The present invention relates to a heat-resistant laminate which is able to have oil-resistance at a high temperature or, particularly to durability in a high temperature retort and is excellent in barrier property. In detail, the present invention relates to a heat-resistant laminate film or sheet comprising two adhesive layers of a heat-resistant adhesive resin disposed between a layer of a polyamide or a polymer of propylene and a layer of a polymer of vinylidene chloride and also between a layer of a polyamide or a polyolefin and the layer of a polymer of vinylidene chloride. More in detail, the present invention relates to a heat-resistant laminate film or sheet comprising a first layer, as one of the outer layers thereof, made of a polymer of propylene or a polyamide; a seventh layer, as the other outer layer thereof, made of a polyolefin or a polyamide; a fourth layer, as a gas-barrier layer, made of a polymer of vinylidene chloride; a second layer and a sixth layer, as adhesive layers (A), made of a modified polyolefin or a mixture of not less than 90% by weight of the modified polyolefin and not more than 10% by weight of a copolymer of ethylene and an acrylic ester or a modified copolymer of ethylene and an acrylic ester and respectively directly jointed to the first layer and the seventh layer; and a third layer and a fifth layer as adhesive layer (B), made of a mixture of 10 to 30% by weight of a modified polyolefin and 90 to 70% by weight of a copolymer of ethylene and an acrylic ester or a modified copolymer of ethylene and an acrylic ester and respectively disposed between the second layer and the fourth layer, and between the fourth layer and the sixth layer and respectively directly jointed to the gas-barrier layer and the adhesive layers (A), and also relates to a process for preparing the heat-resistant laminate film or sheet comprising the steps of providing a polymer of propylene or a polyamide as one of the outer layers thereof; a polyolefin or a polyamide as the other outer layer thereof; a polymer of vinylidene chloride as a gas-barrier layer; a modified polyolefin or a mixture of not less than 90% by weight of the modified polyolefin and not more than 10% by weight of a copolymer of ethylene and an acrylic ester or a modified copolymer of ethylene and an acrylic ester as an adhesive layer(A); and a mixture of 10 to 30% by weight of a modified polyolefin and 90 to 70% by weight of a copolymer of ethylene and an acrylic ester or a modified copolymer of ethylene and an acrylic ester as an adhesive layer (B) in a plasticized condition within a die extruding these resins in the configuration wherein one of the outer layers thereof (first layer) is the polymer of propylene or the polyamide; the other outer layer (seventh layer) is polyolefin or polyamide; a center layer thereof (fourth layer) is polymer of vinylidene chloride as the barrier layer; the adhesive layers (A) (second layer and sixth layer) are a modified polyolefin or a mixture of not less than 90% by weight of the modified polyolefin and not more than 10% by weight of a copolymer of ethylene and an acrylic ester or a modified copolymer of ethylene and an acrylic ester and one of the two adhesive layers (A) (second layer) is directly jointed to one of the outer layers (first layer) and the other adhesive layer(A) (sixth layer) is directly jointed to the other outer layer (seventh layer); the adhesive layers (B) (third layer and fifth layer) are a mixture of 10 to 30% by weight of a modified polyolefin and 90 to 70% by weight of a copolymer of ethylene and an acrylic ester or a modified copolymer of ethylene and an acrylic ester and one of the two adhesive layers(B) (third layer) is disposed between the center layer (fourth layer) and one of the adhesive layers(A) (second layer) and the other adhesive layer(B) (fifth layer) is disposed between the center layer (fourth layer) and the other adhesive layer(A) (sixth layer), and cooling the thus extruded laminate.
Recently, gas-barriering laminate which can be boil-treated or retort-treated have been used in the field of food-packaging, and that laminate provided with more than one layer made of polyamide from the viewpoint of heat-resistance, oil-resistance and strength and also not less than one layer made of a polymer of vinylidene chloride from the viewpoint of gas-barriering have been proposed as the gas-barriering laminate which can be boil-treated or retort-treated (refer to Japanese Patent Publication No. 57-15546 (1982).
However, in the conventional laminate film, the adhesion between the layer of polyamide and the layer of polymer of vinylidene chloride is not sufficient, and particularly, in the case of using such a laminate film in the field where boil-treatment or retort-treatment is carried out, it is necessary to use a layer of an adhesive agent which can maintain a favorable adhesive strength at a high temperature between the layer of polyamide and the layer of polymer of vinylidene chloride.
The Japanese Patent Publication No. 57-15546 (1982) discloses that the two adhesive layers, one of which is made of an adhesive, modified polyolefin and another of which is made of a copolymer of ethylene and vinyl acetate or an acrylic ester, disposed between the layer of polyamide and the layer of polymer of vinylidene chloride shows good adhesive effects. However, under the extremely severe conditions of pressurized hot water-treatment in a retort carried out, for instance at 120.degree. C. for more than 30 min or at 130.degree. C. for more than 10 min, the adhesion is not necessarily sufficient, and accordingly a gas-barrier heat-resistant laminate having layers more excellently adhered together has been demanded.
As a result of the present inventors' studies, it has been found that the disposition of the two kinds of specified adhesive layers between the heat-resistant outer layer of the polymer of propylene, polyolefin or polyamide and the center layer of polymer of vinylidene chloride gives a heat-resistant laminate which can maintain a sufficient and practical inter-layer adhesion (interlaminar strength) even under the severe conditions in the oil-treatment at a high temperature or the pressurized hot water-treatment and exhibits as excellent heat-resistance and gas-barriering property, and based on the inventors' finding, the present invention has been attained.