JP2008044364A - Heat-shrinkable laminated film, molded product using it, heat-shrinkable label and container on which molded product or heat-shrinkable label is mounted - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable laminated film excellent in low temperature shrinkability, shrink finish properties and transparency and suitable for use in a heat-shrinkable label or the like capable of keeping good transparency even at the time of regeneration and addition, and a plastic container on which the heat-shrinkable label comprising the heat-shrinkable laminated film is mounted. <P>SOLUTION: In the heat-shrinkable laminated film obtained by stretching a laminated film composed of at least two layers, that are, a layer (I) and a layer (II) at least in one direction, the layer (I) is constituted of a polylactic acid resin and the layer (II) is constituted of a polypropylene resin of which the melting point is 90-130°C and the content of a propylene monomer unit is 80-99 mass% as a main component respectively. The heat shrinkability in the main shrink direction of the heat-shrinkable laminated film when immersed in hot water of 80°C for 10 sec is set to 20% or above. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable laminated film using a polyolefin-based resin and a polylactic acid-based resin, a molded product using the film, a heat-shrinkable label, and a container equipped with the molded product or the heat-shrinkable label. More specifically, the present invention adds a recyclable resin having excellent heat shrinkage properties, transparency, shrinkage finish properties, and generated from trimming loss such as film ears (hereinafter referred to as “regeneration addition”). .) Heat-shrinkable laminated film suitable for applications such as shrinkable packaging, shrink-bound packaging and shrinkable labels, as well as molded products, heat-shrinkable labels, and molded products or heat-shrinkable labels using the films Related to the container.

  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 may be attached for the purpose of differentiating from other products and improving the visibility of the products. Conventionally, polyvinyl chloride, polyester, polystyrene, polyolefin or the like has been used as a material for the heat-shrinkable label.

  Polyester-based heat-shrinkable film has low stiffness at room temperature (rigidity at room temperature), has low-temperature shrinkability, and has very good natural shrinkage. Yes. However, the polyester-based heat-shrinkable film has a problem that shrinkage spots and wrinkles are easily generated during heat-shrinkage as compared with the polyvinyl chloride-based heat-shrinkable film.

  Polyolefin-based heat-shrinkable films, mainly made of polypropylene resin and polyethylene resin, have also been developed. However, although shrinkage and wrinkles are less likely to occur, sufficient low-temperature heat-shrinkability cannot be obtained. There are problems such as inferiority, and difficulty in sealing with an organic solvent when making a cylindrical bag for use as a PET bottle label.

  For the purpose of solving the problems in the above-described polyolefin heat-shrinkable film, a heat-shrinkable film in which a polyolefin resin is used as a core layer and a polyester resin is laminated on both sides via an adhesive resin layer has been reported (Patent Document 1). reference). However, since this heat-shrinkable film has poor compatibility between the polyester resin of the double-sided layer and the polyolefin resin of the core layer, there has been a problem that the transparency of the whole film is extremely lowered when regenerated and added. .

On the other hand, a shrink sheet having a layer mainly composed of a polyolefin resin and a layer mainly composed of a polylactic acid resin has also been reported (see Patent Document 2). However, this shrinkable sheet is made by the inflation method for the purpose of shrink-wrapping films such as lunch boxes and side dishes sold at convenience stores, etc., and as a heat-shrinkable label application that requires low-temperature high-shrinkability When used, there is a problem that sufficient low temperature shrinkage cannot be obtained. Furthermore, since this shrinkable sheet is a laminated sheet having a polylactic acid resin layer as a core material and a polyolefin resin layer on both outer layers, it is inferior in sealing properties and solvent resistance when making cylindrical seal bags, There was a problem that it was not suitable for shrinkable label applications. Furthermore, when this shrinkable sheet is regenerated and added, light scattering occurs at the interface between the polyolefin resin and the polylactic acid resin, so that there is a problem that the transparency of the film is lowered and good transparency cannot be obtained. .
JP 2002-347184 A JP 2002-019053 A

  The present invention has been made in order to solve the above-described problems of the prior art, and the object of the present invention is to have excellent heat shrinkage characteristics, transparency, shrinkage finish properties, and good transparency even when regenerated. An object of the present invention is to provide a heat-shrinkable laminated film suitable for uses such as shrink wrap, shrink restraint wrap, and shrink label that can maintain the properties.

  Another object of the present invention is to provide a molded product using the film suitable for uses such as shrink wrapping, shrink tying wrapping, and a shrink label, a heat shrinkable label, and a container equipped with the molded product or the heat shrinkable label. Is to provide.

  In order to solve the above problems, the present inventor can maintain good transparency even when a polylactic acid resin is blended with a polyolefin resin layer in a laminated film having a polylactic acid resin layer and a polyolefin resin layer. As a result of intensive studies on the system, it was found that good transparency can be maintained when a polylactic acid resin is blended with a specific polyolefin resin, and the present invention has been completed.

  That is, the subject of this invention is the (I) layer which has a polylactic acid-type resin as a main component, Melting | fusing point is 90 to 130 degreeC, and the content rate of a propylene monomer unit is 80 to 99 mass%. A heat-shrinkable film obtained by stretching at least one layer of a laminated film composed of at least two layers with a (II) layer mainly composed of a polypropylene-based resin, each layer having the following resin as a main component at 80 ° C. This is solved by a heat-shrinkable laminated film (hereinafter also referred to as “the film of the present invention”), which has a heat shrinkage rate of 20% or more when immersed in warm water for 10 seconds. .

  In the film of the present invention, the (II) layer is preferably a layer containing 3 to 30 parts by mass of a polylactic acid-based resin with respect to 100 parts by mass of the polypropylene resin.

  The fill of the present invention is a resin comprising a copolymer of D-lactic acid and L-lactic acid as the polylactic acid resin, and the composition of D-lactic acid and L-lactic acid is D-lactic acid / L-lactic acid = 0. It is preferable to use a polylactic acid resin having a ratio of 2 / 99.8 to 25/75 or 75/25 to 99.8 / 0.2.

  Moreover, the film of this invention can also have (III) layer which has an adhesive resin as a main component at least one layer between (I) layer and (II) layer.

  The film of the present invention preferably has a haze value of 10% or less according to JIS K7105.

  The film of the present invention preferably has a tensile elongation at break of 100% or more and 500% or less in a direction perpendicular to the main shrinkage direction measured under conditions of an atmospheric temperature of 0 ° C. and a tensile speed of 100 mm / min.

  Another object of the present invention is solved by a molded article using the shrinkable film as a base material, a heat-shrinkable label, and a container equipped with the molded article or the heat-shrinkable label.

  The film of the present invention comprises (I) a layer mainly composed of a polylactic acid resin, and (II) a layer mainly composed of a polyolefin resin composed of a specific melting point and a specific propylene monomer unit. Have. Therefore, if it is the present invention, it has excellent heat shrink characteristics and shrink finish, and is suitable for applications such as shrink packaging, shrink restraint packaging, and shrink labels that can maintain excellent transparency even when re-added. A heat-shrinkable laminated film can be provided.

  Furthermore, according to the present invention, it is possible to provide a molded article and a heat-shrinkable label that are suitable for applications such as shrink-wrapping, shrink-bound packaging, and shrink-label having excellent shrink finish and excellent transparency. Furthermore, according to the present invention, it can be fixed in a desired position regardless of the shape of the attachment, and there are no abnormalities such as wrinkles, occurrence of avatars, insufficient shrinkage, etc., and it has a transparent and beautiful appearance. A container equipped with a molded article or a heat-shrinkable label can be provided.

  Hereinafter, the film of the invention, a molded product using the film of the present invention as a base material, a heat-shrinkable label, and a container equipped with the molded product or the heat-shrinkable label (hereinafter, “molded product of the present invention” “book” The “label of the invention” and the “molded product of the present invention” 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, and “orthogonal direction” means a direction perpendicular to the main contraction direction.

[Heat-shrinkable laminated film]
The film of the present invention includes a (I) layer containing a polylactic acid resin as a main component, and a polypropylene system having a melting point of 90 ° C. or more and 130 ° C. or less and a propylene monomer unit content of 80% by mass or more and 99% by mass or less. It is a heat-shrinkable film formed by stretching a laminated film composed of at least two layers of (II) layers mainly composed of a resin in at least one direction.

<(I) layer>
In the present invention, the (I) layer is composed mainly of a polylactic acid resin (hereinafter referred to as “PLA”). PLA which can be used in the (I) 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 PLA used in the present invention is a copolymer of D-lactic acid and L-lactic acid or a mixture of homopolymers of D-lactic acid and L-lactic acid, the constitution of D-lactic acid and L-lactic acid is D-lactic acid. / L-lactic acid = 0.2 / 99.8 to 25/75 or 75/25 to 99.8 / 0.2, preferably D-lactic acid / L-lactic acid = 0.5 / 99.5 20/80 or 80/20 to 99.5 / 0.5 is more preferable, and D-lactic acid / L-lactic acid = 1/99 to 15/85 or 85/15 to 99/1 is further included. preferable.

  PLA consisting of D-lactic acid 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, the constitution of D-lactic acid and L-lactic acid of PLA used in the present invention is D-lactic acid / L-lactic acid = 0.5 / 99.5 to 20/80 or D-lactic acid / L-lactic acid = It is preferable that it is 80 / 20-99.5 / 0.5.

  In the present invention, as a PLA, copolymers of D-lactic acid and L-lactic acid having different copolymerization ratios can be blended and used. In that case, what is necessary is just to adjust so that the value which averaged the copolymerization ratio of D-lactic acid of a some lactic acid-type polymer and L-lactic acid may enter in the said range. By mixing two or more PLAs having different copolymer ratios of D-lactic acid and L-lactic acid according to the intended use and adjusting the crystallinity, it is possible to balance heat resistance and heat shrinkage characteristics. .

  The PLA used in the (I) layer may be a copolymer of lactic acid (D-lactic acid, L-lactic acid) and α-hydroxycarboxylic acid, aliphatic diol, or aliphatic dicarboxylic acid. Here, as the “α-hydroxycarboxylic acid” copolymerized with PLA, optical isomers of lactic acid (D-lactic acid for L-lactic acid and L-lactic acid for D-lactic acid, respectively) , Glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methylbutyric acid, 2-hydroxy Bifunctional aliphatic hydroxycarboxylic acids such as caprolactone, and lactones such as caprolactone, butyl lactone, and valerolactone. Examples of the “aliphatic diol” copolymerized with PLA include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the “aliphatic dicarboxylic acid” to be copolymerized include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid.

  The copolymerization ratio of the copolymer of lactic acid and α-hydroxycarboxylic acid, aliphatic diol, or aliphatic dicarboxylic acid is lactic acid: α-hydroxycarboxylic acid, aliphatic diol or aliphatic dicarboxylic acid = 90: 10-10. : 90 is preferable, more preferably 80:20 to 20:80, and still more preferably 30:70 to 70:30. If the copolymerization ratio is within the above range, a film having a good balance of physical properties such as rigidity, transparency and impact resistance can be obtained.

  The PLA 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, PLA having an arbitrary composition can be obtained by directly dehydrating condensation polymerization of D-lactic acid, L-lactic acid, or a mixture thereof. In addition, in the ring-opening polymerization method, PLA having an arbitrary composition is obtained by ring-opening polymerization of lactide, which is a cyclic dimer of lactic acid, in the presence of a predetermined catalyst while using a polymerization regulator as necessary. Can be obtained. The lactide includes DL-lactide, which is a dimer of L-lactic acid, and PLA having any composition and crystallinity can be obtained by mixing and polymerizing these as necessary. 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 PLA used in the layer (I) is 20,000 or more, preferably 40,000 or more, more preferably 60,000 or more, and the upper limit is 400,000 or less, preferably 350. , 000 or less, more preferably 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.

  Examples of the PLA commercial products include “NatureWorks” (manufactured by NatureWorks LLC) and “LACEA” (manufactured by Mitsui Chemicals).

  In addition, in order to improve the impact resistance of the film, it is preferable to add a rubber component other than PLA to the layer (I) within a range that does not impair the shrinkage properties and the rigidity (back strength) of the film. . Although this rubber component is not particularly limited, aliphatic polyesters other than PLA, aromatic-aliphatic polyesters, diol / dicarboxylic acid / PLA copolymers and core / shell structure rubbers, and ethylene / vinyl acetate copolymer Copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene- (meth) acrylic acid copolymer (EMAA), ethylene-methyl (meth) acrylic acid A copolymer (EMMA) etc. can be used conveniently.

  When an aliphatic polyester other than PLA is used as the rubber component, the aliphatic polyester includes an aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid, and cyclic lactones. Aliphatic polyesters obtained by ring-opening polymerization, synthetic aliphatic polyesters and the like. Examples of the hydroxycarboxylic acid that is a structural unit of the polyhydroxycarboxylic acid include 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, and 2-hydroxy-3. -Homopolymers and copolymers of hydroxycarboxylic acids such as methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaprolacuronic acid.

  As the aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid, one or two or more kinds of aliphatic polyesters 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. 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 suberic 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 the PLA, “Bionole” (manufactured by Showa Polymer Co., Ltd.) obtained by polymerizing succinic acid, 1,4-butanediol and adipic acid is commercially obtained. be able to. Moreover, as a thing obtained by ring-opening condensation of (epsilon) -caprolactone, "Cell Green" (made by Daicel Chemical Industries Ltd.) is mentioned.

  Next, when an aromatic-aliphatic polyester is used as the rubber component, examples of the aromatic-aliphatic polyester include those whose crystallinity is lowered by introducing an aromatic ring between aliphatic chains. Can do. 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. 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. As a copolymer of tetramethylene adipate and terephthalate, EasterBio (manufactured by Eastman Chemicals) and as a copolymer of polybutylene adipate and terephthalate, Ecoflex (manufactured by BASF) can be obtained commercially.

  Next, when a copolymer of PLA, diol, and dicarboxylic acid is used as the rubber component, the structure includes a random copolymer, a block copolymer, and a graft copolymer, 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” (Mitsubishi Chemical Co., Ltd.), and a specific example of the block copolymer or graft copolymer is “Plamate” (Dainippon Ink Chemical Co., Ltd.). Is mentioned.

  A method for producing a copolymer of PLA, diol and dicarboxylic acid is not particularly limited, but a polyester or polyether polyol having a structure obtained by dehydration condensation of diol and dicarboxylic acid is subjected to ring-opening polymerization or transesterification with lactide. The method of obtaining is 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 PLA, 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, when the core-shell structure rubber is used as the rubber component, examples of the core-shell structure rubber include diene-based core-shell polymers such as (meth) acrylic acid-butadiene copolymer and acrylonitrile-butadiene-styrene copolymer, Acrylic core-shell type polymer such as (meth) acrylic acid-styrene-acrylonitrile copolymer, silicone- (meth) acrylic acid-methyl (meth) acrylic acid copolymer, silicone- (meth) acrylic acid-acrylonitrile-styrene Examples thereof include silicone-based core-shell type copolymers such as 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.

  When the (I) layer contains the rubber component, the amount added is 100 parts by mass or less, preferably 80 parts by mass or less, more preferably 100 parts by mass or less, based on 100 parts by mass of the PLA resin contained as the main component of the (I) layer. Is preferably 70 parts by mass or less. If the addition amount of the rubber component is 100 parts by mass or less, the film can be suitably used as a heat-shrink label without impairing the rigidity and transparency of the film, and the lower limit is not particularly limited, but preferably 10 parts by mass or more. It is desirable from the viewpoint of imparting good impact resistance to the film.

<(II) layer>
The (II) layer of the film of the present invention is composed mainly of a polypropylene resin having a melting point of 90 ° C. or more and 130 ° C. or less and a propylene monomer unit content of 80% by mass or more and 99% by mass or less.

  When a heat-shrinkable film is produced using a general polypropylene resin, the polypropylene resin has high crystallinity, and therefore, it has been necessary to process in a relatively high temperature region when thermoforming. Moreover, since general polypropylene resin is inferior in heat shrinkability at low temperature, it is difficult to obtain heat shrink characteristics and flexibility at relatively low temperature when a heat shrinkable film is produced. Furthermore, when PLA is contained in a general polypropylene resin, the general polypropylene resin has a high refractive index, and light scattering occurs at the interface with the PLA, resulting in a problem that the transparency of the entire film is lowered. .

  In the film of the present invention, in order to solve the above-described problem, it is possible to thermoform at a relatively low temperature range from polypropylene resin and to maintain the transparency when PLA is contained. Therefore, a polypropylene resin having a melting point of 90 ° C. or more and 130 ° C. or less and a propylene monomer unit content of 80% by mass or more and 99% by mass or less is used.

  The polypropylene resin has a melting point of 90 ° C. or higher, preferably 95 ° C. or higher, more preferably 100 ° C. or higher, and 130 ° C. or lower, preferably 125 ° C. or lower. If heat-shrinkable film using a polypropylene resin with a melting point within the above range, low-temperature heat-shrinkage characteristics can be obtained, and shrinkage in the orthogonal direction can be suppressed during high-temperature shrinkage. Can be suppressed.

    The content of the propylene monomer unit in the polypropylene resin is 80% by mass or more, preferably 85% by mass or more, more preferably 90% by mass or more, and 99% by mass or less, preferably 97% by mass or less. More preferably, it is 95 mass% or less. If the content of the propylene monomer unit is a film obtained from a polypropylene resin in the above range, the refractive index can be lowered because of low crystallinity, and even when PLA is added to the (II) layer, the interface In addition to being able to maintain transparency by suppressing irregular reflection in the film, it can be obtained from moderate crystallinity and can give the film a waist, heat treatment in a relatively low temperature region is possible, and shrinkage characteristics at a low temperature can be imparted.

  The said polypropylene resin can copolymerize (alpha) -olefin, for example, ethylene, butene, or hexene with a propylene, in order to provide the low temperature characteristic and the softness | flexibility at normal temperature further. Among these, the use of an ethylene-propylene copolymer is particularly preferable because the transparency of the film can be maintained when PLA is contained.

  The polypropylene resin can have a structure such as homo, random, or block, but has a random structure obtained by using a polypropylene resin having a random structure or a metallocene catalyst from the viewpoint of stretchability, transparency, rigidity, and the like. Polypropylene resins are preferred.

  Further, the melt flow rate (MFR) of the polypropylene resin is not particularly limited, but usually MFR (JIS K7210, temperature: 230 ° C., load: 21.2 N (2.16 kg)) is 0. 0.5 g / 10 min or more, preferably 1.0 g / 10 min or more, 15 g / 10 min or less, preferably 10 g / 10 min or less. The MFR of the polypropylene resin can be selected to be similar to the viscosity at the time of melting of the polylactic acid resin in order to obtain a film having a uniform thickness.

  The production method of the polypropylene resin is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst, for example, a multisite catalyst typified by a Ziegler-Natta type catalyst or a single site catalyst typified by a metallocene catalyst. Can be produced by a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method, or the like, or a bulk polymerization method using a radical initiator.

  Examples of the commercially available polypropylene resin include “Wintech” (manufactured by Nippon Polypro) as metallocene polypropylene and “Versify” (manufactured by Dow Chemical) as an ethylene-propylene copolymer. .

  In the present invention, the (II) layer can contain PLA usable in the (I) layer, and further an adhesive resin usable in the (III) layer described later. Thereby, the film of the present invention can be regenerated and added to the (II) layer, and the recyclability of the film can be improved. When the (II) layer contains PLA, the content thereof is 100 parts by mass or less, preferably 80 parts by mass or less, more preferably 100 parts by mass or less with respect to 100 parts by mass of the polypropylene resin contained as the main component of the layer (II). 60 mass parts or less can be contained. Although a minimum is not specifically limited, It is preferable that it is 10 mass parts or more. Since the polypropylene resin used in the present invention has a refractive index lower than that of a general polypropylene resin, the laminated film obtained by setting the PLA content to 100 parts by mass or less with respect to 100 parts by mass of the polyolefin resin. Transparency, rigidity, rupture resistance, shrink finish (cold shrinkage), etc. can be maintained.

  On the other hand, when the (II) layer contains an adhesive resin that can be used in the (III) layer, the upper limit differs depending on the type of adhesive resin, but it is included as a main component of the above (II) layer as a guide 8 parts by mass or less of the adhesive resin, preferably 6 parts by mass or less, and more preferably 5 parts by mass or less can be added to 100 parts by mass of the polypropylene resin. Although a minimum is not specifically limited, It is preferable that it is 1 mass part or more. When the content of the adhesive resin is 8 parts by mass or less with respect to 100 parts by mass of the polyolefin-based resin, the transparency, rupture resistance, shrink finish, and the like of the obtained laminated film can be maintained.

  Further, when PLA is contained in the layer (II), a compatibilizing agent may be added for the purpose of reducing the dispersion diameter of PLA and improving the haze value.

<(III) layer>
The (III) layer constituting the film of the present invention is mainly composed of an adhesive resin that adheres the (I) layer and the (II) layer. The adhesive resin contained as the main component of the (III) layer is not particularly limited as long as it is a resin that can bond the (I) layer and the (II) layer, but is reactive to the PLA of the (I) layer or A resin having both a part having affinity and a part having affinity with the polypropylene resin contained in the (II) layer is preferable, and for example, selected from the group consisting of the following (a), (b) and (c) At least one copolymer or resin can be suitably used.

(A) selected from the group consisting of ethylene monomer units, vinyl acetate, acrylic acid, (meth) acrylic acid, ethyl (meth) acrylate, methyl (meth) acrylic acid, maleic anhydride, and glycidyl methacrylate Copolymer composed of one unit (hereinafter also referred to as “ethylene copolymer”).
(B) Copolymers of soft aromatic hydrocarbons and conjugated diene hydrocarbons or hydrogenated derivatives thereof
(C) Modified polyolefin resin

  First, the ethylene-based copolymer (a) will be described. Examples of the ethylene copolymer include ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene- (meth) acrylic acid copolymer (EMA), and ethylene- (meta ) Ethyl acrylate copolymer (EEA), ethylene-methyl (meth) acrylic acid copolymer (EMMA), ethylene-vinyl acetate-maleic anhydride terpolymer, ethylene-ethyl acrylate-maleic anhydride terpolymer Examples thereof include an original copolymer, an ethylene-glycidyl methacrylate copolymer, an ethylene-vinyl acetate-glycidyl methacrylate terpolymer, and an ethylene-ethyl acrylate-glycidyl methacrylate terpolymer. Among them, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene- (meth) acrylic acid copolymer (EMA), An ethylene-methyl (meth) acrylic acid copolymer (EMMA) can be suitably used.

  The ethylene copolymer has an ethylene monomer unit content of 50% by mass or more, preferably 60% by mass or more, more preferably 65% by mass or more, and 95% by mass or less, preferably 90% by mass or less. More preferably, the content is 85% by mass or less. If the content rate of an ethylene monomer unit is 50 mass% or more, since the rigidity of the whole film can be maintained favorable, it is preferable. On the other hand, if the content of the ethylene monomer unit is 95% by mass or less, the flexibility can be sufficiently maintained, and the stress generated between the (I) layer and the (II) layer when stress is applied to the film. Since the buffering action is exerted, delamination can be suppressed.

  As the ethylene-based copolymer, those having an MFR (JIS K7210, temperature: 190 ° C., load: 21.2 N (2.16 kg)) of 0.1 g / 10 min or more and 10 g / 10 min or less are suitably used. If the MFR is 0.1 g / 10 min or more, the extrudability can be maintained satisfactorily. On the other hand, if 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 copolymer is “EVAFLEX EV40LX” (ethylene content 78 mol%, MFR 2.5 g / 10 min) as an ethylene-vinyl acetate copolymer, and “NUC copolymer” as an ethylene-acrylic acid copolymer (Japan). Unicar), Everflex-EAA (Mitsui / DuPont Polychemical), “REXPEARL EAA” (Nippon Ethylene), “ELVALOY” (Mitsui / DuPont Polychemical) as an ethylene- (meth) acrylic acid copolymer ), “REXPEARL EMA” (manufactured by Nippon Ethylene Co., Ltd.), “REXPEARL EEA” (manufactured by Nippon Ethylene Co., Ltd.) as an ethylene-ethyl acrylate copolymer, “Acryft” as an ethylene-methyl (meth) acrylic acid copolymer (Manufactured by Sumitomo Chemical Co., Ltd.), “Bondyne” (manufactured by Sumitomo Chemical Co., Ltd.), ethylene-methacrylic acid as an ethylene-vinyl acetate-maleic anhydride terpolymer Glycidyl acid copolymer, ethylene-vinyl acetate-glycidyl methacrylate terpolymer, and “bond first” (manufactured by Sumitomo Chemical Co., Ltd.) are commercially available as ethylene-ethyl acrylate-glycidyl methacrylate terpolymer. Available.

  Next, the copolymer (b) of the soft aromatic hydrocarbon and conjugated diene hydrocarbon and the hydrogenated derivative thereof will be described. As the aromatic hydrocarbon constituting the copolymer of the soft aromatic hydrocarbon and the conjugated diene hydrocarbon, styrene is preferably used, and a styrene homologue such as α-methylstyrene may also be used. it can. Examples of conjugated diene hydrocarbons include 1,3-butadiene, 1,2-isoprene, 1,4-isoprene, 1,3-pentadiene, and the like, and these may be hydrogenated derivatives. These may be used alone or in admixture of two or more.

  In the copolymer of aromatic hydrocarbon and conjugated diene hydrocarbon or the hydrogenated derivative thereof, the content of aromatic hydrocarbon is 5% by mass or more, preferably 7% by mass of the total mass of the copolymer. As described above, it is desirable that the soft copolymer be 10% by mass or more and 50% by mass or less, preferably 40% by mass or less, and more preferably 35% by mass or less. If the content of aromatic hydrocarbons is 5% by mass or more, good compatibility is obtained when the film is regenerated and added to the (II) layer, and the transparency of the film is suppressed by suppressing the clouding of the film. it can. On the other hand, if the content of the aromatic hydrocarbon is 50% by mass or less, the layer (I) and the layer (II) can be obtained when stress is applied to the film without reducing the flexibility of the layer (II). The delamination can be suppressed because a buffering action against the stress generated during the working is exerted.

  As a hydrogenated derivative of a copolymer of an aromatic hydrocarbon and a conjugated diene hydrocarbon, a hydrogenated derivative of a styrene-conjugated diene random copolymer can be preferably used. The detailed contents of the hydrogenated derivative of the styrene-conjugated diene random copolymer and the production method thereof are disclosed in JP-A-2-15843, JP-A-2-305814 and JP-A-3-72512. ing.

  As the aromatic hydrocarbon-conjugated diene hydrocarbon copolymer, each of the above-exemplified copolymers can be used alone or in admixture of two or more.

  Commercially available products of aromatic hydrocarbon-conjugated diene hydrocarbon copolymers include styrene-butadiene block copolymer elastomers under the trade name “Tufprene” (manufactured by Asahi Kasei Chemicals), hydrogen of styrene-butadiene block copolymers. Trade name “Tuftec H” (manufactured by Asahi Kasei Chemicals) as additive derivative, trade name “Clayton G” (manufactured by Kraton Japan), trade name “Dynalon” (manufactured by JSR) as hydrogenated derivative of styrene-butadiene random copolymer. ), As a hydrogenated derivative of a styrene-isoprene block copolymer, a trade name “Septon” (Kuraray), and as a styrene-vinylisoprene block copolymer elastomer, a trade name “Hibler” (manufactured by Kuraray Co., Ltd.) and the like.

  Further, the copolymer of the aromatic hydrocarbon and the conjugated diene hydrocarbon or the hydrogenated derivative thereof is an interlayer between the (I) layer mainly composed of a polylactic acid resin by introducing a polar group. Adhesiveness can be further improved. Examples of polar groups to be introduced include acid anhydride groups, carboxylic acid groups, carboxylic acid ester groups, carboxylic acid chloride groups, carboxylic acid amide groups, carboxylic acid groups, sulfonic acid groups, sulfonic acid ester groups, and sulfonic acid chloride groups. Sulfonic acid amide group, sulfonic acid group, epoxy group, amino group, imide group, oxazoline group, hydroxyl group and the like. Typical examples of the copolymer of a styrene compound having a polar group and a conjugated diene or a hydrogenated derivative thereof include maleic anhydride-modified SEBS, maleic anhydride-modified SEPS, epoxy-modified SEBS, and epoxy-modified SEPS. These copolymers can be used alone or in admixture of two or more.

  Examples of the trade name of a copolymer of an aromatic hydrocarbon introduced with a polar group and a conjugated diene hydrocarbon or a hydrogenated derivative thereof include, for example, “Tuftec M” (manufactured by Asahi Kasei Chemicals), “Epo Friend "(manufactured by Daicel Chemical Industries).

  Next, the modified polyolefin resin (c) will be described. In the present invention, the modified polyolefin resin capable of constituting the (III) 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. Examples of unsaturated carboxylic acids or anhydrides thereof include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, itaconic acid, itaconic anhydride or monoepoxy compounds of these derivatives and the above 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. Moreover, these copolymers 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. Further, for modification, these modified monomers are used singly or in combination, and the content is preferably in the range of 0.1% by mass to 5% by mass.
used. Of these, those that have been graft-modified are preferably used.

  Examples of commercially available modified polyolefin resins include “Admer” (manufactured by Mitsui Chemicals) and “Modic” (manufactured by Mitsubishi Chemical).

  In the (III) layer, the copolymers or resins (a) to (c) can be used alone or in admixture of two or more. In that case, the content of the copolymer or resin of the above (a) to (c) can be appropriately determined according to the resin constituting the (I) layer and the (II) layer.

<Layer structure of film>
The film of the present invention can have a two-layer structure if it has at least two layers (I) and (II). Furthermore, you may have layers other than (I) layer and (II) layer, and in that case, a layer structure is not specifically limited. Examples of the layer structure of the film of the present invention include (I) layer / (II) layer, (I) layer / (III) layer / (II) layer, (I) layer / (III) layer / ( II) layer / (III) layer / (II) layer, (I) layer / (III) layer / (II) layer / (III) layer / (I) layer, (II) layer / (III) layer / ( Examples of the layer structure include I) layer / (III) layer / (II) layer. Among them, the more effective laminated structure is (I) layer / (III) layer / (II) layer / (III) layer / (I) layer. By adopting this layer structure, the present invention is excellent in heat shrinkage characteristics, small in natural shrinkage, excellent in transparency at the time of regeneration addition, shrinkable packaging capable of forming a cylindrical seal, shrinkage-bound packaging and shrinkage A heat-shrinkable laminated film suitable for applications such as labels can be obtained with good productivity and economy.

  Next, a film having a five-layer structure of (I) layer / (III) layer / (II) layer / (III) layer / (I) 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 (I) layer to the thickness of 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% or less. The thickness ratio of the (II) layer to the total film thickness is 30% or more, preferably 35% or more, more preferably 40% or more, and the upper limit is 90% or less, preferably 85% or less, more preferably 80%. % Or less. Further, the layer (III) 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 preferably 6 μm or less, preferably 5 μm or less. If the thickness ratio of each layer is within the above range, it has excellent heat shrink characteristics, transparency, solvent sealability, shrink finish, and can be recycled and used for shrink packaging, shrink-bound packaging, shrink labels, etc. A heat-shrinkable laminated film suitable for the above 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 100 μm or less, preferably 90 μm or less, and more preferably 80 μm or less. Further, the lower limit of the total thickness of the film is not particularly limited, but is 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more in consideration of the handleability of the film.

<Physical and mechanical properties>
As for the waist (rigidity at room temperature) of the film of the present invention, the tensile elastic modulus in the direction orthogonal to the main shrinkage direction of the film is preferably 800 MPa or more, more preferably 1,000 MPa, and 1,200 MPa or more. More preferably. Moreover, the upper limit of the tensile elasticity modulus of the heat shrinkable film used normally is about 4,000 MPa, preferably about 3,500 MPa, and more preferably about 3,000 MPa. If the tensile modulus in the direction perpendicular to the main shrinkage direction of the film is 800 MPa or more, the waist as a whole film (rigidity at room temperature) can be increased, and even when the thickness of the film is reduced, the PET bottle When a film made in a container is covered with a labeling machine or the like, it is difficult to cause problems such as being obliquely covered or being liable to decrease the yield due to film folding or the like. The tensile modulus can be measured under the condition of a temperature of 23 ° C. according to JIS K7127.

  In order to set the tensile elastic modulus in the direction perpendicular to the main shrinkage direction of the film to 800 MPa or more, it is important to set the resin composition of each layer within the range specified in the present invention. The thickness ratio with respect to the thickness is preferably 10% or more, and the thickness of the (III) layer is preferably 5 μm or less.

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

  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 about 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 heat shrinkage rate when immersed in warm water at 80 ° C. for 10 seconds is at least one direction, usually 20% or more in the main shrinkage direction, preferably 30% or more, more preferably 40% or more, The upper limit is 85% or less, preferably 80% or less, and more preferably 75% or less.

  The film of the present invention has a thermal shrinkage rate of 5% or more, preferably 7% or more, more preferably 10% or more when immersed in warm water of 70 ° C. for 10 seconds, and the upper limit is 50% or less. , Preferably 45% or less, more preferably 40% or less. By setting the thermal shrinkage rate in the main shrinkage direction at 70 ° C. to 5% or more, shrinkage unevenness that can occur locally when bottles are attached with steam shrinker is reduced, resulting in formation of wrinkles, avatars, etc. Can be suppressed. Further, by setting the upper limit of the heat shrinkage rate to 50% 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.

  When the film of the present invention is used as a heat-shrinkable label, the heat shrinkage rate in the orthogonal direction when immersed in warm water at 80 ° C. for 10 seconds is preferably 5% or less, more preferably 4% or less. Preferably, it is 3% or less. If the film has a thermal shrinkage rate of 5% or less when immersed in warm water at 80 ° C. for 10 seconds, the dimension itself in the direction orthogonal to the main shrinkage direction after shrinkage is shortened, or the printed pattern after shrinkage This is preferable because it tends to cause distortion of characters and characters, and in the case of a square bottle, troubles such as vertical sink are unlikely to occur.

  In the film of the present invention, in order to set the heat shrinkage rate in the main shrinkage direction after being immersed in 80 ° C. warm water for 10 seconds to 20% or more and the heat shrinkage rate in the orthogonal direction to 5% or less, the resin composition of each layer is changed. Although it is important to make it the range prescribed | regulated by this invention, Furthermore, the thickness ratio of the (I) layer with respect to the thickness of the whole film shall be 10% or more, (III) The thickness of a layer shall be 5 micrometers or less, and It is preferable to control the stretching ratio in the range of 2 to 10 times and the stretching temperature in the range of 60 ° C to 130 ° C.

  The natural shrinkage rate of the film of the present invention is preferably 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. It is important that it is less than 2.0%, preferably 2.0% or less, more 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 (I) layer to the total film thickness is 10% or more. It is preferable that

  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 JIS K7105, the haze value of the film is preferably 10% or less, more preferably 7% or less, More preferably, it is 5% or less. If the haze value of the film is 15% or less, the transparency of the film can be obtained and a display effect can be achieved.

  The film of the present invention has a thickness of 50 μm even when the (II) layer contains the PLA used in the (I) layer or the PLA used in the (I) layer and the adhesive resin used in the (III) layer. When the film is measured according to JIS K7105, the haze value of the film is 10% or less, preferably 7% or less, more preferably 5% or less. If the haze value of the film containing PLA or PLA and an adhesive resin in the (II) layer is 10% or less, good transparency can be maintained even when the layer is regenerated and added to the (II) layer. . Thereby, the film of this invention can recycle | reuse the film both ends (ear | edge) etc. which generate | occur | produced in the manufacturing process of a film as a raw material, and can maintain the transparency in the obtained film favorably. The haze value of the film after the regeneration addition can be adjusted by increasing or decreasing the addition amount at the time of regeneration addition. For example, the haze value of the film is adjusted by adjusting the amount of PLA added to the layer (II) to 10 parts by mass or more and 100 parts by mass or less, and the amount of adhesive resin added to the range of 1 part by mass or more and 8 parts by mass or less. It can be made 10% or less.

  The impact resistance of the film of the present invention is evaluated by tensile elongation at break, and in a tensile test at an atmospheric temperature of 0 ° C. and a tensile speed of 100 mm / min, in the orthogonal direction, particularly in label applications, the film take-off (flow) direction (MD ) Of 100% or more, preferably 150% or more, more preferably 200% 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. Further, even 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 100% or more, so that it is difficult to break. On the other hand, the upper limit of the tensile rupture elongation in the orthogonal direction is not particularly limited, but is preferably about 500%.

  In addition, the solvent seal strength at the time of making the film of the present invention is 2N / 15 mm width or more, preferably 4 N / 15 mm width or more, more preferably 6 N / 15 mm width, using the measurement method described in Examples described later. That's it. The solvent seal strength here refers to the peel strength value of the seal portion when the film is formed into a cylindrical shape by a center seal described later. When the film surfaces do not swell sufficiently with the sealing solvent, or when the interlayer adhesion between the (II) layer and the (I) layer is poor, sufficient sealing strength cannot be ensured. In the film of the present invention, the (I) layer is laminated as the front and back layers so that the film surfaces are sufficiently swollen by the organic solvent, and the film surfaces are firmly adhered to each other during the bag making process. Troubles such as peeling off will not occur.

  In order to bring the solvent seal strength of the present invention into the above range, it is important to adjust the resin composition as described in the present invention. As a more specific adjustment method, (I) PLA constituting the layer Examples of the method include adjusting the copolymerization ratio of D-lactic acid and L-lactic acid to lower the crystallinity, and providing an adhesive layer for preventing a decrease in seal strength due to delamination.

  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. And a method of obtaining a film by subjecting the surface to corona discharge treatment and winding it with a winder. (Tubular method) It is also possible to apply a method in which the film produced by the above process is cut into a flat shape, and in the film of the present invention, it is important that the (I) layer and the (II) layer (and (III) layer) are laminated. However, as a lamination method, a method of co-extrusion using a multi-Maniford type die, a method of co-extrusion using a feed block, or the like can be used. Wind, purple Line, a carbon dioxide laser, is reheated by a method such as microwave, a roll method, a tenter method, a tubular method or the like, stretching treatment in at least one axial direction or two axial directions is performed.

  For the draw ratio, the direction corresponding to the main shrinkage direction is 1.5 for the shrinkage mainly in one direction, such as for heat-shrinkable labels, depending on the characteristics of the resin used, the stretching means, the stretching temperature, the desired product form, etc. It is desirable that it is not less than twice, preferably not less than 3.0 times, more preferably not less than 4.0 times, and not more than 10 times, preferably not more than 8.0 times, more preferably not more than 7.0 times. In addition, the orthogonal direction is 1 time or more (1 time indicates that the film is not stretched), preferably 1.01 time or more, more preferably 1.1 times or more, and 2 times or less, preferably 1. It is desirable to select a magnification ratio that is not more than 8 times, more preferably not more than 1.5 times, and 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 50 ° C. or higher, preferably 60 ° C. or higher, and the upper limit is 130 ° C. or lower, preferably 110 ° C. It is controlled within the following range. 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 not limited to any of the above-described components with respect to any one layer or two or more layers of each layer, and various properties such as moldability, productivity, and heat shrinkable film are within the range not significantly impairing the effects of the present invention. Recycled resin generated from trimming loss such as film ears, inorganic particles such as silica, talc, kaolin, calcium carbonate, pigments such as titanium oxide, carbon black, flame retardant, weather resistance, for the purpose of improving and adjusting physical properties Additives such as a stabilizer, a heat stabilizer, an antistatic agent, a melt viscosity improver, a crosslinking agent, a lubricant, a nucleating agent, a plasticizer, and an antiaging agent can be appropriately added.

  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, corners, etc.) 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 detail with reference to examples. In the examples, the film take-up (flow) direction is described as MD, and the perpendicular direction thereof as TD.

(1) Melting point Using a differential scanning calorimetry (DSC) apparatus (Pyris1 DSC (manufactured by Perkin Elmer)), the melting point of the polypropylene resin used was in the temperature range from -40 ° C to 200 ° C, and the heating rate was 10 ° C. The melting point was determined by measuring the melting peak at a temperature of 1 min / min.

(2) Content of propylene monomer unit The content of the propylene monomer unit contained in the used polypropylene resin was measured by NMR.

(3) Storage elastic modulus The obtained film was cut into 4 mm length and 60 mm width, using a viscoelastic spectrometer DVA-200, vibration frequency 10 Hz, strain 0.1%, heating rate 3 ° C./min, between chucks 2 The dynamic viscoelasticity in the longitudinal direction was measured in the range from −150 ° C. to 150 ° C. at 0.5 cm. The storage elastic modulus at 20 ° C. is shown as the storage elastic modulus.

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

(5) Haze The haze value of the film was measured at a film thickness of 50 μm according to JIS K7105.

(6) Low temperature tensile elongation at break The tensile elongation at break of the film was measured according to JIS K7127.

(7) Shrinkage Finishing A film printed with a 10 mm-interval grid was cut into a size of 100 mm in length and 298 mm in width, and 10 mm in both sides in the horizontal direction were stacked and adhered with a THF solvent to produce a cylindrical film. This cylindrical film was attached to a cylindrical PET bottle having a capacity of 1.5 L, and passed through the shrinking tunnel having a length of 3.2 m (3 zones) of the steam heating system in about 4 seconds without rotating. The atmospheric temperature in the tunnel in each zone was adjusted with a steam valve, and was in the range from 70 ° C to 85 ° C. After film coating, the following criteria were used.
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 distortion are remarkably generated, or the shrinkage is not sufficient, and the coating on the bottle is insufficient.

[Example 1]
As shown in Table 1, as a PLA constituting the (I) layer, 50 parts by mass of Nature Works 4060 (manufactured by NatureWorks LLC, L-lactic acid / D-lactic acid = 88/12, hereinafter abbreviated as “PLA1”), Nature Works 4050 (manufactured by NatureWorks LLC, L-lactic acid / D-lactic acid = 95/5, hereinafter abbreviated as “PLA2”), 40 parts by mass, rubber component, methabrene S2001 (manufactured by Mitsubishi Rayon Co., silicone-acrylic core shell structure) Rubber, hereinafter abbreviated as “rubber component 1”.) Using a resin composition consisting of 10 parts by mass, as a polypropylene resin constituting the (II) layer, Wintech WFX6 (manufactured by Nippon Polypro, melting point 125 ° C., PP The content was 97.6% by mass, MFR 2.0 g / 10 min, and hereinafter abbreviated as “PP1”).
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 220 ° C., the thickness of each layer was (I) layer / (II) layer / (I) layer = 30 μm / 190 μm It was coextruded with a two-type three-layer die so as to be / 30 μm, taken up with a cast roll at 50 ° C., and cooled and solidified to obtain a two-type three-layer unstretched laminated sheet having a width of 220 mm and a thickness of 250 μm. Next, a film tenter (manufactured by Kyoto Machine Co., Ltd.) was subjected to a horizontal uniaxial stretching of 5.0 times at a preheating temperature of 70 ° C. and a stretching temperature of 65 ° C., and then heat-treated at 65 ° C., rapidly cooled with cold air, A heat-shrinkable laminated film was obtained. The results of evaluating the obtained film are shown in Table 1.

[Example 2]
As shown in Table 1, (I) a mixed resin containing 45 parts by mass of PLA1 as a PLA constituting the layer, 45 parts by mass of PLA2, and 10 parts by mass of the rubber component 1 as a rubbery component is used. As a polypropylene-based resin, Versify 2300 (manufactured by Dow Chemical Co., Ltd., melting point 93 ° C., PP content: 90 mass%, MFR 1.6 g / 10 min or less is referred to as “PP2”) is used, and the preheating temperature of the film tenter The film was stretched 5.0 times in the transverse uniaxial direction at 80 ° C. and the stretching temperature was 75 ° C., and a heat-shrinkable laminated film was obtained in the same manner as in Example 1 except that the heat treatment temperature was changed to 80 ° C. The results of evaluating the obtained film in the same manner as in Example 1 are shown in Table 1.

[Example 3]
As shown in Table 1, a mixed resin containing 54 parts by mass of PLA1 as a resin constituting the (I) layer, 36 parts by mass of PLA2, and 10 parts by mass of the rubber component 1 as a rubbery component is used. A heat-shrinkable laminated film was obtained in the same manner as in Example 1 except that PP1 was changed to 80 parts by mass and PLA1 was changed to 20 parts by mass as the constituent resin. The results of evaluating the obtained film in the same manner as in Example 1 are shown in Table 1.

[Example 4]
As shown in Table 1, a mixed resin containing 50 parts by mass of PLA1 as a resin constituting the (I) layer, 40 parts by mass of PLA2, and 10 parts by mass of the rubber component 1 as a rubbery component is used to constitute the (II) layer PP resin containing 100 parts by mass of PP1 as the resin to be used, and as the resin constituting the (III) layer, styrene thermoplastic resin manufactured by Kuraray Co., Ltd., trade name “HIBLER 7125” (styrene content 20% by mass) Hereinafter, abbreviated as “TPS”. ), And 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 (I) layer / (III) layer / (II) Layer / (III) layer / (I) layer = 30 μm / 5 μm / 180 μm / 5 μm / 30 μm Co-extruded from 3 types 5 layers die, taken up with cast roll at 50 ° C., cooled and solidified, width 220 mm, thickness An unstretched laminated sheet having a thickness of 250 μm was obtained. Next, the film was stretched 5.0 times in the transverse uniaxial direction at a preheating temperature of 70 ° C. and a stretching temperature of 65 ° C. using a film tenter manufactured by Kyoto Machine Co., Ltd., and heat treated at 65 ° C. A film was obtained. The results of evaluating the obtained film in the same manner as in Example 1 are shown in Table 1.

[Comparative Example 1]
As shown in Table 1, as a resin constituting the (I) layer, a resin composition obtained by mixing 50 parts by mass of PLA1, 40 parts by mass of PLA2, and 10 parts by mass of rubber component 1 as a rubbery component ( II) Nobrene FH3315 (manufactured by Sumitomo Chemical Co., Ltd., melting point: 144 ° C., PP content: 96%, MFR 3.0 g / 10 min, hereinafter referred to as “PP3”) was used as the polypropylene resin constituting the layer.
The thickness of each layer is (I) layer / (II) layer / (I) layer = 30 μm / 190 μm / 30 μm, co-extruded with a two-kind three-layer die, taken up with a cast roll at 50 ° C., cooled and solidified, and width An unstretched laminated sheet of 2 types and 3 layers having a thickness of 220 mm and a thickness of 250 μm was obtained. Other than that was implemented like Example 1, and obtained the heat-shrinkable film. The results of evaluating the obtained film are shown in Table 1.

[Comparative Example 2]
(II) For the PP resin constituting the layer, a heat-shrinkable laminated film was obtained in the same manner as in Example 1 except that a resin composition comprising 80 parts by mass of PP3 and 20 parts by mass of PLA1 was used. . The results of evaluating the obtained film are shown in Table 1.

[Comparative Example 3]
As shown in Table 1, mixed resin containing 50 parts by mass of PLA1 and 40 parts by mass of PLA2 as a resin constituting the (I) layer and 10 parts by mass of rubber component 1 as a rubbery component is used to constitute the (II) layer. PP resin containing 80 parts by mass of PP3 and 20 parts by mass of PLA1 is used as the resin to be used, and “TPS” is introduced as the resin constituting the (III) layer. After feeding into a shaft extruder and melt mixing at a set temperature of 200 ° C., the thickness of each layer is (I) layer / (III) layer / (II) layer / (III) layer / (I) layer = 30 μm / 5 μm / 180 μm It was co-extruded from a 3 type 5 layer die so as to be / 5 μm / 30 μm, taken up by a cast roll at 50 ° C., cooled and solidified to obtain an unstretched laminated sheet having a width of 220 mm and a thickness of 200 μm.
The obtained film was carried out in the same manner as in Example 1 to obtain a heat-shrinkable film. The evaluation results are shown in Table 1.

From Table 1, the heat-shrinkable film in the range defined by the present invention had good shrinkage at 70 ° C. and 80 ° C., and also had good transparency and shrinkage finish. On the other hand, when PO having a high melting point was used for the (II) layer (Comparative Example 1), good shrinkage finish could not be obtained. Moreover, when PLA was contained with PO with high melting | fusing point (Comparative Examples 2 and 3), transparency was inferior.
From this, it can be seen that the film of the present invention is excellent in low-temperature shrinkage, transparency and shrink finish, and can maintain good transparency even when regenerated and added to the (II) layer.

  Since it has excellent heat shrinkage properties, transparency, and shrink finish properties, it is possible to provide a heat shrinkable laminated film suitable for applications such as packaging products that require heat shrinkage, particularly shrink labels. Moreover, since the PLA resin is derived from a plant, the utilization of biomass is promoted.

Claims (9)

A heat-shrinkable film formed by stretching a laminated film consisting of at least two layers of (I) layer and (II) layer in at least one direction, each layer comprising the following resin as a main component, and hot water at 80 ° C. A heat-shrinkable laminated film having a heat shrinkage ratio in the main shrinkage direction of 20% or more when immersed for 10 seconds.
(I) Layer: Polylactic acid resin (II) Layer: Polypropylene resin having a melting point of 90 ° C. or higher and 130 ° C. or lower and a propylene monomer unit content of 80% by mass or higher and 99% by mass or lower.   The heat-shrinkable laminated film according to claim 1, wherein the layer (II) is a layer containing 3 parts by mass or more and 30 parts by mass or less of a polylactic acid resin with respect to 100 parts by mass of the polypropylene resin.   The polylactic acid resin is a resin made of a copolymer of D-lactic acid and L-lactic acid, and the constitution of D-lactic acid and L-lactic acid is D-lactic acid / L-lactic acid = 0.2 / 99. It is 8-25 / 75 or 75 / 25-99.8 / 0.2, The heat-shrinkable laminated film of Claim 1 or 2.   The heat-shrinkable laminated film according to any one of claims 1 to 3, further comprising a (III) layer mainly composed of at least one adhesive resin between the (I) layer and the (II) layer.   The heat-shrinkable laminated film according to any one of claims 1 to 4, wherein a haze value based on JIS K7105 is 10% or less.   The heat according to any one of claims 1 to 5, wherein the tensile elongation at break in the direction perpendicular to the main shrinkage direction measured at an atmospheric temperature of 0 ° C and a tensile speed of 100 mm / min is 100% or more and 500% or less. Shrinkable laminated film.   A molded article using the heat-shrinkable laminated film according to any one of claims 1 to 6 as a base material.   The heat-shrinkable label which used the heat-shrinkable laminated film in any one of Claims 1-6 as a base material.   A container equipped with the molded article according to claim 7 or the heat-shrinkable label according to claim 7.