JP2001301102A - Heat-shrinkable laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable laminated film with a specific gravity less than 0.960 enhanced in printability and dimensional stability, using an olefinic resin. SOLUTION: The heat-shrinkable laminated film is obtained by providing an intermediate layer comprising a propylene resin, a petroleum resin and an adhesive resin between a surface layer and a back layer both of which comprises a styrenic resin to form a laminate. The thicknesses of the respective layers satisfy (surface layer + back layer)/intermediate layer = 1/1.5-1/6 and stretching the laminate at least unidirectionally by 2-8 times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable laminated film used for shrink wrapping, shrink-wrapping wrapping, shrinking labels and the like.

[0002]

2. Description of the Related Art Polyvinyl chloride resin is the most widely used heat-shrinkable film material widely used in shrink wrapping, shrink-wrapping wrapping, shrink labels for plastic containers, shatterproof packaging for glass containers, and cap seals. Well known. This is because a heat-shrinkable film made of a polyvinyl chloride-based resin is practically excellent in mechanical strength, rigidity, optical characteristics, shrinkage characteristics and the like, and has a low cost. However, from the environmental viewpoint that polyvinyl chloride resin generates by-products such as hydrogen chloride gas during combustion after disposal,
Materials that do not contain chlorine other than polyvinyl chloride resins are demanded. One such material is a styrene-based resin. The stretched film made of this styrene resin has high transparency, gloss, rigidity, and
Since it has excellent low-temperature shrinkage properties, it can be used as a heat-shrinkable film.

[0003]

[Problems to be solved by the invention] From the effective use of resources,
Waste plastics are recycled. At that time, a liquid specific gravity separation method utilizing a buoyancy difference with water is used as a method of separating plastics having different materials. When an attempt is made to separate a crushed product of a saturated polyester resin bottle such as polyethylene terephthalate coated with a heat shrinkable label made of a styrene resin using this method, the specific gravity of the saturated polyester resin is from 1.300 to 1 .500
And water, and the specific gravity of the styrene resin is 1.0
30-1.060, slightly heavier than water. For this reason, since both the saturated polyester resin and the styrene resin sink in water, it becomes difficult to separate the saturated polyester resin with high accuracy.

Generally, when printing is performed on the front or back surface of a heat-shrinkable film by a gravure printing method or the like, the specific gravity increases by the amount of printing. For this reason, when this heat-shrinkable film is used as a heat-shrinkable label for a bottle made of a saturated polyester resin, in order to separate it with high accuracy by the liquid specific gravity separation method at the time of recycling, the specific gravity after printing of the heat-shrinkable film is required. Is required to be determined so as to be less than 1.000. In consideration of the specific gravity of the printed portion, the specific gravity of the heat-shrinkable film is 0.96.
Must be less than 0.

As a material for a heat-shrinkable film having a specific gravity of less than 0.960, an olefin resin such as an ethylene resin or a propylene resin is exemplified. Among them, a stretched film made of a propylene-based resin is excellent in transparency and rigidity, and is disclosed in JP-A-49-99645 and JP-A-62-4.
No. 735 discloses a heat-shrinkable film having improved shrinkage characteristics by adding a petroleum-based resin to a propylene-based resin.

However, the heat-shrinkable packaging film is generally subjected to a printing treatment by a gravure printing method or the like on the front surface or the back surface, but the heat-shrinkable film made of an olefin resin has poor printability. Unfortunately, it is necessary to apply a surface treatment such as a corona discharge treatment to the film printing surface. In addition, the heat-shrinkable film made of the resin is liable to cause natural shrinkage (the film slightly shrinks at a slightly higher temperature than normal temperature, for example, in summertime before its original use), and lacks dimensional stability. . Therefore, an object of the present invention is to improve the printability and dimensional stability of a heat-shrinkable film using an olefin-based resin, and to reduce the specific gravity of the heat-shrinkable film to less than 0.960, so that the heat-shrinkable label is It is an object of the present invention to maintain the function and enable recycling, and to accurately separate a crushed product of a heat-shrinkable label and a crushed product of a saturated polyester resin bottle by a liquid specific gravity separation method.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to an intermediate between a propylene resin, a petroleum resin, and an adhesive resin between a front layer and a back layer made of a styrene resin. The layers are provided to form a laminate, and the thickness of each layer of the laminate is (front layer + back layer) / intermediate layer = 1 /
The ratio was 1.5 to 1/6, and the laminate was stretched at least uniaxially 2 to 8 times. As the intermediate layer, a layer made of a propylene-based resin, a petroleum-based resin, and an adhesive resin is used, and since each layer has a predetermined thickness, the specific gravity of the entire laminated film can be less than 0.960, and the Even when used as a label for a polyester resin bottle, accurate separation by the liquid specific gravity separation method is possible at the time of recycling. Further, since the surface layer and the back surface layer are made of a styrene-based resin, the printability and the dimensional stability are excellent, and the obtained laminate has a useful characteristic as a heat-shrinkable film.

[0008]

Embodiments of the present invention will be described below. The heat-shrinkable laminated film (hereinafter, referred to as “laminated film”) according to the present invention is an intermediate film composed of a propylene-based resin, a petroleum-based resin, and an adhesive resin between a front layer and a back layer composed of a styrene-based resin. A laminate is formed by providing layers, and this is stretched. The styrene-based resin used in the present invention is a styrene-based polymer containing a styrene-based monomer represented by the following general formula [A] as a main component.

[0009]

Embedded image

Here, in the formula, R1 represents a hydrogen or an alkyl group, and a methyl group is preferably selected. R2 represents hydrogen or an alkyl group, and an alkyl group having 1 to 5 carbon atoms is preferably selected. By using the styrene-based polymer as the surface layer and the back surface layer of the laminated film, good printability, film rigidity, and dimensional stability can be imparted to the laminated film of the present invention. Examples of the styrene-based monomer include styrene, α-methylstyrene, p-methylstyrene, and the like. The styrene-based polymer includes one or more of these styrene-based monomers. It is a polymer and / or a copolymer containing a copolymerizable monomer other than the styrene-based monomer. Examples of monomers copolymerizable with styrene monomers other than the styrene monomer include conjugated diene monomers and (meth) acrylate monomers.

Examples of the conjugated diene monomer include butadiene, isoprene, 1,3-pentadiene and the like, and one or more of these conjugated diene monomers are included. Further, a block copolymer of the styrene-based polymer and a copolymer containing a conjugated diene-based monomer and / or a copolymerizable monomer other than the conjugated diene-based monomer is used in the present invention. Styrene-based polymers to be used. The structure of the block copolymer and the structure of each block portion are not particularly limited, and examples of the structure of the block copolymer include a linear type and a star type. As the structure of each block portion, for example, a completely symmetric block,
There are asymmetric blocks, tetra blocks, tapered blocks, random blocks, and the like. Further, two or more kinds of block copolymers having different structures, molecular weights, and polymerization methods of the block copolymer and the block portion may be blended.

Among them, the most preferably used is a styrene-butadiene block copolymer (hereinafter abbreviated as "SBS") in which the styrene monomer is styrene and the conjugated diene monomer is butadiene. ). The resin is industrially produced in an extremely large number of types (different types of copolymers, different block structures, different molecular weights, etc.), and a plurality of different SBSs according to the required characteristics.
This is because various film characteristics can be easily controlled by combining. In the above block copolymer, the styrene content in the copolymer is 50 to 95% by weight.
And more preferably 60 to 90% by weight. If the styrene content is less than 50% by weight, the transparency and rigidity of the film,
The heat fusion resistance tends to decrease, and if it exceeds 95% by weight, the impact resistance of the film decreases, which is not preferable. Also,
The (meth) acrylate-based monomer is represented by the following general formula [B] and includes, for example, methyl (meth) acrylate,
Examples thereof include butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate. Here, the above (meth) acrylate indicates acrylate and / or methacrylate.

[0013]

Embedded image

Here, R ₃ represents hydrogen or an alkyl group, and a methyl group is preferably selected. R ₄ represents hydrogen or an alkyl group, and an alkyl group having 1 to 20 carbon atoms is preferably selected. A styrene- (meth) acrylate copolymer comprising one or more of these (meth) acrylate monomers and the styrene monomer is a styrene polymer used in the present invention. It is listed as.
In the styrene- (meth) acrylate copolymer, styrene is the most preferably used styrene monomer, and butyl acrylate is the (meth) acrylate monomer. The styrene content in the styrene-butyl acrylate copolymer is generally from 50 to 98% by weight, and more preferably from 75 to 95% by weight. If the styrene content is less than 50% by weight, the rigidity of the obtained laminated film is undesirably reduced. On the other hand, when the content exceeds 98% by weight, it is difficult to impart low-temperature shrinkage characteristics to the obtained laminated film.

The styrene-butyl acrylate copolymer is very useful for the purpose of imparting a low-temperature shrinkage property, improving strength and elasticity, and reducing costs. However, since the resin is hard and brittle, it is difficult to use the resin alone. However, the resin contains at least one block copolymer composed of a styrene monomer and a conjugated diene monomer. By blending more than one kind, it becomes possible to impart impact resistance to the laminated film. The above-mentioned block copolymer is a homopolymer such as a styrene monomer, for example, styrene, α-methylstyrene, p-methylstyrene, or a copolymer thereof, and / or a copolymer other than the styrene monomer. And a conjugated diene monomer,
For example, homopolymers such as butadiene, isoprene and 1,3-pentadiene, copolymers of these and / or copolymers comprising copolymer blocks containing copolymerizable monomers other than conjugated diene-based monomers It is.

The block copolymer most preferably used in the present invention is a styrene-based monomer in which the styrene monomer is styrene and the conjugated diene monomer is butadiene.
It is a butadiene block copolymer. The surface layer and the back surface layer of the laminated film of the present invention have an affinity with the resin composition constituting the intermediate layer for the purpose of strengthening the adhesion between the layers, as long as the object of the present invention is not hindered. It is more preferable to add an adhesive resin having a high viscosity. Examples of the propylene-based resin used in the present invention include propylene homopolymers such as isotactic polypropylene, and copolymers with α-olefins other than propylene. Examples of the α-olefin component used in the copolymer include ethylene, butene-1, pentene-1, 3-methyl-1-
Butene, hexene-1, 3-methyl-1-pentene, 4
-Methyl-1-pentene, heptene-1, octene-
And α-olefins having 2 to 20 carbon atoms such as 1, nonene-1, decene-1, dodecene-1, tetradecene-1, hexadecene-1, octadecene-1, and eicosene-1. Species or two or more are included in the copolymer. Among them, α- having 2 to 8 carbon atoms
A copolymer with an olefin is preferable, and examples thereof include an ethylene-propylene copolymer, a propylene-butene copolymer, an ethylene-propylene-butene terpolymer, a propylene-hexene copolymer, and a mixture thereof.

The melting point of the propylene resin measured by a differential scanning calorimeter is preferably at most 160 ° C., more preferably from 130 to 145 ° C. If the temperature is lower than 130 ° C., the rigidity of the obtained laminated film decreases, and the film becomes less rigid, which is not preferable. On the other hand, when the temperature exceeds 160 ° C., it is difficult to perform low-temperature stretching of the obtained laminated film,
In some cases, good low-temperature shrinkage characteristics cannot be obtained, and shrinkability at high temperatures also decreases. Further, the propylene resin has a melt flow index (hereinafter abbreviated as “MI”) of 0.2 at a temperature of 230 ° C. and a load of 2.16 kg.
5 to 20 g / 10 min is preferable, and 1 to 10 g / 10 min is more preferable. When MI is less than 0.5 g / 10 minutes,
Extrusion load during melt extrusion may increase,
If it exceeds 20 g / 10 minutes, the stretching stability may decrease.

Examples of the petroleum resin used in the present invention include aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, rosin derivatives, terpene resins, terpene phenol resins and the like, and hydrogenated products thereof. The use of hydrogenated hydrocarbon resins is preferred. For example, as a commercial product,
"Alcon" (manufactured by Arakawa Chemical Industries, Ltd.) and "Clearon" (manufactured by Yashara Chemical Co., Ltd.) are exemplified. The softening point of these petroleum resins is preferably 110 ° C or higher, more preferably 120 to 150 ° C. Softening point is 11
If the temperature is lower than 0 ° C., natural shrinkage of the obtained laminated film may increase, which is not preferable.

The mixing ratio of the petroleum resin in the intermediate layer of the laminated film of the present invention is preferably 5 to 40% by weight, more preferably 10 to 30% by weight, based on the whole resin mixture constituting the intermediate layer. When the compounding amount of the petroleum resin is less than 5% by weight, good low-temperature shrinkage characteristics are not likely to be obtained. When the compounding amount exceeds 40% by weight, the specific gravity of the obtained laminated film is 0.960 or more. When the printed film is used for covering a saturated polyester resin bottle, it may be difficult to accurately separate the recycled film by the liquid specific gravity separation method during recycling.

The above-mentioned adhesive resin is a resin used for improving the adhesion between the above-mentioned intermediate layer and the front and back layers. Examples of the adhesive resin include a modified olefin-based resin containing one or more selected from unsaturated carboxylic acids, unsaturated carboxylic esters, unsaturated carboxylic anhydrides and vinyl acetate, a nylon-based resin, Polyester resin, styrene-butadiene block copolymer or styrene-isoprene block copolymer (hereinafter, referred to as
Abbreviated as "SIS". ), And a styrene-based resin such as a hydrogenated product of the block copolymer, a modified product modified with an unsaturated carboxylic acid or a derivative thereof, a styrene-ethylene graft copolymer, a styrene-ethylene random copolymer, and the like. . Among these, the use of a modified olefin-based adhesive resin and a styrene-based adhesive resin is preferred.

The above-mentioned modified olefin-based adhesive resin is one or more compounds selected from unsaturated carboxylic acids, unsaturated carboxylic esters, unsaturated carboxylic anhydrides and vinyl acetate, and an olefin-based monomer. Copolymer with the body,
Or it is a graft copolymer. Examples of the olefin monomer include ethylene and propylene. Examples of the unsaturated carboxylic acid include acrylic acid and methacrylic acid. Examples of the unsaturated carboxylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and stearyl (meth) acrylate. Acrylate, glycidyl (meth) acrylate and the like can be mentioned. Here, the above (meth) acrylate indicates acrylate and / or methacrylate. Further, as the unsaturated carboxylic anhydride,
For example, maleic anhydride and the like can be mentioned.

The styrene-based adhesive resin is a block copolymer of a styrene-based polymer block and a polymer block composed of a copolymerizable monomer other than the styrene-based monomer. A block copolymer comprising a block and a conjugated diene-based polymer block, a hydrogenated block copolymer obtained by partially or completely hydrogenating a conjugated diene-based polymer block of the block copolymer, or the hydrogenated block copolymer Modified products obtained by modifying a polymer with an unsaturated carboxylic acid or a derivative thereof can be given. In the styrene-based polymer block of the block copolymer, for example, homopolymers such as styrene, α-methylstyrene and p-methylstyrene, copolymers thereof and / or copolymerizable materials other than styrene-based monomers can be used. And copolymers containing various monomers in the block. Further, the conjugated diene-based polymer block includes a homopolymer such as butadiene, isoprene, 1,3-pentadiene, a copolymer thereof, and / or a monomer copolymerizable with the conjugated diene-based monomer. And a copolymer contained therein. Among them, those preferably used are hydrogenated SBS and hydrogenated SIS, and are usually styrene-ethylene-butylene-styrene block copolymer (hereinafter abbreviated as “SEBS”) and styrene. -Ethylene-
It is referred to as a propylene-styrene block copolymer and is commercially available, for example, under the trade names of "Clayton G" of Shell Chemical Co., Ltd., "Tuftec" of Asahi Kasei Corporation, "Septon" of Kuraray Co., Ltd.

The structure of the block copolymer and the structure of each block portion are not particularly limited, and examples of the structure of the block copolymer include a linear type and a star type. As the structure of each block portion, for example, a completely symmetric block,
There are asymmetric blocks, tetra blocks, tapered blocks, random blocks, and the like. The styrene content in the block copolymer used for the intermediate layer is 10 to 75% by weight.
And more preferably 30 to 70% by weight. When the styrene content is less than 10% by weight, the effect as an adhesive resin is hardly obtained, and when it exceeds 75% by weight, the transparency of the obtained laminated film may be reduced. The mixing ratio of the above-mentioned adhesive resin in the intermediate layer of the laminated film of the present invention depends on the styrene content in the adhesive resin used, but is 5 to 50% by weight based on the whole resin mixture constituting the intermediate layer.
And more preferably 10 to 40% by weight. When the mixing ratio of the adhesive resin is less than 5% by weight, the effect as the adhesive resin is hardly exhibited, and when it is more than 50% by weight, the specific gravity of the obtained laminated film easily exceeds 0.960. Become.

The intermediate layer of the laminated film of the present invention may contain an ethylene-α-olefin copolymer and an ethylene-vinyl acetate copolymer in addition to the resin composition described above, as long as the object of the present invention is not hindered. A polymer, an ionomer resin and the like may be mixed and used. In addition, to each of the above resins, if necessary, a plasticizer, an ultraviolet absorber, a light stabilizer, an antioxidant, a stabilizer, a colorant, an antistatic agent, a lubricant, and an inorganic filler may be appropriately added. it can. The thickness of each layer of the laminated film is (front layer + back layer) / intermediate layer = 1 / 1.5
〜 To ６ is preferred, and ２〜 to ５ is preferred. If this value is less than 1/6, the resulting laminated film will have a large natural shrinkage, which may result in a film lacking dimensional stability, which is not practically preferable. On the other hand, when it is larger than 1 / 1.5, the specific gravity of the laminated film tends to be 0.960 or more. Generally, it is desirable that the natural shrinkage of the heat shrinkable film be as small as possible,
For example, if it is less than 2% under conditions of 30 ° C. and about 30 days, there is no practical problem.

The production of the above-mentioned laminated film is not particularly limited. For example, a method in which the above-mentioned front surface layer, back surface layer and intermediate layer are melted by separate extruders, laminated in a die and extruded. Is mentioned. As the extrusion method, any method such as a T-die method and a tubular method can be adopted. The melt-extruded laminated resin is cooled by a cooling roll, air, water, etc., then heated again by a suitable method such as hot air, warm water, infrared ray, microwave, etc., by a roll method, a tenter method, a tubular method, etc. It is stretched uniaxially or biaxially. The stretching temperature varies depending on the softening temperature of each of the resins constituting the laminated film and the use required for the laminated film, but is preferably 60 to 130 ° C, and is preferably 80 to 120 ° C.
Is preferred. When the temperature is lower than 60 ° C., the elastic modulus of the material in the stretching process becomes too high, and the stretchability is lowered, and the stretching tends to be unstable, for example, causing breakage of the film or uneven thickness. When the temperature exceeds 130 ° C., desired shrinkage characteristics are not exhibited, or the elastic modulus of the material in the stretching process is too low, and the material hangs down by its own weight, and the stretching itself becomes impossible.

The stretching ratio is preferably 2 to 8 times, depending on the composition of the laminated film, the stretching means, the stretching temperature, and the desired product form. Whether to use uniaxial stretching or biaxial stretching is determined depending on the intended use. In the case of uniaxial stretching, it is also effective to provide a weak stretching of about 1.01 to 1.8 times in the machine direction for the purpose of improving the mechanical properties of the film. It is also important to provide rapid cooling within a time period in which the molecular orientation of the laminated film after stretching does not relax, in order to impart shrinkage. The stretched laminated film must have a heat shrinkage of at least 10% in one direction for 10 seconds in warm water at 80 ° C. 10
%, A practical function as a heat-shrinkable film may not be exhibited.

Usually, the transparency required of the heat-shrinkable film is preferably 10% or less, more preferably 7% or less, further preferably 5% or less in all hazes. If the film has a total haze of more than 10%, the clear display effect is undesirably reduced. Printing can be performed on the front or back surface of the stretched laminated film by any method such as a gravure printing method, a flexographic printing method, and an offset printing method. At this time, the ratio of the density of the laminated film to water, that is, the specific gravity, is increased by the amount of printing. When the laminated film is used as a covering material of a saturated polyester resin bottle, considering the use of a liquid specific gravity separation method utilizing a buoyancy difference with respect to water during recycling, the specific gravity of the entire laminated film before printing is , Less than 0.960, and preferably 0.900 to 0.959. This allows
After the printing process, the specific gravity of the entire laminated film is 1.000.
And the saturated polyester resin and the resin constituting the laminated film can be separated with high precision.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. In addition, the measurement value and evaluation shown in an Example were performed as follows. Here, the take-up (flow) direction of the laminated film is referred to as a “longitudinal” direction, and the direction perpendicular thereto is referred to as a “lateral” direction.

(1) Thermal Shrinkage The laminated film was cut into a size of 100 mm in length and 100 mm in width, immersed in a hot water bath at 80 ° C. for 10 seconds, and the shrinkage was measured. The heat shrinkage rate was represented by a ratio (%) of the shrinkage amount to the original size before shrinkage in the horizontal direction.

(2) Shrinkage finish A laminated film having grids printed at intervals of 10 mm,
It was cut into a size of 0 mm and 298 mm in width, and the both ends in the horizontal direction were overlapped by 10 mm and bonded using a 1/7 solution of tetrahydrofuran / cyclohexane or by heat sealing to form a cylinder. This cylindrical laminated film was mounted on a cylindrical PET bottle having a capacity of 1.5 liters, and passed through a shrinking tunnel of 3 m by steam heating for 10 seconds without rotating. The blown steam temperature was 97 ° C, and the atmosphere temperature in the tunnel was 87 to 95 ° C. After coating of the film, the size and number of wrinkles, avatars, and strains generated were comprehensively evaluated. The evaluation criteria were as follows: wrinkled, no avatar, lattice distortion was practically no problem, and film adhesion was good. ○, wrinkled, avatar, lattice distortion was noticeable, or insufficient shrinkage was noticeable. Those having problems in practical use were marked with "x".

(3) Natural Shrinkage Rate The film was cut into a size of 100 mm in the vertical direction and 1,000 mm in the horizontal direction, left in a constant temperature bath at 30 ° C. for 30 days, and shrunk in the horizontal direction with respect to the original size before shrinkage. (%).

(4) Total Haze A total thickness was measured at a film thickness of 70 μm using a reflection / transmittance meter HR-110 (Murakami Color Research Laboratory Co., Ltd.) in accordance with JIS K7105.

(5) Tensile modulus Using an Intesco Precision Universal Material Testing Machine Model 205 (manufactured by Intesco Corporation), the tensile temperature was measured in the longitudinal direction at an ambient temperature of 23.
A film test piece having a width of 5 mm was subjected to a tensile test at a tensile speed of 5 mm / min at 300 ° C. and a chuck-to-chuck distance of 300 mm to create a tensile stress-strain curve. Tensile modulus is the tensile stress minus
Using the straight line portion at the beginning of the distortion curve, it was calculated by the following equation. E = σ / ε E: Tensile modulus σ: Difference in stress per unit area (average cross-sectional area of sample before tensile test) between two points on a straight line ε: Difference in strain between the same two points

(6) Specific gravity The specific gravity of the film was calculated from the ratio of the density of the film measured by the density gradient tube method to the density of water at a temperature of 23 ° C. in accordance with JIS K7112.

Example 1 Density 0.890 g / c
m ³ , MI 4 g / 10 min (230 ° C., load 2.16 k
g) of ethylene-propylene-butene terpolymer (Adsyl5C30F, manufactured by Montell Co., Ltd.) at 56% by weight and an alicyclic saturated hydrocarbon resin having a softening point of 125 ° C. (manufactured by Arakawa Chemical Industries, Ltd .: Alcon P-) 125) SEBS (Asahi Chemical Industry Co., Ltd.) obtained by completely hydrogenating a block copolymer comprising 14% by weight, 40% by weight of styrene and 60% by weight of butadiene.
Manufacture: Tuftec H1051) 30% by weight was melt-kneaded using a co-rotating twin screw extruder to obtain pellets. The obtained pellets were put into a 65 mmφ single screw extruder for forming an intermediate layer and melt-kneaded at 180 to 240 ° C.

Also, a styrene-butadiene block copolymer (Asaflex 825, manufactured by Asahi Kasei Kogyo Co., Ltd.) was placed in a 40 mmφ single screw extruder for forming a front layer and a back layer, and heated at 180 to 220 ° C. It was melt-kneaded. Then, the ratio of the thickness of each layer is as follows: surface layer: intermediate layer: backside layer = 1:
The extrusion rate of each extruder was set so that the ratio became 6: 1.
Coextrusion was performed downward from a three-layer die maintained at 0 ° C. After cooling the obtained laminate, it was stretched 4.0 times in the transverse direction in a tenter stretching facility manufactured by Mitsubishi Heavy Industries, Ltd. in a 95 ° C. temperature atmosphere to obtain a 70 μm-thick laminated film. The specific gravity of the obtained laminated film was 0.947. In addition, the characteristics of the obtained laminated film were evaluated. Table 1 shows the results. The heat shrinkage in the transverse direction of this film was 34%, the total haze was 4.1%, and the natural shrinkage was 1.9%. As for the state of the shrink finish, there was no wrinkled avatar, there was no practical problem with shrinkage spots such as lattice distortion, and the adhesion of the film was good.

Example 2 Styrene described in Example 1
50% by weight of butadiene block copolymer is added to styrene-
50% by weight of a butyl acrylate copolymer (manufactured by A & M Polystyrene Co., Ltd .: SC004) was added in an amount of 50% by weight, and the mixture was melt-kneaded using a co-directional twin screw extruder to obtain pellets. The obtained pellets are subjected to 40 m for forming a front layer and a back layer.
A laminated film was obtained in the same manner as in Example 1, except that the mixture was placed in an mφ single screw extruder and melt-kneaded at 180 to 220 ° C. The specific gravity of the obtained laminated film was 0.953. In addition, the characteristics of the obtained laminated film were evaluated. Table 1 shows the results. The heat shrinkage in the transverse direction of this film is 31%, the total haze is 4.0%, and the natural shrinkage is 1.8%.
And was good. As for the state of the shrink finish, there was no wrinkled avatar, there was no practical problem with shrinkage spots such as lattice distortion, and the adhesion of the film was good.

(Example 3) SEBS described in Example 1 was completely hydrogenated with a block copolymer composed of 30% by weight of styrene and 70% by weight of butadiene (SEA: ToughTech H1041 manufactured by Asahi Kasei Kogyo Co., Ltd.). A laminated film was obtained in the same manner as in Example 2, except that the thickness ratio of each layer was changed to be front layer: intermediate layer: back layer = 1: 4: 1. The specific gravity of the obtained laminated film is 0.957.
Met. In addition, the characteristics of the obtained laminated film were evaluated. Table 1 shows the results. The heat shrinkage in the transverse direction of this film was as good as 30%, the total haze was 2.4%, and the natural shrinkage was 1.6%. As for the state of the shrink finish, there was no wrinkled avatar, there was no practical problem with shrinkage spots such as lattice distortion, and the adhesion of the film was good.

(Comparative Example 1) 80% by weight of the ethylene-propylene-butene terpolymer used in Example 1 and 20% by weight of an alicyclic saturated hydrocarbon resin were melt-kneaded using a coaxial twin-screw extruder. Then, a pellet was obtained. 6 pellets obtained
It was put into a 5 mmφ single screw extruder, melt-kneaded at 180 to 240 ° C., and extruded downward from a die. After cooling, the film was stretched 4.0 times in the transverse direction in the above tenter stretching equipment at a temperature of 95 ° C. to obtain a film having a thickness of 70 μm. The specific gravity of the obtained laminated film was 0.921. In addition, the characteristics of the obtained film were evaluated. Table 1 shows the results. The total haze value of this film is 2.
The film was good at 2%, but the heat shrinkage in the transverse direction was as low as 9%, and the natural shrinkage was 2.8%, and the film lacked dimensional stability. In the state of the shrinkage finish, there was clearly a part with insufficient shrinkage.

(Comparative Example 2) In Example 3, except that the extrusion rate of each extruder was set such that the ratio of the thicknesses of the respective layers was: front layer: intermediate layer: back layer = 1: 2: 1. A laminated film was obtained in the same manner as in Example 3. The properties of the obtained laminated film were evaluated. Table 1 shows the results. Although the total haze of this film was 2.1% and the natural shrinkage was 1.5%, it was excellent in transparency and dimensional stability, but had a specific gravity of 0.9.
The film was over 78 and 0.960. The finished shrinkage was free of wrinkles and avatars, had no practical shrinkage such as lattice distortion, and had good film adhesion.

[0041]

[Table 1]

[0042]

According to the present invention, the printability, dimensional stability, and low-temperature shrinkability of a heat-shrinkable film using an olefin resin are improved, and the specific gravity of the heat-shrinkable film is less than 0.960. Thereby, the function of the heat-shrinkable label can be maintained and recycled, and the pulverized product of the heat-shrinkable label and the pulverized product of the saturated polyester resin bottle can be accurately separated by the liquid specific gravity separation method.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 53/02 C08L 53/02 G09F 3/04 G09F 3/04 C // B29K 23:00 B29K 23:00 25:00 25:00 105: 02 105: 02 B29L 9:00 B29L 9:00 F term (reference) 4F100 AK02B AK07B AK12A AK12C AK12G AK25A AK25C AK28A AK28C AK28G AK64B AK67B AK73 AK80B AL01A AL01C AL05B AL00A GB15 JA13 JA20A JA20C YY00A YY00C 4F210 AA04G AA09 AA11 AA12E AA13 AA18 AA21G AA49 AE01 AG01 AG03 QA02 QC03 QG01 QG15 QG18 RC02 RG02 RG04 RG09 RG30 RG43 4J002 BC07X BP01W

Claims (7)

[Claims] An intermediate layer comprising a propylene-based resin, a petroleum-based resin, and an adhesive resin is provided between a front layer and a back layer made of a styrene-based resin to form a laminate. The thickness is (surface layer + back layer) / intermediate layer = 1 /
A heat-shrinkable laminated film having a thickness of 1.5 to 1/6, which is obtained by stretching the laminate at least 2 to 8 times in a uniaxial direction. 2. The propylene resin according to claim 1, wherein the propylene resin is an ethylene-propylene copolymer, a propylene-butene copolymer, an ethylene-propylene-butene terpolymer, or a propylene resin.
The heat-shrinkable laminated film according to claim 1, wherein the heat-shrinkable laminated film is one kind or a mixture of two or more kinds selected from hexene copolymers. 3. The heat-shrinkable laminate according to claim 1, wherein the styrene resin is one or more block copolymers composed of a styrene monomer and a conjugated diene monomer. the film. 4. The styrene-based resin comprises one or more block copolymers composed of a styrene-based monomer and a conjugated diene-based monomer, a styrene-based monomer and (meth) acrylic acid. 3. The heat-shrinkable laminated film according to claim 1, which is a mixture with a copolymer comprising an ester monomer. 5. A hydrogenated block copolymer obtained by partially or completely hydrogenating a block copolymer composed of a styrene-based polymer block and a conjugated diene-based polymer block. The heat-shrinkable laminated film according to any one of claims 1 to 4, wherein the heat-shrinkable laminated film is a mixture of one or more modified products obtained by modifying a polymer with an unsaturated carboxylic acid or a derivative thereof. 6. The adhesive resin according to claim 1, wherein the olefin monomer comprises one or more compounds selected from unsaturated carboxylic acids, unsaturated carboxylic esters, unsaturated carboxylic anhydrides and vinyl acetate. 5. A modified olefin resin which is a copolymer or a graft copolymer.
The heat-shrinkable laminated film according to the above. 7. The heat-shrinkable laminated film according to claim 1, wherein the specific gravity of the film is less than 0.960.