JP5257147B2 - label - Google Patents

Description

  The present invention relates to a label formed of a heat-shrinkable film, and more particularly, to a label having a good tearing condition made of a coated heat-shrinkable polystyrene-based laminated film.

  In recent years, stretched films made of polyvinyl chloride resin, polystyrene resin, polyester resin, etc. (so-called so-called, Heat-shrinkable film) has been widely used. Among such heat-shrinkable films, the polyvinyl chloride film has problems such as low heat resistance, generation of hydrogen chloride gas during incineration, and dioxin generation. In addition, polystyrene film is poor in solvent resistance and heat resistance, and has to use ink with a special composition at the time of printing, and can not withstand boiling treatment at high temperature or storage in a hot warmer. There's a problem. Therefore, polyester-based heat-shrinkable films that have high heat resistance, are easy to incinerate, and have excellent solvent resistance are widely used as shrink labels. The usage tends to increase with the increase.

  However, since the conventional heat-shrinkable polyester film is hardly stretched in the longitudinal direction perpendicular to the main shrinkage direction, the mechanical strength is low, and when it is covered by being shrunk on a plastic bottle or the like as a label, There is a defect that the label cannot be torn well along the perforation (that is, the perforation opening is poor). In addition, when the film is stretched in the longitudinal direction during production in order to improve the perforation opening of the heat-shrinkable polyester film, the mechanical strength increases and the perforation opening improves to some extent, but in the longitudinal direction. Since the shrinkage force is expressed, the appearance (shrinkage finish) may be deteriorated when the plastic bottle is shrunk and coated as a label, or the heat-shrinkable polyester film originally does not heat. Although it shrinks quickly when hung, it is easy to finish at high speed, but it shrinks rapidly, so there is a problem that wrinkles and distortion are likely to occur when the bottle is shrink-fitted.

  Therefore, in order to improve the perforation openability and shrink finish of the heat-shrinkable polyester film, a method of mixing an incompatible thermoplastic resin into the main raw material of the heat-shrinkable polyester film (Patent Document 1) is also available. Proposed.

Japanese Patent Application Laid-Open No. 2002-36312

  According to the method of mixing an incompatible thermoplastic resin into the main raw material of the heat-shrinkable polyester film as described in Patent Document 1, the perforation opening property of the heat-shrinkable polyester film is improved to some extent, but is not necessarily perforated. It is difficult to say that a heat-shrinkable polyester film having sufficient openability is obtained. In addition, since incompatible thermoplastic resin is mixed, transparency is impaired. Moreover, even when the method as disclosed in Patent Document 1 is adopted, the heat-shrinkable polyester film cannot be efficiently produced because it can be stretched only in the width direction during production.

  Therefore, the present inventors have demonstrated good heat-shrinkability and perforation-opening property of a heat-shrinkable film made of polystyrene, and good blocking resistance and solvent adhesive strength of a heat-shrinkable film made of polyester. In order to make it express, it investigated earnestly about the technique which laminates | stacks a polyester film layer on the surface layer of the film which consists of polystyrene.

  It has been found that by adopting the laminated structure as described above, the heat resistance of the polyester film is imparted with the good shrinkage finish and perforation opening property of the polystyrene film, and these characteristics are improved to some extent. However, because of the presence of the polyester film layer, the perforation unsealing property is still inferior to that of the polystyrene film alone, and in practice it is necessary to improve the perforation unsealing property, and polyester and polystyrene are simply laminated. It was found that physical properties cannot be achieved by using only. The present inventors have repeatedly studied to improve this point and have arrived at the present invention.

  An object of the present invention is to obtain a heat-shrinkable polystyrene-based laminated film that exhibits high heat-shrinkability, perforation opening, and heat resistance at the same time in a heat-shrinkable polystyrene-based laminated film. It is an object of the present invention to provide a label having a good tearing condition from such heat shrinkable film.

That is, the present invention has the following configuration.
1. A heat-shrinkable polystyrene-based laminated film, which is formed by laminating a skin layer mainly composed of a polyester-based resin layer on at least one surface of a core layer mainly composed of a polystyrene-based resin, and thermally shrinks with the film width direction as a main shrinkage direction. An annular body that is cut according to the packaging object and bonded at both ends in the film width direction is a label that covers at least a part of the outer periphery of the packaging object by heat shrinking, The perpendicular tear strength in the direction (film longitudinal direction) perpendicular to the main shrinkage direction of the label (film substrate excluding the printing layer) is 90 N / mm to 300 N / mm, and is perpendicular to the main shrinkage direction Direction of contraction when the tensile fracture strength in the direction (film longitudinal direction) is 100 MPa or more and 300 MPa or less and the treatment is performed in hot air at 160 ° C. for 1 minute. Label, wherein the heat shrinkage rate orthogonal directions is 40% or more.
2. The label according to the first item, wherein the adhesion is performed with an organic solvent.
3. The label according to the first or second aspect, wherein perforations or notches are provided along a direction (film longitudinal direction) orthogonal to the main shrinkage direction.

  Note that the perforation means that a plurality of slits are continuously provided in a straight line or a curved line, but includes one in which only one slit is provided. Furthermore, the shape of the slit constituting the perforation is not particularly limited. On the other hand, the notch refers to a notch provided at the edge of the label, and its shape is not particularly limited.

  The heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention is highly shrinkable in the film width direction, which is the main shrinkage direction, and has high mechanical strength in the film longitudinal direction perpendicular to the main shrinkage direction, In the manufactured roll-shaped film, no tightening occurs, the film roll is difficult to wrinkle, and the unsealing property is good. Therefore, the heat-shrinkable polystyrene-based laminated film can be suitably used as a label for containers such as bottles, and can be attached to containers such as bottles very efficiently within a short time. When heat-shrinked later, a good finish with very little wrinkles due to heat-shrinking and insufficient shrinkage can be expressed. In addition, the attached label expresses very good openability. Therefore, the label of the present invention has a good tearing condition, and when the perforation is provided in a direction perpendicular to the main contraction direction with an appropriate force, the coated label is torn cleanly along the perforation. be able to.

It is explanatory drawing which shows the shape of the test piece in the measurement of a right-angled tear strength (In addition, the unit of the length of each part of the test piece in a figure is mm).

  The label of the present invention comprises a heat-shrinkable polystyrene-based laminated film as a base material, and is heat-shrinked by covering at least a part of the outer periphery. Examples of label objects include beverage PET bottles. , Various types of bottles, cans, plastic containers such as confectionery and lunch boxes, paper boxes, and the like (hereinafter collectively referred to as packaging objects). In general, when a label based on a heat-shrinkable polystyrene-based laminated film is heat-shrinked and coated on those objects to be packaged, the label is heat-shrinked by about 2 to 15%. Adhere to objects. Note that the label to be covered with the packaging object may or may not be printed, and the direction perpendicular to the main shrinkage direction of the label (= film longitudinal direction = perforation) Direction) may be provided with perforations and notches.

  In addition, when a label is coated on a packaging object, a method is adopted in which an annular body is formed in advance so that the main shrinkage direction is the circumferential direction, and then the annular body is covered with the packaging object and thermally contracted. However, when forming an annular body in such a manner, in addition to the method of bonding the heat-shrinkable film using various adhesives, the heat-shrinkable film is melted using a high-temperature heating element. It is also possible to use a method of attaching and bonding (melting sealing method) or the like. In addition, when fusing and sealing a heat-shrinkable film, a predetermined automatic bag making machine (for example, Kyoei Printing Machinery Materials Co., Ltd.-RP500) is used, and the fusing blade temperature and angle are set to predetermined conditions (for example, fusing). A method of forming an annular body or a bag at a predetermined speed (for example, 100 pieces / min) after adjusting the blade temperature to 240 ° C. and the blade angle to 70 ° can be employed. In addition, when covering the packaging object with the label, the label is wound around the packaging object, and the overlapped portion is fused and sealed to cover the packaging object and then heat shrink. It is also possible to adopt a method.

  In addition, the label of the present invention is obtained when the right-angle tear strength in the direction perpendicular to the main shrinkage direction per unit thickness of the coated label (film substrate excluding the printing layer) is measured by the following method. The right-angle tear strength is preferably 90 N / mm or more and 300 N / mm or less. Here, since the label is heat-treated and shrunk and attached to the packaging object, the label itself is not as large as the heat-shrinkable property of the label before the heat-shrinking process, but the label is attached. In this case, the direction of contraction is mainly referred to as the main contraction direction (hereinafter the same applies to the labels).

[Measurement method of right-angle tear strength]
When the label was printed, the printed layer of the label was wiped with a cloth soaked with ethyl acetate. A label that is not printed or has a printed layer removed is sampled as a test piece of a predetermined size according to JIS-K-7128. After that, the both ends of the test piece are gripped with a universal tensile testing machine (for example, Autograph manufactured by Shimadzu Corporation), and the direction perpendicular to the main shrinkage direction of the label (= perforation) at a tensile speed of 200 mm / min. Direction), and measure the strength at the time of tensile fracture. Then, the right angle tear strength per unit thickness is calculated using the following formula 1.
Right angle tear strength = strength at tensile fracture ÷ thickness ・ ・ Equation 1

  If the right-angled tear strength in the direction perpendicular to the main shrinkage direction of the label (= perforation direction) is less than 90 N / mm, it may be easily broken by an impact such as a drop during transportation. On the other hand, if the right-angle tear strength in the direction perpendicular to the main shrinkage direction of the label exceeds 300 N / mm, the cut property (easy to tear) in the initial stage at the time of tearing becomes unfavorable. The lower limit of the right-angled tear strength is preferably 110 N / mm or more, more preferably 130 N / mm or more, and particularly preferably 150 N / mm or more. Further, the upper limit value of the right-angled tear strength is preferably 290 N / mm or less, more preferably 270 N / mm or less, further preferably 250 N / mm or less, further preferably 200 N / mm or less, and further preferably 170 N / mm or less. / Mm or less is particularly preferable.

  The label of the present invention has a tensile fracture strength of 100 MPa or more when the tensile fracture strength in the film longitudinal direction of the coated label (film substrate excluding the printing layer) is measured by the following method. It is preferable that it is 300 MPa or less.

[Measurement method of tensile fracture strength]
When the label was printed, the printed layer of the label was wiped with a cloth soaked with ethyl acetate. According to JIS-K-7127, a label that has not been printed or the printed layer is removed is sampled to a predetermined size to obtain a test piece, which is a universal tensile testing machine (for example, auto manufactured by Shimadzu Corporation) Graph) is used to grasp both ends (film longitudinal direction) of the test piece, conduct a tensile test under the condition of a tensile speed of 200 mm / min, and calculate a stress value at break.

  When the tensile fracture strength in the direction orthogonal to the main shrinkage direction of the label (= film longitudinal direction = perforation direction) is less than 100 MPa, when processing from film to label, during processing to apply tension in the film longitudinal direction such as printing There is a drawback that breaks easily. In addition, the lower limit of the tensile fracture strength is preferably 110 MPa or more, more preferably 130 MPa or more, further preferably 160 MPa or more, and particularly preferably 190 MPa or more. The upper limit may be 300 MPa or less, but may be 290 MPa or less.

  In the present invention, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction when treated in hot air at 160 ° C. for 1 minute is preferably 40% or more, more preferably 50% or more, and still more preferably. 60% or more. The orientation of the molecules in the direction perpendicular to the main shrinkage direction increases the tearability in that direction and makes it difficult to break during processing, so it can be found not only in the commercial value but also in the label manufacturing process, but at 160 ° C The inventors have found that the larger the shrinkage ratio, the better the characteristics. This is close to or close to the maximum temperature of the thermal history given to the film by stretching or heat treatment in the film-forming process of a heat-shrinkable polystyrene-based laminated film as used as a substrate in the present invention. Giving the above heat to the label means that it is intended to shrink so as to approach the unstretched state in order to completely eliminate the orientation state of the molecules formed during film formation. This is considered to be due to a certain degree of correlation with the orientation state. In addition, Abbe's refractometer and molecular orientation meter are usually used for evaluating the index indicating the degree of molecular orientation, but in the case of a laminate of a polyester resin layer and a polystyrene resin layer as in the present invention, In some cases, this method cannot be evaluated well, and the shrinkage rate at 160 ° C. can be a measure of the degree of orientation of the entire laminate in consideration of the orientation of both layers. When the shrinkage rate in the direction perpendicular to the main shrinkage direction at 160 ° C. is 40% or more, the desired physical properties can be achieved, but the viewpoint of the draw ratio at which a heat-shrinkable polystyrene-based laminated film as a substrate can be formed can be obtained. Therefore, the upper limit is considered to be about 80%.

  The polyester used for the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention is mainly composed of ethylene terephthalate. That is, it contains 50 mol% or more, preferably 60 mol% or more of ethylene terephthalate. As other dicarboxylic acid components constituting the polyester in the present invention, aromatic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid and orthophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid, And alicyclic dicarboxylic acid.

  Examples of the diol component constituting the polyester used in the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention include ethylene glycol, 1-3 propanediol, 1-4 butanediol, neopentyl glycol, hexanediol, and the like. Examples thereof include aliphatic diols, alicyclic diols such as 1,4-cyclohexanedimethanol, and aromatic diols such as bisphenol A.

  Polyester used for the heat-shrinkable polystyrene laminated film preferably used for the label of the present invention is a cyclic diol such as 1,4-cyclohexanedimethanol or a diol having 3 to 6 carbon atoms (for example, 1-3 propane). Polyesters containing one or more of diol, 1-4 butanediol, neopentyl glycol, hexanediol, etc.) and having a glass transition point (Tg) adjusted to 60 to 80 ° C. are preferred.

  Moreover, the polyester used for the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention is one or more kinds of monomer components that can be an amorphous component in 100 mol% of the polyhydric alcohol component in the total polyester resin. The total is preferably 15 mol% or more, more preferably 17 mol% or more, and particularly preferably 20 mol% or more. Here, examples of the monomer that can be an amorphous component include neopentyl glycol, 1,4-cyclohexanediol, and isophthalic acid.

  In the polyester used for the heat-shrinkable polystyrene-based laminated film, a diol having 8 or more carbon atoms (for example, octanediol) or a trihydric or higher polyhydric alcohol (for example, trimethylolpropane, trimethylolethane, glycerin, diester) It is preferable not to contain glycerin or the like. In the heat-shrinkable polyester film obtained by using polyesters containing these diols or polyhydric alcohols, it is difficult to achieve a necessary high shrinkage rate.

  Moreover, it is preferable not to contain diethylene glycol, triethylene glycol, and polyethylene glycol as much as possible in the polyester used for the heat-shrinkable polystyrene-based laminated film. In particular, diethylene glycol is easily present because it is a by-product component during polyester polymerization. However, in the polyester used in the present invention, the content of diethylene glycol is preferably less than 4 mol%.

  Further, the polystyrene resin constituting the core layer of the heat-shrinkable polystyrene-based resin laminated film preferably used for the label of the present invention is not particularly limited as long as the desired heat-shrinkage characteristics can be expressed. Monomers and copolymers composed of styrene derivatives such as methylstyrene and p-methylstyrene, as well as monomers copolymerizable with styrene and styrene derivatives such as acrylic acid, methacrylic acid, and metal salts thereof (for example, Na , K, Li, Mg, Ca, Zn, Fe, etc.), and copolymers with aliphatic unsaturated carboxylic acids such as acrylic esters and methacrylic esters and their derivatives. In addition, various polystyrenes such as atactic polystyrene, syndiotactic polystyrene, isotactic polystyrene and the like can be used, but when atactic polystyrene is used, the hardness of the resulting heat-shrinkable film becomes appropriate. Therefore, it is preferable.

  On the other hand, by using a polystyrene resin having a syndiotactic structure, it is possible to further improve the mechanical strength and heat resistance. In addition, by using a polystyrene-based resin having a syndiotactic structure, the density of polystyrene is reduced, separation in the recycling process is facilitated, and heat resistance, particularly heat resistance during heat storage, etc. is improved. Further, the change in the printing pitch due to shrinkage with time after film formation is reduced, and it becomes possible to perform high-precision printing as a label. Furthermore, the durability against the solvent contained in the printing ink is improved, and the printability is improved. In addition, the polystyrene resin having a syndiotactic structure has 75% or more diad (2 structural units) in the tacticity for quantifying the phenyl group and / or substituted phenyl group as a side chain by a nuclear magnetic resonance method. And is more preferably 85% or more. On the other hand, the pentad (5 structural units) is preferably 30% or more, and more preferably 50% or more.

  The polystyrene component constituting the polystyrene-based resin includes polystyrene, poly (p-one, m-one, or o-methylstyrene), poly (2,4-1,2,5-1,3,4, or 3, 5 (dimethylstyrene), poly (alkylstyrene) such as poly (p-tertiary butylstyrene), poly (p-, m-, or o-chlorostyrene), poly (p-, m-, or o-bromo) Styrene), poly (p-, m-, or o-fluorostyrene), poly (halogenated styrene) such as poly (O-methyl-p-fluorostyrene), poly (p-, m-, or o-chloromethyl) Poly (halogenated alkyl styrene) such as styrene), poly (alkoxy styrene) such as poly (p, m, or o methoxy styrene), poly (p, m, or o ethoxy styrene), Poly (carbohydrate) such as poly (p-, m-, or o-carboxymethylstyrene) Poly (alkyl ether styrene) such as poly (p-vinyl benzyl propyl ether), poly (alkyl silyl styrene) such as poly (p-trimethylsilyl styrene), and also poly (pinylbenzyl dimethoxy phosphide) ) And the like. In addition, it is also possible to mix | blend a plasticizer, a compatibilizing agent, etc. with a polystyrene-type resin in order to lower | hang a heat shrink start temperature, or to improve impact resistance.

  Moreover, it is preferable to add a thermoplastic resin and / or a rubber component to the polystyrene resin. As thermoplastic resins, polystyrene resins having an atactic structure, polystyrene resins such as AS resin, ABS resin, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, nylon 6, nylon 66, nylon 12, nylon 4 And polyamide resins such as polyhexamethylene adipamide, and polyolefin resins such as polyethylene, polypropylene, and polybutene. On the other hand, the rubber component is preferably a rubbery copolymer containing a styrene compound as a constituent component, and examples thereof include random, block or graft copolymers obtained by copolymerizing at least one of styrene and a rubber component. be able to. Examples of such rubbery copolymers include styrene-butadiene copolymer rubber, styrene-isoprene block copolymer, rubber obtained by hydrogenating a part or all of the butadiene portion, and methyl acrylate-butadiene-styrene. Examples thereof include copolymer rubber, acrylonitrile-butadiene-styrene copolymer rubber, acrylonitrile-alkyl acrylate-butadiene-styrene copolymer rubber, and methyl methacrylate-alkyl acrylate-butadiene-styrene copolymer rubber. The rubbery copolymer containing the above-mentioned styrene compound as a constituent component has a styrene unit, and therefore has good dispersibility with respect to a polystyrene resin having a syndiotactic structure, and has an effect of improving plasticity with respect to the polystyrene resin. large. Moreover, as a compatibility regulator, the rubber-like copolymer which contains the above-mentioned styrene-type compound as the structural component can be used conveniently.

  On the other hand, other rubber components include natural rubber, polybutadiene, polyisoprene, polyisobutylene, neoprene, ethylene-propylene copolymer rubber, urethane rubber, silicone rubber, acrylic rubber, polyether-ester rubber, polyester-ester rubber. Etc. can be used.

  Further, the weight average molecular weight of the polystyrene resin is preferably 10,000 or more, and more preferably 50,000 or more. A film having a weight average molecular weight of less than 10,000 is not preferred because the strength and heat resistance of the film and the heat resistance are likely to be lowered. The upper limit of the weight average molecular weight is not particularly limited, but if the weight average molecular weight exceeds 1,500,000, it may not be preferable because breakage may occur due to an increase in stretching tension.

  In addition, the heat-shrinkable polystyrene resin laminated film preferably used for the label of the present invention is obtained by melt-extruding a polystyrene-based resin chip and a polyester-based resin chip, which are raw materials, using a coextrusion method described later, An unstretched laminated sheet (unstretched laminated film) is formed by laminating a plurality of resin layers, and the unstretched laminated film (unstretched laminated sheet) is biaxially stretched in the longitudinal direction (longitudinal direction) and the lateral direction (width direction). And then rolled into a roll.

The heat-shrinkable polystyrene resin laminated film preferably used for the label of the present invention has a core layer and a skin layer composed of A / B (two types and two layers), A / B / A (two types and three layers), Or it is preferable to have the structure of A / B / C (three types and three layers). In view of curl, an A / B / A configuration that is a symmetric layer configuration is preferable. Incidentally, in the description of the heat-shrinkable polystyrene based resin laminated film of the present invention, among the layers constituting the laminated film, the layer of the heart not located on the outermost side (i.e., A / B / A or A / B, B layer in the case of / C layer structure) and a thick layer in the case of two-kind two-layer structure (that is, B layer in the case of A / B layer structure of thin A layer and thick B layer) It is called a layer. Further, the outermost layer (i.e., A, B layer in the case of A / B layer configuration, A, C layer in the case of A / B / A or A / B / C layer configuration), and two The thin layer in the case of the seed two-layer structure (that is, the A layer in the case of the A / B layer structure of the thin A layer and the thick B layer) is referred to as a skin layer.

  And it is preferable that the heat-shrinkable polystyrene-type resin laminated film in this invention forms a core layer with a polystyrene-type resin, and forms a skin layer with a polyester-type resin. In addition, when it is set as the structure of A / B / C (three types and three layers), the polyester-type resin which comprises A layer, and the polyester-type resin which comprises C can also be made different.

  In addition, an adhesive layer is preferably provided as an intermediate layer between the layers (that is, between the core layer made of polystyrene resin and the skin layer made of polyester resin). As the resin constituting the adhesive layer, olefin-based, ester-based, urethane-based, and acrylic copolymers can be suitably used. Among them, styrene-olefin-based copolymers and styrene-acrylic-based copolymers can be used. The use of a copolymer or the like is preferable because the adhesion between the skin layer and the core layer becomes good. For example, an A / X / B / X / A three-layer five-layer configuration using the X layer as an adhesive layer is a particularly preferable layer configuration.

  The thickness of the adhesive layer is preferably smaller than the thickness of the skin layer, more preferably 1 to 5 μm, and still more preferably 1 to 3 μm.

  On the other hand, in the heat-shrinkable polystyrene resin laminated film, the ratio of the thickness of the skin layer (polyester resin layer) and the core layer (polystyrene resin layer) is in the range of 1: 1 to 1: 5. (Ie, the thickness of the skin layer is preferably about 20 to 50% of the total). In order to effectively reflect both the physical properties of the skin layer and the physical properties of the core layer in the heat-shrinkable polystyrene resin laminated film, the ratio of the thickness of the skin layer to the thickness of the core layer is 1: 2 to 1. It is preferable to adjust to be within the range of 4: 4. As described above, by adjusting the ratio between the thickness of the skin layer and the thickness of the core layer within the range of 1: 1 to 1: 5, the good heat shrinkability of the polystyrene resin constituting the core layer, the sewing machine It is possible to develop good blocking resistance and solvent adhesive strength of the polyester resin constituting the skin layer while exhibiting openability, and the polystyrene resin constituting the core layer is resistant to blocking and solvent adhesion. A situation in which the strength is adversely affected or the polyester resin constituting the skin layer is adversely affected in terms of heat shrinkability and perforation opening is avoided.

  In addition, the thickness of the entire heat-shrinkable polystyrene resin laminated film is not particularly limited, but is preferably 10 to 70 μm if it is used for creating labels for containers stored in a hot warmer, More preferably, it is 60 μm.

  Also, when the ratio of the skin layer (polyester resin) to the core layer (polystyrene resin) is increased, the transparency of the film deteriorates (haze value) when the film edge cut at the time of production is recovered and reused. Will rise). If the end of the film is not collected in order to eliminate such a problem, the manufacturing cost becomes high, and the practicality of the film roll is impaired. Therefore, it is preferable to make the skin layer as thin as possible. From this point, the lower limit of the thickness of the skin layer (single layer) is preferably 2 μm or more, and more preferably 4 μm or more. If the thickness of the skin layer is less than 2 μm, blocking is likely to occur at a high temperature of 100 ° C. or higher, which is not preferable. On the contrary, the upper limit of the thickness of the skin layer is preferably 16 μm or less, more preferably 14 μm or less, further preferably 12 μm or less, and particularly preferably 10 μm or less. When the thickness of the skin layer exceeds 16 μm, it is not preferable because a good perforation opening property may not be obtained.

And it is preferable to adjust the thickness of a core layer to 40 to 90% of the thickness of the whole film by adjusting the thickness of the whole film and the thickness of a skin layer as mentioned above.

In order to produce a laminated film as described above, each layer is formed by forming a substantially unoriented resin sheet having a layer structure of A / B, A / B / A, or A / B / C. The resin (polymer) constituting the resin is melted using a separate extruder, co-extruded, cast onto a rotating drum from a die and rapidly cooled and solidified to obtain a substantially unoriented resin sheet (so-called The coextrusion method) can be suitably employed.

  In addition, in the resin forming the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention, various additives such as waxes, antioxidants, antistatic agents, crystals are used as necessary. A nucleating agent, a viscosity reducing agent, a heat stabilizer, a coloring pigment, an anti-coloring agent, an ultraviolet absorber and the like can be added. In the resin forming the heat-shrinkable polystyrene-based laminated film in the present invention, it is preferable that the workability (slidability) of the polystyrene-based laminated film is improved by adding fine particles as a lubricant. Any fine particles can be selected. Examples of inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate. Examples of the organic fine particles include acrylic resin particles, melamine resin particles, silicone resin particles, and crosslinked polystyrene particles. The average particle size of the fine particles can be appropriately selected as necessary within a range of 0.05 to 3.0 μm (when measured with a Coulter counter).

  As a method of blending the above particles into the resin forming the heat-shrinkable polystyrene-based laminated film, for example, it can be added at any stage of producing the polyester-based resin. After completion of the reaction, it is preferable to add as a slurry dispersed in ethylene glycol or the like at the stage before the start of the polycondensation reaction to advance the polycondensation reaction. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water using a vented kneading extruder and a polyester resin material, or a dried particle and a polyester resin material using a kneading extruder It is also preferable to carry out by a method of blending and the like.

  Furthermore, the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention can be subjected to corona treatment, coating treatment, flame treatment, etc. in order to improve the adhesion of the film surface. .

In addition, the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention has the following formula 2 from the length before and after shrinkage when treated in warm water at 90 ° C. for 10 seconds under no load. It is preferable that the heat shrinkage rate in the width direction of the film calculated by (i.e., hot water heat shrinkage rate of 90 ° C.) is 40% or more and 80% or less.
Thermal shrinkage rate = {(length before shrinkage−length after shrinkage) / length before shrinkage} × 100 (%)

  If the hot water thermal shrinkage in the width direction at 90 ° C. is less than 40%, the shrinkage amount is small, so it is not preferable because wrinkles and tarmi are generated on the label after heat shrinkage, and conversely, the width direction at 90 ° C. If the hot-water heat shrinkage rate exceeds 80%, it is not preferable because when used as a label, the shrinkage tends to occur during heat shrinkage, or so-called “jumping” occurs. In addition, the lower limit of the hot water temperature thermal contraction rate in the width direction at 90 ° C. is preferably 45% or more, more preferably 50% or more, and particularly preferably 55% or more. Further, the upper limit value of the hot water thermal contraction rate in the width direction at 90 ° C. is preferably 75% or less, more preferably 70% or less, and particularly preferably 65% or less.

  Further, the heat-shrinkable polystyrene-based laminated film used in the present invention is a film calculated by the above formula 2 from the length before and after shrinkage when treated for 10 seconds in 90 ° C. warm water with no load. The heat shrinkage rate in the longitudinal direction (that is, hot water heat shrinkage rate at 90 ° C.) is preferably 0% or more and 12% or less, preferably 0% or more and 11% or less, and 0% or more and 10% or less. More preferably, it is more preferably 0% or more and 9% or less, and particularly preferably 0% or more and 8% or less.

  It is preferable that the hot water thermal shrinkage in the longitudinal direction at 90 ° C. is less than 0% (that is, the shrinkage is a negative value) because a good shrink appearance cannot be obtained when used as a bottle label. On the other hand, if the hot water thermal shrinkage rate in the longitudinal direction at 90 ° C. exceeds 12%, it is not preferable because the shrinkage tends to occur during heat shrinkage when used as a label. The lower limit of the hot water heat shrinkage in the longitudinal direction at 90 ° C. is preferably 1% or more, more preferably 2% or more, and particularly preferably 3% or more.

  In addition, the heat-shrinkable polystyrene-based laminated film used in the present invention is a film calculated by the above equation 2 from the length before and after shrinkage when treated for 10 seconds in warm water at 80 ° C. under no load. The film was calculated by the above equation 2 from the length before and after shrinkage, when the heat shrinkage rate in the longitudinal direction was S10 (%), and was similarly treated in warm water at 80 ° C. for 5 seconds under no load. When the thermal contraction rate in the width direction is S5 (%), the ratio S5 / S10 of S5 and S10 is preferably 0.90 or less, and preferably 0.85 or less is 0.80 or less. More preferred.

  The ratio S5 / S10 between S5 and S10 is an index indicating the speed at which the film shrinks. When S5 / S10 exceeds 0.9, the shrinkage proceeds quickly, and the shrink finish when the film is shrink-fitted on the container. Sexuality gets worse. The smaller this ratio, the more slowly it shrinks, so it is considered advantageous for the finish.However, if it is too small, the initial shrinkage will be too slow and it will not be possible to follow high-speed mounting, which is disadvantageous in terms of productivity. Therefore, the lower limit is about 0.6.

  Moreover, the heat-shrinkable polystyrene-based laminated film used in the present invention preferably has a shrinkage stress in the width direction of 3 MPa or more and 20 MPa or less when heated to 90 ° C. If the shrinkage stress in the width direction when heated to 90 ° C is less than 3 MPa, it is not preferable because a good shrinkage appearance cannot be obtained when used as a label on a bottle, and conversely, the width when heated to 90 ° C. When the shrinkage stress in the direction exceeds 20 MPa, when used as a label, distortion tends to occur during heat shrinkage, which is not preferable. In addition, the lower limit value of the shrinkage stress in the width direction when heated to 90 ° C. is more preferably 4 MPa or more, further preferably 5 MPa or more, and particularly preferably 6 MPa or more. Further, the upper limit value of the shrinkage stress in the width direction when heated to 90 ° C. is more preferably 18 MPa or less, even more preferably 16 MPa or less, still more preferably 14 MPa or less, and particularly preferably 12 MPa or less. .

  Further, the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention is contracted by 10% in the width direction in warm water at 80 ° C., and then the perpendicular tear strength in the longitudinal direction per unit thickness by the following method. Is obtained, the right-angled tear strength in the longitudinal direction is preferably 90 N / mm or more and 300 N / mm or less, and more preferably 100 N / mm or more and 250 N / mm or less.

[Measurement method of right-angle tear strength]
The film is shrunk 10% in the width direction in hot water adjusted to 80 ° C., and then sampled as a test piece of a predetermined size according to JIS-K-7128. Thereafter, both ends of the test piece are gripped with a universal tensile tester, and the strength at the time of tensile fracture in the longitudinal direction of the film is measured under the condition of a tensile speed of 200 mm / min. Then, the right angle tear strength per unit thickness is calculated using the following formula 1.
Right angle tear strength = strength at tensile fracture ÷ thickness ・ ・ Equation 1

  When the right-angled tear strength after shrinking 10% in the width direction in warm water at 80 ° C is less than 90 N / mm, it may be easily broken by impacts such as dropping during transportation when used as a label. On the other hand, when the right-angled tear strength exceeds 300 N / mm, the cutting property (easy to tear) at the initial stage of tearing the label becomes unfavorable. The lower limit of the right-angled tear strength is preferably 100 N / mm or more, more preferably 110 N / mm or more, and particularly preferably 120 N / mm or more. Further, the upper limit value of the right-angled tear strength is preferably 270 N / mm or less, and more preferably 250 N / mm or less. If a void is formed in the film by increasing the amount of the additive in the resin, the right angle tear strength can be further reduced.

  Moreover, the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention has a tensile fracture strength of 100 MPa or more and 300 MPa or less when the tensile fracture strength in the longitudinal direction is determined by the following method. Is preferred.

[Measurement method of tensile fracture strength]
In accordance with JIS-K7113, a strip-shaped test piece of a predetermined size is prepared, and both ends of the test piece are gripped by a universal tensile tester, and a tensile test is performed under a condition of a tensile speed of 200 mm / min. The strength (stress) at the time of tensile fracture in the longitudinal direction of the film is calculated as the tensile fracture strength.

  If the tensile fracture strength in the longitudinal direction is less than 100 MPa, it is not preferable because the “waist” (stiffness) when attaching to a bottle or the like as a label becomes weak. On the contrary, if the tensile fracture strength exceeds 300 MPa, the label This is not preferable because the cutability (ease of tearing) at the initial stage of tearing becomes poor. In addition, the lower limit value of the tensile fracture strength is preferably 130 MPa or more, more preferably 150 MPa or more, and particularly preferably 170 MPa or more. Further, the upper limit value of the tensile fracture strength is preferably 280 MPa or less, more preferably 260 MPa or less, and particularly preferably 240 MPa or less.

  Moreover, the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention preferably has a thickness variation in the width direction (thickness variation when the measurement length is 1 m) of 10% or less. If the thickness unevenness in the width direction is more than 10%, it is not preferable because printing spots are likely to occur during printing at the time of label production or shrinkage spots after heat shrinkage are likely to occur. The thickness variation in the width direction is more preferably 8% or less, and particularly preferably 6% or less. Although the thickness variation in the width direction is preferably as small as possible, the lower limit of the thickness variation is considered to be about 1% from the viewpoint of the performance of the film forming apparatus.

  Furthermore, the thickness of the heat-shrinkable polystyrene-based laminated film preferably used in the present invention is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 70 μm, as the heat-shrinkable film for labels.

  In addition, the heat-shrinkable polystyrene-based laminated film preferably used in the present invention preferably has a haze value of 4.0 or more and 13.0 or less. If the haze value exceeds 13.0, the transparency becomes poor and the appearance may be deteriorated during label production. The haze value is more preferably 11.0 or less, and particularly preferably 9.0 or less. In addition, the haze value is preferably as small as possible. However, considering that a predetermined amount of lubricant must be added to the film for the purpose of imparting slipperiness necessary for practical use, the lower limit is about 4.0.

  The heat-shrinkable polystyrene-based laminated film preferably used in the present invention preferably has a thickness variation in the longitudinal direction (thickness variation when the measurement length is 10 m) of 12% or less. When the thickness unevenness in the longitudinal direction is more than 12%, it is not preferable because printed spots are likely to occur during printing at the time of label production or shrinkage spots after heat shrinkage are likely to occur. In addition, the thickness variation in the longitudinal direction is more preferably 10% or less, and particularly preferably 8% or less. Moreover, although the thickness variation in the longitudinal direction is preferably as small as possible, the lower limit of the thickness variation is considered to be about 1% from the viewpoint of the performance of the film forming apparatus.

Furthermore, the heat-shrinkable polystyrene-based laminated film preferably used in the present invention has a solvent adhesive strength of 2 (N / 15 m
m) or more, preferably 4 (N / 15 mm) or more. If the solvent adhesive strength is less than 4 (N / 15 mm), it is not preferable because the label is easily peeled off after the heat shrinkage. The solvent adhesive strength is more preferably 6 (N / 15 mm) or more, and particularly preferably 8 (N / 15 mm) or more. The higher the solvent adhesive strength, the better. However, the upper limit of the solvent adhesive strength is considered to be about 15 (N / 15 mm) in view of the performance of the film forming apparatus.

  In addition, the heat-shrinkable polystyrene-based laminated film preferably used in the present invention preferably has a dynamic friction coefficient (dynamic friction coefficient when the front surface and the back surface of the film are bonded) of 0.1 or more and 0.55 or less. If the dynamic friction coefficient is less than 0.1 or more than 0.55, it is not preferable because the processing characteristics at the time of processing into a label deteriorate. In addition, the lower limit value of the dynamic friction coefficient is more preferably 0.15 or more, and particularly preferably 0.2 or more. Further, the upper limit value of the dynamic friction coefficient is more preferably 0.50 or less, and particularly preferably 0.45 or less.

  The heat-shrinkable polystyrene-based laminated film preferably used in the present invention is a non-stretched laminate obtained by melting the polyester-based resin raw material and the polystyrene-based resin raw material so as to constitute each layer using a separate extruder and co-extrusion. It can be obtained by forming a film, biaxially stretching the unstretched laminated film by a predetermined method shown below, and heat-treating it.

  When the raw material resin is melt-extruded, the raw material is preferably dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer. After the raw material is dried in such a manner, it is melted at a temperature of 200 to 300 ° C. and extruded into a film using an extruder. For this extrusion, any existing method such as a T-die method or a tubular method can be employed.

  And an unstretched laminated | multilayer film can be obtained by rapidly cooling the sheet-like molten resin after extrusion. In addition, as a method of rapidly cooling the molten resin, a method of obtaining a substantially unoriented resin sheet by casting the molten resin on a rotating drum from a die and rapidly solidifying it can be suitably employed.

  Further, as will be described later, the obtained unstretched laminated film is stretched in the longitudinal direction under predetermined conditions, and after the longitudinally stretched film is rapidly cooled, it is heat-treated once, and the heat-treated film is After cooling under conditions, it is possible to obtain a heat-shrinkable polystyrene-based laminated film that is preferably used in the present invention by stretching in the width direction under predetermined conditions and heat treating again. Hereinafter, a preferred film forming method for obtaining a heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention will be described in detail in consideration of the difference from the conventional film-forming method of a heat-shrinkable polystyrene-based laminated film. explain.

[Method for producing heat-shrinkable polystyrene-based laminated film preferably used in the present invention]
As described above, the heat-shrinkable polystyrene-based laminated film is usually produced by stretching only in the direction in which the unstretched laminated film is to be shrunk (that is, the main shrinking direction, usually the width direction). As a result of the study of the conventional production method by the present inventors, it has been found that the following problems exist in the production of the conventional heat-shrinkable polystyrene-based laminated film.
If the film is simply stretched in the width direction, as described above, the mechanical strength in the longitudinal direction is reduced, and the perforation opening property when the label is used is deteriorated. In addition, it is difficult to increase the line speed of the film forming apparatus.
-If the method of extending | stretching to a longitudinal direction is employ | adopted after extending | stretching to the width direction, the contraction force of the width direction cannot fully be expressed, no matter what extending | stretching conditions are employ | adopted. In addition, the contraction force in the longitudinal direction is expressed at the same time, and when finished as a label, the finish after the shrinkage attachment becomes worse.
・ If a method of stretching in the width direction is used after stretching in the length direction, the contraction force in the width direction can be expressed, but the contraction force in the length direction is expressed at the same time. The finish of becomes worse.

Furthermore, based on the problems in the production of the above conventional heat-shrinkable polystyrene-based laminated film, the present inventors further obtain a heat-shrinkable polystyrene-based laminated film having good perforation opening and high productivity. As a result of further discussion, the following findings were obtained.
・ In order to improve the perforation of the perforated label, it is considered necessary to leave some molecules oriented in the longitudinal direction. In order to be good, it is indispensable not to develop contraction force in the longitudinal direction, and for that purpose it is considered necessary to eliminate the tension state of molecules oriented in the longitudinal direction

From the above findings, the present inventors need to have “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” in the film in order to satisfy both the good perforation opening property and the shrinkage finishing property at the same time. I came to think that there is. Then, a trial and error was carried out by paying attention to what kind of stretching would allow “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” to exist in the film. As a result, at the time of film production by the so-called longitudinal-lateral stretching method, which is stretched in the longitudinal direction after being stretched in the longitudinal direction, “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” by taking the following means: It is possible to obtain a heat-shrinkable polystyrene-based laminated film that simultaneously satisfies good perforation opening properties and shrinkage finishing properties, and has devised the present invention.
(1) Control of longitudinal stretching conditions (2) Intermediate heat treatment after longitudinal stretching (3) Natural cooling (interruption of heating) between intermediate heat treatment and transverse stretching
(4) Forced cooling of the film after natural cooling (5) Control of transverse stretching conditions Hereinafter, each of the above-described means will be sequentially described.

(1) Control of longitudinal stretching conditions In the production of a film by the longitudinal-lateral stretching method of the present invention, longitudinal stretching is preferably performed in two stages in order to obtain the film roll of the present invention. That is, a substantially unoriented film is longitudinally stretched at a temperature of 60 ° C. or higher and 110 ° C. or lower so as to have a magnification of 2.2 times or more and 3.0 times or less (first-stage stretching) to 60 ° C. or lower. Without being cooled, the film is stretched longitudinally (second-stage stretching) at a temperature of 70 ° C. or higher and 120 ° C. or lower so as to have a magnification of 1.2 times or more and 1.5 times or less. The longitudinal stretching ratio of the first stage × the longitudinal stretching ratio of the second stage) is preferably 2.8 times or more and 4.5 times or less, and the total longitudinal stretching ratio is 3.0 times or more and 4 times. More preferably, it is longitudinally stretched so as to be 3 times or less.

  Moreover, when longitudinally stretching in two stages as described above, the longitudinal stretching conditions are preferably adjusted so that the heat shrinkage stress in the longitudinal direction of the film after longitudinal stretching is 10 MPa or less. By performing longitudinal stretching under such predetermined conditions, it becomes possible to control the degree of orientation in the longitudinal and width directions of the film and the degree of molecular tension during intermediate heat treatment, lateral stretching, and final heat treatment, which will be described later. As a result, the perforation opening property of the final film can be improved.

  When stretching in the longitudinal direction as described above, if the total longitudinal stretching ratio increases, the contraction rate in the longitudinal direction tends to increase, but by stretching in two stages in the longitudinal direction as described above, The stretching stress in the direction can be reduced, and the shrinkage in the longitudinal direction can be kept low. In addition, when the total longitudinal stretching ratio is high, the stress at the time of stretching in the width direction tends to be high, and it tends to be difficult to control the final shrinkage in the lateral direction, but by stretching in two stages, The stretching stress in the transverse direction can be reduced, and the shrinkage rate in the transverse direction can be easily controlled.

  Furthermore, when the total longitudinal draw ratio is increased, the right-angled tear strength is decreased and the tensile strength in the longitudinal direction is increased. Further, by making the total longitudinal draw ratio close to the transverse draw ratio, it is possible to improve the perforation openability when the label is used. In addition, by stretching in two stages in the longitudinal direction, it is possible to reduce the stretching stress in the transverse direction, thereby creating a highly oriented state in the longitudinal direction that increases the hot air shrinkage at 160 ° C. in the longitudinal direction. The perpendicular tear strength is even lower and the tensile strength in the longitudinal direction is greater. Therefore, it is possible to obtain a label having very good perforation tearability by stretching in two stages in the longitudinal direction and increasing the total longitudinal stretching ratio.

  On the other hand, if the total longitudinal draw ratio exceeds 4.5 times, the orientation in the longitudinal direction becomes high and the solvent adhesive strength becomes low, but by controlling the total longitudinal draw ratio to 4.5 times or less, It is possible to keep the solvent adhesive strength high by suppressing the orientation in the longitudinal direction, and when the total longitudinal draw ratio exceeds 4.5 times, the roughness of the surface layer decreases, so the dynamic friction coefficient However, by controlling the total longitudinal draw ratio to 4.5 times or less, it is possible to suppress the decrease in surface roughness and keep the coefficient of dynamic friction low.

In addition, by stretching in two stages in the longitudinal direction, the stretching stress in the longitudinal direction is reduced, so that the thickness unevenness in the longitudinal direction and the thickness unevenness in the width direction tend to increase, but the total longitudinal stretching ratio is increased. By doing so, the thickness unevenness of a longitudinal direction can be made small, and a haze can also be reduced in connection with it. In addition, by increasing the total longitudinal stretching ratio, the stress during transverse stretching increases, so that thickness unevenness in the width direction can also be reduced.

In addition, by increasing the is the total lengthwise drawing ratio, it is possible to increase the orientation in the longitudinal direction, it is possible to improve the slitting property when wound into final rolls of film after biaxial stretching it can.

(2) Intermediate heat treatment after longitudinal stretching As described above, in order to make “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” exist in the film, it is preferable to thermally relax the molecules oriented in the longitudinal direction. However, conventionally, in the biaxial stretching of the film, if the film is subjected to a high temperature heat treatment between the first axis stretching and the second axis stretching, the film after the heat treatment is crystallized, so that the film is further stretched. It was technical common sense in the industry that it was not possible. However, as a result of trial and error by the inventors, in the longitudinal-transverse stretching method, longitudinal stretching is performed under certain conditions, intermediate heat treatment is performed under predetermined conditions according to the state of the film after the longitudinal stretching, and By applying transverse stretching under predetermined conditions according to the state of the film after the intermediate heat treatment, “molecules that are oriented in the longitudinal direction and do not contribute to the shrinkage force” are generated in the film without causing breakage during transverse stretching. The surprising fact that it can be present.

That is, in the production of a film by the longitudinal-lateral stretching method of the present invention, after longitudinally stretching an unstretched film, a temperature of 130 ° C. or higher and 190 ° C. or lower in a state where both ends in the width direction are held by clips in the tenter. It is preferable to perform heat treatment (hereinafter referred to as intermediate heat treatment) over a period of 1.0 second to 9.0 seconds. By performing such an intermediate heat treatment, “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” can be present in the film. As a result, when the label is used, the perforation is good and the shrinkage spots are not generated. A film that does not occur can be obtained. In any case, it is not possible to have “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” in the film, and the predetermined longitudinal stretching described above is performed. Thus, after the intermediate heat treatment, for the first time, “molecules that are oriented in the longitudinal direction and do not contribute to the shrinkage force” can be present in the film. Then, by performing the predetermined natural cooling, forced cooling, and transverse stretching described later, the molecules are oriented in the width direction while retaining the “molecules that do not contribute to the shrinkage force while being oriented in the longitudinal direction” formed in the film. It is possible to develop a contraction force in the width direction.

  In addition, the minimum of the temperature of intermediate heat processing is preferable in it being 140 degreeC or more, and it is more preferable in it being 150 degreeC or more. Moreover, the upper limit of the temperature of the intermediate heat treatment is preferably 180 ° C. or less, and more preferably 170 ° C. or less. On the other hand, the intermediate heat treatment time is preferably adjusted according to the raw material composition within a range of 1.0 second to 9.0 seconds, and more preferably 3.0 seconds to 7.0 seconds. preferable.

  Moreover, when performing the intermediate heat treatment as described above, it is preferable to adjust the conditions for the intermediate heat treatment so that the heat shrinkage stress in the longitudinal direction of the film after the intermediate heat treatment is 0.5 MPa or less. Furthermore, it is preferable to adjust the conditions of the intermediate heat treatment so that the tensile fracture elongation in the longitudinal direction of the film after the intermediate heat treatment is 100% or more and 170% or less. By performing an intermediate heat treatment under such predetermined conditions, it becomes possible to control the degree of orientation in the longitudinal direction and width direction of the film and the degree of molecular tension during transverse stretching and final heat treatment, and thus the final film. It becomes possible to make the perforation openability of this. In addition, when the tensile fracture elongation in the longitudinal direction of the film after the intermediate heat treatment is less than 100%, the film is fragile, so that the transverse stretchability is poor, and breakage is likely to occur during transverse stretching. On the other hand, if the tensile elongation at break in the longitudinal direction of the film after the intermediate heat treatment exceeds 170%, it becomes difficult to obtain a film with good perforation openability even if the conditions of transverse stretching and final heat treatment are adjusted. .

  Furthermore, when performing the intermediate heat treatment as described above, it is preferable to adjust the conditions for the intermediate heat treatment so that the perpendicular tear strength in the longitudinal direction of the film after the intermediate heat treatment is 260 N / mm or less. By performing an intermediate heat treatment under such a predetermined condition, it becomes possible to suppress a rapid increase in the right-angled tear strength in the longitudinal direction during transverse stretching, and to improve the perforation opening property of the final film. It becomes possible.

  When the intermediate heat treatment is performed as described above, by maintaining the treatment temperature at 130 ° C. or higher, it is possible to reduce the stress that shrinks in the longitudinal direction, and the shrinkage rate in the longitudinal direction can be extremely reduced. Also, if the intermediate heat treatment temperature is higher than 190 ° C, the variation in the shrinkage rate in the lateral direction will increase, but by controlling the intermediate heat treatment temperature to 190 ° C or less, the variation in the shrinkage rate in the horizontal direction will be reduced. It becomes possible to do.

Further, by maintaining the treatment temperature at 130 ° C. or higher, the longitudinal orientation can be increased, and the right-angle tear strength can be kept low. In addition, when the intermediate heat treatment is performed, if the treatment temperature exceeds 190 ° C, the film crystallizes and the tensile strength in the longitudinal direction decreases, but by controlling the intermediate heat treatment temperature to 190 ° C or less, It becomes possible to keep the tensile strength in the longitudinal direction high by suppressing crystallization of the film.

  Further, when the treatment temperature exceeds 190 ° C. during the intermediate heat treatment, the surface layer of the film is crystallized and the solvent adhesive strength is lowered, but by controlling the temperature of the intermediate heat treatment to 190 ° C. or less, It is possible to suppress the crystallization of the surface layer and keep the solvent adhesive strength high. In addition, by maintaining the treatment temperature at 130 ° C. or higher, the surface roughness of the surface layer can be increased appropriately, thereby reducing the friction coefficient.

  Further, when the heat treatment temperature exceeds 190 ° C. during the intermediate heat treatment, shrinkage spots are generated on the film, which tends to increase the thickness unevenness in the longitudinal direction and the thickness unevenness in the width direction. By controlling the temperature to 190 ° C. or lower, the thickness unevenness in the longitudinal direction can be kept small. In addition, during the intermediate heat treatment, if the treatment temperature exceeds 190 ° C., the film will crystallize, and the thickness variation in the width direction tends to increase due to variations in stress during transverse stretching. By controlling the temperature of the intermediate heat treatment to 190 ° C. or less, it becomes possible to suppress crystallization of the film and keep the thickness variation in the width direction small.

  Further, when the intermediate heat treatment is performed, if the treatment temperature exceeds 190 ° C., shrinkage spots are generated on the film, so that the slit property of the film is deteriorated during production or the film is easily broken. However, by controlling the temperature of the intermediate heat treatment to 190 ° C. or less, it becomes possible to suppress the film breakage and maintain good slitting properties.

  In addition, if the processing temperature exceeds 190 ° C during the intermediate heat treatment, the film will crystallize and the haze of the film tends to increase, but the intermediate heat treatment temperature is controlled to 190 ° C or lower. By doing so, the haze of the film can be kept low.

(3) Natural cooling (interruption of heating) between intermediate heat treatment and transverse stretching
In the production of a film by the longitudinal-lateral stretching method of the present invention, as described above, it is preferable to perform an intermediate heat treatment after the longitudinal stretching. It is preferable to pass through an intermediate zone where no aggressive heating operation is performed for a time of less than a second. That is, an intermediate zone is provided in front of the transverse stretching zone of the tenter for transverse stretching, the film after longitudinal stretching is guided to the tenter, and after passing through the intermediate zone for a predetermined time, the transverse stretching is performed. Is preferred. In addition, in the intermediate zone, when the strip-shaped piece of paper is suspended without passing through the film, the accompanying flow and cooling zone accompanying the flow of the film so that the piece of paper hangs down almost completely in the vertical direction. It is preferable to block the hot air from. If the time for passing through the intermediate zone is less than 0.5 seconds, the transverse stretching becomes high-temperature stretching, and the shrinkage rate in the transverse direction cannot be sufficiently increased. On the contrary, it is sufficient that the time for passing through the intermediate zone is 3.0 seconds, and setting it longer than that is not preferable because it wastes equipment. The lower limit of the time for passing through the intermediate zone is preferably 0.7 seconds or more, and more preferably 0.9 seconds or more. Further, the upper limit of the time for passing through the intermediate zone is preferably 2.8 seconds or less, and more preferably 2.6 seconds or less.

(4) Forced cooling of the film after natural cooling In the production of the film by the longitudinal-lateral stretching method of the present invention, the naturally cooled film is not directly stretched as it is, but the film temperature is 80 ° C. or higher and 120 ° C. It is preferable to quench rapidly so that it becomes below ℃. By performing such a rapid cooling treatment, it becomes possible to obtain a film having good perforation opening properties when used as a label. In addition, the lower limit of the temperature of the film after quenching is preferably 85 ° C or higher, and more preferably 90 ° C or higher. Moreover, the upper limit of the temperature of the film after rapid cooling is preferably 115 ° C. or less, and more preferably 110 ° C. or less.

  When the film is rapidly cooled as described above, if the temperature of the film after rapid cooling remains above 120 ° C., the shrinkage rate in the width direction of the film becomes low, and the shrinkability when used as a label is insufficient. However, by controlling the temperature of the cooled film to be 120 ° C. or lower, it is possible to maintain a high shrinkage rate in the width direction of the film.

  Also, when the film is rapidly cooled, if the temperature of the film after quenching remains above 120 ° C, the film will crystallize, haze increases, the tensile strength in the longitudinal direction decreases, and the solvent adhesive strength However, it is possible to keep the haze low and keep the tensile strength in the longitudinal direction and the solvent adhesive strength high by applying quenching so that the temperature of the film after cooling is 120 ° C. or lower. It becomes possible.

  Furthermore, when the film is rapidly cooled, if the temperature of the film after quenching remains higher than 120 ° C., the stress of transverse stretching performed after cooling tends to be small, and the thickness unevenness in the width direction tends to increase. By performing rapid cooling so that the temperature of the film after cooling is 120 ° C. or lower, it is possible to increase the stress of transverse stretching performed after cooling and reduce thickness unevenness in the width direction.

  In addition, when the film is rapidly cooled, if the temperature of the film after quenching remains higher than 120 ° C., the film is likely to be crystallized due to crystallization. By subjecting the film to rapid cooling so that the temperature of the film becomes 120 ° C. or lower, it is possible to suppress the breakage of the film.

(5) Control of transverse stretching conditions In the production of a film by the longitudinal-lateral stretching method of the present invention, it is preferable to transversely stretch the film after longitudinal stretching, intermediate heat treatment, and rapid cooling under predetermined conditions. That is, the transverse stretching is performed so that the magnification is 2.0 times or more and 6.0 times or less at a temperature of 70 ° C. or more and 120 ° C. or less in a state where both ends in the width direction are held by clips in the tenter. preferable. By performing transverse stretching under such predetermined conditions, the molecules are oriented in the width direction while maintaining the “molecules that do not contribute to the shrinkage force while being oriented in the longitudinal direction” formed by longitudinal stretching and intermediate heat treatment. Thus, it is possible to obtain a film having good perforation opening properties when used as a label. The lower limit of the transverse stretching temperature is preferably 75 ° C. or higher, and more preferably 80 ° C. or higher. Moreover, the upper limit of the temperature of transverse stretching is preferably 115 ° C. or less, and more preferably 110 ° C. or less. On the other hand, the lower limit of the transverse stretching ratio is preferably 2.5 times or more, and more preferably 3.0 times or more. Further, the upper limit of the transverse stretching ratio is preferably 5.5 times or less, and more preferably 5.0 times or less.

  When stretching in the transverse direction as described above, if the stretching temperature is increased, the tensile strength in the longitudinal direction is increased, the right-angle tear strength is decreased, and the perforation opening property when the label is formed becomes good.

  Further, when the stretching temperature exceeds 120 ° C., the shrinkage rate in the longitudinal direction becomes high and the shrinkage rate in the width direction becomes low. By controlling the stretching temperature to 120 ° C. or less, the shrinkage rate in the longitudinal direction is reduced. Can be kept low, and the shrinkage rate in the width direction can be kept high.

Further, when the stretching temperature in the lateral stretching increases, the lateral orientation decreases, the solvent adhesive strength increases, the crushing of the lubricant can be prevented, and the friction coefficient can be kept low. In addition, when the stretching temperature in the transverse stretching increases, the voids inside the film decrease, and the haze of the film decreases.

Further, when the stretching temperature exceeds 120 ° C., the thickness variation in the width direction tends to increase, but by controlling the stretching temperature to 120 ° C. or less, the thickness variation in the width direction can be reduced.

  On the other hand, when the stretching temperature is less than 70 ° C., the orientation in the width direction becomes too high, and it becomes easy to break at the time of transverse stretching, or the slit property when the film after biaxial stretching is finally wound on a roll. Although it becomes worse, by controlling the stretching temperature to 70 ° C. or higher, it is possible to reduce breakage during transverse stretching and to improve the slit property during winding.

[Effects of manufacturing process interaction on film properties]
In producing the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention, only one of the longitudinal stretching process, the intermediate heat treatment process, the natural cooling process, the forced cooling process, and the transverse stretching process is performed. It is not possible to improve the properties of the film by itself, and by performing all of the longitudinal stretching process, intermediate heat treatment process, natural cooling process, forced cooling process, and transverse stretching process under predetermined conditions, It is considered that the film characteristics can be improved efficiently. Among the properties of the film, important properties such as perpendicular tear strength in the longitudinal direction, tensile fracture strength in the longitudinal direction, 160 ° C. heat shrinkage in the longitudinal direction, thickness variation in the width direction, coefficient of dynamic friction, and thickness variation in the longitudinal direction The value fluctuates greatly depending on the interaction between a plurality of specific processes.

  That is, in the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention, the right-angled tear strength in the longitudinal direction is preferably adjusted to 90 N / mm or more and 300 N / mm or less, more preferably the right-angled tear in the longitudinal direction. The strength is adjusted to 100 N / mm or more and 270 N / mm or less, more preferably 110 N / mm or more and 250 N / mm or less. The right-angled tear strength in the longitudinal direction is determined by the mutual relationship between the longitudinal stretching step and the intermediate heat treatment step. The effect is very significant. Moreover, if a cavity is made by increasing the amount of additives in the resin as described above, the right-angled tear strength in the longitudinal direction can be adjusted small.

  The heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention preferably has a longitudinal tensile fracture strength of 100 MPa or more and 300 MPa or less. The interaction of the three processes of the longitudinal stretching process, the intermediate heat treatment process, and the transverse stretching process has a great influence.

  The heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention has a heat shrinkage rate in the direction (longitudinal direction) orthogonal to the main shrinkage direction when treated in hot air at 160 ° C. for 1 minute. However, it is preferable to adjust the shrinkage to 160 ° C. in the longitudinal direction because the interaction of the three steps of the longitudinal stretching step, the intermediate heat treatment step, and the transverse stretching step has a great influence.

  Furthermore, the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention is preferably adjusted to have a thickness variation in the width direction of 1.0% or more and 10.0% or less. Is greatly affected by the interaction of the three steps of the longitudinal stretching step, the intermediate heat treatment step, and the transverse stretching step.

  In addition, the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention is preferably adjusted to have a dynamic friction coefficient of 0.1 or more and 0.55 or less. The dynamic friction coefficient includes a longitudinal stretching step and an intermediate heat treatment. Interaction with the process is very significant.

  Moreover, the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention is preferably adjusted to have a thickness variation in the longitudinal direction of 1.0% or more and 12.0% or less. The interaction between the longitudinal stretching process and the intermediate heat treatment process has a great influence.

  Therefore, the label of the present invention can be applied to the heat-shrinkable polystyrene-based laminated film preferably used for the label of the present invention in the direction of perpendicular tearing strength, tensile fracture strength, thickness variation in the width direction, coefficient of dynamic friction, and thickness variation in the longitudinal direction. In order to adjust within the preferable range for use, it is preferable to perform delicate condition adjustment as described in the above (1) to (5) in consideration of the interaction between the steps described above.

  The label of the present invention is formed by covering at least a part of the outer periphery of an object with the heat-shrinkable polystyrene-based laminated film as a base material and subjecting the object to heat shrinkage. Examples include plastic bottles, various bottles, cans, plastic containers such as confectionery and lunch boxes, and paper boxes. In general, when a label based on a heat-shrinkable polystyrene-based laminated film is heat-shrinked and coated on those objects to be packaged, the label is heat-shrinked by about 2 to 15%. Adhere to. In addition, printing may be given to the label coat | covered with a packaging target object, and it does not need to be printed.

  The label can be made by applying an organic solvent slightly inside from the edge of one side of the rectangular film, and immediately rolling the film and bonding the edges together to form a label, or roll Apply the organic solvent slightly inside from the edge of one side of the film wound up in the shape of a film, immediately roll up the film, overlap the edges and adhere, cut the tube to make a label . As the organic solvent for adhesion, cyclic ethers such as 1,3-dioxolane or tetrahydrofuran are preferable. In addition, aromatic hydrocarbons such as benzene, toluene, xylene and trimethylbenzene, halogenated hydrocarbons such as methylene chloride and chloroform, phenols such as phenol, and mixtures thereof can be used.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the embodiments of the examples, and can be appropriately changed without departing from the spirit of the present invention. is there.

  The evaluation method of the film is as follows.

[Thermal shrinkage (hot water thermal shrinkage)]
The film is cut into a 10 cm × 10 cm square, heat-shrinked by treatment in warm water at a predetermined temperature ± 0.5 ° C. for 10 seconds under no load condition, and then measured in the vertical and horizontal dimensions of the film. According to the following formula 2, the thermal shrinkage rate was obtained. The direction in which the heat shrinkage rate is large was taken as the main shrinkage direction.
Thermal shrinkage rate = {(length before shrinkage−length after shrinkage) / length before shrinkage} × 100 (%)

[Maximum heat shrinkage stress value]
The film was cut into a size of main shrinkage direction (width direction) × direction perpendicular to the main shrinkage direction (longitudinal direction) = 200 mm × 15 mm. Then, after adjusting Baldwin's universal tensile testing machine STM-50 to a temperature of 90 ° C., the cut film was set, and the stress value in the main shrinkage direction when held for 10 seconds was measured.

[Right-angle tear strength]
After shrinking the film by 10% in the main shrinkage direction (width direction) in hot water adjusted to 80 ° C., the test piece was sampled by sampling into the shape shown in FIG. 1 according to JIS-K-7128. Produced. After that, grip both ends of the test piece with a universal tensile tester (Autograph, manufactured by Shimadzu Corporation), and measure the strength at the time of tensile fracture in the longitudinal direction under the condition of a tensile speed of 200 mm / min. 1 was used to calculate the right-angle tear strength per unit thickness.
Right angle tear strength = strength at tensile fracture ÷ thickness ・ ・ Equation 1

[Solvent adhesive strength]
The film was sealed by applying 1,3-dioxolane and pasting the two together. Thereafter, the seal portion is cut to a width of 15 mm in a direction orthogonal to the main shrinkage direction of the film (hereinafter referred to as the orthogonal direction), and set in a universal tension tester STM-50 manufactured by Baldwin Co., Ltd. A 180 ° peel test was performed at 200 mm / min. And the tensile strength at that time was made into solvent adhesive strength.

[Measurement method of tensile fracture strength]
In accordance with JIS-K7113, a strip-shaped test piece of a predetermined size is prepared, and both ends of the test piece are gripped by a universal tensile tester, and a tensile test is performed under a condition of a tensile speed of 200 mm / min. The strength (stress) at the time of tensile fracture in the longitudinal direction of the film is calculated as the tensile fracture strength.

[Hot air shrinkage]
Cut a strip of 70 to 90 mm in length in the direction perpendicular to the main shrinkage direction of the film (the longitudinal direction of the film: the direction of the perforation of the normal label) and 10 mm in the main shrinkage direction, and mark it at both ends of the center 50 mm The sample was heat-treated in a hot air oven at a temperature of 160 ° C. for 1 minute.

[Thickness unevenness in the width direction]
The film was sampled into a wide band with a length of 40 mm and a width of 1.2 m, and was measured in the width direction of the film sample at a speed of 5 (m / min) using a continuous contact thickness gauge manufactured by Micron Measuring Instruments Co., Ltd. The thickness was continuously measured along (measurement length was 500 mm). The maximum thickness at the time of measurement was Tmax., The minimum thickness was Tmin., The average thickness was Tave.
Thickness unevenness = {(Tmax.−Tmin.) / Tave.} × 100 (%) Equation 3

[Haze]
Based on JIS-K-7136, it measured using the haze meter (Nippon Denshoku Industries Co., Ltd. make, 300A). In addition, the measurement was performed twice and the average value was calculated | required.

[Longitudinal thickness unevenness]
The film was sampled into a long roll of 12 m long × 40 mm wide, and along the longitudinal direction of the film sample at a speed of 5 (m / min) using a continuous contact thickness gauge manufactured by Micron Measuring Instruments Co., Ltd. The thickness was continuously measured (measurement length was 10 m). The maximum thickness at the time of measurement was Tmax., The minimum thickness was Tmin., And the average thickness was Tave.

[Solvent adhesive strength]
The film was sealed by applying 1,3-dioxolane and pasting the two together. Thereafter, the seal portion is cut to a width of 15 mm in a direction orthogonal to the main shrinkage direction of the film (hereinafter referred to as the orthogonal direction), and set in a universal tension tester STM-50 manufactured by Baldwin Co., Ltd. A 180 ° peel test was performed at 200 mm / min. And the tensile strength at that time was made into solvent adhesive strength.

[Tm (melting point)]
Using a differential scanning calorimeter (model: DSC220) manufactured by Seiko Denshi Kogyo Co., Ltd., 5 mg of an unstretched film was sampled, and from the peak temperature of the endothermic curve when the temperature was raised from room temperature at a heating rate of 10 ° C./min. Asked.

  Moreover, the evaluation method of the label after coating is as follows.

[Measurement method of tensile fracture strength]
The label attached to the packaging object was peeled off, and when the label was printed, the printed layer was wiped off using a cloth soaked with ethyl acetate. A label that is not printed or has a printed layer removed, according to JIS-K-7127, a length of 50 mm in the direction perpendicular to the main shrinkage direction (= film longitudinal direction: perforation direction of normal label) × main Sampling in a rectangular shape with a length of 20 mm in the shrinking direction (film width direction) to make a test piece, using a universal tensile tester (manufactured by Shimadzu Corporation Autograph), both ends of the test piece (in the longitudinal direction) Both ends) were gripped and a tensile test was performed under the condition of a tensile speed of 200 mm / min, and the stress value at break was calculated as the tensile fracture strength.

[Right-angle tear strength]
The label attached to the packaging object was peeled off, and when the label was printed, the printed layer was wiped off using a cloth soaked with ethyl acetate. The test piece was produced by sampling the label which is not printed or remove | excluded the printing layer in the shape shown in FIG. 1 according to JIS-K-7128. The main shrink direction of the film (= the width direction of the film: the direction perpendicular to the perforation direction of the normal label) was taken as the longitudinal direction of the sample piece. After that, grip both ends of the test piece with a universal tensile tester (manufactured by Shimadzu Corporation Autograph), and measure the strength at the time of tensile fracture in the non-shrink direction (longitudinal direction) at a tensile speed of 200 mm / min. The right angle tear strength per unit thickness was calculated using the above equation 1.

[Hot air shrinkage]
The label attached to the packaging object is peeled off, and the length is 70 to 90 mm in the direction orthogonal to the main shrinkage direction of the film (= the longitudinal direction of the film: the perforation direction of the normal label), and the length is 10 mm in the main shrinkage direction. Cut out strips, put marked lines at both ends of the central 50 mm, heat-treat in a hot air oven at a temperature of 160 ° C. for 1 minute, measure the length between marked lines after air cooling, and obtain the shrinkage rate according to Equation 2 above. It was.

[Shrink finish]
The finished state of the label mounted around the packaging object was visually evaluated according to the following criteria.
◎: No wrinkles, jumping up, insufficient shrinkage, and no color spots are observed ○: Wrinkles, jumping up, or insufficient shrinkage cannot be confirmed, but some color spots are seen △: Jumping Neither ascending nor insufficient shrinkage has occurred, but spots on the neck are observed. ×: Wrinkles, jumping up, insufficient shrinkage occurred

[Label adhesion]
Sensory evaluation was performed on the degree of label displacement when the attached label and the packaging object were lightly twisted. If the label did not move, it was marked as ◯.

[Perforation opening]
Fill the packaged object such as a plastic bottle with 500ml of water, refrigerate to 5 ° C, tear the perforation of the label on the bottle immediately after taking it out of the refrigerator with your fingertips, and clean it vertically along the perforation And the number of labels that could be removed from the bottle was counted, and the ratio (%) to 50 samples was calculated.

  Tables 1 and 2 show the properties, compositions, examples, and film production conditions (stretching / heat treatment conditions, etc.) of the polyester raw materials used in the examples and comparative examples, respectively.

  In Table 1, chip A is polyethylene terephthalate containing 30 mol% of cyclohexanedimethanol (CHDM), chip B is polyethylene terephthalate containing 30 mol% of neopentyl glycol, and chip C is polyethylene terephthalate (PET). Chip D is a styrene-butyl acrylate copolymer (SC004 manufactured by PS Japan Co., Ltd.), Chip E is polystyrene (HH203 manufactured by PS Japan Co., Ltd.), and Chip F is a styrene-butadiene block. It is a copolymer (DENKACLEAREN 503L manufactured by Denki Kagaku Kogyo Co., Ltd.), and the chip G is a styrene-conjugated diene block copolymer (Toughprene 126 manufactured by Asahi Kasei Chemical Co., Ltd.). The polyester raw material chips A, B, and C were adjusted as follows.

<Preparation of polyester raw material>
In a stainless steel autoclave equipped with a stirrer, thermometer and partial reflux condenser, 100 mol% of dimethyl terephthalate (DMT) as a dibasic acid component and 100 mol% of ethylene glycol (EG) as a glycol component Was added to the molar ratio of 2.2 times that of the methyl ester, and 0.05 mol% of zinc acetate (based on the acid component) was used as the transesterification catalyst, and the methanol produced was distilled out of the system. The transesterification reaction was carried out. Thereafter, 0.025 mol% of antimony trioxide (based on the acid component) was added as a polycondensation catalyst, and a polycondensation reaction was performed at 280 ° C. under a reduced pressure of 26.6 Pa (0.2 Torr). A polyester (C) of 70 dl / g was obtained. This polyester is polyethylene terephthalate. In the production of the polyester (C), SiO2 (Silicia 266 manufactured by Fuji Silysia) as a lubricant was added at a rate of 8,000 ppm with respect to the polyester. Moreover, the polyester (A, B) shown in Table 1 was synthesize | combined by the method similar to the above. In the table, NPG is neopentyl glycol, and CHDM is 1,4-cyclohexanedimethanol. The intrinsic viscosity of each polyester was 0.80 dl / g for A and 0.72 dl / g for B. Each polyester was appropriately formed into a chip shape.

[Example 1]
Using a co-extrusion method, core layer forming resin, skin layer forming resin, and adhesive layer forming resin are melt-extruded from separate extruders (first to third extruders) and dies (T-die). It is laminated inside, wound around a rotating metal roll cooled to 40 ° C. by an air knife method, and rapidly cooled to have a thickness of 730 μm, a three-kind five-layer structure, that is, an intermediate layer on both sides of the core layer ( Adhesive layers) were laminated, and unstretched films (polystyrene-based resin laminated sheets) having a structure in which skin layers were laminated on the outer sides of the intermediate layers were obtained. The method for forming each layer of the unstretched film (steps until melt extrusion) is as follows. In the following description, the first layer, the second layer, the third layer, the fourth layer, and the fifth layer are referred to in order from the front and back of the polystyrene-based mixed resin laminated sheet (that is, the surface of the fifth layer is a metal Roll contact surface).

-Formation of first layer and fifth layer (skin layer) Each of the above-mentioned chips A and C is preliminarily dried using a blender device, and then 95 parts by weight of chip A and 5 wt. The parts were mixed with a blender and then continuously fed to the hopper directly above the first extruder with a fixed screw feeder. The supplied mixture of chips A and C was melt-extruded from a T die by a single-screw first extruder (melted so as to be laminated outside the intermediate layer laminated outside the front and back of the core layer) Extruded). In the first extruder, the temperature of the first zone is adjusted to 270 ° C., and the temperature of the second zone is adjusted to 220 ° C. After that, it led to the T die. In order to stabilize the extrusion from the T die, a helical type and parallel type gear pump was interposed between the extruder and the T die. In addition, the extrusion temperature of the first extruder was controlled by the PID control method.

-Formation of the second layer and the fourth layer (adhesive layer) After the above-mentioned chip D is pre-dried using a blender device, the pre-dried chip D is placed in a hopper directly above the second extruder. It supplied continuously with the fixed amount screw feeder. Then, the supplied chip D was melt-extruded from the T die by a single-screw second extruder (melt-extruded so as to be laminated on the outer sides of the core layer). In the second extruder, the temperature of the first zone and the temperature of the second zone were both adjusted to 200 ° C. Similarly to the extrusion by the first extruder, a helical type and parallel type gear pump was interposed between the extruder and the T die in order to stabilize the extrusion from the T die. In addition, the extrusion temperature of the second extruder was also controlled by the PID control method in the same manner as the extrusion temperature of the first extruder.

-Formation of third layer (core layer) Each of the above chips E, F, G is preliminarily dried using a blender device, and then these chips E, F, G are fed into a mixing mixer and a quantitative screw feeder. Continuously and separately. The supply amount of chip E was 100 wt % , the supply amount of chip F was 43 wt % , and the supply amount of chip G was 14 wt % . Thereafter, the mixed raw materials of chips E, F, and G mixed in the mixing mixer were continuously and separately supplied to the hopper immediately above the third extruder by a quantitative screw feeder. Then, the supplied chips E, F, and G (mixed ones) were melt-extruded from a T die by a single-screw third extruder. In the third extruder, the temperature of the first zone and the temperature of the second zone were both adjusted to 200 ° C. Also, like the extrusion by the first extruder and the extrusion by the second extruder, in order to stabilize the extrusion from the T die, a helical type and parallel type gear pump was interposed between the extruder and the T die. . In addition, the extrusion temperature of the third extruder was also controlled by the PID control method in the same manner as the extrusion temperatures of the first and second extruders.

  In addition, in the extrusion of resin by each of the above extruders, the discharge amount of the first to third extruders in the formation of the unstretched film is as follows: first layer / second layer / third layer / fourth layer / fifth layer The thickness ratio was adjusted to 6/2/34/2/6. Moreover, also about the extrusion temperature of T-die, temperature control by the PID control system was performed similarly to the 1st-3rd extruder.

  Then, the unstretched film obtained as described above was led to a longitudinal stretching machine in which a plurality of roll groups were continuously arranged, and stretched in two stages in the longitudinal direction using a difference in the rotational speed of the rolls. That is, after preheating an unstretched film on a preheating roll until the film temperature reaches 80 ° C., a low-speed rotating roll set at a surface temperature of 78 ° C. and a medium-speed rotating roll set at a surface temperature of 80 ° C. The film was stretched 2.6 times using the rotational speed difference (first-stage longitudinal stretching). Further, the longitudinally stretched film is longitudinally stretched 1.4 times using a rotational speed difference between a medium-speed rotating roll set at a surface temperature of 95 ° C. and a high-speed rotating roll set at a surface temperature of 30 ° C. Stretched (second-stage longitudinal stretching) (therefore, the total longitudinal stretching ratio was 3.64 times).

  As described above, the film immediately after the longitudinal stretching is forcibly cooled at a cooling rate of 40 ° C./second by a cooling roll set at a surface temperature of 30 ° C. (a high-speed roll positioned immediately after the second-stage longitudinal stretching roll). After that, the cooled film is guided to the tenter, and the intermediate heat treatment zone, the first intermediate zone (natural cooling zone), the cooling zone (forced cooling zone), the second intermediate zone, the transverse stretching zone, and the final heat treatment zone are continuously formed. I let it pass. In the tenter, the length of the first intermediate zone is set to about 40 cm, between the intermediate heat treatment zone and the first intermediate zone, between the first intermediate zone and the cooling zone, and between the cooling zone and the second intermediate zone. Shielding plates were provided between the intermediate zone and between the second intermediate zone and the transverse stretching zone, respectively. Further, in the first intermediate zone and the second intermediate zone, when the strip-shaped paper piece is hung in a state where the film is not passed through, the paper piece from the intermediate heat treatment zone is almost completely hung down in the vertical direction. Hot air, cooling air from the cooling zone, and hot air from the transverse stretching zone were blocked. In addition, when passing the film, the film and the shielding plate are arranged so that most of the accompanying flow accompanying the film flow is blocked by the shielding plate provided between the intermediate heat treatment zone and the first intermediate zone. Adjusted the distance.

  Then, the longitudinally stretched film led to the tenter is first heat treated at a temperature of 160 ° C. for 5.0 seconds in the intermediate heat treatment zone, and then the film after the intermediate heat treatment is led to the first intermediate zone. Natural cooling was achieved by passing through the zone (passing time = approximately 1.0 second). After that, the film after natural cooling is guided to the cooling zone, and is actively cooled by blowing low temperature air until the surface temperature of the film reaches 100 ° C., and the cooled film is guided to the second intermediate zone. Then, it was naturally cooled again by passing through the zone (passing time = about 1.0 second). Further, the film after passing through the second intermediate zone is guided to the transverse stretching zone, preheated until the surface temperature of the film reaches 95 ° C., and then 4.0 times in the width direction (lateral direction) at 95 ° C. Stretched.

  Thereafter, the laterally stretched film is guided to the final heat treatment zone, where it is heat treated at a temperature of 85 ° C. for 5.0 seconds and then cooled, and both edges are cut and removed to obtain a width of 500 mm. The biaxially stretched film of about 50 μm was continuously produced over a predetermined length by winding in a roll. And the characteristic of the obtained film and label was evaluated by the above-mentioned method. The evaluation results are shown in Table 3.

[Example 2]
In the raw material chip used for the first layer and the fifth layer, a biaxially stretched film having a width of about 50 μm is formed to have a width of 500 mm by forming a film under the same conditions as in Example 1 except that polyester B is used instead of polyester A described above. Produced continuously. And the characteristic of the obtained film and label was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Example 3]
Examples except that the discharge amount of each extruder was adjusted so that the thickness ratio of the first layer / second layer / third layer / fourth layer / fifth layer would be 12/2/22/2/12 A biaxially stretched film having a thickness of about 50 μm was continuously produced with a width of 500 mm. And the characteristic of the obtained film and label was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Example 4]
An unstretched film was obtained in the same manner as in Example 1, except that the film thickness was changed to 810 μm by adjusting the discharge amount with respect to Example 1. The unstretched film was subjected to a first stage longitudinal stretching ratio of 2.9 times, and the total longitudinal stretching ratio was changed to 4.06 times, and at an intermediate heat treatment zone at a temperature of 170 ° C. for 8.0 seconds. A biaxially stretched film having a thickness of about 50 μm was continuously produced with a width of 500 mm by forming a film under the same conditions as in Example 1 except that the heat treatment was performed. And the characteristic of the obtained film and label was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Example 5]
An unstretched film was obtained in the same manner as in Example 1, except that the film thickness was changed to 640 μm by adjusting the discharge amount with respect to Example 1. Example 1 except that the unstretched film was heat-treated at a temperature of 155 ° C. in the intermediate heat treatment zone with the first-stage longitudinal stretch ratio being 2.3 times and the total longitudinal stretch ratio being changed to 3.22. The biaxially stretched film of about 50 μm was continuously produced with a width of 500 mm. And the characteristic of the obtained film and label was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Example 6]
An unstretched film was obtained in the same manner as in Example 1 except that the film thickness was changed to 620 μm by adjusting the discharge amount with respect to Example 1. Example 1 except that the unstretched film was heat-treated at a temperature of 155 ° C. in an intermediate heat treatment zone by changing the first-stage longitudinal stretch ratio to 2.2 times and changing the total longitudinal stretch ratio to 3.08 times. The biaxially stretched film of about 50 μm was continuously produced with a width of 500 mm. And the characteristic of the obtained film and label was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Example 7]
As a raw material to be charged into the first extruder, 90% by weight of polyester A and 10% by weight of polyester C are mixed, charged, and melt extruded to form the first layer and the fifth layer. By forming the film under the same conditions, a biaxially stretched film of about 50 μm was continuously produced with a width of 500 mm. And the characteristic of the obtained film and label was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Example 8]
The discharge amount of each extruder was adjusted so that the thickness ratio of the first layer / second layer / third layer / fourth layer / fifth layer was 18/2/10/2/18 and the film thickness was changed to 670 μm. Others were carried out similarly to Example 1, and obtained the unstretched film. By forming the unstretched film under the same conditions as in Example 1 except that the first-stage longitudinal stretching ratio was 2.4 times and the total longitudinal stretching ratio was changed to 3.36 times, a film thickness of about 50 μm was obtained. A biaxially stretched film was continuously produced with a width of 500 mm. And the characteristic of the obtained film and label was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Comparative Example 1]
An unstretched film having a film thickness of 200 μm obtained in the same manner as in Example 1 except that the discharge amount was changed was preheated until the surface temperature of the film reached 80 ° C., and then the width direction (lateral direction at 80 ° C. ) Was uniaxially stretched 4.0 times. Thereafter, the laterally stretched film is guided to the final heat treatment zone, where it is heat treated at a temperature of 85 ° C. for 5.0 seconds and then cooled, and both edges are cut and removed to obtain a width of 500 mm. The film was wound into a roll to produce a laterally uniaxially stretched film of about 50 μm continuously over a predetermined length.

[Comparative Example 2]
Except that the discharge rate of each extruder was adjusted so that the thickness ratio of the first layer / second layer / third layer / fourth layer / fifth layer would be 18/2/10/2/18. The pre-heated unstretched film having a film thickness of 310 μm obtained on the preheating roll until the film temperature reaches 78 ° C., then the low-speed rotating roll set at the surface temperature of 80 ° C. and the surface temperature set at 80 ° C. Further, the film was stretched 1.1 times using the difference in rotational speed with the medium-speed rotating roll. Further, the longitudinally stretched film is longitudinally stretched 1.4 times using a rotational speed difference between a medium-speed rotating roll set at a surface temperature of 92 ° C. and a high-speed rotating roll set at a surface temperature of 30 ° C. The film was stretched (thus, the total longitudinal draw ratio was 1.54). Thereafter, in the same manner as in Example 1, intermediate heat treatment, natural cooling, forced cooling, transverse stretching, and final heat treatment were applied to the film, and both edges were cut and removed, whereby a biaxially stretched film of about 50 μm in width of 500 mm was obtained. Manufactured continuously. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Comparative Example 3]
By forming the film under the same conditions as in Comparative Example 2 except that the thickness of the unstretched film was 370 μm, the transverse stretching ratio was 4.8 times, and the final heat treatment temperature was changed to 90 ° C., biaxial stretching of about 50 μm The film was continuously produced with a width of 500 mm. And the characteristic of the obtained film and label was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

  As is clear from Table 3, the films obtained in Examples 1 to 7 all have high shrinkage in the width direction, which is the main shrinkage direction, and the shrinkage in the longitudinal direction perpendicular to the main shrinkage direction is high. It was very low. In addition, the films obtained in Examples 1 to 7 all have high solvent adhesive strength, small longitudinal thickness unevenness, and a label in the direction perpendicular to the main contraction direction (perforation direction). The heat shrinkage rate at 160 ° C. was large, the label adhesion was good, no shrinkage spots were seen, and the perforation opening property was good. That is, the heat-shrinkable film obtained in the examples and the label using the film were high in quality and extremely practical.

  On the other hand, the label using the heat-shrinkable film obtained in Comparative Examples 1 and 2 has a small 160 ° C. heat shrinkage rate in the direction orthogonal to the main shrinkage direction (perforation direction), and has good perforation openability. There wasn't. That is, the heat-shrinkable film and label obtained in the comparative example were inferior in quality and low in practicality.

  Since the label of this invention has the characteristic which was excellent in perforation openability, it can be used suitably for the use for the packaging of various articles | goods.

  F ・ ・ Film

Claims (3)

  A heat-shrinkable polystyrene-based laminated film, which is formed by laminating a skin layer mainly composed of a polyester-based resin layer on at least one surface of a core layer mainly composed of a polystyrene-based resin, and thermally shrinks with the film width direction as a main shrinkage direction. An annular body which is a base material and is cut according to the packaging object and bonded at both ends in the film width direction is a label which covers at least a part of the outer periphery of the packaging object by heat shrinkage, The perpendicular tear strength in the direction perpendicular to the shrinkage direction (film longitudinal direction) is 90 N / mm to 300 N / mm, and the tensile fracture strength in the direction perpendicular to the main shrinkage direction (film longitudinal direction) is 100 MPa to 300 MPa. And the heat shrinkage rate in the direction orthogonal to the main shrinkage direction when treated in hot air at 160 ° C. for 1 minute is 40% or more. Label.   The label according to claim 1, wherein adhesion is performed with an organic solvent.   The label according to claim 1 or 2, wherein a perforation or a notch is provided along a direction (film longitudinal direction) perpendicular to the main shrinkage direction.

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