JP5760160B2 - Heat shrinkable film - Google Patents

Description

  The present invention relates to a heat shrinkable film. More specifically, the present invention relates to a heat-shrinkable film that does not cause delamination during heat shrinkage and is excellent in appearance and shrinkage workability when used as a shrink label.

  In recent years, plastic bottles such as polyethylene terephthalate bottles (PET bottles) are widely used as containers for beverages such as tea and soft drinks. In these containers, in order to efficiently reuse the used material, it is avoided as much as possible to print directly on the bottle body or attach a label using an adhesive. Therefore, in order to give a necessary display (product name, instruction manual, etc.) or decoration as a product to the bottle, the display or decoration is once printed on a heat-shrinkable film (also referred to as “shrink film”), and the heat A general method is to prepare a shrinkable film as a shrink label and then attach it to a bottle and heat shrink (shrink process) to fix it to the bottle.

  In the above applications, the heat-shrinkable film must have excellent printing properties and have heat-shrinking properties that are suitable for shrinkage treatment. In addition, it must have various mechanical properties (mechanical properties) as a label. I must. However, it is very difficult to satisfy all of these required characteristics at the same time.

  For example, a heat-shrinkable film made of polystyrene resin (especially styrene-butadiene block copolymer) has good shrinkage (heat shrinkage) characteristics (for example, relatively little shrinkage and gentle shrinkage). As a material for shrink labels, it exhibits excellent appearance and heat resistance, and has a high degree of freedom in monomer formulation and copolymer formulation in copolymerization, and it is easy to adjust the rigidity and shrinkage behavior of stretched films. There is an advantage that it is easy to handle. However, since the solvent resistance is inferior, there is a problem that a special ink is required for printing in some cases.

  A heat-shrinkable film made of a polyester-based resin (particularly an amorphous polyester-based resin) has advantages such as good mechanical properties, excellent chemical resistance, and high shrinkage (heat shrinkage). Further, there is a case where it is preferable that the separation from the PET bottle is not required in the disposal process. However, it has a disadvantage that it tends to spontaneously shrink due to its poor heat resistance, and the shrinkage uniformity and shrinkage due to the large shrinkage rate and shrinkage stress tend to cause shrinkage spots and wrinkles after shrinkage.

  In addition, heat-shrinkable films made of polyolefin resins such as polyethylene and polypropylene have advantages such as excellent moldability (moldability) and stretchability, and low specific gravity, which facilitates separation of specific gravity upon disposal. In particular, a heat-shrinkable film made of a copolymer of propylene and α-olefin using a metallocene catalyst has an advantage of exhibiting relatively good shrinkage characteristics. However, there are problems such as a small shrinkage rate, poor printability and center sealability with a solvent, insufficient rigidity, and poor tearability. Among the polyolefin-based resins, the cyclic olefin-based resin is easy to use because it exhibits a high shrinkage ratio, sufficient rigidity, and good center sealability with a solvent. However, since the heat-shrinkable film made of the cyclic olefin-based resin is fragile, there is a problem that it is inferior in mechanical properties as a film alone.

  In recent years, the properties required for heat-shrinkable films have been combined, for example, flexibility and dimensional stability, excellent printability and chemical resistance, waist strength (rigidity), and impact resistance. There is a demand for a combination of properties that cannot be satisfied by a resin. In order to satisfy such a requirement, it is common to select a material that can correspond to each required characteristic, and cope with a laminated film in which these are combined for each layer (see, for example, Patent Document 1).

  However, since the laminated film made of different materials such as the polyester resin, polystyrene resin, and polyolefin resin is combined with layers having different shrinkage characteristics, delamination often occurs during the heat shrinkage treatment. Such peeling often occurs in the vicinity of the center-sealed part (adhesive part) during heat shrinkage when used for shrink label applications, and the edge part of the outer layer of the film that overlaps with the center seal part is outside. It often occurs in a form that drowns. When the shrinkage behavior differs greatly from layer to layer, cavities due to peeling are generated at the edge portion. If the cavity due to the peeling frequently occurs in the center seal portion, the appearance of the entire bottle is greatly impaired, and the commercial value is significantly reduced.

  As a countermeasure to the above problem, many attempts have been made to provide an adhesive layer between layers where peeling easily proceeds, and an adhesive layer such as ethylene-vinyl acetate resin is known (for example, see Patent Document 2). ).

  However, the method of providing an adhesive layer as described above complicates the layer structure of the film, makes production difficult, and often increases the cost significantly. In addition, by providing the adhesive layer, the technical problem of the adhesive layer itself may be combined with the original film problem. For example, a heat-shrinkable film laminated via an adhesive layer requires a process for forming the adhesive layer, which complicates the manufacturing process and requires a device capable of multi-layer lamination. The manufacturing cost is high. Moreover, in heat-shrinkable films that require transparency, the transparency is hindered by the adhesive layer, and particularly when the film is highly shrunk (for example, the heat shrinkage rate is 30% or more), the adhesive layer shrinks. In some cases, unevenness occurs and the optical characteristics (transparency) deteriorate. In addition, since the adhesive layer cannot follow the shrinkage of the film, there is a problem that the shrinkage rate of the film itself is lowered. Furthermore, due to the effect of the adhesive layer, before heat shrink processing (shrink processing), even those having a relatively high interlayer strength soften in the heat shrink process and lose their function as an adhesive layer (adhesive) (adhesion) There is also an example in which peeling progresses because the agent layer is provided.

JP 2002-351332 A International Publication No. 2009/084212 Pamphlet

  Accordingly, in view of the above-described conventional problems, the object of the present invention is to delamination during shrinkage (heat shrinkage) even for heat shrinkable films obtained by laminating different resins having relatively low adhesive strength. An object of the present invention is to provide a heat-shrinkable film that can prevent the above-mentioned problem, has a good appearance, and can be easily manufactured at low cost.

  As a result of intensive studies to achieve the above object, the present inventors have determined that the heat shrinkage behavior of adjacent resin layers in a certain range in a heat shrinkable film obtained by laminating resin layers made of different resins. It has been found that a heat-shrinkable film having a good appearance can be obtained without causing delamination during shrinkage even when an adhesive layer is not provided.

That is, the present invention is a heat-shrinkable film having a resin layer (A layer) and a resin layer (B layer) laminated adjacent to each other, and satisfies all of the following (1 ′) to (6) A heat-shrinkable film is provided. (1 ′) The A layer and the B layer are mainly composed of a styrene-conjugated diene copolymer in which the content of the polyester-based resin or the conjugated diene is 5 to 30% by weight with respect to the total weight of the monomer components. It is a resin layer. However, the polyester resin is a polyester resin composed of a dicarboxylic acid component and a diol component, or a dicarboxylic acid component and a diol component, oxycarboxylic acid, monocarboxylic acid, polyvalent carboxylic acid, monohydric alcohol, And one or more components selected from the group consisting of polyhydric alcohols. (2) The A layer and the B layer are resin layers mainly composed of different kinds of resins. (3) The adhesive strength between the A layer and the B layer in the T-type peel test is 2.5 N / 15 mm or less. (4 ′) The heat shrinkage rate (80 ° C., 30 seconds) in the main orientation direction of the heat shrinkable film is 40 to 85%. (5) The absolute value of the difference between the thermal contraction rate of the A layer (80 ° C., 30 seconds) and the thermal contraction rate of the B layer (80 ° C., 30 seconds), the thermal contraction rate of the A layer (90 ° C, 30 seconds) and the absolute value of the difference between the thermal contraction rates of the B layer (90 ° C, 30 seconds) and the thermal contraction rate of the A layer (98 ° C, 30 seconds) and the thermal contraction rate of the B layer (98 ° C) , 30 seconds), at least one of the absolute values of the difference is 10% or less. (6) A layer and B layer are laminated | stacked by coextrusion, and the extending | stretching process is performed.

Furthermore, the present invention provides the styrene-conjugated diene copolymer , wherein the content of the styrene monomer is 60 to 95% by weight with respect to the total weight of the monomer components, and the content of the conjugated diene. However, the heat-shrinkable film is provided in an amount of 5 to 40% by weight based on the total weight of the monomer components .
Furthermore, the present invention provides the heat-shrinkable film, wherein the polyester resin has a glass transition temperature of 60 to 100 ° C. and the styrene-conjugated diene copolymer has a glass transition temperature of 60 to 120 ° C. .
Further, according to the present invention, the raw material forming the A layer and the raw material forming the B layer have an absolute value (| E ^* |) of complex elastic modulus measured in a dynamic viscoelasticity measurement at a frequency of 10 Hz is 80 Provided is the above heat-shrinkable film having a portion of 30 to 300 MPa in a temperature range of ˜120 ° C.
In addition, in this specification, it is a heat-shrinkable film which has the resin layer (A layer) and resin layer (B layer) which were laminated | stacked adjacent to each other, Comprising: All the following (1)-(5) is satisfy | filled. The heat-shrinkable film characterized by this will also be described. (1) The A layer and the B layer are resin layers mainly composed of one type of resin selected from the group consisting of polyester resins, polystyrene resins, and polyolefin resins (including cyclic polyolefin resins). (2) The A layer and the B layer are resin layers mainly composed of different kinds of resins. (3) The adhesive strength between the A layer and the B layer in the T-type peel test is 2.5 N / 15 mm or less. (4) The heat shrinkage rate (80 ° C., 30 seconds) in the main orientation direction of the heat shrinkable film is 20% or more. (5) The absolute value of the difference between the thermal contraction rate of the A layer (80 ° C., 30 seconds) and the thermal contraction rate of the B layer (80 ° C., 30 seconds), the thermal contraction rate of the A layer (90 ° C, 30 seconds) and the absolute value of the difference between the thermal contraction rates of the B layer (90 ° C, 30 seconds) and the thermal contraction rate of the A layer (98 ° C, 30 seconds) and the thermal contraction rate of the B layer (98 ° C) , 30 seconds), at least one of the absolute values of the difference is 10% or less.

  The heat-shrinkable film of the present invention does not cause delamination during heat shrinkage even when different resins are laminated without using an adhesive layer. For this reason, it has an excellent appearance and can be easily manufactured at low cost. Moreover, since different resin layers are laminated, a heat-shrinkable film in which different functions are combined can be obtained.

[Heat shrinkable film of the present invention]
The heat-shrinkable film of the present invention has one resin layer (A layer) and another resin layer (B layer) different from the A layer laminated adjacent to each other. Note that “laminated adjacent to each other” means a state in which the B layer is directly laminated on the surface of the A layer without any other layer such as an adhesive layer. The heat-shrinkable film of the present invention only needs to have at least an A / B laminated structure in which the A layer and the B layer are laminated without interposing other layers. As long as it does not impair the effects of the present invention, it may further include layers other than the A layer and the B layer (sometimes referred to as “C layer”). In the present specification, the A layer and the B layer each mean a single resin layer.

  Said A layer and B layer are resin layers which have as a main component 1 type of resin chosen from the group which consists of polyester-type resin, polystyrene-type resin, and polyolefin-type resin (including cyclic polyolefin-type resin). In the present specification, the “main component” means a component contained in the resin layer in an amount of 70% by weight or more. That is, each of the A layer and the B layer contains a resin layer containing 70% by weight or more of a polyester resin (hereinafter sometimes referred to as “polyester resin layer”) and 70% by weight or more of a polystyrene resin. Resin layer (hereinafter sometimes referred to as “polystyrene resin layer”) and a resin layer (hereinafter referred to as “polyolefin resin layer”) containing 70% by weight or more of polyolefin resin (including cyclic polyolefin resin). The resin layer may be any one selected from three types of resin layers.

  Further, the A layer and the B layer are resin layers containing different kinds of resins as main components. That is, the combination of the A layer and the B layer [(A layer, B layer)] is (polyester resin layer, polystyrene resin layer), (polyester resin layer, polyolefin resin layer), (polystyrene resin layer, Polyester resin layer), (polystyrene resin layer, polyolefin resin layer), (polyolefin resin layer, polyester resin layer), or (polyolefin resin layer, polystyrene resin layer). The present invention is characterized in that resin layers having different characteristics and mainly composed of different kinds of resins can be laminated.

(Polyester resin layer)
Said polyester-type resin layer is a resin layer which contains a polyester-type resin 70weight% or more (for example, 70-100 weight%) with respect to the total weight of a resin layer. The content of the polyester resin is preferably 90 to 100% by weight. Examples of the polyester resin include various polyesters composed of a dicarboxylic acid component and a diol component.

  Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,5-dimethylterephthalic acid, 5-t-butylisophthalic acid, 4,4′-biphenyldicarboxylic acid, and trans-3,3′-stilbene dicarboxylic acid. , Trans-4,4′-stilbene dicarboxylic acid, 4,4′-dibenzyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6- Naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 2,2,6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid, 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid Acid, 1,2-diphenoxyethane-4,4′-dicarboxylic acid, diphenyl ether dicarboxylic acid, 2,5-a Aromatic dicarboxylic acids such as tracene dicarboxylic acid, 2,5-pyridinedicarboxylic acid, and substituted products thereof; oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid , Undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, icosanedioic acid, docosanedioic acid, 1,12-dodecanedioic acid, and Aliphatic dicarboxylic acids such as these substitutes; 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, cis-1,4-cyclohexanedicarboxylic acid , Trans-1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexa Dicarboxylic acids, and include alicyclic dicarboxylic acids such as substituted versions thereof. These dicarboxylic acid components can be used alone or in combination of two or more.

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

  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 polyvalent carboxylic acids such as trimellitic acid. Structural units such as monohydric alcohols such as polyalkylene glycol monomethyl ether; polyhydric alcohols such as glycerin, pentaerythritol and trimethylolpropane may be included.

  In the present invention, among the polyester resins, aromatic polyester resins are preferably used. The aromatic polyester-based resin means that 50 mol% or more (preferably 70 mol% or more) of the total dicarboxylic acid component is 50 mol% or more (preferably 70 mol% or more of the total diol component). Is a polyester resin whose aromatic diol is 70 mol% or more. Furthermore, an aromatic polyester-based resin which is a polymer, a copolymer, or a mixture obtained by a condensation reaction between a dicarboxylic acid containing an aromatic dicarboxylic acid and a diol containing an aliphatic diol is preferable. Furthermore, the polyester resin is not composed of a single repeating unit, but a modified aromatic polyester resin containing a modifying component (copolymerization component) is particularly preferred. For example, a modified aromatic polyester resin in which at least one of a dicarboxylic acid component or a diol component is composed of two or more components, that is, a modified component in addition to the main component is preferable.

  The aromatic polyester-based resin is not particularly limited, but terephthalic acid is used as a dicarboxylic acid component, polyethylene terephthalate (PET) using ethylene glycol (EG) as a diol component; terephthalic acid is used as a dicarboxylic acid component, Modified aromatic polyester resin using ethylene glycol as the main component and 1,4-cyclohexanedimethanol (CHDM) as the copolymer component as the diol component (sometimes referred to as “CHDM copolymerized PET”); Modified aromatic polyester resin ("2,2-dialkyl-1,3" using terephthalic acid, ethylene glycol as a diol component, and 2,2-dialkyl-1,3-propanediol as a copolymerization component -Propanediol copolymer P Sometimes referred to as T ") are exemplified as preferred. Furthermore, among 2,2-dialkyl-1,3-propanediol copolymerized PET, in particular, a modified aromatic polyester resin (“NPG copolymerized PET” using neopentyl glycol (NPG) as a copolymerization component and Is particularly preferable in terms of cost and productivity. Furthermore, diethylene glycol may be copolymerized from the viewpoint of improving low-temperature shrinkage.

  In the modified aromatic polyester resin, the copolymerization ratio of the copolymerization component used for modification (the ratio of the copolymerized dicarboxylic acid component to the total dicarboxylic acid component, or the ratio of the copolymerized diol component to the total diol component) is the interlayer From the viewpoint of prevention or suppression of peeling, 15 mol% or more (for example, 15 to 40 mol%) is preferable. Among them, for example, in the case of CHDM copolymerized PET, the proportion of CHDM copolymerization is 20 to 40 mol% (EG is 60 to 80 mol%) in the diol component (that is, with respect to 100 mol% of terephthalic acid). More preferably, it is 25-35 mol% (EG is 65-75 mol%). In the case of 2,2-dialkyl-1,3-propanediol copolymerized PET, the proportion of 2,2-dialkyl-1,3-propanediol is 15 to 40 mol% (EG is 60 to 60%) in the diol component. 85 mol%) is preferred. Further, a part of the EG component (preferably 1 to 10 mol% in the diol component) may be replaced with diethylene glycol.

  The polyester resin is preferably a substantially amorphous polyester resin (in particular, an amorphous saturated polyester resin). It is preferable to make the polyester amorphous because good stretching characteristics and shrinkage characteristics can be obtained. Therefore, delamination of the laminated resin layers at the time of heat shrinkage can be prevented or suppressed. Since the aromatic polyester resin becomes difficult to crystallize by being modified as described above, it can be made substantially amorphous by modification.

  The weight-average molecular weight (Mw) of the polyester-based resin is preferably 15000 to 90000, more preferably 30000 to 80000, from the viewpoints of melting behavior, shrinkage characteristics, and stretching characteristics.

  The glass transition temperature (Tg) of the polyester resin is preferably 60 to 100 ° C., more preferably 70 to 85 ° C., from the viewpoints of shrinkage characteristics and stretching characteristics. The Tg can be controlled by the type of polyester, the type of copolymerization component (modification component) used for modification, and the copolymerization ratio. The Tg can be measured by differential scanning calorimetry (DSC).

  Commercially available products may be used as the polyester-based resin. For example, “EMBRACE 21214”, “EMBRACE LV” (above, CHDM copolymerized PET) manufactured by Eastman Chemical Co., Ltd., “Bell Polyester Products” Belpet E02 "(such as NPG copolymerized PET) is available on the market.

  The polyester-based resin layer may contain other additives such as a lubricant, a filler, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a colorant, a pinning agent (alkaline) as necessary. Earth metal) or the like.

(Polystyrene resin layer)
Said polystyrene-type resin layer is a resin layer containing 70 weight% or more (for example, 70-100 weight%) of polystyrene-type resin with respect to the total weight of a resin layer. The content of the polystyrene resin is preferably 90 to 100% by weight. Examples of the polystyrene resins include homopolymers or copolymers of styrene monomers such as general polystyrene (GPPS), which is a homopolymer of styrene; high impact polystyrene (HIPS) obtained by graft-polymerizing styrene to synthetic rubber. ); Copolymers (particularly block copolymers) composed of styrene monomers and diene monomers (conjugated diene) such as butadiene and isoprene, represented by styrene-butadiene block copolymer (SBS). A styrene-conjugated diene copolymer; a styrene-polymerizable unsaturated carboxylic acid ester copolymer that is a copolymer of a styrene monomer and a (meth) acrylate monomer; a styrene-conjugated diene -Polymerizable unsaturated carboxylic acid ester copolymer; copolymer of styrene monomer and (meth) acrylic acid ester monomer RAFT polymerization was clear and high impact polystyrene (graft TIPS), and the like. In the present invention, among them, a styrene-conjugated diene copolymer is preferable. The styrene-conjugated diene copolymer is a copolymer composed of a styrene monomer and a conjugated diene as essential monomer components.

  Although it does not specifically limit as said styrene-type monomer, For example, styrene, alpha-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, p-isobutyl styrene, pt-butyl styrene, Examples include chloromethylstyrene. Among these, styrene is particularly preferable from the viewpoint of physical properties such as strength and moldability. In addition, these styrenic monomers may be used independently and may use 2 or more together.

  The conjugated diene is not particularly limited. For example, 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, Examples include 1,3-hexadiene and chloroprene. Among these, 1,3-butadiene and isoprene are particularly preferable from the viewpoints of improving brittleness and imparting flexibility. These conjugated dienes may be used alone or in combination of two or more.

  In the styrene-conjugated diene copolymer, the content of the styrene monomer is preferably 60 to 95% by weight, more preferably 70 to 85% by weight, based on the total weight of the monomer components. . On the other hand, the content of the conjugated diene is preferably 5 to 40% by weight, more preferably 15 to 30% by weight, based on the total weight of the monomer components. When the content of the styrene monomer is less than 60% by weight (when the content of the conjugated diene exceeds 40% by weight), the film may lose its elasticity or natural shrinkage may increase. When the content of is less than 5% by weight (when the content of the styrenic monomer exceeds 95% by weight), the film may become brittle or the elongation may be low.

  The form of copolymerization of the styrene-conjugated diene copolymer is not particularly limited, such as a random copolymer, a block copolymer, and an alternating copolymer, but a block copolymer is preferable, and a styrene (S) -conjugated diene is preferred. Block (D) type, SDS type, DSD type, SDS type, etc. are mentioned.

Specific examples of the styrene-conjugated diene copolymer include a styrene-butadiene block copolymer (SBS), a styrene-isoprene block copolymer (SIS), and a styrene-butadiene-isoprene block copolymer ( Examples thereof include SBIS), styrene-ethylene- butylene block copolymer (SEBS), and styrene-ethylene-propylene copolymer (SEPS). Among these, styrene-butadiene block copolymer (SBS) and styrene-butadiene-isoprene block copolymer (SBIS) are most preferable.

  The Tg of the polystyrene resin is preferably 60 to 120 ° C, more preferably 75 to 95 ° C, from the viewpoint of shrinkage characteristics. The Tg can be measured by differential scanning calorimetry (DSC).

The density of the polystyrene resin is preferably 1.00 to 1.05 g / cm ³ .

  The Vicat softening point (based on JIS K 7206) of the polystyrene resin is preferably 70 to 90 ° C, more preferably 70 to 85 ° C.

  The melt flow rate (MFR) (conforming to JIS K 7210; temperature 200 ° C./load 49 N) of the polystyrene resin is preferably 1 to 15 g / 10 minutes, more preferably 3 to 10 g / 10 minutes.

  Commercially available products may be used as the polystyrene-based resin, and examples thereof include “Asaflex 830” manufactured by Asahi Kasei Chemicals Corporation and “Clearen 730L” manufactured by Denki Kagaku Kogyo Co., Ltd.

  The polystyrene resin layer may contain other additives such as lubricants, fillers, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, colorants, pinning agents (alkaline) as necessary. Earth metal) or the like.

(Polyolefin resin layer)
The polyolefin resin layer is a resin layer containing 70 wt% or more (for example, 70 to 100 wt%) of a polyolefin resin based on the total weight of the resin layer. The polyolefin resin includes a cyclic polyolefin resin (cyclic olefin resin). The content of the polyolefin resin is preferably 90 to 100% by weight. In the present invention, the polyolefin resin is not particularly limited. For example, a homopolymer of an α-olefin such as ethylene, propylene, 1-butene, 4-methyl-1-pentene (for example, homopolypropylene); ethylene -Copolymers (including olefin elastomers) such as α-olefin copolymers and propylene-α-olefin copolymers; copolymers of cyclic olefins and α-olefins (ethylene, propylene, etc.) or graft modification thereof And amorphous olefin polymers such as ring-opened polymers of cyclic olefins or hydrogenated products thereof or graft-modified products thereof. Among the above, homopolypropylene, propylene-α-olefin copolymer (particularly propylene-α-olefin random copolymer), and ethylene-α-olefin copolymer are preferable. Further, the polyolefin resin is preferably a polyolefin resin obtained by polymerizing with a metallocene catalyst (particularly a linear polyolefin resin obtained by polymerizing with a metallocene catalyst), particularly preferably polymerized with a metallocene catalyst. The obtained polypropylene (metallocene catalyst-based polypropylene) and propylene-α-olefin copolymer (particularly, propylene-α-olefin random copolymer). Moreover, these polyolefin resin can be used individually or in mixture of 2 or more.

  Examples of the α-olefin used as a copolymerization component of the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1 -Α-olefins having about 4 to 20 carbon atoms such as octene, 1-nonene, 1-decene and the like. These copolymer components can be used alone or in admixture of two or more. Among the propylene-α-olefin copolymers, ethylene-propylene random copolymers containing ethylene as a copolymerization component are preferable.

  Commercially available products may be used as the polyolefin resin, such as “Wintech WFX6” (metallocene catalyst polypropylene) manufactured by Nippon Polypro Co., Ltd., “Zeras # 7000, # 5000” manufactured by Mitsubishi Chemical Corporation (propylene— α-olefin copolymer) and “Kernel” manufactured by Nippon Polyethylene Co., Ltd. are commercially available.

  The polyolefin-based resin layer may contain other additives such as lubricants, fillers, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, colorants, pinning agents (alkaline) as necessary. Earth metal) or the like.

  As described above, the heat-shrinkable film of the present invention may have a layer (C layer) other than the A layer and the B layer. Although it does not specifically limit as said C layer, For example, resin layers (a coating layer or the resin layer laminated | stacked by coextrusion), such as a primer coat layer, an anchor coat layer, an easily bonding layer, and an antistatic agent layer, etc. are mentioned. It is done.

  The heat-shrinkable film of the present invention has at least a laminated structure (A layer / B layer) in which the A layer and the B layer are laminated without interposing other layers. The laminated structure of the heat-shrinkable film of the present invention is not particularly limited, but a preferred laminated structure is a two-layer / two-layer laminated structure of A layer / B layer; A layer / B layer / A layer, B layer / A layer / B layer 2 type 3 layer laminated structure is mentioned. In the case of a two-type three-layer structure, particularly from the viewpoint of chemical resistance and printability, a polyester-based resin layer is preferably used as both outer layers, and a polystyrene-based resin layer or a polyolefin-based resin layer is preferable as the central layer. Used.

  In the heat-shrinkable film of the present invention, the A layer and the B layer are preferably uniaxially or biaxially oriented resin layers from the viewpoint of shrinkage characteristics. Further, preferably, the A layer and the B layer are similarly uniaxially or biaxially oriented. When the A layer and the B layer are not oriented, good shrinkage cannot be obtained. The orientation is not particularly limited, such as uniaxial orientation or biaxial orientation, but substantially uniaxial orientation in the width direction, which is strongly oriented in the film width direction (direction that becomes the circumferential direction when the label is formed into a cylinder) is preferable. Moreover, the uniaxial orientation of the longitudinal direction which was strongly oriented in the longitudinal direction (direction orthogonal to the width direction) of a film may be sufficient.

  Although the thickness (total thickness) of the heat-shrinkable film of this invention is not specifically limited, 20-80 micrometers is preferable, More preferably, it is 30-60 micrometers.

  Although the thickness of A layer and B layer (thickness of a single layer) in the heat-shrinkable film of this invention is not specifically limited, 3-45 micrometers is preferable, More preferably, it is 5-40 micrometers.

  In the heat-shrinkable film of the present invention, the adhesive strength between the A layer and the B layer in the T-type peel test is 2.5 N / 15 mm or less, preferably 2.0 N / 15 mm or less, more preferably 1.5 N / 15 mm. It is as follows. Moreover, although the said adhesive strength is not specifically limited, 0.3 N / 15mm or more is preferable, More preferably, it is 0.5 N / 15mm or more, More preferably, it is 1.0 N / 15mm or more. The adhesive strength is the peel strength when the A layer and the B layer of the heat-shrinkable film of the present invention are peeled off at a normal temperature and at a tensile rate of 200 mm / min in accordance with JIS K 6854-3. is there. That the adhesive strength between the A layer and the B layer is 2.5 N / 15 mm or less means that the A layer and the B layer are resin layers that are difficult to adhere to each other. Although the present invention is a heat-shrinkable film in which resin layers having such a low adhesive strength (hard to adhere) are laminated without using an adhesive layer, the shrink (heat-shrinking) process is performed. It is characterized by no delamination.

  The heat-shrinkable film of the present invention has a heat-shrinkage rate (may be referred to as “heat-shrinkage rate (80 ° C., 30 seconds)”) in the main orientation direction at 80 ° C. for 30 seconds (at least 20%) ( For example, 20 to 85%), preferably 40 to 85%. When the heat shrinkage rate (80 ° C., 30 seconds) in the main orientation direction of the heat shrinkable film is 20% or more, shrink labels produced using the film can be used in various shapes of containers (particularly large diameter portions). And a small-diameter portion, and can be used in a container having a large diameter difference between the large-diameter portion and the small-diameter portion. Moreover, in such a high shrinkage heat-shrinkable film, it is a feature of the present invention that delamination during shrink processing can be suppressed.

  The heat shrinkage rate (80 ° C., 30 seconds) in the direction orthogonal to the main orientation direction of the heat shrinkable film of the present invention is not particularly limited, but is preferably −3 to 15%.

  The heat shrinkage rate (80 ° C., 30 seconds) in the main alignment direction of the A layer and the B layer in the heat shrinkable film of the present invention is the heat shrinkage rate (80 ° C., 30 ° C.) in the main alignment direction of the heat shrinkable film of the present invention. From the viewpoint of controlling (30 seconds) within the above range, 20% or more (for example, 20 to 85%) is preferable, and 40 to 85% is more preferable.

  The thermal contraction rate (80 ° C., 30 seconds) can be measured by a hot water immersion test in which a measurement sample is immersed in hot water at 80 ° C. for 30 seconds. In addition, the above-mentioned “main orientation direction” means a direction in which the heat-shrinkable film is mainly subjected to a stretching treatment (direction in which the heat shrinkage rate is the largest), and is generally the film at the time of film production. For example, in the case of a heat-shrinkable film substantially uniaxially stretched in the width direction, it is the width direction.

  Similarly to the above, in this specification, the thermal shrinkage rate under the condition of 90 ° C. for 30 seconds may be referred to as “thermal shrinkage rate (90 ° C., 30 seconds)”. Further, the heat shrinkage rate under the condition of 98 ° C. for 30 seconds may be referred to as “heat shrinkage rate (98 ° C., 30 seconds)”. The thermal contraction rate (90 ° C., 30 seconds) can be measured by a hot water immersion test in which a measurement sample is immersed in hot water at 90 ° C. for 30 seconds. The thermal contraction rate (98 ° C., 30 seconds) can be measured by a hot water immersion test in which a measurement sample is immersed in 98 ° C. hot water for 30 seconds.

In addition, the absolute value of the difference between the heat shrinkage rate of the A layer in the main alignment direction (80 ° C., 30 seconds) and the heat shrinkage rate of the B layer in the main alignment direction (80 ° C., 30 seconds) is expressed as “heat shrinkage rate difference ( 80 ° C.) ”. That is, difference in thermal shrinkage rate (80 ° C.) = | [Thermal shrinkage rate of layer A in the main orientation direction (80 ° C., 30 seconds)] − [thermal shrinkage rate of layer B in the main orientation direction (80 ° C., 30 seconds) ].
Similarly to the above, the absolute value of the difference between the thermal shrinkage rate of the A layer in the main orientation direction (90 ° C., 30 seconds) and the thermal shrinkage rate of the B layer in the main orientation direction (90 ° C., 30 seconds) is expressed as “thermal shrinkage”. It may be referred to as “rate difference (90 ° C.)”. Also, the absolute value of the difference between the thermal shrinkage rate of the A layer in the main orientation direction (98 ° C., 30 seconds) and the thermal shrinkage rate of the B layer in the main orientation direction (98 ° C., 30 seconds) is expressed as “Heat shrinkage rate difference ( 98 ° C.) ”.

  In the heat shrinkable film of the present invention, at least one of the heat shrinkage difference (80 ° C.), the heat shrinkage difference (90 ° C.), and the heat shrinkage difference (98 ° C.) is 10% or less (0 to 10%). And preferably 8% or less. In other words, the minimum value among the heat shrinkage difference (80 ° C.), the heat shrinkage difference (90 ° C.), and the heat shrinkage difference (98 ° C.) is 10% or less (0 to 10%), preferably 8 % Or less. The above is a temperature at which the difference in thermal shrinkage in the main orientation direction between the A layer and the B layer is 10% or less (preferably 8% or less) in the temperature range of 80 to 98 ° C. (temperature range suitable for shrink processing). Means that a range exists. In such a heat-shrinkable film, delamination does not occur at the time of heat shrinkage if it is shrunk by heat shrinkage in a temperature range where the difference in heat shrinkage between the A layer and the B layer is 10% or less. When the above minimum value exceeds 10%, the heat shrinkage behavior of the A layer and the B layer is greatly different during heat shrinkage (only heat shrinkage temperature conditions with greatly different heat shrinkage behaviors can be taken), so that delamination occurs. It tends to occur.

[Method for producing heat-shrinkable film of the present invention]
The heat-shrinkable film of the present invention is preferably produced by forming an unstretched film by multilayer extrusion (coextrusion) and then stretching the unstretched film. That is, in the heat-shrinkable film of the present invention, it is preferable that the A layer and the B layer are laminated by coextrusion and subjected to a stretching treatment.

  In the multilayer extrusion (coextrusion), raw materials (resin or resin composition) for forming a resin layer (A layer, B layer, etc.) are respectively charged into a plurality of extruders each set to a predetermined temperature. Co-extrusion from dies, circular dies, etc. At this time, it is preferable to use a manifold or a feed block to obtain a predetermined laminated structure. Further, if necessary, the supply amount may be adjusted using a gear pump, and it is preferable to remove foreign substances using a filter because film tearing can be reduced. In addition, although extrusion temperature changes also with the kind of raw material to be used and is not specifically limited, It is preferable that the molding temperature area | region of each raw material is adjoining. Specifically, the extrusion temperature of the raw material for forming the polyester resin layer is preferably 190 to 240 ° C., the extrusion temperature of the raw material for forming the polystyrene resin layer is preferably 180 to 220 ° C., and the polyolefin resin layer is formed. The extrusion temperature of the raw material is preferably 180 to 230 ° C. Moreover, it is preferable that the temperature of the confluence | merging part of each raw material and die | dye shall be 190-230 degreeC. An unstretched film (unstretched laminated film) can be obtained by rapidly cooling the polymer subjected to multilayer extrusion using a cooling drum (cooling roll) or the like.

  The heat-shrinkable film of the present invention can be produced by stretching the unstretched film obtained above. Stretching can be selected according to the desired orientation, and may be biaxial stretching in the longitudinal direction (longitudinal direction; MD direction) and width direction (transverse direction; TD direction), or uniaxial stretching in the longitudinal direction or width direction. Good. The stretching method may be any of a roll method, a tenter method, and a tube method. The draw ratio in the above-mentioned drawing treatment varies depending on the use of the heat-shrinkable film and the required heat-shrinkage characteristics, and is not particularly limited. For example, in the case of a heat-shrinkable film substantially stretched uniaxially, the draw ratio in the main orientation direction is preferably 3 to 6 times, more preferably 4 to 5.5 times, and orthogonal to the main orientation direction. The draw ratio in the direction of stretching is preferably 1.01 to 1.5 times, more preferably 1.05 to 1.3 times. In the case of a heat-shrinkable film substantially uniaxially stretched in the width direction, the main orientation direction is the width direction, and the direction perpendicular to the main orientation direction is the longitudinal direction.

  In the heat-shrinkable film of the present invention, the difference in heat shrinkage between the A layer and the B layer can be adjusted by a combination of raw materials forming the A layer and the B layer, a stretching temperature, a stretching ratio, and the like. Among these, the combination of raw materials and the stretching temperature have a particularly great influence. Therefore, the heat shrinkage difference between the A layer and the B layer is controlled, and at least one of the heat shrinkage difference (80 ° C.), the heat shrinkage difference (90 ° C.), and the heat shrinkage difference (98 ° C.) is determined. In order to control to 10% or less, in particular, an appropriate combination of raw materials (resin or resin composition) for forming the A layer and the B layer is selected, and the selected raw materials are stretched at an appropriate stretching temperature. It becomes important. Although the selection method of the suitable combination of the raw material which forms A layer and B layer and the determination method of extending | stretching temperature are not specifically limited, For example, it can carry out as follows.

(Selection of raw materials)
A method for selecting a combination of a raw material for forming the A layer (sometimes referred to as “A layer raw material”) and a raw material for forming the B layer (sometimes referred to as “B layer raw material”) is not particularly limited. It can be performed as follows. The A layer raw material and the B layer raw material are each a single resin or a resin composition containing two or more resins and additives.

The A layer raw material and the B layer raw material have an absolute value (| E ^* |) of a complex elastic modulus measured in a dynamic viscoelasticity measurement (DMA) at a frequency of 10 Hz in a temperature range of 80 to 120 ° C. It is preferable that the resin or the resin composition has a portion of 300 MPa. More specifically, the above dynamic viscoelasticity measurement is as follows. First, an unstretched sheet consisting only of each layer raw material (A layer raw material or B layer raw material) [that is, an A layer unstretched sheet (unstretched A layer) or a B layer unstretched sheet (unstretched B layer)] Is made. The production method (molding method) of the sheet is not particularly limited, and for example, press molding or extrusion molding (single layer extrusion) can be used. Moreover, after forming the unstretched film which has A layer and B layer by multilayer extrusion (coextrusion), an unstretched film is peeled and the unstretched sheet of A layer and the unstretched sheet of B layer are produced, respectively. May be. Next, using the obtained sheet as a sample, dynamic viscoelasticity measurement is performed under conditions of a frequency of 10 Hz and a heating rate of 2 ° C./min.

Selection of the A layer raw material and the B layer raw material can be performed by using the value of | E ^* | by the above dynamic viscoelasticity measurement.

(Determination of stretching temperature)
The method for determining the stretching temperature (stretching temperature of the unstretched film) in the method for producing the heat-shrinkable film of the present invention is not particularly limited, and can be performed, for example, as follows. In addition, the stretching temperature of the unstretched film when producing the heat-shrinkable film of the present invention may be referred to as “stretching temperature at the time of production” in distinction from the following “temporary stretching temperature”. In the present specification, “stretching temperature” means a film temperature during stretching.

  First, in the temperature range of 80 to 120 ° C., temperatures of at least 3 points (preferably 4 points) are determined (hereinafter referred to as “temporary stretching temperature”). The temporary stretching temperature is preferably 5 ° C. or more away from each other. If the absolute value of the difference between the temporary stretching temperatures is less than 5 ° C., the analysis work for determining the stretching temperature during the production may be difficult.

  Next, the unstretched sheet of layer A is uniaxially stretched at the above-mentioned temporary stretching temperature (stretching ratio is 5 times) to obtain a uniaxially stretched film (if the temporary stretching temperature is 3 points, three types of uniaxial A stretched film is obtained). The heat shrinkage (80 ° C., 30 seconds) in the main orientation direction (uniaxial stretching direction) of the uniaxially stretched film is measured, the horizontal axis (x axis) is the temporary stretching temperature, and the vertical axis (y axis) is The graph is plotted on the graph as the heat shrinkage rate (80 ° C., 30 seconds), and a graph showing the relationship of the heat shrinkage rate (80 ° C., 30 seconds) to the temporary stretching temperature for the layer A is obtained. An approximate straight line (sometimes referred to as “straight line (A, 80 ° C.)”) is obtained from each point on the graph (temporary stretching temperature, thermal shrinkage rate (80 ° C., 30 seconds)) by the least square method. Further, similarly for the unstretched sheet of the B layer, a graph representing the relationship of the thermal shrinkage rate (80 ° C., 30 seconds) to the temporary stretching temperature for the B layer, and an approximate straight line (“straight line (B, 80 ° C.) ”).

When the temporary stretching temperature of the graph is in the range of 80 to 120 ° C., the straight line (A, 80 ° C.) obtained above is compared with the straight line (B, 80 ° C.), and the same x value ( The range of x in which the absolute value of the difference in y value (thermal shrinkage rate (80 ° C., 30 seconds)) relative to the provisional stretching temperature) is 10% or less can be adopted as the stretching temperature during the production.
When the straight line (A, 80 ° C.) and the straight line (B, 80 ° C.) intersect, the value of x at the intersection of both straight lines (may be referred to as “Ts (80 ° C.)”) Particularly preferred as the temperature. Furthermore, when the straight line (A, 80 ° C.) slope is a and the straight line (B, 80 ° C.) slope is b, a temperature t satisfying the following formula can be adopted as the stretching temperature during the production.
Ts (80 ° C.) − (10 / | a−b |) ≦ t ≦ Ts (80 ° C.) + (10 / | a−b |)

  Further, the heat shrinkage rate (80 ° C., 30 seconds) is changed to the heat shrinkage rate (90 ° C., 30 seconds) (that is, the heat shrink temperature is changed from 80 ° C. to 90 ° C.), For the unstretched sheet of B and B layers, a graph showing the relationship of the thermal shrinkage rate (90 ° C., 30 seconds) to the temporary stretching temperature, and approximate straight lines (straight line (A, 90 ° C.) and straight line (B, 90 ° C.)) ) The straight line (A, 90 ° C.) and the straight line (B, 90 ° C.) are contrasted, and the y value (thermal shrinkage (90 ° C., 30 seconds) with respect to the same x value (temporary stretching temperature) in both straight lines. The range of x in which the absolute value of the difference in () is 10% or less can be adopted as the stretching temperature during the production.

  Further, the heat shrinkage rate (80 ° C., 30 seconds) was changed to the heat shrinkage rate (98 ° C., 30 seconds) (that is, the heat shrink temperature was changed from 80 ° C. to 98 ° C.), For the unstretched sheet of B and B layers, a graph showing the relationship of the thermal shrinkage rate (98 ° C., 30 seconds) to the temporary stretching temperature, and approximate straight lines (straight line (A, 98 ° C.) and straight line (B, 98 ° C.)) ) The straight line (A, 98 ° C.) and the straight line (B, 98 ° C.) are compared, and the y value (heat shrinkage rate (98 ° C., 30 seconds) with respect to the same x value (temporary stretching temperature) in both straight lines. The range of x in which the absolute value of the difference in () is 10% or less can be adopted as the stretching temperature during the production.

  That is, when the heat shrinkage temperature is 80 ° C., 90 ° C., or 98 ° C., the heat shrinkable film of the present invention can be used as long as the two approximate lines are within 10% in the y-axis direction. The stretching temperature at the time of this production which can produce is obtained.

The “temporary stretching temperature” in the method for determining the stretching temperature is more preferably determined by the following method. In the above-described dynamic viscoelasticity measurement, in the temperature range of 80 to 120 ° C., both | E ^* | of the unstretched sheet of layer A and | E ^* | of the unstretched sheet of layer B are 30 to 300 MPa. Determine the temperature range. The temperature t ₁ , t ₂ , t ₃ , t ₄ is equally taken within the above temperature range (t ₁ is the lower limit temperature of the temperature range, t ₄ is the upper limit temperature, and t ₂ and t ₃ are Each is a temperature that divides the temperature range into three equal parts). Each temperature t ₁ ~t ₄ are separated by at least 5 ° C. or higher _{(e.g., t 2 -t 1 ≧ 5 ℃} ) is preferred. When the temperature range is narrower than 15 ° C., three temperatures t _{1 to} t ₃ may be equally taken within the temperature range (in this case, t ₁ is the lower limit temperature of the temperature range, t ₃ is an upper limit temperature, and t ₂ is a temperature that bisects the temperature range). 4 points t ₁ ~t ₄ which defines the above temperature (or three points t ₁ ~t ₃₎ may be a "stretching temperature provisional".

  In the method for producing a heat-shrinkable film of the present invention, the stretching speed (stretching speed) during stretching of the unstretched film may be constant, may vary with stretching, and is not particularly limited. The strain rate is preferably 0.1 to 1 / second (strain rate), more preferably 0.3 to 0.7 / second. The heat shrinkage rate of the A layer, the B layer and the heat shrinkable film can be finely adjusted by the strain rate.

  In the method for producing a heat-shrinkable film of the present invention, a relaxation step may be provided immediately after the stretching step. The relaxation step can be performed, for example, by taking the conditions such as slightly increasing the film temperature while maintaining the stretching ratio, and slightly decreasing the stretching ratio while maintaining the stretching temperature. Thereby, the stress in a film can be relieve | moderated and the dimensional stability of a heat-shrinkable film can be improved. By the relaxation step, the heat shrinkage rate of the A layer, the B layer, and the heat shrinkable film can be finely adjusted.

[Shrink label]
A shrink label is obtained by using the heat-shrinkable film of the present invention as a base material and providing a printing layer on at least one side thereof. In addition to the printed layer, the shrink label includes a protective layer, an anchor coat layer, a primer coat layer, an adhesive layer (such as a pressure-sensitive adhesive layer and a heat-sensitive adhesive layer), a coating layer, and a nonwoven fabric. A layer of paper or the like may be provided. Although the specific structure of the shrink label of this invention is not specifically limited, For example, layer structures, such as a printing layer / heat-shrinkable film and a printing layer / heat-shrinkable film / printing layer, are illustrated. In addition, the heat-shrinkable film of the present invention can be used as a shrink label by itself even when a printing layer is not provided.

  The shrink label preferably has a printed layer (for example, a layer displaying a trade name, an illustration, handling precautions, etc.) on at least one surface. The printing layer is formed by applying printing ink. From the viewpoint of productivity, workability, and the like, the coating is preferably an off-line coating in which coating is performed using a known and commonly used printing method after film formation. As a printing method, a known and commonly used method can be used, but gravure printing or flexographic printing is preferable.

  The printing ink used for forming the printing layer includes, for example, a pigment, a binder resin, a solvent, and other additives. Although it does not specifically limit as said binder resin, For example, resin, such as an acrylic type, a urethane type, a polyamide type, a vinyl chloride-vinyl acetate copolymer type, a cellulose type, a nitrocellulose type, can be used individually or in combination. As the pigment, white pigments such as titanium oxide (titanium dioxide), indigo pigments such as copper phthalocyanine blue, carbon black, aluminum flakes, mica (mica), and other colored pigments can be selected and used according to the application. In addition, extender pigments such as alumina, calcium carbonate, barium sulfate, silica, and acrylic beads can also be used as pigments for the purpose of adjusting gloss. Examples of the solvent include organic solvents such as toluene, xylene, methyl ethyl ketone, ethyl acetate, methyl alcohol, ethyl alcohol, and isopropyl alcohol, and commonly used solvents such as water.

  Although the said printing layer is not specifically limited, Active energy ray-curable resin layers, such as visible light, an ultraviolet-ray, and an electron beam, may be sufficient. This is effective for preventing deformation of the film due to excessive heat.

  Although the thickness of the said printing layer is not specifically limited, For example, 0.1-10 micrometers is preferable. If the thickness is less than 0.1 μm, it may be difficult to provide a printing layer uniformly, and partial “fading” may occur, decorativeness may be impaired, or printing as designed may be difficult. is there. On the other hand, if the thickness exceeds 10 μm, a large amount of printing ink is consumed, which increases the cost, makes it difficult to apply uniformly, and makes the printing layer brittle and easy to peel off. Moreover, the rigidity of a printing layer becomes high and it may become difficult to follow the shrinkage | contraction of a film at the time of shrink processing.

  The shrink label is, for example, a cylindrical shrink label of a type in which both ends of a base material (heat-shrinkable film) are sealed with a solvent or an adhesive and then fitted into a container, and one end of the label is a container. After being attached to an adherend such as, and winding the label, it can be suitably used as a winding type shrink label in which the other end is overlapped with one end to form a cylinder. The center seal strength of the cylindrical shrink label is preferably 2N / 15 mm or more. When the seal strength is less than 2N / 15 mm, the seal portion may be peeled off after processing or product production, which may reduce the productivity or cause the label to drop off.

  Although the manufacturing method of the said cylindrical shrink label is not specifically limited, For example, it is as follows. After printing on a heat-shrinkable film stretched in the long width direction and providing a print layer, it is slit to a predetermined width to obtain a long label body in which a plurality of labels are continuous in the long direction. This long label is formed in a cylindrical shape so that one side end is outside the other side end so that the main orientation direction (that is, the width direction) of the heat-shrinkable film is the circumferential direction. Then, on one side end of the long label body, a solvent such as 1,3-dioxolane and tetrahydrofuran (THF) or an adhesive (hereinafter referred to as a solvent) is applied to the inner surface with a width of about 2 to 4 mm in the longitudinal direction. The coated portion such as the solvent is overlapped at a position of 5 to 10 mm from the other side end portion, and is adhered (center seal) to the outer surface of the other side end portion. A long cylindrical shrink label) is obtained. By cutting this long tubular shrink label in the width direction, one tubular shrink label can be obtained. In the case where a perforation for label excision is provided, a perforation having a predetermined length and pitch is formed in the longitudinal direction. The perforation can be applied by a conventional method (for example, a method of pressing a disk-shaped blade having a cut portion and a non-cut portion repeatedly formed around it, a method using a laser, or the like). The process stage for perforating can be appropriately selected after the printing process and before and after the cylindrical processing process.

  A labeled container is obtained by mounting the shrink label on the container. Such containers include, for example, soft drink bottles such as PET bottles, milk bottles for home delivery, food containers such as seasonings, alcohol beverage bottles, pharmaceutical containers, chemical containers such as detergents, sprays, cups, etc. This includes noodle containers. The shape of the container includes various shapes such as a cylindrical shape, a square bottle, and a cup type. Further, the material of the container includes plastic such as PET, glass, metal and the like.

  The above-mentioned container with a label can be produced by externally fitting a cylindrical shrink label to a predetermined container, shrinking the label by heat treatment, and closely contacting the container. Examples of the heat treatment include treatment with steam at 80 to 100 ° C. (passing through a heating tunnel filled with steam and steam).

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

Examples 1-3, Comparative Example 1
As a surface layer (A layer) raw material, an amorphous polyester (PET) resin (manufactured by Eastman Chemical Company, “Embrace LV”) was used.
A styrene-butadiene block copolymer (SBS) resin (Asaflex 830 manufactured by Asahi Kasei Chemicals Corporation) was used as a raw material for the center layer (B layer).
The surface layer (A layer) raw material and the center layer (B layer) raw material were separately fed into three single-screw extruders, and extruded at a resin temperature of 220 ° C. by a T-die with a feed block. Then, it cooled and solidified with the cooling roll temperature-controlled at 40 degreeC, and obtained the unstretched sheet (unstretched film) of 3 layer laminated structure. The unstretched sheet was adjusted for extrusion conditions such that the thickness was 300 μm.
The unstretched sheet is stretched 1.2 times in the longitudinal (longitudinal) direction using a stretching roll whose temperature is adjusted to 65 ° C., and then guided to a transverse stretching machine (tenter) under predetermined transverse stretching temperature conditions. Then, the film is stretched 5 times in the width (transverse) direction at a stretching speed of 50% / second (strain speed of 0.5 / second), wound on a roll after the air cooling step, and PET (A layer) / SBS (B layer) / PET (layer A) three-layer laminated heat-shrinkable film (heat-shrinkable film substantially uniaxially stretched in the width direction) was obtained. The heat-shrinkable film was a flat heat-shrinkable film having a thickness of 50 μm and a layer thickness ratio [PET (A layer) / SBS (B layer) / PET (A layer)] = 1: 2: 1. .
The case where the transverse stretching temperature was 85 ° C was Example 1, the case of 90 ° C was Example 2, the case of 95 ° C was Example 3, and the case of 80 ° C was Comparative Example 1.

Example 4, Example 5, Comparative Example 2, Comparative Example 3
As the surface layer (A layer) raw material, an amorphous PET resin (manufactured by Eastman Chemical Company, “Embrac 21214”) was used, and as the central layer (B layer) raw material, an SBS resin (manufactured by Denki Kagaku Kogyo Co., Ltd., “Clearene”). 730L ") was used in the same manner as in Examples 1 to 3 and Comparative Example 1 to obtain a flat three-layer heat-shrinkable film having a thickness of 50 µm.
The case where the transverse stretching temperature was 85 ° C was Example 4, the case of 90 ° C was Example 5, the case of 80 ° C was Comparative Example 2, and the case of 95 ° C was Comparative Example 3.

Examples 6-9
As a surface layer (A layer) raw material, an amorphous PET resin (manufactured by Bell Polyester Products, "E02"), and as a center layer (B layer) raw material, an SBS resin (manufactured by Denki Kagaku Kogyo Co., Ltd., "Clearen 730L") )) And the transverse stretching temperature was changed, and a flat three-layer heat-shrinkable film having a thickness of 50 μm was obtained in the same manner as in Examples 1 to 3 and Comparative Example 1.
The case where the transverse stretching temperature was 85 ° C was Example 6, the case of 90 ° C was Example 7, the case of 95 ° C was Example 8, and the case of 100 ° C was Example 9.

(Evaluation)
Of the heat-shrinkable films obtained in Examples and Comparative Examples, the adhesive strength between the A layer and the B layer, the heat shrinkage rate in the main orientation direction of the heat-shrinkable film (80 ° C., 30 seconds), the A layer in the main orientation direction And B layer heat shrinkage (80 ° C, 30 seconds), heat shrinkage (90 ° C, 30 seconds), heat shrinkage (98 ° C, 30 seconds), heat shrinkage difference (80 ° C), heat shrinkage difference (90 ° C.), heat shrinkage difference (98 ° C.), and delamination deterrence (delamination test) during shrinkage were evaluated by the following methods. The evaluation results are shown in Table 1.
In the following, the longitudinal direction of the heat-shrinkable film is the film forming direction (line direction) of the heat-shrinkable film. On the other hand, the width direction of the heat-shrinkable film refers to a direction orthogonal to the longitudinal direction. The main orientation direction in the heat-shrinkable films obtained in Examples and Comparative Examples is the width direction.

(1) Adhesive strength between layer A and layer B (T-type peel test)
About the heat-shrinkable film produced by the Example and the comparative example, the adhesive strength (delamination strength) of A layer and B layer was measured.
The heat-shrinkable films obtained in Examples and Comparative Examples were cut into 15 mm in the longitudinal direction (film-forming direction of the heat-shrinkable film) and 200 mm in the width direction (direction perpendicular to the film-forming direction). A test piece was obtained.
Using the above test piece, a T-type peel test was performed under the following measurement conditions in accordance with JIS K 6854-3. Peeling was performed between the A and B layers. In addition, before using for a peeling test, a test piece peeled one terminal part previously for a fixed area along the interlayer of A layer and B layer (pre-peeling).
The average value of the peel load was defined as the adhesive strength (interlaminar peel strength) between the A layer and the B layer (N / 15 mm).
(Measurement condition)
Measuring device: Shimadzu Corporation autograph (AG-IS: load cell type 500N)
Measurement temperature and humidity conditions: Temperature 23 ± 2 ° C., humidity 50 ± 5% RH (JIS K 7100, standard temperature state grade 2).
Pre-peeling length of test piece: 50mm
Initial chuck interval (grip interval): 50 mm
Tensile speed (gripping tool moving speed): 200 mm / min Peeling test setting stroke: 150 mm (If broken, it was interrupted and data up to that point was obtained.)
Measurement direction: Length direction of test piece (width direction of heat-shrinkable film)
Number of tests (n number): 3 times

(2) Heat shrinkage rate in the main orientation direction of the heat shrinkable film (80 ° C., 30 seconds)
The heat-shrinkable films obtained in Examples and Comparative Examples were cut into 50 mm in the longitudinal direction and 50 mm in the width direction to obtain test pieces.
The test piece was immersed in an 80 ° C. hot water bath for 30 seconds, taken out, and immediately cooled with water (hot water immersion test).
The dimension in the main orientation direction of the test piece after immersion in hot water was measured, and the thermal shrinkage ratio relative to the dimension in the main orientation direction of the test piece before immersion in hot water was calculated by the following calculation formula.
Thermal shrinkage (%) = (L ₀ −L ₁ ) / L ₀ × 100
L ₀ : dimensions in the main orientation direction before immersion in hot water L ₁ : dimensions in the main orientation direction after immersion in hot water In the examples and comparative examples, the main orientation direction is the width direction of the heat-shrinkable film, and L ₀ Is 50 mm.

(3) Thermal contraction rate of layer A in the main orientation direction (80 ° C., 30 seconds), thermal contraction rate of layer B in the main orientation direction (80 ° C., 30 seconds), difference in thermal contraction rate (80 ° C.)
The heat-shrinkable films obtained in Examples and Comparative Examples were separated into the A layer and the B layer by separating the layer between the A layer and the B layer up to the terminal. Next, each layer (A layer, B layer) was cut into 50 mm in the longitudinal direction and 50 mm in the width direction to obtain single layer test pieces (A layer test piece and B layer test piece).
The heat shrinkage rate was calculated in the same manner as in the above (2) except that the above-mentioned A layer test piece was used as a test piece to obtain “the heat shrinkage rate of the A layer (80 ° C., 30 seconds)”.
Further, except that the above-mentioned B layer test piece was used as a test piece, the heat shrinkage rate was calculated in the same manner as in the above (2) to obtain “B layer heat shrinkage rate (80 ° C., 30 seconds)”. It was.
The absolute value of the difference between the “heat shrinkage rate of layer A (80 ° C., 30 seconds)” and the “heat shrinkage rate of layer B (80 ° C., 30 seconds)” was calculated, and the “heat shrinkage rate difference (80 ° C.)” Got.

(4) Thermal contraction rate of layer A in the main orientation direction (90 ° C., 30 seconds), thermal contraction rate of layer B in the main orientation direction (90 ° C., 30 seconds), difference in thermal contraction rate (90 ° C.)
In the hot water immersion test, except that the test piece was immersed in hot water at 90 ° C. for 30 seconds, the thermal contraction rate of the A layer test piece and the B layer test piece was calculated in the same manner as (3) above. “The thermal contraction rate of layer A (90 ° C., 30 seconds)” and “the thermal contraction rate of layer B (90 ° C., 30 seconds)” were obtained. Also, the absolute value of the difference between the “heat shrinkage rate of layer A (90 ° C., 30 seconds)” and the “heat shrinkage rate of layer B (90 ° C., 30 seconds)” was calculated, and the “heat shrinkage rate difference (90 ° C. ) ”.

(5) Thermal contraction rate of layer A in the main orientation direction (98 ° C., 30 seconds), thermal contraction rate of layer B in the main orientation direction (98 ° C., 30 seconds), difference in thermal contraction rate (98 ° C.)
In the hot water immersion test, except that the test piece was immersed in hot water at 98 ° C. for 30 seconds, the thermal contraction rate of the A layer test piece and the B layer test piece was calculated in the same manner as (3) above. “The thermal contraction rate of layer A (98 ° C., 30 seconds)” and “the thermal contraction rate of layer B (98 ° C., 30 seconds)” were obtained. Also, the absolute value of the difference between the “heat shrinkage rate of layer A (98 ° C., 30 seconds)” and the “heat shrinkage rate of layer B (98 ° C., 30 seconds)” was calculated, and the “heat shrinkage rate difference (98 ° C. ) ”.

(6) Delamination test The heat-shrinkable films obtained in the examples and comparative examples were 104 mm in the longitudinal direction (film-forming direction of the heat-shrinkable film) and 235 mm in the width direction (perpendicular to the film-forming direction). It cut | judged and the film piece was obtained. The film piece is rolled into a cylinder so that the width direction is the circumferential direction (cylinder circumference: 228 mm), center-sealed with a solvent (seal width: 4 mm), and processed into a cylindrical shrink label. Was used as a test piece. Next, the test piece (cylindrical shrink label) was externally attached by hand to a container (a cylindrical body made of an aluminum body having a circumference of 219 mm, a height of 160 mm, and a thickness of 2 mm), and two places up and down with adhesive tape. Was temporarily fixed, then immersed in a hot water bath adjusted to a predetermined temperature for 30 seconds, taken out, and immediately cooled with water. After cooling with water, the state of the end of the film piece at the center seal part was observed visually and by palpation, and classified and evaluated in four stages of ◎, ○, Δ, and × according to the following indicators.
The temperature of the hot water bath was measured and evaluated under three conditions of 80 ° C., 90 ° C., and 98 ° C., respectively. Table 1 shows the evaluation results under the conditions where the best evaluation results were obtained for each example and comparative example.
(Delamination evaluation)
Excellent delamination deterrence at the time of shrinkage (◎): No particular change is observed in the end of the film piece superimposed on the center seal part, both in appearance (visually) and in palpation, before immersion in a hot water bath.
Good delamination deterrence at the time of shrinkage (◯): The formation of ridge lines is felt in palpation at the corners of the end of the film piece that overlaps in the center seal part, but the appearance of peeling is not recognized in appearance.
Usable level of delamination deterrence (△): At the corner of the end of the film piece that overlaps at the center seal part, the epidermis is lifted or contracted by palpation, and slight peeling is recognized at the site. (The lift of the film appears as a white line, but the line is discontinuous and its width is 300 μm or less).
The delamination deterrence during shrinkage is poor (×): Clear peeling is observed at the corner of the end of the film piece that overlaps the center seal part (white lines indicating the lift of the film appear continuously, the line The width is over 300 μm).

  The heat-shrinkable film (Example) satisfying the specified range of the present invention uses different resins for the A layer and the B layer, and the heat shrinkage despite the relatively low adhesive strength between the A layer and the B layer. It had excellent properties that do not cause delamination (delamination) during processing (shrink processing).

Claims (4)

A heat-shrinkable film having a resin layer (A layer) and a resin layer (B layer) laminated adjacent to each other, and satisfying all of the following (1 ′) to (6) Shrink film.
(1 ′) The A layer and the B layer are mainly composed of a styrene-conjugated diene copolymer in which the content of the polyester-based resin or the conjugated diene is 5 to 30% by weight with respect to the total weight of the monomer components. It is a resin layer. However, the polyester resin is a polyester resin composed of a dicarboxylic acid component and a diol component, or a dicarboxylic acid component and a diol component, oxycarboxylic acid, monocarboxylic acid, polyvalent carboxylic acid, monohydric alcohol, And one or more components selected from the group consisting of polyhydric alcohols.
(2) The A layer and the B layer are resin layers mainly composed of different kinds of resins.
(3) The adhesive strength between the A layer and the B layer in the T-type peel test is 2.5 N / 15 mm or less.
(4 ′) The heat shrinkage rate (80 ° C., 30 seconds) in the main orientation direction of the heat shrinkable film is 40 to 85%.
(5) The absolute value of the difference between the thermal contraction rate of the A layer (80 ° C., 30 seconds) and the thermal contraction rate of the B layer (80 ° C., 30 seconds), the thermal contraction rate of the A layer (90 ° C, 30 seconds) and the absolute value of the difference between the thermal contraction rates of the B layer (90 ° C, 30 seconds) and the thermal contraction rate of the A layer (98 ° C, 30 seconds) and the thermal contraction rate of the B layer (98 ° C) , 30 seconds), at least one of the absolute values of the difference is 10% or less.
(6) A layer and B layer are laminated | stacked by coextrusion, and the extending | stretching process is performed.   In the styrene-conjugated diene copolymer, the content of the styrene monomer is 60 to 95% by weight with respect to the total weight of the monomer component, and the content of the conjugated diene is the monomer component. The heat-shrinkable film according to claim 1, wherein the heat-shrinkable film is 5 to 40% by weight based on the total weight.   The heat-shrinkable film according to claim 1 or 2, wherein the polyester-based resin has a glass transition temperature of 60 to 100 ° C, and the styrene-conjugated diene copolymer has a glass transition temperature of 60 to 120 ° C. The raw material forming the A layer and the raw material forming the B layer have a temperature range in which the absolute value (| E ^* |) of the complex elastic modulus measured in the dynamic viscoelasticity measurement at a frequency of 10 Hz is 80 to 120 ° C. And the heat-shrinkable film of any one of Claims 1-3 which has a part used as 30-300 MPa.