JPH09174684A - Heat-shrinkable polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of the shrinkage irregularity in a hot-air type shrink tunnel by specifying the shrinkage factor at the time of heat and the maximum shrinkage velocity of a heat-shrinkable polyester film in one direction. SOLUTION: The polyester heat-shrinkable film has the shrinkage factor at 80 deg.C in one direction of 8 to 24% or preferably 8 to 35%, and the maximum shrinkage velocity at 100 deg.C of 0.5 to 24%/sec and at 140 deg.C of 10 to 40%/sec. The polyester resin used for the film is preferably resin composition which contains aromatic dicarboxylic acid or its ester forming derivative and polyvalent alcohol component as main ingredients and has glass transition temperature of relatively high value. To obtain the shrinkage factor of relatively low temperature of the polyester resin, it is preferable to contain polyoxytetramethylene glycol having a molecular weight of 300 to 3000 of a range of 1 to 10mol%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat-shrinkable polyester film (including a sheet) which exhibits particularly suitable heat-shrinkability in the field of packaging materials such as coating and binding, and does not cause uneven shrinkage. Is.

[0002]

2. Description of the Related Art Tubular bodies formed of heat-shrinkable plastic films are, for example, containers, bottles (including plastic bottles), can rods (pipes, rods, wood, various rods), etc. Abbreviated as a category) or for bundling, particularly covering or partially covering these caps, shoulders, torso, etc., and used for the purpose of marking, protection, bundling, improvement of commercial value, etc. It is widely used in fields such as boxes, plates, bottles, rods, notebooks, etc., such as integrated packaging, or skin packs, which are closely adhered to a covered material, and can be used for applications that utilize shrinkage and shrinkage stress. Be expected. Conventionally, polyvinyl chloride, polystyrene,
Using a heat-shrinkable film such as polyethylene or hydrochloric acid rubber,
This was made into a tubular body and then covered with the above-mentioned containers, or heat-shrinked by integrated packaging. However, these films have poor heat resistance and have a drawback that they cannot be maintained in a film form by melting or bursting when subjected to boil treatment or retort treatment. Furthermore, in applications that require printing, printing pinholes (fine irregularities due to fish eyes due to additives in the film and gel of polymer) may occur due to poor ink transfer, or even if printing is successful, There is also a problem that the film shrinks (shrinkage at room temperature) to cause a dimensional change in the printing pitch.

On the other hand, a polyester-based shrink film has characteristics that greatly improve the above-mentioned drawbacks, and has recently received a great deal of attention. However, the polyester-based heat-shrinkable film is not satisfactory in shrinkage finish as compared with the above-described heat-shrinkable films such as polyvinyl chloride, polystyrene, polyethylene, and hydrochloric acid rubber. For example, when a container such as a PET bottle or a glass bottle is covered and contracted as a label or the like, uneven contraction is likely to occur, air escape from the inside does not proceed smoothly, and problems such as inclusion of air bubbles in the seal part occur. To do. If such shrinkage unevenness occurs, it leads to density unevenness in printing, and the aesthetic appearance of the product is remarkably deteriorated. As a measure for improving this shrinkage unevenness, Japanese Patent Laid-Open No. 5-261816,
As disclosed in JP-A-5-305664, JP-A-6-877, JP-A-6-8322, etc., there are those having improved shrinkage characteristics in hot water at 60 ° C.

[0004]

However, while this alone satisfies the shrinkability at a relatively low temperature, it is insufficient to suppress the occurrence of shrinkage unevenness in the most common hot-air type shrink tunnel. In comparison with the heat-shrinkable films such as polyvinyl chloride, polystyrene, polyethylene, and rubber chloride, the shrink finish is not satisfactory.

[0005]

The present inventors have arrived at the present invention as a result of earnestly examining the heat shrinkage behavior of a polyester heat-shrinkable film in view of the above-mentioned prior art. That is, the polyester heat-shrinkable film of the present invention has a shrinkage rate of 80 ° C. in one direction of 8%.
% Or more and 40% or less, preferably 8% or more and 38% or less, and most preferably 8% or more and 35% or less. 1
If the shrinkage ratio at 80 ° C. in the direction is 8% or less, when the temperature is further increased, rapid shrinkage occurs and shrinkage unevenness occurs. Alternatively, when the temperature is further raised, sufficient shrinkage cannot be obtained, resulting in poor finish. On the other hand, when the shrinkage ratio at 80 ° C. in at least one direction is 40% or more, rapid shrinkage causes uneven shrinkage.

Further, in the present invention, the maximum shrinkage rate is 100% at 0.5% / sec or more and 24% / sec or less, and 140 ° C at 10% or less.
% / Sec or more and 40% / sec or less, preferably 0.5% / at 100 ° C
Second to 22% / sec, 140 ° C 15% / sec to 40% / sec, most preferably 100 ° C 0.5% / sec to 20% / sec, 140 ° C 20% / sec to 40% / sec It is less than a second. When this maximum shrinkage rate is 100% or more and 24% / sec or more, rapid shrinkage tends to cause shrinkage unevenness. 40% maximum contraction rate at 140 ° C
Even at a speed of more than 1 second, uneven shrinkage is likely to occur due to sudden shrinkage.
On the other hand, if it is 0.5% / sec or less at 100 ° C, sufficient shrinkage cannot be obtained, and the finished product tends to be defective. Even at 10% / sec or less at 140 ° C, sufficient shrinkage cannot be obtained, and the finished product tends to be defective. The polyester resin used in the heat-shrinkable polyester film of the present invention contains an aromatic dicarboxylic acid or its ester-forming derivative as a dicarboxylic acid component and a polyhydric alcohol component as main components.

Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalene-1.4- or -2,6-dicarboxylic acid. Examples of these ester derivatives include derivatives such as dialkyl esters and diaryl esters. Further, an aliphatic dicarboxylic acid can be contained within the range that does not impair the effects of the present invention. Examples of the aliphatic dicarboxylic acid that can be used in the present invention include glutaric acid, adipic acid, sebacic acid, dimer acid, azelaic acid, oxalic acid and succinic acid.

The polyhydric alcohol component of the polyester resin used in the heat-shrinkable polyester film of the present invention includes propylene glycol, triethylene glycol, butylene glycol, diethylene glycol, neopentyl glycol, cyclohexanedimethanol, bisphenol compound or its derivative. Ethylene oxide adduct, trimethylolpropane, glycerin, pentaerythritol, polyoxytetramethylene glycol, polyethylene glycol and the like. Also,
Although not a polyhydric alcohol, epsilon caprolactone can be used as well.

The polyester resin composition used in the heat-shrinkable polyester film of the present invention is not limited, but a resin composition which gives a relatively high glass transition temperature of the heat-shrinkable polyester film is preferred. For example, as the aromatic dicarboxylic acid, naphthalene-1.4- or -2,6-dicarboxylic acid or an ester derivative thereof is used in an amount of 10 mol% to 90 mol% in the total dicarboxylic acid component of the polyester resin, terephthalic acid or isophthalic acid. An acid in the range of 10 mol% to 90 mol% is included.

The polyester resin of the present invention has, for example, a molecular weight of 30 in order to ensure the shrinkability at a relatively low temperature.
1 to 0 to 3000 polyoxytetramethylene glycol
It is preferable to contain it in the range of not less than mol% and not more than 10 mol%. If it is less than 1 mol%, the shrinkage at a comparatively low temperature cannot be secured, and if it is more than 10 mol%, the shrinkage at a low temperature becomes large.
It naturally shrinks when stored and cannot be put to practical use. For the purpose of enhancing the effect of the present invention and controlling the amount of shrinkage, it is preferable to contain an aliphatic dicarboxylic acid such as neopentyl glycol in the range of 5 mol% or more and 50 mol% or less.

The polyester may be used alone or in combination of two or more kinds. When two or more kinds are used in combination, it may be a combination of polyethylene terephthalate and a copolyester or a combination of copolyesters. Further, it may be a combination with a homopolyester such as polybutylene terephthalate or polycyclohexylene dimethyl terephthalate. 2
The combined use of two or more polyesters is more preferable because a film having various properties can be produced.

The polyester can be produced by melt polymerization by a conventional method, but is not limited to this and may be a polyester obtained by another polymerization method or melt kneading. If necessary, a lubricant such as titanium dioxide, silica, kaolin or calcium carbonate may be added, and an antistatic agent, an anti-degradation agent, an anti-ultraviolet agent or a dye as a colorant may be added. I can. The intrinsic viscosity of the film base material is preferably 0.50 or more and 1.30 dl / g or less. A film obtained by any method such as an extrusion method or a calender method using such a polymer is finally stretched in one direction from 2.5 times to 7.0 times, preferably from 3.0 times to 6.0 times. The film is stretched 1.0 to 2.0 times or less, preferably 1.1 to 1.8 times in the direction perpendicular to the direction. However, when it is stretched over 2.0 times, the thermal shrinkage in the direction perpendicular to the main shrinkage direction becomes too large, and the finished product becomes wavy. In order to suppress this waviness, it is recommended that the heat shrinkage rate be 15% or less, preferably 9% or less, and more preferably 7% or less.
The stretching method is not particularly limited, and stretching methods such as roll stretching, long gap stretching, and tenter stretching are applied, and the shape may be flat or tubular. In addition, sequential biaxial stretching is effective for stretching, and either order may be first. The heat setting in the stretching is carried out according to the purpose, but in order to prevent the dimensional change under high temperature in summer, a heating zone of 30 to 150 ° C. for about 1 second to 30
It is recommended to pass for 2 seconds. Further, before or after such processing, or both may be expanded up to 70%. In particular, it is preferable to extend in the main direction and relax in the non-contraction direction (direction perpendicular to the main contraction direction), and it is better not to extend in the perpendicular direction.

In order to exert the preferable characteristics of the present invention,
In addition to the above stretching ratio, it is effective to stretch at a temperature near the average glass transition temperature (Tg) of the polymer composition and in several stages (preferably at least 3 stages). . Especially in the above treatment temperature in the main-direction stretching (main shrinkage direction), preheating is from Tg + 0 ° C to +5.
It is important that the stretching is carried out at a temperature difference of 0 ° C. or less so that the temperature gradually rises at a temperature within the range of Tg−20 ° C. to + 30 ° C. In addition, it is also important to stop the stretching once during the stretching, provide a relaxation step, and then perform the second stretching step so that the total stretching ratio becomes a predetermined stretching ratio.

After stretching, the film is cooled while applying tension to the film while keeping the film in a stretched or tensioned state, or by further cooling it, so that the pre- and post-treatment properties become better and more stable. In addition, since the shrinkage rate is in an appropriate range by stretching at multiple stages of temperature in this way, a state in which the difference in shrinkage rate is small with respect to the temperature unevenness of the heat shrinking tunnel is realized, and uneven shrinkage occurs. A film that is difficult to obtain is obtained.

The film of the present invention will be described below from the viewpoint of use. Boiling and retorting are performed in packaging applications, especially in packaging of foods and beverages. No existing heat-shrinkable film can withstand these treatments sufficiently. The film of the present invention can withstand heat sterilization by boil treatment or retort treatment, and also the appearance of the original film, and further the finishability by heat shrinkability is also good, and also polyvinyl chloride or polystyrene heat shrink It has a higher heat shrinkage stress than the film, and is also excellent in cohesion. The details will be described below. (A) Impact resistance One of the roles of the shrink film is to prevent the packaged items from being broken or collapsed. For that purpose, it has high impact resistance and a large shrinkage in the main direction. It is necessary. In that respect, the film of the present invention has a high shrinkage ratio and a high impact resistance, so that a beautiful packaging can be obtained, and further, excellent durability is exhibited in terms of protection of an article to be packaged. This tendency is proved by the drop test. (B) Heat resistance All of the conventional general-purpose films cannot withstand high temperature boil treatment or retort treatment and are inappropriate for sterilization treatment, and they are destroyed during the treatment and lose their functions. The film of (1) shows excellent usefulness as a heat shrinkable film that can be boiled or retorted.

(C) Printability The conventional film has inherent drawbacks with respect to the generation of pinholes and the adhesion to ink by halftone printing, but the polyester film has a chemical resistance and is a copolymer. As a result, the printability was improved because the adhesiveness was improved. (D) Problems of industrial waste In recent years, the use of plastic bottles has been rapidly spreading. When considering the recovery of such a bottle, it is preferable to form the same material, and it is advantageous to apply the film of the present invention to the packaging of a polyester bottle. (E) Shrinkage unevenness The film of the present invention has a high shrinkage ratio and a high shrinkage stress, and since the maximum shrinkage acceleration is appropriate, shrinkage unevenness does not occur.

(Examples) The present invention will be described in detail below by showing Examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The measuring method used in the present invention is shown below. (1) Maximum shrinkage speed First, a DF-42 type dry oven manufactured by Yamato Scientific Co., Ltd.
Set the air flow rate scale to 0 (fan speed: about 460 rpm), set the air damper closed, set the measurement temperature, and raise the temperature. Next, the sample size is the main shrinkage direction 5 cm, and the orthogonal direction 4
Cut out to cm and hang it with a small load of 4.7 g. Furthermore, the sample was placed in a dry oven heated to a predetermined temperature for 0 seconds, and the time change of contraction was recorded with a video camera through a window modified to allow external observation, and quantification was performed every second. It was The maximum change in the shrinkage rates with respect to the time thus obtained was defined as the maximum shrinkage rate.

(2) Shrinkage rate A hot air circulation type thermostat FX-1 type dry oven manufactured by Peng Seisakusho Co., Ltd. is set to the measurement temperature and the temperature is raised. Next, the sample size is cut out into a square with the main shrinking direction of 10 cm and the orthogonal direction of 10 cm, and it is hung on a jig. Further, it is placed in an oven heated to a predetermined temperature for 0 second in time, taken out after 10 seconds, and cooled and fixed at room temperature. Quantification was performed by a method of measuring the shrinkage ratio after cooling and fixing.

(3) Shrinkage Finishing Property A printed heat shrinking film was attached to a glass bottle (300 ml) and passed through a heat shrinking tunnel of 150 ° C. hot air (air velocity of 10 m / sec) to visually judge the finishing property. In addition,
The rank of finishability was evaluated on a scale of 5: 5: Best finishability 4: Good finishability 3: Some shrinkage unevenness (within 2 places) 2: Shrinkage unevenness (3 to 6 places) 1: Many shrinkage unevenness ( 6 or more), and 4 or more were defined as the passing level.

Example 1 Using a stainless steel autoclave, 30 mol% of dimethyl terephthalate and 70 mol% of dimethyl naphthalate as dibasic acid components, 80 mol% of ethylene glycol as glycol component, and 20 mol% of neopentyl glycol.
In the above composition, glycol was added so that it would be twice the molar amount of methyl ester, and zinc acetate was added as a transesterification catalyst to 0.1 mol.
The transesterification reaction was carried out using 05 mol (based on the acid component). Then, 2 mol% of polytetramethylene glycol (molecular weight 650) (based on the acid component), antimony trioxide 0.025 mol (based on the acid component) as a catalyst, and 0.05 mol (based on the acid component) as an additive. hand)
Was polycondensed. As a result, 30 mol% of terephthalic acid component, 70 mol% of 2,6 naphthalenedicarboxylic acid component, 74 mol% of ethylene glycol component, 21 mol% of neopentyl glycol component, and 5 mol of polytetramethylene glycol (molecular weight 650) component A polyester consisting of mol% was obtained. This copolymer had an intrinsic viscosity of 0.70 dl / g. This polyester is melt extruded at 280 ° C. to a thickness of 1
An unstretched film of 80 μm was obtained. The film was stretched 1.1 times in the machine direction at a stretching rate of 10500% / min at 115 ° C, then preheated at 120 ° C for 3 seconds and then stretched in the transverse direction at a first stage of 6300% / min for 6 seconds. 1.5 times at 100 ℃, then hold at 100 ℃ for 3 seconds for a fixed length, then 105 ℃, 110
The film was divided into two zones at 0 ° C. and stretched to a total of 4.1 times. Then, heat treatment was performed at 110 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Example 2 According to the polymerization method of Example 1, 70 mol% of terephthalic acid component
A polyester comprising 30 mol% of 2,6 naphthalenedicarboxylic acid component, 29 mol% of ethylene glycol component, 67 mol% of neopentyl glycol component and 4 mol% of polytetramethylene glycol (molecular weight 650) component was obtained. This copolymer had an intrinsic viscosity of 0.71 dl / g. This polyester was melt extruded at 290 ° C. to obtain an unstretched film having a thickness of 180 μm. The film was stretched 1.1 times in the machine direction at a stretching rate of 11000% / min at 95 ° C., then preheated at 95 ° C. for 3 seconds, then stretched in the transverse direction at a first stage of 7100% / min, 1.5 times at 80 ℃, then 80 ℃
The sample was held at a constant length for 3 seconds, and subsequently stretched to a total of 4.1 times in two zones of 85 ° C and 95 ° C. Then, heat treatment was carried out at 80 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Comparative Example 1 By the polymerization method of Example 1, 80 mol% of terephthalic acid component
A polyester comprising 20 mol% of 2,6 naphthalenedicarboxylic acid component, 94 mol% of ethylene glycol component, 4 mol% of neopentyl glycol component and 2 mol% of polytetramethylene glycol (molecular weight 650) component was obtained. This copolymer had an intrinsic viscosity of 0.70 dl / g. This polyester is melt extruded at 280 ° C to a thickness of 1
An unstretched film of 80 μm was obtained. The film was stretched 1.1 times in the machine direction at 85 ° C. at a stretching speed of 10500% / min,
Preheat at 95 ℃ for 3 seconds, then draw the first stage in the transverse direction 71
Stretching rate at 00% / min, 1.5 times at 85 ° C, then 3 at 85 ° C
The sample was held for a fixed length of time for two seconds, and subsequently stretched to a total of 4.1 times in two zones of 95 ° C and 100 ° C. Then, heat treatment was performed at 100 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Comparative Example 2 By the polymerization method of Example 1, 90 mol% of terephthalic acid component
A polyester comprising 10 mol% of 2,6 naphthalenedicarboxylic acid component, 80 mol% of ethylene glycol component, 19 mol% of neopentyl glycol component and 1 mol% of polytetramethylene glycol (molecular weight 650) component was obtained. This copolymer had an intrinsic viscosity of 0.69 dl / g. This polyester is melt extruded at 295 ° C to a thickness of 18
An unstretched film of 0 μm was obtained. The film vertically
Stretching 1.1 times at 11000% / min, 130 ° C,
Then, preheating was carried out at 125 ° C. for 3 seconds and then in the transverse direction at a drawing speed of 7200% / min, and at 120 ° C., the film was drawn up to 4.1 times. Then 140
Heat treatment was performed at ℃ for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Comparative Example 3 According to the polymerization method of Example 1, 95 mol% of terephthalic acid component
A polyester comprising 5 mol% of 2,6 naphthalenedicarboxylic acid component, 64 mol% of ethylene glycol component, 35 mol% of neopentyl glycol component and 1 mol% of polytetramethylene glycol (molecular weight 650) component was obtained. This copolymer had an intrinsic viscosity of 0.71 dl / g.
This polyester is melt extruded at 275 ℃ and the thickness is 180μ.
An unstretched film of m was obtained. The film is lengthwise 110
It was stretched 1.1 times at a stretching rate of 00% / min at 90 ° C., then preheated at 120 ° C. for 3 seconds, and then stretched in the transverse direction at a stretching rate of 6800% / min at 90 ° C. to 4.0 times. Then, heat treatment was performed at 75 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Comparative Example 4 By the polymerization method of Example 1, a polyester comprising 100 mol% of a terephthalic acid component, 98 mol% of an ethylene glycol component and 2 mol% of a polytetramethylene glycol (molecular weight 650) component was obtained. This copolymer has an intrinsic viscosity of 0.
It was 70 dl / g. This polyester was melt extruded at 285 ° C. to obtain an unstretched film having a thickness of 180 μm. The film was stretched in the machine direction in the machine direction at 9000% / min at 90 ° C. for 1.
Stretched 05 times, then preheated at 110 ℃ for 3 seconds, then transversely
It was stretched to 4.0 times at 85 ° C. at a stretching rate of 6300% / min.
Then, heat treatment was performed at 75 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Comparative Example 5 By the polymerization method of Example 1, 5 mol% of terephthalic acid component
A polyester comprising 95 mol% of 2,6 naphthalenedicarboxylic acid component, 75 mol% of ethylene glycol component, and 25 mol% of neopentyl glycol component was obtained. This copolymer had an intrinsic viscosity of 0.71 dl / g. This polyester was melt extruded at 290 ° C. to obtain an unstretched film having a thickness of 180 μm. The film is stretched 1.1 times in the machine direction at a stretching rate of 11000% / min at 120 ° C. and then preheated at 140 ° C.
C., 3 seconds, then 1st stage stretching in the transverse direction at 6800% / min, 1.5 times at 120.degree. C., followed by a fixed length grip at 120.degree. C. for 3 seconds, followed by two zones of 125.degree. C. and 130.degree. And stretched to a total of 4.1 times. Then heat treatment at 100 ℃ for 5.5
Second, a heat shrinkable film having a thickness of 40 μm was obtained. The physical properties of the obtained film are shown in Table 1.

Comparative Example 6 By the polymerization method of Example 1, 90 mol% of terephthalic acid component
A polyester comprising 10 mol% of 2,6 naphthalenedicarboxylic acid component, 70 mol% of ethylene glycol component and 20 mol% of neopentyl glycol component was obtained. This copolymer had an intrinsic viscosity of 0.72 dl / g. This polyester was melt extruded at 290 ° C. to obtain an unstretched film having a thickness of 180 μm. The film was stretched 1.1 times in the machine direction at a stretching rate of 10000% / min at 100 ° C. and then preheated
C., 3 seconds, then the first stage drawing in the transverse direction at a drawing speed of 7100% / min, 1.5 times at 100.degree. C., then at 100.degree. C. for 3 seconds with constant length grip, and subsequently at 105.degree. C. and 110.degree. C. in 2 zones. And stretched to a total of 4.1 times. Then heat treatment at 105 ℃ for 5.5
Second, a heat shrinkable film having a thickness of 40 μm was obtained. The physical properties of the obtained film are shown in Table 1.

Comparative Example 7 By the polymerization method of Example 1, 82 mol% of terephthalic acid component
A polyester comprising 18 mol% of isophthalic acid component, 95 mol% of ethylene glycol component, and 5 mol% of polytetramethylene glycol (molecular weight 1000) component was obtained. This copolymer had an intrinsic viscosity of 0.70 dl / g. This polyester was melt extruded at 270 ° C. to obtain an unstretched film having a thickness of 180 μm. The film is preheated at 85 ° C. for 3 seconds, then transversely stretched at 7100% / min stretch rate of 4.0 at 65 ° C.
Stretched to double. Then, heat treatment was performed at 60 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. As is clear from Table 1 showing the physical properties of the obtained film, it was found that the film of the present invention had a desired finish.

[0029]

EFFECTS OF THE INVENTION A heat-shrinkable polyester film exhibiting particularly suitable heat-shrinkability in the field of packaging materials such as coating or binding and having good finish is provided.

[0030]

[Table 1]

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[Procedure amendment]

[Submission date] February 5, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0030

[Correction method] Change

[Correction contents]

[0030]

[Table 1]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 7:00 C08L 67:00

Claims (3)

[Claims] 1. A heat-shrinkable polyester film having a shrinkage ratio of 8% or more and 40% at 80 ° C. in one direction.
And the maximum shrinkage rate in one direction is 0.5 at 100 ° C
% / Sec or more and 24% / sec or less, 10% / sec or more 40% / at 140 ° C
A heat-shrinkable polyester film characterized by being less than a second. 2. A heat-shrinkable polyester film according to claim 1, which contains a naphthalene dicarboxylic acid residue. 3. A heat-shrinkable polyester film, wherein the film according to claim 1 contains an orioxytetramethylene glycol residue.