JP2002127326A - Heat-shrinkable multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable multilayer film excellent in transparency, a heat-shrinkable property, rigidity, impact resistance and a tearing-off property of perforations in either case when the film is made of a virgin material or a mixture of the virgin material and a returned material. SOLUTION: The heat-shrinkable multilayer film comprises at least one layer formed by an A component and at least one layer formed by a B component. The A component consists of a copolymer having a specific refractive index consisting of a styrenic monomer and a (meth)acrylate monomer, a rubber- like elastomer resin having a specific refractive index, and a specific block copolymer of a styrenic monomer and a conjugated diene. The B component having a specific refractive index mainly comprises a block copolymer consisting of a styrenic monomer and a conjugated diene, a styrenic polymer, and a copolymer consisting of a styrenic monomer and (meth)acrylate and/or (meth)acrylic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is excellent in transparency, heat shrinkage, rigidity, impact strength, and perforation of a perforated film, both a film obtained from a virgin material and a film obtained by mixing a return material into a virgin material. Heat-shrinkable multilayer film.

[0002]

2. Description of the Related Art Conventionally, heat shrinkable films used as shrink wrapping and shrink labels for containers have good heat shrink properties and finish after shrinkage. For this reason, a styrene-butadiene-based block copolymer film having excellent transparency is used. However, this film has problems such as softness and rigidity and large natural shrinkage depending on the application, and various multilayer films have been proposed to improve these drawbacks (Japanese Patent Application Laid-Open Nos. 9-114380 and 9-114380). 11-77
916). On the other hand, in actual film formation, it is usual to mix the virgin material as a return material with an end of the obtained film or an unnecessary film obtained until a good product is obtained. However, the above various multilayer films are
When the return material is mixed with the virgin material, it becomes cloudy and cannot be used as a film. Also, in recent years, labels with perforations have been attached to PET bottles for the purpose of improving recycling, and labels that are easily cut along these perforations, that is, labels with excellent perforation breakability are desired. I have.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has been made in consideration of the above circumstances.
Excellent heat shrinkage, stiffness, impact strength, and perforation breakability, and heat with excellent transparency, heat shrinkage, rigidity, impact strength, and perforation breakability even for films obtained by mixing return material with virgin material. An object is to provide a shrinkable multilayer film.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have found that a copolymer comprising a styrene monomer and a (meth) acrylate ester having a specific refractive index. And, a rubber-like elastic resin having a specific refractive index, and a composition comprising a block copolymer consisting of a styrene monomer and a conjugated diene of a specific monomer ratio as at least one layer of a multilayer film, Selected from a block copolymer comprising a styrene monomer and a conjugated diene, a styrene polymer, and a copolymer comprising a styrene monomer and a (meth) acrylate and / or (meth) acrylic acid. By forming at least one layer mainly composed of at least one kind of polymer as another layer, the transparency, heat shrinkage, rigidity, impact strength, perforation of a film obtained from a virgin material are obtained. Excellent properties are further transparency in films return material is mixed, heat shrinkable, heading rigidity, impact strength, that multilayer film is obtained having excellent perforation breakage resistance, and have completed the present invention.

That is, the present invention relates to (a) a copolymer comprising a styrene monomer having a refractive index of 1.550 to 1.580 at a temperature of 23 ° C. and a (meth) acrylate (hereinafter referred to as a styrene monomer). (B) a rubber-like elastic resin having a refractive index of 1.535 to 1.550 at a temperature of 23 ° C;
(C) the mass ratio of the styrene monomer to the conjugated diene is 90 /
The mass ratio with the block copolymer of 10 to 60/40 is (a) / (b) / (c) = 50 to 90/3 to 30 /.
(I) a block copolymer (hereinafter referred to as a styrene-based monomer) composed of a styrene-based monomer and a conjugated diene; A conjugated diene block copolymer), (I
I) a styrene-based polymer, and (III) a styrene-based monomer and a (meth) acrylate and / or (meth)
At least one selected from copolymers of acrylic acid
A heat-shrinkable multilayer film mainly composed of at least one kind of polymer and having at least one layer formed of a component B having a refractive index of 1.568 to 1.582 at a temperature of 23 ° C.

Particularly, the front and back layers are (a) a styrene monomer- (meth) acrylate copolymer having a refractive index of 1.550 to 1.580 at a temperature of 23 ° C., and (b) a temperature of 23 ° C. Mass ratio of rubber-like elastic resin having a refractive index of 1.535 to 1.550 and block copolymer (c) having a mass ratio of styrene monomer to conjugated diene of 90/10 to 60/40 Is (a) / (b) / (c) = 50-9
The intermediate layer is formed of an A component (total of 100 parts by mass) which is 0/3 to 30/5 to 45, and the intermediate layer is (I) a styrene monomer-conjugated diene block copolymer, and (II) a styrene polymer. And (III) a styrene monomer and (meth)
Mainly at least one polymer selected from copolymers of acrylic acid esters and / or (meth) acrylic acid, and having a refractive index of 1.56 at a temperature of 23 ° C.
A heat-shrinkable multi-layer film formed with the component B of 8 to 1.582 is preferable.

Further, the front and back layers are composed of (I) a styrene monomer
At least one selected from a conjugated diene block copolymer, (II) a styrene-based polymer, and (III) a copolymer consisting of a styrene-based monomer and (meth) acrylate and / or (meth) acrylic acid And a refractive index at a temperature of 23 ° C. of 1.568 to
A styrene-based monomer- (meth) acrylate copolymer having a refractive index at a temperature of 23 ° C. of 1.550 to 1.580; (B) The refractive index at a temperature of 23 ° C. is 1.535
Mass ratio of (c) styrene monomer to conjugated diene is 90/10 to 60/40.
Is a mass ratio of (a) / (b) /
(C) A heat-shrinkable multilayer film formed from the component A (100 parts by mass in total) in which 50 to 90/3 to 30/5 to 45 is preferable.

Further, as the styrene monomer- (meth) acrylate copolymer having a refractive index of 1.550 to 1.580 at a temperature of 23 ° C. of the component A, a styrene monomer is used. A polymer obtained by polymerizing a monomer in which styrene and a (meth) acrylate monomer are methyl methacrylate, or a styrene monomer is styrene and a (meth) acrylate monomer is methyl methacrylate It is a particularly preferable heat-shrinkable multilayer film to use a polymer obtained by polymerizing a monomer which is n-butyl acrylate.

Hereinafter, the present invention will be described in detail. The styrene monomer and (meth) acrylate used in the (a) styrene monomer- (meth) acrylate copolymer used as the component A of the present invention are as follows. Examples of the styrene-based monomer include styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene, and the like, with styrene being preferred. These styrene monomers may be used alone or in combination of two or more. On the other hand, examples of the (meth) acrylate monomer include methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, and octyl acrylate. Is methyl methacrylate and / or n-butyl acrylate. These (meth) acrylate monomers may be used alone or in combination of two or more. A combination of methyl methacrylate and n-butyl acrylate is a preferred example. Further, if necessary, other monomers can be used as long as the object of the present invention is not impaired. For example, acrylic acid, methacrylic acid,
Maleic acid, itaconic acid, maleic anhydride and the like are used.

(A) Styrene monomer used in the present invention
As a method for producing the (meth) acrylic acid ester copolymer, a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, etc., which are commonly used in the production of styrene-based polymers, are used.
Either a batch polymerization method or a continuous polymerization method can be used.

In these polymerization methods, azo compounds such as azobisbutyronitrile and azobiscyclohexanecarbonitrile, benzoyl peroxide, t-butylperoxybenzoate, and t-butylperoxy-2-ethyl are used as polymerization initiators. Hexanoate, di-t-butyl peroxide, dicumyl peroxide, ethyl-
An organic peroxide such as 3,3-di- (t-butylperoxy) butyrate can be used. If necessary, t-dodecyl mercaptan, n-dodecyl mercaptan, 4-methyl-2,4-diphenylpentene-1 may be added as a molecular weight modifier, and butylbenzyl phthalate or diisobutyl adipate may be added as a plasticizer, if necessary. Good.

(A) Styrene monomer used in the present invention
The refractive index of the (meth) acrylate copolymer at a temperature of 23 ° C is 1.550 to 1.580. 1.5
If it is less than 50, the transparency when the return material is mixed is inferior, and if it exceeds 1.580, the stretching temperature at the time of film production becomes high and the heat shrinkage of the film is inferior, so that it is not practical.

The rubbery elastic resin (b) used in the present invention includes MBS resin and MBAS resin. These rubber-like elastic resins can be used alone or in combination. In addition, it is necessary that the refractive index at the time of use satisfies the range of 1.535 to 1.550 as described later.

For MBS resin and MBAS resin, first, polybutadiene or a copolymer rubber latex of 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, MBS resin is obtained by adding styrene, methyl methacrylate and, if necessary, alkyl acrylate to this rubber latex, and MBAS resin is obtained by adding styrene, methyl methacrylate, alkyl acrylate and / or acrylonitrile, and performing graft polymerization. Can be Examples of the alkyl acrylate used for the MBS resin and the MBAS resin include the same alkyl acrylates as described in the above (a) styrene-based monomer- (meth) acrylate copolymer.

The refractive index of the rubber-like elastic resin (b) used in the present invention at a temperature of 23 ° C. is 1.535 to 1.550.
It is. If it is less than 1.535, the transparency when the return material is mixed is inferior, and if it exceeds 1.550, the impact strength is inferior and cannot be put to practical use.

The (c) block copolymer comprising a styrene monomer and a conjugated diene used in the present invention is prepared by using an organolithium compound as an initiator in an organic solvent and subjecting the styrene monomer and the conjugated diene to specific conditions. Obtained by polymerization. Organic solvents include butane, pentane, hexane,
Aliphatic hydrocarbons such as isopentane, heptane, octane and isooctane; alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane and ethylcyclohexane; and aromatic hydrocarbons such as benzene, toluene, ethylbenzene and xylene Known organic solvents can be used. An organic lithium compound is a compound in which one or more lithium atoms are bonded in a molecule, and examples thereof include ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, and t-butyl lithium. Can be used.

The styrene monomers used include styrene, α-methylstyrene, p-methylstyrene and p-methylstyrene.
Examples thereof include -t-butylstyrene, and styrene is preferable. These styrene monomers are
They may be used alone or in combination of two or more. The conjugated dienes used include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene),
Examples thereof include 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene.
Particularly common ones are 1,3-butadiene and isoprene.

The structure of the block copolymer used is not particularly limited. The entire structure includes a linear copolymer and a star-shaped copolymer. Known coupling agents can be used to increase the molecular weight of the linear copolymer or to form a star. Further, the structure of each block portion constituting the block copolymer may be any of a single block of a styrene monomer or a conjugated diene monomer, a tapered block of both, and a random block. In order to form a tapered block or a random block portion, a known randomizing agent may be used, both may be continuously fed to a polymerization vessel, or may be alternately added little by little.

The mass ratio of the styrene monomer to the conjugated diene is 90/10 to 60/40. If the styrene-based monomer exceeds 90% by mass, the stretching temperature during the production of the film becomes high and the heat shrinkage is poor, and if it is less than 60%, the rigidity is poor and it cannot be put to practical use.

(A) a styrene monomer- (meth) acrylate copolymer constituting the component A of the present invention;
The mass ratio of (b) the rubber-like elastic resin and (c) the block copolymer composed of a styrene monomer and a conjugated diene is as follows:
(A) / (b) / (c) = 50-90 / 3-30 / 5
45 (total 100 parts by mass), preferably 5
The ratio is from 5 to 85/4 to 25/10 to 40, and more preferably from 60 to 80/5 to less than 20/15 to 30.
When the ratio of (a) is less than 50 parts by mass, the rigidity is poor, when it exceeds 90 parts by mass, the impact strength is poor, and when the ratio of (b) is less than 3 parts by mass, the impact strength is poor. If the ratio of (c) is less than 10 parts by mass, the perforation of the sewing machine is inferior, and if it exceeds 45 parts by mass, the rigidity is inferior and cannot be put to practical use.

The method of mixing (a), (b) and (c) is not particularly limited, but may be dry-blended using, for example, a Henschel mixer, a ribbon blender, a V blender, or the like. May be used.

Next, (I) a styrene-based monomer-conjugated diene block copolymer, (II) a styrene-based polymer, and (III) a styrene-based monomer to be used as the component B of the present invention, ) A copolymer comprising an acrylate and / or (meth) acrylic acid will be described. The (I) styrene-based monomer-conjugated diene block copolymer of the present invention is obtained by combining the styrene-based monomer and conjugated diene with the styrene-based monomer and conjugated diene block copolymer (c). It is obtained by polymerization using the same organic solvent and initiator as described above.

Examples of the styrene monomer to be used include the same ones as described in the above (a) styrene monomer- (meth) acrylate copolymer. Examples of the conjugated diene to be used include the same ones as described in (c) the block copolymer of a styrene monomer and a conjugated diene. There is no particular limitation on the structure and composition of the block copolymer used.

The (II) styrene-based polymer used in the present invention includes (a) the styrene-based monomer- (meth) acrylate copolymer and (c) the styrene-based monomer. And conjugated dienes using the same styrenic monomers as described in the block copolymers. Homopolymers or copolymers of these styrenic monomers, and high impact polystyrene (HIPS), etc. Is raised.

The copolymer of (III) styrene monomer and (meth) acrylic acid ester and / or (meth) acrylic acid used in the present invention is a styrene monomer and (meth) acrylic acid. Acid ester and / or (meth)
Obtained by polymerizing acrylic acid. As the styrene monomer, (a) the styrene monomer-
The same styrene-based monomer as described in the (meth) acrylate copolymer or (c) the styrene-based monomer-conjugated diene block copolymer can be used. Examples of the (meth) acrylic acid ester include the same (meth) acrylic acid esters as described in (a) the copolymer of a styrene monomer and a (meth) acrylic acid ester. Also,
Examples of the (meth) acrylic acid include acrylic acid and methacrylic acid.

In the present invention, (I) a styrene monomer-conjugated diene block copolymer, (II) a styrene polymer, and (III) a styrene monomer and (meth) acrylate and / or The copolymer of (meth) acrylic acid may form a layer of the multilayer film alone, or may form a layer of the multilayer film mainly by a mixture of two or more kinds. When mixing, A
The same method as that for the component can be used.

The refractive index of the component B at a temperature of 23 ° C. is 1.568 to 1.582. If it is less than 1.568, the rigidity is inferior. If it exceeds 1.582, the stretching temperature at the time of film production becomes high, and the heat shrinkage of the film is inferior, so that it is not practical.

Each of the (co) polymers used in the present invention may contain, if necessary, an antioxidant, a weathering agent, a lubricant, a plasticizer, a tackifier, a coloring agent, an antistatic agent, a mineral oil, a flame retardant. Additives such as an agent and a filler may be blended within a range that does not impair the effects of the present invention. There are no particular restrictions on the method of blending the additives, for example, Henschel mixer,
Dry blending may be performed using a ribbon blender, a V blender, or the like, or may be melted and pelletized using an extruder. Alternatively, it may be added during the production of each polymer, before the start of polymerization, during the polymerization reaction, or at the stage of post-treatment of the polymer.

The plasticizer used in the present invention includes, for example, aliphatic-basic acid esters such as butyl oleate and glycerin monooleic acid, dibutyl adipate, diisobutyl adipate, di-n-hexyl adipate and di-adipate. Aliphatic dibasic acid esters such as 2-ethylhexyl, dibutyl sabacate, di-2-ethylhexyl sabacate, or dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-n-octyl phthalate, di-phthalate Phthalates such as 2-ethylhexyl are preferred. As a preferable addition amount, it is preferable to add 0 to 3 parts by mass based on 100 parts by mass of the component A.

The heat-shrinkable multilayer film of the present invention is obtained by melting the above-mentioned (co) polymer and resin for the front and back layers and for the intermediate layer by an extruder, and forming a multilayer in a die or a feed block. Thereafter, it is obtained by stretching uniaxially, biaxially or multiaxially. As the die, a known die such as a T die or an annular die can be used. Examples of the uniaxial stretching include a method in which the extruded sheet is stretched by a tenter in a direction perpendicular to the direction of extrusion, and a method in which the extruded tubular film is circumferentially stretched. As an example of biaxial stretching, after the extruded sheet is stretched in the extrusion direction by a roll, a method of stretching in a direction perpendicular to the extrusion direction with a tenter or the like, the extruded tubular film is extruded in the extrusion direction and the circumferential direction. Examples of the method include simultaneous or separate stretching.

In the present invention, the stretching temperature is from 60 to 120.
C is preferred. If the temperature is lower than 60 ° C., the sheet or film is broken at the time of stretching, and if the temperature is higher than 120 ° C., good shrinkage characteristics cannot be obtained, which is not preferable. The stretching ratio is not particularly limited, but is preferably 1.5 to 8 times. 1.
If it is 5 times, the heat shrinkage is insufficient, and if it exceeds 8 times, it is not preferable because stretching is difficult. When using these films as heat-shrinkable labels or packaging materials,
The heat shrinkage must be 20% or more at a temperature of 80 ° C.
If it is less than 20%, a high temperature is required at the time of shrinkage, which adversely affects the coated article, which is not preferable. The thickness of the film is preferably from 10 to 300 μm.

The present invention also provides a heat-shrinkable multilayer film obtained by mixing the return material of the heat-shrinkable multilayer film of the present invention with a virgin material of component A and / or component B. It is intended to form a heat-shrinkable multilayer film having excellent properties, rigidity, impact strength, and perforation breakability. The mixing ratio is not particularly limited, but it is preferable from the viewpoint of transparency that the mixing ratio is not more than 50% by mass (but not 0% by mass) in the virgin material of the component A and / or the component B. .

In the present invention, an antistatic agent or a lubricant may be applied to the surface of the obtained film in order to improve the surface characteristics.

As a use of the heat-shrinkable film of the present invention, a heat-shrinkable label, a heat-shrinkable cap seal, and the like are particularly preferable, but the heat-shrinkable film can also be appropriately used as a packaging film.

[0035]

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

Examples 1 to 6 and Comparative Examples 1 to 12 (a) Raw material polymer A component: (a) Styrene monomer- (meth) acrylate copolymer Styrene as shown in Table 1 A monomer- (meth) acrylate copolymer was used.

[0037]

[Table 1]

A component: (b) Rubber-like elastic resin A rubber-like elastic resin as shown in Table 2 was used.

[0039]

[Table 2]

Component A: (c) Block copolymer comprising styrene monomer and conjugated diene A styrene-butadiene block copolymer as shown in Table 3 was used.

[0041]

[Table 3]

Component B: As shown in Table 4, (I) styrene monomer-conjugated diene block copolymer, (II) styrene polymer, and (III) styrene monomer and (meth) acryl A copolymer composed of an acid ester and / or (meth) acrylic acid was used.

[0043]

[Table 4]

The refractive index was measured for each polymer by injection molding (thickness 2
mm) was measured at a temperature of 23 ° C. using a digital refractometer RX-2000 manufactured by Atago Corporation in accordance with JIS K7105.

(B) Preparation of film (a) Styrene monomer shown in Table 1 as component A
The (meth) acrylic ester copolymer, the rubbery elastic resin (b) shown in Table 2, the styrene monomer-conjugated diene block copolymer shown in Table 3, and the B component as shown in Table 4 Using the indicated polymers, heat-shrinkable multilayer films were prepared in the amounts (parts by mass) of the raw material polymers and the layer ratios (%) of the respective layers shown in Tables 5 to 7. First, the polymer or polymer composition corresponding to each layer was melted by a separate extruder, and the film was multilayered in a T-die to form a sheet having a thickness of 0.3 mm. In addition, a part of the obtained multilayer sheet was pelletized (the pellet is referred to as a return material), and 30% by mass was mixed with a component constituting the intermediate layer, to prepare a sheet in the same manner as described above. Thereafter, using a biaxial stretching device manufactured by Toyo Seisakusho, the film was horizontally uniaxially stretched 5 times at a temperature of 90 ° C. to prepare a stretched film.

Tables 5 to 7 show the physical properties together with the compounding amount (parts by mass) of the raw material polymer and the layer ratio (%) of each layer. In addition,
The refractive index of the front and back layers in Example 3 was 1.573, and the refractive index of the front and back layers in Example 4 was 1.577. Comparative Examples 1 and 2
In Nos. 6 and 8, the sheet could be formed, but no stretched film was obtained.

The physical properties of the film were determined by the following methods. (1) Haze: Measured using a Haze meter (Model NDH-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with ASTM D1003. (2) Heat shrinkage: immersed in warm water of 80 ° C. for 30 seconds and calculated by the following equation. Heat shrinkage (%) = {(L1−L2) / L1} × 100, where L1: length before dipping (stretching direction), L2: 80 ° C.
(3) Tensile modulus: A & D Tensilon Universal Testing Machine (RTC-12), conforming to JIS K6871
10A). (4) Film impact: measured using a stretched film and a film impact tester manufactured by Tester Sangyo. (5) Perforation cutability: The obtained film was perforated with a cut of 0.7 mm and a bridge of 1.4 mm, was torn by hand, and evaluated according to the following criteria. ：: Cuts along perforations △: Deviates from perforations on the way ×: Does not cut along perforations

From the physical properties shown in Tables 5 to 7, the film of the present invention can be used for a film obtained by using a virgin material or a film obtained by mixing a return material into a virgin material. It turns out that it is excellent in impact strength and perforation breakability.

[0049]

[Table 5]

[0050]

[Table 6]

[0051]

[Table 7]

[0052]

According to the present invention, a film obtained by mixing a return material with a virgin material is excellent in transparency, heat shrinkage, rigidity, impact strength, and perforation cutability of a film obtained from a virgin material. Can provide a heat-shrinkable multilayer film having excellent transparency, heat-shrinkability, rigidity, impact strength, and perforation breakability. This film can be used for packaging various articles or printed and used as a label.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 21:00 C08L 21:00 53:02) 53:02) F-term (Reference) 4F071 AA12X AA22X AA33X AA34X AA75 AF14 AF23 AF30 AF31Y AF61 AH04 BA01 BB08 BC01 BC02 4F100 AK12A AK12B AK12C AK12D AK25A AK25B AK25C AK25D AK73A AK73B AK73C AK73D AK80A AK80C AL01A AL01B AL01C AL01D AL02B AL02D AL05A AL05C AN00A AN00C BA03 BA06 BA10A BA10B GB16 JA03 JL01 JL16 JL16A JL16B JL16C JL16D JN01 JN18A JN18B JN18C JN18D 4J002 BC071 BN14X BN16X BP01Y GF00 GG00

Claims (11)

[Claims] (1) The refractive index at a temperature of 23 ° C. is 1.
Styrene monomer having 550 to 1.580 and (meth)
(B) temperature 2
A rubber-like elastic resin having a refractive index of 1.535 to 1.550 at 3 ° C .; and (c) a block copolymer having a mass ratio of a styrene monomer to a conjugated diene of 90/10 to 60/40. Is (a) / (b) / (c) = 50 to 90
At least one layer formed of the A component (total: 100 parts by mass) which is / 3 to 30/5 to 45; and (I) a block copolymer comprising a styrene monomer and a conjugated diene;
(II) a styrene-based polymer and (III) at least one polymer selected from a copolymer of a styrene-based monomer and (meth) acrylate and / or (meth) acrylic acid And a heat-shrinkable multilayer film having at least one layer formed of a component B having a refractive index of 1.568 to 1.582 at a temperature of 23 ° C. 2. The copolymer (A) of component A, wherein the styrene monomer is styrene and the (meth) acrylate monomer is methyl methacrylate, or the styrene monomer is The heat-shrinkable multilayer film according to claim 1, wherein the (meth) acrylate monomer is styrene and is a copolymer of methyl methacrylate and n-butyl acrylate. 3. The rubber-like elastic resin of the component A (b) is M
The heat-shrinkable multilayer film according to claim 1, wherein the heat-shrinkable multilayer film is at least one resin selected from a BS resin and an MBAS resin. 4. The block copolymer (c) of the component A,
The heat-shrinkable multilayer film according to claim 1, which is a block copolymer comprising styrene and butadiene. 5. A component (a) comprising a styrene-methyl methacrylate copolymer and / or a styrene-methyl methacrylate-n-butyl acrylate copolymer, (b)
Is a MBS resin and / or an MBAS resin, and (c) is a block copolymer composed of styrene and butadiene. 6. The heat-shrinkable multilayer film according to claim 1, wherein the component B is a block copolymer comprising styrene and butadiene. 7. A heat-shrinkable multilayer film, wherein the front and back layers are formed of the component A according to claim 1 and the intermediate layer is formed of the component B according to claim 1 or 6. 8. A heat-shrinkable multilayer film, wherein the front and back layers are formed of the component B according to claim 1 or 6, and the intermediate layer is formed of the component A according to claim 1. 9. The return material of the heat-shrinkable multilayer film according to claim 1 is mixed with a virgin material of component A and / or B by 50% by mass or less (but not including 0% by mass). Characteristic heat-shrinkable multilayer film. 10. The heat-shrinkable multilayer film according to claim 7, wherein the return material is mixed with the virgin material of the component A and / or the component B by 50% by mass or less (but not including 0% by mass). Heat shrinkable multilayer film. 11. The virgin material of component A and / or B is mixed with 50% by mass or less (but not 0% by mass) of the return material of the heat-shrinkable multilayer film according to claim 8. Heat shrinkable multilayer film.