JP2006161033A - Propylene resin composition and film thereof - Google Patents

Abstract

A propylene-based resin composition and a film thereof having good impact resistance at low temperature, appearance, heat sealability, food hygiene and blocking resistance are provided.
An ethylene-α-olefin having a propylene-based block copolymer of 70 to 95% by weight, a density of 890 to 925 kg / m ³ , and an n-hexane extraction amount of 0.01 to 2.6% by weight. A propylene-based resin composition containing 5 to 30% by weight of a copolymer and a film thereof (provided that the content of the propylene-based block copolymer and the ethylene-α-olefin copolymer is the total content of the propylene-based resin composition) Based on the weight of 100% by weight, the amount of n-hexane extracted from the ethylene-α-olefin copolymer is based on 100% by weight of the total weight of the ethylene-α-olefin copolymer).
[Selection figure] None

Description

  The present invention relates to a propylene-based resin composition and a film thereof. More specifically, the present invention relates to a propylene-based resin composition having excellent impact resistance at low temperature, appearance, heat sealability, food hygiene and blocking resistance, and a film thereof.

Polypropylene films are widely used in the fields of films, sheets, containers and the like because they are excellent in heat resistance and rigidity.
In recent years, films used in the field of food packaging, for example, films that are used in retort food packaging bags have been required to have heat resistance, rigidity, heat sealability, food hygiene and impact strength. Yes.
As a method for improving the impact resistance of a film used for a retort food packaging bag, a method using a composition in which an amorphous ethylene-α-olefin copolymer is blended with an ethylene-propylene block copolymer is known. Yes.

  For example, in JP-A-6-93061, a Ziegler-Natta type catalyst is used as a film made of a polypropylene block copolymer having good impact resistance at low temperatures and good appearance and blocking resistance. Polypropylene obtained by polymerizing a polymer portion mainly composed of propylene in the first step substantially in the absence of an inert solvent, and then polymerizing an ethylene-propylene copolymer portion in the gas phase in the second step. A film comprising a block copolymer is described.

  Japanese Patent Application Laid-Open No. 2000-191851 discloses a propylene polymer composition having excellent rigidity, impact resistance, and surface hardness, and includes a propylene polymer and a melting peak measured by a differential scanning calorimeter. Describes a propylene-based polymer composition comprising a specific amorphous α-olefin-based polymer that is not observed in FIG.

JP-A 2003-64228 discloses a resin composition for retort food packaging excellent in heat sealability, impact strength and transparency, obtained by polymerization with a polypropylene resin and a single site catalyst, and has a density. Is a resin composition for retort food packaging comprising an ethylene-α-olefin copolymer having an intrinsic viscosity of 1.06 to 0.900 g / cm ³ and an intrinsic viscosity of 1.0 to 1.8 dl / g. .

JP-A-6-93061 JP 2000-191851 A JP 2003-64228 A

  Under such circumstances, an object of the present invention is to provide a propylene-based resin composition having excellent impact resistance at low temperature, appearance, heat sealability, food hygiene and blocking resistance, and a film thereof.

However, the propylene-based resin composition and the film thereof described in the above publications and the like also have a low-temperature impact resistance, appearance, heat sealability, food hygiene, and blocking resistance, and a film thereof There was a need for further improvements in terms of obtaining.
As a result of intensive studies, the present inventor has found that the present invention can solve the above problems, and has completed the present invention.

That is, the present invention
Ethylene-α-olefin copolymer 5 having a propylene-based block copolymer of 70 to 95% by weight, a density of 890 to 925 kg / m ³ and an n-hexane extraction amount of 0.01 to 2.6% by weight. The present invention relates to a propylene-based resin composition containing -30% by weight and a film thereof. (However, the content of the propylene-based block copolymer and the ethylene-α-olefin copolymer is based on 100% by weight of the total weight of the propylene-based resin composition, and n-hexane of the ethylene-α-olefin copolymer. (The extraction amount is based on 100% by weight of the total weight of the ethylene-α-olefin copolymer).

  According to the present invention, it is possible to obtain a propylene-based resin composition having excellent impact resistance at low temperature, appearance, heat sealability, food hygiene, and blocking resistance, and a film thereof.

  The propylene block copolymer used in the present invention comprises a polymer part (component A) obtained by polymerizing a monomer mainly composed of propylene, and at least one selected from ethylene and butene-1 and propylene. A propylene block copolymer containing a copolymer component (component B) obtained by copolymerization.

The propylene block copolymer is preferably 50 to 90% by weight of a polymer part (component A) obtained by polymerizing a monomer mainly composed of propylene, and an ethylene-propylene copolymer component (component B) 10. (The content of the A component and the B component is based on 100% by weight of the total weight of the propylene-based block copolymer), and the intrinsic viscosity of the B component ([η] _B ) There was 1.5~6dl / g, the intrinsic viscosity of component B ([η] _B) and the intrinsic viscosity of the component a ratio _{([η] a) ([} η] B / [η] a) is 0. 5 to 3 propylene-based block copolymers.

  When the B component is an ethylene-propylene copolymer component, the content of the B component is preferably from the viewpoint of excellent balance of impact resistance, heat sealability and blocking resistance, and excellent food hygiene. 10 to 50% by weight (that is, the content of the A component is 50 to 90% by weight), more preferably 15 to 40% by weight (that is, the content of the A component is 60 to 85% by weight). More preferably, it is 20 to 35% by weight (that is, the content of the component A is 65 to 80% by weight).

  When the B component is an ethylene-propylene copolymer component, the content of the structural unit derived from ethylene contained in the B component is excellent in impact resistance at low temperature, blocking resistance and food hygiene, Preferably it is 10 to 60 weight%, More preferably, it is 20 to 50 weight%.

When the B component is an ethylene-propylene copolymer component, the intrinsic viscosity ([η] _B ) of the B component is preferably from the viewpoint of excellent blocking resistance, heat seal strength, food hygiene, and film appearance. 1.5 to 6 dl / g, more preferably 2 to 4.5 dl / g, and still more preferably 2 to 4 dl / g.

When the B component is an ethylene-propylene copolymer component, the ratio of the intrinsic viscosity ([η] _B ) of the B component to the intrinsic viscosity ([η] _A ) of the A component ([η] _B / [η] _A ) From the viewpoint of excellent blocking resistance, heat seal strength, food hygiene, and film appearance, it is preferably 0.5 to 3, more preferably 1 to 2.5.

  The 230 ° C. melt flow rate of the propylene-based block copolymer used in the present invention is usually 1.5 to 10 g / 10 minutes from the viewpoint of improving the film processability and food hygiene, Preferably, it is 2 to 5 g / 10 minutes.

  As a manufacturing method of the propylene-type block copolymer used by this invention, the method of manufacturing with a well-known polymerization method using a well-known catalyst is mentioned.

Known catalysts include, for example,
(1) a Ti—Mg-based catalyst comprising a solid catalyst component in which a Ti compound is combined with a magnesium compound,
(2) a Ziegler-Natta type catalyst comprising a solid catalyst component containing magnesium, titanium and halogen as essential components, an organoaluminum compound, and an electron donating compound used as necessary;
(3) Metallocene catalysts and the like can be mentioned.
Preferred is a Ziegler-Natta catalyst comprising a solid catalyst component containing magnesium, titanium and halogen as essential components, an organoaluminum compound, and an electron donating compound used as necessary.

As a known polymerization method, for example,
(1) A first step in which a monomer mainly composed of propylene is polymerized in the presence of an inert hydrocarbon solvent using one polymerization vessel, and the first step is followed by the first step. A batch polymerization method comprising a second step in which ethylene and propylene are copolymerized in the presence of the prepared polymer;
(2) The first step in which at least two polymerization vessels are arranged in series, and a monomer mainly composed of propylene is polymerized in the absence of an inert hydrocarbon solvent, followed by the first step. For example, a continuous polymerization method comprising a second step of transferring the polymer to the next polymerization tank and copolymerizing ethylene and propylene in the presence of the polymer produced in the first step may be mentioned.
Preferably, from the viewpoint of increasing productivity, the continuous polymerization method of (2) above, and more preferably, the continuous polymerization method of (2) above, wherein the second step is carried out by a gas phase method. This is a continuous polymerization method for polymerization.
In the case of the continuous polymerization method (2), the polymerization tank used in each of the first step and the second step may be one tank or at least two tanks.

The ethylene-α-olefin copolymer used in the present invention is a copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms.
Examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-hexadecene, 1-hexene, Examples include eicosene, 4-methyl-1-pentene, 4-methyl-1-hexene, and these may be used alone or in combination of at least two kinds.
The ethylene-α-olefin copolymer is preferably an ethylene-1-hexene copolymer from the viewpoint of improving heat sealability and impact strength.

The density of the ethylene-α-olefin copolymer used in the present invention is 890 to 925 kg / m ³ , preferably 900 to 915 kg / m ³ . When the density is less than 890 kg / m ³ , heat seal strength and food hygiene may be insufficient, and when it exceeds 925 kg / m ³ , impact strength may be insufficient.

The amount of n-hexane extracted from the ethylene-α-olefin copolymer used in the present invention is 0.01 to 2.6% by weight, preferably 0.5 to 2.6% by weight. However, the amount of n-hexane extracted from the ethylene-α-olefin copolymer is based on 100% by weight of the total weight of the ethylene-α-olefin copolymer.
If the amount of n-hexane extracted is less than 0.01% by weight, the impact strength may be insufficient, and if it exceeds 2.6% by weight, the heat seal strength and food hygiene may be insufficient. .

  The melt flow rate (MFR) of the ethylene-α-olefin copolymer used in the present invention is usually from the viewpoint of improving heat seal strength, film appearance, food hygiene, and impact strength. 5 to 30 g / 10 min, preferably 0.5 to 4 g / min, and more preferably 0.5 to 1 g / 10 min.

As a method for adjusting the n-hexane extract amount of the ethylene-α-olefin copolymer used in the present invention to 0.01 to 2.6% by weight, for example, a metallocene catalyst is used to copolymerize ethylene and α-olefin. A method is mentioned in which the density of the ethylene-α-olefin copolymer is adjusted to 890 to 920 kg / m ³ by polymerization.
Preferably, using a metallocene catalyst, ethylene and α-olefin are copolymerized so that the ethylene-α-olefin copolymer has a density of 890 to 920 kg / m ³ and a melt flow rate (MFR) of 0.5 to A method of setting the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) to 1 to 2.5 is 30 g / 10 minutes.

  Examples of the metallocene catalyst used for the production of the ethylene-α-olefin copolymer include olefin polymerization using a transition metal compound having a group having a cyclopentadiene type anion skeleton (hereinafter referred to as a metallocene transition metal compound). Catalyst.

Examples of metallocene transition metal compounds include:
Formula ML _a X _{na wherein} M is a group 4 or lanthanide series transition metal atom of the periodic table of elements. L is a group having a cyclopentadiene-type anion skeleton or a group containing a hetero atom, At least one is a group having a cyclopentadiene-type anion skeleton, a plurality of L may be mutually linked, X is a halogen atom, a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, n is A valence of a transition metal atom, and a is an integer satisfying 0 <a ≦ n.).

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

The metallocene-based transition metal compound is preferably used in contact with an activation promoter. Examples of the activation cocatalyst include an alumoxane compound, and an activation cocatalyst formed by using an organoaluminum compound in combination with a boron compound such as trityl borate or anilinium borate. Further, it may be used in combination with a particulate carrier including an inorganic carrier such as SiO ₂ and Al ₂ O _{3 and} an organic carrier such as a polymer such as ethylene and styrene.

  The propylene resin composition of the present invention contains a propylene homopolymer, at least one selected from ethylene and 1-butene, and a random copolymer of propylene in order to improve heat resistance and transparency. The content thereof is preferably 25% by weight or less from the viewpoint of improving impact resistance (the total weight of the propylene-based resin composition is 100% by weight).

  The propylene-based resin composition of the present invention has a phenol-based antioxidant and a phosphorus-based antioxidant for the purpose of suppressing the oxidative deterioration of the resin composition or the film and improving heat sealability and blocking resistance when the film is produced. You may contain antioxidant.

  Examples of the phenolic antioxidant include 2,6-di-t-butyl-4-methylphenol and tetrakis [methylene-3 (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate. ] Methane, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methyl) Phenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5 · 5] undecane, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanate Nurate, triethylene glycol-N-bis-3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate, 1,6-hexanediol Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propylate], 2,2-thiobis-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate], α-tocophenols represented by vitamin E, and the like.

  Examples of the phosphorus antioxidant include tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, distearyl pentaerythritol diphosphite, and bis (2,4-di-). t-butylphenyl) pentaerythritol diphosphite, bis (2,4-di-t-butyl-6-methylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite Bis (2,4-dicumylphenyl) pentaerythritol diphosphite, tetrakis (2,4-di-t-butylphenyl) -4,4′-diphenylenediphosnite, 2,2′-methylenebis (4,6 -Di-t-butylphenyl) 2-ethylhexylphosphine 2,2'-ethylidenebis (4,6-di-t-butylphenyl) fluorophosphite, bis (2,4-di-t-butyl-6-methylphenyl) ethyl phosphite, 2- (2 , 4,6-tri-t-butylphenyl) -5-ethyl-5-butyl-1,3,2-oxaphosphorinane, 2,2 ′, 2 ″ -nitrilo [triethyl-tris (3,3 ′ , 5,5′-tetra-t-butyl-1,1′-biphenyl-2,2′-diyl) phosphite and the like.

The content of the propylene-based block copolymer contained in the propylene-based resin composition of the present invention is 70 to 95% by weight, and the content of the ethylene-α-olefin copolymer is 5 to 30% by weight. The content of the ethylene-α-olefin copolymer is preferably 10 to 25% by weight (that is, the content of the propylene-based block copolymer is 75 to 90% by weight). However, the content of the propylene block copolymer and the ethylene-α-olefin copolymer is based on 100% by weight of the total weight of the propylene resin composition.
When the content of the ethylene-α-olefin copolymer is less than 5% by weight, the impact resistance may be insufficient, and when it exceeds 30% by weight, the heat sealability may be insufficient.

The film of the present invention is a film comprising the propylene-based resin composition of the present invention, and preferably a retort food packaging film.
If necessary, a neutralizing agent, an ultraviolet absorber, an antistatic agent, a lubricant, an anti-blocking agent, a nucleating agent, and the like may be added to the retort food packaging film.
The neutralizing agent is preferably a hydrotalcite compound or calcium hydroxide from the viewpoint of preventing smoke during processing.

As a manufacturing method of the film of this invention, a well-known film manufacturing method is mentioned, For example, a T-die method, a tubular method, etc. are mentioned.
The method for producing an unstretched film is preferably a T-die method.
Film thickness is 10-250 micrometers normally, Preferably it is 30-150 micrometers.

  When manufacturing the film of the present invention, from the viewpoint of improving processability and reducing fish eyes, a metal filter having a filtration accuracy of 10 to 150 μm is overlapped from one to several hundreds on the tip of the extruder. The metal filter is preferably a filter composed of sintered fibers having a filtration accuracy of 40 to 80 μm.

  The retort food packaging film of the present invention may be subjected to surface treatment such as corona discharge treatment, flame treatment, plasma treatment, ozone treatment, etc., by a generally used method.

The retort food packaging film of the present invention may be used as at least one layer of a composite film and may be combined with other films.
Examples of other films include a polypropylene biaxially stretched film, a stretched nylon film, a stretched polyterephthalate film, and an aluminum foil.
Examples of the method of combining the retort food packaging film of the present invention with other films include a dry laminating method and an extrusion laminating method.
The use of the retort food packaging film of the present invention is preferably for heavy goods packaging.

Hereinafter, the present invention will be described with reference to examples and specific examples.
The measured value of each item of an Example and a comparative example was measured with the following method.
(1) Content of A component and B component (unit:% by weight)
From the material balance during polymerization of the A component and the B component, the content of the A component (PA) and the content of the B component (PB) were determined.

(2) Intrinsic viscosity ([η], unit: dl / g)
The measurement was performed in 135 ° C. tetralin using an Ubbelohde viscometer. Intrinsic viscosity of component A and component B ([η] _A , [η] _B )
Intrinsic viscosity [η] _A measured after completion of polymerization of component A in the first step, Intrinsic viscosity ([η] _AB ) measured after completion of polymerization in the second step, A component content (PA), B component From the content (PB), the intrinsic viscosity ([η] _B ) of the B component was determined by the following formula.
[Η] _A × (PA / 100) + [η] _B × (PB / 100) = [η] _AB

(3) Content of structural unit derived from ethylene contained in propylene-ethylene copolymer part (component B) (unit: wt%)
It was determined by the IR spectrum method according to the method described in the section of “(ii) Block copolymer” on pages 256 to 257 of Polymer Analysis Handbook (published by Asakura Shoten in 1985).

(4) Melt flow rate (MFR, unit: g / 10 minutes)
According to JIS K7210, it measured by the method of condition-14.

(5) 20 ° C. xylene soluble part (CXS, unit: wt%)
After 5 g of polypropylene was completely dissolved in 500 ml of boiling xylene, the temperature was lowered to 20 ° C. and left for 4 hours or longer. Thereafter, this was separated into a precipitate and a solution, and the filtrate was dried and dried at 70 ° C. under reduced pressure. The weight was measured to determine the content (% by weight).

(5) Molecular weight and molecular weight distribution P. C. (Gel permeation chromatography) was measured under the following conditions. The molecular weight distribution was evaluated by the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn).
Model: 150CV type (Millipore Waters)
Column: Shodex M / S 80
Measurement temperature: 145 ° C
Solvent: Orthodichlorobenzene Sample concentration: 5mg / 8mL
A calibration curve was prepared using standard polystyrene.

(5) Impact resistance (unit: kg · cm / mm)
At −15 ° C., the impact strength of the film was measured using a Toyo Seiki film impact tester and a hemispherical impact head having a diameter of 15 mm.

(6) Transparency (HAZE, unit:%)
It measured according to JIS K7105.

(7) Blocking resistance (unit: kg / 12cm ² )
Using a 150 mm x 30 mm film (collected so that the film forming direction and the long side direction coincide with each other), the films were overlapped, and a load of 500 g was applied to a range of 40 mm x 30 mm, and the state was maintained at 80 ° C for 24 hours. Adjustments were made. Thereafter, the sample was left in an atmosphere of 23 ° C. and 50% humidity for 30 minutes or more, peeled off at a rate of 200 mm / min using a tensile tester manufactured by Toyo Seiki, and the strength required for peeling the sample was measured.

(8) Heat seal strength (unit: kg / 15mm width)
Using a heat sealer manufactured by Toyo Tester Kogyo Co., Ltd., sealing was performed under the following conditions, and then the seal piece was cut into a width of 15 mm and measured using an orientec Tensilon at a peeling angle of 90 °.
[Seal conditions]
Seal bar: Double-sided flat surface heating Seal temperature: 200 ° C
Seal pressure: 1.0 kg / cm ²
Sealing time: 1.0 sec
Backing reinforcement: O-Ny (15 μm)

(9) Film appearance Visual evaluation was performed about the presence or absence of the fish eye of the obtained film. In the evaluation, the case where the fish eye was very large was evaluated as x, the case where the fish eye was relatively large was evaluated as Δ, and the case where the fish eye was small was evaluated as ○.

(10) n-hexane extract amount of pellets (unit: wt%)
A sheet of 25 mm × 25 mm × 100 μm was prepared by press molding at 180 ° C., and this was used as a test piece. The test piece was put in 400 ml of n-hexane adjusted to 50 ° C., and extracted for 2 hours while stirring. After completion of the extraction, the test piece was taken out from the n-hexane solution, and then the n-hexane was evaporated from the n-hexane solution, thereby obtaining the weight ratio of the component extracted into the n-hexane solution.

(11) n-hexane extract amount of film (unit:% by weight)
According to the method described in FDA 177.1520 (d) (3) (ii), the amount of n-hexane extracted from a film having a thickness of 70 μm was measured at 50 ° C.

The polymers used in the examples and comparative examples were as follows.
[Propylene-based block copolymer (1)]
The propylene homopolymer part (component A) is polymerized in the gas phase in the first step using a Ziegler-Natta type catalyst, and then the second step is a copolymer portion of propylene and ethylene (component B) in the gas phase. ) Was polymerized. The obtained copolymer has a component A content of 78% by weight, an intrinsic viscosity ([η] _A ) of 1.8 dl / g, a component B content of 22% by weight, and an intrinsic viscosity ([η] _B ) 3. The content of the structural unit derived from ethylene was 29% by weight and [η] _B / [η] _A was 1.95.
To 100 parts of the above block copolymer powder, 0.01 part by weight of calcium hydroxide, 0.2 part by weight of trade name Irganox 1010 (manufactured by Ciba Specialty Chemicals), and 2,5-dimethyl as a melt flow rate modifier. A suitable amount of -2,5-di (tertiary butyl peroxy) hexane was mixed with a Henschel mixer, and then melt-extruded and pelletized. The melt flow rate of the pellets measured at 230 ° C. was 3 g / 10 minutes.

[Propylene-based block copolymer (2)]
The propylene homopolymer part (component A) is polymerized in the gas phase in the first step using a Ziegler-Natta type catalyst, and then the second step is a copolymer portion of propylene and ethylene (component B) in the gas phase. ) Was polymerized. The resulting copolymer had a component A content of 75% by weight, an intrinsic viscosity ([η] _A ) of 1.8 dl / g, a component B content of 25% by weight, and an intrinsic viscosity ([η] _B ) 3. The content of the structural unit derived from ethylene was 41% by weight and [η] _B / [η] _A was 1.78.
As 100 parts of the above-mentioned block copolymer powder, 0.01 part of calcium hydroxide, 0.1 part of trade name Irganox 1010 (manufactured by Ciba Specialty Chemicals), 0.03 part of vitamin E, and a melt flow rate modifier An appropriate amount of 2,5-dimethyl-2,5-di (tertiary butyl peroxy) hexane was added and mixed with a Henschel mixer, and then melt-extruded and pelletized. The melt flow rate of the pellets measured at 230 ° C. was 3 g / 10 minutes.

[Polypropylene block copolymer (3)]
The propylene homopolymer part (component A) is polymerized in the gas phase in the first step using a Ziegler-Natta type catalyst, and then the second step is a copolymer portion of propylene and ethylene (component B) in the gas phase. ) Was polymerized. The obtained copolymer had an A component content of 79 wt%, an intrinsic viscosity ([η] _A ) of 2.7 dl / g, a B component content of 21 wt%, and an intrinsic viscosity ([η] _B ) of 2. The content of structural units derived from ethylene was 36% by weight, and [η] _B / [η] _A was 1.04.
100 parts of the above block copolymer powder, 0.05 part of calcium stearate, 0.05 part of vitamin E, and 2,5-dimethyl-2,5 di (tertiary butyl peroxy) hexane as a melt flow rate modifier After adding an appropriate amount, the mixture was mixed with a Henschel mixer and then melt-extruded to form pellets. The melt flow rate of the pellets measured at 230 ° C. was 2 g / 10 minutes.

(Propylene homopolymer (1))
Nobrene FS2011DG3 (trade name) manufactured by Sumitomo Chemical Co., Ltd. was used. The melt flow rate measured at 230 ° C. was 2.5 g / 10 minutes.

[Ethylene-α-olefin copolymer (1)]
Sumikacene E FV401 (trade name) manufactured by Sumitomo Chemical Co., Ltd., which is an ethylene-hexene-1 copolymer, was used. The melt flow rate measured at 190 ° C. was 4 g / 10 min, the density was 902 kg / m ³ , the molecular weight distribution (Mw / Mn) was 2.1, and the n-hexane extract was 2.0% by weight.

[Ethylene-α-olefin copolymer (2)]
Tafmer P0280 (trade name) manufactured by Mitsui Chemicals, Inc., which is a propylene-ethylene copolymer, was used. The melt flow rate measured at 190 ° C. was 2.9 g / 10 min, the density was 868 kg / m ³ , the molecular weight distribution (Mw / Mn) was 2.0, and the n-hexane extract amount was 88% by weight.

Example 1
90 mmφ extruder using a metal filter with a filtration accuracy of 40 μm, and a composition obtained by pellet blending 85 parts by weight of propylene-based block copolymer (1) and 15 parts by weight of ethylene-α-olefin copolymer (1), and Melting and kneading were performed using two 65 mmφ extruders, and the mixture was introduced into a feed block type T die (die width 1250 mm, lip opening 1.5 mm), and melt extrusion was performed at a die temperature of 240 ° C.
The extruded molten film was cooled and solidified with a chill roll having a cooling water temperature of 40 ° C. rotating at 50 m / min to obtain an unstretched film having a thickness of 70 μm. Table 1 shows the physical properties of the obtained film.

Example 2
In Example 1, the same procedure as in Example 1 was used, except that a composition obtained by pellet blending 85 parts by weight of propylene-based block copolymer (2) and 15 parts by weight of ethylene-α-olefin copolymer (1) was used. To obtain a film. Table 1 shows the physical properties of the obtained film.

Example 3
In Example 1, a composition obtained by pellet blending 85 parts by weight of a propylene-based block copolymer (3), 15 parts by weight of an ethylene-α-olefin copolymer (1) and 15 parts by weight of a propylene homopolymer (1) was prepared. A film was obtained in the same manner as in Example 1 except that it was used. Table 1 shows the physical properties of the obtained film.

Comparative Example 1
Example 1 was the same as Example 1 except that a composition obtained by pellet blending 85 parts by weight of a propylene-based block copolymer (1) and 3 parts by weight of an ethylene-α-olefin copolymer (2) was used. To obtain a film. Table 1 shows the physical properties of the obtained film.

Comparative Example 2
The same procedure as in Example 1 was used except that a composition obtained by pellet blending 85 parts by weight of the propylene-based block copolymer (1) and 15 parts by weight of the ethylene-α-olefin copolymer (2) was used. To obtain a film. Table 1 shows the physical properties of the obtained film.

It can be seen that Examples 1 to 3 satisfying the requirements of the present invention are films having good impact resistance at low temperatures, appearance, heat sealability, food hygiene and blocking resistance.
On the other hand, Comparative Example 1 using an ethylene-α-olefin copolymer that does not satisfy the density and the n-hexane extraction amount, which are the requirements of the present invention, has insufficient impact resistance. Shows that the heat sealability is insufficient, the amount of n-hexane extracted is large, and the food hygiene is insufficient.

Claims (3)

Ethylene-α-olefin copolymer 5 having a propylene-based block copolymer of 70 to 95% by weight, a density of 890 to 925 kg / m ³ and an n-hexane extraction amount of 0.01 to 2.6% by weight. Propylene-based resin composition containing -30% by weight (provided that the content of the propylene-based block copolymer and ethylene-α-olefin copolymer is based on 100% by weight of the total weight of the propylene-based resin composition) The amount of n-hexane extracted from the ethylene-α-olefin copolymer is based on 100% by weight of the total weight of the ethylene-α-olefin copolymer). The propylene block copolymer is a polymer part (component A) 50 to 90% by weight obtained by polymerizing a monomer mainly composed of propylene, and an ethylene-propylene copolymer part (component B) 10 to 50% by weight. A Ziegler-Natta type catalyst containing at least titanium, magnesium, and halogen as essential components (but based on 100% by weight of the total weight of the propylene-based block copolymer) The component A is produced in the first step, the component B is produced in the second step, and the content of the structural unit derived from ethylene contained in the component B is 10 to 60% by weight. (However, based on 100% by weight of the total weight of the B component), the intrinsic viscosity of the B component ([η] _B ) is 1.5 to 6 dl / g, and the intrinsic viscosity of the B component ([η] _B ) and The propylene-based resin composition according to claim 1, which is a propylene-based block copolymer having a ratio ([η] _B / [η] _A ) of intrinsic viscosity ([η] _A ) of the component _A of 0.5 to 3. object.   A film comprising the propylene-based resin composition according to claim 1.