JP2007161826A - Heat-shrinkable film, heat-shrinkable label and molded article using the film, and container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable film excellent in mechanical characteristics such as heat shrinkability, transparency, impact resistance and the like and excellent in appearance after shrinking, to provide a molded article or a heat-shrinkable label using the heat-shrinkable film and to provide a container having the molded article or the like attached thereto. <P>SOLUTION: The heat-shrinkable film is produced by stretching a mixed resin composition comprising 100 pts.mass of (A) a polylactic acid resin and 20-200 pts.mass of (B) a (meth)acrylic resin in at least uniaxial direction. The heat-shrinkable film is adjusted so that the heat shrinkage factor in a main shrinking direction when immersed in hot water of 80°C for 10 seconds is not less than 20% and the storage elastic modulus (E') at 70°C in a direction perpendicular to the main shrinking direction is not less than 100 MPa. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable film suitable for uses such as a heat-shrinkable label, a heat-shrinkable label or a molded product using the heat-shrinkable film, a heat-shrinkable label mounted thereon, or a molded product Related to the container.

  Generally, containers such as bottles and plastic bottles filled with soft drinks or alcoholic beverages are provided with heat-shrinkable labels to display the type of filled drinks and to decorate the containers. Yes. As a heat-shrinkable film suitable for the use of this heat-shrinkable label, a polyvinyl chloride film, a polyester film, a polystyrene film, or the like is used.

  When the above plastic film is disposed in the natural environment, it may not be decomposed due to its chemical stability, but may be accumulated as dust and may cause a problem of environmental pollution. Moreover, since it is manufactured from fossil resources such as oil, there is a risk of causing the problem of depletion of fossil resources in the future.

  From the viewpoint of reducing the above problems, plant-derived biodegradable plastics such as polylactic acid resins are known as materials that contribute to the saving of fossil resources.

  The above-mentioned polylactic acid-based resin is a plant-derived plastic made from lactic acid obtained from starch such as corn and potato, and has excellent transparency, and thus has attracted particular attention in applications such as films.

  However, since the polylactic acid-based resin is brittle in the material itself, when it is directly molded into a sheet or film, sufficient strength cannot be obtained and it is difficult to put it to practical use. In particular, the uniaxially stretched uniaxially stretched film cannot be improved in brittleness in the direction in which it is not stretched by stretching, and sufficient mechanical properties such as impact resistance cannot be obtained.

  As various methods for improving the mechanical properties such as impact resistance of the polylactic acid-based resin described above, a method of incorporating a resin composition into the polylactic acid-based resin has been proposed. For example, a polylactic acid resin having a specific weight average molecular weight containing a polymethacrylate resin (Patent Document 1), a polylactic acid resin containing an aliphatic polyester other than polylactic acid (Patent Document 2) ), Polylactic acid-based resin containing polycaprolactone (Patent Document 3), polylactic acid-based resin containing polyolefin such as ethylene-vinyl acetate copolymer (Patent Document 4), L-lactic acid and A polylactic acid resin having an adjusted copolymerization ratio of D-lactic acid containing an aliphatic aromatic polyester (Patent Document 5), and a polylactic acid resin containing a polyolefin such as an ethylene-vinyl acetate copolymer. Thing (patent document 6) etc. are disclosed.

Japanese Patent Laying-Open No. 2005-036054 JP-A-9-169896 JP-A-8-300481 JP-A-9-151310 JP 2003-119367 A JP 2001-011214 A

  The main purpose of the polylactic acid-based resin described in Patent Document 1 is to improve its heat resistance and transparency, and there is a problem that it is difficult to adapt to improving shrink finish as a heat shrinkable film. there were.

  The polylactic acid resins described in Patent Documents 2 to 4 are intended to improve brittleness while maintaining the transparency, and are applied as an improvement in shrink finish as a heat shrinkable film. It is difficult.

  The polylactic acid-based resin described in Patent Document 5 can suppress crystallization during heating as a heat-shrinkable film, but has a problem of causing shrinkage spots, wrinkles, and avatars due to rapid shrinkage.

  In addition, the polylactic acid resin described in Patent Document 6 has a problem in that sufficient shrink finish is not yet obtained as a heat-shrinkable film compared to a polyvinyl chloride heat-shrinkable film.

  Therefore, an object of the present invention is to obtain a heat-shrinkable film that is excellent in mechanical properties such as heat-shrinkability, transparency, and impact resistance and excellent in shrink finish.

  In order to solve the above problems, the present invention provides at least a uniaxial mixed resin composition containing 100 parts by mass of a polylactic acid resin (A) and 20 to 200 parts by mass of a (meth) acrylic resin (B). Is a heat-shrinkable film stretched in the direction, the heat shrinkage rate in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is 20% or more and 70% or less, and using a viscoelastic spectrometer, Since the storage elastic modulus (E ′) at 70 ° C. in the direction orthogonal to the main shrinkage direction when measured under the conditions of vibration frequency 10 Hz and strain 0.1% is 100 MPa or more and 1.5 MPa or less. is there.

  This invention uses a mixed resin composition containing a specific amount of a polylactic acid-based resin (A) and a (meth) acrylic resin (B), so that heat shrinkability, transparency, impact resistance, etc. A heat-shrinkable film having excellent mechanical properties and excellent shrinkage finish can be obtained. Moreover, the molded article using the said heat-shrinkable film and a heat-shrinkable label can be obtained.

  Furthermore, a container using the molded product or equipped with the heat-shrinkable label can be obtained.

  Hereinafter, the heat-shrinkable film, molded product, heat-shrinkable label of the present invention, and a container equipped with the molded product or heat-shrinkable label (hereinafter, the film of the present invention, the molded product of the present invention, the label of the present invention, respectively) And also referred to as the container of the present invention).

  In this specification, “with the main component” means that it is allowed to contain other components within a range that does not interfere with the action / effect of the resin constituting each component. It does not limit the rate. Moreover, it means that it occupies the largest ratio among all the structural components of the film of this invention. When the film of the present invention is composed of a single layer, it means that it occupies the largest proportion of the constituent components of the layer, and when the film of the present invention is composed of a laminate, all layers are summed up. It means to occupy the largest proportion among the components. In this specification, the main shrinkage direction of the film means the larger one of the longitudinal direction and the transverse direction in the stretching direction. For example, when the film is attached to a bottle, it is a direction corresponding to the outer peripheral direction.

[Heat shrinkable film]
The film of this invention is obtained by stretching a mixed resin composition containing a polylactic acid resin (A) and an acrylic resin (B) in a predetermined ratio at least in a uniaxial direction.

<Polylactic acid resin (A)>
The polylactic acid resin (A) refers to a homopolymer of lactic acid (hereinafter referred to as lactic acid homopolymer) or a lactic acid copolymer.

  As the lactic acid homopolymer, a structural unit is a homopolymer of L-lactic acid or D-lactic acid (poly (L-lactic acid) or poly (D-lactic acid)), or a structural unit is L-lactic acid or D-lactic acid. The composition which has as a main component the copolymer (poly (DL-lactic acid)) which has both of these, and these mixtures. The copolymerization ratio of the copolymer is not particularly specified, but it is desirable that the copolymer is copolymerized at a ratio that does not exceed the mechanical properties of the lactic acid homopolymer, particularly the Vicat softening point range described below.

  The lactic acid homopolymer can be produced using a known polymerization method such as a condensation polymerization method or a ring-opening polymerization method. For example, in the condensation polymerization method, L-lactic acid or D-lactic acid, or a mixture thereof can be directly dehydrated and condensation polymerized to obtain a lactic acid homopolymer having an arbitrary composition.

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

  Examples of the lactide include L-lactide, which is a dimer of L-lactic acid, D-lactide, which is a dimer of D-lactic acid, and DL-lactide, which is a dimer of D-lactic acid and L-lactic acid. It is done. A lactic acid homopolymer having an arbitrary composition and crystallinity can be obtained by mixing and polymerizing these as necessary.

  Examples of the lactic acid-based copolymer include L-lactic acid and D-lactic acid, α-hydroxycarboxylic acid other than lactic acid and diol and dicarboxylic acid, or L-lactic acid, D-lactic acid, and α other than lactic acid. -The thing which has as a main component the copolymer of hydroxycarboxylic acid or diol, and dicarboxylic acid is mentioned.

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

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

  The copolymerization ratio of lactic acid as the lactic acid copolymer and a copolymer of α-hydroxycarboxylic acid, aliphatic diol, or aliphatic dicarboxylic acid is lactic acid: α-hydroxycarboxylic acid, aliphatic diol, or Aliphatic dicarboxylic acid is preferably 90:10 to 10:90, more preferably 80:20 to 20:80, still more 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 homopolymer and the lactic acid copolymer may be used alone or in combination.

  L-lactic acid and D-lactic acid used as structural units of the lactic acid homopolymer and the lactic acid-based copolymer have a constituent ratio of L-lactic acid: D-lactic acid = 99: 1 to 90:10, or It is preferably in the range of 1:99 to 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, good shrinkage characteristics such as heat shrinkage and shrinkage finish are obtained. It is easy to obtain a heat shrinkable film.

  The Vicat softening point of the polylactic acid resin (A) has a lower limit temperature of 50 ° C. or higher, preferably 55 ° C. or higher, and an upper limit temperature of 95 ° C. or lower, preferably 85 ° C. or lower. If the lower limit temperature of the Vicat softening point 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. On the other hand, if the upper limit temperature is 95 ° C. or lower, the film can be stretched at a low temperature, and good stretch properties can be imparted to the stretched film.

  The polylactic acid-based resin (A) has a weight average molecular weight of 50,000 or more, preferably 100,000 or more and 400,000 or less, preferably 250,000 or less. By setting the lower limit value of the weight average molecular weight to the above value, problems such as a decrease in mechanical strength do not occur, and by setting the upper limit value to the above value, the melt viscosity becomes too high and the molding processability is increased. This is preferable because there is no problem such as lowering.

  Moreover, the said polylactic acid-type resin (A) can contain a small amount of other copolymerization components for the purpose of improving heat resistance. Examples of other copolymer components include aromatic carboxylic acids such as terephthalic acid and aromatic diols such as an ethylene oxide adduct of bisphenol A. Further, for the purpose of increasing the molecular weight, a small amount of a chain extender such as a diisocyanate compound, an epoxy compound, an acid anhydride and the like can be contained.

  Representative examples of the polylactic acid resin (A) preferably used in the present invention include the “Lacia” series manufactured by Mitsui Chemicals, Inc. and the “Nature Works” series manufactured by NatureWorks LLC. Can be mentioned.

<(Meth) acrylic resin (B)>
Next, the (meth) acrylic resin (B) used in the present invention will be described.

  The above (meth) acrylic resin (B) is a homopolymer of methyl acrylate or methyl methacrylate, or a copolymer of 50% by mass or more of methyl acrylate or methyl methacrylate with other vinyl monomers. A polymer (hereinafter collectively referred to as methyl methacrylate copolymer).

  Examples of other vinyl monomers used in the methyl methacrylate copolymer include, for example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid 2 -Methacrylic acid esters such as hydroxyethyl. In addition, acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and the like can be given. Furthermore, unsaturated acids such as methacrylic acid and acrylic acid, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like can be mentioned. Among these vinyl monomers, from the viewpoint of rigidity and moldability, from two or more kinds selected from ethyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid, and methacrylic acid. The copolymer is preferably used.

  In the methyl methacrylate copolymer, an elastomer component such as polybutadiene, butadiene / butyl acrylate copolymer, or polybutyl acrylate copolymer may be mixed as a resin, and a glutaric anhydride unit, A glutarimide unit may be contained as a composition.

  The (meth) acrylic resin (B) used in the present invention has a lower limit of the weight average molecular weight of 20,000 or more, preferably 40,000 or more, more preferably 60,000 or more, and an upper limit of 400. Or less, preferably 350,000 or less, more preferably 300,000 or less. When the weight average molecular weight is 20,000 or more, it is possible to prevent the film from being insufficiently stretched or from becoming brittle. If a weight average molecular weight is 400,000 or less, melt viscosity can be lowered | hung and it is preferable from a viewpoint of manufacture and productivity improvement.

  Examples of the (meth) acrylic resin (B) preferably used in the present invention include “Sumipex” (manufactured by Sumitomo Chemical Co., Ltd.), “Acrypet” (manufactured by Mitsubishi Rayon Co., Ltd.), “Parapet” ( (Manufactured by Kuraray Co., Ltd.), “Artugrass” (manufactured by Atofina Japan), “Delpet” (manufactured by Asahi Kasei Chemicals Corporation), and the like.

<Mixed resin composition>
In the mixed resin composition of the present invention, the (meth) acrylic resin (B) is 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 30 parts with respect to 100 parts by mass of the polylactic acid resin (A). It is important that the content is not less than 200 parts by mass, preferably not more than 200 parts by mass, preferably not more than 180 parts by mass, and more preferably not more than 160 parts by mass. If content of (meth) acrylic-type resin (B) is 10 mass parts or more, the effect which improves the shrinkage | contraction characteristic of a film, shrinkage finishing property, and transparency can be acquired. On the other hand, when the content is 200 parts by mass or less, the stretchability and shrinkage characteristics at low temperatures can be maintained without significantly reducing the impact resistance of the film, and the practical temperature range (70 to 90). It is possible to sufficiently obtain a thermal contraction rate of about 0 ° C.

<Rubber component (C)>
The mixed resin composition can contain a predetermined amount of the rubbery component (C). The rubbery component (C) will be described below.
The rubbery component (C) refers to a rubber component other than the polylactic acid resin (A), and in order to improve the impact resistance of the film obtained from the mixed resin composition, the heat of the film is used. It is preferable to contain the rubbery component (C) within a range that does not impair shrinkage and rigidity.

  Specific examples of the rubbery component (C) include a lactic acid copolymer other than the polylactic acid resin (A), an aliphatic polyester, an aromatic aliphatic polyester, an aromatic polyester, a diol, a dicarboxylic acid, and the lactic acid. Copolymer with homopolymer, core-shell structure rubber, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene-ethyl acrylate copolymer, and ethylene- (meth) acrylic acid Examples thereof include a methyl copolymer. Among these, core-shell structure type rubber is preferably used.

  Examples of the lactic acid copolymer other than the polylactic acid resin (A) of the rubber component (C) include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n as α-hydroxycarboxylic acid units. -Bifunctional aliphatic hydroxycarboxylic acids such as butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid, caprolactone, butyrolactone, valerolactone And lactones. Examples of the diol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid and dodecanedioic acid. Specifically, the product name “Plamate” (manufactured by Dainippon Ink & Chemicals, Inc.) and the product name “GS-PLA” (manufactured by Mitsubishi Chemical) can be obtained commercially.

  Examples of the aliphatic polyester of the rubber 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, and a synthetic aliphatic polyester. Aliphatic polyesters other than the polylactic acid-based resin.

  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, and 1,4-cyclohexane. 1 from each of aliphatic diols such as dimethanol 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. What was obtained by selecting more than one kind and performing condensation polymerization is mentioned. At this time, a desired polymer can be obtained by extending the chain with an isocyanate compound or the like as necessary. As the aliphatic polyester, for example, “Bionore” (manufactured by Showa Polymer Co., Ltd.) and the like can be obtained commercially.

  Examples of the aliphatic polyester obtained by ring-opening polymerization of the cyclic lactones include those obtained by polymerizing one or more kinds of cyclic monomers selected from ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone, and the like. It is done. 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. Specifically, the product name “Cell Green” (manufactured by Daicel Chemical Industries, Ltd.) and the product name “Tone Polymer” (manufactured by Union Carbide Japan Ltd.) are commercially available.

  The aromatic aliphatic polyester or aromatic polyester includes the above aliphatic diol or derivative thereof, or an aromatic diol or derivative thereof such as ethylene oxide adduct of bisphenol A, and the above aliphatic dicarboxylic acid or its derivative. It is obtained by condensation polymerization by selecting one or more of a derivative, or an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,4-naphthalenedicarboxylic acid or paraphenyldicarboxylic acid or a derivative thereof. Can be mentioned. At this time, a desired polymer can be obtained by extending the chain with an isocyanate compound or the like as necessary. Specifically, the product name “Easter Bio” (manufactured by Eastman Chemicals) and the product name “Ecoflex” (manufactured by BASF) are commercially available.

  The lower limit of the weight average molecular weight of the lactic acid copolymer other than the polylactic acid resin (A) used as the rubbery component (C), the aliphatic polyester, the aromatic aliphatic polyester, and the aromatic polyester is 50, It is desirable that the range is 000 or more, preferably 100,000 or more, and the upper limit is 400,000 or less, preferably 250,000 or less. If the lower limit is 50,000 or more, problems such as deterioration of mechanical strength hardly occur. On the other hand, if the upper limit is 400,000 or less, the melt viscosity can be lowered, which is preferable from the viewpoint of production and productivity improvement.

  Examples of the core shell structure type rubber include diene type core shell structure type polymers such as methacrylic acid-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, and acrylic type core shell structure types such as methacrylic acid-styrene-acrylonitrile copolymer. Examples thereof include silicone-based core-shell structure type copolymers such as a polymer, a silicone-methacrylic acid-methylmethacrylic acid copolymer, and a silicone-methacrylic acid-acrylonitrile-styrene copolymer. Among these, a silicone-methacrylic acid-methylmethacrylic acid copolymer having good compatibility with the polylactic acid resin and having a good balance between impact resistance and transparency of the film is more preferably used. Specifically, “methabrene C, S, E, W” (manufactured by Mitsubishi Rayon Co., Ltd.), “Kane Ace” (manufactured by Kaneka Corporation), and the like can be obtained commercially.

  The rubbery component (C) ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) ethyl acrylate copolymer, ethylene- (meth) methyl acrylate copolymer The comonomer content other than ethylene is 20% by mass or more, preferably 40% by mass or more, and 90% by mass or less, preferably 80% by mass or less is preferably used. If the comonomer content other than ethylene is 20% by mass or more, the effect of improving the fracture resistance of the film can be sufficiently obtained, and the transparency can be maintained. If it is 80 mass% or less, the rigidity of the whole film and heat resistance can be maintained favorable. Among these, an ethylene-vinyl acetate copolymer is more preferably used.

  Specifically, as the ethylene-vinyl acetate copolymer, “EVAFLEX” (manufactured by Mitsui DuPont Polychemical Co., Ltd.), “Novatech EVA” (manufactured by Mitsubishi Chemical Corporation), “Ebaslene” (Dainippon Ink Chemical Co., Ltd.) Kogyo Co., Ltd.), "Ebate" (manufactured by Sumitomo Chemical Co., Ltd.), "Soabrene" (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), ethylene-acrylic acid copolymer as "Novatech EAA" (Mitsubishi Chemical Co., Ltd.), ethylene-ethyl acrylate copolymer and ethylene- (meth) acrylic acid copolymer include "Noah Frey AC" (manufactured by Mitsui DuPont Polychemical Co., Ltd.), ethylene-methyl (meth) acrylate As a polymer, “ACRlift” (manufactured by Sumitomo Chemical Co., Ltd.) and the like can be obtained commercially.

  Content of the said rubber-like component (C) is 10 mass parts or more with respect to 100 mass parts of polylactic acid-type resin (A), Preferably it is 15 mass parts or more, More preferably, it is 20 mass parts or more, 100 masses Part or less, preferably 90 parts by weight or less, more preferably 80 parts by weight or less. If it is 10 parts by mass or more, the effect of improving the impact resistance can be obtained, and if it is 100 parts by mass or less, it can be suitably used as a heat-shrink label without impairing the rigidity and transparency of the film.

<Additives>
In the present invention, a polyethylene resin, a polypropylene resin, a polystyrene resin (general-purpose polystyrene (GPPS), rubber-modified impact-resistant polystyrene (HIPS), polystyrene-polybutadiene-polystyrene block co-polymer) can be used as long as the effects of the present invention are not significantly impaired. Polymer (SBS), polystyrene-polyisoprene-polystyrene block copolymer (SIS), polystyrene-poly (ethylene / butylene) block-polystyrene copolymer (SEBS), polystyrene-poly (ethylene / propylene) block-polystyrene copolymer Polymer (SEPS), polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer (SEEPS), styrene-carboxylic acid copolymer, etc.), polyamide resin, polyoxymethylene Thermal plasticizing resin such systems resin may be further contains at least one more.

  In the present invention, a plasticizer is added as necessary for the purpose of improving various properties of impact resistance, transparency, molding processability and heat shrinkable film within a range not impairing the effects of the present invention. Also good. As this plasticizer, dibutyl adipate, diisobutyl adipate, diisononyl adipate, diisodecyl adipate, di (2-ethylhexyl) adipate, di (n-octyl) adipate, di (n-decyl) adipate, dibutyl diglycol adipate, dibutyl sebacate , Di (2-ethylhexyl) sebacate, di (n-hexyl) azelate, di (2-ethylhexyl) azelate, di (2-ethylhexyl) dodecanedionate and the like, diisononyl phthalate, diisodecyl phthalate, di (2- Examples thereof include phthalic acid ester systems such as ethylhexyl) phthalate and trimellitic acid ester systems such as tri (2-ethylhexyl) trimellitate.

  In addition to the above thermoplastic resins and plasticizers, additives are added as necessary for the purpose of improving and adjusting the molding processability, productivity and various physical properties of the heat-shrinkable film as long as the effects of the present invention are not impaired. can do. For example, recycled resin generated from trimming loss such as film ears, inorganic particles such as silica, talc, kaolin, calcium carbonate, pigments such as titanium oxide, carbon black, flame retardant, weather resistance stabilizer, heat stabilizer, Antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, anti-aging agents and the like.

<Heat shrinkable film>
The film structure of the present invention may be a single layer, or may be a laminated structure for imparting new functions such as slipperiness, heat resistance, solvent resistance, and easy adhesion to the surface. For example, the (II) layer and (III) layer having different resin compositions or additives are added to the (I) layer composed of the polylactic acid resin (A), the (meth) acrylic resin (B), and the rubber component (C). When laminated, (I) / (II) two-layer structure, (II) / (I) / (II), (II) / (I) / (III) three-layer structure, or (II) An example is a four-layer structure of / (I) / (III) / (II). Moreover, the ratio of the lamination thickness of each layer can be arbitrarily set according to a use and the objective.

  The total thickness of the film of the present invention is not particularly limited, but is preferably thinner from the viewpoints of transparency, shrinkage workability, raw material cost, and the like. Specifically, the upper limit of the total thickness of the stretched film is 80 μm or less, preferably 70 μm or less, and more preferably 50 μm or less. Further, the lower limit of the total thickness of the heat-shrinkable film is not particularly limited, but it is preferably 20 μm or more in consideration of the handleability of the film.

[Production method]
The film of the present invention can be produced by a known method. The form of the heat-shrinkable film may be either a flat shape or a tube shape. A flat film is preferable because several films can be taken in the width direction and printed on the inner surface. For example, in a method for producing a flat film, a resin is melted using a plurality of extruders, co-extruded from a T die, and cooled and solidified with a chilled roll. After that, roll stretching is performed in the vertical direction, tenter stretching is performed in the horizontal direction, cooling is performed after annealing, and winding is performed by a winder (when printing is performed, the printed surface is subjected to corona discharge treatment). It is what you take. Alternatively, a film produced by a tubular method may be cut open to form a flat film.

  The stretching ratio is 2 times or more and 10 times or less in the longitudinal direction, 2 times or more and 10 times or less in the transverse direction, preferably 3 times or more and 6 times or less in the longitudinal direction, preferably in the direction of shrinking in two directions such as for overlap. The direction is about 3 to 6 times. In a biaxially stretched film stretched at a stretch ratio within these ranges, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction does not become too large. For example, when used as a heat shrinkable label, It is possible to suppress the so-called vertical drawing phenomenon in which the film is thermally contracted in the height direction of the container. On the other hand, in applications that shrink mainly in one direction, such as for heat-shrinkable labels, the direction corresponding to the main shrinkage direction is 2 to 10 times, preferably 4 to 8 times, and the direction orthogonal to the main shrinkage direction. 1 to 2 times or less (1 time means a case where the film is not stretched), preferably 1.01 to 1.5 times, and a stretching ratio substantially in the category of uniaxial stretching is selected. It is desirable to do.

  The stretching temperature needs to be adjusted depending on the glass transition temperature of the contained resin and the properties required for the heat-shrinkable film, but generally the lower limit is 60 ° C. or higher, preferably 70 ° C. or higher, and the upper limit is It may be controlled within a range of 100 ° C. or less, preferably 90 ° C. or less. On the other hand, the draw ratio needs to be adjusted according to the characteristics of the contained resin, etc., the drawing means, the drawing temperature, the target product form, etc., but in the main shrinkage direction, it is 1.5 to 10 times, preferably It is appropriately determined in the direction of one axis or two axes within a range of 3 to 7 times, more preferably 3 to 5 times. Furthermore, even in the case of uniaxial stretching in the transverse direction, it is also effective to stretch the film in the longitudinal direction by 1.05 times or more and 1.8 times or less for the purpose of improving the mechanical properties of the film.

  In addition, the stretched film has a time during which the molecular orientation is not relaxed after heat treatment or relaxation treatment at a temperature of about 50 ° C. or more and 100 ° C. or less for the purpose of reducing the natural shrinkage rate or improving the heat shrinkage properties as necessary. It can be set as a heat-shrinkable film by rapidly cooling in. Furthermore, surface treatment and surface processing such as corona treatment, printing, coating, and vapor deposition, bag making processing and perforation processing using various solvents and heat sealing, and the like can be performed as necessary.

  The film of the present invention is processed from a flat shape to a cylindrical shape or the like by a packaged object and provided for packaging. For example, if a cylindrical container such as a plastic bottle requires printing, first print the required image on one side of a wide flat film wound up on a roll, cut it to a predetermined width, There is a method of folding it so that the center seal (the shape of the seal part is a so-called envelope) and making it cylindrical. As the center sealing method, an organic solvent, a heat seal, an adhesive, an adhesion method using an impulse sealer, or the like can be considered. Among these, an organic solvent bonding method is used from the viewpoint of productivity and appearance.

[Molded products, heat-shrinkable labels and containers]
Since the film of the present invention is excellent in heat shrinkability, shrink finish, transparency and the like of the film, its use is not particularly limited. By forming a printing layer, a vapor deposition layer and other functional layers as necessary, it can be used as various molded products such as bottles (blow bottles), trays, lunch boxes, prepared food containers, dairy products containers and the like. In particular, when the film of the present invention is used as a heat-shrinkable label for food containers (for example, PET bottles, glass bottles, preferably PET bottles for soft drinks or foods), a complicated shape (for example, a cylinder with a narrow center, a corner Can be brought into close contact with the complex shape, and a container with a beautiful label without wrinkles or avatars can be obtained. The molded article and container of this invention can be produced by using a normal molding method. Moreover, it can also be used as a container by combining the said molded article with the molded article which consists of another material.

  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, such as metal, porcelain, glass, paper, polyolefin resin such as polyethylene, polypropylene, polybutene, polyester resin such as polymethacrylate resin, polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate It can be suitably used as a heat-shrinkable label material for a package (container) using at least one selected from a resin and a polyamide-based resin as a constituent material.

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

<Physical and mechanical properties>
[Heat shrinkage]
In the film of the present invention, the lower limit of the heat shrinkage rate in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is 20% or more, preferably 30% or more, and the upper limit is 70% or less, preferably 65%. It is necessary that: Generally, a heat-shrinkable film needs to be sufficiently heat-shrinked at a temperature as low as possible from the viewpoint of the influence of heat on the object to be coated. Therefore, if the film has a thermal shrinkage rate of 20% or more and 70% or less under the above conditions, the film is sufficiently adhered to the object to be coated within the shrinkage processing time, and has a good shrinkage finished appearance without causing spots, wrinkles and avatars. Can be obtained.

  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 isomer of the polylactic acid resin (A) is increased, the content of the (meth) acrylic resin (B) is increased, and the draw ratio is increased. Measures such as 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 perpendicular to the main shrinkage direction is preferably 10% or less when immersed in warm water at 80 ° C. for 10 seconds, It is more preferably 5% or less, and further preferably 3% or less. In the case of a heat-shrinkable film having a heat 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 is shortened, or the printed pattern or character after shrinkage is shortened. The occurrence of distortion or the like can be suppressed, and the occurrence of troubles such as vertical sink can be suppressed even in the case of a square bottle.

[Storage modulus]
In this invention, the storage elastic modulus (E ′) is measured at 70 ° C. in the direction orthogonal to the main shrinkage direction when measured under the conditions of a vibration frequency of 10 Hz and a strain of 0.1% using a viscoelastic spectrometer. It is important to adjust the storage elastic modulus (E ′) to 100 MPa or more and 1.5 GPa or less. If the storage elastic modulus (E ′) at 70 ° C. is 100 MPa or more, the strength in the shrinkage temperature range is maintained, so the shrinkage finish is good even under a wide range of shrinkage conditions, and a beautiful appearance can be obtained. This is preferable from the viewpoint of productivity. The upper limit of the storage elastic modulus (E ′) is not particularly specified, but it is preferably 1.5 GPa or less because the low temperature shrinkage is not impaired, more preferably 1.2 GPa or less, and even more preferably 1 0.0 GPa or less.

  In the film of the present invention, in order to increase the storage elastic modulus (E ′) at 70 ° C., it is preferable to adjust the resin composition and the production method as described in the present invention. Specific adjustment methods thereof include decreasing the optical isomer ratio of the polylactic acid resin (A), increasing the content of the (meth) acrylic resin (B), reducing the amount of plasticizer added, and adjusting the stretching temperature. Examples of the method include raising the temperature and raising the heat treatment temperature. Moreover, in order to reduce the storage elastic modulus (E ′) at 70 ° C., increase the optical isomer ratio of the polylactic acid resin (A), decrease the content of the (meth) acrylic resin (B), Examples include increasing the amount of plasticizer added, lowering the stretching temperature, and lowering the heat treatment temperature.

[Tensile modulus]
The lower limit value of the tensile modulus in the direction perpendicular to the main shrinkage direction of the film of the present invention is preferably 1.2 GPa or more, more preferably 1.4 GPa or more, and further preferably 1.6 GPa or more. preferable. The upper limit value of the tensile elastic modulus of a heat-shrinkable film that is usually used is about 3.0 GPa, preferably about 2.9 GPa, and more preferably about 2.8 GPa. If the tensile elastic modulus is 1.2 GPa or more, the waist as a whole film (rigidity at room temperature) can be increased. As a result, even when the thickness of the film is reduced, when the film made in a container such as a plastic bottle is covered with a labeling machine or the like, it is likely to be covered obliquely or the yield may be reduced due to the film being folded back. The occurrence of problems such as these can be suppressed. The tensile elastic modulus can be measured under the condition of 23 ° C. according to JISK7127.

  In the film of the present invention, it is preferable to adjust the resin composition and the production method as described in the present invention in order to bring the tensile modulus to the above range. In order to increase the tensile modulus as a specific adjustment method, for example, a method of increasing the content of the (meth) acrylic resin (B) or decreasing the content of the rubbery component (C) can be mentioned. It is done.

[transparency]
The transparency of the film of the present invention is, for example, when a film having a thickness of 50 μm is measured according to JIS K7105, the haze value is preferably 10% or less, more preferably 7% or less, and more preferably 5%. More preferably, it is as follows. This is because if the haze value is 10% or less, the transparency of the film can be obtained and a display effect can be obtained.

  In the film of the present invention, in order to make the haze value in the above range, it is preferable to adjust the resin composition and the production method as described in the present invention. As a specific adjustment method, the contents of the (meth) acrylic resin (B) and the rubbery component (C) with respect to the polylactic acid-based resin (A) are lowered, and the refractive indexes of the respective raw materials are made close to each other. Examples thereof include a method of increasing the compatibility of raw materials and increasing the kneading efficiency to reduce the dispersed particle size, lowering the stretching ratio, and slightly increasing the stretching temperature.

[Tensile breaking elongation]
The impact resistance of the film of the present invention is evaluated based on the tensile elongation at break. In a tensile test under a 23 ° C. environment, the elongation rate is 100% in the film take-off (flow) direction (MD) particularly for heat-shrinkable label applications. Above, preferably 150% or more, more preferably 200% or more. If the tensile elongation at break in an environment of 23 ° C. is 100% or more, problems such as breakage of the film during printing and bag-making processes are unlikely to occur. 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 elongation at break is 150% or more because it is difficult to break. Further, a preferable upper limit of the tensile elongation at break is not particularly set, but is desirably about 500% in order to produce a film at a sufficient speed.

  In the film of this invention, in order to make the elongation rate in the tensile test under a 23 ° C. environment within the above range, the resin composition and the production method are preferably configured as described in this invention. Specific adjustment methods include, for example, decreasing the content of (meth) acrylic resin (B) constituting the film, increasing the content of rubbery component (C), and 1. Examples of the method include stretching by 01 times or more.

The present invention will be described below with reference to examples.
In addition, the measured value and evaluation in an experiment example and a comparative example were measured and evaluated by the following methods. The film take-up (flow) direction is referred to as the “longitudinal” direction, and the direction perpendicular thereto is referred to as the “lateral” direction.

(1) Thermal shrinkage rate The film was cut into a size of 100 mm in length and 100 mm in width, and immersed in a hot water bath at 80 ° C. for 10 seconds, and the amount of shrinkage was measured. Regarding the thermal shrinkage rate, the ratio of the shrinkage amount to the original size before shrinkage in the longitudinal direction or the transverse direction was expressed as a% value.

(2) Measurement of dynamic viscoelasticity A film to be measured was cut into a size of 60 mm in length and 4 mm in width, and vibration frequency 10 Hz, strain 0 using a viscoelastic spectrometer (DVA-200, manufactured by IT Measurement Co., Ltd.). 0.1%, temperature rising rate 1 ° C./min, chuck distance 2.5 cm, measurement temperature was measured in the range of 0 to 150 ° C., and the storage elastic modulus at 70 ° C. was measured.

(3) Haze value The haze value of a film with a film thickness of 40 μm was measured according to JIS K7105.

(4) Tensile rupture elongation Based on JIS K7127, it measured about the direction (longitudinal direction) orthogonal to the main shrinkage | contraction direction of a film on the conditions of temperature 23 degreeC and test speed 200mm / min.

(5) Tensile elastic modulus According to JIS K7127, it measured about the direction (longitudinal direction) orthogonal to the main shrinkage direction of a film on the conditions of temperature 23 degreeC.

(6) Shrinkage finishing property A film printed with a 10 mm-interval grid is cut into a size of 170 mm in length (MD) and 114 mm in width (TD), and both ends of the width (TD) are overlapped by 10 mm to form a tetrohydrofuran (THF) solvent. To form a cylindrical film. The cylindrical film is attached to a cylindrical plastic bottle with a capacity of 500 mL and is passed through the shrinking tunnel having a length of 3.2 m (3 zones) of the steam heating method for about 4 seconds without rotating. Coated. The atmospheric temperature in the tunnel in each zone was adjusted to the range of 60 to 90 ° C. by adjusting the amount of steam with a steam valve. The ambient temperature at that time is shown below.
Coating condition 1 ... 65 ° C / 80 ° C / 80 ° C
Coating condition 2 ... 90 ° C / 90 ° C / 60 ° C
Coating condition 3 ... 75 ° C / 85 ° C / 85 ° C
After film coating, the following criteria were evaluated.
A: Shrinkage is sufficient and no wrinkles, avatars, whitening, and lattice distortion occur.
○: Shrinkage is sufficient, but wrinkles, avatars, whitening, and slight distortion of lattices occur, but this is not a problem in practical use.
Δ: Shrinkage is sufficient, but wrinkles, avatars, whitening, and lattice distortions are slightly generated, which may be a problem depending on the application.
X: Shrinkage is insufficient, or wrinkles, avatars, and lattice distortions remarkably occur.

Moreover, the raw material used for each Example and the comparative example is as follows.
(Polylactic acid resin (A) component)
-Polylactic acid resin: Product name “NatureWorks NW4050” manufactured by Nature Works LLC, L-form / D-form weight = 95/5, hereinafter abbreviated as “PLA1”.
-Polylactic acid resin: Product name “NatureWorks NW4032” manufactured by Nature Works LLC, L-form / D-form weight = 99.5 / 0.5, hereinafter abbreviated as “PLA2”.
-Polylactic acid resin: Product name “NatureWorks NW4060” manufactured by NatureWorks LLC, L-form / D-form weight = 88/12, hereinafter abbreviated as “PLA3”.

((Meth) acrylic resin (B) component)
Polymethyl methacrylate resin: product name “Acrypet VH01” manufactured by Mitsubishi Rayon Co., Ltd., hereinafter abbreviated as “PMMA”.

(Rubber (C) component)
Core-shell structure type acrylic-silicone copolymer: trade name “Metablene S2001” manufactured by Mitsubishi Rayon Co., Ltd., hereinafter abbreviated as “Rubber 1”.
Aliphatic polyester resin: Daicel Chemical Industries, Ltd., trade name “Cell Green PH7”, hereinafter abbreviated as “Rubber 2”.
Aliphatic polyester-based resin: Showa High Polymer Co., Ltd. trade name “Bionore 1010”, hereinafter abbreviated as “Rubber 3”.
Aliphatic polyester-based resin: Showa High Polymer Co., Ltd. trade name “Bionole 3003”, hereinafter abbreviated as “Rubber 4”.

(Additive)
・ Polyester plasticizer: manufactured by Dainippon Ink & Chemicals, Inc., trade name “DOZ”, hereinafter abbreviated as “plasticizer”.
Hydrophobic silica particles: product name “Silo Hovic 100” manufactured by Fuji Silysia Chemical Ltd., hereinafter abbreviated as “silica particles”.

(Examples 1-4, Comparative Examples 1-3)
As a resin for (I) layer shown in Table 1, a mixed resin of (A) component, (B) component and (C) component is put into a twin screw extruder (manufactured by Mitsubishi Heavy Industries, Ltd.), and the set temperature is 200 ° C. After melt-mixing and extruding with a T-die die, it was taken up by a cast roll at 50 ° C. and cooled and solidified to obtain an unstretched sheet having a width of 300 mm and 250 μm. Next, the film was stretched 5.0 times in the transverse uniaxial direction at a preheating temperature of 90 ° C. and a stretching temperature of 75 ° C. by a film tenter (Mitsubishi Heavy Industries, Ltd.) to obtain a heat-shrinkable film having a thickness of 50 μm. The physical properties and evaluation results of the obtained film are shown in Table 1.

  The (II) layer resin shown in Table 1 contains a polylactic acid-based resin and silica particles, and the (II) layer resin layer is formed on both sides of the mixed resin layer of the (I) layer. To form unstretched laminated sheets each having a predetermined thickness ratio by a coextrusion method using a feed lock of two types and three layers. This unstretched laminated sheet was made into a heat-shrinkable film having a thickness of 50 μm by the same method as described above.

From Table 1, the film having the composition, thermal shrinkage rate and storage elastic modulus (E ′) specified in the present invention was excellent in transparency, tensile elongation at break, transparency and shrinkage finish. On the other hand, when the amount of (meth) acrylic acid resin is small (Comparative Example 1), the storage elastic modulus (E ′) and shrinkage finish are inferior, and conversely when the amount of (meth) acrylic acid resin is large (Comparative Example). In 2), the film broke and it was impossible to measure the mechanical properties and shrinkage finish. Furthermore, when the (meth) acrylic acid resin was not included (Comparative Example 3), the shrinkage rate was low, and the shrinkage finishing property was considerably inferior.
Thereby, it can be seen that the film of the present invention is excellent in mechanical properties such as heat shrinkability, transparency and impact resistance, and excellent in shrink finish.

Claims (9)

A heat-shrinkable film obtained by stretching a mixed resin composition containing 100 parts by mass of a polylactic acid resin (A) and 20 parts by mass or more and 200 parts by mass or less of a (meth) acrylic resin (B) at least in a uniaxial direction. Yes,
The heat shrinkage rate in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is 20% or more and 70% or less,
In addition, the storage elastic modulus (E ′) at 70 ° C. in a direction orthogonal to the main shrinkage direction when measured under the conditions of a vibration frequency of 10 Hz and a strain of 0.1% using a viscoelastic spectrometer is 100 MPa or more. A heat-shrinkable film of 5 GPa or less.   The heat-shrinkable film according to claim 1, wherein the mixed resin composition contains 10 parts by mass or more and 100 parts by mass or less of the rubber-like component (C).   The heat-shrinkable film according to claim 1 or 2, which has a tensile elongation at break of 100% or more in a direction perpendicular to the main shrinkage direction when measured at 23 ° C and a tensile speed of 200 mm / min based on JIS K7127. .   The heat-shrinkable film according to any one of claims 1 to 3, wherein the polylactic acid resin (A) comprises a copolymer of D-lactic acid and L-lactic acid or a mixed resin composition of the copolymer. .   The (meth) acrylic resin (B) is composed of two or more monomers selected from methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic acid. The heat-shrinkable film according to any one of claims 1 to 4, which is a copolymer or a methyl methacrylate homopolymer.   The rubbery component (C) is a lactic acid copolymer other than the polylactic acid resin (A), an aliphatic polyester, an aromatic aliphatic polyester, an aromatic polyester, a diol, a dicarboxylic acid, and a lactic acid homopolymer. From copolymer, core-shell structure type rubber, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl (meth) acrylate copolymer The heat-shrinkable film according to any one of claims 1 to 5, comprising at least one selected from the above.   A molded article using the heat-shrinkable film according to any one of claims 1 to 6.   A heat-shrinkable label using the heat-shrinkable film according to claim 1.   A container using the molded article according to claim 7 or equipped with the heat-shrinkable label according to claim 8.