JPS6140146A - Manufacture of crosslinked laminate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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.

[Conventional technology]

In recent years, in order to expand the uses of synthetic resin foams, it has been necessary to take advantage of the excellent properties of synthetic resin foams such as heat insulation, heat retention, and elasticity, while also adding various functions such as heat resistance and gas barrier properties. has been studied in various ways.

The present inventors developed a food container (Utility Application No. 59-2
Publication No. 4281.

Japanese Utility Model Application Publication No. 59-24282) and a packaging material in which a polystyrene resin foam sheet and a crosslinked polyolefin foam are laminated (Japanese Utility Model Application Publication No. 57-123225) were previously proposed. These laminated foam sheets and other films were laminated by thermal bonding or dry lamination using an adhesive.

[Problem to be solved]

However, when using a crosslinked resin like the latter, the crosslinked resin has low heat fusion properties, so it is difficult to laminate by heat fusion, and the adhesive strength of the obtained laminate is low. It was difficult to apply it to uses such as containers.

In particular, when both were crosslinked resins, lamination by thermal fusion could hardly be achieved.

In addition, when laminating films of resins that do not exhibit any thermal bonding properties (e.g., polypropylene resin, polyethylene resin, saturated polyester resin, polyamide resin, etc.) by thermal bonding, the same problems as above occur as well. However, since the resin film used is limited, it has the disadvantage that it cannot be applied to various uses.

On the other hand, when using a resin film etc. that does not exhibit heat-fusibility, ordinary adhesives or EVA to obtain high heat-fusibility are used.
Lamination has also been carried out using hot-melt adhesives such as A-based adhesives, but these adhesives, especially the latter, have extremely low heat resistance, so they cannot be used in applications that require heat resistance. there were.

In addition, 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 to solve the above-mentioned conventional problems, and has high adhesive strength, heat resistance, and rigidity.

The purpose of the present invention is to provide an inexpensive method for producing a laminate with excellent properties such as oil resistance and moldability.

[Means for solving problems]

The present invention solves the above problems by laminating a paramethylstyrene resin foam sheet and a thermoplastic resin film and then irradiating them with radiation such as an electron beam.

Further, more preferably, a thermoplastic resin film or a specific thermoplastic resin film that can be crosslinked by radiation irradiation,
After lamination is performed by thermal fusion or by using a radiation crosslinkable or curable radiation-reactive adhesive, radiation is irradiated.

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. is used.

Examples of monomers that can be copolymerized with paramethylstyrene monomers include styrene monomers such as styrene and σ-methylstyrene, methacrylic acid, methyl methacrylate, and ethyl acrylate.

Acrylic thread additives such as acrylonitrile or olefinic monomers such as butadiene.

Various monomers may be mentioned, such as maleic anhydride, and the ortho or meta isomers contained in commercial products of paramethylstyrene monomer can also be used.

These copolymers preferably contain para-methylstyrene in an ao weight % or more in order to facilitate the crosslinking reaction described below.

When using a mixed resin, add 50% by weight of the homopolymer or copolymer of para-methylstyrene mentioned above to other polymers such as polystyrene resin, ABS resin, polyphenylene ether resin, or polyvinyl chloride resin. It is preferable to use a mixture of the above, or a mixture in which the paramethylstyrene component is contained in the mixed resin in an amount of 15% by weight or more.

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. Furthermore, since the specific gravity is low and the softening point is high, the production amount per unit weight can be increased and the cooling time after molding can be shortened, so the productivity of the foamed sheet is good. It also has moldability.

Using such a paramethylstyrene resin, it is made into a foamed sheet using an extrusion foaming means or the like in order to impart heat insulation and heat retention properties, elasticity, and the like.

In this case, volatile organic substances such as propane, butane, dichlorofluoromethane, or carbon dioxide, by heating azodicarbonamide, azodicarbonamide, etc.
A chemical blowing agent that generates an inorganic gas such as nitrogen can be used as appropriate depending on the purpose. Inorganic fillers such as talc, silica, and calcium carbonate can also be used as appropriate.

The paramethylstyrene resin foam sheet made into a foam sheet in this way has an expansion ratio of 1.5 to 40 times and a thickness of 0.
．． 5 to 8I++++++ is preferred.

If the foaming ratio is less than 1.5 times, the insulation and heat retention properties and elasticity will not be sufficient, and if it exceeds 40 times, the rigidity, strength, etc. will be insufficient. If the thickness is less than 0.5 mm, the heat insulation, elasticity, or strength will be low, and if the thickness exceeds 0.5 mm, the thermoformability will be poor, making it difficult to form into a container shape, and it will be uneconomical.

Such foaming ratio and thickness can be arbitrarily set by changing extrusion foaming conditions such as the amount of foaming agent and mold dimensions.

In addition, the thermoplastic resin film laminated on the paramethylstyrene resin foam sheet is used to impart various properties to the laminate, such as gas barrier properties and oil resistance.
Materials are used depending on the purpose.

Among the resins that are the raw materials for thermoplastic resin films, those with gas barrier properties include polyolefin resins such as polyethylene resin, polypropylene resin, and polymethylpentene resin, polyvinyl chloride resin, polyvinylidene chloride resin, and polyethylene resin. Saturated polyester resins such as terephthalate and polybutylene terephthalate, and polyamide resins such as 6-6 nylon are preferred. Further, as those exhibiting oil resistance and heat resistance, polymethylpentene resins, saturated polyester resins, and polycarbonate resins are preferred. In addition to the polycarbonate resins mentioned above, polystyrene resins such as polyphenylene ether resins, polystyrene resins, and paramethylstyrene resins are examples of materials that have rigidity and shape retention. Polystyrene resins such as polystyrene, stretched polystyrene film, and stretched para-methylstyrene film are preferred.

Other acrylic resins such as polymethyl methacrylate and polyacrylonitrile, and ABS resin.

Various thermoplastic resins such as ethylene-vinyl acetate copolymer (EVA) and polyurethane resin can be used.

A thermoplastic resin film made of these resins is laminated onto the paramethylstyrene resin foam sheet by various laminating means.

Various lamination methods such as dry lamination and extrusion lamination can be used, but if water-based or ordinary organic solvent-based adhesives are used, heat resistance may decrease due to residual solvent, or temperature rise or oral This is undesirable because it causes gas to accumulate between the layers, so it is better to laminate by heat fusion (so-called heat lamination) or by using a solvent-free adhesive such as a hot-melt adhesive, especially a radiation-reactive adhesive. .

In the case of thermal fusion, either the paramethylstyrene resin foam sheet or the above thermoplastic resin film may be laminated in a molten state, or they may be laminated together in a molten state as in a coextrusion method. . In addition, the solvent-free adhesive is mainly EVA, with polyethylene resin,
Various hot-melt adhesives containing resins exhibiting tackifier properties are preferable from the viewpoint of workability, and acrylic resins, vinyl resin oligomers, epoxy acrylates, urethane acrylates, polyester acrylates, liquid polybutadiene, etc. Also preferred are radiation crosslinkable oligomers such as. Note that the above-mentioned hot-melt adhesive mainly composed of EVA can also be cured by radiation and is included in the radiation-reactive adhesive.

Further, the thermoplastic resin film may be laminated on at least one side of the foamed paramethylstyrene resin sheet, and may be laminated on both sides depending on the application. One or more thermoplastic resin films may be laminated in combination, and when the film layers are multilayered, two or more functions can be imparted to the laminate.

The thus laminated composite sheet is irradiated with radiation in order to further improve its properties such as heat resistance, oil resistance, and rigidity. Radiation irradiation is carried out at least in the process after lamination and before the thermoforming process, during the thermoforming process, or after the thermoforming process.

In addition, when crosslinking is performed before lamination, there is a drawback that the adhesive strength of the composite sheet is low.

On the other hand, those that are cross-linked after lamination and before molding process, even if the thermoplastic resin film is made of polyethylene resin, which has high plasticity and is prone to breakage during molding process.
Since it is crosslinked and has a high adhesive strength with the paramethylstyrene resin foam sheet, it can be thermoformed without any problems.

In this case, if the degree of crosslinking, which will be described later, is too large, thermoforming becomes difficult, so it is necessary to adjust the degree of crosslinking.

Further, during or after thermoforming, the degree of crosslinking can be adjusted to any desired degree depending on the application.

Note that radiation may be preliminarily irradiated before thermoforming, and radiation may be irradiated again after thermoforming.

In this case, thermoforming can be carried out without any problems, and the degree of crosslinking of the molded product can be adjusted as desired.

In this way, since the present invention crosslinks after lamination, the above-mentioned drawbacks such as low adhesive strength are eliminated.

Furthermore, since the adhesive layer and film layer can be crosslinked at the same time, the overall heat resistance, oil resistance, rigidity, gas barrier properties, etc. can be improved, and the product can be manufactured at low cost with fewer processes.

Radiation includes electron beams, alpha rays, and beta! I, r line.

Various ionizing radiations such as X-rays and neutron beams are used.

Among these, electron beams are preferred from the viewpoint of workability, economy, and adjustment of the degree of crosslinking. 1 to 75 as an electron beam
Mrad, preferably 2 to 5°Mrad, is used.

If it is less than I Mrad, the degree of crosslinking will be small and the heat resistance, adhesive strength, etc. will be insufficient, and if it exceeds 75 Mrad, the degree of crosslinking will be too large and brittleness will occur, causing problems in forming the laminate.

In general, polystyrene resin foam sheets undergo almost no crosslinking reaction even when exposed to electron beams or the like. Furthermore, even if the styrene monomer is modified by copolymerizing it with a polyfunctional polymer such as divinylbenzene for crosslinking, the crosslinking will normally proceed during polymerization, or the crosslinking reaction will proceed during or before the process of forming a foam sheet. As a result, the extrusion foaming efficiency decreases, and in some cases, extrusion foaming becomes impossible.

On the other hand, the paramethylstyrene resin is easily crosslinked without any treatment.

In this case, in order to further increase the crosslinking efficiency, it is preferable to add 1 to 10% by weight of a crosslinking aid such as diallyl phthalate, triallyl cyanurate, or triallyl isocyanurate to the paramethylstyrene resin, and then extrude and foam the resin. Mashishi).

In addition, the said crosslinking aid can be used by adding and kneading with the resin which is the raw material of the said thermoplastic resin film.

By irradiating with such radiation, the paramethylstyrene resin foam sheet is crosslinked, and its heat resistance, rigidity, etc. are significantly improved. Further, it is preferable to use a radiation-crosslinkable thermoplastic resin film or adhesive because these are also crosslinked at the same time, further improving the above-mentioned properties.

Examples of radiation-crosslinkable thermoplastic resin films include those made of polyolefin resins such as polyethylene resin and polypropylene resin, polyamide resins, and polyvinyl chloride resins, and examples of adhesives include EVA-based hot melt adhesives. , radiation-reactive adhesives such as radiation-crosslinked oligomers.

For the reasons mentioned above, the laminate crosslinked in this way has
It has excellent integrity, and the film layer does not break during thermoforming, so it has excellent moldability.

The degree of crosslinking due to radiation irradiation is determined when the gel fraction is 5 to 95.
%. Gel fraction is 5%
If it is less than 95%, various properties such as heat resistance and adhesive strength will not improve much, and if it exceeds 95%, brittleness will increase and manufacturing itself will become difficult, making it uneconomical.

The degree of crosslinking can be adjusted arbitrarily by changing conditions such as the type of film, the acceleration of electron beams, etc., the irradiation dose, the addition of crosslinking aids, and in some cases the addition of radical absorbers. A specific layer can also be crosslinked by combining these.

[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 such characteristics and a thermoplastic resin film, radiation is irradiated to crosslink the foam sheet.
Various properties such as the above heat resistance are improved. In addition, since the layers are laminated by heat fusion or 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 with extremely low heat resistance is used, the adhesive layer is also crosslinked because radiation is irradiated after lamination. In this case, a crosslinking reaction also occurs between each layer. Therefore, when using radiation-crosslinked thermoplastic resin films or radiation-reactive adhesives,
It becomes an integrally crosslinked laminate.

In addition, when laminated by thermal fusion or using a solvent-free adhesive, gas accumulation does not occur between each layer due to heat generation due to radiation irradiation, etc., and the lamination is highly integrated.

As the thermoplastic resin film, those having various properties such as gas parrying properties can be used, and since it can be made into a single layer or a multilayer, various functions can be imparted to the laminate.

Further, the degree of crosslinking can be arbitrarily adjusted by combining conditions such as the type of film and crosslinking auxiliary agent, the dose of radiation, etc.

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 A high impact polystyrene (HIPS) film with a thickness of 100 μm was heat laminated on one side of an extruded foam sheet of rose methyl styrene resin with an expansion ratio of 8 times and a thickness of 1.9, and then an electron beam of 50 Mrad was irradiated. .

The thus obtained laminate has a paramethylstyrene resin foam sheet with a gel fraction of 68% and an IPS
The gel fraction of the 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 examined for the laminate before and after electron beam irradiation, and the results shown in the table below were obtained.

Further, when the adhesive strength was examined according to ASTM-D905-45, the foam layer broke during the peel test, and the strength could not be measured. On the other hand, as a comparison sample,
After irradiating the paramethylstyrene resin foam sheet with an electron beam under the same conditions as above, the HIPS film was similarly heat laminated to produce a laminate with a 0-9 to 9/2 S wrm.
It showed only width strength, which was inferior to the laminate according to the present invention.

Example 2 A paramethylstyrene resin foam sheet with a foaming ratio of 12 times and a thickness of 2.3 rtun containing 5% by weight of triallyl isocyanurate as a crosslinking aid was coated with paramethylstyrene with a thickness of 100 μm containing the same amount of the aid. After heat laminating the resin film, it was irradiated with an electron beam of 25 M rad to obtain a crosslinked laminate.

Both layers of this laminate exhibited a gel fraction of approximately 45%, and even if the layers were heated to 110°C or higher to separate them, it was difficult to separate them, indicating that they had excellent heat resistance. Ta.

Example 3 After laminating a 100 μm thick polyethylene terephthalate resin <PET) film on one side of the same paramethylstyrene resin foam sheet as in Example 2 via a 30 μm thick EVA hot melt adhesive,
A crosslinked laminate was obtained by irradiation with Mrad's electron beam.

The gel fraction of the paramethylstyrene resin foam sheet is 45%.
The gel fraction of the PET film was 0% as a result of extraction using boiling phenol. In addition, although it was not possible to measure the gel fraction of the EVA adhesive layer, when the EVA hot melt adhesive was irradiated with the same dose of electron beam, the gel fraction was approximately 40%. It is presumed that it indicates the gel fraction. In fact, the adhesive has a softening point of 8
It was difficult to separate the layers even when heated to 0° C. or higher, and the film had excellent heat resistance.

Further, this crosslinked laminate showed no change even when immersed in heated oil, and had excellent heat resistance.

Example 4 A crosslinked laminate was obtained in the same manner as in Example 3, except that the PET film in Example 3 was replaced with a low-density polyethylene film having a thickness of 100 ttm. This crosslinked laminate had similar performance to that of Example 3, except that the gel fraction of the low density polyethylene layer was 48%. That is, the adhesive strength was so great that it was difficult to separate each layer under heating, and the heat resistance and oil resistance were also excellent.

In addition, the crosslinked laminates of Examples 1 to 4 have excellent thermoformability and are suitable as materials for automobile ceilings and heat-resistant food containers that require more advanced molding. Met.

〔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 strength, 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, since these are also crosslinked, the heat resistance, rigidity, etc. are further improved. In particular, when using thermoplastic resin films or radiation-reactive adhesives that are cross-linked by radiation, cross-linking reactions occur between each layer and between each layer, resulting in cross-linking 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. In addition, since the degree of crosslinking of the laminate can be adjusted as desired, the laminate can be tailored to suit 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.

Patent applicant Sekisui Plastics Co., Ltd. B1. Rini, dead type

Claims (1)

[Claims] 1. A method for producing a crosslinked laminate, which comprises laminating a paramethylstyrene resin foam sheet and a thermoplastic resin film and then irradiating them with radiation. 2. A patent in which the thermoplastic resin film is a film made of a resin selected from polyolefin resin, polyvinyl chloride resin, polyvinylidene chloride resin, saturated polyester resin, polyamide resin, polycarbonate resin, and polystyrene resin. A method for producing a crosslinked laminate according to claim 1. 3. A method for producing a crosslinked laminate according to claim 1 or 2, which comprises laminating by heat fusion or by using a radiation-reactive adhesive.