Non-stretched food packaging film and food packaging bags

Abstract

To provide an undrawn film for food packaging that retains sufficient performances required for a bag for food packaging and can suppress the blowout of a fuse part during food charging particularly at low temperatures, and provide the bag for food packaging.SOLUTION: An undrawn film 10 is used for bag-making by a fuse seal and comprises three layers of: a surface layer 20, an intermediate layer 30, and a seal layer 40, the surface layer subjected to corona treatment on the surface. The surface layer is predominantly composed of propylene resin. The intermediate layer is predominantly composed of a propylene resin composition that comprises a propylene-ethylene block copolymer with a xylene soluble content of 12% or more of 50 wt.% or more and has a calculated MFR of 6 g / 10 min or less. The seal layer comprises a propylene elastomer with a density of 0.880 g / cm3 or less of 20-80 wt.% and a propylene-ethylene random copolymer of 20-80 wt.%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a non-stretched food packaging film and a food packaging bag using this non-stretched film. [Background technology]

[0002] For example, bags for packaging foods such as bread are made into gusset bags by welding and sealing, and after the food is filled, the opening is sealed by heat sealing. The film that makes up this type of food packaging bag is made of a non-stretch film, and a transparent film or a matte film is selected depending on the type of food to be packaged. In particular, a matte film is preferably used for packaging bags for bread.

[0003] Because the heat sealing of the opening of the packaging bag is performed at high speed, low-temperature heat sealing is required. Furthermore, the packaging bag must be easy to open with little force without stretching or tearing, so that after opening it and removing some of the food, the opening can be resealed with a closure or the like. Thus, a polyolefin multilayer film having a heat-sealable layer composed of 20 to 80% by weight of a propylene-α-olefin random copolymer and 80 to 20% by weight of a butene polymer, and a propylene polymer layer, is known as a food packaging film that has low-temperature heat sealing and easy-open properties while maintaining fusing strength (see, for example, Patent Document 1). This film has excellent low-temperature heat sealing properties and easy-open properties while maintaining fusing strength, making it suitable for use as a packaging bag.

[0004] Another known film used in food packaging bags is a matte laminated film having a print layer containing 70% by mass or more of a propylene-based block copolymer resin, an intermediate layer containing 15 to 90% by mass of a propylene-based block copolymer resin and 5 to 30% by mass of linear low-density polyethylene, and a seal layer (see, for example, Patent Document 2). This matte film has excellent impact resistance, seal strength, abrasion resistance, bag tear resistance, and weld-cut seal strength at low temperatures, making it suitable for use in packaging bread.

[0005] However, with conventional food packaging bags, even if the fusion strength between the sealed surfaces is sufficient, the fusion portion can tear when food such as bread is filled into the bag, particularly during cold seasons such as winter. Therefore, there is a need to maintain the various performance characteristics required for food packaging bags, such as film tear resistance, fusion strength, low-temperature sealability, easy-open properties, and bag-making suitability, and to prevent fusion portion tearing when food is filled into the bag, particularly during low temperatures such as winter. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-210897 [Patent Document 2] WO2017 / 018282 publication Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been proposed in light of the above-mentioned circumstances, and provides a non-stretched food packaging film and a food packaging bag that can maintain the various performance properties required for food packaging bags and can prevent the bag from breaking (tearing) at the fused portion when food is filled, particularly at low temperatures. [Means for solving the problem]

[0008] That is, the invention of claim 1 is a non-oriented film used for bag making by welding and sealing, which comprises three layers: a surface layer, an intermediate layer, and a seal layer, and the surface of the surface layer is subjected to corona treatment, wherein the surface layer is mainly made of a propylene-based resin, the intermediate layer is mainly made of a propylene-based resin composition containing 50% by weight or more of a propylene-ethylene block copolymer having a xylene soluble content of 12% or more and having a calculated MFR of 6 g / 10 min or less as shown in the following formula (i), and the seal layer has a density of 0.880 g / cm 3The present invention relates to an unstretched food packaging film characterized by having a composition of 20 to 80% by weight of the following propylene-based elastomer and 20 to 80% by weight of a propylene random copolymer. MFR X : Calculated MFR (g / 10 min) of propylene resin composition n: total number of propylene-based resins constituting the propylene-based resin composition w i : Blending ratio of propylene-based resin i constituting the propylene-based resin composition MFR i : MFR (g / 10 min) of propylene-based resin i constituting the propylene-based resin composition

[0009]

number

[0010] The invention of claim 2 is a non-oriented film used for bag making by welding and sealing, which comprises three layers: a surface layer, an intermediate layer, and a seal layer, and the surface of the surface layer is subjected to a corona treatment, wherein the surface layer is mainly made of a propylene-based resin, the intermediate layer is mainly made of a propylene-based resin composition containing 50% by weight or more of a propylene-ethylene block copolymer having a xylene soluble content of 12% or more and having a calculated MFR of 6 g / 10 min or less as shown in the above formula (i), and the seal layer has a density of 0.880 g / cm 3 The present invention relates to an unstretched food packaging film characterized by a composition comprising 20 to 80% by weight of the following propylene-based elastomer, 18 to 78% by weight of a propylene random copolymer, and 2 to 20% by weight of a linear low-density polyethylene.

[0011] The invention of claim 3 relates to the non-stretched film for packaging food according to claim 1 or 2, wherein the non-stretched film has a haze value of 40% or more as measured in accordance with JIS K 7136 (2000).

[0012] The invention of claim 4 relates to an unstretched film for food packaging according to any one of claims 1 to 3, wherein the intermediate layer contains 70 to 98% by weight of the propylene-based resin composition and 2 to 30% by weight of a linear low-density polyethylene having a density of 0.910 or more.

[0013] The invention of claim 5 relates to a food packaging bag made from the non-stretched food packaging film according to any one of claims 1 to 4, which is fusion-cut with the sealing layer on the inside.

[0014] The invention of claim 6 relates to the food packaging bag of claim 5, which has a gusset portion at the bottom. [Effects of the Invention]

[0015] According to the invention of claim 1, the non-stretched food packaging film is used for bag making by welding and sealing, and comprises three layers: a surface layer, an intermediate layer, and a seal layer, and the surface of the surface layer is subjected to a corona treatment. The surface layer is mainly made of a propylene-based resin, the intermediate layer is mainly made of a propylene-based resin composition containing 50% by weight or more of a propylene-ethylene block copolymer having a xylene soluble content of 12% or more and having a calculated MFR of 6 g / 10 min or less, and the seal layer has a density of 0.880 g / cm 3 The composition is 20 to 80% by weight of the following propylene-based elastomer and 20 to 80% by weight of a propylene random copolymer, which provides excellent performance for food packaging bags and effectively prevents tearing of fused parts when food is filled at low temperatures.

[0016] According to the invention of claim 2, the non-stretched food packaging film is used for bag making by welding and sealing, and comprises three layers: a surface layer, an intermediate layer, and a seal layer, and the surface of the surface layer is subjected to a corona treatment. The surface layer is mainly made of a propylene-based resin, the intermediate layer is mainly made of a propylene-based resin composition containing 50% by weight or more of a propylene-ethylene block copolymer having a xylene soluble content of 12% or more and having a calculated MFR of 6 g / 10 min or less, and the seal layer has a density of 0.880 g / cm 3The composition of the bag is 20 to 80% by weight of the following propylene-based elastomer, 18 to 78% by weight of propylene random copolymer, and 2 to 20% by weight of linear low-density polyethylene, so that the bag has good performance properties for food packaging, and can effectively prevent tearing of the fused part when food is filled at low temperatures in particular.

[0017] According to the non-stretched food packaging film of the invention of claim 3, in the invention of claim 1 or 2, the non-stretched film has a haze value of 40% or more measured in accordance with JIS K 7136 (2000), so a matte film suitable for packaging foods such as bread is obtained.

[0018] According to the unstretched food packaging film of the invention of claim 4, in the invention of any one of claims 1 to 3, the intermediate layer contains 70 to 98% by weight of the propylene-based resin composition and 2 to 30% by weight of linear low-density polyethylene having a density of 0.910 or more, thereby increasing the stiffness of the film and improving its suitability for bag formation.

[0019] According to the food packaging bag of the invention of claim 5, the bag is made of the non-stretch food packaging film described in any one of claims 1 to 4 and is fusion-cut with the sealing layer on the inside, which improves the strength of the fusion part and prevents the fusion part from tearing when food is filled at low temperatures.

[0020] According to the food packaging bag of the invention of claim 6, in the invention of claim 5, since the bag has a gusset portion at the bottom, bread can be suitably packaged. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic cross-sectional view of a non-stretched food packaging film according to one embodiment of the present invention. [Figure 2] 1 is a schematic plan view of a food packaging bag obtained by melt-cutting a non-stretched food packaging film. FIG. [Figure 3] FIG. 1 is a schematic perspective view showing a process for forming a bag from a non-stretched food packaging film by welding and sealing. [Figure 4] FIG. 1 is a schematic cross-sectional view of a folded portion of a film folded by gusset folding. DETAILED DESCRIPTION OF THE INVENTION

[0022] 1 is a non-stretched film for food packaging that includes three layers: a surface layer 20, an intermediate layer 30, and a sealing layer 40. This film 10 is produced by a known production method such as the T-die method.

[0023] The non-stretched food packaging film 10 is used as a material for food packaging bags for packaging appropriate foods, and is particularly suitable for use as packaging bags for breads such as sliced ​​bread and sweet rolls. The film 10 can be configured to have a transparent or matte appearance depending on the application, and matte films are preferably used for packaging bags for bread. Therefore, when the film 10 is configured to have a matte appearance, it is preferable that the haze value measured in accordance with JIS K 7136 (2000) be 40% or more. By setting the haze value to 40% or more, a matte film suitable for packaging foods such as bread can be obtained. Furthermore, when a transparent film is used, it is preferable that the haze value be less than 10%.

[0024] The surface layer 20 is a layer mainly made of a propylene-based resin. This surface layer 20 corresponds to a printing layer on which appropriate printing is performed. Therefore, in order to obtain good printing performance on the film surface, the surface of the surface layer 20 is subjected to a corona treatment.

[0025] The propylene-based resin is selected from polymers mainly composed of propylene, such as a homopolymer of propylene (homopolypropylene) or a copolymer of propylene with other olefins such as ethylene or butene (propylene copolymer). Specific examples of resins constituting the surface layer 20 include, in the case of a transparent film, a propylene homopolymer, a propylene-ethylene random copolymer, a propylene-ethylene-butene random copolymer, a blend of a propylene homopolymer and a propylene random copolymer, a blend of a propylene homopolymer and / or a propylene random copolymer with an ethylene-based elastomer, and a blend of a propylene homopolymer and / or a propylene random copolymer with a propylene-based elastomer. In the case of a matte film, examples include a propylene-ethylene block copolymer, a blend of a propylene-ethylene block copolymer with polyethylene, and a blend of a homopolypropylene and / or a propylene random copolymer with polyethylene. The method of blending two or more resins can be selected from compounding, dry blending, etc.

[0026] The intermediate layer 30 is a layer primarily made of a propylene-based resin composition containing 50% by weight or more of a propylene-ethylene block copolymer having a xylene-soluble content of 12% or more. The xylene-soluble content of the propylene-ethylene block copolymer is considered to be an elastomer component contained in the propylene-ethylene block copolymer that dissolves in xylene. If the xylene-soluble content of the propylene-ethylene block copolymer is less than 12%, tears may be more likely to occur in the fused area. Furthermore, if the proportion of the propylene-ethylene block copolymer in the intermediate layer 30 is less than 50% by weight, tears may be more likely to occur in the fused area, which is undesirable.

[0027] The propylene-based resin composition for the mid layer 30 is preferably one having a calculated MFR of 6 g / 10 min or less, as shown in the following formula (i): The calculated MFR is considered to be the MFR of the mixed resin, and if the calculated MFR of the propylene-based resin composition is higher than 6 g / 10 min, the fusion zone may be more susceptible to tearing.

[0028]

number

[0029] Here, the symbols in formula (i) are as follows: MFR X : Calculated MFR (g / 10 min) of propylene resin composition n: total number of propylene-based resins constituting the propylene-based resin composition w i : Blending ratio of propylene-based resin i constituting the propylene-based resin composition MFR i : MFR (g / 10 min) of propylene-based resin i constituting the propylene-based resin composition

[0030] In the intermediate layer 30, in order to increase the stiffness of the film and improve the suitability for bag making, a density of 0.910 g / cm 3 It is preferable to blend the above linear low-density polyethylene. The linear low-density polyethylene may be plant-derived or fossil-derived. The preferred blending ratio of the intermediate layer 30 is 70 to 98 wt % of the propylene-based resin composition and 2 to 30 wt % of linear low-density polyethylene having a density of 0.910 or more. If the blending ratio of linear low-density polyethylene is too low, it is difficult to increase the stiffness of the film, while if the blending ratio of linear low-density polyethylene is too high, the stiffness of the film may decrease. Furthermore, if the density of the linear low-density polyethylene is too low, it is difficult to increase the stiffness of the film.

[0031] The sealing layer 40 is the layer that will become the inside of the packaging bag after the bag is made. This sealing layer 40 has a density of 0.880 g / cm 3 The composition is 20 to 80% by weight of the following propylene-based elastomer and 20 to 80% by weight of a propylene random copolymer.

[0032] Propylene-based elastomers produced by metallocene catalysts are particularly preferred. Propylene-based elastomers produced by metallocene catalysts have advantages such as the fact that they contain a small amount of low-molecular-weight components, making the film less sticky, and even when blended in large amounts, they are less likely to cause problems such as slipperiness and blocking. If the blending ratio of the propylene-based elastomer is too low, the seal initiation temperature may become too high, and low-temperature heat sealability may not be achieved. On the other hand, if the blending ratio is too high, the seal initiation temperature may become too low, and easy-openability may not be achieved. If the density of the propylene-based elastomer is 0.880 g / cm 3 If the temperature is higher, the film may stretch when the sealed portion is peeled off, making it difficult to open the film easily.

[0033] Examples of propylene random copolymers include binary random copolymers of propylene and ethylene, binary random copolymers of propylene and an α-olefin, and ternary random copolymers of propylene, ethylene, and an α-olefin having 4 to 12 carbon atoms.

[0034] In another embodiment, the sealing layer has a density of 0.880 g / cm 3 The composition may be 20 to 80% by weight of the following propylene-based elastomer, 18 to 78% by weight of a propylene random copolymer, and 2 to 20% by weight of a linear low-density polyethylene. In the seal layer according to another embodiment, by containing the linear low-density polyethylene in the above-mentioned blending ratio, it is possible to suppress a decrease in heat seal strength over time.

[0035] In addition, various additives such as antiblocking agents, slip agents, antistatic agents, antifogging agents, heat stabilizers, antioxidants, light stabilizers, and nucleating agents, as well as scrap materials, can be added to the surface layer 20, intermediate layer 30, and seal layer 40 as needed, as long as they do not impair the properties of each layer. The various additives can be added directly to the powder after polymerization of each resin, or they can be mixed in any step before preparing a high-concentration masterbatch and obtaining the film. When using a masterbatch, a small amount of resin may be unintentionally mixed in, but this can be used as long as it does not impair the properties of each layer.

[0036] From the viewpoint of ease of handling, strength, etc., the thickness of the film 10 is preferably in the range of 20 to 50 μm, and more preferably 25 to 35 μm. The thickness of each layer is not particularly limited, but for example, the ratio of each layer is set as follows: surface layer 5 to 40%, intermediate layer 30 to 90%, and sealing layer 5 to 30%, and more preferably, the ratio is set as follows: surface layer 10 to 30%, intermediate layer 50 to 83%, and sealing layer 7 to 20%.

[0037] The film 10 of the present invention is used in bag making by welding to obtain food packaging bags. In bag making by welding, a heated welding blade is pressed against the perpendicular direction of the folded portion that will become the bottom of a non-stretched food packaging film that has been folded back with the sealing layer on the inside, cutting and heat-sealing the film to form it into a bag shape. The welding bag making method can be appropriately selected from known methods, and welding bags of any shape, such as a square-bottom gusset bag, can be obtained.

[0038] The embodiment shown in Figure 2 is a food packaging bag 50 having a square bottom gusset portion 53 at a fusion-cut bottom 52. In the illustrated food packaging bag 50, the bag side edge portion (the thick line portion in the figure) 54, which extends from the side edge 51a of the bag body 51 to the side edge 53a of the square bottom gusset portion 53, is a fusion-sealed fusion portion 55. The food packaging bag 50 having the square bottom gusset portion 53 is suitable as a packaging bag for bread.

[0039] Here, the bag-making process for a food packaging bag 50 having a square-bottom gusset portion 52 will be described. First, as shown in FIG. 3(a), the folded portion 11 of the folded film 10 is folded back into a generally W-shape with the sides closed by gusset folding. At this time, the film 10 is folded back so that the sealing layer 40 is on the inside. Next, as shown in FIG. 3(b), the film 10 is folded back, including the gusset-folded folded portion 11, and both side portions 12, 12 of the film 10 (dotted line portions in the figure) corresponding to the perpendicular direction to the folded portion 11 are fusion-sealed. Then, as shown in FIG. 3(c), the film 10 is formed into a bag shape (50A) in which three sides, namely, the folded-back folded portion 11 and the fusion-sealed both side portions, 54, 54, are sealed, thereby obtaining the food packaging bag 50 (see FIG. 4).

[0040] In food packaging bag 50 thus produced by welding and sealing, film 10 is welded and sealed in four layers at gusset-folded fold 11, as shown in Fig. 4. Therefore, at weld-sealed fold 11, the inner seal layers 40 of first film 10a and second film 10b are sealed together (sealed portion 15a), the outer surface layers 20 of second film 10b and third film 10c are sealed together (sealed portion 15b), and the inner seal layers 40 of third film 10c and fourth film 10d are sealed together (sealed portion 15c).

[0041] In the non-stretched food packaging film 10 of the present invention, when bags are made by welding and sealing, not only the sealing layers 40 can be firmly welded and sealed, but also the surface layers 20 can be firmly welded and sealed. [Example]

[0042] [Making a fusion-cut bag] To produce the fusion-cut bags of Prototype Examples 1 to 30, the materials described below were first dry-blended and coextruded using a three-layer coextrusion T-die film molding machine using the T-die method, in the order of surface layer, middle layer, and seal layer, so that the thicknesses of the layers were 8 μm, 18 μm, and 4 μm, respectively, to form non-stretched films corresponding to the fusion-cut bags of Prototype Examples 1 to 30. Next, each of the produced non-stretched films was folded in half with the seal layer on the inside, and then a square-bottom gusset fold was formed at the bottom. The fusion-cut bags of Prototype Examples 1 to 30 were obtained using a fusion-cutting bag-making device (Totani Giken Kogyo Co., Ltd.; "HK-40V") with a fusion-cutting blade tip angle of 120°, a fusion-cutting temperature of 350°C, and a bag-making speed of 194 bags / min.

[0043] [Materials used] The following resins were used as the resin compositions for the surface layer, intermediate layer, and heat seal layer. Regarding the properties of each resin, the melt flow rate (MFR) was measured in accordance with JIS K 7210 (2014), with the propylene-based resin measured at 230°C and 2.16 kg, and the ethylene-based resin measured at 190°C and 2.16 kg. The density was measured in accordance with JIS K 7112.

[0044] The xylene-soluble fraction (%) was also determined for resins A1 to A4. To determine the xylene-soluble fraction, 5 to 6 g of resin was first taken and weighed (weight of resin before dissolution, X). This was then refluxed and dissolved in xylene, cooled, and centrifuged to separate it into a xylene-soluble fraction and an insoluble fraction. The xylene-soluble fraction was further concentrated, and methanol was added to precipitate it. The precipitate was collected by filtration, dried, and weighed (weight of the xylene-soluble precipitate, Y). Therefore, the xylene-soluble fraction Z (%) was calculated from the weight X of the resin before dissolution and the weight Y of the xylene-soluble precipitate according to the following formula (ii):

[0045]

number

[0046] Furthermore, the melting points (°C) of Resins B1 and C1 to C5 were determined. The melting points of the resins were determined in accordance with differential scanning calorimetry (DSC) measurement in accordance with JIS K 7121 (2012), using a differential scanning calorimeter (manufactured by Netsch Japan Co., Ltd.; "DSC 214 Polymer"), by determining the melting peak temperature from the DSC curve obtained when the temperature was raised at a heating rate of 10°C / min.

[0047] Resin A1: Propylene-ethylene block copolymer (Japan Polypropylene Corporation; "BC3HF"), MFR (230°C, 2.16 kg): 8.5 g / 10 min, xylene solubles: 10.6%, density: 0.9 g / cm 3 Resin A2: Propylene-ethylene block copolymer (Prime Polymer Co., Ltd.; "F-274NP"), MFR (230°C, 2.16 kg): 2.5 g / 10 min, xylene solubles: 15.8%, density: 0.9 g / cm 3 Resin A3: Propylene-ethylene block copolymer (Japan Polypropylene Corporation; "BC6DRF"), MFR (230°C, 2.16 kg): 2.5 g / 10 min, xylene solubles: 16.2%, density: 0.9 g / cm 3 Resin A4: Propylene-ethylene block copolymer (Japan Polypropylene Corporation; "BC5FA"), MFR (230°C, 2.16 kg): 3.5 g / 10 min, xylene solubles: 12.4%, density: 0.9 g / cm 3

[0048] Resin B1: Homopolypropylene (Japan Polypropylene Corporation; "FB3B"), MFR (230°C, 2.16 kg): 7.5 g / 10 min, density 0.9 g / cm 3 , melting point 163℃

[0049] Resin C1: Propylene random copolymer (propylene-ethylene random copolymer) (Japan Polypropylene Corporation; "WFW4M"), MFR (230°C, 2.16 kg): 7 g / 10 min, density 0.9 g / cm 3 , melting point 135℃ Resin C2: Propylene random copolymer (propylene-ethylene random copolymer) (Prime Polymer Co., Ltd.; "S235WC"), MFR (230°C, 2.16 kg): 11 g / 10 min, density 0.9 g / cm 3 , melting point 135℃ Resin C3: Propylene random copolymer (propylene-ethylene random copolymer) (Japan Polypropylene Corporation; "WFX5233"), MFR (230°C, 2.16 kg): 7 g / 10 min, density 0.9 g / cm 3 , melting point 130℃ Resin C4: Propylene random copolymer (propylene-ethylene-butene random copolymer) (manufactured by Japan Polypropylene Corporation; "FW4BT"), MFR (230°C, 2.16 kg): 6.5 g / 10 min, density 0.9 g / cm 3 , melting point 138℃ Resin C5: Propylene random copolymer (propylene-ethylene random copolymer) (Japan Polypropylene Corporation; "WFX6"), MFR (230°C, 2.16 kg): 2 g / 10 min, density 0.9 g / cm 3 , melting point 125℃

[0050] Resin D1: Low-density polyethylene (Ube Maruzen Polyethylene Co., Ltd.; "R300"), MFR (190°C, 2.16 kg): 0.35 g / 10 min, density 0.920 g / cm 3

[0051] Resin E1: Plant-derived linear low-density polyethylene (Braskem SLH118), MFR (190°C, 2.16 kg): 1 g / 10 min, density 0.916 g / cm 3 Resin E2: Plant-derived linear low-density polyethylene (Braskem SLH218), MFR (190°C, 2.16 kg): 2.3 g / 10 min, density 0.916 g / cm 3 Resin E3: Plant-derived linear low-density polyethylene (Braskem; "SLL318"), MFR (190°C, 2.16 kg): 2.7 g / 10 min, density 0.918 g / cm 3 Resin E4: Linear low-density polyethylene (Ube Maruzen Polyethylene Co., Ltd.; "1540F"), MFR (190°C, 2.16 kg): 4 g / 10 min, density 0.913 g / cm 3 Resin E5: Linear low-density polyethylene (Ube Maruzen Polyethylene Co., Ltd.; "0540F"), MFR (190°C, 2.16 kg): 4 g / 10 min, density 0.904 g / cm 3 Resin E6: Linear low-density polyethylene (Ube Maruzen Polyethylene Co., Ltd.; "2040FC"), MFR (190°C, 2.16 kg): 5 g / 10 min, density 0.919 g / cm 3 Resin E7: Linear low-density polyethylene (Japan Polyethylene Co., Ltd.; "KF360T"), MFR (190°C, 2.16 kg): 3.5 g / 10 min, density 0.898 g / cm 3

[0052] Resin F1: Metallocene-catalyzed propylene elastomer (ExxonMobil Corporation; "VISTAMAXX3980FL"), MFR (230°C, 2.16 kg): 8 g / 10 min, density 0.878 g / cm 3 Resin F2: Metallocene-catalyzed propylene elastomer (ExxonMobil Corporation; "VISTAMAXX 6102FL"), MFR (230°C, 2.16 kg): 3 g / 10 min, density 0.862 g / cm 3 Resin F3: Metallocene-catalyzed propylene elastomer (ExxonMobil Corporation; "VISTAMAXX3588FL"), MFR (230°C, 2.16 kg): 8 g / 10 min, density 0.889 g / cm 3

[0053] Resin G1: Metallocene-catalyzed ethylene elastomer (Dow Chemical Company; "AFFINITY KC8852G"), MFR (190°C, 2.16 kg): 3 g / 10 min, density 0.875 g / cm 3

[0054] [Prototype 1] Prototype example 1 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0055] [Prototype 2] Prototype example 2 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A3, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0056] [Prototype 3] Prototype example 3 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A4, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0057] [Prototype 4] Prototype example 4 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 80% by weight of resin C3 and 20% by weight of resin F2.

[0058] [Prototype 5] Prototype example 5 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 85% by weight of resin A2 and 15% by weight of resin E5, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0059] [Prototype 6] Prototype example 6 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 60% by weight of resin A2 and 40% by weight of resin E2, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0060] [Prototype 7] Prototype example 7 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 98% by weight of resin A2 and 2% by weight of resin E2, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0061] [Prototype 8] Prototype example 8 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 85% by weight of resin A2 and 15% by weight of resin E1, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0062] [Prototype 9] Prototype example 9 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 85% by weight of resin A2 and 15% by weight of resin E3, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0063] [Prototype 10] Prototype example 10 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 70% by weight of resin A2 and 30% by weight of resin E2, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0064] [Prototype 11] Prototype example 11 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 50% by weight of resin A2, 25% by weight of resin C1, 15% by weight of resin E2, and 10% by weight of resin E4, and the seal layer is made of 80% by weight of resin C3 and 20% by weight of resin F2.

[0065] [Prototype 12] Prototype example 12 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 70% by weight of resin A2, 15% by weight of resin C1, and 15% by weight of resin E2, and the seal layer is made of 80% by weight of resin C3 and 20% by weight of resin F2.

[0066] [Prototype 13] Prototype example 13 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 50% by weight of resin A2, 35% by weight of resin C2, and 15% by weight of resin E2, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0067] [Prototype 14] Prototype example 14 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A1, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0068] [Prototype 15] Prototype example 15 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin B1, and the sealing layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0069] [Prototype 16] Prototype example 16 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin C4, and the sealing layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0070] [Prototype 17] Prototype example 17 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 100% by weight of resin F1.

[0071] [Prototype 18] Prototype example 18 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 100% by weight of resin F3.

[0072] [Prototype 19] Prototype example 19 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 60% by weight of resin C3 and 40% by weight of resin G1.

[0073] [Prototype 20] Prototype example 20 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A2, and the sealing layer is made of 80% by weight of resin C3 and 20% by weight of resin G1.

[0074] [Prototype 21] Prototype example 21 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 30% by weight of resin A2, 55% by weight of resin C5, and 15% by weight of resin E2, and the seal layer is made of 35% by weight of resin C1 and 65% by weight of resin F1.

[0075] [Prototype 22] Prototype example 22 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A2, and the sealing layer is made of 35% by weight of resin C4 and 65% by weight of resin F1.

[0076] [Prototype 23] Prototype example 23 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A2, and the sealing layer is made of 25% by weight of resin C1, 65% by weight of resin F1, and 10% by weight of resin E6.

[0077] [Prototype 24] Prototype example 24 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A2, and the sealing layer is made of 25% by weight of resin C1, 65% by weight of resin F1, and 10% by weight of resin E7.

[0078] [Prototype 25] Prototype example 25 is a fusion-cut bag made of a non-stretched film in which the surface layer is made of 95% by weight of resin A1 and 5% by weight of resin D1, the middle layer is made of 100% by weight of resin A2, and the sealing layer is made of 18% by weight of resin C1, 65% by weight of resin F1, 3.5% by weight of resin E6, and 13.5% by weight of resin E7.

[0079] [Prototype 26] Prototype example 26 is a fusion-cut bag made of a non-stretched film in which the surface layer is 100% by weight of resin C3, the middle layer is 100% by weight of resin A2, and the sealing layer is 35% by weight of resin C1 and 65% by weight of resin F1.

[0080] [Prototype 27] Prototype example 27 is a fusion-cut bag made of a non-stretched film in which the surface layer is 100% by weight of resin C3, the middle layer is 50% by weight of resin A3 and 50% by weight of resin C1, and the sealing layer is 35% by weight of resin C1 and 65% by weight of resin F1.

[0081] [Prototype 28] Prototype example 28 is a fusion-cut bag made of a non-stretched film in which the surface layer is 100% by weight of resin C3, the middle layer is 100% by weight of resin A4, and the sealing layer is 35% by weight of resin C1 and 65% by weight of resin F1.

[0082] [Prototype 29] Prototype example 29 is a fusion-cut bag made of a non-stretched film in which the surface layer is 100% by weight of resin C3, the middle layer is 100% by weight of resin A2, and the sealing layer is 80% by weight of resin C3 and 20% by weight of resin F2.

[0083] [Prototype 30] Prototype example 30 is a fusion-cut bag made of a non-stretched film in which the surface layer is 100% by weight of resin C3, the middle layer is 100% by weight of resin A2, and the sealing layer is 30% by weight of resin C1, 65% by weight of resin F1, and 5% by weight of resin E6.

[0084] For the fusion-cut bags of prototypes 1 to 30, the resin compositions of the layers of the film that constitute the fusion-cut bags are shown in Tables 1 to 5.

[0085] [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] [Table 4]

[0089] [Table 5]

[0090] The performance of each film used in the fusion-cut bags of prototypes 1 to 30 was evaluated by measuring the heat seal initiation temperature, ease of opening, haze value, tensile modulus, fusion strength of the gusset portion, fusion strength of the bag body, and bag breakage at the fusion portion when filling the contents. All tests were carried out in a room at 23°C.

[0091] [Heat seal starting temperature] The heat-sealing initiation temperature of films corresponding to Prototype Examples 1 to 30 was measured according to JIS Z 1713 (2009). Two sheets of each film were prepared and heat-sealed, with the seal layers facing each other, using a heat-sealing tester (Toyo Seiki Seisakusho Co., Ltd.; "Thermal Gradient Tester") with a seal bar size of 10 mm x 25 mm, a sealing pressure of 0.4 MPa, and a sealing time of 1 second. After heat-sealing, 15 mm-wide test pieces were cut out. The heat-sealed test pieces were opened 180° and the sealed portions were peeled at a tensile speed of 200 mm / min using a tensile tester (Shimadzu Corporation; "Small Tabletop Tester EZ-SX") to determine the temperature at which the heat-sealing strength reached 3 N / 15 mm width (heat-sealing initiation temperature). Low-temperature sealability was evaluated as follows: a heat-sealing initiation temperature of 80 to 120°C was rated "Good" (◯), and a heat-sealing initiation temperature of less than 80°C or greater than 120°C was rated "Poor" (×).

[0092] [Easy to open] The films corresponding to Prototype Examples 1 to 30 were tested for ease of opening. Using a heat-sealing tester (Toyo Seiki Seisakusho Co., Ltd.; "Thermal Gradient Tester"), two sheets of each film were prepared, and the seal layers of each were overlapped and heat-sealed at 120°C using the same method as for measuring the heat-sealing initiation temperature. After heat-sealing, 15-mm-wide test pieces were cut out. The heat-sealed test pieces were opened 180° and visually observed for peeling when pulled at a pulling rate of 200 mm / min using a tensile tester (Shimadzu Corporation; "Small Tabletop Tester EZ-SX"). Ease of opening was evaluated as "Good" (◯) if the film peeled without elongation, and "Poor" (×) if the film peeled with elongation. Samples that were not heat-sealed (i.e., lacking low-temperature sealability) were recorded as "No Seal" (-).

[0093] [Haze value] The haze values ​​of the films corresponding to prototypes 1 to 30 were measured in accordance with JIS K 7136 (2000). The haze value (%) is an index of transparency and was measured using a haze meter (Nippon Denshoku Industries Co., Ltd.; "Haze Meter NDH-4000"). For food packaging bags for bread and other foods, matte films tend to look better than transparent films and are preferred by food manufacturers and consumers. Therefore, the haze value was evaluated as follows: a measurement result of 40% or more was rated "excellent (◎)," a measurement result of less than 10% was rated "good (◯)," and a measurement result of 10% or more but less than 40% was rated "unacceptable (×)."

[0094] Tensile modulus The tensile modulus (GPa) of the films corresponding to Prototype Examples 1 to 30 was measured in accordance with JIS K 7127 (1999). A tensile tester (A&D Co., Ltd.; "Tensilon Universal Testing Machine RTF-1310") was used to measure the modulus of elasticity in two directions: the winding direction (MD) of each film and the transverse direction (TD) perpendicular to the MD. The stiffness of the film was evaluated as follows: a result of 0.65 GPa or greater was rated "excellent (◎)," a result of 0.50 GPa or greater was rated "good (◯)," and a result of less than 0.50 GPa was rated "poor (×)."

[0095] [Fusing strength of gusset part] For the fusion-cut bags of prototypes 1 to 30, the fusion strength (N / 15 mm width) of the fusion zone of the gusset (reference numeral 53a in Figure 2) was measured. For this measurement, the fusion zone of the gusset of the fusion-cut bag was cut into a 15 mm width and subjected to a tensile test at 200 mm / min using a tensile tester (Shimadzu Corporation; "Small Tabletop Tester EZ-SX"), with two films clamped between the upper and lower chucks. The maximum strength was measured until the fusion zone broke. The fusion strength of the gusset was evaluated as "Good" (◯) if the measurement result was 15 N / 15 mm width or greater, and "Poor" (×) if the measurement result was less than 15 N / 15 mm width.

[0096] [Bag body fusing strength] The fusion strength (N / 15 mm width) of the fusion portion of the bag body (reference numeral 51a in Figure 2) was measured for the fusion-cut bags of prototypes 1 to 30. For this measurement, a 15 mm width was cut out of the fusion portion of the bag body (non-gusseted portion) of the fusion-cut bag. Using a tensile tester (Shimadzu Corporation; "Small Tabletop Tester EZ-SX"), one film was clamped between the top and bottom chucks and pulled at 200 mm / min to determine the maximum strength until the fusion portion broke. The fusion strength of the bag body was evaluated as "Good" (◯) if the measurement result was 17 N / 15 mm width or greater, and "Poor" (×) if the measurement result was less than 17 N / 15 mm width.

[0097] [Evaluation of tear resistance of the fused part of the bag body] For the fusion-cut bags of prototypes 1 to 30, a tear resistance test was conducted on the fusion portion of the bag body (reference numeral 51a in Figure 2) to evaluate the tear resistance of the fusion portion due to impact when filling the contents (food). In the tear test for the fusion portion, the bag was placed on a table, both hands were placed inside the bag, and the fusion portions on both sides of the bag were slammed hard against the fusion portion. The tear test was visually observed to determine whether or not the fusion portion had ruptured. Five fusion-cut bags of each prototype 1 to 30 were prepared for this test. The tear resistance of the fusion portion when filling the contents was evaluated as follows: if none of the five fusion-cut bags ruptured, the result was "excellent (◎)"; if only one bag ruptured, the result was "good (◯)"; and if two or more bags ruptured, the result was "unacceptable (×)."

[0098] The test results and evaluations for each film corresponding to the fusion-cut bags of Prototype Examples 1 to 30 and for the fusion-cut bags of Prototype Examples 1 to 30 are shown in Tables 6 to 10. The calculated MFR of the propylene-based resin composition (resins A1 to A4, resin B1, resins C1 to C5) in the intermediate layer of each of Prototype Examples 1 to 30 was calculated based on the above formula (i) and is shown in Tables 6 to 10. In Tables 6 to 10, the overall evaluation was given as "good (◯)" when all the evaluations for each test were "good (◯)" or better, and as "bad (×)" when there was even one "bad (×)" or "no seal (-)".

[0099] [Table 6]

[0100] [Table 7]

[0101] [Table 8]

[0102] [Table 9]

[0103] [Table 10]

[0104] [Results and Discussion] As shown in Tables 1 to 5 and Tables 6 to 10, the overall evaluation of prototypes 1 to 13 and 22 to 30 was "good (◯)," while the overall evaluation of prototypes 14 to 21 was "poor (×)." Therefore, the differences in performance between the good prototypes 1 to 13 and 22 to 30 and the bad prototypes 14 to 21 will be considered by comparing the film configuration of each prototype.

[0105] All of the prototypes 1 to 25 had a haze value of 40% or more, while all of the prototypes 26 to 30 had a haze value of less than 10%. That is, in prototypes 1 to 25, a good matte finish was obtained due to the surface layer having a composition mainly composed of a propylene-ethylene block copolymer, and in prototypes 26 to 30, good transparency was obtained due to the surface layer having a composition mainly composed of a propylene random copolymer.

[0106] The propylene-based resin composition constituting the intermediate layer of the non-defective Samples 1-3 and the defective Sample 14 was 100% by weight of propylene-ethylene block copolymer, but the types of propylene-ethylene block copolymers (Resin A1, Resin A2, Resin A3, and Resin A4) differed. Sample 1 used Resin A2 with a xylene-soluble content of 15.8%, Sample 2 used Resin A3 with a xylene-soluble content of 16.2%, and Sample 3 used Resin A4 with a xylene-soluble content of 12.4%. In contrast, Sample 4 used Resin A1 with a xylene-soluble content of 10.6%. The Resin A1 used in Sample 14 had a lower xylene-soluble content than Resins A2 to A4 of Samples 1-3. Furthermore, the calculated MFR of the propylene-based resin composition of the intermediate layer of Sample 14 was higher than that of Samples 1-3. As a result, the fusion section of Prototype 14 was more likely to rupture than Prototypes 1 to 3. Therefore, it is considered that a propylene-based resin composition (propylene-ethylene block copolymer) for the intermediate layer having a high calculated MFR and a low xylene-soluble content (for example, Resin A1; calculated MFR 8.5 g / 10 min, xylene-soluble content 10.6%) is not preferable.

[0107] Defective Sample 15 differs from non-defective Samples 1 to 3 in that it uses homopolypropylene (resin B1) instead of propylene-ethylene block copolymer as the propylene-based resin composition constituting the intermediate layer. Defective Sample 16 also differs from non-defective Samples 1 to 3 in that it uses propylene random copolymer (resin C4) instead of propylene-ethylene block copolymer as the propylene-based resin composition constituting the intermediate layer. Both Samples 15 and 16 were more prone to rupture at the fusion site than Samples 1 to 3. Therefore, it is considered undesirable to use homopolypropylene (resin B1) or propylene random copolymer (resin C4) instead of propylene-ethylene block copolymer as the propylene-based resin composition for the intermediate layer.

[0108] A comparison is made between a good sample, Prototype 13, and a defective sample, Prototype 21. In Prototype 13, the propylene-based resin composition constituting the intermediate layer is primarily (50% by weight or more) composed of a propylene-based resin composition containing a propylene-ethylene block copolymer (resin A2) and a propylene random copolymer (resin C2), and linear low-density polyethylene (resin E2) is blended in. Prototype 21 differs from Prototype 13 in that the blending ratio of the propylene-ethylene block copolymer (resin A2) in the propylene-based resin composition is lower (less than 50% by weight). The melted portion of Prototype 21 was more likely to rupture than Prototype 13. Therefore, it is considered preferable that the propylene-based resin composition of the intermediate layer be primarily (50% by weight or more) composed of a propylene-ethylene block copolymer.

[0109] Here, we compare the good prototype 1 with the good prototypes 5 to 13. In prototype 1, the intermediate layer is 100% by weight of a propylene-based resin composition (propylene-ethylene block copolymer), whereas in prototypes 5 to 13, linear low-density polyethylene (resins E1 to E5) is blended with a propylene-based resin composition (propylene-ethylene block copolymer, or propylene-ethylene block copolymer and propylene random copolymer) as the main component.

[0110] In Prototypes 8 to 13, the tensile modulus in both the winding direction (MD) and the transverse direction (TD) was almost always judged to be "excellent" (◎), indicating improved film stiffness. Furthermore, in Prototype 7, the tensile modulus was judged to be "good" (◯), but the tensile modulus was improved compared to Prototype 1. On the other hand, in Prototypes 5 and 6, no improvement in the tensile modulus was observed compared to Prototype 1. Comparing Prototype 5 with Prototypes 8 and 9, the density of the linear low-density polyethylene (resin E5) used in Prototype 5, which did not improve the tensile modulus, was lower than in Prototypes 8 and 9. Comparing Prototype 6 with Prototypes 7 and 10, Prototype 6, which did not improve the tensile modulus, contained a higher proportion of linear low-density polyethylene (resin E2) than did Prototypes 7 and 10.

[0111] As can be seen from Prototype Examples 1, 5 to 13, by blending linear low-density polyethylene in the intermediate layer, it is possible to improve the stiffness of the film. As for the type of linear low-density polyethylene, 3 Furthermore, the blending ratio of linear low-density polyethylene is preferably about 2 to 30% by weight, because even a small amount (for example, 2% by weight in Prototype 7) improves the tensile modulus, whereas an excessive amount (for example, 40% by weight in Prototype 6) does not improve the tensile modulus.

[0112] The defective prototype 17 differs from the non-defective prototype 1 in that its seal layer is composed of 100% by weight of a metallocene-catalyzed propylene-based elastomer (resin F1) while the non-defective prototype 1 has a seal layer composed of 65% by weight of a metallocene-catalyzed propylene-based elastomer (resin F1) and 35% by weight of a propylene random copolymer (resin C1). In the easy-open test, prototype 17 did not have adequate easy-open performance because the heat-sealed portion stretched and peeled off. Furthermore, the defective prototype 18 is composed of 100% by weight of a propylene-based elastomer (resin F3) with a different density from prototype 17, but similarly did not have adequate easy-open performance.

[0113] Defective Sample 20 differs from non-defective Sample 4 in that the resin in the seal layer is an ethylene elastomer (resin G1) produced by a metallocene catalyst instead of a propylene elastomer (resin F2) produced by a metallocene catalyst. Sample 20's heat seal initiation temperature was 126°C, and heat sealing was not possible at 120°C, resulting in poor low-temperature sealing. Defective Sample 19, which contains a higher proportion of ethylene elastomer (resin G1) than Sample 20 (40% by weight), improved low-temperature sealing and easy-opening properties, but the fusing strength of the fusing portion of the bag itself was insufficient, making the bag prone to tearing.

[0114] As can be seen from Prototypes 1 and 4 and Prototypes 17 to 20, it is considered preferable that the sealing layer be composed of a propylene-based elastomer and a propylene random copolymer. As for the type of propylene-based elastomer, a propylene-based elastomer having a density of 0.880 g / cm 3 It is considered that the blending ratio of the propylene elastomer is preferably about 20 to 80% by weight.

[0115] In Prototype 22, the propylene random copolymer (resin C1: propylene-ethylene random copolymer) used in the seal layer of Prototype 1 was replaced with a different propylene random copolymer (resin C4: propylene-ethylene-butene random copolymer). Although there were slight differences in the heat seal initiation temperature and tensile modulus of elasticity in Prototype 22 compared to Prototype 1, there was no significant effect on the film's performance, and the results were good.

[0116] In prototypes 23 to 25, linear low-density polyethylene was added to suppress deterioration of heat seal strength over time, without changing the blending ratio of the main component (propylene-based elastomer) of the seal layer of prototype 1. Different linear low-density polyethylenes were used in prototypes 23 and 24, and prototype 25 used a mixture of the two types of linear low-density polyethylene used in prototypes 23 and 24. Compared to prototype 1, prototypes 23 to 25 showed slight changes in heat seal temperature and fusing strength of the bag body, but this did not have a significant effect on film performance and were good.

[0117] Samples 26 to 30 are transparent films with a haze value of less than 10%. Samples 26 to 28 showed improvements in tensile modulus and gusset fusing strength compared to Sample 1. Sample 29 also showed improvements in tensile modulus and gusset fusing strength compared to Sample 4. Sample 30, on the other hand, is an example in which linear low-density polyethylene is added to suppress deterioration of heat seal strength over time, without changing the blending ratio of the main component (propylene-based elastomer) of the seal layer of Sample 26. Sample 30, despite containing linear low-density polyethylene, achieved film performance comparable to that of Sample 26.

[0118] As described above, the matte fusion-cut bags of Prototypes 1 to 13 and 22 to 25 were excellent in low-temperature sealability (heat-seal initiation temperature), ease of opening, film stiffness (tensile modulus), fusion strength of the fusion section, and tear resistance of the fusion section when filled with contents (evaluation of tear resistance of the fusion section of the bag body). Similarly, the transparent fusion-cut bags of Prototypes 26 to 30 were excellent in low-temperature sealability (heat-seal initiation temperature), ease of opening, film stiffness (tensile modulus), fusion strength of the fusion section, and tear resistance of the fusion section when filled with contents (evaluation of tear resistance of the fusion section of the bag body). Therefore, while maintaining the necessary performance for food packaging bags, it is possible to effectively prevent tearing of the fusion section when filled with food, even at low temperatures. [Industrial Applicability]

[0119] The non-stretched food packaging film and food packaging bag of the present invention satisfactorily maintain the various properties required for food packaging bags and can suppress the occurrence of tearing at fusion cut portions when food is filled, particularly at low temperatures, making them promising alternatives to conventional non-stretched food packaging films and food packaging bags. [Explanation of symbols]

[0120] 10, 10a-10d Non-stretched film for food packaging 11 Oribe 12 Side of film 15a, 15b, 15c seal part 20 Surface layer 30 Middle Class 40 Sealing Layer 50 Food packaging bags 50A bag-shaped film 51 Bag body 51a Side of bag body 52 Bottom 53 Square bottom gusset 53a Side of the square bottom gusset 54 Bag side 55 Welding seal part

Claims

1. A non-stretched film used for bag making by welding and sealing, comprising three layers: a surface layer, an intermediate layer, and a sealing layer, the surface of which has been subjected to a corona treatment, the surface layer is mainly made of a propylene-based resin, the intermediate layer is mainly made of a propylene-based resin composition containing 50% by weight or more of a propylene-ethylene block copolymer having a xylene-soluble content of 12% or more and having a calculated MFR of 6 g / 10 min or less as shown in the following formula (i): The sealing layer has a density of 0.880 g / cm ３ The composition is 20 to 80% by weight of the following propylene elastomer and 20 to 80% by weight of a propylene random copolymer: A non-stretched food packaging film characterized by: MFR Ｘ : Calculated MFR (g / 10 min) of propylene-based resin composition n: total number of propylene-based resins constituting the propylene-based resin composition w ｉ : Blending ratio of propylene-based resin i constituting the propylene-based resin composition MFR ｉ : MFR (g / 10 min) of propylene-based resin i constituting the propylene-based resin composition [Equation 1]

2. A non-stretched film used for bag making by welding and sealing, comprising three layers: a surface layer, an intermediate layer, and a sealing layer, the surface of which has been subjected to a corona treatment, the surface layer is mainly made of a propylene-based resin, the intermediate layer is mainly made of a propylene-based resin composition containing 50% by weight or more of a propylene-ethylene block copolymer having a xylene-soluble content of 12% or more and having a calculated MFR represented by the above formula (i) of 6 g / 10 min or less; The sealing layer has a density of 0.880 g / cm ３ The composition is 20 to 80% by weight of the following propylene elastomer, 18 to 78% by weight of a propylene random copolymer, and 2 to 20% by weight of a linear low-density polyethylene. A non-stretched food packaging film characterized by:

3. 3. The non-stretched film for food packaging according to claim 1, wherein the non-stretched film has a haze value of 40% or more as measured in accordance with JIS K 7136 (2000).

4. The non-oriented film for food packaging according to any one of claims 1 to 3, wherein the intermediate layer comprises 70 to 98% by weight of the propylene-based resin composition and 2 to 30% by weight of a linear low-density polyethylene having a density of 0.910 or more.

5. A food packaging bag made of the non-stretched food packaging film according to any one of claims 1 to 4, which is fusion-cut with the sealing layer on the inside.

6. 6. The food packaging bag according to claim 5, further comprising a square bottom gusset at the bottom.

Images