Polypropylene-based unoriented film, packaging material, and packaging body

Abstract

To provide a polypropylene-based non-stretched film which can achieve both heat resistance and low temperature sealability at high levels in a balanced manner, and to provide a packaging material and a package obtained using the polypropylene-based non-stretched film.SOLUTION: A polypropylene-based non-stretched film includes a first layer composed of a first resin composition containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B), wherein a ratio ΔHh / ΔHl of a fusion heat quantity ΔHh on a high temperature side and a fusion heat quantity ΔHl on a low temperature side when the fusion heat quantity of the first resin composition is divided at 135°C is 2.5 to 5.8.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to polypropylene-based unoriented films, packaging materials, and packaging bodies. [Background technology]

[0002] Polypropylene-based films are sometimes used as sealant films in various packaging materials, such as food packaging.

[0003] Patent Document 1 below proposes a sealant film containing a specific crystalline propylene polymer, a specific ethylene-α-olefin copolymer, and a specific copolymer in specific amounts.

[0004] Patent Document 2 below proposes an impact-resistant film comprising layers A and B, and optionally a layer C in a specific order. In this impact-resistant film, layer B is mainly composed of a propylene-ethylene block copolymer, layer C is mainly composed of a specific propylene-based random copolymer, and the unbroken bag rate is within a specific range. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2003-119298 [Patent Document 2] Japanese Patent Publication No. 2017-132186 [Overview of the project] [Problems that the invention aims to solve]

[0006] While unoriented polypropylene films can be used as sealant films, these films require heat resistance to withstand retort processing, such as high-temperature sterilization and disinfection at 135°C under high pressure conditions.

[0007] On the other hand, in recent years, due to increased awareness of environmental issues, there has been growing interest in packaging materials made from the same material, so-called monomaterial packaging, in order to make the packaging materials recyclable. When using polypropylene film as a sealant layer, it is required to use polypropylene film as the base material.

[0008] However, for example, biaxially oriented polypropylene film has a lower melting point compared to conventionally used substrates such as biaxially oriented polyamide film (ONy) and biaxially oriented polyester film (PET). Therefore, packaging materials using biaxially oriented polypropylene film as a substrate cannot be heat-sealed at high temperatures during bag manufacturing. However, our research has revealed that using conventional unoriented polypropylene film as a sealant layer does not provide sufficient sealing performance at low temperatures.

[0009] One aspect of this disclosure, made in view of the above circumstances, provides a polypropylene-based unoriented film that can achieve a high level of balance between heat resistance and low-temperature sealing properties. Another aspect of this disclosure provides packaging materials and packaging bodies obtained using the said polypropylene-based unoriented film. [Means for solving the problem]

[0010] A polypropylene-based unoriented film relating to one aspect of this disclosure comprises a first layer composed of a first resin composition containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B), wherein the heat of fusion ΔH of the first resin composition is divided at 135°C, and the heat of fusion ΔH is the heat of fusion on the high-temperature side. h and the heat of fusion ΔH at the low temperature side l Ratio ΔH h / ΔH l However, it is 2.5 to 5.8. The above polypropylene-based unoriented film has a ΔH h / ΔH lHowever, being within this numerical range allows for a high level of balance between heat resistance and low-temperature sealing properties. Such effects cannot be obtained with conventional polypropylene films (for example, the above-mentioned Patent Documents 1 and 2). These effects are particularly suitable for retort packaging materials made of the same polypropylene material.

[0011] In one embodiment, the ethylene content of the propylene-ethylene random copolymer (B) may be 5% by mass or less. In one embodiment, the first resin composition may further contain a thermoplastic elastomer (E). This makes it easier to obtain cold impact resistance in the polypropylene-based unoriented film.

[0012] In one embodiment, the polypropylene-based unoriented film may further comprise a second layer having a multilayer structure and composed of a second resin composition containing a propylene-ethylene block copolymer (C) and an ethylene-propylene copolymer elastomer (D). This makes it easier to obtain cold impact resistance in the polypropylene-based unoriented film.

[0013] In one embodiment, the polypropylene-based unoriented film further comprises a third layer composed of a third resin composition containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B), wherein the third layer is provided between the first and second layers. This makes it easier to suppress distortion and warping in the polypropylene-based unoriented film.

[0014] A packaging material relating to one aspect of this disclosure comprises the above-mentioned polypropylene-based unoriented film and a resin film having a metal oxide vapor-deposited layer. A packaging material relating to another aspect of this disclosure comprises the above-mentioned polypropylene-based unoriented film and a polypropylene-based biaxially oriented film.

[0015] The packaging relating to one aspect of this disclosure is made from the above-mentioned packaging material. [Effects of the Invention]

[0016] According to one aspect of the present disclosure, a polypropylene-based non-stretched film capable of achieving a high-level balance between heat resistance and low-temperature sealability is provided. Further, according to one aspect of the present disclosure, a packaging material and a package obtained using the polypropylene-based non-stretched film are provided.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a cross-sectional view of a polypropylene-based non-stretched film according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of a polypropylene-based non-stretched film according to a second embodiment of the present disclosure. [Figure 3] FIG. 3 is a cross-sectional view of a polypropylene-based non-stretched film according to a third embodiment of the present disclosure. [Figure 4] FIG. 4 is a cross-sectional view of a packaging material according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a cross-sectional view of a packaging material according to another embodiment of the present disclosure. [Figure 6] FIG. 6 is a cross-sectional view of a packaging material according to still another embodiment of the present disclosure. [Figure 7] FIG. 7 is a cross-sectional view of a packaging material according to still another embodiment of the present disclosure. [Figure 8] FIG. 8 is a cross-sectional view of a packaging material according to still another embodiment of the present disclosure. [Figure 9] FIG. 9 is a cross-sectional view of a packaging material according to still another embodiment of the present disclosure. [Figure 10] FIG. 10 is a cross-sectional view of a packaging material according to still another embodiment of the present disclosure. [Figure 11] FIG. 11 is a cross-sectional view of a packaging material according to still another embodiment of the present disclosure. [Figure 12] FIG. 12 is a cross-sectional view of a packaging material according to still another embodiment of the present disclosure.

Modes for Carrying Out the Invention

[0018] Hereinafter, a plurality of embodiments of the present disclosure will be described in detail while referring to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. Also, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[0019] [Polypropylene-based unstretched film] <First Embodiment> Hereinafter, the polypropylene-based unstretched film according to the first embodiment will be described. FIG. 1 is a cross-sectional view of the polypropylene-based unstretched film 10 (hereinafter, also simply referred to as "film 10") according to the present embodiment. The film 10 is composed of a first layer 1 made of a first resin composition containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B). When the heat of fusion of the first resin composition is divided at 135 °C, the heat of fusion ΔH h on the high-temperature side and the heat of fusion ΔH l on the low-temperature side, the ratio ΔH h / ΔH l is 2.5 to 5.8.

[0020] (Propylene homopolymer (A)) The propylene homopolymer (A) can be obtained, for example, by a method of homopolymerizing propylene using a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst.

[0021] As the propylene homopolymer (A), those having a melting start temperature of 150 °C or higher and a melting point of 155 °C or higher when differential scanning calorimetry is performed under the following conditions can be used. When both the melting start temperature and the melting point are within this range, the film 10 has better heat resistance, and for example, after performing a retort treatment at a high temperature, fusion is less likely to occur on the inner surface of the packaging bag.

[0022] (Differential scanning calorimetry conditions) In accordance with JIS K 7121, when the temperature is increased from 25°C to 230°C at a rate of 10°C / min, the point at which the straight line extending the baseline on the low-temperature side of the DSC curve toward the high-temperature side is drawn, and the tangent line drawn so as to be tangent to the curve on the low-temperature side of the melting peak and have the maximum slope, is defined as the melting start temperature, and the temperature at the peak of the melting peak is defined as the melting point.

[0023] As the propylene homopolymer (A), one with a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) in the range of 2.0 to 7.0 g / 10 min can be used. A melt flow rate above the lower limit reduces the extruder load during molding, making it easier to maintain good productivity without a decrease in processing speed. Furthermore, a melt flow rate below the upper limit tends to provide excellent impact resistance.

[0024] (Propylene-ethylene random copolymer (B)) Propylene-ethylene random copolymer (B) can be obtained by copolymerizing ethylene as a comonomer in a main monomer consisting of propylene, for example, using a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst.

[0025] As the propylene-ethylene random copolymer (B), one can be used whose melting point is in the range of 132 to 150°C when measured by differential scanning calorimetry under the following conditions. By using a material with a melting point within this range, film 10 tends to achieve a better balance of heat resistance and low-temperature sealing properties.

[0026] (Differential scanning calorimetry conditions) In accordance with JIS K 7121, the melting point is defined as the temperature at the peak of the melting curve when the temperature is increased from 25°C to 230°C at a rate of 10°C / min.

[0027] The ethylene content of the propylene-ethylene random copolymer (B) is preferably 6% by mass or less. Keeping the ethylene content below the upper limit tends to maintain low-temperature sealing properties without excessively reducing heat resistance, and further suppresses fusion on the inner surface of the packaging bag after retort processing. From this viewpoint, the ethylene content may be 5.5% by mass or less, 5% by mass or less, or 4.5% by mass or less. The lower limit of the ethylene content is not particularly limited, but from the viewpoint of low-temperature sealing properties, it can be 3% by mass.

[0028] The ethylene content of propylene-ethylene random copolymer (B) can be measured according to the quantitative method for ethylene content (IR method) described on pages 412-413 of the Polymer Analysis Handbook (May 10, 2013, 3rd printing), edited by the Polymer Analysis Symposium of the Japan Society for Analytical Science.

[0029] (Thermoplastic elastomer (E)) The first resin composition preferably further contains a thermoplastic elastomer (E) from the viewpoint of improving the cold impact resistance of the film 10 and further improving its low-temperature sealing properties. As the thermoplastic elastomer (E), for example, propylene-α-olefin copolymer elastomers and ethylene-α-olefin copolymer elastomers can be used. These thermoplastic elastomers (E) can be obtained by copolymerizing propylene or ethylene with an α-olefin having 4 to 20 carbon atoms using, for example, a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst.

[0030] Examples of α-olefin components having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-hexadecene, 1-eicosene, 4-methyl-1-pentene, and 4-methyl-1-hexene, with 1-butene and 1-hexene being preferred. The thermoplastic elastomer (E) may have two or more structural units derived from α-olefins having 4 to 20 carbon atoms.

[0031] As a thermoplastic elastomer (E), its density (JIS K 7112) is 860-950 kg / m³. 3 Materials within this range may be used. A density above the lower limit tends to suppress the tackiness of the film 10. Conversely, a density below the upper limit tends to further improve the low-temperature sealing properties of the film 10.

[0032] As the thermoplastic elastomer (E), one with a melt flow rate (MFR: ISO 1133) (temperature 190°C, load 2.16 kg) in the range of 0.5 to 30 g / 10 min may be used. A melt flow rate above the lower limit reduces the extruder load during molding, making it easier to maintain good productivity without a decrease in processing speed. Furthermore, a melt flow rate below the upper limit improves compatibility with propylene homopolymer (A) and propylene-ethylene random copolymer (B), and tends to further improve the heat resistance of film 10.

[0033] The heat of fusion of the first resin composition is measured by differential scanning calorimetry (JIS K 7122). The heat of fusion ratio ΔH of the first resin composition. h / ΔH l It is preferable that the value is between 2.5 and 5.8.

[0034] The film 10 may contain 10 to 50% by mass of propylene homopolymer (A) and 50 to 90% by mass of propylene-ethylene random copolymer (B), based on the total amount of film 10. A content of propylene homopolymer (A) of 10% by mass or more allows film 10 to maintain even better heat resistance. From this viewpoint, the content may be 15% by mass or more, or 20% by mass or more. A content of propylene homopolymer (A) of 50% by mass or less, that is, a content of propylene-ethylene random copolymer (B) of at least 50% by mass, allows film 10 to exhibit even better low-temperature sealing properties. From this viewpoint, the content of propylene homopolymer (A) may be 45% by mass or less, or 40% by mass or less. From the above viewpoints, the content of propylene-ethylene random copolymer (B) may be 45 to 85% by mass or 40 to 80% by mass.

[0035] If the film 10 contains a thermoplastic elastomer (E), the content of the thermoplastic elastomer (E) may be 5.0 to 11.5 parts by mass per 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B). When the content of the thermoplastic elastomer (E) is within the above range, the film 10 tends to achieve a better balance of heat resistance and low-temperature sealing properties at an even higher level.

[0036] The thickness of film 10 is not particularly limited, as long as it is within the range that can be used as a film for packaging materials, for example. However, if the film is too thick, it will result in a cost disadvantage. For this reason, the thickness of film 10 can be 100 μm or less, and may be between 50 and 70 μm.

[0037] <Second Embodiment> The following describes a polypropylene-based unoriented film according to the second embodiment. Unless otherwise described, the film is the same as the polypropylene-based unoriented film according to the first embodiment. Figure 2 is a cross-sectional view of the polypropylene-based unoriented film 11 (hereinafter also simply referred to as "film 11") according to this embodiment. Film 11 comprises a first layer 1 and a second layer 2 composed of a second resin composition containing a propylene-ethylene block copolymer (C) and an ethylene-propylene copolymer elastomer (D). The film 11 easily achieves excellent cold impact resistance by including the second layer 2.

[0038] (Propylene-ethylene block copolymer (C)) The propylene-ethylene block copolymer (C) may be a copolymer obtained by producing a propylene polymer (C1) in the first step, and then producing an ethylene-propylene copolymer (C2) by gas-phase polymerization in the second step. The propylene-ethylene block copolymer (C) may not be a block copolymer in which the propylene polymer ends and the ethylene-propylene copolymer ends are bonded, but rather a type of blended copolymer.

[0039] As the propylene-ethylene block copolymer (C), one with a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) in the range of 0.5 to 2.5 g / 10 min may be used. A melt flow rate above the lower limit reduces the extruder load during molding, making it easier to maintain excellent productivity without a decrease in processing speed. A melt flow rate below the upper limit makes it easier to obtain excellent cold shock resistance for the film 11.

[0040] The propylene-ethylene block copolymer (C) may contain 90-60% by mass of the propylene polymer (C1) and 10-40% by mass of the ethylene-propylene copolymer (C2). Having each component within this range makes it easier to obtain excellent cold shock resistance. From this viewpoint, the propylene-ethylene block copolymer (C) may contain 87.5-65% by mass of the propylene polymer (C1) and 12.5-35% by mass of the ethylene-propylene copolymer (C2), or 85-70% by mass of the propylene polymer (C1) and 15-30% by mass of the ethylene-propylene copolymer (C2).

[0041] The ethylene content of the ethylene-propylene copolymer (C2) contained in the propylene-ethylene block copolymer (C) is not particularly limited, but can be in the range of 20 to 40% by mass. Keeping the ethylene content below the upper limit suppresses the tackiness of the product, making it less susceptible to contamination by tackiness during manufacturing and easier to maintain excellent productivity. Keeping the ethylene content above the lower limit makes it easier to obtain excellent cold shock resistance for film 11.

[0042] (Ethylene-propylene copolymer elastomer (D)) The ethylene-propylene copolymer elastomer (D) can be obtained by slurry polymerization in the presence of an inert hydrocarbon such as hexane, heptane, or kerosene, or a liquefied α-olefin solvent such as propylene, or by gas-phase polymerization without a solvent. Specifically, the ethylene-propylene copolymer elastomer (D) can be obtained using a known multi-stage polymerization method. That is, it is a polymerizable high-rubber-containing polypropylene resin obtained by polymerization of propylene and / or a propylene-α-olefin polymer in a first-stage reactor, followed by copolymerization of propylene and α-olefin in a second-stage reaction. Because the second layer 2 contains the ethylene-propylene copolymer elastomer (D), the film 11 easily obtains excellent cold impact resistance.

[0043] As the ethylene-propylene copolymer elastomer (D), one with a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) in the range of 0.5 to 3.5 g / 10 min can be used. If the melt flow rate is above the lower limit, the extruder load during molding is reduced, making it easier to maintain excellent productivity without a decrease in processing speed. If the melt flow rate is below the upper limit, the compatibility between the propylene-ethylene block copolymer (C) and the ethylene-propylene copolymer elastomer (D) is good, and the packaging material 11 easily achieves impact resistance.

[0044] As the ethylene-propylene copolymer elastomer (D), one can be used in which the mass ratio of propylene content to ethylene content (propylene content / ethylene content) is in the range of 1.5 to 4. Within this range, the packaging material 11 easily achieves excellent cold shock resistance.

[0045] The second layer 2 may contain 90-50% by mass of propylene-ethylene block copolymer (C) and 10-50% by mass of ethylene-propylene copolymer elastomer (D). A propylene-ethylene block copolymer (C) content of 50% by mass or more makes it easier for the packaging material 11 to maintain even better heat resistance. From this viewpoint, the content may be 60% by mass or more, or 70% by mass or more. A propylene-ethylene block copolymer (C) content of 90% by mass or less, that is, a ethylene-propylene copolymer elastomer (D) content of at least 10% by mass or more, allows the packaging material 11 to exhibit excellent cold shock resistance. From this viewpoint, the propylene-ethylene block copolymer (C) content may be 87.5% by mass or less, or 85% by mass or less. From the above viewpoints, the ethylene-propylene copolymer elastomer (D) content may be 12.5-40% by mass or 15-30% by mass.

[0046] The thickness of film 11 may be the same as that of film 10. The ratio of the thickness of the first layer 1 may be 8-30% based on the thickness of film 11. If the ratio of the thickness of the first layer 1 is above the lower limit, it is easier to obtain excellent low-temperature sealing properties, and if it is below the upper limit, the decrease in the heat seal strength of the film can be suppressed, making it easier to obtain practicality. From this viewpoint, the ratio of the thickness of the first layer may be 10-25%.

[0047] The thickness of the second layer 2 may be 20 μm or more. This maintains the film's cold shock resistance and makes it less likely to tear even during low-temperature storage. From this viewpoint, the thickness of the second layer 2 may be 25 μm or more, or even 30 μm or more. There is no particular upper limit to the thickness of the second layer 2, but it can be set to 50 μm to avoid cost disadvantages.

[0048] <Third Embodiment> The following describes a polypropylene-based unoriented film according to the third embodiment. Unless otherwise described, the film is the same as the polypropylene-based unoriented films according to the first and second embodiments, unless it causes any inconvenience. Figure 3 is a cross-sectional view of the polypropylene-based unoriented film 12 (hereinafter also simply referred to as "film 12") according to this embodiment. Film 12 comprises, in this order, a first layer 1, a second layer 2, and a third layer 3 composed of a third resin composition containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B). The presence of the third layer 3 tends to suppress distortion and curling of the film.

[0049] There are no particular restrictions on the ratio of propylene homopolymer (A) and propylene-ethylene random copolymer (B) in the third layer 3, but it is preferable that the ratio is the same as that of the first layer 1 from the viewpoint of suppressing film curling after film formation.

[0050] The thickness of film 12 may be the same as that of film 10. The thickness of the first layer may be 8-21% of the thickness of film 12. If the proportion of the thickness of the first layer 1 is above the lower limit, it is easier to obtain excellent low-temperature sealing properties, and if it is below the upper limit, the decrease in the heat seal strength of the film can be suppressed, making it easier to obtain practicality. From this viewpoint, the proportion of the thickness of the first layer 1 may be 10-15%.

[0051] The thickness of the second layer 2 may be 20 μm or more. This maintains the film's cold shock resistance and makes it less likely to tear even during low-temperature storage. From this viewpoint, the thickness of the second layer 2 may be 25 μm or more, or even 30 μm or more. There is no particular upper limit to the thickness of the second layer 2, but it can be set to 50 μm to avoid cost disadvantages.

[0052] The total thickness of the first layer 1 and the third layer 3 may be 16-42% of the thickness of the film 12. A ratio of the thickness of the first layer 1 above the lower limit makes it easier to obtain excellent low-temperature sealing properties, while a ratio below the upper limit suppresses the decrease in the heat-seal strength of the film 12, thus making it more practical. From this perspective, the ratio of the total thickness of the first layer 1 and the third layer 3 may be 20-35%.

[0053] Although the polypropylene-based unoriented films according to the first to third embodiments have been described in detail above, this disclosure is not limited to the above embodiments. The polypropylene-based unoriented films according to the first to third embodiments can be suitably used as sealant films because they can achieve a good balance of high levels of heat resistance and low-temperature sealing properties. The polypropylene-based unoriented films according to the first to third embodiments can be suitably used in harsh treatments such as boiling water treatment and retort treatment, and can also be suitably used in packaging materials made of the same polypropylene material.

[0054] [Manufacturing method for polypropylene-based unoriented film] The following describes a method for manufacturing polypropylene-based unoriented films according to the above embodiment. The method for manufacturing films 10 to 12 is not particularly limited, and known methods can be used. For example, as a thermoforming method, examples include a melt-kneading method using a general mixer such as a single-screw extruder, a twin-screw extruder, or a multi-screw extruder, and a method in which each component is dissolved or dispersed and mixed, and then the solvent is heated and removed. When considering workability, a single-screw extruder or a twin-screw extruder can be used. When using a single-screw extruder, examples of screws include full-flight screws, screws with mixing elements, barrier-flight screws, and fluted screws, and these can be used without particular limitation. As a twin-screw kneading device, a co-rotating twin-screw extruder and an opposite-rotating twin-screw extruder can be used. As for the screw shape, full-flight screws and kneading disc types can be used without particular limitation.

[0055] In the above method, it is possible to use a method in which films 10 to 12 are melted using a single-screw extruder or a twin-screw extruder, and then formed using a T-die via a feed block or multi-manifold.

[0056] Films 10 to 12 may be subjected to surface modification treatments as needed to improve their suitability for post-processing. For example, surface modification treatments may be performed on the printing surface or the surface in contact with the substrate to improve printability when using a single film or to improve lamination suitability when using a laminate. Examples of surface modification treatments include treatments that generate functional groups by oxidizing the film surface, such as corona discharge treatment, plasma treatment, and flame treatment, as well as wet process modification treatments that form an easily adhesive layer by coating.

[0057] [Packaging material] Films 10 to 12 may be used as standalone films or laminated with a substrate, and there are no particular restrictions on how they are used as packaging materials.

[0058] When films 10 to 12 are used laminated with a substrate, the packaging material may comprise the above-mentioned films and substrate. Such a packaging material can be formed by laminating at least one layer of polypropylene biaxially oriented film (OPP) onto the above-mentioned films to create a laminate. A packaging material obtained using polypropylene biaxially oriented film as the substrate can be called a monomaterial packaging material.

[0059] Furthermore, at least one layer of a biaxially oriented polyamide film (ONy), a biaxially oriented polyester film (PET), a resin film having a metal oxide vapor deposition layer (transparent vapor-deposited film), printing paper, and metal foil (AL foil) may be laminated onto the films 10 to 12 to form a laminate. The resin film having a metal oxide vapor deposition layer may be, for example, one in which a metal oxide vapor deposition layer is provided on the surface of ONy or PET.

[0060] Figures 4 to 12 are cross-sectional views of packaging materials according to one embodiment of the present disclosure. The packaging material 100 shown in Figure 4 comprises a film 10, an adhesive layer 23, and a resin film (transparent vapor-deposited film 24) having a metal oxide vapor-deposited layer in that order. The packaging material 101 shown in Figure 5 comprises a film 11, an adhesive layer 23, and a transparent vapor-deposited film 24 in that order. The packaging material 102 shown in Figure 6 comprises a film 12, an adhesive layer 23, and a transparent vapor-deposited film 24 in that order. The packaging material 103 shown in Figure 7 comprises a film 10, an adhesive layer 25, and a biaxially oriented polypropylene film 26 in that order. The packaging material 104 shown in Figure 8 comprises a film 11, an adhesive layer 25, and a biaxially oriented polypropylene film 26 in that order. The packaging material 105 shown in Figure 9 comprises a film 12, an adhesive layer 25, and a biaxially oriented polypropylene film 26 in that order. The packaging material 106 shown in Figure 10 comprises a film 10, an adhesive layer 23, a transparent vapor-deposited film 24, an adhesive layer 25, and a biaxially oriented polypropylene film 26 in that order. The packaging material 107 shown in Figure 11 comprises a film 11, an adhesive layer 23, a transparent vapor-deposited film 24, an adhesive layer 25, and a biaxially oriented polypropylene film 26 in that order. The packaging material 108 shown in Figure 12 comprises a film 12, an adhesive layer 23, a transparent vapor-deposited film 24, an adhesive layer 25, and a biaxially oriented polypropylene film 26 in that order. Packaging materials 100 to 108 are used so that films 10 to 12 face the contents.

[0061] The manufacturing method for the packaging material can preferably involve a conventional dry lamination method in which the film constituting the packaging material is bonded with an adhesive. However, if necessary, a method of directly extruding and laminating polypropylene-based unoriented films 10-12 onto a substrate can also be employed.

[0062] The laminated structure of the packaging material can be appropriately adjusted according to the required characteristics of the packaging, such as barrier properties to meet the shelf life of the packaged food, size and impact resistance to accommodate the weight of the contents, and visibility of the contents.

[0063] [Packaging] The packaging may be made from the above-mentioned packaging material, and there are no particular restrictions on the method of making the packaging. The above-mentioned packaging material can be used, for example, for flat bags, three-sided bags, gusseted bags, standing pouches, spouted pouches, and beaked pouches. [Examples]

[0064] The present disclosure will be described below in detail based on examples, but the present disclosure is not limited to these examples.

[0065] <Preparation of polypropylene-based unoriented film> (Example 1) The following propylene homopolymer (A) and propylene-ethylene random copolymer (B1) were prepared.

[0066] (Propylene homopolymer (A)) A propylene homopolymer having a melting onset temperature of 153°C, a melting peak temperature of 159°C, and a melt flow rate (MFR: ISO 1133) of 3.0 g / 10 min when differential scanning calorimetry is performed under the following conditions.

[0067] (Differential scanning calorimetry conditions) In accordance with JIS K 7121, when the temperature is increased from 25°C to 230°C at a rate of 10°C / min, the point at which the straight line extending the baseline on the low-temperature side of the DSC curve toward the high-temperature side is drawn, and the tangent line drawn so as to be tangent to the curve on the low-temperature side of the melting peak and have the maximum slope, is defined as the melting start temperature, and the temperature at the peak of the melting peak is defined as the melting point.

[0068] (Propylene-ethylene random copolymer (B1)) A propylene-ethylene random copolymer with a melting point of 147°C and an ethylene content of 3.4% by mass, as measured by differential scanning calorimetry under the following conditions.

[0069] (Differential scanning calorimetry conditions) In accordance with JIS K 7121, the melting point was defined as the temperature at the peak of the melting curve when the temperature was increased from 25°C to 230°C at a rate of 10°C / min.

[0070] The ethylene content was measured according to the quantitative method for ethylene content (IR method) described on pages 412-413 of the Polymer Analysis Handbook (May 10, 2013, 3rd printing), edited by the Polymer Analysis Symposium of the Japan Society for Analytical Science.

[0071] For the formation of a polypropylene-based unoriented film, a resin mixture was used, consisting of 10 parts by mass of propylene homopolymer (A) and 90 parts by mass of propylene-ethylene random copolymer (B1) in pellet form. Each raw material was supplied to an extruder heated to 250°C and kneaded in a molten state. The kneaded raw material was extruded to a thickness of 60 μm using a T-die extruder with a feed block to form a film, thereby producing the film of Example 1.

[0072] (Example 2) The film of Example 2 was prepared in the same manner as in Example 1, except that the mixing ratio of propylene homopolymer (A) and propylene-ethylene random copolymer (B1) was changed as shown in Table 1.

[0073] (Example 3) The film of Example 3 was prepared in the same manner as in Example 1, except that the mixing ratio of propylene homopolymer (A) and propylene-ethylene random copolymer (B1) was changed as shown in Table 1.

[0074] (Example 4) The film of Example 4 was prepared in the same manner as in Example 1, except that a resin mixture was used in which 47.4 parts by mass of propylene homopolymer (A) and 52.6 parts by mass of propylene-ethylene random copolymer (B1) were mixed in pellet form, and then 5.3 parts by mass of elastomer (E1) was mixed with 100 parts by mass of the total amount of propylene homopolymer (A) and propylene-ethylene random copolymer (B1).

[0075] (Elastomer (E1)) Tuffmer A-1085S (trade name, manufactured by Mitsui Chemicals, Inc.) is an ethylene-1-butene copolymer elastomer.

[0076] (Example 5) The film of Example 5 was prepared in the same manner as in Example 4, except that the following elastomer (E2) was used instead of elastomer (E1).

[0077] (Elastomer (E2)) Tuffmer PN-3560 (trade name, manufactured by Mitsui Chemicals, Inc.) is a propylene-ethylene-1-butene copolymer.

[0078] (Example 6) The film of Example 6 was prepared in the same manner as in Example 4, except that the following elastomer (E3) was used instead of elastomer (E1).

[0079] (Elastomer (E3)) Toughmer XM-7090 (trade name, manufactured by Mitsui Chemicals, Inc.) is a propylene-1-butene copolymer elastomer.

[0080] (Comparative Example 1) A film for Comparative Example 1 was prepared in the same manner as in Example 1, except that the following propylene-ethylene random copolymer (B2) was used instead of propylene-ethylene random copolymer (B1).

[0081] (Propylene-ethylene random copolymer (B2)) A propylene-ethylene random copolymer with a melting point of 131°C as measured by differential scanning calorimetry. The melting point is measured in the same manner as for propylene-ethylene random copolymer (B1).

[0082] (Comparative Example 2) The film of Comparative Example 2 was prepared in the same manner as in Comparative Example 1, except that the mixing ratio of propylene homopolymer (A) and propylene-ethylene random copolymer (B2) was changed as shown in Table 1.

[0083] (Comparative Example 3) A film for Comparative Example 3 was prepared in the same manner as in Example 4, except that the mixing ratio of propylene homopolymer (A), propylene-ethylene random copolymer (B1), and elastomer (E1) was changed as shown in Table 1.

[0084] (Comparative Example 4) The film of Comparative Example 4 was prepared in the same manner as in Example 1, except that the mixing ratio of propylene homopolymer (A) and propylene-ethylene random copolymer (B1) was changed as shown in Table 1.

[0085] (Example 7) As materials for the second layer, the following propylene-ethylene block copolymer (C) and ethylene-propylene copolymer elastomer (D) were prepared.

[0086] (Propylene-ethylene block copolymer (C)) A propylene-ethylene block copolymer with a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) of 1.8 g / 10 min, containing 81.5% by mass of propylene polymer and 18.5% by mass of ethylene-propylene copolymer, with an ethylene content of 36.2% by weight in the ethylene-propylene copolymer.

[0087] (Ethylene-propylene copolymer elastomer (D)) An ethylene-propylene copolymer elastomer having a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) of 0.6 g / 10 min and a propylene content / ethylene content (mass ratio) of 2.7.

[0088] For the formation of the first layer, a resin mixture was prepared by mixing 10 parts by mass of propylene homopolymer (A) and 90 parts by mass of propylene-ethylene random copolymer (B1) in pellet form. For the formation of the second layer, a resin mixture was prepared by mixing 70 parts by mass of propylene-ethylene block copolymer (C) and 30 parts by mass of ethylene-propylene copolymer elastomer (D) in pellet form. Each resin mixture was supplied to an extruder heated to 250°C, kneaded in a molten state, and laminated in a T-die extruder with a feed block so that the first layer had a thickness of 15 μm and the second layer had a thickness of 45 μm, thereby producing the film of Example 7.

[0089] (Example 8) The film of Example 8 was prepared in the same manner as in Example 7, except that the mixing ratio of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B1) in the first layer was changed as shown in Table 2.

[0090] (Example 9) The film of Example 9 was prepared in the same manner as in Example 7, except that for the formation of the first layer, 47.4 parts by mass of propylene homopolymer (A) and 52.6 parts by mass of propylene-ethylene random copolymer (B1) were mixed in pellet form, and then 5.3 parts by mass of elastomer (E1) was mixed with the total amount of 100 parts by mass of propylene homopolymer (A) and propylene-ethylene random copolymer (B1) to produce a resin mixture.

[0091] (Example 10) The film of Example 10 was prepared in the same manner as in Example 9, except that elastomer (E2) was used instead of elastomer (E1).

[0092] (Example 11) The film of Example 11 was prepared in the same manner as in Example 9, except that elastomer (E3) was used instead of elastomer (E1).

[0093] (Example 12) For forming the first and third layers, a resin mixture was prepared by mixing 50 parts by mass of propylene homopolymer (A) and 50 parts by mass of propylene-ethylene random copolymer (B1) in pellet form. For forming the second layer, a resin mixture was prepared by mixing 70 parts by mass of propylene-ethylene block copolymer (C) and 30 parts by mass of ethylene-propylene copolymer elastomer (D) in pellet form. Each resin mixture was supplied to an extruder heated to 250°C, kneaded in a molten state, and laminated in a T-die extruder with a feed block so that the first and third layers were 10 μm thick each and the second layer was 40 μm thick, thereby producing the film of Example 12.

[0094] (Comparative Example 5) The film of Comparative Example 5 was prepared in the same manner as in Example 7, except that the following propylene-ethylene random copolymer (B2) was used instead of the propylene-ethylene random copolymer (B1) in the first layer, and the mixing ratio of the propylene homopolymer and the propylene-ethylene random copolymer (B2) was changed as shown in Table 2.

[0095] (Comparative Example 6) A film of Comparative Example 6 was prepared in the same manner as in Example 7, except that the mixing ratio of propylene homopolymer (A) and propylene-ethylene random copolymer (B2) in the first layer was changed as shown in Table 2.

[0096] (Comparative Example 7) The film of Comparative Example 7 was prepared in the same manner as in Example 9, except that the mixing ratio of the propylene homopolymer (A), propylene-ethylene random copolymer (B1), and elastomer (E1) in the first layer was changed as shown in Table 2.

[0097] (Comparative Example 8) The film of Comparative Example 8 was prepared in the same manner as in Example 7, except that the mixing ratio of propylene homopolymer (A) and propylene-ethylene random copolymer (B1) was changed as shown in Table 2.

[0098] <Various evaluations> The films obtained in each example were evaluated as follows. Furthermore, the evaluation results for low-temperature sealing performance and heat resistance were comprehensively judged according to the following criteria. The results are shown in Tables 1 and 2.

[0099] [Evaluation of heat of fusion ratio] For the evaluation of the heat of fusion ratio, the melting curves of the films obtained in each example were measured in accordance with JIS K 7122. The melting curves were measured when the film was heated to 230°C at a heating rate of 10°C / min and cooled to 25°C at a cooling rate of 10°C / min. A differential scanning calorimeter (DSC7000X) manufactured by Hitachi High-Tech Science Corporation was used for the measurements. The heat of fusion was calculated from the melting curve and the line connecting the points where the DSC curve deviates from the baseline and the points where it returns to the baseline. The calculated heat of fusion was divided at 135°C, and the heat of fusion ΔH on the high-temperature side was calculated. h ΔH, the heat of fusion at the low temperature side l As such, the heat of fusion ratio ΔH h / ΔH l The result was calculated.

[0100] [Low-temperature sealing performance evaluation] In the evaluation of low-temperature sealability, laminates were obtained by heat-sealing the first layers of the films obtained in each example. Heat sealing was performed using a heat sealer manufactured by Tester Industries Co., Ltd., with a sealing pressure of 0.2 MPa, a sealing time of 1 second, a sealing width of 5 mm, and a sealing temperature between 140°C and 160°C in 2°C increments. The laminates were cut into 15 mm wide x 80 mm sections. The heat seal strength of the cut laminates was measured using a tensile testing machine (manufactured by Shimadzu Corporation). The measurement was performed at a tensile speed of 300 mm / min. The temperature at which the heat seal strength reached 15 N / 15 mm or higher was defined as the heat seal rise temperature, and a lower heat seal rise temperature was judged to indicate better low-temperature sealability.

[0101] [Heat resistance evaluation] For the heat resistance evaluation, laminates were obtained by heat-sealing the first layers of the films obtained in each example. Heat sealing was performed using a heat sealer manufactured by Tester Industries Co., Ltd., under the following conditions: sealing pressure of 0.05 MPa, sealing time of 30 seconds, sealing width of 10 mm, and sealing temperature of 135 °C. The laminates were cut into 15 mm wide x 80 mm sections. The heat-sealing strength of the heat-sealed portions of the cut laminates was measured using a tensile testing machine (manufactured by Shimadzu Corporation). The measurement was performed by T-peeling the heat-sealed portions at a tensile speed of 300 mm / min. In this measurement, a heat-sealing strength of 2.0 N / 15 mm or less was considered to indicate good heat resistance.

[0102] [Criteria for overall evaluation] ○: The heat seal rise temperature is 156°C or lower and the heat fusion strength is 2.0 N / 15 mm or lower. ×: The heat seal rise temperature is 158°C or higher, or the heat fusion strength is greater than 2.0 N / 15 mm.

[0103] [Table 1]

[0104] [Table 2]

[0105] The gist of this disclosure is found in the following [1] to [8]. [1] A first layer comprising a first resin composition containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B), The heat of fusion ΔH of the first resin composition when the heat of fusion is divided at 135°C. h and the heat of fusion ΔH at the low temperature side l Ratio ΔH h / ΔH l However, it is a polypropylene-based unoriented film with a viscosity of 2.5 to 5.8. [2] The polypropylene-ethylene random copolymer (B) has an ethylene content of 5% by mass or less, as described in [1]. [3] The polypropylene-based unoriented film according to [1] or [2], wherein the first resin composition further contains a thermoplastic elastomer (E). [4] Having a multilayer structure, A polypropylene-based unoriented film according to any one of [1] to [3], further comprising a second layer composed of a second resin composition containing a propylene-ethylene block copolymer (C) and an ethylene-propylene copolymer elastomer (D). [5] Further comprising a third layer made of a third resin composition containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B), The polypropylene-based unoriented film according to [4], wherein a third layer is provided between the first layer and the second layer. A polypropylene-based unoriented film as described in any of [6][1] to [5], A resin film having a metal oxide vapor-deposited layer, Packaging material equipped with the following features. A polypropylene-based unoriented film as described in any of [7][1] to [5], Polypropylene biaxially oriented film and Packaging material equipped with the following features. A package made from the packaging material described in [8], [6], or [7]. [Industrial applicability]

[0106] The polypropylene-based unoriented film disclosed herein achieves a high level of both heat resistance and low-temperature sealing properties, and can be suitably used, for example, as a sealant film for retort packaging materials. [Explanation of Symbols]

[0107] 1...First layer, 2...Second layer, 3...Third layer, 10-12...Polypropylene-based unoriented film, 24...Transparent vapor-deposited film, 100-108...Packaging material.

Claims

1. The first layer comprises a first resin composition containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B), The heat of fusion ΔH on the high-temperature side when the heat of fusion of the first resin composition is divided at 135°C. ｈ and the heat of fusion ΔH on the low-temperature side ｌ Ratio ΔH ｈ / ΔH ｌ However, the range is 2.5 to 5.

8. A polypropylene-based unoriented film wherein the first layer further contains a thermoplastic elastomer (E).

2. The polypropylene-ethylene random copolymer (B) has an ethylene content of 5% by mass or less, as described in claim 1.

3. It has a multilayer structure, The polypropylene-based unstretched film according to claim 1 or 2, further comprising a second layer composed of a second resin composition containing a propylene-ethylene block copolymer (C) and an ethylene-propylene copolymer elastomer (D).

4. The present invention further comprises a third layer composed of a third resin composition containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B), The polypropylene-based unoriented film according to claim 3, comprising the first layer, the second layer, and the third layer in this order.

5. A polypropylene-based unstretched film according to claim 1, A resin film having a metal oxide vapor-deposited layer, Packaging material equipped with the following features.

6. A polypropylene-based unstretched film according to claim 1, Polypropylene biaxially oriented film and Packaging material equipped with the following features.

7. A package made from the packaging material described in claim 5 or 6.

Images