JPH0852816A - Gas permeable film - Google Patents

Abstract

PURPOSE:To raise the permeability of gas without obstructing the permeability and physical properties by a method wherein a nonpermeable hole of a specific depth and a specific mean area is bored at a rate of specific bored density on one side face of a substrate film. CONSTITUTION:A nonpermeable hole of 10<-6>-10<-2>cm<2> in mean hole area, and 1-99.0% as a ratio to thickness of substrate film in depth is bored at a rate of 1-10000 holes/cm<2> in boring density sigma on one side face of the substrate film such as a polyolefin single layer of 10-200mum in thickness or multilayer substrate film or the like by co-extrusion. Further, a product of the S X the sigma meets the relation of the numerical expression, the oxygen gas permeability is improved by 5% or over by being compared with that of a non-bored film, and a haze value is 70% or under to mold a gas permeable film. As a boring method for the nonpermeable hole, there are, for example, plunge rolling, embossing or the like with a roll having cylindrical or needle-shaped projections.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a gas permeable film made of a polymer film. More specifically, the present invention relates to a gas permeable film that is preferably used as a packaging material in the fields of food and medicine.

[0002]

2. Description of the Related Art In the fields of foods and pharmaceuticals, gas permeable films are used as packaging materials for products. For example, in the food sector, food (especially fruits and vegetables,
As a film used for packaging fresh foods such as flowers, it is necessary to permeate gases such as oxygen gas, carbon dioxide gas and water vapor in order to maintain its freshness, and gas sterilization packaging also in the pharmaceutical field. It was necessary to use a gas permeable film as a film for use because it is necessary to permeate ethylene oxide gas or the like for efficient sterilization.

From this point of view, the gas permeable film is as follows: (1) A thermoplastic resin film is heated to a temperature near its melting point and is pressed between two rolls having a sandy surface. A method for producing a breathable satin-finished film, which is passed through (JP-A-48-67347),
(2) A film for storing a desiccant having a predetermined moisture permeability by laminating or coating a substance having a transmittance on a perforated film having a strength higher than a predetermined reference value (JP-A-63-162229). Gazette), and (3) a polymer film for storing or packaging plant material having porosity and predetermined oxygen permeability and water vapor permeability (JP-A-2-73831).
Gazette).

[0004]

However, in the case of the above-mentioned method (1) for producing a breathable satin-finished film, the transparency is poor and both surfaces are embossed (matte-finished), so that a more opaque feeling is obtained. It looks strong. Further, in the case of the desiccant-containing film of the above (2), the holes may be closed by the melted or softened resin in extrusion lamination and heat fusion,
Not only is it difficult to manufacture, but it also requires a laminating process. In the case of a laminate using an adhesive (such as a dry laminate), peeling of the laminate may occur due to contact with moisture or exposure to a high humidity atmosphere. Further, in the case of the polymer film for storing or packaging plant material of (3), it was difficult to uniformly improve the permeability of all permeated gases (oxygen gas, carbon dioxide gas, water vapor). . The present invention has been made in view of the above problems, and can improve the gas permeability without depending on the type of the permeable gas (oxygen gas, carbon dioxide gas, water vapor), and without impairing the transparency and physical properties. An object is to provide a permeability control film.

[0005]

To achieve the above object, according to the present invention, in a gas permeable film comprising a polymer film, (a) its thickness is 10 to 200 μm.
A single layer of polyolefin or a multi-layered base film obtained by co-extrusion, or a multi-layered base film obtained by co-extrusion of polyolefin and polystyrene resin, (b) one side of the base film having an average hole area S of 10 ^{− A} non-through hole having a depth of ⁶ to 10 ^-2 cm ² and a ratio of the depth to the thickness of the base film of 1 to 99.0% has a perforation density σ of 1 to 1 per cm ^2.
The holes are drilled at a rate of 10,000, (c) the average hole area S (cm ² ) and the hole density σ (pieces / cm ² ).
The product of the following equation (I) is satisfied: 10 ⁻⁵ ≦ S × σ ≦ 0.6 (I) (d) The oxygen gas permeability thereof is compared with that of a non-penetrated film having no through holes. By 5% or more, and (e)
A gas-permeable film having a haze value of 70% or less is provided.

The present invention will be specifically described below. 1. Substrate Film As the substrate film used in the present invention, a single layer of polyolefin or a multilayer film obtained by coextrusion, or a multilayer film obtained by coextrusion of polyolefin and polystyrene resin is used. The use of a single-layer or multi-layer film of polyolefin is to improve moisture resistance,
The reason why the multilayer film of polyolefin and polystyrene resin is used is to improve the water vapor permeability.

When the base film is a multi-layer (a multi-layer film of polyolefin or a multi-layer film of polyolefin and polystyrene resin), the multi-layer film is formed by coextrusion as described above. In the case of coextrusion of the polyolefin and the polystyrene resin, it is possible to interpose an adhesive resin therebetween. Examples of the adhesive resin used in this case include unsaturated carboxylic acid-modified polyolefin such as maleic anhydride-modified polyolefin, and ethylene-vinyl acetate copolymer. By using co-extrusion, the process can be simplified, peeling of the laminate is less likely to occur, and the holes can be prevented from being blocked.

The polyolefin used for the substrate film is not particularly limited, but examples thereof include polyethylene, polypropylene, polybutene, ethylene-propylene copolymer, polymethylpentene, ethylene-vinyl acetate copolymer, and polyolefin acid graft copolymer. , Ionomers, ethylene-acrylic acid ester copolymers and mixtures thereof.

The polystyrene resin used for the base film is not particularly limited, and examples thereof include styrene homopolymer and styrene-butadiene copolymer. These may be used alone or as a mixture. Moreover, you may use what mixed the other resin with each simple substance or a mixture.

Additives can be used in combination with the base film. Auxiliary antioxidant, neutralizer, light stabilizer, ultraviolet absorber, heavy metal deactivator, plasticizer, nucleating agent, anti-blocking agent, lubricant, pigment, antibacterial agent, freshness-retaining agent, adsorbent,
Examples thereof include antifogging agents and surfactants. This additive may be kneaded with the raw material resin and extruded, or may be coated on the surface of the base film.

The thickness of the base film is 10 to 200 μm. If it is less than 10 μm, it is difficult to manufacture, and practically sufficient strength cannot be obtained. If it exceeds 200 μm, drilling becomes difficult.

The method for producing the base film is not particularly limited except that coextrusion is used in the case of a multi-layer, and for example, a T-die method, an inflation method and the like can be used. Specifically, in the case of a single layer, the molten resin is extruded from a T die onto a film or a tube. In the case of a multi-layer, it is manufactured by T-die or inflation method after melt lamination.

2. Non-through hole In the present invention, a non-through hole is provided on one surface of the base film.

The average hole area S of the non-through holes is 10 ^-6 to 10
^-2 cm ² Above all, 10 ⁻⁵ to 10 ⁻³ cm ² is preferable. If it is smaller than 10 ^-6 cm ^2, it is difficult to pierce and 10
^If it is larger than ^-2 cm ² , transparency may be impaired. Here, the transparency is whether or not what is wrapped is visible, and is generally indicated by a haze value. Impeding this transparency means increasing the haze value and making it difficult to see the contents. Specifically, it means that the haze value exceeds 70%.

The depth of the non-through holes depends on the permeability, thickness, strength, etc. of the base film itself, but is usually 1 to 99.0 as a ratio of the depth to the thickness of the base film.
%. Above all, 10 to 90% is preferable. If the film thickness is less than 1%, especially in the case of a thin film, it is difficult to perform the drilling process, and the gas permeability cannot be significantly improved. Similarly, if it is deeper than 99.0%, it is difficult to perform drilling, pinholes are likely to be formed, and strength is weakened.

The perforation density σ of the non-through holes is 1 to 10,000 per cm ² . Among them, 20 to 5,000 are preferable, and 50 to 1,000 are particularly preferable. When it is less than 1, the transparency of the transparent substrate cannot be improved, and when it is more than 10,000, transparency and physical properties may be impaired. Here, the physical properties refer to tensile strength, tear strength and the like, and impeding the physical properties means that pinholes are likely to occur and the strength is weakened.

Further, it is necessary that the product of the average hole area S (cm ² ) and the perforation density σ (pieces / cm ² ) satisfy the following formula (I). 10 ⁻⁵ ≦ S × σ ≦ 0.6 (I) When it is less than 10 ⁻⁵ , the oxygen permeability becomes insufficient and the drilling work becomes difficult. If it exceeds 0.6, the transparency is impaired and the physical properties such as tensile properties, pinhole resistance, and heat sealing properties are deteriorated.

There are no particular restrictions on the method of forming the non-through holes, but for example, pressing with a rubber roll or the like onto a roll having a cylindrical or needle-shaped protrusion to emboss it can be mentioned. Further, a method of kneading a foaming agent into the resin used for the base film and co-extruding it can be mentioned.

3. Improvement of gas permeability The material and structure of the base film, and the average hole area, depth, and perforation density of the non-penetrating holes, and the average perforation area x perforation density are set to the above-mentioned constitution, so that the ordinary non-penetrating holes are It is necessary to improve the oxygen gas permeability by 5% or more, as compared with the case of a base film such as a polyolefin film having no perforations.
If it is less than 5%, significant gas permeability cannot be exhibited in terms of variations in the thickness distribution of the gas film, measurement errors, and the like.

[0020]

EXAMPLES The present invention will be described in more detail below with reference to examples. [Example 1] Random polypropylene (PP) (manufactured by Idemitsu Petrochemical Co., Ltd.) and erucamide (manufactured by Nippon Seika Co., Ltd., trade name: Nitron S), inorganic substances (manufactured by Mizusawa Chemical Co., Ltd., trade name:
1 part by weight of Shilton AMT) was mixed and a film of 30 μm was produced by a 30 mmφT die extruder. The average hole area was 10 ⁻⁴ cm ² , the depth was about 15 μm (ratio to the substrate film was 50%), and the perforation density was 5,000 per cm ^2.
The holes that did not penetrate were made. The properties of the non-through holes are summarized in Table 1 (the same applies to the following examples). Table 2 shows the values of oxygen gas, carbon dioxide gas, water vapor permeability, and haze value at this time. The improvement rate (%) of the oxygen gas permeability in Table 2 is shown as a percentage as compared with the non-penetrated hole-unpierced film (Reference Example 1 in this example).

Example 2 Polystyrene (PS) (manufactured by Idemitsu Petrochemical Co., Ltd.), adhesive resin (Admer SF600 manufactured by Mitsui Petrochemical Co., Ltd.), linear low density polyethylene (LL)
(Manufactured by Idemitsu Petrochemical Co., Ltd.) was used to produce a three-layer film having a thickness of 60 μm by the 30 mmφT die multilayer extruder. An average hole area of 10 ⁻⁴ cm ² , a depth of 20 μm (ratio 33%), and a density of 1 cm ^{2 of} 5,000 non-through holes were formed on the LL resin side. Table 2 shows the values of the permeability of oxygen gas, carbon dioxide gas, and water vapor, and the haze value.

Example 3 Using the linear low-density polyethylene (LL) (manufactured by Idemitsu Petrochemical Co., Ltd.), a three-layer film having a thickness of 60 μm was produced with a 30 mmφ T-die multi-layer extruder. At this time, the erucic acid amide and 1 part by weight of the inorganic material were mixed in the sealant layer (layer ratio 30%). In this, an average hole area of 10 ⁻⁴ cm ² , a depth of about 20 μm (ratio to the substrate film: 33%), and 5,000 non-through holes per 1 cm ^{2 of} perforation density were perforated from the layer opposite to the sealant layer. . Table 2 shows the values of oxygen gas, carbon dioxide gas, water vapor permeability, and haze value at this time.

Reference Example 1 Table 2 shows the values of oxygen gas, carbon dioxide gas, water vapor permeability and haze value of the film prepared in Example 1 (one without holes).

Reference Example 2 Table 2 shows the values of oxygen gas, carbon dioxide gas, water vapor permeability, and haze value of the film prepared in Example 2 (without holes).

Reference Example 3 Table 2 shows the values of oxygen gas, carbon dioxide gas, water vapor permeability and haze value of the film prepared in Example 3 (without holes).

[Comparative Example 1] The average hole area was 10 ^-6 cm ² ,
1 hole per 1 cm ² (average hole area × hole density =
The same procedure was performed as in Example 3 except that 10 ^-6 ). Table 2 shows the values of oxygen gas, carbon dioxide gas, water vapor permeability, and haze value in this case.

[Comparative Example 2] The average hole area is 10 ^-2 cm ² ,
The same procedure as in Example 3 was carried out except that the perforation density was 64 per 1 cm ² (average hole area × perforation density = 0.64). In this case, oxygen gas, carbon dioxide gas, water vapor permeability values,
The haze value is shown in Table 2.

[Comparative Example 3] The procedure of Example 3 was repeated except that the hole depth was 0.5 μm (ratio to the thickness of the gas film = 0.83%). Table 2 shows the values of oxygen gas, carbon dioxide gas, water vapor permeability, and haze value in this case.

[Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Average hole area S (cm ² ) Depth (%) Drilling density σ (pieces / cm ² ) S × σ (pieces) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━━ Example 1 10 ^-4 50 5,000 0.5 Example 2 10 ^-4 33 5,000 0.5 Example 3 10 ^-4 33 5,000 0.5 Reference Example 1 Reference Example 2 ── ── ── ── Reference Example 3 ── ── ── ─ ─ Comparative Example 1 10 ^-6 33 33 1 10 ^-6 Comparative Example 2 10 ^-2 33 640 .64 Comparative Example 3 10 ⁻⁴ 0.83 5,000 0.5 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━

[0030]

[Table 2]

[0031]

As described above, according to the present invention,
Provide a gas permeable film that can improve the permeability of the permeable gas without depending on the type of the permeable gas (oxygen gas, carbon dioxide gas, water vapor, etc.) and without impairing the transparency and physical properties of the base film. can do. In addition, the improved permeability has made it possible to maintain freshness by controlling the gas in the packaging of fruits and vegetables, flowers, etc., and to improve the gas permeability of gas sterilization for efficient treatment.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // B01D 71/26 9538-4D 71/28 9538-4D B29K 23:00

Claims (1)

[Claims] 1. A gas-permeable film composed of a polymer film, comprising: (a) a single-layer or multi-extruded multi-layer substrate film of polyolefin having a thickness of 10 to 200 μm; (B) having an average hole area S of 10 ⁻⁶ to 10 ⁻² cm ² on one side of the base film and having a depth corresponding to the thickness of the base film. A non-through hole having a ratio of 1 to 99.0% has a drilling density σ of 1 to 1 per 1 cm ^2.
The holes are drilled at a rate of 10,000, (c) the average hole area S (cm ² ) and the hole density σ (pieces / cm ² ).
The product of the following equation (I) is satisfied: 10 ⁻⁵ ≦ S × σ ≦ 0.6 (I) (d) The oxygen gas permeability thereof is compared with that of a non-penetrated film having no through holes. By 5% or more, and (e)
A gas permeable film having a transparency of 70% or less as a haze value.