JP2009292057A - Heat shrinkable multilayered film and heat shrinkable label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat shrinkable multilayered film which can be attached to a vessel by being heat-shrinked, can suppress the deformation of the vessel and is low in shrinkage stress, and to provide a heat shrinkable label using the l using the heat shrinkable multilayered film as a base film. <P>SOLUTION: The heat shrinkable multilayered film is formed by laminating the front and rear surface layers composed of polyester-based resin and an intermediate layer consisting of polystyrene-based resin via a bonding layer. The maximum shrinkage stress of the film when soaked in warm water of 80°C for 30 seconds is 0.3-1.0 N/10 mm, and the heat shrinkage ratio in the main shrinkage direction when soaked in warm water of 80°C for 10 seconds in the main shrinking direction is 20% or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a heat-shrinkable multilayer film having a low shrinkage stress that can be attached to a container by heat-shrinking and can suppress deformation of the container, and a heat-shrinkable label using the heat-shrinkable multilayer film as a base film About.

In recent years, many of the containers such as lunch boxes and noodles sold at convenience stores and the like are equipped with a heat-shrinkable label obtained by printing a base film made of a heat-shrinkable resin film. Such a heat-shrinkable label has a role of improving designability in addition to displaying contents. Conventionally, as such heat-shrinkable labels, those made of a polyester resin and those made of a polystyrene resin have been used.
However, a heat-shrinkable label made of a polyester-based resin has excellent heat resistance and durability against contents, but has a problem that the container is deformed after being mounted because the shrinkage stress is extremely high. In particular, containers such as lunch boxes and noodles have such a problem that they are thin and easily deformed by an external force.
In addition, when heat-shrinkable labels made of polystyrene-based resins are used for heating lunch boxes and noodles in a microwave oven, the labels may have holes or be greatly deformed due to low heat resistance. Further, depending on the contents of the lunch box or noodles, there is a risk of swelling or melting due to the contents, for example, oil.

As a heat-shrinkable label used for containers such as lunch boxes and noodles, for example, Patent Document 1 discloses a shrink label mainly composed of a polylactic acid-based polymer. However, as described in Patent Document 1, the desired performance cannot be obtained simply by using a polylactic acid-based polymer as a main component.
Under such circumstances, there has been a demand for a heat-shrinkable label having a low shrinkage stress that can be attached to a container by heat-shrinking and can suppress deformation of the container.
JP 2008-30840 A

In view of the above situation, the present invention provides a heat-shrinkable multilayer film having a low shrinkage stress that can be attached to a container by heat-shrinking and can suppress deformation of the container, and the heat-shrinkable multilayer film as a base film. It is an object to provide a heat-shrinkable label.

The present invention is a heat-shrinkable multilayer film in which a front and back layer made of a polyester resin and an intermediate layer made of a polystyrene resin are laminated via an adhesive layer, and is immersed in warm water at 80 ° C. for 30 seconds. Heat shrinkage in which the maximum shrinkage stress is 0.3 to 1.0 N / 10 mm and the heat shrinkage rate in the main shrinkage direction is 20% or more when immersed in warm water at 80 ° C. for 10 seconds. Multi-layer film.
The present invention is described in detail below.

The heat-shrinkable multilayer film of the present invention is obtained by laminating front and back layers made of a polyester resin and an intermediate layer made of a polystyrene resin through an adhesive layer.

In the present invention, the front and back layers are made of a polyester resin.
As said polyester-type resin, what is obtained by polycondensing dicarboxylic acid and diol is mentioned, for example.

The dicarboxylic acid is not particularly limited. For example, o-phthalic acid, terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, octyl succinic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, fumaric acid, Examples include maleic acid, itaconic acid, decamethylene carboxylic acid, anhydrides and lower alkyl esters thereof.
The diol is not particularly limited. For example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, dipropylene glycol, triethylene Glycol, tetraethylene glycol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, neopentyl glycol (2,2-dimethylpropane-1,3-diol), 1,2-hexane Aliphatic diols such as diol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol; 2-bis (4-hydroxycyclohexyl) propane, 2,2-bis (4-hydroxy) B carboxymethyl cyclohexyl) alkylene oxide adducts of propane, 1,4-cyclohexane diol, alicyclic diols such as 1,4-cyclohexanedimethanol.

Among these polyester-based resins, those containing a component derived from terephthalic acid as the dicarboxylic acid component and a component derived from ethylene glycol and 1,4-cyclohexanedimethanol as the diol component are preferred. By using such a polyester resin, high low temperature resistance and heat resistance can be imparted. When it is desired to further improve the low temperature resistance and heat resistance, the content of the component derived from ethylene glycol is 60 to 80 mol%, and the content of the component derived from 1,4-cyclohexanedimethanol is 10 to 40 mol%. It is preferable to use what is. Such a polyester resin may further contain 0 to 20 mol% of a component derived from diethylene glycol.

As a polyester-type resin contained in the said front and back layer, the polyester-type resin which has the composition mentioned above may be used independently, and 2 or more types of polyester-type resins which have the composition mentioned above may be used together. Moreover, although the said polyester-type resin is good also as a thing of a different composition by a surface layer and a back surface layer, in order to suppress the trouble by the curl etc. of a film, it is preferable to set it as the same composition.

Although it does not specifically limit as polystyrene-type resin which comprises the said intermediate | middle layer, For example, an aromatic vinyl hydrocarbon-conjugated diene copolymer or an aromatic vinyl hydrocarbon-conjugated diene copolymer and an aromatic vinyl hydrocarbon- Examples thereof include a mixed resin with an aliphatic unsaturated carboxylic acid ester copolymer.
When the above aromatic vinyl hydrocarbon-conjugated diene copolymer is used, a heat-shrinkable multilayer film with little decrease in elongation under a low temperature atmosphere is obtained.
In addition, when a mixed resin of an aromatic vinyl hydrocarbon-conjugated diene copolymer and an aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer is used, a heat-shrinkable multilayer film excellent in low-temperature shrinkability and Become.

The aromatic vinyl hydrocarbon-conjugated diene copolymer is not particularly limited. For example, as the aromatic vinyl hydrocarbon, for example, styrene, o-methylstyrene, p-methylstyrene, and the like, Examples thereof include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like. These may be used alone or in combination of two or more. Among these, a styrene-butadiene-styrene copolymer (SBS resin) is preferable because it is particularly excellent in low-temperature shrinkage and cut performance at perforations. In order to produce a film with less fish eye, a styrene-isoprene-styrene copolymer (SIS resin) using 2-methyl-1,3-butadiene (isoprene) as a conjugated diene, or a styrene-isoprene. It is preferable to use a butadiene-styrene copolymer (SIBS resin) or the like.

When the SBS resin, SIS resin or SIBS resin is used as the aromatic vinyl hydrocarbon-conjugated diene copolymer, one kind of resin may be used alone, or a plurality of resins may be used in combination. . When used in plural, dry blending may be used, or a compound resin that is kneaded and pelletized using an extruder with a specific composition may be used.
It is preferable to use such resins singly or in combination to have a composition having a styrene content of 65 to 90% by weight and a conjugated diene content of 10 to 35% by weight. A resin having such a composition is particularly excellent in low-temperature shrinkage and perforation. On the other hand, when the conjugated diene content is less than 10% by weight, the film is easily cut when tension is applied to the film, and the film may break unexpectedly when used as a converting or label for printing or the like. . When the conjugated diene content exceeds 35% by weight, foreign matters such as gel may be easily generated during the molding process.

The aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer is not particularly limited, and examples of the aromatic vinyl hydrocarbon include styrene, o-methylstyrene, p-methylstyrene, and the like. Examples of the acid ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. These may be used alone or in combination of two or more.

When a styrene-butyl acrylate copolymer is used as the aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer, the styrene content is 60 to 90% by weight, and the butyl acrylate content is 10 to 40. It is preferable to use what is weight%. By using an aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer having such a composition, a heat-shrinkable label having excellent low-temperature resistance and perforation cutting properties can be obtained.

When a mixed resin of an aromatic vinyl hydrocarbon-conjugated diene copolymer and an aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer is used as the intermediate layer, the aromatic vinyl carbonization in the mixed resin is used. The preferable lower limit of the blending amount of the hydrogen-conjugated diene copolymer is 20% by weight, and the preferable upper limit is 100% by weight. If it is less than 20% by weight, the low-temperature elongation becomes low, and the heat-shrinkable label may be broken when it is accidentally dropped during refrigerated storage.

In the heat-shrinkable multilayer film of the present invention, the intermediate layer may contain an ultraviolet absorber. In this way, by containing an ultraviolet absorber, it is possible to impart ultraviolet cut-off properties, and in particular, excellent cut-off properties of ultraviolet rays (wavelength of 380 nm or less) emitted from sunlight or fluorescent lamps, so that the contents of the container are deteriorated. Can be prevented and storage can be improved.

The ultraviolet absorber is not particularly limited, and examples thereof include 2,4-dihydroxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and 2-hydroxy-4-methoxy. Benzophenone ultraviolet absorbers such as benzophenone-5-sulfonic acid and 2-hydroxy-4-n-octoxybenzophenone; 2- (2′-hydroxy-4′-n-octoxyphenyl) benzotriazole, 2- (2 '-Hydroxy-5'-n-methoxyphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy) -3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2′-hydride) Roxy-5′-tert-octylphenyl) benzotriazole, 2- [2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methyl Benzotriazole ultraviolet absorbers such as phenyl] benzotriazole; benzoate ultraviolet absorbers such as 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate; p-tert- Examples thereof include salicylate ultraviolet absorbers such as butylphenyl salicylate; cyanoacrylate ultraviolet absorbers such as ethyl-2-cyano-3,3-diphenyl acrylate and octyl-2-cyano-3,3-diphenyl acrylate.
Among these, 2- (2′-hydroxy-5′-n-methoxyphenyl) benzotriazole and 2- (2′-hydroxy-3′-tert-butyl) are excellent in balance between ultraviolet absorption and heat resistance. -5'-methylphenyl) -5-chlorobenzotriazole is preferred.

The content of the ultraviolet absorber is preferably 1 part by weight with a preferred lower limit and 10 parts by weight with respect to 100 parts by weight of the material constituting the intermediate layer. When the amount is less than 1 part by weight, the UV-cutting property becomes insufficient, and when used as a shrink label for a container, the content may not be prevented from being deteriorated. The mechanical strength decreases, and breakage or the like may occur when used as a converting or shrink label for printing or the like. The minimum with more preferable content of the said ultraviolet absorber is 2 weight part, and a more preferable upper limit is 8 weight part.

As resin which comprises the said contact bonding layer, if it is generally marketed, it will not be specifically limited, It can use. Of these, it is preferable to use a styrene elastomer, a polyester elastomer, or a modified product thereof.

The styrenic elastomer includes those composed of polystyrene as a hard segment and polybutadiene, polyisoprene, a copolymer of polybutadiene and polyisoprene as a soft segment, and hydrogenated products thereof. The hydrogenated product may be one obtained by hydrogenating a part of polybutadiene or polyisoprene, or may be one obtained by hydrogenating all of them.

Examples of commercially available styrene elastomers include “Tuftec”, “Tufprene” (all manufactured by Asahi Kasei Chemicals), “Clayton” (manufactured by Kraton Polymer Japan), “Dynalon” (manufactured by JSR), “Septon”. (Made by Kuraray Co., Ltd.).

Examples of modified styrene elastomers include modified styrene elastomers modified with functional groups such as carboxylic acid groups, acid anhydride groups, amino groups, epoxy groups, and hydroxyl groups.
The preferable lower limit of the content of functional groups such as the carboxylic acid group, acid anhydride group, amino group, epoxy group and hydroxyl group in the modified styrene elastomer is 0.05% by weight, and the preferable upper limit is 5.0% by weight. . If it is less than 0.05% by weight, the adhesion to the front and back layers may be insufficient, and if it exceeds 5.0% by weight, the resin is thermally deteriorated when the functional group is added, and the gel Such a foreign matter may be easily generated. A more preferred lower limit is 0.1% by weight, and a more preferred upper limit is 3.0% by weight.

The polyester elastomer is preferably a saturated polyester elastomer, and particularly preferably a saturated polyester elastomer containing a polyalkylene ether glycol segment. As the saturated polyester-based elastomer containing a polyalkylene ether glycol segment, for example, a block copolymer composed of an aromatic polyester as a hard segment and a polyalkylene ether glycol or an aliphatic polyester as a soft segment is preferable. Furthermore, a polyester polyether block copolymer having a polyalkylene ether glycol as a soft segment is more preferable.

The polyester polyether block copolymer includes (i) an aliphatic and / or alicyclic diol having 2 to 12 carbon atoms, and (ii) an aromatic dicarboxylic acid and / or an aliphatic dicarboxylic acid or an alkyl ester thereof. And (iii) polyalkylene ether glycol as a raw material, and those obtained by polycondensation of oligomers obtained by esterification reaction or transesterification reaction are preferred.

As said C2-C12 aliphatic and / or alicyclic diol, what is generally used as a raw material of a polyester, especially the raw material of a polyester-type elastomer can be used, for example. Specific examples include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and the like. Among these, 1,4-butanediol or ethylene glycol is preferable, and 1,4-butanediol is particularly preferable. These diols may be used alone or in combination of two or more.

As said aromatic dicarboxylic acid, what is generally used as a raw material of polyester, especially a polyester-type elastomer can be used. Specific examples include terephthalic acid, isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid. Among these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferable, and terephthalic acid is particularly preferable. These aromatic dicarboxylic acids may be used alone or in combination of two or more.

Examples of the alkyl ester of the aromatic dicarboxylic acid include the dimethyl ester and diethyl ester of the aromatic dicarboxylic acid. Of these, dimethyl terephthalate and 2,6-dimethyl naphthalene dicarboxylate are preferable.

The aliphatic dicarboxylic acid is preferably cyclohexane dicarboxylic acid, and the alkyl ester is preferably dimethyl ester or diethyl ester. In addition to the above components, a small amount of a trifunctional alcohol, tricarboxylic acid or ester thereof may be copolymerized, and an aliphatic dicarboxylic acid such as adipic acid or a dialkyl ester thereof may be used as a copolymerization component.

Examples of the polyalkylene ether glycol include polyethylene glycol, poly (1,2- and / or 1,3-propylene ether) glycol, poly (tetramethylene ether) glycol, poly (hexamethylene ether) glycol, and the like. .

The preferable lower limit of the number average molecular weight of the polyalkylene ether glycol is 400, and the preferable upper limit is 6000. By setting it to 400 or more, the block property of the copolymer becomes high, and by setting it to 6000 or less, phase separation in the system hardly occurs and polymer physical properties are easily developed. A more preferred lower limit is 500, a more preferred upper limit is 4000, a still more preferred lower limit is 600, and a still more preferred upper limit is 3000. In addition, in this specification, a number average molecular weight means what was measured by gel permeation chromatography (GPC). The GPC calibration can be performed, for example, by using a POLYTETRAHYDROFURAN calibration kit (manufactured by POLYMER LABORATORIES, UK).

The polyester elastomer may coexist with a rubber component such as natural rubber and synthetic rubber (for example, polyisoprene rubber) and a softening agent such as process oil. By making the softener coexist, the plasticization of the rubber component can be promoted and the fluidity of the resulting thermoplastic resin composition can be improved. The softening agent may be paraffinic, naphthenic, or aromatic. Moreover, in the range which does not impair the effect of this invention, you may add other components, such as resin other than the above, rubber | gum, a filler, an additive, to this resin component and rubber component.

Examples of the filler include calcium carbonate, talc, silica, kaolin, clay, diatomaceous earth, calcium silicate, mica, asbestos, alumina, barium sulfate, aluminum sulfate, calcium sulfate, magnesium carbonate, carbon fiber, glass fiber, and glass bulb. , Molybdenum sulfide, graphite, shirasu balloon and the like. Examples of the additive include a heat resistance stabilizer, a weather resistance stabilizer, a colorant, an antistatic agent, a flame retardant, a nucleating agent, a lubricant, a slip agent, and an antiblocking agent.

As said heat stabilizer, well-known things, such as a phenol type, a phosphorus type, and a sulfur type, can be used, for example. As the weather resistance stabilizer, known ones such as hindered amines and triazoles can be used. Examples of the colorant include carbon black, titanium white, zinc white, red pepper, azo compound, nitroso compound, and phthalocyanine compound. In addition, known antistatic agents, flame retardants, nucleating agents, lubricants, slip agents, antiblocking agents and the like can be used.

Examples of commercially available polyester elastomers include “Primalloy” (manufactured by Mitsubishi Chemical Corporation), “Perprene” (manufactured by Toyobo Co., Ltd.), “Hytrel” (manufactured by Toray DuPont) and the like.

When using a polyester polyether block copolymer composed of polyester and polyalkylene ether glycol as the polyester elastomer, the content of the polyalkylene ether glycol component is preferably 5% by weight, and preferably 90% by weight. is there. When it is 5% by weight or more, it is excellent in flexibility and impact resistance, and when it is 90% by weight or less, it is excellent in hardness and mechanical strength. A more preferred lower limit is 30% by weight, a more preferred upper limit is 80% by weight, and a still more preferred lower limit is 55% by weight. The content of the polyalkylene ether glycol component can be calculated based on the chemical shift of the hydrogen atom and its content using nuclear magnetic resonance spectroscopy (NMR).

The modified polyester elastomer (hereinafter also referred to as a modified polyester elastomer) is obtained by modifying the polyester elastomer using a modifier. The modification reaction for obtaining the modified polyester elastomer is performed, for example, by reacting the polyester elastomer with an α, β-ethylenically unsaturated carboxylic acid as a modifier. In the modification reaction, a radical generator is preferably used. In the modification reaction, a graft reaction in which an α, β-ethylenically unsaturated carboxylic acid or a derivative thereof is added to a polyester elastomer mainly occurs, but a decomposition reaction also occurs. As a result, the modified polyester elastomer has a lower molecular weight and a lower melt viscosity. Further, in the modification reaction, it is generally considered that a transesterification reaction or the like occurs as another reaction, and the obtained reaction product is generally a composition containing unreacted raw materials, etc. The preferable lower limit of the content of the modified polyester elastomer in the obtained reaction product is 10% by weight, the more preferable lower limit is 30% by weight, and the content of the modified polyester elastomer is more preferably 100% by weight.

Examples of the α, β-ethylenically unsaturated carboxylic acid include unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrofumaric acid, itaconic acid, citraconic acid, crotonic acid, and isocrotonic acid; succinic acid 2 -Octen-1-yl anhydride, 2-dodecen-1-yl anhydride, succinic acid 2-octadecen-1-yl anhydride, maleic anhydride, 2,3-dimethylmaleic anhydride, bromomalein Acid anhydride, dichloromaleic acid anhydride, citraconic acid anhydride, itaconic acid anhydride, 1-butene-3,4-dicarboxylic acid anhydride, 1-cyclopentene-1,2-dicarboxylic acid anhydride, 1,2, 3,6-tetrahydrophthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, exo-3,6-epoxy-1,2,3,6-tetra Hydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, methyl-5-norbornene-2,3-dicarboxylic anhydride, endo-bicyclo [2.2.2] oct-5-ene-2 , 3-dicarboxylic acid anhydride, and unsaturated carboxylic acid anhydrides such as bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic acid anhydride. Of these, acid anhydrides are preferred because of their high reactivity. The α, β-ethylenically unsaturated carboxylic acid can be appropriately selected according to the copolymer containing the polyalkylene ether glycol segment to be modified and the modification conditions. Good. The α, β-ethylenically unsaturated carboxylic acid can be used by dissolving in an organic solvent or the like.

Examples of the radical generator include t-butyl hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-bis ( Tertiary butyloxy) hexane, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxybenzoate, benzoyl peroxide, dicumyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene Organic and inorganic peroxides such as dibutyl peroxide, methyl ethyl ketone peroxide, potassium peroxide, hydrogen peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (isobutylamide) dihalide, 2,2'-azobis [2-methyl-N- (2-hydrido Kishiechiru) propionamide], azo compounds such as azodi -t- butane, carbon radical generating agents such as dicumyl like. The radical generator can be appropriately selected according to the type of polyester elastomer used for the modification reaction, the type of α, β-ethylenically unsaturated carboxylic acid and the modification conditions, and two or more types can be used in combination. May be. Furthermore, the radical generator can be used by dissolving in an organic solvent or the like.

A preferable lower limit of the amount of the α, β-ethylenically unsaturated carboxylic acid is 0.01 parts by weight with respect to 100 parts by weight of the polyester elastomer, and a preferable upper limit is 30.0 parts by weight. When the amount is 0.01 parts by weight or more, the modification reaction can be sufficiently performed, and when the amount is 30.0 parts by weight or less, it is economically advantageous. A more preferred lower limit is 0.05 parts by weight, a more preferred upper limit is 5.0 parts by weight, a still more preferred lower limit is 0.10 parts by weight, and a still more preferred upper limit is 1.0 part by weight.

A preferable lower limit of the blending amount of the radical generator is 0.001 part by weight with respect to 100 parts by weight of the polyester elastomer, and a preferable upper limit is 3.00 part by weight. When the amount is 0.001 part by weight or more, the modification reaction is likely to occur, and when the amount is 3.00 part by weight or less, the material strength is less likely to decrease due to low molecular weight (decrease in viscosity) during modification. A more preferred lower limit is 0.005 parts by weight, a more preferred upper limit is 0.50 parts by weight, a still more preferred lower limit is 0.010 parts by weight, a still more preferred upper limit is 0.20 parts by weight, and a particularly preferred upper limit is 0.10 parts by weight. Part.

As the modification reaction for obtaining the modified polyester-based elastomer, known reaction methods such as a melt-kneading reaction method, a solution reaction method, a suspension-dispersion reaction can be used. Reaction methods are preferred.

In the method using the melt kneading reaction method, the above-described components are uniformly mixed at a predetermined blending ratio, and then melt kneaded. Henschel mixer, ribbon blender, V-type blender, etc. can be used for mixing each component, and Banbury mixer, kneader, roll, uniaxial or biaxial multiaxial kneading extruder etc. are used for melt kneading. can do.

The preferable lower limit of the kneading temperature when the melt kneading is performed is 100 ° C., and the preferable upper limit is 300 ° C. By setting it within the above range, thermal deterioration of the resin can be prevented. A more preferred lower limit is 120 ° C., a more preferred upper limit is 280 ° C., a still more preferred lower limit is 150 ° C., and a still more preferred upper limit is 250 ° C.

The preferable lower limit of the modification rate (graft amount) of the modified polyester elastomer is 0.01% by weight, and the preferable upper limit is 10.0% by weight. When the content is 0.01% by weight or more, the affinity with the polyester is increased, and when the content is 10.0% by weight or less, a decrease in strength due to molecular deterioration during modification can be reduced. A more preferred lower limit is 0.03% by weight, a more preferred upper limit is 7.0% by weight, a still more preferred lower limit is 0.05% by weight, and a still more preferred upper limit is 5.0% by weight.

The modification rate (graft amount) of the modified polyester elastomer can be obtained from the spectrum obtained by H ¹ -NMR measurement according to the following formula (1). As the equipment used to the ^H 1 -NMR measurement, for example, it can be used to "GSX-400" (manufactured by Nippon Denshi) and the like.

Graft amount (% by weight) = 100 × [(C ÷ 3 × 98) / {(A × 148 ÷ 4) + (B × 72 ÷ 4) + (C ÷ 3 × 98)}] (1)
In the formula (1), A represents an integral value at 7.8 to 8.4 ppm, B represents an integral value at 1.2 to 2.2 ppm, and C represents an integral value at 2.4 to 2.9 ppm.

The preferable lower limit of the JIS-D hardness of the reaction product containing the modified polyester elastomer obtained by the modification reaction is 10, and the preferable upper limit is 80. By setting it to 10 or more, the mechanical strength is improved, and by setting it to 80 or less, flexibility and impact resistance are improved. A more preferred lower limit is 15, a more preferred upper limit is 70, a still more preferred lower limit is 20, and a still more preferred upper limit is 60. The JIS-D hardness can be measured by using a durometer type D by a method in accordance with JIS K 6253.

If necessary, additives such as an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, and an antiblocking agent may be added to the heat-shrinkable multilayer film of the present invention. In particular, the generation of gel can be suppressed by adding a heat stabilizer or an antioxidant.

When the thickness of the whole film is 30 μm, the preferable lower limit of the thickness of the intermediate layer is 18 μm, and the preferable upper limit is 25 μm. When the thickness is less than 18 μm, the shrinkage stress may not be effectively suppressed. When the thickness exceeds 25 μm, sufficient heat resistance may not be obtained. A more preferable lower limit is 20 μm, and a more preferable upper limit is 25 μm.
The preferable lower limit of the thickness of the front and back layers is 2 μm, and the preferable upper limit is 5 μm. If it is less than 2 μm, sufficient oil resistance and heat resistance may not be obtained, and if it exceeds 5 μm, shrinkage stress may not be effectively suppressed. A more preferable lower limit is 2.5 μm, and a more preferable upper limit is 4.5 μm.
The preferable lower limit of the thickness of the adhesive layer is 0.3 μm, and the preferable upper limit is 1.5 μm. If it is less than 0.3 μm, sufficient adhesive strength may not be obtained, and if it exceeds 1.5 μm, the heat shrinkage characteristics may be deteriorated. A more preferable lower limit is 0.5 μm, and a more preferable upper limit is 1.0 μm.

The preferable lower limit of the total thickness of the heat-shrinkable multilayer film of the present invention is 20 μm, and the preferable upper limit is 45 μm. By making the thickness of the entire heat-shrinkable multilayer film within the above range, it is excellent in economic efficiency and easy to handle. As for the thickness of each layer, it is preferable that the thickness of the front and back layers is 2 to 7.5 μm, and the thickness of the whole layer is 20 to 45 μm by increasing or decreasing the thickness of the intermediate layer and the adhesive layer.

In the heat-shrinkable multilayer film of the present invention, the lower limit of the maximum shrinkage stress when immersed in warm water at 80 ° C. for 30 seconds is 0.3 N / 10 mm, and the upper limit is 1.0 N / 10 mm. When the maximum shrinkage stress is less than 0.3 N / 10 mm, the container is not sufficiently mounted, and when the maximum shrinkage stress exceeds 1.0 N / 10 mm, the container is deformed. The preferable lower limit of the maximum shrinkage stress is 0.4 N / 10 mm, and the preferable upper limit is 0.9 N / 10 mm.
In addition, the said maximum shrinkage stress means the maximum value of the shrinkage stress in the case of measuring the shrinkage stress by immersing the heat-shrinkable multilayer film of the present invention in warm water at 80 ° C. for 30 seconds.

The heat-shrinkable multilayer film of the present invention has a lower limit of the heat shrinkage rate in the main shrinkage direction (the direction in which the shrinkage is greater in the vertical direction or the horizontal direction) when immersed in warm water at 80 ° C. for 10 seconds. %. When the heat shrinkage rate is less than 20%, the heat shrinkable multilayer film cannot be sufficiently attached to the container even if the heat shrinkage is performed. A preferable upper limit is 60%.
The heat shrinkage rate is calculated by cutting the heat-shrinkable multilayer film into a size of 100 mm × 100 mm and immersing it in a hot water bath at 80 ° C. for 10 seconds, and then the ratio of shrinkage to the original size before shrinkage in%. It is the expressed value. The vertical direction is the film flow direction, and the width direction is the width direction.

Moreover, the heat-shrinkable multilayer film of the present invention preferably has a heat shrinkage rate in the main shrinkage direction (the direction in which the shrinkage is greater in the vertical direction or the horizontal direction) when immersed in warm water at 70 ° C. for 10 seconds. The lower limit is 3%, and the preferred upper limit is 30%.

As a method for producing the heat-shrinkable multilayer film of the present invention, for example, a multilayer film in which a front and back layer made of a polyester resin and an intermediate layer made of a polystyrene resin are laminated via an adhesive layer is produced. A process for producing a heat-shrinkable multilayer film comprising Step 1 and Step 2 for stretching the multilayer film, wherein, in Step 2, stretched so that F represented by the following formula (2) is 0.44 to 0.50. Can be used.

Wherein (2), _{t p} is the preheating zone processing time, _{T p} is the preheating zone temperature, _{t s} is the stretching zone processing time, _{T s} is the stretching zone temperature, _{t f} is fixed zone processing time, _{T f} is a fixed zone temperature , Tg represents the calculated glass transition temperature of the heat-shrinkable multilayer film, and L represents the total thickness of the heat-shrinkable multilayer film.

The specific method of the step 1 is not particularly limited, and for example, a method of producing a multilayer film by a method of simultaneously forming each layer by a coextrusion method is suitable. For example, in co-extrusion using a T-die, any of a feed block method, a multi-manifold method, or a method using these in combination may be used as a lamination method. Specifically, for example, a polyester resin having a sulfone group as a resin constituting the front and back layers, a polystyrene resin as a resin constituting the intermediate layer, a modified styrene elastomer and / or a modified polyester elastomer as a resin constituting the adhesive layer And the like, and a method of extruding into a sheet with a multilayer die.

In the step 2, the multilayer film is stretched so that F shown in the formula (2) is 0.44 to 0.50. When F is less than 0.44, when used for a heat-shrinkable label, the heat-shrinkability at the time of wearing may be deteriorated. When F exceeds 0.50, the resulting heat-shrinkable label shrinks. The stress becomes too high, and the container may be damaged when mounted on the container or the like.

In this specification, “calculated glass transition temperature” is obtained by multiplying the glass transition temperature of the resin constituting the front and back layers and the intermediate layer by [(thickness of each layer) / (thickness of the front and back layers + thickness of the intermediate layer)]]. It is the sum of things. For example, the heat-shrinkable multilayer film has a total thickness of 25 μm, and is composed of five layers: surface layer (6 μm) / adhesive layer (0.5 μm) / intermediate layer (12 μm) / adhesive layer (0.5 μm) / back surface layer (6 μm) When the glass transition temperature of the resin constituting the front and back layers is 60 ° C. and the glass transition temperature of the resin constituting the intermediate layer is 70 ° C., the calculated glass transition temperature is 65 ° C.

In the step 2, the multilayer film obtained in the step 1 is passed through a stretching machine having a preheating zone, a stretching zone, and a fixing zone to stretch the multilayer film. At this time, F represented by the above formula (2) is set within the range of 0.44 to 0.50.

The stretching method in step 2 will be described with reference to the drawings.
FIG. 1 is a top view schematically showing an example of a tenter stretching machine that can be used for producing the heat-shrinkable multilayer film of the present invention. The tenter stretching machine shown in FIG. 1 includes a drawer roll 21, a winding roll 22, a temperature-controlled room 10 having a preheating zone A, a stretching zone B, and a fixed zone C, and a rail on which gripping means for transporting the film travels. 11 and.
The gripping means grips both ends of the multilayer film fed out from the drawing roll 21, guides it into a temperature-controlled room having a preheating zone A, a stretching zone B, and a fixing zone C, and opens the film before the winding roll 22. The film released from the gripping means is taken up by the take-up roll 22.

The multilayer film 1 is stretched at a desired stretching ratio by tension from the gripping means while passing through the temperature-controlled room having the preheating zone A, the stretching zone B, and the fixing zone C.
The preheating zone A is a zone in which the multilayer film is conveyed while warming without substantially changing the film width in the direction perpendicular to the traveling direction of the multilayer film.
The stretching zone B is a zone for transporting the multilayer film while increasing the film width in the direction perpendicular to the traveling direction of the multilayer film.
The fixing zone C is a zone in which the multilayer film is conveyed while being cooled without substantially changing the film width in the direction perpendicular to the traveling direction of the multilayer film.
The preheating zone A, the stretching zone B, and the fixed zone C can independently set temperatures, and the temperatures are kept constant in each zone. Further, the processing time and length in the preheating zone A, the stretching zone B, and the fixed zone C can be set as appropriate.

The stretching temperature in the above step 2 needs to be changed depending on the softening temperature of the resin constituting the film and the shrinkage properties required for the heat-shrinkable multilayer film. The preferred lower limit of the stretching temperature is 75 ° C., and the preferred upper limit is 120. The more preferable lower limit is 80 ° C., and the more preferable upper limit is 115 ° C.
Further, the draw ratio in the above step 2 also needs to be changed depending on the softening temperature of the resin constituting the film and the shrinkage characteristics required for the heat-shrinkable multilayer film, but the preferred lower limit of the draw ratio is 3.5 times. The preferred upper limit is 7.0 times.
The stretching may be uniaxial stretching or biaxial stretching.

A heat-shrinkable label can be obtained by using the heat-shrinkable multilayer film of the present invention as a base film. Such a heat-shrinkable label is also one aspect of the present invention.
In the heat-shrinkable label of the present invention, the heat-shrinkable multilayer film may be used as a base film, and other layers such as a printing layer may be laminated as necessary. In addition to the printing layer, other layers may be laminated. For example, an overcoat layer made of an acrylic resin or the like may be laminated on the surface of the front and back layers in order to prevent damage.

As a method of attaching the heat-shrinkable label to the container, usually, the end portions of the heat-shrinkable film are bonded using a solvent and processed into a tube shape (center seal processing) to obtain a heat-shrinkable label. The method of heating and shrinking in a state of covering is adopted.

According to the present invention, a heat-shrinkable multilayer film having a low shrinkage stress that can be attached to a container by heat-shrinking and can suppress deformation of the container, and heat-shrinkage using the heat-shrinkable multilayer film as a base film Sex labels can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Example 1)
As the resin constituting the surface layer and the back layer, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of the component derived from ethylene glycol as the diol component, and 33 mol% of the component derived from 1,4-cyclohexanedimethanol Polyester resin (glass transition temperature 80 ° C.) was used.
As the resin constituting the intermediate layer, a styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene: MFR 5.6 g / 10 min, glass transition temperature 69 ° C.) was used.
As resin constituting the adhesive layer, maleic anhydride-modified styrene-ethylene / butylene-styrene block copolymer (styrene content 30% by weight, maleic anhydride addition amount 0.5% by weight, MFR 4.0 g / 10 min) is used. It was.
These resins were put into an extruder having a barrel temperature of 160 to 250 ° C., extruded from a multilayer die at 250 ° C. into a sheet having a five-layer structure, and cooled and solidified by a take-up roll at 30 ° C. Next, the film was roll-drawn in the MD direction at a draw ratio of 1.5, followed by a preheating zone 112 ° C. (passing time 5.3 seconds), a drawing zone 100 ° C. (passing time 7.8 seconds), and a fixed zone 102 ° C. (passing time) After stretching in the TD direction at a stretching ratio of 6 times in a tenter stretching machine for 5.3 seconds), the total thickness is 30 μm by winding with a winder, and the surface layer (3.2 μm) / adhesive layer ( A heat-shrinkable multilayer film having a five-layer structure of 0.7 μm) / intermediate layer (22.2 μm) / adhesive layer (0.7 μm) / back surface layer (3.2 μm) was obtained.

(Example 2)
As the resin constituting the surface layer and the back layer, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of the component derived from ethylene glycol as the diol component, and 33 mol% of the component derived from 1,4-cyclohexanedimethanol Polyester resin (glass transition temperature 80 ° C.) was used.
As the resin constituting the intermediate layer, a styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene: MFR 5.6 g / 10 min, glass transition temperature 69 ° C.) was used.
As a resin constituting the adhesive layer, a polyester elastomer (manufactured by Mitsubishi Chemical Corporation, Primalloy A1600N, melting point 160 ° C., MFR 5.0 g / 10 min) was used.
A heat-shrinkable multilayer film was obtained in the same manner as in Example 1 except that these resins were used.

(Example 3)
As the resin constituting the surface layer and the back layer, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of the component derived from ethylene glycol as the diol component, and 33 mol% of the component derived from 1,4-cyclohexanedimethanol Polyester resin (glass transition temperature 80 ° C.) was used.
As the resin constituting the intermediate layer, a styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene, MFR 5.6 g / 10 minutes, glass transition temperature 69 ° C.) was used.
As a resin constituting the adhesive layer, a modified polyester elastomer (manufactured by Mitsubishi Chemical Corporation, Primalloy AP IF3003, melting point 180 ° C., MFR 8.0 g / 10 min) was used.
A heat-shrinkable multilayer film was obtained in the same manner as in Example 1 except that these resins were used.

Example 4
As the resin constituting the surface layer and the back layer, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of the component derived from ethylene glycol as the diol component, and 33 mol% of the component derived from 1,4-cyclohexanedimethanol Polyester resin (glass transition temperature 80 ° C.) was used.
As the resin constituting the intermediate layer, a styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene, MFR 5.6 g / 10 minutes, glass transition temperature 69 ° C.) was used.
As resin constituting the adhesive layer, maleic anhydride-modified styrene-ethylene / butylene-styrene block copolymer (styrene content 30% by weight, maleic anhydride addition amount 0.5% by weight, MFR 4.0 g / 10 min) is used. It was.
These resins were put into an extruder having a barrel temperature of 160 to 250 ° C., extruded from a multilayer die at 250 ° C. into a sheet having a three-layer structure, and cooled and solidified by a take-up roll at 30 ° C. Next, roll stretching in the MD direction at a stretching ratio of 1.5 times, followed by a preheating zone 112 ° C. (passing time 5.3 seconds), a stretching zone 103 ° C. (passing time 7.8 seconds), a fixed zone 102 ° C. (passing time 5) .3 seconds) in a tenter stretching machine at a stretching ratio of 6 times and then stretched in the TD direction, and then wound up by a winder, the total thickness is 30 μm, and the surface layer (3.2 μm) / adhesive layer (0 .7 μm) / intermediate layer (22.2 μm) / adhesive layer (0.7 μm) / back surface layer (3.2 μm).

(Example 5)
As the resin constituting the surface layer and the back layer, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of the component derived from ethylene glycol as the diol component, and 33 mol% of the component derived from 1,4-cyclohexanedimethanol Polyester resin (glass transition temperature 80 ° C.) was used.
As the resin constituting the intermediate layer, a styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene, MFR 5.6 g / 10 minutes, glass transition temperature 69 ° C.) was used.
As resin constituting the adhesive layer, maleic anhydride-modified styrene-ethylene / butylene-styrene block copolymer (styrene content 30% by weight, maleic anhydride addition amount 0.5% by weight, MFR 4.0 g / 10 min) is used. It was.
These resins were put into an extruder having a barrel temperature of 160 to 250 ° C., extruded from a multilayer die at 250 ° C. into a sheet having a three-layer structure, and cooled and solidified by a take-up roll at 30 ° C. Next, roll stretching in the MD direction at a stretching ratio of 1.5 times, followed by a preheating zone 112 ° C. (passing time 5.3 seconds), a stretching zone 100 ° C. (passing time 7.8 seconds), a fixed zone 102 ° C. (passing time 5) .3 seconds) in a tenter stretching machine at a stretching ratio of 6 times and then stretched in the TD direction, and then wound up by a winder, the total thickness is 30 μm, and the surface layer (4.8 μm) / adhesive layer (0 .7 μm) / intermediate layer (19.0 μm) / adhesive layer (0.7 μm) / back surface layer (4.8 μm) was obtained.

(Example 6)
As the resin constituting the surface layer and the back layer, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of the component derived from ethylene glycol as the diol component, and 33 mol% of the component derived from 1,4-cyclohexanedimethanol Polyester resin (glass transition temperature 80 ° C.) was used.
As the resin constituting the intermediate layer, a styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene: MFR 5.6 g / 10 min, glass transition temperature 69 ° C.) was used.
As resin constituting the adhesive layer, maleic anhydride-modified styrene-ethylene / butylene-styrene block copolymer (styrene content 30% by weight, maleic anhydride addition amount 0.5% by weight, MFR 4.0 g / 10 min) is used. It was.
These resins were put into an extruder having a barrel temperature of 160 to 250 ° C., extruded from a multilayer die at 250 ° C. into a sheet having a three-layer structure, and cooled and solidified by a take-up roll at 30 ° C. Next, roll stretching in the MD direction at a stretching ratio of 1.5 times, followed by a preheating zone 111 ° C. (passing time 5.3 seconds), a stretching zone 99 ° C. (passing time 7.8 seconds), a fixed zone 99 ° C. (passing time 5) .3 seconds) in a tenter stretching machine at a stretching ratio of 6 times and then stretched in the TD direction, and then wound up by a winder, the total thickness is 30 μm, and the surface layer (3.2 μm) / adhesive layer (0 .7 μm) / intermediate layer (22.2 μm) / adhesive layer (0.7 μm) / back surface layer (3.2 μm).

(Comparative Example 1)
As the resin constituting the surface layer and the back layer, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of the component derived from ethylene glycol as the diol component, and 33 mol% of the component derived from 1,4-cyclohexanedimethanol Polyester resin (glass transition temperature 80 ° C.) was used.
As the resin constituting the intermediate layer, a styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene: MFR 5.6 g / 10 min, glass transition temperature 69 ° C.) was used.
As resin constituting the adhesive layer, maleic anhydride-modified styrene-ethylene / butylene-styrene block copolymer (styrene content 30% by weight, maleic anhydride addition amount 0.5% by weight, MFR 4.0 g / 10 min) is used. It was.
These resins were put into an extruder having a barrel temperature of 160 to 250 ° C., extruded from a multilayer die at 250 ° C. into a sheet having a three-layer structure, and cooled and solidified by a take-up roll at 30 ° C. Next, roll stretching in the MD direction at a stretching ratio of 1.5 times, followed by preheating zone 110 ° C. (passing time 5.3 seconds), stretching zone 97 ° C. (passing time 7.8 seconds), fixing zone 95 ° C. (passing time 5) .3 seconds) in a tenter stretching machine at a stretching ratio of 6 times and then stretched in the TD direction, and then wound up by a winder, the total thickness is 30 μm, and the surface layer (3.2 μm) / adhesive layer (0 .7 μm) / intermediate layer (22.2 μm) / adhesive layer (0.7 μm) / back surface layer (3.2 μm).

(Comparative Example 2)
As the resin constituting the surface layer and the back layer, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of the component derived from ethylene glycol as the diol component, and 33 mol% of the component derived from 1,4-cyclohexanedimethanol Polyester resin (glass transition temperature 80 ° C.) was used.
As the resin constituting the intermediate layer, a styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene: MFR 5.6 g / 10 min, glass transition temperature 69 ° C.) was used.
As resin constituting the adhesive layer, maleic anhydride-modified styrene-ethylene / butylene-styrene block copolymer (styrene content 30% by weight, maleic anhydride addition amount 0.5% by weight, MFR 4.0 g / 10 min) is used. It was.
These resins were put into an extruder having a barrel temperature of 160 to 250 ° C., extruded from a multilayer die at 250 ° C. into a sheet having a three-layer structure, and cooled and solidified by a take-up roll at 30 ° C. Next, roll stretching in the MD direction at a stretching ratio of 1.5 times, followed by preheating zone 115 ° C. (passing time 5.3 seconds), stretching zone 103 ° C. (passing time 7.8 seconds), fixing zone 102 ° C. (passing time 5) .3 seconds) in a tenter stretching machine at a stretching ratio of 6 times and then stretched in the TD direction, and then wound up by a winder, the total thickness is 30 μm, and the surface layer (3.2 μm) / adhesive layer (0 .7 μm) / intermediate layer (22.2 μm) / adhesive layer (0.7 μm) / back surface layer (3.2 μm).

(Evaluation)
The heat shrinkable multilayer films obtained in Examples and Comparative Examples were evaluated by the following methods. The results are shown in Table 1. In Table 1, the preheating zone processing time, preheating zone temperature, stretching zone processing time, stretching zone temperature, fixing zone processing time, fixing zone temperature, calculated glass transition of heat-shrinkable multilayer film in each example and comparative example are shown. The temperature and the total thickness of the heat-shrinkable multilayer film are described.

(1) Heat shrinkage rate The obtained heat shrinkable multilayer film was cut into a size of 100 mm × 100 mm, immersed in warm water at 80 ° C. for 10 seconds, and then the heat shrinkable multilayer film was taken out and subjected to heat treatment. The ratio of the dimension after heating to the previous dimension was calculated. The shrinkage rate was n = 3 and the average value was used. In addition, a value 2% or more away from the average value is not counted.

(2) Shrinkage stress The obtained heat-shrinkable multilayer film was cut into a size of 200 mm × 10 mm so that the TD direction (main shrinkage direction) was the long side, and used as a measurement sample. One of the measurement samples was fixed so that the distance between chucks was 100 mm, and the other was connected to a load cell for measuring the load and set (the output signal from the load cell was recorded by a recorder).
Then, the measurement sample was immersed in warm water adjusted to 80 ° C. for 30 seconds together with the chuck, and the contraction stress when the measurement sample contracted was measured. In addition, the maximum value in 30 seconds was made into the measured value.

According to the present invention, a heat-shrinkable multilayer film having a low shrinkage stress that can be attached to a container by heat-shrinking and can suppress deformation of the container, and heat-shrinkage using the heat-shrinkable multilayer film as a base film Sex labels can be provided.

It is a top view which shows roughly an example of the tenter stretching machine which can be used when manufacturing the heat-shrinkable multilayer film of this invention.

Claims (2)

A heat-shrinkable multilayer film in which a front and back layer made of a polyester-based resin and an intermediate layer made of a polystyrene-based resin are laminated via an adhesive layer,
The maximum shrinkage stress when immersed in warm water at 80 ° C. for 30 seconds is 0.3 to 1.0 N / 10 mm, and
A heat shrinkable multilayer film having a heat shrinkage ratio in the main shrinkage direction of 20% or more when immersed in warm water at 80 ° C. for 10 seconds. A heat-shrinkable label comprising the heat-shrinkable multilayer film according to claim 1.

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