Polypropylene-based sealant film, laminate, and pouch using the same

Abstract

To provide a film and a packaging material which use a polypropylene-based resin as a main component, are excellent in film moldability such as T-die molding, are non-oriented and are excellent in easy tear property in all the directions in the plane, have low-temperature impact resistance, and are excellent in blocking resistance.SOLUTION: A film contains a polypropylene-based resin as a main component, and has tear strength per one film by Elmendorf method according to JIS K 7128-2 (1998) of 30 N / mm or less in all the directions in the plane.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polypropylene-based sealant film used as a sealant for a packaging bag, a laminate using the same, and a pouch.

Background Art

[0002] Conventionally, as a sealant film for high retort packaging that is retort sterilized at a high temperature of 120°C to 135°C, an unstretched film mainly composed of a propylene-ethylene block copolymer (hereinafter referred to as CPP) has been used. Its main usage method is to laminate with a laminate base material layer such as a polyethylene terephthalate stretched film (hereinafter referred to as PET), a nylon stretched film (hereinafter referred to as ONy), an aluminum foil (hereinafter referred to as AL), etc., and after forming a laminate having a structure of PET / ONy / AL / CPP, PET / AL / ONy / CPP, or PET / AL / CPP, it is made into a bag and used.

[0003] However, when an unstretched film obtained by melt-extruding a propylene-ethylene block copolymer resin of Patent Document 1 or Patent Document 2 or a resin in which an ethylene-based elastomer or the like is blended with a propylene-ethylene block copolymer is used for a retort pouch, when opening from a notch portion (a cut provided at an end), the linear cutability is poor, and there has been a problem that the contents are deformed or spilled.

[0004] Therefore, a sealant film used for a retort pouch is required to be capable of being easily opened by tearing from a notch portion without using a cutting tool (easy tearability).

[0005] As a polypropylene-based film having easy tearability, there is a uniaxially stretched film (Patent Document 3) obtained by performing high-magnification stretching in the longitudinal direction. However, although the film of Patent Document 3 has improved tearability in the stretching direction, it is inferior in tearability in all in-plane directions and also has insufficient low-temperature impact resistance for retort applications. Further, there are films (Patent Document 4) containing a sorbitol derivative and films (Patent Document 5) containing a rosin metal salt compound for the purpose of increasing the crystallinity of the film to impart tearability. However, they have a large amount of odor and extract after retort treatment and are not suitable for high-retort applications. Furthermore, there are films (Patent Document 6) containing a crystalline polyethylene resin and films (Patent Document 7) containing polybutene-1 as a crystal nucleating agent. However, since all of them are inferior in low-temperature impact resistance, they are insufficient for high-retort applications.

[0006] As described above, in the prior art, there has been no polypropylene-based unstretched film that has easy tearability in all in-plane directions, has both low-temperature impact resistance, heat sealability, and antiblocking properties, and can be widely used for high-retort applications (sterilization at 125 to 135°C).

[0007] In recent years, the size of pouches for business use and the like has been increasing, and the required level of low-temperature impact resistance has become increasingly high. Also, the required level of the pouch appearance has been increasing, and it is desired to suppress as much as possible the occurrence of a fine uneven appearance, so-called yuzu skin, on the surface of the laminate after retort sterilization.

[0008] In addition, since the slipperiness between the CPP of the laminate and the laminate base material layer is poor, a so-called blocking phenomenon occurs in which the CPP of the laminate and the laminate base material layer adhere to each other in the film forming process, slitting process, bag making process, content filling process, etc. When stored for a long time or at a high temperature, when using the laminated film, it becomes difficult to unwind the film, and there is a problem that the bag making workability and filling workability are significantly reduced.

[0009] In order to solve the above problems, a method of preventing blocking by sprinkling a blocking inhibitor, such as powder of starch subjected to a water-resistant surface treatment, on a sealant, that is, a method of avoiding blocking by the so-called powdering method has been adopted. However, the powdering method has factors that reduce the commercial value, such as damaging the appearance of the bag making, mixing into the food filled with the powder, and having an adverse effect on the taste. There has been a strong demand for the development of a polypropylene-based film that does not require powdering, can be used in a so-called non-powder state, and can be suitably used for high retort applications as a packaging bag or a sealant of a packaging bag.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0011] An object of the present invention is to provide a polypropylene-based sealant film that has excellent tearability in all in-plane directions of the film as a sealant of a packaging bag, is excellent in heat sealability and low temperature impact resistance, is excellent in blocking resistance and can be used without powdering, and is excellent in anti-fingerprint property and can be suitably used for high retort applications, a laminate using the same, and a pouch.

Means for Solving the Problem

[0012] In order to solve the above problems, the present invention is as follows. (1) A film mainly composed of a polypropylene-based resin, characterized in that the tear strength per film by the Elmendorf method in JIS K 7128-2 (1998) is 30 N / mm or less in all in-plane directions, a polypropylene-based sealant film. (2) The polypropylene-based sealant film according to (1), wherein in the yield point stress measurement method in JIS K 7161 (2014), the yield point stress is 25 Mpa or more and 50 Mpa or less in all in-plane directions. (3) The polypropylene-based sealant film according to (1) or (2), wherein the crystallinity in infrared spectroscopy is 60% or more. (4) The 80 ° C · 24-hour blocking shear force between the heat-sealing surfaces of the polypropylene-based sealant film is 5 N / 12 cm 2 The polypropylene-based sealant film according to any one of (1) to (3) below. (5) The polypropylene-based sealant film according to any one of (1) to (4), wherein the center line average roughness (Ra) of at least one side of at least one side is 0.25 μm or more. (6) A polypropylene-based sealant film according to any one of (1) to (5), which is composed of a resin composition mainly containing a polypropylene-based resin and containing 1500 to 10000 ppm of a crystal nucleating agent. (7) The polypropylene-based sealant film according to (6), in which a base layer made of the resin composition and a layer mainly composed of an ethylene-propylene block copolymer are laminated on at least one side thereof. (8) A laminate in which the polypropylene-based sealant film according to any one of (1) to (7) is laminated on one side of a laminate base layer formed by laminating a single layer or two or more layers of films. (9) A pouch formed by heat-sealing and bag-making the polypropylene-based sealant films of the laminate according to (8). The pouch according to (9), which can be torn and split in the longitudinal and transverse directions to take out the contents.

Advantages of the Invention

[0013] When a polypropylene-based sealant film and a laminate using the same are used as the sealant of a packaging bag, it has excellent tearability in all directions within the film surface, excellent heat sealability and low temperature impact resistance, and excellent antiblocking property, so it can be used without powder and can be used for a high retort packaging material with excellent anti-fingerprint property.

Embodiments for Carrying Out the Invention

[0014] The polypropylene-based sealant film of the present invention is a film mainly composed of a polypropylene-based resin, and the tear strength per film in the Elmendorf method in JIS K 7128-2 (1998) is preferably 30 N / mm or less in all directions within the film surface, more preferably 25 N / mm or less. If it exceeds 30 N / mm, the tearability deteriorates.

[0015] Here, "all directions within the film surface" means all 360 degrees of the film surface including the MD (hereinafter abbreviated as MD) and parallel to the MD with respect to the resin take-up direction (hereinafter abbreviated as MD) when extruded from the extruder as a polypropylene-based sealant film. In particular, the in-plane MD direction, the 90-degree film width direction (hereinafter abbreviated as TD) perpendicular to the MD in the plane, and the directions of 45 degrees to the left and right with respect to the MD in the plane are mainly used.

[0016] In the yield point stress measurement method in JIS K 7161 (2014), the yield point stress is preferably 25 Mpa or more and 50 Mpa or less in all directions within the film surface, more preferably 30 Mpa or more and 45 Mpa or less. If it is less than 25 Mpa, the tearability may deteriorate, and if it exceeds 50 Mpa, the low temperature impact resistance may weaken.

[0017] In infrared spectroscopy (hereinafter abbreviated as IR), the crystallinity is preferably 60% or more. If it is less than 60%, the easy tearability and the resistance to human skin may deteriorate in all in-plane directions.

[0018] The blocking shear force after 80°C for 24 hours between the heat-sealing layers of the film is preferably 5 N / 12 cm 2 or less. If the blocking shear force exceeds 5 N / 12 cm 2 there may be a problem with poor opening performance when making a bag without powder.

[0019] The center line average roughness (Ra) of at least one side of the film is preferably 0.25 μm or more. If it is less than 0.25 μm, the films may adhere to each other when making a bag without powder, and there may be a problem with poor opening performance.

[0020] The above (1) to (5) can be achieved, for example, by a combination of a polypropylene-based resin and a crystal nucleating agent masterbatch.

[0021] As the polypropylene-based resin, a homopolypropylene (a) which is a propylene homopolymer, an ethylene-propylene block copolymer (b), a small amount of α-olefins such as ethylene, 1-butene, 1-hexene, and other comonomers, and a propylene-α-olefin random copolymer with other comonomers are preferred. More preferably, a mixture of a homopolypropylene (a) which is a propylene homopolymer and an ethylene-propylene block copolymer (b) is preferred because it can form a film that satisfies the above various properties.

[0022] Homopolypropylene (a) The melt flow rate (MFR) of the above homopolypropylene (a) at 230°C (load 21.18 N) is preferably in the range of 1 to 20 g / 10 minutes from the viewpoints of the dispersibility of the resins and the stable melt film-forming property, preferably in the range of 1 to 10 g / 10 minutes, more preferably in the range of 5 to 8 g / 10 minutes.

[0023] Ethylene-propylene block copolymer (b) The ethylene-propylene block copolymer (b) preferably has a proportion of the xylene-insoluble part at 20 °C of 75 to 85% by mass, an intrinsic viscosity ([η]H) of the insoluble part of 1.7 to 2.0 dl / g, and an intrinsic viscosity ([η]EP) of the soluble part of 2.8 to 3.4 dl / g.

[0024] The xylene-insoluble part at 20 °C and the soluble part are obtained by completely dissolving the ethylene-propylene block copolymer pellets in boiling xylene, then cooling to 20 °C, leaving them standing for 4 hours or more, and then filtering them into a precipitate and a solution. The precipitate is referred to as the xylene-insoluble part at 20 °C, and the part obtained by drying the solution part (filtrate) and drying it under reduced pressure at 70 °C is referred to as the soluble part.

[0025] When the intrinsic viscosity ([η]H) of the insoluble part of the ethylene-propylene block copolymer (b) is less than 1.7 dl / g, the molecular weight of the polypropylene in the sea component may be small, resulting in insufficient low-temperature impact resistance. If it is greater than 2.0 dl / g, conversely, the molecular weight of the polypropylene increases, and cast molding may become difficult. Also, when the intrinsic viscosity ([η]EP) of the xylene-soluble part is less than 2.8 dl / g, the film may become sticky and the antiblocking property may deteriorate. If it is greater than 3.4 dl / g, the dispersed particle diameter of the island component composed of ethylene and ethylene-propylene copolymer rubber components increases, and when packaging oily foods, a persimmon-skin phenomenon may easily occur.

[0026] Examples of the method for producing the ethylene-propylene block copolymer (b) used in the present invention include a method of polymerizing raw materials such as propylene and ethylene using a catalyst. Here, as the catalyst, a Ziegler-Natta type or a metallocene catalyst can be used, and for example, those described in JP-A-07-216017 can be preferably used.

[0027] Specifically, (1) in the presence of an organosilicon compound having an Si-O bond and an ester compound, the general formula Ti(OR) a X4-a (In the formula, R represents a hydrocarbon group having 1 to 20 carbon atoms, X represents a halogen atom, a represents 0 < a ≤ 4, preferably 2 ≤ a ≤ 4, and particularly preferably a = 4.) A solid product obtained by reducing a titanium compound represented by the formula with an organomagnesium compound is treated with an ester compound and then treated with a mixture of an ester compound and titanium tetrachloride or a mixture of an ether compound and titanium tetrachloride to obtain a trivalent titanium compound-containing solid catalyst, (2) an organoaluminum compound, and (3) an electron-donating compound (dialkyldimethoxysilane etc. are preferably used).

[0028] As a method for producing the ethylene-propylene block copolymer (b), from the viewpoints of productivity and low-temperature impact resistance, it is preferable to use a method in which a polymer portion mainly composed of propylene is polymerized in the first step and then an ethylene-propylene copolymer is polymerized in the gas phase in the second step.

[0029] Crystal nucleating agent masterbatch (c) The crystal nucleating agent masterbatch (c) contains 3 to 10% by mass of a crystal nucleating agent containing a metal phosphate. As the carrier resin of the masterbatch, an olefin resin is desirable. For example, a propylene-based random copolymer obtained by randomly copolymerizing ethylene or butene with propylene, homopolypropylene, a propylene-based block copolymer, and a polyethylene-based resin can be mentioned.

[0030] By containing 1500 ppm or more and 10000 ppm or less of the crystal nucleating agent containing the metal phosphate contained in the resin composition of the polypropylene-based sealant film of the present invention, the easy tearability in all in-plane directions can be improved. When the content of the crystal nucleating agent is less than 1500 ppm, the easy tearability is not satisfactory. When it is more than 10000 ppm, further improvement in easy tearability may not be observed, and the heat sealability may deteriorate.

[0031] In addition, although the metal phosphate alone can satisfy the easy tearability, the easy tearability can be further improved by using it in combination with the metal dicarboxylate. Therefore, these crystal nucleating agents may be used in combination.

[0032] Examples of the metal phosphate in the present invention include phosphate ester compounds, etc., and among them, aromatic phosphate metal salts are preferable for the purpose of the present invention. Specifically, sodium-bis(4-t-butylphenyl)phosphate, sodium-bis(4-methylphenyl)phosphate, sodium-bis(4-ethylphenyl)phosphate, sodium-bis(4-i-propylphenyl)phosphate, sodium-bis(4-t-octylphenyl)phosphate, potassium-bis(4-t-butylphenyl)phosphate, calcium-bis(4-t-butylphenyl)phosphate, magnesium-bis(4-t-butylphenyl)phosphate, lithium-bis(4-t-butylphenyl)phosphate, aluminum-bis(4-t-butylphenyl)phosphate, sodium-2,2'-methylene-bis(4,6-di-t-butylphenyl)phosphate, sodium-2,2'-ethylidene-bis(4,6-di-t-butylphenyl)phosphate, lithium-2,2'-methylene-bis(4,6-di-t-butylphenyl)phosphate, lithium-2,2'-ethylidene-bis(4,6-di-t-butylphenyl)phosphate, sodium-2,2'-ethylidene-bis(4-i-propyl-6-t-butylphenyl)phosphate, lithium-2,2'-methylene-bis(4-methyl-6-t-butylphenyl)phosphate, lithium-2,2'-methylene-bis(4-ethyl-6-t-butylphenyl)phosphate, calcium-bis[2,2'-thiobis(4-methyl-6-t-butylphenyl)phosphate], calcium-bis[2,2'-thiobis(4-ethyl-6-t-butylphenyl)phosphate], calcium-bis[2,2'-thiobis-(4,6-di-t-butylphenyl)phosphate], magnesium-bis[2,2'-thiobis(4,6-di-t-butylphenyl)phosphate], magnesium-bis[2,2'-thiobis-(4-t-octylphenyl)phosphate], sodium-2,2'-butylidene-bis(4,6-dimethylphenyl)phosphate, sodium-2,2'-butylidene-bis(4,6-di-t-butylphenyl)phosphate, sodium-2,2'-t-octylmethylene-bis(4,6-di-methylphenyl) phosphate, sodium-2,2'-t-octylmethylene-bis(4,6-di-t-butylphenyl) phosphate, calcium-bis[2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate], magnesium-bis[2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate], barium-bis[2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate], sodium-2,2'-methylene-bis(4-methyl-6-t-butylphenyl) phosphate, sodium-2,2'-methylene-bis(4-ethyl-6-t-butylphenyl) phosphate, sodium-(4,4'-dimethyl-5,6'-di-t-butyl-2,2'-biphenyl) phosphate, calcium-bis[(4,4'-dimethyl-6,6'-di-t-butyl-2,2'-biphenyl) phosphate], sodium-2,2'-ethylidene-bis(4-m-butyl-6-t-butylphenyl) phosphate, sodium-2,2'-methylene-bis(4,6-di-methylphenyl) phosphate, sodium-2,2'-methylene-bis(4,6-di-ethylphenyl) phosphate, potassium-2,2'-ethylidene-bis(4,6-di-t-butylphenyl) phosphate, calcium-bis[2,2'-ethylidene-bis(4,6-di-t-butylphenyl) phosphate], magnesium-bis[2,2'-ethylidene-bis(4,6-di-t-butylphenyl) phosphate], barium-bis[2,2'-ethylidene-bis(4,6-di-t-butylphenyl) phosphate], aluminum-tris[2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate] and aluminum-tris[2,2'-ethylidene-bis(4,6-di-t-butylphenyl) phosphate] and mixtures of two or more of these can be exemplified. Particularly preferred is sodium-2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate.,

[0033] The dicarboxylic acid metal salt in the present invention is a compound represented by the following structural formula (i) disclosed in JP-A-2015-212078.

[0034]

Chemical formula

[0035] (In formula (i), M1 and M2 are sodium, hydrogen, calcium, strontium or lithium, and they may be the same or different. R2, R3, R4, R5, R6, R7, R8, R9, R10 and R11 are a hydrogen atom, a halogen atom, an alkyl group having 1 to 9 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 9 carbon atoms, an alkyleneoxy group having 1 to 9 carbon atoms, an amino group, an alkylamino group having 1 to 9 carbon atoms, or a phenyl group, and they may be the same or different. Any two of R2, R3, R4, R5, R6, R7, R8, R9, R10 and R11 may be bonded together to form a saturated hydrocarbon ring having 3 to 6 carbon atoms together with the cyclohexane ring carbon atoms depicted in formula (i) to which they are bonded. R2 and R3 may be in a trans configuration or a cis configuration.) Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like. Examples of the alkyl group having 1 to 9 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group and the like. Examples of the alkoxy group having 1 to 9 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group and the like. Examples of the alkylamino group having 1 to 9 carbon atoms include a methylamino group, an ethylamino group, a dimethylamino group, a diethylamino group and the like. Examples of the alkyleneoxy group having 1 to 9 carbon atoms include a group represented by the following formula and the like.

[0036] R(R’O)n- (In the formula, R represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R’ represents an alkylene group having 2 or 3 carbon atoms, and n represents an integer of 2 to 4. However, the total number of carbon atoms of R and R’ is 9 or less.) When the alkyleneoxy group having 1 to 9 carbon atoms is the group represented by the above formula, it is preferably H(CH2CH2O)2-, H(CH2CH2O)3-, H(CH2CH2O)4-, CH3(CH2CH2O)2-, CH3(CH2CH2O)3-, CH3(CH2CH2O)4-, CH3CH2(CH2CH2O)2-, CH3CH2(CH2CH2O)3-, (CH3)2CH(CH2CH2O)2-, (CH3)2CH(CH2CH2O)3-, H((CH3)CHCH2O)2-, H((CH3)CHCH2O)3-, CH3((CH3)CHCH2O)2-, or CH3CH2((CH3)CHCH2O)2-.

[0037] In addition, the present invention may further contain 0 to 5000 ppm of a saccharide-based nucleating agent. However, if the content is too high, the odor of the film after retorting may deteriorate, so it is preferably 2000 to 3000 ppm. At that time, more excellent tearability can be satisfied. Examples of the saccharide-based nucleating agent include sorbitol-based, nonitol-based, xylitol-based, etc. Specifically, bis-1,3:2,4-(3'-methyl-4'-fluoro-benzylidene)1-propyl sorbitol, bis-1,3:2,4-(3',4'-dimethylbenzylidene)1'-methyl-2'-propenyl sorbitol, bis-1,3,2,4-dibenzylidene 2',3'-dibromopropyl sorbitol, bis-1,3,2,4-dibenzylidene 2'-bromo-3'-hydroxypropyl sorbitol, bis-1,3:2,4-(3'-bromo-4'-ethylbenzylidene)-1-allyl sorbitol, mono 2,4-(3'-bromo-4'-ethylbenzylidene)-1-allyl sorbitol, bis-1,3:2,4-(4'-ethylbenzylidene)1-allyl sorbitol, bis-1,3:2,4-(3',4'-dimethylbenzylidene)1-methyl sorbitol, 1,2,3-trideoxy-4,6:5,7-bis-[(4-propylphenyl)methylene]-nonitol, bis-1,3:2,4-(4'-ethylbenzylidene)1-allyl sorbitol, bis-1,3:2,4-(5',6',7',8'-tetrahydro-2-naphthaldehyde benzylidene)1-allyl xylitol, bis-1,3:2,4-(3',4'-dimethylbenzylidene)1-propyl xylitol, etc. can be mentioned.

[0038] In addition, by adding 5 to 20 parts by mass of a polypropylene-based polymer (d) or a high melt tension polypropylene (e) to the resin composition of the polypropylene-based sealant film, the tearability in all in-plane directions is improved.

[0039] When the content of the polypropylene-based polymer (d) or the high melt tension polypropylene (e) is less than 5 parts by mass, the effect of tearability may not be obtained, and when it is more than 20 parts by mass, melt fracture may occur and the appearance may be significantly deteriorated.

[0040] Polypropylene polymer (d) The polypropylene polymer (d) is composed of two or more propylene polymers with different molecular weights. The intrinsic viscosity ([η]d1) of the component with the highest molecular weight (d1 component) is 5 dl / g or more and less than 10 dl / g, and it is a propylene polymer that is more than twice the intrinsic viscosity ([η]d) of the entire polypropylene polymer (d). The intrinsic viscosity ([η]d1) of the d1 component, which is the component with the highest molecular weight of this polypropylene polymer (d), needs to be 5 dl / g or more and less than 10 dl / g. If it is less than 5 dl / g, the improvement of easy tearability is not sufficient, and if it is 10 dl / g or more, foreign substances may be generated in the film, which is not preferable. When the intrinsic viscosity ([η]d1) of the d1 component is less than twice the intrinsic viscosity ([η]d) of the entire polypropylene polymer (d), the kneadability deteriorates, and melt fracture is likely to occur. The proportion of the d1 component of the polypropylene polymer (d) is preferably 3 to 25% by mass (assuming the entire polypropylene polymer (d) is 100% by mass).

[0041] High melt tension polypropylene (e) The high melt tension polypropylene (e) can be produced by known methods such as irradiating with electron beams to impart long-chain branches, imparting long-chain branches by modifying in an extruder in the presence of a peroxide and a crosslinking monomer, or imparting a high molecular weight component by multi-stage polymerization to improve the melt tension. The composition may be any of a propylene homopolymer, a propylene-ethylene random copolymer, or a propylene-ethylene block copolymer (b), but in terms of heat resistance, the propylene homopolymer type is preferable.

[0042] The MFR of the above high melt tension polypropylene (e) at 230 °C (load 21.18 N) is preferably in the range of 0.1 to 18 g / 10 minutes, and it is preferable that it is in the range of 0.5 to 9 g / 10 minutes because it is easy to obtain suitable film-forming properties and good compatibility with propylene block copolymers.

[0043] It is preferable that the melt tension (at 230°C) of the above high melt tension polypropylene (e) is in the range of 3 to 26 g, as it enhances the crystallinity of the film and further improves the easy tearability.

[0044] Moreover, by adding 1 to 20% by mass of a low density polyethylene-based polymer (f) to the resin composition of the polypropylene-based sealant film, the low temperature impact resistance and the resistance to user's skin are further improved.

[0045] When the content of the low density polyethylene-based polymer (f) is less than 1% by mass, the improvement effects of the low temperature impact resistance and the resistance to user's skin may not be obtained. Conversely, when it exceeds 20% by mass, the easy tearability may deteriorate.

[0046] When the density of the above low density polyethylene-based polymer (f) is in the range of 0.910 to 0.940 g / cm 3 it is preferable as the dispersibility in the above polypropylene-based resin is good. When the density of such a low density polyethylene-based polymer (f) is less than 0.910 g / cm 3 the blocking resistance may decrease, and when it is higher than 0.940 g / cm 3 the low temperature impact resistance may decrease. Also, it is preferable to use those produced by a metallocene catalyst from the viewpoint of heat sealability.

[0047] Examples of the above low density polyethylene-based polymer (f) include copolymers of ethylene alone or ethylene and α-olefins having 3 or more carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, etc., and those produced by generally known methods can be used. Specifically, high pressure low density polyethylene or linear low density polyethylene can be used. Among them, linear low density polyethylene is preferable because it has higher impact strength and higher heat sealability than high pressure low density polyethylene.

[0048] Furthermore, it is preferable to contain 1 to 5 parts by mass of the high-density polyethylene-based polymer (g) because it does not reduce the easy tearability and improves the low-temperature impact resistance. When the high-density polyethylene-based polymer (g) is contained in an amount exceeding 5 parts by mass, the low-temperature impact resistance does not improve, and the heat sealability may be significantly reduced.

[0049] The above high-density polyethylene-based polymer (g) has a density of 0.92 to 0.97 g / cm 3 and is an ethylene-based polymer having an MFR of 1 to 20 g / 10 minutes at 190 °C and a load of 21.18 N. Preferably, the density is 0.92 to 0.97 g / cm 3 More preferably, it is 0.92 to 0.97 g / cm 3 and is an ethylene homopolymer. When the density of the high-density polyethylene-based polymer (g) is less than 0.92 g / cm 3 , the blocking resistance may deteriorate. When it exceeds 0.97 g / cm 3 , the heat sealability may deteriorate.

[0050] When the MFR of the above high-density polyethylene-based polymer (g) at 190 °C and a load of 21.18 N is less than 1 g / 10 minutes, the transparency may deteriorate. On the other hand, when the MFR exceeds 20 g / 10 minutes, the low-temperature impact resistance may deteriorate.

[0051] Furthermore, by adding a thermoplastic elastomer (h) to the resin composition of the polypropylene-based sealant film, the low-temperature impact resistance and heat sealability are further improved.

[0052] The above-mentioned thermoplastic elastomer (h) has a hard segment phase and a soft segment phase. It has rubber elasticity at 25°C, while in the temperature range of 100°C to 300°C, which is the general thermoplastic molding temperature range, fluidity appears in the hard segment phase, enabling molding processes similar to those of general thermoplastic resins. It refers to a high molecular weight polymer. As the thermoplastic elastomer (h), for example, polyester-based elastomers, polyolefin-based elastomers, polyamide-based elastomers, polyurethane-based elastomers, styrene-based elastomers, and polyacrylic-based elastomers can be used alone or in combination. Among them, from the perspective of the heat sealability of the resulting film, it is preferable to use polyolefin-based elastomers and hydrogenated styrene-based elastomers.

[0053] As the above-mentioned polyolefin-based elastomer, propylene-based elastomers and ethylene-based elastomers are preferable.

[0054] Also, if the various properties described above can be satisfied, the polypropylene-based sealant film of the present invention may be a single-layer film. However, in order to satisfy all of easy tearability, heat sealability, antiblocking property, and low-temperature impact resistance, using the above resin composition as the base layer (B layer), a composite film composed of two layers of A layer / B layer or three layers of A layer / B layer / C layer with a seal layer (A layer) and a surface layer (C layer) laminated on at least one side thereof may also be used.

[0055] In that case, it is preferable that the above A layer and C layer mainly consist of the ethylene-propylene block copolymer (b). Here, the main component means consisting of 50% by mass or more.

[0056] When the ethylene-propylene block copolymer (b) is less than 50% by mass, the low-temperature impact resistance and heat sealability may deteriorate.

[0057] In addition, by using the low-density polyethylene-based polymer (f), high-density polyethylene-based polymer (g), and thermoplastic elastomer (h) in combination with the ethylene-propylene block copolymer (b) of the A layer and C layer, it is preferable because the low-temperature impact resistance, heat sealability, and anti-frostbite property are improved.

[0058] However, if the intrinsic viscosity [η] EP) of the A layer is less than 2.8 dl / g due to the addition of the low-density polyethylene-based polymer (f), the heat sealability may be significantly reduced. When the intrinsic viscosity [η] exceeds 3.4 dl / g, the frostbite phenomenon may easily occur. The ethylene content in the xylene-soluble part is preferably in the range of 20 to 50% by mass. If the content rate is less than 20% by mass, the low-temperature impact resistance at low temperatures may decrease. Conversely, if it is greater than 50% by mass, the easy tearability and anti-blocking property may be insufficient.

[0059] As the ratio of the low-density polyethylene-based polymer (f) in the resin composition constituting the A layer and C layer, it is preferably contained in an amount of 1 to 20% by mass. When the content of the low-density polyethylene-based polymer (f) is less than 1% by mass, the effect of improving the low-temperature impact resistance and anti-frostbite property may not be obtained. Conversely, when it exceeds 20% by mass, the easy tearability may deteriorate.

[0060] Within the range not impairing the object of the present invention, each layer can contain an antioxidant, heat stabilizer, neutralizing agent, antistatic agent, hydrochloric acid absorbent, anti-blocking agent, lubricant, etc. These additives may be used alone or in combination of two or more.

[0061] Here, specific examples of the antioxidant include, as hindered phenols, 4-methyl-2,6-di-t-butylphenol (BHT), octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate (“Irganoox” 1076, “Sumilizer” BP-76), tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (“Irganoox” 1010, “Sumilizer” BP-101), tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate (“Irganoox” 3114, “Adekastab” AO-20), etc. Also, as phosphite (phosphorus-based) antioxidants, tris(2,4-di-t-butylphenyl) phosphite (“Irgafos” 168, “Adekastab” 2112), tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene-diphosphonite (“Sandstab” P-EPQ), bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite (“Ultranox” 626, “Adekastab” PEP-24G), distearyl pentaerythritol diphosphite (“Adekastab” PEP-8), etc. Among them, 2,4,8,10-tetra-t-butyl-6-[3-(3-methyl-4-hydroxy-5-t-butylphenyl)propoxy] dibenz[d,f][1,3,2] dioxaphosphepine (“Sumilizer” GP), which has both functions of these hindered phenols and phosphites, and acrylic acid 2[1-[2-hydroxy-3,5-di-t-pentylphenyl]ethyl]-4,6-di-t-pentylphenyl (“Sumilizer” GS) are preferable. In particular, the combined use of these two is preferable because it is effective in suppressing the decomposition of the xylene-soluble part, especially at 20 °C, during film formation, and greatly contributes to achieving both low-temperature impact resistance and antiblocking properties. When the decomposition of such a xylene-soluble part is promoted, the antiblocking property may deteriorate.

[0062] Note that the addition amount of the antioxidant may be appropriately set in the range of 0.05 to 0.3% by mass, although it depends on the type of antioxidant used.

[0063] In addition, as the neutralizing agent, hydrotalcite compounds, hydroxides, etc. are preferable for reducing fume generation during film formation.

[0064] Next, the polypropylene-based sealant film of the present invention can be produced by known film formation methods such as the T-die method and the tubular method. In particular, the film formation method of the unstretched film by the T-die method is preferable because it is easy to control the birefringence and crystallinity of the film. The film formation method of the film of the present invention by the T-die method is described below, but it is not limited to this method.

[0065] For example, a raw material selected from homopolypropylene (a), ethylene-propylene block copolymer (b), crystal nucleating agent masterbatch (c), polypropylene-based polymer (d), high melt tension polypropylene (e), low density polyethylene-based polymer (f), high density polyethylene (g), and thermoplastic elastomer (h) is mixed at a predetermined blending ratio with a single-screw or twin-screw melt extruder and melt-kneaded. Then, the obtained kneaded product is filtered through a filter and extruded into a film shape from a flat die (for example, a T-die). The thickness ratio of each layer is preferably adjusted to be 50 / 50 to 5 / 95, more preferably 40 / 60 to 10 / 90, and even more preferably 30 / 70 to 20 / 80 when the sealant film is composed of a sealant layer (layer A) and a base layer (layer B) because it is easy to suitably adjust tearability, heat sealability, low temperature impact resistance, and anti-frostbite property. The temperature of the molten polymer extruded from the melt extruder is usually applicable in the range of 180 to 300°C, but 200 to 270°C is preferable in order to prevent decomposition of the polymer and obtain a film of good quality. The film extruded from the T-die is brought into contact with a cooling roll set at a constant temperature of 20 to 90°C, cooled and solidified, and then wound up.

[0066] The film of the present invention may have a two-layer structure of a seal layer (A layer) / base layer (B layer), for example, using a multi-layer co-extrusion die, or a three-layer structure of a seal layer (A layer) / base layer (B layer) / surface layer (C layer) with the surface layer (C layer) laminated. The thickness ratio of each layer is preferably from 1:2:1 to 1:8:1, more preferably from 1:4:1 to 1:6:1, of the seal layer (A layer):base layer (B layer):surface layer (C layer), since it is easy to suitably adjust tearability, heat sealability, and low-temperature impact resistance.

[0067] The polypropylene-based sealant film of the present invention can be stretched after cooling and solidification, but is preferably a non-stretched film that is preferably not substantially stretched. A non-stretched film that is not substantially stretched is preferable in terms of tearability in all in-plane directions and heat sealability. In the present invention, the non-stretched film refers to an extrusion cast film. However, in an actual film-forming process, the film may be slightly oriented in the MD direction or TD direction of the film. Therefore, the birefringence (the difference in refractive index between the MD direction and TD direction of the film, Δn) of the polypropylene-based sealant film of the present invention is -3 ~8.0×10 -3 in the range of, which is preferable in terms of heat sealability, thermal dimensional stability, and tearability. The birefringence (Δn) can be obtained as Δn = R / d by measuring the retardation R (nm) of the sample using the compensator method and the thickness d (nm) of the film at the measurement part.

[0068] The thickness of the film of the present invention obtained in this way is preferably 20 to 300 μm, more preferably 30 to 100 μm.

[0069] Here, as a method for controlling the birefringence in the present invention, for example, the above-mentioned mixed resin is melted at a low temperature in the range of 180°C to 270°C, preferably 200°C to 250°C, cooled on a casting drum maintained at a high temperature of 50 to 90°C, preferably 50 to 70°C, and wound up at a speed of 10 to 100 m / min.

[0070] The polypropylene-based sealant film of the present invention obtained as described above can be used alone as a packaging film, but is preferably used as a sealant film for a retort food packaging bag containing general AL. As the constituent films of the laminate, the usual dry lamination method of bonding using an adhesive can be preferably adopted. However, if necessary, for bonding the film of the present invention to other base material layers, a method of directly extruding and laminating a polyethylene-based resin or a polypropylene-based resin can also be adopted. These laminates use this polypropylene-based unstretched film as the seal layer (inner surface of the bag) and are made into bags such as flat bags and standing pouches for use. For example, the above polypropylene-based sealant film is dry laminated with a laminate base material layer composed of a biaxially stretched polyethylene terephthalate film (PET) with a thickness of 12 μm, a biaxially stretched polyamide film (ONy) with a thickness of 15 μm, and an aluminum foil (AL) with a thickness of 9 μm using a urethane-based adhesive by the dry lamination method to create a laminate having a structure of PET / adhesive / ONy / adhesive / AL / the sealant film. Two of these laminates are used such that the sealant film becomes the inner surface of the bag, and a three-side pouch with a bag-making size of 50 mm × 150 mm can be created using a CA-450-10 type heat sealer manufactured by Fuji Impulse Co., Ltd. with a heating time of 0.8 seconds (sealing temperature: about 180°C) and a cooling time of 3.0 seconds.

[0071] In addition, the laminate structure of these laminates is appropriately selected according to the required characteristics of the packaging bag (for example, barrier performance for satisfying the quality retention period of the food to be packaged, size and low-temperature impact resistance corresponding to the mass of the contents, visibility of the contents, etc.).

Examples

[0072] Hereinafter, the present invention will be specifically described by way of examples, but the scope of the present invention is not limited thereto. Also, the detailed description of the present invention and the measured values of each evaluation item in the examples were measured by the following methods.

[0073] (1) Content of 20°C xylene-soluble part After completely dissolving 5 g of polypropylene pellets in 500 mL of boiling xylene (Kanto Chemical Co., Inc., Grade 1), the temperature was lowered to 20 °C and left standing for 4 hours or more. Then, this was filtered into a precipitate and a solution, and separated into a soluble part and an insoluble part. The soluble part was solidified under reduced pressure of the filtrate and then dried at 70 °C, and its mass was measured to determine the content (mass %).

[0074] (2) Intrinsic viscosity of the 20 °C xylene-insoluble part and soluble part Using the sample separated by the above method, measurement was carried out in tetralin at 135 °C using an Ubbelohde viscometer.

[0075] (3) Melt flow rate (MFR) In accordance with JIS K7210:1999, the propylene-ethylene block copolymer (b) was measured at a temperature of 230 °C and the polyethylene-based polymer was measured at a temperature of 190 °C, each under a load of 21.18 N.

[0076] (4) Melt tension (MS) The melt tension (MS) at 230 °C was measured using a melt tension tester type 2 manufactured by Toyo Seiki Seisaku-sho, Ltd. Inside the apparatus, polypropylene was heated to 230 °C, and the molten polypropylene was extruded from a nozzle with a diameter of 2.095 mm into the atmosphere at 23 °C at a speed of 20 mm / min to form a strand. The tension of the filamentous polypropylene when this strand was taken up at a speed of 3.14 m / min was measured and taken as the melt tension (MS).

[0077] (5) Density Measurement was carried out by a measurement method using a density gradient tube based on JIS K7112:1999.

[0078] (6) Low-temperature impact resistance PET with a thickness of 12 μm, ONy with a thickness of 15 μm, AL with a thickness of 9 μm, and the film of the present invention with a thickness of 70 μm were laminated using a urethane-based adhesive by a normal dry lamination method to create a laminate with a thickness of 115 μm having the following configuration.

[0079] Laminate configuration: PET / adhesive / ONy / adhesive / AL / adhesive / film of the present invention Two sheets of this laminate were arranged such that the film of the present invention was on the inner surface of the bag, and a standing pouch with a bag-making size of 150 mm × 285 mm was created using a CA-450-10 type heat sealer manufactured by Fuji Electric Co., Ltd. with a heating time of 1.4 seconds (sealing temperature: approximately 220°C) and a cooling time of 3.0 seconds. 1000 cm of saline solution with a concentration of 0.1% was filled into this bag. 3 After filling, it was subjected to retort treatment at 135°C for 30 minutes. After storing the bag after retort treatment in a refrigerator at 0°C, it was dropped from a height of 55 cm onto a flat floor surface (n = 20 pieces), and the number of times until the bag burst was recorded. In this evaluation method, if the average value of n = 20 pieces was 5 times or more, the low-temperature impact resistance was considered good and marked as ○, and if it was less than 5 times, it was marked as ×.

[0080] (7) Heat sealability Two seal layers of the same laminate as in item (6) were heat-sealed using a flat heat sealer under the conditions of a seal temperature of 180°C, a seal pressure of 10 N / cm, and a seal time of 1 second. The sample after heat-sealing was subjected to retort treatment at 130°C for 30 minutes, and then the strength of the heat seal was measured using a tensilon manufactured by Orientec Co., Ltd. at a tensile speed of 300 mm / min. In this measurement method, if the strength was 45 N / 15 mm or more, it could be used well for retort foods, so the heat sealability was considered good and marked as ○, and if it was less than 45 N / 15 mm, the heat sealability was marked as ×. 2

[0081] (8) Resistance to user's skin PET with a thickness of 12 μm, ONy with a thickness of 15 μm, AL with a thickness of 9 μm, and the film of the present invention were laminated using a urethane-based adhesive by a normal dry lamination method to create a laminate with a thickness of 115 μm having the following configuration.

[0082] Laminate configuration: PET / adhesive / ONy / adhesive / AL / adhesive / film of the present invention Two sheets of this laminate were arranged such that the film of the present invention was on the inner surface of the bag, and a flat heat sealer was used with a seal temperature of 180°C and a seal pressure of 10 N / cm. 2 ​, heat-sealing was performed under the condition of a sealing time of 1 second to create a three-side bag (flat bag, sealing width 5 mm) with a size of 160 mm × 210 mm (internal dimensions). After filling this bag with commercially available retort curry (retort curry "Kukure Curry - Spicy" manufactured by House Foods Industry Co., Ltd.), the unevenness generation situation on the surface of the laminate immediately after retort treatment at 135 °C for 30 minutes was visually judged. Those with no generation were ranked 1, those with slight generation were ranked 2, those with mild generation were ranked 3, those with clear generation were ranked 4, and those with severe generation were ranked 5 for evaluation. In this evaluation method, ranks 1, 2, and 3 were regarded as having good anti-user skin property and marked as ○, and 4 and above were regarded as having anti-user skin property marked as ×.

[0083] (9) Blocking shear force (N / 12 cm 2 ) A film sample with a width of 30 mm and a length of 100 mm was prepared. The films were overlapped in the range of 30 mm × 40 mm, and a load of 5 N / 12 cm 2 was applied. After heat treatment in an oven at 80 °C for 2.0 hours, it was left in an atmosphere of 23 °C and 65% humidity for 30 minutes or more, and then the shear peel force was measured at a tensile speed of 300 mm / min using a tensilon manufactured by Orientec. If the shear peel force is 10 N / 12 cm 2 or less by this measurement method, the blocking resistance is good and it can be used for non-powder retort, so it is marked as ○, and those higher than 10 N / 12 cm 2 are marked as × for the blocking resistance.

[0084] (10) Elmendorf method tear strength (N / mm) In accordance with JIS K7128-2:1998 (Elmendorf method tear method), in a constant temperature room at 23 °C, the tear strength (N) in the longitudinal direction (MD direction) of the film, the width direction (TD direction) of the film, and the direction 45 degrees to the left and right in the MD direction was measured, and the tear strength was calculated by dividing by the film thickness (mm). For a single polypropylene-based sealant film, if it is 30 N / mm or less per film in all in-plane directions, it was judged to have easy tearability.

[0085] Each component used in the examples and comparative examples is as follows.

[0086] [Homopolypropylene (a) / PP1] A homopolypropylene with an MFR of 4.0 g / 10 min at 230 °C and containing 0.0015% by mass of "Irganox" 1010 as an antioxidant was used. The above homopolypropylene (a) is hereinafter referred to as PP1. [Propylene-ethylene block copolymer (b) / B-PP1] Pellets of a propylene-ethylene block copolymer (b) having a content of 20 °C xylene-insoluble part of 80% by mass, an intrinsic viscosity ([η]H) of 1.90 dl / g, a content of 20 °C xylene-soluble part of 15% by mass, an intrinsic viscosity ([η]EP) of 3.00 dl / g, and an MFR of 2.5 g / 10 min at 230 °C and containing 0.0002% by mass of "Sumilizer" GP and 0.00080% by mass of "Sumilizer" GS as antioxidants were used. The above propylene-ethylene block copolymer (b) is hereinafter referred to as B-P1.

[0087] [Masterbatch (c) containing a crystal nucleating agent of metal phosphate / MB1] A masterbatch (PPMST-0024 manufactured by Tokyo Ink, carrier resin: homopolypropylene (a), MFR: 7 g / 10 min) containing 6% by mass of a crystal nucleating agent of sodium-2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate ("Adekastab" NA-11 manufactured by ADEKA), a metal salt of phosphate ester, was used. Hereinafter, the masterbatch of the crystal nucleating agent of metal phosphate ester is referred to as MB1(c). [Polypropylene-based polymer (d) / PP2] Using the polymerization catalyst described in Example 1 of JP-A-11-228629, propylene was polymerized in the first step to produce a first component in accordance with the polymerization method and polymerization conditions described in the same example. After that, without deactivating the catalyst, the catalyst and the first component were transferred to the second step, and propylene was polymerized in the second step to produce a component having a molecular weight different from that of the first component. In this way, a polypropylene-based polymer (d) was obtained, which consisted of 11% by mass of a propylene polymer component having an intrinsic viscosity of 7.6 dl / g and 89% by mass of a component having an intrinsic viscosity of 1.2 dl / g, and had an overall intrinsic viscosity of 2.0 dl / g. To 100 parts by mass of this polypropylene-based polymer (d), 0.2 part by mass of antioxidant IRGANOX 1010 (trade name, manufactured by Ciba Specialty Chemicals), 0.25 part by mass of antioxidant IRGAFOS 168 (trade name, manufactured by Ciba Specialty Chemicals), and 0.05 part by mass of calcium stearate were mixed, and melt mixing was carried out at 200 °C with a discharge rate of 300 kg / h and a screw rotation speed of 250 rpm using a twin-screw extruder TEM75 (trade name, manufactured by Toshiba Machine Co., Ltd.) to obtain pellets. The MFR of these pellets at 230 °C and a load of 21.18 N was 10 g / 10 min. The above polypropylene-based polymer (d) is hereinafter referred to as PP2.

[0088] [High melt tension polypropylene (e) / HMS-PP] Density 0.90 g / cm 3 And EX6000 manufactured by Nippon Polypropylene Co., Ltd. with an MFR of 2.9 g / 10 min at 230 °C and a load of 21.18 N and a melt tension (MS) of 9 g at 230 °C was used. Hereinafter, it is referred to as HMS-PP (e).

[0089] [Low density polyethylene-based polymer (f) / Low density PE] Density 0.925 g / cm 3 And linear low density polyethylene (FV201 manufactured by Sumitomo Chemical Co., Ltd.) with an MFR of 1.9 g / 10 min and a copolymer component of 1-hexene was used. The above low density polyethylene-based polymer (f) is hereinafter referred to as low density PE1.

[0090] [Low density polyethylene-based polymer (f) / Low density PE2] Density 0.910 g / cm 3 A linear low-density polyethylene (SP1071C manufactured by Prime Polymer Co., Ltd.) with a density of 0.910 g / cm, an MFR of 10.0 g / 10 minutes, and a copolymer component of 1-hexene was used. Hereinafter, the low-density polyethylene-based polymer (f) is referred to as low-density PE2.

[0091] [High-density polyethylene-based polymer (g) / High-density PE1] Density 0.950 g / cm 3 A commercially available high-density ethylene pellet with an MFR of 16.0 g / 10 minutes at 190°C under a load of 21.18 N was used. Hereinafter, the high-density ethylene pellet is referred to as HDPE1.

[0092] [Examples 1 to 25] With the resin compositions shown in Tables 1 and 2, the resin in pellet form was mixed by a blender and supplied to two or three extruders temperature-controlled to 260°C, melt-kneaded, filtered through a filter, and then laminated into a single layer or two or three layers using a multi-manifold die for co-extrusion and extruded into a film. After contacting a cooling roll at a temperature of 50°C and a speed of 60 m / min to cool and solidify, the contact surface side of the cooling roll was subjected to corona discharge treatment to obtain a film with a thickness of 70 μm. In the case of a single-layer film, it was 100% of layer B. In the case of a two-layer film, the thickness ratio of layer A and layer B was 30% for layer A and 70% for layer B. In the case of a three-layer film, the thickness ratio of layer A, layer B, and layer C was 20% for layer A, 60% for layer B, and 20% for layer C.

[0093] As a result of evaluating the film properties, as shown in Tables 1 and 2, a film that satisfies well in terms of tear strength in all in-plane directions, low-temperature impact resistance, anti-blocking shear resistance, anti-fuzzy skin property, heat sealability, in all aspects was obtained. In particular, as a laminate for a sealant of a packaging bag, it was confirmed to have excellent easy-tearability and anti-blocking property in all in-plane directions and can be used without powder.

[0094] [Comparative Examples 1 to 3, 5, 6] With the resin compositions shown in Tables 3 and 4, the resin in pellet form was mixed by a blender and supplied to two or three extruders whose temperature was adjusted to 260°C. After melt-kneading and filtering through a filter, it was extruded into a film form in a single layer or laminated into two or three layers using a multi-manifold die for co-extrusion. After contacting a cooling roll at a temperature of 50°C and a speed of 60 m / min to cool and solidify, the contact surface side of the cooling roll was subjected to corona discharge treatment to obtain a film with a thickness of 350 μm. In the case of a single-layer film, it was 100% of layer B. In the case of a two-layer film, the thickness ratio of layer A and layer B was 30% for layer A and 70% for layer B. In the case of a three-layer film, the thickness ratio of layer A, layer B, and layer C was 20% for layer A, 60% for layer B, and 20% for layer C.

[0095] As a result of evaluating the film properties, they were as shown in Tables 3 and 4, and the tear strength in all in-plane directions was not satisfactory.

[0096] [Comparative Example 4] With the resin composition shown in Table 3, the resin in pellet form was mixed by a blender and supplied to two or three extruders whose temperature was adjusted to 260°C. After melt-kneading and filtering through a filter, it was extruded into a single-layer film form using a multi-manifold die for co-extrusion. After contacting a cooling roll at a temperature of 50°C and a speed of 20 m / min to cool and solidify, the contact surface side of the cooling roll was subjected to corona discharge treatment to obtain a film with a thickness of 350 μm. The obtained film was stretched 5-fold by a longitudinal stretching machine to obtain a film with a thickness of 70 μm.

[0097] As a result of evaluating the film properties, they were as shown in Table 3. The tear strength in all in-plane directions was not satisfactory, and the low-temperature impact resistance and heat sealability were also inferior.

[0098]

Table 1

[0099]

Table 2

[0100]

Table 3

[0101]

Table 4

Industrial Applicability

[0102] Provided are a polypropylene-based sealant film having excellent tearability in all directions within the film plane and excellent heat sealability, low-temperature impact resistance, blocking resistance, and feel-like-skin resistance, and a laminate using the same.

Claims

1. A film mainly composed of a polypropylene-based resin, wherein the polypropylene-based resin is any one of a homopolypropylene (a) that is a propylene homopolymer, an ethylene-propylene block copolymer (b), and a propylene-α-olefin random copolymer with any one of ethylene, 1-butene, and 1-hexene as an α-olefin comonomer, the tear strength per film by the Elmendorf method in JIS K 7128-2 (1998) is 30 N / mm or less in all in-plane directions, and the yield stress is 25 MPa or more and 50 MPa or less in all in-plane directions in the yield stress measurement method in JIS K 7161 (2014). A polypropylene-based sealant film characterized by this.

2. A film mainly composed of a polypropylene-based resin, wherein the polypropylene-based resin is any one of a homopolypropylene (a) that is a propylene homopolymer, an ethylene-propylene block copolymer (b), and a propylene-α-olefin random copolymer with any one of ethylene, 1-butene, and 1-hexene as an α-olefin comonomer, the tear strength per film by the Elmendorf method in JIS K 7128-2 (1998) is 30 N / mm or less in all in-plane directions, the polypropylene-based sealant film is composed of a resin composition mainly composed of a polypropylene-based resin and containing 1500 to 10000 ppm of a crystal nucleating agent, and a base layer composed of the resin composition and a layer mainly composed of an ethylene-propylene block copolymer are laminated on at least one side thereof. A polypropylene-based sealant film characterized by this.

3. The polypropylene-based sealant film according to Claim 1 or 2, wherein the crystallinity in infrared spectroscopy is 60% or more.

4. The blocking shear force after 24 hours at 80°C between the heat-sealing surfaces of the polypropylene-based sealant film is 5 N / 12 cm ２ The polypropylene-based sealant film according to any one of claims 1 to 3 below

5. The polypropylene-based sealant film according to any one of Claims 1 to 4, wherein the center line average roughness (Ra) of at least one side is 0.25 μm or more.

6. A laminate in which the polypropylene-based sealant film according to any one of Claims 1 to 5 is laminated on one side of a laminate base layer formed by laminating a single layer or two or more layers of films.

7. A pouch formed by heat-sealing and bag-making the polypropylene-based sealant films of the laminate according to Claim 6.

8. The pouch according to claim 7, which can be torn and split in the longitudinal and transverse directions to take out the contents.

Images