JP7107657B2 - Heat-shrinkable film, long labels, and tubular labels - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-shrinkable film, a long label, and a tubular label. More specifically, the present invention relates to a heat-shrinkable film, a long label and a tubular label using the heat-shrinkable film.

Currently, plastic bottles such as PET bottles and metal bottles such as bottle cans are widely used as containers for beverages such as tea and soft drinks. These containers are often attached with plastic labels for display, decoration, and functionality. As such plastic labels, for example, shrink labels (heat shrinkable labels) are widely used.

As the shrink label, there is known a shrink label having a different laminated film in which different resin materials are laminated for the purpose of imparting various functions to the label. For example, as a shrink label that achieves both low specific gravity and center sealability with a solvent, a polyolefin resin layer is used as a core material, and resin layers containing polystyrene resin as a main component are laminated on both sides of the core material via an acid-modified polyethylene resin. A label made of a heat-shrinkable label film is known (see, for example, Patent Document 1). In addition to the low specific gravity, the shrink label has good printability, solvent sealability, and dimensional stability. A heat-shrinkable label having a heat-shrinkable laminated film with both outer layers made of styrene resin is known (see, for example, Patent Document 2).

Japanese Patent No. 3286594 JP-A-2002-86637

The shrink label may be obtained as an elongated body in which a plurality of shrink labels are arranged in a row in the longitudinal direction (longitudinal direction). Then, the label long body is formed into a tubular shape by overlapping one end and the other end so that the heat-shrinkable direction is the circumferential direction to form a long tubular label continuous body (long tubular shrink label ), and then cut this long tubular shrink label in the circumferential direction to obtain one tubular shrink label having a predetermined length in the height direction. The cylindrical shrink label thus obtained is fitted onto an adherend such as a container, and is attached to the adherend by subsequent heat shrinking (shrinking) for use.

When the long tubular shrink label is cut in the circumferential direction using a cutter to obtain individual tubular shrink labels, the flat folded long tubular shrink label is crushed by the cutter to separate the inner surfaces of the labels. However, when the innermost surface of the portion to be cut of the long cylindrical shrink label has a resin layer mainly composed of polystyrene resin, the inner surfaces of the labels sometimes adhere to each other. If the inner surfaces of the label are adhered to each other, the label cannot be expanded from a flat shape to a cylindrical shape after being cut, so that it cannot be fitted onto an adherend afterward. The adhesion is considered to be caused by fusion between the heat-shrinkable films due to frictional heat generated by the cutter during cutting, the influence of pressure, and the like.

The present invention was conceived under such circumstances, and an object of the present invention is to provide a resin layer having a resin layer mainly composed of polystyrene resin on the surface, while the inner surfaces are adhered to each other when cut. To provide a heat-shrinkable film capable of obtaining a long tubular label which is difficult to peel off.
Another object of the present invention is to provide a long label body that can obtain a long tubular label whose inner surfaces are difficult to adhere to each other when cut.
Another object of the present invention is to provide a cylindrical shrink label that has good appearance at the top and bottom ends and can be easily fitted onto an adherend.

As a result of intensive studies to achieve the above object, the present inventors have found that a resin layer formed from a resin composition containing a polystyrene resin as a main component and having a bending elastic modulus of a specific value or higher is formed on at least one surface. The static friction coefficient between the resin layers is within a specific range, so that the long cylindrical label has a resin layer containing polystyrene resin as a main component on the surface and the inner surfaces are difficult to adhere to each other when cut. It was found that a heat-shrinkable film is obtainable. The present invention has been completed based on these findings.

That is, the present invention has, on at least one surface, a resin layer formed from a resin composition having a polystyrene resin as a main component and a flexural modulus of 1600 MPa or more, and the static friction coefficient between the resin layers is 0. 0.10 to 0.40.

The polystyrene-based resin preferably contains general-purpose polystyrene.

The present invention also provides a long label, comprising the heat-shrinkable film and a printed layer provided on at least one surface of the heat-shrinkable film. It is preferable that the long label does not have the printed layer in the region to be cut on the resin layer.

The present invention also provides a cylindrical shrink label comprising the heat-shrinkable film and a printed layer provided on at least one surface of the heat-shrinkable film. It is preferable that the tubular shrink label does not have the printed layer on the upper and lower end regions of the inner surface.

The heat-shrinkable film of the present invention having the above-described structure makes it possible to obtain a long tubular label having a resin layer containing a polystyrene-based resin as a main component on the surface and having inner surfaces that are difficult to adhere to each other when cut. It is possible. Further, the long label body of the present invention makes it possible to obtain a long cylindrical shrink label whose inner surfaces are difficult to adhere to each other when cut. Moreover, the cylindrical shrink label of the present invention has good appearance at the upper and lower ends, and can be easily fitted onto the adherend.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of a long body (long label body) of a shrink label, which is an embodiment of a shrink label using the heat-shrinkable film of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of a long tubular shrink label, which is an embodiment of a shrink label using the heat-shrinkable film of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of a tubular shrink label, which is an embodiment of a shrink label using the heat-shrinkable film of the present invention; FIG. 3 is a schematic view (enlarged view of the upper surface of the cross section IV-IV' of FIG. 3) showing an example of a tubular shrink label, which is an embodiment of the shrink label using the heat-shrinkable film of the present invention. It is a schematic diagram showing an example of a rotary cutter.

The heat-shrinkable film (shrink film) of the present invention has, on at least one surface, a resin layer formed from a resin composition containing a polystyrene-based resin as a main component and having a flexural modulus of 1600 MPa or more. The coefficient of static friction between the resin layers is 0.10 to 0.40. In the present specification, a resin layer containing the polystyrene resin as a main component, formed from a resin composition having a flexural modulus of 1600 MPa or more, and having a static friction coefficient between layers of 0.10 to 0.40 is defined as " It may be referred to as "the resin layer of the present invention".

[Heat-shrinkable film of the present invention]
When the heat-shrinkable film of the present invention is used for a shrink label, it becomes a support and has a major influence on the strength, rigidity and shrinkage properties of the label. The heat-shrinkable film of the present invention has the resin layer of the present invention on at least one surface. The heat-shrinkable film of the present invention may have a single-layer structure or a laminated structure. That is, the heat-shrinkable film of the present invention may be a single-layer film, or a laminated film obtained by laminating a plurality of film layers according to required physical properties, applications, and the like. When the heat-shrinkable film of the present invention has a single-layer structure, the heat-shrinkable film of the present invention has a single-layer structure of the resin layer of the present invention. Moreover, in the case of a laminated film, the layer located on at least one surface is the resin layer of the present invention. In the case of a laminated film, it may have two or more identical or different resin layers of the present invention.

(Resin layer of the present invention)
The resin layer of the present invention contains polystyrene-based resin as a main component. The resin that is the main component in the layer (for example, the resin layer of the present invention) that constitutes the heat-shrinkable film is the resin that has the highest mass ratio among the resins that constitute the layer. The content of the polystyrene-based resin in the resin layer of the present invention is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass with respect to the total mass (100% by mass) of the resin layer of the present invention. It is at least 95% by mass, particularly preferably at least 95% by mass. Only one type of the polystyrene-based resin may be used, or two or more types may be used.

The polystyrene-based resin is a polymer composed of a styrene-based monomer as an essential monomer component. That is, it is a polymer containing at least a structural unit derived from a styrene-based monomer in its molecule (in one molecule).

Examples of the styrene-based monomer include, but are not limited to, styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, p-isobutylstyrene, pt-butylstyrene, Chloromethylstyrene and the like can be mentioned. Among them, styrene is preferable from the viewpoint of availability, material cost, and the like. In addition, the said styrenic monomer may use only 1 type, and may use 2 or more types.

The polystyrene-based resin is not particularly limited. Copolymers composed as monomer components; styrene-diene-based copolymers; styrene-polymerizable unsaturated carboxylic acid ester-based copolymers; ), high-impact polystyrene (HIPS) such as polystyrene obtained by graft-polymerizing styrene to synthetic rubber; Polystyrene obtained by dispersing a rubber-like elastomer in a continuous phase of a polymer (copolymer with a polymer) and graft-polymerizing the above-mentioned copolymer on the rubber-like elastomer (referred to as graft type high-impact polystyrene "graft HIPS") ; styrene-based elastomers and the like can be mentioned. In addition, the said polystyrene resin may use only 1 type, and may use 2 or more types.

The resin layer of the present invention preferably contains GPPS as the polystyrene resin. In this case, the bending elastic modulus of the resin composition forming the resin layer of the present invention tends to increase, and the static friction coefficient tends to decrease.

The content of GPPS in the resin layer of the present invention is not particularly limited, but is preferably 0.3 to 3% by mass, more preferably 0.3 to 3% by mass, based on the total mass (100% by mass) of the resin layer of the present invention. 5 to 2% by mass, more preferably 1.1 to 1.7% by mass, particularly preferably 1.2 to 1.4% by mass. When the content ratio is within the above range, adhesion between the inner surfaces of the long cylindrical shrink label is less likely to occur when the long cylindrical shrink label is cut.

Also, the resin layer of the present invention preferably contains a styrene-diene copolymer together with GPPS. In this case, the heat-shrinkable film of the present invention and the shrink label using the same have excellent shrinkage properties, while the bending elastic modulus of the resin composition forming the resin layer of the present invention increases, and the static friction coefficient tends to be smaller.

The styrene-diene copolymer is a copolymer comprising a styrene monomer and a diene (especially a conjugated diene) as essential monomer components. That is, it is a polymer containing at least a structural unit derived from a styrene-based monomer and a structural unit derived from a diene (in particular, a conjugated diene) in its molecule (in one molecule).

The diene is not particularly limited, but is preferably a conjugated diene such as 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 3-pentadiene, 1,3-hexadiene, chloroprene and the like. Among them, 1,3-butadiene is particularly preferable from the viewpoint of stretchability, heat shrinkability and interlaminar strength. That is, the styrene-diene copolymer is preferably a styrene-butadiene copolymer. In addition, the said diene may use only 1 type, and may use 2 or more types.

The monomer components constituting the styrene-diene copolymer may further contain monomer components other than the styrene monomer and the diene. Examples of monomer components other than the styrene-based monomer and the diene include vinyl-based monomers, polymerizable unsaturated carboxylic acid esters, and polymerizable unsaturated carboxylic acid anhydrides.

The form of copolymerization of the styrene-diene-based copolymer is not particularly limited, but examples thereof include random copolymers, block copolymers and graft copolymers. Among them, block copolymers are preferred, and examples thereof include styrene block (S)-diene block (D) type, SDS type, DSD type, and SDSD type. .

Examples of the above styrene-diene-based copolymer block copolymer (styrene-diene block copolymer) include, for example, styrene-butadiene-styrene block copolymer (SBS) and other styrene-butadiene block copolymers (SBC ), styrene-isoprene block copolymers such as styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene-isoprene block copolymers such as styrene-butadiene-isoprene-styrene block copolymer (SBIS), etc. Among them, a styrene-butadiene block copolymer is preferred. In addition, these block copolymers may use only 1 type, and may use 2 or more types.

The styrene-butadiene block copolymer is not particularly limited as long as it is a copolymer having a styrene block polymerized only with a styrene-based monomer and a butadiene block polymerized only with butadiene. Styrene-butadiene block copolymers having styrene blocks at both ends, such as butadiene-styrene block copolymers (SBS) and styrene-butadiene-styrene-butadiene-styrene block copolymers (SBSBS); styrene-butadiene copolymers (SB), styrene-butadiene-styrene-butadiene copolymer (SBSB) and other styrene-butadiene block copolymers having terminal styrene and butadiene blocks; butadiene-styrene-butadiene copolymer (BSB), butadiene -Styrene-butadiene-styrene-butadiene copolymer (BSBSB) and other styrene-butadiene block copolymers having butadiene blocks at both ends. Among them, a styrene-butadiene block copolymer having styrene blocks at both ends is preferred, and SBS is more preferred. These styrene-butadiene block copolymers may be used alone or in combination of two or more.

The styrene-diene block copolymer can be produced by a known or commonly used block copolymer production method. Examples of the method for producing the styrene-diene block copolymer include living polymerization (living radical polymerization, living anion polymerization, living cationic polymerization, etc.). The living polymerization can be carried out by a known or commonly used method.

The content of the styrene-diene copolymer in the resin layer of the present invention is not particularly limited, but is preferably 50 to 99.7% by mass with respect to the total mass (100% by mass) of the resin layer of the present invention. , more preferably 60 to 99.5% by mass, still more preferably 80 to 99% by mass, and particularly preferably 90 to 98% by mass. When the content is within the above range, the heat-shrinkable film of the present invention and the shrink label using the same are excellent in shrinkage properties.

Also, the resin layer of the present invention preferably contains HIPS together with GPPS and a styrene-diene copolymer. In this case, the bending elastic modulus of the resin composition forming the resin layer of the present invention can be easily adjusted within a specific range.

The content of HIPS in the resin layer of the present invention is not particularly limited, but is preferably 0.5 to 10% by mass, more preferably 1 to 10% by mass, relative to the total mass (100% by mass) of the resin layer of the present invention. 5% by mass. When the content ratio is within the above range, the bending elastic modulus of the resin composition forming the resin layer of the present invention can be more easily adjusted within a specific range.

The content ratio of structural units derived from styrene-based monomers in all the polystyrene-based resins contained in the resin layer of the present invention is not particularly limited, but the total mass of the polystyrene-based resin in the resin layer of the present invention ( 100% by mass), preferably 50 to 95% by mass, more preferably 60 to 90% by mass, still more preferably 65 to 85% by mass, and particularly preferably 70 to 80% by mass. When the above content is 50% by mass or more, the heat-shrinkable film of the present invention is moderately hardened, the rigidity of the shrink label is moderately increased, and the shrinkage property when the shrink label is attached tends to be good. be. When the content ratio is 95% by mass or less (especially 85% by mass or less), it is difficult to break even when the unstretched film is stretched at a high magnification, and it becomes easy to obtain a heat-shrinkable film having high heat-shrinkability. . In addition, there is a tendency that moderate shrinkage stress and shrinkage properties can be obtained.

Although the resin layer of the present invention is not particularly limited, it may contain a resin other than a polystyrene-based resin. Examples of resins other than polystyrene-based resins include thermoplastic resins such as polyester-based resins, polyolefin-based resins, vinyl chloride-based resins, polycarbonate-based resins, polyamide-based resins, and thermoplastic elastomers. Only one type of resin other than the above polystyrene-based resin may be used, or two or more types may be used.

The resin layer of the present invention preferably contains a lubricant. When the resin layer of the present invention and the resin composition forming the same contain a lubricant, the bending elastic modulus and the static friction coefficient of the resin composition forming the resin layer of the present invention can be within the ranges specified in the present invention. easier.

Examples of the lubricant include known or commonly used lubricants used in coating layers. Examples include polyethylene wax, polyolefin wax such as polyethylene oxide wax, fatty acid amide, fatty acid ester, paraffin wax, and polytetrafluoroethylene (PTFE). Examples include various waxes (waxes) such as wax and carnauba wax, and resin beads. Other examples include organic or inorganic particles such as silica, alumina, calcium carbonate, barium sulfate, silica, and acrylic beads. Among them, fatty acid amides are preferred. Only one type of the lubricant may be used, or two or more types may be used.

Examples of the fatty acid amides include saturated fatty acid amides, unsaturated fatty acid amides, N-substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, and aromatic bisamides. Examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. N-substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide and the like. Methylolamide includes methylol stearamide and the like. Saturated fatty acid bisamides include methylenebisstearic acid amide, ethylenebiscapric acid amide, ethylenebislauric acid amide, ethylenebisstearic acid amide, ethylenebishydroxystearic acid amide, ethylenebisbehenic acid amide, hexamethylenebisstearic acid amide, hexamethylenebisbehenamide, hexamethylenehydroxystearic acid amide, N,N'-distearyladipic acid amide, N,N'-distearylsebacic acid amide and the like. Examples of the unsaturated fatty acid bisamide include ethylenebisoleic acid amide, ethylenebiserucic acid amide, hexamethylenebisoleic acid amide, N,N'-dioleyladipic acid amide, N,N'-dioleylsebacic acid amide, and the like. be done. Examples of fatty acid ester amides include stearamide ethyl stearate. Examples of aromatic bisamides include m-xylylenebisstearic acid amide, m-xylylenebishydroxystearic acid amide, N,N'-distearyl isophthalic acid amide and the like. Only one type of the fatty acid amide may be used, or two or more types may be used. Among them, since the length of the side chain is moderate, it is possible to impart slipperiness to the film surface while suppressing powder blowing, and the bending elastic modulus and the static friction coefficient of the resin composition forming the resin layer of the present invention are improved by the present invention. It is preferable to use erucic acid amide and ethylene bis-stearic acid amide in combination from the viewpoint of facilitating the adjustment within the specified range.

The content of the lubricant in the resin layer of the present invention is not particularly limited, but is preferably 600 to 5000 mass ppm, more preferably 1000 to 3000 mass ppm, relative to the total mass (100 mass%) of the resin layer of the present invention. ppm, more preferably 1500 to 2500 mass ppm. When the content ratio is within the above range, it becomes easier to set the bending elastic modulus and the static friction coefficient of the resin composition forming the resin layer of the present invention within the ranges specified by the present invention.

The resin layer of the present invention contains a filler, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, and an antifogging agent, in addition to a resin such as a polystyrene resin and a lubricant, within a range that does not impair the effects of the present invention. additives such as additives, flame retardants, coloring agents, pinning agents (alkaline earth metals), softeners, and compatibilizers. Only one kind of these components may be used, or two or more kinds thereof may be used. In addition, the resin layer of the present invention may contain a recovered raw material obtained by re-pelletizing film pieces during film production. The collected raw materials are recycled raw materials including non-product parts such as film edges before and after commercialization, residual parts when product films are extracted from intermediate products, non-standard film scraps, and polymer scraps. However, the recovered raw material is preferably the one produced from the production of the heat-shrinkable film of the present invention (so-called self-collected product).

The resin composition forming the resin layer of the present invention has a flexural modulus of 1,600 MPa or more (eg, 1,600 to 2,100 MPa), preferably 1,620 MPa or more (eg, 1,620 to 1,700 MPa), more preferably 1,640 MPa or more. The flexural modulus can be measured according to JIS K7171. Further, when the resin layer is formed from a mixture of two or more resin compositions, the flexural modulus of each of the two or more resin compositions measured as described above is used to determine the The value obtained by summing the values obtained by multiplying the content ratio of the resin composition may be used as the flexural modulus of the resin composition forming the resin layer of the present invention. More specifically, for example, the resin layer is composed only of the resin composition (RC1) having a flexural modulus of X (MPa) and the resin composition (RC2) having a flexural modulus of Y (MPa). The content ratio of RC1 in 100% by mass of the resin mixture (resin mixture of RC1 and RC2) is W ₁ (% by mass), and the content ratio of RC2 is W ₂ (% by mass) , the flexural modulus of the resin composition forming the resin layer of the present invention can generally be calculated as follows.
Bending elastic modulus (MPa) of the resin composition=(X×W ₁ +Y×W ₂ )/100

The coefficient of static friction between resin layers of the present invention is 0.10 to 0.40, preferably 0.11 to 0.35, more preferably 0.12 to 0.30. The coefficient of static friction can be measured according to JIS K7125 using the heat-shrinkable film of the present invention as a test piece.

The flexural modulus of the resin composition forming the resin layer of the present invention is 1600 MPa or more, and the coefficient of static friction between the resin layers of the present invention is 0.40 or less, so that the heat shrinkable film of the present invention can be used. In the cylindrical body of the shrink label, the inner surfaces are difficult to adhere to each other at the time of cutting. Moreover, since the coefficient of static friction is 0.10 or more, the heat-shrinkable film of the present invention can suppress meandering of the film during printing, in addition to the adhesion being less likely to occur.

The dynamic friction coefficient between the resin layers of the present invention is not particularly limited, but is preferably 0.10 to 0.45, more preferably 0.11 to 0.40, from the viewpoint of excellent printability on heat-shrinkable films. It is more preferably 0.12 to 0.35. The coefficient of dynamic friction can be measured according to JIS K7125 using the heat-shrinkable film of the present invention as a test piece.

The heat-shrinkable film of the present invention is preferably a laminated film having the resin layer of the present invention on at least one surface (especially both surfaces). When the heat-shrinkable film of the present invention is a laminated film, the number of laminations (that is, the total number of resin layers) is two or more, preferably three. Therefore, the heat-shrinkable film of the present invention comprises two resin layers of the present invention and a core layer sandwiched between the two resin layers of the present invention ([resin layer of the present invention/core layer/main layer). Inventive resin layer]) is particularly preferable. The resin layers of the present invention on both surfaces may be the same layer, or the resin layers of the present invention having different compositions, thicknesses, etc. may be used. is preferably

(central layer)
The core layer is preferably a layer containing a thermoplastic resin as a main component (the layer containing the largest proportion by mass). Examples of the thermoplastic resins include polystyrene resins, polyester resins, polyolefin resins, vinyl chloride resins, polycarbonate resins, polyamide resins, thermoplastic elastomers, and the like. Only one type of the thermoplastic resin may be used, or two or more types may be used.

The center layer is, among others, a layer containing polystyrene resin as a main component (the layer containing the largest mass ratio) from the viewpoint of excellent adhesion to the resin layer of the present invention and good finish after heat shrinkage. is particularly preferred. Examples of the polystyrene-based resin in the central layer include those exemplified and explained as the polystyrene-based resin contained in the resin layer of the present invention described above. A butadiene copolymer, more preferably a styrene-butadiene block copolymer, particularly preferably SBS. Further, the polystyrene resin may contain GPPS and HIPS in addition to the styrene-diene copolymer.

The content of the polystyrene-based resin in the core layer is not particularly limited, but is preferably 50% by mass or more (for example, 50 to 100% by mass), more preferably It is 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. When the content is within the above range, the heat-shrinkable film of the present invention and the shrink label using the same are excellent in shrinkage properties.

The content ratio of the styrene-diene copolymer (the total of the styrene-diene copolymer and HIPS when HIPS is included) in the core layer is not particularly limited, but the total weight of the core layer (100% by mass) is preferably 70% by mass or more (for example, 70 to 100% by mass), more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. When the content is 70% by mass or more, the shrinkage properties of the heat-shrinkable film of the present invention and the shrink label using the same are excellent.

The content ratio of structural units derived from styrene-based monomers in all the polystyrene-based resins contained in the core layer is not particularly limited. On the other hand, it is preferably 50 to 95% by mass, more preferably 60 to 90% by mass, even more preferably 65 to 85% by mass, and particularly preferably 70 to 80% by mass. When the above content is 50% by mass or more, the heat-shrinkable film of the present invention is moderately hardened, the rigidity of the shrink label is moderately increased, and the shrinkage property when the shrink label is attached tends to be good. be. When the content ratio is 95% by mass or less (especially 85% by mass or less), it is difficult to break even when the unstretched film is stretched at a high magnification, and it becomes easy to obtain a heat-shrinkable film having high heat-shrinkability. . In addition, there is a tendency that moderate shrinkage stress and shrinkage properties can be obtained.

The core layer may contain a lubricant. Examples of the lubricant include those exemplified and explained as the lubricant that the resin layer of the present invention may contain. When the core layer contains a lubricant, the content of the lubricant in the core layer is not particularly limited, but is preferably 50 to 3000 ppm by mass, more preferably 50 to 3000 ppm by mass relative to the total mass (100% by mass) of the core layer. is 100 to 2000 mass ppm, more preferably 200 to 1500 mass ppm. When the above content is within the above range, it is presumed that the physical properties of the resin layer of the present invention are affected by the oozing of the lubricant from the central layer to the resin layer of the present invention, and the resin forming the resin layer of the present invention. It becomes even easier to set the flexural modulus and the static friction coefficient of the composition within the ranges specified in the present invention.

The core layer may contain, in addition to a resin such as a thermoplastic resin and a lubricant, the additives exemplified and described as additives that may be contained in the resin layer of the present invention as long as the effects of the present invention are not impaired. may contain. Only one kind of these components may be used, or two or more kinds thereof may be used. The core layer may also contain recovered raw materials obtained by re-pelletizing pieces of film from the production of the film. However, the recovered raw material is preferably the one produced from the production of the heat-shrinkable film of the present invention (so-called self-collected product).

Although the core layer is not particularly limited, the bending elastic modulus of the resin composition forming the core layer is preferably 1700 to 2400 MPa, more preferably 1800 to 1900 MPa, still more preferably 1850 to 1875 MPa. When the flexural modulus is within the above range, adhesion between the inner surfaces of the long tubular shrink label is less likely to occur when the label is cut. In addition, the heat-shrinkable film of the present invention becomes more moderate in stiffness, and the finish after heat-shrinking becomes better. Furthermore, the film is less likely to run out during printing. The bending elastic modulus of the resin composition forming the central layer can be obtained in the same manner as the bending elastic modulus of the resin composition forming the resin layer of the present invention. The bending elastic modulus of the resin composition forming the central layer is preferably higher than the bending elastic modulus of the resin composition forming the resin layer of the present invention.

From the viewpoint of exhibiting shrink properties (heat shrinkability), the heat-shrinkable film of the present invention is a film oriented in at least one direction (for example, a film oriented in one direction, a film oriented in one direction and a direction different from one direction). It is preferable that the film is a When the heat-shrinkable film is a laminated film, at least one film layer in the laminated film is preferably oriented, and all film layers are preferably oriented in at least one direction. If all film layers are non-oriented, the film may not exhibit sufficient shrink properties. As the heat-shrinkable film, a film oriented in one direction (uniaxially oriented film) or a film oriented in one direction and in a direction orthogonal to one direction (biaxially oriented film) is often used. Axially oriented films (including substantially unidirectionally stretched films that are stretched primarily in one direction and slightly in a direction perpendicular to that one direction) are commonly used.

The film oriented in at least one direction is obtained by stretching an unstretched film in at least one direction. For example, when the film oriented in at least one direction is a uniaxially oriented film, it is obtained by stretching an unstretched film in one direction, and when it is a biaxially oriented film, the unstretched film is stretched in one direction and the one direction. It is obtained by stretching in the direction perpendicular to the direction. A shrink label using the heat-shrinkable film of the present invention can be heat-shrunk mainly in the orientation direction of the heat-shrinkable film of the present invention.

The heat-shrinkable film of the present invention can be produced by a conventional method such as melt casting or solution casting. When producing a heat-shrinkable film having a laminated structure, as a method of lamination, it is possible to use a commonly used method such as a co-extrusion method or a dry lamination method. As a method of orienting the heat-shrinkable film, for example, the longitudinal direction (film production line direction, also referred to as the machine direction or MD direction) and the width direction (a direction orthogonal to the longitudinal direction, also referred to as the transverse direction or TD direction). stretching in two directions, stretching in one direction of the longitudinal direction or the width direction, or the like can be used. As the stretching method, for example, a roll method, a tenter method, a tube method, or the like can be used. For example, a film that has been stretched substantially in one direction in the width direction is stretched at a temperature of about 70 to 100° C., if necessary, in the longitudinal direction, for example, 1.01 to 1.5 times, preferably 1.0 times. After stretching about 05 to 1.3 times, it can be stretched 3 to 8 times, preferably about 4 to 7 times in the width direction.

The heat shrinkage rate of the heat-shrinkable film of the present invention at 90° C. for 10 seconds in the main shrinking direction (sometimes referred to as “heat shrinkage rate (90° C., 10 seconds)”) is not particularly limited, but 30 ~90% is preferred, more preferably 40-85%. The heat shrinkage rate (90° C., 10 seconds) in the direction perpendicular to the main shrinkage direction of the heat shrinkable film of the present invention is not particularly limited, but is preferably −3 to 15%, more preferably −1 to 10%. is. The above-mentioned "main shrinkage direction" is the direction in which the thermal shrinkage rate is the largest, and is generally the direction in which the main stretching treatment is performed. in the width direction.

If necessary, the surface of the heat-shrinkable film of the present invention may be subjected to conventional surface treatments such as corona discharge treatment, primer treatment, antistatic coating treatment and the like.

When the heat-shrinkable film of the present invention is transparent, the haze (haze) value of the heat-shrinkable film [in accordance with JIS K 7136, converted to a thickness of 40 µm, unit: %] is not particularly limited, but is 10% or less. is preferred, more preferably 7% or less, and still more preferably 5% or less. If the haze value exceeds 10%, the inside of the heat-shrinkable film (the side that becomes the container side when the shrink label is attached to the container) is printed, and the print is shown through the heat-shrinkable film ( In the back print shrink label application, the printed product may become cloudy and the decorativeness may be reduced. However, even if the haze value exceeds 10%, it may be opaque and can be sufficiently used in applications other than the above applications (front-printed shrink labels) in which the print is visible through the heat-shrinkable film. Moreover, the opaque heat-shrinkable film is not particularly limited, but for example, an opaque film, a metal-deposited film, or the like can be used.

Although the thickness of the heat-shrinkable film of the present invention is not particularly limited, it is preferably 10 to 100 μm, more preferably 12 to 80 μm, still more preferably 15 to 60 μm.

When the heat-shrinkable film of the present invention has a three-layer structure of [resin layer of the present invention/central layer/resin layer of the present invention], the thickness of at least one of the resin layers of the present invention (thickness of the cylindrical label) The thickness per layer of the inner side) is preferably 1 to 20 μm, more preferably 3 to 15 μm.

[Shrink label]
The heat-shrinkable film of the present invention is preferably used as a label substrate for shrink labels. In this specification, the shrink label having the heat-shrinkable film of the present invention may be referred to as "the shrink label of the present invention".

The shrink label of the present invention comprises, as layers other than the heat-shrinkable film of the present invention, a printed layer, another film layer such as a nonwoven fabric or a foam sheet, and an adhesive layer (pressure-sensitive adhesive layer, heat-sensitive adhesive layer, etc.). , a protective layer, an anchor coat layer, a primer coat layer, a coating layer, an antistatic layer, an aluminum deposition layer, and the like.

(Print layer)
The printed layer is not particularly limited, and examples thereof include known or commonly used printed layers used in shrink labels. Examples of the printed layer include a solvent-dried printed layer formed with a solvent-dried printing ink and an active-energy-ray-curable printed layer formed with an active-energy-ray-curable printing ink. In addition, as the above-mentioned printed layer, for example, a design printed layer (color printed layer, etc.) such as a product name, illustrations, drawings and designs such as handling precautions (color printed layer, etc.), a back printed layer formed in a single color such as white, a film, Examples include a protective printed layer provided to protect the printed layer, and a primer printed layer provided to increase the adhesion between the film and the printed layer. The printed layer is not particularly limited, but may be provided only on one side of the heat-shrinkable film of the present invention, or may be provided on both sides of the heat-shrinkable film of the present invention. The printed layer may be provided on the entire surface of the heat-shrinkable film of the present invention (the surface on which the printed layer is provided), or may be provided partially. Further, the printed layer is not particularly limited, but may be a single layer or multiple layers. Moreover, the above printed layer can be provided by a well-known or commonly used printing method. Especially, it is preferable that the said printing layer is provided by the gravure printing method or the flexographic printing method.

Although the print layer is not particularly limited, it preferably contains a binder resin as an essential component. Furthermore, if necessary, color pigments such as blue, red, yellow, black and white, and additives such as lubricants, dispersants and antifoaming agents may be included. Each of the above binder resins and the like may be used alone or in combination of two or more.

The binder resin is not particularly limited, and for example, a resin that is used as a binder resin in known or commonly used printing layers and printing inks can be used. Examples of the binder resin include acrylic resins, urethane resins, polyester resins, polyamide resins, cellulose resins (including nitrocellulose resins), vinyl chloride-vinyl acetate copolymer resins, and the like. The color pigment is not particularly limited, and for example, color pigments used in known or commonly used printing layers and printing inks can be used. Examples of the coloring pigment include white pigments such as titanium oxide (titanium dioxide), indigo pigments such as copper phthalocyanine blue, carbon black, aluminum flakes, mica, and other coloring pigments. . Extender pigments such as alumina, calcium carbonate, barium sulfate, silica, and acrylic beads can also be used as the coloring pigments for the purpose of gloss adjustment.

The solvent-drying type printing layer is formed by, for example, applying a printing ink produced by mixing the binder resin, the solvent, and, if necessary, the coloring pigment and other additives using a printing machine. , is provided by volatilizing a solvent. On the other hand, the active energy ray-curable print layer is produced by, for example, mixing the monomer components constituting the binder resin, and, if necessary, the coloring pigment, the solvent, and other additives. After the printing ink is applied using a printing machine, it is dried if necessary, and the above monomer components are polymerized and cured by irradiation with active energy rays (eg, ultraviolet rays).

The thickness of the printed layer is not particularly limited, but is preferably 0.1 to 10 μm, more preferably 0.3 to 5 μm.

The thickness (total thickness) of the shrink label of the present invention is not particularly limited, but is preferably 10 to 110 μm, more preferably 15 to 90 μm, still more preferably 20 to 80 μm.

The shrink label of the present invention may be a front-printed shrink label, a back-printed shrink label, or a double-sided printed shrink label. Among others, the shrink label of the present invention is preferably a back printed shrink label. In this specification, the front printed label is a label that allows the print to be seen without passing through the heat-shrinkable film, and refers to a label that has a design printed layer in front of the heat-shrinkable film when the label is viewed. Further, the back-printed label is a label whose print is visible through the heat-shrinkable film, and refers to a label having a design printed layer on the back side of the heat-shrinkable film when the label is viewed. A double-sided printed label is a label having design printed layers on both sides of a heat-shrinkable film.

The shrink label of the present invention may be a shrink label (individual shrink label) corresponding to one adherend (attached to one adherend), or the individual shrink label may extend in the longitudinal direction ( It may be a long shrink label (long label body) in which a plurality of labels are continuous in the longitudinal direction. When the shrink label of the present invention is a long label, the long label includes the heat-shrinkable film of the present invention and a printed layer provided on at least one surface of the heat-shrinkable film of the present invention. It is preferable to have

The shrink label of the present invention (including a long label; the same applies hereinafter) is formed by disposing the heat-shrinkable film of the present invention so that the resin layer of the present invention is on the inside when the shrink label of the present invention is used as a tubular label. It is preferred to have Moreover, in this case, the shrink label of the present invention preferably has a portion where the resin layer of the present invention is exposed on the surface (the inner surface when a tubular shrink label is formed). As a result, when the shrink label of the present invention is used as a tubular shrink label, adhesion between the inner surfaces during cutting can be prevented.

When the shrink label of the present invention is a long label, on the resin layer of the present invention (in particular, on the resin layer of the present invention which becomes the inner side of the heat-shrinkable film of the present invention when formed into a tubular shape), It is preferable that the region to be cut does not have the printed layer. In the case where the region to be cut on the resin layer of the present invention does not have a printed layer, when the cylindrical shrink label is cut after being made into a cylindrical shrink label, the cylindrical shrink label is crushed by the cutter and the inner surfaces of the region to be cut come into contact with each other. However, since the inner surfaces of the tubular shrink label, ie, the resin layers of the present invention, come into contact with each other in the region to be cut, the inner surfaces are unlikely to adhere to each other for the reason described later.

FIG. 1 is a schematic diagram showing an example of a long shrink label (long label) that is an embodiment of the shrink label of the present invention. In the label long body 1 shown in FIG. 1, one shrink label (individual shrink label) 1a corresponding to one adherend (attached to one adherend) is arranged in the long direction (longitudinal direction). It is a series of several. The portion to be cut 12 is a portion to be cut by a cutter after forming a long cylindrical shrink label. The area to be cut 11 is a peripheral area including the portion to be cut 12, and the printed layer 13 is not provided in this area. Also, the printed layer 13 is not provided on the portion 14 that will be the seal portion when the elongated cylindrical shrink label is formed. In the long label 11, the print layer 13 is provided on the entire surface other than the region to be cut 11 and the portion 14 to be the seal portion.

The shrink label of the present invention is usually produced by continuously applying the above printing ink to at least one surface of the long heat-shrinkable film of the present invention and solidifying it by drying or curing to form a printed layer. , is manufactured as a long shrink label (label strip). A shrink label having a printed layer on at least one surface of the heat-shrinkable film of the present invention can be obtained by applying printing ink to at least one surface of the heat-shrinkable film of the present invention and solidifying it by drying or curing. can be formed. As a method for applying the printing ink, known and commonly used methods can be used, and among them, gravure printing, flexographic printing, and digital printing are preferable. Further, when the applied printing ink is dried or solidified by heating or the like, a general heating device capable of heating on the printing device can be preferably used. From the viewpoint of safety, a hot air heater or the like can be preferably used. For example, the design printed layer is generally formed by applying the printing ink a plurality of times for each color to form a multi-layer printed layer.

When the printing ink is a solvent-drying printing ink, the printing ink is produced by, for example, mixing a binder resin, a solvent, other additives (coloring pigments, etc.), etc., if necessary. Mixing can be performed by a known and commonly used mixing method, and is not particularly limited. , mills such as sand mills, ball mills, bead mills and line mills, and mixing devices such as kneaders. The mixing time (residence time) during mixing is not particularly limited, but is preferably 10 to 120 minutes. The resulting printing ink may be filtered before use, if desired. Each of the above components (binder resin, solvent, and other additives) may be used alone or in combination of two or more.

As the solvent, water, organic solvents, etc., which are usually used for printing inks used in gravure printing, flexographic printing, etc., can be used. Examples of the organic solvent include esters such as acetic esters (e.g., ethyl acetate, propyl acetate, and butyl acetate); alcohols such as methanol, ethanol, isopropyl alcohol, propanol, and butanol; ketones such as methyl ethyl ketone and methyl isobutyl ketone; , xylene and other aromatic hydrocarbons; hexane, octane and other aliphatic hydrocarbons; cyclohexane, methylcyclohexane and other alicyclic hydrocarbons; ethylene glycol, propylene glycol and other glycols; ethylene glycol monopropyl ether, propylene glycol monomethyl ether , propylene glycol monobutyl ether and other glycol ethers; propylene glycol monomethyl ether acetate and other glycol ether esters; The solvent can be removed by drying after applying the printing ink to the heat-shrinkable film of the present invention. The solvent also includes the meaning of "dispersion medium".

When the printing ink is an active energy ray-curable printing ink, the printing ink contains a monomer component constituting a binder resin, a solvent, and other additives (coloring pigments, etc.), etc., if necessary. Manufactured by mixing. Mixing can be performed by a known and commonly used mixing method, and is not particularly limited, but for example, the mixing device exemplified and described as the above-mentioned solvent-drying type printing ink mixing device can be used. The mixing time (residence time) during mixing is not particularly limited, but is preferably 10 to 120 minutes. The resulting printing ink may be filtered before use, if desired. Each of the above components (monomer component, solvent, and other additives) may be used alone or in combination of two or more.

The shrink label of the present invention is, for example, a cylindrical shrink label of a type in which both ends of the label are sealed with a solvent or an adhesive and attached to a container in a cylindrical shape, or a label in which one end of the label is pasted on a container and the label is wound. After that, it can be used as a winding type shrink label (so-called ROSO label) in which the other end is superimposed on one end to form a cylindrical shape. Among the above, the shrink label of the present invention is particularly preferably used for cylindrical shrink labels. That is, the shrink label of the present invention is preferably a cylindrical shrink label. Hereinafter, a cylindrical shrink label using the shrink label of the present invention may be referred to as a "cylindrical shrink label of the present invention".

The tubular shrink label of the present invention is not particularly limited, but can be obtained, for example, as follows. The long label slit to a predetermined width is cut so that the heat-shrinkable direction (that is, the heat-shrinkable direction of the heat-shrinkable film) is the circumferential direction and the other end is outside the one end. to form a tubular shape, seal the overlapped portion in a strip shape with a predetermined width, and join both ends to obtain a long tubular label continuous body (long tubular shrink label) can be done. By cutting this long tubular shrink label in the circumferential direction, one tubular shrink label having a predetermined length in the height direction and corresponding to one adherend (to be attached to one adherend) is produced. Labels (individual tubular shrink labels) can be obtained. The cylindrical shrink label of the present invention includes both the long cylindrical shrink label and the individual cylindrical shrink label.

The tubular shrink label of the present invention preferably has the heat-shrinkable film of the present invention so that the resin layer of the present invention is on the inside. Also, the cylindrical shrink label of the present invention preferably has the heat-shrinkable film of the present invention and a printed layer provided on at least one surface of the heat-shrinkable film of the present invention. The tubular shrink label of the present invention preferably has an exposed portion of the resin layer of the present invention on the inner surface of the tube (tubular label). When the tubular shrink label of the present invention is the long tubular shrink label, it is preferable that the region to be cut on the inner surface is the exposed portion (that is, the region without the printed layer), and the individual tubular In the case of a shrink label, the upper and lower end regions of the inner surface are preferably the exposed portions (that is, the regions without the printed layer).

FIG. 2 is a schematic diagram showing an example of a long tubular continuous label (long tubular shrink label), which is an embodiment of the shrink label of the present invention. The long cylindrical shrink label 2 shown in FIG. 2 is formed by overlapping the other end of the long label body 1 in FIG. It corresponds to a cylindrical body in which the inner surface of one end and the outer surface of one end are joined with a solvent or an adhesive to form a seal portion 24, and it corresponds to one adherend (attaches to one adherend). A single cylindrical shrink label (individual cylindrical shrink label) 2a is arranged in a row in the longitudinal direction (longitudinal direction). The portion to be cut 22 corresponds to the portion to be cut 12 in FIG. 1, and is a portion to be cut by a cutter when obtaining individual cylindrical shrink labels. The planned cutting area 21 corresponds to the planned cutting area 11 in FIG. 1 and is a surrounding area including the planned cutting portion 22 . The long cylindrical shrink label 2 has the heat-shrinkable film of the present invention so that the resin layer of the present invention is on the inside. On the inner side of the long cylindrical shrink label 2, the print layer 23 is not provided in the area 21 to be cut, and the entire surface is printed except for this area and the area corresponding to the seal portion 14 in FIG. A layer 23 is provided. Therefore, the inner surface of the long cylindrical shrink label 2 has a portion (exposed portion) where the resin layer of the present invention is exposed in the region 21 to be cut. For example, the long cylindrical shrink label 2 is flattened during or after forming the cylindrical shape, rolled up, and stored as a rolled body.

FIG. 3 is a schematic diagram showing an example of a tubular shrink label (individual tubular shrink label), which is an embodiment of the shrink label of the present invention. The tubular shrink label 3 shown in FIG. 3 corresponds to the long tubular shrink label 2 shown in FIG. The cylindrical shrink label 3 is formed in a cylindrical shape so that the main shrinking direction of the heat-shrinkable film of the present invention is the circumferential direction D of the cylindrical shrink label, and can be heat-shrunk in that direction. The cylindrical shrink label 3 has the heat-shrinkable film of the present invention so that the resin layer of the present invention is on the inside. Inside the tubular shrink label 3, the upper end portion 31 and the lower end portion 32 are not provided with the printed layer 23, and the upper end portion 31, the lower end portion 32 and the seal portion 34 (specifically, the seal portion in FIG. 1) are not provided. A printed layer 33 is provided on the entire surface except for a region corresponding to the portion 14 that becomes a part. Therefore, the inner surface of the cylindrical shrink label 3 has portions (exposed portions) where the resin layer of the present invention is exposed in the upper and lower end regions.

FIG. 4 is an example of an enlarged view (cross-sectional top view) of the main part near the sealing portion 34 of the cylindrical shrink label 3, that is, a cross section along IV-IV' in FIG. In FIG. 4, both ends of the shrink label are bonded with a solvent or adhesive 44 at the seal portion. Specifically, the cylindrical shrink label is formed in an area excluding a predetermined width area from the end of the other end 46 of one surface (the inner surface of the cylindrical body) of the heat-shrinkable film 41 of the present invention. A design printed layer 42 is formed, and substantially the entire region excluding a region of a predetermined width from the end of the other end portion 46 of one surface of the heat shrinkable film 41 of the present invention so as to cover the design printed layer 42. A back print layer 43 is formed. Therefore, in the cylindrical shrink label 3, the back printed layer 43 and the design printed layer 42 are not formed in a region of a predetermined width from the end of the other end 46, and the heat-shrinkable film 41 of the present invention (especially , the resin layer of the present invention) are exposed to form an exposed film surface, and the seal portion is formed by the exposed film surface formed on the inner surface side of the other end portion 46 of the tubular shrink label 3 and the outer surface of the one end portion 45 ( film exposed surface) are bonded by solvent or adhesive 44 . That is, it is preferable that the heat-shrinkable films 41 of the present invention are bonded to each other with a solvent or an adhesive 44 at the seal portion. Of the two end portions, the non-bonded portion may have a printed layer, such as a back printed layer or a design printed layer, since this does not affect adhesion.

In the cylindrical shrink label 3 in FIG. 4, the one end 45 extends to a position where the end overlaps the back print layer 43 of the other end 46, and the back print layers of the one end 45 and the other end 46 overlap each other. A region is formed in which the 43 overlap each other with the heat-shrinkable film 41 of the present invention interposed therebetween. Therefore, there is no area in the thickness direction where the back print layer 43 does not exist. The cylindrical shrink label of the present invention may have a structure in which the end of one end overlaps the back printed layer on the other end side (overlapping in the thickness direction, that is, overlapping in the surface spreading direction), as shown in FIG. However, the end of the one end and the other end do not extend to the area where the end of the one end overlaps the film exposed surface of the other end, and the end of the one end does not extend to the position where the end of the one end overlaps the back print layer on the other end side. It may be a structure in which the back print layer on the side does not overlap.

Although the width of the seal portion is not particularly limited, it is preferably 0.2 to 10 mm, more preferably 0.3 to 5 mm, still more preferably 0.4 to 2 mm.

Various cutters such as a guillotine cutter and a rotary cutter can be used for cutting the long cylindrical shrink label. Examples of devices used for cutting the long cylindrical shrink label include a guillotine cutter provided with a fixed blade and a movable blade that can move back and forth relative to the fixed blade, and a rotary cutter as shown in FIG. be done. The long tubular shrink label is generally cut by a labeler (label attaching machine) before being attached to a container or the like.

A rotary cutter 51 shown in FIG. 5 (view from one side in the width direction of a roll in which the long cylindrical shrink label 2 is wound in the longitudinal direction) has a fixed blade 52 and a rotary blade 53 that is a movable blade. Prepare. The rotary cutter 51 is arranged, for example, upstream of the labeler. The long cylindrical shrink label 2 is flattened and wound into a roll, and supplied to the labeler as a roll. be done. In the rotary cutter 51, the rotary blade 53 rotates so as to let out the long tubular shrink label 2 downstream, and when the blade edge of the rotary blade 53 comes close to the fixed blade 52, the length sandwiched between the two blades is cut. The cylindrical shrink label 2 is cut so as to be pushed through.

Cylindrical shrink labels are produced by cutting a long cylindrical shrink label as described above. Wear may occur. In particular, when a guillotine cutter or the rotary cutter 51 shown in FIG. 5 is used, cut fusion is likely to occur at the upstream opening of the tubular shrink label due to frictional heat and pressure during cutting. However, since the shrink label of the present invention has the heat-shrinkable film of the present invention having the resin layer of the present invention on the surface thereof, the cutability is relatively excellent, and cut fusion hardly occurs. Also, even if cut fusion occurs, the degree of fusion is small and can be easily separated. For this reason, the shrink label of the present invention can be used not only for labelers equipped with cutters that are difficult to cut and fuse, but also for labelers equipped with cutters that are relatively easy to cut and fuse, and is excellent in versatility.

The tubular shrink label of the present invention may have perforations for label cutting. When the cylindrical shrink label is provided with perforations, the perforations are formed in the longitudinal direction (perpendicular to the circumferential direction) with a predetermined length and pitch. The perforations can be made by a conventional method (for example, a method of pressing a disc-shaped blade around which a cut portion and a non-cut portion are repeatedly formed, a method using a laser, etc.). The perforation step can be appropriately selected after providing the printed layer, before or after the step of processing into a cylindrical shape, or the like.

The heat-shrinkable film of the present invention has, on at least one surface, a resin layer formed from a resin composition containing a polystyrene-based resin as a main component and having a flexural modulus of a specific value or more, and A shrink label that has a coefficient of static friction within a specific range, so that it is possible to obtain a long cylindrical label whose inner surfaces are difficult to adhere to each other when cut while having a resin layer mainly composed of polystyrene resin on the surface. can get. The mechanism by which the inner surfaces (in particular, the heat-shrinkable films) adhere to each other during cutting is presumed as follows. When cutting the long tubular shrink label, the blade of the cutter enters the outer surface of the long tubular shrink label. It propagates from the outer surface to the inner surface of the tubular shrink label. Then, when the inner surfaces come into contact with each other, the stress is propagated to the contact portion. Further, at the time of cutting, heat is generated at the contact point due to friction between the blade of the cutter and the heat-shrinkable film or friction between the movable blade and the fixed blade of the cutter. The inner surfaces of the heat-shrinkable films are adhered to each other due to the stress and frictional heat caused by the plastic deformation generated in this way being applied to the contact points.

In contrast, when the shrink label using the heat-shrinkable film of the present invention is cut, the resin layers of the present invention, which are the inner surfaces of the long cylindrical shrink label, come into contact with each other. When the coefficient of static friction between the resin layers of the present invention is within a specific range, the resin layers of the present invention are slippery, and the stress generated by plastic deformation is used to move the heat-shrinkable film. diffuses, it is difficult to concentrate on the contact portion. In addition, since the resin layer of the present invention is formed from a resin composition having a flexural modulus of a specific value or higher, plastic deformation during cutting is less likely to occur, and stress is less likely to occur. Presumably due to these reasons, the heat-shrinkable film of the present invention provides a long tubular label having a resin layer containing a polystyrene-based resin as a main component on its surface, and the inner surfaces of which are difficult to adhere to each other when cut. It has the effect of being able to

[Labeled container]
Although not particularly limited, the shrink label of the present invention is attached to a container and used as a labeled container. The shrink label of the present invention may be used for adherends other than containers. For example, the shrink label of the present invention (particularly, cylindrical shrink label) is placed around a container so that the shrink label of the present invention is cylindrical, and heat-shrunk to attach the label to the container. A container (labeled container having the shrink label of the present invention) is obtained. Examples of the above containers include soft drink bottles such as PET bottles, milk bottles for home delivery, food containers such as seasonings, alcoholic beverage bottles, pharmaceutical containers, detergents, containers for chemical products such as sprays, and toiletry containers. Containers, cup noodle containers and the like are included. The shape of the container is not particularly limited, but examples thereof include various shapes such as a bottle type such as a cylindrical shape and a rectangular shape, and a cup type. The material of the container is not particularly limited, but examples include plastic such as PET, glass, and metal. A container to which the shrink label of the present invention is attached may be referred to as a "labeled container of the present invention".

The container with the above label is produced, for example, by fitting a cylindrical shrink label (individual cylindrical shrink label) to a predetermined container, then thermally shrinking the cylindrical shrink label by heat treatment, and adhering it to the container ( shrink processing). Examples of the heat treatment method include a method of passing through a hot air tunnel or a steam tunnel, and a method of heating with radiant heat such as infrared rays. In particular, a method of treating with steam at 80 to 100° C. (passing through a heating tunnel filled with steam and steam) is preferred. Dry steam of 101 to 140° C. can also be used. The heat treatment is not particularly limited, but is preferably carried out in a temperature range in which the temperature of the heat-shrinkable film is 85 to 100°C (especially 90 to 97°C). Moreover, the treatment time of the heat treatment is preferably 4 to 20 seconds from the viewpoint of productivity and economy.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. Table 1 shows the raw material compositions of the surface layers of the heat-shrinkable films produced in Examples and Comparative Examples, evaluation results, and the like.

Example 1
(Heat-shrinkable film)
As raw materials for the surface layer, resin composition A (flexural modulus: 1580 MPa) containing 100% by mass of SBS, 780% by mass of erucamide, and 350% by mass of ethylenebisstearic acid amide (75% by mass) and 85% by mass of SBS. % by mass, 5% by mass of GPPS, 10% by mass of HIPS, 4860 ppm by mass of erucamide, and 680 ppm by mass of ethylenebisstearic acid amide Resin composition B (flexural modulus: 1880 MPa) 25% by mass Using.
Resin composition C containing 80% by mass of SBS, 20% by mass of HIPS, 780 ppm by mass of erucamide, and 350 ppm by mass of ethylenebisstearic acid amide as raw materials for the central layer (flexural modulus: 2180 MPa)24. Resin composition D containing 7% by mass, 100% by mass of a styrene-butadiene copolymer, 390% by mass of erucamide, and 180% by mass of ethylenebisstearic acid amide (flexural modulus: 1860 MPa) 47.5 mass %, 25.5% by mass of the resin composition A, and 2.3% by mass of the resin composition B.
The raw material for the surface layer was put into the extruder a heated to 220°C, and the raw material for the center layer was put into the extruder b heated to 220°C. Melt extrusion was performed using the two extruders described above. The melted raw material for the surface layer and the melted raw material for the central layer are combined into a two-kind, three-layer structure of the raw material for the surface layer/the raw material for the central layer/the raw material for the surface layer using a two-kind, three-layer feed block. After extruding from a T-die, it was rapidly cooled on a casting drum cooled to 25° C. to obtain a laminated unstretched film.
Next, the laminated unstretched film is tenter stretched 5 times at 85 ° C. in the width direction, so that it is mainly stretched in the width direction, and the length of the stretched film (heat shrinkable film) having heat shrinkability in the direction is I got a scale body. The heat-shrinkable film has a three-layer structure of [surface layer/center layer/surface layer]. Table 1 shows the flexural modulus of the resin composition forming the surface layer calculated from the flexural modulus of each raw material resin composition and the static friction coefficient between the surface layers in the resulting heat-shrinkable film. That's right.

(cylindrical shrink label)
The long body of the heat-shrinkable film obtained above is used as a long body of a shrink label (long label body), and after slitting the long body of the label to a predetermined width, the width direction is the circumferential direction. One end and the other end are overlapped to form a cylinder, the heat-shrinkable film surfaces of the one end and the other end are sealed with a solvent, and the cylindrical long body of the shrink label (long cylinder A shrinkable label) was obtained. In the obtained long cylindrical shrink label, the surface layer is exposed on the entire inner surface.

Example 2
(Heat-shrinkable film)
70% by mass of the resin composition A and 30% by mass of the resin composition B were used as raw materials for the surface layer, and 35% by mass of SBS, 60% by mass of HIPS, and acrylic resin were used as raw materials for the central layer. Resin composition E (flexural modulus: 1700 MPa) 29.8% by mass containing 5% by mass of resin, Resin composition F (flexural modulus: 2090 MPa) containing 100% by mass of SBS 42.5% by mass, and the above resin A long stretched film (heat-shrinkable film) was obtained in the same manner as in Example 1, except that 23.2% by mass of the composition A and 4.5% by mass of the resin composition B were used.

(cylindrical shrink label)
A long cylindrical shrink label was produced in the same manner as in Example 1 using the long heat-shrinkable film obtained above.

Example 3
(Heat-shrinkable film)
80% by mass of the resin composition A and 20% by mass of the resin composition B are used as raw materials for the surface layer, and 25.5% by mass of the resin composition E is used as the raw material for the central layer. A stretched film (heat-shrinkable film) was obtained.

(cylindrical shrink label)
A long cylindrical shrink label was produced in the same manner as in Example 1 using the long heat-shrinkable film obtained above.

Comparative example 1
(Heat-shrinkable film)
Resin composition G containing 80% by mass of resin composition A, 90% by mass of SBS, 10% by mass of HIPS, 780 ppm by mass of erucic acid amide, and 350 ppm by mass of ethylenebisstearic acid amide as raw materials for the surface layer. (flexural modulus: 1640 MPa) of 20% by mass, and as the raw material for the central layer, 34.0% by mass of the resin composition E, 51.0% by mass of the resin composition F, and the above resin composition A long stretched film (heat-shrinkable film) was obtained in the same manner as in Example 1, except that 12.0% by mass of A and 3.0% by mass of the resin composition G were used.

(cylindrical shrink label)
A long cylindrical shrink label was produced in the same manner as in Example 1 using the long heat-shrinkable film obtained above.

Comparative example 2
(Heat-shrinkable film)
As raw materials for the central layer, 67.0% by mass of the resin composition C, 18.0% by mass of the resin composition D, 12.0% by mass of the resin composition A, and 3.0% by mass of the resin composition G A elongated stretched film (heat-shrinkable film) was obtained in the same manner as in Comparative Example 1, except that the heat-shrinkable film was used.

(cylindrical shrink label)
A long cylindrical shrink label was produced in the same manner as in Comparative Example 1 using the long heat-shrinkable film obtained above.

(evaluation)
The heat-shrinkable films and long cylindrical shrink labels obtained in Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Table 1.

(1) Coefficient of Friction The coefficient of static friction and coefficient of dynamic friction between the surface layers of the heat-shrinkable films obtained in Examples and Comparative Examples were measured according to JIS K7125.
The measuring equipment, measuring conditions, procedures, etc. are as follows.
Measuring instrument: "Friction Tester TR-2" (manufactured by Toyo Seiki Co., Ltd.)
Weight: 200 g±2 g (=1.96 N normal force F _P is generated), having a bottom surface of 63 mm×63 mm, to which felt of the same size was attached.
Sample: A piece of heat-shrinkable film cut to 65mm x 160mm (unshrinkable product)
Friction partner: A piece of heat-shrinkable film cut to 110 mm x 300 mm (unshrinkable product)
Procedure: The sample was wound around the weight so that the surface layer faced outward to obtain the weight with the sample. The weight with the sample has the bottom surface of the weight covered with the sample, and the surface layer of the sample exists over the entire bottom surface of the weight to form a measurement surface (63×63 mm). A weight with a sample is placed on a smooth table on which the heat-shrinkable film piece of the friction partner is fixed with the surface layer facing upward, so that the measurement surface of the weight with the sample is in contact with the surface layer of the friction partner. and started the measurement. Then, the maximum stress obtained first was taken as the static friction force, and the static friction coefficient was calculated from this value. Also, the frictional force acting during the sliding motion was defined as the dynamic frictional force, and the dynamic friction coefficient was calculated from this value.
Measurement distance: 60mm
Speed: 100mm/min

(2) Cut Suitability The long cylindrical shrink labels obtained in Examples and Comparative Examples were cut in the width direction by a rotary cutting machine shown in FIG. Then, the suitability for cutting was evaluated according to the following criteria.
Good suitability for cutting (○): There is no adhesion between the inner surfaces of the label on the cut surface after cutting.
Suitable for cutting (△): On the cut surface after cutting, the inner surfaces of the label are partially adhered to each other, but can be expanded.
Poor cutting aptitude (x): In the cut surface after cutting, the inner surfaces of the label were observed to be adhered to each other over the entire cut surface, and could not be spread.

As is clear from Table 1, when the heat-shrinkable film of the present invention was used (Examples 1 to 3), after cutting the long cylindrical shrink label, adhesion between the inner surfaces of the labels could not be confirmed, or Some were glued together, but could be expanded. On the other hand, when the resin composition forming the surface layer had a small flexural modulus and a large coefficient of static friction between the surface layers (Comparative Examples 1 and 2), the inner surfaces adhered to each other after cutting the long cylindrical shrink label. , could not be opened (expanded) into a cylindrical shape.

1 Elongated Body of Shrink Label 1a Individual Shrink Label 11 Area to be Cut 12 Area to be Cut 13 Printed Layer 14 Portion to be Sealed Part 2 Long Cylindrical Shrink Label 2a Individual Cylindrical Shrink Label 21 Area to be Cut 22 Area to be Cut Part 23 Printed layer 24 Sealed part 3 Cylindrical shrink label 31 Upper end part 32 Lower end part 33 Printed layer 34 Sealed part D Circumferential direction 41 Heat-shrinkable film 42 Design printed layer 43 Back printed layer 44 Solvent or adhesive 45 One end part 46 Others edge

Claims (5)

It has on at least one surface a resin layer formed from a resin composition containing a polystyrene-based resin as a main component and having a bending elastic modulus of 1600 to 2100 MPa, and two of the resin layers and the two resin layers. a heat-shrinkable film comprising a central layer sandwiched therebetween ;
The coefficient of static friction between the resin layers is 0.10 to 0.40,
General-purpose polystyrene is included as the polystyrene-based resin, and the content of general-purpose polystyrene in the resin layer is 0.3 to 3% by mass with respect to the total mass of the resin layer ,
The bending elastic modulus of the resin composition forming the central layer is 1700 to 2400 MPa ,
A heat-shrinkable film in which the bending elastic modulus of the resin composition forming the central layer is higher than the bending elastic modulus of the resin composition forming the resin layer . 2. The heat-shrinkable film according to claim 1, wherein the central layer is a layer containing polystyrene-based resin as a main component. the central layer comprises a lubricant;
The content of the lubricant in the resin layer is 600 to 5000 ppm by mass with respect to the total mass of the resin layer,
3. The heat-shrinkable film according to claim 2, wherein the content of the lubricant in the central layer is 50-3000 ppm by mass relative to the total weight of the central layer. The heat-shrinkable film according to any one of claims 1 to 3, wherein the coefficient of static friction is 0.10 to 0.30. A heat-shrinkable film according to any one of claims 1 to 4 and a printed layer provided on at least one surface of the heat-shrinkable film,
A long cylindrical shrink label that does not have the printed layer in the area to be cut on the resin layer.

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