JP4297911B2 - Heat-shrinkable laminated film, molded product using the film, heat-shrinkable label, and container - Google Patents

Description

  The present invention relates to a heat-shrinkable laminated film using a plant-derived resin, and in particular, a shrink-wrapping that is excellent in low-temperature shrinkability, waist strength (rigidity at room temperature), and shrink finish, and has a small natural shrinkage rate, The present invention relates to a heat-shrinkable laminated film suitable for applications such as shrink-bound packaging and shrinkage labels, molded articles using the film, heat-shrinkable labels, and containers.

  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 and improving the visibility of the products and increasing the product value.

  Among the above heat-shrinkable labels, labeling for PET bottles, for which demand is expected to increase, requires a heat-shrinkable film that has a high shrink-finished appearance at a relatively short time and low temperature and has a small natural shrinkage rate. Has been. 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 of this heat-shrinkable label, for example, polyethylene terephthalate resin or polystyrene resin is used. 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. In contrast, polyolefin (hereinafter sometimes abbreviated as “PO”) resins have relatively few problems with endocrine disrupting chemicals, which are combustion-generated gases and so-called environmental hormones, and the specific gravity is low, so the weight of garbage It is a material with desirable characteristics that leads to reduction of However, the heat-shrinkable film made of this PO-based resin does not have sufficient film rigidity and low-temperature shrinkability, and the shrinkage at the time of heat shrinkage is insufficient. Further, the film shrinks at a temperature slightly higher than room temperature, for example, in summer. However, there is a problem that it is likely to shrink slightly before actual use.

  On the other hand, since these resins are derived from petroleum, there is a current situation that substitute resins for petroleum-derived resins are required due to problems related to the depletion of petroleum.

  As an example of an alternative resin for a petroleum-derived resin, a polylactic acid (hereinafter sometimes abbreviated as “PLA”) resin is known. PLA resin is a plant-derived resin made from lactic acid obtained by fermentation of starch as a raw material, and can be mass-produced by chemical engineering and has excellent characteristics such as transparency and rigidity. For this reason, PLA resins are attracting attention in the field of film packaging materials and injection molding as an alternative material having both low-temperature shrinkage properties and excellent rigidity superior to polyethylene terephthalate resins and polystyrene resins.

  However, since the PLA heat-shrinkable film exhibits a sharp shrinkage rate change with respect to the shrinkage temperature, it is difficult to obtain uniform shrinkage, and there is a problem in terms of shrinkage finish such as shrinkage unevenness.

  On the other hand, a laminated film in which a PO resin and a PLA resin are combined has also been reported (see Patent Documents 1 and 2). 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 1 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 2 has an outer layer containing 35 to 80% by mass of a filler, the stretched film does not have transparency and is inferior in mechanical strength. Furthermore, since the film described in Patent Document 2 has many fine holes on the surface, it is inferior in printability, slipperiness, and the like, and is difficult to use as a label.

  Moreover, the shrink sheet | seat which has the layer which has a PO resin as a main component, and the layer which has a PLA resin as a main component is illustrated (refer patent document 3). However, since the sheet shown in Patent Document 3 is a sheet having a PO layer as an outer layer, it is difficult to seal when carrying out cylindrical seal bag making. Further, this sheet is a shrink sheet formed by an inflation method, and when used as a bottle label that requires low temperature and high shrinkage, there is a drawback that sufficient low temperature shrinkage characteristics cannot be obtained.

In addition, laminated films of PLA resin and PO resin or ethylene-vinyl acetate copolymer (EVA) are also exemplified (see Patent Documents 4 and 5). However, these inventions introduce EVA layers as the front and back layers of the film for the purpose of providing heat sealability, and the effects of the present invention (that is, shrink finish, transparency, solvent sealability, etc.) It was not obtained.
JP 2003-276144 A JP 2002-347184 A JP 2002-019053 A JP 2000-108202 A JP 2004-262029 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide excellent low-temperature shrinkability, waist strength (rigidity at room temperature), and shrink finish using a plant-derived resin. A heat-shrinkable laminated film suitable for applications such as shrink wrapping, shrink-bound wrapping and shrink labels, and having a small natural shrinkage rate, and a molded product using the film, a heat-shrinkable label, and the label Is to provide an open container.

  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 having an intermediate layer and at least three layers of front and back layers laminated on both sides of the intermediate layer, wherein the intermediate layer contains at least one PO-based resin. Heat shrinkage in the film main shrinkage direction when it is composed of a main component layer, the front and back layers are composed of at least one PLA resin as a main component, and heated in warm water at 80 ° C. for 10 seconds. rate is 30% or more, and heat-shrinkable laminated film direction of the heat shrinkage rate orthogonal to the film main shrinking direction when heated for 10 seconds in a 80 ° C. hot water, characterized in der Rukoto 10% or less Can be solved by.

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

  In the heat-shrinkable laminated film of the present invention, the front and back layers are each composed of a PLA resin layer, and the intermediate layer is composed of a PO resin layer. Therefore, according to the present invention, the heat shrink laminate film is composed of a PLA resin alone or a PO resin alone. Shrink packaging, shrink-bound packaging, shrink labels, etc. that have excellent low temperature shrinkability, low strength (rigidity at room temperature), shrink finish, and low natural shrinkage ratio, which could not be obtained with heat shrinkable film A heat-shrinkable laminated film suitable for the above use can be obtained. Moreover, since the PLA resin used in the present invention is a plant-derived resin, the heat-shrinkable laminated film of the present invention is suitable for promoting the use of biomass and aiming for a recycling society.

  In addition, since the heat-shrinkable laminated film of the present invention is used for the molded product and heat-shrinkable label of the present invention, according to the present invention, the molded product with good waist strength and shrinkage finish, heat-shrinkable A label 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, molded product, heat-shrinkable label of the present invention, and a container equipped with the molded product and the label (hereinafter referred to as “film of the present invention”, “molded product of the present invention”, “ The label and the container of the present invention 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, this term does not limit the specific content, but it is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass with respect to the total components of each layer. It is a component occupying at least 100% and at most 100% by mass.

[Heat-shrinkable laminated film]
The first aspect of the film of the present invention comprises at least three layers composed of an intermediate layer mainly composed of a PO-based resin and front and back layers mainly composed of a PLA-based resin formed on both surfaces of the intermediate layer. Have.

<Front and back layers>
In the film of the present invention, the front and back layers are composed of a composition containing a PLA resin as a main component. The film of the present invention has the following advantages because the front and back layers are composed of layers composed of a composition mainly composed of a PLA resin. First, low-temperature shrinkage and rigidity superior to heat-shrinkable films whose front and back layers are made of polyethylene terephthalate resin or polystyrene resin can be obtained. Secondly, since better ink adhesion can be obtained at the time of printing than a heat-shrinkable film whose front and back layers are made of a PO-based resin, corona treatment after film formation can be omitted, and the manufacturing process can be simplified. Thirdly, since the sealing with a solvent such as THF is good at the time of bag making, the use of an adhesive at the time of sealing can be omitted, which can contribute to a reduction in manufacturing cost.

  The type of PLA resin used in the film of the present invention is not particularly limited, but the structural unit is a copolymer of L-lactic acid and D-lactic acid (poly (DL-lactic acid)), and a copolymer of these copolymers. Mixtures can be suitably 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 the PLA resin has such a copolymerization ratio, the crystallinity becomes too low and the heat resistance is inferior, and there is no problem that the films are fused.

  In the film of the present invention, a plurality of PLA 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) are blended. Also good. 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 PLA 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 system can be obtained by using an appropriate catalyst such as tin octylate while using lactide, which is a cyclic dimer of lactic acid, with a polymerization regulator as necessary. A resin is 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 and the like, within a range that does not impair the essential properties of the PLA resin, a small amount of a copolymer component such as α-hydroxycarboxylic acid other than lactic acid, terephthalic acid, etc. At least one selected from the group consisting of aliphatic dicarboxylic acids such as non-aliphatic dicarboxylic acids and succinic acids, non-aliphatic diols such as ethylene oxide adducts of bisphenol A, and aliphatic diols such as ethylene glycol 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 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 = 90: 10 The range is preferably 10:90, more preferably 80:20 to 20:80, and even more preferably 30:70 to 70:30. If the copolymerization ratio is within the above range, a film having a good balance of physical properties such as rigidity, transparency and impact resistance can be obtained.

  The PLA-based resin used in the present invention has a lower limit value of weight average molecular weight of 50,000, preferably 100,000, and an upper limit value of 400,000, 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 PLA resins preferably used in the film of the present invention include commercially available “Lacia” manufactured by Mitsui Chemicals, Inc., “Nature Works” manufactured by NatureWorks LLC, and the like. As mentioned.

  In addition, the film of the present invention is made of an aliphatic polyester resin having a glass transition temperature (Tg) of 0 ° C. or less, an aromatic polyester resin, or the like in order to improve impact resistance or cold resistance. You may blend in the range below 70 mass parts with respect to a mass part. 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, a desired polymer can be obtained by adding an isocyanate compound or the like as necessary.

  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 PLA resins containing such components include trade name “Easter Bio” (manufactured by Eastman Chemicals) and trade name “Ecoflex” (manufactured by BASF).

  In addition, as an aliphatic polyester obtained by ring-opening polymerization of cyclic lactones, one or more kinds of cyclic monomers selected from ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like may be polymerized. The aliphatic polyester obtained by this is mentioned. Thus, what is obtained by ring-opening condensation of ε-caprolactone is commercially available, for example, “Cell Green” (manufactured by Daicel Chemical Industries).

  Examples of synthetic aliphatic polyesters include copolymers of cyclic acid anhydrides such as succinic anhydride and oxiranes such as ethylene oxide and propylene oxide.

  Furthermore, the copolymer of a PLA resin, diol, and dicarboxylic acid can also be used suitably for the film of this invention. Examples of the structure of this copolymer include a random copolymer, a block copolymer, and a graft copolymer, and any structure may be used. However, a block copolymer or a graft copolymer is preferable from the viewpoint of impact resistance and transparency of the film.

  Specific examples of a random copolymer of a PLA resin, a diol, and a dicarboxylic acid include, for example, “GS-Pla” (manufactured by Mitsubishi Chemical Corporation), and specific examples of a block copolymer or a graft copolymer. Is, for example, “Plamate” (manufactured by Dainippon Ink & Chemicals, Inc.).

<Intermediate layer>
In the film of the present invention, the intermediate layer is a layer made of a composition containing a PO resin as a main component.
The PO resin used in the film of the present invention is not particularly limited. Usable PO resins include polyethylene resins, polypropylene resins, and ethylene copolymers such as ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer. It is done. Especially, it is preferable to use a polyethylene-type resin, a polypropylene-type resin, or these mixtures from a viewpoint of a heat shrinkage rate and a moldability. There are various types of polyethylene resins and polypropylene resins depending on the polymerization method and copolymerization component, and the range is not particularly limited. Preferred types are shown below.

The polyethylene resin used in the present invention is usually 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 of 0.92 g / cm ³ less than the low-density polyethylene resin (LDPE), and linear low density polyethylene resin (LLDPE). Among these, linear low density polyethylene resin (LLDPE) is particularly preferably used from the viewpoint of stretchability, impact resistance of the film, transparency, and the like.

  Examples of the linear low density polyethylene resin (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. Among these, 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 density of the polyethylene resin is preferably from 0.800 g / cm ³ or more, more preferably 0.850 g / cm ³ or more, 0.900 g / cm ³ or more, and the upper limit is 0.950 g / cm ³ or less is preferable, 0.940 g / cm ³ or less is more preferable, and 0.930 g / cm ³ or less is more preferable. If the density is 0.800 g / cm ³ or more, the waist (rigidity at room temperature) and heat resistance of the entire film are not significantly lowered, which is practically preferable. On the other hand, if the density is 0.950 g / cm ³ or less, the drawability 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.

  As the polyethylene resin, those having a melt flow rate (MFR: JIS K7210, temperature: 190 ° C., load: 2.16 kg) of 0.1 g / 10 min to 10 g / 10 min are preferably used. When the MFR is 0.1 g / 10 min or more, the extrudability can be maintained satisfactorily. On the other hand, when 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.

  Next, examples of the polypropylene resin used in the present invention include homopropylene resin, random polypropylene resin, block polypropylene resin, and propylene-ethylene rubber. Among these, a random polypropylene resin is particularly preferably used from the viewpoints of stretchability, transparency, rigidity, and the like.

  In the random polypropylene resin, the α-olefin to be copolymerized with propylene preferably includes those having 2 to 20 carbon atoms, more preferably those having 4 to 12 carbon atoms, such as ethylene, 1-butene, 1-pentene. 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene and the like. 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 or more. Preferably, it is 1.0 g / 10 min or more and 15 g / 10 min or less, preferably 10 g / 10 min or less.

  More specifically, these polyethylene resins and polypropylene resins are trade names “Novatech HD, LD, LL”, “Kernel”, “Toughmer A, P” (manufactured by Nippon Polytech Co., Ltd.) and “Suntech HD” as polyethylene resins. , LD "(manufactured by Asahi Kasei Corporation)," HIZEX "" ULTZEX "" EVOLUE "(manufactured by Mitsui Chemicals)," Moretech "(manufactured by Idemitsu Kosan Co., Ltd.)," UBE polyethylene "" UMERIT "(manufactured by Ube Industries)," It is commercially available as “NUC polyethylene” “Nackflex” (manufactured by Nihon Unicar), “engage” (manufactured by Dow Chemical). Also, as polypropylene resins, the trade names “NOVATEC PP”, “WINTEC”, “Toughmer XR” (manufactured by Nippon Polypro), “Mitsui Polypro” (manufactured by Mitsui Chemicals), “Sumitomo Noblen”, “Tough Selenium”, “Excellen EPX” (Sumitomo Chemical) ), “IDEMITSU PP”, “IDEMITSU TPO” (manufactured by Idemitsu Kosan Co., Ltd.), “Adflex”, “Adsyl” (manufactured by Sun Allomer), and the like. These copolymers can be used alone or in admixture of two or more.

  Moreover, the film of this invention can also use suitably the copolymer of the monomer copolymerizable with the said ethylene as PO-type resin. Examples of the copolymer of a monomer copolymerizable with ethylene include an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, and an ethylene-methyl acrylate copolymer. Among these, an ethylene-vinyl acetate copolymer is particularly preferably used from the viewpoints of transparency and economy.

  The ethylene content of the ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer is 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more. And 95% by mass or less, preferably 90% by mass or less, more preferably 85% by mass or less. If ethylene content rate is 50 mass% or more, the rigidity and heat resistance of the whole film can be maintained favorable. Moreover, it is preferable if the ethylene content is 95% by mass or less, since the effect on the fracture resistance of the film can be sufficiently obtained and the transparency can be maintained.

  Examples of commercially available ethylene-vinyl acetate copolymer (EVA) include “Evaflex” (manufactured by Mitsui DuPont Polychemical Co., Ltd.), “Novatech EVA” (manufactured by Mitsubishi Chemical Corporation), and “Ebaslene” (Dainippon Ink Chemical Co., Ltd.). Kogyo Co., Ltd.) and “Evaate” (Sumitomo Chemical Co., Ltd.). Moreover, as a commercial item of an ethylene / ethyl acrylate copolymer (EEA), for example, “Evaflex EEA” (manufactured by Mitsui DuPont Polychemical Co., Ltd.), and as an ethylene / methyl acrylate copolymer, “Elvalloy AC” (Mitsui DuPont Poly) is used. Chemical Co., Ltd.).

  The MFR of the copolymer of the copolymerizable monomer with ethylene is not particularly limited, but usually MFR (JIS K7210, temperature: 190 ° C., load: 2.16 kg) is 0.5 g / It is 10 minutes or more, preferably 1.0 g / 10 minutes or more, and 15 g / 10 minutes or less, preferably 10 g / 10 minutes or less.

  The PO-based resin used in the present invention has a lower limit value of weight average molecular weight of 50,000, preferably 100,000, and an upper limit value of 700,000, preferably 600,000, more preferably 500,000. Preferably there is. 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.

  Further, the production method of the PO-based resin is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst, for example, a multisite catalyst or a metallocene catalyst represented by a Ziegler-Natta type catalyst. Examples thereof include a slurry polymerization method, a solution polymerization method, a bulk polymerization method, and a gas phase polymerization method using a single site catalyst represented by the above, and a bulk polymerization method using a radical initiator.

  Furthermore, in the present invention, an appropriate amount of petroleum resin or the like can be added as necessary for the purpose of adjusting the shrinkage ratio to the PO-based resin. By adding a petroleum resin, stretchability at low temperatures can be maintained, and improvement in heat shrinkage characteristics can be expected.

As the petroleum resin, aromatic petroleum resin from alicyclic petroleum resins and C ₉ components from cyclopentadiene or dimer thereof. Petroleum resins are known to exhibit relatively good compatibility when mixed with PO-based resins and the like, but it is preferable to use hydrogenated derivatives in view of color tone, thermal stability, and compatibility.

  Specifically, Mitsui Chemicals 'product names “Hilets” and “Petrogin”, Arakawa Chemical Industries' product name “Arcon”, Idemitsu Petrochemicals Inc. product name “Imabe”, Tonex Corporation ) And other commercial products such as “Escollets” can be used.

  Some petroleum resins mainly have various softening temperatures depending on the molecular weight. In the present invention, those having a softening temperature of 100 ° C. or higher and 150 ° C. or lower, preferably 110 ° C. or higher and 140 ° C. or lower are preferably used. It is done. If the softening temperature of the petroleum resin is 100 ° C. or higher, the petroleum resin bleeds on the surface of the sheet when mixed with the PO-based resin, causing blocking, or the mechanical strength of the entire sheet is reduced and the sheet is easily broken. This is practically preferable. On the other hand, if the softening temperature is 150 ° C. or lower, the compatibility with the PO-based resin is maintained well, and the petroleum resin bleeds on the film surface over time without causing blocking or a decrease in transparency. ,preferable.

  The amount of petroleum resin added to the intermediate layer is preferably 5 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the PO-based resin constituting the intermediate layer. If the mixing amount of the petroleum resin is 5 parts by mass or more, an effect of improving the glossiness and shrinkage characteristics of the film surface can be obtained. On the other hand, if the amount of the petroleum resin mixed is 80 parts by mass or less, the petroleum resin bleeds on the surface over time, and the occurrence of problems such as easy film blocking and reduced impact resistance. Can be suppressed. For these reasons, the amount of petroleum resin added to the intermediate layer is more preferably 10 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the resin constituting the intermediate layer.

  In addition, the intermediate layer can contain a resin constituting the front and back layers. Since the PLA resin has a refractive index relatively close to that of the PO resin used in the front and back layers, transparency is not hindered when a recycled resin generated from trimming loss such as a film ear is added. Good transparency can be maintained.

  The content of the resin constituting the front and back layers that can be added to the intermediate layer is 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 40 parts by mass or less of the resin constituting the front and back layers with respect to 100 parts by mass of the PO resin constituting the intermediate layer. Is preferably in the range of 30 parts by mass or less. By making the resin constituting the front and back layers 50 parts by mass or less with respect to 100 parts by mass of the PO-based resin constituting the intermediate layer, the transparency of the obtained laminated film can be maintained.

<Adhesive layer>
As a 2nd aspect of the film of this invention, the aspect which has the contact bonding layer aiming at the adhesive improvement between the said intermediate | middle layer and the said front and back layer can be illustrated.

The adhesive layer used in the present invention contains an adhesive resin as a main component.
The adhesive resin is not particularly limited as long as it improves the interlayer adhesion between the intermediate layer and the front and back layers. However, it has a reactivity or affinity for the PLA resin of the front and back layers and the PO of the intermediate layer. A resin having both a part having an affinity with a system resin is 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.

  Further, the “site having an affinity for the PO resin in the intermediate layer” means having a chain having an affinity for the PO resin, and more specifically, a linear or branched saturated hydrocarbon moiety is mainly used. It means having a chain, a block chain, or a graft chain.

  Other preferable resins used for the adhesive layer include soft PO resins, copolymers of styrene hydrocarbons and conjugated diene hydrocarbons, or hydrogenated resins thereof. Specific examples include soft linear low density polyethylene resin, low crystalline polypropylene resin, ethylene-vinyl acetate copolymer, etc., as soft PO resin, and styrene hydrocarbon and conjugated diene hydrocarbon. Examples of the copolymer include a styrene-butadiene copolymer, a styrene-isoprene copolymer, a styrene-ethylene-butadiene copolymer, a styrene-ethylene-propylene copolymer, and a styrene-ethylene-butylene copolymer.

  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 PO resin, “Admer” (Mitsui Chemicals, Inc.) is used as an acid-modified polyolefin resin. ), "Modic" (manufactured by Mitsubishi Chemical Corporation), "Modiper" (manufactured by NOF Corporation), "Bondyne" (manufactured by Sumitomo Chemical Co., Ltd.) as an ethylene-vinyl acetate-maleic anhydride copolymer, ethylene-glycidyl methacrylate Copolymer, ethylene-vinyl acetate-glycidyl methacrylate terpolymer, “bond first” (manufactured by Sumitomo Chemical Co., Ltd.), acid-modified styrene thermoplastic as ethylene-ethyl acrylate-glycidyl methacrylate terpolymer Trade names "Tuftec M" (Asahi Kasei Chemicals), "Epofriend" (Daicel Chemical), styrene hydrocarbon Copolymers with conjugated diene hydrocarbons, or hydrogenated resins thereof such as “Tuftec H” (Asahi Kasei Chemicals), “Clayton” (JSR Kraton Polymer), “Dynalon” (JSR), “Septon” ”(Manufactured by Kuraray Co., Ltd.),“ Hiblar ”(manufactured by Kuraray Co., Ltd.),“ Tufprene ”(manufactured by Asahi Kasei Chemicals Corporation), and the like.

  In the second aspect of the present invention, the intermediate layer can include a PLA resin used in the front and back layers and an adhesive resin used in the adhesive layer. If the resin used in the front and back layers and / or the adhesive layer can be included in the intermediate layer, for example, a recycled film generated from trimming loss such as film ears can be reused, and the manufacturing cost can be reduced. it can. When the intermediate layer contains a resin constituting the front and back layers, the resin constituting the front and back layers is 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 30 with respect to 100 parts by mass of the PO-based resin constituting the intermediate layer. It is desirable that the amount is not more than part by mass. If the resin constituting the front and back layers is 50 parts by mass or less, the transparency at the time of regeneration addition can be maintained without reducing the mechanical strength of the film. Similarly, when the intermediate layer includes a resin constituting the adhesive layer, the resin constituting the adhesive layer is 1 part by mass or more and 30 parts by mass or less, preferably 25 parts by mass with respect to 100 parts by mass of the PO-based resin constituting the intermediate layer. Hereinafter, it is more preferable that the content be 20 parts by mass or less.

  In the present invention, the front and back layers, the intermediate layer, and the adhesive layer are improved in various properties of the molding processability, productivity, and heat shrinkable film within the range that does not significantly impair the effects of the present invention in addition to the components described above. In order to adjust, 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, crosslinking agents, lubricants, Additives such as a nucleating agent, a plasticizer, and an antioxidant can be added as appropriate.

<Layer structure of film>
The film of the present invention comprises an intermediate layer mainly composed of at least one PO resin, and front and back layers mainly composed of at least one PLA resin laminated on both surfaces of the intermediate layer. . Since the film of the present invention is a heat-shrinkable film composed of a PO-based resin and a PLA resin having a relatively close refractive index, even when a recycled resin generated from trimming loss or the like of the film ear is added, the film Transparency can be ensured.

  The layer structure is not particularly limited as long as the film of the present invention has at least the above three layers. Here, the “front and back layers laminated on both surfaces of the intermediate layer” means not only when the front and back layers are laminated adjacent to the intermediate layer (first aspect), but also between the intermediate layer and the front and back layers. A case having three layers (for example, the second embodiment) is also included. 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 a front / back layer / intermediate layer / front / back layer, and a more preferred layer structure is a five-layer structure comprising a front / back layer / adhesive layer / intermediate layer / adhesive layer / front / back layer. It is. 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 front / back layer / intermediate layer / adhesive layer composed of front and back layers and an intermediate layer, which is an example of a preferred embodiment of the present invention, and front / back layer / adhesive layer / intermediate layer / adhesive layer / A film having a five-layer structure composed of front and back layers 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 front and back layers to the total film thickness is 10% or more, preferably 15% or more, more preferably 20% or more, and 80% or less, preferably 70% or less, more preferably 50% or less, most preferably Can be in the range of 45% or less. The thickness ratio of the intermediate layer to the thickness of the entire film is 10% or more, preferably 20% or more, more preferably 30% or more, and 90% or less, preferably 85% or less, more preferably 80% or less. is there.

  When an adhesive layer is provided between the intermediate layer and the front and back layers, the adhesive layer has a function of 0.5 μm or more, preferably 0.75 μm or more, more preferably 1 μm or more, and 6 μm or less, preferably 5 μm or less. is there.

  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 contraction rate of 30% or more in at least one 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 required shrinkage rate required for a heat-shrinkable film applied to the use of shrinkage labels for PET bottles varies depending on the shape, but is generally about 20% to 70%.

  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.

  Considering such industrial productivity, a film having a heat shrinkage rate of 30% or more under the above conditions is preferable because it can sufficiently adhere to the object to be coated within the shrinkage processing time. From these, the heat shrinkage rate when heated in 80 ° C. warm water for 10 seconds is at least 30% or more, preferably 35% or more, more preferably 40% or more in the main shrinkage direction in at least one direction, It is 70% or less, preferably 65% or less, and more preferably 60% or less.

  In the present specification, the “main shrinkage direction” means a direction having a large thermal shrinkage rate in the longitudinal direction (longitudinal direction) and the transverse direction (width direction). The direction corresponding to the direction is meant, and the “orthogonal direction” means a direction perpendicular to the main contraction direction. In the examples of the present specification, the take-up (flow) direction of the laminated film and the direction perpendicular thereto are the same as the “orthogonal direction” and the “main contraction direction”, respectively.

  When the film of the present invention is used as a heat-shrinkable label, the heat shrinkage rate in the orthogonal direction is preferably 10% or less, preferably 5% or less when heated in 80 ° C. warm water for 10 seconds. Is more preferable, and it is further more 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.

  The film of the present invention has a heat shrinkage rate of 5% or more, preferably 7% or more, more preferably 10% or more, and less than 50% when heated in 70 ° C. warm water for 10 seconds. Preferably it is 45% or less, More preferably, it is 40% or less. By setting the lower limit of the heat shrinkage rate in the main film shrinkage direction at 70 ° C. to 5%, shrinkage unevenness that may occur locally when bottles are attached with a steam shrinker is suppressed. As a result, wrinkles, avatars, etc. The formation of can be suppressed. Further, by setting the upper limit of the heat shrinkage rate to less than 50%, extreme shrinkage at low temperatures can be suppressed, and for example, natural shrinkage can be kept small even in a high temperature environment such as summer.

  The heat shrinkage in the direction perpendicular to the film when heated in 70 ° C. warm water for 10 seconds is preferably 10% or less, more preferably 5% or less, and even more 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 the film of the present invention, in order to adjust the thermal shrinkage rate when immersed in warm water at 70 ° C. and 80 ° C. for 10 seconds to the above range, the resin composition is adjusted as described in the present invention, and the stretching temperature is adjusted. Is preferably adjusted to a range described later. For example, when it is desired to further increase the heat shrinkage rate in the main shrinkage direction, it is preferable to use means such as increasing the thickness ratio of the front and back layers, increasing the stretching ratio, and decreasing the stretching temperature.

  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.

  In the film of the present invention, as a means for adjusting the natural shrinkage rate of the film, it is important that the resin composition of each layer is within the range specified in the present invention, but the thickness ratio of the front and back layers to the total film thickness is particularly important. It can be adjusted by increasing it.

  The transparency of the film of the present invention includes the case where a recycled product is added, for example, in applications where transparency is required, for example, in applications where the printed surface printed on the back surface of the film is visible from the surface, When a 50 μm film is measured according to JIS K7105, the haze value is preferably 10% or less, more preferably 7% or less, and even more preferably 5% or less. If the haze value is 10% or less, the transparency of the film can be obtained and a display effect can be obtained.

  In the present invention, the film is stretched at a measurement temperature of −150 ° C. to 150 ° C. under conditions of vibration frequency 10 Hz, strain 0.1%, heating rate 2 ° C./min, and chuck 2.5 cm. The storage elastic modulus (E ′) at 20 ° C. when dynamic viscoelasticity is measured in the direction orthogonal to the direction is preferably in the range of 1,200 MPa to 3,000 MPa, more preferably 1,200 MPa or more. The range is 2,500 MPa or less. If the storage elastic modulus E ′ is 1,200 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 covered film is covered with a labeling machine etc. This is preferable because problems such as a decrease in yield and the like are unlikely to occur. 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 at the time of the secondary processing. .

  In order to set the storage elastic modulus (E ′) at 20 ° C. in the direction perpendicular to the film stretching direction to be in the range of 1,200 MPa to 3,000 MPa, the resin composition of each layer should be in the range specified in the present invention. Although important, it can be adjusted by changing the thickness ratio of the front and back layers, the intermediate layer, and the adhesive layer to the thickness of the entire film. For example, when it is desired to increase the storage elastic modulus (E '), it can be adjusted by increasing the thickness ratio of the front and back layers to the total layer and increasing the rigidity of the resin of the intermediate layer.

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

  In applications where the stretching ratio is contracted in two directions, such as for overlap, the vertical direction is 2 to 10 times, the horizontal direction is 2 to 10 times, preferably the vertical direction is 3 to 6 times, and the horizontal direction Is about 3 to 6 times. On the other hand, in applications such as heat-shrinkable labels that shrink mainly in one direction, the direction corresponding to the main shrinkage direction is 2 to 10 times, preferably 4 to 8 times, and the direction orthogonal to it is 1 or more times. It is desirable to select a magnification ratio that is not more than 2 times (1 time indicates that the film is not stretched), preferably 1.1 times or more and 1.5 times or less, which is substantially in the category of uniaxial stretching. 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 used and the properties required for the heat-shrinkable film, but is generally 50 ° C. or higher, preferably 60 ° C. or higher, and the upper limit is 130 ° C. or lower, preferably 110 ° C. It is controlled within the following range. The draw ratio is 1.5 times to 10 times, preferably 3 times to 7 times, preferably 3 times to 7 times in the main shrinkage direction, depending on the characteristics of the resin used, the stretching means, the stretching temperature, the target product form, etc. Preferably, it is appropriately determined in the direction of one axis or two axes within a range of 3 to 5 times. Further, even in the case of uniaxial stretching in the transverse direction, it is also effective to impart weak stretching of about 1.05 times to 1.8 times in the longitudinal direction for the purpose of improving the mechanical properties of the film. Next, the stretched film is subjected to a heat treatment or relaxation treatment at a temperature of about 50 ° C. or more and 100 ° C. or less for the purpose of reducing the natural shrinkage rate or improving the heat shrink property, if necessary. It cools rapidly within the time not to relax, and becomes a heat-shrinkable film.

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

  The film of the present invention is processed from a flat shape to a cylindrical shape or the like according to an object to be packaged and provided for packaging. When printing is required in a cylindrical container such as a plastic bottle, first print the required image on one side of a wide flat film wound up on a roll, and then cut 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.

[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 a shrink wrap and binding band for various molded products such as bottles (blow bottles), trays, lunch boxes, prepared food containers, dairy products containers and the like. In particular, when the film of the present invention is used as a heat-shrinkable label for food containers (for example, PET bottles, glass bottles, preferably PET bottles for soft drinks or foods), a complicated shape (for example, a cylinder with a narrow center, a corner 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 finishing properties, in addition to the heat-shrinkable label material of plastic molded products that are 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.

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

The present invention will be described below with reference to examples.
In addition, the measured value and evaluation which are shown to an Example were performed as follows. In the examples, the take-up (flow) direction of the laminated film is described as the “longitudinal” direction, 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 (made by IT Measurement Co., Ltd.), the measurement temperature was 10 Hz, the strain was 0.1%, the temperature rising 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. In addition, as the storage elastic modulus (E ′), the storage elastic modulus at 20 ° C. is shown.

(2) Heat Shrinkage 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 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 1,000 mm in width and left in a constant temperature bath at 30 ° C. for 30 days, and the amount of shrinkage relative to the original size before shrinkage in the main shrinkage direction. The ratio was measured and expressed as a% value.

(4) Haze value Based on JIS K7105, the haze value of the film was measured at a film thickness of 50 μm, and 10% or more was evaluated as ×, 5% or more and less than 10% as ◯, and less than 5% as ◎.

(5) Interlaminar adhesive strength The obtained film was cut into a size of 100 mm in length and 298 mm in width, 10 mm on both ends of the film in the horizontal direction, and bonded with a tetrohydrofuran (THF) solvent to prepare a cylindrical film. This cylindrical film is attached to a 1.5 liter cylindrical plastic bottle and passed in 4-8 seconds without rotating in a steam heating type 3.2 m (3 zone) shrink tunnel. It was. 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 when the bottle is mounted, and delamination does not occur even when the label is peeled off from the seal portion.
○: There is no delamination when the bottle is mounted, but delamination occurs when the label is peeled off from the seal portion.
Δ: Slight delamination occurs at the seal portion when the bottle is mounted.
X: When the bottle is mounted, delamination occurs on the entire seal portion.

(6) Shrinkage finish A film printed with a 10 mm-interval grid is cut into a size of 100 mm in length and 298 mm in width, 10 mm on both sides of the film in the horizontal direction, and bonded with a Tetrohydrofuran (THF) solvent to form a cylindrical film Was made. 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 | cover to a bottle is inadequate.

Example 1
As shown in Table 1, as a PLA resin used in the front and back layers, a product name “Nature Works 4060D (L body: D body ratio = 88: 12)” (hereinafter abbreviated as “PLA1”) manufactured by NatureWorks LLC is used. As a PO-based resin used in the intermediate layer, a random PP product name “Wintech WFX4T” (hereinafter abbreviated as “PO1”) manufactured by Nippon Polypro Co., Ltd. and a linear low density manufactured by Ube Industries, Ltd. A mixed resin composition containing 50% by mass of polyethylene trade name “Umerit 0540F” (hereinafter abbreviated as “PO3”) was used. Each resin was put into a separate single-screw extruder manufactured by Mitsubishi Heavy Industries, Ltd., melt-mixed at a set temperature of 200 ° C., and the thickness of each layer in the unstretched laminated sheet was front / back layer / intermediate layer / front / back layer = 45 μm / After coextruding from a two-kind three-layer die so as to be 160 μm / 45 μm, it was 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. Subsequently, the film was stretched 5.0 times in the transverse uniaxial direction at a stretching temperature of 75 ° C. by a film tenter manufactured by Kyoto Machine Co., Ltd., and then rapidly cooled with cold air to obtain a heat-shrinkable laminated film having a thickness of 50 μm. Table 2 shows the results of evaluating the obtained film.

(Example 2)
As shown in Table 1, as a PLA resin used in the front and back layers, PLA1 is 50% by mass and a product name “Nature Works 4050D (L body: D body ratio = 95: 5)” manufactured by NatureWorks LLC (hereinafter “PLA2”). As a PO-based resin used in the intermediate layer, 50% by mass of a mixed resin is used, and PO1: 80% by mass, polyolefin “TPO310V” (hereinafter abbreviated as “PO2”) manufactured by Idemitsu Kosan Co., Ltd .: A 20% by mass mixed resin composition was used, and an acid-modified polyolefin resin trade name “Admer SF731” (hereinafter abbreviated as “AD1”) manufactured by Mitsui Chemicals, Inc. was used as an adhesive layer. Each resin was put into a separate single screw extruder manufactured by Mitsubishi Heavy Industries, Ltd., and after melt mixing at a set temperature of 200 ° C., the thickness of each layer was determined to be front / back layer / adhesive layer / intermediate layer / adhesive layer / front / back layer = 40 μm / After co-extruding from 3 types and 5 layers dies so as to be 10 μm / 150 μm / 10 μm / 40 μm, it was taken up by 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 stretching temperature of 75 ° C., and then quenched with cold air to obtain a heat-shrinkable laminated film having a thickness of 50 μm. Table 2 shows the results of evaluating the obtained film.

(Example 3)
As shown in Table 1, the front and back layers of Example 2 were PLA 1: 90% by mass, a copolymer of polylactic acid resin, diol and dicarboxylic acid manufactured by Dainippon Ink & Chemicals, Inc. (Abbreviated as “rubber component”): 10% by mass of mixed resin, intermediate layer of PO1: 55% by mass, PO2: 30% by mass, hydrogenated petroleum resin manufactured by Arakawa Chemical Co., Ltd. (Abbreviated as “petroleum resin”): 15% by mass mixed resin, except that acid-modified SEBS product name “Tuftec M1913” (hereinafter abbreviated as “AD2”) manufactured by Asahi Kasei Chemicals Co., Ltd. was used as the adhesive layer. Obtained the heat-shrinkable laminated film similarly to Example 2. Table 2 shows the results of evaluating the obtained film.

(Example 4)
As shown in Table 1, the front and back layers of Example 2 were PLA 1:50 mass%, PLA 2: 40 mass%, rubber component: 10 mass% mixed resin, the intermediate layer was PO 1:35 mass%, PO3: 40 mass%. Petroleum resin: 25% by mass mixed resin, and an adhesive layer made of Sumitomo Chemical Co., Ltd., ethylene-ethyl acrylate-glycidyl methacrylate copolymer, trade name “bond first 7M” (hereinafter abbreviated as “AD3”) A heat-shrinkable laminated film was obtained in the same manner as in Example 2 except that was used. Table 2 shows the results of evaluating the obtained film.

(Example 5)
As shown in Table 1, heat shrinkability was the same as in Example 2 except that the adhesive layer of Example 2 was SEBS product name “Tuftec H1221” (hereinafter abbreviated as “AD4”) manufactured by Asahi Kasei Chemicals Corporation. A laminated film was obtained. Table 2 shows the results of evaluating the obtained film.

(Example 6)
As shown in Table 1, Example 1 was used except that the intermediate layer of Example 1 was an ethylene-vinyl acetate copolymer product name “Novatech EVA LV141” (hereinafter abbreviated as “PO4”) manufactured by Nippon Polyethylene Co., Ltd. A heat-shrinkable laminated film was obtained in the same manner as in 1. Table 2 shows the results of evaluating the obtained film.

(Example 7)
As shown in Table 1, Example 2 and Example 2 except that the intermediate layer of Example 3 was a mixed resin of PO 1: 45% by mass, PO2: 30% by mass, petroleum resin: 15% by mass, PLA 1: 10% by mass. Similarly, a heat-shrinkable laminated film was obtained. Table 2 shows the results of evaluating the obtained film.

(Comparative Example 1)
As shown in Table 1, a heat-shrinkable film was obtained in the same manner as in Example 1 except that an unstretched single-layer sheet composed of a PLA single layer without providing an intermediate layer was prepared to have a thickness of 250 μm. . Table 2 shows the results of evaluating the obtained film.

(Comparative Example 2)
As shown in Table 1, heat shrinkability was the same 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 front and back layers. A film was obtained. Table 2 shows the results of evaluating the obtained film. In addition, when trying to produce a cylindrical film by adhering with a tetrohydrofuran (THF) solvent, the suitability for solvent sealing was poor and the bag could not be formed into a cylindrical shape.

(Comparative Example 3)
As shown in Table 1, in Example 1, the thickness of each layer in the unstretched laminated sheet in which the front and back layers were changed to PO1 and the intermediate layer to PLA1 was front and back layers / intermediate layers / front and back layers = 80 μm / 90 μm / 80 μm A heat-shrinkable film was obtained in the same manner as in Example 1 except that the change was made. Table 2 shows the results of evaluating the obtained film. In addition, when trying to produce a cylindrical film by adhering with a tetrohydrofuran (THF) solvent, the suitability for solvent sealing was poor and the bag could not be formed into a cylindrical shape.

(Reference Example 1)
As shown in Table 1, a mixed resin composition of PO 1: 50% by mass and PO2: 50% by mass was used as the PO-based resin of the intermediate layer, and the thickness of each layer in the unstretched laminated sheet was the front / back layer / intermediate layer / A heat-shrinkable laminated film was obtained in the same manner as in Example 1 except that the front and back layers were changed to 105 μm / 40 μm / 105 μm. Table 2 shows the results of evaluating the obtained film.

(Reference Example 2)
As shown in Table 1, a mixed resin composition of PO 1: 50% by mass and PO2: 50% by mass was used as the PO-based resin of the intermediate layer, and the thickness of each layer in the unstretched laminated sheet was the front / back layer / intermediate layer / A heat-shrinkable laminated film was obtained in the same manner as in Example 1 except that the front and back layers were changed to 10 μm / 230 μm / 10 μm. Table 2 shows the results of evaluating the obtained film.

The film of the Example comprised within the range prescribed | regulated by this invention from Table 1 has low-temperature shrinkage | contraction property, waist strength (storage elastic modulus of a laminated film), natural shrinkage | contraction, rise of shrinkage | contraction rate, interlayer adhesiveness, and shrinkage | contraction. The finish was equal to or better than Comparative Examples 1 to 3.
On the other hand, when the intermediate layer does not have a PO-based resin and does not have an adhesive layer (Comparative Example 1), it exhibits a remarkably high shrinkage rate at 70 ° C., is inferior in shrink finish, and is used as a front and back layer. When the PLA resin was not used (Comparative Example 2), the waist strength, the heat shrinkage rate, and the natural shrinkage decreased. Further, when the intermediate layer was composed of PLA resin and the front and back layers were composed of PO resin (Comparative Example 3), the solvent sealability was poor and bag making was impossible.
Moreover, when the thickness of the front and back layers was thick (Reference Example 1), a high heat shrinkage rate was exhibited, and the shrink finish performance was slightly inferior to the films of Examples 1 and 2. On the other hand, when the thickness of the front and back layers was thin (Reference Example 2), the natural shrinkage ratio was increased, and the waist strength and shrinkage finish were slightly inferior to 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 having an intermediate layer and at least three layers of front and back layers laminated on both sides of the intermediate layer,
The intermediate layer is composed of at least one polyolefin resin as a main component,
The front and back layers are composed of at least one polylactic acid resin as a main component,
And the heat shrinkage rate in the main film shrinkage direction when heated in 80 ° C. warm water for 10 seconds is 30% or more, and the direction perpendicular to the film main shrinkage direction when heated in 80 ° C. warm water for 10 seconds. heat-shrinkable laminated film thermal shrinkage, characterized in der Rukoto 10% or less. The heat-shrinkable laminated film according to claim 1, wherein the polylactic acid resin is a resin comprising a copolymer of D-lactic acid and L-lactic acid, or a mixture of the copolymers. The heat-shrinkable laminated film according to claim 1 or 2, 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 3, wherein the thickness ratio of the front and back layers 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 4, further comprising at least one adhesive layer between the intermediate layer and the front and back layers. The heat-shrinkable laminated film according to any one of claims 1 to 5, wherein the intermediate layer contains 50 parts by mass or less of the resin constituting the front and back layers with respect to 100 parts by mass of the polyolefin resin constituting the intermediate layer. The heat-shrinkable laminated film according to any one of claims 1 to 6, wherein a haze value measured in accordance with JIS K7105 is 10% or less. Molded article using as a substrate a heat-shrinkable laminate film according to any one of claims 1 to 7. A heat-shrinkable label using the heat-shrinkable laminated film according to any one of claims 1 to 7 as a substrate. A container equipped with the molded product according to claim 8 or the heat-shrinkable label according to claim 9 .