KR100339000B1 - Polypropylen-based Films and Multilayer Films Thereof - Google Patents

Abstract

The present invention provides a polypropylene-based film suitable as a food packaging material with less occurrence of irregularities on the surface of a film such as citron surface by retort sterilization.

That is, this invention is a copolymer elastomer block 5-30 of (1) 95-70 weight% of (a) polypropylene blocks, and (b) propylene and the alpha-olefin of C2-C12 (except 3). Ethylene-based copolymer of 85 to 98% by weight of propylene-α-olefin block copolymer (I) composed of weight%, and (2) 90 to 70% by weight of ethylene and 3 to 12 carbon atoms of α-olefin. The polypropylene film which has 15 to 2 weight% of copolymer elastomer as a main component is provided.

Description

Polypropylene film and its multilayer film {Polypropylen-based Films and Multilayer Films Thereof}

The present invention is a polypropylene film which is preferably used as a food packaging material such as a film for retort food packaging without generation of irregularities (orange peel or citron surface) on the film surface by heat sterilization such as retort sterilization treatment. And the laminated film.

Conventionally, polypropylene films are inexpensive and are used as various food packaging materials or various medical packaging materials utilizing characteristics such as heat resistance, chemical resistance, and anti-heat sealability. As a retort food packaging material in which heat sterilization such as boil sterilization or retort sterilization is performed after filling the contents, aluminum foil or vinylidene chloride resin and ethylene-vinyl acetate copolymer resin saponified material are used as the gas barrier layer. In combination with the polyamide resin layer, the polyester resin layer, and the like, polypropylene is used for the heat seal layer. As the polypropylene for this use, a film obtained by blending a propylene block copolymer or an ethylene propylene random copolymer with an elastomer component such as ethylene propylene elastomer and polybutene obtained by a thermoplastic elastomer such as a vanadium-based polymerization catalyst is used. .

However, when heat sterilization such as retort sterilization is performed, an uneven surface called an orange peel or citron surface is formed on the surface of the film after heat sterilization, and other substrates are laminated by a lamination method such as dry laminate to form a retort pouch. When created, there was a problem of affecting the whole pouch and significantly impairing the appearance of the product.

As a method of improving this, for example, the method of mix | blending polybutene (patent publication No. 2-32142), the method of using the ethylene-alpha-olefin copolymer superposed | polymerized with the specific catalyst (patent publication No. 7-266520). And Japanese Patent Application Laid-Open No. Hei 7-256841), a method by specific multistage polymerization (Japanese Patent Laid-Open No. 3-44087), a specific laminate (Japanese Patent Laid-Open No. 3-56570), and the like have been proposed.

However, all of the above methods are still insufficient from the viewpoint of preventing the occurrence of citron surface.

This invention is made | formed in view of such a situation, and an object of this invention is to provide the polypropylene film suitable as a food packaging material with little generation | occurrence | production of the uneven | corrugated shape of the film surface, such as the citron surface by a retort sterilization process.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching, the present inventors discovered that the said objective can be achieved by the film which has a specific propylene-alpha-olefin block copolymer and an ethylene-based copolymer as a main component, and based on this knowledge, It was completed.

That is, this invention is a copolymer elastomer block 5-30 of (1) 95-70 weight% of (a) polypropylene blocks, and (b) propylene and the alpha-olefin of C2-C12 (except 3). Ethylene-based copolymer of 85 to 98% by weight of propylene-α-olefin block copolymer (I) composed of weight%, and (2) 90 to 70% by weight of ethylene and 3 to 12 carbon atoms of α-olefin. It is to provide a polypropylene film having 15 to 2% by weight of copolymer elastomer as a main component.

The propylene-α-olefin block copolymer (I) (hereinafter sometimes referred to as "block copolymer I") in the present invention includes (a) 95 to 70 wt% of a polypropylene block, (b) propylene and carbon number It is a block copolymer which consists of 5-30 weight% of copolymer elastomer blocks of the alpha olefin of 2-12 (except 3). (a) The polypropylene block consists of a random copolymer component of propylene and α-olefin having up to 5% by weight of homo polypropylene or other α-olefin component. The other α-olefin component is preferably at most 4.5% by weight, particularly preferably at most 4.0% by weight.

When the other α-olefin component exceeds 5% by weight, rigidity and heat resistance are inhibited, low crystalline components increase, or adhesion of the film occurs, which is not preferable.

On the other hand, (b) the copolymer elastomer block is composed of a copolymer of propylene and an α-olefin having 2 to 12 carbon atoms (except 3), and the copolymerization ratio of the α-olefin of the copolymer elastomer is 30 to 80. Weight percent. The copolymerization ratio is preferably 35 to 75% by weight, particularly preferably 38 to 72% by weight. When the copolymerization ratio of the α-olefin is less than 30% by weight, impact resistance and cold resistance are inferior. On the other hand, when it exceeds 80 weight%, since heat resistance is inhibited, it is not preferable.

Specific examples of the α-olefins of the component (a) and the component (b) include ethylene, 1-butene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 4, 4- dimethyl- 1-pentene, vinyl cyclopentane, a vinyl cyclohexane, etc. are mentioned. These may be one type or may mix and use two or more types.

The content ratio 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. When the copolymerization ratio of the copolymer elastomer is less than 10% by weight, impact resistance and cold resistance are inferior. On the other hand, when it exceeds 30% by weight, retort aptitude such as rigidity and adhesion of the film is inferior, which is not preferable.

The block copolymer (I) of the present invention is obtained by a known method copolymerized using two or more stages of polymerization tanks. For example, T.Ogawa, T. Inaba: J. Appl. Poly. Sci., 18, 3345 -3365 (1974), AJ Lononte: J. Polym. Sci., Part A, 2, 705-709 (1964), and the like.

It is preferable that the block copolymer I of this invention exists in the range of 3.5-5.0 dl / g of intrinsic viscosity of a xylene soluble component, More preferably, it is 3.6-4.7 dl / g, Especially preferably, it is 3.7-4.5 dl / g Range. If the intrinsic viscosity is less than 3.5, heat resistance and citron surface improvement effect are inferior. On the other hand, when it exceeds 5.0 dl / g, a gel, fish eye, etc. generate easily, and there exists a tendency for the external appearance of a film to fall.

In addition, the intrinsic viscosity of a xylene soluble component is once melt | dissolving a polymer in ortho-xylene at 135 degreeC, it cools to 25 degreeC, and precipitates a polymer, and means the intrinsic viscosity of this precipitate. The intrinsic viscosity is a method of dissolving in decahydronaphthalene and measuring at a temperature of 135 ° C. The method according to J.App.Poly.Sci, Vol. 14, pp 2947-2963 (1970) by Elliott et al. have. Specifically, using a Ubbelohde capillary viscometer or Ostwald-Fenske capillary viscometer or the like, the polymer is dissolved in decahydronaphthalene to prepare a solution having a different concentration, and the viscosity of each concentration is measured in a thermostat. These viscosity data can then be obtained by infinitely extrapolating in the form of Huggins.

Ethylene copolymer elastomer (hereinafter referred to as "ethylene elastomer") in the present invention is a copolymer of 90 to 70% by weight of ethylene and 10 to 30% by weight of α-olefin having 3 to 12 carbon atoms, and copolymerization of α-olefin. The proportion is preferably 12 to 28% by weight, particularly preferably 13 to 25% by weight. If the copolymerization ratio of alpha -olefin is less than 10% by weight, the citron surface improving effect is insufficient. On the other hand, if it exceeds 30% by weight, heat resistance and heat seal strength are inhibited, which is not preferable. Specific examples of the α-olefin include propylene, 1-butene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, and vinyl Cyclopentane, vinyl cyclohexane, etc. are mentioned. These may be one type or may mix and use two or more types. Among these, propylene and 1-butene are preferable.

Ethylene-based elastomers generally have a density of 0.85 to 0.90 g / cm 3, preferably 0.86 to 0.89 g / cm 3, particularly preferably 0.87 to 0.89 g / cm 3. If the density is less than 0.85 g / cm 3 or more than 0.90 g / cm 3, the citron surface improvement effect is deteriorated.

The melt flow rate (MFR) measured at a temperature of 230 ° C. and a load of 2.16 Kg is usually 0.1 to 10 g / 10 minutes, preferably 0.2 to 8 g / 10 minutes, particularly preferably 0.3 to 5 g / 10. It is good to be minutes. If the MFR is less than 0.1 g / 10 min, the appearance of the film is deteriorated. On the other hand, when it exceeds 10 g / 10min, since the effect of improving the citron surface is inferior, it is not preferable.

Commercially available products which are preferably used as the ethylene-based elastomer of the present invention include Mitsui Sekiyukagaku Co., Ltd. "trade name: Tafmer" and Nihon Kosei Rubber Co., Ltd. "trade name: JSR EBM".

The polypropylene film of the present invention is obtained by using a known film molding, for example, a T die molding method, a composition containing 85 to 98% by weight of the block copolymer (I) and 15 to 2% by weight of an ethylene elastomer as a main component. Lose. The content of the ethylene elastomer is preferably 12 to 3% by weight, particularly preferably 10 to 4% by weight. When the content of the ethylene-based copolymer elastomer exceeds 15% by weight, the stiffness, heat resistance, and heat seal strength are inferior. On the other hand, if it is less than 2% by weight, the citron surface improving effect and impact resistance are poor, which is not preferable.

Moreover, the polypropylene laminated film of this invention is a (A) layer which consists of the said polypropylene film, (1) (a) 95-70 weight% of polypropylene blocks, (b) propylene and C2-C12 ( However, the propylene-α-olefin block copolymer (II) which consists of 5-30 weight% of copolymer elastomer blocks of the alpha olefin of (except 3), and whose intrinsic viscosity of xylene solubles is 1.5-3.5 dl / g 70 to 95% by weight, (2) 90 to 70% by weight of ethylene and 3 to 15% by weight of ethylene copolymer elastomer, which is a copolymer of 10 to 30% by weight of α-olefin having 3 to 12 carbon atoms, and (3) linear polyethylene resin It is a laminated film which consists of at least 2 layer of (B) layer which consists of a propylene resin film which has 2-15 weight% as a main component.

The (a) polypropylene block and (b) copolymer elastomer block constituting the layer (B) are the same components as the polypropylene block and the copolymer elastomer block of the block copolymer I. However, the intrinsic viscosity of the xylene soluble component of block copolymer (II) needs to be 1.5-3.5 dl / g. The intrinsic viscosity is preferably 1.7 to 3.3 dl / g, and particularly preferably 1.8 to 3.2 dl / g. If 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, since compatibility with a latent linear polyethylene falls and a citron surface improvement effect falls, it is unpreferable.

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

Moreover, the copolymer of ethylene and a C3-C12 alpha olefin is mentioned as linear polyethylene resin. As the α-olefin component, propylene, 1-butene, 1-octene, 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 one type or may mix and use two or more types. Among these, 1-butene and 1-octene are preferable. The copolymerization ratio of the α-olefin is at most 10% by weight or less, preferably 9% by weight or less, and particularly preferably 8% by weight. Moreover, a lower limit is at least 3 weight% or more. If the copolymerization ratio is more than 10% by weight, the effect of improving the citron surface is poor, which is not preferable.

The density of the linear polyethylene is usually 0.88 to 0.930 g / cm 3, preferably 0.89 to 0.925 g / cm 3, 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 minutes, preferably 5 to 25 g / 10 minutes, and particularly preferably 7 to 23 g / 10 minutes. .

(B) layer of this invention consists of 70-95 weight% of block copolymers (II), 3-15 weight% of ethylene-type elastomers, and 2-15 weight% of linear polyethylene resins. 75-93 weight% is preferable and, as for block copolymer (II), 77-91 weight% is especially preferable. If the block copolymer (II) is less than 70% by weight, the stiffness and heat resistance are inferior. On the other hand, when it exceeds 95 weight%, impact resistance and a citron surface are easy to generate | occur | produce, and it is unpreferable.

The ethylenic elastomer is preferably 4 to 13% by weight, particularly preferably 5 to 10% by weight. If the elastomer is less than 3% by weight, the citron surface improving effect is inferior. On the other hand, when it exceeds 15 weight%, heat seal strength falls and it is unpreferable.

The linear polyethylene resin is preferably 3 to 13% by weight, particularly preferably 4 to 10% by weight. If the polyethylene resin is less than 2% by weight, the citron surface improvement effect is inferior. On the other hand, when it exceeds 15 weight%, heat seal strength falls and it is unpreferable.

In addition, it is preferable to use the thing of the block copolymer (I) and (II) propylene block of this invention which has the characteristics of the following (i) and (ii) in the point of prevention of the generation of an oily surface.

(Iii) The isotactic pentad fraction (IP) by ¹³ C nuclear magnetic resonance spectrum is 98.5% or more.

(Ii) the isotactic average chain length (N) is 500 or more;

The isotactic pentad fraction (hereinafter sometimes abbreviated as "IP") is a nuclear magnetic resonance spectrum with isotope carbon according to the method of A.Zambelli, Macromolecules, Vol. 6, p-625 (1973). ¹³ C-NMR) is used to refer to the isotactic fraction in pentad units in the PP molecular chain.

In addition, isotic mean chain length (N) is the isotic mean chain length of the methyl group in a polypropylene molecule, and is based on the method reported by JCRandll (Polymer Sequence Distribution, Academic Press, New York 1977, chapter 2). Can be calculated.

These characteristics are described in detail in Japanese Patent Application Laid-Open No. 8-73547.

The polypropylene film of the present invention can be made into a molded article using a known T die molding method. Usually, shaping | molding temperature is performed in the range of the die temperature of 220-280 degreeC. Moreover, cooling temperature is 40-90 degreeC normally.

The thickness of a film is 20-180 micrometers normally. When the thickness is 20 µm or less, the heat seal strength is poor, which is not preferable. On the other hand, when it exceeds 180 micrometers, heat sealing property and transparency will fall and it is unpreferable. Preferably it is 30-170 micrometers, Especially preferably, it is 40-160 micrometers.

In the case of the multilayer film which consists of (A) layer and (B) layer of this invention, the thickness ratio of (A) layer and (B) layer has a preferable range of 9: 1-1: 9. Preferably it is 8: 2-2: 8, Especially preferably, it is 7: 3-5: 5. By setting it as a multilayer film, it is excellent in heat-sealing strength more than the (A) layer monolayer. Therefore, when using as a retort package laminated | stacked with gas barrier layers, such as an aluminum foil or ethylene vinyl acetate copolymer saponification layer, a polyamide resin layer, and a vinylidene chloride resin layer, or a polyester resin layer, (B) layer When 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 of killing microorganisms which are the main cause of deterioration of food, and is usually carried out at a temperature range of 60 ° C to 135 ° C, depending on the target bacteria. It is called retort sterilization to use the heating steam and the hot water mainly consisting of hot water of 100 degreeC or more during these heat sterilization, and it processes in high temperature short time so that the taste and flavor of the content may not be impaired. For details of these heat sterilizations, see, for example, 芝 崎 勳; “Food Sterilization Engineering”, Lightning, Inc. (March 14, 1981),, 水 潮, 橫山 理 雄; "Theory and Practice of Retort Foods" (January 15, 1981).

For the film of the present invention, other additives conventionally used in thermoplastic resins (for example, antioxidants, weathering stabilizers, antistatic agents, lubricants, antiblocking agents, antifog additives, dyes, pigments, oils, waxes, fillers, etc.) or other thermoplastic resins It can be mix | blended in an appropriate amount in the range which does not impair the objective of this invention.

Examples of such additives include, for example, 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis (6-t- as antioxidants). Butylphenol), 2,2'-methylenebis (4-methyl-6-t-butylphenol), octadecyl 3- (3 ', 5'-di-t-butyl-1'-hydroxyphenyl) propio Nate, 4,4′-thiobis (6-butylphenol), ethyl 2-cyano-3,3-diphenylacrylate, 2- (2′-hydroxy-5-methylphenyl) benzotria as ultraviolet absorber Sol, 2-hydroxy-4-octoxybenzophenone, dimethyl phthalate as a plasticizer, diethyl phthalate, wax, liquid paraffin, phosphate ester, antistatic agents such as pentaerythritol monostearate, sorbitan monopalmitate, sulfated Oleic acid, polyethylene oxide, carbon wax, lubrication agent such as ethylene bis stearamide, butyl stearate, carbon black, phthalocyanine, quinacridone, indolin, azo pigment, titanium oxide, bengal, etc. Glass, assuming fiber, asbestos, mica (mica), come host nitro, calcium silicate, aluminum silicate, calcium carbonate, and many other high molecular compounds may also be blended to an extent that not inhibit the effects of the present invention.

The compounding method of each component of this invention is not specifically limited, A well-known method can be used. For example, after mixing each component with a mixing roll, a Banbury mixer, a Henschel, a turn blender, a ribbon blender, etc., the method of pelletizing using an extruder etc. is mentioned. In the blending method, each component may be dry blended and directly supplied to a molding machine to form a film.

There is no restriction | limiting in particular about the melt flow rate (MFR; 2.16 Kg load, temperature 230 degreeC by JIS K7210) of the film of this invention, It selects according to the shaping | molding method, For example, MFR used for the T die shaping | molding method is 0.5-30 g / 10 min is suitable. Preferably it is 0.8-25 g / 10min, Especially preferably, it is 1.0-20 g / 10min.

The polypropylene film of the present invention uses a well-known dry laminate molding machine or the like, and furthermore, gas barrier layers such as aluminum foil, metal vapor deposition film, silicon oxide vapor deposition film, vinylidene chloride resin and ethylene vinyl acetate copolymer saponifier, polyester Other materials, such as a resin layer, a polyamide resin layer, and a polycarbonate resin layer, can be laminated | stacked and used.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Moreover, the measuring method of the various physical properties used by this invention is shown below.

MFR was implemented based on JIS K7210, Table 1, and conditions 14. The apparatus used the merato indexer by Takara Thermistor Co., Ltd. product.

Intrinsic viscosity was calculated | required the intrinsic viscosity [(eta)] of the xylene soluble component using the Ubbelohde capillary viscometer under the temperature condition of 135 degreeC as a decahydronaphthalene solvent.

Ethylene content was carried out based on the method by ¹³ C-NMR method (Macromolecules, 10, 537 (1997)) reported by CJ Carman et al.

Isomatic pentad fraction (IP):

The mmmm fraction is the isotactic fraction of methyl groups in the polypropylene molecular chain in pentad units. The measurement was performed using JNM-GSX 400 ( ¹³ C nuclear magnetic resonance frequency 100 MHz) by the Nippon Denshi Corporation. Each signal was attributed to Macromolecules, 13,267 (1980) by A.Zambelli et al. Measurement conditions are shown below.

Measurement mode: protondecoupling method

Pulse width: 8.0 ㎲

Pulse repetition period: 3.0 sec

Cumulative recovery: 20000 times

Solvent: Mixed solvent of 1,2,4-trichlorobenzene / heavy benzene (75/25% by volume)

Internal standard: hexamethyldisiloxane

Sample concentration: 300 mg / 3.0ml solvent

Measurement temperature: 120 ℃

Isomatic Average Chain Length (N):

Isotic mean chain length (N) is calculated based on the method reported by J.C.Randall (Polymer Sequence Distribution, Academic Press, New York 1977, chapter 2).

The film impact strength measured the film impact strength and heat seal strength of -5 degreeC using the Toyosei Seiki Seisakusho make film impact tester based on ASTMD781.

Transparency measured haze using the HDM-2DP type haze meter by Suga Shikenkisha, based on JISK7105.

The citron surface generation state was visually judged by the five-step method based on the following criteria the generation state of the uneven | corrugated state (citron surface) of the packaging bag surface layer after retort processing.

One … No occurrence of citron surface is observed

2 … Slightly visible citrus surface with uneven irregularities but can withstand use

3…. The appearance of the citron surface of the uneven unevenness is seen considerably, but can endure use

4 … In the yuzu surface of the certain irregularities shape, I see it in the front of the bag and cannot endure use

5... Slightly irregular shaped citron surface, visible on the front of the packaging bag, can not withstand use

As the block copolymer (I), BPP1 and BPP2 shown in Table 1 produced by multistage polymerization were used, and BPP3 and BPP4 were used as the block copolymer (II). In addition, BPP5 and BPP6 shown in Table 1 were used for comparison. The physical properties of these copolymers are shown in Table 1.

As the ethylene-based elastomer, an ethylene butene copolymer (manufactured by Mitsui Sekiyu Chemical Co., Ltd. "trade name: Tafmer A1085") was used.

As a linear polyethylene resin, an ethylene-butene- having a density of 0.920 g / cm 3 and MFR (measured under conditions of a temperature of 190 ° C. and a load of 2.16 kgf in accordance with JIS K7210) at a weight of 2.16 kgf of 15 g / 10 min. One copolymer was used.

Examples 1-9, Comparative Examples 1-3

[Mixing process]

After mixing each component of (A) layer and each component of (B) layer with the tumbler by the kind and compounding quantity shown in Table 2, it pellets at the temperature of 190-210 degreeC using the twin screw extruder (KTX37 type) by Kobe Seiko Shosha. It was made.

[T die molding]

Each obtained pellet was produced with a 70-micrometer-thick film at the die temperature of 250 degreeC, and the cooling temperature of 70 degreeC using the multilayer T die molding machine by Yoshii Co., Ltd. whose diameter is 40 mm (phi) and the die width of 250 mm. In addition, Examples 4-9 were made into the multilayer laminate film of (A) layer and (B) layer. The impact strength and transparency of each film were measured. The results are shown in Table 3.

[Hit seal]

Using a test sealer manufactured heat sealer, a 12-micrometer-thick polyester film and the respective films were laminated by dry lamination (however, Examples 4 to 9 were laminated to the layer side (B)), and the temperature was 160 ° C, The heat seal process was performed at the pressure of 2 Kg / cm <2> and time 1 second. The heat seal strength of the obtained laminate was measured and the results are shown in Table 3.

[Retort Processing]

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 dry lamination (however, Examples 4 to 9 were laminated to the layer side (B)), and 15 cm × 18. cm packaging bags were produced, and BPP layers were heat-sealed and encapsulated using Ajinomoto Co., Ltd. product "brand name: tinzauros" which is a commercial retort food. Subsequently, the retort process was performed for 30 minutes by the temperature of 121 degreeC using RCS-4OT made from Hisaka Seisakusho Co., Ltd.

After the retort treatment, the citron surface was visually evaluated. The results are shown in Table 3.

Table 1

Type of block copolymer Propylene Block Types Copolymer block MFR (g / 10 min) Intrinsic Viscosity (dl / g) Fender fraction IP (%) Average chain length N Ethylene Content (wt%) Copolymerization Ratio (wt%) Copolymer (Ⅰ) BPP 1 BPP 2 Homo PP 〃 9.69.3 19.219.8 2.83.2 3.84.2 99.599.4 705658 Copolymer (II) BPP 3 BPP 4 〃〃 15.89.8 26.519.7 2.92.5 2.02.8 99.399.4 526688 BPP 5BPP 6 〃〃 9.89.6 19.519.8 2.42.3 3.92.9 97.898.1 204231

Table 2

(A) layer (B) layer BPP Ethylene Elastomer Blending Amount (wt%) Thickness (㎛) BPP Ethylene Elastomer Blending Amount (wt%) Straight chain polyethylene resin compounding amount (% by weight) Thickness (㎛) Kinds Compounding amount (% by weight) Kinds Compounding amount (% by weight) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 BPP 1BPP 2BPP 1BPP 1BPP 2BPP 1BPP 1BPP 2BPP 1 949485949494949485 66156666615 707070201035201520 --- BPP 3BPP 4BPP 4BPP 4BPP 3BPP 4 --- 888888858088 --- 66610106 --- 6665106 --- 506035505550 Comparative Example 1 Comparative Example 2 Comparative Example 3 BPP 5 BPP 5 BPP 5 949494 666 702020 -BPP 6BPP 6 -8885 -610 -65 -5050

Table 3

Film Impact Strength (kg-cm / mm) Transparency Haze (%) Heat Seal Strength (kg / 15mm Width) Citron surface evaluation Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 77851037984951059198 63.165.360.548.14553.243.547.248.1 5.35.65.04.44.25.14.34.54.7 222111111 Comparative Example 1 Comparative Example 2 Comparative Example 3 616369 63.955.251.5 4.23.93.6 543

The polypropylene-based film of the present invention and its multilayer film are preferably used as food packaging materials such as retort food packaging films because they do not generate irregularities (orange peel or citron surface) on the film surface by heat sterilization such as retort sterilization treatment. do.

Claims (6)

(1) Propylene consisting of 95 to 70% by weight of polypropylene block and (b) 5 to 30% by weight of copolymer elastomer block of propylene and α-olefin having 2 to 12 carbon atoms (excluding 3). -alpha -olefin block copolymer (I) 85 to 98% by weight, and (2) 90 to 70% by weight of ethylene and an ethylenic copolymer elastomer 15 to 10 to 30% by weight of a C3-C12 alpha -olefin. Polypropylene type film which has 2 weight% as a main component. The polypropylene-based film according to claim 1, wherein the propylene-α-olefin block copolymer (I) has an intrinsic viscosity of 3.5 x 5.0 dl / g of xylene soluble component. The polypropylene multilayer film which consists of (A) layer which consists of a polypropylene film of Claim 1 or 2, and at least 2 layer of the following (B) layer: (1) 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). 70-95 weight% of propylene-alpha-olefin block copolymers (II) whose intrinsic viscosity of xylene soluble component is 1.5-3.5 dl / g, (2) 90-70 weight% of ethylene, and a C3-C12 alpha-olefin (B) Layer which consists of propylene-type resin film which has 3-15 weight% of ethylene-type copolymer elastomer which is 10-30 weight% copolymer, and (3) 2-15 weight% of linear polyethylene resin as a main component The polypropylene-based laminated film according to claim 3, wherein the total thickness is 40 to 90 µm, and the thickness ratio of the (A) layer and the (B) layer is 9: 1 to 1: 9. The package for retorts using (A) layer of the polypropylene multilayer film of Claim 3 as an innermost layer. The package for retorts using (A) layer of the polypropylene multilayer film of Claim 4 as an innermost layer.