JP4833880B2 - Laminated film and shrink label - Google Patents

Description

  The present invention relates to a heterogeneous laminated film having improved interlayer strength. Specifically, the present invention relates to a laminated film in which a film layer made of a polystyrene resin and a film layer made of a polyester resin are laminated without using an adhesive layer and have excellent interlayer strength.

  At present, in the field of plastic films, heterogeneous laminated films in which different materials are laminated are widely used for the purpose of imparting various different functions to the film. For example, in the field of plastic labels such as shrink labels, different types of laminated films of polystyrene resin and polyester resin are being studied for the purpose of optimizing shrinkage processing characteristics and achieving both shrinkage and chemical resistance ( For example, Patent Document 1).

  However, the resin layer (film layer) composed of the above-mentioned polystyrene resin and the resin layer composed of the polyester resin usually have a low interlayer adhesion between the resin layers, and therefore are based on an adhesive or a polymer having a high affinity for both layers. It was common to laminate through an adhesive layer. For this reason, there has been a problem that the production process becomes complicated and the productivity is lowered.

JP 61-41543 A

  An object of the present invention is to provide a laminated film that exhibits high interlayer strength without providing an adhesive layer in a laminated film of different polymers of a polystyrene resin and a polyester resin.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have laminated a film layer mainly composed of a polystyrene-based resin and a polyester-based resin having a specific melt-viscosity relationship. The present inventors have found that a heterogeneous laminated film having excellent interlayer strength can be obtained without providing an adhesive layer, and the present invention has been completed.

That is, the present invention is a film layer (layer A) comprising a polylactic acid-based polymer as a main component and a polyester-based resin other than a polylactic acid-based polymer that is polybutylene succinate and / or polybutylene succinate adipate. And polystyrene-based resin that is styrene-butadiene-styrene block copolymer (SBS), styrene-butadiene-isoprene copolymer (SBIS), or styrene / butadiene / acryl blend polymer (St / Bd / Ac) as a main component A layered film in which at least one film layer (B layer) is provided and the A layer and the B layer are directly laminated without any other layer, and the resin composition (A Layer resin) and the resin composition (B layer resin) constituting the B layer at 190 ° C. (viscosity rheometer method, shear rate 1) 00 sec ^-1) the absolute value of the difference is 396 Pa · s or less, the temperature at 180 to 240 ° C. of A-layer resin and the B-layer resin - absolute value 6.14 Pa · the difference of the slope of the melt viscosity linear Provided is a laminated film having a temperature of s / ° C. or lower.

  Furthermore, the present invention provides the above laminated film having B layers on both sides of the A layer.

Further, in the present invention, the content of the polylactic acid polymer in the A layer is 50 to 90% by weight, and the content of the polyester resin other than the polylactic acid polymer in the A layer is 10 to 50%. Provided is a laminated film of the above-mentioned weight%.

Furthermore, in the present invention, the polylactic acid polymer has a weight average molecular weight of 5,000 to 100,000, and the polyester film resin other than the polylactic acid polymer has a weight average molecular weight of 5,000 to 100,000. I will provide a.

Furthermore, this invention provides the said laminated | multilayer film whose weight average molecular weights of the said polystyrene resin are 5000-100,000.

Moreover, this invention provides the shrink label using the said laminated | multilayer film.

  The shrink label of the present invention has high productivity because the polyester-based resin film layer and the polystyrene-based resin film layer are laminated without using an adhesive layer. Moreover, the interlayer strength is high, and it is useful because troubles due to delamination between film layers do not occur during use.

  Below, the laminated | multilayer film of this invention are demonstrated in detail.

  The laminated film of the present invention has at least one film layer (hereinafter referred to as A layer) containing a polyester resin as a main component and at least one film layer (hereinafter referred to as B layer) containing a polystyrene resin as a main component. Have one by one. The term “main component” as used in the present application means that the content in each film layer is 50% by weight or more based on the total weight of the film layer, and is more preferable unless otherwise specified. Means 60% by weight or more. Further, the “A layer (B layer) resin” referred to in the present application refers to all components (a composition including a resin component and an additive component other than the resin) constituting the A layer (B layer).

[A layer (polyester resin layer)]
The A layer of the present invention comprises a polyester resin as a main component. The polyester resin used as the A layer resin is not particularly limited as long as it satisfies the relationship of the melt viscosity described later. Any of aliphatic polyester resins, aromatic polyester resins, and aliphatic aromatic polyester resins can be used. However, aliphatic polyester resins are particularly preferred from the viewpoint of melt viscosity characteristics.

  The kind of the said polyester-type resin can be suitably selected according to the use and objective of the laminated | multilayer film of this invention. Among them, for example, a laminated film using a polylactic acid polymer, which is a plant-derived raw material, as a polyester resin is useful in terms of environmental protection because it can reduce the environmental burden in film production. When the A layer of the present invention contains a polylactic acid-based polymer as a main component, the A layer may be composed of only a polylactic acid-based polymer, but may contain a polyester resin other than polylactic acid. From the viewpoint of improving interlayer adhesion and using recovered materials, a small amount of polystyrene resin used for the B layer may be contained. Moreover, the other additive may be included.

  The polylactic acid polymer used in the A layer of the present invention means a polymer containing lactic acid (D-lactic acid, L-lactic acid, DL-lactic acid, or a mixture thereof) as a monomer component. Copolymers of these with hydroxycarboxylic acids or lactones, or copolymers of lactic acid with other dicarboxylic acids and / or diols are also included. Other hydroxycarboxylic acids include, for example, glycolic acid, 2-methyllactic acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxy-3,3-dimethyl Examples include butyric acid and 2-hydroxycaproic acid. Examples of lactones include γ-butyrolactone, δ-valerolactone, and ε-caprolactone. Examples of the dicarboxylic acid include various aliphatic (saturated and unsaturated) dicarboxylic acids, alicyclic dicarboxylic acids, and aromatic dicarboxylic acids. Examples of the diol component include various aliphatic diols and alicyclic diols. These hydroxycarboxylic acids, lactones, dicarboxylic acids, or diols may be mixed with lactic acid in a monomer state and led to a polymer as a random copolymer, an oligomer that has been polymerized in advance as a polyester, or It may be introduced into the polymer in the form of forming a block copolymer with lactic acid as a prepolymer.

  The composition ratio of optical isomers of lactic acid constituting the polylactic acid-based polymer (content ratio of D-form and L-form) varies depending on the required physical properties and is not particularly limited, but from the viewpoint of crystallinity control The ratio of D-lactic acid to the total lactic acid component is 1 to 20% by weight (preferably 1 to 15% by weight), or the ratio of L-lactic acid to the total lactic acid component is 1 to 20% by weight (preferably 1 to 15% by weight). Especially, the case where the ratio of D-lactic acid with respect to all the lactic acid components is 1 to 20 weight% is more preferable.

  The proportion of lactic acid in the total monomers constituting the polylactic acid polymer is generally 50 mol% or more, preferably 65 mol% or more, more preferably 80 mol% or more, for example, 100 mol%. Good. Polylactic acid polymers may be used alone or in admixture of two or more. For example, two or more polylactic acid polymers having different ratios of L-lactic acid and D-lactic acid can be used in combination.

  The polylactic acid polymer is produced, for example, by polymerizing lactic acid produced from starch obtained from corn or potato. The polymerization method is not particularly limited, and a known method such as a condensation polymerization method or a ring-opening polymerization method can be employed. For example, in the polycondensation method, lactic acid or a polylactic acid polymer having an arbitrary composition can be obtained by directly dehydrating condensation of lactic acid and other monomer components. In the ring-opening polymerization method, lactide, which is a cyclic dimer of lactic acid, is polymerized in the presence of a suitable catalyst to obtain a polylactic acid polymer having an arbitrary composition.

  Although the weight average molecular weight of a polylactic acid-type polymer is not specifically limited, From a viewpoint of a mechanical characteristic and melt viscosity, it is 5,000-100,000 normally, Preferably it is about 10,000-50,000. On the other hand, if the molecular weight is too small, the mechanical properties and heat resistance are poor, and if the molecular weight is too large, the molding processability is lowered.

  In the case of using a polylactic acid polymer as the main component of the A layer of the present invention, the content of the polylactic acid polymer in the A layer is from the viewpoint of controlling the melt viscosity to a preferable range of the present invention. It is 50 to 100% by weight relative to the total weight, and preferably 60 to 90% by weight in order to obtain good shrinkage. From the viewpoint of biomass plastics, the polylactic acid polymer is preferably contained in an amount of 25% by weight or more, more preferably 30% by weight or more, and still more preferably 50% by weight or more based on the entire laminated film. It is.

  In the A layer of the present invention, in addition to the polylactic acid polymer, a polyester resin other than the polylactic acid polymer may be contained. Other polyester resins may be any of aliphatic polyester resins, aromatic polyester resins, aliphatic aromatic polyester resins, or a mixture thereof. Among these, an aliphatic polyester resin is preferable.

  The aliphatic polyester-based resin is a polycondensation of an aliphatic or alicyclic diol component and an aliphatic or alicyclic dicarboxylic acid component, a polycondensation of an aliphatic or alicyclic hydroxycarboxylic acid, or a ring-opening polymerization of lactones. Or a combination thereof. Each monomer component can be used in combination. Examples of the aliphatic or alicyclic diol component include ethylene glycol, 1,3-propanediol, propylene glycol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,6- Examples include aliphatic diols such as hexanediol; polyalkylene glycols such as diethylene glycol; alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol. Examples of the aliphatic or alicyclic dicarboxylic acid component include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; And alicyclic dicarboxylic acids such as hydronaphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and 1,3-cyclohexanedicarboxylic acid. As the aliphatic or alicyclic hydroxycarboxylic acid and lactone, those exemplified above can be used. By adding an aliphatic polyester-based resin, extrusion suitability and moldability are improved as compared to the case of a polylactic acid-based polymer alone.

  In the above aliphatic polyester resin, a part of the aliphatic or alicyclic dicarboxylic acid component (for example, about 0.1 to 50 mol%) may be replaced with an aromatic dicarboxylic acid component. The film obtained by adding the polyester (aromatic aliphatic polyester) thus obtained to the polylactic acid polymer is particularly excellent in impact resistance and has a characteristic that it is not easily broken even after being thermally contracted. Examples of the aromatic dicarboxylic acid include isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-biphenyldicarboxylic acid. These can be used alone or in admixture of two or more.

  Typical examples of the aliphatic polyester-based resin include polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polycaprolactone (PCL), polyhydroxybutyric acid and the like. Among these, PBS, PCL, and a mixture thereof are preferably used.

  The weight average molecular weight of the aliphatic polyester resin is not particularly limited, but is preferably 5000 to 100,000, more preferably 10,000 to 50,000, from the viewpoint of mechanical properties and melt viscosity.

  When the aliphatic polyester-based resin is contained in the A layer, the content in the A layer is preferably 10 to 50% by weight, more preferably 10 to 40% by weight, from the viewpoint of controlling the melt viscosity within the preferable range of the present invention. %. Moreover, when content of aliphatic polyester exceeds 50 weight%, transparency may fall.

  The aromatic polyester-based resin may be any polyester that includes an aromatic ring in the structural unit, such as dicarboxylic acid containing an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, ethylene glycol, 1 , 3-propanediol, 1,4-butanediol, and other polymers, copolymers or mixtures thereof by condensation reaction of diols. Specifically, although not particularly limited, polyethylene terephthalate (PET), CHDM copolymerized PET using 1,4-cyclohexanedimethanol (CHDM) as a copolymerization component, adipic acid or isophthalic acid as an acid component is added. Particularly preferred are acid-modified PET and PET in which diethylene glycol or neopentyl glycol is added as a diol component, from the viewpoints of cost, productivity, and the like. The proportion of CHDM copolymerization is preferably 10 to 40 mol%, more preferably 15 to 20 mol%, relative to ethylene glycol. By copolymerizing CHDM at the above ratio, the polyester resin becomes amorphous, which is preferable because adhesion between layers is increased.

  In addition, as described above, the A layer of the present invention is composed of a polylactic acid polymer as a main component, as well as the aliphatic polyester resins, aliphatic aromatic polyester resins, and aromatics listed above. The case where a polyester resin is the main component may be used.

  As the polyester resin used in the A layer of the present invention, an existing product can be used. For example, “Lacia 280, 400, 440” manufactured by Mitsui Chemicals, Inc., “Nature Works” (manufactured by Nature Works) ( Polylactic acid-based polymer); polybutylene succinate “Bionore 1003, 1903” manufactured by Showa Polymer Co., Ltd., polybutylene succinate adipate “Bionore 3003” manufactured by Showa Polymer Co., Ltd., manufactured by Mitsubishi Chemical Corporation Polybutylene succinate “GS-Pla” (aliphatic polyester resin); PET “Novapex” manufactured by Mitsubishi Chemical Corporation, PET “Dianite” manufactured by Mitsubishi Rayon Co., Ltd., CHDM copolymerized PET manufactured by Eastman Chemical “Easter Copolyester”, “Embrac” , Aromatic polyester resin) and the like are preferably exemplified in view of controlling the melt viscosity within the preferred range of the present invention.

  In the A layer of the present invention, in addition to the polylactic acid polymer and other polyester resins, other resin components, for example, biodegradable resins such as aliphatic polyester amide, aliphatic polyester ether, aliphatic polyester carbonate, etc. A small amount (for example, about 3 to 20% by weight with respect to the A layer resin) may be added. These resins can be used alone or in combination of two or more.

  Further, when the A layer is used as a central layer having the B layer on both sides (for example, in the case of a B / A / B type two-layer three-layer configuration), the adhesion between the A layer and the B layer is improved. For the purpose or from the viewpoint of cost reduction and industrial waste reduction, it is preferable to add the recovered raw material within a range not impairing the action or effect of the present invention. Here, the recovered material is a recycled material consisting of non-product parts before and after commercialization, film edges, etc., residual parts when product films are collected from intermediate products, film waste such as non-standard products, and polymer waste. (However, it is limited to those resulting from the production of the laminated film of the present invention). For this reason, when a collection | recovery raw material is included, the A layer contains the polystyrene-type resin used for the B layer. In this case, the added amount of the recovered raw material is preferably 10 to 40% by weight, more preferably 20 to 30% by weight, based on the total weight of the A layer, from the viewpoint of transparency. If the addition amount is less than 10% by weight, the effects of improving extrusion suitability and moldability may not be obtained, and if it exceeds 40% by weight, the transparency may be lowered. Since the recovered raw material is preferably used for the central layer, when the B layer is the central layer, it is preferable to add the recovered raw material to the B layer.

  The layer A of the present invention may contain other additives such as a lubricant, a filler, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a colorant and the like as necessary. Good.

[B layer (polystyrene resin layer)]
The B layer of the present invention comprises a polystyrene resin as a main component. The polystyrene resin used for the B layer is not particularly limited as long as it satisfies the relationship of the melt viscosity described later. Examples of the constituent monomer include styrene, α-methylstyrene, m-methylstyrene, and p-methylstyrene. , P-ethyl styrene, p-isobutyl styrene, p-t-butyl styrene, chloromethyl styrene and the like are not particularly limited as long as the resin contains one or more styrenic monomers.

  Examples of such polystyrene resins include general polystyrene (GPPS), which is a homopolymer of styrene, a homopolymer or copolymer of styrene monomers; a mixture of polystyrene and synthetic rubber (for example, polybutadiene or polyisoprene), High impact polystyrene (HIPS) with styrene grafted on synthetic rubber; styrene monomers such as styrene and diene such as butadiene and isoprene, such as styrene-butadiene-styrene (SBS) block copolymer A styrene-conjugated diene copolymer, which is a copolymer (particularly a block copolymer) composed of a styrene monomer (conjugated diene); a copolymer of a styrene monomer and a (meth) acrylate monomer Styrene-polymerizable unsaturated carboxylic acid ester copolymer which is a polymer; styrene-conjugated diene-polymerizable A carboxylic acid ester copolymer; a rubbery elastic body is dispersed in a continuous phase of a copolymer of a styrene monomer and a (meth) acrylic acid ester monomer; Examples thereof include transparent and high impact polystyrene (graft TIPS) obtained by graft polymerization of a polymer.

  Examples of the conjugated diene used in the styrene-conjugated diene copolymer include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, and the like. , 3-pentadiene, 1,3-hexadiene, chloroprene and the like. Among these, a styrene-butadiene copolymer using 1,3-butadiene as a conjugated diene is particularly preferable. The form of copolymerization is not particularly limited, but a block copolymer is preferable, and styrene block (S) -conjugated diene block (D) type, SDS type, DSD type, S type. -DSD type etc. are mentioned. In the styrene-conjugated diene copolymer, the styrene content is preferably about 55 to 95% by weight (conjugated diene content: 5 to 45% by weight).

  As the styrene-butadiene copolymer, a styrene-butadiene-styrene (SBS) block copolymer is preferable. In the styrene-butadiene block copolymer, the styrene content is preferably 65 to 90% by weight (butadiene content: 10 to 35% by weight), more preferably 75 to 88% by weight (butadiene content: 12 to 25% by weight). %). The melt flow rate (MFR) (JIS K 7210: temperature 200 ° C./load 49 N) of the styrene-butadiene block copolymer is preferably 1 to 20 g / 10 minutes, more preferably 3 to 10 g / 10 minutes. .

Examples of the polymerizable unsaturated carboxylic acid ester used in the styrene-polymerizable unsaturated carboxylic acid ester copolymer include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, ( (Meth) acrylic acid alkyl esters (especially (meth) acrylic acid C _1-10 alkyl esters) such as isobutyl acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate; dimethyl fumarate, Examples thereof include fumaric acid mono- or diesters such as diethyl fumarate; maleic mono- or diesters such as dimethyl maleate and diethyl maleate; itaconic mono- or diesters such as dimethyl itaconate and diethyl itaconate. Among these, methyl acrylate and methyl methacrylate are preferably used because of excellent transparency. In addition, (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms (for example, about 4 to 10 carbon atoms) such as butyl acrylate or butyl methacrylate is stored at a natural heat shrinkage (25 to 35 ° C.). Is preferable because it contributes to a reduction in the shrinkage rate. These polymerizable unsaturated carboxylic acid esters can be used alone or in admixture of two or more. The styrene content in the styrene-polymerizable unsaturated carboxylic acid ester copolymer is preferably 50 to 98% by weight. More preferably, it is 60 to 95 weight%, More preferably, it is 70 to 90 weight%. Here, “(meth) acrylic acid” refers to “acrylic acid and / or methacrylic acid”.

  Examples of the conjugated diene and polymerizable unsaturated carboxylic acid ester copolymer used in the styrene-conjugated diene-polymerizable unsaturated carboxylic acid ester copolymer include the compounds described above. In the styrene-conjugated diene-polymerizable unsaturated carboxylic acid ester copolymer, the styrene content is 50 to 98% by weight, the conjugated diene content is 1 to 45% by weight, and the polymerizable unsaturated carboxylic acid ester copolymer is contained. The amount is preferably 1 to 45% by weight. More preferably, the styrene content is 60 to 90% by weight, the conjugated diene content is 5 to 35% by weight, the polymerizable unsaturated carboxylic acid ester copolymer content is 5 to 35% by weight, and still more preferably the styrene content. Is 65 to 80% by weight, conjugated diene content is 5 to 25% by weight, and polymerizable unsaturated carboxylic acid ester copolymer content is 5 to 25% by weight.

  Among the polystyrene resins used in the B layer of the present invention, from the viewpoint of controlling the melt viscosity within the preferred range of the present invention, among them, styrene-butadiene-styrene block copolymer (SBS), styrene-butadiene-isoprene. A copolymer (SBIS), a styrene / butadiene / acryl blend polymer (St / Bd / Ac) and the like are particularly preferred. These polystyrene resins can also be used as commercially available products, "Asaflex 825" manufactured by Asahi Kasei Chemicals Co., Ltd., "K-resin" manufactured by Philips Co., Ltd. Asaflex Chemicals Co., Ltd. “Asaflex 1100” (above, SBIS); PS Japan Co., Ltd. “SP100” (above, St / Bd / Ac) is available on the market.

  Although the weight average molecular weight of the polystyrene-type resin used for B layer of this invention is not specifically limited, 5000 to 100,000 are preferable from a viewpoint of mechanical characteristics and melt viscosity, More preferably, it is 10,000 to 50,000.

[Melt viscosity characteristics of A layer resin and B layer resin]
The difference (absolute value) in melt viscosity at 190 ° C. between the A layer resin and the B layer resin of the present invention is 850 Pa · s or less (for example, 0 to 850 Pa · s), more preferably 600 Pa · s or less, and still more preferably Is 300 Pa · s or less. The melt viscosity was measured according to JIS K 7199 using a capillary rheometer (for example, “Twin Capiro” manufactured by Rosand), and a value at a shear rate of 1000 sec ⁻¹ was used. When the difference in melt viscosity between the A layer resin and the B layer resin exceeds 850 Pa · s, the flow characteristics of the A layer and the B layer when the A layer and the B layer are laminated by coextrusion are different. The reason is that the stresses remaining in the A layer and the B layer are different, but the interlayer strength between the A layer and the B layer tends to decrease.

  The difference (absolute value) of the slope of the temperature-melt viscosity straight line at 180 to 240 ° C. between the A layer resin and the B layer resin of the present invention is 10 Pa · s / ° C. or less (for example, 0 to 10 Pa · s / ° C.). The pressure is preferably 7 Pa · s / ° C. or less, more preferably 5 Pa · s / ° C. or less. The slope of the temperature-melt viscosity line represents the temperature dependence of the melt viscosity, and the measurement method and shear rate are the same as the melt viscosity. If the difference in temperature dependence of the melt viscosity is greater than 10 Pa · s / ° C, the flow behavior of the A layer resin and the B layer resin with respect to the temperature change in the melt extrusion process will be different. Even in the case where the values are close to each other, the co-extrusion results in a decrease in interlayer strength due to the difference in flow characteristics between the A layer and the B layer.

  Although there was a tendency that high interlaminar strength could not be obtained even if polyester resin and polystyrene resin were laminated by coextrusion, etc., this generally differs in solubility parameter (SP) value of polyester resin and polystyrene resin. It was thought that this was due to poor compatibility. However, in the present invention, even if the polyester resin and the polystyrene resin having different SP values are used, the adhesive layer is selected by selecting a combination having a close melt flow property in the extrusion temperature region of the coextrusion as described above. It was found that excellent interlayer strength could be obtained without providing. This is considered to be because, in the lamination between different polymers, the influence of the difference in flow characteristics at the time of lamination is larger than the influence of the compatibility between the polymers on the interlayer strength. That is, when laminating polymers with significantly different flow characteristics during coextrusion, the degree of orientation of the molecular chains of the polyester resin layer and polystyrene resin layer of the laminated film after extrusion is greatly different, so that there is distortion between the film layers. It is presumed that it is easy to peel off when heat or stretching is applied later.

  The melt viscosity (absolute value) at 190 ° C. of the A layer resin of the present invention is not particularly limited, but is 200 to 1125 Pa · s, more preferably 250 to 750 Pa · s. The melt viscosity (absolute value) at 190 ° C. of the B layer resin is not particularly limited, but is 50 to 500 Pa · s, more preferably 110 to 330 Pa · s. When the melt viscosity exceeds the above range, extrusion characteristics such as fluidity are poor, and there are cases where die streaks are generated and the lamination thickness is not uniform. Moreover, when it is less than the above range, the viscosity is too low, and sheeting or uniform lamination may be difficult. The melt viscosity can be controlled by the molecular weight or the like.

  The slope (absolute value) of the temperature-melt viscosity straight line at 180 to 240 ° C. of the layer A resin of the present invention is not particularly limited, but is 0 to 15 Pa · s / ° C., more preferably 0 to 9 Pa · s / ° C. It is. The slope (absolute value) of the temperature-melt viscosity straight line at 180 to 240 ° C. of the B layer resin is not particularly limited, but is 0 to 10 Pa · s / ° C., more preferably 0 to 7 Pa · s / ° C. is there. If the slope of the temperature-melt viscosity line, that is, the temperature dependence of the melt viscosity is larger than the above range, it may be sensitive to temperature and difficult to control. The temperature dependence of these melt viscosities can be controlled by blending materials having different melt viscosities.

[Laminated film]
The laminated film of the present invention has at least one A layer and B layer described above. A combination of resins used for the A layer and the B layer can be selected from the above-described A layer resin and B layer resin so as to satisfy the above-described melt viscosity and temperature dependency of the melt characteristics. Among them, when used as a shrink film, it is preferable that the B layer contains SBS and / or SBIS as a main component and the A layer contains a polylactic acid polymer or a mixed polymer of a polylactic acid polymer and PBS as a main component. From the viewpoint of green plastic, it is preferable that a biodegradable resin such as a polylactic acid polymer, PBS, or PBSA is contained in an amount of 50% by weight or more of the entire film.

  As a method for laminating the laminated film of the present invention, a known method can be used. However, since the A layer and the B layer of the present invention can exhibit high interlayer strength without using an adhesive layer, an adhesive layer is used. For example, co-extrusion is preferred.

  The general method of coextrusion is a method in which the A layer raw material and the B layer raw material are charged into a plurality of extruders each set to a predetermined temperature and coextruded from a T die, a circular die, or the like. At this time, it is preferable to use a manifold or a merging block to form a predetermined laminated structure. Further, if necessary, the supply amount may be adjusted using a gear pump, and it is preferable to remove foreign substances using a filter because film tearing can be reduced. The extrusion temperature varies depending on the type of the A layer raw material and the B layer raw material to be used, and is not particularly limited. However, the molding temperature region of the A layer raw material and the molding temperature region of the B layer raw material are preferably close to each other, For example, in the case of a polylactic acid polymer, 180 to 220 ° C is preferable, and in the case of a polystyrene resin, 180 to 240 ° C is preferable. An unstretched laminated film (sheet) can be obtained by quenching the coextruded polymer using a cooling drum or the like.

  The laminated structure of the laminated film of the present invention varies depending on the type and use of the A layer resin and B layer resin, and is not particularly limited. However, the A / B two-type two-layer structure, B / A / B, and A / B A / A two-type three-layer structure is preferable. Among these, for example, when a resin mainly composed of a polylactic acid polymer is used as the A-layer resin, B / A / B2 types are used from the viewpoint of improving solvent resistance and ink followability when used as a shrink label. A three-layer configuration is preferred. For example, the two B layers in the case of the B / A / B two-type three-layer configuration may be the same film layer, but have different compositions as long as the polyester resin is a main component. Also good. Further, the laminated film of the present invention may have other layers as long as it includes a laminated film in which the A layer and the B layer are directly laminated. For example, printing ink layer / B layer / A laminated structure such as an A layer / B layer may be used.

  The laminated film of the present invention may be non-oriented or uniaxially or biaxially oriented depending on the application, but is particularly difficult to delaminate even when stretched. Thus, it is preferable that the film is oriented uniaxially or biaxially by stretching. Among them, for example, when the laminated film of the present invention is used for a shrink label, it is suitable because it is difficult to delaminate even during shrinkage, and the shrink film used for the label is suitable for at least one of the A layer and B layer in the film. Each layer is preferably oriented in the same direction. When only one of the A layer and the B layer is oriented, or when all the layers in the film are non-oriented, good shrinkage cannot be obtained. Among them, it is particularly preferable that all the film layers are oriented. The orientation is not particularly limited, such as uniaxial orientation or biaxial orientation, but substantially uniaxial orientation in the width direction, which is strongly oriented in the film width direction (direction that becomes the circumferential direction when the label is formed into a cylinder) is preferable. Further, it may be a substantially uniaxially oriented film in the longitudinal direction that is strongly oriented in the longitudinal direction (direction perpendicular to the width direction) of the film.

  An oriented film such as the uniaxial orientation or the biaxial orientation can be produced by stretching an unstretched laminated film. Stretching can be selected according to the desired orientation, and may be biaxial stretching in the longitudinal direction (longitudinal direction; MD direction) and width direction (transverse direction; TD direction), or uniaxial stretching in the longitudinal direction or width direction. But you can. The stretching method may be any of a roll method, a tenter method, and a tube method. The stretching conditions vary depending on the type of the A layer resin and B layer resin to be used, and are not particularly limited. In general, it is preferably performed at a magnification of about 1.01 to 8 times in the range of 70 to 110 ° C. . For example, in the case of a laminated film for shrink film use having an A layer mainly composed of a polylactic acid-based polymer, at a temperature of about 80 to 110 ° C., for example, 1.01 to 1. After stretching to about 5 times (preferably 1.05 to 1.3 times), it is preferable to stretch about 2 to 8 times (preferably 3 to 6 times) in the width direction.

  The thickness of the laminated film of the present invention varies depending on the application and is not particularly limited, but is generally preferably 10 to 150 μm. For example, in the case of shrink label use, 10 to 100 μm is preferable, more preferably 20 to 80 μm, and still more preferably 30 to 60 μm.

  Further, the thicknesses of the A and B layers of the present invention vary depending on the types of the A layer resin and the B layer resin, the laminated structure, the use of the laminated film, and the like, but are not particularly limited, but generally 4 to 80 μm is preferable.

  For example, when the laminated film is a shrink film composed of an A layer mainly composed of a polylactic acid polymer and a B layer mainly composed of an SBS resin, the thickness of the A layer is preferably 5 to 60 μm, more preferably Is 15-40 μm. The thickness of the B layer is preferably 4 to 40 μm, more preferably 10 to 20 μm. The thickness ratio (A layer / B layer) of B layer (sum of all B layer thicknesses in the film) to A layer (sum of all A layer thicknesses in the film) is 80/20 to 20/80. Is preferred. With respect to the above range, when the A layer is thick, the heat shrinkage rate is high and the workability may be reduced, or the heat shrinkage stress may be small and the followability of the print layer may be inferior. In contrast, when the B layer is thicker than the above range, the production conditions move to a side where productivity is relatively lowered due to a decrease in heat shrinkage rate or an increase in processing temperature. In addition, the load on the environment is relatively large.

  The A layer and the B layer in the laminated film of the present invention have excellent interlayer strength. The interlayer strength between the A layer and the B layer is preferably 2.5 (N / 20 mm) or more, more preferably 3.5 (N / 20 mm) or more, and still more preferably 4.0 (N / 20 mm) or more. is there. When the interlaminar strength is less than 2.5 (N / 20 mm), the film layers may be peeled off after processing or commercialization, resulting in decreased productivity or a cause of complaints.

  The use of the laminated film of the present invention is not particularly limited, but plastic labels such as shrink labels, in-mold labels, tack labels, roll labels (wrap-type glued labels), and heat-sensitive adhesive labels; sheet molding containers; molding cap seals Etc.

  As an example of a preferable use of the laminated film of the present invention, a shrink film for a shrink label using a layer A mainly composed of a polylactic acid polymer and a layer B mainly composed of a polystyrene resin such as an SBS resin can be cited. It is done. A shrink film using polylactic acid, a biodegradable and plant-derived material, is useful from the viewpoint of environmental protection. On the other hand, as an inherent property of polylactic acid, heat shrinkage occurs rapidly. It had a drawback that it was difficult to control the shrinkage behavior. In contrast, in the present invention, by shrinking a heat-shrinkable polystyrene-based resin, heat shrinkage is performed so that high productivity, workability, and beautiful finish can be achieved at the time of shrink processing. The speed can be controlled.

  Also, since the polylactic acid-based polymer has a small heat shrinkage stress, when used alone, the print layer is not suitable for shrinking when the print layer is thick, such as when the print layer is thick or contains a lot of inorganic pigments. There was a drawback in that the film did not follow the heat shrinkage of the film well and the finish was lowered. In contrast, in the present invention, by using a polystyrene-based resin having a large heat shrinkage stress for the B layer, the heat shrinkage stress is improved, and excellent shrink processing followability is obtained.

  When the laminated film of the present invention is used as the shrink film, the thermal shrinkage rate in the main orientation direction (mainly in the direction subjected to the stretching treatment) at 90 ° C. for 10 seconds (warm water treatment) of the laminated film is 30% or more. Preferably, it is 40 to 85%, more preferably 50 to 85%. When the heat shrinkage rate is less than 30%, the shrinkage is not sufficient in the process of closely attaching the label to the container with heat, so that it becomes difficult to follow the shape of the container, and the finish is particularly poor for a container having a complicated shape. Sometimes. In addition, when using as uses other than a shrink film, the thermal contraction rate other than the said range can be suitably selected according to a use.

  When the laminated film of the present invention is used as a transparent film, the transparency (haze value: JIS K 7105) of the laminated film is preferably 10 or less, more preferably 5.0 or less. When the haze value exceeds 10, the inside of the shrink film (the side that becomes the container side when the label is attached to the container) is printed, and in the case of a shrink label that shows printing through the film, , Printing may become cloudy and decorative properties may be reduced. However, even if the haze exceeds 10, it can be sufficiently used in applications other than the above-mentioned applications that show printing through a film.

  When the laminated film of the present invention is used as the above shrink film, the compressive strength (thickness 40 μm: JIS P 8126) of the laminated film is preferably 2N or more, more preferably 3.5N or more, and further preferably 5N or more. . In addition, when the compressive strength is less than 2N, the film becomes weak, and the label is easily bent in the process of attaching the cylindrical shrink label to the container.

  When the laminated film of the present invention is used as the above-described shrink film, the storage stability of the laminated film (natural shrinkage ratio: shrinkage ratio after 30 days at 30 ° C.) is preferably 2% or less, more preferably. Is 1.5% or less, more preferably 1% or less. If the natural shrinkage of the film exceeds 2%, the label will be manufactured, and will undergo large deformation (shrinkage) during storage before processing, making subsequent processing difficult and reducing productivity. Defective mounting to containers, etc. occurs, causing complaints.

  When the laminated film of the present invention is used as the shrink film, the shrinkage stress (85 ° C.) of the laminated film is preferably 1 to 13 MPa, more preferably 2 to 8 MPa, and further preferably 2 to 5 MPa. In the case where the shrinkage stress is less than 1 MPa, the shrinkage followability of the printed layer is lowered, and the finish may be lowered. If it exceeds 13 MPa, the container may be deformed or the contents may overflow when opened.

[Plastic label (shrink label)]
When the laminated film of the present invention is used as a plastic label such as a shrink label, a printed layer (for example, a layer displaying a product name, an illustration, handling precautions, etc.) is provided on at least one surface of the laminated film. The printing layer is formed by applying printing ink. The coating method may be provided by in-line coating that is applied during the production process of the laminated film (for example, after unstretched or longitudinally uniaxially stretched), or may be provided by offline coating that is applied after film formation. Although not particularly limited, off-line coating by a known and commonly used printing method is preferable from the viewpoint of productivity, workability, and the like. As a printing method, a conventional method can be used, but gravure printing or flexographic printing is most preferable. The printing ink used for forming the printing layer is made of, for example, a pigment, a binder resin, a solvent, and other additives. Although it does not specifically limit as said binder resin, For example, resin, such as an acrylic type, a urethane type, a polyamide type, a vinyl chloride-vinyl acetate copolymer type, a cellulose type, a nitrocellulose type, can be used individually or in combination. As the pigment, white pigments such as titanium oxide (titanium dioxide), indigo pigments such as copper phthalocyanine blue, carbon black, aluminum flakes, mica (mica), and other colored pigments can be selected and used in accordance with the application. In addition, extender pigments such as alumina, calcium carbonate, barium sulfate, silica, and acrylic beads can also be used as pigments for the purpose of adjusting gloss. Examples of the solvent include organic solvents such as toluene, xylene, methyl ethyl ketone, ethyl acetate, methyl alcohol, ethyl alcohol, and isopropyl alcohol, and commonly used solvents such as water.

The printing layer of the present invention is not particularly limited, but may be an active energy ray-curable resin layer such as visible light, ultraviolet light, or electron beam. This is effective for preventing deformation of the film due to excessive heat. For example, in the case of curing by ultraviolet rays, an ultraviolet ray (UV) lamp, an ultraviolet LED, an ultraviolet laser, or the like is used, ultraviolet rays having a wavelength of 300 to 460 nm (or near ultraviolet rays), irradiation intensity of 150 to 1000 mJ / cm ² , irradiation time of 0.1. It can be performed under about 3 seconds. In the case of an active energy ray-curable printing layer, it is preferable to add a photopolymerization initiator such as a photoradical polymerization initiator and a photocationic polymerization initiator to the printing ink in addition to the above. Examples of the photo radical polymerization initiator include benzophenone, thioxanthone, acetophenone, and acylphosphine polymerization initiators. Examples of the photo cationic polymerization initiator include diazonium salts, diaryl iodonium salts, and triaryls. Examples include sulfonium salts, silanol / aluminum complexes, sulfonate esters, and imide sulfonates. Although content of these photoinitiators is not specifically limited, 0.5-7 weight% is preferable with respect to the whole printing ink, More preferably, it is 1-5 weight%. Furthermore, you may add a sensitizer to printing ink as needed from a viewpoint of improving production efficiency. In this case, the sensitizer is, for example, an amine-based sensitizer such as an aliphatic, aromatic amine, piperidine, or other amine containing a nitrogen in the ring; an allyl-based or o-tolylthiourea-based urea-based sensitizer; sodium diethyl Sulfur compound sensitizers such as dithiophosphate; Anthracene sensitizers; Nitrile sensitizers such as N, N-disubstituted p-aminobenzonitrile compounds; Phosphorus compound systems such as tri-n-butylphosphine Sensitizers; nitrogen compound sensitizers such as N-nitrosohydroxylamine derivatives and oxazolidine compounds; chlorine compound sensitizers such as carbon tetrachloride. Although it does not specifically limit as content of a sensitizer, 0.1 to 5 weight% is preferable with respect to the whole printing ink, Most preferably, it is 0.3 to 3 weight%.

  When the laminated film of the present invention is used for a plastic label, in addition to the printing layer, for example, a coating layer, a resin layer, an anchor coat layer, a primer coat layer, an adhesive layer, an adhesive resin layer, etc. may be provided. A layer such as a nonwoven fabric, paper, or a metal thin film may be provided as necessary.

  Although the thickness of the printing layer of this invention is not specifically limited, For example, it is about 0.1-10 micrometers. If the thickness is less than 0.1 μm, it may be difficult to provide a uniform printing layer, and partial “blur” may occur, resulting in a loss of decorativeness or printing as designed. May be difficult. In addition, when the thickness exceeds 10 μm, a large amount of printing ink is consumed, which increases the cost, makes it difficult to apply uniformly, makes the printed layer brittle and easily peels off. . Moreover, the rigidity of a printing layer becomes high and it may become difficult to follow the shrinkage | contraction of a film at the time of shrink processing.

  The plastic label using the laminated film of the present invention (especially a shrink label) is, for example, a cylindrical label of a type that is sealed in a cylinder by sealing both ends of the label with a solvent or an adhesive, and is attached to a container. After affixing to a container and winding a label, it can use suitably as a label of the winding system which piles up the other end on one end and makes it cylindrical. The center seal strength of this cylindrical label is preferably 2.5 (N / 20 mm) or more. When the seal strength is less than 2.5 (N / 20 mm), the seal part is peeled off after the processing step or commercialization, and the productivity is lowered or the label is dropped.

  The plastic label using the laminated film of the present invention is attached to a container and used as a labeled container. Such containers include, for example, soft drink bottles such as PET bottles, milk bottles for home delivery, food containers such as seasonings, alcohol beverage bottles, pharmaceutical containers, chemical containers such as detergents, sprays, cups, etc. This includes noodle containers. The shape of the container includes various shapes such as a cylindrical shape, a square bottle, and a cup type. Further, the material of the container includes plastic such as PET, glass, metal and the like.

  Below, although an example of the process which mounts the plastic label (shrink label) using the laminated | multilayer film of this invention to a container is shown, a manufacturing method is not limited to this.

  After printing, the plastic label using the laminated film of the present invention is slit into a predetermined width, wound into a roll, and is used for processing after a plurality of labels are formed in a continuous form in the longitudinal direction. It is done. While feeding one of these rolls, the film is formed into a cylindrical shape so that the main stretching direction (for example, the width direction) of the film is in the circumferential direction. Specifically, a long plastic label is formed into a cylindrical shape, and a solvent or adhesive (such as tetrahydrofuran (THF)) is formed on one side edge of the label in a band shape in the longitudinal direction with a width of about 2 to 4 mm. (Solvent, etc.) is applied to the inner surface, rounded into a cylindrical shape, and the coated portion of the solvent, etc. is superposed at a position of 5 to 10 mm from the other side edge and bonded to the outer surface of the other side edge (center seal) ) To obtain a long cylindrical label continuous body (long cylindrical label). In the case where a perforation for label excision is provided, a perforation having a predetermined length and pitch is formed in the longitudinal direction. The perforation can be applied by a conventional method (for example, a method of pressing a disk-shaped blade having a cut portion and a non-cut portion repeatedly formed around it, a method using a laser, or the like). The process stage for perforating can be appropriately selected after the printing process and before and after the cylindrical processing process.

  Further, after cutting the long cylindrical label, it is attached to a predetermined container, and the container is manufactured by shrinking the label by heat treatment and closely contacting the container. Specifically, the rolled cylindrical label is supplied to an automatic label mounting device (shrink labeler), cut into a required length, and formed into a cylindrical label. The container is externally fitted in a container filled with an object, passed through a hot air tunnel or steam tunnel at a predetermined temperature, or heated and contracted by radiant heat such as infrared rays, and closely adhered to the container to obtain a labeled container. Examples of the heat treatment include treatment with steam at 80 to 100 ° C. (passing through a heating tunnel filled with steam and steam).

[Methods for measuring physical properties and methods for evaluating effects]
(1) Melt viscosity (capillary rheometer method), temperature-slope of melt viscosity straight line (temperature dependence of melt viscosity)
Using a capillary rheometer “Twin Capilo” manufactured by Rosand, melt viscosity at a melting temperature of 190 ° C. and a shear rate of 1000 sec ⁻¹ was measured according to JIS K 7199.
The temperature dependence of the melt viscosity is the same as described above, and the melt viscosity at a melt temperature of 180 ° C., 200 ° C., 220 ° C. and 240 ° C. (shear rate 1000 sec ⁻¹ ) is obtained, and the slope of the approximate straight line by the least square method And the slope of the temperature-melt viscosity straight line at 180 to 240 ° C. (temperature dependence of melt viscosity) (Pa · s / ° C.).
The difference in the melt viscosity between the A layer resin and the B layer resin (absolute value), the difference in the temperature dependence of the melt viscosity between the A layer resin and the B layer resin (difference in the slope of the straight line) (absolute value) evaluated.
(Difference in melt viscosity)
300 (Pa.s) or less: ○
More than 300 (Pa.s) and 850 (Pa.s) or less: Δ
Greater than 850 (Pa.s): ×
(Difference in temperature dependence)
5 (Pa · s / ° C) or less: ○
Greater than 5 (Pa · s / ° C.) and 10 (Pa · s / ° C.) or less: Δ
Greater than 10 (Pa · s / ° C): ×

(2) Film interlayer strength (T-type peeling)
Evaluation was performed using laminated films (thickness 50 μm) obtained in Examples and Comparative Examples.
A strip-shaped sample (160 mm (laminated film width direction) × 20 mm (laminated film longitudinal direction)) having a width of 20 mm in the laminated film longitudinal direction (film forming direction) and long in the laminated film width direction was collected. Hereinafter, the sample width direction refers to the longitudinal direction of the laminated film.
Using the long side direction of the sample (width direction of the laminated film) as the measurement direction, a T-type peel test (based on JIS K 6854-3) is performed under the following conditions, and the peel load between the A layer and the B layer is measured. did.
The average value of the peeling load was defined as the interlayer strength (N / 20 mm), and evaluated according to the following criteria.
4.0 N / 20 mm or more: Excellent interlayer strength (◎)
3.5 N / 20 mm or more and less than 4.0 N / 20 mm: Good interlayer strength (◯)
2.5N / 20mm or more, less than 3.5N / 20mm: Usable level (△)
Less than 2.5N / 20mm: Interlayer strength is inferior (x)
(Measurement condition)
Measuring device: Autograph manufactured by Shimadzu Corporation (AG-IS: load cell type 500N)
Temperature and humidity: Temperature 23 ± 2 ° C, humidity 50 ± 5% RH (JIS K 7000 standard temperature state 2nd grade)
Initial chuck interval: 40 mm
Sample width: 20mm
Number of tests: 3 times Tensile speed: 200 mm / min Stroke: 150 mm (If it broke, it was interrupted and data up to that point was obtained.)
First half deletion range: 50mm
Sensitivity: 1

(3) Thermal shrinkage (90 ° C for 10 seconds)
From the laminated films obtained in Examples and Comparative Examples, a rectangular sample piece having a length of 120 mm (mark interval 100 mm) in the measurement direction (main orientation direction: longitudinal direction or width direction of the laminated film) and a sample width of 5 mm was obtained. create.
The sample piece is heat-treated in warm water at 90 ° C. for 10 seconds (under no load), the difference between the marked lines before and after the heat treatment is read, and the thermal contraction rate is calculated by the following formula.
Shrinkage rate (%) = (L ₀ −L ₁ ) / L ₀ × 100
L ₀ : Size of sample before heat treatment (main orientation direction: longitudinal direction or width direction)
L ₁ : Sample dimensions after heat treatment (same direction as L ₀ )
When the shrinkage rate in the main orientation direction was 30% or more, it was judged that the shrinkage property was good (◯) when used as a shrink film, and when it was less than 30%, the shrinkage property was poor (x).
In the examples, the main orientation direction was the width direction of the laminated film.

(4) Transparency (haze value)
Measurement is performed according to JIS K 7136. In terms of the thickness of 50 μm, the following criteria were used for evaluation.
5.0 or less: Excellent transparency for label use (◎).
Greater than 5.0 and 10 or less: Good transparency for label use (◯).
Greater than 10: Transparency is insufficient for a label application that shows printing through a film (Δ).

(5) Film layer thickness and printing layer thickness The film thickness was measured using a dial gauge.

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. Details of the resins used in each example and comparative example (Table 2) are shown in Table 1. Examples 1 to 5 and Example 11 are referred to as “reference examples”.

Example 1
Polylactic acid resin (“Lacia H-280” manufactured by Mitsui Chemicals, Inc.) (PLA1) was used as the A layer resin. As the B layer resin, a styrene-butadiene-styrene (SBS) block copolymer (“Clearene 431L” manufactured by Denki Kagaku Kogyo Co., Ltd.): number average molecular weight (Mn): 130,000 (SBS) was used.
The PLA1 was charged into the extruder a heated to 180 ° C., and the SBS was charged into the extruder b heated to 180 ° C. Melt extrusion was performed using the above two extruders. The resin extruded from the extruder a is merged using a merge block so that the resin extruded from the extruder b becomes a laminated portion on both sides of the substrate layer, and extruded from the T die, and then on the casting drum. Was quickly cooled to obtain a two-layer / three-layer unstretched film of laminated part (SBS) / base layer part (PLA1) / laminated part (SBS). The lamination thickness ratio of the unstretched film was lamination part / base layer part / lamination part = 1/1/1.
Next, the unstretched film is stretched at a stretching temperature of 100 ° C. by 1.3 times in the longitudinal (longitudinal) direction and 4.5 times in the width (transverse) direction, so that it is mainly uniaxial (width direction). A biaxially stretched laminated film (shrink film) was obtained that shrunk. The total thickness of the film was 50 μm (layer thickness ratio: 1/1/1). The longitudinal stretching was performed when the unstretched film after extrusion was wound, and the lateral stretching was performed by stretching in one direction with a biaxial stretching machine.

Examples 2-17
As shown in Tables 1 and 2, the A layer resin and the B layer resin were changed, and a biaxially stretched laminated film (shrink film) was obtained in the same manner as in Example 1.
In Examples 4, 9, 10, 12-14, 16, and 17, the resin melting temperature was 190 ° C., and in Example 11, 210 ° C. In Example 3, the stretching temperature was 110 ° C.

Comparative Example 1
As shown in Tables 1 and 2, a biaxially stretched laminated film (shrink film) was prepared in the same manner as in Example 1, using resins having greatly different melt viscosities and temperature dependence as the A layer resin and the B layer resin. Obtained. The melting temperature of the resin was 190 ° C.

  As shown in Table 2, laminated films (Examples) made of a polyester resin and a polystyrene resin that satisfy the ranges specified in the present invention for the melt viscosity and the temperature dependency thereof had good interlayer strength. On the other hand, when the melt viscosity of the polyester-based resin and the polystyrene-based resin or the temperature dependency thereof is outside the range defined in the present application (Comparative Example), sufficient interlayer strength cannot be obtained.

Claims (6)

A film layer (layer A) comprising a polylactic acid-based polymer as a main component and a polyester-based resin other than the polylactic acid-based polymer which is polybutylene succinate and / or polybutylene succinate adipate, and styrene-butadiene- A film layer (B ) having a polystyrene resin as a main component, which is a styrene block copolymer (SBS), a styrene-butadiene-isoprene copolymer (SBIS), or a styrene / butadiene / acryl blend polymer (St / Bd / Ac). Layer) at least one layer, and the A layer and the B layer are directly laminated without interposing other layers, and the resin composition (A layer resin) and the B layer constituting the A layer the melt viscosity (capillary rheometer method, shear rate 1000 sec ^-1) at 190 ° C. of the resin composition (B layer resin) constituting the absolute of the difference between Wherein the absolute value of the difference between the gradient of the melt viscosity linear is less than 6.14 Pa · s / ℃ - value is not more than 396 Pa · s, the temperature at 180 to 240 ° C. of A-layer resin and the B layer resin A laminated film.   The laminated film according to claim 1, which has B layers on both sides of the A layer. The content of the polylactic acid polymer in the A layer is 50 to 90% by weight, and the content of the polyester resin other than the polylactic acid polymer in the A layer is 10 to 50% by weight. The laminated film according to 1 or 2. The weight average molecular weight of the polylactic acid polymer is 5,000 to 100,000, and the weight average molecular weight of a polyester resin other than the polylactic acid polymer is 5,000 to 100,000. A laminated film according to 1. The laminated film according to any one of claims 1 to 4, wherein the polystyrene-based resin has a weight average molecular weight of 5,000 to 100,000. The shrink label using the laminated | multilayer film of any one of Claims 1-5.