JP2011110780A - Heat-shrinkable laminated film, molded product using the film, heat-shrinkable label, and container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable laminated film which excels in heat shrinkage characteristics, transparency, and interlayer adhesion at an ordinary temperature, is hard to peel even if treated at a high temperature, is restrained from whitening that occurs when bending the film during processing or the like, and is suitably used for a shrink package, shrink binding package, a shrink label, or the like. <P>SOLUTION: The heat-shrinkable laminated film is formed by extending in at least one direction a film which has two-type three-layer laminate constitution of A layer/B layer/A layer, wherein A layer is composed of a resin composition which includes a polyester based resin as a principal component, B layer is composed of a resin composition which includes 5-90 mass% of a styrene unit; 5-30 mass% of a conjugated diene unit; 0.2-2.0 mass% of a maleic anhydride unit; and 0-40 mass% of an ethylene terephthalate unit, and the rate of heat shrinkage in the main contraction direction when being immersed for 10 seconds into hot water at 80°C is at least 30%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable laminated film, a molded product using the film, a heat-shrinkable label, and a container. More specifically, the present invention relates to a heat-shrinkable laminated film excellent in heat-shrinkage properties, transparency, interlayer adhesion, and printability, and suitable for uses such as shrink-wrapping, shrink-bound packaging, and shrinkage labels, and the film. The present invention relates to a molded article and a container using

  Currently, soft drinks such as juice and alcoholic drinks such as beer are sold in a state of being filled in containers such as bottles and plastic bottles. For the above applications, polyester-based heat-shrink films that are rigid at room temperature, have excellent heat resistance and solvent resistance, and have a small natural shrinkage are mainly used. However, the polyester-based heat-shrinkable film has a problem in that shrinkage spots and wrinkles are likely to occur when mounted on a container because the polyester-based heat-shrinkable film shrinks rapidly. In addition, the shrink film is often provided with a perforation for the purpose of easily removing the shrink label from the container after use, but the polyester heat-shrink film has poor cutability at the perforation, and the label is removed from the container. It may not be easily removed.

  On the other hand, many polystyrene-based heat-shrink films having excellent low-temperature shrinkability are also used. However, the polystyrene-based heat-shrinkable film has a low low-temperature elongation, and has a problem that a label attached to a container breaks when it is accidentally dropped during refrigerated storage. In addition, polystyrene-based heat-shrinkable film has insufficient solvent resistance, so printing with ordinary organic solvent-based gravure ink curls the film or increases the amount of solvent remaining on the label. In many cases, blocking or organic solvent odor occurred.

  As means for solving the above problems, a two-layered three-layer film in which a front and back layer composed of a polyester resin is laminated on an intermediate layer composed of a polystyrene resin has been reported so far (for example, Patent Documents). 1 to 3). However, this two-type three-layer laminated film is usually insufficient from the viewpoint of quality because the film may be rubbed during transportation or may be peeled off by scratching with human nails or the like. There were many. In order to improve the delamination strength of the two-layer three-layer film, Patent Document 4 discloses a film using a resin composition in which the content of styrene units, conjugated diene units, and oxazoline units is adjusted in the center layer. . However, when a film using the above-described resin composition containing an oxazoline unit was examined, a lot of gel-like substances called fish eyes were formed on the film, and when the film was printed, It has been clarified that many spot-like ink jumps (so-called trapping) occur, which may impair the design of the film.

Japanese Patent Publication No. 05-005659 JP-A-7-137212 JP 2002-351332 A JP 2008-207487 A

  The present invention has been made to solve the above-described problems, and has excellent heat shrinkage characteristics, transparency, interlayer adhesion, and printability, and is suitable for applications such as shrink wrap, shrink bundled wrapping, and shrink labels. The object is to provide a shrinkable laminated film.

  Another object of the present invention is to provide a heat-shrinkable film using the heat-shrinkable laminated film, a heat-shrinkable label comprising the heat-shrinkable film, a molded product, and a container equipped with the heat-shrinkable label. Is to provide.

  The present inventor is concerned with the layer structure and composition of a layer containing a polyester resin as a main component and a layer containing at least a styrene unit, a conjugated diene unit, and a maleic anhydride unit. As a result of intensive studies on the relationship with the delamination strength in the film, the present inventors have succeeded in obtaining a film that can solve the above-mentioned problems of the prior art and have completed the present invention.

That is, an object of the present invention is a heat-shrinkable laminated film formed by stretching a film in which an A layer and a B layer comprising the following components are laminated in the order of A layer / B layer / A layer in at least one direction. And a heat-shrinkable laminated film (hereinafter referred to as “the film of the present invention”) having a heat shrinkage rate in the main shrinkage direction of 30% or more when immersed in warm water of 80 ° C. for 10 seconds. Achieved.
Layer A: Resin composition containing a polyester resin as a main component Layer B: Styrene unit 45% to 90% by weight, Conjugated diene unit 5% to 30% by weight, Maleic anhydride unit 0.2% by weight More than 2.0 mass% and the resin composition containing ethylene terephthalate unit 0 mass% or more and 40 mass% or less

  In the film of the present invention, the resin composition constituting the B layer is a polystyrene resin (excluding a styrene-maleic anhydride copolymer) of 50% by mass to 98% by mass, and a styrene-maleic anhydride copolymer. A resin composition in which 2% by mass to 20% by mass of a polymer and 0% by mass to 40% by mass of a polyester resin are mixed is preferable.

  The polystyrene resin contained in the B layer is preferably a styrene hydrocarbon-conjugated diene hydrocarbon copolymer.

  The polyester resin contained in the layer A includes a component derived from terephthalic acid as a dicarboxylic acid component, and a component derived from ethylene glycol and 1,4-cyclohexanedimethanol as a diol component. It is preferable.

  The film of the present invention was obtained by collecting a test piece with a main shrinkage direction of 150 mm and a direction of 15 mm perpendicular to the main shrinkage direction, and then peeling off a part of the A layer from the end face of the test piece in the main shrinkage direction. Then, a peeling portion is formed on the A layer side, and the peeling portion and the peeled portion on the B layer side are respectively sandwiched by a chuck of a tensile tester, and a 180 ° peeling test is performed at a tensile speed of 100 mm / min in the main shrinkage direction. It is preferable that the delamination strength when performing is 1 N / 15 mm width or more.

  Furthermore, the film of the present invention preferably has a haze value based on JIS K7105 of 10% or less.

  The film of the present invention can be used as a molded product using the film as a base material, a heat-shrinkable label, and a container equipped with the molded product or the heat-shrinkable label.

  In the case of the film of the present invention, since the B layer contains maleic anhydride units, the delamination strength due to the interaction at the lamination interface with the A layer containing the polyester resin as the main component can be maintained high. In addition, even when the layer B contains an ethylene terephthalate unit, the mixing property of the polystyrene resin and the polyester resin is improved, and the appearance defect of the film due to kneading unevenness and the thickness defect during film formation can be suppressed. . Therefore, it is possible to provide a heat-shrinkable film having excellent heat-shrinkage characteristics and transparency, and at the same time, capable of suppressing peeling due to scratching by transportation or nail, and having excellent appearance and processing characteristics.

  Moreover, since the molded product of the present invention, the heat-shrinkable label, and the container equipped with the label use the film of the present invention, it has a molded product suitable for packaging applications, a heat-shrinkable label, and excellent aesthetics. A container equipped with the label can be provided.

  Hereinafter, the film, molded product, heat-shrinkable label of the present invention, and a container equipped with the molded product or heat-shrinkable label (hereinafter referred to as “the container of the present invention”) will be described in detail.

  In the present specification, “main component” is intended to allow other components to be included as long as the action and effect of the resin constituting each layer is not hindered. Further, the term does not limit the specific content, but it is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and 100% by mass with respect to the total components of each layer. It is a component that occupies the following ranges.

[Heat-shrinkable laminated film]
The film of the present invention is a heat-shrinkable laminated film formed by stretching a film in which the A layer and B layer comprising the following components are laminated in the order of A layer / B layer / A layer in at least one direction, A heat-shrinkable laminated film having a heat shrinkage rate of 30% or more in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds.

<A layer>
In the film of the present invention, the A layer is composed of a resin composition containing a polyester resin as a main component.

(Polyester resin)
The polyester resin used in the film of the present invention can suppress natural shrinkage while imparting rigidity, rupture resistance and low temperature shrinkage to the film. A polyester resin suitable for the present invention is a polyester resin derived from a dicarboxylic acid residue and a diol residue. Examples of dicarboxylic acid residues include terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2,5-dichloroterephthalic acid, 2-methylterephthalic acid, 4,4-stilbene dicarboxylic acid, 4,4-biphenyldicarboxylic acid , Orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, bisbenzoic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4-diphenyl ether dicarboxylic acid, 4,4-di Aromatic dicarboxylic acids such as phenoxyethanedicarboxylic acid, 5-Na sulfoisophthalic acid, ethylene-bis-p-benzoic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, 1,3-cyclohexanedicarboxylic acid, 1, Aliphatic dicarboxylic acids such as 4-cyclohexanedicarboxylic acid or Residues derived from their esters derivatives. These dicarboxylic acid residues may be used alone or in combination of two or more. Among these, a polyester resin containing a terephthalic acid residue and an ethylene glycol residue is preferably used.

  In the present invention, it is more preferable that at least one of a dicarboxylic acid residue and a diol residue is a mixture composed of two or more types of residues. In the present specification, among the two or more types of residues, a main residue, that is, a residue having the largest mass (mol%) is defined as a first residue, and a smaller amount than the first residue is defined as a second residue. The following residues (namely, second residue, third residue,...) Are assumed. By using such a mixture of dicarboxylic acid residues and diol residues, the crystallinity of the resulting polyester resin can be lowered. Therefore, when used as the A layer, it was further used in the B layer described later. Even in this case, it is preferable because the progress of crystallization can be suppressed.

  Preferred mixtures of diol residues include, for example, the ethylene glycol residue as the first residue, 1,4-butanediol, neopentyl glycol, diethylene glycol, polytetramethylene glycol, and 1,4- Examples thereof include a residue derived from at least one selected from the group consisting of cyclohexanedimethanol, preferably 1,4-cyclohexanedimethanol residue.

  The preferred mixture of dicarboxylic acid residues is, for example, selected from the group consisting of terephthalic acid residues as the first residue and isophthalic acid, 1,4-cyclohexanedicarboxylic acid, succinic acid and adipic acid as the second residue. And a residue derived from at least one kind, preferably an isophthalic acid residue.

  The total content of dicarboxylic acid residues and diol residues below the second residue is the sum of the total amount of dicarboxylic acid residues (100 mol%) and the total amount of diol residues (100 mol%) ( 200 mol%) or more, preferably 20 mol% or more, and 40 mol% or less, preferably 35 mol% or less. If the content rate of the said 2 or less residue is 10 mol% or more, the crystallinity degree of polyester obtained can be restrained low. On the other hand, when the content of the residues of 2 residues or less is 40 mol% or less, the advantages of the first residue can be utilized.

  For example, when the dicarboxylic acid residue is a terephthalic acid residue, the first residue of the diol residue is an ethylene glycol residue, and the second residue is a 1,4-cyclohexanedimethanol residue, the second residue The content of 1,4-cyclohexanedimethanol residues is the total amount of terephthalic acid residues that are dicarboxylic acid residues (100 mol%), ethylene glycol residues, and 1,4-cyclohexanedimethanol residues. 10 mol% or more, preferably 15 mol% or more, more preferably 25 mol% or more, and 40 mol% or less, preferably 38 mol%, based on the total (200 mol%) of the total amount (100 mol%) Hereinafter, it is more preferably in the range of 35 mol% or less. By using an ethylene glycol residue and a 1,4-cyclohexanedimethanol residue as the diol residue within this range, the crystallinity of the obtained polyester is almost lost, and the fracture resistance can be improved.

  Furthermore, in the above example, when the dicarboxylic acid residue is a terephthalic acid residue as the first residue and an isophthalic acid residue as the second residue, the dicarboxylic acid residue is an isophthalic acid residue and a diol residue. The content of 1,4-cyclohexanedimethanol residue is the total amount of terephthalic acid residue and isophthalic acid residue (100 mol%) and the total amount of ethylene glycol residue and 1,4-cyclohexanedimethanol residue. 10 mol% or more, preferably 15 mol% or more, more preferably 25 mol% or more, and 40 mol% or less, preferably 38% mol or less, based on the total (200 mol%) of (100 mol%), More preferably, it is the range of 35 mol% or less.

The refractive index (n ₁ ) of the polyester resin is 1.560 or more and 1.580 or less, preferably 1.565 or more and 1.574 or less.

  The intrinsic viscosity (IV) of the polyester resin is 0.5 dl / g or more, preferably 0.6 dl / g or more, more preferably 0.7 dl / g or more, and 1.5 dl / g or less, preferably It is 1.2 dl / g or less, More preferably, it is 1.0 dl / g or less. If intrinsic viscosity (IV) is 0.5 dl / g or more, it can suppress that a film strength characteristic and heat resistance fall. On the other hand, if the intrinsic viscosity is 1.5 dl / g or less, it is possible to prevent breakage associated with an increase in stretching tension.

  Examples of the above-mentioned commercially available polyester resins include “PETGcopyester” (manufactured by Eastman Chemical), “Embrace” (manufactured by Eastman Chemical), “PETGSKYGREEN” (manufactured by SK Chemical), and the like.

  In the A layer of the film of the present invention, the polyester resin contained in the A layer is 50% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more, based on the total amount of the resin constituting the A layer. Most preferably, other resins than the polyester-based resin may be contained as long as the content is 90% by mass or more. Examples of such resins include polyolefin resins, polystyrene resins, polycarbonate resins, acrylic resins, and the like. Among them, polystyrene resins are preferable.

  The polyester resin used in the film of the present invention includes a monomer having a carboxylic acid residue and an alcohol residue in one molecule in addition to the polyester resin derived from the dicarboxylic acid residue and the diol residue. A polyester resin obtained by polymerizing can also be used. In particular, polylactic acid obtained by condensation polymerization of lactic acid can be suitably used because it imparts rigidity, low-temperature shrinkage, and low natural shrinkage.

  The reason why the A layer of the film of the present invention is composed of a resin composition containing a polyester-based resin as a main component is that it is preferable from the viewpoint of maintaining rigidity of the film, suppressing spontaneous shrinkage, and solvent resistance. When the layer A is composed of a resin composition containing a polyester resin as a main component, the film is less likely to curl when printed using a gravure ink containing an ordinary organic solvent as a main component, and the solvent remains on the label. This is preferable because the amount is increased and blocking after printing or organic solvent odor is less likely to occur.

  In order to impart film slipperiness and prevent blocking, it is preferable to add a method of blending incompatible resins or what is called an antiblocking agent to the A layer of the film of the present invention.

  Examples of the anti-blocking agent include inorganic particles such as silica, talc and calcium carbonate, inorganic oxides, carbonates, or organic particles such as crosslinked acrylic, crosslinked polyester, crosslinked polystyrene, and silicone. . Further, organic particles having a multilayer structure polymerized in multiple stages can also be used. Of these, silica and organic particles are preferably used.

  Since the anti-blocking agent causes slipping and blocking resistance by roughening the film surface, transparency and gloss of the film are hindered unless an appropriate addition amount and type are selected. The antiblocking agent is added in an amount of 0.01% by mass or more, preferably 0.015% by mass or more, more preferably 0.05% by mass or more based on the mass of the entire resin composition constituting the A layer (100% by mass). It is desirable that the content be 02% by mass or more and 2% by mass or less, preferably 1.5% by mass or less, and more preferably 1% by mass or less. If the added amount of the anti-blocking agent is too small (less than 0.01% by mass), the anti-blocking agent is difficult to deposit on the film surface, and it is difficult to form irregularities on the film surface. Difficult to express. On the other hand, if the amount of antiblocking agent is too large (over 2% by mass), excessive unevenness of the film surface is likely to occur, hindering transparency due to surface roughness, winding of a film roll due to excessive slipping, etc. Is likely to occur.

  The shape of the anti-blocking agent is not particularly limited, but it is spherical from the viewpoint of suppressing aggregation in the A layer, uniform dispersion, suppressing irregular reflection of transmitted light, and unevenness formed on the film surface. Those are preferably used. The average particle size of the anti-blocking agent is 0.5 μm or more, preferably 1 μm or more, and is 10 μm or less, preferably 8 μm or less, more preferably 6 μm or less. If the average particle size of the anti-blocking agent is too small (less than 0.5 μm), it is difficult to deposit on the surface, and the anti-blocking agent deposited on the surface has sufficient unevenness to exhibit slipperiness and blocking resistance. It is difficult to give. On the other hand, when the average particle size of the anti-blocking agent is too large (over 10 μm), it is preferable because printing is performed on the film of the present invention and the designability is enhanced, so that ink loss or the like is likely to occur and the appearance of the printed pattern is impaired. Absent. The particle size distribution of the anti-blocking agent is not particularly limited, but a particle having a narrow particle size distribution is preferable from the adverse effect of the particle size. If the particle size distribution becomes too wide, it may be included that deviates from the above-mentioned range of particle sizes that are preferably used, which is not preferable.

<B layer>
The B layer of the film of the present invention includes a styrene unit, a conjugated diene unit, a maleic anhydride unit, and an ethylene terephthalate unit, and is composed of a resin composition composed of these units.

  The content of styrene units contained in the B layer of the film of the present invention is 45% by mass or more, preferably 47% by mass or more, more preferably, when the total amount of the resin composition constituting the B layer is 100% by mass. It is 49 mass% or more, More preferably, it is 51 mass% or more. On the other hand, the upper limit of the styrene unit is 90% by mass or less, preferably 88% by mass or less, more preferably 86% by mass or less, and still more preferably 84% by mass or less. If the content of styrene units is 45% by mass or more, a decrease in film rigidity (film stiffness) is suppressed, and if the styrene unit is 90% by mass or less, a decrease in brittleness and rupture resistance of the film is suppressed. Therefore, it is possible to suppress the occurrence of defects in the secondary processing steps such as the film forming step and the printing / bag making / mounting step.

  The content of the conjugated diene unit contained in the B layer of the film of the present invention is 5% by mass or more, preferably 7% by mass or more, when the total amount of the resin composition constituting the B layer is 100% by mass. More preferably, it is 9 mass% or more. Moreover, the upper limit of the content rate of a conjugated diene unit is 30 mass% or less, Preferably it is 25 mass% or less, More preferably, it is 20 mass% or less. If the content of the conjugated diene unit is 5% by mass or more, the brittleness and breakage resistance of the film can be suppressed, and if the content of the conjugated diene unit is 30% by mass or less, the rigidity of the film ( It is possible to suppress the occurrence of defects in the secondary processing steps such as the film forming step and the printing / bag making / mounting step.

  Furthermore, the content of maleic anhydride units contained in the B layer of the film of the present invention is 0.2% by mass or more, preferably 0.3% by mass with respect to 100% by mass of the resin composition constituting the B layer. As mentioned above, More preferably, it is 0.5 mass% or more. Moreover, the upper limit of the content rate of a maleic anhydride unit is 2.0 mass% or less, Preferably it is 1.8 mass% or less, More preferably, it is 1.5 mass% or less. If the content of maleic anhydride units is 0.2% by mass or more, the delamination strength can be improved, and if the content of maleic anhydride units is 2.0% by mass or less, stretching characteristics It is preferable because the film can be prevented from lowering, can exhibit a heat shrinkage rate, and voids are generated inside the film during stretching, and the film does not whiten.

  The content of the ethylene terephthalate unit in the B layer in the film of the present invention is 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, with respect to 100% by mass of the resin composition constituting the B layer. It is. Further, the lower limit of the content of the ethylene terephthalate unit is 0% by mass or more, preferably 1% by mass or more, and more preferably 3% by mass or more. By including the ethylene terephthalate unit at a content of 30% by mass or less, it becomes possible to improve the delamination strength with the A layer made of a resin composition containing a polyester resin as a main component. Stiffness (film waist) can be improved.

  In the film B layer of the present invention, the content of each of the above structural units is as follows: polystyrene resin (excluding styrene-maleic anhydride copolymer), styrene-maleic anhydride copolymer, and polyester resin. Can be achieved by using a resin composition in which is mixed at a predetermined ratio.

(Polystyrene resin)
As the polystyrene resin used in the B layer of the film of the present invention, a block copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon (excluding a styrene-maleic anhydride copolymer) is preferably used. It is done. Examples of the styrenic hydrocarbon include polystyrene, poly (p-, m- or o-methylstyrene), poly (2,4-, 2,5-, 3, 4- or 3,5-dimethylstyrene), poly Polyalkylstyrenes such as (pt-butylstyrene); poly (o-, m- or p-chlorostyrene), poly (o-, m- or p-bromostyrene), poly (o-, m- or p-fluorostyrene), poly (halogenated styrene) such as poly (o-methyl-p-fluorostyrene); polyhalogenated substituted alkylstyrene such as poly (o-, m- or p-chloromethylstyrene); poly (p -, M- or o-methoxystyrene), poly (alkoxystyrene) such as poly (o-, m- or p-ethoxystyrene); poly (o-, m-, or p-carboxymethyl) Polycarboxyalkyl styrene such as styrene); polyalkyl ether styrene such as poly (p-vinylbenzylpropyl ether); polyalkylsilyl styrene such as poly (p-trimethylsilyl styrene); and polyvinylbenzyl dimethoxy phosphide. . The styrenic hydrocarbon block may contain a copolymerizable monomer other than these homopolymers, copolymers and / or styrenic hydrocarbons.

  Examples of conjugated diene hydrocarbons include butadiene, isoprene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like. Can be mentioned. The conjugated diene hydrocarbon block may contain a copolymerizable monomer other than these homopolymer, copolymer and / or conjugated diene hydrocarbon in the block.

  As one of the block copolymers of styrene hydrocarbons and conjugated diene hydrocarbons preferably used in the B layer, styrene hydrocarbons are styrene and conjugated diene hydrocarbons are butadiene. A butadiene block copolymer (SBS) may be mentioned. SBS has a styrene / butadiene mass% ratio of preferably about (95-60) / (5-40), more preferably (93-60) / (7-40), (90- More preferably, it is about 60) / (10-40). Further, the melt flow rate (MFR) measurement value of SBS (measurement conditions: temperature 200 ° C., load 49 N) is 2 g / 10 min or more, preferably 3 g / 10 min or more, and 15 g / 10 min or less, preferably It is desirable that it is 10 g / 10 min or less, more preferably 8 g / 10 min or less.

  Another example of the styrene-based hydrocarbon and conjugated diene-based hydrocarbon block copolymer preferably used in the film of the present invention is a styrene-isoprene-butadiene block copolymer (SIBS). In SIBS, the mass% ratio of styrene / isoprene / butadiene is preferably (60-90) / (5-40) / (5-30), (60-85) / (10-30) / ( 5 to 25) is more preferable, and (60 to 80) / (10 to 25) / (5 to 20) is more preferable. Further, the melt flow rate (MFR) measurement value (measurement conditions: temperature 200 ° C., load 49 N) of SIBS is 2 g / 10 min or more, preferably 3 g / 10 min or more, and 15 g / 10 min or less, preferably It is desirable that it is 10 g / 10 min or less, more preferably 8 g / 10 min or less. If the butadiene content is high and the isoprene content is low, the butadiene heated inside the extruder or the like may cause a cross-linking reaction to increase the gel-like material. On the other hand, if the butadiene content is low and the isoprene content is high, the raw material unit price may increase and the production cost may increase.

  The polystyrene resin is not limited to a simple substance, and may be a mixture of two or more. For example, when the styrenic resin is a mixture of SBS and SIBS, the mass% ratio of SBS / SIBS is preferably about (90 to 10) / (10 to 90), and (80 to 20) / ( More preferably, it is about 20 to 80), more preferably about (70 to 30) / (30 to 70).

When the polystyrene resin contained in the B layer of the film of the present invention is a block copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon, the refractive index measured in accordance with JIS K7142 of the block copolymer (N ₂ ) is 1.540 or more, preferably 1.550 or more, more preferably 1.555 or more, and 1.600 or less, preferably 1.590 or less, more preferably 1.585 or less. is there. Further, regarding the relationship with the refractive index (n ₁ ) of the polyester-based resin constituting the A layer, the refractive index (n ₂ ) of the block copolymer is ± 0. 0 of the refractive index (n ₁ ) of the polyester-based resin. It is desirable to be within the range of 02, preferably within the range of ± 0.015. By adjusting the difference between the refractive index of the polystyrene resin (n ₂ ) and the refractive index of the polyester resin (n ₁ ) within a predetermined range, a film having good transparency can be obtained.

The block copolymer of the styrene-based hydrocarbon and the conjugated diene-based hydrocarbon has a refractive index (n ₂ ) substantially equal to a desired value by appropriately adjusting the composition ratio of the styrene-based hydrocarbon and the conjugated diene-based hydrocarbon. Can be adjusted. Therefore, when the polyester resin is included in the B layer, n ₁ ± 0.02 is obtained by adjusting the composition ratio of the styrene hydrocarbon and the conjugated diene hydrocarbon corresponding to the refractive index (n ₁ ). A refractive index (n ₂ ) within the range is obtained. This predetermined refractive index may be adjusted with a styrene-based hydrocarbon and a conjugated diene-based hydrocarbon block copolymer alone or may be adjusted by mixing two or more resins.

In the film of the present invention, the polystyrene resin contained in the B layer preferably has a vibration frequency of 10 Hz, a strain of 0.1%, and a storage elastic modulus (E ′) at 0 ° C. of 1.00 × 10 ⁹ Pa or more. More preferably, it is 1.50 × 10 ⁹ Pa or more. The storage elastic modulus (E ′) at 0 ° C. represents the rigidity of the film, that is, the strength of the film. By having a storage elastic modulus (E ′) of 1.00 × 10 ⁹ Pa or more, a film having rigidity in addition to transparency can be obtained. This storage elastic modulus (E ′) is within a range that does not impair the transparency of the block copolymer of the styrene-based hydrocarbon and the conjugated diene-based hydrocarbon as described above, or a mixture of the two or more types of the copolymer. It can be obtained by mixing with other resins.

When a mixture of a block copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon or a mixture of this copolymer and another resin is used as the main component of the B layer, Good results can be obtained by appropriately selecting a copolymer or resin that imparts rigidity with the coalescence or resin. That is, by combining a styrene hydrocarbon-conjugated diene hydrocarbon block copolymer having high fracture resistance with a styrene hydrocarbon-conjugated diene hydrocarbon block copolymer having high rigidity, or high By mixing a styrenic hydrocarbon-conjugated diene hydrocarbon block copolymer having rupture resistance and other types of resins having high rigidity, these styrenic hydrocarbon-conjugated diene hydrocarbons are mixed. The total composition, or a mixture of these and other types of resins, can be adjusted to meet the desired refractive index (n ₂ ) and storage modulus (E ′) at 0 ° C.

Preferred as the styrene-based hydrocarbon-conjugated diene-based hydrocarbon block copolymer capable of imparting fracture resistance are pure block SBS and random block SBS. Among them, the storage elastic modulus (E ′) at 0 ° C. is 1.00 × 10 ⁸ Pa or more and 1.00 × 10 ⁹ Pa or less, and at least one of the peak temperatures of the loss elastic modulus (E ″) is −20. Those having viscoelastic properties at or below 0 ° C. are particularly preferred.If the storage elastic modulus (E ′) at 0 ° C. is 1.00 × 10 ⁸ Pa or more, increasing the blend amount of the resin responsible for the stiffness On the other hand, at the peak temperature of the loss elastic modulus (E ″), the temperature on the low temperature side mainly shows fracture resistance. Although this characteristic varies depending on the stretching conditions, it is difficult to impart sufficient film breakability to the laminated film when the peak temperature of the loss modulus (E ″) does not exist at −20 ° C. or lower in the state before stretching. There is a case.

Further, as a resin capable of imparting rigidity, a copolymer composed of a styrene hydrocarbon having a storage elastic modulus (E ′) at 0 ° C. of 2.00 × 10 ⁹ Pa or more, for example, a styrene resin having a controlled block structure Examples thereof include block copolymers of hydrocarbons and conjugated diene hydrocarbons, polystyrene, styrene hydrocarbons and aliphatic unsaturated carboxylic acid ester copolymers.

As the styrene hydrocarbon-conjugated diene hydrocarbon block copolymer having a controlled block structure, the storage elastic modulus (E ′) at 0 ° C. is 2.00 × 10 ⁹ as a characteristic of the styrene-butadiene block copolymer. SBS that is Pa or higher is exemplified. The composition ratio of styrene-butadiene of SBS satisfying this is preferably adjusted to about styrene / butadiene = (95-80) / (5-20).

  The structure of the block copolymer and the structure of each block part are preferably a random block and a tapered block. More preferably, in order to control the shrinkage characteristics, the peak temperature of the loss modulus (E ″) is 40 ° C. or more, and more preferably, the peak of the clear loss modulus (E ″) is below 40 ° C. There is no temperature. When the peak temperature of the loss elastic modulus (E ″) does not exist up to 40 ° C., the storage elastic modulus characteristic is almost the same as that of polystyrene, so that the rigidity of the film can be imparted. The peak temperature of the loss modulus (E ″) is preferably in the range of 40 ° C. or more and 90 ° C. or less. This peak temperature is a factor that mainly affects the shrinkage rate. If this temperature is in the range of 40 ° C. or more and 90 ° C. or less, the natural shrinkage and the low temperature shrinkage rate are not extremely lowered.

  A polymerization method of a styrene-based hydrocarbon-conjugated diene-based hydrocarbon copolymer that satisfies the above viscoelastic properties is shown below. Usually, after a part of styrene or butadiene is charged to complete the polymerization, a mixture of styrene monomer and butadiene monomer is charged and the polymerization reaction is continued. This preferentially polymerizes butadiene having a higher polymerization activity, and finally a block composed of a single monomer of styrene is generated.

  For example, when styrene is homopolymerized first, and after the polymerization is completed, a mixture of styrene monomer and butadiene monomer is added and polymerization is continued, the styrene / butadiene monomer ratio gradually changes between the styrene block and the butadiene block. A styrene-butadiene block copolymer having a copolymer site is obtained. By providing such a site, a polymer having the above viscoelastic properties can be obtained. In this case, the two peaks due to the butadiene block and the styrene block as described above cannot be clearly confirmed, and it appears that only one peak exists. That is, in a block structure such as SBS of a random block in which a pure block and a butadiene block are clearly present, Tg due to the butadiene block is mainly present at 0 ° C. or less, and therefore, storage modulus at 0 ° C. ( It becomes difficult for E ′) to be not less than a predetermined value.

  Further, regarding the molecular weight, the melt flow rate (MFR) measurement value (measurement conditions: temperature 200 ° C., load 49 N) is adjusted in the range of 2 g / 10 min to 15 g / 10 min. The mixing amount of the styrene-butadiene block copolymer imparting this rigidity is appropriately adjusted according to the characteristics of the heat-shrinkable laminated film, and is preferably 20% by mass or more and 80% by mass or less of the total resin constituting the B layer, preferably Is preferably adjusted in the range of 40% by mass to 70% by mass. If it is 80 mass% or less of resin total amount, the rigidity of a film can be improved significantly and it can suppress that fracture resistance falls. On the other hand, if it is 20 mass% or more of the total resin amount, sufficient rigidity can be imparted to the film.

  The molecular weight of the polystyrene resin contained in the B layer is such that the weight (mass) average molecular weight (Mw) is 100,000 or more, preferably 150,000 or more, and 500,000 or less, preferably 400,000 or less. Preferably it is 300,000 or less. If the weight (mass) average molecular weight (Mw) of the polystyrene-based resin is 100,000 or more, it is preferable that there is no defect that causes deterioration of the film. Furthermore, if the molecular weight of the polystyrene-based resin is 500,000 or less, there is no need to adjust the flow characteristics and there are no defects such as a decrease in extrudability, which is preferable.

  Examples of the above-mentioned commercially available polystyrene resins include “Asaflex” (manufactured by Asahi Kasei Chemicals), “Clearen” (manufactured by Denki Kagaku Kogyo), “K-resin” (manufactured by Philips), and the like.

  When a copolymer of a styrene hydrocarbon and an aliphatic unsaturated carboxylic acid ester is used as the polystyrene resin, the aliphatic unsaturated carboxylic acid ester copolymerized with the styrene hydrocarbon includes methyl (meth) acrylate, butyl (Meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate may be mentioned. Preferably, it is a copolymer of styrene and butyl (meth) acrylate, more preferably styrene is in the range of 70% by mass to 90% by mass, and Tg (peak temperature of loss elastic modulus E ″). The melt flow rate (MFR) measured value (measurement conditions: temperature 200 ° C., load 49 N) is 2 g / 10 min or more and 15 g / 10 min or less. In addition, the said (meth) acrylate shows an acrylate and / or a methacrylate.

  Examples of commercially available copolymers of the above-mentioned styrenic hydrocarbons and aliphatic unsaturated carboxylic acid esters include “TX polymer” (manufactured by Denki Kagaku Kogyo Co., Ltd.), “Planelloy” (manufactured by Nippon A & L Co., Ltd.), and “Cebian”. (Manufactured by Daicel Polymer Co., Ltd.).

  The content of the polystyrene-based resin contained in the B layer is 50% by mass or more, preferably 55% by mass or more, more preferably 60% by mass or more when the total amount of the resin composition constituting the B layer is 100% by mass. It is 98 mass% or less, Preferably it is 97 mass% or less, More preferably, it is 95 mass% or less. The content of the polystyrene-based resin contained in the B layer can be adjusted within the range specified by the present invention, but if it is within the above range, good shrinkage characteristics can be obtained and the delamination strength can be reduced. None is preferred.

(Styrene-maleic anhydride copolymer)
The styrene-maleic anhydride copolymer used in the B layer of the film of the present invention is a copolymer containing a styrene monomer and a maleic anhydride monomer as essential components as constituent monomer units.

  The content of the styrene-maleic anhydride resin contained in the B layer is 2% by mass or more, preferably 2.5% by mass or more, when the total amount of the resin composition constituting the B layer is 100% by mass. Preferably it is 3 mass% or more, and is 20 mass% or less, Preferably it is 15 mass% or less, More preferably, it is 10 mass% or less. The content of the styrene-maleic anhydride copolymer contained in the B layer can be adjusted within the range defined by the present invention, but if within the above range, the delamination strength can be improved, In addition, it is preferable because the stretching characteristics are deteriorated, the expression of the heat shrinkage rate is inhibited, voids are not generated in the film during stretching, and the film is not whitened.

  Examples of the commercially available styrene-maleic anhydride copolymer include “Dylark” (manufactured by Nova Chemicals), “Xiran” (manufactured by Polyscope), and the like.

(Polyester resin contained in layer B)
The film of the present invention can further contain a polyester resin in the B layer at a content of 0% by mass or more and 40% by mass or less.

  As a polyester-type resin used suitably in B layer of the film of this invention, the polyester-type resin used by the above-mentioned A layer can be mentioned. Further, the polyester resin used in the B layer may be the same polyester resin as the polyester resin used in the A layer or a different polyester resin as long as it does not exceed the range defined by the present invention. Further, the polyester resin used in the B layer may be a polyester resin contained in the recycled material.

  Here, the recycled material is a recycled material that is made by flaking, granulating, etc. non-product parts such as film-forming films and film edges before and after products, loss parts after slitting by trimming, etc. Means. It is preferable from the viewpoint of cost reduction and industrial waste reduction that the B layer contains the polyester resin contained in the recycled raw material.

  As long as the characteristics of the film of the present invention are satisfied, the B layer can be mixed with other resins in addition to the polyester resin and the polystyrene resin. Examples of such resins include compatibilizers, polyolefin resins, acrylic resins, and polycarbonate resins. Among them, it is preferable to contain a compatibilizer.

(Additives to each layer)
In addition to the components described above, the film of the present invention has a plasticizer and a plasticizer in each layer for the purpose of improving and adjusting the molding processability, productivity, and various properties of the heat-shrinkable film within a range that does not significantly impair the effects of the present invention. When the total amount of the resin composition constituting each layer of the tackifying resin is 100% by mass, it is 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, and 10% by mass. % Or less, preferably 8% by mass or less, more preferably 5% by mass or less. When the content of the plasticizer and / or tackifying resin is 10% by mass or less with respect to the total amount of the resin, the decrease in melt viscosity and the decrease in heat-resistant fusing property are small, and natural shrinkage hardly occurs. In addition to the plasticizer and tackifier resin, the film of the present invention may have various additives depending on the purpose, such as an ultraviolet absorber, a light stabilizer, an antioxidant, a hydrolysis inhibitor, a stabilizer, and a colorant. In addition, an antistatic agent, a lubricant, an inorganic filler, and the like can be appropriately added according to each application.

<Layer structure of film>
Next, a film having two types and three layers of A layer / B layer / A layer, which is a preferred embodiment of the present invention, will be described.

  In the film of the present invention, the thickness ratio between the A layer and the B layer is that when the A layer is 1, the B layer is 2 or more, preferably 3 or more, more preferably 4 or more, and 12 or less, preferably Is 10 or less, more preferably 8 or less. If the thickness ratio between the A layer and the B layer is 2 or more, generation of wrinkles and the like when the film is attached to the adherend is suppressed, and good shrinkage finish is obtained. Further, if the thickness ratio of the A layer and the B layer is 12 or less, when the A layer and the B layer are laminated, the occurrence of uneven flow of the molten resin can be suppressed, and the film can be laminated uniformly. The rigidity (film waist) is not lowered. In addition, the two A layers on both sides of the B layer may have different thicknesses as long as the thickness ratio is within the above-described range, but the two layers having the same thickness are processed and stored. From the viewpoint of suppressing warpage, wrinkles and the like.

  Although the total thickness of the film of the present invention is not particularly limited, it is preferably thinner from the viewpoint of suppressing raw material costs as much as possible. Specifically, the thickness after stretching is preferably 60 μm or less, and is 55 μm or less. Is more preferably 50 μm or less, and most preferably 45 μm or less.

<Shrinkage characteristics>
The film of the present invention has a heat shrinkage rate in the main shrinkage direction of 30% or more, preferably 35% or more, more preferably 40% or more, and 70% or less when immersed in warm water at 80 ° C. for 10 seconds. Preferably it is 65% or less, More preferably, it is 60% or less. When the heat shrinkage rate in the main shrinkage direction in 80 ° C. warm water is less than 30%, heat shrinkage becomes insufficient when the film of the present invention is mounted on the neck or top of the container as a heat shrinkable label, When the shrinkage rate exceeds 70%, the shrinkage rate of the film becomes excessive than the shrinkage rate required to cover the body of the container, and as a result, abnormalities such as wrinkles and avatars due to sudden shrinkage are likely to occur. It is not preferable because it is difficult to obtain a beautiful shrink finish.

  In the present specification, the “main contraction direction” means a direction in which the stretching direction is larger between the longitudinal direction and the transverse direction, and is a direction corresponding to the outer peripheral direction when the bottle is attached to a bottle, for example.

  When the film of the present invention is used as a PET container label, the thermal shrinkage in the orthogonal direction when immersed in warm water at 80 ° C. for 10 seconds is preferably 20% or less, and more preferably 10% or less. More preferably, it is 8% or less. Further, the thermal contraction rate in the orthogonal direction when immersed in warm water at 70 ° C. for 10 seconds is preferably 10% or less, more preferably 5% or less, and further preferably 3% or less. When the shrinkage rate in the orthogonal direction exceeds 10%, the shrinkage in the vertical direction becomes remarkable after shrinkage in label applications, which may cause a dimensional deviation or an appearance defect.

  The film of the present invention has a thermal shrinkage rate in the main shrinkage direction of 10% or more but less than 30%, preferably 10% or more and 25% or less, more preferably 10% or more and 20 when immersed in warm water at 70 ° C. for 10 seconds. % Or less is preferable. When the heat shrinkage rate in the main shrinkage direction in 70 ° C. warm water is less than 10%, the heat shrinkage force is small. For example, when a laminated film is used as the container label, it cannot be temporarily fixed to the container. Then, the film may be shifted up in the direction of the top surface. On the other hand, when the thermal shrinkage rate in the main shrinkage direction is greater than 30% at 70 ° C., the thermal shrinkage occurs suddenly in the low temperature region, and thus there is a case where the thermal shrinkage cannot be performed at a predetermined position.

  Therefore, if the thermal contraction rate in at least one direction when immersed in warm water at 70 ° C. and 80 ° C. for 10 seconds is within the above range, the laminated film is temporarily fixed to, for example, a container in a low temperature region near 70 ° C. In addition, the shrinkage of the container rapidly starts in a high temperature range exceeding 70 ° C and near 80 ° C. Even on the thin neck and top surface, no abnormalities such as wrinkles and avatars occur, and uniform shrinkage is obtained, resulting in a beautiful shrinkage finish.

  In addition, the film of the present invention has a thermal shrinkage rate of 5% or less, preferably 3% or less, more preferably 1% or less in at least one direction when immersed in warm water at 50 ° C. for 10 seconds. If the thermal shrinkage rate is greater than 5% when immersed in 50 ° C warm water for 10 seconds, the film's natural shrinkage rate is likely to increase. It is thought that the appearance defect that becomes uneven is caused.

  In this specification, “at least one direction” means either or both of the main contraction direction and the direction orthogonal to the main contraction direction, and usually refers to the main contraction direction.

<Transparency>
The transparency of the film of the present invention is evaluated by a haze value measured according to JIS K7105 when the thickness is 40 μm, and the haze value is preferably 10% or less, and 9% or less. Is more preferably 8% or less, and even more preferably less than 6%. If the haze value is 10% or less, good transparency can be obtained, and beautiful printing or the like becomes possible.

<Delamination strength>
The film of the present invention is stretched in at least one direction and formed into a heat-shrinkable film, and a test piece is collected from the heat-shrinkable film with a main shrinkage direction of 150 mm and a direction of 15 mm perpendicular to the main shrinkage direction. A part of the A layer is peeled off from the end surface in the main contraction direction of the test piece to form a peeling part on the A layer side, and the peeling part and the peeled part of the B layer are connected to a chuck of a tensile tester. When the 180 ° peel test is performed at a test speed of 100 mm / min with respect to the main shrinkage direction, the delamination strength is 1 N / 15 mm width or more, preferably 1.3 N / 15 mm width or more, more preferably 1.5 N / The width is 15 mm or more. Since the film of the present invention has a delamination strength of 1 N / 15 mm or more when formed into a heat-shrinkable film, troubles such as vibration during transportation and delamination due to scratching of nails or the like may occur. Absent.

(Method for producing heat-shrinkable film)
In the film of the present invention, the B layer and the A layer disposed on both sides of the B layer are laminated simultaneously or sequentially to produce a laminated film, and then the laminated film is heated to at least one axial direction. It is obtained by stretching.

  The laminated film can be formed simultaneously with the B layer and the A layer by co-extrusion using an extruder equipped with a T die by an existing method such as a T die method or a tubular method. In addition, the laminated film can be sequentially produced by separately forming the resin constituting each layer and then laminating them using a press method or a roll nip method.

  The laminated film is cooled with a cooling roll, air, water, etc., and then reheated by an appropriate method such as hot air, hot water, infrared rays, etc., roll stretching method, tenter stretching method, tubular stretching method, long interval stretching method, etc. Uniaxially or biaxially stretched simultaneously or sequentially. In biaxial stretching, stretching in the MD and TD directions may be performed at the same time, but sequential biaxial stretching in which one of them is performed first is effective, and the order of either MD or TD may be first. The stretching temperature needs to be changed depending on the softening temperature of the resin constituting the film and the use required for the heat-shrinkable laminated film, but is generally 60 ° C., preferably 70 ° C. or more, and 130 ° C. or less, preferably 120 It is controlled in the range of ℃ or less. The draw ratio in the main shrink direction (TD) is 2 times or more, preferably 3 times or more, more preferably 4 times or more, and 7 times depending on the film constituents, stretching means, stretching temperature, and target product form. Hereinafter, it is suitably determined within a range of preferably 6 times or less. Whether to use uniaxial stretching or biaxial stretching is determined by the application of the target product.

  Even in the case of an application that requires shrinkage characteristics in almost one direction, such as a PET container label, it is effective to stretch the film in a range that does not impair the shrinkage characteristics in the vertical direction. The stretching temperature depends on components other than PET, but typically ranges from 60 ° C. to 90 ° C. Furthermore, with respect to the draw ratio, as the size is increased, the fracture resistance is improved, but the heat shrinkage rate is increased accordingly, and it is difficult to obtain a good shrinkage finish. It is particularly preferred that

  Moreover, the film of this invention can provide and hold | maintain shrinkage | contraction property by cooling this film rapidly within the time when the molecular orientation of a stretched film is not relieved after extending | stretching.

[Molded products, heat-shrinkable labels and containers]
The film of the present invention can be used as various molded products such as coating films for containers, binding bands, exterior films, etc. by molding or forming a printing layer, vapor deposition layer and other functional layers as necessary. it can. In particular, the film of the present invention is applied to a heat-shrinkable label for food containers (for example, PET bottles, glass bottles, preferably PET bottles for soft drinks or foods), for example, complex shapes (cylinders with a constricted center, four rounded corners). It can also be used for prisms, pentagons, hexagons, etc.).

  Further, the film of the present invention is not only a heat-shrinkable label material of a plastic molded product that is deformed when heated to a high temperature, but also a material that is extremely different from the film of the present invention in terms of coefficient of thermal expansion, water absorption, etc. At least one selected from polyolefin resins such as porcelain, glass, paper, polyethylene, polypropylene, polybutene, polymethacrylate resins, polycarbonate resins, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, and polyamide resins. It can also be used as a heat-shrinkable label material for a package (container) used as a constituent material.

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

Examples of the film of the present invention, heat-shrinkable labels, and containers equipped with the labels are shown below, but the present invention is not limited by these examples.
In addition, the measured value and evaluation which are shown to an Example were performed as follows. In the examples, the take-up (flow) direction of the laminated film is described as “MD”, and the direction orthogonal thereto is described as “TD”.

<Measurement method>
(1) Thermal Shrinkage The film of the present invention was cut into a size of MD 20 mm and TD 100 mm, and the amount of TD shrinkage was immersed in an 80 ° C. hot water bath for 10 seconds and measured. The thermal shrinkage rate was expressed as a percentage of the shrinkage amount relative to the original size before shrinkage.

(2) Interlaminar peel strength The film of the present invention was formed into a heat-shrinkable film, and a test piece was collected from the obtained film in a size of 150 mm in the main shrinkage direction and 15 mm in the direction perpendicular to the main shrinkage direction. A part of the A layer is peeled off from the end surface in the main contraction direction of the piece to form a peeled portion on the A layer, and the peeled portion and the peeled portion on the B layer side are sandwiched between chucks of a tensile tester. The 180 ° peel test was performed at a test speed of 100 mm / min with respect to the main shrinkage direction. The average value at which the load obtained in the peel test became constant to some extent was evaluated as the delamination strength.
◎: Delamination strength is 1.3 N / 15 mm width or more ○: Delamination strength is 1.0 N / 15 mm width or more and less than 1.3 N / 15 mm width ×: Delamination strength is less than 1.0 N / 15 mm width

(3) Transparency In accordance with JIS K7105, the haze value of a film having a thickness of 40 μm was measured to evaluate transparency.
◎: Haze value is less than 6% ○: Haze value is 6% or more and 10% or less ×: Haze value exceeds 10%

(4) Fish eye evaluation The film edge of the film of this invention was trimmed, the fish eye which exists in the film roll of MD10m and TD500mm was counted visually, and evaluation was implemented.
○: The number of fish eyes is less than 100 Δ: The number of fish eyes is 100 or more and less than 500 ×: The number of fish eyes is 500 or more −: Not measured

Moreover, the raw material used by each Example and the comparative example is as follows.
(Polyester resin)
Copolyester 1 (trade name: SKYGREEN PETG S2008 (manufactured by SK Chemicals), hereinafter abbreviated as “PEs (1)”)
(Polystyrene resin (excluding styrene-maleic anhydride copolymer))
Styrene-butadiene copolymer 1 (styrene / butadiene = 90/10 (mass%), storage elastic modulus E ′ (0 ° C.): 3.15 × 10 ⁹ Pa, peak temperature of loss elastic modulus E ″ 55 ° C.) Hereinafter, it is referred to as “PS (1)”. )
Styrene-butadiene copolymer 2 (trade name: DK-11 (manufactured by Chevron Phillips), hereinafter referred to as “PS (2)”)
(Styrene-maleic anhydride copolymer)
Styrene-maleic anhydride copolymer 1 (styrene / maleic anhydride = 90/10 (mass%), storage elastic modulus E ′ (0 ° C.): 3.44 × 10 ⁹ Pa, peak of loss elastic modulus E ″ Temperature 120 ° C., MFR: 2.0 (230 ° C., 2.16 kg), hereinafter referred to as “SMA (1)”)
Styrene-maleic anhydride copolymer 2 (styrene / maleic anhydride = 84/16 (mass%), storage elastic modulus E ′ (0 ° C.): 3.38 × 10 ⁹ Pa, peak of loss elastic modulus E ″ Temperature 134 ° C., MFR: 2.0 (230 ° C., 2.16 kg), hereinafter referred to as “SMA (2)”)
Styrene-maleic anhydride copolymer 3 (styrene / maleic anhydride = 78/22 (mass%), trade name: Xiran SZ22110 (manufactured by POLYSCOPE), hereinafter referred to as “SMA (3)”)
Styrene-maleic anhydride copolymer 4 (styrene / maleic anhydride = 74/26 (mass%), trade name: Xiran SZ26120 (manufactured by POLYSCOPE), hereinafter referred to as “SMA (4)”)
(Styrene-2-isopropenyl-2-oxazoline copolymer)
Oxazoline group-containing styrene copolymer (styrene / 2-isopropenyl-2-oxazoline = 95/5, trade name: Epocross RPS-1005 (manufactured by Nippon Shokubai Co., Ltd.), hereinafter referred to as “RPS (1)”)

  The resin composition used for forming the laminated film and for the B layer was previously mixed with each of the examples shown in Table 1 and the B layer of the comparative example, and mixed into a twin-screw extruder (manufactured by Mitsubishi Heavy Industries, Ltd.). ), Melted and mixed at a set temperature of 210 ° C., extruded from a strand die with a set temperature of 210 ° C., and then cooled with a water tank, the resin composition was cut with a strand cutter to obtain pellets. The pellet obtained by the said method was used for the resin composition used for the B layer of the Example shown below and a comparative example.

Example 1
After the resin of each layer melted from two single-screw extruders (manufactured by Mitsubishi Heavy Industries, Ltd.) was merged in a feed block conduit for two types and three layers, A layer / B layer / A layer In an apparatus capable of forming a laminated sheet, the polyester resin “PEs (1)” was introduced into a single screw extruder for forming an A layer, and pelletized in advance into a single screw extruder for forming a B layer. After introducing a mixed resin composition (PS (1) 39% by mass, PS (2) 59% by mass, SMA (1) 2% by mass) and melt mixing at each extruder set temperature 210 ° C., the thickness of each layer is Co-extruded so that A layer / B layer / A layer = 25 μm / 150 μm / 25 μm, taken with a cast roll at 60 ° C., and cooled and solidified to obtain an unstretched laminated sheet having a width of 200 mm and a thickness of 200 μm. Next, the film is stretched 5.0 times in the transverse uniaxial direction at a preheating temperature of 90 ° C. and a stretching temperature of 88 ° C. using a film tenter manufactured by Kyoto Machine Co., Ltd., and then heat treated at 60 ° C. Obtained. The evaluation results of the obtained film are shown in Table 1.

(Example 2)
As shown in Table 1, except that the mixed resin composition pelletized beforehand with PS (1) 39 mass%, PS (2) 58 mass%, and SMA (1) 3 mass% was used for the B layer. A heat-shrinkable film was obtained in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.

(Example 3)
As shown in Table 1, except that the mixed resin composition pelletized beforehand with 38% by mass of PS (1), 57% by mass of PS (2) and 5% by mass of SMA (1) was used for the B layer. A heat-shrinkable film was obtained in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.

Example 4
As shown in Table 1, except that the mixed resin composition pre-pelletized with PS (1) 36 mass%, PS (2) 54 mass%, and SMA (1) 10 mass% was used for the B layer. A heat-shrinkable film was obtained in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.

(Example 5)
As shown in Table 1, a mixed resin composition pelletized beforehand with 28% by mass of PS (1), 42% by mass of PS (2), 10% by mass of SMA (1), and 20% by mass of PEs (1) is B A heat-shrinkable film was obtained in the same manner as in Example 1 except that it was used for the layer. The evaluation results of the obtained film are shown in Table 1.

(Example 6)
As shown in Table 1, a mixed resin composition pelletized beforehand with PS (1) 24 mass%, PS (2) 36 mass%, SMA (1) 10 mass%, and PEs (1) 30 mass% is B A heat-shrinkable film was obtained in the same manner as in Example 1 except that it was used for the layer. The evaluation results of the obtained film are shown in Table 1.

(Example 7)
As shown in Table 1, a mixed resin composition pelletized in advance with PS (1) 34 mass%, PS (2) 51 mass%, SMA (2) 10 mass%, and PEs (1) 5 mass% is B A heat-shrinkable film was obtained in the same manner as in Example 1 except that it was used for the layer. The evaluation results of the obtained film are shown in Table 1.

(Example 8)
As shown in Table 1, a mixed resin composition pelletized beforehand with PS (1) 32 mass%, PS (2) 48 mass%, SMA (2) 10 mass%, and PEs (1) 10 mass% is B A heat-shrinkable film was obtained in the same manner as in Example 1 except that it was used for the layer. The evaluation results of the obtained film are shown in Table 1.

Example 9
As shown in Table 1, a mixed resin composition pelletized beforehand with PS (1) 20 mass%, PS (2) 30 mass%, SMA (2) 10 mass%, and PEs (1) 40 mass% is B An unstretched laminated sheet was obtained in the same manner as in Example 1 except that it was used for the layer. Next, under the same stretching conditions as in Example 1, the stretching stress increased and exceeded the allowable load of the stretching equipment used. Therefore, in the same stretching equipment as that used in Example 1, a preheating temperature of 95 ° C. was stretched. After stretching 5.0 times in the transverse uniaxial direction at a temperature of 95 ° C., heat treatment was performed at 60 ° C. to obtain a heat-shrinkable film having a thickness of 40 μm. The evaluation results of the obtained film are shown in Table 1.

(Example 10)
As shown in Table 1, except that the mixed resin composition pelletized beforehand with PS (1) 38 mass%, PS (2) 57 mass%, SMA (3) 5 mass% was used for the B layer. A heat-shrinkable film was obtained in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.

(Example 11)
As shown in Table 1, except that the mixed resin composition pelletized beforehand with PS (1) 38 mass%, PS (2) 57 mass%, SMA (4) 5 mass% was used for the B layer. A heat-shrinkable film was obtained in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 1)
As shown in Table 1, except that the mixed resin composition pelletized in advance with PS (1) 40% by mass and PS (2) 60% by mass was used for the B layer, A heat-shrinkable film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 2)
As shown in Table 1, except that the mixed resin composition pelletized beforehand with PS (1) 32 mass%, PS (2) 48 mass%, and PEs (1) 20 mass% was used for the B layer. A heat-shrinkable film was obtained in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 3)
As shown in Table 1, except that the mixed resin composition pelletized beforehand with PS (1) 40 mass%, PS (2) 59 mass%, SMA (1) 1 mass% was used for the B layer. A heat-shrinkable film was obtained in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 4)
As shown in Table 1, a mixed resin composition pelletized beforehand with PS (1) 24 mass%, PS (2) 36 mass%, SMA (1) 25 mass%, PEs (1) 15 mass% is B A heat-shrinkable film was obtained in the same manner as in Example 1 except that it was used for the layer. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 5)
As shown in Table 1, except that the mixed resin composition pelletized beforehand with PS (1) 20 mass%, PS (2) 30 mass%, SMA (1) 50 mass% was used for the B layer. In the same manner as in Example 1, an unstretched laminated sheet was obtained. Next, under the same stretching conditions as in Example 1, the film broke, so that the film was broken 5.0 times in the transverse uniaxial direction at a preheating temperature of 96 ° C. and a stretching temperature of 94 ° C. using the same stretching equipment as used in Example 1. After stretching, heat treatment was performed at 60 ° C. to obtain a heat-shrinkable film having a thickness of 40 μm. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 6)
As shown in Table 1, a mixed resin composition pelletized beforehand with PS (1) 24 mass%, PS (2) 36 mass%, SMA (2) 20 mass%, and PEs (1) 20 mass% is B An unstretched laminated sheet was obtained in the same manner as in Example 1 except that it was used for the layer. Next, using the same stretching equipment as used in Example 1, the film was stretched 5.0 times in the transverse uniaxial direction at a preheating temperature of 96 ° C. and a stretching temperature of 94 ° C., and then heat-treated at 60 ° C. to a thickness of 40 μm. A heat-shrinkable film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 7)
As shown in Table 1, except that the mixed resin composition pelletized beforehand with PS (1) 20 mass%, PS (2) 30 mass%, SMA (2) 50 mass% was used for the B layer. In the same manner as in Example 1, an unstretched laminated sheet was obtained. Next, under the same stretching conditions as in Example 1, the film broke, so that the film was broken 5.0 times in the transverse uniaxial direction at a preheating temperature of 96 ° C. and a stretching temperature of 94 ° C. using the same stretching equipment as used in Example 1. After stretching, heat treatment was performed at 60 ° C. to obtain a heat-shrinkable film having a thickness of 40 μm. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 8)
As shown in Table 1, except that the mixed resin composition pelletized in advance with PS (1) 8 mass%, PS (2) 12 mass%, SMA (2) 80 mass% was used for the B layer. In the same manner as in Example 1, an unstretched laminated sheet was obtained. Next, the film was stretched 5.0 times in the transverse uniaxial direction at a preheating temperature of 100 ° C. and a stretching temperature of 98 ° C. using the same stretching equipment as used in Example 1, and then heat treated at 60 ° C. It broke. The evaluation results are shown in Table 1.

(Comparative Example 9)
As shown in Table 1, except that the mixed resin composition pelletized in advance with PS (1) 36% by mass, PS (2) 54% by mass, and SMA (3) 10% by mass was used for the B layer. A heat-shrinkable film was obtained in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 10)
As shown in Table 1, except that the mixed resin composition pelletized beforehand with PS (1) 36 mass%, PS (2) 54 mass%, and SMA (4) 10 mass% was used for the B layer. A heat-shrinkable film was obtained in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 11)
As shown in Table 1, except that the mixed resin composition pelletized beforehand with PS (1) 38 mass%, PS (2) 57 mass%, PPS (1) 5 mass% was used for the B layer. A heat-shrinkable film was obtained in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.

From Table 1, the heat-shrinkable films (Examples 1 to 11) obtained from the laminates of the present invention are compared with the two-layer three-layer films (Comparative Examples 1 and 2) that do not have maleic anhydride units in the B layer. It can be seen that this is a heat-shrinkable film having sufficient delamination. Further, when the content of the maleic anhydride unit contained in the B layer deviates below the range defined by the present invention (Comparative Example 3), although it has good shrinkage characteristics and transparency, the adhesive strength with the A layer The effect on the improvement was not expressed. Further, when the content of maleic anhydride units contained in the B layer deviates beyond the range defined by the present invention (Comparative Examples 4 to 10), although the improvement of the adhesive strength with the A layer is observed, the stretch whitening It has become clear that the transparency due to the film is reduced and the heat shrinkage rate is lowered, and the required characteristics as a heat shrinkable laminated film are not satisfied. It became clear that the adhesive strength between the adhesive layers was extremely lowered and did not satisfy the required properties as a heat-shrinkable film.
In addition, in the film having the oxazoline group unit instead of the maleic anhydride unit in the B layer (Comparative Example 11), although an improvement tendency of the adhesive strength with the A layer is seen, it becomes clear that it is insufficient. The film was dotted with many foreign matters called fish eyes, suggesting the possibility of ink skipping during printing (so-called trapping). This is presumed to be derived from excessive reactivity of the oxazoline group unit. On the other hand, in the film (Example 3, Example 5) which has a maleic anhydride unit, the above fish eyes are hardly produced and it turns out that it is a film which has the outstanding printability.
These are effects that can be achieved by adjusting the heat-shrinkable laminated film of the present invention within the range specified by the present invention.

  The film of the present invention is a heat-shrinkable laminated film suitable for uses such as shrink wrapping, shrink-bound wrapping and shrinkage labels, having heat shrink characteristics and transparency, excellent adhesion between layers, and excellent printability. In addition, it can be suitably used for molded articles using the film, particularly shrink labels and the like.

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

Claims (9)

A heat-shrinkable laminated film obtained by stretching at least one direction a film obtained by laminating A layer and B layer comprising the following components in the order of A layer / B layer / A layer,
A heat-shrinkable laminated film having a heat shrinkage rate of 30% or more in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds.
Layer A: Resin composition containing polyester resin as main component Layer B: Styrene unit 45% to 90% by weight, Conjugated diene unit 5% to 30% by weight, Maleic anhydride unit 0.2% by weight More than 2.0 mass% and the resin composition containing ethylene terephthalate unit 0 mass% or more and 40 mass% or less The resin composition constituting the B layer is a polystyrene resin (however, excluding styrene-maleic anhydride copolymer) from 50% by mass to 98% by mass, and from 2% by mass to styrene-maleic anhydride copolymer. The heat-shrinkable laminated film according to claim 1, wherein the heat-shrinkable laminated film is a resin composition in which 20% by mass or less and 0% by mass or more and 40% by mass or less of a polyester resin are mixed. The heat-shrinkable laminated film according to claim 2, wherein the polystyrene-based resin contained in the B layer is a styrene-based hydrocarbon-conjugated diene hydrocarbon copolymer. The polyester resin contained in the A layer contains a component derived from terephthalic acid as a dicarboxylic acid component, and contains a component derived from ethylene glycol and 1,4-cyclohexanedimethanol as a diol component. The heat-shrinkable laminated film according to any one of claims 1 to 3. After collecting a test piece with a size of 150 mm in the main shrinkage direction and 15 mm in a direction perpendicular to the main shrinkage direction, a part of the A layer is peeled off from the end surface in the main shrinkage direction of the test piece and peeled off to the A layer side. When the 180 ° peel test is performed at a tensile rate of 100 mm / min in the main shrinkage direction, the peeled portion and the peeled portion on the B layer side are sandwiched by a chuck of a tensile tester. The heat shrinkable laminated film according to any one of claims 1 to 4, wherein is 1 N / 15 mm width or more. The heat-shrinkable laminated film according to any one of claims 1 to 5, wherein a haze value based on JIS K7105 is 10% or less. A molded article comprising the heat-shrinkable laminated film according to claim 1 as a base material. The heat-shrinkable label which uses the heat-shrinkable laminated film in any one of Claim 1 to 6 as a base material. A container equipped with the molded product according to claim 7 or the heat-shrinkable label according to claim 8.