JP5700920B2 - Heat-shrinkable laminated film, molded product using the film, heat-shrinkable label, and container - Google Patents

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 in which an intermediate layer made of polystyrene resin and front and back layers made of polyester resin are laminated through an adhesive layer made of a modified styrene 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. In addition, a laminated polystyrene resin foam having an adhesive layer composed mainly of a mixture of a polystyrene resin and a polyester polymer is interposed between a film-like aromatic polyester resin and a foam sheet made of a polystyrene resin. It is disclosed (see Patent Document 8). However, these foams are not suitable as heat-shrinkable films for which transparency is required, and although there are descriptions of effects related to adhesive properties, there is little description about bending whitening, and the concept described in the above patent document It is difficult to suppress bending whitening only by introducing it.

JP 61-015443 A JP 07-137212 A JP 2002-351332 A JP 2008-207487 A Japanese Patent No. 2006-015745 JP 2008-037093 A JP 2008-062640 A JP 2001-030439 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 inventor of the present invention has an adhesive composed mainly of a mixed resin composition of a polyester resin and a polystyrene resin between a front and back layer mainly composed of a polyester resin and an intermediate layer mainly composed of a polystyrene resin. As a result of earnestly examining the relationship with the voids generated inside the film after shrinkage in order to suppress the deterioration of the design property due to the folded whitening portion generated when the laminated film has a layer and the composition, It succeeded in obtaining the film which can solve the subject of a prior art, and came to complete this invention.

That is, an object of the present invention is to mainly use a mixed resin composition of a polyester resin and a polystyrene resin between a front and back layer mainly composed of a polyester resin and an intermediate layer mainly composed of a polystyrene resin. A heat-shrinkable film obtained by stretching a laminated film having at least three layers of an adhesive layer as a component in at least one direction, and having a heat shrinkage rate in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds. 20% or more, and the intermediate layer contains 3% by mass to 30% by mass of a polyester resin with respect to 100% by mass of the resin composition constituting the intermediate layer, and the adhesive layer constitutes an adhesive layer The polyester resin is contained in an amount of 40% by mass to 80% by mass with respect to 100% by mass of the mixed resin composition, and either one of the adhesive layer and the intermediate layer, or both But an oxazoline group-containing styrene copolymer as a compatibilizer to promote compatibilization of polyester resin and polystyrene resin relative to the intermediate layer or constituting the adhesive layer resin composition 100 wt%, 5 wt% above 20 wt% or less, contained in the al include the relative adhesive layer mixed resin composition 100% by mass constituting, in the polyester-based resin content of 80 wt% or less than 40 wt%, the main shrinkage direction After bending the heat-shrinkable film with the direction orthogonal to the axis as the axis, when shrinking 10% in the main shrinkage direction in hot water at 90 ° C., within 5 mm around the bent part as an axis, This is achieved by a heat-shrinkable laminated film (hereinafter referred to as “the film of the present invention”) characterized in that the size of voids generated in the adhesive layer is 10 μm or less.

  Moreover, it is preferable that the polystyrene resin contained in one or both of the adhesive layer and the intermediate layer is an aromatic vinyl hydrocarbon-conjugated diene copolymer.

  The polyester resin contained in one or both of the front and back layers and the adhesive layer includes a terephthalic acid residue as a dicarboxylic acid residue, and an ethylene glycol residue as a diol residue. And 1,4-cyclohexanedimethanol residue.

  Further, the film of the present invention was obtained by collecting a test piece with a main shrinkage direction of 150 mm and a direction of 15 mm perpendicular to the main shrinkage direction, and then partially peeling the front and back layers from the end surface of the test piece in the main shrinkage direction. Then, a peeled portion is formed on the front and back layer sides, the peeled portion and the peeled portion on the intermediate layer side are respectively sandwiched by a chuck of a tensile tester, and a 180 ° peel test is performed at a tensile speed of 100 mm / min in the main shrinkage direction. The delamination strength when performed is preferably 1 N / 15 mm width or more.

  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. It is explanatory drawing for demonstrating the state of the film cross section in suitable embodiment (Example 1) of the film of this invention. It is explanatory drawing for demonstrating the state of the cross section of the film (comparative example 2) produced in order to compare with 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 mainly composed of a mixed resin composition of a polyester resin and a polystyrene resin between a front and back layer mainly composed of a polyester resin and an intermediate layer mainly composed of a polystyrene resin. A heat-shrinkable film obtained by stretching a laminated film having at least three adhesive layers in at least one direction, and 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. It is a heat shrinkable laminated film.

<Front and back layers>
In the film of the present invention, the front and back layers are composed of a resin composition containing a polyester resin as a main component.

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

  In the present invention, it is more preferable that at least one of a dicarboxylic acid residue and a diol residue is a mixture composed of two or more types of residues. In the present specification, among the two or more types of residues, a main residue, that is, a residue having the largest mass (mol%) is defined as a first residue, and a smaller amount than the first residue is defined as a second residue. The following residues (namely, second residue, third residue,...) Are assumed. By 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 used as front and back layers, further, an adhesive layer and an intermediate layer described later are used. Even when it is used, it is preferable because the progress of crystallization can be suppressed.

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

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

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

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

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

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

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

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

  The front and back layers of the film of the present invention have a polyester-based resin contained in the front and back layers of 50% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more, based on the total amount of the resin constituting the front and back layers. Most preferably, other resins than the polyester-based resin may be contained as long as the content is 90% by mass or more. Examples of such resins include polyolefin resins, polystyrene resins, polycarbonate resins, and acrylic resins, among which polystyrene resins are preferable.

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

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

  For the front and back layers of the film of the present invention, it is preferable to add a technique of blending incompatible resins or what is called an antiblocking agent in order to impart slipperiness or prevent blocking of the film.

  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 addition amount of the anti-blocking agent is 0.01% by mass or more, preferably 0.015% by mass or more, more preferably 0.005% or more, based on the mass (100% by mass) of the entire resin composition constituting the front and back layers. It is desirable that the content be 02% by mass or more and 2% by mass or less, preferably 1.5% by mass or less, and more preferably 1% by mass or less. If the added amount of the anti-blocking agent is too small (less than 0.01% by mass), the anti-blocking agent is difficult to deposit on the film surface, and it is difficult to form irregularities on the film surface. Difficult to express. On the other hand, if the amount of antiblocking agent is too large (over 2% by mass), excessive unevenness of the film surface is likely to occur, hindering transparency due to surface roughness, winding of a film roll due to excessive slipping, etc. Is likely to occur.

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

<Intermediate layer>
The intermediate layer of the film of the present invention is composed of a resin composition containing a polystyrene resin as a main component.

(Polystyrene resin)
As the polystyrene resin used in the intermediate layer of the film of the present invention, block copolymerization of a styrene 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), poly Polyalkylstyrenes such as (pt-butylstyrene); poly (o-, m- or p-chlorostyrene), poly (o-, m- or p-bromostyrene), poly (o-, m- or p-fluorostyrene), poly (halogenated styrene) such as poly (o-methyl-p-fluorostyrene); polyhalogenated substituted alkylstyrene such as poly (o-, m- or p-chloromethylstyrene); poly (p -, M- or o-methoxystyrene), poly (alkoxystyrene) such as poly (o-, m- or p-ethoxystyrene); poly (o-, m-, or p-carboxymethyl) Polycarboxyalkyl styrene such as styrene); polyalkyl ether styrene such as poly (p-vinylbenzylpropyl ether); polyalkylsilyl styrene such as poly (p-trimethylsilyl styrene); and polyvinylbenzyl dimethoxy phosphide. . The styrenic hydrocarbon block may contain a copolymerizable monomer other than these homopolymers, copolymers and / or styrenic hydrocarbons.

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

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

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

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

  Although the content rate of the polystyrene-type resin contained in an intermediate | middle layer is not specifically limited unless the range prescribed | regulated by this invention is exceeded, 50 mass% with respect to 100 mass% of resin compositions which comprise an intermediate | middle layer. As mentioned above, Preferably it is 60 mass% or more, More preferably, it is 70 mass% or more. However, when GPPS, an oxazoline group-containing styrene copolymer, a styrene-maleic anhydride copolymer described later, or a mixture thereof is included, GPPS, an oxazoline group-containing styrene copolymer, or a styrene-maleic anhydride copolymer is used. Since the polymer Tg (peak temperature of loss modulus E ″) is as high as about 100 ° C. or higher, GPPS to be mixed, oxazoline group-containing styrene copolymer, styrene-maleic anhydride copolymer, or these The content of the mixture is desirably 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less with respect to 100% by mass of the resin composition constituting the intermediate layer.

When the polystyrene resin contained in the intermediate layer of the film of the present invention is a block copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon, the refractive index measured according to JIS K7142 of the block copolymer (N ₂ ) is 1.540 or more, preferably 1.550 or more, more preferably 1.555 or more, and 1.600 or less, preferably 1.590 or less, more preferably 1.585 or less. is there. In addition, in relation to the refractive index (n ₁ ) of the polyester resin constituting the front and back layers, the refractive index (n ₂ ) of the block copolymer is ± 0. 0 of the refractive index (n ₁ ) of the polyester resin. It is desirable to be within the range of 02, preferably within the range of ± 0.015. By adjusting the difference between the refractive index of the polystyrene resin (n ₂ ) and the refractive index of the polyester resin (n ₁ ) within a predetermined range, a film having good transparency can be obtained.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  The content of the copolymer of the styrenic hydrocarbon and the aliphatic unsaturated carboxylic acid ester in the intermediate layer is not particularly limited as long as it does not exceed the range defined by the present invention, but constitutes the intermediate layer. It is adjusted in the range of 20% by mass or more and 70% by mass or less with respect to 100% by mass of the resin composition. 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.

  In addition to the polyester resin and the polystyrene resin, other resins can be mixed in the intermediate layer as long as the characteristics of the film of the present invention are satisfied. Examples of such resins include polyester resins, compatibilizers, polyolefin resins, acrylic resins, polycarbonate resins, etc. Among them, it is preferable to contain polyester resins and compatibilizers described later.

(Polyester resin contained in the intermediate layer)
In the film of the present invention, the intermediate layer preferably further contains a polyester resin. The polyester resin is 30% by mass or less, preferably 25% by mass or less, and more preferably 20% by mass or less, with respect to 100% by mass of the resin composition constituting the intermediate layer. Although the lower limit of the content rate in the case of containing a polyester resin is not particularly limited, it is preferably 3% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more.

  The polyester resin suitably used in the intermediate layer of the film of the present invention is the same as that in the front and back layers described above. Further, the polyester resin used in the intermediate layer may be the same polyester resin as the polyester resin used in the front and back layers or a different polyester resin as long as it does not exceed the range defined in the present invention. Furthermore, the polyester-based resin used in the intermediate layer may be the same polyester-based resin as the polyester-based resin used in the adhesive layer described later or a different polyester-based resin as long as it does not exceed the range defined by the present invention. Further, the polyester resin used in the intermediate layer may be a polyester resin contained in a recycled material generated by trimming loss or the like.

(Compatibilizer contained in the intermediate layer)
The intermediate layer of the film of the present invention may further contain a compatibilizing agent that promotes compatibilization of the polyester resin and the polystyrene resin. The compatibilizing agent is preferably at least one of an oxazoline group-containing styrene copolymer and a styrene-maleic anhydride copolymer, and the same as the adhesive layer described later can be used.

  The content of the compatibilizer in the intermediate layer is not particularly limited as long as it does not exceed the range specified by the present invention, but it is 1% by mass or more with respect to 100% by mass of the resin composition constituting the intermediate layer. Preferably it is 3 mass% or more, More preferably, it is 5 mass% or more, 20 mass% or less, Preferably it is 15 mass% or less, More preferably, it is 10 mass% or less. If the compatibilizer contained in the intermediate layer is in the above range, it can be expected to make the expected thickness uniform and improve interlayer adhesion strength, and prevent significant deterioration in transparency and inhibition of film shrinkage behavior. Can do.

<Adhesive layer>
The film of this invention has the contact bonding layer which has the mixed resin composition of polyester resin and polystyrene resin as a main component between the front and back layers mentioned above and an intermediate | middle layer.

  Conventional adhesive layers for heat-shrinkable films have used polyester-based elastomer resins, polystyrene-based elastomer resins, or other adhesive resins. However, in these resins, when a film is mounted on 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. This is because the film is stretched together with the front and back layers and the intermediate layer at the time of film formation. However, after stretching, the orientation of the elastomer as described above is easy to relax, and in the heat shrinking process, the front and back layers and the intermediate layer are thermally contracted ( This is considered to be because the shrinkage behavior between each layer occurs and the separation occurs due to the interposition of the adhesive layer that has already been relaxed when the orientation of the front and back layers and the intermediate layer is relaxed) . In addition, when these resins are used for the adhesive layer, whitening that occurs when the film is folded during secondary processing such as a bag-making process, so-called folding whitening, occurs, and there is a problem in maintaining the design of the film. There is. This is also a similar concept. Since the orientation of the elastomer as described above is relaxed, voids generated in the adhesive layer during film folding do not shrink due to thermal shrinkage, so that it is bent and whitened even after being attached to a container. Remains, which significantly impairs the appearance. Therefore, in the film of the present invention, the concept of effecting the orientation of the adhesive layer and relaxing the orientation in the heat shrinking process is introduced, and a mixed resin composition of a polyester resin and a polystyrene resin as a resin constituting the adhesive layer; To do.

  The adhesive layer contains a polyester resin at a content of 40% by mass or more, preferably 45% by mass or more, more preferably 50% by mass or more, with respect to 100% by mass of the mixed resin composition constituting the adhesive layer. And it is desirable that it is contained at a content of 80% by mass or less, preferably 75% by mass or less, more preferably 70% by mass or less. If the polyester-based resin is 40% by mass or more, the adhesion to the front and back layers does not decrease, and if it is 80% by mass or less, the adhesion to the intermediate layer does not decrease.

(Polyester resin contained in the adhesive layer)
For the adhesive layer of the film of the present invention, the same polyester resin used for the front and back layers can be used. Further, the polyester resin used in the adhesive layer may be the same as the polyester resin used in the front and back layers or a different polyester resin as long as it satisfies the characteristics of the film of the present invention.

(Polystyrene resin contained in the adhesive layer)
In the adhesive layer of the film of the present invention, the same polystyrene resin used in the intermediate layer can be used. Further, the polystyrene resin used in the adhesive layer may be the same as or different from the polystyrene resin used in the intermediate layer as long as it satisfies the characteristics of the film of the present invention.

When the polystyrene resin contained in the adhesive layer of the film of the present invention is a block copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon, the refractive index measured according to JIS K7142 of the block copolymer (N ₂ ) is 1.540 or more, preferably 1.550 or more, more preferably 1.555 or more, and 1.600 or less, preferably 1.590 or less, more preferably 1.585 or less. is there. Further, regarding the relationship with the refractive index (n ₁ ) of the polyester resin contained in the intermediate layer, the refractive index (n ₂ ) of the block copolymer is ± 0. 0 of the refractive index (n ₁ ) of the polyester resin. It is desirable to be within the range of 02, preferably within the range of ± 0.015. By adjusting the refractive index of the polystyrene resin (n ₂₎ and the refractive index of the polyester resin The difference between the (n ₁₎ within a predetermined range, even when the film by kneading, good transparency The film which has is 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. Accordingly, by adjusting the composition ratio of the styrene hydrocarbon and the conjugated diene hydrocarbon in accordance with the refractive index (n ₁ ) of the polyester resin contained in the adhesive layer, it is within the range of n ₁ ± 0.02. A refractive index (n ₂ ) 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.

  Although the content rate of the said polystyrene-type resin contained in the contact bonding layer of the film of this invention is not specifically limited as long as the characteristic of the film of this invention is satisfy | filled, it is 100 mass% of resin compositions which comprise an contact bonding layer. On the other hand, it is 20 mass% or more, preferably 25 mass% or more, more preferably 30 mass% or more, 60 mass% or less, preferably 55 mass% or less, more preferably 50 mass% or less. If the polystyrene-based resin is 20% by mass or more, the adhesiveness to the intermediate layer does not decrease, and if it is 60% by mass or less, the adhesiveness to the front and back layers does not decrease. However, when GPPS, an oxazoline group-containing styrene copolymer, a styrene-maleic anhydride copolymer described later, or a mixture thereof is included, GPPS, an oxazoline group-containing styrene copolymer, or a styrene-maleic anhydride copolymer is used. Since the Tg (peak temperature of the loss modulus E ″) of the polymer is as high as about 100 ° C. or higher, GPPS to be mixed, oxazoline group-containing styrene copolymer, styrene-maleic anhydride copolymer, or these The content of the mixture is preferably 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less of the total amount of the resin constituting the adhesive layer.GPPS and an oxazoline group-containing styrene copolymer described later If the styrene-maleic anhydride copolymer or a mixture thereof is 20% by mass or less, the stretching characteristics are Without having to lower, also or inhibit the expression of heat shrinkage it is preferred because nor film inside the gap is caused film or whitening during stretching.

In the film of the present invention, the storage elastic modulus (E ′) at a vibration frequency of 10 Hz, strain of 0.1%, and 0 ° C. of the styrene resin contained in the adhesive layer is preferably 1.00 × 10 ⁷ Pa or more. More preferably, it is 1.50 × 10 ⁷ Pa or more. 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 with the front and back layers or the intermediate layer described above can be imparted, and a high temperature atmosphere can be obtained. When contracted, delamination between the front and back layers or the intermediate layer can be suppressed. 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 within a range that does not impair the transparency of the block copolymer of the styrene-based hydrocarbon and the conjugated diene-based hydrocarbon as described above, or a mixture of the two or more types of the copolymer. It can be obtained by mixing with other resins.

Preferable examples of the styrenic hydrocarbon-conjugated diene hydrocarbon block copolymer capable of imparting adhesion to the front and back layers or the intermediate layer are block SBS and random block SBS. 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 preferred: If the storage elastic modulus (E ′) at 0 ° C. is 1.00 × 10 ⁷ Pa or more, the laminate can be formed by increasing the blend amount of the resin responsible for rigidity. When formed into a film, the film can be imparted with stiffness. On the other hand, at the peak temperature of the loss elastic modulus (E ″), the temperature on the low temperature side mainly shows fracture resistance. Although 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 adhesiveness with the front and back layers or the intermediate layer decreases, and the laminated film becomes When molded, it may be difficult to impart sufficient breakability to the film.

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

  The adhesive layer of the film of the present invention can contain other resins in addition to the polyester resin and the polystyrene resin as long as the characteristics of the film of the present invention are satisfied. Examples of such a resin include a compatibilizing agent, a polyolefin resin, an acrylic resin, and a polycarbonate resin described later. Among these, it is preferable to contain a compatibilizer described later.

(Compatibilizer contained in the adhesive layer)
The adhesive layer of the film of the present invention can further contain a compatibilizing agent that promotes compatibilization of the polyester resin and the polystyrene resin. The compatibilizer is not particularly limited as long as the compatibilization of the polyester resin and the polystyrene resin can be promoted, but is preferably at least one of an oxazoline group-containing styrene copolymer and a styrene-maleic anhydride copolymer.

  The compatibilizer that can be contained in the adhesive layer 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 improvement, and furthermore, the interlayer adhesive strength can be improved by using a compatibilizing agent.

  The compatibilizing agent contained in the adhesive layer has a polar group having a high affinity with the polyester resin contained in the adhesive layer or a polar group capable of reacting with the polyester resin, and is also a polystyrene resin contained in the adhesive layer. A styrenic block copolymer or graft copolymer having compatible or high affinity sites. Specific examples of polar groups or reactive functional groups having high affinity with polyester resins include, for example, acid anhydride groups, carboxylic acid groups, carboxylic acid ester groups, carboxylic acid chloride groups, carboxylic acid amide groups, 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, carboxylic acid group or carboxylic ester group, and 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. Specific examples include 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.

  In view of the above, the compatibilizer is preferably at least one of an oxazoline group-containing styrene copolymer and a styrene-maleic anhydride copolymer.

  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.

  The content of the compatibilizer in the adhesive layer is not particularly limited as long as the characteristics of the film of the present invention are satisfied, but it is 1% by mass or more, preferably 100% by mass with respect to 100% by mass of the resin composition constituting the adhesive layer. 3 mass% or more, more preferably 5 mass% or more, 20 mass% or less, preferably 15 mass% or less, more preferably 10 mass% or less. If the compatibilizing agent is in the above range, it can be expected that the thickness is expected to be uniform and the interlayer adhesive strength is improved, and a significant deterioration in transparency and inhibition of the shrinkage behavior of the film 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, as long as the effects of the present invention are not significantly impaired. 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 the 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 hydrolysis inhibitor, a stabilizer, and a colorant. In addition, an antistatic agent, a lubricant, an inorganic filler, and the like can be appropriately added according to each application.

<Layer structure of film>
The film of the present invention comprises at least three layers having an adhesive layer between the front and back layers and the intermediate layer. Preferably, the front / back layer / adhesive layer / intermediate layer / adhesive layer / front / back layer has three types and five layers.

  In the present invention, by adopting the above-described layer structure, the film which is the object of the present invention realizes good shrinkage characteristics and suppression of delamination, and is suitable for applications such as shrink packaging, shrink-bound packaging and shrink labels. A shrinkable laminated film can be obtained with good productivity and economy.

  Next, a film having three types and five layers of front / back layer / adhesive layer / intermediate layer / adhesive layer / front / back layer, which is a preferred embodiment of the present invention, will be described.

  In the film of the present invention, the thickness ratio between the front and back layers and the intermediate layer, when the front and back layers are 1, the intermediate layer is 2 or more, preferably 3 or more, more preferably 4 or more, and 12 or less, preferably Is 10 or less, more preferably 8 or less. The thickness of the adhesive layer is 10% or more of the total thickness of the front and back layers, preferably 15% or more, 150% or less, preferably 100% or less, more preferably 80% or less. It is desirable. If the thickness of the adhesive layer is 10% or more of the total thickness of the front and back layers, a good adhesive effect can be obtained, and 150% or less, that is, 1.5 times or less the total thickness of the front and back layers. In this case, the transparency is not greatly 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 and 20% in at least one direction when immersed in warm water at 70 ° C. for 10 seconds. % Or less is preferable.

  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.

  Further, if the heat shrinkage rate in the main shrinkage direction at 70 ° C. is less than 10%, the heat shrinkage force is small. For example, when a laminated film is used as the container label, it cannot be temporarily fixed to the container. Then, the film may be shifted up in the direction of the top surface. On the other hand, when the thermal shrinkage rate in the main shrinkage direction is greater than 30% at 70 ° C., the thermal shrinkage occurs suddenly in the low temperature region, and thus there is a case where the thermal shrinkage cannot be performed at a predetermined position. On the other hand, if the heat shrinkage rate in the main shrinkage direction at 80 ° C. is less than 30%, the heat shrinkage rate in the main shrinkage direction at 80 ° C. is 30% because heat shrinkage is insufficient at the neck and top surface of the container. It is desirable that the content is 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 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, and 6% or less. More preferably, 5% 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 film of the present invention is stretched in at least one direction and formed into a heat-shrinkable film, and a test piece is collected from the heat-shrinkable film with a main shrinkage direction of 150 mm and a direction of 15 mm perpendicular to the main shrinkage direction. A part of the front and back layers is peeled off from the end surface in the main contraction direction of the test piece to form a peeled part on the front and back layer side, and the peeled part and the peeled part of the intermediate layer are connected to the chuck of the tensile tester. When the 180 ° peel test is performed at a test speed of 100 mm / min with respect to the main shrinkage direction, the delamination strength is 1 N / 15 mm width or more, preferably 1.5 N / 15 mm width or more, more preferably 2 N / 15 mm width. That's it. 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 is a laminated film piece of the present invention, reference numeral 2 is a front and back layer, reference numeral 4 is an adhesive layer, reference numeral 6 is an intermediate layer, reference numeral 8 is an overlapping portion, reference numeral 8w is an overlapping width, reference numeral 10 Is the end face of the front and back layer 2, reference numeral 12 is the end face of the adhesive layer 4, reference numeral 14 is the end face of the intermediate layer 6, reference numeral 16 is a seal portion, reference numeral 18 is a deviation, reference numeral 18w is a deviation width, reference numeral A is one end side, reference numeral B Means the other end side.

  1 and 2 are drawings showing a preferred embodiment of the present invention. 1 and 2 are cross-sectional views in the vicinity of an overlapping portion 8 of a film in which the front and back layers 2, the adhesive layer 4, the intermediate layer 6, the adhesive layer 4, and the front and back layers 2 are laminated in this order from the top. Moreover, the front and back of each drawing are drawings showing the state before the heat treatment, and the bonding is performed between the end surface 10 of the film front and back layer 2 and the end surface of the adhesive layer 4 or the end surface 10 of the front and back layer 2 in the overlapped portion after the heat treatment. And the state which produced the shift | offset | difference between the end surface 12 of the contact bonding layer 4 and the end surface 14 of the intermediate | middle layer 6 is shown. The front and back of FIG. 3 shows the film piece 100 which cut out the film of this invention into the rectangle of the magnitude | size of 110 mm of take-off directions (MD), and the perpendicular direction (TD) 235 mm, and FIG. 2) on the laminated film in which the surface layer or the back layer surface on one end side A of MD) and the back layer surface or the surface layer on the other end side B in the take-up direction (MD) are sealed so as to be parallel to the take-up direction (MD). It is drawing explaining the state which formed the superimposition part 8 of -7mm width.

  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 that a cylindrical film (front and back in FIG. 1) 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. Deviation 18 between the end surface 10 of the surface layer or the back layer 2 in the take-up direction (MD) 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 front layer 6). This shows a state (bonding in FIG. 1).

  Moreover, FIG. 2 shows the 2nd aspect of the shift | offset | difference 19 of the film of this invention. FIG. 2 shows that when a tubular film (front and back in FIG. 2) sealed with the overlapping portion 8 of the film 100 of the present invention is returned to room temperature after heat treatment at 99 ° C., it is sealed at the overlapping portion 8. End surfaces 10 and 12 in the take-up direction (MD) of the surface layer or back layer 2 and the adhesive layer 4 and end surfaces 14 in the take-up direction (MD) of the intermediate layer 6 (or the MD end surface 12 of the adhesive layer 4 and the back layer or surface layer 2) , 10) shows a state in which a deviation 18 occurs (adhesion in FIG. 2). 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 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, the film of the present invention hardly peels 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 even when heat-treated, and an excellent appearance is obtained.

  In the film of the present invention, the ease of peeling can be represented by a shift that occurs between the front and back layers and the adhesive layer after sealing or between the adhesive layer and the intermediate layer. 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) 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 to seal 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, 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 main-shrinkage direction of 200 mm and a direction of 100 mm perpendicular to the main-shrinkage direction from this heat-shrinkable film. After the sample is taken, it is bent into a line object with the direction orthogonal to the main contraction direction as the axis, bent in a size of 100 mm in the main contraction direction and 100 mm in the direction orthogonal to the main contraction direction, and then the folding part is opened again. When the size of the main shrinkage direction is 200 mm and the size of the main shrinkage direction is 100 mm, the bent portion is less likely to be whitened. This is an effect that can be achieved by adjusting the film of the present invention within the range defined by the present invention.

  Further, whitening of the bending depends on conditions such as folding pressure at the time of bending. The whitening of the bent portion is caused by the occurrence of cracks and voids in the bent portion of the substrate. However, the film of the present invention is a film in which the adhesive layer is composed mainly of a mixed resin composition of a polyester resin and a polystyrene resin, and has at least three layers of a front and back layer, an adhesive layer, and an intermediate layer. Is a heat-shrinkable laminated film that 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. Even when the folding process is performed, the shrinkage of the crack or void surrounding the base material (including the adhesive layer) reduces the void generated in the folded part, and the film of the present invention is shrunk into a container or the like. When attached, there is almost no whitening of the bent part. On the other hand, when the adhesive layer of the film of the present invention is replaced with an elastomer or the like, at the time of shrinkage, the adhesive layer made of elastomer is compressed to follow the shrinkage of the front and back layers and the intermediate layer, but the adhesive layer made of elastomer Since it does not shrink itself, cracks and voids caused by bending work remain after shrinkage, and when the heat-shrinkable laminated film is shrunk and attached to a container etc., whitening is observed, which impairs the design of the product. End up.

  In order to confirm the above effect, the film of the present invention is stretched in at least one direction to be formed into a heat-shrinkable film, and the main shrinkage direction is 200 mm from the heat-shrinkable film, and the size is 100 mm perpendicular to the main shrinkage direction. After collecting the test piece, it was bent into a line object with the direction orthogonal to the main contraction direction as the axis, and was bent in a size of 100 mm in the main contraction direction and 100 mm in the direction orthogonal to the main contraction direction, and then the bent portion was again formed. After opening and returning to the original main shrinkage direction of 200 mm and the direction orthogonal to the main shrinkage direction of 100 mm, the film is further loosened in the main shrinkage direction of 110 mm on two metal frames fixed to a width of 130 mm. The metal frame with the film fixed thereon was immersed in a 90 ° C. hot water bath for 10 seconds, and then immersed in 23 ° C. cold water for 30 seconds. As a result of removing the shrunk film from the metal frame and confirming the state of the adhesive layer of the folded part of the film with a scanning electron microscope, the film of the present invention has an adhesive layer within 5 mm around the folded part. It was confirmed that the size of the generated void was less than 5 μm. This is an effect that can be achieved by adjusting the film of the present invention within the range defined by the present invention. The size of the gap for suppressing the bending whitening after shrinkage is 10 μm or less, preferably 5 μm or less, more preferably 3 μm or less, and further preferably 1 μm or less.

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

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

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

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

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

(2) Interlaminar peel strength The film of the present invention was formed into a heat-shrinkable film, and a test piece was collected from the obtained film in a size of 150 mm in the main shrinkage direction and 15 mm in the direction perpendicular to the main shrinkage direction. A part of the front and back layers is peeled off from the end surface in the main shrinkage direction of the piece to form a peeled portion on the front and back layers, and the peeled portion and the peeled portion on the intermediate layer side are sandwiched between chucks of a tensile tester. The 180 ° peel test was performed at a test speed of 100 mm / min with respect to the main shrinkage direction. The average value at which the load obtained in the peel test became constant to some extent was evaluated as the delamination strength.
◎: Delamination strength is 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 In accordance with JIS K7105, the haze value of a film having a thickness of 40 μm was measured to evaluate transparency.
◎: Haze value is less than 5% ○: Haze value is 5% or more and less than 6% △: Haze value is 6% or more and less than 8% ×: Haze value is 8% 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 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 main shrinkage direction of 200 mm and a direction perpendicular to the main shrinkage direction of 100 mm. Folded into a line object with the direction orthogonal to the direction as the axis, bent in a size of 100 mm in the main contraction direction and 100 mm in the direction orthogonal to the main contraction direction, then opened the bent portion again, the original main contraction direction was 200 mm, When the size of 100 mm in the direction orthogonal to the shrinking direction was returned, whether or not the bent portion was whitened was visually confirmed 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.

(6) Confirmation of gap in bent part After the film of the present invention was subjected to the bending whitening evaluation of (5) above, it was used for the bending whitening evaluation of (5) above on the two metal frames fixed to a width of 130 mm. The film was sandwiched in a state where it was slackened in the main shrinkage direction of 110 mm, and the metal frame on which the film was fixed was immersed in a hot water bath at 90 ° C. for 10 seconds, and then immersed in cold water at 23 ° C. for 30 seconds. The shrunken film was removed from the metal frame, and the state of the adhesive layer within 5 mm around the film bent portion before and after shrinkage was confirmed with a scanning electron microscope and evaluated according to the following criteria.
◎: The size of the void generated in the adhesive layer is 1 μm or less. ○: The size of the void generated in the adhesive layer is greater than 1 μm and 3 μm or less. Δ; The size of the void generated in the adhesive layer is greater than 3 μm and 5 μm or more. The size of the void generated in the adhesive layer is larger than 5 μm

Moreover, the raw material used by each Example and the comparative example is as follows.
(Polyester resin)
Copolyester 1 (trade name: SKYGREEN PETG S2008 (manufactured by SK Chemicals), hereinafter abbreviated as “Pes (1)”)
-Copolyester 2 (trade name: EmbreceLV (Eastman Chemical Co., Ltd.), hereinafter abbreviated as "Pes (2)")
Polyester elastomer (trade name: Primalloy A1700N (Mitsubishi Chemical Corporation), hereinafter referred to as “Pes (3)”)
(Polystyrene resin)
Styrene-butadiene copolymer 1 (styrene / butadiene = 90/10 (mass%), storage elastic modulus E ′ (0 ° C.): 3.15 × 10 ⁹ Pa, peak temperature of loss elastic modulus E ″ 55 ° C.) Hereinafter, it is referred to as “PS (1)”. )
Styrene-butadiene copolymer 2 (trade name: DK-11 (manufactured by Chevron Phillips), hereinafter referred to as “PS (2)”)
Styrene-butadiene copolymer 3 (trade name; Asaflex 830 (Asahi Kasei Chemicals Corporation), hereinafter referred to as “PS (3)”)
(Compatibilizer)
Oxazoline group-containing styrene-based 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)”)

  In forming the laminated film, the resin composition used for the adhesive layer and the intermediate layer is biaxially mixed in advance in each example shown in Table 1, the adhesive layer formulation of the comparative example, and the intermediate layer formulation. It was put into an extruder (Mitsubishi Heavy Industries, Ltd.), melted and mixed at a set temperature of 210 ° C., extruded from a strand die at a set temperature of 210 ° C., and then cooled with a water tank, and then cut with a strand cutter. Pellets were obtained. The pellet obtained by the said method was used for the resin composition used for the Example shown below and the contact bonding layer of a comparative example, and an intermediate | middle layer.

( Reference Example 1)
Front and back layers in equipment capable of co-extrusion of front / back layer / adhesive layer / intermediate layer / adhesive layer / front / back layer by 3 single screw extruders (Mitsubishi Heavy Industries, Ltd.) and 3 types 5 layers multi-manifold die Polyester resin “Pes (1)” is introduced into a single-screw extruder that forms a mixture resin composition (Pes (2) 45 mass%, pelletized in advance into a single-screw extruder that forms an adhesive layer. PS (3) 55% by mass) is introduced, and the pelletized mixed resin composition (PS (1) 40% by mass, PS (2) 60% by mass) is introduced into the single-screw extruder that forms the intermediate layer. Then, after melt mixing at each extruder set temperature 210 ° C., co-extrusion so that the thickness of each layer becomes front / back layer / adhesive layer / intermediate layer / adhesive layer / front / back layer = 25 μm / 5 μm / 140 μm / 5 μm / 25 μm, Take it up with a cast roll at ℃, solidify it by cooling An unstretched laminated sheet having a width of 200 mm and a thickness of 200 μm was obtained. 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.

( Reference Example 2)
As shown in Table 1, PS (1) 40 mass%, PS (2) using the mixed resin composition pelletized beforehand by Pes (2) 65 mass% and PS (3) 35 mass% for an adhesive layer. A heat-shrinkable film was obtained in the same manner as in Reference Example 1 except that the mixed resin composition pelletized in advance at 60% by mass was used for the intermediate layer. The evaluation results of the obtained film are shown in Table 1.

( Reference Example 3)
As shown in Table 1, the mixed resin composition pelletized beforehand with 55% by mass of Pes (2) and 45% by mass of PS (3) was used for the adhesive layer, and 25% by mass of Pes (1), PS (1). A heat-shrinkable film was obtained in the same manner as in Reference Example 1 except that the mixed resin composition pelletized in advance at 30% by mass and PS (2) 45% by mass was used for the intermediate layer. The evaluation results of the obtained film are shown in Table 1.

( Reference Example 4 )
As shown in Table 1, a mixed resin composition pelletized beforehand with 65% by mass of Pes (2) and 35% by mass of PS (3) was used for the adhesive layer, and 15% by mass of Pes (1) and PS (1). By using the same method as in Reference Example 1 except that the mixed resin composition pelletized in advance at 30% by mass, PS (2) 45% by mass, and comp (2) 10% by mass was used for the intermediate layer. A film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Reference Example 5 )
As shown in Table 1, the mixed resin composition pelletized beforehand with 60% by mass of Pes (1) and 40% by mass of PS (2) is used for the adhesive layer, and 5% by mass of Pes (1) and PS (1). A heat-shrinkable film was obtained in the same manner as in Reference Example 1 except that the mixed resin composition pelletized in advance at 38% by mass and PS (2) 57% by mass was used for the intermediate layer. The evaluation results of the obtained film are shown in Table 1.

(Example 1)
As shown in Table 1, the mixed resin composition pre-pelletized with Pes (2) 55% by mass and PS (1) 45% by mass was used for the adhesive layer, and Pes (2) 5% by mass, PS (1). Except that the mixed resin composition pre-pelletized with 35% by mass, PS (2) 55% by mass, and comp (1) 5% by mass was used for the intermediate layer, heat shrinkability was obtained in the same manner as in Reference Example 1. A 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 pre-pelletized with 55% by mass of Pes (2), 40% by mass of PS (1) and 5% by mass of comp (1) was used for the adhesive layer, and Pes (2) Reference Example 1 except that a mixed resin composition pre-pelletized at 5% by mass, PS (1) 35% by mass, PS (2) 55% by mass, comp (1) 5% by mass was used for the intermediate layer. A heat-shrinkable film was obtained by the same method. The evaluation results of the obtained film are shown in Table 1.

(Reference Example 6 )
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 adhesive layer, and Pes (1) By using the same method as in Reference Example 1 except that a 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 intermediate layer. A film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Example 3)
As shown in Table 1, the mixed resin composition pelletized beforehand with 70% by mass of Pes (2), 25% by mass of PS (3) and 5% by mass of comp (1) was used for the adhesive layer, and Pes (1) By using the same method as in Reference Example 1 except that a mixed resin composition pelletized in advance at 10% by mass, PS (1) 35% by mass, and PS (2) 50% by mass was used for the intermediate layer. A film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Example 4)
As shown in Table 1, using a mixed resin composition pre-pelletized with 75% by mass of Pes (2), 20% by mass of PS (3) and 5% by mass of comp (1) for the adhesive layer, Pes (1) Heat shrinkability is the same as in Reference Example 1 except that a mixed resin composition pelletized in advance at 15% by mass, PS (1) 35% by mass, and PS (2) 50% by mass is used for the intermediate layer. A 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 pre-pelletized with 55% by mass of Pes (2), 35% by mass of PS (3) and 10% by mass of comp (1) was used for the adhesive layer, and Pes (1) By using the same method as in Reference Example 1 except that a 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 intermediate layer. A film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Example 6)
As shown in Table 1, the 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 adhesive layer, and Pes (1) Heat shrinkability is the same as in Reference Example 1 except that a mixed resin composition pelletized in advance at 15% by mass, PS (1) 35% by mass, and PS (2) 50% by mass is used for the intermediate layer. A film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 1)
Front and back layers in equipment capable of co-extrusion of front / back layer / adhesive layer / intermediate layer / adhesive layer / front / back layer by 3 single screw extruders (Mitsubishi Heavy Industries, Ltd.) and 3 types 5 layers multi-manifold die Polyester resin “Pes (1)” is introduced into a single screw extruder that forms a layer, the single screw extruder that forms an adhesive layer is stopped, and the pellets are mixed into a single screw extruder that forms an intermediate layer in advance. A resin composition (Pes (2) 5% by mass, PS (1) 35% by mass, PS (2) 55% by mass, comp (1) 5% by mass) is introduced and melt mixed at each extruder set temperature 210 ° C. Thereafter, the layers are coextruded so that the thickness of each layer is front / back layer / intermediate layer / front / back layer = 25 μm / 150 μm / 25 μm, taken up by a cast roll at 60 ° C., cooled and solidified, and unstretched laminated sheet having a width of 200 mm and a thickness of 200 μm Got. 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, polyester elastomer “Pes (3)” was used for the adhesive layer (in the resin composition used for the adhesive layer of Comparative Example 2, without pre-pelletizing with a twin-screw extruder, Commercially available pellets were used.), A mixed resin composition pre-pelletized with 10% by mass of Pes (1), 35% by mass of PS (1) and 55% by mass of PS (2) was used for the intermediate layer. Except for the above, 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.

(Comparative Example 3)
As shown in Table 1, the 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 adhesive layer, and Pes (1) By using the same method as in Reference Example 1 except that a mixed resin composition pelletized beforehand at 35% by mass, PS (1) 25% by mass, and PS (2) 40% by mass was used for the intermediate layer. A film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 4)
As shown in Table 1, a mixed resin composition pelletized beforehand with 90% by mass of Pes (2) and 10% by mass of PS (3) was used for the adhesive layer, and 40% by mass of PS (1) and PS (2). A heat-shrinkable film was obtained in the same manner as in Reference Example 1 except that the mixed resin composition pelletized in advance at 60% by mass was used for the intermediate layer. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 5)
As shown in Table 1, the 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 adhesive layer, and Pes (1) By using the same method as in Reference Example 1 except that a mixed resin composition pelletized beforehand at 35% by mass, PS (1) 25% by mass, and PS (2) 40% by mass was used for the intermediate layer. A film was obtained. The evaluation results of the obtained film are shown in Table 1.

The heat-shrinkable film (Examples 1-6 , Reference Examples 1-6 ) obtained from the laminated body of this invention from Table 1 compared with the 2 types 3 layer film (comparative example 1) which does not have an adhesive layer. It can be seen that this is a heat-shrinkable film having sufficient delamination. Further, when the content of the polyester resin contained in the adhesive layer deviates from the range defined by the present invention (Comparative Example 4 and Comparative Example 5), the adhesive strength between the front and back layers and the adhesive layer is extremely reduced, It became clear that the required characteristics as a heat shrinkable film were not satisfied.
In Examples 1-6, it was compared in Reference Example 1 to 6, for example, when comparing Example 1 and Example 2, the resin composition constituting the adhesive layer, compatibilizing defined by the present invention When an agent was added, it turned out that the effect which improves delamination strength can be provided. 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 adhesive layer for the purpose of improving the delamination strength (Comparative Example 2), peeling is observed in the delamination evaluation at high temperature treatment, and bending whitening occurs when the film is folded. It was. On the other hand, regarding Examples 1 to 6 and Reference Examples 1 to 6 , such bending whitening is not confirmed, and it can be seen that the film can achieve further improvement in design.

Further, Reference Example 1, Reference Example 5, the film obtained in Example 3, and Comparative Example 2, by the method described above, was confirmed gap of the bent portion before and after shrinkage. Reference Example 1, Reference Example 5 was subjected to whitening evaluation folding of the resulting film in Example 3, the visual observation, either remains evidence of bending in the bent portion of the film did not occur whitened. On the other hand, when the whitening evaluation of the film obtained in Comparative Example 2 was performed, it was confirmed that a clear whitened line remained in the bent portion of the film visually. However, Reference Example 1, Reference Example 5, was confirmed voids after bleaching bending the film obtained in Example 3, before shrinkage, 1 to the adhesive layer in less than ambient 5mm around an axis of the bent portion of the film Although a void of about ˜2 μm is confirmed, the size of the void in the same portion is 1 μm or less after shrinkage, and the void is not substantially confirmed. The results are shown in FIGS. 4 and 5 and Table 2.

4, 5 show, and Table 2, heat-shrinkable film obtained from the laminate of the present invention (Example 1, Reference Example 5, Example 3), by the contraction, a void generated in the bent portion It was confirmed to be smaller. On the other hand, when the adhesive layer of the film of the present invention was replaced with an elastomer or the like, the size of the void before and after shrinkage was hardly changed, and a void of 5 μm or more was confirmed in the adhesive layer at the bent portion even after shrinkage. From this, the heat-shrinkable film obtained from the laminate of the present invention has cracks or shrinkage of the base material (including the adhesive layer) around the void due to the shrinkage, and the void generated in the bent portion is reduced. When the heat-shrinkable laminated film is shrunk and attached to a container or the like, whitening of the bent portion is hardly observed. Further, even if the bending process conditions such as increasing the folding pressure are strict, the film of the present invention is considered to be able to remarkably relieve the whitening state after shrinkage because the adhesive layer itself has shrinkage. 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.

  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 (7)

At least 3 of the adhesion layer which has as a main component the mixed resin composition of a polyester resin and a polystyrene resin between the front and back layers which have a polyester resin as a main component, and the intermediate layer which has a polystyrene resin as a main component A heat-shrinkable film formed by stretching a laminated film having a layer in at least one direction,
The thermal shrinkage rate in the main shrinkage direction when immersed in warm water of 80 ° C. for 10 seconds is 20% or more,
The intermediate layer contains a polyester resin in an amount of 3% by mass to 30% by mass with respect to 100% by mass of the resin composition constituting the intermediate layer.
The adhesive layer contains the polyester resin in an amount of 40% by mass to 80% by mass with respect to 100% by mass of the mixed resin composition constituting the adhesive layer,
Either one of the adhesive layer and the intermediate layer, or both layers, an oxazoline group-containing styrene copolymer as a compatibilizing agent that promotes compatibilization of the polyester resin and the polystyrene resin, to the adhesive layer resin composition 100% by mass constituting the, 20 mass% to 5 mass% or less, it is contained in al,
After bending the heat-shrinkable film with the direction orthogonal to the main shrinkage direction as an axis, when it is shrunk 10% in the main shrinkage direction in hot water at 90 ° C., the circumference around the bent portion is 5 mm. The heat shrinkable laminated film is characterized in that the size of the voids generated in the adhesive layer is 10 μm or less.   2. The polystyrene resin contained in either one of the adhesive layer and the intermediate layer or both layers is an aromatic vinyl hydrocarbon-conjugated diene copolymer. 3. Heat shrinkable laminated film.   The polyester resin contained in one or both of the front and back layers and the adhesive layer contains a terephthalic acid residue as a dicarboxylic acid residue, and an ethylene glycol residue and 1 as a diol residue. The heat-shrinkable laminated film according to claim 1, comprising a 1,4-cyclohexanedimethanol residue.   After collecting a test piece with a size of 150 mm in the main shrinkage direction and 15 mm in a direction orthogonal to the main shrinkage direction, a part of the front and back layers is peeled off from the end surface in the main shrinkage direction of the test piece and peeled to the front and back layers side. When the 180 ° peel test is performed at a tensile speed of 100 mm / min with respect to the main shrinkage direction, the peel portion and the peeled portion on the intermediate layer side are respectively sandwiched by a chuck of a tensile tester. The heat shrinkable laminated film according to any one of claims 1 to 3, wherein is 1 N / 15 mm width or more.   A molded product comprising the heat-shrinkable laminated film according to claim 1 as a base material.   The heat-shrinkable label which uses the heat-shrinkable laminated film in any one of Claim 1 to 4 as a base material.   A container equipped with the molded product according to claim 5 or the heat-shrinkable label according to claim 6.

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