azobisisobutyronitrile and add 2 parts of azobisisobutyronitrile.
Stirring was performed while heating for hours to obtain an acrylic copolymer with a molecular weight of 150,000. A mixed solvent of ethylene glycol monomethyl ether/meta-xylene/isopropyl alcohol (mixing ratio is 1.2/
0.8/1.5) to adjust the acrylic copolymer concentration to 15%. In order to improve the surface smoothness of the paint film, a silicone leveling agent (BYK - manufactured by Mallinckrodt, trade name: BYK) is used.
-300'') was added in an amount equivalent to 0.1% based on the copolymer. Furthermore, 2-(2'-hydroxy-5'-t-butylphenyl)benzotriazole (manufactured by Nippon Ciba Geigy, trade name "Tinuvin PS") was added in an amount equivalent to 20% of the copolymer. The solution was used as a primer paint. A primer paint was applied to a polycarbonate resin sheet by a dipping method and dried by heating at 100° C. for 30 minutes to form a primer layer with a thickness of 10 to 15 μm on one side. To the top coat obtained in the reference example, 2 parts, 4 parts, and 8 parts of polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd., trade name "Eslec BM-1") were added per 100 parts of the silicone functional silane compound mixture. The mixture was added and thoroughly stirred to completely dissolve, thereby preparing three types of top coats. The top coat was applied to the primer-treated polycarbonate resin sheet by a dipping method and heated at 120° C. for 4 hours to form a hardened top coat layer. Table 1 shows the surface properties of the resulting composite polycarbonate resin sheet. Comparative Example 1 The top coat obtained in Reference Example was applied to the primer-treated polycarbonate resin sheet used in Example, and a cured top coat layer was formed in the same manner as in Example. Its performance is also listed in Table 1. Comparative Example 2 A polycarbonate resin sheet having a cured top coat layer was obtained in the same manner as in Example except that 15.4 parts of polyvinyl butyral resin was used.
Its performance is also listed in Table 1.

[Table] From the results in Table 1, it can be seen that by adding a predetermined amount of polyvinyl butyral resin, the performance of the top coat layer can be maintained at a high level even after heat-resistant treatment.

Claims (1)

[Claims] 1. A primer layer made of a thermoplastic acrylic polymer is formed on the surface of an aromatic polycarbonate molded article, and then (a) 100 parts by weight of an alkyltrialkoxysilane,
100 parts by weight of a curable organopolysiloxane obtained by cohydrolyzing a silane functional silane compound mixture consisting of 10 to 20 parts by weight of dialkyldialkoxysilane and 5 to 20 parts by weight of tetraalkoxysilane; and (b) polyvinyl butyral. A top coat obtained by dissolving 0.5 to 10 parts by weight of resin in a solvent is applied, the solvent is removed, and then heated to form a protective film containing hardened organopolysiloxane, which has excellent surface properties. A method for manufacturing a polycarbonate molded article having a coating film.