JP2008023801A - Heat-shrinkable laminate film, molding and label using the film and container equipped with the molding and label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable laminate film which uses a plant-originated resin, has excellent low-temperature shrinkability, flexibility, stiffness at ordinary temperature, and shrinkage-finishing properties and a small natural shrinkage and is suitable for shrinkage packaging, shrinkage bundling packaging and shrinkage labels, a molding and a heat-shrinkable label, and a container using the molding or the label. <P>SOLUTION: The heat-shrinkable laminate film is formed by drawing, in at least one direction, a laminate film composed of at least two layers of a layer (I) based on a resin of a refractive index of 1.40-1.55 and a layer (II) based on at least one polylactic acid type resin. The laminate film has a shrinkage in the main shrinkage direction of ≥30% and a shrinkage in the direction perpendicular to the main shrinkage direction of ≤10% when immersed in 80°C warm water for 10 seconds. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable laminated film using a plant-derived resin, and is particularly excellent in transparency, low-temperature shrinkability, waist strength (rigidity at room temperature), and shrink finish, and has a natural shrinkage rate. The present invention relates to a heat shrinkable laminated film suitable for small shrink wrapping, shrink tying wrapping, shrinkage labels, and the like, and a molded article using the film, a heat shrinkable label, and the molded article or a container equipped with the label.

  Currently, soft drinks such as juice and alcoholic drinks such as beer are sold in a state of being filled in containers such as bottles and plastic bottles. At that time, a heat-shrinkable label printed on the outside of the container is often attached for the purpose of differentiating from other products, improving the visibility of the products, and increasing the product value.

  In the above-mentioned fields, for use in labeling PET bottles and the like for which demand is expected to increase, there is a demand for a heat-shrinkable film having a high shrink-finished appearance at a relatively short time and at a low temperature and having a small natural shrinkage rate. The reason for this is the need for low temperatures in the labeling process of shrink films that are installed in recent PET bottles. That is, at present, the method of shrinking and labeling the heat-shrinkable film using steam shrinker has become the mainstream, but in order to avoid aseptic filling and quality deterioration due to temperature rise of the contents, the shrinking process can be performed as much as possible. It is desirable to carry out at a low temperature. For this reason, the current shrink film industry is developing heat-shrinkable films that start shrinking at the lowest possible temperature in the steam shrinker during labeling and that have excellent shrink finish characteristics after passing through the steam shrinker. It has been broken.

  As a material for the heat-shrinkable label, for example, polyethylene terephthalate (hereinafter sometimes abbreviated as “PET”) resin or polystyrene (hereinafter abbreviated as “PS”) resin is used. Yes. A stretched film formed of these resins has high transparency, gloss, rigidity, and excellent low-temperature shrinkage characteristics, and therefore can be suitably used as a heat-shrinkable film.

On the other hand, since the PET-based resin and the PS-based resin are both petroleum-derived resins, there is an actual situation that substitute resins for petroleum-derived resins are required due to problems related to the depletion of petroleum. On the other hand, due to the recent problem of CO ² gas emission regulations, it has been pointed out that it is necessary to develop a label using raw materials that are environmentally friendly.

Under such circumstances, a polylactic acid (hereinafter sometimes abbreviated as “PLA”) resin is known as an example of a substitute resin for petroleum-derived resins. This PLA resin is a plant-derived resin that uses lactic acid obtained by fermentation of starch as a raw material, and is characterized in that it can be mass-produced by chemical engineering and is excellent in transparency, rigidity, and the like. Furthermore, because it is a plant-derived raw material, it can not only save fossil resources but also suppress carbon dioxide emissions, and is attracting attention as an environmentally friendly resin.

  However, although the PLA heat-shrinkable film is excellent in rigidity and transparency, it has a drawback that it is very brittle, and shows a sharp shrinkage rate change with respect to the shrinkage temperature, so it is difficult to obtain uniform shrinkage, There was a problem in terms of shrink finish such as shrinkage unevenness.

  In order to improve the brittleness, a film in which various soft resins are mixed with a PLA resin has been proposed (see Patent Documents 1 to 3). However, since these films have a PLA resin as a matrix, it is difficult to obtain the heat shrink characteristics, shrink finish, stretchability, etc. necessary for the heat shrink film even if the purpose and effect are taken into consideration. .

  Moreover, the laminated film which combined PO type resin and PLA type resin has also been reported (refer patent document 4 and 5). However, since the viscosity average molecular weight of the PO resin used in the surface layer is as low as 1,000 to 7,000, the film described in Patent Document 4 sufficiently exhibits physical properties such as mechanical strength and heat resistance. Therefore, it was inappropriate as a heat shrinkable film. Moreover, since the film described in patent document 5 has an outer layer containing 35-80 mass% of fillers, the film after extending | stretching did not have transparency and was inferior to mechanical strength. Furthermore, since the film described in Patent Document 5 has many fine holes on the surface, it is inferior in printability, slipperiness, etc., and is difficult to use as a label.

Further, there is exemplified a shrinkable sheet having a layer mainly composed of a polyolefin resin and a layer mainly composed of polylactic acid (see Patent Document 6). However, this sheet is an attempt to form a shrinkable sheet by the inflation method for the purpose of producing shrink-wrapping films such as lunch boxes and side dishes sold at convenience stores. When used as a label for use, sufficient low temperature shrinkage characteristics could not be obtained.
JP 2005-068232 A JP 05-179110 A JP 09-316310 A JP 2003-276144 A JP 2002-347184 A JP 2002-019053 A

  This invention is made | formed in view of the said subject, The subject of this invention was using the plant-derived resin, and was excellent in low-temperature shrinkage | contraction property, waist strength (rigidity in normal temperature), and shrink-finishing property. Heat shrinkable laminated film suitable for uses such as shrink wrapping, shrink-bound wrapping and shrink labels, and a molded article using the film, a heat-shrinkable label, and the molded article or It is to provide a container equipped with a heat-shrinkable label.

  As a result of intensive studies on the compositions of the front and back layers and the intermediate layer, and further the adhesive layer forming the laminated film, the inventor succeeded in obtaining a laminated film that can solve the above-mentioned problems of the prior art. It came to be completed.

That is, an object of the present invention is a heat-shrinkable laminated film obtained by stretching a laminated film consisting of at least two layers of the following (I) layer and (II) layer in at least one direction. As a component, the shrinkage rate in the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is 30% or more, and the shrinkage rate in the direction perpendicular to the main shrinkage direction is 10% or less. The heat-shrinkable laminated film (hereinafter also referred to as “the film of the present invention”) solves this problem.
(I) Layer: resin having a refractive index of 1.40 to 1.55 (II) Layer: at least one polylactic acid resin

  The film of the present invention preferably has the (I) layer as an intermediate layer and (II) the front and back layers.

  In the film of the present invention, the polylactic acid resin is preferably a resin made of a copolymer of D-lactic acid and L-lactic acid.

  In the film of the present invention, the resin constituting the (I) layer is preferably a polyolefin resin.

  In the film of the present invention, the polyolefin resin is preferably a polyethylene resin, a polypropylene resin, or a mixture thereof.

  In the film of the present invention, the thickness ratio of the (II) layer to the thickness of the entire film is preferably 10% or more and 70% or less.

  The film of the present invention may have at least one (III) layer composed mainly of an adhesive resin between the (I) layer and the (II) layer.

  Another object of the present invention is achieved by a molded article using the heat-shrinkable laminated film of the present invention as a substrate, a heat-shrinkable label, and a container equipped with the molded article or the heat-shrinkable label ( Hereinafter, they are also referred to as “molded article of the present invention”, “label of the present invention” and “container of the present invention” in this order)

  The film of the present invention has the (II) layer mainly composed of a PLA resin and the (I) layer mainly composed of a resin having a refractive index of 1.40 to 1.55. According to this, it is a film with excellent transparency, and excellent low-temperature shrinkage, low back strength (rigidity at room temperature), which has not been obtained with conventional heat-shrinkable films composed of PLA resins alone, A heat-shrinkable laminated film suitable for applications such as shrink wrapping, shrink-bound wrapping, and shrinkage labels, which has shrink finish and has a low natural shrinkage rate, can be obtained. In the present invention, since a plant-derived PLA resin is used, the film of the present invention is suitable for promoting the utilization of biomass and aiming for a recycling society.

  In addition, since the film of the present invention is used for the molded product and label of the present invention, according to the present invention, the molded product has excellent transparency and good shrinkage and shrinkage finish, and heat shrinkage. Sex labels can be provided. Furthermore, since the container of the present invention is equipped with the molded product or the heat-shrinkable label, according to the present invention, a container having a good appearance can be provided.

  Hereinafter, the heat-shrinkable laminated film of the present invention, a molded product, a heat-shrinkable label, and a container equipped with the molded product or the heat-shrinkable label will be described in detail.

  In the present specification, “main component” is intended to allow other components to be included as long as the action and effect of the resin constituting each layer is not hindered. Further, the term does not limit the specific content, but it is in the range of 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more and 100% by mass or less, based on the total components of each layer. Is a component occupying.

  Further, in this specification, the “main shrinkage direction” means a direction in which the thermal shrinkage rate is large between the longitudinal direction (longitudinal direction) of the film and the lateral direction (width direction) of the film. Means a direction corresponding to the outer circumferential direction, and “orthogonal direction” means a direction perpendicular to the main contraction direction.

[Heat-shrinkable laminated film]
The first aspect of the film of the present invention comprises a (I) layer composed mainly of a resin having a refractive index of 1.40 to 1.55, and a PLA resin as a major component (II ) Layer is a heat-shrinkable laminated film formed by stretching a laminated film composed of at least two layers in at least one direction.

<(I) layer>
In the film of the present invention, the layer (I) is a layer mainly composed of a resin having a refractive index of 1.40 to 1.55. The resin having a refractive index of 1.40 or more and 1.55 or less that can be used in the (I) layer of the present invention may have a refractive index in this range, preferably 1.46 or more and 1.52 or less. More preferably, it is 1.46 or more and 1.51 or less. If the refractive index of this resin is within this range, it is possible to maintain transparency when recycling the trimming loss of the film (hereinafter also referred to as “regeneration addition”).

  In the film of the present invention, any resin that satisfies the above refractive index can be used. Examples of resins having such a refractive index include polyolefin resins (refractive index of 1.46 to 1.55), polyamide resins (refractive index of around 1.53), aromatic hydrocarbons and conjugated diene carbonization. And a copolymer with hydrogen (refractive index: 1.53 to 1.55: depending on composition). Among these, polyolefin resins can be preferably used from the viewpoint of heat shrinkage and moldability. Each resin will be described below.

<Polyolefin resin (PO resin)>
The PO resin that can be used in the (I) layer of the film of the present invention is not particularly limited as long as it has a refractive index defined in the present invention. For example, polyethylene resin, polypropylene resin, ethylene- Examples thereof include ethylene-based copolymers such as vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer. From the viewpoint of heat shrinkage and moldability, it is preferable to use a polyethylene resin, a polypropylene resin, or a mixture thereof. Since there are various types of polyethylene resins and polypropylene resins depending on the polymerization method, copolymerization component, and the like, preferred types are shown below, but the range is not limited thereto.

The polyethylene resin usable in the present invention is a high density polyethylene resin (HDPE) having a density of 0.94 g / cm ³ or more and 0.97 g / cm ³ or less, and a density of 0.92 g / cm ³ or more and 0.94 g / cm ³ or less in density polyethylene resin (MDPE), density include 0.92 g / cm ³ less than the low-density polyethylene resin (LDPE) or linear low density polyethylene resin (LLDPE).

The polyethylene resin may be one of the above-mentioned high density, medium density, and low density, or a mixture of two or more. From the viewpoint of film stiffness (at room temperature), shrinkage characteristics, etc. its density is preferably 0.87 g / cm ³ or more 0.970 g / cm ³ or less in the range, 0.875 g / cm ³ or more 0.965 g / cm ³ or less in the range is more preferably, 0.88 g / cm ³ or more A range of 0.96 g / cm ³ or less is more preferable. If the density of the polyethylene resin is 0.87 g / cm ³ or more, the waist (rigidity at room temperature) and heat resistance of the entire film are not significantly lowered, which is preferable in practical use. On the other hand, if the density of the polyethylene resin is 0.97 g / cm ³ or less, the stretchability at a low temperature is maintained, and a heat shrinkage rate in a practical temperature range (about 70 ° C. or more and about 90 ° C. or less) can be sufficiently obtained. This is preferable.

  In the polyethylene resin, a linear low density polyethylene resin (LLDPE) is particularly preferably used from the viewpoints of stretchability, impact resistance of the film, transparency, and the like. Examples of LLDPE include a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, preferably 4 to 12 carbon atoms. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 3-methyl-1-butene, 4- Examples thereof include methyl-1-pentene. Of these, copolymers with 1-butene, 1-hexene and 1-octene are preferably used. Moreover, you may use the alpha olefin to copolymerize individually by 1 type or in combination of 2 or more types.

  The melt flow rate (MFR) of the polyethylene-based resin is not particularly limited. Usually, the MFR (JIS K7210, temperature: 190 ° C., load: 2.16 kg) is 0.5 g / 10 min or more and 15 g. / 10 min or less, and more preferably 1.0 g / 10 min or more and 10 g / 10 min or less. The MFR of the polyethylene resin is preferably selected to be similar to the viscosity at the time of melting the PLA resin in order to obtain a film having a uniform thickness.

  Next, when the PO resin is a polypropylene resin, examples of the polypropylene resin include homopropylene resin, random polypropylene resin, block polypropylene resin, ethylene-propylene rubber, ethylene-butene rubber, and ethylene diene rubber. In general, a polypropylene resin has high crystallinity, high strength, and good heat resistance. However, because of high crystallinity, a high temperature is required at the time of thermoforming. However, in the present invention, thermoformability is excellent even in a relatively low temperature range (I ) To form a layer, it is preferable to use a soft polypropylene resin having relatively low crystallinity.

  When the polypropylene resin is a propylene copolymer, the α-olefin copolymerized with propylene preferably includes those having 2 to 20 carbon atoms, more preferably 4 to 12 carbon atoms, such as ethylene, 1 Examples include -butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene. In the present invention, from the viewpoints of stretchability, heat shrinkage characteristics, impact resistance, transparency, rigidity, and the like of the film, random polypropylene having an ethylene unit content of 2% by mass to 10% by mass as the α-olefin is particularly preferable. Preferably used. Moreover, you may use the alpha olefin to copolymerize individually by 1 type or in combination of 2 or more types.

  Further, the melt flow rate (MFR) of the polypropylene resin is not particularly limited, but usually, MFR (JIS K7210, temperature: 230 ° C., load: 2.16 kg) is 0.5 g / 10 min. It is preferably 15 g / 10 min or less, and 1.0 g / 10 min or more and 10 g / 10 min or less is used. The MFR of polypropylene is preferably selected to be similar to the viscosity at the time of melting of the PLA resin in order to obtain a film having a uniform thickness.

  In the film of the present invention, a copolymer of the PO-based resin and a monomer that can be copolymerized can also be suitably used. Examples of the copolymer of a PO-based resin and a copolymerizable monomer include an ethylene / vinyl acetate copolymer, an ethylene / ethyl acrylate copolymer, and an ethylene / methyl acrylate copolymer.

  When ethylene-vinyl acetate copolymer is used as the PO-based resin, the content of ethylene monomer units in the ethylene-vinyl acetate copolymer is 50% by mass or more, preferably 60% by mass or more, and 95% by mass. Hereinafter, those having a mass of 85% by mass or less are preferably used. If the content rate of an ethylene monomer unit is 50 mass% or more, since the rigidity of the whole film can be maintained favorable, it is preferable. On the other hand, when the content of the ethylene monomer unit is 95% by mass or less, the waist (rigidity at room temperature) and heat resistance of the entire film are not significantly lowered, which is preferable in practice.

  The melt flow rate (MFR) of the ethylene-vinyl acetate copolymer is not particularly limited, but usually MFR (JIS K7210, temperature: 190 ° C., load: 2.16 kg) is 0.5 g / It is preferably 10 minutes or more and 15 g / 10 minutes or less, and more preferably 1.0 g / 10 minutes or more and 10 g / 10 minutes or less. The MFR of the ethylene-vinyl acetate copolymer is preferably selected to be similar to the viscosity at the time of melting of the PLA resin in order to obtain a film having a uniform thickness.

  The PO resin usable in the present invention has a weight average molecular weight of 50,000 or more, preferably 100,000 or more, 700,000 or less, preferably 600,000 or less, more preferably 500,000. Is preferred. If the weight average molecular weight of the PO-based resin is within the above range, practical physical properties such as desired mechanical properties and heat resistance can be expressed, an appropriate melt viscosity can be obtained, and good moldability can be obtained.

  Furthermore, the film of the present invention can be added with an appropriate amount of hydrogenated petroleum resin or the like, if necessary, for the purpose of use such as adjusting the shrinkage ratio to the PO-based resin. In the present invention, hydrocarbon resins refer to petroleum resins, terpene resins, rosin resins, and the like. Examples of petroleum resins include cyclopentadiene or an alicyclic petroleum resin from a dimer thereof and an aromatic petroleum resin from a C9 component. Examples of the terpene resin include terpene resins and terpene-phenol resins from β-pinene. Examples of rosin resins include rosin resins such as gum rosin and wood rosin, and esterified rosin resins modified with glycerin, pentaerythritol, and the like. Hydrocarbon resins are known to exhibit relatively good compatibility when mixed with PO resins and the like, but it is preferable to use a hydrogenated derivative from the viewpoint of color tone, thermal stability, and compatibility. Particularly preferred are hydrogenated petroleum resins and partially hydrogenated petroleum resins.

  Representative examples of PO resins preferably used in the present invention include random polypropylene “Wintech” series manufactured by Nippon Polypro Co., Ltd., polyolefin soft resins “TPO” series manufactured by Idemitsu Kosan Co., Ltd., Ube A linear low density polyethylene “Umerit” series manufactured by Kosan Co., Ltd. can be listed as commercially available.

  Further, the resin constituting the (I) layer of the film of the present invention preferably has a storage elastic modulus (E ′) at 20 ° C. of 10 MPa or more and 2,000 MPa or less when measured at a vibration frequency of 10 Hz, and 50 MPa or more and 1 More preferably, it is 1,000,000 MPa or less. If the storage elastic modulus (E ′) is 2,000 MPa or less, the impact resistance of the laminated film is not lowered. If the storage elastic modulus (E ′) is 10 MPa or more, the rigidity of the laminated film is maintained. can do.

  Further, the resin constituting the (I) layer of the film of the present invention preferably has a storage elastic modulus (E ′) at 70 ° C. of 10 MPa or more and 1,000 MPa or less, as measured at a vibration frequency of 10 Hz, and 50 MPa or more and 700 MPa. More preferably, it is 70 MPa or more and 500 MPa or less. When the storage elastic modulus (E ′) at 70 ° C. is 1,000 MPa or less, the stretchability of the laminated film becomes good, and as a result, it becomes easy to ensure a sufficient shrinkage. On the other hand, when the storage elastic modulus at 70 ° C. is 10 MPa or more, it is possible to maintain the rigidity of the film at the time of shrinkage and to suppress the generation of wrinkles and collapse.

  Since the film of the present invention is a laminated film having a (II) layer containing a PLA resin as a main component, the storage elastic modulus (E ′) is drastically lowered when the glass transition temperature of PLA exceeds about 55 ° C. However, it becomes about 10 MPa or less near 70 ° C., and as a result, good shrinkage characteristics cannot be exhibited. Therefore, in the present invention, by adjusting the storage elastic modulus (E ′) of the resin constituting the (II) layer within the above range, the rigidity (waist) of the film at the time of contraction of the entire film is maintained. Thereby, if it is the film of this invention, generation | occurrence | production of a wrinkle, collapse, etc. can be suppressed.

<(II) layer>
In the present invention, the (II) layer is composed mainly of a PLA resin. In the present invention, in addition to the above-mentioned (I) layer, the (II) layer has a layer mainly composed of a PLA resin, so that it has superior low temperature shrinkage and superior rigidity as compared to a layer made of PET resin or PS resin. It can be applied to a heat-shrinkable film. In the present invention, since the (II) layer is composed of a composition mainly composed of a PLA resin, the heat shrinkage of the layer structure in which the (II) layer is a front and back layer and the (I) layer is an intermediate layer. If it is an adhesive film, good ink adhesion can be obtained at the time of printing, corona treatment after film formation can be omitted, and the production process can be simplified. In addition, by arranging the (II) layer mainly composed of PLA resin as the front and back layers, sealing with a solvent such as THF is good at the time of bag making, so the use of an adhesive at the time of sealing may be omitted. This can contribute to lower manufacturing costs.

  The type of PLA resin used in the (II) layer is not particularly limited, but a copolymer having a structural unit of L-lactic acid and D-lactic acid (poly (DL-lactic acid)) can be preferably used.

  The copolymer whose structural units are L-lactic acid and D-lactic acid has a copolymerization ratio of D-lactic acid and L-lactic acid of D-lactic acid / L-lactic acid = 99.5 / 0.5 to 85/15, Or D-lactic acid / L-lactic acid = 0.5 / 99.5 to 15/85, preferably D-lactic acid / L-lactic acid = 99/1 to 87/13 or D-lactic acid / L-lactic acid = 1/99 It is desirable to be ~ 13/87. If it is a PLA resin having such a copolymerization ratio, the crystallinity is too low, the heat resistance is inferior, and the problem that the films are fused does not occur.

  In the present invention, a plurality of lactic acid resins having different copolymerization ratios of L-lactic acid (hereinafter also referred to as L-form) and D-lactic acid (hereinafter also referred to as D-form) may be blended. In this case, it is preferable to blend such that the average value of the copolymerization ratios of the L-form and D-form of a plurality of lactic acid resins falls within the above range.

  The PLA resin can be polymerized by employing various known methods such as a condensation polymerization method and a ring-opening polymerization method. For example, in the condensation polymerization method, PLA resin having an arbitrary composition can be obtained by directly dehydrating condensation polymerization of L-lactic acid, D-lactic acid, or a mixture thereof. In addition, in the ring-opening polymerization method (lactide method), a PLA resin using a suitable catalyst, for example, tin octylate, etc., using lactide, which is a cyclic dimer of lactic acid, as necessary, using a polymerization regulator or the like. Can be obtained. Lactide includes L-lactide, which is a dimer of L-lactic acid, D-lactide, which is a dimer of D-lactic acid, and DL-lactide composed of L-lactic acid and D-lactic acid, which are necessary. The PLA resin having an arbitrary composition and crystallinity can be obtained by mixing and polymerizing according to the above.

  In the present invention, for the purpose of improving heat resistance, the range does not impair the essential properties of the PLA resin, that is, the PLA resin component may be contained in an amount of 90% by mass or more based on the entire (II) layer. Within such a range, from a group consisting of a non-aliphatic diol such as an α-hydroxycarboxylic acid other than lactic acid, a non-aliphatic dicarboxylic acid such as terephthalic acid, and an ethylene oxide adduct of bisphenol A as a small amount of a copolymer component. At least one selected can be used. For the purpose of increasing the molecular weight, a small amount of a chain extender such as a diisocyanate compound, an epoxy compound, or an acid anhydride can be used.

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

  Examples of the aliphatic diol include ethylene 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, and dodecanedioic acid.

  The weight average molecular weight of the PLA resin usable in the (II) layer is 50,000 or more, preferably 100,000 or more and 400,000 or less, preferably 300,000, more preferably 250,000. It is desirable to be. If the weight average molecular weight of the PLA resin is too small, practical physical properties such as mechanical properties and heat resistance are hardly expressed. If it is too large, the melt viscosity becomes too high and the molding processability may be inferior.

  Representative examples of the PLA resin preferably used in the present invention include the “Lacia” series manufactured by Mitsui Chemicals, Inc. and the “Nature Works” series manufactured by NatureWorks LLC. It is done.

  In the present invention, an aliphatic polyester resin or an aromatic polyester resin having a glass transition temperature (Tg) of 0 ° C. or less is used with respect to 100 parts by mass of the PLA resin in order to improve impact resistance and cold resistance. You may blend in the range below 70 mass parts. Examples of such aliphatic polyester resins include PLAs such as aliphatic polyesters obtained by condensing aliphatic diols and aliphatic dicarboxylic acids, aliphatic polyesters obtained by ring-opening polymerization of cyclic lactones, and synthetic aliphatic polyesters. Aliphatic polyester resin excluding the resin.

  Specifically, aliphatic polyester obtained by condensing aliphatic diol and aliphatic dicarboxylic acid is ethylene glycol, 1,4-butanediol, hexanediol, octanediol, cyclopentanediol, cyclohexanediol, 1,4 -Among aliphatic diols such as cyclohexanedimethanol, or anhydrides or derivatives thereof, and aliphatic dicarboxylic acids such as succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, or anhydrides or derivatives thereof. It can be obtained by selecting one or more of each from the above and performing condensation polymerization. At this time, if desired, a desired polymer can be obtained by jumping up with an isocyanate compound or the like. Moreover, in order to improve heat resistance and mechanical strength, you may copolymerize aromatic monomer components, such as 50 mol% or less of terephthalic acid, as a dicarboxylic acid component.

  Examples of biodegradable plastics containing such components include trade name “Easter Bio” (Eastman Chemicals) and trade name “Ecoflex” (BASF).

In addition, an aliphatic polyester obtained by ring-opening polymerization of cyclic lactones can be obtained by polymerizing by selecting one or more kinds of cyclic monomers from ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like. Can do. Furthermore, examples of the synthetic aliphatic polyester include copolymers of cyclic acid anhydrides such as succinic anhydride and oxiranes such as ethylene oxide and propylene oxide.

<(III) layer>
As a second aspect of the film of the present invention, there is exemplified an aspect in which an (III) layer made of an adhesive resin for the purpose of improving adhesiveness is disposed between the (I) layer and the (II) layer. can do.

  The adhesive resin that can be used in the (III) layer has both a portion having reactivity or affinity for the PLA resin in the (II) layer and a portion having affinity for the resin in the (I) layer. Resins are preferably used.

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

  In addition, the “part having affinity with the resin of the (I) layer” means that it has a chain having affinity with the resin component constituting the (I) layer, although it varies depending on the resin used. More specifically, it means having a linear or branched saturated hydrocarbon moiety as the main chain, block chain or graft chain.

  When the (I) layer is composed of a PO resin as a main component, specific examples include a PO resin or a resin obtained by hydrogenating a copolymer of a styrene hydrocarbon and a conjugated diene hydrocarbon, such as styrene. -Ethylene-butadiene copolymer, styrene-ethylene-propylene copolymer, styrene-ethylene-butylene copolymer and the like.

  As a specific product of a resin having a polar group that has high affinity or can react with the PLA resin and is compatible with the resin of the (I) layer, for example, GMA having an epoxy group Examples thereof include ethylene copolymer and ethylene terpolymer “Bond First” (Sumitomo Chemical) and modified styrene-ethylene-butadiene block copolymer “Tuftec” (Asahi Kasei).

It is also preferable to use at least one copolymer or resin selected from the group consisting of the following (a), (b), and (c) as the adhesive resin that can be used in the (III) layer.
(A) one unit selected from the group consisting of vinyl acetate, acrylic acid, (meth) acrylic acid, ethyl (meth) acrylate, methyl (meth) acrylic acid, maleic anhydride, and glycidyl methacrylate; and ethylene Copolymer comprising monomer units (hereinafter also referred to as “ethylene-based copolymer”)
(B) Copolymers of soft aromatic hydrocarbons and conjugated diene hydrocarbons or hydrogenated derivatives thereof
(C) Modified polyolefin resin

  First, the ethylene-based copolymer (a) will be described. The ethylene copolymer can also function as a compatibilizer in the (I) layer. For example, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene- (meth) acrylic acid copolymer. Polymer, ethylene- (meth) acrylic acid ethyl copolymer, ethylene-methyl (meth) acrylic acid copolymer, ethylene-vinyl acetate-maleic anhydride terpolymer, ethylene-ethyl acrylate-maleic anhydride Examples include terpolymers, ethylene-glycidyl methacrylate copolymers, ethylene-vinyl acetate-glycidyl methacrylate terpolymers, and ethylene-ethyl acrylate-glycidyl methacrylate terpolymers. Among them, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene-methyl (meth) acrylic acid copolymer are used. It can be suitably used.

  The ethylene copolymer has an ethylene monomer unit content of 50% by mass to 95% by mass, preferably 60% by mass to 85% by mass. If the content rate of an ethylene monomer unit is 50 mol% or more, since the rigidity of the whole film can be maintained favorable, it is preferable. On the other hand, if the content of the ethylene unit is 95% by mass or less, the flexibility can be sufficiently maintained, and when the stress is applied to the film, the buffer against the stress generated between the (I) layer and the (II) layer. Since the action works, delamination can be suppressed.

As the ethylene copolymer, those having an MFR (JIS .. K7210, temperature: 190 ° C., load: 2.16 kg) of 0.1 g / 10 min or more and 10 g / 10 min or less are suitably used. If the MFR is 0.1 g / 10 min or more, the extrudability can be maintained satisfactorily. On the other hand, if the MFR is 10 g / 10 min or less, the thickness unevenness of the laminated film and the mechanical strength are hardly lowered, which is preferable. .

The ethylene-based copolymer is an “ethylene-vinyl acetate-maleic anhydride terpolymer” as “Bondyne” (manufactured by Sumitomo Chemical Co., Ltd.), ethylene-glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl methacrylate tri “Bond First” (manufactured by Sumitomo Chemical Co., Ltd.) and the like are commercially available as an original copolymer, an ethylene-ethyl acrylate-glycidyl methacrylate terpolymer.

  Next, the copolymer (b) and the hydrogenated derivative thereof will be described. As the aromatic hydrocarbon constituting the copolymer of the soft aromatic hydrocarbon and the conjugated diene hydrocarbon, styrene is preferably used, and a styrene homologue such as α-methylstyrene may also be used. it can. Examples of conjugated diene hydrocarbons include 1,3-butadiene, 1,2-isoprene, 1,4-isoprene, 1,3-pentadiene, and the like, and these may be hydrogenated derivatives. These may be used alone or in admixture of two or more.

  In the copolymer of aromatic hydrocarbon and conjugated diene hydrocarbon or the hydrogenated derivative thereof, the content of aromatic hydrocarbon is 5% by mass or more, preferably 7% by mass or more of the total amount of the copolymer. More preferably, it is a soft copolymer of 10% by mass or more and 50% by mass or less, preferably 40% by mass or less, more preferably 35% by mass or less. When the aromatic hydrocarbon content is 5% by mass or more, when the film is regenerated and added to the layer (I), good compatibility can be obtained, and clouding of the film can be suppressed. On the other hand, if the content of the aromatic hydrocarbon is 50% by mass or less, the layer (I) and the layer (II) can be obtained when stress is applied to the film without reducing the flexibility of the layer (II). The delamination can be suppressed because a buffering action against the stress generated during the working is exerted.

  As the hydrogenated derivative of the copolymer of the aromatic hydrocarbon and the conjugated diene hydrocarbon, a hydrogenated derivative of a styrene-conjugated diene random copolymer can be preferably used. The detailed contents of the hydrogenated derivative of the styrene-conjugated diene random copolymer and the production method thereof are disclosed in JP-A-2-15843, JP-A-2-305814 and JP-A-3-72512. ing.

  As the aromatic hydrocarbon-conjugated diene hydrocarbon copolymer, each of the above-exemplified copolymers can be used alone or in admixture of two or more.

  Commercially available products of aromatic hydrocarbon-conjugated diene hydrocarbon copolymers include styrene-butadiene block copolymer elastomers under the trade name “Tufprene” (manufactured by Asahi Kasei), hydrogenation of styrene-butadiene block copolymers. Trade name “Tuftec H” (manufactured by Asahi Kasei) as a derivative, trade name “Clayton G” (manufactured by Kraton Japan), trade name “Dynalon” (manufactured by JSR) as a hydrogenated derivative of a styrene-butadiene random copolymer, Examples of the hydrogenated derivative of the styrene-isoprene block copolymer include a trade name “Septon” (Kuraray), and examples of the styrene-vinylisoprene block copolymer elastomer include a trade name “Hiblar” (manufactured by Kuraray).

  In addition, the copolymer of the aromatic hydrocarbon and the conjugated diene hydrocarbon or the hydrogenated derivative thereof is an interlayer between the (II) layer mainly composed of a polylactic acid resin by introducing a polar group. Adhesiveness can be further improved. Examples of polar groups to be introduced include acid anhydride groups, carboxylic acid groups, carboxylic acid ester groups, carboxylic acid chloride groups, carboxylic acid amide groups, carboxylic acid groups, sulfonic acid groups, sulfonic acid ester groups, and sulfonic acid chloride groups. Sulfonic acid amide group, sulfonic acid group, epoxy group, amino group, imide group, oxazoline group, hydroxyl group and the like. Typical examples of the copolymer of a styrene compound having a polar group and a conjugated diene or a hydrogenated derivative thereof include maleic anhydride-modified SEBS, maleic anhydride-modified SEPS, epoxy-modified SEBS, and epoxy-modified SEPS. These copolymers can be used alone or in admixture of two or more.

  Specifically, trade names “Tuftec M” (manufactured by Asahi Kasei Co., Ltd.), “Epofriend” (manufactured by Daicel Chemical Industries, Ltd.) and the like are commercially available.

  Next, the modified polyolefin resin (c) will be described. In the present invention, the modified polyolefin resin capable of constituting the layer (II) refers to a resin mainly composed of an unsaturated carboxylic acid or an anhydride thereof, or a polyolefin modified with a silane coupling agent. Examples of unsaturated carboxylic acids or anhydrides thereof include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, itaconic acid, itaconic anhydride or monoepoxy compounds of these derivatives and the above acids. Examples include ester compounds, reaction products of a polymer having a group capable of reacting with these acids in the molecule and an acid. These metal salts can also be used. Among these, maleic anhydride is more preferably used. Moreover, these copolymers can be used individually or in mixture of 2 or more types, respectively.

  Examples of the silane coupling agent include vinyltriethoxysilane, methacryloyloxytrimethoxysilane, and γ-methacryloyloxypropyltriacetyloxysilane.

  In order to produce the modified polyolefin resin, for example, these modified monomers can be copolymerized in the stage of polymerizing the polymer in advance, or these modified monomers can be graft copolymerized with the polymer once polymerized. For modification, these modified monomers are used alone or in combination, and those having a content in the range of 0.1% by mass or more and 5% by mass or less are preferably used. Of these, those that have been graft-modified are preferably used.

  Specifically, trade names “Admer” (Mitsui Chemicals), “Modic” (Mitsubishi Chemical) are commercially available.

  Further, in the present invention, if it is within the range that does not significantly impair the effects of the present invention, (I) layer, (II) for the purpose of improving and adjusting the molding processability, productivity and various physical properties of the heat shrinkable film. Each layer of layer (III) and inorganic particles such as silica, talc and kaolin, pigments such as titanium oxide and carbon black, flame retardants, weathering stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinks Additives such as agents, lubricants, nucleating agents, plasticizers and anti-aging agents can be added as appropriate.

  The film of the present invention is a film resin of the present invention (hereinafter referred to as “recycled resin”) recycled to at least one layer (preferably (I) layer) selected from the (I) layer, the (II) layer and the (III) layer. ")"). The content of the recycled resin is 50 parts by mass or less, preferably 40 parts by mass or less, and more preferably 30 parts by mass or less with respect to 100 parts by mass of the resin constituting the layer to be contained. If the content of the recycled resin is 50 parts by mass or less, good transparency of the film can be maintained even after the addition.

<Layer structure of film>
The film of the present invention comprises (I) a layer mainly composed of a resin having a refractive index of 1.40 or more and 1.55 or less, and at least one PLA resin as a main component (II). It is composed of at least two layers. Since the film of the present invention is a heat-shrinkable film composed of a resin having a refractive index adjusted to the range of the present invention and a PLA resin, the transparency at the time of return is higher than that of a film composed of a conventional SBS resin and PET resin. Can be secured.

  The film of the present invention only needs to have at least the above-mentioned two layers, and preferably has (I) layer as an intermediate layer, and (II) layer is laminated on both sides of (I) layer as front and back layers. It is a layer structure more than a layer. Here, “the (II) layer is laminated on both surfaces of the (I) layer” means that the (II) layer is laminated as the front and back layers adjacent to the (I) layer as the intermediate layer (first aspect) ) As well as a case where a third layer (for example, the (III) layer exemplified in the second embodiment) is provided between the (I) layer as the intermediate layer and the (II) layer as the front and back layers. The intermediate layer may include the same layer as the front and back layers.

  In the present invention, the laminated structure of the film is a three-layer structure comprising (II) layer / (I) layer / (II) layer, and a more preferable layer structure is (II) layer / (III) layer / (I). It has a five-layer structure consisting of layer / (III) layer / (I) layer. By adopting this layer structure, the object of the present invention is low temperature shrinkability, film waist (rigidity at room temperature), excellent shrink finish, and small natural shrinkage, and delamination of the film is suppressed, A heat-shrinkable laminated film suitable for uses such as shrink wrapping, shrink-bound wrapping and shrinkage labels can be obtained with good productivity and economy.

  Next, a film having a three-layer structure of (II) layer / (I) layer / (II) layer and (II) layer / (III) layer / (I) layer as examples of preferred embodiments of the present invention A film having a five-layer structure consisting of / (III) layer / (II) layer will be described.

  The thickness ratio of each layer may be set in consideration of the above-described effects, and is not particularly limited. The thickness ratio of the (II) layer to the total thickness of the film is 10% or more, preferably 15% or more, more preferably 20% or more, and 70% or less, preferably 50% or less, more preferably 45% or less, Most preferably, it can be 40% or less. The thickness ratio of the (I) layer to the total film thickness is 20% or more, preferably 25% or more, more preferably 30% or more, and 90% or less, preferably 85% or less, more preferably 80%. It is as follows.

  When the (III) layer is provided between the (I) layer and the (II) layer, the (III) layer is 0.5 μm or more, preferably 0.75 μm or more, more preferably 1 μm or more, from the function thereof. It is 6 μm or less, preferably 5 μm or less.

  When the thickness ratio of each layer is within the above range, the film has excellent low temperature shrinkage, low strength (rigidity at room temperature), excellent shrink finish, small natural shrinkage, and delamination of the film is suppressed. A heat-shrinkable laminated film suitable for applications such as packaging, shrink-bound packaging, and shrink labels can be obtained.

  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, more preferably 50 μm or less, and most preferably 40 μm or less. Further, the lower limit of the total thickness of the film is not particularly limited, but is preferably 10 μm or more in consideration of the handleability of the film.

<Physical properties>
(1) Thermal contraction rate
It is important that the film of the present invention has a thermal shrinkage rate of 30% or more in at least one direction and 10% or less in the orthogonal direction when heated in 80 ° C. warm water for 10 seconds. This heat shrinkage rate 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. For example, the shrinkage rate required for a heat-shrinkable film applied to shrinkage labels for PET bottles varies depending on the shape, but is generally about 20% to 70% in the main shrinkage direction.

  Further, the shrinkage processing machine that is most commonly used industrially for label mounting of PET bottles is generally called a steam shrinker that uses steam as a heating medium for shrinking. 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.

  In consideration of such industrial productivity, a film having a thermal shrinkage rate of 30% or more in the main shrinkage direction under the above conditions is preferable because it can sufficiently adhere to the object to be coated within the shrinkage processing time. From these facts, the heat shrinkage rate in the main shrinkage direction when heated in 80 ° C. warm water for 10 seconds is 30% or more, preferably 35% or more, more preferably 40% in at least one direction, usually the main shrinkage direction. Or more, 85% or less, preferably 75% or less, and more preferably 70% or less.

  When the film of the present invention is used as a heat-shrinkable label, the heat shrinkage rate in the orthogonal direction is important to be 10% or less when heated in 80 ° C. warm water for 10 seconds, and is 5% or less. It is preferable that it is 3% or less. If the film has a heat shrinkage rate of 10% or less in the orthogonal direction, the dimension itself in the direction orthogonal to the film main shrinkage direction after shrinkage is likely to be short, or the printed pattern or character distortion after shrinkage is likely to occur. In the case of a square bottle, troubles such as vertical sink are unlikely to occur, which is preferable.

(2) Natural shrinkage rate
The natural shrinkage rate of the film of the present invention is desirably as small as possible. Generally, the natural shrinkage rate of a heat-shrinkable film is, for example, a natural shrinkage rate of 30% or less after storage at 30 ° C. for 30 days, preferably It is desirable that it is 2.0% or less, more preferably 1.5% or less. If the natural shrinkage rate under the above conditions is 3.0%, even if the produced film is stored for a long period of time, it can be stably attached to a container or the like, and it is difficult to cause problems in practice.

(3) Transparency of film
The transparency of the film of the present invention is such that a film with a thickness of 50 μm is compliant with JIS K7105 in applications where transparency is required, for example, applications where the printed surface printed on the back surface of the film is visible from the surface. When measured, the haze value is preferably 15% or less, more preferably 10% or less, further preferably 7% or less, and still more preferably 5% or less. When the haze value is 15% or less, the transparency of the film can be obtained and a display effect can be obtained.

(4) Storage elastic modulus (E ')
In addition, the film of the present invention has a dynamic viscosity at a measurement temperature ranging from −150 ° C. to 150 ° C. under the conditions of a frequency of 10 Hz, a strain of 0.1%, a heating rate of 3 ° C./min, and a chuck spacing of 2.5 cm. When the elasticity measurement is performed, the storage elastic modulus (E ′) at a temperature of 20 ° C. is preferably in the range of 1,100 MPa to 3,000 MPa, more preferably in the range of 1,200 MPa to 2,500 MPa. is there. If the storage elastic modulus E ′ is 1,100 MPa or more, the waist as a whole film (rigidity at room temperature) can be increased, the film becomes too soft and easily deformed, and printing, bag making, etc. 2 When the film is stretched due to roll tension during the next processing, or when the film thickness is reduced, when the film made on a container such as a PET bottle is covered with a labeling machine, the film is slanted or the film is folded back. This is preferable because it is difficult for problems such as the yield to easily decrease. On the other hand, if the storage elastic modulus E ′ is within 3,000 MPa, the film is hard and hardly stretched, and it is easy to wrinkle during secondary processing. .

[Molded products, heat-shrinkable labels and containers]
The film of the present invention is excellent in low-temperature shrinkage, shrinkage finish, transparency, natural shrinkage, etc. of the film, so its use is not particularly limited. By forming a functional layer, it can be used as various molded products such as bottles (blow bottles), trays, lunch boxes, prepared food containers, dairy products containers and the like. In particular, when the film of the present invention is used as a heat-shrinkable label for food containers (for example, PET bottles, glass bottles, preferably PET bottles for soft drinks or foods), a complicated shape (for example, a cylinder with a narrow center, corners, etc.) A rectangular column, pentagonal column, hexagonal column, etc.) can be adhered to the shape, and a container with a beautiful label without wrinkles or avatars can be obtained. The molded article and container of the present invention can be produced by using a normal molding method.

  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, the coefficient of thermal expansion, water absorption, etc. The material is very different from the heat shrinkable film, such as metal, porcelain, glass, paper, polyethylene, polypropylene, polybutene and other polyolefin resins, polymethacrylate resin, polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate, etc. It can be suitably used as a heat-shrinkable label material for a package (container) using at least one selected from polyester-based resins and polyamide-based resins as a constituent material.

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

Hereinafter, the present invention will be described in more detail 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, and the perpendicular direction thereof is described as the “lateral” direction.

(1) 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 3 ° 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. In addition, as a storage elastic modulus, the storage elastic modulus in 20 degreeC was shown.

(2) Thermal contraction rate
The obtained film was cut into a size of 100 mm in length and 100 mm in width, and immersed in a hot water bath at 70 ° C. and 80 ° C. for 10 seconds, and the amount of shrinkage was measured. For the thermal shrinkage, the ratio of shrinkage to the original size before shrinkage was expressed in% in the vertical and horizontal directions.

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

(4) Haze value
In accordance with JIS K7105, the haze value of the film was measured at a film thickness of 50 μm, and 15% or more was evaluated as x, 5% or more and less than 15% as ◯, and less than 5% as ◎.

(5) Interlayer adhesion strength
The obtained film was cut into a size of 100 mm in length and 298 mm in width, and 10 mm on both ends of the film in the horizontal direction were laminated and adhered with a tetrohydrofuran (THF) solvent to produce a cylindrical film. This cylindrical film was attached to a cylindrical PET bottle having a capacity of 1.5 liters, and 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. . The tunnel ambient temperature in each zone was controlled in the range of 70 ° C. to 85 ° C. by adjusting the amount of steam with a steam valve. The state of the film at the time of bottle mounting was confirmed visually and evaluated according to the following criteria.
A: There is no delamination even after the bottle is mounted.
○: Slight delamination occurs at the seal when the bottle is installed.
X: When the bottle is mounted, delamination occurs on the entire seal portion.

(6) Shrinkage finish
A film printed with a grid of 10 mm intervals was cut into a size of 100 mm long × 298 mm wide, and 10 mm in both sides in the horizontal direction were stacked and adhered with a tetrohydrofuran (THF) solvent to produce a cylindrical film. This cylindrical film was attached to a cylindrical PET bottle having a capacity of 1.5 liters, and 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. . The atmospheric temperature in the tunnel in each zone was controlled in the range from 70 ° C to 85 ° C by adjusting the amount of steam with a steam valve. After film coating, the following criteria were evaluated.
A: Shrinkage is sufficient, and wrinkles, avatars and lattice distortion do not occur.
○: Shrinkage is sufficient, but wrinkles, avatars, or lattice distortions occur in some places.
X: Shrinkage is sufficient, but wrinkles, avatars, and lattice distortions are remarkable. Or shrinkage | contraction is not enough and the coating to a bottle is inadequate.

(Example 1)
As shown in Table 1, “Nature Works 4060 (L-body / D-body ratio = 88/12)” (hereinafter abbreviated as “PLA1”) manufactured by NatureWorks LLC as a PLA resin used in the (II) layer. As a PO resin used in the (I) layer, 50% by mass of random PP “Wintech WFX4T: refractive index 1.4971 (hereinafter abbreviated as“ PO1 ”) manufactured by Nippon Polypro Co., Ltd. and Ube Industries, Ltd. ) Made of linear low density polyethylene “Umerit 0540F: 50% by mass of refractive index 1.5025 (hereinafter abbreviated as“ PO3 ”). Each resin was put into a separate single screw extruder manufactured by Mitsubishi Heavy Industries, Ltd., melted and mixed at a set temperature of 200 ° C., and the thickness of each layer in the unstretched laminated sheet was (II) layer / (I) layer / (II ) Layer = 45 μm / 160 μm / 45 μm Co-extruded from a two-type three-layer die, taken up with a cast roll at 40 ° C., and cooled and solidified to obtain an unstretched laminated sheet having a width of 300 mm and a thickness of 250 μm. Next, the film was stretched 5.0 times in the transverse uniaxial direction at a preheating temperature of 105 ° C. and a stretching temperature of 75 ° C. using a film tenter manufactured by Kyoto Machine Co., Ltd., and then rapidly cooled with cold air to form a heat-shrinkable laminated film having a thickness of 50 μm. Obtained. The results of evaluating the obtained film are shown in Table 2.

(Example 2)
As shown in Table 1, as a PLA resin used in the (II) layer, 50 parts by mass of PLA1 and “Nature Works 4050 (L body / D body ratio = 95/5)” manufactured by NatureWorks LLC (hereinafter “ As a PO resin used in the (I) layer, PO1 is 50% by mass and soft polypropylene (refractive index: 1.4855, hereinafter abbreviated as “PO2”) is 50% by mass. A mixed resin composition was used, and a modified polyolefin “Admer SF731” (hereinafter abbreviated as “AD1”) manufactured by Mitsui Chemicals, Inc. was used as an adhesive resin used in the (III) layer. Each resin was put into a separate single screw extruder manufactured by Mitsubishi Heavy Industries, Ltd., melted and mixed at a set temperature of 200 ° C., and then the thickness of each layer was (II) layer / (III) layer / (I) layer / (III ) Layer / (II) layer = co-extruded from 3 types and 5 layers dies so as to be 40 μm / 10 μm / 150 μm / 10 μm / 40 μm, taken by a 40 ° C. cast roll, solidified by cooling, and unstretched with a width of 300 mm and a thickness of 250 μm A laminated sheet was obtained. Next, the film was stretched 5.0 times in the transverse uniaxial direction at a preheating temperature of 105 ° C. and a stretching temperature of 75 ° C. using a film tenter manufactured by Kyoto Machine Co., Ltd., and then rapidly cooled with cold air to form a heat-shrinkable laminated film having a thickness of 50 μm. Obtained. The results of evaluating the obtained film are shown in Table 2.

(Comparative Example 1)
As shown in Table 1, heat was applied in the same manner as in Example 1 except that an unstretched single layer sheet consisting of a single layer of (II) layer was prepared so as to have a thickness of 250 μm without providing (I) layer. A shrinkable film was obtained. The results of evaluating the obtained film are shown in Table 2.

(Comparative Example 2)
As shown in Table 1, heat was applied in the same manner as in Example 1 except that an unstretched single-layer sheet having a thickness of 250 μm composed of PO1: 80% by mass and PO3: 20% by mass was prepared without providing the (II) layer. A shrinkable film was obtained. The results of evaluating the obtained film are shown in Table 2.

From Tables 1 and 2, the films of Examples 1 and 2 constructed within the range specified by the present invention are low temperature shrinkage, low strength (storage elastic modulus of laminated film), natural shrinkage, rise of shrinkage, interlayer The adhesiveness and shrinkage finish were equal to or higher than those of Comparative Examples 1 and 2.
On the other hand, when (I) layer does not have a resin having a refractive index of 1.46 to 1.55, and (III) does not have a layer (Comparative Example 1), the shrinkage is extremely high at 70 ° C. In addition, when the PLA resin was not used as the (II) layer (Comparative Example 2), the waist strength, the heat shrinkage rate, and the natural shrinkage decreased.
Moreover, when the thickness of the (II) layer was thick (Reference Example 1), a high heat shrinkage rate was exhibited, and the shrinkage finishing property was slightly inferior to the films of Examples 1 and 2. On the other hand, when the thickness of the (II) layer was thin (Comparative Example 4), the natural shrinkage ratio was increased, and the waist strength and shrinkage finish were slightly inferior to those of the films of Examples 1 and 2.
From this, the film of the present invention is excellent in low-temperature shrinkage, low strength (rigidity at room temperature), shrinkage finish, natural shrinkage, and suppressed delamination of the film. It turns out that it is a heat-shrinkable laminated film suitable for uses, such as a heat-shrinkable label.

  Since the film of the present invention has excellent low temperature shrinkage, rigidity, shrinkage finish, and low natural shrinkage, it can be suitably used for molded products that require heat shrinkage, particularly shrink labels. Moreover, since the PLA resin used in the present invention is a plant-derived resin, it is suitable for promoting the utilization of biomass and aiming for a recycling society.

Claims (10)

A heat-shrinkable laminated film obtained by stretching a laminated film consisting of at least two layers of the following (I) layer and (II) layer in at least one direction, each layer comprising the following resin as a main component and having a temperature of 80 ° C. A heat-shrinkable laminated film having a shrinkage ratio in the main shrinkage direction of 30% or more when immersed in warm water for 10 seconds and a shrinkage ratio in a direction orthogonal to the main shrinkage direction is 10% or less.
(I) Layer: resin having a refractive index of 1.40 to 1.55 (II) Layer: at least one polylactic acid resin   The heat-shrinkable laminated film according to claim 1, comprising the (I) layer as an intermediate layer and the (II) layer as a front and back layer.   The heat-shrinkable laminated film according to claim 1 or 2, wherein the polylactic acid-based resin is a resin composed of a copolymer of D-lactic acid and L-lactic acid.   The heat-shrinkable laminated film according to any one of claims 1 to 3, wherein the resin constituting the (I) layer is a polyolefin resin.   The heat-shrinkable laminated film according to claim 4, wherein the polyolefin resin is a polyethylene resin, a polypropylene resin, or a mixture thereof.   The heat-shrinkable laminated film according to any one of claims 1 to 5, wherein the thickness ratio of the (II) layer to the thickness of the entire film is 10% or more and 70% or less.   The heat-shrinkable laminated film according to any one of claims 1 to 6, further comprising at least one (III) layer composed mainly of an adhesive resin between the (I) layer and the (II) layer. .   A molded article using the heat-shrinkable laminated film according to claim 1 as a base material.   The heat-shrinkable label using the heat-shrinkable laminated film in any one of Claims 1-7 as a base material.   A container equipped with the molded article according to claim 8 or the heat-shrinkable label according to claim 9.