Non-stretched food packaging film and food packaging bags

Abstract

To provide a non-stretched film for food packaging and a bag for food packaging which improve tear strength of a film by adjustment of a resin composition of a surface layer, and can suppress occurrence of tear at the time of food filling after bag making.SOLUTION: A non-stretched film 10 contains a propylene-based resin as a main component, and has three layers of a surface layer 20, an intermediate layer 30 and a seal layer 40, wherein in the surface layer 20, a ratio of a component having a molecular weight of 1,000,000 or more to a xylene soluble matter of a resin composition constituting the surface layer 20 by gel permeation chromatography (GPC) measurement is 0.5 wt.% or more in the whole resin composition constituting the surface layer 20.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 food 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 non-stretch film, and a transparent film or a matte film is selected depending on the type of food to be packaged.

[0003] Films used in the manufacture of this type of food packaging bag are generally configured to have three layers: a surface layer, an intermediate layer, and a seal layer, and for example, a matte laminated film is known that has a surface 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 Patent Document 1). This matte film has excellent impact resistance, seal strength, abrasion resistance, bag rupture resistance, and weld-cut seal strength at low temperatures.

[0004] When filling food, the manufactured packaging bag is set in an automatic food filling machine, and the food is filled into the packaging bag. If the food comes into forceful contact with a part of the inside of the bag during this food filling process, the impact can cause part of the bag to tear (rupture), resulting in a problem of reduced production yield. To solve this problem, it is possible to improve the tear strength of the film that makes up the packaging bag so that it is less likely to tear. When trying to improve the tear strength of a film, this is usually done by adjusting the type of resin composition and layer thickness of the intermediate layer, which is thicker than the other layers.

[0005] In recent years, carbon neutrality has been required to reduce environmental impact, and in the field of resin films, development of resin films using recycled raw materials such as those from material recycling and chemical recycling, as well as biomass resources, has progressed. However, when a biomass-derived resin is contained in the intermediate layer, the film's tear strength tends to decrease, making it more susceptible to tearing. Therefore, in order to achieve both the use of a biomass-derived resin and improved tear strength, complicated adjustments were required for the type and blending ratio of the resin composition constituting the intermediate layer. Therefore, the inventors conducted extensive research and developed a film in which tear strength was improved by adjusting the resin composition of the surface layer, without the need for complicated adjustments of the resin composition in the intermediate layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2017 / 018282 publication Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been proposed in consideration of the above-mentioned circumstances, and provides a non-stretched film for food packaging and a food packaging bag that can improve the tear strength of the film by adjusting the resin composition of the surface layer, thereby suppressing the occurrence of tearing when food is filled into the bag after it has been made. [Means for solving the problem]

[0008] That is, the invention of claim 1 is a product containing a propylene-based resin as a main component, For making bags by welding and sealing An unstretched film, The surface layer is made of propylene resin as the main component and will become the outside of the packaging bag after bag manufacturing, and the middle layer is made mainly of propylene-ethylene block copolymer. , and a sealing layer that will become the inside of the packaging bag after the bag is made, the sealing layer containing a propylene-based resin as the main component and 20% by weight or more of an olefin-based elastomer. The surface layer relates to an unstretched film for food packaging, characterized in that the proportion of components with a molecular weight of 1,000,000 or more, as measured by gel permeation chromatography (GPC) for xylene-soluble components of the resin composition constituting the surface layer, is 0.5% by weight or more of the total resin composition constituting the surface layer.

[0009] The invention of claim 2 relates to the unstretched film for food packaging according to claim 1, wherein the tear strength of the unstretched film in the machine direction (MD) measured based on the following tear strength test (I) is 6.0 (N) or more.

[0010] In the tear strength test (I), a rectangular test piece 63 mm wide and 75 mm long was cut from the unstretched film so that the short side of the rectangle was parallel to the machine direction (MD), and the test piece was fixed with a fixed jaw and a movable jaw attached to a pendulum of an Elmendorf apparatus so that the tear direction was the machine direction (MD) of the unstretched film, and the pendulum was released to separate the fixed jaw and the movable jaw, and the tear strength (N) required to tear the test piece was measured.

[0011] The invention of claim 3 relates to a food packaging bag made from the non-stretched food packaging film of claim 1 or 2, which is fusion-cut with the sealing layer on the inside.

[0012] The invention of claim 4 relates to the food packaging bag of claim 3, which has a gusset portion at the bottom. [Effects of the Invention]

[0013] According to the non-stretched food packaging film of the invention of claim 1, the main component is a propylene-based resin, For making bags by welding and sealing An unstretched film, The surface layer is made of propylene resin as the main component and will become the outside of the packaging bag after bag manufacturing, and the middle layer is made mainly of propylene-ethylene block copolymer. , and a sealing layer that will become the inside of the packaging bag after the bag is made, the sealing layer containing a propylene-based resin as the main component and 20% by weight or more of an olefin-based elastomer. The surface layer contains xylene-soluble components with a molecular weight of 1,000,000 or more as measured by gel permeation chromatography (GPC) in the resin composition constituting the surface layer, and the proportion of these components is 0.5% by weight or more of the total resin composition constituting the surface layer. Therefore, the tear strength of the film can be improved by adjusting the resin composition of the surface layer without the need for complicated adjustments to the resin composition of the intermediate layer, thereby preventing the bag from tearing when food is filled in after it has been made.

[0014] According to the unstretched food packaging film of the invention of claim 2, in the invention of claim 1, the tear strength of the unstretched film in the machine direction (MD) measured based on the tear strength test (I) is 6.0 (N) or more, so when used as a food packaging bag, it can more effectively prevent tearing when food is filled.

[0015] According to the food packaging bag of the invention of claim 3, the bag is made from the non-stretched food packaging film of claim 1 or 2, and is fused and molded with the sealing layer on the inside, resulting in a packaging bag with properly sealed sides.

[0016] According to the food packaging bag of the invention of claim 4, since the bag of the invention of claim 3 has a gusset portion at the bottom, bread can be suitably packaged. [Brief explanation of the drawings]

[0017] [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

[0018] 1 is an unstretched film for food packaging, primarily composed of a propylene-based resin, and includes three layers: a surface layer 20, an intermediate layer 30, and a seal layer 40. This unstretched film 10 is produced by a known production method such as the T-die method.

[0019] The non-stretched film 10 of the present invention is used as a material for food packaging bags made by welding and sealing, and is configured to be transparent or matte (frosted). There are no particular restrictions on the type of food that can be contained in the food packaging bag, but it is suitably used for packaging breads such as white bread and sweet buns.

[0020] The surface layer 20 is the layer that will become the outer side of the packaging bag after the bag is made. This surface layer 20 functions as a printing layer on which appropriate printing is performed. If necessary, the surface of this surface layer 20 may be subjected to a surface treatment such as a corona treatment to improve the printing performance of the film surface.

[0021] The propylene-based resin constituting the surface layer 20 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 the resin composition constituting the surface layer 20 include a propylene-ethylene block copolymer, a blend of a propylene-ethylene block copolymer and polyethylene, and a blend of a homopolypropylene and / or a propylene random copolymer and polyethylene. The method of blending two or more resins can be selected from compounding, dry blending, etc.

[0022] In particular, in the non-stretched film 10 of the present invention, the surface layer 20 has a xylene-soluble component with a molecular weight of 1,000,000 or more, as measured by gel permeation chromatography (GPC), of 0.5% by weight or more of the total resin composition constituting the surface layer 20. It is believed that the inclusion of a high-molecular-weight component in the surface layer improves the toughness of the non-stretched film 10, making it less likely for a bag to tear even when subjected to impact, thereby preventing bag tearing. Adjusting the resin composition of the surface layer 20 in this way improves the tear strength of the non-stretched film 10.

[0023] The intermediate layer 30 is a layer that imparts stiffness (rigidity) to the film, thereby making the unstretched film 10 suitable for bag making. The intermediate layer 30 is preferably formed so that its thickness in the unstretched film 10 is relatively thicker than that of the other layers. The propylene-based resin that constitutes the intermediate layer 30 is composed mainly of, for example, a propylene-ethylene block copolymer. The type and blending ratio of the resin composition that constitutes the intermediate layer 30 can be conventionally known by adjusting the surface layer 20 as described above, and no complicated adjustments are required.

[0024] To reduce the environmental impact, the intermediate layer 30 may contain recycled materials, such as those obtained through material recycling or chemical recycling, or biomass-derived polyolefin resin. Examples of biomass-derived polyolefin resins include polyethylene-based resins obtained by processing plant materials. Specifically, they are linear low-density polyethylene-based resins obtained by producing ethanol from sugar syrup extracted from plant materials such as sugarcane through alcoholic fermentation using yeast, converting the ethanol to ethylene, and then subjecting the ethanol to a known resinification process. The higher the weight proportion of biomass-derived polyolefin resin in the intermediate layer 30, which accounts for a large portion of the unstretched film 10, the greater the contribution to reducing the environmental impact.

[0025] Furthermore, when a biomass-derived resin is contained in the intermediate layer 30, the tear strength of the film tends to decrease, making it more susceptible to tearing. However, by adjusting the surface layer 20 as described above, the decrease in tear strength of the unstretched film 10 due to the inclusion of a biomass-derived resin is suppressed. Therefore, the biomass-derived resin can be appropriately contained in the resin composition of the intermediate layer 30 without complicated adjustments.

[0026] The sealing layer 40 is the layer that becomes the inside of the packaging bag after bag production and has properties such as low-temperature sealing and easy opening. The propylene-based resin that makes up the sealing layer 40 can be a conventionally known resin composition, and is configured to contain, for example, 20% by weight or more of an olefin-based elastomer. In particular, a propylene-based elastomer produced by a metallocene catalyst is preferred for this sealing layer 40. This propylene-based elastomer has advantages such as being less likely to cause stickiness in the film due to its low content of low-molecular-weight components, and being less likely to cause problems such as slipperiness and blocking even when incorporated in large amounts.

[0027] The unstretched film 10 of the present invention preferably has a film thickness in the range of 20 to 50 μm, more preferably 25 to 35 μm, from the viewpoints of ease of handling, strength, etc. 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%, seal layer 5 to 30%, more preferably surface layer 10 to 30%, intermediate layer 50 to 83%, seal layer 7 to 20%.

[0028] Furthermore, in the case of the unstretched film 10 of the present invention, from the viewpoint of more effectively suppressing the occurrence of tearing when food is filled into the bag when used as a food packaging bag, it is preferable that the tear strength of the unstretched film in the machine direction (MD) measured based on the tear strength test (I) is 6.0 (N) or more.

[0029] The tear strength test (I) was conducted using the Elmendorf tear strength measurement method specified in JIS K 7182-2 (1998), without forming a slit in the test specimen. Specifically, a rectangular test specimen 63 mm wide and 75 mm long was cut from unstretched film 10 so that the short side of the rectangle was parallel to the machine direction (MD). The test specimen was fixed between a fixed jaw and a movable jaw attached to a pendulum of an Elmendorf apparatus so that the tear direction was the machine direction (MD) of the unstretched film 10. The pendulum was then released to separate the fixed jaw from the movable jaw, and the tear strength (N) required to tear the test specimen was measured. The reason for not forming a slit in the test specimen in the tear strength test (I) is that the test was conducted to simulate a situation in which a bag made from this type of film would tear in the unslit portion when filled with food.

[0030] Next, a food packaging bag 50 using the non-stretched film 10 of the present invention will be described, as shown in Figures 2 to 4. The food packaging bag 50 is made by folding the non-stretched food packaging film 10 with the sealing layer 40 on the inside and then welding the folded portion 11, which will become the bottom 52 of the non-stretched film 10, in a direction perpendicular to the folded portion 11, thereby cutting and heat-sealing the non-stretched film 10 to form it into a bag shape. The method for welding the bag can be appropriately selected from known methods, and a welding bag of an appropriate shape, such as a square-bottom gusset bag, can be obtained.

[0031] The food packaging bag 50 of the embodiment shown in Figure 2 has a square bottom gusset 53 at the fusion-cut bottom 52. In this food packaging bag 50, the bag side edge 54 (the bold line portion in the figure) including the side edge 51a of the bag body 51 and the side edge 53a of the square bottom gusset 53 is a fusion-cut and sealed fusion section 55. This packaging bag 50 is produced with the sealing layer 40 of the non-stretch film 10 facing inward, resulting in a bag with the side edge 51a of the bag body 51 properly sealed. The food packaging bag 50 having the square bottom gusset 53 is suitable as a packaging bag for bread.

[0032] Here, the bag-making process for a food packaging bag 50 having a square-bottom gusset portion 53 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, fusion portions 54, 54, are sealed, thereby obtaining the food packaging bag 50 (see FIG. 4).

[0033] 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). [Example]

[0034] [Making packaging bags] To produce the packaging bags of Prototype Examples 1 to 10, 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 to a total thickness of 30 μm to form an unstretched film corresponding to the packaging bags of Prototype Examples 1 to 10, and the surface layer was corona-treated. Next, the resulting unstretched film was folded in half with the seal layer on the inside, and then a square-bottom gusset fold was formed at the bottom. The packaging bags of Prototype Examples 1 to 10 were obtained by fusing the unstretched film using a fusing blade tip angle of 120°, a fusing temperature of 350°C, and a bag-making speed of 194 bags / min using a fusing bag-making device (Totani Giken Kogyo Co., Ltd.: "HK-40V")

[0035] [Materials used] The following resins were used as the resin compositions for the surface layer, intermediate layer, and 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.

[0036] For each resin used, the proportion (%) of xylene-soluble matter with a molecular weight of 1,000,000 or more was determined. To determine the xylene-soluble matter proportion, 5-6 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 precipitate of xylene-soluble matter, Y). Therefore, the xylene-soluble matter proportion, Z (%), was calculated from the weight of resin before dissolution, X, and the weight of precipitate of xylene-soluble matter, Y, according to the following formula (i):

[0037]

number

[0038] The molecular weight distribution of the xylene-soluble fraction obtained by the above procedure was measured using gel permeation chromatography (GPC), and the proportion V (%) of xylene-soluble fraction with a molecular weight of 1,000,000 or more was calculated from the obtained molecular weight distribution. Then, the proportion W (%) of xylene-soluble fraction with a molecular weight of 1,000,000 or more for each resin was calculated based on the following formula (ii). The GPC measurement was performed using an Agilent PL-GPC220 model under the following conditions. A calibration curve was prepared using standard polystyrene, and the molecular weight and molecular weight distribution were calculated as values ​​converted into standard polystyrene. Column: Two Agilent PLgel Olexis columns connected with an Agilent guard column Eluent: o-dichlorobenzene Temperature: 145℃ Flow rate: 1.0ml / min Pretreatment: Hot filtration (0.5 μm filter) Detector: Differential refractometer (RI)

[0039]

number

[0040] Resin A1: Propylene-ethylene block copolymer (Japan Polypropylene Corporation: "BC6DRF"), MFR (230°C, 2.16 kg): 2.5 g / 10 min, xylene solubles with a molecular weight of 1,000,000 or more: 5.2% Resin A2: Propylene-ethylene block copolymer (Japan Polypropylene Corporation: "BC4FC"), MFR (230°C, 2.16 kg): 8.0 g / 10 min, proportion of xylene-soluble matter with a molecular weight of 1,000,000 or more: 3.8% Resin A3: Propylene-ethylene block copolymer (Prime Polymer Co., Ltd.: "F-274NP"), MFR (230°C, 2.16 kg): 2.5 g / 10 min, xylene-soluble fraction with a molecular weight of 1,000,000 or more: 1.5%

[0041] Resin B1: Polypropylene material (Japan Polypropylene Corporation: "BX3FC"), MFR (230°C, 2.16 kg): 8.0 g / 10 min, proportion of xylene-soluble matter with a molecular weight of 1,000,000 or more: 0.0%

[0042] Resin C1: Homopolypropylene (Japan Polypropylene Corporation: "FB3B"), MFR (230°C, 2.16 kg): 7.5 g / 10 min, xylene soluble matter with a molecular weight of 1,000,000 or more: 0.4%

[0043] Resin D1: Propylene random copolymer (Japan Polypropylene Corporation: "FW4BT"), MFR (230°C, 2.16 kg): 6.5 g / 10 min, xylene solubles with a molecular weight of 1,000,000 or more: 0.5% Resin D2: Propylene random copolymer (Japan Polypropylene Corporation: "WXK1233"), MFR (230°C, 2.16 kg): 7.0 g / 10 min, xylene solubles with a molecular weight of 1,000,000 or more: 0.2% Resin D3: Propylene random copolymer (Japan Polypropylene Corporation: "WFW4M"), MFR (230°C, 2.16 kg): 7.0 g / 10 min, xylene solubles with a molecular weight of 1,000,000 or more: 0.3%

[0044] Resin E1: Low-density polyethylene (Ube Maruzen Polyethylene Co., Ltd.: "R300"), MFR (190°C, 2.16 kg): 0.35 g / 10 min, xylene-soluble fraction with a molecular weight of 1,000,000 or more: 0.0%, density: 0.920 g / cm 3

[0045] Resin F1: Plant-derived linear low-density polyethylene (Braskem: SLH118), MFR (190°C, 2.16 kg): 1 g / 10 min, xylene-soluble fraction with a molecular weight of 1,000,000 or more: 0.5%, density: 0.916 g / cm 3

[0046] Resin G1: Metallocene-catalyzed ethylene elastomer (Mitsui Chemicals, Inc.: "P0280"), MFR (190°C, 2.16 kg): 3 g / 10 min, xylene-soluble fraction with a molecular weight of 1,000,000 or more: 0.6%, density: 0.869 g / cm 3

[0047] Resin H1: Metallocene-catalyzed propylene elastomer (ExxonMobil: VISTAMAXX3980FL), MFR (230°C, 2.16 kg): 8 g / 10 min, xylene-soluble fraction with a molecular weight of 1,000,000 or more: 3.8%, density: 0.878 g / cm 3

[0048] [Prototype 1] Prototype example 1 is a packaging bag made from a matte unstretched film with a surface layer consisting of 40% by weight of resin A1, 50% by weight of resin B1, and 10% by weight of resin E1, a middle layer consisting of 100% by weight of resin A3, and a seal layer consisting of 35% by weight of resin D3 and 65% by weight of resin H1, with the surface layer being 4 μm thick, the middle layer being 22 μm thick, and the seal layer being 4 μm thick.

[0049] [Prototype 2] Prototype 2 is a packaging bag made from a matte, unstretched film that was formed using the same composition as Prototype 1, except that the resin composition of the middle layer was changed to 82% by weight of resin A3 and 18% by weight of resin F1.

[0050] [Prototype 3] Prototype 3 is a packaging bag made of a matte, unstretched film that is identical to prototype 1, except that the thickness of each layer is changed to 8 μm for the surface layer, 18 μm for the middle layer, and 4 μm for the seal layer.

[0051] [Prototype 4] Prototype 4 is a packaging bag made from a matte, unstretched film in which the surface layer is 100% by weight of resin A1, the middle layer is 100% by weight of resin A3, and the seal layer is 35% by weight of resin D3 and 65% by weight of resin H1 (the composition of the middle layer and seal layer is the same as in Prototype 1), with the surface layer being 8 μm thick, the middle layer being 18 μm thick, and the seal layer being 4 μm thick (the thickness of each layer is the same as in Prototype 3).

[0052] [Prototype 5] Prototype 5 is a packaging bag made of a matte unstretched film formed in the same manner as Prototype 4, except that the surface layer contains 100% by weight of Resin A2.

[0053] [Prototype 6] Prototype 6 is a packaging bag made of a matte unstretched film formed in the same manner as Prototype 4, except that the surface layer contains 100% by weight of Resin B1.

[0054] [Prototype 7] Prototype 7 is a packaging bag made from a matte, unstretched film that was formed with the same composition as Prototype 6, except that the resin composition of the middle layer was changed to 85% by weight of resin A3 and 15% by weight of resin F1.

[0055] [Prototype 8] Prototype 8 is a packaging bag made from a matte, unstretched film that is identical to prototype 4 except that the surface layer is made of 20% by weight of resin A1 and 80% by weight of resin B1.

[0056] [Prototype 9] Prototype 9 is a packaging bag made of a transparent unstretched film formed in the same manner as Prototype 4, except that the surface layer is made of 100% by weight of Resin D2.

[0057] [Prototype 10] Prototype 10 is a packaging bag made of a transparent, unstretched film that is identical in composition to prototype 4, except that the surface layer is changed to 54% by weight of resin C1, 41% by weight of resin D1, and 5% by weight of resin G1.

[0058] For the packaging bags of Samples 1 to 10, the resin compositions of the layers of the film that make up the packaging bags are shown in Tables 1 and 2.

[0059] [Table 1]

[0060] [Table 2]

[0061] To evaluate the performance of each film used in the packaging bags of prototypes 1 to 10, the proportion of xylene-soluble matter with a molecular weight of 1,000,000 or more in the surface layer, tear strength, haze value, tensile modulus, and fusion strength of the gusset portion were measured. All tests were carried out indoors at 23°C.

[0062] [Xylene soluble content in surface layer] For the unstretched films corresponding to prototype examples 1 to 10, the proportion of xylene-soluble components in the surface layer with a molecular weight of 1,000,000 or more was determined from the blending ratio of the resin material constituting the surface layer and the proportion of xylene-soluble components with a molecular weight of 1,000,000 or more in each resin material.

[0063] [Tear strength] A tear strength test was conducted on the unstretched films corresponding to Prototype Examples 1 to 10. In the tear strength test, a rectangular test piece 63 mm wide and 75 mm long was first cut from unstretched film 10 so that the short side of the rectangle was parallel to the machine direction (MD). The test piece was then clamped between the fixed and movable jaws of an Elmendorf machine so that the tear direction was the machine direction (MD). The pendulum of the movable jaw was then released, separating the fixed and movable jaws to tear the test piece, and the tear strength (N) was measured. This measurement was conducted 16 times for each of Prototype Examples 1 to 10, and the average value was used as the tear strength for each of Prototype Examples 1 to 10. The tear strength was evaluated as follows: a tear strength of 6.0 N or greater was rated as "good" (◯), and a tear strength of less than 6.0 N was rated as "poor" (×).

[0064] [Haze value] The haze values ​​of the unstretched films corresponding to Samples 1 to 10 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 the matte packaging bags of Samples 1 to 8, the haze value was evaluated as "good" (◯) if the measurement result was 40% or more, and "poor" (×) if the measurement result was less than 40%. For the transparent packaging bags of Samples 9 and 10, the haze value was evaluated as "good" (◯) if the measurement result was 10% or less, and "poor" (×) if the measurement result was more than 10%.

[0065] Tensile modulus The tensile modulus (GPa) of the unstretched films corresponding to Prototype Examples 1 to 10 was measured in accordance with JIS K 7127 (1999). A tensile tester (Tensilon Universal Testing Machine RTF-1310, manufactured by A&D Co., Ltd.) was used to measure the modulus of elasticity in two directions: the machine direction (MD) and the transverse direction (TD) perpendicular to the MD. The stiffness of the unstretched films 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 (×)."

[0066] [Fusing strength of gusset part] For the packaging bags of prototypes 1 to 10, the fusion strength (N / 15 mm width) of the fusion portion of the gusset (reference numeral 53a in Figure 2) was measured. For this measurement, the fusion portion of the gusset of the packaging bag was cut out to a width of 15 mm, and using a tensile tester (Shimadzu Corporation; small tabletop tester EZ-SX), two films were clamped in each of the upper and lower chucks and pulled at 200 mm / min to determine the strength at the time the fusion portion broke. The fusion strength of the gusset portion was evaluated as "good (◯)" if the measurement result was 15 N / 15 mm width or more, and "poor (×)" if the measurement result was less than 15 N / 15 mm width.

[0067] The test results and evaluations of each film corresponding to the packaging bags of prototype examples 1 to 10 and the packaging bags of prototype examples 1 to 9 are shown in Tables 3 and 4. In Tables 3 and 4, the overall evaluation was given as "good (◯)" if all the evaluations of each test were "good (◯)" or better, and as "bad (×)" if there was even one "bad (×)".

[0068] [Table 3]

[0069] [Table 4]

[0070] [Results and Discussion] As shown in Tables 1 to 4, prototypes 1 to 5, 8, and 10 received an overall rating of "good (◯)," while prototypes 6, 7, and 9 received an overall rating of "poor (×)." For prototypes 1 to 8, which were made with matte film, there were no significant differences in haze value, tensile modulus, or gusset fusing strength, and all met the required performance. For prototypes 9 and 10, which were made with transparent film, there were no significant differences in haze value, tensile modulus, or gusset fusing strength, and all met the required performance. On the other hand, differences were observed in the proportion of xylene-soluble matter with a molecular weight of 1,000,000 or more in the surface layer and in tear strength between prototypes 1 to 5, 8, and 10, which received an overall rating of "good (◯)," and prototypes 6, 7, and 9, which received an overall rating of "poor (×)."

[0071] In prototype 1, a propylene-ethylene block copolymer (resin A1) having a xylene-soluble content of 5.2% with a molecular weight of 1,000,000 or more was used for the surface layer, and the xylene-soluble content of the entire surface layer was 2.1%, resulting in an extremely good tear strength of 15.3 N.

[0072] In prototype 2, the middle layer of prototype 1 contains plant-derived linear low-density polyethylene (resin F1), and the tear strength required for food packaging bags (6.0 N or more) was achieved. In addition, prototype 3, the middle layer of prototype 1 is made thinner, but the surface layer is made thicker, and the tear strength required for food packaging bags (6.0 N or more) was achieved.

[0073] In prototype 4, the surface layer is formed solely of a propylene-ethylene block copolymer (resin A1) with a xylene soluble fraction of 1,000,000 or more in molecular weight at 5.2%, compared to prototype 3. In prototype 5, the surface layer is formed solely of a propylene-ethylene block copolymer (resin A2) with a xylene soluble fraction of 1,000,000 or more in molecular weight at 3.8%, compared to prototype 3. In prototypes 4 and 5, the tear strength was significantly improved compared to prototype 3.

[0074] Unlike prototype 3, prototype 6 has a surface layer made solely of a polypropylene-based material (resin B1) with 0.0% of xylene-soluble matter having a molecular weight of 1,000,000 or more. In prototype 6, the tear strength was significantly lower than in prototype 3, and the required performance for food packaging bags (6.0 N or more) was not achieved. Furthermore, prototype 7, unlike prototype 6, contains plant-derived linear low-density polyethylene (resin F1) in the middle layer, and therefore did not achieve the tear strength required for food packaging bags (6.0 N or more).

[0075] In prototype 8, the proportion of xylene-soluble matter with a molecular weight of 1,000,000 or more in the surface layer was adjusted to 1.0 compared to prototype 4, and the tear strength performance (6.0 N or more) required for food packaging bags was obtained.

[0076] As can be seen from Prototypes 1 to 8, Prototypes 6 and 7, which had significantly poor tear strength, did not contain xylene-soluble components with a molecular weight of 1,000,000 or more in the surface layer, while Prototypes 1 to 5 and 8, which had excellent tear strength, differed in that they contained xylene-soluble components with a molecular weight of 1,000,000 or more in the surface layer. Therefore, it is believed that the inclusion of xylene-soluble components with a molecular weight of 1,000,000 or more in the surface layer improves the tear strength of the film.

[0077] Comparing Prototype 1 and Prototype 2, Prototype 2 contained a biomass-derived resin in the intermediate layer, which resulted in a lower tear strength of the film than Prototype 1, which did not contain a biomass-derived resin. However, compared to Prototype 7, which also contained a biomass-derived resin in the intermediate layer, Prototype 2 showed improved tear strength. From this, it is believed that Prototype 2, like Prototype 1, was able to maintain the tear strength performance (6.0 N or more) required for food packaging bags despite the influence of the biomass-derived resin by adjusting the proportion of xylene-soluble matter with a molecular weight of 1,000,000 or more in the surface layer to 2.1%.

[0078] In Prototype 3, the middle layer was thinner than in Prototype 1, and as a result the tear strength of the film was lower than in Prototype 1, which had a thicker middle layer. However, in Prototype 3, by adjusting the proportion of xylene-soluble matter with a molecular weight of 1,000,000 or more in the surface layer to 2.1%, it is believed that the tear strength performance (6.0 N or more) required for food packaging bags was maintained even in a film with a thin middle layer.

[0079] In prototypes 4 and 5, the proportion of xylene soluble matter with a molecular weight of 1,000,000 or more in the surface layer is higher than in prototype 3, and the tear strength is also improved. On the other hand, prototype 8 has a lower proportion of xylene soluble matter with a molecular weight of 1,000,000 or more in the surface layer than in prototypes 3 to 5, but still achieved the tear strength performance (6.0 N or more) required for food packaging bags. From prototypes 3 to 5 and 8, it appears that there is a tendency for tear strength to improve by increasing the proportion of xylene soluble matter with a molecular weight of 1,000,000 or more in the surface layer.

[0080] Prototype 9 was a bag made from a transparent film, with the surface layer made solely of a propylene random copolymer (resin D2) with a xylene-soluble content of 0.2% having a molecular weight of 1,000,000 or more. Prototype 9 did not achieve the tear strength (6.0 N or more) required for food packaging bags.

[0081] On the other hand, in prototype 10, the surface layer is composed of homopolypropylene (resin C1) with a xylene soluble content of 0.4% having a molecular weight of 1,000,000 or more, 0.5% propylene random copolymer (resin D1), and 0.6% ethylene elastomer (resin G1), and the xylene soluble content of the entire surface layer is adjusted to 0.5%. In prototype 10, the tear strength was significantly improved compared to prototype 9.

[0082] As can be seen from Prototypes 9 and 10, even if the surface layer contains an insufficient amount of xylene-soluble matter with a molecular weight of 1,000,000 or more, it is believed that sufficient tear strength cannot be obtained. Furthermore, it was found that even transparent films can achieve the performance required for food packaging bags (6.0 N or more), just like matte films, if they contain a sufficient amount of xylene-soluble matter.

[0083] As described above, in the non-oriented film of the present invention, the tear strength of the film can be improved by adjusting the proportion of xylene-soluble components with a molecular weight of 1,000,000 or more in the resin composition constituting the surface layer, without the need for complicated adjustments to the resin composition of the intermediate layer. As a result, the occurrence of tearing during food filling after bag formation can be appropriately suppressed. [Industrial Applicability]

[0084] The non-stretched food packaging film and food packaging bag of the present invention can improve the tear strength of the film by adjusting the resin composition that makes up the surface layer, and can appropriately suppress the occurrence of tearing when food is filled into the bag after it has been made. Therefore, they are promising alternatives to conventional non-stretched food packaging films and food packaging bags. [Explanation of symbols]

[0085] 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 containing a propylene-based resin as a main component and intended for bag making by welding and sealing, a surface layer that is made primarily of a propylene-based resin and that becomes the outside of the packaging bag after bag production; an intermediate layer mainly made of a propylene-ethylene block copolymer; a sealing layer that is the inner side of the packaging bag after the bag is made, the sealing layer containing a propylene-based resin as the main component and 20% by weight or more of an olefin-based elastomer; The surface layer has a xylene-soluble component having a molecular weight of 1,000,000 or more as measured by gel permeation chromatography (GPC) of 0.5% by weight or more of the total resin composition constituting the surface layer. A non-stretched food packaging film characterized by:

2. 2. The non-stretched food packaging film according to claim 1, wherein the tear strength of the non-stretched film in the machine direction (MD) measured based on the following tear strength test (I) is 6.0 (N) or more. Tear strength test (I): A rectangular test piece 63 mm wide and 75 mm long was cut from the unstretched film so that the short side of the rectangle was parallel to the machine direction (MD), and the test piece was fixed by a fixed jaw and a movable jaw attached to a pendulum of an Elmendorf apparatus so that the tear direction was the machine direction (MD) of the unstretched film, and the pendulum was released to separate the fixed jaw and the movable jaw, and the tear strength (N) required to tear the test piece was measured.

3. 3. A food packaging bag made from the non-stretched food packaging film according to claim 1 or 2, the food packaging bag being fusion-cut with the sealing layer on the inside.

4. 4. The food packaging bag according to claim 3, further comprising a square bottom gusset at the bottom.

Images