JPH11277625A - Heat shrinkable polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a wrinkle, a shrinkage mark, a shrinkage strain or the like hardly generate in the case of mounting and shrinking on an outer periphery of a container of a complicated shape, by specifying a ratio of a shrink stress in a main shrinking direction to that in a followed shrinking direction, and a melting sealing strength. SOLUTION: The heat shrinkable polyester film is needed to be 0.05 to 0.45 of a radio (τ1 /τ2 ) of a shrinkage stress (τ2 ) of a main shrinking direction at 90 deg.C to a shrinkage stress (τ1 ) of a followed shrinking direction (perpendicular to the main shrinking direction). Further, its fusing sealing strength is necessary to be 1.2 kg/15 mm width or more. Accordingly, a polyester used here is preferably partly mixed with a polyester having a difference from a crystallizing temperature (Tc2 ) at the time of cooling the melting polymer from a melting point (Tm) for satisfying the sealing strength of 40 deg.C or lower. For example, a polyethylene terephthalate or polybutylene terephthalate is used.

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 particularly, to a heat-shrinkable polyester film attached to the outer periphery of a container having a complicated shape such as a cosmetic container, a fragrance container, and a chemical solution pack. The present invention relates to a heat-shrinkable polyester film which is extremely free of wrinkles, spots of shrinkage, distortion, and the like, and further has excellent fusing sealability.

[0002]

2. Description of the Related Art Conventionally, films made of polyvinyl chloride, polyethylene, etc. have been mainly used as heat-shrinkable films. Recently, however, polyvinyl chloride has a problem of generating chlorine-based gas when incinerated at the time of disposal. Has problems such as difficulty in printing, and heat-shrinkable polyester-based films have attracted attention.

However, when a heat-shrinkable polyester film having shrinkage in only one direction is attached to a container having a complicated shape as described above and shrunk, wrinkles, shrinkage spots, and insufficient shrinkage are likely to occur. It was not satisfactory as a heat-shrinkable film.

In order to avoid such a drawback, Japanese Patent Laid-Open Publication No.
No. 763 discloses a heat-shrinkable polyester film which also shrinks in a direction orthogonal to the main shrinkage direction, and Japanese Patent Application Laid-Open No. 185510/1993 limits the stretching ratio in the machine direction and the transverse direction so as to limit the stretching direction. Discloses a method of controlling the shrinkage rate of a slab to about 15%.

[0005] However, the film obtained by this method has a very low fusing sealing property required for the use of the container, and has a poor practicality.

In order to avoid such a drawback, Japanese Patent No. 25665 is used.
No. 68 discloses a heat-shrinkable polyester film having improved heat sealability.

[0007] However, not only the fusing sealability of the film obtained by the above method is not satisfactory, but also the shrinkage in the direction orthogonal to the main shrinkage direction is small, and wrinkles, shrinkage spots, and distortions occur in the container. It was a film that was easy to generate and was poor in practicality.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the conventional heat-shrinkable polyester-based film. , Shrinkage distortion is unlikely to occur, that is,
An object of the present invention is to provide a heat-shrinkable polyester film having excellent shrink finish and sufficient fusing sealability for practical use.

[0009]

In order to achieve the above-mentioned object, the heat-shrinkable polyester film of the present invention comprises 90
The ratio of main shrinkage direction of the shrinkage stress at ℃ and (tau ₂₎ and slave shrinkage direction of shrinkage stress _{(τ 1) (τ 1 /} τ 2) is 0.05 to 0.4
5, and the fusing seal strength is not less than 1.2 kg / 15 mm width.

[0010] Here, the secondary contraction direction means a direction perpendicular to the main contraction direction.

In a preferred embodiment of the present invention, 95
40% shrinkage in the main shrinkage direction after 10 seconds treatment in hot water
As described above, the contraction rate in the secondary contraction direction can be 15 to 30%.

The heat-shrinkable polyester film having the above-mentioned structure is less likely to cause wrinkles, shrinkage spots, shrinkage distortion and the like even when shrinked by being mounted on a container having a complicated shape.
That is, the shrink finish is excellent, and the fusing sealing property is practically sufficient.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the heat-shrinkable polyester film of the present invention will be described.

The polyester used for the heat-shrinkable polyester film of the present invention has a difference (ΔT) between the melting point (Tm) for satisfying the fusing seal strength and the crystallization temperature (Tc ₂ ) when the molten polymer is cooled. = Tm−Tc ₂ ) is 40 ° C.
The following polyesters are preferably partially used for mixing, and in particular, polyester having a ΔT of 40 ° C. or less is preferably 10 to 40 ° C.
Weight%, and polyester having ΔT of 40 ° C. or less
It is preferable to use 30% by weight.

As an example of such a polyester having a ΔT of 40 ° C. or lower, typically, polybutylene terephthalate, polybutylene naphthalate, or a polyester obtained by copolymerizing an aliphatic acidic component or a long-chain glycol component with these polyesters Can be shown. In the present invention,
In addition to the acidic components consisting of terephthalic acid and naphthalenedicarboxylic acid constituting the polyester having a ΔT of 40 ° C. or less, oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, isophthalic acid, decanedicarboxylic acid, dimer acid One or more known dicarboxylic acids such as butanediol may be used.Also, ethylene glycol, neopentyl glycol, hexamethylene glycol, 1,4-cyclohexane dimethanol, One or more known diols such as dimer acid diol and tetramethylene glycol ethylene oxide adduct may be used.

In order to obtain a heat-shrinkable polyester film having particularly excellent shrink finish, neopentyl glycol is preferably used as one of the diol components.

Further, in order to improve the lubricity of the heat-shrinkable polyester film, it is preferable that the film contains an inorganic lubricant and an organic lubricant. Also, if necessary, stabilizers,
It may contain additives such as a coloring agent, an antioxidant, a solvent eliminating agent, and an antistatic agent.

The heat-shrinkable polyester film of the present invention, the ratio of the main shrinkage direction of the shrinkage stress at 90 ° C. (tau ₂₎ and slave shrinkage direction (main shrinkage direction perpendicular to the direction) of the shrinkage stress (tau ₁₎ (Τ ₁ / τ ₂ ) needs to be 0.05 to 0.45. Further, (τ ₁ / τ ₂ ) is more preferably from 0.08 to 0.40, and most preferably from 0.10 to 0.35. If (τ ₁ / τ ₂ ) is less than 0.05, wrinkles, shrinkage spots, and insufficient shrinkage tend to occur, which is not preferable.
If (τ ₁ / τ ₂ ) exceeds 0.45, distortion is likely to occur in shrinkage, which is not preferable.

The heat-shrinkable polyester film of the present invention must have a fusing seal strength of 1.2 kg / 15 mm width or more, more preferably 1.4 kg / 15 mm width, and 1.6 kg / 15 mm width. Most preferably the width. When the fusing seal strength is less than 1.2 kg / 15 mm width, when shrink-wrapped after R-sealing, not only the seal portion is easily ruptured, but also a whisker-like substance is generated at the time of R-sealing or the film piece is cut to the fusing blade. A heat-shrinkable polyester film which easily adheres and has a remarkably low commercial value is obtained.

In order to achieve the object of the present invention, it is practical to use a polyester film in which the main shrinkage direction is the horizontal direction. Therefore, an example of a film forming method in the case where the main shrinkage direction is the horizontal direction will be described below. The invention naturally includes the case where the main contraction direction is the vertical direction.

In the present invention, a polyester raw material dried using a drier such as a hopper drier or a patrol drier or a vacuum drier, preferably a polyester raw material containing 10 to 40% by weight of polyester having a ΔT of 40 ° C. or less,
More preferably, polyester having ΔT of 40 ° C. or less
200 to 30% by weight of polyester raw material
Extruded at a temperature of 0 ° C. and quenched to obtain an unstretched film. In order to produce a heat-shrinkable polyester film in which the main shrinkage direction is transverse, the obtained unstretched film is
After longitudinal stretching at 1.2 to 1.8 times at 0 to 95 ° C, 80 to 1
A method of stretching horizontally at 10 ° C. by 3 to 5 times is typical, but it goes without saying that stretching conditions can be appropriately set.

[0022]

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 of the present invention.

(1) Shrinkage stress Tensilon with air oven manufactured by Toyo Seiki (model:
Using UTM-4L), the distance between the chucks was 50 mm, the sample shape was 10 cm in the direction for measuring the shrinkage stress, and 2 cm in the direction perpendicular to the measurement direction, and the force developed when heated for 1 minute in a 90 ° C. air oven. It was recorded on a recorder, the maximum value was read, the contraction stress was calculated from the following equation (1) (n = 3), and the average was taken as the contraction stress. Shrinkage stress = (reading value / sample cross-sectional area before heating) (kg / mm ² ) (1)

(2) Fusing seal strength An automatic bag making machine (model: RP50) manufactured by Kyoei Printing Machine Materials Co., Ltd.
Using 0), a fusing blade having a blade angle of 70 ° C. was manufactured at 240 ° C. at a heating bag making speed of 100 bags / min. The fusing seal portion of the bag-made product was cut out at a width of 15 mm, and peel strength (n = 10) measured with a Tensilon (model: STM-T-50BP) manufactured by Toyo Baldwin Co. at a distance between chucks of 50 mm and a pulling speed of 200 mm / min. The average value of) was taken as the fusing seal strength.

(3) Heat Shrinkage The film was cut into a 10 cm × 10 cm square,
After heat-shrinking by treating in hot water of ± 0.5 ° C. for 10 seconds under no load, the film was measured for its vertical and horizontal dimensions, and the heat shrinkage was calculated according to the following equation (2). 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 (%)

(4) Melting point (Tm), crystallization temperature (T
c ₂ ) DSC (model: DSC220) manufactured by Seiko Denshi Kogyo KK
Using 10 mg of polyester raw material from 20 ° C. to 300
The temperature was raised at a rate of 20 ° C./min to 200 ° C., held at 300 ° C. for 3 minutes, and then decreased to a temperature of 100 ° C. at a rate of 20 ° C./min. Is the melting point (Tm), and the peak temperature of the exothermic peak at the time of cooling is the crystallization temperature (Tc ₂ ).

(5) Shrink finish finish Universal shrinker manufactured by Kyowa Denki Co., Ltd. (model: K2
000) and attached to a commercially available laminate tube (Revial Rinse manufactured by Shiseido Co., Ltd.), and a shrinker passage time of 15 seconds, (1 zone temperature / 2 zone temperature) = (160 ° C.)
/ 180 ° C), and the finish was evaluated as follows.
(N = 10) ：: No defect in appearance ×: Wrinkle, insufficient shrinkage

The polyesters used in Examples and Comparative Examples are as shown in Table 1.

[0029]

[Table 1]

(Example 1) 10% by weight of polyester A, 65% by weight of polyester B, 2% of polyester C
The polyester mixed at 5% by weight was melt-extruded from a T-die at 280 ° C. and quenched with a chill roll to obtain an unstretched film. The unstretched film is longitudinally stretched 1.4 times with a multi-roll vertical stretching machine (roll temperature: 85 ° C.), and then preheated by a tenter until the film temperature reaches 95 ° C.
The film was stretched 4.0 times in the transverse direction at 0 ° C. and heat-treated at 90 ° C. for 8 seconds to obtain a heat-shrinkable polyester film having a thickness of 25 μm.

Example 2 10% by weight of polyester A, 65% by weight of polyester B, 2% of polyester D
25 μm in thickness in the same manner as in Example 1 except that the content was 5% by weight.
m of a heat-shrinkable polyester film was obtained.

Example 3 10% by weight of polyester A, 65% by weight of polyester B and 2% of polyester F
25 μm in thickness in the same manner as in Example 1 except that the content was 5% by weight.
m of a heat-shrinkable polyester film was obtained.

(Comparative Example 1) An unstretched film made of the polyester described in Example 1 was preheated to 95 ° C with a tenter and then stretched 4.0 times in the transverse direction at 80 ° C.
Heat treatment was performed at 90 ° C. for 8 seconds to obtain a heat-shrinkable polyester film having a thickness of 25 μm.

Comparative Example 2 A heat-shrinkable polyester film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that polyester A was 35% by weight and polyester B was 65%.

Comparative Example 3 10% by weight of polyester A, 65% by weight of polyester B and 2% of polyester E
25 μm in thickness in the same manner as in Example 1 except that the content was 5% by weight.
m of a heat-shrinkable polyester film was obtained.

Table 2 shows the evaluation results of the films obtained in Examples 1 to 3 and Comparative Examples 1 to 3. As is clear from Table 2, all of the heat-shrinkable polyester films obtained in Examples 1 to 3 show a good shrinkage finish (there are no defects such as insufficient shrinkage, wrinkles, and distortions), and the R-seal processability. The fusing seal strength as a guide was good, and the fusing seal portion showed a good shape (no generation of whiskers, etc.).
As described above, the heat-shrinkable polyester film of the present invention has high quality and high practicability, and is particularly suitable for applications in which the film is shrunk by being attached to a container having a complicated shape after R-sealing. On the other hand, the heat-shrinkable polyester film obtained in Comparative Example 1 has noticeable wrinkles and insufficient shrinkage, and the heat-shrinkable polyester film obtained in Comparative Example 2 has not only noticeable wrinkles but also low fusing seal strength. Inferior in R sealability. The heat-shrinkable polyester film obtained in Comparative Example 3 has low fusing seal strength and is inferior in R seal processability. Thus, in the comparative examples, the heat-shrinkable polyester films were all inferior in quality and low in practicability.

[0037]

[Table 2]

[0038]

According to the heat-shrinkable polyester film of the present invention, the occurrence of wrinkles, distortions and insufficient shrinkage after shrinkage is extremely small, and the fusing sealability is excellent.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shinichiro Okumura 344 Maehata, Kizu, Oji, Inuyama-shi, Aichi Prefecture Inside the Inuyama Plant of Toyobo Co., Ltd. In the Inuyama Plant of Toyobo Co., Ltd. (72) Inventor Masatoshi Hashimoto 344 Maehata, Kizu, Oji, Inuyama-shi, Aichi Prefecture In the Inuyama Plant of Toyo Boseki Co., Ltd. Toyobo Co., Ltd.

Claims (2)

[Claims] 1. A ratio between the main shrinkage direction of the shrinkage stress at 90 ℃ (τ ₂₎ and slave shrinkage direction of shrinkage stress (τ ₁₎ (τ ₁ /
τ ₂ ) is 0.05 to 0.45, and the fusing seal strength is 1.2 kg / 15 mm width or more. 2. The shrinkage in the main shrinkage direction after treatment in hot water at 95 ° C. for 10 seconds is 40% or more, and the shrinkage ratio in the sub-shrinkage direction is 15 to 30%. Heat-shrinkable polyester film.