TWI632069B - Heat shrinkable multilayer film and heat shrinkable label - Google Patents

Abstract

The present invention provides a heat-shrinkable multilayer film which is excellent not only at a normal temperature but also at a low temperature, and has excellent adhesion between the front and back layers and the intermediate layer, can effectively prevent interlayer peeling, and is not easily left in the crease portion after heat shrinkage. White stripes. Further, a heat shrinkable label obtained by using the heat-shrinkable multilayer film is provided.

The present invention is a heat-shrinkable multilayer film obtained by laminating an inner layer and an intermediate layer, wherein the inner layer contains a polyester resin, and the intermediate layer contains a polystyrene resin, and the adhesive layer contains 20 ~65% by weight of polystyrene resin and 35 to 80% by weight of polyester elastomer.

Description

Heat shrinkable multilayer film and heat shrinkable label

The present invention relates to a heat-shrinkable multilayer film which is excellent not only at normal temperature but also at a low temperature, and has excellent adhesion between the front and back layers and the intermediate layer, can effectively prevent interlayer peeling, and is less likely to leave white streaks in the crease portion. Further, the present invention relates to a heat-shrinkable label obtained by using the heat-shrinkable multilayer film.

In recent years, a heat-shrinkable label obtained by printing a base film made of a heat-shrinkable resin or the like is attached to a container such as a PET bottle or a metal can.

In the heat-shrinkable label, a polystyrene-based resin film is often used in terms of excellent low-temperature shrinkability. However, the polystyrene resin film has a problem of insufficient heat resistance and solvent resistance. Therefore, attempts have also been made to use a polyester resin film which is excellent in heat resistance and solvent resistance. However, since the polyester resin film is inferior in low-temperature shrinkability and shrinks rapidly, wrinkles are likely to occur when attached to a container. Further, in order to reuse the container, a perforation line is often provided in the heat-shrinkable label, so that the heat-shrinkable label can be easily peeled off from the container after use, but the perforation line of the polyester-based resin film is inferior in cutting property.

In order to solve such a problem, for example, a multilayer film having an inner layer containing a polyester resin and an intermediate layer containing a polystyrene resin has been studied. However, in the multilayer film, an important problem is to prevent peeling between the layers.

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 mixture of a polyester resin and a polystyrene resin is used. Next, a layer of a heat-shrinkable multilayer film of an adhesive resin. However, in such a heat-shrinkable multilayer film, there is a problem that the bonding strength between the front and back layers and the intermediate layer is low, and the bonding strength between the layers is insufficient.

Further, Patent Document 2 describes a soft polystyrene resin having a styrene content of 10 to 50%, a modified styrene resin containing a large amount of an elastomer component, or a high affinity with a polyester and being compatible. A resin or a mixture thereof is used as a heat-shrinkable laminated film of an adhesive resin of an adhesive layer.

However, in such heat-shrinkable laminated films, there is a problem in that after printing is performed as a label, the bonding strength between the front and back layers and the intermediate layer is lowered, and the bonding strength between the layers is insufficient.

Further, Patent Document 3 discloses a heat-shrinkable multilayer film using a polyester elastomer as a component constituting the adhesive layer.

However, in such a heat-shrinkable multilayer film, for example, when a heat-shrinkable label is produced, when the sealing step is used to bend the film, the heat-shrinkable label is covered in the container to be thermally shrunk, and then The white streaks remain in the crease portion, thus impairing the appearance of the film.

In addition, for example, a heat-shrinkable label having a multilayer film in which an adhesive layer is provided between an inner surface layer containing a polyester resin and an intermediate layer containing a polystyrene resin is also used in a low temperature environment such as winter. When the heat-shrinkable label is stored and the PET bottle is mounted or the installation site is in a low-temperature environment, peeling occurs between the layers of the heat-shrinkable label when heat shrinkage occurs, resulting in poor appearance, or the heat-shrinkable label Bad conditions from the peeling of the PET bottle.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-315416

Patent Document 2: Japanese Laid-Open Patent Publication No. 2006-015745

Patent Document 3: Japanese Laid-Open Patent Publication No. 2008-037093

It is an object of the present invention to provide a heat-shrinkable multilayer film which is not only at room temperature Under the low temperature, the surface layer and the intermediate layer are also excellent in adhesion, which can effectively prevent interlayer peeling, and it is difficult to leave white streaks in the crease portion after heat shrinkage. Further, an object of the present invention is to provide a heat-shrinkable label obtained by using the heat-shrinkable multilayer film.

The present invention relates to a heat-shrinkable multilayer film comprising a front layer comprising a polyester resin and an intermediate layer containing a polystyrene resin, wherein the adhesive layer comprises 20 to 65 wt% of polyphenylene. A vinyl resin and a polyester elastomer of 35 to 80% by weight.

The invention is described in detail below.

The present inventors have found that an inner layer containing a polyester resin and an intermediate layer containing a polystyrene resin are laminated via an adhesive layer containing a polystyrene resin and a polyester elastomer having a specific mixing ratio. It is possible to obtain a heat-shrinkable multilayer film which is capable of improving the adhesion strength between the respective layers (hereinafter also referred to as interlayer strength) at a normal temperature and at a low temperature, and which does not easily cause white streaks in the crease portion. The heat-shrinkable multilayer film which is excellent in such adhesion and crease whitening property can also be used in the case of a heat-shrinkable label for a container such as a PET bottle.

In this specification, "normal temperature" means 18 to 28 ° C, and "low temperature" means 0 to 10 ° C.

The heat-shrinkable multilayer film of the present invention has an inner surface layer and an intermediate layer.

In the present specification, the term “surface layer” means both the front layer and the back layer. Therefore, the heat-shrinkable multilayer film of the present invention has a structure in which an intermediate layer is sandwiched between a front layer and a back layer.

The above surface layer contains a polyester resin.

The polyester-based resin is, for example, obtained by polycondensation of a dicarboxylic acid component and a diol component. In particular, as the dicarboxylic acid component, an aromatic polyester-based resin having a terephthalic acid content of 100 mol% and a terephthalic acid content of 55 mol% or more is preferable. Further, the dicarboxylic acid component may contain phthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, sebacic acid, octyl succinic acid in addition to the above terephthalic acid. , cyclohexanedicarboxylic acid, naphthalene dicarboxylic acid, fumaric acid, maleic acid, itaconic acid, decamethylene carboxylic acid, anhydrides and lower alkyl esters Wait.

The diol component is not particularly limited, and examples thereof include ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, and 1,6-. Hexanediol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, neopentyl glycol (2,2-dimethyl Propane-1,3-diol), 1,2-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentane An aliphatic diol such as a diol, 2-ethyl-1,3-hexanediol or polytetramethylene ether glycol; 2,2-bis(4-hydroxycyclohexyl)propane, 2,2-double An alkylene oxide adduct of (4-hydroxycyclohexyl)propane, an alicyclic diol such as 1,4-cyclohexanediol or 1,4-cyclohexanedimethanol, or the like.

The polyester-based resin preferably contains a component derived from terephthalic acid as a dicarboxylic acid component and contains a component derived from ethylene glycol and/or 1,4-cyclohexanedimethanol as a component. The diol component. By using such an aromatic polyester-based random copolymer resin, excellent shrinkability can be imparted to the heat-shrinkable multilayer film.

In the case where the shrinkage property is to be further improved, it is preferred to use a component derived from ethylene glycol in a monomer content of 100% by mole of the diol component of 60 to 80 mol% derived from 1,4-cyclohexanedimethanol. The content of the ingredients is 10 to 40 mol%.

The aromatic polyester-based random copolymer resin may further contain 0 to 30 mol%, preferably 1 to 25 mol%, more preferably 2 to 20 mol%, of the component derived from diethylene glycol. By using diethylene glycol, the tensile elongation at break of the heat-shrinkable multilayer film in the main shrinkage direction is improved, and interlayer peeling occurs when the perforation line is torn, and only the inner surface of the inner surface side remains in the container. When the component derived from diethylene glycol exceeds 30 mol%, the low-temperature shrinkability of the heat-shrinkable multilayer film becomes too high, and wrinkles are likely to occur when attached to a container.

Further, as the polyester-based resin containing the component derived from terephthalic acid as the dicarboxylic acid component, a component containing 1,4-butanediol may be used as the diol component. Such a polyester resin is generally referred to as a polybutylene terephthalate resin.

The above polybutylene terephthalate resin is preferably combined with the above-mentioned terephthalic acid-containing resin. An aromatic polyester-based random copolymer resin which is a dicarboxylic acid component and contains a component derived from ethylene glycol and 1,4-cyclohexanedimethanol as a diol component is used in combination. By using such a mixed resin, more excellent finishability can be imparted.

The polybutylene terephthalate-based resin is a polybutylene terephthalate-based resin composed only of a component derived from terephthalic acid and a component derived from 1,4-butanediol. Further, it may be a polybutylene terephthalate resin containing a dicarboxylic acid component other than the terephthalic acid component and/or a diol component other than the component derived from 1,4-butanediol.

Further, the content of the dicarboxylic acid component other than the component derived from terephthalic acid is preferably 10 mol% or less of 100 mol% of the dicarboxylic acid component. When it exceeds 10 mol%, the heat resistance of the above-mentioned polybutylene terephthalate-based resin may be lowered, and it may become economically disadvantageous. Further, the content of the diol component other than the component derived from 1,4-butanediol is preferably 10 mol% or less of 100 mol% of the diol component. When it exceeds 10 mol%, the heat resistance of the above-mentioned polybutylene terephthalate-based resin may be lowered, and it may become economically disadvantageous.

The amount of the polybutylene terephthalate-based resin to be added is not particularly limited, but is preferably 30% by weight or less. When it exceeds 30% by weight, the natural shrinkage ratio may increase or the rigidity of the film may decrease.

The preferred lower limit of the glass transition temperature of the polyester-based resin constituting the inner surface layer is 55 ° C, and the upper limit is preferably 95 ° C. When the glass transition temperature is less than 55 ° C, the shrinkage initiation temperature of the heat-shrinkable multilayer film may become too low, or the natural shrinkage ratio may become large, or blocking may occur easily. When the glass transition temperature exceeds 95° C., the heat-shrinkable multilayer film may have a low-temperature shrinkage property and shrinkage completion property, or a decrease in the low-temperature shrinkage property over time, or a resin whitening may easily occur during stretching. A preferred lower limit of the above glass transition temperature is 60 ° C, and a preferred upper limit is 90 ° C. A lower limit is 65 ° C, and a lower limit is 85 ° C. Further, the glass transition temperature of the above polyester resin can be measured by a method in accordance with JIS K 7121 (1987).

The lower limit of the tensile elastic modulus of the above polyester-based resin constituting the inner layer More than 1000 MPa, a preferred upper limit is 4000 MPa. When the tensile elastic modulus is 1000 MPa or less, the shrinkage initiation temperature of the heat-shrinkable film may become too low, or the natural shrinkage ratio may become large. When the tensile modulus is more than 4,000 MPa, the heat-shrinkable multilayer film may have a low-temperature shrinkage property and shrinkage completion property, or a decrease in the low-temperature shrinkage property over time may be increased. A preferred lower limit of the above tensile modulus is 1500 MPa, and a preferred upper limit is 3700 MPa.

Further, the above tensile elastic modulus can be measured by a method in accordance with ASTM-D882 (Test A).

For example, "Easter", "EmbraceLv" (manufactured by Eastman Chemical Co., Ltd.), "Bellpet" (manufactured by Bell Polyester Products), and "Novaduran" (Mitsubishi) are mentioned as a commercial product of the above-mentioned polyester resin. Engineering by Plastic-Plastics).

As the polyester-based resin contained in the above-mentioned surface layer, a polyester-based resin having the above composition may be used alone, or two or more kinds of polyester-based resins having the above composition may be used in combination. Further, the polyester-based resin may be a polyester-based resin having a different composition in the front layer and the back layer. However, in order to suppress failure due to curling of the film or the like, a polyester-based resin having the same composition is preferable.

The above-mentioned surface layer may also contain antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, lubricants, antistatic agents, anti-blocking agents, flame retardants, antibacterial agents, fluorescent brighteners, colorants, etc., as needed. additive.

The intermediate layer contains a polystyrene resin.

Examples of the polystyrene-based resin include an aromatic vinyl hydrocarbon-conjugated diene copolymer, an aromatic vinyl hydrocarbon-conjugated diene copolymer, and an aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer. Mixed resin, rubber modified impact-resistant polystyrene, etc. By using the above polystyrene-based resin, the heat-shrinkable multilayer film of the present invention can be shrunk from a low temperature and has high shrinkage.

In the present specification, the term "aromatic vinyl hydrocarbon-conjugated diene copolymer" means A copolymer derived from an aromatic vinyl hydrocarbon component and a component derived from a conjugated diene.

The aromatic vinyl hydrocarbon is not particularly limited, and examples thereof include styrene, o-methyl styrene, and p-methyl styrene. These may be used singly or in combination of two or more. The conjugated diene is not particularly limited, and examples thereof include 1,3-butadiene, 2-methyl-1,3-butadiene, and 2,3-dimethyl-1,3-butadiene. 1,3-pentadiene, 1,3-hexadiene, and the like. These may be used singly or in combination of two or more.

In particular, the aromatic vinyl hydrocarbon-conjugated diene copolymer preferably contains a styrene-butadiene copolymer (SBS resin) in terms of excellent heat shrinkability. Further, in order to produce a heat-shrinkable multilayer film having less fish eyes, the above aromatic vinyl hydrocarbon-conjugated diene copolymer preferably contains 2-methyl-1,3-butadiene (isoprene). A styrene-isoprene copolymer (SIS resin) or a styrene-isoprene-butadiene copolymer (SIBS) as the conjugated diene.

Further, the aromatic vinyl hydrocarbon-conjugated diene copolymer may contain any one of SBS resin, SIS resin and SIBS resin alone, or may be combined and contained in plural kinds. Further, when a plurality of kinds of the SBS resin, the SIS resin, and the SIBS resin are used, the respective resins may be blended, or a composite resin obtained by tempering each resin with a specific composition using an extruder may be used.

In the case where the above-mentioned aromatic vinyl hydrocarbon-conjugated diene copolymer contains SBS resin, SIS resin and SIBS resin alone or in plural, it is preferable to obtain a heat-shrinkable multilayer film which is excellent in heat shrinkability. The content of styrene in the 100% by weight of the aromatic vinyl hydrocarbon-conjugated diene copolymer is 65 to 90% by weight, and the content of the conjugated diene is 10 to 35% by weight. When the styrene content is more than 90% by weight or the conjugated diene content is less than 10% by weight, the heat-shrinkable multilayer film may be easily broken when it is subjected to tension, or may be accidentally broken during processing such as printing. When the styrene content is less than 65% by weight or the conjugated diene content is more than 35% by weight, foreign matter such as gel is likely to be generated during molding, or the toughness of the heat-shrinkable multilayer film is weakened, resulting in operability. Poor situation.

In this specification, the copolymerization of aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester The term refers to a copolymer containing a component derived from an aromatic vinyl hydrocarbon and a component derived from an aliphatic unsaturated carboxylic acid ester.

The aromatic vinyl hydrocarbon is not particularly limited, and an aromatic vinyl hydrocarbon similar to the aromatic vinyl hydrocarbon exemplified in the above aromatic vinyl hydrocarbon-conjugated diene copolymer can be used. The aliphatic unsaturated carboxylic acid ester is not particularly limited, and examples thereof include methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and (meth)acrylic acid. Lauryl ester, stearyl (meth) acrylate, and the like. Here, the (meth) acrylate means both an acrylate and a methacrylate.

When a styrene-butyl acrylate copolymer is used as the above aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer, it is preferably styrene occupied by 100% by weight of the above styrene-butyl acrylate copolymer. The content is 60 to 90% by weight, and the content of butyl acrylate is 10 to 40% by weight. By using the aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer having such a composition, a heat-shrinkable multilayer film excellent in heat shrinkability can be obtained.

The mixed resin of the above aromatic vinyl hydrocarbon-conjugated diene copolymer and the above aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer is not particularly limited, and is preferably the above aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid. The content of the acid ester copolymer is 80% by weight or less of a mixed resin.

The rubber-modified impact-resistant polystyrene refers to a basic phase composed of a continuous phase and a dispersed phase, and the continuous phase is composed of a terpolymer of styrene, an alkyl methacrylate, and an alkyl acrylate. The dispersed phase is composed of a rubber component mainly composed of a conjugated diene.

Examples of the alkyl methacrylate forming the continuous phase include methyl methacrylate and ethyl methacrylate. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. Ester and the like.

The ratio of styrene in the copolymer forming the above continuous phase is preferably from 20 to 80% by weight, more preferably from 30 to 70% by weight. The ratio of the alkyl methacrylate is preferably from 10 to 50% by weight, more preferably from 15 to 40% by weight. The ratio of the alkyl acrylate is preferably from 1 to 30% by weight, more preferably from 5 to 20% by weight. the amount%.

The rubber component mainly composed of the conjugated diene forming the dispersed phase is preferably a styrene-butadiene copolymer having a polybutadiene or a styrene content of 5 to 30% by weight.

The particle diameter of the rubber component mainly composed of the conjugated diene forming the dispersed phase is preferably 0.1 to 1.2 μm, more preferably 0.3 to 0.8 μm. When the particle diameter is less than 0.1 μm, the impact resistance of the rubber-modified impact-resistant polystyrene may be insufficient. When the particle diameter is more than 1.2 μm, the transparency of the intermediate layer may be lowered.

In the above rubber-modified impact-resistant polystyrene, the ratio of the continuous phase composed of the terpolymer of styrene, alkyl methacrylate, and alkyl acrylate is preferably 70 to 95% by weight. The ratio of the dispersed phase composed of the rubber component of the main component of the conjugated diene is preferably 5 to 20% by weight. When the ratio of the dispersed phase is less than 5% by weight, the impact resistance of the rubber-modified impact-resistant polystyrene may be insufficient, and if it is more than 20% by weight, the transparency of the intermediate layer may be lowered. .

A preferred lower limit of the thicar softening temperature of the above polystyrene-based resin is 60 ° C, and a preferred upper limit is 85 ° C. When the above-mentioned Fica softening temperature is less than 60 ° C, the low-temperature shrinkability of the heat-shrinkable multilayer film becomes too high, and wrinkles are likely to occur when attached to a container. When the above-mentioned Fica softening temperature exceeds 85 ° C, the low-temperature shrinkability of the heat-shrinkable multilayer film is lowered, and an uncontracted portion is likely to be generated when it is attached to a container. A lower limit of the above-mentioned Pena softening temperature is 65 ° C, and a more preferred upper limit is 80 ° C. Further, the above Ficam softening temperature can be measured by a method in accordance with JIS K 7206 (1999).

A preferred lower limit of the MFR (melt flow rate) of the above polystyrene resin at 200 ° C is 2 g/10 min, and a preferred upper limit is 15 g/10 min. If the MFR at 200 ° C is less than 2 g/10 minutes, the production of the film becomes difficult. If the MFR at 200 ° C exceeds 15 g/10 minutes, the mechanical strength of the film becomes low and it becomes unsatisfactory for practical use. A lower limit of the MFR of 200 ° C is 4 g/10 min, and a more preferred upper limit is 12 g/10 min. Furthermore, the MFR can be measured by the method according to ISO 1133.

For example, "Clearen" (manufactured by Denki Kagaku Co., Ltd.), "Asaflex" (manufactured by Asahi Kasei Chemicals Co., Ltd.), "Styrolux" (manufactured by BASF Corporation), and "" are commercially available as the polystyrene-based resin constituting the intermediate layer. PSJ-polystyrene" (made by PS JAPAN Co., Ltd.).

The intermediate layer may also contain an antioxidant, a heat stabilizer, a UV absorber, a light stabilizer, a lubricant, an antistatic agent, an anti-blocking agent, a flame retardant, an antibacterial agent, a fluorescent whitening agent, a coloring agent, etc., as needed. additive.

In the heat-shrinkable multilayer film of the present invention, the surface layer and the intermediate layer are laminated via a laminate, and the adhesive layer contains 20 to 65 wt% of a polystyrene resin and 35 to 80% by weight of a polyester elastomer. body.

By using such an adhesive layer, the adhesion strength between the layers of the heat-shrinkable multilayer film can be improved not only at normal temperature but also at a low temperature, and white streaks generated in the crease portion when the heat-shrinkable multilayer film is bent can be suppressed. .

The polystyrene resin used for the above-mentioned adhesive layer may be the same as the polystyrene resin used in the above intermediate layer, or may be used differently. In the case where a different one is used, it is preferably one which is softer than the polystyrene resin used for the intermediate layer.

The polystyrene-based resin used for the above-mentioned adhesive layer preferably contains an aromatic vinyl hydrocarbon-conjugated diene copolymer, and particularly preferably contains a styrene-butadiene copolymer (SBS). Resin). In the case of using a styrene-butadiene copolymer, it is preferred that the content of butadiene is larger than that of the styrene-butadiene copolymer used for the intermediate layer from the viewpoint of excellent adhesion. By. Moreover, in order to produce a heat-shrinkable multilayer film which is more excellent in adhesion, it is preferable to contain a styrene-isoprene copolymer (SIS resin), a styrene-isoprene-butadiene copolymer (SIBS), or the like. The styrene-isoprene copolymer used 2-methyl-1,3-butadiene (isoprene) as the conjugated diene of the above aromatic vinyl hydrocarbon-conjugated diene copolymer. Further, the hydrogenated styrene resin may be contained in a range which does not become a main component of the polystyrene resin: styrene-butyl obtained by hydrogenating an aromatic vinyl hydrocarbon-conjugated diene copolymer A diene-butene copolymer (SBBS resin) or a styrene-ethylene-butene copolymer (SEBS resin) or the like. When the hydrogenated styrene resin is a main component in the polystyrene resin, the transparency is liable to lower.

Further, the polystyrene-based resin may contain any one of SBS resin, SIS resin, and SIBS resin, or may be combined and contained in plural. Further, when a plurality of kinds of SBS resin, SIS resin, SIBS resin, SBBS resin or SEBS resin are used, each resin may be blended, or a resin obtained by using a specific composition in an extruder may be used. Composite resin.

When the polystyrene-based resin is an aromatic vinyl hydrocarbon-conjugated diene copolymer and the SBS resin, the SIS resin, and the SIBS resin are used alone or in plural, in particular, heat having excellent adhesion between the layers is obtained. In the shrinkable multilayer film, it is preferred that the content of styrene in the 100% by weight of the aromatic vinyl hydrocarbon-conjugated diene copolymer is 50 to 90% by weight, and the content of the conjugated diene is 10 to 50. weight%. When the styrene content is less than 50% by weight or the conjugated diene content is more than 50% by weight, foreign matter such as gel may easily occur during molding. When the styrene content exceeds 90% by weight or the conjugated diene content is less than 10% by weight, the adhesion strength between the layers is liable to lower.

In the case where a hydrogenated styrene resin is mixed with the above polystyrene resin, in particular, in order to obtain a heat-shrinkable multilayer film having excellent adhesion strength between layers, the styrene content of the hydrogenated styrene resin is preferably 20 to 80% by weight, butadiene-butene or ethylene-butene content is 20 to 80% by weight. If the styrene content is less than 20% by weight, the adhesion strength between the layers is liable to lower. When the styrene content exceeds 80% by weight, the heat resistance is lowered.

A preferred lower limit of the thicar softening temperature of the polystyrene resin used in the above-mentioned adhesive layer is 50 ° C, and a preferred upper limit is 85 ° C. When the above-mentioned Fica softening temperature is less than 50 ° C, the heat-shrinkable multilayer film is liable to cause interlayer peeling between the layers due to heating when it is attached to the container. When the above-mentioned Fica softening temperature exceeds 85 ° C, the adhesive strength of the heat-shrinkable multilayer film is liable to lower. The lower limit of the above-mentioned Fica softening temperature is 55 ° C, and the lower limit is preferably 60 ° C, and the lower limit is 65 ° C. A better upper limit is 80 °C. Further, the above Ficam softening temperature can be measured by a method in accordance with JIS K 7206 (1999).

A preferred lower limit of the MFR (melt flow rate) at 200 ° C of the polystyrene resin used for the above-mentioned adhesive layer is 2 g/10 min, and a preferred upper limit is 15 g/10 min. When the MFR at 200 ° C is less than 2 g/10 minutes, the resin tends to stay in the extruder in a continuous production step to generate foreign matter such as a gel. When the MFR at 200 ° C exceeds 15 g/10 minutes, the pressure is not sufficiently applied in the film forming step, and the thickness variation tends to increase. A lower limit of the MFR of 200 ° C is 4 g/10 min, and a more preferred upper limit is 12 g/10 min. Furthermore, the MFR can be measured by the method according to ISO 1133.

The polyester-based elastic system used for the above-mentioned adhesive layer is composed of a polyester as a hard segment and a polyether or polyester which is a rubber-elastic soft segment. Specifically, for example, it can be cited as a hard segment. a block copolymer composed of an aromatic polyester and an aliphatic polyether as a soft segment, or a block copolymer composed of an aromatic polyester as a hard segment and an aliphatic polyester as a soft segment, It is preferably a saturated polyester-based elastomer, and particularly preferably a saturated polyester-based elastomer containing a polyalkylene ether glycol segment as a soft segment.

As the saturated polyester elastomer containing the polyalkylene glycol diol segment, for example, it is preferably composed of an aromatic polyester as a hard segment and a polyalkylene glycol as a soft segment. Segment copolymer.

When a block copolymer composed of an aromatic polyester and a polyalkylene ether glycol is used as the above polyester elastomer, a preferred lower limit of the ratio of the segment composed of the polyalkylene glycol It is 5% by weight, and a preferred upper limit is 90% by weight. If it is less than 5% by weight, the adhesion to the intermediate layer is lowered, and if it exceeds 90% by weight, the adhesion to the surface layer is lowered. A lower limit is more preferably 30% by weight, still more preferably 80% by weight, and still more preferably 55% by weight.

Examples of the polyalkylene glycol of the above-mentioned polyalkylene glycol include polyethylene glycol, poly(propylene ether) glycol, poly(tetramethylene ether) glycol, and poly(hexamethylene ether) glycol.

The preferred lower limit of the number average molecular weight of the above polyalkylene glycol is 400. A preferred upper limit is 6000. A lower limit is preferably 600, a higher limit is 4000, and a preferred lower limit is 1000, and a preferred upper limit is 3000. It is preferred to obtain a good interlayer strength by using a polyalkylene ether glycol having a number average molecular weight within the above range. Further, in the present specification, the number average molecular weight means a person measured by gel chromatography (GPC).

The method for producing the polyester-based elastomer is not particularly limited, and for example, it can be produced by (i) an aliphatic and/or alicyclic diol having 2 to 12 carbon atoms, and (ii) an aromatic compound. a dicarboxylic acid and/or an alicyclic 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, which is obtained by an esterification reaction or a transesterification reaction. After the polymer, the oligomer is further condensed.

As the aliphatic and/or alicyclic diol having 2 to 12 carbon atoms, for example, a material which is often used as a raw material of a polyester, particularly a polyester-based thermoplastic elastomer can be used. Specific examples thereof include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol. Among these, ethylene glycol and 1,4-butanediol are preferred, and 1,4-butanediol is more preferred. These may be used singly or in combination of two or more.

As the aromatic dicarboxylic acid and/or alicyclic dicarboxylic acid, for example, a material which is usually used as a raw material of a polyester, particularly a polyester-based thermoplastic elastomer can be used. Specific examples thereof include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and cyclohexanedicarboxylic acid. Among these, terephthalic acid and 2,6-naphthalene dicarboxylic acid are preferred, and terephthalic acid is more preferred. These may be used singly or in combination of two or more.

For example, the product name "PRIMALLOY" (manufactured by Mitsubishi Chemical Corporation), the product name "PELPRENE" (manufactured by Toyobo Co., Ltd.), and the product name "HYTREL" (DU PONT-TORAY) are listed as a commercial product of the polyester-based elastomer. Company manufacturing) and so on.

The melting point of the above polyester elastomer is preferably from 120 to 200 °C. When the temperature is less than 120 ° C, the heat resistance is lowered, and when the heat shrinkable label is applied to the container, peeling tends to occur from the solvent-sealed portion. If it exceeds 200 ° C, sufficient adhesive strength may not be obtained. Better The limit is 130 ° C, and the upper limit is 190 ° C.

Further, the above melting point can be measured by a differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-60) according to the method of JIS-K 7121 (1987).

The melting point of the above polyester elastomer depends on the copolymerization ratio or structure of the polyester as the hard segment and the polyether or polyester as the soft segment. In general, the melting point of the polyester elastomer tends to depend on the copolymerization amount of the polyether or the polyester as the soft segment, and if the copolymerization amount of the polyether or the polyester is large, the melting point becomes low, and if it is small, the melting point changes. high.

Moreover, the melting point of the polyester which is a hard segment of the polyester elastomer can be adjusted by changing the copolymerization component, and the melting point of the entire polyester elastomer can be adjusted.

Further, when the molecular weight of the polyether or polyester as the soft segment is small, the terminal endurability of the obtained polyester elastomer is lowered, so that the melting point is liable to lower.

A preferred lower limit of the JIS-D hardness of the above polyester elastomer is 10, and a preferred upper limit is 80. By setting the JIS-D hardness to 10 or more, the mechanical strength of the above-mentioned adhesive layer is improved. By setting the JIS-D hardness to 80 or less, the flexibility and impact resistance of the above-mentioned adhesive layer are improved. A lower limit of the JIS-D hardness is preferably 15 and a higher limit is 70. Further preferably, the lower limit is 20, and the upper limit is preferably 60.

Further, the above JIS-D hardness can be measured by using a D-type hardness meter in accordance with the method of JIS K 6253 (2012).

A preferred lower limit of the specific gravity of the above polyester elastomer is 0.95, and a preferred 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 when the heat-shrinkable label is applied to the container can be suppressed. Further, by setting the specific gravity to 1.20 or less, the adhesion strength between the front and back layers and the intermediate layer can be improved.

A lower limit of the above specific gravity is 0.98, and a higher limit is 1.18.

Further, the above specific gravity can be measured by using the underwater displacement method in accordance with the method of JIS K 7112 (1999).

A preferred lower limit of the tensile elastic modulus of the polyester elastomer constituting the adhesive layer is 1 MPa, and a preferred upper limit is 1000 MPa. When the tensile elastic modulus is less than 1 MPa, the mechanical strength of the above-mentioned adhesive layer is liable to lower. When the tensile elastic modulus exceeds 1000 MPa, the adhesion strength between the front and back layers and the intermediate layer is liable to lower. A more preferable lower limit of the above tensile elastic modulus is 5 MPa, and a more preferable upper limit is 900 MPa. Further, the above tensile elastic modulus can be measured by a method in accordance with ASTM-882 (Test A).

A preferred lower limit of the glass transition temperature of the polyester elastomer constituting the adhesive layer is -70 ° C, and a preferred upper limit is 0 ° C. When the glass transition temperature is less than -70 ° C, resin adhesion occurs and the handleability is likely to be deteriorated. When the glass transition temperature exceeds 0 ° C, the adhesion strength between the front and back layers and the intermediate layer is liable to lower. A more preferred lower limit of the glass transition temperature is -60 ° C, and a more preferred upper limit is -5 ° C. Further, the glass transition temperature of the above polyester elastomer can be calculated from the tan δ peak obtained by the method according to JIS K 7244 (1999).

The polyester elastomer may also be a modified product. The modified elastomer can be exemplified by a polyester elastomer in which the polyester elastomer is grafted with, for example, an α,β-ethylenically unsaturated carboxylic acid.

Examples of the above α,β-ethylenically unsaturated carboxylic acid include acrylic acid, maleic acid, fumaric acid, tetrahydrofumaric acid, itaconic acid, citraconic acid, and crotonic acid. , unsaturated carboxylic acid such as methacrylic acid; 2-octene-1-yl succinic anhydride, 2-dodecen-1-yl succinic anhydride, 2-octadecene-1-yl succinic anhydride, butene Diacid anhydride, 2,3-dimethyl maleic anhydride, bromine maleic anhydride, dichloromaleic anhydride, citraconic anhydride, itaconic anhydride, 1-butene-3,4-dicarboxylate Anhydride, 1-cyclopentene-1,2-dicarboxylic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, external 3 ,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride, 5-northene-2,3-dicarboxylic anhydride, methyl-5-northene-2,3-di Unsaturated carboxylic anhydride, internal bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic anhydride, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic anhydride Carboxylic anhydride. Among these, an acid anhydride is preferred in terms of high reactivity.

In the above-mentioned adhesive layer, the lower limit of the content of the above polystyrene-based resin is 20% by weight, and the upper limit is 65% by weight.

When the content of the above polystyrene-based resin is less than 20% by weight, when the film is strongly bent in order to produce a heat-shrinkable label, white streaks remain in the crease portion, which impairs the appearance of the film. When the content of the above polystyrene-based resin exceeds 65% by weight, sufficient interlayer strength cannot be obtained at a low temperature, and interlayer peeling tends to occur in actual use. A preferred lower limit of the content of the above polystyrene-based resin is 25% by weight, a more preferred lower limit is 30% by weight, a preferred upper limit is 60% by weight, a more preferred upper limit is 55% by weight, and a particularly preferred upper limit is 49% by weight.

In the above adhesive layer, the lower limit of the content of the polyester elastomer is 35% by weight, and the upper limit is 80% by weight.

When the content of the polyester elastomer is less than 35% by weight, sufficient interlayer strength cannot be obtained at a low temperature, and interlayer peeling tends to occur in actual use. When the content of the polyester-based elastomer exceeds 80% by weight, white streaks remain in the crease portion when the film is strongly bent, and the appearance of the film is impaired. A preferred lower limit of the content of the above polyester elastomer is 40% by weight, further preferably a lower limit of 45% by weight, a particularly preferred lower limit of 51% by weight, a preferred upper limit of 75% by weight, and further preferably an upper limit of 70% by weight.

In the above-mentioned adhesive layer, a styrene-butadiene copolymer (SBS resin) and benzene using 2-methyl-1,3-butadiene (isoprene) are preferable as the polystyrene resin. Ethylene-isoprene copolymer (SIS resin), styrene-isoprene-butadiene copolymer (SIBS), and the like. Further, the polyester elastomer preferably contains a block copolymer composed of a polyester as a hard segment and a polyalkylene glycol as a soft segment, and may be a modified product.

The above adhesive layer may also contain an antioxidant, a heat stabilizer, an ultraviolet absorber, a light stabilizer, a lubricant, an antistatic agent, an anti-blocking agent, a flame retardant, an antibacterial agent, a fluorescent whitening agent, a coloring agent, etc. as needed. additive.

A preferred lower limit of the thickness of the entire heat-shrinkable multilayer film of the present invention is 10 The preferred upper limit is μm, the lower limit is preferably 15 μm, the upper limit is more preferably 80 μm, and the lower limit is preferably 20 μm, and further preferably the upper limit is 70 μm. When the thickness of the entire heat-shrinkable multilayer film is within the above range, excellent heat shrinkability, excellent conversion properties such as printing or intermediate sealing, and excellent mountability can be obtained.

Further, in the heat-shrinkable multilayer film of the present invention, a preferred lower limit of the thickness of the front and back layers with respect to the entire thickness of the heat-shrinkable multilayer film is 5%, and a preferred upper limit is 25%, and the thickness of the intermediate layer is relative to A preferred lower limit of the thickness of the heat-shrinkable multilayer film as a whole is 50%, and a preferred upper limit is 90%. When the thickness of the above-mentioned surface layer and the intermediate layer is within the above range, high-rise strength, high transparency, and the like can be obtained.

In the heat-shrinkable multilayer film of the present invention, a preferred lower limit of the thickness of the adhesive layer is 0.3 μm, and a preferred upper limit is 3.0 μm. When the thickness of the above-mentioned adhesive layer is less than 0.3 μm, the above-mentioned adhesive layer may not have sufficient adhesion. When the thickness of the above-mentioned adhesive layer exceeds 3.0 μm, the heat shrinkable multilayer film may have poor heat shrinkage characteristics and optical properties. A more preferable lower limit of the thickness of the above-mentioned adhesive layer is 0.5 μm, and a more preferable upper limit is 2.0 μm.

Further, by reducing the thickness of the adhesive layer and adjusting the thickness of the front and back layers and the intermediate layer, the thickness of the entire heat-shrinkable multilayer film can be adjusted.

Further, for example, the heat-shrinkable multilayer film of the present invention has a five-layer structure of a front layer (A) / a back layer (E) / an intermediate layer (B) / an adhesive layer (E) / a back layer (C), and is heat-shrinkable. When the thickness of the entire multilayer film is 40 μm, the thickness of the front layer (A) and the back layer (C) is preferably 2.0 to 10.0 μm, more preferably 3.0 to 8.0 μm. Further, the thickness of the above-mentioned adhesive layer (E) is preferably from 0.3 to 3.0 μm, more preferably from 0.5 to 2.0 μm. Further, the thickness of the intermediate layer (B) is preferably from 19.0 to 35.4 μm, more preferably from 20.0 to 33.0 μm.

Further, the heat-shrinkable multilayer film of the present invention may also be as the front layer (A) / the subsequent layer (E) / the intermediate layer (B) / the subsequent layer (E) / the intermediate layer (B) / the subsequent layer (E) / intermediate The layer (B) / the subsequent layer (E) / the back layer (C) are repeatedly formed between the front layer (A) and the back layer (C). Layer (E) / intermediate layer (C) / subsequent layer (E) units. When the thickness of the entire heat-shrinkable multilayer film is 40 μm, the thickness of the front layer (A) and the back layer (C) is preferably 2.0 to 10.0 μm, more preferably 3.0 to 8.0. Further, the total thickness of the above-mentioned adhesive layer (E) is preferably from 1.0 to 10.0 μm, more preferably from 1.5 to 8.0 μm. Further, the total thickness of the intermediate layer (B) is preferably from 18.0 to 34.0 μm, more preferably from 19.0 to 31.0 μm.

As a method of repeating the above-mentioned bonding layer (E) / intermediate layer (C) / bonding layer (E) between the front layer (A) and the back layer (C), it is possible to join by a feed block. The resin extruded from a plurality of extruders may also be used to form a repeating unit using a multiplier after temporarily merging the subsequent layer (E) / intermediate layer (C) / subsequent layer (E) units.

When the above-mentioned adhesive layer (E) / intermediate layer (C) / adhesive layer (E) unit is repeatedly formed between the front layer (A) and the back layer (C), stress is dispersed when an impact is applied to the label, and peeling can be suppressed. .

In the heat-shrinkable multilayer film of the present invention, the shrinkage ratio in the main shrinkage direction is preferably from 5 to 50%, more preferably from 8 to 47%, still more preferably from 10 to 45%, at 70 ° C for 10 seconds. Preferably, it is 15 to 45%, preferably 35 to 70% at 80 ° C for 10 seconds, more preferably 38 to 69%, further preferably 41 to 68%, particularly preferably 43 to 67%, in boiling water 10 The second is preferably 65 to 85%, more preferably 68 to 83%, and still more preferably 70 to 82%. By setting such a shrinkage ratio, it is possible to impart excellent shrinkage completion properties in hot air passages and steam passages.

The heat-shrinkable multilayer film of the present invention preferably has an interlayer strength of 0.50 to 2.00 N/10 mm at a normal temperature in a direction orthogonal to the main shrinkage direction (TD direction) (MD direction). If the interlayer strength is less than 0.50 N/10 mm, there is a case where delamination occurs when the heat shrinkable label is applied to the container. A lower limit of the above interlayer strength is 0.60 N/10 mm, and a preferred lower limit is 0.70 N/10 mm.

Further, the heat-shrinkable multilayer film of the present invention preferably has an interlayer strength of 0.50 to 2.00 N/10 mm in the main shrinkage direction (TD direction). If the above interlayer strength is less than 0.50N/10mm, it is in the container When the label is coated, corrugated cardboard is transported to cause delamination due to abrasion. A lower limit of the above interlayer strength is 0.60 N/10 mm, and a preferred lower limit is 0.70 N/10 mm.

The heat-shrinkable multilayer film of the present invention preferably has an interlayer strength of 0.50 to 2.00 N/10 mm at a low temperature in the main shrinkage direction (TD direction). If the interlayer strength is less than 0.50 N/10 mm, there is a case where delamination occurs when the label is placed on the mounting machine at a low temperature, or delamination occurs due to abrasion when the container is covered with a label and the corrugated cardboard is transported at a low temperature. A lower limit of the above interlayer strength is 0.60 N/10 mm, and a preferred lower limit is 0.70 N/10 mm.

Further, the interlayer strength may be, for example, an interlaminar strength when the measurement sample is peeled off in the MD direction and the TD direction in the 180-degree direction using a peeling tester or an autostereograph.

The method for producing the heat-shrinkable multilayer film of the present invention is not particularly limited, and a method of simultaneously forming each layer by a co-extrusion method is preferred. In the case where the above co-extrusion method is a co-extrusion using a T-die, the method of laminating may be either a feed sleeve method, a multi-manifold method, or a combination of the methods.

Specific examples of the method for producing the heat-shrinkable multilayer film of the present invention include: introducing a material constituting the surface layer, the intermediate layer, and the back layer into an extruder, and using a multilayer mold sheet Extrusion, after cooling and solidification by a take-up roll, it is extended in a single axis or a double axis.

As the method of the above extension, for example, a roll stretching method, a tenter stretching method, or a combination thereof may be used. The stretching temperature is changed depending on the softening temperature of the resin constituting the film, the shrinkage characteristics required for the heat-shrinkable multilayer film, and the like, and the lower limit is preferably 65 ° C, preferably the upper limit is 120 ° C, and the lower limit is preferably 70 ° C, more preferably the upper limit. It is 115 °C. The stretching ratio in the main shrinkage direction is changed depending on the resin constituting the film, the stretching means, the stretching temperature, and the like, and is preferably 3 times or more, more preferably 4 times or more, and is preferably 7 times or less, more preferably 6.5 times or less. . By setting such an extension temperature and a stretching ratio, excellent thickness precision can be achieved, and delamination can be prevented from occurring when the perforation line is torn, and only the inner surface of the inner surface side remains in the container.

The use of the heat-shrinkable multilayer film of the present invention is not particularly limited, and the heat of the present invention is high in terms of high interlayer strength, suppression of peeling between layers when the container is attached to the container, and peeling of the perforation line, and excellent transparency. The shrinkable multilayer film can be preferably used as, for example, a heat-shrinkable label base film which is attached to a container such as a PET bottle or a metal can. The heat-shrinkable label obtained by using the heat-shrinkable multilayer film of the present invention is also one of the inventions.

According to the present invention, it is possible to provide a heat-shrinkable multilayer film which is excellent in adhesion between the front and back layers and the intermediate layer, and which can effectively prevent interlayer peeling and which is less likely to have white streaks in the crease portion.

Further, in the case where the heat-shrinkable multilayer film of the present invention is assumed to have interlayer peeling, since the interlayer strength is not uneven, peeling failure (zipping) does not occur. Further, the heat-shrinkable multilayer film of the present invention is characterized in that peeling of the heat-shrinkable label is less likely to occur because interlayer peeling at the interface between the front surface layer and the adhesive layer does not occur. Further, the heat-shrinkable multilayer film of the present invention has an excellent transparency and maintains transparency after mounting.

Further, according to the present invention, it is possible to provide a heat-shrinkable label obtained by using the heat-shrinkable multilayer film. The heat-shrinkable label of the present invention is less likely to cause interlayer peeling in the solvent-sealed portion, and the peeling of the heat-shrinkable label can be effectively prevented.

1‧‧‧The inner layer

2‧‧‧Intermediate

3‧‧‧Next layer

Fig. 1 is a schematic view showing a method of peeling off a film in interlayer strength evaluation.

Fig. 2 is a schematic view showing a method of peeling off a film in interlayer strength evaluation.

Fig. 3 is a schematic view showing a heat-shrinkable multilayer film in the case where peeling occurs at the interface between the intermediate layer and the adhesive layer.

Fig. 4 is a schematic view showing a heat-shrinkable multilayer film in the case where peeling occurs at the interface between the surface layer and the adhesive layer.

Fig. 5 is a schematic view of a heat shrinkable label used for label bending evaluation.

Fig. 6 is a photograph showing an example of a case where crease whitening cannot be observed in the evaluation of crease whitening.

Fig. 7 is a photograph showing an example of a case where crease whitening can be observed in evaluation of crease whitening.

Hereinafter, embodiments of the invention will be described in detail, but the invention is not limited to the embodiments.

The following materials were used in the examples and comparative examples.

(Polyester resin)

. PET-1: 100 mol% of terephthalic acid as a dicarboxylic acid component, 65 mol% of a glycol-derived component as a diol component, and 12 mol% of a diethylene glycol-derived component And an aromatic polyester-based random copolymer resin derived from 1,4-cyclohexanedimethanol having a molar content of 23 mol% and a tensile modulus of 2000 MPa (glass transition temperature of 69 ° C)

. PET-2: 100 mol% of terephthalic acid as a dicarboxylic acid component, 68 mol% of a glycol-derived component as a diol component, and 2 mol% of a diethylene glycol-derived component An aromatic polyester-based random copolymer resin having a tensile modulus of 1950 MPa derived from 1,4-cyclohexanedimethanol of 30 mol% (glass transition temperature of 85 ° C)

(polystyrene resin)

. PS-1: styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene; Fika softening temperature of 72 ° C, MFR 5.6 g/10 min)

. PS-2: styrene-butadiene copolymer (80% by weight of styrene, 20% by weight of butadiene; Fika softening temperature of 75 ° C, MFR 5.5 g/10 min)

. PS-3: styrene-butadiene copolymer (84% by weight of styrene, 16% by weight of butadiene; Penka softening temperature of 75 ° C, MFR 6.2 g/10 min)

. PS-4: styrene-butadiene copolymer (80% by weight of styrene, 20% by weight of butadiene; Fika softening temperature of 76 ° C, MFR 9.7 g/10 min)

. PS-5: styrene-butadiene copolymer (71% by weight of styrene, 29% by weight of butadiene; Fika softening temperature of 72 ° C, MFR 6.1 g/10 min)

. PS-6: styrene-butadiene copolymer (72% by weight of styrene, 28% by weight of butadiene; Pena softening temperature of 78 ° C, MFR 7.2 g/10 min)

. PS-7: styrene-butadiene copolymer (76 wt% styrene, 24 wt% butadiene; Fica softening temperature 80 ° C, MFR 8.4 g/10 min)

. PS-8: styrene-ethylene-butene copolymer (67% by weight of styrene, 33% by weight of ethylene-butene; MFR: 5.3 g/10 min, JIS-D hardness: 71)

(Polyester elastomer)

. TPE-1: a polyester elastomer composed of a polyester as a hard segment and a polyalkylene glycol as a soft segment (melting point 163 ° C, specific gravity 1.15, JIS-D hardness 40, glass transition temperature - 35 ° C, tensile modulus of elasticity 38 MPa)

. TPE-2: a polyester elastomer composed of a polyester as a hard segment and a polyalkylene glycol as a soft segment and modified with maleic acid (melting point 183 ° C, specific gravity 1.07, JIS-D hardness 39, glass transition temperature -47 ° C, tensile modulus of elasticity 35 MPa)

The glass transition temperature of each of the polyester resins was measured by a differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-60) in accordance with the method of JIS K 7121 (1987).

The Fika softening temperature is obtained by applying a test piece from each polystyrene resin according to the method according to JIS K 7206 (1999), and applying a load of 10 N to the needle-shaped indenter placed on the test piece at 120 ° C / The speed of h is raised, and the temperature at which the needle-shaped indenter enters 1 mm is confirmed.

The MFR was measured by melting the respective polystyrene resins at 200 ° C according to the method of ISO 1133, and measuring the amount of resin discharged in 10 minutes under a load of 5 kg.

The melting point is obtained by using a differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-60) at a temperature rising rate of 10 ° C /min according to the method of JIS-K 7121 (1987). Sex measurement.

The specific gravity was measured for each polyester elastomer by a water displacement method using ethanol as an immersion liquid according to the method of JIS K 7112 (1999) (manufactured by Alpha Mirage Co., Ltd., electronic hydrometer MD-300S).

The JIS-D hardness was measured for each polyester-based elastomer by a durometer according to the method of JIS-K 6235 (2012) (manufactured by Kobunchi Co., Ltd., ASKER D-type rubber hardness meter).

The glass transition temperature of each of the polyester elastomers was measured in a tensile mode by a dynamic viscoelasticity measuring apparatus (Q800 manufactured by TA Instruments Japan Co., Ltd.) according to the method of JIS K 7244 (1999).

The tensile modulus of elasticity was measured for each of the unstretched sheets of the polyester-based resin and the polyester-based elastomer by using the Strograph VE10 manufactured by Toyo Seiki Seisakusho Co., Ltd. according to the method of ASTM-D882.

(Example 1)

As the resin constituting the inner layer, a polyester resin (PET-1) was used.

As the resin constituting the intermediate layer, a polystyrene resin (PS-1) is used.

As the resin constituting the adhesive layer, 60% by weight (60 parts by weight) of a polystyrene resin (PS-5) and 40% by weight (40 parts by weight) of a polyester elastomer (TPE-1) were used.

The extruder was introduced into a extruder having a cylinder temperature of 160 to 250 ° C, and extruded into a sheet of a 5-layer structure from a multilayer mold of 250 ° C, and solidified by a take-up roll of 30 ° C. Then, in a tenter stretching machine having a preheating zone of 105 ° C, an extended zone of 90 ° C, and a heat-fixing zone of 85 ° C, extending at a stretching ratio of 6 times, and then taking up by a coiler, thereby obtaining a direction orthogonal to the main shrinking direction. The heat-shrinkable multilayer film in which the direction is MD and the main shrinkage direction becomes TD.

The obtained heat-shrinkable multilayer film has a total thickness of 35 μm and is 5 of the surface layer (4.0 μm) / the subsequent layer (0.8 μm) / the intermediate layer (25.4 μm) / the subsequent layer (0.8 μm) / the surface layer (4.0 μm) Layer structure.

(Example 2)

As the resin constituting the adhesive layer, 60% by weight of a polystyrene resin (PS-6) and 40% by weight of a polyester elastomer (TPE-1) were used.

Further, in the same manner as in Example 1, a total thickness of 35 μm was obtained, and it was an inner layer (3.7 μm) / an adhesive layer (0.7 μm) / an intermediate layer (26.2 μm) / an adhesive layer (0.7 μm) / an inner layer (3.7 A film of a 5-layer structure of μm).

(Example 3)

As the resin constituting the intermediate layer, a polystyrene resin (PS-2) is used.

As the resin constituting the adhesive layer, 50% by weight of a polystyrene resin (PS-5) and 50% by weight of a polyester elastomer (TPE-2) were used.

Further, in the same manner as in Example 1, a total thickness of 35 μm was obtained, and it was an inner layer (5.0 μm) / an adhesive layer (0.7 μm) / an intermediate layer (23.6 μm) / an adhesive layer (0.7 μm) / an inner layer (5.0 A film of a 5-layer structure of μm).

(Example 4)

As the resin constituting the intermediate layer, a polystyrene resin (PS-2) is used.

As the resin constituting the adhesive layer, 40% by weight of polystyrene resin (PS-5) and 60% by weight of polyester elastomer (TPE-1) were used.

Further, in the same manner as in Example 1, a total thickness of 35 μm was obtained, and it was an inner layer (4.0 μm) / a back layer (0.8 μm) / an intermediate layer (25.4 μm) / an adhesive layer (0.8 μm) / an inner layer (4.0 A film of a 5-layer structure of μm).

(Example 5)

As the resin constituting the intermediate layer, a polystyrene resin (PS-3) is used.

As the resin constituting the adhesive layer, 40% by weight of a polystyrene resin (PS-5) and 60% by weight of a polyester elastomer (TPE-2) were used.

Further, in the same manner as in Example 1, a total thickness of 35 μm was obtained, and it was an inner layer (5.0 μm) / an adhesive layer (0.8 μm) / an intermediate layer (23.4 μm) / an adhesive layer (0.8 μm) / an inner layer (5.0 A film of a 5-layer structure of μm).

(Example 6)

As the resin constituting the inner layer, a polyester resin (PET-2) was used.

As the resin constituting the intermediate layer, a polystyrene resin (PS-4) is used.

As the resin constituting the adhesive layer, 20% by weight of a polystyrene resin (PS-5) and 80% by weight of a polyester elastomer (TPE-2) were used.

Further, in the same manner as in Example 1, a total thickness of 35 μm was obtained, and it was an epiphysical layer (3.5 μm) / an adhesive layer (0.8 μm) / an intermediate layer (26.4 μm) / an adhesive layer (0.8 μm) / an inner layer (3.5 A film of a 5-layer structure of μm).

(Example 7)

As the resin constituting the inner layer, a polyester resin (PET-2) was used.

As the resin constituting the intermediate layer, a polystyrene resin (PS-3) is used.

As the resin constituting the adhesive layer, 50% by weight of a polystyrene resin (PS-6) and 50% by weight of a polyester elastomer (TPE-1) were used.

Further, in the same manner as in Example 1, a total thickness of 35 μm was obtained, and it was an inner layer (4.0 μm) / a back layer (0.8 μm) / an intermediate layer (25.4 μm) / an adhesive layer (0.8 μm) / an inner layer (4.0 A film of a 5-layer structure of μm).

(Example 8)

As the resin constituting the inner layer, a polyester resin (PET-2) was used.

As the resin constituting the intermediate layer, a polystyrene resin (PS-2) is used.

As the resin constituting the adhesive layer, 25% by weight of a polystyrene resin (PS-7) and 75% by weight of a polyester elastomer (TPE-2) were used.

Further, in the same manner as in Example 1, a total thickness of 35 μm was obtained, and it was an epiphysical layer (3.5 μm) / an adhesive layer (0.8 μm) / an intermediate layer (26.4 μm) / an adhesive layer (0.8 μm) / an inner layer (3.5 A film of a 5-layer structure of μm).

(Example 9)

As the resin constituting the inner layer, a polyester resin (PET-1) was used.

As the resin constituting the intermediate layer, a polystyrene resin (PS-1) is used.

As the resin constituting the adhesive layer, 20% by weight of a polystyrene resin (PS-5), 15% by weight of a polystyrene resin (PS-8), and 65% by weight of a polyester elastomer (TPE-1) were used.

Further, in the same manner as in Example 1, a total thickness of 40 μm was obtained, and it was an inner layer (4.5 μm) / an adhesive layer (0.9 μm) / an intermediate layer (29.2 μm) / an adhesive layer (0.9 μm) / an inner layer (4.5 A film of a 5-layer structure of μm).

(Comparative Example 1)

As the resin constituting the adhesive layer, 75 wt% of a polystyrene resin (PS-5) and 25 wt% of a polyester elastomer (TPE-1) were used.

Further, in the same manner as in Example 1, a total thickness of 40 μm was obtained, and it was an inner layer (5.5 μm) / an adhesive layer (0.8 μm) / an intermediate layer (27.4 μm) / an adhesive layer (0.8 μm) / an inner layer (5.5). A film of a 5-layer structure of μm).

(Comparative Example 2)

As the resin constituting the intermediate layer, a polystyrene resin (PS-2) is used.

As the resin constituting the adhesive layer, 15% by weight of a polystyrene resin (PS-6) and 85% by weight of a polyester elastomer (TPE-2) were used.

Further, in the same manner as in Example 1, a total thickness of 35 μm was obtained, and it was an inner layer (5.0 μm) / an adhesive layer (0.7 μm) / an intermediate layer (23.6 μm) / an adhesive layer (0.7 μm) / an inner layer (5.0 A film of a 5-layer structure of μm).

(Comparative Example 3)

As the resin constituting the inner layer, a polyester resin (PET-2) was used.

As the resin constituting the intermediate layer, a polystyrene resin (PS-2) is used.

As the resin constituting the adhesive layer, a polyester elastomer (TPE-2) was used.

Further, in the same manner as in Example 1, a total thickness of 35 μm was obtained, and it was an inner layer (5.0 μm) / an adhesive layer (0.7 μm) / an intermediate layer (23.6 μm) / an adhesive layer (0.7 μm) / an inner layer (5.0 A film of a 5-layer structure of μm).

(Comparative Example 4)

As the resin constituting the adhesive layer, 25% by weight of a polystyrene resin (PS-5) and 75% by weight of a polyester resin (PET-1) were used.

Further, in the same manner as in Example 1, a total thickness of 40 μm was obtained, and it was an inner layer (5.0 μm) / an adhesive layer (0.8 μm) / an intermediate layer (28.4 μm) / an adhesive layer (0.8 μm) / an inner layer (5.0 A film of a 5-layer structure of μm).

(Comparative Example 5)

As the resin constituting the adhesive layer, 25% by weight of a polystyrene resin (PS-1) and 75% by weight of a polyester resin (PET-1) were used.

Further, in the same manner as in Example 1, a total thickness of 40 μm was obtained, and it was an inner layer (5.0 μm) / an adhesive layer (0.8 μm) / an intermediate layer (28.4 μm) / an adhesive layer (0.8 μm) / an inner layer (5.0 A film of a 5-layer structure of μm).

(Comparative Example 6)

As the resin constituting the adhesive layer, 75 wt% of a polystyrene resin (PS-1) and 25 wt% of a polyester resin (PET-1) were used.

Further, in the same manner as in Example 1, a total thickness of 40 μm was obtained, and it was an inner layer (5.0 μm) / an adhesive layer (0.8 μm) / an intermediate layer (28.4 μm) / an adhesive layer (0.8 μm) / an inner layer (5.0 A film of a 5-layer structure of μm).

(Evaluation)

The heat-shrinkable multilayer film obtained in the examples and the comparative examples was subjected to the following evaluation. The composition and evaluation results of the heat-shrinkable multilayer film are shown in Table 1.

(1) Heat shrinkage rate

The heat-shrinkable multilayer film was cut into a shrinkage direction (TD) of 100 mm × a direction perpendicular to the main shrinkage direction (MD) of 100 mm, and immersed in warm water of 70 ° C for 10 seconds, and then the heat-shrinkable multilayer film was taken out, immediately. Immerse in tap water for 10 seconds. The length (L) of one side of the TD of the heat-shrinkable multilayer film was measured, and the heat shrinkage ratio in the TD direction was obtained by the following formula (1).

Heat shrinkage rate (%) = {(100-L) / 100} × 100 (1)

Further, the shrinkage rate uses the average of the number of samples (n) = 3. The heat shrinkage rate was also measured in the same manner for warm water and boiling water of 80 °C.

(2) Interlaminar strength at normal temperature

The heat-shrinkable multilayer film was cut into a size of 100 mm in length × 10 mm in width, and one of the end portions of the film was peeled off between layers as shown in FIG. The peeling tester (Peling TESTER HEIDON-17, manufactured by Shinto Scientific Co., Ltd.) was used to measure the strength at room temperature (23 ° C) when peeling in the 180-degree direction at a tensile speed of 500 mm/min in the longitudinal direction of the sample as shown in FIG. 2 . (N/10mm). 1 and 2 are schematic views showing a method of peeling off a film in interlayer strength evaluation.

The test was carried out such that the longitudinal direction became the main contraction direction (TD) or the direction orthogonal to the main contraction direction (MD).

Furthermore, 10 tests were performed in both directions of MD and TD, and the average value of the interlayer strength in each direction of MD and TD was obtained.

The average value of the interlayer strength in each direction of the obtained MD and TD was evaluated based on the following criteria. When the evaluation is "○", it is possible to suppress the label peeling failure or the like when the heat shrinkable label is attached to a container or the like.

(interlayer strength in the MD direction)

The average interlayer strength is set to 0.50 N/10 mm or more to "○", and the less than 0.50 N/10 mm is set to "X".

(interlayer strength in the TD direction)

The average interlayer strength is 0.50N/10mm or more and is set to "○", which will not be 0.50N/10mm. Set to "X".

(3) Determination of the peeling surface at normal temperature

The interlaminar peel strength measurement at normal temperature was observed, and the interlaminar peeling interface at the time of measurement in the TD direction was observed and evaluated according to the following criteria.

(peeling surface judgment)

The case where the interlayer is peeled off to the interface between the intermediate layer and the subsequent layer is "○", and the case where the interlayer is peeled off to the interface between the front and back layers is "x".

When the heat shrinkable label is installed in the container, there is a label folding caused by the mounting machine. When the load is equal, the surface layer on the outer side of the heat-shrinkable label is damaged. If damage occurs in the surface layer, the interlayer peeling is performed starting from the damage, and in the worst case, the label is peeled off after mounting. Whether or not the label is peeled off differs depending on which interface of the heat-shrinkable multilayer film is peeled off. Fig. 3 is a schematic view showing a heat-shrinkable multilayer film in the case where peeling occurs at the interface between the intermediate layer and the adhesive layer, and Fig. 4 is a schematic view showing the heat-shrinkable multilayer film in the case where peeling occurs at the interface between the surface layer and the adhesive layer. .

When the interlayer peeling occurs at the interface between the intermediate layer and the adhesive layer as shown in FIG. 3, even if the damage occurs due to the mounting machine, if the damage does not penetrate the surface layer and the adhesive layer, interlayer peeling is not performed, and labeling is less likely to occur. Stripped. On the other hand, when the interlayer peeling occurs at the interface between the surface layer and the adhesive layer as shown in Fig. 4, interlayer peeling occurs only when the surface layer is damaged, causing peeling of the label.

(4) Is there any peeling failure at normal temperature?

The heat-shrinkable multilayer film was cut into a size of 100 mm in length × 10 mm in width, and after standing at normal temperature (23 ° C) for 10 minutes, one portion of the film end portion was peeled off in the same manner as in the measurement of interlayer strength. The presence or absence of peeling failure was evaluated on the basis of the following criteria. If the evaluation of "etc." is "Yes", it is known that the interlayer strength is uneven.

The term "poor peeling" refers to the unevenness of the interlayer strength when the heat-shrinkable multilayer film is peeled off. The portion having a high interlayer strength is high in peeling resistance, and the peeling resistance is low in a portion where the interlayer strength is low. Therefore, the peeling resistance is not fixed, and the portion where the peeling is stopped and the portion where the peeling is instantaneously occur are regularly or irregularly present.

(with or without peeling)

There are: traces of striped patterns appearing in the inner layer of the peeled watch.

None: There are no traces of striped patterns in the inner layer of the peeled watch.

(5) Interlayer strength at low temperature

The heat-shrinkable multilayer film was cut into a size of 100 mm in length × 10 mm in width, and after standing at a low temperature (5 ° C) for 10 minutes, the interlaminar strength (N/10 mm) was measured. The measurement was carried out in the same manner as the evaluation of the interlayer strength at normal temperature, except that the measurement temperature was set to 5 °C.

The inter-layer intensity and the minimum value in the TD direction were measured each time each measurement was performed. In the 10 tests, the average of the inter-layer intensities in the TD directions of each measurement was taken as the average value in the TD direction, and the average of the minimum values of the respective measurements was taken as the TD direction. Minimum value. In the evaluation at low temperature, in particular, by measuring the interlayer strength in the TD direction, it is understood that the resistance to interlayer peeling when a load is applied to the TD direction of the heat-shrinkable label by a mounting machine or the like in a low-temperature environment. Further, by obtaining the average value and the minimum value of the interlayer strengths in the TD direction, the magnitude of the interlayer peeling strength distribution in a low temperature environment can be known.

(interlayer strength in the TD direction)

The average interlayer strength is set to 0.50 N/10 mm or more to "○", and the less than 0.50 N/10 mm is set to "X".

(6) Determination of the peeling surface at low temperature

In the measurement of the interlayer peel strength at a low temperature, the interlayer peeling interface at the time of measurement in the TD direction was observed, and the evaluation was performed on the same basis as the peeling surface judgment at normal temperature.

(7) Is there any peeling failure at low temperature?

The heat-shrinkable multilayer film was cut into a size of 100 mm in length × 10 mm in width, and after standing at a low temperature (5° C.) for 10 minutes, one of the end portions of the film was layered as in the interlayer strength measurement. Stripped. The presence or absence of peeling failure was evaluated on the same basis as the peeling failure at normal temperature.

(8) Evaluation of interlayer peeling after label bending

The obtained heat-shrinkable multilayer film was cut into a width of 227 mm in the TD direction, and a solvent in which 30 parts by weight of cyclohexane was mixed with 100 parts by weight of 1,4-dioxolane was parallel to the MD direction. The 3 mm coating was flatly folded and joined into a cylindrical shape so that the width in the TD direction became 108 mm. The heat-shrinkable multilayer film which is a cylindrical shape was cut into a width of 100 mm in the MD direction as shown in Fig. 5 to prepare a heat-shrinkable label. Fig. 5 is a schematic view of a heat shrinkable label used for label bending evaluation. The both ends of the label are also referred to as "solvent sealing portions" by the solvent.

Then, both ends of the sealing portion of the heat-shrinkable label were held by fingers in a low-temperature (5 ° C) atmosphere, and the label was bent 20 times in a force applied in the TD direction. The operation of bending the label is performed at 6 places of the heat shrinkable label to obtain a heat-shrinkable label after bending.

The appearance of the subsequent portion of the bottle-shaped can container having a diameter of about 66 mm and having a diameter of about 66 mm was immersed in boiling water for 10 seconds, and was heat-shrinked and covered in the container, and the following criteria were used. Evaluation.

○: Interlaminar peeling of the solvent-sealed portion was not produced in all of the ten labels.

△: 1 to 2 labels in 10 sheets of labels, resulting in interlayer peeling of the solvent-sealed portion.

×: Three or more labels among the ten sheets of labels produced interlayer peeling of the solvent-sealed portion.

(9) Evaluation of crease whitening

The heat-shrinkable multilayer film (film width: 500 mm) was printed by FINESTAR Black (manufactured by Toyo Ink Co., Ltd.) by gravure printing, and then printed using FINESTAR White (manufactured by Toyo Ink Co., Ltd.). Thereby, a heat-shrinkable multilayer film which was subjected to two-color back printing of black and white was obtained. As the printing plate, a plate made by direct laser plate making with a depth of 30 μm and a line number of 175 lines was used.

Then, the heat-shrinkable multilayer film was cut from the black printed portion into a rectangle having a MD direction of 100 mm × TD direction of 200 mm. The cut sample was placed on the inside of the printed surface at room temperature (23 °C) Pressing the rubber roller twice at a speed of 2s/100mm under the 2kg load in parallel with the MD direction, thereby forming a crease after cutting the sample, unfolding the cut sample, and then at a speed of 2s/100mm under a load of 2kg. Press the rubber roller once to restore the crease to its original state. Thereafter, a jig capable of restricting the shrinkage ratio in the TD direction was used, and the sample was immersed in warm water of 75 ° C for 7 seconds and contracted by 5% in the TD direction. The appearance of the crease at this time was evaluated according to the following criteria.

Furthermore, the evaluation of the appearance was performed by irradiating the light of the fluorescent lamp at an angle of 45 degrees from the sample, and visually conducting the position of 10 people at an angle of 45 degrees opposite to that of the fluorescent lamp. An example of the case where the crease whitening cannot be observed is shown in Fig. 6, and an example of the case where the crease is self-contained can be seen in Fig. 7.

(crease whitening evaluation)

○: All 10 people could not observe the crease whitening.

△: crease whitening was observed in 2 or less of 10 people.

×: Crease whitening was observed in 3 or more of 10 people.

(10) Change in transparency before and after heat treatment

The haze value before and after the heat treatment of the heat-shrinkable multilayer film was measured, and the rate of change was determined. The heat treatment was carried out by the same method as measuring the heat shrinkage rate, and immersed in boiling water for 10 seconds. Further, the haze was measured in accordance with ASTM D-1003 using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.).

The rate of change was determined using the following formula.

Rate of change = (haze value after heat treatment / haze value before heat treatment) × 100

○: The rate of change is less than 400%

×: The rate of change is 400% or more

(Overview)

○: In the evaluation of the above (1) to (10), there is no "X".

×: There is one or more "x" in the evaluation of the above (1) to (10).

In the heat-shrinkable multilayer film obtained in Examples 1 to 9, good results were obtained in all evaluations. Further, even if peeling occurs between the heat-shrinkable multilayer film and the peeling occurs at the interface between the intermediate layer and the adhesive layer, peeling of the label does not occur.

On the other hand, when the mixing ratio of the resin constituting the adhesive layer as in Comparative Examples 1 to 6 does not satisfy the range specified by the present invention, the interlayer strength at a low temperature is lowered, or the crease whitening is strongly bent in the solvent sealing step. The appearance is poor, or the interlayer peeling occurs due to the impact when mounted on the container. Moreover, peeling failure occurs at a low temperature.

According to the present invention, it is possible to provide a heat-shrinkable multilayer film which is excellent not only at normal temperature but also at a low temperature, and has excellent adhesion between the front and back layers and the intermediate layer, can effectively prevent interlayer peeling, and is not easily folded after heat shrinkage. The white streaks remain in the traces. Moreover, according to the present invention, it is possible to provide a heat-shrinkable label obtained by using the heat-shrinkable multilayer film.

Claims (8)

A heat-shrinkable multilayer film comprising a front layer comprising a polyester resin and an intermediate layer containing a polystyrene resin, wherein the adhesive layer comprises a layer of 20 to 35% by weight. A styrene resin and a polyester elastomer of 65 to 80% by weight. The heat-shrinkable multilayer film of the first aspect of the invention, wherein the polystyrene-based resin-based aromatic vinyl hydrocarbon-conjugated diene copolymer constituting the adhesive layer. The heat-shrinkable multilayer film according to claim 1, wherein the polyester elastomer constituting the adhesive layer has a melting point of 120 to 200 °C. The heat-shrinkable multilayer film of claim 2, wherein the polyester elastomer constituting the adhesive layer has a melting point of 120 to 200 °C. The heat-shrinkable multilayer film of claim 1, 2, 3 or 4, wherein the polyester elastomer constituting the adhesive layer has a specific gravity of 0.95 to 1.20. The heat-shrinkable multilayer film of claim 1, 2, 3 or 4, wherein the polyester elastomer constituting the adhesive layer is modified with an α,β-ethylenically unsaturated carboxylic acid. The heat-shrinkable multilayer film according to claim 5, wherein the polyester elastomer constituting the adhesive layer is modified with an α,β-ethylenically unsaturated carboxylic acid. A heat-shrinkable label obtained by using a heat-shrinkable multilayer film of the first, second, third, fourth, fifth, sixth or seventh aspect of the patent application.