JP2011161880A - Heat-shrinkable polyolefinic film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyolefinic film that is free of delamination and has a good solvent bonding with an organic solvent. <P>SOLUTION: The heat-shrinkable polyolefinic film is obtained by stretching at least uniaxially a multi-layered film consisting of three layers; an intermediate layer and outer layers arranged on both the sides of the intermediate layer. The intermediate layer [A] is constituted of a resin component composed of 10-40 mass% of a cyclic olefinic resin, 10-40 mass% of a hydrogenated styrenic elastomer, and 35-70 mass% of a polypropylenic copolymer resin. The outer layers [B] are constituted of a resin component composed of 40-80 mass% of a cyclic olefinic resin, 10-40 mass% of a hydrogenated styrenic elastomer and 5-30% of a polypropylenic copolymer resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable polyolefin-based film, and more particularly to a heat-shrinkable polyolefin-based film suitable for label use for PET bottles.

  2. Description of the Related Art In recent years, shrink labels have been widely used for the purpose of label packaging and the like that serve to protect glass bottles or plastic bottles and display products in order to improve the appearance of packaged products. As plastic materials used for these purposes, polyvinyl chloride resins, polystyrene resins, polyester resins, polyolefin resins and the like are known.

  However, although the polyvinyl chloride resin label has excellent shrink characteristics, it has environmental problems such as generation of chlorine gas during combustion. A label using a polystyrene-based resin or a polyester-based resin has good heat shrinkability, but has a drawback that floating separation is difficult due to a small specific gravity difference from a PET bottle.

  A shrink label made of polyolefin has a large specific gravity difference from a PET bottle and can be floated and separated. However, since polyethylene and polypropylene cannot be bonded with a solvent, there is a drawback that a conventional cylindrical label manufacturing apparatus cannot be used. In order to eliminate this drawback, for example, it has been proposed to use a cyclic olefin resin (Patent Document 1). By using the cyclic olefin-based resin, not only the solvent adhesion is possible, but also the effect of increasing the heat shrinkage rate and improving the film rigidity can be obtained.

  However, the cyclic olefin-based resin has an effect of exhibiting solvent adhesiveness with an organic solvent, but has a hard and brittle property, and thus has a problem that the film is easily torn during secondary processing such as printing. In addition, when multiple layers are formed to improve shrinkage characteristics, problems such as easy delamination have occurred.

JP-A-8-165357

  The present invention has been made paying attention to the above-described problems, and an object thereof is to provide a heat-shrinkable olefin film having no delamination and good solvent adhesion with an organic solvent.

The heat-shrinkable polyolefin film according to claim 1 of the present invention is composed of three layers including an intermediate layer and outer layers provided on both sides of the intermediate layer.
The intermediate layer [A] is composed of a resin component consisting of 10 to 40% by mass of a cyclic olefin resin, 10 to 40% by mass of a hydrogenated styrene elastomer and 35 to 70% by mass of a polypropylene copolymer resin, and the outer layer [B ] At least a multilayer film composed of three layers comprising a resin component consisting of 40 to 80% by mass of a cyclic olefin resin, 10 to 40% by mass of a hydrogenated styrene elastomer and 5 to 30% of a polypropylene copolymer resin It is characterized by stretching in a uniaxial direction.

  The three layers consisting of the intermediate layer [A] and the outer layer [B] provided on both sides of the intermediate layer [A] are composed of resin components consisting of a cyclic olefin resin, a hydrogenated styrene elastomer and a polypropylene copolymer resin. The intermediate layer [A] and the outer layer [B] provided on both sides of the intermediate layer [A] have different blending ratios, so that heat shrinkability, printability, solvent sealability, recyclability due to low specific gravity, A heat shrinkable polyolefin film excellent in delamination resistance and the like can be obtained.

  The heat-shrinkable polyolefin film according to claim 2, wherein the total amount of the three layers of each resin component with respect to the total amount of the resin components of the three layers composed of the intermediate layer [A] and the two outer layers [B] is It is characterized by being 20-50 mass% of cyclic olefin resin, 10-40 mass% of hydrogenated styrene elastomer, and 40-65 mass% of polypropylene copolymer resin, respectively.

  By setting the total amount of the resin components of the three layers within a specific range, a heat-shrinkable polyolefin film excellent in low specific gravity, heat shrinkability, cost, and the like can be obtained.

  The heat-shrinkable polyolefin film according to claim 3 is characterized in that a ratio of the thickness of the intermediate layer [A] to the thickness of the entire heat-shrinkable polyolefin film is 50 to 80%.

  By increasing the thickness of the intermediate layer [A] having a large amount of the polypropylene copolymer resin, heat shrinkage characteristics, specific gravity, and the like are improved.

  The heat-shrinkable polyolefin film according to claim 4, wherein the hydrogenated styrene elastomer comprises a hydrogenated derivative of a copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon, and the content of the styrene hydrocarbon. Is 5 mass% or more and 50 mass% or less.

  By setting the content of the styrene hydrocarbon in the hydrogenated styrene elastomer within a specific range, the compatibility between the cyclic olefin resin and the polypropylene copolymer resin is improved, and the generation of fish eyes is reduced.

  The heat-shrinkable polyolefin film according to claim 5 has a heat shrinkage rate of 35% or more in the maximum shrinkage direction when the sample of the shrinkable polyolefin film is immersed in hot water at 100 ° C. for 10 seconds. It is characterized by.

  If the heat shrink rate of the heat shrinkable polyolefin film is 35% or more when immersed in hot water at 100 ° C. for 10 seconds, it follows the enveloping material when used as a heat shrinkable label. Good properties.

  Since the heat-shrinkable polyolefin film of the present invention has a small specific gravity, when used for a PET bottle label, the specific gravity difference from the PET bottle is large and floating separation is possible. Moreover, by setting the resin composition of the three layers constituting the heat-shrinkable polyolefin film to a specific range, it has excellent delamination resistance and heat-shrinkage characteristics, and does not break during printing or center seal processing. When a solvent such as cyclohexane or tetrahydrofuran is used as the adhesive solvent, the solvent adhesiveness is good and the center seal can be easily performed by a normal solvent adhesive method.

  The heat-shrinkable polyolefin film of the present invention comprises three layers comprising an intermediate layer and outer layers provided on both sides of the intermediate layer, each layer comprising a cyclic olefin resin, a hydrogenated styrene elastomer and a polypropylene copolymer resin. It is comprised with the resin composition which consists of.

  The cyclic olefin-based resin is a general generic name, and specifically, (a) a ring-opening (co) polymer of a cyclic olefin and (b) a ring-opening (co) polymer of a cyclic olefin are required. Accordingly, a hydrogenated polymer, (c) a random copolymer of a cyclic olefin and an α-olefin such as ethylene or propylene. Other examples include (d) graft modified products obtained by modifying (a) to (c) with an unsaturated carboxylic acid or a derivative thereof. These cyclic olefin-based resins may be used alone or in combination of two or more.

  Commercially available cyclic olefin-based resins may be used. For example, as a copolymer of cyclic olefin and ethylene, “TOPAS” (Topas Advanced Polymers GmbH), “Apel” (Mitsui Chemicals), cyclic olefin polymer "Zeonoa" (manufactured by Nippon Zeon) and the like. In addition, the above-described cyclic olefin-based resin may be used alone or in combination of two or more.

  The cyclic olefin-based resin as described above has an effect of increasing the heat shrinkage rate necessary for a heat-shrinkable film, increasing the rigidity (waist) of the film, and improving the adhesion with an organic solvent. On the other hand, since the cyclic olefin-based resin has a hard and brittle property, the film is easily broken during processing such as printing.

  The glass transition temperature of the cyclic olefin resin is preferably 50 ° C. or higher and 140 ° C. or lower, more preferably 60 ° C. or higher and 110 ° C. or lower. If the glass transition temperature is 50 ° C. or higher, the natural shrinkage rate can be reduced, and it is difficult to cause wrinkles and tarmi on the roll, and the occurrence of blocking due to tightening is suppressed, which is preferable. Moreover, if the glass transition temperature is 140 ° C. or less, the stretchability during film formation is good, thickness unevenness hardly occurs, and the appearance is also good.

  Next, the hydrogenated styrene elastomer comprises a hydrogenated derivative of a copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon, and is a random copolymer or block of a styrene hydrocarbon and a conjugated diene hydrocarbon. Examples include hydrogenated derivatives of copolymers. Examples of the styrene hydrocarbon include styrene, α-methyl styrene, 4-methyl styrene, 4-propyl styrene, 1-vinyl naphthalene, 2-vinyl naphthalene, and the conjugated diene hydrocarbon includes, for example, 1, 3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, phenylbutadiene and the like. One or more polymerization components can be used.

  The styrene content in the hydrogenated styrene-based elastomer is preferably 5 to 65% by mass, and more preferably 10 to 60% by mass. If the content of styrene is 5% by mass or more, the rigidity of the resulting film is high, and the resulting film tends to be strong. On the other hand, if it exceeds 65% by mass, the difference in average refractive index from the resin composition becomes large, so that the transparency of the resulting film is lowered and the effect of improving the impact characteristics is also lowered. End up.

  Specific examples include hydrogenated styrene-butadiene block copolymer (SEB), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), hydrogenated styrene-isoprene block copolymer (SEP), hydrogenated styrene- Examples include isoprene-styrene block copolymer (SEPS), hydrogenated styrene-butadiene random copolymer, styrene-ethylene-propylene random copolymer, styrene-ethylene-butylene random copolymer. Specific products include Dynalon (manufactured by JSR), Clayton G (manufactured by Kraton Polymer Japan), Tuftec (manufactured by Asahi Kasei Chemicals), Septon, and Hibler (manufactured by Kuraray). In addition, the above-described hydrogenated styrene elastomer may be used alone or in combination of two or more.

  By adding the hydrogenated styrene-based elastomer, compatibility between the cyclic olefin-based resin and the polypropylene-based copolymer resin is improved, and transparency and heat shrinkage characteristics are improved. Moreover, since the hydrogenated styrene-based elastomer plays a role as an elastic body, an effect of improving the impact resistance of the obtained film is also obtained.

  Next, examples of the polypropylene copolymer resin include a propylene-α-olefin random copolymer and a propylene-α-olefin block copolymer containing propylene as a main component. Here, examples of the α-olefin include α-olefins having 2 to 20 carbon atoms other than propylene, preferably ethylene, 1-butene, 1-hexene, 1-octene, and the like. It is also possible to use seeds. Preferred copolymers containing these include propylene-ethylene random copolymer, propylene-butene random copolymer, propylene-ethylene-butene random copolymer, propylene-butene copolymer, propylene-hexene copolymer, etc. These may be used alone or in combination of two or more thereof.

  The polypropylene-based copolymer resin is more preferably a propylene-α-olefin random copolymer because the heat shrinkability is improved because the crystallinity is lowered. As for content of the alpha olefin in this random copolymer, 2.0-30 mass% is preferable. In particular, when the α-olefin is ethylene, it is preferably 2.0 to 10% by mass, and more preferably 2.0 to 6.0% by mass. With such a content, since it has appropriate crystallinity, the shrinkage and the waist of the film at room temperature are particularly suitable.

  In addition, the melt flow rate (hereinafter abbreviated as “MFR”) of the polypropylene-based copolymer resin is a value measured at a load of 230 ° C. and 21.18 N according to JIS K 7210. 10 minutes is preferable, and 0.5 to 5 g / 10 minutes is more preferable. When the MFR is 0.4 g / 10 min or more, the load during extrusion does not become too high, and the productivity is stabilized. Moreover, if MFR is 20 g / 10min or less, the stable extending | stretching can be performed. A commercially available polypropylene copolymer resin can be used, and Wintech WFX4TA and Wintech WFX6 (manufactured by Nippon Polypro), which are polypropylene copolymer resins polymerized using a metallocene catalyst, are preferred.

  The polypropylene copolymer resin according to the present invention preferably has a crystal melting peak temperature measured by a differential scanning calorimeter of 100 to 150 ° C. Here, if the crystal melting peak temperature is less than 100 ° C., heat resistance may be insufficient. If it exceeds 150 ° C., stretching may be difficult, and heat shrinkability may also be reduced.

  The resin component of the intermediate layer [A] of the heat-shrinkable polyolefin film of the present invention is 10 to 40% by mass, preferably 15 to 35% by mass of cyclic olefin resin, and 10 to 40% by mass of hydrogenated styrene elastomer. , Preferably 15 to 35% by mass and polypropylene copolymer resin of 35 to 70% by mass, preferably 40 to 60% by mass.

  When the blending amount of the cyclic olefin resin is less than 10% by mass with respect to the resin component constituting the intermediate layer [A], the stiffness of the film is sufficiently strong. Moreover, since the specific gravity of a film becomes small enough if the compounding quantity of cyclic olefin resin is 40 mass% or less with respect to the resin component which comprises intermediate | middle layer [A], it is preferable.

  If the compounding amount of the hydrogenated styrene-based elastomer is 10% by mass or more based on the resin component constituting the intermediate layer [A] with respect to the resin component constituting the intermediate layer [A], the shrinkage, The impact resistance and delamination improvement effects are fully exhibited. Moreover, if the compounding quantity of hydrogenated styrene-type elastomer is 40 mass% or less with respect to the resin component which comprises intermediate | middle layer [A], the elasticity of the obtained film will become strong and natural shrinkage will be reduced. Have.

  If the polypropylene copolymer resin is 35% by mass or more with respect to the resin component constituting the intermediate layer [A], the specific gravity of the film is sufficiently small. Further, if the polypropylene copolymer resin is 70% by mass or less with respect to the resin component constituting the intermediate layer [A], the thermal shrinkage rate is excellent.

  Next, the resin component of the outer layer [B] of the heat-shrinkable polyolefin film of the present invention is 40 to 80% by mass, preferably 50 to 75% by mass of cyclic olefin resin, and 10 to 40 of hydrogenated styrene elastomer. It is composed of 5% by mass, preferably 15-35% by mass, and 5-30%, preferably 7-25% by mass of polypropylene copolymer resin.

  If the cyclic olefin-based resin is 40% by mass or more with respect to the resin component constituting the outer layer [B], the film has sufficient stiffness and sufficient solvent seal strength. Moreover, when the cyclic olefin resin exceeds 80% by mass with respect to the resin component constituting the outer layer [B], there is a drawback that the specific gravity of the film increases.

  If the compounding amount of the hydrogenated styrene elastomer is 10% by mass or more with respect to the resin component constituting the outer layer [B], the shrinkage, impact resistance, and delamination improving effects are sufficiently exhibited. Moreover, if the compounding amount of the hydrogenated styrene-based elastomer is 40% by mass or less with respect to the resin component constituting the outer layer [B], the resulting film has an advantage that the elasticity of the film is increased and the natural shrinkage is reduced. Have.

  When the blending amount of the polypropylene copolymer resin is 5% by mass or more with respect to the resin component constituting the outer layer [B], the interlayer adhesion is good. If the blending amount of the polypropylene copolymer resin is 30% by mass or less with respect to the resin component constituting the outer layer [B], sufficient sealing strength is ensured.

  The total amount of the three layers of each resin component relative to the total amount of the resin components of the three layers comprising the intermediate layer [A] and the two outer layers [B] constituting the heat-shrinkable polyolefin film of the present invention is cyclic. It is preferable to set it as the range of 20-50 mass% of olefin resin, 10-40 mass% of hydrogenated styrene-type elastomers, and 40-65 mass% of polypropylene copolymer resins.

  If the total amount of the cyclic olefin-based resin with respect to the total amount of the resin components of the three layers constituting the heat-shrinkable polyolefin-based film is 20% by mass or more, the heat shrinkage rate of the film will be sufficiently large, and if it is 50% by mass or less. The specific gravity of the film is sufficiently small.

  If the hydrogenated styrene-based elastomer is 10% by mass or more based on the total amount of the resin components of the three layers constituting the heat-shrinkable polyolefin-based film, the generation of fish eyes is suppressed, the interlayer adhesion is good, and 40% by mass. % Or less, the stiffness of the film is sufficient.

  If the polypropylene copolymer resin is 40% by mass or more with respect to the total amount of the resin components of the three layers constituting the heat-shrinkable polyolefin film, the specific gravity of the film is sufficiently small, and if it is 65% by mass or less, the film The heat shrinkage rate is sufficiently large.

  The thickness of the heat-shrinkable polyolefin film according to the present invention is not particularly limited, but is preferably 100 μm or less, more preferably 30 to 80 μm, considering the use as a label. In addition, the ratio of the total thickness of the two outer layers to the thickness of the entire heat-shrinkable polyolefin film is preferably in the range of 0.1 to 0.6, more preferably in the range of 0.15 to 0.5. If the ratio of the total thickness of the two outer layers to the thickness of the entire heat-shrinkable polyolefin film is 0.1 or more, sufficient solvent adhesive strength can be obtained when the outer layer is used as the solvent adhesive layer. In addition, it is preferable that the ratio of the total thickness of the two outer layers to the thickness of the entire heat-shrinkable polyolefin film is 0.6 or less because the outer layer portion having a large specific gravity does not increase excessively.

  The specific gravity of the heat-shrinkable polyolefin film according to the present invention, when used as a PET bottle label, is obtained by pulverizing a polyester resin having a large specific gravity and a heat-shrinkable polyolefin film label having a small specific gravity, and then using water to differentiate the specific gravity. It is desirable that it can be separated by Since printing is performed when used as a label, the specific gravity of the heat-shrinkable polyolefin film itself is 0.96 or less, preferably 0.95 or less.

  The heat-shrinkable polyolefin film of the present invention has a heat shrinkage rate of 35% in the maximum shrinkage direction when dipped in hot water at 100 ° C. for 10 seconds and then dipped in water at 25 ° C. for 10 seconds. That's it. The measurement and calculation of the heat shrinkage rate is based on the method described later. When the heat shrinkage rate is less than 35%, the label made of the heat shrinkable polyolefin film is insufficiently shrunk when the container is coated and shrunk. The thermal shrinkage is preferably 40% or more, more preferably 45% or more. The heat shrinkage can be achieved by a combination of the resin composition of the film, the layer structure of the film, and the stretching conditions described below.

  Moreover, the heat-shrinkable polyolefin film of the present invention has a natural shrinkage ratio of 2% or less, preferably 1.5% or less after storage for 1 week in a thermostatic bath maintained at 40 ° C. The measurement and calculation of the natural shrinkage rate are as described below. If the natural shrinkage is 2% or less, even if it has passed for a long time from the production of the heat-shrinkable polyolefin film to the secondary processing such as printing, as a result, it shows a large and even heat shrinkage, When attached to a container as a label, distortion of the film or printed pattern and insufficient follow-up to the container are unlikely to occur.

  In addition, although the structure of the heat-shrinkable polyolefin film according to the present invention is as described above, a known resin other than the above, an antioxidant, if necessary, as long as the object of the present invention is not impaired. A heat stabilizer, an antistatic agent, an antiblocking agent, a slip agent, a nucleating agent, an ultraviolet absorber, a colorant and the like can be appropriately contained. Of these, the addition of antistatic agents, anti-blocking agents, slip agents, etc. is particularly effective for improving anti-blocking properties. However, excessive addition inhibits solvent adhesion, so the amount added should be considered carefully. There is a need to.

  Next, a method for forming a heat-shrinkable polyolefin film according to the present invention will be described. The heat-shrinkable polyolefin film of the present invention is, for example, a film obtained by melt-extruding a resin raw material as described above at 220 to 250 ° C. by a T-die extrusion method at least twice in a uniaxial direction by a tenter stretching method, a roll stretching method, or the like. As described above, the film is produced by stretching by 3 times or more, more preferably by 4.5 times or more. The draw ratio in one axial direction is preferably 12 times or less, and more preferably 10 times or less. A necessary heat shrinkage rate can be secured by stretching at the draw ratio. The stretching method may be uniaxial stretching or biaxial stretching, but is preferably uniaxially stretched in a direction perpendicular to the flow direction of the film. In the case of biaxial stretching, it is preferable to stretch within a range of 1.1 to 2 times in a direction orthogonal to the main stretching direction. Prior to stretching, the film may be preheated, and the preheating temperature is preferably 80 ° C. or higher and 120 ° C. or lower. The stretching temperature is preferably from 70 ° C to 110 ° C. Further, the heat setting after stretching is preferably performed at 70 ° C. to 85 ° C., and the relaxation treatment during the heat setting is preferably in the range of 0 to 10%.

  Next, the configuration and operational effects of the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, and is appropriate within a range not departing from the gist of the preceding and following descriptions. It is also possible to carry out by modifying the above, and they are all included in the technical scope of the present invention. In addition, the measuring method of various characteristic values in this specification is as follows.

[specific gravity]
Based on JIS K7112-1999, the specific gravity of the film was determined from the ratio of the density of the film measured by the density gradient tube method and the density of water at a temperature of 23 ° C.

[Fish eye]
A sample of A4 size is taken from any part of the film and the size of the fish eye is confirmed.
○: The maximum diameter of the fish eye is less than 0.3 mm.
X: The maximum diameter of a fish eye is 0.3 mm or more.

[Solvent seal strength]
A sample having a main shrinkage direction of 300 mm × 100 mm in the direction perpendicular to the main shrinkage direction was taken from the film-formed film at an arbitrary position, and 10% by mass of cyclohexane and n-hexane 90 at positions 10 mm from both ends of the main shrinkage direction. A cylindrical label was prepared by solvent-sealing using a mixed solvent consisting of mass%, and a seal sample of the cylindrical label cut out at a width of 5 mm was used as a measurement sample. Both ends of the seal part were set in an “autograph type tensile tester” manufactured by Shimadzu Corporation, and evaluated at a tensile rate of 200 mm / min in a 180 ° peel test.
○: 50 g / 5 mm or more.
Δ: 20 g / 5 mm or more and less than 50 g / 5 mm.
X: Less than 20 g / 5mm.

[Delamination]
A cross-cut tape peeling test was conducted in accordance with JIS D0202-1988. Using cellophane tape ("CT24" manufactured by Nichiban), the film was adhered to the film with the belly of the finger and then peeled off. Judgment was evaluated by the number of squares that did not peel out of 100 squares.
○: The outer layer portion does not peel at all.
(Triangle | delta): Peeling of an outer-layer part is 1-49 or less places.
X: The peeling of the outer layer portion is 50 or more.

[Heat shrinkage]
The film is cut into a square of 100 mm × 100 mm so that one side is parallel to the film flow direction, and is immersed in a hot water tank maintained at 98 ± 2 ° C. for 10 seconds. Immediately after the elapse of 10 seconds, the film was immersed in a separately prepared 25 ° C. water bath for 10 seconds, and then the length of the film in the main shrinkage direction was measured.
Heat shrinkage rate (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)

[Natural shrinkage]
The film is cut into a 500 mm × 500 mm square so that one side is parallel to the film flow direction, and this is stored in a thermostatic bath maintained at 40 ° C. for one week, and then the length of the film in the main shrinkage direction is measured. Then, the natural shrinkage rate was obtained by the following formula.
Natural shrinkage (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)

The raw materials such as resins used in Examples and Comparative Examples are as follows.
COR-1: Cyclic olefin resin “TOPAS 8007” (manufactured by Polyplastics), ethylene-cyclic olefin copolymer resin, glass transition temperature 80 ° C., specific gravity 1.02, MFR 32 g / 10 min (260 ° C., 2.16 kg)
COR-2: Cyclic olefin resin “Apel APL6509T” (manufactured by Mitsui Chemicals), ethylene-cycloolefin copolymer resin, glass transition temperature 80 ° C., specific gravity 1.02, MFR 30 g / 10 min (260 ° C., 2.16 kg)
HSE-1: Hydrogenated styrene-based elastomer “HIBLER KL7350” (manufactured by Kuraray), styrene-ethylene-propylene-styrene block copolymer resin, specific gravity 0.95, MFR 22.8 g / 10 min (200 ° C., 10 kg)
HSE-2: Hydrogenated styrene elastomer “Septon S2007” (manufactured by Kuraray), styrene-ethylene-propylene-styrene block copolymer resin, specific gravity 0.91, MFR 4 g / 10 min (200 ° C., 10 kg)
PPC: Polypropylene copolymer resin “Wintech WFX6” (manufactured by Nippon Polypro), propylene-ethylene random copolymer resin produced with metathelon catalyst, specific gravity 0.9, MFR 3 g / 10 min (200 ° C., 10 kg)
PP: Polypropylene resin “F113G” (manufactured by prime polymer), polypropylene homopolymer, specific gravity 0.9, MFR 3 g / 10 min (200 ° C., 10 kg)
HPR: Hydrogenated petroleum resin “Alcon P140” (Arakawa Chemical Industries), specific gravity 0.999, melting point 140 ° C.
AOC: α-olefin copolymer resin “Toughmer BL2481” (manufactured by Mitsui Chemicals, flexibility, adhesion improver), butene-propylene copolymer resin, specific gravity 0.9, MFR 4 g / 10 min (190 ° C., 2.16 kg)

[Example 1]
In the outer layer, a resin composition obtained by mixing 70 parts by mass of a cyclic olefin resin “TOPAS 8007”, 20 parts by mass of a hydrogenated styrene elastomer “Hibler KL7350” and 10 parts by mass of a propylene copolymer resin “Wintech WFX6” In the intermediate layer, a resin composition in which 28 parts by mass of a cyclic olefin resin “TOPAS 8007”, 19 parts by mass of a hydrogenated styrene elastomer “Hibler KL7350” and 53 parts by mass of a propylene copolymer resin “Wintech WFX6” are mixed. Then, each was put into a separate extruder, co-extruded from a T-die at 240 ° C., cooled and solidified with a cooling roll maintained at 30 ° C., preheated at 90 ° C., and then longitudinally using a roll drawing machine. The film was stretched 5 times to obtain a flat heat-shrinkable polyolefin film. The stretched film had an outer layer of 7.5 μm, an intermediate layer of 35 μm, and a total thickness of 50 μm. The test results are shown in Table 1.

[Examples 2 to 5]
In the same manner as in Example 1, the outer layer and intermediate layer resin compositions shown in Table 1 were co-extruded from a T die, cooled and solidified with a cooling roll maintained at 30 ° C., preheated at 90 ° C., and then roll stretched. Using a machine, the film was stretched 3.5 times in the longitudinal direction to obtain a flat heat-shrinkable polyolefin film. The stretched film had an outer layer of 7.5 μm, an intermediate layer of 35 μm, and a total thickness of 50 μm. The test results are shown in Table 1.

  As can be seen from Table 1, the heat-shrinkable polyolefin films of Examples 1 to 5 are free from fish eyes and delamination and have good physical properties such as shrinkage.

[Comparative Examples 1-6]
In the same manner as in Example 1, the outer layer and intermediate layer resin compositions shown in Table 2 were coextruded from a T-die, cooled and solidified with a cooling roll maintained at 30 ° C., preheated at 90 ° C., and then a roll drawing machine. Was used and stretched 3.5 times in the longitudinal direction to obtain a flat heat-shrinkable polyolefin film. The stretched film had an outer layer of 7.5 μm, an intermediate layer of 35 μm, and a total thickness of 50 μm. The test results are shown in Table 2.

  As can be seen from Table 2, Comparative Examples 1 and 2 have defects in fisheye and delamination, and Comparative Example 3 has a defect in seal strength. Moreover, Comparative Examples 4-6 has the fault that a natural shrinkage rate exceeds 2%. Furthermore, since the specific gravity of Comparative Example 4 exceeds 0.96, when used as a label, the floating separation from the PET bottle is hindered. Further, Comparative Example 5 has a heat shrinkage rate of 32%, and when used as a heat shrinkable film, the followability to the container is poor.

[Comparative Example 7]
70 parts by mass of a cyclic olefin resin “TOPAS 8007”, 20 parts by mass of a hydrogenated styrene elastomer “Hibler KL7350” and 10 parts by mass of a propylene copolymer resin “Wintech WFX6” used for the outer layer of Example 1 were mixed. The resulting resin composition was extruded as a single layer from a T-die, cooled and solidified with a cooling roll maintained at 30 ° C., preheated at 90 ° C., and then stretched 3.5 times in the longitudinal direction using a roll stretching machine and flattened. A heat-shrinkable polyolefin film having a thickness of 50 μm was obtained. The test results are shown in Table 3.
This film was good with a heat shrinkage of 60% and a natural shrinkage of 0.78%. However, the film had poor solvent resistance, and the film was broken by the tension during high-speed printing. Since it exceeded 0.98, it was difficult to separate printed labels using water.

[Comparative Example 8]
28 parts by mass of a cyclic olefin resin “TOPAS 8007”, 19 parts by mass of a hydrogenated styrene elastomer “Hibler KL7350” and 53 parts by mass of a propylene copolymer resin “Wintech WFX6” used for the intermediate layer of Example 1 The mixed resin composition is extruded as a single layer from a T-die, cooled and solidified with a cooling roll maintained at 30 ° C., preheated at 90 ° C., and stretched 3.5 times in the longitudinal direction using a roll stretching machine. A flat heat-shrinkable polyolefin film having a thickness of 50 μm was obtained. The test results are shown in Table 3.
This film has a heat shrinkage ratio of 33% and a natural shrinkage ratio of 2.32%, which is inferior in shrinkage properties and has drawbacks such as insufficient sealing strength due to a solvent.

  Since the specific gravity of the heat-shrinkable polyolefin film of the present invention is small, when used for a PET bottle label, the specific gravity difference from the PET bottle is large and floating separation is possible. Therefore, PET bottles that are consumed in large quantities are recycled. Useful when using. Moreover, by setting the resin composition of the three layers constituting the heat-shrinkable polyolefin film to a specific range, it has excellent delamination resistance and heat-shrinkage characteristics, and does not break during printing or center seal processing. When a solvent such as cyclohexane or tetrahydrofuran is used as the adhesive solvent, it has good solvent adhesion and can be easily center-sealed by the usual solvent bonding method. Absent.

Claims (5)

It consists of three layers consisting of an intermediate layer and an outer layer provided on both sides of the intermediate layer,
The intermediate layer [A] is composed of a resin component consisting of 10 to 40% by mass of a cyclic olefin resin, 10 to 40% by mass of a hydrogenated styrene elastomer and 35 to 70% by mass of a polypropylene copolymer resin,
The outer layer [B] is composed of three layers composed of a resin component composed of 40 to 80% by mass of a cyclic olefin resin, 10 to 40% by mass of a hydrogenated styrene elastomer and 5 to 30% of a polypropylene copolymer resin. A heat-shrinkable polyolefin film, wherein the multilayer film is stretched in at least a uniaxial direction.   The total amount of the three layers of each resin component with respect to the total amount of the resin components of the three layers consisting of the intermediate layer [A] and the two outer layers [B] is 25 to 50% by mass of the cyclic olefin resin, respectively, and hydrogenated The heat-shrinkable polyolefin film according to claim 1, wherein the heat-shrinkable polyolefin film comprises 10 to 40% by mass of a styrene elastomer and 40 to 65% by mass of a polypropylene copolymer resin.   3. The heat-shrinkable polyolefin film according to claim 1, wherein a ratio of the thickness of the intermediate layer [A] to the thickness of the entire heat-shrinkable polyolefin film is 50 to 80%.   A resin in which the hydrogenated styrene elastomer is a hydrogenated derivative of a copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon, and the content of the styrene hydrocarbon is 5% by mass or more and 50% by mass or less. The heat-shrinkable polyolefin film according to any one of claims 1 to 3.   5. The thermal shrinkage rate in the maximum shrinkage direction when the sample of the shrinkable polyolefin film is immersed in hot water at 100 ° C. for 10 seconds is 35% or more. The heat-shrinkable polyolefin film described.