JPH0527543B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a plastic molded article having a coating layer on its surface. More specifically, a primer layer of a coating composition made of a specific alkyl methacrylate and/or a copolymer of an alkyl acrylate and a vinyl compound is applied to a plastic molded article, and a coating made of a solution-type fluororesin paint is applied to the primer layer. This invention relates to a plastic molded article formed with layers. [Prior Art] Plastic molded bodies are widely used in various fields, taking advantage of the properties of plastic itself, and are often used outdoors. For example, taking advantage of the transparency of plastics, they are used in various window glass replacements, roofing materials, transparent soundproof walls, outdoor light protection materials, vehicle lighting, windshields, etc. However, when plastic molded articles are used outdoors, they are exposed to sunlight, wind and rain, and tend to discolor and deteriorate over time, and their gloss and transparency tend to decrease. Conventional methods for suppressing this tendency include: (1) A method of blending a UV absorber or a light stabilizer into a plastic material and molding it to obtain a molded article containing the UV absorber. (2) A method of applying a coating composition containing a weather resistance improver to the surface of a plastic molded body to obtain a molded body with a coating layer formed thereon (see Japanese Patent Publication No. 1975-29756) (3) Improving weather resistance A method is known in which a plastic molded body is obtained by laminating and covering a plastic molded body with a pre-formed film containing an additive (see Japanese Patent Publication No. 19119/1983). However, in method (1), the deterioration prevention effect is still insufficient, and in method (2), it is difficult to simultaneously maintain weather resistance, adhesion, and appearance. Method 3) not only requires complicated molding operations in order to prevent air bubbles from remaining between the molded body and the film and prevent wrinkles from forming, but also has inherent problems such as peeling due to insufficient adhesion. . Under these circumstances, improvements have been made to coating compositions for methods of obtaining plastic molded articles on which a coating layer has been formed, and Japanese Patent Application Laid-open No. 149335/1983 proposes a coating composition made of an acrylic copolymer. However, ultraviolet rays cause yellowing and surface deterioration, making it difficult to maintain transparency over a long period of time. In recent years, solution-type fluororesin coatings have been developed that have even better weather resistance than acrylic copolymers. 1977-
This is proposed in publications such as Publication No. 138236. However, solution type fluororesin paints have a problem of poor adhesion to plastic moldings, and the paint peels off after long-term use, resulting in low durability. Furthermore, depending on the type of plastic molded base material, for example, acrylic resin has extremely low adhesion to solution-type fluororesin paints. Furthermore, depending on the solvent used in the solution-type fluororesin paint, the plastic molding may develop cracks, so-called solvent cracks. [Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems in plastic molded articles coated with a solution-type fluororesin paint. The object of the present invention is to maintain initial adhesion even after long-term outdoor use in a plastic molded article having a coating layer of a solution-type fluororesin paint;
Another object of the present invention is to provide a plastic molded article having a coating layer that does not cause yellowing or deterioration of the plastic. Still another object is to provide a coating composition and a primer layer that can form a primer layer with excellent properties when coating a plastic molded article with a solution-type fluororesin paint. [Means for Solving the Problems] The present invention provides a plastic molded article having carbon atoms of 1 to 1.
A primer layer is provided based on a coating composition consisting of a copolymer of an alkyl methacrylate and/or alkyl acrylate having 8 alkyl groups and a vinyl compound having at least one functional group selected from a hydroxyl group, a carboxyl group, and an epoxy group. A plastic molded article characterized in that the primer layer is provided with a coating layer of a solution-type fluororesin paint containing an ultraviolet absorber and a curing agent and made of a fluoroolefin-alkyl vinyl ether copolymer. be. In the present invention, the coating composition for the primer layer formed on the plastic molded article has 1 to 8 carbon atoms.
It consists of a copolymer of an alkyl methacrylate or alkyl acrylate having an alkyl group, or a copolymer thereof, and a vinyl compound having at least one functional group selected from a hydroxyl group, a carboxyl group, and an epoxy group. Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and n-butyl methacrylate. Examples of the alkyl acrylate include monomers such as methyl acrylate, ethyl acrylate, n-propyl acrylate, and n-butyl acrylate. It can be used suitably. Examples of vinyl compounds having a functional group include 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, and 2-hydroxypropyl methacrylate.
Examples of compounds having a carboxyl group such as hydroxyethyl acrylate and hydroxypropyl acrylate include acrylic acid, methacrylic acid, maleic acid, and itaconic acid, and examples of compounds having an epoxy group include glycidyl methacrylate. The following monomers can be suitably used. In the copolymer of alkyl methacrylate and/or alkyl acrylate and a vinyl compound having a functional group, the vinyl compound is present in the copolymer.
It is desirable that it be contained in an amount of 0.01 to 80 mol%, preferably 0.05 to 50 mol%, particularly preferably 0.1 to 20 mol%. If the proportion of the vinyl compound contained in the copolymer is less than the above range, adhesion to the plastic molded article will be poor, while if it is greater, the weather resistance will decrease. A copolymer of alkyl methacrylate and/or alkyl acrylate and a vinyl compound having a functional group can be obtained by a conventional method of mixing each monomer with a polymerization initiator and polymerizing the mixture by heating. The copolymer can be used as a coating composition for a plastic molded body using one or two of general organic solvents such as ketones, esters, aromatic compounds, aliphatic hydrocarbon compounds, and alcohols.
It is dissolved and prepared by more than one species. The amount of copolymer in the coating composition is not particularly limited, but from the viewpoint of forming a precoat layer on a plastic molded article, strength, etc., it is 1 to 30% by weight.
It is preferable that Additionally, additives that are commonly used in paints, such as antifoaming agents, leveling agents, and ultraviolet absorbers, may be added to the coating composition. The primer layer formed on the plastic molded article of the present invention can be formed by applying the above coating composition by a commonly used coating method such as spraying, brushing, dipping, or using a flow coater. After coating, the primer layer is formed by air drying at room temperature for usually 5 minutes or more, and then heating and curing at a temperature lower than the softening temperature of the plastic, preferably about 10° C. lower. The thickness of the primer layer to be formed is preferably 0.5 to 20 μm in terms of strength, transparency, and adhesion to the solution-type fluororesin paint provided on the layer. It is adjusted depending on the coating conditions at the time. In the present invention, the solution-type fluororesin used for the coating layer provided on the primer layer has as its main components polyvinylidene fluoride, tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene-tetra Examples include fluoroethylene copolymers, and copolymers of fluoroolefins and alkyl vinyl ethers such as tetrafluoroethylene or chlorotrifluoroethylene, but fluoroethylene copolymers have a high fluorine content and are solvent-soluble. Preferably, it is an olefin-alkyl vinyl ether copolymer. Preferred components of the fluoroolefin are tetrafluoroethylene and chlorotrifluoroethylene, and preferred vinyl ether components include alkyl vinyl ethers containing a linear, branched or cyclic alkyl group having about 2 to 8 carbon atoms; Examples include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, hydroxybutyl vinyl ether, cyclohexyl vinyl ether, and fluorovinyl ether. In the solution-type fluororesin paint, the fluoroolefin-vinyl ether copolymer that can be suitably used contains 30 to 70 mol% and 70 to 30 mol% of units based on fluoroolefin and vinyl ether, respectively, and is in an uncured state. The intrinsic viscosity [η] measured in tetrahydrofuran at 30℃ is
It is preferably about 0.1 to 2.0 dl/g. Further, the hydroxyl value is preferably 20 to 80 in relation to the hydroxyl group contained as a curing site in the fluoroolefin-alkyl vinyl ether copolymer. Solvents used in solution-type fluororesin paints include ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and butyl acetate, aromatic compounds such as toluene and xylene, and aliphatic hydrocarbons such as octane and hexane. Compounds, alcohols such as propanol and butanol, and various general organic solvents. In the present invention, 0.5 to 50 parts by weight, preferably 0.5 to 50 parts by weight per 100 parts by weight of the fluorine-containing copolymer as described above.
1.0 to 30 parts by weight of UV absorber is added. If the amount is too small, sufficient weather resistance effect cannot be achieved, and if it is too large, it may cause bleed-out, decrease in transparency of the coating layer, decrease in adhesion with the precoat layer, etc. This is not preferable since it is disadvantageous in terms of cost. As ultraviolet absorbers, conventionally known or well-known 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-(1- methyl-2-hydroxy)ethoxybenzophenone,
Benzophenone series such as 2-hydroxy-4-(2-hydroxy-3-methacryloxy)propoxybenzophenone or 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2
Benzotriazole-based compounds such as -(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole are used alone or in combination.
In addition, additives such as antifoaming agents, antistatic agents, pigments, dispersion stabilizers, viscosity modifiers, leveling agents, antigelation agents, etc., which are blended in ordinary paints, may also be blended. The solution-type fluororesin paint of the present invention can be obtained by dissolving the above-mentioned fluorine-containing copolymer, ultraviolet absorber, and other additives in the above-mentioned organic solvent. It is preferable that the solvent dissolves the copolymer, the ultraviolet absorber, and other additives well, and the organic solvents listed above are used alone or in appropriate combinations. In the solution-type fluororesin paint, the concentration of the composition consisting of the fluorine-containing copolymer and ultraviolet rays is adjusted to 1 to 60% by weight, preferably 5 to 40% by weight to form the coating layer. It is suitable for workability. The prepared solution-type fluororesin paint is applied to the surface of plastic molded objects and other articles to form a coating with excellent gloss by volatilizing the solvent, and can be used as is as a so-called lacquer-type paint. However, it is preferable to add a polyfunctional compound that is reactive with the hydroxyl group contained in the copolymer as a crosslinking site as a curing agent component and use it as a curable coating material. In this case, polyvalent isocyanates, such as non-yellowing diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate, and adducts thereof are particularly useful as curing agents. In this case, it is also possible to accelerate curing by adding a known catalyst, and in addition to polyvalent isocyanate-based catalysts, melamine-based catalysts such as butylated melamine, methylated melamine, epoxy-modified melamine, and methylated urea may be used. , urea-based curing agents such as butylated urea, or metal alkoxide-based curing agents can also be used. The solution-type fluororesin paints described above are prepared using various equipment commonly used for making paints, such as ball mills, paint shakers, sand mills, jet mills, three-roll mills, kneaders, etc. . At this time, additives such as those exemplified above may also be added. In the present invention, the coating layer of the solution-type fluororesin paint provided on the primer layer has a thickness of 3 to 50μ,
It is important that the thickness is preferably about 5 to 40μ. If the thickness deviates from this range, various problems will occur and it will be disadvantageous in terms of cost, so it is not preferable.
The method for forming the coating layer is carried out in accordance with the method for forming the primer layer. In the present invention, plastic molded articles in various forms made of various materials can be used. The plastic molded article having a coating layer of the present invention has a specific primer layer and a specific coating layer provided on the primer layer, so that the weather resistance is greatly improved.
Favorable results can be obtained when applied to materials that are suitable for outdoor use in terms of mechanical properties and the like, but whose use is restricted in terms of weather resistance. Such materials include polycarbonate resin, acrylic resin, vinyl chloride resin, polystyrene resin, and ABS.
Resins are exemplified, and are particularly suitable for materials that tend to yellow and deteriorate when exposed outdoors. Further, in terms of shape, it may be a sheet, a film, a rod, a corrugated plate, or other irregularly shaped products. [Example] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 1 90 g of methyl methacrylate, 10 g of 2-hydroxyethyl methacrylate, and 340 g of 2-ethoxyethanol as a polymerization solvent were added to a reactor equipped with a stirrer and a reflux condenser, and after stirring and mixing, azobisisobutylene was added as a polymerization initiator. Nitrile 0.05
g was added and dissolved. Next, a copolymerization reaction was carried out at a temperature of 80°C with stirring for 7 hours to obtain a viscous and transparent product. Further solvent was added to this product to prepare a coating composition having a solids concentration of about 15% by weight. Separately, prepare a polycarbonate plate (colorless and transparent, 30cm x 30cm) as a plastic molding, wash it with water, dry it, then apply the above-prepared coating composition on its surface with an applicator, dry it at room temperature, and heat it to 120℃. Hold in a regulated oven for 30 minutes,
A uniform primer layer with a thickness of about 10 μm was formed. Next, a solution-type fluororesin paint (Lumiflon LF-200, a product of Asahi Glass Co., Ltd.) made of a fluoroolefin-alkyl vinyl ether copolymer using xylene as a solvent with a solid concentration of 50% by weight was further diluted with methyl isobutyl ketone. The solid content was adjusted to a concentration of 25% by weight, and 2-hydroxy-4-
Octoxybenzophenone (Biosoap #130: Kyodo Yakuhin Co., Ltd. product) based on solid content
After adding 18 Phr of an isocyanate curing agent (Coronate EH, a product of Nippon Polyurethane Co., Ltd.) and adjusting the amount by mixing and stirring, it was applied onto the primer layer using an applicator. After coating, it was dried at room temperature and kept in a heating oven adjusted to 120° C. for 30 minutes to form a uniform coating layer with a thickness of about 20 μm, thereby obtaining a plastic molded article having a coating layer. The adhesion of the coating layer of the obtained plastic molded article was measured using a sunshine weather meter before and after treatment for 2,000 hours and 4,000 hours according to the method of ASTM-3359, and evaluated by the number of remaining squares. In addition, yellowing deterioration was measured before and after the same treatment using a color measuring device (SM-3, manufactured by Suga Test Instruments Co., Ltd.). Adhesion measurement results and yellowing deterioration difference before and after treatment (△YI)
and are shown in Table 1. From Table 1, it is clear that the coating layer of the plastic molded article having the coating layer of the present invention has excellent adhesion and durability, and has a remarkable effect on yellowing and deterioration of the base plastic. Examples 2 to 5 In the primer layer composition of Example 1, methyl methacrylate, 2-hydroxyethyl methacrylate, and the ultraviolet absorber were replaced with the compounds shown in Table 1, and a part of the polycarbonate plate as a plastic molded article was replaced. A plastic molded article having a coating layer was obtained in the same manner as in Example 1 except that an acrylic plate was used. The adhesion and yellowing of the coating layer of the obtained plastic molded article were measured in the same manner as in Example 1. The results are shown in Table 1. Comparative Examples 1 to 5 In Examples 1 to 5, a plastic molded body without a primer layer, a plastic molded body in which a coating layer containing no ultraviolet absorber was formed in a solution-type fluororesin paint, and a plastic molded body in which a coating layer containing no ultraviolet absorber was formed in the solution-type fluororesin paint were formed, and the primer composition was methyl. Plastic molded bodies as shown in Table 1 were obtained in the same manner as in the examples, including plastic molded bodies on which a coating layer containing no ultraviolet absorber was formed in place of methacrylate. Example 1 about the obtained plastic molded body
The characteristics were measured in the same manner as above, and the results are shown in Table 1. As can be seen from Table 1, none of the properties satisfied all of the properties of solvent crack, adhesion, and weather resistance.

【table】

〔Effect of the invention〕

Due to the presence of the specific primer layer, the plastic molded article having the coating layer of the present invention greatly improves the adhesion of the coating layer made of fluororesin provided on the primer layer, which has been a major drawback in the past. The effect of completely eliminating the occurrence of solvent cracks was also observed. In particular, the properties of the coating layer made of fluororesin, such as weather resistance, are synergistically improved, making plastics suitable for outdoor use in terms of mechanical properties, but whose use is restricted due to weather resistance. When applied to molded objects, it suppresses reductions in transparency, yellowing, and strength over a long period of time, and also has excellent chemical resistance, making it possible to apply it to a variety of applications. It is something that you have.

Claims (1)

[Scope of Claims] 1. A vinyl compound having an alkyl methacrylate and/or alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and at least one functional group selected from a hydroxyl group, a carboxyl group, and an epoxy group, in a plastic molded article. A solution type fluororesin paint comprising a coating composition comprising a copolymer with a fluoroolefin-alkyl vinyl ether copolymer and containing an ultraviolet absorber and a curing agent on the primer layer. 1. A plastic molded article comprising a coating layer of. 2. The plastic molded article according to claim 1, wherein the ultraviolet absorber is a benzophenone-based and/or benzotriazole-based ultraviolet absorber. 3. The plastic molded article according to claim 1, wherein the plastic molded article is a molded article made of polycarbonate resin, acrylic resin, vinyl chloride resin, polystyrene resin, or ABS resin.