JP7276394B2 - Laminated films and packaging materials - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminated film used as a packaging material for foods and medical products, and more particularly to a laminated film used as a packaging material having excellent impact resistance at low temperatures.

BACKGROUND ART Conventionally, films mainly composed of polypropylene-based resins have been widely used as packaging materials for foods, medical products, and the like because of their high rigidity and high surface gloss. However, polypropylene resin alone may not provide sufficient impact resistance at low temperatures. A laminated film or the like that is laminated to improve impact resistance at low temperatures is used (see Patent Document 1).

JP-A-2001-105468

By laminating a polypropylene-based resin layer and two linear ethylene-α-olefin copolymer layers with specific densities, the above-mentioned laminated film is suitable for automatic packaging and has excellent impact strength at low temperatures. This laminated film has been realized, and can be suitably applied to the packaging of frozen foods.

However, due to the recent development of freezing technology such as the diversification of the contents to be frozen packaged and the lower freezing temperature, there is a demand for further improvement of impact resistance at low temperatures in order to suppress the breakage of packaging bags. It is

The problem to be solved by the present invention is to provide a laminated film that can achieve excellent impact resistance even at very low temperatures while having suitable rigidity.

Furthermore, the problem to be solved by the present invention is, in addition to the above, to provide a laminated film excellent in film-forming properties.

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 problems.

Since the laminated film of the present invention has excellent impact resistance due to its suitable rigidity, bag breakage is less likely to occur even when it is applied to packaging applications. In particular, it has excellent impact resistance even at a low temperature much lower than 0 ° C., for example, at a low temperature of -15 ° C., so it can be stored and stored at low temperatures. It can be suitably applied as a packaging application of. In addition, since excellent film-forming properties can be realized, it can be suitably applied to food applications that require 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 resin as 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) is MFR (230 ° C. ) is a laminated film containing a polypropylene 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 by containing the polypropylene-based resin as a main resin component, suitable rigidity and surface heat resistance are achieved. can. In addition, it becomes easier to obtain a laminated film with 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, a polypropylene resin (a1) having an MFR (230° C.) of 12 g/10 min or less is contained as the polypropylene resin in the surface layer (A). By containing the propylene-based resin (a1), excellent impact resistance can be achieved even at a low temperature much 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. Also, the lower limit of MFR is not particularly limited as long as it is within a range in which a laminated film can be formed, but it is preferably 0.5 g/10 min or more. In particular, from the viewpoint of film-forming properties, it is more preferably 3 g/10 min or more, and even more preferably 6 g/10 min or more.

The polypropylene 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 within the above range, it becomes easier to achieve suitable impact resistance and suitability for packaging machines. Moreover, suitable heat resistance can be realized. The melting point refers to the melting peak by differential scanning calorimeter.

The surface layer (A) is composed mainly of the polypropylene-based resin described above, and may be used in combination with other resins capable of being coextruded as long as the effects of the present invention are not impaired. In addition, "contained as the main resin component" specifically means that 70% by mass or more of the resin component used in the surface layer (A) is a polypropylene resin, and 80% by mass or more is polypropylene. It is preferably a polypropylene-based resin, and more preferably 90% by mass or more is a polypropylene-based 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 resin (a1) having an 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 preferably 90% by mass or more. is more preferable. By setting the content of the polypropylene-based resin (a1) within this range, it becomes easier to achieve good rigidity and excellent impact resistance at low temperatures.

Various resins used for packaging films can be used as resins other than the above-described polypropylene-based resins for use in the surface layer (A), and among them, olefin-based resins such as ethylene-based resins can be preferably used. Examples of ethylene-based resins include polyethylene resins such as very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), linear medium density polyethylene (LMDPE), medium density polyethylene (MDPE), Ethylene-vinyl acetate copolymer (EVA) and the like can be used.

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

A cyclic polyolefin-based resin may be used as the olefin-based resin, but 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 5% by mass. % or less, and it is also preferable not to use it substantially.

In the surface layer (A) used in the present invention, resins other than those described above may be used in combination. Examples of other resins include thermoplastic elastomers such as polyethylene elastomers, polypropylene elastomers, and butene elastomers; 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) ethylene-based copolymers such as ethylene-based copolymers; furthermore, ionomers of ethylene-acrylic acid copolymers, ionomers of ethylene-methacrylic acid copolymers, and the like can be exemplified.

When other resins are used, the content thereof is preferably 30% by mass or less, more preferably 30% by mass or less, of the resin component contained in the surface layer (A). It is more preferably 10% by mass or less, and even more preferably 5% by mass or less.

In the surface layer (A), various additives may be appropriately used in combination with the above resin components. As additives, for example, lubricants, antiblocking agents, ultraviolet absorbers, light stabilizers, antistatic agents, antifogging agents, coloring agents, and the like can be used as appropriate. When these additives are used, they are used in an amount of preferably 2 parts by mass or less, more preferably about 0.01 to 1 part by mass, per 100 parts by mass of the resin component used in the surface layer (A).

The thickness ratio of the surface layer (A) to the total thickness of the laminated film facilitates obtaining suitable rigidity and excellent impact resistance at low temperatures, so the thickness ratio of the surface layer (A) to the total thickness of the laminated film is is preferably in the range of 45 to 10%, more 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 containing linear low-density polyethylene as a main component. By using the intermediate layer (B), suitable impact resistance at low temperatures can be achieved. In addition, it becomes easier to achieve good suitability for packaging machines. The density of the linear low-density polyethylene used for the intermediate layer (B) is preferably 0.950 g/cm ³ or less, more preferably 0.940 g/cm ³ or less, since good impact resistance can be easily obtained. . Also, 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 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 within this range, it is preferable in that good film formability can be obtained.

In the present invention, the content of the linear low-density polyethylene in the intermediate layer (B) is set to 70% by mass or more in the resin component contained in the intermediate layer (B), so that suitable sealing properties and low temperature It becomes easy to obtain excellent impact resistance of The content is preferably 75% by mass or more, more preferably 80% by mass or more, and even more 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. Moreover, if the total content is within the above range, two or more types of linear low-density polyethylene having different densities, MFRs, etc. 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, moldability of multilayer films, and high heat seal strength can be obtained. preferred because it is

In the intermediate layer (B), resins other than the linear low-density polyethylene may be used in combination within a range that does not impair the effects of the present invention. Other resins that can be used in combination include, for example, polyethylene resins other than the linear low-density polyethylene resins exemplified for the surface layer (A), and olefin resins such as polypropylene resins. When an olefin-based resin is used as a resin other than the linear low-density polyethylene, the content thereof in the resin component contained in the intermediate layer (B) is preferably 30% by mass or less, and 10% by mass or less. and more preferably 5% by mass or less.

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

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

In the intermediate layer (B), various additives may be appropriately used in combination with the above resin components. As additives, for example, lubricants, antiblocking agents, ultraviolet absorbers, light stabilizers, antistatic agents, antifogging agents, coloring agents, and the like can be used as appropriate. 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, per 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 containing linear low density polyethylene as a main component. By laminating a plurality of layers containing the linear low-density polyethylene as a main component, good impact resistance and heat sealability can be achieved. 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 because good sealing properties and impact resistance can be obtained. Further, 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 preferable to be An appropriate density may be selected according to the required properties of the film.

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

In the present invention, the content of the linear low-density polyethylene in the heat-seal layer (C) is set to 70% by mass or more of the resin component contained in the heat-seal layer (C), thereby achieving suitable sealing properties and low-temperature It becomes easy to obtain excellent impact resistance under the condition. 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. Moreover, 100% by mass of the resin component contained in the heat seal layer (C) may be linear low-density polyethylene. Moreover, if the total content is within the above range, two or more types of linear low-density polyethylene having different densities, MFRs, etc. may be used in combination.

In the heat seal layer (C), resins other than the linear low-density polyethylene may be used in combination within a range that does not impair the effects of the present invention. Other resins that can be used in combination include, for example, polyethylene resins other than the linear low-density polyethylene resins exemplified for the surface layer (A), and olefin resins such as polypropylene resins. When an olefin-based resin is used as a resin other than the linear low-density polyethylene, the content thereof in the resin component contained in the heat seal layer (C) is preferably 30% by mass or less, preferably 10% by mass. It is more preferably 5% by mass or less, more preferably 5% by mass or less.

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 heat seal layer (C) is preferably 10% by mass or less. It is more preferable to make it not more than mass %, and it is also preferable not to use it substantially.

In addition, in the heat seal layer (C), other resins than the above may be used in combination, and the other resins include the 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 30% by mass or less, more preferably 30% by mass or less, of the resin component contained in the heat seal layer (C). , more preferably 10% by mass or less, and even more preferably 5% by mass or less.

In the heat seal layer (C), various additives may be appropriately used in combination with the above resin components. As additives, for example, lubricants, antiblocking agents, ultraviolet absorbers, light stabilizers, antistatic agents, antifogging agents, coloring agents, and the like can be used as appropriate. When these additives are used, they are used in an amount of preferably 2 parts by mass or less, more preferably about 0.01 to 1 part by mass, per 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 laminate 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), intermediate layer (B) and heat seal layer (C) are laminated in the order of (A)/(B)/(C). Due to this structure, the laminated film of the present invention can achieve suitable impact resistance even at low temperatures, particularly at low temperatures such as -15°C, which is significantly below 0°C. In addition, it has good film-forming properties, and can realize suitable rigidity, sealability, 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. If the thickness of the film is within this range, it is easy to obtain excellent impact resistance, rigidity, sealability, 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 4-32 μm, more preferably 6-28 μm. The thickness of the heat seal layer (C) is preferably 2-18 μm, more preferably 4-12 μm.

The laminated film of the present invention preferably has a seal strength of 5 N/15 mm or 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 strength of 0.5 J or more, more preferably 0.7 J or more, as measured by a film impact method. The impact strength is the impact strength measured after conditioning the 40 μm laminate film at -15°C.

The method for producing the laminated film of the present invention is not particularly limited. After heating and melting with a coextrusion multilayer die method, feed block method, etc., in the molten state, (A) / (B) / (C) are laminated in order, and then a film is formed by inflation, T-die chill roll method, etc. A co-extrusion method in which the This coextrusion method is preferable because the thickness ratio of each layer can be adjusted relatively freely, and a laminated film excellent in sanitation 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 production method, secondary forming such as deep drawing forming by vacuum forming is also possible.

Further, the resin layer (A) is preferably surface-treated in order to improve adhesion to printing ink and lamination suitability when used as a sealant film for lamination. Examples of such surface treatment 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 preferred.

Packaging materials made of the laminated film of the present invention include packaging bags and packaging containers used for food, medicine, industrial parts, sundries, magazines and the like.

The packaging bag is a package formed by stacking and heat sealing the heat seal layers (C) of the laminated film of the present invention, or by stacking and heat sealing the surface layer (A) and the heat seal layer (C). A bag is preferred. For example, two sheets of the laminated film are cut into a desired size of a packaging bag, and after stacking them and heat-sealing three sides to form a bag, the content is 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 ends of a rolled film into a cylindrical shape using an automatic packaging machine and then sealing the top and bottom.

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

The laminated film of the present invention can also be used by bonding it to other substrates. Other substrates that can be used at this time are not particularly limited, but from the viewpoint of easily expressing the effects of the present invention, a plastic substrate having high rigidity and high gloss, especially a 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 tearability, for example, biaxially stretched polyester (PET), easily tearable biaxially stretched polyester (PET), biaxially stretched polypropylene (OPP), biaxially stretched polyamide ( PA), coextruded biaxially oriented polypropylene with ethylene vinyl alcohol copolymer (EVOH) as the core layer, biaxially oriented ethylene vinyl alcohol copolymer (EVOH), coextruded biaxially coated with polyvinylidene chloride (PVDC) Examples include oriented polypropylene. These may be used singly or in combination.

Lamination methods for laminating the substrate on the laminated film obtained by the above production method to form a laminated film include, for example, methods such as dry lamination, wet lamination, non-solvent lamination, and extrusion lamination.

Examples of adhesives used in the dry lamination include polyether-polyurethane adhesives and polyester-polyurethane adhesives. Although various adhesives can be used, it is preferable to use a 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, or a rubber-based adhesive containing rosin abieethyleneate. Those containing tackifiers such as esters, terpene-phenol copolymers, terpene-indene copolymers, or 2-ethylhexyl acrylate-n-butyl acrylate copolymers, 2-ethylhexyl acrylate-ethyl acrylate- 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, in an organic solvent can be used.

The packaging material using the laminated film of the present invention is formed with any desired tear initiation portion such as V notch, I notch, perforation, microporous, etc. in the seal portion in order to weaken initial tear strength and improve unsealability. preferably.

EXAMPLES 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)
As resin components for forming each layer of the surface layer (A), intermediate layer (B1), and heat seal layer (C), the following resins were used to prepare a resin mixture forming each layer. A resin mixture forming each layer is supplied to each of 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. /26 μm/6 μm, they were 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 with 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 , MFR 4.0 g/10 min) (hereinafter referred to as LLDPE (2)) and 30 parts by mass.
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 following resin was used for the surface layer (A).
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 following resin was used for the surface layer (A).
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 following resin was used for the surface layer (A).
Surface layer (A): 100 parts by mass of propylene homopolymer (density: 0.900 g/cm ³ , MFR: 2.5 g/10 min) (hereinafter referred to as PP (4)).

(Example 5)
As resin components for 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 a resin mixture forming each layer. bottom. A resin mixture forming each layer is supplied to each of four extruders, and each layer of a laminated film formed of 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 that the average thickness of was 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 with a total thickness of 40 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 following resin was used for the surface layer (A).
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 following resin was used for the surface layer (A).
Surface layer (A): 100 parts by mass of 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 test pieces by standing in a thermostatic chamber adjusted to 0°C for 4 hours, and in a thermostatic chamber adjusted to -15°C for 4 hours. For each test piece, a BU-302 film impact tester manufactured by Tester Sangyo Co., Ltd. was used to attach a 1.0-inch head to the tip of a pendulum, and the impact strength was measured by the film impact method.
○: impact strength is 0.70 (J) or more ×: impact strength is less than 0.70 (J)

[Film formability]
A film having a thickness of 50 m was formed under the conditions of Examples and Comparative Examples, and the appearance of the film after the film formation was observed.
◎: Good film formation ○: Film formation is possible, but there is a slight appearance defect (melting feeling) ×: Film formation is impossible

[Heat seal strength]
Using the films obtained in Examples and Comparative Examples, a test piece was heat-sealed with a seal width of 10 mm under the conditions of 130 ° C., 0.2 MPa, 1 second, cut into a width of 15 mm, and a tensile tester. to measure the seal strength. The same evaluation was performed 3 times, and the average value of these 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

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 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 formability.

Claims (6)

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 the main resin component, and the polypropylene resin in the surface layer (A) has an MFR (230 ° C.) of 8 to 12 g / A laminated film characterized by containing a polypropylene resin (a1) for 10 minutes and being unstretched . 2. The laminated film according to claim 1, wherein the total thickness of said laminated film is in the range of 20 to 50 μm. The laminated film according to claim 1, wherein the laminated film is laminated by a coextrusion method. The laminated film according to claim 1, wherein the laminated film has an impact strength at -15°C of 0.7 J or more. A method for producing a laminated film in which a surface layer (A), an intermediate layer (B) and a heat seal layer (C) are laminated by a coextrusion method, wherein the surface layer (A) contains a polypropylene resin as 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) is MFR (230 ° C.) of 8 to 12 g/10 min containing a polypropylene resin (a1). A packaging material using the laminated film according to any one of claims 1 to 4 .