Freshness preservation bags for fruits and vegetables, packaging containing fruits and vegetables, and method for preserving the freshness of fruits and vegetables.

Abstract

To provide a fresh produce preservation bag that maintains the excellent freshness of produce while also offering easy opening and durability. [Solution] The fresh produce preservation bag of the present invention is made of a synthetic resin film, the synthetic resin film contains polypropylene, the ratio of the tear strength in the MD direction (N / cm) of the synthetic resin film to the tear strength in the TD direction (N / cm), measured by the right-angle tear method in accordance with JIS K7128-3 (MD / TD) is 2.2 or more, and the static friction coefficient between the outer surfaces of the fresh produce preservation bag, measured by a friction test in accordance with JIS K7125, is 0.23 or less.

Description

[Technical Field]

[0001] The present invention relates to a freshness-preserving bag for fruits and vegetables, a package containing fruits and vegetables, and a method for preserving the freshness of fruits and vegetables. More specifically, it relates to a freshness-preserving bag for fruits and vegetables, a package containing fruits and vegetables, a method for preserving the freshness of fruits and vegetables, a synthetic resin film used to manufacture a freshness-preserving bag for fruits and vegetables, and a roll in which the synthetic resin film is wound into a roll. [Background technology]

[0002] Traditionally, a method for preserving the freshness of harvested fruits and vegetables has been known to be by adjusting the oxygen and carbon dioxide concentrations to appropriately suppress the respiration of the produce. Packaging materials used for preserving the freshness of fruits and vegetables in this way are known as MA (Modified Atmosphere) packaging. In recent years, with the growing interest in MA packaging, packaging materials are required to have improved performance in various aspects, including gas permeability, processability, strength, ease of packaging, and appearance.

[0003] For example, Patent Document 1 (Japanese Patent Application Publication No. 2023-106849) discloses a film for preserving the freshness of fruits and vegetables, in which the coefficient of dynamic friction μ' between the inner surfaces is controlled at a 40°C environment, taking into account that the packaging film may come into direct contact with the fruits and vegetables, and in order to suppress the deterioration of the freshness of the fruits and vegetables caused by the film itself. Furthermore, Patent Document 2 (Japanese Patent Publication No. 2022-119289) discloses a freshness-preserving film that is thin, has excellent conformability to contents, does not reduce seal strength, is less prone to whitening due to anti-fogging agent bleeding, and has deodorizing properties. Specifically, it discloses that the freshness-preserving film uses a specific polypropylene resin and a specific deodorizing nanofiller. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-106849 [Patent Document 2] Japanese Patent Publication No. 2022-119289 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the technologies disclosed in Patent Documents 1 and 2 did not focus on the condition or usability of the packaging bag after the fruits and vegetables have been packaged in it. The present inventor focused on the fact that after the fruits and vegetables have been packaged in the packaging bag, the outer surface of the bag may become easily torn due to friction during transport of the package containing the fruits and vegetables, or the packaging bag may become difficult to tear and open.

[0006] Therefore, the inventors diligently conducted research to improve the durability of the outer surface of the packaging bag against friction, etc., while maintaining the ease of opening the packaging bag. As a result, they found that simultaneously controlling the tear strength and static friction coefficient of the synthetic resin film is effective, and thus completed the present invention. [Means for solving the problem]

[0007] According to the present invention, the following technologies relating to packaging bags for fruits and vegetables are provided.

[0008] [1] A fresh produce preservation bag made of synthetic resin film, The aforementioned synthetic resin film contains polypropylene, The ratio (MD / TD) of the tear strength in the MD direction (N / cm) of the synthetic resin film to the tear strength in the TD direction (N / cm), measured by the right-angle tear method in accordance with JIS K7128-3, is 2.2 or greater. A fresh produce freshness preservation bag wherein the static friction coefficient measured by a friction test in accordance with JIS K7125 between the outer surfaces of the fresh produce freshness preservation bag is 0.23 or less. [2] [1] A fresh produce freshness preservation bag as described above, A fresh produce freshness preservation bag conforming to JIS K7127 for fresh produce freshness preservation bags, having a tensile strength of 130 MPa to 170 MPa, measured under the conditions of MD direction and tensile speed of 500 mm / min. [3] A fresh produce preservation bag as described in [1] or [2], The synthetic resin film is a single-layer film containing polypropylene, or a multilayer film having a layer containing polypropylene, for fresh produce preservation bags. [4] A fresh produce preservation bag described in any one of [1] to [3], The aforementioned fresh produce preservation bag is a fresh produce preservation bag having through holes with a pore diameter of 100 μm or more. [5] A package containing fresh produce, in which fresh produce is placed in a fresh produce preservation bag as described in any one of [1] to [4]. [6] A method for preserving the freshness of fruits and vegetables, comprising the step of placing the fruits and vegetables in a freshness-preserving bag for fruits and vegetables described in any one of [1] to [4]. [7] A synthetic resin film used for manufacturing a freshness-preserving bag for fruits and vegetables as described in any one of [1] to [4], A synthetic resin film having a static friction coefficient of 0.2 or less, as measured by a friction test in accordance with JIS K7125, between at least one of its surfaces, and configured such that surface becomes the outer surface of a fresh produce preservation bag. [8] [7] A wound body in which the synthetic resin film described above is wound in a roll shape. [Effects of the Invention]

[0009] According to the present invention, a fresh produce preservation bag is provided that maintains the good freshness of fresh produce while also achieving both easy opening and durability of the packaging bag. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below.

[0011] In this specification, the notation "X to Y" in the description of a numerical range represents X or more and Y or less, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less". Also, in this specification, the MD direction represents the Machine Direction, which is intended to be the resin flow direction, and the TD direction represents the Transverse Direction, which is intended to be the direction perpendicular to the MD direction.

[0012] <Fresh produce freshness - maintaining bag> The fresh produce freshness - maintaining bag of this embodiment (hereinafter also referred to as "packaging bag") is made of a synthetic resin film, and the synthetic resin film contains polypropylene. The ratio (MD / TD) of the tearing strength (N / cm) in the MD direction of the synthetic resin film measured by the right - angle tearing method according to JIS K7128 - 3 to the tearing strength (N / cm) in the TD direction of the synthetic resin film is 2.2 or more. The static friction coefficient measured by the friction test according to JIS K7125 between the outer surfaces of the fresh produce freshness - maintaining bag is 0.23 or less.

[0013] Thereby, while obtaining the freshness - maintaining effect of fresh produce, it is possible to achieve both high - level easy - opening property and durability of the packaging bag. Although the details of such reasons are not clear, it is considered as follows. When the synthetic resin film is extrusion - molded, molecules are oriented in the direction in which the resin is extruded and flows, so the tensile strength and the like tend to be high in the MD direction. The higher the ratio (MD / TD) of the tearing strength (N / cm), the more anisotropic the synthetic resin film is. Therefore, by setting the ratio (MD / TD) of the tearing strength (N / cm) to 2.2 or more, it becomes easy to tear in the MD direction. As a result, it can be easily torn by hand and can be torn in a straight - line direction from the cut - out part, so it is considered that good easy - opening property can be obtained. Also, by controlling the static friction coefficient between the outer surfaces of the packaging bag, the friction when the fresh - produce - containing package is rubbed can be reduced, and it is possible to suppress excessive force and friction from being applied to the packaging bag, making it easier to improve the durability of the packaging bag.

[0014] The ratio (MD / TD) of the above-mentioned tearing strength (N / cm) is 2.2 or more, preferably 2.3 or more, and more preferably 2.4 or more. The upper limit of the ratio (MD / TD) of the above-mentioned tearing strength (N / cm) is not particularly limited, but from the viewpoint of maintaining good processability and formability of the packaging bag, it is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.0 or less.

[0015] The tearing strength (N / cm) in the MD direction is preferably 1000 to 5000 N / cm, more preferably 1500 to 4000 N / cm, and even more preferably 2000 to 3500 N / cm.

[0016] The static friction coefficient measured by the friction test according to JIS K7125 between the outer surfaces of the above-mentioned packaging bags is 0.23 or less, preferably 0.22 or less, more preferably 0.21 or less, and even more preferably 0.20 or less.

[0017] The packaging bag further preferably conforms to JIS K7127 of the fresh fruit and vegetable freshness-keeping bag, and the tensile strength measured under the conditions of the MD direction and a tensile speed of 500 mm / min is 130 to 170 MPa, more preferably 135 to 165 MPa.

[0018] By controlling the tensile strength, an appropriate strength against tension can be obtained for the packaging bag. Therefore, while making the durability during the conveyance of the packaging bag higher, by maintaining the strength of the packaging bag, deformation or breakage of the bag at the time of opening can be suppressed.

[0019] In the present embodiment, a packaging bag satisfying the above-mentioned ratio of tearing strength (N / cm), static friction coefficient, and tensile strength can be realized, for example, by selecting polypropylene, adjusting the content of polyethylene, devising the thickness, layer structure, and manufacturing method of the synthetic resin film. Examples of the manufacturing method of the synthetic resin film include adjusting the stretching conditions of the synthetic resin film, particularly controlling the stretching ratio in the MD direction and the TD direction, and annealing treatment of the synthetic resin film.

[0020] [Bag shape] The packaging bag of this embodiment is a bag formed from a synthetic resin film, and its shape is not particularly limited; it can be a two-sided bag, a three-sided bag, a back-sealed bag (gusseted bag), a pouch, a gusseted bag, etc. A two-sided bag is a bag in which a synthetic resin film is folded in half, with the folded part as the bottom and both sides sealed. A three-sided bag is a bag in which two layers of synthetic resin film are overlapped and the bottom and both sides are sealed.

[0021] (Manufacturing method for packaging bags) The manufacturing method for the packaging bag can be appropriately determined according to the bag shape and other factors, and known methods can be used. Furthermore, the static friction coefficient of the outer surface of the packaging bag can be achieved by appropriately combining the synthetic resin film and the manufacturing method of the packaging bag.

[0022] The size of the packaging bag in this embodiment can be approximately 100mm x 100mm to 300mm x 450mm for packaging fresh produce intended for general consumers.

[0023] [Through hole] The packaging bag may or may not have through holes. The presence or absence of through holes allows for stable adjustment of water vapor permeability and oxygen permeability.

[0024] The planar shape of the through-hole may be, for example, circular, polygonal, or a slit. Circular is not limited to a perfect circle, but includes approximately circular shapes. In addition to circular shapes, semicircular or crescent shapes are also acceptable. A polygon is any shape enclosed by three or more line segments, such as a triangle, quadrilateral, or pentagon. A slit is a cut or narrow gap that penetrates the synthetic resin sheet constituting the packaging material, and may be a straight line, curve, L-shaped, or X-shaped, with no particular limitations on its length.

[0025] If through-holes are formed, the average diameter of the through-holes is preferably 10 μm to 200 μm, more preferably 50 to 180 μm, even more preferably 100 to 150 μm, and especially preferably 110 to 130 μm. Setting the average diameter above the lower limit improves the oxygen permeability of the packaging, making it easier to suppress the generation of off-odors. On the other hand, setting the average diameter below the upper limit prevents the entry of foreign matter while maintaining the MA effect, making it easier to preserve the freshness of fruits and vegetables. The average diameter of the through-hole is calculated by assuming the through-hole is a perfect circle, based on the area of ​​the opening.

[0026] Furthermore, the packaging bag may have through holes with a diameter of 4 mm or more. It may also have so-called punch holes.

[0027] The number of punch holes is preferably 1 to 20 per packaging bag, more preferably 1 to 10, even more preferably 1 to 5, and especially preferably 1 to 3, in order to suppress increased respiration and drying due to excessive gas permeability and to help maintain freshness.

[0028] The above-mentioned through holes may be formed in the resin film beforehand when manufacturing the packaging bag, may be formed after the resin film has been formed into a packaging bag, or may be formed before or after the resin film has been formed into a packaging bag.

[0029] The method for forming the through-hole described above is not particularly limited, and known methods can be employed. Examples of such known methods include laser processing, needle processing including a hot needle, and methods using molds such as a roll cutter.

[0030] [Oxygen permeability] Oxygen permeability of packaging bags at 23°C and 60% RH (cc / m³) 2The day's ATM is preferably 500 to 30,000, more preferably 800 to 20,000, even more preferably 1,000 to 10,000, and still more preferably 1,000 to 6,000.

[0031] Oxygen permeability can be calculated, for example, by measuring the oxygen concentration inside a packaging bag immediately after filling it with nitrogen and then measuring the oxygen concentration inside the packaging bag after it has been left for a certain period of time after filling it with nitrogen, and then calculating the oxygen concentration gradient.

[0032] [Water vapor transmission rate] The water vapor permeability of the packaging bag at 40°C is preferably 1 g / (m³) from the viewpoint of releasing water vapor due to the respiration of fresh produce. 2 (day) or more, more preferably 3g / (m 2 It is more than one day. On the other hand, the water vapor permeability of the packaging bag at 40°C is preferably 300 g / (m³) from the viewpoint of suppressing the respiration of fresh produce. 2 • day) or less, more preferably 100g / (m 2 • day) or less, and more preferably 50 g / (m 2 • day) or less, and more preferably 10 g / (m 2 It is less than or equal to (day).

[0033] Water vapor transmission can be measured using a method compliant with JIS Z 0208 (Cup method).

[0034] Furthermore, in the present invention, the oxygen permeability and water vapor permeability (moisture permeability) of the packaging bag can be adjusted by controlling the selection of the synthetic resin film material, the film manufacturing method, the film layer structure, the presence or absence of through holes and the average diameter of the through holes, the presence or absence of unpenetrated grooves, and so on.

[0035] <Synthetic resin film> Synthetic resin film is used to manufacture the above-mentioned freshness-preserving bags for fruits and vegetables. The synthetic resin film is a long sheet, either in the form of a single leaf or wound into a roll. From the viewpoint of increasing the manufacturing efficiency of packaging bags, it is preferable that the synthetic resin film be a long sheet wound into a roll. The roll may be formed by winding the synthetic resin film around a core, or it may be rolled up without a core. The synthetic resin film may have a distinct front and back side, or it may not have a distinct front and back side, and can be appropriately set according to the manufacturing method, shape, and intended use of the packaging bag.

[0036] The synthetic resin film preferably has a static friction coefficient of 0.23 or less, more preferably 0.22 or less, even more preferably 0.21 or less, and most preferably 0.20 or less, measured by a friction test in accordance with JIS K7125, between at least one of its surfaces, and is configured such that this surface becomes the outer surface of the fresh produce preservation bag. This makes it easier to improve the durability of the packaging bag.

[0037] (raw materials) The synthetic resin film is preferably transparent or semi-transparent, and more preferably transparent, from the viewpoint of allowing the fruits and vegetables to be seen from the outside. It may also be printed with information for the purpose of identifying the fruits and vegetables. The synthetic resin may also use biomass-derived raw materials in part.

[0038] The synthetic resin constituting the synthetic resin film does not need to contain polypropylene, and is not particularly limited as long as it can be used for packaging fruits and vegetables; known synthetic resins can be used. This allows for good freshness preservation while suppressing deformation under localized loads.

[0039] Examples of polypropylenes mentioned above include homopolymers, random copolymers, and block copolymers. More specifically, examples of homopolymers include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene, while examples of random copolymers include ethylene-propylene copolymers, propylene-1-butene copolymers, and propylene-octene copolymers. Among these, homopolymers are preferred.

[0040] The synthetic resin film may have a film made of polypropylene, or it may have a film made of a resin material which is a mixture of polypropylene and other resins.

[0041] Other resins include, for example, polyethylene resin, polyamide resin, polyvinyl chloride, polystyrene, acrylic resin, polyester resins such as polyethylene terephthalate and polylactic acid.

[0042] Examples of polyethylene resins mentioned above include various polyethylenes and ethylene copolymers. Specific examples include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene (L-LDPE), metallocene-linear low-density polyethylene, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-α-olefin copolymer, and other copolymers or ionomers. The linear low-density polyethylene described above is typically a copolymer of ethylene and a small amount of α-olefin. The type of α-olefin is not particularly limited. Typical α-olefins include 1-propylene, 1-butene, 1-hexene, 4-methylpentene-1, and 1-octene, which have 3 to 10 carbon atoms. The ethylene content of ethylene-propylene copolymers is typically 4.5% or less.

[0043] Examples of the polyamide resins mentioned above include nylon. Nylon can be nylon 6, nylon 11, nylon 12, nylon 66, nylon 6-10, nylon 6-12, nylon 6-T, nylon 6-I, nylon 9T, nylon M5T, polymetaxylylene adipamide (MXD nylon), etc., and can be used individually or in combination of two or more. Among these, nylon 6, nylon 11, nylon 12, and nylon 66 individually or in combination of two or more are preferred, and nylon 6 and nylon 66 individually or in combination of two are even more preferred.

[0044] The synthetic resin film may contain additives such as antifogging agents, antiblocking agents, heat stabilizers, lubricants, impact modifiers, processing aids, antistatic agents, ultraviolet absorbers, antioxidants, weather degradation inhibitors, fillers, and pigments, as needed, to the extent that they do not impair the performance of the synthetic resin film.

[0045] The anti-fogging agents mentioned above include those that wet and spread water through hydrogen bonding by hydroxyl groups. Specific examples of anti-fogging agents include glycerin laurate, diglycerin laurate, decaglycerin laurate, glycerin monostearate, and sorbitan stearate.

[0046] Examples of the above antiblocking agents include particulate inorganic compounds such as silica, alumina, alumina silicate, and diatomaceous earth; and particulate organic compounds such as polyethylene, cross-linked polyethylene, polymethyl methacrylate, and cross-linked polymethyl methacrylate. By using an antiblocking agent, the handling properties of synthetic resin films can be improved, such as when winding the film into a roll during the molding process.

[0047] (Film manufacturing method) The method for obtaining the synthetic resin film is not particularly limited. Examples of known methods for obtaining a synthetic resin film include extrusion, inflation, and calendering. Furthermore, the synthetic resin film may be subjected to stretching or annealing. Stretching is typically biaxial stretching. The stretching ratio is not particularly limited, but for example, it can be approximately 2 to 10 times in both the MD and TD directions. Annealing can be performed at a temperature of 130 to 175°C for several tens of seconds to several hours. Furthermore, the conditions may be adjusted as appropriate to achieve the above-mentioned ratio of tear strength (N / cm), coefficient of static friction, and tensile strength.

[0048] (Layer composition) The synthetic resin film may be a single layer or a multilayer film of two or more layers. It may be a single layer film made of polypropylene, a multilayer film including a layer made of polypropylene, a single layer film made of a resin material mixed with polypropylene and another resin, or a multilayer film including a layer made of a resin material mixed with polypropylene and another resin. Among these, a single layer film made of polypropylene or a multilayer film including a layer made of polypropylene is preferred, and a single layer film made of polypropylene is more preferred. Furthermore, it is even more preferable that the film be a stretched polypropylene film.

[0049] By creating a multilayer structure for synthetic resin films, desired functionality can be enhanced. For example, by adding functions such as slipperiness to the surface layer of the synthetic resin film, the handling and heat-sealing properties of the synthetic resin film can be improved, and packaging bags with an excellent balance of stretchability and rigidity can be reliably obtained. Furthermore, for example, by creating a two- or three-layer structure for the synthetic resin film and making at least one of the surface layers a layer containing an antiblocking agent, slipperiness can be obtained.

[0050] In the case of a multilayered synthetic resin film, the base resins of each layer may be the same or different. From the viewpoint of obtaining good adhesion between layers, it is preferable that each layer uses the same resin.

[0051] When a synthetic resin film is multilayered, the thickness of each layer may be the same or different. For example, in a three-layer structure, the thickness of the intermediate layer may be the greatest, and the thickness of the surface layer may be the lowest. The surface layer is preferably 10-20% of the total thickness of the synthetic resin film, and more preferably 12-17%.

[0052] Known methods such as dry lamination, extrusion lamination, co-extrusion, and coating can be used as appropriate to obtain multilayer films. From the viewpoint of improving interlayer adhesion and controlling layer thickness, co-extrusion is preferable.

[0053] (Thickness) The thickness of the synthetic resin film is preferably 5 to 200 μm, more preferably 10 to 100 μm, even more preferably 15 to 80 μm, and most preferably 20 to 50 μm. By making the thickness of the synthetic resin film greater than or equal to the lower limit mentioned above, the strength of the packaging bag is increased, suppressing deformation due to external stress while ensuring a stable freshness preservation effect. By making the thickness of the synthetic resin film greater than or equal to the upper limit mentioned above, the flexibility (suppleness) of the packaging bag can be maintained.

[0054] [Fruits and vegetables] In this embodiment, "fresh produce" refers to uncooked vegetables from which non-edible parts of soil-grown or hydroponically grown vegetables, such as roots, peels, cores, stems, seeds, and flowers, have been removed, with the edible portion of the vegetable being prepared with consideration for ease of eating and simple preparation.

[0055] As for fruits and vegetables, there are no particular limitations, but for example, semi-heading and heading vegetables such as cabbage, Chinese cabbage, lettuce (lettuce, leaf lettuce, romaine lettuce, sunny lettuce, salad lettuce, ssamjang, etc.), and Brussels sprouts; spinach, komatsuna, mizuna, bok choy, rapeseed (kakina), non-heading lettuce (romaine lettuce, sunny lettuce, etc.), garland chrysanthemum, stem vine, santouna, rapeseed, curly lettuce, kousaitai, urui, field wasabi, flower wasabi, watercress, arugula, shepherd's purse, petit vert, ice plant, leaf radish, etc.; root vegetables such as sweet potato, potato, nagaimo, yamaimo, taro, jinenjo, and yamatoimo, radish, carrot, burdock, turnip, ginger; leeks, ta Examples include: onions, chives and other Allium vegetables; broccoli and cauliflower; cucurbitaceous fruits and vegetables such as cucumbers and pumpkins; nightshade fruits and vegetables such as eggplants, tomatoes, cherry tomatoes, bell peppers, and paprikas; and fruits and vegetables such as okra, bitter melon, zucchini, and sweet corn; immature beans such as edamame, snow peas, green beans, and broad beans; stem vegetables such as celery, asparagus, and wasabi; herbs such as myoga ginger, perilla, water dropwort, mitsuba, and herbs (thyme, sage, parsley, Italian parsley, rosemary, oregano, lemon balm, chives, lavender, salad burnet, lamb's ear, arugula, dandelion, and nasturtium); and mushrooms. These may be packaged individually or in combination of two or more types.

[0056] Fresh produce may be cut as appropriate, taking into consideration purchasing and consumption, and may be roughly divided into 1 / 8 to 1 / 2 portions, for example, in terms of purchasing appeal, such as cabbage, Chinese cabbage, and pumpkin. Furthermore, it may be cut into bite-sized pieces or julienned for raw consumption in salads, or for cooking in stir-fries.

[0057] <Packaged fruit and vegetable product> The fruit and vegetable packaging of this embodiment (hereinafter also referred to as "packaging") contains fruit and vegetable in the fruit and vegetable freshness preservation bag described above. This improves the freshness preservation effect of the fruit and vegetable.

[0058] It is preferable that the packaging has a sealed opening after the fruits and vegetables have been packaged. Sealing may be achieved, for example, by heat-sealing the opening of the bag, or by using materials such as back sealing tape, cable ties, rubber bands, or crimping.

[0059] The amount of produce contained in the packaging bag may vary depending on the size of the container, the type of produce, and the intended use of the packaging. For produce intended for general consumers, for example, from the viewpoint of easy consumption immediately after opening and ease of carrying and handling, the amount is preferably 50 to 1000 g, more preferably 100 to 800 g. Furthermore, from the viewpoint of obtaining a more significant effect in suppressing deformation against localized loads, the amount of produce contained in the packaging bag is preferably 300 g or more, and more preferably 400 g or more.

[0060] <Methods for maintaining freshness> The freshness preservation method of this embodiment includes the step of storing the produce using the above-described package containing the produce. Storage can be carried out by known methods, but it is preferable to store the packaged product at an ambient temperature of 2 to 20°C. Ambient temperature refers to, for example, the temperature setting of the refrigerator or refrigerator where the packaged product is stored, or the temperature control setting of the display case where the packaged product is displayed in a store. It does not refer to a precisely measured temperature around the packaged product. Furthermore, it is sufficient for the average ambient temperature to be between 2 and 20°C, and it may temporarily drop to around 10°C due to unavoidable circumstances such as opening and closing doors during transport of the packaged product.

[0061] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0062] The present invention will be described in detail below based on examples and comparative examples. It should be noted that the present invention is not limited to the examples provided.

[0063] <Measurement> • Measurement of tear strength (N / cm) Right-angle tear test specimens were prepared based on the right-angle tear method conforming to JIS K7128-3 "Plastics - Test methods for tear strength of films and sheets - Part 3: Right-angle tear method". Two types of right-angle tear test specimens were prepared: one with the longitudinal direction of the right-angle tear test specimen aligned with the MD direction of the synthetic resin film, and another with the longitudinal direction of the right-angle tear test specimen aligned with the TD direction of the synthetic resin film. Each test specimen was subjected to tension under the following conditions, and the maximum load at which the specimen was completely torn was determined and defined as the tear strength (N / cm). (conditions) • Tensile testing machine: "ENSILON RTH-1225" manufactured by A&D Company, Limited. • Tensile speed: 200 mm / min ·Environment: 23℃, 50%RH

[0064] • Static friction coefficient The static friction coefficient between the outer surfaces of the fresh produce preservation bags was measured using a friction test in accordance with JIS K7125. Specifically, the synthetic resin films that form the outer surfaces of the fresh produce preservation bags were stacked one above the other so that they faced each other, and under the following conditions, a weight was placed on the upper synthetic resin film, and the upper synthetic resin film was slid on the lower synthetic resin film to measure the static friction coefficient. (conditions) • Upper synthetic resin film: 80 x 200 mm • Tensile testing machine: "TENSILON RTH-1225" A&D Company, Limited • Weight of the sinker: 200g • Contact area between the weight and the upper synthetic resin film: 40 cm 2 • Tensile speed: 100 mm / min ·Environment: 23℃, 50%RH

[0065] • Measurement of tensile strength (MPa) In accordance with JIS K7127, strip-shaped test pieces were prepared with the longitudinal direction being the MD direction of the synthetic resin film. Each of the prepared test pieces was pulled in the longitudinal direction under the following conditions, and the tensile strength (MPa) was measured. (Conditions) · Tensile testing machine: "TENSILON RTH-1225" A&D Company, Limited · Tensile speed: 200 mm / min · Environment: 23°C, 50% RH · Test piece shape: Type 1 dumbbell

[0066] · Measurement of oxygen permeability (cc / m 2 · day·atm) at 23°C, 60% RH (1) Enclosure of nitrogen gas Using a synthetic resin film consisting of the raw materials and thickness shown in Table 1, a measurement bag was fabricated. After sealing the bag by heat sealing or the like, the bag was degassed using an aspirator or the like. The degassing was carried out until both sides of the bag adhered together. Next, nitrogen gas (purity 99.9% or higher) was filled into this bag using a white rigid syringe. The injection amount of nitrogen gas was adjusted according to the bag size, and as much gas as possible was filled within the range where the film constituting the bag was not under tension and was slightly loose, and it was measured using the scale of the white rigid syringe. Note that the degassing and injection of nitrogen gas were carried out, for example, by piercing the bag with an injection needle. When piercing the injection needle, double-sided tape was pasted on the film constituting the bag, and further an adhesive tape made of polypropylene film (hereinafter referred to as "PP tape") was pasted thereon. Also, after pulling out the injection needle, the needle hole was quickly sealed with the PP tape. The tape pasted on the bag was made to fit within an area of 4.5 cm 2 or less. Also, when the film constituting the bag was a microporous film, the micropores were not blocked with tape. <00003​​The initial oxygen concentration (C0) inside the bag immediately after filling with nitrogen gas (t=0) was measured. The gas inside the bag was sampled, and the initial oxygen concentration (C0) inside the bag was determined by gas chromatography (TCD). C0 was 0.2% or less; if it exceeded this, the procedure was repeated. The sampled gas for oxygen concentration measurement was 10cc or less. When injecting into the gas chromatograph, a constant amount of approximately 1cc was injected. In addition, measurements of standard gases (two or more points containing approximately 1% and 10% oxygen) were also performed by injecting the same amount of gas, and a calibration curve was created. (3) Storage of the bag The bags used for initial oxygen concentration measurement were stored at 23°C and 60% RH (in a temperature- and humidity-controlled cabinet). During this time, the bags were left undisturbed so that no objects were placed on top of them and the cabinet's fan did not directly blow air onto them. (4) Measurement of oxygen concentration inside the bag during storage and calculation of oxygen permeation rate The oxygen concentration inside the bag was measured at a total of 3 to 5 points, with at least two points measured immediately after nitrogen gas filling and again at least 3 hours later, within the range of 1% to 7%. A proportional relationship (correlation coefficient of 0.98 or higher) must be established between the elapsed time t (hr) and the oxygen concentration inside the bag. If the correlation coefficient was not established, the test was repeated. If the oxygen permeability rate of the film constituting the bag was too high, causing the increase in oxygen concentration inside the bag to be too rapid and failing to meet this condition, a bag could be created by laminating a portion of the film with a known oxygen permeability rate smaller than that of the film being measured, and the same procedure was followed. In this case, the surface area of ​​the bag was calculated excluding the portion laminated with the other known film, and the oxygen permeability rate of the measured film was obtained by subtracting the oxygen permeability rate of the known film portion from the calculated oxygen permeability rate. The oxygen permeation rate was calculated using the value obtained over the longer elapsed time, as shown in formula (i) below. F = 1.143 × (Ct - C0) × V / t (i) F: Oxygen permeation rate (cc / bag day atm) Ct: Oxygen concentration inside the bag t hours after nitrogen gas filling (%) C0: Oxygen concentration inside the bag immediately after filling with nitrogen gas (%) V: Amount of nitrogen gas filled (cc) t: Time elapsed since gas filling (hr)

[0067] Water vapor transmission rate at 40°C (g / m³) 2 Measurement (day) Measurements were taken using synthetic resin films with the raw materials and thicknesses shown in Table 1, in accordance with JIS Z 0208 (cup method).

[0068] [Examples, Comparative Examples] (1) Preparation of synthetic resin film <Example 1> First, commercially available polypropylene resin (homopolymer) was prepared as the raw material. Next, the molten material was extruded from a T-die at a temperature of 230°C and stretched using a roll stretcher (8 times in the MD direction and 4 times in the TD direction) to obtain a biaxially oriented polypropylene film (synthetic resin film) with the thickness (μm) shown in Table 1. At this time, the temperature of the rolls of the roll stretcher was set to 140°C. After that, an annealing treatment was performed to obtain the synthetic resin film. Next, using the obtained synthetic resin film, two layers were stacked with the inner layers facing inward, and heat-sealed on three sides using an impulse sealer (Fuji Impulse Co., Ltd., FI-400Y-10PK) to form a 10 mm wide heat-sealed section at 160°C for 1 second, thereby producing a packaging bag with the bag size (inner dimensions) shown in Table 1.

[0069] <Example 2> A synthetic resin film was obtained in the same manner as in Example 1, except that the extrusion conditions from the T-die were adjusted to achieve the thickness (μm) shown in Table 1. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was manufactured in the same manner as in Example 1.

[0070] <Example 3> A synthetic resin film was obtained in the same manner as in Example 1, except that the extrusion conditions from the T-die were adjusted to achieve the thickness (μm) shown in Table 1, and no annealing treatment was performed. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was manufactured in the same manner as in Example 1.

[0071] <Example 4> A synthetic resin film was obtained in the same manner as in Example 1, except that the extrusion conditions from the T-die were adjusted to achieve the thickness (μm) shown in Table 1, and no annealing treatment was performed. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was made in the same manner as in Example 1, with one through hole (hole diameter 120 μm) provided.

[0072] <Example 5> A synthetic resin film was obtained in the same manner as in Example 1, except that the extrusion conditions from the T-die were adjusted to achieve the thickness (μm) shown in Table 1. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was manufactured in the same manner as in Example 1.

[0073] <Comparative Example 1> A synthetic resin film was obtained in the same manner as in Example 1, except that the extrusion conditions from the T-die were adjusted to achieve the thickness (μm) shown in Table 1, and stretching and annealing treatments were omitted. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was manufactured in the same manner as in Example 1.

[0074] <Comparative Example 2> A synthetic resin film was obtained in the same manner as in Example 1, except that the stretching conditions were set to 4 times in the MD direction and 6 times in the TD direction, and no annealing treatment was performed. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was manufactured in the same manner as in Example 1.

[0075] <Rating> The following evaluations were performed on the obtained packaging. [Freshness preservation] 150g of fresh shredded cabbage was placed in each of the resulting packaging bags, and the bags were sealed to create fruit and vegetable packages, which were then stored at 10°C for 3 days. Afterward, the cabbage was removed, its appearance was observed, and its freshness retention was evaluated according to the following criteria. (standard) ◎: No loss of freshness whatsoever ○: Slightly reduced freshness △: Clearly shows a decline in freshness. ×: Significant deterioration in freshness

[0076] [Easy to open] The fresh produce packaging prepared in the freshness preservation evaluation described above was used to evaluate the ease of opening. Specifically, the ease of opening the packaging bag was evaluated according to the following criteria when force was applied to tear it horizontally from the cut at the top of the bag. (standard) ◎: Can be opened straight horizontally by hand. ○: Can be opened horizontally by hand. △: When handled manually, it bends horizontally, but can still be opened. ×: Difficult to open by hand

[0077] [Durability] Ten packs of fresh produce prepared for the freshness preservation evaluation were placed in a cardboard box and subjected to a 5-hour vibration test during transport. The condition of the packages was then evaluated according to the following criteria. (standard) ◎: No folds, wrinkles, tears, or pinholes in any of the bags. ○: No tears or pinholes in any of the bags. △: Some bags have tears or pinholes. ×: At least one of the following has occurred in all bags: tearing or pinholes.

[0078] [Table 1]

Claims

1. A fresh produce preservation bag made of synthetic resin film, The aforementioned synthetic resin film contains polypropylene, The ratio (MD / TD) of the tear strength in the MD direction (N / cm) of the synthetic resin film to the tear strength in the TD direction (N / cm), measured by the right-angle tear method in accordance with JIS K7128-3, is 2.2 or greater. A fresh produce freshness preservation bag wherein the static friction coefficient measured by a friction test in accordance with JIS K7125 between the outer surfaces of the fresh produce freshness preservation bag is 0.23 or less.

2. A fresh produce freshness preservation bag according to claim 1, A fresh produce freshness preservation bag conforming to JIS K7127 for fresh produce freshness preservation bags, wherein the tensile strength measured in the MD direction at a tensile speed of 500 mm / min is between 130 MPa and 170 MPa.

3. A fresh produce preservation bag according to claim 1 or 2, The synthetic resin film is a single-layer film containing polypropylene, or a multilayer film having a layer containing polypropylene, for fresh produce preservation bags.

4. A fresh produce preservation bag according to claim 1 or 2, The aforementioned fresh produce preservation bag is a fresh produce preservation bag having through holes with a pore diameter of 100 μm or more.

5. A package containing fresh produce, wherein fresh produce is contained in a fresh produce preservation bag according to claim 1 or 2.

6. A method for preserving the freshness of fruits and vegetables, comprising the step of placing the fruits and vegetables in a freshness-preserving bag for fruits and vegetables described in claim 1 or 2.

7. A synthetic resin film used to manufacture a fresh produce preservation bag according to claim 1 or 2, A synthetic resin film having a static friction coefficient of 0.2 or less, as measured by a friction test in accordance with JIS K7125, between at least one of its surfaces, and configured such that surface becomes the outer surface of a fresh produce preservation bag.

8. A wound body in which the synthetic resin film described in claim 7 is wound in a roll shape.

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