JP2005194466A - Heat shrinkable polyester base film and heat shrinkable label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat shrinkable polyester base film which is excellent in cuttability along the direction rectangular to a maximum shrinkage direction and has a heat shrinkage property suitable for use in a label. <P>SOLUTION: The heat shrinkable polyester base film comprises a polyester wherein 100 mol% of a polyhydric alcohol component comprises 10 mol% or more of 1,4-cyclohexane dimethanol, 2 mol% or more of neopentyl glycol, and 12-40 mol% of the total of the 1,4-cyclohexanedimethanol and the neopentyl glycol; has a heat shrinkage rate of 50% or more along the maximum shrinkage direction as measured using a 10 cm×10 cm square cut sample which is dipped in 98°C hot water for 10 sec to take out and then in 25°C water for 10 sec to take out; and has a resistance of 1,800 mN or less against the propagation of a notch along the direction rectangular to the maximum shrinkage direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat-shrinkable polyester film. More specifically, after shrinkage of a heat-shrinkable film, shrinkage whitening, shrinkage spots, wrinkles, and distortion are extremely small, and the tearability along the perforation (cut property) And a heat-shrinkable polyester film suitable for labeling.

  The heat-shrinkable plastic film is widely used for applications such as shrink wrapping and shrinkage labels by utilizing the property of shrinking by heating. Among them, stretched films such as polyvinyl chloride films, polystyrene films, and polyester films are used for labels, cap seals, and integrated packaging in various containers such as polyethylene terephthalate (PET) containers, polyethylene containers, and glass containers. (For example, Patent Document 1).

  Among these, the polyvinyl chloride film has excellent shrinkage properties, but 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 film is used as a shrinkable 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, a polystyrene film can be evaluated for its good finished appearance after shrinkage, but it is poor in solvent resistance, so an ink with 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 and off-flavor are generated during the incineration.

  Polyester films without these problems are highly expected as shrink labels to replace polyvinyl chloride films and polystyrene films, and the amount of use tends to increase as the amount of PET container used increases.

  However, the conventional heat-shrinkable polyester film has been required to be further improved in its properties. In particular, when PET bottles are recycled, there is a movement to improve the quality of recycled PET by removing the label to which the printing ink is attached from the bottle. However, conventional heat-shrinkable polyester films are perforated. Even if a small hole is provided in a direction perpendicular to the maximum shrinkage direction (longitudinal direction when the bottle is covered), it is difficult to break along the perforation. On the other hand, there was a problem that it was torn in the shrinking direction and could not be easily removed from the bottle. This is a problem peculiar to heat-shrinkable films in that the shrinkage direction of the film is the stretching direction, so that the molecular chains are stretched and easily broken between the molecular chains.

In order to solve such a problem, a method has been considered in which a resin component that is incompatible with polyester is added so as to be easily broken along the perforation (for example, Patent Document 2). However, the addition of an incompatible resin may cause deterioration of the transparency of the film and roughness of the film surface, and a method that does not cause such disadvantages has been demanded.
Japanese Patent Publication No. 7-33063 JP 2002-363212 A

  Accordingly, an object of the present invention is to provide a heat-shrinkable polyester film that has excellent tearability (cutability) in a direction perpendicular to the maximum shrinkage direction and has heat-shrink characteristics suitable for label applications.

  In the heat-shrinkable polyester-based film, the present invention that has solved the above-mentioned problems is characterized in that, among 100 mol% of the polyhydric alcohol component of the polyester constituting the film, 1,4-cyclohexanedimethanol is 10 mol% or more, neo Pentyl glycol is 2 mol% or more, and the total amount of 1,4-cyclohexanedimethanol and neopentyl glycol is 12 to 40 mol%, and a sample cut into a 10 cm × 10 cm square shape is heated at 98 ° C. Pulled up by dipping in 10 seconds and then dipped in water at 25 ° C. for 10 seconds, the thermal shrinkage rate in the maximum shrinkage direction is 50% or more, and the tear propagation resistance value in the direction perpendicular to the maximum shrinkage direction Is 1800 mN or less.

  In the film, the refractive index Nx in the direction orthogonal to the maximum shrinkage direction is preferably 1.5590 or more. Moreover, it is preferable that 2 mol% or more is 1, 4- butanediol among 100 mol% of the polyhydric alcohol component of the polyester which comprises the said film. A heat-shrinkable label using the heat-shrinkable polyester film is also included in the present invention.

  The heat-shrinkable polyester film of the present invention is extremely free of shrinkage whitening, shrinkage spots, wrinkles and distortion after shrinkage, and is excellent in cutability in a direction perpendicular to the shrinkage direction. Therefore, the film and label of the present invention are suitable for various coated labels including labels such as PET bottles.

  The heat-shrinkable polyester film of the present invention is formed using a polyester composed of 100 mol% of a known polyvalent carboxylic acid component and 100 mol% of a polyhydric alcohol component. In 100 mol% of the polyhydric alcohol component, it is necessary that 1,4-cyclohexanedimethanol is contained in an amount of 10 mol% or more and neopentyl glycol is contained in an amount of 2 mol% or more. In the heat-shrinkable polyester film of the present invention, an ethylene terephthalate unit is a main component of polyester in order to exhibit tear resistance, strength, heat resistance, etc., but if there are too many ethylene terephthalate units, It becomes too hot and inferior in heat shrinkability. For this reason, appropriate amounts of the above 1,4-cyclohexanedimethanol and neopentyl glycol are added to lower the crystallinity of the polyester to increase the degree of amorphization and to develop a higher heat shrinkage rate.

  The reason for using 10 mol% or more of 1,4-cyclohexanedimethanol in 100 mol% of the polyhydric alcohol component is particularly to suppress whitening and the like during shrinkage. The amount of 1,4-cyclohexanedimethanol is more preferably 12 mol% or more, and further preferably 14 mol% or more. In addition, in order to improve the shrink finish in a low temperature range, 2 mol% or more of neopentyl glycol must be contained in 100 mol% of the polyhydric alcohol component. A more preferable amount of neopentyl glycol is 4 mol% or more, and further preferably 6 mol% or more.

  The total amount of 1,4-cyclohexanedimethanol and neopentyl glycol is 12 mol% or more, but in order to improve the shrink finish and cutability, 1,4- The total amount of cyclohexanedimethanol and neopentyl glycol is more preferably 16 mol% or more, and further preferably 20 mol% or more. However, if 1,4-cyclohexanedimethanol and neopentyl glycol are used in excess of 40 mol%, the shrinkage rate of the film becomes excessively higher than necessary, and the label misalignment or pattern distortion occurs in the heat shrinking process. May occur. Further, since the solvent resistance of the film is lowered, the film is whitened by an ink solvent (such as ethyl acetate) in the printing process, or the tear resistance of the film is lowered. Therefore, the total amount thereof is more preferably 37 mol% or less, and further preferably 35 mol% or less.

  Moreover, it is also a preferable embodiment in the polyester of the present invention to use 1,4-butanediol as the polyhydric alcohol. 1,4-Butanediol also lowers the crystallinity of the polyester to increase the degree of amorphization and develop a higher heat shrinkage rate, so that the resulting film exhibits excellent shrinkage finish in a relatively low temperature range become. In addition, the solvent adhesion is excellent. In order to obtain these effects, it is preferable to use 2 mol% or more of 1,4-butanediol in 100 mol% of the polyhydric alcohol component. A more preferred lower limit is 3 mol%, and a more preferred lower limit is 5 mol%. However, if there is too much 1,4-butanediol component, the number of ethylene terephthalate units responsible for properties such as tear resistance, strength, and heat resistance of the film decreases, so the upper limit is preferably 35 mol%, A preferable upper limit is 30 mol%.

  As another polyhydric alcohol, ethylene glycol for forming an ethylene terephthalate unit is used. In addition, diethylene glycol, dimer diol, propylene glycol, triethylene glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1 , 3-propanediol, 1,9-nonanediol, alkylene glycol such as 1,10-decanediol, alkylene oxide adducts of bisphenol compounds or derivatives thereof, trimethylolpropane, glycerin, pentaerythritol, polyoxytetramethylene glycol, Polyethylene glycol or the like can be used in combination. Moreover, although it is not a polyhydric alcohol, you may use a part of (epsilon) -caprolactone.

  Considering the tear resistance, strength, heat resistance, etc. of the film, it is preferable to select the polyester so that the ethylene terephthalate unit is 50 mol% or more as the structural unit of the polyester film. Therefore, it is preferable to use 50 mol% or more of terephthalic acid (or an ester thereof) in 100 mol% of the polyvalent carboxylic acid component and 50 mol% or more of ethylene glycol in 100 mol% of the polyhydric alcohol component. As for an ethylene terephthalate unit, 55 mol% or more is more preferable, and 60 mol% or more is further more preferable. However, in the present invention, in 100 mol% of the polyhydric alcohol component, 1,4-cyclohexanedimethanol and neopentyl glycol are essentially used in total of 12 mol% or more, so ethylene glycol is used in 88 mol% or less. . Further, when 2,4-butanediol is used in an amount of 2 mol% or more, the ethylene glycol is 86% or less.

  As dicarboxylic acid components other than terephthalic acid, aromatic dicarboxylic acids, ester-forming derivatives thereof, aliphatic dicarboxylic acids, and the like can be used. Examples of the aromatic dicarboxylic acid include isophthalic acid, naphthalene-1,4- or -2,6-dicarboxylic acid, and 5-sodium sulfoisophthalic acid. Examples of these ester derivatives include derivatives such as dialkyl esters and diaryl esters. Examples of the aliphatic dicarboxylic acid include dimer acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid, and succinic acid. Furthermore, an oxycarboxylic acid such as p-oxybenzoic acid, and a polyvalent carboxylic acid such as trimellitic anhydride or pyromellitic anhydride may be used in combination as necessary.

  In the heat-shrinkable polyester film of the present invention, the heat shrinkage rate in the maximum shrinkage direction is 50% or more when dipped in warm water at 98 ° C. for 10 seconds and then dipped in water at 25 ° C. for 10 seconds. Must. The reason why the thermal shrinkage rate is less than 50% is that when the container such as a bottle is covered and shrunk as a label, it does not adhere to the container and a poor appearance occurs. The heat shrinkage rate in the maximum direction is more preferably 60% or more, and still more preferably 70% or more.

The above-mentioned “heat shrinkage rate in the maximum shrinkage direction” means the heat shrinkage rate in the direction in which the sample is most shrunk, and the maximum shrinkage direction is determined by the length of the square sample in the vertical or horizontal direction. It is done. The heat shrinkage rate in the maximum shrinkage direction in hot water at 98 ° C. was immersed in 98 ± 0.5 ° C. warm water for 10 seconds in a no-load state and immediately heat-shrinked, and then immediately in 25 ± 0.5 ° C. water. Measure the length of the film in the vertical and horizontal directions after being immersed in a no-load state for 10 seconds. From the length before shrinkage (10 cm) and the length after shrinkage in the direction of most shrinkage, Ask.
Heat shrinkage rate = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)

  The heat-shrinkable polyester film of the present invention must have a tear propagation resistance value of 1800 mN or less. It is a numerical value for the purpose of good cutting performance. The tear propagation resistance value was measured using the rectangular test piece shown in FIG. 3 of JIS K7128-2 by the Elmendorf tear method defined in JIS K7128-2 in the direction orthogonal to the maximum shrinkage direction of the film. Adopt value. If this value is 1800 mN or less, it cannot be said that the cutting property is good, and it is difficult to tear the label after shrinkage at the perforation and peel it off the bottle. A more preferable tear propagation resistance value is 1600 mN or less, and further preferably 1400 mN or less.

  On the other hand, whether or not the cutting property of the film is good can also be grasped by looking at the refractive index Nx in the direction orthogonal to the maximum shrinkage direction. That is, the present inventors have found that the tear propagation resistance value is 1800 mN or less when the refractive index Nx is 1.5590 or more. This refractive index Nx can be measured by an Abbe refractometer. The refractive index Nx is more preferably 1.5595 or more, and further preferably 1.5598 or more.

  The polyester used as the raw material of the film of the present invention can be produced by melt polymerization according to a conventional method. For example, the polyester is prepared using a direct esterification method in which a polycarboxylic acid and a polyhydric alcohol are directly reacted; a transesterification method in which a polyvalent carboxylic acid dimethyl ester is reacted with a polyhydric alcohol, and the like. The preparation may be carried out by either a batch method or a continuous method. The degree of polymerization of the polyester is preferably 0.5 to 1.3 dl / g in terms of intrinsic viscosity.

  In addition to polymerization catalysts such as antimony oxide, germanium oxide, and titanium compounds, Mg salts such as magnesium acetate and magnesium chloride, calcium acetate, calcium chloride, etc. are used in polyester to prevent problems such as coloring and gel generation. Ca salt, manganese acetate, manganese chloride and other Mn salts, zinc chloride, zinc acetate and other Zn salts, cobalt chloride, cobalt acetate and other Co salts as metal ions, 300 ppm (mass basis, below) The same), phosphoric acid or phosphoric acid ester derivatives such as phosphoric acid trimethyl ester and phosphoric acid triethyl ester may be added in an amount of 200 ppm or less in terms of phosphorus (P). If the total amount of metal ions other than the above polymerization catalyst is 300 ppm with respect to the polyester and the amount of P exceeds 200 ppm, not only the coloring of the polyester becomes remarkable, but also the heat resistance and hydrolysis resistance of the polyester are remarkably lowered. . At this time, the mass ratio (P / M) of the total P amount (P) and the total metal ion amount (M) is 0.4 to 1.0 in terms of heat resistance, hydrolysis resistance, and the like. Is preferred. When the mass ratio (P / M) is less than 0.4 or exceeds 1.0, the film may be colored or coarse particles may be mixed in the film, which is not preferable. The timing of adding the above metal ions, phosphoric acid and derivatives thereof is not particularly limited. In general, metal ions are added at the time of raw material charging, that is, before transesterification or esterification, and phosphoric acids are added before polycondensation reaction. It is preferable to do this. Moreover, you may add various well-known additives in a raw material composition as needed. Examples of the additive include lubricants such as titanium dioxide, fine-particle silica, kaolin, and calcium carbonate; antistatic agents; anti-aging agents; ultraviolet absorbers; and colorants (dyes and the like).

  The raw material composition is dried using a dryer such as a hopper dryer or paddle dryer or a vacuum dryer, and extruded into a film at a temperature of 200 to 300 ° C. using an extruder. Alternatively, an undried polyester raw material chip is similarly extruded into a film while removing moisture in a vented extruder. As the polyester chip at this time, the copolyester having the composition described above may be used alone, or two or more kinds of polyesters having different compositions may be mixed and used so that the final composition falls within the range described above. May be. When extruding, any existing method such as T-die method or tubular method may be adopted. After extrusion, it is cooled rapidly to obtain an unstretched film. The “unstretched film” includes a film on which a tension necessary for feeding the film in the manufacturing process is applied.

  Stretching is performed on the unstretched film. The stretching treatment may be performed continuously after cooling with the above-described casting roll or the like, or may be wound up into a roll after cooling and then performed. Since it is practical in terms of production efficiency that the maximum shrinkage direction is the film transverse (width) direction, an example of a stretching method in the case where the maximum shrinkage direction is the transverse direction will be shown below. Even when the maximum shrinkage direction is the longitudinal (longitudinal) direction of the film, the film can be stretched in accordance with ordinary operations such as changing the stretching direction by 90 ° in the following method.

In order to make the thickness distribution of the heat-shrinkable polyester film uniform, it is preferable to perform a preheating step prior to the stretching step when stretching in the transverse direction using a tenter or the like. The film surface temperature is within a range of Tg + 0 ° C. to Tg + 60 ° C. at a low wind speed so that the coefficient is 0.00544 J / cm ² · sec · ° C. or less (0.0013 calories / cm ² · sec · ° C.). It is preferable to perform heating until. Stretching in the transverse direction is performed at a predetermined temperature within a range of Tg-20 ° C to Tg + 40 ° C, and is stretched 2.3 to 7.3 times, preferably 2.5 to 6.0 times. Thereafter, heat treatment is performed at 50 to 100 ° C. with 0 to 15% elongation or 0 to 15% relaxation, and further heat treatment is performed at 40 to 100 ° C. as necessary to obtain a heat-shrinkable polyester film. . As a stretching method, not only horizontal uniaxial stretching with a tenter but also stretching in the longitudinal direction by 1.0 to 2.2, preferably 1.1 to 1.8 times may be performed. This longitudinal (corresponding to the direction perpendicular to the maximum shrinking direction) stretching process improves the cut property and can satisfy the above-mentioned tear propagation resistance value and refractive index requirements. However, it is not preferable to stretch the film in excess of 2.2 times because the shrinkage rate in the direction perpendicular to the shrinkage direction increases and defects such as vertical shrinkage occur. When biaxial stretching is performed in this manner, either sequential biaxial stretching or simultaneous biaxial stretching may be performed, and restretching may be performed as necessary. Further, in the sequential biaxial stretching, any of stretching methods such as vertical and horizontal, horizontal and vertical, vertical and horizontal and horizontal and vertical and horizontal directions may be used. Focusing on the point of suppressing the internal heat generation of the film due to stretching and reducing the film temperature unevenness in the width direction, the heat transfer coefficient of the stretching process is 0.00377 J / cm ² · sec · ° C. (0.0009 calorie / cm ² · sec · ° C.) or higher. 0.00544 to 0.00837 J / cm ² · sec · ° C. (0.0013 to 0.0020 calories / cm ² · sec · ° C.) is more preferable.

  Although the total thickness of the heat-shrinkable polyester film of the present invention is not particularly limited, for example, a heat-shrinkable polyester film for labels is recommended to be 10 to 200 μm, preferably 20 to 100 μm.

  In order to use the heat-shrinkable polyester film as a heat-shrinkable label, for example, the heat-shrinkable film before shrinkage is stored for a predetermined time in an environment where temperature and humidity are controlled, and is taken out, and a known tubular molding apparatus is used. Is used to apply an adhesive solvent with a predetermined width slightly inward from the edge of one side of one end of the film, and the film is immediately rolled up, the ends are overlapped and bonded, and processed into a tube. This tube can be cut into a predetermined length to obtain the heat-shrinkable label of the present invention.

  The film can be bonded by a melt bonding method in which a part of the film is melted, but it is preferable to use a solvent from the viewpoint of suppressing fluctuations in the heat shrinkage characteristics of the label. Examples of solvents that can be used include aromatic hydrocarbons such as benzene, toluene, xylene, and trimethylbenzene; halogenated hydrocarbons such as methylene chloride and chloroform; phenols such as phenol; furans such as tetrahydrofuran; -Organic solvents such as oxolanes such as dioxolane; among others, 1,3-dioxolane and tetrahydrofuran are preferable because of their high safety. The heat-shrinkable label can be coated after being attached to a container such as a PET bottle and then heat-shrinkable by a known heat-shrinking means (hot air tunnel, steam tunnel, etc.).

  Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are not intended to limit the present invention, and modifications and implementations within the scope of the present invention are included in the present invention. The measuring method of the physical property of the film obtained by the Example and the comparative example is as follows.

(1) Thermal shrinkage rate The film was cut into a 10 cm × 10 cm square, immersed in 98 ± 0.5 ° C. warm water for 10 seconds under no load, and then thermally shrunk, then immediately 25 ± 0.5 ° C. Is immersed in water for 10 seconds, and then the length and width of the sample are measured. The heat shrinkage rate is calculated from the following formula: Heat shrinkage rate (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)
The value obtained according to The direction with the largest shrinkage rate was defined as the maximum shrinkage direction.

(2) Tear propagation resistance value The tear propagation resistance value is shown in FIG. 3 of JIS K7128-2, employing the Elmendorf tear method defined in JIS K7128-2 in the direction orthogonal to the maximum shrinkage direction of the film. It is a value measured using a rectangular test piece.

(3) Refractive index Nx in the direction orthogonal to the maximum shrinkage direction
Using an Abbe refractometer, the maximum shrinkage direction of the film, the direction perpendicular to this direction, and the refractive index in the thickness direction were measured. Table 2 shows only the refractive index Nx in the direction orthogonal to the maximum shrinkage direction.

(4) Solvent adhesiveness With the heat-shrinkable film wrapped around a paper tube, it was left in a thermo-hygrostat controlled at an ambient temperature of 30 ° C. ± 1 ° C. and a relative humidity of 85 ± 2% for 250 hours. After printing three colors with grass-colored, gold-colored, and white-colored inks manufactured by Toyo Ink Co., Ltd., using a center seal machine, a solvent was bonded with tetrahydrofuran to form a tube, which was wound in a folded state. The tube roll was left in a constant temperature and humidity chamber at a temperature of 23 ° C. ± 1 ° C. and a relative humidity of 65% ± 2% for 24 hours, then taken out, rolled up, and checked for adhesion. Evaluation was made with x indicating a part that was easily peeled by hand, △ indicating that it was peeled by hand with a light resistance, and ○ indicating that there was no part easily peeled by hand. ○ is a pass.

(5) Shrinkage finish The tube produced for the above-mentioned solvent adhesion evaluation was cut to produce a heat-shrinkable label. For those that could not be solvent-bonded, heat sealing was performed to produce a label. Next, the label was attached to a 500 ml square PET bottle, and then passed through an 85 ° C. steam tunnel (Fuji Astec Inc.) for 5 seconds to shrink the label. The degree of shrinkage whitening and shrinkage spots was judged visually, and the shrinkage finish was evaluated in five stages. Standards are 5: Best finish, 4: Good finish, 3: Shrinkage whitening or slight shrinkage spots (within 2 places), 2: Shrinkage whitening or shrinkage spots (3-5 places), 1: Shrinkage whitening or As the number of shrinkage spots (6 or more), 4 or more was judged as acceptable, and 3 or less was judged as defective.

(6) Perforation cut defect rate Heat shrinkability with two perforations (hole size: φ0.7 mm, hole interval: 2.5 mm) across the bonded part of the tube created in (4) The label was attached to a PET bottle and shrunk in the same manner as in (5). Before reaching the bottom edge of the label when the adhesive part is peeled off from the top edge of the label, the number of cuts other than at the perforation is regarded as defective. The following formula: Defect rate (%) = 100 x (defective Number) ÷ (total number of tests)
The defect rate was calculated.

Synthesis example 1
In a stainless steel autoclave equipped with a stirrer, thermometer and partial reflux condenser, 100 mol% of dimethyl terephthalate (DMT) as a dibasic acid component and 100 mol% of ethylene glycol (EG) as a glycol component Was added to the molar ratio of 2.2 times that of the methyl ester, and 0.05 mol% of zinc acetate (based on the acid component) was used as the transesterification catalyst, and the methanol produced was distilled out of the system. The transesterification reaction was carried out. Thereafter, 0.025 mol% of antimony trioxide (based on the acid component) was added as a polycondensation catalyst, and a polycondensation reaction was performed at 280 ° C. under a reduced pressure of 26.6 Pa (0.2 Torr). A polyester (A) of 70 dl / g was obtained. This polyester is polyethylene terephthalate. Further, polyesters shown in Table 1 were synthesized by the same method as described above. In the table, NPG is neopentyl glycol, CHDM is 1,4-cyclohexanedimethanol, and BD is 1,4-butanediol. The intrinsic viscosity of each polyester was 0.72 dl / g for B, 0.80 dl / g for C, and 1.15 dl / g for D. Each polyester was appropriately chipped.

Example 1
Polyester A: 6% by mass, Polyester B: 14% by mass, Polyester C: 56% by mass, Polyester D: Mixed by a ratio of 24% by mass, melt-extruded with a single screw extruder at 280 ° C., and then rapidly cooled. An unstretched film having a thickness of 200 μm was obtained. This unstretched film was preheated at 80 ° C., then stretched 1.88 times in the machine direction at 88 ° C., preheated at 85 ° C., and then stretched 4.0 times at 75 ° C. in the transverse direction, followed by 81 ° C. Then, heat treatment was performed in a tension state to obtain a heat-shrinkable polyester film having a thickness of 45 μm. The physical properties of the obtained film are shown in Table 2.

Comparative Example 1
Polyester A: 6% by mass, Polyester B: 14% by mass, Polyester C: 56% by mass, Polyester D: Mixed by a ratio of 24% by mass, melt-extruded with a single screw extruder at 280 ° C., and then rapidly cooled. An unstretched film having a thickness of 180 μm was obtained. This unstretched film is preheated at 85 ° C. and then stretched 4.0 times in the transverse direction at 85 ° C., followed by heat treatment in a tension state at 81 ° C. to obtain a heat-shrinkable polyester film having a thickness of 45 μm. It was. The physical properties of the obtained film are shown in Table 2.

Comparative Example 2
In Comparative Example 1, an unstretched film was obtained in the same manner as in Comparative Example 1, except that the composition of each polyester was changed as shown in Table 1. This unstretched film is preheated at 95 ° C. and then stretched 4.0 times in the transverse direction at 85 ° C., followed by heat treatment in a tension state at 81 ° C. to obtain a heat-shrinkable polyester film having a thickness of 45 μm. It was. The physical properties of the obtained film are shown in Table 2.

Comparative Example 3
In Comparative Example 1, an unstretched film was obtained in the same manner as in Comparative Example 1, except that the composition of each polyester was changed as shown in Table 1. This unstretched film is preheated at 83 ° C. and then stretched 4.0 times at 71 ° C. in the transverse direction, followed by heat treatment in a tension state at 70 ° C. to obtain a heat-shrinkable polyester film having a thickness of 45 μm. It was. The physical properties of the obtained film are shown in Table 2.

Comparative Example 4
In Comparative Example 1, an unstretched film was obtained in the same manner as in Comparative Example 1, except that the composition of each polyester was changed as shown in Table 1. This unstretched film is preheated at 83 ° C. and then stretched 4.0 times at 71 ° C. in the transverse direction, followed by heat treatment in a tension state at 70 ° C. to obtain a heat-shrinkable polyester film having a thickness of 45 μm. It was. The physical properties of the obtained film are shown in Table 2.

Example 2
Polyester A: 6% by mass, Polyester B: 14% by mass, Polyester C: 56% by mass, Polyester D: Mixed by a ratio of 24% by mass, melt-extruded with a single screw extruder at 280 ° C., and then rapidly cooled. An unstretched film having a thickness of 250 μm was obtained. This unstretched film is preheated at 80 ° C. and then stretched 4.0 times in the transverse direction at 75 ° C., followed by heat treatment in a tension state at 81 ° C. to obtain a heat-shrinkable polyester film having a thickness of 45 μm. It was. The physical properties of the obtained film are shown in Table 2.

Claims (4)

In the heat-shrinkable polyester film, among 100 mol% of the polyhydric alcohol component of the polyester constituting the film, 1,4-cyclohexanedimethanol is 10 mol% or more, neopentyl glycol is 2 mol% or more, and The total amount of 1,4-cyclohexanedimethanol and neopentyl glycol is 12 to 40 mol%,
When the sample cut into a 10 cm × 10 cm square shape is dipped in 98 ° C. warm water for 10 seconds and then dipped in 25 ° C. water for 10 seconds, the heat shrinkage rate in the maximum shrinkage direction is 50% or more. And
A heat-shrinkable polyester film having a tear propagation resistance value in a direction perpendicular to the maximum shrinkage direction of 1800 mN or less.   The heat-shrinkable polyester film according to claim 1, wherein the refractive index Nx in the direction orthogonal to the maximum shrinkage direction is 1.5590 or more.   The heat-shrinkable polyester film according to claim 1 or 2, wherein 1,4-butanediol is 2 mol% or more in 100 mol% of the polyhydric alcohol component of the polyester constituting the film.   A heat-shrinkable label using the heat-shrinkable polyester film according to claim 1.