JP2008239712A - Heat-shrinkable film, molded article obtained by using heat-shrinkable film, heat-shrinkable label, and container obtained by using molded article or provided with label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable film that has a light environmental load, is excellent in heat-shrinking properties, impact resistance, transparency, mechanical properties and shrinking finish properties, and is suitable for applications such as shrink packaging, shrink bundling packaging or shrinkable labels. <P>SOLUTION: The heat-shrinkable film is composed of a mixed resin comprising as main components a polylactic acid resin and a soft acrylic resin with a mass ratio of the polylactic acid resin to the soft acrylic resin of 95/5-50/50 or has at least one mixed resin layer, where the polylactic acid resin comprises a copolymer of D-lactic acid and L-lactic acid or a mixed resin comprised of the copolymer while the soft acrylic resin has a storage elastic modulus (E') of at least 0.1 MPa and at most 100 MPa at 20°C as measured with an oscillation frequency of 10 Hz and has a heat shrinkage factor of at least 20% in the main shrinking direction when stretched at least in one direction and immersed in hot water of 80°C for 10 sec. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable film, a molded article using the heat-shrinkable film, a heat-shrinkable label, and a container equipped with the molded article or the label, and more particularly, excellent shrinkage characteristics and heat resistance. Further, heat shrinkable films suitable for applications such as shrink wrapping, shrink-bound wrapping, and shrink labels, as well as molded articles using the heat shrinkable films, heat shrinkable labels, and molded articles using or the labels Relates to a container equipped with.

  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.

  On the other hand, the effective use of exhaustible resources has recently been emphasized, and the use of renewable resources has become an important issue. Currently, the most noticeable solution is the use of plant-based plastics. This plant-derived plastic not only uses non-depleted resources, but can save exhaustible resources during plastic production, and also has excellent recyclability.

  Among these plant-derived plastics, polylactic acid resins are made from lactic acid obtained by fermentation of starch, can be mass-produced by chemical engineering, and have excellent transparency and rigidity. As an alternative material for polyester (polyethylene terephthalate), it has attracted attention in the field of film packaging materials and injection molding.

  However, when polylactic acid is used as a material for heat-shrinkable labels, it is rigid at room temperature, has low-temperature shrinkability, and has good natural shrinkage, but it is a very brittle material. There is a problem that sometimes contraction spots and wrinkles are likely to occur. 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 Document 2). However, compared to PVC heat-shrinkable films, it is still difficult to say that the shrink finish is sufficient.

  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 3), polycaprolactone (see Patent Document 4), a copolymer polyolefin such as an ethylene-vinyl acetate copolymer (see Patent Document 5), 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.

  Furthermore, as a technique for improving the brittleness of a polylactic acid-based resin, a film made of polylactic acid and a polyolefin compound (see Patent Document 6), a molded product made of polylactic acid and a modified olefin compound (see Patent Document 7) or a composition ( Patent Document 8), a molded product made of polylactic acid and syndiotactic polypropylene (see Patent Document 9), a polymer mainly composed of lactic acid, an aliphatic carboxylic acid, and an aliphatic mainly composed of a chain molecular diol. A plasticized polylactic acid film comprising a polyester plasticizer (see Patent Document 10), a biodegradable resin composition comprising a polylactic acid and an epoxidized diene block copolymer (see Patent Document 11), polylactic acid , A lactic acid polymer composition comprising aliphatic polyester and polycaprolactone (see Patent Document 12), crystalline polylactic acid, and natural rubber And polylactic acid resin composition comprising at least one rubber component selected from polyisoprene methods using (Patent Document 13 reference) and the like have been disclosed.

  However, when the above polycaprolactone, modified olefin compound, epoxidized diene block copolymer, natural rubber, polyisoprene, etc. are mixed with lactic acid resin, the impact resistance is improved, but as a result, transparency For example, it is difficult to say that the technique is sufficient for use in applications where it is necessary to check contents such as packaging materials.

  In addition, a polyacetal resin and diene rubber, natural rubber, silicone rubber, polyurethane rubber, or a multilayer structure including at least one selected from a styrene unit and a butadiene unit in a shell layer of methyl (meth) acrylate in a core layer, etc. A technique for improving impact resistance by blending an impact modifier with a polylactic acid resin is known (see Patent Document 14), but it is not sufficient as a heat shrinkable film.

  Furthermore, a technique (see Patent Document 15) for blending a graph obtained by graft polymerization of a rubbery polymer and a vinyl monomer into a polylactic acid resin and a copolymer has been proposed. Not enough.

On the other hand, a method (see Patent Documents 16 and 17) of blending an acrylic raw material with a polylactic acid resin has been proposed, but the purpose is to improve heat resistance and transparency, and it is difficult to adapt as an improvement in fracture resistance. Furthermore, a stretched film in which a polylactic acid resin having a specific mass average molecular weight and a polymethacrylate resin are blended is known (see Patent Document 18). However, the technique disclosed in Patent Document 18 is mainly for the purpose of improving the heat resistance and transparency of the polylactic acid-based resin film, and as an improvement in the fracture resistance of the heat-shrinkable film as in the present invention. Is difficult to adapt.
JP 2003-119367 A JP 2001-11214 A JP-A-9-169896 JP-A-8-300481 JP-A-9-151310 JP 2005-68232 A JP 09-316310 A Japanese Patent Laid-Open No. 5-179110 JP-A-10-251498 JP 2000-191895 A JP 2000-219803 A JP 2001-031853 A JP 2003-183488 A JP 2003-286400 A JP 2004-285258 A JP 2004-269720 A JP-A-2005-171204 JP 2005-36054 A

The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to respond to the environment such as CO ₂ emission reduction and oil depletion problem by using mainly polylactic acid which is a plant-derived raw material. It is possible to obtain a heat-shrinkable film that is excellent in heat shrinkage properties, impact resistance, transparency, mechanical properties, shrinkage finish, and suitable for applications such as shrink wrapping, shrink-bound packaging, and shrink labels. .

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

  An object of the present invention is a mixed resin containing a polylactic acid resin and a soft acrylic resin as main components, and a mass ratio of the polylactic acid resin to the soft acrylic resin being 95/5 to 50/50. Or at least one mixed resin layer, and the polylactic acid resin is a copolymer of D-lactic acid and L-lactic acid, or a mixed resin of this copolymer, and the soft acrylic resin is Storage elastic modulus (E ′) at 20 ° C. measured at a vibration frequency of 10 Hz is 0.1 MPa or more and 100 MPa or less, stretched in at least one direction and immersed in 80 ° C. warm water for 10 seconds. This is achieved by using a heat-shrinkable film having a heat shrinkage ratio of 20% or more.

  In the heat-shrinkable film of the present invention, the D / L ratio between D-lactic acid and L-lactic acid is preferably 3/97 to 15/85, or 85/15 to 97/3.

  In the heat-shrinkable film of the present invention, the soft acrylic resin contains at least one polymer block (A) composed of an acrylate ester (a) and a chemistry different from the acrylate ester (a). It is also preferable to have at least one polymer block (B) composed of (meth) acrylic acid ester (b-1) having a structure. In the present specification, “(meth) acryl” means “acryl or methacryl”.

  In the heat-shrinkable film of the present invention, the acrylic acid ester (a) and the (meth) acrylic acid ester (b-1) are methyl methacrylate, ethyl acrylate, n-butyl acrylate, and acrylic acid 2 -It is preferably at least one selected from the group consisting of ethylhexyl.

  In the heat-shrinkable film of the present invention, the storage elastic modulus (E ′) at 70 ° C. when measured at a vibration frequency of 10 Hz of the soft acrylic resin is also preferably 0.1 MPa or more and 50 MPa or less.

  Furthermore, in the heat-shrinkable film of the present invention, the tensile elongation at break in the direction orthogonal to the main shrinkage direction when measured at an atmospheric temperature of 0 ° C. and a tensile speed of 100 mm / min is preferably 100% or more.

  Another object of the present invention is achieved by a molded article using the heat-shrinkable film of the present invention as a base material, a heat-shrinkable label, a molded article, and a container equipped with the heat-shrinkable label.

  According to the present invention, since a stretched film having a predetermined heat shrinkage ratio is used using a mixed resin containing a soft acrylic resin at a predetermined ratio, heat shrink characteristics, impact resistance, transparency and mechanical characteristics, and Excellent shrinkage finish.

  Furthermore, according to the present invention, a molded product using the heat-shrinkable film suitable for uses such as shrink-wrapping, shrink-bound packaging, and shrink-label, a heat-shrinkable label, and a container equipped with the molded product or the heat-shrinkable label. 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”).

[Heat shrinkable film]
The film of the present invention is a film having at least one layer composed of a mixed resin containing a polylactic acid resin and a soft acrylic resin as main components.

  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.

<Polylactic acid resin>
The polylactic acid-based resin refers to a homopolymer of D-lactic acid or L-lactic acid, or a copolymer thereof. Specifically, poly (D-lactic acid) whose structural unit is D-lactic acid, the structural unit is There are poly (L-lactic acid) which is L-lactic acid, and poly (DL-lactic acid) which is a copolymer of L-lactic acid and D-lactic acid, and the copolymerization ratio of D-lactic acid and L-lactic acid. Also included are mixed resins of a plurality of the above-mentioned copolymers having different.

  The copolymer of L-lactic acid and D-lactic acid has a copolymerization ratio of D-lactic acid and L-lactic acid (hereinafter abbreviated as “D / L ratio”) of 3/97 to 15/85, or It is preferably 85/15 to 97/3, more preferably 5/95 to 15/85, or 85/15 to 95/5, and 8/92 to 15/85, or 85/15 to 92. / 8 is more preferable, and 10/90 to 15/85, or 85/15 to 90/10 is most preferable.

  When the copolymerization ratio of D-lactic acid is higher than 97 or less than 3, it exhibits very high crystallinity, has a high melting point, and tends to be excellent in heat resistance and mechanical properties. However, when used as a heat-shrinkable film, it usually involves printing and a bag-making process using a solvent, so that the crystallinity of the constituent material itself can be lowered appropriately in order to improve printability and solvent sealability. Necessary. 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. Furthermore, even if the film has crystallization suppressed by adjusting the stretching conditions, crystallization proceeds prior to shrinkage due to heating during heat shrinkage, and as a result, there is a tendency to cause shrinkage unevenness or insufficient shrinkage.

  On the other hand, when the copolymerization ratio of D-lactic acid is less than 85 or higher than 15, the crystallinity is almost completely lost. As a result, when the labels collide with each other after heat shrinkage, they are fused by heat. Troubles such as being easily occur. Therefore, by adjusting the composition ratio of D-lactic acid and L-lactic acid in the polylactic acid resin within the above range, it is possible to obtain a heat-shrinkable film having excellent shrinkage characteristics that does not cause the problems described above. Become.

  The film of the present invention is more preferable because it is possible to blend polylactic acid resins having different D / L ratios, and blending can more easily adjust the D / L ratio of the polylactic acid resins. . In this case, the average value of the D / L ratios of a plurality of lactic acid polymers may be set within the above range. By blending two or more polylactic acid resins having different D / L ratios and adjusting the crystallinity according to the intended use, it is possible to balance heat resistance and heat shrinkage characteristics.

  The polylactic acid-based resin may be a copolymer of lactic acid and α-hydroxycarboxylic acid, aliphatic diol, or aliphatic dicarboxylic acid as long as the effects of the present invention are not impaired.

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

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

  The copolymerization ratio in the copolymer of lactic acid and α-hydroxycarboxylic acid is not particularly limited, but the higher the occupancy ratio of lactic acid, the less the consumption of petroleum resources, which is preferable. It is preferable to copolymerize at a ratio not exceeding. Specifically, the copolymerization ratio of 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 = It is 95 / 5-10 / 90, preferably 90 / 10-20 / 80, more preferably 80 / 20-30 / 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.

  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 the polymerization method of the polylactic acid-based resin, a known method such as a condensation polymerization method or a ring-opening polymerization method can 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 necessary, 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.

  As a commercial item of the said polylactic acid-type resin, "NatureWorks" (made by Nature Works LLC), "LACEA" (made by Mitsui Chemicals, Inc.) etc. are mentioned, for example.

<Soft acrylic resin>
In the present invention, the soft acrylic resin used is an acrylic resin having flexibility. Specifically, the storage elastic modulus (E ′) at 20 ° C. when measured at a vibration frequency of 10 Hz is 100 MPa or less. Yes, more preferably 50 MPa or less, still more preferably 10 MPa or less. On the other hand, the lower limit of the storage elastic modulus under similar conditions is 0.1 MPa or more, and preferably 1.0 MPa or more.

  If the storage elastic modulus is 100 MPa or less, the effect of improving the rupture resistance is not lowered, and the occurrence of significant appearance defects can be suppressed, and if it is 0.1 MPa or more, the entire film is stretched. Can do.

  Specifically, the soft acrylic resin used in the film of the present invention has at least one polymer block (A) composed of an acrylate ester (a) and a chemical structure different from the acrylate ester. It is preferable that it is a soft acrylic resin which has at least 1 polymer block (B) comprised by the (meth) acrylic acid ester (b-1) which has.

(Polymer block (A))
The acrylic ester (a) used for forming the polymer block (A) is not particularly limited. Any acrylic ester composed of an acrylic acid component and an alcohol component may be used, but an acrylic ester having an alcohol component having 1 to 15 carbon atoms is preferred. Specific examples of preferred acrylic acid esters include acrylic acid 1 such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and the like. Secondary alkyl ester: glycidyl acrylate, allyl acrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate, trimethoxysilylpropyl acrylate, trifluoroethyl acrylate, isopropyl acrylate, t-butyl acrylate, acrylic Examples thereof include sec-butyl acid, cyclohexyl acrylate, isobornyl acrylate, trimethylsilyl acrylate, and the like. One kind or two or more kinds of acrylic acid ester (a) may be used.

(Polymer block (B))
The (meth) acrylic acid ester (b-1) used for forming the polymer block (B) has a different chemical structure from the acrylic acid ester (a) used for forming the polymer block (A). Have In the present specification, “(meth) acryl” means “acryl or methacryl”.

  Typical examples of the methacrylic acid ester that can be used as the (meth) acrylic acid ester (b-1) include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate. Methacrylic acid alkyl esters such as t-butyl methacrylate, 2-ethylhexyl methacrylate and lauryl methacrylate; cycloalkyl esters such as cyclohexyl methacrylate; aryl methacrylates such as phenyl methacrylate; benzyl methacrylate and the like Methacrylic acid aralkyl ester; glycidyl methacrylate; allyl methacrylate; trimethylsilyl methacrylate; trimethoxysilylpropyl methacrylate;

(composition)
In the film of the present invention, one or more of the polymerizable monomers described above may be used as the acrylic ester (a) and the (meth) acrylic ester (b-1). Among the above representative examples, acrylic ester (a) and (meth) acrylic ester (b-1) are methyl methacrylate, ethyl acrylate, n-butyl acrylate, and 2-ethyl acrylate. It is preferable to use at least one selected from the group consisting of xylyl from the viewpoint of physical properties of the resulting film.

(Construction)
The number of polymer blocks of the block copolymer having one or more polymer blocks (A) and one or more polymer blocks (B) used in the film of the present invention, the arrangement of polymer blocks, There are no particular limitations on the molecular weight and stereoregularity of the polymer block and the molecular weight of the entire block copolymer. However, the block copolymer capable of exhibiting particularly good properties as a thermoplastic elastomer has one or more polymer blocks (A) and two or more polymer blocks (B) in the block copolymer. The block structure is preferably a triblock or more. For the purpose of producing a block copolymer having excellent heat resistance, it is preferable that the stereoregularity in the polymer block (B) be 70% or more syndiotacticity by triad, and 80% or more. More preferably, it is syndiotacticity. For this purpose, it is preferred to use mainly methacrylic esters.

  In the film of the present invention, in particular, n-butyl acrylate is used as the acrylic ester (a), and methyl methacrylate is used as the (meth) acrylic ester (b-1). Most preferred from the viewpoint. It becomes easy to adjust the storage elastic modulus by mainly using both raw materials. For example, when it is desired to reduce the storage elastic modulus, it can be achieved by increasing the content of the n-butyl acrylate block. On the other hand, when it is desired to increase the storage elastic modulus, the content of methyl methacrylate is increased. Can be achieved.

  The (meth) acrylic acid ester (b-1) in the soft acrylic resin used in the film of the present invention, more specifically, methyl methacrylate is preferably 5% by mass or more, more preferably 10% by mass or more. 20% by mass or more is more preferable. The upper limit is preferably 60% by mass or less, more preferably 50% by mass or less, and further preferably 40% by mass or less. By setting the content of methyl methacrylate in the above range, it becomes possible to obtain a predetermined storage elastic modulus characteristic.

(Molecular weight)
In the film of the present invention, the molecular weight of each polymer block and the entire block copolymer in the target block copolymer can be appropriately adjusted according to the application. In general, the number average molecular weight of the polymer block (A) is in the range of 1,000 to 1,000,000, and the number average molecular weight of the polymer block (B) is 1,000 to 1,000,000. The number average molecular weight of the entire block copolymer is in the range of 3,000 to 3,000,000. By making it within this range, the moldability, handleability and mechanical properties of the resulting block copolymer are preferable.

  Further, the soft acrylic resin used in the film of the present invention preferably has a storage elastic modulus (E ′) at 70 ° C. of 0.1 MPa or more and 50 MPa or less when measured at a vibration frequency of 10 Hz, and is 30 MPa or less. More preferably. On the other hand, the storage elastic modulus under the same conditions is 0.1 MPa or more, and preferably 1.0 MPa or more.

  The purpose of setting the storage elastic modulus at 70 ° C. of the soft acrylic resin used in the film of the present invention to the above range is to improve the fracture resistance and shrink finish of the film. That is, by setting the storage elastic modulus to 50 MPa or less, it becomes possible to further improve the fracture resistance of the film of the present invention. On the other hand, by setting the storage elastic modulus to 0.1 MPa or more, the elastic modulus can be prevented from drastically decreasing during heat shrinkage at 60 ° C. to 80 ° C., and good shrinkage finish can be obtained.

  The melt flow rate (MFR) of the soft acrylic resin used in the film of the present invention is usually MFR (JIS K7210, temperature: 190 ° C., load: 21.18N), preferably 1.0 g / 10 min or more. Is 5.0 g / 10 min or more and 30 g / 10 min or less, preferably 25 g / 10 min or less, more preferably 20 g / 10 min or less.

  Examples of the soft acrylic resin include trade name “LA polymer” (manufactured by Kuraray Co., Ltd.).

<Mass ratio of polylactic acid resin to soft acrylic resin>
In the film of the present invention, it is important that the mass ratio of the polylactic acid resin and the soft acrylic resin is 95/5 to 50/50. The mass ratio is more preferably 90/10 to 60/40, and still more preferably 85/15 to 70/30. By setting the mass ratio of the soft acrylic resin to the mass of the polylactic acid resin to 5 or more, the effect of improving the fracture resistance can be expected. On the other hand, maintaining the mass ratio of the soft acrylic resin to the mass of the polylactic acid resin at 50 or less makes it possible to maintain the waist of the entire film.

<Additives to mixed resin>
Furthermore, in the film of the present invention, a methyl methacrylate polymer, a polyethylene resin, and a polypropylene resin having a methyl methacrylate content of 70% by mass or more in the mixed resin as long as the effects of the invention are not significantly impaired. A copolymer of a monomer copolymerizable with ethylene, specifically, at least one thermoplastic resin such as an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-methyl acrylate copolymer, or the like. More than one species can be further contained.

  Polystyrene resins (GPPS (general purpose polystyrene), HIPS (high impact polystyrene), SBS (styrene-butadiene copolymer), SIS (styrene-isoprene copolymer), SEBS (styrene-ethylene-butylene-styrene copolymer) Polymerization), SEPS (styrene-ethylene-propylene-styrene copolymer), styrene-carboxylic acid copolymer, etc.), polyamide resins, polyoxymethylene resins, and other thermoplastic resins. can do.

  Among the above-mentioned additives, a methyl methacrylate polymer having a methyl methacrylate content of 70% by mass or more can be compatible with the polylactic acid resin, so that it can be shrunk by blending with the polylactic acid resin. It is preferable because it is a resin that can adjust the glass transition temperature that affects it and is effective in improving the shrink finish.

  The content of the thermoplastic resin is 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, and 30% by mass or less, preferably 25% by mass with respect to the total amount of the resin constituting the film. % Or less, more preferably 20% by mass or less.

  Examples of commercially available thermoplastic resins include “Sumipex” (manufactured by Sumitomo Chemical Co., Ltd.), “Acripet” (manufactured by Mitsubishi Rayon Co., Ltd.), “Parapet” (manufactured by Kuraray Co., Ltd.), and “Artuglass”. ("Atofina Japan"), "Delpet" (Asahi Kasei Co., Ltd.).

  Furthermore, in the film of the present invention, a soft resin is used for the purpose of improving the impact resistance, transparency, molding processability and various properties of the heat-shrinkable film in the above mixed resin within a range that does not significantly impair the effects of the present invention. May be added.

  Examples of the soft resin include an aliphatic polyester resin excluding a polylactic acid resin, an aromatic aliphatic polyester resin, a core-shell structure type rubber, a copolymer of a diol, a dicarboxylic acid, and a lactic acid resin.

  Among the above-mentioned soft resins, aliphatic polyester resins excluding polylactic acid resins are preferable. The aliphatic polyester resin excluding the polylactic acid resin is an aliphatic polyester mainly composed of an aliphatic dicarboxylic acid or a derivative thereof and an aliphatic polyhydric alcohol. Examples of the aliphatic dicarboxylic acid residue constituting the aliphatic polyester resin include residues derived from succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like. Examples of the aliphatic polyhydric alcohol residue include aliphatic diol residues derived from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like.

  The aliphatic dicarboxylic acid residue preferably used in the film of the present invention is a succinic acid residue or an adipic acid residue, and the aliphatic polyhydric alcohol residue is a 1,4-butanediol residue.

  Furthermore, the aliphatic dicarboxylic acid suitably used in the film of the present invention preferably has a melting point of 100 ° C. or higher and 170 ° C. or lower. By adjusting the melting point to the range, the aliphatic polyester can maintain a crystalline state even in the range of 60 ° C. to 100 ° C. in which the normal shrinkage is performed. As a result, it plays a role like a column at the time of shrinkage. As a result, it is possible to obtain even better shrinkage finish.

  The content of the aliphatic polyester resin excluding the polylactic acid is 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, and 30% by mass or less, preferably 25% by mass or less. More preferably, it is 20 mass% or less.

  Further, as the core-shell structure rubber, the following can be used more suitably.

  Of those having the core-shell structure, those having a silicone acrylic composite rubber are particularly preferably used. As a specific example, the core portion is made of a copolymer of a siloxane compound and a (meth) acrylic monomer, and the shell portion is made of a homopolymer or copolymer of a (meth) acrylic monomer. Is mentioned.

  Examples of the siloxane compound include dimethylsiloxane. Moreover, as a (meth) acrylic-type monomer used for a core part, butyl (meth) acrylate, 2-ethylhexyl acrylate, etc. are mentioned. Furthermore, examples of the (meth) acrylic monomer used for the shell part include methyl (meth) acrylate.

  The content of the core-shell structured rubber is 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, and 30% by mass or less, preferably 25% with respect to the total amount of the resin constituting the film. It is at most 20% by mass, more preferably at most 20% by mass.

  In the film of the present invention, a plasticizer may be further added as long as the effects of the present invention are not significantly impaired for the purpose of improving various properties of the impact resistance, transparency, molding processability and heat shrinkable film. Examples of the plasticizer include fatty acid ester plasticizers, phthalate ester plasticizers, trimellitic ester plasticizers, and the like.

  Specific examples of the fatty acid ester plasticizer include dibutyl adipate, diisobutyl adipate, diisononyl adipate, diisodecyl adipate, di (2-ethylhexyl) adipate, di (n-octyl) adipate, di (n-decyl) adipate, dibutyldipropyl Examples include glycol adipate, dibutyl sebacate, di (2-ethylhexyl) sebacate, di (n-hexyl) azelate, di (2-ethylhexyl) azelate, di (2-ethylhexyl) dodecanedionate and the like.

  Specific examples of the phthalate ester plasticizer include diisononyl phthalate, diisodecyl phthalate, and di (2-ethylhexyl) phthalate. Further, specific examples of the trimellitic acid ester plasticizer include tri (2-ethylhexyl) trimellitate.

<Film production method>
The film of this invention can be manufactured by a well-known method using the said mixed resin. 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. In the case of printing, annealing, cooling, and printing, a corona discharge treatment is performed on the surface, and the film is obtained by winding with a winder. Moreover, the method of cutting open the film manufactured by the tubular method and making it planar is also mentioned.

  The stretching ratio in the stretching is such that the longitudinal direction is 2 to 10 times, the transverse direction is 2 to 10 times, and preferably 3 to 6 times in the longitudinal direction, for applications such as overlapping and shrinking in two directions. Hereinafter, 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 3 to 7 times, more preferably 3 to 5 times. The direction perpendicular thereto is 1 or more and 2 or less (1 time indicates that the film is not stretched), preferably 1.01 or more and 1.5 or less, and substantially uniaxially stretched. It is desirable to select a magnification ratio in the category of. 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.

  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.

  In addition, 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. .

<Film structure>
The layer structure of the film of the present invention may be a single layer, or as a laminated structure for the purpose of imparting surface functional properties such as slipperiness, heat resistance, solvent resistance, and easy adhesion to the film surface. Also good. That is, it may be a laminate having at least one mixed resin layer. For example, as shown to FIG. 1 (A), the film which consists of a single layer of the layer (I) which consists of mixed resin of this invention may be sufficient. Moreover, as shown to FIG. 1 (B), the film provided with the layer structure which laminated | stacked layer (II) from which a resin composition or an additive differs on layer (I) which consists of mixed resin of this invention may be sufficient. Further, as shown in FIGS. 2A, 2B, and 2C, layers (I) and (III) having different resin compositions or additives are added to the layer (I) made of the mixed resin of the present invention. )
(II) / (I) / (II),
(II) / (I) / (III),
(II) / (I) / (III) / (II)
Examples of films having a layer structure such as Moreover, the lamination ratio of each layer can be suitably adjusted according to a use and the objective.

  In the film of the present invention, the preferred layer structure is when the layer (II) is a layer containing a polylactic acid resin as a main component. In particular, the D / L ratio of the polylactic acid resin constituting the layer (II) is preferably different from the D / L ratio constituting the layer (I). By adjusting the D / L ratio and changing the crystallinity in the layer (I) and the layer (II), better shrink finish can be realized.

  Examples of the method for forming the laminate include a co-extrusion method, a method of forming a film of each layer, and then superposing and heat-sealing, a method of bonding with an adhesive, and the like.

  The total thickness of the film of the present invention is not particularly limited, whether it is a single layer or a laminate, but it is preferably thinner from the viewpoint of transparency, shrinkage workability, raw material cost, and the like. Specifically, the total thickness of the stretched film is preferably 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.

<Physical and mechanical properties>
(Shrinkage factor)
In the film of the present invention, it is important that the thermal shrinkage rate in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is 20% or more, 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. At present, the shrinking machine most industrially used for labeling of plastic bottles is generally called “steam shrinker” using 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 thermal shrinkage rate in the main shrinkage direction of the film when immersed in warm water at 80 ° C. for 10 seconds is 20% or more, the film is sufficiently adhered to the coated object within the shrinkage processing time. It is preferable because it can produce a good shrink-finished appearance without spots, wrinkles and avatars. From this, the film of the present invention preferably has a heat shrinkage at 80 ° C. of 20% or more and 70% or less.

  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.

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

  In addition, although the upper limit of said heat shrinkage is not described, since heat shrinkage does not become shorter than the length of the film before extending | stretching, the upper limit of heat shrinkage is a shrinkage rate used as the film length before extending | stretching. .

(transparency)
Regarding the transparency of the film of the present invention, when a film having a thickness of 50 μm is measured according to JIS K7105, the haze value is preferably 20% or less, more preferably 15% or less, and more preferably 10% or less. Is more preferable, and it is still more preferable that it is 7% or less. When the haze value is 20% 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 can be evaluated by the tensile elongation at break. In the tensile test at an atmospheric temperature of 0 ° C., the tensile elongation at break is 100% or more, preferably 150% or more, more preferably 200% or more in the film take-off (flow) direction (MD), particularly for label applications. is there. A tensile elongation at break of 100% or more at an atmospheric temperature of 0 ° C. is preferable because it is difficult to cause problems such as film breakage during printing and bag making processes. 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, and if too much elongation is applied, the rigidity of the film tends to decrease.

<Molded products, heat-shrinkable labels, containers>
The film of the present invention can be processed from a flat shape to a cylindrical shape or the like according to an object to be packaged and used 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 it to the required width while the print side is inside. The center seal (the shape of the seal portion is a so-called envelope) may be folded into a cylindrical shape. As the center sealing method, an organic solvent bonding method, a heat sealing method, an adhesive method, and an impulse sealer method can be considered. Among these, from the viewpoint of productivity and appearance, an adhesion method using an organic solvent is preferably used.

  In addition, the film of the present invention is excellent in heat shrink characteristics, shrink finish, transparency and the like of the film, so its use is not particularly limited. By laminating and forming functional layers, 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.

  Further, particularly when the film of the present invention is used as a heat-shrinkable label for food containers (for example, PET bottles, glass bottles, preferably PET bottles for soft drinks or foods), a cylindrical shape with a complicated shape (for example, a constricted center) , Square prisms, pentagonal columns, hexagonal columns, etc.) can be adhered to the shape, and a container with a beautiful label without wrinkles or avatars can be obtained. The molded article and container of the present invention can be produced by using a normal molding method.

  In addition, since the film of the present invention has excellent low temperature shrinkage and shrinkage finish properties, in addition to the heat shrinkable label material of a plastic molded product that is deformed when heated to a high temperature, it has a coefficient of thermal expansion and water absorption. Material 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 be suitably used as a heat-shrinkable label material for a plastic package (container) using at least one selected from polyester-based resins and polyamide-based resins as constituent materials.

  As the material constituting the plastic package, in addition to the above resins, polystyrene, rubber-modified impact-resistant polystyrene (HIPS), styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer Polymer, acrylonitrile-butadiene-styrene copolymer (ABS), (meth) acrylic acid-butadiene-styrene copolymer (MBS), polyvinyl chloride resin, phenol resin, urea resin, melamine resin, epoxy resin, A saturated polyester resin, a silicone resin, etc. can be mentioned. These plastic packages may be a mixture of two or more resins or a laminate.

  The present invention will be described below with reference to examples.

  In addition, the 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 “lateral” 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) Tensile elongation at break The obtained film was cut into a size of 110 mm in the direction perpendicular to the main shrinkage direction (longitudinal direction) and 15 mm in the main shrinkage direction, in accordance with JIS K6732, at a pulling rate of 100 mm / min. The tensile elongation in the direction (longitudinal direction) perpendicular to the main shrinkage direction of the film at an atmospheric temperature of 0 ° C. was measured, and the average value of ten measurements was shown in Table 1.

(3) Haze value The haze value indicating the transparency of the film was measured in accordance with JIS K7105.

(4) Storage elastic modulus (E ')
The obtained film was accurately cut into a size of 4 mm wide × 60 mm long to prepare a sample. Using a viscoelastic spectrometer DVA-200 (produced by IT Measurement Co., Ltd.), the measurement temperature was 10 Hz, the strain was 0.1%, the heating rate was 2 ° C./min, and the chuck was 2.5 cm. The dynamic viscoelasticity was measured in the longitudinal direction in the range of −150 ° C. to 150 ° C. The storage elastic modulus (E ′) at 20 ° C. and 70 ° C. is shown in Table 1 as the storage elastic modulus (E ′).

Moreover, the raw material used by each Example and the comparative example is as follows.
(Polylactic acid resin)
-Polylactic acid-based resin: manufactured by Nature Works LLC, trade name: NatureWorks 4050, L-form / D-form weight = 95/5, hereinafter abbreviated as “NW4050”.

(Soft acrylic resin)
Soft acrylic resin: Kuraray Co., Ltd., trade name: LA2250, methylmethacrylate-n-butyl acrylate block copolymer (= 30/70), hereinafter abbreviated as “LA2250”.

(Hard acrylic resin)
Acrylic resin: manufactured by Mitsubishi Rayon Co., Ltd. Trade name: Acrypet VH01, methyl methacrylate resin), hereinafter abbreviated as “VH01”.
-Acrylic resin: manufactured by Sumitomo Chemical Co., Ltd. Trade name: Sumipex FA, methyl methacrylate-n-butyl acrylate random copolymerization (= 60/40), hereinafter abbreviated as "FA".

(Polypropylene resin)
Polyolefin resin: manufactured by Nippon Polypropylene Co., Ltd., trade name: Novatec FY6H, polypropylene polymer, hereinafter abbreviated as “FY6H”.

(Polyethylene resin)
Polyethylene resin: manufactured by Nippon Polyethylene Co., Ltd., trade name: Kernel KF271, polyethylene polymer, hereinafter abbreviated as “KF271”.

(Aliphatic polyester)
Aliphatic polyester: manufactured by Mitsubishi Chemical Corp. Product name: GS-Pla AZ91T (polybutylene succinate) Hereinafter, abbreviated as “GS-Pla”.

(Examples 1 and 2, Comparative Examples 1 to 5)
A mixed resin obtained by mixing a polylactic acid resin, a soft acrylic resin, and other resins and additives shown in Table 1 is put into a twin-screw extruder (manufactured by Mitsubishi Heavy Industries, Ltd.), and a set temperature of 200 ° C. After being melt-mixed and extruded from a die having a set temperature of 200 ° C., it was taken up with a cast roll at 50 ° C. and cooled and solidified to obtain an unstretched sheet. 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 Kyoto Machine Co., Ltd.). A heat-shrinkable film was obtained. Table 1 shows the evaluation results of the obtained film.

  As shown in Table 1, the heat-shrinkable films (Examples 1 and 2) defined in the present invention were excellent in the evaluation results of each performance (both tensile rupture elongation and transparency were compatible). On the other hand, the film of Comparative Examples 1-5 which consists only of a layer which does not contain a soft acrylic resin has not been able to achieve both tensile elongation at break and transparency.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. However, the present invention can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification, and heat-shrinkable films accompanying such changes are also included in the technical scope of the present invention. Must be understood as

It is sectional drawing which shows schematically the aspect of the layer structure of the heat-shrinkable film of this invention. It is sectional drawing which shows schematically the other aspect of the layer structure of the heat-shrinkable film of this invention.

Explanation of symbols

(I) Layer composed of the mixed resin of the present invention (II) Layer different in resin composition or additive from the layer composed of the mixed resin of the present invention (III) Resin composition or additive different from the layer composed of the mixed resin of the present invention Different layers of

Claims (9)

Contains polylactic acid resin and soft acrylic resin as main components,
It consists of a mixed resin in which the mass ratio of the polylactic acid resin and the soft acrylic resin is 95/5 to 50/50, or has at least one mixed resin layer,
The polylactic acid resin comprises a copolymer of D-lactic acid and L-lactic acid, or a mixed resin of this copolymer,
The soft acrylic resin has a storage elastic modulus (E ′) at 20 ° C. of 0.1 MPa to 100 MPa when measured at a vibration frequency of 10 Hz,
A heat-shrinkable film having a heat shrinkage ratio of 20% or more in the main shrinkage direction when stretched in at least one direction and immersed in warm water at 80 ° C. for 10 seconds. The heat-shrinkable film according to claim 1, wherein the D / L ratio of the D-lactic acid and the L-lactic acid is 3/97 to 15/85, or 85/15 to 97/3. (Meth) acrylic acid ester in which the soft acrylic resin has a chemical structure different from that of at least one polymer block (A) composed of acrylic acid ester (a) and the acrylic acid ester (a) The heat-shrinkable film according to claim 1 or 2, comprising at least one polymer block (B) composed of (b-1). The acrylic ester (a) and (meth) acrylic ester (b-1) are selected from the group consisting of methyl methacrylate, ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. The heat-shrinkable film according to claim 3, which is at least one kind. The heat-shrinkable film according to claim 1, wherein the storage elastic modulus (E ′) at 70 ° C. when measured at a vibration frequency of 10 Hz of the soft acrylic resin is 0.1 MPa or more and 50 MPa or less. The heat-shrinkable film according to any one of claims 1 to 5, wherein a tensile breaking elongation in a direction orthogonal to a main shrinkage direction when measured at an atmospheric temperature of 0 ° C and a tensile speed of 100 mm / min is 100% or more. . A molded article using the heat-shrinkable film according to any one of claims 1 to 6 as a base material. The heat-shrinkable label which used the heat-shrinkable film in any one of Claims 1-6 as a base material. A container equipped with the molded product according to claim 7 or the heat-shrinkable label according to claim 8.

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