JP2020006522A - Laminate film and packaging material - Google Patents

Abstract

To provide a laminate film which can achieve excellent impact resistance in extremely low temperature while having preferable rigidity.SOLUTION: There is provided a laminate film in which a surface layer (A), an intermediate layer (B) and a heat seal layer (C) are laminated, in which the surface layer (A) is a layer containing a polypropylene-based resin as a main resin component, the intermediate layer (B) and the heat seal layer (C) are layers containing straight chain low density polyethylene as a main resin component, and the laminate film containing a polypropylene resin (a1) having MFR (230°C) of 12 g/10 min or less as the polypropylene resin in the surface layer (A) can achieve excellent impact resistance even in low temperature while having preferable rigidity.SELECTED DRAWING: None

Description

  The present invention relates to a laminated film used for packaging materials such as foods and medical products, and more particularly to a laminated film used for packaging materials having excellent low-temperature impact resistance.

  2. Description of the Related Art Conventionally, a film mainly composed of a polypropylene-based resin has high rigidity and a high surface gloss, and thus has been widely used as a packaging material for foods, medical products, and the like. However, impact resistance at low temperatures may not be sufficiently obtained only with the polypropylene-based resin, and in applications such as frozen food packaging, a linear ethylene-α-olefin copolymer layer may be formed on the polypropylene-based resin layer. 2. Description of the Related Art A laminated film or the like which is laminated to improve impact resistance at a low temperature has been used (see Patent Document 1).

JP 2001-105468 A

  By laminating a polypropylene-based resin layer and two linear ethylene-α-olefin copolymer layers having a specific density, the laminated film has excellent impact strength at a low temperature together with automatic packaging suitability. It is a realized laminated film, which can be suitably applied to packaging of frozen foods.

  However, with the development of refrigeration technology in recent years, such as diversification of contents to be frozen and lowering of the freezing temperature, further improvement in impact resistance at low temperatures to suppress breakage of packaging bags is required. Have been.

  The problem to be solved by the present invention is to provide a laminated film having excellent rigidity and excellent impact resistance even at a very low temperature.

  A further problem to be solved by the present invention is to provide a laminated film excellent in film formability in addition to the above.

  A laminated film in which a surface layer (A), an intermediate layer (B), and a heat seal layer (C) are laminated, wherein the surface layer (A) is a layer mainly composed of a polypropylene-based resin. The layer (B) and the heat seal layer (C) are layers containing a linear low-density polyethylene as a main resin component, and the polypropylene resin in the surface layer (A) has an MFR (230 ° C.) of 12 g / 10 min or less. This problem is solved by a laminated film containing a polypropylene resin (a1).

  Since the laminated film of the present invention has excellent impact resistance due to suitable rigidity, it does not easily cause bag breakage even when applied to packaging applications. In particular, since it has excellent impact resistance even at a low temperature significantly lower than 0 ° C., for example, at a low temperature of −15 ° C., it is stored and stored at a low temperature, and is used for packaging such as food use and medical use, especially frozen food. It can be suitably applied as a packaging application. Further, since excellent film formability can be realized, it can be suitably applied to food applications requiring a good appearance.

  The laminated film of the present invention is a laminated film in which a surface layer (A), an intermediate layer (B), and a heat seal layer (C) are laminated, wherein the surface layer (A) is composed of a polypropylene resin and a main resin component. The intermediate layer (B) and the heat seal layer (C) are layers containing linear low-density polyethylene as a main resin component, and the polypropylene resin in the surface layer (A) has an MFR (230 ° C.) ) Is a laminated film containing a polypropylene-based resin (a1) of 12 g / 10 min or less.

[Surface layer (A)]
The surface layer (A) of the laminated film of the present invention is a layer containing a polypropylene-based resin as a main resin component, and achieves suitable rigidity and surface heat resistance by containing the polypropylene-based resin as a main resin component. it can. In addition, it becomes easy to obtain a laminated film having a good appearance. As the polypropylene resin, a propylene homopolymer, a propylene-α-olefin random copolymer, a propylene-α-olefin block copolymer, or the like can be used. Each of these may be used alone or in combination. Among these, a homopolymer of propylene can be preferably used because high rigidity and transparency are easily obtained.

  In the present invention, the polypropylene resin in the surface layer (A) contains a polypropylene resin (a1) having an MFR (230 ° C.) of 12 g / 10 min or less. By containing the propylene-based resin (a1), excellent impact resistance can be realized even at a low temperature significantly lower than 0 ° C., for example, at a low temperature of −15 ° C. The MFR (230 ° C.) of the propylene-based resin (a1) is preferably 10 g / 10 min or less, more preferably 8 g / 10 min or less. The lower limit of the MFR is not particularly limited as long as the laminated film can be formed, but is preferably 0.5 g / 10 min or more. In particular, from the viewpoint of film formability, it is more preferably 3 g / 10 min or more, and further preferably 6 g / 10 min or more.

  The melting point of the polypropylene resin in the surface layer (A) is preferably 155 to 170 ° C, more preferably 158 to 165 ° C. By using polypropylene having a melting point within the above range, suitable impact resistance and suitability for packaging machines can be easily realized. Also, suitable heat resistance can be realized. The melting point refers to a melting peak by a differential scanning calorimeter.

  The surface layer (A) contains the above-mentioned polypropylene-based resin as a main component, and may use another resin that can be co-extruded as long as the effects of the present invention are not impaired. The term “main resin component” specifically means that 70% by mass or more of the resin component used for the surface layer (A) is a polypropylene resin, and 80% by mass or more is a polypropylene resin. The resin is preferably a resin, and more preferably 90% by mass or more is a polypropylene resin. It is also preferable that all of the resin components in the surface layer (A) are polypropylene resins.

  The content of the polypropylene resin (a1) having the above MFR (230 ° C.) of 12 g / 10 min or less in the polypropylene resin used for the surface layer (A) is preferably 70% by mass or more, and more preferably 90% by mass or more. Is more preferable. By setting the content of the polypropylene-based resin (a1) in the above range, it is easy to realize good rigidity and excellent impact resistance at low temperatures.

  As the resin other than the polypropylene resin used for the surface layer (A), various resins used for a packaging film can be used, and among them, an olefin resin such as an ethylene resin can be preferably used. Examples of the ethylene-based resin include polyethylene resins such as very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), linear medium density polyethylene (LMDPE), and medium density polyethylene (MDPE); Ethylene-vinyl acetate copolymer (EVA) or the like can be used.

  When an olefin-based resin other than the propylene-based resin is used as the resin component used in the surface layer (A), its content is 30% by mass or less in the resin component contained in the surface layer (A). Is preferably 10% by mass or less, more preferably 5% by mass or less.

  Further, a cyclic polyolefin resin may be used as the olefin resin, but the content of the cyclic polyolefin resin in the resin component contained in the surface layer (A) is preferably 10% by mass or less, and preferably 5% by mass. % Is more preferable, and it is also preferable not to use substantially.

  In the surface layer (A) used in the present invention, other resins other than those described above may be used in combination. Examples of the other resin include thermoplastic elastomers such as polyethylene-based elastomer, polypropylene-based elastomer and butene-based elastomer; ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene -Methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA) And ethylene-copolymers such as ethylene-acrylic acid copolymers, and ionomers of ethylene-methacrylic acid copolymers.

  When the other resin is used, its content is preferably used at 30% by mass or less in the resin component contained in the surface layer (A), more preferably at 30% by mass or less, The content is more preferably 10% by mass or less, and further preferably 5% by mass or less.

  In the surface layer (A), various additives and the like may be appropriately used in addition to the above resin components. As the additive, for example, a lubricant, an antiblocking agent, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antifogging agent, a coloring agent, and the like can be appropriately used. When these additives are used, they are preferably used in an amount of 2 parts by mass or less, more preferably about 0.01 to 1 part by mass, based on 100 parts by mass of the resin component used in the surface layer (A).

  The ratio of the thickness of the surface layer (A) to the total thickness of the laminated film is determined as the ratio of the thickness of the surface layer (A) to the total thickness of the laminated film because suitable rigidity and excellent impact resistance at low temperatures are easily obtained. Is preferably in the range of 45 to 10%, and particularly preferably in the range of 30 to 15%.

[Intermediate layer (B)]
The intermediate layer (B) of the laminated film of the present invention is a layer mainly composed of linear low-density polyethylene. By using the intermediate layer (B), suitable impact resistance at low temperatures can be realized. In addition, good packaging machine suitability can be easily realized. The density of linear low density polyethylene used in the intermediate layer (B), since the easily obtained good impact resistance, preferably 0.950 g / cm ³ or less, more preferably at 0.940 g / cm ³ or less . Further, it is preferably 0.900 g / cm ³ or more, more preferably 0.910 g / cm ³ or more.

  The MFR of the linear low-density polyethylene used for the intermediate layer (B) is 0.5 to 50 g / 10 min (190 ° C., 21.18 N), preferably 1 to 30 g / 10 min (190 ° C., 21.18 N). , More preferably 2 to 20 g / 10 min (190 ° C., 21.18 N). When the MFR is in this range, it is preferable in that good film formability can be obtained.

  In the present invention, by setting the content of the linear low-density polyethylene in the intermediate layer (B) to 70% by mass or more of the resin component contained in the intermediate layer (B), it is possible to obtain favorable sealing properties and low temperature. It is easy to obtain excellent impact resistance. The content is preferably at least 75% by mass, more preferably at least 80% by mass, even more preferably at least 90% by mass in the resin component contained in the intermediate layer (B). . Further, 100% by mass of the resin component contained in the intermediate layer (B) may be linear low-density polyethylene. If the total content is within the above range, two or more linear low-density polyethylenes having different densities and MFRs may be used in combination.

  The thickness ratio of the intermediate layer (B) to the total thickness of the laminated film is preferably from 80 to 10%, more preferably from 70 to 15%, from the viewpoint of good packaging machine suitability and low-temperature impact resistance. preferable.

  When the density, MFR and thickness ratio of the linear low-density polyethylene used for the intermediate layer (B) are within the above ranges, sufficient impact resistance at low temperatures, moldability of a multilayer film, and high heat seal strength can be obtained. Is preferred.

  In the intermediate layer (B), a resin other than the above-mentioned linear low-density polyethylene may be used in combination as long as the effects of the present invention are not impaired. Examples of other resin types that can be used in combination include, for example, polyethylene resins other than the linear low-density polyethylene resins exemplified in the surface layer (A), and olefin resins such as polypropylene resins. When an olefin resin is used as the resin other than the linear low-density polyethylene, its content is preferably 30% by mass or less in the resin component contained in the intermediate layer (B), preferably 10% by mass or less. Is more preferable, and the content is more preferably 5% by mass or less.

  Further, a cyclic polyolefin resin may be used as the olefin resin, but the content of the cyclic polyolefin resin in the resin component contained in the intermediate layer (B) is preferably 10% by mass or less, and preferably 5% by mass. % Is more preferable, and it is also preferable not to use substantially.

  In the intermediate layer (B), other resins other than those described above may be used in combination. Examples of the other resins include thermoplastic elastomers and ethylene copolymers exemplified in the surface layer (A). Examples include ionomers. When the other resin is used, its content is preferably used at 30% by mass or less of the resin component contained in the intermediate layer (B), more preferably at 30% by mass or less, The content is more preferably 10% by mass or less, and further preferably 5% by mass or less.

  In the intermediate layer (B), various additives and the like may be appropriately used in addition to the above resin components. As the additive, for example, a lubricant, an antiblocking agent, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antifogging agent, a coloring agent, and the like can be appropriately used. When these additives are used, they are preferably used in an amount of 2 parts by mass or less, more preferably about 0.01 to 1 part by mass, based on 100 parts by mass of the resin component used in the intermediate layer (B).

[Heat seal layer (C)]
The heat seal layer (C) used in the laminated film of the present invention is a layer mainly composed of linear low-density polyethylene. By laminating a plurality of layers mainly composed of the linear low-density polyethylene, good impact resistance and heat sealability can be realized. The density of the linear low-density polyethylene used for the heat seal layer (C) is preferably 0.880 to 0.940 g / cm ³ , since good sealing properties and impact resistance can be obtained. When heat resistance such as heat sterilization is required, 0.916 to 0.940 g / cm ³ is preferable, and when low temperature heat sealability and packaging speed are required, 0.880 to 0.915 g / cm ^3. It is preferred that An appropriate density may be selected according to the required characteristics of the film.

  The MFR of the linear low-density polyethylene is 0.5 to 50 g / 10 min (190 ° C., 21.18 N), preferably 1 to 30 g / 10 min (190 ° C., 21.18 N), more preferably 2 to 20 g / min. 10 minutes (190 ° C., 21.18 N). When the MFR is in this range, it is preferable in that good film formability can be obtained.

  In the present invention, by setting the content of the linear low-density polyethylene in the heat seal layer (C) to 70% by mass or more in the resin component contained in the heat seal layer (C), favorable sealing properties and low temperature can be obtained. It is easy to obtain excellent impact resistance underneath. The content is preferably 75% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more in the resin component contained in the heat seal layer (C). preferable. Further, 100% by mass of the resin component contained in the heat seal layer (C) may be linear low density polyethylene. If the total content is within the above range, two or more linear low-density polyethylenes having different densities and MFRs may be used in combination.

  In the heat seal layer (C), a resin other than the above-mentioned linear low density polyethylene may be used in combination as long as the effects of the present invention are not impaired. Examples of other resin types that can be used in combination include, for example, polyethylene resins other than the linear low-density polyethylene resins exemplified in the surface layer (A), and olefin resins such as polypropylene resins. When an olefin resin is used as the resin other than the linear low-density polyethylene, its content is preferably 30% by mass or less in the resin component contained in the heat seal layer (C), and preferably 10% by mass. It is more preferably at most 5% by mass.

  Although a cyclic polyolefin resin may be used as the olefin resin, the content of the cyclic polyolefin resin in the resin component contained in the heat seal layer (C) is preferably 10% by mass or less, and preferably 5% by mass or less. It is more preferable that the content be not more than mass%, and it is also preferable not to use substantially.

  In the heat seal layer (C), other resins other than those described above may be used in combination. Examples of the other resins include thermoplastic elastomers and ethylene copolymers exemplified in the surface layer (A). , Ionomers and the like. When the other resin is used, its content is preferably used at 30% by mass or less in the resin component contained in the heat seal layer (C), and more preferably at 30% by mass or less. , More preferably 10% by mass or less, further preferably 5% by mass or less.

  In the heat seal layer (C), various additives and the like may be appropriately used in addition to the above resin components. As the additive, for example, a lubricant, an antiblocking agent, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antifogging agent, a coloring agent, and the like can be appropriately used. When these additives are used, they are preferably used in an amount of 2 parts by mass or less, more preferably about 0.01 to 1 part by mass, based on 100 parts by mass of the resin component used in the heat seal layer (C).

  The thickness ratio of the heat seal layer (C) to the laminated film (I) is preferably from 5 to 45%, more preferably from 10 to 30%, from the viewpoint of heat sealability and low-temperature impact resistance. .

[Laminated film]
The laminated film of the present invention is a laminated film in which the surface layer (A), the intermediate layer (B) and the heat seal layer (C) are laminated in the order of (A) / (B) / (C). The laminated film of the present invention can realize suitable impact resistance even at a low temperature, particularly at a low temperature such as −15 ° C., which is much lower than 0 ° C., by the above configuration. In addition, it has good film-forming properties, and can realize suitable rigidity, sealing properties, and suitability for packaging machines.

  The laminated film of the present invention preferably has a thickness of 15 to 100 μm, more preferably 20 to 50 μm. When the thickness of the film is in this range, it becomes easy to obtain excellent impact resistance, rigidity, sealing properties, suitability for packaging machines, and the like at low temperatures.

  The thickness of each layer is not particularly limited. For example, the thickness of the surface layer (A) is preferably 4 to 18 μm, and more preferably 6 to 12 μm. The thickness of the intermediate layer (B) is preferably from 4 to 32 μm, more preferably from 6 to 28 μm. The thickness of the heat seal layer (C) is preferably from 2 to 18 μm, more preferably from 4 to 12 μm.

  The laminated film of the present invention preferably has a seal strength of 5 N / 15 mm or more, and more preferably 10 N / 15 mm or more, from the viewpoint of protecting the contents.

  The laminated film of the present invention preferably has an impact resistance measured by a film impact method of 0.5 J or more, more preferably 0.7 J or more. The impact strength is an impact strength measured after conditioning a 40 μm laminated film at −15 ° C.

  The method for producing the laminated film of the present invention is not particularly limited. For example, each resin or resin mixture used for the surface layer (A), the intermediate layer (B), and the heat seal layer (C) may be separately extruded. And laminated in the order of (A) / (B) / (C) in a molten state by a method such as a co-extrusion multilayer die method or a feed block method, and then a film is formed by inflation or T-die chill roll method. Coextrusion method. This coextrusion method is preferable because the thickness ratio of each layer can be adjusted relatively freely, and a laminated film excellent in hygiene and cost performance can be obtained.

  Since the laminated film of the present invention is obtained as a substantially non-stretched laminated film by the above-mentioned production method, secondary forming such as deep drawing by vacuum forming is also possible.

  Further, in order to improve the adhesiveness with a printing ink and the suitability for lamination when used as a sealant film for lamination, it is preferable to subject the resin layer (A) to a surface treatment. Examples of such surface treatment include, for example, corona treatment, plasma treatment, chromic acid treatment, flame treatment, hot air treatment, surface oxidation treatment such as ozone / ultraviolet treatment, and surface unevenness treatment such as sandblasting. Preferably, it is a corona treatment.

  Examples of the packaging material comprising the laminated film of the present invention include packaging bags, packaging containers, and the like used for food, medicine, industrial parts, sundries, magazines, and the like.

  The packaging bag is formed by laminating the heat seal layers (C) of the laminated film of the present invention and heat sealing them, or by laminating the surface layer (A) and the heat seal layer (C) and heat sealing. It is preferably a bag. For example, the two laminated films are cut out to a desired size of a packaging bag, and they are stacked and heat-sealed on three sides to form a bag, and then the contents are filled from one side not heat-sealed. It can be used as a packaging bag by heat sealing. Further, it is also possible to form a packaging bag by sealing the end of the roll-shaped film into a cylindrical shape with an automatic packaging machine and then sealing the upper and lower sides.

  It is also possible to form a packaging bag / container by stacking another heat-sealable film on the heat-seal layer (C) and heat-sealing it. In this case, as another film to be used, a film such as LDPE or EVA having relatively low mechanical strength can be used.

  The laminated film of the present invention can be used even when attached to another substrate. Other substrates that can be used at this time are not particularly limited, but from the viewpoint of easily exhibiting the effects of the present invention, a plastic substrate having high rigidity and high gloss, in particular, biaxial It is preferable to use a stretched resin film. For applications that do not require transparency, aluminum foil can be used alone or in combination.

  As the stretched resin film, from the viewpoint of easy tearing properties, for example, biaxially stretched polyester (PET), easily tearable biaxially stretched polyester (PET), biaxially stretched polypropylene (OPP), biaxially stretched polyamide ( PA), co-extruded biaxially-stretched polypropylene with ethylene-vinyl alcohol copolymer (EVOH) as the central layer, bi-axially stretched ethylene-vinyl alcohol copolymer (EVOH), co-extrusion biaxially coated with polyvinylidene chloride (PVDC) Stretched polypropylene and the like. These may be used alone or in combination.

  When the base material is laminated on the laminated film obtained by the above-mentioned production method to form a laminated film, examples of the laminating method include dry lamination, wet lamination, non-solvent lamination, and extrusion lamination.

  Examples of the adhesive used in the dry lamination include a polyether-polyurethane-based adhesive and a polyester-polyurethane-based adhesive. Further, various pressure-sensitive adhesives can be used, but it is preferable to use a pressure-sensitive pressure-sensitive adhesive. Examples of the pressure-sensitive adhesive include polyisobutylene rubber, butyl rubber, a rubber-based adhesive obtained by dissolving a mixture thereof in an organic solvent such as benzene, toluene, xylene, and hexane; Ester, terpene / phenol copolymer, terpene / indene copolymer and other tackifiers, or 2-ethylhexyl acrylate / n-butyl acrylate copolymer, 2-ethylhexyl acrylate / ethyl acrylate An acrylic adhesive obtained by dissolving an acrylic copolymer having a glass transition point of −20 ° C. or less, such as a methyl methacrylate copolymer, with an organic solvent can be used.

  In the packaging material using the laminated film of the present invention, an arbitrary tear start portion such as a V notch, an I notch, a perforation, or a microporous is formed in the seal portion to reduce the initial tear strength and improve the opening property. Is preferred.

  Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. Hereinafter, “parts” and “%” are based on mass unless otherwise specified.

(Example 1)
The following resin was used as a resin component for forming each layer of the surface layer (A), the intermediate layer (B1), and the heat seal layer (C), and a resin mixture for forming each layer was prepared. The resin mixture forming each layer is supplied to three extruders, and the average thickness of each layer of the laminated film formed of the surface layer (A) / intermediate layer (B1) / heat seal layer (C) is 8 μm. / 26 μm / 6 μm was co-extruded from a T-die at an extrusion temperature of 250 ° C. and cooled with a water-cooled metal cooling roll at 40 ° C. to form a laminated film having a total thickness of 40 μm.
Surface layer (A): 100 parts by mass of propylene homopolymer (density: 0.900 g / cm ³ , MFR: 11.5 g / 10 min) (hereinafter referred to as PP (1)).
Intermediate layer (B1): 70 parts by mass of linear low-density polyethylene (density 0.920 g / cm ³ , MFR 4.0 g / 10 min) (hereinafter referred to as LLDPE (1)) and linear low-density polyethylene (density) 0.931 g / cm ³ , 4.0 g / 10 min MFR (hereinafter referred to as LLDPE (2)).
Heat seal layer (C): 100 parts by mass of linear low-density polyethylene (density 0.904 / cm ³ , MFR 4.0 g / 10 min (hereinafter referred to as LLDPE (3)).

(Example 2)
A laminated film was obtained in the same manner as in Example 1, except that the resin used for the surface layer (A) was changed to the following components.
Surface layer (A): 100 parts by mass of propylene homopolymer (density 0.900 g / cm ³ , MFR 8.0 g / 10 min) (hereinafter referred to as PP (2)).

(Example 3)
A laminated film was obtained in the same manner as in Example 1, except that the resin used for the surface layer (A) was changed to the following components.
Surface layer (A): 100 parts by mass of propylene homopolymer (density 0.900 g / cm ³ , MFR 3.0 g / 10 min) (hereinafter referred to as PP (3)).

(Example 4)
A laminated film was obtained in the same manner as in Example 1, except that the resin used for the surface layer (A) was changed to the following components.
Surface layer (A): 100 parts by mass of a propylene homopolymer (density 0.900 g / cm ³ , MFR 2.5 g / 10 min) (hereinafter referred to as PP (4)).

(Example 5)
The following resin is used as a resin component for forming each layer of the surface layer (A), the intermediate layer (B1), the intermediate layer (B2), and the heat seal layer (C), and a resin mixture for forming each layer is adjusted. did. The resin mixture forming each layer is supplied to each of four extruders, and each layer of the laminated film formed by the surface layer (A) / intermediate layer (B1) / intermediate layer (B2) / heat seal layer (C) Was co-extruded from a T-die at an extrusion temperature of 250 ° C. so as to have an average thickness of 8 μm / 13 μm / 13 μm / 6 μm, and cooled with a water-cooled metal cooling roll at 40 ° C. to form a laminated film having a total thickness of 40 μm. .
Surface layer (A): 100 parts by mass of PP (2).
Intermediate layer (B1): a mixture of LLDPE (1) 70 parts by mass and LLDPE 30 parts by mass.
Intermediate layer (B2): a mixture of 70 parts by mass of LLDPE (1) and 30 parts by mass of LLDPE.
Heat seal layer (C): 100 parts by mass of LLDPE (3).

(Comparative Example 1)
A laminated film was obtained in the same manner as in Example 1, except that the resin used for the surface layer (A) was changed to the following components.
Surface layer (A): 100 parts by mass of propylene homopolymer (density 0.900 g / cm ³ , MFR 13.0 g / 10 min) (hereinafter referred to as PP (5)).

(Comparative Example 2)
A laminated film was obtained in the same manner as in Example 1, except that the resin used for the surface layer (A) was changed to the following components.
Surface layer (A): 100 parts by mass of a propylene homopolymer (density 0.900 g / cm ³ , MFR 20.0 g / 10 min) (hereinafter referred to as PP (6)).

[Shock resistance]
Test pieces were prepared by allowing the films obtained in Examples and Comparative Examples to stand for 4 hours in a thermostatic chamber adjusted to 0 ° C., and to prepare test pieces that were allowed to stand in a thermostatic chamber adjusted to −15 ° C. for 4 hours. For each test piece, using a BU-302 type film impact tester manufactured by Tester Sangyo, a 1.0-inch head was attached to the tip of the pendulum, and the impact strength was measured by a film impact method.
：: Impact strength of 0.70 (J) or more ×: Impact strength of less than 0.70 (J)

[Film formation property]
A film was formed to a thickness of 50 m under the conditions of the example and the comparative example, and the appearance of the film after the film formation was observed.
◎: Good film formability ：: Film formation is possible, but there is some poor appearance (meramel feeling) ×: Film formation not possible

[Heat seal strength]
Using the films obtained in Examples and Comparative Examples, a test piece heat-sealed with a seal width of 10 mm under conditions of 130 ° C., 0.2 MPa and 1 second was cut, cut into a width of 15 mm, and subjected to a tensile tester. , The seal strength was measured. The same evaluation was performed three times, and the average value was used as the evaluation result.
：: Heat seal strength is 5 N / 15 mm or more ×: Heat seal strength is less than 5 N / 15 mm

  Tables 1 and 2 show the results obtained above.

  As is clear from the above table, the laminated films of the present invention of Examples 1 to 4 had excellent impact resistance at a very low temperature of -15 ° C and also had good film-forming properties. On the other hand, the laminated films of Comparative Examples 1 and 2 could not have both favorable impact resistance and film formability.

Claims (5)

  A laminated film in which a surface layer (A), an intermediate layer (B), and a heat seal layer (C) are laminated, wherein the surface layer (A) is a layer mainly composed of a polypropylene-based resin. The layer (B) and the heat seal layer (C) are layers containing a linear low-density polyethylene as a main resin component, and the polypropylene resin in the surface layer (A) has an MFR (230 ° C.) of 12 g / 10 min or less. A laminated film comprising the polypropylene resin (a1).   The laminated film according to claim 1, wherein the polypropylene resin (a1) in the surface layer (A) has an MFR (230 ° C) of 6 g / 10 min or more.   The laminated film according to claim 1, wherein a total thickness of the laminated film is in a range of 20 to 60 μm.   The laminated film according to any one of claims 1 to 3, wherein the laminated film has an impact strength at -15 ° C of 0.7 J or more. A packaging material using the laminated film according to claim 1.