JPH0126868B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a laminate, and more particularly to a laminate suitable for sheet forming. Currently, containers for packaging foods, etc.
Although various resin molded products have been proposed, the sheet forming method is generally widely used as a manufacturing method for these products because the molding equipment is inexpensive and the molding process is easy. In such a molding method, polystyrene is mainly used as the sheet material because of its good moldability. Furthermore, in recent years, resin molded products such as cups and trays are required to have barrier properties as the contents become more diverse. An object of the present invention is to provide a laminate having a polystyrene layer and a saponified ethylene-vinyl acetate copolymer layer having high barrier properties. By drawing the laminate of the present invention, food packaging containers such as cups and trays having high barrier properties can be obtained. By the way, the present inventor has discovered that in order to laminate a polystyrene film or sheet and a saponified ethylene-vinyl acetate copolymer film or sheet, for example, a method of laminating using an adhesive, or a method of laminating both. An attempt was made to laminate one or more layers of a resin composition between the two and perform thermal adhesion or coextrusion. However, when a polystyrene film or sheet and a saponified ethylene-vinyl acetate copolymer film or sheet are laminated using an adhesive, peeling at the adhesive layer occurs during deep drawing molding.
Also, there is a problem that layer cutting occurs. In addition, even in the method of laminating one or more layers of the above resin composition, thermal bonding, and co-extrusion molding, there is a problem that no sufficient adhesive strength can be obtained, and delamination occurs when deep drawing is performed. be. The present inventor further addresses the above problems by:
As a result of various studies, we created an ethylene-vinyl acetate copolymer resin with a vinyl acetate content of 5 to 50% by weight, which was obtained by graft polymerizing styrene monomer to 20 to 80% by weight of an ethylenically unsaturated monomer having a carbonyl group. An adhesive composition layer comprising 20 to 80% by weight of a polyolefin graft-polymerized with polystyrene and a saponified ethylene-vinyl acetate copolymer is strongly thermally bonded to polystyrene and a saponified ethylene-vinyl acetate copolymer; When polystyrene and saponified ethylene-vinyl acetate copolymer were coextruded and formed into a sheet, they found that the three layers were strongly adhered, and based on this knowledge, they completed the present invention. . The above-mentioned present invention will be explained in more detail below. First, the layer structure of the laminate of the present invention will be explained with reference to the drawings. As shown in FIG. ~50% by weight ethylene-vinyl acetate copolymer resin20~
An adhesive composition layer (hereinafter referred to as "adhesive composition layer") comprising 80% by weight and 20 to 80% by weight of polyolefin grafted with an ethylenically unsaturated monomer having a carbonyl group. (abbreviated).
2 and a saponified ethylene-vinyl acetate copolymer layer (hereinafter referred to as "saponified layer") 3 are sequentially laminated. Next, to give an example of another aspect of the laminate of the present invention, as shown in FIG. 2, like the laminate shown in FIG. Composition layer 2 and saponified layer 3
Seed layers are sequentially laminated, and further the saponified layer 3
A 5-layer laminate structure in which the adhesive composition 2 and the polystyrene layer 1 are sequentially laminated on top of the adhesive composition 2 and the polystyrene layer 1 may be used. In addition, although a five-layer multilayer coextruded sheet was used in the above, the layer structure and number of layers other than the part laminated in the order of polystyrene layer, adhesive composition layer, and saponified material layer are limited to the above. It is not necessary to use a suitable layer structure. That is, the layer structure in the present invention is based on the layer structure shown in FIG. 1 above, and an appropriate layer may be provided on the layer structure. In the present invention described above, as the polystyrene constituting the polystyrene layer, for example, GP polystyrene, high impact polystyrene, medium impact polystyrene, etc. can be used. Next, in the above-mentioned invention, the styrene monomer is ethylene-vinyl acid containing 5 to 50% by weight.
Examples of methods for graft polymerizing a vinyl acetate copolymer resin and methods for graft polymerizing an ethylenically unsaturated monomer having a carbonyl group onto a polyolefin include a method in which a graft reaction is performed in a solution state (for example, Japanese Patent Publication No. 15422/1983). (see official bulletin),
A method of performing a graft reaction in a molten state (for example, see Japanese Patent Publication No. 43-27421), another method of performing a graft reaction in a slurry state, and a method of performing a graft reaction using heat and shear force in a kneader (for example, a method of performing a graft reaction in a kneader)
There are various methods such as (see Publication No. 18522). Next, in the above-mentioned present invention, ethylene containing 5 to 50% by weight of vinyl acetate is prepared by graft polymerizing the styrene monomer constituting the adhesive composition layer.
As the vinyl acetate copolymer resin, for example, one obtained by polymerization using a known free catalyst polymerization method can be used. In addition, if the content of the ethylene-vinyl acetate copolymer obtained by graft polymerizing the styrene monomer in the adhesive composition layer of the present invention is less than 20% by weight, the adhesive force between the adhesive composition layer and the polystyrene layer becomes weak.
If the content of ethylene-vinyl acetate copolymer grafted with styrene monomer exceeds 80% by weight, the suitability for molding and processing deteriorates. Therefore, in the present invention, the content of ethylene-vinyl acetate copolymer is
20-80% by weight is preferred. In addition, in the present invention, if the amount of polyolefin graft-polymerized with an ethylenically unsaturated monomer having a carbonyl group is less than 20% by weight, the adhesive force between the adhesive composition layer and the saponified material layer becomes weak, and the polyolefin having a carbonyl group is If the amount of polyolefin graft-polymerized with an ethylenically unsaturated monomer exceeds 80% by weight, the adhesive strength between the adhesive composition layer and the polystyrene layer becomes weak. The amount of polyolefin grafted with a saturated monomer is preferably 20 to 80% by weight. Next, examples of the ethylenically unsaturated monomer having a carbonyl group in the present invention include carboxylic acids, carboxylic acid salts, carboxylic acid anhydrides,
Carbonyl based on carboxylic acid ester, carboxylic acid amide or imide, aldehyde, ketone, etc.

[Formula] Group alone or cyano (-C≡N) group; hydroxy group; ether group; oxirane

[Formula] One type or a combination of two or more types of ethylenically unsaturated monomers having a ring etc. can be used, and suitable examples thereof are as follows. A Ethylenically unsaturated carboxylic acid: acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, 5-norbornene-2,3-dicarboxylic acid, etc. B Ethylenically unsaturated carboxylic anhydride: maleic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, tetrahydrophthalic anhydride, etc. C Ethylenically unsaturated ester: ethyl acrylate, methyl methacrylate, 2-ethylhexyl acrylate, mono- or di-ethyl maleate, vinyl acetate, vinyl propionate, propyl γ-hydroxymethacrylate,
β-hydroxyethyl acrylate, glycidyl acrylate, glycidyl methacrylate, β
-N-ethylaminoethyl acrylate, etc. D Ethylenically unsaturated amide or imide: acrylamide, methacrylamide, maleimide, etc. E Ethylenically unsaturated aldehyde or ketone:
Acrolein, methacrolein, vinyl methyl ketone, vinyl butyl ketone, etc. In the present invention, among the above-mentioned monomers, ethylenically unsaturated carboxylic acids and ethylenically unsaturated carboxylic anhydrides are particularly preferred, and these monomers may be used alone or in combination with other monomers. Used in combination with the body. In addition, as the polyolefin in the present invention, polyethylene, ethylene-α-olefin copolymer, polyα-olefin such as polypropylene, polybutene, polyisobutylene, polydiolefin such as polybutadiene, polyisoprene, or copolymers thereof, etc. are used. It is possible. Next, in the present invention, as the saponified ethylene-vinyl acetate copolymer having an ethylene content of 20 to 50 mol% and a saponification degree of 90% or more constituting the saponified layer, known ones can be used, Then,
In the present invention, if the ethylene content is less than 20 mol%, there will be no moisture resistance or water resistance, and if it is more than 50 mol%, the barrier properties will decrease, so the ethylene content is preferably 20 to 50 mol%. Also, if the degree of saponification is less than 90%, the barrier properties will deteriorate, so the degree of saponification must be 90% or more. Furthermore, in the present invention, other resins that can be further laminated in addition to the three layers of the polystyrene layer, adhesive composition layer, and saponified layer include:
For example, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-
Saponified vinyl acetate copolymer, ethylene-α-olefin copolymer elastomer, styrene-butadiene-acrylonitrile copolymer, styrene-
Resins such as acrylonitrile copolymer, polyamide, polycarbonate, polysulfone, polyacetal, polymethyl methacrylate, polyphenylene oxide, polyurethane, polyethylene terephthalate, and polybutylene terephthalate can be used in a single layer or in combination. Next, the method for producing the laminate of the present invention will be explained. There are various methods for producing the laminate of the present invention. A method in which the three layers are thermally bonded by laminating a layer sheet and a film and then heating and pressurizing them together, or a coextrusion film of each resin constituting the adhesive composition layer and the saponified material layer is created. Then, there is a method of thermally bonding a polystyrene film or sheet constituting the polystyrene layer to the laminated film. In addition, heating methods in the present invention include heat treatment using an induction heating roll, heat treatment by blowing hot air with a dryer, heat treatment using flame, etc., and at a temperature of 80°C to 300°C, preferably 120°C to 250°C. It is preferable to perform heat treatment. In the present invention, a laminate having a five-layer structure as shown in FIG. 2 can be manufactured by a coextrusion method, etc., and a coextrusion sheet having the layer structure of the laminate shown in FIG. The required temperature is 150℃~250℃,
Preferably it is 180°C to 240°C. Further, in the laminate of the present invention, the basic layer structure is a polystyrene layer, an adhesive composition layer, and a saponified material layer, and the same or different layers can be optionally provided in addition to this. but,
In this case, the layers can be laminated by any method such as a lamination method using an ordinary adhesive or an extrusion lamination method. Next, a brief description of the molding method using the laminate of the present invention includes, for example, a vacuum molding method, a pressure molding method, a vacuum pressure molding method, and the like. Alternatively, a form-fill-seal method (FFS method) may be used, which involves forming, filling, sealing, and cutting. The laminate obtained by the present invention can be strongly bonded to a polystyrene layer through only one adhesive composition layer, has good drawability, and does not cause delamination during molding. It has extremely high barrier properties and can be used in various resin containers such as cups and trays. In addition, this resin container has good smoothness on the outer and inner surfaces of the container, and can be used for miso, soy sauce, desserts, youth, margarine, etc., which require high barrier properties.
It can be used in a variety of ways, such as containers for packaging foods such as butter and alcoholic beverages, and containers for packaging drugs. Next, the present invention will be described in more detail with reference to Examples. Example 1 Ethylene-vinyl acetate copolymer resin 50% by weight with a vinyl acetate content of 28% by weight and a melt index of 12.5g/10 minutes graft polymerized onto a 800μ high-impact polystyrene sheet with a styrene addition amount of 20% by weight. and melt index 1.8
g/10 min, maleic anhydride addition amount 0.3 with specific gravity 0.905
A composition film containing 50% by weight of a low-density polyethylene resin graft-polymerized at 30 μm was laminated, and a saponified ethylene-vinyl acetate copolymer film (ethylene content: 30 mol%, degree of saponification) was laminated. 99.2%) were laminated to a thickness of 17 μm and thermally bonded by passing them through a Teflon-treated induction heating roll (temperature: 190°C) (Figure 1). When the adhesive strength between each layer of this three-layer laminate was measured, the adhesive strength between the polystyrene layer and the adhesive composition layer was 1600 gw/15 mm width, and the adhesive strength between the adhesive composition layer and the saponified material layer was 1300 gw/15 mm width. It was hot. Example 2 Melt flow index 10.5g/10min, specific gravity
1.04 high impact polystyrene (manufactured by Nippon Steel Chemical Co., Ltd., Estyrene H-60) as a polystyrene layer, graft polymerized with styrene addition of 20%, vinyl acetate content 28% by weight, melt index 12.5g 50% by weight of low density polyethylene resin graft polymerized with 50% by weight of ethylene-vinyl acetate copolymer resin for /10 minutes and 0.3% by weight of maleic anhydride with a melt index of 1.8g/10 minutes and a specific gravity of 0.905. The adhesive composition layer is a resin made by blending the above, the saponified ethylene-vinyl acetate copolymer having an ethylene content of 33 mol%, a degree of saponification of 99.5 mol% and a melting point of 180°C is used as the saponified material layer,
Coextrusion sheet molding was carried out as shown in the figure. The thickness of each layer is 500μ for the polystyrene layer, 30μ for the adhesive composition, and 40μ for the saponified layer, and the extrusion temperature is
The temperature was 220℃. When the adhesive strength between each layer of this coextruded sheet was measured, the adhesive strength between the polystyrene layer and the adhesive composition layer was 1300 gw/15 mm width, and the adhesive strength between the adhesive composition layer and the saponified material layer was 1300 gw/15 mm width. It was hot. Further, the sheet was subjected to deep-drawing pressure forming, but no peeling between layers or film breakage occurred, and the forming condition was good. Example 3 800μ high impact polystyrene sheet 1
70% by weight of an ethylene-vinyl acetate copolymer resin with a vinyl acetate content of 28% by weight and a melt index of 12.5/10 minutes, which was graft-polymerized with a styrene content of 20% by weight, and a melt index of 1.8.
g/10 min, maleic anhydride addition amount 0.3 with specific gravity 0.905
An adhesive composition film 2 containing 30% by weight of a low-density polyethylene resin graft-polymerized is laminated to a thickness of 20 μm, and ethylene-
Saponified vinyl acetate copolymer, Film 3 (ethylene content 30 mol%, degree of saponification 99.2%) 17μ
Laminated, melt index 1.8g/10 minutes,
A 20μ low-density polyethylene resin film 4 graft-polymerized with a specific gravity of 0.905 and an added amount of maleic anhydride of 0.3% by weight was laminated, and Saranex-
26, 5 (Product name manufactured by Asahi Dow Co., Ltd. Thickness 64 μ polyethylene /
A laminate of polyvinylidene chloride/polyethylene) was laminated and thermally bonded by passing it through a Teflon-treated induction heating roll (temperature: 190°C).
figure). When the adhesive strength between each layer of this laminate was measured, the adhesive strength between the polystyrene layer and the adhesive composition layer was 1500 gw/15 mm width, and the adhesive strength between the adhesive composition layer and the saponified layer was 1300 gw/15 mm width, and the adhesive strength between the polystyrene layer and the adhesive composition layer was 1300 gw/15 mm width. The compound layer and the low density polyethylene layer grafted with maleic anhydride could not be separated, and the low density polyethylene layer grafted with maleic anhydride Saranex 26 could not be peeled off. Further, the sheet was subjected to deep-drawing pressure forming, but no peeling between layers or film breakage occurred, and the forming condition was good.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the layer structure of the laminate of the present invention, and FIGS. 2 and 3 are sectional views showing another embodiment of the layer structure of the laminate of the invention. 1...Polystyrene layer, 2...Adhesive composition layer, 3...Saponified ethylene-vinyl acetate copolymer layer.

Claims (1)

[Scope of Claims] 1. Ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 5 to 50% by weight and 20 to 80% by weight, which is obtained by graft polymerizing a polystyrene layer and a styrene monomer.
20 to 20% polyolefin, which is obtained by graft polymerizing ethylenically unsaturated monomers having carbonyl groups,
Three layers are laminated in the above order: an adhesive composition layer with a ratio of 80% by weight and a saponified ethylene-vinyl acetate copolymer layer with an ethylene content of 20 to 50 mol% and a saponification degree of 90% or more. A laminate made of 2 Ethylene-vinyl acetate copolymer resin with a vinyl acetate content of 5-50% by weight, which is obtained by graft polymerizing a polystyrene layer and a styrene monomer, from 20 to 80% by weight
20 to 20% polyolefin, which is obtained by graft polymerizing ethylenically unsaturated monomers having carbonyl groups,
An adhesive composition layer formed by blending in a ratio of 80% by weight, a saponified ethylene-vinyl acetate copolymer layer with an ethylene content of 20 to 50 mol% and a saponification degree of 90% or more, the above adhesive composition layer, and 5 of the above saponified layer
A laminate made by laminating layers in sequence.