Multilayer films, packaging materials, and packaging.

Abstract

Invention details;

Description

Multilayer film, packaging material and packaging body

[0001] The present disclosure relates to multilayer films, packaging materials, and packages.

[0002] Polypropylene-based films are sometimes used as sealant films in various packaging materials such as food packaging because they have excellent rigidity and heat resistance and are inexpensive.

[0003] Patent Document 1 proposes a polypropylene-based composite film composed of three layers, characterized in that the middle layer is made of a propylene-ethylene block copolymer resin and both surface layers are made of a propylene-based random copolymer.

[0004] JP 2017-132186 A

[0005] The polypropylene film used in sealant films is required to have heat-sealing properties as well as cold impact resistance so that the bag will not break even when stored at low temperatures. Furthermore, while materials other than sealant films, such as aluminum substrates, have traditionally been used to impart concealment properties to packaging materials, the ability to impart concealment properties to sealant films would promote the diversification of packaging materials.

[0006] In order to impart a hiding function to a film, it is conceivable to incorporate a pigment such as titanium oxide, but the addition of a pigment can cause a decrease in cold impact resistance, so it is not easy to achieve both hiding power and cold impact resistance at the same time.

[0007] Therefore, an object of one aspect of the present disclosure is to provide a multilayer film that can be used as a sealant film and has sufficient concealing properties while also having excellent cold impact resistance. Other aspects of the present disclosure also aim to provide a packaging material including the multilayer film, and a package produced from the packaging material.

[0008] Some aspects of the present disclosure provide the following [1] to

[15] .

[0009] [1] A multilayer film comprising a heat seal layer and a concealing layer provided on the heat seal layer, wherein the heat seal layer contains a propylene homopolymer (A) and / or a propylene-based copolymer resin (B), and the concealing layer contains a propylene-ethylene block copolymer resin (C), an ethylene-propylene copolymer elastomer (D), and titanium oxide (E), and the content of the titanium oxide (E) in the concealing layer is 0.10 to 30.00 mass% based on the total mass of the concealing layer.

[0010] [2] The multilayer film according to [1], wherein the heat seal layer contains a propylene-based copolymer resin (B), and the melting point of the propylene-based copolymer resin (B) is 132 to 150°C.

[0011] [3] The multilayer film according to [1] or [2], wherein the heat seal layer contains a propylene-based copolymer resin (B), and the ethylene content in the propylene-based copolymer resin (B) is 3.0 to 6.0 mass% based on the total mass of the propylene-based copolymer resin (B).

[0012] [4] The multilayer film according to any one of [1] to [3], wherein the content of the propylene homopolymer (A) in the heat seal layer is 10 to 70 mass% based on the total mass of the heat seal layer, and the content of the propylene copolymer resin (B) in the heat seal layer is 30 to 90 mass% based on the total mass of the heat seal layer.

[0013] [5] The multilayer film according to any one of [1] to [4], wherein the mass ratio of the content of the propylene copolymer resin (B) to the content of the propylene homopolymer (A) in the heat seal layer is 0.10 to 9.00.

[0014] [6] The multilayer film according to any one of [1] to [5], wherein the content of the propylene-ethylene block copolymer resin (C) in the concealing layer is 35 to 90 mass% based on the total mass of the concealing layer, and the content of the ethylene-propylene copolymer elastomer (D) in the concealing layer is 10 to 50 mass% based on the total mass of the concealing layer.

[0015] [7] The multilayer film according to any one of [1] to [6], wherein the mass ratio of the content of the ethylene-propylene copolymer elastomer (D) to the content of the propylene-ethylene block copolymer resin (C) in the concealing layer is 0.10 to 1.00.

[0016] [8] The multilayer film according to any one of [1] to [7], wherein the propylene content is 70% by mass or more based on the total mass of the multilayer film.

[0017] [9] The multilayer film according to any one of [1] to [8], wherein the thickness of the heat seal layer is 8 to 30% of the thickness of the multilayer film.

[0018]

[10] The multilayer film according to any one of [1] to [9], wherein the thickness of the concealing layer is 20 μm or more.

[0019]

[11] The multilayer film according to any one of [1] to

[10] , comprising the heat seal layer, the concealing layer, and a laminate layer in this order, wherein the laminate layer contains a propylene homopolymer (A) and / or a propylene-based copolymer resin (B).

[0020]

[12] The multilayer film according to

[11] , wherein the total thickness of the heat seal layer and the laminate layer is 16 to 42% of the thickness of the multilayer film.

[0021]

[13] A packaging material comprising the multilayer film according to any one of [1] to

[12] .

[0022]

[14] The packaging material according to

[13] , further comprising a biaxially oriented polypropylene film on the side of the multilayer film opposite to the heat seal layer side when viewed from the concealing layer.

[0023]

[15] A package made from the packaging material according to

[13] or

[14] .

[0024] According to one aspect of the present disclosure, it is possible to provide a multilayer film that can be used as a sealant film and has sufficient concealing properties while also having excellent cold impact resistance. Also, according to other aspects of the present disclosure, it is possible to provide a packaging material including the multilayer film, and a package made from the packaging material.

[0025] Fig. 1 is a schematic cross-sectional view showing one embodiment of a multilayer film of the present disclosure. Fig. 2 is a schematic cross-sectional view showing another embodiment of a multilayer film of the present disclosure. Fig. 3 is a schematic cross-sectional view showing one embodiment of a packaging material of the present disclosure. Fig. 4 is a schematic cross-sectional view showing another embodiment of a packaging material of the present disclosure.

[0026] In this specification, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​before and after "to" are the same. In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of a numerical range of another stage. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with a value shown in the Examples. Furthermore, the upper and lower limits individually described may be combined in any manner. Furthermore, the polymerization raw materials for the resins described in this specification (propylene homopolymer (A), propylene-based copolymer resin (B), propylene-ethylene block copolymer resin (C), and ethylene-propylene copolymer elastomer (D)) are not particularly limited in terms of their source of production, and any raw materials can be used, such as components refined from conventional petroleum, components produced by chemical recycling methods, and plant-derived components.

[0027] <Multilayer Film> Figure 1 is a cross-sectional view of a multilayer film according to an embodiment of the present disclosure. The multilayer film 10 comprises a heat-sealable layer 1 and a concealing layer 2 provided on the heat-sealable layer 1. The heat-sealable layer contains a propylene homopolymer (A) and / or a propylene-based copolymer resin (B), and the concealing layer 2 contains a propylene-ethylene block copolymer resin (C), an ethylene-propylene copolymer elastomer (D), and titanium oxide (E). The content of titanium oxide (E) in the concealing layer 2 is 0.10 to 30.00 mass% based on the total mass of the concealing layer 2.

[0028] 2 is a cross-sectional view of a multilayer film according to another embodiment of the present disclosure. The multilayer film 11 includes a heat-sealable layer 1, a concealing layer 2, and a laminate layer 3, in this order. The heat-sealable layer 1 and the concealing layer 2 are the same as the heat-sealable layer 1 and the concealing layer 2 in the multilayer film 10. The laminate layer 3 contains a propylene homopolymer (A) and / or a propylene-based copolymer resin (B).

[0029] The multilayer films (10, 11) can be used as sealant films (e.g., polypropylene-based non-stretch sealant films) and have excellent cold impact resistance while maintaining sufficient concealment properties. Therefore, the multilayer films (10, 11) are suitable for use as packaging materials (e.g., packaging sealant films, or packaging films comprising a packaging sealant film and a substrate). The multilayer films (10, 11) may be used as a standalone film or may be laminated with a substrate. When the multilayer films (10, 11) are used as packaging materials, the method of use as a packaging material is not particularly limited.

[0030] The cold impact resistance of the multilayer film (10, 11) can be evaluated by the impact strength of the film during low-temperature storage. Specifically, the impact strength of the film is measured using a film impact tester under conditions of a temperature of -5°C, a weighing weight of 1.5 J, and a bullet size of 1 / 2 inch. The impact strength of the film measured under these conditions is, for example, 6.00 J / mm or more (e.g., 6.00 to 12.00 J / mm), and can be increased to 7.00 J / mm or more, 8.00 J / mm or more, 9.00 J / mm or more, 10.00 J / mm or more, or 11.00 J / mm or more by adjusting the composition and thickness of each layer.

[0031] The hiding power of the multilayer film (10, 11) can be evaluated by transmission density. The transmission density is the common logarithm of the reciprocal of the transmittance and can be measured using a transmission densitometer (e.g., a portable transmission densitometer manufactured by X-RITE Corporation). The transmission density of the multilayer film (10, 11) is, for example, 0.20 or more (e.g., 0.20 to 0.80), and can also be set to 0.30 or more, 0.40 or more, 0.50 or more, 0.60 or more, or 0.70 or more by adjusting the composition and thickness of each layer.

[0032] Meanwhile, in the field of packaging materials for food, etc., efforts are underway to develop "mono-material" packaging materials made from a single material. The multilayer film has sufficient concealing properties without containing non-polypropylene materials such as aluminum substrates that have traditionally been used to impart concealing properties to packaging materials, and is therefore particularly suitable for use in mono-material packaging materials that require concealing properties.

[0033] In mono-material applications, the sealant film and the substrate are made of the same material, which inevitably means that the melting points of the sealant film and the substrate are close to each other, making it easier for the sealant film and the substrate to melt during the heat-sealing process. Therefore, sealant films used in mono-material packaging materials are sometimes required to have excellent heat-sealing properties at low temperatures (hereinafter also referred to as "low-temperature sealing properties"). In this regard, the multilayer film can also have excellent low-temperature sealing properties by using a low-melting-point material (e.g., a propylene-based copolymer resin (B) with a melting point of 150°C or less) as the material for the heat-sealing layer.

[0034] Each layer of the multilayer film (10, 11) will be described in detail below, and reference numerals will be omitted in the following description.

[0035] (Heat Seal Layer) The heat seal layer contains, for example, a propylene homopolymer (A) and / or a propylene-based copolymer resin (B).

[0036] [Propylene Homopolymer (A)] The propylene homopolymer (A) is a propylene homopolymer obtainable by homopolymerizing propylene using, for example, a Ziegler-Natta catalyst, a metallocene catalyst, or a half-metallocene catalyst. When the heat seal layer contains the propylene homopolymer (A), the multilayer film also exhibits excellent heat resistance (hereinafter also simply referred to as "heat resistance") that can withstand retort treatment, which involves pressure treatment at high temperatures of 120 to 135°C to perform pasteurization and sterilization. Therefore, it can be said that a multilayer film having a heat seal layer containing the propylene homopolymer (A) can be suitably used for packaging applications that are subjected to severe treatments such as boiling water treatment and retort treatment.

[0037] The propylene homopolymer (A) may have, for example, a melting onset temperature of 150°C or higher and a melting point (peak melting temperature) of 155°C or higher. A propylene homopolymer (A) having both a melting onset temperature and a melting point within this range has better heat resistance, and is less likely to fuse to the inner surface of a packaging bag, for example, after high-temperature retort treatment. From the viewpoint of obtaining even better heat resistance, the melting onset temperature of the propylene homopolymer (A) may be 151°C or higher or 152°C or higher, and the melting point of the propylene homopolymer (A) may be 156°C or higher or 158°C or higher. The melting onset temperature of the propylene homopolymer (A) is, for example, 160°C or lower, and from the viewpoint of obtaining better low-temperature sealability, it may be 155°C or lower or 153°C or lower. The melting point of the propylene homopolymer (A) is, for example, 170°C or lower, and from the viewpoint of obtaining better low-temperature sealability, it may be 165°C or lower or 160°C or lower. From the above viewpoints, the melting initiation temperature of the propylene homopolymer (A) may be, for example, 150 to 160° C., and the melting point of the propylene homopolymer (A) may be, for example, 155 to 170° C. In this specification, the melting initiation temperature and the melting point are values ​​determined by differential scanning calorimetry in accordance with JIS K 7121.

[0038] The propylene homopolymer (A) may have a melt flow rate (MFR) in the range of 2.0 to 7.0 g / 10 min. A melt flow rate of at least the lower limit reduces the load on the extruder during molding, making it difficult for the processing speed to decrease and facilitating the maintenance of excellent productivity. Furthermore, a melt flow rate of at most the upper limit tends to result in a heat seal layer with superior cold impact resistance. From these perspectives, the melt flow rate of the propylene homopolymer (A) may be 2.5 to 6.0 g / 10 min or 3.0 to 5.0 g / 10 min. In this specification, the melt flow rate is a value measured in accordance with ISO 1133 at a temperature of 230°C and a load of 2.16 kg.

[0039] [Propylene-Based Copolymer Resin (B)] The propylene-based copolymer resin (B) is a resin obtained by copolymerizing propylene with another copolymerizable monomer (comonomer).

[0040] The propylene-based copolymer resin (B) may have a melting point lower than that of the propylene homopolymer (A). The melting point of the propylene-based copolymer resin (B) is preferably 150°C or lower. When the heat-sealable layer contains a propylene-based resin having such a melting point, the multilayer film also exhibits excellent low-temperature sealing properties. Such a multilayer film is more preferably used as a sealant film for monomaterial packaging materials. From the viewpoint of achieving superior heat resistance and cold impact resistance, the melting point of the propylene-based copolymer resin (B) may be 132°C or higher, 135°C or higher, 140°C or higher, or 145°C or higher. From the above viewpoint, the melting point of the propylene-based copolymer resin (B) may be, for example, 132 to 150°C, 135 to 150°C, 140 to 150°C, or 145 to 150°C. From the viewpoint of achieving a better balance between heat resistance and low-temperature sealability, the melting initiation temperature of the propylene-based copolymer resin (B) may be 120 to 145° C., 125 to 145° C., or 135 to 145° C. The melting point of the propylene-based copolymer resin (B) after the heat-seal layer has been formed can be determined by separating the heat-seal layer and measuring the melting points of each layer, for example, by a high-temperature LC method using graphite carbon as an adsorbent.

[0041] The propylene-based copolymer resin (B) may be a resin obtained by copolymerization of a copolymerization monomer containing propylene and ethylene (a resin containing a copolymer of propylene and ethylene). From the viewpoint of achieving superior low-temperature sealability of the multilayer film, the propylene-based copolymer resin (B) may contain a propylene-ethylene random copolymer. The propylene-ethylene random copolymer can be obtained by copolymerizing a main monomer consisting of propylene with ethylene as a comonomer using, for example, a Ziegler-Natta catalyst, a metallocene catalyst, or a half-metallocene catalyst. The copolymer constituting the propylene-based copolymer resin (B) may be one type or multiple types. When the propylene-based copolymer resin (B) is a mixture of multiple types of copolymers, the melting point of the mixture is taken as the melting point of the propylene-based copolymer resin (B).

[0042] The ethylene content in the propylene-based copolymer resin (B) may be 6.0% by mass or less, based on the total mass of the propylene-based copolymer resin (B). An ethylene content of 6.0% by mass or less maintains low-temperature sealability without excessively reducing heat resistance, and can suppress fusion on the inner surface of the packaging bag after retort treatment. To achieve this effect more significantly, the ethylene content may be 5.5% by mass or less or 4.5% by mass or less. The lower limit of the ethylene content is not particularly limited, but may be 3.0% by mass from the viewpoint of low-temperature sealability. From these viewpoints, the ethylene content in the propylene-based copolymer resin (B) may be 3.0 to 6.0% by mass, 3.0 to 5.5% by mass, or 3.0 to 4.5% by mass, based on the total mass of the propylene-based copolymer resin (B).

[0043] The ethylene content of the propylene copolymer resin (B) can be measured according to the ethylene content determination method (IR method) described on pages 412 to 413 of Polymer Analysis Handbook (May 10, 2013, 3rd printing), edited by the Polymer Analysis Forum, Japan Analytical Society.

[0044] The melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) of the propylene-based copolymer resin (B) may be 1.0 to 10.0 g / 10 min. When the melt flow rate is equal to or greater than the lower limit, the load on the extruder during molding is reduced, the processing speed is less likely to decrease, and excellent productivity is easily maintained. When the melt flow rate is equal to or less than the upper limit, the heat seal layer is likely to have excellent cold impact resistance. From these viewpoints, the melt flow rate of the propylene-based copolymer resin (B) may be 2.0 to 9.0 g / 10 min or 3.0 to 8.0 g / 10 min.

[0045] The components contained in the heat seal layer have been described above, but the heat seal layer may contain components other than the propylene homopolymer (A) and the propylene copolymer resin (B). However, from the viewpoint of use in monomaterial packaging materials composed of the same polypropylene-based material, the propylene content in the heat seal layer is preferably 70% by mass or more. The propylene content in the heat seal layer can be measured by Raman spectroscopy.

[0046] From the viewpoint of achieving both excellent heat resistance and excellent low-temperature sealability, the heat-seal layer preferably contains both a propylene homopolymer (A) and a propylene-based copolymer resin (B), and more preferably contains a propylene homopolymer (A) and a propylene-based copolymer resin (B) having a melting point of 132 to 150° C. When the heat-seal layer contains both a propylene homopolymer (A) and a propylene-based copolymer resin (B), from the viewpoint of achieving a better balance between heat resistance and low-temperature sealability, it is preferable that the content of the propylene homopolymer (A) in the heat-seal layer be 10 to 70 mass% based on the total mass of the heat-seal layer, and the content of the propylene copolymer resin (B) (preferably a propylene copolymer resin (B) having a melting point of 132 to 150° C.) in the heat-seal layer be 30 to 90 mass% based on the total mass of the heat-seal layer.

[0047] From the viewpoint of superior heat resistance, the content of the propylene homopolymer (A) in the heat-seal layer may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more, based on the total mass of the heat-seal layer. From the viewpoint of superior low-temperature sealability and cold impact resistance, the content of the propylene homopolymer (A) in the heat-seal layer may be 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, or 50% by mass or less, based on the total mass of the heat-seal layer. From these viewpoints, the content of the propylene homopolymer (A) in the heat-seal layer may be 10 to 70% by mass, 15 to 65% by mass, 20 to 60% by mass, 30 to 55% by mass, 40 to 55% by mass, 10 to 50% by mass, or 50 to 70% by mass, based on the total mass of the heat-seal layer. The content of the propylene homopolymer (A) in the heat seal layer may be 75 to 100% by mass based on the total mass of the heat seal layer, from the viewpoint of achieving better low-temperature sealing properties.

[0048] From the viewpoint of achieving better low-temperature sealability and cold impact resistance, the content of the propylene-based copolymer resin (B) in the heat-seal layer may be 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, or 50% by mass or more, based on the total mass of the heat-seal layer. From the viewpoint of achieving better heat resistance, the content of the propylene-based copolymer resin (B) in the heat-seal layer may be 90% by mass or less, 85% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less, based on the total mass of the heat-seal layer. From these viewpoints, the content of the propylene-based copolymer resin (B) in the heat-seal layer may be 30 to 90% by mass, 35 to 85% by mass, 40 to 80% by mass, 45 to 70% by mass, 45 to 60% by mass, 50 to 90% by mass, or 35 to 50% by mass, based on the total mass of the heat-seal layer. The content of the propylene homopolymer (B) in the heat seal layer may be 0 to 25% by mass based on the total mass of the heat seal layer, from the viewpoint of achieving better low-temperature sealability.

[0049] The mass ratio [(B) / (A)] of the content of the propylene copolymer resin (B) to the content of the propylene homopolymer (A) in the heat seal layer may be 0.10 to 9.00 from the viewpoint of achieving better heat resistance and cold impact resistance. The mass ratio [(B) / (A)] may be 0.20 or more, 0.40 or more, or 0.80 or more, and may be 5.00 or less, 2.50 or less, or 1.50 or less from the viewpoint of achieving even better heat resistance and cold impact resistance.

[0050] (Concealing Layer) The concealing layer contains a propylene-ethylene block copolymer resin (C), an ethylene-propylene copolymer elastomer (D), and titanium oxide (E). Because the concealing layer contains 0.10% by mass or more of titanium oxide (E), the multilayer film has concealing properties. Furthermore, because the concealing layer contains the propylene-ethylene block copolymer resin (C) and the ethylene-propylene copolymer elastomer (D), and the content of titanium oxide (E) is kept to 30.00% by mass or less, it is possible to achieve both the concealing properties provided by the titanium oxide (E) and excellent cold impact resistance.

[0051] [Propylene-Ethylene Block Copolymer Resin (C)] The propylene-ethylene block copolymer resin (C) is a resin obtained by block copolymerization of propylene and ethylene.

[0052] The propylene-ethylene block copolymer resin (C) contains, for example, a propylene homopolymer component (c1) and an ethylene-propylene copolymer component (c2), which is a copolymer of ethylene and propylene (e.g., a random copolymer). Such a propylene-ethylene block copolymer resin (C) can be obtained, for example, by producing the propylene homopolymer component (c1) in a first step, and then producing the ethylene-propylene copolymer component (c2) by gas-phase polymerization in the presence of the propylene homopolymer component (c1) in a second step. For example, a Ziegler-Natta catalyst, a metallocene catalyst, a half-metallocene catalyst, or the like can be used for the polymerization. It is generally considered that the propylene-ethylene block copolymer resin (C) obtained by this method is not a block copolymer in which a propylene homopolymer end and an ethylene-propylene copolymer end are bonded (a block copolymer constituted by repeating blocks of a propylene homopolymer component (c1) and a block of an ethylene-propylene copolymer component (c2)), but is a mixture of a propylene homopolymer component (c1) and an ethylene-propylene copolymer component (c2).

[0053] The propylene-ethylene block copolymer resin (C) may contain 60.0 to 90.0 mass% of the propylene homopolymer component (c1) and 10.0 to 40.0 mass% of the ethylene-propylene copolymer component (c2), based on the total mass of the propylene-ethylene block copolymer resin (C). Having the contents of each component within the above ranges makes it easier to obtain better cold impact resistance. From the above viewpoint, the content of the propylene homopolymer component (c1) in the propylene-ethylene block copolymer resin (C) may be 65.0 to 87.5 mass% or 70.0 to 85.0 mass%, based on the total mass of the propylene-ethylene block copolymer resin (C). Similarly, the content of the ethylene-propylene copolymer component (c2) in the propylene-ethylene block copolymer resin (C) may be 12.5 to 35.0 mass% or 15.0 to 30.0 mass% based on the total mass of the propylene-ethylene block copolymer resin (C).

[0054] The ethylene content in the ethylene-propylene copolymer component (c2) may be 20.0 to 40.0% by mass, based on the total mass of the ethylene-propylene copolymer component (c2). When the ethylene content is equal to or less than the upper limit, the tackiness of the product can be suppressed, contamination due to tackiness of the product during production is less likely to occur, and excellent productivity can be easily maintained. When the ethylene content is equal to or more than the lower limit, better cold impact resistance can be easily obtained.

[0055] The ethylene content of the ethylene-propylene copolymer component (c2) can be measured according to the ethylene content determination method (IR method) described on pages 412-413 of Polymer Analysis Handbook (May 10, 2013, 3rd printing), edited by the Polymer Analysis Forum, Japan Analytical Society.

[0056] The propylene-ethylene block copolymer resin (C) may have 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. When the melt flow rate is equal to or greater than the lower limit, the load on the extruder during molding is reduced, the processing speed is less likely to decrease, and excellent productivity is easily maintained. When the melt flow rate is equal to or less than the upper limit, the concealing layer is likely to have excellent cold impact resistance. From these viewpoints, the melt flow rate of the propylene-ethylene block copolymer resin (C) may be 1.0 to 2.2 g / 10 min or 1.5 to 2.0 g / 10 min.

[0057] [Ethylene-Propylene Copolymer Elastomer (D)] The ethylene-propylene copolymer elastomer (D) is an elastomer obtained by block copolymerization of propylene and ethylene.

[0058] The ethylene-propylene copolymer elastomer (D) can be obtained, for example, by a slurry polymerization method carried out in the presence of an inert hydrocarbon such as hexane, heptane, kerosene, or a liquefied α-olefin solvent such as propylene, or by a gas-phase polymerization method without a solvent. Specifically, the ethylene-propylene copolymer elastomer (D) can be obtained using a known multi-stage polymerization method. That is, the ethylene-propylene copolymer elastomer (D) may be a polymerized high-rubber polypropylene resin obtained by polymerizing propylene and / or a propylene-α-olefin polymer in a first-stage reactor and then copolymerizing propylene with an α-olefin in a second-stage reactor. For example, a Ziegler-Natta catalyst, a metallocene catalyst, a half-metallocene catalyst, or the like can be used for the polymerization.

[0059] The melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) of the ethylene-propylene copolymer elastomer (D) may be 0.5 to 3.5 g / 10 min. When the melt flow rate is equal to or greater than the lower limit, the load on the extruder during molding is reduced, the processing speed is less likely to decrease, and excellent productivity is easily maintained. When the melt flow rate is equal to or less than the upper limit, the compatibility between the propylene-ethylene block copolymer resin (C) and the ethylene-propylene copolymer elastomer (D) is improved, and better cold impact resistance is easily obtained.

[0060] The mass ratio of the propylene content to the ethylene content [propylene content / ethylene content] in the ethylene-propylene copolymer elastomer (D) may be 1.5 to 4.0, 2.0 to 3.5, or 2.5 to 3.0, from the viewpoint of easily obtaining even better cold impact resistance.

[0061] The propylene content of the ethylene-propylene copolymer elastomer (D) can be measured by Raman spectroscopy. Alternatively, the ethylene content of the ethylene-propylene copolymer elastomer (D) can be measured according to the ethylene content determination method (IR method) described on pages 412-413 of Polymer Analysis Handbook (May 10, 2013, 3rd edition), edited by the Polymer Analysis Forum, Japan Analytical Society.

[0062] [Titanium oxide (E)] Titanium oxide (E) is, for example, in the form of particles and is dispersed in the heat seal layer. The average particle size of titanium oxide may be 0.10 to 0.50 μm, or may be 0.15 to 0.40 μm, or 0.20 to 0.30 μm. The average particle size of titanium oxide is a value measured by a laser diffraction / scattering method.

[0063] The components contained in the concealing layer have been described above, but the concealing layer may contain components other than the propylene-ethylene block copolymer resin (C), the ethylene-propylene copolymer elastomer (D), and the titanium oxide (E). However, from the perspective of use in monomaterial packaging materials composed of the same polypropylene-based material, the propylene content in the concealing layer is preferably 70% by mass or more. The propylene content in the concealing layer can be measured by Raman spectroscopy.

[0064] From the viewpoint of achieving better heat resistance, the content of the propylene-ethylene block copolymer resin (C) in the concealing layer may be 35% by mass or more, 50% by mass or more, or 60% by mass or more, based on the total mass of the concealing layer. From the viewpoint of achieving better cold impact resistance, the content of the propylene-ethylene block copolymer resin (C) in the concealing layer may be 90% by mass or less, 80% by mass or less, or 70% by mass or less, based on the total mass of the concealing layer. From these viewpoints, the content of the propylene-ethylene block copolymer resin (C) in the concealing layer may be 35 to 90% by mass, 50 to 80% by mass, 50 to 70% by mass, or 60 to 80% by mass, based on the total mass of the concealing layer.

[0065] From the viewpoint of achieving better cold impact resistance, the content of the ethylene-propylene copolymer elastomer (D) in the concealing layer may be 10% by mass or more, 15% by mass or more, or 20% by mass or more, based on the total mass of the concealing layer. From the viewpoint of achieving better heat resistance, the content of the ethylene-propylene copolymer elastomer (D) in the concealing layer may be 50% by mass or less, 40% by mass or less, or 30% by mass or less, based on the total mass of the concealing layer. From these viewpoints, the content of the ethylene-propylene copolymer elastomer (D) in the concealing layer may be 10 to 50% by mass, 10 to 40% by mass, 15 to 40% by mass, or 20 to 30% by mass, based on the total mass of the concealing layer.

[0066] The mass ratio [(D) / (C)] of the content of the ethylene-propylene copolymer elastomer (D) to the content of the propylene-ethylene block copolymer resin (C) in the concealing layer is preferably 0.10 to 1.00 from the viewpoint of better heat resistance and cold impact resistance. The mass ratio [(D) / (C)] may be 0.20 or more, 0.30 or more, or 0.40 or more from the viewpoint of even better cold impact resistance. The mass ratio [(D) / (C)] may be 0.80 or less, 0.60 or less, or 0.40 or less from the viewpoint of even better heat resistance.

[0067] The content of titanium oxide (E) in the hiding layer is 0.10 to 30.00% by mass. From the viewpoint of more excellent hiding properties, the content of titanium oxide (E) in the hiding layer may be 1.00% by mass or more, 5.00% by mass or more, 7.00% by mass or more, or 10.00% by mass or more, based on the total mass of the hiding layer. From the viewpoint of more excellent cold impact resistance, the content of titanium oxide (E) in the hiding layer may be 23.00% by mass or less, 20.00% by mass or less, 15.00% by mass or less, 12.00% by mass or less, or 8.00% by mass or less, based on the total mass of the hiding layer.

[0068] (Laminate Layer) The laminate layer is a layer having laminating properties with respect to a substrate, etc. The laminate layer contains the propylene homopolymer (A) and / or the propylene copolymer resin (B) described in the heat seal layer. By providing the laminate layer, distortion and curling of the multilayer film can be easily suppressed.

[0069] The blending ratio of the propylene homopolymer (A) and the propylene copolymer resin (B) in the laminate layer is not particularly limited, but from the viewpoint of suppressing film curl after film formation, it is preferable that the blending ratio be the same as that of the heat seal layer. That is, the content of the propylene homopolymer (A) in the laminate layer is preferably 10 to 70 mass% based on the total mass of the laminate layer, and the content of the propylene copolymer resin (B) in the laminate layer is preferably 30 to 90 mass% based on the total mass of the laminate layer. Other characteristics of the laminate layer may be the same as those of the heat seal layer described above. For example, the melting point of the propylene copolymer resin (B) contained in the laminate layer may be 132 to 150°C. Furthermore, for example, the propylene content in the laminate layer may be 70 mass% or more. The propylene content in the laminate layer can be measured by Raman spectroscopy.

[0070] (Layer Thickness) The thickness of the multilayer film is not particularly limited as long as it is usable as a film for packaging, for example, but if the film is too thick, it will be cost-deductible. Therefore, the thickness of the multilayer film may be 100 μm or less (e.g., 50 to 100 μm) or 70 μm or less (e.g., 50 to 70 μm).

[0071] The thickness of the heat-seal layer may be 8 to 30% based on the thickness of the multilayer film. When the thickness ratio of the heat-seal layer is equal to or greater than the above-mentioned lower limit, better cold impact resistance is likely to be obtained. Furthermore, when the thickness ratio of the heat-seal layer is equal to or less than the above-mentioned upper limit, better low-temperature sealing properties are likely to be obtained. From these viewpoints, the thickness of the heat-seal layer may be 8 to 25%, 10 to 25%, 8 to 21%, or 10 to 21% based on the thickness of the multilayer film. The thickness of the heat-seal layer may be, for example, 5 to 20 μm.

[0072] The thickness of the concealing layer may be 20 μm or more from the viewpoint of achieving a better balance between concealing properties and cold impact resistance. From this viewpoint, the thickness of the concealing layer may be 25 μm or more, 30 μm or more, 35 μm or more, or 40 μm or more. The upper limit of the thickness of the concealing layer is not particularly limited, but may be 60 μm or less or 50 μm or less because it would be cost disadvantageous.

[0073] From the viewpoint of achieving a better balance between hiding power and cold impact resistance, the thickness of the concealing layer may be 50 to 92% of the thickness of the multilayer film. The thickness of the concealing layer may be 58% or more, 60% or more, 65% or more, 70% or more, 75% or more, or 79% or more, or may be 90% or less, 84% or less, 80% or less, or 85% or less, of the thickness of the multilayer film.

[0074] When a laminate layer is provided, the total thickness of the heat-seal layer and the laminate layer may be 16% or more, 20% or more, or 25% or more, and 42% or less, 40% or less, or 35% or less, based on the thickness of the multilayer film. When the ratio of the total thickness of the heat-seal layer and the laminate layer is equal to or greater than the above-mentioned lower limit, better cold impact resistance is likely to be obtained. Furthermore, when the ratio of the total thickness of the heat-seal layer and the laminate layer is equal to or less than the above-mentioned upper limit, better low-temperature sealing properties are likely to be obtained. From these perspectives, the total thickness of the heat-seal layer and the laminate layer may be 16 to 42%, 20 to 40%, or 25 to 35% based on the thickness of the multilayer film. The total thickness of the heat-seal layer and the laminate layer may be, for example, 10 to 40 μm.

[0075] The method for producing the multilayer film is not particularly limited, and known methods can be used. For example, thermoforming methods include melt-kneading methods using common mixers such as single-screw extruders, twin-screw extruders, and multi-screw extruders, and methods in which the components are dissolved or dispersed and mixed and then the solvent is removed by heating. Considering workability, single-screw extruders or twin-screw extruders can be used. When using a single-screw extruder, the screw can be a full-flight screw, a screw with a mixing element, a barrier-flight screw, a fluted screw, or the like, and these can be used without particular limitations. Examples of twin-screw kneading devices that can be used include co-rotating twin-screw extruders and counter-rotating twin-screw extruders, and the screw shape can be a full-flight screw, a kneading disk type, or the like, without particular limitations.

[0076] In the above method, it is possible to use a method in which the multilayer film is melted in a single-screw extruder or twin-screw extruder, and then passed through a feed block or multi-manifold to form a film in a T-die.

[0077] The obtained multilayer film may be subjected to a surface modification treatment as needed to improve suitability for subsequent processes. For example, to improve printability when used as a single film or lamination suitability when used in a laminated state, a surface modification treatment may be performed on the printing surface or the surface that comes into contact with the substrate. 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, and modification treatments using a wet process that forms an easy-adhesion layer by coating.

[0078] The multilayer film of the present disclosure has been described above, but the multilayer film of the present disclosure is not limited to the above embodiment. For example, the multilayer film may include layers other than the heat seal layer, the concealing layer, and the laminate layer. However, from the viewpoint of using the multilayer film as a mono-material packaging material composed of the same polypropylene-based material and from the viewpoint of obtaining better low-temperature sealing properties, the propylene content in the multilayer film (based on the total mass of the multilayer film) is preferably 70 mass% or more. The propylene content in the multilayer film can be measured by Raman spectroscopy.

[0079] <Packaging Material> Another embodiment of the present disclosure relates to a packaging material including a multilayer film. The multilayer film used in the packaging material includes a heat seal layer and a concealing layer provided on the heat seal layer, wherein the heat seal layer contains a propylene homopolymer (A) and / or a propylene-based copolymer resin (B), and the concealing layer contains a propylene-ethylene block copolymer resin (C), an ethylene-propylene copolymer elastomer (D), and titanium oxide (E), and the content of titanium oxide (E) in the concealing layer is 0.10 to 30.00 mass% based on the total mass of the concealing layer. This multilayer film may be the multilayer film of the above embodiment. The packaging material may consist of only the multilayer film, or may include the multilayer film and a substrate.

[0080] A packaging material comprising a multilayer film and a substrate can be obtained, for example, by laminating at least one substrate, such as a biaxially oriented polyamide film (ONy), a biaxially oriented polyester film (PET), a biaxially oriented polypropylene film (OPP), printed paper, metal foil (AL foil), or a transparent vapor-deposited film, onto the multilayer film to form a laminate. The substrate may be disposed on the opposite side of the heat seal layer from the concealing layer of the multilayer film. From the viewpoint of making the packaging material a mono-material packaging material (single-material packaging material), it is preferable to use a biaxially oriented polypropylene film (OPP) as the substrate. In other words, the packaging material may be a single-material packaging material comprising a biaxially oriented polypropylene film and a multilayer film. Conventionally, an aluminum substrate or the like is used to impart concealing properties to packaging materials, but the packaging material of the present embodiment comprises the above-mentioned multilayer film, and therefore has sufficient concealing properties without using a substrate having concealing properties such as an aluminum substrate.

[0081] When the packaging material is a laminate, its layer structure is not particularly limited and can be appropriately adjusted depending on the required properties of the package, such as barrier properties that meet the shelf life of the packaged food, size and impact resistance that can accommodate the weight of the contents, visibility of the contents, etc. The packaging material may be, for example, a laminate as shown in FIG. 3. The packaging material 100 shown in the figure comprises a multilayer film 10, an adhesive layer 4, a transparent vapor deposition film 5, an adhesive layer 6, and a substrate (substrate film) 7, in this order. The multilayer film 10 comprises, from the outer layer side of the packaging material 100, a heat seal layer 1 and a concealing layer 2, in this order. That is, the concealing layer 2 is located closer to the inner layer than the heat seal layer 1. The packaging material may also be, for example, a laminate as shown in FIG. 4. The packaging material 101 shown in the figure comprises a multilayer film 11, an adhesive layer 4, a transparent vapor deposition film 5, an adhesive layer 6, and a substrate (substrate film) 7, in this order. The multilayer film 11 comprises, from the outer layer side of the packaging material 101, a heat seal layer 1, a concealing layer 2, and a laminate layer 3 in this order. That is, the concealing layer 2 and the laminate layer 3 are located on the inner layer side of the heat seal layer 1. These packaging materials (100, 101) are used so that the multilayer film (10, 11) side faces the contents.

[0082] The manufacturing method of the packaging material (100, 101) can suitably be a conventional dry lamination method in which the films constituting the packaging material (100, 101) are bonded together using an adhesive, but if necessary, a method in which the multilayer film is extrusion laminated directly onto the substrate can also be used.

[0083] <Packaging> Another embodiment of the present disclosure relates to a packaging body produced from a packaging material. The packaging material used for the packaging body includes a multilayer film comprising a heat seal layer and a concealing layer provided on the heat seal layer, wherein the heat seal layer contains a propylene homopolymer (A) and / or a propylene-based copolymer resin (B), and the concealing layer contains a propylene-ethylene block copolymer resin (C), an ethylene-propylene copolymer elastomer (D), and titanium oxide (E), and the content of titanium oxide (E) in the concealing layer is 0.10 to 30.00 mass% based on the total mass of the concealing layer. This packaging material may be any of the packaging materials described above.

[0084] There are no particular limitations on the manufacturing style of the package, and the package may be, for example, a flat bag, a three-sided bag, a two-sided bag, a gusseted bag, a standing pouch, a pouch with a spout, a pouch with a beak, or the like, using the multilayer film of the packaging material as a sealing material.

[0085] The present disclosure will be described in more detail below using examples and comparative examples, but the present disclosure is not limited to the following examples.

[0086] <Material Preparation> The following propylene homopolymer (A), propylene copolymer resin (B), propylene-ethylene block copolymer resin (C), and ethylene-propylene copolymer elastomer (D) were prepared. The melting initiation temperature and melting point of the materials shown below were determined by differential scanning calorimetry in accordance with JIS K 7121. The melt flow rate was measured at 230°C under a load of 2.16 kg in accordance with ISO 1133. The ethylene content was measured according to the ethylene content determination method (IR method) described on pages 412-413 of the Polymer Analysis Handbook (May 10, 2013, 3rd edition) edited by the Polymer Analysis Forum of the Japan Analytical Society. The propylene content of the materials shown below was measured by Raman spectroscopy.

[0087] (Propylene homopolymer (A)) Resin (A): A propylene homopolymer having a melting initiation temperature of 153°C, a melting point (melting peak temperature) of 159°C, and a melt flow rate of 3.0 g / 10 min.

[0088] (Propylene-based copolymer resins (B)) Resin (B1): A propylene-ethylene random copolymer having a melting onset temperature of 142°C, a melting point (peak melting temperature) of 147°C, a melt flow rate of 7.5 g / 10 min, and an ethylene content of 3.4% by mass. Resin (B2): A propylene-ethylene random copolymer having a melting onset temperature of 122°C, a melting point (peak melting temperature) of 133°C, a melt flow rate of 7.0 g / 10 min, and an ethylene content of 5.8% by mass. Resin (B3): A propylene-ethylene random copolymer having a melting onset temperature of 120°C, a melting point (peak melting temperature) of 131°C, a melt flow rate of 6.5 g / 10 min, and an ethylene content of 23.7% by mass.

[0089] (Propylene-ethylene block copolymer resin (C)) Resin (C): A propylene-ethylene block copolymer resin having a melt flow rate of 1.8 g / 10 min, containing 81.5 mass% of a propylene homopolymer component (c1) and 18.5 mass% of an ethylene-propylene copolymer component (c2), wherein the ethylene content of the ethylene-propylene copolymer component (c2) is 36.2 mass%.

[0090] (Ethylene-Propylene Copolymer Elastomer (D)) Elastomer (D): An ethylene-propylene copolymer elastomer having a melt flow rate of 0.6 g / 10 min and a mass ratio of the propylene content to the ethylene content [propylene content / ethylene content] of 2.7.

[0091] (Titanium oxide (E)) Titanium oxide PEONY HP WHITE series manufactured by DIC Corporation, Model number: L-11232-MPT

[0092] Example 1 (Preparation of Laminated Film) For forming a heat seal layer, 50% by mass of resin (A) which is a propylene homopolymer (A) and 50% by mass of resin (B1) which is a propylene copolymer resin (B) were mixed in the form of pellets to prepare a mixture (I). For forming a concealing layer, resin (C) which is a propylene-ethylene block copolymer resin (C) and elastomer (D) which is an ethylene-propylene copolymer elastomer (D) were mixed in the form of pellets so that the mass ratio of elastomer (D) to resin (C) (ratio [elastomer (D) / resin (C)]) was 0.20 to prepare a mixture (II). This mixture (II) was then mixed with titanium oxide (E) so that the content of titanium oxide (E) in the total mixture was 11.25% by mass to prepare a mixture (III).

[0093] The mixtures (I) and (III) were fed to an extruder controlled at 250°C, kneaded in a molten state, and laminated in a T-die extruder equipped with a feed block so that the heat seal layer had a thickness of 15 μm and the concealing layer had a thickness of 45 μm to produce the film of Example 1. In the obtained film, the propylene content in the heat seal layer and the propylene content in the concealing layer were both 70 mass% or more.

[0094] Examples 2 to 4 Films of Examples 2 to 4 were produced in the same manner as in Example 1, except that the mixing ratio of resin (A) and resin (B1) in mixture (I) was changed as shown in Table 1. The propylene content in the heat seal layer and the propylene content in the concealing layer of the obtained films were both 70% by mass or more.

[0095] Example 5 A film of Example 5 was produced in the same manner as in Example 1, except that the mixing ratio of resin (C) and elastomer (D) in mixture (II) (ratio [elastomer (D) / resin (C)]) was changed as shown in Table 1. In the obtained film, the propylene content in the heat seal layer and the propylene content in the concealing layer were both 70 mass% or more.

[0096] Examples 6 and 7 Films of Examples 6 and 7 were produced in the same manner as in Example 5, except that the mixing ratio of titanium oxide (E) in the mixture (III) was changed as shown in Table 1. In the obtained films, the propylene content in the heat seal layer and the propylene content in the concealing layer were both 70 mass% or more.

[0097] Example 8 A film of Example 8 was produced in the same manner as in Example 1, except that resin (B2) was used instead of resin (B1). The propylene content in the heat seal layer and the propylene content in the concealing layer of the obtained film were both 70% by mass or more.

[0098] Examples 9 and 10 Films of Examples 9 and 10 were produced in the same manner as in Example 8, except that the mixing ratio of resin (A) and resin (B2) in mixture (I) was changed as shown in Table 2. The propylene content in the heat seal layer and the propylene content in the concealing layer of the obtained films were both 70% by mass or more.

[0099] Example 11 A film of Example 11 was produced in the same manner as in Example 1, except that the heat seal layer was formed using resin (A) alone instead of mixture (I) (i.e., resin (B1) was not used). The propylene content in the heat seal layer and the propylene content in the concealing layer of the obtained film were both 70 mass% or more.

[0100] Example 12 A film of Example 12 was produced in the same manner as in Example 1, except that the heat seal layer was formed using resin (B1) alone instead of mixture (I) (i.e., resin (A) was not used). The propylene content in the heat seal layer and the propylene content in the concealing layer of the obtained film were both 70 mass% or more.

[0101] Example 13 A film of Example 13 was produced in the same manner as in Example 3, except that resin (B3) was used instead of resin (B1). The propylene content in the heat seal layer and the propylene content in the concealing layer of the obtained film were both 70% by mass or more.

[0102] Example 14 A film of Example 14 was produced in the same manner as in Example 1, except that the layer thicknesses of the heat seal layer and the concealing layer were changed as shown in Table 2. In the obtained film, the propylene content in the heat seal layer and the propylene content in the concealing layer were both 70 mass% or more.

[0103] Comparative Example 1 A film of Comparative Example 1 was produced in the same manner as in Example 1, except that a mixture (III) was prepared using resin (C) instead of mixture (II) (i.e., elastomer (D) was not used).

[0104] <Comparative Example 2> A film of Comparative Example 2 was produced in the same manner as in Example 1, except that the mixture (II) was used instead of the mixture (III) to form the hiding layer (i.e., titanium oxide (E) was not used).

[0105] Example 15 A mixture (I) for forming a heat seal layer and a mixture (III) for forming a concealing layer were prepared in the same manner as in Example 1. In addition, a mixture (IV) having the same composition as the mixture (I) for forming the heat seal layer was prepared for forming a laminate layer.

[0106] The above mixtures (I), (III), and (IV) were fed to an extruder controlled at 250°C, kneaded in a molten state, and laminated in a T-die extruder having a feed block so that the heat-seal layer and the laminate layer were each 10 μm thick and the concealing layer was 40 μm thick, producing the film of Example 15. The propylene content in the heat-seal layer, the propylene content in the concealing layer, and the propylene content in the laminate layer of the obtained film were all 70 mass% or more.

[0107] Examples 16, 17, 23, and 24 Films of Examples 16, 17, 23, and 24 were each produced in the same manner as in Example 15, except that the mixing ratio of resin (A) and resin (B1) in mixture (I) and mixture (IV) was changed as shown in Table 3. The propylene content in the heat seal layer, the propylene content in the concealing layer, and the propylene content in the laminate layer of the obtained films were all 70% by mass or more.

[0108] Example 18 The film of Example 18 was produced in the same manner as in Example 15, except that the mixing ratio of resin (C) and elastomer (D) in mixture (II) (ratio [elastomer (D) / resin (C)]) was changed as shown in Table 3. In the obtained film, the propylene content in the heat seal layer, the propylene content in the concealing layer, and the propylene content in the laminate layer were all 70 mass% or more.

[0109] Examples 19 to 22 and Comparative Example 3 Films of Examples 19 to 22 and Comparative Example 3 were each produced in the same manner as in Example 18, except that the mixing ratio of titanium oxide (E) in the mixture (III) was changed as shown in Table 3. The propylene content in the heat seal layer, the propylene content in the concealing layer, and the propylene content in the laminate layer of the obtained films were all 70% by mass or more.

[0110] <Various Evaluations> The films obtained in each example were evaluated as follows. The results are shown in Tables 1 to 3.

[0111] [Evaluation of cold impact resistance] The impact strength of the films obtained in each example during low-temperature storage was measured under conditions of a temperature of -5°C, a weight of 1.5 J, and a bullet size of 1 / 2 inch using a film impact tester manufactured by Toyo Seiki Co., Ltd. An impact strength (film impact) of 6.00 J / mm or more was determined to be excellent in cold impact resistance.

[0112] [Hiding property] The hiding property of the film obtained in each example was evaluated using a portable transmission densitometer (Model No. 341C) manufactured by X-RITE Co., Ltd. When the measured transmission density was 0.20 or more, it was determined that sufficient hiding property was obtained.

[0113] [Evaluation of low-temperature sealability] A 12 μm-thick biaxially oriented polyester film (PET), a 9 μm-thick AL foil, a 15 μm-thick biaxially oriented polyamide film (ONy), and the film obtained in each example (polypropylene-based film) were bonded together using a urethane-based adhesive by a conventional dry lamination method to prepare a laminate having the following configuration: Laminate configuration: PET / adhesive / AL foil / adhesive / ONy / adhesive / polypropylene-based film. Note that the film in each example was bonded to the ONy so that the heat-sealable layer was on the outer layer side (the outermost layer of the laminate).

[0114] Two sheets of the laminate obtained above were prepared, and the polypropylene films of these laminates were heat-sealed together using a heat sealer manufactured by Tester Sangyo Co., Ltd. under conditions of a sealing pressure of 0.2 MPa, a sealing time of 1 second, and a sealing width of 5 mm, with sealing temperatures between 140°C and 160°C in 5°C increments. After heat sealing at each temperature, the sealed portion was cut into 15 mm wide x 80 mm pieces and the heat seal strength was measured using a tensile tester manufactured by Shimadzu Corporation at a tensile speed of 300 mm / min. The lower the temperature (sealing temperature) at which the heat seal strength reached 40 N / 15 mm or more, the better the low-temperature sealability was judged to be. The sealing temperatures shown in Tables 1 to 3 are the temperatures at which the heat seal strength reached 40 N / 15 mm or more.

[0115] [Heat resistance evaluation] A 130 mm x 180 mm bag was prepared using the film obtained in each example. The inner surfaces of the bags were sealed together without any contents inside, and retort treatment was performed at 135°C for 40 minutes. Thereafter, the seals on three sides were cut, and the film was peeled off by hand to evaluate post-retort fusion. Films that were easy to peel off were rated A, those that felt tacky were rated B, and those that deformed upon peeling were rated C.

[0116]

[0117]

[0118]

[0119] 1...heat seal layer, 2...concealing layer, 3...laminate layer, 4...adhesive layer, 5...transparent vapor deposition film, 6...adhesive layer, 7...substrate film, 10, 11...multilayer film, 100, 101...packaging material.

Claims

DEPCT6806 / 02 / 25681. Multilayer film consisting of: a heat sealing layer; and a cover layer provided on the heat sealing layer, where the heat sealing layer consists of polypropylene homopolymer (A) and / or propylene-based copolymer resin (B), the cover layer consists of polypropylene-ethylene block copolymer resin (C), ethylene-propylene copolymer elastomer (D), and titanium oxide (E), and the amount of titanium oxide (E) in the cover layer is 0.10 percent to 30.00 percent by reference mass.

1. The total mass of the covering layer.

2. Multilayer film according to claim 1, in which the heat seal layer consists of a polypropylene-based copolymer resin (B), and the polypropylene-based copolymer resin (B) has a melting point of 132 °C to 150 °C.

3. Multilayer film according to claim 1, in which the heat seal layer consists of a polypropylene-based copolymer resin (B), and the ethylene content in the polypropylene-based copolymer resin (B) is 3.0 percent to 6 percent.0 percent by mass reference of the total mass of the polypropylene copolymer resin (B) 4. Multilayer film under any one of the claims 1 to 3, where the amount of polypropylene homopolymer (A) in the heat seal layer is 10 percent to 70 percent by mass reference of the total mass of the heat seal layer, and the amount of polypropylene copolymer resin (B) in the heat seal layer is 30 percent to 90 percent by mass reference of the total mass of the heat seal layer 5. Multilayer film under any one of the claims 1 to 3, where the mass ratio of the amount of polypropylene copolymer resin (B) to the amount of polypropylene homopolymer (A) in the heat seal layer is 0.10 to 9.00 6.Multilayer films under any one of the claims 1 through 3, where the amount of propylene-ethylene copolymer block resin (C) in the cover layer is 35 percent to 90 percent by reference mass of the total cover layer mass, and the amount of ethylene-propylene copolymer elastomer (D) in the cover layer is 10 percent to 50 percent by reference mass of the total cover layer mass.

7. Multilayer films under any one of the claims 1 through 3, where the mass ratio of the amount of ethylene-propylene 8. Multilayer films under any of the claims 1 through 3, where the amount of propylene by mass or more is 70 percent by mass of the multilayer film; 9. Multilayer films under any of the claims 1 through 3, where the thickness of the thermal seal layer is 8 percent to 30 percent of the thickness of the multilayer film; 10.

11. Multilayer films under any of the claims 1 through 3, in which the thickness of the covering layer is 20 nm or more.

12. Multilayer films under any of the claims 1 through 3, in which the multilayer film is composed of a heat sealing layer, a covering layer, and a laminate layer, respectively, and the laminate layer is composed of polypropylene homopolymer (A) and / or a polypropylene-based copolymer resin (B).

13. Multilayer films under claim 11, in which the total thickness of the heat sealing layer and the laminate layer is 16 percent to 42 percent reference to the thickness of the multilayer film.

14. Packaging materials which are composed of multilayer films under any of the claims 1 through 3.

15. Packaging materials under claim 13, which are additionally composed of a bidirectional stretch polypropylene film on the opposite side of the heat sealing layer when viewed from the covering layer of the multilayer film.

16. Packaging manufactured as bags from the packaging materials under claim 14.

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