Invention title: heat-shrinkable multilayer film and heat-shrinkable label
Technical field
[0001]
The present invention relates to a heat-shrinkable multilayer film capable of producing a heat-shrinkable label having high sealing strength regardless of the interlayer strength and also having excellent transparency. The present invention also relates to a heat-shrinkable label made of the heat-shrinkable multilayer film.
Background technology
[0002]
In recent years, many containers such as PET bottles and metal cans are equipped with a heat-shrinkable label obtained by printing or the like on a base film made of a heat-shrinkable resin.
Polystyrene-based resin films are often used for heat-shrinkable labels because they have excellent low-temperature shrinkage. However, the polystyrene-based resin film has a problem of insufficient heat resistance and solvent resistance. Therefore, attempts have been made to use a polyester-based resin film having excellent heat resistance and solvent resistance, but since the polyester-based resin film has poor low-temperature shrinkage and shrinks rapidly, wrinkles are formed when it is attached to a container. Likely to happen. In addition, the heat-shrinkable label is often provided with perforations so that the heat-shrinkable label can be easily peeled off from the container after use in order to recycle the container. Poor cutability at perforations.
[0003]
In order to solve such a problem, for example, a multilayer film having a front and back layer containing a polyester resin and an intermediate layer containing a polystyrene resin has been studied, but in the multilayer film, between the layers. Preventing peeling is an important issue.
In order to prevent peeling between the layers, an adhesive layer is provided between the front and back layers and the intermediate layer. In Patent Document 1, a hard polyester resin and a soft resin are used as the adhesive resin for the adhesive layer. A heat-shrinkable multilayer film using a polyester-based resin, a soft styrene-based resin, a hard styrene-based resin, or a mixture thereof has been described.
Prior art literature
Patent documents
[0004]
Patent Document 1: Japanese Unexamined Patent Publication No. 2010-241055
Outline of the invention
Problems to be solved by the invention
[0005]
The heat-shrinkable multilayer film is used as a heat-shrinkable label in which one end and the other end are overlapped to form a cylinder, and the overlapped portion is welded by a solvent seal as shown in FIG. The heat-shrinkable label is attached to a container such as a PET bottle in close contact with the heat-shrinkable label by passing it through a heating furnace and heat-shrinking it.
During thermal shrinkage, stress due to shrinkage acts on the solvent seal portion, and if the interlayer strength is weak, sufficient seal strength cannot be obtained. Therefore, as shown in FIG. 2, delamination occurs at the solvent seal portion, and the solvent seal is provided. There is a problem that the peeling of the portion spreads due to shrinkage and causes a poor appearance, and the film described in Patent Document 1 has the effect of suppressing the peeling of the solvent-sealed portion even though the interlayer strength can be improved. There was a problem that it was inadequate.
[0006]
An object of the present invention is to provide a heat-shrinkable multilayer film capable of producing a heat-shrinkable label having high sealing strength regardless of the interlayer strength and also having excellent transparency. Another object of the present invention is to provide a heat-shrinkable label using the heat-shrinkable multilayer film.
Means to solve problems
[0007]
The present invention is a heat-shrinkable multilayer film in which a front and back layer containing a polyester resin and an intermediate layer containing a polystyrene resin are laminated via an adhesive layer, and the adhesive layer is a glass transition. It is a heat-shrinkable multilayer film characterized by containing a polyester resin having a temperature of 77 ° C. or lower.
Hereinafter, the present invention will be described in detail.
[0008]
The present inventors have laminated a front and back layer containing a polyester resin and an intermediate layer containing a polystyrene resin via an adhesive layer containing a polyester resin having specific physical properties, thereby increasing the interlayer strength. Regardless, it has been found that a heat-shrinkable label with high sealing strength can be obtained. Further, they have found that a heat-shrinkable label having an excellent appearance can be obtained without deteriorating transparency, and have completed the present invention.
[0009]
The heat-shrinkable multilayer film of the present invention has a front and back layer and an intermediate layer.
In the present specification, the front and back layers mean both the front surface layer and the back surface layer. Therefore, the heat-shrinkable multilayer film of the present invention has a structure in which the intermediate layer is sandwiched between the front surface layer and the back surface layer.
[0010]
(Front and back layers)
The front and back layers contain a polyester resin.
Examples of the polyester-based resin include those obtained by polycondensing a dicarboxylic acid component and a diol component.
Examples of the dicarboxylic acid include terephthalic acid, o-phthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, octylsuccinic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, fumaric acid, maleic acid, and itacon. Examples thereof include acids, decamethylenecarboxylic acids, anhydrides thereof and lower alkyl esters.
As the dicarboxylic acid, terephthalic acid and isophthalic acid are preferable.
[0011]
Of the 100 mol% of the dicarboxylic acid component, the preferable lower limit of the content of the component derived from terephthalic acid is 50 mol%, the more preferable lower limit is 60 mol%, the further preferable lower limit is 65 mol%, and the preferable upper limit is 100 mol%. ..
Further, in the 100 mol% of the dicarboxylic acid component, the preferable lower limit of the content of the component derived from isophthalic acid is 0 mol%, the preferable upper limit is 40 mol%, the more preferable upper limit is 35 mol%, and the further preferable upper limit is 33 mol%. Is.
[0012]
Examples of the diol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, dipropylene glycol, triethylene glycol, and tetraethylene. Glycol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, neopentyl glycol (2,2-dimethylpropane-1,3-diol), 1,2-hexanediol, 2, Adipose diols such as 5-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, and polytetramethylene ether glycol; Alicyclic type such as 2,2-bis (4-hydroxycyclohexyl) propane, alkylene oxide adduct of 2,2-bis (4-hydroxycyclohexyl) propane, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, etc. Examples include diols.
As the diol, ethylene glycol, 1,4-butanediol, diethylene glycol, and 1,4-cyclohexanedimethanol are preferable.
[0013]
Of the 100 mol% of the diol component, the preferable lower limit of the content of the component derived from ethylene glycol is 40 mol%, the more preferable lower limit is 50 mol%, the further preferable lower limit is 60 mol%, and the preferable upper limit is 100 mol%.
In the 100 mol% of the diol component, the preferable lower limit of the content of the component derived from diethylene glycol is 0 mol%, the preferable upper limit is 40 mol%, the more preferable upper limit is 30 mol%, and the further preferable upper limit is 25 mol%.
Of the 100 mol% of the diol component, the preferable lower limit of the content of the component derived from 1,4-cyclohexanedimethanol is 0 mol%, the preferable upper limit is 70 mol%, the more preferable upper limit is 60 mol%, and the further preferable upper limit is 50. It is mol%.
[0014]
Among the polyester-based resins, those containing a component derived from terephthalic acid as a dicarboxylic acid component and a component derived from ethylene glycol and / or 1,4-cyclohexanedimethanol as a diol component are used. preferable. By using such an aromatic polyester-based random copolymer resin, excellent shrinkage can be imparted to the heat-shrinkable multilayer film.
[0015]
The preferable lower limit of the glass transition temperature of the polyester resin constituting the front and back layers is 55 ° C., the more preferable lower limit is 60 ° C., the more preferable lower limit is 65 ° C., the preferable upper limit is 95 ° C., the more preferable upper limit is 90 ° C., and the further preferable upper limit. Is 85 ° C.
When the glass transition temperature is 55 ° C. or higher, it is possible to prevent the shrinkage start temperature of the heat-shrinkable multilayer film from becoming too low, the natural shrinkage rate from becoming large, and blocking from being likely to occur. .. When the glass transition temperature is 95 ° C. or lower, the low-temperature shrinkage and shrinkage finish of the heat-shrinkable multilayer film are deteriorated, the low-temperature shrinkage is greatly reduced with time, and resin whitening occurs during stretching. It is possible to prevent it from becoming easy.
The glass transition temperature can be measured by a method conforming to ISO 3146.
[0016]
The preferable lower limit of the tensile elastic modulus of the polyester resin constituting the front and back layers exceeds 1000 MPa, and the preferable upper limit is 4000 MPa. When the tensile elastic modulus exceeds 1000 MPa, it is possible to prevent the shrinkage start temperature of the heat-shrinkable film from becoming too low or the natural shrinkage rate from becoming large. When the tensile elastic modulus is 4000 MPa or less, it is possible to prevent the low-temperature shrinkage and shrinkage finish of the heat-shrinkable multilayer film from being lowered and the low-temperature shrinkage from being significantly lowered over time. The more preferable lower limit of the tensile elastic modulus is 1500 MPa, and the more preferable upper limit is 3700 MPa.
The tensile elastic modulus can be measured by a method based on ASTM-D882 (TestA).
[0017]
Commercially available polyester resins constituting the front and back layers include, for example, "Easter", "EmbraceLv" (manufactured by Eastman Chemical Company), "Bellpet" (manufactured by Bell Polyester Products), and "Novaduran" (Mitsubishi Engineering). (Made by Plastics) and the like.
[0018]
As the polyester-based resin contained in the front and back layers, the polyester-based resin having the above-mentioned composition may be used alone, or two or more kinds of polyester-based resins having the above-mentioned composition may be used in combination.
[0019]
The front and back layers are, if necessary, antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, lubricants, antistatic agents, antiblocking agents, flame retardants, antibacterial agents, fluorescent whitening agents, colorants, etc. May contain the additive of.
[0020]
(Intermediate layer)
The intermediate layer contains a polystyrene-based resin.
Examples of the polystyrene-based resin include aromatic vinyl hydrocarbon-conjugated diene copolymer, aromatic vinyl hydrocarbon-conjugated diene copolymer and aromatic vinyl hydrocarbon-lipid unsaturated carboxylic acid ester copolymer. Examples thereof include mixed resins of the above, rubber-modified impact-resistant polystyrene, and the like. By using the above-mentioned polystyrene-based resin, the heat-shrinkable multilayer film of the present invention can start shrinking from a low temperature and has high shrinkage.
[0021]
In the present specification, the aromatic vinyl hydrocarbon-conjugated diene copolymer means a copolymer containing a component derived from an aromatic vinyl hydrocarbon and a component derived from a conjugated diene.
The aromatic vinyl hydrocarbon is not particularly limited, and examples thereof include styrene, o-methylstyrene, and p-methylstyrene. These may be used alone or in combination of two or more.
The conjugated diene is not particularly limited, and is, for example, 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. And so on. These may be used alone or in combination of two or more.
[0022]
Since the aromatic vinyl hydrocarbon-conjugated diene copolymer is particularly excellent in heat shrinkage, it is preferable to contain a styrene-butadiene copolymer (SBS resin). Further, in the aromatic vinyl hydrocarbon-conjugated diene copolymer, 2-methyl-1,3-butadiene (isoprene) is used as the conjugated diene in order to produce a heat-shrinkable multilayer film having less fish eyes. It is preferable to contain the styrene-isoprene copolymer (SIS resin), styrene-isoprene-butadiene copolymer (SIBS resin) and the like used.
The aromatic vinyl hydrocarbon-conjugated diene copolymer may contain any one of the SBS resin, the SIS resin and the SIBS resin alone, or may contain a plurality of them in combination. When a plurality of SBS resin, SIS resin and SIBS resin are used, each resin may be dry-blended, and a compound resin obtained by kneading each resin with a specific composition using an extruder and pelletizing the resin is used. You may.
[0023]
The styrene content in the polystyrene-based resin 100% by weight has a preferable lower limit of 65% by weight, a more preferable lower limit of 70% by weight, a further preferable lower limit of 76% by weight, a preferable upper limit of 90% by weight, and a more preferable upper limit of 85% by weight. %, A more preferred upper limit is 83% by weight.
When the styrene content is 65% by weight or more, foreign substances such as gel are less likely to be generated during the molding process, and the mechanical strength of the heat-shrinkable film can be sufficiently increased. Further, when the styrene content is 65% by weight or more, good sealing strength can be obtained.
When the styrene content is 90% by weight or less, it is possible to prevent breakage when tension is applied to the heat-shrinkable film or during processing such as printing.
The preferred lower limit of the conjugated diene content in 100% by weight of the polystyrene resin is 10% by weight, the more preferable lower limit is 15% by weight, the more preferable lower limit is 17% by weight, the preferable upper limit is 35% by weight, and the more preferable upper limit is 35% by weight. Is 30% by weight, and a more preferable upper limit is 24% by weight.
When the conjugated diene content is 10% by weight or more, it is possible to prevent breakage when tension is applied to the heat-shrinkable film or during processing such as printing.
When the conjugated diene content is 35% by weight or less, foreign substances such as gel are less likely to be generated during the molding process, and the mechanical strength of the heat-shrinkable film can be sufficiently increased. Further, when the conjugated diene content is 35% by weight or less, good sealing strength can be obtained.
[0024]
The preferred lower limit of the vicut softening temperature of the polystyrene resin is 60 ° C., the more preferable lower limit is 65 ° C., the more preferable lower limit is 67 ° C., the preferable upper limit is 85 ° C., the more preferable upper limit is 80 ° C., and the further preferable upper limit is 77 ° C. ..
When the Vicat softening temperature is 60 ° C. or higher, the low-temperature shrinkage of the heat-shrinkable multilayer film does not become too high, and wrinkles can be prevented from occurring when the film is attached to the container. When the Vicat softening temperature is 85 ° C. or lower, the low-temperature shrinkage of the heat-shrinkable multilayer film is improved, and the generation of non-shrinkable portions can be prevented when the film is mounted on a container. The Vicat softening temperature can be measured by a method according to ISO 306: 1994.
[0025]
The preferable lower limit of MFR (melt flow rate) of the polystyrene resin at 200 ° C. is 2 g / 10 minutes, and the preferable upper limit is 15 g / 10 minutes. If the MFR at 200 ° C. is less than 2 g / 10 minutes, it becomes difficult to form a film. If the MFR at 200 ° C. exceeds 15 g / 10 minutes, the mechanical strength of the film becomes low and it becomes unusable for practical use. The more preferable lower limit of MFR at 200 ° C. is 4 g / 10 minutes, and the more preferable upper limit is 12 g / 10 minutes. The MFR can be measured by a method conforming to ISO 1133.
[0026]
Examples of commercially available polystyrene-based resins constituting the intermediate layer include "Clearlen" (manufactured by Denki Kagaku Kogyo Co., Ltd.), "Asaflex" (manufactured by Asahi Kasei Chemicals Co., Ltd.), "Styrolux" (manufactured by BASF), and "PSJ". -Polystyrene "(manufactured by PS Japan Corporation) and the like.
[0027]
The intermediate layer may contain additives such as antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, lubricants, antioxidants, flame retardants, antibacterial agents, fluorescent whitening agents, and colorants, if necessary. It may be contained.
[0028]
(Adhesive layer)
The heat-shrinkable multilayer film of the present invention is formed by laminating the front and back layers and the intermediate layer via an adhesive layer containing a polyester resin having a glass transition temperature of 77 ° C. or lower. be.
By using such an adhesive layer, it is possible to produce a heat-shrinkable label having high sealing strength and excellent transparency regardless of the interlayer strength.
[0029]
As the polyester-based resin constituting the adhesive layer, the same polyester-based resin as that used for the front and back layers described above may be used, or another polyester-based resin may be used.
[0030]
In the polyester resin constituting the adhesive layer, the preferable lower limit of the content of the component derived from terephthalic acid is 60 mol%, the more preferable lower limit is 65 mol%, and the further preferable lower limit is 67 in the 100 mol% of the dicarboxylic acid component. Mol%, preferably the upper limit is 100 mol%.
Further, in the 100 mol% of the dicarboxylic acid component, the preferable lower limit of the content of the component derived from isophthalic acid is 0 mol%, the preferable upper limit is 40 mol%, the more preferable upper limit is 35 mol%, and the further preferable upper limit is 33 mol%. Is.
Of the 100 mol% of the diol component, the preferable lower limit of the content of the component derived from ethylene glycol is 50 mol%, the more preferable lower limit is 60 mol%, the further preferable lower limit is 63 mol%, and the preferable upper limit is 100 mol%.
In the 100 mol% of the diol component, the preferable lower limit of the content of the component derived from diethylene glycol is 0 mol%, the preferable upper limit is 30 mol%, the more preferable upper limit is 25 mol%, and the further preferable upper limit is 22 mol%.
Of the 100 mol% of the diol component, the preferable lower limit of the content of the component derived from 1,4-cyclohexanedimethanol is 0 mol%, the preferable upper limit is 25 mol%, the more preferable upper limit is 22 mol%, and the further preferable upper limit is 20. It is mol%.
[0031]
The glass transition temperature of the polyester resin constituting the adhesive layer is 77 ° C. or lower.
When the glass transition temperature is 77 ° C. or lower, good sealing strength can be obtained.
The glass transition temperature has a preferable lower limit of 60 ° C., a more preferable lower limit of 62 ° C., a further preferable lower limit of 65 ° C., a preferable upper limit of 76 ° C., a more preferable upper limit of 75 ° C., and a further preferable upper limit of 73 ° C.
Further, the difference between the glass temperature of the polyester resin constituting the adhesive layer and the glass transition temperature of the polyester resin constituting the front and back layers is preferably 10 ° C. or less.
When the difference in the glass transition temperature is 10 ° C. or less, good sealing strength can be obtained.
The glass transition temperature can be measured by a method conforming to ISO 3146.
[0032]
The content of the polyester resin in the adhesive layer has a preferable lower limit of 4.7% by weight and a preferable upper limit of 96% by weight.
When the content of the polyester resin is in the above range, good sealing strength can be obtained.
Regarding the content of the polyester resin, a more preferable lower limit is 47.5% by weight, a further preferable lower limit is 48% by weight, a further preferable lower limit is 49% by weight, a more preferable upper limit is 95% by weight, and a further preferable upper limit is 94% by weight. %, Still more preferred is 93% by weight.
[0033]
As the polystyrene-based resin constituting the adhesive layer, the same polystyrene-based resin as that used for the above-mentioned intermediate layer may be used, or another polystyrene-based resin may be used. When another one is used, one softer than the polystyrene-based resin used for the intermediate layer is preferable.
[0034]
The polystyrene-based resin constituting the adhesive layer preferably contains an aromatic vinyl hydrocarbon-conjugated diene copolymer because of its excellent adhesiveness, and in particular, a styrene-butadiene copolymer (SBS resin). Is preferably contained. When a styrene-butadiene copolymer is used, it is preferable that the content of butadiene is higher than that of the styrene-butadiene copolymer used in the intermediate layer from the viewpoint of excellent adhesiveness. Further, in order to produce a heat-shrinkable multilayer film having better adhesiveness, 2-methyl-1,3-butadiene (isoprene) was used as the conjugated diene of the above aromatic vinyl hydrocarbon-conjugated diene copolymer. It is preferable to contain a styrene-isoprene copolymer (SIS resin), a styrene-isoprene-butadiene copolymer (SIBS resin) and the like. Further, a hydrogenated styrene resin such as a styrene-butadiene-butylene copolymer (SBBS resin) or a styrene-ethylene-butylene copolymer (SEBS resin) obtained by hydrogenating an aromatic vinyl hydrocarbon-conjugated diene copolymer. May be contained in a range that does not become the main component of the polystyrene-based resin. When the hydrogenated styrene resin becomes the main component in the polystyrene resin, the transparency tends to decrease.
The polystyrene-based resin may contain any one of the SBS resin, the SIS resin, and the SIBS resin alone, or may contain a plurality of the same in combination. When a plurality of SBS resin, SIS resin, SIBS resin, SBBS resin or SEBS resin are used, each resin may be dry-blended, and each resin is kneaded with a specific composition using an extruder. A pelletized compound resin may be used.
[0035]
Regarding the styrene content in 100% by weight of the polystyrene-based resin, a preferable lower limit is 50% by weight, a more preferable lower limit is 60% by weight, a further preferable lower limit is 73% by weight, a further preferable lower limit is 75% by weight, and a particularly preferable lower limit is 75% by weight. 76% by weight, a preferred upper limit is 98% by weight, a more preferred upper limit is 95% by weight, a further preferred upper limit is 93% by weight, a further preferred upper limit is 92% by weight, and a particularly preferred upper limit is 90% by weight.
When the styrene content is 50% by weight or more, it is possible to prevent the generation of foreign substances such as gel during the molding process. When the styrene content is 98% by weight or less, the interlayer strength can be sufficiently improved.
The butadiene content in 100% by weight of the polystyrene-based resin has a preferable lower limit of 2% by weight, a more preferable lower limit of 5% by weight, a further preferable lower limit of 7% by weight, a further preferable lower limit of 8% by weight, and a particularly preferable lower limit of 8% by weight. 10% by weight, a preferred upper limit is 50% by weight, a more preferred upper limit is 40% by weight, a further preferred upper limit is 27% by weight, a further preferred upper limit is 25% by weight, and a particularly preferred upper limit is 24% by weight.
When the butadiene content is 2% by weight or more, the interlayer strength can be sufficiently improved. When the butadiene content is 50% by weight or less, it is possible to prevent the generation of foreign substances such as gel during molding.
[0036]
The preferred lower limit of the vicut softening temperature of the polystyrene resin constituting the adhesive layer is 30 ° C, the more preferable lower limit is 40 ° C, the more preferable lower limit is 42 ° C, the particularly preferable lower limit is 45 ° C, the preferable upper limit is 85 ° C, and the more preferable upper limit. Is 80 ° C., a more preferable upper limit is 77 ° C., and a particularly preferable upper limit is 75 ° C.
When the Vicat softening temperature is 30 ° C. or higher, the heat-shrinkable multilayer film can prevent delamination between the layers due to heating when the film is attached to the container. When the Vicat softening temperature is 85 ° C. or lower, the adhesive strength of the heat-shrinkable multilayer film can be further improved.
The Vicat softening temperature can be measured by a method conforming to ISO 306.
[0037]
The preferable lower limit of MFR (melt flow rate) of the polystyrene resin constituting the adhesive layer at 200 ° C. is 2 g / 10 minutes, and the preferable upper limit is 15 g / 10 minutes. If the MFR at 200 ° C. is less than 2 g / 10 minutes, the resin stays in the extruder in the continuous production process, and foreign matter such as gel is likely to be generated. When the MFR at 200 ° C. exceeds 15 g / 10 minutes, sufficient pressure is not applied in the film forming process, and the thickness variation tends to be large. The more preferable lower limit of MFR at 200 ° C. is 4 g / 10 minutes, and the more preferable upper limit is 12 g / 10 minutes. The MFR can be measured by a method conforming to ISO 1133.
[0038]
The content of the polystyrene-based resin in the adhesive layer has a preferable lower limit of 2% by weight and a preferable upper limit of 95% by weight.
When the content of the polystyrene resin is in the above range, good sealing strength can be obtained.
The content of the polystyrene-based resin has a more preferable lower limit of 2.5% by weight, a further preferable lower limit of 3% by weight, a further preferable lower limit of 4% by weight, a more preferable upper limit of 47.5% by weight, and a further preferable upper limit. 47% by weight, and even more preferably 46% by weight.
[0039]
The polyester-based elastomer used for the adhesive layer is composed of polyester as a hard segment and polyether or polyester which is a soft segment rich in rubber elasticity.
Examples of the polyester which is the hard segment include aromatic polyester and the like.
Examples of the polyester which is the soft segment include aliphatic polyesters.
Further, examples of the polyether which is the soft segment include aliphatic polyethers such as polyalkylene ether glycol and the like.
Among them, a block polymer composed of an aromatic polyester as a hard segment and an aliphatic polyether as a soft segment, or a block composed of an aromatic polyester as a hard segment and an aliphatic polyester as a soft segment. A copolymer is preferable, and a block copolymer composed of an aromatic polyester as a hard segment and a polyalkylene ether glycol as a soft segment is more preferable.
[0040]
When a block copolymer composed of aromatic polyester and polyalkylene ether glycol is used as the polyester-based elastomer, the ratio of the segment composed of polyalkylene ether glycol is preferably 5% by weight in the lower limit and 90% by weight in the upper limit. be. If it is less than 5% by weight, the adhesiveness to the intermediate layer is lowered, and if it exceeds 90% by weight, the adhesiveness to the front and back layers is lowered. A more preferable lower limit is 30% by weight, a more preferable upper limit is 80% by weight, and a further preferable lower limit is 55% by weight.
[0041]
Examples of the polyalkylene ether glycol include polyethylene glycol, poly (propylene ether) glycol, poly (tetramethylene ether) glycol, poly (hexamethylene ether) glycol and the like.
[0042]
The preferred lower limit of the number average molecular weight of the polyalkylene ether glycol is 400, and the preferred upper limit is 6000. A more preferable lower limit is 600, a more preferable upper limit is 4000, a further preferable lower limit is 1000, and a further preferable upper limit is 3000. By using a polyalkylene ether glycol having a number average molecular weight within the above range, good interlayer strength can be obtained, which is preferable. In this specification, the number average molecular weight is measured by gel permeation chromatography (GPC).
[0043]
The method for producing the polyester-based elastomer is not particularly limited, and for example, (i) an aliphatic and / or alicyclic diol having 2 to 12 carbon atoms and (ii) an aromatic dicarboxylic acid and / or an alicyclic diol are produced. Using a dicarboxylic acid or an ester thereof and (iii) a polyalkylene ether glycol having a number average molecular weight of 400 to 6000 as a raw material, an oligomer is obtained by an esterification reaction or an ester exchange reaction, and then the oligomer is further polycondensed. Can be produced.
[0044]
As the aliphatic and / or alicyclic diol having 2 to 12 carbon atoms, for example, those commonly used as raw materials for polyesters, particularly polyester-based thermoplastic elastomers can be used. Specific examples thereof include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol. Of these, ethylene glycol and 1,4-butanediol are preferable, and 1,4-butanediol is more preferable. These may be used alone or in combination of two or more.
[0045]
As the aromatic dicarboxylic acid and / or the alicyclic dicarboxylic acid, for example, those commonly used as raw materials for polyesters, particularly polyester-based thermoplastic elastomers can be used. Specific examples thereof include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid and the like. Of these, terephthalic acid and 2,6-naphthalenedicarboxylic acid are preferable, and terephthalic acid is more preferable. These may be used alone or in combination of two or more.
[0046]
Among the above polyester elastomers, those commercially available include, for example, the product name "Primaloy" (manufactured by Mitsubishi Chemical Corporation), the product name "Perprene" (manufactured by Toyobo Co., Ltd.), and the product name "Hitrel" (Toray DuPont). Made) and the like.
[0047]
The melting point of the polystel-based elastomer is preferably 120 to 200 ° C. If the temperature is lower than 120 ° C, the heat resistance is lowered, and when the container is coated as a heat-shrinkable label, peeling easily occurs from the solvent-sealed portion, and if the temperature exceeds 200 ° C, sufficient adhesive strength may not be obtained. .. A more preferable lower limit is 130 ° C., and a more preferable upper limit is 190 ° C.
The melting point can be measured by a method based on ISO 3146 using a differential scanning calorimeter (DSC-60 manufactured by Shimadzu Corporation).
[0048]
The melting point of the polyester-based elastomer is due to the copolymerization ratio and structure of the polyester which is a hard segment and the polyether or polyester which is a soft segment. In general, the melting point of a polyester-based elastomer tends to depend on the copolymerization amount of a polyether or polyester which is a soft segment. When the copolymerization amount of the polyether or polyester is large, the melting point is low, and when the copolymerization amount is low, the melting point is high.
Further, the melting point of polyester, which is a hard segment constituting the polyester-based elastomer, can be adjusted by changing the copolymerization component, and the melting point of the entire polyester-based elastomer can be adjusted.
Further, when the molecular weight of the soft segment of the polyether or polyester is reduced, the blocking property of the obtained polyester-based elastomer is lowered, so that the melting point is likely to be lowered.
[0049]
The preferable lower limit of the durometer hardness of the polyester-based elastomer is 10, and the preferred upper limit is 80. By setting the durometer hardness to 10 or more, the mechanical strength of the adhesive layer is improved. By setting the durometer hardness to 80 or less, the flexibility and impact resistance of the adhesive layer are improved. The more preferable lower limit of the durometer hardness is 15, the more preferable upper limit is 70, the more preferable lower limit is 20, and the still more preferable upper limit is 60.
The durometer hardness can be measured by using the durometer type D by a method conforming to ISO 18517.
[0050]
The preferable lower limit of the specific gravity of the polyester-based elastomer is 0.95, and the preferable upper limit is 1.20. By setting the specific gravity to 0.95 or more, heat resistance can be imparted, and peeling from the solvent-sealed portion can be suppressed when the container is coated as a heat-shrinkable label. Further, by setting the specific gravity to 1.20 or less, the adhesive strength between the front and back layers and the intermediate layer can be increased.
The more preferable lower limit of the specific gravity is 0.98, and the more preferable upper limit is 1.18.
The specific gravity can be measured by an underwater substitution method by a method according to ASTM D 792.
[0051]
The preferable lower limit of the tensile elastic modulus of the polyester-based elastomer constituting the adhesive layer is 1 MPa, and the preferable upper limit is 1000 MPa. If the tensile elastic modulus is less than 1 MPa, the mechanical strength of the adhesive layer tends to decrease. When the tensile elastic modulus exceeds 1000 MPa, the adhesive strength between the front and back layers and the intermediate layer tends to decrease. The more preferable lower limit of the tensile elastic modulus is 5 MPa, and the more preferable upper limit is 900 MPa. The tensile modulus can be measured by a method according to ASTM-882 (TestA).
[0052]
The preferable lower limit of the glass transition temperature of the polyester elastomer constituting the adhesive layer is −70 ° C., the more preferable lower limit is −35 ° C., the more preferable lower limit is −30 ° C., the preferred upper limit is 55 ° C., and the more preferable upper limit is 53 ° C. A more preferable upper limit is 50 ° C.
When the glass transition temperature is −70 ° C. or higher, resin blocking is less likely to occur, and the handleability can be improved. When the glass transition temperature is 55 ° C. or lower, the adhesive strength between the front and back layers and the intermediate layer can be improved.
The glass transition temperature of the polyester-based elastomer can be calculated from the tan δ peak obtained by a method based on ISO 6721-4.
[0053]
The polyester-based elastomer may be a modified product. As the modified product, for example, a polyester-based elastomer modified by grafting an α, β-ethylenically unsaturated carboxylic acid onto the polyester-based elastomer can be exemplified.
Examples of the α, β-ethylenic unsaturated carboxylic acid include unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrofumaric acid, itaconic acid, citraconic acid, crotonic acid and isocrotonic acid; succinic acid 2 -Octen-1-yl anhydride, 2-dodecene-1-yl succinate, 2-octadecene-1-yl succinate, maleic anhydride, 2,3-dimethylmaleic anhydride, bromomalein Acid Anhydride, Dichloromaleic Anhydride, Citraconic Acid Anhydride, Itaconic Acid Anhydride, 1-Buten-3,4-dicarboxylic Acid Anhydride, 1-Cyclopentene-1,2-dicarboxylic Acid Anhydride, 1,2, 3,6-Tetrahydrophthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride, 5-norbornen- 2,3-dicarboxylic acid anhydride, methyl-5-norbornen-2,3-dicarboxylic acid anhydride, endo-bicyclo [2.2.2] Oct-5-en-2,3-dicarboxylic acid anhydride, bicyclo [2.2.2] Examples thereof include unsaturated carboxylic acid anhydrides such as Oct-7-en-2,3,5,6-tetracarboxylic acid anhydride. Among these, acid anhydride is preferable because of its high reactivity.
[0054]
The content of the polyester-based elastomer in the adhesive layer has a preferable lower limit of 0.3% by weight and a preferable upper limit of 80% by weight.
When the content of the polyester-based elastomer is in the above range, good sealing strength can be obtained.
The content of the polyester-based elastomer has a more preferable lower limit of 0.5% by weight, a further preferable lower limit of 0.7% by weight, a further preferable lower limit of 0.8% by weight, a more preferable upper limit of 28% by weight, and further preferable. The upper limit is 27% by weight, and the more preferable upper limit is 26% by weight.
[0055]
The adhesive layer contains additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, a light stabilizer, a lubricant, an antioxidant, a flame retardant, an antibacterial agent, a fluorescent whitening agent, and a colorant, if necessary. You may.
[0056]
(Film)
The thickness of the entire heat-shrinkable multilayer film of the present invention has a preferable lower limit of 10 μm, a preferable upper limit of 100 μm, a more preferable lower limit of 15 μm, a more preferable upper limit of 80 μm, a further preferable lower limit of 20 μm, and further. The preferred upper limit is 70 μm. When the thickness of the entire heat-shrinkable multilayer film is within the above range, excellent heat-shrinkability, excellent converting property such as printing or center sealing, and excellent wearability can be obtained.
Further, in the heat-shrinkable multilayer film of the present invention, the thickness of the front and back layers is preferably 5% at a preferable lower limit and 25% at a preferable upper limit with respect to the thickness of the entire heat-shrinkable multilayer film, and the thickness of the intermediate layer is The preferred lower limit for the thickness of the entire heat-shrinkable multilayer film is 50%, and the preferred upper limit is 90%. When the thickness of the front and back layers and the intermediate layer is within the above range, high interlayer strength, high transparency and the like can be obtained.
[0057]
In the heat-shrinkable multilayer film of the present invention, the thickness of the adhesive layer has a preferable lower limit of 0.3 μm and a preferable upper limit of 3.0 μm. If the thickness of the adhesive layer is less than 0.3 μm, the adhesive layer may not have sufficient adhesiveness. If the thickness of the adhesive layer exceeds 3.0 μm, the heat shrinkage characteristics and optical characteristics of the heat-shrinkable multilayer film may deteriorate. The more preferable lower limit of the thickness of the adhesive layer is 0.5 μm, and the more preferable upper limit is 2.0 μm.
By adjusting the thickness of the front and back layers and the intermediate layer by subtracting the thickness of the adhesive layer, the thickness of the entire heat-shrinkable multilayer film can be adjusted.
[0058]
Further, for example, the heat-shrinkable multilayer film of the present invention has a five-layer structure of a front surface layer (A) / an adhesive layer (E) / an intermediate layer (B) / an adhesive layer (E) / a back surface layer (C), and has a thermal structure. When the thickness of the entire shrinkable multilayer film is 40 μm, the thickness of the front surface layer (A) and the back surface layer (C) is preferably 2.0 to 10.0 μm, respectively, preferably 3.0. It is more preferably about 8.0 μm. The thickness of the adhesive layer (E) is preferably 0.3 to 3.0 μm, more preferably 0.5 to 2.0 μm. The thickness of the intermediate layer (B) is preferably 19.0 to 35.4 μm, more preferably 20.0 to 33.0 μm.
[0059]
Further, the heat-shrinkable multilayer film of the present invention has a surface layer (A) / adhesive layer (E) / intermediate layer (B) / adhesive layer (E) / intermediate layer (B) / adhesive layer (E) / intermediate layer (B). ) / Adhesive layer (E) / Adhesive layer (C) / Intermediate layer (C) / Adhesive layer (E) unit is repeated between the front surface layer (A) and the back surface layer (C). It may be configured. When the total thickness of the heat-shrinkable multilayer film is 40 μm, the thickness of the front surface layer (A) and the back surface layer (C) is preferably 2.0 to 10.0 μm, respectively. It is more preferably 0 to 8.0. The total thickness of the adhesive layer (E) is preferably 1.0 to 10.0 μm, more preferably 1.5 to 8.0 μm. The total thickness of the intermediate layer (B) is preferably 18.0 to 34.0 μm, more preferably 19.0 to 31.0 μm.
[0060]
As a method of repeatedly forming the adhesive layer (E) / intermediate layer (C) / adhesive layer (E) unit between the front surface layer (A) and the back surface layer (C), a resin extruded from a plurality of extruders is used. The units may be merged by a feed block, or the adhesive layer (E) / intermediate layer (C) / adhesive layer (E) units may be merged and then the repeating unit may be formed by using a multiplier.
[0061]
When the adhesive layer (E) / intermediate layer (C) / adhesive layer (E) unit is repeatedly configured between the front surface layer (A) and the back surface layer (C), stress is dispersed and peeled off when an impact is applied to the label. Can be suppressed.
[0062]
In the heat-shrinkable multilayer film of the present invention, the shrinkage rate in the main shrinkage direction is preferably 5 to 50%, more preferably 8 to 47%, still more preferably 10 to 45%, and particularly preferably 15 to 15 at 70 ° C. for 10 seconds. 45%, preferably 35-70% at 80 ° C. for 10 seconds, more preferably 38-69%, still more preferably 41-68%, particularly preferably 43-67%, preferably 65-85% in boiling water for 10 seconds. , More preferably 68 to 83%, still more preferably 70 to 82%. By setting such a shrinkage rate, excellent shrinkage finish can be imparted in hot air tunnels and steam tunnels.
[0063]
In the heat-shrinkable multilayer film of the present invention, the preferable lower limit of the interlayer strength at room temperature in the direction orthogonal to the main shrinkage direction (TD direction) (MD direction) is 0.05 N / 10 mm, and the more preferable lower limit is 0.1 N / 10 mm. The preferred upper limit is 15N / 10mm, and the more preferable upper limit is 10N / 10mm.
Further, in the heat-shrinkable multilayer film of the present invention, the preferable lower limit of the interlayer strength in the main shrinkage direction (TD direction) is 0.05 N / 10 mm, the more preferable lower limit is 0.1 N / 10 mm, and the preferable upper limit is 15 N / 10 mm. The preferred upper limit is 10 N / 10 mm.
[0064]
In the heat-shrinkable multilayer film of the present invention, the preferable lower limit of the seal strength is 2.35 N / 10 mm, the more preferable lower limit is 2.4 N / 10 mm, the preferable upper limit is 15 N / 10 mm, and the more preferable upper limit is 10 N / 10 mm.
[0065]
The method for producing the heat-shrinkable multilayer film of the present invention is not particularly limited, but a method in which each layer is simultaneously molded by a coextrusion method is preferable. When the coextrusion method is coextrusion with a T-die, the laminating method may be a feed block method, a multi-manifold method, or a method in which these are used in combination.
[0066]
As a method for producing the heat-shrinkable multilayer film of the present invention, specifically, for example, the raw materials constituting the front and back layers, the intermediate layer and the adhesive layer are charged into an extruder, and a sheet is formed by using a multilayer die. A method of extruding the film, cooling and solidifying it with a take-up roll, and then stretching it to one or two axes can be mentioned.
As the stretching method, for example, a roll stretching method, a tenter stretching method, or a combination thereof can be used. The stretching temperature varies depending on the softening temperature of the resin constituting the film, the shrinkage characteristics required for the heat-shrinkable multilayer film, etc., but the preferable lower limit is 65 ° C, the preferable upper limit is 120 ° C, and the more preferable lower limit is 70 ° C. A more preferable upper limit is 115 ° C. The stretching ratio in the main shrinkage direction varies depending on the resin constituting the film, the stretching means, the stretching temperature, etc., but is preferably 3 times or more, more preferably 4 times or more, preferably 7 times or less, and more. It is preferably 6.5 times or less. By setting such a stretching temperature and stretching ratio, excellent thickness accuracy can be achieved, and when the perforations are torn, delamination occurs and only the front and back layers on the inner surface side remain in the container. It can be prevented.
[0067]
The use of the heat-shrinkable multilayer film of the present invention is not particularly limited, but the heat-shrinkable multilayer film of the present invention can produce a heat-shrinkable label having high sealing strength regardless of the interlayer strength, and also has transparency. Since it is excellent, it is suitably used as a base film for heat-shrinkable labels attached to containers such as PET bottles and metal cans. A heat-shrinkable label using the heat-shrinkable multilayer film of the present invention is also one of the present inventions.
Effect of the invention
[0068]
According to the present invention, it is possible to produce a heat-shrinkable label having high sealing strength regardless of the interlayer strength, and it is possible to provide a heat-shrinkable multilayer film having excellent transparency. Further, it is possible to provide a heat-shrinkable label using the heat-shrinkable multilayer film.
A brief description of the drawing
[0069]
[Fig. 1] Fig. 1 is a schematic view showing a solvent-sealed portion of a heat-shrinkable label.
[Fig. 2] Fig. 2 is a schematic view showing a peeled state of a solvent seal portion.
[Fig. 3] Fig. 3 is a schematic diagram showing a film peeling method in an interlayer strength evaluation.
FIG. 4 is a schematic diagram showing a film peeling method in an interlayer strength evaluation.
Embodiment for carrying out the invention
[0070]
Hereinafter, embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
In the examples and comparative examples, the following raw materials were used.
[0071]
(Polymer resin)
-PET-1: 100 mol% of the dicarboxylic acid component derived from terephthalic acid, 65 mol% of the diol component derived from ethylene glycol, 20 mol% of the component derived from diethylene glycol, 1 , 4-Aromatic polyester copolymer containing 15 mol% of component derived from cyclohexanedimethanol (glass transition temperature 69 ° C.)
・ PET-2: 70 mol% of component derived from terephthalic acid as a dicarboxylic acid component, isophthal Aromatic polyester copolymer containing 30 mol% of an acid-derived component and 100 mol% of an ethylene glycol-derived component as a diol component (glass transition temperature 70 ° C.)
・ PET-3: To terephthalic acid as a dicarboxylic acid component Aroma containing 100 mol% of the derived component, 70 mol% of the component derived from ethylene glycol as a diol component, 10 mol% of the component derived from diethylene glycol, and 20 mol% of the component derived from 1,4-cyclohexanedimethanol. Group polyester copolymer (glass transition temperature 72 ° C.)
・ PET-4: 100 mol% of component derived from terephthalic acid as a dicarboxylic acid component <70 mol% of component derived from ethylene glycol as a diol component, 1,4- Aromatic polyester copolymer containing 30 mol% of a component derived from cyclohexanedimethanol (glass transition temperature 82 ° C.)
(polystyrene resin)
PS-1: styrene-butadiene block copolymer (styrene component 76% by weight, 24% by weight of butadiene component, Vicat softening temperature 70 ° C, MFR 8 g / 10 minutes)
-PS-2: styrene-butadiene block copolymer (78% by weight of styrene component, 22% by weight of butadiene component, Vicat softening temperature 72 ° C., MFR 7g / 10 minutes)
(Polyester-based elastomer) -TPE
-1: As a hard segment Non-modifying polyester-polyester block copolymer composed of polyester and polyether as a soft segment (manufactured by Toray DuPont, Hytrel 2521, durometer hardness 55, glass transition temperature 45 ° C)
[0072]
(Example 1)
As the resin constituting the front and back layers, 100% by weight of a polyester resin (PET-1) was used.
As the resin constituting the intermediate layer, 100% by weight of polystyrene resin (PS-2) was used.
As the resin constituting the adhesive layer, 75% by weight of the polyester resin (PET-1), 20% by weight of the polystyrene resin (PS-1) and 5% by weight of the polyester elastomer (TPE-1) were used.
These were put into an extruder having a barrel temperature of 160 to 250 ° C., extruded into a sheet having a five-layer structure from a multilayer die at 250 ° C., and cooled and solidified by a take-up roll at 30 ° C. Then, after stretching at a stretching ratio of 6 times in a tenter stretching machine having a preheating zone of 105 ° C., a stretching zone of 90 ° C., and a heat fixing zone of 85 ° C., the film is wound by a winder so that the direction orthogonal to the main contraction direction is MD. , A heat-shrinkable multilayer film having a main shrinkage direction of TD was obtained.
The obtained heat-shrinkable multilayer film has a total thickness of 40 μm, and has a front / back layer (5.5 μm) / adhesive layer (0.9 μm) / intermediate layer (27.2 μm) / adhesive layer (0.9 μm) / front and back. It had a five-layer structure of layers (5.5 μm).
[0073]
(Example 2)
As the resin constituting the adhesive layer, 75% by weight of polyester resin (PET-2), 20% by weight of polystyrene resin (PS-1) and 5% by weight of polyester elastomer (TPE-1) are used. Using.
A heat-shrinkable multilayer film having a five-layer structure was obtained in the same manner as in Example 1.
[0074]
(Example 3)
As the resin constituting the adhesive layer, 75% by weight of polyester resin (PET-3), 20% by weight of polystyrene resin (PS-1) and 5% by weight of polyester elastomer (TPE-1) are used. Using.
A heat-shrinkable multilayer film having a five-layer structure was obtained in the same manner as in Example 1.
[0075]
(Example 4)
As the resin constituting the adhesive layer, 50% by weight of polyester resin (PET-1), 45% by weight of polystyrene resin (PS-1) and 5% by weight of polyester elastomer (TPE-1) are used. Using.
A heat-shrinkable multilayer film having a five-layer structure was obtained in the same manner as in Example 1.
[0076]
(Example 5)
As the resin constituting the adhesive layer, 90% by weight of polyester resin (PET-1), 5% by weight of polystyrene resin (PS-1) and 5% by weight of polyester elastomer (TPE-1) are used. Using.
A heat-shrinkable multilayer film having a five-layer structure was obtained in the same manner as in Example 1.
[0077]
(Example 6)
As the resin constituting the adhesive layer, 85% by weight of polyester resin (PET-1), 10% by weight of polystyrene resin (PS-1) and 5% by weight of polyester elastomer (TPE-1) are used. Using.
A heat-shrinkable multilayer film having a five-layer structure was obtained in the same manner as in Example 1.
[0078]
(Example 7)
As the resin constituting the adhesive layer, 79% by weight of polyester resin (PET-1), 20% by weight of polystyrene resin (PS-1) and 1% by weight of polyester elastomer (TPE-1) are used. Using.
A heat-shrinkable multilayer film having a five-layer structure was obtained in the same manner as in Example 1.
[0079]
(Example 8)
As the resin constituting the adhesive layer, 77% by weight of polyester resin (PET-1), 20% by weight of polystyrene resin (PS-1) and 3% by weight of polyester elastomer (TPE-1) are used. Using.
A heat-shrinkable multilayer film having a five-layer structure was obtained in the same manner as in Example 1.
[0080] [0080]
(Example 9)
As the resin constituting the adhesive layer, 55% by weight of polyester resin (PET-1), 20% by weight of polystyrene resin (PS-1) and 25% by weight of polyester elastomer (TPE-1) are used. Using.
A heat-shrinkable multilayer film having a five-layer structure was obtained in the same manner as in Example 1.
[0081]
(Comparative Example 1)
As the resin constituting the adhesive layer, 75% by weight of polyester resin (PET-4), 20% by weight of polystyrene resin (PS-1) and 5% by weight of polyester elastomer (TPE-1) are used. Using.
A heat-shrinkable multilayer film having a five-layer structure was obtained in the same manner as in Example 1.
[0082]
(Evaluation)
The heat-shrinkable multilayer films obtained in Examples and Comparative Examples were evaluated as follows. Table 1 shows the composition and evaluation results of the heat-shrinkable multilayer film.
[0083]
(1) Delamination strength A
heat-shrinkable multilayer film is cut into a size of 100 mm in length × 10 mm in width, and a part of the edge of the film is delaminated as shown in FIG. As shown in the above, the strength when peeled in the 180-degree direction was measured using a detachability strength tester (HEIDON TYPE17, manufactured by Shinto Kagaku Co., Ltd.). Regarding the delamination strength, the delamination strength in the TD direction and the MD direction was measured using four test pieces for each Example and Comparative Example, and the average value was calculated.
[0084]
(2) Seal strength
Both ends of the heat-shrinkable multilayer film are bonded using a mixed solvent of 100 parts by weight of 1,3-dioxolane and 30 parts by weight of cyclohexane, and the bonded seal portion within a width of 10 mm is 100 mm in length × Cut to a size of 10 mm in width, peel off a part of the seal part, and then peel off in the 180 ° C direction at a tensile speed of 200 mm / min. ) Was measured. Regarding the seal strength, the seal strength in the TD direction was measured using four test pieces for each Example and Comparative Example, the average value was calculated, and the seal strength was evaluated according to the following criteria.
〇: Seal strength is 2.4 N / 10 mm or more
×: Seal strength is less than 2.4 N / 10 mm Further
, the relationship with delamination strength was evaluated according to the following criteria.
〇: Delamination strength in either the TD direction or MD direction is 0.5 N / 10 mm or less, seal strength is 2.4 N / 10 mm or more
Δ: Delamination strength in both the TD direction and MD direction is 0.5 N / 10 mm. Exceeds, seal strength is 2.4N / 10mm or more
×: Seal strength is less than 2.4N / 10mm
[0085]
(3) Haze
The obtained heat-shrinkable multilayer film was measured for haze by a method conforming to JIS K 7136 using NDH5000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.) and evaluated according to the following criteria.
〇: Haze is less than 6%
×: Haze is 6% or more
[0086]
[table 1]

Industrial applicability
[0087]
According to the present invention, it is possible to produce a heat-shrinkable label having high sealing strength regardless of the interlayer strength, and it is possible to provide a heat-shrinkable multilayer film having excellent transparency. Further, it is possible to provide a heat-shrinkable label using the heat-shrinkable multilayer film.
Code description
[0088]
1 Front and back layers
2 Intermediate layer
3 Adhesive layer
The scope of the claims
[Claim 1]
A heat-shrinkable multilayer film in which a front and back layer containing a polyester resin and an intermediate layer containing a polystyrene resin are laminated via an adhesive layer, and the
adhesive layer has a glass transition temperature of 77 ° C.
A heat-shrinkable multilayer film comprising the following polyester-based resin .
[Claim 2]
The first aspect of claim 1, wherein the adhesive layer contains 2 to 95% by weight of a polystyrene resin, 4.7 to 96% by weight of a polyester resin, and 0.3 to 80% by weight of a polyester elastomer. Heat shrinkable multilayer film.
[Claim 3]
The polyester resin constituting the adhesive layer contains a dicarboxylic acid component and a diol component, and among the 100 mol% of the dicarboxylic acid component, 60 to 100 mol% of the component derived from terephthalic acid and the component derived from isophthalic acid are contained. It contains 0 to 40 mol%, and out of 100 mol% of the diol component, 50 to 100 mol% is a component derived from ethylene glycol, 0 to 25 mol% is a component derived from diethylene glycol, and 1,4-cyclohexanedimethanol is derived. The heat-shrinkable multilayer film according to claim 1 or 2, which contains 0 to 25 mol% of the components to be used.
[Claim 4]
The heat-shrinkable multilayer film according to claim 1, 2 or 3, wherein the polystyrene-based resin constituting the adhesive layer is an aromatic vinyl hydrocarbon-conjugated diene copolymer.
[Claim 5]
The heat-shrinkable multilayer film according to claim 1, 2, 3 or 4, wherein the polyester-based elastomer constituting the adhesive layer is composed of polyester as a hard segment and polyether as a soft segment.
[Claim 6]
A heat-shrinkable label comprising the heat-shrinkable multilayer film according to claim 1, 2, 3, 4 or 5.