JP2021126834A - Heat-shrinkable film and heat-shrinkable label - Google Patents

Abstract

To provide a heat-shrinkable multilayer film that can reduce an amount of use of fossil resources and can express high performance in physical properties such as mechanical properties, and a heat-shrinkable label having the heat-shrinkable multilayer film.SOLUTION: A heat-shrinkable film has at least one of a layer containing a polyester resin and a layer containing a polystyrenic resin, the heat-shrinkable film containing a biomass-derived component.SELECTED DRAWING: None

Description

The present invention relates to a heat-shrinkable film capable of reducing the amount of fossil resources used and exhibiting high performance in terms of physical properties such as mechanical properties. It also relates to a heat shrinkable label containing the heat shrinkable film.

In recent years, many containers such as PET bottles and glass bottles are equipped with heat-shrinkable labels obtained by printing or the like on a base film made of a thermoplastic resin.
Polystyrene-based resin films having excellent low-temperature shrinkage and polyester-based resin films having excellent heat resistance and solvent resistance are often used for heat-shrinkable labels.
Further, a multilayer film having a front and back layer containing a polyester resin and an intermediate layer containing a polystyrene resin has been studied so as to have both of these characteristics.

On the other hand, in recent years, there has been an increasing demand for the construction of a sound material-cycle society and a low-carbon society toward the realization of a sustainable society, and it is desired to break away from fossil resources. Since all of the polystyrene-based resins and the like use petroleum resources as raw materials, they have problems such as depletion of petroleum resources and generation of harmful gas in continuous use.

In response to such problems, attempts have been made to produce polyester-based resins, which are general-purpose plastics, from biomass raw materials.
For example, Patent Document 1 discloses a method for producing a resin raw material such as ethylene glycol and terephthalic acid using biomass as a raw material.

JP-A-2007-176873

An object of the present invention is to provide a heat-shrinkable film capable of reducing the amount of fossil resources used and exhibiting high performance in terms of physical properties such as mechanical properties. Another object of the present invention is to provide a heat-shrinkable label containing the heat-shrinkable film.

The present invention is a heat-shrinkable film having at least one layer among a layer containing a polyester-based resin and a layer containing a polystyrene-based resin, and the heat-shrinkable film is a heat-shrinkable film containing a component derived from biomass. It is a sex film.
Hereinafter, the present invention will be described in detail.

The present inventors mechanically use a resin containing a biomass-derived component in a heat-shrinkable film having at least one layer among a layer containing a polyester-based resin and a layer containing a polystyrene-based resin. It has been found that a heat-shrinkable film capable of exhibiting high performance in terms of physical properties such as characteristics can be obtained. In addition, "biomass" means "renewable, biologically-derived organic resources excluding fossil resources".
Therefore, it has been found that the amount of raw materials obtained from fossil resources can be reduced as compared with the conventional case, and the amount of fossil resources used can be reduced, and the present invention has been completed.

The heat-shrinkable film of the present invention has at least one layer among a layer containing a polyester-based resin and a layer containing a polystyrene-based resin.
The heat-shrinkable film of the present invention may be composed of only a layer containing a polyester resin, or may be composed of only a layer containing a polystyrene resin, and the front and back surfaces containing the polyester resin. It may have a layer and an intermediate layer containing a polystyrene resin.
Further, when the heat-shrinkable film of the present invention is composed of only one layer containing a polyester resin, it may have only one layer containing the polyester resin, and may have two or more layers. It may be a thing.
Further, when the heat-shrinkable film of the present invention is composed of only a layer containing a polystyrene-based resin, the film may have only one layer containing the polystyrene-based resin, and may have two or more layers. It may be a thing.
In the present specification, the front and back layers mean both the front surface layer and the back surface layer.

When the heat-shrinkable film of the present invention has a front and back layer and an intermediate layer, at least one of the polyester resin constituting the front and back layers and the polystyrene resin constituting the intermediate layer contains a component derived from biomass. It suffices, and only the polyester-based resin constituting the front and back layers may contain a biomass-derived component, and only the polystyrene-based resin constituting the intermediate layer may contain a biomass-derived raw material. Further, both the polyester-based resin and the polystyrene-based resin may contain a component derived from biomass.
Whether or not the polyester resin and the polystyrene resin contain biomass-derived components can be confirmed by the presence or absence of radioactive carbon (C14) in the resin.
Since carbon dioxide in the atmosphere contains C14 in a certain ratio (105.5 pMC), it is known that the content of C14 in plants that grow by taking in carbon dioxide in the atmosphere is also about 105.5 pMC. Has been done. It is also known that fossil resources contain almost no C14. Therefore, by measuring the ratio of C14 contained in the total carbon atoms in the polyester resin or the polystyrene resin, it is possible to confirm whether or not the biomass-derived component is contained.
The presence or absence of the above-mentioned radioactive carbon (C14) can be confirmed, for example, by using the same method as the measurement of the biomass degree described later.

When the heat-shrinkable film of the present invention is composed of only the layer containing the polyester-based resin, the polyester-based resin constituting the layer containing the polyester-based resin is composed of only the polyester-based resin containing a component derived from biomass. It may be a polyester resin containing a biomass-derived component and a polyester resin not containing a biomass-derived component.
When the heat-shrinkable film of the present invention has the front and back layers and the intermediate layer, the polyester resin constituting the layer containing the polyester resin may contain a component derived from biomass. It may not contain components derived from biomass. Further, the polyester-based resin may contain a polyester-based resin containing a biomass-derived component and a polyester-based resin containing no biomass-derived component.

Examples of the polyester-based resin constituting the layer containing the polyester-based resin include those obtained by polycondensing a dicarboxylic acid component and a diol component.
When the polyester-based resin contains a biomass-derived component, the polyester-based resin may contain a biomass-derived dicarboxylic acid component, may contain a biomass-derived diol component, and may contain biomass. It may contain both a derived dicarboxylic acid component and a biomass-derived 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 itacone. Acids, decamethylenecarboxylic acids, anhydrides thereof, lower alkyl esters and the like can be mentioned.
As the dicarboxylic acid, terephthalic acid and isophthalic acid are preferable.

Of the 100 mol% of the dicarboxylic acid component, the component derived from terephthalic acid is preferably contained in an amount of 50 to 100 mol%, more preferably 60 to 100 mol%.
Further, out of 100 mol% of the dicarboxylic acid component, it is preferable to contain 0 to 50 mol% of the component derived from isophthalic acid, and more preferably 0 to 40 mol%.

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, Aliphatic diols such as 5-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 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.

Of the 100 mol% of the diol component, the component derived from ethylene glycol is preferably contained in an amount of 40 to 100 mol%, more preferably 50 to 100 mol%.
Of the 100 mol% of the diol component, the component derived from diethylene glycol is preferably contained in an amount of 0 to 40 mol%, more preferably 0 to 30 mol%.
Of the 100 mol% of the diol component, the component derived from 1,4-cyclohexanedimethanol is preferably contained in an amount of 0 to 70 mol%, more preferably 0 to 60 mol%.

The diol component may contain a component derived from biomass, and among them, the diol component derived from biomass is derived from ethylene glycol, 1,4-butanediol, diethylene glycol, and 1,4-cyclohexanedimethanol. It preferably contains a component, and more preferably contains a component derived from ethylene glycol.
Examples of the above-mentioned ethylene glycol derived from biomass include those using biomass ethanol produced from biomass as a raw material. For example, the above-mentioned ethylene glycol derived from biomass can be produced by a conventionally known method using biomass ethanol as a raw material.

The content of the biomass-derived component in the diol component is preferably 30 mol% or more, more preferably 50 mol% or more, and preferably 100 mol% or less.
Within the above range, there is an advantage of reducing the environmental load.

The content of biomass-derived ethylene glycol in the diol component is preferably 30 mol% or more, more preferably 50 mol% or more, and preferably 100 mol% or less.

The biomass degree of the polyester resin is preferably 1% or more, more preferably 5% or more, and preferably 100% or less.
Within the above range, there is an advantage of reducing the environmental load.
The biomass degree is a value obtained by measuring the content of the ancestor derived from biomass by measuring radiocarbon (C14). The biomass degree can be measured using an accelerator mass spectrometer based on ISO16620-2: 2015.

Further, the polyester-based resin may contain a plurality of polyester-based resins having different biomass degrees.
When the polyester resin is a mixed resin containing a plurality of polyester resins having different biomass degrees, the biomass degree of the mixed resin can be measured based on ISO16620-2: 2015. The biomass degree can also be calculated based on the weight ratio of each polyester resin in the mixed resin and the biomass degree.

When the polyester resin contains a polyester resin containing a biomass-derived component, the content of the polyester resin containing a biomass-derived component in the polyester resin has a preferable lower limit of 5% by weight and a more preferable lower limit of 10. By weight%, the preferred upper limit is 100% by weight.

The preferable lower limit of the glass transition temperature of the polyester resin is 55 ° C., and the preferable upper limit is 95 ° C. If the glass transition temperature is less than 55 ° C., the shrinkage start temperature of the heat-shrinkable multilayer film may become too low, the natural shrinkage rate may increase, or blocking may easily occur. When the glass transition temperature exceeds 95 ° C., the low-temperature shrinkage and shrinkage finish of the heat-shrinkable multilayer film are reduced, the low-temperature shrinkage is significantly reduced over time, and resin whitening is likely to occur during stretching. It may become. The more preferable lower limit of the glass transition temperature is 60 ° C., and the more preferable upper limit is 90 ° C. A more preferable lower limit is 65 ° C., and a further preferable upper limit is 85 ° C.
The glass transition temperature can be measured by a method conforming to ISO 3146. When the polyester resin is a mixed resin containing a plurality of polyester resins having different glass transition temperatures, the glass transition temperature of the mixed resin is the weight ratio of each polyester resin in the mixed resin to the glass transition temperature. It means the apparent glass transition temperature calculated based on.

The preferable lower limit of the tensile elastic modulus of the polyester resin exceeds 1000 MPa, and the preferable upper limit is 4000 MPa. If the tensile elastic modulus is 1000 MPa or less, the shrinkage start temperature of the heat-shrinkable film may become too low, or the natural shrinkage rate may increase. If the tensile elastic modulus exceeds 4000 MPa, the low-temperature shrinkage and shrinkage finish of the heat-shrinkable multilayer film may decrease, or the low-temperature shrinkage over time may decrease significantly. 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).

As the polyester-based resin constituting the layer containing the polyester-based resin, 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. good.

The layer containing the polyester resin can be used as an antioxidant, a heat stabilizer, an ultraviolet absorber, a light stabilizer, a lubricant, an antistatic agent, an antiblocking agent, a flame retardant, an antibacterial agent, and a fluorescent whitening agent, if necessary. It may contain additives such as agents and colorants.

When the heat-shrinkable film of the present invention is composed of only the polystyrene-based resin-containing layer, the polystyrene-based resin constituting the polystyrene-based resin-containing layer is composed of only the polystyrene-based resin containing a biomass-derived component. It may be a polystyrene resin containing a biomass-derived component and a polystyrene resin containing no biomass-derived component.
When the heat-shrinkable film of the present invention has the front and back layers and the intermediate layer, the polystyrene resin constituting the layer containing the polystyrene resin may contain a component derived from biomass. It may not contain components derived from biomass. Further, the polystyrene-based resin may contain a polystyrene-based resin containing a biomass-derived component and a polystyrene-based resin containing no biomass-derived component.

Examples of the polystyrene-based resin constituting the layer containing the polystyrene-based resin include aromatic vinyl hydrocarbon-conjugated diene copolymer, aromatic vinyl hydrocarbon-conjugated diene copolymer and aromatic vinyl hydrocarbon-fat. Examples thereof include a mixed resin with a group unsaturated carboxylic acid ester copolymer and rubber-modified impact-resistant polystyrene. By using the above polystyrene-based resin, the heat-shrinkable multilayer film of the present invention can start shrinking from a low temperature and has high shrinkage.

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.
Further, the component derived from the aromatic vinyl hydrocarbon may contain a component derived from biomass. Further, the component derived from the conjugated diene may contain a component derived from biomass.
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, 1,3-hexadiene. And so on. These may be used alone or in combination of two or more.

The aromatic vinyl hydrocarbon-conjugated diene copolymer is particularly excellent in heat shrinkage, and therefore preferably contains 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 prepare 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) 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 and pelletizing each resin with a specific composition using an extruder is used. You may.

Among the aromatic vinyl hydrocarbon components, the content of the biomass-derived component is preferably 5% by weight or more, more preferably 30% by weight or more, and preferably 100% by weight or less.
The content of the biomass-derived component in the conjugated diene component is preferably 5% by weight or more, more preferably 30% by weight or more, and preferably 100% by weight or less.

The polystyrene-based resin preferably has a styrene component content of 65% by weight or more, more preferably 70% by weight or more, preferably 90% by weight or less, and preferably 85% by weight or less. Is more preferable.
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. 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.

Further, the polystyrene-based resin preferably contains a styrene component derived from biomass.
Examples of the biomass-derived styrene include those made from ethylene produced from biomass-derived naphtha as a raw material. For example, the above-mentioned biomass-derived styrene can be produced by a conventionally known method using biomass-derived naphtha as a raw material.

When the polystyrene-based resin contains a styrene component derived from biomass, the content of the styrene-derived component derived from biomass in the polystyrene-based resin is preferably 5% by weight or more, more preferably 30% by weight or more. , 100% by weight or less is preferable.

The polystyrene-based resin preferably has a conjugated diene content of 10% by weight or more, more preferably 15% by weight or more, preferably 35% by weight or less, and preferably 30% by weight or less. More preferred.

Further, the polystyrene-based resin preferably contains a conjugated diene component derived from biomass, and more preferably contains a butadiene component derived from biomass.
Examples of the above-mentioned biomass-derived butadiene include those produced from biomass-derived naphtha as a raw material. For example, the above-mentioned biomass-derived butadiene can be produced by a conventionally known method using biomass-derived naphtha as a raw material.

When the polystyrene-based resin contains a biomass-derived conjugated diene component, the content of the biomass-derived conjugated diene component in the polystyrene-based resin is preferably 5% by weight or more, preferably 30% by weight or more. More preferably, it is 100% by weight or less.

When the polystyrene-based resin contains a biomass-derived butadiene component, the content of the biomass-derived butadiene component in the polystyrene-based resin is preferably 5% by weight or more, more preferably 30% by weight or more. , 100% by weight or less is preferable.

The content of the biomass-derived component in the polystyrene resin is preferably 5% by weight or more, more preferably 30% by weight or more, and preferably 100% by weight or less.

The biomass degree of the polystyrene resin is preferably 10% or more, more preferably 30% or more, and preferably 100% or less.
The biomass degree can be measured using an accelerator mass spectrometer based on ISO16620-2: 2015.

Further, the polystyrene-based resin may contain a plurality of polystyrene-based resins having different biomass degrees.
When the polystyrene-based resin is a mixed resin containing a plurality of polystyrene-based resins having different biomass degrees, the biomass degree of the mixed resin can be measured based on ISO16620-2: 2015. The biomass degree can also be calculated based on the weight ratio of each polystyrene-based resin in the mixed resin and the biomass degree.

The preferable lower limit of the Vicat softening temperature of the polystyrene resin is 60 ° C., and the preferable upper limit is 85 ° C. If the Vicat softening temperature is less than 60 ° C., the low-temperature shrinkage of the heat-shrinkable multilayer film becomes too high, and wrinkles are likely to occur when the film is mounted on a container. When the Vicat softening temperature exceeds 85 ° C., the low temperature shrinkage of the heat-shrinkable multilayer film is lowered, and an unshrinked portion is likely to occur when the film is mounted on a container. The more preferable lower limit of the Vicat softening temperature is 65 ° C., and the more preferable upper limit is 80 ° C. The Vicat softening temperature can be measured by a method based on ISO 306: 1994.
When the polystyrene-based resin is a mixed resin containing a plurality of polystyrene-based resins having different Vicat softening temperatures, the Vicut softening temperature of the mixed resin is the weight ratio of each polystyrene-based resin in the mixed resin and the Bicut softening. It means the apparent polystyrene softening temperature calculated based on the temperature.

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 compliant with ISO1133.

The layer containing the polystyrene resin can be used as an antioxidant, a heat stabilizer, an ultraviolet absorber, a light stabilizer, a lubricant, an antistatic agent, a flame retardant, an antibacterial agent, an optical brightener, and a colorant, if necessary. Etc. may be contained.

When the heat-shrinkable film of the present invention has the front and back layers and the intermediate layer, the heat-shrinkable film of the present invention may consist of the front and back layers and the intermediate layer, and between the front and back layers and the intermediate layer. An adhesive layer may be interposed in the.

As the resin constituting the adhesive layer, an adhesive resin such as a styrene-based elastomer, a polyester-based elastomer, or a modified product thereof can be used.
Further, a mixed resin of a polyester resin, a polystyrene resin and a polyester elastomer can also be used.

The styrene-based elastomer includes polystyrene as a hard segment and polybutadiene, polyisoprene as a soft segment, a copolymer of polybutadiene and polyisoprene, and hydrogenated products thereof. The hydrogenated product may be a hydrogenated product in which a part of polybutadiene or polyisoprene is hydrogenated, or a hydrogenated product in which all of the polybutadiene or polyisoprene is hydrogenated.

Examples of commercially available styrene-based elastomers include "Tough Tech", "Tough Plen" (all manufactured by Asahi Kasei Chemicals), "Clayton" (manufactured by Kraton Polymer Japan), "Dynaron" (manufactured by JSR), and "Septon". "(Made by Kuraray) and the like.

Examples of the modified product of the styrene-based elastomer include those modified by a functional group such as a carboxylic acid group, an acid anhydride group, an amino group, an epoxy group and a hydroxyl group.
The preferable lower limit of the content of functional groups such as carboxylic acid group, acid anhydride group, amino group, epoxy group and hydroxyl group in the modified product of the styrene-based elastomer is 0.05% by weight, and the preferable upper limit is 5.0% by weight. Is. If the content is less than 0.05% by weight, the adhesiveness to the front surface layer and the back surface layer may be insufficient, and if it exceeds 5.0% by weight, the functional group is added. The resin may be thermally deteriorated and foreign substances such as gel may be easily generated. The more preferable lower limit of the content is 0.1% by weight, and the more preferable upper limit is 3.0% by weight.

The polyester-based elastomer is preferably a saturated polyester-based elastomer, and particularly preferably a saturated polyester-based elastomer containing a polyalkylene ether glycol segment. As the saturated polyester-based elastomer containing the polyalkylene ether glycol segment, for example, a block copolymer composed of an aromatic polyester which is a hard segment and a polyalkylene ether glycol or an aliphatic polyester which is a soft segment is preferable. Further, a polyester polyether block copolymer having a polyalkylene ether glycol as a soft segment is more preferable.

The polyester polyether block copolymer includes (i) an aliphatic and / or alicyclic diol having 2 to 12 carbon atoms, and (ii) an aromatic dicarboxylic acid and / or an aliphatic dicarboxylic acid or an alkyl ester thereof. And (iii) a polyalkylene ether glycol as a raw material, and an oligomer obtained by an esterification reaction or an ester exchange reaction is polycondensed.

As the aliphatic and / or alicyclic diol having 2 to 12 carbon atoms, for example, those generally used as a raw material for polyester, particularly a raw material for polyester-based elastomer, can be used. Specific examples thereof include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol. Among these, 1,4-butanediol or ethylene glycol is preferable, and 1,4-butanediol is particularly preferable. These diols may be used alone or in combination of two or more.

As the aromatic dicarboxylic acid, those generally used as a raw material for a polyester, particularly a raw material for a polyester-based elastomer can be used. Specific examples thereof include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid and the like. Among these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferable, and terephthalic acid is particularly preferable. These aromatic dicarboxylic acids may be used alone or in combination of two or more.

Examples of the alkyl ester of the aromatic dicarboxylic acid include dimethyl ester and diethyl ester of the aromatic dicarboxylic acid. Of these, dimethyl terephthalate and 2,6-dimethylnaphthalene dicarboxylate are preferable.

As the aliphatic dicarboxylic acid, cyclohexanedicarboxylic acid and the like are preferable, and as the alkyl ester thereof, dimethyl ester, diethyl ester and the like are preferable. In addition to the above components, a trifunctional alcohol, a tricarboxylic acid or an ester thereof may be copolymerized in a small amount, and an aliphatic dicarboxylic acid such as adipic acid or a dialkyl ester thereof may be used as a copolymerization component.

Examples of the polyalkylene ether glycol include polyethylene glycol, poly (1,2- and / or 1,3-propylene ether) glycol, poly (tetramethylene ether) glycol, poly (hexamethylene ether) glycol and the like. ..

The preferable lower limit of the number average molecular weight of the polyalkylene ether glycol is 400, and the preferable upper limit is 6000. When the number average molecular weight is 400 or more, the blocking property of the copolymer is enhanced, and when it is 6000 or less, phase separation in the system is unlikely to occur, and the polymer physical properties are easily expressed. The more preferable lower limit of the number average molecular weight is 500, the more preferable upper limit is 4000, the further preferable lower limit is 600, and the further preferable upper limit is 3000. In the present specification, the number average molecular weight means that measured by gel permeation chromatography (GPC). Further, the calibration of the GPC can be performed by using, for example, a POLYTETRAHYDROFURAN calibration kit (manufactured by POLYMER LABORATORIES in the United Kingdom).

When the adhesive layer contains a mixed resin of polyester resin, polystyrene resin and polyester elastomer, the polyester resin is the same as the polyester resin constituting the layer containing the polyester resin. Can be used. Further, as the polystyrene-based resin, the same one as the polystyrene-based resin constituting the layer containing the polystyrene-based resin can be used.
The polyester-based resin constituting the adhesive layer may contain a biomass-derived component or may not contain a biomass-derived component.
The polystyrene-based resin constituting the adhesive layer may contain a biomass-derived component or may not contain a biomass-derived component.

In the heat-shrinkable film of the present invention, the preferable lower limit of the biomass degree is 1%, the more preferable lower limit is 2%, the more preferable lower limit is 10%, the preferable upper limit is 100%, the more preferable upper limit is 95%, and the further preferable upper limit is 50. %.
Within the above range, there is an advantage that the environmental load can be reduced without impairing economic rationality and film performance.
The biomass degree can be measured using an accelerator mass spectrometer based on ISO16620-2: 2015.

The preferred lower limit of the thickness of the heat-shrinkable film of the present invention is 30 μm, and the preferred upper limit is 60 μm. By setting the thickness of the heat-shrinkable multilayer film within the above range, it is excellent in economy and easy to handle.

When the heat-shrinkable film of the present invention has a front and back layers and an intermediate layer, the preferable lower limit of the thickness of the intermediate layer when the total thickness of the heat-shrinkable film of the present invention is 45 μm is preferably 22 μm. The upper limit is 37 μm. When it is 22 μm or more, sufficient perforations can be imparted, and when it is 37 μm or less, sufficient heat resistance can be imparted. A more preferred lower limit is 26 μm and a more preferred upper limit is 36 μm.
When the heat-shrinkable film of the present invention has a front-back layer and an intermediate layer, the preferable lower limit of the thickness of the front-back layer is 3 μm, and the preferred upper limit is 3 μm when the total thickness of the heat-shrinkable film of the present invention is 45 μm. It is 10 μm. When it is 3 μm or more, sufficient oil resistance and heat resistance can be imparted, and when it is 10 μm or less, sufficient cutability at perforations can be imparted. A more preferable lower limit is 4 μm, and a more preferable upper limit is 8 μm.
When the heat-shrinkable film of the present invention has a front and back layers and an intermediate layer, the preferable lower limit of the thickness of the adhesive layer when the total thickness of the heat-shrinkable film of the present invention is 45 μm is 0.7 μm, which is preferable. The upper limit is 1.5 μm. When it is 0.7 μm or more, sufficient adhesive strength can be imparted, and when it is 1.5 μm or less, sufficient heat shrinkage characteristics can be imparted. A more preferable lower limit is 0.8 μm, and a more preferable upper limit is 1.3 μm.

Regarding the heat shrinkage characteristics of the heat shrinkable film of the present invention, when immersed in warm water at 70 ° C. for 10 seconds, the preferable lower limit of the heat shrinkage rate in the MD direction (direction orthogonal to the main shrinkage direction) is -12%. A more preferred lower limit is −7%, a preferred upper limit is 8%, and a more preferred upper limit is 3%. Further, the preferable lower limit of the heat shrinkage rate in the TD direction (main shrinkage direction) is 5%, the more preferable lower limit is 10%, the preferable upper limit is 65%, and the more preferable upper limit is 50%.
Within the above range, deformation of the container can be prevented, and rapid shrinkage due to heating can be prevented to suppress the occurrence of wrinkles and the like.
The heat shrinkage when immersed in warm water at 70 ° C. for 10 seconds means that a sample of a heat-shrinkable multilayer film was cut into a size of 100 mm × 100 mm and immersed in warm water at 70 ° C. for 10 seconds. It is a value expressed in% of the rate of change of the dimension after heating with respect to the dimension before heat treatment.

Regarding the heat shrinkage characteristics of the heat shrinkable film of the present invention, when immersed in warm water at 80 ° C. for 10 seconds, the preferable lower limit of the heat shrinkage rate in the MD direction (direction orthogonal to the main shrinkage direction) is -12%. A more preferred lower limit is -7%, a preferred upper limit is 8%, and a more preferred upper limit is 3%. Further, the preferable lower limit of the heat shrinkage rate in the TD direction (main shrinkage direction) is 35%, the more preferable lower limit is 45%, the preferable upper limit is 70%, and the more preferable upper limit is 65%.
The heat shrinkage when immersed in warm water at 80 ° C. for 10 seconds means that a sample of a heat-shrinkable multilayer film was cut into a size of 100 mm × 100 mm and immersed in warm water at 80 ° C. for 10 seconds. It is a value expressed in% of the rate of change of the dimension after heating with respect to the dimension before heat treatment.

Regarding the heat shrinkage characteristics of the heat shrinkable film of the present invention, when immersed in warm water at 90 ° C. for 10 seconds, the preferable lower limit of the heat shrinkage rate in the MD direction (direction orthogonal to the main shrinkage direction) is -10%. A more preferred lower limit is -5%, a preferred upper limit is 15%, and a more preferred upper limit is 10%. Further, the preferable lower limit of the heat shrinkage rate in the TD direction (main shrinkage direction) is 50%, the more preferable lower limit is 55%, the preferable upper limit is 80%, and the more preferable upper limit is 75%.
The heat shrinkage when immersed in warm water at 90 ° C. for 10 seconds means that a sample of a heat-shrinkable multilayer film was cut into a size of 100 mm × 100 mm and immersed in warm water at 90 ° C. for 10 seconds. It is a value expressed in% of the rate of change of the dimension after heating with respect to the dimension before heat treatment.

Regarding the heat shrinkage characteristics of the heat shrinkable film of the present invention, when immersed in warm water at 98 ° C. for 10 seconds, the preferable lower limit of the heat shrinkage rate in the MD direction (direction orthogonal to the main shrinkage direction) is 0%. The preferred lower limit is 5%, the preferred upper limit is 25%, and the more preferred upper limit is 20%. Further, the preferable lower limit of the heat shrinkage rate in the TD direction (main shrinkage direction) is 55%, the more preferable lower limit is 65%, the preferable upper limit is 85%, and the more preferable upper limit is 80%.
The heat shrinkage when immersed in warm water at 98 ° C. for 10 seconds means that a sample of a heat-shrinkable multilayer film was cut into a size of 100 mm × 100 mm and immersed in warm water at 98 ° C. for 10 seconds. It is a value expressed in% of the rate of change of the dimension after heating with respect to the dimension before heat treatment.

The natural shrinkage rate of the heat-shrinkable film of the present invention in the TD direction is preferably 3% when left at 40 ° C. for 7 days. When the natural shrinkage rate is 3% or less, the dimensional change is unlikely to occur when the heat-shrinkable film of the present invention is stored, and defects during printing can be prevented. The more preferable upper limit of the natural shrinkage rate is 2%.

The method for producing the heat-shrinkable 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. For example, in 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. Specifically, for example, a raw material constituting a layer containing a polyester resin, a raw material constituting a layer containing a polystyrene resin, and if necessary, a raw material constituting an adhesive layer are put into an extruder, and the die is used. A method can be used in which the resin is extruded into a sheet, cooled and solidified by a take-up roll, and then stretched in one or two axes.

By using the heat-shrinkable film of the present invention as a base film, a heat-shrinkable label can be obtained. Such a heat shrinkable label is also one of the present inventions.
In the heat-shrinkable label of the present invention, the heat-shrinkable multilayer film may be used as a base film, and other layers such as a printing layer may be laminated, if necessary.

As a method of attaching a heat-shrinkable label to a container, usually, after bonding the edges of the heat-shrinkable multilayer film with a solvent and processing it into a tube shape (center seal processing), the heat-shrinkable label is obtained. A method of heating and shrinking while covering the container is adopted.

According to the present invention, it is possible to provide a heat-shrinkable film capable of reducing the amount of fossil resources used and exhibiting high performance in terms of physical properties such as mechanical properties. In addition, a heat-shrinkable label containing the heat-shrinkable film can be provided.

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 reference examples, the following raw materials were used.

(Polyester resin)
-PET-1: Polyester resin containing a biomass component (component derived from terephthalic acid as a dicarboxylic acid component: 100 mol%, component derived from ethylene glycol as a diol component: 100 mol%, glass transition temperature: 75 ° C.)
-PET-2: Polyester resin containing no biomass component (component derived from terephthalic acid as a dicarboxylic acid component: 100 mol%, component derived from ethylene glycol as a diol component: 100 mol%, glass transition temperature: 75 ° C.)
-PET-3: Polyester resin containing a biomass component (component derived from terephthalic acid as a dicarboxylic acid component: 77 mol%, component derived from isophthalic acid: 23 mol%, component derived from ethylene glycol as a diol component: 100 mol) %, Glass transition temperature: 71 ° C)
-PET-4: Polyester resin containing no biomass component (component derived from terephthalic acid as a dicarboxylic acid component: 77 mol%, component derived from isophthalic acid: 23 mol%, component derived from ethylene glycol as a diol component: 100 Mol%, glass transition temperature: 71 ° C)
-PET-5: Polyester resin containing no biomass component (component derived from terephthalic acid as a dicarboxylic acid component: 100 mol%, component derived from ethylene glycol as a diol component: 65 mol%, component derived from diethylene glycol: 20 mol) %, Ingredients derived from 1,4-cyclohexanedimethanol: 15 mol%, glass transition temperature: 69 ° C.)

(Polystyrene resin)
PS-1: Biomass component-free styrene-butadiene copolymer (styrene component: 76% by weight, butadiene component: 24% by weight, Vicat softening temperature: 70 ° C.)
PS-2: Biomass component-free styrene-butadiene copolymer (styrene component: 70% by weight, butadiene component: 30% by weight, Vicat softening temperature: 72 ° C.)
PS-3: Biomass component-free styrene-butadiene copolymer (styrene component: 84% by weight, butadiene component: 16% by weight, Vicat softening temperature: 75 ° C.)
PS-4: Biomass component-containing styrene-butadiene copolymer (styrene component: 75% by weight, butadiene component: 25% by weight, Vicat softening temperature: 62 ° C.)
PS-5: Biomass component-containing styrene-butadiene copolymer (styrene component: 90% by weight, butadiene component: 10% by weight, Vicat softening temperature: 72 ° C.)

(Examples 1 to 5, Reference Examples 1 to 3)
As the resin constituting the front and back layers, the polyester-based resin shown in Table 1 was used.
As the resin constituting the intermediate layer, the polystyrene-based resin shown in Table 1 was used.
These were put into an extruder having a barrel temperature of 160 to 250 ° C., extruded into a sheet having a three-layer structure from a multi-layer die at 250 ° C., and cooled and solidified by a take-up roll at 30 ° C. Next, after stretching at a stretching ratio of 6 times in a tenter stretching machine with a preheating zone of 115 ° C., a stretching zone of 90 ° C., and a heat fixing zone of 85 ° C., the film is wound by a winding machine 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 film has a total thickness of 40 μm, a layer ratio (thickness ratio) of front / back layer / intermediate layer / front / back layer = 1/5/1, and a layer ratio (weight ratio) of front / back layer / intermediate. It had a three-layer structure of layer / front and back layers = 1/6/1.

(Examples 6 and 7, Reference Example 4)
As the resin constituting the heat-shrinkable film, the polyester-based resin shown in Table 1 was used.
This was put into an extruder having a barrel temperature of 160 to 250 ° C., extruded from a single-layer die at 250 ° C. into a sheet having a single-layer structure, and cooled and solidified by a take-up roll at 30 ° C. Next, after stretching at a stretching ratio of 6 times in a tenter stretching machine with a preheating zone of 115 ° C., a stretching zone of 90 ° C., and a heat fixing zone of 85 ° C., the film is wound by a winding machine 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 film had a total thickness of 40 μm.

(Examples 8 and 9, Reference Example 5)
As the resin constituting the heat-shrinkable film, the polystyrene-based resin shown in Table 1 was used.
These were put into an extruder having a barrel temperature of 160 to 250 ° C., extruded from a single-layer die at 250 ° C. into a sheet having a single-layer structure, and cooled and solidified by a take-up roll at 30 ° C. Next, after stretching at a stretching ratio of 6 times in a tenter stretching machine with a preheating zone of 115 ° C., a stretching zone of 90 ° C., and a heat fixing zone of 85 ° C., the film is wound by a winding machine 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 film had a total thickness of 40 μm.

(evaluation)
The following evaluations were made on the obtained heat-shrinkable films in Examples and Reference Examples. The results are shown in Table 1.

(1) Biomass degree With respect to the obtained heat-shrinkable film, the concentration of radiocarbon (C14) was determined using an accelerator mass spectrometer (NEC, 9SDH-2) based on ISO16620-2: 2015. , The degree of biomass was measured.

(2) Heat shrinkage rate The obtained heat shrinkable film is cut into a size of 100 mm × 100 mm, immersed in warm water at 70 ° C., 80 ° C., 90 ° C., and 98 ° C. for 10 seconds, and then heat shrinkage. The sex film was taken out, and the ratio of the dimension after heating to the dimension before heat treatment was calculated. The shrinkage rate was set to n = 3 and the average value was used.

(3) Haze The obtained heat-shrinkable film was measured for haze using a haze meter (NDH-5000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) in accordance with JIS K-7136 (2000).

According to the present invention, it is possible to provide a heat-shrinkable multilayer film capable of reducing the amount of fossil resources used and exhibiting high performance in terms of physical properties such as mechanical properties. In addition, a heat-shrinkable label containing the heat-shrinkable film can be provided.

Claims (4)

A heat-shrinkable film having at least one layer among a layer containing a polyester resin and a layer containing a polystyrene resin.
The heat-shrinkable film is a heat-shrinkable film containing a component derived from biomass. It has a front and back layer containing a polyester resin and an intermediate layer containing a polystyrene resin.
The heat-shrinkable film according to claim 1, wherein at least one of the polyester-based resin and the polystyrene-based resin contains a component derived from biomass. The heat-shrinkable film according to claim 1 or 2, wherein the degree of biomass is 1 to 50%. A heat-shrinkable label comprising the heat-shrinkable film according to claim 1, 2 or 3.