JP2018118744A - Wrapping bag of fruit and vegetables - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wrapping bag made of a novel resin film which enables preserving freshness of fruit and vegetables for a relatively longer time period.SOLUTION: Fruit and vegetables are packed and sealed in a wrapping bag made of biaxially drawn polypropylene film which has at least two layers such as a sealing layer and a base material layer, for example. The wrapping bag for fruit and vegetables has following characteristics such as (a) the film contains propylene random copolymer in the sealing layer, (b) oxygen penetration of the film is within the range of 900-2,600 cm/m24h atm, and carbon dioxide penetration of the film is within the range of 2,500-7,600 cm/m24h atm (c) the wrapping bag is filled with inert gases including carbon dioxide, and a ratio of carbon dioxide in the gases is within the range of 1-20 vol.% and (d) the wrapping bag is heat sealed with fruit and vegetables inside.SELECTED DRAWING: None

Description

  The present invention belongs to the technical field of biaxially oriented polypropylene film. The present invention relates to a fruit and vegetable package in which fruits and vegetables are sealed in a packaging bag made of such a resin film, and also relates to a packaging bag made of the resin film and the resin film.

Fruits and vegetables such as raw vegetables, fruits, persimmons, and mushrooms are packaged and distributed in a bag-shaped resin film to maintain freshness and protect them from damage caused by contact with the outside. As the resin film, a polypropylene film is generally used because of its excellent transparency, gloss and rigidity.
A packaging machine such as a vertical pillow machine is used as an apparatus for processing this resin film into a bag shape and automatically packaging fruits and vegetables such as raw vegetables. With a vertical pillow machine, first the resin film is made into a cylinder, the bottom of the bag is sealed, the contents are put in from the top of the bag, and finally the top of the bag is sealed, so that the contents are packaged in a bag-like resin film. It is a device to do.

  As a resin film for automatically packaging such fruits and vegetables, for example, a biaxially stretched polypropylene film having at least three layers of a surface layer, a base material layer, and a seal layer, and a propylene random copolymer in the seal layer A resin film containing 75 to 93% by weight of coalescence and 7 to 25% by weight of polyethylene resin is known (see Patent Document 1). Since this resin film is excellent in heat seal strength and excellent in hot tack at the time of filling the contents, the resin film processed into a bag shape is suitable for packaging fruits and vegetables.

At present, for example, when cut vegetables are put in a packaging bag made of a resin film and distributed and sold, the sales period is generally about three days after the cut vegetables are packed, but the freshness of fruits and vegetables is as much as possible. The resin film or its packaging bag is also required to be held for a long time. As a resin film pursuing such long-term maintenance of fresh food, for example, a surface layer (A) made of a polypropylene resin on the surface of a base material layer made of a polyethylene resin containing an antifogging agent, and the other An unstretched antifogging laminated film comprising a three-layer laminate in which a surface layer (B) made of a polypropylene resin is laminated on the surface and satisfies the following requirements (a) to (c) is known. (See Patent Document 2).
(A) The amount of antifogging agent contained in the base material layer is 60 to 100% by weight of the amount of antifogging agent contained in the three-layer laminate.
(B) Surface layer (A) thickness / base material layer thickness / surface layer (B) thickness = 1.0 to 4.0 / 1.0 to 8.0 / 1.0 The thickness of the laminate is in the range of 10 to 60 μm.
(C) The oxygen permeability T is in the range of 2000 to 8000 cc / m ² × 24 hr × atm.

  The film maintains the freshness of fresh food by giving the film appropriate oxygen permeability.

JP-A-2015-199228 JP2015-164790A

  The main object of the present invention is to provide a fruit and vegetable package in which the freshness of fruits and vegetables (appearance (inhibition of browning), suppression of bacterial count, etc.) is maintained for a relatively long time by a packaging bag made of a certain new resin film. And Another object is to provide a packaging bag made of the resin film and the resin film.

  As a result of intensive studies, the present inventors have found that the packaging bag is a mixed resin containing a propylene-based random copolymer in the seal layer and having a certain oxygen permeability and carbon dioxide gas permeability. It was found that the above-mentioned problems can be solved by filling the inside of the packaging bag with an inert gas containing carbon dioxide, and sealing the fruits and vegetables therein, and completed the present invention.

  As this invention, the following fruit and vegetable package can be mentioned, for example.

[1] The fruit and vegetables are sealed in a packaging bag made of a biaxially stretched polypropylene film having at least two layers of a seal layer and a base material layer, and the following matters (a) to (d) are included. And fruit and vegetable packaging.
(A) the film contains a propylene random copolymer in the seal layer;
(B) When the film is measured by a differential pressure method, the oxygen permeability is in the range of 900 to 2,600 cm ³ / m ² · 24 h · atm, and the carbon dioxide gas permeability is 2,500 to 7,600 cm ³ / in the range of m ² · 24h · atm,
(C) The inside of the packaging bag is filled with an inert gas containing carbon dioxide, and the ratio of the carbon dioxide concentration in the inert gas is in the range of 1 to 20% by volume; and (d) the above The packaging bag is heat sealed with fruits and vegetables.
[2] The fruit and vegetable package according to the above [1], wherein the seal layer further contains a polyethylene resin.
[3] The fruits and vegetables package according to [1] or [2] above, wherein the fruits and vegetables are lettuce.

According to the present invention, the freshness of fruits and vegetables packaged with a resin film, mainly cut vegetables (especially cut lettuce), can be kept relatively long.

  The fruit and vegetables package of the present invention (hereinafter referred to as “the present invention package”) is obtained by sealing fruits and vegetables in a packaging bag made of a biaxially oriented polypropylene film having at least two layers of a sealing layer and a base material layer. And has the following items (a) to (d).

(A) the film contains a propylene random copolymer in the seal layer;
(B) When the film is measured by a differential pressure method, the oxygen permeability is in the range of 900 to 2,600 cm ³ / m ² · 24 h · atm, and the carbon dioxide gas permeability is 2,500 to 7,600 cm ³ / in the range of m ² · 24h · atm,
(C) The inside of the packaging bag is filled with an inert gas containing carbon dioxide, and the proportion of carbon dioxide in the inert gas is in the range of 1 to 20% by volume; and (d) the packaging The bag is heat sealed with fruits and vegetables.

1 Resin Film According to the Present Invention A resin film according to the present invention (hereinafter referred to as “the present film”) is a biaxially stretched polypropylene film having at least three layers of a sealing layer and a base material layer, When the layer contains a propylene random copolymer and measured by a differential pressure method, the oxygen permeability is in the range of 900 to 2,600 cm ³ / m ² · 24 h · atm, and the carbon dioxide gas permeability is 2,500 to It is within the range of 7,600 cm ³ / m ² · 24 h · atm. Hereinafter, the film of the present invention will be described in detail.

1.1 Seal layer of the film of the present invention The seal layer of the film of the present invention is, for example, a layer that becomes the inside of a cylinder when the resin film is first formed into a cylindrical shape when packaging fruits and vegetables with a vertical pillow machine, In the seal portion, the seal layers adhere to each other.
The seal layer contains a propylene random copolymer.

  The propylene random copolymer is a copolymer of propylene and other α-olefin. Examples of such α-olefins other than propylene include α-olefins other than propylene having 2 to 20 carbon atoms, and specifically include, for example, ethylene, 1-butene, 1-pentene, and 1-hexene. 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 3-methyl-1-butene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, -Eicosene, cyclopentene, cycloheptene, norbornene, 5-ethyl-2-norbornene, tetracyclododecene, 2-ethyl-1,4,5,8-dimethano-1,2,3,4,4a, 5,8, Examples include 8a-octahydronaphthalene. Among these, C2-C4, for example, ethylene and butene are preferable, and ethylene is more preferable. These α-olefins other than propylene may be one kind or a combination of two or more kinds.

  The content of α-olefin other than propylene in the propylene random copolymer is preferably 14% by weight or less, and more preferably 10% by weight or less.

  The propylene random copolymer is not particularly limited as long as it is a random copolymer of propylene and other α-olefins. Specifically, for example, propylene-ethylene random copolymer, propylene-butene A random copolymer, a propylene-ethylene-butene random copolymer, etc. can be mentioned. Among these, a propylene-ethylene-butene random copolymer is preferable.

  Among the propylene-based random copolymers, the melt flow rate (MFR) value when measured under conditions of 230 ° C. and 21.18 N (2.16 Kg) load in accordance with ISO 1133 (1997) is 0.5 to A propylene random copolymer within the range of 20 g / 10 min is preferred. Further, a propylene random copolymer having a melt flow rate value in the range of 4 to 8 g / 10 min is more preferable. The melt flow rate (MFR) value of the polymer can be appropriately adjusted depending on the type and content of α-olefin other than propylene, the molecular weight of the polymer, and the degree of polymerization.

The sealing layer of the film of the present invention may further contain a polyethylene resin as necessary.
The polyethylene resin is a copolymer of ethylene and other α-olefin. Examples of such α-olefins other than ethylene include α-olefins having 3 to 20 carbon atoms. Specific examples include propylene, 1-butene, 3-methyl-1-butene, 3- Methyl-1-pentene, 4-methyl-1-pentene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, etc. Is mentioned. Among these, C3-C8, for example, 1-hexene, 4-methyl-1-pentene, and 1-octene are preferable. These α-olefins other than ethylene may be used alone or in combination of two or more.

  As a content ratio of ethylene and the other α-olefin in the polyethylene-based resin, ethylene is usually 75 to 100% by weight, and other α-olefins are 0 to 25% by weight, preferably ethylene is 85% by weight. ˜99.9 wt%, other α-olefin is 0.1 to 15 wt%, more preferably 90 to 99.5 wt%, and other α-olefin is 0.5 to 10 wt% %, More preferably 90 to 99% by weight of ethylene and 1 to 10% by weight of other α-olefins.

Among the polyethylene-based resins, the melt flow rate (MFR) value measured at 190 ° C. and 21.18 N (2.16 Kg) load in accordance with ISO 1133 (1997) is 0.5 to 20 g / 10 min. Polyethylene resins that are within the range are preferred. Moreover, the polyethylene-type resin whose said melt flow rate value exists in the range of 2-4 g / 10min is more preferable.
Further, among the polyethylene resins, a polyethylene resin having a density in the range of 0.85 to 0.90 g / cm ³ when measured in accordance with JIS K 7112 is preferable, and 0.86 to 0.89 g / A polyethylene-based resin that is in the range of cm ³ is more preferable.

  When the polyethylene resin is added to the seal layer, the content of the propylene random copolymer and the polyethylene resin is 75 to 93% by weight for the propylene random copolymer and 7 to 25% by weight for the polyethylene resin. Preferably, the propylene random copolymer is 80 to 90% by weight and the polyethylene resin is 10 to 20% by weight, more preferably the propylene random copolymer is 80 to 85% by weight, and the polyethylene resin is 15 to 20% by weight.

  The sealing layer may contain an antiblocking agent or a lubricant as long as the surfaces of the resin films are smooth and prevent the resin films from adhering to each other as long as the transparency is not impaired. Examples of such an anti-blocking agent include generally used inorganic silica, kaolin, zeolite, etc., or organic crosslinked acrylic beads. Examples of the lubricant include calcium stearate. Only one type of anti-blocking agent and lubricant may be used, or two or more types may be used in combination.

  The amount of the anti-blocking agent or lubricant added can be appropriately adjusted depending on the type of the resin, etc., but 0.05 to 30 parts by weight is appropriate with respect to 100 parts by weight of the resin constituting the layer, preferably 0.5 to 20 parts by weight.

  The sealing layer may be composed of not only one layer but also two or more layers. By further providing a layer between the outermost seal layer and the base material layer, it is preferable because the interlayer strength between the base material layer and the seal layer is improved and the seal strength is also improved.

1.2 Base layer of the film of the present invention The base layer of the film of the present invention preferably contains a crystalline polypropylene resin as a main component.

The crystalline polypropylene resin is not particularly limited as long as it is a crystalline propylene resin, but a crystalline polypropylene resin having a melting point of 155 ° C. to 165 ° C. is preferable.
Here, the main component generally means that the crystalline polypropylene resin in the base material layer is 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more.

  The crystalline polypropylene resin having a melting point of 155 ° C. to 165 ° C. is a propylene homopolymer or a copolymer of propylene and other α-olefins. Examples of α-olefins other than propylene include α-olefins other than propylene having 2 to 10 carbon atoms. Specific examples include ethylene, 1-butene, 1-pentene, 1-hexene and the like. Can be mentioned. Among these, C2-C4, for example, ethylene and 1-butene are preferable and ethylene is more preferable. These α-olefins other than propylene may be one kind or a combination of two or more kinds. The content of α-olefin other than propylene is suitably 1.3% by weight or less, preferably 0.5% by weight or less.

  Among the crystalline polypropylene resins having a melting point of 155 ° C. to 165 ° C., melt flow rate (MFR) when measured under conditions of 230 ° C. and 21.18 N (2.16 Kg) load in accordance with ISO 1133 (1997) The value is preferably in the range of 0.5 to 20 g / 10 min. Further, a crystalline polypropylene resin having a melting point of 155 ° C. to 165 ° C. in which the melt flow rate value is in the range of 2 to 4 g / 10 minutes is more preferable. The melt flow rate (MFR) value of the polymer can be appropriately adjusted depending on the type and content of α-olefin other than propylene, the molecular weight of the polymer, and the degree of polymerization.

Further, among the crystalline polypropylene resins having a melting point of 155 ° C. to 165 ° C., those having an isotactic pentad fraction (IP) by ¹³ C nuclear magnetic resonance spectrum of 94.0% to 96.0% are more preferred. preferable.

  The base material layer may be a single layer or two or more layers containing the same or different types of crystalline polypropylene resins as main components.

  The base material layer can contain an antifogging agent for the purpose of imparting antifogging performance to the film. Such an antifogging agent is generally added to the base material layer. However, after film formation of the present invention, it diffuses into the surface layer and the sealing layer, so it is used for packaging high moisture content. When it is applied, good antifogging properties are exhibited. Such an antifogging agent is not particularly limited as long as it meets the purpose, and an antifogging agent conventionally used for an antifogging film can be used as it is. Specifically, for example, three systems of alkyldiethanolamine, alkyldiethanolamine fatty acid ester, and glycerin fatty acid ester can be mentioned.

  The alkyl group in the alkyldiethanolamine is usually one having 8 to 22 carbon atoms, preferably 12 to 18 carbon atoms. Specific examples of the alkyldiethanolamine include lauryl diethanolamine, myristyl diethanolamine, palmityl diethanolamine, stearyl diethanolamine, and oleyl diethanolamine.

  The fatty acid ester group in the alkyldiethanolamine fatty acid ester is usually a saturated or unsaturated fatty acid ester having 8 to 22 carbon atoms, preferably 12 to 22 carbon atoms, and preferably the latter unsaturated fatty acid ester. Specific alkyl diethanolamine fatty acid esters include lauryl diethanolamine monostearate, myristyl diethanolamine monooleate, lauryl diethanolamine monostearate, palmityl diethanolamine monostearate, stearyl diethanolamine monopalmitylate, stearyl diethanolamine monoester. Examples thereof include stearic acid ester and oleyl diethanolamine monostearic acid ester.

  Examples of the fatty acid ester group in the glycerin fatty acid ester include the same fatty acid ester groups as in the above alkyldiethanolamine fatty acid ester. Further, the number of fatty acid ester groups bonded to —OH of glycerin is preferably 1 or 2, more preferably 1 fatty acid ester monoglyceride.

  Each of the above antifogging agents is used in the form of one kind or a mixture of two to three kinds in the above-mentioned system, and in the form of a mixture of two or three kinds in another kind. It is more preferable to use a mixture of three kinds, that is, a three-component mixture of an alkyldiethanolamine, an alkyldiethanolamine fatty acid ester and a fatty acid ester monoglyceride, and the alkyldiethanolamine fatty acid ester as a main component.

  The addition amount of the antifogging agent may be appropriately adjusted depending on the type of the antifogging agent and the like, but 5,000 to 15,000 ppm is appropriate, and 4,000 to 10,000 ppm is preferable. When the addition amount of the antifogging agent is less than 5,000 ppm, sufficient antifogging effect may not be obtained, and when it exceeds 15,000 ppm, the surface bleeds out more than necessary and the transparency deteriorates. There is.

1.4 Gas permeability of the film of the present invention The film of the present invention has a certain gas permeability. Specifically, the film of the present invention has an oxygen permeability in the range of 900 to 2,600 cm ³ / m ² · 24 h · atm and a carbon dioxide permeability of 2,500 to 7 when measured by a differential pressure method. , 600 cm ³ / m ² · 24 h · atm. Preferably, the oxygen permeability is in the range of 950 to 2,000 cm ³ / m ² · 24 h · atm, and the carbon dioxide gas permeability is in the range of 3,000 to 5,000 cm ³ / m ² · 24 h · atm. is there. More preferably, the oxygen permeability is in the range of 1,000 to 1,500 cm ³ / m ² · 24 h · atm, and the carbon dioxide gas permeability is 3,500 to 4,000 cm ³ / m ² · 24 h · atm. Within range. The differential pressure method is measured according to JIS K-7126-1: 2006.

If the oxygen permeability is less than 900 cm ³ / m ² · 24 h · atm, odor may be generated. If the oxygen permeability is higher than 2,600 cm ³ / m ² · 24 h · atm, there is a risk of browning. If the carbon dioxide permeability is less than 2,500 cm ³ / m ² · 24 h · atm, the bacteria-suppressing action may be reduced. If the carbon dioxide gas permeability is higher than 7,600 cm ³ / m ² · 24 h · atm, it may cause wilting or bitterness.

1.5 Others The film of the present invention has at least two layers of a sealing layer and a base material layer. When each of the layers is formed into a packaging bag, the outer side is a base material layer, and the inner side is a seal. Layer order.

The thickness of each layer in the film of the present invention is as follows.
When the total thickness of the film is in the range of 20 to 50 μm, preferably in the range of 25 to 45 μm, the sealing layer is in the range of 1.5 to 12 μm, preferably in the range of 2 to 6 μm. The layer is in the range of 8-48.5 μm, preferably in the range of 16-48 μm. When the thickness of the sealing layer is within this range, it is preferable because the film has good sealing strength and is easy to handle.

An appropriate amount of various additives can be further mixed in the film of the present invention. Examples of such additives include nucleating agents, antioxidants, flame retardants, antistatic agents, fillers, and pigments.
In addition to the two layers, the film of the present invention may have other layers such as an opening providing layer and a gas barrier providing layer.

  The production method of the film of the present invention is not particularly limited and a known method can be used. However, in consideration of productivity and physical properties of the completed film, a flat sheet is formed by extrusion, and then sequentially biaxially. The film of the present invention is preferably produced by stretching.

  More specifically, each of the extruders set at an appropriate temperature is charged with the resin constituting the sealing layer and the resin constituting the base material layer, and after melting and kneading the resin in the extruder, 210 Extruded into a sheet form from a T-die at a temperature of 250C. In this case, a feed block method or a multi-manifold method may be used to form a two-layer structure. The extruded sheet is cooled and solidified by a cooling roll at 25 ° C. and sent to the longitudinal stretching step. The longitudinal stretching is constituted by a heated roll set at 130 ° C. to 140 ° C., and is stretched in the longitudinal direction (hereinafter referred to as MD direction) due to the speed difference between the rolls. There are no particular restrictions on the number of heating rolls, but at least two heating rolls on the low speed side and the high speed side are necessary. The draw ratio of longitudinal drawing is 4 to 6 times, preferably 4.5 to 5.5 times. Next, it is sent to a transverse stretching step by a tenter and stretched in the transverse direction (hereinafter referred to as TD direction). The tenter is divided into preheating, stretching, and annealing zones. The preheating zone is set to 165 ° C to 170 ° C, the stretching zone is set to 165 ° C to 170 ° C, and the annealing zone is set to 165 ° C to 170 ° C. The stretching ratio in the stretching zone is preferably about 6 to 10 times. After being stretched, it is cooled and fixed in an annealing zone, and then wound up by a winder to form a film roll.

In the production of the film of the present invention, after leaving the annealing zone of the tenter, it is preferable to perform a known surface treatment such as corona discharge treatment, flame treatment, ultraviolet irradiation treatment and the like before winding with a winder. In particular, it is preferable to perform a corona discharge treatment. By performing the surface treatment, the film surface can be given a wetting tension to enhance the antifogging effect, and the adhesion to the printing ink when printing on the film surface can also be improved. In this corona discharge treatment, both the surface layer surface and the seal layer surface may be treated, or one of the surface layer surface and the seal layer surface may be treated. The strength of the corona discharge treatment is preferably in the range of 1.8 × 10 ^{2 to} 9.0 × 10 ² J / m ^2. May be.

The wetting tension of the surface of the biaxially stretched polypropylene film (present film) thus obtained is preferably 38 to 44 mN / m. When the wetting tension is less than 38 mN / m, the antifogging property is not sufficiently exhibited, and in the case of printing, the adhesiveness of the printing ink is inferior. If the wetting tension exceeds 44 mN / m, the anti-fogging agent bleeds out to the surface, causing whitening and blocking, and also causing a decrease in the fusing seal strength.

2 Packaging Bag Comprising the Present Film Next, the packaging bag composed of the present film (hereinafter referred to as “the present invention bag”) will be described in detail.

This invention bag can be shape | molded with an automatic packaging machine etc. using this invention film.
The film of the present invention is particularly suitable for forming a packaging bag with a vertical pillow packaging machine because it has excellent hot tack at the time of filling the contents, but when forming with a packaging machine such as a horizontal pillow packaging machine. Can also be used.

Examples of the contents enclosed in the bag of the present invention include agricultural products such as fruits and vegetables (eg, raw vegetables, fruits, strawberries, mushrooms), and fruits and vegetables are preferred. Examples of such fruits and vegetables include vegetables such as leek, sprouts, spinach, broccoli and peppers; or cut vegetables such as cabbage, lettuce and carrot. Among them, cut vegetables such as cut lettuce are preferable.

3 Sealing the Fruits and Vegetables in the Present Bag When the fruits and vegetables are sealed in the present bag, the present bag is sufficiently filled (gas purge) with an inert gas containing carbon dioxide (carbon dioxide). Examples of the inert gas other than the carbon dioxide gas include nitrogen gas, argon gas, and helium gas. Among these, a mixed gas of carbon dioxide gas and nitrogen gas is preferable.
The proportion of carbon dioxide in the inert gas is suitably in the range of 1 to 20% by volume, preferably in the range of 3 to 18% by volume, and more preferably in the range of 5 to 15% by volume. If the amount is less than 1% by volume, the bacteriostatic action and the browning-inhibiting effect may not be sufficiently obtained. If the amount is more than 20% by volume, bitterness and smell of fruits and vegetables and early wilting may be a concern.

After being sufficiently filled with an inert gas containing carbon dioxide gas, the bag of the present invention is heat sealed and sealed by a conventional method in a state where the fruits and vegetables are contained, and the package of the present invention is manufactured.

  Hereinafter, the present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these examples.

The raw materials used for the production of the biaxially stretched polypropylene film are as follows.
PP-1: Propylene homopolymer (MFR: 3.0 g / 10 min, melting point: 161 ° C., density: 0.9 g / cm ³ )
PP-2: propylene-ethylene copolymer (ethylene component: 7% by weight, MFR: 5.0 g / 10 min, melting point: 132 ° C., density: 0.9 g / cm ³ )
PP-3: propylene-ethylene-butene copolymer (ethylene component: 3.4% by weight, butene component: 1.4% by weight, MFR: 5.0 g / 10 min, melting point: 125 ° C., density: 0.9 g / Cm ³ )
PE: linear low density polyethylene (MFR: 3.5 g / 10 min, melting point: 60 ° C., density: 0.88 g / cm ³ )
Antifoggant: Mixture of stearyl monoglyceride 15.6% by weight, stearyl diethanolamine monostearate 76.9% by weight, and stearyl diethanolamine 7.5% by weight AB agent: silica

A biaxially stretched polypropylene film composed of a seal layer and a base material layer was produced according to the following procedure with the resin composition shown in Table 1 below.
The resin constituting each layer is put into each extruder, and is laminated in the order of base material layer / seal layer, co-extruded from a multilayer T die at a temperature of 230 ° C., cooled and solidified by a cooling roll at 25 ° C. To obtain an original sheet. Next, the sheet is heated to 130 ° C., roll-rolled 4.6 times in the MD direction, preheated at a set temperature 165 ° C. with a tenter, stretched 10 times in the TD direction at the set temperature 165 ° C., and then set temperature 165 After annealing at 0 ° C. and exiting the tenter, the substrate layer side was subjected to corona discharge treatment at 6.6 × 10 ² J / m ² and the seal layer side at 4.8 × 10 ² J / m ^2. A biaxially oriented polypropylene film having a gas permeability shown in Table 1 below (total thickness of the film is 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, or 60 μm). Film etc.).

The gas permeability was measured by the following method.
<Gas permeability test>
The gas permeability test of the film uses a 10 cm square film piece as a measurement sample, and uses a gas permeability measuring device (differential pressure type) (manufactured by Toyo Seiki Seisakusho Co., Ltd.), according to the instrument manual, by the differential pressure method, and the set pressure 101 .3 kPa, set temperature 23.0 ° C.

[Examples 1-6, Comparative Examples 1-5] Manufacture of the Package of the Present Invention The package of the present invention was manufactured by the following procedure using the obtained biaxially stretched polypropylene film.
It was set in a vertical pillow packaging machine (manufactured by Taisei Machinery Co., Ltd.) and bag making was performed. First, the former is formed into a cylindrical film (width 200 mm) with the sealing layer as the inner surface, and the end of the film is heat-sealed at a temperature of 220 ° C. along the flow direction, and then the lower end of the cylindrical film is Heat-sealing was performed at a temperature of 130 ° C. in a direction orthogonal to the flow direction, and a cylindrical film was formed in which the upper portion where the bottom portion and the back portion were heat-sealed was opened. Next, the content (cut lettuce, 95 g) weighed to a certain amount was put into a cylindrical film, and the bag was filled with gas (gas purge). Then, heat sealing was performed at a temperature of 210 ° C. at a pitch of 250 mm in a direction orthogonal to the film flow direction, and the central portion of the heat sealing portion was cut in the transverse direction.

The bag filled with the contents by the above steps was sealed on the upper side and the bottom, and the package of the present invention was formed. The seal width of the heat seal in the production is 10 mm. The bag size of the manufactured package is 250 mm in the flow direction and 200 mm in the width direction.
The freshness maintenance evaluation was performed using the obtained packaging bag. The results are shown in Table 2.

  The freshness maintenance evaluation test was conducted as follows.

<Freshness maintenance evaluation test>
(1) Bacterial count measurement Bacterial count measurement is performed by storing a package containing cut lettuce in a refrigerator set at 5 ° C for a period of 5 days and using a food hygiene tester "BACcT" (manufactured by Nippon Bacteriological Test Inc.) The number of general viable bacteria in cut lettuce as the contents of the package was evaluated.
When the number of bacteria was less than 10 ⁵ / g, “◯” was given, and when 10 ⁵ / g or more was given, “×”.

(2) Appearance Appearance was performed by storing a package enclosing cut lettuce as the contents in a refrigerator set at 5 ° C. for a period of 5 days and observing changes in cut lettuce. “Appearance” visually evaluated the browning of the contents. Those where browning was not confirmed were marked with “◯”, and those with browning confirmed were marked with “x”.

(3) Odor The odor was stored for 5 days in a refrigerator set at 5 ° C. in a packaging bag containing cut lettuce as the content, and the odor of the content was evaluated sensorily. The thing without a odor was set as "(circle)", and the thing with a odor was set as "*". As the odor, amine odor and carbon dioxide odor were confirmed.

Since the package of the present invention can maintain the freshness of fruits and vegetables, especially cut vegetables such as cut lettuce, for a relatively long time, it is useful in distribution and sales in the fruits and vegetables market.

Claims (3)

The fruit and vegetables are sealed in a packaging bag made of a biaxially oriented polypropylene film having at least two layers of a sealing layer and a base material layer, and has the following matters (a) to (d), Fruit and vegetable packaging.
(A) the film contains a propylene random copolymer in the seal layer;
(B) When the film is measured by a differential pressure method, the oxygen permeability is in the range of 900 to 2,600 cm ³ / m ² · 24 h · atm, and the carbon dioxide gas permeability is 2,500 to 7,600 cm ³ / in the range of m ² · 24h · atm,
(C) The inside of the packaging bag is filled with an inert gas containing carbon dioxide, and the proportion of carbon dioxide in the inert gas is in the range of 1 to 20% by volume; and (d) the packaging The bag is heat sealed with fruits and vegetables. The fruit and vegetable package of Claim 1 which contains a polyethylene-type resin further in a seal layer. The fruits and vegetables package according to claim 1 or 2, wherein the fruits and vegetables are lettuce.