JPH04344222A - Polyester type shrink film - Google Patents

Abstract

PURPOSE:To eliminate the non-uniformity due to shrinkage and to prevent trouble such as the exposure of a base material by condensing a dicarboxylic acid component and a specific mixed diol component and stretching the obtained polyester film in specific magnification to impart specific heat shrinkability thereto. CONSTITUTION:A polyester film is constituted of a dicarboxylic acid component unit based on terephthalic acid and a mixed diol component unit consisting of ethylene glycol 99-95mol.% and cyclohexanedimethanol 1-5mol.% and stretched 1.5-2.5 times unidirectionally, for example, longitudinally using a roll type stretching machine or a tenter type stretching machine. Further, a heat- shrinkage factor in one direction, for example, in a longitudinal direction is set to 25% or less at 80 deg.C and 35% or more at 100 deg.C, pref., 40-50%. When the heat-shrinkage factor is 25% or more at 80 deg.C, the exposure of a base material is easy to generate and, when the heat-shrinkage factor is 50% or more at 100 deg.C, it is feared that the non-uniformity of shrinkage at the time of mounting is generated.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a novel polyester shrink film, and more specifically, it is free from distortion or wrinkles in the design due to uneven shrinkage during installation, and the film does not break due to further shrinkage during post-processing after installation. The present invention relates to a polyester shrink film that does not cause problems such as peeling, peeling, and exposure of the base material, and is suitable for use as a label for wrapping around glass bottles, dry batteries, etc.

0002

[Prior Art] In recent years, polyester shrink films have not only excellent transparency but also shrinkage during transportation and storage.
In other words, it is attracting attention as a label or packaging material that can be applied to plastic bottles, glass bottles, etc. by heating and shrinking it, since it does not cause insufficient dimensions or deterioration of flatness due to natural shrinkage. In order to develop the necessary heat shrinkage rate, a large amount of copolymer component was added to polyethylene terephthalate (Japanese Patent Application Laid-open No. 15683-1983).
3) and blending polyethylene terephthalate with copolymers thereof (Japanese Patent Publication No. 64-10332).

[0003] Incidentally, vertically wound labels are often used as body wrapping labels for glass bottles, dry batteries, etc. from the point of view of workability, and up until now, polyvinyl chloride-based vertical shrink films have often been used. . However, in recent years, due to industrial waste issues, polyester-based vertical shrink films have become more desirable than polyvinyl chloride-based vertical shrink films, and the base materials for these films include the above-mentioned copolymers and combinations of them and polyethylene terephrate. Blend products are beginning to be used.

However, conventional polyester shrink films made of polyester copolymers and blends of them with polyethylene terephrate have a higher performance compared to polyvinyl chloride and polystyrene films that have been commonly used as shrink films. It is expensive, and the heat shrinkage rate is highly temperature dependent, and the heat shrinkage rate rapidly increases near the glass transition temperature, which causes distortions and wrinkles in the design due to uneven shrinkage during installation, resulting in poor finish. In addition to deteriorating the appearance, further shrinkage occurs during heat sterilization treatment after installation, heat resistance tests of dry batteries, etc., resulting in problems such as film breakage, peeling, and exposure of the base material.

[0005]

[Problems to be Solved by the Invention] The present invention overcomes the drawbacks of conventional polyester shrink films, and provides a good finished appearance with no distortion or wrinkles in the design due to uneven shrinkage during installation. To provide an inexpensive polyester shrink film that does not cause troubles such as film breakage, peeling, and exposure of the base material due to further shrinkage during post-processing such as heat sterilization treatment after installation and heat resistance test of dry batteries. It was made for the purpose of

[0006]

[Means for Solving the Problems] As a result of intensive research to develop a polyester shrink film having the above-mentioned preferable properties, the present inventors have found that a dicarboxylic acid component mainly composed of terephthalic acid and a specific composition have been developed. We have discovered that this objective can be achieved by using a shrink film with specific heat-shrinkable properties, which is made by stretching a polyester film obtained by polycondensation with a mixed diol component in one direction at a specific ratio. Based on this, the present invention was completed.

That is, the present invention provides dicarboxylic acid component units mainly composed of terephthalic acid and ethylene glycol 9
9-95 mol% and cyclohexanedimethanol 1-5
A polyester film composed of mixed diol component units consisting of mol% is stretched 1.5 to 2.5 times in one direction, and the heat shrinkage rate in one direction is 25 at 80°C.
% or less, and 35% or more at 100°C.

[0008] In the shrink film of the present invention,
The longitudinal heat shrinkage rate is 25% or less at 80°C, 100
It is necessary that it be 35% or more, preferably in the range of 40 to 50% at ℃. Heat shrinkage rate at 80℃ is 2
If it exceeds 5%, further shrinkage may cause film breakage, peeling, and exposure of the base material during post-processing such as heat sterilization after installation or heat resistance testing of dry batteries.
If the thermal shrinkage rate at 100° C. is less than 35%, the shrinkage will be insufficient and it will not be possible to sufficiently adhere to portions that require high shrinkage such as edges. In addition, if the heat shrinkage rate at 100℃ exceeds 50%, the increase in heat shrinkage rate at 80 to 100℃ will be too large, which will easily cause distortions and wrinkles in the design due to uneven shrinkage during installation, and the finished appearance will deteriorate. There is a risk of damage, which is not desirable.

The polyester used in the present invention is formed by a polycondensation reaction between a dicarboxylic acid component mainly consisting of terephthalic acid and a mixed diol component having a specific composition, and has a glass transition temperature of 75°C or higher. Things are advantageous. If the glass transition temperature is less than 75°C,
Under any stretching conditions, there is a risk that a film that satisfies the heat shrinkage characteristics described above may not be obtained.In particular, for films with a glass transition temperature of 77°C or higher, there is a wide range of stretching conditions to choose from.
suitable.

The dicarboxylic acid component units in the polyester preferably contain 95 mol% or more, particularly 98 mol% or more of terephthalic acid units. When the proportion of terephthalic acid units in the dicarboxylic acid component units decreases, the mechanical strength of the resulting film tends to decrease. Examples of carboxylic acid units other than terephthalic acid units that may be present in the dicarboxylic acid component unit include isophthalic acid, biphenyl dicarboxylic acid, 5-tert-butyl isophthalic acid,
,2,6,6-tetramethylbiphenyldicarboxylic acid,
Aromatic dicarboxylic acid units such as 2,6-naphthalene dicarboxylic acid, 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid, oxalic acid, succinic acid,
Units of aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and 1,10-decanedioic acid, and units of polycarboxylic acids such as trimellitic acid and 1,2,4,5-benzenetetracarboxylic acid, etc. Can be mentioned. The proportion of carboxylic acid units other than these terephthalic acid units is desirably 5 mol% or less, preferably 2 mol% or less, based on the total carboxylic acid units, but as for the components that lower the glass transition temperature, For the reasons mentioned above, it is desirable to further limit the content.

On the other hand, the diol component units include 99 to 95 mol% of ethylene glycol units, preferably 98 to 96 mol% of cyclohexanedimethanol units, and 1 to 5 mol% of cyclohexanedimethanol units.
Preferably, it consists of 2 to 4 mol%, and if the cyclohexanedimethanol unit is less than 1 mol%, the heat shrinkage rate will be difficult to reach 35% or more at 100°C, and if it exceeds 5 mol%, the heat shrinkage rate will be low. Under stretching conditions of 35% or more at 100°C, on the other hand, the heat shrinkage rate at 80°C cannot be suppressed to 25% or less.

In addition to the above-mentioned ethylene glycol and cyclohexanedimethanol units, the diol component units of the polyester used in the present invention may contain small amounts of other diols or other diols, if desired, to the extent that they do not adversely affect the physical properties of the polyester. It may also contain units of polyols.

Examples of such diols and polyols include diethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, xylylene glycol, glycerin, pentaerythritol, and trimethylolpropane. etc. can be mentioned.

The polyester used in the present invention is prepared by subjecting the dicarboxylic acid component and mixed diol component to a polycondensation reaction according to a conventional polyester manufacturing method.
can be manufactured. In this case, if necessary, as the dicarboxylic acid component, a reactive functional derivative of the dicarboxylic acid,
For example, acid halides and acid esters can be used, and the reaction can also be carried out in the presence of a reaction solvent, a condensing agent, a catalyst, and the like. The degree of polymerization of the polyester of the present invention is not particularly limited, but the intrinsic viscosity is 0.50.
-1.20, preferably in the range of 0.60-0.90.

The shrink film of the present invention is produced by forming the polyester thus obtained into a film, and using a roll-type stretching machine or a tenter-type stretching machine, it is unidirectionally stretched.
For example, 1.5 to 2.5 times in the vertical direction, preferably 1.7 to 2.5 times
It can be produced by stretching 2.3 times. If the stretching ratio is outside the above range, the heat shrinkage rate at 100° C. will not be 35% or more, and the object of the present invention will not be achieved. The reason for this is not necessarily clear, but
It is expected that the correlation between the degree of orientation, represented by birefringence, and the degree of crystallinity, represented by specific gravity, can be elucidated.

In this film forming, for example, after drying the polyester obtained by the above-mentioned polycondensation,
It is carried out by melt extrusion at a temperature of 15°C to form a film with a thickness of 30 to 300 μm on a casting drum with a surface temperature of 15 to 70°C.

[0017] Further, the stretching treatment is carried out by stretching the cast film thus obtained by 1.5 to 2.5 times, preferably 1.7 to 2. This is done by stretching 3 times. If this stretching temperature is lower than the glass transition temperature, stretching is difficult, and in order to stretch uniformly, it is necessary to
It is desirable to conduct the reaction at a temperature higher than 50°C, preferably 15 to 40°C. Also, if necessary, 1.1 to 1.5 in the horizontal direction.
It may be stretched approximately twice as long. After stretching, the film is heat-treated at a temperature ranging from the usual stretching temperature to 15° C. lower than the stretching temperature, and then cooled and wound up.

As mentioned above, the polyester shrink film of the present invention needs to have a heat shrinkage rate of 25% or less at 80°C and 35% or more at 100°C in one direction. The heat shrinkage rate is 100
It is desirable that it be within ±10% at °C.

The thickness of the film of the present invention is not particularly limited, but is usually 15 to 150 μm, preferably 20 μm.
It is selected in the range of ~70 μm. In addition, the polyester shrink film of the present invention is subjected to surface treatments such as corona discharge treatment and plasma irradiation treatment, as well as various coatings such as plasma treatment and antistatic coating, to improve the adhesion of printing ink, metal deposition, slipperiness, etc. Anti-blocking properties, easy sealing properties, antistatic properties, etc. can also be improved.

[0020]

Effects of the Invention The polyester shrink film of the present invention has the necessary heat shrinkability as a vertical shrink film for body-wrapping labels, and has an excellent finished appearance when worn.
In addition, it has an excellent property that it does not cause problems such as film breakage, peeling, and exposure of the base material due to further shrinkage during post-processing after installation, and is inexpensive, so it can be used for body wrap labels for glass bottles and dry batteries. It is most suitable as a vertical shrink film, and can be used in a wide range of other packaging material fields that can exhibit the effects of the above characteristics.

[0021]

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way. The heat shrinkage rate, fitability, fitability after hot water immersion treatment, and glass transition temperature for each example were determined according to the following methods.

(1) Heat shrinkage rate Shrink film was cut into 100 mm square samples, and the samples were immersed in a glycerin bath adjusted to 80°C and 100°C for 30 seconds, and then the vertical or horizontal dimensions were measured. , the respective heat shrinkage rates are

[Formula 1] I asked for it according to.

(2) Attachability to glass bottles, attachability after soaking in hot water A shrink film with a grid pattern is wrapped around a commercially available glass bottle for drink preparations, with the vertical direction of the film aligned with the circumferential direction of the bottle. After bonding the joints with a polyester adhesive, they were put through a shrink tunnel at 160° C. for 5 seconds to be shrink-fitted, and the degree of deformation in the grid pattern and the presence or absence of wrinkles were observed. Thereafter, the film was immersed in warm water at 85° C. for 30 minutes, and the film was judged for breakage, peeling, etc. at the adhesive portion. Evaluation: ○: Good, △: Slightly poor, ×: Poor

[0024]
(3) Glass transition temperature Using a PerkinElmer DSC measurement device, the temperature was raised to 300°C at a rate of 20°C/min under a nitrogen stream, and then 200°C.
Rapidly cool down to 20°C at a rate of 20°C/min, and then cool again to 20°C/min after 5 minutes.
The temperature was raised to 300° C. at a rate of 1 minute, and the glass transition temperature (midpoint) at that time was determined.

Example 1 A predetermined amount of a mixture consisting of terephthalic acid, ethylene glycol, and cyclohexanedimethanol was charged into a stainless steel autoclave, and a polycondensation reaction was carried out according to a conventional method until the intrinsic viscosity reached 0.80. A polyester polymer having a glass transition temperature of 78° C. was produced by continuing until the temperature reached 78° C. This product is composed of 100 mol% of terephthalic acid units as dicarboxylic acid component units, 97 mol% of ethylene glycol units as diol component units, and 3 mol% of cyclohexanedimethanol units.

The polyester polymer thus obtained was heated to a surface temperature of 3 using a T-die at a temperature of 270°C.
Melt extruded onto casting drum at 0°C, thickness 10
A film of 0 μm was formed. Next, this film was stretched twice in the longitudinal direction using a roll-type longitudinal stretching machine at a temperature of 110°C, and then heat-treated at 105°C to obtain a shrink film having a thickness of 50 μm. Table 3 shows the physical properties of this shrink film.

Example 2 A shrink film having a thickness of 50 μm was obtained in exactly the same manner as in Example 1, except that the stretching temperature was changed to 100° C. The physical properties of this product are shown in Table 3.

Examples 3 and 4, Comparative Examples 1 and 2 Using the same polyester polymer as in Example 1, films with the thickness shown in Table 1 were formed, and the stretching was performed at the stretching temperature and stretching ratio shown in Table 1. Longitudinal stretching was performed in the same manner as in Example 1 to obtain a shrink film with a thickness of 50 μm. Table 3 shows the physical properties of this shrink film.

[Table 1]

Comparative Examples 3 to 9 Using the dicarboxylic acid component and diol component shown in Table 2,
A polyester polymer having an intrinsic viscosity of 0.80 was produced in the same manner as in Example 1. Table 2 shows the proportions of these polyester polymer structural units and their glass transition temperatures.

Next, using these polyester polymers, a film having the thickness shown in Table 2 was formed and longitudinally stretched in the same manner as in Example 1 at the stretching temperature and stretching ratio shown in Table 2. A shrink film having a thickness of 50 μm was obtained by heat treatment at a temperature 5° C. lower than the stretching temperature. Table 3 shows the physical properties of this shrink film.

[Table 2]

[Table 3]

[0031] As is clear from Table 3, the polyester shrink film of the present invention has the necessary heat shrinkability as a vertical shrink film for body wrap labels, has an excellent finished appearance when installed, and has a good appearance after being installed. It does not cause any trouble during processing. On the other hand, in comparison examples, those with a heat shrinkage rate of less than 35% at 100°C have insufficient shrinkage, so parts that require high shrinkage such as edges are not sufficiently adhered, and the heat shrinkage rate at 100°C is 35%. % or more, those with a heat shrinkage rate of more than 25% at 80°C are undesirable because they cause further shrinkage in the hot water immersion test of glass bottles, resulting in film breakage, peeling, and exposure of the base material. In addition, the heat shrinkage rate at 100℃ exceeds 50% and is 80 to 100%.
If the increase in thermal shrinkage rate in °C is too large, the pattern will be distorted or wrinkled due to uneven shrinkage during installation, resulting in poor finished appearance.

Claims (2)

[Claims] Claim 1: A polyester film composed of a dicarboxylic acid component unit mainly composed of terephthalic acid and a mixed diol component unit consisting of 99 to 95 mol % of ethylene glycol and 1 to 5 mol % of cyclohexanedimethanol. Stretched by 1.5 to 2.5 times in the direction, the heat shrinkage rate in one direction is 25% or less at 80 °C, 100 °C
A polyester shrink film characterized in that it has a content of 35% or more. 2. The polyester shrink film according to claim 1, wherein one direction is the longitudinal direction.