JP2003001766A - Heat-shrinkable multilayered film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable multilayered film excellent in the ballance of physical properties such as transparency, rigidity, impact strength or the like, suppressed in natural shrinkability and also excellent in low temperature shrinkability even if the film is obtained from a virgin material or the virgin material mixed with a return material. SOLUTION: The heat-shrinkable multilayered film is formed from at least one layer comprising a resin component containing at least two kinds of specific block copolymers each consisting of styrene and conjugated diene and at least other layer comprising a resin component based on at least one kind of a polymer selected from a block copolymer consisting of a styrenic monomer and conjugated diene, a styrenic polymer and a copolymer consisting of a styrenic monomer and (meth)acrylic ester and/or (meth)acrylic acid.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a film obtained from a virgin material or a film obtained by mixing a virgin material with a return material, which is excellent in physical property balance such as transparency, rigidity and impact strength and has a natural shrinkage property. The present invention relates to a heat-shrinkable multilayer film which is suppressed and has excellent low-temperature shrinkability.

[0002]

2. Description of the Related Art Conventionally, heat-shrinkable films used for shrink-wrapping and shrink-wrapping of containers have good heat-shrinkability and a good finish after shrinkage, and also have a problem of harmful substances such as polyvinyl chloride when discarded. A styrene-butadiene-based block copolymer film is used because it does not exist. However, this film has problems that it is soft and stiff, and has a large natural shrinkage, and various multilayer films have been proposed to improve these drawbacks (JP-A-9-11438).
No. 0, JP-A No. 11-77916). On the other hand, the actual film formation is usually carried out by mixing the end of the obtained film or an unnecessary film formed until a good product is obtained with a virgin material as a return material. However,
The above various multilayer films have a problem that they cannot be used as a film because they become cloudy when the return material is mixed with a virgin material, and the physical property balance such as impact resistance, rigidity, and heat shrinkage property becomes poor. It was

[0003]

SUMMARY OF THE INVENTION In view of the above situation, the present invention is directed to the transparency of a film obtained from a virgin material,
It is an object of the present invention to provide a heat-shrinkable multi-layer film which has an excellent balance of physical properties such as rigidity and impact strength, suppresses natural shrinkage, and has excellent low-temperature shrinkability. Furthermore, even the film obtained by mixing the return material into the virgin material is transparent,
It is an object of the present invention to provide a heat-shrinkable multi-layer film which has an excellent balance of physical properties such as rigidity and impact strength, suppresses natural shrinkage, and has excellent low-temperature shrinkability.

[0004]

Means for Solving the Problems As a result of intensive studies aimed at achieving such an object, the present inventors have found that at least two block copolymers containing styrene and a conjugated diene having a refractive index within a specific range are contained. The resin component to be used is at least one layer of a heat-shrinkable film, the glass transition temperatures of the two block copolymers are within a specific range, and the glass transition temperature difference is within a specific range. And at least one selected from the group consisting of a block copolymer containing styrene and a conjugated diene, a styrene polymer, and a copolymer containing a styrene monomer and (meth) acrylic acid ester and / or (meth) acrylic acid. By forming at least one layer mainly composed of a polymer and having a refractive index in a specific range as the other layer, the transparency and rigidity of the film obtained from the virgin material, A good balance of physical properties 撃強 degree such as natural shrinkage is suppressed, and excellent in low temperature shrinkability,
Further, it has been found that a multilayer film having a good balance of physical properties such as transparency, rigidity and impact strength even in a film containing a return material, suppressing natural shrinkage, and having excellent low-temperature shrinkability can be obtained. It came to completion.

That is, the present invention is a heat-shrinkable multi-layer film having at least one layer formed of the following resin component A and at least one layer formed of the following resin component B. Is. Resin component A: (i) a block copolymer having a random copolymer block portion composed of a styrene monomer and a conjugated diene, and (ii) a glass transition temperature of 60 to 100 ° C.
And (iii) a block copolymer (I) composed of a styrene-based monomer and a conjugated diene having a refractive index in the range of 1.565 to 1.583 at a temperature of 23 ° C., (i)
v) A block copolymer having a random copolymer block portion composed of a styrene monomer and a conjugated diene,
(V) The glass transition temperature is 3 to 10 ° C. higher than the glass transition temperature of the block copolymer (I), and (vi) the temperature is 23 ° C.
Containing a styrene-based monomer having a refractive index in the range of 1.565 to 1.583 and a block copolymer (II) composed of a conjugated diene, the block copolymer (I) and the block copolymer ( A resin component in which the ratio of II) is block copolymer (I) / block copolymer (II) = 10/90 to 90/10 (mass ratio). Resin component B: Block copolymer (III) consisting of styrene monomer and conjugated diene, styrene polymer (IV), and styrene monomer and (meth) acrylic acid ester and / or (meth) acrylic Mainly contains at least one polymer selected from copolymers (V) consisting of acids, and has a refractive index of 1.565 to 1.583 at a temperature of 23 ° C.
Is a resin component.

The present invention will be described in detail below. The resin component A of the present invention contains the block copolymer (I) and the block copolymer (II). The block copolymer (I) of the present invention is (i) a block copolymer having a random copolymer block portion composed of a styrene monomer and a conjugated diene, and (ii) having a glass transition temperature of 60 to It is in the range of 100 ° C., and (iii) the refractive index at a temperature of 23 ° C. is 1.
It is in the range of 565 to 1.583. And, the weight average molecular weight thereof is preferably 150,000 to 250,000. The block copolymer (I) is obtained by polymerizing a styrene-based monomer and a conjugated diene in an organic solvent using an organic lithium compound as an initiator under known conditions. As the organic solvent, butane, pentane, hexane, isopentane, heptane, octane, aliphatic hydrocarbons such as isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, alicyclic hydrocarbon such as ethylcyclohexane or benzene, toluene, Known organic solvents such as 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, and se.
c-Butyl lithium, t-butyl lithium, etc. can be used.

Examples of the styrene type monomer used include styrene, α-methylstyrene, p-methylstyrene and p-methylstyrene.
Although examples thereof include -t-butylstyrene, styrene is preferable. These styrenic monomers are
They may be used alone or in combination of two or more. Moreover, as the conjugated diene used, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene),
2,3-Dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like can be mentioned, but particularly common ones are 1,3-butadiene and isoprene.

The structure of each block portion other than the random copolymer block portion composed of the styrene-based monomer and the conjugated diene constituting the block copolymer (I) is a polymer block mainly composed of the styrene-based monomer. Or a polymer block mainly composed of a conjugated diene, or a tapered block composed of a styrene-based monomer and a conjugated diene.
In order to form a random copolymer block portion composed of a styrene-based monomer and a conjugated diene, a known randomizing agent may be used, both may be continuously fed to a polymerization vessel, or they may be alternately added in small amounts. . The bond structure of each block part constituting the block copolymer (I) is preferably a polymer block made of a styrene-based monomer (hereinafter abbreviated as PS block) -a polymer block made of a conjugated diene (hereinafter PBd block). A random copolymer block (hereinafter abbreviated as SB block) composed of a styrene-based monomer and a conjugated diene-PS block, PS block-SB block-PS block, and the like. Further, the structure of the block copolymer (I) used is not particularly limited, and a linear diblock copolymer, a triblock copolymer, or a multiblock copolymer having 4 or more blocks is used as the structure. Or a star-shaped copolymer in which one end of these block copolymers is bonded. Further, a known coupling agent can be used for increasing the molecular weight of the linear copolymer or forming it into a star shape.

The mass ratio of the styrene monomer to the conjugated diene in the block copolymer (I) is not particularly limited, but is preferably 95/5 to 60/40. If the styrene-based monomer exceeds 95% by mass, the heat shrinkability is poor, and if it is less than 60%, the rigidity is poor. If the glass transition temperature of the block copolymer (I) is not in the range of 60 to 100 ° C, the natural shrinkability of the resulting heat-shrinkable multilayer film is not suppressed, and the low temperature shrinkability is deteriorated, which is not preferable.

Further, the block copolymer (I) used in the present invention has a weight average molecular weight of 150,000 to 250.
It is preferably in the range of 000. When the weight average molecular weight is in the range of 150,000 to 250,000, the moldability of the heat-shrinkable multilayer film is good, and the natural shrinkability of the heat-shrinkable multilayer film is well suppressed, and the low-temperature shrinkability is improved. Will be even better. Further, the transparency when the return material is mixed is further improved.

The block copolymer (I) used in the present invention has a refractive index of 1.565 at a temperature of 23 ° C.
It is necessary to be in the range of ˜1.583. Temperature 23
If the refractive index at ° C is out of the range of 1.565 to 1.583, the transparency when the return material is mixed is poor and it cannot be put to practical use.

The block copolymer (II) of the present invention comprises (i
v) A block copolymer having a random copolymer block portion composed of a styrene monomer and a conjugated diene,
(V) The glass transition temperature is 3 to 10 ° C. higher than the glass transition temperature of the block copolymer (I), and (vi) the temperature is 23 ° C.
Has a refractive index of 1.565 to 1.583. And, preferably the weight average molecular weight is 5000
It is 0-150,000. The block copolymer (II) is
It can be obtained by polymerizing a styrene monomer and a conjugated diene in the same manner as the block copolymer (I). The styrene monomer and the conjugated diene used are the same as in the case of the block copolymer (I).

The structure of each block portion other than the random copolymer block portion comprising the styrene-based monomer and the conjugated diene constituting the block copolymer (II) is the same as that of the block copolymer (I). Any of a polymer block mainly composed of a styrene-based monomer, a polymer block mainly composed of a conjugated diene, or a tapered block composed of a styrene-based monomer and a conjugated diene may be used. The bonding structure of each block part constituting the block copolymer (II) is preferably PS block-PBd block-SB block-PS block, PS block-SB block-PS.
Examples include blocks. In addition, the structure of the block copolymer (II) used is not particularly limited, and a linear diblock copolymer, a triblock copolymer, or a multiblock copolymer having 4 or more blocks is used as the structure. Or a star-shaped copolymer in which one end of these block copolymers is bonded. Known coupling agents can be used to increase the molecular weight of the linear copolymer or to make it into a star shape.

The mass ratio of the styrene monomer to the conjugated diene in the block copolymer (II) is not particularly limited, but is preferably 95/5 to 60/40. If the styrene-based monomer exceeds 95% by mass, the heat shrinkability is poor, and if it is less than 60%, the rigidity is poor. Further, if the glass transition temperature of the block copolymer (II) is not higher than the glass transition temperature of the block copolymer (I) by 3 to 10 ° C, the natural shrinkability of the heat-shrinkable multilayer film obtained is not suppressed, Further, the low temperature shrinkability is also deteriorated, which is not preferable. To make the glass transition temperature of the block copolymer (II) higher than the glass transition temperature of the block copolymer (I) by 3 to 10 ° C., for example, a styrene-based monomer in the block copolymer (II) is used. The ratio of the styrene-based monomer at the time of polymerizing the random copolymer block part consisting of the styrene-based monomer and the conjugated diene, the random copolymer block part consisting of the styrene-based monomer and the conjugated diene in the block copolymer (I) It may be controlled so as to be higher than the ratio of the styrene-based monomer structure. Furthermore, regarding the heat-shrinkable multilayer film obtained in the present invention, in order to achieve both the effect of suppressing the natural shrinkability and the excellent low-temperature shrinkability, the glass transition temperature of the block copolymer (II) is It is essential that the temperature is higher than the glass transition temperature of (I) by 3 to 10 ° C. Preferably, the glass transition temperature is the block copolymer (I)
3 to 7 ° C higher than the glass transition temperature of.
The difference between the glass transition temperature of the block copolymer (II) and the glass transition temperature of the block copolymer (I) is less than 3 ° C. or 1
If the temperature exceeds 0 ° C, not only the effect of suppressing the natural shrinkability of the heat-shrinkable multilayer film and the excellent low-temperature shrinkability cannot be achieved, but also the physical properties such as transparency, impact strength, and rigidity are poor. Is not preferable.

The block copolymer (I used in the present invention
The weight average molecular weight of I) is more preferably in the range of 50,000 to 150,000. Weight average molecular weight is 500
When it is in the range of 00-150,000, the processability into a heat-shrinkable multilayer film becomes good, and further, the natural shrinkability of the heat-shrinkable multilayer film is well suppressed, and the low-temperature shrinkability becomes further excellent. . Further, the transparency when the return material is mixed is further improved. The glass transition temperature of the block copolymers (I) and (II) used in the present invention is not particularly limited in the measuring method, but it is measured by a known method such as DSC or dynamic viscoelasticity, preferably DSC. Is used. The weight average molecular weights of the block copolymers (I) and (II) are polystyrene conversion values by gel permeation chromatography (GPC).

The block copolymer (II) used in the present invention has a refractive index of 1.565 at a temperature of 23 ° C.
It is necessary to be in the range of ˜1.583. 1.56
If it is less than 5 or more than 1.583, the transparency when the return material is mixed is poor and it cannot be put to practical use. Further, the block copolymer (I) and the block copolymer (I
The ratio of I) is block copolymer (I) / block copolymer (II) = 10/90 to 90/10 (weight ratio), more preferably block copolymer (I) / block copolymer (I). II) = 30/70 to 70/30 (weight ratio).
When the ratio of the block copolymer (I) and the block copolymer (II) is within the above range, the effect of suppressing the natural shrinkability of the heat-shrinkable film and the excellent low-temperature shrinkability are more easily compatible with each other, preferable.

Further, in the resin component A of the present invention, in addition to the block copolymer (I) and the block copolymer (II),
If necessary, a styrene-based copolymer can be contained. As the styrene-based copolymer, the same styrene-based monomer as described in the above block copolymers (I) and (II) is used, and a homopolymer of these styrene-based monomers or a styrene-based monomer thereof is used. A copolymer of a monomer and a copolymerizable monomer, and further impact-resistant polystyrene (HIP
S), and block copolymers other than the block copolymer (I) and the block copolymer (II). As a copolymer of a styrene-based monomer and a monomer copolymerizable therewith, a styrene-methyl methacrylate copolymer,
Styrene-based monomer- (meth) acrylic acid ester copolymers such as styrene-n-butyl acrylate copolymer, styrene-methyl methacrylate-n-butyl acrylate copolymer, polybutadiene rubber, styrene-
Rubber-modified styrene-based monomer obtained by copolymerizing styrene-based monomer and (meth) acrylic acid ester in the presence of rubber such as butadiene random copolymer rubber and styrene-butadiene block copolymer rubber- (meth) Examples thereof include acrylic acid ester copolymers and rubber-like elastic materials such as MBS resin and MBAS resin.

For the MBS resin and the MBAS resin, first, a polybutadiene or a copolymer rubber latex containing styrene as a main component with styrene 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 styrene, methylmethacrylate and / or alkyl acrylate in this rubber latex, and MBAS resin is styrene, methylmethacrylate,
It is obtained by adding an alkyl acrylate and / or acrylonitrile and carrying out graft polymerization. MB
Examples of the alkyl acrylate used for the AS resin include the same as those described in the above (a) styrene-based monomer- (meth) acrylic acid ester copolymer.

Among these, as the styrene-based copolymer,
Preferably, a styrene monomer homopolymer, high impact polystyrene (HIPS), styrene-n-butyl acrylate copolymer, styrene-methyl methacrylate-
Examples thereof include n-butyl acrylate copolymer, styrene-butadiene block copolymer other than the block copolymer (I) and block copolymer (II).

The method of mixing the block copolymer (I) and the block copolymer (II) and, if necessary, the styrene-based copolymer for obtaining the resin component A is not particularly limited, but for example, a Henschel mixer Dry blending may be performed with a ribbon blender, a V blender, or the like, and the mixture may be melted with an extruder and pelletized.

Next, the styrene-based monomer-conjugated diene block copolymer (III) used as the resin component B of the present invention, the styrene-based polymer (IV), and the styrene-based monomer and (meth) acrylic. The copolymer (V) comprising an acid ester and / or (meth) acrylic acid will be described.

The styrenic monomer-conjugated diene block copolymer (III) of the present invention contains the styrenic monomer and the conjugated diene as described in the block copolymers (I) and (II) above. It can be obtained by polymerization using the organic solvent and the initiator. Examples of the styrene-based monomer used include the same as those described in the block copolymers (I) and (II). Further, as the conjugated diene used, the same ones as described in the above block copolymers (I) and (II) can be mentioned. The block copolymer used is preferably a block copolymer composed of styrene and butadiene in which the mass ratio of the styrene-based monomer and the conjugated diene is 90/10 to 60/40.

Next, as the styrene-based polymer (IV) used in the present invention, the same styrene-based monomer as described in the above block copolymers (I) and (II) is used,
Examples thereof include homopolymers of these styrene-based monomers, copolymers of styrene-based monomers and monomers copolymerizable therewith, and high impact polystyrene (HIPS).
As a copolymer of a styrene-based monomer and a monomer copolymerizable therewith, obtained by using acrylonitrile, maleic acid, itaconic acid, maleic anhydride, phenylmaleimide, etc. as the copolymerizable monomer. And the like. Specific examples thereof include a styrene-maleic anhydride copolymer, a styrene-maleic acid copolymer, a styrene-itaconic acid copolymer, a styrene-phenylmaleimide copolymer, a styrene-acrylonitrile copolymer and the like.

The copolymer (V) composed of the styrene-based monomer and the (meth) acrylic acid ester and / or (meth) acrylic acid used in the present invention is a styrene-based monomer and a (meth) acrylic resin. Obtained by polymerizing acid ester and / or (meth) acrylic acid. Examples of the styrene-based monomer include the same styrene-based monomer as described in the block copolymers (I) and (II). On the other hand, examples of the (meth) acrylic acid ester monomer include methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, and the like. Is methyl methacrylate and / or n
-Butyl acrylate. These (meth) acrylic acid ester monomers may be used alone or in combination of two or more kinds. A combination of methyl methacrylate and n-butyl acrylate is a suitable example. Examples of (meth) acrylic acid include acrylic acid and methacrylic acid. Further, if necessary, other monomers may be used within the range not impairing the object of the present invention. For example, maleic acid, itaconic acid, maleic anhydride or the like is used as the copolymerizable monomer.

In the present invention, the styrene-based monomer-conjugated diene block copolymer (III) and the styrene-based polymer (I
V), a copolymer (V) comprising a styrene monomer and a (meth) acrylic acid ester and / or (meth) acrylic acid
May form a layer of a multilayer film independently, or may form a layer of a multilayer film mainly with a mixture of two or more kinds. When mixing, the same method as in the case of the resin component A can be used. Preferably,
Styrene-based monomer-conjugated diene block copolymer (II
A mixture of I) and a styrene polymer (IV) is used as a resin component B to form one layer of a multilayer film, or a styrene monomer-conjugated diene block copolymer (II
I) is preferably used alone as the resin component B. Particularly preferably, a mixture of HIPS and a block copolymer of styrene and butadiene is used as the resin component B,
Alternatively, a block copolymer composed of styrene and butadiene may be used alone as the resin component B.

Further, the refractive index of the resin component B at a temperature of 23 ° C. needs to be in the range of 1.565 to 1.583. If it is less than 1.565 or more than 1.583, the transparency when the return material is mixed is poor and it cannot be put to practical use. When the resin component B is composed of a mixture of a plurality of polymers (assumed to be n kinds), the temperature of the resin component B is 23
The refractive index (denoted as Y) at ° C in the present invention is
Polymer component i constituting the resin component B (i-th component (i =
Y = (a1 × w1) + (when the refractive index at a temperature of 23 ° C.) and the weight fraction of the polymer component i in the resin component B are wi. a2 × w2) + ... + (ai
Xwi) + ... + (an × wn).

In addition, each (co) polymer used in the present invention contains, if necessary, an antioxidant, a lubricant, a weathering agent, a plasticizer, a tackifier, a colorant, an antistatic agent, a mineral oil, and a flame retardant. Additives such as agents and fillers may be added within a range that does not impair the effects of the present invention. The method of blending the additive is not particularly limited, but for example, a Henschel mixer,
It may be dry blended with a ribbon blender, a V blender, or the like, and may be melted and pelletized with an extruder. Alternatively, it may be added during the production of each polymer, before the initiation of polymerization, during the polymerization reaction, or after the treatment of the polymer.

Examples of the plasticizer used in the present invention include butyl oleate, glycerin monooleic acid and other aliphatic-basic acid esters, dibutyl adipate, diisobutyl adipate, di-n-hexyl adipate, di-adipate. Aliphatic-dibasic acid ester 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, 0 to 3 parts by mass is preferably added to 100 parts by mass of the resin component A or the resin component B.

The heat-shrinkable multilayer film of the present invention is
The film is a two-layer film, a three-layer film, a four-layer film, a five-layer film, or a multilayer film of more than three layers, preferably three or more layers, and particularly preferably three.
It is a film of layers. In the case of a three-layer film, the front and back layers may be formed of the resin component A and the intermediate layer may be formed of the resin component B, or the front and back layers may be formed of the resin component B and the intermediate layer may be formed of the resin component A. Good. Above all, the resin component B is used for the front and back layers.
It is preferable that the intermediate layer is formed with the resin component A.

In the heat-shrinkable multilayer film of the present invention, the above resin components for the front and back layers and the intermediate layer are melted by an extruder,
It can be obtained by uniaxially, biaxially or polyaxially stretching it after forming multiple layers in a die or a feed block. Known dies such as a T die and a ring die can be used. As an example of uniaxial stretching, a method of stretching the extruded sheet in a direction orthogonal to the extrusion direction with a tenter,
Examples include a method of stretching the extruded tubular film in the circumferential direction. As an example 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 present invention, the stretching temperature is 60 to 120.
C is preferred. If the temperature is 60 ° C., the sheet or film will be broken during stretching, and if it exceeds 120 ° C., good shrinkage properties cannot be obtained, which is not preferable. The draw ratio is
Although not particularly limited, it 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 multilayer films are used as heat-shrinkable labels or packaging materials, the heat shrinkage rate 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 shrinking, which adversely affects the article to be coated, which is not preferable. The thickness of the multilayer film is preferably 10 to 300 μm.

The heat-shrinkable multilayer film obtained by mixing the return material of the heat-shrinkable multilayer film of the present invention with the virgin material of the component A and / or the component B has a natural shrinkability suppressed and is transparent. Excellent in heat resistance, low temperature heat shrinkage, rigidity and impact strength. The mixing ratio is not particularly limited, but preferably 50% by mass or less (however, 0% by mass is not included) is mixed with the virgin material of the component A and / or the component B from the viewpoint of transparency.

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

The heat-shrinkable multi-layer film of the present invention is particularly suitable for heat-shrinkable labels, heat-shrinkable cap seals and the like, but can also be suitably used for packaging films and the like.

[0035]

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

[0036]

Reference Example 1 (1) 245 kg of cyclohexane as a polymerization solvent and 4.1 kg of a styrene monomer were charged into a reaction vessel and kept at 30 ° C. Cyclohexane was used as the polymerization solvent in Reference Examples 2 to 9 below. (2) To this, 750 mL of a 10 wt% cyclohexane solution of n-butyllithium, which is a polymerization catalyst solution, was added to anionically polymerize the styrene monomer. A 10 wt% cyclohexane solution of n-butyllithium was used for all the polymerization catalyst solutions of Reference Examples 2 to 9 below. (3) After the styrene monomer was completely consumed, 7.1 kg of butadiene was added all at once while keeping the internal temperature of the reaction system at 40 ° C., and the reaction was continued. (4) After the butadiene gas was completely consumed, the total amount of the reaction system was kept at 75.2 kg while keeping the internal temperature of the reaction system at 80 ° C.
The above styrene monomer and 11.2 kg of butadiene in total were simultaneously added at a constant addition rate of 57.1 kg / h and 8.5 kg / h, respectively, and the state was maintained for 5 minutes after the addition was completed. (5) After the internal temperature was lowered to 50 ° C., 4.1 kg of styrene monomer was further added all at once to complete the polymerization. (6) Finally, all polymerization active terminals are deactivated with water to have a weight average molecular weight of 182,000, and a polymer having a polystyrene block portion and a polybutadiene block portion and a styrene and butadiene random structure portion is included. A polymerization liquid was obtained.

[0037]

[Reference Example 2] (1) 490 kg of a polymerization solvent and 8.4 kg of a styrene monomer were charged into a reaction vessel and kept at 30 ° C. (2) 1620 mL of the polymerization catalyst solution was added to this, and the styrene monomer was anionically polymerized. (3) After the styrene monomer was completely consumed, 22.1 kg of butadiene was added all at once while keeping the internal temperature of the reaction system at 50 ° C. to continue the reaction. (4) After the butadiene gas is completely consumed, while maintaining the internal temperature of the reaction system at 80 ° C., a total amount of styrene monomer of 157.5 kg and a total amount of butadiene of 13.7 kg are added.
Both of them were simultaneously added at a constant addition rate of 98.3 kg / h and 8.5 kg / h, and the state was kept for 5 minutes after the addition was completed. (5) Further, 8.4 kg of styrene monomer was added all at once to complete the polymerization. (6) Finally, all the polymerization active terminals are deactivated with water to have a weight average molecular weight of 146,000 and includes a polymer having a polystyrene block portion and a polybutadiene block portion, and a styrene and butadiene random structure portion. A polymerization liquid was obtained.

[0038]

Reference Example 3 (1) 490 kg of a polymerization solvent and 5.3 kg of a styrene monomer were charged into a reaction vessel and kept at 30 ° C. (2) 1100 mL of the polymerization catalyst solution was added to this, and the styrene monomer was anionically polymerized. (3) After the styrene monomer was completely consumed, 10.5 kg of butadiene was added all at once while keeping the internal temperature of the reaction system at 50 ° C., and the reaction was continued. (4) After the butadiene gas was completely consumed, while maintaining the internal temperature of the reaction system at 80 ° C., a total amount of 164.4 kg of styrene monomer and a total amount of 24.6 kg of butadiene were added.
Both of them were simultaneously added at a constant addition rate of 56.8 kg / h and 8.5 kg / h, respectively, and the state was maintained for 5 minutes after the addition was completed. (5) Further, 5.3 kg of styrene monomer was added all at once to complete the polymerization. (6) Finally, a polymer having a weight average molecular weight of 214,000 by deactivating all polymerization active terminals with water and having a polystyrene block part and a polybutadiene block part, and a random structure part of styrene and butadiene is included. A polymerization liquid was obtained.

[0039]

Reference Example 4 (1) 490 kg of a polymerization solvent and 84.0 kg of a styrene monomer were charged into a reaction vessel and kept at 30 ° C. (2) 1500 mL of the polymerization catalyst solution was added to this, and the styrene monomer was anionically polymerized. (3) After the styrene monomer was completely consumed, while maintaining the internal temperature of the reaction system at 50 ° C., 42 kg of butadiene was added all at once and the reaction was continued. (4) After the butadiene gas was completely consumed, 84.0 kg of styrene monomer was added while the internal temperature of the reaction system was kept at 50 ° C. to complete the polymerization. (5) Finally, all the polymerization active terminals were deactivated with water to obtain a polymerization solution having a weight average molecular weight of 140,000 and containing a polymer having a polystyrene block part and a polybutadiene block part.

[0040]

Reference Example 5 (1) 385 kg of a polymerization solvent and 74.3 kg of a styrene monomer were charged into a reaction vessel and kept at 30 ° C. (2) 1700 mL of the polymerization catalyst solution was added to this, and the styrene monomer was anionically polymerized. (3) After the styrene monomer was completely consumed, 16.5 kg of butadiene was added all at once while keeping the internal temperature of the reaction system at 45 ° C., and the reaction was continued. (4) After the butadiene gas was completely consumed, while maintaining the internal temperature of the reaction system at 60 ° C., 74.3 kg of styrene monomer was added to complete the polymerization. (5) Finally, all the polymerization active terminals were deactivated with water to obtain a polymerization liquid containing a polymer having a weight average molecular weight of 115,000 and having a polystyrene block portion and a polybutadiene block portion.

[0041]

Reference Example 6 (1) 385 kg of a polymerization solvent and 49.5 kg of a styrene monomer were charged into a reaction vessel and kept at 30 ° C. (2) 1700 mL of the polymerization catalyst solution was added to this, and the styrene monomer was anionically polymerized. (3) After the styrene monomer was completely consumed, 66.0 kg of butadiene was added all at once while keeping the internal temperature of the reaction system at 45 ° C., and the reaction was continued. (4) After the butadiene gas was completely consumed, 49.5 kg of a styrene monomer was added while maintaining the internal temperature of the reaction system at 60 ° C. to complete the polymerization. (5) Finally, all the polymerization active terminals were deactivated with water to obtain a polymerization solution having a weight average molecular weight of 105,000 and containing a polymer having a polystyrene block part and a polybutadiene block part.

[0042]

Reference Example 7 (1) 385 kg of a polymerization solvent and 66 kg of a styrene monomer were charged into a reaction vessel and kept at 30 ° C. (2) 900 mL of the polymerization catalyst solution was added to this, and the styrene monomer was anionically polymerized. (3) After the styrene monomer was completely consumed, 33 kg of butadiene was added all at once while keeping the internal temperature of the reaction system at 45 ° C., and the reaction was continued. (4) After the butadiene gas was completely consumed, 66 kg of styrene monomer was added to complete the polymerization while maintaining the internal temperature of the reaction system at 60 ° C. (5) Finally, all the polymerization active terminals were deactivated with water to obtain a polymerization liquid having a weight average molecular weight of 170,000 and containing a polymer having a polystyrene block portion and a polybutadiene block portion.

[0043]

Reference Example 8 (1) 385 kg of a polymerization solvent and 78.4 kg of a styrene monomer were charged into a reaction vessel and kept at 30 ° C. (2) 900 mL of the polymerization catalyst solution was added to this, and the styrene monomer was anionically polymerized. (3) After the styrene monomer was completely consumed, 8.2 kg of butadiene was added all at once while keeping the internal temperature of the reaction system at 45 ° C., and the reaction was continued. (4) After the butadiene gas was completely consumed, 78.4 kg of styrene monomer was added to complete the polymerization while maintaining the internal temperature of the reaction system at 60 ° C. (5) Finally, all the polymerization active terminals were deactivated with water to obtain a polymerization solution containing a polymer having a weight average molecular weight of 165,000 and having a polystyrene block portion and a polybutadiene block portion.

[0044]

[Reference Example 9] (1) 385 kg of a polymerization solvent and 53.6 kg of a styrene monomer were charged into a reaction vessel and kept at 30 ° C. (2) 900 mL of the polymerization catalyst solution was added to this, and the styrene monomer was anionically polymerized. (3) After the styrene monomer was completely consumed, 57.8 kg of butadiene was added all at once while keeping the internal temperature of the reaction system at 45 ° C., and the reaction was continued. (4) After the butadiene gas was completely consumed, 53.6 kg of styrene monomer was added while the internal temperature of the reaction system was kept at 60 ° C. to complete the polymerization. (5) Finally, all the polymerization active terminals were deactivated with water to obtain a polymerization solution containing a polymer having a weight average molecular weight of 175,000 and having a polystyrene block part and a polybutadiene block part.

Each of the polymers a1 to a9 of Reference Examples 1 to 9 in solution was prepared by preliminarily concentrating the polymerization solvent and then devolatilized by a vent type extruder to form pellets. 1 and 2 are shown. Each of the obtained polymers was subjected to the test described below.

[0046]

Reference Example 10 100 parts by weight of a solution containing 91.6% by weight of styrene monomer and 8.4% by weight of ethylbenzene, 1,1-bis (tert-butylperoxyl) 3,
A solution consisting of 0.025 parts by weight of 3,5-trimethylcyclohexane was continuously fed into the first polymerization machine, and a stirring polymerization reaction was carried out at a polymerization temperature of 130 ° C., and then the whole amount was continuously added to a plug flow type reactor. Charge and polymerize. After that, it was polymerized to a polymerization rate of 85%, the solution was supplied to a vent type extruder, the volatile components were removed at 230 ° C under reduced pressure, the molten strand was pulled out from the die, cooled with water, cut with a cutter and pelletized. Polymer b1 of The properties of the polymer are shown in Table 2 and subjected to the test described later.

[0047]

[Reference Example 11] Butadiene rubber (Diene 55 manufactured by Asahi Kasei
A) 100 parts by weight of a solution prepared by dissolving 5.5% by weight of styrene monomer in 86.1% by weight and 8.4% by weight of ethylbenzene and 1,1-bis (tert-butylperoxyl)
A solution consisting of 0.017 parts by weight of 3,3,5-trimethylcyclohexane was continuously fed to the first polymerization machine,
After carrying out a stirring polymerization reaction at a polymerization temperature of ° C, the whole amount was continuously charged into a plug flow type reactor to carry out polymerization. After that, it was polymerized to a polymerization rate of 85%, the solution was supplied to a vent type extruder, the volatile components were removed at 230 ° C under reduced pressure, the molten strand was pulled out from the die, cooled with water, cut with a cutter and pelletized. Polymer b2 of The properties of the polymer are shown in Table 2 and subjected to the test described later.

[0048]

Reference Example 12 86.1% by weight of styrene monomer and n-
Butyl acrylate 9.2% by weight and ethylbenzene 8.
100 parts by weight of a 4% by weight solution and 1,1-bis (t
tert-butylperoxyl) 3,3,5-trimethylcyclohexane (0.027 parts by weight) was continuously fed into the first polymerization machine, and the mixture was stirred and polymerized at a polymerization temperature of 130 ° C, followed by plug flow. The whole amount was continuously charged into the type reactor to carry out polymerization. After that, it was polymerized to a polymerization rate of 85%, the solution was supplied to a vent type extruder, the volatile components were removed at 230 ° C under reduced pressure, the molten strand was pulled out from the die, cooled with water, cut with a cutter and pelletized. Polymer b3 of The properties of the polymer are shown in Table 2 and subjected to the test described later.

The weight average molecular weight of the block copolymer was measured by the GPC method under the following conditions. Solvent (mobile phase): THF, deaerator: ERMA ER
C-3310, Pump: JASCO Corporation PU-980, Flow rate 1.0 ml / min, Autosampler: Tosoh AS-8
020, column oven: Hitachi L-5030,
Set temperature 40 ℃, Column configuration: TSKgurdco manufactured by Tosoh Corporation
lumn MP (× L) 6.0 mm ID × 4.0 cm 1 piece, and TSK-GEL MULTIPORE HXL-M manufactured by Tosoh Corporation
7.8 mm ID x 30.0 cm 2 pieces, total 3 pieces, detector: RI Hitachi L-3350, data processing: SIC480 data station.

The glass transition point of the block copolymer was measured using the DSC-200 and SSC-5000 series manufactured by Seiko Instruments Inc. under the following conditions. The temperature is raised from room temperature to the temperature of the melting point of polystyrene plus alpha, held at that temperature for about 10 minutes, and cooled to the glass transition temperature of polybutadiene minus alpha at a cooling rate of 20 to 25 ° C./min (n = 1. ), The temperature is again raised to the melting point of polystyrene plus the temperature of alpha, and the temperature is maintained for about 10 minutes and cooled to the glass transition temperature of polybutadiene minus the temperature of alpha at a cooling rate of 20 to 25 ° C./min (n = 2). ) The average value of the two measurement results was recorded.

The refractive index is the injection molded product (thickness 2) of each polymer.
mm) was measured at a temperature of 23 ° C. using a digital refractometer RX-2000 manufactured by Atago Co., Ltd. according to JIS K7105.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

Examples 1 to 5 and

[Comparative Examples 1 to 7] (a) Raw material polymer Block copolymer: Polymer a1 obtained in Reference Examples 1 to 9
.About.a9 block copolymers were used. Styrene-based polymer and copolymer composed of styrene-based monomer and (meth) acrylic acid ester and / or (meth) acrylic acid:
The polymers of polymers b1 to b3 obtained in Reference Examples 10 to 12 were used.

(B) Production of film Using the polymers shown in Tables 1 and 2, the amount of raw material polymer in each layer shown in Tables 3 to 5 was adjusted by the blending amount (parts by mass) and layer ratio (%). A shrinkable multilayer film was prepared. First, the polymers or polymer compositions corresponding to the respective layers were melted by separate extruders and 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 (this pellet is referred to as a return material), 30% by mass was mixed with the components constituting the intermediate layer, and a sheet was prepared by the same method as above. After that, using a biaxial stretching device manufactured by Toyo Seisakusho,
A stretched film was prepared by transversely uniaxially stretching it 5 times at a temperature of 90 ° C.

Tables 3 to 5 show the blending amount (parts by mass) of the raw material polymer for each layer and the layer ratio (%) together with the physical properties. In addition,
The refractive index of the front and back layers of Example 2 and Comparative Examples 1 to 5 and the intermediate layer of Example 5 is 1.573, the refractive index of the front and back layers of Example 3 is 1.577, and the refractive index of the front and back layers of Example 4 is Was 1.573. Further, in Comparative Examples 1 and 3, sheet formation was possible, but a stretched film was not obtained.

The physical properties of the film were determined by the following methods. (1) Haze: Measured using a Haze meter (NDH-1001DP type) manufactured by Nippon Denshoku Industries in accordance with ASTM D1003. (2) Thermal contraction rate: It was immersed in warm water of 80 ° C. for 30 seconds and calculated from the following formula. Thermal shrinkage (%) = {(L1-L2) / L1} × 100, where L1: length before dipping (stretching direction), L2: 80 ° C.
Length after shrinkage by dipping in warm water for 30 seconds (stretching direction) (3) Spontaneous shrinkage ratio: 100 mm in length from film, 10 in width
A sample was cut into a size of 0 mm and left in a constant temperature bath in an atmosphere of 30 ° C. for 30 days, and the main shrinkage direction was defined as a percentage (%) calculated from a value obtained by dividing the shrinkage length by the original dimension. (4) Tensile Modulus: According to JIS k6871, Tensilon Universal Testing Machine (RTC-12 manufactured by A & D Co., Ltd.
10A). (5) Film impact: Measured with a film impact tester manufactured by Tester Sangyo using a stretched film.

From the physical properties shown in Tables 3 to 5, the film of the present invention, whether it is a film obtained from a virgin material or a film obtained by mixing a virgin material with a return material, has transparency, rigidity, impact strength and the like. It can be seen that the material has an excellent balance of physical properties, suppresses spontaneous shrinkage, and also has good low-temperature heat shrinkability.

[0059]

[Table 3]

[0060]

[Table 4]

[0061]

[Table 5]

[0062]

According to the present invention, both the film obtained from a virgin material and the film obtained by mixing a return material into a virgin material are suppressed in natural shrinkability and have good heat shrinkability even at low temperatures. It is possible to provide a heat-shrinkable multi-layer film which has excellent physical properties such as transparency, rigidity and impact strength. The film can be used for packaging various articles or can be printed and used as a label.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shingo Hanazato             3-5-1 Asahimachi, Machida, Tokyo             Central Research Institute F term (reference) 4F100 AK12A AK12B AK25B AK28A                       AK28B AK73B AL02A AL02B                       AL05A BA02 BA15 GB15                       JA03 JA05A JA07A JN18A                       JN18B YY00A YY00B                 4J002 BC06W BC07W BH01W BN14W                       BP01W BP01X FD020 GF00                       GG02

Claims (8)

[Claims] 1. A heat-shrinkable multi-layer film comprising at least one layer formed of the following resin component A and at least one layer formed of the following resin component B. Resin component A: (i) a block copolymer having a random copolymer block portion composed of a styrene monomer and a conjugated diene, and (ii) a glass transition temperature of 60 to 100 ° C.
And (iii) a block copolymer (I) composed of a styrene-based monomer and a conjugated diene having a refractive index in the range of 1.565 to 1.583 at a temperature of 23 ° C., (i)
v) A block copolymer having a random copolymer block portion composed of a styrene monomer and a conjugated diene,
(V) The glass transition temperature is 3 to 10 ° C. higher than the glass transition temperature of the block copolymer (I), and (vi) the temperature is 23 ° C.
Containing a styrene-based monomer having a refractive index in the range of 1.565 to 1.583 and a block copolymer (II) composed of a conjugated diene, the block copolymer (I) and the block copolymer ( A resin component in which the ratio of II) is block copolymer (I) / block copolymer (II) = 10/90 to 90/10 (mass ratio). Resin component B: Block copolymer (III) consisting of styrene monomer and conjugated diene, styrene polymer (IV), and styrene monomer and (meth) acrylic acid ester and / or (meth) acrylic Mainly contains at least one polymer selected from copolymers (V) consisting of acids, and has a refractive index of 1.565 to 1.583 at a temperature of 23 ° C.
Is a resin component. 2. The mass ratio of the styrene monomer to the conjugated diene in the block copolymer (I) and the block copolymer (II) of the resin component A is 95/5 to 60/40, respectively. The heat-shrinkable multilayer film according to claim 1. 3. The resin component A contains a block copolymer (I), a block copolymer (II), and a styrene polymer other than (I) or (II). The heat-shrinkable multilayer film according to any one of 1 or 2. 4. The weight average molecular weight of the block copolymer (I) of the resin component A is 150,000 to 250,000, and the weight average molecular weight of the block copolymer (II) is 50,000 to 1
It is 50,000, The heat-shrinkable multilayer film according to any one of claims 1 to 3. 5. The resin component B is a block copolymer (III) composed of styrene and butadiene having a mass ratio of styrene-based monomer and conjugated diene of 90/10 to 60/40. Item 5. A heat-shrinkable multilayer film according to any one of items 1 to 4. 6. The front and back layers are formed of the resin component A according to any one of claims 1 to 4, and the intermediate layer is formed of the resin component B according to any one of claims 1 or 5. Characteristic heat shrinkable multilayer film. 7. The front and back layers are formed of the resin component B according to claim 1 or 5, and the intermediate layer is formed of the resin component A according to any one of claims 1 to 4. Characteristic heat shrinkable multilayer film. 8. The virgin material of the resin component A and / or the resin component B containing the return material of the heat-shrinkable multilayer film according to claim 1 in an amount of 50% by mass or less (however, 0% by mass is included). No) A heat-shrinkable multilayer film characterized by being mixed.