JP2008284757A - Shrink film and shrink label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shrink film which can show a high interlayer strength, with regard to the laminated shrink film obtained by laminating different polymers i.e. a polyolefin-based resin and a polyester-based resin. <P>SOLUTION: This shrink film has a lamination structure consisting of a surface layer (A layer) formed of a resin composition A composed mainly of an amorphous polyester-based resin, an intermediate layer (B layer) which contains not less than 35 wt.% polyolefin-based resin with a reactive functional group and is formed of a resin composition B composed mainly of a polyolefin-based resin, and a central layer (C layer) formed of a resin composition C composed mainly of a polyolefin-based resin. These layers are laminated in the order of the A layer/B layer/C layer/B layer/A layer without the intervention of the other layers. Besides, the absolute value of a difference in the melting viscosity of the resin compositions A to C at 220°C between the resin compositions, is not more than 300 Pa s. In addition, the absolute value of a difference in the gradient of the temperature-melt viscosity straight line at 200 to 240°C, is not more than 7 Pa s/°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heterogeneous laminated shrink film having improved interlayer strength. More specifically, the present invention relates to a shrink film having a film layer made of a polyolefin resin and a film layer made of a polyester resin, having a low specific gravity and excellent shrinkage characteristics, and further having a superior interlayer strength. Moreover, it is related with the shrink label which provided the printing layer in this shrink film.

  Currently, in the field of plastic films, different types of laminated films in which different resin materials are laminated are widely used for the purpose of imparting various different functions to the film. For example, a heat-shrinkable film in which a polyester resin and a polystyrene resin are laminated is known (for example, see Patent Documents 1 to 6).

  On the other hand, from the viewpoint that the specific gravity is small and light, and it is easy to separate from PET bottles using the difference in specific gravity at the time of collection, polyolefin resin is used as the center layer, and further, the adhesive resin layer is interposed. By providing a surface layer made of non-polyolefin resin such as polyester resin, heat shrinkability consisting of a laminated film of polyolefin resin and polyester resin with improved properties such as low temperature shrinkage, center sealability, printability, etc. Label films are known (see, for example, Patent Document 7).

  However, the laminated film made of polyolefin resin and polyester resin cannot be said to have sufficient interlayer strength. For example, when used for shrink label applications, labeling is triggered by the center-sealed part (adhesive part) when heat-shrinked. There was a problem such as delamination at the end. That is, a shrink film having a laminated structure using a polyolefin resin as a center layer and a polyester resin as a surface layer, and having an excellent shrink film having both low density, shrinkage characteristics and practically suitable interlayer strength can be obtained. The current situation is not.

JP 2006-159901 A JP 2006-159902 A JP 2006-159903 A JP 2006-159906 A JP 2006-15745 A JP 2006-123482 A JP 11-262981 A

  An object of the present invention is to provide a shrink film exhibiting high interlayer strength in a laminated shrink film of different polymers of polyolefin resin and polyester resin. Another object of the present invention is to provide a shrink label using the shrink film.

  As a result of intensive studies to achieve the above object, the present inventors have found that a polyolefin resin having a reactive functional group is present between a central layer composed of a polyolefin resin and a surface layer composed of a polyester resin. Excellent interlaminar strength by controlling the melt viscosity of the resin composition that constitutes each layer to a specific relationship with a laminated constitution of 3 types and 5 layers that include a specific amount and an intermediate layer composed of a polyolefin resin. The present inventors have found that a heterogeneous laminated film having the above can be obtained and completed the present invention.

That is, the present invention contains a surface layer (A layer) composed of a resin composition A mainly composed of an amorphous polyester resin, 35% by weight or more of a polyolefin resin having a reactive functional group, An intermediate layer (B layer) composed of a resin composition B mainly composed of a resin based resin and a central layer (C layer) composed of a resin composition C composed mainly of a polyolefin resin are comprised of an A layer / B layer / C layer / B layer / A layer in the order of layers without any other layers, and the resin composition A, the resin composition B, and the resin composition C A shrink film satisfying the following relationships (1) and (2) is provided.
(1) The absolute value of the difference in melt viscosity (capillary rheometer method, shear rate 100 sec ⁻¹ ) at 220 ° C. between the resin compositions is 300 Pa · s or less.
(2) The absolute value of the difference in the slope of the temperature-melt viscosity straight line at 200 to 240 ° C. between the resin compositions is 7 Pa · s / ° C. or less.

  Furthermore, this invention provides the said shrink film whose polyolefin resin which has a reactive functional group contained in the resin composition B is a dicarboxylic anhydride modified polyolefin resin.

  Furthermore, this invention provides the said shrink film which the resin composition C has as a main component the polypropylene obtained by superposing | polymerizing using a metallocene catalyst.

  Furthermore, this invention provides the shrink label which provided the printing layer in the at least one surface side of the said shrink film.

  Since the shrink film of the present invention has a central layer made of a polyolefin-based resin, the specific gravity is small and light, and when used as a shrink label, it can be easily separated from a PET bottle or the like by utilizing the difference in specific gravity at the time of recovery. Furthermore, by having a surface layer made of a polyester-based resin, it has excellent shrinkage characteristics and strength characteristics. Moreover, the interlayer strength of each layer is high, and troubles due to delamination do not occur in the manufacturing process and distribution process. It is also excellent in transparency. For this reason, it is useful as a shrink label attached to a container such as a PET bottle.

  Below, the shrink film of this invention is demonstrated in detail.

  The shrink film of the present invention includes a surface layer (hereinafter referred to as “A layer”) composed of a resin composition A containing a polyester resin as a main component, a polyolefin resin having a reactive functional group, and a polyolefin film. An intermediate layer composed of a resin composition B mainly composed of a resin (hereinafter referred to as “B layer”), and a central layer composed of a resin composition C composed mainly of a polyolefin resin (hereinafter referred to as “layer B”). (Referred to as “C layer”). As used herein, “main component” means that the content in each resin composition is 50% by weight or more based on the total weight of the resin composition, unless otherwise specified. More preferably, it means 60% by weight or more.

  In the shrink film of the present invention, the A to C layers are in the order of A layer (surface layer) / B layer (intermediate layer) / C layer (center layer) / B layer (intermediate layer) / A layer (surface layer). It has a three-kind five-layer laminated structure laminated without interposing other layers. The A layer and the B layer provided on both sides of the C layer may be layers having the same resin composition, or may be layers having different compositions (for example, the A1 layer and the A2 layer). . The shrink film of the present invention may be a film composed only of the above-mentioned three types and five layers, or any film that can be provided in-line in the film forming process of the above three types and five layers. The film may have a layer other than the above three-type five-layer film. Examples of such a layer include coating layers such as an anchor coat layer, an easy adhesion layer, and an antistatic agent layer.

[Resin composition A]
The surface layer (A layer) in the shrink film of this invention is comprised from the resin composition A which has an amorphous polyester-type resin as a main component. The amorphous polyester resin is a substantially amorphous polyester resin.

  Said “substantially amorphous” means that the crystallinity value measured by the differential scanning calorimetry (DSC) method (measured at a heating rate of 10 ° C./min) is 10% or less, It is preferably 5% or less, more preferably one having almost no melting point (melting peak) by the DSC method (that is, a crystallinity of 0%). The crystallinity can be calculated from the value of heat of crystal fusion obtained by DSC measurement using a sample with a clear crystallinity fixed by the X-ray method or the like as a standard. The heat of crystal melting is, for example, using a DSC (differential scanning calorimetry) device manufactured by Seiko Instruments Inc., performing a nitrogen seal at a sample amount of 10 mg and a heating rate of 10 ° C./min. The temperature can be determined from the area of the melting peak when the temperature is lowered to room temperature and then raised again. The crystallinity is preferably measured from a single resin, but when measured in a mixed state, the melting peak of the target polyester resin can be obtained by subtracting the melting peak of the resin to be mixed. That's fine.

  The amorphous polyester-based resin is not particularly limited as long as it is substantially amorphous and satisfies the relationship of the melt viscosity described later. For example, the amorphous polyester-based resin includes a dicarboxylic acid component and a diol component. Various polyesters are mentioned.

  Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 5-t-butylisophthalic acid, 4,4′-biphenyldicarboxylic acid, trans-3,3′-stilbene dicarboxylic acid, and trans-4,4. '-Stilbene dicarboxylic acid, 4,4'-dibenzyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2, 7-naphthalenedicarboxylic acid, 2,2,6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid, 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid, 1,2- Aromatic dicals such as diphenoxyethane-4,4′-dicarboxylic acid, diphenyl ether dicarboxylic acid, and substituted products thereof Acid; oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, Aliphatic dicarboxylic acids such as heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, icosanedioic acid, docosanedioic acid, 1,12-dodecanedioic acid, and their substitutions; 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, cis-1,4-cyclohexanedicarboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and these And alicyclic dicarboxylic acids such as substitution products thereof. These dicarboxylic acid components can be used alone or in combination of two or more.

  Examples of the diol component include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,2 -Dimethyl-1,3-propanediol (neopentyl glycol), 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2,4-dimethyl-1,3-hexanediol, 1,10-decanediol, polyethylene glycol, polypropylene Aliphatic diols such as glycol; 1,2-cyclohexanedimethanol, 1,3-cyclohexane Cycloaliphatic diols such as sandimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol; 2,2-bis (4′-β-hydroxyethoxydiphenyl) Examples thereof include ethylene oxide adducts of bisphenol compounds such as propane and bis (4′-β-hydroxyethoxyphenyl) sulfone, and aromatic diols such as xylylene glycol. These diol components can be used alone or in combination of two or more.

  In addition to the above, the amorphous polyester-based resin may include oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid; monocarboxylic acids such as benzoic acid and benzoylbenzoic acid; A structural unit such as a monovalent alcohol such as a polyvalent carboxylic acid; a monohydric alcohol such as polyalkylene glycol monomethyl ether; a polyhydric alcohol such as glycerin, pentaerythritol, or trimethylolpropane may be included.

  Among the amorphous polyester resins used in the resin composition A, among the above, in polyethylene terephthalate (PET) using terephthalic acid as the dicarboxylic acid component and ethylene glycol (EG) as the diol component, the dicarboxylic acid component and / or Alternatively, modified PET in which part of the diol component is replaced with another dicarboxylic acid component and / or diol component is preferably exemplified. Examples of the dicarboxylic acid component used in the modified PET include cyclohexane dicarboxylic acid, adipic acid, and isophthalic acid. Examples of the diol component include 1,4-cyclohexanedimethanol (CHDM), neopentyl glycol (NPG), and diethylene glycol.

  Specifically, as the modified PET, terephthalic acid is used as a dicarboxylic acid component, EG is used as a main component and diol is used as a diol component, and CHDM is used as a copolymerization component (hereinafter referred to as CHDM copolymerized PET) or neoplastic. A copolymerized polyester using pentyl glycol (NPG) as a copolymerization component (hereinafter referred to as NPG copolymerized PET) is preferable from the viewpoints of cost, productivity, and the like. Furthermore, diethylene glycol may be copolymerized from the viewpoint of improving low-temperature shrinkage.

  In the modified PET, the copolymerization ratio of the copolymerization component used for modification (the ratio of the copolymerized dicarboxylic acid component to the total dicarboxylic acid component or the ratio of the copolymerized diolic acid component to the total diolic acid component) further increases the interlayer strength. From the viewpoint of improvement, 15 mol% or more (for example, 15 to 40 mol%) is preferable. Among them, for example, in the case of CHDM copolymerized PET, the proportion of CHDM copolymerization is 20 to 40 mol% (EG is 60 to 80 mol%) in the diol component (that is, with respect to 100 mol% of terephthalic acid). More preferably, it is 25-35 mol% (EG is 65-75 mol%). Moreover, in the case of NPG copolymerized PET, 15-40 mol% (EG is 60-85 mol%) in a diol component is preferable. Further, a part (preferably 10 mol% or less) of the EG component may be replaced with diethylene glycol.

  As described above, by modifying the polyester to be amorphous, the fluidity at the melting temperature of the A layer can be lowered and brought close to the behavior of the B layer, so that the interlayer strength is improved.

  The weight average molecular weight of the amorphous polyester resin is preferably 50000 to 90000, more preferably 60000 to 80000, from the viewpoint of controlling the melting behavior within a preferable range. Furthermore, in the case of NPG copolymerized PET, it is preferably 50000 to 80000, more preferably 60000 to 70000.

  The IV value (intrinsic viscosity) of the amorphous polyester resin is preferably 0.70 (dl / g) or more, more preferably 0.7 to 0.9 (dl / g), from the viewpoint of interlayer strength. More preferably, it is 0.75-0.85 (dl / g). The glass transition temperature (Tg) of the amorphous polyester resin is preferably 70 to 100 ° C., more preferably 70 to 80 ° C., from the viewpoint of shrinkage suitability.

  As the amorphous polyester-based resin, existing products can be used. For example, “Easter Polymer”, “EMBRACE” (above, CHDM copolymerized PET) manufactured by Eastman Chemical; Bell Polyester Products Co., Ltd. “Belpet” (NPG copolymerized PET) and the like are available on the market.

  The content of the amorphous polyester resin with respect to the total weight of the resin composition constituting the A layer of the present invention is preferably 50 to 100% by weight, more preferably from the viewpoint of shrinkability (shrinkage ratio), specific gravity and the like. 80 to 100% by weight.

  The resin composition A may contain other additives such as a lubricant, a filler, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, and a colorant as necessary. Good.

[Resin composition B]
The intermediate layer (B layer) in the shrink label of the present invention is composed of a resin composition B containing a polyolefin resin as a main component. Moreover, the resin composition B contains the polyolefin-type resin which has a reactive functional group as an essential structural component.

  The reactive functional group in the polyolefin-based resin having the reactive functional group is a functional group that reacts or interacts with the ester bond portion of the polyester (such as hydrogen bond), and is not particularly limited. Carboxylic acid anhydrides), hydroxyl groups, oxazoline groups, isocyanate groups, epoxy groups and the like. Among these, from the viewpoint of improving the interlayer strength, a dicarboxylic anhydride group (dicarboxylic anhydride modified) and an epoxy group (epoxy modified) are preferable, and a maleic anhydride group (maleic anhydride modified) is particularly preferable.

  The reactive functional group may be grafted to the polyolefin polymer main chain or may be introduced into the polymer main chain by copolymerization. In the present invention, the term “modified” includes both “grafted” and “copolymerized”.

  That is, the polyolefin resin having a reactive functional group is preferably a dicarboxylic anhydride modified polyolefin resin, more preferably a maleic anhydride modified polyolefin resin (maleic anhydride grafted polyolefin resin or maleic anhydride copolymer polyolefin). Resin). Among these, maleic anhydride-grafted polyolefin resin is particularly preferable.

  When the reactive functional group is introduced by grafting, for example, in maleic anhydride grafted polyolefin, the reactive functional group (maleic anhydride group) is 0 in carbon constituting the main chain of the polyolefin resin. It is preferable to graft on about 1 to 20% of carbon, and more preferably about 0.5 to 10%.

  The polyolefin resin component that is the skeleton of the polyolefin-based resin having the reactive functional group is not particularly limited, but polypropylene, modified polypropylene (acrylic modified, etc.), low density polyethylene (LDPE), linear low Polyethylene such as density polyethylene (LLDPE), metallocene catalyst system LLDPE (mLLDPE), ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, cyclic olefin copolymer (COC), etc. Is preferred. Among these, acrylic modified polypropylene (most preferably, propylene-acrylic acid copolymer) is particularly preferable.

  The weight average molecular weight of the polyolefin-based resin having a reactive functional group is preferably 100,000 to 500,000, more preferably 200,000 to 400,000, from the viewpoint of controlling the melting behavior within a preferable range. Among these, in the case of a maleic anhydride-modified polyolefin resin, 100,000 to 400,000 is preferable, and 200,000 to 300,000 is more preferable.

  Commercially available products may be used as the polyolefin-based resin having a reactive functional group, such as “Modic AP” (maleic anhydride-modified polyolefin resin) manufactured by Mitsubishi Chemical Corporation, “Admer” manufactured by Mitsui Chemicals, Inc. ”(Maleic anhydride modified polyolefin resin), Arkema“ Olevac ”(Maleic anhydride modified polyolefin resin), Arkema“ Bondyne ”(acrylic acid / maleic anhydride copolymer polyolefin resin), Arkema“ Rotada ”(acrylic acid) -Glycidyl methacrylate copolymer polyolefin) and the like.

  The content of the polyolefin-based resin having the reactive functional group in the resin composition B is 35 to 100% by weight with respect to the total weight of the resin composition B, and from the viewpoint of adhesiveness (interlayer strength). It is preferably 40 to 100% by weight. When the content is less than 35% by weight, the resin component having a functional group takes a dispersed structure that becomes an island of sea-island structure, the effect of the functional group is reduced, and the interlayer strength between the A layer and the B layer is reduced. Therefore, delamination is likely to occur.

  The polyolefin resin that is the main component of the resin composition B may be a polyolefin resin having the above functional group (single or mixed resin), or a polyolefin resin having the above functional group and other polyolefin resins. The mixed resin may be used. When the resin composition B is composed of two or more polyolefin resins, the total amount of the polyolefin resins in the resin composition B may be 50% by weight or more with respect to the resin composition B. The content of the polyolefin-based resin is 50 to 100% by weight, and more preferably 80 to 100% by weight. When the content of the polyolefin-based resin in the resin composition B is less than 50% by weight, the interlayer strength between the B layer and the C layer is lowered, and delamination tends to occur.

  The polyolefin resin other than the polyolefin resin having the functional group is not particularly limited. For example, a homopolymer such as polyethylene (PE), polypropylene (PP), polybutylene, polymethylpentene (PMP); ethylene-α -Copolymers (including elastomers) such as olefin copolymers and propylene-α-olefin copolymers; copolymers of cyclic olefins and α-olefins (ethylene, propylene, etc.) or graft modified products thereof, cyclic olefins Non-cyclic cyclic olefin polymers such as ring-opened polymers or hydrogenated products thereof or graft-modified products thereof. Among these, from the viewpoint of interlayer strength, polypropylene, propylene-α-olefin random copolymer, and ethylene-α-olefin copolymer are preferable, and polypropylene (metallocene catalyst obtained by polymerization with a metallocene catalyst is particularly preferable. Type polypropylene), a propylene-α-olefin random copolymer. Moreover, these polyolefin resin can be used individually or in mixture of 2 or more types.

  The α-olefin used as a copolymerization component of the propylene-α-olefin copolymer is ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1- Examples include α-olefins having about 4 to 20 carbon atoms such as octene, 1-nonene, 1-decene. These copolymerization components can be used alone or in admixture of two or more. Among these, preferred are ethylene-propylene random copolymers having ethylene as a copolymerization component. In this ethylene-propylene random copolymer, the ratio of ethylene and propylene is, for example, (the former / the latter (weight ratio) = 2/98 to 5/95 (preferably 3/97 to 4.5 / 95.5)). It can be selected from a range of degrees.

  Furthermore, the ethylene-propylene random copolymer is a copolymer obtained by copolymerization using a metallocene catalyst in that it can improve the low temperature shrinkage of about 60 to 80 ° C. and the fit to the container during heat shrinkage. Polymers are preferred. In addition, those having an isotactic index of 90% or more are preferable from the viewpoint of low temperature shrinkage and film waist strength. As the metallocene catalyst, a known or commonly used metallocene catalyst for olefin polymerization can be used. The copolymerization method is not particularly limited, and a known polymerization method such as a slurry method, a solution polymerization method, or a gas phase method can be employed.

  Examples of the polyolefin-based resin include “Wintech WFX6” (metallocene catalyst-based polypropylene) manufactured by Nippon Polypro Co., Ltd., “Zeras # 7000, # 5000” (propylene-α-olefin copolymer) manufactured by Mitsubishi Chemical Corporation, “Kernel” manufactured by Nippon Polyethylene Co., Ltd. is commercially available.

  The weight average molecular weight of the olefin resin is preferably 100,000 to 500,000, more preferably 200,000 to 400,000, from the viewpoint of controlling the melting behavior within a preferable range.

  The polyolefin resin preferably has a melting point of 100 to 150 ° C, more preferably 120 to 140 ° C. The melt flow rate (MFR) is preferably from 0.1 to 10 (g / 10 minutes), more preferably from 1 to 5 (g / 10 minutes). When the melting point or MFR is out of the above range, the difference in production conditions with the polyester resin becomes large, making it difficult to form a sheet by co-extrusion and subsequent stretching, resulting in poor productivity such as film breakage and sufficient orientation. In some cases, the shrinkage may not be improved.

  The resin composition B may contain a tackifier (tackifier) such as petroleum resin or terpene resin in order to achieve high shrinkage. Examples of the tackifier include rosin resin (rosin, polymerized rosin, hydrogenated rosin and derivatives thereof, resin acid dimer, etc.), terpene resin (terpene resin, aromatic modified terpene resin, hydrogenated terpene resin, terpene). -Phenol resin), petroleum resin (aliphatic, aromatic, alicyclic) and the like. Among these, petroleum resin is preferable. A tackifier can be used individually or in combination of 2 or more types. The addition amount in the case of adding a tackifier is preferably less than 50% by weight (for example, 10 to 30% by weight) based on the total weight of the resin composition B. When the addition amount is 50% by weight or more, the shrink performance may be deteriorated or the film may become brittle. Moreover, if it is less than 10 weight%, the effect of addition may be small. As the above-mentioned tackifier, “Arcon” manufactured by Arakawa Chemical Co., Ltd. can be obtained as a commercial product, and a polyolefin resin containing petroleum resin (for example, “Wintech 1987FC” manufactured by Nippon Polypro Co., Ltd.): metallocene catalyst Polypropylene (70% by weight) / polyethylene (5% by weight) / petroleum resin 25% by weight mixed resin) can also be used.

  In addition, in the B layer (namely, resin composition B) of the shrink film of this invention, the collection | recovery raw material may be included in the range which does not impair the effect of this invention. In this case, the amount of the recovered raw material is about 1 to 30% by weight with respect to the total weight of the resin composition B. Recovered raw materials are non-product parts such as before and after commercialization and film edges, remaining parts when product films are collected from intermediate products, non-standard film waste, polymer waste, and recycled raw materials ( However, it is limited to those resulting from the manufacture of the shrink film of the present invention).

[Resin composition C]
The center layer (C layer) in the shrink film of this invention is comprised from the resin composition C which has polyolefin resin as a main component.

  Although it does not specifically limit as polyolefin-type resin which comprises the resin composition C, For example, homopolymers, such as polyethylene (PE), polypropylene (PP), polybutylene, polymethylpentene (PMP); Polymers, copolymers such as propylene-α-olefin copolymers (including olefin-based elastomers); copolymers of cyclic olefins and α-olefins (ethylene, propylene, etc.) or graft modified products thereof, cyclic olefins Examples thereof include amorphous cyclic olefin polymers such as ring-opening polymers or hydrogenated products thereof or graft-modified products thereof. Among these, polypropylene, propylene-α-olefin random copolymer, and ethylene-α-olefin copolymer are preferable from the viewpoint of shrinkage characteristics and interlayer strength, and particularly preferably polypropylene obtained by polymerization with a metallocene catalyst. (Metallocene catalyst-based polypropylene), a propylene-α-olefin random copolymer. Moreover, these polyolefin resin can be used individually or in mixture of 2 or more types.

  The α-olefin used as a copolymerization component of the propylene-α-olefin copolymer is ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1- Examples include α-olefins having about 4 to 20 carbon atoms such as octene, 1-nonene, 1-decene. These copolymerization components can be used alone or in admixture of two or more. Among these, preferred are ethylene-propylene random copolymers having ethylene as a copolymerization component. In this ethylene-propylene random copolymer, the ratio of ethylene and propylene is, for example, (the former / the latter (weight ratio) = 2/98 to 5/95 (preferably 3/97 to 4.5 / 95.5)). It can be selected from a range of degrees.

  Furthermore, the ethylene-propylene random copolymer is a copolymer obtained by copolymerization using a metallocene catalyst in that it can improve the low temperature shrinkage of about 60 to 80 ° C. and the fit to the container during heat shrinkage. Polymers are preferred. In addition, those having an isotactic index of 90% or more are preferable from the viewpoint of low temperature shrinkage and film waist strength. As the metallocene catalyst, a known or commonly used metallocene catalyst for olefin polymerization can be used. The copolymerization method is not particularly limited, and a known polymerization method such as a slurry method, a solution polymerization method, or a gas phase method can be employed.

  As the polyolefin resin, “Wintech WFX6, 1987FC” manufactured by Nippon Polypro Co., Ltd., “Zeras # 7000, # 5000” manufactured by Mitsubishi Chemical Corporation, “Kernel” manufactured by Nippon Polyethylene Co., Ltd. are available as commercial products. Is possible.

  The weight average molecular weight of the olefin resin is preferably 100,000 to 500,000, more preferably 200,000 to 400,000, from the viewpoint of controlling the melting behavior within a preferable range.

  The polyolefin resin preferably has a melting point of 100 to 150 ° C, more preferably 120 to 140 ° C. The melt flow rate (MFR) is preferably from 0.1 to 10 (g / 10 minutes), more preferably from 1 to 5 (g / 10 minutes). When the melting point or MFR is out of the above range, the difference in production conditions with the polyester resin becomes large, making it difficult to form a sheet by co-extrusion and subsequent stretching, resulting in poor productivity such as film breakage and sufficient orientation. In some cases, the shrinkage may not be improved.

  In addition, although it does not specifically limit, As the polyolefin resin which comprises the resin composition C, it is preferable not to use the polyolefin resin which has a functional group illustrated as resin used for the resin composition B. Since the C layer in the present invention is a thick layer, when a polyolefin resin having a relatively expensive functional group is used as the C layer, the cost may be increased or the shrinkage characteristics may be lowered. Moreover, the direction which uses the polyolefin-type resin which does not have a functional group tends to improve the extending | stretching characteristic in molding temperature. When the recovered raw material is added to the resin composition C, a polyolefin resin having a functional group may be contained in the resin composition C. Even in this case, the content of the polyolefin resin having a functional group is The amount of the resin composition C is preferably less than 5% by weight.

  Content of the said polyolefin-type resin is 50 weight% or more with respect to the total weight of the resin composition C, Preferably it is 70-100 weight%, More preferably, it is 70-80 weight%. If the content of the polyolefin resin in the resin composition C is less than 50% by weight, the specific gravity may not be lowered or the shrinkage characteristics may be deteriorated. In addition, when using 2 or more types of polyolefin resin, the total amount of polyolefin resin should just satisfy said relationship.

  The resin composition C may contain a tackifier (tackifier) such as petroleum resin in order to improve the high shrinkage, the strength of the waist and the prevention of natural shrinkage. As the tackifier, a tackifier resin similar to that exemplified in the resin composition B can be used. The addition amount in the case of adding a tackifier is preferably 5 to 30% by weight, more preferably 10 to 25% by weight, based on the total weight of the resin composition C. If the amount added exceeds 30% by weight, the shrink film may become brittle. Moreover, if it is less than 5 weight%, the effect of addition may be small.

  Among the above, the resin composition C is particularly preferably exemplified by a mixed resin of a metallocene catalyst polypropylene, a metallocene catalyst polypropylene (main component), a petroleum resin and / or an olefin elastomer from the viewpoint of imparting shrinkage. The In addition, as said olefin type elastomer, well-known and usual olefin type elastomers (olefin type thermoplastic elastomer etc.) can be used, but it is not specifically limited, For example, ethylene-propylene copolymer elastomer, ethylene-propylene-diene copolymer elastomer Preferred examples include ethylene-based elastomers such as conjugated diene rubbers such as butadiene rubber and isoprene rubber.

  In addition, the shrink film of this invention may contain the collection | recovery raw material in C layer (namely, resin composition C) in the range which does not impair the effect of this invention. In this case, the amount of the recovered raw material is about 1 to 30% by weight with respect to the total weight of the resin composition C.

[Melt viscosity characteristics of resin compositions A to C]
The difference (absolute value) in melt viscosity at 220 ° C. between the resin compositions of the resin compositions A to C used in the present invention (that is, all of A and B, B and C, and C and A) is It is 300 Pa · s or less (for example, 0 to 300 Pa · s), and more preferably 250 Pa · s or less. The melt viscosity was measured according to JIS K 7199 using a capillary rheometer (for example, “Twin Capillo” manufactured by Rosand), and a value at a shear rate of 100 sec ⁻¹ was used. When the difference in melt viscosity exceeds 300 Pa · s, it is assumed that the flow characteristics of each layer resin are different during lamination by coextrusion, and the stress remaining in the resin layer is different due to this. However, the interlayer strength tends to decrease.

  The difference (absolute value) of the slope of the temperature-melt viscosity line at 200 to 240 ° C. between the resin compositions A to C used in the present invention is 7 Pa · s / ° C. or less (for example, 0 to 7 Pa). · S / ° C), more preferably 6 Pa · s / ° C or less. The slope of the temperature-melt viscosity line represents the temperature dependence of the melt viscosity, and the measurement method and shear rate are the same as the melt viscosity. If the difference in temperature dependence of melt viscosity is greater than 7 Pa · s / ° C, the flow behavior of each layer resin with respect to temperature change in the melt extrusion process will be different, so even if the melt viscosity at 220 ° C is close. However, in the coextrusion, the flow characteristics of each layer resin are different, and the interlayer strength decreases.

  Generally, even if a polyester resin and a polyolefin resin are laminated by coextrusion or the like, there is a tendency that a high interlayer strength cannot be obtained. In contrast, by laminating via an adhesive resin layer, Improvements have been made to improve interlayer strength. However, even when the adhesive resin layers are laminated in this way, there is a problem that the interlayer strength is lowered when shrinking. On the other hand, in the present invention, as described above, by selecting a combination of resins having similar melt flow characteristics in the extrusion temperature region of coextrusion, excellent interlayer strength can be obtained even when shrinkage processing is performed. I found out that This is presumably because the difference in flow characteristics during lamination greatly affects the interlayer strength. That is, when laminating polymers with significantly different flow characteristics during coextrusion, the degree of orientation of the molecular chains of the polyester resin layer and polyolefin resin layer of the laminated film after extrusion is greatly different, so that there is distortion between the film layers. Even if it is bonded via an adhesive resin layer, sufficient interlayer strength cannot be exhibited.

  The melt viscosity (absolute value) at 220 ° C. of the resin composition A used in the present invention is not particularly limited, but is 300 to 700 Pa · s, more preferably 300 to 650 Pa · s. Moreover, the melt viscosity (absolute value) at 220 ° C. of the resin composition B is not particularly limited, but is 200 to 500 Pa · s, and more preferably 300 to 450 Pa · s. Furthermore, the melt viscosity (absolute value) at 220 ° C. of the resin composition C is not particularly limited, but is 200 to 500 Pa · s, more preferably 300 to 450 Pa · s. When the melt viscosity exceeds the above range, extrusion characteristics such as fluidity are poor, and there are cases where die streaks are generated and the thickness of the laminate is not uniform. Moreover, when it is less than the above range, the viscosity is too low, and sheeting or uniform lamination may be difficult. The melt viscosity can be controlled by adding a plasticizer in addition to the structure and molecular weight of the polymer used. For example, the polyolefin elastomer described above can be used as the plasticizer.

  The slope (absolute value) of the temperature-melt viscosity straight line at 200 to 240 ° C. of the resin composition A used in the present invention is not particularly limited, but is 8 to 16 Pa · s / ° C., more preferably 8 to 12 Pa ··. s / ° C. Further, the slope (absolute value) of the temperature-melt viscosity line at 200 to 240 ° C. of the resin composition B is not particularly limited, but is 2 to 10 Pa · s / ° C., more preferably 6 to 10 Pa · s / ° C. It is. Furthermore, the slope (absolute value) of the temperature-melt viscosity line at 200 to 240 ° C. of the resin composition C is not particularly limited, but is 2 to 10 Pa · s / ° C., more preferably 5 to 10 Pa · s / ° C. is there. If the slope of the temperature-melt viscosity line, that is, the temperature dependence of the melt viscosity is larger than the above range, it may be sensitive to temperature and difficult to control. The temperature dependence of these melt viscosities can be controlled by adding a plasticizer in addition to the structure and molecular weight of the polymer used.

[Shrink film]
As described above, the shrink film of the present invention is formed in the order of A layer (surface layer) / B layer (intermediate layer) / C layer (center layer) / B layer (intermediate layer) / A layer (surface layer) in this order. This is a laminated structure including a laminated structure of three types and five layers in which the C layer is laminated without interposing other layers. Specifically, although not particularly limited, a laminated structure of A / B / C / B / A is preferably exemplified.

  The A / B / C / B / A three-kind five-layer laminated structure is formed by coextrusion. The general method of coextrusion is a method in which the resin compositions A to C are respectively charged into a plurality of extruders each set to a predetermined temperature and coextruded from a T die, a circular die, or the like. At this time, it is preferable to use a manifold or a merging block to form a predetermined laminated 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. The extrusion temperature varies depending on the types of the resin compositions A to C to be used, and is not particularly limited. However, it is preferable that the molding temperature regions of the resin compositions are close to each other. Specifically, the extrusion temperature of the resin composition A (A layer) is preferably 210 to 240 ° C., the resin composition B (B layer) is 190 to 220 ° C., and the resin composition C (C layer) is 180 to 220. ° C is preferred. An unstretched laminated film (sheet) can be obtained by quenching the coextruded polymer using a cooling drum or the like.

  The shrink film of the present invention is a uniaxially or biaxially oriented film from the viewpoint of shrinkage characteristics, and it is necessary that five layers of A / B / C / B / A in the film are oriented. When the five layers of A / B / C / B / A are non-oriented, good shrinkage cannot be obtained. The orientation is not particularly limited, such as uniaxial orientation or biaxial orientation, but substantially uniaxial orientation in the width direction, which is strongly oriented in the film width direction (direction that becomes the circumferential direction when the label is formed into a cylinder) is preferable. Further, it may be a substantially uniaxially oriented film in the longitudinal direction that is strongly oriented in the longitudinal direction (direction perpendicular to the width direction) of the film.

  An oriented film such as the uniaxial orientation or the biaxial orientation can be produced by stretching an unstretched laminated film. Stretching can be selected according to the desired orientation, and may be biaxial stretching in the longitudinal direction (longitudinal direction; MD direction) and width direction (transverse direction; TD direction), or uniaxial stretching in the longitudinal direction or width direction. But you can. The stretching method may be any of a roll method, a tenter method, and a tube method. The stretching conditions vary depending on the types of resin compositions A to C used, and are not particularly limited, but are generally in the range of 70 to 110 ° C. and about 1.01 to 8 times in the longitudinal and width directions. It is preferable to carry out at a magnification. For example, the film is stretched about 1.01 to 1.5 times (preferably 1.05 to 1.3 times) in the longitudinal direction and then stretched about 2 to 8 times (preferably 3 to 6 times) in the width direction. Is preferred.

  In the shrink film of the present invention, the thickness of the A layer (one layer) is not particularly limited, but is preferably 3 to 15 μm, more preferably 5 to 10 μm. If the thickness of the A layer exceeds 15 μm, the shrinkage may occur rapidly, and if it is less than 3 μm, the shrinkage may be insufficient.

  In the shrink film of the present invention, the thickness of the B layer (one layer) is not particularly limited, but is preferably 3 to 15 μm, more preferably 5 to 10 μm. When the thickness of the B layer exceeds 15 μm, the shrinkage may be nonuniform, and when it is less than 3 μm, it may be difficult to form the layer.

  In the shrink film of the present invention, the thickness of the C layer (one layer) is not particularly limited, but is preferably 10 to 70 μm, and more preferably 20 to 30 μm. If the thickness of the C layer exceeds 70 μm, the shrinkage rate may decrease, and if it is less than 10 μm, the shrinkage may occur rapidly.

  In the shrink film of the present invention, when the total thickness is 100%, the thickness ratio of the A layer (total of two layers) and the B layer (total of two layers) is preferably 2 to 50%. Further, the thickness ratio of the C layer is preferably 40 to 95%.

  Although the thickness of the shrink film of this invention is not specifically limited, 20-100 micrometers is preferable, More preferably, it is 20-80 micrometers, More preferably, it is 30-60 micrometers.

  In the shrink film of the present invention, the surface layer (A layer) has a polyester resin as a main component, and therefore has high shrinkability, and can impart wear resistance and chemical resistance to the surface. Since the central layer (C layer) is mainly composed of a polyolefin resin, the shrink label has a low specific gravity, and in addition, the shrinkage behavior can be moderated by suppressing rapid shrinkage of the label. The intermediate layer (B layer) has high adhesion to both the A layer and the C layer, and plays a role of improving interlayer strength. By laminating these layers in the above-described laminated structure and further controlling the melt viscosity characteristics of the resin composition used in each layer within a specific range, the density is high, even after shrink processing. A shrink film (or a shrink label using the same) having interlayer strength can be obtained.

[Shrink label]
By using the shrink film of the present invention as a base material and providing a printing layer on at least one side thereof, it can be preferably used as a shrink label. In addition to the printed layer, the shrink label may be provided with a protective layer, an anchor coat layer, a primer coat layer, a resin layer such as an adhesive layer (pressure sensitive, heat sensitive, etc.), a coating layer, Furthermore, you may provide layers, such as a nonwoven fabric and paper. As a specific configuration of the shrink label of the present invention, for example, a layer configuration such as printing layer / A / B / C / B / A, printing layer / A / B / C / B / A / printing layer is preferably exemplified. The In addition, the shrink film of this invention can also be used for shrink label use by itself, even when a printing layer is not provided.

  The shrink label of the present invention has a printed layer (for example, a layer displaying a product name, an illustration, handling precautions, etc.) on at least one surface. The printing layer is formed by applying printing ink. From the viewpoint of productivity, workability, and the like, the coating method is preferably provided by an off-line coating in which coating is performed using a known printing method after film formation. As a printing method, a conventional method can be used, but gravure printing or flexographic printing is most preferable. The printing ink used for forming the printing layer is made of, for example, a pigment, a binder resin, a solvent, and other additives. Although it does not specifically limit as said binder resin, For example, resin, such as an acrylic type, a urethane type, a polyamide type, a vinyl chloride-vinyl acetate copolymer type, a cellulose type, a nitrocellulose type, can be used individually or in combination. As the pigment, 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 in accordance with the application. In addition, extender pigments such as alumina, calcium carbonate, barium sulfate, silica, and acrylic beads can also be used as pigments for the purpose of adjusting gloss. Examples of the solvent include organic solvents such as toluene, xylene, methyl ethyl ketone, ethyl acetate, methyl alcohol, ethyl alcohol, and isopropyl alcohol, and commonly used solvents such as water.

Although the said printing layer is not specifically limited, Active energy ray-curable resin layers, such as visible light, an ultraviolet-ray, and an electron beam, may be sufficient. This is effective for preventing deformation of the film due to excessive heat. For example, in the case of curing by ultraviolet rays, an ultraviolet (UV) lamp, such as using an ultraviolet LED or an ultraviolet laser, ultraviolet ray having a wavelength 300～460Nm (or near UV), irradiation intensity 150~1000mJ / cm ^2, irradiation time 0.1 It can be performed under about 3 seconds. In the case of an active energy ray-curable printing layer, it is preferable to add a photopolymerization initiator such as a photoradical polymerization initiator and a photocationic polymerization initiator to the printing ink in addition to the above. Examples of the photo radical polymerization initiator include benzophenone, thioxanthone, acetophenone, and acylphosphine polymerization initiators. Examples of the photo cationic polymerization initiator include diazonium salts, diaryl iodonium salts, and triaryls. Examples include sulfonium salts, silanol / aluminum complexes, sulfonate esters, and imide sulfonates. Although content of these photoinitiators is not specifically limited, 0.5-7 weight% is preferable with respect to the whole printing ink, More preferably, it is 1-5 weight%. Furthermore, you may add a sensitizer to printing ink as needed from a viewpoint of improving production efficiency. In this case, the sensitizer is, for example, an amine-based sensitizer such as an aliphatic, aromatic amine, piperidine, or other amine containing a nitrogen in the ring; an allyl-based or o-tolylthiourea-based urea-based sensitizer; sodium diethyl Sulfur compound sensitizers such as dithiophosphate; Anthracene sensitizers; Nitrile sensitizers such as N, N-disubstituted-p-aminobenzonitrile compounds; Phosphorus compound systems such as tri-n-butylphosphine Sensitizers; nitrogen compound sensitizers such as N-nitrosohydroxylamine derivatives and oxazolidine compounds; chlorine compound sensitizers such as carbon tetrachloride. Although it does not specifically limit as content of a sensitizer, 0.1 to 5 weight% is preferable with respect to the whole printing ink, Most preferably, it is 0.3 to 3 weight%.

  Although the thickness of the said printing layer is not specifically limited, For example, it is about 0.1-10 micrometers. If the thickness is less than 0.1 μm, it may be difficult to provide a uniform printing layer, and partial “blur” may occur, resulting in a loss of decorativeness or printing as designed. May be difficult. In addition, when the thickness exceeds 10 μm, a large amount of printing ink is consumed, which increases the cost, makes it difficult to apply uniformly, makes the printed layer brittle and easily peels off. . Moreover, the rigidity of a printing layer becomes high and it may become difficult to follow the shrinkage | contraction of a film at the time of shrink processing.

[Physical properties of shrink film]
The shrink film of the present invention has excellent interlayer strength. The interlayer strength (interlayer strength of the shrink film after stretching orientation) is preferably 1 (N / 30 mm) or more, more preferably 2 (N / 30 mm) or more. When the interlaminar strength is less than 1 (N / 30 mm), the film layers may be peeled off after processing or commercialization, resulting in reduced productivity or quality problems.

  The shrinkage ratio in the main orientation direction (mainly in the direction subjected to the stretching treatment) at 90 ° C. for 10 seconds (warm water treatment) of the shrink film (before shrink processing) of the present invention is preferably 15% or more, more preferably 25 to 25%. 80%, more preferably 30 to 70%. When the heat shrinkage rate is less than 15%, the shrinkage is not sufficient in the process of closely attaching the label to the container with heat, making it difficult to follow the shape of the container, and the finish is particularly poor for a complex shaped container. Sometimes.

  In addition, as for the thermal contraction rate of the direction orthogonal to the said main orientation direction in 90 degreeC 10 second (warm water process) of the shrink film (before shrink process) of this invention, -5-15% is preferable.

  The compressive strength (thickness 40 μm: JIS P 8126) of the shrink film (before shrink processing) of the present invention is preferably 2N or more, more preferably 3.5N or more, and further preferably 5N or more. In addition, when the compressive strength is less than 2N, the waist of the label becomes weak, and the label tends to be bent in the process of mounting the cylindrical shrink label on the container.

  The transparency (transparency) (haze value: JIS K 7105, converted to 40 μm thickness) (unit:%) of the shrink film (A / B / C / B / A3 type five-layer laminated film) of the present invention is preferably less than 10. More preferably, it is less than 5.0, More preferably, it is less than 2.0. When the haze value is 10 or more, the inside of the shrink film (the side that becomes the container side when the label is attached to the container) is printed, and in the case of a shrink label that shows printing through the film, Printing may be cloudy and decorative properties may be reduced. However, even if the haze is 10 or more, it can be sufficiently used in applications other than the above-mentioned applications that show printing through a film.

[processing]
The shrink label of the present invention is, for example, a cylindrical label of a type in which both ends of the label are sealed with a solvent or an adhesive and attached to the container, or one end of the label is attached to the container and the label is wound The other end can be suitably used as a winding-type label that overlaps with one end to form a cylinder. The center seal strength of this cylindrical label is preferably 2 N / 30 mm or more. When the seal strength is less than 2 N / 30 mm, the seal part may be peeled off after processing or commercialization, which may reduce productivity and cause label dropout.

  Although the manufacturing method of the said cylindrical label is not specifically limited, For example, it is as follows. After the shrink label of the present invention is printed on a long shrink film, it is slit into a predetermined width, wound into a roll, and after the roll is formed into a plurality of continuous labels in the long direction, Used for processing. While feeding one of these rolls, the film is formed into a cylindrical shape so that the main stretching direction (for example, the width direction) of the film is the circumferential direction. Specifically, a long shrink label is formed into a cylindrical shape, and a solvent or adhesive (such as tetrahydrofuran (THF)) having a width of about 2 to 4 mm in the longitudinal direction on one side edge of the label. (Solvent, etc.) is applied to the inner surface, rounded into a cylindrical shape, and the coated portion of the solvent, etc. is superposed at a position of 5 to 10 mm from the other side edge and bonded to the outer surface of the other side edge (center seal) ) To obtain a long cylindrical label continuous body (long cylindrical shrink label). In the case where a perforation for label excision is provided, a perforation having a predetermined length and pitch is formed in the longitudinal direction. The perforation can be applied by a conventional method (for example, a method of pressing a disk-shaped blade having a cut portion and a non-cut portion repeatedly formed around it, a method using a laser, or the like). The process stage for perforating can be appropriately selected after the printing process and before and after the cylindrical processing process.

  The shrink label of the present invention is attached to a container and used as a labeled container. Such containers include, for example, 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, cups, etc. This includes noodle containers. The shape of the container includes various shapes such as a cylindrical shape, a square bottle, and a cup type. Further, the material of the container includes plastic such as PET, glass, metal and the like.

  The above-mentioned container with a label can be produced by cutting a long cylindrical shrink label, mounting it on a predetermined container, shrinking the label by heat treatment, and closely contacting the container. Specifically, the above-described long cylindrical shrink label in a roll shape is supplied to an automatic label mounting device (shrink labeler), cut into a required length, and formed into a cylindrical shrink label. A shrink label is externally fitted to a container filled with the contents, and is passed through a hot air tunnel or steam tunnel at a predetermined temperature, or is heat-shrinked by radiant heat such as infrared rays, and is brought into close contact with the container to obtain a labeled container. . Examples of the heat treatment include treatment with steam at 80 to 100 ° C. (passing through a heating tunnel filled with steam and steam).

[Methods for measuring physical properties and methods for evaluating effects]
(1) Melt viscosity (capillary rheometer method), temperature-slope of melt viscosity straight line (temperature dependence of melt viscosity)
Using a capillary rheometer “Twin Capilo” manufactured by Rosand, the melt viscosity of the resin compositions A to C at a melting temperature of 220 ° C. and a shear rate of 100 sec ⁻¹ was measured according to JIS K 7199.
The temperature dependence of the melt viscosity was determined in the same manner as described above by obtaining the melt viscosity (shear rate 100 sec ^-1 ) at the melt temperature (200 ° C, 220 ° C, 240 ° C), and having the slope of the approximate straight line by the least square method. The slope of the temperature-melt viscosity straight line at 200 to 240 ° C. (temperature dependence of melt viscosity) (Pa · s / ° C.).
Calculate the difference (absolute value) in the melt viscosity of each of the resin compositions A and B, B and C, and C and A, the difference in temperature dependence of the melt viscosity (difference in the slope of the straight line) (absolute value), The maximum value was calculated.

(2) Thermal shrinkage (90 ° C for 10 seconds)
From the shrink film (before shrink processing) obtained in the examples and comparative examples, the measurement direction (main orientation direction: longitudinal direction or width direction of the base film) is 120 mm in length (mark interval 100 mm), and the sample width is 5 mm. A rectangular sample piece is prepared.
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 : Size of sample before heat treatment (main orientation direction: longitudinal direction or width direction)
L ₁ : Sample dimensions after heat treatment (same direction as L ₀ )
The shrinkage characteristics were evaluated from the heat shrinkage rate (shrinkage rate) in the main orientation direction according to the following criteria. In the examples, the main orientation direction was the width direction of the shrink film.
30% or more: ◎ (excellent shrinkage properties)
25% or more and less than 30%: ○ (good shrinkage characteristics)
15% or more and less than 25%: △ (usable level)
Less than 15%: × (defective shrinkage property)

(3) Compressive strength (ring crush method)
Evaluation was performed using a shrink film (before shrink processing) (film thickness 40 μm) obtained by the methods of Examples and Comparative Examples.
In accordance with JIS P 8126, the compressive strength of the shrink label was measured under the following conditions. The measurement direction is the longitudinal direction.
Measuring device: Shimadzu Corporation autograph (AGS-50G: load cell type 500N)
Sample size: 15 mm (longitudinal direction) x 152.4 mm (width direction)
Number of tests: 5 times The measurement result of the compressive strength was judged according to the following criteria.
2N or more: ○ (Good compression strength)
Less than 2N: x (compression strength is inferior)

(4) Interlaminar strength (T-type peeling)
Evaluation was performed using the shrink films obtained in Examples and Comparative Examples.
A strip-shaped sample (200 mm (shrink film width direction) × 30 mm (shrink film length direction)) having a width of 30 mm in the length direction (shrink film forming direction) and long in the width direction (direction perpendicular to the length direction) is collected. did. Hereinafter, the sample width direction refers to the longitudinal direction of the shrink film.
With the long side direction of the sample (the width direction of the shrink film) as the measurement direction, a T-type peel test (based on JIS K 6854-3) was performed under the following conditions to measure the peel load between the layers.
The average value of the peeling load was defined as the interlayer strength (N / 30 mm), and evaluated according to the following criteria.
Substrate breaks without delamination: ◎ (Excellent interlayer strength)
2N / 30mm or more: ○ (good interlayer strength)
1N / 30mm or more, less than 2N / 30mm: △ (Available level)
Less than 1 N / 30 mm: x (interlayer strength is inferior)
(Measurement condition)
Measuring device: Autograph manufactured by Shimadzu Corporation (AG-IS: load cell type 500N)
Temperature and humidity: Temperature 23 ± 2 ° C, humidity 50 ± 5% RH (JIS K 7000 standard temperature state 2nd grade)
Initial chuck interval: 40 mm
Sample width: 30mm
Number of tests: 3 times Tensile speed: 200 mm / min Stroke: 150 mm (If it broke, it was interrupted and data up to that point was obtained.)
First half deletion range: 50mm
Sensitivity: 1
In addition, the said interlayer strength shall be evaluated about the interlayer with the weakest interlayer strength in a laminated structure, and it evaluated by the interlayer strength of A layer and B layer in an Example and a comparative example.

(5) Transparency (haze value)
Using the shrink film (thickness 40 μm) obtained in Examples and Comparative Examples, measurement was performed according to JIS K 7105. In the case of films having different thicknesses, the thickness may be converted to 40 μm.
From the haze value (unit:%), the following criteria were used for evaluation.
Less than 2.0: ◎ (excellent transparency)
2.0 or more and less than 5.0: ○ (good transparency)
5.0 or more and less than 10: △ (usable level)
10 or more: × (poor transparency)

(6) Hot air finish suitability The long shrink films obtained in the examples and comparative examples were rolled into a cylindrical shape so that the width direction (main orientation direction) of the base film was the circumferential direction, and tetrahydrofuran (THF ) To provide a long cylindrical shrink label.
The above-described long cylindrical shrink label is supplied to an automatic label mounting device (LSA-9130 manufactured by Fujia Tech Co., Ltd.), and the cylindrical shrink label obtained by cutting in the width direction is used as a container (manufactured by Toyo Seikan Co., Ltd.). 500 ml heat-resistant square PET bottle) and heated and shrunk by blowing hot air at 200 ° C. to obtain a labeled container.
When the delamination is not seen at the center seal part and the upper and lower ends of the label, the hot air finish is good (○), and when the delamination is seen at the center seal part or the upper and lower ends of the label, the hot air finish is poor (×). did.

(7) Water vapor finish suitability The shrink labels obtained in Examples and Comparative Examples were rolled into a cylindrical shape so that the width direction (main orientation direction) of the base film was the circumferential direction, and centered with tetrahydrofuran (THF). Sealed to obtain a long cylindrical shrink label.
The above long cylindrical shrink label is supplied to an automatic label mounting apparatus (STS-1936 manufactured by Fujistec Co., Ltd.) and cut into each label while mounted on a container (500 ml heat-resistant square PET bottle manufactured by Toyo Seikan Co., Ltd.) And it heat-shrinked with the steam tunnel with an atmospheric temperature of 90 degreeC, and it was set as the labeled container.
Water vapor finish is good (○) when no delamination is seen at the center seal and upper / lower end of the label, and water vapor finish is poor (×) when delamination is seen at the center seal or upper / lower end of the label did.

  EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. Tables 1 and 2 show the composition and physical properties of the resin composition of each layer used for producing the shrink film in Examples and the evaluation results of the obtained shrink film and shrink label. In addition, the unit of the compounding quantity of Table 1 and Table 2 is a weight part in each resin composition, and the inclination of a temperature-melt viscosity straight line is an absolute value.

Example 1
As shown in Table 1, as resin composition A, 100 parts by weight of NPG-modified amorphous polyester resin (“Belpet E-02” manufactured by Bell Polyester Products Co., Ltd.) was used. In addition, as resin composition B, 100 parts by weight of maleic anhydride-modified olefin resin (“Modic AP F534A” manufactured by Mitsubishi Chemical Corporation) was used. Furthermore, as resin composition C, 100 parts by weight of a metallocene catalyst-based polypropylene resin (“Wintech WFX6” manufactured by Nippon Polypro Co., Ltd.) was used.
The resin composition A was charged in the extruder a heated to 220 ° C., the resin composition B in the extruder b heated to 210 ° C., and the resin composition C in the extruder c heated to 200 ° C. Melt extrusion was performed using the above three extruders. The resin extruded from the extruder c is the center layer, the resin extruded from the extruder b is on both sides of the center layer, and the resin extruded from the extruder a is further merged by using a merge block. After being extruded from a T-die (slit spacing 1 mm), it was rapidly cooled on a casting drum cooled to 25 ° C. to obtain a three-kind five-layer laminated unstretched film (thickness: 200 μm). The lamination thickness ratio of the unstretched film was surface layer / intermediate layer / center layer / intermediate layer / surface layer (A / B / C / B / A) = 1/4/1/1.
Next, the unstretched film with adjusted thickness is stretched 1.2 times at 90 ° C. in the longitudinal direction, and then stretched 5 times at 90 ° C. in the width direction, so that biaxial stretching mainly shrinks in the uniaxial direction. A film was obtained. The film forming speed was adjusted to obtain a shrink film having a total film thickness of 40 μm (layer thickness ratio: 1/4/1/1).
Moreover, Dainippon Ink Industries Co., Ltd. "fine wrap NTV" was gravure-printed on the obtained shrink film, the printing layer was formed in thickness of 5 micrometers, and the shrink label was obtained.
As shown in Table 1, the obtained shrink film had good shrinkage characteristics (shrinkage rate), compressive strength, interlayer strength, and transparency. Furthermore, the obtained shrink label had a good finish when it was shrink-processed using a hot air tunnel or a steam tunnel.

Examples 2 and 3
As shown in Table 1, a shrink film and a shrink label were obtained in the same manner as in Example 1 except that the resin type and the resin composition used for the resin composition B (intermediate layer) were changed.
As shown in Table 1, the obtained shrink film and shrink label were good results in all evaluations.

Examples 4 and 5
As shown in Table 1, a shrink film and a shrink label were obtained in the same manner as in Example 3 except that the resin type and resin composition used for the resin composition C (center layer) were changed.
As shown in Table 1, the obtained shrink film and shrink label were good results in all evaluations.

Examples 6 and 7
As shown in Table 1, a shrink film and a shrink label were obtained in the same manner as in Example 1 except that the resin type and the resin composition used for the resin composition B (intermediate layer) were changed.
As shown in Table 1, the obtained shrink film and shrink label were good results in all evaluations.

Example 8
As shown in Table 1, a resin film used for the resin composition A (surface layer) was changed to obtain a shrink film and a shrink label in the same manner as in Example 6.
As shown in Table 1, the obtained shrink film and shrink label were good results in all evaluations.

Comparative Example 1
As shown in Table 1, a shrink film and a shrink label were obtained in the same manner as in Example 1 using the same resin as the resin composition C as the resin composition B.
The obtained shrink film and shrink label had low interlayer strength, delamination occurred during shrinkage processing, and the finish suitability was poor.

Comparative Example 2
As shown in Table 1, the amount of the polyolefin-based resin having a reactive functional group in the resin composition B was reduced, and a shrink film and a shrink label were obtained in the same manner as in Example 3.
The obtained shrink film and shrink label had low interlayer strength, and there was a possibility of delamination during shrinkage processing and use.

Comparative Example 3
As shown in Table 1, the resin composition A was changed to obtain a shrink film and a shrink label in the same manner as in Example 6.
The obtained shrink film and shrink label had low interlayer strength, and there was a possibility of delamination during shrinkage processing and use. Moreover, the finish suitability was inferior.

Examples 9, 10
As shown in Table 2, a resin film used for the resin composition B (intermediate layer) was changed to obtain a shrink film and a shrink label in the same manner as in Example 1.
As shown in Table 2, the obtained shrink film and shrink label were good results in all evaluations.

Claims (4)

A surface layer (A layer) composed of a resin composition A mainly composed of an amorphous polyester resin, containing 35% by weight or more of a polyolefin resin having a reactive functional group, and comprising a polyolefin resin as a main component An intermediate layer (B layer) composed of the resin composition B and a central layer (C layer) composed of the resin composition C mainly composed of a polyolefin resin are A layer / B layer / C layer. In the order of / B layer / A layer, it has a laminated structure laminated without other layers, and the resin composition A, the resin composition B, and the resin composition C are the following (1): And the shrink film characterized by satisfy | filling the relationship of (2).
(1) The absolute value of the difference in melt viscosity (capillary rheometer method, shear rate 100 sec ⁻¹ ) at 220 ° C. between the resin compositions is 300 Pa · s or less.
(2) The absolute value of the difference in the slope of the temperature-melt viscosity straight line at 200 to 240 ° C. between the resin compositions is 7 Pa · s / ° C. or less.   The shrink film according to claim 1, wherein the polyolefin-based resin having a reactive functional group contained in the resin composition B is a dicarboxylic acid anhydride-modified polyolefin-based resin.   The shrink film according to claim 1 or 2, wherein the resin composition C is mainly composed of polypropylene obtained by polymerization using a metallocene catalyst.   The shrink label which provided the printing layer in the at least one surface side of the shrink film in any one of Claims 1-3.