JPH0559321A - Coating material and coated molding - Google Patents

Abstract

PURPOSE:To provide a coating material composed of a alpha-methylstyrene copolymer having a specific composition and giving a coating film having high surface hardness, strong adhesiveness to a substrate and excellent durability, transparency and weather resistance. CONSTITUTION:The objective material is composed of an alpha-methylstyrene copolymer having a weight-average molecular weight of 50,000-200,000 and consisting of (A) 10-40wt.% of alpha-methylstyrene unit, (B) 40-90wt.% of methyl methacrylate unit and (C) 0-30wt.% of monomer unit copolymerizable with the above units. The monomer giving the unit C is e.g. styrene and acrylonitrile. The alpha- methylstyrene copolymer is preferably produced by a differential polymerization such as continuous bulk polymerization or continuous solution polymerization using a complete-mixing reactor. The coating of the coating material is preferably performed by producing a film of the coating material and hot-pressing the film to a substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating material comprising an α-methylstyrene copolymer, and a resin molded product coated with this coating material. More specifically, it has good transparency, surface hardness and weather resistance. And a coating material made of an α-methylstyrene copolymer having excellent adhesion to a substrate, and a resin molded product coated with the coating material.

[0002]

2. Description of the Related Art Plastic materials include polymethylmethacrylate, polycarbonate, ABS resin, polyvinyl chloride, polystyrene, etc., which are applied to films, sheets, lenses, etc. due to their light weight and good moldability. Has been done. In particular, since polycarbonate is transparent and has excellent mechanical properties, it is used as a material for structural parts in place of glass, and is also used for various purposes. However, the surface hardness of plastic is not sufficient as compared with metal or glass, and there is a strong demand for improving the surface characteristics. Conventionally, a method of hard-coating a plastic surface has been used for the purpose of eliminating these drawbacks. For example, a method of applying a thermosetting melamine resin coating and forming a protective film by thermosetting (JP-A-47-33164, JP-A-48-80175, JP-A-51-1).
1127) or a method of forming a protective film made of organopolysiloxane by heat curing (Japanese Patent Laid-Open No. 52-13).
8656, JP-A-60-252633, US Pat. No. 3,707,367, etc.) have been proposed. However, in these methods of forming a protective film by heating and curing, it is necessary to treat the molded article under the severe conditions of high temperature and long time for curing, and this treatment impairs the mechanical properties of the base plastic. There is a risk. Further, there is a problem in the adhesion between the base material and the protective film. On the other hand, as an alternative to heat curing, a method of forming a protective film by using a polyfunctional acrylic compound as a coating material and irradiating it with ultraviolet rays or electron beams (Japanese Patent Laid-Open No. 53-7771 and Japanese Patent Publication No. 49-71). Japanese Patent Publication No. 14859 and Japanese Patent Publication No. 52-47763) are also proposed. The method proposed here has the advantage that the curing is completed in a short time, but the adhesion between the base material and the protective film is not satisfactory, and the durability of the protective film, especially the weather resistance, is Are inadequate to react to energy rays. In order to improve the adhesion between the base material and the protective film, for example, as described in JP-A-58-101120, a method is proposed in which a plastic surface is treated with an alkali and then coated with an ultraviolet curable resin. Has been done.

[0003]

An object of the present invention is to obtain a coating material having high surface hardness, good adhesion to a base material and excellent durability.

[0004]

According to the present invention, the weight average molecular weight is in the range of 50,000 to 200,000, the proportion of α-methylstyrene units is 10 to 40% by weight, and the proportion of methyl methacrylate units is 40 to 40%. It is a coating material for coating on a thermoplastic resin, which comprises 90% by weight and an α-methylstyrene-based copolymer in which the proportion of monomer units copolymerizable therewith is 0 to 30% by weight. The present invention also provides a transparent thermoplastic surface with α
-A resin molded product obtained by coating a methylstyrene-based copolymer. Furthermore, the present invention is a resin molded product obtained by coating a transparent thermoplastic resin with an α-methylstyrene copolymer which is a polycarbonate. Regarding the molecular weight of the coating material of the present invention, the weight average molecular weight (in terms of polystyrene) is in the range of 50,000 to 200,000, preferably 7
It is in the range of 10,000 to 150,000. If the molecular weight is less than 50,000, the mechanical properties will be low and the protective film will be cracked, making it unsuitable as a coating material. On the other hand, when the molecular weight exceeds 200,000, the protective film is colored unfavorably and the weather resistance is deteriorated, and in this case, it is also unsuitable as a coating material.

In the coating material of the present invention, the proportion of α-methylstyrene units is 10 to 40% by weight, the proportion of methyl methacrylate units is 40 to 90% by weight, and the proportion of monomer units copolymerizable therewith is 0. -30% by weight, but preferably the proportion of α-methylstyrene units is 15 to 28% by weight, the proportion of methyl methacrylate units is 50 to 60% by weight, and the proportion of monomer units copolymerizable therewith. Is 10 to 20% by weight. If the proportion of α-methylstyrene units contained in the copolymer is less than 10% by weight, the heat resistance will be poor, and if it exceeds 40% by weight, when the coating material is coated on the base material, cracks will occur over time. May occur, resulting in poor mechanical strength. Similarly, the proportion of methyl methacrylate units is 40% by weight.
If it is less than 90%, the mechanical strength is poor, and if it exceeds 90% by weight, the heat resistance is poor. Similarly, if the proportion of copolymerizable monomer units exceeds 30% by weight, the heat resistance will be significantly reduced. Examples of the copolymerizable monomer include styrene, maleic anhydride, acrylonitrile, N-phenylmaleimide, methacrylic acid, acrylic acid, acrylic acid esters such as ethyl acrylate, propyl acrylate, and n.
-Butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, benzyl acrylate, methacrylic acid esters such as ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate,
Examples thereof include benzyl methacrylate.

The coating material of the present invention is produced by differential polymerization such as continuous bulk polymerization or continuous solution polymerization using a completely mixed reactor. When the coating material of the present invention is produced by differential polymerization, the composition and molecular weight of the coating material are uniform, and the appearance is good, which is preferable, but batch type bulk or solution polymerization is also possible.
It is also possible to add a rubber component such as polybutadiene when producing the coating material of the present invention. As the polymerization initiator, a peroxide and / or an azo compound used in ordinary radical polymerization can be used. It is also possible to add an appropriate amount of a chain transfer agent such as alkyl mercaptan to control the molecular weight.

As a method of coating the base material with the coating material of the present invention, a method of producing a film of the coating material and press-bonding the film to the base material by applying heat and pressure is preferable. When heat and pressure are applied to the base material and the film for pressure bonding, the method for producing the film used for coating is to melt the coating material using an extruder or the like and then discharge it from the die, or to coat the coating material with, for example, chloroform or the like. It is possible to use a method in which the solvent is dissolved in the solvent and the solution is cast thinly and then the solvent is removed by vacuum drying. In addition, as a method of coating the film on the substrate, a method of directly applying the solution of the coating material on the substrate and removing the solvent by a method such as vacuum drying is also taken, and after removing the solvent as necessary. It is also possible to apply heat and pressure.
It is also possible to coat the base material with the coating material by immersing the base material in a solution of the coating material of the present invention. Furthermore, the substrate can be coated by coextrusion of the coating material of the present invention and the substrate such as multi-layer extrusion.

The coating material of the present invention contains a release agent within a range that does not impair transparency and other necessary properties.
It is possible to contain additives such as an ultraviolet absorber, an antioxidant, a heat stabilizer, an antistatic agent, and a dye for coloring, if necessary. The thickness of the film of the coating material on the resin molded product obtained by coating the surface of the transparent thermoplastic resin of the present invention with the coating material is preferably 5 μm or more. If the thickness of the film of the coating material is less than 5 μm, the surface hardness of the base material has an effect, so that a resin molded product having an improved surface hardness of the base material cannot be obtained. As the thickness of the film coated on the surface of the base material increases, the influence of the surface hardness of the base material decreases, so that a resin molded product having a high surface hardness can be obtained.

The base material of the resin molded article coated with the coating material of the present invention is, for example, polycarbonate, polyacrylate, polyamide, polystyrene, polymethylmethacrylate, ABS resin, polypropylene, styrene.
There may be mentioned thermoplastics such as -butadiene copolymer. In particular, polycarbonate is preferable because it is transparent, has high impact resistance, is excellent in transparency and heat resistance, and has good adhesiveness with the coating material of the present invention. When polycarbonate is used as the base material of the resin molded article coated with the coating material of the present invention, the coating material of the present invention has excellent adhesion to the polycarbonate, and therefore it is not necessary to use an adhesive agent. However, the adhesion to the coating material of the present invention may not be good depending on the type of the base material, and when such a base material is used, the adhesiveness can be improved by using an adhesive.

The resin molded product coated with the coating material of the present invention may have any shape such as a plate, a hollow container and a cylinder. A suitable coating method can be selected from the above-mentioned coating methods depending on the shape of the substrate. When the method of coating the base material with the coating material by applying heat and pressure is adopted, the shape of the base material is preferably a plate shape.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Each test was conducted by the following method. (Production example of coating material) Production of α-methylstyrene-methyl methacrylate copolymer
Example Methyl methacrylate 375g, α-methylstyrene 12
Benzyl peroxide 1000m as an initiator for 5g
g, 1000 mg of tert-dodecyl mercaptan as a polymerization degree regulator were added, and the mixture was stirred for 48 hours while maintaining the reaction temperature at 110 ° C. The reaction product was poured into methanol to remove unreacted monomers and dried, and then the powder of methyl methacrylate-α-methylstyrene copolymer 40
5.1 g was obtained. The obtained copolymer contained 77% by weight of methyl methacrylate unit.

Α-methylstyrene-methyl methacrylate-
Production Example of Styrene Copolymer Methyl methacrylate 275 g, α-methylstyrene 15
0 g and 75 g of styrene were reacted in the same manner as in the above-mentioned production example of the α-methylstyrene-methyl methacrylate copolymer to produce an α-methylstyrene-methyl methacrylate-styrene copolymer. The obtained copolymer had a methyl methacrylate unit of 59.4% by weight and a styrene unit of 18.0.
% By weight.

Α-methylstyrene-methyl methacrylate-
Production Example of Maleic Anhydride Copolymer Methyl methacrylate 333 g, α-methylstyrene 14
0 g and 2.7 g of maleic anhydride were reacted in the same manner as in the production example of the above α-methylstyrene-methyl methacrylate copolymer to give α-methylstyrene-methyl methacrylate-
A maleic anhydride copolymer was prepared. The obtained copolymer contained 76.0% by weight of methyl methacrylate unit and 2.4% by weight of maleic anhydride unit.

(Example of Production of Film from Coating Material) Each coating material was melted using a Minimax extruder manufactured by US Custom Scientific Fic Instruments Co., Ltd., and a melt of the coating material was extruded from a die to form a film. ..

A film of the produced coating material was coated on polycarbonate and the following measurements were carried out. (Measurement of surface hardness) Pencil hardness was measured according to JIS K5400. (Measurement of Adhesion) According to JIS K5400, the adhesion of the coating material to the base material was visually observed by the cross cut method, and the presence or absence of peeling of the coating material from the base material was observed.
Then, the presence or absence of peeling of the coating material from the base material was visually observed by a cross-cut tape method. (Heat resistance) According to JIS K5400, the surface condition was visually observed by immersing in boiling water for 10 minutes. afterwards,
After removing water from the surface and left for 2 hours, the presence or absence of peeling of the coating material from the base material was visually observed by the cross-cutting method, and further the peeling of the coating material from the base material was observed by the cross-cut tape method. Tables 1 to 7 show the results of Examples and Comparative Examples in which each film was coated on polycarbonate. In the table, α-methylstyrene αMSt, methyl methacrylate is MMA, styrene is St, and maleic anhydride is MA.
Displayed as H.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

[Table 6]

[0022]

[Table 7]

[0023]

According to the present invention, a coating material having good transparency, surface hardness, heat resistance, and weather resistance, and a coating material having a higher surface hardness than the substrate by coating the coating material on the substrate. A resin molded product can be obtained.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Toshinasa Tanaka 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Inside Nippon Steel Corporation Advanced Technology Research Laboratories (72) Masao Kimura 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Address Inside Nippon Steel Corporation Advanced Technology Research Laboratories

Claims (3)

[Claims] 1. The weight average molecular weight is in the range of 50,000 to 200,000, the proportion of α-methylstyrene unit is 10 to 40% by weight, the proportion of methyl methacrylate unit is 40 to 90% by weight, and The ratio of polymerizable monomer units is 0
To 30% by weight of α-methylstyrene-based copolymer for coating on thermoplastics 2. A resin molded product obtained by coating the surface of a transparent thermoplastic with the α-methylstyrene-based copolymer according to claim 1. 3. The resin molded article according to claim 2, wherein the transparent thermoplastic is polycarbonate.