JPH061369A - Packaging material for frozen food - Google Patents

Abstract

PURPOSE:To provide a packaging material for frozen food with excellent anti- bending property and gas barrier property, in the form of packaging film. CONSTITUTION:For a packaging material with gas barrier property, which consists of a plastic base and a silicon oxide thin film layer provided at least on one surface of the plastic base, the specific gravity of the thin film is made to be 1.80-2.20. By doing this, a packaging material for frozen food which has an excellent gas barrier property and high anti-bending property, is superior in the barrier characteristics at low temperature, and of which the comprehensive practical utility properties are excellent is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frozen food packaging material, and more particularly to a frozen food packaging material which is transparent and has a sufficient barrier property against oxygen and water vapor even in a wide temperature range.

[0002]

2. Description of the Related Art Agricultural products (eda beans, mixed vegetables,
Sweet corn, etc.), marine products (squid, shrimp, etc.), livestock products (beef, chicken, pork, etc.), cooked foods (meat dumplings, croquettes, hamburgers, etc.) are packed in a pack for long-term storage, and frozen or chilled. Often saved. As such a packaging material, a composite film obtained by laminating a film of polyester, nylon, polypropylene or the like with a film of heat sealable polyethylene, unstretched polypropylene or the like is often used in consideration of cold resistance. Further, as a packaging material for frozen foods using a ceramic thin film (silicon oxide), Japanese Patent Application Laid-Open No. 1-20243
7 are proposed.

[0003]

The polymer film composite film has a poor barrier property against oxygen and water vapor, with an emphasis on cold resistance. Due to the oxygen gas that has penetrated into the bag even during freezing, However, it may not be suitable for long-term storage because discoloration from the cut of meat etc. may occur, and there was a problem that the quality of the contents immediately deteriorates when exposed to normal temperature . In order to improve this point, a packaging material for frozen foods using a ceramic thin film (silicon oxide) has been proposed, but it does not have high flex resistance, so be careful in post-processing such as laminating and bag making, and handling afterwards. Was required.

[0004]

The frozen food packaging material of the present invention is a packaging material having a gas barrier property comprising a plastic substrate and a silicon oxide thin film layer provided on at least one surface of the plastic substrate. A packaging material for frozen foods, wherein the thin film has a specific gravity of 1.80 to 2.20, or a frozen food packaging in which a heat seal layer is further provided on the thin film layer. It is a material.

The plastic substrate referred to in the present invention is a film obtained by melt-extruding an organic polymer and, if necessary, stretching, cooling and heat-setting in the longitudinal direction and / or the width direction. As the organic polymer, polyethylene, polypropylene, polyethylene terephthalate, polyethylene-2,6-naphthalate, nylon 6, nylon 4,
Examples thereof include nylon 66, nylon 12, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, wholly aromatic polyamide, polyamideimide, polyimide, polyetherimide, polysulfone, polyphenylene sulfide, and polyphenylene oxide. Further, these (organic polymer) organic polymers may be copolymerized or blended with a small amount of another organic polymer.
Among these, nylon, PET, polypropylene, and saponified ethylene-vinyl acetate copolymer are particularly preferable in terms of microwave permeability and strength as a packaging bag.

Further, known additives such as an ultraviolet absorber, an antistatic agent, a plasticizer, a lubricant and a coloring agent may be added to the organic polymer, and the transparency thereof is not particularly limited. However, when used as a transparent gas barrier film, those having a transmittance of 50% or more are preferable. As long as the plastic substrate in the present invention does not impair the object of the present invention, prior to laminating the thin film layer, the film is subjected to corona discharge treatment,
Glow discharge treatment or other surface roughening treatment may be performed, and known anchor coat treatment, printing, or decoration may be performed. The thickness of the plastic substrate in the present invention is preferably in the range of 5 to 500 μm,
More preferably, it is in the range of 8 to 300 μm.

The silicon oxide thin film in the present invention means Si, S
It is considered to be composed of iO, SiO _{2 and the} like, and their ratio also differs depending on the preparation conditions. A trace amount (up to 3% of all components) in this component within the range where the characteristics are not impaired.
Other components may be included. The thickness of the thin film is not particularly limited, but is preferably 50 to 8000 Å from the viewpoint of gas barrier property and flexibility. For the production of such a silicon oxide thin film, a vacuum vapor deposition method, a sputtering method,
PVD method (physical vapor deposition method) such as ion plating,
Alternatively, a CVD method (chemical vapor deposition method) or the like is appropriately used. For example, in the vacuum vapor deposition method, SiO or a mixture of Si and SiO ₂ is used as the vapor deposition source material, and
As a heating method, resistance heating, high frequency induction heating, electronic beam heating or the like can be used. Further, as the reactive gas, oxygen, nitrogen, water vapor or the like may be introduced, or reactive vapor deposition using means such as ozone addition or ion assist may be used. Further, the production conditions may be changed as long as the object of the present invention is not impaired by applying a bias or the like to the substrate, raising the substrate temperature, or cooling. The same applies to other preparation methods such as the sputtering method and the CVD method.
Further, the product of the present invention may be used as it is, but may be used by laminating or coating another organic polymer film or thin layer.

The specific gravity as used in the present invention means the ratio of the mass of a substance occupying a certain volume at a certain temperature to the mass of a standard substance having the same volume (water at 4 ° C.). The measurement of specific gravity is
Usually, the mass and volume of an object may be measured and the ratio to the mass of water of the same volume at 4 ° C. may be obtained, but it is difficult to measure the volume in the measurement of the thin film of the present invention. Therefore, first, the thin film is peeled from the substrate, or only the substrate is melted to form a single film made of only the thin film, and then (JIS K
7112), it is desirable to use a specific gravity measurement method. For example, in the float-sink method, the sample can be dipped in a solution of known specific gravity, and the specific gravity of the thin film can be measured from the floating state. As this solution, a mixed solution of carbon tetrachloride and bromoform, or methylene iodide can be used. The specific gravity value can also be measured by a density gradient tube method in which a single membrane is immersed in a solution having a continuous density gradient.

When the specific gravity of the thin film thus obtained is smaller than 1.80, the structure of the silicon oxide thin film becomes rough and sufficient gas barrier properties cannot be obtained. Also,
When the specific gravity of the thin film is greater than 2.20, the initial gas barrier property after film formation is excellent, but the film becomes too hard and mechanical properties, particularly gelbo property are poor, and after printing, laminating, bag making, etc. Due to the process, sterilization treatment, and subsequent handling during freezing, there is a large possibility that the gas barrier property will deteriorate, and it is not suitable for use as a packaging material for frozen foods. For the above reasons, the specific gravity of the silicon oxide-based thin film is preferably 1.80 to 2.20, more preferably 1.95 to 2.15 as a packaging material for frozen foods.

The frozen food packaging material of the present invention is transparent and has a high barrier property. That is, the oxygen permeability is 3.0 cc / m ² · 24 hrs or less and the water permeability is 3.0 g / m ² · 24 hrs or less, and a high barrier property is maintained even during sterilization treatment and frozen storage. . Therefore, the food packaged with the packaging material of the present invention, sterilized, and frozen-stored can be stored for a long time. Further, the packaging material for frozen foods of the present invention is characterized in that the barrier property is less deteriorated even by high temperature treatment. Therefore, it is also possible to retort a food packaged with the packaging material of the present invention and then store it frozen. Further, after frozen storage for a longer period of time, it is possible to heat them in a microwave oven or boil them while packaging them.

The frozen food packaging material of the present invention comprises meat balls,
It can be used as a solid packaging bag for hamburgers, croquettes or the like, or a liquid packaging bag for gratin, sauces, soups or the like. The use form of the frozen food packaging material of the present invention is required in the case of applications such as bags, lids, cups, tubes, and standing bags. Further, it may be printed for decoration or for explaining the contents, or may be laminated with a design film, a reinforcing agent or the like. In addition, because it has excellent gelbo characteristics, there is little deterioration in the printing, laminating, and bag making processes, and even after it is made into a bag,
Do not take extra care when handling it. Since the packaging material of the present invention is resistant to retort treatment, microwave irradiation, etc., sterilization treatment of the packaged food is retort treatment,
There is no particular limitation such as microwave irradiation. Next, the present invention will be described with reference to examples.

Example 1 As a vapor deposition source, particulate Si (purity 99.99%) and Si having a size of about 3 to 5 mm and Si
Using O ₂ (purity 99.9%) by the electron beam evaporation method,
12 μm thick PET film (Toyobo Co., Ltd .: E50)
07) A silicon oxide-based gas barrier thin film was formed thereon.
The vapor deposition material was divided into two without mixing. An electron gun (hereinafter referred to as an EB gun) is used as a heating source, and Si and SiO are used.
Each of the _two was heated in a time division manner. The emission current of the EB gun at that time is set to 0.7 to 1.8 A, and Si and SiO
The heating ratio to ₂ was changed from 10:10 to 60:10. The film feed speed was changed from 30 to 120 m / min to form a film having a thickness of 500 to 4000 Å. Further, the vapor pressure is changed from 1 × 10 ⁻⁵ to 8 × 10 ⁻³ by changing the supply amount of oxygen gas.
The conditions were changed up to Torr.

The specific gravity of the film thus obtained was determined by PET.
After the film was dissolved, the film was measured by the float-sink method. Further, a 60 μm-thick unstretched polypropylene film (OPP film) was dry-laminated to the composite film on PET using a two-component curing type polyurethane adhesive (thickness 2 μm) and packaged. To obtain a plastic film. The oxygen barrier property of this packaging film was measured at a low temperature of −20 ° C. and room temperature. Also, the oxygen barrier property was similarly measured after the gelbo treatment.

Method of measuring oxygen transmission rate The oxygen transmission rate of the prepared gas barrier film is measured by an oxygen transmission rate measuring apparatus (OX-TRAN manufactured by Modern Controls Co., Ltd.).
100). -Test method of flex fatigue resistance (hereinafter gelbo property) Flex fatigue resistance was evaluated using a so-called gelbo flex tester (manufactured by Rigaku Kogyo Co., Ltd.). The condition is (MIL-B131H) 112 inch x 8 inc.
The sample piece of h was made into a cylindrical shape with a diameter of 3 (1/2) inch,
Both ends are held, the initial gripping interval is set to 7 inches, a twist of 400 degrees is applied at a stroke of 3 (1/2) inch, and this reciprocating motion is repeated 40 times / min.
At a temperature of 20 ° C. and a relative humidity of 65%.
The oxygen transmission rate measured in this manner was about 1 to 2 cc at both room temperature and low temperature, which was very excellent. In addition, 100
The temperature-dependent results after the spinning gelbo test also increased only around 2 cc, and a packaging film having excellent temperature characteristics and overall characteristics was obtained. 10cm x 15 using this film
A pillow type bag having a size of cm was prepared and used as a sample for long-term storage experiment.

Comparative Example 1 A silicon oxide type transparent gas barrier thin film was formed by EB vapor deposition in the same manner as in Example 1, and the obtained sample was measured for specific gravity and subjected to low temperature, room temperature or gelbo treatment. The oxygen barrier properties were measured. As a result, the barrier property at room temperature or at a low temperature after the gelbo treatment was insufficient at 5 cc or more, which was unsatisfactory in the comprehensive judgment. Using this film, a sample bag for long-term storage experiments was prepared in the same manner as in (Example 1). (Example 2) As a vapor deposition source, particulate SiO having a size of about 3 to 5 mm (purity 99.9%) was used, and a PET film having a thickness of 12 μm (Toyobo Co., Ltd .: E5000) was prepared by a resistance heating vapor deposition method. ), A silicon oxide-based gas barrier thin film was formed thereon. The high frequency power at that time is 3.5 kW,
The film feed speed was changed from 30 to 120 m / min to form a film having a thickness of 500 to 4000 Å. The vapor pressure is 1.0 × 10 ⁻⁵ to 8 × by changing the supply amount of oxygen gas.
The conditions were changed to 10 ^-3 Toor. The specific gravity of the film thus obtained was measured after dissolving the PET film. Thereafter, a packaging film was prepared and the oxygen barrier property was measured in the same manner as in (Example 1). In addition, using this film, a sample bag for long-term storage experiment was prepared in the same manner as in (Example 1).

(Comparative Example 2) A silicon oxide gas barrier thin film was formed by the resistance heating vapor deposition method in the same manner as in Example 2, and the obtained sample was measured for specific gravity and subjected to low temperature, normal temperature or gelbo treatment. Later oxygen barrier properties were measured.
As a result, the oxygen barrier property or the gelbo property at room temperature or at low temperature was insufficient, and the overall judgment was unsatisfactory. Using this film, a sample bag for long-term storage experiments was similarly prepared. Comparative Example 3 A PET film having a thickness of 12 μm has a thickness of 5 μm.
m polyvinylidene chloride layer is formed and then the thickness is 60 μm
The CPP film of 1 was dry-laminated in the same manner as in Example 1 to prepare a bag film. Also, using this film, a sample bag for long-term storage experiments was similarly prepared.

Next, in order to carry out a long-term storage stability test,
A representative bag of Examples 1 and 2 and Comparative Examples 1 to 3 was filled with a hamburger to prepare a completely sealed sample, which was then retort-treated (120 ° C. × 30 mi).
n) was performed. After storing these in a refrigerator (-20 ° C) for 2 months, changes in the contents were observed. As a result, the examples of the present invention were normal, but the comparative examples 1 and 2 showed abnormalities. In Comparative Example 3, the film was whitened and the contents could not be seen due to the retort treatment. (Table 3)

[0018]

INDUSTRIAL APPLICABILITY In a packaging material having a gas barrier property, which comprises a plastic substrate and a silicon oxide thin film layer provided on at least one surface of the plastic substrate, the specific gravity of the thin film is set to 1.80 to 2.20. By doing so, it is possible to provide a frozen food packaging material having excellent gas barrier properties, high flex resistance, and high barrier properties at low temperatures, and having excellent overall practical properties.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Otani 2-1-1 Katata, Otsu City, Shiga Toyobo Co., Ltd. (72) Inventor Toshiyuki Ohtani 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. General Research Institute (72) Inventor Yozo Yamada 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. General Research Institute

Claims (2)

[Claims] 1. A packaging material having a gas barrier property, comprising a plastic substrate and a silicon oxide thin film layer provided on at least one surface of the plastic substrate, wherein the thin film has a specific gravity of 1.80 to 2.20. Frozen food packaging material characterized by being present. 2. The frozen food packaging material according to claim 1, further comprising a heat seal layer provided on the thin film layer.