JPH1171473A - Thermally shrinkable polyester-based film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester-based film which exhibits a good finish in shrinking by specifying the shrinking properties of the film so that the thermal shrinkage in the main shrinkage direction after being treated in warm water for a specified time is equal to or higher than a specified value and the ratio between the above-obtd. thermal shrinkage and that obtd. by changing the treating time is equal to or lower than a specified value. SOLUTION: This is a polyester-based film which has such shrinking properties that the thermal shrinkage [HS 30] in the main shrinkage direction after being treated in 80 deg.C water for 30 sec is 30% or higher; that the ratio [HS5/HS30] of the thermal shrinkage [BS5] in the main shrinkage direction after being treated in 80 deg.C water for 5 sec to the above-obtd. thermal shrinkage console is 0.8 or lower; that the shrinkages in the main shrinkage direction and in the perpendicular direction in 80 deg.C water are 10% or lower; and that the film has a max. value only when treated for 0-30 sec. The film is prepd. from polyethylene naphthalate, polybutylene naphthalate/terephthalate copolymer or the like and pref. contains Mg, Co, and P in concns.(ppm) satisfying the relations represented by 80.0<=Mg<=300.0, 2.0<=Co<=40.0, and 2.0<=(Mg+Co)/ P<=5.0.

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 a method for producing the same. The present invention relates to a suitable heat-shrinkable polyester film and a method for producing the same.

[0002]

2. Description of the Related Art Heat-shrinkable films are particularly used in the field of shrinkable films for labeling bottle barrels.
Films made of polyethylene etc. have been mainly used, but in recent years, polyvinyl chloride has problems such as generation of chlorine-based gas when incinerated at the time of disposal, and polyethylene has problems such as difficulty in printing. In addition, heat-shrinkable polyester films have attracted attention due to the additional problem that it is necessary to separate labels of resins other than PET for recovery. However, the heat-shrinkable polyester film often shrinks sharply, and remains unsatisfactory as a shrinkable film for labels such as wrinkles, shrinkage spots, and distortion remaining after shrinkage. In order to avoid some of these drawbacks, Japanese Patent Application Laid-Open No. 1-110931 discloses a method of improving the shrink finish by remarkably reducing the elongation at break in the direction perpendicular to the main shrink direction.

[0003] However, the film obtained by this method is not only easily broken when tension is applied in the steps of printing, labeling and the like, but also easily broken when ordinary transportation is carried out with the contents filled. Therefore, the film was not practical as a shrinkable film for labels. In Japanese Patent Application Laid-Open No. 63-309424, 75
There is disclosed a method for obtaining a heat-shrinkable polyester film having improved shrink finish by controlling shrinkage characteristics at a temperature of ° C. Also, JP-A-4-170
No. 437 discloses a heat-shrinkable polyester film obtained by compounding a polybutylene terephthalate polymer and a polyethylene naphthalate polymer.

[0004]

However, the film obtained by the above method has not yet been satisfactory as a shrinkable film for labels. In PET bottles, which are the mainstream of recent beverage containers, the shape of the bottle is rapidly changing from a conventional round shape to a square shape in view of shrinkage to a refrigerator. And Japanese Patent Application Laid-Open No. 4-17037. When a cylindrical label made of a heat-shrinkable polyester film is attached to the body of a rectangular bottle, a flat portion other than the corner of the bottle is curved in an arch shape after shrinkage (a defect referred to as "Tatehike"). Cheap. Since square PET bottles are becoming the mainstream of beverage containers, there is a need to develop a heat-shrinkable polyester film that is less likely to cause vertical shrinkage when used as a label on the bottle. In addition to these, the present invention provides a heat-shrinkable polyester film suitable for label use, which has good transparency and good ink coloring, and furthermore has a shrink finish property, that is, extremely little wrinkles, shrinkage spots, and distortions after shrinkage. The purpose is to do.

[0005]

According to the present invention, the heat shrinkage [HS30] in the main shrinkage direction after treatment in hot water of 80 ° C. for 30 seconds is 30%.
% Or more and the ratio [HS5 / HS30] to the heat shrinkage [HS5] in the direction of main shrinkage after treatment in hot water at 80 ° C. for 5 seconds is 0.8 or less to achieve the effect of the present invention. is there. In addition, in another embodiment, the shrinkage in the direction perpendicular to the main shrinkage direction in hot water at 80 ° C. is 10% or less, and has only a maximum value in the treatment of 0 to 30 seconds.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below. As the polyester used for the heat-shrinkable polyester film of the present invention, a naphthalate polyester having butylene naphthalate and ethylene naphthalate as repeating units is used. The naphthalate-based polyester is preferably a mixture of polybutylene naphthalate or a polybutylene naphthalate / terephthalate copolymer and polyethylene naphthalate or a polyethylene naphthalate / terephthalate copolymer or a polyethylene / polybutylene / naphthalate / terephthalate copolymer. .

It is preferable that at least one of the naphthalate-based polyesters satisfies the following formulas (1) to (3). (1) 80.0 ≦ Mg ≦ 300.0 (2) 2.0 ≦ Co ≦ 40.0 (3) 2.0 ≦ (Mg + Co) /P≦5.0 (wherein Mg, Co, and P are magnesium Amount of compound, cobalt compound and phosphorus compound as magnesium atom, cobalt atom and phosphorus atom with respect to polyester (ppm)
The quantification of metal atoms is determined by the atomic weight (pp
m)).

In the naphthalate-based polyester used in the present invention, when the added amount of magnesium is less than 80.0 ppm, the electrostatic adhesion at the time of melt-extrusion to a cooling roll tends to decrease, and the appearance of the obtained film tends to deteriorate. . On the other hand, if it exceeds 300 ppm, the hydrolysis resistance is apt to decrease, and the obtained film becomes brittle. When the addition amount of cobalt is less than 2.0 ppm, the yellow tint of the film becomes strong, and when it exceeds 40.0 ppm, the film becomes blackish, which is not practically preferable. (Mg + Co) / P
If it is less than 2.0, the compatibility will be poor when mixed with other polyesters, so that the transparency of the resulting film will be reduced, and the practicality will be poor. If it exceeds 5.0, the yellow tint of the film becomes strong, which is not preferable for practical use.

In the present invention, as an acid component other than terephthalic acid and naphthalenedicarboxylic acid, one of known dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, isophthalic acid and dimer acid is used. Or two or more may be used, and ethylene glycol,
As a glycol component other than butanediol, one or more known diols such as propylene glycol, neopentyl glycol, hexamethylene glycol, 1,4-cyclohexanedimethanol, and dimer acid diol may be used. In order to obtain a heat-shrinkable polyester film having particularly excellent shrink finish, it is preferable to use a polyester in which neopentyl glycol is the remaining glycol component.

Further, it is preferable to include an inorganic lubricant and an organic lubricant in order to improve the lubricity of the heat-shrinkable film. Further, if necessary, additives such as a stabilizer, a coloring agent, an antioxidant, a solvent eliminating agent, and an antistatic agent may be contained.

The heat shrinkable film of the present invention has a heat shrinkage [HS30] of 30% or more in the main shrinkage direction (direction having the largest shrinkage ratio) after being treated in hot water at 80 ° C. for 30 seconds, and at 80 ° C.
Heat shrinkage in the direction of main shrinkage [HS5
] [HS5 / HS30] must be 0.8 or less. If the shrinkage ratio after the treatment for 30 seconds is less than 30%, the amount of shrinkage when shrinking as a label becomes insufficient, and the film does not adhere sufficiently to the container or the film easily wrinkles, which is not preferable.

When the heat shrinkage ratio [HS5 / HS30] is 0.1.
If it exceeds 8, undesirably, vertical shrinkage is likely to occur when the label is shrunk with a square bottle.

Although the heat shrinkage of the heat shrinkable film of the present invention in the direction orthogonal to the main shrinkage direction is not particularly limited, the heat shrinkage after treatment in hot water at 80 ° C. for 0 to 30 seconds is 10%. % Or less, and need to have only a local maximum. If the heat shrinkage in the direction orthogonal to the main shrinkage direction exceeds 10%, the shrinkage of the design when shrinking as a label is undesirably large. Further, when the label does not have a maximum value, that is, when the label decreases monotonously, a horizontal wrinkle easily occurs when the label is shrunk, which is not preferable. On the other hand, if the label monotonically increases, the shrinkage of the label increases when the label is shrunk, which is not preferable.

The polyester raw material used in the present invention is dried using a drier such as a hopper drier or a paddle drier, or a vacuum drier, and extruded into a film at a temperature of 200 to 300 ° C. For extrusion, any existing method such as a T-die method or a tubular method may be employed. After extrusion, it is quenched to obtain an unstretched film. The stretching process is performed on the unstretched film. However, in order to achieve the object of the present invention, the transverse direction is practical as the main shrinking direction. In the case where the main shrinkage direction is the longitudinal direction, the film can be formed according to a normal operation, except that the stretching direction in the following method is changed by 90 degrees.

Further, if attention is paid to making the thickness distribution of the intended heat-shrinkable polyester film uniform,
When the film is stretched in the transverse direction using a tenter, the heat conduction coefficient is set to 0.00 in a preheating process performed prior to the stretching process.
It is preferable to perform heating at a low wind speed of 13 calories / cm ² · sec · ° C. or less until a predetermined film temperature is reached.
The stretching in the transverse direction is performed at a temperature of Tg-20 ° C. to Tg + 40 ° C. by 2.5 to 6.0 times, preferably 3.0 to 5.5 times. Thereafter, a heat-shrinkable polyester film is obtained by performing heat treatment at 70 to 100 ° C. while elongating at 3 to 15%.

As a stretching method, not only a uniaxial stretching in a tenter but also a slight stretching in a longitudinal direction is possible. The biaxial stretching may be either sequential biaxial stretching or simultaneous biaxial stretching, and may be performed again if necessary. Focusing on suppressing the internal heat generation of the film due to stretching and reducing the film temperature unevenness in the width direction, the heat transfer coefficient of the stretching process is 0.0009 calories / cm ² · s.
ec · ° C. or higher, preferably 0.0011 to 0.0017
The condition of calories / cm ² · sec · ° C is good. As described above, the present invention is achieved by a combination of a film raw material composition and a stretching method.

[0017]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist. In addition, in this invention, the evaluation method of a naphthalate type polyester and a film is as follows. (1) Quantification of metal atoms The atomic weight (ppm) was determined by a fluorescent X-ray method.

(2) Heat shrinkage in the main shrinkage direction, shrinkage ratio, and maximum value in the direction perpendicular to the main shrinkage direction The film is cut into a square of 10 cm × 10 cm, and is not placed in warm water at a predetermined temperature of ± 0.5 ° C. After heat-shrinking by treating for 10 seconds under a load, the film was measured in the vertical and horizontal directions, and the heat shrinkage was calculated according to the following equation (1). The direction in which the heat shrinkage was large was defined as the main shrinkage direction. Heat shrinkage = (length before shrinkage−length after shrinkage / length before shrinkage) × 100 (%) (1) Formula The shrinkage ratio is 80 ° C. 30 in warm water calculated by the above formula.
Ratio [HS30] after 5 seconds and [HS5] after 5 seconds [HS
5 / HS30]. The maximum value was the maximum value of the shrinkage rate in the direction perpendicular to the main shrinkage direction during the treatment at 80 ° C. in warm water for 30 seconds or less.

(3) Shrink finish finish Using a steam tunnel (model: SH-1500-L) manufactured by Fuji Astec Inc, 1.5 round P
Using an ET bottle (a bottle used for commercially available oolong tea manufactured by Suntory Ltd.), a tunnel passage time of 10 seconds,
The test was performed at 1 zone temperature / 2 zone temperature of 75 ° C / 85 ° C. (Number of samples n = 10) The heat-shrinkable film was previously printed in three colors with grass, gold, and white inks of Toyo Ink Mfg. Co., Ltd. The finish was evaluated visually, and the criteria were as follows. did. No wrinkles, color spots, or insufficient shrinkage occurred → ○ Color spots occurred → △ Crater-like wrinkles or insufficient shrinkage occurred → ×

(4) Two-sided PET bottle using a steam tunnel (model: SH-1500-L) manufactured by Tatehike Fuji Astec Inc (a bottle used for natural water of Minami Alps manufactured by Suntory Ltd.) And tunnel transit time 1
The test was performed at 0 second, 1 zone temperature / 2 zone temperature of 80 ° C./85° C. (N = 10) The heat-shrinkable film was previously printed in three colors with grass, gold, and white inks of Toyo Ink Manufacturing Co., Ltd. This was performed by the displacement of the lower part of the label (the interval mm indicated by...).
The polyester used in the examples is as follows.

[0021]

[Table 1]

Example 1 35% by weight of polyester A, 40% by weight of polyester B and 1% of polyester C
A polyester obtained by mixing 0% by weight and 15% by weight of polyester E was extruded at 280 ° C. and rapidly cooled to obtain an unstretched film. The unstretched film was transversely stretched 2.3 times at 90 ° C., further 1.5 times at 80 ° C., and heat-treated at 90 ° C. for 20 seconds to obtain a heat-shrinkable polyester film having a thickness of 45 μm.

Example 2 35% by weight of polyester A, 40% by weight of polyester B and 1% of polyester C
A heat-shrinkable polyester film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that 5% by weight and 10% by weight of polyester E were used.

Example 3 35% by weight of polyester A, 40% by weight of polyester B and 2% of polyester D
A thickness of 45 was obtained by the method described in Example 1 except that the weight was changed to 5 weight.
A μm heat-shrinkable polyester film was obtained.

Comparative Example 1 35% by weight of polyester A, 40% by weight of polyester B and 2% of polyester E
A thickness of 4% was obtained by the method described in Example 1 except that the thickness was 4% by weight.
A 5 μm heat-shrinkable polyester film was obtained.

Comparative Example 2 35% by weight of polyester A, 40% by weight of polyester B and 2% of polyester C
A thickness of 4% was obtained by the method described in Example 1 except that the thickness was 4% by weight.
A 5 μm heat-shrinkable polyester film was obtained.

Comparative Example 3 35% by weight of polyester A, 30% by weight of polyester B and 2% of polyester C
A heat-shrinkable polyester film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that 5% by weight and 10% by weight of polyester F were used.

(Comparative Examples 4 and 5) Except that heat fixing was not performed in Example 1 (Comparative Example 4), and 9 in transverse stretching.
A heat-shrinkable polyester film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that the ratio was increased 3.5 times at 0 ° C. (Comparative Example 5). (Example 4) In Example 1, a mixture of 70% by weight of polyester G and 30% by weight of polyester H (HP-1000 of Toagosei Chemical Co., Ltd.) was used as a raw material. The film was stretched twice, then heat-treated at 90 ° C. for 3 seconds, and rapidly cooled under 10% elongation.

The evaluation results of the films obtained in Examples 1 to 4 and Comparative Examples 1 to 5 are shown in Table 1. As is clear from Table 2, all of the films obtained in Examples 1 to 4 show a good shrinkage finish (there are no defects such as wrinkles or insufficient shrinkage), and hardly cause vertical shrinkage. Thus, the heat-shrinkable polyester film of the present invention has high quality and high practicability, and is particularly excellent for shrink labels. On the other hand, the film obtained in Comparative Example 1 is apt to cause vertical shrinkage, and the film obtained in Comparative Example 2 suffers from insufficient shrinkage. Therefore, it can be said that all of the films are inferior in quality as heat-shrinkable polyester films for labels. Further, the films obtained in Comparative Examples 3 to 5 have a small vertical shrinkage improving effect.

[0030]

The heat-shrinkable polyester film of the present invention according to the first aspect is less likely to cause vertical shrinkage and has less wrinkles, shrinkage spots and distortion after shrinkage. Further, the method for producing a heat-shrinkable polyester film of the present invention according to claim 2 is unlikely to cause vertical shrinkage, and after shrinkage, wrinkles, shrinkage spots,
A heat-shrinkable polyester film with little distortion can be easily obtained.

[0031]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a side view showing a shrinkage of a shrinkable film in a PET bottle body after shrinkage.

[Description of Signs] 1 PET bottle 2 Shrink film 3 Tatehike

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutomu Miko Inayama Pref., Aichi Pref. Inuyama Factory, Toyobo Co., Ltd. Inuyama Factory Co., Ltd.

Claims (3)

[Claims] 1. The heat shrinkage in the main shrinkage direction [HS30] after treatment in hot water at 80 ° C. for 30 seconds is 30% or more, and the heat shrinkage ratio in the main shrinkage direction after treatment in hot water at 80 ° C. for 5 seconds. [HS5]
Wherein the ratio [HS5 / HS30] is 0.8 or less. 2. The heat shrinkage [HS30] in the main shrinkage direction after treatment in hot water of 80 ° C. for 30 seconds according to claim 1 is 40% or more, and the main shrinkage rate after treatment in hot water of 80 ° C. for 5 seconds. A heat-shrinkable polyester film having a ratio [HS5 / HS30] to the heat shrinkage [HS5] in the direction of 0.7 or less. 3. The film according to claim 1, wherein the shrinkage in a direction perpendicular to the main shrinkage direction in hot water at 80 ° C. is 10% or less, and has only a maximum value in 0 to 30 seconds treatment. Heat-shrinkable polyester film.