JP2003094520A - Heat-shrinkable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable (multilayered) film and a heat-shrinkable label having good shrink capacity and natural shrinkage resistance and good perforation cutting properties. SOLUTION: The heat shrinkable film having good perforation cutting properties is obtained by stretching a film comprising a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene or a block copolymer composition based thereon. The morphology of the block copolymer or the block copolymer composition based thereon includes a rubber phase and a plastic phase and the rubber phase of the lamellar or block copolymer is preferably present as a rod or a particle with a particle size of 15 nm or more.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to good heat shrinkability,
The present invention relates to a heat-shrinkable (multi-layer) film having natural shrinkage resistance and good perforation of a sewing machine, and a heat-shrinkable label.

[0002]

2. Description of the Related Art Conventionally, heat-shrinkable films used as shrink-wrap packaging and shrink-wrap labels for containers have good heat-shrinkability and a good finish after shrinkage, and even when discarded, environmental problems such as polyvinyl chloride can be avoided. A film formed by molding a styrene-butadiene block copolymer is used because it does not exist. In addition, by performing block copolymerization of a vinyl aromatic hydrocarbon and a conjugated diene with an alkyl lithium as an initiator in an organic solvent by living anionic polymerization, the mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene or the addition method may be changed. It is known that the structure of the copolymer can be diversified by the method, and a block copolymer having various physical properties can be obtained, and a heat-shrinkable film using these is known as follows. For example, JP-A-59-49938
In the gazette, a specific polystyrene composition consisting of a styrene-butadiene block copolymer, another styrene-butadiene copolymer, a polystyrene-based polymer, and a rubber-modified styrene-based polymer is prepared by an inflation method in a single operation. By promoting molecular orientation, high tensile strength impact resistance,
It is described that a heat-shrinkable film having elongation and suitable as a transparent and high-gloss packaging material can be obtained. Further, JP-A-7-144365 discloses a styrene-butadiene block copolymer having a butadiene block content of 4 to 35% in the total polymer, or a mixture of the styrene and butadiene block copolymer under specific conditions. A styrene-based shrinkable film which is a stretched biaxially stretched film and has a tensile elongation at break of 10% or more in the longitudinal direction at 0 ° C. and which is excellent in breaking resistance, shrinkage characteristics and rigidity is described. However, the conventionally used styrene-based heat-shrinkable label has good heat-shrinkability and natural shrinkage resistance, but the perforation of the sewing machine when the label is peeled off after use is not at a satisfactory level. The improvement was desired.

[0003]

SUMMARY OF THE INVENTION In view of the above situation, the present invention provides a heat-shrinkable (multilayer) film which has good shrinkage performance and natural shrinkage resistance and has good perforation of the sewing machine. It is intended to provide a heat shrinkable label.

[0004]

As a result of intensive studies to solve the above problems, the present inventors have found that a thermoplastic resin mainly composed of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene or The present invention finds a heat-shrinkable (multilayer) film and a heat-shrinkable label, which are obtained by stretching a film made of the composition, have good shrinkage performance and natural shrinkage resistance, and have good perforation of the sewing machine. Has been completed.

That is, according to the present invention, a heat shrinkage with good perforation of a sewing machine, which is obtained by stretching a film made of a thermoplastic resin mainly comprising a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene or a composition thereof ( (Multilayer) film and heat-shrinkable label. In the present invention, the heat shrinkage (the morphology of the block copolymer is composed of a rubber phase and a plastic phase, and the rubber phase of the lamella or the block copolymer is present as rods or particles having a particle size of 15 nm or more ( (Multilayer) film and heat-shrinkable label. The block copolymer of the present invention or the block copolymer composition containing the block copolymer as a main component is formed by stretching a block copolymer composition containing the following (a) and, if necessary, (b): Shrink (multilayer) films and heat-shrinkable labels are preferred. (A) The mass ratio of vinyl aromatic hydrocarbon to conjugated diene is 5
Block copolymer of 0/50 to 90/10 and a vinyl aromatic hydrocarbon block ratio of 85% or less, a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, (b) (i) to (v) below.
At least one vinyl aromatic hydrocarbon-based polymer selected from (i) a block copolymer of a vinyl aromatic hydrocarbon different from (a) and a conjugated diene (ii) a vinyl aromatic hydrocarbon polymer (iii) ) Copolymer composed of vinyl aromatic hydrocarbon and (meth) acrylic acid (iv) Copolymer composed of vinyl aromatic hydrocarbon and (meth) acrylic acid ester (v) Rubber-modified styrene-based polymer (provided that In (iii) and (iv), the mass ratio of the vinyl aromatic hydrocarbon and the comonomer copolymerized with the vinyl aromatic hydrocarbon is 5 to 99:95 to 1.) Further, the present invention comprises at least one. A heat-shrinkable multilayer film and a heat-shrinkable label, the layers of which are formed of the above block copolymer composition.

The present invention will be described in detail below. The morphology of the heat-shrinkable film of the present invention, the heat-shrinkable label, and the block copolymer of the present invention in the case of a multilayer, or the block copolymer composition containing the block copolymer as a main component is a transmission electron micrograph by an ultrathin section method. Can be observed at.
The morphology of the block copolymer of the present invention or the block copolymer composition mainly comprising the block copolymer composition is composed of a rubber phase and a plastic phase, and the rubber phase of the lamella or block copolymer is a rod or 15 nm or more, preferably 20 n
It is preferable that the particles exist in the form of particles having a particle size of m or more and 200 nm or less, and more preferably 20 nm or more and 100
nm or less. As a sample for observation with a transmission electron micrograph, pellets of a block copolymer or a block copolymer composition containing the block copolymer as a main component cut in a direction perpendicular to the extrusion direction can be used.

The vinyl aromatic hydrocarbon (a) used in the block copolymer of the vinyl aromatic hydrocarbon and the conjugated diene used in the present invention includes styrene, o-methylstyrene, p-methylstyrene and p- Tert-butyl styrene, 2,4-dimethyl styrene, 2,5-dimethyl styrene, α-methyl styrene, vinyl naphthalene, vinyl anthracene and the like can be mentioned, but styrene is particularly commonly used.

The conjugated diene used in the production of the block copolymer (a) used in the present invention is 1,3-
Butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,
Examples include 3-pentadiene and 1,3-hexadiene, and particularly common examples include 1,3-butadiene and isoprene.

The mass ratio of the vinyl aromatic hydrocarbon to the conjugated diene is 50/50 to 90/10, preferably 70/30 to 85/15. When the mass ratio of vinyl aromatic hydrocarbon is less than 50 mass%, the rigidity of the film is 9
If it exceeds 0% by mass, the stretching temperature during the production of the film will be high, and the heat shrinkability of the film will be poor, so that it cannot be put to practical use.

The structure of the block copolymer used in the present invention and the structure of each block portion are not particularly limited. The structure of the block copolymer includes, for example, a linear or star block copolymer composed of a polymer block mainly containing vinyl aromatic hydrocarbons and a polymer block mainly containing a conjugated diene. Further, even if the vinyl aromatic hydrocarbon copolymerized in the polymer block mainly vinyl aromatic hydrocarbon or the polymer block mainly conjugated diene is evenly distributed in the polymer block, It may be distributed in a tapered shape.

The block ratio of vinyl aromatic hydrocarbon in the block copolymer (a) is 85% or less, particularly preferably 25 to 85%. If the block rate is less than 25%, the rigidity of the film is lowered, and if it exceeds 85%, the heat shrinkability tends to be lowered. The block ratio of vinyl aromatic hydrocarbon is obtained by the following equation. That is,
Block rate (%) = (W1 / W0) × 100. Here, W1 represents the mass of the block polymer chain of the vinyl aromatic hydrocarbon in the copolymer, and W0 represents the total mass of the vinyl aromatic hydrocarbon in the block copolymer. In addition, W1 in the above formula
Discloses a block copolymer in a known document “Rubber Chemistry and Technology (Y. TANAKA, et.a.
l. , RUBBER CHEMISTRY AND TEC
HNOLOGY) ” 58 , p. 16 (1985), ozone decomposition was carried out, and the obtained vinyl aromatic hydrocarbon polymer component was subjected to gel permeation chromatography (hereinafter abbreviated as GPC) measurement and corresponded to a chromatogram. The number average molecular weight of 3,000 was determined from the calibration curve prepared using standard polystyrene and styrene oligomer.
Those exceeding the above were quantitatively determined from the peak area. An ultraviolet spectroscopic detector whose wavelength was set to 254 nm was used as a detector.

The number average molecular weight of the block copolymer (a) used in the present invention is preferably 40,000 to 500,000, particularly preferably 80,000 to 300,000.
It is 0. If it is less than 40,000, sufficient rigidity and impact resistance of the block copolymer composition cannot be obtained.
If it exceeds 000, the workability is deteriorated, which is not preferable. The number average molecular weight of the block copolymer in the present invention was determined by a conventional method using a gel permeation chromatograph (hereinafter abbreviated as GPC).

Next, the production of the block copolymer (a) of the present invention will be described. The block copolymer (a) can be produced by polymerizing a vinyl aromatic hydrocarbon and a conjugated diene monomer in an organic solvent using an organic lithium compound as an initiator. As the organic solvent, butane, pentane, hexane, isopentane, heptane, octane, aliphatic hydrocarbons such as isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, alicyclic hydrocarbons such as ethylcyclohexane, or benzene, toluene Aromatic hydrocarbons such as ethylbenzene and xylene can be used.

The organic lithium compound is a compound in which one or more lithium atoms are bonded in the molecule, and examples thereof include ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, t.
A monofunctional organolithium compound such as ert-butyllithium, a polyfunctional organolithium compound such as hexamethylenedilithium, butadienyldilithium, and isoprenyldilithium can be used.

As the vinyl aromatic hydrocarbon and the conjugated diene used in the present invention, those described above can be used, and one kind or two or more kinds can be selected and used for the polymerization. Then, in the living anionic polymerization using the organolithium compound as an initiator, almost all of the vinyl aromatic hydrocarbon and the conjugated diene used in the polymerization reaction are converted into a polymer.

In the present invention, the molecular weight of the block copolymer (a) can be controlled by the amount of the initiator added to the total amount of the monomers added. The molecular weight of the vinyl aromatic hydrocarbon block after ozone decomposition of the block copolymer of (a) can be controlled by the ratio of the initiator to the monomer and the ratio of the vinyl aromatic hydrocarbon and the conjugated diene.

The block ratio of the vinyl aromatic hydrocarbon in the block copolymer (a) can be controlled by the addition amount of the randomizing agent when the vinyl aromatic hydrocarbon and the conjugated diene are copolymerized. Tetrahydrofuran (THF) is mainly used as the randomizing agent, but other ethers, amines, thioethers, phosphoramides, alkylbenzene sulfonates, potassium or sodium alkoxides and the like can also be used.

Suitable ethers as the randomizing agent include dimethyl ether, diethyl ether, diphenyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, etc. in addition to THF. As amines, tertiary amines such as trimethylamine, triethylamine, tetramethylethylenediamine, as well as cyclic amines can be used. In addition, triphenylphosphine, hexamethylphosphoramide, potassium or sodium alkylbenzene sulfonate, potassium or sodium butoxide, etc. can be used as the randomizing agent.

The addition amount of the randomizing agent is preferably 0.001 to 10 parts by mass with respect to 100 parts by mass of all charged monomers. The addition time may be before the start of the polymerization reaction or before the polymerization of the copolymer chain. Further, it can be additionally added if necessary.

In addition, the block ratio can also be obtained by mechanically continuously feeding the vinyl aromatic hydrocarbon and the conjugated diene to the polymerization vessel or by alternately adding the vinyl aromatic hydrocarbon and the conjugated diene to the polymerization vessel in small amounts. You can control.

The block copolymer thus obtained contains a polymerization terminator such as water, alcohol and carbon dioxide,
It is inactivated by adding an amount sufficient to inactivate the active end. As a method of recovering the copolymer from the obtained block copolymer solution, a method of precipitating with a poor solvent such as methanol, a method of evaporating and precipitating the solvent by a heating roll or the like (drum dryer method), a concentrator is used. Any method such as a method of removing the solvent with a vent type extruder after concentrating the solution, a method of dispersing the solution in water and blowing steam to heat and remove the solvent to recover the copolymer (steam stripping method) can be used. The method can be adopted.

The polymer (b) used in the present invention is at least one vinyl aromatic hydrocarbon polymer selected from the following (i) to (v). (I) Block copolymer of vinyl aromatic hydrocarbon and conjugated diene different from (a) (ii) Vinyl aromatic hydrocarbon polymer (iii) Copolymer composed of vinyl aromatic hydrocarbon and (meth) acrylic acid Copolymer (iv) Copolymer consisting of vinyl aromatic hydrocarbon and (meth) acrylic acid ester (v) Rubber-modified styrene-based polymer (provided that vinyl aromatic hydrocarbon and this vinyl are used in the above (iii) and (iv)) The mass ratio of the comonomer copolymerized with the aromatic hydrocarbon is 5 to 99:95 to 1.)

The block copolymer of vinyl aromatic hydrocarbon and conjugated diene different from (a) of (i) is a block copolymer of vinyl aromatic hydrocarbon and conjugated diene shown in (a) above. Any vinyl aromatic hydrocarbon other than
A conjugated diene block copolymer is used.

As the vinyl aromatic hydrocarbon polymer (ii), a homopolymer of the above-mentioned vinyl aromatic hydrocarbon or a copolymer of two or more kinds is used. Particularly common is polystyrene.

The copolymer (iii) consisting of vinyl aromatic hydrocarbon and (meth) acrylic acid can be obtained by polymerizing the above vinyl aromatic hydrocarbon and (meth) acrylic acid. Each monomer may be used alone or in combination of two or more. Examples of (meth) acrylic acid include acrylic acid and methacrylic acid.

The copolymer (iv) of vinyl aromatic hydrocarbon and (meth) acrylic acid ester is obtained by polymerizing the above vinyl aromatic hydrocarbon and (meth) acrylic acid ester. Each monomer can be used alone or in combination of two or more.

As the (meth) acrylic acid ester, methyl acrylate, ethyl acrylate, acrylic acid -n-
Butyl (or referred to as n-butyl acrylate), isobutyl acrylate, hexyl acrylate, (2-ethyl) hexyl acrylate, methyl methacrylate (or referred to as methyl methacrylate), ethyl methacrylate,
Butyl methacrylate, methacrylic acid (2-hydroxy)
Ethyl etc. are mentioned.

The copolymer (iii) or (iv) has a mass ratio of vinyl aromatic hydrocarbon and (meth) acrylic acid or vinyl aromatic hydrocarbon and (meth) acrylic ester of 5 to 99:95. ~ 1, preferably 40-99:
It is obtained by polymerizing a monomer mixture of 60 to 1, more preferably 70 to 99:30.

The rubber-modified styrenic polymer (v) is obtained by polymerizing a mixture of vinyl aromatic hydrocarbon or a monomer copolymerizable therewith and various elastomers. As the vinyl aromatic hydrocarbon, those described in the production of the block copolymer of the above (a) are used, and as the monomer copolymerizable with this, (meth)
Acrylic acid, (meth) acrylic acid ester and the like are used. Further, as the elastomer, butadiene rubber, styrene-butadiene rubber, styrene-butadiene block copolymer elastomer, chloroprene rubber, natural rubber and the like are used. Particularly preferred rubber-modified styrene-based polymer is impact-resistant rubber-modified styrene resin (HIP
S).

For the MBS resin and MBAS resin, first, polybutadiene or a copolymer rubber latex with styrene containing butadiene as a main component is produced by a known emulsion polymerization method. At this time, a crosslinking agent or a chain transfer agent may be used. Next, the MBS resin is obtained by adding styrene, methyl methacrylate and / or alkyl acrylate to this rubber latex, and the MBAS resin by adding styrene, methyl methacrylate, acrylonitrile and / or alkyl acrylate, and performing graft polymerization.
Examples of the alkyl acrylate used for the MBS resin and the MBAS resin include the alkyl acrylate described in the above-mentioned (iii) vinyl aromatic hydrocarbon and (meth) acrylic acid ester copolymer.

In the present invention, the mass ratio of the block copolymer (a) to the polymers (b) (i) to (v) is preferably 20 to 100: 0 to 80, based on 100 as the whole composition,
It is more preferably 40 to 100: 0 to 60, and particularly preferably 50 to 100: 0 to 50. If the amount of the block copolymer (a) is less than 20 parts by mass, the shrinkability of the heat-shrinkable film will be insufficient.

The morphology of the block copolymer of the present invention or the block copolymer composition mainly containing the block copolymer is
In order to include the rubber phase and the plastic phase, and the rubber phase of the lamella or block copolymer exists as rods or particles having a particle size of 15 nm or more, the block copolymer or the block copolymer mainly composed of the block copolymer is used. The volume ratio of the rubber phase and the plastic phase in the combined composition may be controlled within an appropriate range depending on the compatibility of the rubber phase and the plastic phase in each case. For example, when the block copolymer of the present invention is a so-called clear cut vinyl aromatic hydrocarbon-conjugated diene block copolymer, the volume ratio of the vinyl aromatic hydrocarbon block and the conjugated diene block is the so-called copolymerization. In the case of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, each of which has a rubber part, the volume of the rubber phase and the plastic phase depends on whether the copolymerized part is included in the rubber phase or the plastic phase. In the case of a composition obtained by mixing polystyrene with a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, the volume ratio between the vinyl aromatic hydrocarbon block and the polystyrene and the volume of the conjugated diene block is calculated. The composition of the copolymer and the composition of the composition may be appropriately selected in consideration. As a more specific example, a block copolymer (composition) having a structure as shown in Example 1 of the present specification can be used.

Various additives can be added to the block copolymer composition of the present invention as required. As additives, various stabilizers, processing aids, light resistance improvers, softeners, plasticizers, antistatic agents, antifogging agents, mineral oils, fillers,
Pigments, flame retardants, lubricants and the like can be mentioned.

As the above-mentioned stabilizer, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-) is used.
5-methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3,5-di-ter
t-pentylphenyl) ethyl] -4,6-di-ter
t-pentylphenyl acrylate, 2,6-di-te
Examples thereof include phenolic antioxidants such as rt-butyl-4-methylphenol, and phosphorus antioxidants such as trisnonylphenyl phosphite. As the processing aid, the light resistance improver, the softening agent, the plasticizer, the antistatic agent, the antifogging agent, the mineral oil, the filler, the pigment, the flame retardant and the like, there can be used general known ones. Examples of the lubricant include methylphenyl polysiloxane, fatty acid, fatty acid glycerin ester, fatty acid amide, hydrocarbon wax and the like.

The block copolymer composition of the present invention comprises
It can be obtained by mixing (a) and (b), but the mixing method is not particularly specified, but may be dry blended with, for example, a Henschel mixer, ribbon blender, V blender, etc., and further melted with an extruder. May be pelletized. Alternatively, during the production of each polymer, before the initiation of polymerization,
It may be added during the polymerization reaction, at a stage such as after-treatment of the polymer. When additives are added as needed, for example, the additives may be added to (a) and (b) at a predetermined ratio, and the same mixing method as described above may be used.

The heat-shrinkable film of the present invention is obtained by uniaxially, biaxially or polyaxially stretching a sheet or a film extruded by a known method, for example, a T-die method or a tubular method, using the above composition. To be

In the heat-shrinkable film of the present invention, at least one layer is formed of the block copolymer comprising the above-mentioned (a) and (b) or a block-copolymer composition composition mainly containing the block copolymer. However, when the heat-shrinkable film of the present invention is a heat-shrinkable multilayer film, at least one of the outermost layers is the above block copolymer or a block copolymer composition containing the same as the main component. It is preferable that at least one outer layer or the other layer in the case of two layers is a layer formed from the following (b ′). (B ') at least one vinyl aromatic hydrocarbon-based polymer selected from the following (i') to (v '), (i') a block copolymer of vinyl aromatic hydrocarbon and a conjugated diene (ii) ') Vinyl aromatic hydrocarbon polymer (iii') Copolymer composed of vinyl aromatic hydrocarbon and (meth) acrylic acid (iv ') Copolymer composed of vinyl aromatic hydrocarbon and (meth) acrylic acid ester (V ') The rubber-modified styrene polymer (provided that the mass ratio of the vinyl aromatic hydrocarbon to the comonomer copolymerized with the vinyl aromatic hydrocarbon in the above (iii') and (iv ') is 5 to 99). : 95-1.) (I ') of (b') may be the same as (a) or (i) of (b). Also, (b ')
The polymers of (ii ') to (v') of (b) are (ii) to
The same as the polymer of (v) is used. Also,
The polymer (b ') may be the same as or different from the polymer (b). The inner layer or the other layer in the case of two layers is a styrene-butadiene block copolymer, polystyrene, styrene-n-butyl acrylate copolymer, styrene-n-butyl acrylate-methyl methacrylate copolymer, impact-resistant rubber modified Styrene resin (HIP
More preferably, it is a layer formed of at least one polymer component selected from S), MBS resin and MBAS resin.

In the heat-shrinkable multilayer film of the present invention, the above resins for front and back layers and intermediate layer are each melted by an extruder, and the resulting resin is multilayered in a die or a feed block and then uniaxially, biaxially or It is obtained by stretching in multiple axes. As the die used in the heat-shrinkable film and the heat-shrinkable multilayer film, known ones such as a T-die and a ring die can be used. Examples of uniaxial stretching include a method of stretching an extruded sheet with a tenter in a direction orthogonal to the extrusion direction, a method of stretching an extruded tubular film in the circumferential direction, and the like. Examples of biaxial stretching, after stretching the extruded sheet in the extrusion direction with a roll, a method of stretching in a direction orthogonal to the extrusion direction with a tenter, the extruded tubular film in the extrusion direction and the circumferential direction. Examples include a method of stretching simultaneously or separately. In the multilayer film, the inner layer does not have to be a single layer and may have two or more layers.

In the present invention, the stretching temperature is 60 to 120.
C is preferred. At 60 ° C., the film is broken during stretching, and when it exceeds 120 ° C., good shrinkage properties cannot be obtained, which is not preferable. Particularly preferred is the range of Tg + 5 ° C. to Tg + 20 ° C. with respect to the glass transition temperature (Tg) of the composition constituting the film. In the case of a multilayer film, the T of the polymer composition of the layer having the lowest Tg
With respect to g, the range of Tg + 5 ° C. to Tg + 20 ° C. is particularly preferable. The draw ratio is not particularly limited, but is preferably 1.5 to 8 times. If it is less than 1.5 times, the heat shrinkage tends to be insufficient, and if it exceeds 8 times, stretching is difficult, which is not preferable. When these films are used as heat-shrinkable labels or packaging materials, the heat shrinkage rate is 70 ° C for 10 seconds and 10
% Or more is preferable. If the heat shrinkage ratio is less than 10%, a high temperature is required at the time of shrinkage, which may adversely affect the coated article. A preferable heat shrinkage ratio is 15% or more at the same temperature. Also, the natural shrinkage rate is 40 ° C 7
It is preferably 2.5% or less per day. The film thickness is preferably 10 to 300 μm.

As the use of the heat-shrinkable film and the heat-shrinkable multilayer film of the present invention, a heat-shrinkable label, a heat-shrinkable cap seal and the like are particularly suitable, but in addition, they may be appropriately used for a packaging film and the like. You can The heat-shrinkable label can be produced by a known method, and can be produced, for example, by solvent-sealing the stretched film in the circumferential direction.

The perforation of the present invention is a group of continuous small holes in the form of a perforation line. In the case of a heat-shrinkable label, for example, a large number of cuts are formed in a direction orthogonal to the high shrinkage direction of the heat-shrinkable label. And / or perforations that are engraved in a parallel direction, and are continuous perforations that are provided to facilitate the detachment of the label when it is separated from the container covered with the heat shrink label after use. It is a group of holes. Further, in the present invention, good perforation of perforations means that the heat-shrinkable film or the heat-shrinkable label engraved with perforations is torn along the perforations (evaluation of perforation of perforations of Examples of the present application. Refer to the method), the break does not come off the perforation. The container when the heat-shrinkable film or the heat-shrinkable multilayer film of the present invention is used as a heat-shrinkable label is not particularly limited, but a container made of polyethylene terephthalate (abbreviated as PET), a glass container,
Alternatively, an aluminum container or the like is preferably used.

[0042]

EXAMPLES The present invention will be further described with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 4 and Comparative Example 1 (a) vinyl aromatic hydrocarbon-conjugated diene block copolymer shown in Table 1 and (b) vinyl aromatic hydrocarbon-based copolymer shown in Table 2 A block copolymer composition was produced by mixing the coalescences in a Henschel mixer according to the formulations shown in Table 4 and then melting and pelletizing them in an extruder. The film should have a thickness of 0.3 at a temperature of 210 ° C.
A sheet of mm was extruded and then uniaxially stretched 5 times at a stretching temperature shown in Table 4 using a biaxial stretching device manufactured by Toyo Seiki Seisaku-sho, Ltd. to prepare a stretched film.

In Table 4, the physical properties are shown together with the blending amount (parts by mass) of each component.

Examples 5 to 9 and Comparative Example 2 (a) Component (a) used in the heat-shrinkable multilayer film: A vinyl aromatic hydrocarbon-conjugated diene block copolymer as shown in Table 1 was used. .

[0046]

[Table 1]

Component (b): (i) as shown in Table 2.
Block copolymer of vinyl aromatic hydrocarbon and conjugated diene different from (a), (ii) vinyl aromatic hydrocarbon polymer, (iii) copolymer of vinyl aromatic hydrocarbon and (meth) acrylic acid , (Iv) a copolymer of vinyl aromatic hydrocarbon and (meth) acrylic acid ester,
(V) A rubber-modified styrene polymer was used.

[0048]

[Table 2]

Component (d): A vinyl aromatic hydrocarbon polymer as shown in Table 3 was used.

[0050]

[Table 3]

(B) Production of film (a) Vinyl aromatic hydrocarbon-conjugated diene block copolymer shown in Table 1, (b) Vinyl aromatic hydrocarbon polymer shown in Table 2, and Table 3 Using the vinyl aromatic hydrocarbon-based polymer (d) shown in Table 1, a heat-shrinkable multilayer film was prepared with the blending amount (parts by mass) of the raw material polymer and the layer ratio (%) shown in Table 5. . The film was prepared by first melting a polymer or polymer composition corresponding to each layer with a separate extruder and forming a multilayer in a T die to form a sheet having a thickness of 0.3 mm.
After that, a biaxial stretching device manufactured by Toyo Seiki Seisaku-sho, Ltd. was used to draw a stretched film by transversely uniaxially stretching 5 times at the stretching temperature shown in Table 5.

Table 5 shows the blending amount (parts by mass) of the raw material polymer in each layer and the layer ratio (%) together with the physical properties.

The physical properties of the block copolymer (composition) and the film were determined by the following methods. (1) Method for measuring particle size of rubber particles in block copolymer (composition) Pellets were trimmed in a direction perpendicular to the extrusion direction with a microtome, dyed with osmic acid, washed with water, dried, and then a thickness of 2
It was thinned to 0 μm and observed with a transmission electron microscope (black indicates rubber phase). The osmium acid staining was carried out by immersing in an aqueous 4% -4 osmium oxide solution at 40 ° C for 48 hours. (2) Glass transition temperature (Tg) The glass transition temperature (Tg) of the polymer composition was determined from the peak value by measuring the loss modulus by the dynamic viscoelastic method according to the following procedure. (I) Each polymer pellet was hot-pressed under the condition of 200 to 250 ° C to prepare a sheet having a thickness of 0.1 to 0.5 mm. (Ii) A test piece of an appropriate size was cut out from this sheet and stored in a room at 23 ° C. and 50% RH for 24 hours or more. Then, the loss modulus inherent to the polymer as the test piece was measured using the following apparatus. The measurement was performed while changing the temperature. Device: Rheometrics solid viscoelasticity measuring device R
SA2 (set temperature range: room temperature to 130 ° C., set temperature rising rate: 4 ° C./min, measurement frequency: 1 Hz) (3) Heat shrinkage rate: It was immersed in hot water of 70 ° C. for 10 seconds and calculated from the following formula. Thermal shrinkage (%) = {(L1-L2) / L1} × 100, where L1: length before immersion (stretching direction), L2: 70 ° C.
Length after shrinkage by dipping in warm water for 10 seconds (stretching direction) (4) Natural shrinkage: The natural shrinkage of the film was measured by the following method. A test piece having a MD direction of about 75 mm and a TD direction of about 400 mm was cut out from the stretched film produced under the same conditions as the stretched film whose thermal shrinkage was measured. Marks at intervals of 300.0 mm were attached in the TD direction of this test piece. The stretched film was stored in an environmental tester at 40 ° C. After 7 days of storage, take out the film and remove the distance L between the marked lines.
(Mm) was measured to the unit of 0.1 mm using a caliper. The natural shrinkage ratio was calculated by the following formula 1.

[0054]

[Equation 1]

(5) Perforation of the sewing machine The obtained film was cut to 0.7 mm and the bridge 1.
After perforating in a direction of 4 mm and a direction with a high shrinkage rate, place the film on the table, hold one side of the perforation with your hand, grasp the other side with your finger, and tear it parallel to the table The condition when the sample was exposed was evaluated according to the following criteria. ○: Cuts along the perforation △: Shifts from the perforation on the way ×: Does not cut according to the perforation

From the results shown in Tables 4 and 5, it can be seen that the heat-shrinkable film of the present invention is excellent in perforation of the sewing machine.

[0057]

[Table 4]

[0058]

[Table 5]

[0059]

The heat-shrinkable film using the block copolymer composition of the present invention is excellent in heat shrinkability and natural shrinkability,
Further, since the perforation of the sewing machine is good, these films can be suitably used as various packaging films such as labels with various prints and cap seals.

[Brief description of drawings]

FIG. 1 is a transmission electron micrograph (lamella or rod) of the block copolymer composition of Example 1.

FIG. 2 is a transmission electron microscopic photograph of the block copolymer composition of Example 2 (rubber phase having a particle size of 15 nm or more).

FIG. 3 is a transmission electron micrograph of the block copolymer composition of Comparative Example 1 (rubber phase is slightly dispersed).

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08J 5/18 CET C08J 5/18 CET 4J002 C08L 25/00 C08L 25/00 53/02 53/02 // B29K 25:00 B29K 25:00 105: 02 105: 02 B29L 7:00 B29L 7:00 F Term (reference) 3E067 AA11 AB99 BA21A BB14A BB25A CA01 EB03 FA04 FB01 3E086 AB03 AD16 BA02 BA04 BA15 BA33 BB67 CA40 4F071 AA12X AA12X AA32X AA33X AA75 AF61 BA01 BB06 BB07 BB08 BB09 BC01 BC17 4F100 AK12A AK12B AK25B AK28A AK28B AL01B AL02A AL02B AL06B AN00B BA02 BA07 BA15 GB90 JJ10 JK10B JL00 4F210 AA13F AE01 AG01 AG03 RA03 RC02 RG02 RG04 RG43 4J002 BC032 BC042 BC072 BN152 BP011 BP012 FD030 FD170 GG01 GG02

Claims (13)

[Claims] 1. A heat-shrinkable film having a good perforation property of a sewing machine, which is obtained by stretching a film made of a block copolymer of vinyl aromatic hydrocarbon and a conjugated diene or a block copolymer composition mainly composed of the block copolymer. 2. The morphology of the block copolymer or the block copolymer composition comprising the block copolymer as a main component includes a rubber phase and a plastic phase, and the rubber phase of the lamella or block copolymer has a rod or a particle size of 15 nm or more. The heat-shrinkable film according to claim 1, which is present as particles. 3. A block copolymer or a block copolymer composition containing the block copolymer as a main component contains the following (a) and, if necessary, (b): Alternatively, the heat-shrinkable film described in 2. (A) The mass ratio of vinyl aromatic hydrocarbon to conjugated diene is 5
Block copolymer of 0/50 to 90/10 and a vinyl aromatic hydrocarbon block ratio of 85% or less, a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, (b) (i) to (v) below.
At least one vinyl aromatic hydrocarbon-based polymer selected from (i) a block copolymer of a vinyl aromatic hydrocarbon different from (a) and a conjugated diene (ii) a vinyl aromatic hydrocarbon polymer (iii) ) Copolymer composed of vinyl aromatic hydrocarbon and (meth) acrylic acid (iv) Copolymer composed of vinyl aromatic hydrocarbon and (meth) acrylic acid ester (v) Rubber-modified styrene-based polymer (provided that In (iii) and (iv), the mass ratio of the vinyl aromatic hydrocarbon and the comonomer copolymerized with the vinyl aromatic hydrocarbon is 5 to 99:95 to 1.) 4. The heat-shrinkable film according to claim 3, wherein the mass ratio of (a) and (b) is 20 to 100: 0 to 80, with the total composition being 100. 5. (a) and (i) are styrene-butadiene block copolymers, (ii) is polystyrene,
(Iii) is a styrene-methacrylic acid copolymer, (i
v) is at least one polymer selected from styrene-n-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, and styrene-n-butyl acrylate-methyl methacrylate copolymer; The heat-shrinkable film according to claim 3, which is an impact rubber-modified styrene resin. 6. A perforation machine, characterized in that at least one layer is formed of the block copolymer according to any one of claims 1 to 5 or a block copolymer composition mainly composed of the block copolymer. Heat-shrinkable multilayer film with good properties. 7. The heat according to claim 6, wherein at least one outer layer in the case of three or more layers or another layer in the case of two layers is a layer formed from the following (b ′). Shrinkable multilayer film. (B ') at least one vinyl aromatic hydrocarbon-based polymer selected from the following (i') to (v '), (i') block copolymer of vinyl aromatic hydrocarbon and conjugated diene (ii) ') Vinyl aromatic hydrocarbon polymer (iii') Copolymer composed of vinyl aromatic hydrocarbon and (meth) acrylic acid (iv ') Copolymer composed of vinyl aromatic hydrocarbon and (meth) acrylic acid ester (V ') The rubber-modified styrene-based polymer (provided that the vinyl aromatic hydrocarbon and the comonomer copolymerized with the vinyl aromatic hydrocarbon in the above (iii') and (iv ') have a mass ratio of 5 to 99). : 95-1.) 8. A styrene-butadiene block copolymer, wherein at least one outer layer or the other layer when it is two layers,
At least one polymer component selected from polystyrene, styrene-n-butyl acrylate copolymer, styrene-n-butyl acrylate-methyl methacrylate copolymer, impact resistant rubber-modified styrene resin, MBS resin and MBAS resin. The heat-shrinkable multilayer film according to claim 6, which is a layer formed by. 9. The heat-shrinkable film or the heat-shrinkable multilayer film according to claim 1, which has a heat shrinkage rate of 10% or more at 70 ° C. for 10 seconds. 10. The natural shrinkage ratio is 2.5% at 40 ° C. for 7 days.
The heat-shrinkable film or heat-shrinkable multilayer film according to any one of claims 1 to 9, wherein: 11. A heat-shrinkable label comprising the heat-shrinkable film or the heat-shrinkable multilayer film according to any one of claims 1 to 10. 12. A perforated heat-shrinkable label, comprising the heat-shrinkable film or the heat-shrinkable multilayer film according to any one of claims 1 to 10. 13. A container coated with the heat-shrinkable label according to claim 11.