JP2013111826A - Laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated film having considerably excellent low-temperature drop bag-breaking strength after heat treatment even when reducing the thickness of a thermal bonding film (a thermal bonding layer), having sufficient shock resistance even at low temperatures, having less degradation of the heat-seal strength even after heat treatment such as pressurization and heat-sterilization treatment, and having excellent rigidity.SOLUTION: In the laminated film, a thermal bonding layer is laminated on one side of a base material layer, which consists of a biaxially stretched film with its thickness being in a range of 5-50 μm while a propylene.α-olefin random copolymer (A-1) of the specified amount with its melting point being in a range of 120-150°C, a propylene copolymer composition (E-1) containing propylene.α-olefin random copolymer (B-1) with its intrinsic viscosity [η] being 2.0-10.0 dl/g, and ethylene.α-olefin random copolymer (C) with its density being in a range of 0.865-0.910 g/cm, is biaxially stretched.

Description

  The present invention is excellent in rigidity and impact strength, and even when heat treatment such as pressure and heat sterilization is performed, the decrease in heat seal strength is small, and the drop bag breaking strength at low temperature after heat treatment is excellent. The present invention relates to a laminated film for packaging such as a sterilized package, and a propylene copolymer composition suitable for the laminated film.

  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). Further, 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).

  On the other hand, 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 also 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). Weak, for example, cannot be used as a heat-sealing layer for retort films that require high heat-sealing strength

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

  Even if the thickness of the heat-seal film (heat-seal layer) is reduced, the present invention has excellent low-temperature drop bag breaking strength after heat treatment and sufficient impact resistance even at low temperatures. An object is to obtain a laminated film that is less likely to have a decrease in heat-sealing strength even if heat treatment such as pressure and heat sterilization is performed, and that is excellent in transparency and rigidity.

In the present invention, 50 to 90% by mass of the propylene / α-olefin random copolymer (A-1) having a melting point in the range of 120 to 150 ° C. and an intrinsic viscosity [η] of 2. 0 to 10.0 dl / g, and the content of units derived from propylene is 60 to 90% by mass (the total of units derived from propylene and units derived from α-olefin is 100% by mass). Randomization of ethylene having an α-olefin random copolymer (B-1) of 1 to 25% by mass and a density of 0.865 to 0.910 g / cm ³ and an α-olefin having 4 or more carbon atoms Propylene copolymer composition (E-1) containing 5 to 30% by mass of copolymer (C) [(A-1) + (B-1) + (C) = 100% by mass]. ] It is related with the laminated | multilayer film characterized by laminating | stacking the heat sealing | fusion layer which consists of a biaxially stretched film in the range of 5-50 micrometers in thickness formed by biaxially stretching.

The composition of the present invention has a propylene / α-olefin random copolymer (A-1) having a melting point of 120 to 150 ° C. in an amount of 50 to 90% by mass and an intrinsic viscosity [η] of 2.0 to 10%. 0.0 dl / g, and the content of units derived from propylene is 60 to 90% by mass (the total of units derived from propylene and units derived from α-olefin is 100% by mass). Random copolymerization of ethylene having an olefin random copolymer (B-1) of 1 to 25% by mass and a density of 0.865 to 0.910 g / cm ³ and an α-olefin having 4 or more carbon atoms Propylene copolymer composition (E-1) [(A-1) + (B-1) + (C) = 100% by mass) containing 5 to 30% by mass of the coalescence (C). ].

  The laminated film of the present invention has excellent bag drop strength at a low temperature after heat treatment and low temperature heat sealability even when the thickness of the heat-sealing layer made of a biaxially stretched film is as thin as 5 to 50 μm. Excellent heat fusion strength (heat seal strength), less decrease in heat seal strength after heat treatment (pressurization and heat treatment), sufficient impact resistance even at low temperatures, transparency and rigidity Also have.

<Propylene / α-olefin random copolymer (A-1)>
Propylene / α-olefin random copolymer component (A-1) which is one of the polymer components contained in the propylene copolymer composition (E-1) forming the heat-sealing layer of the laminated film of the present invention Is usually a propylene / α-olefin random copolymer containing 90 to 98% by mass, preferably 92 to 98% by mass, of units derived from propylene. 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 0.5 to 20 g. / 10 minutes, more preferably in the range of 1.0 to 10 g / 10 minutes. When the MFR is in the above range, the propylene copolymer composition (E-1) can be easily formed into a biaxially stretched film, and heat formed from a biaxially stretched film excellent in low temperature impact resistance and heat seal strength. A fused layer can be obtained.

  The propylene / α-olefin random copolymer (A-1) according to the present invention has a melting point of usually 120 to 150 ° C, preferably 140 to 147 ° C. Within this range, the balance of heat seal strength, rigidity, and bag drop strength is particularly good. Further, when a copolymer having a melting point of 120 to 139 ° C. is used, the flexibility is particularly excellent.

  The propylene / α-olefin random copolymer (A-1) 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)>
Propylene / α-olefin random copolymer component (B-1) which is one of the polymer components contained in the propylene copolymer composition (E-1) forming the heat-sealing layer of the laminated film of the present invention The propylene / α-olefin random is usually 60 to 90% by weight, preferably 60 to 89% by weight, more preferably 61 to 82% by weight, and even more preferably 65 to 79% by weight, of units derived from propylene. It is a copolymer (provided that the total of units derived from propylene and 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 the retort treatment is good. And when the unit derived from propylene is low, incompatibility with the matrix is increased, and it is considered that, for example, when the biaxially stretched film is retorted, the elastomeric component tends to be enlarged, which is more advantageous in this respect. It is thought that.

  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 / α-olefin random copolymer (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-1) forming the heat-sealing layer of the laminated film of the present invention, has a density there 0.865~0.910g / cm ^3, preferably a copolymer in the range of 0.875~0.900g / cm ^3, ethylene and 4 or more carbon atoms, preferably 4 to 10 α- It is a random copolymer with olefin. 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 density of the ethylene / α-olefin random copolymer (C) according to the present invention is as follows: a preheat temperature of 190 ° C., a heating time of 2 minutes, and a heating pressure of 100 kg / cm ³ using a press molding machine. A press sheet having a thickness of 0.5 mm formed by press molding is used as a measurement sample, and is obtained by measurement with a density gradient tube.

  In the ethylene / α-olefin random copolymer (C) according to the present invention, the unit derived from ethylene is usually 70 to 95 mol%, preferably 80 to 93 mol%, and the melting point is usually 100 ° C. or less. When the melting point is present or absent and the melting point is present, the upper limit is preferably 90 ° C., and the lower limit is not particularly limited, but for example, 40 ° C., and further 60 ° C. can be exemplified.

<Propylene copolymer composition (E-1)>
The propylene copolymer composition (E-1) that forms the heat-sealing layer of the laminated film of the present invention is 50 to 90% by mass of the propylene / α-olefin random copolymer (A-1), preferably 55 to 85 mass%, more preferably 60 to 80 mass%, 1 to 25 mass%, preferably 2 to 20 mass%, more preferably 2 to 20 mass% of the propylene / α-olefin random copolymer (B-1). 18% by mass, and 5 to 30% by mass, preferably 10 to 25% by mass, and more preferably 10 to 25% by mass of the ethylene / α-olefin random copolymer (C) [However, (A-1) + ( B-1) + (C) = 100% by mass. It is a composition containing.

  One of preferred embodiments is that the propylene / α-olefin random copolymer (A-1) is 55 to 85% by mass, and the propylene / α-olefin random copolymer (B-1) is preferably 2 to 20%. It is a composition containing 10 to 25% by mass of the ethylene / α-olefin random copolymer (C).

  In a further preferred embodiment, 60-80% by mass of the propylene / α-olefin random copolymer (A-1) and 2-18% by mass of the propylene / α-olefin random copolymer (B-1). %, And 10-25% by mass of the ethylene / α-olefin random copolymer (C).

  A composition containing less than 50% by mass of the propylene / α-olefin random copolymer (A-1) may be inferior in low-temperature impact strength or heat sealability even when biaxially stretched to form a heat-sealing layer. The composition exceeding 90% by mass may be inferior in blocking resistance when biaxially stretched to form a heat-fusible layer.

  The composition containing less than 1% by mass of the propylene / α-olefin random copolymer (B-1) may be inferior in low-temperature impact strength even when biaxially stretched to form a heat-fusible layer. Exceeding compositions may be inferior in transparency even when biaxially stretched to form a heat-fusible layer.

  A composition having an ethylene / α-olefin random copolymer (C) of less than 5% by mass may be inferior in low-temperature impact strength even if it is biaxially stretched to form a heat-sealing layer, while a composition exceeding 30% by mass. The product may be inferior in transparency even if it is biaxially stretched to form a heat fusion layer.

  The incompatible composition (polymer blend or block copolymer) generally has a sea-island structure (cluster structure), and the propylene polymer (A-1) matrix in the composition of the present invention contains an elastomer component. (C) and (B-1) form a morphology that is considered to be dispersed as domains. 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.

  For example, the propylene copolymer composition of the present invention including the propylene / α-olefin random copolymer (A-1) having such a sea-island structure is 5 times longer and 10 times wide. When the dispersed particle diameter of the film obtained by biaxial stretching was observed, it was found that the dispersed diameter was finely dispersed to a level of submicron or less (the dispersed 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, an elastomeric component having a lower compatibility with the propylene / α-olefin random copolymer (A-1), for example, having a higher ethylene content, is less likely to have a relatively small dispersion diameter when stretched. It is thought that it is easy to form a structure suitable for exhibiting the strength of a falling body at a low temperature.

  Furthermore, when an ethylene polymer (D) described later having a melting point higher than the retort processing temperature is present, it acts like a bracing that suppresses interfacial (interphase) peeling from the matrix phase accompanying the enlargement of the elastomeric component. Therefore, we believe that the drop bag breaking strength after the retort treatment may be further improved.

  The propylene copolymer composition (E-1) according to the present invention usually has an MFR [load: 2160 g, temperature: 230 ° C.] of 1.0 to 10 g / 10 min, preferably 1.0 to 5.0 g / 10 minutes. By setting the MFR within the above range, a biaxially stretched film can be easily formed, and a heat-sealing layer excellent in low-temperature impact strength can be obtained.

<Method for producing propylene copolymer composition (E-1)>
The propylene copolymer composition (E-1) according to the present invention includes the propylene / α-olefin random copolymer (A-1), the propylene / α-olefin random copolymer (B-1), and , A method of mixing the ethylene / α-olefin random copolymer (C) in a desired range, and a composition of two or more of these components, for example, (A-1) and (B-1) Can be manufactured in advance, and then the remaining component (C) is 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, when manufacturing the composition of (A-1) and (B-1), it is good also by manufacturing what is called a propylene block copolymer by multistage polymerization. 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.

  In addition, these (A-1), (B-1) and (C) are mixed by a method in which two or more of these are previously in a solution state and then the solvent is removed, and if necessary, other components. The composition according to the present invention may be produced by melt-kneading together.

  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-1) 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.

  Further, in the propylene copolymer composition (E-1), if necessary, the following ethylene polymer (D) is added in a small amount, for example, the sum of (A-1), (B-1) and (C). You may add about 1-20 mass parts with respect to 100 mass parts. In this case, it is possible to further improve the drop bag breaking impact strength at a low temperature.

<Ethylene polymer (D)>
The ethylene polymer (D) is an ethylene homopolymer having a melting point (Tm1) of 120 to 135 ° C, preferably 125 to 135 ° C, or ethylene and α having 3 or more carbon atoms, preferably 3 to 10 carbon atoms. -Random copolymers with olefins. 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 an ethylene polymer having a melting point (Tm1) of less than 120 ° C. is used, the heat resistance of the biaxially stretched film may be lowered.
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 density of the ethylene polymer (D) according to the present invention is usually 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.

  When an ethylene polymer (D) having a melting point higher than the retort treatment temperature is present, retort treatment is performed because it acts like a brace that suppresses interfacial (interphase) separation from the matrix phase accompanying the enlargement of the elastomeric component. We believe that the drop bag breaking strength at a later low temperature may further improve.

  Further, the propylene copolymer composition (E-1) or each polymer constituting the propylene copolymer composition (E-1) according to the present invention is 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 (heat fusion layer)>
The heat-sealing layer constituting the laminated film of the present invention is a heat-sealing layer formed by biaxially stretching the propylene copolymer composition (E-1) or (E-2), and has a thickness of 5 -50 μm, preferably in the range of 10-50 μm. When a heat-sealing layer having a thickness of less than 5 μm is used as a laminated film, there is a possibility that the bag drop strength may be insufficient. On the other hand, a heat-sealing layer having a thickness of more than 50 μm has a heat seal strength and a bag drop strength. The cost advantage of maintaining the performance and being thin is reduced.
Moreover, since the heat sealing | fusion layer of this invention is excellent in transparency, the freedom degree of product design is high.

As long as the heat-fusion layer of the present invention is composed of the propylene copolymer composition (E-1), it may be a single layer or a multilayer of two or more layers.
For example, when the heat fusion layer 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, respectively. Thickness. The thickness of the surface layer is preferably 0.5 to 15 μm, particularly 1 to 10 μm.

As described above, when the heat-fusible layer is formed of multiple layers, quality control is easy and the final yield is increased, which is advantageous in terms of cost.
Further, the surface of the heat-sealing layer according to 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.

<Method for producing biaxially stretched film (heat-sealing layer)>
The heat-sealing layer according to the present invention can be molded from the propylene copolymer composition (E-1) 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 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.

<Base material layer>
As a base material layer constituting the laminated film of the present invention, various known base material layers can be used. The base material layer according to the present invention has a thickness of usually 10 to 70 μm, preferably 20 to 50 μm.

  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 Examples thereof include a vinyl chloride film, a polyvinylidene chloride film, and a thermoplastic resin film such as a film made of polyolefin such as polypropylene, an aluminum foil, paper, and the like.

  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 substrate layer may be a single 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.

<Laminated film>
The laminated film of the present invention is a laminated film in which a heat-sealing layer formed by biaxially stretching the propylene copolymer composition (E-1) is laminated on one side of the base material layer.

  When laminating the base material layer and the heat-sealing layer according to the present invention, various known adhesive layers between the base material layer and the heat-sealing layer, for example, a urethane-based or isocyanate-based material on the base material layer. It can also be manufactured by applying an anchor coating agent and dry laminating a heat-sealing layer on one side, or extruding and laminating a thermoplastic resin as a base material layer on one side of the heat-sealing layer. .

The laminated film of the present invention has a high heat-sealing strength (peeling strength of the heat-sealed portion) of the heat-sealing layer when used for a packaging material, and is at least 20 (N / 15 mm) peel strength, heat resistance, low temperature impact strength, rigidity, etc. Depending on the type of substrate layer, high gas barrier properties, mechanical strength, etc. are imparted. Therefore, it is suitable as a medicine for heat sterilization or pressure / heat sterilization, or as a film for packaging retort food. Moreover, the drop bag breaking strength at low temperature after heat treatment is remarkably excellent. In other words, when used for packaging materials, heat seal strength of heat-sealing layer (peel strength of heat seal part), peel strength after heat treatment under high temperature and high pressure, heat resistance, low temperature impact strength, rigidity, 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.
The laminated 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 packs (fills) a medicine or food (a material to be packaged) as a content with the biaxially stretched heat-fusible layer of the laminated film of the present invention inside. The contents are hermetically packaged by heat-sealing the heat-sealing layer.
The following combination can be mentioned as an example of the laminated | multilayer film used for the package for heat sterilization.

  Polyester layer / biaxially stretched thermal fusion layer, polyamide layer / biaxially stretched thermal fusion layer, polyester layer / polyamide layer / biaxially stretched thermal fusion layer, polyester layer / aluminum foil / Biaxially stretched heat-sealable layer, polyester layer / polyamide layer / aluminum foil / biaxially stretched heat-sealable layer, polyamide layer / polyvinylidene chloride layer / polyester layer / biaxially stretched heat Examples thereof include a fusion layer.

  Since the heat sealing layer formed by biaxial stretching in this way is arranged in the innermost layer to form the heat seal portion, the package is firmly heat sealed, and is heat sterilized, pressurized and After the heat sterilization treatment, 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 has a low risk of leakage of the contents of food, 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 composition, and the physical-property value for evaluating a film were calculated | required by the test method described below.

(1) Polymer, method for measuring physical properties of composition <Propylene / α-olefin random copolymer (A-1), 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) , 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 propylene / α-olefin random copolymer (B-1) or propylene / α-olefin random copolymer (B-2) is dissolved in decalin, and the viscosity of the solution Measurement was performed at 135 ° C., and the intrinsic viscosity [η] (dl / g) was determined from the measured value.

<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).

(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) Physical property measuring method of biaxially stretched film The following measurement was performed using a 40-micrometer-thick biaxially stretched film (for heat-fusion layers).

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

<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 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.

(3) Method for measuring physical properties of laminated film <Heat seal strength (HS strength)>
As a laminated film used for heat seal strength measurement, 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 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 bonded to the biaxially stretched polyamide film side using a laminating machine. A laminated film was obtained. 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 are prepared as laminated films used in the falling bag test. After laminating the axially stretched polyamide film using a laminating machine, the corona-treated surface of the biaxially stretched film (heat fusion layer) is pasted to the biaxially stretched polyamide film side using a laminating machine, A laminated film was obtained. The laminated film is a biaxially stretched polyethylene terephthalate film / biaxially stretched polyamide film / biaxially stretched film.

  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 biaxially stretched ethylene polymer multilayer film of the obtained laminate 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 random copolymer (a-1-1) produced with a solid Ti catalyst [MFR: 2.3 g / 10 min, derived from ethylene Content of units to be cut: 2.6 mass%, melting point: 145 ° C.], and propylene / ethylene random copolymer (a-1-2) [MFR: 1.2 g / 10 min, of units derived from ethylene Content: 4.0% by mass, melting point: 139 ° C.).

(2) 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 less than 120 ° C.] was used.

(3) 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].

(4) 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.

(5) Propylene / ethylene random copolymer Propylene / ethylene random copolymer produced by 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.].

[Example 1]
<Production of propylene-based copolymer composition (e-3)>
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) was weighed at a ratio of 15% by mass [(a-1-1) + (b-1-1) + (c-1) = 100% by mass]], and then 220 ° C. using a twin screw extruder. A propylene-based copolymer composition (e-3) was obtained by kneading at a resin temperature of. The MFR of the obtained propylene-based copolymer composition was 2 g / 10 minutes.

<Manufacture of biaxially stretched film (heat fusion layer)>
Using the propylene copolymer composition (e-3), biaxial stretching was performed to obtain a heat-sealing layer. The propylene copolymer composition (e-3) 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-3) is used so that the surface layer / inner layer / surface layer extrusion 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.

[Example 2]
Instead of the propylene copolymer composition (e-3) 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 laminated film 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.

[Comparative Example 1]
Instead of the propylene copolymer composition (e-3) 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-sealing layer) and a laminated film were obtained in the same manner as in Example 1 except that the propylene-based copolymer composition (e-1) [MFR = 2 g / 10 min] was used.
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.

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

[Comparative Example 2]
Instead of the propylene copolymer composition (e-3) 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 a laminated film are obtained in the same manner as in Example 1 except that a propylene-based copolymer composition (e-2) [MFR = 2 g / 10 min] is used. It was.
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.

The laminated film of the present invention has a heat fusion strength (heat seal strength) of, for example, more than 8 N / 15 mm even though the thickness of the biaxially stretched heat fusion layer is in the range of 5 to 50 μm. Also, it is strong at 20 N / 15 mm or more, and there is little decrease in heat seal strength after heat treatment (pressurization / heat treatment), and it is excellent in dropping bag breaking strength at low temperature when retort-treated as a bag. Since it has the characteristics, it can be suitably used as a medicine for heat sterilization or pressure / heat sterilization, or a film for packaging retort food.
The composition of this invention can be used suitably for manufacture of the said biaxially stretched film, for example.

Claims (4)

On one side of the base material layer, the propylene / α-olefin random copolymer (A-1) having a melting point in the range of 120 to 150 ° C. is 50 to 90% by mass, and the intrinsic viscosity [η] is 2.0 to 10%. Propylene / α-olefin random having a content of 0 dl / g and a unit derived from propylene of 60 to 90% by mass (the total of units derived from propylene and units derived from α-olefin is 100% by mass) Random copolymer of ethylene and α-olefin having 4 or more carbon atoms in the range of 1 to 25% by mass of copolymer (B-1) and density of 0.865 to 0.910 g / cm ³ ( Propylene copolymer composition (E-1) containing 5 to 30% by mass of C) ((A-1) + (B-1) + (C) = 100% by mass). ] Is formed by laminating a heat-sealing layer made of a biaxially stretched film having a thickness in the range of 5 to 50 μm.   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 laminated film according to claim 1.   A film for packaging a heated and sterilized package comprising the laminated film according to claim 1. 50 to 90% by mass of propylene / α-olefin random copolymer (A-1) having a melting point of 120 to 150 ° C., intrinsic viscosity [η] of 2.0 to 10.0 dl / g, derived from propylene Propylene / α-olefin random copolymer (B-) containing 60 to 90% by mass of units to be removed (the total of units derived from propylene and units derived from α-olefin is 100% by mass). 1) 1 to 25% by mass, and a random copolymer (C) of ethylene having a density of 0.865 to 0.910 g / cm ³ and an α-olefin having 4 or more carbon atoms is 5 to 30 Propylene copolymer composition (E-1) [(A-1) + (B-1) + (C) = 100% by mass) ].