JPH05278181A - Coating material and molded article covered therewith - Google Patents

Abstract

PURPOSE:To provide coating material, which is excellent in surface hardness, wear resistance and weatherability and has favorable adhesion to plastic base material. CONSTITUTION:The coating material concerned is for covering thermoplastic characterized by being made of (meth)acrylic acid ester-based thermoplastic resin, which contains no alpha-methyl styrene unit substantially and has resin layer made of alpha-methyl styrene-based copolymer on the surface. Further, the resin molded article is obtained by covering the surface of transparent thermoplastic base material with the above-mentioned coating material. The above-mentioned material is profitably used as laminated film, which improves the surface hardness, wear resistance and weatherability, by covering the surface of the plastic base material.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a coating material comprising a surface-cured thermoplastic resin which is excellent in improving the surface hardness, abrasion resistance, scratch resistance, weather resistance and adhesion of a plastic substrate and a coating material such as this. The present invention relates to a resin molded product coated with a coating material.

[0002]

2. Description of the Related Art Aromatic polycarbonates have excellent impact resistance and high transparency, so they are used as a structural component material to replace glass by taking advantage of their original characteristics, and also used for various purposes. It is well known that this is done. However, such a plastic substrate is also inferior in various surface characteristics such as surface hardness, abrasion resistance, scratch resistance, and weather resistance to metal and glass, and its use is naturally restricted.

Therefore, conventionally, in order to eliminate these drawbacks, a method of applying a hard coat to the surface of the plastic substrate has been adopted. For example, a method of applying a thermosetting melamine resin coating on the surface of a plastic substrate of a molded article and thermosetting to form a protective film (JP-A-47-3).
3,164, JP-A-48-80,175,
JP-A-51-11 / 127) or a method of forming a protective film made of organopolysiloxane on the surface of a substrate by heat curing (JP-A-52-138,656, JP-A-60-252). 633, US Pat. No. 3,707,3
No. 67 specification) has been proposed. However, in the method of forming a protective film on the surface of a plastic substrate by these heat curing treatments, the molded product is exposed to severe conditions of high temperature and long time during this heat curing treatment. There was a risk of impairing the mechanical properties of the plastic. Furthermore, there is a problem in the adhesion between the plastic substrate and the protective film.

On the other hand, as an alternative method to such a heat curing treatment, a polyfunctional acrylic compound is used as a paint,
A method of forming a protective film by irradiating ultraviolet rays or electron beams (Japanese Patent Application Laid-Open No. 53-7,771 and Japanese Patent Publication No. 49-
No. 14,859 and Japanese Patent Publication No. 52-47,763) are also proposed. However, even though such a method has an advantage that the curing treatment can be completed in a short time, the adhesiveness between the plastic substrate and the protective film is not satisfactory, and the durability of the protective film is not satisfactory. In particular, the weather resistance was necessarily insufficient because the protective film responds to energy rays.

A method for coating a polycarbonate with a thermoplastic acrylic resin film coated with an energy ray-curable polyfunctional acrylic compound in order to improve the adhesion between the plastic substrate and the protective film (Japanese Patent Laid-Open Publication No. Sho. 60-38,438, JP-A-63-64,744.
However, in such a method, crazing is likely to occur on the plastic substrate, and on the other hand, in the case where such a trouble is unlikely to occur, the adhesion of the protective film to the substrate is deteriorated. was there. As described above, it has not yet been obtained that the surface of the plastic base material has excellent surface hardness, abrasion resistance, scratch resistance, adhesion, and weather resistance.

[0006]

Therefore, as a result of earnest studies to find a method for solving such a problem, the present inventors have found that a specific thermoplastic resin film is a (meth) acrylic acid ester-based thermoplastic resin. It was found that what was laminated on the film can achieve the purpose extremely efficiently,
The present invention has been completed. Therefore, an object of the present invention is to provide a coating material which is applied to the surface of a plastic such as polycarbonate and improves its surface hardness, abrasion resistance, scratch resistance, weather resistance and the like. In particular, coatings with excellent adhesion can be quickly and easily performed, and in fields where it is desirable to effectively utilize the original characteristics of plastic such as light weight and transparency, for example, coatings used for surface coating of plastic lenses and decorative boards. To provide the material. A further object of the present invention is to provide a resin molded product obtained by coating the surface of a thermoplastic with such a coating material.

[0007]

Means for Solving the Problems That is, the present invention has a (meth) acrylic acid ester-based thermoplastic resin having a resin layer of an α-methylstyrene copolymer on the surface thereof and substantially not containing an α-methylstyrene unit. It is a coating material for coating on a thermoplastic made of a resin film. In the present invention, the α-methylstyrene-based copolymer forming the resin layer has a weight average molecular weight range of 5 to 200,000, an α-methylstyrene unit ratio of 10 to 40% by weight, and methacrylic acid The proportion of methyl acid units is 40 to 90% by weight, and the proportion of monomer units copolymerizable with them is 0 to 3
It is preferably 0% by weight.

The present invention is also a resin molded product obtained by coating the surface of a transparent thermoplastic with such a coating material. Furthermore, in the present invention, the transparent thermoplastic resin is preferably polycarbonate, and the surface thereof is substantially free of α-methylstyrene unit having an α-methylstyrene copolymer resin film (meth) acrylic ester. A resin molded product obtained by coating a thermoplastic resin film.

Regarding the molecular weight of the α-methylstyrene copolymer used in the present invention, the weight average molecular weight (in terms of polystyrene) is preferably in the range of 50,000 to 200,000, and preferably in the range of 70 to 150,000. When the molecular weight is less than 50,000, the mechanical properties are deteriorated and the protective film is apt to crack, which is not suitable as a coating material. On the contrary, when the molecular weight exceeds 200,000, the protective film is colored unfavorably and the weather resistance is deteriorated, and in this case also, it is not suitable as a coating material.

The α-methylstyrene copolymer used in the present invention is an α-methylstyrene copolymer containing an α-methylstyrene unit. From the viewpoint of transparency, hardness, adhesion, etc., α-methylstyrene and (meth) acrylic are used. Copolymers with acid esters are preferred. Specifically, a composition range in which 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 to 30% by weight. And the proportion of α-methylstyrene units is preferably 15 to 28% by weight, the proportion of methyl methacrylate units is 50 to 80% by weight, and the proportion of monomer units copolymerizable therewith is 0 to. 20% by weight. If the proportion of α-methylstyrene units contained in this 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 a farastic substrate, it will change over time. Cracks may occur in the steel, resulting in poor mechanical strength. Similarly, if the proportion of methyl methacrylate units is less than 40% by weight, the mechanical strength will be poor, and if it exceeds 90% by weight, the heat resistance will be 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, etc., as well as ethyl acrylate, propyl acrylate, n-butyl acrylate, Acrylic esters such as isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, and benzyl acrylate, ethyl methacrylate, propyl methacrylate,
Examples thereof include methacrylic acid esters such as n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate.

The α-methylstyrene copolymer used in the present invention can be produced by a differential polymerization method such as continuous bulk polymerization or continuous solution polymerization using a complete mixing type reactor. When an α-methylstyrene-based copolymer is produced by this differential polymerization method, its composition and molecular weight become uniform,
This is preferable because it gives a good appearance, but the present invention is not limited to this, and batch polymerization or solution polymerization is also possible. Further, a rubber component such as polybutadiene can be added when producing the α-methylstyrene copolymer used in the present invention. And, as the polymerization initiator used in producing the α-methylstyrene-based copolymer, a peroxide and / or an azo compound used in ordinary radical polymerization can be used, and in order to control the molecular weight. It is also possible to add an appropriate amount of a chain transfer agent such as alkyl mercaptan.

The α-methylstyrene copolymer used in the present invention preferably has a transparency of 80% or more in total light transmittance and a pencil hardness of 3H or more.
If the transparency is less than 80% in total light transmittance, it is not suitable as a transparent thermoplastic coating material, and if the hardness is less than 3H in pencil hardness, the effect of modifying the surface hardness of the plastic base material by the coating is improved. poor.

Various additives may be added to the α-methylstyrene copolymer used in the present invention within a range not impairing transparency and other necessary properties. Examples of such additives include, for example, n-octadecyl-3- (3 ', 5'-di-tert-butyl-
4'-hydroxyphenyl) propionate, pentaerythrityl-tetrakis [3- (3,5-di-tert.
-Butyl-4-hydroxyphenyl) propionate]
Hindered phenolic compounds such as Tris (2,4
-Di-tert-butylphenyl) phosphite and other phosphite compounds, and tetrakis [methylene-3-
(Dodecylthio) propionate] methane and other thioether compounds, etc., flame retardants such as tetrabromobisphenol A, decabromodiphenyl oxide and other bromine compounds, and antistatic agents such as the Electrostopper series [Kao] (stock)
], Daspar series [Miyashi Yushi Co., Ltd.], TB
-123, TB-128 [manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.] and the like can be mentioned. In addition, it is possible to add a dye or the like for coloring, if necessary.

In the coating material of the present invention, the resin layer made of the α-methylstyrene copolymer has a thickness of 5 to 300 μm, preferably 40 to 150 μm.
If the film thickness of the α-methylstyrene copolymer resin layer is less than 5 μm, the surface hardness of the plastic base material is affected, so that a resin molded product with improved surface hardness cannot be obtained.
On the contrary, even if the film thickness exceeds 300 μm, the surface hardness is not improved, and the melt pressure bonding condition becomes severe.

The (meth) acrylic acid ester-based thermoplastic resin used in the present invention is substantially free of α-methylstyrene units, preferably transparent and T
g is 120 ° C. or less. If Tg is higher than 120 ° C., the melt pressure bonding condition becomes high, which is disadvantageous.

The (meth) acrylic acid ester-based thermoplastic resin film used in the present invention has a thickness of 2 to 200.
μm, preferably about 20 to 100 μm.
If the film thickness is less than 2 μm, the surface hardness of the plastic substrate is affected, and a resin molded product having a sufficiently improved surface hardness cannot be obtained. On the contrary, even when the film thickness exceeds 200 μm, the surface hardness is not improved, and the melt pressure bonding condition becomes strict. For such a (meth) acrylic acid ester-based thermoplastic resin film, those having excellent adhesiveness to a plastic substrate such as α-methylstyrene-based copolymer and polycarbonate are preferable. Specific examples thereof include a copolymer mainly composed of polymethylmethacrylate such as polymethylmethacrylate or a methylmethacrylate-styrene random copolymer resin.

In the coating material of the present invention, one surface of the coating material is an α-methylstyrene copolymer resin film, and the other surface is substantially free of α-methylstyrene unit (meth) acrylic acid ester-based polymer film. As long as it is a plastic resin film, the (meth) acrylic acid ester-based thermoplastic resin film which does not substantially contain the α-methylstyrene unit used in the present invention may be a single film or a laminated film. Alternatively, a composite or coextruded film with another film can be used.

As a method of coating the coating material of the present invention on a plastic substrate, a method of producing a film of the coating material and subjecting the film to the substrate by heat and pressure and melt-pressing is preferable. And
When heat and pressure are applied to the base material and the film in this way, the film used for coating is produced by melting the coating material using an extruder or the like and then discharging it from a die, or coating. For example, a method of dissolving the material in a solvent such as chloroform and casting it thinly, and then removing the solvent by vacuum drying or the like is possible.
Further, in the method of coating the coating material on the plastic substrate, it is also possible to directly apply the solution of the resin constituting the coating material directly on the substrate and remove the solvent by a method such as vacuum drying. Further, if necessary, it is possible to further apply heat and pressure after removing the solvent. The substrate can also be coated by a method of coextrusion of the coating material of the present invention and the substrate such as multilayer extrusion.

Examples of plastic substrates for resin molded articles coated with the coating material of the present invention include polycarbonate, polyarylate, polyamide, polystyrene, polymethylmethacrylate, ABS resin, polypropylene and styrene-butadiene copolymer. Mention may be made of thermoplastics. In particular, polycarbonate has high impact resistance, is excellent in transparency and heat resistance, and also has good adhesion to the coating material of the present invention, so that the surface hardness without impairing the excellent properties of these polycarbonates. It is preferable in that it can improve. When polycarbonate is used as the plastic substrate, the coating material of the present invention has excellent adhesion to the polycarbonate, so that it is not necessary to use an adhesive agent. However, the adhesiveness with the coating material of the present invention may be insufficient depending on the type of the plastic substrate, and in such a case, the adhesiveness can be improved by using an adhesive.

The resin molded article coated with the coating material of the present invention may be in the form of a plate, a hollow container, a cylinder or the like, and its shape is not limited. A suitable coating method can be selected from the above-mentioned coating methods depending on the shape of the plastic substrate. When the method of applying the coating material to the base material by applying heat and pressure is adopted, the shape of the base material is preferably a plate shape.

[0022]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, each evaluation was performed using the following method. (1) Surface hardness The surface hardness was evaluated in accordance with a pencil scratch test corresponding to JIS K5400 (General paint test method). (2) Peel Strength (Adhesion) a) Goosense Tape Peeling Test: This was performed in accordance with the goosen eye tape peeling method corresponding to JIS K5400 (General test method for coating materials). In other words, 1 mm x on the cured film formed on the polycarbonate resin plate.
100 pieces of 1 mm squares were made, an adhesive tape was attached to this, and the adhesive tape was rapidly peeled off, and the number of squares that the coating material of the present invention did not peel off from the polycarbonate substrate was obtained and evaluated. b) Boiling water resistance test: After performing the agglomerate tape peeling test of a) above, JI
A boiling water resistance test is performed in accordance with a boiling water resistance test method corresponding to SK5400 (paint general test method).
An adhesive tape was attached to this, and the adhesive tape was rapidly peeled off, and the number of streaks in which the coating material of the present invention did not separate from the polycarbonate substrate was determined and evaluated.

Example 1 A PMMA film having a surface hardness of 2H and a total light transmittance of 95% on a polycarbonate substrate having a total light transmittance of 90% and a thickness of 2 mm (trade name of Kanegafuchi Chemical Industry Co., Ltd .: (Sanjuren, film thickness 30 μm), and the weight average molecular weight is 120,000, the proportion of α-methylstyrene units is 25% by weight, the proportion of methyl methacrylate units is 75% by weight, and the surface hardness is 4H, α-methylstyrene-methyl methacrylate copolymer resin film with a total light transmittance of 95% is adhered, and melt-pressed for 5 seconds at a temperature of 140 ° C. and a pressure of 31.5 kg / cm ² for surface hardening. The obtained polycarbonate plate was obtained. With respect to the polycarbonate plate thus obtained, its surface hardness and peel strength were evaluated by the methods described above. The results are shown in Table 1.

Examples 2 to 4 Examples 2 and 3 are the same as the above Examples except that the film thickness of the α-methylstyrene-methyl methacrylate copolymer resin film and the melt pressure bonding conditions were changed as shown in Table 1. A surface-hardened polycarbonate plate was obtained in the same manner as in 1. Also,
In Example 4, a PMMA film (trade name: manufactured by Mitsubishi Rayon Co., Ltd.) having a surface hardness of 2H and a total light transmittance of 95%.
A surface-hardened polycarbonate plate was obtained in the same manner as in Example 1 except that acryprene and a film thickness of 30 μm) were used. The surface hardness and the peel strength of the obtained polycarbonate plates of Examples 2 to 4 were evaluated by the methods described above. The results are shown in Table 1.

Comparative Examples 1 to 4 In the case where the PMMA film was not included and the case where the α-methylstyrene-methyl methacrylate copolymer resin film was not included, a surface-hardened polycarbonate plate was prepared in the same manner as in Example 1 above. Obtained. Comparative Examples 1 to 1 obtained
The surface hardness and the peel strength of the polycarbonate plate of No. 4 were evaluated by the methods described above. The results are shown in Table 1.

In each of the examples and comparative examples, the transparency was 80% or more in total light transmittance.

[0027]

[Table 1]

[0028]

INDUSTRIAL APPLICABILITY The coating material of the present invention is particularly useful for use as a laminated film for improving the surface hardness and abrasion resistance of a plastic substrate, and simply press-bonding or welding without providing a primer layer as in the conventional case. It is possible to obtain a surface-cured resin molded product by simply doing so, which is extremely useful industrially.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ikuo Yamaoka 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa, Nippon Steel Corporation Advanced Technology Research Laboratories (72) Masao Kimura Ida, Nakahara-ku, Kawasaki-shi, Kanagawa 1618, Nippon Steel Corporation Advanced Technology Research Laboratories

Claims (4)

[Claims] 1. A heat comprising a (meth) acrylic acid ester-based thermoplastic resin film having an α-methylstyrene copolymer resin layer on the surface thereof and substantially not containing an α-methylstyrene unit. Coating material for coating on plastics. 2. The α-methylstyrene copolymer has a weight average molecular weight in the range of 5 to 200,000, an α-methylstyrene unit ratio of 10 to 40% by weight, and a methyl methacrylate unit ratio of 40 to 90% by weight. The coating material according to claim 1, wherein the proportion of monomer units copolymerizable with these is 0 to 30% by weight. 3. A resin molded product obtained by coating the surface of a transparent thermoplastic base material with the coating material according to claim 1. 4. The resin molded article according to claim 3, wherein the transparent thermoplastic is polycarbonate.