JP4878837B2 - Heat-shrinkable film, molded article using the heat-shrinkable film, heat-shrinkable label, and container using or fitted with the molded article - Google Patents

Description

  The present invention relates to a heat-shrinkable film, and a molded article using the heat-shrinkable film, a heat-shrinkable label, and a container using or fitted with the molded article. A heat-shrinkable film excellent in heat resistance and suitable for applications such as shrink-wrapping, shrink-bound packaging and shrink-labeling, and a molded article using the heat-shrinkable film, a heat-shrinkable label, and this molded article Or a container equipped with this label.

  Currently, soft drinks such as juice and alcoholic drinks such as beer are sold in a state of being filled in a container such as a bottle or a plastic bottle. At that time, in order to differentiate from other products and improve the visibility of the products, a heat-shrinkable label printed on the outside of the container is attached. As a material for the heat-shrinkable label, polyvinyl chloride (PVC), polystyrene, aromatic polyester or the like is generally used.

  As a heat-shrinkable film that is rigid at room temperature, has low-temperature shrinkage, and has good natural shrinkage for use as the heat-shrinkable label, polyester-based, particularly low-crystalline copolymerized polyethylene terephthalate Films based on (PET) or polylactic acid are mainly used. However, these polyester-based heat-shrinkable films have a problem that shrinkage spots and wrinkles are likely to occur during heat-shrinking compared to PVC-based heat-shrinkable films. In addition, the polylactic acid-based heat-shrinkable film also has a problem that when heated, crystallization proceeds and sufficient heat-shrinkage characteristics cannot be obtained.

  As means for solving the above problem, a film in which the copolymerization ratio of L-lactic acid and D-lactic acid in a polylactic acid resin is adjusted is known (see Patent Document 1). However, although this film can suppress crystallization during heating, the problem of causing spots, wrinkles, and avatars due to rapid shrinkage cannot be sufficiently solved.

  In addition, attempts have been made to improve shrink finish by adjusting the crystallinity of the polylactic acid resin and further blending an aliphatic polyester resin (see Patent Documents 2 and 3, etc.). However, compared to PVC heat-shrinkable films, it is still difficult to say that the shrink finish is sufficient.

  Furthermore, a stretched film in which a polylactic acid resin having a specific weight average molecular weight and a polymethacrylate resin are blended is known (Patent Document 4). However, the present invention is mainly intended to improve the heat resistance and transparency of the polylactic acid-based resin film, and is difficult to apply as an improvement in shrink finish of the heat-shrinkable film as in the present invention.

  Furthermore, since the polylactic acid-based resin is brittle, the material itself has a problem that when it is molded into a single sheet or film, sufficient strength cannot be obtained and it is difficult to put it into practical use.

  Containing an aliphatic polyester other than polylactic acid (see Patent Document 5), polycaprolactone (see Patent Document 6), a copolymer polyolefin such as an ethylene-vinyl acetate copolymer (see Patent Document 7), etc. The method of making it known is known. These mainly have the purpose of improving brittleness while maintaining the transparency of the polylactic acid-based resin film, and there still remains an insufficient point with respect to shrink finish.

JP 2003-119367 A JP 2001-11214 A JP 2000-280342 A JP 2005-36054 A JP 09-169896 A JP-A-8-300481 JP-A-9-151310

  The present invention has been made in view of the above problems, and the object of the present invention is excellent in heat shrink characteristics of the heat shrinkable film, mechanical properties such as impact resistance and transparency, and shrink finish, and shrinkage. The object is to obtain a heat-shrinkable film suitable for applications such as packaging, shrink-bound packaging and shrink labels.

  Another object of the present invention is to provide a molded article using the heat-shrinkable film, a heat-shrinkable label and the molded article suitable for applications such as shrink-wrapping, shrink-bound packaging and shrink-labeling, or heat shrinking. The object is to obtain a container with a sex label.

  The present invention comprises a (I) layer composed of a mixed resin containing a polylactic acid resin (A), a (meth) acrylic resin (B), and a rubbery component (C), and a polylactic acid resin (A ) Having at least two layers with (II) layer as a main component, and having a shrinkage ratio in the main shrinkage direction of 20% or more when stretched in at least one direction and immersed in warm water at 80 ° C. for 10 seconds. The said subject was solved by using a shrinkable film.

  According to the present invention, as the (I) layer, a film having a predetermined heat shrinkage rate using a mixed resin containing the three components (A), (B), and (C) is used. Excellent mechanical properties such as impact resistance and transparency, and excellent shrinkage finish.

  Furthermore, according to the present invention, a molded product using the heat-shrinkable film, a heat-shrinkable label and the molded product, or a heat-shrinkable label, which are suitable for applications such as shrink wrapping, shrink tying wrapping and shrinking labels. A container equipped with can be provided.

  Hereinafter, the heat-shrinkable film, molded product, heat-shrinkable label, and container equipped with the molded product or heat-shrinkable label according to the present invention (hereinafter referred to as “the film of the present invention” and “the molded product of the present invention”, respectively) , “The label of the present invention” and “the container of the present invention”).

  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 film]
The film of the present invention comprises a polylactic acid resin (hereinafter referred to as “component (A)”), a (meth) acrylic resin (hereinafter referred to as “component (B)”), and a rubbery component (hereinafter referred to as “component (A)”). (I) layer composed of a mixed resin (hereinafter referred to simply as “mixed resin”) containing “(C) component”), and the component (A) as a main component (II) ) Layer and at least two layers, stretched in at least one direction, and has a predetermined shrinkage rate.

<(A) component (polylactic acid resin)>
The polylactic acid-based resin as the component (A) refers to a homopolymer of D-lactic acid or L-lactic acid, or a copolymer thereof. Specifically, a poly (D -Lactic acid), poly (L-lactic acid) whose structural unit is L-lactic acid, and poly (DL-lactic acid) which is a copolymer of L-lactic acid and D-lactic acid, and these copolymers. These mixed resins are also included.

  The copolymer of L-lactic acid and D-lactic acid has a constitutional ratio of D-lactic acid to L-lactic acid (hereinafter abbreviated as “D / L ratio”) of 1/99 to 25/75, Or 99/1 to 75/25, preferably 3/97 to 20/80, or 97/3 to 80/20, more preferably 5/95 to 15/85, or 95/5. More preferably, it is 85/15.

  When the D / L ratio is 0/100 or 100/0, very high crystallinity is exhibited, the melting point is high, and the heat resistance and mechanical properties tend to be excellent. However, when it is used as a heat-shrinkable film, it usually involves printing and a bag making process using a solvent. Therefore, in order to improve the printability and the solvent sealability, the crystallinity of the constituent material itself is moderately lowered. Is required. Moreover, when crystallinity is too high, orientation crystallization advances at the time of extending | stretching, and there exists a tendency for the film shrinkage | contraction characteristic at the time of heating to fall. Therefore, in the film of the present invention, the D / L ratio is preferably greater than 1/99 or less than 99/1. On the other hand, when the D / L ratio is more than 25/75 or less than 75/25, it is desirable because the rupture resistance can be prevented from greatly decreasing.

  In the present invention, in order to adjust the D / L ratio of the polylactic acid resin more easily, it is possible to blend polylactic acid resins having different copolymerization ratios of D-lactic acid and L-lactic acid. In this case, the average value of the D / L ratio may be set within the above range. Two or more polylactic acid resins with different copolymer ratios of D-lactic acid and L-lactic acid are blended according to the intended use, and the crystallinity is adjusted to balance heat resistance and heat shrinkage characteristics. be able to.

  The component (A) may be a copolymer of D-lactic acid and / or L-lactic acid and α-hydroxycarboxylic acid, aliphatic diol, or aliphatic dicarboxylic acid.

  Examples of the α-hydroxycarboxylic acid include optical isomers of lactic acid (D-lactic acid for L-lactic acid and L-lactic acid for D-lactic acid), glycolic acid, 3-hydroxybutyric acid, 4 Bifunctional aliphatic hydroxy-carboxylic acids such as -hydroxybutyric acid, 2-hydroxyn-butyric acid, 2-hydroxy3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methylbutyric acid, 2-hydroxycaprolactone acid, etc. Examples include lactones such as caprolactone, butyl lactone and valerolactone.

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

  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 = 95: 5 10:90, preferably 90:10 to 20:80, more preferably 80:20 to 30:70. 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.

  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 DL-lactide, which is a dimer of L-lactic acid. By mixing and polymerizing these as required, a polylactic acid resin having an arbitrary composition and crystallinity can be obtained. it can. Furthermore, a small amount of chain extender such as a diisocyanate compound, diepoxy compound, acid anhydride, acid chloride, etc. may be used for the purpose of increasing the molecular weight.

  The weight (mass) average molecular weight of the polylactic acid-based resin is 20,000 or more, preferably 40,000 or more, more preferably 60,000 or more, and the upper limit is 400,000 or less, preferably 350,000 or less. More preferably, it is 300,000 or less. When the weight (mass) average molecular weight is 20,000 or more, an appropriate resin cohesive force can be obtained, and the film can be prevented from being insufficiently stretched or embrittled. On the other hand, if the weight (mass) average molecular weight is 400,000 or less, the melt viscosity can be lowered, which is preferable from the viewpoint of production and productivity improvement.

  As a commercial item of the said (A) component, "NatureWorks" (made by Nature Works), "LACEA" (made by Mitsui Chemicals, Inc.) etc. are mentioned, for example.

<(B) component ((meth) acrylic resin)>
Next, the (meth) acrylic resin that is the component (B) will be described. In the present specification, “(meth) acryl” means “acryl or methacryl”.

  The (meth) acrylic resin as the component (B) is a methyl methacrylate homopolymer or 50% by mass or more of methyl methacrylate and two or more monomers selected from other vinyl monomers. It is a copolymer. Examples of the vinyl monomer include (meth) acrylic acid esters, unsaturated acids, styrene, α-methylstyrene, (meth) acrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like.

  Specific examples of the (meth) acrylic acid esters include methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, and (meth) acrylic. Examples include benzyl acid, 2-ethylhexyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate. Moreover, (meth) acrylic acid etc. are mentioned as said unsaturated acids.

  The copolymer may further contain an elastomer component such as polybutadiene, butadiene-butyl acrylate copolymer, polybutyl acrylate copolymer, glutaric anhydride units, and glutarimide units. Among these, from the viewpoint of rigidity and moldability, polymethyl methacrylate (PMMA), which is a homopolymer of methyl methacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, acrylic A copolymer composed of two or more monomers selected from acid butyl, acrylic acid, and methacrylic acid is preferably used.

  The weight (mass) average molecular weight of the component (B) is 20,000 or more, preferably 40,000 or more, more preferably 60,000 or more. Moreover, an upper limit is 400,000 or less, Preferably it is 350,000 or less, More preferably, it is 300,000 or less. When the weight (mass) average molecular weight is 20,000 or more, it is possible to prevent the film from being insufficiently stretched or embrittled. On the other hand, if the weight (mass) average molecular weight is 400,000 or less, the melt viscosity can be lowered, which is preferable from the viewpoint of production and productivity improvement.

  Examples of commercially available products of the component (B) include “SUMIPEX” (manufactured by Sumitomo Chemical Co., Ltd.), “Acripet” (manufactured by Mitsubishi Rayon Co., Ltd.), “Parapet” (manufactured by Kuraray Co., Ltd.), “ Artugrass (manufactured by Atofina Japan), "Delpet" (manufactured by Asahi Kasei Corporation), and the like.

  The addition amount of the component (B) is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more with respect to the total amount of the mixed resin constituting the (I) layer. Moreover, the addition amount is preferably 30% by mass or less, more preferably 25% by mass or less, and further preferably 20% by mass or less. If content of (B) component is 5 mass% or more, the effect which improves the shrinkage | contraction characteristic of a film, shrinkage finishing property, and transparency can fully be acquired. On the other hand, if it is 30% by mass or less, the impact resistance of the film is not significantly reduced, the stretchability and shrinkage characteristics at low temperature can be maintained, and heat shrinkage in a practical temperature range (about 70 to 90 ° C.). This is preferable because a sufficient rate can be obtained.

<(C) component (rubber-like component)>
Next, the rubber-like component which is (C) component is demonstrated.
In order to improve the impact resistance of the film, the component (C) is added with other rubber components other than the polylactic acid-based resin within a range not impairing the heat shrinkability and the rigidity of the film.

  The component (C) is not particularly limited, but is an aliphatic polyester other than a polylactic acid resin, an aromatic aliphatic polyester, a copolymer of a diol, a dicarboxylic acid and a lactic acid resin, or a core-shell structure type rubber. , Ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene- (meth) acrylic acid copolymer (EMA), ethylene -Methyl (meth) acrylic acid copolymer (EMMA) etc. are used suitably. Among these, core-shell structure rubber can be used more suitably.

  Examples of the aliphatic polyester include polyhydroxycarboxylic acid, aliphatic polyester obtained by condensing aliphatic diol and aliphatic dicarboxylic acid, aliphatic polyester obtained by ring-opening polymerization of cyclic lactone, and synthetic system An aliphatic polyester etc. can be mentioned.

  Examples of the polyhydroxycarboxylic acid include 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, and 2-methyllactic acid. , Homopolymers and copolymers of hydroxycarboxylic acids such as 2-hydroxycaprolacuronic acid.

  As the aliphatic polyester obtained by condensing the aliphatic diol and the aliphatic dicarboxylic acid, one or two or more kinds of aliphatic polyesters and aliphatic dicarboxylic acids described below are condensed. Alternatively, a polymer that can be obtained as a desired polymer by jumping up the molecular weight with an isocyanate compound or the like, if necessary, can be mentioned.

  Here, typical examples of the aliphatic diol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and the like. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, and the like.

  Examples of the aliphatic polyester obtained by ring-opening condensation of the above-mentioned cyclic lactones include ring-opening polymers such as ε-caprolactone, σ-valerolactone, and β-methyl-σ-valerolactone, which are cyclic monomers. Can be mentioned. The cyclic monomer can be copolymerized by selecting not only one kind but also plural kinds.

  Furthermore, examples of the synthetic aliphatic polyester include a copolymer of a cyclic acid anhydride and an oxirane, such as a copolymer of succinic anhydride and ethylene oxide, a copolymer of propion oxide, and the like. it can.

  Typical aliphatic polyesters other than these polylactic acid resins include “Bionole” (produced by Showa Polymer Co., Ltd.), a product obtained by polymerizing succinic acid, 1,4-butanediol and adipic acid. Name) etc. can be obtained commercially. Moreover, as a thing obtained by ring-opening condensation of (epsilon) -caprolactone, "Cell Green" (The Daicel Chemical Industries Ltd. make, brand name) etc. are mentioned.

  Next, as the aromatic aliphatic polyester, those having crystallinity lowered by introducing an aromatic ring between aliphatic chains can be used. The aromatic aliphatic polyester is obtained, for example, by condensing an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic diol.

  Examples of the aromatic dicarboxylic acid include isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and terephthalic acid is most preferably used. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, and adipic acid is most preferably used. Furthermore, examples of the aliphatic diol include those described above. Two or more types of aromatic dicarboxylic acids, aliphatic dicarboxylic acids or aliphatic diols may be used.

  Typical examples of the aromatic aliphatic polyester include a copolymer of tetramethylene adipate and terephthalate, a copolymer of polybutylene adipate and terephthalate, and the like. EsterBio (manufactured by Eastman Chemicals) as a copolymer of tetramethylene adipate and terephthalate, and Ecoflex (manufactured by BASF) as a copolymer of polybutylene adipate and terephthalate can be obtained commercially.

  Examples of the structure of the copolymer of the diol, dicarboxylic acid, and polylactic acid resin include a random copolymer, a block copolymer, and a graft copolymer, and any structure may be used. However, from the viewpoint of impact resistance and transparency of the film, block copolymers and graft copolymers are preferred. Specific examples of the random copolymer include “GS-Pla” (trade name, manufactured by Mitsubishi Chemical Corporation), and specific examples of the block copolymer or graft copolymer include “Plamate” (Dainippon Ink Chemical Co., Ltd.). Kogyo Co., Ltd. product name).

  The method for producing the copolymer of the polylactic acid resin, diol and dicarboxylic acid is not particularly limited. For example, a polyester or polyether polyol having a structure obtained by dehydration condensation of diol and dicarboxylic acid is opened with lactide. Examples thereof include a method obtained by ring polymerization or transesterification. Another example is a method in which a polyester or polyether polyol having a structure obtained by dehydration condensation of a diol and a dicarboxylic acid is obtained by dehydration / deglycolization condensation or transesterification with a polylactic acid resin.

  The copolymer of the polylactic acid-based resin, the diol, and the dicarboxylic acid can be adjusted to a predetermined molecular weight using an isocyanate compound or a carboxylic acid anhydride. However, from the viewpoints of workability and mechanical properties, the weight (mass) average molecular weight is 50,000 or more, preferably 100,000 or more, and 300,000 or less, preferably 250,000 or less. .

  Moreover, the said core-shell structure rubber means the rubber-like component which has a two-layer structure of a core part and a shell part. This core-shell structure rubber has a high impact resistance improvement effect and is finely dispersed in the component (A) by being combined with the component (A), so that the impact resistance is greatly reduced without substantially impairing the transparency of the lactic acid resin. Can be improved.

  Examples of the core-shell structure rubber include diene-based core-shell type polymers such as methacrylic acid-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylic core-shell type polymers such as methacrylic acid-styrene-acrylonitrile copolymer, And silicone-based core-shell copolymers such as silicone-methacrylic acid-methylmethacrylic acid copolymer and silicone-methacrylic acid-acrylonitrile-styrene copolymer. Among these, a silicone-methacrylic acid-methylmethacrylic acid copolymer that has good compatibility with the polylactic acid resin and can balance the impact resistance and transparency of the film is more preferably used. As specific examples, “Metablene C.S.E.W.” (trade name, manufactured by Mitsubishi Rayon Co., Ltd.), “Kane Ace” (trade name, manufactured by Kaneka Corp.), and the like are commercially available.

Further, the ethylene - vinyl acetate copolymer (EVA), ethylene - A acrylic acid copolymer (EAA), ethylene - (meth) acrylic acid copolymer polymer (EMA), ethylene - methyl (meth) acrylate copolymer As the polymer (EMMA), those having a comonomer content other than ethylene of 20% by mass or more, preferably 40% by mass or more, and 90% by mass or less, preferably 80% by mass are suitably used. If the comonomer content other than ethylene is 20% by mass or more, the effect on the rupture resistance of the film can be sufficiently obtained, and transparency can be maintained, which is preferable. On the other hand, if it is 90 mass% or less, since the rigidity and heat resistance of the whole film can be maintained favorable, it is preferable. Among these, ethylene-vinyl acetate copolymer (EVA) is more preferably used.

  Examples of the ethylene-vinyl acetate copolymer (EVA) include “EVAFLEX” (trade name, manufactured by Mitsui DuPont Polychemical Co., Ltd.), “Novatech EVA” (trade name, manufactured by Mitsubishi Chemical Corporation), “Evaslen” (large) Nippon Ink Chemical Co., Ltd. (trade name), “Evertate” (Sumitomo Chemical Co., Ltd. product name), “Soabrene” (Nippon Synthetic Chemical Co., Ltd. product name), etc. are commercially available.

  As the ethylene-acrylic acid copolymer (EAA), “Novatech EAA” (trade name, manufactured by Mitsubishi Chemical Corporation) is commercially available. Furthermore, as the ethylene- (meth) acrylic acid copolymer (EMA), “NOAFLOY AC” (trade name, manufactured by Mitsui DuPont Polychemical Co., Ltd.) and the like are commercially available. Furthermore, as an ethylene-methyl (meth) acrylic acid copolymer (EMMA), “ACRIFT” (trade name, manufactured by Sumitomo Chemical Co., Ltd.) and the like are commercially available.

The amount of the rubbery component (C) added is preferably 5% by mass or more, 10% by mass or more, more preferably 15% by mass or more, based on the total amount of the mixed resin constituting the layer (I). The mass% is preferably 40% by mass or less , and more preferably 30% by mass or less . If it is 5% by mass or more, the impact resistance improvement effect can be exhibited, and if it is 50% by mass or less, it can be suitably used as a heat shrink label without impairing the rigidity and transparency of the film. .

<Laminated structure>
Film structure of the present invention, component (A) as described above, the principal component and configured (I) layer, wherein the component (A) from the component (B) and (C) a mixed resin containing the components The layer structure is not particularly limited as long as it has at least two layers (II). In addition to the (I) layer, the properties of the heat-shrinkable film, particularly the shrinkage properties can be easily adjusted by laminating with the (II) layer containing polylactic acid resin as a main component.

  The film of the present invention can further improve the shrinkage characteristics and rupture resistance by laminating the (I) layer and the (II) layer having different D-form content in order to improve the shrinkage characteristics. .

  As a specific D / L ratio, the D / L ratio of the lactic acid resin constituting the layer (I) is 5/95 to 15/85, or 85/15 to 95/5 under the above relationship. It is preferably 7/93 to 13/87 or more preferably 87/13 to 93/7. Moreover, it is preferable that D / L ratio of the lactic acid-type resin which comprises a (II) layer is 5 / 95-10 / 90, or 90 / 10-95 / 5, 6 / 94-9 / 91, or 91 More preferably, it is / 9 to 94/6. By adjusting the D / L ratio of the (I) layer and the (II) layer as described above, the degree of crystallization can be controlled within an appropriate range, and the occurrence of defects such as shrinkage unevenness due to crystallization can be suppressed. At the same time, better shrink finish can be realized.

  In addition, “having at least two layers of (I) layer and (II) layer” means not only an embodiment in which the (II) layer is laminated on one side or both sides adjacent to the (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. Preferably, an intermediate layer (I) layer and a surface layer (II) layer as a two or three layer structure ((II) layer / (I) layer / (II) layer), or an intermediate layer and a surface layer There are three types and five layers (such as (II) layer / adhesive layer / (I) layer / adhesive layer / (II) layer)).

  In the present invention, the most preferable laminated structure is a two-kind three-layer structure of “(II) layer / (I) layer / (II) layer”. This is because the surface adjustment becomes easier by using the (II) layer containing the polylactic acid resin (A) as a main component as the surface layer.

  In the present invention, the lamination ratio of each layer is not particularly limited, but the ratio of the (I) layer is preferably 50% or more and 95% or less, more preferably 60% or more and 90% or less with respect to the total thickness. preferable. This is because if the layer (I) is within the above range, the fracture resistance and shrinkage finish will be good.

<Other additives>
In the present invention, polyethylene resin, polypropylene resin, polystyrene resin (general-purpose polystyrene (GPPS), high-impact polystyrene (HIPS), styrene-butadiene copolymer (SBS)) as long as the effects of the present invention are not significantly impaired. Styrene-isoprene copolymer (SIS), styrene-ethylene-butadiene copolymer (SEBS), styrene-ethylene-propylene copolymer (SEPS), styrene-carboxylic acid copolymer, etc.), polyamide resin, poly At least one thermoplastic resin such as an oxymethylene resin can be mixed with the mixed resin constituting the layer (I).

  In addition to the component (A), other resins can be mixed with the resin constituting the layer (II) as long as the effects of the invention are not impaired.

  Furthermore, in the above-mentioned (I) layer and (II) layer, in order to improve the various properties of impact resistance, transparency, moldability and heat-shrinkable film within the range that does not significantly impair the effect of the present invention, A plasticizer may be added.

  Examples of the plasticizer to be added include dibutyl adipate, diisobutyl adipate, diisononyl adipate, diisodecyl adipate, di (2-ethylhexyl) adipate, di (n-octyl) adipate, di (n-decyl) adipate, dibutyl diglycol adipate, Fatty acid ester systems such as dibutyl sebacate, di (2-ethylhexyl) sebacate, di (n-hexyl) azelate, di (2-ethylhexyl) azelate, di (2-ethylhexyl) dodecanedionate. Phthalate esters such as diisononyl phthalate, diisodecyl phthalate, and di (2-ethylhexyl) phthalate. And trimellitic acid ester type such as tri (2-ethylhexyl) trimellitate.

  When the plasticizer is added, it is particularly preferable to add it only to the (I) layer. Although it is possible to add a plasticizer to the layer (II), it is difficult to add an amount sufficient to exert the effect because there is a concern about the precipitation of the plasticizer over time. It is. Specific properties that are concerned by the plasticizer deposition over time include film blocking, slipperiness change, and poor appearance.

  In the present invention, in addition to the components described above, trimming of film ears and the like is performed for the purpose of improving and adjusting various properties of the moldability, productivity, and heat shrinkable film within a range that does not significantly impair the effects of the present invention. Recycled resin generated from loss, inorganic particles such as silica, talc, kaolin, calcium carbonate, pigments such as titanium oxide and carbon black, flame retardant, weather resistance stabilizer, heat stabilizer, antistatic agent, melt viscosity improver Additives such as cross-linking agents, lubricants, nucleating agents, anti-aging agents can be added as appropriate.

  Although the total thickness of the film of the present invention is not particularly limited, it is preferably thinner from the viewpoints of transparency, shrinkage workability, raw material cost, and the like. Specifically, 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 film is not particularly limited, but is preferably 20 μm or more in consideration of the handleability of the film.

<Manufacturing method>
The film of the present invention can be produced by a known method. The form of the film may be either flat or tube-like, but the flat form is preferable in terms of productivity (a few products can be taken in the width direction of the original film) and printing on the inner surface. . As a method for producing a flat film, for example, a resin is melted by using a plurality of extruders, co-extruded from a T die, solidified by cooling with a chilled roll, roll-stretched in the vertical direction, and tenter-stretched in the horizontal direction. An example is a method of obtaining a film by winding, annealing, cooling, and winding with a winder (corona discharge treatment is applied to the surface when printing is performed). Moreover, the method of cutting open the film manufactured by the tubular method and making it flat is also applicable.

In applications where the stretching ratio is contracted in two directions, such as for overlap, the vertical direction is 2 to 10 times, the horizontal direction is 2 to 10 times, preferably the vertical direction is 3 to 6 times, and the horizontal direction Is about 3 to 6 times. On the other hand, in applications such as heat-shrinkable labels that shrink mainly in one direction, the direction corresponding to the main shrinkage direction is 2 to 10 times, preferably 4 to 8 times, and the direction orthogonal to it is 1 or more times. It is desirable to select a magnification ratio of 2 times or less, preferably 1.01 times or more and 1.5 times or less, which is substantially in the category of uniaxial stretching. Note that one fold may refer to If you have not stretched.

  A biaxially stretched film stretched at a stretch ratio within the above range does not have an excessively large thermal shrinkage rate in the direction orthogonal to the main shrinkage direction.For example, when used as a shrinkage label, It is preferable because the so-called vertical shrinkage phenomenon, in which the film is thermally contracted in the vertical direction, can be suppressed.

  The stretching temperature needs to be changed depending on the glass transition temperature of the resin to be used and the properties required for the heat-shrinkable film, but is generally 60 ° C. or higher, preferably 70 ° C. or higher, and the upper limit is 100 ° C. or lower, preferably 90 ° C. It is controlled within the following range. The draw ratio is 1.5 times to 10 times, preferably 3 times to 7 times, preferably 3 times to 7 times in the main shrinkage direction, depending on the characteristics of the resin used, the stretching means, the stretching temperature, the target product form, etc. Preferably, it is appropriately determined in the direction of one axis or two axes within a range of 3 to 5 times. Even in the case of uniaxial stretching in the transverse direction, it is also effective to impart weak stretching of about 1.05 to 1.8 times in the longitudinal direction for the purpose of improving the mechanical properties of the film. Next, the stretched film is subjected to a 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 shrink property, if necessary. It cools rapidly within the time not to relax, and becomes a heat-shrinkable film.

  Further, the film of the present invention can be subjected to surface treatment such as corona treatment, printing, coating, vapor deposition, and surface treatment as needed, and further, bag making processing and perforation processing using various solvents and heat sealing.

  The film of the present invention is processed from a flat shape to a cylindrical shape or the like according to an object to be packaged and provided for packaging. When printing is required in a cylindrical container such as a plastic bottle, first print the required image on one side of a wide flat film wound up on a roll, and then cut the print to the required width while the printing side is inside. It suffices to fold and seal the center to make it cylindrical. In this case, the shape of the seal portion is so-called envelope pasting.

  Examples of the center sealing method include an adhesion method using an organic solvent, a heat sealing method, an adhesive method, and an impulse sealer method. Among these, from the viewpoint of productivity and appearance, an adhesion method using an organic solvent is preferably used.

<Physical and mechanical properties of heat-shrinkable film>
(Shrinkage factor)
In the film of the present invention, it is important that the shrinkage ratio in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is 20% or more, and more preferably 30% or more. This is an index for determining the adaptability to the shrinking process in a relatively short time (several seconds to about several tens of seconds) such as the use of shrinkage labels for PET bottles.
The “main shrinkage direction” means the larger one of the longitudinal direction and the transverse direction in the stretching direction. For example, when attached to a bottle, it is a direction corresponding to the outer circumferential direction.

  At present, the shrinkage processing machine most commonly used industrially for labeling of PET bottles is generally called a steam shrinker that uses steam as a heating medium for shrinking. Furthermore, the 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. However, in the case of a film with high temperature dependence and extremely different shrinkage ratios depending on the temperature, parts with different shrinkage behavior tend to occur with respect to the temperature spots in the steam shrinker, so shrinkage spots, wrinkles, avatars, etc. occur. However, the shrink-finished appearance tends to deteriorate. From the viewpoint of including these industrial productivity, if the shrinkage rate in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is 20% or more, it can sufficiently adhere to the coated object within the shrinkage processing time, In addition, it is preferable because spots, wrinkles, and avatars are not generated and a good shrink-finished appearance can be obtained. From this, the film of the present invention preferably has a shrinkage ratio in the main shrinkage direction at 80 ° C. of 20% or more and 70% or less.

  Although the upper limit of the heat shrinkage is not described, since the heat shrinkage does not shorten the length of the film before stretching, the upper limit of the heat shrinkage is a shrinkage rate that becomes the film length before stretching. .

  On the other hand, by reducing the shrinkage rate in the direction perpendicular to the main shrinkage direction, it is possible to obtain more excellent shrinkage finish. When the film of the present invention is used as a heat-shrinkable label, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction is preferably 5% or less when immersed in warm water at 80 ° C. for 10 seconds. More preferably, it is more preferably 3% or less. If the film has a thermal shrinkage rate of 5% 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 characters after shrinkage may be distorted. In the case of a square bottle, it is preferable because troubles such as vertical sink are unlikely to occur. In this case, the lower limit of the heat shrinkage rate is 0%.

(transparency)
Regarding the transparency of the film of the present invention, 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% or less. More preferably it is. If the haze value is 10% or less, the transparency of the film can be obtained and a display effect can be obtained.

(Tensile elongation at break)
The impact resistance of the film of the present invention is evaluated by the tensile elongation at break, and in a tensile test under a 0 ° C. environment, the elongation is preferably 100% or more in the film take-off (flow) direction (MD), particularly for label applications. 150% or more, more preferably 200% or more. If the tensile elongation at break in an environment of 0 ° C. is 100% or more, such a problem that the film is not easily broken at the time of printing and bag making is preferable. Also, when the tension applied to the film increases as the speed of processes such as printing and bag making increases, it is preferable that the tensile breaking elongation is 150% or more, so that it is 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.

[Molded products, heat-shrinkable labels and containers]
The film of the present invention is excellent in the heat shrink property, shrink finish, transparency, etc. of the film, so its use is not particularly limited, but if necessary, a printing layer, a vapor deposition layer and other functional layers may be added. By forming, it can be used as a base material for various molded products such as bottles (blow bottles), trays, lunch boxes, prepared food containers, dairy products containers and the like. The obtained molded product can be used as a container or the like.

  In addition, the film of the present invention can be used as a base material for a heat-shrinkable label for food containers (for example, PET bottles, glass bottles, preferably PET bottles for soft drinks or foods). In this case, even a complicated shape (for example, a cylinder with a narrow center, a square column with a corner, a pentagonal column, a hexagonal column, etc.) can be closely attached to the shape and is mounted beautifully without wrinkles or avatars. Label. And the food container which installed the label can be used as a container.

  In addition, the said molded article and container can be produced by using a normal shaping | molding method.

  Since the film of the present invention has excellent low temperature shrinkage and shrinkage finish properties, in addition to heat-shrinkable label materials used for plastic molded products that are deformed when heated to high temperatures, it has a coefficient of thermal expansion and water absorption. Materials very different from the heat-shrinkable film of the present invention, for example, polyolefin resin such as metal, porcelain, glass, paper, polyethylene, polypropylene, polybutene, polymethacrylate resin, polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate It can utilize suitably as a heat-shrinkable label raw material of the package (container) which used at least 1 sort (s) chosen from polyester-type resins, such as such as a constituent material.

  As a material constituting the plastic package in which the film of the present invention can be used, 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 resins or a laminate.

The present invention will be described below with reference to examples.
In addition, the measured value and evaluation which are shown to an Example were performed as follows. In the examples, the take-up (flow) direction of the laminated film is described as the “longitudinal” direction (or MD), and the perpendicular direction thereof is described as the “transverse” direction (or TD).

<Measurement method>
(1) Thermal contraction 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 shrinkage was measured. For the thermal shrinkage, the ratio of shrinkage to the original size before shrinkage is expressed as a% value in the longitudinal direction or the transverse direction.

(2) Haze The haze value of the film was measured according to JIS K7105.

(3) Tensile elongation at break In order to evaluate the film production process and the fracture resistance during use, the following measurements were performed.
The obtained film was cut into a size of MD110 mm × TD15 mm, and 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 in accordance with JIS K6732, and the average of ten measurements. Values are shown in the table.

(4) Shrinkage Finishing A film printed with a grid of 10 mm intervals was cut into a size of MD 170 mm × TD 114 mm, and both ends of TD were overlapped by 10 mm and adhered with a Tetrohydrofuran (THF) solvent to produce 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 set to a range of 70 to 85 ° C. by adjusting the amount of steam with a steam valve.

After film coating, the following criteria were evaluated.
◎: Shrinkage is sufficient and no wrinkles, avatars, whitening, or lattice distortions occur. ○: Shrinkage is sufficient, but wrinkles, avatars, whitening, and lattice distortions occur only slightly, but there is no practical problem. : Shrinkage is sufficient, but wrinkles, avatars, whitening, and lattice distortions are slightly caused, which may be a problem depending on the application. ×: Shrinkage is insufficient, or wrinkles, avatars, and lattice distortions are noticeably generated.

Moreover, the raw material used by each Example and the comparative example is as follows.
<(A) component (polylactic acid resin)>
-Polylactic acid-based resin: manufactured by Nature Works, Inc. Product name: NatureWorks 4050, L-form / D-form weight = 95/5, hereinafter abbreviated as “A-1”.
-Polylactic acid resin ... manufactured by Nature Works, Inc. Product name: NatureWorks 4060, L-form / D-form weight = 88/12, hereinafter abbreviated as “A-2”.

<(B) component ((meth) acrylic resin)>
-Methyl methacrylate resin: manufactured by Mitsubishi Rayon Co., Ltd. Trade name: Acrypet VH01, hereinafter abbreviated as "B-1".

<(C) component (rubber-like component)>
Core shell structure type rubber: manufactured by Mitsubishi Rayon Co., Ltd. Trade name: Metablen S2001, core shell structure acrylic-silicone copolymer, hereinafter abbreviated as “C-1”.
Aliphatic polyester other than polylactic acid resin: manufactured by Showa Polymer Co., Ltd. Product name: Bionore 3003, polybutylene succinate-adipate copolymer, hereinafter abbreviated as “C-2”.

(Examples 1-4, Comparative Examples 1 and 2, Reference Example)
As (I) layer resin shown in Table 1, (A) component, (B) component, and (C) component are mixed and mixed resin (in the case of a comparative example, it selects from (A) component thru | or (C) component) In addition, as the resin for the (II) layer shown in Table 1, a resin mainly composed of the component (A) was obtained, and each was separated into a separate twin-screw extruder (Mitsubishi Heavy Industries, Ltd. ) Manufactured), melted and mixed at a set temperature of 200 ° C., and extruded from a two-kind / three-layer die at a set temperature of 200 ° C. so as to have a configuration of “(II) / (I) / (II)”. Then, it was taken up with a cast roll at 50 ° C. and cooled and solidified to obtain an unstretched sheet having a width of 300 mm and a thickness of 250 μm.
Next, the film was stretched in the machine direction under the conditions shown in Table 1 using a roll longitudinal stretching machine, and then stretched in the transverse direction under the conditions shown in Table 1 using a film tenter (manufactured by Mitsubishi Heavy Industries, Ltd.). A heat-shrinkable film was obtained. The evaluation results of the obtained film are shown in Table 1.

From Table 1, the film consisting of the composition defined in the present invention was good in impact resistance, transparency and shrink finish. On the other hand, when the film does not contain the component (B) (Comparative Example 1), the shrinkage finish is poor, and when the component (C) is not contained (Comparative Example 2), the impact resistance is poor. . Furthermore, favorable transparency was obtained by adjusting D / L ratio of (A) component contained in (I) layer and (II) layer from Examples 1-4 and a reference example.
As a result, the film of the present invention has excellent heat shrink properties, mechanical properties such as impact resistance and transparency, and shrink finish performance of heat shrinkable films, and is suitable for applications such as shrink packaging, shrink-bound packaging, and shrink labels. It turns out that it is a suitable heat-shrinkable film.

Claims (7)

The (I) layer composed of a mixed resin containing a polylactic acid resin (A), a (meth) acrylic resin (B), and a rubbery component (C), and the polylactic acid resin (A) as a main component (II) and at least two layers,
The content of the (meth) acrylic resin (B) is 5% by mass to 30% by mass with respect to the total amount of the mixed resin,
The content of the rubbery component (C) is 5% by mass or more and 50% by mass or less with respect to the total amount of the mixed resin,
A heat-shrinkable film having a shrinkage ratio in the main shrinkage direction of 20% or more when stretched in at least one direction and immersed in warm water at 80 ° C. for 10 seconds. The polylactic acid resin (A) is composed of a copolymer of D-lactic acid and L-lactic acid, or a mixed resin of this copolymer, and is contained in the layer (I). The D / L ratio of 5/95 to 15/85, or 85/15 to 95/5, and the D / L ratio of the polylactic acid resin (A) contained in the layer (II) is 5 The heat-shrinkable film according to claim 1 , which is / 95 to 10/90 or 90/10 to 95/5. The (meth) acrylic resin (B) is selected from methyl methacrylate homopolymer, or methyl methacrylate, ethyl (meth) acrylate, butyl (meth) acrylate, methyl acrylate, and (meth) acrylic acid. a copolymer of two or more monomers heat-shrinkable film according to claim 1 or 2, which. The rubbery component (C) is an aliphatic polyester other than the polylactic acid resin, an aromatic aliphatic polyester, a copolymer of a diol, a dicarboxylic acid and a lactic acid resin, a core-shell structure type rubber, an ethylene-vinyl acetate copolymer. At least one selected from a polymer, an ethylene-acrylic acid copolymer, an ethylene-ethyl acrylate copolymer, an ethylene- (meth) acrylic acid copolymer, and an ethylene-methyl (meth) acrylic acid copolymer heat-shrinkable film according to any one of a claims 1 to 3. Molded article using as a substrate a heat-shrinkable film according to any one of claims 1 to 4. Heat-shrinkable label employing the heat-shrinkable film according as the substrate in any one of claims 1 to 4. A container using the molded article according to claim 5 or equipped with the heat-shrinkable label according to claim 6 .