JP2007130970A - Shrink film, shrink label and container with the label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shrink film which has excellent shrink performance and compressive strength and high interlayer strength between film layers of a laminate, a shrink label which is manufactured from the shrink film at an excellent productivity and a container labeled with the label. <P>SOLUTION: The shrink film has a layer composed of a polyester-based resin at least on one side of a film layer containing 50-90 wt.% of a styrene-butadiene copolymer and 10-30 wt.% of polybutene. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a shrink film having excellent rigidity and shrinkage characteristics and having high interlayer strength, a shrink label, and a container equipped with the label.

  Currently, plastic bottles such as PET bottles and metal bottles such as bottle cans are widely used as containers for beverages such as tea and soft drinks. These containers are often equipped with plastic labels for display, decoration, and functionality. In recent years, water vapor and hot air have been used because of their good trackability and increased display area. A heat-shrinkable plastic film (shrink film) that is made to follow and attach to a container by being shrunk by is widely used.

  The above shrink film has shrinkability to obtain good followability to the container during coating treatment, rigidity (waist strength) to prevent buckling when attaching the label to the container, In view of stable production and supply, storage stability (small natural shrinkage) is required.

  In order to achieve both shrinkage and rigidity, there is known a shrink film made of a laminate having an intermediate layer made of polystyrene resin having good shrinkage and a surface layer made of polyester resin having high rigidity (for example, Patent Documents 1 and 2). However, since the shrink film made of the above laminate is laminated with different materials, the interlayer strength between the film layers is relatively weak. It had the problem of peeling.

  On the other hand, petroleum resins are known as tackifiers that are blended with elastomers such as styrene-butadiene copolymers and exhibit an adhesive effect, and are different from the field of shrink film, but have oil resistance and gas barrier properties. As a purpose, a laminated sheet having a base layer made of polystyrene resin and petroleum resin and a surface layer made of polyester resin derived from cyclohexanedimethanol is known (for example, see Patent Document 3). However, the petroleum resin is expensive because it is expensive. Furthermore, the use of a high molecular weight solid petroleum resin results in poor dispersibility. Increasing the content of petroleum resin to increase the interlaminar strength causes phase separation, resulting in decreased transparency and impact resistance. It had the problem of antinomy.

JP 2002-351332 A JP 2004-170715 A JP 7-290659 A

  An object of the present invention is to provide excellent shrink film and shrink label which have high productivity and beautiful finish without causing deterioration of transparency, and having both shrinkage characteristics and rigidity, and which do not cause trouble due to delamination. And providing a container equipped with the label.

  As a result of intensive studies to achieve the above object, the present inventors have achieved both shrinkability and rigidity by using a film having an intermediate layer composed of a styrene-butadiene copolymer and a laminated portion composed of a polyester resin, Moreover, by adding a specific amount of polybutene to the polystyrene resin, it is possible to obtain an excellent shrink film having high transparency and high interlayer strength between film layers, a shrink label using the shrink film, and a container equipped with the label. The present invention has been completed by finding out what can be done.

  That is, the present invention provides a film layer (B layer) made of a polyester resin on at least one side of a film layer (A layer) containing 50 to 90% by weight of a styrene-butadiene copolymer and 10 to 30% by weight of polybutene. A shrink film is provided.

  Furthermore, this invention provides said shrink film by which A layer and B layer are laminated | stacked without passing through another layer.

  Furthermore, the present invention is a shrink film having an A layer, a B layer, and a C layer composed of a styrene-butadiene copolymer, a polybutene, and a polyester resin, in the order of A layer / C layer / B layer, respectively. The above-described shrink film is provided in which the layers are laminated without any other layers.

  Furthermore, this invention provides the shrink label which provides a printing layer in the surface of at least one of the shrink film of the said invention.

  Furthermore, this invention provides the container with a label with which the shrink label of the said invention was mounted | worn.

  Since the shrink film of the present invention has a high shrinkability, it has a beautiful finish even when mounted on a container having a complicated shape. In addition, the rigidity is high, and even when the label is thinned, there is no trouble such as buckling at the time of mounting, and there is no decrease in productivity due to the occurrence of defective products during processing. Furthermore, delamination is unlikely to occur, and troubles due to delamination in the production process and the market are reduced. Therefore, it is particularly useful as a label used for PET bottles and the like.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the shrink film of the present invention. The shrink film 1 shown in FIG. 1 is composed of three film layers of a base layer portion 3 (A layer) and laminated portions 2 (B layer) on both sides thereof.

  The shrink film of the present invention includes at least two films, a film layer (referred to as A layer) mainly composed of styrene-butadiene copolymer and polybutene, and a film layer (referred to as B layer) mainly composed of polyester resin. Has a layer. Further, if necessary, a film layer made of a styrene-butadiene copolymer, polybutene, and a polyester-based resin and provided as an intermediate layer between the A layer and the B layer (referred to as a C layer) may be included. Among these, the A layer mainly plays a role of exhibiting interlayer strength and shrinkage characteristics (characteristics in which wrinkles are not easily generated due to slow shrinkage) between the A layer and the B layer (when the C layer is not provided). The B layer has a role of imparting shrinkage properties (high shrinkage) and rigidity. When the C layer is provided, the C layer plays a role of increasing the interlayer strength between the film layers without impairing the contractility.

  The laminated structure of the shrink film of the present invention is formed by laminating a B layer on at least one of the A layers. When it consists of only the A layer and the B layer, it may have a two-layer structure composed of A layer / B layer or a three-layer structure composed of B layer / A layer / B layer. From the standpoint of preventing “warping”, a three-layer structure consisting of B layer / A layer / B layer is most preferable. In particular, in order to improve the rigidity of the entire shrink film, it is preferable to provide a high strength film layer (that is, B layer) on the surface layer. Moreover, it is preferable to provide B layer in a surface layer (outermost layer) also from viewpoints, such as solvent resistance and oil resistance. Further, when the C layer is provided, the C layer is provided so as to be positioned between the A layer and the B layer. A five-layer structure consisting of layer / A layer / C layer / B layer is exemplified. Moreover, the structure by which A layer / B layer was provided in at least one of the film layers comprised from a styrene-butadiene block copolymer (SBS) (for example, B layer / A layer / SBS layer, B layer / A layer / SBS layer / A layer / B layer and the like are exemplified). In particular, when the central layer is an SBS layer, a shrink label excellent in economic efficiency and transparency can be achieved. In this case, the A layer plays a role of further improving the interlayer strength between the SBS layer and the B layer. By using the resin composition of the present invention, an excellent interlayer strength can be achieved without an adhesive layer. From the viewpoint of productivity and the like, the above A layer, B layer, C layer and SBS layer are It is preferable that the layers are directly laminated without any other layer such as an adhesive layer. More preferably, it is a lamination by coextrusion.

  The shrink film of the present invention is preferably oriented in at least one direction. In this case, at least the A layer may be oriented, but preferably all the film layers are oriented. If all layers are non-oriented, it is often difficult to achieve the good shrinkage properties, stiffness, and interlayer strength of the present invention.

  The A layer of the shrink film of the present invention contains a styrene-butadiene copolymer and polybutene.

  The styrene-butadiene copolymer used in the A layer of the present invention is a styrene-butadiene block copolymer (SBS). In the case of a random copolymer, the effect of the present invention cannot be obtained. The content of the styrene block in the copolymer is not particularly limited, but is preferably 65 to 90% by weight (butadiene block content: 10 to 35% by weight), more preferably 75 to 88 from the viewpoint of processability. % By weight (butadiene block 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. is there. As the styrene-butadiene block copolymer, “Asaflex” manufactured by Asahi Kasei Chemicals Corporation, “K-resin” manufactured by Philips Co., Ltd., and the like are available on the market.

  The content of the styrene-butadiene copolymer in the A layer of the present invention is 50 to 90% by weight, preferably 70 to 90% by weight, in the resin component of the A layer. When the content of styrene-butadiene is less than 50% by weight, the heat shrinkage rate is lowered, so that workability is lowered.

  The polybutene used for the A layer of the present invention is obtained by polymerizing 1-butene, 2-butene and the like. Further, although not particularly limited, from the viewpoint of stabilization, the polybutene may be hydrogenated. Since polyethylene and polypropylene have high crystallinity, they cannot be used in the present invention because they are phase-separated from the styrene-butadiene copolymer to reduce transparency and film formation stability. Further, in the case of a petroleum resin having a larger number of repeating units than polybutene such as polypentene, the resin itself is expensive, resulting in an increase in cost or a high viscosity of the resin. In order to obtain a good mixed state, it is necessary to once prepare a blend polymer by melt extrusion, which complicates the process and increases the cost. When polybutene is used, the balance between viscosity and low crystallinity is suitable, and it is possible to suppress phase separation due to crystallization during melt molding and orientation while maintaining miscibility with the styrene-butadiene copolymer. preferable. Moreover, it can be obtained at a low cost, and can be directly added to and mixed with a melt extruder without being formed into a master pellet during melt extrusion, and is excellent in productivity.

  As for the weight average molecular weight of the polybutene used for A layer of this invention, 200-5000 are preferable, More preferably, it is 350-3000.

  The kinematic viscosity (JIS K 2283) at a temperature of 100 ° C. of the polybutene used in the A layer of the present invention is preferably 4 to 4000 cst, more preferably 30 to 1000 cst.

  As the polybutene satisfying these preferable ranges, existing commercial products may be used. For example, “Idemitsu polybutene (H series, R series)” manufactured by Idemitsu Kosan Co., Ltd. is commercially available.

  The content of polybutene in the A layer of the present invention is 10 to 30% by weight, preferably 10 to 25% by weight, and more preferably 12 to 18% by weight in the resin component of the A layer. When the content of polybutene is less than 10% by weight, the interlaminar strength is lowered, and the film layers are easily peeled off. Moreover, when content exceeds 30 weight%, a styrene-butadiene copolymer and a polybutene will raise | generate phase separation, and transparency will deteriorate. It should be noted that the content of polybutene and the interlayer strength between the A layer and the B layer are surprisingly not linear, and the interlayer strength is temporarily lowered when a small amount of about 5% by weight is added than when not added. Further, when the addition amount is further increased, the interlayer strength is improved. That is, the polybutene addition amount and the interlayer strength show a curve relationship in which the addition amount is about 5% by weight as a minimum.

  It is preferable that the styrene-butadiene copolymer and polybutene in the A layer of the present invention are substantially compatible. When each of them is phase-separated, the productivity may be lowered, for example, the film may be broken in the stretching process, or the film may be clouded, and the effects of the present invention may not be obtained. Preferred examples of the method of compatibilizing the resin in layer A include controlling the contents of the styrene-butadiene copolymer and polybutene within the above range, and setting the MFR, viscosity, molecular weight, etc. within the above range. .

  In the layer A of the present invention, resins and additives other than the styrene-butadiene copolymer and polybutene may be added within a range not impairing the effects of the present invention. As the resin to be added, for example, a polyester resin similar to that used for the B layer is preferably exemplified. The polyester resin used in the B layer may be added to the A layer as a recovered raw material, or may be added for the purpose of improving the interlayer strength between the A layer and the B layer. Good. In this case, the addition amount of the polyester-based resin is preferably 5 to 20% by weight in the resin component of the A layer. Examples of the additive include pigments, dyes, lubricants, antioxidants, ultraviolet absorbers, deodorants, and stabilizers. Among them, it is preferable to add a pigment when providing the light shielding effect or the like to the shrink film of the present invention. In that case, the pigments include white pigments such as titanium oxide (titanium dioxide), indigo pigments such as copper phthalocyanine blue, carbon black, aluminum flakes, mica (mica), alumina, calcium carbonate, barium sulfate, silica, acrylic beads, etc. Can be selected and used according to the application. Among these, titanium oxide is particularly preferable. These pigments are preferably added in an amount of 10 to 30 parts by weight with respect to 100 parts by weight of the resin component of the A layer.

  The B layer of the shrink film of the present invention contains a polyester resin as a main component. “Become a main component” means that the polyester resin is 80% by weight or more in the resin component of the B layer as described above. Preferably it is 90 weight% or more, More preferably, it is 95 weight% or more. Examples of the polyester resin used in the B layer of the present invention include various polyesters composed of a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 5-t-butylisophthalic acid, 4,4′-biphenyldicarboxylic acid, trans-3,3′-stilbene dicarboxylic acid, and trans-4,4. '-Stilbene dicarboxylic acid, 4,4'-dibenzyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2, 7-naphthalenedicarboxylic acid, 2,2,6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid, 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid, 1,2- Aromatic dicals such as diphenoxyethane-4,4′-dicarboxylic acid, diphenyl ether dicarboxylic acid, and substituted products thereof Acid; oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, Aliphatic dicarboxylic acids such as heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, icosanedioic acid, docosanedioic acid, 1,12-dodecanedioic acid, and their substitutions; 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, cis-1,4-cyclohexanedicarboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and these And alicyclic dicarboxylic acids such as substitution products thereof. These dicarboxylic acid components can be used alone or in combination of two or more.

  Examples of the diol component include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,2 -Dimethyl-1,3-propanediol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octane Aliphatic acids such as diol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2,4-dimethyl-1,3-hexanediol, 1,10-decanediol, polyethylene glycol, polypropylene glycol Diol; 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4 Cycloaliphatic diols such as cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol; 2,2-bis (4′-β-hydroxyethoxydiphenyl) propane, bis (4′- Examples thereof include ethylene oxide adducts of bisphenol compounds such as β-hydroxyethoxyphenyl) sulfone and aromatic diols such as xylylene glycol. These diol components can be used alone or in combination of two or more.

  In addition to the above, the polyester-based resin includes oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid; monocarboxylic acids such as benzoic acid and benzoylbenzoic acid; and polyvalent carboxylic acids such as trimellitic acid. Structural units such as monohydric alcohols such as polyalkylene glycol monomethyl ether; polyhydric alcohols such as glycerin, pentaerythritol and trimethylolpropane may be included.

  The polyester resin used in the B layer of the present invention is not particularly limited, but terephthalic acid is used as the dicarboxylic acid component, ethylene glycol is the main component as the diol component, and 1,4-cyclohexanedimethanol (CHDM) is the copolymerization component. The copolyester used as (hereinafter referred to as CHDM copolymerized PET) is particularly preferred from the viewpoints of cost, productivity, and improvement in interlayer strength with the A layer. In this case, the copolymerization ratio of CHDM is preferably 10 to 40 (mol%), more preferably 20 to 30 (mol%) with respect to ethylene glycol. By copolymerizing CHDM at the above ratio, the polyester resin becomes amorphous, so that the followability of the B layer with respect to the A layer becomes good during production, and the adhesion between the layers becomes high, which is preferable. As the CHDM copolymerized PET, an existing product can be used. For example, “Easter Copolymer”, “Embrac” manufactured by Eastman Chemical Co., etc. are available on the market.

  As described above, the polyester resin used in the B layer of the present invention is not particularly limited, but is preferably substantially amorphous. Note that “substantially amorphous” means that the crystallinity value measured by DSC method (measured at a heating rate of 10 ° C./min) is 10% or less, preferably 5% or less, More preferably, the melting point by the DSC method is hardly seen (that is, the degree of crystallinity is 0%). The crystallinity can be calculated from the value of heat of fusion obtained by DSC measurement using a sample with a clear crystallinity fixed by the X-ray method or the like as a standard. The crystal melting heat was measured by using a DSC (Differential Scanning Calorimetry) apparatus manufactured by Seiko Instruments Inc., performing a nitrogen seal at a sample amount of 10 mg and a heating rate of 10 ° C./min. The temperature is obtained from the area of the melting peak when the temperature is lowered again and then raised again. The crystallinity is preferably measured from a single resin, but when measured in a mixed state, the melting peak may be obtained by subtracting the melting peak of the resin to be mixed.

  When the shrink film of this invention has C layer, it is possible to use resin illustrated above for the polyester-type resin used for C layer. Especially, when using the same resin as the polyester resin used in the B layer, the interlayer strength with each film layer is improved, which is preferable. In particular, it is preferable that the polyester-based resin is substantially amorphous. When crystalline polyester is used, phase separation occurs when mixed with the polystyrene-based resin, and the film becomes cloudy, resulting in a decrease in transparency. There is a case. Originally, crystalline resins are prone to phase separation when mixed with other resins, and even if they are miscible during melting, only the polyester component crystallizes and causes phase separation during film processing. Because there is. In addition, it is preferable from the viewpoint of improving the interlayer strength that the styrene-butadiene copolymer and polybutene have the same molecular weight and composition as those used for the A layer.

  When the shrink film of the present invention has a C layer, the content of the styrene-ethylene butadiene copolymer in the resin component of the C layer is preferably 10 to 80% by weight, more preferably 20 to 70% by weight. Further, the content of polybutene is preferably 10 to 30% by weight, more preferably 10 to 20% by weight. Furthermore, the content of the polyester resin is preferably 10 to 50% by weight, more preferably 20 to 40% by weight.

  The features of the shrink film of the present invention are as follows: (1) The elasticity of the film (flexural rigidity) is obtained by providing a B layer having a high rigidity on the surface layer portion, with the A layer having a flexible and excellent shrinkage property as a base layer. And (2) Affinity with polyester without causing shrinkage reduction or cloudiness by containing a certain amount of polybutene in the polystyrene resin of the A layer. And the interlayer strength is improved. Usually, since polyester resin and polystyrene resin have low affinity, the interlayer strength between the respective film layers laminated by coextrusion or the like is weak and easily peeled off at the interface. In the present invention, it is considered that the adhesion between the layers is increased by adding polybutene to the A layer. In addition, the adhesion to the container is improved. For applications that require higher interlayer strength, the C layer made of the A layer resin and the B layer resin is used as an intermediate layer, so that the affinity is further increased and the adhesive strength is increased. As described above, in the present invention, the film layer resins can be physically and chemically adhered to each other without using an adhesive or the like. It is preferable not to provide a layer such as an adhesive between the A layer and the B layer of the present invention (including the C layer when the C layer is provided). When an adhesive layer such as an easy-adhesion coating is provided, the process becomes complicated, which may be disadvantageous in terms of cost and may have reduced transparency. Moreover, it may be easily deteriorated by heat or the like.

  Although the thickness of the shrink film of this invention changes with uses and is not specifically limited, 10-80 micrometers is preferable, More preferably, it is 20-60 micrometers. The thickness of the A layer is not particularly limited, but is preferably 5 to 60 μm, more preferably 10 to 40 μm, and the thickness of the B layer (one side) is not particularly limited, but is preferably 2 to 10 μm, more preferably 5 10 μm. The layer thicknesses of the B layers provided on both sides of the A layer may be different from each other, but are preferably film layers having the same thickness. When the thicknesses of the B layers on both sides differ greatly, the heat received in the processing step may cause “sludge” or the like in the film, which may reduce productivity and workability. Moreover, when providing C layer, 2-10 micrometers is preferable and, as for the thickness of C layer, More preferably, it is 2-5 micrometers.

  The thickness ratio of the A layer and the B layer of the present invention is not particularly limited, but the A layer / B layer (the total when the B layer is 2 layers) is preferably 5/5 to 9/1, more preferably 6 / 4 to 8/2. When the thickness of the A layer is relatively smaller than the above range, the shrinkage characteristics may be deteriorated and the finish in the mounting process on the container may be deteriorated. Further, if the B layer is relatively thinner than the above range, the film becomes weak and troubles such as buckling may occur in the manufacturing and processing steps.

  The strength (compressive strength: JIS P 8126) of the shrink film of the present invention is preferably 3N or more, more preferably 5N or more. When the compressive strength is less than 3N, the label is likely to be bent in the process of attaching the cylindrical shrink label to the container.

  The thermal shrinkage rate at 100 ° C. for 10 seconds (warm water treatment) in the width direction of the shrink film of the present invention is preferably 50% or more, more preferably 60 to 80%. If the thermal shrinkage rate is less than 50%, the shrink label is not sufficiently contracted in the process of heat-adhering the shrink label to the container, making it difficult to follow the shape of the container. May be.

  The thermal shrinkage rate at 90 ° C. for 10 seconds in the longitudinal direction of the shrink film of the present invention is preferably from −3 to 15%, more preferably from −1 to 10% from the viewpoints of wearability and workability of the shrink label. is there.

  In addition, the longitudinal direction of a film here means the line direction of a film production line, and in the case of a cylindrical shrink label, it is usually the height direction of the label. Moreover, the width direction of a film means the direction orthogonal to the said longitudinal direction, and in the case of a cylindrical shrink label, it is used so that it may become the circumferential direction of a normal label.

  The storage stability of the shrink film of the present invention (natural shrinkage rate: shrinkage rate after 7 days at 40 ° C.) is preferably 2% or less, more preferably 1.5% or less. If the film has a natural shrinkage rate of over 2%, it will cause large deformation (shrinkage) while it is stored before processing after manufacturing a shrink label, making subsequent processing difficult and reducing productivity. Or poor mounting on the container, causing complaints.

  When the shrink film of the present invention is used for applications requiring transparency, the transparency (haze value: JIS K 7136) is preferably 7.0 or less, more preferably 5.0 or less. It is. When the haze value exceeds 7.0, printing is performed on the inside of the shrink film (the side that becomes the container side when the label is attached to the container). In some cases, the printing may become cloudy and the decorativeness may deteriorate.

  The interlayer strength of the shrink film of the present invention is preferably 1.0 (N / 30 mm) or more, more preferably 1.5 (N / 30 mm) or more. When the interlaminar strength is less than 1.0 (N / 30 mm), the film layers are peeled off after processing or commercialization, thereby reducing productivity or causing a complaint.

  The surface layer of the shrink film of the present invention can be further provided with a printed layer, a coating layer, a resin layer, an anchor coat layer, a primer coat layer, an adhesive layer, an adhesive resin layer, a heat-sensitive adhesive layer, etc. A layer of paper, plastic or the like may be provided as necessary. In particular, a shrink label can be obtained by providing a printed layer on at least one surface layer of the shrink film of the present invention. The printed layer should preferably be provided on one of the surfaces, and if it is applied to the inner side (that is, the container side) when it is mounted on a container, the printed layer will be peeled off or soiled when distributed in the market. It is preferable because there is no Especially, it is preferable to provide a printing layer on the surface of B layer.

  The printing layer of the present invention is a layer displaying a product name, an illustration, handling precautions, and the like, and can be formed by a conventional printing method such as gravure printing or flexographic printing. The printing ink used for forming the printing layer is composed of, for example, a pigment, a binder resin, and a solvent. Examples of the binder resin include acrylic, urethane, polyamide, vinyl chloride-vinyl acetate copolymer, cellulose, and nitrocellulose. A general resin such as a system can be used. The thickness of the printing layer is not particularly limited and is, for example, about 0.1 to 10 μm.

  By attaching the shrink label to a container, a container with a label can be obtained. 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, the shrink film of this invention and the manufacturing method of the shrink label using this shrink film and a container with a label are demonstrated. The production method of the present invention is not limited to this.

  In the following description, in the order of the process, the original film after stretching is “shrink film”, the one subjected to printing treatment is “long shrink label”, and further processed into a cylindrical shape with a long length. It is described as “long cylindrical shrink label”.

[Shrink film]
The styrene-butadiene copolymer, polybutene, and polyester resin used in the shrink film of the present invention can be polymerized using a known technique. These resins can also be obtained on the market.

  As a method of mixing the styrene-butadiene copolymer and polybutene used in the A layer, a blend polymer may be prepared in advance, but when the styrene-butadiene copolymer is melt-extruded, liquid polybutene is added. A direct addition method is preferred from the viewpoint of improving productivity. In the case of producing a blend polymer, preferred blending methods include blending by melt kneading with a biaxial kneader, blending by dissolution / desolvation in a cosolvent, and the like.

  Next, an unstretched laminated film is produced using the obtained raw material. As a lamination method, a conventional method such as a coextrusion method or an extrusion lamination method can be used. From the viewpoint of productivity, the coextrusion method is preferably used. Below, the example of the coextrusion method is shown.

A styrene-butadiene copolymer (or a blend polymer of styrene-butadiene and polybutene) is introduced into the extruder a set at a predetermined temperature, and a polyester resin is introduced into the extruder b, and the polymer is melted and sent out. At this time, it is preferable to adjust the supply amount using a gear pump, if necessary, because the polymer supply amount is stabilized and the thickness accuracy of the film layer is improved. When the co-extruded polybutene is directly added, it is preferable to add a predetermined amount of liquid polybutene from the port of the extruder a. Moreover, it is preferable to remove foreign matters using a filter between the extruder and the joining portion because film tearing can be reduced. Next, the polymers of the extruder a and the extruder b are merged using a manifold, a merge block or the like to form a predetermined laminated structure, and then extruded from a T die, a circular die, or the like. Quench using a cooling drum or the like to create an unstretched laminated film.
From the viewpoint of fluidity and deterioration prevention, the temperature of the extruder a is preferably 130 to 200 ° C, and the temperature of the extruder b is preferably 200 to 250 ° C. Further, if necessary, other admixtures such as a lubricant, an antistatic agent, an antifogging agent and an antioxidant may be mixed. Further, when the C layer is provided or when the B layers having different thicknesses are provided on both sides of the A layer, coextrusion may be performed using three extruders.

  Next, the obtained unstretched laminated film is stretched to produce a long shrink film. The stretching may be biaxial stretching in the longitudinal direction (longitudinal direction; MD direction) and width direction (transverse direction; TD direction), or may be uniaxial stretching in the longitudinal direction or the width direction. The stretching method may be any of a roll method, a tenter method, and a tube method. The stretching treatment is performed at a temperature of about 70 to 110 ° C., if necessary, for example, 1.01 to 1.5 times in the longitudinal direction, preferably about 1.05 to 1.3 times, and then 3 in the width direction. It is often carried out by stretching about 6 times, preferably about 4 to 5.5 times.

  The surface of the shrink film of the present invention may be subjected to a conventional surface treatment such as corona discharge treatment or in-line coating, if necessary.

[Shrink label]
Next, after forming a printing layer on at least one surface of the long shrink film obtained as described above to produce a long shrink label, the long shrink shrink is formed into a cylindrical shape. Make a label. The method is shown below.

  The obtained elongated shrink film is subjected to a printing process. As a printing method, a conventional method can be used. For example, it can be formed by gravure printing or flexographic printing. After printing, it is slit to a predetermined width and wound into a roll shape to obtain a roll-like product of a long shrink label.

  Next, while rolling out the roll-like material, the shrink film is formed into a cylindrical shape so that the width direction of the shrink film is the circumferential direction of the label and the printing layer is inside. Specifically, after a long shrink label is formed into a cylindrical shape, a solvent or an adhesive (such as tetrahydrofuran (THF)) having a width of about 2 to 4 mm in a longitudinal direction on one side edge of the label ( The solvent is applied to the inner surface, and the coated portion of the solvent is superimposed on the outer surface of the other side edge portion and adhered to the outer surface (center seal), and is a long cylindrical shrink label continuous body. To obtain a long cylindrical shrink label. In addition, it is preferable that the part which coats said solvent etc. is not printed.

  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.

[Container with label]
Finally, the long cylindrical shrink label obtained above is cut and then attached to a predetermined container, and the label is contracted by heat treatment, and a container with a label is prepared by closely contacting the container.

  The above long cylindrical shrink label is supplied to an automatic label mounting device (shrink labeler), cut to the required length, and then externally fitted into a container filled with contents, and a hot air tunnel or steam tunnel at a predetermined temperature is attached. Passed or heated with radiant heat such as infrared rays to cause heat shrinkage and adhere to the container to obtain a labeled container. Examples of the heat treatment include treatment with 90 ° C. steam.

[Methods for measuring physical properties and methods for evaluating effects]

(1) Interlaminar strength (T-type peeling)
Evaluation was performed using unstretched films (thickness 300 μm) of Examples and Comparative Examples. A strip-shaped sample having a width of 30 mm in the shrink film longitudinal direction (film forming direction) and long in the shrink film width direction was collected. Hereinafter, the sample width direction refers to the longitudinal direction of the shrink film.
A T-type peel test (based on JIS K 6854-3) was performed with the long side direction of the sample (the width direction of the shrink film) as the measurement direction. The A layer and the B layer were peeled off from the end portion of the sample, the end portions on the A layer side and the B layer side were chucked, and pulled by a tensile tester, and a T-type peel test was performed under the following conditions. . In Example 4, the interlayer strength between the B layer and the C layer was measured.
The peel strength (crosshead travel distance) is the average value of peel weights of 50 mm to 250 mm, which is the interlayer strength (N / 30 mm). If the interlayer strength is 1.5 N or more, the interlayer strength is high (◯), 1 N or more In the case of less than 1.5N, the usable level (Δ), and in the case of less than 1N, the interlayer strength was judged to be insufficient (x).
Measuring device: Shimadzu Corporation autograph (AGS-50G: 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: 50 mm
Sample width: 30mm
Number of tests: 3 times Crosshead moving speed: 200 mm / min

(2) Compressive strength (ring crush method)
Evaluation was performed using a shrink film (film thickness 40 μm) obtained by the methods of Examples and Comparative Examples.
Based on JIS P 8126, the compressive strength of the shrink film was measured under the following conditions. The measurement direction is the longitudinal direction. As a result of the measurement, those having a compressive strength of 5N or more have good buckling resistance (◯), those having a compressive strength of 3N or more and less than 5N are usable levels (Δ), and those having a compressive strength of less than 3N have poor buckling resistance (× ).
Measuring device: Shimadzu Corporation autograph (AGS-50G: load cell type 500N)
Sample size: 15 mm (longitudinal direction) x 152.4 mm (width direction)
Number of tests: 5

(3) Shrinkage rate (100 ° C heat shrinkage rate)
A square sample piece of 100 mm (film longitudinal direction) × 100 mm (film width direction) was prepared from the obtained shrink film.
The sample piece was heat-treated in 100 ° C. boiling water for 10 seconds (under no load), the dimensions (width direction) of the sample before and after the heat treatment were read, and the heat shrinkage rate was calculated by the following formula. The average value of the test number of 5 times was defined as the shrinkage rate.
Those having a shrinkage ratio of 60% or more were judged to have good shrinkage characteristics (◯), those having 50% or more and less than 60% were usable levels (Δ), and those having less than 50% were judged to have poor shrinkage characteristics (×).
Shrinkage rate (%) = (L0−L1) / L0 × 100
L0: dimension of sample before heat treatment (longitudinal direction or width direction)
L1: Dimension of sample after heat treatment (same direction as L0)

(4) Transparency (haze value)
Evaluation was performed using a shrink film (film thickness 40 μm) obtained by the methods of Examples and Comparative Examples.
Measurement was carried out according to JIS K 7136. When the haze was 5 or less, the transparency was good (◯). When the haze was more than 5 and 7 or less, it was judged as a level (Δ) that can be used as a label application, and when it exceeded 7, the transparency was judged to be poor (x).
In addition, what is necessary is just to convert and evaluate to 40 micrometers thickness about the sample from which thickness differs.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
Asa styrene-butadiene block copolymer (SBS), “Asaflex 825” (styrene / butadiene = 80/20, MFR (200 ° C., 5 kgf) = 6) manufactured by Asahi Kasei Chemicals Corporation (resin A1) Was used. As the polybutene, “300H” (molecular weight: 1500, viscosity (100 ° C.) = 810 cst) (resin A2) manufactured by Idemitsu Kosan Co., Ltd. was used.
As the polyester resin of the B layer, CHDM copolymerized PET (“EMBRACE” manufactured by Eastman Chemical Co .; copolymerization ratio (molar ratio) 70:30) of ethylene glycol and 1,4-cyclohexanedimethanol (resin B1) was used. . Resin B1 had a crystallinity of 0% as measured by DSC method (no crystal melting peak was observed), and was a substantially amorphous polyester.
The resin A1 (90 parts by weight) is charged from the hopper into the extruder a heated to 170 to 200 ° C. and melted, and the resin A2 (10 parts by weight) is supplied while being metered from a port provided in the middle of the extruder. Mixed. In the extruder b heated to 200 to 250 ° C., 100 parts by weight of the resin B1 was charged. Melt extrusion was performed using the above two extruders. The resin extruded from the extruder b is merged using a merge block so that the resin is extruded on both sides of the resin layer extruded from the extruder a, and extruded from a T-die (slit spacing 1.0 mm), and then 25 ° C. The film was rapidly cooled on a casting drum cooled to 2 to obtain a B1 / (mixed polymer of A1 and A2) / B1 two-layer three-layer unstretched film (thickness 300 μm). The lamination thickness ratio of the unstretched film was lamination part / base layer part / lamination part = 1/3/1. As shown in Table 1, the obtained unstretched film had good interlayer strength.
Next, an unstretched film with adjusted thickness is stretched 1.10 times at 85 ° C. in the longitudinal direction using a roll stretching machine, and then tenter stretched at 95 ° C. in the width direction by 5.0 times. A biaxially stretched film shrinking mainly in the uniaxial direction was obtained. By adjusting the film forming speed, a shrink film having a total film thickness of 40 μm (layer thickness ratio: 1/3/1) was obtained.
As shown in Table 1, the obtained shrink film had excellent characteristics in terms of compressive strength, shrinkage, transparency, and the like.
Subsequently, urethane ink (trade name “NT-HIRAMIC”, manufactured by Dainichi Seika Kogyo Co., Ltd.) was applied to one side of the obtained shrink film (thickness 40 μm) by gravure printing to form a printed layer, I got a shrink label. Furthermore, it was rolled into a cylindrical shape so that the printing surface was inside and the width direction of the film was the circumferential direction, and center-sealed with tetrahydrofuran (THF) to obtain a long cylindrical shrink label. Finally, the above long cylindrical shrink label is supplied to an automatic label mounting device (STS-1936 manufactured by Fujistec Corp.) and cut into each label, while a container (500 ml heat-resistant square PET bottle manufactured by Toyo Seikan Co., Ltd.) And heated and shrunk in a steam tunnel with an atmospheric temperature of 90 ° C. to obtain a labeled container.
In the above printing process, label mounting process, etc., troubles such as coating failure and buckling did not occur, the productivity was good, and the obtained labeled container was also excellent.

Examples 2 and 3
An unstretched film (film thickness of 300 μm), a shrink film (film thickness of 40 μm), and the same as in Example 1 except that the mixing ratio of A1 and A2 charged into the extruder a was changed as shown in Table 1. A labeled container was obtained.
The obtained unstretched film and shrink film had excellent characteristics as shown in Table 1. Moreover, productivity was also good and the finish of the obtained labeled container was also excellent.

Example 4
Three extruders (extruder a, extruder b, and extruder c) were used. The resin extruded from the extruder c is joined on both sides of the resin layer extruded from the extruder a, and the resin extruded from the extruder b is joined on both sides using a merging block. In the same manner as in Example 1, a five-layer unstretched film (film thickness 300 μm), a shrink film (film thickness 40 μm), and a labeled container were obtained. As shown in Table 1, A1 and A2 were used for the extruder a, B1 was used for the extruder b, and A1, A2, and B1 were used for the extruder c.
The obtained unstretched film and shrink film had excellent characteristics as shown in Table 1. Moreover, productivity was also good and the finish of the obtained labeled container was also excellent.

Comparative Example 1
As shown in Table 1, an unstretched film, a shrink film, and a labeled container were obtained in the same manner as in Example 1 except that the resin A2 was not used as the raw material to be fed into the extruder a, and the resin A1 was used. .
As a result, as shown in Table 1, the unstretched film was inferior in interlayer strength. In addition, in the production process of shrink labels and labeled containers, troubles due to delamination occurred, resulting in decreased productivity.

Comparative Examples 2 and 3
An unstretched film, a shrink film, and a labeled container were obtained in the same manner as in Example 1 except that the mixing ratio of A1 and A2 charged into the extruder a was changed as shown in Table 1.
The obtained unstretched film was inferior in interlayer strength when the amount of polybutene added was small (Comparative Example 2). When the addition amount is large (Comparative Example 3), film tearing is likely to occur in the production process, and the productivity is inferior. It was inferior in strength, shrinkage, and transparency. Moreover, in the production process of shrink labels and labeled containers, troubles due to delamination occurred in the case of Comparative Example 2, and buckling occurred in the case of Comparative Example 3, both of which lowered productivity. In addition, the finished containers with labels were inferior.

Comparative Example 4
In the same manner as in Example 1, except that GPPS (polystyrene for general use) (manufactured by Toyostyrene Co., Ltd., “Toyostyrene G200C”) was used as a raw material to be fed into the extruder a, A stretched film, a shrink film, and a labeled container were obtained.
The obtained unstretched film was inferior in interlayer strength. Furthermore, the shrinkability of the shrink film was inferior. Further, in the production process of shrink labels and labeled containers, productivity was lowered due to troubles caused by delamination, and the finished containers with labels were inferior.

It is a schematic sectional drawing which shows an example of the shrink label of this invention.

Explanation of symbols

1 Shrink film 2 Laminating part (B layer)
3 Base layer (A layer)

Claims (5)

  It has a film layer (B layer) made of a polyester resin on at least one side of a film layer (A layer) containing 50 to 90% by weight of a styrene-butadiene copolymer and 10 to 30% by weight of polybutene. Shrink film.   The shrink film according to claim 1, wherein the A layer and the B layer are laminated without interposing other layers.   A shrink film having an A layer, a B layer, and a C layer made of a styrene-butadiene copolymer, polybutene, and a polyester-based resin, and each layer is another layer in the order of A layer / C layer / B layer. The shrink film of Claim 1 currently laminated | stacked without interposing.   The shrink label which provides a printing layer in the surface of at least one of the shrink film of any one of Claims 1-3.   A labeled container to which the shrink label according to claim 4 is attached.

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