JPH0827261A - Heat-shrinkable polyester film - Google Patents

Abstract

PURPOSE:To prepare a heat-shrinkable polyester film having a high shrinkage factor at relatively low temperatures, excellent in shrink-adherence to a container such as a bottle and ink-adhesive properties and having no shrink- unevenness. CONSTITUTION:This heat-shrinkable polyester film is made of a polyester resin which comprises a acid components mainly comprising an aromatic dicarboxylic acid or its ester forming derivative and alcohol components mainly comprising ethylene glycol. The sum of a ratio of acid components except terephthalic acid to the total acid components and a ratio of alcohol components except ethylene glycol to the total alcohol components is in the range of 5-40mol%. The polyester resin contains 1-30mol% cyclohexanedimethanol component based on the total alcohol components and 0.3-3mol% of an alkali metal salt of sulfobenzenedicarboxylic acid based on the total acid components.

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 used for various packaging materials, and more specifically, a shrink coating having excellent shrinkage characteristics at low temperature and ink adhesion and having no shrinkage unevenness. The present invention relates to a heat-shrinkable polyester film that can be provided.

[0002]

2. Description of the Related Art Heat-shrinkable plastic films are used for marking and protecting containers, fishing rods, condensers, rod-shaped fluorescent lamps, etc.
It is used for bundling, improving the added value of products, etc., and is also used for the integrated packaging of books and notebooks and the close packaging.
At present, it is expected to develop various applications in many other fields by utilizing the shrinkability and shrinkage stress of the heat-shrinkable film.

Conventionally, as materials for heat-shrinkable films,
Resins such as polyvinyl chloride, polystyrene, and polyolefin have been used. However, such resins have drawbacks in heat resistance, weather resistance, chemical resistance and the like. For example, although polyvinyl chloride film can be used as a heat-shrinkable film having various shrinkage characteristics, fish eyes are likely to occur frequently, and the product printed with this film has a poor aesthetic appearance and a reduced commercial value. It was easy to become what I did. Also, in order to obtain a heat-shrinkable film without fish eyes, excessive quality control is required,
There was a problem that the film production cost increased remarkably. Furthermore, polyvinyl chloride causes pollution problems when incinerated at the time of disposal, and additives such as plasticizers in the polyvinyl chloride resin bleed out over time, causing dirt and other contamination, and It was not preferable in terms of sex.

On the other hand, a heat-shrinkable film obtained from polystyrene has a good finish after shrinkage, but has a low solvent resistance, so that a special ink must be used for printing, and even at room temperature. It had to be stored in a cool place due to spontaneous shrinkage. In addition, there is a big problem in the disposal because it needs to be incinerated at a high temperature and a large amount of black smoke and a strange odor are generated during the incineration. As a material capable of solving these problems, polyester film is highly expected, and its usage amount has been remarkably increasing.

[0005]

However, the conventional heat-shrinkable polyester film has not been sufficiently satisfactory in its heat-shrinkability. In particular, shrinkage unevenness is likely to occur during shrinkage, and when coating and shrinking on containers such as PET bottles, polyethylene bottles, glass bottles, the characters and patterns printed on the film cannot be reproduced well, and the film can be sufficiently adhered to the container. There were problems such as not being there.

Further, it is inferior in shrinkability at low temperature as compared with polystyrene film or the like, and must be shrunk at high temperature in order to obtain a required shrinkage amount, which causes deformation and whitening of bottles and the like. He also had points. In particular, when used as a label for a polyethylene bottle, the polyethylene bottle itself is inferior in heat resistance to a PET bottle and the like, and therefore shrinking work must be performed at a lower temperature, for example, about 70 ° C. A heat-shrinkable film having excellent characteristics is required.

In response to such a demand, Japanese Patent Application No. 4-11
As described in Japanese Patent Application No. 0963 and Japanese Patent Application No. 4-110964, a heat shrinkable polyester having a shrinkage initiation temperature of 50 ° C. or less by using a polyester resin copolymerized with a specific copolymerization component. A film, a heat-shrinkable polyester film in which uneven shrinkage is less likely to occur by controlling the shrinkage speed, and the like have been proposed. However, even in such a heat-shrinkable polyester film, the problem of shrinkage unevenness has not been completely solved. For example, once shrinkage unevenness occurs during shrinkage, the generated shrinkage unevenness is fixed and shrinkage unevenness is fixed. It had a problem that it could not be removed. In addition, these heat-shrinkable polyester films cannot be printed without using an expensive special ink for exclusive use of a polyether film, and in a general-purpose ink such as for a polyvinyl chloride film, a sink mark of the printed ink occurs, There is also a problem that the printed ink is transferred to other parts. The object of the present invention is to have excellent shrinkage properties and ink adhesion at low temperatures,
An object of the present invention is to provide an excellent heat-shrinkable polyester film that does not cause uneven shrinkage and remains.

[0008]

In view of such circumstances, the inventors of the present invention have arrived at the present invention as a result of earnestly investigating a polyester resin constituting a heat-shrinkable film. That is, the heat-shrinkable polyester film of the present invention is composed of a polyester resin composed of an acid component having an aromatic dicarboxylic acid or an ester-forming derivative thereof as a main component and an alcohol component having ethylene glycol as a main component, and the polyester resin is entirely When the ratio of the acid component other than terephthalic acid in the acid component (A mol%) and the ratio of the alcohol component other than ethylene glycol in the total alcohol component (B mol%) are in the range of 10 mol% ≦ A + B ≦ 40 mol% Yes, the cyclohexanedimethanol component is contained in a proportion of 1 to 30 mol% in all alcohol components, and the alkali metal salt of sulfobenzenedicarboxylic acid is contained in a proportion of 0.3 to 3 mol% in all acid components. It is characterized by.

The polyester resin used in the heat-shrinkable polyester film of the present invention comprises an acid component containing aromatic dicarboxylic acid or its ester-forming derivative as a main component and an alcohol component containing ethylene glycol as a main component. The ratio (A mol%) of acid components other than terephthalic acid in the total acid components and the ratio (B mol%) of alcohol components other than ethylene glycol in the total alcohol components are
It is necessary that the range of 10 mol% ≦ A + B ≦ 40 mol% is satisfied. This is the ratio (A mol%) of acid components other than terephthalic acid in the total acid components and the ratio (B mol%) of alcohol components other than ethylene glycol in the total alcohol components.
If the sum (A + B) is less than 10 mol%, sufficient solvent adhesiveness cannot be obtained, and conversely, if it exceeds 40 mol%, the solvent resistance of the film itself is poor and film formation is possible. This is because no resin is obtained, preferably 15 to 35.
It is in the range of mol%.

In the present invention, examples of the aromatic dicarboxylic acid constituting the polyester resin include terephthalic acid, isophthalic acid, naphthalene-1,4- or -2,6-dicarboxylic acid. These aromatic dicarboxylic acids or their ester-forming derivatives are preferably contained in the acid component of the polyester resin in an amount of 70 mol% or more, more preferably 80 mol% or more. this is,
This is because when the aromatic dicarboxylic acid or its ester-forming derivative is less than 70 mol%, the mechanical strength of the formed polyester film tends to decrease. From the viewpoint of the mechanical strength of the film, the proportion of terephthalic acid in all the acid components is preferably 60 mol% or more, more preferably 70 mol% or more.

Further, the present invention is characterized by containing an alkali metal salt of sulfobenzenedicarboxylic acid as an acid component for the purpose of improving the adhesiveness to general-purpose inks for polyvinyl chloride films and the like. Examples of the alkali metal salt of sulfobenzenedicarboxylic acid include 5-sodium sulfobenzene- represented by the following general formula (1).
Examples thereof include 1,3-dicarboxylic acid, 2-sodium sulfobenzene-1,4-dicarboxylic acid, 4-sodium sulfobenzene-1,3-dicarboxylic acid, and ester-forming derivatives thereof. Other alkali metals include sodium. Examples thereof include lithium and calcium, and among them, sodium 5-sulfoisophthalate is preferable.

[0012]

Embedded image

(In the formula, R ₁ and R ₂ are hydrogen or 1 to 1 carbon atoms.
6 represents an alkyl group, and M represents an alkali metal.) These alkali metal salts of sulfobenzenedicarboxylic acid are contained in the total acid component in an amount of 0.3 to 3 mol%,
It is preferably in the range of 0.5 to 2 mol%. This is because when the content ratio of the alkali metal salt of sulfobenzenedicarboxylic acid is less than 0.3 mol%, the adhesiveness to general-purpose ink is not sufficiently improved, and conversely, when it exceeds 3 mol%, the polyester content is increased. This is because the viscosity of the resin is rapidly increased during the polymerization reaction of the resin, the desired polyester resin cannot be obtained, or the polyester resin cannot be taken out from the reaction vessel.

Further, in the present invention, for the purpose of enhancing the effect of the present invention and increasing the amount of heat shrinkage, an aliphatic dicarboxylic acid or its ester-forming derivative is contained in the polyester resin in an amount of less than 20 mol%, It may be contained preferably in the range of less than 15 mol%. This is because when these aliphatic dicarboxylic acid components are contained in an amount of 20 mol% or more,
This is because the mechanical strength of the polyester film may be reduced. Examples of the aliphatic dicarboxylic acid that can be used in the present invention include glutaric acid, adipic acid, sebacic acid,
Azelaic acid, oxalic acid, succinic acid and the like can be mentioned.

In the present invention, the alcohol component constituting the polyester resin is mainly composed of ethylene glycol, and the total alcohol component contains ethylene glycol in an amount of 50 mol% or more, preferably 70 mol% or more. It is a thing. This is because when the content of ethylene glycol is less than 50 mol%, the polymerization reactivity tends to decrease during the production of the resin, and the resin having the desired degree of polymerization may not be obtained. is there.

Further, in the present invention, a cyclohexanedimethanol component is contained as an alcohol component for the purpose of reducing the occurrence of shrinkage unevenness and alleviating the shrinkage unevenness.
The content ratio of the cyclohexanedimethanol component is in the range of 1 to 30 mol%, preferably 5 to 25 mol% in the total alcohol component. If the proportion of the cyclohexanedimethanol component is less than 1 mol%, uneven shrinkage is likely to occur, and the phenomenon of increasing shrinkage in a relatively high temperature range does not appear, and uneven shrinkage cannot be sufficiently relaxed. This is because, on the contrary, when it exceeds 30 mol%, the shrinkage initiation temperature becomes high and the shrinkage property at low temperature is deteriorated. In this way, by containing the cyclohexanedimethanol component as the alcohol component in a specific ratio, it is possible to increase the shrinkage ratio in a relatively high temperature range, and when shrinkage unevenness occurs in a relatively low temperature range. Moreover, the generated shrinkage unevenness can be alleviated in a relatively high temperature region, and excellent shrinkage coating without shrinkage unevenness can be performed.

In addition to the above alcohol components, ethylene oxide adducts of bisphenol compounds or their derivatives, butanediol, propylene glycol, triethylene glycol, diethylene glycol, neopentyl glycol, polyethylene glycol, polytetramethylene glycol, etc. The alcohol component can be used within a range that does not impair the effects of the present invention.

In the present invention, rapid contraction is suppressed,
For the purpose of further reducing shrinkage unevenness, a trivalent or higher polyvalent carboxylic acid or polyhydric alcohol may be used. Specific examples of the trivalent or higher polycarboxylic acid or polyhydric alcohol include polycarboxylic acids such as trimellitic acid, pyromellitic acid and their anhydrides, trimethylolpropane, trimethylolethane, glycerin, diglycerin, Examples include polyhydric alcohols such as pentaerythritol. Of these, trimethylolpropane, trimellitic acid, and pentaerythritol are preferable from the viewpoints of thermal stability during film formation and reactivity during polycondensation.

In the present invention, the polyester resin is not limited to a single polyester resin, but may be a mixed polyester resin in which two or more polyester resins are mixed, and the proportion of acid components other than terephthalic acid in the total acid component (A
Mol%) and the proportion of alcohol components other than ethylene glycol in all alcohol components (B mol%) are 10 mol%
≦ A + B ≦ 50 mol%, the ratio of cyclohexanedimethanol component is 1 to 30 mol% in all alcohol components, and alkali metal salt of sulfobenzenedicarboxylic acid is 0.3 to 3 mol% in all acid components. As long as it includes.

The polyester resin of the present invention can be produced by a known direct polymerization method or transesterification method,
The degree of polymerization is not particularly limited, but the intrinsic viscosity (measured at 25 ° C. in a mixed solution of phenol / tetrachloroethane by weight) is 0.5 because of the moldability of the raw film.
The thing of -1.2 is preferable.

The resulting polyester resin is molded into a heat-shrinkable polyester film by the following method, for example. First, after drying the polyester resin, melt it,
Melt extrusion is performed from a die, and a raw film is formed by a casting method or a calendar method. Next, this raw film was set to 3 from the glass transition temperature (Tg) of the polyester resin.
1.5 to 5.0 times in the longitudinal or transverse direction, preferably 1.0 at a temperature higher than ℃, preferably higher than 5 ℃
The film is stretched to 4.8 times to give a high shrinkage rate to the film. Further, if necessary, it is stretched 1.0 to 1.8 times, preferably 1.0 to 1.5 times in the direction perpendicular to the stretching direction. This is effective in improving the tensile strength of the film and preventing the shrinkage in the stretching direction from shrinking more than necessary.

The film is stretched by a method such as simultaneous biaxial stretching, sequential biaxial stretching, uniaxial stretching, etc. Either longitudinal stretching or transverse stretching may be performed first. The stretched heat-shrinkable polyester film can be used as a product as it is, but may be heat-treated at a temperature of 50 to 150 ° C. for several seconds to several tens seconds from the viewpoint of dimensional stability and the like. By performing such heat treatment,
The polyester film of the present invention can exhibit desirable properties such as adjustment of the shrinkage ratio in the shrinking direction, reduction of time-dependent shrinkage of the unshrinked film during storage, and reduction of shrinkage unevenness.

The heat-shrinkable polyester film of the present invention has a shrinkage ratio of 5% or more when it is immersed in warm water of 60 ° C. for 1 minute without weighting to shrink, and it is 1% without load in warm water of 80 ° C. It is preferable that the shrinkage ratio when soaked for a minute to shrink is 30% or more. This is because if the shrinkage ratio at 60 ° C. is less than 5%, the film tends not to be sufficiently adhered to the container, and the heating temperature in the shrinking process must be increased, and the heating temperature in the shrinking process is increased. This is because the container such as a bottle is deformed or whitened, and the heat-shrinkable film is rapidly shrunk to cause uneven shrinkage. Considering the occurrence of uneven shrinkage due to abrupt shrinkage when the film shrinks, the shrinkage ratio at 60 ° C. is more preferably in the range of 10 to 30%. If the shrinkage ratio at 80 ° C is less than 30%, a sufficient shrinkage amount cannot be obtained,
This is because the adhesion of the film to the container tends to be insufficient, and it tends to be difficult to completely cover a container or the like having a particularly complicated shape. Considering the occurrence of shrinkage unevenness due to abrupt shrinkage when the film shrinks, it is more preferable that the shrinkage ratio at 80 ° C. is in the range of 35 to 60%.
Further, in the present invention, it is preferable that the shrinkage initiation temperature is 50 ° C. or lower in order to obtain excellent low temperature shrinkage characteristics, and more preferably at least 1 at 50 ° C.
%, More preferably 2% or more.

The thickness of the heat-shrinkable polyester film of the present invention is not particularly limited, but it is 1 to 600 μm.
Those in the range of are practically used. 6 to 380 μm for packaging applications, especially packaging of foods, beverages, pharmaceuticals, etc.
Those in the range of are used. When used for labels such as PET bottles, polyethylene bottles and glass bottles, those having a range of 20 to 70 μm are used.

In the present invention, in order to impart more specific performance, various conventionally known processing treatments and suitable additives can be added. Examples of processing include ultraviolet rays and α
Irradiation with rays, β rays, γ rays or electron rays, corona treatment,
Examples thereof include plasma irradiation treatment, flame treatment and the like, coating of resin such as vinylidene chloride, polyvinyl alcohol, polyamide and polyolefin, laminate, vapor deposition of metal and the like. Examples of additives include polyamide, polyolefin, polymethylmethacrylate, resins such as polycarbonate, silica, talc, kaolin, inorganic particles such as calcium carbonate, titanium oxide, pigments such as carbon black, ultraviolet absorbers, release agents, and the like. Flame retardants and the like can be mentioned.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples. The shrinkage ratio in the examples is 150 m in the stretching direction.
m, a polyester film cut into a size of 20 mm in a direction perpendicular to the m, and marked lines at intervals of 100 mm 6
When immersed in each warm water of 0 ° C. and 80 ° C. for 1 minute without load, the length before shrinkage (L) and the length after shrinkage (L ′) were measured in the stretching direction of the film, and the following formula was used. Sought by.

[0027]

## EQU1 ## Shrinkage (%) = {(L-L ') / L} × 100 Heat unevenness is 150 mm in the stretching direction and 2 in the direction perpendicular to it.
A polyester film cut into a size of 0 mm
After heat-shrinking for 1 minute with no load in warm water at 80 ° C,
The appearance of shrinkage unevenness on the film was evaluated in three stages: ◯: Almost no shrinkage unevenness was observed. Δ: Some shrinkage unevenness was found. ×: Shrinkage unevenness was noticeable.

The ink adhesiveness is 100 mm in the stretching direction,
After subjecting the polyester film cut out in a size of 20 mm in the perpendicular direction to corona treatment with an output of 15 W,
The polyvinyl chloride film ink was applied to the corona-treated surface using a bar coater, left at room temperature for 24 hours and then a mending tape was attached, and further left at room temperature for 24 hours, then at a temperature of 25 ° C. and a pulling speed of 40 mm. / Sec,
A T-peel test was conducted on 5 samples using an autograph manufactured by Shimadzu Corporation with a chuck interval of 50 mm. ◎: No ink peeled on all 5 ○: Ink peeled on 1 × Evaluation was made on the basis of the fact that peeling of the ink was observed in two or more pieces.

Example 1 99.7 mol parts of terephthalic acid, 0.3 mol part of sodium 5-sulfoisophthalate, 140 mol parts of ethylene glycol and 5 mol parts of cyclohexanedimethanol were placed in a reaction vessel, and an ester reaction was performed under nitrogen pressure. Have done enough. Next, trimethyl phosphate as a stabilizer was added to the total acid component in an amount of 50 ppm, antimony trioxide was added as a polymerization catalyst in an amount of 300 ppm, and titanium tetrabutoxide was added to the total acid component in an amount of 500 ppm. While maintaining the temperature at 280 ° C., a polycondensation reaction was performed for 3 hours under a reduced pressure of 5 mmHg or less to obtain a polyester resin. After drying the obtained polyester resin, 270 ° C.
A raw film was prepared by melt-extruding from a T-die at the resin temperature of. This raw film was stretched at 80 ° C. (T
The film was uniaxially stretched 4.5 times in the D direction) to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the resin composition of the obtained film, the measurement result of the shrinkage ratio, the shrinkage unevenness, and the evaluation result of the ink adhesiveness.

Example 2 94 mol parts of terephthalic acid, 5 mol parts of isophthalic acid, 5-
Sodium sulfoisophthalate 1 mol part, ethylene glycol 140 mol part, cyclohexanedimethanol 10
A molar part was placed in a reaction vessel, and the ester reaction was sufficiently performed under nitrogen pressure. Next, trimethyl phosphate as a stabilizer is 50 ppm with respect to all acid components, and antimony trioxide as a polymerization catalyst is 300 ppm with respect to all acid components.
500 pp of titanium tetrabutoxide for all acid components
m, and the temperature inside the reaction vessel was maintained at 280 ° C.
Polycondensation reaction was performed for 3 hours under reduced pressure of mmHg or less to obtain a polyester resin. After drying the obtained polyester resin, it is melt extruded from a T die at a resin temperature of 270 ° C.
A raw film was created. This raw film is at 80 ℃
Uniaxially stretching 4.5 times in the stretching direction (TD direction),
A heat-shrinkable polyester film having a thickness of 40 μm was obtained.
Table 1 shows the resin composition of the obtained film, the measurement result of the shrinkage ratio, the shrinkage unevenness, and the evaluation result of the ink adhesiveness.

Example 3 90 mol parts of terephthalic acid, 8 mol parts of adipic acid, 2 mol parts of sodium 5-sulfoisophthalate, 140 mol parts of ethylene glycol, and 22 mol parts of cyclohexanedimethanol were placed in a reaction vessel and pressurized under nitrogen. The ester reaction was carried out sufficiently. Next, trimethyl phosphate as a stabilizer is 50 ppm with respect to all acid components, antimony trioxide as a polymerization catalyst is 300 ppm with respect to all acid components, and titanium tetrabutoxide is 500 ppm with respect to all acid components.
Add and maintain the temperature in the reaction vessel at 280 ° C.
Polycondensation reaction was performed for 3 hours under reduced pressure of mHg or less to obtain a polyester resin. The obtained polyester resin was dried and then melt-extruded from a T die at a resin temperature of 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 4.5 times in the stretching direction (TD direction) at 80 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the resin composition of the obtained film, the measurement result of the shrinkage ratio, the shrinkage unevenness, and the evaluation result of the ink adhesiveness.

Example 4 90 mol parts of terephthalic acid, 7 mol parts of adipic acid, 3 mol parts of sodium 5-sulfoisophthalate, 140 mol parts of ethylene glycol, and 30 mol parts of cyclohexanedimethanol were placed in a reaction vessel and pressurized with nitrogen. The ester reaction was carried out sufficiently. Next, trimethyl phosphate as a stabilizer is 50 ppm with respect to all acid components, antimony trioxide as a polymerization catalyst is 300 ppm with respect to all acid components, and titanium tetrabutoxide is 500 ppm with respect to all acid components.
Add and maintain the temperature in the reaction vessel at 280 ° C.
Polycondensation reaction was performed for 3 hours under reduced pressure of mHg or less to obtain a polyester resin. The obtained polyester resin was dried and then melt-extruded from a T die at a resin temperature of 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 4.5 times in the stretching direction (TD direction) at 80 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the resin composition of the obtained film, the measurement result of the shrinkage ratio, the shrinkage unevenness, and the evaluation result of the ink adhesiveness.

Comparative Example 1 100 parts by mole of terephthalic acid, 140 parts of ethylene glycol
A molar part was placed in a reaction vessel, and the ester reaction was sufficiently performed under nitrogen pressure. Next, trimethyl phosphate as a stabilizer was added to the total acid component in an amount of 50 ppm, and antimony trioxide was added as a polymerization catalyst in an amount of 400 ppm to the total acid component.
Polycondensation reaction was performed for 3 hours under a reduced pressure of Hg or less to obtain a polyester resin. The obtained polyester resin was dried and then melt-extruded from a T die at a resin temperature of 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 4.5 times in the stretching direction (TD direction) at 85 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the resin composition of the obtained film, the measurement result of the shrinkage ratio, the shrinkage unevenness, and the evaluation result of the ink adhesiveness.

Comparative Example 2 100 parts by mole of terephthalic acid, 140 parts of ethylene glycol
A molar part and 2 molar parts of cyclohexanedimethanol were placed in a reaction vessel, and the ester reaction was sufficiently carried out under nitrogen pressure.
Next, trimethyl phosphate as a stabilizer was added to the total acid components in an amount of 50 ppm, and antimony trioxide was added as a polymerization catalyst in an amount of 400 ppm to the total acid components. Polycondensation reaction was performed under reduced pressure for 3 hours to obtain a polyester resin.
The obtained polyester resin was dried and then melt-extruded from a T die at a resin temperature of 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 4.5 times in the stretching direction (TD direction) at 85 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the resin composition of the obtained film, the measurement result of the shrinkage ratio, the shrinkage unevenness, and the evaluation result of the ink adhesiveness.

Comparative Example 3 100 mol parts of terephthalic acid, 10 mol parts of sodium 5-sulfoisophthalate, 140 mol parts of ethylene glycol and 30 mol parts of cyclohexanedimethanol were placed in a reaction vessel, and the ester reaction was sufficiently performed under nitrogen pressure. It was Next, trimethyl phosphate as a stabilizer is added to the total acid component in an amount of 50 ppm, and antimony trioxide is added as a polymerization catalyst in an amount of 400 ppm to the total acid component. Although the polycondensation reaction was carried out for 3 hours under reduced pressure, the polyester resin could not be taken out from the reaction vessel due to a rapid increase in viscosity during the polymerization.

Comparative Example 4 99.7 mol parts of terephthalic acid, 0.3 mol part of sodium 5-sulfoisophthalate, 140 mol parts of ethylene glycol and 35 mol parts of cyclohexanedimethanol were placed in a reaction vessel, and the ester reaction was carried out under nitrogen pressure. Have done enough.
Next, trimethyl phosphate as a stabilizer was added to the total acid components in an amount of 50 ppm, and titanium tetrabutoxide as a polymerization catalyst was added to the total acid components in an amount of 400 ppm, and the temperature in the reaction vessel was maintained at 280 ° C. Polycondensation reaction was performed under reduced pressure for 3 hours to obtain a polyester resin. After drying the obtained polyester resin, 270
A raw film was prepared by melt extrusion from a T die at a resin temperature of ° C. This raw film is uniaxially stretched 4.5 times in the stretching direction (TD direction) at 85 ° C. to obtain a thickness of 40 μm.
A heat-shrinkable polyester film of m was obtained. Resin composition of the obtained film, measurement results of shrinkage and shrinkage unevenness,
The results of evaluation of ink adhesion are shown in Table 1.

Comparative Example 5 100 parts by mole of terephthalic acid and 140 parts of ethylene glycol
A molar part and 5 molar parts of cyclohexanedimethanol were put in a reaction vessel, and the ester reaction was sufficiently carried out under nitrogen pressure.
Next, trimethyl phosphate as a stabilizer was added to the total acid component in an amount of 50 ppm, antimony trioxide was added as a polymerization catalyst in an amount of 300 ppm, and titanium tetrabutoxide was added to the total acid component in an amount of 500 ppm. While maintaining the temperature at 280 ° C., a polycondensation reaction was performed for 3 hours under a reduced pressure of 5 mmHg or less to obtain a polyester resin. After drying the obtained polyester resin, 270 ° C.
A raw film was prepared by melt-extruding from a T-die at the resin temperature of. This raw film was stretched at 80 ° C. (T
The film was uniaxially stretched 4.5 times in the D direction) to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the resin composition of the obtained film, the measurement result of the shrinkage ratio, the shrinkage unevenness, and the evaluation result of the ink adhesiveness.

Comparative Example 6 60 mol parts of terephthalic acid, 40 mol parts of isophthalic acid, 140 mol parts of ethylene glycol, and 5 mol parts of cyclohexanedimethanol were placed in a reaction vessel, and the ester reaction was sufficiently carried out under nitrogen pressure. Next, trimethyl phosphate as a stabilizer is added to the total acid component at 50 ppm, and antimony trioxide as a polymerization catalyst is added to the total acid component at 400 ppm
ppm was added, the temperature in the reaction vessel was maintained at 280 ° C., and a polycondensation reaction was performed for 3 hours under a reduced pressure of 5 mmHg or less to obtain a polyester resin.

After drying the obtained polyester resin,
A raw film was prepared by melt extrusion from a T die at a resin temperature of 270 ° C. This raw film was very brittle and could not be formed as a shrink film.

Comparative Example 7 94 mol parts of terephthalic acid, 6 mol parts of sodium 5-sulfoisophthalate, 130 mol parts of ethylene glycol, and 12 mol parts of cyclohexanedimethanol were placed in a reaction vessel, and the ester reaction was sufficiently performed under nitrogen pressure. It was Next, 100 ppm of trimethyl phosphate as a stabilizer was added to all the acid components, and 450 ppm of antimony trioxide was added as a polymerization catalyst to all the acid components, and the temperature in the reaction vessel was kept at 280 ° C. to 5 mmHg or less. Polycondensation reaction was performed under reduced pressure for 3 hours to obtain a polyester resin. The obtained polyester resin was dried and then melt-extruded from a T die at a resin temperature of 270 ° C. to prepare a raw film. This raw film was very brittle and could not be formed as a shrink film.

[0041]

[Table 1]

The components shown in the table are as follows. TPA: terephthalic acid component IPA: isophthalic acid component ADA: adipic acid component SINa: 5-sodium sulfoisophthalate component EG: ethylene glycol component CHDM: cyclohexanedimethanol component

[0043]

EFFECT OF THE INVENTION The heat-shrinkable polyester film of the present invention has a high heat-shrinkage ratio even at a relatively low temperature, has excellent shrinkage adhesion to a container such as a bottle and ink adhesion, and has a shrinkage-free shrink coating. Is something that
It has excellent practicality as various packaging materials.
It is suitable as a heat shrink label for plastic bottles.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tajiri Zouun 2-4-1, Ushikawa-dori, Toyohashi-shi, Aichi Sanryo Rayon Co., Ltd. Toyohashi Plant

Claims (1)

[Claims] 1. A polyester resin comprising an acid component containing an aromatic dicarboxylic acid or an ester-forming derivative thereof as a main component and an alcohol component containing ethylene glycol as a main component, and the polyester resin is other than terephthalic acid in all acid components. The ratio of the acid component (A mol%) and the ratio of the alcohol component other than ethylene glycol (B mol%) in the total alcohol component are in the range of 5 mol% ≦ A + B ≦ 40 mol%, and Cyclohexanedimethanol component is contained in a proportion of 1 to 30 mol%, and alkali metal salt of sulfobenzenedicarboxylic acid is contained in a proportion of 0.3 to 3 mol% in all acid components. Polyester film.