JPH0126865B2 - - 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. 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. Furthermore, even in the methods of laminating one or more layers of the above resin compositions and thermally adhering or coextruding them, there is a problem in that sufficient adhesive strength cannot 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 found that an ethylenically unsaturated monomer having a carbonyl group was graft-polymerized to 20% to 80% by weight of an ethylene-vinyl acetate copolymer resin with a vinyl acetate content of 5% to 50% by weight. An adhesive composition containing 20% to 80% by weight of a diluted polyolefin can be strongly thermally bonded to a saponified polystyrene and ethylene-vinyl acetate copolymer layer, and When polystyrene and saponified ethylene-vinyl acetate copolymer were coextruded and formed into a sheet,
It was discovered that the three layers were strongly bonded, and the present invention was completed based on this knowledge. 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. - Adhesive composition comprising vinyl acetate copolymer resin 20% to 80% by weight and polyolefin grafted with an ethylenically unsaturated monomer having a carbonyl group in a proportion of 20% to 80% by weight. Three types of layers are sequentially laminated: a material layer (hereinafter abbreviated as "adhesive composition layer") 2 and an ethylene-vinyl acetate copolymer saponified material layer (hereinafter abbreviated as "saponified material layer") 3. It consists of the following configuration. Next, to give an example of a laminate of another aspect of the laminate of the present invention, as shown in FIG. 2, the polystyrene layer 1, adhesive composition is Consisting of five layers: three types of layers, a material layer 2 and a saponified material layer 3, are laminated in sequence, and an adhesive composition layer 2 and a polystyrene layer 1 are further laminated in sequence on the saponified material layer 3. A laminate structure may also be used. In the above, a five-layer multilayer coextruded sheet was used, but the layer structure and number of layers other than the part where the polystyrene layer, adhesive composition layer, and saponified material layer are laminated in this order are limited to the above. It is not limited to this, but any suitable layer structure may be used. 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 present invention described above, the vinyl acetate content constituting the adhesive composition layer is 5% by weight to 50% by weight.
As the weight percent ethylene-vinyl acetate copolymer resin, for example, one obtained by polymerization using a known free catalyst polymerization method can be used. In addition, if the ethylene-vinyl acetate copolymer content of the adhesive composition layer in the present invention is 20% by weight or less, the adhesive strength between the adhesive composition layer and the polystyrene layer becomes weak, and the ethylene-vinyl acetate copolymer content becomes weak. If it exceeds 80% by weight, the suitability for molding and processing deteriorates. Therefore, in the present invention, the ethylene-vinyl acetate copolymer content is preferably 20% to 80% by weight. Next, in the present invention, the polyolefin obtained by graft-polymerizing an ethylenically unsaturated monomer having a carbonyl group can be obtained by, for example, a graft reaction method in a solution state (for example,
15422), a method in which the graft reaction is carried out in a molten state (for example, see Japanese Patent Publication No. 43-27421), other methods in which the graft reaction is carried out in a slurry state, and a method in which the graft reaction is carried out using heat and shear force in a kneader (for example, in the Those obtained by various methods such as (see Japanese Publication No. 43-18522) can be used. 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 polyolefin graft-polymerized with a saturated monomer preferably has an amount of 20% to 80% by weight. Next, the ethylenically unsaturated monomer having a carbonyl group in the present invention includes, for example, carboxylic acid, carboxylic acid salt, carboxylic acid anhydride, carboxylic acid ester, carboxylic acid amide or imide, aldehyde, ketone. Carbonyl based on 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 aldehydes or ketones: 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 polypropylene, polybutene, poly-α-olefin such as polyisobutylene, polydiolefin such as polybutadiene, polyisoprene, or copolymers thereof may be used. obtain. 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 a single layer sheet and a film are laminated, and then the three layers are thermally bonded by heating and pressurizing them together, or a coextrusion film of each resin constituting the adhesive composition layer and the saponified material layer. There is a method in which a polystyrene film or sheet constituting a polystyrene layer is thermally bonded 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 according to the present invention, the layer structure has a basic three-layer structure of a polystyrene layer, an adhesive composition layer, and a saponified layer, and the same or another layer can be optionally provided in addition to this. However, in this case, the layers can be laminated by any method such as a lamination method using a normal 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 800μ high impact polystyrene sheet,
50% by weight of ethylene-vinyl acetate copolymer resin with vinyl acetate content of 28% by weight, melt index of 18g/10 minutes, and melt index of 1.8g/10 minutes.
A composition film containing 50% by weight of a low-density polyethylene resin graft-polymerized with 0.3% by weight of maleic anhydride with a specific gravity of 0.905 for 10 minutes.
Laminated with 30μ of saponified ethylene-vinyl acetate copolymer film (ethylene content: 30 mol%, degree of saponification: 99.2%) and then laminated with 17μ of saponified ethylene-vinyl acetate copolymer film (ethylene content: 30 mol%, degree of saponification: 99.2%), and placed on a Teflon-treated induction heating roll (temperature: 190°C). Thermal bonding was carried out through the process (Fig. 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 1800 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 (Estyrene H-60 manufactured by Nippon Steel Chemical Co., Ltd.) as the polystyrene layer, vinyl acetate content 28% by weight, melt index 18g/10min ethylene-vinyl acetate copolymer resin 50 Weight % and melt index
1.8g/10min, maleic anhydride addition amount with specific gravity 0.905
The adhesive composition layer is made of a resin blended with 50% by weight of low density polyethylene resin graft-polymerized at 0.3% by weight, with an ethylene content of 33 mol%, a degree of saponification of 99.5 mol%, and a melting point of 180°C. A saponified vinyl copolymer was used as the saponified layer, and a coextrusion sheet was formed as shown in FIG. The thickness of each layer was 500μ for the polystyrene layer, 30μ for the adhesive composition layer, and 40μ for the saponified material layer, and the extrusion temperature was 220°C. 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 1500 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 ethylene-vinyl acetate copolymer resin with a vinyl acetate content of 28% by weight and a melt index of 18g/10 min, 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%) was laminated at 17 μm, and the melt index was 1.8 g/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 /
Polyvinylidene chloride/polyethylene laminate) were laminated and thermally bonded by passing them 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 pressure air 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 material layer.

Claims (1)

[Claims] 1. Polystyrene layer, vinyl acetate content 5% by weight
or 50% by weight of an ethylene-vinyl acetate copolymer resin from 20% to 80% by weight of a polyolefin in which an ethylenically unsaturated monomer having a carbonyl group is graft-polymerized in a proportion of 20% to 80% by weight. A laminate formed by laminating three layers in the above order: an adhesive composition layer formed by blending the compound, and a saponified ethylene-vinyl acetate copolymer layer having an ethylene content of 20 to 50 mol% and a saponification degree of 90% or more. . 2 Polystyrene layer, polyolefin in which an ethylenically unsaturated monomer having a carbonyl group is graft-polymerized to an ethylene-vinyl acetate copolymer resin with a vinyl acetate content of 5% to 50% by weight from 20% to 80% by weight. 20% to 80% by weight
a saponified ethylene-vinyl acetate copolymer layer having an ethylene content of 20 to 50 mol% and a degree of saponification of 90% or more; A laminate made by sequentially stacking five compound layers.