Film used for packaging bags for fruits and vegetables

Abstract

To provide a film that can suppress swelling (degassing return) of degassing packaging bag as a film used for a packaging bag for fruits and vegetables.SOLUTION: A film used for a packaging bag of fruits and vegetables.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a film used for packaging bags for fruits and vegetables. [Background technology]

[0002] Fresh vegetables, fruits, potatoes, mushrooms, and other produce are distributed in bags made of plastic film to preserve their freshness and protect them from damage due to contact with the outside world.

[0003] Packaging machines such as vertical pillow machines are used to process this resin film into bags and automatically package fresh vegetables and other fruits and vegetables. A vertical pillow machine is a device that first forms the resin film into a cylindrical shape, then seals the bottom of the bag, then places the contents into the bag from above, and finally seals the top of the bag, thereby packaging the contents in the bag-shaped resin film. If the weight of the contents is applied to the sealed portion (bottom of the bag) immediately after sealing, there is a risk that the sealed portion will open in the case of heavy items such as fresh vegetables.

[0004] Therefore, the present applicant has provided a film for packaging fruits and vegetables (Patent Document 1). This polypropylene-based film for packaging has excellent heat seal strength and excellent hot tack when filling the contents, so the seal is difficult to open even when the contents are relatively heavy, such as raw vegetables, and can be efficiently packaged using a vertical pillow packaging machine.

[0005] Furthermore, among fruits and vegetables, bean sprouts are packaged in bags made of polyethylene film, polypropylene film, etc. after harvesting, and are distributed and sold at low temperatures. Although bean sprouts are distributed and sold at low temperatures, they are susceptible to deterioration.

[0006] Therefore, the present applicant has provided a packaging film that extends the shelf life of bean sprouts and the like (Patent Document 2). This bean sprout packaging film has an excellent deodorizing effect against methyl sulfide, which is generated when bean sprouts deteriorate.

[0007] In addition, a freshness-preserving packaging bag for bean sprouts or mushrooms has been disclosed (Patent Document 3) that aims to prevent the package from expanding over time when harvested bean sprouts or mushrooms are stored in a vacuum-packaged state. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6302726 [Patent Document 2] Patent No. 4854881 [Patent Document 3] Japanese Patent Application Publication No. 2018-76081 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a film that can be used for packaging bags for fruits and vegetables and that can suppress swelling (return of air after degassing) of evacuated packaging bags. [Means for solving the problem]

[0010] The present invention relates to packaging bags for fruits and vegetables, particularly bean sprouts. As materials for packaging bags for fruits and vegetables, particularly bean sprouts, polyethylene, polypropylene, etc. are used. Bean sprouts are easily spoiled, even when distributed at low temperatures. The bean sprouts are packaged in vacuum packaging, with the air removed from the bag.

[0011] This has the effect of suppressing the breathing of the bean sprouts. This vacuum packaging gives the bag a firm texture, improving its handling and display properties. However, some vacuumed bags may contain air and become slightly bloated when they are put on the shelves in stores. As a result, they lose their "firmness" when picked up and are less suitable for display.

[0012] The inventors have discovered that swelling of vacuum-packaged bags does not occur unless the amount of gas entering and leaving the bag exceeds the gas permeability of the synthetic resin used in the film. As a result, they have come to provide a film that can be used for vacuum packaging and that can suppress swelling (return of gas after degassing) of vacuum-packaged bags.

[0013] Gas enters and exits through the seal that is made when the bag is made. Gas enters and exits through imperfect seals. By achieving stable sealing, it is possible to reduce swelling (return of gas after degassing) in vacuum packaging bags.

[0014] The present inventors have found that swelling of evacuated packaging bags (return of air after evacuating) can be suppressed by providing a film used in packaging bags for fruits and vegetables with the following characteristics.

[0015] Section 1. A film used for packaging bags for fruits and vegetables, The film is characterized by having at least one seal layer containing a propylene-based random copolymer and a polyethylene-based resin.

[0016] Section 2. The film is a biaxially oriented polypropylene film having at least three layers: a surface layer, a base layer, and a seal layer; Item 2. The film according to item 1, wherein the sealing layer contains 60% to 95% by weight of a propylene random copolymer and 5% to 40% by weight of a polyethylene resin.

[0017] Section 3. 3. The film according to item 1 or 2, wherein the fruit or vegetable is bean sprouts.

[0018] Section 4. Item 3. A vacuum packaging bag for bean sprouts, using the film according to item 1 or 2.

[0019] Section 5. Using film used for packaging bags for fruits and vegetables, The film is a biaxially oriented polypropylene film having at least three layers: a surface layer, a base layer, and a seal layer; the sealing layer contains 60% by weight to 95% by weight of a propylene-based random copolymer and 5% by weight to 40% by weight of a polyethylene-based resin; Packaging fruits and vegetables using the fill. A method for preventing return of degassed food after vacuum packaging. [Effects of the Invention]

[0020] The present invention can provide a film that can be used as a packaging bag for fruits and vegetables, and that can suppress swelling (return of air after degassing) of the evacuated packaging bag. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention relates to a film used for packaging bags for fruits and vegetables.

[0022] In the present invention, in the film used for packaging bags for fruits and vegetables, the fruits and vegetables are preferably bean sprouts.

[0023] The present invention also relates to a vacuum packaging bag for bean sprouts using the film.

[0024] The present invention relates to a method for preventing return of air after vacuum packaging, which method includes a step of packaging fruits and vegetables using a film used for packaging bags for fruits and vegetables.

[0025] (1) Film used for packaging bags for fruits and vegetables The present invention is a film used for packaging bags for fruits and vegetables, The film is characterized by having at least one sealing layer containing a propylene-based random copolymer and a polyethylene-based resin.

[0026] In the present invention, the film is a biaxially oriented polypropylene film having at least three layers: a surface layer, a base layer, and a seal layer; The sealing layer preferably contains 60% to 95% by weight of a propylene-based random copolymer and 5% to 40% by weight of a polyethylene-based resin.

[0027] In the present invention, the fruit or vegetable is preferably bean sprouts.

[0028] The present invention relates to a vacuum packaging bag for bean sprouts using the film.

[0029] (1-1) Sealing layer The film of the present invention has at least one seal layer.

[0030] For example, when packaging fruits and vegetables using a vertical pillow machine, the sealing layer is the layer that becomes the inside of the tube when the resin film is first formed into a cylindrical shape, and the sealing layers are bonded to each other at the sealed portion.

[0031] The sealing layer contains a propylene random copolymer and a polyethylene resin. The sealing layer preferably contains 60 to 95% by weight of the propylene random copolymer and 5 to 40% by weight of the polyethylene resin.

[0032] Propylene-based random copolymer The propylene random copolymer is a copolymer of propylene and another α-olefin.

[0033] Examples of the α-olefin other than propylene include α-olefins other than propylene having 2 to 20 carbon atoms. Specific examples include ethylene, 1-butene, 1-pentene, 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, 1-eicosene, cyclopentene, cycloheptene, norbornene, 5-ethyl-2-norbornene, tetracyclododecene, and 2-ethyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene.

[0034] Among these, α-olefins having 2 to 4 carbon atoms, such as ethylene and butene, are preferred, and ethylene is more preferred. These α-olefins other than propylene may be used alone or in combination of two or more.

[0035] The content of α-olefins other than propylene in the propylene random copolymer is preferably 14% by weight or less, more preferably 10% by weight or less.

[0036] The propylene-based random copolymer is not particularly limited as long as it is a random copolymer of propylene and another α-olefin, and specific examples thereof include a propylene-ethylene random copolymer, a propylene-butene random copolymer, a propylene-ethylene-butene random copolymer, etc. Among these, a propylene-ethylene-butene random copolymer is preferred.

[0037] Among propylene-based random copolymers, those having a melt flow rate (MFR) value of 0.5 g / 10 min to 20 g / 10 min when measured according to ISO 1133 (1997) at 230°C under a load of 21.18 N (2.16 kg) are preferred. Furthermore, those having an MFR value of 4 g / 10 min to 8 g / 10 min are more preferred. The MFR value of the polymer can be adjusted appropriately by changing the type and content of α-olefins other than propylene, the molecular weight of the polymer, and the degree of polymerization.

[0038] Polyethylene Resin Polyethylene resins are copolymers of ethylene and other α-olefins.

[0039] Examples of the α-olefin other than ethylene include α-olefins having 3 to 20 carbon atoms, and 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, and 1-eicosene.

[0040] Of these, preferred are those having a carbon number of 3 to 8, such as 1-hexene, 4-methyl-1-pentene, and 1-octene. These α-olefins other than ethylene may be used alone or in combination of two or more.

[0041] The content ratio of ethylene to other α-olefins in the polyethylene resin is usually 75% by weight to 100% by weight of ethylene and 0% by weight to 25% by weight of other α-olefins, preferably 85% by weight to 99.9% by weight of ethylene and 0.1% by weight to 15% by weight of other α-olefins, more preferably 90% by weight to 99.5% by weight of ethylene and 0.5% by weight to 10% by weight of other α-olefins, and even more preferably 90% by weight to 99% by weight of ethylene and 1% by weight to 10% by weight of other α-olefins.

[0042] Among polyethylene resins, those having a melt flow rate (MFR) value of 0.5 g / 10 min to 20 g / 10 min measured at 190°C under a load of 21.18 N (2.16 kg) in accordance with ISO 1133 (1997) are preferred, and those having an MFR value of 2 g / 10 min to 4 g / 10 min are more preferred.

[0043] Furthermore, among polyethylene resins, the density measured in accordance with JIS K 7112 is 850 kg / m 3 ~900Kg / m 3 Polyethylene resins in the range of 860 kg / m are preferred. 3 ~890Kg / m 3Polyethylene resins in the range of are more preferred.

[0044] Content ratio In the film of the present invention, the sealing layer preferably contains 60% to 95% by weight of a propylene-based random copolymer and 5% to 40% by weight of a polyethylene-based resin.

[0045] The content of the propylene random copolymer in the seal layer is more preferably 62 to 94% by weight, even more preferably 63 to 93% by weight, and particularly preferably 65 to 91% by weight. If the content of the propylene random copolymer is more than 95% by weight, sufficient heat seal strength may not be obtained, and if it is less than 60% by weight, hot tackiness may be reduced.

[0046] The content of the polyethylene resin in the seal layer is more preferably 6 to 38% by weight, even more preferably 7 to 37% by weight, and particularly preferably 9 to 35% by weight. If the content of the polyethylene resin is less than 5% by weight, sufficient heat seal strength may not be obtained, and if it is more than 40% by weight, hot tackiness may be reduced.

[0047] Anti-blocking agents or lubricants The sealing layer may contain an antiblocking agent or a lubricant to a degree that does not impair transparency, in order to smooth the surface of the resin film and prevent adhesion of resin films to each other. Examples of such antiblocking agents include commonly used inorganic silica, kaolin, zeolite, etc., and organic crosslinked acrylic beads, etc. Examples of lubricants include calcium stearate, etc. The antiblocking agent and the lubricant may each be used alone, or two or more types may be used in combination.

[0048] The amount of the antiblocking agent or lubricant added can be adjusted as appropriate depending on the type of resin, etc., but is suitably 0.05 to 30 parts by weight, and preferably 0.5 to 20 parts by weight, per 100 parts by weight of the resin constituting the layer.

[0049] (1-2) Base material layer In the present invention, the film is preferably a biaxially oriented polypropylene film having at least three layers: a surface layer, a base layer, and a seal layer. The base layer is an intermediate layer sandwiched between the seal layer and the surface layer described below.

[0050] The base layer preferably contains a crystalline polypropylene resin as a main component.

[0051] Crystalline polypropylene resin 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 preferred.

[0052] The crystalline polypropylene resin having a melting point of 155°C to 165°C is, for example, a propylene homopolymer or a copolymer of propylene and another α-olefin.

[0053] Examples of the α-olefin other than propylene include α-olefins other than propylene having 2 to 10 carbon atoms, specifically ethylene, 1-butene, 1-pentene, 1-hexene, etc. Among these, α-olefins having 2 to 4 carbon atoms, such as ethylene and 1-butene, are preferred, and ethylene is more preferred. These α-olefins other than propylene may be used alone or in combination of two or more.

[0054] The content of α-olefins other than propylene is suitably 1.3% by weight or less, preferably 0.8% by weight or less.

[0055] The main component usually means that the crystalline polypropylene resin having a melting point of 155°C to 165°C in the base layer accounts for 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more.

[0056] Anti-fogging agent The substrate layer may contain an anti-fogging agent to impart anti-fogging properties to the film. Such anti-fogging agents are generally added to the substrate layer, but after the film of the present invention is formed, they diffuse into the surface layer and seal layer, thereby exhibiting good anti-fogging properties when used to package moisture-rich contents. The anti-fogging agent is not particularly limited as long as it is suitable for the intended purpose, and anti-fogging agents conventionally used in anti-fogging films can be used as is. Specific examples include alkyldiethanolamines, alkyldiethanolamine fatty acid esters, and glycerin fatty acid esters.

[0057] The alkyl group in the alkyldiethanolamine usually has a carbon number of 8 to 22, preferably 12 to 18. Specific examples of alkyldiethanolamine include lauryldiethanolamine, myristyldiethanolamine, palmityldiethanolamine, stearyldiethanolamine, and oleyldiethanolamine.

[0058] 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 examples of the alkyldiethanolamine fatty acid ester include lauryldiethanolamine monostearate, myristyldiethanolamine monooleate, lauryldiethanolamine monostearate, palmityldiethanolamine monostearate, stearyldiethanolamine monopalmitate, stearyldiethanolamine monostearate, and oleyldiethanolamine monostearate.

[0059] The fatty acid ester group in the glycerin fatty acid ester can be the same as the fatty acid ester group in the alkyldiethanolamine fatty acid ester described above. The number of fatty acid ester groups bonded to the -OH group of glycerin is preferably one or two, and more preferably one fatty acid ester monoglyceride.

[0060] The above anti-fogging agents are preferably used in the form of a single type or a mixture of 2 to 3 types in the same system, or in the form of a mixture of 2 to 3 types in different systems. It is particularly preferred that the anti-fogging agents be used in the form of a mixture of 3 types in different systems, that is, a three-component mixture of alkyldiethanolamine, alkyldiethanolamine fatty acid ester, and fatty acid ester monoglyceride, with alkyldiethanolamine fatty acid ester as the main component.

[0061] The amount of anti-fogging agent added may be adjusted appropriately depending on the type of anti-fogging agent, etc., but is suitably 5,000 ppm to 15,000 ppm, and preferably 4,000 ppm to 10,000 ppm. If the amount of anti-fogging agent added is less than 5,000 ppm, a sufficient anti-fogging effect may not be obtained, and if it exceeds 15,000 ppm, excessive bleed-out to the surface may occur, resulting in a deterioration in transparency.

[0062] (1-3) Surface layer In the present invention, the film is preferably a biaxially oriented polypropylene film having at least three layers: a surface layer, a base layer, and a seal layer. The surface layer is the layer that becomes the outer surface when the resin film is formed into a packaging bag.

[0063] The surface layer preferably contains a polypropylene resin.

[0064] Polypropylene Resin The polypropylene-based resin is a propylene homopolymer or a copolymer of propylene and another α-olefin. Examples of the α-olefin other than propylene include α-olefins other than propylene having 2 to 10 carbon atoms. Specific examples include α-olefins such as ethylene, 1-butene, 1-pentene, and 1-hexene. Among these, α-olefins having 2 to 4 carbon atoms, such as ethylene and 1-butene, are preferred, and ethylene is more preferred. These α-olefins other than propylene may be used alone or in combination of two or more. The content of the α-olefin other than propylene is suitably 14% by weight or less, and preferably 10% by weight or less.

[0065] Among polypropylene-based resins, the melt flow rate (MFR) value measured in accordance with ISO 1133 (1997) at 230°C under a load of 21.18 N (2.16 kg) is preferably in the range of 0.5 g / 10 min to 20 g / 10 min. Furthermore, polypropylene-based resins having an MFR value in the range of 4 g / 10 min to 8 g / 10 min are more preferred. The MFR value of the polymer can be adjusted appropriately by the type and content of α-olefins other than propylene, the molecular weight of the polymer, and the degree of polymerization.

[0066] Furthermore, the polypropylene resin preferably has a melting point within the range of 120°C to 165°C.

[0067] Anti-blocking agents or lubricants The surface layer may contain an antiblocking agent or a lubricant to a degree that does not impair transparency, in order to smooth the surface of the resin film and prevent adhesion of resin films to each other. The preferred types and amounts of the antiblocking agent or lubricant are the same as those described for the sealing layer.

[0068] (1-4) Film composition The film of the present invention has at least three layers: a surface layer, a base layer, and a seal layer. When the film of the present invention is formed into a packaging bag, these layers are arranged in the following order: the surface layer on the outer surface, the base layer in the middle, and the seal layer on the inner surface.

[0069] Thickness of each layer of the film The total thickness of the film of the present invention is usually within the range of 10 μm to 80 μm, and preferably within the range of 10 μm to 40 μm.

[0070] The sealing layer is usually in the range of 1.0 μm to 12 μm, and preferably in the range of 1.2 μm to 6 μm.

[0071] The thickness of the substrate layer is usually within the range of 1 μm to 40 μm, and preferably within the range of 2 μm to 25 μm.

[0072] The surface layer is usually in the range of 0.3 μm to 40 μm, and preferably in the range of 0.5 μm to 37 μm.

[0073] When the thickness of the sealing layer and the surface layer is within this range, the film has good sealing strength and is easy to handle.

[0074] The film of the present invention may further contain various additives in appropriate amounts, such as nucleating agents, antioxidants, flame retardants, antistatic agents, fillers, and pigments.

[0075] The film of the present invention may have other layers such as an aperture-imparting layer and a gas barrier layer in addition to the three layers described above.

[0076] (2) Film manufacturing method By using the film of the present invention, a stable seal can be achieved and degassing can be reduced. By using the film of the present invention, there are no defective parts in the sealed part, and gas does not enter or leave through the sealed part when the film is made into a bag.

[0077] The method for producing the film of the present invention is not particularly limited, and known methods can be used.

[0078] In consideration of productivity and the physical properties of the finished film, the film of the present invention is preferably produced by extruding a flat sheet and then sequentially biaxially stretching it to produce a film.

[0079] More specifically, the resins constituting the surface layer, the resin constituting the base layer, and the resin constituting the seal layer are respectively fed into three extruders set at appropriate temperatures, and after the resins are melted and kneaded in the extruders, they are extruded into a sheet form through a T-die at 210°C to 250°C. In this case, either a feedblock system or a multi-manifold system may be used to form a three-layer structure.

[0080] The extruded sheet is cooled and solidified by cooling rolls at 25°C and then sent to the longitudinal stretching process. The longitudinal stretching is performed using heating rolls set at 130°C to 140°C, and the sheet is stretched in the longitudinal direction (hereinafter referred to as MD direction) depending on the speed difference between the rolls. There is no particular restriction on the number of heating rolls, but at least two rolls, one on the low speed side and one on the high speed side, are required. The stretching ratio for the longitudinal stretching is 4 to 6 times, preferably 4.5 to 5.5 times.

[0081] The film is then sent to a transverse stretching process using a tenter, where it is stretched in the transverse direction (hereinafter referred to as the TD direction). The tenter is divided into preheating, stretching, and annealing zones, with the preheating zone set to 165°C to 170°C, the stretching zone set to 165°C to 170°C, and the annealing zone set to 165°C to 170°C. The stretching ratio in the stretching zone is preferably about 6 to 10 times. After stretching, the film is cooled and fixed in the annealing zone, and then wound up on a winder to form a film roll.

[0082] In the production of the film of the present invention, after the film leaves the annealing zone of the tenter and before being wound up by a winder, it is preferable to subject the film to a known surface treatment such as corona discharge treatment, flame treatment, ultraviolet irradiation treatment, etc., and from the viewpoint of simplicity, corona discharge treatment is particularly preferable. By subjecting the film to such surface treatment, it is possible to impart wet tension to the surface of the film and enhance the anti-fogging effect. This not only improves adhesion to printing ink when printing on the film surface, but also increases adhesion to the printing ink.

[0083] The corona discharge treatment may be performed on both the surface layer surface and the sealing layer surface, or on only one of the surface layer surface or the sealing layer surface. 2 J / m 2 ~9.0×10 2 J / m 2 When both sides are treated, the strength of both sides may be the same or different.

[0084] The surface wet tension of the biaxially stretched polypropylene film of the present invention is preferably 38 mN / m to 44 mN / m. If the wet tension is less than 38 mN / m, the anti-fogging properties are not sufficiently exhibited, and when printing, the adhesion of printing ink is poor, which is undesirable. If the wet tension exceeds 44 mN / m, the anti-fogging agent will bleed out to the surface severely, causing whitening and blocking, as well as a decrease in the welding seal strength, which is undesirable.

[0085] (3) Using film to make bags The present invention includes a packaging bag for fruits and vegetables using the film.

[0086] The present invention includes a vacuum packaging bag for bean sprouts using the film.

[0087] The packaging bag of the present invention can be formed using the film of the present invention by an automatic packaging machine or the like. Packaging machines such as vertical pillow machines are used to process the film into a bag shape and automatically package fresh produce such as raw vegetables. A vertical pillow machine is a device that first forms a (resin) film into a cylindrical shape, then seals the bottom of the bag, then places the contents into the bag from above, sandwiches the bag and the contents between sponges, pushes out the air inside the bag to degas it, and finally seals the top of the bag, thereby packaging the contents in a bag-shaped (resin) film.

[0088] The film of the present invention has excellent hot tack when filled with contents, and is therefore particularly suitable for use when forming packaging bags using a vertical pillow packaging machine. The film of the present invention can also be used when forming bags using other packaging machines, such as a horizontal pillow packaging machine.

[0089] The contents to be packaged in the packaging bag of the present invention are not particularly limited as long as they can be packaged, but examples include agricultural products such as fresh vegetables (e.g., raw vegetables, fruits, potatoes, mushrooms, etc.), with agricultural products being preferred.

[0090] Examples of agricultural products include vegetables such as green onions, bean sprouts, spinach, broccoli, and bell peppers; cut vegetables such as cabbage, lettuce, and carrots; fruits such as strawberries, bananas, and lemons; and mushrooms such as enoki mushrooms, maitake mushrooms, shimeji mushrooms, and shiitake mushrooms. Of these, bean sprouts and cut vegetables are preferred.

[0091] By using the film of the present invention, a stable seal can be achieved and degassing can be reduced. By using the film of the present invention, there are no defective parts in the sealed part, and gas does not enter or leave through the sealed part when the film is made into a bag.

[0092] (4) How to prevent re-gassing after vacuum packaging The present invention includes a method for preventing return of air after vacuum packaging using a film used in packaging bags for fruits and vegetables.

[0093] The present invention uses a film used for packaging bags for fruits and vegetables, The film is a biaxially oriented polypropylene film having at least three layers: a surface layer, a base layer, and a seal layer; the sealing layer contains 60% by weight to 95% by weight of a propylene-based random copolymer and 5% by weight to 40% by weight of a polyethylene-based resin; Packaging fruits and vegetables using the fill. This is a method for preventing return of degassed food after vacuum packaging.

[0094] The details of the film are as described above.

[0095] The process of packaging fruits and vegetables using fill is carried out, for example, using a packaging machine such as a vertical pillow machine as described above.

[0096] In the present invention, the fruit or vegetable is preferably bean sprouts.

[0097] By using the film of the present invention, a stable seal can be achieved and degassing can be reduced. By using the film of the present invention, there are no defective parts in the sealed part, and gas does not enter or leave through the sealed part when the film is made into a bag. [Example]

[0098] The present invention will be described with reference to examples, but the present invention is not limited to these examples in any way.

[0099] (1) Raw materials for packaging film PP-1: Propylene-ethylene copolymer Ethylene content: 0.5% by weight, MFR: 3.0 g / 10 min, melting point: 161°C, density: 900 kg / m 3 PP-2: Propylene-ethylene copolymer Ethylene content: 0.4% by weight, MFR: 2.3 g / 10 min, melting point: 160°C, density: 900 kg / m 3 PP-3: Propylene-ethylene-butene copolymer Ethylene component: 3.4% by weight, butene component: 1.4% by weight, MFR: 5.0g / 10min, Melting point: 125℃, Density: 900kg / m 3 LLDPE: Linear low density polyethylene MFR: 3.5g / 10min, Melting point: 60℃, Density: 880kg / m 3

[0100] (2) Packaging bag manufacturing conditions The packaging bags were made using an automatic weighing and packaging machine DT-1080 (manufactured by Daisei Machinery) under the following conditions. Shot rate: 56 shots / min Bag making pitch: 224 mm Packet size: 200g of bean sprouts Vertical sealing temperature: 220℃ Horizontal sealing temperature: 140℃ Degassing sponge: Yes

[0101] (3) Example Example 1 Resin constituting the surface layer: PP-1 (100% by weight) Resin constituting the base layer: PP-2 (100% by weight) Resins constituting the sealing layer: PP-3 (80% by weight) and PE-1 (20% by weight) The resins constituting each layer were fed into three extruders, and the layers were laminated in the order of surface layer / base layer / seal layer, co-extruded through a three-layer T-die at 230°C, cooled and solidified with a cooling roll at 25°C to obtain a raw sheet. The sheet was then heated to 130°C and stretched 4.6 times in the MD direction, and then preheated in a tenter at a set temperature of 165°C and stretched 10 times in the TD direction at a set temperature of 165°C.

[0102] Next, the sheet was annealed at a set temperature of 165°C, and after leaving the tenter, the surface layer side was 2 J / m 2 The seal layer side is 4.8 x 10 2 J / m 2 The film was then wound up on a winder to obtain a film of the present invention. The total thickness of the obtained film was 25 μm, and the thicknesses of the individual layers were: surface layer / base layer / sealing layer=2 μm / 19 μm / 4 μm.

[0103] Example 2 A film of the present invention was obtained in the same manner as in Example 1, except that the total thickness of the film was 20 μm and the thicknesses of the individual layers were surface layer / base layer / sealing layer = 2 μm / 15 μm / 3 μm.

[0104] (Comparative Example 1) A film was obtained in the same manner as in Example 1, except that PP-3 was used as 100% by weight of the resin constituting the sealing layer.

[0105] A method of processing film into a bag shape Using a vertical pillow machine as an automatic packaging machine, the obtained film was processed into a bag shape and fresh vegetables and other fruits and vegetables were packaged. Using the vertical pillow machine, first, the (resin) film was formed into a cylindrical shape, then the bottom of the bag was sealed, the contents were then placed into the bag from above, and the bag and contents were sandwiched between sponges to push out the air inside the bag and degas it. Finally, the top of the bag was sealed, packaging the contents in the bag-shaped (resin) film.

[0106] (4) Evaluation test of packaging bags Heat seal strength measurement The two films were stacked with the sealing layer surfaces facing each other, and then heat-sealed using a heat seal tester (HG-100 manufactured by Toyo Seiki Seisakusho) under conditions of a temperature of 140°C, a pressure of 0.2 MPa, and a sealing time of 1.0 second.

[0107] The obtained samples were cut into a length of 200 mm and a width of 15 mm, and the heat seal strength was measured by a T-peel test using a peel tester (Peeling Tester Heidon-17 manufactured by Shinto Scientific Co., Ltd.) at a tensile speed of 200 mm / min. The measurement was carried out five times, and the average value was calculated.

[0108] Those having a seal strength of 6N / 15mm or more were judged to be "good."

[0109] Degassing return confirmation test A live bag evaluation was conducted. The percentage of bags containing fruit and vegetables that had air infiltration was investigated. The investigation into deaeration reversion was carried out by visually checking whether air had entered the bag and by touching whether the bean sprouts inside the bag had shifted. It was determined that deaeration reversion had occurred when the bag was inflated or the bean sprouts moved.

[0110] [Table 1]

[0111] By using the film of the present invention, a stable seal can be achieved and the return of gas can be reduced. By using the film of the present invention, there are no defective parts in the sealed part, and gas does not enter or leave through the sealed part when the film is made into a bag.

Claims

1. A film used for packaging bags for fruits and vegetables, The total thickness of the film is 10 μm or more and less than 15 μm, The packaging of the fruits and vegetables using the packaging bag is carried out by an automatic packaging machine, The film is a biaxially oriented polypropylene film having at least three layers: a surface layer, a base layer, and a seal layer; The polypropylene resin of the surface layer has a melting point of 120°C to 165°C, the sealing layer contains a propylene-based random copolymer and a polyethylene-based resin, A film characterized in that when two sheets of the film are stacked with the sealing layer surfaces facing each other and heat-sealed under conditions of a temperature of 140°C, a pressure of 0.2 MPa, and a sealing time of 1.0 second, the heat seal strength is 7 N / 15 mm or more and 10 N / 15 mm or less.

2. 2. The film according to claim 1, wherein the thickness of the sealing layer is 3 μm or more and 4 μm or less.

3. 3. The film according to claim 1, wherein the sealing layer contains 60% to 95% by weight of a propylene-based random copolymer and 5% to 40% by weight of a polyethylene-based resin.

4. The film according to claim 1 , wherein the fruit or vegetable is bean sprouts.

5. A vacuum packaging bag for bean sprouts, using the film according to any one of claims 1 to 3.

6. Using film used for packaging bags for fruits and vegetables, The total thickness of the film is 10 μm or more and less than 15 μm, The film is a biaxially oriented polypropylene film having at least three layers: a surface layer, a base layer, and a seal layer; The polypropylene resin of the surface layer has a melting point of 120°C to 165°C, the sealing layer contains 60% by weight to 95% by weight of a propylene-based random copolymer and 5% by weight to 40% by weight of a polyethylene-based resin; When two sheets of the film are stacked with the seal layer surfaces facing each other and heat-sealed under conditions of a temperature of 140°C, a pressure of 0.2 MPa, and a sealing time of 1.0 second, the heat seal strength is 7 N / 15 mm or more and 10 N / 15 mm or less, packaging fruits and vegetables with the film, A method for preventing return of air after vacuum packaging, characterized in that the packaging of the fruits and vegetables with the film is carried out by an automatic packaging machine.

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