JPS5933130B2 - Surface treatment method for styrene resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface treatment of plastic molded products made of polystyrene, and particularly to a method for producing plastic molded products having excellent hardness and aesthetic appearance.

Polystyrene resin has excellent moldability, and the resulting molded products are also transparent and beautiful, and are used in a variety of fields, but their soft surface makes them susceptible to sticking and abrasion. Therefore, the ease with which polystyrene molded products are damaged has become a major drawback, and the emergence of a method for improving the surface properties of polystyrene molded products has been eagerly awaited.

To achieve this purpose, a method has been developed in which a thermosetting resin is dissolved in an organic solvent and then heat treated to produce a polystyrene resin molded product with a wear-resistant film. Since the softening point is lower than the crosslinking start temperature of the thermosetting resin, the polystyrene molded product deforms when the above-mentioned crosslinked and cured film is formed on the surface of the polystyrene molded product, making it difficult to produce the desired molded product. . In addition, methods using electron beams or ultraviolet rays as a crosslinking energy source for the coating film have been studied to form a cured coating film;
These methods have the disadvantage that it is not possible to produce a cured coating film with sufficient adhesion, and that it peels off due to impact or abrasion. Therefore, the inventors of the present invention conducted a detailed study to obtain a polystyrene molded product with a cured coating without the above-mentioned disadvantages, and found that the surface of the styrene resin molded product that needs to be painted is treated in advance by irradiation with a specific amount of ultraviolet rays at a specific amount of energy. Then, a specific solvent-free paint is applied and cross-linked and cured by irradiation with the above-mentioned light, resulting in a product that has high hardness without impairing the properties of the styrene resin and has good adhesion to the styrene resin. A styrenic resin product with an excellent appearance protected by a coating film has been obtained.

That is, in the present invention, the surface of a styrene-based resin molded product that requires painting is irradiated in advance with light from a high-pressure mercury lamp with a wavelength of 2,000 to 8,000λ so that the irradiation amount is in the range of 5 x 102 to 5 x 104 watt seconds/m, and then styrene, which is coated with a solvent-free paint mainly containing a compound having two or more polymerizable unsaturated groups in one molecule and a photopolymerization initiator, and subjected to cross-linking and curing treatment by irradiation with the above-mentioned light beam. It is in the surface processing method of resins.

Wavelengths of 2000 to 800 when carrying out the present invention
When irradiating an unpainted styrene resin molded product with a 0λ light beam, a light beam with a wavelength of less than 2000λ is easily affected by the gas in the irradiation atmosphere, making it difficult to bring out the desired irradiation effect. However, it is difficult to bring out the effect of treating styrene-based resin molded products with light, that is, the effect of improving the adhesion of the cured film to the styrene-based resin molded product.

Furthermore, if the amount of irradiation of the light beam to the styrene-based resin molded product is too small, the effect will not be sufficient, and if it is too large, the properties of the styrene-based resin will tend to deteriorate, so it is not preferable. It is preferable to set the light amount to 102 to 5×104 watt seconds/wl.

If the amount of light is less than 5 x 102 watts/d, it is difficult to fully bring out the effects of the present invention, while if the amount of light is more than 5 x 104 watts/d, the styrene resin in the cured film will be damaged. This is not preferable because the adhesion of the base material tends to deteriorate, and the properties of the base material itself also tend to deteriorate. Furthermore, if the treatment is left for too long after the light irradiation treatment, the treatment effect tends to be reduced, so it is preferable to form the crosslinkable film within one day and night after the light irradiation treatment. In the present invention, it is necessary to use a high-pressure mercury lamp as an ultraviolet generating device, and by using this device, ultraviolet irradiation treatment can be performed for several seconds, and as a result, deterioration of the properties of the styrene resin can be prevented.

Furthermore, a low-pressure mercury lamp requires a long irradiation time, which is not preferable. Compounds that can be crosslinked and cured by light irradiation that can be used to form a crosslinked and cured film on styrene resin treated with light rays mainly include compounds that have two or more polymerizable unsaturated groups in one molecule. Specific examples of these include ethylene glycol diacrylate or dimethacrylate, diethylene glycol diacrylate or dimethacrylate, triethylene glycol diacrylate or dimethacrylate, tetraethylene glycol diacrylate or dimethacrylate, propylene glycol diacrylate or dimethacrylate. methacrylate, butylene glycol diacrylate or dimethacrylate, pentanediol diacrylate or dimethacrylate, hexanediol diacrylate or dimethacrylate, bisphenol A dioxyethyl ether diacrylate, bisphenol A dioxypropyl ether dimethacrylate, glycerin diacrylate or Dimethacrylate, glycerol triacrylate or trimethacrylate, trimethylolpropane diacrylate or dimethacrylate, trimethylolpropane triacrylate or trimethacrylate, pentaerythritol diacrylate or dimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate or tetramethacrylate, dimethacrylate glycerin tetraacrylate or tetramethacrylate, dipentaerythritol hexaacrylate or hexamethacrylate, neopentyl glycol diacrylate or methacrylate, addition reaction products of acrylic or methacrylic acid with glycidyl acrylate or methacrylate, diacrylate or dimethacrylate of dievoxy compounds, di- or tri-acrylates of triepoxy compounds, or di- or trimethacrylates, di-, tri-, or tetraacrylates of tetraepoxy compounds;
Alternatively, di-, tri-, or tetra-methacrylate can be mentioned.

Specific examples of epoxy compounds used as starting materials for obtaining the above-mentioned unsaturated compounds include bisphenol A;
and epichlorohydrin or methylepichlorohydrin, commercially available products include Kohon 562 and Kohon 82.
8, Kohon 834, Kohon 864, Kohon 1001, Kohon 1004 (manufactured by Ciel Chemical Co., Ltd.), dicarboxylic acid,
For example, diglycidyl esters such as adipic acid, sebacic acid, and phthalic acid; trimethylolproban triglycidyl ether; pentaerythritol tetraglycidyl ether; Mention may be made of drying or drying oils, polyepoxy compounds having an epoxy equivalent weight of about 100 to about 1000, such as epoxidized polybutadiene.

Other urethanized di-, tri-, or tetra-acrylates or methacrylates can be used in the same way, and these compounds have a diisocyanate content per mole of hydroxyl group of the di-, tri-, or tetrapolyol used in producing the polyol diacrylates. and hydroxyl group-containing vinyl monomers such as hydroxyethyl acrylate and hydroxypropyl methacrylate in a proportion of 1 mole each.

Furthermore, repeating units of diols and dicarboxylic acids are 1 to 1.
Polyester diacrylates or methacrylates with a degree of condensation of 20 can also be used. The coating material used in the practice of the present invention contains a photopolymerization initiator capable of crosslinking and curing the coating material by irradiation with the above-mentioned light, such as benzoin,
It is necessary to add benzoin methyl ether, benzoin ethyl ether, benzophenone, Michler's ketone, acetophenone, diethoxyacetophenone, etc. in a proportion of 0.5 to 10% by weight.

These paints can also be used as clear paints, but even if pigments, especially flat metal powders or flat particles, are used as pigments to form a metallic-like hardened film, they will not produce a coated product with a sufficiently cross-linked hardened film. It is preferable because it can be done. Specific examples of these metallic pigments include metal powders obtained by flattening aluminum, stainless steel, bronze, copper, etc., colored mica, and fine powders of films processed by metal vapor deposition or sputtering. The present invention has a high industrial value because it allows relatively easy surface treatment of styrenic resins, especially surface hardening treatment, which was thought to be extremely difficult.

The present invention will be explained in more detail with reference to Examples below.

Example 1 A styrene resin plate was pretreated by irradiation with ultraviolet rays under the conditions shown in Table 1, and then treated with 50 parts of acrylic acid adduct of epoxy resin (Ebicoat #828, manufactured by Ciel Chemical Co., Ltd.) and trimethylolpropane triacrylate. 30 copies, 1
・Apply a transparent coating material consisting of 20 parts of 6-hexanediol diacrylate and 5 parts of benzoin methyl ether to a thickness of about 10μ, and give 80 Watts/CT! Ultraviolet rays were irradiated for 5 seconds using an L high-pressure mercury lamp.

Table 1 summarizes the surface hardness and coating film adhesion measurement results of the surface-treated styrene resin plate obtained.

As is clear from Table 1, the surface-treated styrene resin plate obtained by the method of the present invention exhibits excellent performance.
Adhesion is 1m! This refers to the number of coated films in which no abnormality was observed after 100 spaced grids were made and the cellophane tape was peeled off.

Example 2 A styrene resin plate with an ultraviolet intensity of 5 x 104 watts/m
50 parts of urethane acrylate, 15 parts of pentaerythritol tetraacrylate, obtained by addition reaction with bisphenol A dioxypropyl ether, xylylene diisocyanate, and 2-hydroxyethyl acrylate after irradiation treatment to obtain an ultraviolet irradiation amount of 100 parts of a resin composition (a) consisting of 35 parts of 1,4-butanediol diacrylate and 5 parts of benzophenone was kneaded with 5 parts of talc and 5 parts of phthalocyanine blue to obtain a colored resin.This colored resin was screen printed on 250 meshes. After printing using a press, a printing plate with good adhesion was obtained when irradiated with ultraviolet rays for 3 seconds using a high-pressure mercury lamp of 80 W/CTL.

Example 3 Epoxy resin (Epicote #828, manufactured by Ciel Chemical Co., Ltd.)
50 parts of an acrylic acid adduct of A low-foamed polystyrene extrusion molded product made by adding 7% by weight of aluminum paste to a resin composition was pretreated with ultraviolet light under the conditions shown in parentheses in Table 1, and the product was coated with about 17 μm of aluminum paste. 80 Watts/C after applying to
After irradiating with ultraviolet rays for 3 seconds using a 7 rL high-pressure mercury lamp, the product was further irradiated with light emitted from the high-pressure mercury lamp for 3 seconds in water, resulting in a metallic finished painted product with a crosslinked film with excellent adhesion and hardness. It was done.

Claims (1)

[Claims] 1. The surface of the styrene resin molded product that needs to be painted is coated with a wavelength of 200 in advance.
The irradiation amount is 5x from a high-pressure mercury lamp of 0 to 8000 Å.
Irradiation treatment is carried out so that the radiation rate is within the range of 10^2 to 5 x 10^4 watts/m^2, and then a compound having two or more polymerizable unsaturated groups in one molecule and a photopolymerization initiator are added. A method for surface treatment of styrenic resin, which is characterized by applying a solvent-free paint and subjecting it to cross-linking and curing treatment by irradiating it with the above-mentioned light beam. 2. As a solvent-free paint applied to styrenic resin molded products that have been subjected to light irradiation treatment, a paint mainly containing a compound having two or more polymerizable unsaturated groups in one molecule, a photopolymerization initiator, and a metallic pigment is used. 2. A method for surface treatment of styrenic resin according to claim 1, characterized in that the styrenic resin is coated and treated with light irradiation. 3 Wavelength 2000 as the curing treatment condition for the applied paint
After first irradiating a light beam of ~8000 Å in an air atmosphere,
3. The method for surface processing a styrenic resin according to claim 1 or 2, characterized in that the method uses the condition of irradiating the light beam in water.