JPH0237938B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for surface treatment of polycarbonate resin molded articles. Specifically, the present invention relates to a surface treatment method for improving weather resistance and abrasion resistance by subjecting the surface of a polycarbonate resin molded article to special treatment. In general, polycarbonate resins are widely used in various fields because they have excellent electrical properties, mechanical properties, impact resistance, transparency, heat resistance, etc. However, on the other hand, they have low surface hardness and are easily It has drawbacks such as being easily scratched, easily abraded, and having poor chemical resistance. As a method for improving these drawbacks, there is a method of coating the surface of a polycarbonate resin molded article with a surface treatment agent, and many proposals have been made in the past. One of these is by applying organopolysiloxane resin as a paint to molded products.
Conventionally, methods for imparting surface hardness and chemical resistance have been proposed. For example, surface hardness can be improved by applying a partial hydrolysis condensate of organotrialkoxysilane alone, a partial hydrolysis condensate of tetraalkoxysilane and organotrialkoxysilane, or a partial hydrolysis condensate of organotrialkoxysilane filled with colloidal silica. Although excellent molded products can be obtained, these paints have fairly good adhesion when the molded product is polymethyl methacrylate, but they have problems with adhesion to polycarbonate resin molded products. In particular, it had disadvantages such as poor weather resistance, peeling of the coating layer, and discoloration of the molded product, and was not satisfactory. The inventors of the present invention have conducted intensive studies to solve the drawbacks of the conventional techniques and to provide a surface treatment method that can impart good weather resistance and abrasion resistance to the surface of polycarbonate resin molded products, and as a result, they have arrived at the present invention. Ivy. That is, the gist of the present invention is that (i) a copolymer of methyl methacrylate and methyl acrylate is applied to the surface of a polycarbonate resin molded article, and the copolymerization ratio is 5 parts by weight of methyl acrylate to 100 parts by weight of methyl methacrylate. ~12 parts by weight, consisting of a copolymer with a viscosity average degree of polymerization in the range of 500 to 5000, (ii) an ultraviolet absorber, and (iii) an organic solvent,
The amount of methyl methacrylate and methyl acrylate copolymer (i) is 1 to 7 parts by weight, and the amount of ultraviolet absorber (ii) is 0.5 to 7 parts by weight, based on the total of 100 parts by weight of (i), (ii), and (iii).
parts by weight of the undercoat composition are applied and dried to form an undercoat layer, and further, on top of the undercoat layer, (iv) a topcoat whose main component is organopolysiloxane filled with colloidal silica is applied. The present invention relates to a surface treatment method for a polycarbonate resin molded article, which improves weather resistance and scratch resistance, and is characterized by thermal curing. The present invention will be explained in more detail below. The polycarbonate resin that is the raw material for the polycarbonate resin molded product in the present invention includes:
Any known material can be used. Various polycarbonates are well known, but the typical ones have the following general formula: (In the formula, X is a general formula

[Formula] (R′ is a hydrogen atom or or hydrocarbon group), -O-, -S-,

[Formula] and Beauty

It represents a divalent group selected from the group consisting of [Formula]. R represents a monovalent group selected from the group consisting of a hydrogen atom, a hydrocarbon group, and a halogen atom, and may be the same or different. ) is a polycarbonate having a repeating unit represented by Among these polycarbonates, 2,
Polycarbonates made from 2'-bis(4-hydroxyphenyl) alkanes, particularly 2,2'-bis(4-hydroxyphenyl)propane (hereinafter abbreviated as bisphenol A), are preferred. Furthermore, polyester carbonate obtained by copolymerizing the above-mentioned bisphenol A with an aromatic dicarboxylic acid is also included. The molded article made of polycarbonate resin may be of any shape, such as a sheet, film, pipe, or block-like body manufactured by a conventional molding method such as injection molding or extrusion molding. In the present invention, first, an undercoat paint is applied to a polycarbonate resin molded article. As an undercoat,
A copolymer of methyl methacrylate and methyl acrylate (hereinafter referred to as polymethyl methacrylate copolymer) is used. The content of the copolymer component methyl acrylate is related to the adhesion with the top coat layer and the occurrence of cracks in the top coat layer due to heating, and the content of methyl acrylate exhibiting the best physical properties is 5 to 12% by weight. If the content of methyl acrylate is low, adhesion will be poor, and if the content is high, cracks will appear. Further, the viscosity average degree of polymerization of the polymethyl methacrylate copolymer is suitably 500 to 5000 for handling purposes. Here, the viscosity average degree of polymerization is calculated from the following viscosity formula by determining the specific viscosity (ηsp) using an acetone solution. [η] = 7.7×10 ^-5 Mn ^0.70 ……(2) Viscosity average degree of polymerization = Mn/100 ……(3) The measurement temperature was 30°C, and the solution concentration (C) was 0.5 g/
Use 100 ml and k′=0.64. The undercoat paint contains an ultraviolet absorber. As this ultraviolet absorber, a benzophenone type or triazine type ultraviolet absorber is used.
Also effective are oxalic acid anilide derivative ultraviolet absorbers. Examples of benzophenones include 2-hydroxy-4-n-octoxybenzophenone,
Examples of 2,4-dihydroxybenzophenone and triazine series include 2(2'-hydroxy-5'-methylphenyl)benzotriazole and 2(2'-hydroxy-3'-t-butyl-5'methylphenyl).
-5 chlorobenzotriazole, 2(2'-hydroxy-3',5'-di-tert-butylphenyl)-5
-Chlorobenzotriazole is mentioned. In addition, as an example of the oxalic acid anilide derivative system, N-
(2-ethylphenyl)N'-(2-ethoxy-5
-t-butylphenyl oxalic acid diamide). The undercoat is used by dissolving the polymethyl methacrylate copolymer and ultraviolet absorber in a solvent. Ester-based solvents,
One or more of ketone, ether, halogenated carbon, or aromatic hydrocarbon solvents are used. Particularly suitable solvents include ethyl cellosolve, butyl cellosolve, methyl ethyl ketone,
Ethyl acetate, butyl acetate, isobutanol, n-
There are butanol, isopropyl alcohol, diacetone alcohol and mixtures thereof. The content of polymethyl methacrylate copolymer contained in the undercoat is 1 to 7% by weight. If the polymer concentration is higher than this, cracks will occur when a silicone-based top coating, which will be described later, is applied and cured by heating. The content of ultraviolet absorber in the undercoat is
The content should be 0.5 to 7% by weight. If the content is less than this, the polycarbonate resin will turn yellow in a weather test and its adhesion will decrease. Moreover, if the content is higher than this, it will have a negative effect on adhesion. Furthermore, if the content of the ultraviolet absorber exceeds the content of the polymethyl methacrylate copolymer, the adhesion will be poor. To apply the undercoat paint to the surface of the polycarbonate resin molded product, brushing, dipping, roll coating, spray coating, flow coating, etc. are possible. In the present invention, the heat treatment conditions after application of the undercoat are preferably 80°C to 120°C for 5 to 120 minutes.
After applying the undercoat and heat treatment, a topcoat is applied. The top coat is a paint whose main component is organopolysiloxane filled with colloidal silica. Colloidal silica is a stable colloidal solution of silica that has been made easier to use, and can be produced by various conventionally known methods.
trademark), Syton (manufactured by Monsanto Company, trademark),
Examples include those known by trade names such as Nalcoag (manufactured by Nalco Corporation, trademark) and Snowtex (manufactured by Nissan Chemical Co., Ltd., trademark). Organopolysiloxanes generally have the general formula R ² Si(OR ¹ ) ³ (R ¹ is a hydrocarbon group having 1 to 6 carbon atoms, such as methyl, ethyl, isopropyl, isobutyl, etc.; R ² is the same as R ¹ above). In addition to similar hydrocarbon groups,
Vinyl group, γ-glycidoxypropyl group, γ-
(meth)acryloxypropyl group, phenyl group, and 3,3,3-trifluoropropyl group);
Partial hydrolysis condensate of dialkyl alkoxysilane represented by R ² R ³ Si(OR ¹ ) ₂ (R ¹ and R ² have the same meaning as above, R ³ has the same meaning as R ² ). No. 3451838, Japanese Patent Publication No. 53-130732,
(described in Japanese Patent Application Laid-Open No. 56-161475), but also

[Formula] (R ⁴ and R ⁵ are the same or different alkyl groups,
R ⁶ and R ⁷ are the same or different substituted or unsubstituted monovalent hydrocarbon groups, and A is a divalent hydrocarbon group or a divalent organic group containing an oxygen atom or a sulfur atom. Also included are condensates of organosilicon compounds represented by (a and b are 2 or 3) (these are described, for example, in JP-A-161475-1983). The mixing ratio of colloidal silica and organopolysiloxane is preferably 10 to 70% by weight of colloidal silica and 90 to 30% by weight of organopolysiloxane. The top coat paint contains alcohol generated during the condensation reaction, but it may also be dissolved or dispersed in any organic solvent, water, or a mixture thereof, as required. Examples of this organic solvent include methanol, ethanol, and n-propanol. Examples include lower fatty acid alcohols such as , iso-butyl alcohol and iso-propanol, polyhydric alcohols such as ethylene glycol, methyl cellosolve, and ethyl cellosolve, and their ethers and esters.
In addition, suitable amounts of various surfactants such as siloxane surfactants and fluorinated alkyl surfactants may be added to the top coat for the purpose of obtaining a film having a smooth surface. The method for applying this top coat can be performed in the same manner as the method for applying the undercoat. The heat curing conditions after applying the top coat are 80~
A temperature of 120°C and 10 to 180 minutes is appropriate. The surface-treated polycarbonate resin molded product of the present invention can be used, for example, in windows, skylights, windshields,
Good use as plastic cleaners, furniture or auto parts. As described in detail above, the present invention is a highly advantageous invention in practice, as weather resistance and abrasion resistance can be imparted to the surface of a polycarbonate resin molded article by subjecting it to special treatment. Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the Examples unless the gist of the invention is exceeded. Note that in the following, "parts" indicate "parts by weight." Examples 1 to 3, Comparative Examples 1 to 5 Preparation of undercoat: Methyl methacrylate (MMA)/methyl acrylate (MA) copolymer was polymerized using peroxide as a polymerization initiator and mercaptan as a chain transfer agent. Then, we created polymers with different copolymerization composition ratios and degrees of polymerization. Dissolve 2.5 parts of this polymer in 35.5 parts of isobutanol, 38.5 parts of diacetone alcohol, and 26 parts of methyl ethyl ketone, and then add and dissolve 2.0 parts of 2-hydroxy-4-n-octoxybenzophenone as an ultraviolet absorber (UV agent). It was used as an undercoat paint. Preparation of topcoat: methyltrimethoxysilane
600 g of water-dispersed colloidal silica (SiO ₂ min 31% by weight) was gradually added dropwise to 500 g with stirring, and stirring was continued for an additional 4 hours after the dropwise addition was completed. At this time, the pH of the liquid is 3
It is necessary to adjust it to ~6. This liquid was diluted with 1000 g of isopropanol to prepare a top coat. 3mm thick polycarbonate [Mitsubishi Chemical Industries, Ltd.]
After cleaning Novarex (trademark)] with ethyl alcohol, the above-mentioned undercoat paint was applied by dipping, air-dried, and then heat-treated at 120°C for 30 minutes. A top coat is applied to the base coated sheet using the dipping method, and after air drying, it is heat cured at 100℃ for 60 minutes.
A sample was obtained. The following various properties of the obtained samples were evaluated. The evaluation method is as follows. Adhesion (Round tape peeling test) Using a razor blade, make 11 vertical and horizontal cuts at 1 mm intervals on the paint-applied surface of the sample to create 100 cuts, and then adhere well with commercially available cellophane tape.
When peeled in the 90°C direction, the number of coated layers remaining without peeling (X) is expressed as X/100. Weather resistance: Using Sunshine Weather Meter WE-SUN-HC manufactured by Suga Test Instruments Co., Ltd., the sample was exposed to a black panel temperature of 63±3℃, sprayed for 12 minutes/60 minutes, 60±3
Irradiated under conditions of %RH, 200 hours, 400 hours, 600 hours
Adhesion after time irradiation (grip tape peeling test) and colorability (YI value) before and after 200 hours of irradiation are measured. YI value: Yellow index according to ASTM D1925. Heat resistance Place the sample in an oven and leave it at 120℃ for 1 hour, then take it out and check for cracks. The results obtained are shown in Table 1.

[Table] * Adhesion immediately after coating and heat curing Examples 4 to 6 and Comparative Examples 6 to 12 The methyl methacrylate and methyl acrylate copolymer used in the undercoat were used in Example 2, and the concentration of this polymer and Samples were prepared in exactly the same manner as in Example 1, except that the amount of ultraviolet absorber (UV agent) added was changed as shown in Table 2, and various properties were evaluated in the same manner. The results are shown in Table 2.

[Table] *1 Comparison example of concentration in undercoat paint 13 Topcoat paint was dip-coated on the same polycarbonate sheet as in Example 1 without applying primer, and the coating was applied at 100°C and 60°C.
The initial adhesion after curing was 0/100.

Claims (1)

[Claims] 1. On the surface of the polycarbonate resin molded product, (i)
A copolymer of methyl methacrylate and methyl acrylate, in which the copolymerization ratio is 5 to 12 parts by weight of methyl acrylate to 100 parts by weight of methyl methacrylate, and the viscosity average degree of polymerization is in the range of 500 to 5000. , (ii) an ultraviolet absorber and (iii) an organic solvent, in which 1 to 100 parts of the methyl methacrylate and methyl acrylate copolymer of (i) are added to 100 parts by weight of (i), (ii) and (iii) in total. An undercoat composition containing 7 parts by weight and 0.5 to 7 parts by weight of the ultraviolet absorber (ii) is applied and dried to form an undercoat layer, and further on the undercoat layer (iv) colloidal A method for surface treatment of polycarbonate resin molded articles to improve weather resistance and scratch resistance, characterized by applying a top coat containing silica-filled organopolysiloxane as a main component and curing it under heat.