JPH0228310B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention is applicable to vegetables, root vegetables, fruits, flowers, flowering plants, mushrooms, etc. (hereinafter referred to as fruits and vegetables in a broad sense herein), which have physiological effects even after being harvested. The present invention relates to a method for increasing the value of a packaged product by maintaining its freshness during storage. [Conventional technology] In recent years, many fruits and vegetables such as fresh vegetables, fruits, fresh flowers, and mushrooms have been transitioned from open-field cultivation to planned multiplex and diversified cultivation using horticultural facility cultivation. It is often necessary to harvest and package large quantities of fruits and vegetables within a country. In addition, since the harvest period for fruits and vegetables that are mainly grown in open fields is fixed, a large amount of the harvest must be packaged and shipped within a short period of time. The biggest problem in the distribution process up to the point of crossing the border is how best to maintain freshness at the time of harvest. In order to meet these demands, research is actively underway to improve packaging films with a focus on preserving freshness, and the present applicant has also proposed several improved packaging films. By the way, fruits and vegetables such as those mentioned above do not immediately lose their physiological effects after being harvested, and especially for a while after harvest, they exhibit physiological effects that are almost the same as before harvest. Furthermore, if they are kept under appropriate storage conditions, their physiological effects will continue for a longer period of time, and as long as they maintain their physiological effects, fruits and vegetables will maintain good freshness. In other words, if it is not stored in a good condition, it will lose its sustained physiological function and will deteriorate prematurely. It is known that the physiological effects of fruits and vegetables in a packaged state include a decrease in moisture due to transpiration, consumption of atmospheric oxygen and generation of carbon dioxide due to respiration, and temperature rise due to generation of carbon dioxide and heat generation. As the oxygen concentration decreases, the carbon dioxide concentration increases, and since heat is not dissipated, the internal temperature of the package rises. The respiration process becomes more active above a certain temperature, and at high temperatures it becomes more susceptible to decomposition due to the stuffiness phenomenon. In addition, the transpiration effect becomes greater in an atmosphere of high temperature or low humidity, and as a result, it becomes more likely to rot in the high temperature and high humidity environment. Therefore, in order to improve the freshness retention effect during storage by taking into account the physiological effects mentioned above, ventilation is improved by making holes of an appropriate size in the packaging bag or cutting the bottom of the bag. Attempts have been made to increase the temperature, prevent a decrease in oxygen concentration, prevent an increase in carbon dioxide concentration, and suppress temperature rise. However, these are only temporary measures, and do not necessarily equalize the temperature distribution and gas composition inside the packaging bag, leading to localized decay, especially in areas that cannot be seen from the outside. This can have the unintended consequence of deceiving consumers. Furthermore, there is a fatal defect in that the packaging bag may tear at the opening or cut portion during the packaging or distribution process of fruits and vegetables. Furthermore, depending on the type of fruits and vegetables, if a perforated film is used, insects may enter the film or water may enter during the distribution process, resulting in a significant deterioration in quality, so it may not be desirable to make holes. From this point of view, it is desirable to develop a packaging film that can maintain the inside of the package at a temperature and gas composition suitable for the physiological effects of the fruits and vegetables without having to perform perforation or cutting on the packaging bag. However, to date, no packaging film has been proposed that meets these purposes. Moreover, in the packaging bags for fruits and vegetables that use packaging films that are currently in practical use, the moisture produced by the transpiration of fruits and vegetables or the evaporation of adhering moisture adheres to the inner surface of the packaging bag, causing cloudiness and clouding of the contents. Another problem is that things become difficult to see from the outside. For example, although polyethylene film has a moderate water vapor permeability, it lacks oxygen and carbon dioxide gas permeability, which causes fruit and vegetables to suffocate during short-term storage, resulting in loss of freshness. Although the respiration effect of fruits and vegetables can be maintained for a long period of time due to their permeability to oxygen and carbon dioxide, the water vapor permeability is too high and the evaporation effect of water becomes significant, causing discoloration or wilting of fruits and vegetables in a short period of time. However, it is not possible to maintain good freshness over a long period of time. Moreover, all of the above-mentioned films have poor antifogging properties, which not only lowers the commercial value in terms of appearance, but also causes so-called water rot when fruits and vegetables come into direct contact with moisture condensed in the cloudy areas. [Problems to be Solved by the Invention] The present invention has been made focusing on the above-mentioned circumstances, and its purpose is to improve water vapor permeability,
The present invention aims to provide a method that can maintain the freshness of fruits and vegetables for a long period of time by using a multilayer film that is permeable to oxygen and carbon dioxide, and has anti-fog properties and sealing properties. [Means for solving the problems] The configuration of the method of the present invention specified as requirements for achieving the above objectives is as follows: water vapor permeability is 15 to 200 g/m ² / 24 hr / 40°C; oxygen permeability is 3000～35000c.c./m ²・24hr・
ATM・20℃・90%RH、Carbon gas permeability 12000~130000c.c./ ^m2・
24hr・ATM・20℃・90%RH
A multilayer film is used that exhibits anti-fogging properties during repeated temperature changes at 40°C, and the surface layer has a fusing sealing property, and fruits and vegetables are prepared with the surface on which the antifogging agent is present and has the fusing sealing property facing inside. The gist lies in the way it is packaged. [Function] The multilayer film used in the present invention has specified water vapor permeability, oxygen permeability, and carbon dioxide gas permeability, and also has an antifogging agent and a melt cut on the surface layer on the side that comes into contact with fruits and vegetables when used for packaging purposes. Since it is characterized by its sealing properties, the reasons for determining each of the above characteristics will be explained below. Water vapor permeability: 15 to 200 g/m ² , 24 hr, 40°C It is an important characteristic in preventing the phenomenon of rot and suppressing rot, as well as in preventing fruits and vegetables from wilting, discoloration (yellowing or browning), softening, loss of elasticity, etc. due to lack of humidity.
If the water vapor permeability is less than 15 g/m ² / 24 hr / 40°C, fruits and vegetables are likely to rot due to swelling caused by excessive humidity, while if it exceeds 200 g / m ² / 24 hr / 40°C, there may be insufficient humidity inside the packaging bag. Fruits and vegetables tend to wilt, change color, etc., and in either case, a satisfactory freshness-keeping effect cannot be obtained. A more preferable water vapor permeability range is 20 to 150 g/m ² , 24 hr, and 40° C. in order to ensure a good freshness-keeping effect. Oxygen permeability: ^{3000-35000c.c./m2}・24hr・
ATM・20℃・90%RH Oxygen permeability is an extremely important characteristic for sustaining physiological effects by compensating for the decrease in oxygen concentration due to respiration by permeation of external air. .c.／ ^m2・24hr・atm・20℃・90%RH
If the amount is less than 100%, the amount of internal oxygen will be insufficient when packaging fruits and vegetables, which have a significant respiration effect (high oxygen consumption), resulting in suffocation, and a sufficient freshness-keeping effect will not be exhibited. On the other hand, 35000c.c./m ²・24hr・atm・20
If the temperature exceeds 90% ℃ and 90% RH, there is no risk of oxygen deficiency, but in the case of fruits and vegetables that develop mold due to the invasion of bacteria from the outside, the freshness-keeping effect will actually decrease. A more preferable range of oxygen permeability is 4000 to 20000
cc/ ^m2・24hr・atm・20℃・90%RH. Carbon dioxide permeability: ^{12000-130000c.c./m2}・
24hr/ATM/20℃/90%RH Carbon dioxide gas permeability maintains the appropriate gas composition within the packaging bag, guarantees the respiration of fruits and vegetables, avoids carbon dioxide damage, and prevents bacterial invasion and proliferation. This property is also effective in preventing spoilage due to the permeability of ^12000c.c./m2 , 24hr, ATM, 20℃, 90%.
If the RH is less than RH, the carbon dioxide concentration in the packaging bag becomes too high, which inhibits the respiration of fruits and vegetables, leading to a rapid decline in freshness and taste. On the other hand, 130000c.c./m ² , 24hr, atm, 20℃, 90%
When the RH is exceeded, the CO ₂ concentration inside the packaging bag becomes too low, and the anti-corrosion and deterioration suppressing effects are no longer effectively exhibited. A more preferable range of carbon dioxide permeability is 15,000~
^{100000c.c./m2}・24hr・ATM・20℃・90%RH. The multilayer film used in the present invention must have the above-mentioned water vapor, oxygen, and carbon dioxide permeability all within the specified range, and even if any one of the permeability is out of the specified range, the The purpose of the invention cannot be achieved. Furthermore, an antifogging agent must be present on the surface layer of this multilayer film on the side that comes into contact with fruits and vegetables so as to exhibit antifogging properties during storage and distribution. That is, in the present invention, the antifogging effect is extremely important not only to prevent the inner surface of the packaging bag from becoming cloudy and thereby increasing the product value, but also to prevent the contents from being spoiled by water droplets that are formed as clouding progresses. In order to maintain excellent anti-fog properties over a long period of time during the distribution process, consideration should be given to temperature changes during storage and distribution.
An antifogging agent must be present in the surface layer that continuously exhibits antifogging properties during repeated temperature changes between 2040°C, preferably between 040°C, using the antifogging property evaluation method described below. Must be. As mentioned above, the present invention is intended for packaging fruits and vegetables that continue to have physiological effects even after harvesting, and since it is preferable to store them at room temperature rather than freezing, the anti-fogging properties of the present invention are set. As a tentative standard, the antifogging property was determined by the following method and was determined by the antifogging durability test when the temperature was repeatedly changed between 2040°C for one day or more. (Anti-fog property evaluation method) Fill a 200 c.c. beaker with 150 c.c. of 40°C warm water, and place the sample over the beaker with the anti-fog side facing inside. Then keep at 20℃ for 6hr, and then keep at 40℃ for 6hr. This temperature change is repeated twice (total of 24 hours), and judgment is made based on whether the contents of the container can be clearly observed through the film surface. The type of antifogging agent to be present in the surface layer is not particularly limited, and in addition to conventionally known antifogging agents, all substances that can exhibit antifogging properties such as antistatic agents and activators can be used. If necessary, two or more types can be used in combination. These antifogging agents can be directly mixed into the surface layer constituent materials, or they can be mixed only into the base layer constituent materials and diffused and transferred to the surface layer after lamination, thereby imparting antifogging properties to the surface layer. is also possible. The amount of antifogging agent present in the surface layer varies depending on the type of antifogging agent, so it is not appropriate to specify it uniformly, but it is preferably in the range of 0.3 to 3% by weight.
However, if it is less than 0.3% by weight, the antifogging performance will be insufficient, making it difficult to satisfy the required characteristics of the present invention;
If it exceeds % by weight, not only will the surface layer become white and the transparency will decrease, but also the water that adheres to the inner surface of the bag due to evaporation of fruits and vegetables will cause cloudiness, which will significantly reduce the product value. will also occur. It is also possible to use the surface tension of the surface layer as a simple method to evaluate the antifogging property of the film before bag making, and according to the inventors' confirmation, the surface tension is 38 dyne/ It has become clear that by adjusting the amount of antifogging agent present so that it is at least cm, it is possible to ensure antifogging durability that meets the objective. Incidentally, when packaging fruits and vegetables, a melt-cut seal is often used to seal them, but in order to prevent the seal from peeling off and being opened during filling or distribution of fruits and vegetables, it is necessary to The fusing seal strength when fusing and sealing must be 3.0Kg-cm/15mm or more, and if the fusing seal strength is insufficient, the seal may peel off when filling or handling fruits and vegetables. Must be careful.
The above fusing seal temperature was determined based on the general fusing seal temperature currently in practical use. It can be used without any problems. Multilayer films with the above characteristics are
Although they can be manufactured by coextrusion of synthetic resins that meet the respective required characteristics, in-line lamination method, etc., the most preferable base layer constituent materials and surface layer constituent materials are given in consideration of the relationship with the above-mentioned required properties. The explanation is as follows. First, the base layer not only ensures the minimum mechanical strength required for the film, but also has the greatest effect on the permeability of water vapor, oxygen, and carbon dioxide, and should be made of the following materials: A base layer can be obtained which fulfills the above-mentioned purpose. That is, the base layer constituent materials include one or more α-olefin copolymers having a carbon number of 2 to 10, and one or more monomer units consisting of vinyl acetate, acrylic acid, and styrene. A preferred mixture is a mixture with one or more copolymers containing 5 to 80% by weight of the former, and the mixing ratio is 30 to 90% by weight for the former and 10 to 70% by weight for the latter. Specific examples of the above α-olefin having 2 to 10 carbonates include ethylene, propylene, butene, hexene, heptene, etc., but ethylene, propylene, and butene are more common. When a random copolymer or block copolymer of two or more of the above α-olefins is used, a base layer satisfying all of the above permeability values can be obtained more easily. The copolymerization ratio in this case may be arbitrarily determined depending on the type of α-olefin to be combined. In addition, the copolymer constituting the above is preferably a copolymer containing 5 to 80% by weight of monomer units consisting of vinyl acetate, acrylic acid, and styrene in the total components of the copolymer, and these monomers and The monomers to be combined may be copolymerizable monomers, but particularly preferred are α-olefins such as ethylene and propylene, acrylic esters, methacrylic esters, and butadiene. If the weight of the monomer units consisting of vinyl acetate, acrylic acid, and styrene in the copolymer is less than 5% or more than 80%, it will be difficult to satisfy all of the above-mentioned permeability requirements. If it exceeds %, the haze of the base film tends to deteriorate, and problems such as a decrease in the sealing properties of the weld and the formation of whiskers at the weld are likely to occur. The mixing ratio of the above and above is preferably in the range of 30 to 90% by weight of the former and 10 to 70% by weight of the latter,
By specifying such a blending ratio range, it is possible to ensure well-balanced performance in all of the above-mentioned permeability, as well as mechanical properties such as strength, transparency, and sealability. By the way, if the blending ratio of the copolymer is less than 30% by weight,
The transparency of the base film may decrease. On the other hand, if the copolymer content exceeds 90% by weight, it may become difficult to keep the gas permeability within the range defined by the present invention. For example, even if the oxygen permeability and carbon dioxide gas permeability fall within the set ranges, problems may arise if the water vapor permeability falls outside the set ranges, and in this case, it is difficult to obtain a packaging atmosphere suitable for the physiological effects of fruits and vegetables. Become. In addition, when blending the above, 230℃
The melt index of the formulation in
100/10min, more preferably 2~50g/10min
It is preferable to select the above formulation so that: Next, the surface layer constituent material must not only maintain excellent antifogging properties over a long period of time due to the presence of the antifogging agent, but also have excellent melt sealing properties. As a layer constituent material, a random copolymer obtained from two or more types selected from α-olefin monomers having a carbon number of 2 to 10 (ethylene, propylene, butene, pentene, hexene, octene, decene, etc.) Alternatively, block copolymers are preferred, and these copolymers may be used alone or in combination. Particularly preferable surface layer constituent materials in order to improve the weld sealing properties have a melting point of 80 to 150.
℃-olefin homopolymer, copolymer, or a mixture of two or more thereof as a main component. Methods for making the antifogging agent present in the surface layer constituent film include a method in which the antifogging agent is mixed into the surface layer constituent material itself, and a method in which an appropriate amount of the antifogging agent is included in the base layer film. Keep it
It is also possible to adopt a method in which the antifogging agent is transferred into the film constituting the surface layer by diffusion after lamination.
In this case, the amount of antifogging agent mixed into the base layer film is preferably 0.3 to 3% by weight, more preferably 0.4 to 2.2% by weight, and if it is less than 0.3% by weight, the amount of diffusion and transfer toward the surface layer film is insufficient. Because the surface layer becomes insufficient, it is not possible to provide sufficient anti-fog performance to the surface layer, and on the other hand, 3
If it exceeds % by weight, although the antifogging properties of the surface layer portion side can be sufficiently enhanced, the surface layer film will undergo a whitening phenomenon and its commercial value will be poor. However, when the base layer film contains 0.3 to 3% by weight of an antifogging agent and is laminated with the surface layer film, the antifogging agent in the base layer film gradually diffuses and migrates toward the surface layer film, resulting in a long It exhibits good anti-fog properties over a period of time and maintains its freshness at the time of harvest. The means for forming the composite film from the base layer constituent material and the surface layer constituent material is not particularly limited, and as mentioned above, it may be carried out by a well-known method such as coextrusion method or in-line lamination method. There are also no particular restrictions on the thickness of the base layer and surface layer, but the most common ones considering economic efficiency and physical properties are: base layer: about 4 to 200 μm, surface layer: about 0.3 to 200 μm.
It is about 8 μm. Also, the thickness ratio between the base layer and the surface layer (total thickness when both outer surfaces are surface layers) is
99.5-60: 0.5-40 is common. The most basic composite form of the film of the present invention is one in which a surface layer and a base layer are laminated, but surface layers are laminated on both sides of this base layer to provide antifogging and heat sealing properties on both sides. or printing on one side of the base layer (the side opposite to the surface layer laminated surface, however, if both surface layers have antifogging properties or heat sealing properties, one of the surface layers) Of course, it is also possible to perform processing, and all of these are included in the technical scope of the present invention. In addition, the films constituting the base layer and the surface layer may contain lubricants, anti-blocking agents, etc. as necessary.
Antioxidants, ultraviolet absorbers, colorants, antistatic agents, etc. may be added, and if desired, the multilayer film may be uniaxially or biaxially stretched to improve its physical properties. The multilayer film obtained in this way is most commonly filled with fruits and vegetables after bag making and sold to the market either sealed or unsealed, but in some cases fruits and vegetables are wrapped in the film and secured with tape. It can also be used for wrapping vegetables and fruits. EXAMPLES Next, examples will be given to further clarify the present invention, but the present invention is not limited by the following examples. In the following examples, "%" means "% by weight" unless otherwise specified. Furthermore, the methods for measuring the permeability of water vapor, oxygen, and carbon dioxide defined in the present invention were as follows. Water vapor permeability: Measured in accordance with the moisture permeability test method for moisture-proof packaging materials specified by method B of JIS-Z-0208. Oxygen permeability and carbon dioxide permeability: JIS-Z-
Measured according to the gas permeability test method in the "Test method for food-use plastic films" stipulated in 1707. However, for each gas, the volume at 20℃ is not converted to standard temperature, and
It was calculated as the amount of penetration per 24 hours. [Example] Example 1 An ethylene/propylene copolymer (ethylene content: 5%) and an ethylene/vinyl acetate copolymer with a vinyl acetate content of 28% were mixed into 65% of the former and 35% of the latter. The base layer constituent material is mixed in a ratio of 1:1 with propylene/butene-1 copolymer (butene-1 content: 18%) and butene/ethylene copolymer (ethylene content: 3.5%). A surface layer constituent material consisting of a mixed composition blended in a co-weight ratio (however, 6% higher fatty acid ester monoglyceride was mixed as an antifogging agent in the surface layer constituent material)
A multilayer film in which a surface layer is laminated on both sides of a base layer is produced using a coextrusion method (extrusion temperature: 260°C, cooling: 20°C), followed by longitudinal stretching at a magnification of 3 times and transverse stretching. Biaxial stretching was carried out at a magnification of 8 times, and a corona discharge treatment was performed on both sides to obtain a three-layer film having a base layer of 16 μm and a surface layer of 2 μm×2 (both sides), totaling 20 μm. The surface tension of one side (A) of this film is 42
dynes/cm, surface tension on the other side (B) is 38 dynes/cm
It was cm. Table 1 shows the properties of the multilayer film.

[Table] A packaging bag was made with the (A) side of this composite film inside, and freshly harvested eggplants were sealed in this bag to examine changes in freshness during storage. The respiration rate of eggplant is 15℃.
20CO ₂ mg/Kg・hr at 25℃
110CO ₂ mg/Kg・hr. The results are summarized in Table 4 (1) below. Example 2 Propylene-butene-1 copolymer (butene-1
content: 20%) and ethylene-styrene copolymer (styrene content: 40%), 90% of the former and 90% of the latter.
Base layer constituent material (0.8% higher fatty acid ester monoglyceride as antifogging agent)
), propylene-butene-1 copolymer (butene-1 content: 18%), and propylene-butene-1 copolymer (butene-1 content: 18%)
1 copolymer (butene-1 content: 30%) and the former
A composite film with a three-layer structure was produced in the same manner as in Example 1 using the surface layer constituent material blended at a ratio of 70% and the latter 30% (extrusion temperature: 250°C, cooling: 25°C). After that, the longitudinal stretching magnification was 2.5 times,
Biaxial stretching was performed at a transverse stretching ratio of 7.8 times, and the base layer was 20 μm thick.
Laminated surface layer on both sides of 1.5μm each, total wall thickness
A 23 μm three-layer film was obtained. The surface tension on one side (A) of this film is 41 dynes/cm, and the surface tension on the opposite side (B) is 38 dynes/cm. It showed cloudiness. The properties of the film are shown in Table 2.

[Table] A packaging bag was made with the (A) side of this film inside, and freshly harvested edamame was sealed in this bag to examine changes in freshness during storage. The respiration rate of edamame is 70 CO ₂ mg/at 15℃.
Kg・hr, 380 CO ₂ mg/Kg・hr at 25°C. The results are shown in Table 4 (2) below. Example 3 Two cucumbers were sealed in the packaging bag obtained in Example 1, and changes in freshness during storage were examined in the same manner. The respiration rate of this cucumber is 20 CO ₂ mg/Kg at 15℃.
hr, 130 CO ₂ mg/Kg·hr at 25°C. The results are shown in Table 4 (3). Comparative Example 1 A multilayer film was produced in exactly the same manner as in Example 1, except that the addition of the antifogging agent to the surface layer constituent material was omitted, and then biaxial stretching and corona discharge were carried out in the same manner as in Example 1. Eggplants were packaged using a treated multilayer film (film characteristics are shown in Table 3 below), and changes in freshness during storage were examined. The results are shown in Table 4 (1) below. The antifogging properties of this film were poor, and a large amount of water droplets were observed adhering to the inner surface one day after the film was sealed. Comparative Example 2 The base layer constituent material used in Example 1 (however, 1% higher aliphatic ester monoglyceride was blended as an antifogging agent) was used alone, and biaxial stretching and corona discharge treatment were performed in the same manner as in Example 1. A 20 μm single layer film was obtained. Table 3 shows the properties of the single layer film.

[Table] A bag was made from the obtained single-layer film, and eggplants were sealed in the bag in the same manner as in Example 1. Changes in freshness during storage were examined, and the results shown in Table 4 (1) below were obtained. It was done. For comparison, Table 4 (1) to (3) shows the case without packaging and
Experimental results for sealed packaging using OPP film (biaxially oriented polypropylene film) and PE film (polyethylene film) are also listed. The evaluation criteria for the freshness retention test shown in Tables 4 (1) to (3) were as shown in Table 5.

【table】

【table】

【table】

[Table] Example 4 As shown in Table 6, propylene butene 1 (18%) was applied to both sides of the base layer constituent material made of various polymeric materials.
After laminating the surface layer constituent material made of a copolymer (each containing 1% higher aliphatic monoglyceride as an antifogging agent) by coextrusion, it was stretched biaxially to a size of 2.5 times in length and 7.5 times in width, and then stretched on both sides. A multilayer film was obtained by corona discharge treatment so that the surface tension of each film was 39 dynes/cm. Table 7 shows the water vapor permeability, oxygen permeability, carbon dioxide permeability, antifogging property, and fusing seal strength of each of the obtained multilayer films.

【table】

[Table] Using each of the multilayer films A to H obtained above,
Make a mm x 180 mm bag and put 70 kidney beans in it.
The freshness change during storage was examined in the same manner as above. The storage conditions were 35°C x 70%RH. The results are shown in Table 8 (1) and (2), and the multilayer films (B, D, F,
The film using film A has a good freshness retention effect overall, whereas the film A has too low water vapor permeability, so moisture does not dissipate, resulting in poor deterioration in terms of sulking and odor. is remarkable. On the other hand, Film C has too high water vapor permeability,
The interior becomes dehydrated, causing discoloration and softening.
Films E and G both had oxygen permeability and carbon dioxide permeability outside the specified range, and the discoloration due to lack of breathing was particularly significant.

【table】

[Table] [Effects of the Invention] The present invention is configured as described above.
Since the permeability of oxygen and carbon dioxide gas is properly adjusted, fruits and vegetables can maintain their physiological effects even after being sealed, and their freshness can be significantly extended. In addition, this multilayer film has excellent anti-fog properties and long-lasting anti-fog properties, so it may become difficult to see the contents during the distribution process, lowering the product value, or moisture condensing in the cloudy areas may cause There is no fear that the fruits and vegetables will be spoiled as a result of this, and the appearance of the fruits and vegetables can be prevented from degrading as a product, and the fruits and vegetables can be supplied to consumers in a fresh state.

Claims (1)

[Claims] 1. Water vapor permeability is 15 ^to 200 g/ ^m 2.24 hr. at 40°C. Oxygen permeability is 3000 to 35000 c.c./m 2.24 hr.
ATM・20℃・90%RH、Carbon dioxide permeability 12000~130000c.c./ ^m2・
24hr・ATM・20℃・90%RH
A multilayer film is used that exhibits antifogging properties during repeated temperature changes between 40°C and has a melt-cutting sealing property on the surface layer, with the surface on which the antifogging agent is present and has the melt-cutting sealing property facing inside. A method for preserving the freshness of fruits and vegetables, characterized by packaging the fruits and vegetables in a container. (Anti-fog property evaluation method) Fill a 200 c.c. beaker with 150 c.c. of 40°C warm water, and place the sample over the beaker with the anti-fog side facing inside. Then kept at 20℃ for 6 hours and then at 40℃ for 6 hours.
Hold in time. This temperature change is repeated twice (total of 24 hours), and judgment is made based on whether the contents of the container can be clearly observed through the film surface. 2. The freshness preservation method according to claim 1, wherein the multilayer film exhibits a sealing strength of 3.0 Kg·cm/15 mm or more when cut and sealed at 270°C. 3 One or more types of α-olefin copolymers having 2 to 10 carbon atoms: 30 to 90% by weight and one or more monomer units consisting of vinyl acetate, acrylic acid, and styrene in an amount of 5 to 80% of the total constituents. 3. The method of preserving freshness according to claim 1 or 2, wherein a multilayer film is used in which the base layer is a mixture of one or more copolymers accounting for 10 to 70% by weight. 4. The freshness preservation method according to any one of claims 1 to 3, wherein the antifogging multilayer film is used as a surface layer constituent material of an α-olefin copolymer having 2 to 10 carbon atoms.