JPWO2017056542A1 - Multilayer heat shrink film - Google Patents

Abstract

The present invention is a multilayer heat-shrinkable film suitable for accumulation packaging of contents (packaged articles), which has excellent binding force and strength, and can be easily torn and taken out. I will provide a. The present invention is a multilayer heat-shrinkable film containing a polyethylene resin, wherein (1) the ionomer is contained in at least one layer, and (2) the layer containing the ionomer is composed of the ionomer and the polyethylene resin. (3) the length in the TD direction of the island phase of the sea-island structure in the TD cross section formed by cutting in a direction (TD direction) perpendicular to the film winding direction (MD direction). Provided is a multilayer heat-shrinkable film having an aspect ratio ((length in TD direction) / (length in ZD direction)) of 4 or more with respect to the length in the film thickness direction (ZD direction).

Description

  The present invention relates to a multilayer heat shrink film (shrink film). The heat-shrinkable film can be used, for example, for applications in which accumulated products (can beverages, plastic bottle beverages, paper-packed beverages, etc.) are wrapped and heat-shrinkable film is shrunk by heat treatment and accumulated.

  Conventionally, canned beverages, plastic bottle beverages, paper-packed beverages and the like have been transported in a form that is easy to circulate in units of 24 cans, 6 bottles, etc., and have been opened at retail stores and arranged in stores. However, there is a problem that a large amount of cardboard must be disposed after unpacking. In recent years, there are increasing cases where consumers purchase cardboards at mass merchandise stores and take them home, and disposal of cardboards at home has become a problem.

  In light of the above problems, a method for collecting and packaging products with a heat-shrinkable film that is inexpensive and easy to dispose of has been proposed, but it satisfies all the properties of binding force and strength (shrinkability), and tearability (openability). At present, no heat shrinkable film has been obtained.

  As a heat shrink film, for example, Patent Document 1 discloses a multilayer thermoplastic film for packaging, which includes (a) a layer of polyolefin, and (b) a layer of a blend of polyolefin and ionomer, and omnidirectional tearing. A multilayer thermoplastic film for packaging, which is easy to display, is disclosed (claim 1). In patent document 1, although tearability is examined, shrinkage is not examined, and this film has insufficient binding force and strength.

  Patent Document 2 has at least three layers of both surface layers and an inner layer sandwiched therebetween, and at least one of the surface layers contains a specific ethylene-α-olefin copolymer and exhibits a specific heat of fusion. The inner layer includes a composition comprising a specific ethylene-α-olefin copolymer and a specific long-chain ethylene-α-olefin copolymer and / or a specific high-pressure low-density polyethylene. A heat shrinkable multilayer film is disclosed (claim 1). In Patent Document 2, the shrinkability is examined, but the tearability is not examined.

  Patent Document 3 discloses a laminated film composed of at least three layers, in which both surface layers are composed mainly of the component (A) that is an ethylene polymer, and the intermediate layer is a component (B) that is an ionomer. The thickness ratio of the intermediate layer to the total film thickness of the intermediate layer is 35 to 90%, and the total value of the heat shrinkage in the vertical and horizontal directions when immersed in an oil bath at 80 ° C. for 10 seconds is A stretch shrink laminate film of 30% or more is disclosed (claim 1). In Patent Document 3, the shrinkability is examined, but the tearability is not examined. Further, in Patent Document 3, only the case where both surface layers are mainly composed of an ethylene-vinyl acetate copolymer is specifically studied in the Examples. In the case of blending with an elastic modulus of 100 MPa or more necessary for packaging, there is a problem that the shrinkage rate is insufficient and the tearability is also insufficient.

  Therefore, it is desired to develop a heat shrinkable film that satisfies all the properties of binding force and strength (shrinkability) and tearability (openability).

Special table 2004-517751 gazette JP 2008-221725 A JP 2006-272802 A

  The present invention is a multilayer heat-shrinkable film suitable for accumulation packaging of contents (packaged articles), which has excellent binding force and strength, and can be easily torn and taken out. The purpose is to provide.

  As a result of intensive studies to achieve the above object, the present inventor, as a result, in a multilayer heat-shrinkable film containing a polyethylene resin, at least one layer contains an ionomer, and the ionomer-containing layer comprises an ionomer and polyethylene. The length of the island phase of the sea-island structure in the TD cross section formed by cutting in a direction (TD direction) perpendicular to the film winding direction (MD direction) The present invention has found that a multilayer heat-shrinkable film having an aspect ratio ((length in TD direction) / (length in ZD direction)) with a length in the film thickness direction (ZD direction) of 4 or more can achieve the above object. It came to complete.

That is, this invention relates to the following multilayer heat shrink film.
1. A multilayer heat shrink film containing a polyethylene resin,
(1) At least one layer contains an ionomer,
(2) The layer containing the ionomer has a sea-island structure of the ionomer and the polyethylene resin,
(3) The length in the TD direction and the film thickness direction (ZD direction) of the island phase of the sea-island structure in the TD cross section formed by cutting in the direction (TD direction) perpendicular to the film winding direction (MD direction) ) Aspect ratio ((length in TD direction) / (length in ZD direction)) is 4 or more,
A multilayer heat shrinkable film characterized by the above.
2. The Elmendorf tear strength in the direction perpendicular to the film winding direction (MD direction) (TD direction) is 1 N or less, and the thermal shrinkage in the TD direction at 130 ° C. measured in accordance with JIS Z1709 is 15 Item 2. The multilayer heat shrinkable film according to Item 1, which is at least%.
3. Item 3. The multilayer heat-shrinkable film according to Item 1 or 2, wherein the Elmendorf tear strength in the film winding direction (MD direction) is 1 N or less.
4). The multilayer heat shrinkable film has a layer structure in which an A layer (outer layer), a B layer (intermediate layer), and a C layer (inner layer) are laminated in that order, or an A layer (outer layer), a B layer (intermediate layer). The multilayer heat-shrinkable film according to any one of Items 1 to 3, wherein the layer) and the A layer (inner layer) are laminated in that order, and the B layer contains an ionomer.
5). Item 5. The multilayer heat shrinkable film according to Item 4, wherein the B layer contains 1 to 70% by mass of a polyethylene resin with respect to 100% by mass of the resin component.
6). The multilayer heat shrinkable film has a layer structure in which an A layer (outer layer), a B layer (intermediate layer), and a C layer (inner layer) are laminated in that order, or an A layer (outer layer), a B layer (intermediate layer). Layer) and A layer (inner layer) are laminated in that order. The layer A has a density of 0.915 to 0.930 g / cm ³ and an MFR of 0.1 to 2.0 g / 10 min. Low density polyethylene, and linear low density polyethylene having a density of 0.900 to 0.940 g / cm ³ and MFR of 0.1 to 4.0 g / 10 min, and the content of the linear low density polyethylene Is a multilayer heat shrinkable film according to any one of Items 1 to 5, which is 10 to 90% by mass relative to 100% by mass of the resin component of the A layer.
7). The multilayer heat shrinkable film has a layer structure in which an A layer (outer layer), a B layer (intermediate layer), and a C layer (inner layer) are laminated in that order, or an A layer (outer layer), a B layer (intermediate layer). Layer) and A layer (inner layer) are laminated in that order. The layer A has a density of 0.915 to 0.930 g / cm ³ and an MFR of 0.1 to 2.0 g / 10 min. Low density polyethylene, and high density polyethylene having a density of 0.940 to 0.960 g / cm ³ and MFR of 0.1 to 4.0 g / 10 min. Item 6. The multilayer heat shrinkable film according to any one of Items 1 to 5, which is 10 to 90% by mass relative to 100% by mass of the resin component.

  The multilayer heat-shrinkable film of the present invention is suitable for accumulation packaging of contents (packaged articles), has excellent binding force and strength, and can be easily torn and taken out of the contents.

It is a schematic diagram of the manufacturing method which manufactures the multilayer heat shrink film of this invention by the inflation method. It is a figure which shows one aspect | mode of use of the multilayer heat shrink film of this invention. Specifically, it is a perspective view showing a state (after heat shrinkage) in which six 350 mL can beverages are prepared and stacked and packaged with the multilayer heat shrink film of the present invention. It is a schematic diagram which shows an example of the manufacturing method of the multilayer film of this invention. It is a schematic diagram which shows a cyclic | annular die lip. It is an enlarged photograph by TEM of the TD cross section of the multilayer heat-shrink film of Example 1 which performed image processing. It is an enlarged photograph by TEM of the TD cross section of the multilayer heat-shrink film of Example 4 which performed image processing.

Multilayer heat shrink film The present invention is a multilayer heat shrink film containing a polyethylene resin,
(1) At least one layer contains an ionomer,
(2) The layer containing the ionomer has a sea-island structure of the ionomer and the polyethylene resin,
(3) The length in the TD direction and the film thickness direction (ZD direction) of the island phase of the sea-island structure in the TD cross section formed by cutting in the direction (TD direction) perpendicular to the film winding direction (MD direction) ) In aspect ratio ((length in TD direction) / (length in ZD direction)) is 4 or more.

  The multilayer heat-shrinkable film of the present invention having the above characteristics contains a polyethylene resin, and satisfies the requirements (1) to (3) above, so that it is suitable for integrated packaging of contents (packages), In addition to having excellent binding force and strength, the contents can be taken out easily by tearing.

  The MD direction and the TD direction in the case where the multilayer heat shrinkable film of the present invention is produced by an inflation method to be described later will be described with reference to the drawings. FIG. 1 is a schematic view of a production method for producing a multilayer heat shrinkable film of the present invention by an inflation method. In FIG. 1, a multilayer heat-shrinkable film 1 of the present invention is extruded from the annular die lip of a circular die 2 from the bottom to the top of the paper, that is, in the direction of the dotted arrow 3, and is wound up in a subsequent step. . At this time, the film is stretched in the direction of the dotted line 4 at a specific blow ratio. When the multilayer heat-shrinkable film of the present invention is produced by an inflation method, in the multilayer heat-shrinkable film of the present invention, the film winding direction (MD direction) is the direction of dotted line 3, and the film winding direction (MD direction) The direction perpendicular to the direction (TD direction) is the direction of the dotted line 4.

  The multilayer heat-shrinkable film of the present invention contains a polyethylene-based resin and is not limited as long as the above requirements (1) to (3) are satisfied. For example, the number of laminated layers may be any number of laminated layers of about 2 to 5 layers. Can be adopted. For example, the number of layers can be increased by using a composition in which an ionomer is included in a specific layer, achieving higher tearability and shrinkage, or adding known stabilizers such as light stabilizers, antioxidants, ultraviolet absorbers, lubricants, and pigments. The agent can be adjusted according to necessity, for example, by blending the agent in separate layers. And it is preferable to set so that an adjacent layer can distinguish a composition.

  The multilayer heat-shrinkable film of the present invention is not limited as long as the number of layers is a multilayer as described above. The multilayer heat-shrinkable film of the present invention contains a polyethylene-based resin, but it only needs to contain a polyethylene-based resin in its entirety, and any layer has a sea-island structure of a polyethylene-based resin and an ionomer. If you do.

  In the present invention, specifically, a layer configuration in which an A layer (outer layer), a B layer (intermediate layer), and a C layer (inner layer) are laminated in this order, or an A layer (outer layer), a B layer (intermediate layer). ) And A layer (inner layer) are preferably laminated in that order. Among them, it is preferable that the B layer (intermediate layer) has a sea-island structure of an ionomer and a polyethylene resin. In addition, the above-mentioned “outer layer” and “inner layer” indicate the outer layer as the “outer layer” and the inner layer as the “layer” when the contents are integrated and wrapped with the multilayer heat shrink film. ing.

  In the multilayer heat-shrinkable film of the present invention, when the B layer (intermediate layer) contains an ionomer, the B layer contains 1 to 80% by mass of a polyethylene resin with respect to 100% by mass of the resin component of the layer. It is preferable to contain 3-70 mass%, and it is more preferable to contain. When the content of the polyethylene-based resin in the B layer is in the above range, the interlayer strength can be improved and sufficient sealing properties can be exhibited, and sufficient tearing properties can be exhibited in the MD direction and the TD direction.

  In this specification, “resin component” includes “polyethylene resin” and “ionomer”, but “polyethylene resin” and “ionomer” are different components and are distinguished from each other.

  The thickness of the multilayer heat shrinkable film of the present invention is not limited, but is preferably about 20 to 150 μm, and more preferably about 30 to 120 μm. The thickness of each layer constituting the multilayer heat-shrinkable film is not limited and can be appropriately set according to the characteristics of the final product. For example, the A layer (outer layer), the B layer (intermediate layer), and the C layer (inner layer) If the layer structure is laminated, or if the A layer (outer layer), the B layer (intermediate layer) and the A layer (inner layer) are laminated in that order, the B layer ( The ratio of the thickness of the intermediate layer is preferably 10 to 80%, more preferably 15 to 70%.

  The multilayer heat-shrinkable film of the present invention contains a polyethylene resin in its entirety. The multilayer heat-shrinkable film of the present invention preferably contains a polyethylene resin as a main component. Here, in the present invention, “having a polyethylene-based resin as a main component” means that 60% by mass or more of a polyethylene-based resin is included with respect to 100% by mass of the resin component contained in the entire multilayer heat-shrinkable film. 70 mass% or more is more preferable, and 80 mass% or more is still more preferable.

  It does not specifically limit as a polyethylene-type resin, Low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE) can be illustrated. These polyethylene resins can be used alone or in admixture of two or more.

  As the polyethylene resin, a resin containing 30% by mass or more of low density polyethylene (LDPE) is preferable in order to obtain a high heat shrinkage rate. More specifically, LDPE is more preferably 35% by mass or more, and may be 100% by mass of LDPE. When LDPE and other polyethylene resins are used in combination, for example, linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), etc. may be used. it can. By using LDPE and these other polyethylene resins in combination, the strength of the multilayer heat-shrinkable film can be improved. These polyethylene resins other than LDPE can be used alone or in admixture of two or more.

  In the present invention, it is preferable to use LDPE alone or a mixture of LDPE and LLDPE and / or HDPE as the polyethylene resin.

LDPE is a polyethylene resin (homopolyethylene) having a density in the range of 0.910 to 0.930 g / cm ³ , and examples thereof include those produced by high-pressure radical polymerization using a radical initiator. In addition, the density in this specification is the value measured on the conditions of JIS K7112: 1999 underwater substitution method (A method) and 25 degreeC.

In the present invention, it is preferable to set the density of the multilayer heat shrinkable film to 0.925 g / cm ³ or more, and more preferably set to 0.930 g / cm ³ or more. For this reason, it is preferable to select a LDPE having a relatively high density. The density of LDPE is preferably 0.915~0.930g / cm ^3, more preferably 0.920~0.930g / cm ^3. In order to obtain excellent binding properties (shrinkability) and film forming stability of the multilayer heat shrinkable film, the melt flow rate (MFR) of LDPE is preferably 0.05 to 2.0 g / 10 min. 0.1 to 2.0 g / 10 min is more preferable, and 0.2 to 1.0 g / 10 min is still more preferable. The MFR in the present specification is a value measured under the conditions of JIS K7210: 1999, Method A, 190 ° C., and load 21.18N unless otherwise specified.

  There is no clear distinction between LLDPE and MDPE, but there are cases where they are distinguished for convenience depending on density. LLDPE and MDPE can be obtained by copolymerizing ethylene and α-olefin using a single-site catalyst such as Ziegler catalyst or metallocene catalyst, and density can be adjusted by adjusting the type and amount of α-olefin. The range can be controlled.

  Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like. These α-olefins can be used alone or in combination of two or more.

A wide range of products with a density of LLDPE of 0.870 to 0.945 g / cm ³ is commercially available. In the present invention, it is preferable to set the density of the multilayer heat-shrinkable film to 0.925 g / cm ³ or more. For this reason, it is preferable to select a LLDPE having a relatively high density. The density of LLDPE is preferably 0.900~0.940g / cm ^3, more preferably from .910-.940 / cm ^3. Further, the MFR of LLDPE is preferably from 0.1 to 4.0 g / 10 minutes, more preferably from 0.5 to 2.0 g / 10 minutes. When the MFR of LLDPE is in the above range, the film-forming property is stable, and the heat shrinkable film can exhibit better binding properties (shrinkability).

In addition, MDPE refers to LLDPE having a density of about 0.930 to 0.945 / cm ³ , and a commercially available product having an MFR of about 0.05 to 2.0 g / 10 min may be used. it can.

Is not particularly limited as HDPE, density is preferably ^{0.940~0.960g / cm 3, 0.945~0.960g / cm} 3 is more preferable. Moreover, in order to obtain the excellent binding property (shrinkability) and film forming stability of the multilayer heat-shrinkable film, the melt flow rate (MFR) of HDPE is preferably 0.1 to 4.0 g / 10 min. More preferably, it is 5 to 2.0 g / 10 minutes.

The layer configuration of the multilayer heat-shrinkable film of the present invention is a layer configuration in which an A layer (outer layer), a B layer (intermediate layer), and a C layer (inner layer) are laminated in that order, or an A layer (outer layer) and a B layer. In the case where the (intermediate layer) and the A layer (inner layer) are layered in this order, the A layer has a density of 0.915 to 0.930 g / cm ³ and an MFR of 0.1 to 2.0 g / 10. It is preferable to contain an LDPE of a minute, and an LLDPE having a density of 0.900 to 0.940 g / cm ³ and an MFR of 0.1 to 4.0 g / 10 minutes. In the case of the said structure, 10-90 mass% is preferable with respect to 100 mass% of resin components of A layer, and, as for content in the A layer of LDPE, 20-90 mass% is more preferable. When the content of LDPE in the A layer is in the above range, the multilayer heat shrinkable film can exhibit sufficient shrinkage. Moreover, 10-90 mass% is preferable with respect to 100 mass% of resin components of A layer, and, as for content in the A layer of LLDPE, 10-80 mass% is more preferable. When the content of LLDPE in the A layer is within the above range, the multilayer heat-shrinkable film can exhibit sufficient breaking strength.

Moreover, the layer constitution of the multilayer heat shrinkable film of the present invention is a layer constitution in which an A layer (outer layer), a B layer (intermediate layer) and a C layer (inner layer) are laminated in that order, or an A layer (outer layer), When the B layer (intermediate layer) and the A layer (inner layer) are layered in that order, the A layer has a density of 0.940 to 0.960 g / cm ³ and an MFR of 0.1 to 4.0 g / 10. It is preferable to contain high density polyethylene (HDPE). In the case of the said structure, 5-90 mass% is preferable with respect to 100 mass% of resin components of A layer, and, as for content in the A layer of HDPE, 5-85 mass% is more preferable, and 10-85 mass% is further. 10 to 80% by mass is preferable. When the content of HDPE in the A layer is in the above range, the multilayer heat-shrinkable film can exhibit sufficient breaking strength.

Moreover, the layer constitution of the multilayer heat shrinkable film of the present invention is a layer constitution in which an A layer (outer layer), a B layer (intermediate layer) and a C layer (inner layer) are laminated in that order, or an A layer (outer layer), In the case where the B layer (intermediate layer) and the A layer (inner layer) are laminated in that order, the A layer has a density of 0.915 to 0.930 g / cm ³ and an MFR of 0.1 to 2.0 g. It is preferable to contain low density polyethylene (LDPE) / 10 minutes and high density polyethylene (HDPE) having a density of 0.940 to 0.960 g / cm ³ and an MFR of 0.1 to 4.0 g / 10 minutes. In the case of the said structure, 10-90 mass% is preferable with respect to 100 mass% of resin components of A layer, and, as for content in the A layer of LDPE, 20-90 mass% is more preferable. When the content of LDPE in the A layer is in the above range, the multilayer heat shrinkable film can exhibit sufficient shrinkage. Moreover, 10-90 mass% is preferable with respect to 100 mass% of resin components in A layer, and, as for content in the A layer of HDPE, 10-80 mass% is more preferable. When the content of HDPE in the A layer is in the above range, the multilayer heat-shrinkable film can exhibit sufficient breaking strength.

  The multilayer heat-shrinkable film of the present invention contains an ionomer in at least one layer. In the present specification, “polyethylene resin” and “ionomer” are different components and are distinguished from each other.

  An ionomer is a resinous polymer in which part or all of an olefin polymer is neutralized with metal ions. Examples of the olefin polymer include olefin-unsaturated carboxylic acid copolymers and modified products of olefin polymers.

  Examples of the olefin forming the olefin-unsaturated carboxylic acid copolymer include ethylene and propylene. That is, specific examples of the olefin-unsaturated carboxylic acid copolymer include an ethylene-unsaturated carboxylic acid copolymer and a propylene-unsaturated carboxylic acid copolymer.

  As the unsaturated carboxylic acid constituting the olefin-unsaturated carboxylic acid copolymer, acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, monomethyl maleate, A monoethyl maleate etc. can be illustrated. Among these, acrylic acid or methacrylic acid is preferable. Moreover, as said unsaturated carboxylic acid, unsaturated carboxylic acid ester may be used and the saponification thing of the said unsaturated carboxylic acid ester may be used.

  The olefin-unsaturated carboxylic acid copolymer is a copolymer having an unsaturated carboxylic acid content of preferably 1 to 25% by mass, more preferably 3 to 23% by mass, and still more preferably 4 to 20% by mass. Yes, it may be not only a binary copolymer of an olefin and an unsaturated carboxylic acid but also a multi-component copolymer in which other monomers are optionally copolymerized. When the content of the unsaturated carboxylic acid is within the above range, the multilayer heat-shrinkable film can exhibit more sufficient tearability, and an increase in hygroscopicity can be suppressed and excellent moldability can be exhibited. .

  Other monomers that may be optionally copolymerized include vinyl acetate, vinyl esters such as vinyl propionate, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, and n-acrylate. Examples include butyl, isooctyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, dimethyl maleate, diethyl maleate, and the like, carbon monoxide, sulfur dioxide, etc. be able to. These other monomers may be copolymerized within a range of, for example, 0 to 30% by weight, preferably 0 to 20% by weight. Such other monomers are preferably not contained, and even if it is contained, it is preferably copolymerized in an amount of about 15% by mass or less.

  Examples of the modified product of the olefin polymer include a modified product obtained by reacting an olefin polymer such as polyethylene or polypropylene with a carboxylic acid or a carboxylic anhydride to add a carboxyl group or a carboxylic anhydride group. .

  As the ionomer, the olefin-unsaturated carboxylic acid copolymer and the modified olefin polymer are 10 to 100 mol%, preferably 10 to 80 mol% of the carboxyl group, carboxylic acid ester group and carboxylic anhydride group. Those neutralized with metal ions can be suitably used. When the degree of neutralization of the carboxyl group, carboxylic acid ester group, and carboxylic anhydride group is within the above range, it is possible to suppress a decrease in tearability of the multilayer heat shrinkable film. Here, examples of the metal ions include alkali metals such as lithium, sodium and potassium, alkaline earth metals such as magnesium and calcium, and ions such as zinc. Among them, lithium, sodium, potassium, magnesium or zinc is preferable. In particular, it is more preferable to use an ionomer having sodium as an ion source in that the multilayer heat shrinkable film is excellent in tearability.

  As the ionomer, for example, those described in International Publication No. 2010/024286 and JP-A-6-192512 can be used.

  The ionomer MFR is preferably 0.1 to 4.0 g / 10 min, and preferably 0.5 to 2.0 g / 10 min in terms of excellent moldability and film physical properties in the production process. More preferred.

  The multilayer heat-shrinkable film of the present invention preferably contains 10 to 56% by mass of the above-mentioned ionomer, based on 100% by mass of the resin component forming the multilayer heat-shrinkable film. It is more preferable. By setting the content of the ionomer in the entire multilayer heat-shrinkable film within the above range, the multilayer heat-shrinkable film of the present invention can exhibit excellent heat shrinkability and tearability.

  In the multilayer heat-shrinkable film of the present invention, when the B layer (intermediate layer) contains an ionomer, the B layer contains 20 to 99% by mass of ionomer with respect to 100% by mass of the resin component of the layer. Is preferable, and it is more preferable to contain 30-97 mass%. When the content of the ionomer in the B layer is in the above range, an increase in tear strength in the MD direction and the TD direction of the multilayer heat shrinkable film of the present invention can be suppressed.

  The layer containing the ionomer may contain, in addition to the polyethylene resin, other ionic copolymers that are not neutralized with metal ions in addition to the ionomer. As the other ionic copolymer that is not neutralized with the metal ion, an ethylene-unsaturated carboxylic acid copolymer that is not neutralized with the metal ion used in the preparation of the ionomer can be used. The unsaturated carboxylic acid copolymer may be the same as or different from the ethylene-unsaturated carboxylic acid copolymer used to prepare the ionomer used in the layer containing the ionomer.

  In the multilayer heat shrinkable film of the present invention, the layer containing the ionomer has a sea-island structure of an ionomer and a polyethylene resin, and is cut in a direction (TD direction) perpendicular to the film winding direction (MD direction). The aspect ratio between the length in the TD direction and the length in the film thickness direction (ZD direction) of the island phase of the sea-island structure in the TD cross section formed as described above is 4 or more.

The sea-island structure is obtained by dyeing a multilayer heat-shrinkable film with RuO ₄ and then cutting the multilayer heat-shrinkable film, and observing the cut surface with a transmission electron microscope (TEM) at an observation magnification of 1000 to 50000 times. This can be confirmed by taking an enlarged picture. In the TEM image, the ionomer is stained with RuO ₄ and appears black.

  In the sea-island structure, depending on the mixing ratio of the ionomer and the polyethylene resin, the ionomer may be an island phase, the polyethylene resin may be an island phase, and both phases may be continuous phases.

The aspect ratio is a value obtained by dividing the length of the island phase of the sea-island structure in the TD cross section in the TD direction by the length of the island phase in the ZD direction, and is a value calculated by the following equation.
(Aspect ratio) = (Length in TD direction) / (Length in ZD direction)
When the polyethylene resin and the ionomer are continuous phases, the aspect ratio is evaluated with the phase formed by the ionomer as the island phase.

  In the multilayer heat shrinkable film of the present invention, the aspect ratio is 4 or more. When the aspect ratio is less than 4, the tear strength of the multilayer heat-shrinkable film is increased and cannot be easily torn, making it difficult to take out the contents. The aspect ratio is preferably 7 or more, and more preferably 10 or more. The upper limit of the aspect ratio is not particularly limited, and becomes infinite when the polyethylene resin and the ionomer are continuous phases.

  The aspect ratio can be measured by the following measurement method.

First, a heat shrink film or a multilayer heat shrink film is dyed with RuO ₄ and then cut. The cut surface is observed with a transmission electron microscope (TEM) at an observation magnification of 5000 to 30000 times, and an enlarged photograph is taken. The ionomer phase is stained with RuO ₄ and is photographed in black by an enlarged photograph by TEM. At this time, the observation magnification may be adjusted to a magnification at which the dispersed structure of the island phase can be determined and 10 to 500 dispersed phases can be confirmed in the photograph.

  Next, the aspect ratio of the island phase is calculated in the enlarged photograph. The aspect ratio of the island phase is the ratio of the length in the TD direction passing through the center of gravity of the dispersed phase and the length in the ZD direction (thickness direction) using “WinROOF Ver5.03” which is image processing software made by Mitani Corporation. Can be calculated as

  Hereinafter, a method for calculating the aspect ratio of the island phase in the TD cross section and the length of the island phase in the TD cross section in the ZD direction using the “WinROOF Ver5.03” in the case where the ionomer forms the island phase. This will be described in detail.

First, a pretreatment for accurately extracting the ionomer phase stained black with RuO ₄ is performed.

(I) Extraction of unstained polyethylene layer The “image processing”, “intensity”, “lookup table conversion”, and “brightness extraction” commands are sequentially executed, and the parameters are set to 128 to 255. The ionomer phase dyed black by the above command has a density of 0 and is uniformly separated white.

(Ii) Binarization “Binary processing” and “binarization with a single threshold” are executed with the threshold set to 100. This binarizes the ionomer phase to white and the polyethylene layer to black.

  (Iii) “Image processing”, “emphasis”, and “inversion” commands are executed. As a result, white and black are reversed to change the ionomer phase to black and the polyethylene phase to white.

(Iv) Noise removal “Binary processing” and “deletion” are executed with the threshold set to 1 or less. Thereby, the noise on the black spots in the polyethylene resin layer is removed. The threshold value is designated while checking the image according to the photographing magnification.

  Subsequently, the process which smoothes the shape of a phase is performed.

  (V) Perform “binary processing” and “expansion” twice. This fills in the blank areas and the indentations in the area.

  (Vi) Perform “binary processing” and “shrink” twice. As a result, the protrusion is removed and returned to the size before expansion.

  Finally, shape analysis is performed to determine the cutting length.

  (Vii) “Measurement” and “shape feature” are performed, and “cutting length” is selected and executed. Thereby, the maximum length and the minimum length passing through the center of gravity of the region are calculated.

In the above measurement method, since the TD cross section of the multilayer heat-shrinkable film is observed, when the multilayer heat-shrinkable film is manufactured by an inflation method described later, the minimum length of the island phase is substantially the ZD cut length of the island phase. Thus, the maximum length of the island phase in the TD cross section becomes the TD cut length of the island phase. From the above TD cut length and ZD cut length, the aspect ratio of the island phase in the TD cross section was calculated by the following formula.
(Aspect ratio of island phase in TD cross section) = (TD cut length) / (ZD cut length)

  When the polyethylene layer forms an island phase, the processing target is white. Therefore, the execution in (vii) may be performed without performing the “inversion” processing in (iii).

  The ZD cut length of the island phase of the sea-island structure is not particularly limited, but is preferably 0.5 μm or less, and more preferably 0.3 μm or less from the viewpoints of binding property, tearability, and shrinkability. The ZD cut length is preferably 0.01 μm or more, more preferably 0.03 μm or more, from the viewpoint that sufficient tearability can be exhibited.

  In the case where the layer structure of the multilayer heat shrinkable film of the present invention is a layer structure in which an A layer (outer layer), a B layer (intermediate layer), and a C layer (inner layer) are laminated in this order, a resin component that forms the C layer Although it will not specifically limit if it differs from the resin component of A layer, For example, a polypropylene, ethylene-vinyl acetate copolymer, etc. are mentioned.

  In addition, as the resin component forming the C layer, if the C layer is not the same layer as the A layer, a resin component containing the same resin as the polyethylene resin included in the resin component forming the A layer is used. May be. In this case, the resin component forming the C layer contains, for example, the same LDPE, LLDPE, MDPE, HDPE, and the like contained in the resin component forming the A layer. The resin component different from content in the resin component which forms A layer is mentioned. Among these, resin components having different contents of LLDPE and HDPE can be mentioned.

  Further, as the resin component forming the C layer, the same type of resin as the polyethylene resin contained in the resin component forming the A layer may be used as long as the C layer is not the same layer as the A layer. In this case, the resin component forming the C layer is the same type as the LDPE, LLDPE, MDPE, HDPE, etc. included in the resin component forming the A layer. Unlike this, resin components having different properties such as density and MFR as resin components can be mentioned.

  The Elmendorf tear strength in the direction (TD direction) perpendicular to the film winding direction (MD direction) of the multilayer heat shrinkable film of the present invention is preferably 1 N or less. When the Elmendorf tear strength in the TD direction is 1 N or less, the multilayer heat-shrinkable film can exhibit more excellent tearability. The Elmendorf tear strength in the TD direction is more preferably 0.1 to 1N, and still more preferably 0.2 to 0.8N. By setting the Elmendorf tear strength within the above range, the multilayer heat-shrinkable film has a better binding force and can be more easily torn to take out the contents.

  The Elmendorf tear strength in the film winding direction (MD direction) of the multilayer heat shrinkable film of the present invention is preferably 1 N or less. By setting the Elmendorf tear strength in the MD direction within the above-described range, the multilayer heat-shrinkable film has a better binding force and can be more easily torn to take out the contents. The Elmendorf tear strength in the MD direction is more preferably 0.01 to 1N, and still more preferably 0.1 to 0.8N.

  The multilayer heat-shrinkable film of the present invention can be torn straight along the TD direction regardless of the Elmendorf tear strength in the MD direction. In particular, when a multilayer heat-shrinkable film is manufactured by a manufacturing method described later, the above characteristics become remarkable. The above characteristics are the same even when the Elmendorf tear strength in the MD direction is lower than the Elmendorf tear strength in the TD direction. Thereby, when tearing the multilayer heat-shrinkable film and taking out the contents, it becomes easy to tear in the TD direction, so that it can be torn straight along the TD direction at the time of tearing, and the contents can be taken out more easily. In addition, the tear strength in this specification is the value measured by the Elmendorf method based on JISK7128-2.

  The multilayer heat shrinkable film of the present invention preferably has a heat shrinkage rate in the TD direction at 130 ° C. measured in accordance with JIS Z1709 of 15% or more. By setting the heat shrinkage ratio to 15% or more, it is possible to obtain a multilayer heat shrink film that has a better binding force and is more suitable for heavy weight packaging, and it is difficult for wrinkles to remain after packaging. A decrease in designability is suppressed, and a decrease in tearability is also suppressed. The thermal shrinkage rate in the TD direction is more preferably 15 to 40%, still more preferably 20 to 40%. By setting the heat shrinkage rate in the TD direction within the above range, the multilayer heat shrinkable film exhibits better binding force. Further, the heat shrinkage rate in the MD direction is preferably 30 to 80%, and more preferably 50 to 75%. In addition, 130 degreeC shrinkage | contraction rate in this specification is the value measured by the measuring method based on JISZ1709 (however, temperature conditions were changed into 120 degreeC from 120 degreeC) using silicone oil as a heat-medium liquid.

In the multilayer heat-shrinkable film of the present invention, the density is preferably 0.925 g / cm ³ or more, and the MFR is preferably 0.1 to 2.0 g / 10 minutes. By having the above-mentioned specific composition and specific density and MFR, it is more suitable for accumulation packaging (especially sleeve packaging or pillow packaging) of contents (packaged items), has excellent binding power and strength, and easily The contents can be taken out by tearing. Examples of the contents (packaged items) include can drinks, plastic bottle drinks, paper pack drinks, and the like, and can be packaged in units of 24 cans, 6 bottles, and the like. FIG. 2 illustrates a state where can beverages are integrated and packaged in units of 6 using the multilayer heat shrinkable film of the present invention.

Production method of multilayer heat-shrinkable film The production method of the multilayer heat-shrinkable film of the present invention is not particularly limited. For example, it is a production method for producing the multilayer heat-shrinkable film by an inflation method, and the blow ratio is 1.5 to And the diameter (inner diameter) of the annular die lip is D, and the bubble diameter of the multilayer heat-shrinkable film at the same height as D from the end of the annular die lip is 2D or less.

  As the inflation method, a multilayer inflation method is used when producing a multilayer heat-shrinkable film. The multilayer inflation method generally prepares a molten resin composition by melting and kneading components such as resins constituting each layer in an extruder, and supplies the resin composition from the extruder to a circular die. The resin composition is coextruded from a circular die to form a cylindrical film, and compressed air is supplied from the center of the circular die to stretch the formed cylindrical film in the circumferential direction. To produce a multilayer heat shrink film.

  An example of the manufacturing method of the multilayer film of this invention is demonstrated using figures. FIG. 3 is a schematic view showing an example of a method for producing a multilayer heat shrinkable film of the present invention, and FIG. 4 is a schematic view showing an annular die lip. In FIG. 3, the multilayer heat-shrinkable film 1 of the present invention is extruded from the annular die lip of the circular die 2 upward from the bottom of the paper, that is, in the direction of the dotted arrow 3 and wound in a subsequent process. .

  In the above manufacturing method, as shown in FIG. 4, when the diameter (inner diameter) of the annular die lip of the circular die 2 is D, the same height as D from the end 21 of the die lip in FIG. It is preferable that the diameter of the cylindrical heat-shrink film 1 at the same height as D from the end 21 of the sheet, that is, the bubble diameter L1 is 2D or less. When the bubble diameter is 2D or less, the multilayer heat shrinkable film is excellent in heat shrinkability in the TD direction. The bubble diameter is more preferably 1.8D or less. The bubble diameter is preferably 1.1D or more. When the bubble diameter is 1.1D or more, the multilayer heat shrinkable film is excellent in heat shrinkability in the TD direction. The above “the same height as D” is a position away from the end 21 of the die lip by the same distance as D in the normal direction from the plane including the end 21 of the die lip.

3 and 4, the multilayer heat shrinkable film 1 is preferably stretched in the direction of the dotted line 4 at a blow ratio of 1.5-6. In addition, the said blow ratio is the circle | round | yen of the circumference (t1) of the heat shrink film 1 in the edge part 21 of a die lip in FIG. 3, and the heat shrink film 1 above a paper surface rather than the frost line L2 in FIG. It is a ratio obtained by calculating the ratio with the circumferential length (t2) by the following equation.
(Blow ratio) = (t2) / (t1)

  When the blow ratio is 1.5 or more, the multilayer heat shrinkable film is more excellent in heat shrinkability in the TD direction. When the blow ratio is 6 or less, the stretching stability is excellent, and the occurrence of film breakage and the like is suppressed. The blow ratio is more preferably 2.0 to 6.0, still more preferably 2.0 to 5.5, and particularly preferably 2.2 to 5.5.

  The inflation molding temperature is the highest melting temperature among melting peak temperatures exhibited by the resin component obtained by mixing at least one selected from LLDPE, LDPE, HDPE and ionomer contained in each layer constituting the multilayer heat shrinkable film. It is preferable that the temperature be equal to or higher than the peak temperature. Preferably, (the highest melting peak temperature) + 40 ° C. to (the highest melting peak temperature) + 80 ° C. Specifically, 160 to 200 ° C. is preferable.

  When the temperature of inflation molding is the melting point + 40 ° C. or higher, these resins are in a sufficiently molten state, and melt film formation by inflation molding becomes easy. On the other hand, when the temperature of inflation molding is the above melting point + 80 ° C. or less, the bubbles can be stabilized and the layer thickness can be made uniform, and the generation of fish eyes, foreign matters and the like due to resin deterioration can be suppressed. In the present specification, the melting point is a value measured by differential scanning calorimetry in accordance with JIS K7121.

  According to the above production method, the multilayer heat-shrinkable film of the present invention, that is, a multilayer heat-shrinkable film containing a polyethylene resin, (1) containing an ionomer in at least one layer, and (2) containing the ionomer In the TD cross section formed by cutting in a direction (TD direction) perpendicular to the film winding direction (MD direction), the layer having a sea-island structure of the ionomer and the polyethylene-based resin Multi-layer heat in which the aspect ratio ((length in TD direction) / (length in ZD direction)) between the length in the TD direction and the length in the film thickness direction (ZD direction) of the island phase of the sea-island structure is 4 or more The shrink film can be easily manufactured by an inflation method. Moreover, according to the said manufacturing method, the Elmendorf tear strength in the direction (TD direction) perpendicular | vertical with respect to a film winding direction (MD direction) is 1 N or less, and at 130 degreeC measured based on JISZ1709 It is possible to make a multilayer film having a heat shrinkage rate of 15% or more in the TD direction, and further to a multilayer heat shrink film having an Elmendorf tear strength of 1 N or less in the film winding direction (MD direction). Become.

Packaging Method Using Multilayer Heat Shrink Film The method for packaging contents using the multilayer heat shrink film of the present invention is not particularly limited, and conventionally known packaging methods can be used. Examples of such a packaging method include a packaging method using a packaging method such as an L-shaped packaging machine, a pillow packaging machine, a sleeve packaging machine, and a wound sleeve packaging machine. In particular, unwrapped polyethylene heat-shrinkable films are preferably used in sleeve packaging and wound sleeve packaging.

  After roughly packing the contents by the above-mentioned packaging method, throwing it into the shrink tunnel, raising the temperature inside the shrink tunnel above the shrinkage temperature of the multilayer heat shrink film, heating and cooling, shrink and wrap Good. The heating temperature can be appropriately set depending on the length of the shrink tunnel and the line speed, but is generally in the range of 130 to 240 ° C. When the heating temperature is in the above range, the multilayer heat-shrinkable film can be sufficiently shrunk to exhibit an excellent binding force, and the melting of the multilayer heat-shrinkable film is suppressed and the generation of holes is suppressed.

  The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the scope of the examples.

  The following raw materials were used as raw materials for preparing a multilayer heat shrinkable film, and multilayer heat shrinkable films of Examples and Comparative Examples were prepared by the following method.

(material)
- LDPE (manufactured by Asahi Kasei Corporation, Suntec LD M2204, MFR = 0.4g / 10 min, density 0.922g / cm ³⁾ · LLDPE (manufactured by Dow Chemical, Elite 5100, MFR = 0.85g / 10 min, density 0.920 g / cm ³ ) · LLDPE (Dow Chemical, Dow Rex 2645G, MFR = 0.9g / 10min, density 0.919g / cm ³ ) · HDPE (Asahi Kasei, Suntech HD S362, MFR = 0.8g / 10min, density 0.952g / cm ³ ) ・ Ionomer (Mitsui DuPont, Hi Milan 1601, MFR = 1.3g / 10min, density 0.940g / cm ³ )

Examples 1 to 13 and Comparative Example 1
(Preparation of multilayer heat shrink film)
A multilayer inflation film forming apparatus was prepared in which three extruders (for forming each of the inner layer, the intermediate layer and the outer layer) were connected to a circular multilayer die having a lip gap of 1.0 mm via a connector.

  Next, LDPE, LLDPE, HDPE, and ionomer were mixed in the formulation shown in Table 1, supplied to each of the extruders, melted and kneaded at 190 ° C., and the molten resin was transferred from the circular die to a die temperature of 190 ° C. The film was discharged (co-extruded) under the above conditions, and the blow ratio in the transverse direction was adjusted as shown in Table 1 to form a melt film. The diameter (inner diameter) D of the circular die lip of the circular die was 150 mm. Moreover, the bubble diameter of the multilayer heat-shrinkable film at the position extruded 150 mm (the same height as D) from the end of the annular die lip was adjusted as shown in Table 1.

  By the above, the multilayer heat-shrink film of Examples 1-13 and the comparative example 1 with the total thickness of 40 micrometers or 25 micrometers was prepared.

  The following evaluation was performed about the multilayer heat-shrink film of each Example and the comparative example.

<130 ° C shrinkage>
The temperature condition was changed from 120 ° C. to 130 ° C. by a measurement method based on JIS Z1709, and measurement was performed using silicone oil as the heat transfer fluid. The measurement was performed about MD direction and TD direction using the heat-shrinkable film and multilayer heat-shrinkable film before heat shrinkage.

<Tear strength>
The multilayer heat-shrinkable film before heat shrinkage was measured by the Elmendorf method in accordance with JIS K7128-2.

<Aspect ratio of island phase and length of island phase in ZD direction>
The aspect ratio of the island phase in the TD cross section and the length in the ZD direction of the island phase in the TD cross section were measured by the following methods.

First, the multilayer heat shrink film was dyed with RuO ₄ and then cut. The cut surface was observed with a transmission electron microscope (TEM) at an observation magnification of 5000, and an enlarged photograph was taken. The ionomer phase was stained with RuO _{4 and} photographed in black by an enlarged photograph by TEM. At this time, the dispersed structure of the island phase could be determined, and 10 to 500 dispersed phases could be confirmed in the photograph.

  Next, the aspect ratio of the island phase was calculated in the enlarged photograph. The aspect ratio of the island phase is the ratio of the length in the TD direction passing through the center of gravity of the dispersed phase and the length in the ZD direction (thickness direction) using “WinROOF Ver5.03” which is image processing software made by Mitani Corporation. Calculated as

  When the ionomer forms an island phase, the above-mentioned “WinROOF Ver5.03” is used, and the aspect ratio of the island phase in the TD cross section and the length of the island phase in the TD cross section in the ZD direction are calculated by the following methods. did.

First, a pretreatment for accurately extracting the ionomer phase stained black with RuO ₄ was performed.

(I) Extraction of unstained polyethylene layer The “image processing”, “intensity”, “lookup table conversion”, and “brightness extraction” commands are sequentially executed, and the parameters are set to 128 to 255. The ionomer phase stained black by the above command had a concentration of 0 and was uniformly separated into white.

(Ii) Binarization “Binary processing” and “binarization with a single threshold” are executed with the threshold set to 100. This binarized the ionomer phase to white and the polyethylene layer to black.

  (Iii) The “image processing”, “emphasis”, and “inversion” commands were executed. As a result, white and black were reversed to change the ionomer phase to black and the polyethylene phase to white.

(Iv) Noise removal “Binary processing” and “deletion” were executed with the threshold value set to 1 or less. Thereby, the noise on the black spots in the polyethylene resin layer was removed. The threshold value was specified while checking the image according to the shooting magnification.

  Subsequently, the process which smoothes the shape of a phase was performed.

  (V) “Binary processing” and “expansion” were performed twice. This filled in the voids in the area and the indentation at the boundary.

  (Vi) “Binary processing” and “shrinkage” were performed twice. As a result, the protrusion was removed and returned to the size before expansion.

  Finally, shape analysis was performed to determine the cutting length.

  (Vii) “Measurement” and “shape feature” were performed, and “cut length” was selected and executed. Thus, the maximum length and the minimum length passing through the center of gravity of the region were calculated.

In the above measurement method, since the multilayer heat shrinkable film is manufactured by the inflation method in order to observe the TD cross section of the multilayer heat shrinkable film, the minimum length of the island phase is substantially the ZD cut length of the island phase, In the TD cross section, the maximum length of the island phase is the TD cut length of the island phase. From the above TD cut length and ZD cut length, the aspect ratio of the island phase in the TD cross section was calculated by the following formula.
Aspect ratio of island phase in TD cross section = TD cut length / ZD cut length

  When the polyethylene layer forms an island phase, the processing target is white. Therefore, the execution in (vii) was performed without performing the “inversion” processing in (iii).

  FIG. 5 shows an enlarged photograph by TEM of the TD cross section of the multilayer heat shrinkable film of Example 1 subjected to the above-described image processing. In FIG. 5, the longitudinal direction of the island phase photographed in black is the TD direction.

  FIG. 6 shows an enlarged photograph of the TD cross section of the multilayer heat-shrinkable film of Example 4 subjected to the above-described image processing by TEM. In FIG. 6, the longitudinal direction of the island phase photographed in white is the TD direction.

  The results are shown in Table 1.

  The multilayer heat-shrinkable film of the present invention has excellent binding force and strength, and can be easily torn and taken out of its contents, so that it can be suitably used for packaging, particularly for integrated packaging. In particular, it can be suitably used for collecting and packaging relatively heavy articles such as PET bottles and can drinks.

  DESCRIPTION OF SYMBOLS 1 ... Multi-layer heat shrink film, 2 ... Circular die, 3 ... Dotted arrow, 4 ... Dotted line, 5 ... Multi-layer heat shrink film, 6 ... Can, 7 ... Sleeve mouth

Claims (7)

A multilayer heat shrink film containing a polyethylene resin,
(1) At least one layer contains an ionomer,
(2) The layer containing the ionomer has a sea-island structure of the ionomer and the polyethylene resin,
(3) The length in the TD direction and the film thickness direction (ZD direction) of the island phase of the sea-island structure in the TD cross section formed by cutting in the direction (TD direction) perpendicular to the film winding direction (MD direction) ) Aspect ratio ((length in TD direction) / (length in ZD direction)) is 4 or more,
A multilayer heat shrinkable film characterized by the above.   The Elmendorf tear strength in the direction perpendicular to the film winding direction (MD direction) (TD direction) is 1 N or less, and the thermal shrinkage in the TD direction at 130 ° C. measured in accordance with JIS Z1709 is 15 The multilayer heat-shrinkable film according to claim 1, which is at least%.   The multilayer heat-shrinkable film according to claim 1 or 2, wherein the Elmendorf tear strength in the film winding direction (MD direction) is 1 N or less.   The multilayer heat shrinkable film has a layer structure in which an A layer (outer layer), a B layer (intermediate layer), and a C layer (inner layer) are laminated in that order, or an A layer (outer layer), a B layer (intermediate layer). The multilayer heat-shrinkable film according to any one of claims 1 to 3, which has a layer structure in which a layer) and an A layer (inner layer) are laminated in this order, and the B layer contains an ionomer.   The multilayer heat-shrink film according to claim 4, wherein the B layer contains 1 to 70% by mass of a polyethylene resin with respect to 100% by mass of the resin component. The multilayer heat shrinkable film has a layer structure in which an A layer (outer layer), a B layer (intermediate layer), and a C layer (inner layer) are laminated in that order, or an A layer (outer layer), a B layer (intermediate layer). Layer) and A layer (inner layer) are laminated in that order. The layer A has a density of 0.915 to 0.930 g / cm ³ and an MFR of 0.1 to 2.0 g / 10 min. Low density polyethylene, and linear low density polyethylene having a density of 0.900 to 0.940 g / cm ³ and MFR of 0.1 to 4.0 g / 10 min, and the content of the linear low density polyethylene Is a multilayer heat shrinkable film according to any one of claims 1 to 5, which is 10 to 90% by mass with respect to 100% by mass of the resin component of the A layer. The multilayer heat shrinkable film has a layer structure in which an A layer (outer layer), a B layer (intermediate layer), and a C layer (inner layer) are laminated in that order, or an A layer (outer layer), a B layer (intermediate layer). Layer) and A layer (inner layer) are laminated in that order. The layer A has a density of 0.915 to 0.930 g / cm ³ and an MFR of 0.1 to 2.0 g / 10 min. Low density polyethylene, and high density polyethylene having a density of 0.940 to 0.960 g / cm ³ and MFR of 0.1 to 4.0 g / 10 min. The multilayer heat-shrinkable film according to any one of claims 1 to 5, which is 10 to 90% by mass with respect to 100% by mass of the resin component.

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