JPH05305971A - High frequency sterilizing packaging material - Google Patents

Abstract

PURPOSE:To provide a high frequency sterilizing packaging film material excellent in bend resisting and gas-barrier properties. CONSTITUTION:The packaging material is a gas-barrier type consisting of a plastic base material and a thin film layer constituted of aluminum oxide formed on at least one side of the plastic base material. The specific gravity of the thin film set at 2.70-3.30 imparts the packaging material an excellent gas-barrier property and the subsequent application of high frequency offers a high frequency sterilizing packaging material high in gas-barrier and bend resisting properties and excellent in practical application as a whole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent microwave sterilization packaging material having a high barrier property.

[0002]

2. Description of the Related Art Various methods have been used to maximize the shelf life in food packaging, and among them, sterilization by microwave irradiation is attracting attention because of its excellent properties and is becoming widespread. That is, the heating rate and the heating efficiency are high, and even a complicated shape can be uniformly heated. Further, it has many excellent features as food sterilization such that the operation and control of the device are easy and the safety is high, and the working environment can be kept clean. Therefore, when packaging foods such as milk, juice, sake, ham, hamburger, sausage, pudding, bento, side dish, sake, it is widely practiced to sterilize the packaging container and contents by microwave irradiation and package the contents. .. Such sterilized packaging materials include microwave-permeable ethylene-vinyl acetate common saponified film, etc.
Put the contents in a polyvinylidene chloride film (for example, Toyobo Co., Ltd. ester film-EK (trade name)), a transparent laminate film having a polyvinyl alcohol film as a core layer, or a tray of foamed styrene resin,
Examples include stretch-wrapped polyvinyl chloride film. Further, as a packaging material for microwave sterilization using a ceramic thin film (silicon oxide), there is disclosed in Japanese Patent Laid-Open No. 1-22.
5542 has been proposed.

[0003]

However, such conventional packaging materials are designed to have a barrier property against oxygen gas and moisture as much as possible in order to prevent the growth of microorganisms and the oxidation of foods. , Films of saponified ethylene-vinyl acetate copolymer and polyvinyl alcohol films have extremely poor barrier properties when the humidity is high, and vinylidene chloride resin films and laminate films coated with the resins are vinylidene chloride resins. Since the heat resistance of is poor, the barrier property after microwave sterilization treatment is significantly reduced, and even if general viable bacteria can be reduced by microwave sterilization,
I couldn't store it for a long time. Furthermore, regarding the film using the ceramics thin film, there is no problem in initial gas barrier properties and heat resistance, but it does not have high bending resistance, and it requires careful attention in the post-process such as laminating and bag making, and the subsequent handling. there were.

[0004]

The packaging material for microwave sterilization of the present invention is a packaging material having a gas barrier property comprising a plastic base material and an aluminum oxide thin film layer provided on at least one surface of the plastic base material. The microwave sterilization material according to claim 1, wherein the specific gravity of the thin film is 2.70 to 3.30, or a heat layer is further provided on the thin film layer. It is a material.

The plastic substrate referred to in the present invention may be a plastic film having good microwave transparency and being hardly deteriorated by microwave sterilization treatment. According to the longitudinal direction,
And, or, a film stretched in the width direction, cooled, heat-fixed, as the organic polymer, polyethylene,
Polypropylene, polyethylene terephthalate, polyethylene-2,6-naphthalate, nylon 6, nylon 4, nylon 66, nylon 12, polyvinyl chloride,
Examples thereof include 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 from the viewpoint 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 layers, the film is subjected to corona discharge treatment,
It may be subjected to glow discharge treatment or other surface roughening treatment, or may be subjected to known anchor coat treatment, printing or decoration. The plastic substrate in the present invention preferably has a thickness in the range of 5 to 500 μm,
More preferably, it is in the range of 8 to 300 μm.

The aluminum oxide thin film in the present invention is considered to be composed of Al, AlO, Al ₂ O _{3 and the} like, and the ratio of these also differs depending on the forming conditions. This component may contain a trace amount (up to 3% with respect to all components) of other components as long as the characteristics are not impaired. The thickness of the thin film is not particularly limited, but from the viewpoint of gas barrier property and flexibility, it is preferably 50 to 8000Å. In order to form such an aluminum oxide thin film, a PV such as a vacuum deposition method, a sputtering method, or an ion plating method is used.
The D method (physical vapor deposition method), the CVD method (chemical vapor deposition method), or the like is appropriately used. For example, in the vacuum vapor deposition method, Al, Al ₂ O ₃ or the like is used as the vapor deposition source material, and resistance heating, high frequency induction heating, electron beam heating or the like can be used as the heating method. Also, as a reactive gas, oxygen, nitrogen, water vapor, etc. may be introduced,
Reactive vapor deposition using means such as ozone addition or ion assist may be used. Further, the preparation 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 substrate. The same applies to other preparation methods such as the sputtering method and the CVD method. 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 referred to 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
Normally, the mass and volume of an object may be measured and the ratio to the mass of the same volume of water 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.

If the specific gravity of the thin film thus obtained is smaller than 2.70, the structure of the aluminum oxide thin film becomes rough and a sufficient gas barrier property cannot be obtained. When the specific gravity of the thin film is larger than 3.30,
Although the initial gas barrier property after film formation is excellent, the film becomes too hard and mechanical properties, especially gelbo property is inferior. It is not suitable for use as a packaging material because the possibility of deterioration of the product is increased.
From the above reasons, the preferable specific gravity of the aluminum oxide thin film as a packaging material for microwave sterilization is 2.70 to 3.
30 and more preferably 2.80 to 3.20.

The microwave sterilization packaging material of the present invention is transparent and has a high barrier property. That is, the oxygen permeability is 4.0 cc / m ² · 24 hrs or less and the water permeability is 3.0 g / m ² · 24 hrs or less, and the high barrier property is maintained even after the microwave sterilization treatment. Therefore, the food packaged with the packaging material of the present invention and subjected to microwave sterilization can be stored for a long period of time. The use form of the packaging material for microwave sterilization of the present invention includes bags, lids, cups, tubes, standing bags and trays. The heat seal layer is required for applications such as bags, tubes and standing bags. Further, it may be printed for decoration or description of the contents, or may be laminated with a design film or a reinforcing agent. Also, because it has excellent gelbo characteristics, there is little deterioration in the laminating process, printing process, bag making process,
Even after it has been made into a bag, care should be taken when handling it. The microwave sterilization treatment of the food packaged with the packaging material of the present invention is performed by microwave irradiation, for example, 10
It may be performed by heating to about 0 to 140 ° C.
Next, the present invention will be described with reference to examples.

Example 1 As a vapor deposition source, particulate Al having a size of about 3 to 5 mm was used.
PET film with a thickness of 12 μm (Toyobo Co., Ltd .: E) using ₂ O ₃ (purity 99.9%) by an electron beam evaporation method.
An aluminum oxide-based gas barrier thin film was formed on 5007). An electron gun (hereinafter referred to as an EB gun) was used as a heating source, and the emission current was set to 0.7 to 1.8A. The film feed speed is changed from 40 to 100 m / min,
A 500-4000 Å thick film was made. Further, the vapor pressure is changed from 1 × 10 ⁻⁵ to 8 × 10 ⁻³ Tor by changing the supply amount of oxygen gas.
The conditions were changed to r.

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. A plastic film was obtained. The packaging film was heated by microwave irradiation (130 ° C. × 10 minutes) or subjected to gelbo treatment, and then the oxygen barrier property was measured. (Table 1)

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 referred to as 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 thus measured is
It was very excellent, around 1.0 cc. In addition, 100
The result after the round gelbo test was only about 2 cc. Also, a packaging film for microwave sterilization having excellent overall characteristics was obtained even after irradiation with microwaves, while maintaining a barrier property of 4.0 cc or less. 10cm x 1 using this film
A pillow type bag having a size of 5 cm was produced.

Comparative Example 1 An aluminum oxide type transparent gas barrier thin film was formed by EB evaporation in the same manner as in Example 1, and the obtained sample was measured for specific gravity and microwave irradiation, or oxygen barrier properties after gelbo treatment. I measured. As a result, either the oxygen barrier property, the barrier property after microwave irradiation, or the gelbo property became insufficient, resulting in a poor overall evaluation. Using this film, a bag similar to that of (Example 1) was prepared. (Table 2)

Example 2 As a vapor deposition source, particulate Al having a size of about 3 to 5 mm was used.
(Purity of 99.9%) by high frequency induction heating evaporation method,
12 μm thick PET film (Toyobo Co., Ltd .: E50)
00) was formed on the aluminum oxide gas barrier thin film. At that time, the high frequency power was set to 3.5 kW, and the film feed speed was changed to 30 to 100 m / min.
A 0-4000 A thick film was made. The vapor pressure is 1.0 × 10 ⁻⁵ to 8 × 10 ⁻³ T by changing the supply amount of oxygen gas.
The condition was changed to oor. The specific gravity of the thus obtained film was measured after dissolving the PET film. Hereinafter, in the same manner as in Example 1, a packaging film was prepared and the oxygen barrier property was measured. (Table 1)

Comparative Example 2 An aluminum oxide gas barrier thin film was formed by the high frequency induction heating vapor deposition method as in Example 2, and the obtained sample was subjected to specific gravity measurement and microwave sterilization treatment, or gelbo treatment. The oxygen barrier property of was measured. As a result, either the oxygen barrier property, the microwave irradiation, or the gelbo property became insufficient, resulting in a poor overall evaluation. (Table 2) Further, in order to carry out a long-term storability test, a representative bag of the examples and comparative examples was filled with a hamburger to prepare a completely sealed sample. This sample was subjected to microwave sterilization (120 ° C x 30 minutes) treatment, and allowed to stand at room temperature for 3
The odor, color and taste were examined after holding for 0 days. As a result, the examples of the present invention were normal, but the comparative examples showed abnormalities. (Table 3)

[0018]

EFFECT OF THE INVENTION In a packaging material having a gas barrier property comprising a plastic substrate and an aluminum oxide thin film layer provided on at least one surface of the plastic substrate, the specific gravity of the thin film is 2.70 to 3.30. By doing so, it is possible to provide a packaging material for microwave sterilization, which has excellent gas barrier properties, high barrier properties after microwave irradiation, and high bending resistance, and overall excellent practical properties.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location // A61L 2/12 8718-4C (72) Inventor Toshio Uno 2-chome Katata, Otsu City, Shiga Prefecture No. 1 Toyobo Co., Ltd. Research Institute (72) Inventor Toru Kotani 1-1 1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Institute (72) Inventor Yozo Yamada 2-chome Katata Otsu, Shiga Prefecture No. 1 Toyobo Co., Ltd. Research Institute

Claims (2)

[Claims] 1. A packaging material having a gas barrier property, which comprises a plastic substrate and an aluminum oxide thin film layer provided on at least one side of the plastic substrate, and the thin film has a specific gravity of 2.70 to 3.30. A material for microwave sterilization characterized by being present. 2. The thin film layer according to claim 1, further comprising:
Material for microwave sterilization provided with a tote layer.