JPS5869051A - Coextruded composite film for boil sterilization - 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 coextruded composite film for deep-drawn bottom material that can be suitably used for packaging foods that require boiling sterilization.

For processed foods such as sliced ham and kamaboko, the food is filled into a deep-drawn 9-formed film, the lid is sealed, and the package is packed at ♂O℃~! Boil sterilization treatment is carried out at 00°C to prevent the proliferation and contamination of microorganisms and increase the preservation effect of the contents. The main films for deep-drawn bottom materials used in such boil sterilization applications are composite films produced by dry lamination, such as polypropylene/polyvinylidene chloride coated polyamide/ethylene-vinyl acetate. There are copolymers and polypropylene/saponified ethylene-vinyl acetate copolymers/ethylene-vinyl acetate copolymers.

However, the former composite film has the drawback of poor transparency and deep drawing formability, and the latter composite film has the same drawbacks of poor transparency and pinhole resistance. Therefore, efforts have been made to improve the above-mentioned drawbacks by using various composite films produced by coextrusion. Although such coextruded composite films could improve the above drawbacks,
Unique problems associated with boil sterilization, such as whitening of the film during boil sterilization and pronking of packages (
The reality is that problems such as damp heat blocking) have not been completely resolved.

The present inventors conducted various studies in order to solve the problems associated with the boil sterilization treatment described above for coextruded composite films, and found that they used 12-nylon resin as the polyamide resin, and added the resin to the outside of the composite film. It was discovered that the structure of the layers has a remarkable effect, and the gist of this is that the first layer is made of 7.2 nylon resin.

The second layer is a saponified ethylene-vinyl acetate copolymer, and the third layer is a saponified ethylene-vinyl acetate copolymer.
This is a coextruded composite film for boil sterilization consisting of a modified polyolefin layer and a sealant layer as the ninth layer.

/2 The reason why nylon resin is used as the first layer (outer layer) is that it is very effective in preventing film whitening, moist heat blocking, and film curling during boiling sterilization treatment, and is more effective than other polyamide resins. No effect was observed when using nylon resin. It is thought that the high degree of crystallinity and low hygroscopicity of the 12 nylon resin contribute to this. Note that the thickness of the /j nylon resin layer is preferably in the range of j to /jμ.

The saponified ethylene-vinyl acetate copolymer used for the second layer has an ethylene content of jt)-40 molt, a degree of saponification of j molt or more, and a thickness of 10 μm.
Above, 10 to 30μ is more preferable in terms of storage stability of contents and cost. Foods with an ethylene content of less than 30 moles have a high degree of crystallinity, resulting in poor moldability during coextrusion molding or pressure-pressure (or vacuum) molding, and foods with an ethylene content of less than 60 moles have poor oxygen barrier properties. It is unsuitable for storage. If the degree of saponification is less than J Morch, boiling sterilization will result in cloudiness due to extremely small amounts of moisture penetrating from the outside, and peeling between film layers.

The modified polyolefin used in the third layer is a polyolefin resin grafted with at least one monomer selected from unsaturated carboxylic acid, acid, or a derivative thereof. The second layer of saponified ethylene-vinyl acetate copolymer is firmly adhered. The thickness of the third layer is 10-3
It is preferable to set it in the range of 0μ.

The sealing material layer of the second layer uses a sealing material selected from ionomer resin, polyethylene, or a copolymer of ethylene and other components to improve the sealing performance with the lid material and completely protect the contents. It is to make it. The thickness of the th layer is j
A value between O and /30μ is preferable.

Note that a modified polyolefin layer, which is the same as the third layer, may be provided between the first layer and the second layer, thereby improving the adhesive strength between the layers.

In the present invention, resin layers having the above structure are laminated by coextrusion method, so transparency, deep drawing formability, and pinhole resistance are good, and in boiling sterilization treatment at 0°C or higher, moist heat blocking and film formation are achieved. A coextruded composite film that does not cause whitening, curling, etc. and has good physical properties and appearance for use as a deep-drawn bottom material can be obtained.

This will be explained below using examples.

〔Example〕

A commercially available composite film (sample Nn3, t) produced by the method was heated at 100° C. for seconds using a deep drawing machine MVP-G07 manufactured by Mitsubishi Heavy Industries, Ltd. so that the first layer was on the outside.
Diameter ioormn depth, 2J'1 at gauge pressure of 0~
It was drawn and formed into a size of lllll+.

Immediately insert a slice of diameter into the formed hole.
・Mu, 200? After filling the package with the following lid material and vacuum packaging, each package was cut into a rectangle of / A Ota x / 30 ms. As the lid material, a film consisting of unstretched polypropylene (thickness 20μ)/cellophane coated with vinylidene chloride (30μ)/ionomer resin (30μ) was used. Each package obtained was heated at 0°C for 30 minutes.
Boil sterilization treatment was performed for 0 minutes, and moist heat blocking and film whitening of the packages were observed immediately after the treatment, and the boil sterilization-treated packages were further incubated at S℃, ioo
% relative humidity, and the appearance after storage for 3 weeks (
Wrinkles on the bottom, curling of the film), pinhole resistance, and gas barrier properties are shown in Table 1.

Pinhole resistance was determined by stacking 10 tons of each package in 3 rows and 7 stacks in an A-type single cardboard case, and
After 5 horizontal drops from a height of 0 cm and 7 drops on 6 sides, the packaging was checked for the presence of re-hin holes using the energization method.
This is the number of packages in which pin poles occurred.

The gas barrier properties were determined after a molded product with a diameter of 100 mfJ x depth of 2jIIIK was created using each component film as the bottom material and aluminum (RIθμ)/polyethylene (10゜μ) as the lid material. filled with nitrogen gas (
(100% relative humidity atmosphere inside the molded product) jtl:X7
These are the measured values of oxygen permeability of each constituent film after being left in an atmosphere of 5% relative humidity.

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

/+2PA; /2-nylon EVAOH; Saponified ethylene-vinyl acetate copolymer Ad; Modified polyolefin (Atomer LP-30!, manufactured by Mitsui Petrochemical Industries, Ltd.) Ionomer; Ionomer resin EVA; Ethylene-vinyl acetate copolymer OFF ; Unstretched polypropylene PA; g-Nylon coated PA; 6-nylon coated with vinylidene chloride copolymer - Samples / and A are the products of the present invention, and are characterized by moist heat blocking by boiling sterilization treatment, film No whitening,
Furthermore, no change in appearance was observed after treatment. The pinhole resistance and gas barrier properties were also good. Sample 3, which was a dry laminated product, had poor gas barrier properties, and wrinkles appeared at the bottom after 3 weeks of storage. Similarly, sample G, which is a dry laminated product, had poor pinhole resistance. Sample j, a coextruded product using the same resin as the product of the present invention and having EVAOH in the outermost layer, showed wet heat pronking and film whitening due to boil sterilization treatment. In addition, in sample 6, a coextruded product in which &FA was used instead of /2PA in the outermost layer, poor appearance such as wrinkles at the bottom and curling of the film occurred after 3 weeks of storage after boiling sterilization.

Claims (1)

[Claims] A coextruded composite film for boil sterilization in which the seventh layer is a /,7 nylon resin, the second layer is a saponified ethylene-vinyl acetate copolymer, the third layer is a modified polyolefin, and the third layer is a sealing material layer.