JP5562453B2 - Method for producing foam heat-shrinkable multilayer film and method for producing foam heat-shrinkable label - Google Patents

Description

The present invention, when used for a shrink label used in a heating container or the like, can produce a foam heat shrinkable multilayer film that can achieve high shrinkage and productivity and is excellent in heat resistance and shrink finish. The present invention relates to a method and a method for producing a foam heat-shrinkable label using a foam heat-shrinkable multilayer film obtained by the production method as a base film.

As labels using heat-shrinkable films used for beverage containers and the like, labels made of various materials such as polystyrene resins, polyester resins and polyolefin resins are used. Among these, a label using a foam film is known as a label used for the purpose of keeping the contents of the container warm and preventing the glass container from collapsing.
A label using such a foamed film may be required to have durability and heat resistance higher than those normally used. Particularly, a foamed label used for a container that is heated and used is high. Thermal insulation is required.

As the material of the foam film, polyolefin resin and polystyrene resin are generally used because of easy foaming. However, a foamed film made of a polystyrene resin cannot be used for a heating container or the like because of its low heat resistance.
In addition, the foam sheet made of a heat-shrinkable polyester resin as disclosed in Patent Document 1 is excellent in shrinkability, but is used when the shrink finish is poor and beautiful finish is required. I could not.

Patent Document 2 discloses a cylindrical shrink label obtained by laminating a soft foam sheet having a thickness of 0.3 to 2.0 mm on a base material made of a heat-shrinkable film.
However, since such a cylindrical shrink label uses a non-shrinkable soft foam sheet, during heat mounting, the soft foam sheet inhibits shrinkage of the base material made of a heat shrinkable film, and shrinks the entire shrink label. Since the rate decreased, it could not be used for containers that require high shrinkage. In addition, wrinkles are likely to occur during shrinkage and the shrinkage finish is poor.

On the other hand, Patent Document 3 discloses a multilayer foam shrink film in which a heat shrink film made of a polyester resin is laminated to a heat shrink foam film made of a polystyrene resin for the purpose of improving shrink finish. Is disclosed.
However, such a multilayer foam shrink film has a problem that the shrinkage rate and shrink finish are deteriorated as compared with the film before lamination. Furthermore, when a heat-shrinkable foam film made of a polystyrene-based resin is formed alone, the draw ratio becomes as low as about 3 times, so that the production efficiency is extremely poor.

JP 2003-26843 A Japanese Patent No. 3422907 International Publication No. 2005/005527 Pamphlet

In view of the above situation, the present invention is capable of realizing high shrinkability and productivity when used in a shrink label used for a heating container or the like, and is heat-shrinkable foam having excellent heat resistance and shrink finish. An object of the present invention is to provide a method for producing a heat-shrinkable multilayer film and a method for producing a foam heat-shrinkable label using a heat-shrinkable multilayer film obtained by the production method as a base film.

The present invention relates to a heat-shrinkable non-heat-shrinkable layer composed of a polyester-based resin comprising at least a heat-shrinkable foamed layer composed of a polystyrene-based resin, a dicarboxylic acid component, and a diol component derived from ethylene glycol and 1,4-cyclohexanedimethanol. This is a method for producing a foam heat-shrinkable multilayer film in which a foam heat-shrinkable multilayer film having a foam layer is formed using a coextrusion method.
The present invention is described in detail below.

As a result of intensive studies, the inventors of the present invention have used a conventional method such as a dry laminating method to laminate a foamed layer and a non-foamed layer, the solvent contained in the adhesive, and the heat generated when the adhesive is dried. It has been found that relaxation of the stretched orientation of the film causes a significant decrease in the shrinkage rate and the shrinkage finish when the container is covered. As a result of further intensive studies, the inventors of the present invention formed a foamed heat-shrinkable multilayer film having a foamed layer made of polystyrene resin and a non-foamed layer made of polyester resin by a coextrusion method. It has been found that the stretched orientation is maintained, the shrinkage rate can be prevented from being lowered, and the production efficiency can be improved, and the present invention has been completed.

The foam heat-shrinkable multilayer film obtained by the present invention has a heat-shrinkable foam layer made of polystyrene resin. The heat-shrinkable foam layer has a structure in which closed cells or open cells are formed in a polystyrene resin as a matrix resin.

The polystyrene resin constituting the heat-shrinkable foam layer is not particularly limited as long as it has heat-shrinkability and can be foamed. For example, an aromatic vinyl hydrocarbon-conjugated diene copolymer, or Examples thereof include a mixed resin of an aromatic vinyl hydrocarbon-conjugated diene copolymer and an aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer.
Since the aromatic vinyl hydrocarbon-conjugated diene copolymer is excellent in low-temperature shrinkage, the obtained foam heat-shrinkable label can be easily attached to a container without generating wrinkles or the like. In addition, the shrink finish is excellent.
Further, 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, the shrinkage finish is excellent.

The aromatic vinyl hydrocarbon-conjugated diene copolymer is not particularly limited. For example, aromatic vinyl hydrocarbons include styrene, o-methylstyrene, p-methylstyrene and the like, 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.

The aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymer is not particularly limited, and 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, it is possible to obtain a foamed heat-shrinkable label having excellent shrinkage finishing properties and perforation cutting properties.

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 heat-shrinkable foam layer, the fragrance in the mixed resin is used. The preferable lower limit of the amount of the group vinyl hydrocarbon-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 foamed heat-shrinkable label may be broken during conversion. Shrinkage may increase. A more preferred lower limit is 30% by weight, and a more preferred upper limit is 70% by weight.

The foam heat-shrinkable multilayer film obtained by the present invention has a heat-shrinkable non-foamed layer made of a polyester resin.
The polyester resin constituting the heat-shrinkable non-foamed layer is not particularly limited as long as it has heat-shrinkability and heat resistance. For example, a resin obtained by polycondensation of dicarboxylic acid and diol is used. Can be used.
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.

Examples of the polyester resin include lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, Using a resin obtained by condensation polymerization or ring-opening polymerization of a bifunctional aliphatic hydroxycarboxylic acid such as 2-methylbutyric acid or 2-hydroxycaprolactone acid, or an α-hydroxycarboxylic acid such as lactone such as caprolactone or butyllactone May be.

Among these polyester resins, those containing a component derived from terephthalic acid as the dicarboxylic acid component and a component derived from ethylene glycol and 1,4-cyclohexanedimethanol as the diol component are preferred. By using such a polyester-based resin, particularly high heat resistance and solvent resistance can be imparted to the obtained heat-shrinkable multilayer film of the present invention.
In addition, when imparting particularly high heat 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 to 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 heat-shrinkable non-foaming 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 production of foam heat-shrinkable labels, it is common practice to use trimmed pieces of stretched ears or recycled films as return materials again. Usually, such a return material is mixed with a polystyrene resin as a raw material for the heat-shrinkable foam layer, but the polystyrene resin and the polyester resin are different in properties such as the melting point and are suitable for molding of the polystyrene resin. When the film was formed at a high temperature, the polyester resin was sometimes 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.

The foam heat-shrinkable multilayer film obtained by the present invention preferably further has an adhesive layer made of a thermoplastic resin between the heat-shrinkable non-foamed layer and the heat-shrinkable foam layer. As the resin constituting the adhesive layer, any commercially available resin can be used without particular limitation as long as it can be dissolved by a solvent used at the time of center sealing. More preferably, a styrene elastomer, a polyester elastomer, or a modified product thereof is used. Such an adhesive layer has a high affinity for both the polystyrene resin constituting the heat-shrinkable foam layer and the polyester resin constituting the heat-shrinkable non-foamed layer, and can bond them with high strength. . Moreover, since it can be molded by a coextrusion method together with a heat-shrinkable foam layer and a heat-shrinkable non-foamed layer, it is excellent in productivity.

The styrenic elastomer includes those composed of polystyrene as a hard segment and polybutadiene, polyisoprene, a copolymer of polybutadiene and polyisoprene as a soft segment, and hydrogenated products thereof. The hydrogenated product may be one obtained by hydrogenating a part of polybutadiene or polyisoprene, or may be one obtained by hydrogenating all of them.

Examples of commercially available styrene elastomers include “Tuftec”, “Tufprene” (all manufactured by Asahi Kasei Chemicals), “Clayton” (manufactured by Kraton Polymer Japan), “Dynalon” (manufactured by JSR), “Septon”. (Made by Kuraray Co., Ltd.).

Examples of the modified styrenic elastomer include those modified with a functional group such as a carboxylic acid group, an acid anhydride group, an amino group, an epoxy group, and a hydroxyl group.
The preferred lower limit of the content of functional groups such as carboxylic acid groups, acid anhydride groups, amino groups, epoxy groups and hydroxyl groups in the modified styrene elastomer is 0.05% by weight, and the preferred upper limit is 5.0% by weight. It is. If it is less than 0.05% by weight, the adhesion to the heat-shrinkable non-foamed layer may be insufficient, and if it exceeds 5.0% by weight, the resin is heated when the functional group is added. It may deteriorate and foreign matter such as gel 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 polyester elastomer is preferably a saturated polyester elastomer, and particularly preferably a saturated polyester elastomer containing a polyalkylene ether glycol segment. As the saturated polyester-based elastomer containing a polyalkylene ether glycol segment, for example, a block copolymer composed of an aromatic polyester as a hard segment and a polyalkylene ether glycol or an aliphatic polyester as a soft segment is preferable. Furthermore, a polyester polyether block copolymer having a polyalkylene ether glycol as a soft segment is more preferable.

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

As said C2-C12 aliphatic and / or alicyclic diol, what is generally used as a raw material of a polyester, especially the raw material of a polyester-type elastomer can be used, for example. Specific examples include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and the like. Among these, 1,4-butanediol or ethylene glycol is preferable, and 1,4-butanediol is particularly preferable. These diols may be used alone or in combination of two or more.

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

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

The aliphatic dicarboxylic acid is preferably cyclohexane dicarboxylic acid, and the alkyl ester is preferably dimethyl ester or diethyl ester. In addition to the above components, a small amount of a trifunctional alcohol, tricarboxylic acid or ester thereof may be copolymerized, and an aliphatic dicarboxylic acid such as adipic acid or a dialkyl ester thereof may be used as a copolymerization component.

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

The preferable lower limit of the number average molecular weight of the polyalkylene ether glycol is 400, and the preferable upper limit is 6000. By setting it to 400 or more, the block property of the copolymer becomes high, and by setting it to 6000 or less, phase separation in the system hardly occurs and polymer physical properties are easily developed. A more preferred lower limit is 500, a more preferred upper limit is 4000, a still more preferred lower limit is 600, and a still more preferred upper limit is 3000. In addition, in this specification, a number average molecular weight means what was measured by gel permeation chromatography (GPC). The GPC calibration can be performed, for example, by using a POLYTETRAHYDROFURAN calibration kit (manufactured by POLYMER LABORATORIES, UK).

The polyester elastomer may coexist with a rubber component such as natural rubber and synthetic rubber (for example, polyisoprene rubber) and a softening agent such as process oil. By making the softener coexist, the plasticization of the rubber component can be promoted and the fluidity of the resulting thermoplastic resin composition can be improved. The softening agent may be paraffinic, naphthenic, or aromatic. Moreover, in the range which does not impair the effect of this invention, you may add other components, such as resin other than the above, rubber | gum, a filler, an additive, to this resin component and rubber component.

Examples of the filler include calcium carbonate, talc, silica, kaolin, clay, diatomaceous earth, calcium silicate, mica, asbestos, alumina, barium sulfate, aluminum sulfate, calcium sulfate, magnesium carbonate, carbon fiber, glass fiber, and glass bulb. , Molybdenum sulfide, graphite, shirasu balloon and the like. Examples of the additive include a heat resistance stabilizer, a weather resistance stabilizer, a colorant, an antistatic agent, a flame retardant, a nucleating agent, a lubricant, a slip agent, and an antiblocking agent.

As said heat stabilizer, well-known things, such as a phenol type, a phosphorus type, and a sulfur type, can be used, for example. As the weather resistance stabilizer, known ones such as hindered amines and triazoles can be used. Examples of the colorant include carbon black, titanium white, zinc white, red pepper, azo compound, nitroso compound, and phthalocyanine compound. In addition, known antistatic agents, flame retardants, nucleating agents, lubricants, slip agents, antiblocking agents and the like can be used.

Examples of commercially available polyester elastomers include “Primalloy” (manufactured by Mitsubishi Chemical Corporation), “Perprene” (manufactured by Toyobo Co., Ltd.), “Hytrel” (manufactured by Toray DuPont) and the like.

When using a polyester polyether block copolymer composed of polyester and polyalkylene ether glycol as the polyester elastomer, the content of the polyalkylene ether glycol component is preferably 5% by weight, and preferably 90% by weight. is there. When it is 5% by weight or more, it is excellent in flexibility and impact resistance, and when it is 90% by weight or less, it is excellent in hardness and mechanical strength. A more preferred lower limit is 30% by weight, a more preferred upper limit is 80% by weight, and a still more preferred lower limit is 55% by weight. The content of the polyalkylene ether glycol component can be calculated based on the chemical shift of the hydrogen atom and its content using nuclear magnetic resonance spectroscopy (NMR).

The modified polyester elastomer (hereinafter also referred to as a modified polyester elastomer) is obtained by modifying the polyester elastomer using a modifier. The modification reaction for obtaining the modified polyester elastomer is performed, for example, by reacting the polyester elastomer with an α, β-ethylenically unsaturated carboxylic acid as a modifier. In the modification reaction, a radical generator is preferably used. In the modification reaction, a graft reaction in which an α, β-ethylenically unsaturated carboxylic acid or a derivative thereof is added to a polyester elastomer mainly occurs, but a decomposition reaction also occurs. As a result, the modified polyester elastomer has a lower molecular weight and a lower melt viscosity. Further, in the modification reaction, it is generally considered that a transesterification reaction or the like occurs as another reaction, and the obtained reaction product is generally a composition containing unreacted raw materials, etc. The preferable lower limit of the content of the modified polyester elastomer in the obtained reaction product is 10% by weight, the more preferable lower limit is 30% by weight, and the content of the modified polyester elastomer is more preferably 100% by weight.

Examples of the α, β-ethylenically unsaturated carboxylic acid include unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrofumaric acid, itaconic acid, citraconic acid, crotonic acid, and isocrotonic acid; succinic acid 2 -Octen-1-yl anhydride, 2-dodecen-1-yl anhydride, succinic acid 2-octadecen-1-yl anhydride, maleic anhydride, 2,3-dimethylmaleic anhydride, bromomalein Acid anhydride, dichloromaleic acid anhydride, citraconic acid anhydride, itaconic acid anhydride, 1-butene-3,4-dicarboxylic acid anhydride, 1-cyclopentene-1,2-dicarboxylic acid anhydride, 1,2, 3,6-tetrahydrophthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, exo-3,6-epoxy-1,2,3,6-tetra Hydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, methyl-5-norbornene-2,3-dicarboxylic anhydride, endo-bicyclo [2.2.2] oct-5-ene-2 , 3-dicarboxylic acid anhydride, and unsaturated carboxylic acid anhydrides such as bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic acid anhydride. Of these, acid anhydrides are preferred because of their high reactivity. The α, β-ethylenically unsaturated carboxylic acid can be appropriately selected according to the copolymer containing the polyalkylene ether glycol segment to be modified and the modification conditions. Good. The α, β-ethylenically unsaturated carboxylic acid can be used by dissolving in an organic solvent or the like.

Examples of the radical generator include t-butyl hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-bis ( Tertiary butyloxy) hexane, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxybenzoate, benzoyl peroxide, dicumyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene Organic and inorganic peroxides such as dibutyl peroxide, methyl ethyl ketone peroxide, potassium peroxide, hydrogen peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (isobutylamide) dihalide, 2,2'-azobis [2-methyl-N- (2-hydrido Kishiechiru) propionamide], azo compounds such as azodi -t- butane, carbon radical generating agents such as dicumyl like. The radical generator can be appropriately selected according to the type of polyester elastomer used for the modification reaction, the type of α, β-ethylenically unsaturated carboxylic acid and the modification conditions, and two or more types can be used in combination. May be. Furthermore, the radical generator can be used by dissolving in an organic solvent or the like.

A preferable lower limit of the amount of the α, β-ethylenically unsaturated carboxylic acid is 0.01 parts by weight with respect to 100 parts by weight of the polyester elastomer, and a preferable upper limit is 30.0 parts by weight. When the amount is 0.01 parts by weight or more, the modification reaction can be sufficiently performed, and when the amount is 30.0 parts by weight or less, it is economically advantageous. A more preferred lower limit is 0.05 parts by weight, a more preferred upper limit is 5.0 parts by weight, a still more preferred lower limit is 0.10 parts by weight, and a still more preferred upper limit is 1.0 part by weight.

A preferable lower limit of the blending amount of the radical generator is 0.001 part by weight with respect to 100 parts by weight of the polyester elastomer, and a preferable upper limit is 3.00 part by weight. When the amount is 0.001 part by weight or more, the modification reaction is likely to occur, and when the amount is 3.00 part by weight or less, the material strength is less likely to decrease due to low molecular weight (decrease in viscosity) during modification. A more preferred lower limit is 0.005 parts by weight, a more preferred upper limit is 0.50 parts by weight, a still more preferred lower limit is 0.010 parts by weight, a still more preferred upper limit is 0.20 parts by weight, and a particularly preferred upper limit is 0.10 parts by weight. Part.

As the modification reaction for obtaining the modified polyester-based elastomer, known reaction methods such as a melt-kneading reaction method, a solution reaction method, a suspension-dispersion reaction can be used. Reaction methods are preferred.

In the method using the melt kneading reaction method, the above-described components are uniformly mixed at a predetermined blending ratio, and then melt kneaded. Henschel mixer, ribbon blender, V-type blender, etc. can be used for mixing each component, and Banbury mixer, kneader, roll, uniaxial or biaxial multi-screw kneading extruder etc. are used for melt-kneading. can do.

The preferable lower limit of the kneading temperature when the melt kneading is performed is 100 ° C., and the preferable upper limit is 300 ° C. By setting it within the above range, thermal deterioration of the resin can be prevented. A more preferred lower limit is 120 ° C., a more preferred upper limit is 280 ° C., a still more preferred lower limit is 150 ° C., and a still more preferred upper limit is 250 ° C.

The preferable lower limit of the modification rate (graft amount) of the modified polyester elastomer is 0.01% by weight, and the preferable upper limit is 10.0% by weight. When the content is 0.01% by weight or more, the affinity with the polyester is increased, and when the content is 10.0% by weight or less, a decrease in strength due to molecular deterioration during modification can be reduced. A more preferred lower limit is 0.03% by weight, a more preferred upper limit is 7.0% by weight, a still more preferred lower limit is 0.05% by weight, and a still more preferred upper limit is 5.0% by weight.

The modification rate (graft amount) of the modified polyester elastomer can be obtained from the spectrum obtained by H ¹ -NMR measurement according to the following formula (1). As the equipment used to the ^H 1 -NMR measurement, for example, it can be used to "GSX-400" (manufactured by Nippon Denshi) and the like.

Graft amount (% by weight) = 100 × [(C ÷ 3 × 98) / {(A × 148 ÷ 4) + (B × 72 ÷ 4) + (C ÷ 3 × 98)}] (1)
In the formula (1), A represents an integral value at 7.8 to 8.4 ppm, B represents an integral value at 1.2 to 2.2 ppm, and C represents an integral value at 2.4 to 2.9 ppm.

The preferable lower limit of the JIS-D hardness of the reaction product containing the modified polyester elastomer obtained by the modification reaction is 10, and the preferable upper limit is 80. By setting it to 10 or more, the mechanical strength is improved, and by setting it to 80 or less, flexibility and impact resistance are improved. A more preferred lower limit is 15, a more preferred upper limit is 70, a still more preferred lower limit is 20, and a still more preferred upper limit is 60. The JIS-D hardness can be measured by using a durometer type D by a method in accordance with JIS K 6253.

The minimum with preferable thickness of the whole foam heat-shrinkable multilayer film obtained by this invention is 70 micrometers, and a preferable upper limit is 300 micrometers. If it is less than 70 μm, the heat retaining properties and the heat insulation properties may be lowered, and if it exceeds 300 μm, the handleability may be lowered.

In this invention, the minimum with the preferable ratio of the thickness of a heat-shrinkable foam layer is 5% with respect to the thickness of the whole foam heat-shrinkable multilayer film, and a preferable upper limit is 99%. If it is less than 5%, the heat retaining properties and the heat insulation properties may be lowered, and if it exceeds 99%, the heat resistance may be lowered.

The preferable lower limit of the thickness of the adhesive layer is 0.5 μm, and the preferable upper limit is 3.0 μm. A more preferable lower limit is 0.7 μm, and a more preferable upper limit is 2.0 μm. If it is less than 0.5 μm, sufficient adhesive strength may not be obtained, and if it exceeds 3.0 μm, the heat shrinkage characteristics may be deteriorated.

The preferable lower limit of the specific gravity of the heat-shrinkable multilayer film obtained by the present invention is 0.30, and the preferable upper limit is 1.10. A more preferred lower limit is 0.40, and a more preferred upper limit is 1.00. If it is less than 0.30, the strength of the foamed heat-shrinkable multilayer film is lowered, and the film may be broken when converting. When it exceeds 1.10, the heat retaining property and the heat insulating property may be deteriorated.

Regarding the heat shrink property of the heat-shrinkable multilayer film obtained by the present invention, the preferred lower limit of the shrinkage when immersed in warm water at 70 ° C. for 10 seconds is 5%, and the preferred upper limit is 60%. If it is less than 5%, a large amount of heat is required at the time of wearing, which may cause deterioration of the container and film and increase in cost. If it exceeds 60%, it will shrink rapidly due to heating, so wrinkles, etc. Is likely to occur. A more preferred lower limit is 10%, a more preferred upper limit is 55%, a still more preferred lower limit is 15%, and a still more preferred upper limit is 45%.
The shrinkage rate when immersed in warm water at 70 ° C. for 10 seconds means that the foamed heat-shrinkable multilayer film is cut so as to have an MD of 100 mm and TD of 100 mm, and immersed in warm water of 70 ° C. for 10 seconds. The ratio of the dimension which contracted after the heating to the dimension before the heat treatment was measured and expressed in%.

The foam heat-shrinkable multilayer film obtained by the present invention is formed by coextrusion.
By forming each layer at the same time using the above coextrusion, it is necessary to use a solvent-based adhesive as compared with the case of forming each layer separately and then laminating them by a method such as a dry laminating method. In addition, since it is not necessary to perform a step of drying the adhesive, the stretched orientation of the film is not relaxed during film formation, and a foamed heat-shrinkable multilayer film having a high shrinkage rate can be obtained. In addition, it is possible to continuously form a film with a high draw ratio, compared with the case where only a heat-shrinkable foam layer with poor productivity is formed alone, and to realize excellent production efficiency. it can.

Examples of the film formation by the coextrusion method include coextrusion using a T die, and in the coextrusion by the T die, a feed block method, a multi-manifold method, or a combination thereof is used as a lamination method. The method can be used. Specifically, for example, a polystyrene resin and a foaming agent as raw materials constituting the heat-shrinkable foam layer, and a polyester resin as raw materials constituting the heat-shrinkable non-foamed layer are respectively put into an extruder, and a sheet is formed by a multilayer die. It is possible to use a method of uniaxially or biaxially stretching after being extruded into a shape and cooled and solidified by a take-up roll. In such a method, when the polystyrene resin is melted, the polystyrene resin is foamed by heating to the decomposition temperature of the foaming agent, whereby a heat-shrinkable foam layer can be obtained.

Examples of the foaming agent include azo compounds, nitroso compounds, hydrazine derivatives, semicarbazide compounds, azide compounds, tetrazole compounds, isocyanate compounds, bicarbonates, nitrites, and the like. Moreover, in order to accelerate | stimulate decomposition | disassembly, you may add a foaming adjuvant suitably. Instead of the foaming agent, a microcapsule having a low boiling point hydrocarbon in the outer shell made of a thermoplastic resin may be used. Examples of the thermoplastic resin include acrylic acid and its esters, methacrylic acid and its esters, nitriles, and vinylidene compounds. Examples of the low boiling point hydrocarbon include n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, cyclohexane, heptane, octane and the like. Moreover, you may use together the said foaming agent and the said microcapsule.

As a method of forming the heat-shrinkable foam layer, in addition to the method of adding the foaming agent and microcapsules described above, a method of directly supplying gas to the melted resin in the extrusion molding, or a resin pellet as a raw material For example, a method of impregnating a foaming gas with a gas can be used.
In the method of directly supplying the gas, examples of the gas to be supplied include carbon dioxide, propane, butane, n-pentane, dichlorodifluoromethane, dichloromonofluoromethane, trichloromonofluoromethane, methanol, ethanol, water, and the like. It is done.

The stretching temperature needs to be changed depending on the softening temperature of the resin constituting the film and the shrinkage characteristics required for the heat-shrinkable multilayer film, but the preferred lower limit of the stretching temperature is 75 ° C, the preferred upper limit is 120 ° C, A preferred lower limit is 80 ° C and a more preferred upper limit is 115 ° C.

The foamed heat-shrinkable multilayer film obtained by the present invention may be added with an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, an antiblocking agent, a flame retardant, a colorant, a pigment, etc., if necessary. Good. In particular, by adding a colorant or a pigment, the transparency of the foamed heat-shrinkable multilayer film can be reduced, and the appearance can be improved.

In the foam heat-shrinkable multilayer film obtained by the present invention, a printed layer or a non-foamed resin layer may be further formed as necessary. When a printed layer is formed on the heat-shrinkable non-foamed layer, the film is excellent in appearance.

By using the foam heat-shrinkable multilayer film obtained by the present invention as a base film, a foam heat-shrinkable label can be obtained. A method for producing such a foam heat-shrinkable label is also one aspect of the present invention.
The foamed heat-shrinkable label obtained by the present invention may be laminated with a print layer, a non-foamed resin layer, or the like as necessary, using the foamed heat-shrinkable multilayer film as a base film.

As a method of attaching a foam heat-shrinkable label to a container, a foamed heat-shrinkable label is usually obtained by bonding between ends of a foam heat-shrinkable multilayer film using a solvent and processing into a tube shape (center seal processing). After that, a method is adopted in which the container is heated and contracted while being covered.

According to the present invention, when used for a shrink label used in a heating container or the like, a foamed heat-shrinkable multilayer film that can achieve high shrinkage and productivity and is excellent in heat resistance and shrinkage finish. And a method for producing a foam heat-shrinkable label using a foam heat-shrinkable multilayer film obtained by the production method as a base film.

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 a resin constituting the heat-shrinkable non-foamed layer, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of the component derived from ethylene glycol is used as the diol component, and 33 mol% of the component derived from 1,4-cyclohexanedimethanol The contained polyester resin was used.
As a component constituting the heat-shrinkable foam layer, a foaming agent is used with respect to 100 parts by weight of a styrene-butadiene copolymer (styrene 78 wt%, butadiene 22 wt%: Vicat softening point 71 ° C., MFR 6.2 g / 10 min). A bicarbonate-based foaming agent master batch (Polyslen ES275, manufactured by Eiwa Kasei Kogyo Co., Ltd.) 2.5 parts by weight was added.
These resins were put into an extruder having a barrel temperature of 160 to 250 ° C., extruded from a multilayer die at 220 ° C. into a two-layered sheet, and cooled and solidified by a take-up roll at 30 ° C. Next, the film was stretched at a stretch ratio of 5 in a tenter stretching machine having a preheating zone of 110 ° C., a stretching zone of 90 ° C., and a heat setting zone of 80 ° C., and then wound up with a winder to obtain a foam heat-shrinkable multilayer film. .
The resulting foamed heat-shrinkable multilayer film had a total thickness of 127 μm and consisted of a two-layer structure of heat-shrinkable non-foamed layer (7 μm) / heat-shrinkable foamed layer (120 μm).
In addition, it was 0.79 when the specific gravity of the obtained foam heat-shrinkable multilayer film was measured using the electronic hydrometer (the Alpha Mirage company make, MD-300S).
About the obtained foam heat-shrinkable multilayer film, after superimposing both ends of the film so that the heat-shrinkable foam layer is on the inside, after performing a center seal using a mixed solvent of 1,3-dioxolane and cyclohexane, By folding it flat, a cylindrical shrink label with a fold diameter of 85 mm was obtained.

(Example 2)
As a resin constituting the heat-shrinkable non-foamed layer, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of the component derived from ethylene glycol is used as the diol component, and 33 mol% of the component derived from 1,4-cyclohexanedimethanol The contained polyester resin was used.
As a component constituting the heat-shrinkable foam layer, a foaming agent is used with respect to 100 parts by weight of a styrene-butadiene copolymer (styrene 78 wt%, butadiene 22 wt%: Vicat softening point 71 ° C., MFR 6.2 g / 10 min). A bicarbonate-based foaming agent master batch (Polyslen ES275, manufactured by Eiwa Kasei Kogyo Co., Ltd.) 2.5 parts by weight was added.
As resin constituting the adhesive layer, maleic anhydride-modified styrene-ethylene / butylene-styrene block copolymer (styrene content 30% by weight, maleic anhydride addition amount 0.5% by weight, MFR 4.0 g / 10 min) is used. It was.
A foamed heat-shrinkable multilayer film was obtained in the same manner as in Example 1 except that these resins were used.
The resulting foamed heat-shrinkable multilayer film has a total thickness of 128 μm, and has a three-layer structure of heat-shrinkable non-foamed layer (7 μm) / adhesive layer (1 μm) / heat-shrinkable foamed layer (120 μm). there were.
With respect to the obtained foamed heat-shrinkable multilayer film, the specific gravity was measured by the same method as in Example 1. As a result, it was 0.91.
Using the obtained foam heat-shrinkable multilayer film, a cylindrical shrink label was obtained in the same manner as in Example 1.

(Example 3)
As a resin constituting the heat-shrinkable non-foamed layer, terephthalic acid is used as a dicarboxylic acid component, a component derived from ethylene glycol as a diol component is 70 mol%, and a component derived from 1,4-cyclohexanedimethanol is 20 mol%. A polyester resin containing 10 mol% of a component derived from diethylene glycol was used.
As a component constituting the heat-shrinkable foam layer, a foaming agent is used with respect to 100 parts by weight of a styrene-butadiene copolymer (styrene 78 wt%, butadiene 22 wt%: Vicat softening point 71 ° C., MFR 6.2 g / 10 min). A bicarbonate-based foaming agent master batch (Polyslen ES275, manufactured by Eiwa Kasei Kogyo Co., Ltd.) 2.5 parts by weight was added.
As a resin constituting the adhesive layer, a polyester-based elastomer (manufactured by Mitsubishi Chemical Corporation, Primalloy A1600N, melting point 160 ° C., MFR 5.0 g / 10 min) was used.
A foamed heat-shrinkable multilayer film was obtained in the same manner as in Example 1 except that these resins were used.
The resulting foamed heat-shrinkable multilayer film has a total thickness of 186 μm, and heat-shrinkable non-foamed layer (7 μm) / adhesive layer (1 μm) / heat-shrinkable foamed layer (170 μm) / adhesive layer (1 μm) / heat It consisted of 5 layers of shrinkable non-foamed layers (7 μm).
With respect to the obtained foamed heat-shrinkable multilayer film, the specific gravity was measured by the same method as in Example 1. As a result, it was 0.46.
Using the obtained foam heat-shrinkable multilayer film, a cylindrical shrink label was obtained in the same manner as in Example 1.

(Example 4)
As a resin constituting the heat-shrinkable non-foamed layer, terephthalic acid is used as a dicarboxylic acid component, a component derived from ethylene glycol as a diol component is 70 mol%, and a component derived from 1,4-cyclohexanedimethanol is 20 mol%. A polyester resin containing 10 mol% of a component derived from diethylene glycol was used.
As a component constituting the heat-shrinkable foam layer, a foaming agent is used with respect to 100 parts by weight of a styrene-butadiene copolymer (styrene 78 wt%, butadiene 22 wt%: Vicat softening point 71 ° C., MFR 6.2 g / 10 min). A bicarbonate-based foaming agent master batch (Polyslen ES275, manufactured by Eiwa Kasei Kogyo Co., Ltd.) of 3.0 parts by weight was used.
As a resin constituting the adhesive layer, a polyester-based elastomer (manufactured by Mitsubishi Chemical Corporation, Primalloy A1600N, melting point 160 ° C., MFR 5.0 g / 10 min) was used.
A foamed heat-shrinkable multilayer film was obtained in the same manner as in Example 1 except that these resins were used.
The resulting foamed heat-shrinkable multilayer film has a total thickness of 136 μm, and heat-shrinkable non-foamed layer (7 μm) / adhesive layer (1 μm) / heat-shrinkable foamed layer (120 μm) / adhesive layer (1 μm) / heat It consisted of 5 layers of shrinkable non-foamed layers (7 μm).
With respect to the obtained foamed heat-shrinkable multilayer film, the specific gravity was measured by the same method as in Example 1. As a result, it was 0.85.
Using the obtained foam heat-shrinkable multilayer film, a cylindrical shrink label was obtained in the same manner as in Example 1.

(Comparative Example 1)
For 100 parts by weight of a styrene-butadiene copolymer (78% by weight of styrene, 22% by weight of butadiene: Vicat softening point 71 ° C., MFR 6.2 g / 10 min), a bicarbonate-based foaming agent master batch (Polyslen) ES275, manufactured by Eiwa Kasei Kogyo Co., Ltd.), added with 2.5 parts by weight, placed in an extruder having a barrel temperature of 160 to 250 ° C., extruded from a multilayer die at 220 ° C. into a sheet, and a take-up roll at 30 ° C. And solidified by cooling. Next, after stretching at a stretching ratio of 3 in a tenter stretching machine having a preheating zone of 110 ° C., a stretching zone of 90 ° C., and a heat setting zone of 80 ° C., a wound heat-shrinkable film having a thickness of 120 μm is obtained by winding with a winder. Obtained.
The specific heat density of the obtained foamed heat-shrinkable film was measured by the same method as in Example 1. As a result, it was 0.71.
Using the obtained foam heat-shrinkable film, a cylindrical shrink label was obtained in the same manner as in Example 1.

(Comparative Example 2)
Adhesive (LX-401A, manufactured by Dainippon Ink & Chemicals, Inc.) and curing agent on one side of a resin film made of non-foamed polyester resin (Gunze, Fancy Wrap TAS, thickness 30 μm, shrinkage 22%) (Dai Nippon Ink Chemical Co., Ltd., SP-60) After applying an adhesive composition containing ethyl acetate in a ratio of 1: 1: 3, the heat-shrinkable foam film obtained in Comparative Example 1 was applied. The foamed heat-shrinkable multilayer film was obtained by dry lamination by drying in a drying furnace composed of 2.5 m × 3 zones (60 ° C.-70 ° C.-80 ° C.).
With respect to the obtained foamed heat-shrinkable multilayer film, the specific gravity was measured by the same method as in Example 1. As a result, it was 0.86.
Using the obtained foam heat-shrinkable multilayer film, a cylindrical shrink label was obtained in the same manner as in Example 1.

(Evaluation)
(1) Shrinkage ratio measurement The foamed heat-shrinkable multilayer film was cut out so as to have an MD of 100 mm and a TD of 100 mm, and the TD length L after being immersed in warm water at 70 ° C. for 10 seconds was measured. ) To calculate the shrinkage rate.
Shrinkage rate (%) = {(100−L) / 100} × 100 (2)

(2) Shrinkage finish The obtained shrink label is covered with a metal can container (with a diameter of 52 mm and a cap at the top), and using a steam tunnel (manufactured by FUJI TECH, SH-5000), set temperature: 80- 85-95 ° C., tunnel passage time: Shrinked in 8 seconds and attached to a metal can container.
O: Wrinkles were not recognized at all.
X: Even one wrinkle was recognized.

(3) Heat resistance The metal can containers come into contact with each other in a hot warmer (SW126OP-53, manufactured by Nippon Heater Equipment Co., Ltd.) in which the metal can container equipped with the shrink label obtained in “(2) Shrinkage finish” is heated. The state of the metal can container and the shrink label was visually observed and evaluated according to the following criteria.
◯: There was no blocking between metal can containers, and no wrinkles or tears were observed on the shrink label.
X: Blocking between metal can containers and wrinkles and tears were observed on the shrink label.

According to the present invention, when used for a shrink label used in a heating container or the like, a foamed heat-shrinkable multilayer film that can achieve high shrinkage and productivity and is excellent in heat resistance and shrinkage finish. And a method for producing a foam heat-shrinkable label using a foam heat-shrinkable multilayer film obtained by the production method as a base film.

Claims (4)

At least a heat-shrinkable foam layer made of a polystyrene-based resin, a dicarboxylic acid component, and a heat-shrinkable non-foamed layer made of a polyester-based resin containing a diol component derived from ethylene glycol and 1,4-cyclohexanedimethanol A process for producing a foamed heat-shrinkable multilayer film, comprising forming the foamed heat-shrinkable multilayer film using a coextrusion method. The method for producing a heat-shrinkable multilayer film according to claim 1, further comprising an adhesive layer made of a thermoplastic resin between the heat-shrinkable foam layer and the heat-shrinkable non-foamed layer. The method for producing a heat-shrinkable multilayer film according to claim 2, wherein the resin constituting the adhesive layer is a styrene-based elastomer, a polyester-based elastomer, or a modified product thereof. A method for producing a foam heat-shrinkable label, comprising using a foam heat-shrinkable multilayer film obtained by the method for producing a heat-shrinkable multilayer film according to claim 1, 2 or 3.