JP2003041028A - Heat-shrinkable polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester film having excellent shrinking characteristics in a wide temperature region, without shrinkage whitening, uneven shrinkage, wrinkles, strain or longitudinal shrink marks, having excellent breaking resistance and solvent adhesiveness, and suitable as labels. SOLUTION: This heat-shrinkable polyester film has >=50% heat shrinkage percentage in the maximum shrinking direction in hot water at 95 deg.C for 10 s and <=10% number of test specimens having <=5% breaking elongation when the heat-shrinkable polyester film is preserved in the environment at 30 deg.C and 85% relative humidity for 2 weeks and tensile tests are carried out on a plurality of test specimens in the rectangular direction to the maximum shrinkage direction of the preserved films at right angles under conditions of 100 mm distance between chucks, 15 mm test specimen width, 23 deg.C temperature and 200 mm/min speed of testing rate of stressing. The polyester film can be adhered with a nonchlorine organic solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable polyester film, and more specifically, a heat-shrinkable polyester film having extremely few defects such as shrinkage whitening after shrinkage and shrinkage spots, wrinkles, distortions and vertical sink marks. It's about film.

[0002]

2. Description of the Related Art Heat-shrinkable plastic films are widely used for shrink-wrapping, shrink-labeling, etc. due to their property of shrinking by heating. Among them, stretched films such as polyvinyl chloride film, polystyrene film and polyester film are used for label or cap seal or integrated packaging in various containers such as polyethylene terephthalate (PET) container, polyethylene container and glass container. It is used.

However, the polyvinyl chloride film has a low heat resistance and generates hydrogen chloride gas when incinerated.
It has problems such as causing dioxin. Further, when the heat-shrinkable vinyl chloride resin 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 excellent finished appearance after shrinkage, but since it has poor solvent resistance, it is necessary to use an ink having a special composition for printing. Further, the polystyrene resin needs to be incinerated at a high temperature and also has a problem that a large amount of black smoke and a strange odor are generated during incineration.

Polyester films free from these problems are highly expected as shrink labels that replace polyvinyl chloride films and polystyrene films.
As the usage of PET containers increases, the usage also tends to increase.

However, the conventional heat-shrinkable polyester film has also been required to be further improved in its shrinkage property. In particular, when shrinking, shrinkage spots and wrinkles occur, and the letters and patterns printed on the film before shrinking are
When a container such as a bottle, a polyethylene bottle, or a glass bottle is shrunk by coating, it may be distorted after shrinking, and there has been a user's request to reduce this distortion as much as possible.

Further, compared with heat-shrinkable polystyrene film, polyester film may be inferior in shrinkability at low temperature, and therefore, it has to be shrunk at high temperature in order to obtain a required shrinkage amount. Deformation or bleaching may occur.

By the way, when the heat-shrinkable film is used for the actual coating process of the container, it is subjected to a printing process if necessary, and then processed into a label (cylindrical label), a tube, a bag or the like. The inside of a shrink tunnel (steam tunnel) of the type that attaches these processed films to a container and blows steam to shrink heat, or a shrink tunnel of the type that blows hot air to shrink heat (hot air tunnel) It is placed on a conveyor or the like, passed through it, heat-shrinked, and brought into close contact with the container.

The steam tunnel has a better heat transfer efficiency than the hot air tunnel and can be more uniformly heated and shrunk. As compared with the hot air tunnel, a good shrink finish appearance can be obtained. The polyester film has a problem that the shrink finish after passing through the steam tunnel is not so good as compared with the polyvinyl chloride film and the polystyrene film.

When a hot-air tunnel is used which tends to cause temperature unevenness during heat shrinkage, shrinkage whitening, shrinkage unevenness, wrinkles, distortion, etc. are likely to occur in the polyester film, and shrinkage whitening is a problem in terms of product appearance. Was becoming. Further, there is a problem that the polyester film is inferior to the polyvinyl chloride film and the polystyrene film in the shrink finish property after passing through the hot air tunnel.

Further, if the degree of stretching is increased in order to secure the shrinkage, the film is likely to break in the direction orthogonal to the shrinking direction, causing troubles in the printing process, the label processing process, or the film after shrinking. Sometimes.
This breakage trouble is likely to occur when stored for a long period of time in a relatively high temperature atmosphere of 30 ° C. or higher, and it has been desired to improve this breakage trouble.

[0012]

The present invention solves the problems of the conventional heat-shrinkable polyester film as described above, and has excellent shrinkage characteristics in a wide temperature range from low temperature to high temperature. Shrinkage whitening, shrinkage spots, wrinkles, distortion,
It is an object of the present invention to provide a heat-shrinkable polyester film suitable for label applications, in which the occurrence of vertical shrinkage is extremely small and the tear resistance and solvent adhesion are excellent.

[0013]

The heat-shrinkable polyester film of the present invention is prepared by cutting a sample of the heat-shrinkable polyester film cut into a square shape of 10 cm × 10 cm.
Immerse in warm water at 95 ° C for 10 seconds and pull up, then 25
The heat-shrinkable polyester film is stored for 2 weeks in an environment of a temperature of 30 ° C. and a relative humidity of 85% when the heat-shrinkage ratio in the maximum shrinkage direction when immersed in water at 10 ° C. for 10 seconds and pulled up is 50% or more. The tensile test in the direction orthogonal to the maximum shrinkage direction of the film after the storage was carried out for a plurality of test pieces with a chuck distance of 100 mm, a test piece width of 15 mm,
When performed at a temperature of 23 ° C. and a pulling speed of 200 mm / min, the number of test pieces having a breaking elongation of 5% or less is 10 of the total number of test pieces.
% Or less and can be bonded with a non-chlorine organic solvent. With this configuration, it is possible to provide a heat-shrinkable polyester film having excellent shrinkage properties in a wide temperature range from low temperature to high temperature, good shrink finish, and excellent tear resistance and solvent adhesion. did it.

Of the polyhydric alcohol components constituting the polyester, the 1,4-cyclohexanedimethanol component is 10 mol% or more, the neopentyl glycol component is 2 mol% or more, and the 1,4-cyclohexanedimethanol component is And the total amount of neopentyl glycol component is 12
It is preferably ˜40 mol%. By using these polyhydric alcohol components, shrink whitening, shrinkage spots, wrinkles,
The occurrence of distortion and vertical sinking is further reduced, and it is particularly effective in suppressing shrinkage whitening in a hot air tunnel. The polyhydric alcohol component further contains 1,4-butanediol component.
It is preferably contained in an amount of at least mol%, and the appearance of shrinkage finish becomes beautiful especially in a low temperature range.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-shrinkable polyester film of the present invention is obtained by immersing a sample cut into a square shape of 10 cm × 10 cm in warm water of 95 ° C. for 10 seconds and then immediately pulling it in water of 25 ° C. for 10 seconds. The thermal shrinkage in the maximum shrinkage direction when immersed and pulled up must be 50% or more. When the heat shrinkage rate of the film is less than 50%, the heat shrinkage force of the film is insufficient, and when the film is shrunk by covering the container or the like, the film does not adhere to the container and an appearance defect occurs, which is not preferable. The higher the heat shrinkage is, the more preferable. Therefore, the more preferable heat shrinkage is 60% or more, and further preferably 70% or more.

Here, the thermal contraction rate in the maximum contraction direction means the thermal contraction rate in the most contracted direction of the sample,
The maximum contraction direction is determined by the length of the square in the vertical direction or the horizontal direction (or the diagonal direction). Also, heat shrinkage (%)
Is 10 cm x 10 cm sample immersed in warm water of 95 ° C ± 0.5 ° C for 10 seconds under no load condition to cause heat shrinkage, and then in water of 25 ° C ± 0.5 ° C under no load condition. The length of the film in the machine direction and the transverse direction (or the oblique direction) after being immersed for 10 seconds was measured, and the following equation: heat shrinkage rate = 100 × (length before shrinkage−length after shrinkage) ÷ (before shrinkage) (Length of)).

The present invention also provides a heat-shrinkable polyester film having excellent tear resistance. As a guide, a heat-shrinkable polyester film is used under the environment of a temperature of 30 ° C. and a relative humidity of 85%. After being stored for 2 weeks, a tensile test in a direction orthogonal to the maximum shrinkage direction of the film after the storage was performed. A plurality of test pieces had a chuck distance of 100 mm, a test piece width of 15 mm, a temperature of 23 ° C., and a pulling speed of 200 mm / min. Elongation at break of 5%
The number of test pieces below must be 10% or less of the total number of test pieces. Before the tensile test, the heat-shrinkable polyester film is stored for 2 weeks in an environment of a temperature of 30 ° C. and a relative humidity of 85%.
Since it is stored at 25 ° C., it is possible to accelerate the deterioration of tear resistance by storing it at a temperature higher than the normal storage condition of 30 ° C. and high humidity of 85% relative humidity for 2 weeks. is there. Further, the tensile test in the direction orthogonal to the maximum shrinkage direction is carried out by stretching the polyester molecular chains along the shrinkage direction to increase the strength in the maximum shrinkage direction, while the direction orthogonal to this direction is This is because the entanglement between adjacent molecular chains is reduced and the strength is reduced, and the molecular chains are easily broken, that is, the molecular chains are easily torn along the orientation direction.

The fact that the number of test pieces having a breaking elongation of 5% or less is 10% or less of the total number of test pieces means that in other words, a film that breaks before being stretched by 5% has a total number of test pieces. Is 10% (10%) or less. The smaller the number of test pieces having a breaking elongation of 5% or less, the more preferable. Films satisfying the above conditions have excellent tear resistance even when stored under high temperature and high humidity, so that loss due to cutting of the film during printing or tubing can be reduced, and high speed. Processing is possible.

Further, the heat-shrinkable polyester film of the present invention is preferably a film which can be adhered with a solvent for processing into a cylindrical label, and in consideration of generation of toxic substances due to halogen such as chlorine atom. Therefore, it is also an essential requirement to be able to bond with a non-chlorine organic solvent. Since the film of the preferred embodiment of the present invention has excellent solvent adhesiveness, a strong adhesive portion can be formed without using a highly toxic non-chlorine organic solvent.

Specific solvents that can be used include aromatic hydrocarbons such as benzene, toluene, xylene and trimethylbenzene; phenols such as phenol; furans such as tetrahydrofuran; oxolanes such as 1,3-dioxolane. In particular, it is preferable to use tetrahydrofuran or 1,3-dioxolane from the viewpoint of safety.

In order to satisfy the above-mentioned requirements for tear resistance and to enhance the properties relating to the physical strength of the film such as film strength and heat resistance, the polyester film has a crystalline unit (ethylene terephthalate unit, etc.). However, the thermal shrinkage rate is low only with the crystalline unit, and a high thermal shrinkage rate of 50% or more cannot be achieved by hot water treatment at 95 ° C. for 10 seconds. Therefore, in the present invention, the composition of the polyester film is adjusted and the heat shrinkability is enhanced by using 1,4-cyclohexanedimethanol and neopentyl glycol as constituent components.

1,4-cyclohexanedimethanol is
It has the effect of increasing the degree of amorphization and exhibiting heat shrinkability. In addition, the use of 1,4-cyclohexanedimethanol improves shrink finish and solvent adhesion. In order to sufficiently obtain these effects, it is preferable that 1,4-cyclohexanedimethanol is 10 mol% or more in 100% of the polyhydric alcohol component.

Further, the shrinkage whitening phenomenon is likely to occur when heat shrinking is performed in a hot air tunnel, or when heat shrinking is performed after being stored in an atmosphere of 30 ° C. or higher for a long period of time. It is considered that this shrinkage whitening phenomenon may occur because the molecular chain of the polyester is partially crystallized and the light refractive index of the crystal part is different from that of the amorphous part. Shrinkage whitening is a phenomenon that is not preferable as a label because it reduces transparency, but this shrinkage whitening phenomenon could also be suppressed by using 1,4-cyclohexanedimethanol. 1,
The amount of 4-cyclohexanedimethanol is more preferably 12 mol% or more, further preferably 14 mol% or more.

Further, the polyhydric alcohol component 100 mol%
It is also a preferred embodiment that neopentyl glycol is contained in an amount of 2 mol% or more. Since neopentyl glycol has the action of lowering the Tg of polyester, good shrink finish can be obtained in the low temperature range. Therefore, by using an appropriate amount of neopentyl glycol, a film exhibiting a heat shrinkage force in a wide temperature range from low temperature to high temperature can be obtained. The more preferable amount of neopentyl glycol is 4 mol% or more, and further preferably 6 mol% or more.

As described above, in the heat-shrinkable polyester film of the present invention, a crystalline ethylene terephthalate unit is used as a constituent component of the polyester base in order to exhibit tear resistance, strength, heat resistance and the like. Is desirable. Then, it is preferable that the use of the above 1,4-cyclohexanedimethanol and neopentyl glycol lowers the crystallinity of the polyester, increases the degree of amorphization, and exhibits a high heat shrinkage rate. Therefore, when the total amount of 1,4-cyclohexanedimethanol and neopentyl glycol is less than 12 mol%, the ethylene terephthalate unit increases and the crystallinity of the polyester increases, resulting in insufficient shrinkage and whitening phenomenon due to partial crystallization. May occur. Also, the solvent resistance becomes too high,
When a film is adhered to a tubular body using a solvent such as tetrahydrofuran or 1,3-dioxolane, adhesion failure may occur, which is not preferable. The total amount of 1,4-cyclohexanedimethanol and neopentyl glycol in 100 mol% of the polyhydric alcohol component is more preferably 16 mol% or more, further preferably 20 mol% or more. In addition, in 1,4-cyclohexanedimethanol and neopentyl glycol, it is preferable to use more 1,4-cyclohexanedimethanol than neopentyl glycol. This is because the more 1,4-cyclohexanedimethanol is more effective in suppressing the above-mentioned shrinkage whitening phenomenon.

However, 100 mol% of polyhydric alcohol component
It is desired that the total amount of 1,4-cyclohexanedimethanol and neopentyl glycol is suppressed to 40 mol% or less. If 1,4-cyclohexanedimethanol and neopentyl glycol are used in a total amount of more than 40 mol%, the shrinkage rate of the film becomes excessively high, resulting in label misalignment and pattern distortion in the heat shrinking process. There is a risk of Further, since the solvent resistance of the film is lowered, the solvent of the ink (ethyl acetate or the like) causes whitening of the film in the printing step and the tear resistance of the film is lowered, which is not preferable. Therefore, the total amount of these is 3
7 mol% or less is more preferable, and 35 mol% or less is further preferable.

As the polyhydric alcohol component, 1,4
Using butanediol is also a preferred embodiment in the polyester of the present invention. Since 1,4-butanediol lowers the Tg of the polyester and contributes to the expression of low-temperature shrinkability, the resulting film exhibits excellent shrink finish even in a relatively low temperature range. Also, the solvent adhesiveness becomes excellent. In order to obtain these effects, in 100 mol% of the polyhydric alcohol component, 1,
It is preferable to use 4-butanediol in an amount of 2 mol% or more. A more preferred lower limit is 3 mol%, and a still more preferred lower limit is 5 mol%. However, when the amount of the 1,4-butanediol component is too much, the number of ethylene terephthalate units responsible for properties such as tear resistance, strength, and heat resistance of the film decreases, so that 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-propane Alkylene glycols such as diols, 1,9-nonanediols and 1,10-decanediols, alkylene oxide adducts of bisphenol compounds or their derivatives,
Trimethylolpropane, glycerin, pentaerythritol, polyoxytetramethylene glycol, polyethylene glycol and the like can also be used in combination.

As the polycarboxylic acid component, aromatic dicarboxylic acids, their ester-forming derivatives, aliphatic dicarboxylic acids and the like can be used. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalene-
1,4- or -2,6-dicarboxylic acid, 5-sodium sulfoisophthalic acid and the like can be mentioned. 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. Further, an oxycarboxylic acid such as p-oxybenzoic acid or a polyvalent carboxylic acid such as trimellitic anhydride or pyromellitic dianhydride may be used in combination as necessary.

The polyester does not necessarily have to be produced from 100 mol% of the polyvalent carboxylic acids and 100 mol% of the polyhydric alcohol, and a polyester unit is formed by ring-opening polymerization of lactones (ε-caprolactone etc.). Good. The combined use of lactones has the function of increasing the degree of amorphism. When calculating the ratio (mol%) of each component in the dicarboxylic acid component and the polyhydric alcohol component, the ring-opening component of the lactone is calculated as corresponding to both the dicarboxylic acid component and the polyhydric alcohol component. To do.

The crystalline ethylene terephthalate unit is preferably contained in an amount of 50 mol% or more as a unit constituting the polyester from the viewpoint of tear resistance and the like. Therefore, in 100 mol% of the polyhydric alcohol component, ethylene glycol is included. 50 mol% or more, polyvalent carboxylic acid component 1
It is preferable to use terephthalic acid (or its ester) in an amount of 50 mol% or more in 00 mol%. The ethylene terephthalate unit content is more preferably 55 mol% or more, further preferably 60 mol% or more. However, in the present invention, it is preferable to use 12 mol% or more of 1,4-cyclohexanedimethanol and neopentyl glycol in 100 mol% of the polyhydric alcohol component. Therefore, ethylene glycol is preferably set to 88 mol% at the maximum. . When 2 mol% or more of butanediol is used in combination, ethylene glycol is preferably 86% or less at the maximum.

Polyesters can be produced by melt polymerization by a conventional method, but the so-called direct polymerization method, which is a direct polymerization method of directly reacting a polyvalent carboxylic acid and a glycol to polycondensate the obtained oligomer, a dimethyl ester of a polyvalent carboxylic acid A so-called transesterification method and the like, in which the body and glycol are subjected to transesterification reaction and then polycondensed,
Any manufacturing method can be applied. Further, it may be a polyester obtained by another polymerization method. The degree of polymerization of polyester is 0.3 to
It is preferably 1.3 dl / g.

In order to prevent inconveniences such as coloring and gel formation, the polyester contains, 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, Ca salts such as calcium chloride, manganese acetate,
Mn salts such as manganese chloride, Zn such as zinc chloride and zinc acetate
A salt, a Co salt such as cobalt chloride, or cobalt acetate is used as a metal ion in an amount of 300 ppm or less with respect to polyester, and phosphoric acid or a phosphoric acid ester derivative such as phosphoric acid trimethyl ester or phosphoric acid triethyl ester is phosphorus (P).
You may add 200 ppm or less in conversion.

The total amount of metal ions other than the above polymerization catalyst is 300 ppm with respect to polyester, and the P amount is 200 pp.
If it exceeds m, not only is the coloring of the polyester noticeable, but also the heat resistance and hydrolysis resistance of the polyester are significantly reduced, which is not preferable. At this time, in terms of heat resistance, hydrolysis resistance, etc., the mass ratio (P / M) of the total amount of P (P) and the total amount of metal ions (M) is 0.4 to 1.0. Is preferred. If 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 into the film, which is not preferable.

The timing of addition of the metal ions and phosphoric acid and its derivatives is not particularly limited. Generally, the metal ions are charged at the time of charging the raw materials, that is, before transesterification or esterification, and the phosphoric acids are subjected to a polycondensation reaction. It is preferably added before.

If necessary, fine particles of silica, titanium dioxide, kaolin, calcium carbonate or the like may be added to the film raw material, and further, an antioxidant, an ultraviolet absorber, an antistatic agent, a coloring agent, an antibacterial agent. Etc. can also be added.

The polyester film can be obtained by a publicly known method described below. As a means of incorporating a plurality of components in the heat-shrinkable polyester film, copolymerization is carried out to obtain this copolymerized polyester. There are a method of using alone and a method of blending different kinds of homopolyesters or copolyesters.

In the system in which the copolyester is used alone, a copolyester obtained from the polyhydric alcohol component having the above-mentioned specific composition and terephthalic acid and other polycarboxylic acid components may be used. On the other hand, the method of blending polyesters having different compositions can be preferably used because the characteristics of the film can be easily changed only by changing the blending ratio and industrial production of various kinds of films can be supported.

In the blending method, specifically, it is preferable to blend and use two or more kinds of polyesters having different Tg. For example, when blending two types of polyesters, a polyvalent carboxylic acid component essentially containing terephthalic acid, a copolymerized polyester composed of ethylene glycol and neopentyl glycol, and a polyvalent carboxylic acid component of terephthalic acid, Polyhydric alcohol component is a blend system of ethylene glycol and copolyester consisting of 1,4-cyclohexanedimethanol; polyethylene terephthalate (PET), polyhydric carboxylic acid component is terephthalic acid, polyhydric alcohol is ethylene glycol and neo. Blend system of pentyl glycol and copolyester which is 1,4-cyclohexanedimethanol; polybutylene terephthalate (PBT), polyvalent carboxylic acid component is terephthalic acid, polyhydric alcohol is ethylene glycol and neopentyl glyco When blend system such as the copolymerized polyester consisting of 1,4-cyclohexanedimethanol. Of course, polyhydric alcohols other than those exemplified above may be used in combination, and polyvalent carboxylic acids other than terephthalic acid may be used in combination.

In the three kinds of mixed systems, the polyvalent carboxylic acid component is terephthalic acid, and the polyhydric alcohol is ethylene glycol, neopentyl glycol and 1,4-cyclohexanedimethanol, a copolyester, and PET.
And a PBT blend system; a copolyester in which the polycarboxylic acid component is terephthalic acid and the polyhydric alcohol is ethylene glycol and neopentyl glycol;
A blend system of PET with a polyester having a polycarboxylic acid component of terephthalic acid and a polyhydric alcohol of 1,4-cyclohexanedimethanol; a polycarboxylic acid component of terephthalic acid and a polyhydric alcohol of ethylene glycol and neo A blend system of a copolymerized polyester which is pentyl glycol, a polyester having a polycarboxylic acid component of terephthalic acid and a polyhydric alcohol of 1,4-cyclohexanedimethanol, and PBT; a polycarboxylic acid component of which is terephthalic acid. A blended system of PET and PBT with a copolyester in which the polyhydric alcohol is ethylene glycol, neopentyl glycol and 1,4-cyclohexanedimethanol; terephthalic acid is the polyvalent carboxylic acid component and ethylene glycol is the polyhydric alcohol. And 1,4
A blend system of PBT with a copolyester which is cyclohexanedimethanol, a polyvalent carboxylic acid component is terephthalic acid, and a polyhydric alcohol is ethylene glycol and 1,4-butanediol. . Of course, polyhydric alcohols other than those exemplified above may be used in combination, and polyvalent carboxylic acids other than terephthalic acid may be used in combination. In addition, you may blend 4 or more types of polyester.

As a specific method for producing a film, the raw material polyester chips are dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer,
It is extruded into a film at a temperature of 200 to 300 ° C. using an extruder. Alternatively, the undried polyester raw material chips are similarly extruded into a film shape while removing water in a vent type extruder. Any existing method such as a T-die method or a tubular method may be adopted for extrusion. After extrusion, it is rapidly cooled using a casting roll or the like to obtain an unstretched film. In addition, in this "unstretched film",
The film to which the tension necessary for feeding the film is applied is also included.

The unstretched film is stretched. The stretching treatment may be performed continuously after cooling with the above casting roll or the like, or may be performed after being once wound into a roll after cooling.

Since it is practical in terms of production efficiency that the maximum shrinking direction is the lateral (width) direction of the film, an example of the stretching method in which the main shrinking direction is the lateral direction will be shown below. In addition,
Even when the maximum shrinkage direction is the film longitudinal (longitudinal) direction,
Stretching can be carried out according to a usual operation such as changing the stretching direction by 90 ° in the following method.

Focusing on making the thickness distribution of the heat-shrinkable polyester film uniform, it is preferable to carry out a preliminary heating step prior to the stretching step when stretching in the transverse direction using a tenter or the like. In the heating process, the heat transfer coefficient is 0.00544 J / cm ² · sec · ° C (0.
0013 calories / cm ² · sec · ° C) or less, the film surface temperature is Tg + 0 ° C to Tg at a low wind speed.
It is preferable to heat to a certain temperature within the range of + 60 ° C.

The stretching in the transverse direction is Tg-20 ° C. to Tg + 4.
At a predetermined temperature within the range of 0 ° C., the film is stretched 2.3 to 7.3 times, preferably 2.5 to 6.0 times. Then, 50 ℃ ~ 1
Heat treatment is performed at a predetermined temperature within the range of 10 ° C. while stretching 0 to 15% or relaxing 0 to 15%.
Further, the heat treatment may be performed at a predetermined temperature within the range of 50 ° C to 100 ° C. In order to improve the heat shrinkage properties and tear resistance, which are the objectives of the present invention, after stretching, a two-step heat treatment is performed in a tensioned state (0% elongation and 0% relaxation) in the range of 50 to 100 ° C. It is preferable to carry out. In this two-step heat treatment method,
Most preferably, the heat treatment is performed first at a high temperature and then at a lower temperature. Further, when the second heat treatment is performed at a temperature lower than 50 ° C., shrinkage whitening is likely to occur particularly after aging under high temperature acceleration, and the film having a preferable composition of the present invention has good tear resistance. And shrinkage finish properties may not be obtained, which is not preferable.

In this transverse stretching step, it is preferable to use equipment capable of reducing the fluctuation of the film surface temperature. That is, in the stretching step, a preheating step before stretching, a stretching step, a heat treatment step after stretching, a relaxation treatment,
Although there is a re-stretching step, etc., in particular, in the preheating step, the stretching step and the heat treatment step after stretching, the fluctuation range of the surface temperature of the film measured at an arbitrary point is within the average temperature ± 1 ° C. Average temperature ±
More preferably, it is within 0.5 ° C. This is because if the fluctuation range of the surface temperature of the film is small, the film is stretched and heat-treated at the same temperature over the entire length of the film, and the heat shrinkage behavior becomes uniform. To reduce the fluctuation of the film surface temperature, use, for example, a wind speed fluctuation suppressing facility equipped with an inverter so that the speed of the hot air that heats the film can be controlled, or use a heat source of 50 kPa or less (5 kgf / c).
It is advisable to use equipment that can suppress temperature fluctuations of hot air by using low-pressure steam of m ² or less).

As a stretching method, not only transverse uniaxial stretching with a tenter but also longitudinal stretching of 1.0 to 4.0 times, preferably 1.1 to 2.0 times may be performed. Good. When biaxial stretching is performed in this manner, either sequential biaxial stretching or simultaneous biaxial stretching may be performed, and re-stretching may be performed as necessary. Further, in the sequential biaxial stretching, the stretching order may be any of vertical and horizontal, horizontal and vertical, vertical and horizontal vertical, horizontal and vertical, and the like. Even when these longitudinal stretching step or biaxial stretching step is adopted, it is preferable to minimize the fluctuation of the film surface temperature in the preliminary heating step, the stretching step, etc., as in the case of the horizontal stretching.

The internal heat generation of the film due to stretching is suppressed,
Focusing on the point of reducing the film temperature unevenness in the width direction,
The heat transfer coefficient in the drawing process is 0.00377 J / cm ² ·
sec ・ ° C (0.0009 calories / cm ²・ sec ・
C.) or higher is preferable. 0.00544-0.
00837 J / cm ² · sec · ° C (0.0013 ~
0.0020 calories / cm ² · sec · ° C) is more preferable.

The thickness of the heat-shrinkable polyester film of the present invention is not particularly limited, but for example, as a heat-shrinkable polyester film for labels, it is 10 to 20.
0 μm is preferable, and 20 to 100 μm is more preferable.

[0050]

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and the present invention is not limited to the cases where modifications are made without departing from the spirit of the present invention. included. The methods for measuring the physical properties of the films obtained in Examples and Comparative Examples are as follows.

(1) Film (or chip) The composition film (or chip) is dissolved in a solvent in which chloroform D (manufactured by Eurysop) and chloroform D1 (manufactured by Eurysop) are mixed at a ratio of 10: 1 (volume ratio). Then, a sample solution is prepared, and NMR (“GEMINI-20
0 ”; manufactured by Varian) was used to measure the proton NMR of the sample solution under the conditions of a temperature of 23 ° C. and an integration number of 64 times. In the NMR measurement, the peak intensity of a predetermined methylene proton was calculated to calculate the constituent ratio of the monomers constituting the polyester.

(2) The heat shrinkage film was cut into a square of 10 cm × 10 cm to obtain 95
After immersing in warm water of ℃ ± 0.5 ℃ for 10 seconds under no load condition to cause heat shrinkage, and then immersing in water of 25 ℃ ± 0.5 ℃ for 10 seconds, lengthwise and transverse length of the sample It is a value obtained by measuring the height and according to the following formula. Thermal shrinkage (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage) The direction with the largest shrinkage was defined as the maximum shrinkage direction.

(3) Tear resistance The film was exposed to 2 ° C in an environment of a temperature of 30 ° C and a relative humidity of 85%.
Save for a week. According to JISK 7127, a tensile test is performed in a direction orthogonal to the maximum shrinkage direction of the film after storage. The number of test pieces was 20. Test piece length 200m
m, distance between chucks 100 mm, test piece width 15 mm, temperature 23 ° C., pulling speed 200 mm / min. The total number of test pieces (2
The percentage was defined as the tear resistance (%).

(4) Atmosphere temperature of 30 ° C. ± 1 with the solvent adhesive film wound on a paper tube
25 in a thermo-hygrostat controlled at 85 ℃ and relative humidity of 85 ± 2%.
After leaving it for 0 hours, take it out, print three colors with the grass-colored, gold-colored, and white inks manufactured by Toyo Ink Mfg. Co., Ltd., using a center seal machine, solvent-bond it with tetrahydrofuran to make a tube, and fold it in two. I wound up in a state. This tube roll was left in a thermo-hygrostat at a temperature of 23 ± 1 ° C. and a relative humidity of 65 ± 2% for 24 hours, then taken out, rewound, and the adhesiveness was checked. The adhesive part that can be easily peeled by hand without resistance is ×, the one that can be peeled by hand with a light resistance is △, and the one that cannot be easily peeled by hand is ○.
Evaluated as. ○ means pass.

(5) Shrinkage Finishing Property The tube produced for the evaluation of the solvent adhesiveness was cut to prepare a heat-shrinkable polyester film label.
For those that could not be solvent-bonded, heat sealing was performed to create a label. Then, after attaching the label to a glass bottle with a capacity of 300 ml, 160 ° C (wind speed 10 m
/ Sec) for 13 seconds to shrink the label. The degree of shrinkage whitening and shrinkage unevenness was visually judged, and the shrinkage finish property was evaluated in five levels. The criteria are: 5: best finishability, 4: good finishability, 3: shrink whitening or some shrinkage unevenness (within 2 places), 2: shrink whitening or shrinkage unevenness (3 to 5 places), 1: shrink whitening or If there are many shrinkage spots (6 or more places), 4 or more is a pass level and 3 or less is a defect.

Synthesis Example 1 (Synthesis of Polyester) In a stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux type cooler, 100 mol% of dimethyl terephthalate (DMT) as a polycarboxylic acid component was added.
And, as a polyhydric alcohol component, ethylene glycol (EG) is 99 mol% and diethylene glycol (DEG)
1 mol% was charged so that the polyhydric alcohol was 2.2 times the molar ratio of the methyl ester, and 0.05 mol% (based on the acid component) of zinc acetate as the transesterification catalyst, and the produced methanol. The transesterification reaction was carried out while distilling out of the system. After that, 0.025 mol% of antimony trioxide was added as a polycondensation catalyst (based on the acid component), and 280
The polycondensation reaction is performed under reduced pressure conditions of 26.7 Pa at
Polyester A having an intrinsic viscosity of 0.70 dl / g was obtained. The composition is shown in Table 1.

Synthesis Examples 2 to 4 By the same method as in Synthesis Example 1, polyesters B to D shown in Table 1 were obtained. In the table, NPG is neopentyl glycol, CHDM is 1,4-cyclohexanedimethanol, and BD is 1,4-butanediol. The intrinsic viscosity of each polyester is B 0.72 dl / g, C
Was 0.80 dl / g and D was 1.15 dl / g.
Each polyester was appropriately chipped.

[0058]

[Table 1]

Example 1 Each chip obtained in the above synthesis example was pre-dried separately, and as shown in Table 1, 4% by mass of chip A and 2 chips of chip B were used.
4% by mass, 56% by mass of chip C and 16% by mass of chip D were mixed, melt-extruded by a single-screw extruder at 280 ° C., and then rapidly cooled to obtain an unstretched film having a thickness of 180 μm. It was After preheating this unstretched film at 75 ° C for 10 seconds, it was stretched in the transverse direction at 69 ° C by 4.0 times with a tenter,
Subsequently, heat treatment is performed in a tension state at 84 ° C for 14 seconds, and further, heat treatment is performed in a tension state at 66 ° C for 12 seconds to obtain a thickness of 4
A 5 μm heat-shrinkable polyester film was obtained. Table 2 shows the physical properties of the obtained film.

Example 2 Each chip obtained in the above synthesis example was separately predried, and as shown in Table 1, chip A was 20% by mass, chip B was 8% by mass, and chip C was 56% by mass. Chip D was mixed at a ratio of 16% by mass, melt-extruded at 280 ° C. with a single-screw extruder, and then rapidly cooled to obtain an unstretched film having a thickness of 180 μm. After preheating this unstretched film at 78 ° C. for 10 seconds, it was stretched in the transverse direction at 71 ° C. by 4.0 times with a tenter,
Subsequently, heat treatment is performed in a tension state at 80 ° C. for 14 seconds, and further, heat treatment is performed in a tension state at 53 ° C. for 12 seconds to obtain a thickness of 4
A 5 μm heat-shrinkable polyester film was obtained. Table 2 shows the physical properties of the obtained film.

Comparative Example 1 Each of the chips obtained in the above synthesis example was separately predried, and as shown in Table 1, chip A was 37% by mass, chip B was 58% by mass, and chip D was 5% by mass. Mixed at a ratio of 28
Melt extrude with a single screw extruder at 0 ° C, then quench,
An unstretched film having a thickness of 180 μm was obtained. This unstretched film was preheated at 75 ° C for 10 seconds, then stretched in the transverse direction at 71 ° C by 4.0 times in a tenter, and then heat-treated in a tensioned state at 81 ° C for 14 seconds and further at 43 ° C for 12 seconds. Heat treatment was performed in this state to obtain a heat-shrinkable polyester film having a thickness of 45 μm. Table 2 shows the physical properties of the obtained film.

Comparative Example 2 Each of the chips obtained in the above synthesis example was separately pre-dried, and as shown in Table 1, chip A was 19% by mass, chip C was 62% by mass, and chip D was 19% by mass. Mix in the ratio of 2
It was melt extruded at 80 ° C. with a single-screw extruder and then rapidly cooled to obtain an unstretched film having a thickness of 180 μm. This unstretched film was preheated at 74 ° C for 10 seconds, then stretched in the transverse direction at 70 ° C by 4.0 times in a tenter, and subsequently at 76 ° C at 14 ° C.
Heat treatment was performed for 10 seconds in a tensioned state, and further heat treatment was performed for 12 seconds at 41 ° C. in a tensioned state to obtain a heat-shrinkable polyester film having a thickness of 45 μm. Table 2 shows the physical properties of the obtained film.

Comparative Example 3 Each of the chips obtained in the above synthesis example was separately pre-dried, and as shown in Table 1, chip A was 55% by mass, chip B was 8% by mass, and chip C was 27% by mass. Chip D was mixed at a ratio of 10% by mass, melt-extruded at 280 ° C. by a single-screw extruder, and then rapidly cooled to obtain an unstretched film having a thickness of 180 μm. After preheating this unstretched film at 83 ° C. for 10 seconds, it was stretched in the transverse direction at 71 ° C. by 4.0 times with a tenter,
Subsequently, heat treatment was carried out at 70 ° C. for 14 seconds under tension, and further heat treatment was carried out at 43 ° C. for 12 seconds under tension to obtain a heat-shrinkable polyester film having a thickness of 45 μm. Table 2 shows the physical properties of the obtained film.

Comparative Example 4 Each of the chips obtained in the above synthesis example was separately pre-dried, and as shown in Table 1, chip A was 35% by mass, chip B was 8% by mass, and chip C was 27% by mass. Chip D was mixed at a ratio of 30% by mass, melt-extruded at 280 ° C. with a single-screw extruder, and then rapidly cooled to obtain an unstretched film having a thickness of 180 μm. After preheating this unstretched film at 83 ° C. for 10 seconds, it was stretched in the transverse direction at 71 ° C. by 4.0 times with a tenter,
Subsequently, heat treatment was carried out at 70 ° C. for 14 seconds under tension, and further heat treatment was carried out at 43 ° C. for 12 seconds under tension to obtain a heat-shrinkable polyester film having a thickness of 45 μm. Table 2 shows the physical properties of the obtained film.

[0065]

[Table 2]

[0066]

EFFECTS OF THE INVENTION The heat-shrinkable polyester film of the present invention has a very small amount of defects such as shrinkage whitening, shrinkage spots, wrinkles, distortion, and vertical shrinkage during shrinkage, and a beautiful shrinkage finish appearance can be obtained. . In particular, it was possible to find a film having excellent tear resistance by accurately grasping the conditions for accelerating the aging. Furthermore, the heat-shrinkable polyester film of the present invention is also excellent in solvent adhesiveness and can be suitably used for applications such as shrink labels, cap seals, shrink wrapping and the like.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nagano             344 Maebata, East Inuyama, Inuyama City, Aichi Prefecture             Inuyama Factory, Yobo Co., Ltd. F-term (reference) 4F071 AA44 AA45 AA46 AA88 AF36                       AF58 AF61 AH04 AH06 BA01                       BB06 BB07 BC01                 4J029 AA03 AB07 AD01 AE03 BA03                       BA04 BA05 BA07 BA09 BA10                       BD04A BF09 BF18 BF23                       BF24 CA02 CA04 CA05 CA06                       CB03A CB05A CB05B CB06A                       CC05A CC06A JA081 JA091                       JA111 JA121 JA231 JA251                       JA261 JC411 JC481 JC531                       JC571 JC581 JE182 JF021                       JF031 JF041 JF131 JF141                       JF151 JF161 KB05 KB25                       KE02 KE03 KE05

Claims (3)

[Claims] 1. A heat-shrinkable polyester film, which is obtained by cutting a 10 cm × 10 cm square sample of the heat-shrinkable polyester film into hot water at 95 ° C.
The heat shrinkage in the maximum shrinkage direction is 50% when it is immersed in water for 25 seconds and then pulled up, and then immersed in water at 25 ° C for 10 seconds.
The heat shrinkable polyester film is stored for 2 weeks in an environment of a temperature of 30 ° C. and a relative humidity of 85%, and a tensile test in a direction orthogonal to the maximum shrinkage direction of the film after storage is performed using a plurality of test pieces. When the distance between chucks was 100 mm, the width of the test piece was 15 mm, the temperature was 23 ° C., and the tensile speed was 200 mm / min, the number of test pieces having a breaking elongation of 5% or less was 10% or less of the total number of test pieces. A heat-shrinkable polyester film, which can be adhered with a chlorine-free organic solvent. 2. In the heat-shrinkable polyester film, 1,4-cyclohexanedimethanol component is 10 mol% or more and neopentyl glycol component is 2 mol% or more of the polyhydric alcohol component, and 1, The heat-shrinkable polyester film according to claim 1, wherein the total amount of the 4-cyclohexanedimethanol component and the neopentyl glycol component is 12 to 40 mol%. 3. The polyhydric alcohol component further comprises:
The heat-shrinkable polyester film according to claim 1, wherein the 1,4-butanediol component is contained in an amount of 2 mol% or more.