JPS5820444A - Co-extruded composite film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a four-layer coextruded composite film for deep-draw bottoming for food packaging such as sliced ham.

Currently, various types of composite films made by coextrusion are being double-layered as films for deep-drawing 9-bottom films such as sliced ham. Among these, Otsu-6 Otsu nylon copolymer, which has a polyamide position of 1, is one of the constituent materials / This composite film is made of
It has excellent deep drawing formability and is characterized by the fact that wrinkles do not form at the bottom immediately after forming or wrinkles occur over time, but if stored for a long period of about 3 weeks or more, the molded product may curl. J: Appearance defects were observed.

However, the curling of the film due to the influence of immersion in the atmosphere has not been completely resolved.

The present invention aims to improve the above drawbacks, and its gist is that the first layer is an ethylene chloride and the second layer is a 7.
2 nylon resin, the third layer is a modified polyolefin, the ninth layer is a sealing material layer selected from ionomer resin, polyethylene, or a copolymer of ethylene and other components,
It is a four-layer coextruded composite film in which the thickness of the second layer ranges from 0 to /jμ.

Saponified ethylene-vinyl acetate copolymer (hereinafter referred to as “EVA”)
It's called OHJ. ) layer as the first layer (outer layer) is to provide gas barrier properties to the composite film, to suppress dimensional changes due to moisture absorption of the Ωth layer, the nylon layer, and to prevent light ripples on the surface of the film. This is for the purpose of granting.

The BVA OH to be used should have an ethylene content of 30 to 2 mol %, a saponification degree of 9 J mol or more, and a thickness of 10 to 30 μm or more to preserve the contents. This is undesirable in terms of performance and cost. If the ethylene content is less than 30 mol%, the crystallinity will be high and the forming force during coextrusion molding or pressure (or vacuum) molding will be poor, and if it exceeds 60 mol%, the oxygen barrier property will be poor. It deteriorates and becomes unsuitable for food preservation. If the degree of saponification is less than 9J molar ratio, if heat treatment such as molding is performed, a trace amount of water that penetrates from the outside will become white. This may cause scratches or peeling between film layers.

The reason why 7.2 nylon resin is used in the second layer is to provide strength to the composite film itself and to minimize the influence of humidity. 7.2 The nylon resin used is one obtained by polymerizing ordinary ω-laurolactam.

7.2 The thickness of the nylon layer is most preferably in the range fd, t~/oμ.

That is, if the thickness of the 7.2 nylon layer is less than tμ, the strength (pinhole resistance) of the composite film will be insufficient.

If the thickness exceeds /μ, the tensile stress increases, resulting in poor elongation and poor formability. In addition, the shrinkage stress increases when the dimensions change due to moisture absorption, resulting in deformation of the contents, wrinkles at the bottom over time, and curling at the periphery.

The modified polyolefin used in the third layer is a polyolefin resin grafted with at least one kind of unsaturated carboxylic acid or its conductor. The sealing material layer and the 7.2 nylon layer of the β-th layer are firmly adhered, and the nylon layer and the sealing material layer, which have conventionally caused delamination, are firmly adhered. In addition, the thinner the nylon layer mentioned above, the lower the strength, so it is necessary to reinforce the strength with a third layer, and the thickness of the third layer should be in the range of d10 to 30/l. :stomach.

The seventh layer, the sealing layer, uses a sealing material selected from ionomer resin, polyethylene, or a copolymer of ethylene and other components to ensure sealing performance with the lid material and protect the contents of the comb. Make it perfect. What is the thickness of the 7th layer? A value between θ and /3θμ is preferable.

In the present invention, resin layers having the above structure are laminated by a coextrusion method, so deep drawing does not cause wrinkles or curls at the peripheral edge during pressure (or vacuum) molding. I) Coextrusion with a good appearance when used as a bottom A laminated film is obtained.

This will be explained below using examples.

〔Example〕

Each of the composite films shown in Table-/ was drawn with the deep drawing machine MV'P-G0/ mold manufactured by Mitsubishi Heavy Industries ■ so that the first layer was on the outside.
After heating for θθ'Q X j seconds with a pressure of 3.0 to 9/d, it was molded to a diameter of 100 mm and a depth of 4-3 Q mm. Immediately fill the formed hole with 20θg of sliced ham with a diameter of 9gmm, cover it with the following lid material and vacuum pack it, then /AOr
Each package was cut into a rectangular shape of rrm×/JOrnm. Each of the obtained packages was stored in an atmosphere at 5°C and /θθ relative humidity, and the appearance (wrinkles on the bottom, curling of the film) and pinhole resistance (note) after storage for a certain period of time were measured.
/ Shown in /.

The lid material is made of unstretched polypropylene (thickness: 20 μm).
) / Cellophane coated with vinylidene chloride (30μ)
/ A film made of ionomer resin (30μ) was used.

Note: Each 70-year-old package was stacked in 3 rows and 7 stacks in a pinhole-resistant type A single cardboard case, and the package was dropped horizontally from a height of 6 otyn 5 times, and the package was dropped after dropping. The presence or absence of pinholes was confirmed using the energization method.

In addition, in the table, the resin used for the film is indicated by the following symbol.

/, 2PA: /, 2-nylon A d: 1 polyolefin (Atomer LF-30
EVAOH: Ethylene content 75 mol%, saponified Ijj
9qJ-mol% saponified ethylene-vinyl acetate copolymer Otsu-6APA: 6-Otsu nylon content 43 is 73-Weight section Otsu-AA nylon ionomer: Ionomer resin (Himilan, manufactured by Mitsui Polychemicals (incorporated)) EVA: Ethylene-vinyl acetate copolymer with vinyl acetate content j% (Note) ○... Evening) Good △... Slightly bad ×...
- Samples &/ to λ in the defect list are within the scope of the present invention, with no wrinkles on the bottom or curling of the film after long-term storage, and extremely good pinhole resistance. Met. The thickness of nylon is 7.2/t with the same standard as the invented product.
Items with a test score of 3 over 11 will be stored for a long time (3 weeks)
The bottom of the film was wrinkled and the film was slightly curled. Similarly, the thickness of /Ω nylon! Samples with a sample diameter of less than μ had poor surface j pinhole properties. Sample plate 5 using Otsu-Ot nylon had a good appearance after 1 week, but the film curled after 3 weeks.

Claims (1)

[Claims] The first layer is a saponified ethylene-vinyl acetate copolymer with an ethylene content of 30 to 1.0 mol% and a saponification degree of 9 mol% or more, the Ωth layer is a non-nylon resin, and the third layer is a saponified ethylene-vinyl acetate copolymer with an ethylene content of 30 to 1.0 mol%. Modified polyolefin, the ninth layer consists of a sealing material layer selected from an ionomer resin, polyethylene, or a copolymer of ethylene and other components, and the thickness of the second layer is
A range of four-layer coextruded composite films.