JP7143867B2 - Freshness-preserving packaging container for fruits and vegetables, package containing fruits and vegetables, and method for preserving freshness of fruits and vegetables - Google Patents

Description

TECHNICAL FIELD The present invention relates to a freshness-preserving packaging container for fruits and vegetables, a package containing fruits and vegetables, and a method for preserving freshness of fruits and vegetables. More specifically, the present invention relates to a freshness-preserving packaging container for fruits and vegetables, a package containing fruits and vegetables in which fruits and vegetables are packaged in the container, and a method for preserving freshness of fruits and vegetables using the container.

Fruits and vegetables such as vegetables and fruits continue to have respiration even after they are harvested. For this reason, during storage, distribution, or preservation after harvesting, energy is consumed by the respiration of fruits and vegetables themselves, resulting in deterioration of freshness.
Therefore, studies have been made so far to suppress deterioration of the freshness of fruits and vegetables by packaging the fruits and vegetables with a packaging material whose air permeability is adjusted.

For example, Patent Literature 1 describes a packaging material in which a hole is provided in a resin film and a "freshness-preserving label" for controlling gas permeability is attached to the hole. The freshness-preserving label here is a microporous film having a pore size in the range of 0.01 to 0.5 μm and a perforated film having an average pore size in the range of 100 to 500 μm, which are superimposed and thermally bonded, and It is characterized by providing an adhesive layer around the outer surface of the microporous membrane or perforated film.
According to Patent Literature 1, it is said that freshness of fruits and vegetables can be easily maintained by packaging fruits and vegetables using such a packaging material with controlled gas permeability.

JP-A-10-262548

As in Patent Document 1, it is conceivable to adjust the breathability of the resin film by forming holes in the resin film and attaching a breathable material capable of controlling gas permeability to the holes. .
In addition, it is conceivable to manufacture a freshness-preserving packaging container for fruits and vegetables using a resin film whose air permeability is adjusted in this way, and to package fruits and vegetables using the freshness-preserving packaging container for fruits and vegetables.

It is preferable that the freshness-preserving packaging container for fruits and vegetables not only retains the freshness of fruits and vegetables with appropriate air permeability, but also has practically good characteristics as a “packaging container”.
From one viewpoint, (i) the opening can be closed with a sufficiently strong strength by heat sealing, and (ii) when opening the container, the heat-sealed portion can be easily peeled off and opened. A holding package is preferred in practice.
From another point of view, a chuck (zipper) may be attached to the opening of the freshness-preserving packaging container for fruits and vegetables. Normally, when a zipper is attached to a freshness-preserving packaging container for fruits and vegetables by heat-sealing, it is required that the zipper be difficult to remove.
From the viewpoint of these practical properties as a packaging container, the packaging material described in Patent Document 1 has room for improvement.

The present invention has been made in view of such circumstances. SUMMARY OF THE INVENTION An object of the present invention is to provide a freshness-preserving packaging container for fruits and vegetables having practically favorable characteristics.

As a result of intensive studies, the inventors of the present invention completed the invention provided below and solved the above problems.

According to the invention,
A freshness-preserving packaging container for fruits and vegetables made of a resin film,
The resin film has a microcrystal size of 2.5 to 3.5 nm as determined by an X-ray diffraction method ,
The degree of orientation of the resin film determined by an X-ray diffraction method is 70 to 85%,
The freshness-preserving packaging container for fruits and vegetables is provided , wherein the resin film contains oriented polypropylene .

Moreover, according to the present invention,
A fruit and vegetable-containing package is provided in which the fruit and vegetable is packaged in the above freshness-preserving packaging container.

Moreover, according to the present invention,
A method for preserving freshness of fruits and vegetables is provided, comprising packaging the fruits and vegetables using the freshness-preserving packaging container for fruits and vegetables.

ADVANTAGE OF THE INVENTION According to this invention, the heat-sealing property is favorable, and the freshness-preserving packaging container for fruits and vegetables from which the heat-sealed part can be peeled easily is provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed typically an example of the freshness-preserving packaging container for fruits and vegetables.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The drawings are for illustrative purposes only. The shape and dimensional ratio of each member in the drawings do not necessarily correspond to the actual article.

In this specification, the term "substantially" means that it includes a range that takes into account manufacturing tolerances, assembly variations, and the like, unless otherwise explicitly stated.
In this specification, the notation "X to Y" in the description of numerical ranges means X or more and Y or less, unless otherwise specified. For example, "1 to 5% by mass" means "1% by mass or more and 5% by mass or less".
The notation "(meth)acryl" used herein represents a concept that includes both acryl and methacryl. The same applies to similar notations such as "(meth)acrylate".

<Packaging containers for preserving freshness of fruits and vegetables>
FIG. 1 is a diagram schematically showing an example of the freshness-preserving packaging container for fruits and vegetables of the present embodiment (hereinafter also referred to as “container 1”).
The container 1 is composed of a resin film 3 .
The resin film 3 is provided with holes 5 having a diameter of 1 to 10 mm.
A breathable material 7 is attached to the resin film 3 so as to cover the holes 5 . “So as to cover the hole 5” means that the hole 5 as a whole overlaps with the breathable material 7 when the hole 5 and the perimeter of the breathable material 7 are viewed from the outer surface side of the container 1 .
The microcrystal size of the resin film 3 determined by the X-ray diffraction method is 2.5 to 3.5 nm, preferably 2.8 to 3.3 nm.

The "microcrystal size" can be obtained, for example, by applying data obtained by X-ray diffraction measurement of a resin film to the following formula known as Scherrer's formula in the polymer field. For example, when the resin film is polypropylene, the (111) plane can be adopted as the measurement plane (of course, other planes may be used).
D=0.94λ/(β cos θ)
D: crystallite size λ: X-ray wavelength used for measurement (1.54 Å for Cu-Kα rays)
β: half-value width of the measurement surface peak (unit: rad)
θ: Bragg angle of the measurement surface (unit: rad)

Incidentally, when the crystallite size is determined by the X-ray diffraction method, X-rays are normally made incident from the ND direction (Normal Direction) of the resin film 3 .

In general, the melting behavior of a polymer depends not only on the primary structure of the polymer but also on the crystallization state of the polymer.
Since the microcrystal size of the resin in the resin film 3 is 3.5 nm or less, it is presumed that the resin responds "quickly" to the heat during heat sealing and melts. For this reason, it is presumed that sufficient heat-sealing properties can be obtained and a chuck (zipper) can be attached with sufficient strength.
In addition, since the microcrystal size of the resin in the resin film 3 is 2.5 nm or more, the resin does not "melt too much" within the range of temperature and time for heat sealing that is usually performed, and the resin does not excessively melt. It is speculated that melting and subsequent sticking are suppressed. For this reason, it is presumed that the heat-sealed portion can be easily peeled off with an appropriate force.
Just to make sure, the present invention should not be construed as being limited by the speculation above.

In order to set the microcrystal size of the resin film 3 to 2.5 to 3.5 nm as determined by the X-ray diffraction method, it is preferable to form the film from an appropriate material under appropriate conditions. Details of materials and film forming conditions will be described later.
Of course, the method for making the crystallite size 2.5 to 3.5 nm is not limited to the method described in this specification. In manufacturing the resin film 3, a known method can be used as appropriate.

Continuing the specific description of the container 1 .

(resin film)
The material of the resin film 3 is not particularly limited. A resin film having a microcrystal size of 2.5 to 3.5 nm and capable of packaging fruits and vegetables can be appropriately used.
The resin film 3 may be stretched or unstretched. From the viewpoint of optimizing the crystallite size, stretching treatment is preferred.

From availability, cost, ease of perforation, etc., the resin film is at least one selected from the group consisting of polyethylene, ethylene copolymer, polypropylene, polyvinyl chloride, polystyrene, (meth)acrylic resin, polyester resin and polyamide resin. It is preferable to include
The resin film 3 may contain only one resin, or may contain two or more resins.

In particular, the resin film 3 preferably contains at least one selected from the group consisting of oriented polypropylene and linear low-density polyethylene.

The polypropylene of the oriented polypropylene may be a homopolymer of propylene, a block copolymer of propylene, a random copolymer of propylene, or the like. Examples of random or block copolymers of propylene include random or block copolymers of propylene monomers and α-olefins having 2 or 4 to 10 carbon atoms. Among them, random copolymers or block copolymers of propylene and ethylene are preferred.
"Orientation" of oriented polypropylene is usually biaxial orientation. The draw ratio is not particularly limited, but can be, for example, about 2 to 5 times in each of the MD direction and the TD direction.

Linear low density polyethylene (L-LDPE) is usually a copolymer of ethylene and some amount of α-olefin. The type of α-olefin is not particularly limited. Typical α-olefins include α-olefins having 3 to 10 carbon atoms such as 1-butene, 1-hexene, 4-methylpentene-1,1-octene.

The resin film 3 may contain additives such as an anti-fogging agent and an anti-condensing agent in addition to the resin. By including an appropriate additive in the resin film 3, the resin film 3 can be provided with desirable properties for packaging and storage of fruits and vegetables.
Specific examples of antifog agents include glycerin laurate, diglycerin laurate, decaglycerin laurate, glycerin monostearate, sorbitan stearate and the like.

In terms of anti-fogging properties and anti-condensing properties, the contact angle of water on the inner surface of the container 1 is preferably 3 to 60°, more preferably 10 to 59°, still more preferably 20 to 58°.
The contact angle may be adjusted by using additives such as anti-fogging agents and anti-condensing agents, by applying some kind of treatment to the surface of the resin film 3, or by both of these. good too. The resin film 3 preferably includes anti-fogging properties in terms of convenience and certainty of effects.

The contact angle for water is measured by, for example, using a commercially available contact angle meter (eg, DROPMASTER-501 manufactured by Kyowa Interface Science Co., Ltd.), and applying 2 μL of purified water to the surface of the measurement target by the droplet method for 7 seconds. It can be determined by measuring the water contact angle afterward.

The degree of orientation of the resin film 3 determined by an X-ray diffraction method is preferably 70 to 85%, more preferably 73 to 84%. When the degree of orientation is an appropriate value, the melting behavior of the resin due to heat during heat-sealing is further controlled, and the heat-sealing property and peelability of the heat-sealed portion are considered to be further improved.
When the degree of orientation is determined by the X-ray diffraction method, X-rays are normally made to enter the resin film 3 from the TD (Transverse Direction: horizontal axis direction).

The degree of orientation (%) is usually obtained by the formula {(180−Wh)/180}×100. Wh is the half width (°) of the crystalline peak.

The thickness of the resin film 3 is preferably 15-50 μm, more preferably 20-45 μm. When the thickness of the resin film 3 is 15 μm or more, the strength of the container 1 can be easily increased. When the thickness of the resin film 3 is 50 μm or less, the flexibility (suppleness) of the container 1 can be maintained.

A method for obtaining the resin film 3 is not particularly limited. Examples of methods for obtaining a resin film include known methods such as extrusion, inflation and calendering.
The resin film 3 may be a single layer or a multilayer of two or more layers. As a method for obtaining a multilayer film, known methods such as dry lamination, extrusion lamination, co-extrusion and coating can be appropriately used.

As a specific example, when polypropylene is used as a raw material, a resin film having a microcrystal size of 2.5 to 3.5 nm can be easily produced by forming a polypropylene film according to the following procedure. Below, in particular, the roll temperature of the roll drawing machine is important.
(1) Polypropylene as a raw material is melted at 200 to 230°C.
(2) The melted polypropylene is extruded through a die and then stretched by a roll stretching machine for about 10 seconds in the MD and TD directions by about 2 to 5 times each.
At this time, the temperature of the rolls of the roll stretching machine is set to, for example, 65 to 95°C, preferably about 75 to 95°C.
(3) The stretched film is cooled by bringing it into contact with a cooling roll set at about 20°C. The cooling time is, for example, about 1 to 2 seconds.
(4) Wind the cooled film on a room temperature take-up roll.

Just to be sure, if there is a commercially available resin film with a crystallite size of 2.5 to 3.5 nm, it may be used as the resin film 3 .

(hole)
The diameter of the holes 5 is 1-10 mm, more preferably 2-8 mm, as described above. By adjusting the diameter of the holes 5, it is easy to obtain appropriate air permeability according to the type of fruits and vegetables.
If the shape of the hole 5 cannot be regarded as substantially circular, the diameter of the hole 5 can be the diameter of a perfect circle having the same area as the opening area of the hole 5 (equivalent circle diameter).
(The shape of the hole 5 may be, for example, rectangular. However, from the point of view of suitability for manufacturing, the shape of the hole 5 is preferably substantially circular.)

The method of providing the holes 5 (punching method) is not particularly limited. Holes 5 are typically punch holes. In other words, the holes 5 may be formed by using a punching device used in the field of packaging materials. The holes 5 may be provided by other methods, for example, by pressing a hot needle of suitable thickness.

The ratio of the area of the holes 5 to the area of the outer surface of the container 1 is preferably 0.005-0.03%, more preferably 0.008-0.025%. By adjusting this ratio, it is possible to obtain air permeability more suitable for maintaining the freshness of fruits and vegetables.

The resin film 3 may have only one hole 5, or may have a plurality of holes 5 (for example, 2 to 8 holes).
When a plurality of holes 5 are provided in the resin film 3 , all of the plurality of holes 5 are preferably covered with the air-permeable material 7 from the viewpoint of air permeability adjustment. Moreover, it is preferable that all the diameters of the plurality of holes 5 are 1 to 10 mm.

(breathable material)
The breathable material 7 is normally present on the outer surface side of the container 1 (for reasons such as ease of manufacture). The breathable material 7 may be on the inner surface side of the container 1 .

The air-permeable material 7 may be attached to the resin film 3 by, for example, an adhesive, but is preferably attached to the resin film 3 by thermal adhesion. By attaching the air-permeable material 7 to the resin film 3 by thermal bonding, peeling of the air-permeable material 7 due to moisture or the like is suppressed, there is no need to use additional materials, and the "protrusion" of the adhesive when using an adhesive is suppressed. ” problem does not occur, and other advantages can be obtained.
In addition, since the microcrystal size of the resin film 3 is 2.5 to 3.5 nm, the adhesive force between the resin film 3 and the air-permeable material 7 can be sufficiently increased. In addition, it is possible to obtain the advantage that the air-permeable material 7 is less likely to come off when the container 1 is used.

Just to be sure, the entire perimeter of the hole 5 in the resin film 3 is normally fixed to the air-permeable material 7 . As a result, when the upper opening of the container 1 shown in FIG. Further, it becomes easier to obtain the effect of ventilation control by the breathable material 7 .

The breathable material 7 can be any material that is more breathable than the resin film 3 . From the standpoint of availability and appropriate air permeability, the air-permeable material 7 is preferably paper, woven fabric, or non-woven fabric.

The paper, woven fabric or non-woven fabric that constitutes the breathable material 7 is usually made of natural fibers and/or synthetic fibers. Paper, woven or non-woven fabrics can contain one or more fibers.
Examples of natural fibers include fibers containing cellulose and keratin. Synthetic fibers include polyester, polyamide, polyolefin, polyurethane and the like. Of course, fibers other than these are not excluded.
There are no particular restrictions on the method of manufacturing the paper, woven fabric or non-woven fabric. For nonwoven fabrics, for example, nonwoven fabrics obtained by known methods such as flash spinning, melt blowing, spunbonding, and spunlacing can be used. As for the woven fabric, the weaving method is not particularly limited.

From the viewpoint of further enhancing the adhesiveness of the resin film 3 and the breathable material 7 by heat sealing (making it difficult to remove the breathable material 7), the breathable material 7 preferably contains a thermoplastic resin. More specifically, the air-permeable material 7 preferably contains the thermoplastic resin (such as polypropylene) mentioned as the material of the resin film 3 .
When the air-permeable material 7 is paper, woven fabric or non-woven fabric, the air-permeable material 7 can contain, for example, a fibrous thermoplastic resin (a part or all of the fibers constituting the paper, woven fabric or non-woven fabric). can be a fibrous thermoplastic). Alternatively, the thermoplastic resin may be present in the "interstices" of the fibers in the paper, woven or non-woven fabric.

As the breathable material 7 available on the market, paper, woven fabric, or non-woven fabric used for food filters (tea bags, etc.) can preferably be mentioned. In particular, some food filters are heat-sealable. Therefore, by using a heat-bondable food filter as the air-permeable material 7, the air-permeable material 7 can be easily attached to the resin film 3 by heat-bonding. In addition, the food filter is preferable because the container 1 is used for "packaging of fruits and vegetables".
Commercial products of paper, woven fabric or non-woven fabric used for food filters include "Heat Pack" and "Heatron" series of Nippon Paper Papylia Co., Ltd., and the like.

(Form, size, etc. of packaging container)
The shape and size of the container 1 are not particularly limited as long as it can pack fruits and vegetables. The shape of the container 1 is typically bag-like, more specifically, a quadrangular (rectangular, square, etc.) bag-like shape.
Although it is only an example, the size of the container 1 can be about 100 mm×100 mm to 250 mm×350 mm for packaging of fruits and vegetables for general consumers.

Means for closing the opening, such as a zipper (not shown in FIG. 1), may be provided in the vicinity of the opening at the top of the container 1 shown in FIG. On the other hand, the container 1 itself may not be provided with means for closing the opening. In this case, for example, the opening may be closed with a heat seal, an adhesive tape, a rubber band, a string, or the like.

The container 1 provided with a zipper (zipper) is manufactured, for example, by the following procedure.
(1) First, a male zipper tape and a female zipper tape are attached by heat-sealing to the inside of each of two resin films facing each other. The male zipper tape and female zipper tape are usually made of thermoplastic resin.
(2) After that, the four sides of the resin film are heat-sealed and/or fused to obtain a container 1 (bag) of desired size.
For a method of manufacturing a container with a zipper (zipper), for example, JP-A-2000-226042, JP-A-2011-200507, and JP-A-4787833 can be referred to. Attaching a chuck (zipper) to the vicinity of the opening of the container 1 is not particularly special, and a known technique may be applied as appropriate.
In this embodiment, the microcrystal size of the resin film 3 is appropriate. As a result, the male zipper tape or female zipper tape and the resin film 3 can be fused sufficiently strongly.

(Container manufacturing method)
A manufacturing method of the container 1 is not particularly limited.
When manufacturing the bag-like container 1, the method of making the bag is not particularly limited. Known bag-making methods (methods such as heat sealing and fusion cutting) can be applied as appropriate.
The holes 5 can be provided, for example, by a punching device or a hot needle, as described above.
The air-permeable material 7 can be attached to the resin film 3 by, for example, a heat sealing method (thermal bonding) or a method using an adhesive, as described above.
The method of manufacturing the container 1 provided with a chuck (zipper) is as described above.

When the container 1 is bag-shaped, from the viewpoint of manufacturing efficiency, the manufacturing procedure of (1) perforation of the resin film, (2) attachment of a breathable material, (3) bag making, or (1) A manufacturing procedure of perforating a resin film, (2) making a bag, and (3) attaching a breathable material is preferable. Of course, the manufacturing procedure is not limited to this.

Arbitrary characters and patterns may be printed on the container 1 . Printing may be done at any stage in the manufacture of the container. The method of printing, the type of ink used for printing, and the like may be appropriately selected according to the purpose of printing.

<Packaging body containing fruits and vegetables, method for maintaining freshness of fruits and vegetables>
By packaging (preferably sealing) fruits and vegetables in the freshness-preserving packaging container for fruits and vegetables of the present embodiment (for example, container 1 described above), a package containing fruits and vegetables can be produced. In addition, by packaging fruits and vegetables using the freshness-preserving packaging container for fruits and vegetables of the present embodiment (for example, container 1 described above), the freshness of fruits and vegetables can be maintained (the deterioration of fruits and vegetables can be suppressed).

As an example, first, a container 1 is prepared, and an appropriate amount of fruits and vegetables is accommodated in its internal space. After that, the opening of the container 1 is heat-sealed (heat-sealed) to form a heat-sealed portion (the seal width is typically about 10 mm). Through the above procedure, a fruit and vegetable-containing package in which fruit and vegetables are packaged can be obtained. Then, the freshness of the packaged fruits and vegetables can be maintained (the deterioration of the fruits and vegetables can be suppressed).
The opening may be closed by adhesive tape, rubber band, string, etc. instead of heat sealing. Moreover, when the container 1 itself is provided with a means (for example, a chuck) for closing the opening, the opening may be closed by the means. In short, any closing method may be used as long as it sufficiently restricts the entry and exit of gas through the opening.

Fruits and vegetables that can be packaged are not particularly limited. Specific examples of fruits and vegetables include plantain, spinach, Japanese mustard spinach, mizuna, mibuna, asparagus, Chinese cabbage, lettuce, thyme, sage, parsley, Italian parsley, rosemary, oregano, lemon balm, chives, lavender, salad burnet, lamb's ear, and rocket. , Dandelion, Nasturtium, Basil, Arugula, Watercress, Moroheiya, Celery, Kale, Green onion, Cabbage, Chinese cabbage, Shungiku, Saladana, Lettuce, Japanese butterbur, Nabana, Bok choy, Japanese mitsuba, Japanese parsley, Brussels sprouts, Broccoli, Cauliflower, Japanese ginger, Japanese radish, Carrots, burdocks, radishes, turnips, sweet potatoes, potatoes, Chinese yam, yam, taro, ginenjo, yamatoimo, bell peppers, paprika, shishito, cucumbers, eggplants, tomatoes, cherry tomatoes, pumpkins, bitter melons, okra, sweet corn, edamame beans, snow peas, Green beans, fava beans, mushrooms, and the like can be mentioned. It is also effective for fruits such as citrus fruits, apples, pears, grapes, blueberries, persimmons and strawberries, and cut flowers.
Fruits and vegetables may be in a state of being cut, such as so-called cut vegetables or cut fruits.

The amount of fruits and vegetables contained in the bag may vary depending on the size of the bag, the type of fruits and vegetables, and the like. For fruits and vegetables for general consumers, one example is 50 to 1000 g, preferably 100 to 800 g.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than those described above can be adopted. Moreover, the present invention is not limited to the above-described embodiments, and includes modifications, improvements, etc. within the scope of achieving the object of the present invention.
Examples of reference forms are added below.
1.
A freshness-preserving packaging container for fruits and vegetables made of a resin film,
The resin film is provided with holes having a diameter of 1 to 10 mm,
A breathable material is attached to the resin film so as to cover the hole,
The freshness-preserving packaging container for fruits and vegetables, wherein the resin film has a microcrystal size of 2.5 to 3.5 nm as determined by an X-ray diffraction method.
2.
1. The freshness-preserving packaging container for fruits and vegetables according to
The freshness-preserving packaging container for fruits and vegetables, wherein the degree of orientation of the resin film determined by an X-ray diffraction method is 70 to 85%.
3.
1. or 2. The freshness-preserving packaging container for fruits and vegetables according to
The resin film contains an antifogging agent,
The freshness-preserving packaging container for fruits and vegetables, wherein the contact angle of the resin film to water on the inner surface of the container is 3 to 60°.
4.
1. ~3. The freshness-preserving packaging container for fruits and vegetables according to any one of
The freshness-preserving packaging container for fruits and vegetables, wherein the air-permeable material is attached to the resin film by thermal adhesion.
5.
1. ~ 4. The freshness-preserving packaging container for fruits and vegetables according to any one of
The freshness-preserving packaging container for fruits and vegetables, wherein the air-permeable material is paper, woven fabric, or non-woven fabric.
6.
1. ~ 5. The freshness-preserving packaging container for fruits and vegetables according to any one of
A freshness-preserving packaging container for fruits and vegetables, wherein the ratio of the area of the holes to the area of the outer surface of the container is 0.005 to 0.03%.
7.
1. ~6. The freshness-preserving packaging container for fruits and vegetables according to any one of
The freshness-preserving packaging container for fruits and vegetables, wherein the resin film contains at least one selected from the group consisting of oriented polypropylene and linear low-density polyethylene.
8.
1. ~7. A package containing fruits and vegetables, which is packaged in the freshness-preserving packaging container for fruits and vegetables according to any one of the above.
9.
1. ~7. A freshness-preserving method for fruits and vegetables, comprising packaging the fruits and vegetables using the freshness-preserving packaging container for fruits and vegetables according to any one of the above.

Embodiments of the present invention will be described in detail based on examples and comparative examples. It should be noted that the invention is not limited to the examples.

<Preparation of resin film>
(Production of Film 1)
Commercially available polypropylene resin was melted at 200° C., and an antifogging agent obtained by mixing diglycerin laurate and decaglycerin laurate at a mass ratio of 98:2 was added to a concentration of 7% by mass. This was extruded from a die and then stretched 3 times in the MD direction and 3 times in the TD direction over 10 seconds using a roll stretching machine. At this time, the temperature of the rolls of the roll stretching machine was set to 90°C.
The film obtained by stretching was cooled with a roll set at 20° C. for 2 seconds, and then wound with a roll at room temperature (no particular temperature control).

(Production of film 2)
Commercially available polypropylene resin was melted at 200° C., and an antifogging agent obtained by mixing diglycerin laurate and decaglycerin laurate at a mass ratio of 98:2 was added to a concentration of 7% by mass. This was extruded from a die and then stretched 3 times in the MD direction and 3 times in the TD direction over 10 seconds using a roll stretching machine. At this time, the temperature of the rolls of the roll drawing machine was set to 80°C.
The film obtained by stretching was cooled with a roll set at 20° C. for 2 seconds, and then wound with a roll at room temperature (no particular temperature control).

(Production of comparative film 1)
Commercially available polypropylene resin was melted at 200° C., and an antifogging agent obtained by mixing diglycerin laurate and decaglycerin laurate at a mass ratio of 98:2 was added to a concentration of 7% by mass. This was extruded from a die and then stretched 3 times in the MD direction and 3 times in the TD direction over 10 seconds using a roll stretching machine. At this time, the temperature of the rolls of the roll drawing machine was set to 70°C.
The film obtained by stretching was cooled with a roll set at 20° C. for 2 seconds, and then wound with a roll at room temperature (no particular temperature control).

(Production of comparative film 2)
Commercially available polypropylene resin was melted at 200° C., and an antifogging agent obtained by mixing diglycerin laurate and decaglycerin laurate at a mass ratio of 98:2 was added to a concentration of 7% by mass. This was extruded from a die and then stretched 3 times in the MD direction and 3 times in the TD direction over 20 seconds using a roll stretching machine. At this time, the temperature of the rolls of the roll drawing machine was set to 100°C.
The film obtained by stretching was cooled with a roll set at 20° C. for 2 seconds, and then wound with a roll at room temperature (no particular temperature control).

Each film was analyzed using an X-ray structure analyzer "NANO Viewer" manufactured by Rigaku, and the crystallite size and degree of orientation were determined by analyzing the obtained data.
The formulas for determining the crystallite size and degree of orientation are as described above. The (111) plane of polypropylene was used as the measurement plane. The setting of the apparatus, the preparation of the sample for measurement, and the direction of incidence of X-rays are described below.
Details of the measurement conditions are as follows.
[Device Settings]
・Tube voltage, tube current: 40 kV, 40 mA
・Tube: Cu
・Beam size: 2mm x 8mm
・Irradiation time: 10min
・Measurement mode: extended measurement ・Camera distance: 96.93cm
[Sample for measurement]
- Microcrystal size measurement: A film was cut into a size of 10 mm x 10 mm, and four films were piled up and fixed in the automatic sample changer of the apparatus in the MD direction. An X-ray was applied to this from the ND direction.
- Orientation degree measurement: A film was cut into a size of 2 mm x 10 mm, and 8 sheets were piled up and fixed in the automatic sample changer of the apparatus with the MD direction aligned. X-rays were applied to this from the TD direction.

In addition, the contact angle of each film with respect to water was measured using DROPMASTER-50 manufactured by Kyowa Interface Science Co., Ltd. by the droplet method. Obtained by measuring.

<Preparation of breathable material>
A polypropylene non-woven fabric manufactured by TRSCO, product number: 955-0559, basis weight: 30 g/m ² , thickness: 0.25 mm was prepared.

<Manufacturing of freshness-preserving containers for fruits and vegetables>
According to the following procedure, freshness-preserving containers for fruits and vegetables of each example and each comparative example were manufactured.
(1) Preparation of film and air-permeable material Two sheets of the prepared film were cut into the sizes shown in Table 1 and prepared. In addition, breathable materials (circular, 15 mm in diameter) were prepared by the number of holes to be drilled in (2) below.
(2) Perforation One of the two films prepared in (1) was perforated using a punching device. The diameter of the hole was 4 mm, and the number of holes was one.
(3) Attachment of air-permeable material An air-permeable material was attached to the holes of the film by heat sealing. Specifically, (i) first, a breathable material is placed over the holes in the film, and (ii) a circular shape is placed over the breathable material according to the diameter of the holes and the size of the breathable material. of hot plate (120° C.) was pressed. As a result, the entire peripheries of the holes in the resin film were fixed to the air-permeable material.
(4) Bag Making Two sheets of film (one with holes and one without air-permeable material) were stacked so that the four corners were aligned. Then, using an impulse sealer, three sides (both sides and bottom) were heat-sealed. As the impulse sealer, FI-400Y-10PK manufactured by Fuji Impulse Co., Ltd. was used. The heat-sealing process was performed under the conditions of 160° C. and a sealing time of 1 second. This formed a heat-sealed portion with a width of 10 mm.
In making the bag, the air-permeable material was placed on the outside of the bag.
A sufficient number of bags were produced for the following evaluations.

<Evaluation>
(Heat seal strength (peel strength))
The heat seal strength was measured in the following manner.
・Measurement environment: 23°C, 50% RH
- Sample preparation: Two pieces of 15 mm width were cut out from each film and heat-sealed at 160°C in parallel with the width direction to a width of 5 mm.
・Measurement: Tensilon universal testing machine RTC-1210 manufactured by Orientec Co., Ltd. was used, the interval between grips was set to 70 mm, and the sample was pulled in the direction of 180° at a speed of 300 mm/min. Then, the maximum strength when the heat-sealed portion was peeled off was determined. The measurement was performed 3 times, and the average value of the 3 times was taken as the heat seal strength.

(Bag breakage resistance)
First, 100 cc of nitrogen gas was sealed in the container (bag) of each example and comparative example, and the opening was heat-sealed to prepare a nitrogen gas-filled bag. The conditions for heat sealing were the same for each bag.
After that, the evaluator was asked to push the inflated bag containing nitrogen gas by hand to evaluate whether it would be easily opened.
Ten nitrogen gas-filled bags were prepared for each of the examples and comparative examples, and evaluated by 10 evaluators. If less than 2 people answered that they opened the package easily, it was rated as ◯ (good), and if more than 2 people answered that it was opened easily, it was rated as x (poor).

(Ease of opening the heat-sealed part)
First, the opening of the container (bag) was heat-sealed and closed under conditions of 160° C. and 1 second.
After heat-sealing, 10 evaluators were asked to manually open the portion closed by heat-sealing. If 9 or more people answered that it was easy to open the package, it was rated as ◯ (good), and if less than 9 people answered that it was easy to open, it was rated as x (poor).

(Ease of opening when processed into a zipper bag)
In the above <Manufacturing of freshness-preserving container for fruits and vegetables>, (4) before making the bag, the step of attaching the male zipper tape and the female zipper tape near the opening of the final bag by heat-sealing. added. In this way, bags provided with zippers were produced (20 bags each for each example and comparative example).
Twenty evaluators were asked to open the zipped bag. and,
・Accepted products that can be opened smoothly without problems,
・When opening the bag, the attached zipper tape was removed, or the flexibility of the opening was lost due to excessive heat-sealing between the zipper tape and the bag, making it difficult to open. It was accepted as a product.
As a final evaluation, ◯ (good) was given when there were 18 or more acceptable bags, and x (bad) was given when there were less than 18 bags.

(difficult to remove breathable material)
First, 200 g of green soybeans were put in a bag, and the opening was heat-sealed closed, and 20 bags were prepared for each example and comparative example.
The prepared 20 bags were placed in a cardboard with a size of 400 mm×250 mm×300 mm, and the cardboard was closed. Then, it was shaken up and down for 5 minutes. The shaking method was set to 10 cm in the vertical direction and 1 reciprocation for 1 second.
After that, each bag was checked, and if the air-permeable material was not peeled off, it was judged as an OK product, and if there was a peeled part, it was judged as an NG product. When the number of acceptable products was 18 bags or more, it was evaluated as ◯ (good), and when it was less than 18 bags, it was evaluated as × (bad).

Various information and evaluation results regarding the film are summarized in the table below.

As shown in Table 1, the bag breakage resistance, ease of opening of the heat-sealed portion, ease of opening of the heat-sealed portion, ease of opening when processed into a zipper bag, and air permeability of the freshness-preserving packaging containers for fruits and vegetables of Examples 1 and 2 In all cases, the difficulty of removal was good. In other words, the fruit and vegetable freshness-preserving packaging containers of Examples 1 and 2 had practically excellent characteristics. This is probably because the resin film has a microcrystal size of 2.5 to 3.5 nm as determined by the X-ray diffraction method, so that the strength of the heat-sealed/heat-sealed portion is moderate. . In other words, the resin film has a microcrystal size of 2.5 to 3.5 nm as determined by the X-ray diffraction method, so that the "peel strength" shown in the table is "not too large and not too small. It is considered that this led to good performance.
In Comparative Example 1, the size of the microcrystals was too small, so that the resin "melted too much" during heat sealing, and the opening of the heat-sealed portion became difficult.
In Comparative Example 2, the microcrystal size was too large, so the resin was not sufficiently melted during heat sealing or heat sealing, and heat sealing/heat sealing with sufficient strength was not possible.

<Evaluation of freshness retention>
200 g of fresh green soybeans were put into the freshness-keeping container of each example, and the opening was sealed by heat-sealing. This was stored for 5 days in an environment of 20°C and 50% RH.
10 evaluators evaluated whether the discoloration (yellowing), troche (floating water, i.e., exudation of moisture due to the progression of putrefaction), and odor of the edamame after storage were at a level at which they could be sold as commercial products. did.
In each evaluation, more than 6 out of 10 people evaluated that "it is at a level where it can be sold as a product". That is, it was confirmed that the fruit and vegetable freshness-keeping container of each example had sufficient performance as a "fruit and vegetable freshness-keeping" container.

1 container (freshness-preserving packaging container for fruits and vegetables)
3 resin film 5 hole 7 breathable material

Claims (9)

A freshness-preserving packaging container for fruits and vegetables made of a resin film,
The resin film has a microcrystal size of 2.5 to 3.5 nm as determined by an X-ray diffraction method ,
The degree of orientation of the resin film determined by an X-ray diffraction method is 70 to 85%,
The freshness-preserving packaging container for fruits and vegetables , wherein the resin film contains oriented polypropylene . The freshness-preserving packaging container for fruits and vegetables according to claim 1 ,
The resin film contains an antifogging agent,
The freshness-preserving packaging container for fruits and vegetables, wherein the contact angle of the resin film to water on the inner surface of the container is 3 to 60°. The freshness-preserving packaging container for fruits and vegetables according to claim 1 or 2,
The freshness-preserving package for fruits and vegetables, wherein the resin film has a microcrystal size of 2.8 to 3.0 nm as determined by an X-ray diffraction method. The freshness-preserving packaging container for fruits and vegetables according to any one of claims 1 to 3,
A freshness-preserving packaging container for fruits and vegetables, wherein the degree of orientation of the resin film determined by an X-ray diffraction method is 74.9 to 83.3%. The freshness-preserving packaging container for fruits and vegetables according to any one of claims 1 to 4,
A freshness-preserving packaging container for fruits and vegetables, wherein the resin film is provided with holes. The fruit and vegetable freshness-preserving packaging container according to claim 5,
The freshness-preserving packaging container for fruits and vegetables, wherein the hole has a diameter of 1 to 10 mm. The fruit and vegetable freshness-preserving packaging container according to claim 5 or 6 ,
A freshness-preserving packaging container for fruits and vegetables, wherein the ratio of the area of the holes to the area of the outer surface of the container is 0.005 to 0.03%. A package containing fruits and vegetables, which is obtained by packaging fruits and vegetables in the freshness-preserving packaging container for fruits and vegetables according to any one of claims 1 to 7. A method for preserving freshness of fruits and vegetables, comprising packaging the fruits and vegetables using the freshness-preserving packaging container for fruits and vegetables according to any one of claims 1 to 7.

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