JP2010000799A - Heat-shrinkable polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester film which has high shrinkability in a longitudinal direction as the main shrinkage direction, has a high mechanical strength in a width direction, moreover, hardly causes wrinkles in a produced film roll and has good perforated line openability. <P>SOLUTION: In the heat-shrinkable polyester film, the main shrinkage direction is the longitudinal direction. In addition, the hot-water shrinkage ratio in the longitudinal direction when the film is treated in hot water at 90°C for 10 sec, the hot-water shrinkage ratio in the width direction when the film is treated in hot water at 90°C for 10 sec, the thickness spots in the longitudinal direction and the natural shrinkage ratio after aging at 40°C and 65% RH for 700 hr or more are adjusted to fall in the predetermined ranges respectively. <P>COPYRIGHT: (C)2010,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 resins 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. Further, when a polyvinyl chloride resin film is used as a shrink label for a PET container or the like, there is a problem that the label and the container must be separated when the container is recycled. On the other hand, polystyrene-based films have a good finished appearance after shrinkage, but have poor solvent resistance, so that there is 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, as a normal heat-shrinkable polyester-based film, a film that greatly shrinks in the width direction is widely used. 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. As for the longitudinal direction, only low-stretching is often performed, and some are not stretched. As described above, a film that is only stretched at a low magnification in the longitudinal direction or a film that is stretched only in the width direction has a drawback 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 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 has been a demand for a film that thermally shrinks in the longitudinal direction, which can be wound around a bottle directly from a film roll and mounted (so-called wrap round). Furthermore, in recent years, a wrapping method has been developed in which a container is closed by covering the periphery of a synthetic resin single-open container such as a lunch box with a strip-shaped film. 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.

  In order to eliminate the problems of mechanical strength in the direction perpendicular to the main shrinkage direction as described above, and to develop a function of shrinking in the longitudinal direction, the unstretched film is made longitudinal (also referred to as longitudinal direction), width direction (horizontal direction) In the longitudinal direction, the film is stretched by 2.0 to 5.0 times and then re-stretched by 1.1 times or more in the longitudinal direction to develop shrinkage in the longitudinal direction, and the Young's modulus in the longitudinal direction and the width direction. There is known a heat-shrinkable polyester film in which the Young's modulus is adjusted to be a predetermined value or more (Patent Document 1).

JP-A-8-244114

  However, although the heat-shrinkable polyester film of Patent Document 1 described above has good mechanical strength in the longitudinal direction and width direction, it has various characteristics when used as an industrial product and characteristics when used as a package. It is not necessarily sufficient. That is, when the present inventors performed a supplementary test in a pilot plant (film width = 1.5 m) in order to obtain the heat-shrinkable polyester film of Patent Document 1, the obtained heat-shrinkable polyester film of Patent Document 1 was obtained. Although it exhibits a certain degree of mechanical strength in the longitudinal direction and the width direction, it has a large natural shrinkage rate when left at room temperature for a certain period of time. It was found that there was a problem that wrinkles were likely to enter the film roll. Furthermore, it was also found that the heat-shrinkable polyester film obtained by the above-described test has poor tearability (so-called perforation opening) when tearing along a perforation perpendicular to the main shrinkage direction. Further, it was found that the shrinkage in the longitudinal direction, which is the main shrinkage direction, is not always sufficient, and it cannot be applied to a wide range of packaging.

  The object of the present invention is to eliminate the problems of the heat-shrinkable polyester film of Patent Document 1, and to have high mechanical strength in the width direction perpendicular to the main shrinkage direction, and to tighten the roll-like film produced. It is an object to provide a heat-shrinkable polyester film that does not cause wrinkles and that has a good perforation opening property. Furthermore, in addition to the above characteristics, it is an object of the present invention to provide a heat-shrinkable polyester film that is highly shrinkable in the longitudinal direction, which is the main shrinkage direction, and can be applied to applications requiring a high shrinkage rate.

Among the present inventions, the invention described in claim 1 contains ethylene terephthalate as a main constituent and contains at least 10 mol% of one or more monomer components that can be amorphous components in all polyester resin components. In addition, it is 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, and satisfies the following requirements (1) to (4): is there.
(1) The hot water thermal shrinkage in the longitudinal direction is 15% or more and 80% or less when treated in warm water at 90 ° C. for 10 seconds. (2) Treated in warm water at 90 ° C. for 10 seconds. The hot-water heat shrinkage in the width direction perpendicular to the longitudinal direction is 0% or more and 17% or less (3) The thickness unevenness in the longitudinal direction is 10% or less (4) 40 ° C. and 65% RH atmosphere The natural shrinkage rate in the main shrinkage direction after aging for 700 hours is 0.05% to 1.5%.

  The invention described in claim 2 is the invention described in claim 1, wherein the hot water thermal shrinkage in the longitudinal direction when treated in warm water at 90 ° C. for 10 seconds is 15% or more and less than 40%. In addition, the refractive index in the longitudinal direction is 1.570 or more and 1.590 or less, and the refractive index in the width direction is 1.570 or more and 1.620 or less.

  In the invention described in claim 3, in the invention described in claim 1 or 2, the main component of the monomer that can be an amorphous component in all the polyester resin components is neopentyl glycol, 1, 4 -Any one of cyclohexanedimethanol and isophthalic acid.

  The invention described in claim 4 is the invention described in any one of claims 1 to 3, wherein the Elmendorf tear load in the longitudinal direction and the width direction is applied after contracting 10% in the longitudinal direction in warm water at 80 ° C. The Elmendorf ratio in the case of measurement is 0.15 or more and 1.5 or less.

  The invention described in claim 5 is the invention described in any one of claims 1 to 4, wherein the right-angled tear in the width direction per unit thickness after shrinking 10% in the longitudinal direction in warm water at 80 ° C. The strength is 100 N / mm or more and 300 N / mm or less.

  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 100 ° C. or higher and 170 ° C. or lower for 1.0 second or longer and 10.0 seconds or shorter, and then cooled until the surface temperature of the film becomes 30 ° C. or higher and 70 ° C. or lower. And then stretched in the longitudinal direction at a temperature of Tg + 5 ° C. or more and Tg + 80 ° C. or less at a magnification of 2.0 times or more and 7 times or less, and then the film surface temperature at a cooling rate of 30 ° C./second or more and 70 ° C./second or less. 45 ° C or higher It is characterized in that the cooling until 75 ° C. or less.

  The heat-shrinkable polyester film of the present invention has high mechanical strength in the width direction perpendicular to the main shrinkage direction, and does not cause winding tightness in the produced roll-shaped film, so that it is difficult for wrinkles to enter the film roll. Opening ability is good. In addition, the shrinkability in the longitudinal direction, which is the main shrinkage direction, is high. 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 within a short time. When heat-shrinking after mounting, a good finish with very little wrinkles due to heat-shrinking and insufficient shrinkage can be expressed. In addition, the attached label will exhibit very good perforation opening.

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).

  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 by using a polyester containing 3 mol% or more of these aliphatic dicarboxylic acids has insufficient film stiffness during 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.

  Further, the polyester used in the heat-shrinkable polyester film of the present invention has a total of 10 mol% or more of at least one monomer component that can be an amorphous component in 100 mol% of the polyhydric alcohol component in all the polyester resins. It is necessary to be 15 mol% or more, more preferably 17 mol% or more, and particularly preferably 20 mol% or more. Here, examples of the monomer that can be an amorphous component include neopentyl glycol, 1,4-cyclohexanediol, and isophthalic acid.

  In the polyester used in 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, glycerin) is used. , Diglycerin and the like) are preferably not contained. 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.

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 80% or less.
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 amount of shrinkage is small when used as a label. On the other hand, if the hot water thermal contraction rate in the longitudinal direction at 90 ° C exceeds 80%, when used as a label, the shrinkage tends to occur at the time of thermal contraction, or so-called "flying up" may occur. It is not preferable. In addition, the lower limit value of the hot water heat shrinkage in the longitudinal direction at 90 ° C. is preferably 20% or more, more preferably 25% or more, and particularly preferably 30% or more. Further, the upper limit value of the hot water heat shrinkage in the longitudinal direction at 90 ° C. is preferably 75% or less, more preferably 70% or less, and particularly preferably 65% or less.

In addition, when the film of the present invention is preliminarily formed into a bottle after forming a cylindrical label whose main shrinkage direction is the circumferential direction (attached around a bottle or the like), the hot water in the longitudinal direction at 90 ° C. The thermal contraction rate is preferably 40% or more and 80% or less. As described above, when a cylindrical label whose main shrinkage direction is the circumferential direction is formed in advance and then fitted into the bottle, the shrinkage amount is small when the hot water thermal shrinkage rate in the longitudinal direction at 90 ° C. is less than 40%. For this reason, the label after heat shrinkage is not preferable because wrinkles and tarmi are generated. On the contrary, if the hot water heat shrinkage in the longitudinal direction at 90 ° C. exceeds 80%, the label is used during heat shrinkage. It is not preferable because the shrinkage tends to be distorted or a so-called “jump” occurs. In addition, when forming the cylindrical label which makes the main shrinkage direction the circumferential direction previously, when fitting in a bottle, the lower limit of the hot water thermal shrinkage rate in the longitudinal direction at 90 ° C. is preferably 45% or more. 50% or more, more preferably 55% or more. Further, the upper limit value of the hot water heat shrinkage in the longitudinal direction at 90 ° C. is preferably 75% or less, more preferably 70% or less, and particularly preferably 65% or less. Hereinafter, the use such as fitting of a cylindrical body suitable for a film having a hot water thermal shrinkage in the longitudinal direction at 90 ° C. of 40% or more and 80% or less as described above may be referred to as a high shrinkage use.

  In addition, when the film of the present invention is mounted by wrapping around the bottle directly from the film roll by the wrap round method, the hot water heat shrinkage in the longitudinal direction at 90 ° C. is preferably 15% or more and less than 40%. . 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 a shrinkage distortion is likely to occur during the thermal contraction after winding as a label by a body winding method, or so-called “jumping” occurs. Absent. In addition, the lower limit of the hot water heat shrinkage in the longitudinal direction at 90 ° C. is preferably 17% or more, more preferably 19% or more, and particularly preferably 21% or more. Further, the upper limit value 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. Hereinafter, the above uses may be referred to as lap round uses.

  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 0% or more and 17% or less.

  If the hot water thermal contraction rate in the width direction at 90 ° C. is less than 0%, it is not preferable because a good shrink appearance cannot be obtained when used as a label on a bottle, and conversely, the hot water heat heat in the width direction at 90 ° C. When the shrinkage rate exceeds 17%, it is not preferable because when used as a label, the shrinkage tends to occur during heat shrinkage. The upper limit of the hot water heat shrinkage in the width direction at 90 ° C. is preferably 15% or less, more preferably 14% or less, even more preferably 13% or less, and particularly preferably 12% or less. Preferably, it is 11% or less. In consideration of the essential characteristics of the polyester-based resin as a raw material, the lower limit value of the hot water heat shrinkage in the width direction at 90 ° C. is considered to be about 0%.

  In addition, the heat-shrinkable polyester film of the present invention was subjected to 10% shrinkage in the longitudinal direction in warm water at 80 ° C., and then the right-angled tear strength per unit thickness was determined by the following method. The 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 by 10% in the longitudinal direction in hot water 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

  When the right-angled tear strength after shrinking 10% 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 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 10% 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. The Elmendorf ratio, which is the ratio of the Elmendorf tear load, is preferably 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 needs to have a natural shrinkage ratio of 0.05% or more and 1.5% or less after aging for 700 hours in an atmosphere of 40 ° C. and 65% RH. 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 when the product wound in a roll shape is stored, 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.

The heat-shrinkable polyester film of the present invention preferably has a refractive index in the longitudinal direction of 1.570 or more and 1.620 or less. If the refractive index in the longitudinal direction exceeds 1.620, the solvent adhesiveness when forming a label is deteriorated, which is not preferable. On the other hand, if it is less than 1.570, 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 less than 1.600, preferably 1.595 or less, more preferably 1.593 or less, and particularly preferably 1.590. On the other hand, the lower limit value of the refractive index in the longitudinal direction is preferably 1.575 or more. Furthermore, in high shrinkage applications, the lower limit of the refractive index in the longitudinal direction is preferably 1.580 or more, more preferably 1.583 or more, and particularly preferably 1.585 or more. In addition, when the film of the present invention is wrapped around the bottle directly from the film roll by the wrap round method, the refractive index in the longitudinal direction is preferably 1.570 or more and 1.590 or less. The upper limit of the refractive index in the longitudinal direction for wrap round applications is preferably 1.587 or less, and particularly preferably 1.585 or less.

The heat-shrinkable polyester film of the present invention preferably has a refractive index in the width direction of 1.570 or more and 1.620 or less. If the refractive index in the width direction exceeds 1.620, the solvent adhesiveness when forming a label is deteriorated, which is not preferable. On the other hand, if it is less than 1.570, it is not preferable because the cut property when used as a label is deteriorated. The upper limit of the refractive index in the width direction is preferably 1.610 or less, more preferably 1.600 or less, and even more preferably 1.595 or less. The lower limit of the refractive index in the width direction is preferably 1.575 or more, and more preferably 1.580 or more. Furthermore, in high shrinkage applications, the upper limit of the refractive index in the width direction is preferably 1.590 or less, more preferably 1.588 or less, and particularly preferably 1.586 or less. When the film of the present invention is wrapped around a bottle directly from a film roll by a wrap round method, the upper limit of the refractive index in the width direction is preferably 1.610 or less, more preferably 1.605 or less. preferable.

On the other hand, in the present invention, the maximum heat shrinkage stress value in the longitudinal direction of the film is preferably 2.5 (MPa) or more and 20 (MPa) or less. When the maximum heat shrinkage stress value in the longitudinal direction of the film is less than 2.5 (MPa), when the PET bottle cap is opened and thermally shrunk as a label, the PET bottle cap is released together with the cap. This is not preferable because the label may rotate to deteriorate the opening of the cap. If the maximum heat shrinkage stress value in the longitudinal direction of the film is too low, shrinkage is insufficient during heat shrinkage, and a good appearance cannot be obtained. The lower limit value of the maximum heat shrinkage stress value in the longitudinal direction of the film is more preferably 3.0 (MPa) or more, and particularly preferably 3.5 (MPa) or more. On the other hand, when the maximum heat shrinkage stress value exceeds 20 (MPa), the shrinkage rate is fast and wrinkles are likely to occur. Further, the upper limit value of the maximum heat shrinkage stress value in the longitudinal direction of the film is more preferably 19 (MPa) or less, and particularly preferably 18 (MPa) or less.
In order to keep the opening of the cap favorable in the case of high shrinkage, the lower limit of the maximum heat shrinkage stress value in the longitudinal direction of the film is more preferably 6 (MPa) or more, and further preferably 7 (MPa) or more. It is especially preferable that it is 8 (MPa) or more.
In the case of wrap round use, shrinkage strain is likely to occur during heat shrinkage after body winding, so the upper limit of the maximum heat shrinkage stress value in the longitudinal direction of the film is preferably 7 MPa or less. More preferably, it is 6.5 MPa or less, More preferably, it is 6.0 MPa or less, Especially preferably, it is 5.5 MPa or less.

  Furthermore, the heat-shrinkable polyester film of the present invention preferably has a solvent adhesive strength of 4 (N / 15 mm) or more. If the solvent adhesive strength is less than 4 (N / 15 mm), it is not preferable because the label is easily peeled off after the heat shrinkage. The solvent adhesive strength is more preferably 4.5 (N / 15 mm) or more, and particularly preferably 5 (N / 15 mm) or more. In particular, in the case of high shrinkage, it is preferable to satisfy the above characteristics.

  In addition, the heat-shrinkable polyester film of the present invention preferably has a thickness unevenness of 10% or less in the longitudinal direction. When the thickness unevenness in the longitudinal direction is more than 10%, it is not preferable because printing spots are likely to occur during printing at the time of label production or shrinkage spots after heat shrinkage are likely to occur. In addition, the thickness variation in the longitudinal direction is more preferably 8% or less, and more preferably 6% or less.

  The heat shrinkage rate, the maximum heat shrinkage stress value, the solvent adhesive strength, and the thickness unevenness of the film in the longitudinal direction of the heat shrink film are achieved by using the preferred film composition described above and combining with the preferred production method described later. Is possible.

  Furthermore, it is preferable that the heat-shrinkable polyester film of the present invention does not detect the endothermic curve peak during melting point measurement in differential scanning calorimetry (DSC). By making the polyester constituting the film amorphous, the peak of the endothermic curve at the time of measuring the melting point becomes more difficult to express. Highly amorphous to such an extent that the endothermic curve peak at the time of melting point measurement does not appear, thereby improving the solvent adhesion strength and increasing the heat shrinkage rate and the maximum heat shrinkage stress value, and controlling them within the above-mentioned preferable ranges. Easy to do.

  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 the width direction after extending | stretching previously to a longitudinal direction is employ | adopted, it will become unnecessary to shrink | contract in the width direction and the shrinkage | contraction amount to a longitudinal direction will become inadequate. As described above, 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. However, according to the pilot test by the inventors of the present invention, in this method, the obtained film has a large natural shrinkage rate, wrinkles in the longitudinal direction occur in the manufactured film roll, and the perforation opening property Was also bad. further,
It was found that a film having high shrinkability in the longitudinal direction, which is the main shrinkage direction, cannot be obtained. 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.

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 in the longitudinal direction of the film, the natural shrinkage rate, depending on the conditions in each stretching step, The inventors studied diligently how the perforation opening changes. As a result, the present inventors have found out that when the film is manufactured by the transverse-longitudinal stretching method, the following measures are taken to increase the amount of shrinkage in the longitudinal direction, thereby enabling continuous and stable production. In addition, when the following measures are taken, the natural shrinkage rate of the film is reduced, wrinkles are difficult to enter into the film roll after manufacture, and the perforation opening property of the film is remarkably good. It turns out that there is a surprising side effect that And the present inventors came to devise this invention based on those knowledge.
(1) Control of shrinkage stress after stretching in the width direction (2) Blocking of heating between stretching in the width direction and intermediate heat treatment (3) Trimming of film edge before stretching in the longitudinal direction (4) Control of Cooling Rate of Film after Longitudinal Drawing Hereinafter, each of the above-described means will be described in order.

(1) Control of shrinkage stress after stretching in the width direction In the production of a film by the transverse-longitudinal stretching method of the present invention, after stretching an unstretched film in the width direction, the temperature is 100 ° C. or more and less than 170 ° C. It is necessary to perform heat treatment (hereinafter referred to as intermediate heat treatment) for a period of time between 0.0 seconds and 10.0 seconds. By performing such an intermediate heat treatment, it is possible to obtain a film having good perforation cutability and no shrinkage spots when used as a label. The reason why it becomes possible to obtain a film having good perforation cutability and no shrinkage spots by performing a specific intermediate heat treatment after transverse stretching is not clear, but by performing a specific intermediate heat treatment, It is thought that it is possible to reduce the shrinkage stress in the width direction while leaving some molecular orientation in the width direction. In addition, the minimum of the temperature of heat processing is preferable in it being 110 degreeC or more, and it is more preferable in it being 115 degreeC or more. Moreover, the upper limit of the temperature of heat processing is preferable in it being 165 degrees C or less, and it is more preferable in it being 160 degrees C or less. On the other hand, the heat treatment time needs to be appropriately adjusted according to the raw material composition within a range of 1.0 second to 10.0 seconds.

  In addition, the unstretched film is stretched in the width direction 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. It is necessary to do so. 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. 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.

(2) Interruption of heating between stretching in the width direction and intermediate heat treatment In the production of a film by the transverse-longitudinal stretching method of the present invention, it is necessary to perform an intermediate heat treatment after transverse stretching as described above. Between the transverse stretching and the intermediate heat treatment, it is necessary to pass through an intermediate zone in which no aggressive heating operation is performed for a time period of 0.5 seconds to 3.0 seconds. That is, considering production costs, it is preferable to perform transverse stretching and intermediate heat treatment in the same tenter, but in the production of the film of the present invention, between the transverse stretching zone and the heat treatment zone in the tenter. It is preferable to provide an intermediate zone. In addition, in the intermediate zone, when the strip-shaped paper piece is hung in a state where the film is not passed, the hot air from the drawing zone and the heat treatment zone is blocked so that the paper piece hangs almost completely in the vertical direction. Is preferred. And in manufacture of the film of this invention, it is preferable to guide the film after transverse stretching to this intermediate zone, and to let the intermediate zone pass over predetermined time. If the time for passing through the intermediate zone is less than 0.5 seconds, the hot air in the transverse stretching zone flows into the heat fixing zone due to the accompanying flow of the passing film, which makes it difficult to control the temperature of the intermediate heat treatment in the heat fixing zone. . On the contrary, it is sufficient that the time for passing through the intermediate zone is 3.0 seconds, and setting it longer than that is not preferable because it wastes equipment. The lower limit of the time for passing through the intermediate zone is preferably 0.7 seconds or more, and more preferably 0.9 seconds or more. Further, the upper limit of the time for passing through the intermediate zone is preferably 2.5 seconds or less, and more preferably 2.0 seconds or less.

(3) next to the trimming present invention before the film ends extending in a longitudinal direction - in the production of the film by longitudinal stretching method, prior to stretching the film subjected to the intermediate heat treatment in the long side direction, when the film edge It is preferable to trim a thick portion (mainly a clip gripping portion at the time of transverse stretching) that is not sufficiently transversely stretched. More specifically, a thick portion at the edge of the film using a tool such as a cutter in a portion having a thickness of about 1.1 to 1.3 times the thickness of the central portion located at the right and left edges of the film. It is preferable that only the remaining portion is stretched in the longitudinal direction while cutting the thick portion and removing the thick portion. When trimming the film edge as described above, it is preferable to cool the film before trimming so that the surface temperature 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.

  In this way, by trimming the end of the film before stretching in the longitudinal direction, the film once heat-set can be stretched uniformly in the longitudinal direction, and for the first time, stable and continuous production without breakage is possible. It becomes. In addition, it is possible to obtain a film having a large shrinkage in the longitudinal direction (main shrinkage direction). 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. In addition, extending | stretching to a longitudinal direction is the temperature of Tg + 5 degreeC or more and Tg + 80 degrees C or less by the method (method of extending | stretching using the speed difference of a roll) etc. using the longitudinal drawing machine which has arrange | positioned several roll groups continuously. Therefore, it is necessary to carry out so that the magnification is 2.0 times or more and 7.0 times or less.

(4) Control of cooling rate of film after longitudinal stretching In the production of a film by the transverse-longitudinal stretching method of the present invention, as described above, after intermediate stretching after transverse stretching and stretching in the longitudinal direction, 30 ° C It is preferable to cool the film until the surface temperature becomes 45 ° C. or higher and 75 ° C. or lower at a cooling rate of 70 ° C./second or more. Thus, the natural shrinkage rate can be reduced for the first time by cooling the film at an appropriate speed. If the cooling rate is lower than 30 ° C./second or the surface temperature after cooling is higher than 75 ° C., it is not preferable because a low natural shrinkage rate cannot be obtained. On the other hand, if the cooling rate is so rapid that the cooling rate exceeds 70 ° C./second, the degree of shrinkage in the width direction of the film (so-called neck-in) increases, and the film surface is easily damaged, which is not preferable. .

  Note that only one of the above-mentioned means (1) to (4) is effective for heat shrinkability in the longitudinal direction of the film, perforation openability, low natural shrinkage, and stable film-forming properties. It does not contribute, but by using the means of (1) to (4) in combination, the heat shrinkability in the longitudinal direction, the perforation opening property, the low natural shrinkage rate, and the stable film forming property It is thought that it becomes possible to express.

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

Moreover, the evaluation method of a 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.

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

[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). 9 and Comparative Examples 1 to 3 and 5 were measured for shrinkage in the longitudinal direction and in Comparative Example 4 in the width direction), and the natural shrinkage rate was calculated by the above equation 4.

[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 10% in the main shrinking direction (hereinafter referred to as pre-shrinking) by immersing in warm water at 80 ° C. for 2 seconds. 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.

[Right-angle tear strength]
After shrinking the film by 10% in the main shrinkage direction in hot water 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.

[Thickness unevenness in the main shrinkage direction]
The film was sampled into a long roll having a length of 30 m and a width of 40 mm, and measured at a speed of 5 (m / min) using a continuous contact thickness gauge manufactured by Micron Measuring Instruments Co., Ltd. In the sampling of the roll-shaped film sample described above, the length direction of the film sample was set as the main shrinkage direction of the film. The maximum thickness at the time of measurement was Tmax, the minimum thickness was Tmin., The average thickness was Tave.
Thickness unevenness = {(Tmax.−Tmin.) / Tave.} × 100 (%)

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

[Shrink finish (tubular fitting)]
The heat-shrinkable film was preliminarily printed in three colors with grass, gold, and white ink from Toyo Ink Manufacturing Co., Ltd. And by adhering both ends of the printed film with dioxolane, a cylindrical label (the main shrinkage direction of the heat-shrinkable film is the circumferential direction, and the outer peripheral length is 1.05 times the outer peripheral length of the bottle to be mounted. A certain cylindrical label) was created. After that, the cylindrical label is put on a 500 ml PET bottle (bore diameter 62 mm, minimum neck diameter 25 mm) and using a steam tunnel (model: SH-1500-L) manufactured by Fuji Astec Inc. The label was attached by heat shrinking at a zone temperature of 80 ° C. for 2.5 seconds. At the time of mounting, the neck portion was adjusted so that a portion with a diameter of 40 mm was one end of the label. The finish after 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 slight color spots are seen △: Jumping Neither ascending nor insufficient shrinkage has occurred, but spots on the neck are observed. X: Wrinkles, jumping up, insufficient shrinkage occurred

[Shrink finish (wrap 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 minimum diameter of 25 mm at the neck and a “neck” provided so that the diameter of the center of the barrel becomes 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 portion (the portion 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 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 slight color spots are seen △: Jumping Neither ascending nor insufficient shrinkage has occurred, but spots on the neck are observed. X: 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. in 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. In addition, 100 parts of this solution, just before use, 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Darocur (registered trademark) 1173: manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator 3 An active energy ray (UV) curable adhesive was obtained by adding part by mass. The molecular weight of urethane acrylate was 2000. The composition of the adhesive is summarized in Table 3. 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.

[Label adhesion]
A label was attached to a PET bottle under the same conditions as those described above for measuring the shrink finish (cylinder fitting). When the attached label and the PET bottle were lightly twisted, it was marked as ◯ if the label did not move, or marked as x if it slipped through or the label and the bottle were misaligned. When the film is directly wound around a PET bottle or the like and attached, the edge of the film is adhered to the PET bottle, so that the label adhesion does not become a problem.

[Perforation opening]
A label having a perforation in advance in a direction perpendicular to the main shrinkage direction was attached to a PET bottle under the same conditions as the above-described shrinkage finishing measurement conditions (incorporation of a cylindrical body). However, the perforations were formed by putting holes having a length of 1 mm at intervals of 1 mm, and two perforations were provided in the longitudinal direction (height direction) of the label over a width of 22 mm and a length of 120 mm. The bottle is then filled with 500 ml of water, refrigerated to 5 ° C., tearing the perforation of the bottle label immediately after removal from the refrigerator with the fingertips, tearing it cleanly along the perforation in the vertical direction, and removing the label from the bottle The number that could be removed was counted, and the ratio (%) to 50 samples was calculated.

[Comprehensive evaluation]
As described above, as a result of evaluating shrink finish (cylinder fitting), shrink finish (wrap / round), label adhesion, and perforation openability, the cylindrical fit method (previously the circumferential direction is the main shrink direction) After forming the cylindrical label to be attached to the PET bottle, etc., or wrap round method (wrapping the film directly around the PET bottle so that the main shrinkage direction is the circumferential direction) ) If it can be used practically as a heat shrinkable film by any of the above methods), it can be used as a heat shrinkable film in any of the tubular body fitting method and the wrap round method. If it could not be used practically, it was marked as x.

  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)
Polyester 3: Consists of 82.5 mol% of terephthalic acid units and 17.5 mol% of isophthalic acid units as the dicarboxylic acid component, and ethylene glycol as the diol component.
Polyester 4: Polyester composed of 70 mol% ethylene glycol, 30 mol% 1,4-cyclohexanedimethanol and terephthalic acid (IV 0.75 dl / g)

[Example 1]
The above polyester 1 and polyester 2 were mixed at a weight ratio of 90:10 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 360 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 preheating the unstretched film led to the tenter until the film temperature reaches 90 ° C., the film is stretched 4 times at 75 ° C. in the transverse direction in the transverse stretching zone and passed through the intermediate zone (pass Time = about 1.2 seconds), the film was led to an intermediate heat treatment zone and heat treated at a temperature of 130 ° C. for 2.0 seconds to obtain a transversely uniaxially stretched film having a thickness of 90 μm. 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. It extended | stretched 3 times between the extending | stretching rolls set to (3). 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, the cooled film is guided to a tenter (second tenter), heat-treated in an atmosphere of 95 ° C. for 2.0 seconds in the second tenter, cooled, and both edges are cut and removed. A film roll made of a heat-shrinkable polyester film was obtained by continuously forming a biaxially stretched film of about 30 μm over a predetermined length. And the characteristic of the obtained film was evaluated by the above-mentioned method. The evaluation results are shown in Table 3.

[Example 2]
A heat-shrinkable film was continuously produced by the same method as in Example 1 except that polyester 1 and polyester 2 were mixed at a weight ratio of 70:30 and charged into an extruder. 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]
A heat-shrinkable film was continuously produced in the same manner as in Example 1 except that the transverse stretch ratio in the tenter (first tenter) was changed to 5.0 times. The biaxially stretched heat-shrinkable polyester film had a thickness of about 24 μm. 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 4]
A heat-shrinkable film was continuously produced by the same method as in Example 1 except that the temperature of the intermediate heat treatment in the tenter (first tenter) was changed to 140 ° C. The biaxially stretched heat-shrinkable polyester film had a thickness of about 24 μm. 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 5]
A heat-shrinkable film was continuously produced by the same method as in Example 1 except that the temperature of the stretching roll in the longitudinal stretching machine was changed to 92 ° C. and the stretching ratio in the longitudinal direction was changed to 5.0 times. The biaxially stretched heat-shrinkable polyester film had a thickness of about 18 μm. 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 6]
A heat-shrinkable film was continuously produced in the same manner as in Example 1 except that the temperature of the stretching roll in the longitudinal stretching machine was changed to 92 ° C. and the stretching ratio in the longitudinal direction was changed to 7.0 times. The biaxially stretched heat-shrinkable polyester film had a thickness of about 13 μm. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[ Reference Example 1 ]
A heat-shrinkable film was continuously produced by the same method as in Example 1 except that the stretching ratio in the longitudinal direction in the longitudinal stretching machine was changed to 1.5. The biaxially stretched heat-shrinkable polyester film had a thickness of about 60 μm. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[ Reference Example 2 ]
Implemented except that the raw material resin to be fed into the extruder was changed to a mixture of polyester 4 and polyester 2 at a weight ratio of 90:10, and the longitudinal draw ratio in the longitudinal stretcher was changed to 1.5 times. A heat-shrinkable film was continuously produced by the same method as in Example 1. The biaxially stretched heat-shrinkable polyester film had a thickness of about 60 μm. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[ Reference Example 3 ]
According to the same method as in Example 1, except that the transverse stretching ratio in the tenter (first tenter) was changed to 4.5 times and the longitudinal stretching ratio in the longitudinal stretching machine was changed to 1.5 times. A heat shrinkable film was continuously produced. The biaxially stretched heat-shrinkable polyester film had a thickness of about 27 μm. 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]
The above-described polyester 3 is put into an extruder, melted at 265 ° C., extruded from a T die, wound around a rotating metal roll cooled to a surface temperature of 30 ° C., and rapidly cooled, thereby an unstretched film having a thickness of 360 μm Got. The take-up speed of the unstretched film was the same as in Example 1. Thereafter, the unstretched film is led to a longitudinal stretching machine (first longitudinal stretching machine) in which a plurality of roll groups are continuously arranged, preheated on a preheating roll, and then stretched at a surface temperature of 88 ° C. The film was stretched 2.7 times between rolls. Further, the film stretched in the longitudinal direction is led to a tenter (first tenter) in which a transverse stretching zone and a heat treatment zone are continuously provided, and the transverse stretching zone is at a stretching temperature of 97 ° C. and is transversely stretched at 97 ° C. After stretching 5 times, heat treatment was performed at 125 ° C. in a heat treatment zone. Thereafter, the heat-treated film is guided to a longitudinal stretching machine (second longitudinal stretching machine) in which a plurality of roll groups are continuously arranged, preheated on a preheating roll, and then stretched at a surface temperature of 98 ° C. Longitudinal stretching was again performed 1.5 times between the rolls. Furthermore, the film stretched again in the longitudinal direction is guided to a tenter (second tenter), heat-treated at 85 ° C., cooled, and both edges are cut and removed, whereby a biaxially stretched film of about 35 μm is stretched over a predetermined length. The film was continuously formed to obtain a heat-shrinkable polyester film roll. The surface temperature of the film after heat treatment and before cooling was about 75 ° C., and was cooled to about 25 ° C. in about 2.0 seconds (cooling rate = 25 ° C./second). 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]
A heat-shrinkable film was continuously produced by the same method as in Example 1 except that polyester 1 and polyester 2 were mixed at a weight ratio of 40:60 and charged into an extruder. The biaxially stretched heat-shrinkable polyester film had a thickness of about 13 μm. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

[Comparative Example 3]
A heat-shrinkable film was continuously produced by the same method as in Example 1 except that the temperature of the intermediate heat treatment in the tenter (first tenter) was changed to 70 ° 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 4]
By guiding the unstretched film to a tenter and preheating until the film temperature reaches 90 ° C., the film is stretched 4.0 times in the transverse direction at a stretching temperature of 75 ° C., cooled, and both edges are cut and removed. About 45 μm laterally uniaxially stretched film was continuously formed over a predetermined length to obtain a heat-shrinkable polyester film roll. The surface temperature of the film after heat treatment and before cooling was about 75 ° C., and was cooled to about 35 ° C. in about 2.0 seconds (cooling rate = 20 ° C./second). And the characteristic of the obtained film was evaluated by the above-mentioned method. The evaluation results are shown in Table 3. In the film of Comparative Example 5, the width direction is the main shrinkage direction, and the longitudinal direction is the direction orthogonal to the main shrinkage direction.

[Comparative Example 5]
A heat-shrinkable film was continuously produced by the same method as in Comparative Example 1 except that the draw ratio at the time of longitudinal stretching again with the second longitudinal stretching machine was 3.0 times. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.

As is clear from Table 3, the films obtained in Examples 1 to 6 and Reference Examples 1 to 3 all have high shrinkability in the longitudinal direction, which is the main shrinkage direction, and are perpendicular to the main shrinkage direction. The shrinkage in the direction was very low. In addition, all the films obtained in Examples 1 to 6 had high solvent adhesive strength, good label adhesion, no shrinkage spots, and good shrinkage finish (cylinder fitting method). On the other hand, the films obtained in Reference Examples 1 to 3 had good shrinkage finish (wrap round method). Moreover, the film obtained in Reference Example 1 had a high solvent adhesive strength. Furthermore, the heat-shrinkable polyester films of Examples 1 to 6 and Reference Examples 1 to 3 have good perforation openability and a small natural shrinkage rate, and wrinkles are generated in the produced film roll. There wasn't. That is, the heat-shrinkable polyester films obtained in Examples 1 to 6 and Reference Examples 1 to 3 all had high label quality and were extremely practical.

  In contrast, the heat-shrinkable film obtained in Comparative Example 1 was poor in label adhesion and perforation opening. Moreover, the heat-shrinkable films obtained in Comparative Examples 2 and 3 all had a high heat shrinkage rate in the film width direction, had poor label adhesion, and caused shrinkage spots. On the other hand, the film obtained in Comparative Example 4 (the main shrinkage direction is the width direction) had good shrinkage finish (cylindrical body fitting method), but was poor in perforation openability. In addition, the film obtained in Comparative Example 5 (the main shrinkage direction is the width direction) has a large thermal shrinkage rate in the direction orthogonal to the main shrinkage direction, shrinkage spots are generated, and the perforation openability is poor. The natural shrinkage ratio was large, and wrinkles occurred on the manufactured film roll. That is, the heat-shrinkable polyester film obtained in Comparative Examples 1 to 5 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.

F ・ ・ Film.

Claims (6)

It has ethylene terephthalate as a main constituent, contains at least 10 mol% of one or more monomer components that can be amorphous components in all polyester resin components, and is formed in a long shape with a constant width. It is a heat-shrinkable polyester film whose shrinkage direction is the longitudinal direction,
A heat shrinkable polyester film characterized by satisfying the following requirements (1) to (4).
(1) The hot water thermal shrinkage in the longitudinal direction is 15% or more and 80% or less when treated in warm water at 90 ° C. for 10 seconds. (2) Treated in warm water at 90 ° C. for 10 seconds. The hot-water heat shrinkage in the width direction perpendicular to the longitudinal direction is 0% or more and 17% or less (3) The thickness unevenness in the longitudinal direction is 10% or less (4) 40 ° C. and 65% RH atmosphere The natural shrinkage rate in the main shrinkage direction after aging for 700 hours is 0.05% to 1.5%.   The hot water thermal contraction rate in the longitudinal direction when treated in warm water at 90 ° C. for 10 seconds is 15% or more and less than 40%, the refractive index in the longitudinal direction is 1.570 or more and 1.590 or less, and the width The heat-shrinkable polyester film according to claim 1, wherein the refractive index in the direction is 1.570 or more and 1.620 or less.   The main component of a monomer that can be an amorphous component in all the polyester resin components is any one of neopentyl glycol, 1,4-cyclohexanedimethanol, and isophthalic acid, or claim 1 Item 3. The heat-shrinkable polyester film according to Item 2.   The Elmendorf ratio in the case where the Elmendorf tear load in the longitudinal direction and the width direction is measured after shrinking 10% in the longitudinal direction in warm water at 80 ° C. is 0.15 or more and 1.5 or less. The heat-shrinkable polyester film according to any one of?   5. The right-angled tear strength in the width direction per unit thickness after shrinking 10% in the longitudinal direction in warm water at 80 ° C. is 100 N / mm or more and 300 N / mm or less. The heat-shrinkable polyester film described in 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 100 ° C. or more and 170 ° C. or less for a time of 1.0 second or more and 10.0 seconds or less. After cooling down to 70 ° C. or higher, the film is stretched at a temperature of Tg + 5 ° C. or more and Tg + 80 ° C. or less in the longitudinal direction at a magnification of 2.0 times or more and 7 times or less. A method for producing a heat-shrinkable polyester film, wherein the film is cooled at a cooling rate until the surface temperature of the film becomes 45 ° C. or higher and 75 ° C. or lower.

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