JP2009114422A - Heat-shrinkable polyester-based film and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester film which has not only the high shrink properties at the longitudinal direction of the main shrinkage direction and the high mechanical strengths at the width direction crossing at a right angle to the main shrinkage direction, but also the good shrink finish, tenacity and toughness at the time of heat shrinking after the body wrapping. <P>SOLUTION: In the present heat-shrinkable polyester-based film, a main shrinkage direction is the longitudinal direction. The film has been regulated so that the values of the following properties are within respective given ranges: the degree of the longitudinal direction hot-water heat shrinkage through the 10-second treatment in 90°C water, the degree of the width-direction hot-water heat shrinkage through the 10-second treatment in 90°C hot water, the longitudinal direction shrinkage stress in the 10-second 90°C treatment, the longitudinal direction Young's modulus before the rupture and the degree of natural shrinkage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable polyester film and a method for producing the same, and more particularly to a heat-shrinkable polyester film suitable for labeling and a method for producing the same.

  In recent years, it has been made of various types of resin for applications such as exterior packaging for improving the appearance of packages, packaging for avoiding direct collision of contents, and label packaging that also serves to protect glass bottles or plastic bottles and display products. Heat shrink 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 polyethylene terephthalate (PET) containers, polyethylene containers, glass containers, etc. Used for cap seal or 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 resin film is used as a shrink label for a PET container or the like, there is also a problem that the label and the container must be separated when the container is recycled. 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. Therefore, a polyester film having high heat resistance, easy incineration, and excellent solvent resistance has come to be widely used as a shrink label. , Usage tends to increase.

  Moreover, what is shrink | contracted greatly in the width direction is widely utilized as a normal heat-shrinkable polyester-type film (patent document 1). In such a heat-shrinkable polyester film whose width direction is the main shrinkage direction, the film is stretched at a high magnification in the width direction in order to develop shrinkage characteristics in the width direction, but is orthogonal to the main shrinkage direction. With regard to the direction (longitudinal direction), only low magnification stretching is often performed, and some are not stretched. As such, a film that has been stretched only at a low magnification in a direction orthogonal to the main shrinkage direction, or a film that has been stretched only in the main shrinkage direction is inferior in mechanical strength in the direction orthogonal to the main shrinkage direction. There are drawbacks.

JP-A-9-239833

  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 the annular body is formed so as to be in the circumferential direction, the annular body must be cut into a predetermined length and attached to the bottle. Therefore, it is difficult to attach a label made of a heat-shrinkable film that shrinks in the width direction to the bottle at a high speed. Therefore, recently, there is a demand for a film that is directly attached from the film roll to the periphery of the bottle and that is heat-shrinkable in the longitudinal direction so that it can be wound (wrapped round), and the demand will increase dramatically in the future. Expected.

  Therefore, the applicants diligently studied to obtain a heat-shrinkable film having a high mechanical strength in a direction (width direction) in which the main shrinkage direction is the longitudinal direction and orthogonal to the main shrinkage direction. It was found that a heat shrinkable film having a main shrinkage direction in the longitudinal direction and a high mechanical strength in the width direction can be obtained by a special process of intermediate heat treatment-longitudinal stretching, and the heat shrinkable film was 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 previously filed by the applicants has a major shrinkage direction in the longitudinal direction and excellent mechanical strength in the width direction, but in the longitudinal direction. Some of them have a hot water shrinkage rate or heat shrinkage stress that is too high, and the shrinkage finish when the film rolls directly around the bottle and then heat shrinks is not necessarily good. Moreover, when the body roll is directly wound around the bottle 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 so much. If the hot water shrinkage rate or heat shrinkage stress is too high, the force of tightening the bottle when wrapped around the bottle and heat shrinking becomes too strong, and there is a possibility that spilling may occur when opening the bottle. is there. 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. End up. In addition, some heat-shrinkable films obtained by the above-described process of transverse stretching-intermediate heat treatment-longitudinal stretching have insufficient toughness (toughness) and toughness, and such toughness and toughness. When a film with 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.

  The object of the present invention is to solve the problems of the conventional heat-shrinkable film, have good shrinkability in the longitudinal direction, which is the main shrinkage direction, and high mechanical strength in the width direction perpendicular to the main shrinkage direction. In addition, an object of the present invention is to provide a heat-shrinkable polyester film that has good shrinkage finishing performance when it is heat-shrinked after being wound around a bottle directly from a film roll and has good workability during post-processing.

Among the present inventions, the invention described in claim 1 is mainly composed of ethylene terephthalate, and in all polyester resin components constituting the film, a glycol component other than ethylene glycol or a dicarboxylic acid component other than terephthalic acid. Is a heat-shrinkable polyester film containing at least one, 15 mol% or more and 40 mol% or less, and is formed in a long shape with a constant width, and the main shrinkage direction is the longitudinal direction, The following requirements (1) to (5) are satisfied.
(1) The hot water heat shrinkage in the longitudinal direction is 15% or more and less than 40% when treated in warm water at 90 ° C. for 10 seconds. (2) Treated in warm water at 90 ° C. for 10 seconds. When the heat shrinkage rate in the width direction perpendicular to the longitudinal direction 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 (4) The Young's modulus before breaking in the longitudinal direction of the film is 0.05 GPa or more and 0.15 GPa or less (5) 700 hours or more in an atmosphere of 40 ° C. and 65% RH The natural shrinkage after aging is 0.05% or more and 1.5% or less

  The invention described in claim 2 is the invention described in claim 1, wherein the perpendicular tear strength in the width direction per unit thickness after shrinking 3% in the longitudinal direction in hot water at 80 ° C. is 100 N / mm. The above is 300 N / mm or less.

  The invention described in claim 3 is the Elmendorf in the case where the Elmendorf tear load in the longitudinal direction and the width direction is measured after shrinking 3% in the longitudinal direction in warm water at 80 ° C. in the invention described in claim 1. The ratio is 0.15 or more and 1.5 or less.

  The invention described in claim 4 is the invention described in claim 1, characterized in that the refractive index in the longitudinal direction and the refractive index in the width direction are both 1.560 or more and less than 1.600. It is.

  The invention described in claim 5 is characterized in that, in the invention described in claim 1, ethylene terephthalate is a main constituent, and the main component of the copolymer component is neopentyl glycol, 1,4-cyclohexanedi. It is one of methanol, and the dicarboxylic acid component is isophthalic acid.

  Invention of Claim 6 is a manufacturing method for manufacturing continuously the heat-shrinkable polyester-type film in any one of Claims 1-5, Comprising: An unstretched film is width | variety within a tenter. An intermediate zone in which aggressive heating operation is not performed after stretching at a magnification of 2.5 times to 6.0 times in the width direction at a temperature of Tg + 5 ° C. or more and Tg + 40 ° C. or less with both ends of the direction held by clips. And then heat treated at a temperature of 75 ° C. or higher and 140 ° C. or lower for a time of 1.0 second or longer and 20.0 seconds or shorter, and a film surface at a cooling rate of 30 ° C./second or higher and 70 ° C. or lower. After rapidly cooling until the temperature reaches 45 ° C. or higher and 75 ° C. or lower, after stretching at a magnification of 2.0 times or more and 5.5 times or less in the longitudinal direction at a temperature of Tg + 5 ° C. or more and Tg + 80 ° C. or less, the inside of the tenter At both ends in the width direction Is characterized in that to relax within the range of 1% to 30% in the width direction while heating at 140 ° C. temperature below 90 ° C. or more while holding the clip.

  The invention described in claim 7 is the clip according to the invention described in claim 6, wherein the film is heat-treated and rapidly cooled, and before stretching in the longitudinal direction, at both edges in the width direction of the film. The gripping portion is cut and removed.

  The heat-shrinkable polyester film of the present invention has good shrinkage in the longitudinal direction, which is the main shrinkage direction, and not only high mechanical strength in the width direction perpendicular to the main shrinkage direction, but also directly from the film roll to the bottle. The shrink finish is good when it is heat-shrinked after being wound around. In addition, the toughness and toughness are high, and even when a high tension is applied during post-processing, it is difficult to break, and large-scale troubles can be prevented with high accuracy. Therefore, the heat-shrinkable polyester film of the present invention can be suitably used as a label for a container such as a bottle, and can be attached to a container such as a bottle very efficiently and cleanly within a short time. In addition, according to the method for producing a heat-shrinkable polyester film of the present invention, the shrinkability in the longitudinal direction is good and the mechanical strength in the width direction is high, and the shrinkage finish at the time of heat shrinkage after the body winding is good. Thus, a heat-shrinkable polyester film having good workability during post-processing can be efficiently produced at low cost.

  Examples of the dicarboxylic acid component constituting the polyester used in the present invention include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, and orthophthalic acid, and aliphatics such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid. Examples thereof include dicarboxylic acids and alicyclic dicarboxylic acids.

  When an aliphatic dicarboxylic acid (for example, adipic acid, sebacic acid, decanedicarboxylic acid, etc.) is contained, the content is preferably less than 3 mol%. A heat-shrinkable polyester film obtained using a polyester containing 3 mol% or more of these aliphatic dicarboxylic acids has insufficient film stiffness at high-speed mounting.

  Further, it is preferable not to contain a trivalent or higher polyvalent carboxylic acid (for example, trimellitic acid, pyromellitic acid, and their anhydrides). In a heat-shrinkable polyester film obtained using a polyester containing these polyvalent carboxylic acids, it is difficult to achieve a 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, and hexanediol, and 1,4-cyclohexanedimethanol. Aromatic diols such as alicyclic diol and bisphenol A can be mentioned.

  The polyester used in the heat-shrinkable polyester film of the present invention is a cyclic diol such as 1,4-cyclohexanedimethanol, or a diol having 3 to 6 carbon atoms (for example, 1-3 propanediol, 1-4 butanediol). , Neopentyl glycol, hexanediol, and the like), and a polyester having a glass transition point (Tg) adjusted to 60 to 80 ° C. is preferable.

  The polyester used in the heat-shrinkable polyester film of the present invention preferably has a glycol component other than ethylene glycol or a dicarboxylic acid component other than terephthalic acid in the total polyester resin of 15 mol% or more. More preferably, it is 17 mol% or more, and particularly preferably 20 mol% or more. Here, examples of the main component that can be a glycol component or a dicarboxylic acid component as a copolymer component include neopentyl glycol, 1,4-cyclohexanediol, and isophthalic acid, and these may be mixed as necessary. Is also possible. When the content of the copolymer component (glycol component other than ethylene glycol or dicarboxylic acid component other than terephthalic acid) exceeds 40 mol%, the solvent resistance of the film is lowered, and the solvent of the ink is used in the printing process. (Ethyl acetate or the like) is not preferable because whitening of the film occurs or the tear resistance of the film decreases. Further, the content of the copolymer component is more preferably 37 mol% or less, and particularly preferably 35 mol% or less.

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

  Moreover, it is preferable not to contain diethylene glycol, triethylene glycol, and polyethylene glycol as much as possible in the polyester used for the heat-shrinkable polyester film of the present invention. 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 heat-shrinkable polyester film of the present invention is a longitudinal direction of the film calculated by the following formula 1 from the length before and after shrinkage when treated for 10 seconds in 90 ° C. warm water without load. The heat shrinkage ratio (that is, the hot water heat shrinkage ratio 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 (%)

  If the hot water heat shrinkage in the longitudinal direction at 90 ° C. is less than 15%, the shrinkage is small, so it is not preferable because wrinkles and tarmi are generated at the time of heat shrinkage after being wound by a body winding method as a label. When the hot water thermal contraction rate in the longitudinal direction at 90 ° C. is 40% or more, it is preferable because shrinkage distortion is likely to occur at the time of thermal contraction after being wound as a label by a body winding method, or so-called “jumping” occurs. Absent. In addition, the lower limit value of the hot water thermal contraction rate in the longitudinal direction at 90 ° C. is preferably 17% or more, more preferably 19% or more, and particularly preferably 21% or more. The upper limit of 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.

  The heat-shrinkable polyester film of the present invention is a film width direction calculated by the above formula 1 from the length before and after shrinkage when treated for 10 seconds in 90 ° C. warm water without load. It is necessary that the hot water thermal contraction rate is -5% or more and 5% or less.

  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. If the thermal contraction rate exceeds 5%, it is not preferable because shrinkage distortion is likely to occur during thermal contraction after winding as a label by the body winding method. In addition, the lower limit of the hot water temperature thermal contraction rate 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 upper limit of 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.

  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 or more and 7.0 MPa or less when processed 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. In addition, the lower limit of 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 upper limit value of 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.

  In addition, the heat-shrinkable polyester film of the present invention requires that the Young's modulus before break calculated in the following method is 0.05 GPa or more and 0.15 GPa or less before break.

[Measurement method of Young's modulus before fracture]
In accordance with ASTM-D882, a film sample cut into a predetermined size (length: 150 mm × width: 10 mm) was tested with a tensile tester in an atmosphere of a temperature of 25 ° C. and a humidity of 65% RH, and the test length was 100 mm. Thus, a stress-strain curve is obtained when both ends (both ends along the longitudinal direction) are gripped and 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. 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 lower limit of the Young's modulus before break 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.

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

[Measurement method of right-angle tear strength]
After shrinking the film in the longitudinal direction by 3% in a hot water temperature adjusted to 80 ° C., it is sampled as a test piece of a predetermined size according to JIS-K-7128. Thereafter, both ends of the test piece are grasped with a universal tensile tester, and the strength 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 per unit thickness is calculated using the following equation 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, it may be easily broken by an impact such as dropping during transportation when used as a label. On the other hand, if the right-angled tear strength exceeds 300 N / mm, the cutting property (easy to tear) at the initial stage of tearing the label becomes unfavorable. The lower limit of the right-angled tear strength is preferably 125 N / mm or more, more preferably 150 N / mm or more, and particularly preferably 175 N / mm or more. Moreover, the upper limit of the right-angled tear strength is preferably 275 N / mm or less, more preferably 250 N / mm or less, and particularly preferably 225 N / mm or less.

  In addition, the heat-shrinkable polyester film of the present invention was subjected to 3% shrinkage in the longitudinal direction in warm water at 80 ° C., and the Elmendorf tear load in the longitudinal direction and the width direction was determined by the following method. It is preferable that the Elmendorf ratio, which is the ratio of the Elmendorf tear load, is 0.15 or more and 1.5 or less.

[Measurement method of Elmendorf ratio]
The film is attached to a rectangular frame having a predetermined length in a state of being loosened in advance (that is, both ends of the film are gripped by the frame). Then, the film is contracted by 10% in the longitudinal direction by immersing in warm water at 80 ° C. for about 5 seconds until the slack film is in a tension state in the frame (until the slack disappears). Thereafter, the Elmendorf tear load in the longitudinal direction and the width direction of the film is measured according to JIS-K-7128, and the Elmendorf ratio is calculated using the following equation 3.
Elmendorf ratio = Elmendorf tear load in the longitudinal direction ÷ Elmendorf tear load in the width direction.

  If the Elmendorf ratio is less than 0.15, it is not preferable because it is difficult to tear straight along the perforation when used as a label. On the other hand, if the Elmendorf ratio exceeds 1.5, it is not preferable because it is easy to tear at a position shifted from the perforation. The lower limit value of the Elmendorf ratio is preferably 0.20 or more, more preferably 0.25 or more, and particularly preferably 0.3 or more. The upper limit value of the Elmendorf ratio is preferably 1.4 or less, more preferably 1.3 or less, and particularly preferably 1.2 or less.

Further, the heat shrinkable polyester film of the present invention has a natural shrinkage ratio of 0.05% or more and 1.5% or less after aging for 700 hours or more in an atmosphere of 40 ° C. and 65% RH. is necessary. The natural shrinkage rate can be calculated using the following equation 4.
Natural shrinkage rate = {(length before aging−length after aging) / length before aging} × 100 (%)

  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 roll is easily wrinkled. 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.

  Moreover, the heat-shrinkable polyester film of the present invention preferably has a refractive index in the longitudinal direction of 1.560 or more and less than 1.600. When the refractive index in the longitudinal direction exceeds 1.600, the solvent adhesiveness when forming a label is deteriorated, which is not preferable. On the other hand, if it is less than 1.560, it is not preferable because the cut property when used as a label is deteriorated. The upper limit of the refractive index in the longitudinal direction is preferably 1.597 or less, and more preferably 1.594 or less. Moreover, the lower limit value of the refractive index in the longitudinal direction is preferably 1.563 or more, and more preferably 1.566 or more.

  The heat-shrinkable polyester film of the present invention preferably has a refractive index in the width direction of 1.560 or more and less than 1.600. If the refractive index in the width direction exceeds 1.600, the solvent adhesiveness when making a label deteriorates, which is not preferable. On the other hand, if it is less than 1.560, it is not preferable because the cut property when used as a label is deteriorated. Note that the upper limit of the refractive index in the width direction is preferably 1.598 or less, and more preferably 1.596 or less. The lower limit of the refractive index in the width direction is preferably 1.565 or more, and more preferably 1.570 or more.

  In addition, the heat-shrinkable polyester film of the present invention preferably has a thickness variation of 20% or less in the longitudinal direction. If the thickness unevenness in the longitudinal direction is more than 20%, it is not preferable because printing spots are likely to occur during printing at the time of label production or shrinkage spots are likely to occur after heat shrinkage. The thickness unevenness in the longitudinal direction is more preferably 15% or less, and more preferably 10% or less.

  The heat shrinkage film in the longitudinal direction, the heat shrinkage rate in the width direction, the Young's modulus before breaking, the maximum heat shrinkage stress, the right-angle tear strength, the Elmendorf ratio, the natural shrinkage rate, and the thickness unevenness are determined using the above-mentioned preferred film composition. This can be achieved by combining with a preferable production method described later.

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

  Further, the heat-shrinkable polyester film of the present invention is formed by melting and extruding the above-described polyester raw material with an extruder to form an unstretched film, and biaxially stretching the unstretched film by the following method and heat-treating it. Can be obtained.

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

  Further, as will be described later, the obtained unstretched film was stretched in the width direction under predetermined conditions, and then heat-treated once, and then stretched in the longitudinal direction under predetermined conditions. By rapidly cooling, the heat-shrinkable polyester film of the present invention can be obtained. Hereinafter, a preferred biaxial stretching / heat treatment method for obtaining the heat-shrinkable polyester film of the present invention will be described in detail in consideration of the difference from the conventional biaxial stretching / heat treatment method of the 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. 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 pilot test of their pilot aircraft, in this method, a film having sufficient shrinkability in the longitudinal direction, which is the main shrinkage direction, cannot be obtained, and wrinkles in the width direction are generated in 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 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 contraction 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 more 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 hot water temperature shrinkage rate and the natural shrinkage rate in the longitudinal direction of the film depend on the conditions in each stretching step. We studied 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, it is 75 ° C or more and 140 ° C or less. Heat treatment (hereinafter referred to as intermediate heat treatment) is preferably performed at a temperature for a time of 1.0 second to 20.0 seconds. By performing such an 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 needs to be appropriately adjusted according to the raw material composition within the range of 1.0 second or more and 20.0 seconds or less.

(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 preferable 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 in a state where both ends in the width direction are held by clips in the tenter. That is, in order to obtain a heat-shrinkable film having an appropriate hot-water heat shrinkage rate of 15% or more and less than 40% as in the heat-shrinkable film of the present invention, the hot-water heat shrinkage rate (90 ° C.) in the longitudinal direction is 15% or more. If the hot water heat shrinkage rate in the longitudinal direction is adjusted simply by adjusting the draw ratio in the longitudinal direction, it is difficult to accurately express the desired hot water heat shrinkage rate in the longitudinal direction of the film. Yes, once the film is stretched in the machine direction at a higher ratio than the stretch ratio that can produce the desired hot water heat shrinkage ratio, the final heat set (final set) is applied to the film, and at the same time, relaxation treatment in the width direction is performed. It is preferable to adjust so that the hot water heat shrinkage rate can be reduced to give the desired hot water heat shrinkage rate. In this way, the film is stretched in the machine direction at a high magnification and then relaxed by an appropriate amount in the width direction while applying the final heat set to slightly reduce the hot film heat shrinkage in the machine direction and width direction of the final film. By adjusting, it is possible to improve the shrinkage finish when the label is wound by the body winding method and 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 above-mentioned means (a) and (b), a heat-shrinkable polyester film having a very good shrinkage finish at the time of heat-shrinking after body winding and a good toughness, viscosity and toughness is obtained. Is possible. Further, only one of the above-mentioned means (a) and (b) is limited in heat shrinkage in the longitudinal direction of the film, low natural shrinkage rate, stable film forming property, and shrinkage after body winding. It does not contribute effectively to the shrinkage finish, toughness and toughness of the steel, and by combining the means (a) and (b), the heat shrinkage in the longitudinal direction and the low natural shrinkage are very efficient. It is considered that the rate, stable film forming property, good shrinkage finish property, toughness, toughness and the like can be expressed at the same time.

  In addition, in manufacture of the film by the horizontal-longitudinal stretch method of the above-mentioned this invention, extending | stretching to the width direction of an unstretched film is Tg + 5 degreeC or more Tg + 40 in the state which hold | gripped the both ends of the width direction in the tenter with the clip. It is preferable to carry out so that the magnification is 2.5 times or more and 6.0 times or less at a temperature of ℃ or less. 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 lower limit of the transverse stretching temperature is preferably Tg + 10 ° C. or more, and more preferably Tg + 15 ° C. or more. Moreover, the upper limit of the temperature of transverse stretching is preferably Tg + 35 ° C. or less, and more preferably Tg + 30 ° C. or less. On the other hand, 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, and on the contrary, 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. In addition, the lower limit of the transverse stretching ratio is preferably 3.0 times or more, and more preferably 3.5 times or more. Further, the upper limit of the transverse stretching ratio is preferably 5.5 times or less, and more preferably 5.0 times or less.

  In addition, in the production of the film by the transverse-longitudinal stretching method of the present invention described above, 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 ( You may trim mainly the clip holding part at the time of horizontal stretching (especially when using highly crystalline resin as a raw material, trimming is preferable). More specifically, in a portion having a thickness of about 1.1 to 1.3 times the thickness of the central portion located at the left and right edges of the film, the thickness at the edge of the film using a tool such as a cutter. It is possible to adopt a method in which only the remaining part is stretched in the longitudinal direction while cutting the part and removing the thick part. Further, when trimming the film edge as described above, it is preferable to cool the film so that the surface temperature of the film before trimming is 50 ° C. or less. By cooling the film in this way, trimming can be performed without disturbing the cut surface. In addition, the trimming of the film edge can be performed using a normal cutter or the like. However, when a round blade having a circumferential cutting edge is used, a situation in which the cutting edge is locally dulled does not occur. Can be continued to be cut sharply over a long period of time, and a situation in which breakage at the time of stretching in the longitudinal direction does not occur is preferable. When a highly crystalline resin is used as a raw material, the film once heat-set can be stretched uniformly in the longitudinal direction by trimming the end of the film before stretching in the longitudinal direction as described above. It becomes possible, and the continuous production of the stable film without a fracture | rupture is attained. 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.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the embodiments of the examples, and can be appropriately changed without departing from the spirit of the present invention. is there. Tables 1 and 2 show the properties, compositions, examples, and film production conditions (stretching / heat treatment conditions, etc.) of the raw materials used in the examples and comparative examples, respectively.

  The evaluation method of the film is as follows.

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

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

[Thermal shrinkage (hot water thermal shrinkage)]
The film is cut into a 10 cm × 10 cm square, heat-shrinked by treatment in warm water at a predetermined temperature ± 0.5 ° C. for 10 seconds under no load condition, and then measured in the vertical and horizontal dimensions of the film. According to the above formula 1, the thermal shrinkage rate was obtained. The direction in which the heat shrinkage rate is large was taken as the main shrinkage direction.

[Maximum heat shrinkage stress value]
The stretched film was cut into a size of main shrinkage direction × direction orthogonal to the main shrinkage direction = 200 mm × 15 mm. Thereafter, a universal tensile testing machine STM-50 manufactured by Baldwin Co., Ltd. was adjusted to a temperature of 90 ° C., the cut film was set, and the stress value when held for 10 seconds was measured.

[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 was used with an autograph manufactured by Shimadzu Corporation under an atmosphere of a temperature of 25 ° C. and a humidity of 65% RH. A stress-strain curve was obtained 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 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. did.

[Right-angle tear strength]
After the film was shrunk 3% in the main shrinking direction in a hot water temperature adjusted to 80 ° C., a test piece was prepared by sampling into the shape shown in FIG. 1 according to JIS-K-7128 (note that In the sampling, the longitudinal direction of the test piece was defined as the main shrinkage direction of the film). After that, grasp both ends of the test piece with a universal tensile tester (Autograph made by Shimadzu Corporation), and measure the strength at the time of tensile fracture in the width direction of the film under the condition of a tensile speed of 200 mm / min. The right angle tear strength per unit thickness was calculated using Equation 2 above.

[Elmendorf ratio]
The obtained film is attached to a rectangular frame in a state of being loosened in advance (with both ends of the film being gripped by the frame), and until the loose film is in a tension state within the frame (until loosening), about 5 The film was shrunk by 3% in the main shrinking direction by immersing it in warm water at 80 ° C. for 2 seconds (hereinafter referred to as preliminary shrinkage). After that, in accordance with JIS-K-7128, the main shrinkage direction × orthogonal direction = 75 mm × 63 mm is cut out and perpendicular to the edge from the center of the long edge (edge along the main shrinkage direction). A test piece was prepared by inserting a slit (cut) of 20 mm. And the measurement of the Elmendorf tear load of the orthogonal direction was performed using the produced test piece. In addition, after preliminarily shrinking the film in the main shrinkage direction by the same method as described above, the test piece was prepared by switching the main shrinkage direction and the orthogonal direction of the film, and measuring the Elmendorf tear load in the main shrinkage direction. It was. Then, the Elmendorf ratio was calculated from the obtained main contraction direction and the Elmendorf tear load in the direction orthogonal to the main contraction direction using the above Equation 3.

[Natural shrinkage]
The obtained film was cut into a size of main shrinkage direction × orthogonal direction = 200 mm × 30 mm, and allowed to stand (aging) in an atmosphere of 40 ° C. × 65% RH for 700 hours, and then the main shrink direction of the film (Example 1 to Example 1). 3 and Comparative Examples 1 and 2, the amount of shrinkage in the longitudinal direction) was measured, and the natural shrinkage rate was calculated by the above equation 4.

[Refractive index in thickness direction and width direction]
Using an “Abbe refractometer 4T type” manufactured by Atago Co., Ltd., each sample film was measured after being allowed to stand in an atmosphere of 23 ° C. and 65% RH for 2 hours or more.

[Shrinking finish when shrinking after body wrapping (wrapping round)]
The heat-shrinkable film is printed in three colors with grass, gold, and white ink from Toyo Ink Mfg. Co., Ltd. The printed heat-shrinkable film is 230 mm long x 100 mm wide so that its longitudinal direction is vertical. Cut out at the size of. The length of the film cut out in a state where a 265 ml aluminum bottle can (with a barrel diameter of 68 mm, a neck diameter of 25 mm, and a constriction provided so that the diameter of the center of the barrel is 60 mm) An active energy ray produced by the following method at three locations on the edge of the bottle can contact surface side of the short side of the film while winding the film so that one of the sides is along the bottom of the feeling A (UV) curable adhesive was applied in the form of dots to fix the film to a bottle can. Next, the same active energy ray-curable adhesive is applied to the edge of the other end of the wound film, and the other edge is overlapped with the edge of the edge previously fixed to the bottle can with a width of 5 mm. The adhesive layer applied to the other end edge was sandwiched. Immediately thereafter, the adhesive part (the part where the edges of the film overlap each other) was irradiated with ultraviolet rays of 3 kW (120 W / cm) × 1 lamp air-cooled mercury lamp to 100 mJ / cm ² , Both ends were cured and bonded to produce a bottle can with a heat-shrinkable label. Subsequently, the bottle can with heat-shrinkable label was immediately sent to a steam furnace shrink tunnel that was 3 m long and kept at 92 ° C. after passing the label, and allowed to pass over 10 seconds to shrink the label. And brought into close contact with the outer periphery of the bottle can. When the film was mounted, the neck portion was adjusted so that a portion with a diameter of 40 mm was one end of the label. Thereafter, the finish after shrinkage was visually evaluated in the following four stages.
◎: No wrinkles, jumping up, insufficient shrinkage, and no color spots are observed ○: Wrinkles, jumping up, or insufficient shrinkage cannot be confirmed, but some color spots are seen △: Jumping Neither ascending nor insufficient shrinkage has occurred, but spots on the neck are observed. ×: Wrinkles, jumping up, insufficient shrinkage occurred

<Method for producing active energy ray (UV) curable adhesive>
In a reaction vessel equipped with a thermometer, stirrer, distillation column, condenser, and decompression device, 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 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 copolymerized polyester polyol. The molecular weight of the polyester polyol was 1600. Next, 100 parts of copolymer polyester polyol and 120 parts of phenoxyethyl acrylate are charged into a reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser. After dissolution, 15 parts of isophorone diisocyanate and 0.05 part of dibutyltin dilaurate are charged. After reacting at 70 to 80 ° C. for 2 hours, 5 parts of 2-hydroxyethyl acrylate was further added and reacted at 70 to 80 ° C. to obtain a phenoxyethyl acrylate solution of urethane acrylate resin. And with respect to 100 parts of this solution, 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Darocur (registered trademark) 1173: manufactured by Ciba Specialty Chemicals Co., Ltd.) was used as a photopolymerization initiator immediately before use. 3 parts by mass was added to obtain an active energy ray (UV) curable adhesive. The molecular weight of urethane acrylate was 2000. In addition, the molecular weight in the above is a number average molecular weight, and is a result (polystyrene conversion) measured using GPC150c (manufactured by Waters) with tetrahydrofuran as an eluent. During the measurement, the column temperature was 35 ° C. and the flow rate was 1 ml / min.

  Moreover, the polyester used for the Example and the comparative example is as follows.

Polyester 1: Polyester composed of 70 mol% ethylene glycol, 30 mol% neopentyl glycol and terephthalic acid (IV 0.72 dl / g)
Polyester 2: Polyethylene terephthalate (IV 0.75 dl / g)

[Example 1]
Polyester 1 and polyester 2 described above were mixed at a weight ratio of 70:30 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 (rotational speed of the metal roll) is about 20 m / min. Met. Moreover, Tg of the unstretched film was 67 degreeC. Thereafter, the unstretched film was guided 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. Blocked.

  And after pre-heating the unstretched film led to the tenter until the film temperature reaches 90 ° C., the film is stretched 3.7 times at 85 ° C. in the transverse direction in the transverse stretching zone and passed through the intermediate zone. (Passing time = approximately 1.2 seconds), a transversely uniaxially stretched film having a thickness of 60 μm is obtained by heat-treating at a temperature of 105 ° C. for 6.0 seconds while being led to an intermediate heat treatment zone and relaxing 10% in the width direction. Obtained. Thereafter, 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.

  Further, the film having the edge trimmed as described above is guided 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 95 ° C. The film was stretched 2.2 times between the stretching rolls set to 1. 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.

  Then, after the cooled film is guided to a tenter (second tenter) and heat-treated (final set) for 5.0 seconds while being relaxed by 15% in the width direction in an atmosphere of 115 ° C. in the second tenter. By cooling and removing both edges by cutting, a film roll formed by winding a biaxially stretched film (heat-shrinkable film) of about 30 μm over a predetermined length was obtained. And the characteristic of the obtained film was evaluated by the above-mentioned method. The evaluation results are shown in Table 3.

[Example 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 heat-shrinkable film was continuously produced by the same method as in Example 1 except that the temperature during heat relaxation was changed to 120 ° C. and the amount of relaxation during relaxation in the width direction was changed to 20%. . And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Example 3]
The unstretched film having a thickness of 240 μm obtained in the same manner as in Example 1 was changed to 4.0 times the transverse stretch ratio in the first tenter, and the longitudinal stretch ratio was changed to 2.4 times. A heat-shrinkable film was continuously produced by the same method as in Example 1 except that the temperature when relaxing in the width direction in the second tenter was changed to 120 ° C. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Comparative Example 1]
A 300 μm unstretched film obtained in the same manner as in Example 1 was led to the first tenter, preheated until the film temperature reached 90 ° C., and then 4.0 times at 75 ° C. in the transverse direction in the transverse stretching zone. After stretching and passing through the intermediate zone (passing time = about 1.2 seconds), it is guided to the intermediate heat treatment zone and heat-treated at a temperature of 130 ° C. for 6.0 seconds while being relaxed by 10% in the width direction. Thus, a laterally uniaxially stretched film having a thickness of 80 μm was obtained. Thereafter, in the same manner as in Example 1, the edge of the laterally uniaxially stretched film (a portion having a thickness of about 1.2 times the thickness of the central film) was cut, and the end of the film located outside the cutting site was cut. The film after continuous removal and edge trimming is guided to a longitudinal stretching machine, preheated on a preheating roll until the film temperature reaches 70 ° C., and then between the stretching rolls set at a surface temperature of 95 ° C. Stretched by a factor of 0.0. Thereafter, the film after longitudinal stretching was forcibly cooled by a cooling roll in the same manner as in Example 1, and then led to the second tenter, and 10% in the width direction in an atmosphere of 87 ° C. in the second tenter. While being relaxed, it was heat treated for 5.0 seconds and then cooled, and both edges were cut and removed to wind up a biaxially stretched film (heat-shrinkable film) of about 30 μm over a predetermined length. A film roll was obtained. And the characteristic of the obtained film was evaluated by the above-mentioned method. The evaluation results are shown in Table 3.

[Comparative Example 2]
The 180 μm unstretched film obtained in the same manner as in Example 1 was led 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. A transversely uniaxially stretched film having a thickness of 45 μm was obtained by heat treatment at a temperature of 110 ° C. for 6.0 seconds. Thereafter, the laterally uniaxially stretched film is guided to a longitudinal stretching machine in which a plurality of roll groups are continuously arranged, preheated until the film temperature reaches 70 ° C. on the preheating roll, and then set to a surface temperature of 90 ° C. The film was stretched 1.5 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. 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. A film roll formed by winding a biaxially stretched film (heat-shrinkable film) over a predetermined length was obtained. And the characteristic of the obtained film was evaluated by the above-mentioned method. The evaluation results are shown in Table 3.

  As is apparent from Table 3, the films obtained in Examples 1 to 3 all have hot water shrinkage in the longitudinal direction (main shrinkage direction), hot water shrinkage in the width direction, and Young's modulus before breakage. It was within the scope of the invention, and the shrinkage finish, toughness, and toughness at the time of heat shrinkage after body winding were good. Furthermore, the heat-shrinkable polyester films of Examples 1 to 3 had a small natural shrinkage rate, and wrinkles were not generated on the produced film roll. That is, the heat-shrinkable polyester films obtained in the examples all have high label quality and are very practical.

  On the other hand, the heat-shrinkable film obtained in Comparative Example 1 does not fall within the scope of the present invention in terms of the hot water shrinkage in the longitudinal direction (main shrinkage direction) and the hot water shrinkage in the width direction. The shrinkage finish property at the time of shrinkage was poor. In addition, the heat shrinkable film obtained in Comparative Example 2 does not fall within the scope of the present invention in terms of the hot water shrinkage in the orthogonal direction and the Young's modulus before breakage, and the shrinkage finish at the time of heat shrinkage after the body winding is insufficient. The toughness and toughness were poor. That is, the heat-shrinkable polyester film obtained in Comparative Examples 1 and 2 was inferior in quality as a label and low in practicality.

  Since the heat-shrinkable polyester film of the present invention has excellent processing characteristics as described above, it can be suitably used for bottle labeling.

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

  F ・ ・ Film.

Claims (7)

Ethylene terephthalate is the main component, and all the polyester components constituting the film contain at least one glycol component other than ethylene glycol or a dicarboxylic acid component other than terephthalic acid, 15 mol% or more and 40 mol% or less. And a heat-shrinkable polyester film that is formed in a long shape with a constant width and whose main shrinkage direction is the longitudinal direction,
A heat-shrinkable polyester film characterized by satisfying the following requirements (1) to (5).
(1) The hot water heat shrinkage in the longitudinal direction is 15% or more and less than 40% when treated in warm water at 90 ° C. for 10 seconds. (2) Treated in warm water at 90 ° C. for 10 seconds. When the heat shrinkage rate in the width direction perpendicular to the longitudinal direction 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 (4) The Young's modulus before breaking in the longitudinal direction of the film is 0.05 GPa or more and 0.15 GPa or less (5) 700 hours or more in an atmosphere of 40 ° C. and 65% RH The natural shrinkage after aging is 0.05% or more and 1.5% or less   2. The thermal shrinkage according to claim 1, wherein a right-angled tear strength per unit thickness after shrinkage in the longitudinal direction by 3% in warm water at 80 ° C. is 100 N / mm or more and 300 N / mm or less. Polyester film.   The Elmendorf ratio is 0.15 or more and 1.5 or less when the Elmendorf tear load in the longitudinal direction and the width direction is measured after shrinking 3% in the longitudinal direction in warm water at 80 ° C. The heat-shrinkable polyester film described in 1.   The heat-shrinkable polyester film according to claim 1, wherein both the refractive index in the longitudinal direction and the refractive index in the width direction are 1.560 or more and less than 1.600.   Ethylene terephthalate is the main constituent, the main component of the copolymer component is that the glycol component is either neopentyl glycol or 1,4-cyclohexanedimethanol, and the dicarboxylic acid component is isophthalic acid The heat-shrinkable polyester film according to claim 1. A production method for continuously producing the heat-shrinkable polyester film according to claim 1,
After stretching an unstretched film at a temperature of Tg + 5 ° C. or more and Tg + 40 ° C. or less at a magnification of 2.5 times or more and 6.0 times or less in a state where both ends in the width direction are held by clips in the tenter, positively After passing through an intermediate zone in which a typical heating operation is not performed, heat treatment is performed at a temperature of 75 ° C. or more and 140 ° C. or less for a time of 1.0 second or more and 20.0 seconds or less, and 30 ° C./second or more and 70 ° C./second or less. The film is rapidly cooled at a cooling rate of less than a second until the surface temperature of the film reaches 45 ° C. or more and 75 ° C. or less, and then, at a temperature of Tg + 5 ° C. or more and Tg + 80 ° C. or less, 2.0 to 5.5 times in the longitudinal direction. After stretching at a magnification of 1, it is relaxed 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 a clip. Features Method for producing a heat-shrinkable polyester film of.   7. The heat-shrinkability according to claim 6, wherein the film gripping portions at both edges in the width direction of the film are cut and removed after the film is heat-treated and rapidly cooled and before stretching in the longitudinal direction. A method for producing a polyester film.

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