JP2022042574A - Polypropylene sealant film and laminate - Google Patents

Abstract

To provide a polypropylene sealant film that can be easily torn in the film longitudinal direction and excels in heat sealability, low-temperature impact resistance, blocking resistance, and orange peel resistance, and a laminate including the same.SOLUTION: A polypropylene sealant film consists of two layers: at least A layer and B layer. The A layer is predominantly composed of a propylene ethylene block copolymer (a). The B layer is predominantly composed of a propylene polymer (b). Each layer contains metal phosphate of 0.0015-0.01 wt.%. The film has a tear strength of 20 N/mm or less in the longitudinal direction .SELECTED DRAWING: None

Description

The present invention relates to a polypropylene-based sealant film used as a sealant for packaging bags and a laminate using the same.

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 (hereinafter sometimes referred to as CPP) containing a propylene / ethylene block copolymer as a main component is used. It has been. Its main usage is a laminated base material layer such as polyethylene terephthalate stretched film (hereinafter sometimes referred to as PET), nylon stretched film (hereinafter sometimes referred to as ONy), aluminum foil (hereinafter sometimes referred to as AL) and the like. It is used by laminating with PET / ONy / AL foil / CPP, PET / AL / ONy / CPP, or a laminated body having a PET / AL / CPP configuration, and then making a bag.

However, when a non-stretched film formed by melt-extruding a resin obtained by blending a propylene / ethylene block copolymer or a propylene / ethylene block copolymer with an ethylene-based elastomer in Patent Documents 1 and 2 is used for the retort pouch. When opening from the notch portion (cut end provided at the end portion), the straight cut property is poor, and there is a problem that the contents are deformed or spilled.

Therefore, the sealant film used for the retort pouch is required to be able to be opened by easily tearing it from the notch portion without using a blade (easy tearing property).

As a polypropylene-based film having easy tearability, there is a uniaxially stretched film (Patent Document 3) that is stretched at a high magnification in the vertical direction. The film of Patent Document 3 has improved tearability but is resistant to low temperatures. Impact resistance was insufficient for retort use. Further, there are a film containing a sorbitol derivative (Patent Document 4) and a film containing a rosin metal salt compound (Patent Document 5) for the purpose of increasing the crystallinity of the film and imparting tearability. , There are many odors and extracts after retort treatment, and it is not suitable for high retort applications. Further, there are a film containing a crystalline polyethylene resin (Patent Document 6) and a film containing polybutene-1 as a crystal nucleating agent (Patent Document 7), both of which are inferior in low temperature impact resistance. Therefore, it was insufficient for high retort use.

As described above, in the prior art, the resin has easy tearing property in the extrusion direction (hereinafter sometimes referred to as flow direction (MD)), and also has low temperature impact resistance, heat sealability, and blocking resistance. There was no polypropylene-based unstretched film that could be widely used for high-retort applications (sterilized at 125 to 135 ° C).

In recent years, the size of pouches for commercial use has increased, and the required level of low temperature impact resistance has become higher and higher. In addition, the required level of pouch appearance is increasing, and it is desired to suppress the occurrence of fine uneven appearance, so-called yuzu skin, which occurs on the surface of the laminate after retort sterilization.

Further, since the CPP of the laminated body and the laminated base material layer have poor slipperiness, the CPP of the laminated body and the laminated base material layer adhere to each other in the film forming process, the slit process, the bag making process, the content filling process, and the like. A so-called blocking phenomenon occurs, and when the laminated film is stored for a long period of time or in a high temperature state, it becomes difficult to unwind the film, and there is a problem that the bag making workability and the filling workability are remarkably deteriorated.

In order to solve the above problems, a method of sprinkling a blocking inhibitor, for example, a powder such as starch having a water resistant surface treatment on a sealant to prevent blocking, a method of avoiding blocking by a so-called powdering method has been adopted. However, the powdering method is a factor that reduces the commercial value, such as spoiling the appearance of the bag making, mixing it with the food filled with powder, and adversely affecting the taste, so there is no need for powdering. , So-called non-powder, and a polypropylene-based film that can be suitably used for high retort applications as a packaging bag or a sealant for a packaging bag has been strongly desired.

Japanese Patent Application Laid-Open No. 2003-105164 Japanese Unexamined Patent Publication No. 2000-186159 Japanese Unexamined Patent Publication No. 7-138423 Japanese Unexamined Patent Publication No. 1-299831 Japanese Unexamined Patent Publication No. 11-255910 Japanese Unexamined Patent Publication No. 10-316772 Japanese Patent No. 381263

The subject of the present invention is that it has excellent tearability in the flow direction (MD) of the resin as a sealant for packaging bags, has excellent heat sealability and low temperature impact resistance, and is used as a non-powder because of excellent blocking resistance. It is an object of the present invention to provide a polypropylene-based sealant film which can be suitably used for high-retort pouches because of its excellent resistance to shavings and a laminate using the same.

As a result of various studies, the present inventors have solved the above-mentioned problems.

That is, the present invention is a film composed of at least two layers, A layer and B layer. The A layer contains a propylene / ethylene block copolymer (a) as a main component, and the B layer contains a propylene polymer (b). A polypropylene-based sealant film containing 0.0015 to 0.01% by weight of a metal phosphate as a main component and having a tear strength in the longitudinal direction of the film of 20 N / mm or less in each layer.

Further, the polypropylene-based sealant film of the present invention is a laminated body laminated on one side of a laminated base material layer formed by laminating a single layer or two or more films.

When the polypropylene-based sealant film of the present invention and the laminate using the same are used as a sealant for a packaging bag, it has excellent tearability in the longitudinal direction of the film, excellent heat sealability and low temperature impact resistance, and resistance to low temperature impact. Since it has excellent blocking properties, it can be used as a non-powder, and can be used as a packaging material for high retort pouches, which has excellent resistance to loose skin.

In the propylene / ethylene block copolymer (a) of the A layer in the present invention, the proportion of the xylene insoluble portion at 20 ° C. is 75 to 85% by weight, and the ultimate viscosity ([η] H) of the insoluble portion is 1.7 to 2. It is preferably 0.0 dl / g and the ultimate viscosity ([η] EP) of the soluble part is 2.8 to 3.4 dl / g. The 20 ° C. xylene insoluble part and the soluble part are the propylene / ethylene block copolymer pellets, which are completely dissolved in boiling xylene, then cooled to 20 ° C. and left to stand for 4 hours or more, and then this. The precipitate was separated into a precipitate and a solution, and the precipitate was referred to as a xylene insoluble portion at 20 ° C. Call it.

When the intrinsic viscosity ([η] H) of the insoluble portion of the propylene / ethylene block copolymer (a) is smaller than 1.7 dl / g, the molecular weight of polypropylene, which is a sea component, is small, so that it has low temperature impact resistance and resistance to low temperature impact. The bending whitening property may be insufficient, and if it is larger than 2.0 dl / g, on the contrary, the molecular weight of polypropylene may become too large and cast molding may be difficult.

If the ultimate viscosity ([η] EP) of the xylene-soluble portion is smaller than 2.8 dl / g, the film may become sticky and the blocking resistance may deteriorate. If it is larger than 3.4 dl / g, polyethylene and ethylene may be deteriorated. The dispersed particle size of the island component composed of the propylene copolymer rubber component becomes large, and when an oil-based food is packaged, a loose skin phenomenon may easily occur.

Examples of the method for producing the propylene / ethylene block copolymer (a) 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, a metallocene catalyst, or the like can be used, and for example, those listed in JP-A-07-216017 can be preferably used. Specifically, (1) in the presence of an organosilicon compound and an ester compound having a Si—O bond, the general formula Ti (OR) _aX4 -a (in the formula, R is a hydrocarbon group having 1 to 20 carbon atoms). , X represents a halogen atom, a represents a number of 0 <a ≦ 4, preferably 2 ≦ a ≦ 4, and particularly preferably a = 4) is reduced with an organomagnesium compound. The obtained solid product is treated with an ester compound and then treated with a mixture of an ether compound and titanium tetrachloride or a mixture of an ether compound and titanium tetrachloride and an ester compound to obtain a trivalent titanium compound-containing solid catalyst. , (2) an organoaluminum compound, and (3) an electron-donating compound (dialkyldimethoxysilane or the like is preferably used).

As a method for producing the propylene / ethylene block copolymer (a), from the viewpoint of productivity and low temperature impact resistance, a polymer portion mainly composed of propylene is used in the first step in the absence of a substantially inactive agent. It is preferable to use a method of polymerizing and then polymerizing the ethylene / propylene copolymer in the gas phase in the second step.

The layer A is composed of a layer containing the propylene / ethylene block copolymer (a) as a main component, and the main component is 50% by weight or more. When the propylene / ethylene block copolymer (a) is less than 50% by weight, the low temperature impact resistance and the sealing strength are deteriorated.

The melt flow rate (hereinafter, may be abbreviated as MFR) of the propylene / ethylene block copolymer (a) at 230 ° C. (load: 21.18N) is 1 to 20 g / 20 g / from the viewpoint of dispersibility between resins. The range of 10 minutes is preferable, the range of 1 to 10 g / 10 minutes is more preferable, and the range of 5 to 8 g / 10 minutes is further preferable.

The propylene polymer (b) of the B layer in the present invention preferably contains homopolypropylene, which is a polymer of propylene alone, as a main component. By using the propylene polymer (b) as a main component, the easy tearing property and the blocking resistance are improved. Here, the main component means that it is composed of 50% by weight or more.

The MFR of the propylene polymer (b) at 230 ° C. (load 21.18N) is preferably in the range of 1 to 20 g / 10 minutes from the viewpoint of dispersibility between resins and stable melt film forming property. It is more preferably in the range of ~ 10 g / 10 minutes, and even more preferably in the range of 5 to 8 g / 10 minutes.

In the polypropylene-based sealant film of the present invention, it is preferable to use the low-density polyethylene-based polymer (c) in combination with the A layer and the B layer, thereby improving the low-temperature impact resistance and the yuzu-skin resistance.

However, due to the addition of the low-density polyethylene-based polymer (c), the sealing strength may be significantly reduced unless the ultimate viscosity [η] EP) of the layer A is 2.8 dl / g or more. If the ultimate viscosity [η] EP exceeds 3.4 dl / g, the yuzu skin phenomenon may easily occur. The ethylene content of the xylene-soluble portion is preferably in the range of 20 to 50% by weight. If the content is less than 20% by weight, the low temperature impact resistance at low temperature may be lowered, and conversely, if the content is larger than 50% by weight, the easy tearing property and the blocking resistance may be insufficient.

In the present invention, the low-density polyethylene-based polymer (c) preferably contains 1 to 12% by weight as a composition ratio in the resin composition constituting the polypropylene-based sealant film. If the content of the low-density polyethylene-based polymer (c) is less than 1% by weight, the effect of improving low-temperature impact resistance and resistance to yuzu skin may not be obtained, and conversely, if it exceeds 12% by weight. , Easy tearing may worsen.

When the density of the low-density polyethylene-based polymer (c) used in the present invention is in the range of 0.920 to 0.940 g / cm ³ , the propylene / ethylene block copolymer (a) and the propylene polymer (b) Good dispersibility in and preferable. The polyethylene-based polymer is ethylene alone or a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, etc., and is generally used. Those manufactured by the methods known to can be used. Specifically, high-pressure low-density polyethylene and linear low-density polyethylene can be used. Among them, linear low-density polyethylene has higher impact strength and higher sealing strength than high-pressure low-density polyethylene, so that it is linear. Low density polyethylene is preferable.

If the density of the low-density polyethylene-based polymer is less than 0.920 g / cm ³ , the blocking resistance may decrease, and if it is higher than 0.940 g / cm ³ , the low-temperature impact resistance may decrease. Further, it is preferable to use a catalyst produced by a metallocene catalyst from the viewpoint of seal strength.

Further, the polypropylene-based sealant film of the present invention can satisfy the easy tearability by containing 0.0015 to 0.01% by weight of a crystal nucleating agent containing a metal phosphate in each layer. When it is contained in only one layer, the easy tearability cannot be satisfied, and even when the crystal nucleating agent is less than 0.0015% by weight, the easy tearability cannot be satisfied. If it is more than 0.01% by weight, further improvement in the easy tearing property is not observed, and the sealing property is deteriorated. In addition, the easy tearing property can be satisfied by the phosphoric acid metal salt alone, but the easy tearing property is further improved by using it in combination with the dicarboxylic acid metal salt. Therefore, even if these crystal nucleating agents are used in combination. good.

Examples of the phosphoric acid metal salt in the present invention include phosphoric acid ester compounds, and among them, aromatic phosphoric acid ester 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'-Buchilidene-bis (4,6-di-methylphenyl) 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) Le) Phenyl 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 (2,2'-methylene-bis (4,6-di-t-butylphenyl) phosphate] 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) Phenyl phosphate, calcium-bis [(4,4-'dimethyl-6,6'-di-t-butyl-2,2'-biphenyl) Phenyl Phenyl], Sodium-2,2'-Etilidene-bis (4-m-butyl-6-t-butylphenyl) Phenyl Phenyl, Sodium-2,2'-methylene-bis (4,6-di-methylphenyl) ) Phenyl, sodium-2,2'-methylene-bis (4,6-di-ethylphenyl) phosphate, potassium-2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phos Fate, calcium-bis [2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phosphate], magnesium-bis [2,2'-ethylidene-bis (4,6-di-t) -Butylphenyl) Phenyl Phenyl], Barium-Bis [2,2-'Etilidene-Bis (4,6-di-t-Butylphenyl) Phenyl Phenyl], Aluminum-Tris [2,2'-Methylene-Bis (4) , 6-di-t-butylfell) phosphate], and aluminum-tris [2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phosphate]
And a mixture of two or more of these can be exemplified.

In particular, sodium-2,2'-methylene-bis (4,6-di-t-butylphenyl) phosphate is preferable.

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.

In formula (i), M1 and M2 are sodium, hydrogen, calcium, strontium or lithium, which 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, and 1 carbon atom. It is an alkyleneoxy group of ~ 9, an amino group, an alkylamino group having 1 to 9 carbon atoms, or a phenyl group, and may be the same or different. Any two of R2, R3, R4, R5, R6, R7, R8, R9, R10 and R11 are bonded together with the cyclohexane ring carbon atom depicted in formula (i) to which they are bonded. In addition, a saturated hydrocarbon ring having 3 to 6 carbon atoms may be formed. R2 and R3 may be in a transformer arrangement or a cis arrangement.

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.

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 carbon atoms. 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 a group represented by the above formula, H (CH ₂ CH ₂ O) _2- , H (CH ₂ CH ₂ O) _3- , H ( CH ₂ CH ₂ O) _4- , CH ₃ (CH ₂ CH ₂ O) _2- , CH ₃ (CH ₂ CH ₂ O) _3- , CH ₃ (CH ₂ CH ₂ O) _4- , CH ₃ CH ₂ (CH 2 CH 2 O) CH ₂ CH ₂ O) _2- , CH ₃ CH ₂ (CH ₂ CH ₂ O) _3- , (CH ₃ ) ₂ CH (CH ₂ CH ₂ O) _2- , (CH ₃ ) ₂ CH (CH ₂ CH ₂ ) O) _3- , H ((CH ₃ ) CHCH ₂ O) _2- , H ((CH ₃ ) CHCH ₂ O) _3- , CH ₃ ((CH ₃ ) CHCH ₂ O) _2- , or CH ₃ CH ₂ ((CH ₃ ) CHCH ₂ O) _2- .

The present invention may further contain 0 to 0.005% by weight of a saccharide-based nucleating agent. However, if the content is large, the odor of the film after retort may be deteriorated. Therefore, if the content is preferably 0.002 to 0.003% by weight, more excellent easy tearing property can be satisfied. The saccharide-based nucleating agent includes sorbitol-based, nonitol-based, xylitol-based, and specifically, bis-1,3: 2,4- (3'-methyl-4'-fluoro-benzylidene) 1-propyl. Sorbitol, bis-1,3: 2,4- (3', 4'-dimethylbenzidene) 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-Allylsorbitol, mono 2,4- (3'-bromo-4'-ethylbenzylidene) -1-allylsorbitol, bis-1,3: 2,4- (4'-ethylbenzylidene) 1-allyl Sorbitol, bis-1,3: 2,4- (3', 4'-dimethylbenzylidene) 1-methylsorbitol, 1,2,3-trideoxy-4,6: 5,7-bis-[(4-propyl) Phenyl) 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-allylxylitol, bis-1,3: 2,4- (3', 4'-dimethylbenzidlidene) 1-propylxylitol and the like can be mentioned.

The crystal nucleating agent used in the present invention is better to be used in a masterbatch containing 3 to 10% by weight from the viewpoint of dispersibility. As the carrier resin of the master batch, an olefin resin is desirable, and examples thereof include a propylene-based random copolymer in which ethylene or butene is randomly copolymerized with propylene, a homopolypropylene, a propylene-based block copolymer, and a polyethylene-based resin. ..

Further, the polypropylene-based sealant film of the present invention contains 5 to 20 parts by weight of a propylene-based polymer (d) containing a propylene polymer component having an ultimate viscosity [η] of 5 dl / g or more and less than 10 dl / g. Is preferable. If the ultimate viscosity [η] is less than 5 dl / g, the improvement in tearability may not be sufficient, and if it is 10 dl / g or more, foreign matter may be generated in the film. By kneading the propylene-based polymer (d) with the propylene / ethylene block copolymer (a), the propylene polymer (b), and the low-density polyethylene-based resin (c), uniform kneading and melting are performed. Stable extrusion during film formation is possible, the orientation of the film in the MD direction can be increased, and the tearability is improved.

It is preferable that each layer contains 5 to 20 parts by weight of the propylene-based polymer (d), and if it is less than 5 parts by weight, there may be no effect of easy tearing property, and if it is more than 20 parts by weight, melt fracture occurs. In some cases, the see-through property of the appearance may be significantly deteriorated.

The 230 ° C. MFR of the propylene-based polymer (d) is preferably in the range of 10 to 20 g / 10 minutes from the viewpoint of improving miscibility with other polymers and low temperature impact resistance.

The propylene-based polymer (d) is a polymer obtained by polymerizing a monomer mainly composed of propylene, for example, a homopolymer of propylene, a random copolymer of propylene and 5% by weight or less of ethylene, and propylene. A random copolymer of 10% by weight or less of butene, or a ternary random polymer of propylene, 5% by weight or less of ethylene, and 10% by weight or less of butene can be used.

As a method for producing the propylene-based polymer (d), for example, the method described in JP-A-11-228629 can be used, and the extreme viscosity of the propylene polymer component and the extreme viscosity of the entire propylene-based polymer (d) can be used. As a method for adjusting the melt flow rate, a method of adding a molecular weight adjusting agent such as hydrogen gas or a metal compound in each step during polymerization can be used.

Further, it is preferable to contain 5 to 20 parts by weight of high melt tension polypropylene (e) in each layer because the easy tearability is further improved. High melt tension polypropylene can be subjected to long-chain branching by irradiation with electron beams, long-chain branching by modification in the extruder in the presence of peroxide and crosslinked monomer, or high-molecular-weight polypropylene by multistage polymerization. It can be produced by a known method such as adding a component 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, but the propylene homopolymer type is preferable in terms of heat resistance.

The MFR of the 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, preferably in the range of 0.5 to 9 g / 10 minutes. It is preferable because it facilitates film-forming properties and good compatibility with propylene-based block copolymers.

Further, it is preferable that the melt tension (230 ° C.) of the high melt tension polypropylene (e) is in the range of 3 to 26 g because the crystallinity of each layer is enhanced and the easy tearability is further improved.

Further, it is preferable to contain 1 to 5% by weight of the high-density polyethylene-based polymer (f) in each layer because the tearability is not lowered and the low-temperature impact resistance is dramatically improved. If the high-density polyethylene-based polymer (f) is contained in an amount of less than 1% by weight, the content effect may not be obtained, and if it is contained in an amount of more than 5% by weight, the low temperature impact resistance may not be improved and the sealing strength may be significantly reduced. be.

Further, the density of the high-density polyethylene-based polymer (f) is preferably 0.92 to 0.97 g / cm ³ , and the ethylene-based weight has an MFR of 1 to 20 g / 10 minutes at 190 ° C. and a load of 21.18 N. The coalescence is preferable, and the ethylene homopolymer of 0.93 to 0.97 g / cm ³ is more preferable. If the density of the high-density polyethylene-based polymer (f) is less than 0.92 g / cm ³ , the blocking resistance may deteriorate, and if it exceeds 0.97 g / cm ³ , the sealing property may deteriorate. There is.

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

The polypropylene-based sealant film of the present invention contains antioxidants, heat-stabilizing agents, neutralizing agents, antistatic agents, hydrochloric acid absorbers, antiblocking agents, lubricants, nucleating agents, etc., as long as the object of the present invention is not impaired. Can include. These additives may be used alone or in combination of two or more.

Here, specific examples of the antioxidant are 4-methyl-2,6-di-t-butylphenol (BHT) and octadecyl-3- (3,5-di-t-butyl-4) as hindered phenols. -Hydroxyphenyl) propionate ("Irganox" 1076, "Sumilizer" BP-76), tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane ("Irganox" 1010, "Sumilizer" BP-101), Tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate ("Irganox" 3114, "Adecastab" AO-20), etc.
Further, as a phosphite-based (phosphorus-based) antioxidant, tris (2,4-di-t-butylphenyl) phosphite ("Irgafos" 168, "Adecastab" 2112), tetrakis (2,4-di-t). -Butylphenyl) -4-4'-biphenylene-diphosphonite ("Sandstab" P-EPQ), bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite ("Ultranox" 626, "Adecastab" PEP -24G), distealyl pentaerythritol diphosphite (“Adecastab” PEP-8), etc.
Above all, 2,4,8,10-tetra-t-butyl-6- [3- (3-methyl-4-hydroxy-5-t-butyl), which has both the functions of these hindered phenols and phosphites. Phenyl) propoxy] dibenz [d, f] [1,3,2] dioxaphosphepine (“Sumilizer” GP), and acrylic acid 2 [1- [2-hydroxy-3,5-di-t- [Pentylphenyl] ethyl] -4,6-di-t-pentylphenyl (“Sumilizer” GS) is preferable, and the combined use of both is particularly effective in suppressing the decomposition of the xylene-soluble portion at 20 ° C. in film formation. It is preferable because it exerts a high temperature impact resistance and greatly contributes to both low temperature impact resistance and blocking resistance. If the decomposition of the xylene-soluble portion is promoted, the blocking resistance may deteriorate.

The amount of the antioxidant added may be appropriately set in the range of 0.05 to 0.3% by weight, although it depends on the type of the antioxidant used.

Further, as the neutralizing agent, hydrotalcite compounds, hydroxylation and the like are preferable for reducing smoke generation during film formation.

Next, the polypropylene-based sealant film of the present invention can be produced by a known film-forming method such as a T-die method or a tubular method, and in particular, an unstretched film-forming method by the T-die method is used. , It is preferable because it is easy to control the birefringence and crystallinity of the film. The method for forming a polypropylene-based sealant film of the present invention by the T-die method is described below, but the present invention is not limited to these methods.

A uniaxial or biaxial melt extruder is used to melt-knead the propylene / ethylene block copolymer (a), pellets or powder of the propylene polymer (b), and a metal phosphate salt in a predetermined blending ratio, and then obtain the obtained product. It can be produced by filtering the kneaded product with a filter and extruding it into a film from a flat die (for example, T die). Since the thickness ratio of each layer can be easily adjusted for easy tearing property, sealing property, and low temperature impact resistance, when the sealant film is composed of an inner layer (A layer) and an outer layer (B layer), the inner layer (A) is used. The thickness ratio represented by the layer) / outer layer (layer B) is preferably 50/50 to 5/95, more preferably 40/60 to 10/90, and 30/70 to 20/80. Is more preferable. The temperature of the molten polymer extruded from the melt extruder is usually 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 to a constant temperature of 20 to 90 ° C., cooled and solidified, and then wound up.

The polypropylene-based sealant film of the present invention may be formed into three layers of A layer / B layer / C layer in which a C layer is laminated on the opposite side of the inner layer (A layer) and the outer layer (B layer) from the A layer (inner layer). good. As the C layer, for example, a layer containing an olefin resin can be preferably used, and a suitable sealing property and tearing property can be easily obtained. Therefore, the same layer as the inner layer (A layer) or the outer layer (B layer) is used. It is preferable, and it is particularly preferable to use a layer similar to the inner layer (layer A). Since the thickness ratio of each layer can be easily adjusted for easy tearing property, sealing property, and impact resistance, the inner layer (A layer): outer layer (B layer): outermost layer (C layer) = 1: 2: 1. It is preferably 1: 8: 1, more preferably 1: 4: 1 to 1: 6: 1.

Although the polypropylene-based sealant film of the present invention can be stretched after cooling and solidifying, it is preferably an unstretched film that is substantially not stretched. An unstretched film that is not substantially stretched is preferable because it is not necessary to excessively raise the heat-sealing temperature at the time of heat-sealing (heat-sealing can be performed at a relatively low temperature). Further, in the present invention, the unstretched film refers to an extruded cast film, but in an actual film forming process, it is slightly oriented in the film MD direction or the width direction (hereinafter, may be abbreviated as TD direction). The double refractive index (difference between the refractive index of the film in the MD direction and the TD direction, Δn) of the polypropylene-based sealant film of the present invention is 3.5 × 10 ^-3 to 8.0 × 10. The range of ⁻³ is preferable in terms of heat sealability, thermal dimensional stability, and easy tearing property. The birefringence (Δn) can be determined by measuring the retardation R (nm) of the sample using the compensator method and setting Δn = R / d from the film thickness d (nm) of the measuring portion. can.

The thickness of the polypropylene-based sealant film of the present invention thus obtained is preferably 20 to 300 μm, more preferably 30 to 100 μm.

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

The tear strength of the polypropylene-based sealant film obtained as described above in the MD direction is preferably 20 N / mm or less, more preferably 15 N / mm or less, and the tear strength is good even after laminating with another substrate. It is good, has high low temperature impact resistance and seal strength, and is preferable.

As described above, using the polypropylene-based sealant film of the present invention having a thickness of 70 μm, a biaxially stretched polyethylene terephthalate film (PET) having a thickness of 12 μm, a biaxially stretched polyamide film (ONy) having a thickness of 15 μm, and a thickness. A laminated base material layer made of 9 μm aluminum foil (AL) and the polypropylene-based sealant film are bonded together by a dry laminating method using a urethane-based adhesive, and PET / adhesive / ONy / adhesive / AL / the sealant. A laminate having a film structure was prepared, and the two laminates were heated with a CA-450-10 type heat sealer manufactured by Fuji Impulse Co., Ltd. so that the sealant film was on the inner surface of the bag, and the heating time was 0.8. Create a three-way pouch with a bag making size of 50 mm x 150 mm in seconds (seal temperature: about 180 ° C) and a cooling time of 3.0 seconds, retort at 120 ° C for 30 minutes, and then measure based on JIS-K71281. It is desirable that the tearing force is 10 N (absolute value) or less. If it exceeds 10N, the CPP may stretch and become inferior in tearability.

The polypropylene-based sealant film of the present invention can be used alone as a film for packaging, but can be preferably used as a sealant film for a retort food packaging bag containing AL foil. As the constituent film of the laminate, a normal dry laminating method of laminating using an adhesive can be preferably adopted, but if necessary, polyethylene is directly bonded to the polypropylene-based sealant film of the present invention and another base material layer. A method of extruding and laminating a based resin or a polypropylene based resin can also be adopted. These laminates are used after being processed into a flat bag, a standing pouch, or the like by using the polypropylene-based sealant film of the present invention as a sealing layer (inner surface of the bag).

In addition, the laminated structure of these laminates has the required characteristics of the packaging bag (for example, barrier performance for satisfying the quality retention period of the food to be packaged, size / low temperature impact resistance corresponding to the weight of the contents, visibility of the contents). Etc.), and it is selected as appropriate.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. In addition, the detailed description of the present invention and the measured values of each evaluation item in the examples were measured by the following methods.

(1) Content of xylene-soluble part at 20 ° C. After 5 g of polypropylene pellets are completely dissolved in 500 mL of boiling xylene (Kanto Chemical Co., Inc., first grade), the temperature is lowered to 20 ° C. and left 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 and then dried at 70 ° C., and the weight thereof was measured to determine the content (% by weight).

(2) Extreme Viscosity of Xylene Insoluble Part and Soluble Part at 20 ° C. Using the sample separated by the above method, measurement was performed in tetralin at 135 ° C. using a Ubbelohde viscometer.

(3) Melt flow rate (MFR)
According to JIS K7210: 1999, the propylene-based polymer and the propylene-ethylene block copolymer were measured at a temperature of 230 ° C., and the polyethylene-based polymer was measured at a temperature of 190 ° C. under a load of 21.18 N.

(4) Melt tension (MS)
For the melt tension (MS) at 230 ° C, using a melt tension tester type 2 manufactured by Toyo Seiki Seisakusho Co., Ltd., the polypropylene is heated to 230 ° C in the apparatus, and the molten polypropylene is 20 mm / from a nozzle having a diameter of 2.095 mm. It was extruded into the atmosphere at 23 ° C. at a rate of 1 minute to form a strand, and the tension of the filamentous polypropylene when the strand was taken up at a rate of 3.14 m / min was measured and used as a melt tension (MS).

(5) Density Based on JIS K7112: 1999, the measurement was performed by a measuring method using a density gradient tube.

(6) Low temperature impact resistance PET with a thickness of 12 μm, ONy with a thickness of 15 μm, AL foil with a thickness of 9 μm, and a polypropylene-based sealant film with a thickness of 70 μm are usually used with a urethane adhesive. A laminate having the following structure and a thickness of 115 μm was prepared by laminating by the dry laminating method of.

Laminate structure: PET / adhesive / ONy / adhesive / AL foil / adhesive / polypropylene-based sealant film of the present invention (referred to as laminate 1)
A CA-450-10 type heat sealer manufactured by Fuji Impulse Co., Ltd. was used with the polypropylene-based sealant film of the present invention on the inner surface of the two laminated bodies, and the heating time was 1.4 seconds (sealing temperature: about). A standing pouch having a bag making size of 150 mm × 285 mm was prepared at 220 ° C.) and a cooling time of 3.0 seconds. This bag is filled with 1000 cm ³ of saline solution having a concentration of 0.1%, and then retorted at 135 ° C. for 30 minutes. After the retort-treated bag is stored in a refrigerator at 0 ° C., it is dropped from a height of 55 cm onto a flat floor (n number 20 pieces), and the number of times until the bag is broken is recorded. In this evaluation method, if the average value of 20 n-numbers is 15 times or more, the low-temperature impact resistance for business use is good (〇), and if it is less than 15 times, the low-temperature impact resistance is inferior (×).

(7) Heat seal (HS) strength Two seal layers of the same laminate as in (6) are used under the conditions of a flat plate heat sealer, a seal temperature of 180 ° C, a seal pressure of 10 N / cm ² , and a seal time of 1 second. The heat-sealed sample was retorted at 130 ° C. for 30 minutes, and then the heat-sealed strength was measured at a tensile speed of 300 mm / min using Tencilon manufactured by Orientec. If the seal strength is 45 N / 15 mm or more in this measurement method, it can be used satisfactorily for retort pouch use (〇), and if it is less than 45 N / 15 mm, the heat seal strength is insufficient (×).

(8) Anti-use skin generation The two laminates of the laminate 1 of (6) are sealed at a temperature of 180 ° C. using a flat plate heat sealer so that the polypropylene-based sealant film of the present invention is on the inner surface of the bag. Heat-sealing was performed under the conditions of a sealing pressure of 10 N / cm ² and a sealing time of 1 second to prepare a three-sided bag (flat bag, sealing width 5 mm) having a size of 160 mm × 210 mm (internal dimensions). After filling this bag with a commercially available retort curry (retort curry "Kukure Curry / Dry" manufactured by House Foods Industry Co., Ltd.), the state of unevenness on the surface of the laminate immediately after being retort-treated at 135 ° C. for 30 minutes was visually determined. Those with no yuzu skin were evaluated as rank 1, those with slight occurrence as rank 2, those with mild occurrence as rank 3, those with clear occurrence as rank 4, and those with severe occurrence as rank 5. In this evaluation method, ranks 1 and 2 were rated as having good yuzu skin resistance (〇), and ranks 4 and 5 were rated as inferior to yuzu skin resistance (x).

(9) Blocking resistance (N / 12cm ² )
Prepare a film sample with a width of 30 mm and a length of 100 mm, superimpose the films in a range of 30 mm × 40 mm, apply a load of 5N / 12 cm ² , heat-treat in an oven at 80 ° C for 24 hours, and then heat at 23 ° C. After being left in an atmosphere of 65% humidity for 30 minutes or more, the shear peeling force was measured at a tensile speed of 300 mm / min using Tencilon manufactured by Orientec. In this measurement method, if the shear peeling force is 10 N / ¹² cm ² or less, the blocking resistance is good and it can be used as a non-powder retort. did.

(10) Tear strength (N / mm) of polypropylene-based sealant film
In accordance with JIS K71281, a 75 mm cut is made in the MD direction in the center of the width of the strip with a width of 50 mm (TD direction) and a length of 150 mm (MD direction) of the test piece in a constant temperature room at 23 ° C, and the speed is 200 mm / min. The tear strength (N) in the MD direction was measured with, and the tear strength was calculated by dividing by the thickness (mm) of the film. It was judged that the polypropylene-based sealant film alone has an easy tearing property if it is 20 N / mm or less. MD is the longitudinal direction of the film and TD is the width direction of the film.

(11) Birefringence index (Δn)
Using a POH-type polarizing microscope manufactured by Nikon Corporation, the retardation R (nm) of the sample was measured using the compensator method, and Δn = R / d was determined from the film thickness d (nm) of the measuring section. I asked.

(12) Tearing force of the laminated body (N)
Using a CA-450-10 type heat sealer manufactured by Fuji Impulse Co., Ltd., heat the two laminated bodies of the laminated body 1 of (6) so that the sealant film is on the inner surface of the bag, and the heating time is 0.8 seconds (seal). (Temperature: about 180 ° C.), cooling time 3.0 seconds, a three-way pouch with a bag making size of 50 mm × 150 mm was prepared, retorted at 120 ° C. for 30 minutes, and then measured based on JIS-K-7128-1. If the tearing force is 10 N (absolute value) or less, it can be said that the CPP does not extend and there is a straight cut property.

(13) See-through property The state of occurrence of unevenness on the surface of the laminated body 1 of the laminated body 1 of (6) was visually determined.

Those with no unevenness were evaluated as rank 1, those with slight unevenness as rank 2, those with slight occurrence as rank 3, those with clear occurrence as rank 4, and those with severe occurrence as rank 5. In this evaluation method, ranks 1, 2 and 3 were rated as good see-through and marked as 〇.

The components used in the examples and comparative examples are as follows.

[Propene / Ethylene Block Copolymer (a) / B-PP1]
The content of the 20 ° C. xylene insoluble part is 80% by weight, its ultimate viscosity ([η] H) is 1.90 dl / g, and the content of the 20 ° C. xylene soluble part is 20% by weight, its ultimate viscosity ([η]]. EP) is 3.00 dl / g, MFR at 230 ° C. is 2.3 g / 10 minutes, and propylene containing "Sumilizer" GP 0.0003% by weight and "Sumilizer" GS 0.00075% by weight as antioxidants. Ethylene block copolymer pellets were used. The above-mentioned propylene / ethylene block copolymer (a) is hereinafter referred to as B-PP1.

[Propene / Ethylene Block Copolymer (a) / B-PP2]
The content of the 20 ° C. xylene insoluble part is 80% by weight, its ultimate viscosity ([η] H) is 1.60 dl / g, and the content of the 20 ° C. xylene soluble part is 12% by weight, its ultimate viscosity ([η]]. EP) is an MFR containing 2.00 dl / g of 2.00 dl / g propylene / ethylene block copolymer containing "Sumilizer" (registered trademark) GP0.0003% by weight and "Sumilizer" (registered trademark) GS0.00075% by weight as antioxidants. A propylene / ethylene block copolymer pellet having a viscosity of 8.0 g / 10 min was used. Hereinafter, it is referred to as B-PP2.

[Propene / Ethylene Block Copolymer (a) / B-PP3]
The content of the 20 ° C. xylene insoluble part is 88% by weight, its ultimate viscosity ([η] H) is 2.00 dl / g, and the content of the 20 ° C. xylene soluble part is 12% by weight, its ultimate viscosity ([η]]. EP) is 3.60 dl / g, MFR is 0.8 g / 10 minutes, and the weight of the propylene / ethylene block containing "Sumilizer" GP 0.0003% by weight and "Sumilizer" GS 0.00075% by weight as antioxidants. Combined pellets were used. The above-mentioned propylene / ethylene block copolymer (a) is hereinafter referred to as B-PP3.

[Propene polymer (b) / PP1]
Homopolypropylene having an MFR of 5.0 g / 10 min at 230 ° C. and containing 0.001% by weight of "Irganox" 1010 as an antioxidant was used. The above homopolypropylene will be referred to as PP1 below.

[Low density polyethylene polymer (c) / Low density PE1]
A linear low-density polyethylene (FV201 manufactured by Sumitomo Chemical Co., Ltd.) having a density of 0.925 g / cm ³ and an MFR of 1.9 g / 10 minutes and a copolymerization component of 1-hexene was used. The above-mentioned low-density polyethylene-based polymer (c) is hereinafter referred to as low-density PE1.

[Low density polyethylene polymer (c) / Low density PE2]
A linear low-density polyethylene (SP1071C manufactured by Prime Polymer Co., Ltd.) having a density of 0.910 g / cm ³ and an MFR of 10.0 g / 10 minutes and a copolymerization component of 1-hexene was used. The above-mentioned low-density polyethylene-based polymer (c) is hereinafter referred to as low-density PE2.

[Propylene-based polymer (d) / PP2]
First, propylene is polymerized in the first step using the polymerization catalyst described in Example 1 of JP-A-11-228629 in accordance with the polymerization method and polymerization conditions described in the same example. After producing the components of, the catalyst and the first component are transferred to the second step without deactivating the catalyst, and propylene is polymerized in the second step to generate a component having a molecular weight different from that of the first component. Depending on the method, the propylene polymer component having an ultimate viscosity of 7.6 dl / g is composed of 9% by weight and the component having an ultimate viscosity of 1.2 dl / g is 91% by weight, and the total ultimate viscosity is 1.8 dl / g. A certain propylene-based polymer (d) was obtained. 0.2 parts by weight of the antioxidant IRGANOX1010 (trade name, manufactured by Ciba Specialty-Chemicals) and the antioxidant IRGAFOS168 (trade name, manufactured by Ciba Specialty-Chemicals) with respect to 100 parts by weight of the propylene-based polymer (d). 0.25 parts by weight and 0.05 parts by weight of calcium stearate are mixed and melt-mixed at 200 ° C. with a twin-screw extruder TEM75 (trade name, manufactured by Toshiba Machine Co., Ltd.) at a discharge rate of 300 kg / hour and a screw rotation speed of 250 rpm. Was performed to obtain pellets. The MFR of this pellet at 230 ° C. and a load of 21.18 N was 14 g / 10 min. The above-mentioned propylene-based polymer (d) is hereinafter referred to as PP2.

[High melt tension polypropylene (e) / HMS-PP]
EX6000 manufactured by Japan Polypropylene Corporation was used, which has a density of 0.90 g / cm ³ , an MFR of 2.9 g / 10 minutes at 230 ° C. and a load of 21.18 N, and a melt tension (MS) of 9 g at 230 ° C. .. Hereinafter, it is referred to as HMS-PP.

[High Density Polyethylene Polymer (f) / High Density PE1]
Commercially available high density ethylene pellets with a density of 0.950 g / cm ³ at 190 ° C. and a load of 21.18 N and an MFR of 16.0 g / 10 min were used. Hereinafter, the high-density ethylene pellet is referred to as HDPE1.

[Phosphoric acid metal salt crystal nucleating agent / MB1]
Contains 6% by weight of a crystal nucleating agent of sodium-2,2'-methylene-bis (4,6-di-t-butylphenyl) phosphate (ADEKA "ADEKA STAB" NA-11), which is a phosphate ester metal salt. A master batch (PPMST-0024 manufactured by Tokyo Ink, carrier resin: homopolypoly, MFR: 7 g / 10 minutes) was used. Hereinafter, the masterbatch of the crystal nucleating agent of the phosphoric acid ester metal salt is referred to as MB1.

[Examples 1 to 24]
With the resin composition shown in Tables 1 and 2, the pelletized resin is mixed by a blender, supplied to two or three extruders whose temperature has been adjusted to 260 ° C., melt-kneaded, filtered through a filter, and then filtered. A multi-manifold base for co-extrusion, laminated in two or three layers and extruded into a film, contacted with a cooling roll at a temperature of 50 ° C. and a speed of 60 m / min to cool and solidify, and then the A layer. The opposite side was subjected to corona discharge treatment to obtain a film having a thickness of 70 μm. In the case of the two-layer film, the thickness ratios of the A layer and the B layer were 30% for the A layer and 70% for the B layer. In the case of the three-layer film, the thickness ratios of the A layer, the B layer and the C layer were 20% for the A layer, 60% for the B layer, and 20% for the C layer.

As a result of evaluating the film characteristics, as shown in Tables 1 and 2, a film satisfying a good balance in all of tear strength, low temperature impact resistance, Δn, blocking shear resistance, yuzu skin resistance, and sealing strength was obtained, and particularly laminated. As a body, it was confirmed that it can be used as a sealant for packaging bags without powder because it has excellent tearability and blocking resistance in the longitudinal direction of the film (MD).

[Comparative Examples 1 to 8]
With the resin composition shown in Tables 3 and 4, the pellets are mixed by a blender, supplied to an extruder, melt-kneaded, filtered through a filter, then extruded from a T-die at 240 ° C. at 60 m / min, and cooled at 50 ° C. After being cooled and solidified by contacting with, one side was subjected to corona discharge treatment to obtain a film having a thickness of 70 μm.

Comparative Examples 1, 3, 5, and 7 had very poor tearability.

Comparative Examples 2, 4, 6 and 8 had poor heat-sealing properties and low-temperature impact resistance, and could not be suitably used for high-retort applications.

Claims (9)

It is a film consisting of at least two layers, A layer and B layer. The A layer contains a propylene / ethylene block copolymer (a) as a main component, and the B layer contains a propylene polymer (b) as a main component. A polypropylene-based sealant film containing 0.0015 to 0.01% by weight of a metal phosphate salt and having a tear strength in the longitudinal direction of the film of 20 N / mm or less. The polypropylene-based sealant film according to claim 1, wherein each layer contains 2 to 15% by weight of the low-density polyethylene-based polymer (c). 1. 2. The polypropylene-based sealant film according to 2. The polypropylene-based sealant film according to any one of claims 1 to 3, wherein each layer contains 5 to 20 parts by weight of high melt tension polypropylene (e). Claim 1 is a three-layer structure of A layer / B layer / C layer in which a C layer is laminated on the opposite side of the B layer from the A layer, and the C layer contains a propylene / ethylene block copolymer as a main component. The polypropylene-based sealant film according to any one of 4 to 4. The polypropylene-based sealant film according to any one of claims 1 to 5, wherein the birefringence is in the range of 3.5 × 10 ^-3 to 8.0 × 10 ^-3 . The polypropylene-based sealant film according to claim 3 or 4, wherein each layer contains 1 to 5% by weight of the high-density polyethylene-based polymer (f). A laminate in which the polypropylene-based sealant film according to any one of claims 1 to 7 is laminated on one side of a laminated base material layer formed by laminating a single layer or two or more films. A 12 μm thick biaxially stretched polypropylene terephthalate film (PET), a 15 μm thick biaxially stretched polyamide film (ONy), a 9 μm thick aluminum foil (AL) laminated substrate layer, and a 70 μm thick claim. The polypropylene-based sealant film according to any one of 1 to 7 is bonded to each other by a dry laminating method using a urethane-based adhesive, and a laminate having a composition of PET / adhesive / ONy / adhesive / AL / polypropylene-based sealant film. With the polypropylene-based sealant film on the inner surface of the bag, a CA-450-10 type heat sealer manufactured by Fuji Impulse Co., Ltd. was used to heat the two laminated bodies for 1.0 second (sealing temperature). : Approximately 220 ° C), with a cooling time of 3.0 seconds, a three-way pouch with a bag making size of 50 mm × 150 mm was prepared, retorted at 120 ° C for 30 minutes, and then measured in the longitudinal direction of the film based on JIS-K71281. A laminated film having a tearing force of 10 N (absolute value) or less.