JP2016182674A - Shrink film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shrink film which suppresses occurrence of natural shrinkage, has high rigidity, is excellent in thermal shrinkability, and has thermal shrinkability in an MD direction.SOLUTION: There is provided a shrink film which has thermal shrinkability in an MD direction, and has a five-layer structure of surface layer/A layer/B layer/A layer/surface layer or surface layer/B layer/A layer/B layer/surface layer, where the surface layer is a layer containing an amorphous cyclic olefin-based polymer or a polypropylene-based resin as a main component, the A layer is a layer containing 10-49 wt.% of a polypropylene-based elastomer and 5-90 wt.% of an amorphous cyclic olefin-based polymer, and the B layer is a layer containing a polypropylene-based elastomer as a main component.SELECTED DRAWING: None

Description

  The present invention relates to a shrink film. More specifically, the present invention relates to a shrink film having heat shrinkability in the MD direction, having high rigidity and excellent heat shrinkability while suppressing the occurrence of natural shrinkage.

  Currently, plastic bottles such as PET bottles and metal bottles such as bottle cans are widely used as containers for beverages such as tea and soft drinks. In many cases, plastic labels are attached to these containers for display, decoration, and functionality. As such a plastic label, for example, a shrink label in which a printing layer is provided on a shrink film (heat-shrinkable film) from the merits of decoration, workability (followability to containers), a wide display area, and the like. Widely used.

  Among the above-mentioned shrink labels, a flat label is wound around a container or mandrel, and both ends of the label are overlapped. Then, both ends of the label are sealed to form a cylinder, which is thermally shrunk and attached to the container. As a shrink film used in a case called “shrink label”, a shrink film stretched in the MD direction is generally used. A polyester film is known as a shrink film stretched in the MD direction (see, for example, Patent Document 1). The polyester film has high rigidity and excellent resistance (solvent resistance) to a solvent such as a solvent contained in printing ink.

  In addition, as the shrink film stretched in the MD direction, a film having a layer containing a polyolefin resin is known (see, for example, Patent Document 2). A film having a layer containing the polyolefin resin has a lower specific gravity than a polyester film.

JP-A-4-344222 JP 2014-28513 A

  However, since the polyester film has a relatively low heat shrinkability, a wrapping type shrink label using the film has a problem that a label following property to an adherend such as a container is relatively low.

  In addition, the film having a layer containing the polyolefin-based resin has low rigidity, and the wrapping type shrink label using the film has a tendency to become weak, and the label is attached when the label is attached to the adherend. There was a tendency for poor mounting. In addition, a film having a layer containing a polyolefin-based resin is prone to spontaneous shrinkage, and when the wrapping type shrink label using the film is stored in a roll, natural shrinkage occurs, so-called "winding tightening" Tended to occur.

  Accordingly, the present situation is that a shrink film having high heat shrinkability in the MD direction and having high rigidity and excellent heat shrinkability while suppressing the occurrence of natural shrinkage is required.

  Accordingly, an object of the present invention is to provide a shrink film having heat shrinkability in the MD direction, having high rigidity and excellent heat shrinkability while suppressing the occurrence of natural shrinkage.

  That is, the present invention has heat shrinkability in the MD direction, and has a five-layer structure of surface layer / A layer / B layer / A layer / surface layer or surface layer / B layer / A layer / B layer / surface layer. The surface layer is a layer mainly composed of an amorphous cyclic olefin polymer or a polypropylene resin, and the A layer is composed of 10 to 49% by weight of a polypropylene elastomer and an amorphous cyclic olefin polymer. There is provided a shrink film which is a layer containing 5 to 90% by weight of a coalescence, and wherein the B layer is a layer mainly composed of a polypropylene-based elastomer.

  Moreover, this invention provides the said shrink film whose said A layer is a layer which contains a polypropylene resin or a polyethylene resin further.

  In addition, the present invention provides the shrink film, wherein the polypropylene elastomer in the A layer and the polypropylene elastomer in the B layer are propylene-α-olefin copolymer elastomers.

  Moreover, this invention provides the said shrink film whose said A layer is a layer containing 1-50 weight% of polypropylene-type resin.

  Moreover, this invention provides the said shrink film whose said A layer is a layer containing 1 to 70 weight% of polyethylene-type resin.

  Since the shrink film of the present invention has the above-described configuration, it has high rigidity and excellent heat shrinkability while suppressing the occurrence of spontaneous shrinkage. For this reason, the shrink label using the shrink film of the present invention is excellent in heat shrinkability when attached to an adherend, and the occurrence of spontaneous shrinkage is suppressed, so that winding tightening hardly occurs. Moreover, the shrink label using the shrink film of the present invention is less likely to cause label mounting failure when mounted on an adherend.

  The shrink film of this invention has three types of layers, a surface layer, A layer, and B layer. The shrink film of the present invention has a five-layer structure of [surface layer / A layer / B layer / A layer / surface layer] or [surface layer / B layer / A layer / B layer / surface layer]. In the present specification, the layer located at the center of the five-layer structure may be referred to as a “center layer”. The layer located between the center layer and the surface layer may be referred to as an “intermediate layer”. For example, in a five-layer configuration of [surface layer / A layer / B layer / A layer / surface layer], the A layer is an intermediate layer and the B layer is a central layer.

(Surface layer)
A surface layer is the outermost layer of both surfaces of the shrink film of this invention. The surface layer is a layer (resin layer) mainly composed of an amorphous cyclic olefin polymer or a polypropylene resin. The surface layer is a layer mainly composed of a polyolefin-based resin. By using an amorphous cyclic olefin polymer or a polypropylene-based resin as a main component as a polyolefin-based resin, the shrink film of the present invention is a polypropylene-based resin. Even if it is the structure which has A layer and B layer containing an elastomer, the rigidity of a shrink film can be made high. Especially, it is preferable that a surface layer is a layer which has an amorphous cyclic olefin type polymer as a main component from a viewpoint of making rigidity more moderate, and a printability viewpoint.

  In the present specification, the “main component” refers to a material (component) that is the largest in terms of weight among materials (components) contained in the layer. In addition, a layer (mixed resin layer) in which two or more types of resins among the resins contained in the layer are present corresponds in principle to any layer containing each of the two or more types of resins as a main component. . For example, a mixed resin layer containing 50% by weight of an amorphous cyclic olefin polymer and 50% by weight of a polypropylene resin is also a layer mainly composed of an amorphous cyclic olefin polymer, and a polypropylene resin. It is also a layer containing as a main component.

  When the surface layer is mainly composed of an amorphous cyclic olefin polymer, the surface layer contains an amorphous cyclic olefin polymer as an essential component. The amorphous cycloolefin polymer may be used alone or in combination of two or more. The surface layer may contain a resin other than the amorphous cyclic olefin polymer.

  Examples of the amorphous cyclic olefin polymer include a copolymer of an α-olefin such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene and at least one cyclic olefin. (Sometimes referred to as "cyclic olefin copolymer") and cyclic olefin ring-opening polymer or hydrogenated product thereof (sometimes referred to as "cyclic olefin ring-opening polymer or hydrogenated product thereof") Is mentioned. The cyclic olefin copolymer, the cyclic olefin ring-opening polymer, or the hydrogenated product thereof also includes a graft-modified product thereof.

Examples of the cyclic olefin used in the amorphous cyclic olefin polymer used in the surface layer include bicyclo [2.2.1] hept-2-ene (norbornene), tetracyclo [4.4.0.1 ^{2 , 5} . 1 ^7,10 ] -3-dodecene, hexacyclo [6.6.1.1 ^3,6 . 1 ^10,13 . 0 ^2,7 . 0 ^9,14] -4-heptadecene, octacyclo [8.8.0.1 ^2,9. 1 ^4,7 . 1 ^11,18 . 1 ^13,16 . 0 ^3,8 . 0 ^12,17 ] -5-docosene, pentacyclo [6.6.1.1 ^3,6 . 0 ^2,7 . 0 ^9,14] -4-hexadecene, heptacyclo-5-icosene, heptacyclo-5-henicosenoic, tricyclo [4.3.0.1 ^{2, 5]-3-decene,} tricyclo [4.4.0.1 ^{2 , 5} ] -3-undecene, pentacyclo [6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13 ] -4-pentadecene, pentacyclopentadecadiene, pentacyclo [4.7.0.1 ^2,5 . 0 ^8,13 . 1 ^9,12] -3-pentadecene, Nonashikuro [9.10.1.1 ^{4, 7.} 1 ^13,20 . 1 ^15,18 . 0 ^2,10 . 0 ^12,21 . 0 ^14,19] -5-pentacosene and the like polycyclic olefins such. Of these, norbornene is preferable. These cyclic olefins may have a substituent such as an ester group such as a methoxycarbonyl group or an ethoxycarbonyl group; an alkyl group such as a methyl group; a haloalkyl group; a cyano group;

  The cyclic olefin copolymer is, for example, the α-olefin and the cyclic olefin in hydrocarbon solvents such as hexane, heptane, octane, cyclohexane, benzene, toluene, xylene, so-called Ziegler catalyst, metallocene catalyst, etc. It can be obtained by polymerization using a catalyst. Such cyclic olefin copolymers are commercially available, and for example, “Apel” manufactured by Mitsui Chemicals, Inc., “TOPAS” manufactured by Polyplastics Co., Ltd., and the like can be used.

  The ring-opening polymer of the cyclic olefin or the hydrogenated product thereof is usually obtained by subjecting one or more of the cyclic olefins to metathesis polymerization (ring-opening polymerization) using a molybdenum compound or a tungsten compound as a catalyst. The polymer obtained can be further hydrogenated. Such ring-opened polymers of cyclic olefins or hydrogenated products thereof are commercially available. For example, “Arton” manufactured by JSR Corporation, “Zeonex” manufactured by Nippon Zeon Co., Ltd., “Zeonor”, and the like can be used.

  As an amorphous cyclic olefin type polymer used for a surface layer, a cyclic olefin copolymer is more preferable. When a polyolefin-based resin such as a polyethylene-based resin is mixed, the cyclic olefin copolymer has a high compatibility and compatibility with the polyolefin-based resin, and a shrink film excellent in transparency and impact resistance can be obtained.

  The glass transition temperature (Tg) of the amorphous cyclic olefin polymer used for the surface layer is preferably 30 to 80 ° C., more preferably 50 to 80 ° C., and still more preferably 60 to 80 ° C. from the viewpoint of stretchability. Most preferably, it is 60 to 75 ° C (particularly about 70 ° C). The glass transition temperature of the amorphous cyclic olefin-based polymer can be adjusted by the type of monomer component (for example, cyclic olefin) and the blending ratio thereof. The glass transition temperature (Tg) can be measured by DSC (differential scanning calorimetry) in accordance with, for example, JIS K7121. The DSC measurement is not particularly limited. For example, the DSC measurement can be performed using a differential scanning calorimeter “DSC6200” manufactured by Seiko Instruments Inc. under a temperature rising rate of 10 ° C./min.

  When the amorphous cyclic olefin polymer used for the surface layer is a cyclic olefin copolymer, the content of the structural unit derived from the cyclic olefin (for example, norbornene, etc.) as the monomer component is determined from the viewpoint of heat shrinkability. From 50 to 75% by weight, preferably 60 to 70% by weight, based on all cyclic olefin copolymers (100% by weight) contained in the surface layer. For example, when the cyclic olefin copolymer contains a structural unit derived from norbornene, it is preferable that the norbornene content in the cyclic olefin copolymer is within the above range.

The density of the amorphous cyclic olefin polymer used for the surface layer is not particularly limited, but is preferably 0.90 to 1.10 g / cm ³ , more preferably 0.00 from the viewpoint of making the shrink film have a low specific gravity. 95 to 1.05 g / cm ³ . When two or more kinds of amorphous cyclic olefin polymers are contained in the surface layer, the density of the amorphous cyclic olefin polymers is determined based on the density of all the amorphous cyclic olefin polymers contained in the surface layer. It is the density after mixing.

  When the surface layer is a layer mainly composed of an amorphous cyclic olefin polymer, the content of the amorphous cyclic olefin polymer in the surface layer is not particularly limited, but the total weight of the surface layer (100 % By weight) is preferably 50% by weight or more, more preferably 60% by weight or more, and still more preferably 70% by weight or more. The upper limit of the content may be 100% by weight, but is preferably 95% by weight or less, more preferably 90% by weight or less. When the content is 50% by weight or more, the heat shrinkability and rigidity of the shrink film are more excellent. Further, the stretchability and printability of the shrink film are improved. The content of the amorphous cyclic olefin polymer is the total content of all the amorphous cyclic olefin polymers contained in the surface layer.

  When the surface layer is a layer mainly composed of an amorphous cyclic olefin polymer, the surface layer is not particularly limited, but whitening prevention by oils and fats (preventing whitening of fingerprints) while maintaining the transparency of the surface layer. From the viewpoint of reducing the specific gravity of the shrink film, it is preferable to contain a polyethylene resin. The said polyethylene-type resin may use only 1 type, and may use 2 or more types.

  The polyethylene-based resin is a polymer composed of a monomer component containing ethylene as a main component, that is, a polymer containing a constituent unit derived from ethylene in the molecule (in one molecule) as a main component. . Examples of the polyethylene resin include ethylene homopolymers, copolymers composed of ethylene and one or more monomer components (monomer components other than ethylene) as essential monomer components (ethylene copolymer). Polymer). In the present specification, the “main component” in the resin, like the “main component” in the layer, is the largest in terms of weight among the monomer components or resin constituent units constituting the resin. Monomer component or structural unit.

  Examples of monomer components other than ethylene include: α-olefins; vinyl monomers such as vinyl chloride and vinyl acetate; (meth) acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, 5 -Unsaturated carboxylic acids such as norbornene-2,3-dicarboxylic acid; unsaturated carboxylic anhydrides such as maleic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, tetrahydrophthalic anhydride; Methyl) methacrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylic 3-hydroxypropyl acid, glycidyl (meth) acrylate, monoethyl maleate, male Unsaturated carboxylic acid esters such as diethyl, acrylamide, methacrylamide, unsaturated amides or imides, such as maleimide; (meth) sodium acrylate, and the like unsaturated carboxylic acid salt such as zinc (meth) acrylate. Only 1 type may be used for monomer components other than the said ethylene, and 2 or more types may be used for it.

  Examples of the α-olefin include carbon numbers such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene. Examples thereof include 3 to 20 α-olefins (preferably α-olefins having 3 to 10 carbon atoms, more preferably α-olefins having 4 to 8 carbon atoms). Only 1 type may be used for the said alpha olefin, and 2 or more types may be used for it.

  Examples of the ethylene copolymer include a copolymer composed of ethylene and one or more α-olefins as essential monomer components (ethylene-α-olefin copolymer); an ethylene-vinyl acetate copolymer. Polymer (EVA); ethylene-carboxylic acid copolymer such as ethylene-acrylic acid copolymer (EAA) and ethylene-methacrylic acid copolymer (EMAA); ethylene-ethyl acrylate copolymer (EEA) ), And ethylene-carboxylic acid ester copolymers such as ethylene-methyl methacrylate copolymer (EMMA).

Examples of the polyethylene resin include low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), and are not particularly limited, but LLDPE is particularly preferable from the viewpoint of heat shrinkability. The LDPE refers to polyethylene having a low density of about 0.850 to 0.945 g / cm ³ which contains a structural unit derived from ethylene as a main component and is produced by a high pressure method. The LLDPE refers to a low-density polyethylene of about 0.850 to 0.945 g / cm ³ that contains a structural unit derived from ethylene as a main component, is produced by a medium / low pressure method, and has a short chain branch.

  Content of the structural unit derived from ethylene in the polyethylene resin (100 wt%), that is, content of ethylene in all monomer components (100 wt%) constituting the polyethylene resin is particularly limited. However, it is preferably 50% by weight or more, more preferably 80% by weight or more, further preferably 85% by weight or more, particularly preferably 90% by weight or more, and the upper limit is 100% by weight, 99% by weight, 98% by weight. % Or 95% by weight.

  Among the polyethylene resins, an ethylene-α-olefin copolymer is particularly preferable. The ethylene-α-olefin copolymer may contain structural units derived from monomer components other than ethylene and α-olefin. Further, the content of structural units derived from the α-olefin in the ethylene-α-olefin copolymer (100% by weight), that is, all monomer components constituting the ethylene-α-olefin copolymer ( The content of α-olefin in (100 wt%) is not particularly limited, but is preferably 1 to 20 wt%, more preferably 2 to 15 wt%, and still more preferably 5 to 10 wt%. The total of the content of structural units derived from ethylene and the content of structural units derived from α-olefin in the ethylene-α-olefin copolymer (100 wt%), that is, the ethylene-α-olefin copolymer The total of ethylene content and α-olefin content in all monomer components (100% by weight) constituting the coalescence is not particularly limited, but is preferably 90% by weight or more, more preferably 95% by weight or more. More preferably, it is 97% by weight or more, and particularly preferably 98% by weight or more.

Although the density of the said polyethylene-type resin is not specifically limited, 0.850 g / cm < ³ > or more is preferable, More preferably, it is 0.870 g / cm < ³ > or more, More preferably, it is 0.890 g / cm < ³ > or more. Although the upper limit of the said density is not specifically limited, 0.950 g / cm < ³ > is preferable, More preferably, it is 0.935 g / cm < ³ >. The melt flow rate (MFR) (temperature 190 ° C., load 2.16 kg) of the polyethylene resin is not particularly limited, but is preferably 1 to 30 g / 10 minutes from the viewpoint of melt extrusion suitability and productivity. Preferably it is 1-10 g / 10min.

  Although the said polyethylene-type resin is not specifically limited, The polyethylene-type resin (metallocene catalyst-type polyethylene resin) obtained by superposing | polymerizing using a metallocene catalyst is preferable. As the metallocene catalyst, a known or commonly used metallocene catalyst for olefin polymerization can be used. The polymerization method (copolymerization method) of the polyethylene resin is not particularly limited, and examples thereof include known polymerization methods such as a slurry method, a solution polymerization method, and a gas phase method.

  As the polyethylene-based resin, commercially available products may be used. For example, “Umerit 4540F”, “Umerit 3540F”, “Umerit 2540F”, “Umerit 1540F”, “Umerit 0540F”, “Umerit 5540F”, “ "Umerit 2040FC", "Umerit 0520F", "Umerit 1520F", "Umerit 0520F", "Umerit 715FT", Prime Polymer's "Evolution SP1520", "Evolution SP2040", "Evolution SP0540", Nippon Polyethylene Corporation “Kernel KF260T”, “Kernel KF360T”, “Kernel KF380”, “Kernel KS340T” (metallocene catalyst system LLDPE), Ube Maruzen Polyethylene ( “F234” (LDPE) manufactured by U.S. Co., Ltd., “V206” manufactured by Ube Maruzen Polyethylene Co., Ltd., “Novatech EVA Series” manufactured by Nippon Polyethylene Co., Ltd. (hereinafter, EVA), and the like are available on the market.

  When the surface layer is mainly composed of an amorphous cyclic olefin polymer and further contains a polyethylene resin, the content of the polyethylene resin in the surface layer is not particularly limited, but the total weight of the surface layer (100 wt. %) Is preferably 1% by weight or more and less than 50% by weight, more preferably 5 to 40% by weight (5% to 40% by weight), and still more preferably 10 to 30% by weight. When the content is 1% by weight or more, the effect of containing the polyethylene resin is more easily obtained. On the other hand, when the content is less than 50% by weight, the content of the amorphous cyclic olefin polymer as a main component can be relatively increased, and it has high stretchability, printability, heat shrinkability, and rigidity. A shrink film is easily obtained.

  Therefore, when the surface layer is a layer mainly composed of an amorphous cyclic olefin polymer, the surface layer contains an amorphous cyclic olefin polymer with respect to the total weight (100% by weight) of the surface layer. It is particularly preferable to contain 70 to 90% by weight and 10 to 30% by weight of a polyethylene resin (particularly, LLDPE).

  When a surface layer has a polypropylene resin as a main component, the surface layer contains a polypropylene resin as an essential component. As for the said polypropylene resin, only 1 type may be used and 2 or more types may be used. The surface layer may contain a resin other than the polypropylene resin. In the present specification, unless otherwise specified, the polypropylene-based resin does not include a polypropylene-based elastomer described later.

  The polypropylene resin is a polymer composed of a monomer component having propylene as a main component (that is, a polymer having a constituent unit derived from propylene as a main component in a molecule (in one molecule)), It will not specifically limit if it has the property as a plastomer. The polypropylene resin is not particularly limited. For example, a propylene homopolymer (homopolypropylene), propylene and at least one monomer component (a monomer component other than propylene) are essential monomer components. The copolymer comprised as (propylene copolymer) etc. are mentioned.

  Examples of the monomer component other than propylene include ethylene and monomer components exemplified and explained as monomer components other than ethylene in the above-described ethylene copolymer (excluding propylene). It is done. As the propylene copolymer, among them, a copolymer composed of propylene and one or more α-olefins as essential monomer components (propylene-α-olefin copolymer) is preferable.

  The propylene-α-olefin copolymer is a copolymer containing at least a structural unit derived from propylene and a structural unit derived from an α-olefin in a molecule (in one molecule). Examples of the α-olefin used as a copolymerization component of the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-heptene. , 1-octene, 1-nonene, 1-decene and the like, such as α-olefin having 4 to 20 carbon atoms. Only 1 type may be used for the said alpha olefin, and 2 or more types may be used for it. The propylene copolymer (propylene-α-olefin copolymer or the like) may be a block copolymer, a random copolymer, or a graft copolymer. Among these, a random copolymer is more preferable.

  Among the above, the propylene-α-olefin copolymer is particularly preferably a propylene-ethylene copolymer. In the propylene-ethylene copolymer, the ratio of ethylene to propylene is, for example, the former / the latter (weight ratio) = 1/99 to 30/70 (preferably 2/98 to 25/75, more preferably 3/97. It can be selected from the range of about 20/80). The propylene-ethylene copolymer may be in any form of a block copolymer, a random copolymer, and a graft copolymer, and an α-olefin other than ethylene and propylene is further copolymerized. Also good. The propylene-ethylene copolymer is preferably a propylene-ethylene random copolymer. In the case of the propylene-ethylene random copolymer, the ratio of ethylene to propylene is more preferably the former / the latter (weight ratio) = 1/99 to 10/90, further preferably 2/98 to 5/95, and particularly preferably. Is 3/97 to 4.5 / 95.5. The propylene-ethylene random copolymer preferably has an isotactic index of 90% or more from the viewpoint of low-temperature shrinkage and high shrink film rigidity.

  Although the said polypropylene resin is not specifically limited, The polypropylene resin obtained by superposing | polymerizing using a metallocene catalyst (metallocene catalyst polypropylene resin) is preferable. As the metallocene catalyst, a known or commonly used metallocene catalyst for olefin polymerization can be used. It does not specifically limit as a polymerization method (copolymerization method) of the said polypropylene resin, Well-known polymerization methods, such as a slurry method, solution polymerization method, and a gas phase method, are mentioned.

  The propylene content in the polypropylene resin (that is, the content of the structural unit derived from propylene in the polypropylene resin) is not particularly limited, but from the viewpoint of heat shrinkability, strength, and density of the shrink film, It is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 80% by weight or more, and particularly preferably 85% by weight or more with respect to the total weight (100% by weight) of the resin. The upper limit of the propylene content may be 100% by weight.

  Further, the content of structural units derived from the α-olefin in the propylene-α-olefin copolymer (100% by weight), that is, all the monomer components constituting the propylene-α-olefin copolymer ( The content of α-olefin in (100 wt%) is not particularly limited, but is preferably 1 to 40 wt%, more preferably 2 to 30 wt%, and still more preferably 3 to 25 wt%. The total of the content of the structural unit derived from propylene and the content of the structural unit derived from α-olefin in the propylene-α-olefin copolymer (100% by weight), that is, the propylene-α-olefin copolymer The total of the content of propylene and the content of α-olefin in all monomer components (100% by weight) constituting the coalescence is not particularly limited, but is preferably 90% by weight or more, more preferably 95% by weight or more. More preferably, it is 97% by weight or more, and particularly preferably 98% by weight or more.

The density of the polypropylene-based resin is not particularly limited, but is preferably 0.885 g / cm ³ or more, more preferably 0.890 g / cm ³ or more, more preferably, 0.895 g / cm ³ or more, particularly preferably 0 900 g / cm ³ or more. Although the upper limit of the said density is not specifically limited, 0.950 g / cm < ³ > is preferable.

  Commercially available products may be used as the polypropylene-based resin. “Wintech WFX6”, “Wintech WFX4”, “Wintech WFX4T”, “Wintech WFX4TA”, “Wintech WFW4” manufactured by Nippon Polypro Co., Ltd. , "Wintech WFW4F", "Wintech WFW5T", "Wintech 1987FC" (above, metallocene catalyst-based propylene-ethylene random copolymer), "Zeras # 7000", "Zeras # 5000" manufactured by Mitsubishi Chemical Corporation “NOVATEC FB3HAT”, “NOVATEC FW3GT”, “NOVATEC FW4BT”, “NOVATEC FX4E”, “NOVATEC FX4G”, etc., manufactured by Nippon Polypro Co., Ltd. are available on the market.

  When the surface layer is a layer mainly composed of a polypropylene resin, the content of the polypropylene resin in the surface layer is not particularly limited, but is 50% by weight with respect to the total weight (100% by weight) of the surface layer. The above is preferable, more preferably 70% by weight or more, further preferably 80% by weight or more, and particularly preferably 90% by weight or more. The upper limit of the content may be 100% by weight. When the content is 50% by weight or more, the rigidity of the shrink film is more excellent. The content of the polypropylene resin is the total content of all the polypropylene resins contained in the surface layer.

  When the surface layer is a layer containing a polypropylene resin as a main component, the surface layer contains a hydrocarbon resin from the viewpoint of further suppressing natural shrinkage and further improving heat shrinkability and rigidity. Also good. Examples of the hydrocarbon resins include rosin resins (rosin, polymerized rosin, hydrogenated rosin, derivatives thereof, resin acid dimers, etc.), terpene resins (terpene resins, aromatic modified terpene resins, hydrogenated terpene resins). Terpene-phenol resins, etc.), petroleum resins (aliphatic, aromatic, alicyclic) and the like. Among these, petroleum resin is preferable. The hydrocarbon resin may be used alone or in combination of two or more. The addition amount in the case of adding a hydrocarbon resin is preferably 5 to 30 parts by weight, more preferably 10 to 25 parts by weight, based on the total weight (100 parts by weight) of the polypropylene resin. The addition amount of 30 parts by weight or less is preferable because the shrink film is not easily brittle. Moreover, since the effect of addition is fully acquired as it is 5 weight part or more, it is preferable.

  As long as the surface layer does not impair the effects of the present invention, other resins (non-crystalline cyclic olefin polymers, polypropylene resins, resins other than polyethylene resins), lubricants, fillers, thermal stabilizers, oxidation You may contain additives, such as an inhibitor, a ultraviolet absorber, an antistatic agent, an antifogging agent, a flame retardant, a coloring agent, and a pinning agent (alkaline earth metal).

(A layer)
The layer A is a layer (resin layer) containing 10 to 49% by weight of a polypropylene elastomer and 5 to 90% by weight of an amorphous cyclic olefin polymer. By including such an A layer, the shrink film of the present invention can have high rigidity and heat shrinkability while suppressing natural shrinkage.

  The A layer contains a polypropylene elastomer and an amorphous cyclic olefin polymer as essential components. Each of the polypropylene elastomer and the amorphous cyclic olefin polymer may be used alone or in combination of two or more. The A layer may contain a resin other than the polypropylene elastomer and the amorphous cyclic olefin polymer.

  Although it does not specifically limit as an amorphous cyclic olefin type polymer contained in A layer, The amorphous illustrated and explained as an amorphous cyclic olefin type polymer which may be contained in the above-mentioned surface layer Cyclic olefin polymers and the like. The amorphous cyclic olefin polymer may be the same amorphous cyclic olefin polymer as the amorphous cyclic olefin polymer that may be contained in the surface layer, or a different amorphous material. A cyclic olefin polymer may be used. Further, from the viewpoint of recyclability, an amorphous cyclic olefin-based polymer that may be contained in the surface layer as a recovered raw material can be used, and therefore the amorphous that may be contained in the surface layer. The same amorphous cyclic olefin polymer as the crystalline cyclic olefin polymer is preferred. The preferred amorphous cyclic olefin-based polymer contained in the A layer is a preferred amorphous cyclic olefin exemplified and explained as an amorphous cyclic olefin-based polymer that may be contained in the surface layer. Olefin polymers can be used.

  The content of the amorphous cyclic olefin polymer in the A layer is 5 to 90% by weight with respect to the total weight (100% by weight) of the A layer. When the content is 5% by weight or more, the rigidity and heat shrinkability of the shrink film can be increased. In addition, when the content is less than 5% by weight, it is difficult to obtain the effect of using the amorphous cyclic olefin polymer. On the other hand, when the content is 90% by weight or less, the shrink film does not become too hard and is excellent in flexibility. The lower limit of the content is preferably 6% by weight, more preferably 7% by weight. The upper limit of the content is preferably 89% by weight, more preferably 88% by weight, still more preferably 87% by weight, still more preferably 85% by weight, and particularly preferably 82% by weight. When the surface layer is a layer mainly composed of an amorphous cyclic olefin polymer, the content is preferably 7 to 80% by weight, more preferably 10 to 70% by weight, and still more preferably 15 to 15%. 60% by weight. When the surface layer is a layer mainly composed of a polypropylene resin, the content is preferably 5 to 50% by weight, more preferably 10 to 45% by weight, and still more preferably 15 to 40% by weight. . In addition, content of the said amorphous cyclic olefin type polymer is a total amount of content of all the amorphous cyclic olefin type polymers contained in A layer.

  Although it does not specifically limit as a polypropylene-type elastomer contained in A layer, The polypropylene-type elastomer etc. which were illustrated and demonstrated as a polypropylene-type elastomer contained in the below-mentioned B layer are mentioned. The polypropylene elastomer may be the same polypropylene elastomer as the polypropylene elastomer contained in the layer B, or may be a different polypropylene elastomer. Further, from the viewpoint of recyclability, since the polypropylene elastomer contained in the B layer can be used as a recovered raw material, the same polypropylene elastomer as the polypropylene elastomer contained in the B layer is preferable. As the preferred polypropylene elastomer contained in the A layer, preferred polypropylene elastomers exemplified and explained as the polypropylene elastomer contained in the B layer described later can be used.

  The content of the polypropylene-based elastomer in the A layer is 10 to 49% by weight, preferably 12 to 40% by weight, more preferably 13 to 35% by weight, based on the total weight (100% by weight) of the A layer. It is. Heat shrinkability can be made high, suppressing the natural shrinkage | contraction of a shrink film as the said content is 10 weight% or more. When the content is less than 10% by weight, it is difficult to obtain the effect of using a polypropylene elastomer. On the other hand, when the content is 49% by weight or less, the rigidity of the shrink film can be further increased, and the shrinkage stress of the shrink label using the shrink film can be further increased. Moreover, it is excellent also in transparency. In addition, content of the said polypropylene-type elastomer is a total amount of content of all the polypropylene-type elastomers contained in A layer.

  The total content of the amorphous cyclic olefin polymer and the polypropylene elastomer in the layer A is not particularly limited, but is preferably 15% by weight or more, more preferably 20% by weight or more, and further preferably 25% by weight or more. Particularly preferably, it is 30% by weight or more. When the total content is 15% by weight or more, it becomes easy to obtain higher rigidity and heat shrinkability while suppressing natural shrinkage of the shrink film. The upper limit of the total content is not particularly limited, but may be 100% by weight, 98% by weight, 90% by weight, 85% by weight, or 80% by weight.

  The layer A preferably further contains a polypropylene resin or a polyethylene resin. Since the polypropylene resin has higher flexibility than the amorphous cyclic olefin polymer, the layer A contains the polypropylene resin, so that the rigidity of the shrink film can be appropriately increased without reducing the flexibility of the shrink film. can do. Moreover, when A layer contains a polyethylene-type resin, the heat shrinkability of a shrink film, a softness | flexibility, and a shrinkage stress can be improved more.

  Although it does not specifically limit as a polypropylene resin which may be contained in A layer, The polypropylene resin etc. which were illustrated and demonstrated as a polypropylene resin which may be contained in the above-mentioned surface layer are mentioned. The polypropylene resin may be the same polypropylene resin as the polypropylene resin that may be included in the surface layer, or may be a different polypropylene resin. In addition, from the viewpoint of recyclability, it is possible to use a polypropylene resin that may be contained in the surface layer as a collected raw material, and therefore the same polypropylene as the polypropylene resin that may be contained in the surface layer Based resins are preferred. As the preferred polypropylene resin that may be contained in the A layer, preferred polypropylene resins exemplified and explained as the polypropylene resin that may be contained in the surface layer described above can be used.

  When the A layer contains a polypropylene resin, the content of the polypropylene resin in the A layer is not particularly limited, but is preferably 1 to 50% by weight with respect to the total weight (100% by weight) of the A layer. More preferably, it is 3 to 45% by weight. When the content is 1% by weight or more, the rigidity can be increased without reducing the flexibility of the shrink film. On the other hand, when the content is 50% by weight or less, the heat shrinkability is hardly lowered. When the surface layer is a layer mainly composed of an amorphous cyclic olefin polymer, the content is preferably 1 to 30% by weight, and more preferably 3 to 20% by weight. When the surface layer is a layer containing a polypropylene resin as a main component, the content is preferably 10 to 50% by weight, more preferably 15 to 45% by weight. In addition, content of the said polypropylene resin is a total amount of content of all the polypropylene resins contained in A layer.

  Although it does not specifically limit as a polyethylene-type resin which may be contained in A layer, The polyethylene-type resin etc. which were illustrated and demonstrated as the polyethylene-type resin which may be contained in the above-mentioned surface layer are mentioned. The polyethylene-based resin may be the same polyethylene-based resin as the polyethylene-based resin that may be included in the surface layer, or may be a different polyethylene-based resin. Further, from the viewpoint of recyclability, since the polyethylene resin that may be contained in the surface layer can be used as a collected raw material, the same polyethylene as the polyethylene resin that may be contained in the surface layer Based resins are preferred. As the preferred polyethylene resin that may be contained in the A layer, preferred polyethylene resins exemplified and explained as the polyethylene resin that may be contained in the surface layer described above can be used.

  When the A layer contains a polyethylene resin, the content of the polyethylene resin in the A layer is not particularly limited, but is preferably 1 to 70% by weight with respect to the total weight (100% by weight) of the A layer, More preferably, it is 5-65 weight%, More preferably, it is 10-60 weight%, Most preferably, it is 15-50 weight%. When the content is within the above range, the heat shrinkability and flexibility of the shrink film can be further increased, and the shrinkage stress of the label can be further improved. In addition, content of the said polyethylene-type resin is a total amount of content of all the polyethylene-type resins contained in A layer.

  As described above, the layer A includes, among others, a layer containing a polypropylene elastomer, an amorphous cyclic olefin polymer, and a polypropylene resin, or a polypropylene elastomer, an amorphous cyclic olefin polymer, and A layer containing a polyethylene resin is preferred. In particular, the A layer is preferably a layer containing a polypropylene elastomer, an amorphous cyclic olefin polymer, a polypropylene resin, and a polyethylene resin. In addition, when A layer has such a structure, content of each resin can be suitably selected from the above-mentioned range so that a sum total may be 100 weight% or less, respectively.

  In particular, when the surface layer is a layer containing an amorphous cyclic olefin polymer as a main component and further containing a polyethylene resin, the A layer is preferably a layer containing a polyethylene resin. Moreover, when a surface layer is a layer which has a polypropylene resin as a main component, it is preferable that A layer is a layer containing a polypropylene resin.

  The total content of the amorphous cyclic olefin polymer, the polypropylene elastomer, the polyethylene resin, and the polypropylene resin in the layer A is not particularly limited, but is preferably 50% by weight or more, more preferably 60% by weight. More preferably, it is 70% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more. The upper limit of the content may be 100% by weight.

  A layer contains an amorphous cyclic olefin type polymer and a polypropylene-type elastomer with specific content, respectively. Thereby, the shrink film of the present invention has high rigidity and heat shrinkability while suppressing natural shrinkage. And by including a polypropylene resin in addition to these, rigidity can be made high, providing a softness | flexibility, without reducing the heat shrinkability of a shrink film. Further, by including a polyethylene resin in addition to the amorphous cyclic olefin polymer and the polypropylene elastomer, the heat shrinkability of the shrink film is further improved, and the flexibility and the shrinkage stress are also improved. Moreover, when both polypropylene-type resin and polyethylene-type resin are contained, both effects by including these are acquired. Furthermore, by setting all the contents of the amorphous cyclic olefin polymer, the polypropylene elastomer, the polypropylene resin, and the polyethylene resin within the above ranges, resistance to natural shrinkage, rigidity, heat shrinkage A shrink film having the best balance of properties, shrinkage stress, and flexibility can be obtained.

  The layer A is within the range not impairing the effects of the present invention, and includes lubricants, fillers, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, antifogging agents, flame retardants, colorants, pinning agents (alkalis). An additive such as an earth metal) may be contained. Moreover, A layer may contain the collection | recovery raw material which re-pelletized the film piece at the time of film manufacture.

(B layer)
The B layer is a layer (resin layer) mainly composed of a polypropylene-based elastomer. By including such a B layer, the shrink film of the present invention can have high heat shrinkability while suppressing natural shrinkage.

  The B layer contains a polypropylene-based elastomer as an essential component. As for the said polypropylene-type elastomer, only 1 type may be used and 2 or more types may be used. Moreover, B layer may contain resin other than the said polypropylene-type elastomer.

  The polypropylene elastomer is a polymer composed of a monomer component having propylene as a main component (that is, a polymer having a constituent unit derived from propylene as a main component in a molecule (in one molecule)), There is no particular limitation as long as it has properties as an elastomer.

  Examples of the polypropylene-based elastomer include a copolymer elastomer (propylene copolymer elastomer) composed of propylene and one or more monomer components (monomer components other than propylene) as essential monomer components. Etc. The polypropylene elastomer also includes a thermoplastic elastomer in which a rubber component such as ethylene-propylene rubber (EPM) or ethylene-propylene-diene rubber (EPDM) is finely dispersed in a polypropylene resin.

  Examples of the monomer component other than propylene include monomer components exemplified and explained as monomer components other than propylene in the above-mentioned propylene-based resin, and dienes. As the polypropylene-based elastomer, a copolymer elastomer (propylene-α-olefin copolymer elastomer) composed of propylene and one or more α-olefins as essential monomer components is particularly preferable.

  Examples of the α-olefin used as the monomer component of the propylene-α-olefin copolymer elastomer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1 -C4-C20 alpha olefins, such as heptene, 1-octene, 1-nonene, 1-decene, are mentioned. Among these α-olefins, ethylene is preferable. Therefore, as the propylene-α-olefin copolymer elastomer, a propylene-ethylene copolymer elastomer is particularly preferable.

  Content of structural unit derived from α-olefin in the propylene-α-olefin copolymer elastomer (100% by weight), that is, all monomer components constituting the propylene-α-olefin copolymer elastomer ( The content of α-olefin in (100 wt%) is not particularly limited, but is preferably 6 to 25 wt%, more preferably 7 to 25 wt%. When the propylene-α-olefin copolymer elastomer is a propylene-ethylene copolymer elastomer, the content of the structural unit derived from ethylene in the propylene-ethylene copolymer elastomer is particularly preferably 8 to 12% by weight. .

  Examples of the diene include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, Examples include chloroprene. In addition, the said diene may use only 1 type and may use 2 or more types.

  The polypropylene elastomer preferably has a heat of fusion (Hf) of 75 J / g or less. The heat of fusion can be lowered by incorporating a monomer component other than propylene such as stereo error, regio error, and α-olefin and diene. When the polypropylene elastomer is a propylene-α-olefin copolymer elastomer, the heat of fusion of the propylene-α-olefin copolymer elastomer is preferably 0.5 to 50 J / g. The heat of fusion can be measured according to ASTM E-794-95 (version E-794-01).

The polypropylene elastomer preferably has a triad tacticity (triad tacticity) composed of three propylene units of 75% or more (preferably 90% or more). The triplet stereoregularity can be obtained by using ¹³ C-NMR measurement. Specifically, for example, it can be calculated by the method described in US Patent Application Publication No. 2004/0236042.

  It is particularly preferable that the polypropylene elastomer has a heat of fusion of 75 J / g or less and a triplet stereoregularity composed of three propylene units of 75% or more.

The Mooney viscosity ML _{(1 + 4) at} 125 ° C. of the polypropylene elastomer (particularly propylene-α-olefin copolymer elastomer) is not particularly limited, but is preferably less than 100, more preferably less than 60, and still more preferably. Is less than 30. The Mooney viscosity can be measured according to ASTM D1646.

  The molecular weight distribution (Mw / Mn) of the polypropylene elastomer (particularly, propylene-α-olefin copolymer elastomer) is not particularly limited, but is preferably 1.8 to 3. The molecular weight distribution can be measured using GPC.

  As the polypropylene-based elastomer, a known or conventional polypropylene-based elastomer can be used. The polypropylene-based elastomer includes a bridged metallocene catalyst (see, for example, WO 1999/007788), a pyridine amine catalyst (see, for example, WO 2003/040201), and a non-bridged metallocene catalyst (see, for example, US Pat. It can be prepared preferably by solution polymerization using various types of single-site catalysts such as No. 5969070).

The density of the polypropylene-based elastomer is not particularly limited, from the viewpoint of the shrink film with low specific gravity, preferably from 0.800 g / cm ³ or more, more preferably 0.830 g / cm ³ or more, more preferably 0.840g / Cm ³ or more, particularly preferably 0.850 g / cm ³ or more. The upper limit of the density is not particularly limited, but is preferably 0.950 g / cm ³ or less, more preferably less than 0.900 g / cm ³ , still more preferably less than 0.895 g / cm ³ , and particularly preferably 0.890 g / cm ^3. Less than cm ³ , most preferably 0.885 g / cm ³ or less. In addition, when 2 or more types of polypropylene elastomers are contained in B layer, the density of a polypropylene elastomer is a density after mixing all the polypropylene elastomers contained in B layer.

  Commercially available products may be used as the polypropylene elastomer, for example, “Vistamaxx series” (for example, “Vistamaxx 3020FL”, “Vistamaxx 3980FL”, “Vistamaxx 6102”, “Vistamaxx 6102FL”, manufactured by ExxonMobil Chemical Co., Ltd.) , “Vistamaxx 6202”, “Vistamaxx 6202FL”, etc.), “Versify Series” manufactured by Dow Chemical Co., Ltd., etc. are available on the market.

  The content of the polypropylene-based elastomer in the B layer is not particularly limited, but is preferably 50% by weight or more, more preferably 60% by weight or more, and still more preferably 70% with respect to the total weight (100% by weight) of the B layer. % By weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more. When the content is 50% by weight or more, the shrinkage of the shrink film can be made more difficult to occur. The upper limit of the content may be 100% by weight. In addition, content of the said polypropylene-type elastomer is a total amount of content of all the polypropylene-type elastomers contained in B layer.

  Layer B is within the range not impairing the effects of the present invention, and includes lubricants, fillers, heat stabilizers, antioxidants, UV absorbers, antistatic agents, antifogging agents, flame retardants, colorants, pinning agents (alkali An additive such as an earth metal) may be contained. Moreover, B layer may contain the collection | recovery raw material which re-pelletized the film piece at the time of film manufacture.

[Shrink film]
The shrink film of the present invention is composed of [surface layer / A layer / B layer / A layer / surface layer] or [surface layer / B layer / A layer / B layer / surface layer] (5 layers of 3 types). Layered structure). The surface layer is laminated on both sides of a three-layer laminate in which A layers and B layers are alternately laminated. In the above five-layer configuration, each layer is laminated without interposing another layer between each layer (between the surface layer and the A layer, between the surface layer and the B layer, and between the A layer and the B layer). Yes. Among them, the shrink film of the present invention is [surface layer / A layer / B layer / A layer / from the viewpoint of transparency and easy suppression of natural shrinkage, and easy to obtain higher rigidity and heat shrinkability. The surface layer] is preferably composed of five layers.

  The shrink film of the present invention has heat shrinkability at least in the MD direction. Generally, the shrink label of the winding system is wound so that the MD direction of the shrink film is the circumferential direction of the container, and the shrink label is attached to the container by heat shrinking in the circumferential direction. Since the shrink film of the present invention has heat shrinkability at least in the MD direction, it is particularly preferably used as a shrink film for a winding type shrink label. The MD direction refers to the film production line direction (also referred to as the longitudinal direction).

  The shrink film of the present invention may have heat shrinkability in a direction other than the MD direction. As a direction other than the MD direction, a TD direction (a direction orthogonal to the MD direction, also referred to as a width direction) is preferable. In this case, it is preferable that the main shrinkage direction of the shrink film is the MD direction. The “main shrinkage direction” is the direction having the largest thermal shrinkage rate, and is generally the direction in which the stretching process is mainly performed.

  The shrink film of the present invention is preferably a film oriented at least in the MD direction from the viewpoint of exhibiting heat shrinkability in at least the MD direction. Furthermore, it is preferable that all the resin layers (surface layer, A layer, and B layer) are films oriented in at least the MD direction. As the shrink film, a uniaxially oriented film oriented in one direction in the MD direction or a biaxially oriented film oriented in the MD direction and the TD direction is often used, and among them, a uniaxially oriented film (stretched mainly in the MD direction) is often used. And a film that is slightly stretched in the TD direction and substantially stretched in one direction in the MD direction) is generally used.

  The film oriented at least in the MD direction can be obtained by stretching an unstretched film at least in the MD direction. For example, when the film oriented at least in the MD direction is a uniaxially oriented film, it is obtained by stretching an unstretched film in the MD direction, and is not obtained in the case of a biaxially oriented film oriented in the MD and TD directions It is obtained by stretching the stretched film in the MD direction and the TD direction. In addition, the shrink label of this invention can be mainly heat-shrinked in the orientation direction of the shrink film of this invention.

  Although content of the polypropylene-type elastomer in the shrink film of this invention is not specifically limited, 10-60 weight% is preferable with respect to the total weight (100 weight%) of a shrink film, More preferably, 15-50 weight% More preferably, it is 20 to 45% by weight. When the content is 10% by weight or more, the natural shrinkage of the shrink film is more easily suppressed, and the heat shrinkability and flexibility of the shrink film are more excellent. On the other hand, when the content is 60% by weight or less, the rigidity becomes higher.

  The content of the amorphous cyclic olefin polymer in the shrink film of the present invention is not particularly limited, but is preferably 5 to 85% by weight, more preferably based on the total weight (100% by weight) of the shrink film. It is 10 to 80% by weight, more preferably 15 to 75% by weight. When the content is 5% by weight or more, the heat shrinkability and rigidity of the shrink film are further increased. On the other hand, when the content is 85% by weight or less, the flexibility of the shrink film is more excellent.

  When the surface layer is a layer mainly composed of an amorphous cyclic olefin polymer, the content of the amorphous cyclic olefin polymer in the shrink film of the present invention is, among other things, the total weight of the shrink film (100 15 to 80% by weight, preferably 25 to 75% by weight, more preferably 30 to 70% by weight, and particularly preferably 40 to 65% by weight. When the surface layer is a layer mainly composed of a polypropylene resin, the content is preferably 5 to 50% by weight, more preferably 8 to 40% by weight, and still more preferably 10 to 30% by weight. .

  When the shrink film of the present invention contains a polyethylene resin, the content of the polyethylene resin in the shrink film of the present invention is not particularly limited, but is 3% with respect to the total weight (100% by weight) of the shrink film. % Or more and less than 50% by weight, more preferably 5 to 40% by weight. When the content is within the above range, a shrink film having more appropriate shrinkage stress, flexibility, and heat shrinkability can be obtained.

  When the shrink film of the present invention contains a polypropylene resin, the content of the polypropylene resin in the shrink film of the present invention is not particularly limited, but is 1 weight with respect to the total weight (100 wt%) of the shrink film. % Or more and less than 70% by weight, more preferably 2 to 50% by weight. When the surface layer is a layer mainly composed of an amorphous cyclic olefin polymer, the content is preferably 1 to 30% by weight, and more preferably 2 to 20% by weight. When the surface layer is a layer containing a polypropylene resin as a main component, the content is preferably 10% by weight or more and less than 70% by weight, more preferably 20 to 60% by weight, still more preferably 30 to 55% by weight. %.

  When the shrink film of the present invention contains a polypropylene resin, the total content of the amorphous cyclic olefin polymer and the polypropylene resin in the shrink film of the present invention is not particularly limited. 10 to 85 weight% is preferable with respect to a weight (100 weight%), More preferably, it is 15 to 80 weight%, More preferably, it is 30 to 75 weight%.

  The shrinkage rate of the shrink film of the present invention (before shrink processing) in the main shrinkage direction at 90 ° C. for 10 seconds (warm water treatment) (sometimes referred to as “thermal shrinkage rate (90 ° C., 10 seconds)”) Although not particularly limited, 45% or more (for example, 45 to 80%) is preferable. When the thermal shrinkage rate (90 ° C., 10 seconds) is less than 45%, in the shrink processing step in which the shrink label is closely adhered to the container by heat, the shrinkage is not sufficient, and it becomes difficult to follow the shape of the container. The finish may be poor for shaped containers.

  In addition, although the thermal contraction rate (90 degreeC, 10 second) of the direction orthogonal to the main contraction direction of the shrink film (before shrink process) of this invention is not specifically limited, -5-15% is preferable, More preferably -3 to 10%.

The natural shrinkage rate in the MD direction of the shrink film (before shrink processing) of the present invention is not particularly limited, but is preferably 5% or less, more preferably 4% or less, and still more preferably 3% or less. The natural shrinkage ratio is, the MD direction of the length of the shrink film obtained by making (K _1), and the length of the MD direction after leaving for 30 days in an atmosphere of the shrink film 30 ° C. (K ₂ ) And can be obtained by the following formula.
Natural shrinkage (%) = {(K ₁ −K ₂ ) / K ₁ } × 100

  Although the thickness (total thickness) of the shrink film of this invention is not specifically limited, 10-100 micrometers is preferable, More preferably, it is 15-80 micrometers, More preferably, it is 20-70 micrometers. The rigidity of a shrink film can be made higher as the said thickness is 10 micrometers or more. On the other hand, when the thickness is 100 μm or less, the heat shrinkability of the shrink film can be further increased.

  The thickness of the surface layer (the thickness of one layer) is not particularly limited, but is preferably 0.5 to 30 μm, and more preferably 1 to 15 μm. When the thickness is 0.5 μm or more, an effect of improving the rigidity of the shrink film is easily obtained, which is preferable. When the thickness is 30 μm or less, the flexibility of the film can be improved. In addition, the thickness of the surface layer of the both surfaces in the shrink film of this invention may be the same, and may mutually differ.

  Although the thickness of the said center layer is not specifically limited, 1-60 micrometers is preferable, More preferably, it is 2-30 micrometers. When the thickness is 1 μm or more, the effect of suppressing the natural shrinkage of the shrink film and the effect of improving the heat shrinkability are more sufficiently obtained. The rigidity of a shrink film can be made higher as the said thickness is 60 micrometers or less.

  The thickness of the intermediate layer (thickness of one layer) is not particularly limited, but is preferably 2 to 40 μm, more preferably 3 to 25 μm. When the thickness is 2 μm or more, the effect of suppressing the natural shrinkage of the shrink film and the effect of improving the heat shrinkability are more sufficiently obtained. The rigidity of a shrink film can be made higher as the said thickness is 40 micrometers or less. In addition, the thickness of two intermediate | middle layers in the shrink film of this invention may be the same, and may mutually differ.

  In the shrink film of the present invention, the thickness of the A layer (the thickness of one layer) is preferably larger than the thickness of the B layer (the thickness of one layer).

  The ratio of the thickness of the surface layer (total thickness of the two surface layers) to the thickness (total thickness) of the shrink film is not particularly limited, but is preferably 5 to 70%, more preferably 8 to 50%, and even more preferably. 10 to 40%. By the said ratio being in the said range, it is excellent by the rigidity of a shrink film.

  Although the ratio of the thickness of A layer with respect to the thickness (total thickness) of a shrink film is not specifically limited, 10 to 75% is preferable, More preferably, it is 20 to 70%, More preferably, it is 30 to 65%. When the ratio is within the above range, the shrink film is more excellent in rigidity and heat shrinkability, and is less likely to spontaneously shrink. In addition, when two A layers exist in the shrink film of this invention, the ratio of the thickness of the said A layer is a ratio of the total thickness of two A layers.

  Although the ratio of the thickness of B layer with respect to the thickness (total thickness) of a shrink film is not specifically limited, 5-75% is preferable, More preferably, it is 10-65%, More preferably, it is 20-60%. When the said ratio is in the said range, it is excellent in the heat shrinkability of a shrink film, and it becomes difficult to occur natural shrinkage more. In addition, when two B layers exist in the shrink film of this invention, the ratio of the thickness of the said B layer is a ratio of the total thickness of two B layers.

  When the shrink film of the present invention is transparent, the haze value [based on JIS K 7136, converted to a thickness of 40 μm, unit:%] of the shrink film is not particularly limited, but is preferably 10% or less. Preferably it is 7% or less, More preferably, it is 5% or less. When the haze value exceeds 10%, the inside of the shrink film (the side that becomes the container side when the shrink label is attached to the container) is printed, and the shrink label that shows the print through the shrink film (back printed shrink label) When used as a product, the printing may become cloudy and the decorativeness may deteriorate. However, even if the haze value exceeds 10%, it may be opaque in applications other than the above-described applications (print printed shrink labels) that show printing through a shrink film, and can be used sufficiently.

The density of the shrink film of the present invention is not particularly limited, from the viewpoint of the shrink label and low specific gravity less than 1 g / cm ³ (e.g., less than 0.87 g / cm ³ or more 1 g / cm ^3), more preferably Is 0.98 g / cm ³ or less (for example, 0.89 g / cm ³ or more and less than 0.98 g / cm ³ ), more preferably 0.97 g / cm ³ or less (for example, 0.90 g / cm ³ or more and 0.97 g). / Cm ³ ).

  The shrink film of the present invention is preferably produced by a melt film forming method. The five-layer structure is preferably formed by coextrusion (multilayer extrusion). That is, the shrink film of the present invention is preferably produced by a melt extrusion method (particularly a coextrusion method). More specifically, the shrink film of the present invention is preferably produced by forming an unstretched film (unstretched sheet) by melt extrusion (coextrusion) and then stretching the unstretched film. Further, the surface of the shrink film may be subjected to a conventional surface treatment such as a corona discharge treatment, if necessary.

  When a mixed raw material is used as a raw material for forming each layer (surface layer, A layer, B layer) of the shrink film, the mixing method of each component is not particularly limited. For example, the mixed raw material may be obtained by dry blending. And each component may be melt-kneaded using a uniaxial or biaxial kneader to obtain a mixed raw material. Moreover, you may use a master pellet (For example, what mixed the specific component with comparatively high density | concentration).

  In the melt extrusion (coextrusion), each of the raw materials (resin or resin composition) for forming each layer (surface layer, A layer, B layer) is charged into each of a plurality of extruders set to a predetermined temperature, Melt extrusion (coextrusion) from a T die, a circular die or the like. At this time, it is preferable to use a manifold or a feed block to form a predetermined layer structure. Further, if necessary, the supply amount may be adjusted using a gear pump, and it is preferable to remove foreign substances using a filter because film tearing can be reduced. In addition, although extrusion temperature changes also with the kind of raw material to be used and is not specifically limited, 150-250 degreeC is preferable. Moreover, it is preferable that the temperature of a junction part or die | dye shall be 200-250 degreeC. An unstretched laminated film (sheet) can be obtained by quenching the coextruded polymer using a cooling drum (cooling roll) or the like.

  The shrink film of the present invention can be produced by stretching the unstretched laminated film. When producing the shrink film of the present invention, the unstretched laminated film is stretched at least in the MD direction. The stretching may be biaxial stretching in the MD direction and TD direction, or uniaxial stretching in the MD direction. As the stretching method, any method such as a roll method, a tenter method, and a tube method may be used. In the case of biaxial stretching, biaxial stretching may be performed simultaneously, or biaxial stretching may be sequentially performed. More specifically, for example, the film is stretched in the MD direction at a stretching temperature of 70 to 100 ° C. and a stretching ratio of 2 to 8 times (preferably 3 to 7 times) by a roll method.

  In the present invention, it is particularly important to use a combination of an A layer containing an amorphous cyclic olefin polymer and a polypropylene elastomer in a specific content, and a B layer mainly composed of a polypropylene elastomer, Furthermore, the amorphous cyclic olefin-based polymer or the both sides of the configuration in which the A layer and the B layer are alternately combined ([A layer / B layer / A layer] or [B layer / A layer / B layer]) or By having a surface layer mainly composed of a polypropylene resin, it was possible to increase rigidity and heat shrinkability while suppressing natural shrinkage. Furthermore, it is possible to have excellent stretching aptitude.

  The shrink film of the present invention has heat shrinkability in the MD direction, suppresses spontaneous shrinkage, and is used for shrink labels (especially winding type shrink labels) from the viewpoint of excellent rigidity and heat shrinkability. Particularly preferred. In addition, in this specification, the shrink label which has the shrink film of this invention may be called the shrink label of this invention.

[Shrink label]
The shrink label of the present invention is a shrink label having at least the shrink film of the present invention. The shrink label of the present invention may have a layer other than the shrink film of the present invention.

(Layers other than the shrink film of the present invention)
The layers other than the shrink film of the present invention included in the shrink label of the present invention are not particularly limited, but include a printing layer, a protective layer, an anchor coat layer, a primer coat layer, a coating layer, an antistatic layer, an aluminum vapor deposition layer, and the like. Is mentioned.

(Print layer)
The print layer is not particularly limited, and examples thereof include known or commonly used print layers used in shrink labels. Examples of the printing layer include a solvent-drying printing layer and an ultraviolet curable printing layer. In addition, examples of the print layer include design print layers (color print layers and the like) such as product names, illustrations, handling precautions, and the like, background print layers formed in a single color such as white, films, and the like. Examples thereof include a protective printing layer provided for protecting the printing layer and a primer printing layer provided for improving the adhesion between the film and the printing layer. Although the said printing layer is not specifically limited, You may be provided only in the single side | surface side of the shrink film of this invention, and may be provided in the both surfaces side of the shrink film of this invention. Moreover, the said printing layer may be provided in the whole surface (surface on the side in which a printing layer is provided) of the shrink film of this invention, and may be provided in part. Furthermore, the printing layer is not particularly limited, but may be a single layer or a multilayer. Further, the printing layer can be provided by a known or common printing method. Especially, it is preferable that the said printing layer is provided by the gravure printing method or the flexographic printing method.

  Although the said printing layer is not specifically limited, It is preferable that binder resin is included as an essential component. Furthermore, it may contain additives such as color pigments such as blue, red, yellow, black, white, lubricants, dispersants, antifoaming agents, etc., as necessary. Each of the binder resins may be used alone or in combination of two or more.

  The binder resin is not particularly limited, and for example, a resin used as a binder resin in a known or commonly used printing layer or printing ink can be used. Examples of the binder resin include acrylic resins, urethane resins, polyester resins, polyamide resins, cellulose resins (including nitrocellulose resins), vinyl chloride-vinyl acetate copolymer resins, and the like. The color pigment is not particularly limited, and for example, a color pigment used in a known or conventional printing layer or printing ink can be used. For example, white pigments such as titanium oxide (titanium dioxide), indigo pigments such as copper phthalocyanine blue, carbon black, aluminum flakes, mica (mica), and other colored pigments can be selected and used according to the application. . In addition to the above color pigments, extender pigments such as alumina, calcium carbonate, barium sulfate, silica, and acrylic beads can also be used for the purpose of adjusting gloss.

  The solvent-dried printing layer is, for example, after applying the printing ink produced by mixing the binder resin, the solvent, and, if necessary, the coloring pigment and other additives, using a printing machine. It is provided by volatilizing the solvent. On the other hand, the ultraviolet curable printing layer is, for example, a printing ink produced by mixing the monomer component constituting the binder resin, and if necessary, the coloring pigment, solvent, and other additives. Is applied using a printing machine, and then the monomer component is polymerized and cured by ultraviolet irradiation.

  Although the thickness of the said printing layer is not specifically limited, For example, 0.1-10 micrometers is preferable, More preferably, it is 0.3-5 micrometers.

  Although the thickness (total thickness) of the shrink label of this invention is not specifically limited, 10-110 micrometers is preferable, More preferably, it is 15-90 micrometers, More preferably, it is 20-80 micrometers.

Density of the shrink label of the present invention is not particularly limited, from the viewpoint of the shrink label and low density, preferably less than 1 g / cm ^3, more preferably less than 0.99 g / cm ^3, more preferably 0.98 g / less than cm ³ . Moreover, the minimum of the said density is 0.92 g / cm < ³ > or more, for example.

  Since the shrink film of the present invention has heat shrinkability in the MD direction and is excellent in rigidity and heat shrinkability while suppressing spontaneous shrinkage, it is particularly preferably used for winding type shrink labels. Hereinafter, the shrink label of the winding system using the shrink film of the present invention may be referred to as “the shrink label of the winding system of the present invention”.

  Although the manufacturing method of the shrink label of the winding system of this invention is not specifically limited, For example, it is as follows. A long shrink film of the present invention having heat shrinkability in the MD direction (long direction) is prepared, and a printing layer is provided on the long shrink film of the present invention by a well-known conventional printing method. A plurality of shrinks of the present invention having heat shrinkability in the MD direction are provided by arranging a plurality of label designs so as to be aligned in the longitudinal direction and then slitting to a predetermined width (adjusting the dimension in the height direction of the label). A long label body in which the labels are continuous in the long direction (MD direction) is obtained. By cutting the long label body into individual labels having a predetermined length, the wrapping type shrink label of the present invention is obtained.

  Thereafter, the wrapping type shrink label of the present invention can be attached to a container or the like by, for example, “Roll-on Shrink-on labeling method” or the like. Specifically, for example, a flat label is wound around a container or a mandrel so that the MD direction having heat shrinkage is the circumferential direction, and both ends of the label are overlapped, and then both ends are joined to form a cylindrical shape. Then, the container is fitted to the container by heat shrinking the label of the container fitted with the cylindrical label. The said joining can be performed by using heat welding, such as heat sealing, or a solvent.

[Container with label]
Although the shrink label of this invention is not specifically limited, It mounts | wears with a container and is used as a labeled container. In addition, the shrink label of this invention may be used for adherends other than a container. For example, after fixing one end of the label of the shrink label of the winding method of the present invention to the container, and then winding the label along the outer periphery of the container so that the MD direction having heat shrinkage is the circumferential direction, Label the label by attaching the two ends (both ends) of the shrink label so that the other end overlaps with the other end, and then following and adhering to the container by, for example, heat shrinking with hot air or steam. An attached container is obtained. In addition, the shrink label of the winding method of the present invention is wound around a mandrel so that the MD direction having heat shrinkage is the circumferential direction, both ends of the label are overlapped, and then both ends are joined. A container with a label is obtained by making it into a cylindrical shape, covering the container with the container, and heat-shrinking the container in the same manner as described above so that the container is attached in close contact with the container. In addition, the container equipped with the shrink label of the present invention may be referred to as “the labeled container of the present invention”.

  Examples of the container include soft drink bottles such as PET bottles, milk bottles for home delivery, food containers such as seasonings, alcohol beverage bottles, pharmaceutical containers, chemical containers such as detergents, sprays, and toiletries containers , Cup noodle containers and the like. Although it does not specifically limit as a shape of the said container, For example, various shapes, such as bottle types, such as cylindrical shape and a square shape, and a cup type, are mentioned. The material of the container is not particularly limited, and examples thereof include plastic such as PET, glass, and metal.

  The above-mentioned container with a label can be produced by, for example, fitting a shrink shrink label on a predetermined container into a predetermined container, and then thermally shrinking the shrink shrink label by heat treatment so as to follow and closely adhere to the container (shrink processing). . Examples of the heat treatment method include a method of passing through a hot air tunnel or a steam tunnel, a method of heating with radiant heat such as infrared rays, and the like. In particular, a method of treating with steam at 80 to 100 ° C. (passing through a heating tunnel filled with steam and steam) is preferable. Moreover, 101-140 degreeC dry steam can also be used. Although the said heat processing is not specifically limited, It is preferable to implement in the temperature range from which the temperature of a shrink film will be 85-100 degreeC (especially 90-97 degreeC). Moreover, the processing time of heat processing has a preferable 2 to 20 second from a viewpoint of productivity and economical efficiency.

  EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

  Table 1 shows the composition of the raw material for the surface layer, the raw material for the intermediate layer, the raw material for the central layer, the composition of the shrink film produced in the examples and comparative examples, the evaluation results, and the like used in the examples.

Example 1
(material)
As the raw material constituting the intermediate layer (raw material for the intermediate layer), 18.4% by weight of a polypropylene elastomer A (product name “Vistamaxx 3980FL” manufactured by ExxonMobil Chemical Co., Ltd.), amorphous cyclic olefin polymer A (poly 38.3% by weight of a plastic product (trade name “TOPAS”) and 43.3% by weight of a polyethylene resin A (manufactured by Prime Polymer Co., Ltd., trade name “Evolu SP0540”) were used.
100% by weight of the polypropylene-based elastomer A was used as a raw material constituting the central layer (a raw material for the central layer).
As raw materials constituting the surface layer (surface layer raw material), 85% by weight of amorphous cyclic olefin polymer A and 15% by weight of polyethylene resin A were used.

(Shrink film)
The raw material for the intermediate layer was charged into the extruder a heated to 220 ° C., the raw material for the central layer was charged into the extruder b heated to 220 ° C., and the raw material for the surface layer was charged into the extruder c heated to 250 ° C. Melt extrusion (coextrusion) was performed using the three extruders. The resin extruded from the extruder b becomes the center layer, the resin extruded from the extruder a becomes the layers on both sides (intermediate layer) of the center layer, and the resin extruded from the extruder c becomes the layers on both sides (surface layer). Thus, after merging using a merging block and extruding from a T die (slit interval: 1 mm), it was rapidly cooled on a casting drum cooled to 25 ° C. to obtain a three-kind five-layer laminated unstretched film.
Next, the length of the stretched film (shrink film) which is mainly stretched in the MD direction and has heat shrinkability in the MD direction by stretching the unstretched film whose thickness is adjusted 5 times at 80 ° C. in the MD direction. A scale was obtained. In the shrink film obtained in Example 1, the intermediate layer is the A layer and the center layer is the B layer.

Examples 2 to 6, Comparative Examples 1 and 2
As shown in Table 1, by changing the composition and component ratio of the intermediate layer raw material, the central layer raw material, the surface layer raw material, the thickness of each layer, etc. Obtained. In addition, as the polypropylene resin, polypropylene resin A (manufactured by Nippon Polypro Co., Ltd., trade name “Wintech WFW5T”) was used. In addition, in the shrink film obtained in Examples 2-6, an intermediate | middle layer is A layer and a center layer is B layer.

(Evaluation)
The following evaluation was performed about the shrink film obtained by the Example and the comparative example. The evaluation results are shown in Table 1.

(1) Compressive strength (rigidity) (ring crush method)
Evaluation was performed using the shrink film (before shrink processing) obtained in the examples and comparative examples. Based on JIS P 8126, the compressive strength of the shrink film was measured under the following conditions. The measurement direction is the TD direction of the shrink film.
Measuring device: Shimadzu Corporation autograph (AGS-50G: load cell type 500N)
Sample size: 15 mm (TD direction) × 152.4 mm (MD direction: main shrinkage direction)
Number of tests: 5 times The compressive strength was evaluated according to the following criteria. The results are shown in Table 1.
Compressive strength is good (O): 1.2N or more Compressive strength is poor (x): Less than 1.2N

(2) Heat shrinkability The measurement of heat shrinkage (90 ° C., 10 seconds) will be described as an example.
From the shrink film (before shrink processing) obtained in the examples and comparative examples, a rectangular sample having a length of 120 mm (mark interval 100 mm) and a sample width of 5 mm in the measurement direction (main shrinkage direction: MD direction of the shrink film) Make a piece.
The sample piece is heat-treated in warm water at 90 ° C. for 10 seconds (under no load), the difference between the marked lines before and after the heat treatment is read, and the thermal contraction rate is calculated by the following formula.
Shrinkage rate (%) = (L ₀ −L ₁ ) / L ₀ × 100
L ₀ : dimension of the sample before heat treatment (main shrinkage direction: MD direction)
L ₁ : Sample dimensions after heat treatment (same direction as L ₀ )
The heat shrinkability was evaluated according to the following criteria from the heat shrinkage rate (shrinkage rate) in the main shrinkage direction. The results are shown in Table 1.
Excellent heat shrinkability (O): Shrinkage is 45% or more Thermal shrinkage is poor (x): Shrinkage is less than 45%

(3) Natural shrinkage rate A test piece having a length of 300 mm [M ₁ (mm)] and a width of 10 mm was cut out in the MD direction of the shrink films obtained in Examples and Comparative Examples, and this was cut at 30 ° C. The length M ₂ (mm) of the test piece after being left in the atmosphere for 30 days was measured, and the natural shrinkage rate was determined by the following formula. The results are shown in Table 1.
Natural shrinkage (%) = {(M ₁ −M ₂ ) / M ₁ } × 100

  As can be seen from Table 1, the shrink film (Examples 1 to 6) of the present invention was suppressed in natural shrinkage and excellent in heat shrinkability and rigidity. On the other hand, when it does not have either the A layer or the B layer as the intermediate layer and the center layer (Comparative Examples 1 and 2), the shrink film having high rigidity and excellent heat shrinkability is suppressed while suppressing the occurrence of natural shrinkage. It was not obtained.

Claims (5)

Has heat shrinkability in the MD direction,
It consists of 5 layers of surface layer / A layer / B layer / A layer / surface layer or surface layer / B layer / A layer / B layer / surface layer,
The surface layer is a layer mainly composed of an amorphous cyclic olefin polymer or a polypropylene resin,
The A layer is a layer containing 10 to 49% by weight of a polypropylene elastomer and 5 to 90% by weight of an amorphous cyclic olefin polymer,
A shrink film, wherein the B layer is a layer mainly composed of a polypropylene-based elastomer.   The shrink film according to claim 1, wherein the A layer is a layer further containing a polypropylene resin or a polyethylene resin.   The shrink film according to claim 1 or 2, wherein the polypropylene-based elastomer in the A layer and the polypropylene-based elastomer in the B layer are propylene-α-olefin copolymer elastomers.   The shrink film according to claim 1, wherein the A layer is a layer containing 1 to 50% by weight of a polypropylene resin.   The shrink film according to any one of claims 1 to 4, wherein the A layer is a layer containing 1 to 70% by weight of a polyethylene resin.