JP2013112736A - Propylene polymer composition and application thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a propylene polymer composition suitable for obtaining a biaxially oriented film, which has sufficiently low temperature impact resistance even if the thickness of a heat seal film (a heat seal layer) is reduced, hardly causes reduction in heat seal strength even by heat treatment such as retort sterilization, and has excellent dropping bag breakage strength at low temperature after the heat treatment; and the biaxially oriented film having these properties.SOLUTION: The propylene polymer composition (E-2) includes: a specific amount of a propylene-α-olefin random copolymer (A-1) having the melting point (Tm2) within a range of 120-150°C; a propylene polymer (A-2) having the melting point (Tm3) within a range of 155-170°C; a propylene-α-olefin random copolymer (B-1) having limiting viscosity [η] of 2.0-10.0 dl/g; and an ethylene-α-olefin random copolymer (C) having a density within a range of 0.865-0.910 g/cm. The biaxially oriented film consisting of the propylene copolymer composition is also provided.

Description

  The present invention is excellent in transparency, rigidity, impact resistance, small decrease in heat seal strength even after heat treatment such as pressure and heat sterilization, and excellent drop bag breaking strength at low temperature after heat treatment The present invention relates to a propylene-based polymer composition suitable for obtaining a biaxially stretched film suitable for packaging such as a heated / sterilized package and the use thereof.

  In response to social changes such as aging, increasing the number of nuclear families, increasing the number of single employees, or increasing the number of working people, bags of pre-cooked foods are expected due to diversification of food culture, shortening of cooking time, and convenience. It is often used to purchase so-called retort food that has been sterilized under pressure and heat after it has been sealed in a container, and when necessary, heat the retort food together with the bag in hot water, take out the contents, and provide for meals. It has become like this. Such retort foods have begun to spread not only for general household use but also for business use. For this reason, a packaging material capable of packaging a large amount of food at once is required.

  Conventionally, for this application, a blend film of polypropylene and ethylene / α-olefin copolymer rubber, a polypropylene block copolymer film, or a blend film of the polypropylene block copolymer and ethylene / α-olefin copolymer rubber Etc. are used because of their excellent heat resistance and low temperature impact resistance. However, such a film still cannot be said to have a good balance between low-temperature impact resistance and blocking resistance, and heat seal strength tends to decrease after retorting.

  As a method for preventing a decrease in heat seal strength after retort treatment, for example, a propylene / α-olefin block copolymer composed of 95 to 70% by weight of a polypropylene block and 5 to 30% by weight of an elastomer block is used as a heat seal layer. (Patent Document 1: Japanese Patent Laid-Open No. 2000-255012). In addition, in order to improve the low temperature impact resistance, heat seal strength, heat resistance, etc. of the retort film, the intrinsic viscosity [η] of the paraxylene soluble part is 1.5 to 2.8 (dl / g). A composition in which 1 to 10% by weight of ethylene / α-olefin copolymer rubber is added to 90 to 99% by weight of an ethylene block copolymer has been proposed (Patent Document 2: JP 2000-119480 A).

  In addition, it has rigidity and low-temperature impact resistance, is excellent in blocking resistance and heat seal strength, and is suitably used for food packaging such as packaging materials for retort foods with little decrease in heat seal strength after heat treatment. A composition comprising a propylene polymer component (A), a propylene / α-olefin random copolymer component (B), and a random copolymer component (C) of ethylene and an α-olefin having 4 or more carbon atoms (patent) Document 3: Japanese Patent Laid-Open No. 2003-96251) has been proposed.

  Furthermore, as a propylene polymer component, a method using a propylene random copolymer having a melting point of 140 to 155 ° C. polymerized by a metallocene catalyst system has been proposed (Patent Document 4: JP 2009-84379 A). Yes.

  However, when these films are used for the heat-sealing layer of the retort film, it is necessary to maintain the drop bag breaking strength and the low-temperature impact resistance, so the thickness must be increased to 60 to 70 μm. The current situation is inferior in bending resistance (pinhole resistance).

  On the other hand, as an example of obtaining a thin film by biaxial stretching, a crystalline propylene / ethylene random copolymer component containing 10 mol% or less of units derived from ethylene and 10 to 40 mol% of units derived from ethylene Use of a propylene / ethylene random block copolymer containing a low crystalline or amorphous propylene / ethylene random copolymer component for a heat seal layer of a biaxially stretched polypropylene film (for example, Patent Document 5: Japanese Patent Laid-Open No. Hei 9- No. 227757 and Patent Document 6: Japanese Patent Laid-Open No. 2005-305767), the biaxially stretched film has a heat seal strength of 440 to 780 g / 15 mm (4.3 to 7.6 N / 15 mm). It is weak and cannot be used as a heat-sealing layer for a retort film. In recent years, there are cases where it is required to suppress the tearing of the bag due to a drop or the like during refrigerated transportation, and an improvement in the strength of the dropped bag at low temperatures is also desired.

  However, these patent documents merely show an example in which a film is produced, and does not mention the drop bag breaking strength after retorting.

JP 2000-255012 A JP 2000-119480 A JP 2003-96251 A JP 2009-84379 A JP-A-9-227757 JP 2005-305767 A

  The present invention is excellent in mechanical properties such as rigidity and transparency, has little decrease in heat seal strength even after heat treatment such as retort sterilization treatment, particularly excellent in drop bag breaking strength at low temperature after heat treatment, and blocking resistance It aims at obtaining the biaxially stretched film provided with the propylene-type polymer composition suitable for obtaining the biaxially stretched film which also has, and the said performance.

In the present invention, the propylene / α-olefin random copolymer (A-1) having a melting point (Tm2) in the range of 120 to 150 ° C is 10 to 70% by mass, and the melting point (Tm3) is in the range of 155 to 170 ° C. 10 to 40% by mass of a certain propylene polymer (A-2), and the content of the structural unit derived from propylene is 60 to 90% by mass (the total of the structural unit derived from propylene and the structural unit derived from α-olefin is 100% by mass) 1-25 mass% of propylene / α-olefin random copolymer (B-1) having an intrinsic viscosity [η] of 2.0-10.0 dl / g and a density of 0.865-0. 5 to 30% by mass of ethylene / α-olefin random copolymer (C), which is a random copolymer of ethylene and α-olefin having 4 or more carbon atoms in the range of 910 g / cm ³ [provided that (A-1) (A-2) + (B-1) + (C) = a 100 wt%. ] The propylene copolymer composition (E-2) characterized by the above, the biaxially stretched film obtained from the said composition, and its use.

  The propylene copolymer composition (E-2) of the present invention is excellent in mechanical properties such as transparency and rigidity, blocking resistance, excellent low-temperature heat-sealability, and heat by biaxially stretching the composition. High fusing strength, less decrease in heat seal strength after heat treatment (pressurization / heat treatment), and excellent bag drop strength when made into bags, especially drop bag breaking strength at low temperatures after heat treatment A biaxially stretched film is obtained.

<Propylene / α-olefin random copolymer (A-1)>
The propylene / α-olefin random copolymer (A-1), which is one of the polymer components contained in the propylene copolymer composition (E-2) of the present invention, generally has 90 units derived from propylene. A propylene / α-olefin random copolymer containing ˜98 mass%, preferably 92-98 mass%.

  The α-olefin that is a copolymer component constituting the propylene / α-olefin random copolymer (A-1) is usually an α-olefin having 2 to 10 carbon atoms other than propylene, such as ethylene, 1-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene and 1-octene, preferably ethylene and 1-butene In particular, ethylene is preferred.

  The propylene / α-olefin random copolymer (A-1) according to the present invention usually has an MFR (load: 2160 g, temperature: 230 ° C.) of 0.5 to 50 g / 10 minutes, preferably 2 to 50 g / 10. Minutes. When the MFR is in the above range, the propylene copolymer composition (E-2) can be easily formed into a biaxially stretched film, and a biaxially stretched film excellent in low-temperature impact strength can be obtained. For example, a material having an MFR in the range of 20 to 50 g / 10 minutes, particularly 20 to 40 g / 10 minutes may be used.

  The propylene / α-olefin random copolymer (A-1) according to the present invention has a melting point (Tm2) in the range of 120 to 150 ° C, preferably 130 to 147 ° C. When the melting point is in the above range, a biaxially stretched film having an excellent balance of heat seal strength, rigidity and bag drop impact strength can be obtained.

  When a propylene copolymer having a melting point (Tm2) of less than 120 ° C. is used, it may be difficult to form a biaxially stretched film. On the other hand, when a propylene copolymer having a melting point exceeding 150 ° C. is used, when the composition containing the copolymer is biaxially stretched, a biaxially stretched film having sufficient impact strength and falling bag strength is obtained. There is a risk of not being able to.

  The propylene / α-olefin random copolymer (A-1) according to the present invention can be produced using an olefin polymerization catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. As an example of a Ziegler-Natta catalyst, an active magnesium compound, a titanium compound, a halogen compound, and a solid titanium catalyst component having an internal electron donor as essential components are supported on an organic or inorganic carrier, and the periodic table groups I to 1 are included therein. Examples include a catalyst system in which an organometallic compound component of a Group III metal is added and an external electron donor is further added.

<Propylene polymer (A-2)>
The propylene polymer (A-2), which is one of the polymer components contained in the propylene copolymer composition (E-2) of the present invention, is usually a propylene homopolymer or a C2-C10 polymer. A polymer containing a unit derived from an α-olefin is usually 5.0% by mass or less, preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and a propylene homopolymer is particularly preferable.

  The α-olefin which is a copolymerization component of the propylene polymer (A-2) is usually an α-olefin having 2 to 10 carbon atoms other than propylene, such as ethylene, 1-butene and 3-methyl-1 -Butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene and 1-octene, ethylene and 1-butene are preferable, and ethylene is particularly preferable.

  The propylene polymer (A-2) according to the present invention usually has an MFR (load: 2160 g, temperature: 230 ° C.) of 0.5 to 50, preferably 2 to 50. When the MFR is in the above range, the propylene copolymer composition (E-2) can be easily formed into a biaxially stretched film, and a biaxially stretched film excellent in impact strength can be obtained. For example, an MFR having a range of 2 to 20 g / 10 min, preferably 2 to 10 g / 10 min may be used.

The propylene polymer (A-2) according to the present invention has a melting point (Tm3) of 155 to 170 ° C, preferably 158 to 167 ° C.
When a propylene copolymer having a melting point (Tm3) of less than 155 ° C. is used, the heat resistance of the biaxially stretched film may be reduced.

  The propylene polymer (A-2) according to the present invention can be produced using an olefin polymerization catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. As an example of a Ziegler-Natta catalyst, an active magnesium compound, a titanium compound, a halogen compound, and a solid titanium catalyst component having an internal electron donor as essential components are supported on an organic or inorganic carrier, and the periodic table groups I to 1 are included therein. Examples include a catalyst system in which an organometallic compound component of a Group III metal is added and an external electron donor is further added.

<Propylene / α-olefin random copolymer (B-1)>
The propylene / α-olefin random copolymer component (B-1), which is one of the polymer components contained in the propylene copolymer composition (E-2) of the present invention, usually has units derived from propylene. 60-90% by mass, preferably 60-89% by mass, more preferably 61-82% by mass, and even more preferably 65-79% by mass of a propylene / α-olefin random copolymer (provided that propylene The total of the unit derived from the unit derived from α-olefin and the unit derived from the α-olefin is 100% by mass).

  When the unit derived from propylene is in the above range, the drop bag breaking strength after the retort treatment is good. And when the amount of units derived from propylene is low, the incompatibility with the matrix increases, so it is considered that when the biaxially stretched film is retorted, for example, the elastomeric component tends to enlarge. It is considered more advantageous.

  The propylene / α-olefin random copolymer component (B-1) according to the present invention is usually an amorphous or low crystalline copolymer, and usually has no melting point or a melting point of less than 120 ° C. It is a copolymer.

  The α-olefin which is a copolymer component constituting the propylene / α-olefin random copolymer (B-1) according to the present invention is usually an α-olefin having 2 to 10 carbon atoms other than propylene, For example, ethylene, 1-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, ethylene and 1 -Butene is preferred, especially ethylene.

  The propylene / α-olefin random copolymer (B-1) according to the present invention usually has an intrinsic viscosity [η] measured at 135 ° C. in a decalin solvent of 2.0 to 10.0 dl / g, preferably 2. It is a copolymer in the range of 3 to 9.0 dl / g, more preferably 2.5 to 8.0 dl / g. Within this range, the drop bag breaking strength at a low temperature after the retort treatment is good. If in this range, incompatibility with the matrix is particularly increased, when the biaxially stretched film is retorted, it is considered that, for example, the elastomeric component tends to be enlarged, and this point is considered more advantageous. . Furthermore, when the heat seal strength after the retort treatment is used for a particularly required application, the intrinsic viscosity [η] is more preferably 4.0 dl / g or more.

  The propylene polymer (B-1) according to the present invention can be produced using an olefin polymerization catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. As an example of a Ziegler-Natta catalyst, an active magnesium compound, a titanium compound, a halogen compound, and a solid titanium catalyst component having an internal electron donor as essential components are supported on an organic or inorganic carrier, and the periodic table groups I to 1 are included therein. Examples include a catalyst system in which an organometallic compound component of a Group III metal is added and an external electron donor is further added.

<Ethylene / α-olefin random copolymer (C)>
The ethylene / α-olefin random copolymer (C), which is one of the polymer components contained in the propylene copolymer composition (E-2) of the present invention, has a density of 0.865 to 0.910 g / cm. ³ , preferably a copolymer in the range of 0.875 to 0.900 g / cm ³ , and a random copolymer of ethylene and an α-olefin having 4 or more carbon atoms, preferably 4 to 10 carbon atoms. Specific examples of α-olefins include 1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-tetradecene and 1-octadecene. Can do. Among these, 1-butene, 1-hexene, and 1-octene are particularly preferable. These α-olefins may be used alone or in combination of two or more. It may also be a mixture with different ethylene / α-olefin random copolymers.

  Specific examples of the preferred copolymer include an ethylene / 1-butene random copolymer, an ethylene / 1-hexene random copolymer, and an ethylene / 1-octene random copolymer.

  The ethylene / α-olefin random copolymer (C) according to the present invention usually has an MFR (load: 2160 g, temperature: 230 ° C.) of 0.5 to 10 g / 10 min, preferably 0.5 to 7. 0 g / 10 min.

  The ethylene / α-olefin random copolymer (C) according to the present invention usually has a melting point of 100 ° C. or lower or does not exist, and when a melting point is present, the upper limit is preferably 90 ° C. Although there is no particular limitation, for example, 40 ° C., and further 60 ° C. can be exemplified.

  The ethylene / α-olefin random copolymer (C) according to the present invention can be produced using an olefin polymerization catalyst such as a Ziegler-Natta catalyst (such as a vanadium catalyst) or a metallocene catalyst.

<Propylene copolymer composition (E-2)>
The propylene copolymer composition (E-2) of the present invention comprises the propylene / α-olefin random copolymer (A-1) in an amount of 10 to 70% by mass, preferably 15 to 65% by mass, and the propylene polymer. (A-2) is 10 to 40% by mass, preferably 10 to 35% by mass, and the propylene / α-olefin random copolymer (B-1) is 1 to 25% by mass, preferably 2 to 20% by mass, And the ethylene / α-olefin random copolymer (C) in an amount of 5 to 30% by mass, preferably 10 to 25% by mass [However, (A-1) + (A-2) + (B-1) + (C ) = 100 mass%. The amount of (A-1) + (A-2) is not particularly limited, but is preferably 50 to 90% by mass, more preferably 55 to 85% by mass, and still more preferably 60 to 80% by mass. It is a composition containing.

  One of the preferable embodiments of the propylene copolymer composition (E-2) of the present invention is the propylene / α-olefin random copolymer (A-1) in an amount of 10 to 70% by mass, and the propylene polymer (A-2). -2) 10 to 40% by mass, 1 to 25% by mass of the propylene / α-olefin random copolymer (B-1), and 5 to 30% of the ethylene / α-olefin random copolymer (C). Mass [However, (A-1) + (A-2) + (B-1) + (C) = 100 mass%. Moreover, (A-1) + (A-2) is an aspect which is 55-85 mass%.

  One of the more preferable embodiments of the propylene copolymer composition (E-2) of the present invention is the propylene / α-olefin random copolymer (A-1) 15 to 65% by mass, the propylene polymer ( 10 to 35% by mass of A-2), 2 to 20% by mass of the propylene / α-olefin random copolymer (B-1), and 10 to 10% of the ethylene / α-olefin random copolymer (C). 25% by mass [However, (A-1) + (A-2) + (B-1) + (C) = 100% by mass) Moreover, (A-1) + (A-2) is 55-85 mass%. It is a composition containing.

  One of the more preferable embodiments of the propylene copolymer composition (E-2) of the present invention is the propylene / α-olefin random copolymer (A-1) in an amount of 15 to 65% by mass, and the propylene polymer ( 10 to 35% by mass of A-2), 2 to 20% by mass of the propylene / α-olefin random copolymer (B-1), and 10 to 10% of the ethylene / α-olefin random copolymer (C). 25% by mass [However, (A-1) + (A-2) + (B-1) + (C) = 100% by mass) Moreover, (A-1) + (A-2) is 60-80 mass%. It is a composition containing.

  The propylene copolymer composition (E-2) of the present invention is usually in the range of 120 to 155.0 ° C., preferably 130 to 155.0 ° C., and a propylene / α-olefin random copolymer (A- It has a melting peak (Tp2) based on 1) and a melting peak (Tp3) based on the propylene polymer (A-2) in the range of 155.1 to 167 ° C, preferably 158 to 165 ° C.

  A composition having a propylene / α-olefin random copolymer (A-1) of less than 10% by mass may be inferior in impact strength when formed into a biaxially stretched film, while a composition having more than 70% by mass is When the biaxially stretched film is used, the blocking resistance may be inferior.

  When the composition having a propylene polymer (A-2) of less than 10% by mass is made into a biaxially stretched film, the anti-blocking property may be inferior. On the other hand, a composition having more than 40% by mass is a biaxially stretched film. In such a case, heat sealability and impact strength may be inferior.

Further, the propylene · alpha-olefin random copolymer the amount of _{(A-1) W A-} 1, propylene polymer the amount of (A-2) in the case of the _{W A-2, W A-} 1 / ( The value of W _A-1 + W _A-2 ) is preferably 0.5 or more, and more preferably 0.6 or more.

  A composition containing less than 1% by mass of the propylene / α-olefin random copolymer (B-1) may be inferior in impact strength when formed into a biaxially stretched film, while a composition exceeding 25% by mass is When the biaxially stretched film is used, the transparency may be inferior.

  A composition having an ethylene / α-olefin random copolymer (C) of less than 5% by mass may be inferior in impact strength when a biaxially stretched film is used. When an axially stretched film is used, the transparency may be inferior.

  The incompatible composition (polymer blend or block copolymer) generally has a sea-island structure (cluster structure), and the propylene / α-olefin random copolymer (A-1) in the composition of the present invention and It is considered that ethylene / α-olefin random copolymer (C) and propylene / α-olefin random copolymer (B-1), which are elastomer components, are dispersed as domains in the matrix of propylene polymer (A-2). Form the morphology It is known that an aspect having a certain dispersion diameter has a better impact resistance balance than a so-called compatibilized state where the domain is not observed or a dispersion diameter is very small. In particular, the tendency is prominent at low temperatures.

  The inventors of the present invention using the propylene / α-olefin random copolymer (A-1) and the propylene polymer (A-2) having such a sea-island structure, for example, 5 times in length. When the dispersed particle diameter of the film obtained by biaxial stretching 10 times in width was observed, it was found that the dispersion diameter was finely dispersed to a degree of submicron or less (dispersion diameter before stretching was several microns). . Surprisingly, the packaging bag using a laminated film with the biaxially stretched film as the innermost layer (heat-sealing layer) has a dramatic impact resistance (drop bag breaking strength) at low temperatures after retorting. Improvement was observed. According to the morphology observation of the heat-sealing layer, the dispersed particle size was close to a micron level. It is considered that the aforementioned submicron dispersed particles aggregated during the retort processing. At this time, when the melting point of the propylene / α-olefin random copolymer (A-1) used as the matrix component is within the range of the present invention, the retort processing temperature has higher mobility of the elastomeric component, This component tends to aggregate and may lead to an improvement in the impact resistance balance. This is one of the presumed reasons why the effect appears within the scope of the present invention.

  In addition, the lower the compatibility with the propylene / α-olefin random copolymer (A-1) and the propylene polymer (A-2), for example, the elastomeric component having a higher ethylene content, the dispersion diameter is relatively larger at the time of stretching. Therefore, it is considered that it is easy to form a structure suitable for developing a drop strength at a low temperature after retorting a film obtained by biaxially stretching the composition.

In the propylene copolymer composition (E-2) of the present invention, MFR [load: 2160 g, temperature: 230 ° C.] is not particularly limited, but is normal. It is 2 to 15 g / 10 minutes, preferably 2 to 10 g / 10 minutes. By setting MFR within the above range, a biaxially stretched film can be easily formed, and a biaxially stretched film excellent in impact strength and heat seal strength can be obtained.
MFR (MFR _{A-1 + A-2} ) of the composition obtained by blending the component (A-1) and the component (A-2) according to the existing ratio in the composition, and the component (B) MFR (MFR _{B + C} ) of the composition obtained by blending the component (C) according to the existing ratio in the composition is (MFR _{A-1 + A-2} ) / MFR (MFR _{B + C} ) is preferably 6 to 50, more preferably 12 to 50, and still more preferably 20 to 50. When it exists in this range, the blocking resistance of a film can be improved especially.

<Method for producing propylene copolymer composition (E-2)>
The propylene copolymer composition (E-2) of the present invention comprises the propylene / α-olefin random copolymer (A-1), the propylene polymer (A-2), and the propylene / α-olefin random copolymer. A method of mixing the polymer (B-1) and the ethylene / α-olefin random copolymer (C) within a desired range, two or more of these components, for example, (A-1) and ( A-2) and (B), (A-2) and (B), (A-1), (A-2) and (B) are prepared in advance, and then the remaining components Can be produced by a blending method.

  For example, when a composition comprising two or more components as described above is produced in advance, it may be melt-mixed according to a conventional method, or may be produced by so-called multistage polymerization in which different components are polymerized at different stages. good. For example, in the case of producing a composition of (A-1) and (B), (A-2) and (B), (A-1), (A-2) and (B), so-called multistage polymerization is used. It is also possible to produce a block copolymer. The multistage polymerization may be performed in one polymerization vessel, or each step may be performed using a plurality of polymerization vessels. The plurality of polymerization vessels may be used in parallel or in series.

  These (A-1), (A-2), (B) and (C) are mixed by a method of removing two or more of these in advance and then removing the solvent, if necessary. Further, the composition according to the present invention may be produced by melt-kneading together with other components.

  Further, in some cases, the composition according to the present invention supplies each component constituting the composition according to the present invention or a mixture of two or more components and the remaining components to the material supply portion of the molding machine. Then, the composition may be prepared at the kneading part of the molding machine and molded as it is.

<Additives>
In the propylene copolymer composition (E-2) according to the present invention, a propylene / α-olefin random copolymer (B-1) and an ethylene / α-olefin random copolymer (C) are optionally added. Elastomer components other than) can be added. Examples of such elastomer components include ethylene / propylene / diene copolymer rubber, ethylene / 1-butene / diene copolymer rubber, propylene / 1-butene copolymer rubber, styrene / butadiene block copolymer or styrene / isoprene block. Mention may be made of hydrogenated products of copolymers.

  Moreover, in each polymer which comprises the propylene copolymer composition (E-2) or the propylene copolymer composition (E-2) according to the present invention, within a range not impairing the object of the present invention, Antioxidants, heat stabilizers, lubricants, antistatic agents, hydrochloric acid absorbents, antiblocking agents, slip agents, nucleating agents, pigments, dyes, or various polymers may be blended.

  Examples of the antioxidant include a phenolic antioxidant, an organic phosphite antioxidant, a thioether antioxidant, a hindered amine antioxidant, and the like. Examples of the antiblocking agent include aluminum oxide, fine powder silica, polymethyl methacrylate powder, and silicon resin.

Examples of the slip agent include bisamides such as ethylene bisstearamide, higher fatty acid amides such as oleic acid amide and erucic acid amide. Examples of the lubricant include higher fatty acid metal salts such as calcium stearate, zinc stearate, and metal montanate, and polyolefin waxes such as polyethylene wax and polypropylene wax. Examples of the nucleating agent include rosin nucleating agents such as dibenzylidene sorbitol and partial metal salts of rosin acid, aluminum nucleating agents, and talc.
The composition of the present invention can be molded and used by various molding methods such as melt molding.

<Biaxially stretched film>
The biaxially stretched film of the present invention is the propylene copolymer composition (E-2) or a biaxially stretched film, and usually has a thickness of 5 μm or more, preferably 5 to 55 μm, more preferably 10 It is in the range of ˜50 μm. A film having a thickness of less than 5 μm may be a packaging material having insufficient bag drop strength when used for a heat-sealing layer.

  The upper limit of the thickness of the biaxially stretched film of the present invention is not particularly limited, but a film exceeding 50 μm has the cost advantage of maintaining its heat seal performance and bag breaking strength performance and being thin. May fade.

The biaxially stretched film of the present invention can be a film having a thickness of 50 to 100 μm depending on the application.
As long as the biaxially stretched film of the present invention is composed of the propylene copolymer composition (E-2), it may be a single layer or a multilayer of two or more layers.

  For example, when the biaxially stretched film has a three-layer configuration, the thickness of the inner layer is usually 50 to 99% of the total thickness, and the thickness of both surface layers is 0.5 to 25% of the total thickness, respectively. Thickness. The thickness of the surface layer is preferably 0.5 to 15 μm, particularly 1 to 10 μm.

Thus, when the biaxially stretched film is a multilayer, quality control is easy, the final yield is increased, and there is a cost advantage.
In addition, the surface of the biaxially stretched film of the present invention may be subjected to surface treatment such as corona treatment or flame treatment on one side or both sides as necessary in order to improve the adhesion to the base material layer.

  When the biaxially stretched film of the present invention is used as a packaging material, physical properties such as heat seal strength of the film layer (peel strength of the heat seal portion), peel strength retention after heat treatment under high temperature and high pressure, The balance with drop bag breaking strength at low temperature after heat treatment is remarkably excellent. Therefore, it is suitable as a film for retort food packaging. Further, it tends to be excellent in blocking resistance. Furthermore, the biaxially stretched film of the present invention has a small thermal shrinkage rate, that is, excellent dimensional stability during heating.

<Method for producing biaxially stretched film>
In the present invention, the biaxially stretched film can be formed from the propylene copolymer composition (E-2) using a known biaxially stretched film forming method.

For biaxial stretching, methods such as sequential biaxial stretching, simultaneous biaxial stretching, and multistage stretching are appropriately employed.
As conditions for biaxial stretching, known biaxially stretched film production conditions, for example, in the sequential biaxial stretching method, the longitudinal stretching temperature ranges from 100 ° C. to 145 ° C., the stretching ratio ranges from 4 to 7 times, and the transverse stretching temperature. Of 150 to 190 ° C. and a draw ratio of 8 to 11 times.

<Multilayer biaxially stretched film>
The multilayer biaxially stretched film of the present invention is a film obtained by laminating a base material layer on one side of the biaxially stretched film.

  The substrate layer is not particularly limited as long as it can be used as a packaging material in the form of a sheet, film, tray or container. Examples of the base material layer include polyethylene terephthalate, a film made of polyester represented by polyethylene naphthalate, a polycarbonate film, a polyamide film made of nylon 6, nylon 66, etc., an ethylene / vinyl alcohol copolymer film, a polyvinyl alcohol film, a poly Thermoplastic resin films such as vinyl chloride films, polyvinylidene chloride films, and films made of polyolefins such as polypropylene, or sheets made of these thermoplastic resins, as well as trays or cup-shaped containers thermoformed from sheets, aluminum foil, Examples of those shapes are paper.

  The base material layer made of a thermoplastic resin film may be an unstretched film or a uniaxially or biaxially stretched film. Of course, the base material layer may be one layer or two or more layers. The thermoplastic resin film may be a film in which a metal such as aluminum, zinc or silica, an inorganic material, or an oxide thereof is deposited.

  As a method for laminating the biaxially stretched film (for retort packaging) and the base material layer according to the present invention, a generally performed laminating method can be employed as it is, and in that case (for retort packaging) biaxially stretched film. An adhesive layer can be provided between the substrate layer and the substrate layer. For example, a urethane-based or isocyanate-based anchor coating agent is applied to the base material layer, and the biaxially stretched film (for retort packaging) of the present invention is dry laminated thereon, or the biaxially stretched film (for retort packaging) It can also be produced by a method of extrusion lamination or extrusion coating of a thermoplastic resin as a base material layer.

  The multilayer biaxially stretched film of the present invention has a high heat seal strength (peel strength at the heat seal portion) of the film layer when used as a packaging material, and is at least 20 N / h, for example, even after heat treatment under high temperature and high pressure. Since it has a peel strength of 15 mm, it is suitable as a retort food packaging film. Moreover, the drop bag breaking strength at low temperature after heat treatment is remarkably excellent. Further, it tends to be excellent in blocking resistance.

  In other words, when the multilayer biaxially stretched film of the present invention is used as a packaging material, the heat seal strength of the film layer (peel strength of the heat seal part), the peel strength retention after heat treatment under high temperature and high pressure, etc. The balance between the physical properties of the film and the strength of dropped bag breakage at low temperatures after heat treatment is remarkably excellent. Therefore, it is suitable as a film for retort food packaging. Further, it tends to be excellent in blocking resistance.

  The multilayer biaxially stretched film of the present invention has heat resistance, low temperature impact strength, high heat seal strength, rigidity, etc. by using the biaxially stretched film as a heat-sealing layer (heat seal layer). Depending on the type of the base material layer, high gas barrier properties, mechanical strength, and the like are imparted, and therefore it is suitable as a medicine for heat sterilization or pressure / heat sterilization, or as a film for packaging retort food. The multilayer biaxially stretched film of the present invention can be used as a packaging material in a film state, or can be used as a packaging material after changing to the shape of a tray or a container.

<Packaging for heat sterilization>
The packaging body for heat sterilization according to the present invention uses the packaging material comprising the biaxially stretched film or multilayer biaxially stretched film of the present invention, and when the multilayer biaxially stretched film is used, the biaxially stretched film layer faces inside. The contents are sealed and packaged by packaging (filling) a medicine or food (a material to be packaged) as a product and heat-sealing the biaxially stretched film layer.

  The packaging material may be a biaxially stretched film, but is preferable because the multilayer biaxially stretched film described above can utilize the characteristics of the base material layer. Moreover, when using as a package for heat sterilization, the said base material layer is normally laminated | stacked on the single side | surface of the biaxially stretched film. Examples of the multilayer biaxially stretched film include the following combinations.

  Polyester layer / biaxially stretched film, polyamide layer / biaxially stretched film, polyester layer / polyamide layer / biaxially stretched film, polyester layer / aluminum foil / biaxially stretched film, polyester layer / polyamide layer / aluminum foil / biaxially stretched Examples include films, polyamide layers / polyvinylidene chloride layers / polyester layers / biaxially stretched films, and the like.

  Thus, since the biaxially stretched film layer is arranged in the innermost layer to form the heat seal portion, the package is firmly heat sealed, and after the heat sterilization, pressure / heat sterilization treatment In addition, the drop bag breaking strength at a low temperature is excellent, and a high heat seal strength is maintained. Therefore, such a package for heat sterilization is less likely to cause leakage of food contents, for example, when transported at low temperatures or handled in stores or at home, etc., and at room temperature or under refrigeration / freezing. Even if it is stored for a long period of time, the contents can be kept almost unchanged.

EXAMPLES Next, although an Example demonstrates this invention in detail, this invention is not restrict | limited at all by those Examples.
In addition, the physical property value which shows the property of a polymer and a composition, and the physical property value for evaluating a film were calculated | required by the test method described below.

(1) Method for measuring physical properties of polymer and composition <Propylene / α-olefin random copolymer (A-1), Propylene polymer (A-2), Propylene / α-olefin random copolymer (B-1) ) Composition determination method>
Using an ECX400P nuclear magnetic resonance apparatus manufactured by JEOL Ltd., the composition was determined under the following conditions.

Solvent: orthodichlorobenzene / heavy benzene (80/20 vol%) mixed solvent,
Sample concentration: 60 mg / 0.6 mL, measurement temperature: 120 ° C.,
Observation nucleus: ¹³ C (100 MHz),
Sequence: single pulse proton decoupling,
Pulse width: 4.7 μsec (45 ° pulse),
Repeat time: 5.5 seconds,
Integration count: 8,000 times or more,
33.12 ppm of the methine carbon signal (in propylene units) of the ethylene-propylene-ethylene chain, or 128 ppm of heavy benzene carbon when this was difficult to confirm.

The attribution of the peak is
Macromolecules, 11 (1) , 33 (1978), which is a literature on propylene / ethylene copolymer analysis
Macromolecules, 15 (2) , 353 (1982), which is a literature on ethylene / butene copolymers
Macromolecules, 11 (3) , 592 (1978), which is a literature on propylene / butene copolymers
Based on
Based on this, the composition ratio of the copolymer was determined from the absorption intensity ratio of each peak.

<Intrinsic viscosity [η]>
Using a Ubbelohde viscometer, a polymer sample of the propylene / α-olefin random copolymer (B-1) is dissolved in decalin, the viscosity of the solution is measured at 135 ° C., and the intrinsic viscosity [η ] (Dl / g) was determined.

<Melt flow rate (MFR)>
Based on ASTM D-1238, the measurement was performed under the conditions of 230 ° C. and a load of 2.16 kg.
<Melting point (Tm)>
The melting point (Tm) (° C.) of the polymer was determined by performing measurement under the following measurement conditions using a differential scanning calorimeter [DSC, manufactured by Perkin Elmer, Inc. (Diamond DSC)] in accordance with JIS K7121. . In addition, the peak of the endothermic peak in the third step when the measurement was performed under the following measurement conditions was defined as the melting point (Tm). In the case where there are a plurality of endothermic peaks, the peak of the endothermic peak where the peak height is maximum was taken as the melting point (Tm).
Moreover, the melting peak of the composition was defined as a plurality of endothermic peaks when measured under the following conditions as melting peak (Tp).

(Measurement condition)
Measurement environment: Nitrogen gas atmosphere Sample amount: About 5 mg is precisely weighed.
Sample shape: Press film (press molding at 230 ° C., thickness: 200 to 400 μm)
Sample pan: Sample pan made of aluminum with a flat bottom First step: Temperature is raised from 30 ° C. to 240 ° C. at 10 ° C./min, and held for 10 minutes.
Second step: Decrease in temperature to 30 ° C. at 10 ° C./min.
Third step: The temperature was raised to 240 ° C. at 10 ° C./min.

(2) Measuring method of film physical properties The following measurements were performed using a biaxially stretched film of a propylene copolymer composition having a thickness of 40 μm.

<Haze:%>
Measured according to ASTM D-1003.
<Elastic modulus: MPa>
A strip-shaped test piece of 15 mm width and 200 mm length is cut out from a biaxially stretched film so that the length direction is the film flow direction (MD) and the width direction (TD), and Tensilon RT1225 type manufactured by Orientec is used. Then, the elastic modulus was measured according to JISK7127.

<Tear strength: g / per sheet>
Using a light-load tear tester (manufactured by Toyo Seiki Seisakusho), a rectangular test piece with a length of 63.5 mm (long side) in the tear direction and a width of 50 mm (short side) perpendicular to the tear direction from the biaxially stretched film Was cut, a 12.7 mm cut was made in the center of the short side, and a tear test was performed to determine the tear strength (g / sheet).

<Heat shrinkage:%>
A 100 mm wide square test piece was cut out from the biaxially stretched film and allowed to stand in an oven at 120 ° C. for 15 minutes. Thereafter, the test piece was taken out from the oven and allowed to stand at an ambient temperature of 23 ° C. for 30 minutes or longer, and then the length of each side of the square test piece was measured and used as the amount of change. The thermal contraction rate was calculated from the following formula.
Heat shrink value = (100−A) / 100 × 100
A: Length of the side of the square after standing in the oven

<Impact strength: kg · cm>
Using a film impact tester manufactured by Toyo Seiki Seisakusho, using a 0.5 inch diameter hemisphere at the tip, cutting out a 100 mm square test piece from a biaxially stretched film, and impact strength at an ambient temperature of 23 ° C Was measured.

<Blocking resistance: N>
A strip-shaped test piece having a width of 20 mm and a length of 100 mm was cut out from the biaxially stretched film so that the length direction was the film flow direction (MD) and the width direction (TD), and the seal surfaces were overlapped. A load of 250 g / cm ² was applied to the overlapped portion, and the plate was left in an oven at 55 ° C. for 24 hours. After standing, the shear peel strength was measured at room temperature using Tensilon RT1225 manufactured by Orientec.

(3) Physical property measurement method of multilayer biaxially stretched film <Heat seal strength>
A biaxially stretched polyethylene terephthalate film (thickness: 12 μm), a biaxially stretched polyamide film (thickness: 15 μm), and a biaxially stretched film (heat fusion layer) are available as multilayer biaxially stretched films used for heat seal strength measurement. After laminating the biaxially stretched polyethylene terephthalate film and the biaxially stretched polyamide film using a laminating machine, the corona-treated surface of the biaxially stretched film is placed on the biaxially stretched polyamide film side. To obtain a laminated film. The laminated film is a biaxially stretched polyethylene terephthalate film / biaxially stretched polyamide film / biaxially stretched film (heat fusion layer).

  Using a Toyo Seiki heat seal tester, cut out a test piece with a width of 100 mm and a length of 150 mm from the laminated film, fold it in half, the heater is 180 ° C to 230 ° C, the pressure is 0.2 MPa, and the sealing time is 1 second. After performing heat sealing, the sealed test piece was cut into a test piece having a width of 15 mm, and peel strength was measured using Tensilon RT1225 manufactured by Orientec.

  On the other hand, the heat seal strength after retort sterilization was measured by the following method. That is, the test piece prepared by the above method was placed in a hot water shower type high-pressure and high-temperature sterilization treatment apparatus, treated at 121 ° C. for 30 minutes, and then cooled. Next, the heat seal strength (N / 15 mm) was measured by the same method as described above.

<Bag drop strength>
A biaxially stretched polyethylene terephthalate film (thickness: 12 μm), a biaxially stretched polyamide film (thickness: 15 μm), and a biaxially stretched film (heat-bonding layer) are prepared as multilayer biaxially stretched films used in the falling bag test. After laminating a biaxially stretched polyethylene terephthalate film and a biaxially stretched polyamide film using a laminating machine, the corona-treated surface of the biaxially stretched film is placed on the biaxially stretched polyamide film side using a laminating machine. A laminated laminate film was obtained. The laminated film is a biaxially stretched polyethylene terephthalate film / biaxially stretched polyamide film / biaxially stretched film (heat fusion layer).

  The anchor agent used was a mixture of Takelac A310, Takenate A3 (Mitsui Chemicals) and ethyl acetate (Made by Wakashima Pure Chemicals) as a solvent. The obtained laminated film was used inside a packaging bag, and a three-side sealed bag having a longitudinal direction of 175 mm and a lateral direction of 125 mm was prepared using a bag making machine. The seal width is 10 mm. The prepared three-sided seal bag was filled with 200 ml of water, air was released, and the mouth was sealed.

After 20 such bags were prepared and allowed to stand in an atmosphere of 5 ° C. for 24 hours, a single bag was dropped from a height of 100 cm so that the horizontal direction would be the drop direction, similar to the bag size. One set of drops from the surface part with a weight of 500 g of a large size was repeated, and the drop was repeated up to 20 sets, and the number of times until bag breaking was counted. The number of times until 20 bags were broken was averaged, and the average value was defined as the average number of broken bags.
The polymers used in Examples and Comparative Examples of the present invention are shown below.

(1) Propylene / α-olefin random copolymer (A-1)
As propylene / α-olefin random copolymer (A-1), propylene / ethylene / 1-butene random copolymer (a-1-4) produced with a solid Ti catalyst [MFR: 32 g / 10 min, ethylene / 1-butene content: 2.3 / 2.0 mass%, melting point (Tm2) measured by DSC: 137 ° C.], propylene / ethylene random copolymer (a-1- 1) [MFR: 2.3 g / 10 min, content of units derived from ethylene: 2.6 mass%, melting point: 145 ° C.], and propylene / ethylene random copolymer (a-1-2) [ MFR: 1.2 g / 10 min, content of units derived from ethylene: 4.0% by mass, melting point: 139 ° C.].

(2) Propylene polymer (A-2)
As the propylene polymer (A-2), a propylene homopolymer (a-2-2) [MFR: 7 g / 10 min, melting point (Tm3): 163 ° C.] produced with a solid Ti catalyst was used.

(3) Propylene / α-olefin random copolymer (B-1)
As propylene / α-olefin random copolymer (B-1), propylene / ethylene random copolymer (b-1-1) produced with a solid Ti catalyst [Intrinsic viscosity [η]: 2.7 dl / g, Content of units derived from ethylene: 32% by mass, melting point: present at less than 120 ° C.] was used.

(4) Ethylene / α-olefin random copolymer (C)
As ethylene / α-olefin random copolymer (C), ethylene / 1-butene random copolymer (c-1) produced by a single site catalyst [density: 0.880 g / cm ³ , MFR: 0.9 g / 10 minutes, content of units derived from ethylene: 79% by mass (88.3 mol%), melting point: present at 80 ° C. or lower].

(5) Propylene homopolymer A propylene homopolymer (f-1) [MFR: 1.6 g / 10 min, melting point: 165 ° C.] produced with a solid Ti catalyst was used as the propylene homopolymer.

(6) Propylene / ethylene random copolymer As propylene / ethylene random copolymer, propylene / ethylene random copolymer (f-2) produced with a solid Ti catalyst [content of units derived from ethylene: 1. 2 mass%, MFR: 1.5 g / 10 min, melting point: 155 ° C.].

[Example 1]
<Production of propylene-based copolymer composition (e-5)>
Propylene / ethylene / 1-butene random copolymer (a-1-4): 52% by mass, propylene homopolymer (a-2-2): 20% by mass, propylene / ethylene random copolymer (b-1) -1): 13% by mass and ethylene / 1-butene random copolymer (c-1): 15% by mass [(a-1-4) + (a-2-2) + (b-1- 1) + (c-1) = 100% by mass] and then melt-kneaded at a resin temperature of 220 ° C. using a twin screw extruder to obtain a propylene copolymer composition (e-5). It was. MFR of the obtained propylene copolymer composition (e-5) was 7 g / 10 minutes.

  In addition, propylene / ethylene / 1-butene random copolymer (a-1-4): 52 parts by mass, propylene homopolymer (a-2-2): 20 parts by mass, a total of 72 parts by mass was biaxially extruded. The MFR (230 ° C.) of the composition obtained by melt-kneading in the same manner as described above was 21.0 g / 10 min.

  In addition, propylene / ethylene random copolymer (b-1-1): 13 parts by mass, ethylene / 1-butene random copolymer (c-1): 15 parts by mass, and a total of 28 parts by mass as described above. The MFR (230 ° C.) of the composition obtained by melt-kneading was 0.6 g / 10 min.

  The obtained propylene copolymer composition (e-5) had an MFR of 7 g / 10 min, and had a melting peak (Tp2) at 149.8 ° C. and a melting peak (Tp3) at 160.6 ° C. .

<Manufacture of biaxially stretched film (heat fusion layer)>
Using the propylene copolymer composition (e-5), biaxial stretching was performed to obtain a heat-sealing layer. The propylene copolymer composition (e-5) used contained tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′hydroxyphenyl) propionate] methane as a heat-resistant stabilizer product (Nippon Ciba-Gaiky product) Name Irganox 1010) 1000 ppm and calcium stearate (manufactured by NOF Corporation) 1000 ppm were blended.

  The heat-sealing layer has a three-layer structure, and the propylene copolymer composition (e-5) is used so that the surface layer / inner layer / surface layer extrusion rate ratio is (1/10/1). Each was melt-extruded using a screw extruder, extruded using a multi-manifold type T-die, and rapidly cooled on a cooling roll to obtain a multilayer sheet having a thickness of about 1.5 mm. This multilayer sheet was heated at 120 ° C. and stretched 5 times in the flow direction (longitudinal direction) of the multilayer sheet. The multilayer sheet stretched 5 times was heated at 160 ° C. and stretched 10 times in the direction (transverse direction) perpendicular to the flow direction. The thickness of the inner layer: 34 μm, the thickness of each surface layer: 3 μm (total) A heat seal composed of a three-layer multilayer film having a thickness of 40 μm was obtained, and the surface layer laminated with the base material layer of the heat seal layer was subjected to corona treatment.

<Manufacture of laminated film>
A biaxially stretched polyethylene terephthalate film (thickness: 12 μm), a biaxially stretched polyamide film (thickness: 15 μm) and a biaxially stretched film (heat fusion layer) are prepared. After laminating the film using a laminator, the corona-treated surface of the biaxially stretched film is bonded to the biaxially stretched polyamide film side by dry lamination using a urethane adhesive, and biaxially stretched. A laminated film composed of a polyethylene terephthalate film / biaxially stretched polyamide film / biaxially stretched film (heat fusion layer) was obtained.
The physical properties of the obtained heat-fusible layer and laminated film were measured by the above methods. The results are shown in Table 1.

[Reference Example 1]
72% by mass of propylene / ethylene random copolymer (a-1-1), 13% by mass of propylene / ethylene random copolymer (b-1-1), and ethylene / 1-butene random copolymer (c -1) 15% by mass [(a-1-1) + (b-1-1) + (c-1) = 100% by mass]] propylene-based copolymer composition (e-3) [MFR = 2 g / 10 min] was carried out in the same manner as in Example 1 to obtain a biaxially stretched film (heat fusion layer) and a multilayer biaxially stretched film.
The physical properties of the obtained heat-fusible layer and multilayer biaxially stretched film were measured by the above methods. The results are shown in Table 1.

[Reference Example 2]
Instead of the propylene copolymer composition (e-5) used in Example 1, propylene / ethylene random copolymer (a-1-2): 72% by mass, propylene / ethylene random copolymer (b- 1-1): 13% by mass, and ethylene / 1-butene random copolymer (c-1): 15% by mass [(a-1-2) + (b-1-1) + (c-1) = 100% by mass], except that a propylene-based copolymer composition (e-4) [MFR = 2 g / 10 min] was used, and the same procedure as in Example 1 was carried out, and a biaxially stretched film (heat fusion layer) and A multilayer biaxially stretched film was obtained.
The physical properties of the obtained heat-fusible layer and multilayer biaxially stretched film were measured by the above methods. The results are shown in Table 1.

[Comparative Example 1]
Instead of the propylene copolymer composition (e-5) used in Example 1, propylene homopolymer (f-1): 72% by mass, propylene / ethylene random copolymer (b-1-1): 13% by mass, and ethylene / 1-butene random copolymer (c-1): 15% by mass [(f-1) + (b-1-1) + (c-1) = 100% by mass] A biaxially stretched film (heat fusion layer) and a multilayer biaxially stretched film are obtained in the same manner as in Example 1 except that the propylene copolymer composition (E-2) [MFR = 2 g / 10 min] is used. It was.

The physical properties of the obtained heat-fusible layer and multilayer biaxially stretched film were measured by the above methods. The results are shown in Table 1.
Propylene / ethylene random copolymer (b-1-1): 13 parts by mass, ethylene / 1-butene random copolymer (c-1): 15 parts by mass, a total of 28 parts by mass was the same as described above. The composition obtained by kneading had an MFR (230 ° C.) of 0.6 g / 10 min.

[Comparative Example 2]
Instead of the propylene copolymer composition (e-5) used in Example 1, propylene / ethylene random copolymer (f-2): 72% by mass, propylene / ethylene random copolymer (b-1-) 1): 13% by mass, and ethylene / 1-butene random copolymer (c-1): 15% by mass [(f-2) + (b-1-1) + (c-1) = 100% by mass A biaxially stretched film (heat-sealing layer) and multilayer biaxially stretched in the same manner as in Example 1 except that a propylene-based copolymer composition (e-2) [MFR = 2 g / 10 min] is used. A film was obtained.
The physical properties of the obtained heat-fusible layer and multilayer biaxially stretched film were measured by the above methods. The results are shown in Table 1.

For example, even when the biaxially stretched film of the present invention is as thin as 5 to 50 μm, the heat-sealing strength (heat seal strength) can exceed 8 N / 15 mm, and can be as strong as 20 N / 15 mm or more. In addition, there is little decrease in heat seal strength after heat treatment (pressurization / heat treatment), and the bag tear resistance at low temperature when the bag is retort-treated is excellent and has blocking resistance. Since it has, it can be widely used as a packaging material.
The composition of this invention can be used suitably for manufacture of the said biaxially stretched film, for example.

Claims (5)

10 to 70% by mass of a propylene / α-olefin random copolymer (A-1) having a melting point (Tm2) in the range of 120 to 150 ° C., and a propylene polymer having a melting point (Tm3) in the range of 155 to 170 ° C. (A-2) is 10 to 40% by mass, the intrinsic viscosity [η] is 2.0 to 10.0 dl / g, and the content of propylene-derived structural units is 60 to 90% by mass (propylene-derived structural units 1 to 25% by mass of a propylene / α-olefin random copolymer (B-1), and a density of 0.865 to 0.910 g. 5 to 30% by mass of ethylene / α-olefin random copolymer (C), which is a random copolymer of ethylene and α-olefin having 4 or more carbon atoms in the range of / cm ³ [(A-1 ) + (A-2 + (B-1) + (C) = a 100 wt%. ] The biaxially stretched film which consists of a propylene copolymer composition (E-2) characterized by the above-mentioned.   A multilayer biaxially stretched film comprising a base material layer laminated on one side of the biaxially stretched film according to claim 1.   The base material layer is a base material layer selected from aluminum, paper, polyester resin film, polycarbonate film, polyamide film, ethylene / vinyl alcohol copolymer film, polyvinyl alcohol film, polyvinyl chloride film, and polyvinylidene chloride film. The multilayer biaxially stretched film according to claim 2.   The multilayer biaxially stretched film according to claim 2 or 3, wherein the multilayer biaxially stretched film is used for packaging heated and sterilized packages using the biaxially stretched film as a heat-sealing layer. 10 to 70% by mass of a propylene / α-olefin random copolymer (A-1) having a melting point (Tm2) in the range of 120 to 150 ° C., and a propylene polymer having a melting point (Tm3) in the range of 155 to 170 ° C. (A-2) is 10 to 40% by mass, the intrinsic viscosity [η] is 2.0 to 10.0 dl / g, and the content of propylene-derived structural units is 60 to 90% by mass (propylene-derived structural units 1 to 25% by mass of a propylene / α-olefin random copolymer (B-1), and a density of 0.865 to 0.910 g. 5 to 30% by mass of ethylene / α-olefin random copolymer (C), which is a random copolymer of ethylene and α-olefin having 4 or more carbon atoms in the range of / cm ³ [(A-1 ) + (A-2 + (B-1) + (C) = a 100 wt%. ] Propylene copolymer composition (E-2) characterized by the above-mentioned.