JP2007160635A - Heat-shrinkable hole-having film, molding using the film, heat-shrinkable label, and container using the molding or fitted with the label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To be superior in high rigidity, breakage resistance, and shrinkage characteristics, small in natural shrinkage, and low in bulk density by using a polylactic acid resin derived from vegetable and to easily carry out liquid specific gravity separation when used as a label for a PET bottle. <P>SOLUTION: A film has at least two layers of a layer (I) composed of a mixed resin composition containing a component (A) of a prescribed polylactic acid resin composition and a component (B) of a prescribed polyolefin resin composition and a layer (II) composed of a mixed resin composition containing the component (A) and a component (C) of a prescribed soft component and is stretched in at least one direction. The ratio D/L of the layer (I) and the layer (II) is within a prescribed range. In the layer (I), the aspect ratio of a dispersion domain made of the component B dispersed in a matrix of the component (A) is 5-50. A heat-shrinkable hole-having film having a prescribed coefficient of heat shrinkage is used. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable void-containing film, a molded article using the heat-shrinkable void-containing film, a heat-shrinkable label, and a container using the molded article or attached with the label. Specifically, the heat-shrinkable pore-containing film having a small bulk specific gravity and excellent printability, high rigidity, rupture resistance, and shrinkage characteristics, and a molded product using the heat-shrinkable pore-containing film, heat shrinkage The present invention relates to a sex label and a container using this molded product or equipped with this label.

  Conventionally, heat shrinkable films have been used for packaging and bundling applications such as containers. Polyvinyl chloride, polystyrene, polyester, etc. are mainly used as a raw material for this heat-shrinkable film.

  Since all of these use petroleum resources as raw materials, the problem of exhaustion of petroleum resources, the problem of generating harmful gases during combustion after use, and the calories burned are too high for continuous use. Therefore, it has problems such as damaging the combustion furnace and shortening the life of the furnace.

  As a material for solving these problems, polylactic acid, which is derived from plants and can be industrially produced, has attracted attention. In other words, polylactic acid uses corn and other biomass as a raw material, so it is suitable for aiming for a sustainable society. Also, it does not generate harmful gases during combustion, and its combustion calories are low, which can damage the combustion furnace. Absent.

  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 rupture resistance of this polylactic acid, a heat-shrinkable film to which a soft component compatible with polylactic acid is added has also been proposed (see Patent Document 1, etc.). Although this film has improved the problem of fracture resistance to some extent by adding a soft component, there is a problem that rigidity is reduced and natural shrinkage is increased.

  On the other hand, when using heat-shrinkable labels for PET (polyethylene terephthalate) bottles that are currently increasing in consumption, heat-shrinkable labels can be easily separated from PET bottles from the viewpoint of recycling used PET bottles. Is desirable. 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 heat-shrinkable label described in Patent Document 1 has a bulk specific gravity greater than 1, it has been submerged in water together with PET bottle flakes, and is difficult to separate.

  In addition, for the purpose of reducing the bulk specific gravity of the heat-shrinkable label, a method is known in which an incompatible component is added to a thermoplastic resin and then stretched in one or more directions to form voids. And also about polylactic acid, the film which reduced the bulk specific gravity by extending | stretching after adding an incompatible resin is described in patent document 2 grade | etc.,. However, this film cannot be used as a heat-shrinkable label because it is heat-treated after being stretched in the biaxial direction.

  Further, Patent Document 3 and the like describe a heat-shrinkable film in which pores are formed by adding an incompatible resin to a polyester resin other than polylactic acid and then stretching. 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.

  Furthermore, in order to adjust the shrink finish of the polylactic acid-based shrink film, adjusting the isomer ratio of polylactic acid is described in Patent Document 4, etc., but for application to a film in which pores are formed, ,Not listed.

JP 2003-119367 A JP 2002-146071 A JP 2003-321562 A JP 2001-011214 A

  The present invention has been made in view of the above problems, and the object of the present invention is to use a plant-derived polylactic acid-based resin, which has high rigidity, rupture resistance, excellent shrinkage characteristics, and small natural shrinkage, Furthermore, when the bulk specific gravity is small and it is used as a label for a PET bottle, the liquid specific gravity can be easily separated, and a heat shrinkable film is provided.

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

  This invention comprises a component (A) comprising a copolymer of a monomer mixture containing D-lactic acid and L-lactic acid, or a polylactic acid resin composition comprising as a main component a mixture of this copolymer, A) A component containing an incompatible polyolefin-based resin composition (B) in the component, and the content of the component (B) is 10 parts by mass or more and 90 parts by mass or less with respect to 100 parts by mass of the component (A) (I) layer comprised with a resin composition, the said (A) component, (C) component which consists of the following predetermined soft component, and (C) component content is (A) component 100 It is a film stretched in at least one axial direction, having at least two layers with (II) layer composed of a mixed resin composition that is 5 parts by mass or more and 50 parts by mass or less with respect to parts by mass, In the layer, the D / L ratio of the component (A) is 1/99 to 10/90 or 99 / In the layer (II), the D / L ratio of the component (A) is 6/94 to 15/85 or 94/6 to 85/15. In the layer (I), (A) The aspect ratio of the dispersion domain consisting of component (B) dispersed in the matrix consisting of component is 5 to 50 and the thermal shrinkage rate in the main film shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is 20% or more. Thus, the above-mentioned problem has been solved.

  The component (C) includes aliphatic polyesters other than polylactic acid resins, aromatic aliphatic polyesters, copolymers of diol, dicarboxylic acid, and lactic acid resins, core-shell structure rubber, ethylene-vinyl acetate copolymer. A soft component comprising at least one selected from a polymer, an ethylene-ethyl acrylate copolymer, an ethylene- (meth) acrylic acid copolymer, an ethylene- (meth) methyl acrylate copolymer, and a styrene-based elastomer. Say.

  The heat-shrinkable pore-containing film of the present invention (hereinafter also referred to as the film of the present invention) has a lactic acid-based resin composition as a main component, and is therefore useful for promoting the use of biomass and building a recycling society. It is.

  The film of the present invention has a layer in which a predetermined component (A) and a component (B) are mixed at a predetermined ratio, and further has a predetermined D / L ratio. Since the aspect ratio of the component (B) in the component (A) is adjusted, excellent rigidity, rupture resistance and heat shrinkage characteristics can be imparted, and the natural shrinkage rate can be reduced.

  Furthermore, since the film of the present invention has pores, it can be made to have a bulk specific gravity of 0.50 or more and less than 1.00, and a liquid specific gravity method with a plastic for containers having a specific gravity of 1.0 or more, such as PET. This makes it possible to sort by and excels in recyclability.

  Furthermore, the film of the present invention has excellent heat resistance and shrinkage characteristics by adjusting the crystallinity of the polylactic acid-based resin in each of the layers (I) and (II) for each layer, as well as printability and bag making. Excellent sealing and design. Furthermore, since the film of the present invention contains pores, it is excellent in heat insulating properties, light shielding properties, and cushioning properties.

  Hereinafter, the film, molded product, heat-shrinkable label, and container equipped with this molded product or heat-shrinkable label will be described in detail.

  In the present specification, “main component” is intended to allow other components to be included as long as the action and effect of the resin constituting each layer is not hindered. 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 mixed resin composition containing the following components (A) and (B), and a mixed resin containing the following components (A) and (C): It is a film stretched in at least one axial direction and having at least two layers (II) composed of the composition.

[(I) layer]
As described above, the (I) layer constituting the film of the present invention is composed of a mixed resin composition containing the following components (A) and (B).

<(A) component>
The component (A) refers to a homopolymer or copolymer of a monomer mixture containing D-lactic acid and L-lactic acid, or a polylactic acid resin composition containing as a main component a mixture of this copolymer. . As the monomer constituting the monomer mixture, in addition to the above-described D-lactic acid and L-lactic acid, α-hydroxycarboxylic acid other than lactic acid, diol, dicarboxylic acid and other copolymerization components can be mentioned.

  Examples of the α-hydroxycarboxylic acid unit include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, and 2-hydroxy-3-methylbutyric acid. , Bifunctional aliphatic hydroxycarboxylic acids such as 2-methyllactic acid and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone and valerolactone.

  Examples of the diol unit include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the dicarboxylic acid unit include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid.

  The proportion of the copolymer component in the copolymer is not particularly limited, but the higher the proportion of lactic acid, the less the consumption of petroleum resources, which is preferable, and the copolymer is in a proportion not exceeding the Vicat softening point range described below. It is preferable. Specifically, the copolymerization ratio of the copolymer of lactic acid and α-hydroxycarboxylic acid, aliphatic diol, or aliphatic dicarboxylic acid is 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.

  A homopolymer having a constitutional ratio of D-lactic acid and L-lactic acid of 100: 0 or 0: 100 exhibits very high crystallinity, has a high melting point, and tends to be excellent in heat resistance and mechanical properties. However, when used as a heat-shrinkable film, it usually involves printing and a bag making process using a solvent, so it is necessary to moderately reduce the crystallinity of the component material itself in order to improve printability and solvent sealability. It becomes. Also, if the crystallinity is excessively high, orientational crystallization proceeds during stretching, and the film shrinkage property during heating tends to decrease, and even in a film that suppresses crystallization by adjusting stretching conditions, etc. May cause crystallization to proceed prior to shrinkage due to heating during heat shrinkage, resulting in shrinkage unevenness or insufficient shrinkage. On the other hand, in the case of a DL-lactic acid copolymer, it is known that the crystallinity decreases as the proportion of the optical isomer increases. Therefore, when using a polylactic acid-type resin composition as a heat-shrinkable film, it is preferable to adjust the crystallinity by appropriately adjusting the copolymerization ratio of the DL-lactic acid copolymer.

  By the way, as a method for adjusting the D-form and the L-form, a blend of two or more types of DL-lactic acid having different constituent ratios of D-lactic acid and L-lactic acid is blended even if it is adjusted by copolymerization. It is also possible to adjust by doing.

  In the film of the present invention, the constituent ratio of D-lactic acid and L-lactic acid constituting the polylactic acid-based resin composition constituting the component (A) (hereinafter abbreviated as “D / L ratio”) is as follows. It is preferably in the range of 1/99 to 10/90, or in the range of 99/1 to 90/10, preferably in the range of 3/97 to 7/93, or in the range of 97/3 to 93/7. Further preferred.

  When the D / L ratio is within the above range, a film having a desired bulk specific gravity can be obtained by causing sufficient hole formation in the hole forming step described later. On the other hand, when the D / L ratio is outside the above range, the crystallinity becomes high, and the shrinkage rate is lowered due to the crystallization, making it difficult to use as a heat shrink film.

  The weight (mass) average molecular weight of the copolymer contained in the component (A) is not less than 50,000, preferably not less than 100,000, and not more than 400,000, preferably not more than 250,000. It is desirable. If the weight (mass) average molecular weight is within this range, an appropriate melt viscosity can be obtained, and good molding processing can be achieved.

  The Vicat softening point of the component (A) 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 component (A) is 50 ° C. or higher, natural shrinkage can be suppressed even when the obtained heat-shrinkable pore-containing film is left at a temperature slightly higher than room temperature, for example, in summer. Moreover, if the Vicat softening point of (A) component is 95 degrees C or less, low temperature extending | stretching will be realizable at the time of extending | stretching of a film, and a favorable shrinkage characteristic can be given to the obtained film.

  As the polymerization method for the component (A), a known method such as a condensation polymerization method or a ring-opening polymerization method may be employed. For example, in the case of a condensation polymerization method, a polylactic acid resin having an arbitrary composition can be obtained by directly dehydrating condensation polymerization of D-lactic acid, L-lactic acid, or a mixture thereof. Further, in the ring-opening polymerization method, a lactide which is a cyclic dimer of lactic acid is subjected to ring-opening polymerization in the presence of a predetermined catalyst while using a polymerization regulator or the like, if necessary. A lactic acid resin can be obtained. The lactide includes 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. There is a polylactic acid resin having an arbitrary composition and crystallinity by mixing and polymerizing as necessary.

  The component (A) can contain a small amount of other copolymer components for the purpose of improving heat resistance. Examples of such copolymer components include non-aliphatic carboxylic acids such as terephthalic acid, non-aliphatic diols such as bisphenol A ethylene oxide adducts, and the like. Furthermore, the component (A) can also 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.

  As typical resin compositions that can be used as the component (A), for example, the “Lacia” series manufactured by Mitsui Chemicals, Inc., the “Nature Works” series manufactured by Nature Works LLC, and the like are commercially available. As mentioned.

<(B) component>
The component (B) refers to a polyolefin resin composition that is incompatible with the component (A). Here, “incompatible” means that when the mixed resin composition of the component (A) and the component (B) is observed using an optical device such as an electron microscope, B) A state in which the component forms a domain having an average diameter of 0.1 μm or more.

  As the resin constituting the polyolefin resin composition, high-density polyethylene, low-density polyethylene, linear low-density polyethylene and other polyethylene resins, highly crystalline homopolypropylene, random polypropylene and other polypropylene resins, polymethylterpene, Or these mixed resin etc. are mentioned, Preferably it is a highly crystalline polypropylene. These resins can be used alone or in admixture of two or more.

  More specifically, the resin constituting the polyolefin-based resin composition is, as a polyethylene-based resin, trade names “Novatech HD, LD, LL”, “Kernel”, “Toughmer A, P” (manufactured by Nippon Polytech 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. In addition, as the polypropylene resin, trade names “Novatech PP”, “WINTEC”, “Toughmer XR” (manufactured by Nippon Polypro Co., Ltd.), “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 density of the polyolefin resin composition 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 , and still more preferably. The range is 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.

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

  The polyolefin-based resin composition has a storage elastic modulus at 80 ° C. measured at a frequency of 10 Hz and a strain of 0.1% of 0.25 GPa or more, preferably 0.4 GPa or more and 2.0 GPa or less. It is. If the storage elastic modulus is 0.25 GPa or more, pores can be imparted to the film in the stretching step described later. If the storage elastic modulus is 2.0 GPa or less, desired crystallinity is obtained and specific gravity is obtained. Therefore, it is easy to obtain a film having a target bulk specific gravity.

  Since the component (B) is incompatible with the component (A), the layer (I) in which both components are mixed has a sea-island structure. As will be described later, in the (I) layer of the film of the present invention, since the (A) component is present more than the (B) component, the (A) component forms a sea part, that is, a matrix, and the (B) component is It forms an island part, that is, a distributed domain. Details will be described later.

  In the mixed resin composition in the layer (I), the component (B) is 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 30 parts by mass or more, with respect to 100 parts by mass of the component (A). And 90 parts by mass or less, preferably 80 parts by mass or less.

  In the (I) layer, the 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. A matrix is formed, and the component (B) forms a dispersion domain. 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.

  In particular, when the content of the component (B) is 10 parts by mass or more, pores can be formed in the (I) layer, and the bulk specific gravity of the stretched film 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.

<Additives other than (A) component and (B) component>
In addition to the mixed resin composition in which the component (A) and the component (B) are mixed, the layer (I) is optionally provided with a plasticizer and a heat stabilizer as long as the effects of the present invention are not impaired. , Antioxidants, UV absorbers, light stabilizers, pigments, colorants, lubricants, nucleating agents, hydrolysis inhibitors, and the like. In that case, an additive can be included at 10 mass parts or less with respect to the mass of the said mixed resin composition, Preferably it is 5 mass parts or less.

  Further, in the layer (I), in addition to the mixed resin composition, a glass transition temperature (for the purpose of further improving impact resistance and cold resistance within a range not impairing the effects of the present invention, if necessary. An aliphatic polyester resin or an aromatic polyester resin having a Tg) of 0 ° C. or less, a core-shell structure type rubber, an ethylene-vinyl acetate copolymer (EVA), or the like is 70 parts by mass or less with respect to 100 parts by mass of the polylactic acid resin. You may contain in the range.

  Examples of such aliphatic polyester resins include 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 PLA resins are exemplified.

  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, Among aliphatic diols such as 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 And one obtained by condensation polymerization by selecting one or more of each. At this time, a desired polymer can be obtained by jumping up with an isocyanate compound or the like as necessary.

  In addition, as the aliphatic polyester obtained by ring-opening polymerization of cyclic lactones, those obtained by polymerizing one or more kinds of cyclic monomers selected from ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone, etc. 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.

[(II) layer]
As described above, the layer (II) constituting the film of the present invention is composed of a mixed resin composition containing the following components (A) and (C). In addition to the (I) layer containing pores, the film of this invention is provided with a printability and solvent sealability by disposing a (II) layer having no pores or having a low pore content. Etc. can be improved. Further, in the (I) layer and the (II) layer, the void formation / shrinkage characteristics can be adjusted to a preferable range by changing the copolymer ratio (D / L ratio) of the polylactic acid resin composition to be used.

<(A) component>
The (A) component used in the (II) layer can be the same as the (A) component used in the (I) layer.

  However, the D / L ratio of the component (A) is different from the component (A) used in the layer (I) described above. That is, in the (II) layer, it is important that the D / L ratio of the component (A) is in the range of 6/94 to 15/85, or in the range of 94/6 to 85/15. A range of 93 to 12/88 or a range of 93/7 to 88/12 is preferable.

  If the D / L ratio is within the above range, it is preferable because the degree of crystallization can be suppressed to an appropriate range, and the occurrence of defects such as shrinkage unevenness due to crystallization can be suppressed. Adhesion and seal strength can be improved. On the other hand, when the D / L ratio exceeds the above range, the rupture resistance of the film may be extremely lowered.

<(C) component>
The component (C) used in the layer (II) is a soft component. In the present invention, by mixing the component (C) in the layer (II), the difference in elastic modulus from the layer (I) can be reduced, and as a result, the film can be reduced in rigidity. Moreover, the improvement of the interlayer adhesive strength of the (I) layer and the (II) layer can also be expected. In addition, further improvement in fracture resistance and shrinkage finish can be expected. The component (A) used in the layer (II) is a soft component, although a polylactic acid resin composition having a D / L ratio in a predetermined range is selected in order to improve shrinkage finish. By mixing these, the adhesive force between the (I) layer and the (II) layer is improved, and the shrinkage rate change due to temperature change is alleviated. As a result, the interlayer adhesive strength is improved, and the difference in shrinkage ratio due to temperature unevenness during heat shrinkage is reduced, so that the finish is improved.

As the component (C), a resin composition having a storage elastic modulus at 23 ° C. of 1 × 10 ⁹ Pa or less, more preferably 5 × 10 ⁸ Pa or less is used. If it becomes 1 × 10 ⁹ Pa or less, delamination at the time of sealing can be suppressed without impairing the properties of the heat-shrinkable film due to the addition.

  Specifically, as the component (C), aliphatic polyester other than polylactic acid resin, aromatic aliphatic polyester, copolymer 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 (such as EMMA) Styrene-isoprene copolymer (SIS), styrene-butadiene copolymer (SBS), styrene-ethylene-butylene copolymer (SEBS), styrenic elastomers such as acid-modified SEBS, and the like. Aliphatic polyesters other than polylactic acid resins, aromatic aliphatic polyesters, diols, dicarboxylic acids, and lactic acids Copolymers of fat, core-shell structure type rubbers, and ethylene - vinyl acetate copolymer (EVA) or the like is preferably used.

  Examples of the aliphatic polyester resin other than the polylactic acid-based resin include, for example, 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, and a synthetic fat. Aliphatic polyester resins excluding PLA resins such as aliphatic polyesters can be mentioned.

  Here, specific examples of the aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid include ethylene glycol, 1,4-butanediol, hexanediol, octanediol, cyclopentanediol, cyclohexanediol, 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 And one obtained by condensation polymerization by selecting one or more of them. At this time, a desired polymer can be obtained by jumping up with an isocyanate compound or the like as necessary.

  The ethylene-vinyl acetate copolymer (EVA), ethylene- (meth) acrylic acid copolymer (EAA), ethylene- (meth) acrylic acid ester copolymer (EMA), ethylene-methyl (meth) acrylic acid ester As the copolymer (EMMA), those having a comonomer content other than ethylene of 10% by mass to 90% by mass, preferably 40% by mass to 80% by mass are suitably used. By making it within the above range, it is possible to prevent the deterioration of the solvent sealing property while giving sufficient softness to the (II) layer.

  The styrene-isoprene copolymer (SIS), styrene-butadiene copolymer (SBS), styrene-ethylene-butylene copolymer (SEBS), styrene elastomers such as acid-modified SEBS, etc. Is from 10 to 50 mass, preferably from 20 to 40 mass. By setting it in the above range, it becomes possible to impart sufficient softness to the (II) layer.

  Content of the said (C) component is 5 mass parts or more with respect to 100 mass parts of (A) component, Preferably it is 10 mass parts or more, It is 50 mass parts or less, Preferably it is 40 mass parts or less. It is preferable. If the component (C) is 5 parts by mass or less, the effect of addition cannot be obtained, and if it is 50 parts by mass or more, other shrinkage characteristics and rigidity tend to be affected.

  Examples of lactic acid-based copolymers other than the above-mentioned commercially available polylactic acid-based resins include, for example, the trade name “Puramate” (manufactured by Dainippon Ink and Chemicals) and the trade name “GS-PLA” (Mitsubishi). Chemical Co., Ltd.).

<Additives other than (A) component and (C) component to (II) layer>
The layer (II) has the purpose of improving interlayer adhesion, reducing bulk specific gravity, etc. within a range that does not impair various properties required as a surface layer, such as printability, solvent sealability, and adhesion resistance. A thermoplastic resin other than the polylactic acid-based resin composition can be included. As thermoplastic resins other than this polylactic acid resin composition, polyolefin resins, polystyrene resins, acrylic resins, amide resins, aliphatic polyester resins, aromatic polyester resins, aliphatic aromatic polyester resins Etc.

  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.

(Laminated structure)
As long as the film of this invention has at least two layers of the above-mentioned (I) layer and (II) layer, a layer structure will not be specifically limited. 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 also included for the purpose of imparting improved adhesion, barrier properties, concealing properties, heat insulating properties, etc. between the (I) layer and the (II) layer.

  A preferred layer structure is a two-layer / three-layer structure ((II) layer / (I) layer / (II) layer) having an (I) layer as an intermediate layer and a (II) layer as a surface layer, or an intermediate layer (II) layer is the surface layer, such as layer structure of 3 types and 5 layers ((II) layer / adhesive layer / (I) layer / adhesive layer / (II) layer) having an adhesive layer between the surface layer. A layer structure is mentioned.

  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 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%. It is as follows. By adjusting the thickness ratio within the above range, the thermal contraction rate can be easily adjusted appropriately.

  When an adhesive layer is provided between the (I) layer and the (II) layer, the adhesive layer has a function of 0.5 μm or more, preferably 0.75 μm or more, more preferably 1 μm or more, and 6 μm or less. The thickness is preferably 5 μm or less.

  If the thickness ratio of each layer is in the above range, the shrinkage packaging, shrink-bound packaging, which has excellent film stiffness (rigidity at room temperature), shrink finish, natural shrinkage, and suppressed delamination of the film, A heat-shrinkable laminated film suitable for applications such as shrinkage labels can be obtained with a good balance.

  When the film of the present invention has an adhesive layer between the (I) layer and the (II) layer, the adhesive resin constituting the adhesive layer is included as a main component of the (I) layer and the (II) layer ( A resin having a site having reactivity or affinity for component A) and a site having affinity for component (B) or component (C) is preferably used.

  Here, “having reactivity or affinity for the component (A)” means having a functional group having a high affinity with the component (A) or a functional group capable of reacting with the component (A). . Examples of functional groups having such properties 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, and sulfonic acid ester groups. , Sulfonic acid chloride groups, sulfonic acid amide groups, sulfonic acid groups, epoxy groups, amino groups, imide groups, or oxazoline groups, among others, acid anhydride groups, carboxylic acid groups, or carboxylic acid esters Groups are preferred.

  In addition, the “site having an affinity for the component (B) or the component (C)” means having a chain having an affinity for the component (B) or the component (C). Or it means having a branched saturated hydrocarbon moiety as the main chain, block chain, or graft chain. Specific examples include polyolefin resins or resins obtained by hydrogenating copolymers of styrene hydrocarbons and conjugated diene hydrocarbons, such as styrene-ethylene-butylene copolymers and styrene-ethylene-propylene copolymers. Can be mentioned.

  As a specific product of a resin having a polar group that has a high affinity or can react with the component (A) and is compatible with the component (B) or the component (C), for example, an epoxy group is included. Examples thereof include ethylene copolymer with ethylene glycol and ethylene terpolymer “Bond First” (Sumitomo Chemical Co., Ltd.), modified styrene-ethylene-butadiene block copolymer “Tuftec” (Asahi Kasei Chemicals Co., Ltd.), and the like.

[Production Method of Film of the Present Invention]
This invention film is produced by stretching the unstretched film in which the (I) layer and the (II) layer are laminated in at least one direction.

  Specifically, first, a mixed resin composition constituting the (I) layer and a mixed resin composition constituting the (II) layer are produced. This can be produced by mixing the component (A), the component (B) and other components, or by mixing the component (A), the component (C) and other components. As this mixing method, etc., a method of obtaining a pre-compound using a same-direction twin-screw extruder, a kneader, a Henschel mixer, etc., or directly mixing the two components into a film extruder without mixing them in advance, mixing and film There is a method of performing molding with the same apparatus.

  Next, in the film forming method, the above-described components or pre-compounds are respectively charged into an extruder and melt-extruded. Then, 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 the present invention, it is important that the (I) layer and the (II) layer (adhesive layer between the (I) layer and the (II) layer, if necessary) are laminated. As a lamination method, a method of co-extrusion using a multi-manifold type die, a method of co-extrusion using a feed block, a single layer film of (I) layer and (II) layer is obtained separately, and then thermal lamination is performed. A known method such as a lamination method 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. Stretch in the axial direction. At this time, peeling occurs at the interface between the matrix and the domain, and pores are formed. Thereby, the film of this invention can be produced. Whether the stretching is uniaxial stretching or biaxial stretching can be appropriately determined depending on the intended application.

  The stretching temperature can vary depending on the softening temperature of the component (A), the component (B), the component (C), etc., the use of the resulting heat-shrinkable pore-containing film, etc., preferably 60 ° C. or higher. 65 degreeC or more is further more preferable, 85 degreeC or less is preferable and 80 degreeC or less is more preferable. If the stretching temperature is 60 ° C. or higher, it is possible to prevent the raw material from having an excessively high elastic modulus during the stretching process, so that good stretchability can be obtained, and film breakage and thickness unevenness can be suppressed. On the other hand, if the stretching temperature is 85 ° C. or lower, desired shrinkage characteristics can be expressed, and the stretchability of the component (B) can be suppressed, and peeling at the interface between the matrix and the dispersion domain is promoted. Can be obtained, and the bulk specific gravity can be made less than 1.0.

  The draw ratio in the drawing step can be appropriately selected according to the composition of the mixed resin composition in which the component (A) and the component (B) are mixed, the drawing means, the drawing temperature, the desired product form, and the like. . For example, the draw ratio is 1.5 times or more, preferably 3 times or more and 8 times or less, preferably 6 times or less. If the draw ratio is 1.5 times or more, suitable shrinkage characteristics and sufficient pores can be obtained, and the bulk specific gravity can be made less than 1.0. Moreover, if the upper limit of the draw ratio is about 8 times, practical performance 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 component (B) is elongated in the MD direction as described later, it is perpendicular to the stretching direction. It is preferable that pores can be easily formed by stretching in the direction, that is, the TD direction.

In the case of uniaxial stretching, mechanical properties of the heat-shrinkable pore-containing film obtained by applying a weak stretching of about 1.01 to 1.8 times in the direction orthogonal to the main film shrinkage direction as necessary. Is more preferable because it is 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.

<Method for Adjusting Aspect Ratio of Dispersion Domain Consisting of Component (B) in (I) Layer>
By the way, since the cooling roll used by the said film manufacturing method exists under the said extruder, the state by which the film extruded from the said extruder was extended a little by its own weight by the time it reached a cooling roll become. 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 composed of the component (A) but also the dispersed domain composed of the component (B) Is also extended in a direction (flow direction) orthogonal to the main contraction direction. For this reason, especially the dispersion domain which consists of (B) component will be in the state extended | stretched in the flow direction (direction orthogonal to a film main shrinkage | contraction direction). At this time, the aspect ratio of the dispersed domain comprising the component (B) is adjusted to 5 or more, preferably 10 or more, more preferably 15 or more, and 50 or less, preferably 40 or less, more preferably 35 or less. Is desirable.

  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 component (B) so that the aspect ratio is in the above range in the component (A) which is the matrix, the heat-shrinkable pore-containing film obtained can be obtained at a low temperature. Breaking resistance can be imparted. If the aspect ratio is 5 or more, the film can be given breakage resistance at low temperatures, and if the aspect ratio is 50 or less, the (I) layer is likely to generate pores and has a desired bulk specific gravity. can get.

  The aspect ratio 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 It is possible to control the aspect ratio of the dispersion domain composed of the component (B).

  In this way, when the dispersion domain composed of the component (B) has a predetermined aspect ratio, the dispersion domain composed of the component (B) is parallel to the outer surface of the film and is unidirectional. That is, the film extends in the film flow direction (direction orthogonal to the film main shrinkage 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 shrinking direction), a dispersion domain composed of component A and component (B) It is easier to cause separation at the boundary between and a higher porosity.

<MFR of component (B)>
In order to realize the aspect ratio of the dispersion domain composed of the component (B), the melt flow rate (MRF) of the component (B) is 1.0 g / 10 min or more, preferably 1.5 g / 10 min or more, And it is 5.0 g / 10min or less, Preferably it is 4.5 g / 10min. If the MRF of the component (B) is 1.0 g / 10 min or more, the size of the dispersion domain becomes too large when the sea-island structure is formed, the dispersion state is poor, and vacancies are difficult to be generated uniformly. It is preferable without causing such problems as. On the other hand, if the melt flow rate of the polyolefin-based resin composition is 5.0 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 the low temperature This is preferable without causing problems such as failure to sufficiently impart fracture resistance.

[Physical properties]
[Bulk specific gravity]
The film according to the present invention preferably has a bulk specific gravity of 0.50 or more and less than 1.00. 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 suitable without causing problems such as insufficient strength of the film due to the existing pores.

  Examples of a method for adjusting the bulk specific gravity to a desired value include, for example, a method of increasing the mixing ratio of the component having a smaller specific gravity among the components (A) and (B), increasing the stretching ratio, and stretching temperature. The method of adjusting by the method etc. which produce many void | holes by operating extending | stretching conditions, such as lowering | hanging, is mentioned.

[Heat shrinkage]
The film according to the present invention has a heat shrinkage rate in the film main shrinkage direction of 10% when immersed in warm water at 80 ° C. for 10 seconds, preferably 25% or more, more preferably 25% or more, more preferably 30% or more, And 80% or less is required, 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.

  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, the ratio of the optical isomers of the polylactic acid resin composition (A) in the (I) layer and (II) layer is increased. Means such as lowering the content of the component, lowering the content of the soft component (C) in the layer (II), increasing the stretching ratio, and lowering the stretching temperature may be used.

  When the film of the present invention is used as a heat-shrinkable label, the heat shrinkage rate in the direction orthogonal to the film 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 the heat-shrinkable film is, for example, preferably 1.5% or less after 30 days of storage at 30 ° C. Is preferably 1.0% or less, more preferably 0.5% 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.

  In the film of the present invention, in order to adjust the natural shrinkage ratio 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 range described later. 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 component (B) is decreased, and the content of the soft component (C) It is advisable to use means such as reducing the stretching ratio, decreasing the stretching ratio, increasing the stretching temperature, increasing the temperature of heat setting after stretching, or lengthening the heat setting time after stretching.

(Fracture resistance)
The fracture resistance of the heat-shrinkable pore-containing film according to the present invention was evaluated by the tensile elongation at break, and in the tensile test under the environment of 0 ° C., particularly in the label application, the elongation rate in the film take-off (flow) direction (MD). Is 150% or more, preferably 200% or more, and more preferably 250% or more. If the tensile elongation at break in an environment of 0 ° C. is 150% or more, it is difficult to cause problems such as film breakage at the time of printing and bag making, which is preferable. Further, even 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 200% or more, which makes it difficult to break.

  The upper limit is not particularly limited, but considering the current process speed, it is considered that about 500% is sufficient. On the other hand, when trying to give too much elongation, the rigidity (tensile modulus) of the film decreases. It tends to end up.

  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 component (B), increasing the content of the soft component (C), or giving weak stretching to the MD may be used. Good.

[Rigidity (tensile modulus)]
As for the waist (rigidity at normal temperature) of the film of the present invention, the tensile elastic modulus in the direction orthogonal 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.

  The upper limit is not particularly limited, but is generally about 3.0 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 becomes 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, means such as lowering the content of the component (B), lowering the content of the soft component (C), or giving weak stretching in the direction perpendicular to the main shrinkage direction are used. Good.

[Use]
Since the film of the present invention has pores, light rays are refracted and reflected at the interface between the (A) component resin or the (B) component resin and air, and as a whole, an opaque white-like appearance is exhibited. For example, it is particularly suitable for applications that require light shielding properties. 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, so 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.

  Particularly 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, a corner 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 obtained molded product can be used as a container or the like.

  The molded article and container of the present invention can be produced by using a normal molding method.

  When the film of this invention is used as a heat shrink label for PET bottles or the like, it is in a contracted state at the time of recycling, but it is preferable that the film can be fractionated by the liquid specific gravity method even after the 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 0.99 or less, and more preferably 0.7 or more and 0.00. It is desirable that it is 98 or less. If the bulk specific gravity 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 is 0.50 or more, it is suitable 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 high temperatures, the thermal expansion coefficient, water absorption, etc. Material very different from the film, for example, polyolefin resin such as metal, porcelain, glass, paper, polyethylene, polypropylene, polybutene, polyester resin such as polymethacrylate resin, polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate In addition, it can be suitably used as a heat-shrinkable label material for a package (container) using at least one selected from polyamide-based resins as a constituent material.

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

The present invention will be described below with reference to examples.
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 (MFR)]
Yasuda Seiki Seisakusho Co., Ltd .: Melt index rate (120 SAS-2000) was used, and 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 (E ')]
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 wide and 60 mm long, and a viscoelastic spectrometer (IT measurement (IT measurement ( Co., Ltd .: DVA-200), longitudinal frequency (longitudinal direction) in the range of vibration frequency 10 Hz, strain 0.1%, heating rate 1 ° C./min, chuck 2.5 cm, measuring temperature 40-150 ° C. Was measured. And the storage elastic modulus (E ') in 80 degreeC was measured.

[aspect ratio]
The obtained film was cut into a size of about TD 1 mm × MD 10 mm × thickness 80 μm with a microtome and observed with 10 electron microscopes, and the aspect ratio of the domain consisting of the component (B) incompatible with the component (A) in the film (Major axis / minor axis) was calculated.

[Ink adhesion]
Using a bar coater, a special gravure ink OS-M (indigo color) manufactured by Dainichi Seika Kogyo Co., Ltd. was applied to a film obtained by appropriately diluting with a solvent. Paste (Nichiban Co., Ltd. Elpac LP-18) and rub it 5 times with your finger. Immediately thereafter, the serotape was peeled off at once, and the amount of the ink peeled off was visually observed. Evaluation was performed according to the following criteria.
○: There is no peeling of ink.
Δ: Partially peeled, but more part remaining.
X: Completely peeled off.

[Bulk specific gravity]
The obtained film was precisely cut into a size of MD 100 mm × TD 100 mm, 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)

[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 size of MD110 mm × TD15 mm, the tensile elongation at MD of the film at an atmospheric temperature of 0 ° C. was measured at a tensile speed of 100 mm / min according to JISK6732, and the average of ten measurements. Values are 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 MD5 mm × TD400 mm, a tensile test was performed at a test speed of 5.0 mm / min with a chuck interval of 80.0 mm under the condition of a temperature of 23 ° C., and the beginning of the tensile stress-strain curve. Using the straight line portion, the calculation was performed according to the following equation.
E = σ / ε
E: Tensile modulus σ: Difference in stress per unit area (average cross-sectional area of sample before tensile test) between two points on a straight line

[Shrink finish]
A film printed with a grid of 10 mm intervals was cut to a size of MD 100 mm × TD 298 mm, and both ends of TD were overlapped 10 mm and bonded with a solvent or the like to form a cylinder. This cylindrical film was attached to a PET bottle having a capacity of 500 milliliters, and passed through the steam heating type 3.2 m (3 zones) shrink tunnel for about 4 seconds without rotating. The atmospheric temperature in the tunnel in each zone was set to a range of 80 to 90 ° C. by adjusting the amount of steam with a steam valve. The passed film was visually evaluated according to the following criteria.
A: Shrinkage is sufficient, and there is no wrinkle, avatar or lattice distortion, and adhesion is good.
○: Shrinkage is sufficient, but wrinkles, avatars, lattice distortion is slightly present, or the shrinkage rate in the vertical direction is slightly conspicuous, but there is no practical problem.
X: Insufficient lateral shrinkage or longitudinal shrinkage is conspicuous and causes a practical problem.

[Natural shrinkage]
The obtained film was cut into a size of 100 mm in length (MD) and 1000 mm in width (TD) and left in a thermostatic bath at 30 ° C. for 30 days, and the amount of shrinkage relative to the original size before shrinkage was measured in the main shrinkage direction. The ratio was expressed as a% value.

Moreover, the raw material used by each Example and the comparative example is as follows.
((A) component)
-Polylactic acid-based resin: manufactured by Nature Works LLC, trade name: NatureWorks 4050, L-form / D-form weight = 95/5, hereinafter abbreviated as “PLA1”.
-Polylactic acid-based resin: manufactured by Nature Works LLC, trade name: Nature Works 4060, L-form / D-form weight = 88/12, hereinafter abbreviated as “PLA2”.

((B) component)
-Polypropylene resin: manufactured by Nippon Polypro Co., Ltd. Trade name: FY6H, hereinafter abbreviated as “PO1”.
-Polypropylene resin: manufactured by Nippon Polypro Co., Ltd. Trade name: FB3HAT, hereinafter abbreviated as “PO2”.

((C) component)
Aliphatic polyesters other than polylactic acid resin: Showa High Polymer Co., Ltd. Product name: Bionore 3003, polybutylene succinate / adipate copolymer, storage elastic modulus at 23 ° C. = 3.92 × 10 ⁸ Pa, below , “BN”.
Polyethylene-polyvinyl acetate copolymer: manufactured by Dainippon Ink & Chemicals, Inc. Trade name: Ebaslen 260, storage elastic modulus at 23 ° C. = 2.42 × 10 ⁷ Pa, hereinafter abbreviated as “EVA”.

(Examples 1-4, Comparative Examples 1-4)
As the resin for (I) layer shown in Table 1, (A) component and (B) component are dry blended, and using a small-sized same-direction twin screw extruder (Mitsubishi Heavy Industries, Ltd., 40 mmφ), 200 ° C., The mixture was kneaded at 100 rpm, extruded into a strand shape, quenched in a water tank, and then cut to prepare a mixed resin pellet.
Moreover, as resin for (II) layer shown in Table 1, (A) component and (C) component were dry blended, and the pellet of mixed resin was produced using the method similar to said method.
Each of the obtained pellets is put into a separate single screw extruder (manufactured by Mitsubishi Heavy Industries, Ltd.), melted and mixed at a set temperature of 200 ° C., coextruded from a two-kind / three-layer die, and a cast roll at 60 ° C. Was taken and cooled and 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 80 ° C. and a stretching temperature of 71 ° C. by a film tenter (manufactured by Kyoto Machine Co., Ltd.), and then rapidly cooled with cold air to heat-shrinkable air having a thickness of 80 μm A hole-containing film was obtained. The evaluation results of the obtained film are shown in Table 1.
In Example 3, the same method as in Example 1 was adopted except that the aspect ratio was changed by adjusting the lip gap of the die and the take-up speed of the cast roll when producing the unstretched laminated sheet.
The stretching temperature in Example 2 was 72 ° C., and the stretching temperature in Comparative Example 1 was 73 ° C.

  From Table 1, the film having the composition, heat shrinkage rate, and aspect ratio defined in the present invention was excellent in breakage resistance, ink adhesion, and spontaneous shrinkage resistance.

  On the other hand, when the soft component (C component) was not used in the (II) layer (Comparative Examples 1 and 2), the fracture resistance and the ink adhesion were poor. Further, when the aspect ratio was high (Comparative Example 3), the bulk specific gravity was high, and the fracture resistance and shrinkage finish were inferior. In addition, when the D / L ratio of the polylactic acid resin of the (II) layer was high (Comparative Example 4), no voids were formed during stretching, and the bulk specific gravity was large and remarkable.

  Thus, the heat-shrinkable film of the present invention is excellent in mechanical properties such as heat-shrinkability, rupture resistance and printing properties, and can reduce the bulk specific gravity and suppress the amount of resin used. I understand.

Claims (6)

It is composed of a mixed resin composition containing the following component (A) and component (B), wherein the content of component (B) is 10 parts by mass or more and 90 parts by mass or less with respect to 100 parts by mass of component (A). (I) layer,
The following (A) component and (C) component are included, and it is comprised with the mixed resin composition whose content of (C) component is 5 to 50 mass parts with respect to 100 mass parts of (A) component. (II) a film having at least two layers with a layer and stretched in at least one axial direction;
In the (I) layer, the D / L ratio of the component (A) is 1/99 to 10/90 or 99/1 to 90/10,
In the (II) layer, the D / L ratio of the component (A) is 6/94 to 15/85 or 94/6 to 85/15,
In the layer (I), the aspect ratio of the dispersion domain composed of the component (B) dispersed in the matrix composed of the component (A) is 5 or more and 50 or less,
A heat-shrinkable pore-containing film having a heat shrinkage rate of 20% or more in the main film shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds.
(A) Component: a copolymer of a monomer mixture containing D-lactic acid and L-lactic acid, or a polylactic acid resin composition comprising as a main component a mixture of this copolymer (B) Component: (A) Component Incompatible polyolefin resin composition (C) component: aliphatic polyester other than polylactic acid resin, aromatic aliphatic polyester, copolymer of diol, dicarboxylic acid and lactic acid resin, core shell structure type rubber, At least one selected from ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) methyl acrylate copolymer, and styrene-based elastomer Soft component consisting of the above   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.   A molded article using the heat-shrinkable pore-containing film according to claim 1 as a base material.   A heat-shrinkable label using the heat-shrinkable pore-containing film according to any one of claims 1 to 3 as a substrate.   A container using the molded article according to claim 4 or equipped with the heat-shrinkable label according to claim 5.