JP5033326B2 - Heat-shrinkable pore-containing film, molded article using the film, heat-shrinkable label, and container - Google Patents

Description

  The present invention relates to a heat-shrinkable pore-containing film, a molded product using the film, a heat-shrinkable label, and a container, and more specifically, while imparting high rigidity to a heat-shrinkable film that suppresses the use of petroleum resources, The present invention relates to a heat-shrinkable hole-containing film, a heat-shrinkable label, and a container that have pores to express lightness, heat insulation, and concealment, are excellent in rigidity and fracture resistance, and have small spontaneous shrinkage.

  At present, a heat shrinkable film that shrinks by heating and adheres to the container or the like is often used for packaging or binding the container or the like.

  Conventionally, polyvinyl chloride resin, polystyrene resin, polyester resin and the like have been mainly used as raw materials for such heat-shrinkable films. However, since these resins all use depleted petroleum resources as raw materials, it has been necessary to reduce the amount of use from the viewpoint of resource protection.

  Also, depending on the resin, there may be problems such as generation of toxic substances during combustion when incinerated after use, damage to the combustion furnace due to excessive combustion calories, and shortening the life of the furnace, and decomposition by microorganisms during disposal. However, there is a problem that the shape is maintained over a long period of time and causes environmental pollution.

  Polylactic acid is attracting attention as a material for solving problems caused by the use of these resins. Polylactic acid is suitable for aiming at a sustainable society because it can be produced industrially from biomass such as corn. In addition, there is no risk of damaging the combustion furnace because it does not generate toxic substances during combustion and the calorie burned is lower than that of resin made from petroleum, and it can be decomposed by microorganisms even when discarded in the environment. It has a favorable characteristic of being.

  However, when polylactic acid is used as a raw material for heat-shrinkable labels, it has the characteristics of high rigidity, excellent low-temperature shrinkability, and low spontaneous shrinkage, but there is a problem in fracture resistance. It was difficult to produce a quality heat-shrinkable label. In order to improve the rupture resistance of such polylactic acid, a heat-shrinkable film to which a soft component compatible with polylactic acid is added has been studied. For example, Patent Document 1 describes it.

  Also, not only heat-shrinkable labels, but also by forming pores in molded products using thermoplastic resins, reducing the volume specific gravity of the molded products, reducing the amount of resin used and reducing the environmental burden, Furthermore, it is known that functions such as light shielding properties, heat insulating properties, cushioning properties and the like can be imparted. Various methods are used for forming the pores. In the case of a stretched film using a thermoplastic resin, there is a method of stretching in at least one direction after adding an incompatible component to the thermoplastic resin. Are known.

  In order to create a heat-shrinkable pore-containing label having such pores, after adding incompatible components to the resin used for the heat-shrinkable label, the pores are formed by stretching in one direction or multiple directions Is used. Regarding polylactic acid, Patent Document 2 discloses a film in which pores are formed by stretching after adding an incompatible resin to the polylactic acid to reduce the bulk specific gravity. Further, Patent Document 3 discloses a heat-shrinkable film in which a polyester resin other than polylactic acid is used and an incompatible resin is similarly added and stretched to form pores.

JP 2003-119367 A JP 2002-146071 A JP 2003-321562 A

  However, in the heat-shrinkable film in which a soft component is added to polylactic acid as described in Patent Document 1, there is a problem that the rigidity is reduced and the natural shrinkage is increased, and the above-described pore formation is caused. As a result, the amount of resin used was not reduced and desirable functions were not provided.

  Moreover, since the pore film as described in Patent Document 2 is heat-treated after stretching, it cannot be used as a heat-shrinkable label. Furthermore, as described in Patent Document 3, a heat-shrinkable film obtained by adding an incompatible resin to a polyester-based resin is more difficult to form pores during stretching than a film using polylactic acid, Since specific gravity is larger than the film using polylactic acid and polyester resin is a petroleum-derived raw material, it was not effective from the viewpoint of resource protection.

  Therefore, the present invention mainly uses plant-derived polylactic acid to give a heat-shrinkable film that suppresses the use of petroleum resources to have high rigidity and to have pores to reduce weight, heat insulation, and concealment. Heat-shrinkable pore-containing film that exhibits excellent properties, excellent rigidity and breakage resistance, and has a small natural shrinkage, and a molded product, a heat-shrinkable label, and this molded product or heat-shrinkable label that make use of the properties of the film The object is to provide a container equipped with the.

  This invention contains 10 to 90 parts by mass of the polyolefin resin composition (B) and 20 parts by mass of the soft component (C) with respect to 100 parts by mass of the polylactic acid resin composition (A). An unstretched film composed of a resin composition containing at least part and not more than 80 parts by weight is stretched at least uniaxially, contains pores, and is immersed in warm water at 80 ° C. for 10 seconds. The above problem was solved by producing a heat-shrinkable pore-containing film having a shrinkage ratio of 20% or more and 80% or less.

  That is, the heat-shrinkable pore-containing film of the present invention (hereinafter also referred to as the film of the present invention) includes not only the polylactic acid resin composition (A) but also the polyolefin resin composition (B) and the soft film. By including both component (C) in the above range and stretching it so as to have the above-mentioned shrinkage rate, it is possible to reliably form more pores than those in which only the soft component (C) is added. In addition to being excellent in light-shielding properties, heat insulating properties, and light weight, the necessary shrinkage can be ensured by sufficient stretching. In addition, since necessary pores are generated due to the difference in stretchability between the polylactic acid resin composition (A) and the soft component (C) and the polyolefin resin composition (B) that is incompatible with these, The lightness, heat insulation, and concealment due to the holes can be sufficiently secured.

  Since the heat-shrinkable pore-containing film according to the present invention is mainly composed of a polylactic acid-based resin, it is useful in suppressing consumption of petroleum resources and building a recycling society. In addition, the film obtained by stretching an unstretched film made of the resin composition having the above composition easily creates pores by stretching, and the pores exhibit lightness, heat insulation, and concealment. Furthermore, since this resin composition is excellent in rupture resistance, has a small spontaneous shrinkage, and the resulting film has high rigidity, it can be utilized as a useful heat-shrinkable film.

The present invention will be described in detail below.
This invention contains 10 to 90 parts by mass of the polyolefin resin composition (B) and 20 parts by mass of the soft component (C) with respect to 100 parts by mass of the polylactic acid resin composition (A). It is a heat-shrinkable film obtained by stretching an unstretched film composed of a resin composition containing at least part and not more than 80 parts by weight at least uniaxially.

  The said polylactic acid-type resin composition (A) means the composition which has lactic acid as a main component. Specifically, a homopolymer of lactic acid, or a lactic acid copolymer mainly composed of a copolymer of lactic acid and an α-hydroxycarboxylic acid other than lactic acid, a diol component and a dicarboxylic acid component, or both. Is also included. The main component means that other components may be included as long as the effect of the heat-shrinkable pore-containing film according to the present invention is not hindered. It is preferable to occupy the above, and more preferably 90% by mass or more.

  Here, lactic acid refers to both D-lactic acid and L-lactic acid, and examples of the lactic acid homopolymer include poly (D-lactic acid), which is a homopolymer of D-lactic acid, and L-lactic acid. Examples thereof include poly (L-lactic acid) which is a homopolymer, poly (DL-lactic acid) composed of a copolymer of L-lactic acid and D-lactic acid, and a mixture thereof. Hereinafter, a polymer composed only of these lactic acids is referred to as a lactic acid resin. Moreover, the lactic acid-type copolymer which has as a main component the copolymer of lactic acid and (alpha) -hydroxycarboxylic acid other than lactic acid, a diol component, a dicarboxylic acid component, or both of these uses lactic acid to be used as D-lactic acid or Any of only L-lactic acid and what is both D-lactic acid and L-lactic acid may be sufficient.

  However, in both cases of the lactic acid-based resin and the lactic acid-based copolymer, when both D-lactic acid and L-lactic acid are included as lactic acid, the shrinkage is greater than that including only one of the lactic acids. This is preferable because unevenness can be suppressed. Specifically, the constituent ratio of D-lactic acid and L-lactic acid constituting the lactic acid resin and the lactic acid copolymer is in the range of L-lactic acid: D-lactic acid = 99: 1 to 90:10, Or it is preferable that it is the range of 1: 99-10: 90. If the ratio of L-lactic acid or D-lactic acid is 99% or less, shrinkage unevenness can be suppressed, and if the ratio is 90% or more, a film having sufficient shrinkage characteristics can be easily obtained.

In the case of using the lactic acid-based copolymer, the copolymerization ratio of the constituent components is not particularly limited. However, the higher the ratio of lactic acid, the less the consumption of petroleum resources, which is preferable. It is preferable to copolymerize at a ratio not exceeding.
Specifically, the copolymerization ratio of a copolymer of lactic acid and an α-hydroxycarboxylic acid, an aliphatic diol, or an aliphatic dicarboxylic acid is a mass ratio of lactic acid: α-hydroxycarboxylic acid, aliphatic diol, or Aliphatic dicarboxylic acid = 100: 0 to 95: 5, preferably 90:10 to 10:90, more preferably 80:20 to 20:80, and most preferably 30:70 to 70:30. If the copolymerization ratio is within the above range, a film having a good balance of physical properties such as rigidity, transparency and impact resistance can be obtained.

  The lactic acid resin and lactic acid copolymer may be used alone or in combination.

  In addition, when a ring-opening polymerization method (lactide method) is used for the production of the lactic acid-based resin, lactide, which is a cyclic dimer of lactic acid, is used in the presence of a predetermined catalyst while using a polymerization regulator as necessary. A ring-opening polymerization can be carried out underneath to obtain a lactic acid resin having an arbitrary composition. Examples of the lactide used 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. Is mentioned. By mixing and polymerizing these as necessary, the lactic acid resin having an arbitrary composition and crystallinity can be obtained.

  Examples of the α-hydroxycarboxylic acid that is a monomer used in the production of the lactic acid copolymer include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, and 2-hydroxy. Examples include bifunctional aliphatic hydroxycarboxylic acids such as −3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone, and valerolactone. .

  As said diol component which is a monomer used for manufacture of the said lactic acid-type copolymer, ethylene glycol, propylene glycol, 1, 4- butane diol, 1, 4- cyclohexane dimethanol etc. are mentioned. Examples of the dicarboxylic acid component include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid.

  The polylactic acid resin composition (A) may contain a small amount of other copolymerization components in order to improve 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, the polylactic acid-based resin composition (A) may contain a small amount of a chain extender such as a diisocyanate compound, an epoxy compound, an acid anhydride, etc. for the purpose of increasing the molecular weight.

  The Vicat softening point of the polylactic acid-based resin composition (A) is preferably 50 ° C. or higher, and preferably 55 ° C. or higher. If the Vicat softening point is 50 ° C. or higher, the resulting heat-shrinkable pore-containing film can suppress natural shrinkage even if it is left at a temperature slightly higher than room temperature, for example, in summer, but it is less than 50 ° C. There is a possibility that the natural contraction cannot be suppressed. On the other hand, the Vicat softening point is preferably 95 ° C. or less, and preferably 85 ° C. or less. When it exceeds 95 ° C., it becomes difficult to perform low-temperature stretching at the time of stretching the film, and it becomes difficult to give good shrinkage characteristics to the obtained film.

  The mass average molecular weight of the polylactic acid-based resin composition (A) is preferably 50,000 or more, and more preferably 100,000 or more. If the mass average molecular weight is 50,000 or more, it is preferable that problems such as inferior mechanical strength hardly occur. On the other hand, it is good that it is 400,000 or less, and it is more preferred if it is in the range of 250,000 or less. If it is 400,000 or less, it is preferable that the melt viscosity becomes too high and it is difficult to cause problems such as deterioration of molding processability.

  Typical resin compositions that can be used as the polylactic acid-based resin composition (A) include the “Lacia” series manufactured by Mitsui Chemicals, Inc., the “Nature Works” series manufactured by Nature Works LLC, and the like. Listed as commercially available.

  The polyolefin resin composition (B) is a resin mainly composed of a polyolefin resin that is incompatible with the polylactic acid resin composition (A) and the soft component (C). This incompatible means that the polylactic acid resin composition (A) and the mixed resin composition of the soft component (C) and the polyolefin resin composition (B) are optical devices such as an electron microscope. When it observes using this, it means that the said polyolefin-type resin composition (B) will be in the state which forms the domain in the said polylactic acid-type resin composition (A) and the said soft component (C). In the heat-shrinkable pore-containing film according to the present invention, the polylactic acid resin composition (A) and the soft component (C) are more present than the polyolefin resin composition (B). The polylactic acid resin composition (A) and the soft component (C) form a sea part, that is, a matrix, and the polyolefin resin composition (B) forms an island part, that is, a dispersion domain.

  Examples of such a polyolefin resin composition (B) include polyethylene resins such as high density polyethylene, low density polyethylene and linear low density polyethylene, polypropylene resins such as high crystalline homopolypropylene and random polypropylene, polymethyl Examples thereof include pentene or a mixed resin thereof, and high crystalline homopolypropylene is preferable. These resins can be used alone or in admixture of two or more.

  More specifically, as these polyolefin resin compositions (B), trade names “Novatech HD, LD, LL”, “Kernel”, “Toughmer A, P” (Nippon Polyethylene Co., Ltd.), “ Suntech HD, LD (Asahi Kasei Life & Living Co., Ltd.), HIZEX, ULTZEX, EVOLUE (Mitsui Chemicals Co., Ltd.), More Tech (Idemitsu Kosan Co., Ltd.), UBE Polyethylene “UMERIT” (manufactured by Ube Industries, Ltd.), “NUC polyethylene”, “Nackflex” (manufactured by Nihon Unicar Co., Ltd.), “engage” (manufactured by Dow Chemical Co., Ltd.) and the like are commercially available. Also, as the polypropylene resin, trade names “NOVATEC 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 Allomer Co., Ltd.) and the like are commercially available. In addition, “TPX” (manufactured by Mitsui Chemicals, Inc.) is commercially available as a polymethylpentene resin. These can be used alone or in admixture of two or more.

  The polyolefin-based resin composition (B) preferably has a storage elastic modulus at 80 ° C. of 0.25 GPa or more, more preferably 0.4 GPa or more when measured at a frequency of 10 Hz and a strain of 0.1%. When the storage elastic modulus is less than 0.25 GPa, pores may not be imparted to the film in the stretching step described below. On the other hand, the storage elastic modulus under the same conditions is preferably 2.0 GPa or less. If it exceeds 2.00 GPa, the desired crystallinity becomes difficult to obtain, and the specific gravity becomes too large, so that it may not be possible to obtain a film having the intended bulk specific gravity.

  The polyolefin resin composition (B) preferably has a melt flow rate (hereinafter abbreviated as “MFR”) measured based on JIS K7211 of 0.5 g / 10 min or more. More preferably, it is 0.0 g / 10 min or more. The MFR is preferably 50 g / 10 min or less, more preferably 35 g / 10 min or less, and further preferably 20 g / 10 min or less. If the MFR of the polyolefin resin composition (B) is 1.0 g / 10 min or more, the size of the dispersed domain becomes too large when the sea-island structure is formed on the film, the dispersion state is poor, and the pores are uniform. This is preferable without causing problems such as being difficult to occur. On the other hand, if the MFR of the polyolefin resin composition (B) is 50 g / 10 min or less, the size of the dispersed domain is reduced when the sea-island structure is formed, the strength of the domain itself is reduced, and This is suitable without causing problems such as insufficient rupture resistance.

  The polyolefin resin composition (B) can exist as a dispersed domain in the matrix component composed of the polylactic acid resin composition (A) and the soft component (C). The size and shape of the dispersion domain can be appropriately determined depending on kneading conditions, sheeting conditions, stretching ratio, stretching direction, and the like. The longitudinal direction of the dispersed domain after stretching, that is, the cross-sectional shape in the direction parallel to the stretching direction is preferably elliptical. When the cross-sectional shape is an ellipse, the maximum axial length in the minor axis direction of the dispersion domain is preferably 0.1 μm or more, more preferably 0.2 μm or more, and further preferably 0.3 μm or more. On the other hand, the maximum axial length in the minor axis direction is preferably 5 μm or less, and more preferably 4 μm or less. If the maximum axial length in the minor axis direction is 0.1 μm or more, peeling occurs at the interface between the matrix and the dispersion domain, which is suitable for forming pores. If the maximum axial length is 5 μm or less, It is preferable because remarkable unevenness is hardly generated on the surface and the appearance can be kept uniform.

The density of the polyolefin-based resin composition (B) is preferably in the range of 0.50 g / cm ^{3 to} 1.00 g / cm ³ , more preferably 0.65 g / cm ^{3 to} 0.96 g / cm ³ , More preferably, it is the range of 0.80 g / cm ³ or more and 0.92 g / cm ³ or less. If the density is 1.00 g / cm ³ or less, the effect of reducing the specific gravity of the entire film is great, and if the density is 0.50 g / cm ³ or more, there are problems such as lack of rigidity and difficulty in forming pores during stretching. It is hard to occur and is preferable.

  The polyolefin resin used as the polyolefin resin composition (B) has a specific gravity smaller than that of the polylactic acid resin composition (A). Therefore, the heat-shrinkable pore-containing film according to the present invention (hereinafter abbreviated as “the film of the present invention”) is compared with the film made of the polylactic acid resin composition (A) alone, Specific gravity can be made smaller. Furthermore, bulk specific gravity can be made smaller by the void | hole produced at the time of extending | stretching by the presence of the said polyolefin resin composition (B).

  The soft component (C) is a rubber component exhibiting rubber elasticity other than the polylactic acid-based resin composition (A). For the purpose of improving the impact resistance of the film of the present invention, the rigidity of the film of the present invention is increased. It can add within the range which does not impair. The soft component (C) is not particularly limited, but other than the polylactic acid resin composition (A), a lactic acid copolymer, aliphatic polyester, and aromatic aliphatic polyester having a Tg of 0 ° C. or less. , Copolymer of diol, dicarboxylic acid and lactic acid resin, core-shell structure type rubber, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer Polymer (EEA), ethylene- (meth) acrylic acid copolymer (EMA), ethylene-methyl (meth) acrylic acid copolymer (EMMA), and the like are preferably used. Among these, the core-shell structure rubber is excellent in dispersibility with respect to the polylactic acid-based resin composition (A), so that the effect of improving impact resistance is large and it is difficult to inhibit the formation of pores.

  Specific examples of the lactic acid copolymer other than the polylactic acid resin composition (A) used for the soft component (C) include an α-hydroxycarboxylic acid homopolymer excluding lactic acid, a diol residue and dicarboxylic acid. A copolymer with an acid residue, or a copolymer thereof, and examples of the α-hydroxycarboxylic acid residue include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, Residues derived from bifunctional aliphatic hydroxycarboxylic acids such as 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid, caprolactone, butyrolactone, Examples thereof include residues derived from lactones such as valerolactone. Examples of the diol residue include residues derived from ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the dicarboxylic acid residue include residues derived from succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like.

  Examples of commercially available lactic acid copolymers other than the above-mentioned polylactic acid resin composition (A) include, for example, the trade name “Puramate” (manufactured by Dainippon Ink & Chemicals, Inc.) and the trade name “GS”. -PLA "(manufactured by Mitsubishi Chemical Corporation).

  Examples of the aliphatic polyester used as the soft component (C) include an aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid, an aliphatic polyester obtained by ring-opening polymerization of a cyclic lactone, Examples include aliphatic polyester resins excluding PLA resins such as synthetic aliphatic polyesters.

  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 Aliphatic diols such as 1,4-cyclohexanedimethanol or their anhydrides and derivatives, and aliphatic dicarboxylic acids such as succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, or their anhydrides and derivatives 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 extending the chain with an isocyanate compound or the like as necessary.

  As a commercially available example of the above aliphatic polyester, “Bionore” (manufactured by Showa Polymer Co., Ltd.) can be exemplified.

  In addition, as the aliphatic polyester obtained by ring-opening polymerization of the above cyclic lactones, one or more kinds of cyclic monomers selected from ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like were polymerized. Things. 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.

  Examples of commercially available aliphatic polyesters include the trade name “Cell Green” (manufactured by Daicel Chemical Industries, Ltd.) and the trade name “Tone Polymer” (manufactured by Union Carbide Japan). It is done.

  Furthermore, the aromatic aliphatic polyester resin used as the soft component (C) is an aliphatic diol or derivative thereof, an aliphatic dicarboxylic acid or derivative thereof, and an aromatic dicarboxylic acid or derivative thereof. It is a thing. The aromatic polyester resin is obtained by condensation polymerization of an aromatic dicarboxylic acid or a derivative thereof and an aromatic dicarboxylic acid or a derivative thereof. Among these, examples of the aromatic diol or its derivative include an ethylene oxide adduct of bisphenol A. In addition, examples of the aromatic dicarboxylic acid or a derivative thereof include terephthalic acid, isophthalic acid, orthophthalic acid, 2,4-naphthalenedicarboxylic acid, and paraphenyldicarboxylic acid. In this condensation polymerization, a desired polymer can be obtained by extending the chain with an isocyanate compound or the like as necessary.

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

  The mass (weight) average molecular weight of the lactic acid copolymer, aliphatic polyester resin, aromatic polyester resin, and aliphatic-aromatic polyester resin used as the soft component (C) is preferably 50,000 or more, More preferably, it is 100,000 or more. If it is 50,000 or more, it is difficult to cause problems such as poor mechanical strength. On the other hand, it is preferable that it is 400,000 or less, and it is more preferable that it is 250,000 or less. If it is 400,000 or less, it is difficult to cause problems such as a decrease in molding processability due to excessive increase in melt viscosity.

  Examples of the core-shell structure rubber used as the soft component (C) include diene-based core-shell polymers such as methacrylic acid-butadiene copolymer and acrylonitrile-butadiene-styrene copolymer, and methacrylic acid-styrene-acrylonitrile copolymer. Examples include acrylic core-shell type polymers such as polymers, silicone-based core-shell type copolymers such as silicone-methacrylic acid-methyl methacrylic acid copolymers, and silicone-methacrylic acid-acrylonitrile-styrene copolymers. Among these, a silicone-methacrylic acid-methylmethacrylic acid copolymer having good compatibility with the polylactic acid-based resin composition (A) and having a good balance between impact resistance and transparency of the film is more preferably used. .

  The mass (weight) average molecular weight of the shell part of the core-shell structure rubber is preferably 10,000 or more, and more preferably 50,000 or more. If it is 10,000 or more, problems such as poor mechanical strength are unlikely to occur, which is preferable. On the other hand, the weight average molecular weight is preferably 1,500,000 or less, and more preferably 100,000 or less. If it is 1,500,000 or less, the melt viscosity becomes too high and it is difficult to cause problems such as deterioration of molding processability.

  Examples of commercially available core-shell structured rubbers include “Metablene C, S, E, W” (manufactured by Mitsubishi Rayon Co., Ltd.), “Kane Ace” (manufactured by Kaneka Corporation), and the like. .

  Further, ethylene-vinyl acetate copolymer (EVA), ethylene- (meth) acrylic acid copolymer (EAA), ethylene- (meth) acrylic acid ester copolymer (EMA) used as the soft component (C). The ethylene-methyl (meth) acrylic acid ester copolymer (EMMA) preferably has a comonomer content other than ethylene of 20% by mass to 90% by mass, preferably 40% by mass to 80% by mass. used. If the comonomer content other than ethylene is 20% by mass or more, the effect on the rupture resistance of the film can be sufficiently obtained, and transparency can be maintained, which is preferable. On the other hand, if the comonomer content other than ethylene is 80% by mass or less, the rigidity and heat resistance of the entire film can be favorably maintained, which is preferable. Among these, ethylene-vinyl acetate copolymer (EVA) is more preferably used.

  The melt flow rate (MFR) of the EVA, EAA, and EMMA is not particularly limited, but the MFR (value at JIS K 7210, temperature: 190 ° C., load: 2.16 kg) is usually 0.00. It is preferably 5 g / 10 min or more and 15 g / 10 min or less, and more preferably 1.0 g / 10 min or more and 10 g / 10 min or less.

  Examples of the commercially available soft component (C) include "EVAFLEX" (manufactured by Mitsui DuPont Polychemical Co., Ltd.) and "Novatech EVA" (Mitsubishi Chemical Corporation) as the ethylene-vinyl acetate copolymer (EVA). ), "Ebaslene" (Dainippon Ink Chemical Co., Ltd.), "Evatate" (Sumitomo Chemical Co., Ltd.), "Soabrene" (Nippon Synthetic Chemical Co., Ltd.), ethylene-acrylic acid copolymer As the coalescence (EAA), “Novatech EAA” (manufactured by Mitsubishi Chemical Corporation), ethylene-ethyl acrylate copolymer (EMA) and ethylene- (meth) acrylic acid copolymer (EMA) as “Noah Frey AC” (Mitsui DuPont Polychemical Co., Ltd.) and ethylene-methyl (meth) acrylic acid copolymer (EMMA) include “ACRlift” (manufactured by Sumitomo Chemical Co., Ltd.) It is.

The mass ratio of the polylactic acid resin composition (A) to the polyolefin resin composition (B) is based on 100 parts by mass of the polylactic acid resin composition (A), and the polyolefin resin composition. (B) needs to be 10 parts by mass or more, preferably 20 parts by mass or more, and more preferably 30 parts by mass or more. Moreover, the upper limit of the said mass ratio of a polyolefin-type resin composition (B) is 90 mass parts or less, and it is more preferable in it being 80 mass parts or less.
If the content of the polyolefin resin composition (B) is 20 parts by mass or more with respect to 100 parts by mass of the polylactic acid resin composition, it is preferable because pores can be formed in the layer. On the other hand, when the content is 90 parts by mass or less, it is preferable because a sea-island structure that is uniformly dispersed in the matrix can be formed.

  The mass ratio of the polylactic acid resin composition (A) to the soft component (C) is 20 parts by mass with respect to 100 parts by mass of the polylactic acid resin composition (A). It is necessary to be 30 parts by mass or more, preferably 30 parts by mass or more, and more preferably 40 parts by mass or more. Moreover, the upper limit of the said mass ratio of a soft component (C) is 80 mass parts or less, and it is more preferable in it being 70 mass parts or less. If the content of the soft component (C) is 20 parts by mass or more with respect to 100 parts by mass of the polylactic acid resin composition, it is preferable because fracture resistance can be imparted. On the other hand, if this content is 80 parts by mass or less, it is preferable because rigidity is not lowered.

<Hole>
The resin composition containing the polylactic acid-based resin composition (A), the polyolefin-based resin composition (B), and the soft component (C) includes the polylactic acid-based resin composition (A) and the soft component. (C) forms a matrix, and the polyolefin resin composition (B) forms a dispersion domain. By stretching the film comprising the above-mentioned resin composition containing the polyolefin-based resin composition (B) at the above-mentioned mass ratio to form a sea-island structure as a whole, peeling is caused at the interface between the matrix and the dispersion domain. Thus, holes can be formed. Thereby, the film with small bulk specific gravity mentioned later and favorable light-shielding property and heat insulation can be obtained.

  At the time of film production, the matrix component (that is, the polylactic acid resin composition (A) and the soft component (C)) and the dispersion domain (that is, the polyolefin resin composition (B)) are also orthogonal to the main shrinkage direction (flow). In particular, the dispersion domain (polyolefin-based resin composition (B)) is stretched in the flow direction (direction perpendicular to the main film shrinkage direction). The aspect ratio of the dispersion domain (polyolefin resin composition (B)) at this time is greater than 1, preferably 3 or more, more preferably 5 or more, and 50 or less, preferably 40 or less, more preferably 35. It is desirable to adjust to be as follows. If the aspect ratio of the dispersion domain (polyolefin-based resin composition (B)) is larger than 1, pores are easily generated when stretched in the direction perpendicular to the flow direction, and if the aspect ratio is 50 or less, It is preferable because the dispersion domain becomes too fine and it is difficult to cause a problem that pores are hardly generated even if it is stretched.

When the dispersion domain (polyolefin-based resin composition (B)) has a predetermined aspect ratio, the dispersion domain is parallel to the outer surface of the film and is unidirectional, that is, the film flow direction ( The film extends in the direction perpendicular to the main film shrinkage direction. For this reason, the matrix (polylactic acid resin composition (A) and the soft component) is formed by setting one stretching direction of uniaxial stretching or one stretching direction of biaxial stretching to a direction perpendicular to the flow direction (film main shrinkage direction). (C)) and the dispersion domain (polyolefin-based resin composition (B)) are more likely to be peeled off, and many pores can be formed.
In the present specification, the “main shrinkage direction” means a direction having a large shrinkage ratio among the vertical direction and the horizontal direction, and is a direction corresponding to the outer circumferential direction when the bottle is attached to a bottle, for example. Further, the “direction orthogonal to the main shrinkage direction” refers to a direction orthogonal to the direction with large yield shrinkage.

<Method for producing heat-shrinkable pore-containing film>
The film of the present invention can be produced by stretching an unstretched film made of the resin composition in at least a uniaxial direction. Specifically, the polylactic acid resin composition (A), the polyolefin resin composition (B), and the soft component (C) are first mixed at the mass mixing ratio to obtain the resin composition. Further, additives such as a plasticizer, 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 added as necessary. As a method of mixing, for example, there is a method of obtaining a pre-compound using a same-direction twin-screw extruder, a kneader, a Henschel mixer or the like.

  Next, as a method of forming a film, the above resin composition is put into an extruder and melt-extruded. The melt-extruded film is cooled with a cooling roll, air, water or the like. As the extrusion method at this time, a known method such as a T-die method or a tubular method can be employed.

  In addition, the film is not formed after these components are mixed in advance, but the polylactic acid resin composition (A), the polyolefin resin composition (B), and the soft component which are constituent components of the resin mixture. (C) may be directly charged into a film extruder, and mixing and film forming may be performed in the same apparatus.

  The obtained unstretched film is reheated by a method such as hot air, warm air, ultraviolet light, carbon dioxide laser, microwave, etc., and at least one direction, that is, uniaxial direction or by roll method, tenter method, tubular method, etc. By stretching in the biaxial direction, peeling occurs at the interface between the matrix and the domain, and pores are formed, whereby the heat-shrinkable pore-containing film according to the present invention can be produced. Whether the stretching is uniaxial stretching or biaxial stretching can be determined as appropriate depending on the use of the film to be produced.

  The temperature at which the stretching is performed is the softening temperature of the polylactic acid resin composition (A), the polyolefin resin composition (B), and the soft component (C), and the heat-shrinkable pore-containing film obtained. Although it may fluctuate | varies by a use etc., it is preferable in it being 60 degreeC or more, and it is further more preferable in it being 65 degreeC or more. If the stretching temperature is 60 ° C. or higher, the elastic modulus of the raw material is increased in the stretching process, and it is difficult to obtain good stretchability, and it is difficult to cause a problem that film breakage and thickness unevenness occur. On the other hand, it is preferably 85 ° C. or lower and more preferably 80 ° C. or lower. When the stretching temperature is 85 ° C. or lower, it is difficult to cause problems such as failure to express desired shrinkage characteristics, and peeling at the interface between the matrix and the dispersion domain is not promoted and sufficient pores cannot be obtained. is there.

  The draw ratio at the time of the above stretching is the composition of the resin composition obtained by mixing the polylactic acid resin composition (A), the polyolefin resin composition (B) component and the soft component (C), and stretching. Although it can select suitably according to a means, extending | stretching temperature, the target product form, etc., generally it is 1.5 times or more, and it is more preferable that it is 3 times or more. If the draw ratio is 1.5 times or more, it is preferable that sufficient pores cannot be obtained and a desired function cannot be obtained, and the draw ratio is 8 times or less. And preferably 6 times or less. If it is 8 times or less, there is no problem such as a problem in strength, practical performance can be obtained, and holes can be sufficiently formed.

  The stretching direction in the stretching step can be appropriately selected depending on the intended use, but the film of the present invention has a structure in which the dispersion domain of the polyolefin-based resin composition (B) extends in the film take-up direction (MD). Therefore, stretching in the direction perpendicular to the extension direction (TD) is preferable because pores can be easily formed.

  Further, even in the case of uniaxial stretching, if a weak stretching of about 1.01 times to 1.8 times is given in a direction orthogonal to the main shrinkage direction of the film as necessary, the resulting heat shrinkable void-containing film machine It is more preferable because the physical properties are improved.

  The aspect ratio of the dispersed domain is preferably generated by a 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 (polyolefin resin composition (B)) can be controlled.

  The film of the present invention may be used in a single layer, or two or more layers for the purpose of adjusting shrinkage properties, printing properties, solvent sealing properties, barrier properties, concealing properties, heat insulating properties, viewability, etc. Lamination may be performed so as to have a layer structure of Examples of the layer to be laminated include a printing layer and a vapor deposition layer. When used in a single layer configuration, the thickness of the film is 30 μm or more, preferably 40 μm or more, more preferably 50 μm or more, and 200 μm or less, preferably 175 μm or less, more preferably 150 μm or less. Moreover, when using by a laminated structure, using as an intermediate | middle layer is preferable. In that case, the thickness ratio of the film of the present invention to the thickness of the entire film is 20% or more, preferably 25% or more, more preferably 30% or more, and 95% or less, preferably 90% or less, more preferably 85. % Or less is desirable.

  When the film of the present invention is used as part of a laminated structure, the layer structure is not particularly limited. When the film of the present invention is represented by the (I) layer and the second layer is represented by the (II) layer, the layer configuration is an embodiment in which the (II) layer is laminated on one or both sides adjacent to the (I) layer. In addition, the case of having a third layer for the purpose of imparting improved adhesion, barrier property, concealing property, heat insulating property, etc. between the (I) layer and the (II) layer is also included. Preferably, an intermediate layer (I) layer and a surface layer (II) layer as a two-kind / three-layer structure ((II) layer / (I) layer / (II) layer), or an intermediate layer and a surface layer There are three types and five layers having an adhesive layer (layer (II) / adhesive layer / (I) layer / adhesive layer / (II) layer)).

  The resin composition used for layers other than the (I) layer is not particularly limited, but considering the adhesiveness with the (I) layer, the recyclability of the entire film, etc., the poly used for the (I) layer. It is preferable to comprise the lactic acid resin composition (A) as a main component. Furthermore, the (II) layer has improved interlayer adhesion, reduced bulk specific gravity, and rupture resistance within a range that does not impair various properties required as a surface layer such as printability, solvent sealability, and fusion resistance. Thermoplastic resins other than the polylactic acid resin composition can be included for the purpose of improving the shrinkage and adjusting the shrinkage characteristics. Examples of thermoplastic resins other than polylactic acid resin compositions include polyolefin resins, polystyrene resins, acrylic resins, amide resins, aliphatic and / or aromatic polyester resins, among which the polyolefins mentioned above A resin composition (B) and a soft component (C) can also be used suitably.

  In addition, the resin composition constituting the (I) layer and the (II) layer may include a plasticizer, a heat stabilizer, an antioxidant, a UV absorber, a light as long as the effects of the present invention are not impaired. Additives such as stabilizers, pigments, colorants, lubricants, nucleating agents, and hydrolysis inhibitors may be added.

  The above-mentioned laminated film is a method of stretching an unstretched film in which the (I) layer and other layers are laminated in at least one direction, or (I) an unstretched film of other layers after stretching the layer in at least one direction. Alternatively, it can be produced by a method of laminating a stretched film with heat or a solvent by a known method, or a method of (I) stretching a layer in at least one direction and then coating a resin composition used for other layers by a known method. .

  The film of this invention needs to have a shrinkage rate of 20% or more when immersed in warm water of 80 ° C. for 10 seconds, preferably 25% or more, and more preferably 30% or more. On the other hand, the shrinkage rate needs to be 80% or less, preferably 75% or less. This is because, for example, a heat-shrinkable label such as a heat-shrinkable label used for packaging of a PET bottle or the like requires a heat shrinkage rate of at least 20%, while heat shrinkage exceeds 80%. This is because it becomes difficult to control the later form. The shrinkage rate is the difference between the length before and after shrinkage when the original length is 100%.

  At present, as an example of the shrinkage processing machine that is most commonly used industrially for labeling of PET bottles, there is one generally called a steam shrinker that uses water vapor as a heating medium for shrinking. The heat-shrinkable label must be sufficiently heat-shrinked at the lowest possible temperature from the viewpoint of the effect of heat on the object to be coated, and moreover, with the recent speeding up of the labeling process, it is required to shrink quickly at a lower temperature. Is getting higher. 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.

  In the film of the present invention, in order to adjust the heat shrinkage rate in the main shrinkage direction when immersed in warm water of 80 ° C. for 10 seconds to the above range, the resin composition is adjusted as described in the present invention and stretched. It is preferable to adjust the temperature to a range described later. For example, when it is desired to further increase the heat shrinkage rate, increase the optical isomer ratio of the polylactic acid resin composition (A), increase the content of the soft component (C), increase the draw ratio, Means such as lowering the temperature may be used.

  When the film of the present invention is used as a label, the thermal shrinkage rate in the direction orthogonal to the shrinkage direction of the film is preferably 10% or less when immersed in warm water at 80 ° C. for 10 seconds, and preferably 5% or less. It is more preferable that it is 3% or less. If the film has a thermal shrinkage rate of more than 10% in the direction perpendicular to the main shrinkage direction, the dimensions in the direction perpendicular to the main shrinkage direction after shrinkage will be shortened, and the printed pattern and characters will be distorted after shrinkage. In the case of a square bottle, problems such as vertical sinks and other troubles cannot be ignored.

  The natural shrinkage rate of the film of the present invention is desirably as small as possible. For example, the natural shrinkage rate after storage at 30 ° C. for 30 days is 3.0% or less, preferably 2.0% or less, more preferably 1.5%. % Or less is desirable. 2. When the natural shrinkage rate under the above conditions is 3.0% or less, 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. If it exceeds 0%, a problem may occur in the adhesion stability.

  In the film of the present invention, in order to adjust the natural shrinkage rate to the above range, it is preferable to adjust the resin composition as described in the present invention and to adjust the stretching temperature to the above range. For example, when it is desired to further reduce the natural shrinkage rate, the optical isomer ratio of the polylactic acid resin composition (A) is decreased, the content of the soft component (C) is decreased, the stretch ratio is decreased, It is preferable to use means such as increasing the temperature, increasing the temperature of heat setting after stretching, or extending the time of heat setting after stretching.

  Moreover, since the film of this invention has a void | hole, the bulk specific gravity at the time of setting it as a film falls rather than the true specific gravity of resin used for the film of this invention. The ratio of the bulk specific gravity to the true specific gravity of the film of the present invention is 50% or more, preferably 60% or more, more preferably 70% or more, and 90% or less, preferably 85% or less, more preferably 80% or less. Is desirable. If the ratio of the bulk specific gravity to the true specific gravity is less than 50%, there is a possibility that defects such as insufficient strength of the film may occur due to the excessive proportion of pores. On the other hand, if it exceeds 90%, the formation of pores is too small, and the light shielding property and the heat insulating property may be insufficient.

  In addition, when the bulk specific gravity is less than 1.0, when the film containing the heat-shrinkable pore-containing film is used as a coating label on a polyethylene terephthalate bottle, it is easily separated from polyethylene terephthalate by the liquid specific gravity method. It is more preferable.

  As a method of adjusting the bulk specific gravity to a desired value, for example, among the polylactic acid resin composition (A), the polyolefin resin composition (B), and the soft component (C), Examples thereof include a method of increasing the mixing ratio and a method of generating a large number of pores by operating stretching conditions such as increasing the stretching ratio in the above range and decreasing the stretching temperature.

  The film of the present invention has a light blocking property (light blocking property) of opaque white by light rays being refracted and reflected at the interface between the resin composition and the pores, and part of the light rays being absorbed in the resin composition. have. In the ultraviolet region of 240 nm or more and 400 nm or less, which may cause deterioration or alteration of the contents, and in the range of 240 nm or more and 800 nm or less (ultraviolet visible region) including the visible region of 400 nm or more and 800 nm or less related to the concealability of the contents The light transmittance measured based on JIS K 7015 is required to be 50% or less at any wavelength, preferably 40% or less, and more preferably 30% or less. If it is 50% or less, the light-shielding property is insufficient, and it is difficult to develop the problem of lack of content protection and concealment, which is preferable.

  In the film of the present invention, in order to adjust the light transmittance of 240 nm or more and 800 nm or less to the above range, the resin composition is adjusted as described in the present invention, and the stretching temperature is adjusted to the above range. preferable. For example, when it is desired to further reduce the light transmittance, the optical isomer ratio of the polylactic acid resin composition (A) is decreased, the content of the polyolefin resin (B) is increased, and the soft component (C) Means such as lowering the content, increasing the draw ratio, and lowering the stretching temperature may be used. It is also effective to add pigments, colorants, inorganic particles, etc. within a range that does not deteriorate various properties such as shrinkage and rupture resistance.

  Furthermore, since the film of this invention has a void | hole, heat conduction efficiency becomes low rather than the film using the general thermoplastic resin without a void | hole. For this reason, it can use especially suitably for the use as which the heat insulation and heat retention property, such as a label for hot drinks, are calculated.

  Beverages that are heated and sold by hot-warmers such as beverage vending machines and convenience stores are sold at 60 to 70 ° C. in consideration of temperature distribution in the vending machine. This beverage container made of metal has a significantly higher thermal conductivity than glass or resin beverage containers, so even if it is heated at the same temperature, it is easier to feel the heat. It needs to be relieved. The heat-shrinkable film of the present invention has pores and can be suitably used because it is difficult to transfer heat from the beverage container by covering the holes.

  Examples of methods for further improving the heat insulation and heat retention include reducing the optical isomer ratio of the polylactic acid resin composition (A), increasing the content of the polyolefin resin (B), and the soft component (C). It is advisable to use means such as lowering the content, increasing the draw ratio, and lowering the stretching temperature.

  The fracture resistance of the heat-shrinkable void-containing film according to the present invention is evaluated by the tensile elongation at break of JIS K 7127. In a tensile test under an environment of 0 ° C., particularly for label applications, the tensile elongation at break in the film take-off direction (MD) is preferably 100% or more, more preferably 150% or more, and even more preferably 200% or more. preferable. If the tensile elongation at break in an environment of 0 ° C. is less than 100%, there is a high risk of problems such as breakage of the film during processes such as printing and bag making. Further, if the tensile elongation at break is 150% or more, it is more preferable that the film does not easily break even when the tension applied to the film increases as the speed of processes such as printing and bag making increases. Further, although the upper limit value is not particularly specified, it can be considered that about 500% is sufficient in consideration of the current process speed.

  In the film of the present invention, in order to adjust the tensile elongation at break at 0 ° C. to the above range, the resin composition is adjusted as described in the present invention, and the stretching temperature is adjusted to the range described later. Is preferred. For example, when it is desired to further improve the tensile elongation at break, means such as increasing the content of the soft component (C) or giving weak extension to MD may be used.

  The stiffness of the film of the present invention, that is, the rigidity at normal temperature, is preferably 1.2 GPa or more, more preferably 1.4 GPa or more, and more preferably 1.6 GPa or more in the direction perpendicular to the main shrinkage direction. More preferably. When the film thickness is less than 1.2 GPa, especially when the film thickness is reduced, when the film made in a container such as a PET bottle is covered with a labeling machine, the yield is reduced due to slanting or folding of the film. It is easy for problems to occur. On the other hand, the upper limit of the tensile elastic modulus of the heat-shrinkable film is generally about 3.0 GPa, preferably about 2.9 GPa, and more preferably about 2.8 GPa. If it is 3.0 GPa or less, the elastic modulus becomes too high, and it is difficult to cause a problem that the texture is stiff during use.

  In the film of this invention, in order to adjust the waist at room temperature to the above range, it is preferable to adjust the resin composition as described in this invention and to adjust the stretching temperature to the range described later. For example, when it is desired to further improve the waist, it is preferable to use means such as reducing the content of the soft component (C) or giving weak stretching in a direction orthogonal to the main shrinkage direction.

  The film of the present invention can be used as various molded products such as plastic bottles such as blow bottles, trays, lunch boxes, prepared food containers, and dairy products containers. For the production of such a molded article, a general method for producing a molded article can be used.

  The film of the present invention can also be used as a heat-shrinkable label for food containers such as PET bottles and glass bottles for soft drinks and foods. Even a complicated shape such as a quadrangular prism, a pentagonal column, or a hexagonal column can be brought into close contact with the shape by heat shrinkage, and a container having a beautiful label with no wrinkles or avatars can be obtained. A general heat shrinking method can be used as the heat shrinking method for mounting.

  Since the film of the present invention has excellent low-temperature shrinkability and shrinkage finish, when used as a heat-shrinkable label, it can be used as a heat-shrinkable label for plastic molded products that are deformed when heated to high temperatures, The film can be suitably used as a heat-shrinkable label for a package made of a material that is extremely different from the heat-shrinkable pore-containing film of the present invention in terms of coefficient of thermal expansion and water absorption. Examples of the material forming the package include, for example, polyolefin resins such as metal, porcelain, glass, paper, polyethylene, polypropylene, and polybutene, polymethacrylate resins, polycarbonate resins, polyethylene terephthalate, and polybutylene. The thing using at least 1 sort (s) chosen from polyester-type resins, such as a terephthalate, and a polyamide-type resin as a structural material is mentioned.

  Further, as a material constituting the package in which the film of the present invention can be used as a heat-shrinkable label, polystyrene, rubber-modified impact-resistant polystyrene (HIPS), styrene-butyl acrylate Polymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, acrylonitrile-butadiene-styrene copolymer (MBS), polyvinyl chloride resin, phenol resin, urea resin, melamine resin, epoxy resin, unsaturated A polyester resin, a silicone resin, etc. can be mentioned, The mixture of these 2 or more types may be sufficient, and a laminated body may be sufficient.

  Hereinafter, the present invention will be described more specifically with reference to examples. First, the resin used and the method for producing the heat-shrinkable pore-containing film will be described.

[Polylactic acid resin composition (A)]
・ Product made by Nature Works LLC: NatureWorks 4050, L body / D body = 95/5 (hereinafter referred to as “PLA1”)
・ Product made by Nature Works LLC: NatureWorks 4060, L body / D body = 95/5 (hereinafter referred to as “PLA2”)

[Polyolefin resin composition (B)]
-Nippon Polypro Co., Ltd .: Polypropylene resin Novatec FY6H (elastic modulus at 80 ° C. = 0.72 GPa MFR = 1.9 g / 10 min) (hereinafter referred to as “PO1”)

[Soft component (C)]
・ Dainippon Ink Co., Ltd .: Puramate PD150, lactic acid copolymer (hereinafter referred to as “Soft 1”)
・ Mitsubishi Rayon Co., Ltd .: Metabrene S2001, core-shell structure acrylic-silicone copolymer (hereinafter referred to as “soft 2”)
・ Showa High Polymer Co., Ltd .: Bionore 3003, polybutylene succinate / adipate copolymer (hereinafter referred to as “soft 3”)
[Other additives]
・ Shiraishi Calcium Co., Ltd .: Opti White, special calcined kaolin clay (hereinafter referred to as “inorganic particles”)

(Method for producing heat-shrinkable pore-containing film)
(Examples 1 to 3)
The polylactic acid resin composition (A), the polyolefin resin composition (B), and the soft component (C) were mixed at the mixing ratios shown in Table 1, respectively, and mixed into a twin-screw extruder (Mitsubishi Heavy Industries, Ltd.). The mixture was melted and mixed at a set temperature of 200 ° C., extruded from a die at a set temperature of 200 ° C., taken up by a cast roll at 50 ° C., and cooled and solidified to obtain an unstretched film having a width of 300 mm and a thickness of 200 μm.
The obtained unstretched film was stretched 1.05 times at 65-75 ° C. by a roll longitudinal stretching machine (Mitsubishi Heavy Industries, Ltd.), and then a film tenter (Mitsubishi Heavy Industries, Ltd.) preheating temperature 80-90. The film was stretched 4.0 times in the horizontal axis direction at a stretching temperature of 65 to 75 ° C. to obtain a heat-shrinkable pore-containing film having a thickness of 80 μm.

Example 4
PLA2 is used for 100 parts by mass on both sides of the (I) layer composed of the mixed resin of the polylactic acid resin composition (A), the polyolefin resin composition (B) and the soft component (C) shown in Table 1. After obtaining an unstretched film laminated by a co-extrusion method using a 300 mm wide, two-kind, three-layer multi-manifold die so as to form a layer (II), the film was stretched by the above-described method to a thickness of 80 μm (surface layer: 8 μm Heat-shrinkable pore-containing film / intermediate layer 64 μm / back layer 8 μm).

(Comparative Examples 1 to 4)
The polylactic acid-based resin composition (A), the polyolefin-based resin composition (B), other inorganic particles, and the soft component (C) were mixed at the mixing ratios shown in Table 1, and the same as the method described in Example 1 A heat-shrinkable pore-containing film and a heat-shrinkable film were obtained.

(Comparative Example 5)
After mixing at the mixing ratio shown in Table 1 and stretching the unstretched film in the same manner as described in Example 1, heat setting was performed in an 80 ° C. atmosphere to obtain a pore-containing film.

  The following evaluation was performed about the obtained heat-shrinkable void-containing film. The results are shown in Table 1, respectively. In the following text, the film take-up direction is described as MD, and the orthogonal direction as TD.

[Shrinkage measurement]
The obtained film was cut into a size of MD 100 mm × TD 100 mm, immersed in a hot water bath at 80 ° C. for 10 seconds to shrink, and the length in the MD direction and the TD direction after shrinkage relative to the original size before shrinkage was measured, The ratio of the change width to the original size was determined, and the larger value of the ratio was determined. If this value was 30% or more and 75% or less, it was evaluated as ◯, 20% or more but less than 30% or more than 75% and 80% or less was evaluated as Δ, and otherwise, it was evaluated as ×.

[Measurement of tensile elongation at break (breaking resistance)]
The obtained film was cut into a size of MD 100 mm × TD 4 mm, and the tensile elongation in the MD direction of the film at an atmospheric temperature of 0 ° C. was measured at a tensile speed of 100 mm / min in accordance with JIS K 7127. The average value was obtained. A sample having an elongation exceeding 150% was evaluated as ◯, a sample having 100% or more and less than 150% was evaluated as △, and the others were evaluated as ×.

[Measurement of tensile modulus (rigidity)]
The obtained film was cut into a size of MD 100 mm × TD 4 mm, and measured in a direction (longitudinal direction) perpendicular to the main shrinkage direction of the film under the condition of a temperature of 23 ° C. according to JIS K 7127.

[Measurement of natural shrinkage]
The obtained film was cut into a size of MD 100 mm × TD 1000 mm, left in a thermostatic chamber at 30 ° C. for 30 days, and the length after shrinkage relative to the original size before shrinkage in each direction was measured to determine the ratio of shrinkage width. The higher ratio was obtained as the natural shrinkage rate. When this natural shrinkage was 1.5% or less, it was evaluated as ◯, when it was over 1.5% and 3.0% or less, it was evaluated as Δ, and when it was over 3.0%, it was evaluated as x.

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

[Measurement of particle diameter of polyolefin resin composition (B)]
The obtained film was cut into a size of TD 10 mm × MD 1 mm × thickness 80 μm with a microtome, and 10 dispersed domain shapes at the center of the film thickness were observed with an electron microscope, and the average value of the maximum width in the flow direction was taken as the major axis. The average value of the maximum widths in the thickness direction of the dispersion domain was calculated as the minor axis.

[True specific gravity measurement]
The true specific gravity of the resin used as the d1, d2 ··· (g / cm 3), the mass of the respective resin and r1, r2 ···, calculated as follows true specific gravity (g / cm ³⁾ did.
True specific gravity = (d1 × r1 + d2 × r2 + ...) / (r1 + r2 + ...) (1)

[Bulk specific gravity measurement]
The obtained film was cut into a size of MD100 mm × TD100 mm, mass w (g) was measured, the thickness of the film was measured at 50 points, and the average thickness t (μm) was obtained. The bulk specific gravity (g / cm ³ ) was calculated.
Bulk specific gravity = (w / t) × 100 (2)

[Light transmittance measurement]
The obtained film was cut into a size of MD 50 mm × TD 50 mm, and a spectrophotometer (“U-4000”, manufactured by Hitachi, Ltd.) to which an integrating sphere was attached had a scanning period of 0.5 nm from wavelength 240 nm to 800 nm. The light transmittance was measured at, and the case where the maximum value of the light transmittance exceeded 50% was evaluated as x, the value of 50 to 25% was evaluated as ◯, and the value of less than 25% was evaluated as ◎.

[Insulation measurement]
The obtained film was cut into a size of MD98 mm × TD208 mm and coated with a metal can (Toyo Seikan Co., Ltd .: TEC200) coated with the film of the present invention shrunk to a shrinkage rate of 20%. 190 mL of hot water was poured, immediately held with a bare hand, and the number of seconds that could be kept without feeling the heat was measured and evaluated as follows.
Calculate the average value of the number of seconds measured by three measurers (25-year-old male, 25-year-old female, 35-year-old male). did. In addition, what was able to continue holding for 60 seconds or more was evaluated as 60 seconds.

From Table 1, a film having a composition, a heat shrinkage rate and a storage elastic modulus (E ′), a bulk specific gravity, and a particle diameter defined in the present invention were excellent in impact resistance, light shielding properties and heat insulation properties. On the other hand, when the polyolefin resin (B) and the soft component (C) are not used (Comparative Example 1), the fracture resistance is not satisfied at all, and the resin is composed of the polylactic acid resin (A) and the soft component (C). In the films (Comparative Examples 2 to 4), voids did not occur during stretching, so the bulk specific gravity was large, and the light shielding properties and heat insulating properties were remarkably inferior. Moreover, when a heat component was further used without using a soft component (Comparative Example 3), the shrinkage rate was extremely low and it was difficult to use it for a heat-shrinkable label. Furthermore, the film (Comparative Example 5) which did not contain the soft component (C) and was heat-set hardly contracted.
As a result, the heat-shrinkable film of the present invention is excellent in mechanical properties such as heat-shrinkability, impact resistance, light-shielding properties and heat insulation properties, and can reduce the bulk specific gravity and suppress the amount of resin used. I understand that there is.

Claims (11)

10 parts by mass or more and 90 parts by mass or less of the polyolefin resin composition (B) and 20 parts by mass or more and 80 parts by mass or less of the soft component (C) with respect to 100 parts by mass of the polylactic acid resin composition (A). At least an unstretched film comprising a resin composition that is contained in a mass ratio and in which the polyolefin resin composition (B) forms a domain in the polylactic acid resin composition (A) and the soft component (C). Stretched more than one axis,
Contain holes, 80 ° C. in the main shrinkage direction of shrinkage when immersed for 10 seconds in hot water of 20% or more state, and are 80% or less,
A heat-shrinkable pore-containing film in which the polylactic acid resin composition (A) and the soft component (C) form a sea portion, and the polyolefin resin composition (B) forms an island portion .   The constituent ratio of the D-form and L-form of the lactic acid which comprises the said polylactic acid-type resin composition (A) is 1:99 thru | or 10:90, or 99: 1 thru | or 90:10. Heat shrinkable pore-containing film.   The soft component (C) is an aliphatic polyester other than the polylactic acid resin composition (A), an aromatic aliphatic polyester, a copolymer of a diol, a dicarboxylic acid, and a lactic acid resin, a core-shell structure rubber, and ethylene -Selected from vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene- (meth) acrylic acid copolymer, and ethylene-methyl (meth) acrylic acid copolymer The heat-shrinkable pore-containing film according to claim 1 or 2, which is a resin or a resin mixture comprising at least one kind.   The storage modulus of the polyolefin resin composition (B) measured under conditions of a temperature of 80 ° C, a frequency of 10 Hz, and a strain of 0.1% is 0.25 GPa or more and 2.00 GPa or less. The heat-shrinkable pore-containing film according to any one of the above.   The heat according to any one of claims 1 to 4, wherein a bulk specific gravity of the heat-shrinkable void-containing film is 50% or more and 90% or less with respect to a true specific gravity of a resin used for the heat-shrinkable void-containing film. Shrinkable pore-containing film.   The heat-shrinkable hole-containing film according to any one of claims 1 to 5, wherein the heat-shrinkable hole-containing film has a light transmittance of 50% or less in a range of 240 nm to 800 nm.   The maximum axis length in the minor axis direction of the polyolefin resin composition (B) dispersed in the heat-shrinkable pore-containing film is 0.1 μm or more and 5 μm or less. The heat-shrinkable pore-containing film as described.   The heat-shrinkable void-containing film according to any one of claims 1 to 7, wherein a tensile elongation at break at 0 ° C according to JIS K7127 is 100% or more.   A molded article using the heat-shrinkable pore-containing film according to any one of claims 1 to 8.   A heat-shrinkable label using the heat-shrinkable pore-containing film according to any one of claims 1 to 8.   A container equipped with the molded product according to claim 9 or the heat-shrinkable label according to claim 10.