JP2021192985A - Laminate film and packaging material - Google Patents

Abstract

To provide a laminate film which can achieve excellent impact resistance even under extremely low temperature while having suitable 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. 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 a polypropylene-based resin (a1) having an MFR (230°C) of 8-12 g/10 min is contained as the polypropylene-based resin in the surface layer (A). The laminate film can achieve excellent impact resistance under low temperature while having suitable 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 impact resistance at low temperatures.

Conventionally, films mainly composed of polypropylene-based resins have high rigidity and high surface gloss, and are therefore widely used as packaging materials for foods and medical products. However, polypropylene-based resin alone may not provide sufficient impact resistance at low temperatures, and in applications such as frozen food packaging, a linear ethylene-α-olefin copolymer layer may be used as the polypropylene-based resin layer. Laminated films and the like that are laminated to improve impact resistance at low temperatures are used (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2001-105468

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 low temperatures as well as suitability for automatic packaging. It is a realized laminated film and can be suitably applied to packaging applications for frozen foods.

However, due to the recent development of freezing technology such as the diversification of the contents to be frozen and packaged and the lowering of the freezing temperature, it is required to further improve the impact resistance under low temperature to prevent the packaging bag from breaking. Has been done.

An object to be solved by the present invention is to provide a laminated film which can realize excellent impact resistance even at a very low temperature while having suitable rigidity.

Further, an object to be solved by the present invention is to provide a laminated film having excellent film forming property 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 containing a polypropylene-based resin as a main resin component, and the intermediate. The 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.) of 12 g / 10 min or less. A laminated film containing a polypropylene-based resin (a1) solves the above-mentioned problems.

Since the laminated film of the present invention has excellent impact resistance due to its suitable rigidity, bag breakage is unlikely to occur even when applied to packaging applications. In particular, since it has excellent impact resistance even at low temperatures well below 0 ° C, for example, at low temperatures of -15 ° C, it is stored and stored at low temperatures, and is used for packaging such as food applications and medical products, especially frozen foods. Can be suitably applied as a packaging application. Further, since excellent film forming property 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, and the surface layer (A) contains a polypropylene-based resin as a main resin component. The intermediate layer (B) and the heat-sealed layer (C) are layers containing linear low-density polyethylene as a main resin component, and MFR (230 ° C.) is used as the polypropylene-based resin in the surface layer (A). ) Is a laminated film containing a polypropylene resin (a1) having a weight 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 by containing the polypropylene-based resin as a main resin component, suitable rigidity and surface heat resistance are realized. can. In addition, it becomes easy to obtain a laminated film having a good appearance. As the polypropylene-based 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 it is easy to obtain high rigidity and transparency.

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

The polypropylene-based resin in the surface layer (A) preferably has a melting point of 155 to 170 ° C, more preferably 158 to 165 ° C. By using polypropylene having a melting point in the above range, it becomes easy to realize suitable impact resistance and packaging machine suitability. In addition, suitable heat resistance can be realized. The melting point refers to the melting peak by the differential scanning calorimeter.

The surface layer (A) contains the polypropylene-based resin as a main component, and other resins that can be coextruded may be used in combination as long as the effects of the present invention are not impaired. In addition, "referred to as a main resin component" specifically means that 70% by mass or more of the resin component used for the surface layer (A) is polypropylene-based resin, and 80% by mass or more is polypropylene. It is preferably a based 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-based resins.

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

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

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

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

A resin other than the above may be used in combination with the surface layer (A) used in the present invention. Examples of the other resin include thermoplastic elastomers such as polyethylene-based elastomers, polypropylene-based elastomers, and butene-based elastomers; ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), and ethylene. -Methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA) Etc., and examples thereof include an ionomer of an ethylene-acrylic acid copolymer, an ionomer of an ethylene-methacrylic acid copolymer, and the like.

When the above other resin is used, it is preferable to use it in an amount of 30% by mass or less, and more preferably 30% by mass or less in the resin component contained in the surface layer (A). It is more preferably 10% by mass or less, and further preferably 5% by mass or less.

In addition to the above resin components, various additives and the like may be appropriately used in combination in the surface layer (A). As the additive, for example, a lubricant, an anti-blocking agent, an ultraviolet absorber, a light stabilizer, an antistatic agent, an anti-fog agent, a colorant and the like can be appropriately used. When these additives are used, they are preferably used in an amount of preferably 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 for the surface layer (A).

The thickness ratio of the surface layer (A) to the total thickness of the laminated film is defined as the thickness ratio of the surface layer (A) to the total thickness of the laminated film because it is easy to obtain suitable rigidity and excellent impact resistance at low temperature. Is preferably in the range of 45 to 10%, and particularly preferably in the range of 30 to 15%.

[Middle layer (B)]
The intermediate layer (B) of the laminated film of the present invention is a layer containing linear low-density polyethylene as a main component. By using the intermediate layer (B), suitable impact resistance at low temperatures can be realized. In addition, it becomes easy to realize good packaging machine suitability. 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, and 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 minutes (190 ° C., 21.18N), preferably 1 to 30 g / 10 minutes (190 ° C., 21.18N). , More preferably 2 to 20 g / 10 minutes (190 ° C., 21.18 N). When the MFR is in this range, good film forming property can be obtained, which is preferable.

In the present invention, the content of the linear low-density polyethylene in the intermediate layer (B) is 70% by mass or more in the resin component contained in the intermediate layer (B), so that the sealing property is suitable and the temperature is low. It becomes easy to obtain excellent impact resistance. The content is preferably 75% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more 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. Further, if the total content is within the above range, two or more kinds of linear low-density polyethylene 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 80 to 10%, more preferably 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, formability of the multilayer film, and high heat-sealing strength can be obtained. It is preferable because it can be used.

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

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 intermediate layer (B) is preferably 10% by mass or less, and is preferably 5% by mass. % Or less, and it is also preferable not to use it substantially.

Further, a resin other than the above may be used in combination in the intermediate layer (B), and examples of the other resin include the thermoplastic elastomer and the ethylene-based copolymer exemplified in the surface layer (A). Ionomer and the like can be exemplified. When the other resin is used, it is preferable to use it in an amount of 30% by mass or less, and more preferably 30% by mass or less in the resin component contained in the intermediate layer (B). It is more preferably 10% by mass or less, and further preferably 5% by mass or less.

In addition to the above resin components, various additives and the like may be appropriately used in combination in the intermediate layer (B). As the additive, for example, a lubricant, an anti-blocking agent, an ultraviolet absorber, a light stabilizer, an antistatic agent, an anti-fog agent, a colorant and the like can be appropriately used. When these additives are used, they are preferably used in an amount of preferably 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 for 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 containing linear low-density polyethylene as a main component. Good impact resistance and heat sealability can be realized by laminating a plurality of layers containing the linear low-density polyethylene as a main component. The density of the linear low-density polyethylene used for the heat-sealing layer (C) is preferably ^{0.880 to 0.940 g / cm 3 because good sealing properties and impact resistance can be obtained.} Further, when heat resistance is required for heat sterilization, 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 is required.} It is preferable 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 minutes (190 ° C., 21.18 N), preferably 1 to 30 g / 10 minutes (190 ° C., 21.18 N), more preferably 2 to 20 g / min. 10 minutes (190 ° C., 21.18N). When the MFR is in this range, good film forming property can be obtained, which is preferable.

In the present invention, the content of the linear low-density polyethylene in the heat-seal layer (C) is 70% by mass or more of the resin component contained in the heat-seal layer (C), so that suitable sealing properties and low temperature are achieved. It is easy to obtain excellent impact resistance underneath. The content is preferably 75% by mass or more, more preferably 80% by mass or more, and further 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. Further, if the total content is within the above range, two or more kinds of linear low-density polyethylene 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 effect of the present invention is not impaired. Examples of other resin types that can be used in combination include polyethylene-based resins other than the linear low-density polyethylene-based resin exemplified in the surface layer (A), and olefin-based resins such as polypropylene-based resin. When an olefin resin is used as the resin other than the linear low-density polyethylene, the content thereof is preferably 30% by mass or less of the resin component contained in the heat seal layer (C), preferably 10% by mass. It is more preferably less than or equal to 5% by mass or less.

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. It is more preferably to be mass% or less, and it is also preferable not to use it substantially.

Further, a resin other than the above may be used in combination in the heat seal layer (C), and examples of the other resin include the thermoplastic elastomer and the ethylene-based copolymer exemplified in the surface layer (A). , Ionomer, etc. can be exemplified. When the other resin is used, it is preferable to use it in an amount of 30% by mass or less, and more preferably 30% by mass or less in the resin component contained in the heat seal layer (C). It is more preferably 10% by mass or less, and further preferably 5% by mass or less.

In addition to the above resin components, various additives and the like may be appropriately used in combination in the heat seal layer (C). As the additive, for example, a lubricant, an anti-blocking agent, an ultraviolet absorber, a light stabilizer, an antistatic agent, an anti-fog agent, a colorant and the like can be appropriately used. When these additives are used, they are preferably used in an amount of preferably 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 for the heat seal layer (C).

The thickness ratio of the heat seal layer (C) to the laminated film (I) is preferably 5 to 45%, more preferably 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). With this configuration, 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. 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 film thickness of 15 to 100 μm, more preferably 20 to 50 μm. When the thickness of the film is within this range, it becomes easy to obtain excellent impact resistance, rigidity, sealing property, suitability for packaging machines, etc. at low temperatures.

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

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

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

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

Since the laminated film of the present invention can be obtained as a substantially unstretched laminated film by the above-mentioned manufacturing method, secondary molding such as deep drawing by vacuum forming is also possible.

Further, in order to improve the adhesiveness with the printing ink and the laminating suitability when used as a sealant film for laminating, it is preferable to apply a surface treatment to the resin layer (A). Examples of such surface treatments include 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. Corona treatment is preferable.

Examples of the packaging material made of the laminated film of the present invention include packaging bags and containers used for applications such as foods, chemicals, industrial parts, miscellaneous goods, and magazines.

The packaging bag is a package formed by superimposing heat-sealing layers (C) of the laminated film of the present invention on each other to heat-seal, or by superimposing a surface layer (A) and a heat-sealing layer (C) on each other to heat-seal. It is preferably a bag. For example, the two laminated films are cut out to the desired size of the 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 that is not heat-sealed. It can be used as a packaging bag by heat-sealing and sealing. Furthermore, it is also possible to form a packaging bag by sealing the end of a roll-shaped film in a cylindrical shape with an automatic packaging machine and then sealing the top and bottom.

It is also possible to form a packaging bag / container by superimposing and heat-sealing the heat-sealing layer (C) and another heat-sealing film. At that time, as another film to be used, a film such as LDPE or EVA having a relatively weak mechanical strength can be used.

The laminated film of the present invention can also be used by laminating it with another base material. The other base material that can be used at this time is not particularly limited, but from the viewpoint of easily exhibiting the effects of the present invention, a plastic base material having high rigidity and high gloss, particularly biaxial It is preferable to use a stretched resin film. In addition, aluminum foil can be used alone or in combination for applications that do not require transparency.

Examples of the stretched resin film include biaxially stretched polyester (PET), easily tearable biaxially stretched polyester (PET), biaxially stretched polypropylene (OPP), and biaxially stretched polyamide (PET), biaxially stretched polypropylene (OPP), and biaxially stretched polyamide (PET). PA), co-extruded biaxially stretched polypropylene with ethylene vinyl alcohol copolymer (EVOH) as the central layer, biaxially stretched ethylene vinyl alcohol copolymer (EVOH), and co-extruded biaxially coated with polyvinylidene chloride (PVDC). Examples thereof include stretched polypropylene. These may be used alone or in combination.

Examples of the laminating method in the case of laminating the base material on the laminated film obtained by the above manufacturing method to form a laminated film include methods such as 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, a polyester-polyurethane-based adhesive, and the like. Although various pressure-sensitive adhesives can be used, it is preferable to use a pressure-sensitive pressure-sensitive adhesive. Examples of the pressure-sensitive pressure-sensitive adhesive include polyisobutylene rubber, butyl rubber, a rubber-based pressure-sensitive adhesive obtained by dissolving a mixture thereof in an organic solvent such as benzene, toluene, xylene, and hexane, or rosin abiethylene acid in these rubber-based pressure-sensitive adhesives. A mixture containing a tackifier such as an ester, a terpene / phenol copolymer, a terpene / inden copolymer, or a 2-ethylhexyl acrylate / n-butyl acrylate copolymer, a 2-ethylhexyl acrylate / ethyl acrylate. Examples thereof include an acrylic pressure-sensitive adhesive obtained by dissolving an acrylic copolymer having a glass transition point of −20 ° C. or lower, such as a methyl methacrylate copolymer, with an organic solvent.

In the packaging material using the laminated film of the present invention, in order to weaken the initial tear strength and improve the openability, an arbitrary tear start portion such as a V notch, an I notch, a perforation, or a microporous is formed in the seal portion. It is preferable to do so.

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

(Example 1)
The following resins were used as the resin components forming the surface layer (A), the intermediate layer (B1), and the heat seal layer (C), respectively, to prepare a resin mixture forming each layer. The resin mixture forming each layer is supplied to each of the three extruders, and the average thickness of each layer of the laminated film formed by the surface layer (A) / intermediate layer (B1) / heat seal layer (C) is 8 μm. It was co-extruded from the 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 so as to be / 26 μm / 6 μm.
Surface layer (A): 100 parts by mass of a propylene homopolymer (density 0.900 g / cm ³ , MFR 11.5 g / 10 min) (hereinafter referred to as PP (1)).
Intermediate layer (B1): Linear low-density polyethylene (density 0.920 g / cm ³ , MFR 4.0 g / 10 min) (hereinafter referred to as LLDPE (1)) 70 parts by mass and linear low-density polyethylene (density) 0.931 g / cm ³ , MFR 4.0 g / 10 min) (hereinafter referred to as LLDPE (2)) 30 parts by mass.
Heat-sealed layer (C): Linear low-density polyethylene (density 0.904 / cm ³ , MFR 4.0 g / 10 min (hereinafter referred to as LLDPE (3)) 100 parts by mass.

(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 the following component.
Surface layer (A): 100 parts by mass of a 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 the following component.
Surface layer (A): 100 parts by mass of a 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 the following component.
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)
As the resin component forming each layer of the surface layer (A), the intermediate layer (B1), the intermediate layer (B2), and the heat seal layer (C), the following resins are used to prepare the resin mixture forming each layer. did. Each layer of the laminated film formed by the surface layer (A) / intermediate layer (B1) / intermediate layer (B2) / heat seal layer (C) by supplying the resin mixture forming each layer to each of the four extruders. Was co-extruded from the 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 so that the average thickness of the film was 8 μm / 13 μm / 13 μm / 6 μm. ..
Surface layer (A): 100 parts by mass of PP (2).
Intermediate layer (B1): A mixture of 70 parts by mass of LLDPE (1) and 30 parts by mass of LLDPE.
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 the following component.
Surface layer (A): 100 parts by mass of a 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 the following component.
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)).

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

[Film film property]
A 50 m film was formed under the conditions of Examples and Comparative Examples, and the appearance of the film after the film was observed was observed.
◎: Good film formation ○: Film formation is possible, but there is some appearance defect (mellow feeling) ×: Film formation is not possible

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

The results obtained above are shown in Tables 1 and 2.

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 suitable impact resistance and film forming property.

Claims (4)

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 containing a polypropylene-based resin as a main resin component, and the intermediate. The layer (B) and the heat seal layer (C) are layers containing linear low-density polyethylene as a main resin component, and the polypropylene-based resin in the surface layer (A) contains 8 to 12 g / MFR (230 ° C.). A laminated film containing 10 min of polypropylene-based resin (a1). The laminated film according to claim 1 , wherein the total thickness of the laminated film is in the range of 20 to 50 μm. The laminated film according to claim 1 or 2, wherein the laminated film has an impact strength of 0.7 J or more at −15 ° C. A packaging material using the laminated film according to any one of claims 1 to 3.