WO2022138039A1

WO2022138039A1 - Shrink film

Info

Publication number: WO2022138039A1
Application number: PCT/JP2021/044198
Authority: WO
Inventors: 有貴節田; 洋松岡; 英訓土橋; 真志阪野
Original assignee: 株式会社フジシールインターナショナル
Priority date: 2020-12-24
Filing date: 2021-12-02
Publication date: 2022-06-30
Also published as: JPWO2022138039A1

Abstract

Provided is a shrink film in which a biomass-derived polystyrene resin is used and which has exceptional shrink finishing properties.　This shrink film has thermal shrinkage properties mainly in one direction, the shrink film including a styrene-butadiene copolymer that has constituent units derived from biomass-derived styrene monomers, and being such that the content proportion of a resin that has a Vicat softening temperature of 75-90°C (inclusive) relative to the entire mass of the shrink film is 45 mass% or greater.

Description

Shrink film

The present invention relates to a shrink film.

Currently, plastic bottles such as PET bottles and metal bottles such as bottle cans are widely used as beverage containers for tea and soft drinks. Plastic labels are often attached to these containers for display, decorativeness, and functionality. As such a plastic label, for example, a shrink label in which a print layer is provided on a shrink film (heat shrinkable film) is widely used because of merits such as decorativeness, processability (followability to a container), and a wide display area. in use.

As the shrink film used for the shrink label, a polystyrene-based resin or a polyester-based resin is known (see Patent Document 1).

International Publication No. 99/29490

In recent years, from the viewpoint of environmental protection, shrink films using biomass raw materials, which are materials derived from industrial waste and plants, have been demanded. As a shrink film using a biomass raw material, for example, a shrink film using polylactic acid, which is a biodegradable and plant-derived material, is known. However, a practical shrink film using a polystyrene resin as a biomass raw material is not known.

Further, when a shrink film using a polystyrene resin is attached to an object to be attached as a shrink label, heat shrinkage occurs in a direction orthogonal to the main shrinkage direction (orthogonal direction), and the design provided on the label is distorted. Due to the misalignment of the design, the sense of unity with the object to be attached is impaired, wrinkles are generated, and the like, and as a result, the shrinkage finish may be deteriorated.

Therefore, an object of the present invention is to provide a shrink film using a polystyrene-based resin derived from biomass and having an excellent shrinkage finish.

The present invention is a shrink film having a heat shrinkage mainly in one direction.
Containing a styrene-butadiene copolymer having a structural unit derived from a biomass-derived styrene-based monomer,
Provided is a shrink film in which the content ratio of a resin having a Vicat softening temperature of 75 ° C. or higher and 90 ° C. or lower is 45% by mass or more with respect to the total mass of the shrink film.

The shrink film includes a base layer portion having one or more layers and surface layers provided on both sides of the base layer portion.
The base layer portion has a layer (A layer) containing the styrene-butadiene copolymer as a layer in the base layer portion.
The layer A is a layer in which the content ratio of the styrene-butadiene copolymer is 20% by mass or more, and the content ratio of the resin having a Vicat softening temperature of 75 ° C. or higher and 90 ° C. or lower is 15% by mass or more. Is preferable.

It is preferable that the surface layer does not contain the styrene-butadiene copolymer, or the content ratio of the styrene-butadiene copolymer in the surface layer is less than 5% by mass.

By having the above-mentioned structure, the shrink film of the present invention uses a polystyrene-based resin derived from biomass and has an excellent shrinkage finish. Therefore, the shrink film of the present invention and the shrink label using the shrink film have practicality, and can reduce the amount of CO ₂ generated when a petroleum-derived styrene-based monomer is used.

It is the schematic (partial sectional view) which shows an example of the shrink film of this invention. It is the schematic (partial sectional view) which shows another example of the shrink film of this invention. It is a schematic diagram (partial sectional view) which shows still another example of the shrink film of this invention. It is a schematic diagram which shows an example of the cylindrical shrink label which is one Embodiment of the shrink label using the shrink film of this invention. FIG. 4 is an enlarged view of a main part of the AA'cross section of the tubular shrink label shown in FIG.

[Shrink film]
The shrink film of the present invention contains at least a styrene-butadiene copolymer having a structural unit derived from a styrene-based monomer derived from biomass.

Further, the shrink film of the present invention contains a resin having a Vicat softening temperature of 75 ° C. or higher and 90 ° C. or lower. In the present specification, a resin having a Vicat softening temperature of 75 ° C. or higher and 90 ° C. or lower may be referred to as "high Vicat resin". When the Vicat softening temperature of the styrene-butadiene copolymer is 75 ° C. or higher and 90 ° C. or lower, the styrene-butadiene copolymer corresponds to the high bicut resin. The Vicat softening temperature of the high Vicut resin is preferably 75 ° C. or higher and 85 ° C. or lower.

(Biomass styrene-butadiene copolymer)
The styrene-butadiene copolymer is a copolymer composed of a styrene-based monomer derived from biomass and butadiene as an essential monomer component. That is, it is a polymer containing at least a structural unit derived from a styrene-based monomer derived from biomass and a structural unit derived from butadiene in the molecule (in one molecule). In the present specification, the styrene-butadiene copolymer containing a structural unit derived from a biomass-derived styrene-based monomer may be referred to as a "biomass styrene-butadiene copolymer". The structural unit derived from butadiene in the biomass styrene-butadiene copolymer may be derived from biomass or petroleum.

Examples of the biomass-derived styrene-based monomer include those extracted from bionaphtha derived from pulp waste materials such as furniture and wood chips and industrial waste such as swill. The above-mentioned garbage may be garbage other than food. Examples of the styrene-based monomer include styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, p-isobutylstyrene, pt-butylstyrene, chloromethylstyrene and the like. Can be mentioned. Of these, styrene is preferable from the viewpoint of availability, material price, and the like. As the styrene-based monomer, only one kind may be used, or two or more kinds may be used.

The content ratio of the structural unit derived from the styrene-based monomer derived from the biomass is the total mass (100% by mass) of the structural unit derived from the total styrene-based monomer in the biomass styrene-butadiene copolymer. It is preferably 20% by mass or more, more preferably 50% by mass or more, still more preferably 80% by mass or more, and particularly preferably 95% by mass or more.

The monomer component constituting the biomass styrene-butadiene copolymer may further contain the styrene-based monomer derived from the biomass and other monomer components other than butadiene. Examples of the other monomer components include petroleum-derived styrene-based monomers, dienes other than butadiene, vinyl-based monomers, polymerizable unsaturated carboxylic acid esters, and polymerizable unsaturated anhydrous carboxylic acids.

The form of copolymerization of the styrene-butadiene copolymer is not particularly limited, and examples thereof include random copolymers, block copolymers, and graft copolymers. Among them, block copolymers are preferable, and examples thereof include styrene block (S) -diene block (D) type, SDS type, DSD type, SSD-D type and the like. ..

Examples of the block copolymer of the biomass styrene-butadiene copolymer include a styrene-butadiene block copolymer (SBC) such as a styrene-butadiene-styrene block copolymer (SBS) and a styrene-butadiene-isoprene-styrene. Examples thereof include styrene-butadiene-isoprene block copolymers such as block copolymers (SBIS), and among them, styrene-butadiene block copolymers are preferable. As these block copolymers, only one kind may be used, or two or more kinds may be used.

The styrene-butadiene block copolymer may be any polymer having a styrene block polymerized only with a styrene-based monomer and a butadiene block polymerized only with butadiene, and is not particularly limited. For example, styrene-. A styrene-butadiene block copolymer having a styrene block at both ends, such as a butadiene-styrene block copolymer (SBS), a styrene-butadiene-styrene-butadiene-styrene block copolymer (SBSBS); a styrene-butadiene copolymer. (SB), styrene-butadiene block copolymer having a styrene block such as styrene-butadiene-styrene-butadiene copolymer (SBSB) and a butadiene block at the ends; butadiene-styrene-butadiene copolymer (BSB), butadiene Examples thereof include a styrene-butadiene block copolymer having a butadiene block at both ends, such as a styrene-butadiene-styrene-butadiene copolymer (BSBSB). Of these, a styrene-butadiene block copolymer having a styrene block at both ends is preferable, and SBS is more preferable. As these styrene-butadiene block copolymers, only one kind may be used, or two or more kinds may be used.

The styrene-butadiene block copolymer can be produced by a known or conventional method for producing a block copolymer. As a method for producing the above-mentioned styrene-butadiene block copolymer, for example, living polymerization (living radical polymerization, living anionic polymerization, living cation) in which the molecular weight, molecular weight distribution, terminal structure and the like of the styrene-butadiene block copolymer can be easily controlled. Polymerization, etc.). The living polymerization can be carried out by a known or conventional method.

The biomass styrene-butadiene copolymer is not particularly limited, but the content ratio of the structural unit derived from the styrene-based monomer is 50 with respect to the total mass (100% by mass) of the biomass styrene-butadiene copolymer. It is preferably ~ 98% by mass, more preferably 60 to 95% by mass, still more preferably 65 to 92% by mass, and particularly preferably 70 to 90% by mass.
When the content ratio is 50% by mass or more, the shrink film is appropriately hardened, the rigidity of the shrink label using the shrink film of the present invention is appropriately increased, and the shrinkage characteristics when the shrink label is attached are good. Tend to be. When the content ratio is 98% by mass or less, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish tends to be better.

The above-mentioned biomass styrene-butadiene copolymer is not particularly limited, but the content ratio of the structural unit derived from butadiene is 2 to 50% by mass with respect to the total mass (100% by mass) of the biomass styrene-butadiene copolymer. Is preferable, more preferably 5 to 40% by mass, still more preferably 8 to 35% by mass, and particularly preferably 10 to 30% by mass. When the content ratio is 50% by mass or less, the shrink film is appropriately hardened, the rigidity of the shrink label using the shrink film of the present invention is appropriately increased, and the shrinkage characteristics when the shrink label is attached are good. Tend to be. When the content ratio is 2% by mass or more, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish tends to be better.

The Vicat softening temperature of the biomass styrene-butadiene copolymer may be 75 ° C. or higher or lower than 75 ° C., and is not particularly limited. The Vicat softening temperature of the biomass styrene-butadiene copolymer is preferably 75 ° C. or higher and 90 ° C. or lower.

In the present specification, the vicut softening temperature of the resin can be measured based on, for example, JIS K7206. Further, the Vicat softening temperature refers to each of the resins used for producing the shrink film, and when the resin used is a polymer alloy, the Vicat softening temperature in units of the polymer alloy is used.

As the above-mentioned biomass styrene-butadiene copolymer, a commercially available product may be used, and examples thereof include "Stylolux M" manufactured by Stylolation Co., Ltd.

The content ratio of the biomass styrene-butadiene copolymer in the shrink film of the present invention is preferably 10 to 90% by mass, more preferably 15 to 90% by mass, based on the total mass (100% by mass) of the shrink film of the present invention. It is 70% by mass, more preferably 20 to 60% by mass, and particularly preferably 20 to 50% by mass. When the content ratio is 10% by mass or more, there are many raw materials derived from biomass, and the amount of CO ₂ generated can be further reduced as compared with the case where a polystyrene resin derived from petroleum is used. When the content ratio is 90% by mass or less, the content ratio of other resins can be relatively increased, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrink film such as shrinkage finish and cut suitability is required. The performance to be achieved can be further optimized.

(High bicut resin)
The shrink film of the present invention contains the above high bicut resin as an essential component. As a result, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish is excellent. Examples of the high bicut resin include known and commonly used resins having a vicut softening temperature of 75 ° C. or higher and 90 ° C. or lower. The resin includes, for example, a polyester resin, a polystyrene resin, a polyolefin resin, a vinyl chloride resin, a polycarbonate resin, a polyamide resin, and a thermoplastic elastomer as long as the Vicat softening temperature is 75 ° C. or higher and 90 ° C. or lower. Examples thereof include thermoplastic resins such as. As the high bicut resin, polyester-based resin and polystyrene-based resin are particularly preferable. As the high bicut resin, only one kind may be used, or two or more kinds may be used.

Examples of the polystyrene-based resin as the high-vicut resin include the above-mentioned biomass styrene-butadiene copolymer and other polystyrene-based resins. The polystyrene-based resin is a polymer composed of a styrene-based monomer as an essential monomer component. That is, the polystyrene-based resin is a polymer containing at least a structural unit derived from a styrene-based monomer in the molecule (in one molecule).

The styrene-based monomer in the above-mentioned other polystyrene-based resin may be derived from biomass or petroleum, but is preferably derived from petroleum. When the other polystyrene-based resin is a styrene-butadiene copolymer other than the biomass styrene-butadiene copolymer, the styrene-based monomer is derived from petroleum. Examples of the styrene-based monomer include those exemplified and described as the styrene-based monomer in the above-mentioned biomass styrene-butadiene copolymer. Of these, styrene is preferable from the viewpoint of availability, material price, and the like. As the styrene-based monomer, only one kind may be used, or two or more kinds may be used.

The polystyrene-based resin includes, for example, a homopolymer of a styrene-based monomer such as general-purpose polystyrene (GPPS), which is a homopolymer of styrene; and only two or more kinds of styrene-based monomers as a monomer component. Polymers; styrene-diene-based copolymers; styrene-polymerizable unsaturated carboxylic acid ester-based copolymers; copolymers of polystyrene and synthetic rubber (eg, polybutadiene, polyisoprene, etc.), synthesis Impact-resistant polystyrene (HIPS) such as polystyrene obtained by graft-polymerizing styrene on rubber; a polymer containing a styrene-based monomer (for example, a styrene-based monomer and a (meth) acrylic acid ester-based monomer co-existing with each other. A polystyrene in which a rubber-like elastic body is dispersed in a continuous phase of a polymer) and the copolymer is graft-polymerized on the rubber-like elastic body (graft type impact-resistant polystyrene "graft HIPS"); styrene-based elastomer; Two or more of these polymer alloys and the like can be mentioned. As the polystyrene-based resin, a styrene-diene-based copolymer, HIPS, grafted HIPS, or a polymer alloy thereof is preferable from the viewpoint of excellent shrinkage characteristics.
As the polystyrene-based resin, only one kind may be used, or two or more kinds may be used.

The styrene-diene-based copolymer is a copolymer composed of a styrene-based monomer and a diene (particularly, a conjugated diene) as essential monomer components. That is, it is a polymer containing at least a structural unit derived from a styrene-based monomer and a structural unit derived from a diene (particularly, a conjugated diene) in the molecule (in one molecule).

The diene is not particularly limited, but a conjugated diene is preferable, and for example, 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 1, Examples thereof include 3-pentadiene, 1,3-hexadiene and chloroprene. Of these, 1,3-butadiene is particularly preferable. That is, as the styrene-diene-based copolymer, a styrene-butadiene copolymer is preferable. Only one kind of the above-mentioned diene may be used, or two or more kinds may be used.

The monomer component constituting the styrene-diene copolymer may further contain a monomer component other than the styrene-based monomer and the diene. Examples of the monomer component other than the styrene-based monomer and the diene include vinyl-based monomers, polymerizable unsaturated carboxylic acid esters, and polymerizable unsaturated anhydrous carboxylic acids.

The form of copolymerization of the styrene-diene copolymer is not particularly limited, and examples thereof include random copolymers, block copolymers, and graft copolymers. Of these, block copolymers are preferable.

Examples of the block copolymer (styrene-diene block copolymer) of the styrene-diene-based copolymer include a styrene-butadiene block copolymer such as a styrene-butadiene-styrene block copolymer and styrene-isoprene-. Examples thereof include styrene-isoprene block copolymers such as styrene block copolymer (SIS) and styrene-butadiene-isoprene block copolymers such as styrene-butadiene / isoprene-styrene block copolymers, among which styrene-butadiene Block copolymers are preferred. Examples of the styrene-butadiene block copolymer include those exemplified and described as the above-mentioned biomass styrene-butadiene copolymer. As these block copolymers, only one kind may be used, or two or more kinds may be used.

The styrene-diene block copolymer can be produced by a known or conventional method for producing a block copolymer. As a method for producing the styrene-diene block copolymer, for example, living polymerization (living radical polymerization, living anionic polymerization, living cation) in which the molecular weight, molecular weight distribution, terminal structure and the like of the styrene-diene block copolymer can be easily controlled. Polymerization, etc.). The living polymerization can be carried out by a known or conventional method.

The styrene-diene-based copolymer is not particularly limited, but the content ratio of the structural unit derived from the styrene-based monomer is 50 with respect to the total mass (100% by mass) of the styrene-diene-based copolymer. It is preferably ~ 98% by mass, more preferably 60 to 95% by mass, still more preferably 65 to 92% by mass, and particularly preferably 70 to 90% by mass. When the content ratio is 50% by mass or more, the shrink film is appropriately hardened, the rigidity of the shrink label using the shrink film of the present invention is appropriately increased, and the shrinkage characteristics when the shrink label is attached are good. Tend to be. When the content ratio is 98% by mass or less, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish tends to be better.

The styrene-diene-based copolymer is not particularly limited, but the content ratio of the constituent unit derived from diene is 2 to 50% by mass with respect to the total mass (100% by mass) of the styrene-diene-based copolymer. Is preferable, more preferably 5 to 40% by mass, still more preferably 8 to 35% by mass, and particularly preferably 10 to 30% by mass. When the content ratio is 50% by mass or less, the shrink film is appropriately hardened, the rigidity of the shrink label using the shrink film of the present invention is appropriately increased, and the shrinkage characteristics when the shrink label is attached are good. Tend to be. When the content ratio is 2% by mass or more, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish tends to be better.

Examples of the polyester-based resin include polyesters composed of a dicarboxylic acid component and a diol component as essential constituents (that is, a polyester containing at least a constituent unit derived from a dicarboxylic acid and a constituent unit derived from a diol) and polylactic acid. Examples thereof include a system polymer and a polyester system elastomer. The main polyesters containing at least a structural unit derived from a dicarboxylic acid and a structural unit derived from a diol include polymers, copolymers or mixtures thereof by a condensation reaction of a dicarboxylic acid and a diol. As the polyester-based resin, a soft polyester-based resin such as polyethylene terephthalate to which a plasticizer is added may be used.

Examples of the dicarboxylic acid (dicarboxylic acid component) include terephthalic acid, isophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 5-t-butylisophthalic acid, 4,4'-biphenyldicarboxylic acid, and trans-3. , 3'-Stylbenzicarboxylic acid, trans-4,4'-stillbenzdicarboxylic acid, 4,4'-dibenzyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,3-naphthalene Dicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 2,2,6,6-tetramethylbiphenyl-4,4'-dicarboxylic acid, 1,1,3-trimethyl-3-phenyl Inden-4,5-dicarboxylic acid, 1,2-diphenoxyetane-4,4'-dicarboxylic acid, diphenyletherdicarboxylic acid, 2,5-anthracenedicarboxylic acid, 2,5-pyridinedicarboxylic acid, and their substitutes. Aromatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelli acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, etc. An aliphatic dicarboxylic acid such as pentadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecandioic acid, icosandioic acid, docosandioic acid, 1,12-dodecandionic acid, and their substitutes; 1,3-cyclopentane. Dicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6 -Decahydronaphthalenedicarboxylic acids, alicyclic dicarboxylic acids such as their substitutes, and the like can be mentioned. As the dicarboxylic acid, only one kind may be used, or two or more kinds may be used.

Examples of the diol (diol component) include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. , 2,2-Dimethyl-1,3-propanediol (neopentyl glycol), 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,3 -Propanediol, 1,8-octanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2,4-dimethyl-1,3-hexanediol, 1,10-decanediol, Aliper diols such as polyethylene glycol and polypropylene glycol; 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3- Alicyclic diols such as cyclobutanediol; ethylene oxide adducts of bisphenol compounds such as 2,2-bis (4-β-hydroxyethoxyphenyl) propane and bis (4-β-hydroxyethoxyphenyl) sulfones, xylylene glycol and the like. Aromatic diols and the like. As the above diol, only one kind may be used, or two or more kinds may be used.

In addition to the above, the polyester-based resin includes oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid; monocarboxylic acids such as benzoic acid and benzoylbenzoic acid; and polyhydric carboxylic acids such as trimellitic acid. A monohydric alcohol such as polyalkylene glycol monomethyl ether; a constituent unit derived from a polyhydric alcohol such as glycerin, pentaerythritol, trimethylolpropane or the like may be contained.

Among them, the aromatic polyester resin is preferable as the polyester resin from the viewpoint of shrinkage characteristics, rigidity, mechanical strength and the like. The aromatic polyester resin has 50 mol% or more (preferably 70 mol% or more) of the total dicarboxylic acid component and / or 50 mol% or more (preferably 70 mol% or more) of the total diol component. Is a polyester resin in which 70 mol% or more) is an aromatic diol. Further, an aromatic polyester resin which is a polymer, a copolymer, or a mixture thereof by a condensation reaction between a dicarboxylic acid containing an aromatic dicarboxylic acid and a diol containing an aliphatic diol is preferable.

The aromatic polyester-based resin is not composed of a single repeating unit from the viewpoint of increasing the heat shrinkage rate and being superior in shrinkage characteristics and rigidity by making the polyester-based resin amorphous. A modified aromatic polyester resin containing a modifying component (copolymer component) is preferable. The modified aromatic polyester-based resin includes, for example, a modified aromatic polyester-based resin in which at least one of a dicarboxylic acid component and a diol component is composed of two or more components, that is, a modified aromatic polyester-based resin is contained in addition to the main component. Resin is preferred. In other words, the aromatic polyester-based resin is preferably a modified aromatic polyester-based resin containing a structural unit derived from at least two or more dicarboxylic acids and / or a structural unit derived from at least two or more diols.

Among the above, the modified aromatic polyester resin is a part of the dicarboxylic acid component and / or the diol component in polyethylene terephthalate (PET) using terephthalic acid as the dicarboxylic acid component and ethylene glycol (EG) as the diol component. A modified PET in which is replaced with a modifying component (ie, another dicarboxylic acid component and / or another diol component) is preferably exemplified.

Examples of the dicarboxylic acid component used as the modifying component (copolymerization component) of the modified aromatic polyester resin (particularly, modified PET) include cyclohexanedicarboxylic acid, adipic acid, and isophthalic acid. Of these, isophthalic acid is preferable. Examples of the diol component used as the denaturing component include 2,2-dialkyl-1,3-propanediol such as 1,4-cyclohexanedimethanol (CHDM) and neopentyl glycol (NPG), and diethylene glycol. Of these, CHDM, 2,2-dialkyl-1,3-propanediol (particularly NPG) is preferable. The alkyl group in the above 2,2-dialkyl-1,3-propanediol is preferably an alkyl group having 1 to 6 carbon atoms, and the two alkyl groups may be the same alkyl group or different. It may be an alkyl group.

The aromatic polyester-based resin is not particularly limited, but specifically, polyethylene terephthalate (PET) using terephthalic acid as the dicarboxylic acid component and EG as the diol component; a dicarboxylic acid component from the viewpoint of shrinkage characteristics. A modified aromatic polyester resin using terephthalic acid as the main component (for example, the most abundant diol component) and CHDM as the copolymerization component (sometimes referred to as "CHDM copolymerized PET"). A modified aromatic polyester resin using terephthalic acid as the dicarboxylic acid component, ethylene glycol as the diol component as the main component, and 2,2-dialkyl-1,3-propanediol as the copolymerization component ("2,2-". It may be referred to as "dialkyl-1,3-propanediol copolymerized PET"). Among the above 2,2-dialkyl-1,3-propanediol copolymerized PETs, in particular, a modified fragrance using terephthalic acid as the dicarboxylic acid component, ethylene glycol as the diol component as the main component, and NPG as the copolymerization component. Group polyester resins (sometimes referred to as "NPG copolymerized PET") are preferred. The aromatic polyester-based resin is particularly preferably CHDM copolymerized PET and / or 2,2-dialkyl-1,3-propanediol copolymerized PET, and more preferably CHDM copolymerized PET and / or NPG copolymerized PET. From the viewpoint of shrinkage characteristics, CHDM copolymerized PET is most preferable. In the above CHDM copolymerized PET and 2,2-dialkyl-1,3-propanediol copolymerized PET, copolymerization components other than CHDM and 2,2-dialkyl-1,3-propanediol are used, respectively. For example, isophthalic acid or diethylene glycol may be further copolymerized.

The aromatic polyester-based resin is preferably a substantially amorphous aromatic polyester-based resin, and more preferably an aromatic polyester-based resin which is an amorphous saturated polyester-based resin. Although not particularly limited, the aromatic polyester-based resin can be made substantially amorphous by, for example, because it becomes difficult to crystallize by being modified as described above. By making the aromatic polyester resin amorphous, extrusion at a relatively low temperature becomes possible. As a result, the layer formability at the time of extrusion processing is improved, and the shrinkage property of the shrink film is improved.

The crystallinity of the polyester resin measured by the differential scanning calorimetry (DSC) method (measured at a heating rate of 10 ° C./min) is preferably 15% or less, more preferably 10% or less. Further, it is most preferable that the polyester resin has almost no melting point (melting peak) when measured by the DSC method (that is, a resin having a crystallinity of 0%). The crystallinity can be calculated from the value of the heat of fusion of crystals obtained by DSC measurement, using a sample having a clear crystallinity measured by an X-ray method or the like as a standard. For the heat of fusion of crystals, for example, a DSC (differential scanning calorimetry) device manufactured by Seiko Instruments Co., Ltd. is used, the sample amount is 10 mg, the temperature rise rate is 10 ° C./min, nitrogen sealing is performed, and the temperature rises to the melting point or higher once. It can be obtained from the area of the melting peak when the temperature is raised again after warming and lowering to room temperature. The crystallinity is preferably measured from a single resin, but when measured in a mixed state, the melting peak of the mixed resin is subtracted from the melting peak of the target aromatic polyester resin. You just have to ask. The same applies to the crystallinity of the polyester-based resin that may be contained in the layer in the base layer portion.

The weight average molecular weight (Mw) of the polyester resin is preferably 15,000 to 100,000, more preferably 15,000 to 90,000, still more preferably 30,000 to 30,000 from the viewpoint of melting behavior and shrinkage behavior. It is 90,000, particularly preferably 30,000 to 80,000. In the case of 2,2-dialkyl-1,3-propanediol copolymerized PET, 50,000 to 70,000 is particularly preferable. In the present specification, the weight average molecular weight (Mw) is not particularly limited, but can be measured by, for example, GPC using polystyrene as a standard substance.

Commercially available products may be used as the polyester resin, for example, "EMBRACE 21214" manufactured by Eastman Chemical (Eastman Chemical), "EMBRACE LV" (above CHDM copolymerized PET), and Bell Polyester Products Co., Ltd. "Belpet MGG200" (2,2-dialkyl-1,3-propanediol copolymer PET), "Belpet E02" (NPG copolymer PET) manufactured by Bell Polyester Products Co., Ltd., "Sky Green" manufactured by SK Chemical Co., Ltd. Etc. are available on the market.

The content of the high bicut resin in the shrink film of the present invention is 45% by mass or more, preferably 50% by mass or more, more preferably 50% by mass, based on the total mass (100% by mass) of the shrink film of the present invention. It is 70% by mass or more, more preferably 90% by mass or more.
When the content ratio is 45% by mass or more, the heat shrinkage rate in the orthogonal direction becomes appropriate, and the shrinkage finish of the shrink film is excellent. The upper limit of the content ratio is 100% by mass, preferably 99% by mass.

The content ratio of the high bicut resin in the layer to be the surface of at least one (preferably both) of the shrink film of the present invention is preferably 50% by mass or more (for example, 50 to 100% by mass), more preferably 70% by mass. % Or more, more preferably 90% by mass or more. When the content ratio is 50% by mass or more, the printability on the shrink film is more excellent. In addition, cut fusion is unlikely to occur when manufacturing a tubular shrink label, which will be described later, that is, it is more excellent in cut suitability. When the shrink film of the present invention is composed of a single film layer, the single layer is the surface layer, and when the shrink film of the present invention is composed of a plurality of film layers, the surface layer described later is the surface layer. Corresponds to.

The shrink film of the present invention may contain a resin having a Vicat softening temperature of 55 ° C. or higher and lower than 75 ° C. In the present specification, a resin having a Vicat softening temperature of 55 ° C. or higher and lower than 75 ° C. may be referred to as "low Vicat resin". When the shrink film of the present invention contains the above-mentioned low vicut resin, the natural shrinkage of the shrink film can be further suppressed.

Examples of the low bicut resin include known and commonly used resins having a vicut softening temperature of 55 ° C. or higher and lower than 75 ° C. Examples of the resin include the thermoplastic resins exemplified and described as the above-mentioned high bicut resin as long as the vicut softening temperature is 55 ° C. or higher and lower than 75 ° C. As the low bicut resin, polyester-based resin and polystyrene-based resin are particularly preferable. As the low bicut resin, only one kind may be used, or two or more kinds may be used.

The content of the low bicut resin in the shrink film of the present invention is preferably 0 to 55% by mass, more preferably more than 0% by mass and 55% by mass, based on the total mass (100% by mass) of the shrink film of the present invention. % Or less, more preferably 1 to 55% by mass.

The content ratio of the resin having a Vicat softening temperature of 55 ° C. or higher and 90 ° C. or lower in the shrink film of the present invention, that is, the total content ratio of the high Vicat resin and the low Vicut resin is the total mass of the shrink film of the present invention. 95% by mass or more (for example, 95 to 100% by mass) is preferable, and 99% by mass or more is more preferable with respect to (100% by mass). When the content ratio is 95% by mass or more, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish of the shrink film is more excellent.

In the shrink film of the present invention, the mass ratio of the high bicut resin to the low vicut resin (the former: the latter) is preferably 45 to 100: 55 to 0, more preferably 45 to 99: 55 to 1. When the mass ratio of the high bicut resin is 45 or more, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish of the shrink film is more excellent. In particular, it is preferable that the total content ratio of the high bicut resin and the low bicut resin is 95% by mass or more, and the mass ratio is within the above range.

The shrink film of the present invention is a lubricant, a filler, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antioxidant, an antifogging agent, a flame retardant, a colorant, and a pinning within a range that does not impair the effect of the present invention. It may contain additives such as agents (alkaline earth metals), softeners, and compatibilizers. Only one kind of these components may be used, or two or more kinds thereof may be used. Above all, by containing a lubricant, it is excellent in cutting suitability.

The surface layer of at least one (preferably both) of the shrink film of the present invention preferably contains a lubricant. Even when the inner layer of the shrink film of the present invention contains a lubricant, the cut suitability is excellent, but when the layer to be the surface of the shrink film of the present invention contains a lubricant, the cut suitability is more excellent.

Further, the shrink film of the present invention may contain a recovery raw material obtained by repelletizing a film piece at the time of film production. The recovered raw material is a recycled raw material composed of non-product parts such as before and after commercialization and film edges, residual parts when a product film is collected from an intermediate product, film scraps such as non-standard products, and polymer scraps. However, the recovered raw material is preferably one produced from the production of the shrink film of the present invention (so-called self-recovered product).

The surface of the shrink film of the present invention may be provided with an antistatic layer or an anchor coat layer as long as the effects of the present invention are not impaired. Further, the surface of the shrink film of the present invention may be subjected to conventional surface treatment such as corona discharge treatment, primer treatment, antistatic coating treatment and the like, if necessary.

(Structure of shrink film)
The shrink film of the present invention may be composed of a single film layer or may be composed of a plurality of film layers. When the shrink film of the present invention is composed of a plurality of film layers, two or more of the biomass styrene-butadiene copolymer, the high bicut resin, and the low vicut resin are contained in the same film layer. It may be contained in different film layers.

When the shrink film of the present invention is composed of a plurality of film layers, it is preferable that the shrink film of the present invention includes a base layer portion and surface layers provided on both sides of the base layer portion. Such a shrink film of the present invention has a layer structure of a surface layer / base layer portion / surface layer, and preferably the base layer portion and the surface layer are directly laminated. The surface layers on both sides of the base layer portion in the shrink film may be the same layer or different layers (layers having different resin compositions and layer thicknesses). ..

The base layer portion preferably has at least a layer (A layer) containing the biomass styrene-butadiene copolymer as a layer in the base layer portion. That is, the shrink film is a shrink film having a base layer portion and surface layers provided on both sides of the base layer portion, and the base layer portion has at least an A layer as a layer in the base layer portion. Is preferable.
When the base layer portion has the A layer, the proportion of the biomass raw material in the entire shrink film can be increased while suppressing the content of the biomass styrene-butadiene copolymer in the surface layer.
In the present specification, the layer containing the biomass styrene-butadiene copolymer may be referred to as "A layer".

The base layer portion is a portion sandwiched between two surface layers. The base layer portion has one or more layers. The base layer portion preferably contains 1 to 65 layers, and more preferably 3 to 65 layers. When the number of layers is three or more, the thickness of each layer can be made relatively thin, so that the rigidity and transparency are excellent as compared with the case of one layer. In addition, the shrinkage behavior during heat shrinkage can be slowed down, and the shrinkage finish is excellent.

The number of layers of the A layer in the base layer portion is not particularly limited, but is 50% or more (preferably 70% or more, more preferably 90% or more) with respect to the number of layers of the base layer portion. Is preferable.

When the base layer portion is composed of only one A layer, the shrink film of the present invention has a layer structure of [surface layer / A layer / surface layer]. FIG. 1 shows an embodiment of a shrink film in which the base layer portion is composed of only one layer A. The shrink film 1 shown in FIG. 1 includes a base layer portion 12 made of a single layer A layer 12a and surface layers 11 provided on both sides of the base layer portion 12.

When the base layer portion includes two or more layers, the base layer portion is not particularly limited, but it is preferable that the base layer portion further includes at least one adhesive resin layer as the layer in the base layer portion. In particular, it is more preferable to include an adhesive resin layer as the outermost layer in the base layer portion. When the base layer portion contains the adhesive resin layer as the outermost layer of the base layer portion, the adhesiveness between the surface layer and the A layer in the base layer portion can be improved, and delamination can be prevented from occurring even after heat shrinkage. Further, since the adhesive resin layer does not impair the adhesiveness even if it is interposed between the A layer and the A layer, the rigidity of the shrink label is obtained by interposing the adhesive resin layer between the A layers in the base layer portion. Can also be used to increase the height.
The adhesive resin layer is not particularly limited as long as it is a layer having a composition different from that of the adjacent layer, and is, for example, an A layer having a composition different from that of the adjacent A layer (for example, a combination of an A1 layer and an A2 layer described later). You may.

When the base layer portion includes three or more layers, the base layer portion is a layer in the base layer portion, and is located inside the two outermost layers located on both end faces in the thickness direction and the inner side in the thickness direction sandwiched between the outermost layers. It is composed of a plurality of intermediate layers. That is, the base layer portion has a structure of [outermost layer / intermediate layer (/ ... / intermediate layer) / outermost layer]. When there are a plurality of A layers in the base layer portion, all or some of the plurality of A layers in the base layer portion may be the same layer or different layers (layers). It may be a layer having a different resin composition or layer thickness. Similarly, when there are a plurality of adhesive resin layers in the base layer portion, all or some of the plurality of adhesive resin layers in the base layer portion may be the same layer or each other. It may be a different layer (a layer having a different resin composition or layer thickness constituting the layer). Further, the base layer portion may include a layer other than the A layer and the adhesive resin layer as long as the effect of the present invention is not impaired. Further, the A layer and the adhesive resin layer may be the outermost layer of the base layer portion, the intermediate layer, or both of them, respectively, may be included in the base layer portion.

FIG. 2 shows an embodiment of the shrink film when the base layer portion includes the A layer and contains three layers. The shrink film 1 shown in FIG. 2 includes a base layer portion 12 and surface layers 11 provided on both sides of the base layer portion 12. The base layer portion 12 is composed of an A layer 12a as an intermediate layer and an adhesive resin layer 12b as an outermost layer.

FIG. 3 shows an embodiment of the shrink film when the base layer portion includes the A layer and 9 layers. The shrink film 1 shown in FIG. 3 includes a base layer portion 12 and surface layers 11 provided on both sides of the base layer portion 12. In the base layer portion 12, the A layer 12a and the adhesive resin layer 12b are alternately laminated, and the A layer 12a is interposed between all the adhesive resin layers 12b. The outermost layer of the base layer portion 12 is an adhesive resin layer 12b.

The layer A in the base layer portion contains at least the above-mentioned biomass styrene-butadiene copolymer in the layer. The content ratio of the biomass styrene-butadiene copolymer in the A layer is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 50 with respect to the total mass (100% by mass) of the A layer. It is mass% or more. When the content ratio is 20% by mass or more, the ratio of the biomass raw material can be further increased.

The layer A may contain a thermoplastic resin other than the above-mentioned biomass styrene-butadiene copolymer. Examples of the other thermoplastic resin include the high bicut resin and the low vicut resin. As the above-mentioned other thermoplastic resin, only one kind may be used, or two or more kinds may be used.

The A layer may contain the above high bicut resin. When the layer A contains the high bicut resin, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish of the shrink film is more excellent. As the high bicut resin, polystyrene-based resin and polyester-based resin are particularly preferable. As the polystyrene-based resin, a styrene-diene-based copolymer is preferable, and a styrene-butadiene copolymer is more preferable. Further, it is preferable that the high bicut resin further contains HIPS. The high bicut resin may be the biomass styrene-butadiene copolymer.

The content ratio of the high bicut resin in the A layer is preferably 15% by mass or more (for example, 15 to 100% by mass), more preferably 30% by mass or more, based on the total mass (100% by mass) of the A layer. More preferably, it is 50% by mass or more. When the content ratio is 15% by mass or more, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish of the shrink film is more excellent.

The A layer may contain the above low bicut resin. When the A layer contains the low bicut resin, the natural shrinkage of the shrink film can be further suppressed. As the low bicut resin, polystyrene-based resin is preferable, styrene-diene-based copolymer is more preferable, and styrene-butadiene copolymer is more preferable. Further, it is preferable that the low bicut resin further contains HIPS. The low bicut resin may be the biomass styrene-butadiene copolymer.

The content ratio of the low bicut resin in the A layer is preferably 0 to 85% by mass, more preferably more than 0% by mass and 85% by mass or less, still more preferably, with respect to the total mass (100% by mass) of the A layer. It is 1 to 70% by mass, particularly preferably 5 to 50% by mass.

The content ratio of the resin having a Vicat softening temperature of 55 ° C. or higher and 90 ° C. or lower in the A layer, that is, the total content ratio of the high Vicat resin and the low Vicut resin is the total mass (100% by mass) of the A layer. On the other hand, 95% by mass or more (for example, 95 to 100% by mass) is preferable, and 99% by mass or more is more preferable. When the content ratio is 95% by mass or more, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish of the shrink film is more excellent.

In the layer A, the mass ratio of the high bicut resin to the low vicut resin (the former: the latter) is preferably 15 to 100: 85 to 0, more preferably 45 to 100: 55 to 0, and even more preferably 45 to 99. : 55 to 1. When the mass ratio of the high bicut resin is 15 or more, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish of the shrink film is more excellent. In particular, it is preferable that the total content ratio of the high bicut resin and the low bicut resin is 95% by mass or more, and the mass ratio is within the above range.

The layer A may contain the additives exemplified as those which the shrink film of the present invention may contain, as long as the effects of the present invention are not impaired. Only one kind of these components may be used, or two or more kinds thereof may be used. Further, the layer A may contain a recovery raw material obtained by repelletizing a film piece at the time of film production. Above all, by containing a lubricant, it is excellent in cutting suitability.

The surface layer preferably contains a polystyrene resin and / or a polyester resin as a main component. In addition, in this specification, "containing as a main component" means that it is contained as a component having the largest mass ratio. When the surface layer contains a polystyrene resin as a main component, it is superior to the shrinkage finish. When the surface layer contains a polyester resin as a main component, it is excellent in printability and heat shrinkage.

Examples of the polystyrene-based resin include the biomass styrene-butadiene copolymer, the high bicut resin, and the low bicut resin. The polystyrene-based resin preferably contains the high bicut resin. When the surface layer contains a polystyrene resin as a main component, the content ratio of the polystyrene resin in the surface layer is preferably more than 50% by mass, more preferably 70% by mass or more, still more preferably 90% by mass or more.

Examples of the polyester-based resin include the high bicut resin and the low bicut resin. The polyester-based resin preferably contains the high bicut resin. When the surface layer contains the polyester resin as a main component, the content ratio of the polyester resin in the surface layer is preferably more than 50% by mass, more preferably 70% by mass or more, still more preferably 90% by mass or more.

The content ratio of the high bicut resin in the surface layer is preferably 95% by mass or more, more preferably 98% by mass or more, based on the total mass (100% by mass) of the surface layer. When the content ratio is 95% by mass or more, it is more excellent in printability when forming a print layer on the surface of the shrink film. In particular, it is preferable that the content ratio of the polystyrene-based resin and / or the polyester-based resin having a Vicat softening temperature of 75 ° C. or higher and 90 ° C. or lower is within the above range.

The content ratio of the biomass styrene-butadiene copolymer in the surface layer is preferably less than 5% by mass and particularly preferably not contained in the total mass (100% by mass) of the surface layer.
When the content ratio is less than 5% by mass, it is more excellent in printability when forming a print layer on the surface of the shrink film.

The surface layer may contain the additives exemplified as those which the shrink film of the present invention may contain, as long as the effect of the present invention is not impaired. Only one kind of these components may be used, or two or more kinds thereof may be used. Further, the surface layer may contain a recovery raw material obtained by repelletizing a film piece at the time of film production. Above all, it is preferable to contain a lubricant from the viewpoint of being more excellent in cutting suitability.

The base layer portion preferably contains at least an A layer (A1 layer) having a polystyrene-based resin content of 95% by mass or more as a layer in the base layer portion. The content ratio of the polystyrene-based resin in the A1 layer is 95% by mass or more (for example, 95 to 100% by mass), preferably 98% by mass or more, with respect to the total mass (100% by mass) of the A1 layer. When the A1 layer is included, the heat shrinkage rate in the orthogonal direction becomes more appropriate, and the shrinkage finish of the shrink film is more excellent.

The base layer portion may include an A layer (A2 layer) containing a polyester resin and a polystyrene resin. When the surface layer is a layer containing a polyester resin as a main component, if the A2 layer is included, the adhesiveness between the surface layer and the A1 layer is excellent. Both the A1 layer and the A2 layer correspond to the A layer.

The content ratio of the polyester resin in the A2 layer is preferably 10 to 90% by mass, more preferably 15 to 70% by mass, still more preferably 20% by mass or more, based on the total mass (100% by mass) of the A2 layer. It is less than 50% by mass. The content ratio of the polystyrene resin in the A2 layer is preferably 10 to 90% by mass, more preferably 30 to 85% by mass, and further preferably 50% by mass with respect to the total mass (100% by mass) of the A2 layer. It is more than% and 80% by mass or less.

The number of layers of the A1 layer and / or the A2 layer in the base layer portion is not particularly limited, but is 50% or more (preferably 70% or more, more preferably 90% or more) with respect to the number of layers of the base layer portion. It is preferable that the number of layers is the same.

When the base layer portion has an A1 layer and an A2 layer, it is preferable that the base layer portion has a laminated structure in which the A1 layer and the A2 layer are adjacent to each other. When the base layer portion has the laminated structure, the A1 layer has no problem in adhesion to the A2 layer, and can be used for optimizing the shrinkage rate and increasing the compressive strength and rigidity of the shrink label. ,preferable.

In the base layer portion, the A2 layer preferably intervenes between two or more A1 layers, and more preferably intervenes between all A1 layers in the base layer portion except the outermost layer. Further, the A1 layer preferably intervenes between two or more A2 layers, and more preferably intervenes between all A2 layers in the base layer portion except the outermost layer. In particular, in the base layer portion, the A1 layer and the A2 layer are not particularly limited, but are preferably laminated alternately, and more preferably directly laminated alternately without interposing another layer. That is, it is most preferable that the base layer portion contains, as layers in the base layer portion, A1 layer and A2 layer alternately, for a total of 3 to 65 layers.

The laminated structure of the base layer portion is not particularly limited, but specifically, a laminated structure (A1 layer / A2) in which the “A1 layer / A2 layer” is repeated as a repeating unit without interposing a layer other than the A1 layer and the A2 layer. Layer / A1 layer / A2 layer / ... / A1 layer / A2 layer / A1 layer), (A2 layer / A1 layer / A2 layer / A1 layer / ... / A2 layer / A1 layer / A2 layer) , (A1 layer / A2 layer / A1 layer / A2 layer / ... / A1 layer / A2 layer) or (A2 layer / A1 layer / A2 layer / A1 layer / ... / A2 layer / A1 layer) Is preferable.

The outermost layers on both sides of the base layer portion may be an A1 layer or an A2 layer, but both sides are preferably an A2 layer. When the A2 layer is used as the outermost layer of the base layer portion, both the surface layer and the A2 layer contain a polyester resin, and both the A1 layer and the A2 layer contain a polystyrene resin, so that the surface layer and the base layer portion shrink. Delamination that tends to occur during processing (during heat shrinkage) can be suppressed, which is preferable. Further, since the stress at the time of heat shrinkage becomes small and the layers are less likely to shift, the rigidity can be increased without lowering the interlayer strength, which is preferable.

Although not particularly limited, in the base layer portion, it is preferable that all A1 layers are formed from the same raw material, and it is preferable that all A2 layers are formed from the same raw material. That is, it is preferable that the A1 layers and the A2 layers are each formed from the same raw material. In particular, it is preferable that all A1 layers are layers having the same composition, and it is preferable that all A2 layers are layers having the same composition.

(Characteristics of shrink film)
The shrink film of the present invention has heat shrinkage mainly in one direction. Examples of such a shrink film include a film oriented in one direction (uniaxially oriented film). Further, it is preferable that all the film layers constituting the shrink film of the present invention are uniaxially oriented films. The uniaxially oriented film may be a film that is mainly stretched in one direction and slightly stretched in a direction orthogonal to the one direction, and is substantially stretched in one direction.

The uniaxially oriented film is obtained by stretching an unstretched film in one direction. The shrink label using the shrink film of the present invention can mainly heat shrink in the orientation direction of the shrink film of the present invention.

The heat shrinkage of the shrink film (before shrink processing) of the present invention at 90 ° C. for 10 seconds (warm water treatment) in the main shrinkage direction is not particularly limited, but is preferably 50% or more (for example, 50 to 90%). , More preferably 55% or more (for example, 55 to 85%), still more preferably 60% or more (for example, 60 to 80%). The "main shrinkage direction" is the direction in which the heat shrinkage rate is the largest, and is generally the direction in which the film is mainly stretched. For example, a film stretched substantially in one direction in the width direction. In some cases, it is in the width direction.

The heat shrinkage of the shrink film (before shrink processing) of the present invention at 70 ° C. for 10 seconds (warm water treatment) in the main shrinkage direction is not particularly limited, but is preferably 1 to 20%, more preferably 3 to 10. %.

The heat shrinkage rate (80 ° C., 10 seconds) of the shrink film (before shrink processing) of the present invention in the direction orthogonal to the main shrinkage direction (orthogonal direction) is not particularly limited, but is 9.5% or less (for example,-. 5 to 9.5%) is preferable, and more preferably 9.0% or less (for example, -3 to 9.0%).

The thickness (total thickness) of the shrink film of the present invention is not particularly limited, but is preferably 10 to 100 μm, more preferably 15 to 50 μm, and even more preferably 20 to 45 μm. When the thickness is 10 μm or more, the rigidity of the shrink label is excellent.

When the shrink film of the present invention has the base layer portion and the surface layer, the thickness of the surface layer (thickness of one layer) is not particularly limited, but is preferably 1 to 15 μm, more preferably 2 to 10 μm, and even more preferably. Is 2.5 to 8 μm. When the thickness is 15 μm or less, it is possible to suppress a significant decrease in film elongation at room temperature, which is preferable. When the thickness is 1 μm or more, the rigidity of the shrink label is more excellent. The thickness of each surface layer on both sides of the base layer portion may be the same or different from each other.

When the shrink film of the present invention has the base layer portion and the surface layer, the thickness of the base layer portion is not particularly limited, but is preferably 8 to 90 μm, more preferably 10 to 45 μm, and further preferably 11 to 40 μm. .. When the thickness is 8 μm or more, the rigidity of the shrink label can be made more appropriate.

When the shrink film of the present invention has the base layer portion and the surface layer, the thickness of the layer (thickness per layer) in the base layer portion is not particularly limited, but is preferably 0.2 to 15 μm, more preferably 0.2 to 15 μm. It is 0.3 to 10 μm. When the thickness is 0.2 μm or more, the rigidity of the shrink label is more excellent. The thicknesses of the plurality of layers in the base layer portion may be the same or different from each other in all or part of them.

When the shrink film of the present invention has the base layer portion and the surface layer, the thickness of the outermost layer (thickness per layer) of the base layer portion is not particularly limited, but is 0.2 μm or more (for example, 0.2 to 0.2). 15 μm) is preferable, and more preferably 0.3 to 10 μm. The thickness of the intermediate layer (thickness per layer) is not particularly limited, but is preferably 0.3 μm or more (for example, 0.3 to 15 μm), and more preferably 0.6 to 10 μm.

When the shrink film of the present invention has the base layer portion and the surface layer, the ratio of the thickness of the surface layer (total of the thicknesses of all the surface layers) to the thickness of the base layer portion [(thickness of the surface layer) :( base layer portion). The thickness)] is not particularly limited, but is preferably 1: 1 to 1:14, more preferably 1: 1 to 1: 8, and particularly preferably 1: 1 to 1: 4. It is preferable that the base layer portion is thicker than the above ratio of 1: 1 because the effect of improving the transparency by multi-layering can be easily obtained. On the other hand, when the surface layer is thicker than the above ratio of 1:14, the heat shrinkage and rigidity of the shrink label are further improved, which is preferable.

When the shrink film of the present invention has an A1 layer and an A2 layer as layers in the base layer portion, the thickness of the A1 layer (total thickness of all A1 layers) and the thickness of the A2 layer (total thickness of all A2 layers). The ratio [(thickness of A1 layer) :( thickness of A2 layer)] is not particularly limited, but is preferably 2: 1 to 1:10, and more preferably 1: 1 to 1: 8. It is preferable that the A2 layer is thicker than the above ratio of 2: 1 because it is easy to obtain higher transparency and more appropriate heat shrinkage and rigidity. On the other hand, when the A1 layer is thicker than the above ratio of 1:10, the adhesive strength between the layers in the base layer portion is less likely to decrease, and delamination is less likely to occur, which is preferable.

The coefficient of static friction between at least one surface of the shrink film of the present invention is preferably 0.40 or less, more preferably 0.35 or less, still more preferably 0.30. When the static friction coefficient is 0.40 or less, the cutting suitability is excellent. The lower limit of the static friction coefficient is, for example, 0.10. The static friction coefficient can be measured according to JIS K7125 using the shrink film of the present invention as a test piece.

The coefficient of dynamic friction between at least one surface of the shrink film of the present invention is preferably 0.40 or less, more preferably 0.38 or less, still more preferably 0.36 or less. When the dynamic friction coefficient is within the above range, the printability on a shrink film is excellent. The lower limit of the dynamic friction coefficient is, for example, 0.10. The dynamic friction coefficient can be measured according to JIS K7125 using the shrink film of the present invention as a test piece.

The tensile elastic modulus of the shrink film of the present invention is preferably 1.0 MPa or more, more preferably 1.1 MPa or more. When the tensile elastic modulus is 1.0 MPa or more, the mounting stability on the object to be mounted is excellent. The upper limit of the tensile elastic modulus may be 2.0 MPa or 1.8 MPa. The tensile elastic modulus can be measured based on JIS K7161-1.

[Shrink label]
A shrink label can be obtained by using the shrink film of the present invention. The shrink label is a shrink label including at least the shrink film of the present invention. The shrink label may include a layer other than the shrink film of the present invention.

(Layer other than the shrink film of the present invention)
The layer other than the shrink film of the present invention contained in the shrink label is not particularly limited, but is not particularly limited, but is a printing layer, another film layer such as a non-woven fabric or a foamed sheet, and an adhesive layer (pressure sensitive adhesive layer, heat-sensitive adhesive). Agent layer, etc.), protective layer, anchor coat layer, primer coat layer, coating layer, antistatic layer, aluminum vapor deposition layer and the like.

(Print layer)
The print layer is not particularly limited, and examples thereof include known and conventional print layers used in shrink labels. Examples of the printing layer include a solvent-drying type printing layer formed by a solvent-drying type printing ink, an active energy ray-curable printing layer formed by an active energy ray-curable printing ink, and the like. The printing layer includes, for example, a design printing layer (color printing layer, etc.) such as a figure or design of a product name, an illustration, handling precautions, a back printing layer formed of a single color such as white, a film, or the like. Examples thereof include a protective print layer provided to protect the print layer, a primer print layer provided to enhance the adhesion between the film and the print layer, and the like. The print layer is not particularly limited, but may be provided only on one side of the shrink film of the present invention, or may be provided on both sides of the shrink film of the present invention. Further, the print layer may be provided on the entire surface (the surface on the side where the print layer is provided) of the shrink film of the present invention, or may be provided on a part of the surface. Further, the print layer is not particularly limited, but may be a single layer or a plurality of layers. Further, the print layer can be provided by a well-known or conventional printing method. Above all, it is preferable that the printing layer is provided by a gravure printing method or a flexographic printing method.

The print layer is not particularly limited, but preferably contains a binder resin as an essential component. Further, if necessary, it may contain coloring pigments such as blue, red, yellow, black and white, and additives such as lubricants, dispersants and defoamers. As the binder resin and the like, only one kind may be used, or two or more kinds may be used.

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

The solvent-drying type printing layer is formed by applying, for example, a printing ink produced by mixing the binder resin, the solvent, and if necessary, the coloring pigment and other additives, using a printing machine. , Provided by volatilizing the solvent. On the other hand, the active energy ray-curable printing layer was produced by, for example, mixing the monomer components constituting the binder resin,, if necessary, the coloring pigment, the solvent, and other additives. After the printing ink is applied using a printing machine, it is dried if necessary, and the above-mentioned monomer component is polymerized and cured by irradiation with active energy rays (for example, ultraviolet rays).

The thickness of the print layer is not particularly limited, but is preferably 0.1 to 10 μm, more preferably 0.3 to 5 μm, for example.

The printing layer can be formed by applying printing ink on at least one surface of the shrink film of the present invention and solidifying it by drying or curing. As a method for applying the printing ink, a known and commonly used method can be used, and among them, gravure printing, flexographic printing, and digital printing are preferable. Further, when the applied printing ink is dried or solidified by heating or the like, a general heating device capable of heating on the printing device can be preferably used. From the viewpoint of safety, a hot air heater or the like can be preferably used. For example, in a design printing layer, the printing ink is generally applied a plurality of times for each color to form a printing layer that is a plurality of layers.

When the printing ink is a solvent-drying type printing ink, the printing ink is produced by mixing, for example, a binder resin, a solvent, and other additives (coloring pigments, etc.), if necessary. Mixing can be performed by a known and conventional mixing method, and is not particularly limited, and for example, a mixer such as a paint shaker, a butterfly mixer, a planetary mixer, a pony mixer, a dissolver, a tank mixer, a homomixer, a homodisper, or a roll mill. , Sand mills, ball mills, bead mills, line mills and other mills, kneaders and other mixing devices are used. The mixing time (residence time) at the time of mixing is not particularly limited, but is preferably 10 to 120 minutes. The obtained printing ink may be used after being filtered, if necessary. As each of the above components (binder resin, solvent, and other additives), only one kind may be used, or two or more kinds may be used.

As the solvent, water or an organic solvent usually used for printing inks used for gravure printing, flexographic printing and the like can be used. Examples of the organic solvent include esters such as acetates (eg, ethyl acetate, propyl acetate, butyl acetate); alcohols such as methanol, ethanol, isopropyl alcohol, propanol and butanol; ketones such as methyl ethyl ketone and methyl isobutyl ketone; toluene. Aromatic hydrocarbons such as xylene; aliphatic hydrocarbons such as hexane and octane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; glycols such as ethylene glycol and propylene glycol; ethylene glycol monopropyl ether and propylene glycol monomethyl ether , Glycol ethers such as propylene glycol monobutyl ether; glycol ether esters such as propylene glycol monomethyl ether acetate and the like. The solvent can be removed by drying after applying the printing ink to the shrink film of the present invention. The solvent also includes the meaning of "dispersion medium".

When the printing ink is an active energy ray-curable printing ink, the printing ink contains monomer components, solvents, and other additives (coloring pigments, etc.) constituting the binder resin, if necessary. Manufactured by mixing. The mixing can be performed by a known and conventional mixing method, and the mixing device is not particularly limited, and for example, the mixing device exemplified and described as the above-mentioned solvent-drying type printing ink mixing device can be used. The mixing time (residence time) at the time of mixing is not particularly limited, but is preferably 10 to 120 minutes. The obtained printing ink may be used after being filtered, if necessary. As each of the above components (monomer component, solvent, and other additives), only one type may be used, or two or more types may be used.

The thickness (total thickness) of the shrink label is not particularly limited, but is preferably 10 to 110 μm, more preferably 15 to 90 μm, and even more preferably 20 to 80 μm.

The shrink label may be a front print shrink label, a back print shrink label, or a double-sided print shrink label. Above all, the shrink film of the present invention is particularly useful as a back-printed shrink label from the viewpoint of excellent shrinkage finish. In the present specification, the front print label is a label that shows printing without passing through a shrink film, and means a label having a design printing layer in front of the shrink film when the label is viewed. The back print label is a label that shows printing through a shrink film, and refers to a label that has a design printing layer on the back side of the shrink film when the label is viewed. The double-sided printing label means a label having a design printing layer on both sides of the shrink film.

The shrink label is, for example, a tubular shrink label of a type in which both ends of the label are sealed with a solvent or an adhesive to form a cylinder and attached to the container, or one end of the label is attached to the container, the label is wound, and then the label is wound. It can be used as a wrapping type shrink label in which the other end is overlapped with one end to form a tubular shape. Among the above, the shrink label is particularly preferably used for a tubular shrink label. That is, the shrink label is preferably a cylindrical shrink label.

An example of a cylindrical shrink label, which is a preferred embodiment of the shrink label, will be described with reference to FIGS. 4 and 5. The tubular shrink label 2 shown in FIG. 4 is formed by superimposing the other end portion on the outer side of one end portion of the shrink label formed in a rectangular shape to form a cylinder, and the inner surface of the other end portion and the outer surface of the one end portion are formed. It is a tubular body formed by joining with a solvent or an adhesive to form a sealing portion 21. The tubular shrink label 2 includes a shrink film 1, and the shrink film 1 is at least oriented in the circumferential direction D of the tubular shrink label 2 and is heat-shrinkable in that direction. The tubular shrink label is preferably attached so that the circumferential direction is the main contraction direction. Further, even in the case of a winding type shrink label, it is preferable that the label is formed into a cylinder so that the circumferential direction is the main contraction direction (that is, the stretching direction).

FIG. 5 is an enlarged view of a cross section of AA'in FIG. 4, that is, a main part of the tubular shrink label 2 near the seal portion. In the seal portion 21, both ends of the shrink label are a solvent or an adhesive 33. It is joined with. Specifically, in the shrink label, a design print layer 32 is formed in a region excluding a region having a predetermined width from the other end of one surface (cylindrical inner surface side surface) of the shrink film 1. The back surface printing layer 31 is formed in substantially the entire area excluding the region having a predetermined width from the end of the other end of one surface of the shrink film 1 so as to cover the design printing layer 32. Therefore, the back surface printing layer 31 and the design printing layer 32 are not formed on the tubular shrink label 2 in the region having a predetermined width from the other end, the shrink film 1 is exposed, and the exposed film surface is exposed. The sealed portion 21 is formed by joining a film exposed surface formed on the inner surface side of the other end of the tubular shrink label 2 and an outer surface (film exposed surface) of one end thereof with a solvent or an adhesive 33. There is. That is, in the sealing portion 21, it is preferable that the shrink films 1 are bonded to each other with a solvent or an adhesive 33. Of the above-mentioned both end portions, the portions that are not joined may have a print layer because the adhesiveness is not affected even if the back print layer, the design print layer, or the like has a print layer.

In the tubular shrink label 2 in FIG. 5, one end extends to a position where the end overlaps with the back printing layer 31 at the other end, and the back printing layer 31 at one end and the other end shrinks with each other. Overlapping regions are formed via the film 1. Therefore, there is no region where the back print layer 31 does not exist in the thickness direction. The tubular shrink label 2 may have a structure that overlaps the end of one end and the back printing layer on the other end side (overlaps in the thickness direction, that is, overlaps in the surface spreading direction) as shown in FIG. The end of one end and the other end do not extend to the area where the end of one end overlaps the exposed surface of the film at the other end and the end of one end does not extend to the position where it overlaps the back print layer on the other end side. The structure may not overlap with the back print layer.

The width of the seal portion is not particularly limited, but is preferably 0.2 to 10 mm, more preferably 0.3 to 5 mm, and even more preferably 0.4 to 2 mm.

(Manufacturing method of tubular shrink label)
The method for manufacturing the tubular shrink label is not particularly limited, but is, for example, as follows. A long shrink label is slit to a predetermined width to obtain a long label body in which a plurality of shrink labels are connected in the long direction (longitudinal direction). This long label body is formed into a tubular shape by overlapping so that the heat-shrinkable direction (that is, the heat-shrinkable direction of the shrink film) is the circumferential direction and the other end is on the outside of one end. , The overlapped portion is sealed in a strip shape with a predetermined width and both ends are joined to obtain a long tubular label continuum (long tubular shrink label). By cutting this long tubular shrink label in the circumferential direction, one tubular shrink label having a predetermined length in the height direction can be obtained. When providing a perforation for cutting a label, a conventional method (for example, a method of pressing a disc-shaped blade in which a cut portion and a non-cut portion are repeatedly formed around the perforation, a method of using a laser, etc.) is used. Can be applied. The process of perforating can be appropriately selected, such as after the printing layer is provided or before and after the process of processing into a cylindrical shape.

The tubular shrink label is manufactured by cutting the long tubular shrink label as described above, but depending on the shrink label, the inner surfaces of the label adhere (join) to each other at the time of cutting, so-called cut fusion. Arrival may occur. In particular, when a guillotine cutter or a rotary cutter is used, cut fusion is likely to occur in the opening on the upstream side of the tubular shrink label due to, for example, the influence of frictional heat or pressing during cutting. However, when the shrink film of the present invention is excellent in cut suitability, cut fusion is unlikely to occur. Further, even if cut fusion occurs, the degree of fusion is small and it can be easily separated. Therefore, the shrink label can be used not only for a labeler equipped with a cutter that is difficult to cut and fuse, but also for a labeler equipped with a cutter that is relatively easy to cut and fuse, and is excellent in versatility.

[Labeled container]
The shrink label is not particularly limited, but is attached to a container and used as a labeled container. The shrink label may be used for an adherend other than the container.
For example, by arranging the shrink label (particularly, a tubular shrink label) around the container so that the shrink label has a cylindrical shape and attaching it to the container by heat shrinking, the labeled container (the shrink label) (the shrink label). A labeled container with a label) is obtained. The above containers include, for example, soft drink bottles such as PET bottles, home delivery milk bottles, food containers such as seasonings, alcoholic beverage bottles, pharmaceutical containers, detergents, chemical product containers such as sprays, and toiletries. Includes containers, cup noodle containers, etc. The shape of the container is not particularly limited, and examples thereof include various shapes such as a bottle type such as a cylinder and a square shape, and a cup type. The material of the container is not particularly limited, and examples thereof include plastics such as PET, glass, and metal.

The above-mentioned container with a label can be produced, for example, by fitting a tubular shrink label to a predetermined container and then heat-shrinking the tubular shrink label by heat treatment to bring it into close contact with the container (shrink processing). Examples of the heat treatment method include a method of passing through a hot air tunnel and a steam tunnel, a method of heating with radiant heat such as infrared rays, and the like. In particular, a method of treating with steam at 80 to 100 ° C. (passing through a heating tunnel filled with steam and steam) is preferable. Further, dry steam at 101 to 140 ° C. can also be used. The heat treatment is not particularly limited, but is preferably carried out in a temperature range in which the temperature of the shrink film is 85 to 100 ° C. (particularly 90 to 97 ° C.). The shrink label can be used for containers that require a high heat shrinkage rate. Further, the treatment time of the heat treatment is preferably 4 to 20 seconds from the viewpoint of productivity and economy.

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

Table 1 shows information on the raw materials used in Examples and Comparative Examples. In addition, Table 2 shows the configurations and evaluation results of the shrink films and shrink labels produced in Examples and Comparative Examples. In Table 2, "-" indicates that the evaluation was not performed.

Example 1
(material)
80% by mass of polystyrene-based resin composition D (Vicat softening temperature: 82 ° C.) and 20 mass% of polystyrene-based resin composition E (Vicat softening temperature: 83 ° C.) as raw materials constituting the surface layer (raw materials for surface layer). %Using. The raw material for the surface layer is SBS (derived from petroleum) containing 1% by mass of GPPS and 2% by mass of HIPS.
As a raw material constituting the central layer (raw material for the central layer), 100 mass of polystyrene resin A (trade name "Stylolux M", manufactured by Stylollution Co., Ltd., Vicat softening temperature: 76 ° C., biomass styrene-butadiene copolymer) %Using.

(Shrink film)
The raw material for the central layer was put into the extruder x heated to 220 ° C., and the raw material for the surface layer was put into the extruder z heated to 250 ° C. Melt extrusion was performed using the above two extruders. The melted central layer raw material and the melted surface layer raw material are composed of two types and three layers of surface layer raw material / central layer raw material / surface layer raw material by using a feed block having a merging method of two types and three layers. The laminated body of was produced.
Further, the laminate was extruded from a T-die and then rapidly cooled on a casting drum cooled to 25 ° C. to obtain a laminated unstretched film having surface layers on both sides of the central layer.
Next, the laminated unstretched film is tenter-stretched 5 times at 85 ° C. in the width direction to be mainly stretched in the width direction, and the length of the stretched film (shrink film) mainly having heat shrinkage in the direction. I got a scale.

(Cylindrical shrink label)
A design printing layer and a white background printing layer were formed on the long body of the shrink film obtained above by a gravure printing machine to obtain a long body of a shrink label. Next, the long body of the shrink label is slit to have a predetermined width, and then one end and the other end are overlapped to form a cylinder so that the width direction is the circumferential direction, and the one end and the other end are formed into a cylinder. The shrink film surfaces of the portions were sealed with a solvent to obtain a tubular elongated body (long tubular shrink label) of the shrink label.

Example 2
As a raw material for the central layer, polystyrene resin A is 80% by mass, polystyrene resin B (trade name "Stylolux S", manufactured by Stylollution Co., Ltd., Vicat softening temperature: 70 ° C., styrene-butadiene copolymer (derived from petroleum)). ) Was used in an amount of 20% by mass, and a shrink film and a long tubular shrink label were produced in the same manner as in Example 1.

Example 3
A shrink film and a long tubular shrink label were produced in the same manner as in Example 1 except that polystyrene-based resin A was used in an amount of 50% by mass and polystyrene-based resin B was used in an amount of 50% by mass as raw materials for the central layer.

Example 4
A shrink film and a long tubular shrink label were produced in the same manner as in Example 1 except that polystyrene-based resin A was used in an amount of 20% by mass and polystyrene-based resin B was used in an amount of 80% by mass as raw materials for the central layer.

Comparative Example 1
A shrink film and a long tubular shrink label were produced in the same manner as in Example 1 except that polystyrene-based resin B was used in an amount of 100% by mass as a raw material for the central layer.

Comparative Example 2
Except for the fact that 100% by mass of polystyrene resin C (trade name "Stylolux T", manufactured by Stylollution, Vicat softening temperature: 62 ° C, styrene-butadiene copolymer (derived from petroleum)) was used as a raw material for the central layer. Made a shrink film and a long tubular shrink label in the same manner as in Example 1.

Comparative Example 3
A shrink film and a long tubular shrink label were produced in the same manner as in Example 1 except that polystyrene-based resin B was used in an amount of 50% by mass and polystyrene-based resin C was used in an amount of 50% by mass as raw materials for the central layer.

The shrink films obtained in Examples 1 to 4 and Comparative Examples 1 to 3 have a two-kind, three-layer structure of [surface layer / center layer / surface layer]. Therefore, in the shrink film, the base layer portion is composed of a single central layer. The central layer in Examples 1 to 4 corresponds to the A layer.

Example 5
(material)
As the raw material for the central layer, 50% by mass of the polystyrene-based resin composition D and 50% by mass of the polystyrene-based resin A were used.
As a raw material (raw material for the adhesive resin layer) constituting the adhesive resin layer, 30% by mass of polyester resin A (trade name "EMBRACE LV", manufactured by Eastman Chemical Company, Vicut softening temperature: 76 ° C.), polystyrene resin A is used. 70% by mass was used.
As a raw material for the surface layer, 100% by mass of polyester resin A was used.

(Shrink film)
The raw material for the central layer was put into the extruder heated to 220 ° C., the raw material for the adhesive resin layer was put into the extruder b heated to 220 ° C., and the raw material for the surface layer was put into the extruder c heated to 220 ° C. Melt extrusion was performed using the above three extruders. The molten center layer raw material and the melted adhesive resin layer raw material are combined into two types, an adhesive resin layer raw material / a central layer raw material / an adhesive resin layer raw material, using a feed block having a merging method of two types and three layers. A three-layered laminate was prepared, extruded from a T-die, and then rapidly cooled on a casting drum cooled to 25 ° C. to obtain a laminated unstretched film having surface layers on both sides of the base layer portion. ..
Next, the laminated unstretched film is tenter-stretched 5 times at 85 ° C. in the width direction to be mainly stretched in the width direction, and is a long body of a stretched film (shrink film) having heat shrinkage in the direction. Got

(Cylindrical shrink label)
A long tubular shrink label was produced in the same manner as in Example 1 except that the shrink film obtained above was used.

Example 6
A shrink film and a long tubular shrink label were produced in the same manner as in Example 5 except that polystyrene-based resin A was used in an amount of 100% by mass as a raw material for the central layer.

The shrink films of Examples 5 and 6 have a three-kind five-layer structure of [surface layer / adhesive resin layer / center layer / adhesive resin layer / surface layer]. Therefore, in the shrink film, the base layer portion has a three-layer structure of [adhesive resin layer / center layer / adhesive resin layer], and the outermost layer of the base layer portion is an adhesive resin layer. The central layer corresponds to the A1 layer, and the adhesive resin layer corresponds to the A2 layer.

Example 7
(material)
As the raw material for the central layer, 50% by mass of the polystyrene-based resin composition D and 50% by mass of the polystyrene-based resin A were used.
As a raw material for the adhesive resin layer, 30% by mass of polyester-based resin A and 70% by mass of polystyrene-based resin A were used.
As a raw material for the surface layer, 100% by mass of polyester resin A was used.

(Shrink film)
The raw material for the central layer was put into the extruder heated to 220 ° C., the raw material for the adhesive resin layer was put into the extruder b heated to 220 ° C., and the raw material for the surface layer was put into the extruder c heated to 220 ° C. Melt extrusion was performed using the above three extruders. A raw material for an adhesive resin layer / center using a laminating device that combines a molten core layer raw material and a melted adhesive resin layer raw material in combination with a feed block with a two-kind, three-layer type and a multiplier divided into four parts. The two-kind three-layer structure of the raw material for the layer / the raw material for the adhesive resin layer is divided, merged, and laminated as one repeating unit, and the laminated body (I) (the above two-kind three-layer structure is laminated four times (number of repetitions 4)). The melted raw material for the surface layer was merged and laminated on both sides of the laminated body (I) using a feed block to obtain a laminated body (II). Further, the laminate (II) was extruded from a T-die and then rapidly cooled on a casting drum cooled to 25 ° C. to obtain a laminated unstretched film having surface layers on both sides of the base layer portion. ..
Next, the laminated unstretched film is tenter-stretched 5 times at 85 ° C. in the width direction to be mainly stretched in the width direction, and is a long body of a stretched film (shrink film) having heat shrinkage in the direction. Got

Example 8
A shrink film and a long tubular shrink label were produced in the same manner as in Example 7 except that polystyrene-based resin A was used in an amount of 100% by mass as a raw material for the central layer.

Comparative Example 4
50% by mass of polystyrene resin B and 50% by mass of polystyrene resin C were used as raw materials for the central layer, and 30% by mass of polyester resin A and polystyrene resin B were used as raw materials for the adhesive resin layer. A shrink film and a long tubular shrink label were produced in the same manner as in Example 7 except that 21% by mass and 49% by mass of polystyrene resin C were used.

The shrink films of Examples 7 and 8 and Comparative Example 4 were [surface layer / adhesive resin layer / center layer / adhesive resin layer / center layer / adhesive resin layer / center layer / adhesive resin layer / center layer / adhesive. Resin layer / surface layer] has 3 types and 11 layers. Therefore, in the shrink film, the base layer portion has a nine-layer structure of [adhesive resin layer / center layer / adhesive resin layer / center layer / adhesive resin layer / center layer / adhesive resin layer / center layer / adhesive resin layer]. The outermost layer of the base layer portion is an adhesive resin layer. The central layer in Examples 7 and 8 corresponds to the A1 layer, and the adhesive resin layer corresponds to the A2 layer, respectively.

(evaluation)
The shrink films and long tubular shrink labels obtained in Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Table 2.

(1) Tensile elastic modulus From the shrink film (before shrink processing) obtained in Examples and Comparative Examples, 150 mm (width direction; main contraction direction, marked line spacing 10 mm) × 15 mm (longitudinal direction; with respect to main contraction direction). A rectangular sample piece (in the orthogonal direction) was prepared. The tensile elastic modulus of the above sample piece was measured at a test speed of 10 mm / min based on JIS K7161-1.

(2) Thermal shrinkage rate in the orthogonal direction From the shrink film (before shrink processing) obtained in Examples and Comparative Examples, 120 mm (width direction; main shrinkage direction, marked line spacing 10 mm) × 5 mm (longitudinal direction; main shrinkage direction) A rectangular sample piece (in the direction orthogonal to the direction) was prepared.
The above sample piece is heat-treated in warm water at 90 ° C. for 10 seconds (under no load), the difference in the marked line spacing before and after the heat treatment is read, and the heat shrinkage rate is calculated in the direction orthogonal to the main shrinkage direction by the following formula. Calculated.
Shrinkage rate (%) = (L ₀ -L ₁ ) / L ₀ × 100 L ₀ : Dimensions of sample piece before heat treatment (main shrinkage direction)
L ₁ : Dimensions of the sample after heat treatment (in the same direction as L ₀ )

(3) Friction coefficient With respect to the shrink films obtained in Examples and Comparative Examples, the static friction coefficient and the dynamic friction coefficient between the surfaces thereof were measured according to JIS K7125.
The measuring equipment, measuring conditions, procedures, etc. are as follows.
Measuring equipment: "Friction Tester TR-2" (manufactured by Toyo Seiki Co., Ltd.)
Weight: 200 g ± 2 g (= 1.96 _N normal force FP is generated), has a bottom surface of 63 mm × 63 mm, and a felt of the same size is attached to the bottom surface.
Sample: Shrink film piece cut to 65 mm x 160 mm (non-shrinkable product)
Friction partner: Shrink film piece cut to 110 mm x 300 mm (non-shrinkable product) Procedure: A sample was wound around a weight so that the surface faced outward, and a weight with a sample was obtained. In the weight with a sample, the bottom surface of the weight is covered with the sample, and the surface of the sample exists over the entire bottom surface of the weight to form a measurement surface (63 × 63 mm). A weight with a sample is placed on a smooth table fixed with the shrink film piece of the friction partner facing upward so that the measurement surface of the weight with the sample is in contact with the surface of the friction partner. Started. Then, the maximum stress obtained first was taken as the static friction force, and the static friction coefficient was calculated from this value. Further, the frictional force acting during the sliding motion was taken as the dynamic frictional force, and the dynamic friction coefficient was calculated from this value.
Measurement distance: 60 mm
Speed: 100 mm / min

(4) Cutability When the long tubular shrink labels obtained in Examples and Comparative Examples were cut in the width direction with a rotary cutting machine, the degree of adhesion of the cut surface was confirmed. Then, the cut suitability was evaluated according to the following criteria.
Good cutability (○): There is no adhesion between the inner surfaces of the labels on the cut surface after cutting.
Cut suitability is possible (△): On the cut surface after cutting, some of the inner surfaces of the labels are adhered to each other, but they can be expanded.
Poor cut suitability (x): On the cut surface after cutting, adhesion between the inner surfaces of the labels was observed as a whole, and the label could not be expanded.

(5) CO ₂ reduction rate Based on the fact that the CO ₂ reduction rate of the polystyrene-based resin A is 74% by mass, it was calculated from the content of the polystyrene-based resin A.

As is clear from Table 2, when the shrink film of the present invention is used (Example), the heat shrinkage rate in the orthogonal direction is small while using the polystyrene-based resin using the styrene-based monomer derived from biomass. It had an excellent shrinkage finish and could be used practically. Further, in Examples 5 to 8, after cutting the long tubular shrink label, adhesion between the inner surfaces of the labels could not be confirmed, and the cutting suitability was excellent. The shrink film having poor cutability can be used by appropriately selecting a cutting method for a long tubular label.

1 Shrink film 11 Surface layer 12 Base layer 12a A layer 12b Adhesive resin layer 2 Cylindrical shrink label 21 Seal part D Circumferential direction 31 Back printing layer 32 Design printing layer 33 Solvent or adhesive

Claims

A shrink film that is mainly heat-shrinkable in one direction.
Containing a styrene-butadiene copolymer having a structural unit derived from a biomass-derived styrene-based monomer,
A shrink film having a resin content of 45% by mass or more and a Vicat softening temperature of 75 ° C. or higher and 90 ° C. or lower with respect to the total mass of the shrink film.
A base layer portion having one or more layers and a surface layer provided on both sides of the base layer portion are provided.
The base layer portion has a layer (A layer) containing the styrene-butadiene copolymer as a layer in the base layer portion.
The layer A is a layer in which the content ratio of the styrene-butadiene copolymer is 20% by mass or more, and the content ratio of the resin having a Vicat softening temperature of 75 ° C. or higher and 90 ° C. or lower is 15% by mass or more. The shrink film according to claim 1.
The shrink film according to claim 2, wherein the surface layer does not contain the styrene-butadiene copolymer, or the content ratio of the styrene-butadiene copolymer in the surface layer is less than 5% by mass.