JPH09132708A - Selectively gas-penetrable film and wrapping film comprising the same and used for carbon dioxide-generating food - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a selectively gas penetrable film large in the ratio of carbon dioxide penetrability to oxygen penetrability, small in the relative humidity dependency of the selective penetrability, and extremely useful as a film for wrapping carbon dioxide-generating foods such as natural cheeses, raw devil's tongues or raw yams. SOLUTION: This selectively gas-penetrable film comprises (A) an aliphatic polyamide resin film containing (B) 0.01-10.0wt.% of a compound selected from alkylene glycol monomers and its polyers and (C) 0.1-10.0wt.% of water, and has the ratio of the carbon dioxide penetrability of the film to its oxygen penetrability under conditions comprising a temperature of 23 deg.C and a relative humidity of 80%. This wrapping film for carbon dioxide-generating foods comprises the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas selective permeable film having a large ratio of carbon dioxide gas permeability to oxygen permeability of a synthetic resin film (hereinafter, also referred to as a selection ratio) and its use.

[0002]

2. Description of the Related Art Natural cheese is currently a laminated film of polyamide and polyethylene, a laminated film of PVDC coated on a laminated body of polyamide and polyethylene, or a laminated body of polystyrene and ethylene vinyl alcohol copolymer resin. It is packaged in a deep drawing container thermoformed with a sheet.

Since cheese produces carbon dioxide gas by respiration of lactic acid bacteria, it is distributed and sold at a low temperature in order to keep the gas generation amount low. Further, in order to suppress deterioration of the cheese due to oxidation, it is necessary to suppress the permeation of oxygen into the inside of the package.

[0004] Garlic is put in a polyethylene or polypropylene net in a state where the garlic is still attached, packed in a cardboard box and distributed at room temperature. Further, the peeled garlic is put in a polyethylene film bag, and the bag mouth is not folded and is folded and packed in a cardboard box and distributed at room temperature.

The reason why the garlic package is not sealed is that carbon dioxide gas is generated by the breathing of garlic and the bag or container of the sealed package expands. Furthermore, if there is a large amount of oxygen in the package, bacterilia breed on garlic and mold develops. On the other hand, when the amount of oxygen is low, garlic may digest the autologous tissue and give off a strange odor.

[0006] Garlic having such properties is convenient for cooking if it is peeled off and packaged and then sold, and it is desired that the peeled garlic be distributed in a hermetically sealed state. .

[0007] The yam is put in a cardboard box as it is for distribution with the skin attached, or is cut into an appropriate size and vacuum-packaged in a bag of a laminated film such as nylon and polyethylene for sale. Has been done.

[0008] This yam has a problem that the hands become itchy especially during cooking, and it is desired to sell the yam after it is peeled and shredded. Some products have been sold by being wrapped in a laminated film of nylon and polyethylene, but since the bag is inflated because carbon dioxide gas is generated due to the breath of yams, it is sold with a carbon dioxide gas absorbent enclosed. ing.

Foods such as those to be packaged that generate carbon dioxide gas in the process of distribution need to release carbon dioxide gas from the inside of the package, and foods whose quality is accelerated by oxygen are further packaged. It is necessary to keep the permeation of oxygen gas into the interior as low as possible. A packaging material, particularly a food packaging material, having properties that meet such purposes, that is, a so-called gas-selective permeability that allows good permeation of carbon dioxide gas and low permeation of oxygen gas, is desired.

As an example of such a packaging material, Japanese Patent Laid-Open No. 5-2 is known.
JP-A-22215 discloses a composition of polyvinyl alcohol having a specific degree of saponification and a polymer of alkylene glycol, and a composition comprising the composition and a saponified ethylene / vinyl acetate copolymer (EVOH). An extruded product is described. However, the extruded products of these compositions have room for improvement in water resistance, and there is still a point to be improved that the gas permeability has a large humidity dependency.

Further, Japanese Patent Laid-Open No. 7-3012 describes a laminated film made of polyolefin, copolyamide, and ionomer for packaging of a cheese, which does not expand due to carbon dioxide gas generated during the aging of the cheese. It is written. However, its effect is limited to specific humidity conditions.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the relative humidity dependence of the ratio of carbon dioxide gas permeability to oxygen gas permeability of a packaging film, which is such a problem.

[0013]

The present inventors have proposed a film of a resin composition comprising an aliphatic polyamide resin and an alkylene glycol monomer or a polymer thereof, which contains substantially no water. The present invention has been completed by discovering that the above-mentioned film containing the compound has a large ratio of carbon dioxide permeability to oxygen permeability and can reduce the dependency of selective permeability on relative humidity.

That is, in the present invention, 0.1 to 10.0 mass% of a compound (B) selected from an alkylene glycol monomer and a polymer thereof and water (C) are added to an aliphatic polyamide resin film. Gas selection containing 0.1 to 10.0% by mass, wherein the ratio of carbon dioxide permeability to oxygen permeability of the film under conditions of temperature 23 ° C. and relative humidity 80% is 10 to 30. It is a transparent film.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The aliphatic polyamide resin (A) used in the present invention is, for example, nylon 6, nylon 9, nylon 11, nylon 12, nylon 66, nylon 6
9, nylon 610, nylon 6-12, nylon 6-
66, nylon 6-69, nylon 6-66-610 and the like. Among these, nylon 6 and nylon 6
6 is preferably used. Moreover, you may use each individually or in mixture.

The compound (B) used in the present invention is selected from alkylene glycol monomers or polymers thereof. These are highly water-absorbent and water-retaining and have a high carbon dioxide adsorption capacity. Examples of the monomer include ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol and 3,3-butanediol. It can be illustrated.
Examples of these polymers include polyethylene glycol-
(Hereinafter abbreviated as PEG) and the like. It may also be a mixture of these simple substances and polymers.

This PEG is suitable as the above polymer. When the composition of the aliphatic polyamide resin and PEG is melt extruded to form a film, the mass average molecular weight is 40.
A PEG of 0 or more is preferred because it is less likely to escape during this extrusion process. On the other hand, the upper limit of the weight average molecular weight of PEG is
From the viewpoint of compatibility with the aliphatic polyamide resin, those having a mass average molecular weight of 2000 or less are preferable.

The water (C) used in the present invention is preferably water that does not have a sanitary problem and is drinkable.

The composition of the aliphatic polyamide resin film and the compound (B) and water (C) will be described. The lower limit of the addition amount of the compound (B) (meaning the content in the film, and adding means to include it. The same applies hereinafter) is 0.1 part by mass, and the preferable addition amount is 0. 0.5 to 10% by mass, more preferably 1 to 8% by mass
It is. When 0.1 part by mass of the compound (B) is added,
The water retention of the film is improved and the ratio of carbon dioxide permeability to oxygen permeability of the film is improved. Compound (B)
The ratio of the carbon dioxide gas permeability to the oxygen gas permeability of the film increases with an increase in the addition amount of.

However, in order to increase the amount of the compound (B) added to the aliphatic polyamide resin film, the amount of (B) added must be increased at the stage of forming the film from the aliphatic polyamide composition. In addition, the amount of the compound (B) escaping in the extrusion step also increases, and the compound (B) bleeds out from the obtained film. Therefore, the upper limit of the addition amount of the compound (B) is preferably 10% by mass.

As a method of incorporating the compound (B) into the aliphatic polyamide resin film, a mixture of the aliphatic polyamide resin (A) and the compound (B) is extruded using a twin-screw kneading extruder to be pelletized, Further, the pellets are molded with a single screw extruder using a T die or a circular die to obtain a film. In addition, a composition obtained by mixing a predetermined amount of the aliphatic polyamide resin (A) and the compound (B) is processed using a twin-screw kneading extruder using a T die or a circular die to obtain a film. You can also

The method of adding water (C) to the molded film obtained by the above method is to store the film in a humidity controller or spray water (C) or an aqueous alcohol solution on the film surface. Or coating them.

As another method of adding the compound (B),
Compound (B) on the film of aliphatic polyamide resin (A)
When a polymer such as PEG is used as the compound (B), an aqueous solution or an alcohol such as methanol, ethanol or propanol is added because the polymer has a high viscosity. However, it is also an effective method to improve the wettability of the aliphatic polyamide resin (A) on the film surface and further to increase the permeation rate of (B) into the film. From the viewpoint of food hygiene, ethanol Use is preferred. When the aqueous solution is used, water (C) can be added at the same time as the compound (B).

The amount of water (C) added was 0.
It is preferably 1 to 10 parts by mass. If the amount of water (C) added is less than 0.1 parts by mass, the selection ratio will be 10 or less, and the object cannot be achieved. On the other hand, if the amount added exceeds 10 parts by mass, the film becomes too soft, and the film is stretched at the stage of use in packaging, especially when applied to a packaging machine, which makes it impractical.

The gas permselective film of the present invention can be obtained by the method described above.

The aliphatic polyamide resin (A) is rich in hydrophilicity and easily absorbs water, but on the contrary, water easily evaporates, and in the film in which the compound (B) is not added to the aliphatic polyamide resin film, the water content therein is increased. Keeping the amount constant is extremely difficult.

The gas permselective film of the present invention may be a stretched film or an unstretched film. Further, it may be used as a single layer or as a laminated film. In the case of laminating with the gas permselective film of the present invention, for example, at least one layer of polyolefin resin and at least one layer of adhesive resin may be laminated by a coextrusion method or a lamination method, or a resin to be laminated. The order of layers can be arbitrarily selected.

Specific examples of the resin to be laminated are polyolefin resins such as low density polyethylene, linear low density polyethylene, ultra low density polyethylene, ethylene / α-olefin copolymer, ionomer resin, ethylene Acrylic acid copolymers, ethylene vinyl acetate copolymers and the like are listed. Further, as the adhesive resin, an unsaturated carboxylic acid such as maleic acid, fumaric acid, or acrylic acid in the homopolymer or copolymer of the above polyolefins or an acid anhydride thereof or an ester of an unsaturated carboxylic acid thereof is used. A modified polymer graft-polymerized or a mixture thereof may be mentioned. The layer thickness of the polyolefin resin layer to be laminated is appropriately set within a range that does not impair the gas selective permeability of the present invention.

[0029]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples.

(Examples 1 to 3) Nylon 6-66 (manufactured by Toray Industries, Amylan CM6041XF, 80% -15% composition, melting point 195 ° C) was added to polyethylene glycol (manufactured by Sanyo Kasei Co., PEG600) (hereinafter referred to as PEG Abbreviation) is 1.0
% (Example 1), 2.0% (Example 2), 3.0% (Example 3) were added and melted using a twin-screw extruder (BT-30 manufactured by Plastic Engineering Laboratory Co., Ltd.). Pellets were prepared by melt extrusion at a resin temperature of 245 ° C. The pellets were melt-extruded again using a circular die with a single-screw extruder (screw diameter 40 mm), and a film was formed by an inflation method. The thickness of the formed film was 30 μm. Gravure roll (180 lines,
Using a coater having a cone depth of 31 μm), an aqueous solution containing 50% by mass of ethanol was applied, and the film speed was 40.
The film was wound into a roll while being dried with hot air at a temperature of 90 ° C. at m / min, and then left at 25 ° C. and 70% RH for 25 hours to obtain the target film. Table 1 shows the results of measuring the oxygen permeability, carbon dioxide permeability, PEG content, and water content of this film. The ratio (selection ratio) of carbon dioxide permeability to oxygen permeability is 10 even at a humidity of 20% RH.
The above is shown.

(Comparative Example 1) Nylon 6-66 used in Example 1 (Amylan CM6041XF, 80 manufactured by Toray Industries, Inc.)
% -15% composition, melting point 195 ° C.) was melt extruded by a single screw extruder (screw diameter 40 mm) using a circular die, and a film was formed by an inflation method. The thickness of the formed film was 30 μm. Table 1 shows the results of measuring the oxygen permeability, carbon dioxide gas permeability and water content of this film. This film had a low gas permeability selectivity, especially at 20% RH.

(Examples 4 to 6) Nylon 6 having a thickness of 25 μm
Alcohol containing 2.5% by mass (Example 4), 5.0% by mass (Example 5) and 10.0% by mass (Example 6) of polyethylene glycol on the surface of the shrinkable film. Using a coater in which an aqueous solution of 50% by mass and 2.0% by mass of sucrose fatty acid ester (DK Ester F-20W, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was placed in a gravure roll (180 lines, cone depth 31 μm). Then, the film was wound at a film speed of 40 m / min while being dried with hot air of 90 ° C. These roll films were left standing at 25 ° C. and 70% RH for 3 days to impregnate the film with polyethylene glycol and water. The oxygen permeability, carbon dioxide permeability, PEG content, and water content of these films were measured and are shown in Table 2. The heat shrinkage ratio of these films in hot water at 80 ° C. for 3 minutes was 15% in Example 1 in the machine direction / transverse direction, respectively.
17%, Example 2 is 17% / 18%, Example 3 is 17%
/ 18%.

Comparative Example 2 The nylon 6 film used in Example 4 was subjected to no coating treatment, and the gas permeability of the film was measured in the same manner as in Example 4 and the results are shown in Table 2. . The temperature of this film is 23 ℃ and the humidity is 20%.
Carbon dioxide permeability at RH was low.

[0034]

[Table 1]

[0035]

[Table 2]

(Measurement Method) <Oxygen Gas Permeability> O manufactured by Modern Control
It was measured at 23 ° C., 20% RH, 80% RH according to ASTM D3985-8 using xtran2 / 20. <Carbon dioxide permeability> P manufactured by Modern Control
Using ermatoran C-N, 23 ℃, 20% R
It was measured at H and 80% RH. <Water Content of Film> About 1 g of a film sample was weighed (Ma) and dried in a gear oven at 105 ° C. for 1 hour. Then, a desicque containing silica gel at 23 ° C.
After cooling in water, the film sample is weighed (Mb),
Formula: Moisture content = 100 × (Ma−Mb) / Ma <Polyethylene glycol content%> About 10 g of a film sample was weighed (F), filled in a cylindrical filter paper, and then extracted with a methanol solvent using a Soxhlet extractor at 80 ° C. for 24 hours, The mass (P) of the methanol extract was weighed and calculated by the formula: content% = 100 × P / F. <Hot water shrinkage of film> Sample film length 50m
m, cut into a square with a width of 50 mm, and place in hot water at 80 ° C for 3
Immerse for a minute, then cool at room temperature of 23 ° C., measure the vertical and horizontal lengths (L1) and (L2) respectively, and calculate by the formula: vertical shrinkage rate = 100 × (50−L1) / 50, horizontal Shrinkage rate = 1
It was determined by 00 × (50−L2) / 50.

[0037]

EFFECTS OF THE INVENTION The gas permselective film provided by the present invention has a large ratio of carbon dioxide gas permeability to oxygen permeability, and has small relative humidity dependency of selective permeability. Therefore,
It is extremely useful as a packaging film for carbon dioxide-generating foods such as natural cheese, cheese, raw garlic, and raw yam.

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Claims (3)

[Claims] 1. An aliphatic polyamide resin film containing 0.1 to 10.0% by mass of a compound (B) selected from alkylene glycol monomers and polymers thereof and 0.1% of water (C). A gas-selective permeable film containing -10.0 mass% and having a ratio of carbon dioxide permeability to oxygen permeability of the film of 10 to 30 under a condition of a temperature of 23 ° C and a relative humidity of 80%. 2. A gas permselective film, wherein at least one of the layers of the film is the film of claim 1. 3. A packaging film for carbon dioxide-generating food, which comprises the gas selective permeable film according to claim 1.