JP2001354827A - Block copolymer composition and heat-shrinkable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable film suitable for packaging for a beverage container, cap sealing and the like, excellent in low temperature shrinkability, spontaneous shrinkability, rigidity and comprising a block copolymer composition capable of being formed into a thin wall and excellent in dimensional stability and the low temperature shrinkability. SOLUTION: Disclosed are a composition comprising (I) a block copolymer having a specific structure in which weight ratio between a vinyl aromatic hydrocarbon and a conjugated diene is 65/35 to 80/20 and (II) a block copolymer having a specific structure in which weight ratio between a vinyl aromatic hydrocarbon and a conjugated diene is more than 80/20 and is 95/5 or less, and a heat-shrinkable film comprising the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable film excellent in natural shrinkage, low-temperature shrinkage, rigidity, transparency and impact resistance.

[0002]

2. Description of the Related Art A block copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene having a relatively high content of a vinyl aromatic hydrocarbon is used for injection molding by utilizing properties such as transparency and impact resistance. It is used for extrusion molding of sheets and films. In particular, heat-shrinkable films using a block copolymer resin consisting of a vinyl aromatic hydrocarbon and a conjugated diene are used to reduce the residual monomer and plasticizer of the conventionally used vinyl chloride resin and the generation of hydrogen chloride during incineration. Since there is no problem, it is used for food packaging, cap seals, labels, and the like. Properties required for heat-shrinkable films include natural shrinkage, low-temperature shrinkage, transparency, mechanical strength, and suitability for packaging machines. Until now, various studies have been made to improve these properties and obtain a good balance of physical properties.

For example, Japanese Patent Application Laid-Open No. 57-34921 discloses a method for producing a heat-shrinkable film by preheating a styrene-butadiene block copolymer within a melting point range and then stretching the same in order to improve heat shrinkability. Japanese Unexamined Patent Publication No. 58-108112 discloses a styrene-based resin shrink film in which a biaxially stretched film of a styrene-butadiene block copolymer has a specific orientation relaxation stress in order to improve shrinkage characteristics. No. 221348 discloses mechanical properties, optical properties,
In order to obtain a composition having excellent stretching characteristics and crack resistance, the content of the aliphatic unsaturated carboxylic acid derivative is 5 to 80.
Composition of a vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative copolymer having a Vicat softening point not exceeding 90 ° C. by weight and a copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene block But Japanese Patent Application Laid-Open No. 60-224520.
In order to obtain a heat-shrinkable film excellent in shrinkage properties and environmental destruction resistance, a heat-shrinkable film having a specific Tg in a segment of a block copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene, JP-A-60-224522
In order to obtain a heat-shrinkable film excellent in shrinkage properties and environmental destruction resistance, a heat-shrinkable film comprising a composition of a block copolymer composed of a vinyl aromatic hydrocarbon having a specific structure and a conjugated diene, JP-A-61-25819 discloses a method for obtaining a shrinkable film having excellent low-temperature shrinkage, optical properties, crack resistance, dimensional stability, etc., in which the vinyl aromatic hydrocarbon content is 95 to 20% by weight and the vicat softening is carried out. 9 points
A low-temperature shrinkable film obtained by stretching a composition of a vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative copolymer not exceeding 0 ° C. and a copolymer of a vinyl aromatic hydrocarbon and a conjugated diene block is formed. Japanese Patent Application Laid-Open No. 4-52129 discloses a random copolymer of a specific Tg containing a styrene-based hydrocarbon and a block copolymer comprising a styrene-based hydrocarbon and a conjugated diene hydrocarbon in order to improve the natural shrinkage at room temperature. In order to obtain a transparent heat-shrinkable film having excellent aging stability and impact resistance, a heat-shrinkable polystyrene-based film made of the unified composition has a Vicat softening point of 105 ° C. Not more than vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative copolymer and copolymer comprising vinyl aromatic hydrocarbon and conjugated diene block In the composition, the heat shrinkable rigid film characterized in specific heat shrinkage force, JP 6-220278
In order to obtain a composition in which transparency, rigidity and low-temperature surface impact property are balanced, a copolymer comprising a vinyl aromatic hydrocarbon having a specific structure and a molecular weight distribution and a conjugated diene block and a vinyl aromatic A composition with a hydrogen- (meth) acrylate copolymer resin is disclosed in JP-A-7-216.
No. 187 discloses a block copolymer having a vinyl aromatic hydrocarbon block having a specific structure and a copolymer block of a vinyl aromatic hydrocarbon and a conjugated diene in order to obtain a resin composition having excellent transparency and impact resistance. A transparent high-strength resin composition containing a copolymer of a vinyl aromatic hydrocarbon and a (meth) acrylate is described. However, these block copolymers composed of a vinyl aromatic hydrocarbon and a conjugated diene or a composition of the block copolymer and a copolymer of a vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative are naturally shrinkable. The balance between low temperature shrinkage, stiffness, transparency and impact resistance is not sufficient, and these documents do not disclose how to improve them and still point to problems in the market.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a heat-shrinkable film for natural shrinkage, low-temperature shrinkage, rigidity,
An object of the present invention is to provide a block copolymer composition having an excellent balance of physical properties such as transparency and impact resistance.

[0005]

Means for Solving the Problems The present invention relates to (I) comprising at least one plastic polymer segment A and at least one elastomer polymer segment B, wherein a vinyl aromatic hydrocarbon and a conjugated diene are A block copolymer having a weight ratio of 65/35 to 80/20, wherein the weight ratio of the vinyl aromatic hydrocarbon to the conjugated diene is 85/15 to 98/2;
The segment B is composed of a copolymer in which the weight ratio of the vinyl aromatic hydrocarbon to the conjugated diene is 20/80 to 60/40, and the block ratio of the vinyl aromatic hydrocarbon incorporated in the block copolymer is 20 to 55% by weight, a block copolymer having a Vicat softening temperature in a range of 50 to 75 ° C;

(II) having at least one plastic polymer segment A and at least one elastomeric polymer segment B, wherein the weight ratio of vinyl aromatic hydrocarbon to conjugated diene exceeds 80/20; A block copolymer having a dynamic viscoelasticity function tan δ of at least one peak at 90 to 125 ° C., wherein the block copolymer has a peak of 95/5 or less. A) a block copolymer composition having a weight ratio of 10/90 to 90/10;

The block copolymer (I) and (I)
II) A styrene-n-butyl acrylate copolymer having a styrene content of 75 to 90% by weight and an n-butyl acrylate content of 25 to 10% by weight, and a weight ratio of (I) to (III) Is a block copolymer composition having a ratio of 10/90 to 90/10,

The above (I) block copolymer, the above (II) block copolymer, and the above (III) styrene-n-butyl acrylate copolymer,
(I) is 10 to 80% by weight, and (II) is 10 to 80%, with the total amount of (II) and (III) being 100% by weight.
% By weight, (III) in the range of 5 to 50% by weight of the block copolymer composition,

The above block copolymer composition is stretched, and the heat shrinkage at 65 ° C. in the stretching direction is 1
0-60%, tensile modulus in the stretching direction is 7000
It relates to a heat-shrinkable film having a weight of 30,000 Kg / cm ² .

Hereinafter, the present invention will be described in detail. The plastic polymer segment A of the block copolymer (I) used in the present invention has at least one, preferably two or more, plastic polymer segments A and at least one elastomeric polymer segment B. The weight ratio of vinyl aromatic hydrocarbon to conjugated diene is 65/35 to 8
0/20, preferably 67/33 to 77/23.
If the ratio of the vinyl aromatic hydrocarbon to the conjugated diene is less than 65/35, the rigidity is poor, and if it is more than 80/20, the impact resistance is undesirably reduced. The plastic polymer segment A of the block copolymer (I) is composed of a copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene, and the ratio of the vinyl aromatic hydrocarbon to the conjugated diene is 85/1.
It is 5 to 98/2, preferably 88/12 to 95/5. When the weight ratio of the vinyl aromatic hydrocarbon to the conjugated diene of the plastic polymer segment A is less than 85/15, the rigidity and hot water fusibility of the molded article decrease, and when it exceeds 98/2, the low-temperature shrinkability is poor, so that it is preferable. Absent.

The elastomeric polymer segment B of the block copolymer (I) is composed of a copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene, and the weight ratio of the vinyl aromatic hydrocarbon to the conjugated diene is 20/80. ６０60/40, preferably 30/70 to 55/45. If the weight ratio of the vinyl aromatic hydrocarbon to the conjugated diene in the elastomeric polymer segment B is less than 20/80, the natural shrinkage is inferior, and if it exceeds 60/40, the impact resistance decreases, which is not preferable. The block ratio of the vinyl aromatic hydrocarbon incorporated in the block copolymer (I) is 20 to 55% by weight, preferably 25 to 50% by weight. If the block ratio is less than 10% by weight, the rigidity of the molded article is reduced, and if it exceeds 60% by weight, the low-temperature shrinkage is inferior.

The Vicat softening temperature of the block copolymer (I) is in the range of 50 to 75 ° C, preferably 55 to 70 ° C. If the Vicat softening temperature is less than 50 ° C., the hot water fusibility is poor, and if it exceeds 75 ° C., the low temperature shrinkage is poor, which is not preferable. The block ratio of the vinyl aromatic hydrocarbon incorporated in the block copolymer (I) is measured by oxidative decomposition of the block copolymer with tertiary butyl hydroperoxide using osmium tetroxide as a catalyst. Method (IM KOLTHOFF, eta
l. , J. et al. Polym. Sci. 1,429 (194
Using the vinyl aromatic hydrocarbon polymer block component obtained by the method described in 6)) (however, a vinyl aromatic hydrocarbon polymer component having an average degree of polymerization of about 30 or less is excluded), the following formula is used. Means the value obtained from Block rate (% by weight)
= (Weight of vinyl aromatic hydrocarbon polymer block in block copolymer / weight of total vinyl aromatic hydrocarbon in block copolymer) × 100

The block copolymer (I) used in the present invention
The plastic polymer segment A of I) has at least one, preferably two or more, plastic polymer segments A and at least one elastomeric polymer segment B, and comprises a vinyl aromatic hydrocarbon and a conjugated diene. Is more than 80/20 and not more than 95/5, preferably 83/17 to 92/7. When the ratio of the vinyl aromatic hydrocarbon to the conjugated diene is 80/20 or less, the rigidity is poor, and when it exceeds 95/5, the impact resistance is undesirably reduced.

The peak temperature of the dynamic viscoelastic function tan δ of the block copolymer (II) is in the range of 90 to 125 ° C., preferably 95 to 120 ° C.
An nδ peak is required. The peak temperature of tan δ is 90
If the temperature is lower than 0 ° C, the hot-water-fusibility decreases, and if the temperature exceeds 125 ° C, natural shrinkage deteriorates, which is not preferable.

The dynamic viscoelastic function tan δ is DMA983
(Manufactured by DUPONT Co., Ltd.), and the peak temperature is the temperature at which the first derivative of the change in the value of tan δ with respect to the temperature becomes zero. The peak temperature of tan δ is adjusted by the weight ratio of the vinyl aromatic hydrocarbon and the conjugated diene of the plastic polymer segment A and the elastomer polymer segment B, the molecular weight of the block copolymer, and the like.

The block copolymer (I) used in the present invention
And the vinyl aromatic hydrocarbons of the plastic polymer segment A and the elastomeric polymer segment B of (II) may be distributed uniformly in the polymer block or may be distributed in a tapered (gradual decreasing) shape. . Further, in the copolymer portion, a plurality of portions where the vinyl aromatic hydrocarbon is uniformly distributed and / or a plurality of portions where the vinyl aromatic hydrocarbon is distributed in a tapered shape may coexist. The copolymer portion can be controlled by changing the weight, weight ratio, polymerization reactivity ratio and the like of the vinyl aromatic hydrocarbon and the conjugated diene. As a specific method, (a) a mixture of a vinyl aromatic hydrocarbon and a conjugated diene is continuously supplied to a polymerization system for polymerization. as well as/
Alternatively, (b) a method of copolymerizing a vinyl aromatic hydrocarbon with a conjugated diene using a polar compound or a randomizing agent can be employed.

Examples of polar compounds and randomizing agents include ethers such as tetrahydrofuran, diethylene glycol dimethyl ether and diethylene glycol dibutyl ether, amines such as triethylamine and tetramethylethylenediamine, thioethers, phosphines, phosphoramides, alkylbenzene sulfonates, potassium And alkoxides of sodium. The microstructure of the conjugated diene polymer in the copolymer portion of the vinyl aromatic hydrocarbon and the conjugated diene can be adjusted by adding a predetermined amount of a polar compound or the like.

The block copolymer (I) used in the present invention
And (II) are represented by the general formula: (AB) _n , A- (BA) _n , B- (AB) _{n + 1} (where n is an integer of 1 or more; Typically 1-5
It is. ) Or a general formula: [(AB) _k ] _{m + 2-} X, [(AB) _k- A] _{m + 2-} X [(BA ) _K ] _{m + 2} −X, [(BA) _k −B] _{m + 2} −X

(Where A is a plastic polymer segment, B is an elastomeric polymer segment,
X is, for example, silicon tetrachloride, tin tetrachloride, 1,3 bis (N, N-glycidylaminomethyl) cyclohexane,
It shows the residue of a coupling agent such as epoxidized soybean oil or the residue of an initiator such as a polyfunctional organolithium compound. k and m are integers of 1 to 5. ), Or a mixture of these block copolymers having any polymer structure.

The molecular weight of these block copolymers can be arbitrarily adjusted depending on the amount of catalyst used in the polymerization. However, from the viewpoint of moldability, a melt flow index (JISK-6) is used.
Measured according to 870. The condition is a G condition, a temperature of 200 ° C., a load of 5 kg) is 0.1 to 50 g / 10 min, and preferably 1 to 50 g / 10 min.
２０20 g / 10 min. The block copolymer used in the present invention is obtained by polymerizing a vinyl aromatic hydrocarbon and a conjugated diene in a hydrocarbon solvent using an organolithium compound as an initiator.

The vinyl aromatic hydrocarbon used in the present invention includes styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinyl There are anthracene, 1,1-diphenylethylene and the like, and particularly common one is styrene. These may be used alone or in combination of two or more. The conjugated diene is a diolefin having a pair of conjugated double bonds, for example, 1,3-butadiene, 2-olefin.
Methyl-1,3-butadiene (isoprene), 2,3-
Examples thereof include dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene, and particularly common ones include 1,3-butadiene and isoprene. These may be used alone or in combination of two or more.

As the hydrocarbon solvent, butane, pentane,
Aliphatic hydrocarbons such as hexane, isopentane, heptane and octane, cyclopentane, methylcyclopentane,
Alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, and ethylcyclohexane, and aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene can be used. These may be used alone or in combination of two or more.

The organic lithium compound is an organic monolithium compound, an organic dilithium compound, or an organic polylithium compound in which one or more lithium atoms are bonded in a molecule.
Specific examples of these include ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, hexamethylene dilithium, butadienyl dilithium, isoprenyl dilithium and the like. No. These may be used alone or in combination of two or more.

The polymerization temperature for producing the block copolymer used in the present invention is generally from -10 ° C to 150 ° C, preferably from 40 ° C to 120 ° C. The time required for the polymerization varies depending on the conditions, but is usually within 10 hours, particularly preferably 0.5 to 5 hours. Further, it is desirable to replace the atmosphere of the polymerization system with an inert gas such as nitrogen gas. The polymerization pressure is not particularly limited, as long as it is a pressure range sufficient to maintain the monomer and the solvent in a liquid phase within the above-mentioned polymerization temperature range. Furthermore, it is necessary to take care that impurities such as water, oxygen, carbon dioxide, etc. which inactivate the catalyst and the living polymer do not enter the polymerization system.

When the composition of the present invention comprises the block copolymers (I) and (II), their weight ratio is 10
/ 90-90 / 10, preferably 20 / 80-80 / 2
0. If the weight ratio of the block copolymers (I) and (II) is out of the range of the present invention, the balance between impact resistance and rigidity is undesirably reduced.

Styrene-acrylic acid n used in the present invention
Styrene content in the butyl copolymer (III) is 75
９０90% by weight, preferably 80-88% by weight. If the styrene content is less than 75% by weight or more than 90% by weight, the transparency of the composition with the vinyl aromatic hydrocarbon-conjugated diene block copolymer deteriorates, which is not preferable. Styrene-n-butyl acrylate copolymer (I
As the production method of II), a known method for producing a styrene resin, for example, a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, or the like can be used. Melt flow rate of styrene-n-butyl acrylate copolymer (III) (hereinafter referred to as MFR) [based on JIS K-6870,
G conditions (measured at a temperature of 200 ° C. and a load of 5 kg)] are from 0.1 to 20 g / 10 min, preferably 1
-10 g / 10 min is recommended.

The composition of the present invention comprises a block copolymer (I) and a styrene-n-butyl acrylate copolymer (I).
II), their weight ratio is between 10/90 and 9
0/10, preferably 20/80 to 80/20.
If the weight ratio of the block copolymer (I) to the styrene-n-butyl acrylate copolymer (III) is out of the range of the present invention, the balance between impact resistance and rigidity is unfavorably reduced.

The composition according to the present invention comprises a block copolymer (I), a block copolymer (II) and styrene-
The weight ratio of the copolymer composed of the n-butyl acrylate copolymer (III) is 1 with respect to the total amount of (I), (II) and (III).
(I) as 10 to 80% by weight, (I)
I) 10 to 80% by weight, (III) 5 to 50% by weight,
Preferably, 15 to 75% by weight of (I) and 15 to 75% by weight of (II)
75% by weight and (III) in the range of 5 to 40% by weight. The block copolymer (I) and the block copolymer (I)
I) and styrene-n-butyl acrylate copolymer (II)
If the weight ratio of I) is out of the range of the present invention, the balance of impact resistance, rigidity and low-temperature shrinkage is undesirably reduced.

In the block copolymer composition of the present invention, 2-t-amyl-6- [1- (3,5-di-t) is used as a stabilizer.
-Amyl-2-hydroxyphenyl) ethyl] -4-t
-A gel suppressing effect can be obtained by adding 0.05 to 3 parts by weight, more preferably 0.1 to 2 parts by weight, of amylphenyl acrylate to 100 parts by weight of the block copolymer composition. When the amount of the stabilizer is less than 0.05 part by weight, there is no gel-suppressing effect, and when the amount exceeds 3 parts by weight, it does not contribute to the gel suppressing effect more than the present invention.

The block copolymer composition of the present invention contains n-
Octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2-tert-butyl-6
-(3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2,4-bis [(octylthio) methyl] -o-cresol, tetrakis [methylene-3- (3,5 -Di-t-butyl-4
-Hydroxyphenyl) propionate] methane, 1,
3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene,
2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,3
At least one phenolic stabilizer such as 5-triazine;
The seeds were added in an amount of 0.
05 to 3 parts by weight, tris- (nonylphenyl) phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite, 2-[[2,4
8,10-tetrakis (1,1-dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphen-6-yl] oxy] -N, N-bis [2-[[2 ,
4,8,10-tetrakis (1,1-dimethylethyl)
Organic phosphates such as dibenzo [d, f] [1,3,2] dioxaphosphen-6-yl] oxy] -ethyl] -ethanamine and tris (2,4-di-t-butylphenyl) phosphite At least one kind of an organic phosphite-based stabilizer can be added in an amount of 0.05 to 3 parts by weight based on 100 parts by weight of the block copolymer.

Various polymers and additives can be added to the block copolymer composition used in the present invention according to the purpose. Suitable polymers include a block copolymer elastomer of a vinyl aromatic hydrocarbon and a conjugated diene having a vinyl aromatic hydrocarbon content of 10 to 50% by weight, a rubber-modified impact-resistant polystyrene, a non-rubber-modified polystyrene,
Examples thereof include styrene / acrylate copolymers and polyethylene terephthalate, and these polymers may be added in an amount of 1 to 95% by weight, preferably 3 to 90% by weight.

Suitable additives include softeners such as coumarone-indene resin, terpene resin and oil, and plasticizers. Further, various stabilizers, pigments, antiblocking agents, antistatic agents, lubricants and the like can be added. Incidentally, as an antiblocking agent, antistatic agent, lubricant, for example, fatty acid amide, ethylene bis stearamide, sorbitan monostearate, saturated fatty acid ester of fatty acid alcohol, pentaerythritol fatty acid ester and the like, and as an ultraviolet absorber, pt-butylphenyl salicylate,
2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-
Butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,5-bis- [5'-t-butylbenzooxazolyl- (2)] thiophene, etc., "Handbook of additives for plastics and rubber" (Chemical Industry) can be used. These are generally 0.01
To 5% by weight, preferably 0.05 to 3% by weight.

To obtain a heat-shrinkable uniaxially or biaxially stretched film from the block copolymer composition used in the present invention,
The block copolymer is extruded at 150 to 250 ° C, preferably 170 to 220 ° C, into a flat or tubular shape from a usual T die or annular die, and the obtained unstretched material is substantially uniaxially stretched or stretched. Axial stretching. For example, in the case of uniaxial stretching, in the case of a film or sheet, the film is stretched in the extrusion direction by a calendar roll or the like, or in a direction perpendicular to the extrusion direction by a tenter or the like, and in the case of a tube, in the extrusion direction or circumferential direction of the tube. Stretch. In the case of biaxial stretching, in the case of a film or sheet, the extruded film or sheet is stretched in the longitudinal direction by a metal roll or the like, and then stretched in the transverse direction by a tenter or the like. The film is stretched simultaneously or separately in the circumferential direction of the tube, that is, in the direction perpendicular to the tube axis.

In the present invention, the stretching temperature is from 60 to 110.
It is preferable that the film is stretched at a stretching temperature of 1.5 to 8 times, preferably 2 to 6 times in the machine direction and / or the transverse direction at 80 ° C., preferably 80 to 100 ° C. If the stretching temperature is lower than 60 ° C., breakage occurs during stretching and it is difficult to obtain a desired heat-shrinkable film, and if it exceeds 110 ° C., it is difficult to obtain a product having good shrinkage characteristics. The stretching ratio is selected within the above range so as to correspond to the required shrinkage ratio depending on the application.
If the ratio is less than 2 times, the heat shrinkage ratio is small, which is not preferable for heat shrink wrapping, and a stretching ratio exceeding 8 times is not preferable for stable production in the stretching process. In the case of biaxial stretching, the stretching ratio in the machine direction and the transverse direction may be the same or different.

The uniaxially stretched or biaxially stretched heat-shrinkable film is then subjected, if necessary, to a temperature of 60 to 105 ° C., preferably 8 to 105 ° C.
It is also possible to carry out heat treatment at 0 to 95 ° C. for a short time, for example, 3 to 60 seconds, preferably 10 to 40 seconds, to implement a means for preventing natural shrinkage at room temperature. To use the thus obtained heat-shrinkable film as a heat-shrinkable packaging material or a heat-shrinkable label material, the heat shrinkage at 65 ° C. in the stretching direction is 10 to 80%, preferably 1 to 80%.
Must be 5-70%.

When the heat shrinkage ratio in the stretching direction is less than 10%, the shrinkage property is poor, so that it is necessary to adjust the step to a high temperature and uniform in the shrink wrapping step or to heat it for a long time. It is not preferable because packaging of the resulting product becomes impossible or the shrink wrapping processing ability is reduced, and if it exceeds 80%, the natural shrinkage of the film becomes large, which is not preferable. In the present invention, 65 ° C.
Is a measure of the low-temperature shrinkage and is uniaxially stretched or 2
This is the heat shrinkage in each stretching direction of the molded article when the axially stretched film is immersed for 5 minutes in a heat medium that does not impair the properties of the molded article such as hot water, silicone oil, and glycerin at 65 ° C.

Further, the uniaxially stretched or biaxially stretched film of the present invention has a tensile modulus of 7000 to 3 in the stretching direction.
0000 Kg / cm ² , preferably 10,000 to 250
It is necessary for the heat shrink wrapping material to be 00 Kg / cm ² . Tensile modulus in the stretching direction is 7000 Kg /
If it is less than ² cm ² , settling occurs in the shrink wrapping process and normal packaging cannot be performed, which is not preferable.
If it exceeds m ² , the impact resistance of the film is undesirably reduced.

When the uniaxially stretched or biaxially stretched film of the present invention is used as a heat shrinkable wrapping material, the temperature is preferably from 130 to 300 ° C., preferably from 150 to 300 ° C., in order to achieve a desired heat shrinkage.
Heat shrinkage can be performed by heating at a temperature of 250 ° C. for several seconds to several minutes, preferably 1 to 60 seconds.

The heat-shrinkable film of the present invention has at least 3
It may be a multilayer laminate having a layer structure. As a form of use as a multilayer laminate, for example, a form disclosed in Japanese Patent Publication No. 3-5306 is specifically mentioned. The block copolymer composition of the present invention may be used for the intermediate layer and both outer layers, but is preferably used for the intermediate layer.
Preferred form of the multilayer film is a block copolymer (I)
And a composition of a block copolymer (II) or a composition of a block copolymer (I) and a styrene-n-butyl acrylate copolymer (III) as an intermediate layer, and vinyl aromatic hydrocarbons in both outer layers. Block copolymer composed of conjugated diene (unlike the inner layer component, GPPS, HIP
S may be added in an amount of 0.1 to 20% by weight).

The thickness of the multilayer film is 20 to 200 μm,
Preferably, the thickness is 30 to 100 μm, and the ratio of the thickness of the inner layer to both surface layers is 5/95 to 45/55, preferably 10/90.
３５35/65. The preferred amount of the vinyl aromatic hydrocarbon and the total amount of the styrene-n-butyl acrylate copolymer in the multilayer film for obtaining the natural shrinkage, low-temperature shrinkage and rigidity as the multilayer film are the total amount of the entire multilayer film. When the amount is 100% by weight, it is 70 to 95% by weight, preferably 75 to 92% by weight.

The heat-shrinkable film comprising the block copolymer composition of the present invention is superior in hygiene as compared with a conventional vinyl chloride resin-based film, and its properties are utilized in various applications such as fresh foods. , Confectionery packaging, clothing, stationery, etc. As a particularly preferred application, after printing characters and designs on the uniaxially stretched film of the block copolymer specified in the present invention, the surface of the object to be packaged such as a plastic molded product, a metal product, a glass container, and porcelain is subjected to heat shrinkage. Use as a material for a so-called heat-shrinkable label, which is used in close contact, may be mentioned.

In particular, the uniaxially stretched heat-shrinkable film of the present invention is excellent in low-temperature shrinkage, rigidity and natural shrinkage.
In addition to the heat-shrinkable label material of a plastic molded product that deforms when heated to a high temperature, a material having a coefficient of thermal expansion, water absorption and the like that is extremely different from the block copolymer of the present invention, such as metal, porcelain, glass, and paper Polyethylene resin such as polyethylene, polypropylene, polybutene, polymethacrylate resin, polycarbonate resin, polyethylene terephthalate, polyester resin such as polybutylene terephthalate, and at least one selected from polyamide resin were used as constituent materials. It can be suitably used as a heat-shrinkable label material for containers.

The plastic container in which the heat-shrinkable block copolymer film of the present invention can be used is, in addition to the above resins, polystyrene, rubber-modified impact-resistant polystyrene (HIPS), styrene-butyl acrylate. Copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, acrylonitrile-butadiene-styrene copolymer (ABS), methacrylate-butadiene-styrene copolymer (M
BS), polyvinyl chloride resin, polyvinyl chloride resin, phenol resin, urea resin, melamine resin, epoxy resin, unsaturated polyester resin, silicone resin and the like.

These plastic containers may be a mixture of two or more resins or a laminate. When a heat-shrinkable film obtained by uniaxially stretching the block copolymer composition defined in the present invention is used as a heat-shrinkable label material, the heat shrinkage at 65 ° C. in a direction perpendicular to the stretching direction is used. Is less than 10%, preferably 5% or less. Therefore, in the present invention, to perform uniaxial stretching as a heat-shrinkable label means that the heat shrinkage at 65 ° C. in the stretching direction is 10 to 6%.
Stretching is performed so that the thermal shrinkage in the direction perpendicular to the stretching direction at 0% is less than 10%. In the present invention, the thickness of the film is generally adjusted to 10 to 300 μm, preferably 30 to 100 μm.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but they do not limit the scope of the present invention. Table 1 shows the block copolymer (I), Table 2 shows the block copolymer (II), and Table 3 shows the styrene used in Examples and Comparative Examples.
An n-butyl acrylate copolymer was shown. The block copolymers (I) and (II) were prepared by using n-butyllithium as a catalyst in a cyclohexane solvent and using tetramethylethylenediamine as a randomizing agent, and a styrene content (% by weight) shown in Table 1 and a plastic polymer segment A. Block copolymer (I) having a styrene content (% by weight), a styrene content (% by weight) of the elastomeric polymer segment B, a block ratio (% by weight) and a Vicat softening temperature (° C.)
And a block copolymer (II) having a styrene content (% by weight) and a peak temperature of tan δ shown in Table 2.

The styrene content is the amount of styrene and butadiene added, the block ratio is the styrene content of segment A and segment B, and the Vicat softening temperature is the styrene content of segment A and segment B, the ratio by mass and the molecular weight of the block copolymer. The peak temperature of tan δ was adjusted by the styrene content of segment A and segment B, the ratio by weight, and the molecular weight of the block copolymer. The measurement of the Vicat softening temperature was performed using a test piece that was compression-molded to a thickness of 3 mm.
Measured according to -1525 (load 1 kg, temperature rising rate.
2 ° C./min).

The block copolymer A-1 was produced as follows. Using an autoclave with a stirrer, under a nitrogen gas atmosphere, 0.08 part by weight of n-butyllithium and 0.08 part by weight of tetramethylethylenediamine were added to a cyclohexane solution containing 31.5 parts by weight of styrene and 3.5 parts by weight of 1,3-butadiene. After adding 03 parts by weight and polymerizing at 75 ° C. for 30 minutes, a cyclohexane solution containing 16.8 parts by weight of styrene and 23.2 parts by weight of 1,3-butadiene was continuously added and polymerized at 75 ° C. for 60 minutes. did. Next, styrene 22.
A cyclohexane solution containing 5 parts by weight and 2.5 parts by weight of 1,3-butadiene was continuously added and polymerized at 75 ° C. for 25 minutes. Thereafter, methanol was added to the polymerization vessel at a molar ratio of 0.9 times the amount of n-butyllithium to terminate the polymerization, and 2-t-amyl-6- [1- (3,5-di-t) was used as a stabilizer.
-Amyl-2-hydroxyphenyl) ethyl] -4-t
-Amylphenyl acrylate was added in an amount of 0.6 part by weight based on 100 parts by weight of the block copolymer composition, and then the solvent was removed to obtain a block copolymer.

The peak temperature of tan δ is DMA983 (D
UPON Corporation), and the measurement was performed at the resonance frequency (Reso).
nant), the temperature rising rate is -100 to 14 at 2 ° C./min.
In the range of 0 ° C, the sample was a compression molded product about 3 mm thick and about 12.5 mm wide attached to an arm about 15 mm long.
It was measured at itude = 0.2 mm. Styrene-
N-butyl acrylate copolymer C-1 was prepared with a stirrer 1
Into a 0 L autoclave, 5 kg of styrene and n-butyl acrylate were added in the ratio shown in Table 3, and 0.3 kg of ethylbenzene and a predetermined amount of 1,1 bis (t-butylperoxy) cyclohexane were added to adjust MFR. After polymerization at 110 to 150 ° C. for 2 to 10 hours, unreacted styrene, n-butyl acrylate, and ethylbenzene were recovered with a vent extruder to produce the polymer. Incidentally, the MFR of C-1
Was 3.0.

[0049]

EXAMPLES 1-6, COMPARATIVE EXAMPLES 1-5 Film performance was measured by measuring the composition of the block copolymer and styrene-n-butyl acrylate copolymer shown in Table 4 with the type and amount of 40 mm.
It was formed into a sheet having a thickness of 0.25 mm at 200 ° C. using an extruder, and then uniaxially stretched five times with a tenter to the horizontal axis to obtain a film having a thickness of about 60 μm. Table 4 shows the film performance of the obtained heat shrinkable film. The stretched film performance using the block copolymer composition of the present invention is a rigidity represented by a tensile modulus, a low-temperature shrinkage represented by a 65 ° C. shrinkage, a natural shrinkage, and a puncture resistance represented by a puncture impact strength. It turns out that it is excellent in the impact property, the hot water fusion property, and the transparency represented by Haze. The sheet and film properties shown in Table 4 were measured by the following methods.

(1) Tensile modulus: JIS K-6732
And the values in the stretching direction are shown. The unit is Kg / c
m ² . (2) Shrinkage at 65 ° C .: The stretched film was immersed in silicone oil at 65 ° C. for 5 minutes and calculated by the following equation. Heat shrinkage (%) = (L−L1) / L × 100, L: length before shrinkage, L1: length after shrinkage.

(3) Natural shrinkage: A stretched film having a shrinkage of 40% measured at 80 ° C. was left at 35 ° C. for 5 days, and calculated by the following equation. Natural shrinkage (%) = (L2-L3)
/ L2 × 100, L2: length before standing, L3: length after standing. The smaller the natural shrinkage is, the better the natural shrinkage is. (4) Puncture impact strength: based on JIS P-8134, unit is Kg · cm.

(5) Hot water fusing property: The stretched film was wound around a glass bottle having a diameter of about 8 cm, left in a stack of three bales in 70 ° C. hot water for 5 minutes, and the fusion state of the film was visually judged. The criterion for ◎ was no fusion at all, ○ was slightly fused but separated immediately, and × was fused and not separated immediately. (6) Haze: Liquid paraffin was applied to the sheet surface before stretching, and measured in accordance with ASTM D1003.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

[0056]

[Table 4]

[0057]

The heat-shrinkable film obtained by using the block copolymer composition of the present invention is transparent and has excellent rigidity, natural shrinkage, low-temperature shrinkage, hot-water fusion property and impact resistance. In addition, it is possible to simultaneously achieve thinning of a film, dimensional stability and low-temperature shrinkage, and it can be suitably used for beverage container packaging, cap seals, various labels, and the like.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 9:00 B29K 9:00 105: 02 105: 02 B29L 7:00 B29L 7:00 F term ( Reference) 4F071 AA22 AA75 AA85 AF20Y AF61Y AH04 BB07 BC01 4F210 AA13F AA21F AA47F AE01 AG01 RA03 RC02 RG02 RG04 RG43 4J002 BC07Y BP01W BP01X GG02 4J026 HA05 HA06 HA14 H15 H20 HB HAB HA06 H06 HAB

Claims (4)

[Claims] (I) It has at least one plastic polymer segment A and at least one elastomer polymer segment B, and the weight ratio of vinyl aromatic hydrocarbon to conjugated diene is 65/35 to 80/20 block copolymer, wherein segment A has a weight ratio of vinyl aromatic hydrocarbon to conjugated diene of 85/15 to 98/2; segment B is conjugated to vinyl aromatic hydrocarbon. A copolymer having a weight ratio to a diene of 20/80 to 60/40, a block ratio of vinyl aromatic hydrocarbon incorporated in the block copolymer being 20 to 55% by weight, and a Vicat softening temperature. (II) at least one plastic polymer segment A and at least one elastomeric polymer segment. Weight ratio between the vinyl aromatic hydrocarbon and the conjugated diene exceeds 80/20,
5 or less, the peak of the function tan δ of the dynamic viscoelasticity of the block copolymer is 90 to 125 ° C.
Consisting of a block copolymer having at least one
A block copolymer composition wherein the weight ratio of (I) and (II) is 10/90 to 90/10. (I) having at least one plastic polymer segment A and at least one elastomeric polymer segment B, wherein the weight ratio of vinyl aromatic hydrocarbon to conjugated diene is 65/35 to 80/20 block copolymer, wherein segment A has a weight ratio of vinyl aromatic hydrocarbon to conjugated diene of 85/15 to 98/2; segment B is conjugated to vinyl aromatic hydrocarbon. A copolymer having a weight ratio to a diene of 20/80 to 60/40, a block ratio of vinyl aromatic hydrocarbon incorporated in the block copolymer being 20 to 55% by weight, and a Vicat softening temperature. A block copolymer having a styrene content of 75 to 75 ° C, and a styrene content of 75 to 75 ° C.
90% by weight, n-butyl acrylate content of 25 to 10
% Of a styrene-n-butyl acrylate copolymer having a weight ratio of (I) to (III) of 10/90.
~ 90/10 block copolymer composition. (I) having at least one plastic polymer segment A and at least one elastomeric polymer segment B, wherein the weight ratio of vinyl aromatic hydrocarbon to conjugated diene is 65/35 to 3. 80/20 block copolymer, wherein segment A has a weight ratio of vinyl aromatic hydrocarbon to conjugated diene of 85/15 to 98/2; segment B is conjugated to vinyl aromatic hydrocarbon. A copolymer having a weight ratio to a diene of 20/80 to 60/40, a block ratio of vinyl aromatic hydrocarbon incorporated in the block copolymer being 20 to 55% by weight, and a Vicat softening temperature. (II) at least one plastic polymer segment A and at least one elastomeric polymer segment. Weight ratio between the vinyl aromatic hydrocarbon and the conjugated diene exceeds 80/20,
5 or less, the peak of the function tan δ of the dynamic viscoelasticity of the block copolymer is 90 to 125 ° C.
A block copolymer having at least one of (II)
I) styrene content of 75 to 90% by weight, acrylic acid n
-Styrene having a butyl content of 25 to 10% by weight
Consisting of n-butyl acrylate copolymer, (I) and (I)
The weight ratio of (I) to (III) is 10 to 80% by weight, and (II) is 10 to 8%, with the total amount being 100% by weight.
A block copolymer composition comprising 0% by weight and (III) in the range of 5 to 50% by weight. 4. A stretched block copolymer composition according to claim 1, having a heat shrinkage of 10 to 60% at 65 ° C. in the stretching direction and a tensile modulus of 70 in the stretching direction.
A heat-shrinkable film having a thickness of 00 to 30,000 kg / cm ² .