JP2000256532A - Polypropylene-based film and multilayer film thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polypropylene-based film slightly developing such uneven patterns on the film surface as citron-like skin caused by retorting process, and suitable as a food packaging material. SOLUTION: This polypropylene-based film consists mainly of (1) 85 to 98 wt.% of a propylene-α-olefin block copolymer comprising (a) 95 to 70 wt.% of polypropylene block and (b) 5-30 wt.% of copolymer elastomer block of propylene and an α-olefin wherein the number of carbon atoms is 2 to 12 (excluding 3), and (2) 15 to 2 wt.% of an ethylene-based copolymer elastomer as a copolymer of 90-70 wt.% of ethylene and 10 to 30 wt.% of a 3-12C α-olefin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention does not generate irregularities (orange peel or yuzu skin) on the film surface due to heat sterilization such as retort sterilization, and is suitably used as a food packaging material such as a film for packaging a retort food. The present invention relates to a polypropylene film and a laminated film thereof.

[0002]

2. Description of the Related Art Hitherto, polypropylene films have been used as various food packaging materials and various medical packaging materials by making use of features such as low cost, heat resistance, chemical resistance and easy heat sealing. After filling the contents, packaging materials for retort foods that are subjected to heat sterilization such as boil sterilization and retort sterilization include aluminum foil, vinylidene chloride resin, and saponified ethylene-vinyl acetate copolymer resin gas barrier layer. The heat seal layer is made of polypropylene in combination with a polyamide resin layer and a polyester resin layer. As polypropylene for this purpose,
A film formed by blending a propylene block copolymer or an ethylene-propylene random copolymer with a thermoplastic elastomer, for example, an ethylene-propylene elastomer obtained by a vanadium-based polymerization catalyst and an elastomer component such as polybutene, is used.

[0003] However, when heat sterilization such as retort sterilization is performed, an uneven surface called orange peel or yuzu skin is formed on the surface of the film after heat sterilization, and another substrate is laminated by a lamination method such as dry lamination. When laminating and making a retort pouch, there is a problem that the whole pouch is affected and the appearance of the product is significantly impaired. As a method for improving this, for example, a method of blending polybutene (Japanese Patent Publication No. 2-32142), a method of using an ethylene-α-olefin copolymer polymerized by a specific catalyst (Japanese Patent Application Laid-Open No. 7-266520). JP-A-7-256841
Japanese Patent Application Laid-Open No. 3-4), a method using a specific multi-stage polymerization
4087), a specific laminate (Japanese Unexamined Patent Publication No. Hei 3-5657).
No. 0) has been proposed.

[0004]

However, all of the above methods are still insufficient from the viewpoint of preventing the occurrence of yuzu skin. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polypropylene-based film suitable as a food packaging material with less occurrence of uneven patterns on the film surface such as yuzu skin by retort sterilization. And

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above-mentioned object can be achieved by using a film containing a specific propylene-α-olefin block copolymer and an ethylene-based copolymer as main components. The inventors have found what can be achieved, and have completed the present invention based on this finding. That is, the present invention provides (1) (a) a polypropylene block 9
5 to 70% by weight, (b) propylene and 2 to 12 carbon atoms
Propylene-α-olefin block copolymer (I) consisting of 5 to 30% by weight of a copolymer elastomer block (excluding 3) with α-olefin (I) 85 to 98
15% by weight and (2) a copolymer of 90 to 70% by weight of ethylene and 10 to 30% by weight of an α-olefin having 3 to 12 carbon atoms.
An object of the present invention is to provide a polypropylene-based film whose main component is weight%.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Propylene-α- in the present invention
The olefin block copolymer (I) (hereinafter sometimes referred to as “block copolymer I”) comprises (a) 95 to 70% by weight of a polypropylene block, (b) propylene and 2 to 12 carbon atoms (provided that (Excluding No. 3) is a block copolymer comprising 5 to 30% by weight of an elastomer block with an α-olefin. (A) The polypropylene block is composed of a homopolypropylene or a random copolymer component of propylene and an α-olefin having an α-olefin component of 5% by weight or less. The other α-olefin component is preferably at most 4.5% by weight, particularly preferably at most 4.0% by weight. The other α-olefin component is 5
If the content is more than 10% by weight, rigidity and heat resistance are impaired, and low crystallinity components are increased, and cohesion of films occurs, which is not preferable.

On the other hand, the copolymer elastomer block (b) comprises a copolymer of propylene and an α-olefin having 4 to 12 carbon atoms (excluding 3), and the α-olefin of the copolymer elastomer Copolymerization ratio of 30 to
80% by weight. The copolymerization ratio is preferably 35 to 75.
%, Particularly preferably 38 to 72% by weight. α-
When the copolymerization ratio of the olefin is less than 30% by weight, impact resistance and cold resistance are poor. On the other hand, if it exceeds 80% by weight, heat resistance is impaired, which is not preferred. Specific examples of the α-olefin of component (a) and component (b) include ethylene, 1-butene, 3-methyl-1-butene, 3-methyl-1-pentene, and 4-methyl-1-pentene. , 4,4
-Dimethyl-1-pentene, vinylcyclopentane, vinylcyclohexane and the like. These may be used alone or in combination of two or more.

[0008] The content of the copolymer elastomer block in the block copolymer I of the present invention is 10 to 30% by weight, preferably 12 to 28% by weight, particularly preferably 14 to 25% by weight. If the copolymerization ratio of the copolymer elastomer is less than 10% by weight, impact resistance and cold resistance are poor. On the other hand, if it exceeds 30% by weight, rigidity and retort aptitude such as mutual adhesion of films are inferior, so that it is not preferable. The block copolymer (I) of the present invention is obtained by a known method in which copolymerization is performed using two or more polymerization tanks. For example, T. Ogawa, T. Inaba: J. Appl. Polym .Sci., 18,3
345-3365 (1974), AJ Lononte: J. Polym. Sci., Part A, 2,
705-709 (1964).

The block copolymer I of the present invention preferably has an intrinsic viscosity of the xylene-soluble component in the range of 3.5 to 5.0 dl / g, more preferably 3.6 to 4.7 d.
1 / g, particularly preferably in the range of 3.7 to 4.5 dl / g. If the intrinsic viscosity is less than 3.5 dl / g, the heat resistance and the effect on improving the skin of the skin are poor. On the other hand, if it exceeds 5.0 dl / g, gels, fish eyes, etc. tend to be generated, and the appearance of the film tends to be poor. The intrinsic viscosity of the xylene-soluble component refers to the intrinsic viscosity of the precipitate after the polymer is dissolved in ortho-xylene at 135 ° C. and then cooled to 25 ° C. to precipitate the polymer. The intrinsic viscosity is a method of dissolving in decahydronaphthalene and measuring at a temperature of 135 ° C.
J. Elliott et al. App. P
oly. Sci, Vol. 14, pp2947-296
3 (1970). In particular,
Uhellohde capillary viscometer or Ostwald-F
The polymer is dissolved in decahydronaphthalene to prepare solutions having different concentrations, and the viscosities at the respective concentrations are measured in a thermostat using an enke capillary viscometer or the like. Next, these viscosity data can be obtained by infinite extrapolation using the Huggins equation.

The ethylene copolymer elastomer (hereinafter referred to as "ethylene elastomer") in the present invention is:
It is a copolymer of 90 to 70% by weight of ethylene and 10 to 30% by weight of an α-olefin having 3 to 12 carbon atoms, and the copolymerization ratio of the α-olefin is preferably 12 to 28% by weight, particularly 13 to 25% by weight. % Is preferred. If the copolymerization ratio of α-olefin is less than 10% by weight, the effect of improving yuzu skin is poor. On the other hand, if it exceeds 30% by weight, heat resistance and heat sealing strength are impaired, which is not preferable. Specific examples of the α-olefin include propylene, 1-butene,
Methyl-1-butene, 3-methyl-1-pentene, 4-
Examples thereof include methyl-1-pentene, 4,4-dimethyl-1-pentene, vinylcyclopentane, and vinylcyclohexane. These may be used alone or in combination of two or more. Among these, propylene and 1-butene are preferred.

The ethylene elastomer generally has a density of 0.85 to 0.90 g / cm ³ , preferably 0.1 to 0.9 g / cm ³ .
86 to 0.89 g / cm ³ , particularly preferably 0.87 to 0.87 g / cm ³
0.89 g / cm ³ is good. 0.85 g / cm ³ density
If it is less than 0.90 g / cm ³ , the effect of improving yuzu skin will be poor. In addition, temperature 230 ° C, load 2.16K
The melt flow rate (MFR) measured in grams is usually 0.1 to 10 g / 10 min, preferably 0.2 to 8
g / 10 minutes, particularly preferably 0.3 to 5 g / 10 minutes. If the MFR is less than 0.1 g / 10 minutes, the appearance of the film will be poor. On the other hand, if it exceeds 10 g / 10 minutes, the effect of improving the yuzu skin is inferior. Commercial products that can be suitably used as the ethylene-based elastomer of the present invention include "Tuffmer" (trade name) manufactured by Mitsui Petrochemical Co., Ltd. and "JSR EBM" (trade name) manufactured by Nippon Synthetic Rubber Co., Ltd.

The polypropylene-based film of the present invention can be prepared by subjecting a composition containing 85 to 98% by weight of the block copolymer (I) and 15 to 2% by weight of an ethylene-based elastomer to a known film forming method, for example, T-die forming. Obtained using the method. The content of the ethylene-based elastomer is preferably 12 to 3% by weight, and particularly preferably 10 to 4% by weight. When the content exceeds 15% by weight, rigidity and heat resistance are poor.
On the other hand, if it is less than 2% by weight, the effect of improving yuzu skin and the pitting resistance are poor, which is not preferable. When the content of the ethylene-based copolymer elastomer is 2% by weight or less, it is not preferable because the effect of improving the skin quality and the impact resistance are poor. On the other hand, if it exceeds 15% by weight, heat resistance and heat sealing strength are undesirably reduced.

Further, the polypropylene-based laminated film of the present invention comprises the above-mentioned polypropylene-based film (A).
Layers and (1) (a) polypropylene blocks 95 to 70
And (b) 5 to 30% by weight of a copolymer elastomer block of (b) propylene and an α-olefin having 2 to 12 (excluding 3) carbon atoms. Propylene-α-olefin block copolymer (II) having a content of 5 to 3.5 dl / g
Wt%, (2) 90 to 70 wt% ethylene and 3 to 3 carbon atoms
Ethylene copolymer elastomer which is a copolymer with 10 to 30% by weight of α-olefin of 3 to 15% by weight
And (3) a linear polyethylene resin composed of a propylene-based resin film containing 2 to 15% by weight as a main component (B).
It is a laminated film composed of at least two layers.

The (A) polypropylene block and the (b) copolymer elastomer block constituting the (B) layer are:
It is the same component as the polypropylene block and the copolymer elastomer block of the block copolymer I. However, it is necessary that the intrinsic viscosity of the xylene-soluble component of the block copolymer (II) is 1.5 to 3.5 dl / g.
The intrinsic viscosity is preferably from 1.7 to 3.3 dl / g, and particularly preferably from 1.8 to 3.2 dl / g. When the intrinsic viscosity is less than 1.5 dl / g, impact resistance, blocking resistance and cold resistance are poor. On the other hand, when it exceeds 3.5 (dl / g), the compatibility with the linear polyethylene described below is inferior, and the effect of improving yuzu skin is inferior.

The ethylene copolymer elastomer constituting the layer (B) is the same resin as that of the polypropylene film.

Further, as the linear polyethylene resin,
Copolymers of ethylene and an α-olefin having 3 to 12 carbon atoms are exemplified. As the α-olefin component, propylene, 1-butene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 4,4
-Dimethyl-1-pentene, vinylcyclopentane, vinylcyclohexane and the like. These may be used alone or in combination of two or more. Among these, 1-butene and octene are preferred.
The copolymerization ratio of α-olefin is at most 10% by weight or less, preferably 9% by weight or less, particularly preferably 8% by weight. The lower limit is at least 3% by weight or more. If the copolymerization ratio exceeds 10% by weight, the effect of improving yuzu skin is poor, which is not preferable. The linear polyethylene generally has a density of 0.88 to 0.930 g / cm.
³ , preferably 0.89 to 0.925 g / cm ³
And particularly preferably 0.90 to 0.925 g / cm ³ . The melt flow rate (MFR) at a temperature of 190 ° C. and a load of 2.16 kg is usually 1 to 30 g / 10 min, preferably 5 to 25 g / 10 min, and particularly preferably 7 to 10 g / 10 min.
２３23 g / 10 min.

The layer (B) of the present invention comprises 70 to 95% by weight of the block copolymer (II), 3 to
15% by weight and 2 to 15% by weight of linear polyethylene resin
Consists of 75 to 93% by weight of the block copolymer (II)
, And particularly preferably 77 to 91% by weight. If the content of the block copolymer (II) is less than 70% by weight, rigidity and heat resistance are poor. On the other hand, when the content exceeds 95% by weight, the impact resistance and the unpleasant skin easily occur, which is not preferable. The content of the ethylene-based elastomer is preferably 4 to 13% by weight, particularly 5 to 10% by weight.
% By weight is preferred. When the amount of the elastomer is less than 3% by weight, the effect of improving the skin of the skin is poor. On the other hand, if it exceeds 15% by weight, the heat seal strength is inferior and is not preferred. The content of the linear polyethylene resin is preferably 3 to 13% by weight, particularly preferably 4 to 10% by weight. If the content of the polyethylene resin is less than 2% by weight, the effect of improving yuzu skin is inferior. On the other hand, if it exceeds 15% by weight, the heat seal strength is inferior and is not preferred.

Furthermore, when the (a) propylene block of the block copolymers (I) and (II) in the present invention has the following characteristics (I) and (ii), furthermore, the use of the propylene block in preventing the occurrence of blemishes is further improved. preferable. (I) Isotactic pentad fraction (IP) by ¹³ C nuclear magnetic resonance spectrum is 98.5% or more. (Ii) Isotactic average chain length (N) is 500 or more. A. Zambelli, Macromolecules, V.
ol. 6, p-625 (1973) and refers to IP in pendant units in the PP molecular chain measured using nuclear magnetic resonance spectrum ( ¹³ C-NMR) with isotope carbon. The average isotactic chain length (N) is the average isotactic chain length of a methyl group in a polypropylene molecule, and is a method reported by JCRandll (Polymer Sequence Distribution, Academic Press, N
ew York 1977, chapter2). These characteristics are described in detail in JP-A-8-73547.

The polypropylene film of the present invention can be formed into a molded product by using a known T-die molding method. Usually, the molding is performed at a die temperature of 220 to 280 ° C. The cooling temperature is usually 40 to 90 ° C. The thickness of the film is usually 20 to 180 μm. When the thickness is 20 μm or less, the heat seal strength is inferior, which is not preferable. On the other hand, when it exceeds 180 μm, heat sealability and transparency are inferior. Preferably, 30 to 170 μm, particularly preferably 40 to 160 μm
m.

In the case of the multilayer film of the present invention comprising the layers (A) and (B), the thickness ratio of the layers (A) and (B) is preferably in the range of 9: 1 to 1: 9. Preferably 8: 2-2:
8, particularly preferably 7: 3 to 5: 5. By forming a multilayer film, the heat seal strength is further superior to that of the single layer (A). Therefore, when used as a retort package laminated with a gas barrier layer such as an aluminum foil layer, a saponified ethylene-vinyl acetate copolymer layer, a polyamide resin layer and a vinylidene chloride resin layer, or a polyester resin layer, (B) When the layer is used as the innermost (heat seal) layer, a package having excellent heat seal strength can be obtained.

The heat sterilization of the present invention is a method for killing microorganisms, which are the main cause of food deterioration, and is usually carried out at a temperature of 60 ° C. to 135 ° C., depending on the target bacteria. . Of these heat sterilizations, retort sterilization using heating steam at a temperature of 100 ° C. or higher and moist heat mainly containing hot water is performed at a high temperature for a short time so as not to impair the taste and flavor of the contents. For details of these heat sterilization, see, for example, Isao Shibazaki;
24 (issued March 14, 1981); Shio Shimizu, Rio Yokoyama; "Theory and Practice of Retort Food", Koshobo (issued January 15, 1981).

For the film of the present invention, other additives commonly used for thermoplastic resins (eg, antioxidants, weathering stabilizers, antistatic agents, lubricants, antiblocking agents, antifogging agents, dyes) , Pigments, oils, waxes, fillers, etc.) and other thermoplastic resins can be added in an appropriate amount within a range not to impair the object of the present invention. For example, examples of such additives include 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol,
4'-thiobis- (6-t-butylphenol), 2,
2-methylene-bis (4-methyl-6-t-butylphenol), octadecyl 3- (3 ′, 5′-di-t-butyl-1′-hydroxyphenyl) propinate, 4,
4'-thiobis- (6-butylphenol), and as an ultraviolet absorber, ethyl-2-cyano-3, 3-diphenylacrylate, 2- (2'-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxy-4 Octoxybenzophenone, dimethyl phthalate, diethyl phthalate as a plasticizer, wax, liquid paraffin, phosphate ester, pentaerythritol monostearate, sorbitan monopalmitate as an antistatic agent, sulfated oleic acid, polyethylene oxide, Carbon wax, ethylene bis stearamide, butyl stearate, etc. as a lubricant, carbon black, phthalocyanine, quinacridone, indoline, azo pigment, titanium oxide, bengalara, etc. as coloring agents, glass fiber, asbestos, my , Wollastonite, calcium silicate, aluminum silicate, calcium carbonate, also many other high molecular compounds may be blended to the extent that effect can not be inhibited in the present invention.

The method of compounding each component of the present invention is not particularly limited, and a known method can be used. For example, mixing rolls, Banbury mixers and Henschel,
After mixing the respective components with a mixer such as a tumbler or a ribbon blender, a method of forming pellets using an extruder or the like may be used. Further, in the blending method, each component may be dry-blended and directly supplied to a molding machine to form a film. Melt flow rate (MFR; JIS K) of the film of the present invention
The load is 2.16 Kg according to 7210 and the temperature is 230 ° C.), and is not particularly limited, and is selected by a molding method. For example, the MFR used in the T-die molding method is 0.5 to 30.
g / 10 minutes is appropriate. Preferably, 0.8 to 25 g
/ 10 minutes, particularly preferably 1.0 to 20 g / 10 minutes.

The polypropylene film of the present invention can be obtained by using a known dry laminating machine or the like,
Other materials such as metal vapor deposition film, silicon oxide vapor deposition film, gas barrier layer such as vinyldene chloride resin and saponified ethylene-vinyl acetate copolymer, polyester resin layer, polyamide resin layer and polycarbonate resin layer may be laminated and used. it can.

[0025]

The present invention will be described in more detail with reference to the following examples. The methods for measuring various physical properties used in the present invention are described below. The MFR was performed in accordance with JIS K7210, Table 1, Condition 14. The apparatus used was a melt indexer manufactured by Takara Co., Ltd. Intrinsic viscosity is Ubbelohe
Using a capillary viscometer, the intrinsic viscosity [η] of the xylene-soluble component was determined under a temperature condition of 135 ° C. as a decahydronaphthalene solvent. The ethylene content was determined by the ¹³ C-NMR method reported by CJ Carman et al.
cromolecules, 10 , 537 (1977). Isotactic pentad fraction (IP): The mmmm fraction is an isotactic fraction of pentad of a methyl group in a polypropylene molecular chain. The measurement was performed by JNM-GSX400 ( ¹³ C nuclear resonance frequency 1) manufactured by JEOL Ltd.
00 MHz). Each signal is
A. Zambelli et al., Macromolecules, 13 , 267 (1980). The measurement conditions are shown below. Measurement mode: Proton decoupling method Pulse width: 8.0 μs Pulse repetition period: 3.0 sec Number of integrations: 20000 Solvent: Mixed solvent of 1,2,4-trichlorobenzene / deuterated benzene (75/25% by volume) Internal standard : Hexamethyldisiloxane Sample concentration: 300mg / 3.0ml Solvent Measurement temperature: 120 ° C

Average isotactic chain length (N): The average isotactic chain length (N) is determined by the method reported by JCRandall (Polymer Sequence Distributio).
n, Academic Press, New York 1977, chapter 2). Film impact strength is ASTM
Based on D781, a film impact tester at -5 ° C and heat seal strength were measured using a film impact tester manufactured by Toyo Seiki Seisaku-sho, Ltd. As for the transparency, the occurrence state of the scum was visually determined by a five-step method based on the following criteria, in which the swelling state of the surface layer of the packaging bag after the retort treatment was observed. 1 ····························································································· It can withstand the use of things that can be used 4 ······································································ Seen not to use

Further, as the block copolymer (I), BP-1 and BP shown in Table 1 which were produced by multistage polymerization
-2 as BP-3 and B as block copolymer (II)
P-4 was used. For comparison, the BP shown in Table 1 was used.
-A and BP-B were used. Table 1 shows the physical properties of these copolymers. Ethylene as an ethylene-based elastomer
A butene copolymer ("Tuffmer A1085" manufactured by Mitsui Petrochemical Co., Ltd.) was used. As a linear polyethylene resin, a density of 0.920 g / cm ³ and MFR (JISK
7210, temperature 190 ° C, load 2.16kgf
The ethylene-butene-1 copolymer having a butene-1 content of 6.5% by weight and a content of 15 g / 10 minutes was used.

Examples 1 to 9 and Comparative Examples 1 to 3 [Kneading treatment] After mixing each component of the (A) layer and each component of the (B) layer with a kind and amount shown in Table 2 by a tumbler, Kobe Steel Ltd. Pellets were formed at a temperature of 190 to 210 ° C. using a twin-screw extruder (Model KTX37) manufactured by the company. [T-die molding] Each of the obtained pellets has a diameter of 40 mm.
Using a multi-layer T-die molding machine manufactured by Yoshii Iron Works Co., Ltd. having a φ and a die width of 250 mm, a die temperature of 250 ° C. and a cooling temperature of 70
At 70 ° C., a film having a thickness of 70 μm was prepared. Examples 4 to 9 were multilayer laminate films of the (A) layer and the (B) layer. The impact strength and transparency of each film were measured. Table 3 shows the results.

[Heat Seal] Using a heat sealer manufactured by Tester Sangyo Co., a polyester film having a thickness of 12 μm and each of the above films were laminated by a dry lamination method (however, Examples 4 to 9 were laminated on the (B) layer side). The heat sealing treatment was performed at a temperature of 160 ° C., a pressure of 2 kg / cm ² and a time of 1 second. The heat seal strength of the obtained laminate was measured, and the results are shown in Table 3.

[Retort treatment] A polyester film having a thickness of 12 μm, an aluminum foil having a thickness of 9 μm, and various BPP films shown in Table 2 were laminated by a dry lamination method (however, Examples 4 to 9 were laminated on the (B) layer side). , 15
A packaging bag of cm x 18 cm was prepared and a commercial retort food product "Ajinomoto Co., Ltd."
, And the BPP layers were heat-sealed and sealed. Next, RCS-4OT manufactured by Hisaka Manufacturing Co., Ltd.
A retort treatment was performed at 21 ° C. for 30 minutes. After the retort treatment, the Yuzu skin was visually evaluated. Table 3 shows the results.
Shown in

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

EFFECTS OF THE INVENTION Since the polypropylene film of the present invention and its multilayer film do not have irregularities (orange peel or yuzu skin) on the film surface due to heat sterilization such as retort sterilization, foods such as films for packaging retort foods. It is suitably used as a packaging material.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08J 5/18 CES C08J 5/18 CES // (C08L 53/00 23:08) (C08L 53/00 23 : 08 23:06) F term (reference) 3E086 AD01 BA04 BA15 BB02 BB05 BB41 BB51 BB74 BB90 CA03 CA28 4F071 AA15 AA20 AA75 AH04 BB06 BC01 4F100 AK62A AK62B AK64A AK64B AK65 AK66A AL02A02B02A02A02A05 JA20B JK10 JK14 JL12 JN01 YY00A YY00B 4J002 BB033 BB052 BP031 GF00 GG02

Claims (5)

[Claims] 1. (1) (a) Polypropylene block 9
5 to 70% by weight, (b) propylene and 2 to 12 carbon atoms
Propylene-α-olefin block copolymer (I) consisting of 5 to 30% by weight of a copolymer elastomer block (excluding 3) with α-olefin (I) 85 to 98
15% by weight and (2) a copolymer of 90 to 70% by weight of ethylene and 10 to 30% by weight of an α-olefin having 3 to 12 carbon atoms.
A polypropylene-based film whose main component is weight%. 2. The (a) propylene-α-olefin block copolymer has an intrinsic viscosity of a xylene-soluble component of 3.5 to 3.5.
The polypropylene-based film according to claim 1, wherein the content is 5.0 dl / g. 3. A polypropylene-based multilayer film comprising at least two layers of the (A) layer comprising the polypropylene film according to claim 1 and the following (B) layer. (1) (a) 95 to 70% by weight of a polypropylene block
And (b) 5 to 30% by weight of a copolymer elastomer block of propylene and an α-olefin having 2 to 12 carbon atoms (excluding 3), and the intrinsic viscosity of the xylene-soluble component is 1.5 to 5%. 70-95% by weight of a propylene-α-olefin block copolymer (II) having a content of 3.5 dl / g,
(2) α having 90 to 70% by weight of ethylene and 3 to 12 carbon atoms
-A propylene-based resin film mainly composed of 3 to 15% by weight of an ethylene copolymer elastomer which is a copolymer with 10 to 30% by weight of an olefin and (2) 2 to 15% by weight of a linear polyethylene resin. (B) layer 4. The polypropylene-based laminated film according to claim 3, wherein the total thickness is 40 to 90 μm and the thickness ratio between the layer (A) and the layer (B) is 9: 1 to 1: 9. 5. A package for a retort, wherein the layer (A) of the polypropylene-based multilayer film according to claim 3 or 4 is used as an innermost layer.