JP5294974B2 - 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 excelling in heat shrinkage characteristics, transparency and interlayer adhesion at an ordinary temperature, hard to peel even if treated at a high temperature and restrained from whitening that occurs when bending the film during processing or the like, and suitably used for a shrink package, shrink binding package, a shrink label, or the like. <P>SOLUTION: An A-layer is composed of a resin composition containing polyester-based resin as a main component, a B-layer is composed of a resin composition containing polystyrene-based resin and polyester-based resin less than the content of polyester-based resin contained in the A-layer, and a C-layer is composed of a resin composition containing polystyrene-based resin and polyester-based resin less than the content of polyester-based resin contained in the B-layer. A heat shrinkage rate in a main shrinkage direction when the heat-shrinkable laminated film obtained by extending a laminated film of these layers at least in one direction is submerged in hot water of 80&deg;C for 10 seconds, is 20% or more. <P>COPYRIGHT: (C)2011,JPO&amp;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 is excellent in heat shrink properties, transparency, interlayer adhesion at room temperature, hardly peeled even when processed at high temperature, and whitening that occurs when a film is bent during processing (so-called folding whitening) The present invention relates to a heat-shrinkable laminated film suitable for uses such as shrink wrapping, shrink-bound wrapping and shrinkage labels, and molded articles and containers using the film.

  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 using a reactive group such as an oxazoline group to increase the interlayer adhesion strength with the polyester resin of the surface layer, the length of the merging time between the surface layer and the center layer during extrusion greatly affects the peel strength. In order to improve productivity, when the line speed is increased, the strength may be remarkably lowered, so that there are many insufficient places.

  Moreover, in order to improve the delamination strength of the two-type three-layer film, a method of forming an adhesive layer between the surface layer and the back layer is also employed. For example, Patent Document 5 discloses a heat-shrinkable laminated film obtained by laminating an intermediate layer made of polystyrene resin and front and back layers made of polyester resin through an adhesive layer made of olefin resin. However, when the heat-shrinkable laminated film is attached to a container, there is a problem that the surface layer and the back layer are peeled off in the heat-shrinking process, and an excellent appearance cannot be obtained. Moreover, the film which has a polyester-type elastomer in the contact bonding layer is disclosed as a method of improving the peeling which arises by a heat shrink process or a residual solvent (for example, refer patent document 6, 7). Although these films have an effect on adhesiveness and the like, whitening that occurs when the film is bent during processing, that is, so-called folding whitening, may occur, which may cause problems in maintaining the design of the film.

Japanese Patent Publication No. 05-005659 JP-A-7-137212 JP 2002-351332 A JP 2008-207487 A JP 2006-15745 A JP 2008-037093 A JP 2008-62640 A

  The present invention has been made to solve the above-mentioned problems, and is excellent in heat shrinkage properties, transparency, interlayer adhesion at room temperature, hardly peeled off even when processed at high temperature, and is bent during processing. An object of the present invention is to provide a heat-shrinkable laminated film suitable for applications such as shrink wrapping, shrink tying wrapping, and shrinkage labels, which suppresses whitening (so-called folding whitening) that occurs at the time.

  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 has a composition of (A) layer formed from a resin composition containing a polyester resin as a main component, (B) layer containing polyester resin and polystyrene resin, and (C) layer. As a result of intensive studies, the present inventors have succeeded in obtaining a film that can solve the above-described 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 obtained by stretching a laminated film comprising at least three layers having a (B) layer between the following (A) layer and (C) layer in at least one direction. A heat shrinkable laminate film (hereinafter referred to as “the film of the present invention”) having a heat shrinkage ratio of 20% or more in the main shrinkage direction when immersed in warm water of 80 ° C. for 10 seconds. Is achieved.
(A) layer: a resin composition containing a polyester resin as a main component (B) layer: a polyester containing a polyester resin and a polystyrene resin, and the content of the polyester resin contained in the (A) layer Resin composition (C) layer with less content of polyester resin: containing polyester resin and polystyrene resin, the polyester resin content being less than the polyester resin content of layer (B) Resin composition
The (B) layer, the (C) layer, or the (B) layer and the (C) layer further contain a compatibilizing agent that promotes compatibilization of the polyester resin and the polystyrene resin, The compatibilizing agent is at least one of the following (a) to (e).
(A) Oxazoline group-containing styrene copolymer
(B) Styrene-maleic anhydride copolymer
(C) Polyester elastomer or modified polyester elastomer
(D) Polystyrene elastomer or modified polystyrene elastomer
(E) A resin composition in which a trunk component and a branch component are different, and the trunk component or the branch component of the graft copolymer is a polyester resin or a polystyrene resin.

  Moreover, it is preferable that the polystyrene resin contained in the (C) layer contains an aromatic vinyl hydrocarbon-conjugated diene copolymer.

  Moreover, the polyester-type resin which comprises the said (A) layer contains the component derived from terephthalic acid as a dicarboxylic acid component, and the component derived from ethylene glycol and 1, 4- cyclohexane dimethanol as a diol component. Is preferred.

  Further, the (A) layer is the outermost layer, and it is preferable that the (A) / (B) / (C) / (B) / (A) has a three-kind five-layer structure.

  After collecting a test piece from the heat-shrinkable film with a main shrinkage direction of 150 mm and a direction perpendicular to the main shrinkage direction of 15 mm, a part of the layer (A) is peeled off from the end surface of the test piece in the main shrinkage direction. When the peeling portion of the layer (A) and the peeled portion including the layer (C) are sandwiched by a chuck of a tensile tester, and a 180 degree peeling test is performed at a test speed of 100 mm / min with respect to the main shrinkage direction. The delamination strength is preferably 1 N / 15 mm width or more.

  Furthermore, it is preferable that the haze value based on JIS K7105 is 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.

  If it is a film of the present invention, it exhibits excellent heat shrinkage properties and transparency, and at the same time, it is possible to suppress peeling due to scratching by transportation and nail, and to suppress peeling at high temperature processing in the bottle mounting process, Can provide a heat-shrinkable film having excellent appearance and processing characteristics, which suppresses whitening that occurs when the film is bent during processing, etc., which is difficult to achieve with conventional techniques.

  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.

It is sectional drawing (the 1) of the superposition part vicinity in the suitable embodiment of the film of this invention. It is sectional drawing (the 2) of the overlapping part vicinity in the preferred embodiment of the film of this invention. It is explanatory drawing explaining the state which formed the overlap part in the suitable embodiment of the film of this invention.

  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 obtained by stretching a laminated film consisting of at least three layers having a (B) layer between the following (A) layer and (C) layer in at least one direction. The heat shrinkable laminated film is characterized in that the heat shrinkage rate in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is 20% or more.
(A) layer: a resin composition containing a polyester resin as a main component (B) layer: a polyester containing a polyester resin and a polystyrene resin, and the content of the polyester resin contained in the (A) layer Resin composition (C) layer with less content of polyester resin: containing polyester resin and polystyrene resin, the polyester resin content being less than the polyester resin content of layer (B) Resin composition
The (B) layer, the (C) layer, or the (B) layer and the (C) layer further contain a compatibilizing agent that promotes compatibilization of the polyester resin and the polystyrene resin, The compatibilizing agent is at least one of the following (a) to (e).
(A) Oxazoline group-containing styrene copolymer
(B) Styrene-maleic anhydride copolymer
(C) Polyester elastomer or modified polyester elastomer
(D) Polystyrene elastomer or modified polystyrene elastomer
(E) A resin composition in which a trunk component and a branch component are different, and the trunk component or the branch component of the graft copolymer is a polyester resin or a polystyrene resin.

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

(Polyester resin)
The polyester resin constituting the layer (A) of the film of the present invention can suppress spontaneous 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 It includes residues derived from these ester derivatives. These dicarboxylic acid residues may contain one kind alone or two or more kinds. As the polyester resin, a polyester resin containing terephthalic acid and ethylene glycol 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 making the dicarboxylic acid residue and the diol residue into such a mixture system, the crystallinity of the obtained polyester resin can be lowered. Therefore, when it is used as the (A) layer, it will be described later (B). Even when it is used for the layer (C), it is preferable because the progress of crystallization can be suppressed.

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

  The preferred dicarboxylic acid residue mixture is, for example, selected from the group consisting of terephthalic acid residue as the first residue and isophthalic acid, 1,4-cyclohexanedicarboxylic acid, succinic acid and adipic acid as the second residue. Examples thereof include 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-based resins include “PETGcopyester6763” (manufactured by Eastman Chemical), “Embrace LV” (manufactured by Eastman Chemical), “PETGSKYGREENS2008” (manufactured by SK Chemical).

  The polyester resin contained in the (A) layer is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more based on the total amount of the resin constituting the (A) layer. You may contain other resin other than a polyester-type resin. Examples of such resins include polyolefin resins, polystyrene resins, polycarbonate resins, and acrylic resins, among which polystyrene resins are preferable.

  As the polyester resin used in the layer (A) of the film of the present invention, in addition to the polyester resin derived from the dicarboxylic acid residue and the diol residue, carboxylic acid residues and alcohol residues are 1 A polyester resin obtained by polymerizing a monomer having in the molecule 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 (A) layer of the film of the present invention is preferably the outermost layer from the viewpoint of maintaining the rigidity of the film, suppressing spontaneous shrinkage, and solvent resistance. (A) When the layer is the outermost layer, when printed using a normal organic solvent-based gravure ink, the film curls, the amount of solvent remaining on the label increases, blocking occurs after printing, Organic solvent odor is less likely to occur and is preferable.

  When the (A) layer of the film of the present invention is the outermost layer, a technique of blending an incompatible resin with the layer constituting the outermost layer of the film or an antiblocking agent in order to prevent slipping or blocking of the film It is preferable to add what is called.

  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 same applies to the heat-shrinkable film when the layer (A) is the outermost layer. The addition amount of the anti-blocking agent is preferably 0.01% by mass or more and 2% by mass or less, based on the mass (100% by mass) of the entire resin composition constituting the layer (A). The mass% is more preferably 1.5% by mass or less, and further preferably 0.02% by mass or more and 1% by mass or less. When the addition amount of the anti-blocking agent is too small, it is difficult for the anti-blocking agent to be deposited on the film surface and it is difficult to form irregularities on the film surface, so that it is difficult to exhibit sufficient slipping and blocking resistance. On the other hand, when the amount is too large, excessive unevenness of the film surface is likely to occur, and the transparency of the film due to surface roughness is inhibited, and the roll of the film roll is apt to be wound due to excessive slipping.

  The shape of the antiblocking agent is not particularly limited, but (A) from the viewpoint of suppressing aggregation in the layer, uniform dispersion, suppressing irregular reflection of transmitted light, and unevenness formed on the film surface. A spherical one is preferably used. The particle size of the antiblocking agent is preferably from 0.5 μm to 10 μm, more preferably from 1 μm to 8 μm, and even more preferably from 1 μm to 6 μm. When the particle size of the anti-blocking agent is too small, it is difficult to deposit on the surface, and it is difficult to impart sufficient unevenness to express slipperiness and blocking resistance even in the beads deposited on the surface. On the other hand, when the particle size of the anti-blocking agent is too large, printing is performed on the film of the present invention to enhance the design, so that ink loss or the like is likely to occur and the appearance of the printed design is impaired, which is not preferable. 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>
In the present invention, the (B) layer is provided between the (A) layer described above and the (C) layer described later. Furthermore, the layer (B) includes a polyester resin and a polystyrene resin, and the content of the polyester resin is composed of a resin composition main component that is less than the content of the polyester resin included in the layer (A). Is done.

(Polyester resin)
The polyester resin suitably used in the (B) layer of the film of the present invention is the same as that in the above (A) layer. The polyester resin used in the (B) layer may be the same polyester resin as the polyester resin used in the (A) layer as long as it does not exceed the range specified by the present invention. A polyester resin different from the polyester resin used in the layer may be used. Furthermore, the polyester-based resin used in the (B) layer may be a polyester-based resin similar to the polyester-based resin used in the later-described (C) layer as long as it does not exceed the range defined by the present invention. A polyester resin different from the polyester resin used in the layer C) may be used.

(Polystyrene resin)
As the styrenic resin used in the (B) layer of the film of the present invention, block copolymerization of a styrenic hydrocarbon and a conjugated diene hydrocarbon is preferably used. Examples of the styrenic hydrocarbon include polystyrene, poly (p-, m- or o-methylstyrene), poly (2,4-, 2,5-, 3,4- or 3,5-dimethylstyrene), Polyalkylstyrenes such as poly (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 (o-, m-, or p-ethoxystyrene) and other polyalkoxystyrenes; poly (o-, m-, or p-carboxymethylstyrene), etc. Li carboxyalkyl styrene, poly (p- trimethylsilylstyrene) polyalkyl silyl styrene such as; poly (p- vinylbenzyl ether) and poly alkyl ether styrene more polyvinyl benzyl dimethoxyphosphinyl sulfide, and the like. The styrenic hydrocarbon block may contain a homopolymer, a copolymer and / or a copolymerizable monomer other than the styrenic hydrocarbon in the block.

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

  As one of the block copolymers of styrene hydrocarbon and conjugated diene hydrocarbon preferably used in the layer (B) of the present invention, the styrene hydrocarbon is styrene and the conjugated diene hydrocarbon is butadiene. There is a styrene-butadiene block copolymer (SBS). SBS preferably has a styrene / butadiene mass% ratio of 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) measured 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.

  In the present invention, a styrene-isoprene-butadiene block copolymer (SIBS) is also preferably used as the styrene hydrocarbon and conjugated diene hydrocarbon block copolymer. 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, when the butadiene content is low and the isoprene content is high, the cross-linking reaction of butadiene may be suppressed, and the gel-like product may be suppressed.

  The styrenic resin composition 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 20-80), more preferably about (70-30) / (30-70).

  Although the content rate of the said styrene resin composition contained in the (B) layer of the film of this invention is not specifically limited unless it exceeds the range which this invention prescribes | regulates, it comprises the (B) layer. The total amount of the resin composition is preferably 15% by mass or more, more preferably 20% by mass or more, and further preferably 25% by mass or more. However, when GPPS is contained, the TPS (peak temperature of loss elastic modulus E ″) of GPPS is as high as about 100 ° C., so the content of GPPS to be mixed is 20 of the total amount of resin constituting the (B) layer. It is desirable that the content is not more than mass%, preferably not more than 15 mass%, more preferably not more than 10 mass%.

When the styrene resin composition contained in the layer (B) of the film of the present invention is a block copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon, it is measured according to JIS K7142 of the block copolymer. The refractive index (n ₂ ) obtained is desirably within the range of ± 0.02, preferably ± 0.015 of the refractive index (n ₁ ) of the polyester resin composition contained in the layer (B). In other words, preferably it has a refractive index of the above-described polyester resin than _{(n 1),} a styrene-based hydrocarbon used - refractive index of the conjugated diene hydrocarbon block copolymer _(n 2) is 1.540 or more 1.600 or less Is more preferable, and it is 1.550 or more and 1.590 or less, More preferably, it is 1.555 or more and 1.585 or less. Thus, even when the film is kneaded and formed into a film 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, it is good. A film having excellent 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, by adjusting the composition ratio of the styrene hydrocarbon and the conjugated diene hydrocarbon corresponding to the refractive index (n ₁ ) of the polyester resin composition used in the layer (B), n ₁ ± 0.02 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 present invention, the storage elastic modulus (E ′) at 0 ° C. of the styrenic resin composition contained in the layer (B) is preferably 1.00 × 10 ⁷ Pa or more, and 1.50 × 10 ⁷ Pa. More preferably, it is the above. The storage elastic modulus (E ′) at 0 ° C. represents the rigidity of the film, that is, the strength of the film when the styrenic resin composition is formed into a film having a predetermined thickness. When the film of the present invention is formed by having a storage elastic modulus (E ′) of 1.00 × 10 ⁷ Pa or more, the adhesiveness to the above-described (A) layer or (C) layer described later is imparted. In addition, delamination between the (A) layer and the (C) layer can be suppressed when shrinking in a high temperature atmosphere. More importantly, whitening that occurs when the film is bent during processing, that is, so-called folding whitening, can be suppressed, which is preferable. This storage elastic modulus (E ′) is a block copolymer of the above-mentioned styrenic hydrocarbon and conjugated diene hydrocarbon, a mixture of two or more of these copolymers, or a range that does not impair transparency. It can be obtained by mixing with other resins.

When using a mixed system of a block copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon or a mixed system of the copolymer and another resin as the polystyrene resin used for the layer (B), Good results can be obtained by appropriately selecting a copolymer or resin that bears fracture resistance and a copolymer or resin that bears rigidity. 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 styrenic hydrocarbon-conjugated diene hydrocarbon block copolymers having fracture resistance and other types of resin compositions having high rigidity, their styrene hydrocarbon-conjugated diene carbonization The total composition of hydrogen, or a mixture of them with other types of resins, can be adjusted to meet the desired refractive index (n ₂ ) and storage modulus (E ′) at 0 ° C.

A block SBS and a random block SBS are preferable as the styrene-based hydrocarbon-conjugated diene-based hydrocarbon block copolymer capable of imparting adhesiveness to the layer (A) or the layer (C) described later. Among them, the storage elastic modulus (E ′) at 0 ° C. is 1.00 × 10 ⁷ Pa or more and 5.00 × 10 ⁹ Pa or less, and at least one of the peak temperatures of the loss elastic modulus (E ″) is 0 ° C. Those having the following viscoelastic properties are particularly preferable: If the storage elastic modulus at 0 ° C. is 1.0 × 10 ⁷ Pa or more, the laminate is formed into a film by increasing the blend amount of the resin responsible for rigidity. In some cases, it is possible to impart stiffness to the film. 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 the characteristics vary depending on the stretching conditions, if the peak temperature of the loss modulus (E ″) does not exist below 0 ° C. before stretching, the adhesion with the (A) layer or the (C) layer decreases. When a laminated film is formed into a film, it may be difficult to impart sufficient breakability to the film.

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.

The styrene hydrocarbon-conjugated diene hydrocarbon block copolymer having a controlled block structure has a storage elastic modulus (E ′) at 0 ° C. of 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 molecular weight of the styrenic resin composition contained in the (B) layer of the film of the present invention has a weight (mass) average molecular weight (Mw) of 100,000 or more, preferably 150,000 or more and 500,000 or less. , Preferably 400,000 or less, more preferably 300,000 or less. If the weight (mass) average molecular weight (Mw) of a styrene resin is 100,000 or more, it is preferable without a defect which causes deterioration of a film. Furthermore, it is preferable that the weight (mass) average molecular weight (Mw) of the styrene-based resin composition is 500,000 or less because there is no need to adjust the flow characteristics and there are no defects such as a decrease in extrudability.

  When a copolymer of a styrene hydrocarbon and an aliphatic unsaturated carboxylic acid ester is used as the styrenic resin composition, the aliphatic unsaturated carboxylic acid ester copolymerized with the styrene hydrocarbon is methyl (meth) acrylate. , Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate. 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 ″). One having a melt flow rate (MFR) measurement value (measurement conditions: temperature 200 ° C., load 49 N) of 2 g / 10 min or more and 15 g / 10 min or less is used. And acrylate and / or methacrylate.

  The resin composition contained in the layer (B) is not particularly limited as long as it does not exceed the range defined by the present invention, but other resin compositions can be mixed in addition to the polyester resin and polystyrene resin. . Examples of such a resin composition include a compatibilizer, a polyolefin resin composition, an acrylic resin composition, and a polycarbonate resin composition, which will be described later. Among these, it is preferable to contain a compatibilizer described later.

(Compatibilizer)
The (B) layer of the film of the present invention further contains a compatibilizer that promotes compatibilization of the polyester resin and the polystyrene resin, and the compatibilizer is at least one of the following (a) to (e): It is preferable that it is.
(A) oxazoline group-containing styrene copolymer (b) styrene-maleic anhydride copolymer (c) polyester elastomer or modified polyester elastomer (d) polystyrene elastomer or modified polystyrene elastomer (e) A resin composition comprising a graft copolymer having different branch components, wherein the trunk component or the branch component of the graft copolymer is a polyester resin or a polystyrene resin.

  The compatibilizing agent that can be contained in the layer (B) of the film of the present invention improves the dispersibility of the polyester-based resin and styrene-based resin, improves the transparency of the film, and achieves uniform thickness. It is preferable from the viewpoint of improving productivity, and further, the interlayer adhesive strength can be improved by using a compatibilizing agent.

  The compatibilizer contained in the layer (B) has a polar group having a high affinity with the polyester resin contained in the layer (B) or a polar group capable of reacting with the polyester resin, and the layer (B) It is a styrene block copolymer or graft copolymer that is compatible with the contained polystyrene resin or has a high affinity site. Specific examples of the polar group having high affinity with the polyester resin or the functional group capable of reacting include, for example, an acid anhydride group, a carboxylic acid group, a carboxylic acid ester group, a carboxylic acid chloride group, a carboxylic acid amide group, Examples include carboxylic acid groups, sulfonic acid groups, sulfonic acid ester groups, sulfonic acid chloride groups, sulfonic acid amide groups, sulfonic acid groups, epoxy groups, amino groups, imide groups, or oxazoline groups. An anhydride group, a carboxylic acid group or a carboxylic acid ester group, and an oxazoline group are preferred.

  Moreover, having a site | part compatible with a styrene resin means having a chain | strand which has affinity with a styrene resin, for example. Specifically, a random copolymer having a styrene chain, a styrene copolymer segment or the like as a main chain, a block chain or a graft chain, or having a styrene monomer unit may be used.

In view of the above, the compatibilizer is preferably at least one of the following (a) to (e).
(A) oxazoline group-containing styrene copolymer (b) styrene-maleic anhydride copolymer (c) polyester elastomer or modified polyester elastomer (d) polystyrene elastomer or modified polystyrene elastomer (e) A resin composition comprising a graft copolymer having different branch components, wherein the trunk component or the branch component of the graft copolymer is a polyester resin or a polystyrene resin.

  Examples of the oxazoline group-containing styrenic copolymer include Epocros (manufactured by Nippon Shokubai Co., Ltd.).

  Examples of the styrene-maleic anhydride copolymer include Dylark series (manufactured by NOVACchemicals), Xiran series (manufactured by Polyscope), and the like.

  Examples of polyester elastomers or modified polyester elastomers include Primalloy (Mitsubishi Chemical), Perprene (Toyobo), Hytrel (Toray DuPont), Byron (Toyobo), Polyester (Nippon Synthetic Chemical Industry) Etc.).

  Examples of the polystyrene-based elastomer or the modified polystyrene-based elastomer include Dynalon (manufactured by JSR), Tuftec (manufactured by Asahi Kasei Chemicals), Hibler, and Septon (manufactured by Kuraray).

  As the resin composition in which the trunk component and the branch component are different and the trunk component or the branch component of the graft copolymer is a polyester resin or a polystyrene resin, Modiper (manufactured by NOF Corporation) ), Reseda (manufactured by Toagosei Co., Ltd.), VMX (manufactured by Mitsubishi Chemical Corporation), and the like.

  The content of the compatibilizer in the layer (B) is not particularly limited as long as it does not exceed the range defined by the present invention, but is 1 for 100% by mass of the resin composition constituting the layer (B). It is at least mass%, preferably at least 3 mass%, more preferably at least 5 mass%, at most 40 mass%, preferably at most 35 mass%, more preferably at most 30 mass%. If the compatibilizing agent is in the above range, it can be expected that the thickness is expected to be uniform and the interlayer adhesion strength is improved, and a significant deterioration in transparency can be prevented.

<(C) layer>
In the present invention, the (C) layer contains a polyester resin and a polystyrene resin, and the content of the polyester resin is less than the content of the polyester resin contained in the layer (B). Consists of

(Polyester resin)
The polyester resin suitably used in the (C) layer of the film of the present invention is the same as that in the above (A) layer. Further, the polyester resin used in the (C) layer may be the same polyester resin as the polyester resin used in the (A) layer, as long as it does not exceed the range specified by the present invention. A polyester resin different from the polyester resin used in the layer may be used. Furthermore, the polyester resin used in the (C) layer may be a polyester resin similar to the polyester resin used in the (B) layer, as long as it does not exceed the range specified by the present invention. A polyester resin different from the polyester resin used in the layer may be used. In addition, the polyester resin used in the (C) layer may be a polyester resin contained in a recycled material generated by trimming loss or the like.

(Polystyrene resin)
As the styrene resin used in the (C) layer of the film of the present invention, block copolymerization of a styrene hydrocarbon and a conjugated diene hydrocarbon is preferably used. Examples of styrenic hydrocarbons 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), polyhalogenated styrenes such as poly (o-methyl-p-fluorostyrene); polyhalogenated substituted alkylstyrenes 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-carboxymethylstyrene) Examples include recarboxyalkyl 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 homopolymer, a copolymer and / or a copolymerizable monomer other than the styrenic hydrocarbon in the block.

  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 homopolymers, copolymers and / or conjugated diene hydrocarbons in the block.

  (C) As one of the block copolymers of styrene hydrocarbon and conjugated diene hydrocarbon preferably used in the layer, styrene hydrocarbon is styrene and conjugated diene hydrocarbon is butadiene. -Butadiene type block copolymer (SBS) is 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 hydrocarbon and conjugated diene hydrocarbon block copolymer preferably used in 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 styrenic 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).

  The content of the styrenic resin contained in the (C) layer is not particularly limited as long as it does not exceed the range defined by the present invention, but is 50% by mass of the total amount of the resin composition constituting the (C) layer. Preferably, it is 55% by mass or more, and more preferably 60% by mass or more. However, when GPPS is contained, TPS (peak temperature of loss elastic modulus E ″) of GPPS is as high as about 100 ° C., so the content of GPPS to be mixed is 20 of the total amount of resin constituting the (C) layer. It is desirable that the content is not more than mass%, preferably not more than 15 mass%, more preferably not more than 10 mass%.

The block copolymer of the styrene hydrocarbon and the conjugated diene hydrocarbon is measured according to JIS K7142 by appropriately adjusting the composition ratio of the styrene hydrocarbon and the conjugated diene hydrocarbon. The rate (n ₂ ) can be adjusted to a substantially desired value. Therefore, by adjusting the composition ratio of the styrene hydrocarbon and the conjugated diene hydrocarbon used in the (C) layer in accordance with the refractive index (n ₁ ) of the polyester resin used in the (C) layer, n A refractive index (n ₂ ) in the range of ₁ ± 0.02 is obtained. In other words, preferably it has a refractive index of the above-described polyester resin than _{(n 1),} a styrene-based hydrocarbon used - refractive index of the conjugated diene hydrocarbon block copolymer _(n 2) is 1.540 or more 1.600 or less Is more preferable, and it is 1.550 or more and 1.590 or less, More preferably, it is 1.555 or more and 1.585 or less. 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 present invention, the vibration frequency of the styrene resin contained in the layer (C) is 10 Hz, the strain is 0.1%, and the storage elastic modulus (E ′) at 0 ° C. is preferably 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 a block copolymer of the above-mentioned styrenic hydrocarbon and conjugated diene hydrocarbon, a mixture of two or more of these copolymers, or a range that does not impair transparency. It can be obtained by mixing with other resins.

(C) 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 layer, the fracture resistance is assumed. Good results can be obtained by appropriately selecting a copolymer or resin and a copolymer or resin that imparts rigidity. 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 at 0 ° C. is 1.0 × 10 ⁸ Pa or more, the strength of the waist is imparted by increasing the blend amount of the resin responsible for rigidity. 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 (C) 20% by mass or more and 80% by mass or less of the total resin constituting the layer. In addition, it is desirable to adjust 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-based resin contained in the (C) layer has a weight (mass) average molecular weight (Mw) of 100,000 or more, preferably 150,000 or more, and 500,000 or less, preferably 400,000 or less. Further, it is desirable that 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.

  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.

  The content of the copolymer of styrene-based hydrocarbon and aliphatic unsaturated carboxylic acid ester in the (C) layer is not particularly limited as long as it does not exceed the range defined by the present invention. It adjusts in 20 to 70 mass% of range with respect to the resin composition total amount which comprises a layer. If mixed at 70% by mass or less, the rigidity of the film can be greatly improved and good fracture resistance can be maintained. Moreover, if it mixes by 20 mass% or more, sufficient rigidity can be provided to a film.

  The layer (C) is not particularly limited as long as it does not exceed the range defined by the present invention, but other resins may be mixed in addition to the polyester resin and the polystyrene resin. Examples of such resins include compatibilizers described later, polyolefin resins, acrylic resins, polycarbonate resins, and the like. Among them, it is preferable to include a compatibilizer described later.

(Compatibilizer)
The (C) layer of the film of the present invention further contains a compatibilizer that promotes compatibilization of the polyester resin and the polystyrene resin, and the compatibilizer is at least one of the following (a) to (e): It is preferable that the compatibilizing agent used in the (C) layer is the same as that in the (B) layer.
(A) oxazoline group-containing styrene copolymer (b) styrene-maleic anhydride copolymer (c) polyester elastomer or modified polyester elastomer (d) polystyrene elastomer or modified polystyrene elastomer (e) A resin composition comprising a graft copolymer having different branch components, wherein the trunk component or the branch component of the graft copolymer is a polyester resin or a polystyrene resin.

  The content of the compatibilizing agent in the (C) layer is not particularly limited as long as it does not exceed the range specified by the present invention, but is 1 for 100% by mass of the resin composition constituting the (C) layer. It is at least mass%, preferably at least 3 mass%, more preferably at least 5 mass%, at most 40 mass%, preferably at most 35 mass%, more preferably at most 30 mass%. If the compatibilizing agent is in the above range, it can be expected that the thickness is expected to be uniform and the interlayer adhesion strength is improved, and a significant deterioration in transparency can be prevented.

(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. The tackifier resin 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, based on the total amount of resin constituting each layer. More preferably, it can be contained in the range of 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 stabilizer, a colorant, an antistatic agent, Lubricants, inorganic fillers, and the like can be appropriately added depending on each application.

<Layer structure of film>
The film structure of the present invention is not particularly limited as long as the film has a laminated structure composed of at least three layers having a (B) layer between the (A) layer and the (C) layer.

    In the present invention, the preferred laminated structure is a three-kind five-layer structure of (A) / (B) / (C) / (B) / (A), with the (A) layer being the outermost layer. By adopting this layer structure, the heat shrinkable laminated film suitable for uses such as shrink wrapping, shrink tying wrapping and shrink wrap labels, which has achieved the good shrinkage characteristics of the film and the suppression of delamination as the object of the present invention. Can be obtained with good productivity and economy.

  Next, a film of 3 types and 5 layers of (A) / (B) / (C) / (B) / (A), which is one of the preferred embodiments of the present invention, will be described.

  In the film of the present invention, the thickness ratio of the (A) layer to the (C) layer is such that when the (A) layer is 1, the (C) layer is 2 or more, preferably 3 or more, more preferably 4 or more. And 12 or less, preferably 10 or less, more preferably 8 or less. The thickness of the (B) layer is 10% or more of the total thickness of the (A) layer, preferably 15% or more, 150% or less, preferably 100% or less, more preferably 80% or less. Thickness is desirable. When the thickness of the (B) layer is 10% or more of the total thickness of the (A) layer, a good adhesive effect is obtained, and 150% or less, that is, 1 of the total thickness of the (A) layer. If the thickness is 5 times or less, the transparency is not significantly reduced.

  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 of 20% or more in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds. Preferably it is 25% or more, more preferably 30% or more, and 70% or less, preferably 65% or less, more preferably 60% or less. Moreover, it is preferable that the thermal shrinkage rate when immersed in warm water at 50 ° C. for 10 seconds is 5% or less, preferably 3% or less, more preferably 1% or less in at least one direction. The film of the present invention has a thermal shrinkage rate of 10% or more and less than 30%, preferably 10% or more and 25% or less, more preferably 10% or more in at least one direction when immersed in warm water at 70 ° C. for 10 seconds. A range of 20% or less is preferred.

  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. Here, the “main contraction direction” means a direction in which the stretching direction is larger between the longitudinal direction and the lateral direction, and is, for example, a direction corresponding to the outer peripheral direction when being attached to a bottle.

  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 addition, when the thermal shrinkage rate in the main shrinkage direction near 70 ° C. is less than 10%, the heat shrinkage force is small. For example, when the laminated film is used as the container label, the container cannot be temporarily fixed. When the temperature is high, the film may be displaced in the direction of the top surface. On the other hand, if the thermal contraction rate in the main contraction direction is higher than 30% at around 70 ° C., the thermal contraction may occur suddenly in a low temperature region, so that the thermal contraction may not be performed at a predetermined position. On the other hand, if the heat shrinkage rate in the main shrinkage direction near 80 ° C. is less than 30%, the heat shrinkage rate in the main shrinkage direction near 80 ° C. It is 30% or more, preferably 40% or more, more preferably 50% or more.

  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.

  When the film of the present invention is used as a PET container label, the thermal contraction rate in the orthogonal direction when immersed in warm water at 80 ° C. for 10 seconds is preferably 20% or less, more preferably 10% or less. 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.

<Transparency>
The transparency of the heat-shrinkable laminated film of the present invention is evaluated by a haze value measured according to JIS K7105. The haze value is preferably 10% or less, more preferably 8% or less. % Or less is more preferable. If the haze value is 10% or less, good transparency can be obtained, and beautiful printing or the like becomes possible.

<Delamination strength>
The heat-shrinkable laminated film of the present invention is formed into a heat-shrinkable film by stretching in at least one direction, and a test piece having a size of 150 mm in the main shrinkage direction and 15 mm in the direction perpendicular to the main shrinkage direction from the heat-shrinkable film. After the sample is collected, the layer (A) is partially peeled from the end surface in the main contraction direction of the test piece, and the peeled portion of the layer (A) and the peeled portion including the layer (C) are subjected to a tensile test. The delamination strength is 1N / 15 mm width or more, preferably 1.5 N / 15 mm width or more, when the 180 degree peel test is performed at a test speed of 100 mm / min with respect to the main shrinkage direction. Preferably it is 2N / 15mm width 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.

<Difference width in the overlapped part>
Next, the shift width of the overlapping portion in the film of the present invention will be described with reference to the drawings. 1 to 3, reference numeral 100 denotes a laminated film piece of the present invention, reference numeral 2 denotes an (A) layer, reference numeral 4 denotes a (B) layer, reference numeral 6 denotes a (C) layer, reference numeral 8 denotes an overlapping portion, reference numeral 8w Is the overlapping width, reference numeral 10 is the end face of the layer 2, reference numeral 12 is the end face of the layer 4, reference numeral 14 is the end face of the layer 6, reference numeral 16 is the seal portion, reference numeral 18 is the displacement, reference numeral 18 w Is a deviation width, symbol A is one end side, and symbol B is the other end side.

  1 and 2 are drawings showing a preferred embodiment of the present invention. FIGS. 1 and 2 show the vicinity of an overlapping portion 8 of a film in which (A) layer 2, (B) layer 4, (C) layer 6, (B) layer 4, and (A) layer 2 are laminated in this order. It is sectional drawing. Moreover, (a) is drawing which shows the state before heat processing among each drawing, (b) is between the end surface 10 of the (A) layer 2 of a film, and the end surface of the layer 4 in a superposition part after heat processing. Or (A) shows a state in which a deviation occurs between the end face 10 of the layer 2 and the end face 12 of the (B) layer 4 and the end face 14 of the (C) layer 6. FIG. 3A shows a film piece 100 obtained by cutting the film of the present invention into a rectangle having a size of 110 mm in the take-up direction (MD) and a right angle direction (TD) of 235 mm, and FIG. Is a laminate in which the surface layer or back layer surface on one end side A in the take-up direction (MD) and the back layer surface or surface layer on the other end side B in the take-off direction (MD) are sealed in parallel to the take-up direction (MD). It is drawing explaining the state which formed the overlapping part 8 of width 2-7mm on the film.

  As shown in FIG. 3, a rectangular film piece 100 is obtained by cutting out from the film roll of the present invention to a size of 110 mm in the take-up direction (MD) and 235 mm in the perpendicular direction (TD). Then, the surface of the surface layer or the back layer 2 on one end side A of the MD of the film piece 100 and the surface of the back layer or the surface layer 2 on the other end side B are sealed so as to be parallel to the MD, and 2 to 2 on the film. A cylindrical film having a 7 mm wide overlapping portion 8 is prepared. Subsequently, this cylindrical film is heat-treated at 99 ° C. In the present invention, “heat-treating at 99 ° C.” means a state in which a film is put on a 350 ml capacity square bottle and immersed in 99 ° C. warm water for 10 seconds.

  When the film of the present invention is returned to room temperature after the heat treatment at 99 ° C., the film of the present invention is between the MD end surface 10 of the surface layer or the back layer 2 and the MD end surface 12 of the adhesive layer 4 sealed by the overlapping portion 8, Alternatively, the deviation width 18w of the deviation 18 between the MD end face of the surface layer or the back layer 2 and the MD end faces 10, 12 of the adhesive layer 4 and the MD end face 14 of the intermediate layer 6 is the overlap width 8w of the overlap portion 8. Is within 5%.

  FIG. 1 shows a first embodiment of film misalignment 18 of the present invention. FIG. 1 shows a case where a tubular film (FIG. 1 (a)) sealed with the overlapping portion 8 of the film 100 of the present invention is sealed at the overlapping portion 8 when it is returned to room temperature after heat treatment at 99 ° C. Between the end surface 10 in the take-off direction (MD) of the surface layer or the back layer 2 and the end surface 12 of the adhesive layer 4 (or the intermediate layer 6, the adhesive layer 4, and the MD end surfaces 14, 12, 10 of the surface layer 6). The state (FIG.1 (b)) in which the gap | deviation 18 has arisen is shown.

  Moreover, FIG. 2 shows the 2nd aspect of the shift | offset | difference 19 of the film of this invention. FIG. 2 shows that the cylindrical film (FIG. 2A) sealed with the overlapping portion 8 of the film 100 of the present invention is sealed at the overlapping portion 8 when it is returned to room temperature after heat treatment at 99 ° C. End surface 10, 12 in the take-up direction (MD) between the surface layer or back layer 2 and the adhesive layer 4 and the end surface 14 in the take-up direction (MD) of the intermediate layer 6 (or the MD of the adhesive layer 4 and the back layer or the surface layer 2) The state (FIG.2 (b)) in which the shift | offset | difference 18 produced between the end surfaces 12 and 10) is shown. In these cases, the deviation width 18 is within 5% with respect to the overlapping width 8 w of the overlapping portion 8.

  When a laminated film having front and back layers made of a conventional polyester-based resin is subjected to heat treatment, a phenomenon of peeling between the front and back layers and the adhesive layer or between the front and back layers and the adhesive layer and the intermediate layer is observed. There was a problem that a good appearance could not be obtained. On the other hand, in the film of the present invention, peeling occurs between the (A) layer and the (B) layer or between the (A) layer and the (B) layer and the (C) layer even when heat treatment is performed. It is difficult to obtain an excellent appearance.

  In the film of the present invention, the ease of peeling can be expressed by a gap generated between the (A) layer and the (B) layer or the (B) layer and the (C) layer after sealing. That is, in the film of the present invention, when the film is heat-treated at 99 ° C. and then returned to room temperature, the back layer or the back surface of the back surface sealed in the overlapped portion or the back surface (MD) end surface and the adhesive layer take-off direction The deviation width between the end face of (MD) or the deviation width between the end face of the back layer or the surface layer and the adhesive layer in the take-up direction (MD) and the end face of the intermediate layer in the take-up direction (MD) is the overlap. It is within 5%, preferably within 3%, more preferably within 2% with respect to the overlap width of the mating portion. If the deviation in the overlapped portion after the heat treatment is within 5%, there is no separation between the one outer layer and the adhesive layer or the adhesive layer and the inner layer even after the heat treatment, and an excellent appearance can be maintained.

  The overlapping portion seals the surface of the front and back layers on one end side in the take-up direction (MD) and the surface of the front and back layers on the other end side in the take-up direction (MD) so as to be parallel to the take-up direction (MD). It is a part formed by overlapping the laminated film with a width of 2 to 7 mm. Solvents used for sealing the surface layer or back layer on one end and the back layer or surface layer on the other end include pentane, n-hexane, diethyl ether, heptane, octane, cyclohexane, isopropyl acetate, and acetic acid-n-. Butyl, n-propyl acetate, carbon tetrachloride, xylene, ethyl acetate, toluene, benzene, methyl methyl ketone, methyl acetate, methylene chloride, tetrahydrofuran, dioxolane, acetone, isopropanol, ethanol, methanol, or at least two of these solvents The mixed solvent which consists of a seed | species solvent can be mentioned. Further, the seal width is at least 2 mm width or more, preferably 3 mm width or more, 7 mm width or less, preferably 5 mm or less.

<Bending whitening>
The heat-shrinkable laminated film of the present invention is formed into a heat-shrinkable film by stretching in at least one direction, and a test piece having a size of 100 mm in the main shrinkage direction and 200 mm in the direction orthogonal to the main shrinkage direction from the heat-shrinkable film. After being bent into a line object with the direction orthogonal to the main contraction direction as the axis, bent in a size of 50 mm in the main contraction direction and 200 mm in the direction orthogonal to the main contraction direction, and then opened the bent portion again. When the size of the main contraction direction is 100 mm and the direction is 200 mm perpendicular to the main contraction direction, the bent portion is less likely to be whitened. This is an effect that can be achieved by adjusting the heat-shrinkable laminated film of the present invention within the range specified by the present invention.

(Method for producing heat-shrinkable film)
The film of the present invention comprises an intermediate layer containing a polystyrene resin as a main component, a front and back layer containing a polyester resin as a main component disposed on both sides of the intermediate layer, and a front and back layer and an intermediate layer. An adhesive layer formed therebetween is laminated simultaneously or sequentially to produce a laminated film, and then the laminated film is heated and obtained by stretching in at least one axial direction.

  The laminated film can be produced simultaneously with an intermediate layer, front and back layers and an adhesive 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 forming 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, soft drink or food PET bottles, glass bottles, preferably PET bottles), for example, complicated shapes (centered cylinder, rounded four 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 shrinkage direction of the piece, the peeled part of the (A) layer and the peeled part including the (C) layer are sandwiched between chucks of a tensile tester, A 180 degree peel test was conducted at a test speed of 100 mm / min in the shrink 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 2N / 15mm width or more ○: Delamination strength is 1N / 15mm width or more and less than 2N / 15mm width ×: Delamination strength is less than 1N / 15mm width

(3) Transparency Based on JIS K7105, the haze value of a film having a thickness of 40 μm was measured to evaluate transparency.
◎: Haze value is less than 5% ○: Haze value is 5% or more and less than 8% △: Haze value is 8% or more and less than 10% ×: Haze value is 10% or more

(4) Delamination evaluation during high temperature treatment The obtained film was slit to 235 mm width on TD, and both ends of TD were overlapped by 10 mm with a bag making machine, and the film end face was 75/25 in tetrahydrofuran / cyclohexane volume fraction. Sealed at a width of 5 mm with the solvent mixed in the above to produce a cylindrical film. The cylindrical film was cut into 110 mm in MD (direction perpendicular to the TD direction), mounted on a square-shaped PET bottle having a capacity of 350 mL, immersed in 99 ° C. warm water for 10 seconds, and then returned to room temperature. After film coating, the following criteria were used for evaluation.
(Double-circle): The shift | offset | difference width in the end surface of a mounting label is 0% or more and less than 2% with respect to the overlap width of the overlapping part of a film.
○: The deviation width at the end face of the mounting label is 2% or more and 5% or less with respect to the overlapping width of the overlapping portion of the film.
X: The deviation width at the end face of the mounting label is larger than 5% with respect to the overlapping width of the overlapping portion of the film, and the outer layer and the inner layer of the mounting label are separated.

(5) Bending whitening evaluation After the film of the present invention was formed into a heat-shrinkable film, a test piece was collected from the obtained film in a main shrinkage direction of 100 mm and a direction of 200 mm perpendicular to the main shrinkage direction, and then the main shrinkage. Folded into a line object with the direction orthogonal to the direction as the axis, bent in a size of 50 mm in the main shrinkage direction and 200 mm in the direction perpendicular to the main shrinkage direction, and then opened the bent portion again, the original main shrinkage direction 100 mm, When the size of 200 mm in the direction orthogonal to the main contraction direction was returned, it was confirmed whether the bent portion was whitened and evaluated according to the following criteria.
◯: Traces of folding at the folded part of the film remain but do not whiten.
X: A clear whitened line remains in the folded portion of the film.

Moreover, the raw material used by each Example and the comparative example is as follows.
(Polyester resin)
Copolyester, trade name: SKYGREEN PETG S2008 (manufactured by SK Chemicals), hereinafter abbreviated as “Pes (1)”.
-Copolyester, trade name: EmbreceLV (manufactured by Eastman Chemical Co., Ltd.), hereinafter abbreviated as “Pes (2)”.
(Polystyrene resin)
Styrene / butadiene = 90/10 (mass%), storage elastic modulus E ′ (0 ° C.): 3.15 × 10 ⁹ Pa, loss elastic modulus E ″ styrene-butadiene copolymer having a peak temperature of 55 ° C. It is called “PS (1)”.
-Styrene-butadiene copolymer, trade name: DK-11 (manufactured by Chevron Phillips), hereinafter referred to as "PS (2)".
-Styrene-butadiene copolymer, trade name: Asaflex 830 (manufactured by Asahi Kasei Chemicals), hereinafter referred to as "PS (3)".
(Compatibilizer)
Oxazoline group-containing styrene copolymer, trade name: Epocross RPS-1005 (manufactured by Nippon Shokubai Co., Ltd.), hereinafter referred to as “comp (1)”.
Styrene-maleic anhydride copolymer, trade name: Dylark 232 (manufactured by Nova Chemicals), hereinafter referred to as “comp (2)”.
Polyester elastomer, trade name: Primalloy A1700 (manufactured by Mitsubishi Chemical Corporation), hereinafter referred to as “comp (3)”.
Modified styrenic elastomer, trade name: Dynalon 8630P (manufactured by JSR), hereinafter referred to as “comp (4)”.
(Ethylene-glycidyl methacrylate) -polystyrene graft copolymer, trade name: Modiper A4100 (manufactured by NOF Corporation), hereinafter referred to as “comp (5)”.

  In forming the laminated film, the resin compositions used for the (B) layer and the (C) layer were previously prepared in the examples shown in Table 1, the (B) layer composition of the comparative example, and the (C) layer composition. The resin composition was mixed and charged into a twin screw extruder (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 in a water bath. Then, a pellet was obtained by cutting with a strand cutter. The pellet obtained by the said method was used for the resin composition used for the Example shown below and the (B) layer of a comparative example, and the (C) layer.

( Reference Example 1)
Lamination of (A) layer / (B) layer / (C) layer / (B) layer / (A) layer using three single-screw extruders (Mitsubishi Heavy Industries, Ltd.) and 3 types 5 layers multi-manifold die In equipment capable of coextrusion, the polyester resin “Pes (1)” is introduced into the single screw extruder for forming the (A) layer, and pelletized in advance to the single screw extruder for forming the (B) layer. The mixed resin composition (Pes (1) 60% by mass, PS (2) 40% by mass) was introduced into a single screw extruder for forming the (C) layer, and the pelletized mixed resin composition (Pes ( 1) 5 mass%, PS (1) 38 mass%, PS (2) 57 mass%), and after melt mixing at each extruder set temperature 210 ° C., the thickness of each layer is (A) layer / (B ) Layer / (C) layer / (B) layer / (A) layer = 25 μm / 5 μm / 140 μm / 5 μm / 25 μm The sheet was taken up 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 was stretched 5.0 times in the transverse uniaxial direction at a preheating temperature of 93 ° C. and a stretching temperature of 90 ° C., and then heat treated at 63 ° C. to obtain a 40 μm thick heat-shrinkable film. Obtained. The evaluation results of the obtained film are shown in Table 1.

(Example 1 )
As shown in Table 1, the mixed resin composition pelletized beforehand with Pes (2) 55 mass% and PS (3) 45 mass% was used for the (B) layer, and Pes (2) 5 mass%, PS ( 1) By the same method as in Reference Example 1 except that the mixed resin composition pre-pelletized at 35% by mass, PS (2) 55% by mass, and comp (1) 5% by mass was used for the (C) layer. A heat-shrinkable film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Example 2 )
As shown in Table 1, a mixed resin composition pelletized beforehand with 55% by mass of Pes (2), 40% by mass of PS (3), and 5% by mass of comp (1) was used for the layer (B). 2) Except that the mixed resin composition pelletized in advance at 5% by mass, PS (1) 35% by mass, PS (2) 55% by mass, comp (1) 5% by mass was used for the (C) layer. A heat-shrinkable film was obtained in the same manner as in Reference Example 1. The evaluation results of the obtained film are shown in Table 1.

(Example 3 )
As shown in Table 1, a mixed resin composition pelletized beforehand with 65% by mass of Pes (2), 30% by mass of PS (3) and 5% by mass of comp (2) was used for the (B) layer, and Pes ( 1) By the same method as in Reference Example 1 except that the mixed resin composition pelletized in advance at 25% by mass, PS (1) 30% by mass, and PS (2) 45% by mass was used for the (C) layer. A heat-shrinkable film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Example 4 )
As shown in Table 1, the mixed resin composition pelletized beforehand with 45% by mass of Pes (2), 35% by mass of PS (3) and 20% by mass of comp (3) was used for the (B) layer, and Pes ( 1) By the same method as in Reference Example 1 except that the mixed resin composition pelletized in advance at 10% by mass, PS (1) 35% by mass, and PS (2) 55% by mass was used for the (C) layer. A heat-shrinkable film was obtained. 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 55% by mass of Pes (2), 40% by mass of PS (1) and 5% by mass of comp (4) was used for the (B) layer, and Pes ( 2) Except that the mixed resin composition pelletized in advance at 5% by mass, PS (1) 35% by mass, PS (2) 55% by mass, comp (1) 5% by mass was used for the (C) layer. A heat-shrinkable film was obtained in the same manner as in Reference Example 1. 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 55% by mass of Pes (2), 40% by mass of PS (1) and 5% by mass of comp (5) was used for the (B) layer, and Pes ( 2) Except that the mixed resin composition pelletized in advance at 5% by mass, PS (1) 35% by mass, PS (2) 55% by mass, comp (1) 5% by mass was used for the (C) layer. A heat-shrinkable film was obtained in the same manner as in Reference Example 1. The evaluation results of the obtained film are shown in Table 1.

(Example 7 )
As shown in Table 1, a mixed resin composition pelletized beforehand with Pes (2) 55 mass%, PS (3) 35 mass%, comp (1) 10 mass% was used for the (B) layer, and Pes ( 1) By the same method as in Reference Example 1 except that the mixed resin composition pelletized in advance at 10% by mass, PS (1) 35% by mass, and PS (2) 55% by mass was used for the (C) layer. A heat-shrinkable film was obtained. 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 55% by mass of Pes (2), 40% by mass of PS (3), and 5% by mass of comp (1) was used for the layer (B). 1) By the same method as in Reference Example 1 except that the mixed resin composition pelletized beforehand at 15% by mass, PS (1) 35% by mass, and PS (2) 50% by mass was used for the (C) layer. A heat-shrinkable film was obtained. 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 55% by mass of Pes (2), 40% by mass of PS (3), and 5% by mass of comp (1) was used for the layer (B). 1) By the same method as in Reference Example 1 except that the mixed resin composition pelletized in advance at 35% by mass, PS (1) 25% by mass, and PS (2) 40% by mass was used for the (C) layer. A heat-shrinkable film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 1)
Lamination of (A) layer / (B) layer / (C) layer / (B) layer / (A) layer using three single-screw extruders (Mitsubishi Heavy Industries, Ltd.) and 3 types 5 layers multi-manifold die In equipment capable of coextrusion, the polyester resin “Pes (1)” is introduced into the single screw extruder for forming the layer (A), and the single screw extruder for forming the layer (B) is stopped. ) In the single-screw extruder forming the layer, the pre-pelleted mixed resin composition (Pes (2) 5 mass%, PS (1) 35 mass%, PS (2) 55 mass%, comp (1) 5 mass) %) And melt-mixed at each extruder set temperature 210 ° C., and then coextruded so that the thickness of each layer is (A) layer / (C) layer / (A) layer = 25 μm / 150 μm / 25 μm, 60 An unstretched laminated sheet having a width of 200 mm and a thickness of 200 μm is taken up by a cast roll at 0 ° C. It was. Next, the film was stretched 5.0 times in the transverse uniaxial direction at a preheating temperature of 93 ° C. and a stretching temperature of 90 ° C., and then heat treated at 63 ° C. to obtain a 40 μm thick heat-shrinkable film. Obtained. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 2)
As shown in Table 1, comp (3) was used for the (B) layer (in the resin composition used for the (B) layer of Comparative Example 2, it was commercially available without pre-pelletizing with a twin screw extruder. The mixed resin composition pelletized beforehand with 10% by mass of Pes (1), 35% by mass of PS (1) and 55% by mass of PS (2) is used for the (C) layer. A heat-shrinkable film was obtained in the same manner as in Reference Example 1 except that. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 3)
As shown in Table 1, a mixed resin composition pelletized beforehand with 15% by mass of Pes (1), 80% by mass of PS (3) and 5% by mass of comp (1) was used for the (B) layer, and Pes ( 1) By the same method as in Reference Example 1 except that the mixed resin composition pelletized in advance at 35% by mass, PS (1) 25% by mass, and PS (2) 40% by mass was used for the (C) layer. A heat-shrinkable film was obtained. The evaluation results of the obtained film are shown in Table 1.

From Table 1, the heat-shrinkable films (Examples 1 to 9 ) obtained from the laminates of the present invention have sufficient layers as compared with the two-type three-layer film (Comparative Example 1) that does not have the (B) layer. It turns out that it is a heat-shrinkable film which has peeling. When the content of the polyester resin contained in the (A) layer, (B) layer, and (C) layer deviates from the range defined by the present invention (Comparative Example 3), the (A) layer and (B) It became clear that the adhesive strength between the layers was extremely lowered and did not satisfy the required properties as a heat-shrinkable film.
Further, when comparing Examples 1 9, for example, when comparing Example 1 and Example 2, in the resin composition constituting the layer (B) was added compatibilizer defined by the present invention In this case, it has been found that the effect of improving the delamination strength can be imparted. Further, it was found that the use of the compatibilizing agent defined by the present invention can sufficiently achieve the function as a heat-shrinkable film without adversely affecting transparency and delamination in high-temperature treatment.
Furthermore, when a polyester elastomer is used for the layer (B) for the purpose of improving the delamination strength (Comparative Example 2), peeling is observed in the delamination evaluation in the high temperature treatment, and when the film is folded, bending whitening occurs. It was happening. On the other hand, with respect to Examples 1 9. Such bending whitening was not observed, it is understood that the film can achieve further improvement of the design.

  The film of the present invention has heat shrink characteristics and transparency, has excellent interlayer adhesion at room temperature, and does not easily peel off even when processed at high temperatures. Also, whitening that occurs when the film is folded during processing, etc. It can be suitably used for heat-shrinkable laminated films suitable for uses such as shrink wrapping, shrink-bound wrapping and shrink labels, which suppresses so-called folding whitening, and molded products using the films, particularly shrink labels. .

  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.

DESCRIPTION OF SYMBOLS 100 Film piece 2 Outer layer 4 Adhesive layer 6 Inner layer 8 Overlapping part 8w Overlapping width 10 End face of outer layer 12 End face of adhesive layer 14 End face of inner layer 16 Seal part 18 Deviation 18w Deviation width A One end side B Other end side

Claims (9)

A heat-shrinkable laminated film formed by stretching at least one laminated film comprising at least three layers having a (B) layer between the (A) layer and the (C) layer comprising the following resin composition. A heat shrinkable laminate film having a heat shrinkage ratio in the main shrinkage direction of 20% or more when immersed in warm water at 80 ° C. for 10 seconds.
(A) layer: a resin composition containing a polyester resin as a main component (B) layer: a polyester containing a polyester resin and a polystyrene resin, and the content of the polyester resin contained in the (A) layer Resin composition (C) layer with less content of polyester resin: containing polyester resin and polystyrene resin, the polyester resin content being less than the polyester resin content of layer (B) Resin composition
The (B) layer, the (C) layer, or the (B) layer and the (C) layer further contain a compatibilizing agent that promotes compatibilization of the polyester resin and the polystyrene resin, The compatibilizing agent is at least one of the following (a) to (e).
(A) Oxazoline group-containing styrene copolymer
(B) Styrene-maleic anhydride copolymer
(C) Polyester elastomer or modified polyester elastomer
(D) Polystyrene elastomer or modified polystyrene elastomer
(E) A resin composition in which a trunk component and a branch component are different, and the trunk component or the branch component of the graft copolymer is a polyester resin or a polystyrene resin. The heat-shrinkable laminated film according to claim 1, wherein the polystyrene-based resin contained in the layer (C) contains an aromatic vinyl hydrocarbon-conjugated diene copolymer. The polyester resin constituting 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. heat-shrinkable laminated film according to claim 1 or 2,. Wherein (A) layer is the outermost layer, (A) / (B) / (C) / (B) / any of claims 1 to 3, characterized in that it consists of three 5-layer structure of (A) The heat-shrinkable laminated film described in 1. After collecting a test piece from the heat-shrinkable film with a main shrinkage direction of 150 mm and a direction perpendicular to the main shrinkage direction of 15 mm, a part of the layer (A) is peeled off from the end surface of the test piece in the main shrinkage direction. When the peeling portion of the layer (A) and the portion to be peeled including the layer (C) are sandwiched by a chuck of a tensile tester and a 180 degree peeling test is performed at a test speed of 100 mm / min with respect to the main shrinkage direction. The heat-shrinkable laminated film according to any one of claims 1 to 4 , wherein the delamination strength 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. Molded article formed as the base material of the heat-shrinkable laminate film according to any one of claims 1 to 6. The heat-shrinkable label which uses the heat-shrinkable laminated film in any one of Claim 1 to 6 as a base material. The molded article according to claim 7, or a container fitted with a heat-shrinkable label according to claim 8.

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