JP2009161249A - Heat-shrinkable label and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a label made of a heat-shrinkable polyester film whose longitudinal direction is the main shrinking direction, and which can be stuck at a high speed when it is mounted on a container, exhibits good finishing properties, and is suitable for mounting while it is wound on the container. <P>SOLUTION: The heat-shrinkable label is formed into a continuous body by irradiating an active energy ray-curable adhesive coated part of the film prepared by winding an at least uni-axially oriented heat-shrinkable polyester film around the container with active energy rays. <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 coating 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. , By a special process of transverse stretching-intermediate heat treatment-longitudinal stretching, the main shrinkage direction is the longitudinal direction, and it is found that a heat-shrinkable film with high mechanical strength in the width direction can be obtained. Proposed earlier (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 in the longitudinal direction. Some of them were too high in stress, and the shrinkage finish when the film was wound directly from the film roll around the bottle and then thermally shrunk was not necessarily good. Also, when winding around the bottle directly from the film roll, it can be wound so as to adhere to 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, conversely, 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 wrapped around the bottle and heat shrinks, and spills occur when opening the bottle There is a fear.

  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 of it. 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 risk 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. Resulting in. Further, when, for example, a hot melt adhesive is used as the adhesive, there is a problem that the distortion of the label due to the heat of the adhesive and insufficient shrinkage in the subsequent process are likely to occur.

On the other hand, solvent bonding is also possible, but since the label is wrapped around a standing container, the solvent viscosity is too low and the coating becomes uneven due to dripping or splashing, and the surroundings are contaminated. There is a problem such as. Also, considering high-speed mounting from the viewpoint of productivity improvement, 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.
JP 2005-292195 A

  The present invention solves the above 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. An object is to provide a label made of a conductive polyester film.

The present invention that has achieved the above object comprises an active energy ray curable adhesive-applied portion of a film made of a heat-shrinkable polyester film stretched at least uniaxially and wound around a container. A heat-shrinkable label formed into a continuous body by irradiating
The heat-shrinkable polyester film has ethylene terephthalate as a main unit, and units derived from glycols other than ethylene glycol and / or units derived from dicarboxylic acids other than terephthalic acid are 15 mol% to 40 mol in 100 mol% of all polyester units. % Heat-shrinkable label characterized in that the main shrinkage direction is a heat-shrinkable polyester film whose longitudinal shrinkage direction satisfies the following requirements (1) to (5).
(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 natural shrinkage ratio after aging for 700 hours or more in an atmosphere of 40 ° C. and 65% RH is 0.05% or more and 1.5% or less.

  In the heat-shrinkable polyester-based label, the right-angled tear strength per unit thickness after the heat-shrinkable polyester-based film is shrunk 3% in the longitudinal direction in warm water at 80 ° C. is 100 N / mm or more. It is preferable that it is 300 N / mm or less.

  In the present invention, an active energy ray-curable adhesive is applied to a part of the film before, after, or while winding a polyester film that satisfies the above requirements around the container. The manufacturing method of the heat-shrinkable label shape | molded to a continuous body by irradiating an energy ray is also included.

  In the above production method, an active energy ray-curable adhesive is applied in advance to a part of the container and / or the heat-shrinkable polyester film, and the container and the heat-shrinkable polyester film are adhered. It is preferable to include the process to keep.

  According to the present invention, a heat-shrinkable polyester-based film that can be bonded at high speed when mounted on a container, has good finish, and further has a main shrinkage direction as a main shrinkage direction suitable for mounting while being wound around the container. A label consisting of can be provided. 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 obtained from a heat-shrinkable polyester-based film that is stretched at least uniaxially and whose main shrinkage direction is a longitudinal direction, and is an active energy ray-curable film of a film wound around a container The present invention relates to a heat-shrinkable label that is formed into a continuous body by irradiating an adhesive application portion with active energy rays.

[About polyester]
The dicarboxylic acid component constituting the polyester used as a raw material for the heat-shrinkable polyester film used in the present invention includes terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, orthophthalic acid and other aromatic dicarboxylic acids, adipic acid, and azelaic acid. Aliphatic dicarboxylic acids such as sebacic acid and decanedicarboxylic acid, and alicyclic dicarboxylic acids are preferably used. 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 is mainly composed of ethylene terephthalate. 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 17 mol% or more, and more preferably 20 mol% or more. As glycols other than ethylene glycol, neopentyl glycol and 1,4-cyclohexanedimethanol are preferable in terms of shrinkage finishing properties and the like. As the unit derived from dicarboxylic acid other than terephthalic acid, isophthalic acid is preferable. 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. The unit content 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, 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.

[Requirement (1)]
The heat-shrinkable polyester film used for the label of the present invention is calculated from the following formula 1 from the length before and after shrinkage when treated (immersed) in 90 ° C. warm water under no load for 10 seconds. It is necessary that the heat shrinkage rate (that is, hot water heat shrinkage rate of 90 ° C.) in the main shrinkage direction (longitudinal direction) of the film to be formed is 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 heat shrinkage 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 heat shrinkage. When the direction of the hot-water heat shrinkage in the direction is 40% or more, the shrinkage tends to occur during the heat shrinkage after being wound as a label by the body winding method, or so-called “jumping” occurs. 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. 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 rate in the width direction of the film calculated from the length before and after shrinkage by the above formula 1 when treated for 10 seconds in 90 ° C. warm water with no load. -5% to 5%. When the heat shrinkage rate in the width direction at 90 ° C. is less than −5%, it is not preferable because a good shrink appearance cannot be obtained when used as a bottle label. When the thermal shrinkage rate exceeds 5%, it is not preferable because, when used as a label, the shrinkage tends to occur during the thermal shrinkage. 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. Further, the hot water heat shrinkage 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 point of elongation (back calculation from the elongation ratio at break) to the point of break is calculated as the Young's modulus before breakage. To do.

  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. If 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 unfavorable. In addition, the lower limit of the Young's modulus before fracture 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 upper limit of 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)]
The heat shrinkable polyester film has a natural shrinkage rate (longitudinal direction) of 0.05% or more and 1.5% or less after aging (storage) in an atmosphere of 40 ° C. and 65% RH for 700 hours or more. It is necessary to be. The natural shrinkage rate can be calculated using the following formula 2.
Natural shrinkage rate = {(length before aging−length after aging) / length before aging} × 100 (%) Formula 2

  When the natural shrinkage rate exceeds 1.5%, it is not preferable because the product is wound in a roll shape and winding tightening occurs, and the film is likely to wrinkle. The smaller the natural shrinkage rate, the better. However, from the viewpoint of measurement accuracy, about 0.05% is considered to be the lower limit. The natural shrinkage rate is preferably 1.3% or less, more preferably 1.1% or less, and particularly preferably 1.0% or less.

[Right-angle tear strength]
A heat-shrinkable polyester film is subjected to 3% shrinkage in the longitudinal direction in warm water at 80 ° C., and then the right-angle tear strength in the width direction is obtained when the right-angle tear strength per unit thickness is determined by the following method. The 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. Subsequently, after dipping in water at 25 ° C., the water may be removed and wiped off.

Then, it samples as a test piece of a predetermined | prescribed magnitude | size according to JISK-7128-3 from the film after the said shrinkage | contraction. 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 3.
Right angle tear strength = strength at tensile fracture ÷ thickness Equation 3

  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 preferably 125 N / mm or more, more preferably 150 N / mm or more, and further 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 in the label of the present invention is obtained by melt-extruding the polyester raw material with an extruder to form an unstretched film, and biaxially stretching the unstretched film by the method shown below. It can be obtained by heat treatment. 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. For this extrusion, any existing method such as a T-die method or a tubular method can be employed.

  And an unstretched film is 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 film that shrinks in the longitudinal direction from the past, a wide film cannot be produced simply by stretching an unstretched film in the longitudinal direction, resulting in poor productivity and thickness. A good film without spots cannot be produced. Moreover, if the method of extending | stretching to a longitudinal direction is previously employ | adopted after extending | stretching to the width direction, 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 the follow-up test with the pilot aircraft of the present inventors, this method cannot obtain a film having sufficient shrinkage in the longitudinal direction, which is the main shrinkage direction, and the produced film roll is wrinkled in the width direction. It became clear that it became easy to generate | occur | produce. 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 had a large natural shrinkage rate, and the wrinkle of the longitudinal direction generate | occur | produced in 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), hot water shrinkage in the longitudinal direction of the film, natural shrinkage, etc. depending on the conditions in each stretching step We intensively studied how the characteristics change. 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 the 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, it is 75 ° C or more and 140 ° C or less. It is necessary to perform heat treatment (hereinafter referred to as intermediate heat treatment) at a temperature for 1.0 second to 20.0 seconds. By performing this intermediate heat treatment, it is possible to obtain a film that hardly causes shrinkage spots when used as a label. The reason why it is possible to obtain a film that hardly causes 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) The final set after longitudinal stretching and the 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 performing the intermediate heat treatment 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. That is, 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, the hot-water heat shrinkage rate (90 ° C.) in the longitudinal direction is 15% or more and less than 40%. However, simply adjusting the hot water heat shrinkage rate in the longitudinal direction by simply adjusting the draw ratio in the longitudinal direction makes it difficult to accurately express the desired hot water heat shrinkage rate in the longitudinal direction of the film. is there. 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 at the same time, the width direction It is preferable that the hot water heat shrinkage rate is reduced by applying a relaxation treatment to the desired hot water heat shrinkage rate. 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. In addition, 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 stretching ratio is preferably 3.0 times or more, more preferably 3.5 times or more, and 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.

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

[Adhesion by irradiation with active energy rays]
Next, the active energy ray curable adhesive will be described. In the present invention, an active energy ray-curable adhesive is used to bond the ends of the heat-shrinkable polyester film wound around the container for high-speed bonding. The adhesive used in the present invention is an adhesive using a solvent-free liquid resin that can be cured using active energy rays, particularly ultraviolet rays or electron beams, and includes urethane (meth) acrylate, epoxy (Meth) acrylate, polyester (meth) acrylate, etc. are mentioned.

  Among these, in the present invention, an active energy ray-curable adhesive made of urethane (meth) acrylate is particularly preferable from the viewpoint of adhesion to a heat-shrinkable polyester film, and among them, polyester polyol is used as a polyol component. The urethane (meth) acrylate obtained is preferred.

Most preferably, among the components obtained by reacting the following raw material compounds (1) to (3), the number of repeating units of the raw material compound (1) is 2 or more and 2 per structural unit of the raw material compound (1). And urethane acrylate (A) having a molecular weight of 1000 to 20000 having 7 to 11 urethane bond groups and / or urea bond groups, tetrahydrofurfuryl (meth) acrylate, phenoxyethyl (meth) acrylate, toluyloxyethyl (meth) An active energy ray-curable adhesive containing at least one radically polymerizable monomer (B) selected from the group consisting of) acrylate, N-vinylpyrrolidone and (meth) acryloylmorpholine is preferred.
(1) Copolyester polyol containing a structural unit derived from an aromatic dicarboxylic acid in an amount of 40 mol% or more in 100 mol% of a structural unit derived from a dicarboxylic acid and having a molecular weight of 1000 to 10,000 (2) Polyisocyanate compound (3) Compound having one or more (meth) acryloyloxy groups and one or more hydroxyl groups

  The (1) copolymer polyester polyol is obtained from a dicarboxylic acid component and a glycol component. Aromatic dicarboxylic acid, which is an essential component, is a dicarboxylic acid having an aromatic group in the molecule, such as phthalic anhydride, terephthalic acid, isophthalic acid, orthophthalic acid, and 1,5-naphthalic acid. It is mentioned as a typical thing. If necessary, a small amount of tri- and tetracarboxylic acids such as trimellitic acid, trimesic acid and pyromellitic acid may be contained. Examples of dicarboxylic acids that can be copolymerized other than aromatic dicarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid, 1,2-hexahydrophthalic acid, 1,3- Hexahydrophthalic acid, 1,4-hexahydrophthalic acid, alicyclic dicarboxylic acids such as perhydronaphthalenedicarboxylic acid, fumaric acid, maleic acid, itaconic acid and other unsaturated dicarboxylic acids, tetrahydrophthalic acid, cyclobutene dicarboxylic acid And unsaturated alicyclic dicarboxylic acids such as p-hydroxyethyloxybenzoic acid and ε-caprolactone.

  Examples of the glycol component include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, and neopentyl. Glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, spiroglycol, 1,4-phenylene glycol, 1,4-phenylene glycol ethylene oxide Adducts, ethylene oxide adducts and propylene oxide adducts of bisphenol A, ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A, polyethylene glycol, polypropylene glycol, And the like diols such as tetramethylene glycol. If necessary, a small amount of triols and tetraols such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol may be contained.

In order to obtain a copolyester polyol from such a dicarboxylic acid component and a glycol component, the glycol raw material may be synthesized in excess relative to the dicarboxylic acid raw material. At this time, it is desirable to synthesize so that the carboxyl group terminal is less than 50 eq / 10 ⁶ g in the copolymerized polyester. When it becomes 50 eq / 10 ⁶ g or more, when synthesizing a urethane acrylate (A) described later, the number of inactive terminals in the reaction with the polyisocyanate compound (2) increases so that the intended urethane acrylate cannot be obtained. There exists a possibility that the sclerosis | hardenability with respect to an active energy ray may fall. Carboxyl terminus or less, more preferably 30eq / 10 ⁶ g, more preferably not more than 20eq / 10 ⁶ g. In the reaction, a known esterification catalyst may be used if necessary.

  The polyester polyol (1) used in the present invention contains a structural unit derived from an aromatic dicarboxylic acid in an amount of 40 mol% or more out of 100 mol% in the structural unit derived from dicarboxylic acid, and has a molecular weight in the range of 1000 to 10,000. preferable. If the aromatic dicarboxylic acid component is less than 40 mol%, the adhesiveness is lowered, and the heat resistance of the cured product is also lowered, which is not preferable. On the other hand, if the molecular weight is less than 1000, the adhesiveness is lowered and the flexibility of the cured product may be insufficient. When the molecular weight exceeds 10,000, the urethanization reactivity may be lowered, and the viscosity becomes high, so that the handling property may be lowered.

  Examples of the polyisocyanate compound (2) used in the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, biphenylmethane diisocyanate, m-phenylene diisocyanate, hexamethylene diisocyanate, tetra Methylene diisocyanate, 3,3′-dimethoxy-4,4′-biphenylene diisocyanate, 2,4-naphthalene diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 4,4′-diphenylene diisocyanate, 4, , 4'-diisocyanate diphenyl ether, 1,5'-naphthalene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, 1,3-diisocyanate methyl ester Rohekisan, 1,4-diisocyanate dicyclohexane, 4,4'-diisocyanate dicyclohexane, 4,4'-diisocyanate dicyclohexylmethane diisocyanate compounds such as isophorone diisocyanate. Moreover, if it is 7 mol% or less among all the isocyanate compounds, you may contain triisocyanate compounds, such as a trimer of 2, 4- tolylene diisocyanate and a trimer of hexamethylene diisocyanate. Of these isocyanate compounds, isophorone diisocyanate and hexamethylene diisocyanate are particularly preferred in terms of weather resistance.

  Examples of the compound (3) having one or more (meth) acryloyloxy groups and one or more hydroxyl groups used in the present invention include mono (meth) acrylates of glycols such as ethylene glycol, diethylene glycol and hexamethylene glycol; 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate; mono (meth) acrylate of a triol compound such as trimethylolpropane, glycerin, trimethylolethane, etc. And di (meth) acrylates; mono (meth) acrylates, di (meth) acrylates, tri (meth) acrylates of tetravalent or higher polyols such as pentaerythritol and dipentaerythritol; glycerin monoallylamine Le, hydroxyl group-containing acrylic compounds such as glycerol diacrylate ether.

  In the urethane acrylate (A) used in the present invention, a polyol and / or a polyamine (4) other than the above (1) may be used as a chain extender, if necessary. Examples of the polyol other than (1) include the glycol component of the copolymer polyester polyol (1) such as ethylene glycol and propylene glycol. Examples of the polyamine include hexamethylenediamine, diaminodiphenylmethane, N-methyldiethanolamine, and high molecular weight polyamines such as terminal aminated polybutadiene having two or more primary or secondary amino groups in the molecule. Further, water may be used in the same manner as these compounds.

  The urethane acrylate (A) used in the present invention is obtained by reacting the copolymer polyester polyol (1) with the polyisocyanate compound (2) at [NCO] / [OH] <2 to obtain an isocyanate-terminated urethane prepolymer. Thereafter, the compound (3) having one or more (meth) acryloyloxy groups and one or more hydrogen groups can be obtained. As another production method, the copolymerized polyester polyol (1) and the polyisocyanate compound (2) are reacted with [NCO] / [OH] ≧ 2 to obtain an isocyanate-terminated prepolymer, and then one or more ( It can be obtained by reacting a compound (3) having a (meth) acryloyloxy group and one or more hydrogen groups with a polyol and / or polyamine (4) other than the above (1). The urethane acrylate (A) can also be obtained by a method in which the raw material compounds (1) to (3) (if necessary (4)) are charged at a constant ratio and reacted. In addition, you may add a well-known catalyst as needed at the time of reaction.

  The urethane acrylate (A) according to the present invention thus obtained preferably has a molecular weight in the range of 1000 to 20000, the number of repeating units in the molecule is 2 or more, and 2. per structural unit. It preferably has 7 to 11 urethane bonding groups and / or urea bonding groups. When the molecular weight is less than 1000, the strain at the time of curing increases, and the adhesiveness may be deteriorated, which is not preferable. When the molecular weight exceeds 20000, compatibility with the later-described radical polymerizable monomer (B) is deteriorated, and as a result, problems such as excessively high viscosity and difficulty in use may occur. When the number of repeating units is one, the strength and adhesiveness of the cured product may be insufficient. Further, even if the number of repeating units is 2 or more, if the number of urethane bonding groups and / or urea bonding groups in the molecule is less than 2.7 per unit of polyester polyol (1) as a constituent component, May decrease or the toughness of the cured product may be insufficient. Exceeding 11 is not preferable because the adhesiveness is lowered and the viscosity may be increased by urethane bonding or the like.

  The active energy ray-curable adhesive contains a radical polymerizable monomer (B). The radical polymerizable monomer (B) is selected from the group consisting of tetrahydrofurfuryl (meth) acrylate, phenoxyethyl (meth) acrylate, toluyloxyethyl (meth) acrylate, N-vinylpyrrolidone and (meth) acryloylmorpholine. More than a species of monomer. Although other known radically polymerizable monomers may be added, the above-mentioned radically polymerizable monomer (B) is preferably used because of its excellent adhesion to polyester.

  Active energy ray-curable adhesives using these compounds are preferable because they are excellent in curability for active energy rays, adhesion to polyester, flexibility, weather resistance, water resistance, heat resistance and chemical resistance.

  If necessary, a photopolymerization initiator (C) can be added to the active energy ray-curable adhesive of the present invention. As photopolymerization initiators, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane- 1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propane-1 Acetophenones such as -one, benzoin ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, hydroxy Nzophenone, 4-benzoyl-4′-methyl-diphenyl sulfide, alkylated benzophenone, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 4-benzoyl-N, N-dimethyl-N -[2- (1-oxo-2-propenyloxy) ethyl] benzenemethananium bromide, benzophenones such as (4-benzoylbenzyl) trimethylammonium chloride, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2, Examples thereof include thioxanthones such as 4-diethylthioxanthone and 2,4-dichlorothioxanthone. These may be used alone or in combination.

In addition to the photopolymerization initiator (C), triethanolamine, methyldiethanolamine, triethanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, benzoic acid ( Photosensitizers such as 2-dimethylamino) ethyl, 4,4′-dimethylaminobenzophenone, 4,4′-diethylaminobenzophenone may be used in combination.

  The active energy ray-curable adhesive of the present invention is a combination of the urethane acrylate (A) and the radical polymerizable monomer (B), and is added with a photopolymerization initiator (C) if necessary. The blending ratio can be arbitrarily set, but the range of (A) / (B) / (C) = 10 to 70/10 to 70/0 to 10 is preferable in terms of mass ratio. When the component (A) is less than 10% by mass, the properties of the urethane acrylate are lost, which is not preferable because the adhesiveness is deteriorated and the flexibility and wrinkle resistance are reduced. Moreover, when a component (A) exceeds 70 mass%, while a viscosity becomes high too much and use becomes difficult, the sclerosis | hardenability with respect to an active energy ray worsens, and is unpreferable.

  As a method for producing the active energy ray curable adhesive of the present invention, there is a method of synthesizing the urethane acrylate (A) by the above method and then blending the radical polymerizable monomer (B). As another method, there is a method of synthesizing the urethane acrylate (A) using the radical polymerizable monomer (B) as a reaction solvent.

Components other than the components (A) to (C) can be added to the active energy ray-curable adhesive of the present invention as necessary. For example, in order to improve the adhesive strength, it is effective to add an epoxy resin or a polyisocyanate compound. In addition, other resins, plasticizers, antifoaming agents, leveling agents, solvents, stabilizers and the like may be added depending on the properties of the adhesive. The active energy rays used for curing in the present invention are ultraviolet rays, electron beams, γ rays, neutron rays and the like. When ultraviolet rays are used, it is desirable to add the aforementioned photopolymerization initiator to the active energy ray-curable adhesive. As the electron beam irradiator, a scanning method or a curtain beam method can be adopted, and the absorbed dose is 1 to 20 Mrad, preferably 2 to 15 Mrad. For ultraviolet irradiation, a mercury lamp or a metal halide lamp or the like can UV irradiation machine used with the irradiation dose is preferably in the range of ^{50~5000mJ / cm 2, 100~1000mJ / cm} 2 is more preferable.

  The active energy ray-curable adhesive may contain an organic solvent. The organic solvent that can be used in the present invention is limited to a volatile one, and most or all of the organic solvent needs to be volatilized by heat drying or the like before curing with active energy rays. Usable solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and other ketones, methyl acetate, ethyl acetate and other esters, tetrahydrofuran, dioxane, ethers such as ethylene glycol monomethyl ether, benzene, toluene, xylene, etc. Aromatic hydrocarbons, aliphatic hydrocarbons such as hexane and heptane, alcohols such as methanol, ethanol and isopropyl alcohol, or mixtures thereof. These solvents may be used during the synthesis of the urethane acrylate (A), and in this case, they can be used as they are.

[Label production method]
Next, the manufacturing method of the heat-shrinkable label of this invention is demonstrated. First, if necessary, a label design is printed on a heat-shrinkable polyester film, and this is wound into a roll. The film is fed from the roll and cut into a predetermined length. Apply the active energy ray-curable adhesive to all or part of the film (for example, part or all of the film edge) before winding the wound film around the container, or after wrapping. The other end is preferably overlapped to cover the entire circumference of the container. That is, in the present invention, an embodiment in which an adhesive is applied to a cut film and then the film is wound around a container; after the film is wound around the container, the adhesive is applied to the film end and the other film end is wound A mode in which the film is bonded to the part; and a mode in which the film is wound around the container and the adhesive is applied simultaneously; both can be adopted. If the adhesive is cured by irradiating the adhesive part with active energy rays, the heat-shrinkable label of the present invention can be obtained. The film may be unwound from a roll, applied with an adhesive while being wound around a container, and then cut. Moreover, when starting to wind around a container, an adhesive may be applied to the container and / or the film in order to fix the film and the container and facilitate the subsequent operation. A known adhesive can be used as the adhesive to be applied first. However, the use of the active energy ray-curable adhesive of the present invention makes it possible to achieve high-speed productivity, curability to active energy rays, adhesion to polyester, flexibility. It is excellent in weather resistance, water resistance, heat resistance and chemical resistance. This operation can be performed continuously.

  The application thickness of the active energy ray-curable adhesive is not particularly limited, but it is preferably as thin as possible from the economical aspect. Therefore, the coating thickness is preferably 5.0 μm or less, and more preferably 3.0 μm or less. It is a major feature of the present invention that the film can be bonded instantaneously and firmly by applying such an extremely thin layer of active energy ray-curable adhesive.

  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 2, 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 treated (immersed) in warm water at a predetermined temperature ± 0.5 ° C. for 10 seconds under no load to cause heat shrinkage. The film was taken out and 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 to obtain a film sample. 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.

[Natural shrinkage]
The obtained film was cut into a main shrinkage direction × orthogonal direction = 200 mm × 30 mm size and allowed to stand (aging) in an atmosphere of 40 ° C. × 65% RH for 700 hours, and then the amount of shrinkage in the main shrinkage direction of the film was measured. The natural shrinkage rate was calculated according to Equation 2.
Natural shrinkage rate = {(length before aging-1length after aging) / length before aging} × 100 (%) Formula 2

[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 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. Subsequently, after dipping in water at 25 ° C., the water may be removed and wiped off.

Next, a test piece F having a 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. Thereafter, both ends of the test piece are grasped with a universal tensile tester (trade name “Tensilon”; manufactured by Toyo Seiki Co., Ltd.), and the strength (N) at the time of tensile fracture in the width direction of the film is measured 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 3.
Right angle tear strength = strength at tensile fracture ÷ thickness Equation 3

[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).

[Tm (melting point)]
Using the above differential scanning calorimeter (model: DSC220), 5 mg of unstretched film was sampled, and the peak of the heat flow rate curve (DSC curve) when the temperature was raised from room temperature (23 ° C) at a rate of temperature rise of 10 ° C / min. Was set to Tm (melting point).

[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]
About the label after heat shrink with which the bottle was mounted | worn, sensory evaluation was carried out about how the film peeled when the film end which has come out on the surface of the part where films were bonded together was scratched by hand (nail). The case where the film was sufficiently adhered without being peeled was rated as “◯”, the case where the film was adhered but peeled off with a light force was evaluated as “Δ”, and the case where the film was not adhered was marked as “X”.

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

[Production Method of 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, 30 parts of polyester 2) was mixed and charged into an extruder. Thereafter, the mixed resin was melted at 280 ° C., extruded from a T-die, wound around a rotating metal roll cooled to a surface temperature of 30 ° C., and rapidly cooled to obtain an unstretched film having a thickness of 200 μm. 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 for 6.0 seconds at a temperature of 105 ° C. while being led to an intermediate heat treatment zone and relaxing 10% in the width direction. The obtained laterally uniaxially stretched film had a thickness of 60 μm. 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, by cutting and removing both edges, a biaxially stretched film of about 30 μm was wound up over a predetermined length to obtain a film roll comprising the heat-shrinkable polyester film 1. The production conditions are shown in Table 1, and the characteristics of the film 1 are shown in Table 2.

[Production Method of Polyester Film 2]
While changing the mixing ratio (weight ratio) of the raw material 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 processed in the width direction in the second tenter. The polyester film 2 is continuously produced by the same method as that of the polyester film 1 except that the temperature at the time of heat relaxation is changed to 120 ° C. and the amount of relaxation at the time of relaxation in the width direction is changed to 20%. did. The Tg of the unstretched film was 67 ° C. The production conditions are shown in Table 1, and the evaluation results of the film 2 are shown in Table 2.

[Production Method of Polyester Film 3]
While changing the transverse stretch ratio in the first tenter to 4.0 times, the longitudinal stretch ratio is changed to 2.4 times, and the temperature at which the film after longitudinal stretching is relaxed in the width direction in the second tenter is 120. A polyester film 3 was continuously produced by the same method as in Example polyester film 1 except that the temperature was changed to ° C. The production conditions are shown in Table 1, and the evaluation results of the film 3 are shown in Table 2.

[Method for producing polyester film 4]
An unstretched film having a thickness of 180 μm obtained in the same manner as the polyester film 1 was guided to a tenter (first tenter) in which a transverse stretching zone and an intermediate heat treatment zone were continuously provided. 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. (cooling rate: 45 ° C./second).

  Then, the cooled film is guided to a tenter (second tenter), and is heat-treated in an atmosphere of 110 ° C. for 5.0 seconds in the second tenter (relaxation amount 0%), and both edges are cut and removed. By doing so, a biaxially stretched film (heat-shrinkable film) of about 30 μm was wound up over a predetermined length, and a film roll made of heat-shrinkable polyester film 4 was obtained. The production conditions are shown in Table 1, and the evaluation results of the film 4 are shown in Table 2.

[Method for producing active energy ray (UV) curable adhesive 1]
440 parts of dimethyl terephthalate, 440 parts of dimethyl isophthalate, 412 parts of ethylene glycol, 393 parts of hexanediol, and 0.5 part of tetrabutoxy titanate are placed in a reaction vessel equipped with a thermometer, a stirrer, a distillation column, a condenser, and a decompressor. The mixture was heated at 150 to 230 ° C. for 120 minutes to cause transesterification. Next, the reaction system was depressurized to 10 mmHg, and the reaction was carried out by raising the temperature to 250 ° C. over 30 minutes to obtain a copolymer polyester polyol. The molecular weight of the polyester polyol was 1600.

Next, in a reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser, 100 parts of the above copolyester polyol and 120 parts of phenoxyethyl acrylate were charged and dissolved, and then 15 parts of isophorone diisocyanate and 0.05 parts of dibutyltin dilaurate. Was added and reacted at 70-80 ° C. by adding 5 parts of 2-hydroxyethyl acrylate to obtain a phenoxyethyl acrylate solution of urethane acrylate. Immediately before use, 100 parts of this solution was mixed with 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Darocur (registered trademark) 1173: manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator. 3 parts by mass was added to obtain an active energy ray (UV) curable adhesive 1. The molecular weight of urethane acrylate was 2000, and the carboxyl group terminal amount was 5 eq / 10 ⁶ g. The composition of the adhesive is shown in Table 3.

  In addition, all the said molecular weights are number average molecular weights, and are the results (polystyrene conversion) which measured using GPC150c (made by Waters) by using tetrahydrofuran as an eluent. The column temperature was 35 ° C. and the flow rate was 1 ml / min.

[Production method of UV curable adhesive 2]
A tetrahydrofurfuryl acrylate solution of urethane acrylate was obtained in the same manner as in the active energy ray-curable adhesive 1 except that 120 parts of tetrahydrofurfuryl acrylate was used instead of 120 parts of phenoxyethyl acrylate. As in the case of the adhesive 1, a photopolymerization initiator was added immediately before use to obtain a UV curable adhesive 2. The composition of the adhesive is shown in Table 3.

[Production method of UV curable adhesive 3]
An acryloylmorpholine solution of urethane acrylate was obtained in the same manner as in the active energy ray-curable adhesive 1 except that 120 parts of acryloylmorpholine was used instead of 120 parts of phenoxyethyl acrylate. Similarly to the case of the adhesive 1, a photopolymerization initiator was added immediately before use to obtain a UV curable adhesive 3. The composition of the adhesive is shown in Table 3.

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., and the film roll was cut into a length of 230 mm × width 100 mm so that the lengthwise direction was vertical. It was. While standing up a 265 ml aluminum bottle can (maximum body diameter 68 mm, neck diameter 30 mm) while winding the film so that one of the long sides of the cut out film is along the bottom of the can, The active energy ray-curable adhesive 1 was applied in the form of dots in the upper, lower, and center of one end on the bottle can contact surface side, and the film was fixed to the bottle can.

Then, the active energy ray-curable adhesive 1 is applied to the other end of the wound film, and this one end is overlapped with 5 mm on one end previously fixed to the bottle can so as to sandwich the adhesive layer, Immediately irradiate this bonded part with 3 kW (120 W / cm) x 1 lamp air-cooled mercury lamp so that ultraviolet rays become 100 mJ / cm ² and both ends of the film are cured and bonded to produce a bottle can with a heat-shrinkable label. did.

  Subsequently, the bottle can with heat-shrinkable label was immediately sent to a steam furnace shrink tunnel 3 m long and kept at 92 ° C. after passing the label, and allowed to pass over 10 seconds to shrink the label. Then, it was brought into close contact with the outer periphery of the bottle can to obtain a package (a container with a label after shrinkage). The package had good shrinkage finish and good adhesion at the label bonding part. The evaluation results 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 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 are shown in Table 4.

Example 4
A package was obtained in the same manner as in Example 1 except that the active energy ray-curable adhesive 2 was used as the adhesive for pasting the film, the bottle can and the film ends. The evaluation results are shown in Table 4.

Example 5
A package was obtained in the same manner as in Example 1 except that the active energy ray-curable adhesive 3 was used as an adhesive for attaching the film, the bottle can and the film ends. The evaluation results are shown in Table 4.

Comparative Example 1
Packaging in the same manner as in Example 1 except that a commercially available ethylene-vinyl acetate hot melt adhesive (softening point: 85 ° C.) was used as an adhesive for attaching the film to the bottle can and the film ends. Got the body. Due to the heat at the time of applying the hot melt adhesive, the shrinkage finish was deteriorated, and the label bonded portion was also lightly peeled off by hand, so that sufficient adhesiveness was not obtained.

Comparative Example 2
Although the attachment of the film ends after wrapping the film around the bottle was attempted by solvent adhesion using 1,3-dioxolane, an attempt was made to attach the label by the same method as in Example 1, Since the solvent dripped or splashed, uniform coating could not be performed, and the film could not be laminated well.

Comparative Example 3
A package was obtained in the same manner as in Example 1 except that the polyester film 4 was used as the heat-shrinkable polyester film. The polyester film 4 has a high hot-shrinkage rate in the orthogonal direction of the heat-shrinkable film and a low Young's modulus before breakage, so that the shrinkage finish performance at the time of heat-shrinking after the body winding is insufficient, and the toughness and toughness properties are poor. It was.

  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 (4)

Made of a heat-shrinkable polyester film stretched at least uniaxially and formed into a continuous body by irradiating the active energy ray-curable adhesive application part of the film wound around the container with active energy rays 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 natural shrinkage ratio after aging for 700 hours or more in an atmosphere of 40 ° C. and 65% RH is 0.05% or more and 1.5% or less.   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.   It is a manufacturing method of the heat-shrinkable label of Claim 1 or 2, Comprising: Before winding the heat-shrinkable polyester film of Claim 1 or 2 around a container, after winding, or winding However, the manufacturing method of the heat-shrinkable label characterized by apply | coating an active energy ray hardening-type adhesive agent to a part of film, irradiating an active energy ray, and shape | molding in a continuous body.   Claims including a step of previously applying an active energy ray-curable adhesive to a part of the container and / or the heat-shrinkable polyester film, and pasting the container and the heat-shrinkable polyester film. Item 4. A method for producing a heat-shrinkable label according to Item 3.

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