Resin composition for retort sealant film, retort sealant film, multilayer film, and method for producing retort sealant film

Abstract

To provide a multilayer film and a retort sealant film which can be heat-sealed at a low temperature and exhibit excellent retort fusion resistance, a resin composition capable of forming the retort sealant film, and a method for producing the retort sealant film.SOLUTION: A resin composition for a retort sealant film comprising a propylene-based polymer A containing a structural unit derived from propylene and a structural unit derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms and having a melt flow rate of 1 to 10g / 10 min and a melting point of 135 to 150°C. and an ethylene-based polymer B, a retort sealant film containing the resin composition, a multilayer film comprising the film, and a method for producing the retort sealant film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition for a retort sealant film, a retort sealant film, a multilayer film, and a method for producing a retort sealant film. [Background technology]

[0002] Conventionally, for example, films used in various packaging materials have been known that have a structure in which a biaxially oriented film such as polyethylene terephthalate (PET) or nylon is used as a base film, and a polypropylene (PP)-based unoriented film is laminated to this base film as a sealant film. This film is heat-sealed to form a storage space with the sealant film on the inside, to form a packaging bag. In terms of workability, productivity, and maintaining the ability to seal the contents, it is common for films used in packaging bags to have the sealant film laminated over almost the entire surface of the base film, i.e., the inner surface of the heat-sealed portion and the inner surface of the storage space are formed from the same sheet. Patent Document 1 describes the following polypropylene resin as a material composition for forming such a sealant film. "A polypropylene resin comprising 65 to 75% by weight of a propylene polymer (A) and 35 to 25% by weight of a propylene-ethylene random copolymer (B), and satisfying all of the following requirements (1), (2), and (3) (wherein the total weight of the propylene polymer (A) and the propylene-ethylene random copolymer (B) is 100% by weight). Requirement (1): The intrinsic viscosity ([η]B) of the propylene-ethylene random copolymer (B) is 3.0 to 4.5 dl / g. Requirement (2): The ratio ([η]B / [η]A) of the intrinsic viscosity ([η]A) of the propylene-ethylene random copolymer (B) to the intrinsic viscosity ([η]A) of the propylene polymer (A) is 1.9 to 2.6. Requirement (3): The amount of n-hexane extractables is 3.0% by weight or less (where the total weight of the polypropylene resin is 100% by weight). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-209635 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been an increasing demand for recycling of films used in packaging materials, and the shift to monomaterials is being promoted. Specifically, from the perspective of promoting recycling, it is considered preferable to use a polypropylene-based biaxially oriented film, which is the same type as a sealant film made of polypropylene, as the base film. However, polypropylene-based biaxially oriented films have inferior heat resistance compared to polyethylene terephthalate-based biaxially oriented films. For this reason, there is a demand for a sealant film that can be heat-sealed at low temperatures without melting the base film, which is a polypropylene-based biaxially oriented film, and a resin composition that can form this sealant film.

[0005]

[0003] Incidentally, when packaging bags formed using sealant films are used, for example, for packaging retort food, they are typically heated and sterilized while the food is contained in the packaging bag. During this process, there is a risk that the sealant films present on the inner surface of the storage space that contains the food will fuse together. Therefore, there is a demand for a sealant film that has excellent properties that prevent the sealant films from fusing together within the sterilization temperature range (also referred to as "retort fusion resistance" in the present invention), and for a resin composition that can form a sealant film that exhibits excellent retort fusion resistance. However, Patent Document 1 does not consider the low-temperature heat-sealing property (also referred to as "low-temperature sealability" in the present invention) or retort fusion resistance of the resin composition that forms the sealant film.

[0006] An object of the present invention is to provide a multilayer film and a retort sealant film that can be heat-sealed at low temperatures and exhibits excellent resistance to retort fusion. Another object of the present invention is to provide a resin composition capable of forming a retort sealant film and a method for producing a retort sealant film. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have found that, by identifying the structural units constituting the propylene polymer in a resin composition containing a propylene polymer and an ethylene polymer, and then using a propylene polymer having a melt flow rate and melting point set within a specific range in combination with an ethylene polymer, a film formed from this resin composition can achieve strong heat sealing even at temperatures that do not melt a biaxially stretched polypropylene film, while at the same time being difficult to heat-seal at sterilization temperatures, thereby achieving the contradictory properties of heat-sealability (sealing temperature). Furthermore, the present inventors have found that, by utilizing the above-mentioned excellent properties, the resin composition containing the propylene polymer and the ethylene polymer is suitable as a resin composition for forming a retort sealant film (retort sealant layer) in a film for packaging retort food. The present invention was completed through further research based on these findings.

[0008] That is, the object of the present invention has been achieved by the following means. <1> a propylene-based polymer A that contains structural units derived from propylene and structural units derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms, and that has a melt flow rate of 1 to 10 g / 10 min measured at 230°C under a load of 2.16 kg and a melting point of 135 to 150°C; and an ethylene polymer B, Resin composition for retort sealant film. <2> The propylene polymer A has a melt flow rate of 1 to 5 g / 10 min. <1> The resin composition for a retort sealant film according to claim 1. <3> the propylene polymer A contains 85% by mass or more and less than 98% by mass of structural units derived from propylene and more than 2% by mass and 15% by mass or less of structural units derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms; <1> or <2> The resin composition for a retort sealant film according to claim 1. <4> The density of the ethylene polymer B is 0.915 to 0.965 g / cm 3 That is, <1> ~ <3> The resin composition for a retort sealant film according to any one of claims 1 to 4. <5> The composition further contains a heterophasic propylene polymerization material C including a propylene polymer C-1 containing 98% by mass or more of structural units derived from propylene, and a propylene-α-olefin copolymer C-2 containing more than 40% by mass but less than 85% by mass of structural units derived from propylene and more than 15% by mass but less than 60% by mass of structural units derived from at least one selected from ethylene and α-olefins having 4 to 12 carbon atoms, <1> ~ <4> The resin composition for a retort sealant film according to any one of claims 1 to 4. <6> With respect to 100 parts by mass of the total content of the polymers contained in the resin composition, the content of the propylene polymer A is 50 to 95 parts by mass, the content of the ethylene polymer B is 5 to 50 parts by mass; <1> ~ <4> The resin composition for a retort sealant film according to any one of claims 1 to 4. <7> With respect to 100 parts by mass of the total content of the polymers contained in the resin composition, the content of the propylene polymer A is 45 to 90 parts by mass, the content of the ethylene polymer B is 5 to 50 parts by mass, the content of the heterophasic propylene polymerization material C is 5 to 40 parts by mass; <5> The resin composition for a retort sealant film according to claim 1. <8> The composition further contains a masterbatch in which an organic peroxide is impregnated into a powdery polyolefin in an amount of 1 to 30% by mass (wherein the total amount of the organic peroxide and the powdery polyolefin is 100% by mass). <1> ~ <7> The resin composition for a retort sealant film according to any one of claims 1 to 4. <9> The resin composition contains 0.005 to 0.3 parts by mass of the organic peroxide relative to 100 parts by mass of the total amount of polymers contained in the resin composition. <8> The resin composition for a retort sealant film according to claim 1. <10> the above <1> ~ <9> A retort sealant film comprising the resin composition for a retort sealant film according to any one of claims 1 to 4. <11> The thickness is 5 to 200 μm. <10> The retort sealant film according to claim 1. <12> the above <10> or <11> A multilayer film comprising the retort sealant film according to claim 1 as a retort sealant layer. <13> the above <1> ~ <9> a melt-kneading step of melt-kneading the resin composition for a retort sealant film according to any one of the preceding claims; an extrusion step of extruding the melt-kneaded resin composition; and forming a film from the extruded resin composition. [Effects of the Invention]

[0009] The present invention can provide a multilayer film and a retort sealant film that can be heat-sealed at low temperatures and exhibits excellent resistance to retort fusion. The present invention also provides a resin composition capable of forming a retort sealant film and a method for producing a retort sealant film. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be specifically described below, but is not limited to the specific embodiments shown below.

[0011] [[Terminology Explanation]] In the present invention and this specification, the term "α-olefin" refers to an olefin having a carbon-carbon double bond at the terminal side (α-position). In the present invention and this specification, the bonding mode (arrangement of structural units) of two or more structural units in a copolymer that becomes a resin or elastomer is not particularly limited, and unless otherwise specified, may be any bonding mode, such as random bonding (random copolymer), block bonding (block copolymer), alternating bonding (alternating copolymer), or graft bonding (graft copolymer).

[0012] In the present invention and this specification, the "olefin polymer" (also referred to as polyolefin) is not particularly limited and includes polymers of one or more α-olefins, such as ethylene polymers and propylene polymers.

[0013] Olefin polymers are made up of, for example, carbon-14 ( 14 The polymer may be a polymer containing carbon atoms (monomers) that have been recycled (mechanically recycled).

[0014] Carbon 14( contained in olefin polymers 14 The concentration of carbon (C) is calculated as pMC (percentage of moderate carbon: unit %) using the AMS (Accelerator mass spectrometry) method specified in ISO 16620-2:2019. Carbon dioxide in the atmosphere contains carbon-14( 14 C) is contained in a certain proportion, so plants that grow by absorbing carbon dioxide from the atmosphere, such as corn and trees, 14 On the other hand, fossil resources such as petroleum, which are thought to have been stored underground for a long time, contain carbon-14( 14 It is also known that carbon-14 (C) is hardly contained in the constituent elements of olefin polymers by using plant-derived substances as raw materials for the monomers used in the production of olefin polymers.14 C) can be contained.

[0015] In the production of olefin-based polymers, monomers derived from fossil resources (hereinafter referred to as "fossil resource-derived monomers"; for example, fossil resource-derived ethylene, fossil resource-derived propylene, fossil resource-derived 1-butene, fossil resource-derived 1-hexene, etc.), monomers derived from plants (hereinafter referred to as "plant-derived monomers"; for example, plant-derived ethylene, plant-derived propylene, plant-derived 1-butene, plant-derived 1-hexene, etc.), monomers obtained by chemical recycling (hereinafter referred to as "chemically recycled monomers"; for example, chemically recycled ethylene, chemically recycled propylene, chemically recycled 1-butene, chemically recycled 1-hexene, etc.), etc. can be used, and these can be used in combination of two or more types. Specific combinations of monomers that can be used in producing an olefin polymer are not particularly limited and include combinations of two or more monomers appropriately selected from fossil resource-derived monomers, plant-derived monomers, and chemically recycled monomers. Examples include a combination of a fossil resource-derived monomer and a plant-derived monomer, a combination of a fossil resource-derived monomer and a chemically recycled monomer, a combination of a plant-derived monomer and a chemically recycled monomer, and a combination of a fossil resource-derived monomer, a plant-derived monomer, and a chemically recycled monomer.

[0016] Specific combinations of monomers that can be used in producing olefin-based polymers include, for example, the following combinations (E1) to (E3) for polyethylene-based polymers, and the following combinations (P1) to (P3) for polypropylene-based polymers. (E1) A combination of two or three types of ethylene selected from fossil resource-derived ethylene, plant-derived ethylene, and chemically recycled ethylene (E2) A combination of one or more ethylenes selected from fossil resource-derived ethylene, plant-derived ethylene, and chemically recycled ethylene, and one or more 1-butenes selected from fossil resource-derived 1-butene, plant-derived 1-butene, and chemically recycled 1-butene. (E3) A combination of one or more ethylenes selected from fossil resource-derived ethylene, plant-derived ethylene, and chemically recycled ethylene, and one or more 1-hexenes selected from fossil resource-derived 1-hexene, plant-derived 1-hexene, and chemically recycled 1-hexene. (E4) A combination of one or more ethylenes selected from fossil resource-derived ethylene, plant-derived ethylene, and chemically recycled ethylene, one or more 1-butenes selected from fossil resource-derived 1-butene, plant-derived 1-butene, and chemically recycled 1-butene, and one or more 1-hexenes selected from fossil resource-derived 1-hexene, plant-derived 1-hexene, and chemically recycled 1-hexene.

[0017] (P1) A combination of two or three types of propylene selected from fossil resource-derived propylene, plant-derived propylene, and chemically recycled propylene. (P2) A combination of one or more propylenes selected from fossil resource-derived propylene, plant-derived propylene, and chemically recycled propylene, and one or more ethylenes selected from fossil resource-derived ethylene, plant-derived ethylene, and chemically recycled ethylene. (P3) A combination of one or more propylenes selected from fossil resource-derived propylene, plant-derived propylene, and chemically recycled propylene, and one or more 1-butenes selected from fossil resource-derived 1-butene, plant-derived 1-butene, and chemically recycled 1-butene.

[0018] Fossil resource-derived monomers are derived from carbon that makes up carbon compounds that are fossil resources (underground resources) such as petroleum, coal, and natural gas, and are generally made up of carbon-14 ( 14C). Methods for producing fossil resource-derived monomers include known methods, such as cracking petroleum-derived naphtha and ethane, and dehydrogenating ethane and propane to produce olefins.

[0019] Plant-derived monomers (also called biomass-derived monomers) are derived from carbon circulating on the earth's surface as plants and animals, and are monomers obtained from any renewable natural raw materials and their residues, such as those derived from plants or animals, including fungi, yeast, algae, and bacteria. Plant-derived monomers generally contain carbon-14 ( 14 C) at a certain rate, for example, 10 -12 At a rate of about 14 carbon ( 14 C). Examples of methods for producing plant-derived monomers include known methods, such as cracking bionaphtha, vegetable oil, or animal oil; dehydrogenation of biopropane; methods of separating alcohol from fermented products such as sugars extracted from plant materials such as sugarcane or corn and then subjecting it to a dehydration reaction (see, for example, JP-T-2010-511634, JP-T-2011-506628, and JP-T-2013-503647); and methods of subjecting ethylene obtained from plant-derived ethanol to a metathesis reaction with n-butene (see, for example, WO 2007 / 055361).

[0020] Chemically recycled monomers are derived from carbon generated by the decomposition and combustion of waste, and their carbon-14( 14 C) The content varies depending on the waste. Methods for producing chemically recycled monomers include known methods, such as thermal decomposition of waste plastics (see, for example, JP-A-2017-512246, etc.), cracking of waste vegetable oil, waste animal oil, etc. (see, for example, JP-A-2018-522087, etc.), and gasification, alcohol conversion, and dehydration of waste such as food waste, biomass waste, food waste, waste oil, waste wood, paper waste, and waste plastic (see, for example, JP-A-2019-167424, WO 2021 / 006245, etc.).

[0021] When two or more types of fossil resource-derived monomers, plant-derived monomers, and chemically recycled monomers are used in the production of olefin polymers, the monomers produced individually can be appropriately combined, as described above. Furthermore, by using a mixture of a fossil resource-derived compound and a plant-derived compound, a mixture of a fossil resource-derived compound and a chemically recycled compound, a mixture of a plant-derived compound and a chemically recycled compound, or a mixture of a fossil resource-derived compound, a plant-derived compound, and a chemically recycled compound as a raw material or intermediate in the monomer (olefin) production process, a mixture containing the above-mentioned combination of monomers can be used instead of the above-mentioned combination of monomers.

[0022] Carbon 14( 14 As the ethylene polymer (polyethylene resin) containing C), commercially available polyethylene resins can be used, such as the "I'M GREEN" (green polyethylene) series manufactured by Braskem, the "TRUCIRCLE" series manufactured by SABIC, and the "CirculenRenew" series manufactured by LyondellBasell.

[0023] Carbon 14( 14 As the polypropylene-based polymer (polypropylene resin) containing C), commercially available polypropylene resins can be used, such as the "Bornewables" series manufactured by Borealis, the "TRUCIRCLE" series manufactured by SABIC, and the "CirculenRenew" series manufactured by LyondellBasell.

[0024] Carbon 14( of olefin polymer 14The carbon-14 (C) concentration (content) is not particularly limited, but from the viewpoint of reducing the environmental load, for example, it is preferably 0.2 pMC (%) or more, more preferably 0.5 pMC (%) or more, even more preferably 1 pMC (%) or more, particularly preferably 5 pMC (%) or more, and most preferably 10 pMC (%) or more, as measured by the above-mentioned method. 14 C) The upper limit of the concentration is not particularly limited, but from the viewpoint of cost, for example, the pMC(%) measured by the above-mentioned measurement method is preferably 99 pMC(%) or less, more preferably 95 pMC(%) or less, even more preferably 90 pMC(%) or less, particularly preferably 70 pMC(%) or less, and most preferably 50 pMC(%) or less.

[0025] Carbon 14( of olefin polymer 14 C) The concentration can be adjusted by changing the ratio of the fossil resource-derived monomer, plant-derived monomer, and chemically recycled monomer used in the production of the olefin polymer.

[0026] In the present invention and this specification, unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass".

[0027] In the present invention and this specification, when describing content, physical properties, etc., by indicating a numerical range, if the upper and lower limits of the numerical range are described separately, any of the upper and lower limits can be appropriately combined to form a specific numerical range. On the other hand, when describing multiple numerical ranges expressed using "to", the upper and lower limits forming the numerical range are not limited to the specific combination written before and after "to" as a specific numerical range, but can be a numerical range obtained by appropriately combining the upper and lower limits of each numerical range. Note that in the present invention and this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the upper and lower limits.

[0028] In the present invention and this specification, the term "melt flow rate (MFR)" means "melt mass flow rate" and, unless otherwise specified, is the melt flow rate (unit: g / 10 min) measured in accordance with JIS K 7210-1:2014 and JIS K 7210-2:2014 under conditions of a temperature of 230°C and a load of 2.16 kgf.

[0029] [[Resin composition]] The resin composition of the present invention contains a propylene-based polymer A and an ethylene-based polymer B, which contain structural units derived from propylene and structural units derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms, and have a melt flow rate of 1 to 10 g / 10 min measured at 230°C under a load of 2.16 kg and a melting point of 135 to 150°C. The resin composition of the present invention containing the propylene polymer A and the ethylene polymer B, and the film containing (formed from) the resin composition of the present invention, can be strongly heat-sealed even at low temperatures (e.g., 140 to 180°C) without melting, for example, a biaxially stretched polypropylene film, and exhibits excellent low-temperature sealing properties (excellent heat-sealing strength at low temperatures).On the other hand, at sterilization temperatures (e.g., 100 to 135°C) employed in the sterilization treatment of retort foods, they are less likely to heat-seal to each other and exhibit excellent retort fusion resistance. Taking advantage of the excellent properties described above, the resin composition of the present invention is suitably used as a resin composition for forming a retort sealant film provided in a film for packaging retort food.

[0030] First, the components contained in the resin composition of the present invention will be described. The resin composition of the present invention may contain one or more types of each of the components.

[0031] [Propylene Polymer A] In the present invention, a propylene-based polymer refers to a polymer containing structural units derived from propylene (also referred to as "propylene structural units") in an amount of more than 50% by mass relative to all structural units (100% by mass).

[0032] The propylene polymer A contained in the resin composition of the present invention contains a propylene structural unit and a structural unit derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms. The propylene polymer A has a melt flow rate (MFR) of 1 to 10 g / 10 min measured at 230°C under a load of 2.16 kg, and a melting point of 135 to 150°C.

[0033] When the MFR (measured by the above method) of the propylene polymer A is in the range of 1 to 10 g / 10 min, the resin composition of the present invention has excellent film formability and can achieve both low-temperature sealability and retort weld resistance. Specifically, when the MFR is less than 1 g / 10 min, the film formability is poor, and when the MFR exceeds 10 g / 10 min, both low-temperature sealability and retort weld resistance cannot be achieved. In one preferred embodiment, the MFR of the propylene polymer A is 1 to 5 g / 10 min, since this allows the resin composition to maintain excellent film formability and retort weld resistance while further improving low-temperature sealability and achieving both low-temperature sealability and retort weld resistance at high levels. In this preferred embodiment, the MFR of the propylene polymer A is more preferably 1 to 3.5 g / 10 min, even more preferably 1 to 3 g / 10 min, and particularly preferably 1 to 2.5 g / 10 min, from the viewpoint of achieving a high level of both low-temperature sealability and retort weld resistance in a well-balanced manner. On the other hand, in another preferred embodiment, the MFR of the propylene polymer A is 7.0 to 10 g / 10 min, from the viewpoint of achieving a high level of both low-temperature sealability and retort weld resistance while maintaining excellent film formability. In this preferred embodiment, the MFR of the propylene polymer A is more preferably 7.5 to 10 g / 10 min, even more preferably 7.5 to 9.5 g / 10 min, and particularly preferably 7.5 to 9.0 g / 10 min, from the viewpoint of achieving a high level of both low-temperature sealability and retort weld resistance in a well-balanced manner.

[0034] When the melting point (Tm) of the propylene polymer A is in the range of 135 to 150°C, both low-temperature sealability and retort weld resistance can be achieved. Specifically, when the Tm is less than 135°C, the retort weld resistance decreases, and when the Tm is more than 150°C, the low-temperature sealability decreases. The Tm of the propylene polymer A is preferably 135 to 145°C, more preferably 138 to 145°C, and even more preferably 138 to 142°C, in order to achieve a high level of both low-temperature sealability and retort weld resistance in a well-balanced manner. The melting point of the propylene polymer A is a melting point measured by differential scanning calorimetry (DSC), and specifically, is a value measured by the measurement method described in the examples below.

[0035] In the propylene polymer A, the MFR and melting point can be appropriately combined within the above-mentioned ranges, and the above-mentioned preferred MFR can be combined with the above-mentioned preferred melting point. Examples of the combination of MFR and melting point include a combination of an MFR of 1 to 10 g / 10 min with a melting point of 135 to 150°C, and preferred examples include a combination of an MFR of 1 to 5 g / 10 min or 7.0 to 10 g / 10 min with a melting point of 135 to 145°C. In the above combinations, the MFR can be within the above-mentioned more preferred, even more preferred, or particularly preferred ranges, and the melting point can be within the above-mentioned more preferred, even more preferred ranges.

[0036] The propylene polymer A is a copolymer containing propylene structural units and structural units derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms. In the present invention, the propylene polymer A does not include a propylene homopolymer or a heterophasic propylene polymerization material C described below, and is preferably a random copolymer containing propylene structural units and structural units derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms.

[0037] The α-olefin may have 4 to 12 carbon atoms, and preferably 4 to 8. Examples of α-olefins having 4 to 12 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, and 4-methyl-1-hexene, and 1-butene is preferred. The propylene polymer B may contain one or more types of ethylene structural units and olefin structural units, and preferably one to three types.

[0038] The propylene polymer A includes a random copolymer containing a propylene structural unit and a unit derived from ethylene (also referred to as an "ethylene structural unit"). The propylene polymer A also encompasses random copolymers containing propylene structural units and units derived from an α-olefin having 4 to 12 carbon atoms (also referred to as "olefin structural units"). Examples of the random copolymer include a propylene-1-butene random copolymer, a propylene-1-hexene random copolymer, a propylene-1-octene random copolymer, and a propylene-1-decene random copolymer. The propylene polymer A includes a random copolymer containing a propylene structural unit, an ethylene structural unit, and an olefin structural unit, and examples of this random copolymer include a propylene-ethylene-1-butene copolymer, a propylene-ethylene-1-hexene copolymer, a propylene-ethylene-1-octene copolymer, and a propylene-ethylene-1-decene copolymer.

[0039] In the propylene polymer A, the content of propylene structural units relative to all structural units (100% by mass) may be 50% by mass or more, preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 94% by mass or more. On the other hand, the content of propylene structural units may be less than 100% by mass, preferably 99% by mass or less, more preferably less than 98% by mass, even more preferably 97.5% by mass or less, and particularly preferably 97% by mass or less.

[0040] In the propylene polymer A, the total content of the ethylene structural units and the olefin structural units may be more than 0% by mass, preferably 1.0% by mass or more, more preferably more than 2.0% by mass, even more preferably 2.5% by mass or more, and particularly preferably 3.0% by mass or more, relative to all structural units (100% by mass). On the other hand, the total content of the ethylene structural units and the olefin structural units may be less than 100% by mass, preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 6.0% by mass or less.

[0041] In the propylene polymer A, the content of the ethylene structural units can be appropriately set in consideration of the total content, for example, 0.5 to 5.0 mass% and preferably 1.0 to 4.5 mass% relative to all structural units (100 mass%). The content of the olefin structural units can be appropriately set in consideration of the total content, for example, 1.0 to 8.0 mass% and preferably 1.5 to 7.0 mass% relative to all structural units (100 mass%).

[0042] In the resin composition of the present invention, it is preferable that the propylene polymer A contains a propylene polymer containing 85% by mass or more but less than 98% by mass of structural units derived from propylene and more than 2% by mass but less than 15% by mass of structural units derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms, from the viewpoint of low-temperature sealability and retort welding resistance. The resin composition of the present invention may contain, as the propylene polymer A, a propylene polymer (A-1) in which the content of propylene structural units is 98% by mass or more relative to all structural units (100% by mass). The content of propylene structural units in this propylene polymer (A-1) is preferably 99% by mass or more and 100% by mass or less, more preferably 100% by mass. That is, the propylene polymer (A-1) is preferably a propylene homopolymer. The propylene polymer (A-1) may contain structural units derived from at least one selected from ethylene and α-olefins having 4 to 12 carbon atoms. The total content of these structural units is preferably 2% by mass or less, more preferably 0% by mass or more and less than 1% by mass relative to all structural units. The α-olefins having 4 to 12 carbon atoms are as described above. In one embodiment of the resin composition of the present invention, it is preferable that the resin composition does not contain a propylene polymer (A-1). In the present invention, the fact that the resin composition does not contain a propylene polymer (A-1) means that the content of the propylene polymer (A-1) in the resin composition is 10 mass % or less.

[0043] The propylene polymer A is preferably a crystalline propylene polymer. In the present invention, "crystalline" means that the propylene polymer contains a portion in which propylene structural units are arranged in an orderly manner.

[0044] The method for producing the propylene polymer A is not particularly limited, and examples thereof include a method of polymerizing raw materials such as propylene or ethylene using a Ziegler-Natta catalyst, a metallocene catalyst, etc. The polymerization method is not particularly limited, and examples thereof include a method of polymerizing in an inert solvent such as hexane, heptane, toluene, or xylene, a method of polymerizing in liquid propylene or ethylene, a method of adding a catalyst to gaseous propylene or ethylene and polymerizing in a gas phase, or a polymerization method that combines these methods.

[0045] As described above, the propylene polymer A used in the present invention may contain, for example, carbon 14 ( 14 The polymer may be a polymer containing carbon atoms (monomers) that have been recycled (mechanically recycled).

[0046] [Ethylene polymer B] In the present invention, the ethylene-based polymer refers to a polymer containing ethylene structural units in an amount of more than 50% by mass relative to all structural units (100% by mass). The ethylene-based polymer B is not particularly limited, and examples thereof include polymers containing ethylene structural units in an amount of 60% by mass or more relative to the total structural units (100% by mass). Specific examples include ethylene homopolymers and ethylene-based copolymers containing ethylene structural units in an amount of more than 50% by mass but less than 100% by mass relative to the total structural units. Preferred ethylene-based copolymers include copolymers containing 60 to 98% by mass of ethylene structural units relative to the total structural units (100% by mass) and 2 to 40% by mass of the olefin structural units derived from an α-olefin having 4 to 12 carbon atoms relative to the total structural units. The content of the ethylene structural units in the ethylene-based copolymer is more preferably 70 to 95% by mass, even more preferably 75 to 95% by mass, and particularly preferably 80 to 95% by mass relative to the total structural units. The content of the olefin structural units in the ethylene-based copolymer is more preferably 5 to 30% by mass, even more preferably 5 to 25% by mass, and particularly preferably 5 to 20% by mass relative to the total structural units.

[0047] The α-olefin may have 4 to 12 carbon atoms, preferably 4 to 8. Examples of the α-olefin having 4 to 12 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, and 4-methyl-1-hexene, and from the viewpoint of improving heat seal strength, 1-butene or 1-hexene is preferred. The olefin structural unit contained in the ethylene polymer B may be one type or two or more types, and preferably one or two types.

[0048] The ethylene polymer B is not particularly limited, but is preferably polyethylene, including high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), very-low-density polyethylene (VLDPE), and ultra-high-molecular-weight polyethylene. Among these, high-density polyethylene and low-density polyethylene are preferred because, when used in combination with the propylene copolymer A, they can achieve both low-temperature sealability and retort fusion resistance while maintaining film formability. Low-density polyethylene includes high-pressure low-density polyethylene produced by the tubular method or the vessel method, as well as linear low-density polyethylene (LLDPE), which is a copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms. As low-density polyethylene, linear low-density polyethylene is preferred in terms of low-temperature sealing properties and retort fusion resistance. In the present invention, the density is 0.940 g / cm 3 High density polyethylene is polyethylene with a density of 0.925 g / cm 3 Exceeds 0.940g / cm 3 Polyethylene with a density of 0.911 g / cm or less is considered medium-density polyethylene. 3 Exceeds 0.925g / cm 3 Polyethylenes that satisfy the following conditions are considered to be low-density polyethylenes.

[0049] The density of the ethylene polymer B is not particularly limited and is, for example, 0.850 to 0.970 g / cm 3However, in order to achieve both low-temperature sealing properties and retort fusion resistance, a value of 0.915 to 0.965 g / cm is preferred. 3 It is preferable that the density is 0.920 to 0.965 g / cm 3 More preferably, it is 0.920 to 0.960 g / cm 3 The ethylene polymer B falling within the above preferred range is a low-density polyethylene having a density of 0.915 to 0.925 g / cm 3 Low density polyethylene and high density polyethylene with a density of 0.945 to 0.965 g / cm 3 High density polyethylene is an example. In the present invention, the density of the ethylene polymer B is a value measured in accordance with JIS K 6922-1, as will be described later.

[0050] The MFR of the ethylene polymer B (measured by the above-mentioned method under measurement conditions of a temperature of 190°C and a load of 2.16 kg) is not particularly limited and can be, for example, 0.1 to 50 g / 10 min. However, in terms of achieving excellent film formability of the resin composition of the present invention and achieving both low-temperature sealability and retort fusion resistance, it is preferably 0.3 to 10.0 g / 10 min, more preferably 0.3 to 5.0 g / 10 min, and even more preferably 0.3 to 3.0 g / 10 min.

[0051] The melting point (Tm) of the ethylene polymer B is not particularly limited, but is, for example, preferably 100° C. or higher and lower than 140° C., and more preferably 110° C. or higher and lower than 140° C. When the Tm of the ethylene polymer B is within the above range, both low-temperature sealability and retort fusion resistance can be achieved. The melting point of the ethylene polymer B is a melting point measured by differential scanning calorimetry (DSC), and specifically, is a value measured by the measurement method described in the examples below.

[0052] The molecular weight distribution of the ethylene-based polymer B is not particularly limited. For example, it is preferably from 1 to 10, more preferably from 1 to 7, and still more preferably from 2 to 7. When the molecular weight distribution of the ethylene-based polymer B is 1 or more, the extrusion load is reduced and the processability is good. Further, when the molecular weight distribution of the ethylene-based polymer B is 10 or less, a film excellent in impact resistance at low temperature can be obtained. The "molecular weight distribution" is the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography (hereinafter sometimes referred to as "GPC").

[0053] The ethylene-based polymer B can be produced by a conventional polymerization method. For example, it can be produced using various catalysts such as a metallocene catalyst. The metallocene catalyst is, for example, an olefin polymerization catalyst formed using a transition metal compound having a group with a cyclopentadiene-shaped anion skeleton (hereinafter sometimes referred to as a "metallocene-based transition metal compound").

[0054] Examples of the metallocene-based transition metal compound include a compound represented by the formula: ML a X (n-a) In the formula, M is a transition metal atom of Group 4 of the periodic table of elements or a lanthanide series. L is a group having a cyclopentadiene-shaped anion skeleton or a group containing a hetero atom, and at least one is a group having a cyclopentadiene-shaped anion skeleton. A plurality of Ls may be crosslinked to each other. X is a halogen atom, a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. n represents the valence of the transition metal atom, and a is an integer satisfying 0 < a ≦ n.

[0055] Examples of the metallocene transition metal compound represented by the above formula include bis(1,3-n-butylmethylcyclopentadienyl)zirconium dichloride, bis(1,3-n-propylmethylcyclopentadienyl)zirconium dichloride, bis(n-butylcyclopentadienyl)zirconium dichloride, bis(1,3-dimethylcyclopentadienyl)zirconium dichloride, bis(1,3-diethylcyclopentadienyl)zirconium dichloride, ethylenebis(indenyl)zirconium dichloride, ethylenebis(4-methyl-1-indenyl)zirconium dichloride, and ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride.

[0056] The metallocene transition metal compound is preferably used in contact with an activating cocatalyst. Examples of the activating cocatalyst include an alumoxane compound and an organoaluminum compound in combination with a boron compound such as trityl borate or anilinium borate. The metallocene transition metal compound may also be used in combination with a particulate support, including an inorganic support such as SiO2 or Al2O3, or an organic support such as a polymer of ethylene or styrene.

[0057] As described above, the ethylene polymer B used in the present invention may contain, for example, carbon 14 ( 14 The polymer may be a polymer containing carbon atoms (monomers) that have been recycled (mechanically recycled).

[0058] [Heterophasic propylene polymer material C] The resin composition of the present invention preferably contains a heterophasic propylene polymer material C in addition to the propylene copolymer A and the ethylene polymer B. The heterophasic propylene polymerization material C is a material comprising a propylene-based polymer C-1 containing 98% by mass or more of structural units derived from propylene, and a propylene-α-olefin copolymer C-2 containing more than 40% by mass but not more than 85% by mass of structural units derived from propylene and more than 15% by mass but less than 60% by mass of structural units derived from at least one selected from ethylene and α-olefins having 4 to 12 carbon atoms.

[0059] The propylene polymer C-1 constituting the heterophasic propylene polymerization material C contains 98% by mass or more of propylene structural units. The content of propylene structural units in the propylene polymer C-1 is preferably 99% by mass or more and 100% by mass or less, more preferably 100% by mass. That is, the propylene polymer C-1 may be a propylene homopolymer.

[0060] The propylene polymer C-1 may contain structural units derived from at least one selected from the group consisting of ethylene and α-olefins having 4 to 12 carbon atoms. The content of structural units derived from at least one selected from the group consisting of ethylene and α-olefins having 4 to 12 carbon atoms in the propylene polymer C-1 is preferably 2% by mass or less, and more preferably more than 0% by mass and 1% by mass or less.

[0061] The propylene-α-olefin copolymer C-2 constituting the heterophasic propylene polymerization material C contains more than 40% by mass and not more than 85% by mass of propylene structural units and more than 15% by mass and less than 60% by mass of structural units derived from at least one selected from ethylene and α-olefins having 4 to 12 carbon atoms.

[0062] The content of propylene structural units in the propylene-α-olefin copolymer C-2 is preferably more than 50% by mass and not more than 80% by mass, more preferably from 60% by mass to 80% by mass, and the content of structural units derived from at least one selected from ethylene and α-olefins having 4 to 12 carbon atoms is preferably from 20% by mass to less than 50% by mass, more preferably from 20% by mass to 40% by mass.

[0063] In one embodiment of the heterophasic propylene polymerization material C, the propylene polymer C-1 is preferably a propylene homopolymer, and the propylene-α-olefin copolymer C-2 is preferably a propylene-ethylene copolymer. In this case, the content of the propylene homopolymer C-1 is preferably 50 to 90% by mass, more preferably 60 to 90% by mass, and even more preferably 60 to 80% by mass, based on the total mass of the propylene homopolymer C-1 and the propylene-ethylene copolymer C-2, in order to achieve an excellent balance between low-temperature sealability and retort welding resistance. The content of the propylene-ethylene copolymer C-2 is preferably 10 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 20 to 40% by mass, based on the total mass of the propylene homopolymer C-1 and the propylene-ethylene copolymer C-2, in order to achieve an excellent balance between low-temperature sealability and retort welding resistance.

[0064] In one embodiment of the heterophasic propylene polymerization material containing a propylene homopolymer C-1 and a propylene-ethylene copolymer C-2, the propylene-ethylene copolymer C-2 preferably has a propylene structural unit content of more than 50% by mass but less than 85% by mass and an ethylene structural unit content of more than 15% by mass but less than 50% by mass, in order to have excellent low-temperature sealability (seal strength).

[0065] The α-olefin having 4 to 12 carbon atoms used in the heterophasic propylene polymerization material C is not particularly limited, and examples thereof include the α-olefins having 4 to 12 carbon atoms in the propylene polymer A, such as 1-butene, 1-hexene, and 1-octene, with 1-butene being more preferred. The structural unit derived from the α-olefin having 4 to 12 carbon atoms may be a structural unit derived from one type of α-olefin alone, or may be a structural unit derived from two or more types of α-olefins.

[0066] Examples of methods for producing heterophasic propylene polymerization material C include polymerizing the raw material propylene with ethylene and / or α-olefins using a Ziegler-Natta catalyst, a metallocene catalyst, etc. Examples of polymerization methods for heterophasic propylene polymerization material C include polymerization in an inert solvent such as hexane, heptane, toluene, or xylene, polymerization in liquid propylene or ethylene, polymerization in the gas phase by adding a catalyst to gaseous propylene or ethylene, or polymerization using a combination of these methods.

[0067] From the viewpoint of productivity, the method for producing the heterophasic propylene polymerization material C is preferably a method for obtaining the heterophasic propylene polymerization material C by multistage polymerization, in which a first step is carried out to produce a propylene polymer C-1 substantially in the absence of an inert solvent, and then a second step is carried out to produce a propylene-α-olefin copolymer C-2 by polymerizing propylene and at least one member selected from the group consisting of ethylene and α-olefins having 4 to 12 carbon atoms in a gas phase in the presence of the propylene polymer C-1.

[0068] Methods for adjusting the ethylene content of the propylene polymer C-1 and the propylene-α-olefin copolymer C-2 include adding appropriate amounts of hydrogen gas, a molecular weight regulator such as a metal compound, and ethylene in each step of the polymerization, and adjusting the temperature, pressure, etc. during the polymerization.

[0069] The production ratio of the propylene polymer C-1 and the propylene-α-olefin copolymer C-2 can be controlled by the polymerization time in the first and second steps, the size of the polymerization vessel, the amount of polymer held in the polymerization vessel, the polymerization temperature, the polymerization pressure, etc. If necessary, drying may be carried out at a temperature below the melting point of the polypropylene to remove residual solvent in the polypropylene and ultralow molecular weight oligomers produced as by-products during production. Examples of drying methods include those described in JP-A-55-75410 and JP-A-2565753.

[0070] The melt flow rate (MFR) of the heterophasic propylene polymerization material C obtained in the second step, measured at a temperature of 230°C and a load of 2.16 kg, is preferably 0.001 g / 10 min or more and 10 g / 10 min or less, more preferably 0.01 g / 10 min or more and 10 g / 10 min or less, and even more preferably 0.01 g / 10 min or more and 5 g / 10 min or less, from the viewpoint of improving the processability and hygienic properties of the film.

[0071] As described above, the propylene polymer C-1 and the propylene polymer C-2 contained in the heterophasic propylene polymer material C used in the present invention each contain, for example, carbon-14 ( 14 The polymer may be a polymer containing carbon atoms (monomers) that have been recycled (mechanically recycled).

[0072] [Masterbatch] The resin composition of the present invention may contain a masterbatch in which 1 to 30 mass % of an organic peroxide is impregnated into a powdered polyolefin. The inclusion of a masterbatch in the resin composition of the present invention allows adjustment of the MFR, improving the ease of handling and safety of the organic peroxide compared to directly mixing the organic peroxide. Furthermore, the dispersibility of the organic peroxide can be improved, resulting in high levels of both low-temperature sealability and retort fusion resistance. In the resin composition of the present invention, the masterbatch may be present in its original form, or the organic peroxide and the powdered polyolefin may be present independently, and the organic peroxide may be decomposed in some cases.

[0073] The organic peroxide contained in the masterbatch is not particularly limited, and is preferably a solid at 10° C. or higher but lower than 30° C., or a liquid at 10° C. or higher but lower than 120° C. It also includes a solid at 10° C. or higher but lower than 30° C. that dissolves and becomes liquid in a temperature range up to 120° C. upon heating. Examples of organic peroxides that are solid at temperatures between 10°C and 30°C include those in powder or granule form. There are no particular restrictions on the particle size, but from the perspective of ease of handling and the objective of preparing a uniform masterbatch, the particle size is usually 100 to 2000 μm (or passing through a 9-mesh sieve), preferably 100 to 1000 μm (or passing through a 16-mesh sieve), and more preferably 100 to 500 μm (or passing through a 32-mesh sieve). Here, the particle size refers to the particle size at 50% weight percentage on the particle size accumulation curve (hereinafter referred to as "D50").

[0074] Examples of organic peroxides include alkyl peroxides, diacyl peroxides, ester peroxides, and carbonate peroxides. Examples of alkyl peroxides include dicumyl peroxide, di-tert-butyl peroxide, di-tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, tert-butylcumyl, 1,3-bis(tert-butylperoxyisopropyl)benzene, and 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane.

[0075] Examples of diacyl peroxides include benzoyl peroxide, lauroyl peroxide, and decanoyl peroxide. Examples of peroxide esters include 1,1,3,3-tetramethylbutylperoxyneodecanoate, α-cumylperoxyneodecanoate, tert-butylperoxyneodecanoate, tert-butylperoxyneoheptanoate, tert-butylperoxypivalate, tert-hexylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, and tert-amylperoxyl-2-ethylhexanoate. peroxymethyl tert-butyl ether, tert-butyl ...

[0076] Examples of peroxycarbonates include di-3-methoxybutyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, diisopropyl peroxycarbonate, tert-butylperoxyisopropyl carbonate, di(4-t-butylcyclohexyl) peroxydicarbonate, dicetyl peroxydicarbonate, and dimyristyl peroxydicarbonate.

[0077] The organic peroxide is preferably an alkyl peroxide, more preferably 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,3-bis(tert-butylperoxyisopropyl)benzene or 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane.

[0078] A masterbatch is an impregnated powder (masterbatch) prepared by impregnating a powdered polyolefin with an organic peroxide, and in this specification, this impregnated powder is referred to as a "masterbatch." Use of such a masterbatch improves the ease of handling of the organic peroxide during processing of the resin composition, and can further enhance low-temperature sealability and retort fusion resistance. The masterbatch may contain one or more organic peroxides, and the content of the organic peroxide in the masterbatch is 1 to 30% by mass, preferably 3 to 20% by mass, relative to 100% by mass of the total amount of the organic peroxide and the powdery polyolefin.

[0079] The particle size (D50) corresponding to 50% mass percentage on the particle size accumulation curve of the powdered polyolefin obtained by a laser diffraction particle size distribution measurement method is preferably 200 to 700 μm from the viewpoint of dispersibility of the organic peroxide during processing of the polypropylene resin composition.

[0080] The powdered polyolefin contained in the masterbatch is, in one embodiment, a propylene homopolymer, in another embodiment, a propylene copolymer having structural units derived from propylene and at least one structural unit selected from structural units derived from ethylene and structural units derived from an α-olefin having 4 to 10 carbon atoms, and in yet another embodiment, a mixture thereof. Note that the "structural units derived from ethylene" and the "structural units derived from an α-olefin having 4 to 10 carbon atoms" may be collectively referred to as "structural units derived from a comonomer."

[0081] The powdery polyolefin is preferably a polyolefin having 80 to 100 mass% of structural units derived from propylene and 0 to 20 mass% of structural units derived from comonomers (wherein the total of the structural units derived from propylene and the structural units derived from comonomers is 100 mass%).

[0082] The content of the structural units derived from propylene and the structural units derived from comonomers contained in the propylene copolymer as the powdery polyolefin is preferably 80 to 99.9% by mass, and 0.1 to 20% by mass; more preferably 85 to 99.9% by mass, and 0.1 to 15% by mass; still more preferably 90 to 99% by mass, and 1 to 10% by mass; and particularly preferably 90 to 97% by mass, and 3 to 10% by mass (wherein the total of the structural units derived from propylene and the structural units derived from comonomers is 100% by mass).

[0083] The α-olefin having 4 to 10 carbon atoms contained in the propylene copolymer is not particularly limited, and examples thereof include the α-olefins having 4 to 12 carbon atoms in the propylene polymer A, such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 1-decene, and preferably 1-butene, 1-hexene, or 1-octene. The structural units derived from the comonomer contained in the powdery polyolefin may be of one type or two or more types.

[0084] Examples of propylene copolymers include propylene-ethylene random copolymers, random copolymers of propylene and an α-olefin having 4 to 10 carbon atoms, and random copolymers of propylene, ethylene, and an α-olefin having 4 to 10 carbon atoms. Examples of random copolymers of propylene and an α-olefin having 4 to 10 carbon atoms include propylene-1-butene random copolymers, propylene-1-hexene random copolymers, propylene-1-octene random copolymers, and propylene-1-decene random copolymers. Examples of random copolymers of propylene, ethylene, and an α-olefin having 4 to 10 carbon atoms include propylene-ethylene-1-butene copolymers, propylene-ethylene-1-hexene copolymers, propylene-ethylene-1-octene copolymers, and propylene-ethylene-1-decene copolymers. The powdered polyolefin for the masterbatch may be a mixture of these propylene copolymers, or a mixture of a propylene homopolymer and a propylene copolymer.

[0085] The powdery polyolefin is preferably propylene-ethylene random copolymer particles, propylene-1-butene random copolymer particles, or propylene-ethylene-1-butene random copolymer particles, and more preferably propylene-ethylene random copolymer particles having 90 to 97% by mass of structural units derived from propylene and 3 to 10% by mass of structural units derived from ethylene, propylene-1-butene random copolymer particles having 90 to 97% by mass of structural units derived from propylene and 3 to 10% by mass of structural units derived from 1-butene, or propylene-1-butene random copolymer particles having 80 to 98% by mass of structural units derived from propylene, 1 to 10% by mass of structural units derived from ethylene, and 1 to 10% by mass of structural units derived from 1-butene. and propylene-ethylene-1-butene random copolymer particles having 93 to 97% by mass of structural units derived from propylene and 3 to 7% by mass of structural units derived from ethylene, more preferably propylene-ethylene random copolymer particles having 93 to 97% by mass of structural units derived from propylene and 3 to 7% by mass of structural units derived from 1-butene, propylene-1-butene random copolymer particles having 93 to 97% by mass of structural units derived from propylene and 3 to 7% by mass of structural units derived from 1-butene, or propylene-ethylene-1-butene random copolymer particles having 85 to 98% by mass of structural units derived from propylene, 1 to 5% by mass of structural units derived from ethylene, and 1 to 10% by mass of structural units derived from 1-butene.

[0086] The powdered polyolefin is preferably a crystalline copolymer of propylene and another olefin. The degree of crystallinity of the copolymer can be expressed by the amount of 20°C xylene solubles (hereinafter referred to as CXS) contained in the copolymer. A high CXS content of the copolymer indicates that the copolymer has a high amorphous content and low crystallinity, while a low CXS content of the copolymer indicates that the copolymer has a low amorphous content and high crystallinity.

[0087] The CXS content in the powdery polyolefin is preferably 0.5% by mass or more and less than 20% by mass, more preferably 0.5% by mass or more and less than 10% by mass, and even more preferably 1% by mass or more and less than 5% by mass.

[0088] The melting point of the powdery polyolefin is preferably 120°C or higher and lower than 160°C. Here, the melting point refers to the peak temperature of the endothermic curve measured by differential scanning calorimetry (DSC). The melting point of the powdery polyolefin, like the CXS content, is an indicator of the degree of crystallinity of the powdery polyolefin used in the masterbatch.

[0089] The MFR of the powdery polyolefin measured at a temperature of 230°C and a load of 2.16 kg is preferably 1 to 50 g / 10 min, more preferably 1 to 30 g / 10 min, and even more preferably 2 to 20 g / 10 min, from the viewpoint of the physical properties of the resulting film.

[0090] The intrinsic viscosity ([η]) of the powdery polyolefin measured in tetralin at 135°C is preferably 1 dl / g or more and less than 3 dl / g, more preferably 1.3 dl / g or more and less than 3 dl / g, and even more preferably 1.5 dl / g or more and less than 2.5 dl / g, from the viewpoint of the physical properties of the resulting film.

[0091] The apparent bulk density of the powdered polyolefin is preferably 0.20 g / cm 3 More than 0.45g / cm 3 is less than.

[0092] The powdered polyolefin is preferably a collection of particles with particle sizes distributed within a specific range. The particle size distribution is determined by a laser diffraction particle size distribution measurement method (a dry method that does not use a medium). The dry laser diffraction particle size distribution measurement method is a method of measuring particle size distribution without using a solvent using a laser diffraction particle size distribution measurement device (e.g., HELOS&RODOS (trade name) manufactured by Sympatec).

[0093] The content of particles having a particle diameter of less than 100 μm in the powdered polyolefin is preferably 1% by mass or more and less than 20% by mass, the content of particles having a particle diameter of less than 300 μm is preferably 5% by mass or more and less than 80% by mass, and the content of particles having a particle diameter of less than 1000 μm is preferably 80% by mass or more. The particle diameter (D50) corresponding to 50% by mass on the particle diameter accumulation curve of the powdered polyolefin is preferably 100 μm or more and less than 700 μm, and the particle diameter (hereinafter referred to as D99) corresponding to 99% by mass on the particle diameter accumulation curve is preferably 500 μm or more and less than 2000 μm.

[0094] Regarding the particle size distribution of the powdered polyolefin, from the viewpoints of increasing the content of organic peroxide in the masterbatch, uniformity of the concentration, and ease of handling of the masterbatch, it is preferable that the content of particles having a particle size of less than 100 μm is 1% by mass or more and less than 10% by mass, the content of particles having a particle size of less than 300 μm is 10% by mass or more and less than 70% by mass, the content of particles having a particle size of less than 1000 μm is 80% by mass or more, and D50 is 20 and D99 is 700 μm or more and less than 2000 μm, and more preferably, the content of particles with a particle diameter of less than 100 μm is 1 mass% or more and less than 5 mass%, the content of particles with a particle diameter of less than 300 μm is 10 mass% or more and less than 50 mass%, the content of particles with a particle diameter of less than 1000 μm is 80 mass% or more, D50 is 300 μm or more and less than 700 μm, and D99 is 900 μm or more and less than 2000 μm.

[0095] Examples of powdery polyolefins include polyolefin particles produced by a known polymerization method using an olefin as a monomer and a known polymerization catalyst; particles obtained by pulverizing polyolefins produced by a known polymerization method; and particles obtained by melt-kneading polyolefins produced by a known polymerization method at a temperature equal to or higher than their melting point, followed by cooling and solidifying the polyolefins, and pulverizing the resulting solids.

[0096] Examples of polymerization catalysts used in the production of polyolefin particles or polyolefins include Ziegler-type catalyst systems; Ziegler-Natta-type catalyst systems; catalyst systems consisting of a compound of a Group IV transition metal of the periodic table having a cyclopentadienyl ring and an alkylaluminoxane; catalyst systems consisting of a compound of a Group IV transition metal of the periodic table having a cyclopentadienyl ring, a compound that reacts with the compound to form an ionic complex, and an organoaluminum compound; and catalyst systems in which catalytic components such as a compound of a Group IV transition metal of the periodic table having a cyclopentadienyl ring, a compound that forms an ionic complex, and an organoaluminum compound are supported on inorganic particles such as silica and clay minerals. These catalyst systems are described, for example, in JP-A-61-218606, JP-A-5-194685, JP-A-7-216017, JP-A-9-316147, JP-A-10-212319, JP-A-2004-182981, and JP-A-2004-067850. In this specification, the contents of the above-mentioned patent documents can be referenced as appropriate, and the contents thereof are incorporated herein as is. The polymerization catalyst may be a prepolymerization catalyst prepared by prepolymerizing a monomer in the presence of the above-mentioned catalyst system.

[0097] Examples of methods for producing polyolefin particles or polyolefins include bulk polymerization, in which polymerization is carried out using a liquid olefin as a medium at the polymerization temperature; solution polymerization or slurry polymerization, in which polymerization is carried out in an inert hydrocarbon solvent such as propane, butane, isobutane, pentane, hexane, heptane, and octane; and gas-phase polymerization, in which gaseous monomers are polymerized in the medium. These polymerization methods can be carried out batchwise, continuously, or a combination of these. These polymerization methods can also be carried out in a continuous, multistage manner, using two or more connected polymerization reactors to adjust the polymer composition and properties in each reactor. Among these, from an industrial and economical perspective, continuous gas-phase polymerization or bulk-gas-phase polymerization, in which bulk polymerization and gas-phase polymerization are carried out continuously, are preferred. The polymerization conditions in these polymerization methods, such as polymerization temperature, polymerization pressure, monomer concentration, catalyst input, and polymerization time, are appropriately determined depending on the powdered polyolefin used in the masterbatch. The polyolefin particles or polyolefin may be dried below its melting temperature to remove by-products such as very low molecular weight oligomers and residual solvent in the polymer.

[0098] When the powdery polyolefin used in the masterbatch is a particle obtained by melt-kneading a polyolefin at a temperature above its melting point, followed by cooling and solidifying it, and pulverizing the solidified product, the melt-kneading method may be a method of melt-kneading at a temperature above its melting point using a known melt-kneading device such as a melt extruder or a Banbury mixer. When the polyolefin is a propylene polymer, the temperature during melt-kneading is preferably 180°C or higher, more preferably 180 to 300°C, and even more preferably 180 to 250°C.

[0099] Examples of known melt-kneading devices include single-screw extruders such as SE (registered trademark) manufactured by Toshiba Machine Co., Ltd., FS (registered trademark) manufactured by Ikegai Corporation, and SZW (registered trademark) manufactured by Technovel Corporation; co-rotating twin-screw extruders such as ZSK (registered trademark) manufactured by Coperion Werner Pfleiderer, TEM (registered trademark) manufactured by Toshiba Machine Co., Ltd., TEX (registered trademark) manufactured by The Japan Steel Works, Ltd., and KZW (registered trademark) manufactured by Technovel Corporation; and counter-rotating twin-screw extruders such as CMP (registered trademark) manufactured by The Japan Steel Works, Ltd., and FCM (registered trademark), NCM (registered trademark), and LCM (registered trademark) manufactured by Kobe Steel, Ltd.

[0100] Examples of the shape of the solidified product obtained by melt-kneading polyolefin and then cooling and solidifying it include strands, sheets, flat plates, and pellets obtained by cutting the strands to an appropriate length.

[0101] The powdered polyolefin used in the masterbatch may contain known additives such as neutralizers and antioxidants to stabilize the polyolefin by inhibiting oxidative degradation during storage. The additives may be blended by known blending methods such as stirring and mixing using a mixer or melt-kneading. When blended, the amount of the additives is usually 0.001 to 0.5 parts by mass, preferably 0.01 to 0.2 parts by mass, per 100 parts by mass of the powdered polyolefin.

[0102] When using, as the powdered polyolefin, particles obtained by pulverizing a polyolefin, or particles obtained by melt-kneading a polyolefin at a temperature above its melting point, then cooling and solidifying it, and pulverizing the resulting solid, a known pulverizing device can be used to produce the particles.

[0103] Examples of known grinding devices include a spiral mill, turbo mill, pin mill, hammer mill, JET mill, jet stream grinder (single track jet mill, jet-o mill), cutter mill, rotary cutter mill, bead mill, ball mill, roll mill, star mill, jaw crusher mill, impeller mill, vibration mill, and impact grinder.

[0104] A preferred pulverization method for obtaining powdered polyolefin having a desired particle size distribution is freeze-pulverization using liquid nitrogen. The freeze-grinding method is a method in which particles obtained by grinding polyolefin in a liquid nitrogen (approximately -196°C) atmosphere, or particles obtained by melt-kneading polyolefin at a temperature above its melting point, then cooling and solidifying it, and grinding the resulting solidified material, are cooled to a temperature below its brittle point, and then ground using a grinder such as a turbo mill, pin mill, hammer mill, Linrex mill, impeller mill, or spiral mill.

[0105] Furthermore, the particles obtained by pulverizing the polyolefin can be passed through a filter to achieve the desired particle size distribution. Such a filter can be of any known specification. Known filters include woven wire mesh, crimped wire mesh, welded wire mesh, demister, spiral wire mesh, laminated metal filters, and sintered metal filters. Examples of woven wire mesh include plain weave wire mesh, twill weave wire mesh, satin weave wire mesh, plain dutch weave wire mesh, and twill dutch weave wire mesh. The filter material may be either metal or resin, and is preferably stainless steel. The pulverized polyolefin particles may be passed through a single filter or multiple stacked filters. Furthermore, the particles may be passed through filters in one stage or two or more stages. Filters with different specifications (material, shape, aperture size, etc.) may also be used in combination. The aperture size of the filter is determined appropriately depending on the desired particle size distribution. From the viewpoints of increasing the organic peroxide content in the masterbatch, ensuring uniformity of the concentration, and obtaining a powdery polyolefin that is easy to handle as a masterbatch, the filter size is preferably 100 to 3000 μm, more preferably 300 to 2000 μm, and even more preferably 300 to 1500 μm. The filter opening is a value determined by the maximum particle size (μm) of glass beads that pass through the filter medium according to the method of JIS B 8356.

[0106] When the powdered polyolefin used in the masterbatch is a particle obtained by pulverizing a polyolefin, the polyolefin particles must satisfy a specific particle size distribution from the viewpoint of efficiently producing a masterbatch that can contain an organic peroxide at a high concentration and has excellent handleability, and the polyolefin used for pulverization preferably has a large particle size.

[0107] When the powdered polyolefin used in the masterbatch is particles obtained by pulverizing a polyolefin, the size of the polyolefin before pulverization, represented by D50, is preferably 700 to 5000 μm, more preferably 700 to 3000 μm, and even more preferably 700 to 1500 μm.

[0108] When the powdered polyolefin used in the masterbatch is a particle obtained by melt-kneading a polyolefin at a temperature equal to or higher than its melting point, subsequently cooling and solidifying the polyolefin, and pulverizing the resulting solid, the size of the solid, expressed as the length of the longest part, is usually 1 to 50 mm, preferably 2 to 10 mm, and more preferably 2 to 5 mm. From the viewpoints of productivity and production stability of the particles obtained by pulverizing the solid, the shape of the solid is preferably a pellet having a diameter of 2 to 5 mm.

[0109] A preferred method for impregnating the powdered polyolefin used in the masterbatch with an organic peroxide is to add the organic peroxide while mixing the powdered polyolefin using a known mixer, such as a tumble mixer, a Henschel mixer, or a super mixer.

[0110] As described above, the powdered polyolefin used in the masterbatch contains, for example, carbon-14 ( 14 The polymer may be a polymer containing carbon atoms (monomers) that have been recycled (mechanically recycled).

[0111] [Optional ingredients (other ingredients)] The resin composition of the present invention may contain various additives or other resins as further optional components (other components) in addition to the components already explained above.

[0112] The additives are not particularly limited and include, for example, antioxidants, neutralizing agents, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, adhesives, inorganic pigments, organic pigments, antifogging agents, antiblocking agents, melt flow rate adjusters, light stabilizers, flame retardants, processing aids, pigment dispersants, foaming agents, foam nucleating agents, etc. Examples of the antioxidants include phenolic antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, etc., and composite antioxidants having a unit that combines a phenolic antioxidant mechanism and a phosphorus-based antioxidant mechanism in one molecule can also be used. Examples of other resins include elastomers such as styrene-based copolymer rubbers obtained by hydrogenating styrene-butadiene-styrene copolymers and styrene-isoprene-styrene copolymers.

[0113] [Composition (content) of resin composition] In the resin composition of the present invention, the contents of the propylene polymer A, ethylene polymer B, heterophasic propylene polymer material C, and further components such as master batches, additives, and other resins are determined appropriately.

[0114] In the resin composition of the present invention, the content of the propylene polymer A relative to 100 parts by mass of the total content of the polymers contained in the resin composition is preferably 50 to 95 parts by mass, more preferably 60 to 95 parts by mass, even more preferably 70 to 95 parts by mass, and particularly preferably 70 to 90 parts by mass. In one preferred embodiment of the present invention, the content of the propylene polymer A relative to 100 parts by mass of the total content of the polymers contained in the resin composition of the present invention is 83 parts by mass or more. In this preferred embodiment, the content of the propylene polymer A is more preferably 85 parts by mass or more, and the upper limit can be any of the values ​​described above. The content of ethylene polymer B relative to 100 parts by mass of the total content of polymers contained in the resin composition is preferably 5 to 50 parts by mass, more preferably 5 to 40 parts by mass, even more preferably 5 to 30 parts by mass, and particularly preferably 10 to 30 parts by mass. In one preferred embodiment of the present invention, the content of ethylene polymer B is 17 parts by mass or less relative to 100 parts by mass of the total content of polymers contained in the resin composition of the present invention. In this preferred embodiment, the content of ethylene polymer B is more preferably 15 parts by mass or less, and the lower limit can be any of the values ​​described above. In the resin composition of the present invention, the content of propylene polymer A and the content of ethylene polymer B can be appropriately combined within the above-mentioned ranges. In the present invention, the total content of polymers contained in the resin composition (100 parts by mass) refers to the total content of the propylene polymer A, the ethylene polymer B, and the heterophasic propylene polymer material C.

[0115] When the resin composition of the present invention contains the heterophasic propylene polymer material C, the contents of the propylene polymer A and the ethylene polymer B can be within the above ranges, but are preferably within the following ranges. That is, in the resin composition of the present invention containing heterophasic propylene polymerization material C, the content of propylene polymer A relative to 100 parts by mass of the total polymer content in the resin composition is preferably 45 to 90 parts by mass, more preferably 50 to 90 parts by mass, even more preferably 60 to 85 parts by mass, particularly preferably 70 to 85 parts by mass, and most preferably 70 to 85 parts by mass. Furthermore, the content of ethylene polymer B relative to 100 parts by mass of the total polymer content in the resin composition is preferably 5 to 50 parts by mass, more preferably 5 to 40 parts by mass, even more preferably 5 to 30 parts by mass, and particularly preferably 10 to 25 parts by mass. Furthermore, the content of heterophasic propylene polymerization material C relative to 100 parts by mass of the total polymer content in the resin composition is preferably 5 to 40 parts by mass, more preferably 5 to 30 parts by mass, even more preferably 10 to 30 parts by mass, and particularly preferably 10 to 20 parts by mass. In the resin composition of the present invention, the content of the propylene polymer A, the content of the ethylene polymer B, and the content of the heterophasic propylene polymer material C can be appropriately combined within the above-mentioned ranges. The lower limit of the content of the propylene polymer A and the upper limit of the content of the ethylene polymer B can also be set to 83 parts by mass and 17 parts by mass, respectively, as in the above-mentioned preferred embodiment.

[0116] When the resin composition of the present invention contains the above-mentioned masterbatch, the contents of the organic peroxide and the masterbatch are determined appropriately. For example, the content of the organic peroxide derived from the masterbatch contained in the resin composition of the present invention is preferably 0.005 parts by mass or more, more preferably 0.01 parts by mass or more, and is preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, and even more preferably 0.2 parts by mass or less, relative to 100 parts by mass of the total content of the polymers contained in the resin composition, in order to achieve both high levels of low-temperature sealability and retort welding resistance. In the present invention, the content of the masterbatch can be specified in addition to or instead of the content of the organic peroxide itself. In this case, the content of the masterbatch relative to 100 parts by mass of the total content of the polymers contained in the resin composition can be, for example, 0.01 to 3.0 parts by mass, and is preferably 0.01 to 2.0 parts by mass, more preferably 0.01 to 1.5 parts by mass, and even more preferably 0.1 to 1.5 parts by mass, in order to achieve both high levels of low-temperature sealability and retort welding resistance.

[0117] In the resin composition of the present invention, the content of additives and the content of other resins relative to the total content of polymers contained in the resin composition (100 parts by mass) can each be appropriately determined and can be, for example, 0.01 to 0.5 parts by mass.

[0118] [Characteristics of resin composition] In the resin composition of the present invention, the MFR (230°C, 2.16 kgf) is not particularly limited and can be set appropriately, and is preferably 1 to 200 g / 10 min, more preferably 1 to 100 g / 10 min, and even more preferably 1 to 10 g / 10 min.

[0119] In the present invention and this specification, the resin composition of the present invention is usually a non-crosslinked or uncrosslinked resin composition, but when the resin composition of the present invention contains the above-mentioned masterbatch, it may become a crosslinked resin composition by decomposition of the organic peroxide. That is, the resin composition of the present invention includes both an embodiment that is a non-crosslinked or uncrosslinked resin composition and an embodiment that is a crosslinked resin composition. In the present invention and this specification, the resin composition of the present invention is not particularly limited in terms of its properties and form as long as it contains a propylene polymer A and an ethylene polymer B, and includes a melt-kneaded product of each component, such as an unmolded product such as a strand or pellet, as well as a molded product. In the present invention and this specification, the term "unmolded product" refers to a product that is not molded into a shape (usually a film) or dimensions suitable for various applications but is used as a molding material, and the term "molded product" refers to a product that is molded into a shape (usually a film) or dimensions suitable for various applications.

[0120] [Method for preparing resin composition] The resin composition of the present invention can be produced by a known method, and can usually be produced by melt-kneading the components already described. The order in which the components are kneaded is not particularly limited. For example, all of the components may be charged into a melt-kneading device at once and kneaded, or a mixture obtained by kneading some of the components may be kneaded with the remaining components. The melt-kneading temperature is not particularly limited, and can be, for example, the melt-kneading temperature in the method for producing the retort sealant film of the present invention described below. When the resin composition of the present invention contains the masterbatch, the organic peroxide may decompose during preparation of the resin composition, usually resulting in a crosslinked resin composition in which the ethylene polymer B is crosslinked.

[0121] [[Retort sealant film]] The retort sealant film of the present invention is a film-like (sheet-like) molded article containing the above-mentioned resin composition of the present invention, and is usually a molded article obtained by molding a molten mixture of the above-mentioned components or the resin composition of the present invention into a film by a known molding method. The retort sealant film of the present invention is set to an appropriate form taking into consideration the mode of use, etc., and may be, for example, a strip-like film or a short film (sheet film), but a long film is preferred. A retort sealant film containing the resin composition of the present invention exhibits excellent low-temperature sealing properties and retort fusion resistance, and is therefore suitable for use as a retort sealant film provided in a film for packaging retort food, or as a film constituting the multilayer film of the present invention.

[0122] The retort sealant film of the present invention may be an unstretched film or may be an oriented film obtained by uniaxially or biaxially stretching an unstretched film, but is preferably an unstretched film. In the present invention, the statement that the retort sealant film of the present invention contains the resin composition of the present invention means that the retort sealant film of the present invention is formed from the resin composition of the present invention (a film-shaped molded article of the resin composition of the present invention). That is, the retort sealant film of the present invention may be formed from the resin composition of the present invention, and includes both an embodiment in which the retort sealant film contains the resin composition of the present invention in a state in which the composition of the resin composition is maintained (for example, an embodiment in which the retort sealant film contains the non-crosslinked or uncrosslinked resin composition of the present invention) and an embodiment in which the retort sealant film contains the resin composition of the present invention in a state in which the resin composition is crosslinked with an organic peroxide.

[0123] The retort sealant film of the present invention may have a single-layer structure or a multi-layer structure in which multiple layers are laminated. Furthermore, the retort sealant film of the present invention may be modified, such as by appropriate (surface) treatment or by changing the composition of the resin composition of the present invention, in order to further enhance predetermined functions, such as low-temperature sealing property and retort fusion resistance, in the region that will become the heat-sealed portion and / or the region that will become the storage space when made into a retort food packaging bag. In the present invention, the retort sealant film exhibits low-temperature sealing property and retort fusion resistance as an integrated sheet formed from a single resin composition of the present invention, and therefore, in one preferred embodiment, these modifications are not made.

[0124] The thickness of the retort sealant film of the present invention is not particularly limited, and is, for example, preferably 5 to 200 μm, more preferably 30 to 150 μm.

[0125] [Manufacturing method of retort sealant film] The method for producing the retort sealant film of the present invention is not particularly limited, and examples thereof include film production methods such as the T-die method, inflation method, and calendar method that are commonly used for film production.

[0126] The retort sealant film of the present invention can be suitably produced by a production method including a melt-kneading step of melt-kneading the resin composition of the present invention, an extrusion step of extruding the melt-kneaded resin composition, and a film-forming step of forming the extruded resin composition into a film.

[0127] In the melt-kneading step, the resin composition of the present invention is melt-kneaded. That is, the propylene polymer A, the ethylene polymer B, the heterophasic propylene polymer material C, the masterbatch, additives, and other resins are melt-kneaded to produce a molten resin composition of the present invention. Melt-kneading can be performed using conventional methods and devices. For example, the components are mixed using a mixing device such as a Henschel mixer, ribbon blender, or tumble mixer, followed by melt-kneading. Another example is a method in which the components are continuously fed at a constant rate using a constant-rate feeder to obtain a homogeneous mixture, and then the resulting mixture is melt-kneaded using a single-screw or twin-screw or more extruder, a Banbury mixer, a roll mixer, or the like. The resin temperature during melt-kneading is not particularly limited, but is preferably 190 to 320°C, more preferably 210 to 280°C.

[0128] The extrusion step is carried out by extruding the melt-kneaded resin composition through a T-die using any of various known extruders. The extrusion temperature at this time is not particularly limited, but can be, for example, 190 to 320° C. The extrusion temperature is the temperature of the T-die itself. When the resin composition of the present invention contains the masterbatch, the organic peroxide decomposes in the melt-kneading step and / or the extrusion step, and the crosslinking reaction of the resin composition of the present invention, usually the ethylene polymer B, progresses to form a crosslinked resin composition.

[0129] The film-forming step is a step in which the composition extruded from the T-die is cooled and solidified while being wound up on a chill roll to form a film. The cooling temperature at this time is not particularly limited, but can be, for example, 20 to 140° C. In the film-forming step, a film having a predetermined thickness is formed.

[0130] Multilayer film The multilayer film of the present invention is a laminated film having a multilayer structure comprising the retort sealant film of the present invention as a retort sealant layer of a retort food packaging bag. The multilayer film of the present invention exhibits the excellent properties of the retort sealant film of the present invention, exhibiting excellent low-temperature sealing properties and retort fusion resistance, and is therefore suitable for use as a material for retort food packaging bags.

[0131] The number of layers (number of laminations) constituting the multilayer film of the present invention is not particularly limited and is determined appropriately depending on the required characteristics of the retort food packaging bag, and can usually be 2 to 5 layers, with 2 or 3 layers being preferred. The multilayer film of the present invention may contain, in addition to the retort sealant film of the present invention, other layers appropriate for the intended use, function, etc. For example, one embodiment of the multilayer film of the present invention is a multilayer film (preferably a non-stretched multilayer film) comprising the retort sealant film of the present invention and a layer made of a resin composition other than the resin composition of the present invention. This multilayer film can be produced by co-extruding the resin composition of the present invention and a resin composition other than the resin composition of the present invention, for example, using a T-die. Another embodiment of the multilayer film of the present invention is a multilayer film comprising the retort sealant film of the present invention and various functional layers (e.g., a substrate layer, a barrier layer, a transfer layer, a printing layer). More specifically, this may be a multilayer film comprising a substrate layer (preferably a stretched film), a barrier layer, and the retort sealant film of the present invention (preferably a non-stretched film) laminated in this order. This multilayer film can be produced by laminating the retort sealant film of the present invention and various functional layers, for example, by dry lamination. The thickness (total thickness) of the multilayer film of the present invention is not particularly limited, and is, for example, preferably from 5 to 500 μm, more preferably from 30 to 150 μm.

[0132] [Multi-layer film for retort food packaging bags] The multilayer film of the present invention is preferably a multilayer film for use in packaging bags for retort food, comprising a substrate layer and a retort sealant layer, in that the excellent properties of the retort sealant film of the present invention can be utilized. A multilayer film for packaging bags for retort food corresponds to another embodiment of the multilayer film of the present invention.

[0133] <Base material layer> The substrate layer is generally a biaxially stretched film comprising a thermoplastic resin. The thermoplastic resin is not particularly limited, but examples thereof include polyethylene terephthalate (PET), nylon 6, nylon 6,6, and propylene-based polymers. Propylene-based polymers are particularly preferred because they can promote mono-materialization while taking advantage of the excellent properties of the retort sealant film of the present invention. The thermoplastic resin may be any known resin that forms the base layer of a retort food packaging bag. Examples of propylene-based polymers include propylene homopolymers, random copolymers of at least one type of propylene structural unit, ethylene structural unit, and olefin structural unit, and heterophasic propylene polymer material C. As described above, the propylene-based polymer that forms the base layer may also be a polymer containing, for example, carbon-14 ( 14 Polymers containing carbon (C), polymers containing material recycled (mechanically recycled) carbon elements (monomers), etc. One or more types of thermoplastic resins can be used. The thickness of the base layer is preferably 10 to 40% of the total thickness of the multilayer film of the present invention, particularly the total thickness of the base layer and the retort sealant layer, more preferably 10 to 35%, and even more preferably 15 to 35%.

[0134] The substrate layer can be formed by preparing a thermoplastic resin composition containing a thermoplastic resin and molding this resin composition into a film using the film-forming method described above. Thereafter, if necessary, the obtained film-shaped molded product of the thermoplastic resin composition can be stretched, for example, by roll stretching, tenter stretching, tubular stretching, or the like to produce a stretched film. The stretching ratio is not particularly limited, but can be, for example, 1.5 to 20 times, and preferably 2 to 15 times. The thermoplastic resin composition can be prepared by melt-kneading a thermoplastic resin and appropriate components at an appropriate temperature, for example, a temperature at which the thermoplastic resin melts.

[0135] <Retort sealant layer> The retort sealant layer is composed of the retort sealant film of the present invention. The thickness of the retort sealant layer is preferably 60 to 90%, more preferably 65 to 90%, and even more preferably 65 to 85% of the total thickness of the multilayer film of the present invention, particularly the total thickness of the base layer and the retort sealant layer. By setting the thickness of the base layer and the retort sealant layer within the above ranges, the retort sealant film of the present invention can effectively exhibit excellent low-temperature sealing properties and retort fusion resistance.

[0136] The multilayer film can also be a composite film having a substrate layer and a retort sealant layer, as well as a barrier layer, a transfer layer, etc., between the substrate layer and the retort sealant layer. Examples of the barrier layer include stretched nylon film, aluminum foil, aluminum-deposited PET film, transparent vapor-deposited PET film, aluminum-deposited stretched polypropylene film, transparent vapor-deposited stretched polypropylene film, and polyvinylidene chloride film. The thickness of the barrier layer is not particularly limited, but is preferably, for example, 5 to 20 μm. The transfer layer can be formed from nylon film, biaxially oriented polypropylene film, polyethylene terephthalate film, etc. The thickness of the transfer layer is not particularly limited, but is preferably, for example, 10 to 20 μm.

[0137] The multilayer film of the present invention may be subjected to a surface treatment such as corona discharge treatment, flame treatment, plasma treatment, ozone treatment, etc., by a method commonly used in industry. A printed layer may also be provided as a surface layer of the multilayer film.

[0138] [Multilayer film manufacturing method] The multilayer film of the present invention can be formed by laminating a retort sealant layer and an appropriate layer. The method for laminating the retort sealant layer and the appropriate layer is not particularly limited, and examples thereof include known film production methods such as dry lamination, extrusion lamination, T-die lamination, and tubular lamination. Examples of methods for combining the barrier layer and the transfer layer include dry lamination and extrusion lamination.

[0139] [Multilayer film applications] The multilayer film can be used for packaging, such as packaging food, textiles, and miscellaneous goods. Among these, the multilayer film is preferably used for packaging retort food, which is subjected to heat treatment at the above-mentioned temperatures. The multilayer film is also preferably used as a material for forming packaging bags. The packaging bag is preferably a retort pouch. [Example]

[0140] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0141] In the following description, "%" and "parts" that represent amounts are by mass unless otherwise specified.

[0142] The measured values ​​of each item in the examples and comparative examples were measured by the following methods.

[0143] [Method of measuring physical properties] The content (unit: mass%) of structural units derived from ethylene in the propylene-ethylene copolymer composition was determined by the IR spectroscopy method described on page 256 of Polymer Analysis Handbook (published by Asakura Shoten in 1985).

[0144] The contents of the propylene polymer and the propylene-ethylene copolymer contained in the heterophasic propylene polymer material were obtained from the mass balance during the polymerization of each.

[0145] The content of ethylene structural units in the propylene-ethylene copolymer contained in the heterophasic propylene polymerization material was calculated by measuring the IR spectrum of the entire heterophasic propylene polymerization material C and then calculating it using the following formula (1) in accordance with "(ii) Method for Block Copolymers" described on page 616 of the Polymer Analysis Handbook (published by Kinokuniya in 1995). Here, ET, EA, and EB in formula (1) represent the content of ethylene structural units in the entire heterophasic propylene polymerization material, the content of ethylene structural units in the propylene polymer, and the content of ethylene structural units in the propylene-ethylene copolymer, respectively, and PA and PB represent the content of the propylene polymer and the propylene-ethylene copolymer, respectively. EB = (ET - EA × PA) / PB Equation (1)

[0146] (1) Melt flow rate (MFR, unit: g / 10 min) The melt flow rate of the propylene polymer composition was measured at a temperature of 230° C. and a load of 2.16 kg according to the method specified in JIS K 7210, as described above. The melt flow rate of the ethylene polymer composition was measured at a temperature of 190° C. and a load of 2.16 kg in accordance with the method specified in JIS K 7210, as described above.

[0147] (2) Melting point (Tm, unit: °C) Using a differential scanning calorimeter (PerkinElmer), an aluminum pan containing a sample of approximately 10 mg of the resin composition was heated under a nitrogen atmosphere (2-1) at 230°C for 5 minutes, then cooled from 230°C to 0°C at a rate of 5°C / min (2-2). The sample was then heated at 0°C for 5 minutes (2-3), and then heated from 0°C to 230°C at a rate of 5°C / min (2-4). The temperature of the maximum peak of the melting endothermic curve obtained by calorimetry in step (2-4) was taken as the melting point (Tm). The melting point of indium (In) measured in step (2-4) using the same method as above was 156.6°C.

[0148] (3) Density (unit: kg / m 3 ) The density of the ethylene polymer B was measured in accordance with JIS K 6922-1.

[0149] (4) Measurement of heat seal strength at low temperature (unit: N / 15 mm) The strength of the heat-sealed portion was measured when a composite film obtained by dry laminating a retort sealant film and a 15 μm-thick biaxially oriented nylon film was heat-sealed at low temperatures. Specifically, using a heat sealer manufactured by Toyo Tester Kogyo Co., Ltd., the composite film was folded in half with the retort sealant film on the inside, and the edges on the opposite sides to the folded portion were heat-sealed in a strip shape along the extension direction of the folded portion under the following conditions. With the edges heat-sealed in this state, six 15 mm wide test pieces (any length) were cut out perpendicular to the seal width direction. Each cut test piece had a 10 mm x 15 mm sealed area. Using a tensile tester (Orientec Tensilon) at a peel angle of 90° and a tensile speed of 200 mm / min, the maximum peel strength was measured when the heat-sealed area of ​​each test piece was peeled in the 15 mm wide, 10 mm long direction. The average of the maximum peel strengths for each test piece was calculated, and this average was used as the low-temperature heat-seal strength. In the present invention, excellent low-temperature sealing properties means that the heat seal strength at low temperatures measured by the above-mentioned method is 30 N / 15 mm or more, and it can be said that a value of 35 N / 15 mm or more is even better, and that a value of 50 N / 15 mm or more is extremely good. Sealing bar: Flat double-sided heating Sealing temperature: 170℃ Sealing pressure: 1.0kg / cm 2 Sealing time: 1.0 seconds Seal width: 10mm

[0150] (5) Evaluation of retort adhesion resistance (unit: N / 12cm 2 ) Two 100mm x 30mm retort sealant films were stacked together, and then a 500g weight with a contact area of ​​40mm x 30mm was placed on top of them, followed by heat treatment for 30 minutes in an oven at 130°C. The resulting laminate of two retort sealant films was left in an atmosphere of 23°C and 50% humidity for at least 30 minutes, after which the maximum shear peel strength was measured at a pulling rate of 200mm / min, and this shear peel strength was used as an index for evaluating retort welding resistance. In the present invention, excellent retort fusion resistance means a shear peel strength of 17.5 N / 12 cm as measured by the above method. 2 This means that the resistance is less than 10N / 12cm 2 The following can be considered extremely excellent.

[0151] [Components used in Examples and Comparative Examples] The components used in the examples and comparative examples are shown below.

[0152] [Propylene-ethylene copolymer A-1] Propylene and ethylene were copolymerized in the gas phase using a Ziegler-Natta catalyst to obtain propylene-ethylene copolymer A-1. The ethylene unit content in propylene-ethylene copolymer A-1 was 3.9% by mass, the melt flow rate was 1.3 g / 10 min, and the melting point was 140°C.

[0153] [Propylene-ethylene copolymer composition A-2] Propylene and ethylene were copolymerized in the gas phase using a Ziegler-Natta catalyst to obtain propylene-ethylene copolymer A-2. The obtained propylene-ethylene copolymer A-2 (100 parts by mass) was mixed with 0.05 parts by mass of calcium stearate, 0.1 parts by mass of Irganox 1010 (BASF), and 0.19 parts by mass of Irgafos 168 (BASF) in a Henschel mixer, and then melt-extruded to obtain pellet-shaped propylene-ethylene copolymer composition A-2. The obtained pellet-shaped propylene-ethylene copolymer composition A-2 had an ethylene structural unit content of 3.3% by mass, a melt flow rate of 2.8 g / 10 min, and a melting point of 144 ° C.

[0154] [Propylene-ethylene copolymer A-3] Propylene and ethylene were copolymerized in the gas phase using a Ziegler-Natta catalyst to obtain propylene-ethylene copolymer A-3. The ethylene unit content in the copolymer A-3 was 3.9% by mass, the melt flow rate was 6.2 g / 10 min, and the melting point was 140°C.

[0155] [Propylene-ethylene copolymer A-4] Propylene and ethylene were copolymerized in the gas phase using a Ziegler-Natta catalyst to obtain propylene-ethylene copolymer A-4. The ethylene unit content in propylene-ethylene copolymer A-4 was 5.3% by mass, the melt flow rate was 1.0 g / 10 min, and the melting point was 133°C.

[0156] [Propylene-ethylene copolymer A-5] Propylene was polymerized in the gas phase using a Ziegler-Natta catalyst to obtain propylene homopolymer A-5. The melt flow rate of propylene homopolymer A-5 was 2.5 g / 10 min and the melting point was 158°C.

[0157] [Propylene-ethylene copolymer composition A-6] Propylene and ethylene were copolymerized in the gas phase using a Ziegler-Natta catalyst to obtain propylene-ethylene copolymer A-6. The resulting propylene-ethylene copolymer A-6 (100 parts by mass) was mixed with 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (BASF), 0.05 parts by mass of Irgafos 168 (BASF), and an appropriate amount of melt flow rate modifier (2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) in a Henschel mixer, followed by melt extrusion to obtain pelleted propylene-ethylene copolymer composition A-6. The resulting pelleted propylene-ethylene copolymer composition A-6 had an ethylene structural unit content of 3.9% by mass, a melt flow rate of 9.2 g / 10 min, and a melting point of 144 °C.

[0158] [Ethylene-propylene-butene terpolymer A-7] Propylene, ethylene, and butene were copolymerized in the gas phase using a Ziegler-Natta catalyst to obtain ethylene-propylene-butene terpolymer A-7. The ethylene content of the copolymer A-7 was 2.7% by mass, the butene content was 6.4% by mass, the melt flow rate was 6.4 g / 10 min, and the melting point was 136°C.

[0159] [Propylene-ethylene copolymer A-8] Propylene and ethylene were copolymerized in the gas phase using a Ziegler-Natta catalyst to obtain propylene-ethylene copolymer A-8. The resulting propylene-ethylene copolymer A-8 (100 parts by mass) was mixed with 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (BASF), 0.05 parts by mass of Irgafos 168 (BASF), and an appropriate amount of melt flow rate modifier (2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) in a Henschel mixer, followed by melt extrusion to obtain pelleted propylene-ethylene copolymer composition A-8. The resulting pelleted propylene-ethylene copolymer composition A-8 had an ethylene structural unit content of 3.9% by mass, a melt flow rate of 14.2 g / 10 min, and a melting point of 144 °C.

[0160] [Ethylene-based polymer composition B-1] As the ethylene-based polymer composition B-1, high-density polyethylene E3100 (trade name) manufactured by Keiyo Polyethylene Co., Ltd. was used. The ethylene-based polymer composition B-1 had a melt flow rate of 1.0 g / 10 min and a density of 0.952 g / cm. 3 and the melting point was 133°C.

[0161] [Ethylene-based polymer composition B-2] As the ethylene polymer composition B-2, high-density polyethylene Hizex3300F (trade name) manufactured by Prime Polymer Co., Ltd. was used. The ethylene polymer composition B-2 had a melt flow rate of 1.1 g / 10 min and a density of 0.949 g / cm. 3 and the melting point was 130°C.

[0162] [Ethylene-based polymer composition B-3] As the ethylene-based polymer composition B-3, an ethylene-1-hexene copolymer (LLDPE) composition, Sumikathene α FZ103-0 (trade name), manufactured by Sumitomo Chemical Co., Ltd., was used. The ethylene-based polymer composition B-3 had a melt flow rate of 0.8 g / 10 min and a density of 0.925 g / cm. 3 and the melting point was 119°C.

[0163] [Ethylene-based polymer composition B-4] As the ethylene-based polymer composition B-4, an ethylene-1-hexene copolymer (LLDPE) composition, Sumikathene E FV205 (trade name), manufactured by Sumitomo Chemical Co., Ltd., was used. The ethylene-based polymer composition B-4 had a melt flow rate of 2.2 g / 10 min and a density of 0.921 g / cm. 3 and the melting point was 123°C.

[0164] [Ethylene-based polymer composition B-5] As the ethylene-based polymer composition B-5, an ethylene-1-butene-1-hexene copolymer composition, Sumikathene EP GT050 (trade name), manufactured by Sumitomo Chemical Co., Ltd., was used. The ethylene-based polymer composition B-5 had a melt flow rate of 0.3 g / 10 min and a density of 0.922 g / cm. 3 and the melting point was 110°C.

[0165] [Ethylene-based polymer composition B-6] As the ethylene polymer composition B-6, a low-density polyethylene (SUMIKACENE G201-F) manufactured by Sumitomo Chemical Co., Ltd. was used. The melt flow rate of the ethylene polymer composition B-6 was 2.0 g / 10 min, and the density was 0.919 g / cm 3 and the melting point was 107°C.

[0166] [Propylene-based polymer composition C] Using a Ziegler-Natta catalyst, propylene was polymerized in the gas phase in the first step, and then propylene and ethylene were copolymerized in the gas phase in the second step to obtain a heterophasic propylene polymerization material C consisting of a propylene homopolymer C-1 and a propylene-ethylene copolymer C-2. The content of propylene homopolymer C-1 in the obtained heterophasic propylene polymerization material C was 70% by mass, and the content of propylene-ethylene copolymer C-2 was 30% by mass. The content of ethylene structural units in the heterophasic propylene polymerization material C was 28% by mass. Heterophagic propylene polymer material C (100 parts by mass) was mixed with 0.005 parts by mass of calcium hydroxide, 0.075 parts by mass of Sumilizer GP (2,4,8,10-tetra-t-butyl-6-[3-(3-methyl-4-hydroxy-5-t-butylphenyl)propoxy]dibenzo[d,f][1,3,2]dioxaphosphepine, manufactured by Sumitomo Chemical Co., Ltd.), 0.03 parts by mass of Sumilizer GS (2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl]phenyl acrylate, manufactured by Sumitomo Chemical Co., Ltd.), and an appropriate amount of melt flow rate adjuster (2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) in a Henschel mixer, and then melt-extruded to obtain pellets of heterophasic propylene polymer composition C. The resulting propylene polymer composition C had a melt flow rate (230°C, load 2.16 kgf) of 3 g / 10 min.

[0167] [Organic peroxide masterbatch] Propylene, ethylene, and 1-butene were copolymerized in the gas phase using a Ziegler-Natta catalyst to obtain a propylene-ethylene-1-butene copolymer. The resulting propylene-ethylene-1-butene copolymer had an ethylene unit content of 2.2% by mass, an 1-butene unit content of 4.5% by mass, a melt flow rate of 7.0 g / 10 min, and a melting point of 140°C. The resulting propylene-ethylene-1-butene copolymer was thoroughly cooled with liquid nitrogen and then continuously pulverized by passing it through an impeller mill. The resulting propylene-ethylene-1-butene copolymer was then filtered and classified to obtain a powdered polyolefin with a particle size D50 of 400 μm. This powder was then impregnated with 8% by mass of Perhexa 25B (manufactured by Nippon Oil & Fats Corporation, chemical name: 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane). An organic peroxide masterbatch was thus prepared.

[0168] [Example 1: Resin composition 1] Propylene-ethylene copolymer A-1 (90 parts by mass) and ethylene polymer composition B-1 (10 parts by mass) were mixed with 0.01 part by mass of calcium hydroxide, 0.05 part by mass of Irganox 1010 (manufactured by BASF), and 0.05 part by mass of Irgafos 168 (manufactured by BASF) in a Henschel mixer, and then melt-extruded at 270°C to obtain pellet-shaped resin composition 1. The raw material composition of resin composition 1 is shown in Table 1.

[0169] The obtained pellet-like resin composition 1 was melt-extruded at a resin temperature of 280°C using a 50mm T-die film-forming device (Tanabe Plastics Co., Ltd.: V-50-F600 film-forming device with a 400mm wide T-die). The extrusion was then cooled and solidified while being wound up on a chill roll through which 50°C cooling water was passed, yielding a 70µm-thick retort sealant film 1. The retort fusion resistance of the obtained retort sealant film 1 was evaluated according to the evaluation method described above. Furthermore, the heat seal strength at low temperatures of the composite film 1 produced using the obtained retort sealant film 1 was measured according to the evaluation method described above. The results are shown in Table 2.

[0170] [Example 2: Resin Composition 2] Propylene-ethylene copolymer A-1 (90 parts by mass) and ethylene polymer composition B-1 (10 parts by mass) were mixed with 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (manufactured by BASF), 0.05 parts by mass of Irgafos 168 (manufactured by BASF), and 0.35 parts by mass of an organic peroxide masterbatch in a Henschel mixer, and then melt-extruded at 270°C to obtain pellets of crosslinked resin composition 2. The raw material composition of resin composition 2 is shown in Table 1. A retort sealant film 2 and a composite film 2 were produced in the same manner as in Example 1, except that the pellet-shaped resin composition 2 was used, and their properties were evaluated. The results are shown in Table 2.

[0171] [Example 3: Resin Composition 3] Propylene-ethylene copolymer A-1 (80 parts by mass) and ethylene polymer composition B-2 (20 parts by mass) were mixed with 0.01 parts by mass of calcium hydroxide, 0.1 parts by mass of Sumilizer GP (2,4,8,10-tetra-t-butyl-6-[3-(3-methyl-4-hydroxy-5-t-butylphenyl)propoxy]dibenzo[d,f][1,3,2]dioxaphosphepine, manufactured by Sumitomo Chemical Co., Ltd.), 0.1 parts by mass of Irgafos 168 (manufactured by BASF), and 0.35 parts by mass of organic peroxide masterbatch in a Henschel mixer, and then melt-extruded at 270 ° C. to obtain pellet-shaped crosslinked resin composition 3. The raw material composition of resin composition 3 is shown in Table 1. A retort sealant film 3 and a composite film 3 were produced in the same manner as in Example 1, except that the obtained pellet-shaped resin composition 3 was used, and their properties were evaluated. The results are shown in Table 2.

[0172] Example 4: Resin Composition 4 Resin composition 4 (the raw material composition of resin composition 4 is shown in Table 1) was prepared by pellet-blending propylene-ethylene copolymer composition A-2 (90 parts by mass) and ethylene polymer composition B-1 (10 parts by mass). The resin was melt-extruded at a resin temperature of 280°C using the T-die film-forming apparatus described above, and then cooled and solidified while being wound up on a chill roll through which cooling water at 50°C was passed, yielding retort sealant film 4 with a thickness of 70 μm. The retort fusion resistance was evaluated using the obtained sealant film 4. Furthermore, the heat seal strength at low temperatures was measured for composite film 4 produced using the obtained retort sealant film 4 according to the evaluation method described above. The results are shown in Table 2.

[0173] [Example 5: Resin Composition 5] Propylene-ethylene copolymer A-1 (80 parts by mass) and ethylene polymer composition B-3 (20 parts by mass) were mixed with 0.01 parts by mass of calcium hydroxide, 0.1 parts by mass of Sumilizer GP (2,4,8,10-tetra-t-butyl-6-[3-(3-methyl-4-hydroxy-5-t-butylphenyl)propoxy]dibenzo[d,f][1,3,2]dioxaphosphepine, manufactured by Sumitomo Chemical Co., Ltd.), 0.1 parts by mass of Irgafos 168 (manufactured by BASF), and 0.35 parts by mass of organic peroxide masterbatch in a Henschel mixer, and then melt-extruded at 270 ° C. to obtain pellet-shaped crosslinked resin composition 5. The raw material composition of resin composition 5 is shown in Table 1. A retort sealant film 5 and a composite film 5 were produced in the same manner as in Example 1, except that the obtained pellet-shaped resin composition 5 was used, and the properties thereof were evaluated. The results are shown in Table 2.

[0174] [Example 6: Resin Composition 6] Propylene-ethylene copolymer A-1 (80 parts by mass), ethylene polymer composition B-4 (20 parts by mass), 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (manufactured by BASF), 0.05 parts by mass of Irgafos 168 (manufactured by BASF), and 0.60 parts by mass of an organic peroxide masterbatch were mixed in a Henschel mixer, and then melt-extruded at 270°C to obtain pellets of crosslinked resin composition 6. The raw material composition of resin composition 6 is shown in Table 1. A retort sealant film 6 and a composite film 6 were produced in the same manner as in Example 1, except that the obtained pellet-shaped resin composition 6 was used, and their properties were evaluated. The results are shown in Table 2.

[0175] [Example 7: Resin Composition 7] Propylene-ethylene copolymer A-3 (90 parts by mass) and ethylene polymer composition B-1 (10 parts by mass) were mixed with 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (manufactured by BASF), and 0.05 parts by mass of Irgafos 168 (manufactured by BASF) in a Henschel mixer, and then melt-extruded at 270°C to obtain pellet-shaped resin composition 7. The raw material composition of resin composition 7 is shown in Table 1. A retort sealant film 7 and a composite film 7 were produced in the same manner as in Example 1, except that the obtained pellet-shaped resin composition 7 was used, and their properties were evaluated. The results are shown in Table 2.

[0176] [Example 8: Resin Composition 8] Propylene-ethylene copolymer A-1 (85 parts by mass) and ethylene polymer composition B-5 (15 parts by mass) were mixed with 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (BASF), 0.05 parts by mass of Irgafos 168 (BASF), and 0.35 parts by mass of an organic peroxide masterbatch in a Henschel mixer, and then melt-extruded at 270°C to obtain pellet-shaped resin composition 8. The raw material composition of resin composition 8 is shown in Table 1. A retort sealant film 8 and a composite film 8 were produced in the same manner as in Example 1, except that the obtained pellet-shaped resin composition 8 was used, and their properties were evaluated. The results are shown in Table 2.

[0177] [Example 9: Resin Composition 9] Propylene-ethylene copolymer A-3 (85 parts by mass) and ethylene polymer composition B-5 (15 parts by mass) were mixed with 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (BASF), 0.05 parts by mass of Irgafos 168 (BASF), and 0.35 parts by mass of an organic peroxide masterbatch in a Henschel mixer, and then melt-extruded at 270°C to obtain pellet-shaped resin composition 9. The raw material composition of resin composition 9 is shown in Table 1. A retort sealant film 9 and a composite film 9 were produced in the same manner as in Example 1, except that the obtained pellet-shaped resin composition 9 was used, and their properties were evaluated. The results are shown in Table 2.

[0178] Example 10: Resin Composition 10 A retort sealant film 10 and a composite film 10 were produced in the same manner as in Example 4, except that resin composition 10 (the raw material composition of resin composition 10 is shown in Table 1) prepared by pellet-blending propylene-ethylene copolymer composition A-6 (90 parts by mass) and ethylene polymer composition B-1 (10 parts by mass) was used, and their properties were evaluated. The results are shown in Table 2.

[0179] [Example 11: Resin Composition 11] Ethylene-propylene-butene terpolymer A-7 (91 parts by mass) and ethylene polymer composition B-5 (9 parts by mass) were mixed with 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (BASF), 0.05 parts by mass of Irgafos 168 (BASF), and 0.1 parts by mass of an organic peroxide masterbatch in a Henschel mixer, and then melt-extruded at 270°C to obtain pellet-shaped resin composition 11. The raw material composition of resin composition 11 is shown in Table 1. A retort sealant film 11 and a composite film 11 were produced in the same manner as in Example 1, except for using the obtained pellet-shaped resin composition 11, and their properties were evaluated. The results are shown in Table 2.

[0180] [Comparative Example 1: Resin composition C1] Propylene-ethylene copolymer A-4 (90 parts by mass) and ethylene polymer composition B-1 (10 parts by mass) were mixed with 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (BASF), 0.05 parts by mass of Irgafos 168 (BASF), and 0.35 parts by mass of an organic peroxide masterbatch in a Henschel mixer, and then melt-extruded at 270 ° C. to obtain pellets of crosslinked resin composition C1. The raw material composition of resin composition C1 is shown in Table 1. Except for using the obtained pellet-shaped resin composition C1, a retort sealant film C1 and a composite film C1 were produced in the same manner as in Example 1, and their properties were evaluated. The results are shown in Table 2.

[0181] Comparative Example 2: Resin Composition C2 Propylene-ethylene copolymer A-4 (80 parts by mass) and ethylene polymer composition B-1 (20 parts by mass) were mixed with 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (BASF), 0.05 parts by mass of Irgafos 168 (BASF), and 0.45 parts by mass of an organic peroxide masterbatch in a Henschel mixer, and then melt-extruded at 220 ° C. to obtain pellet-shaped crosslinked resin composition C2. The raw material composition of resin composition C2 is shown in Table 1. Except for using the obtained pellet-shaped resin composition C2, a retort sealant film C2 and a composite film C2 were produced in the same manner as in Example 1, and their properties were evaluated. The results are shown in Table 2.

[0182] Comparative Example 3: Resin Composition C3 Propylene homopolymer A-5 (90 parts by mass) and ethylene polymer composition B-1 (10 parts by mass) were mixed with 0.01 parts by mass of calcium hydroxide, 0.05 parts by mass of Irganox 1010 (BASF), 0.05 parts by mass of Irgafos 168 (BASF), and 0.35 parts by mass of an organic peroxide masterbatch in a Henschel mixer, and then melt-extruded at 270 ° C. to obtain pellet-shaped crosslinked resin composition C3. The raw material composition of resin composition C3 is shown in Table 1. Except for using the obtained pellet-shaped resin composition C3, a retort sealant film C3 and a composite film C3 were produced in the same manner as in Example 1, and their properties were evaluated. The results are shown in Table 2.

[0183] [Comparative Example 4: Resin composition C4] Propylene-based polymer composition C (100 parts by mass) was melt-extruded at a resin temperature of 280°C, and then cooled and solidified while being wound around a chill roll through which cooling water at 50°C was passed, to obtain a retort sealant film C4 with a thickness of 70 μm. This retort sealant film C4 was used to evaluate its retort fusion resistance. Furthermore, the heat seal strength at low temperatures was measured for a composite film C4 produced using the obtained sealant film C4 according to the evaluation method described above. The results are shown in Table 2.

[0184] [Comparative Example 5: Resin composition C5] A retort sealant film C5 and a composite film C5 were produced in the same manner as in Example 4, except that resin composition C5 (the raw material composition of resin composition C5 is shown in Table 1) was used, which was prepared by pellet-blending propylene-ethylene copolymer composition A-8 (80 parts by mass) and ethylene polymer composition B-1 (20 parts by mass). The properties of these films were evaluated. The results are shown in Table 2.

[0185] [Comparative Example 6: Resin composition C6] A retort sealant film C6 and a composite film C6 were produced in the same manner as in Example 4, except that resin composition C6 (the raw material composition of resin composition C6 is shown in Table 1) was used, which was prepared by pellet-blending propylene-ethylene copolymer composition A-8 (80 parts by mass) and ethylene polymer composition B-6 (20 parts by mass). The properties of these films were evaluated. The results are shown in Table 2.

[0186] [Table 1]

[0187] [Table 2]

[0188] As is clear from the results shown in Tables 1 and 2, resin compositions C1 to C3, C5, and C6, which contain a propylene polymer other than propylene polymer A that contains propylene structural units and at least one of ethylene structural units and olefin structural units and satisfies the MFR and melting point requirements and are used in combination with ethylene polymer B, are poor in at least one of retort fusion resistance and low-temperature sealability, and cannot be used as a material for forming a retort sealant film. Furthermore, resin composition C4, which uses only heterophasic propylene polymerization material C, which is currently the main material for retort sealant films, is poor in low-temperature sealability and does not function adequately as a material for forming a retort sealant film, and is also unable to fully meet the trend toward monomaterials.

[0189] In contrast, the resin compositions of Examples 1 to 11, in which a propylene polymer A containing propylene structural units, ethylene structural units, and / or olefin structural units and satisfying the MFR and melting point requirements was used in combination with an ethylene polymer B, all exhibited high heat seal strength at low temperatures and excellent low-temperature sealability when formed into retort sealant films, as well as low shear peel strength and excellent retort fusion resistance. Even in a single sheet, these mutually contradictory properties were achieved. Resin composition 1 of Example 1, in which a propylene polymer A having an MFR of 1 to 5 g / 10 min was used in combination with an ethylene polymer B, further enhanced low-temperature heat seal strength, while resin composition 10 of Example 10, in which a propylene polymer A having an MFR of 7 to 10 g / 10 min was used in combination with an ethylene polymer B, further enhanced retort fusion resistance and low-temperature sealability. In a particularly preferred embodiment, the low-temperature sealability can be further improved while maintaining excellent retort welding resistance, and both low-temperature sealability and retort welding resistance can be achieved at high levels.

[0190] The resin composition of the present invention, which has such excellent properties, is suitable as a material for forming a retort sealant film that requires both of the above properties, and is particularly suitable as a material for forming a mono-material retort sealant film.The above results show that by using the resin composition and the retort sealant film of the present invention as the retort sealant layer of a retort food packaging bag, it is possible to produce a retort food packaging bag that combines excellent low-temperature sealing properties and retort fusion resistance.

Claims

1. a propylene-based polymer A that contains structural units derived from propylene and structural units derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms, and that has a melt flow rate of 1 to 10 g / 10 min measured at 230°C under a load of 2.16 kg and a melting point of 135 to 150°C; and an ethylene polymer B, Resin composition for retort sealant film.

2. 2. The resin composition for a retort sealant film according to claim 1, wherein the propylene polymer A has a melt flow rate of 1 to 5 g / 10 min.

3. 2. The resin composition for a retort sealant film according to claim 1, wherein the propylene polymer A contains 85% by mass or more and less than 98% by mass of structural units derived from propylene and more than 2% by mass and 15% by mass or less of structural units derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms.

4. The density of the ethylene polymer B is 0.915 to 0.965 g / cm ３ The resin composition for a retort sealant film according to claim 1,

5. 2. The resin composition for a retort sealant film according to claim 1, further comprising a heterophasic propylene polymerization material C comprising: a propylene polymer C-1 containing 98% by mass or more of structural units derived from propylene; and a propylene-α-olefin copolymer C-2 containing more than 40% by mass but less than 85% by mass of structural units derived from propylene and more than 15% by mass but less than 60% by mass of structural units derived from at least one selected from ethylene and an α-olefin having 4 to 12 carbon atoms.

6. With respect to 100 parts by mass of the total content of the polymers contained in the resin composition, the content of the propylene polymer A is 50 to 95 parts by mass, the content of the ethylene polymer B is 5 to 50 parts by mass; The resin composition for a retort sealant film according to claim 1.

7. With respect to 100 parts by mass of the total content of the polymers contained in the resin composition, the content of the propylene polymer A is 45 to 90 parts by mass, the content of the ethylene polymer B is 5 to 50 parts by mass, The content of the heterophasic propylene polymerization material C is 5 to 40 parts by mass. The resin composition for a retort sealant film according to claim 5 .

8. 2. The resin composition for a retort sealant film according to claim 1, further comprising a masterbatch in which an organic peroxide is impregnated into a powdery polyolefin in an amount of 1 to 30% by mass (wherein the total amount of the organic peroxide and the powdery polyolefin is taken as 100% by mass).

9. The resin composition for a retort sealant film according to claim 8, wherein the organic peroxide is contained in an amount of 0.005 to 0.3 parts by mass per 100 parts by mass of the total content of the polymers contained in the resin composition.

10. A retort sealant film comprising the resin composition for a retort sealant film according to any one of claims 1 to 9.

11. The retort sealant film according to claim 10, having a thickness of 5 to 200 μm.

12. A multilayer film comprising the retort sealant film according to claim 10 as a retort sealant layer.

13. A melt-kneading step of melt-kneading the resin composition for a retort sealant film according to any one of claims 1 to 9; an extrusion step of extruding the melt-kneaded resin composition; and forming a film from the extruded resin composition.

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