JP2000263705A - Freshness retaining film and air-permeable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film which does not allow penetration of microbes or the like and allows permeation of a required minimum amount oxygen gas for vegetables/fruits to respire and generated steam by laminating a heat-fusible organic resin film with a specific crystallinity to an organic resin film to set the oxygen gas and steam permeable amounts at each specific level. SOLUTION: This freshness retaingin film is a laminated film 4 obtained by bonding and laminating a heat-fusible organic resin film 3 with 60% or less crystallinity on one face of at least one kind of an organic resin film 1 with rigidity and having a large amount of permeating steam through an adhesive 2. Numerous non-through holes 5 are perforated across the area from either of the surfaces of the laminated film 4 to the heat-fusible organic resin film 3 on the second surface side. The laminated film 4 shows 4,000-200,000 cc/m2 25 deg.C day latm oxygen gas permeable amount and 50 g/m2 40 deg.C 90% RH day or more steam permeable rate. The film 4 rapidly releases the steam generated by the respiration of vegetables/fruits to the outside and thereby prevents them from being rotted due to water droplets by packaging the vegetables/fruits with the film 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a freshness retaining film and a breathable film.

[0002]

2. Description of the Related Art Generally, in order to maintain the freshness of fruits and vegetables, a method of putting fruits and vegetables in a modified atmosphere (MA) and a controlled atmosphere (CA) are used.
The method of putting fruits and vegetables in e) is known.

[0003] In the former MA method, the fruits and vegetables are hermetically sealed in a plastic film to reduce the oxygen concentration in the packaging material due to the respiration of the fruits and vegetables, thereby increasing the carbon dioxide gas concentration. The respiration of the fruits and vegetables is suppressed by increasing the concentration of the fruits, and the freshness of the fruits and vegetables is maintained.

In the latter CA method, the growth of the fruits and vegetables is controlled by controlling the amount of permeation of oxygen which enters into the inside from the outside air through the packaging material and the amount of permeation of carbon dioxide which is breathed and discharged by the stored fruits and vegetables. (Deterioration) is delayed to maintain the freshness of fruits and vegetables.

[0005] Further, it is required that the freshness retaining film has a structure in which water vapor evaporating from fruits and vegetables is permeated or adsorbed to prevent dew condensation on the film surface which causes decay.

As a conventional freshness retaining film, a film obtained by dispersing Otani stone, zeolite and coral stone in a polyethylene film is known. This freshness preserving film is mainly aimed at the MA effect,
It has a CA effect. However, the freshness retaining film does not have a sufficient CA effect as long as the film has a slightly higher gas permeability than a polyethylene film. Further, most of the particles such as the valley stone are dispersed in the film, and only a small amount of the particles are exposed on the surface.

[0007] Recently, as a film for maintaining freshness,
P-Plus films aiming at the CA effect are known.
This film was developed in the UK and sold by Sumitomo Bakelite in Japan. The gas permeation amount suitable for the fruits and vegetables to be packed is calculated in advance, and an organic resin film such as polyethylene film is laser-ordered to several μm order. Are formed. However, the P-Plus film has only a slight control of the amount of water vapor permeated, and has no function of adsorbing water vapor or the like. For this reason, if water vapor is generated when the fruits and vegetables are hermetically sealed and packaged with the film, the water vapor may condense on the film surface and cause rot from the portions of the fruits and vegetables that come into contact with the dew drops.

On the other hand, an antifogging film in which a surfactant is applied to the surface of an organic resin film such as a biaxially stretched polypropylene film, or a surfactant is kneaded inside, is known. This film is used to openly package fruits and vegetables and to allow water vapor evaporated from the fruits and vegetables to flow down without dew condensation on the surface of the packaging material. However, the anti-fog film merely prevents the occurrence of dew condensation, and water droplets flow down and accumulate at the bottom of the packaging material, so that fruits and vegetables come into contact with the water droplets, causing rot from the contact points. Further, the anti-fog film cannot expect the CA effect.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an oxygen gas permeation amount suitable for minimizing the respiration of fruits and vegetables and impermeable to bacteria and germs, and water vapor generated by respiration of fruits and vegetables. To provide a freshness maintaining film having a water vapor transmission amount that allows the water to permeate and release the water immediately.

It is another object of the present invention to provide a breathable film having a suitable air permeability and a water vapor permeability capable of releasing a proper amount of water vapor.

[0011]

According to the present invention, there is provided a freshness retaining film comprising a heat-fusible organic resin film having a crystallinity of 60% or less and a rigid organic resin film having at least one layer. A film having an oxygen gas permeation amount of 4000 to 200,000 cc / m ² · 25 ° C. · day · 1a
tm, characterized by having a water vapor transmission rate of 50 g / m ² · 40 ° C. · 90% RH · day or more.

Another freshness retaining film according to the present invention is:
A laminated film in which a heat-fusible organic resin film having a crystallinity of 60% or less is laminated on at least one layer of an organic resin film having rigidity, and the organic resin film from one of the front surface to the back surface side A large number of non-penetrating holes are formed.

Still another freshness retaining film according to the present invention is an organic resin film having a rigidity of at least one layer having a large number of through holes formed on the entire surface and having a crystallinity of 60%.
A laminated film obtained by laminating the following heat-fusible organic resin films, wherein a large number of non-through holes are perforated from any one surface to the back surface side organic resin film. .

The air-permeable film according to the present invention is a laminated film in which a heat-fusible organic resin film having a crystallinity of 60% or less is laminated on a non-woven fabric, and has a gas permeability of 0 to 100.
0 seconds, the amount of water vapor permeated is 100 to 1500 g / m ² · 40 ° C.
・ It is characterized by being 90% RH day.

Another breathable film according to the present invention is a laminated film in which a non-woven fabric is laminated with a heat-fusible organic resin film having a crystallinity of 60% or less, wherein a large number of through holes are formed. It is characterized by the following.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a freshness retaining film according to the present invention will be described in detail with reference to the drawings.

The freshness maintaining film is a laminated film in which a heat-fusible organic resin film is laminated on at least one layer of an organic resin film having rigidity.
It has an oxygen gas permeation amount of ２００200,000 cc / m ² · 25 ° C. · day · 1 atm and a water vapor permeation amount of 50 g / m ² · 40 ° C. · 90% RH · day or more.

Examples of the rigid organic resin include uniaxial or biaxially oriented polypropylene, polyethylene terephthalate, polyvinyl chloride, ethylene-vinyl acetate copolymer, fluororesin, polyamide, polycarbonate, polyimide, polyetheretherketone, and the like. Polyether ketone, or 2 selected from these resins
Mixed resins of at least one kind can be mentioned.

The rigid organic resin film is
It is desirable to have a thickness of 10 to 100 μm, more preferably 10 to 30 μm.

As the heat-fusible organic resin film having a crystallinity of 60% or less, for example, a density of 0.90-0.
Metallocene polyethylene (LLDPE) having a melt flow rate of 0.5 to ³⁰ and a vinyl acetate content of 5 to 25% by weight, for example, ethylene vinyl acetate copolymer resin (EVA), ethylene ethyl acrylate resin Ethylene vinyl acetate copolymer such as (EEA) and methyl acrylate content of 10 to 30% by weight
And at least one resin selected from methyl acrylate copolymers such as, for example, ethyl methacrylate resin (EMA), ethyl methacrylate methyl resin (EMMA), and ethylene-methacrylic acid copolymer (EMAA);
It is preferable to use a mixed resin with low-density polyethylene (LDPE). In particular, a mixed resin composed of 35 to 45% by weight of the metallocene-based polyethylene, 35 to 45% by weight of the copolymer, and 10 to 30% by weight of the low-density polyethylene is preferable because of having high water vapor permeability.

The heat-fusible organic resin film having a crystallinity of not more than 60% preferably has a thickness of 20 to 50 μm.

In the freshness maintaining film of the present invention, 40
By having an oxygen gas permeation rate of 00 to 200,000 cc / m ² · 25 ° C. · day · 1 atm, when fruits and vegetables such as vegetables and fruits are wrapped with the packaging material made from this film, the respiration of the fruits and vegetables etc. Can be moderately suppressed.

In the freshness retaining film of the present invention, 50
g / m ² , 40 ° C., 90% RH day or more, and when the fruits and vegetables such as vegetables and fruits are wrapped with the packaging material made of this film, the respiration of the fruits and vegetables etc. The water vapor generated by the above can be quickly transmitted and released to the outside, so that rot due to water droplets or the like can be suppressed. The oxygen permeation amount is in the above range (4000 to 20,000).
When the control is shifted to the higher side in ^{0cc / m 2 · 25 ℃ ·} day · 1atm) in the higher respiratory degree of fruits or vegetables or the like,
Accordingly, the amount of released steam increases. In this case, it is desirable to control the water vapor transmission rate to a higher side. However, since the amount of water vapor permeation is generally governed by the film material, the upper limit is 300 g / m ² · 40 ° C. · 9
It is about 0% RH day.

The specific structure of the freshness retaining film having the above-mentioned oxygen transmission amount and water vapor transmission amount will be described with reference to FIGS.

1) Freshness retaining film having the structure shown in FIG. 1 This freshness retaining film is made of nylon having a large water vapor transmission rate (for example, about 200 g / m ² · 40 ° C. · 9 at a thickness of 15 μm).
A heat-fusible organic resin film 3 having a crystallinity of 60% or less is adhered to one surface of an organic resin film 1 having rigidity such as 0% RH / day) via an adhesive layer 2 and laminated. The film 4 has a structure in which a large number of non-through holes 5 are formed from any one of, for example, the organic resin film 1 having rigidity from the front surface to the heat-fusible organic resin film 3 on the back surface side.

The above-mentioned rigid organic resin film comprises:
It is desirable to have a thickness of 10 to 100 μm, more preferably 10 to 30 μm.

For the heat-fusible organic resin film 1 having a crystallinity of not more than 60%, it is preferable to use a mixed resin composed of the metallocene-based polyethylene, the copolymer and the low-density polyethylene described above. In particular, 35 to 45% by weight of the metallocene-based polyethylene and the copolymer 35
A mixed resin composed of the low-density polyethylene and the low-density polyethylene is preferable because it has high water vapor permeability.

The heat-fusible organic resin film 1 comprises 2
It preferably has a thickness of 0 to 50 μm.

The non-through holes are formed in order to increase the gas permeation amount of the freshness retaining film of the present invention.
It is preferable that the laminated film 4 has an average opening diameter of μm and the perforation density (forming density) in the laminated film 4 is 500 to 5000 / cm ² .

The reason why the average opening diameter of the large number of non-through holes 5 formed in the laminated film 4 is defined to be 5 to 400 μm is as follows.
If the ratio deviates from this range, it becomes difficult to obtain a freshness retaining film having the above-mentioned oxygen transmission amount. More preferably, the average opening diameter of the non-through holes is 10 to 100 μm.

The reason why the density of the large number of non-through holes 5 perforated in the laminated film 4 is defined to be 500 to 5000 holes / cm ² is that if the density deviates from this range, the freshness retaining film having the above-mentioned oxygen permeability will be obtained. It becomes difficult to obtain. More preferably, the formation density of the large number of non-through holes is 1000 to 2
500 / cm ² . In addition, the upper limit of the formation density of the non-through holes is 5000 holes / cm ² in one treatment when a porous film manufacturing apparatus described later is used.

The thickness (t) between the bottom of the large number of non-through holes 4 and the back surface of the heat-fusible organic resin film 3 is 1 to
Preferably it is 2 μm.

The freshness retaining film having the structure shown in FIG. 1 is manufactured, for example, by the following method.

First, a predetermined adhesive layer is formed on one surface of the rigid organic resin film by, for example, a coating method. Subsequently, a heat-fusible organic resin film having a crystallinity of 60% or less is laminated on the adhesive layer of the organic resin film by, for example, an extrusion molding technique. Thereafter, a large number of non-through holes are formed from the rigid organic resin film side of the laminated film using the porous film manufacturing apparatus disclosed in Japanese Patent Publication No. 6-61859 invented by the present inventors. By doing so, a freshness retaining film is produced.

The apparatus for producing a porous film comprises a supply means for supplying the above-mentioned laminated film (long laminated film); a large number of particles having a Mohs hardness of 5 or more (for example, diamond particles) having sharp corners are coated on the surface. A rotatable first roll attached to a first roll, and a second roll rotatable in a direction opposite to the roll, wherein the first and second rolls are arranged to face each other and between them. A perforating unit in which one of the rolls is fixed and the other is movably arranged in a direction opposite to the one roll while allowing the long film to pass therethrough; and the unit is movable. And pressure adjusting means for adjusting the pressing force of the rolls on the film.

In FIG. 1, the organic resin film having rigidity is one layer, but may be two or more layers. The non-through holes may be formed from the heat-fusible resin film side to the back surface of the rigid organic resin film.

2) Freshness retaining film having the structure of FIG. 2 This freshness retaining film is a uniaxially oriented polypropylene (OPP) having a low water vapor transmission rate; for example, about 7 g at a thickness of 20 μm.
/ M ² · 40 ° C · 90% RH · day) or polyethylene terephthalate (PET; for example, about 30 g / m ² · 4 at a thickness of 12 µm)
A large number of fine through-holes 6 are formed on the entire surface of an organic resin film 1 having rigidity such as 0 ° C./90% RH / day), and an adhesive layer 2 is formed on one surface of the organic resin film 1 via an adhesive layer 2. The heat-fusible organic resin film 3 having a crystallinity of 60% or less is bonded and laminated, and
For example, it has a structure in which a number of non-through holes 5 are formed from the front surface of the organic resin film 1 having rigidity to the heat-fusible organic resin film 3 on the back surface side.

The above-mentioned rigid organic resin film comprises:
It is desirable to have a thickness of 10 to 100 μm, more preferably 10 to 30 μm.

The through holes are formed in order to increase the amount of water vapor permeated through the rigid organic resin film 1 and have an average opening diameter of 1 to 80 μm and are formed into the rigid organic resin film 1. Drilling density (forming density)
Is preferably set to 100 / cm ² or more.

The reason why the average opening diameter of the large number of through-holes 6 formed in the organic resin film 1 having rigidity is defined to be 1 to 80 μm is that if the value deviates from this range, the above-mentioned water vapor transmission rate (50 g / m ⁽ 2.40 ° C./90% RH / day or more). More preferably, the average opening diameter of the through hole 6 is 5 to 20 μm.

[0041] The defined a number of density of the through-holes 6 were formed in the organic resin film 1 having the rigidity to 100 / cm ² or more, when less than 100 / cm ^2, the water vapor permeability of the aforementioned (50 g / m ² , 40 ° C., 90% RH, day or more). More preferably, the formation density of the large number of through holes 6 is 5
It is more than 00 pieces / cm ² . The upper limit of the formation density of the non-through holes is 5,000 / cm ² in one treatment when the above-described porous film manufacturing apparatus is used.

For the heat-fusible organic resin film having a crystallinity of not more than 60%, it is preferable to use a mixed resin comprising the metallocene-based polyethylene, the copolymer and the low-density polyethylene described above. In particular, 35 to 45% by weight of the metallocene-based polyethylene and 35 to 45% by weight of the copolymer
45% by weight and 10 to 30% by weight of the low density polyethylene
Is preferable because of having high water vapor permeability.

The heat-fusible organic resin film has a thickness of 20
It preferably has a thickness of ５０50 μm.

The non-through holes 5 are formed to increase the gas permeation amount of the freshness retaining film of the present invention.
5 to 5 for the same reason as described for the freshness retaining film
It has an average opening diameter of 400 μm, more preferably 10 to 100 μm, and the perforation density (forming density) in the laminated film is 500 to 5000 holes / cm ² , more preferably 1000 to 2500 holes / cm ² . Is preferred.

The thickness (t) between the bottom of the large number of non-through holes 4 and the back surface of the heat-fusible organic resin film 3 is 1 to
Preferably it is 2 μm.

The freshness retaining film having the structure shown in FIG. 2 is manufactured, for example, by the following method.

First, a large number of through holes are formed in the rigid organic resin film by using, for example, a porous film manufacturing apparatus disclosed in Japanese Patent Publication No. 6-61859. A predetermined adhesive layer is formed on one surface of the organic resin film having a large number of through holes by, for example, a coating method. Subsequently, a heat-fusible organic resin film having a crystallinity of 60% or less is laminated on the adhesive layer of the organic resin film by, for example, an extrusion molding technique. Thereafter, a number of non-through holes are formed from the rigid organic resin film side of the laminated film by using the porous film manufacturing apparatus disclosed in the above-mentioned Japanese Patent Publication No. 6-61859. Produce a retaining film.

In FIG. 2, the organic resin film having rigidity is one layer, but may be two or more layers. The non-through holes may be formed from the heat-fusible resin film side to the back surface of the rigid organic resin film.

3) Freshness retaining film having the structure of FIG. 3 This freshness retaining film is a uniaxially oriented polypropylene (OPP) having a low water vapor transmission rate; for example, about 7 g at a thickness of 20 μm.
/ M ² · 40 ° C · 90% RH · day) or polyethylene terephthalate (PET; for example, about 30 g / m ² · 4 at a thickness of 12 µm)
A large number of fine through-holes 6 are formed on the entire surface of the organic resin film 1 having a rigidity such as 0 ° C./90% RH / day). A laminated film 7 in which the following heat-fusible organic resin films 3 are laminated, and one of them, for example, from the front surface of the rigid organic resin film 1 to the back surface of the heat-fusible organic resin film 3 It has a structure in which many non-through holes 5 are formed.

The organic resin film having rigidity includes:
It is desirable to have a thickness of 10 to 100 μm, more preferably 10 to 30 μm.

The through holes are formed in order to increase the amount of water vapor permeated by the rigid organic resin film 1, and are preferably 1 to 80 μm, more preferably 1 to 80 μm, for the same reason as described for the freshness retaining film in 2). Has an average opening diameter of 5 to 20 μm and a density of 100 holes / cm ² perforated into the organic resin film 1 having the rigidity.
As described above, it is more preferable to set the number to 500 pieces / cm ² or more.

For the heat-fusible organic resin film having a crystallinity of not more than 60%, it is preferable to use a mixed resin comprising the metallocene-based polyethylene, the copolymer and the low-density polyethylene described above. In particular, 35 to 45% by weight of the metallocene-based polyethylene and 35 to 45% by weight of the copolymer
45% by weight and 10 to 30% by weight of the low density polyethylene
Is preferable because of having high water vapor permeability.

The heat-fusible organic resin film has a thickness of 20
It preferably has a thickness of ５０50 μm.

The non-through holes 5 are formed to increase the gas permeation amount of the freshness retaining film of the present invention.
5 to 5 for the same reason as described for the freshness retaining film
It has an average opening diameter of 400 μm, more preferably 10 to 100 μm, and the perforation density (forming density) in the laminated film is 500 to 5000 holes / cm ² , more preferably 1000 to 2500 holes / cm ² . Is preferred.

The thickness (t) between the bottom of the large number of non-through holes 4 and the back surface of the heat-fusible organic resin film 3 is 1 to
Preferably it is 2 μm.

The freshness retaining film having the structure shown in FIG. 3 is manufactured, for example, by the following method.

First, a large number of through holes are formed in the rigid organic resin film by using, for example, a porous film manufacturing apparatus disclosed in Japanese Patent Publication No. 6-61859. A heat-fusible organic resin film having a crystallinity of 60% or less is laminated on one surface of the organic resin film having a large number of through holes by, for example, an extrusion molding technique. At this time, the heat-fusible resin penetrates into a large number of through-holes of the organic resin film having the rigidity, and has a high adhesion to the organic resin film having the rigidity without an adhesive agent due to its anchoring action. It can be laminated with force. Thereafter, a number of non-through holes are formed from the rigid organic resin film side of the laminated film by using the porous film manufacturing apparatus disclosed in the above-mentioned Japanese Patent Publication No. 6-61859. Produce a retaining film.

In FIG. 3, the organic resin film having rigidity is one layer, but two or more organic resin films laminated with an adhesive layer therebetween may be used. The non-through holes may be formed from the heat-fusible resin film side to the back surface of the rigid organic resin film.

The freshness maintaining film according to the present invention described above is a laminated film in which a heat-fusible organic resin film having a crystallinity of 60% or less is laminated on at least one rigid organic resin film. And 4000-20
Oxygen gas permeation amount of ^{0000cc / m 2 · 25 ℃ ·} day · 1atm,
It has a water vapor transmission rate of 50 g / m ² · 40 ° C. · 90% RH · day or more. For this reason, when vegetables and fruits such as fruits are wrapped in a packaging material made from this film, the breathing of the fruits and vegetables can be appropriately suppressed, and the water vapor generated by the breathing of the fruits and vegetables can be suppressed. It can be quickly released to the outside to prevent spoilage due to water droplets and the like.
As a result, the freshness of fruits and vegetables can be maintained for a long period of time.

The freshness maintaining film having the structure shown in FIGS. 1 to 3 has an oxygen gas permeation amount of 4000 to 200,000.
^{cc / m 2 · 25 ℃ ·} day · 1atm, water vapor permeation amount was 50 g / m
^It has characteristics of 2.40 ° C, 90% RH, day or more, and can maintain the freshness of fruits and vegetables over a long period of time.

That is, a packaging material for packaging fruits and vegetables is generally formed by laminating a heat-fusible resin film such as polyethylene on one side of a rigid organic resin film such as nylon via an adhesive layer. I have. The heat-fusible resin film is an essential film for heat-sealing the films when they are formed into a bag.

Incidentally, the nylon is, for example, 15 μm
Water vapor permeation rate of 200 g / m ² · 40
Despite having good water vapor permeability of 90 ° C / 90% RH / day, the amount of oxygen permeation is about 100cc / m ²・ 25 ° C ・ day ・ 1atm, which is too low for moderately breathing fruits and vegetables etc. It becomes difficult to maintain the freshness of the period.

On the other hand, polyethylene, which is a general heat-fusible resin film, has an oxygen permeation amount of about 4000 cc / m ² · 25 ° C. · day · 1 atm suitable for appropriately breathing fruits and vegetables. The amount of permeation is, for example, about 10 g / m ² , 40 ° C., 90% RH, day at a thickness of 30 μm. It is difficult to quickly release water vapor released from fruits and vegetables to the outside, and dew condensation on the inner surface of the packaging material. Generates and causes fruit and vegetables to rot.

Therefore, the above-mentioned laminated film obtained by laminating a polyethylene film on a nylon film via an adhesive layer does not have a sufficient amount of oxygen permeation and water vapor permeation important for maintaining freshness of fruits and vegetables.

From the above, the present inventors have found that a heat-fusible organic resin film having a crystallinity of 60% or less has a high water vapor transmission rate. In particular, a density of 0.90
0.93 g / cm ³ , melt flow rate 0.5-3
0 metallocene-based polyethylene (LLDPE) and ethylene-vinyl acetate-based copolymer such as ethylene vinyl acetate copolymer resin (EVA) and ethylene ethyl acrylate resin (EEA) having a vinyl acetate content of 5 to 25% by weight. Coalescence, and the content of methyl acrylate is 10 to 30
% By weight of, for example, ethyl methacrylate resin (EMA),
A mixed resin of at least one resin selected from methyl acrylate copolymers such as ethyl methacrylate methyl resin (EMMA) and ethylene-methacrylic acid copolymer (EMAA), and low density polyethylene (LDPE);
More preferably, the metallocene-based polyethylene 35-4
A heat-fusible organic resin film having a crystallinity of 60% or less, comprising a mixed resin of 5% by weight, 35 to 45% by weight of the copolymer, and 10 to 30% by weight of the low-density polyethylene, has an appropriate oxygen permeability. Volume and water vapor transmission rate. Specifically, when the thickness is 20 μm, 25,000 to 30000 cc
/ M ²・ 25 ℃ ・ day ・ 1atm oxygen gas permeation amount, 120 ～ 20
^{0g / m 2 · 40 ℃ ·} 90% RH · day or more has a water vapor transmission for the case of a thickness of 30 [mu] m, 15000～20000Cc
/ M ² · 25 ° C · day · 1 atm oxygen gas permeation amount, 65-100
g / m ² , 40 ° C., 90% RH, day.

As shown in FIG.
0% or less of the heat-fusible organic resin film 3 is made of nylon having a large water vapor transmission rate (for example, about 200 μm in thickness of 15 μm).
g / m ² · 40 ° C. · 90% RH · day) by laminating on one side of an organic resin film 1 having an adhesive layer 2 so as to have a water vapor transmission rate of 50 g / m ² · 40. ℃ 9
A laminated film 4 of 0% RH day or more can be realized. However, since the laminated film 4 reflects the properties of a film having a small amount of oxygen permeation, for example, a nylon film, it does not suffocate vegetables and the like and has a suitable amount of oxygen permeation for appropriately breathing. No.

From the above, the laminated film 4
For example, the heat-fusible organic resin film 3 from the front surface to the back surface of the rigid organic resin film 1
By drilling a large number of non-through holes 5 over
An oxygen permeation amount of 4000 to 200000 cc / m ² · 25 ° C. · day · 1 atm can be provided. In particular, a non-through hole 5 having an average opening diameter of 10 to 100 μm
By piercing at a density of 00 to 2500 pieces / cm ² , 4000 to 200,000 cc / m ² · 25 ° C. · day · 1atm
Can be imparted with good reproducibility.

Accordingly, the freshness retaining film having the structure shown in FIG. 1 is superposed such that the heat-fusible organic resin film 3 having a crystallinity of 60% or less is located on the inner surface side, and the heat-fusible organic resin film around the film is maintained. When a bag-like packaging material is produced by heat-sealing the base resin films 3 with each other, and for example, fruits and vegetables are stored in the packaging material, the respiration of the fruits and vegetables can be appropriately suppressed by the oxygen permeation amount of the freshness retaining film. In addition, water vapor generated by breathing of the fruits and vegetables can be quickly released to the outside by the amount of water vapor permeated by the freshness retaining film, and rot caused by water droplets generated on the inner surface of the packaging material can be suppressed. As a result, the freshness of the fruits and vegetables can be maintained for a long period of time.

When a packaging material is prepared from the freshness retaining film shown in FIG. 1, a nylon film having a polar group and having a high water vapor dissolution rate is positioned on the inner side to further increase the water vapor transmission rate. It becomes possible.

As shown in FIGS. 2 and 3, uniaxially oriented polypropylene having a low water vapor transmission rate (OPP; for example, about 7 g / m ² · 40 ° C. 90% RH day at a thickness of 20 μm)
Or polyethylene terephthalate (PET; thickness 1
A large number of fine through-holes 6 are formed on the entire surface of the organic resin film 1 having a rigidity of about 30 g / m ² at 40 ° C. and 90% RH day at 2 μm, thereby greatly increasing the amount of water vapor permeation. Can be increased.

The above-mentioned heat-fusible organic resin film 3 having a crystallinity of 60% or less is provided on one surface of such an organic resin film 1 having rigidity such as OPP having a large number of fine through holes 6 on the entire surface. Through an adhesive layer 2 or by directly laminating, so that the water vapor transmission rate is 50 g / m ^2.
・ Laminated film 4 of 40 ° C / 90% RH / day or more can be realized. However, since the laminated film 4 reflects the properties of a rigid organic resin film 1 such as a film having a small oxygen permeation amount, for example, an OPP film,
It does not have a suitable amount of oxygen permeation that does not cause suffocation of fruits and vegetables or the like and allows proper respiration.

From the above, the laminated film 4
For example, the heat-fusible organic resin film 3 from the front surface to the back surface of the rigid organic resin film 1
By drilling a large number of non-through holes 5 over
An oxygen permeation amount of 4000 to 200000 cc / m ² · 25 ° C. · day · 1 atm can be provided.

Therefore, the freshness retaining film having the structure shown in FIGS. 2 and 3 is overlaid so that the heat-fusible organic resin film 3 having a crystallinity of 60% or less is located on the inner surface side, and the peripheral heat-fusible organic resin film 3 is disposed. When the bag-like packaging material is prepared by heat-sealing the adhesive organic resin films 3 to each other and, for example, fruits and vegetables are stored in the packaging material, the respiration of the fruits and vegetables is appropriately suppressed by the oxygen permeation amount of the freshness retaining film. And the water vapor permeated by the freshness retaining film can quickly release the water vapor generated by breathing the fruits and vegetables to the outside, thereby suppressing rot caused by water droplets generated on the inner surface of the packaging material. . As a result, the freshness of the fruits and vegetables can be maintained for a long period of time.

Next, the breathable film according to the present invention will be described in detail.

This breathable film is a laminated film obtained by laminating a heat-fusible organic resin film having a crystallinity of 60% or less on a nonwoven fabric, and has a gas permeability of 0 to 1000 seconds and a gas permeability of 100 to 1500 g / g. It has a water vapor transmission rate of m ² · 40 ° C · 90% RH · day.

As the non-woven fabric, for example, a non-woven fabric made of fibers of an organic resin such as nylon, uniaxially or biaxially drawn polypropylene, or polyethylene terephthalate is used.

For the heat-fusible organic resin film having a crystallinity of 60% or less, it is preferable to use a mixed resin comprising the metallocene polyethylene, the copolymer and the low-density polyethylene described above. In particular, 35 to 45% by weight of the metallocene-based polyethylene and 35 to 45% by weight of the copolymer
45% by weight and 10 to 30% by weight of the low density polyethylene
Is preferable because of having high water vapor permeability.

The heat-fusible organic resin film contains 20
It preferably has a thickness of ５０50 μm.

In the gas permeable film of the present invention,
Having an air permeability of 2,000 seconds allows a suitable amount of oxygen to permeate the interior of the packaging made from this film.

In the breathable film of the present invention, 100
By having a water vapor transmission rate of １1500 g / m ² 4040 ° C.9090% RHdayday, it becomes possible to release the water vapor inside the packaging material made from this film to the outside at an appropriate speed.

The specific structure of the gas permeable film having the above-mentioned oxygen permeability and water vapor permeability will be described with reference to FIG.

This breathable film is a laminated film 14 in which a heat-fusible organic resin film 12 having a crystallinity of not more than 60% is laminated on a nonwoven fabric 11 with an adhesive layer 13 interposed therebetween. From the film 12 to the adhesive layer 13
Over a large number of fine through-holes 15.

For the heat-fusible organic resin film 12 having a crystallinity of 60% or less, it is preferable to use a mixed resin composed of the metallocene polyethylene, the copolymer and the low-density polyethylene described above. In particular, 35 to 45% by weight of the metallocene-based polyethylene and the copolymer 3
A mixed resin composed of 5 to 45% by weight and 10 to 30% by weight of the low-density polyethylene is preferable since it has high water vapor permeability.

The heat-fusible organic resin film 12 is
It preferably has a thickness of 20 to 50 μm.

The through holes 15 are formed to increase the air permeability of the air permeable film of the present invention,
And the density of perforations (forming density) in the heat-fusible organic resin film 12 and the adhesive layer 13
Is preferably 50 to 2000 particles / cm ² .

The average opening diameter of the large number of through holes 15 is 1 to
If the thickness is set to 100 μm, if it is out of this range, it is difficult to obtain a breathable film having the above-mentioned oxygen permeability. More preferably, the average opening diameter of the through hole is,
10 to 50 μm.

The density of the large number of through holes 15 is set to 50 to 20.
If the number is set to 00 pieces / cm ^{2, if} it is out of this range, it becomes difficult to obtain a breathable film having the above-mentioned air permeability. More preferably, the formation density of the large number of through holes is 100 to 1000 holes / cm ² . The upper limit of the formation density of the through holes is 5,000 / cm ² in one treatment when a porous film manufacturing apparatus described later is used.

The breathable film having the structure shown in FIG. 4 is manufactured, for example, by the following method.

First, a predetermined adhesive layer is formed on one surface of the nonwoven fabric by, for example, a coating method. Subsequently, a heat-fusible organic resin film having a crystallinity of 60% or more is laminated on the adhesive layer of the organic resin film by, for example, an extrusion molding technique. Thereafter, a large number of through-holes from the heat-fusible film 12 to the adhesive layer 13 are formed in the laminated film using the porous film manufacturing apparatus disclosed in Japanese Patent Publication No. 6-61859. By piercing, a breathable film is manufactured.

The air-permeable film according to the present invention allows a heat-fusible organic resin film having a crystallinity of 60% or less to be directly laminated on a non-woven fabric without using an adhesive layer by, for example, an extrusion molding technique. I do.

The air-permeable film according to the present invention described above is a laminated film in which a heat-fusible organic resin film having a crystallinity of 60% or less is laminated on a nonwoven fabric.
Air permeability of 2,000 seconds, and 100-1500 g / m ² · 4
It has a water vapor transmission rate of 0 ° C / 90% RH / day. For this reason,
When a disposable hand warmer is made using a packaging material made from this film, a suitable amount of oxygen can be supplied to the internal exothermic agent to generate heat, and the steam generated by the heat generation can be discharged to the outside at a suitable speed. The release can suppress excessive temperature rise. As a result, it is possible to obtain a disposable hand warmer that can heat a predetermined body part for a long time without causing burns.

The air permeable film having the structure shown in FIG. 4 described above has an air permeability of 0 to 1000 and a water vapor transmission rate of 100 to 1
It has the characteristics of 500 g / m ² · 40 ° C. · 90% RH · day, and can be effectively used as a packaging material for disposable hand warmers, for example.

That is, the packaging material of the disposable hand warmer has a structure in which a porous heat-fusible film having fine labyrinth holes therein is used as a base film, and a nonwoven fabric is laminated on one side. The heat-fusible resin film is an essential film for heat-sealing the films when forming the bag.

However, since the porous heat-fusible film has an excessive amount of water vapor permeation, when the heat generated by the heat generating agent contained therein is heated, the water vapor sufficiently contributes to the suppression of the temperature rise. Before being released to the outside. For this reason, it has been carried out to improve the porous heat-fusible film, for example, to reduce the water vapor transmission rate by increasing the thickness.

Therefore, the packaging material for the disposable hand warmer described above has a problem that the cost is increased.

From the above, the present inventors have found that a heat-fusible organic resin film having a crystallinity of 60% or less has a high water vapor transmission rate. In particular, a density of 0.90
0.93 g / cm ³ , melt flow rate 0.5-3
0 metallocene-based polyethylene (LLDPE) and ethylene-vinyl acetate-based copolymer such as ethylene vinyl acetate copolymer resin (EVA) and ethylene ethyl acrylate resin (EEA) having a vinyl acetate content of 5 to 25% by weight. Coalescence, and the content of methyl acrylate is 10 to 30
% By weight of, for example, ethyl methacrylate resin (EMA),
A mixed resin of at least one resin selected from methyl acrylate copolymers such as ethyl methacrylate methyl resin (EMMA) and ethylene-methacrylic acid copolymer (EMAA), and low density polyethylene (LDPE);
More preferably, the metallocene-based polyethylene 35-4
A heat-fusible organic resin film having a crystallinity of 60% or less, comprising a mixed resin of 5% by weight, 35 to 45% by weight of the copolymer, and 10 to 30% by weight of the low-density polyethylene,
It has adequate oxygen and water vapor transmission rates. Specifically, when the thickness is 20 μm, 25000 to 30000c
c / m ² · 25 ° C · day · 1 atm permeation of oxygen gas, 120 ~ 2
^{00g / m 2 · 40 ℃ ·} 90% RH · day or more has a water vapor transmission for the case of a thickness of 30 [mu] m, 15000～20000C
c / m ² · 25 ° C · day · 1atm oxygen gas permeation, 65-10
It has a water vapor transmission rate of 0 g / m ² · 40 ° C. · 90% RH · day or more.

As shown in FIG.
0% or less of the heat-fusible organic resin film 12
For example, by laminating on one side via an adhesive layer 13, the water vapor transmission rate is 50 g / m ² · 40 ° C. · 90% RH · d
ay or more laminated film 14 can be realized. However, the laminated film 14 does not have air permeability suitable for oxidizing and generating heat of the exothermic agent, reflecting the air permeability of the heat-fusible organic resin film 12 having a crystallinity of 60% or less. .

From the above, the laminated film 1
4 from the heat-fusible organic resin film 12 to the adhesive layer 13
By drilling a large number of through holes 15 over
An air permeability of 0 to 1000 seconds can be provided. In particular, 1 to 10
A through hole 15 having an average opening diameter of 0 μm, more preferably 10 to 50 μm is formed in the laminated film 14 by 50 to 20 μm.
00 pieces / cm ² , more preferably 100 to 1000 pieces / cm ²
By piercing at a density of cm ² , air permeability in the above range can be imparted with good reproducibility.

Therefore, the freshness retaining film having the structure shown in FIG. 4 is overlaid so that the heat-fusible organic resin film 12 having a crystallinity of 60% or less is located on the inner surface side, and the heat-fusible organic resin film around the film is held. When the base resin films 12 are heat-sealed to form a bag-like packaging material, for example, a heating agent is stored in the packaging material and sealed to form a disposable hand warmer. The adhesive organic resin film 12 and the large number of through holes 15 can supply an appropriate amount of oxygen to the internal exothermic agent to generate heat, and generate water vapor generated by the heat generation to remove the water vapor generated by the heat generation. To an outside at an appropriate speed, thereby suppressing an excessive rise in temperature. As a result, it is possible to obtain a disposable hand warmer that can heat a predetermined body part for a long time without causing a burn.

[0100]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

Example 1 First, the density was 0.869 g /
Metallocene-based polyethylene (LLDPE) having a melt flow rate of 0.5 cm ³ (trade name, manufactured by Dow Chemical Co .; Encage) 42% by weight and a methyl acrylate content of 21
Ethyl methacrylate resin (EMA) having a melt flow rate of 20.0% by weight [trade name of Epson Chemical Company;
Optima] 42% by weight and low-density polyethylene (LDPE) having a melt flow rate of 0.8 [trade name: NUC-8507 manufactured by Nippon Unicar; 16% by weight] are kneaded at room temperature by twin-screw extrusion to give a crystallinity of 40. % Of a heat-fusible resin was prepared. This heat-fusible resin has an oxygen permeability of 25,000 cc / m ² · 25 ° C. · d when formed into a film having a thickness of 20 μm.
ay · 1 atm, the water vapor permeation amount of ^{190g / m 2 · 40 ℃ ·} 90% R
H.day, when the film having a thickness of 30 μm was formed, the oxygen permeation amount was 20000 cc / m ² · 25 ° C. · day · 1 atm, and the water vapor permeation amount was 100 g / m ² · 40 ° C. · 90% RH · day. Was.

Then, it was adhered to one side of a 15 μm-thick nylon film (oxygen permeability: 100 cc / m ² · 25 ° C. · 1 atm, water vapor permeability: 200 g / m ² · 40 ° C. · 90% RH · day). An agent (trade name: RU-40, manufactured by Rock Paint Co., Ltd.) was applied to form an adhesive layer having a thickness of 2 μm. Then,
The crystallinity of 4 is formed on the adhesive layer of the nylon film.
A heat-fusible organic resin film having a thickness of 30 μm was laminated by extruding a 0% heat-fusible organic resin by an extrusion molding technique. Thereafter, a large number of non-through holes are formed from the nylon film side of the laminated film by using the porous film manufacturing apparatus disclosed in Japanese Patent Publication No. 6-61859 described above, as shown in FIG. 1 described above. Manufactures a freshness retaining film with a structure. The non-through holes have an average opening diameter of 50 μm, and 1000 /
Drilled at a density of cm ² .

(Reference Example 1) A freshness maintaining film similar to that of Example 1 was produced except that no non-penetration holes were formed in the laminated film.

Example 2 A freshness retaining film similar to that of Example 1 was produced except that a heat-fusible film having a crystallinity of 40% and a thickness of 20 μm was used.

(Reference Example 2) A freshness retaining film similar to that of Example 2 was produced, except that a non-through hole was not formed in the laminated film.

Examples 1 and 2 and Reference Examples 1 and 2
The freshness retaining film was measured for the amount of oxygen transmission and the amount of water vapor transmission from the heat-fusible resin film side. The amount of oxygen permeation was measured using a trade name of JASCO Corp .; 5 kg of a 10 cm diameter sample cut from the freshness retaining film using a gas palm at an oxygen concentration of 100%, 25 ° C. and 65% RH.
/ Cm ² . The amount of water vapor permeation is determined by the Swiss Dr. Product name manufactured by Lyssy; L80-4
A sample having a diameter of 10 cm cut out from the freshness retaining film using a Model 000 was measured at 40 ° C. and 90% RH according to JIS K7129A. The results are shown in Table 1 below.

Further, the freshness retaining films of Example 2 and Reference Example 2 were measured for the amount of oxygen permeation and the amount of water vapor permeation from the nylon film side. This is shown in Table 1 below as Example 3 and Reference Example 3.

[0108]

[Table 1]

As is clear from Table 1, Examples 1 and 2 were used.
It can be seen that the freshness retaining film obtained by the method has a higher oxygen permeation amount as compared with Reference Examples 1 and 2 in which a non-through hole is not formed.

Example 4 First, an OPP having a thickness of 20 μm was used.
Film (oxygen ^{permeability; 2000cc / m 2 · 25 ℃} · day ·
1 atm, the water vapor permeability ^{of; 7g / m 2 · 40 ℃} · 90% RH · da
In y), a large number of through-holes were formed by using the porous film manufacturing apparatus disclosed in Japanese Patent Publication No. 6-61859. The through-hole has an average opening diameter of 25 μm,
And the OPP film was perforated at a density of 500 pieces / cm ² . Subsequently, a heat-fusible organic resin having a crystallinity of 40% similar to that of Example 1 was directly laminated on one surface of the OPP film having a large number of through-holes by extrusion molding technology to form a 30 μm-thick heat-fusible organic resin. An adhesive organic resin film was laminated. Thereafter, a large number of non-perforated holes are formed from the OPP film side of the laminated film using the porous film manufacturing apparatus disclosed in Japanese Patent Publication No. 6-61859, as shown in FIG. Manufactures a freshness retaining film with a structure. The unpenetrated holes had an average opening diameter of 100 μm and the laminated film had 1500 holes / c.
Drilled at a density of m ² .

Reference Example 4 A freshness preserving film was produced in the same manner as in Example 4, except that an OPP film having no through-hole was used and no non-through-hole was formed in the laminated film.

Example 5 A freshness retaining film was produced in the same manner as in Example 1 except that a heat-fusible film having a crystallinity of 40% and a thickness of 20 μm was used.

(Reference Example 5) A freshness retaining film similar to that of Example 5 was produced, except that an OPP film having no through-hole was used and no non-through-hole was formed in the laminated film.

Example 6 First, PET having a thickness of 12 μm
Film (oxygen ^{permeability; 100cc / m 2 · 25 ℃} · day · 1a
tm, water vapor permeability ^{of; 30g / m 2 · 40 ℃} · 90% RH · day)
On the other hand, a large number of through-holes were formed using the porous film manufacturing apparatus disclosed in Japanese Patent Publication No. 6-61859. The through-holes had an average opening diameter of 25 μm and were formed in the PET film at a density of 500 / cm ² . Subsequently, a heat-fusible organic resin having a crystallinity of 40% similar to that of Example 1 was directly laminated on one side of the PET film having a large number of through-holes by an extrusion molding technique to form a heat-fusible organic resin having a thickness of 30 μm. An adhesive organic resin film was laminated. Thereafter, a large number of non-perforated holes are formed from the PET film side of the laminated film using the porous film manufacturing apparatus disclosed in Japanese Patent Publication No. 6-61859 described above, thereby forming the laminated film as shown in FIG. Manufactures a freshness retaining film with a structure. The non-through holes had an average opening diameter of 100 μm, and 2,000 holes / cm ^{2 in the} laminated film.
Drilled at a density of

(Reference Example 6) A freshness retaining film similar to that of Example 6 was produced except that a PET film having no through-hole was used and no non-through-hole was formed in the laminated film.

Example 7 A freshness retaining film was produced in the same manner as in Example 6, except that a heat-fusible film having a crystallinity of 40% and a thickness of 20 μm was used.

(Reference Example 7) A freshness retaining film similar to that of Example 7 was produced except that a PET film having no through-hole was used and no non-through-hole was formed in the laminated film.

The obtained Examples 4 to 7 and Reference Examples 4 to 7
The freshness retaining film was measured for the amount of oxygen permeation and the amount of water vapor permeation from the heat-fusible resin film side in the same manner as in Example 1. The results are shown in Table 2 below.

[0119]

[Table 2]

As apparent from Table 2 above, Examples 4 to 7 were used.
Is higher than that of Reference Examples 4 to 7 in which no through-hole is formed in the OPP or PET film and no non-through-hole is formed in the stage of the laminated film. It can be seen that it has a water vapor transmission rate.

A packaging material was prepared from the freshness retaining films of Examples 1 to 7, and a bundle of spinach was stored in the packaging material, and the opening was closed. After leaving each packaging material in which the bundle of spinach was stored and sealed at room temperature for one week, the state of the spinach was observed. As a result, Examples 1 to 7
The spinach stored in the packaging material made of the freshness retaining film was fresh green before being stored in the packaging material.

Example 8 First, a heat-fusible organic resin having a crystallinity of 40% similar to that of Example 1 was extruded on one surface of a nonwoven fabric made of PET fibers and having a basis weight of 25 g / m ^2. And a 20 μm-thick heat-fusible organic resin film was laminated. Thereafter, a large number of through holes are drilled from the heat-fusible organic resin film side of the laminated film using the porous film manufacturing apparatus disclosed in Japanese Patent Publication No. 6-61859. A conductive film was produced. The through holes have an average opening diameter of 20 μm, and the laminated film has 200 holes / c.
Drilled at a density of m ² .

(Reference Example 8) A breathable film similar to that of Example 8 was produced except that no through-hole was formed in the laminated film.

Example 9 A breathable film was produced in the same manner as in Example 8, except that through holes having an average opening diameter of 50 μm were formed in the laminated film at a density of 100 / cm ² .

For the obtained breathable films of Examples 8 and 9 and Reference Example 8, the amount of water vapor permeation was measured from the heat-fusible resin film side in the same manner as in Example 1. In addition, the air permeability of these air permeable films was measured. The air permeability was measured by Oken method. The results are shown in Table 3 below.

[0126]

[Table 3]

As apparent from Table 3 above, Examples 8 and 9 were used.
It can be seen that the air permeable film obtained by the above has higher air permeability and water vapor transmission rate than the air permeable film of Reference Example 8 in which no through hole is formed in the stage of the laminated film.

A packaging material was prepared from the air-permeable films of Examples 8 and 9, and a disposable hand warmer was prepared by containing an oxygen-exothermic exothermic agent in the packaging material. These disposable hand warmers were able to warm a given body part for a long period of time without causing burns during use.

[0129]

As described above, according to the present invention, the permeation amount of oxygen gas suitable for minimizing the respiration of fruits and vegetables without impermeable bacteria and germs and the generation of oxygen gas by the respiration of fruits and vegetables are achieved. It is possible to provide a freshness maintaining film having a water vapor transmission amount that allows water vapor to be transmitted and released quickly.

Further, according to the present invention, it is possible to provide a breathable film having a suitable air permeability and a water vapor permeability capable of releasing a proper amount of water vapor, and suitable for a packaging material of a disposable hand warmer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a freshness retaining film according to the present invention.

FIG. 2 is a cross-sectional view showing another freshness retaining film according to the present invention.

FIG. 3 is a cross-sectional view showing still another freshness retaining film according to the present invention.

FIG. 4 is a cross-sectional view showing a breathable film according to the present invention.

[Explanation of symbols]

1: Organic resin film having rigidity, 3, 12: heat-fusible organic resin film having a crystallinity of 60% or less, 4: laminated film, 5: non-through hole. 6, 15 ... through-holes.

Continued on front page F-term (reference) 3E086 BA04 BA15 BA43 BB02 BB05 BB51 CA17 CA18 4F100 AK01A AK01B AK06B AK07A AK42A AK48A AK63B AK68B AK71B AL05B BA02 BA33 CB00 DC11A DC11B DG15B DJ10B13 EJ15J DJB12 YY00B

Claims (14)

[Claims] 1. A laminated film comprising a heat-fusible organic resin film having a crystallinity of not more than 60% and at least one rigid organic resin film having a degree of crystallization of not more than 60%. ^{/ m 2 · 25 ℃ · day} ·
1 atm, the water vapor permeation amount was ^{50g / m 2 · 40 ℃ ·} 90% RH · da
a film for maintaining freshness, wherein the film thickness is y or more. 2. A laminated film comprising a heat-fusible organic resin film having a degree of crystallinity of 60% or less laminated on at least one rigid organic resin film, wherein the film has a degree of crystallinity of 60% or less. A freshness preserving film, wherein a large number of fine non-through holes are formed over the organic resin film of (1). 3. The organic resin film having rigidity is a nylon film.
The freshness retaining film as described in the above. 4. A lamination in which a heat-fusible organic resin film having a crystallinity of 60% or less is laminated on at least one rigid organic resin film having a large number of fine through holes formed on the entire surface. A freshness preserving film, wherein a number of fine non-through holes are perforated from any one surface to the back side organic resin film. 5. The freshness retaining film according to claim 4, wherein the rigid organic resin film is a uniaxially or biaxially stretched polypropylene film or a polyethylene terephthalate film. 6. The through-hole having an average opening diameter of 0.5 to 100 μm and being formed in the rigid organic resin film at a density of 100 / cm ² or more. The freshness retaining film according to claim 4, wherein 7. The heat-fusible organic resin film having a crystallinity of 60% or less has a density of 0.90 to 0.93 g / c.
m ³ , a metallocene-based polyethylene having a melt flow rate of 0.5 to ³⁰ , an ethylene-vinyl acetate-based copolymer having a vinyl acetate content of 5 to 25% by weight, and an acrylic acid having a methyl acrylate content of 10 to 30% by weight 5. The freshness retaining film according to claim 1, wherein the film is a mixed resin of at least one resin selected from a methyl copolymer and low-density polyethylene. 8. The mixed resin according to claim 7, comprising 35 to 45% by weight of the metallocene-based polyethylene, 35 to 45% by weight of the copolymer, and 10 to 30% by weight of the low-density polyethylene. The freshness retaining film as described in the above. 9. The unpenetrated hole has an average opening diameter of 5 to 400 μm, and the laminated film has a mean opening diameter of 500 to 500 μm.
5. The freshness retaining film according to claim 2, wherein the film is perforated at a density of 0 / cm ² . 10. A laminated film obtained by laminating a heat-fusible organic resin film having a crystallinity of 60% or less on a nonwoven fabric, having a gas permeability of 0 to 1000 seconds and a water vapor transmission rate of 100 to 100%.
A breathable film characterized by being 1500 g / m ² · 40 ° C. · 90% RH · day. 11. A laminated film comprising a non-woven fabric laminated with a heat-fusible organic resin film having a crystallinity of 60% or less, wherein a number of fine through holes are formed. . 12. The heat-fusible organic resin film having a crystallinity of 60% or less has a density of 0.90 to 0.93 g /.
cm ³ , a metallocene-based polyethylene having a melt flow rate of 0.5 to ³⁰ and a vinyl acetate content of 5 to 25% by weight.
And a mixed resin of low-density polyethylene and at least one resin selected from ethylene vinyl acetate copolymers and methyl acrylate copolymers having a methyl acrylate content of 10 to 30% by weight. The breathable film according to claim 11, wherein 13. The mixed resin comprises 35 to 45% by weight of the metallocene-based polyethylene and 35 to 45% of the copolymer.
13. The breathable film according to claim 12, comprising 10% by weight and 10 to 30% by weight of the low-density polyethylene. 14. The heat-fusible organic resin film according to claim 14, wherein the through-holes have an average opening diameter of 1 to 100 μm, and are formed at a density of 50 to 2000 / cm ^{2 in} the heat-fusible organic resin film. The freshness retaining film according to claim 10, wherein