JP3019935B2 - Retort food packaging material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging material for retort foods, and more particularly, to a barrier property against oxygen and water vapor even when exposed to high temperatures during retort treatment.
The present invention relates to a packaging material for a retort food, which has little deterioration in transparency and seal strength, and has little deterioration in post-processing and handling such as lamination and printing.

[0002]

2. Description of the Related Art Retort foods, such as curries, meat sauces for spaghetti, meat preparations, or semi-cooked foods, which can be stored for a long period of time and are easy to cook, are widely available on the market. . A packaging material for a retort food must have excellent barrier properties and seal strength so that the contents are not deteriorated by permeation of oxygen, water vapor, and the like into the inside. As such a packaging material, a material obtained by laminating an aluminum foil, a vapor-deposited thin film, or the like with a non-stretched polypropylene film having heat sealing properties is often used.

[0003]

However, when a film laminated with an aluminum foil is used as a packaging material for retort foods, the contents cannot be confirmed because the aluminum foil is opaque, and it is inconvenient for shopping. On the other hand, examples of a transparent and barrier film include a polyvinylidene chloride-based resin film and a base film coated with a polyvinylidene chloride-based resin. However, since the polyvinylidene chloride resin has poor heat resistance, the barrier property is extremely deteriorated at a high temperature of retort treatment (for example, at 110 ° C. or more),
Further, since the transparency of the film is lost due to the whitening of the film, it is difficult to use the film as a packaging material for retort foods. Also, even at room temperature, the barrier is not enough, so the storage period is generally shorter than that of laminated aluminum foil, and the film loses its flexibility and raises the film cost to increase the barrier property. There is such a problem. Furthermore, recently, there is a problem such as generation of chlorine gas at the time of incineration of refuse, and there is a concern that the influence on the global environment may be caused.

On the other hand, as a gas barrier film whose contents can be seen and which can be used in a microwave oven, S
ix Oy (for example, SiO ₂ ) (JP-B-51-48511)
No. ₂ ) and a gas barrier film on which Al ₂ O ₃ is deposited (Japanese Patent Application Laid-Open No. 62-101287), which have attracted attention. It is still insufficient. That is, to have retort resistance,
Although a thin film thickness of a certain degree or more (for example, 2000 mm) is required, there is a problem that it is better to be as thin as possible in order to improve bending resistance. There are many things that require careful handling.

[0005] In view of the above, the present invention is transparent and has excellent barrier properties and seal strength, and even when exposed to the high temperature of retort treatment, the barrier property, transparency and seal strength are less deteriorated, and An object of the present invention is to provide a packaging material for retort food having high bending resistance.

The packaging material for retort foods of the present invention is a packaging material having a gas barrier property comprising a plastic film and a thin film layer mainly composed of aluminum oxide and silicon oxide. A retort food packaging material, wherein the ratio of aluminum oxide is 20% by weight or more and 99% by weight or less, and the specific gravity of the thin film satisfies the following formula: D = 0.01A + b ( Here, D: specific gravity of the thin film, A: weight% of aluminum oxide in the thin film) 1.6 ≦ b ≦ 2.2. Alternatively, it is a retort food packaging material further comprising a heat layer on the thin film layer.

The plastic substrate referred to in the present invention is a film obtained by melt-extruding an organic polymer and stretching, cooling, and heat setting in the longitudinal direction and / or the width direction as necessary. Organic polymers include polyethylene, polypropylene, polyethylene terephthalate, polyethylene-2,6-naphthalate, nylon 6, nylon 4,
Nylon 66, nylon 12, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, wholly aromatic polyamide, polyamide imide, polyimide, polyether imide, polysulfone, polyphenylene sulfide, polyphenylene oxide and the like. These (organic polymer) organic polymers may be copolymerized or blended in small amounts with other organic polymers.

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, a film having a transmittance of 50% or more is preferred. As long as the plastic substrate in the present invention does not impair the purpose of the present invention, prior to laminating the thin film layer, the substrate is subjected to corona discharge treatment, glow discharge treatment, and other surface roughening treatment. Well,
Further, a known anchor coat treatment, printing, and decoration may be applied. The thickness of the plastic substrate in the present invention is preferably in the range of 5 to 500 μm, more preferably 8 to 300 μm.

The thin film containing aluminum oxide or silicon oxide as a main component in the present invention is considered to be composed of a mixture of aluminum oxide and silicon oxide or a compound. Here, aluminum oxide means A
It is composed of a mixture of various aluminum oxides such as 1, AlO, Al ₂ O _3, etc., and their contents in aluminum oxide vary depending on the preparation conditions. Silicon oxide refers to Si, Si
It is considered to be composed of O, SiO _{2 and the} like, and these ratios also differ depending on the preparation conditions. In the present invention, the ratio of aluminum oxide in the thin film is 20% by weight or more and 99% or more.
% By weight, preferably from 30% by weight to 95% by weight.
% By weight or less. Also, this component may contain a trace amount (up to 3% of all components) of other components as long as the characteristics are not impaired. The thickness of the thin film is not particularly limited, but is preferably from 50 to 8000 °, more preferably from 70 to 5000 °, from the viewpoint of gas barrier properties and flexibility. In order to form such a thin film containing aluminum oxide and silicon oxide as main components, P thin films such as a vacuum deposition method, a sputtering method, and an ion plating method are used.
A VD method (physical vapor deposition method), a CVD method (chemical vapor deposition method), or the like is appropriately used. For example, in a vacuum deposition method, Al ₂ O ₃ and SiO ₂ , a mixture of Al and SiO ₂ , and the like are used as a deposition source material, and a heating method is resistance heating, high-frequency induction heating, electron beam heating. Etc. can be used. Further, oxygen, nitrogen, water vapor, or the like may be introduced as a reactive gas, or reactive vapor deposition using means such as ozone addition or ion assist may be used. Also,
The production conditions may be changed as long as the object of the present invention is not impaired, such as applying a bias to the substrate, increasing the substrate temperature, or cooling. Sputter method and CVD
The same applies to other creation methods such as the law.

The specific gravity referred to in the present invention refers to 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 the object may be measured, and the ratio of the mass to the same volume of water at 4 ° C. may be determined. Then, first, the thin film is peeled off from the substrate or only the substrate is dissolved to form a single film consisting of only the thin film.
It is desirable to use a specific gravity measurement method as described in 7112). For example, in the flotation method, a sample is immersed in a solution having a known specific gravity, and the specific gravity of the thin film can be measured from the flotation state. As this solution, a mixed solution of carbon tetrachloride and bromoform, methylene iodide, or the like can be used. The specific gravity value can also be measured by a density gradient tube method in which a single film is immersed in a solution having a continuous density gradient.

The relationship between the specific gravity of the thin film thus obtained and the weight percent of aluminum oxide in the thin film is expressed by D
= 0.01A + b (D: specific gravity of the thin film, A: weight% of aluminum oxide in the thin film). In a region where the value of b is smaller than 1.6, aluminum oxide and silicon oxide are the main components. The structure of the thin film becomes coarse, and sufficient gas barrier properties cannot be obtained. In the case where the value of the specific gravity of the thin film is in a region where the b value is larger than 2.2,
Although the initial gas barrier properties after film formation are excellent, the films are too hard, the mechanical properties, especially the gelling properties, are inferior, and the gas barrier properties after the treatment are greatly reduced, so that they are not suitable for use as packaging materials. For the above reasons, the specific gravity of a thin film containing aluminum oxide / silicon oxide as a main component, which is preferable as a packaging material for retort foods, is expressed by D = 0.0 as the relationship between the specific gravity of the thin film and the aluminum oxide composition ratio in the thin film.
When expressed by a relational expression of 1A + b (D: specific gravity of the thin film, A: weight% of aluminum oxide in the thin film), the value of b is 1.6 to 2.2, more preferably 1.7 to 2.2. It is one.

The retort food packaging material of the present invention is transparent and has high barrier properties. That is, the oxygen permeability is 3.0 cc / m ² · 24 hrs or less and the moisture permeability is 3.0 g / m ² · 24 hrs or less.
Therefore, the food packaged with the packaging material of the present invention can be stored for a long time. Furthermore, the retort food packaging material of the present invention is characterized in that the gas barrier properties are not deteriorated even by a high-temperature heat treatment. That is, 100-130 ° C
Thus, it is possible to withstand the retort treatment for 10 to 60 minutes. Use forms of the packaging material for retort foods of the present invention include bags, lid materials, cups, tubes, standing bags, trays and the like. The heat seal layer is necessary for applications such as bags, tubes, and standing bags, but is not necessarily required for applications such as cups, lid materials, and trays. Furthermore, since the gelling characteristics are excellent, there is little deterioration in the laminating process and the printing process. Further, even after being made into a bag, the handling thereof does not require excessive care. Next, the present invention will be described with reference to examples.

Example 1 As a deposition source, particulate Al having a size of about 3 to 5 mm was used.
₂ O ₃ (purity 99.5%) and SiO ₂ (purity 99.9%)
%) And a 12 μm thick PET by electron beam evaporation.
An aluminum oxide and silicon oxide thin film was formed on a film (Toyobo Co., Ltd .: E5100). The deposition material is
Without mixing, ha - mosquitoes within scan - the partition into two in Bonn plate, using a single electron gun (hereinafter EB gun) as a heat source, Al ₂
O ₃ and SiO ₂ were each heated in a time sharing manner. At that time, the emission current of the EB gun was changed to 0.8 to 2.2 A, and the heating ratio of Al ₂ O ₃ to SiO ₂ was 20:10.
５０50: 10, and the composition was changed. The film feed speed is changed from 30 to 120 m / min,
A 5000A thick film was made. Further, the vapor pressure is changed from 1 × 10 ⁻⁵ to 8 × 10 ⁻³ To by changing the supply amount of oxygen gas.
The conditions were changed up to rr. The specific gravity of the thus obtained film was measured by a floatation method after dissolving the PET film. Furthermore, for the composite film on PET, a thickness of 4
Unstretched polypropylene film (OPP film) of 0 μm is used as a two-component curing type polyurethane adhesive (2 μm in thickness)
Was used for dry lamination to obtain a plastic film for packaging. After subjecting this packaging film to retort treatment (120 degrees × 30 minutes) or gelbo treatment, the oxygen barrier properties were measured.

Oxygen Permeability Measurement Method The oxygen permeability of the prepared gas barrier film is measured by an oxygen permeability measuring device (OX-TRAN manufactured by Modern Controls).
100). Test method for flex fatigue resistance (hereinafter referred to as gelbo property) The flex fatigue resistance was evaluated using a so-called gelbo flex tester (manufactured by Rigaku Corporation). The condition is 112 inch × 8 inch with (MIL-B131H)
The sample piece of the channel is cylindrical with a diameter of 3 (1/2) inch, the both ends are held, the initial holding interval is 7 inches, and the stroke is 3 (1/2) inch and a twist of 400 degrees is applied. Reciprocating motion 40 times / m
The test was conducted at a speed of 20 ° C. and a relative humidity of 65%. The oxygen transmittance measured in this way was very excellent, about 1.0 cc. Furthermore, the result after the 200 times gelbo test also showed a rise of only about 2 to 3 cc, and a packaging material for retorts having excellent overall characteristics was obtained. (Table 1, Table 2)

Comparative Example 1 An aluminum oxide silicon oxide-based transparent gas barrier thin film was prepared by EB evaporation in the same manner as in Example 1, and the obtained sample was subjected to specific gravity measurement and retort treatment, or oxygen barrier after gelbo treatment. Sex was measured. As a result, one of the oxygen barrier properties, retort resistance, and gelbo properties became insufficient, and the overall judgment was poor.
(Table 1, Table 2)

Example 2 As an evaporation source, particulate Al having a size of about 3 to 5 mm was used.
Aluminum oxide silicon oxide based gas barrier thin film on PET film (Toyobo Co., Ltd .: E5007) using high-frequency induction heating vapor deposition method (purity 99.9%) and SiO ₂ (purity 99.9%). Was formed. The high-frequency power at that time was set to 5.5 kW, and the film feed speed was set to 3
Change to 0-120m / min, 500-4000A
A thick film was made. The vapor pressure was varied from 1.0 × 10 ^-5 to 8 × 10 ^-3 Torr by changing the supply amount of oxygen gas. The specific gravity of the thus obtained film was measured after dissolving the PET film. In the same manner as in the following (Example 1), a packaging film was prepared, and the oxygen barrier property was measured. (Tables 3 and 4)

Comparative Example 2 An aluminum oxide silicon oxide-based gas barrier thin film was formed by a high-frequency induction heating vapor deposition method in the same manner as in Example 2, and the obtained sample was subjected to specific gravity measurement and retort treatment.
Alternatively, the oxygen barrier properties after the gelbo treatment were measured. As a result, one of the oxygen barrier properties, retort resistance, and gelbo properties became insufficient, and the overall judgment was poor. (Tables 3 and 4)

In order to perform a long-term storage test,
Representative of the bags obtained in Examples and Comparative Examples are
Mussitu were packed to make a completely sealed sample.
The sample was subjected to a retort treatment, and after being kept at room temperature for 30 days, odor, color and taste were examined. As a result, the examples of the present invention were normal, but the comparative examples showed abnormalities.
(Table 5)

[0018]

According to the present invention, in a packaging material having a gas barrier property comprising a plastic substrate and a thin film layer mainly composed of aluminum oxide and silicon oxide provided on at least one surface of the plastic substrate, the ratio of aluminum oxide in the thin film Is not less than 20% by weight and not more than 99% by weight, and the relation between the specific gravity of the thin film and the composition ratio of aluminum oxide in the thin film is D = 0.01A + b (D: specific gravity of the thin film, A: weight of aluminum oxide in the thin film) %),
By setting the specific gravity of the thin film within the range represented by 1.6 ≦ b ≦ 2.2, a retort food having excellent gas barrier properties, high retort resistance, high flexibility and excellent overall practical characteristics. Can provide packaging materials.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

[Table 4]

[0023]

[Table 5]

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideomi Kobe 2-1-1 Katata, Otsu-shi, Shiga Toyo Spinning Co., Ltd. (72) Inventor Yozo Yamada 2-1-1 Katata, Otsu-shi, Shiga Examiner, Ryoichi Mizobuchi, Research Laboratory, Toyobo Co., Ltd. (56) References JP-A-3-278946 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65D 81/24 B32B 9 / 00 B32B 27/00 C23C 14/08

Claims (2)

(57) [Claims] 1. A packaging material having a gas barrier property comprising a plastic substrate and a thin film layer mainly composed of aluminum oxide and silicon oxide provided on at least one surface of the plastic substrate, wherein aluminum oxide is contained in the thin film. Is 20% by weight or more and 99% by weight or less, and the specific gravity of the thin film satisfies the following expression. D = 0.01A + b, where D: specific gravity of the thin film, A: weight% of aluminum oxide in the thin film 1.6 ≦ b ≦ 2.2 2. The thin film layer according to claim 1, further comprising a heat sink.
A packaging material for retort foods provided with a toseal layer.