JPH0255219B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a laminate, particularly a crosslinked laminate having excellent adhesive strength, heat resistance, etc. [Prior art] In recent years, in order to expand the uses of synthetic resin foams,
Various studies are being conducted to take advantage of the excellent properties of synthetic resin foams, such as heat insulation and heat retention, and elasticity, while also adding various functions such as heat resistance and gas barrier properties. The present inventors have developed a food container made of a polystyrene foam sheet laminated with a polybutylene terephthalate resin film or a polymethylpentene resin film (Utility Model Application No. 59-24281, Utility Model Application No. 59-24282).
We have previously proposed a packaging material (Japanese Utility Model Application Publication No. 123225/1983) in which a polystyrene resin foam sheet and a crosslinked polyolefin foam are laminated.
These laminated foam sheets and other films were laminated by heat fusion or dry lamination using an adhesive. [Problem to be solved] However, when using a crosslinked resin as in the latter case, the crosslinked resin has low thermal adhesiveness;
Since it is difficult to laminate the laminate by heat fusion, and the adhesive strength of the obtained laminate is low, it has been difficult to apply it to uses such as containers. In particular, when both were crosslinked resins, lamination by heat fusion could hardly be achieved. In addition, resins that do not exhibit any heat fusibility (for example,
When laminating films (polypropylene resin, polyethylene resin, saturated polyester resin, polyamide resin, etc.) by heat fusion, there are not only the same problems as above, but also the resin films that can be used are limited, making it difficult for various applications. The disadvantage was that it could not be adapted to On the other hand, when using resin films that do not exhibit heat-bonding properties, lamination is also carried out using regular adhesives or hot-melt adhesives such as EVA-based adhesives to obtain high heat-bonding properties. However, these adhesives, especially the latter, have extremely low heat resistance and therefore cannot be used in applications requiring heat resistance. Furthermore, since the main material is a polystyrene resin foam sheet that has poor heat resistance, oil resistance, etc., it has not been possible to fundamentally solve the heat resistance and other problems. The present invention was made in order to solve the above-mentioned conventional problems, and provides a method for manufacturing an inexpensive laminate that has high adhesive strength and excellent properties such as heat resistance, rigidity, oil resistance, and moldability. The purpose is to provide. [Means for Solving the Problems] The present invention involves bonding a paramethylstyrene resin foam sheet and a thermoplastic resin film by thermal fusion.
Alternatively, the above problems can be solved by laminating them using an adhesive and irradiating them with radiation. Hereinafter, a method for manufacturing a crosslinked laminate according to the present invention will be explained. Paramethylstyrene resin, which is the material for paramethylstyrene resin foam sheets, is a homopolymer of paramethylstyrene monomer, a copolymer with other monomers, or a mixture of these polymers and other polymers. be done. Monomers that can be copolymerized with paramethylstyrene monomer include styrene monomers such as styrene and α-methylstyrene, acrylic monomers such as methacrylic acid, methyl methacrylate, ethyl acrylate, and acrylonitrile, and olefinic monomers such as butadiene. , maleic anhydride, and the ortho or meta isomer contained in industrial products of paramethylstyrene monomer can also be used. These copolymers preferably contain 30% by weight or more of paramethylstyrene in order to facilitate the crosslinking reaction described below. When using a mixed resin, add 50% by weight of the above-mentioned para-methylstyrene homopolymer or copolymer to other polymers such as polystyrene resin, ABS resin, polyphenylene ether resin, or polyvinyl chloride resin. A mixture of the above, or a mixture containing 15% by weight or more of the paramethylstyrene component in the mixed resin is preferred. As shown in the table below, such paramethylstyrene resins have a higher glass transition temperature and higher softening point than polystyrene resins, are thermally stable, and have high hardness and rigidity. Moreover, because the specific gravity is low and the softening point is high, the production volume per unit weight can be increased.
Furthermore, since the cooling time after molding can be shortened, the productivity of the foamed sheet is good. It also has moldability.

[Effect]

Paramethylstyrene resin, which is the material for paramethylstyrene resin foam sheets, is more easily crosslinked by radiation irradiation than polystyrene resin, and also has superior properties such as heat resistance. After laminating a foam sheet made of para-methylstyrene resin with these characteristics and a thermoplastic resin film, radiation is irradiated, which crosslinks the foam sheet and improves various properties such as the heat resistance. do. In addition, since the layers are laminated by heat fusion or using an adhesive and then irradiated with radiation, there is no need to use pre-crosslinked resin films, and various thermoplastic resin films that cannot be heat fused can also be used. can. Furthermore, even if a hot-melt adhesive or the like having extremely low heat resistance is used, the adhesive layer will also be crosslinked because it is irradiated with radiation after lamination.
In this case, a crosslinking reaction also occurs between each layer. Therefore, when a thermoplastic resin film or a radiation-reactive adhesive that is crosslinked by radiation is used, the result is an integrally crosslinked laminate. In addition, when laminated by heat fusion or using a solvent-free adhesive, gas accumulation does not occur between each layer due to heat generation due to radiation irradiation, etc.
Great lamination integrity. As the thermoplastic resin film, those having various properties such as gas barrier properties can be used, and since it is possible to have a single layer or multiple layers, various functions can be imparted to the laminate. Furthermore, the degree of crosslinking can be arbitrarily adjusted by combining conditions such as the type of film, crosslinking aid, and radiation dose. Furthermore, foam sheeting and lamination can be carried out by ordinary methods without requiring any special measures, and since radiation, which is a high-energy beam, is used, the crosslinking rate is high. [Example] Example 1 One side of an extruded foam sheet of para-methylstyrene resin with a foaming ratio of 8 times and a thickness of 1.9 mm is 100 μm thick.
A high impact polystyrene (HIPS) film was heat laminated and then irradiated with a 50 Mrad electron beam. The thus obtained laminate has a paramethylstyrene resin foam sheet with a gel fraction of 68%.
The gel fraction of the HIPS film was 0% (gel fraction is the weight percent of insoluble matter after extraction with boiling toluene for 10 hours). In addition, as for heat resistance, the dimensional change rate when heated at 110° C. for 2 minutes was investigated for the laminate before and after electron beam irradiation, and the results shown in the table below were obtained.

〔Effect of the invention〕

According to the crosslinked manufacturing method according to the present invention, since the paramethylstyrene resin foam sheet is crosslinked, a laminate having various properties such as heat resistance, oil resistance, and rigidity can be obtained. Moreover, since the foamed sheet and thermoplastic resin film are laminated by heat fusion or using an adhesive and then irradiated with radiation, a crosslinking reaction occurs between each layer, which is difficult to achieve with conventional heat fusion and increases the adhesive strength. It is possible to use various thermoplastic resin films that could not be used due to their small adhesive properties, and a laminate with high adhesive strength can be obtained. Furthermore, even if a hot melt adhesive or the like having extremely low heat resistance is used, the heat resistance, rigidity, etc. are further improved because these are also crosslinked. In particular, when using thermoplastic resin films or radiation-reactive adhesives that are crosslinked by radiation, crosslinking reactions occur between each layer and between each layer, resulting in crosslinking and improving adhesive strength, heat resistance, oil resistance, rigidity, etc. Various characteristics become significantly larger. In addition, the crosslinked laminate has high integrity for the above reasons, and the film does not locally thin or break during thermoforming, so it has good thermoformability, and various types of films can be used as the film. can. Since various thermoplastic resin films can be used in this manner, various functions can be imparted to the laminate, and the laminate can be applied to a wide variety of uses. Further, since the degree of crosslinking of the laminate can be adjusted arbitrarily, the laminate can be formed depending on the application. Furthermore, the para-methylstyrene resin, which is the material for the foam sheet, has a low specific gravity and a high softening point, so the productivity of the foam sheet is high, and the lamination process can be carried out using normal methods, and it can be easily processed by irradiation with radiation. The crosslinking reaction occurs quickly and can be carried out at high speeds, and since the crosslinking is carried out by irradiating radiation after lamination, it is more economical than individually crosslinking in advance, and radiation can be applied in a line consistent with the lamination process. Since it can be irradiated and is more economical, it is possible to provide an inexpensive crosslinked laminate suitable for mass production. In particular, when a radiation-reactive adhesive is used, the lamination process and the entire crosslinking of the laminate can be performed simultaneously, so it has excellent properties and is economical and inexpensive. The crosslinked laminate obtained by the present invention is suitable for use as a material for automobile ceilings, food containers that require heat resistance, and various containers such as fruit trays.

Claims (1)

[Claims] 1. A crosslinked laminate characterized in that a paramethylstyrene resin foam sheet and a thermoplastic resin film are laminated by heat fusion or using an adhesive, and then irradiated with radiation. manufacturing method. 2. A patent claim in which the thermoplastic resin film is a film made of a resin selected from polyolefin resins, polyvinyl chloride resins, polyvinylidene chloride resins, saturated polyester resins, polyamide resins, polycarbonate resins, and polystyrene resins. A method for producing a crosslinked laminate according to item 1.