Non-stretched film and food packaging bags

Abstract

The present invention provides a non-stretched film made of a propylene-based resin that has various film properties suitable for use in food packaging bags and that can suppress changes in heat seal strength over time, and a food packaging bag using the film. [Solution] The unstretched film (10) consists of three layers: a surface layer (20), an intermediate layer (30), and a sealing layer (40). The surface layer and the intermediate layer are mainly made of propylene-based resin, and the sealing layer is composed of a composition containing 20-80% by weight of a single-site catalyzed elastomer, 18-78% by weight of a propylene random copolymer, and 2-20% by weight of linear low-density polyethylene.

Description

[Technical Field]

[0001] The present invention relates to a non-stretched film and a food packaging bag using the 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 to manufacture this type of food packaging bag are generally configured with three layers: a surface layer, an intermediate layer, and a seal layer, and are required to have the various properties necessary for food packaging bags, such as film tear resistance, fusing strength, low-temperature sealing properties, easy-open properties, and bag formability. Thus, a non-stretched film made of a propylene-based resin that has excellent easy-open properties and fusing strength is known as a film for packaging bags (see Patent Document 1). In this non-stretched film, the surface layer, intermediate layer, and heat-sealing layer each contain a propylene-based resin as a main component, and the heat-sealing layer contains 50 to 90% by weight of a propylene-based resin and 10 to 50% by mass of an ethylene-1-butene copolymer rubber.

[0004] Another known example is a polyolefin multilayer film having a heat-sealable layer made 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 (see Patent Document 2). This film has excellent low-temperature heat-sealability and easy-open properties while maintaining its fusing strength, and is therefore suitable for use as a packaging bag.

[0005] However, among such unstretched films with easy-to-open properties, the heat-seal strength decreases over time (for example, one day after heat sealing), which poses a problem that even if the opening of the bag is heat-sealed to achieve the desired strength, the openability changes over time.

[0006] On the other hand, there is also an easy-open film that suppresses changes in heat seal strength over time (see, for example, Patent Document 3). This film is composed of a layer of propylene-based resin or ethylene-based resin and a seal layer consisting of 40 to 87% by weight of ethylene-α-olefin copolymer resin, 10 to 40% by weight of crystalline polypropylene, and 3 to 20% by weight of low-molecular-weight polyethylene wax, and it is described that the xylene-soluble fraction at 5°C and density of the ethylene-α-olefin copolymer in the seal layer satisfy a specific relationship, resulting in little change in low-temperature heat sealability over time.

[0007] Incidentally, in films that are heat-cut and sealed to package foods such as bread, it is preferable that the surface layer, intermediate layer, and sealing layer are each composed mainly of the same type of resin, such as a propylene-based resin, in terms of compatibility between the layers, as in Patent Document 1. Therefore, even in this type of non-oriented film made of a propylene-based resin, it is necessary to suppress changes in heat-seal strength over time. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] WO2021 / 039352 publication [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-210897 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-172794 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been proposed in light of the above-mentioned circumstances, and provides a non-oriented film made of a propylene-based resin that has various film properties suitable for use in food packaging bags and can suppress changes in heat seal strength over time, and a food packaging bag using this film. [Means for solving the problem]

[0010] That is, the invention of claim 1 relates to a non-stretched film consisting of three layers: a surface layer, an intermediate layer, and a sealing layer, wherein the surface layer and the intermediate layer are mainly made of a propylene-based resin, and the sealing layer has a composition containing 20 to 80% by weight of an elastomer produced by a single-site catalyst, 18 to 78% by weight of a propylene random copolymer, and 2 to 20% by weight of a linear low-density polyethylene.

[0011] A second aspect of the present invention relates to the non-stretched film according to the first aspect, wherein the intermediate layer contains a propylene-ethylene block copolymer.

[0012] The invention of claim 3 relates to a food packaging bag using the non-stretched film described in claim 1 or 2, characterized in that the food packaging bag is fused and made with the sealing layer of the non-stretched film on the inside. [Effects of the Invention]

[0013] The unstretched film of the invention of claim 1 is an unstretched film consisting of three layers: a surface layer, an intermediate layer, and a sealing layer, wherein the surface layer and the intermediate layer are primarily made of a propylene-based resin, and the sealing layer is composed of a composition containing 20 to 80% by weight of a single-site catalyzed elastomer, 18 to 78% by weight of a propylene random copolymer, and 2 to 20% by weight of linear low-density polyethylene.Therefore, the film has various excellent film properties suitable for use in food packaging bags, and can appropriately suppress changes in heat seal strength over time.

[0014] According to the non-stretched film of the invention of claim 2, in the invention of claim 1, the intermediate layer contains a propylene-ethylene block copolymer, so that tears are less likely to occur in the fused portion after fusion-cutting bag formation.

[0015] According to the food packaging bag of the invention of claim 3, the food packaging bag is made using the non-stretched film of claim 1 or 2, and is produced by fusion cutting with the sealing layer of the non-stretched film on the inside, so that the sides are properly sealed, thereby providing a packaging bag in which changes in heat seal strength over time are suppressed. [Brief explanation of the drawings]

[0016] [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

[0017] 1 is a non-stretched film made of a propylene-based resin and consisting of three layers: a surface layer 20, an intermediate layer 30, and a seal layer 40. This film 10 is produced by a known production method such as a T-die method.

[0018] The non-stretched film 10 of the present invention is used primarily as a material for food packaging bags that are produced by welding and sealing. The film 10 can be configured to have a transparent or matte appearance (frosted finish) depending on the intended use. When the non-stretched film 10 is configured to have a matte finish, it is preferable that the haze value measured in accordance with JIS K 7136 (2000) be 40% or more. On the other hand, when the film is configured to be transparent, it is preferable that the haze value be less than 10%.

[0019] The surface layer 20 is the layer that will become the outer side of the packaging bag after bag production, and corresponds to 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.

[0020] The intermediate layer 30 is a layer that imparts stiffness (rigidity) to the film and thereby makes the non-stretched film 10 suitable for bag making. It is preferable that the thickness of the intermediate layer 30 in the non-stretched film 10 is formed to be relatively thick compared to the other layers.

[0021] The surface layer 20 and the intermediate layer 30 are composed mainly of a propylene-based resin, with a resin other than the propylene-based resin being mixed in as needed. 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). The blending ratio of the propylene-based resin is not particularly limited as long as it is the largest ratio among the blended resins, including the case where the propylene-based resin is 100% by weight.

[0022] Specific examples of resins constituting the surface layer 20 include, in the case of a transparent film, propylene homopolymer, propylene-ethylene random copolymer, and propylene-ethylene-butene random copolymer. These may be used alone or in combination. Furthermore, an elastomer component such as an ethylene-based elastomer, a propylene-based elastomer, or a styrene-based elastomer may also be added to these. When an elastomer component is added, the blending amount should be within 10% by weight. A blending amount exceeding 10% by weight reduces heat resistance, potentially resulting in adhesion of the film to the hot blade of a fusion-cutting bag-making machine. In the case of a matte film, examples include propylene-ethylene block copolymers, blends of propylene-ethylene block copolymers and polyethylene, and blends of homopolypropylene and / or propylene random copolymers and polyethylene. Methods for blending two or more resins include compounding and dry blending.

[0023] The resin constituting the mid layer 30 preferably has a composition containing a propylene-ethylene block copolymer. The propylene-ethylene block copolymer preferably has 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%, there is a risk that cracks will easily occur in the fused portion.

[0024] The melt flow rate (MFR) of the resin composition constituting the surface layer 20 and the intermediate layer 30 is not particularly limited, but from the viewpoint of film formability and the occurrence of poor appearance (whiskers) in the weld-sealed portion, it is preferably 0.1 to 20 g / 10 min, and more preferably 1 to 13 g / 10 min, under the conditions of 230°C and a load of 2.16 kg as specified in JIS K 7210. The MFR of the resin composition constituting the surface layer 20 and the intermediate layer 30 may be measured by actually mixing the resin composition and pelletizing it in an extruder, or more simply, it may be calculated as a calculated MFR from the MFRs of the respective constituent resins using the following formula (i):

[0025]

number

[0026] Here, the symbols in formula (i) are as follows: MFR X : Calculated MFR of resin composition (g / 10 min) n: total number of resins constituting the resin composition w i : Blending ratio of resin i constituting the resin composition MFR i : MFR (g / 10 min) of resin i constituting the resin composition

[0027] The sealing layer 40 is the layer that becomes the inside of the packaging bag after the bag is made, and has properties such as low-temperature sealing property and easy opening property. 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 elastomer, 18 to 78% by weight of a propylene random copolymer, and 2 to 20% by weight of a linear low-density polyethylene.

[0028] Propylene-based elastomers produced with a single-site catalyst (metallocene catalyst or geometrically constrained catalyst) are particularly preferred. Propylene-based elastomers produced with a single-site catalyst have advantages such as the fact that they contain fewer low-molecular-weight components, making the film less sticky, and that even when the blending ratio is large, 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 melt flow rate is higher, the film may stretch when the sealed portion is peeled, which may result in an inability to easily open the film. The melt flow rate (MFR) of the propylene-based elastomer is not particularly limited, but from the viewpoint of film formability and the occurrence of poor appearance (whiskers) in the weld-cut sealed portion, it is preferably 0.1 to 20 g / 10 min, and more preferably 1 to 13 g / 10 min, under the conditions of 230°C and a load of 2.16 kg as specified in JIS K 7210.

[0029] Propylene random copolymers are resins that adjust the heat-sealing initiation temperature and ensure heat-sealing performance. Examples of such 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 butene. The melting point of the propylene random copolymer is preferably 120°C or higher, more preferably 125°C or higher, to ensure heat-sealing performance. The melt flow rate (MFR) of the propylene random copolymer is not particularly limited, but is preferably 0.1 to 20 g / 10 min, more preferably 1 to 13 g / 10 min, under the conditions of 230°C and a load of 2.16 kg as specified in JIS K 7210, from the viewpoints of film formability and the occurrence of poor appearance (whiskers) at the weld-sealed portion.

[0030] Linear low-density polyethylene is a random copolymer of ethylene and an α-olefin having 3 to 8 carbon atoms. When blended into the seal layer 40 in the above-mentioned blending ratio, deterioration of heat seal strength over time is suppressed. Specific α-olefins for linear low-density polyethylene include, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene, and multiple types may be used. If the α-olefin has fewer than 3 carbon atoms, the introduction of the α-olefin is meaningless. Furthermore, it is almost impossible to obtain a resin containing an α-olefin having 9 or more carbon atoms. Therefore, taking into consideration realistic availability and appropriate performance, the appropriate range for the carbon number of the α-olefin is 3 to 8. The melt flow rate (MFR) of the linear low-density polyethylene is not particularly limited, but from the viewpoint of film formability, it is preferably 0.1 to 20 g / 10 min, and more preferably 1 to 10 g / 10 min, under the conditions of 190°C and a load of 2.16 kg as specified in JIS K 7210. Furthermore, the density of the linear low-density polyethylene is preferably 0.940 or less, and more preferably 0.930 or less. The linear low-density polyethylene may be plant-derived or fossil-derived.

[0031] The materials used in the non-stretched film 10 of the present invention can be freely selected from fossil-derived, biomass-derived, material-recycled, and chemical-recycled materials. Furthermore, 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 sealing 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, small amounts of resin may be unintentionally blended, but this can be used as long as it does not impair the properties of each layer.

[0032] From the viewpoints of ease of handling and strength, the film 10 preferably has a thickness in the range of 20 to 50 μm, more preferably 25 to 40 μm. Furthermore, the thickness of each layer is not particularly limited, but the thickness of the surface layer and the sealing layer is preferably 2 μm or more, more preferably 3 μm or more. The proportions of each layer are set, for example, as follows: surface layer 5 to 40%, intermediate layer 30 to 90%, sealing layer 5 to 30%, more preferably surface layer 10 to 30%, intermediate layer 50 to 83%, sealing layer 7 to 20%.

[0033] 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.

[0034] 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.

[0035] 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).

[0036] 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).

[0037] 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]

[0038] [Making a fusion-cut bag] To produce the fusion-cut bags (food packaging bags) of Prototype Examples 1 to 19, the materials described below were first dry-blended and co-extruded using a three-layer co-extrusion 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 19. 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 bags were then fusion-cut 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, to obtain the fusion-cut bags of Prototype Examples 1 to 19.

[0039] [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, and the density was measured in accordance with JIS K 7112.

[0040] The xylene-soluble fraction (%) of resins A1 and A2 was also determined. To determine the xylene-soluble fraction, 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 xylene-soluble precipitate, Y). From the weight of resin before dissolution, X, and the weight of the xylene-soluble precipitate, Y, the xylene-soluble fraction (%) was calculated according to the following formula (ii):

[0041]

number

[0042] Furthermore, the melting points (°C) of Resins B1 to B3 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.

[0043] 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

[0044] Resin B1: 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 B2: 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 B3: 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℃

[0045] Resin C1: 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

[0046] Resin D1: Single-site catalyzed propylene elastomer (Dow Chemical Company; "VERSIFY3200"), MFR (230°C, 2.16 kg): 8 g / 10 min, density 0.876 g / cm 3 Resin D2: Single-site catalyzed propylene elastomer (ExxonMobil Corporation; "VISTAMAXX 6102FL"), MFR (230°C, 2.16 kg): 3 g / 10 min, density 0.862 g / cm 3 Resin D3: Single-site catalyzed propylene elastomer (ExxonMobil Corporation; "VISTAMAXX3588FL"), MFR (230°C, 2.16 kg): 8 g / 10 min, density 0.889 g / cm 3

[0047] 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: 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 E3: Linear low-density polyethylene (KF360T, manufactured by Japan Polyethylene Co., Ltd.), MFR (190°C, 2.16 kg): 3.5 g / 10 min, density 0.898 g / cm 3

[0048] Resin F1: High-density polyethylene (Prime Polymer Co., Ltd.; "1300J"), MFR (190°C, 2.16 kg): 13 g / 10 min, density 0.960 g / cm 3

[0049] [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 C1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 33% by weight of resin B1, 65% by weight of resin D1, and 2% by weight of resin E2.

[0050] [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 C1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 31% by weight of resin B1, 65% by weight of resin D1, and 4% by weight of resin E2.

[0051] [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 C1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 25% by weight of resin B1, 65% by weight of resin D1, and 10% by weight of resin E2.

[0052] [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 C1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 31% by weight of resin B1, 65% by weight of resin D1, and 4% by weight of resin E3.

[0053] [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 C1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 29% by weight of resin B1, 65% by weight of resin D1, and 6% by weight of resin E3.

[0054] [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 C1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 25% by weight of resin B1, 65% by weight of resin D1, and 10% by weight of resin E3.

[0055] [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 C1, the middle layer is made of 100% by weight of resin A2, and the sealing layer is made of 25% by weight of resin B1, 65% by weight of resin D1, 3.5% by weight of resin E2, and 6.5% by weight of resin E3.

[0056] [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 C1, the middle layer is made of 100% by weight of resin A2, and the sealing layer is made of 18% by weight of resin B1, 65% by weight of resin D1, 3.5% by weight of resin E2, and 13.5% by weight of resin E3.

[0057] [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 C1, the middle layer is made of 100% by weight of resin A2, and the sealing layer is made of 43.7% by weight of resin B2, 50% by weight of resin D2, and 6.3% by weight of resin E2.

[0058] [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 C1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 74.4% by weight of resin B2, 20% by weight of resin D2, and 5.6% by weight of resin E2.

[0059] [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 C1, the middle layer is made of 70% by weight of resin A2, 15% by weight of resin B1, and 15% by weight of resin E1, and the seal layer is made of 74.4% by weight of resin B2, 20% by weight of resin D2, and 5.6% by weight of resin E2.

[0060] [Prototype 12] Prototype example 12 is a fusion-cut bag made of a non-stretched film in which the surface layer is 100% by weight of resin B2, the middle layer is 100% by weight of resin A2, and the sealing layer is 30% by weight of resin B3, 65% by weight of resin D1, and 5% by weight of resin E2.

[0061] [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 C1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 35% by weight of resin B1 and 65% by weight of resin D1.

[0062] [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 C1, the middle layer is made of 100% by weight of resin A2, and the seal layer is made of 100% by weight of resin D3.

[0063] [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 C1, the middle layer is made of 100% by weight of resin A2, and the sealing layer is made of 33% by weight of resin B1, 65% by weight of resin D1, and 2% by weight of resin F1.

[0064] [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 C1, the middle layer is made of 100% by weight of resin A2, and the sealing layer is made of 32% by weight of resin B1, 65% by weight of resin D1, and 3% by weight of resin F1.

[0065] [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 C1, the middle layer is made of 100% by weight of resin E2, and the sealing layer is made of 29% by weight of resin B1, 65% by weight of resin D1, and 6% by weight of resin E2.

[0066] [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 C1, the middle layer is made of 100% by weight of resin E2, and the sealing layer is made of 35% by weight of resin B1 and 65% by weight of resin D1.

[0067] [Prototype 19] Prototype example 19 is a fusion-cut bag made of a non-stretched film in which the surface layer is 100% by weight of resin B2, the middle layer is 100% by weight of resin A2, and the sealing layer is 35% by weight of resin B3 and 65% by weight of resin D1.

[0068] For the fusion-cut bags of prototypes 1 to 19, the resin compositions of the layers of the film that constitute the fusion-cut bags are shown in Tables 1 to 3.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] The performance of each film used in the fusion-cut bags of prototypes 1 to 19 was evaluated by measuring the heat-seal initiation temperature (immediately after, one day after, and change over time), ease of opening (immediately after, one day after), haze value, tensile modulus, fusion strength of the gusset portion, and fusion strength of the bag itself. All tests were conducted in a room at 23°C.

[0073] [Heat sealing start temperature (immediately after)] The heat-seal initiation temperature of films corresponding to Prototype Examples 1 to 19 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. Immediately after heat-sealing, 15 mm-wide test pieces were cut out. The heat-sealed fused 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-seal strength reached 3 N / 15 mm width (heat-seal initiation temperature). Low-temperature sealability was evaluated as follows: a heat-seal initiation temperature between 80 and 120°C was rated "Good" (◯), and a heat-seal initiation temperature below 80°C or above 120°C was rated "Poor" (×).

[0074] [Heat seal starting temperature (after 1 day)] The heat-seal initiation temperature of the films corresponding to Prototype Examples 1 to 19 was measured according to JIS Z 1713 (2009). Two sheets of each film were prepared and heat-sealed, with the seal layers overlapping, 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, the films were left at 23°C for 1 day, after which 15 mm-wide test pieces were cut out. The heat-sealed test pieces were opened 180° and the sealed portions were peeled off 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-seal strength reached 3 N / 15 mm width (heat-seal initiation temperature). The low-temperature sealability was evaluated as follows: when the measured heat seal initiation temperature was 80 to 120°C, it was rated as "good (◯)"; when it was less than 80°C or more than 120°C, it was rated as "poor (×)".

[0075] [Heat seal initiation temperature (change over time)] For the films corresponding to Prototype Examples 1 to 19, the temperature (°C) at which the heat-sealing initiation temperature changed over time was calculated by subtracting the measured value for "heat-sealing initiation temperature (immediately after)" from the measured value for "heat-sealing initiation temperature (one day later)." The change in heat-sealing strength over time was evaluated by rating it as "good (◯)" if the temperature change over time was less than 7°C, and "bad (×)" if it was 7°C or higher.

[0076] [Easy to open (immediately after opening)] The films corresponding to Prototype Examples 1 to 19 were tested for ease of opening. Using a heat-sealing tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.; "Thermal Gradient Tester"), two sheets of each film were prepared, 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. Immediately after heat-sealing, 15 mm-wide test pieces were cut out, and the heat-sealed fused test pieces were opened 180°. The test pieces were then pulled at a pulling rate of 200 mm / min using a tensile tester (manufactured by Shimadzu Corporation; "Small Tabletop Tester EZ-SX"), and the peeling state was visually observed. Ease of opening was evaluated as follows: if the film peeled without elongation, it was rated "Good" (◯); if it peeled with elongation, it was rated "Poor" (×).

[0077] [Easy to open (after 1 day)] The films corresponding to Prototype Examples 1 to 19 were tested for ease of opening. Using a heat-sealing tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.; "Thermal Gradient Tester"), two sheets of each film were prepared, 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 leaving the film at 23°C for one day, 15-mm-wide test pieces were cut out. The heat-sealed test pieces were opened 180° and visually inspected for peeling when pulled at a pulling rate of 200 mm / min using a tensile tester (manufactured by Shimadzu Corporation; "Small Tabletop Tester EZ-SX") to evaluate ease of opening. If the film peeled without elongation, it was rated "Good" (◯), and if it peeled with elongation, it was rated "Poor" (×).

[0078] [Haze value] The haze values ​​of the films corresponding to Prototype Examples 1 to 19 were measured in accordance with JIS K 7136 (2000). The haze value (%) is an index of transparency, and was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd.; "Haze Meter NDH-4000").

[0079] Tensile modulus The tensile modulus (GPa) of the films corresponding to Prototype Examples 1 to 19 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 (×)."

[0080] [Fusing strength of gusset part] For the fusion-cut bags of prototypes 1 to 19, 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.

[0081] [Bag body fusing strength] For the fusion-cut bags of prototypes 1 to 19, the fusion strength (N / 15 mm width) of the fusion portion of the bag body (reference numeral 51a in Figure 2) was measured. 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.

[0082] The test results and evaluations for each film corresponding to the fusion-cut bags of prototype examples 1 to 19 and for the fusion-cut bags of prototype examples 1 to 19 are shown in Tables 4 to 6. In Tables 4 to 6, the overall evaluation was given as "good (◯)" if all the evaluations for each test were "good (◯)" or better, and as "bad (×)" if there was even one "bad (×)."

[0083] [Table 4]

[0084] [Table 5]

[0085] [Table 6]

[0086] [Results and Discussion] As shown in Tables 1 to 3 and Tables 4 to 6, the overall evaluation of prototypes 1 to 12 was "good (◯)," while the overall evaluation of prototypes 13 to 19 was "poor (×)." Therefore, the difference in performance between the good prototypes 1 to 12 and the bad prototypes 13 to 19 will be considered by comparing the film configuration of each prototype.

[0087] The haze values ​​of prototypes 1 to 11 and 13 to 18 were all 40% or higher, while the haze values ​​of prototypes 12 and 19 were all less than 10%. That is, prototypes 1 to 11 and 13 to 18 had a surface layer mainly composed of a propylene-ethylene block copolymer, resulting in a good matte finish, while prototypes 12 and 19 had a surface layer mainly composed of a propylene random copolymer, resulting in good transparency.

[0088] First, prototype 13 is a fusion-cut bag made of a conventional propylene-based resin film that does not contain linear low-density polyethylene in the sealing layer. In addition, prototype 14 is a bag made of a relatively high-density (0.889 g / cm) film that does not contain linear low-density polyethylene in the sealing layer. 3 ) propylene-based elastomer without blending linear low-density polyethylene. Comparing prototypes 1 to 8 with prototypes 13 and 14, prototypes 1 to 8 differ from the resin composition of prototype 13 in that linear low-density polyethylene is blended into the sealing layer without changing the blending ratio of resin D1 (propylene-based elastomer) as the main component.

[0089] In prototype 13, which is made of a conventional film, the change in heat seal initiation temperature over time was 10°C, and the heat seal strength decreased significantly over time. In contrast, prototypes 1 to 8, which contain linear low-density polyethylene in the seal layer, all showed a small change in heat seal initiation temperature over time, and the change in heat seal strength over time was suppressed compared to prototype 13. In prototype 14, the change in heat seal initiation temperature over time was small, but easy opening was not achieved.

[0090] Comparing prototypes 1 to 6, prototypes 1 to 3 and prototypes 4 to 6 differ in the type of linear low-density polyethylene blended in the sealing layer, with the linear low-density polyethylene (resin E2) in prototypes 1 to 3 having a higher density than the linear low-density polyethylene (resin E3) in prototypes 4 to 6. Comparing prototypes 2 and 4, and prototypes 3 and 6, which have the same blend ratio of linear low-density polyethylene, no significant differences in performance were observed despite the different types of linear low-density polyethylene.

[0091] In Prototypes 1 to 3, the blending ratio of linear low-density polyethylene was varied. As the blending ratio of linear low-density polyethylene increased, the heat-sealing initiation temperature decreased, and the change in the heat-sealing initiation temperature over time tended to be suppressed. A similar trend was observed in Prototypes 4 to 6. Meanwhile, Prototypes 7 and 8 blended different types of linear low-density polyethylene (resin E2 and resin E3) into the seal layer. The blending ratio of linear low-density polyethylene in Prototype 7 was 10% by weight (resin E2 and resin E3 combined), and no significant difference in performance was observed compared to Prototypes 3 and 6, which had the same blending ratio. Prototype 8 had a higher blending ratio of resin E3 (linear low-density polyethylene with a lower density than resin E2) compared to Prototype 7, and the heat-sealing initiation temperature decreased compared to Prototype 7.

[0092] In Prototypes 9 and 10, the melting point of the propylene random copolymer and the density and blending ratio of the propylene-based elastomer in the seal layer were changed compared to Prototypes 1 to 3. Thus, by changing the melting point of the propylene random copolymer, the density of the propylene-based elastomer, and their blending ratios in the seal layer, the heat-sealing temperature could be appropriately controlled. As can be seen from Prototype 9, no significant changes were observed in the performance characteristics even when different propylene random copolymers or propylene-based elastomers were blended. Furthermore, Prototype 10 had a lower blending ratio of the propylene-based elastomer in the seal layer compared to Prototype 9, resulting in a higher heat-sealing initiation temperature. Furthermore, Prototype 11, compared to Prototype 10, blended a propylene random copolymer (resin B1) and linear low-density polyethylene (resin E1) in the intermediate layer. The tensile modulus of Prototype 11 was improved compared to Prototype 10.

[0093] In contrast to Prototype 1, Prototype 15 contains high-density polyethylene (resin F1) instead of linear low-density polyethylene (resin E2) in the seal layer. In Prototype 15, the change in heat-seal initiation temperature over time was 11°C, the heat-seal strength decreased significantly over time, and easy-open properties were not achieved after one day. Similar results were obtained with Prototype 16, which contained a higher proportion of high-density polyethylene (resin F1) than Prototype 15.

[0094] In prototype 17, the seal layer of the film contains linear low-density polyethylene, and the middle layer is made of linear low-density polyethylene (resin E1). While prototype 17 showed little change in the heat-seal initiation temperature over time, it did not achieve easy opening, and the tensile modulus and the melt-cutting strength of the bag body were significantly reduced. Furthermore, in prototype 18, linear low-density polyethylene (resin E2) was not blended into the seal layer, as compared to prototype 17. In prototype 18, the heat-seal initiation temperature changed more significantly over time than in prototype 17.

[0095] Prototypes 12 and 19 are fusion-cut bags made of transparent film, with Prototype 12 containing linear low-density polyethylene (resin E2) in the seal layer and Prototype 19 not containing linear low-density polyethylene (resin E2) in the seal layer. Prototype 12 showed little change in heat-seal initiation temperature over time, whereas Prototype 19 showed a large change in heat-seal initiation temperature over time.

[0096] As can be seen from the comparison of Prototype Examples 1 to 8 with Prototype Example 13, Prototype Examples 1 to 8, in which linear low-density polyethylene was blended into the seal layer, showed a small change in heat-seal initiation temperature over time. On the other hand, when high-density polyethylene was blended into the seal layer instead of linear low-density polyethylene, as in Prototype Examples 15 and 16, the change in heat-seal initiation temperature over time could not be reduced. Therefore, it was found that blending linear low-density polyethylene into the seal layer reduced the change in heat-seal initiation temperature over time and suppressed the change in heat-seal strength over time. Furthermore, as can be seen from the comparison of Prototype Examples 12 and 19, it was found that even in the transparent type, blending linear low-density polyethylene (resin E2) into the seal layer, as in Prototype Example 12, suppressed the change in heat-seal strength over time.

[0097] As can be seen from Prototypes 1 to 8, the higher the proportion of linear low-density polyethylene in the seal layer, the lower the heat-seal initiation temperature and the more suppressed the change in heat-seal strength over time. Furthermore, as can be seen from Prototypes 10, 11, 17, and 18, even when the intermediate layer and seal layer are composed of various resin compositions, the addition of linear low-density polyethylene to the seal layer suppresses the change in heat-seal strength over time. However, even if the change in heat-seal strength over time is suppressed, as in Prototypes 14 and 17, if other film properties are insufficient, the film is not suitable for use as a food packaging bag.

[0098] Therefore, in order to ensure various film properties suitable for use in food packaging bags and to consider the influence of linear low-density polyethylene on the properties of the sealing layer, the blending ratio of the resin composition of the sealing layer was set at a density of 0.880 g / cm 3 It is considered preferable that the following propylene elastomer is about 20 to 80% by weight, the propylene random copolymer is about 18 to 78% by weight, and the linear low-density polyethylene is about 2 to 20% by weight.

[0099] As described above, the fusion-cut bags of prototypes 1 to 12 were made of a film primarily composed of a propylene-based resin, and exhibited excellent low-temperature sealability (heat-seal initiation temperature), ease of opening, matte finish or transparency (haze value), film stiffness (tensile modulus), and fusion strength at the fusion-cut portion. In particular, the change in heat-seal initiation temperature over time was reduced compared to conventional films. Therefore, these propylene-based resin films possess excellent film properties suitable for use in food packaging bags, and the change in heat-seal strength over time can be appropriately suppressed. [Industrial Applicability]

[0100] 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 in particular, the change in heat seal strength over time is appropriately suppressed. Therefore, they are promising alternatives to conventional non-stretched food packaging films and food packaging bags. [Explanation of symbols]

[0101] 10, 10a to 10d Unstretched film 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 consisting of three layers: a surface layer, an intermediate layer, and a seal layer, the surface layer and the intermediate layer are mainly made of a propylene-based resin, The sealing layer is 20 to 80 weight percent of a single-site catalyzed elastomer; 18 to 78% by weight of a propylene random copolymer; A composition containing 2 to 20% by weight of linear low-density polyethylene A non-stretched film characterized by:

2. 2. The unstretched film according to claim 1, wherein the intermediate layer comprises a propylene-ethylene block copolymer.

3. 3. A food packaging bag using the non-stretch film according to claim 1 or 2, characterized in that the food packaging bag is produced by fusion cutting with the seal layer of the non-stretch film facing inside.

Images