JP2007182030A - Heat shrinkable multilayered resin film and shrink label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat shrinkable multilayered resin film capable of effectively preventing the degradation of a content in a container by an ultraviolet ray when using as a shrink label for the container and which is excellent in cutting properties on a perforated line and in oil resistance, and a shrink label using the heat shrinkable multilayered resin film as a base film. <P>SOLUTION: The heat shrinkable multilayered resin film comprises an intermediate layer of a polystyrene resin and outer face layers of a polyester resin overlaid on the both sides of the intermediate layer, wherein the intermediate layer contains an ultraviolet ray absorbing agent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention, when used as a shrink label for a container, can effectively prevent deterioration of the contents of the container due to ultraviolet rays, and has excellent heat-shrinkable multilayer resin film with excellent cut and oil resistance at the perforation. And a shrink label using the heat-shrinkable multilayer resin film as a base film.

Many plastic containers such as plastic bottles are provided with a shrink label obtained by printing or the like on a base film made of a heat-shrinkable resin film. However, in recent years, compared with storage using a metal bowl, the contents of the container are deteriorated by sunlight or ultraviolet rays emitted from a fluorescent lamp, and the storage property is deteriorated. For example, chlorophyll contained in edible oil or the like is decomposed at a wavelength of 300 nm or less and causes quality deterioration. Moreover, the citral used as a fragrance | flavor, such as a drink, changes to the component with an unpleasant fragrance by the light of 300-350 nm. In addition, amino acids such as tryptophan and tyrosine contained in sake change color by light of 320 to 380 nm. Therefore, in recent years, a shrink film having an ultraviolet ray-cutting property has been put into practical use in order to prevent the taste and flavor from being deteriorated or changed due to ultraviolet rays or discoloration of the contents of the container.

As such shrink labels, those made of polystyrene resin are mainly used because of their excellent low-temperature shrinkability. For example, Patent Document 1 discloses a polystyrene-based resin film having a three-layer structure, from both outer layers. Also disclosed is an ultraviolet-absorbing polystyrene-based resin heat-shrinkable film in which the blending amount of the ultraviolet absorber in the intermediate layer is increased.

However, the heat-shrinkable polystyrene film having such a configuration has a problem that light having a wavelength of 400 nm or less cannot be sufficiently absorbed unless a large amount of ultraviolet absorber is added.
In addition, when a large amount of the ultraviolet absorber is added, there is a problem that the ultraviolet absorber bleeds out and disadvantageous in terms of cost. In addition, the polystyrene film has insufficient oil resistance, and when a label is attached to a container of contents containing oil, there is a problem that the film shrinks or dissolves due to adhesion of the oil.

On the other hand, instead of polystyrene resin films, attempts have been made to use heat-shrinkable polyester films with UV absorbers added to polyester films with excellent low-temperature resistance, solvent resistance, and oil resistance as shrink labels. For example, Patent Document 2 discloses an excellent UV-cutting property, heat resistance by a method of adding a UV absorber to a heat-shrinkable polyester film or a method of adding UV light to an inner layer of a laminated polyester film of two or more layers. A polyester-based resin film realizing shrinkage is disclosed.

However, since the polyester film has a high molding temperature, when the extrusion molding is performed, the ultraviolet absorbent sublimates and volatilizes from the die, thereby causing deterioration of the working environment and taking up the film extruded from the die. Productivity was reduced due to contamination of the roll. Further, when the molding temperature is lowered in order to prevent thermal degradation of the ultraviolet absorber, the productivity of the film is remarkably lowered. Furthermore, the shrink film is often provided with a perforation for peeling so that the shrink label can be easily peeled off from the container after use in order to recycle the container. There was also a problem that the cut property at the perforation was poor and the shrink label could not be easily peeled off from the container.
Therefore, there has been a need for a heat-shrinkable multilayer resin film having excellent ultraviolet ray cutting properties and perforation cutting properties without deteriorating the working environment and reducing productivity.
JP 2002-326324 A JP 2001-330882 A

In view of the above situation, the present invention can effectively prevent deterioration of the contents of a container due to ultraviolet rays when used as a shrink label for a container, and has a heat-shrinkable multilayer that is excellent in cut performance at perforations. It aims at providing the shrink label which uses a resin film and this heat-shrinkable multilayer resin film as a base film.

The present invention is a heat-shrinkable multilayer resin film comprising an intermediate layer made of polystyrene resin and an outer surface layer made of polyester resin sandwiching the intermediate layer, the intermediate layer containing an ultraviolet absorber. It is a heat-shrinkable multilayer resin film.
The present invention is described in detail below.

As a result of intensive studies, the inventors have added ultraviolet rays to an intermediate layer of a heat-shrinkable multilayer resin film comprising an intermediate layer made of polystyrene resin and an outer surface layer made of polyester resin sandwiching the intermediate layer. The UV absorber does not bleed out or undergo thermal degradation, and can achieve both an excellent UV absorption effect and perforation cut performance, and a polyester resin or polystyrene resin can be used alone. It has been found that it is possible to solve the problems associated with adding an ultraviolet absorber to a heat-shrinkable multilayer film, and the present invention has been completed.

The heat-shrinkable multilayer resin film of the present invention comprises an intermediate layer made of a polystyrene resin and an outer surface layer made of a polyester resin that sandwiches the intermediate layer.

Examples of the polystyrene resin constituting the intermediate layer include aromatic vinyl hydrocarbon-conjugated diene copolymers, aromatic vinyl hydrocarbon-conjugated diene copolymers, and aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acids. Examples thereof include a mixed resin with an ester copolymer.
Since the aromatic vinyl hydrocarbon-conjugated diene copolymer is excellent in low-temperature shrinkage, the resulting shrink film can be easily attached to a container without causing wrinkles and the like, and cut at the perforation. It is also excellent in properties.
In addition, since a mixed resin of an aromatic vinyl hydrocarbon-conjugated diene copolymer and an aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer is excellent in low-temperature elongation when used as a film, it can be obtained. The resulting shrink film has high low temperature resistance and excellent cut performance at the perforation.

The aromatic vinyl hydrocarbon-conjugated diene copolymer is not particularly limited. For example, aromatic vinyl hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, and conjugated dienes are 1,3- Examples include butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like. These may be used alone or in combination of two or more. Among these, a styrene-butadiene-styrene copolymer (SBS resin) is preferable because it is particularly excellent in low-temperature shrinkage and cut performance at perforations. In order to produce a film with less fish eye, a styrene-isoprene-styrene copolymer (SIS resin) using 2-methyl-1,3-butadiene (isoprene) as a conjugated diene, or a styrene-isoprene. -It is preferable to use a butadiene-styrene copolymer (SIBS resin) or the like.

When the SBS resin, SIS resin or SIBS resin is used as the aromatic vinyl hydrocarbon-conjugated diene copolymer, one kind of resin may be used alone, or a plurality of resins may be used in combination. . When used in plural, dry blending may be used, or a compound resin that is kneaded and pelletized using an extruder with a specific composition may be used.
It is preferable to use such resins singly or in combination to have a composition having a styrene content of 65 to 90% by weight and a conjugated diene content of 10 to 35% by weight. A resin having such a composition is particularly excellent in low-temperature shrinkage and perforation. On the other hand, when the conjugated diene content is less than 10% by weight, the film is easily cut when tension is applied to the film, and the film may break unexpectedly when used as a converting or label for printing or the like. . When the conjugated diene content exceeds 35% by weight, foreign matters such as gel may be easily generated during the molding process.

Furthermore, as the aromatic vinyl hydrocarbon-conjugated diene copolymer, an aromatic vinyl hydrocarbon-conjugated diene copolymer having isoprene as the conjugated diene component may be used. In particular, when an aromatic vinyl hydrocarbon-conjugated diene copolymer having a high proportion of butadiene is used, crosslinking due to the butadiene component tends to proceed during molding, resulting in fish eyes and printability. Inconveniences such as deterioration will occur. In contrast, when an aromatic vinyl hydrocarbon-conjugated diene copolymer having isoprene as a conjugated diene component is used, cross-linking during molding is suppressed, so that generation of foreign matters such as gels can be prevented. .
This is because the butadiene component of the aromatic vinyl hydrocarbon-conjugated diene copolymer generates reactive radicals by heating during molding, thereby dehydrogenating other compounds or double bonds. It is considered that the isoprene component generates radicals having poor reactivity and is bonded to each other to suppress the progress of the crosslinking, while it is likely to cause chain crosslinking.

The aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer is not particularly limited. Examples of the aromatic vinyl hydrocarbon include styrene, o-methylstyrene, p-methylstyrene, and the like. Examples of the acid ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. These may be used alone or in combination of two or more.

When a styrene-butyl acrylate copolymer is used as the aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer, the styrene content is 60 to 90% by weight, and the butyl acrylate content is 10 to 40. It is preferable to use what is weight%. By using the aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer having such a composition, a shrink label excellent in low temperature resistance and perforation cutting property can be obtained.

When a mixed resin of an aromatic vinyl hydrocarbon-conjugated diene copolymer and an aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer is used as the intermediate layer, the aromatic vinyl carbonization in the mixed resin is used. The preferable lower limit of the blending amount of the hydrogen-conjugated diene copolymer is 20% by weight, and the preferable upper limit is 80% by weight. If it is less than 20% by weight, the low-temperature elongation becomes low and the shrink film may be torn when accidentally dropped during refrigerated storage. If it exceeds 80% by weight, shrinkage during storage of the shrink film, so-called natural shrinkage may occur. May increase. A more preferred lower limit is 30% by weight, and a more preferred upper limit is 70% by weight.

In the heat-shrinkable multilayer resin film of the present invention, the intermediate layer contains an ultraviolet absorber.
In this way, by adding an ultraviolet absorber, it is possible to impart an ultraviolet-cutting property, and the heat-shrinkable multilayer resin film of the present invention cuts particularly ultraviolet rays (wavelength of 380 nm or less) emitted from sunlight or fluorescent lamps. Since it is excellent in property, deterioration of the contents of a container can be prevented and storage property can be improved.
In addition, by including the ultraviolet absorber only in the intermediate layer made of polystyrene resin, problems such as thermal deterioration and roll contamination when the ultraviolet absorber is added to the polyester resin can be solved. In addition, even when the content of the ultraviolet absorber is small, the desired ultraviolet cutting property can be achieved, which is advantageous in terms of cost.

Examples of the ultraviolet absorber include 2,4-dihydroxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5 Benzophenone ultraviolet absorbers such as sulfonic acid and 2-hydroxy-4-n-octoxybenzophenone; 2- (2′-hydroxy-4′-n-octoxyphenyl) benzotriazole, 2- (2′-hydroxy- 5′-n-methoxyphenyl) benzotriazole, 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′, 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-5'- ert-octylphenyl) benzotriazole, 2- [2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl] benzotriazole, etc. Benzotriazole ultraviolet absorbers; benzoate ultraviolet absorbers such as 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate; p-tert-butylphenyl salicylate Salicylate ultraviolet absorbers; and cyanoacrylate ultraviolet absorbers such as ethyl-2-cyano-3,3-diphenyl acrylate and octyl-2-cyano-3,3-diphenyl acrylate.
Among these, 2- (2′-hydroxy-5′-n-methoxyphenyl) benzotriazole, 2- (2′-hydroxy-3′-tert) is excellent because it has an excellent balance between ultraviolet absorption and heat resistance. -Butyl-5'-methylphenyl) -5-chlorobenzotriazole is preferred.

The content of the ultraviolet absorber is preferably 1 part by weight with respect to 100 parts by weight of the material constituting the intermediate layer such as the base resin and the recycled material, and 10 parts by weight with respect to the preferable upper limit. When the amount is less than 1 part by weight, the UV-cutting property is insufficient, and when used as a shrink label for a container, deterioration of the contents may not be prevented. The mechanical strength of the paper decreases, and when used as a converting or shrink label for printing or the like, breakage or the like may occur. The minimum with more preferable content of the said ultraviolet absorber is 2 weight part, and a more preferable upper limit is 8 weight part.

The polyester resin constituting the outer surface layer can be obtained by condensation polymerization of dicarboxylic acid and diol.
The dicarboxylic acid is not particularly limited. For example, o-phthalic acid, terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, octyl succinic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, fumaric acid, Examples include maleic acid, itaconic acid, decamethylene carboxylic acid, anhydrides and lower alkyl esters thereof.
The diol is not particularly limited. For example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, dipropylene glycol, triethylene Glycol, tetraethylene glycol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, neopentyl glycol (2,2-dimethylpropane-1,3-diol), 1,2-hexane Aliphatic diols such as diol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol; 2-bis (4-hydroxycyclohexyl) propane, 2,2-bis (4-hydroxy) B carboxymethyl cyclohexyl) alkylene oxide adducts of propane, 1,4-cyclohexane diol, alicyclic diols such as 1,4-cyclohexanedimethanol.

Among these polyester-based resins, those containing a component derived from terephthalic acid as the dicarboxylic acid component and those derived from ethylene glycol and 1,4-cyclohexanedimethanol as the diol component are suitable. is there. By using such a polyester resin, particularly high low temperature resistance and solvent resistance can be imparted to the resulting heat-shrinkable multilayer resin film of the present invention.
In addition, when imparting particularly high low temperature resistance and solvent resistance, the content of the component derived from ethylene glycol is 60 to 80 mol%, and the content of the component derived from 1,4-cyclohexanedimethanol is 10 It is preferable to use one that is ˜40 mol%. Such a polyester resin may further contain 0 to 20 mol% of a component derived from diethylene glycol.
As a polyester-type resin which comprises the said outer surface layer, the polyester-type resin which has the composition mentioned above may be used independently, and 2 or more types of polyester-type resins which have the composition mentioned above may be used together.

As the polyester resin, a resin having a crystal melting temperature of 240 ° C. or lower is preferably used. In the manufacture of shrink films, it is common practice to use stretched ear trimming pieces and recycled films as return materials again. Usually, such a return material is mixed with a polystyrene resin as a raw material for the intermediate layer. However, since the polystyrene resin and the polyester resin have different properties such as a melting point, the temperature is suitable for molding the polystyrene resin. When film molding is performed, the polyester resin may be extruded in an unmelted state. However, by using a polyester resin having a relatively low crystal melting temperature or no crystal melting temperature, it is possible to prevent an unmelted product of the polyester resin from becoming a foreign substance in the film after molding. On the other hand, when the crystal melting temperature exceeds 240 ° C., when molding as a return material, undissolved polyester-based resin remains as foreign matter on the film, resulting in appearance failure or ink at the time of printing. In some cases, a problem such as a printing failure occurs due to flying. More preferably, it is 220 degrees C or less.

In the heat-shrinkable multilayer resin film of the present invention, the intermediate layer and the outer layer have at least one functional group selected from the group consisting of a carboxylic acid group, an acid anhydride group, an amino group, an epoxy group, and a hydroxyl group. It is preferably bonded by an adhesive layer made of a hydrogenated product of an aromatic vinyl hydrocarbon-conjugated diene copolymer in the molecule. Such an adhesive layer has a high affinity for either the polystyrene resin constituting the intermediate layer or the polyester resin constituting the outer surface layer, and can bond them with high strength. In addition, since it dissolves or swells in a solvent that dissolves the polyester resin constituting the outer surface layer, the solvent can penetrate into the interior of the shrink label during center sealing, and delamination occurs during subsequent heat shrinkage. Can be prevented. Furthermore, since it can be molded by the coextrusion method together with the intermediate layer and the outer surface layer, it is excellent in productivity.

Hydrogenation of an aromatic vinyl hydrocarbon-conjugated diene copolymer having in its molecule at least one functional group selected from the group consisting of the carboxylic acid group, acid anhydride group, amino group, epoxy group and hydroxyl group Although it does not specifically limit as a thing, For example, maleic anhydride modified styrene-ethylene / butylene-styrene block copolymer (maleic anhydride modified SEBS resin), amine modified styrene-ethylene / butylene-styrene block copolymer (amine modified) SEBS resin), amine-modified styrene-butadiene / butylene-styrene block copolymer (amine-modified SBBS resin) or carboxylic acid-modified styrene-butadiene / butylene-styrene block copolymer (carboxylic acid-modified SBBS resin) are suitable. .

Both the SEBS resin and the SBBS resin can be obtained by hydrogenating the SBS resin, and further, grafted with maleic anhydride or reacted with an amine compound, a carboxylic acid compound or the like to form an amine or carboxylic acid at the terminal portion. A modified product can be easily obtained by adding an acid.

Hydrogenation of an aromatic vinyl hydrocarbon-conjugated diene copolymer having in its molecule at least one functional group selected from the group consisting of the carboxylic acid group, acid anhydride group, amino group, epoxy group and hydroxyl group The preferable lower limit of the content of the aromatic vinyl hydrocarbon component in the product is 20% by weight, and the preferable upper limit is 80% by weight. When it is less than 20% by weight, delamination tends to occur when a shrink label is attached. When it exceeds 80% by weight, the tackiness of the adhesive layer is lowered, and sufficient adhesive strength may not be obtained. A more preferred upper limit is 50% by weight.

Hydrogenation of an aromatic vinyl hydrocarbon-conjugated diene copolymer having in its molecule at least one functional group selected from the group consisting of the carboxylic acid group, acid anhydride group, amino group, epoxy group and hydroxyl group The minimum with preferable content of the said functional group in a thing is 0.05 weight%, and a preferable upper limit is 5.0 weight%. If it is less than 0.05% by weight, the adhesion to the outer surface layer may be insufficient, and if it exceeds 5.0% by weight, the resin is thermally deteriorated when the functional group is added, and the gel Such a foreign matter may be easily generated. A more preferred lower limit is 0.1% by weight, and a more preferred upper limit is 3.0% by weight.

The preferable lower limit of the thickness of the heat-shrinkable multilayer resin film of the present invention is 30 μm, and the preferable upper limit is 60 μm. If it is less than 30 μm, it tends to break, and if it exceeds 60 μm, the perforation cut property may be lowered.

The preferable lower limit of the thickness of the intermediate layer is 50% of the total thickness of the heat-shrinkable multilayer resin film, and the preferable upper limit is 85%. If it is less than 50%, the cut performance at the perforation may not be obtained, and if it exceeds 85%, the film surface is likely to be scratched, and the ultraviolet absorber may bleed from there.
The preferable lower limit of the thickness of the outer surface layer is 5% of the total thickness of the heat-shrinkable multilayer resin film, and the preferable upper limit is 24%. If it is less than 5%, sufficient oil resistance and low temperature resistance may not be obtained, and if it exceeds 24%, sufficient cut performance at the perforation may not be obtained.
The preferable lower limit of the thickness of the adhesive layer is 0.7 μm, and the preferable upper limit is 1.5 μm. If it is less than 0.7 μm, sufficient adhesive strength may not be obtained, and if it exceeds 1.5 μm, the heat shrinkage characteristics may be deteriorated. A more preferable lower limit is 0.8 μm, and a more preferable upper limit is 1.3 μm.

The method for producing the heat-shrinkable multilayer resin film of the present invention is not particularly limited, but a method of simultaneously molding each layer by a coextrusion method is preferable. For example, in co-extrusion using a T-die, any of a feed block method, a multi-manifold method, or a method using these in combination may be used as a lamination method. In particular, by setting the temperature after the portion where the resin of each layer joins to preferably 230 ° C. or higher, more preferably 240 ° C. or higher, a multilayer film having good adhesion of each layer can be obtained.
Further, the method for adding the ultraviolet absorber is not particularly limited, for example, a method in which the ultraviolet absorber is directly charged into an extruder; a preparation after preparing a master batch by kneading the ultraviolet absorber in the polystyrene resin. The master batch method etc. which mix | blend and dilute the prepared master batch are mentioned.

If necessary, additives such as an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, and an antiblocking agent may be added to the heat-shrinkable multilayer resin film of the present invention. In particular, the generation of gel can be suppressed by adding a heat stabilizer or an antioxidant.

A shrink label can be obtained by using the heat-shrinkable multilayer resin film of the present invention as a base film. Such a shrink label is also one aspect of the present invention.
In the shrink label of the present invention, the heat-shrinkable multilayer resin film may be used as a base film, and other layers such as a print layer may be laminated as necessary.

According to the present invention, when used as a shrink label for a container, the contents of the container can be effectively prevented from being deteriorated by ultraviolet rays, and the heat-shrinkable multilayer having excellent cut performance and oil resistance at the perforation. A shrink label using a resin film and the heat-shrinkable multilayer resin film as a base film can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
As the outer surface layer, terephthalic acid was used as a dicarboxylic acid component, and a polyester resin containing 67 mol% of a component derived from ethylene glycol and 33 mol% of a component derived from 1,4-cyclohexanedimethanol was used as a diol component. .
As an intermediate layer, styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene: Vicat softening point 72 ° C., MFR 5.6 g / 10 min) is used as an ultraviolet absorber in an amount of 2- (2 ′ -Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole added with 2.5 parts by weight was used.
As an adhesive layer, a maleic anhydride adduct of a hydrogenated styrene-butadiene copolymer (styrene content 30% by weight, maleic anhydride addition amount 0.5% by weight, MFR 4.0 g / 10 min, specific gravity 0.91) Using.
Using these resins, a heat-shrinkable multilayer composed of five layers of outer surface layer (6 μm) / adhesive layer (1 μm) / intermediate layer (31 μm) / adhesive layer (1 μm) / outer surface layer (6 μm) by coextrusion. A resin film was extruded and used as a shrink label.

(Example 2)
As an outer surface layer, terephthalic acid is used as a dicarboxylic acid component, a component derived from ethylene glycol as a diol component is 70 mol%, a component derived from diethylene glycol is 10 mol%, and a component derived from 1,4-cyclohexanedimethanol is 20 A polyester resin containing mol% was used.
As an intermediate layer, 50 parts by weight of a styrene-butyl acrylate copolymer (82% by weight of styrene, 18% by weight of butyl acrylate: Vicat softening point 62 ° C., MFR 5.5 g / 10 min), and a styrene-butadiene copolymer ( Styrene 77% by weight, butadiene 23% by weight: Vicat softening point 82 ° C., MFR 6.0 g / 10 min) mixed resin with 50 parts by weight, 2- (2′-hydroxy-3′-tert-butyl) as an ultraviolet absorber What added 3.0 weight part of -5'-methylphenyl) -5-chlorobenzotriazole was used.
As an adhesive layer, a maleic anhydride adduct of a hydrogenated styrene-butadiene copolymer (styrene content 30% by weight, maleic anhydride addition 1.0% by weight, MFR 4.0 g / 10 min, specific gravity 0.92). Using.
Using these resins, a heat-shrinkable multilayer composed of five layers of outer surface layer (6 μm) / adhesive layer (1 μm) / intermediate layer (31 μm) / adhesive layer (1 μm) / outer surface layer (6 μm) by coextrusion. A resin film was extruded and used as a shrink label.

(Example 3)
As the outer surface layer, terephthalic acid was used as a dicarboxylic acid component, and a polyester resin containing 67 mol% of a component derived from ethylene glycol and 33 mol% of a component derived from 1,4-cyclohexanedimethanol was used as a diol component. .
As an intermediate layer, styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene: Vicat softening point 72 ° C., MFR 5.6 g / 10 min) is used as an ultraviolet absorber in an amount of 2- (2 ′ What added 7.5 weight part of -hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole was used.
As an adhesive layer, a maleic anhydride adduct of a hydrogenated styrene-butadiene copolymer (styrene content 30% by weight, maleic anhydride addition amount 0.5% by weight, MFR 4.0 g / 10 min, specific gravity 0.91) Using.
Using these resins, a heat-shrinkable multilayer composed of five layers of outer surface layer (6 μm) / adhesive layer (1 μm) / intermediate layer (31 μm) / adhesive layer (1 μm) / outer surface layer (6 μm) by coextrusion. A resin film was extruded and used as a shrink label.

(Comparative Example 1)
In the same manner as in Example 1 except that 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole was not added as an ultraviolet absorber, a shrink label was formed. Obtained.

(Comparative Example 2)
As an outer surface layer, a polystyrene resin made of a styrene-butadiene copolymer (styrene 78% by weight, butadiene 22% by weight: Vicat softening point 72 ° C., MFR 5.6 g / 10 min) was used.
As an intermediate layer, styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene: Vicat softening point 72 ° C., MFR 5.6 g / 10 min) is used as an ultraviolet absorber in an amount of 2- (2 ′ -Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole added with 2.5 parts by weight was used.
Using these resins, a heat-shrinkable multilayer resin film having a three-layer structure of outer surface layer (7 μm) / intermediate layer (31 μm) / outer surface layer (7 μm) was extruded by a coextrusion method, and this was used as a shrink label.

(Comparative Example 3)
As an outer surface layer, a polystyrene resin made of a styrene-butadiene copolymer (styrene 78% by weight, butadiene 22% by weight: Vicat softening point 72 ° C., MFR 5.6 g / 10 min) was used.
As an intermediate layer, styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene: Vicat softening point 72 ° C., MFR 5.6 g / 10 min) is used as an ultraviolet absorber in an amount of 2- (2 ′ What added 7.5 weight part of -hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole was used.
Using these resins, a heat-shrinkable multilayer resin film having a three-layer structure of outer surface layer (7 μm) / intermediate layer (31 μm) / outer surface layer (7 μm) was extruded by a coextrusion method, and this was used as a shrink label.

(Comparative Example 4)
As the outer surface layer, terephthalic acid was used as a dicarboxylic acid component, and a polyester resin containing 67 mol% of a component derived from ethylene glycol and 33 mol% of a component derived from 1,4-cyclohexanedimethanol was used as a diol component. .
As an intermediate layer, 100 parts by weight of a polyester resin containing terephthalic acid as a dicarboxylic acid component, 67 mol% of a component derived from ethylene glycol as a diol component, and 33 mol% of a component derived from 1,4-cyclohexanedimethanol On the other hand, what added 2.5 weight part of 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole as an ultraviolet absorber was used.
Using these resins, a heat-shrinkable multilayer resin film having a three-layer structure of outer surface layer (7 μm) / intermediate layer (31 μm) / outer surface layer (7 μm) was extruded by a coextrusion method, and this was used as a shrink label.

(Evaluation)
About the shrink label manufactured in Examples 1-3 and Comparative Examples 1-4, it evaluated by the following method. The results are shown in Table 1.

(1) Ultraviolet transmittance About the obtained shrink label, the transmittance of ultraviolet rays (wavelength: 200 to 380 nm) was measured using a spectrophotometer (U-3410, manufactured by Hitachi, Ltd.). The scan speed was 120 nm / min. In addition, if the ultraviolet transmittance is less than 1% in all the regions of 200 to 380 nm, it is considered that the ultraviolet transmittance is sufficient. Table 1 shows the maximum ultraviolet transmittance at 200 to 380 nm.

(2) Presence / absence of bleed The obtained shrink label was stored for 1 week immediately after film formation in an atmosphere of temperature 23 ° C. and humidity 55%, and then the surface of the film was wiped with a finger to determine the presence / absence of bleed as follows. It was evaluated by.
◯: There was no substance attached to the finger.
X: The powdery substance adhered to the finger.

(3) Contamination of the roll After completion of coextrusion, the dirt on the cooling roll of the take-up machine was visually observed, and it was observed whether or not clouding derived from bleeding of the ultraviolet absorbent was observed.
○: No cloudiness was observed.
X: Cloudiness was recognized.

(4) Cutability at perforation 30 PET bottles (with no delamination or wrinkles) that were equipped with tear labels were torn by hand from the perforations and the shrink labels were removed. The state at this time was observed, and the heat resistance was evaluated according to the following criteria.
◯: The easy perforation was broken and the shrink label could be removed.
X: Some were hard to remove by hand.

(5) After applying edible oil on the 30 shrink labels of the container equipped with the oil resistant shrink label, the state of the shrink label was visually observed and the oil resistance was evaluated according to the following criteria.
○: No wrinkles or tears were found on the shrink label.
X: Wrinkles and tears were observed on the shrink label.

According to the present invention, when used as a shrink label for a container, the contents of the container can be effectively prevented from being deteriorated by ultraviolet rays, and the heat-shrinkable multilayer having excellent cut performance and oil resistance at the perforation. A shrink label using a resin film and the heat-shrinkable multilayer resin film as a base film can be provided.

Claims (3)

A heat-shrinkable multilayer resin film comprising an intermediate layer made of polystyrene resin and an outer surface layer made of polyester resin sandwiching the intermediate layer,
The heat-shrinkable multilayer resin film, wherein the intermediate layer contains an ultraviolet absorber. An aromatic vinyl hydrocarbon having at least one functional group selected from the group consisting of a carboxylic acid group, an acid anhydride group, an amino group, an epoxy group and a hydroxyl group in the molecule between the intermediate layer and the outer surface layer The heat-shrinkable multilayer resin film according to claim 1, further comprising an adhesive layer made of a hydrogenated conjugated diene copolymer. A shrink label comprising the heat-shrinkable multilayer resin film according to claim 1.