JPH01202436A - Packing material for retortable pouch - Google Patents

Abstract

PURPOSE:To obtain packaging material having excellent barrier property, transparency and sealing strength, all of which do not deteriorate even at a high temperature of retorting process by a structure wherein a transparent thin coating layer made of specified silicon oxide is provided on one side of a plastic base material. CONSTITUTION:The packaging material concerned for retortable pouch consists of a plastic base material and a transparent thin coating layer made of silicon oxide, in which the ratio of silicon atom to oxygen atom is 1:0.3-1.8 and which is provided on one side of the plastic base material and has barrier property. The favorable range of the thickness of the transparent thin coating layer is 400-3000Angstrom . If said thickness is below 400Angstrom , no satisfy barrier property is obtained. If said thickness exceeds 3000Angstrom , high production cost and, in addition, easy generation of crack result. The barrier property and transparency of the transparent thin silicon oxide coating layer do not deteriorate even at the high temperature of retorting process. Further, even when no anchoring treatment to enhance the adherence between the base film and a heat-sealing layer is carried out, no deterioration of the sealing strength occurs before and after the retorting treatment.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to packaging materials for retort food.

More specifically, the present invention relates to a transparent packaging material for retort food whose barrier properties against oxygen and water vapor, transparency, and seal strength do not deteriorate even when exposed to high temperatures during retort processing.

[Prior art] Retort food, which is a back-packaged package of cooked or semi-cooked foods such as curry, meat sauce for spaghetti, and meat preparations, has become widely available on the market in recent years because it can be stored for a long time and is easy to prepare. . Packaging materials for retort food must have excellent barrier properties and sealing strength to prevent oxygen, water vapor, etc. from permeating into the bag and altering the contents.

As such a packaging material, a material obtained by laminating aluminum foil with an unstretched polypropylene film having heat sealability is often used.

[Problems to be Solved by the Invention] However, when a film laminated with aluminum foil is used for retort food packaging, the contents cannot be confirmed because the aluminum foil is opaque, making it difficult for consumers to check the product at the store. Can not. Furthermore, at production plants, aluminum foil is heavier than plastic film, so it is difficult to handle during work in each process and during transportation between each process. In addition, in packaging materials for retort foods laminated with aluminum foil, in order to obtain sufficient sealing strength before and after retort processing, anchor treatments such as electric discharge treatment, chemical treatment, or coating with an anchor agent are applied for boat fishing. It is necessary to increase the adhesion strength between the layers.

On the other hand, examples of films that are transparent and have barrier properties include polyvinylidene chloride resin films and base films coated with polyvinylidene chloride resin. However, since polyvinylidene chloride resin has poor heat resistance, its barrier properties deteriorate extremely under the high temperatures of retort processing (for example, 110°C or higher), and the film turns white and loses its transparency, so it cannot be used for retort foods. Difficult to use as packaging material. In addition, the barrier properties are not sufficient even at room temperature, so the shelf life is generally shorter than those laminated with aluminum foil.In order to improve the barrier properties, it is necessary to increase the thickness of the film, and the flexibility of the film There are problems such as loss of character and increased film cost.

In view of the above points, the present invention provides a retort food product that is transparent, has excellent barrier properties and seal strength, and whose barrier properties, transparency and seal strength do not deteriorate even when exposed to high temperatures during retort processing. The purpose is to provide packaging materials.

[Means for Solving the Problems] The retort food packaging material of the present invention includes a plastic base material and a ratio of silicon atoms to oxygen atoms provided on one side of the plastic base material, l: 0.3 to 2. It is characterized by consisting of a transparent thin film layer of silicon oxide.

[Function] In the present invention, the transparent thin film layer of silicon oxide does not deteriorate its barrier properties and transparency even under the high temperature of retort processing, and the transparent thin film layer of silicon oxide is bonded to the base film and the heat seal layer. Since it also improves the adhesion with the material, the seal strength does not deteriorate before and after retort treatment even without anchor treatment.

[Example] The transparent plastic substrate used as the base film used in the present invention may be any material that has heat resistance that can withstand the temperature of retort treatment, such as nylon, polyester, ethylene-vinyl alcohol copolymer, polycarbonate, polycarbonate, etc. A film or sheet material of acrylonitrile, polypropylene, etc. is used. In terms of heat resistance and cost during retort processing, polyester,
Nylon is preferred. The thickness varies depending on the purpose of use of the packaging material, and is appropriately selected from a wide range from 6 to too'. The silicon oxide in the transparent thin film layer has a ratio of silicon atoms to oxygen atoms of 1:0.3 to 2, preferably 1.
:0.3-1.8, especially <L:0.7-1.3. If the proportion of oxygen atoms is greater than the above range, the barrier properties will deteriorate, especially if the proportion of oxygen atoms is l:
If the amount is more than 2, the desired barrier properties cannot be achieved. On the other hand, if the proportion of oxygen atoms is less than the above range, the barrier properties will be good, but the transparency will be poor. Particularly preferred is one in which the ratio of silicon atoms to oxygen atoms is approximately 1:1.

The thickness of the transparent thin film layer is preferably in the range of 400 to 3000. If the thickness is less than 400, sufficient barrier properties cannot be obtained, and if it exceeds 3,000, the cost will increase. In addition, cracks are likely to occur, and the degree of discoloration increases as the thickness increases.

For forming such a transparent thin film layer of silicon oxide, a physical vapor deposition (PVD) method such as a vacuum evaporation method, a sputtering method, an ion blating method, or a chemical vapor deposition (CVD) method is appropriately used. In the vacuum evaporation method, SlO or a mixture of Sl and 5i02 is used as the evaporation source material, and in order to arbitrarily change the ratio of silicon atoms to oxygen atoms in the transparent thin film layer within the above range, the evaporation source material may be SlO or a mixture of Sl and 5i02. 5I
This can be carried out by a method such as binary vapor deposition using 02 and changing these ratios.

The packaging material of the present invention may be used as it is depending on the intended use, or may be further provided with a heat seal layer or a protective film on the transparent thin film layer.

There are no particular restrictions on the heat-sealing layer, and it is usually unoriented polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, or ethylene-acrylic acid copolymer. Examples include ethylene-based ionomers such as copolymers. The heat seal layer is usually provided by dry lamination or extrusion.

The thickness may be in the range of 20 to 100 μm, preferably 40 to 80 μm.

The protective layer is provided by laminating a film of polyester, nylon, ethylene-vinyl alcohol copolymer, or the like, or by coating with a heat-resistant epoxy resin, melamine resin, urethane resin, polyester resin, or the like.

The retort food packaging material of the present invention is transparent and has high barrier properties. That is, the oxygen permeability is 2.
0cc/rr?・24hrs or less and moisture permeability of 3
．． It is 0g/nf・24hrs or less. Therefore, foods packaged with the packaging material of the present invention can be stored for a long period of time.

Also, because it is transparent, consumers can check the contents at the store before making a purchase.

Furthermore, the retort food packaging material of the present invention is characterized in that the barrier properties and transparency do not deteriorate even when subjected to high-temperature heat treatment. That is, it can withstand retort treatment at 100-140°C, especially at 105-140°C for 10-60 minutes. Therefore, it has become possible to retort food packaged with the packaging material of the present invention, store it for a long period of time, and then heat it and serve it as a meal. .

The usage form of the retort food packaging material of the present invention is as follows:
There are bags, lids, cups, tubes, standing bags, trays, etc. The heat seal layer can be used for bags, tubes,
Although it is necessary for applications such as standing bags, it is not necessarily necessary for applications such as cups, lids, and trays.

Furthermore, it may be printed for decoration or to explain the contents, or it may be bonded with a printing film for decoration or a nylon film as a reinforcing material to form a composite.

Next, the packaging material for retort food according to the present invention will be described with reference to Examples.

Example 1 Thickness 12. SIO on one side of ci polyester film
An Si0 layer with a thickness of 800 mm was formed by vacuum evaporation using SiO as an evaporation source.Furthermore, a 40-fold unstretched polypropylene film was coated with a polyester adhesive to a thickness of 3 μm on the evaporation surface, and the layer was heated at 80°C for 20 minutes. After drying for seconds, 2kg/cl
A film for bags was produced by dry laminating under a pressure of -100° C. for 1 second.

Example 2 A bag film was produced in the same manner as in Example 1, except that a transparent thin film layer of 8 layers with a thickness of 800 mm was formed using a mixture of Sl and 8102 as the evaporation source.

Comparative Example 1 A bag film was produced by dry laminating an unstretched polypropylene film with a thickness of 40 times on a polyester film with a thickness of 12ρ in the same manner as in Example 1.

Comparative Example 2 A polyvinylidene chloride layer with a thickness of 5 m is formed on a polyester film with a thickness of 12 m, and then an unstretched polypropylene film with a thickness of 40 m is dry laminated in the same manner as in Example 1 to produce a film for bags. was created.

Comparative Example 3 Dry lamination of aluminum foil with a thickness of 12 AIm on a polyester film with a thickness of 12 items, and further with a thickness of 40
The unstretched polypropylene film was dry laminated in the same manner as in Example 1 to produce a bag film.

The bag films obtained in Example 1.2 and Comparative Examples 1 to 3 were made into bags, filled with meat sauce for spaghetti and completely sealed, and then retorted at 130° C. for 20 minutes. Table 1 shows the results of retort suitability, barrier properties and transparency before and after retort treatment.

For barrier testing, oxygen gas permeability was measured by MO
CON method, water vapor permeability according to JIS-Z-02081:
Therefore, this was done by measuring. Therefore, the smaller the value, the better the barrier properties.

Retort suitability was determined by the ratio of oxygen and water vapor permeability before and after retorting (ie, oxygen (or water vapor) permeability after retorting/oxygen (or water vapor) permeability before retorting). The evaluation criteria are as follows.

○・・・The above ratio is about 1 for both oxygen and water vapor
゜△...The ratio is about 1 to 3 for either oxygen or water vapor, but the other is greater than about 3.

×・・・・・・The above ratio is about 3 for both oxygen and water vapor.
bigger.

Furthermore, in order to conduct a long-term storage test, each of the obtained bags was filled with meat sauce for spaghetti and completely sealed, then retorted and stored at room temperature for one year, after which the odor, color, and taste of the meat sauce were examined. The results are shown in Table 2.

[Blank below] [Effects of the Invention As explained above, the packaging material for retort food of the present invention is transparent and has excellent barrier properties, and the barrier properties do not deteriorate even at high temperatures, and the base film and heat sealability are excellent. Adhesion with the layer is enhanced by the transparent thin film layer of silicon oxide, and it is possible to maintain strong sealing strength even before and after high-temperature treatment such as retort treatment.

Procedural amendment (salmon) l Indication of the case 1986 Patent Application No. 26342 2 Name of the invention Packaging material for retort food 3 Person making the amendment Relationship to the case Patent applicant address Nishinotoin, Bukkoji-dori, Shimogyo-ku, Kyoto City Seijinki Zokuyamacho 1
81 No. 4 Agent 540 Address 2-22 Tanimachi, Chuo-ku, Osaka 5 Subject of amendment (1) "Claims" column of the specification ('2J
Contents of amendment in column 6 of "Detailed Description of the Invention" of the specification (1) "Claims" shall be amended as shown in the attached "Amended Scope of Claims".

(2) "rl:o, 3-2" on page 4, lines 16-17 of the specification is corrected to "rl:o, 3-1.8".

(3) On page 5, pages 20 to 6, line 1, the F ratio is corrected to ``the ratio is 1:0.3 to 1.8, especially.''

(4) Correct "1:2" in line 4 of page 6 to rl:L, 8J.

7 List of Attached Documents (1) Amended Claims 1 Amended Claims 1. A plastic base material and a ratio of silicon atoms to oxygen atoms provided on one side of the plastic base material. 1: O
A transparent packaging material for retort food having barrier properties, comprising a transparent thin film layer of silicon oxide having a molecular weight of J~1.8.

2. The retort food packaging material according to claim 1, further comprising a heat seal layer on the transparent thin film layer. "that's all

Claims (1)

[Claims] 1. A plastic base material and a silicon atom to oxygen atom ratio provided on one side of the plastic base material of 1:0.3 to 1:0.3.
2. A transparent retort food packaging material having barrier properties comprising a transparent thin film layer of silicon oxide. 2. The retort food packaging material according to claim 1, further comprising a heat seal layer on the transparent thin film layer.