JP2011157512A - Block copolymer composition and heat shrinkable film for packaging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding material for a packaging film which is formed of a specific block copolymer resin composition and has excellent heat shrinking property, tear break resistance, and transparency; and a heat shrinkable film for packaging. <P>SOLUTION: The heat shrinkable film for packaging is formed of the block copolymer resin composition. In the block copolymer resin composition, which is a copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, a mass ratio of the vinyl aromatic hydrocarbon to the conjugated diene is 80/20 to 60/40, a weight-average molecular weight is 50,000-200,000, and at least one loss tangent peak is obtained at -30°C or lower in the dynamic viscoelasticity measurement. In the heat shrinkable film for packaging, a longitudinal shrinkage percentage at 120°C is 20% or more, tear strength is 50 N/mm or more, a break displacement is 10 mm or more, and the haze degree is less than 10%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a vinyl aromatic hydrocarbon block copolymer resin composition and a heat shrinkable film for packaging using the same.

Polyethylene-based resin films are widely used as films for stacking and bundling packaging. A multilayer film in which an ethylene α-olefin copolymer is laminated on a polypropylene resin layer has been proposed.
These technologies include the following.

JP 2002-36358 A JP-A-11-70625

An object of the present invention is to provide a block copolymer resin composition containing a specific vinyl aromatic hydrocarbon block copolymer and a heat shrinkable film for packaging.

That is, this invention consists of the summary characterized by the following.
1. A molding material for a packaging film comprising a block copolymer composition (a) satisfying the following (i) to (iii), which is a copolymer composition of a vinyl aromatic hydrocarbon and a conjugated diene.
(I) Mass ratio of vinyl aromatic hydrocarbon to conjugated diene is 80/20 to 60/40
(Ii) A weight average molecular weight of 50,000 to 200,000
(Iii) At least one loss tangent peak obtained by dynamic viscoelasticity measurement is present at −30 ° C. or lower.
2. The block copolymer composition (a) described in 1 above and at least one vinyl aromatic hydrocarbon polymer selected from the following (b) or (c) are 100 / 0.5 to 60 by mass ratio: / 40, and the content of the conjugated diene polymer of the block copolymer composition (a) in the resin composition is 20 to 39% by mass. Molding material for packaging film containing the composition.
(B) Rubber-modified vinyl aromatic hydrocarbon polymer (c) Vinyl aromatic hydrocarbon polymer The molding material for packaging films whose said vinyl aromatic hydrocarbon of 1 and 2 is styrene and whose conjugated diene is 1, 3- butadiene.
4). The packaging film which has the characteristics of (1)-(3) shape | molded using the molding material for packaging films as described in any one of said 1-3.
(1) Longitudinal shrinkage at 120 ° C. is 20% or more (2) Tear strength is 50 N / mm or more, and displacement amount to 10 mm or more until tearing during tear test (3) Cloudiness is less than 10% 5 . At least one layer made of the molding material for packaging film according to any one of the above 1 to 3, and at least one layer made of at least one polyolefin selected from an ethylene polymer or a propylene copolymer. And a packaging film having the characteristics of (1) to (3).
(1) Longitudinal shrinkage at 120 ° C. is 20% or more. (2) The tear strength is 50 N / mm or more, and the displacement until the break during the tear test is 10 mm or more. (3) The haze is less than 10% 6 . The shrink package which was tightly_contact | adhered to the packaged object by heat shrink using the packaging film of said 4 or 5, and was tensioned.

Since the block copolymer resin composition of the present invention is excellent in heat shrinkability, tear resistance and transparency, it is useful for heat shrink films for packaging such as integrated packaging and bundled packaging.

 Hereinafter, the block copolymer resin composition of the present invention will be described in detail.

The block copolymer constituting the block copolymer resin composition (a) is prepared by using an organic lithium compound as a polymerization initiator in an organic solvent and one or more vinyl aromatic hydrocarbon monomers and one or more conjugates. It can be produced by subjecting a diene monomer to living anion polymerization.

<Vinyl aromatic hydrocarbon-conjugated diene block copolymer resin composition (a)>
Examples of the vinyl aromatic hydrocarbon used in the block copolymer resin composition (a) of vinyl aromatic hydrocarbon and conjugated diene used in the present invention include styrene, o-methylstyrene, p-methylstyrene, p- Examples thereof include tert-butyl styrene, 2,4-dimethyl styrene, 2,5-dimethyl styrene, α-methyl styrene, vinyl naphthalene, vinyl anthracene and the like, and styrene is particularly common.

Examples of the conjugated diene used in the production of the block copolymer resin composition (a) of vinyl aromatic hydrocarbon and conjugated diene used in the present invention include 1,3-butadiene and 2-methyl-1,3-butadiene. (Isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like can be mentioned, and 1,3-butadiene is particularly common.

The mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the block copolymer resin composition (a) used in the present invention is 80/20 to 60/40, preferably 76/24 to 65/35. is there.

The weight average molecular weight of the block copolymer resin composition (a) used in the present invention is preferably 50,000 to 300,000, particularly preferably 100,000 to 200,000. When the weight average molecular weight of the block copolymer is less than 50,000, molding processability is lowered and a good film cannot be obtained. On the other hand, if the weight average molecular weight of the block copolymer resin composition exceeds 300,000, fish eyes are likely to be generated during molding and a good film cannot be obtained. In addition, the weight average molecular weight of the block copolymer in this invention was calculated | required in accordance with the conventional method using the gel permeation chromatograph (henceforth GPC).

The block copolymer constituting the block copolymer resin composition (a) used in the present invention is a block portion having one end portion made of vinyl aromatic hydrocarbon, and the block portion following this is a conjugated diene. It consists of vinyl aromatic hydrocarbons. The structure is not particularly limited, but preferred examples include those having the following general formula.
(I) AB
(Ii) A-B-A
(Iii) A-C-A
(Iv) A-C-B
(V) A-C-B-A
(Vi) ABB
(Vii) ABBBA
(Viii) (AB) n-X
(Ix) (ABA) n-X
(X) (A-C-A) n-X
(Xi) (A-C-B) n-X
(Xii) (A-C-B-C) n-X
In the general formula, A represents a polymer chain of vinyl aromatic hydrocarbon, B represents a copolymer chain of vinyl aromatic hydrocarbon and conjugated diene, and C represents a polymer chain of conjugated diene. X is a residue of a polyfunctional coupling agent or a residue of a polyfunctional organolithium compound, and n represents an integer of 2-4. Even if there are a plurality of A, B or C in the general formula, the molecular weight, the mass ratio of the conjugated diene, the distribution state of the vinyl aromatic hydrocarbon and the conjugated diene in the copolymer chain are independent and the same. There is no need. The molecular weight and composition distribution of the copolymer chain B are controlled mainly by the addition amount and addition method of the vinyl aromatic hydrocarbon monomer and the conjugated diene monomer. As the block copolymer resin composition (a), those having the structures (i) to (xii) may be used alone or a plurality of mixtures may be used.

<Manufacture of block copolymer>
The block copolymer constituting the block copolymer resin composition (a) is produced by polymerizing a vinyl aromatic hydrocarbon monomer and a conjugated diene monomer in an organic solvent using an organolithium compound as an initiator. it can. Examples of the organic solvent include aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, octane and isooctane, alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane and ethylcyclohexane, or ethylbenzene, Aromatic hydrocarbons such as xylene can be used.

An organic lithium compound is a compound in which one or more lithium atoms are bonded in the molecule, such as ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, and tert-butyl lithium. Monofunctional organolithium compounds, polyfunctional organolithium compounds such as hexamethylene dilithium, butadienyl dilithium, and isoprenyl dilithium can be used.

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

For example, when obtaining a block copolymer having a vinyl aromatic hydrocarbon block part and a tapered block part following it, the vinyl aromatic hydrocarbon monomer is first charged, and after the reaction is completed, the vinyl aromatic hydrocarbon is obtained. A monomer and a conjugated diene monomer may be charged simultaneously.
At this time, the composition ratio of the tapered portion changes with the growth of the block portion due to the difference in the reactivity ratio between the vinyl aromatic hydrocarbon and the conjugated diene, but this can be adjusted by the concentration of the randomizing agent.

The randomizing agent is a polar molecule, and tetrahydrofuran (THF) is mainly used, but other ethers, amines, thioethers, phosphoramides, alkylbenzene sulfonates, potassium or sodium alkoxides, and the like can also be used. Suitable ethers include dimethyl ether, diethyl ether, diphenyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether and the like in addition to THF. As the amines, tertiary amines such as trimethylamine, triethylamine, tetramethylethylenediamine, cyclic amines and the like can be used. In addition, triphenylphosphine, hexamethylphosphoramide, potassium or sodium alkylbenzene sulfonate, potassium or sodium butoxide and the like can also be used as a randomizing agent.

As addition amount of a randomizing agent, 0.001-10 mass parts is preferable with respect to 100 mass parts of all preparation monomers. The timing of addition may be before the start of the polymerization reaction or before the polymerization of the copolymer chain. Further, it can be added as required.

Examples of the polyfunctional coupling agent used in the present invention include silicon tetrachloride, epoxidized soybean oil, and organic carboxylic acid ester. The addition amount of the coupling agent may be any effective amount, but is preferably set so that the reaction site of the coupling agent is present in a stoichiometric amount or more with respect to the living active terminal. Specifically, it is preferable to set the addition amount of the coupling agent so that 1 to 2 equivalents of reaction sites exist with respect to the number of moles of living active terminals present in the polymerization solution before the coupling step.

The molecular weight of the block copolymer constituting the block copolymer resin composition (a) used in the present invention can be controlled by the amount of initiator added relative to the total amount of monomers added.

The block copolymer thus obtained should be added with a sufficient amount of a polymerization terminator such as water, alcohol, organic acid, inorganic acid, and phenolic compound to inactivate the active terminal. Is inactivated. Since the deactivation stoichiometric number of the polymerization active terminal is proportional to the stoichiometric number of the added polymerization terminator, only a part of the polymerization active terminal is deactivated during the polymerization, and then additional raw material monomers are added. In addition, a production method in which polymerization is further continued can be employed. There is no particular limitation on the number of deactivations during the process unless all the polymerization active terminals are deactivated. However, it is necessary to deactivate all active ends when the polymerization is completed.

As a method of recovering the copolymer from the obtained block copolymer solution, a method of precipitating with a poor solvent such as methanol, a method of precipitating by evaporating the solvent with a heating roll or the like (drum dryer method), a concentrator Any method, such as a method of removing the solvent with a vented extruder after concentrating the solution, a method of dispersing the solution in water, blowing the water vapor to remove the solvent by heating (steam stripping method), etc. The method can be adopted.

In the block copolymer composition (a) used in the present invention, various additives can be mixed as necessary within a range not impairing the object of the present invention. Examples of additives include various stabilizers, processing aids, weather resistance improvers, softeners, plasticizers, antistatic agents, antifogging agents, mineral oils, fillers, pigments, dyes, flame retardants, lubricants, and the like.

Examples of the stabilizer include 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3, 5-di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl acrylate, phenol-based antioxidants such as 2,6-di-tert-butyl-4-methylphenol, trisnonylphenylphosphine Examples thereof include phosphorus antioxidants such as phyto and tris (2,4-di-tert-butylphenyl) phosphite. Commonly known processing aids, light resistance improvers, softeners, plasticizers, antistatic agents, antifogging agents, mineral oils, fillers, pigments, flame retardants and the like can be mentioned. Examples of the lubricant include dimethylpolysiloxane, methylphenylpolysiloxane, fatty acid, glycerin fatty acid ester, diglycerin difatty acid ester, fatty acid amide, fatty acid bisamide, and hydrocarbon wax.

The block copolymer composition (a) used in the present invention can also be obtained by mixing the block copolymer, and the mixing method is not particularly specified. For example, dry blending with a Henschel mixer, a ribbon blender, a V blender, etc. Alternatively, it may be melted and pelletized by an extruder. Alternatively, it may be added at the stage of production of each polymer, before the start of polymerization, in the middle of the polymerization reaction, or after treatment of the polymer.

The dynamic viscoelasticity of the block copolymer resin composition (a) used in the present invention is such that the test pellet is made into a sheet by a hot press and then the room temperature is adjusted to 23 ° C. and the relative humidity is 50% RH. After being cured for 24 hours or longer, the test sample was subjected to stress and strain in the tensile direction at a frequency of 1 Hz, and measured while raising the temperature at a rate of 4 ° C./min. At this time, at least one peak of loss tangent value of the copolymer composition of the present invention is present at -30 ° C. or lower. More preferably, it is -40 degrees C or less.

<Rubber-modified vinyl aromatic hydrocarbon polymer (b)>
The rubber-modified vinyl aromatic hydrocarbon polymer constituting component (b) used in the present invention is obtained by polymerizing a mixture of vinyl aromatic hydrocarbon or a monomer copolymerizable therewith and various elastomers. It is done. As the vinyl aromatic hydrocarbon, those described above are used, and as the monomer copolymerizable therewith, for example, (meth) acrylic acid, (meth) acrylic acid ester and the like are used. Examples of the elastomer include butadiene rubber, styrene-butadiene rubber, styrene-butadiene block copolymer elastomer, chloroprene rubber, and natural rubber. As the rubber-modified styrenic polymer thus obtained, impact-resistant polystyrene (HIPS) obtained from styrene and butadiene rubber is preferable.

<Vinyl aromatic hydrocarbon polymer (c)>
As the vinyl aromatic hydrocarbon polymer constituting the component (c) used in the present invention, the homopolymers of vinyl aromatic hydrocarbons listed above or copolymers using two or more kinds are used. Particularly common is polystyrene.

The mass ratio of the vinyl aromatic hydrocarbon polymer component (b) and / or (c) mixed in the block copolymer resin composition (a) of the present invention is (a) / [(b) and / or (C)] = 99.5 / 0.5 to 60/40, preferably 99/1 to 80/20.

<Packaging film>
The packaging film of the present invention can be obtained by melting the block copolymer resin composition with an extruder and stretching it uniaxially or biaxially. Examples of the extrusion method include a T-die method and an inflation method (tubular method) using a circular die, but the inflation method is preferred. In addition, when manufacturing a film using an extruder, the temperature of an extruder has preferable 160-260 degreeC.

Examples of the stretching method include a tenter method and an inflation method (including single bubble and double bubble methods). In the case of biaxial stretching, sequential stretching or simultaneous biaxial stretching may be used, but in the case of the inflation method, simultaneous biaxial stretching is preferable in terms of film formation stability. Moreover, when manufacturing the packaging film of this invention by a biaxial stretching method, 80-150 degreeC is preferable for extending | stretching temperature. If the stretching temperature is less than 80 ° C., the film may break during stretching. On the other hand, when the stretching temperature exceeds 150 ° C., good shrinkage characteristics of the film may not be obtained. A particularly preferred stretching temperature is in the range of Tg + 5 ° C. to Tg + 20 ° C. with respect to the glass transition temperature (Tg) of the composition constituting the film. The glass transition temperature (Tg) is obtained from the peak temperature of the loss elastic modulus of the composition constituting the film. The stretching ratio is not particularly limited, but is preferably 2 to 50 times, preferably 3 to 30 times in terms of area stretching ratio. A draw ratio is suitably adjusted according to a heat shrinkage rate etc. which are required by a use.

Although the thickness of the film obtained by extending | stretching can be made into the arbitrary thickness of the range of 10-90 micrometers according to a use, Preferably it is 15-80 micrometers.

The film using the resin composition of the present invention may be a single layer, but can be a laminated film as long as the properties of the film of the present invention are not impaired. The resin to be laminated is not particularly limited, but in this application, polyolefins such as ethylene polymers and propylene polymers are preferable.

For ethylene polymers, use high-density polyethylene, medium-density polyethylene, low-density polyethylene, copolymers with vinyl compounds copolymerizable with ethylene (for example, ethylene-α-olefin copolymers), or single-site catalysts. And ethylene-based polymers.
Examples of the propylene-based polymer include homopolypropylene and a copolymer with a vinyl compound copolymerizable with propylene (for example, propylene-α-olefin copolymer). These ethylene polymers and propylene polymers may be used alone or in combination. Furthermore, the resin composition of the present invention may be mixed. These laminated resins preferably have a melt flow rate (hereinafter referred to as MFR) of 1.0 to 30 g / 10 min at 230 ° C. and 2.16 kgf.

The layer structure of the laminated film is not particularly limited, but two or more layers are preferable. In the case of two or more layers of three or more layers, a method of simultaneously extruding using a plurality of extruders and laminating with a T die or a circular die is common. The layer ratio is not particularly limited as long as the layer containing the block copolymer resin composition of the present invention is a main component.

The film of the present invention may contain a lubricant, a plasticizer, an antioxidant, an antistatic agent, an ultraviolet absorber, an antifogging agent, an antiblocking agent, an inorganic filler, a crystal nucleating agent, a colorant and the like as long as the properties are not impaired. Good. Examples of the addition method include a method of directly applying to a film, a method of kneading and adding to a resin, and a method of diluting and adding a master batch.

When the film of the present invention is used as a heat shrinkable film for packaging, the heat shrinkage rate is preferably 20% or more at 120 ° C. for 10 seconds in the longitudinal direction. If the heat shrinkage rate is less than 20%, a high temperature is required at the time of shrinkage, so that the productivity of the coated package may be reduced, or the thermal load may be increased, which may affect the environment.

The tear strength of the film of the present invention is preferably 50 N / mm or more in the longitudinal direction for the purpose of maintaining practical strength. If the tear strength is less than 50 N / mm and the amount of displacement until breakage is less than 10 mm, the integrated package or the bundled package tends to break, which is not preferable. The tear test is measured using an angle-type tear test piece in accordance with JIS K6252.

In order to use the film of the present invention for packaging, the haze is preferably less than 10%. More preferably, it is 6% or less.

The integrated package or the bundled package of the present invention can be produced by a known shrink tunnel. The heating method of the shrink tunnel may be a steam method or a hot air method, but a form having a preheating portion and a main heating portion is preferable in terms of thermal efficiency.

The present invention will be described below with reference to examples. However, the present invention is not limited to these examples.

Examples 1-6 and Comparative Examples 1-6
<Molding material used for film>
Production of Block Copolymer Resin Composition (a) [Reference Example 1]
(1) Into a reaction vessel, 300 kg of cyclohexane containing 150 ppm of tetrahydrofuran and 22 kg of styrene monomer were charged and kept at 30 ° C.
(2) A 10% by mass cyclohexane solution of n-butyllithium was added as a polymerization catalyst solution, and the styrene monomer was anionically polymerized.
(3) After the styrene monomer was completely consumed, 33 kg of styrene monomer and 45 kg of butadiene were simultaneously added while maintaining the internal temperature of the reaction system at 70 ° C., and the reaction was continued.
(4) After completion of the reaction, 330 g of water was added to deactivate the polymerization reaction to obtain a polymer solution.
(5) 0.4 parts by mass of Sumitomo Chemical Co., Ltd. Sumilizer GS and 0.3 parts by mass of Adeka Co., Ltd. AO-50F were dissolved as a stabilizer per 100 parts by mass of charged monomers.
(6) The polymerization solution obtained above was designated as A-1.
(7) 300 kg of cyclohexane containing 150 ppm of tetrahydrofuran and 34 kg of styrene monomer were charged in a reaction vessel and kept at 30 ° C.
(8) A 10% by mass cyclohexane solution of n-butyllithium was added as a polymerization catalyst solution to anionic polymerize the styrene monomer.
(9) After the styrene monomer was completely consumed, 51 kg of styrene monomer and 15 kg of butadiene were simultaneously added while maintaining the internal temperature of the reaction system at 70 ° C., and the reaction was continued.
(10) After the reaction was completed, 330 g of water was added to deactivate the polymerization reaction to obtain a polymer solution.
(11) Summarizer GS manufactured by Sumitomo Chemical Co., Ltd. 0.4 parts by mass and Ade-50 Co., Ltd. AO-50F manufactured by 0.3 parts by mass were dissolved as a stabilizer per 100 parts by mass of charged monomers.
(12) The polymerization solution obtained by the operations of (7)-(11) was designated as A-2.
(13) The polymer solutions A-1 and A-2 were blended at a weight ratio of 1: 2, and then pre-concentrated and devolatilized by a twin-screw extruder with a vacuum vent to produce a block copolymer composition a -1 was obtained.

Block copolymer compositions a-2 to 8 were obtained by adjusting the addition amount and addition method of the styrene monomer, butadiene, and n-butyllithium solution by the above operation. Table 1 shows the obtained block copolymer resin composition (a).

The conjugated diene content of the block copolymer resin composition (a) shown in Table 1 was determined by adding a certain amount of iodine monochloride / carbon tetrachloride solution after dissolving the sample in chloroform, leaving it in the dark, It was determined by a so-called halogen addition method in which iodine monochloride was titrated with an alcoholic sodium thiosulfate normal solution and the amount of diene was calculated from the added iodine monochloride.

The molecular weight of the block copolymer resin composition (a) shown in Table 1 was measured using the following apparatus.
Device name: Tosoh HLC-8220GPC
Column used: Showa Denko product name ShodexGPCKF-404 in-line 4-column temperature: 40 ° C
Detection method: UV spectroscopy (254 nm)
Mobile phase: tetrahydrofuran Sample concentration: 2% by mass
Calibration curve: Standard polystyrene (manufactured by Polymer Laboratories)

  The peak of the loss tangent value (tan δ) of the block copolymer resin composition (a) shown in Table 1 is obtained under the conditions of 10 mm between chucks, frequency 1 Hz, and strain 0.1 using Rheometrics RSA-III. Then, stress and strain in the tensile direction were added, and the temperature range of −120 ° C. to 120 ° C. was measured while increasing the temperature at a rate of 4 ° C./min. The test piece was cured by compressing and forming a sheet (thickness 0.2 mm) using a hot press, and then storing the sheet in a room adjusted to 23 ° C. and relative humidity 50% RH for 24 hours or more. After the treatment, it was used for measurement.

Toyo styrene E640N made by Toyo Styrene is used as the rubber-modified vinyl aromatic hydrocarbon polymer (b) shown in Table 2, and Toyo Styrol G200C made by Toyo Styrene is used as the vinyl aromatic hydrocarbon polymer (c) shown in Table 3. Was used.

<Manufacture of film>
Each of the materials mixed in accordance with the formulation shown in Tables 4 to 5 was blown into an inflation film forming machine (screw diameter 50 mm, single axis, L / D = 28, ring die diameter 90 mm, lip opening 1 mm), and cylinder temperature 200 ° C. The tube was extruded at a discharge rate of 15 kg / h with the setting and the die temperature set at 200 ° C. Air was injected into the extruded tube, and at the same time, the air ring was cooled by applying cold air to the maximum diameter portion of the bubble to obtain a film having a thickness of 50 μm via a pinch roll. However, in Comparative Examples 4 to 6, the film forming property was poor and no film was obtained.

In Tables 4-5, the physical property was shown with the mixing | blending prescription of the raw material.

The thermal shrinkage was immersed in an oil bath at 120 ° C. for 10 seconds, calculated from the following formula, and evaluated according to the following evaluation criteria.
Thermal contraction rate = {(L1-L2) / L1} × 100
(However, L1: length before immersion (stretching direction), L2: length after contraction immersed in warm water of 120 ° C. for 10 seconds (stretching direction)).

The tear strength is measured in accordance with JIS K6854-3 by using a punching jig and measuring it at a test speed of 500 mm / min with a tensile tester. It was obtained by dividing. In addition, the amount of displacement until breakage was determined.

The haze was measured according to JIS K7136.

Example 7
<Lamination with polyolefin>
The block copolymer resin composition a-1 is used as an intermediate layer, and a prime polymer random polypropylene F329RA (MFR: 25 g / 10 min) is used as a front and back layer, and a layer ratio of 10/80/10 is extruded using a multilayer inflation film forming machine. A 50 μm film was prepared at a temperature of 230 ° C. The film properties of the obtained film are shown in Table 4.

Comparative Example 7
<Polyethylene film>
A mixture of 70% by mass of high density polyethylene (MFR: 1 g / 10 min) and 30% by mass of linear low density polyethylene (MFR: 2 g / 10 min) was extruded at the film forming machine used in Example 1. A single-layer film of 50 μm was prepared at 230 ° C. The film properties of the obtained film are shown in Table 5.

<Processing of packaging film>
The cylindrical films obtained in Examples 1 to 7, Comparative Examples 1 to 3, and Comparative Example 7 were slit to obtain packaging films.

<Manufacture of integrated packaging>
Six 500 ml PET bottles equipped with polystyrene shrink labels were arranged in 3 rows x 2 rows, and the outer periphery was covered with the packaging film of Example 1 of the present invention. At that time, both ends of the packaging film were overlapped at the bottom of the plastic bottle. After that, they were packed in a shrink tunnel with a line speed of 7.5 m / min. The shrinkage finish and binding property of the integrated package were good, and the appearance of the film was also good. Examples 2 to 7 were carried out under the same conditions, but similarly good packaging bodies were obtained. In Comparative Examples 1 to 3, the binding property was good, but the film was broken when the package was lifted. In addition, the polyethylene film of Comparative Example 7 had poor shrinkage and binding properties under the same temperature condition.

The molding material comprising the block copolymer resin composition of the present invention is suitably used as a heat shrink film for integrated packaging or bundle packaging.

Claims (6)

A molding material for a packaging film comprising a block copolymer composition (a) satisfying the following (i) to (iii), which is a copolymer composition of a vinyl aromatic hydrocarbon and a conjugated diene.
(I) Mass ratio of vinyl aromatic hydrocarbon to conjugated diene is 80/20 to 60/40
(Ii) A weight average molecular weight of 50,000 to 200,000
(Iii) At least one loss tangent peak obtained by dynamic viscoelasticity measurement is present at −30 ° C. or lower. The block copolymer composition (a) and at least one vinyl aromatic hydrocarbon polymer selected from the following (b) or (c) have a mass ratio of 100 / 0.5 to 60/40. A resin composition, characterized in that the content of the conjugated diene polymer of the block copolymer composition (a) in the resin composition is 20 to 39% by mass. Molding material for packaging film.
(B) Rubber-modified vinyl aromatic hydrocarbon polymer (c) Vinyl aromatic hydrocarbon polymer The molding material for packaging films according to claim 1 or 2, wherein the vinyl aromatic hydrocarbon is styrene and the conjugated diene is 1,3-butadiene. The packaging film which has the characteristics of (1)-(3) shape | molded using the molding material for packaging films as described in any one of Claims 1-3.
(1) The shrinkage in the longitudinal direction at 120 ° C. is 20% or more. (2) The tear strength is 50 N / mm or more, and the displacement until the break during the tear test is 10 mm or more. (3) The haze is less than 10%. The layer made of the molding material for packaging film according to any one of claims 1 to 3, and at least one layer made of at least one kind of polyolefin selected from an ethylene polymer or a propylene copolymer. And a packaging film having the characteristics of (1) to (3).
(1) The shrinkage in the longitudinal direction at 120 ° C. is 20% or more. (2) The tear strength is 50 N / mm or more, and the displacement until the break during the tear test is 10 mm or more. (3) The haze is less than 10%. A shrink wrapping body, which is tightly adhered to a package object by heat shrinkage using the wrapping film according to claim 4 or 5.