JP4964537B2 - Heat-shrinkable pore-containing film, molded product based on the film, heat-shrinkable label, and container - Google Patents

Description

  The present invention relates to a heat-shrinkable pore-containing film, a molded article using the film, a heat-shrinkable label, and a container equipped with these. More specifically, the present invention has a heat-shrinkable pore-containing film having a low bulk specific gravity and excellent printability, high rigidity, rupture resistance, and shrinkage characteristics, and a molded article, a heat-shrinkable label, and a film using the film. It relates to a container equipped with these.

  Conventionally, heat shrinkable films have been used for packaging and bundling applications such as containers. As a raw material for the heat-shrinkable film, polyvinyl chloride, polystyrene, polyester or the like is mainly used. Since all of these use petroleum resources as raw materials, if they are used continuously in the future, they may cause a problem of exhaustion of petroleum resources. These raw materials also have problems such as generating harmful gases during combustion after use, burning calories too high, damaging the combustion furnace and shortening the life of the furnace.

  As a material for solving these problems, polylactic acid that is derived from plants and can be industrially produced has recently attracted attention. That is, since polylactic acid uses corn or other biomass as a raw material, it is suitable for aiming at a sustainable society. Further, no harmful gas is generated during combustion, and the combustion calorie is low, so that the combustion furnace is not damaged.

  However, when polylactic acid is used as the material for the heat-shrinkable label, it has the characteristics of high rigidity, excellent low-temperature shrinkability and low spontaneous shrinkage, but there is a problem in fracture resistance. It has been difficult to produce quality heat-shrinkable labels.

  In order to improve the fracture resistance of polylactic acid, a heat-shrinkable film to which a soft component compatible with polylactic acid is added has also been proposed (for example, see Patent Document 1). This film can improve the rupture resistance problem to some extent by adding a soft component, but on the other hand, there is a problem that the rigidity is reduced and the natural shrinkage is increased.

  On the other hand, when a heat-shrinkable label is used for a PET bottle whose consumption is currently increasing, it is desirable that the heat-shrinkable label can be easily separated from the PET bottle from the viewpoint of recycling the used PET bottle. As a method for separating the heat-shrinkable label from the PET bottle, a liquid specific gravity separation method is used in which flakes of the PET bottle pulverized together with the heat-shrinkable label are put into water, and only PET flakes having a large specific gravity are submerged in water and recovered. It has been. However, since the bulk specific gravity of the heat-shrinkable label described in Patent Document 1 is greater than 1, the label also sunk in water together with the PET bottle flakes, making it difficult to separate.

  On the other hand, for the purpose of reducing the bulk specific gravity of the thermoplastic resin, a method is known in which an incompatible component is added and then stretched in one or more directions to form voids. Even in a film using a polylactic acid resin, a film having a reduced bulk specific gravity by stretching after adding an incompatible resin has been reported (for example, see Patent Document 2). However, this film cannot be used as a heat-shrinkable label because it is heat-treated after being stretched in the biaxial direction.

In addition, a heat-shrinkable film in which an incompatible resin is added to a polyester resin other than polylactic acid and then stretched to form pores has been proposed (see, for example, Patent Document 3). However, the polyester resin used in this heat-shrinkable film has a drawback that it is difficult to form pores at the time of stretching compared to polylactic acid.
JP 2003-119367 A JP 2002-146071 A JP 2003-321562 A

  This invention is made | formed in view of the said subject, The subject of this invention is small when a bulk specific gravity is small using a plant-derived polylactic acid-type resin, and when it is used as a label for PET bottles, it is easy. An object of the present invention is to provide a heat-shrinkable film that can be separated by liquid specific gravity, has high rigidity, rupture resistance, and shrinkage characteristics, and has small natural shrinkage.

  Another object of the present invention is to provide a heat-shrinkable label, a molded product and a container using the film suitable for applications such as shrink wrapping, shrink-bound wrapping and shrinkage labels.

  As a result of diligent studies focusing on polylactic acid resins and polyolefin resins, the present inventor can solve the above problems as long as the film has a layer in which polylactic acid resins and polyolefin resins are mixed at a predetermined ratio. As a result, the present invention has been completed.

That is, the object of the present invention is achieved by the following heat-shrinkable pore-containing film.
(I) layer composed of a mixed resin composition comprising the following A component and B component as main components, and the content of B component is 10 parts by mass or more and 90 parts by mass or less with respect to 100 parts by mass of A component; From the B component dispersed in the matrix composed of the A component in the (I) layer, having at least two layers (II) composed of a resin composition mainly composed of the following A component The aspect ratio of the dispersion domain in the direction perpendicular to the main shrinkage direction to the main shrinkage direction is 5 or more and 50 or less, and the thermal shrinkage rate in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is 20% or more. A heat-shrinkable pore-containing film, wherein
Component A: Polylactic acid resin composition comprising a copolymer of D-lactic acid and L-lactic acid Component B: Incompatible with component A, the storage elastic modulus at 80 ° C. measured at a vibration frequency of 10 Hz is 0. Polyolefin-based resin composition that is 25 GPa or more and 2.0 GPa or less

  For the heat-shrinkable pore-containing film of the present invention (hereinafter referred to as “the film of the present invention”), a polyolefin resin composition having a melt flow rate of 1.0 g / 10 min or more and 5.0 g / 10 min or less is used. It is preferable.

  The film of the present invention preferably has a bulk specific gravity of 0.50 or more and less than 1.00.

The film of the present invention preferably has a bulk specific gravity of less than 1.00 after heat shrinkage in the range of 25% or less.
Moreover, it is preferable that the tensile elasticity modulus of the film of this invention in the direction orthogonal to the main shrinkage direction is 1.2 GPa or more.

  Moreover, the film of this invention can be used as a base material of a molded article or a heat-shrinkable label.

  Moreover, the molded article or heat-shrinkable label of the present invention can be used by being mounted on a container.

  The film of the present invention has a layer in which a predetermined A component and a B component are mixed in a predetermined ratio, and in this layer, the aspect ratio of the B component in the A component is adjusted. An excellent rigidity, rupture resistance, and heat shrinkage characteristics can be imparted to the shrinkable pore-containing film, and the natural shrinkage rate can be reduced. Moreover, since the film of this invention has a lactic acid-type resin composition as a main component, it is useful when promoting the use of biomass and building a recycling-type society.

  In addition, since the film of the present invention has a bulk specific gravity of 0.50 or more and less than 1.00, it can be separated from a plastic for containers having a specific gravity of 1.0 or more by a liquid specific gravity method, and can be recycled. Excellent.

  Furthermore, since the film of the present invention is a laminate of the (I) layer containing pores and the (II) layer having a smooth surface, it is excellent in printability, bag-making sealability and designability. ing. Furthermore, since the film of this invention contains a void | hole, it is excellent also in heat insulation, light-shielding property, and cushioning properties.

Hereinafter, the film, heat-shrinkable label, molded product of the present invention, and a container equipped with the label or molded product will be described in detail.
In the present specification, “contains as a main component” is intended to allow other components to be included within a range that does not interfere with the action and effect of the resin constituting each layer. Furthermore, although this term does not restrict | limit a specific content rate, it is a component which occupies 70 mass% or more of the whole component of each layer, Preferably it is 80 mass% or more, More preferably, it is 90 mass% or more.

[Heat-shrinkable pore-containing film]
The film of the present invention comprises a (I) layer composed of a resin composition in which the following A component and B component are mixed, and a (II) layer composed of a resin composition mainly composed of the following A component: And a heat-shrinkable pore-containing film obtained by stretching an unstretched laminated film composed of at least two layers in at least one axial direction.

<(I) layer>
(A component)
The polylactic acid resin composition used as the component A includes a homopolymer of lactic acid (specifically, a homopolymer of a structural unit of L-lactic acid or D-lactic acid (that is, poly (L-lactic acid) or poly (L D-lactic acid))), a copolymer having structural units having both L-lactic acid and D-lactic acid (that is, poly (DL-lactic acid)), and a mixture thereof (hereinafter referred to as “lactic acid resin”). The resin composition which has as a main component is mentioned. Furthermore, the polylactic acid-based resin composition includes L-lactic acid and D-lactic acid, and a lactic acid copolymer mainly composed of a copolymer of α-hydroxycarboxylic acid and / or diol component other than lactic acid and a dicarboxylic acid component. Polymers (hereinafter referred to as “lactic acid copolymers”) are also included. The copolymerization ratio in the copolymerization component is not particularly specified, but it is desirable to carry out the copolymerization at a ratio that does not exceed the mechanical properties of the lactic acid resin, particularly the Vicat softening point range described later. The lactic acid resin and lactic acid copolymer may be used alone or in combination.

  The lactic acid resin can be produced using a known polymerization method such as a condensation polymerization method or a ring-opening polymerization method. For example, when the condensation polymerization method is used, L-lactic acid, D-lactic acid, or a mixture thereof can be directly subjected to dehydration condensation polymerization to obtain a lactic acid-based resin having an arbitrary composition.

  In addition, when the ring-opening polymerization method (lactide method) is used, lactide, which is a cyclic dimer of lactic acid, is subjected to ring-opening polymerization in the presence of a predetermined catalyst using a polymerization regulator or the like as necessary. Thus, a lactic acid resin having an arbitrary composition can be obtained.

  Examples of the lactide include L-lactide, which is a dimer of L-lactic acid, D-lactide, which is a dimer of D-lactic acid, and DL-lactide, which is a dimer of D-lactic acid and L-lactic acid. Can be mentioned. By mixing and polymerizing these as required, polylactic acid having an arbitrary composition and crystallinity can be obtained.

  As the α-hydroxycarboxylic acid component constituting the lactic acid copolymer, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, Examples thereof include bifunctional aliphatic hydroxycarboxylic acids such as 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone, and valerolactone.

  Examples of the diol component used as the monomer of the lactic acid copolymer include ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the dicarboxylic acid component include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid.

  The composition ratio (copolymerization ratio) of D-lactic acid and L-lactic acid constituting the lactic acid resin or lactic acid copolymer is D-lactic acid / L-lactic acid = 1/99, preferably 3/97. Preferably it is 5/95, more preferably 8/92, most preferably 10/90 and 15/85, preferably 13/87, more preferably 12/88, even more preferably 10/90. Or 99/1, preferably 97/3, more preferably 95/5, even more preferably 92/8, most preferably 90/10, and 85/15, preferably 87/13, more preferably It is preferable to adjust to the range of 88/12, more preferably 90/10. It is preferable that the content of L-lactic acid or D-lactic acid is 99% by mass or less because the degree of crystallization can be suppressed to an appropriate range and shrinkage unevenness associated with crystallization can be reduced. Moreover, by setting the content to 85% by mass or more, sufficient pores can be formed, and a film having a desired bulk specific gravity can be obtained.

  The Vicat softening point of the polylactic acid-based resin composition is 50 ° C. or higher, preferably 55 ° C. or higher, and is 95 ° C. or lower, preferably 85 ° C. or lower. If the Vicat softening point of the polylactic acid-based resin composition is 50 ° C. or higher, natural shrinkage can be suppressed even if the resulting heat-shrinkable pore-containing film is left at a temperature slightly higher than room temperature (for example, indoor temperature in summer). . Moreover, if the Vicat softening point of a polylactic acid-type resin composition is 95 degrees C or less, low temperature extending | stretching can be implement | achieved at the time of extending | stretching a film, and a favorable shrinkage characteristic can be given to the obtained film.

  The polylactic acid resin composition has a weight average molecular weight of 50,000 or more, preferably 100,000 or more and 400,000 or less, preferably 250,000 or less. By setting the lower limit of the weight average molecular weight to 50,000, there is no problem such as inferior mechanical strength, and it is preferable, and by setting the upper limit of the weight average molecular weight to 400,000, the melt viscosity becomes high. This is preferable because it does not cause problems such as deterioration of molding processability.

  Representative examples of the commercially available polylactic acid-based resin composition include “Lacia” series manufactured by Mitsui Chemicals, Inc., “Nature Works” series manufactured by Nature Works LLC, and the like. .

  Moreover, the said polylactic acid-type resin composition can also contain a small amount of other copolymerization components for the purpose of improving heat resistance. Examples of such copolymer components include aromatic carboxylic acids such as terephthalic acid, aromatic diols such as ethylene oxide adducts of bisphenol A, and the like. Furthermore, A component can also contain a small amount of chain extenders, for example, a diisocyanate compound, an epoxy compound, an acid anhydride, etc. for the purpose of increasing the molecular weight.

  Furthermore, for the purpose of improving impact resistance and cold resistance, the polylactic acid resin composition is a lactic acid copolymer having a glass transition temperature (Tg) of 0 ° C. or lower, an aliphatic polyester resin, an aromatic polyester resin, Or you may contain aliphatic-aromatic polyester in the range of 70 mass parts or less with respect to 100 mass parts of polylactic acid-type resin.

  Specific examples of the lactic acid copolymer having a Tg of 0 ° C. or lower include α-hydroxycarboxylic acid components such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2- Examples include bifunctional aliphatic hydroxycarboxylic acids such as hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone, and valerolactone. It is done. Examples of the diol component include ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and the like. Examples of the dicarboxylic acid component include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid.

  Examples of commercially available lactic acid copolymers having a Tg of 0 ° C. or lower include, for example, trade name “Plamate” (Dainippon Ink Chemical Co., Ltd.) and trade name “GS-PLA” (Mitsubishi Chemical Corporation). Etc.

  Examples of the aliphatic polyester resins include PLA polyesters such as aliphatic polyesters obtained by condensing aliphatic diols and aliphatic dicarboxylic acids, aliphatic polyesters obtained by ring-opening polymerization of cyclic lactones, and synthetic aliphatic polyesters. Aliphatic polyester resins excluding the resin can be mentioned.

  Specific examples of the aliphatic polyester obtained by condensing the aliphatic diol and the aliphatic dicarboxylic acid include ethylene glycol, 1,4-butanediol, hexanediol, octanediol, cyclopentanediol, cyclohexanediol, 1 Of aliphatic diols such as 1,4-cyclohexanedimethanol or anhydrides or derivatives thereof, and aliphatic dicarboxylic acids such as succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, or anhydrides or derivatives thereof. Examples thereof include one obtained by selecting one or more of them from each other and performing condensation polymerization. At this time, a desired polymer can be obtained by jumping up with an isocyanate compound or the like as necessary.

  Specific examples of commercially available aliphatic polyesters include “Bionole” (manufactured by Showa Polymer Co., Ltd.).

  Specific examples of the aliphatic-aromatic polyester resin and aromatic polyester resin include aromatic diols or derivatives thereof, aliphatic dicarboxylic acids or derivatives thereof, and aromatics such as ethylene oxide adducts of bisphenol A. Examples include diols or derivatives thereof, terephthalic acid, isophthalic acid, orthophthalic acid, aromatic dicarboxylic acids such as 2,4-naphthalenedicarboxylic acid and paraphenyldicarboxylic acid or derivatives thereof, respectively, obtained by condensation polymerization. It is done. At this time, a desired polymer can be obtained by jumping up with an isocyanate compound or the like as necessary.

  Examples of the commercially available aliphatic-aromatic polyester resins or aromatic polyester resins include the trade name “Easter Bio” (manufactured by Eastman Chemicals) and the trade name “Ecoflex” (manufactured by BASF). Etc.

  In addition, as the aliphatic polyester obtained by ring-opening polymerization of cyclic lactones, one obtained by polymerizing one or more kinds of cyclic monomers selected from ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone, and the like is used. Can be mentioned. Furthermore, examples of the synthetic aliphatic polyester include copolymers of cyclic acid anhydrides such as succinic anhydride and oxiranes such as ethylene oxide and propylene oxide.

  Commercially available examples include the trade name “Cell Green” (manufactured by Daicel Chemical) and the trade name “Tone Polymer” (manufactured by Union Carbide Japan).

  The weight average molecular weights of the lactic acid copolymer having an Tg of 0 ° C. or less, the aliphatic polyester resin, the aromatic polyester resin, and the aliphatic-aromatic polyester resin are all 50,000 or more, preferably 100,000 or more, And it is desirable that it is in the range of 400,000 or less, preferably 250,000 or less. By setting the lower limit of the weight average molecular weight of these resins to 50,000, it is preferable that there is no problem such as poor mechanical strength. By setting the upper limit to 400,000, the melt viscosity is high. It is preferable that it does not cause problems such as deterioration of molding processability due to becoming too much.

(B component)
In the present invention, the B component is incompatible with the A component, and is measured by raising the temperature at a vibration frequency of 10 Hz, a strain of 0.1%, a spacing of 2.5 cm, and a heating rate of 1 ° C./min. Is a polyolefin resin composition having a storage elastic modulus at 80 ° C. of from 0.25 GPa to 2.0 GPa.

  In the present specification, “incompatible” means that when the mixed resin composition of the A component and the B component is observed using an optical device such as an electron microscope, the B component has a major axis or a short diameter in the A component. A state in which domains having an average diameter of 0.1 μm or more are formed. Examples of such polyolefin resins include polyethylene resins such as high density polyethylene, low density polyethylene, and linear low density polyethylene, polypropylene resins such as highly crystalline homopolypropylene and random polypropylene, polymethylterpene, or the like. Examples thereof include mixed resins.

  More specifically, as B-component commercial products, the trade names “Novatech HD, LD, LL”, “Kernel”, “Toughmer A, P” (Nippon Polyethylene Co., Ltd.), “Suntech HD, LD” are used as polyethylene resins. "(Asahi Kasei Life & Living Co., Ltd.)", "HIZEX" "ULTZEX" "EVOLUE" (Mitsui Chemicals Co., Ltd.), "Moretech" (manufactured by Idemitsu Kosan Co., Ltd.), "UBE polyethylene" "UMERIT" ( Ube Industries, Ltd.), “NUC polyethylene”, “Nack Flex” (manufactured by Nippon Unicar Co., Ltd.), “engage” (manufactured by Dow Chemical Co., Ltd.), and the like. Commercially available polypropylene resins include “Novatech PP”, “WINTEC”, “Toughmer XR” (manufactured by Nippon Polypro), “Mitsui Polypro” (manufactured by Mitsui Chemicals), “Sumitomo Noblen”, “Tough Selenium”. “Excellen EPX” (manufactured by Sumitomo Chemical Co., Ltd.), “IDEMITSU PP”, “IDEMITSU TPO” (manufactured by Idemitsu Kosan Co., Ltd.), “Adflex” “Adsyl” (manufactured by Sun Aroma Co., Ltd.), and the like. Moreover, "TPX" (made by Mitsui Chemicals, Inc.) is mentioned as a commercial item of a polymethylpentene resin. These can be used alone or in admixture of two or more.

  Since the polyolefin resin used as the B component has a specific gravity smaller than that of the polylactic acid resin composition used as the A component, the film containing the mixed resin composition of the A component and the B component is a film composed of the A component alone. Compared with the case, specific gravity can be made smaller.

  The B component has a storage elastic modulus at 80 ° C. when measured by raising the temperature from 40 ° C. to 150 ° C. at a vibration frequency of 10 Hz, a strain of 0.1%, a gap of 2.5 cm, and a heating rate of 1 ° C./min. It is 0.25 GPa or more, preferably 0.40 GPa or more and 2.00 GPa or less. If the storage elastic modulus is 0.25 GPa or more, pores can be imparted to the film in the stretching step described later, and if the storage elastic modulus is 2.00 GPa or less, the desired crystallinity is obtained and the specific gravity is also high. Since it can be made relatively small, it is easy to obtain a film having a desired bulk specific gravity.

  Since the B component is incompatible with the A component, a sea-island structure is formed in the (I) layer where both components are mixed. As will be described later, in the (I) layer of the film of the present invention, since there is more A component than B component, the A component forms the sea part, that is, the matrix, and the B component forms the island part, that is, the dispersion domain. To do. Details will be described later.

  (I) A layer consists of a mixed resin composition which mixed B component 10 mass part or more and 90 mass parts or less with respect to said A component 100 mass part. The content of the B component is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and 90 parts by mass or less, more preferably 80 parts by mass or less, with respect to 100 parts by mass of the A component. is there.

  In the (I) layer, the mixed resin composition in which the A component and the B component are mixed contains the A component more than the B component as described above. Therefore, the A component forms a matrix and the B component forms a dispersion domain. To do. Therefore, the (I) layer forms a sea-island structure and is stretched to cause peeling at the interface between the matrix and the dispersion domain, thereby forming voids. If content of B component is 10 mass parts or more, a void | hole can be formed in (I) layer and the bulk specific gravity of the film after extending | stretching can be suppressed to less than 1.0. On the other hand, if content of B component is 90 mass parts or less, a sea-island structure can be formed in (I) layer, and the film which has a favorable mechanical characteristic and fracture resistance can be obtained.

(filler)
The film of the present invention can form pores by containing the A component and the B component, thereby suppressing light transmittance (that is, imparting light-shielding properties), but further filling. The light transmittance can be further suppressed by containing an agent (hereinafter also referred to as “C component”).

  Component C may be either an inorganic filler or an organic filler as long as it can impart light-shielding properties to the film. Inorganic fillers include calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, aluminum hydroxide, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide , Titanium oxide, alumina, mica, asbestos powder, shirasu balloon, zeolite, silicate clay and the like, and calcium carbonate, talc, clay, silica, diatomaceous earth, barium sulfate and the like are particularly preferable. Examples of the organic filler include cellulose powders such as wood powder and pulp powder. These may be used alone or as a mixture of two or more.

  The component C preferably has a large difference in refractive index from the component A as the base resin constituting the film, that is, an inorganic filler having a large refractive index. Specifically, calcium carbonate, barium sulfate, titanium oxide, or zinc oxide having a refractive index of 1.6 or more is preferably used, and among these, titanium oxide is more preferably used. By using titanium oxide, it absorbs the wavelength in the ultraviolet region of 280 to 380 nm, which deteriorates the contents, so that the light shielding property of the film can be imparted with a smaller filling amount, and the effect is obtained even with a thin wall. be able to.

Examples of the titanium oxide include crystalline titanium oxides such as anatase type titanium oxide and rutile type titanium oxide. From the viewpoint of increasing the difference in refractive index from the base resin, titanium oxide having a refractive index of 2.7 or more is preferable. For example, a crystal form of rutile titanium oxide is preferably used.

  Among titanium oxides, it is possible to minimize the yellowness of the appearance by using high-purity titanium oxide. High-purity titanium oxide is titanium oxide that has a small light absorption ability for visible light, for example, a low content of colored elements such as vanadium, iron, niobium, copper, and manganese. In the present invention, the content of vanadium A titanium oxide having an amount of 5 ppm or less, preferably 3 ppm or less, more preferably 2 ppm or less is referred to as high-purity titanium oxide. From the viewpoint of reducing the light absorption ability of high-purity titanium oxide, it is preferable to reduce iron, niobium, copper, manganese, etc., which are other coloring elements contained in titanium oxide.

  In the (I) layer of the present invention, titanium oxide and other fillers can be used in combination. In addition, in order to improve dispersibility in resins other than the C component (that is, the A component and the B component), a silicone compound, a polyhydric alcohol compound, an amine compound, a fatty acid, and a fatty acid ester are formed on the surface of the C component. You may use what gave surface treatment by the above.

  Examples of the surface treatment agent include at least one selected from the group consisting of at least one inorganic compound selected from the group consisting of alumina, silica, zirconia, and the like, a siloxane compound, a silane coupling agent, a polyol, and polyethylene glycol. Various organic compounds can be used. Moreover, you may use combining these inorganic compounds and organic compounds.

  As for the size of component C, when titanium oxide is used, the particle diameter is 0.1 μm or more, preferably 0.2 μm or more, and 1 μm or less, preferably 0.5 μm or less in terms of equivalent circle diameter. When the particle diameter of titanium oxide is 0.1 μm or more in terms of equivalent circle diameter, the dispersibility in the mixed resin composition of component A and component B is good, and a homogeneous film can be obtained. Further, if the particle diameter of titanium oxide is 1 μm or less in equivalent circle diameter, the interface between the mixed resin composition of component A and component B and titanium oxide is densely formed, so that the light shielding property can be further improved. it can.

  The content of the C component contained in the (I) layer of the film of the present invention is 100% in the mixed resin composition of the A component and the B component, considering the light shielding properties, mechanical properties, productivity, etc. of the film. 1 part by weight or more, preferably 2 parts by weight or more, more preferably 5 parts by weight or more, 25 parts by weight or less, preferably 20 parts by weight or less, more preferably 15 parts by weight or less. is necessary. Since the film of the present invention has pores, the C component plays an auxiliary role in the light shielding function, so that if the content is 1 part by mass or more, it can sufficiently function as a light shielding film. . In addition, when the content of the C component is 25 parts by mass or less, functions necessary for the heat shrink film, rupture resistance, and shrinkage characteristics can be ensured.

(Soft component)
In the film of the present invention, it is preferable to add a soft component (hereinafter referred to as “D component”) for the purpose of further improving fracture resistance. Examples of such component D include aliphatic polyesters other than the above component A, aromatic aliphatic polyesters, copolymers of diol, dicarboxylic acid, and lactic acid resin, core-shell structure type rubber, ethylene-vinyl acetate copolymer ( EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene- (meth) acrylic acid copolymer (EAA, EMA), ethylene- (meth) methyl acrylate copolymer (EAMA, EMMA), styrene- Styrene elastomers such as isobutylene copolymer (SIS), styrene-butadiene copolymer (SBS), styrene-ethylene-butadiene copolymer (SEBS), and acid-modified SEBS are preferably used. Aliphatic polyesters other than ingredients, aromatic aliphatic polyesters, diols, dicarboxylic acids and lactic acid-based trees Copolymers of core-shell structure type rubbers, and ethylene - vinyl acetate copolymer (EVA) and the like are more preferably used.

  The content of component D is 5 parts by mass or more, preferably 10 parts by mass or more, and 70 parts by mass or less, preferably 50 parts by mass with respect to 100 parts by mass of the mixed resin composition of component A and component B. Part or less, more preferably 30 parts by weight or less. If the content of the D component is 5 parts by mass or more, the effect of adding the D component is obtained, and if it is 30 parts by mass or less, the shrinkage characteristics and the rigidity are not affected.

  In the layer (I), in addition to the mixed resin composition obtained by mixing the A component and the B component (the C component and the D component as necessary), the plasticity may be used as long as the effects of the present invention are not impaired. Additives such as an agent, a heat stabilizer, an antioxidant, a UV absorber, a light stabilizer, a pigment, a colorant, a lubricant, a nucleating agent, and a hydrolysis inhibitor can be included. In that case, an additive can be included at 10 mass parts or less with respect to the mass of a mixed resin composition, Preferably it is 5 mass parts or less.

<(II) layer>
The film of this invention has the (II) layer which does not contain a void | hole other than the said (I) layer containing a void | hole. By disposing the (II) layer in the (I) layer, it is possible to improve printability, solvent sealability and the like. Further, in the (I) layer and the (II) layer, the void formation / shrinkage characteristics can be adjusted within a preferable range by changing the copolymer ratio of the polylactic acid resin composition to be used.

  The (II) layer is a layer composed mainly of the polylactic acid resin composition which is the component A. Furthermore, the (II) layer has the purpose of improving interlaminar adhesion and reducing bulk specific gravity as long as it does not impair the properties required for the surface layer, such as printability, solvent sealability, and fusion resistance. A thermoplastic resin other than the polylactic acid-based resin composition can be included. Examples of thermoplastic resins other than the polylactic acid resin composition include polyolefin resins, polystyrene resins, acrylic resins, amide resins, aliphatic and / or aromatic polyester resins.

  In addition, the resin composition in the layer (II) includes, if necessary, a plasticizer, a heat stabilizer, an antioxidant, a UV absorber, a light stabilizer, a pigment, and a colorant as long as the effects of the present invention are not impaired. Additives such as lubricants, nucleating agents and hydrolysis inhibitors may be added.

<Layer structure of film>
The film structure of the present invention is not particularly limited as long as it has at least two layers of the (I) layer and the (II) layer. Here, “having at least two layers of (I) layer and (II) layer” is not only an embodiment in which (II) layer is laminated on one side or both sides adjacent to (I) layer, The case of having a third layer is included for the purpose of imparting improved adhesion, barrier properties, concealing properties, heat insulation properties, etc. between the (I) layer and the (II) layer. Preferably, an intermediate layer (I) layer and a surface layer (II) layer as a two or three layer structure ((II) layer / (I) layer / (II) layer), or an intermediate layer and a surface layer There are three types and five layers (such as (II) layer / adhesive layer / (I) layer / adhesive layer / (II) layer)).

  The thickness ratio of the (I) layer and the (II) layer may be set in consideration of the above-described effects, and is not particularly limited. For example, in the case of a film having a layer structure of (I) layer as the intermediate layer and (II) layer as the surface layer, the thickness ratio of the (II) layer to the total film thickness is 5% or more, preferably 10% or more, It is preferably 15% or more and 70% or less, preferably 50% or less, more preferably 45% or less, and most preferably 40% or less. The thickness ratio of the (I) layer to the total film thickness is 20% or more, preferably 25% or more, more preferably 30% or more, and 95% or less, preferably 90% or less, more preferably 85%. It is as follows.

For the purpose of improving the interlayer adhesion between the (I) layer and the (II) layer, when an adhesive resin layer mainly composed of an adhesive resin is provided between the two layers, the following (a), ( It is preferable to use an adhesive resin whose main component is at least one copolymer or resin selected from the group consisting of b) and (c).
(A) One unit selected from the group consisting of ethylene, vinyl acetate, acrylic acid, (meth) acrylic acid, ethyl (meth) acrylate, methyl (meth) acrylic acid, maleic anhydride, and glycidyl methacrylate (Hereinafter also referred to as “ethylene-based copolymer”)
(B) Copolymer of soft aromatic hydrocarbon and conjugated diene hydrocarbon or hydrogenated derivative thereof (c) Modified polyolefin resin

  First, the ethylene-based copolymer (a) will be described. Examples of the ethylene copolymer include ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) ethyl acrylate copolymer, ethylene -Methyl (meth) acrylic acid copolymer, ethylene-vinyl acetate-maleic anhydride terpolymer, ethylene-ethyl acrylate-maleic anhydride terpolymer, ethylene-glycidyl methacrylate copolymer, ethylene -Vinyl acetate-glycidyl methacrylate terpolymer, ethylene-ethyl acrylate-glycidyl methacrylate terpolymer. Among them, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene-methyl (meth) acrylic acid copolymer are used. It can be suitably used.

  The ethylene copolymer preferably has an ethylene unit content of 30% by mass to 90% by mass, and preferably 40% by mass to 80% by mass. If the content rate of an ethylene unit is 30 mass% or more, since the rigidity of the whole film can be maintained favorable, it is preferable. On the other hand, if the content of the ethylene unit is 90% by mass or less, the flexibility can be sufficiently maintained, and when the stress is applied to the film, the buffer against the stress generated between the (I) layer and the (II) layer. Since the action works, delamination can be suppressed.

  The ethylene copolymer has an MFR (JIS K7210, temperature: 190 ° C., load: 21.18 N) of 0.1 g / 10 min or more, preferably 0.5 g / 10 min or more, and 10 g / 10 min or less. Preferably, 8.0 g / 10 min or less is suitably used. When the MFR is 0.1 g / 10 min or more, the extrudability can be maintained satisfactorily. On the other hand, when the MFR is 10 g / 10 min or less, the thickness unevenness of the laminated film and the mechanical strength are hardly lowered, which is preferable.

  The ethylene-based copolymer is an “ethylene-vinyl acetate-maleic anhydride terpolymer” as “Bondyne” (manufactured by Sumitomo Chemical Co., Ltd.), ethylene-glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl methacrylate tri “Bond First” (manufactured by Sumitomo Chemical Co., Ltd.) and the like are commercially available as an original copolymer, an ethylene-ethyl acrylate-glycidyl methacrylate terpolymer.

  Next, the copolymer (b) and the hydrogenated derivative thereof will be described. As the aromatic hydrocarbon constituting the copolymer of the soft aromatic hydrocarbon and the conjugated diene hydrocarbon, styrene hydrocarbon is preferably used, and styrene, o-methylstyrene, p-methylstyrene. , Styrene homologues such as p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene and vinylanthracene can also be used. Conjugated diene hydrocarbons are olefins having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl. Examples include -1,3-butadiene, 1,2-isoprene, 1,4-isoprene, 1,3-pentadiene, 1,3-hexadiene, and the like, and these may be hydrogenated derivatives. These may be used alone or in admixture of two or more.

  The above aromatic hydrocarbon and conjugated diene hydrocarbon copolymer or hydrogenated derivative thereof has an aromatic hydrocarbon content (preferably a styrene hydrocarbon content) of the total amount of the copolymer. 5% by weight or more, preferably 7% by weight or more, more preferably 10% by weight or more, and 50% by weight or less, preferably 40% by weight or less, more preferably 35% by weight or less. It is desirable to be. If the aromatic hydrocarbon content is 5% by mass or more, good compatibility is obtained when the recycled film is regenerated and added to the (I) layer. On the other hand, if the content of the aromatic hydrocarbon is 50% by mass or less, the (III) layer or the (II) layer is obtained when stress is applied to the film without reducing the flexibility of the (III) layer. Delamination can be suppressed since a buffering action against the stress generated between the two works.

  As a hydrogenated derivative of a copolymer of an aromatic hydrocarbon and a conjugated diene hydrocarbon, a hydrogenated derivative of a styrene-conjugated diene random copolymer can be preferably used. The detailed contents of the hydrogenated derivative of the styrene-conjugated diene random copolymer and the production method thereof are disclosed in JP-A-2-15843, JP-A-2-305814 and JP-A-3-72512. ing.

  As the aromatic hydrocarbon-conjugated diene hydrocarbon copolymer, each of the above-exemplified copolymers can be used alone or in admixture of two or more.

  Commercially available products of aromatic hydrocarbon-conjugated diene hydrocarbon copolymer include styrene-butadiene block copolymer elastomer as trade name “Tufprene” (manufactured by Asahi Kasei Co., Ltd.), hydrogenation of styrene-butadiene block copolymer Trade name “Tuftec H” (manufactured by Asahi Kasei Chemicals) as a derivative, trade name “Clayton G” (manufactured by Kraton Japan), and trade name “Dynalon” (manufactured by JSR) as a hydrogenated derivative of a styrene-butadiene random copolymer. As a hydrogenated derivative of a styrene-isoprene block copolymer, a trade name “Septon” (Kuraray), and as a styrene-vinylisoprene block copolymer elastomer, a trade name “Hibler” (manufactured by Kuraray Co., Ltd.) can be mentioned.

  In addition, the copolymer of aromatic hydrocarbon and conjugated diene hydrocarbon or its hydrogenated derivative has an interlayer adhesion with the (II) layer mainly composed of component A by introducing a polar group. Can be further improved. Examples of polar groups to be introduced include acid anhydride groups, carboxylic acid groups, carboxylic acid ester groups, carboxylic acid chloride groups, carboxylic acid amide groups, carboxylic acid groups, sulfonic acid groups, sulfonic acid ester groups, and sulfonic acid chloride groups. Sulfonic acid amide group, sulfonic acid group, epoxy group, amino group, imide group, oxazoline group, hydroxyl group and the like. Copolymers of aromatic hydrocarbons (preferably styrenic hydrocarbons) introduced with polar groups and conjugated dienes or their hydrogenated derivatives include maleic anhydride modified SEBS, maleic anhydride modified SEPS, epoxy modified SEBS, epoxy modified A typical example is SEPS. When modified with a carboxylic acid such as maleic anhydride, the content of carboxylic acid is 0.5% by mass or more, preferably 0.8% by mass or more, more preferably 1.0% by mass or more, and 3% by mass. Hereinafter, it is preferably 2.5% by mass or less, more preferably 2.0% by mass or less, and the content of aromatic hydrocarbon is 5% by mass or more, preferably 7% by mass or more, more preferably 10% by mass. % Or more and 50% by mass or less, preferably 40% by mass or less, more preferably 35% by mass or less. If the content of the carboxylic acid to be modified is in the above range, a stable adhesive resin can be obtained, and the interlayer strength between the (I) layer and the (II) layer can be increased. Also, if the content of aromatic hydrocarbon is within the above range, even if recycled film is regenerated and added, good compatibility can be obtained and the film can be obtained without reducing the flexibility of (III) layer. When stress is applied to, delamination can be suppressed because a buffering action against stress generated between the (I) layer and the (II) layer works. These copolymers can be used alone or in admixture of two or more.

  Specifically, trade names “Tuftec M” (manufactured by Asahi Kasei Chemicals), “Epofriend” (manufactured by Daicel Chemical), and the like are commercially available.

  Next, the modified polyolefin resin (c) will be described. In the present invention, the modified polyolefin resin capable of constituting the (III) layer refers to a resin mainly composed of an unsaturated carboxylic acid or an anhydride thereof, or a polyolefin modified with a silane coupling agent. Examples of unsaturated carboxylic acids or anhydrides thereof include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, itaconic acid, itaconic anhydride or monoepoxy compounds of these derivatives and the above acids. Examples include ester compounds, reaction products of a polymer having a group capable of reacting with these acids in the molecule and an acid. These metal salts can also be used. Among these, maleic anhydride is more preferably used. Moreover, these copolymers can be used individually or in mixture of 2 or more types, respectively.

  Examples of the silane coupling agent include vinyltriethoxysilane, methacryloyloxytrimethoxysilane, and γ-methacryloyloxypropyltriacetyloxysilane.

  In order to produce the modified polyolefin resin, for example, these modified monomers can be copolymerized in the stage of polymerizing the polymer in advance, or these modified monomers can be graft copolymerized with the polymer once polymerized. For modification, these modified monomers are used alone or in combination, and those having a content in the range of 0.1% by mass or more and 5% by mass or less are preferably used. Of these, those that have been graft-modified are preferably used.

  Specifically, trade names “Admer” (Mitsui Chemicals), “Modic” (Mitsubishi Chemical) are commercially available.

  The film of the present invention can also contain the film resin of the present invention (hereinafter also referred to as “recycled resin”) recycled to the (I) layer. The content of the recycled resin is 50 parts by mass or less, preferably 40 parts by mass or less, and more preferably 30 parts by mass or less with respect to 100 parts by mass of the resin constituting the layer to be contained. When the content of the recycled resin is 50 parts by mass or less, rigidity, shrinkage characteristics, and rupture resistance can be maintained.

<Film production method>
In the film of the present invention, the (I) layer composed of the mixed resin composition obtained by mixing the A component and the B component is stretched in at least one direction in a direction perpendicular to the major axis direction of the dispersion domain composed of the B component. It is essential that
That is, the film of the present invention is a method of stretching an unstretched film obtained by laminating the (I) layer and the (II) layer composed mainly of the above component A in at least one direction, or at least the (I) layer. After stretching in one direction, (II) a method of laminating an unstretched film or stretched film with heat or a solvent by a known method, or (I) a resin comprising component A after stretching a layer in at least one direction The composition can be produced by a method of coating by a known method.

An example of a specific manufacturing method is shown.
First, as a method of mixing the A component and the B component, there is a method of obtaining a pre-compound using a same-direction twin-screw extruder, a kneader, a Henschel mixer, or the like. Further, both components may be directly fed into a film extruder without being mixed in advance, and mixing and film forming may be performed by the same apparatus.

  In the production method of the film, the A component, the B component, or a mixture obtained by compounding these components is put into an extruder, and melt extrusion molding is performed. As the extrusion method at this time, a known method such as a T-die method or a tubular method can be employed. The melt-extruded film is cooled with a cooling roll, air, water or the like. In the present invention, it is important that the (I) layer and the (II) layer are laminated. As a lamination method, a co-extrusion method using a multi-manifold type die or a feed block is used. Known methods such as a method of extruding, a method of separately obtaining single layer films of the (I) layer and the (II) layer and then laminating by thermal lamination can be employed.

  The obtained laminated unstretched film is reheated by a method such as hot air, warm air, ultraviolet light, carbon dioxide laser, microwave, etc., and is at least one direction, that is, uniaxial direction or two directions by a roll method, a tenter method, a tubular method or the like. The film of the present invention can be produced by stretching in the axial direction, causing separation at the interface between the matrix and the domain, and forming pores. Whether the stretching is uniaxial stretching or biaxial stretching can be appropriately determined depending on the intended application.

  The stretching temperature may vary depending on the softening temperature of the A component and B component, the use of the resulting heat-shrinkable pore-containing film, etc., preferably 60 ° C. or higher, more preferably 65 ° C. or higher, 85 ° C. or lower, More preferably, it is in the range of 80 ° C. or lower. When the stretching temperature is 60 ° C. or higher, it is possible to suppress the elastic modulus of the raw material from becoming too high in the stretching process, to obtain good stretchability, and to suppress film breakage and thickness unevenness. On the other hand, if the stretching temperature is 85 ° C. or lower, desired shrinkage characteristics can be exhibited, and the stretchability of the B component is suppressed, and peeling at the interface between the matrix and the dispersion domain is promoted. Voids can be obtained and the bulk specific gravity can be less than 1.0.

  The draw ratio in the drawing step can be appropriately selected according to the constituent composition of the mixed resin composition obtained by mixing the A component and the B component, the drawing means, the drawing temperature, the target product form, and the like. For example, the draw ratio is 1.5 times or more, preferably 3.0 times or more, and 8.0 times or less, preferably 6.0 times or less. If the draw ratio is 1.5 times or more, appropriate shrinkage characteristics and sufficient pores can be obtained, and the bulk specific gravity can be adjusted to less than 1.0. Moreover, although it has practical performance by making the upper limit of a draw ratio about 80 times, it can be obtained.

  The stretching direction in the stretching step can be appropriately selected depending on the intended use. However, since the film of the present invention has a structure in which the dispersion domain of the B component extends in the MD direction as described later, That is, it is preferable that pores can be easily formed by stretching in the TD direction.

Further, in the case of uniaxial stretching, if a weak stretching of about 1.01 to 1.8 times is applied in a direction orthogonal to the main shrinkage direction of the film as necessary, the mechanical properties of the heat-shrinkable void-containing film obtained It is more preferable because the physical properties are improved.
In the present specification, the “main shrinkage direction” means a direction in which stretching is large between the longitudinal direction and the transverse direction. For example, in the case of mounting on a bottle, the direction corresponds to the outer circumferential direction. The “direction orthogonal to the main shrinkage direction” refers to a direction orthogonal to the direction in which stretching is large.

  By the way, since the cooling roll used at the said film manufacturing process exists under the said extruder, it will be in the state extended a little by the dead weight until the film extruded from the said extruder reaches | attains a cooling roll. . At this time, the film is in a high temperature state because it is extruded from the extruder, and in the (I) layer constituting the film, not only the matrix (component A) but also the dispersion domain (component B) has a main shrinkage direction. In particular, the dispersion domain (component B) is extended in the direction perpendicular to the flow direction (flow direction), and is extended in the flow direction (direction perpendicular to the main film shrinkage direction). At this time, the aspect ratio of the dispersion domain (component B) to the main shrinkage direction perpendicular to the main shrinkage direction is 5 or more, preferably 10 or more, more preferably 15 or more, and 50 or less, preferably 40 or less. More preferably, it is desirable to adjust to 35 or less. When a film composed of the component A alone is formed, the film itself becomes brittle. On the other hand, by including a dispersion domain composed of the B component so that the aspect ratio is within the above range in the A component which is the matrix, the heat-shrinkable void-containing film obtained has low-temperature rupture resistance. Can be granted. If the aspect ratio of the dispersion domain (component B) is 5 or more, the film can be given breakage resistance at low temperatures, and if the aspect ratio is 50 or less, voids are formed in the (I) layer. It is easy and a desired bulk specific gravity can be obtained.

  The aspect ratio is preferably generated by the above-described method based on the weight of the film, but this may not be sufficient. In such a case, it is desirable to stretch a little between the extruder and the cooling roll. That is, by changing the thickness of the stretched film to be formed with respect to the interval (lip gap) of the extrusion die of the extruder, the film is stretched in the flow direction (direction perpendicular to the main film shrinkage direction), and depending on the ratio The aspect ratio of the dispersion domain (B component) can be controlled.

  When the dispersion domain (B component) has a predetermined aspect ratio, the dispersion domain (B component) is parallel to the outer surface of the film and is in one direction, that is, the film flow direction (film main direction). It extends in a direction perpendicular to the shrinking direction. For this reason, by making one stretching direction of uniaxial stretching or one stretching direction of biaxial stretching a direction perpendicular to the flow direction (film main shrinkage direction), the matrix (component A) and the dispersion domain (component B) It becomes easier to cause separation of the boundary, and a higher porosity can be obtained.

  In order to realize the aspect ratio of the dispersion domain (component B), the component B has a melt flow rate of 1.0 g / 10 min or more, preferably 1.5 g / 10 min or more, and 5.0 g / 10 min. Hereinafter, it is desirable to use a polyolefin-based resin composition that is preferably 4.5 g / 10 min. If the melt flow rate of the polyolefin resin composition is 1.0 g / 10 min or more, the size of the dispersed domain becomes too large when the above-mentioned sea-island structure is formed, or the dispersed state is poor and the pores are uniform. It is suitable without causing problems such as being difficult to occur. On the other hand, if the melt flow rate of the polyolefin resin composition is 5.0 g / 10 min or less, the size of the dispersed domain is reduced when the above-mentioned sea-island structure is formed, the strength of the domain itself is reduced, and the low temperature This is preferable without causing problems such as failure to sufficiently impart fracture resistance.

<Bulk specific gravity>
The bulk specific gravity of the film of the present invention is 0.50 or more, more preferably 0.60 or more, further preferably 0.70 or more, less than 1.00, preferably 0.95 or less, more preferably 0.90. The following is desirable. If the bulk specific gravity is less than 1.00, it is easy and preferable to separate this film by the liquid specific gravity method. On the other hand, if the bulk specific gravity is 0.50 or more, it is preferable without causing problems such as insufficient strength of the film due to the existing pores.

  As a method of adjusting the bulk specific gravity to a desired value, among the A component and B component, a method of increasing the mixing ratio of the component having a smaller specific gravity, increasing the draw ratio, lowering the stretching temperature, etc. And a method of generating a large number of pores by manipulating the stretching conditions.

<Heat shrinkability>
The film of the invention has a thermal shrinkage rate of 20% or more when immersed in warm water at 80 ° C. for 10 seconds, preferably 25% or more, more preferably 30% or more, and 80% or less, Preferably it is 75% or less. For example, a heat-shrinkable film applied to a shrinkable label for a PET bottle varies depending on its shape, but generally a heat shrinkage rate of about 20% to 70% is required. This is in order to be able to respond appropriately.

  Further, the shrinkage processing machine that is most commonly used industrially for label mounting of PET bottles is generally called a steam shrinker that uses steam as a heating medium for shrinking. The heat-shrinkable film needs to sufficiently heat-shrink at a temperature as low as possible from the viewpoint of the influence of heat on the object to be coated. Furthermore, with the recent increase in the speed of the labeling process, there has been an increasing demand for shrinking quickly at a lower temperature. In consideration of such industrial productivity, a film having a heat shrinkage rate of 20% or more under the above conditions is preferable because it can sufficiently adhere to the object to be coated within the shrinkage processing time.

  When the film of the present invention is used as a heat-shrinkable label, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction is preferably 10% or less when immersed in warm water at 80 ° C. for 10 seconds, It is more preferably 5% or less, and further preferably 3% or less. If the film has a thermal shrinkage rate of 10% or less in the direction perpendicular to the main shrinkage direction, the dimension itself in the direction perpendicular to the main shrinkage direction after shrinkage may be shortened, or the printed pattern or character distortion after shrinkage may occur. In the case of a square bottle, it is preferable because troubles such as vertical sink are unlikely to occur.

<Natural shrinkage>
The natural shrinkage rate of the film of the present invention is desirably as small as possible. Generally, the natural shrinkage rate of a heat-shrinkable film is, for example, a natural shrinkage rate of 30% or less after storage at 30 ° C. for 30 days, preferably It is desirable that it is 2.0% or less, more preferably 1.5% or less. If the natural shrinkage rate under the above conditions is 3.0%, even if the produced film is stored for a long period of time, it can be stably attached to a container or the like, and it is difficult to cause problems in practice.

<Fracture resistance>
The rupture resistance of the film of the present invention is evaluated by the tensile rupture elongation, and in a tensile test under a 0 ° C. environment, the elongation is 100% or more in the film take-off (flow) direction (MD), particularly for label applications, preferably 150% or more, more preferably 200% or more. If the tensile elongation at break in an environment of 0 ° C. is 100% or more, it is difficult to cause problems such as breakage of the film at the time of printing / bag making and the like. Also, when the tension applied to the film increases as the speed of processes such as printing and bag making increases, it is preferable that the tensile breaking elongation is 100% or more because it is difficult to break.

<Rigidity>
As for the waist (rigidity at room temperature) of the film of the present invention, the tensile elastic modulus in the direction perpendicular to the main shrinkage direction of the film is preferably 1.2 GPa or more, more preferably 1.4 GPa. More preferably, it is 6 GPa or more. Moreover, the upper limit of the tensile elasticity modulus of the heat shrinkable film normally used is about 3.0 GPa, preferably about 2.9 GPa, and more preferably about 2.8 GPa. If the tensile modulus in the direction perpendicular to the main shrinkage direction of the film is 1.2 GPa or more, the waist as a whole film (rigidity at room temperature) can be increased, especially when the thickness of the film is reduced, When a bag made of a plastic bottle or the like is covered with a labeling machine or the like, problems such as being obliquely covered or the yield being liable to decrease due to the film being folded back are less likely to occur.

  In addition, since the film of the present invention has pores, light rays are refracted and reflected at the interface between the A component or the B component and air, and the appearance of an opaque white-like appearance as a whole. It is particularly suitable for such as. Furthermore, since it has pores, its heat conduction efficiency is lower than that of ordinary thermoplastic resins, and it is particularly suitable for applications that require heat insulation and heat retention, such as labels for hot beverages. Furthermore, since it has pores, it has excellent cushioning properties and is suitable for protection applications such as those that are easily broken and those that are easily broken.

[Molded products, heat-shrinkable labels and containers]
The film of the present invention is excellent in printability, high rigidity, rupture resistance, shrink finish, etc. of the film, and its use is not particularly limited. By forming a functional layer, it can be used as various molded products such as bottles (blow bottles), trays, lunch boxes, prepared food containers, dairy products containers and the like. In particular, when the film of the present invention is used as a heat-shrinkable label for food containers (for example, PET bottles, glass bottles, preferably PET bottles for soft drinks or foods), a complicated shape (for example, a cylinder with a narrow center, corners, etc.) A rectangular column, pentagonal column, hexagonal column, etc.) can be adhered to the shape, and a container with a beautiful label without wrinkles or avatars can be obtained. The molded article and container of the present invention can be produced by using a normal molding method.

  When the film of the present invention is used as a heat-shrinkable label for PET bottles or the like, it is in a contracted state at the time of recycling, but it is preferable that it can be fractionated by the liquid specific gravity method even after contraction. Specifically, for example, the bulk specific gravity after shrinking in a range of 25% or less is 0.50 or more and less than 1.00, preferably 0.60 or more and 0.95 or less, and more preferably 0.70 or more and 0.00. It is desirable that it is 90 or less. If the bulk specific gravity after shrinkage is less than 1.00, the film can be separated by a liquid specific gravity method and can be separated. On the other hand, if the bulk specific gravity after shrinkage is 0.50 or more, it is preferable without causing problems such as insufficient strength of the film due to the existing pores.

  Since the film of the present invention has excellent low-temperature shrinkage and shrinkage finishing properties, in addition to the heat-shrinkable label material of plastic molded products that are deformed when heated to a high temperature, the coefficient of thermal expansion, water absorption, etc. The material is very different from the heat shrinkable film, such as metal, porcelain, glass, paper, polyethylene, polypropylene, polybutene and other polyolefin resins, polymethacrylate resin, polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate, etc. It can be suitably used as a heat-shrinkable label material for a package (container) using at least one selected from polyester-based resins and polyamide-based resins as a constituent material.

  As a material constituting the plastic package in which the film of the present invention can be used, in addition to the above resins, polystyrene, rubber-modified impact-resistant polystyrene (HIPS), styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, Styrene-maleic anhydride copolymer, acrylonitrile-butadiene-styrene copolymer (ABS), methacrylate ester-butadiene-styrene copolymer (MBS), polyvinyl chloride resin, phenol resin, urea resin, melamine resin, Examples thereof include an epoxy resin, an unsaturated polyester resin, and a silicone resin. These plastic packages may be a mixture of two or more resins or a laminate.

Hereinafter, the present invention will be described in detail with reference to experimental examples and comparative examples, but the present invention is not limited thereto.
In addition, the physical-property value and evaluation in an experiment example and a comparative example measured and evaluated by the following method. Here, the film take-up (flow) direction is described as MD, and the direction orthogonal thereto is described as TD.

(Measurement method and evaluation method)
[Melt flow rate]
Using a melt indexer (120SAS-2000) manufactured by Yasuda Seiki Seisakusho, the melt flow rate of the polyolefin resin composition was measured according to JIS K7210 (measurement temperature: 230 ° C., load: 21.18 N).

[Dynamic viscoelasticity measurement]
A film having a thickness of 200 μm was prepared using a polyolefin-based resin by a hot press apparatus (manufactured by Shindo Metal Industry Co., Ltd.), then cut into a size of 4 mm × 60 mm, and a viscoelastic spectrometer (manufactured by IT Measurement Co., Ltd .: DVA-). 200), 2.5 cm between chucks, vibration frequency 10 Hz, strain 0.1%, temperature rising rate 1 ° C./min, measuring temperature 40 ° C. to 150 ° C. in the longitudinal direction (side length 60 mm) The storage elastic modulus at 80 ° C. was measured.

[aspect ratio]
The obtained film was cut into a size of TD 1 mm × MD 10 mm with a microtome and observed with an electron microscope at 10 locations. The aspect ratio (long diameter / short) of MD of a domain composed of B component incompatible with A component in the film. Diameter) was calculated.

[Printability]
Using a bar coater, a special gravure ink OS-M (blue) manufactured by Dainichi Seika Kogyo Co., Ltd. was applied to a film obtained by appropriately diluting with a solvent, and the state of the coated surface was as follows. Judged by criteria.
○: The ink is uniformly applied without unevenness.
(Triangle | delta): There exists an unevenness in the ink application | coating surface and there is a part where the ink is not apply | coated.
X: Almost no ink is applied.

[Bulk specific gravity]
The obtained film was accurately cut into a size of MD10 cm × TD10 cm, the mass w (g) was measured, the thickness t (μm) of 50 points of the film was measured, and the bulk specific gravity (g / cm ³ ) was determined by the following formula. ) Was calculated.
Bulk specific gravity = (w / t) × 100

[Bulk specific gravity after heat shrink]
Whether or not the film to be measured is shrunk 25% at 80 ° C. and then finely crushed into small pieces of MD1 cm × TD1 cm and floated on water (that is, whether the bulk specific gravity is less than 1.00 g / cm ³⁾ Was determined according to the following criteria.
○: When everything floats △: When there is something that floats and sinks, or when there is something floating in the water ×: When everything sinks

[Fracture resistance]
In order to evaluate the manufacturing process of the film and the fracture resistance during use, the following measurements were performed.
The obtained film was cut into a strip of MD 110 mm × TD 15 mm, and the tensile elongation at MD of the film at an ambient temperature of 0 ° C. was measured at a distance of 40 mm between chucks and a tensile speed of 100 mm / min according to JIS K6732, The average value of the measured values is shown in the table.

[Heat shrinkage]
The obtained film was cut into a size of MD 100 mm × TD 100 mm, immersed in an 80 ° C. hot water bath for 10 seconds, and the amount of shrinkage was measured. As the thermal shrinkage rate, a larger value of the ratio of the shrinkage amount to the original size before shrinkage, MD / TD, was expressed as a% value.

[Tensile modulus]
In order to evaluate the rigidity of the obtained film, the following measurements were performed.
The obtained film was cut into a size of MD 400 mm × TD 5 mm, and in accordance with JIS K7127, the direction perpendicular to the main shrinkage direction of the film (MD) under the conditions of a distance between chucks of 300 mm, a tensile speed of 5 mm / min, and an ambient temperature of 23 ° C. Was measured.

[Natural shrinkage]
The obtained film was cut into a size of MD100 mm × TD1000 mm, left in a thermostatic chamber at 30 ° C. for 30 days, the amount of shrinkage relative to the original size before shrinkage was measured in the main shrinkage direction, and the ratio was expressed as a% value. did.

Example 1
As shown in Table 1, as the A component used in the (I) layer, a polylactic acid-based resin “Nature Works 4050D (L-form: D-form = 95: 5, weight average molecular weight 200,000, or less) manufactured by Nature Works LLC. "PLA1" is abbreviated as "PLA1".) 100 parts by mass, and as a B component, 30 parts by mass of polypropylene resin "FY6H (hereinafter abbreviated as" PO1 ")" manufactured by Nippon Polypro Co., Ltd. is dry blended. Using a 40 mmφ small-sized same-direction twin screw extruder, the mixture was kneaded at 200 ° C. and 100 rpm, extruded into a strand shape, rapidly cooled in a water tank, and then cut to produce pellets.
As the resin composition used for the (II) layer, 50 parts by mass of the above-mentioned “PLA1” and a polylactic acid resin Nature Works 4060D manufactured by Nature Works LLC (L-form: D-form = 88: 12, weight average molecular weight 200,000) (Hereinafter abbreviated as “PLA2”) and 50 parts by mass were dry blended, and pellets were produced by the method described above.
The obtained pellets are put into separate single-screw extruders manufactured by Mitsubishi Heavy Industries, Ltd., melt-mixed at a set temperature of 200 ° C., then co-extruded from a two-type three-layer die, taken up with a cast roll at 60 ° C., and cooled. Solidified to obtain an unstretched laminated sheet. Next, the film was stretched 4.0 times in the transverse uniaxial direction at a preheating temperature of 75 ° C. and a stretching temperature of 72 ° C. using a film tenter manufactured by Kyoto Machine Co., Ltd., and then rapidly cooled with cold air to give a heat-shrinkable pore having a thickness of 80 μm. A containing film was obtained.
Table 2 shows the measurement and evaluation results of the obtained film.

(Example 2)
As shown in Table 1, a heat-shrinkable pore-containing film was obtained in the same manner as in Example 1 except that the amount of “PO1” added in Example 1 was changed to 60 parts by mass.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Example 3)
As shown in Table 1, in Example 1, when the unstretched laminated sheet was prepared, the aspect ratio was changed by adjusting the lip gap of the die and the take-up speed of the cast roll. Thus, a heat-shrinkable pore-containing film was obtained.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

Example 4
As shown in Table 1, in Example 1, the component A in the (I) layer was mixed with 80 parts by mass of “PLA1” and 20 parts by mass of “PLA2”, and the component B was made by Nippon Polypro Co., Ltd. ) Polypropylene “FL6H” (hereinafter abbreviated as “PO2”) 20 parts by mass, and the resin composition used in the (II) layer was changed to “PLA1” 100 parts by mass. Similarly, a heat-shrinkable pore-containing film was obtained.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 1)
As shown in Table 1, in Example 1, the content of “PO1” is changed to 20 parts by mass, and the lip gap of the die and the take-up speed of the cast roll are adjusted when an unstretched laminated sheet is produced. A heat-shrinkable film was obtained in the same manner as in Example 1 except that the aspect ratio was changed.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 2)
As shown in Table 1, a heat-shrinkable film was obtained in the same manner as in Example 1 except that the amount of “PO1” added in Example 1 was changed to 5 parts by mass.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 3)
As shown in Table 1, a heat-shrinkable film was obtained in the same manner as in Example 1 except that the amount of “PO1” added in Example 1 was changed to 100 parts by mass.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 4)
As shown in Table 1, a heat-shrinkable pore-containing film was obtained in the same manner as in Example 1 except that in Example 1, the (II) layer was not formed and only the (I) layer was used. It was.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 5)
As shown in Table 1, the same procedure as in Example 1 was carried out except that, in Example 1, the B component in the (I) layer was changed to 40 parts by mass of Nippon Polypro's polypropylene “FB3HAT (hereinafter abbreviated as“ PO3 ”)”. Thus, a heat shrinkable film was obtained.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 6)
As shown in Table 1, in Example 1, instead of the B component in the (I) layer, a polybutylene succinate resin “Bionore” (hereinafter “BN”) which is a resin composition compatible with the A component instead of the B component "Abbreviated") "A heat-shrinkable film was obtained in the same manner as in Example 1 except that 30 parts by mass was added.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

From Table 1 and 2, the film of the range prescribed | regulated by this invention was small in bulk specific gravity, and was excellent in recyclability, rigidity, low temperature shrinkability, and natural shrinkage (Examples 1 thru | or 4).
On the other hand, when the aspect ratio is out of the range of the present invention, the obtained film is inferior in fracture resistance or does not sufficiently form pores, so the bulk specific gravity is slightly larger than the desired value. Thus, the fracture resistance was poor (Comparative Examples 1 and 5). In addition, when the component B in the layer (I) is outside the scope of the present invention, the obtained film did not exhibit sufficient fracture resistance and shrinkage characteristics, and did not form sufficient pores. The bulk specific gravity was also larger than the desired value (Comparative Examples 2 and 3). Moreover, when it did not have a (II) layer, the obtained film expressed the favorable mechanical physical property, but when an ink was apply | coated, some nonuniformity arose (comparative example 4). In addition, when a resin compatible with the component A was used in the layer (I), the obtained film showed good fracture resistance, but almost no pores were formed, so that the bulk specific gravity is desired. And the natural shrinkage was slightly inferior (Comparative Example 6).
As a result, the film of the present invention has a low bulk specific gravity, excellent recyclability, rigidity, low-temperature shrinkability, and natural shrinkage, and is suitable for applications such as shrink-wrapping, shrink-bound packaging, and heat-shrinkable labels. It turns out that it is a hole containing film.

  The film of the present invention has a small bulk specific gravity and is excellent in printability, high rigidity, rupture resistance, and shrinkage characteristics, and therefore can be suitably used for molded products that require heat shrinkage, particularly shrink labels. Can do. Moreover, since the PLA resin used in the present invention is a plant-derived resin, it is suitable for promoting the utilization of biomass and aiming for a recycling society.

Claims (8)

(I) layer composed of a mixed resin composition containing the following A component and B component as main components, and the content of B component is 10 parts by mass or more and 90 parts by mass or less with respect to 100 parts by mass of A component When,
It has at least two layers with the (II) layer comprised with the resin composition which has the following A component as a main component,
In the layer (I), the aspect ratio with respect to the main shrinkage direction in the direction orthogonal to the main shrinkage direction of the dispersion domain composed of the B component dispersed in the matrix composed of the A component is 5 or more and 50 or less,
A heat-shrinkable pore-containing film, wherein the heat shrinkage rate in the main shrinkage direction when immersed in warm water of 80 ° C. for 10 seconds is 20% or more.
A component: polylactic acid resin composition comprising a copolymer of D-lactic acid and L-lactic acid as a main component B component: incompatible with the A component, vibration frequency 10 Hz, strain 0.1%, between chucks Polyolefin resin composition having a storage elastic modulus at 80 ° C. of 0.25 GPa or more and 2.0 GPa or less when measured by raising the temperature at 2.5 cm and a heating rate of 1 ° C./min.   The heat-shrinkable pore-containing film according to claim 1, wherein the polyolefin resin composition has a melt flow rate of 1.0 g / 10 min to 5.0 g / 10 min.   The heat-shrinkable pore-containing film according to claim 1 or 2, wherein the bulk specific gravity is 0.50 or more and less than 1.00.   The heat-shrinkable void-containing film according to claim 3, wherein the bulk specific gravity after heat-shrinking in a range of 25% or less is less than 1.00. The heat-shrinkable pore-containing film according to any one of claims 1 to 4, wherein a tensile elastic modulus in a direction orthogonal to the main shrinkage direction is 1.2 GPa or more. A molded article using the heat-shrinkable pore-containing film according to any one of claims 1 to 5 as a base material. A heat-shrinkable label using the heat-shrinkable pore-containing film according to any one of claims 1 to 5 as a substrate. A container equipped with the molded article according to claim 6 or the heat-shrinkable label according to claim 7 .