WO2013080854A1 - Propylene-based polymer composition, biaxially stretched film, and use therefor - Google Patents

Abstract

The present invention pertains to a propylene copolymer composition comprising: 10-70 mass% of a propylene/α-olefin random copolymer (A-1) having a melting point (Tm2) in the range of 120-150°C; 10-40 mass% of a propylene polymer (A-2) having a melting point (Tm3) in the range of 155-170°C; 1-20 mass% of an ethylene polymer (D) having a melting point (Tm1) in the range of 120-135°C; 1-25 mass% of a propylene/α-olefin random copolymer (B-1) having an intrinsic viscosity (η) of 2.0-10.0 dl/g and containing 60-90 mass% propylene-derived constituent units; and 5-30 mass% of an ethylene/ α-olefin random copolymer (C), which is a random copolymer of ethylene having a density of 0.865-0.910 g/cm³ and a C₄ or higher α-olefin (where (A-1) + (A-2) + (D) + (B-1) + (C) = 100 mass%).

Description

Propylene polymer composition, biaxially stretched film and use thereof

The present invention is excellent in mechanical properties such as transparency and rigidity, has a small decrease in heat seal strength even after heat treatment such as pressurization and heat sterilization, and is excellent in drop bag breaking strength at low temperature after heat treatment. The present invention relates to a propylene-based polymer composition suitable for packaging such as a heated / sterilized package, a biaxially stretched film comprising the composition, and 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 pressurized and heat-sterilized after being put in a container and sealed, and when necessary, heat the retort food together with the bag in hot water, take out the contents, and provide for meals. It is becoming. 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 mass of a polypropylene block and 5 to 30% by mass 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 mass of ethylene / α-olefin copolymer rubber is added to 90 to 99% by mass 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 polymerized by a metallocene catalyst system and having a melting point in the range of 140 to 155 ° C. (Patent Document 4: JP 2009-84379 A) has been proposed. 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 that the thickness must be 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 are contained. 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 Application 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 bag breaking strength at low temperatures is also desired.

However, these patent documents merely show an example of producing a film, and do not mention the drop bag breaking strength after the retort treatment.

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 60% 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), 1 to 20% by mass of an ethylene polymer (D) having a melting point (Tm1) in the range of 120 to 135 ° C., and an 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 (the total of propylene-derived structural units and α-olefin-derived structural units is 100% by mass) 1 to 25% by mass of the propylene / α-olefin random copolymer (B-1), and ethylene having a density in the range of 0.865 to 0.910 g / cm ³ and α having 4 or more carbon atoms. -Run with olefins 5-30% by mass of an ethylene / α-olefin random copolymer (C), which is a copolymer of [A-1) + (A-2) + (D) + (B-1) + (C) = 100% by mass. A propylene copolymer composition (E-3), a biaxially stretched film obtained from the composition (E-3), and use thereof.

The propylene copolymer composition (E-3) of the present invention is excellent in mechanical properties such as transparency and rigidity, anti-blocking property, excellent low-temperature heat sealability, heat resistance by biaxial stretching of 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-3) of the present invention, generally has 90 units derived from propylene. A propylene / α-olefin random copolymer containing ˜98% by mass, preferably 92-98% by mass.

The α-olefin which is a copolymer component constituting the propylene / α-olefin random copolymer (A-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 (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-3) can be easily formed into a biaxially stretched film, and a biaxially stretched film having sufficient 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, the heat resistance of the resulting biaxially stretched film may be reduced. Moreover, the block king resistance is lowered due to a decrease in the hardness of the film surface.

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 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-3) of the present invention, is usually a homopolymer of propylene or a carbon number of 2 to 10 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, and examples thereof include 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 preferred, and ethylene is particularly preferred.

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-3) can be easily formed into a biaxially stretched film, and a biaxially stretched film having sufficient impact strength can be obtained. For example, an MFR having a range of 2 to 20 g / 10 minutes, preferably 2 to 10 g / 10 minutes 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 lowered.

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 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 polymer (D)>
The ethylene polymer (D) which is one of the polymer components contained in the propylene copolymer composition (E-3) of the present invention has a melting point (Tm1) of 120 to 135 ° C, preferably 125 to 135 ° C. A homopolymer of ethylene in the range or a random copolymer of ethylene and an α-olefin having 3 or more carbon atoms, preferably 3 to 10 carbon atoms. Specific examples of α-olefins include propylene, 1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-tetradecene and 1-octadecene. Can be mentioned. Among these, propylene, 1-butene, 1-hexene and 1-octene are particularly preferable. These α-olefins may be used alone or in combination of two or more. Moreover, the mixture with a different ethylene polymer may be sufficient.

When using an ethylene polymer having a melting point (Tm1) of less than 120 ° C., the heat resistance of the biaxially stretched film may be reduced.

The ethylene polymer (D) according to the present invention usually has an MFR (load: 2160 g, temperature: 230 ° C.) of 0.1 to 10 g / 10 minutes, preferably 0.1 to 2.0 g / 10 minutes, more preferably Is 0.3 to 1.0 g / 10 min.

The ethylene polymer (D) according to the present invention usually has a density in the range of 0.945 to 0.980 g / cm ³ , preferably 0.950 to 0.970 g / cm ³ .

The ethylene polymer (D) according to the present invention can be produced using an olefin polymerization catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.

<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-3) of the present invention, usually has units derived from propylene. A propylene / α-olefin random copolymer containing 60 to 90% by mass, preferably 60 to 89% by mass, more preferably 61 to 82% by mass, and even more preferably 65 to 79% by mass (provided that it is derived from propylene). The total of the units to be derived and the units derived from α-olefin is 100% by mass). When the unit derived from propylene is in the above range, the drop bag breaking strength after retorting a film obtained by biaxial stretching of the composition is good. When the unit derived from propylene is low, incompatibility with the matrix is increased, and it is considered that, for example, the elastomeric component tends to enlarge when the biaxially stretched film is retorted, which is more advantageous in this respect. It is believed that there is.

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 a limiting viscosity [η] measured at 135 ° C. in a decalin solvent of 2.0 to 10.0 dl / g, preferably 2. The copolymer is 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 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-3) of the present invention, has a density of usually 0.865 to 0.910 g. / cm ^3, preferably a copolymer in the range of 0.875 ~ 0.900g / cm ^3, ethylene and 4 or more carbon atoms, a random copolymer of preferably from 4 ~ 10 alpha-olefin is there. 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. Of 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. Further, it may be a mixture with different ethylene / α-olefin random copolymers.

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

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 g / 10 minutes.

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., 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-3)>
The propylene copolymer composition (E-3) 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, the ethylene polymer (D) is 1 to 20% by mass, preferably 3 to 17% by mass, the propylene / α-olefin random copolymer. The polymer (B-1) is 1 to 25% by mass, preferably 2 to 20% by mass, and the ethylene / α-olefin random copolymer (C) is 5 to 30% by mass, preferably 10 to 25% by mass [ However, (A-1) + (A-2) + (D) + (B-1) + (C) = 100 mass%. The amount of (A-1) + (A-2) is not particularly limited, but is preferably 50 to 90% by mass in view of heat resistance, more preferably 55 to 85% by mass, and still more preferably 60 to 90% by mass. 80 parts by mass. It is a composition containing. In the above composition, the amount of the ethylene polymer (D) is more preferably 6 to 14% by mass from the viewpoint of the balance between the low temperature bag drop impact after the retort treatment and the film appearance.

One of the preferred embodiments of the propylene copolymer composition (E-3) 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-3). -2) 10 to 40% by mass, the ethylene polymer (D) 1 to 20% by mass, the propylene / α-olefin random copolymer (B-1) 1 to 25% by mass, and the ethylene 5-30% by mass of α-olefin random copolymer (C) [However, (A-1) + (A-2) + (D) + (B-1) + (C) = 100% by mass) . Further, (A-1) + (A-2) is 55-85% by mass. It is a composition containing.

One of the more preferred embodiments of the propylene copolymer composition (E-3) 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 ( A-2) is 10 to 35% by mass, the ethylene polymer (D) is 3 to 17% by mass, the propylene / α-olefin random copolymer (B-1) is 2 to 20% by mass, and the ethylene .Alpha.-olefin random copolymer (C) of 10 to 25% by mass [where (A-1) + (A-2) + (D) + (B-1) + (C) = 100% by mass To do. Further, (A-1) + (A-2) is 55-85% by mass. It is a composition containing.

One of the more preferable embodiments of the propylene copolymer composition (E-3) of the present invention is that the propylene / α-olefin random copolymer (A-1) is contained in an amount of 15 to 65% by mass, and the propylene polymer ( A-2) is 10 to 35% by mass, the ethylene polymer (D) is 3 to 17% by mass, the propylene / α-olefin random copolymer (B-1) is 2 to 20% by mass, and the ethylene .Alpha.-olefin random copolymer (C) of 10 to 25% by mass [where (A-1) + (A-2) + (D) + (B-1) + (C) = 100% by mass To do. Further, (A-1) + (A-2) is 60-80% by mass. It is a composition containing.

One of the more preferable embodiments of the propylene copolymer composition (E-3) of the present invention is that the propylene / α-olefin random copolymer (A-1) is contained in an amount of 20 to 60% by mass, and the propylene polymer ( 10 to 30% by mass of A-2), 6 to 14% by mass of the ethylene polymer (D), 5 to 20% by mass of the propylene / α-olefin random copolymer (B-1), and the ethylene .Alpha.-olefin random copolymer (C) of 10 to 25% by mass [where (A-1) + (A-2) + (D) + (B-1) + (C) = 100% by mass To do. Further, (A-1) + (A-2) is 60-80% by mass. It is a composition containing.

The propylene copolymer composition (E-3) of the present invention usually has a propylene / α-olefin random copolymer (A-) in the range of 135.1 to 155.0 ° C., preferably 140 to 155.0 ° C. Melting peak based on 1) (Tp2), melting peak based on propylene polymer (A-2) (Tp3) in the range of 155.1 to 168 ° C., preferably 158 to 165 ° C., and 120 to 135.0 ° C. The melting peak (Tp1) based on the ethylene polymer (D) is preferably in the range of 120 to 130 ° C.

The propylene copolymer composition (E-3) of the present invention usually has an endotherm (ΔH) at 100 to 180 ° C. in DSC of 40 to 65 J / g, preferably 43 to 63 J / g. In addition, the endothermic amount (ΔH ₁ ) at 100 to 130 ° C. is 10 to 35 J / g, preferably 15 to 30 J / g, and the endothermic amount (ΔH ₂ ) at 130 to 150 ° C. is 10 to 20 J / g, preferably 11 The endotherm (ΔH ₃ ) in the range of ˜15 J / g and 150 to 180 ° C. is in the range of 10 to 30 J / g, preferably 11 to 27 J / g.

A composition containing less than 10% by mass of the propylene / α-olefin random copolymer (A-1) may be inferior in low-temperature impact strength or heat sealability when formed into a biaxially stretched film, while 60% by mass. When the composition exceeds 2, the heat resistance is lowered when the biaxially stretched film is formed, and the blocking resistance may be deteriorated due to the decrease in the hardness of the film surface.

A composition having a propylene polymer (A-2) of less than 10% by mass may be inferior in heat resistance when formed into a biaxially stretched film, while a composition having more than 40% by mass is in a biaxially stretched film. In such a case, the low temperature impact strength and heat sealability 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.

When the composition in which the ethylene polymer (D) is less than 1% by mass is made into a biaxially stretched film, the anti-blocking property may be inferior. In some cases, transparency and heat sealability may be inferior.

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 formed into a biaxially stretched film. 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 used the propylene / α-olefin random copolymer (A-1) and the propylene polymer (A-2) having such a sea-island structure, for example, five 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). . In the bag making with this film as the innermost layer, the impact resistance (drop bag breaking strength) at low temperature after the retort treatment was surprisingly improved dramatically. According to the morphology observation of the bag, 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 repulsion 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.

Further, an elastomeric component having a lower compatibility with the propylene / α-olefin random copolymer (A-1) and the propylene polymer (A-2), for example, having a higher ethylene content, has a relative dispersion diameter at the time of stretching. Therefore, it is considered that it may be easy to form a structure suitable for expressing a falling body strength at a low temperature after retorting.

Furthermore, when an ethylene polymer (D) having a melting point higher than the retorting temperature is present, it acts like a brace that suppresses the interface (interphase) separation with the matrix phase accompanying the enlargement of the elastomeric component. It is thought that the drop bag breaking strength after retorting the film obtained by biaxially stretching the composition may further improve.

The propylene copolymer composition (E-3) of the present invention is not particularly limited in MFR [load: 2160 g, temperature: 230 ° C.], but usually 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 having sufficient low-temperature impact strength can be obtained.

The propylene copolymer composition (E-3) of the present invention has an MFR of a composition obtained by blending the components (A-1) and (A-2) in the proportions present in the composition. (MFR _{A-1 + A-2} ), (B) component, (C) component, and (D) component were blended according to the existing ratio in the composition, MFR (MFR _{B + C + D} ) is preferably (MFR _{A-1 + A-2} ) / MFR (MFR _{B + C + D} ) = 6-50, more preferably 12-50, and 20-50 More preferably. When it exists in this range, the blocking resistance of the biaxially stretched film obtained in particular can be improved.

<Method for producing propylene copolymer composition (E-3)>
The propylene copolymer composition (E-3) of the present invention comprises the propylene / α-olefin random copolymer (A-1), the propylene polymer (A-2), the ethylene polymer (D), A method of mixing the propylene / α-olefin random copolymer (B-1) and the ethylene / α-olefin random copolymer (C) in a desired range, and two or more of these components For example, (A-1) and (A-2), (A-1) and (B), (A-2) and (B), (A-1), (A-2) and (B) The composition may be prepared in advance, and then the remaining components may be blended.

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), (C), and (D) are mixed by a method in which two or more of these are previously in a solution state and the solvent is removed. If necessary, the composition according to the present invention may be produced by melt-kneading together with other components.

Further, in some cases, the propylene copolymer composition (E-3) of the present invention may be prepared by combining each constituent component constituting the composition, or a mixture of two or more types of each constituent component with the remaining components. The composition may be supplied to the material supply part and prepared in the kneading part of the molding machine and molded as it is.

Propylene / α-olefin random copolymer (A-1), propylene polymer (A-2), ethylene polymer (D), propylene / α-olefin random copolymer (B-1), The melting point of the ethylene / α-olefin random copolymer (C) and the melting peak temperature of the propylene copolymer composition (E-3) were determined according to JIS-K7121 by a differential scanning calorimeter [DSC, manufactured by PerkinElmer, Inc. (Diamond DSC)] can be obtained by performing measurement under the following measurement conditions. In addition, in the polymer, the vertex 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). When there are a plurality of endothermic peaks, the endothermic peak vertex at which the peak height is maximum is defined as the melting point (Tm).

The melting peak of the composition was 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: 200-400 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.

2nd step: temperature decreased to 30 ° C. at 10 ° C./min.

Third step: raising the temperature to 240 ° C. at 10 ° C./min In addition, in measuring the heat of fusion of the propylene copolymer composition (E-3) of the present invention, DSC (manufactured by TA Instruments) was used, and 25 The temperature was raised from 0 ° C. to 250 ° C. and held for 10 minutes, then the temperature was lowered to −50 ° C., and then the temperature was raised from −50 ° C. to 250 ° C. (the temperature raising rate was 10 ° C./min).

Of the endothermic peaks at the third step, the endothermic amount at 100 to 180 ° C. is ΔH, the endothermic amount at 100 to 130 ° C. is ΔH ₁ , the endothermic amount at 130 to 150 ° C. is ΔH ₂ , and the endothermic amount at 150 to 180 ° C. The amount of heat was ΔH ₃ .

<Additives>
The propylene copolymer composition (E-3) of the present invention includes a propylene / α-olefin random copolymer (B-1) and an ethylene / α-olefin random copolymer (C) as necessary. Other elastomer components 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.

In addition, the propylene copolymer composition (E-3) of the present invention or each polymer constituting the propylene copolymer composition (E-3) of the present invention has a range that does not impair the object of the present invention. In addition, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a hydrochloric acid absorbent, an antiblocking agent, a slip agent, a nucleating agent, a pigment, a dye, or various polymers may be blended.

Examples of the antioxidant include phenolic antioxidants, organic phosphite antioxidants, thioether antioxidants, hindered amine antioxidants, 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 propylene copolymer composition (E-3) of the present invention can be used by being molded by various molding methods such as melt molding.

<Biaxially stretched film>
The biaxially stretched film of the present invention is a film obtained by biaxially stretching the propylene copolymer composition (E-3), 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.

The biaxially stretched film of the present invention may be a single layer or a multilayer of two or more layers as long as it is composed of the propylene copolymer composition (E-3).

For example, when the biaxially stretched film has a three-layer structure, 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. Thickness. Further, 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 and the final yield is high, which has 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 or both sides as necessary in order to improve the adhesion with the base material layer.

The biaxially stretched film of the present invention has mechanical strength such as transparency and rigidity, low temperature heat sealability, heat fusion strength (heat seal strength), heat seal strength retention after heat treatment (pressurization / heat treatment), etc. The balance between the physical properties of the bag and the drop bag breaking strength at low temperatures after heat treatment when formed into a bag is excellent. 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>
The biaxially stretched film of the present invention can be molded from the propylene copolymer composition (E-3) using a known biaxially stretched film molding method.

For biaxial stretching, methods such as sequential biaxial stretching, simultaneous biaxial stretching, and multistage stretching are appropriately employed.

As the biaxial stretching conditions, known biaxially stretched film production conditions, for example, in the sequential biaxial stretching method, the longitudinal stretching temperature is 100 ° C. to 145 ° C., the stretching ratio is 4 to 7 times, and the transverse stretching temperature is In the range of 150 to 190 ° C. and the draw ratio in the range 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 of laminating the biaxially stretched film of the present invention and the base material layer, a generally performed laminating method can be employed as it is, and in that case, an adhesive layer is provided between the biaxially stretched film and the base material layer. Can be provided. For example, a urethane-based or isocyanate-based anchor coating agent is applied to the base material layer, and the biaxially stretched film of the present invention is dry laminated thereon, or a thermoplastic resin that becomes the base material layer is applied to the biaxially stretched film. It can also be produced by extrusion lamination or extrusion coating.

The multilayer biaxially stretched film of the present invention has a high heat-sealing strength (peeling strength of the heat-sealed portion) of the film layer when used for a packaging material, for example, at least 20 even after heat treatment under high temperature and high pressure. Since the heat seal strength of (N / 15 mm) is maintained, it is suitable as a retort food packaging film.

Also, the drop bag breaking strength at low temperature after heat treatment is remarkably excellent. In other words, the multilayer biaxially stretched film of the present invention retains the heat seal strength of the film layer (peel strength of the heat seal portion) and the heat seal strength after heat treatment (pressurization / heat treatment) when used as a packaging material. The balance between physical properties such as mechanical properties, rigidity, and other physical properties, and the strength of dropped bags at low temperatures after heat treatment in the case of bags is excellent. Further, it tends to be excellent in blocking resistance.

The multilayer biaxially stretched film of the present invention has mechanical strength such as heat resistance, high heat seal strength, and rigidity by using the biaxially stretched film as a heat-sealing layer (heat seal layer). Depending on the type of the 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 package for heat sterilization according to the present invention uses the packaging material made of 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 above-described multilayer biaxially stretched film 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.

Next, the present invention will be described in more detail through examples, but the present invention is not limited by these examples.

In addition, the physical property value which shows the property of 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,
The ethylene-propylene-ethylene chain methine carbon signal (in propylene units) of 33.12 ppm or, if this is difficult to confirm, 128 ppm of heavy benzene carbon was used.

The attribution of the peak is
Macromolecules, 11 (1) , 3 (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) was dissolved in decalin, the viscosity of the solution was 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.

(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.

<Young's 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.

Thermal shrinkage value = (100−A) / 100 × 100
A: Length of side of square after standing in oven <impact strength: kg · cm>
Using a film impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd., 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 23 ° C ambient temperature. 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>
Biaxially stretched polyethylene terephthalate film (thickness: 12 μm), biaxially stretched polyamide film (thickness: 15 μm) and a biaxially stretched film of propylene copolymer composition are used as multilayer biaxially stretched films used for heat seal strength measurement. Prepare the biaxially stretched polyethylene terephthalate film and the biaxially stretched polyamide film using a laminating machine, and then use the laminating machine to place the biaxially stretched propylene copolymer film on the biaxially stretched polyamide film side. Thus, a multilayer biaxially stretched film of biaxially stretched polyethylene terephthalate film / biaxially stretched polyamide film / biaxially stretched propylene copolymer film (heat fusion layer) was obtained. Using a Toyo Seiki heat seal tester, cut out a 100 mm wide and 150 mm long test piece from a multilayer biaxially stretched film, fold it in half, heat the heater at 180 ° C to 230 ° C, the pressure at 0.2 MPa, and the sealing time After heat sealing in 1 second, the sealed test piece was cut into a test piece having a width of 15 mm, and the peel strength was measured using Tensilon RT1225 type manufactured by Orientec.

On the other hand, the heat seal strength after the retort sterilization treatment 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 film made of a biaxially stretched polyethylene terephthalate film (thickness: 12 μm), a biaxially stretched polyamide film (thickness: 15 μm), and a propylene copolymer composition is used as a multilayer biaxially stretched film used in the falling bag test. Prepare the biaxially stretched polyethylene terephthalate film and the biaxially stretched polyamide film by using a laminating machine, and then laminate the laminated film and the biaxially stretched propylene copolymer film on the biaxially stretched polyamide film side. A multilayer biaxially stretched film was obtained by laminating using a machine. The multilayer biaxially stretched film is a biaxially stretched film composed of a biaxially stretched polyethylene terephthalate film / biaxially stretched polyamide film / propylene copolymer composition. 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 multilayer biaxially stretched 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 preparing 20 such bags and leaving them to stand in an atmosphere of 5 ° C. for 24 hours, dropping from a height of 100 cm to the lateral direction of one bag, the same as the bag size One set of drops from the surface part with a weight of 500 g of a proper size was made, and the drop was repeated up to 20 sets, and the number of times until the bag was broken 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.

Polymers used in Examples and Comparative Examples of the present invention are shown below.

(1) Propylene / α-olefin random copolymer (A-1)
Propylene / ethylene / 1-butene random copolymer (a-1-4) produced with solid Ti catalyst as propylene / α-olefin random copolymer (A-1) [MFR: 32 g / 10 min, ethylene And 1-butene content: 2.3 / 2.0% by mass, melting point (Tm2) measured by DSC: 137 ° 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) Ethylene polymer (D)
High density polyethylene (d-1) produced with a solid Ti catalyst as the ethylene polymer (D) [MFR: 0.57 g / 10 min, density: 0.961 g / cm ³ , melting point (Tm1): 131 ° C.] Was used.

(4) 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, Ethylene content: 32% by mass, melting point: present at less than 120 ° C.].

(5) Ethylene / α-olefin random copolymer (C)
As ethylene / α-olefin random copolymer (C), ethylene / 1-butene random copolymer (c-1) produced with a single site catalyst (density: 0.88 g / cm ³ , MFR: 0.9 g / 10 minutes, ethylene content: 79% by mass (88.3 mol%), melting point: present at 80 ° C. or lower].

(6) 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.

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

(8) Propylene / α-olefin random copolymer (A-1)
Propylene / ethylene random copolymer (a-1-1) produced with solid Ti catalyst as propylene / α-olefin random copolymer (A-1) [MFR: 2.3 g / 10 min, derived from ethylene Content of units to be cut: 2.6% by mass, melting point: 145 ° C.] was used.

(9) Propylene / α-olefin random copolymer (A-1)
As propylene / α-olefin random copolymer (A-1), propylene / ethylene random copolymer (a-1-2) [MFR: 1.2 g / 10 min, content of units derived from ethylene: 4 0.0 mass%, melting point: 139 ° C.].

[Example 1]
<Production of propylene-based copolymer composition (e-6)>
Propylene / ethylene / 1-butene random copolymer (a-1-4): 44% by mass, propylene homopolymer (a-2-2): 20% by mass, high-density polyethylene (d-1): 8% 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) + (d-1) + (b-1-1) + (c-1) = 100% by mass], and a resin temperature of 220 ° C. using a twin screw extruder. And kneaded to obtain a propylene-based copolymer composition (e-6). The propylene copolymer composition obtained had an MFR of 6 g / 10 min.

The resulting propylene copolymer composition had an MFR of 6 g / 10 min, a melting peak at 127.6 ° C. (Tp1), a melting peak at 148.7 ° C. (Tp2), and a melting peak at 161.5 ° C. It had a peak (Tp3).

In addition, propylene / ethylene / 1-butene random copolymer (a-1-4): 44 parts by mass, propylene homopolymer (a-2-2): 20 parts by mass, a total of 64 parts by mass was twin-screw extruded. The MFR (230 ° C.) of the composition obtained by melt-kneading in the same manner as above was 19.9 g / 10 min.

Further, high density polyethylene (d-1): 8 parts by mass, propylene / ethylene random copolymer (b-1-1): 13 parts by mass, ethylene / 1-butene random copolymer (c-1): The MFR (230 ° C.) of the composition obtained by melt-kneading 15 parts by mass and a total of 36 parts by mass in the same manner as described above was 0.6 g / 10 min.

<Manufacture of biaxially stretched film (heat fusion layer)>
Using the propylene copolymer composition (e-6), biaxial stretching was performed to obtain a heat-sealing layer. The propylene copolymer composition (e-6) used contained tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′hydroxyphenyl) propionate] methane as a heat-resistant stabilizer (product of Nippon Ciba-Gaiky) 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-6) 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 multilayer biaxially stretched film>
Biaxially stretched polyethylene terephthalate film (thickness: 12 μm), biaxially stretched polyamide film (thickness: 15 μm) and a biaxially stretched film (heat-sealed layer) comprising the propylene copolymer composition (e-6) Prepare the biaxially stretched polyethylene terephthalate film and the biaxially stretched polyamide film using a laminator, and then apply the corona-treated surface of the biaxially stretched film to the biaxially stretched polyamide film side. Were laminated together by dry lamination to obtain a laminated film composed of a biaxially stretched polyethylene terephthalate film / biaxially stretched polyamide film / biaxially stretched film (heat fusion layer).

The physical properties of the obtained biaxially stretched film (heat fusion layer), multilayer biaxially stretched film and the like were measured by the above methods. The results are shown in Table 1.

[Example 2]
Instead of the propylene copolymer composition (e-6) used in Example 1, propylene / ethylene / 1-butene random copolymer (a-1-4): 48 mass%, propylene homopolymer (a -2-2): 20% by mass, high density polyethylene (d-1): 4% 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) + (d-1) + (b-1-1) + (c-1) = 100 %)] Except that a propylene-based copolymer composition (e-7) [MFR = 6.4 g / 10 min] is used, 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.

The propylene / ethylene / 1-butene random copolymer (a-1-4): 48 parts by mass, the propylene homopolymer (a-2-2): 20 parts by mass, a total of 68 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 20.5 g / 10 minutes.

High density polyethylene (d-1): 4 parts by mass, propylene / ethylene random copolymer (b-1-1): 13 parts by mass, ethylene / 1-butene random copolymer (c-1): 15 The MFR (230 ° C.) of the composition obtained by melting and kneading a total of 32 parts by mass in the same manner as described above was 0.6 g / 10 min.

The resulting propylene copolymer composition had an MFR of 6.4 g / 10 min, a melting peak at 126.7 ° C (Tp1), a melting peak at 148.1 ° C (Tp2), and a temperature at 161.2 ° C. It had a melting peak (Tp3).

Example 3
Instead of the propylene copolymer composition (e-6) used in Example 1, propylene / ethylene / 1-butene random copolymer (a-1-4): 36% by mass, propylene homopolymer (a -2-2): 20% by mass, high density polyethylene (d-1): 16% by mass, propylene / ethylene random copolymer (b-1-1): 13% by mass, and ethylene / 1-butene random copolymer Polymer (c-1): 15% by mass [(a-1-4) + (a-2-2) + (d-1) + (b-1-1) + (c-1) = 100 mass %] [MFR = 5.3 g / 10 min), except that the same procedure as in Example 1 was performed to obtain a composition (e-8), a biaxially stretched film (heat-sealing layer), and a multilayer biaxially stretched film. 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.

In addition, propylene / ethylene / 1-butene random copolymer (a-1-4): 36 parts by mass, propylene homopolymer (a-2-2): 20 parts by mass, a total of 56 parts by mass was twin-screw extruded. The MFR (230 ° C.) of the composition obtained by melt-kneading in the same manner as described above was 18.6 g / 10 minutes.

Further, high density polyethylene (d-1): 16 parts by mass, propylene / ethylene random copolymer (b-1-1): 13 parts by mass, ethylene / 1-butene random copolymer (c-1): 15 The MFR (230 ° C.) of the composition obtained by melt-kneading in the same manner as above was 32 g by mass, and 0.6 g / 10 min.

The propylene copolymer composition obtained had an MFR of 5.3 g / 10 min, a melting peak (Tp1) at 128.3 ° C, a melting peak (Tp2) at 149.4 ° C, and 162.0 ° C. Had a melting peak (Tp3).

[Comparative Example 1]
Instead of the propylene copolymer composition (e-6) 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] Propylene copolymer composition [MFR = 2 g / 10 min] The same procedure as in Example 1 was conducted except that the composition (e-1) was used, and a biaxially stretched film (heat fusion layer) and a multilayer biaxially stretched film were used. Got.

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 MFR (230 ° C.) of the composition obtained by melt-kneading was 0.6 g / 10 min.

The obtained propylene-based copolymer composition had an MFR of 2 g / 10 min and had a melting peak only at 163.5 ° C.

[Comparative Example 2]
Instead of the propylene copolymer composition (e-6) used in Example 1, propylene / ethylene random copolymer (f-2): 72 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 The composition (E-3), a biaxially stretched film (heat-sealing layer), and a multilayer are produced in the same manner as in Example 1 except that a propylene-based copolymer composition [MFR = 2 g / 10 min] is used. A biaxially stretched film was obtained.

The obtained propylene-based copolymer composition had a melting peak only at 153.3 ° C.

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 1]
Instead of the propylene copolymer composition (e-6) used in Example 1, 72% by mass of propylene / ethylene random copolymer (a-1-1), propylene / ethylene random copolymer (b- 1-1) 13% by mass, and ethylene / 1-butene random copolymer (c-1) 15% by mass [(a-1-1) + (b-1-1) + (c-1) = 100% by mass] was carried out in the same manner as in Example 1 except that a propylene-based copolymer composition (e-3) was used, to obtain a biaxially stretched film (heat fusion layer) and a multilayer biaxially stretched film. .

The obtained propylene copolymer composition had a melting peak only at 141.9 ° C.

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-6) used in Example 1, propylene / ethylene random copolymer (a-1-2): 72 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 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-sealed layer) and A multilayer biaxially stretched film was obtained.

The obtained propylene-based copolymer composition had a melting peak only at 139.0 ° C.

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 3]
Instead of the propylene copolymer composition (e-6) used in Example 1, propylene / ethylene / 1-butene random copolymer (a-1-4): 52 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]] propylene copolymer composition (e-5) [MFR = 7 g / 10 min] was used 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.

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 twin-screw 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, a total of 28 parts by mass was the same as described above. The MFR (230 ° C.) of the composition obtained by melt-kneading was 0.6 g / 10 min.

The resulting propylene copolymer composition had an MFR of 7 g / 10 min, and had a melting peak at 149.8 ° C. and a melting peak at 160.6 ° C.

The biaxially stretched film obtained from the composition of the present invention has a heat fusion strength (heat seal strength) exceeding 8 N / 15 mm, especially 20 N / 15 mm, even when the thickness is as thin as 5 to 50 μm. It is possible to strengthen as above, and there is little decrease in heat seal strength after heat treatment (pressurization / heat treatment), and it is excellent in drop bag breaking strength at low temperature after retorting in a bag. Since it has characteristics, it can be widely used as a packaging material.

The composition of the present invention can be suitably used for the production of the above biaxially stretched film, for example.

Claims (5)

1. A 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 a propylene polymer having a melting point (Tm3) in the range of 155 to 170 ° C. 10 to 40% by mass of (A-2), 1 to 20% by mass of ethylene polymer (D) having a melting point (Tm1) in the range of 120 to 135 ° C., and an intrinsic viscosity [η] of 2. Propylene with 0 to 10.0 dl / g and a propylene-derived constituent unit content of 60 to 90% by mass (the total of propylene-derived constituent units and α-olefin-derived constituent units is 100% by mass) .Alpha.-olefin random copolymer (B-1) in an amount of 1 to 25% by mass and an ethylene having a density in the range of 0.865 to 0.910 g / cm ³ and an α-olefin having 4 or more carbon atoms; Random 5 to 30% by mass of ethylene / α-olefin random copolymer (C), which is a polymer [provided that (A-1) + (A-2) + (D) + (B-1) + (C) = 100% by mass. A propylene copolymer composition (E-3).
2. A biaxially stretched film comprising the propylene copolymer composition (E-3) according to claim 1.
3. A multilayer biaxially stretched film in which a base material layer is laminated on one side of the biaxially stretched film according to claim 2.
4. 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 3.
5. The multilayer biaxially stretched film according to claim 3 or 4, wherein the multilayer biaxially stretched film is used for packaging a heated and sterilized package using the biaxially stretched film as a heat-sealing layer.