JP2010214900A - Heat-shrinkable laminated film, molding and label using the film, and vessel with the molding and label attached thereto - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable film formed by using plant-derived resin with excellent environmental suitability, having excellent transparency, low temperature shrinkability, toughness, shrinking finishing property with small natural shrinkage suited to shrinkable labels, a molding and a vessel with the heat-shrinkable label attached thereto. <P>SOLUTION: The heat-shrinkable laminated film is formed by stretching film laminated with a polylactic acid-based resin front surface on an intermediate layer of polystyrene-based resin via an adhesive layer, in at least one direction. The adhesive layer is constituted of at least one kind of copolymer or resin selected among a group consisting of polyester resin, ethylenic copolymer, modified polyolefinic resin and polyamide. The heat-shrinkable laminated film is suited to applications for shrink package, shrink bundling package and shrink labels, the heat-shrinkable laminated film using plant-derived resin with excellent environmental suitability, having excellent transparency, low temperature shrinkability, toughness, shrinking finishing property with small natural shrinkage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable laminated film using a plant-derived resin, a molded article and a label using the film, and a container equipped with the molded article and the label.

  Currently, soft drinks such as juice and alcoholic drinks such as beer are sold in a state of being filled in containers such as bottles and plastic bottles. At that time, a heat-shrinkable label printed on the outside of the container is often attached for the purpose of differentiating from other products, improving the visibility of the products, and increasing the product value.

  In the above-mentioned fields, for use in labeling PET bottles and the like for which demand is expected to increase, there is a demand for a heat-shrinkable film having a high shrink-finished appearance at a relatively short time and at a low temperature and having a small natural shrinkage rate. The reason for this is the need for low temperatures in the labeling process of shrink films that are installed in recent PET bottles. That is, at present, the method of shrinking and labeling the heat-shrinkable film using steam shrinker has become the mainstream, but in order to avoid aseptic filling and quality deterioration due to temperature rise of the contents, the shrinking process can be performed as much as possible. It is desirable to carry out at a low temperature. For this reason, the current shrink film industry is developing heat-shrinkable films that start shrinking at the lowest possible temperature in the steam shrinker during labeling and that have excellent shrink finish characteristics after passing through the steam shrinker. It has been broken.

  As a material for the heat-shrinkable label, for example, polyethylene terephthalate (hereinafter sometimes abbreviated as “PET”) resin or polystyrene (hereinafter abbreviated as “PS”) resin is used. Yes. A stretched film formed of these resins has high transparency, gloss, rigidity, and excellent low-temperature shrinkage characteristics, and therefore can be suitably used as a heat-shrinkable film.

On the other hand, since the PET-based resin and the PS-based resin are both petroleum-derived resins, there is an actual situation that substitute resins for petroleum-derived resins are required due to problems related to the depletion of petroleum. On the other hand, due to the recent problem of CO ₂ gas emission regulations, the necessity of developing labels using raw materials that are environmentally friendly has been pointed out.

  Under such circumstances, a polylactic acid (hereinafter sometimes abbreviated as “PLA”) resin is known as an example of a substitute resin for petroleum-derived resins. This PLA resin is a plant-derived resin that uses lactic acid obtained by fermentation of starch as a raw material, and is characterized in that it can be mass-produced by chemical engineering and is excellent in transparency, rigidity, and the like. Furthermore, because it is a plant-derived raw material, it can not only save fossil resources but also suppress carbon dioxide emissions, and is attracting attention as an environmentally friendly resin.

  However, although the PLA heat-shrinkable film is excellent in rigidity and transparency, it has a drawback that it is very brittle, and shows a sharp shrinkage rate change with respect to the shrinkage temperature, so it is difficult to obtain uniform shrinkage, There was a problem in terms of shrink finish such as shrinkage unevenness.

  In order to improve the brittleness, a film in which various soft resins are mixed with a PLA resin has been proposed (see Patent Documents 1 to 3). However, since these films have a PLA resin as a matrix, it is difficult to obtain the heat shrink characteristics, shrink finish, stretchability, etc. necessary for the heat shrink film even if the purpose and effect are taken into consideration. .

A laminated film in which a PLA resin layer (A layer) and a polystyrene resin layer (B layer) are combined has also been reported (see Patent Document 4). However, since the heat-shrinkable film described in Patent Document 4 is a film in which the A layer and the B layer are laminated without an adhesive layer,
Since the difference in shrinkage stress between the PLA resin used in the A layer and the polystyrene resin used in the B layer is large, a delamination phenomenon occurs when the film shrinks, resulting in poor design.

In addition, when used for drinking PET bottles, etc., labeling by printing is performed for the purpose of differentiating from other companies and improving the image for customers. Printing ink used in the printing process Since generally contains an organic solvent, a trace amount of organic solvent remains on the printed surface after printing and drying. Patent Document 5 describes a heat-shrinkable film having a surface layer made of a heat-sealable resin and an inner layer made of a plant-derived resin. When the heat-shrinkable film is used, the adhesiveness between the surface layer and the inner layer is affected by the residual solvent, and the adhesive strength between the surface layer and the inner layer after the printing process is increased before the printing process is performed. There was a new problem that it was significantly reduced compared to the above.
Therefore, when used as a heat-shrinkable label for containers, there is no peeling between the surface layer and the intermediate layer at the time of mounting, and it has excellent heat resistance, oil resistance, perforation cutability, and appearance, and in the printing process There has been a demand for a heat-shrinkable multilayer film that is less affected by the organic solvent used and has sufficient adhesive strength even after the printing process.

JP 2005-068232 A JP 05-179110 A JP 09-316310 A JP 2008-1098 A JP 2007-283531 A

  This invention is made | formed in view of the said subject, The subject of this invention was using the plant-derived resin excellent in environmental suitability, excellent transparency, low temperature shrinkability, waist strength (at room temperature) Rigidity), shrink finish, and low natural shrinkage, suitable for applications such as shrink wrapping, shrink tying wrapping and shrink labels, and molded products using the film, heat shrink Another object of the present invention is to provide an adhesive label and a container equipped with the molded article or the heat-shrinkable label.

  As a result of intensive studies on the composition of the surface layer, the intermediate layer, and the adhesive layer that form the laminated film, the present inventor succeeded in obtaining a laminated film that can solve the above-mentioned problems of the prior art. It came to be completed. That is, the object of the present invention is achieved by the following heat-shrinkable laminated film (hereinafter “the film of the present invention”).

The first aspect of the present invention is a heat-shrinkable laminate obtained by stretching a film in which a surface layer mainly composed of a polylactic acid resin is laminated on an intermediate layer containing a polystyrene resin via an adhesive layer in at least one direction. A heat shrinkage characterized in that the film is a film, and the adhesive layer is composed of at least one copolymer or resin selected from the group consisting of (a), (b), (c) and (d) below. It is a conductive laminated film.
(A) a block copolymer comprising a polyester and a polyalkylene ether glycol, or a polyester resin obtained by modifying this copolymer with a functional group of an acid or epoxy resin,
(B) at least one selected from the group consisting of vinyl acetate, acrylic acid, methacrylic acid, ethyl acrylate, ethyl methacrylate, methyl acrylate, methyl methacrylate, maleic anhydride, and glycidyl methacrylate, and ethylene An ethylene copolymer, or a mixture of the copolymers,
(C) modified polyolefin resin,
(D) a polyamide-based resin,

  In the first aspect of the present invention, the polystyrene resin is preferably a styrene hydrocarbon-conjugated diene hydrocarbon copolymer (a copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon).

  In the first aspect of the present invention, the polystyrene resin may be a mixed resin of a styrene hydrocarbon-conjugated diene hydrocarbon copolymer and a styrene hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer. preferable. The styrene hydrocarbon-conjugated diene hydrocarbon copolymer is preferably a styrene-butadiene-styrene copolymer, a styrene-isoprene-butadiene-styrene copolymer, or a mixture thereof.

  In the first invention, the polylactic acid resin is preferably a copolymer of D-lactic acid and L-lactic acid, and the ratio of D-lactic acid to L-lactic acid (D / L ratio) is “ 3/97 "to" 15/85 "or" 85/15 "to" 97/3 "is preferable.

  The heat-shrinkable laminated film of the first invention is preferably stretched in at least one direction, and has a heat shrinkage rate of 20% or more in the film main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds. Preferably there is.

  In 1st this invention, it is preferable that the thickness ratio of the intermediate | middle layer with respect to the thickness of the whole film is 10% or more and 70% or less.

  The second aspect of the present invention is a molded article using the first heat-shrinkable laminated film as a substrate (hereinafter sometimes referred to as the molded article of the present invention).

  3rd this invention is a heat-shrinkable label (henceforth a label of this invention) using the 1st heat-shrinkable laminated film as a base material.

The fourth aspect of the present invention is a container equipped with the molded article of the second aspect of the present invention or the heat-shrinkable label of the third aspect of the present invention (hereinafter sometimes referred to as the container of the present invention).

  According to the film of the present invention, it has excellent transparency, low temperature shrinkability, low strength (rigidity at room temperature), shrink finish, small natural shrinkage, shrink wrap, shrink bundled wrap, shrink labels, etc. It is possible to provide a heat-shrinkable laminated film suitable for use in the above. Furthermore, since a plant-derived PLA resin is used, the film of the present invention is suitable for promoting the utilization of biomass and aiming for a recycling society.

  In addition, since the film of the present invention is used for the molded product and label of the present invention, according to the present invention, the molded product has excellent transparency and good shrinkage and shrinkage finish, and heat shrinkage. Sex labels can be provided. Furthermore, since the container of the present invention is equipped with the molded product or the heat-shrinkable label, according to the present invention, a container having a good appearance can be provided.

  Hereinafter, the heat-shrinkable laminated film of the present invention, a molded product, a heat-shrinkable label, and a container equipped with the molded product or the heat-shrinkable label will be described in detail.

  In the present specification, “main component” is intended to allow other components to be included as long as the action and effect of the resin constituting each layer is not hindered. Further, the term does not limit the specific content, but it is in the range of 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more and 100% by mass or less, based on the total components of each layer. Is a component occupying.

  Further, in this specification, the “main shrinkage direction” means a direction in which the thermal shrinkage rate is large between the longitudinal direction (longitudinal direction) of the film and the lateral direction (width direction) of the film. Means a direction corresponding to the outer circumferential direction. The “orthogonal direction” means a direction orthogonal to the main contraction direction.

<Heat-shrinkable laminated film>
The heat-shrinkable laminated film of the present invention has a surface layer composed mainly of a polylactic acid resin, an intermediate layer composed mainly of a polystyrene resin, and an adhesive layer between the surface layer and the intermediate layer. Therefore, an adhesive layer mainly composed of an adhesive resin is provided.

<Surface layer>
In the present invention, the surface layer contains a polylactic acid resin as a main component. The polylactic acid resin used in the surface layer is a homopolymer of D-lactic acid or L-lactic acid or a copolymer thereof, and a mixture thereof is also included. More specifically, poly (D-lactic acid) whose structural unit is D-lactic acid, poly (L-lactic acid) whose structural unit is L-lactic acid, and a copolymer of L-lactic acid and D-lactic acid. Poly (DL-lactic acid) or a mixture thereof.

  When the polylactic acid resin used in the present invention is a copolymer of D-lactic acid and L-lactic acid, the copolymerization ratio of D-lactic acid and L-lactic acid is D-lactic acid: L-lactic acid = “99”. .8: 0.2 ”to“ 75:25 ”or D-lactic acid: L-lactic acid =“ 0.2: 99.8 ”to“ 25:75 ”, preferably D-lactic acid: L -Lactic acid = "99.5: 0.5" to "80:20" or D-lactic acid: L-lactic acid = "0.5: 99.5" to "20:80" is more preferable. . Polylactic acid composed of D-lactic acid alone or L-lactic acid alone exhibits very high crystallinity, has a high melting point, and tends to be excellent in heat resistance and mechanical properties. However, when used as a heat-shrinkable film, it usually involves printing and a bag making process using a solvent, so that the crystallinity of the constituent material itself can be lowered appropriately in order to improve printability and solvent sealability. Necessary. Moreover, when crystallinity is too high, orientation crystallization advances at the time of extending | stretching, and there exists a tendency for shrinkage | contraction characteristic to fall. From these facts, the polylactic acid resin used in the present invention has a ratio of D-lactic acid to L-lactic acid (D / L ratio) of 1/99 to 15/85, or 85/15 to 99/1. Preferably, it is preferably 3/97 to 15/85, or 85/15 to 97/3, more preferably 5/95 to 15/85, or 85/15 to 95/5. .

  In the present invention, the polylactic acid resin can be used by mixing polylactic acid resins having different copolymerization ratios. In that case, what is necessary is just to make it the value which averaged the copolymerization ratio of D-lactic acid and L-lactic acid of several polylactic acid-type resin in the said range. Two or more types of polylactic acid resins having different copolymer ratios of D-lactic acid and L-lactic acid are mixed in accordance with the intended use, and the crystallinity is adjusted to balance heat resistance and heat shrinkage characteristics. be able to.

  The polylactic acid resin used in the surface layer may be a copolymer of lactic acid and α-hydroxycarboxylic acid, aliphatic diol, and aliphatic dicarboxylic acid. Here, the “α-hydroxycarboxylic acid” copolymerized with the polylactic acid-based resin includes glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxyn-butyric acid, 2-hydroxy3,3-dimethyl. Examples thereof include bifunctional aliphatic hydroxy-carboxylic acids such as butyric acid, 2-hydroxy-3-methylbutyric acid, 2-methylbutyric acid, and 2-hydroxycaprolactone acid, and lactones such as caprolactone, butyllactone, and valerolactone. Examples of the “aliphatic diol” copolymerized with the polylactic acid resin include ethylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Examples of the “aliphatic dicarboxylic acid” to be copolymerized include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid.

  The polylactic acid-based resin can be produced by a known polymerization method such as a condensation polymerization method or a ring-opening polymerization method. For example, in the case of a condensation polymerization method, a polylactic acid resin having an arbitrary composition can be obtained by directly dehydrating condensation polymerization of D-lactic acid, L-lactic acid, or a mixture thereof. Further, in the ring-opening polymerization method, a lactide which is a cyclic dimer of lactic acid is subjected to ring-opening polymerization in the presence of a predetermined catalyst while using a polymerization regulator or the like, if necessary. A lactic acid resin can be obtained. The lactide includes DL-lactide, which is a dimer of L-lactic acid. By mixing and polymerizing these as necessary, a polylactic acid resin having an arbitrary composition and crystallinity can be obtained. it can. Furthermore, a small amount of chain extender such as a diisocyanate compound, diepoxy compound, acid anhydride, acid chloride, etc. may be used for the purpose of increasing the molecular weight.

  The weight (mass) average molecular weight of the polylactic acid resin used in the surface layer has a lower limit of 20,000 or more, preferably 40,000 or more, more preferably 60,000 or more, and an upper limit of 400,000 or less. Preferably it is 350,000 or less, More preferably, it is 300,000 or less. When the weight (mass) average molecular weight is 20,000 or more, an appropriate resin cohesive force can be obtained, and the film can be prevented from being insufficiently stretched or embrittled. On the other hand, if the weight (mass) average molecular weight is 400,000 or less, the melt viscosity can be lowered, which is preferable from the viewpoint of production and productivity improvement.

  As a commercial item of the said polylactic acid-type resin, "NatureWorks" (made by Cargill Dow), "LACEA" (made by Mitsui Chemicals) etc. are mentioned, for example.

  In addition, in order to improve the impact resistance of the film, other rubber components other than polylactic acid-based resins may be added to the surface layer within a range that does not impair the shrinkage characteristics and film rigidity (back strength). preferable. Although this rubber component is not particularly limited, aliphatic polyester other than polylactic acid resin, aromatic-aliphatic polyester, copolymer of diol, dicarboxylic acid and polylactic acid resin, core shell structure rubber, ethylene -Vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer (EMA), ethylene- (meth) acrylic An acid methyl copolymer (EMMA) etc. can be used conveniently.

  Examples of the aliphatic polyester include polyhydroxycarboxylic acids, aliphatic polyesters obtained by condensing aliphatic diols and aliphatic dicarboxylic acids, aliphatic polyesters obtained by ring-opening polymerization of cyclic lactones, and synthetic aliphatics. Examples include polyester. Examples of the hydroxycarboxylic acid include 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, A homopolymer or copolymer of hydroxycarboxylic acid such as 2-hydroxycaprolacuronic acid can be used.

  As the aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid, one or two or more kinds of aliphatic diols and aliphatic dicarboxylic acids described below are condensed or condensed, Or the polymer which can be obtained as a desired polymer | macromolecule can be mentioned by jumping up molecular weight with an isocyanate compound etc. as needed. Here, examples of the aliphatic diol include ethylene glycol, propylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, and suberin. Examples include acid, sebacic acid, dodecanedioic acid and the like.

  In addition, examples of the aliphatic polyester obtained by ring-opening condensation of cyclic lactones include ring-opening polymers such as ε-caprolactone, σ-valerolactone, and β-methyl-σ-valerolactone, which are cyclic monomers. These cyclic monomers can be copolymerized by selecting not only one kind but also plural kinds.

  Examples of synthetic aliphatic polyesters include copolymers of cyclic acid anhydrides and oxiranes, such as copolymers of succinic anhydride and ethylene oxide, copolymers of propion oxide, and the like. it can.

  As a typical aliphatic polyester other than these polylactic acid-based resins, “Bionore” (manufactured by Showa Polymer Co., Ltd.) obtained by polymerizing succinic acid, 1,4-butanediol and adipic acid is commercially available. Can be obtained. Moreover, as a thing obtained by ring-opening condensation of (epsilon) -caprolactone, "Cell Green" (made by Daicel Chemical Industries Ltd.) is mentioned.

  Next, as the aromatic-aliphatic polyester, those having crystallinity lowered by introducing an aromatic ring between the aliphatic chains can be used. The aromatic-aliphatic polyester is obtained, for example, by condensing an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic diol.

  Here, examples of the aromatic dicarboxylic acid include isophthalic acid, terephthalic acid, and 2,6-naphthalenedicarboxylic acid, and terephthalic acid is most preferably used. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, and adipic acid is most preferably used. Examples of the aliphatic diol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Two or more types of aromatic dicarboxylic acids, aliphatic dicarboxylic acids or aliphatic diols may be used.

  Typical examples of the aromatic-aliphatic polyester include a copolymer of tetramethylene adipate and terephthalate, a copolymer of polybutylene adipate and terephthalate, and the like. EsterBio (manufactured by Eastman Chemicals) as a copolymer of tetramethylene adipate and terephthalate, and Ecoflex (manufactured by BASF) as a copolymer of polybutylene adipate and terephthalate can be obtained commercially.

  Examples of the structure of the polylactic acid resin, diol and dicarboxylic acid copolymer include random copolymers, block copolymers, and graft copolymers, and any structure may be used. However, a block copolymer or a graft copolymer is preferable from the viewpoint of impact resistance and transparency of the film. A specific example of the random copolymer is “GS-Pla” (manufactured by Mitsubishi Chemical Corporation), and a specific example of the block copolymer or graft copolymer is “Plamate” (manufactured by DIC).

  The production method of the copolymer of polylactic acid resin, diol and dicarboxylic acid is not particularly limited, but polyester or polyether polyol having a structure obtained by dehydration condensation of diol and dicarboxylic acid is converted to lactide and ring-opening polymerization or transesterification. The method obtained by letting it be mentioned. Further, there is a method in which a polyester or polyether polyol having a structure obtained by dehydration condensation of a diol and a dicarboxylic acid is obtained by dehydration / deglycolization condensation or transesterification with a polylactic acid resin.

  The copolymer of polylactic acid resin, diol and dicarboxylic acid can be manually adjusted to a predetermined molecular weight using an isocyanate compound or a carboxylic acid anhydride. However, from the viewpoint of workability and mechanical properties, the weight (mass) average molecular weight is 50,000 or more, preferably 100,000 or more, and 300,000 or less, preferably 250,000 or less.

  Next, examples of the core-shell structure rubber that can be contained in the surface layer include diene-based core-shell type polymers such as (meth) acrylic acid-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, and (meth) acrylic acid. -Acrylic core shell type polymer such as styrene-acrylonitrile copolymer, silicone- (meth) acrylic acid-methyl (meth) acrylic acid copolymer, silicone- (meth) acrylic acid-acrylonitrile-styrene copolymer, etc. Examples include silicone-based core-shell type copolymers. Among these, a silicone- (meth) acrylic acid-methyl (meth) acrylic acid copolymer having good compatibility with the polylactic acid resin and having a good balance between impact resistance and transparency of the film is more preferably used. .

  Specifically, “Metablene” (manufactured by Mitsubishi Rayon Co., Ltd.), “Kane Ace” (manufactured by Kaneka Corporation), etc. are commercially available.

  Next, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer, which can be contained in the surface layer As an union (EMA) and an ethylene-methyl (meth) acrylate copolymer (EMMA), the ethylene content is 50 mol% or more, preferably 60 mol% or more, and 95 mol% or less, preferably 85 mol. % Or less is preferably used. If the ethylene content is 50 mol% or more, the rigidity and heat resistance of the entire film can be maintained satisfactorily. If the ethylene unit content is 95 mol% or less, the effect on the fracture resistance of the film is sufficient. In addition to being obtained, it is preferable because transparency can be maintained. Among these, ethylene-vinyl acetate copolymer (EVA) can be used more suitably.

  As a commercial item of ethylene-vinyl acetate copolymer (EVA), for example, “EVAFLEX” (manufactured by Mitsui DuPont Polychemical Co., Ltd.), “Novatech EVA” (manufactured by Mitsubishi Chemical Corporation), “Ebaslene” (manufactured by DIC Corporation), "Evatate" (manufactured by Sumitomo Chemical Co., Ltd.) and ethylene-acrylic acid copolymer (EAA) include "Novatech EAA" (manufactured by Mitsubishi Chemical Corporation), ethylene-ethyl acrylate copolymer (EEA) and ethylene-methacrylic acid copolymer Examples of the polymer (EMA) include “Noah Frey AC” (manufactured by Mitsui DuPont Polychemical Co., Ltd.), and examples of the ethylene- (meth) methyl acrylate copolymer (EMMA) include “Aclift” (manufactured by Sumitomo Chemical Co., Ltd.). It is done.

  The addition amount of the rubber component is 5 parts by mass or more, preferably 7 parts by mass or more, more preferably 10 parts by mass or more, and 100 parts by mass with respect to 100 parts by mass of the polylactic acid resin contained as a main component of the surface layer. Part or less, preferably 80 parts by weight or less, more preferably 70 parts by weight or less. By setting the addition amount of the rubber component to 5 parts by mass or more, good impact resistance can be imparted to the film. Moreover, the addition amount of a rubber component shall be 100 mass parts or less, and it can use suitably as a heat shrink label, without impairing the rigidity and transparency of a film.

<Adhesive layer>
The adhesive layer constituting the film of the present invention is mainly composed of an adhesive resin that adheres the surface layer and an intermediate layer described later. The adhesive resin contained as the main component of the adhesive layer is not particularly limited as long as it is a resin capable of bonding the surface layer and the intermediate layer, and includes the following (a), (b), (c) and (d). It is preferable to use at least one copolymer or resin selected from the group.
(A) Block copolymer comprising polyester and polyalkylene ether glycol, or polyester resin obtained by modifying the copolymer with acid or acid anhydride (b) vinyl acetate, acrylic acid, methacrylic acid, acrylic acid Ethylene-based copolymer consisting of at least one selected from the group consisting of ethyl, ethyl methacrylate, methyl acrylate, methyl methacrylate, maleic anhydride, and glycidyl methacrylate and ethylene, or a mixture of these copolymers ( c) Modified polyolefin resin (d) Polyamide resin

  First, the polyester resin (a) will be described. The polyester resin mainly means a polyester elastomer. The polyester elastomer is composed of polyester as a hard segment and a soft segment rich in rubber elasticity. For example, a block composed of polyester as a hard segment and polyalkylene ether glycol as a soft segment. A copolymer etc. are mentioned.

  When a block copolymer composed of polyester and polyalkylene ether glycol is used as the polyester-based elastomer, the lower limit of the segment composed of polyalkylene ether glycol is preferably 30% by mass or more, more preferably 50% by mass or more. The upper limit is preferably 80% by mass or less, and more preferably 75% by mass or less. If the proportion of the segment made of polyalkylene ether glycol is too small, the adhesion to the intermediate layer may be reduced, and conversely if too large, the adhesion to the surface layer may be reduced.

  Examples of the polyalkylene ether glycol include polyethylene glycol, poly (propylene ether) glycol, poly (tetramethylene ether) glycol, poly (hexamethylene ether) glycol, and the like.

  The lower limit of the number average molecular weight of the polyalkylene ether glycol is preferably 400 or more, more preferably 600 or more, still more preferably 1000 or more, and the upper limit is preferably 6000 or less, more preferably 4000 or less, still more preferably 3000 or less. It is. Use of a polyalkylene ether glycol having a number average molecular weight within the above range is preferable because good interlayer strength can be obtained. In the present specification, the number average molecular weight refers to that measured by gel permeation chromatography (GPC).

  Although it does not specifically limit as a method of producing the said polyester-type elastomer, For example, (i) C2-C12 aliphatic and / or alicyclic diol, (ii) Aromatic dicarboxylic acid and / or alicyclic A dicarboxylic acid or an ester thereof and (iii) a polyalkylene ether glycol having a number average molecular weight of 400 to 6000 are used as raw materials to obtain an oligomer by an esterification reaction or a transesterification reaction, and then the oligomer is further polycondensed. Can be produced.

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

  As said aromatic dicarboxylic acid and / or alicyclic dicarboxylic acid, what is conventionally used as a raw material of polyester, especially as a raw material of a polyester-type thermoplastic elastomer can be used, for example. Examples thereof include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid and the like. Among these, terephthalic acid and 2,6-naphthalenedicarboxylic acid are preferable, and terephthalic acid is more preferable. These may be used alone or in combination of two or more.

  Among the above-mentioned polyester elastomers, for example, the product name “Primalloy” (manufactured by Mitsubishi Chemical Corporation), the product name “Perprene” (manufactured by Toyobo Co., Ltd.), and the product name “Hytrel” (Toray DuPont) Manufactured) and the like.

  The polyester-based elastomer described above may be modified with an acid or an acid anhydride (hereinafter also referred to as “modified polyester-based elastomer”). The modified polyester elastomer is obtained by modifying a polyester elastomer with a modifier. The modification reaction for obtaining the modified polyester elastomer is performed, for example, by reacting the polyester elastomer with an α, β-ethylenically unsaturated carboxylic acid as a modifier. In the modification reaction, it is preferable to use a radical generator.

  Examples of the α, β-ethylenically unsaturated carboxylic acid include unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrofumaric acid, itaconic acid, citraconic acid, crotonic acid, and isocrotonic acid; succinic acid 2 -Octen-1-yl anhydride, 2-dodecen-1-yl anhydride, succinic acid 2-octadecen-1-yl anhydride, maleic anhydride, 2,3-dimethylmaleic anhydride, bromomalein Acid anhydride, dichloromaleic acid anhydride, citraconic acid anhydride, itaconic acid anhydride, 1-butene-3,4-dicarboxylic acid anhydride, 1-cyclopentene-1,2-dicarboxylic acid anhydride, 1,2, 3,6-tetrahydrophthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, exo-3,6-epoxy-1,2,3,6-tetra Hydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, methyl-5-norbornene-2,3-dicarboxylic anhydride, endo-bicyclo [2.2.2] oct-5-ene-2 , 3-dicarboxylic acid anhydride, and unsaturated carboxylic acid anhydrides such as bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic acid anhydride. Of these, acid anhydrides are preferred because of their high reactivity. These may be used alone or in combination of two or more.

  Examples of the radical generator include t-butyl hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-bis ( Tertiary butyloxy) hexane, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxybenzoate, benzoyl peroxide, dicumyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene Organic and inorganic peroxides such as dibutyl peroxide, methyl ethyl ketone peroxide, potassium peroxide, hydrogen peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (isobutylamide) dihalide, 2,2′-azobis [2-methyl-N- (2-hydride Kishiechiru) propionamide], azo compounds such as azodi -t- butane, carbon radical generating agents such as dicumyl like. These may be used alone or in combination of two or more.

  Next, the ethylene-based copolymer (b) will be described. Examples of the ethylene copolymer include ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-ethyl methacrylate copolymer. Copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate-maleic anhydride terpolymer, ethylene-ethyl acrylate-maleic anhydride terpolymer, ethylene -Glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl methacrylate terpolymer, ethylene-ethyl acrylate-glycidyl methacrylate terpolymer. Among them, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer Polymers and ethylene-methyl methacrylate copolymers can be suitably used.

  The ethylene copolymer has an ethylene unit content of 50 mol% or more and 95 mol% or less, preferably 60 mol% or more and 85 mol% or less. An ethylene unit content of 50 mol% or more is preferable because the rigidity of the entire film can be maintained satisfactorily. On the other hand, if the ethylene unit content is 95 mol% or less, the flexibility can be sufficiently maintained, and when a stress is applied to the film, a buffering action against the stress generated between the surface layer and the intermediate layer works. , Delamination can be suppressed.

  As the ethylene-based copolymer, those having an MFR (JISK7210, temperature: 190 ° C., load: 21.18 N) of 0.1 g / 10 min or more and 10 g / 10 min or less are suitably used. When the MFR is 0.1 g / 10 min or more, the extrudability can be maintained satisfactorily. On the other hand, when the MFR is 10 g / 10 min or less, the thickness unevenness of the laminated film and the mechanical strength are hardly lowered, which is preferable.

  The ethylene-based copolymer is an “ethylene-vinyl acetate-maleic anhydride terpolymer” as “Bondyne” (manufactured by Sumitomo Chemical Co., Ltd.), ethylene-glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl methacrylate tri “Bond First” (manufactured by Sumitomo Chemical Co., Ltd.) and the like are commercially available as an original copolymer, an ethylene-ethyl acrylate-glycidyl methacrylate terpolymer.

  Next, the modified polyolefin resin (c) will be described. In the present invention, the modified polyolefin resin capable of constituting the adhesive layer refers to a resin mainly composed of an unsaturated carboxylic acid or an anhydride thereof, or a polyolefin modified with a silane coupling agent. As unsaturated carboxylic acid or its anhydride, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, itaconic acid, itaconic anhydride, or derivatives thereof, or the above various acids Examples include ester compounds, reaction products of a polymer having a group capable of reacting with these acids in the molecule and an acid. These metal salts can also be used. Among these, maleic anhydride is more preferably used. In addition, a modified polyolefin resin can be used individually or in mixture of 2 or more types, respectively.

  Examples of the silane coupling agent include vinyltriethoxysilane, methacryloyloxytrimethoxysilane, and γ-methacryloyloxypropyltriacetyloxysilane.

  In order to produce the modified polyolefin resin, for example, these modified monomers can be copolymerized in the stage of polymerizing the polymer in advance, or these modified monomers can be graft copolymerized with the polymer once polymerized. These modified monomers may be used alone or in combination, and those having a content in the range of 0.1% by mass to 5% by mass are preferably used. Of these, those that have been graft-modified are preferably used.

  As the modified polyolefin resin, specifically, trade names “Admer” (manufactured by Mitsui Chemicals), “Modic” (manufactured by Mitsubishi Chemical) and the like are commercially available.

  Next, the polyamide-based resin (d) will be described. In the present invention, the polyamide-based resin capable of constituting the adhesive layer is mainly composed of amino acid, lactam or diamine and dicarboxylic acid. Representative examples of amino acids as the raw material include 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and the like. Representative examples of lactams include ε-caprolactam and ω-laurolactam. Typical examples of diamines include tetramethylene diamine, hexamethylene diamine, 2-methylpentamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,4- / 2,4,4-trimethylhexamethylene diamine, 5-methylnonamethylenediamine, metaxylylenediamine, paraxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 1-amino-3-aminomethyl-3, 5,5-trimethylcyclohexane, bis (4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, bis (aminopropyl) piperazine, amino Fats such as ethyl piperazine , Alicyclic, include those aromatic. Representative examples of dicarboxylic acids include adipic acid, peric acid, azelaic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5 -Aliphatic, alicyclic and aromatic such as sodium sulfoisophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid and the like.

  As the polyamide-based resin (d), homopolymers or copolymers derived from these raw materials can be used alone or as a mixture. Specifically, homopolymers such as nylon 6, nylon 11, and nylon 12, nylon 6/66, nylon 6/66/610, nylon 6/12, nylon 66/61/6, nylon 6/66/610/12 Or a resin mainly composed of a polyamide-based elastomer or the like based on these copolymers.

  Specifically, the product name “UBESTA” (manufactured by Ube Industries), the product name “Glax” (manufactured by DIC), the product name “Novamid” (manufactured by Mitsubishi Engineering Plastics), and the product name “Hyper Alloy Actimator” (Riken Techno Co., Ltd.) and the like are commercially available.

  The said adhesive layer can also use the copolymer or resin of said (a) thru | or (d) individually or in mixture of 2 or more types. In that case, the content of the copolymers (a) to (d) or the resin can be appropriately determined according to the resin constituting the surface layer and the intermediate layer.

<Intermediate layer>
In the present invention, the resin suitably used as the resin constituting the intermediate layer is a polystyrene resin. The polystyrene resin includes various polystyrene resins, and among them, it is preferable to use a block copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon. The block copolymer described in this specification is a pure block in which the resin is pure for each block, a random block in which the copolymer components are mixed to form a block, and the copolymer component concentration. However, in order to satisfy viscoelastic characteristics, the block portion is preferably a random block or a tapered block.

  Examples of the styrene hydrocarbon in the block copolymer of styrene hydrocarbon and conjugated diene hydrocarbon include styrene, o-methyl styrene, p-methyl styrene, α-methyl styrene, etc. The hydrocarbon block portion may be a homopolymer thereof, a copolymer thereof, or may contain a copolymerizable monomer other than the styrenic hydrocarbon in the block.

  Examples of the conjugated diene hydrocarbon include butadiene, isoprene, 1,3-pentadiene, and the conjugated diene hydrocarbon block portion may be a homopolymer or a copolymer thereof. Alternatively, a copolymerizable monomer other than the conjugated diene hydrocarbon may be included in the block.

  The copolymer of the styrene hydrocarbon and the conjugated diene hydrocarbon is 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more based on the mass of the entire intermediate layer. If the content of the copolymer with respect to the mass of the entire intermediate layer is 50% by mass or more, the effect of the copolymer of the styrene hydrocarbon and the conjugated diene hydrocarbon in the intermediate layer, that is, the shrink finish is sufficient. This is preferable because it can be exhibited.

  One of the block copolymers of styrene hydrocarbons and conjugated diene hydrocarbons preferably used in the present invention is a styrene-butadiene in which the styrene hydrocarbon is styrene and the conjugated diene hydrocarbon is butadiene. -Styrene block copolymer (SBS). SBS preferably has a styrene / butadiene mass% ratio of “95 to 60” / “5 to 40”, and more preferably “90 to 60” / “10 to 40”. The measured value of melt flow rate (MFR) of SBS (measuring conditions: temperature 200 ° C., load 49 N) is preferably 2 g / 10 min or more, more preferably 3 g / 10 min or more, and preferably 15 g / min. It is 10 minutes or less, more preferably 10 g / 10 minutes or less.

  Examples of the styrene-butadiene-styrene block copolymer include Asaflex series (Asahi Kasei Chemicals), Clearen series (Electrochemical Co., Ltd.), K resin (Chevron Phillips), Styrolux (BASF) , Finacria (manufactured by Atofina).

  Another block copolymer preferably used in the present invention is styrene-isoprene-butadiene-styrene block copolymer (SIBS). In SIBS, the mass ratio of styrene / isoprene / butadiene is preferably “60 to 90” / “10 to 40” / “5 to 30”, and “60 to 80” / “10 to 25” / “5”. More preferably, it is ˜20 ”. Further, the measured value of melt flow rate (MFR) of SIBS (measuring conditions: temperature 200 ° C., load 49 N) is preferably 2 g / 10 min or more, more preferably 3 g / 10 min or more, and preferably the upper limit. It is 15 g / 10 min or less, more preferably 10 g / 10 min or less. If the butadiene content and the isoprene content are within the above ranges, the crosslinking reaction of butadiene heated inside the extruder or the like can be suppressed, and the generation of gel-like materials can be suppressed, and also from the viewpoint of the raw material unit price. As the styrene-isoprene-butadiene-styrene block copolymer, for example, Asaflex I series (manufactured by Asahi Kasei Chemicals) is commercially available.

  The block copolymer of styrene-based hydrocarbon and conjugated diene-based hydrocarbon used in the intermediate layer may be a mixture of two or more types. That is, even if the block copolymer of each styrene hydrocarbon and conjugated diene hydrocarbon alone does not satisfy the predetermined viscoelastic property of the present invention shown below, the predetermined viscoelastic property of the present invention is mixed after mixing. A mixture satisfying the above can also be used.

The storage elastic modulus (E ′ (0)) of the styrene hydrocarbon-conjugated diene hydrocarbon copolymer constituting the intermediate layer at 0 ° C. is 5.0 × 10 ⁸ Pa or more, preferably 7.0 × 10. It is preferably ⁸ Pa or more and 1.0 × 10 ⁹ Pa or less. The storage elastic modulus (E ′ (50)) of the styrene hydrocarbon-conjugated diene hydrocarbon copolymer constituting the intermediate layer at 50 ° C. is 1.5 × 10 ⁸ Pa or more, preferably 1.5 × 10. It is desirable that it is ⁸ Pa or more and 2.0 × 10 ⁹ Pa or less. In order to adjust the storage elastic modulus (E ′ (0) and (50)) of the styrene hydrocarbon-conjugated diene hydrocarbon copolymer at 0 ° C. and 50 ° C. to the above range, for example, styrene hydrocarbon -The loss elastic modulus (E ") peak of the conjugated diene hydrocarbon copolymer is present in the range of -80 ° C to 0 ° C, preferably -80 ° C to -20 ° C, or the butadiene block and the styrene block. On the other hand, the storage elastic modulus (E ′ (90)) of the styrene hydrocarbon-conjugated diene hydrocarbon copolymer at 90 ° C. is 1.0 × 10 ⁷ Pa or more. Preferably, it is 5.0 × 10 ⁷ Pa or more and 2.0 × 10 ⁸ Pa or less, and the styrene hydrocarbon-conjugated diene hydrocarbon copolymer at 90 ° C. is 1.0 ×. 10 ⁷ Pa or more In order to achieve this, it can be adjusted by bringing the styrene block such as SBS close to a pure block, and therefore, the butadiene portion of the styrene hydrocarbon-conjugated diene hydrocarbon copolymer used in the intermediate layer of the present invention. The storage elastic modulus (E ′) at 0 ° C., 50 ° C., and 90 ° C. can be adjusted to a predetermined range by making the block structure a random block and making the block structure of the styrene portion close to a pure block. .

  Further, in the present invention, the surface layer, the adhesive layer and the intermediate layer are provided for the purpose of improving / adjusting the physical properties of the moldability, productivity and heat shrinkable laminated film, as long as the effects of the present invention are not significantly impaired. In each layer, inorganic particles such as silica, talc and kaolin, pigments such as titanium oxide and carbon black, flame retardants, weathering stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nuclei Additives such as agents, plasticizers, anti-aging agents can be added as appropriate.

<Layer structure of film>
The film structure of the present invention is not particularly limited as long as it has at least a three-layer structure having an adhesive layer between the surface layer and the intermediate layer. As an example, surface layer / adhesive layer / intermediate layer, surface layer / adhesive layer / intermediate layer / adhesive layer / intermediate layer, surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer, intermediate layer / adhesive layer / surface layer / Adhesive layer / intermediate layer, etc. Among them, a more effective laminated structure is surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer. By adopting this layer structure, the heat shrink property which is the object of the present invention is excellent, the natural shrinkage is small, the transparency is excellent, and the heat shrink property suitable for applications such as shrink wrap, shrink bundled wrapping and shrink labels. A laminated film can be obtained with good productivity and economy.

  Next, a film having a five-layer structure of surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer, which is one of the preferred embodiments of the present invention, will be described.

  The thickness ratio of each layer may be set in consideration of the above-described effects, and is not particularly limited. The thickness ratio of the surface layer to the entire film is 10% or more, preferably 15% or more, more preferably 20%, and the upper limit of the thickness ratio is 70% or less, preferably 60% or less, more preferably 50%. It is as follows. The thickness ratio of the intermediate layer to the entire film is 20% or more, preferably 25% or more, more preferably 30% or more, and the upper limit is 80% or less, preferably 75% or less, more preferably 70% or less. It is. Furthermore, the adhesive layer has a function of 0.5 μm or more, preferably 0.75 μm or more, more preferably 1 μm or more, and the upper limit is desirably 6 μm or less, preferably 5 μm or less. If the thickness ratio of each layer is within the above range, shrink packaging and shrink-bound packaging with excellent film stiffness (rigidity at room temperature), shrink finish, transparency, natural shrinkage, and suppressed delamination of the film And heat shrinkable laminated film suitable for applications such as shrinkage labels can be obtained with a good balance.

  Although the total thickness of the film of the present invention is not particularly limited, it is preferably thinner from the viewpoints of transparency, shrinkage workability, raw material cost, and the like. Specifically, the total thickness of the stretched film is preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less. Further, the lower limit of the total thickness of the film is not particularly limited, but is preferably 20 μm or more in consideration of the handleability of the film.

<Physical and mechanical properties>
The film of the present invention was measured for dynamic viscoelasticity at a measurement temperature in the range of −150 ° C. to 150 ° C. under conditions of a frequency of 10 Hz, a strain of 0.1%, a heating rate of 3 ° C./min, and a chuck spacing of 2.5 cm The storage elastic modulus (E ′) at a temperature of 23 ° C. is 1,100 MPa or more, preferably 1,200 MPa or more, more preferably 1,500 MPa or more, and 3,000 MPa or less, preferably 2,700 MPa. Hereinafter, it is more preferably 2,500 MPa or less. If the storage elastic modulus E ′ is 1,100 MPa or more, the waist as a whole film (rigidity at room temperature) can be increased, the film becomes too soft and easily deformed, and printing, bag making, etc. 2 When the film is stretched due to roll tension during the next processing, or when the film thickness is reduced, when the covered film is covered with a labeling machine etc. This is preferable because problems such as a decrease in yield and the like are unlikely to occur. On the other hand, if the storage elastic modulus E ′ is within 3,000 MPa, the film is hard and hardly stretched, and it is easy to wrinkle during secondary processing. .

  Next, it is important that the film of the present invention has a thermal shrinkage rate of 20% or more in at least one direction when immersed in warm water at 80 ° C. for 10 seconds.

  This is an index for determining the adaptability to the shrinking process in a relatively short time (several seconds to about several tens of seconds) such as the use of shrinkage labels for PET bottles. For example, the required shrinkage rate required for a heat-shrinkable film applied to the use of shrinkage labels for PET bottles varies depending on the shape, but is generally 20% to 70%.

  Further, the shrinkage processing machine that is most commonly used industrially for label mounting of PET bottles is generally called a steam shrinker that uses steam as a heating medium for shrinking. The heat-shrinkable film needs to sufficiently heat-shrink at a temperature as low as possible from the viewpoint of the influence of heat on the object to be coated. Furthermore, with the recent increase in the speed of the labeling process, there has been an increasing demand for shrinking quickly at a lower temperature. In consideration of such industrial productivity, a film having a heat shrinkage rate of 20% or more under the above conditions is preferable because it can sufficiently adhere to the object to be coated within the shrinkage processing time. From these facts, the thermal shrinkage rate when immersed in warm water at 80 ° C. for 10 seconds is at least 20%, preferably at least 30%, more preferably at least 40% in at least one direction, usually the main shrinkage direction. The upper limit is 85% or less, preferably 80% or less, and more preferably 75% or less. In the present specification, the “main shrinkage direction” means a direction in which the thermal shrinkage rate is large in the longitudinal direction (longitudinal direction) of the film and the lateral direction (width direction) of the film. Means a direction corresponding to the outer circumferential direction, and “orthogonal direction” means a direction perpendicular to the main contraction direction.

  When the film of the present invention is used as a heat-shrinkable label, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction is preferably 10% or less when immersed in warm water at 80 ° C. for 10 seconds, It is more preferably 5% or less, and further preferably 3% or less. If the film has a thermal shrinkage rate of 10% or less in the direction perpendicular to the main shrinkage direction, the dimension itself in the direction perpendicular to the main shrinkage direction after shrinkage may be shortened, or the printed pattern or character distortion after shrinkage may occur. In the case of a square bottle, it is preferable because troubles such as vertical sink are unlikely to occur.

  The film of the present invention has a thermal shrinkage rate of 5% or more, preferably 10% or more, more preferably 15% or more when immersed in warm water at 70 ° C. for 10 seconds, and the upper limit is 35%. Below, it is preferably 30% or less, more preferably 25% or less. By setting the thermal shrinkage rate in the main shrinkage direction of the film at 70 ° C. to 5% or more, shrinkage unevenness that can be locally generated when a bottle is attached with a steam shrinker is reduced. As a result, wrinkles, avatars, etc. Formation can be suppressed. Further, by setting the upper limit of the heat shrinkage rate to 35% or less, extreme shrinkage at low temperatures can be suppressed, and for example, natural shrinkage can be kept small even in a high temperature environment such as summer. Further, the thermal shrinkage rate in the direction orthogonal to the main shrinkage direction of the film when immersed in warm water at 70 ° C. for 10 seconds is preferably 10% or less, more preferably 5% or less, and 3% or less. More preferably.

  The film of the present invention has a heat shrinkage rate of 40% or more, preferably 50% or more when immersed in warm water at 90 ° C. for 10 seconds. By adjusting the heat shrinkage rate in the main film shrinkage direction at 90 ° C. as described above, the bottle can be attached to a bottle that requires a high shrinkage rate (an irregular bottle such as a gourd shape).

  In the present invention, the heat shrinkage rate in the main shrinkage direction of the film is 20% to 85% at 80 ° C., 5% to 35% at 70 ° C., and the heat shrinkage rate in the orthogonal direction is 10% or less at 80 ° C. In order to achieve the above, it is important that the resin composition of each layer is within the range specified in the present invention, but the thickness ratio of the surface layer to the entire film is 10% or more, and the thickness of the adhesive layer is It is preferable that the thickness is 6 μm or less, and the stretching ratio is controlled in the range of 2 to 10 times and the stretching temperature in the range of 60 to 130 ° C.

  The natural shrinkage rate of the film of the present invention is desirably as small as possible. Generally, the natural shrinkage rate of a heat-shrinkable film is, for example, a natural shrinkage rate of 3.0% after 30 days storage at 30 ° C. and 50% RH. Is preferably less than 2.0%, more preferably 2.0% or less, and most preferably 1.5% or less. If the natural shrinkage rate under the above conditions is less than 3.0%, even if the produced film is stored for a long period of time, it can be stably attached to a container or the like, and problems are hardly caused in practice. As a means for adjusting the natural shrinkage rate of the film, it is important that the resin composition of each layer is within the range specified in the present invention. In particular, the thickness ratio of the surface layer to the entire film is 10% or more. It is preferable.

  The transparency of the film of the present invention is, for example, when a film having a thickness of 50 μm is measured according to JISK7105, the haze value of the film is preferably 10% or less, more preferably 7% or less. More preferably, it is% or less. If the haze value of the film is 10% or less, the transparency of the film can be obtained and a display effect can be achieved.

  The impact resistance of the film of the present invention is evaluated by the tensile elongation at break, and in a tensile test under an environment of 0 ° C., particularly in the label application, the elongation is 150% or more in the film take-off (flow) direction (MD), preferably Is 200% or more, more preferably 250% or more. If the tensile elongation at break in an environment of 0 ° C. is 100% or more, such a problem that the film is not easily broken at the time of printing and bag making is preferable. Also, when the tension applied to the film increases as the speed of processes such as printing and bag making increases, it is preferable that the tensile breaking elongation is 150% or more, so that it is difficult to break.

  The delamination strength (seal strength) of the film of the present invention is practically measured by the measurement method described in the examples described later. Under a 23 ° C. and 50% RH environment, the test speed is 200 mm in TD by the T-type peeling method. 2N / 15mm width or more, preferably 4N / 15mm width or more, more preferably 6N / 15mm width or more, and 15N / 15mm width or less from the viewpoint of solvent resistance of the film surface. Is preferred. Since the film of the present invention has a delamination strength of at least 2 N / 15 mm, troubles such as peeling of the seal portion during use do not occur. As a means for ensuring the delamination strength of the film, it is important to set the resin composition of each layer within the range specified in the present invention. In particular, the thickness of the adhesive layer is 0.5 μm or more, It is important that the resin is defined by the present invention.

  The film of the present invention can be produced by a known method. The form of the film may be either flat or tube-like, but the flat form is preferable in terms of productivity (a few products can be taken in the width direction of the original film) and printing on the inner surface. . As a method for producing a flat film, for example, a resin is melted by using a plurality of extruders, co-extruded from a T die, solidified by cooling with a chilled roll, roll-stretched in the vertical direction, and tenter-stretched in the horizontal direction. An example is a method of obtaining a film by winding, annealing, cooling, and winding with a winder (corona discharge treatment is applied to the surface when printing is performed). Moreover, the method of cutting open the film manufactured by the tubular method and making it flat is also applicable.

  In applications where the stretching ratio is contracted in two directions, such as for overlap, the vertical direction is 2 to 10 times, the horizontal direction is 2 to 10 times, preferably the vertical direction is 3 to 6 times, and the horizontal direction Is about 3 to 6 times. On the other hand, in applications such as heat-shrinkable labels that shrink mainly in one direction, the direction corresponding to the main shrinkage direction is 2 to 10 times, preferably 4 to 8 times, and the direction orthogonal to it is 1 or more times. It is desirable to select a magnification ratio that is not more than 2 times (1 time indicates that the film is not stretched), preferably 1.1 times or more and 1.5 times or less, which is substantially in the category of uniaxial stretching. A biaxially stretched film stretched at a stretch ratio within the above range does not have an excessively large thermal shrinkage rate in the direction orthogonal to the main shrinkage direction.For example, when used as a shrinkage label, It is preferable because the so-called vertical shrinkage phenomenon, in which the film is thermally contracted in the vertical direction, can be suppressed.

  The stretching temperature needs to be changed depending on the glass transition temperature of the resin used and the properties required for the heat-shrinkable film, but is generally 60 ° C. or higher, preferably 70 ° C. or higher, and the upper limit is 130 ° C. or lower, preferably 110 ° C. It is controlled within the following range. The draw ratio is 1.5 times to 10 times, preferably 3 times to 7 times, preferably 3 times to 7 times in the main shrinkage direction, depending on the characteristics of the resin used, the stretching means, the stretching temperature, the target product form, etc. Preferably, it is appropriately determined in the direction of one axis or two axes within a range of 3 to 5 times. Even in the case of uniaxial stretching in the transverse direction, it is also effective to impart weak stretching of about 1.05 to 1.8 times in the longitudinal direction for the purpose of improving the mechanical properties of the film. Next, the stretched film is subjected to a heat treatment or relaxation treatment at a temperature of about 50 ° C. or more and 100 ° C. or less for the purpose of reducing the natural shrinkage rate or improving the heat shrink property, if necessary. It cools rapidly within the time not to relax, and becomes a heat-shrinkable film.

  Further, the film of the present invention can be subjected to surface treatment such as corona treatment, printing, coating, vapor deposition, and surface treatment as needed, and further, bag making processing and perforation processing using various solvents and heat sealing.

  The film of the present invention is processed from a flat shape to a cylindrical shape or the like according to an object to be packaged and provided for packaging. When printing is required in a cylindrical container such as a plastic bottle, first print the required image on one side of a wide flat film wound up on a roll, and then cut it to the required width while the print side is inside. The center seal (the shape of the seal portion is a so-called envelope) may be folded into a cylindrical shape. As the center sealing method, an organic solvent bonding method, a heat sealing method, an adhesive method, and an impulse sealer method can be considered. Among these, from the viewpoint of productivity and appearance, an adhesion method using an organic solvent is preferably used.

<Molded products, heat-shrinkable labels and containers>
The film of the present invention is excellent in low-temperature shrinkage, shrinkage finish, transparency, natural shrinkage, etc. of the film, so its use is not particularly limited. By forming a functional layer, it can be used as various molded products such as bottles (blow bottles), trays, lunch boxes, prepared food containers, dairy products containers and the like. In particular, when the film of the present invention is used as a heat-shrinkable label for food containers (for example, PET bottles, glass bottles, preferably PET bottles for soft drinks or foods), a complicated shape (for example, a cylinder with a narrow center, a corner A rectangular column, pentagonal column, hexagonal column, etc.) can be adhered to the shape, and a container with a beautiful label without wrinkles or avatars can be obtained. The molded article and container of the present invention can be produced by using a normal molding method.

  Since the film of the present invention has excellent low-temperature shrinkage and shrinkage finish properties, in addition to the heat-shrinkable label material of a plastic molded product that is deformed when heated to a high temperature, the coefficient of thermal expansion, water absorption, etc. The material is very different from the heat shrinkable film, such as metal, porcelain, glass, paper, polyethylene, polypropylene, polybutene and other polyolefin resins, polymethacrylate resin, polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate, etc. It can be suitably used as a heat-shrinkable label material for a package (container) using at least one selected from polyester-based resins and polyamide-based resins as a constituent material.

  As a material constituting the plastic package in which the film of the present invention can be used, in addition to the above resins, polystyrene, rubber-modified impact-resistant polystyrene (HIPS), styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, Styrene-maleic anhydride copolymer, acrylonitrile-butadiene-styrene copolymer (ABS), (meth) acrylic acid-butadiene-styrene copolymer (MBS), polyvinyl chloride resin, phenol resin, urea resin, melamine Examples thereof include resins, epoxy resins, unsaturated polyester resins, and silicone resins. These plastic packages may be a mixture of two or more resins or a laminate.

Hereinafter, the present invention will be described in more detail with reference to examples.
In addition, measurement and evaluation of the measured value shown in the Example were performed as follows. In the examples, the take-up (flow) direction of the laminated film is described as the “longitudinal” direction, and the perpendicular direction thereof is described as the “lateral” direction.

(1) Storage elastic modulus (E ')
The obtained film was accurately cut into a size of 4 mm wide × 60 mm long to prepare a sample. Using a viscoelastic spectrometer DVA-200 (manufactured by IT Measurement Co., Ltd.), the measurement temperature is −150 under the conditions of vibration frequency 10 Hz, strain 0.1%, heating rate 3 ° C./min, and chuck 2.5 cm. The dynamic viscoelasticity was measured in the longitudinal direction in the range of from ° C to 150 ° C. In addition, as a storage elastic modulus, the storage elastic modulus in 23 degreeC was shown.

(2) Thermal contraction rate The obtained film was cut into a size of 100 mm in length and 100 mm in width, and immersed in a hot water bath at 70 ° C., 80 ° C. and 90 ° C. for 10 seconds, and the shrinkage was measured. For the thermal shrinkage, the ratio of shrinkage to the original size before shrinkage was expressed in% in the vertical and horizontal directions.

(3) Natural shrinkage rate The obtained film was cut into a size of 100 mm in length and 1000 mm in width and left in a constant temperature bath at 30 ° C. for 30 days to measure the amount of shrinkage relative to the original size before shrinkage in the main shrinkage direction. The ratio was expressed as a% value.

(4) Haze value In accordance with JIS K7105, the haze value of the film is measured at a film thickness of 50 μm, and 15% or more is indicated as “×”, 5% or more and 15% as “◯”, and less than 5% as “◎”. evaluated.

(5) Interlaminar adhesive strength The obtained film was cut into a size of 165 mm in length and 235 mm in width, 10 mm on both ends of the film in the horizontal direction, and bonded with a methyl ethyl ketone (MEK) solvent to prepare a cylindrical film. This cylindrical film was attached to a cylindrical PET bottle having a capacity of 1.5 liters, and passed through the steam heating type 3.2 m (3 zones) shrink tunnel for about 5 seconds without rotating. . The tunnel ambient temperature in each zone was controlled in the range of 70 ° C. to 85 ° C. by adjusting the amount of steam with a steam valve. The state of the film at the time of bottle mounting was confirmed visually and evaluated according to the following criteria.
A: There is no delamination even after the bottle is mounted.
○: Slight delamination occurs at the seal when the bottle is installed.
X: When the bottle is mounted, delamination occurs on the entire seal portion.

(6) Shrinkage finish A film printed with a 10 mm-interval grid is cut into a size of 165 mm in length and 235 mm in width, 10 mm on both sides of the film in the horizontal direction, and bonded with methyl ethyl ketone (MEK) solvent to produce a cylindrical film did. This cylindrical film was attached to a 500 ml square PET bottle, and passed through the steam heating type 3.2 m (3 zone) shrink tunnel for about 5 seconds without rotating. The atmospheric temperature in the tunnel in each zone was controlled in the range from 70 ° C. to 100 ° C. by adjusting the amount of steam with a steam valve. After film coating, the following criteria were evaluated.
A: Shrinkage is sufficient, and wrinkles, avatars and lattice distortion do not occur.
○: Shrinkage is sufficient, but wrinkles, avatars, or lattice distortions occur in some places.
X: Shrinkage is sufficient, but wrinkles, avatars, and lattice distortions are remarkable. Or shrinkage | contraction is not enough and the coating to a bottle is inadequate.

Example 1
Polystyrene resin as intermediate layer: SBS (styrene / butadiene = 76/24 (mass%), storage elastic modulus E ′ = 7 × 10 ⁸ Pa at 0 ° C., peak temperature E ″ of loss elastic modulus = 103 ° C., 103 C., hereinafter abbreviated as “SBS1”). Further, as a surface layer, a polylactic acid resin, “NatureWorks 4060 (L body / D body ratio = 88/12)” (hereinafter abbreviated as “PLA1”) manufactured by NatureWorks LLC, a polylactic acid resin, “NatureWorks 4042 (L Body / D body ratio = 95/5) (hereinafter abbreviated as “PLA2”), “Plamate PD-150” (hereinafter abbreviated as “PLA3”) manufactured by DIC, and PLA1 / PLA2 / PLA3 = 43. What mixed in the mass ratio of / 47/10 was used. Furthermore, as the adhesive layer, a polyester resin, a product name “Primalloy C1910N” (hereinafter abbreviated as AD1) manufactured by Mitsubishi Chemical Corporation was used. Each resin was put into a separate single screw extruder manufactured by Mitsubishi Heavy Industries, Ltd., and after melt mixing at a set temperature of 200 ° C., the thickness of each layer was surface layer / adhesive layer / intermediate layer / adhesive layer / surface layer = 25 μm / 5 μm / It was co-extruded from a three-kind five-layer die so as to be 190 μm / 5 μm / 25 μm, taken up with a cast roll at 50 ° C., cooled and solidified to obtain an unstretched laminated sheet having a width of 200 mm and a thickness of 250 μm. Next, the film was stretched 5.0 times in the transverse uniaxial direction at a preheating temperature of 80 ° C. and a stretching temperature of 80 ° C. with a film tenter manufactured by Kyoto Machine Co., Ltd., and then quenched with cold air to obtain a heat-shrinkable laminated film having a thickness of 50 μm. It was. The results of evaluating the obtained film are shown in Table 1.

(Example 2)
As shown in Table 1, in Example 1, the polyester resin used in the adhesive layer was changed to an ethylene copolymer “bond first 7M” (hereinafter abbreviated as AD2) manufactured by Sumitomo Chemical Co., Ltd. A heat-shrinkable laminated film was obtained in the same manner as in 1.

Example 3
As shown in Table 1, in Example 1, except that the polyester resin used for the adhesive layer was changed to Mitsui Chemicals, modified polyolefin resin, trade name “Admer SE800” (hereinafter abbreviated as AD3). A heat-shrinkable laminated film was obtained in the same manner as in Example 1.

Example 4
As shown in Table 1, heat was applied in the same manner as in Example 1 except that the polyester resin used in the adhesive layer in Example 1 was changed to Ube Industries' product name “UBESTA3030XA” (hereinafter abbreviated as AD4). A shrinkable laminated film was obtained.

(Example 5)
As shown in Table 1, in Example 1, the polystyrene resin used for the intermediate layer was SBS2 (styrene / butadiene = 77/23 (mass%), storage elastic modulus at 0 ° C. E ′ = 1.5 × 10 ^9. A heat-shrinkable laminated film was obtained in the same manner as in Example 1, except that the peak temperature E ″ of loss elastic modulus was E ″ = − 35 ° C., 90 ° C., hereinafter abbreviated as “SBS2”.

(Example 6)
As shown in Table 1, in Example 1, the same as Example 1 except that the polylactic acid resin used as the surface layer was changed to a mixture of PLA1 / PLA2 / PLA3 = 60/30/10. A heat-shrinkable laminated film was obtained.

(Comparative example)
As shown in Table 1, in Example 1, there was no adhesive layer, and the thickness of each layer in the unstretched laminated sheet was as follows: surface layer / intermediate layer / surface layer = 30 μm / 140 μm / 30 μm. Similarly, a heat-shrinkable laminated film was obtained. The results of evaluating the obtained film are shown in Table 1. There was a problem that peeling occurred between the layers during shrinkage.

  From Table 1, the films of Examples 1 to 6 constituted by layers within the range defined by the present invention are waist (tensile elastic modulus of laminated film), heat shrinkage rate, natural shrinkage rate, transparency, delamination strength. And the shrinkage finish was good. On the other hand, when there was no adhesive layer (comparative example), sufficient delamination strength could not be obtained, and delamination occurred during the test. Thus, the film of the present invention is excellent in rigidity, excellent in heat shrink characteristics, small in natural shrinkage, excellent in interlayer strength and shrink finish, and suitable for uses such as shrink wrapping, shrink tying wrapping and heat shrinkable labels. It turns out that it is a heat shrinkable laminated film.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. However, it can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification, and a heat-shrinkable laminated film with such a change, and a molded article using the film as a base material And heat-shrinkable labels, and containers equipped with the molded articles and labels should also be understood as being within the scope of the present invention.

  Since the film of the present invention has excellent low temperature shrinkage, rigidity, shrinkage finish, and low natural shrinkage, it can be suitably used for molded products that require heat shrinkage, particularly shrink labels. Moreover, since the PLA resin used in the present invention is a plant-derived resin, it is suitable for promoting the utilization of biomass and aiming for a recycling society.

Claims (10)

A heat-shrinkable laminated film obtained by stretching a film in which a surface layer mainly composed of a polylactic acid-based resin is laminated on an intermediate layer containing a polystyrene-based resin via an adhesive layer in at least one direction. A heat-shrinkable laminated film, wherein the layer is composed of at least one copolymer or resin selected from the group consisting of the following (a), (b), (c) and (d).
(A) a block copolymer comprising a polyester and a polyalkylene ether glycol or a polyester resin obtained by modifying the copolymer with an acid or an acid anhydride,
(B) at least one selected from the group consisting of vinyl acetate, acrylic acid, methacrylic acid, ethyl acrylate, ethyl methacrylate, methyl acrylate, methyl methacrylate, maleic anhydride, and glycidyl methacrylate, and ethylene An ethylene copolymer, or a mixture of the copolymers,
(C) modified polyolefin resin,
(D) a polyamide-based resin, The heat-shrinkable laminated film according to claim 1, wherein the polystyrene-based resin is a styrene-based hydrocarbon-conjugated diene-based hydrocarbon copolymer. The said polystyrene resin is a mixed resin of a styrene hydrocarbon-conjugated diene hydrocarbon copolymer and a styrene hydrocarbon-aliphatic unsaturated carboxylic ester copolymer. Heat shrinkable laminated film. The styrenic hydrocarbon-conjugated diene hydrocarbon copolymer is a styrene-butadiene-styrene copolymer, a styrene-isoprene-butadiene-styrene copolymer, or a mixture thereof. The heat-shrinkable laminated film as described. The polylactic acid resin is a copolymer of D-lactic acid and L-lactic acid, and the ratio of D-lactic acid to L-lactic acid (D / L ratio) is 3/97 to 15/85, or 85 It is / 15-97 / 3, The heat-shrinkable laminated film in any one of Claims 1-4. The laminated film is stretched in at least one direction, and the thermal shrinkage rate in the main film shrinkage direction when immersed in warm water at 80 ° C for 10 seconds is 20% or more, according to any one of claims 1 to 5. Heat shrinkable laminated film. The heat-shrinkable laminated film according to any one of claims 1 to 6, wherein the thickness ratio of the intermediate layer to the thickness of the entire film is from 10% to 70%. A molded article using the heat-shrinkable laminated film according to claim 1 as a base material. The heat-shrinkable label using the heat-shrinkable laminated film in any one of Claims 1-7 as a base material. A container equipped with the molded product according to claim 8 or the heat-shrinkable label according to claim 9.