JP2009163233A - Heat shrinkable label and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a label to be bonded to a vessel at high speed with excellent finish and made of heat shrinkable polyester film shrinking mainly in the longitudinal direction suitable for mounting on the vessel, and to provide a light-weight heat shrinkable label having good appearance, excellent ray cutting performance, even when printing is applied. <P>SOLUTION: This heat shrinkable label is made of at least a monoaxially stretched heat shrinkable polyester film and is molded into a tubular shape by overlapping an end part of the film on a predetermined position of the film, irradiating the portion where the films are overlapped with laser, and welding them. This heat shrinkable label is molded by using the heat shrinkable polyester film having heat shrinkage ratio in hot water in the longitudinal direction of 15% or more and less than 40% when treated in the hot water at 90°C for 10 seconds and having the direction of main shrinkage having white color or a cavity as its longitudinal direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable label, and more particularly to a heat-shrinkable label for covering bottles such as PET bottles (polyethylene terephthalate (PET) bottles) and glass bottles, and a method for producing the same.

  In recent years, heat from various resins has been used for exterior packaging to improve the appearance of packages, packaging to avoid direct collision of contents, label packaging that protects glass bottles or plastic bottles and displays products. Shrinkable plastic films are widely used. Among these heat-shrinkable plastic films, stretched films made of polyvinyl chloride resin, polystyrene resin, polyester resin, etc. are used in various containers such as PET containers, polyethylene containers, glass containers, labels, cap seals or Used for integrated packaging purposes.

  However, although the polyvinyl chloride film has excellent shrinkage properties, it has low heat resistance and also has problems such as generation of hydrogen chloride gas during incineration and causing dioxins. In addition, when a polyvinyl chloride film is used as a shrink label for a PET container or the like, there is also a problem that when the container is recycled, the label and the container must be separated. On the other hand, the polystyrene film has a good finished appearance after shrinkage, but has poor solvent resistance, and therefore has a problem that an ink having a special composition must be used for printing. In addition, the polystyrene film needs to be incinerated at a high temperature and has a problem that a large amount of black smoke is generated with a strange odor during incineration.

  For this reason, polyester films having high heat resistance, easy incineration, and excellent solvent resistance have come to be widely used as heat-shrinkable labels, which increases the circulation of PET containers. Along with this, usage tends to increase.

  Up to now, as the heat-shrinkable polyester film, those which are largely shrunk in the width direction have been widely used. The heat-shrinkable polyester film whose width direction is the main shrinkage direction is stretched at a high magnification in the width direction in order to develop shrinkage characteristics in the width direction. In many cases, low-stretching is only performed, and some are not stretched. Such a film that has been stretched at a low magnification in the longitudinal direction or a film that has been stretched only in the width direction has a disadvantage that the mechanical strength in the longitudinal direction is inferior.

  In addition, since the label of the bottle must be circular and heat-shrinked in the circumferential direction after being attached to the bottle, when the heat-shrinkable film that heat-shrinks in the width direction is attached as a label, the width direction of the film is After an annular body (tube) is formed so as to be in the circumferential direction, the annular body must be cut into predetermined lengths and attached to the bottle. Therefore, it becomes more difficult to attach a label made of a heat-shrinkable film that heat-shrinks in the width direction to the bottle as the production speed increases.

  For this reason, recently, there has been a demand for a film that is heat-shrinkable in the longitudinal direction and can be mounted directly around the bottle from a film roll. Furthermore, in recent years, a wrapping method for holding a container closed by covering the periphery of a synthetic resin single-open container such as a lunch box with a strip-shaped film has been developed. It is also suitable for such packaging applications. Therefore, the demand for the film shrinking in the longitudinal direction is expected to increase dramatically in the future.

  From these facts, the applicants diligently studied to obtain a heat-shrinkable film having a high mechanical strength in a direction (width direction) perpendicular to the main shrinkage direction in which the main shrinkage direction is the longitudinal direction. The heat shrinkable film is found to be obtained by a special process of transverse stretching-intermediate heat treatment-longitudinal stretching in which the main shrinkage direction is the longitudinal direction and the mechanical strength is high in the width direction. And previously proposed (Japanese Patent Application No. 2006-165212).

  However, the heat-shrinkable film obtained by the process of transverse stretching-intermediate heat treatment-longitudinal stretching has the main shrinkage direction as the longitudinal direction and excellent mechanical strength in the width direction, but the hot water shrinkage rate and heat shrinkage stress in the longitudinal direction. In some cases, the shrinkage finish is not necessarily good when the film is heat-shrinked after being wound around the bottle directly from the film roll. Moreover, when the body roll is directly wound around the bottle from the film roll, it is possible to wind the film so that the film is in close contact with the bottle to some extent, so there is no need to increase the hot water shrinkage rate or heat shrinkage stress in the longitudinal direction. In addition, if the hot water shrinkage rate or heat shrinkage stress in the longitudinal direction is too high, the force of tightening the bottle becomes too strong when it is wrapped around the bottle and thermally shrunk, and the bottle spills when opening the bottle. May occur.

  Furthermore, when used as a label for a PET bottle having a “neck” at the center, if the hot water shrinkage rate or heat shrinkage stress in the longitudinal direction is too high, the finished state after heat shrinkage will deteriorate. There was also a risk. In addition, some of the heat-shrinkable films obtained by the process of transverse stretching, intermediate heat treatment, and longitudinal stretching described above have insufficient toughness (toughness) and toughness, and such toughness and toughness are also present. When a film having insufficient properties is post-processed, there is a possibility that a large-scale trouble may occur due to the film breaking when a strong tension is applied.

  In addition, in order to form a film continuum (label) by attaching a film shrinking in the longitudinal direction to a container such as a bottle, one end of a film having an appropriate length is stuck on the container, and the film is placed on the outer periphery of the container. Is used, and the film ends are overlapped and bonded so that the other film end faces up (for example, Patent Document 1). Examples of the adhesion between these containers and films, or film edges include adhesion with an adhesive, adhesion with an adhesive, adhesion with a solvent, and adhesion with a heat seal.

  However, as a sticking method used in the process of attaching these films to a container, sufficient adhesive strength cannot be obtained when a pressure sensitive adhesive is used, and label displacement or peeling occurs during heat treatment for shrinkage. However, when, for example, a hot melt adhesive is used as the adhesive, there has been a problem that label distortion due to the heat of the adhesive and insufficient shrinkage in subsequent processes are likely to occur. In addition, from the viewpoint of design and strength, the use of complicated containers with large irregularities is increasing as the shape of containers such as bottles, but if you try to stick the film directly to these complicated shaped containers, It is difficult to press the overlapping portion of the film located in the concave portion, and the method of sticking using an adhesive or the like sometimes fails to bond well.

  On the other hand, solvent adhesion is also possible, but since the label is wrapped with the container standing, the solvent viscosity is too low in solvent adhesion, and the application becomes uneven due to dripping or splashing, and the surroundings are contaminated. There's a problem. Furthermore, considering high-speed mounting from the viewpoint of improving productivity, it is important to perform the adhesive treatment in a short time, and a heat seal method is also conceivable. However, high-speed and uniform treatment is difficult with the heat seal method.

By the way, such a heat-shrinkable label needs to be separated from the bottle when the PET bottle is recycled. As one method for separating the bottle and the label, there is a method in which both are pulverized while being mixed, and the mixture is stirred in water to separate using the difference in specific gravity. When this method is adopted, the specific gravity of PET, which is the main raw material of the bottle, is about 1.4. Since it is difficult to lower the specific gravity of the polyester resin for labeling, a method of reducing the apparent density by incorporating a large number of cavities inside the film has been considered (see Patent Documents 2 and 3). However, these films have the following problems.
I. By providing the cavity, the roughness of the surface is increased, the appearance of the printed label becomes poor, and the aesthetic appearance is impaired.
B. Since the whiteness is insufficient or the total light transmittance is too high, the contents can be seen through, and the appearance of the label printed on the surface becomes poor and the aesthetic appearance is impaired.
C. The balance of roughness on both sides is poor, and aesthetics and wearability are not compatible.
D. The apparent specific gravity after shrinkage is high, and it is difficult to separate and collect due to the specific gravity difference from the bottle.
E. Since adhesion with a solvent or a swelling agent could not be performed, there are poor appearance and poor workability of the joint.

  On the other hand, recently, shrinkage labels are increasingly used for the purpose of protecting the contents of containers from ultraviolet rays. Although the specific cut property varies depending on the contents, in the case of foods and beverages, alteration or coloring of the contents occurs at a wavelength of 360 nm to 400 nm, which is ultraviolet light in the long wavelength region, so that the long wavelength region, particularly 380 nm and 400 nm. The cutting ability is important. However, none of the conventional heat-shrinkable labels cuts the ultraviolet rays in the long wavelength region described above.

Conventionally, heat-shrinkable labels are usually subjected to white printing after pattern printing on the inside of the film. The thickness of the printing ink is usually about 3 μm, which is insufficient for light blocking. For this reason, light blocking is attempted by a method of performing white printing twice, but this is disadvantageous in terms of quality factors (change in shrinkage characteristics due to ink thickness, etc.), delivery time, and cost.
JP 2005-292195 A Japanese Patent Publication No. 7-33063 JP-A-5-111960

  The present invention solves the above-mentioned problems, can be bonded at high speed when mounted on a container, has good finish, and further has a heat shrinkage whose main shrinkage direction is the longitudinal direction suitable for mounting on a container. It is an object to provide a label made of a conductive polyester film.

  Another object of the present invention is to provide a heat-shrinkable polyester-based label that is lightweight and excellent in aesthetics, has light-cutting properties without printing or processing, and has excellent aesthetics even when printed. It is to provide.

The present invention that has solved the above-mentioned problems is composed of a heat-shrinkable polyester film stretched at least uniaxially. The film end is overlapped at a predetermined position of the film, and a laser is irradiated to the overlapping portion of the films. A heat-shrinkable label formed into a tube shape by welding,
The heat-shrinkable polyester film has ethylene terephthalate as a main constituent unit, and a unit derived from glycol other than ethylene glycol and / or a unit derived from dicarboxylic acid other than terephthalic acid is at least 15 mol% in 100 mol% of all polyester units 40 The heat-shrinkable label is characterized by being a heat-shrinkable polyester film composed of a polyester having a mol% or less and satisfying the following requirements (1) to (5) in which the main shrinkage direction is a heat-shrinkable polyester film in the longitudinal direction. .
(1) The hot-water heat shrinkage in the longitudinal direction when treated for 10 seconds in 90 ° C. warm water is 15% or more and less than 40%.
(2) The hot water heat shrinkage in the width direction orthogonal to the longitudinal direction when treated in 90 ° C. warm water for 10 seconds is −5% or more and 5% or less,
(3) The maximum heat shrinkage stress in the longitudinal direction when treated at 90 ° C. for 10 seconds is 2.5 MPa or more and 7.0 MPa or less,
(4) Young's modulus before break in the longitudinal direction of the film is 0.05 GPa or more and 0.15 GPa or less,
(5) The whiteness is 70 or more or has a cavity.

  In the heat-shrinkable polyester label, the right-angled tear strength per unit thickness after shrinkage of the heat-shrinkable polyester film in warm water at 80 ° C. in the longitudinal direction by 3% is 100 N / mm or more and 300 N. / Mm or less is preferable.

  The laser used for welding the overlapped portions of the films is preferably a carbon dioxide laser.

  The present invention is characterized in that the end of the polyester film satisfying each of the above requirements is overlaid at a predetermined position of the film, and the portion where the films overlap is irradiated with a laser and welded to form a tube shape. Also included is a method of manufacturing a heat shrinkable label.

  In the above manufacturing method, before mounting on the container, the end of the film is preliminarily stacked at a predetermined position of the film, and the portion where the films overlap is irradiated with a laser to form a tube, and then The film may be attached to the container, or after the film is wound directly on the container, the end of the film is overlaid at a predetermined position of the film, and the part where the films overlap is irradiated with a laser to be welded. The manufacturing method which shape | molds in a tube shape may be sufficient.

  According to the present invention, a label made of a heat-shrinkable polyester film that can be bonded at high speed when mounted on a container, has good finish, and has a main shrinkage direction as a main shrinkage direction suitable for mounting on a container. Could be provided. The heat-shrinkable label of the present invention is lightweight and excellent in aesthetics, has light-cutting properties without being printed or processed, and has excellent aesthetics even when printed. Therefore, it is useful as a heat-shrinkable label for bottles such as PET bottles and glass bottles.

  The present invention relates to a heat-shrinkable label formed into a tube shape obtained from a heat-shrinkable polyester-based film that is stretched at least uniaxially and whose main shrinkage direction is a longitudinal direction. It is related with the heat-shrinkable label which is what was shape | molded in the tube shape by irradiating a laser to the part which the films overlapped, and welding.

[About polyester]
Examples of the dicarboxylic acid component constituting the polyester used as a raw material for the heat-shrinkable polyester film used in the present invention include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, orthophthalic acid and other aromatic dicarboxylic acids, adipic acid, and azelaic acid. Preferred are aliphatic dicarboxylic acids such as sebacic acid and decanedicarboxylic acid, and dicarboxylic acid components such as alicyclic dicarboxylic acids. It is preferable not to use a trivalent or higher polyvalent carboxylic acid (for example, trimellitic acid, pyromellitic acid, and their anhydrides). The heat-shrinkable polyester film obtained using the polyester containing these polyvalent carboxylic acids is difficult to achieve the necessary high shrinkage rate.

  Examples of the diol component constituting the polyester used in the present invention include aliphatic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, hexanediol, and 1,4-cyclohexanedimethanol. And alicyclic diols such as bisphenol A and aromatic diols such as bisphenol A. It is preferable not to use a diol having 8 or more carbon atoms (for example, octanediol) or a trihydric or higher polyhydric alcohol (for example, trimethylolpropane, trimethylolethane, glycerin, diglycerin, etc.). The heat-shrinkable polyester film obtained by using polyesters containing these diols or polyhydric alcohols is difficult to achieve the necessary high shrinkage rate.

  The polyester used for the heat-shrinkable polyester film of the present invention has an ethylene terephthalate unit as a main constituent unit. The “main” means that it is 60 mol% or more in 100 mol% of all units constituting the polyester. In this polyester, units derived from glycols other than ethylene glycol and / or units derived from dicarboxylic acids other than terephthalic acid are 15 mol% or more and 40 mol% or less in 100 mol% of all polyester units. The unit derived from glycol other than ethylene glycol and / or the unit derived from dicarboxylic acid other than terephthalic acid is preferably at least 17 mol%, more preferably at least 20 mol%. As glycols other than ethylene glycol, neopentyl glycol and 1,4-cyclohexanedimethanol are preferable in terms of shrinkage finishing properties and the like. As dicarboxylic acids other than terephthalic acid, isophthalic acid is preferred. However, if the unit derived from glycol other than ethylene glycol and / or the unit derived from dicarboxylic acid other than terephthalic acid exceeds 40 mol%, the solvent resistance of the film is lowered, and the ink solvent (such as ethyl acetate) is reduced in the printing process. ), Whitening of the film occurs or the tear resistance of the film decreases. Further, the content of these units is more preferably 37 mol% or less, and particularly preferably 35 mol% or less. The unit derived from glycol other than ethylene glycol is an ester unit composed of glycol other than ethylene glycol and terephthalic acid, for example, and the unit derived from dicarboxylic acid other than terephthalic acid is a dicarboxylic acid other than terephthalic acid and, for example, This means an ester unit composed of ethylene glycol.

  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 polyester film. In particular, although diethylene glycol is likely to be present because it is a by-product component during polyester polymerization, it is preferable that the content of diethylene glycol is less than 4 mol% in the polyester used in the present invention. The intrinsic viscosity of the polyester used in the present invention is preferably 0.50 or more, more preferably 0.60 or more, and particularly preferably 0.65 or more. If the intrinsic viscosity of the polyester is less than 0.50, the crystallinity becomes high and a sufficient shrinkage cannot be obtained, which is not preferable.

  In order to improve the slipperiness of the film, it is also preferable to incorporate fine particles such as an organic lubricant and an inorganic lubricant. As needed, you may contain additives, such as a stabilizer, a coloring agent, antioxidant, and an antifoamer. Fine particles imparting slipperiness include known inert external particles such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate, lithium fluoride, and the like in the melt film formation of polyester resin. Examples thereof include insoluble high-melting-point organic compounds, cross-linked polymers, and metal compound catalysts used at the time of polyester synthesis, for example, internal particles formed inside the polymer during the production of the polyester by alkali metal compounds, alkaline earth metal compounds and the like. The fine particles are preferably 0.005 to 0.9% by mass in the film, and the average particle size is preferably 0.001 to 3.5 μm.

[Requirement (1)]
The heat-shrinkable polyester film used for the heat-shrinkable label of the present invention has the following formula from the length before and after shrinkage when treated (immersed) in 90 ° C. warm water for 10 seconds under no load. The heat shrinkage rate in the main shrinkage direction (longitudinal direction) of the film calculated by 1 (that is, the hot water heat shrinkage rate at 90 ° C.) needs to be 15% or more and less than 40%.
Thermal shrinkage rate = {(length before shrinkage−length after shrinkage) / length before shrinkage} × 100 (%) Formula 1

  If the hot water thermal contraction rate in the longitudinal direction at 90 ° C. is less than 15%, the shrinkage amount is small, and therefore, it is not preferable because wrinkles and tarmi are generated on the label after thermal contraction. When the hot water heat shrinkage rate in the direction is 40% or more, the shrinkage tends to occur during heat shrinkage after winding as a label by the body winding method, or so-called “jumping” occurs, which is not preferable. The hot water heat shrinkage in the longitudinal direction at 90 ° C. is preferably 17% or more, more preferably 19% or more, and particularly preferably 21% or more. Further, the hot water heat shrinkage in the longitudinal direction at 90 ° C. is preferably 38% or less, more preferably 36% or less, and particularly preferably 34% or less.

[Requirement (2)]
The heat-shrinkable polyester film has a hot-water heat shrinkage ratio in the width direction of the film calculated by the above equation 1 from the length before and after shrinkage when treated in warm water at 90 ° C. for 10 seconds without load. -5% to 5%. If the hot shrinkage in the width direction at 90 ° C. is less than −5%, a good shrink appearance cannot be obtained when used as a bottle label, and conversely, the hot water in the width direction at 90 ° C. When the thermal shrinkage rate exceeds 5%, it is not preferable because the shrinkage tends to occur at the time of thermal shrinkage when used as a label. The hot water heat shrinkage in the width direction at 90 ° C. is preferably −4% or more, more preferably −3% or more, and particularly preferably −2% or more. Moreover, the hot water temperature thermal contraction rate in the width direction at 90 ° C. is preferably 4% or less, more preferably 3% or less, and particularly preferably 2% or less.

[Requirement (3)]
The heat-shrinkable polyester film of the present invention needs to have a maximum heat shrinkage stress in the longitudinal direction of 2.5 MPa to 7.0 MPa when treated at 90 ° C. for 10 seconds. When the maximum heat shrinkage stress in the longitudinal direction at 90 ° C. is less than 2.5 MPa, it is preferable that when used as a bottle label, the shrinkage is insufficient at the time of heat shrinkage after body winding, and a good appearance cannot be obtained. On the other hand, if the maximum heat shrinkage stress in the longitudinal direction at 90 ° C. exceeds 7.0 MPa, it is not preferable because shrinkage distortion is likely to occur during heat shrinkage after body winding. The maximum heat shrinkage stress in the longitudinal direction at 90 ° C. is preferably 3.0 MPa or more, more preferably 3.5 MPa or more, and particularly preferably 4.0 MPa or more. Further, the maximum heat shrinkage stress in the longitudinal direction at 90 ° C. is preferably 6.5 MPa or less, more preferably 6.0 MPa or less, and particularly preferably 5.5 MPa or less.

[Requirement (4)]
It is also important that the heat-shrinkable polyester film of the present invention has a longitudinal Young's modulus in the longitudinal direction calculated by the following method of 0.05 GPa or more and 0.15 GPa or less.

・ Measurement method of Young's modulus before breakage A film sample cut into a predetermined size (length 150 mm × width 10 mm) according to ASTM-D882 is used in a 25 ° C. and 65% RH atmosphere using a tensile tester. The both ends (both ends along the longitudinal direction) are gripped so that the sample length becomes 100 mm, and a stress-strain curve is measured when the sample is pulled at a pulling speed of 200 mm / min. Then, the average value of the ratio of stress to strain from the time when the wire is stretched up to 90% of the stretch magnification at the time of breakage (back calculation from the stretch magnification at the time of breakage) to the time of breakage is calculated as the Young's modulus before breakage.

  If the Young's modulus before break in the longitudinal direction is less than 0.05 GPa, the film is not preferable because the toughness and toughness of the film are insufficient and the film is easily broken when a strong tension is applied during post-processing. When the Young's modulus before breaking in the direction exceeds 0.15 GPa, the toughness and toughness of the film are too high, and the cutability at the time of cutting the film is not preferable. The Young's modulus before breaking in the longitudinal direction is preferably 0.06 GPa or more, more preferably 0.07 GPa or more, and particularly preferably 0.08 GPa or more. The Young's modulus before break in the longitudinal direction is preferably 0.14 GPa or less, more preferably 0.13 GPa or less, and particularly preferably 0.12 GPa or less.

[Requirement (5)]
Next, requirement (5) will be described. The film for producing a heat-shrinkable label of the present invention must have a whiteness of 70 or more or contain a cavity. The whiteness is preferably 75 or more, more preferably 80 or more. If it is less than 70, the contents may be seen through, or the printed matter may be difficult to see. The whiteness is a value obtained by the JIS L1015 ^1981- B method. In the present invention, the total light transmittance of the film is preferably 30% or less. More preferably, it is 25% or less, more preferably 20% or less, and particularly preferably 15% or less. If it exceeds 30%, the contents may be seen through, or the printed matter may be difficult to see.

  In order to give an appropriate whiteness to the heat-shrinkable film, for example, it is preferable to contain fine cavities inside the film. For example, foamed materials and the like may be mixed and extruded, but by mixing an incompatible thermoplastic resin (hereinafter sometimes simply referred to as an incompatible resin) in polyester and stretching it in at least one axial direction. A method of obtaining a cavity is preferred. The type of the incompatible resin is arbitrary, and is not particularly limited as long as it is incompatible with the polyester. Specific examples include polystyrene resins, polyolefin resins, polyacrylic resins, polycarbonate resins, polysulfone resins, and cellulose resins. In particular, from the viewpoint of forming the cavity, a polyolefin resin such as a polystyrene resin, a polymethylpentene resin, or a polypropylene resin is preferable.

  Polystyrene resin refers to a thermoplastic resin containing a polystyrene structure as a basic component, and graft or block copolymerization of other components in addition to homopolymers such as atactic polystyrene, syndiotactic polystyrene, isotactic polystyrene, etc. Modified resins, such as impact-resistant polystyrene resins and styrene-butadiene block copolymers, and also thermoplastic resins having compatibility with these polystyrene resins, such as polyphenylene ether, are included.

  The polymethylpentene resin is a polymer having units derived from 4-methylpentene-1 at 80 mol% or more, preferably 90 mol% or more, and other components include ethylene, propylene, butene- Examples are derived units from 1,3-methylbutene-1, and the like. The melt flow rate of the polymethylpentene resin is preferably 200 g / 10 min or less, more preferably 30 g / 10 min or less. This is because when the melt flow rate exceeds 200 g / 10 min, it is difficult to obtain the effect of reducing the weight of the film.

  The polypropylene resin in the present invention includes modified resins obtained by grafting or block copolymerizing other components in addition to homopolymers such as isotactic polypropylene and syndiotactic polypropylene.

  The amount of the incompatible resin varies depending on the target degree of whiteness, but is 3% by mass to 39% by mass with respect to the entire polymer mixture of the polyester raw material and the incompatible resin. More preferably, it is 8 mass%-35 mass%, More preferably, it is 10 mass%-30 mass%. If the amount of incompatible resin is too small, there is a limit to increasing the amount of voids generated, and it may be difficult to obtain a desired whiteness. On the other hand, if the amount of the incompatible resin is too large, the heat resistance and strength of the polyester film, particularly the strength of the waist may be impaired.

  In addition, when the heat-shrinkable film used in the present invention has a layer A containing a large number of cavities inside as described later, a total of 100 masses of the polyester raw material and the incompatible resin forming the cavities-containing layer A It is preferable to set the amount of the incompatible resin in the above range with respect to%.

  In preparing the polymer mixture obtained by mixing the polyester and the incompatible resin, for example, the chips of each resin may be mixed and melt-kneaded in an extruder, and then extruded, or both may be preliminarily mixed by a kneader. A kneaded resin may be further melt extruded from an extruder. In addition, a chip obtained by adding an incompatible resin in the polyester polymerization step and stirring and dispersing may be melt-extruded.

  The film in the present invention is preferably provided with a layer B having fewer cavities than the A layer on at least one side of the layer A containing a large number of cavities inside. In order to achieve this configuration, different raw materials are charged into different extruders A and B, melted, bonded in a molten state before or in the T-die, and solidified in close contact with the cooling roll, and then described later. It is preferable to stretch by the method. At this time, it is preferable that the incompatible resin of the B layer is less than the A layer as a raw material. By doing so, there are few cavities in the B layer, the surface is less rough, and the film does not impair the aesthetics of printing. Further, since there is no portion where there are not many cavities in the film, the film does not become weak and the film has excellent wearability. Further, a three-layer structure such as B / A / B or B / A / C may be used. When the C layer is provided, the content of the cavities is arbitrary, but the fine particles for controlling slippage between the bottle and the film during shrinkage can be added. The thickness ratio of the A layer and the B layer is preferably A / B = 2/1 or more, more preferably 4/1 or more, and further preferably 6/1 or more. If it is less than 1/1, it is difficult to achieve both the aesthetics of printability and the reduction of specific gravity. B / A / B is preferable for suppressing undesirable curling after the shrinkage treatment.

[Right-angle tear strength]
The heat-shrinkable polyester film of the present invention was shrunk 3% in the longitudinal direction in warm water at 80 ° C., and then the right-angled tear strength per unit thickness was determined by the following method. The right-angled tear strength is preferably 100 N / mm or more and 300 N / mm or less.

-Method for measuring right-angle tear strength Cut the film before heat shrink so that the main shrink direction is the longitudinal direction, and fix both ends in the longitudinal direction to a rectangular frame. At this time, the sample is loosened and fixed to the frame so as to be 3% longer than the length of the frame. The sample is immersed together with the frame in warm water of 80 ± 0.5 ° C., and the film is contracted by 3% in the main contraction direction for about 5 seconds until the loose film becomes a tension state in the frame. Then, after immersing in 25 degreeC water, it may take out and wipe off moisture.

Subsequently, a test piece of a predetermined size is sampled from the film after shrinkage according to JIS K 7128-3. Thereafter, both ends of the test piece are gripped with a universal tensile tester, and the strength (N) at the time of tensile fracture in the width direction of the film is measured under the condition of a tensile speed of 200 mm / min. Then, the right angle tear strength (N / mm) per unit thickness (mm) is calculated using the following formula 2.
Right angle tear strength = strength at tensile fracture ÷ thickness Equation 2

  If the right-angled tear strength after shrinking 3% in the longitudinal direction in warm water at 80 ° C is less than 100 N / mm, when used as a label, it may be easily broken by an impact such as dropping during transportation. On the other hand, if the right-angled tear strength is greater than 300 N / mm, the cutability (ease of tearing) when tearing the label becomes unfavorable. The right-angle tear strength is more preferably 125 N / mm or more, further preferably 150 N / mm or more, and particularly preferably 175 N / mm or more. The right-angled tear strength is more preferably 275 N / mm or less, further preferably 250 N / mm or less, and particularly preferably 225 N / mm or less.

[Film Production Method]
The heat-shrinkable polyester film used for the label of the present invention is obtained by melting and extruding a polymer mixture of the above-described polyester raw material and an incompatible resin (which may contain fine particles if necessary) using an extruder. It can be obtained by forming a stretched film and biaxially stretching and heat-treating the unstretched film by the method shown below. The polyester can be obtained by polycondensing the above-described preferred dicarboxylic acid component and diol component by a known method. Usually, two or more kinds of chip-like polyester are mixed and used as a raw material for the film.

  When the raw material resin is melt-extruded, the polyester raw material is preferably dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer. After the polyester 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. In extruding, any existing method such as a T-die method or a tubular method can be employed.

  And an unstretched 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 from a die onto a rotating drum and rapidly solidifying it can be suitably employed.

  Further, as will be described later, the obtained unstretched film is stretched in the width direction under predetermined conditions, and then once heat-treated, and then stretched in the longitudinal direction (longitudinal stretching) under the predetermined conditions. By rapidly cooling the subsequent film, a heat-shrinkable polyester film used for the label of the present invention is obtained. Hereinafter, a preferable biaxial stretching / heat treatment method for obtaining a heat-shrinkable polyester film will be described in detail in consideration of differences from the conventional biaxial stretching / heat treatment method of a heat-shrinkable polyester film.

[Preferable stretching and heat treatment method for heat-shrinkable polyester film]
A normal heat-shrinkable polyester film is produced by stretching an unstretched film in the direction in which it is desired to shrink. Although there was a high demand for heat-shrinkable polyester films that shrink in the longitudinal direction from the past, simply stretching an unstretched film in the longitudinal direction makes it impossible to produce a wide film, resulting in poor productivity and thickness. A film with good spots cannot be produced. Moreover, if the method of extending | stretching to a longitudinal direction after extending | stretching previously to the width direction is employ | adopted, the shrinkage | contraction amount to a longitudinal direction will become inadequate, or it will shrink | contract unnecessarily in the width direction.

  For example, JP-A-8-244114 discloses a method of stretching an unstretched film in the order of length-width-length under predetermined conditions in order to improve the mechanical properties in the longitudinal direction. According to their pilot test, it was not possible to obtain a film with sufficient shrinkage in the longitudinal direction, which is the main shrinkage direction, and wrinkles in the width direction were produced on the produced film roll. It became clear that it became easy to do. In addition, if the longitudinal stretching ratio (the first stage longitudinal stretching ratio or the second stage longitudinal stretching ratio) is increased to increase the contractibility in the longitudinal direction, the film is finally stretched in the longitudinal direction. It has also been found that it is difficult to carry out a continuous and stable production due to frequent breaks. Moreover, the film obtained by the said additional test wrinkled in the longitudinal direction on the manufactured film roll.

  In order to finally increase the amount of shrinkage in the longitudinal direction, the present inventors have disadvantaged the method of stretching in the longitudinal direction after biaxial stretching in the longitudinal direction and the width direction as disclosed in JP-A-8-244114. It was considered that it would be advantageous to simply stretch in the width direction and then stretch in the longitudinal direction. And in such a method of stretching in the longitudinal direction after stretching in the width direction (hereinafter, simply referred to as a transverse-longitudinal stretching method), the characteristics such as the hot water shrinkage in the longitudinal direction of the film depend on the conditions in each stretching step. We studied earnestly about how it changes. As a result, when the film is produced by the transverse-longitudinal stretching method, the hot water shrinkage in the longitudinal direction is performed by applying the means (a) described later (control of the shrinkage stress by applying an intermediate heat treatment after stretching in the width direction). It has been found that the rate and heat shrinkage stress can be increased, and it becomes possible to produce continuously and stably.

  However, the heat-shrinkable film subjected to the means (a) (that is, a heat-shrinkable film obtained by a special process of “lateral stretching-intermediate heat treatment-longitudinal stretching”) has a main shrinking direction in the longitudinal direction. Although it has excellent mechanical strength in the width direction, there are some that have too high rate of hot water shrinkage and heat shrinkage stress in the longitudinal direction, and the shrinkage finish when the film rolls directly around the bottle and then heat shrinks. Was not necessarily good. In addition, it has been found that simply adopting the process of “lateral stretching—intermediate heat treatment—longitudinal stretching” does not necessarily mean that the toughness, viscosity and toughness of the film are good.

  Therefore, the present inventors have intensively studied whether or not the shrinkage finish property at the time of thermal shrinkage after body winding can be improved by treating the film after being subjected to transverse stretching-intermediate heat treatment-longitudinal stretching. As a result, the film after the process of transverse stretching-intermediate heat treatment-longitudinal stretching is subjected to the means of (b) described later (final heat setting after longitudinal stretching and implementation of relaxation treatment in the width direction), It has been found that the shrinkage finishing performance at the time of heat shrinkage after body winding can be drastically improved, and the present invention has been devised. Hereinafter, the means (a) and (b) will be sequentially described.

(A) Control of shrinkage stress by intermediate heat treatment after stretching in the width direction In the production of a film by the transverse-longitudinal stretching method of the present invention, after stretching an unstretched film in the width direction, the temperature is 75 ° C or more and 140 ° C or less. It is necessary to perform heat treatment (hereinafter referred to as intermediate heat treatment) for 1.0 second to 20.0 seconds. By performing this intermediate heat treatment, it is possible to obtain a film that does not cause shrinkage spots when used as a label. The reason why it is possible to obtain a film that does not cause shrinkage spots by performing a specific intermediate heat treatment after transverse stretching is not clear, but by performing a specific intermediate heat treatment, molecular orientation in the width direction can be improved. It is thought that it may be possible to reduce the shrinkage stress in the width direction while remaining to some extent. In addition, the minimum of the temperature of heat processing is preferable in it being 85 degreeC or more, and it is more preferable in it being 90 degreeC or more. Moreover, the upper limit of the temperature of heat processing is preferable in it being 135 degrees C or less, and it is more preferable in it being 130 degrees C or less. On the other hand, the heat treatment time may be appropriately adjusted according to the raw material composition within a range of 1.0 second to 20.0 seconds.

(B) Final set after longitudinal stretching and relaxation treatment in the width direction In the production of the film by the transverse-longitudinal stretching method of the present invention, as described above, after the intermediate heat treatment is performed after the transverse stretching, It is necessary to relax within a range of 1% or more and 30% or less in the width direction while heating at a temperature of 90 ° C. or more and 140 ° C. or less while holding both ends of the width direction in the tenter with clips. In order to obtain a heat-shrinkable film having a relatively low hot-water heat shrinkage rate of 15% or more and less than 40% like the heat-shrinkable film of the present invention, Further, it is difficult to accurately express the desired hot water heat shrinkage rate in the longitudinal direction of the film only by adjusting the hot water heat shrinkage rate in the longitudinal direction by adjusting the draw ratio in the longitudinal direction. Therefore, once the film is stretched in the machine direction so as to have a higher magnification than the draw ratio at which a desired hot water heat shrinkage ratio can be exhibited, the final heat set (final set) is applied to the film and simultaneously in the width direction. It is preferable to reduce the hot water heat shrinkage rate by performing the relaxation treatment so that the desired hot water heat shrinkage rate is obtained. In this way, after stretching the film in the machine direction at a high magnification, it is relaxed by an appropriate amount in the width direction while applying the final heat set, and the hot film heat shrinkage in the machine direction and width direction of the final film is reduced. By fine adjustment, it is possible to improve the shrinkage finish when the label is wound around the container by the body winding method and then thermally contracted. When the relaxation temperature is lower than 90 ° C or higher than 140 ° C, it is difficult to finely adjust the hot water heat shrinkage in the width direction, which is not preferable. On the other hand, if the relaxation amount is less than 1%, fine adjustment of the hot water heat shrinkage rate in the width direction becomes difficult, which is not preferable. On the contrary, if the relaxation amount exceeds 30%, the hot water heat shrinkage rate in the longitudinal direction is small. Since adjustment becomes difficult, it is not preferable.

  By taking the measures (a) and (b) described above, it becomes possible to obtain a heat-shrinkable polyester film having good toughness, viscosity and toughness, and the shrinkage finish at the time of heat-shrinking after body winding is also extremely high. Become good. Further, only one of the above-described means (a) and (b) is the heat shrinkability in the longitudinal direction of the film, the low natural shrinkage rate, the stable film forming property, and the shrinkage at the time of shrinkage after the body winding. It does not contribute effectively to the finish, toughness and toughness, but by combining the means (a) and (b), it is very efficient, moderate heat shrinkability in the longitudinal direction, and low natural shrinkage. It is considered that it is possible to develop the rate, stable film forming property, good shrinkage finish property, toughness, toughness and the like.

  In the production of the film by the transverse-longitudinal stretching method of the present invention described above, the unstretched film is stretched in the width (transverse) direction in a state where both ends in the width direction are held by clips in the tenter, Tg + 5 It is necessary to carry out so that the magnification is 2.5 times or more and 6.0 times or less at a temperature of ℃ to Tg + 40 ℃. If the stretching temperature is lower than Tg + 5 ° C., it is not preferable because breakage is likely to occur during stretching. On the other hand, if it exceeds Tg + 40 ° C., thickness unevenness in the width direction is deteriorated, which is not preferable. The temperature of transverse stretching is preferably Tg + 10 ° C. or higher, more preferably Tg + 15 ° C. or higher, preferably Tg + 35 ° C. or lower, and more preferably Tg + 30 ° C. or lower. Further, if the draw ratio in the width direction is less than 2.5 times, not only the productivity is deteriorated but also the thickness unevenness in the width direction is deteriorated, which is not preferable. On the other hand, if it exceeds 6.0 times, breakage occurs at the time of drawing. In addition, it is not preferable because a large amount of energy and a large apparatus are required for relaxation, and productivity deteriorates. The transverse draw ratio is preferably 3.0 times or more, more preferably 3.5 times or more, preferably 5.5 times or less, and more preferably 5.0 times or less.

  In the production of a film by the transverse-longitudinal stretching method of the present invention, before the film subjected to the intermediate heat treatment is stretched in the longitudinal direction, a thick portion that is not sufficiently transversely stretched at the edge of the film (mainly during transverse stretching) May be trimmed (particularly, when a highly crystalline resin is used as a raw material, trimming is preferable). Specifically, it is located in the vicinity of the left and right edges of the film, and a portion (thick portion) having a thickness of about 1.1 to 1.3 times the thickness of the central portion is cut using a tool such as a cutter. A method of stretching only the remaining part in the longitudinal direction while removing the thick part can be employed.

  When trimming the film edge, it is preferable to cool the film so that the surface temperature of the film before trimming is 50 ° C. or lower. By cooling the film in this way, trimming can be performed without disturbing the cut surface. In addition, trimming of the film edge can be performed using a normal cutter or the like, but if a round blade having a circumferential cutting edge is used, a situation in which the cutting edge is locally dulled does not occur, and the film edge is This is preferable because it can continue to be cut sharply over a long period of time and does not cause a breakage during stretching in the longitudinal direction.

  When using a highly crystalline resin as a raw material, trimming the edge of the film before stretching in the longitudinal direction makes it possible to stretch the film once heat-set uniformly in the longitudinal direction, and break it. It is possible to continuously produce a stable film without any problems. Furthermore, since the film can be uniformly stretched in the longitudinal direction, a film having a small thickness unevenness in the longitudinal direction can be obtained. In addition, by trimming the end of the film, bowing during stretching in the longitudinal direction is avoided, and a film having a small difference in physical properties between the left and right can be obtained.

  Although the thickness of the heat-shrinkable polyester film is not particularly limited, the heat-shrinkable film for labels is preferably 10 to 200 μm, and more preferably 20 to 100 μm.

[Laser welding]
The heat-shrinkable label of the present invention is obtained by superimposing one end of a heat-shrinkable polyester film on the other end and irradiating the overlapped portion with a laser beam from the outer surface of the film to partially melt the contact surface between the film and the film. By bringing the contact surfaces into close contact with each other and cooling, the two are joined and integrated.

As a laser light source used for laser welding, various kinds of lasers such as solid lasers (Nd: YAG excitation, semiconductor laser excitation, etc.), semiconductor lasers (as long as an absorber corresponding to each wavelength laser is included) are used. 650 to 980 nm), tunable diode laser (630 to 1550 nm), titanium sapphire laser (Nd: YAG excitation, 690 to 1000 nm), carbon dioxide gas (CO ₂ ) laser (10600 nm), and the like can be used. Among these laser light sources, carbon dioxide laser can be bonded between colorless and transparent heat-shrinkable polyester film without adding a specific absorbent, and can be used for various printing and designs. It is preferable to produce a label by irradiating a carbon dioxide laser.

  As laser irradiation conditions, it is necessary to adjust appropriately according to the composition and thickness of the heat-shrinkable polyester film to be used. For example, in the case of a carbon dioxide laser, the scanning speed is 20 m / min to 200 m / min, the beam diameter is 1 to The conditions of 4 mm, focal length 20 to 100 mm, and output 10 to 100 W are preferable. Under conditions outside this range, sufficient partial melting of the film by the laser cannot be obtained, resulting in poor adhesion, labels may be peeled off during shrinkage mounting or product distribution, or the film may melt too much due to the laser. It may be cut off without being bonded.

  In the present invention, since the film is bonded by laser welding without using a solvent, a pressure sensitive adhesive, etc., a label can be produced in a clean state without a solvent odor, and a label having sufficient adhesive strength can be obtained at high speed. Can do. Further, the adhesive strength can be adjusted by adjusting the intensity of the laser light, the irradiation time (exposure amount, etc.), and the bonding strength can be reduced with a relatively small exposure amount, for example. Therefore, if necessary, the label can be easily peeled from the container to facilitate recycling.

[Label production method]
Next, the manufacturing method of the heat-shrinkable label of this invention is demonstrated. First, a label design is printed on a heat-shrinkable polyester film, if necessary, and wound into a roll. The film is fed out from the roll, and the entire circumference of the cylindrical body is covered so that the film is superimposed on the end of the film while the film is wound around a cylindrical body of an appropriate size that matches the outer periphery of the container. Laser irradiation is applied to the overlapped part of the film to partially melt the contact surface of the film and bring the contact surface into close contact. By cooling, the two are joined, integrated, formed into a tube, and then bonded. The heat-shrinkable label of the present invention can be obtained by cutting excess film along the portion. After unwinding the film from the roll, the film is cut into a predetermined length in advance, and the other end is overlapped on the end of the film while the cut film is wound around the tubular body to cover the entire circumference of the tubular body The label of the present invention can also be obtained by irradiating the overlapped portion with a laser to join the contact surfaces of the films. A package in which the label is in close contact with the container can be manufactured by attaching the obtained label to a desired position of the container and applying a shrinkage treatment. Alternatively, the label of the present invention can be obtained by wrapping the film directly around the container so as to cover the entire circumference of the container and irradiating the laser beam onto the overlapped portion of the film. Also in this case, the film fed out from the roll may be wound around the container as it is, or the film fed out may be wound around the container after being cut into a predetermined length.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited to these Examples at all. First, the evaluation method of the film and label produced in the Example and the comparative example is demonstrated. The evaluation results of the films are summarized in Table 3, and the evaluation results of the labels are summarized in Table 4. In the following description, “part” means “part by mass”.

[Heat shrinkage (hot water heat shrinkage)]
The film was cut into a 10 cm × 10 cm square, and heat-shrinked in hot water at a predetermined temperature ± 0.5 ° C. for 10 seconds under no load. The film was immediately immersed in water at 25 ° C. ± 0.5 ° C. for 10 seconds, and then the vertical and horizontal dimensions of the film were measured. 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 (%) Formula 1

[Maximum heat shrinkage stress value]
The film was cut into a size of main shrinkage direction × orthogonal direction = 200 mm × 15 mm. Baldwin Co., Ltd. Universal Tensile Tester STM-50 was adjusted to a temperature of 90 ° C., the cut film was set, and the maximum stress value was determined when held for 10 seconds.

[Measurement method of Young's modulus before fracture]
In accordance with ASTM-D882, a film sample cut into a length of 150 mm and a width of 10 mm is set to a sample length of 100 mm using an autograph manufactured by Shimadzu Corporation under an atmosphere of 25 ° C. and 65% RH. A stress-strain curve was measured when both ends (both ends along the longitudinal direction) were gripped and pulled at a pulling speed of 200 mm / min. Then, the average value of the ratio of stress to strain from the time of elongation to the magnification of 90% of the elongation at break (back calculation from the elongation at break) to the time of break was calculated as the Young's modulus before break.

[Whiteness]
The whiteness was measured according to JIS L1015 ^1981- B method using Z-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.

[Total light transmittance]
Total light transmittance was determined with NDH-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.

[Measurement method of right-angle tear strength]
The film before heat shrinkage is cut so that the main shrinkage direction is the longitudinal direction, and both ends in the longitudinal direction are fixed to a rectangular frame. At this time, the sample is loosened and fixed to the frame so as to be 3% longer than the length of the frame. The sample is immersed frame by frame in warm water of 80 ± 0.5 ° C., and the film is contracted by 3% in the main contraction direction for about 5 seconds until the loose film becomes a tension state in the frame. Subsequently, after dipping in water at 25 ° C., the water may be removed and wiped off.

Then, the test piece F of the shape shown in FIG. 1 was cut out from the film after shrinkage according to JIS K 7128-3. When cutting out, the longitudinal direction of the test piece was set as the main shrinkage direction of the film. Then, grip both ends of the test piece with a universal tensile tester (trade name “Tensilon”; manufactured by Toyo Seiki Co., Ltd.), and measure the strength (N) at the time of tensile fracture in the width direction of the film at a tensile speed of 200 mm / min. Went. The right angle tear strength (N / mm) per unit thickness (mm) was calculated using the following formula 2.
Right angle tear strength = strength at tensile fracture ÷ thickness Equation 2

[Tg (glass transition temperature)]
Using a differential scanning calorimeter (model: DSC220) manufactured by Seiko Denshi Kogyo Co., Ltd., 5 mg of an unstretched film was sampled and heated from −40 ° C. to 120 ° C. at a heating rate of 10 ° C./min. The curve (DSC curve) was measured. A tangent line was drawn before and after the inflection point of the DSC curve, and the intersection was defined as Tg (glass transition temperature).

[Label adhesion]
Sensory evaluation was performed on the degree of label displacement when the bottle after heat shrinkage and the label attached to the bottle were lightly twisted. When the label did not move, it was marked as “◯”, and when the label slipped or the label and the bottle were displaced, “x” was marked.

[Adhesiveness of label bonding part]
For the label after heat shrinkage attached to the bottle, sensory evaluation of how the film was peeled off when the film end on the surface of the part where the films were bonded together was scratched by hand (nail) . Those that did not peel off and adhered well were marked with ◯, those that adhered but peeled off with a light force were marked with Δ, and those that did not adhere were marked with ×.

[Shrink finish]
Evaluation of the finish after heat shrinkage attachment to the bottle was performed visually, and the criteria were as follows.
◎: No wrinkles, jumping up or insufficient shrinkage, and no color spots are observed. ○: Wrinkles, jumping up or insufficient shrinkage cannot be confirmed, but some color spots are seen. Neither ascending nor insufficient shrinkage has occurred, but spots on the neck are observed. ×: Wrinkles, jumping up, insufficient shrinkage occurred

[Label openability]
A label having a notch with a length of 2 mm in a direction perpendicular to the main shrinkage direction was attached to a PET bottle and thermally shrunk. However, the notch was provided on the upper side of the label when the bottle was erected. Thereafter, the bottle with the label attached was refrigerated at 5 ° C. for 24 hours, and the label of the bottle immediately after being taken out of the refrigerator was torn with a fingertip from the notch portion. The number of bottles that were torn up in the vertical direction and the label could be easily removed from the bottles was counted, and the ratio (%) to 50 samples was calculated.

[Polyester film 1]
70 parts of polyester 1 (IV: 0.72 dl / g) composed of 70 mol% of ethylene glycol, 30 mol% of neopentyl glycol and 100 mol% of terephthalic acid, polyethylene terephthalate (IV: 0.75 dl / g: hereinafter, polyester 2 ) 30 parts, 10 parts of polystyrene (“G797N”: manufactured by Nippon Polystyrene Co., Ltd.), and 10 parts of titanium dioxide (“TA-300”: manufactured by Fuji Titanium Co., Ltd .: average particle size of 0.39 μm) are mixed to prepare a raw material for the A layer. It was. For the B layer, a mixture of the above polyester 1 and polyester 2 at 70:30 (mass ratio) was used. The raw materials of layer A and layer B are put into separate twin screw extruders, mixed and melted, joined together with a feed block, melt-extruded from a T-die at 280 ° C, and cooled to a surface temperature of 30 ° C. The unstretched film having a thickness of 200 μm and having a laminated structure of B / A / B was obtained (B / A / B = 10 μm / 180 μm / 10 μm) by winding on a rotating metal roll and quenching. At this time, the take-up speed of the unstretched film (the rotation speed of the metal roll) was about 20 m / min. Moreover, Tg of the unstretched film was 67 degreeC. Thereafter, the unstretched film was led to a tenter (first tenter) in which a transverse stretching zone, an intermediate zone, and an intermediate heat treatment zone were continuously provided. In the tenter, the length of the intermediate zone located between the transverse stretching zone and the intermediate heat treatment zone is set to about 40 cm. In addition, in the intermediate zone, when the strip-shaped paper piece is hung in a state where the film is not passed through, the hot air from the stretching zone and the hot air from the heat treatment zone are blown so that the paper piece hangs almost completely in the vertical direction. It was cut off.

  The pre-stretched film led to the tenter is preheated until the film temperature reaches 90 ° C., and then stretched 3.7 times at 85 ° C. in the transverse direction in the transverse stretching zone, and after passing through the intermediate zone (pass Time = about 1.2 seconds), the heat treatment was conducted at 105 ° C. for 6.0 seconds while being led to the intermediate heat treatment zone and relaxed by 10% in the width direction. A transversely uniaxially stretched film having a thickness of 60 μm was obtained. Subsequently, using a pair of left and right trimming devices (configured by a round blade having a circumferential cutting edge) provided behind the tenter, the edge of the laterally uniaxially stretched film (about the thickness of the film at the center) A portion having a thickness of 1.2 times) was cut, and the end portion of the film located outside the cut site was continuously removed.

  The film with the end trimmed is guided to a longitudinal stretching machine in which a plurality of roll groups are continuously arranged, preheated on a preheating roll until the film temperature reaches 70 ° C., and then set to a surface temperature of 95 ° C. The film was stretched 2.2 times between the stretched rolls. Thereafter, the longitudinally stretched film was forcibly cooled by a cooling roll set at a surface temperature of 25 ° C. The surface temperature of the film before cooling was about 75 ° C., and the surface temperature of the film after cooling was about 25 ° C. The time required for cooling from 70 ° C. to 25 ° C. was about 1.0 second, and the film cooling rate was 45 ° C./second.

  The cooled film was guided to a tenter (second tenter), and was heat-treated for 5.0 seconds in an atmosphere of 115 ° C. while being relaxed by 15% in the width direction, and then cooled. After cooling, both end portions were cut and removed, whereby a biaxially stretched film of about 30 μm was wound up over a predetermined length to obtain a film roll made of the heat-shrinkable polyester film 1. The composition of each layer is shown in Table 1, the production conditions are shown in Table 2, and the characteristics of the film are shown in Table 3.

[Polyester film 2]
The film was produced in the same manner as in the production example of film 1, except that 10 parts of polypropylene resin ("FO-50F": manufactured by Grand Polymer Co., Ltd.) was used instead of 10 parts of polystyrene added to the raw material of layer A in the production of film 1. 2 was produced continuously. The composition of each layer is shown in Table 1, the production conditions are shown in Table 2, and the characteristics of the film are shown in Table 3.

[Polyester film 3]
While changing the mixing ratio (mass ratio) of polyester 1 and polyester 2 to 90:10, the longitudinal stretching ratio is changed to 2.4 times, and the film after longitudinal stretching is thermally relaxed in the width direction in the second tenter. The film 3 was continuously produced by the same method as in the production example of the film 1 except that the temperature during the treatment was changed to 120 ° C. and the relaxation amount during relaxation in the width direction was changed to 20%. As in the film 1, polystyrene and titanium dioxide are added to the A layer. In addition, Tg of the unstretched film was 67 degreeC. The composition of each layer is shown in Table 1, the production conditions are shown in Table 2, and the characteristics of the film are shown in Table 3.

[Polyester film 4]
For an unstretched film having a thickness of 240 μm (B / A / B = 12 μm / 216 μm / 12 μm) obtained in the same manner as in the production example of film 1, the transverse stretch ratio in the first tenter was changed to 4.0 times. The method similar to the production example of the film 1 except that the longitudinal stretching ratio was changed to 2.4 times, and the temperature when the film after longitudinal stretching was relaxed in the width direction in the second tenter was changed to 120 ° C. Thus, the heat-shrinkable film 4 was continuously produced. The composition of each layer is shown in Table 1, the production conditions are shown in Table 2, and the characteristics of the film are shown in Table 3.

[Polyester film 5]
Biaxially stretched heat in the same manner as film 1 except that only a raw material of layer A in the production example of film 1 was used to obtain an unstretched film having a single layer thickness of 200 μm and a biaxially stretched film of about 30 μm. A shrinkable polyester film 5 was continuously produced. The composition of the layers is shown in Table 1, the production conditions are shown in Table 2, and the film properties are shown in Table 3.

[Polyester film 6 (for comparison)]
A biaxially stretched heat-shrinkable polyester film was continuously produced in the same manner as the film 5 (single layer) without using polystyrene and titanium dioxide. The composition of the layers is shown in Table 1, the production conditions are shown in Table 2, and the film properties are shown in Table 3.

[Polyester film 7 (for comparison)]
A tenter (first tenter) in which a 180 μm unstretched film obtained in the same manner as film 5 (single layer) was used except that polystyrene and titanium dioxide were not used, and a transverse stretch zone and an intermediate heat treatment zone were continuously provided. Led to. And after preheating the unstretched film guided to the tenter until the film temperature reaches 90 ° C., the film is stretched 4.0 times at 75 ° C. in the transverse direction in the transverse stretching zone, and then led to the intermediate heat treatment zone. The film was heat-treated at 110 ° C. for 6.0 seconds to obtain a horizontal uniaxially stretched film having a thickness of 45 μm. Subsequently, the laterally uniaxially stretched film is led to a longitudinal stretching machine in which a plurality of roll groups are continuously arranged, and preheated until the film temperature reaches 70 ° C. on the preheating roll, and then the surface temperature is set to 90 ° C. The film was stretched 1.5 times between the stretched rolls. The longitudinally stretched film was forcibly cooled by a cooling roll set at a surface temperature of 25 ° C. The cooling rate was 45 ° C./second.

  Then, the cooled film is guided to a tenter (second tenter), and heat-treated for 5.0 seconds in an atmosphere of 110 ° C. in the second tenter, and both edges are cut and removed, thereby removing about 30 μm. The biaxially stretched film (heat-shrinkable film) was wound up over a predetermined length to obtain a roll of film 7. The composition of the layers is shown in Table 1, the production conditions are shown in Table 2, and the film properties are shown in Table 3.

  As is apparent from Table 3, the films for labels 1 to 5 of the present invention have hot water shrinkage in the longitudinal direction (main shrinkage direction), hot water shrinkage in the width direction, maximum heat shrinkage stress, Young's modulus before breaking, and whiteness. Are within the scope of the present invention, and the total light transmittance and the right-angle tear strength were also good. Moreover, wrinkles were not generated on the film roll.

  However, the comparative films 6 and 7 were inferior in terms of whiteness and total light transmittance because they did not have cavities. Furthermore, it was found that the comparative film 7 was inferior in hot water shrinkage in the orthogonal direction and Young's modulus before breaking.

Example 1
Using the polyester film 1 roll, three-color printing was performed with grass, gold, and white ink from Toyo Ink Manufacturing Co., Ltd., slit into a width of 100 mm, and a printed film roll was prepared. The above-mentioned printed film roll is unwound on an upright paper cylinder having a diameter of 70 mm and a height of 150 mm so that the printing surface is inward and the longitudinal direction of the film is parallel to the cylinder circumferential direction of the cylinder Wound the film. At the place where the film just goes around the outer periphery of the cylinder and the films overlap each other, using an oscillator with a maximum output of 40 W, laser light wavelength: 10.6 μm, output: 20 W, focal length: 20 mm, laser scanning speed 50 m A carbon dioxide laser was irradiated under the condition of / min, and the wound film was welded to form a continuous body to produce a heat-shrinkable label. With the 290 ml aluminum bottle can upright (maximum diameter of the barrel is 68 mm, diameter of the neck is 30 mm), the printing surface faces the outer surface of the bottle so that one end of the film is along the bottom of the can Put the label on it, put it into a steam furnace shrink tunnel that is 3m long and kept at 92 ° C, and let it pass for 10 seconds, so that the label shrinks and adheres to the outer periphery of the bottle can. (Container with label after shrinkage) was obtained. The package had good shrinkage finish and good adhesion at the label bonding part. The evaluation results as labels are shown in Table 4.

Example 2
A package was obtained in the same manner as in Example 1 except that the polyester film 2 was used as the heat-shrinkable polyester film. The evaluation results as labels are shown in Table 4.

Example 3
A package was obtained in the same manner as in Example 1 except that the polyester film 3 was used as the heat-shrinkable polyester film. The evaluation results as labels are shown in Table 4.

Example 4
A polyester film 4 was used as a heat-shrinkable polyester film, and a package was obtained in the same manner as in Example 1 except that the output was set to 30 W as the carbon dioxide laser irradiation condition at the time of film edge welding. . The evaluation results as labels are shown in Table 4.

Example 5
A packaging body in the same manner as in Example 1 except that the polyester film 5 is used as the heat-shrinkable polyester film, and the scanning speed is set to 30 m / min as the irradiation condition of the carbon dioxide laser at the time of bonding the film ends. Got. The evaluation results as labels are shown in Table 4.

Comparative Example 1
A package was obtained by the same method as in Example 1 except that the film edges were bonded to each other using a commercially available ethylene-vinyl acetate hot melt adhesive (softening point: 85 ° C.). Due to the heat at the time of applying the hot melt adhesive, the shrink finish was deteriorated, and the label-laminated part was peeled lightly by hand, and sufficient adhesiveness was not obtained.

Comparative Example 2
The attachment of the label was tried by the same method as in Example 1 except that the film edges were bonded together by solvent adhesion using 1,3-dioxolane. The film could not be laminated successfully.

Comparative Example 3
A package was obtained in the same manner as in Example 1 except that the polyester film 6 was used as the heat-shrinkable polyester film. There was no problem in particular except for the whiteness and the total light transmittance (Table 3).

Comparative Example 4
A package was obtained in the same manner as in Example 1 except that the polyester film 7 was used as the heat-shrinkable polyester film. The shrink finish was insufficient.

  The heat-shrinkable label of the present invention is suitable for bottle labels such as PET bottles and glass bottles.

It is explanatory drawing which shows the shape of the test piece at the time of measuring a right-angled tear strength.

Explanation of symbols

  F film

Claims (7)

It is made of a heat-shrinkable polyester film stretched at least uniaxially, and is formed into a tube shape by overlapping the film end portion at a predetermined position of the film and irradiating the overlapping portion of the film with laser. A heat shrinkable label,
The heat-shrinkable polyester film has ethylene terephthalate as a main constituent unit, and a unit derived from glycol other than ethylene glycol and / or a unit derived from dicarboxylic acid other than terephthalic acid is at least 15 mol% in 100 mol% of all polyester units 40 A heat-shrinkable label characterized by being a heat-shrinkable polyester film comprising a polyester having a mol% or less and satisfying the following requirements (1) to (5) in which the main shrinkage direction is a longitudinal direction.
(1) The hot-water heat shrinkage in the longitudinal direction when treated for 10 seconds in 90 ° C. warm water is 15% or more and less than 40%.
(2) The hot water heat shrinkage in the width direction orthogonal to the longitudinal direction when treated in 90 ° C. warm water for 10 seconds is −5% or more and 5% or less,
(3) The maximum heat shrinkage stress in the longitudinal direction when treated at 90 ° C. for 10 seconds is 2.5 MPa or more and 7.0 MPa or less,
(4) Young's modulus before break in the longitudinal direction of the film is 0.05 GPa or more and 0.15 GPa or less,
(5) The whiteness is 70 or more or has a cavity.   2. The perpendicular tear strength in the width direction per unit thickness after the heat-shrinkable polyester film is shrunk in the longitudinal direction by 3% in warm water at 80 ° C. is 100 N / mm or more and 300 N / mm or less. Heat shrinkable label.   The heat-shrinkable label according to claim 1 or 2, wherein the laser used for welding the overlapping portions of the films is a carbon dioxide gas laser.   It is a method of manufacturing the heat-shrinkable label according to any one of claims 1 to 3, wherein the ends of the heat-shrinkable polyester film described in claim 1 are overlapped at predetermined positions of the film, A method for producing a heat-shrinkable label, which is formed into a tube shape by irradiating and welding the overlapped portion with a laser.   The method for producing a heat-shrinkable label according to claim 4, wherein the laser used for welding the overlapping portions of the films is a carbon dioxide gas laser.   Prior to mounting on a container, the end of the film is preliminarily stacked at a predetermined position on the film, and the part where the films overlap is irradiated with a laser to form a tube, and then mounted on the container The manufacturing method of the heat-shrinkable label of Claim 4 or 5 containing. The film is directly wound around a container, and then the end of the film is overlapped at a predetermined position of the film, and the portion where the films overlap is irradiated with a laser to form a tube shape. 6. A method for producing a heat-shrinkable label according to 4 or 5.

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