JPS6217243Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a composite film for deep drawing.
More specifically, the present invention relates to a composite film which is characterized in that curl-prevented packaging can be obtained when used as a bottom material for deep drawing to obtain packaging in which contents such as sliced ham are packaged in a non-boiled manner. Deep drawing is a deep drawing machine such as the FV-600 series manufactured by Omori Kikai Kogyo Co., Ltd., which is used to form a composite film into a predetermined shape with a certain depth. After filling the contents, the composite film for the bottom material is molded using the machine described above in order to seal it with the composite film for the lid material to obtain a package, and the film referred to here generally refers to a sheet. It is used as a general name that includes relatively thick sheets called . In the case of packages for sliced ham, etc., there are two types: boil-sterilized packages that are packed in a general room, and non-boiled packages that are packed in a sterile packaging room. It is a composite film used as a material. Currently, deep drawing packaging methods are being adopted for food packaging such as sliced ham, and there are composite films made using various manufacturing methods. It is a composite film made by coextrusion, which can be made by dry lamination in terms of formability, cost, and transparency, but is superior to these methods, and is a bottom material where the contents are stored after being formed. This concerns the composite film on the side. Currently, composite films for bottom material side for deep drawing include unoriented polypropylene (CPP)/PVDC coated nylon (KNy)/seal layer (S), saponified ethylene-vinyl acetate copolymer/nylon (Ny)/
S, Ny/saponified ethylene-vinyl acetate copolymer/S, Ny/S, KNy/S, etc. are used, and Ny is used in all composite films, but this is Ny that is formed by deep drawing. Although it is used because it has moderate flexibility and stiffness and good pinhole resistance, it is used in the surface layer like Ny/S and KNy/S.
When Ny is used, since Ny has water absorption properties, the water absorption rate of Ny changes depending on the surrounding air condition, and the flange portion 1 of the package curls inward or outward, making it almost unusable except for certain products. In addition, in an attempt to solve this problem, Ny such as CPP/KNy/S and saponified ethylene-vinyl acetate copolymer/Ny/S
as an intermediate layer, and CPP with low moisture permeability on the surface of Ny.
A composite film laminated with a saponified ethylene-vinyl acetate copolymer has been devised and used, but when a composite film with this structure is used as a bottom film to pack sliced ham, etc., there is little problem at first, but super CPP and saponified ethylene-vinyl acetate copolymer also have a slight moisture permeability due to the atmospheric conditions in the case and the passage of time after packaging.
Although this was much smaller than when Ny was used in the surface layer, the water absorption rate of Ny changed, causing the package to curl, and if storage conditions were poor, it could lose its value as a product. For this reason, the inventors of the present invention have previously considered that it is essential to use Ny as the bottom material film for deep drawing in non-boiling packaging in which the contents such as sliced ham are not sterilized by boiling, from the viewpoint of mechanical suitability for packaging machines. However, without using Ny, it can be continuously molded with mechanical suitability comparable to that of Ny, giving the package appropriate stiffness and flexibility, and the resulting package has gas barrier properties that make it suitable for use in stores. In order to extend the elf's life and obtain the curl-free package, which is our greatest desire, we investigated whether there was a bottom material film for deep drawing, and found a composite film with the structure of the present invention. It was confirmed that a package in which the film was used as the bottom film for deep drawing of non-boil packaging did not curl even under the ambient air conditions at the store. The composite film of the present invention is a composite film in which the surface layer 2 is made of a saponified ethylene-vinyl acetate copolymer resin and the inner layer 3 is made of an ionomer resin, and the thickness of each layer is smaller than the total thickness. The saponified vinyl acetate copolymer resin layer has a thickness of 5 to 30%, and the inner layer ionomer resin layer has a thickness of 95 to 70%, and there is an adhesive layer or adhesive resin layer between the layers that can bond the layers. There is a composite film that has A feature of the composite film of the present invention is that it is used as a bottom material for deep drawing and does not contain Ny, so the package does not curl under ambient conditions. Regarding the structure of the composite film of the present invention, the saponified ethylene-vinyl acetate copolymer of the surface layer has an ethylene content of 25 to 75 mol% and a saponification degree of 90 mol% or more, and the film layer has barrier properties. It is a layer that is warm, has very low hygroscopicity, has mechanical suitability for packaging machines, and is used to impart gloss to the surface of the package. The ionomer resin of the inner layer has pinhole resistance and sealing properties with the lid material, and has good deep drawability, so it is an essential layer for the composite film of the present invention, along with the saponified ethylene-vinyl acetate copolymer of the surface layer. And,
There are two types of ionomer resins: Na type and Zn type. Either type may be used for the composite film of this invention, but Na type is superior in terms of deep drawability, but in order to obtain a curl-free package. Zn-type ionomer resin, which has much lower water absorption than Na-type, is desirable for this purpose, but it is selected appropriately depending on the contents to be wrapped. Examples and comparative examples of the present invention are shown in Table 1. As mentioned above, since the adhesive resin layer is provided between the surface layer and the inner layer, as in Examples 1 and 2, saponified ethylene-vinyl acetate copolymer/(ethylene-vinyl acetate copolymer)/ionomer, Saponified ethylene-vinyl acetate copolymer/(PE)/
It has an ionomer-like composition. Note that the composite film 4 for the lid material that is sealed with the composite film for the bottom material side for deep drawing of the present invention is polyester (PET)/PVDC coated cellophane (KM)/sealing resin (S), biaxially oriented polypropylene. (OPP)/KM/S, KOP/S and KPET/
S is used, but the combination of bottom material and lid material is selected as appropriate depending on the intended use. In this way, when the composite film of the present invention is used as a bottom material film in deep drawing, it has good mechanical suitability for packaging machines, good barrier properties, and has a high water absorption rate in the surface layer or intermediate layer as in the conventional method. Even if a moisture-proof film is used for the surface layer, the composite film does not contain Ny, which begins to absorb moisture due to the atmospheric conditions inside the case and the passage of time, so the package does not curl, and the surface layer does not curl. Since a glossy saponified ethylene-vinyl acetate copolymer resin is used, it is possible to provide a package with good appearance. In this way, the package using the composite film of the present invention as a bottom material film is a non-boil pack that is packed in a sterile room, and the surface layer is made of ethylene-vinyl acetate copolymer with good barrier properties. Since the compound resin is used, the shelf life of the product is long, and since the inner layer uses an ionomer resin with good deep drawability, it is suitable for packaging machines.Furthermore, if a Zn type ionomer resin is used, the product will have a long shelf life. Since it has less water absorption, it is less affected by the ambient air conditions at stores such as show cases, and can provide a curl-free package. 【table】

[Brief explanation of the drawing]

FIG. 1 is a diagram of a package using the composite film of the present invention as a bottom material.

Claims (1)

[Scope of utility model registration request] The thickness composition ratio of the composite film is 5 to 30% of the total thickness.
A surface layer made of saponified ethylene-vinyl acetate copolymer resin, an inner layer made of 95 to 70% ionomer resin, and an adhesive resin layer between the layers, which has a curl-preventing effect and is used for non-boiling purposes. Composite film for deep drawing.