JPH11301748A - Plastic film showing gas permeability due to increased pressure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic film capable of preventing either external germs or moisture from entering and ensuring permeability due to increased pressure of gas generated inside. SOLUTION: A permeable resin film 2 with a thickness of about 3 to 10 μm is applied to form and cover one surface of a porous film 1 having some fine holes 10 therein and then a non-permeable film 3 having some cut slits 30 is applied to cover the other surface of the porous film 1. Then, the non- permeable film 3 is applied outside to cause the cut slits 30 to be opened due to an increased pressure from inside and then gas flowed from inside escapes from some cut slits 30 opened through some fine holes 10 from the permeable resin film 2, resulting in that the film may become a gas permeable one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for various packaging materials, seal lids, and the like. The present invention relates to a plastic film that becomes gas permeable.

[0002]

2. Description of the Related Art Conventionally, gas-permeable films used for various packaging materials and seal lids are expensive, have a small amount of permeation, and lack transparency of a material body. In addition, at present, relatively large holes are additionally provided to ensure ventilation, but there is a problem that foreign matters may enter through the holes and the environment may become unsanitary depending on the surrounding environment. Was. In this regard, the inventor of the present application disclosed in the earlier application (Japanese Patent Application Laid-Open No. Hei 8-244847) that an ultra-thin permeable resin film was applied to one side of a perforated film in which micropores were formed to improve the permeability. Although such a film was provided, there was a drawback that the film was easily broken by handling.

Further, in the application, paper or nonwoven fabric is adhered to the other surface of the perforated film for reinforcement, but it is difficult to adjust the amount of transmission due to poor permeability and transparency of paper. The nonwoven fabric has problems that foreign matter and germs cannot be prevented from entering, especially water, and printing cannot be performed well.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention is to prevent the invasion of various bacteria and moisture from the outside and to ensure that the film is permeable by the gas pressure generated inside.
An object of the present invention is to provide a strong, printable plastic film that is difficult to tear.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention is intended to be used as a film for a gas permeable portion such as a packaging bag or a seal cover, and is provided on one side of a perforated plastic film having through holes. A resin film is adhered and formed, and a cutout impermeable plastic film is adhered to the other surface of the perforated film, and the impermeable film is used by arranging it outside. Thereby, the cut is opened by the pressure increase from the inside of the impermeable film,
It is characterized in that gas from the inside escapes from the cut opening opened through the through hole from the permeable resin membrane or its break portion to the outside. Note that the permeable resin film may be an ultrathin layer having a thickness of 3 to 10 μm, and it is optimal that the cut has a length of 0.5 to 5 mm.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to illustrated embodiments. In the embodiment shown in FIGS. 1 and 2,
Reference numeral 1 denotes a 30 μm-thick perforated film 1 having a number of micropores 10 penetrated through a stretched polypropylene film, and a translucent resin film 2 made of an ultrathin polyethylene resin having an average thickness of 5 μm is applied to one surface of the film 1 by extrusion lamination. . The fine holes 10 of the perforated film 1 are provided with a hole diameter of 0.4 mm and are provided at intervals of 0.5 mm.

[0007] Actually, the fine holes 10 of the perforated film 1 are used.
The transparent resin film 2 is formed only on the opening of
0 is closed, and the portions other than the micropores 10 are integrated with the perforated film 1 so that the lamination cannot be distinguished.

On the other surface of the perforated film 1, an impermeable film 3 made of polyester with cuts 30 scattered at predetermined intervals is applied via an adhesive 4. Its thickness is about 12 μm. Further, the cut 30 is 1
It is about 2 mm in length, and can be penetrated by inserting a mold blade or piercing a rotating blade into the film 3 during passage.

The adhesive 4 is applied not in the entire surface as shown in FIG. 2 but in a regular lattice pattern. Therefore, as shown in FIG. In the adhesive portion 40, the micropores 10 are opened as they are and are covered with the film 3.

With such a structure, an ultra-thin permeable resin film 2 is formed on one surface of the perforated film 1, but since the resin film 2 is extremely thin, pinholes and voids in a molecular structure are formed. The effect of permeability of gas such as oxygen and carbon dioxide gas from the pores can be obtained naturally. However, in the normal state in which the cut 30 is closed, gas transmission is prevented by the impermeable film 3.

As shown in FIG. 3, the film of this embodiment is a packaging bag in which the permeable resin film 2 is adhered to each other by heat sealing or the like, with the impermeable film 3 facing the outside, and contains cooked goods. In this state, since the cut 30 is normally closed, entry of various bacteria and moisture into the inside can be prevented.

If this is heated in a microwave oven,
Due to the gas generated from the cooked food and the thermal expansion inside the bag, the internal pressure of the bag sharply increases, and the bag expands, as shown in FIG.
Since a part of the permeable resin film 2 is broken and the cut 30 is pressed from the inside and opened, gas and vapor escape from the cut 30 opened through the micropores 10 from the permeable resin film 2. Thereby, the bag is prevented from being damaged and the bag is cooked by heating. In addition, by adjusting the opening area of the cut 30 or the perforation area of the micropores 10, overevaporation of the moisture in the bag can be prevented, and the necessary steam content can be secured and cooking can be performed well.

Further, it may be used as a storage bag for fermented foods such as pickles, mushrooms, natto, miso, etc., or medicines that generate gas, etc. Usually, since the cuts 30 are closed, various bacteria and moisture may enter the inside. When the internal pressure of the bag increases due to the gas generated from the contents, the bag expands and cuts 3 opened from the permeable resin membrane 2 through the fine holes 10.
The gas escapes from zero.

Furthermore, when ethylene gas, carbon dioxide gas, etc., which are often found in spoiled foods, are generated and accumulated in the micropores 10 from the permeable resin film 2, the pressure in the micropores 10 increases, and the cuts 30 are opened. The gas is released outside.

Further, since printing can be performed on the inner surface of the outer impermeable film 3, the display of the film and the contents can be ensured, and the printed surface can be prevented from directly touching the stored foods and the like, and the sanitary condition can be improved. It can be held, and because of its three-layer structure, it has excellent strength and is hard to break.

Although the present embodiment has the above-described configuration, the present invention is not limited to this. For example, regardless of the number, size, and perforating means of the through holes provided in the perforated plastic film as a base material, the size may be about 1 to 5 mm, but 1 mm.
The following are optimal. In the case where the fine hole 10 as a through hole is provided by heat, as shown in FIG. 5, a projecting step 11 is provided around the hole end of the fine hole 10, and the adhesive 4 having normal viscosity is Since it does not enter the micropores 10 because it is obstructed by the protruding steps 11, it is possible to secure a transmission amount corresponding to the total opening area of the micropores 10.

Further, there is no limitation on means for applying a permeable resin film to one surface of the perforated film. Further, the means for attaching the impermeable film to the other surface of the perforated film is also appropriate, and it is sufficient that the cuts can partially communicate with the through holes of the effective film by partially adhering.

The length of the cut made in the impermeable film is also arbitrary, and the length and the number of cuts may be adjusted according to the amount of degassing. The material and thickness of the perforated film, the permeable resin film, and the impermeable film are not limited, and may be plastic. The perforated film and the impermeable film may be a composite film. Further, as shown in FIG. 6, it may be used as a sealing lid for a container or the like in addition to the packaging bag.

[0019]

According to the first aspect of the present invention, the cut is opened because the internal pressure in the package is increased, or the internal surface of the impermeable film is pressurized due to the accumulation of gas in the through hole. Gas and vapor are released from the cuts opened through the through holes from the permeable resin membrane and its break, preventing breakage in microwave ovens and in gas generation containers. Can hold the contents well. In addition, in the normal state, the cuts are closed, so that invasion of various bacteria and moisture can be prevented from the outside, and printing can be secured inside the impermeable film on the outside, and the display function can be secured, and the strength is excellent because of the three-layer structure It is hard to break. According to the second aspect, the gas permeability is excellent because of the extremely thin film. According to claim 3, it is suitable for use in a bag or a seal portion for a microwave oven.

[Brief description of the drawings]

FIG. 1 is an enlarged vertical sectional view of a main part showing one embodiment of the present invention.

FIG. 2 is a cutaway plan view showing the stacked state.

FIG. 3 is an enlarged vertical sectional view of an upper portion used for a bag body.

FIG. 4 is an enlarged vertical sectional view of a main part showing a degassing state.

FIG. 5 is an enlarged longitudinal sectional view of a main part showing another embodiment.

FIG. 6 is an enlarged longitudinal sectional view of a main part used for a seal lid of a container.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Effective film 10 Micropore 11 Protruding part 2 Permeable resin film 3 Impermeable film 30 Cut 4 Adhesive 40 Non-adhesive part

Claims (3)

[Claims] The present invention is used as a film for a gas permeable portion such as a packaging bag or a seal lid. A permeable resin film is formed on one surface of a perforated plastic film having through holes. On the other side of the perforated film, a plastic impermeable film with a notch is applied,
By arranging the impermeable film on the outside and using the impermeable film, the cut is opened by the pressure increase from the inside, and the gas from the inside is passed through the through hole from the permeable resin film or a broken portion thereof. A plastic film that becomes gas permeable by pressurization, characterized in that it escapes through an open cut. 2. The plastic film according to claim 1, wherein the permeable resin film is a very thin layer having a thickness of 3 to 10 μm. 3. The plastic film according to claim 1, wherein said cut has a length of 0.5 to 5 mm.