JPH0337505B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composite film for deep drawing, which is suitable for packaging foods such as sliced ham, and particularly has an excellent appearance. A composite film for deep drawing for packaging sliced ham etc. preferably includes a polyamide resin layer that provides pinhole resistance and a sealing resin layer that provides heat sealability with the lid material. Various structures having a gas barrier resin layer are generally used. One of the important qualities of a composite film for deep drawing is that it has an excellent appearance without wrinkles on the top of the molded product after deep drawing. Conventionally,
None of the molded products having the above structure had a satisfactory appearance without wrinkles on the top of the molded product. The inventors of the present invention have conducted various studies on the causes of wrinkles occurring on the top of molded products, and have found that polyamide resin, one of the resins constituting the composite film, is most responsible. Therefore, nylon 6, which is usually used as polyamide resin,
We considered reducing the thickness of the polyamide resin layer made of nylon, 6-66 nylon, etc. to reduce the effect as much as possible, but by making it thinner, the pinhole resistance deteriorates, and depending on the molding conditions, It has the disadvantage that pinholes are likely to occur. The present invention improves the appearance without reducing the thickness of the polyamide resin layer by using a copolyamide resin having a specific composition. The copolyamide resin used in the present invention is 6
A polycondensate of hexamethylene diamine and terephthalic acid with nylon as the main component (hereinafter referred to as "6-6T nylon"); It is a polycondensate with an acid (hereinafter referred to as "6-6I nylon"). Further, a combination of both of the above acids may be used. The composition ratio of the copolymerized polyamide resin is 95 to 80% by weight of 6 nylon, and 5 to 20% by weight of 6T nylon, 6I nylon, or a mixture thereof.
It is preferable that the other components are in the range of 5% by weight.
If it is less than % by weight, no effect of appearance improvement can be seen.
Moreover, if the weight of other components exceeds 20, it is difficult to produce a copolymer, which is disadvantageous. Regarding the layer structure other than the polyamide resin layer in the composite film of the present invention, various resins can be used or combined. Ionomer resins, polyethylene, and copolymers of ethylene and other components can be suitably used as the sealing resin, and saponified ethylene-vinyl acetate copolymers can be used as the gas barrier resin layer. Furthermore, adhesive resin such as modified polyolefin may be interposed for the purpose of improving the adhesive strength between the layers. Regarding the method for manufacturing the composite film of the present invention,
A method in which each resin layer is laminated by coextrusion is preferred from the viewpoint of the properties and productivity of the resulting film. The present invention will be explained below with reference to Examples. Example: Composite films with each configuration described below were processed using a deep drawing machine MVP manufactured by Mitsubishi Heavy Industries, Ltd. so that the first layer was on the outside.
-3.0Kg/cm ² after heating at 100℃ for 2 seconds with type 401
It was drawn to a size of 100 mm in diameter and 30 mm in depth using a gauge pressure of . diameter into the hole that is immediately formed.
Each package was filled with 200 g of 98 mm sliced ham, covered with the following lid material, vacuum packaged, and then cut into a 160 mm x 130 mm rectangle. 1 of each package obtained
Table 1 shows the evaluation results of the appearance (wrinkles on the top, etc.) and pinhole resistance after being left for a week (in an atmosphere of 5° C. and 100% relative humidity). Regarding the wrinkles on the top, the heating conditions during deep drawing were also evaluated at 90°C for 2 seconds. As the lid material, a film consisting of unstretched polypropylene (thickness 20μ)/cellophane coated with vinylidene chloride (30μ)/ionomer resin (30μ) was used. The appearance was evaluated by visual observation and was rated as excellent (◎) with no defects, good (◎) with almost no defects, and problematic (△) with visible defects. The pinhole resistance was evaluated by performing draw forming under the above-mentioned forming conditions using two types of molds with different depths. Items with no pinholes up to a depth of 40 mm (◎) and items with no pinholes up to a depth of 30 mm (○) were rated. Invention Product 1 The first gas barrier resin layer (outer layer) is a saponified ethylene-vinyl acetate copolymer with an ethylene content of 45 mol% and a saponification degree of 99.5 mol%, and the second polyamide resin layer is 6T nylon. The content of is 10
% by weight of 6-6T nylon, the third layer was modified polyolefin (ADMER-LF-305, manufactured by Mitsui Petrochemical Industries, Ltd.), and the fourth layer was a sealing resin layer with a vinyl acetate content of 5%. Each resin was laminated in a coextrusion annular die at a set temperature of 230° C. to form an ethylene-vinyl acetate copolymer, and then cooled to obtain a blown film with a diameter of 270 mm. The thickness of each layer is 30μ for the first layer, 10μ for the second layer, 15μ for the third layer, and 95μ for the fourth layer. Invention Product 2 Using the same material as Invention Product 1, a composite film with a different thickness structure was obtained. The first layer has a thickness of 30μ, the second layer has a thickness of 30μ, the third layer has a thickness of 15μ, and the fourth layer has a thickness of 75μ. Invention Product 3 A composite film using the same materials as Invention Product 1, except that 6-6I nylon with a 6I nylon content of 10% by weight was used as the second polyamide resin layer. The first layer is 30μ, the second layer is 10μ, the third layer is 15μ,
The fourth layer is 95μ. Invention Product 4 Using the same material as Invention Product 3, a composite film with a different thickness structure was obtained. The first layer has a thickness of 30μ, the second layer has a thickness of 30μ, the third layer has a thickness of 15μ, and the fourth layer has a thickness of 75μ. Comparative Product 1 A composite film using the same materials as Invention Product 1, except that 6-66 nylon with a 66 nylon content of 15% by weight was used as the second polyamide resin layer.
1st layer 30μ, 2nd layer 10μ, 3rd layer 15μ, 4th layer
The layer is 95μ. Comparison product 2 Composite film using the same material as comparison product 1 but with a different thickness structure. The first layer is 30μ, the second layer is 30μ,
The thickness of the third layer is 15μ, and the thickness of the fourth layer is 75μ.

【table】

[Table] From Table-1, compared to the invention products 1 to 4, comparative product 1, which uses a different resin for the polyamide resin layer,
In No. 2, the appearance is inferior and the molding conditions are low (90℃).
x 2 seconds), it can be seen that wrinkles appear on the top. In particular, it can be seen that the comparative product 2, which has a thick wall, has a poor appearance. On the other hand, it can be seen that the products of the present invention, even those with thick walls (Invention Products 2 and 4), have an excellent appearance, and wrinkles do not occur at the top even under low temperature molding conditions. As described above, the present invention provides a composite film for deep drawing that is suitable for food packaging, and its effects are significantly large.

Claims (1)

[Claims] 1. In a composite film for deep drawing having at least a polyamide resin layer and a sealing resin layer, the polyamide resin layer is mainly composed of nylon 6, and other components are a polycondensate of hexamethylene diamine and terephthalic acid and/or isophthalic acid. A composite film for deep drawing, characterized by being made of a copolymerized polyamide resin.