JPH09272150A - Heat-shrinkable polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent no-uniformity of printing density from being generated by bringing tanδ(specified) temp., tanδ(max.) temp. and tanδ temp. width of dynamic viscoelastic characteristics in at least one direction of the longitudinal or transverse direction of a heat-shrinkable polyester film respectively in a specified value range. SOLUTION: A heat-shrinkable film made of a polyester film has tanδ(0.08) temp. of 30-70 deg.C in dynamic viscoelastic characteristics in one direction and tanδ(max.) temp. of 80-130 deg.C in dynamic viscoelastic characteristics in one direction and tanδ temp. width of 25-100 deg.C in dynamic viscoelastic characteristics in one direction. By cooling the film while a stress is applied on the film under extended or stretched condition after drawing or cooling furthermore continuously, the pre- and after-treatment characteristics are improved and stabilized. By drawing the film in multi-stage temp. like this, the max. shrinking acceleration is decreased to obtain a film wherein non-uniformity of shrinkage is hardly generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention exhibits heat shrinkage characteristics particularly suitable in the field of packaging materials such as coating and binding, and heat shrinkable polyester films (including sheets; hereinafter the same) without uneven shrinkage. It is about.

[0002]

2. Description of the Related Art Tubular bodies formed of heat-shrinkable plastic films are, for example, containers, bottles (including plastic bottles), can rods (pipes, rods, wood, various rods), etc. Abbreviated as a category) or for bundling, particularly covering or partially covering these caps, shoulders, torso, etc., and used for the purpose of marking, protection, bundling, improvement of commercial value, etc. It is widely used in fields such as boxes, plates, bottles, rods, notebooks, etc., such as integrated packaging, or skin packs, which are closely adhered to a covered material, and can be used for applications that utilize shrinkage and shrinkage stress. Be expected. In the field of shrink films for labels, films made of polyvinyl chloride, polyethylene, etc. have been mainly used, but in recent years, the problem of flammability at the time of disposal or P
Heat-shrinkable polyester films are attracting attention in terms of recoverability after mounting on ET bottles. However,
Many heat-shrinkable polyester films shrink rapidly, which is not satisfactory as a shrink film for labels. In order to avoid such a drawback, JP-A-1-
Japanese Patent No. 110931 discloses a method of improving shrinkage finishability by significantly reducing the breaking elongation in the direction orthogonal to the main shrinkage direction. However, the film obtained by the method not only easily breaks when tension is applied in a process such as printing and labeling, but label breakage easily occurs when the normal transportation is performed with the contents filled, so that the label is easily broken. It was a film with very little practicality as a shrink film for automobiles. Further, the polyester-based heat-shrinkable film is not satisfactory in shrinkage finish as compared with the above-mentioned heat-shrinkable films such as polyvinyl chloride, polystyrene, polyethylene or hydrochloric acid rubber. As a measure for improving the shrink finish, it is 75 in Japanese Unexamined Patent Publication No. 63-309424.
A method for obtaining a heat-shrinkable polyester film having improved shrink finish by controlling the shrinkability at 0 ° C, JP-A-5-261816, JP-A-5-305664, and JP-A-6-305164.
877, Japanese Patent Laid-Open No. 6-8322, and the like, those having improved shrinkage characteristics in hot water at 60 ° C. are disclosed.

[0003]

However, the polyester-based heat-shrinkable film is the above-mentioned polyvinyl chloride,
Compared to heat-shrinkable films such as polystyrene, polyethylene, or rubber chloride, the shrink finish is still unsatisfactory. For example, when a container such as a PET bottle or a glass bottle is covered and contracted as a label or the like, uneven contraction is likely to occur, air escape from the inside does not proceed smoothly, and problems such as inclusion of air bubbles in the seal part occur. To do. If such shrinkage unevenness occurs, it leads to density unevenness in printing, and the aesthetic appearance of the product is remarkably deteriorated.

[0004]

The present inventors have arrived at the present invention as a result of earnestly examining the heat shrinkage behavior of a polyester heat-shrinkable film in view of the above-mentioned prior art. That is, the polyester heat-shrinkable film of the present invention has a tan δ of dynamic viscoelasticity in one direction.
(0.08) It is necessary that the temperature is 30 ° C or higher and 70 ° C or lower. One-way dynamic viscoelastic property tan δ (0.08) temperature is 30 ℃
In the following, it will become unusable because it will naturally shrink when stored at room temperature in summer. On the other hand, when the tan δ (0.08) temperature of the dynamic viscoelastic property in one direction is 70 ° C or higher, uneven shrinkage occurs.

In the present invention, preferably, the tan δ (0.08) temperature of the unidirectional dynamic viscoelastic property is 35 ° C. or more and 70 ° C. or less. T for dynamic viscoelastic properties in one direction
When the anδ (0.08) temperature is 35 ° C or lower, natural shrinkage cannot be ignored,
Cannot be used. On the other hand, t of the dynamic viscoelasticity in one direction
When the an δ (0.08) temperature is 70 ° C. or higher, uneven shrinkage occurs.

In the present invention, more preferably 1
Tan δ (0.08) temperature of dynamic viscoelastic property in the direction of direction is 35 ℃ or more 70
It is necessary to be less than or equal to ° C. When the tan δ (0.08) temperature of the dynamic viscoelastic property in one direction is 35 ° C or lower, it may become unusable due to spontaneous shrinkage. On the other hand, when the tan δ (0.08) temperature of the dynamic viscoelastic property in one direction is 70 ° C or higher, uneven shrinkage occurs.

Further, in the present invention, it is necessary that the tan δ (maximum) temperature of the dynamic viscoelastic property in one direction is 80 ° C. or higher and 130 ° C. or lower. When the tan δ (maximum) temperature of the dynamic viscoelastic property in one direction is 80 ° C or less, uneven shrinkage occurs. The tanδ (maximum) temperature of the dynamic viscoelastic property in one direction is 1
Shrinkage unevenness occurs even at 30 ° C or higher. Further, in the present invention, it is necessary that the tan δ (maximum) temperature of the dynamic viscoelastic property in one direction is preferably 85 ° C or higher and 130 ° C or lower. The tan δ (maximum) temperature of the dynamic viscoelastic property in one direction is 85.
When the temperature is lower than ℃, some shrinkage unevenness occurs. Even if the tan δ (maximum) temperature of the dynamic viscoelastic property in one direction is 130 ° C or more, uneven shrinkage occurs. In the present invention, more preferably 1
Tanδ (maximum) temperature of the dynamic viscoelastic property in the direction of 90 ° C or more
It must be below 130 ° C. When the tan δ (maximum) temperature of the dynamic viscoelastic property in one direction is 90 ° C or less, uneven shrinkage slightly occurs. Tanδ of dynamic viscoelasticity in one direction
Even if the (maximum) temperature is 130 ° C or more, uneven shrinkage occurs.

Further, in the present invention, it is necessary that the tan δ temperature range of the dynamic viscoelastic property in one direction is 25 ° C. or more and 100 ° C. or less. Tanδ of dynamic viscoelasticity in one direction
When the temperature range is 25 ° C or less, uneven shrinkage occurs. Even if the tan δ temperature range of the dynamic viscoelastic property in one direction is 100 ° C or more, uneven shrinkage occurs.

Further, in the present invention, it is preferable that the tan δ temperature range of the dynamic viscoelastic property in one direction is 30 ° C. or more and 100 ° C. or less. Tan of dynamic viscoelastic property in one direction
When the δ temperature range is 30 ° C or less, some shrinkage unevenness occurs. Even if the tan δ temperature range of the dynamic viscoelastic property in one direction is 100 ° C or more, uneven shrinkage occurs.

In the present invention, more preferably 1
Tanδ temperature range of dynamic viscoelasticity in the direction of direction is 35 ℃ or more 100 ℃
It must be: When the tan δ temperature range of the dynamic viscoelastic property in one direction is 35 ° C or less, the shrinkage unevenness slightly occurs. Tan δ temperature range of dynamic viscoelasticity in one direction is 100 ℃
Even above, shrinkage unevenness occurs. The polyester resin used in the heat-shrinkable polyester film of the present invention contains an aromatic dicarboxylic acid or its ester-forming derivative as a dicarboxylic acid component and a polyhydric alcohol component as main components. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalene-1.4- or -2,6-dicarboxylic acid, and the like. Examples of these ester derivatives include derivatives such as dialkyl esters and diaryl esters. Further, an aliphatic dicarboxylic acid can be contained within the range that does not impair the effects of the present invention. Examples of the aliphatic dicarboxylic acid that can be used in the present invention include glutaric acid, adipic acid, sebacic acid, dimer acid, azelaic acid, oxalic acid and succinic acid. Examples of the polyhydric alcohol component of the polyester resin used in the heat-shrinkable polyester film of the present invention include propylene glycol, triethylene glycol, butylene glycol, diethylene glycol, neopentyl glycol, cyclohexanedimethanol, bisphenol compound or ethylene oxide of its derivative. Examples thereof include adducts, trimethylolpropane, glycerin, pentaerythritol, polyoxytetramethylene glycol, polyethylene glycol and the like. Also,
Although not a polyhydric alcohol, epsilon caprolactone can be used as well.

The polyester resin used in the heat-shrinkable polyester film of the present invention is not limited to the copolymerization component. The polyester may be used alone or in combination of two or more. When two or more kinds are used in combination, it may be a combination of polyethylene terephthalate and a copolyester or a combination of copolyesters. Further, it may be a combination with a homopolyester such as polybutylene terephthalate or polycyclohexylene dimethyl terephthalate. It is more preferable to use two or more kinds of polyester in combination, because a film having various properties can be produced. The temperature range of the dynamic viscoelasticity tan δ of the present invention can be set to a preferable temperature range depending on the constituent components of the polyester resin. Particularly, a method of mixing two or more kinds of polyesters having different Tg is effective as a means for achieving the present invention. Specific polyester resins that achieve the tan δ temperature range of the dynamic viscoelasticity of the present invention include, for example, a dicarboxylic acid component consisting of terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and a glycol component consisting of ethylene glycol and neopentyl. A copolyester composed of glycol and polytetramethylene glycol (molecular weight 650) may be mentioned. The polyester can be produced by melt polymerization by a conventional method, but the polyester is not limited to this and may be a polyester obtained by another polymerization method. The degree of polymerization of the polyester is preferably 0.3 or more and 1.2 or less in terms of intrinsic viscosity.

If necessary, a lubricant such as titanium dioxide, silica, kaolin or calcium carbonate may be added, and an antistatic agent, a deterioration preventing agent, an ultraviolet ray preventing agent or a dye as a colorant may be added. You can also do it. The preferable intrinsic viscosity as a film substrate is 0.50 or more and 1.30.
dl / g or less. A film obtained by any method such as an extrusion method or a calendar method using such a polymer is finally 2.5 times to 7.0 times in one direction, preferably 3.0 times to 6.
Stretched to 0 times and 1.0 to 2.0 in the direction perpendicular to the direction.
Stretching is performed up to twice, preferably 1.1 times to 1.8 times.
However, when it is stretched over 2.0 times, the thermal shrinkage in the direction perpendicular to the main shrinkage direction becomes too large, and the finished product becomes wavy. To suppress this waviness, the heat shrinkage rate should be 15
% Or less, preferably 9% or less, more preferably 7% or less is recommended. There is no particular limitation on the stretching method, roll stretching, long gap stretching, stretching method such as tenter stretching is applied, also in the shape surface is flat,
It does not matter which one is tubular. In addition, sequential biaxial stretching is effective for stretching, and either order may be first. Although the heat setting in the stretching is carried out depending on the purpose, it is recommended to pass through a heating zone of 30 to 150 ° C. for about 1 to 30 seconds in order to prevent dimensional change under high temperature in summer.
Further, before or after such processing, or both may be expanded up to 70%. In particular, it is preferable to extend in the main direction and relax in the non-contraction direction (direction perpendicular to the main contraction direction), and it is better not to extend in the perpendicular direction. In order to exert the preferable characteristics of the present invention, not only the draw ratio but also the temperature near the average glass transition temperature (Tg) of the polymer composition and the temperature in several stages (preferably two or more stages) are set. An effective means is to separately stretch. Especially, the above-mentioned treatment temperature in the main direction stretching (main shrinkage direction) is such that preheating is Tg + 0 ° C to + 50 ° C or less and stretching is a temperature within the range of Tg-20 ° C to + 30 ° C. It is important to stretch with a temperature difference. In the middle of the stretching, the stretching is stopped once,
It is also important to provide a relaxation process by returning the stretching ratio, and then perform the second stretching process so that the total stretching ratio becomes a predetermined ratio.

After stretching, the pre-treatment and post-treatment characteristics are improved and more stable by cooling the film while applying a stress to the film while keeping it in a stretched or tensioned state, or by further cooling the film. In addition, since the maximum shrinkage acceleration is reduced by stretching in multiple stages of temperature in this way, a film that does not easily cause shrinkage unevenness that shrinks with a small speed difference even with respect to temperature unevenness of the heat shrink tunnel can be obtained. can get. Hereinafter, the film of the present invention will be described in terms of applications. For packaging applications, especially food and beverage packaging,
Boil processing and retort processing are performed. No existing heat-shrinkable film can withstand these treatments sufficiently. The film of the present invention can withstand heat sterilization by boil treatment or retort treatment, and also the appearance of the original film, and further the finishability by heat shrinkability is also good, and also polyvinyl chloride or polystyrene heat shrink It has a higher heat shrinkage stress than the film, and is also excellent in cohesion.

A more specific description will be given below. (A) Impact resistance One of the roles of the shrink film is to prevent the packaged items from being broken or collapsed. For that purpose, it has high impact resistance and a large shrinkage in the main direction. It is necessary. In that respect, the film of the present invention has a high shrinkage ratio and a high impact resistance, so that a beautiful packaging can be obtained, and further, excellent durability is exhibited in terms of protection of an article to be packaged. This tendency is proved by the drop test.

(B) Printability The conventional film has inherent drawbacks with respect to the generation of pinholes and the adhesion to ink by halftone printing, but the polyester film has a chemical resistance and is a copolymer. As a result, the printability was improved because the adhesiveness was improved.

(C) Industrial Waste Problem In recent years, the use of plastic bottles has been rapidly spreading. When considering the recovery of such a bottle, it is preferable to form the same material, and it is advantageous to apply the film of the present invention to the packaging of a polyester bottle.

(D) Shrinkage unevenness The film of the present invention has a high shrinkage ratio and a high shrinkage stress, and since the shrinkage speed is appropriate, shrinkage unevenness does not occur.

EXAMPLES The present invention will be described in detail below by showing Examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The measuring method used in the present invention is shown below. (1) Dynamic viscoelastic property It is measured by a dynamic viscoelasticity measuring device manufactured by IT Measurement Co., Ltd., and the measurement length is 3 cm, the displacement is 0.25%, and the frequency is 10 Hz. The temperature at which tan δ becomes 0.08 is tan δ ( 0.08) temperature, tan
The temperature at which δ is maximum is tanδ (maximum) temperature, and the temperature obtained from tanδ (maximum) temperature −tanδ (0.08) temperature is tanδ
It was quantified as a temperature range. The sample size was cut into 4 cm in the shrinking direction and 5 mm in the perpendicular direction, and the average value of the values at two locations was used.

(2) Natural shrinkage Using a hot air circulation thermostat FX-1 type dry oven manufactured by Peng Seisakusho Co., Ltd., the sample size was cut into a square of 10 cm in the main shrinking direction and 10 cm in the orthogonal direction, and mounted on a jig. Lower. Further, the shrinkage rate after leaving it in an oven heated to 35 ° C. for 10 days was set to 1% or less as a pass level.

(3) Shrinkage Finishing Property A printed heat shrinking film was attached to a glass bottle (300 ml) and passed through a heat shrinking tunnel of 150 ° C. hot air (air velocity of 10 m / sec) to visually judge the finishing property. In addition,
The rank of finishability was evaluated on a scale of 5: 5: Best finishability 4: Good finishability 3: Some shrinkage unevenness (within 2 places) 2: Shrinkage unevenness (3 to 6 places) 1: Many shrinkage unevenness ( 6 or more), and 4 or more were defined as the passing level.

Example 1 Using a stainless steel autoclave, 0 mol% of dimethylene terephthalate as a dibasic acid component, 100 mol% of dimethylene naphthalate, 29 mol% of ethylene glycol as a glycol component, and neopentyl glycol 66.
A glycol composition was prepared so that the amount of glycol was twice that of methyl ester, and the transesterification reaction was carried out using 0.05 mol of zinc acetate (based on the acid component) as a transesterification catalyst. Then, polytetramethylene glycol (molecular weight 650) 5 mol% (based on the acid component), antimony trioxide 0.025 mol (based on the acid component) as a catalyst, and 0.05 mol (based on the acid component) as an additive. hand)
Was polycondensed. As a result, 0 mol% of terephthalic acid component and 100 mol% of 2,6 naphthalenedicarboxylic acid component,
A polyester comprising 29 mol% of ethylene glycol component, 66 mol% of neopentyl glycol component and 5 mol% of polytetramethylene glycol (molecular weight 650) component was obtained. This copolymer had an intrinsic viscosity of 0.70 dl / g. This polyester is melt extruded at 280 ° C.
An unstretched film of 200 μm was obtained. Preheat the film 1
20 ℃, 3 seconds, then the first stretching in the transverse direction at 100 ℃ 1.
5 times, followed by a relaxation process of 6% at 95 ° C, and then
The film was divided into two zones of 105 ° C and 110 ° C and stretched to a total of 4.1 times. Then heat treatment at 110 ℃ for 5.5 seconds to a thickness of 40μ
A heat shrinkable film of m was obtained. The physical properties of the obtained film are shown in Table 1.

Example 2 According to the polymerization method of Example 1, 70 mol% of terephthalic acid component
A polyester comprising 30 mol% of 2,6 naphthalenedicarboxylic acid component, 40 mol% of ethylene glycol component, 56 mol% of neopentyl glycol component, and 4 mol% of polytetramethylene glycol (molecular weight 650) component was obtained. This copolymer had an intrinsic viscosity of 0.71 dl / g. This polyester is melt extruded at 290 ° C. to a thickness of 1
An unstretched film of 80 μm was obtained. Preheat the film 95
℃, 3 seconds, then draw the first step in the transverse direction at 80 ℃ 1.5 times,
Then, it goes through a relaxation process of 6% at 85 ° C, then 85 ° C,
The film was divided into two zones at 95 ° C and stretched to a total of 4.1 times. Then, heat treatment was carried out at 80 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Example 3 According to the polymerization method of Example 1, 60 mol% of terephthalic acid component
A polyester comprising 40 mol% of 2,6 naphthalenedicarboxylic acid component, 46 mol% of ethylene glycol component, 50 mol% of neopentyl glycol component and 4 mol% of polytetramethylene glycol (molecular weight 650) component was obtained. This copolymer had an intrinsic viscosity of 0.69 dl / g.
This polyester is melt extruded at 280 ° C. to a thickness of 180
A μm unstretched film was obtained. Preheat the film to 95 ° C,
3 seconds, then 1st stretching in transverse direction 1.4 times at 85 ℃, followed by 5% relaxation step at 85 ℃, then 85 ℃, 95 ℃
It was divided into 2 zones and stretched to a total of 4.1 times. Then
Heat treatment was performed at 100 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Comparative Example 1 10 mol% of terephthalic acid component was prepared by the polymerization method of Example 1.
A polyester comprising 90 mol% of 2,6 naphthalenedicarboxylic acid component, 50 mol% of ethylene glycol component, 49 mol% of neopentyl glycol component and 1 mol% of polytetramethylene glycol (molecular weight 650) component was obtained. This copolymer had an intrinsic viscosity of 0.70 dl / g. This polyester is melt extruded at 280 ° C to a thickness of 18
An unstretched film of 0 μm was obtained. Preheat the film 125
C., 3 seconds, and then transversely stretched at 120.degree. C. up to 4.1 times. Then, heat treatment was performed at 140 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Comparative Example 2 By the polymerization method of Example 1, 95 mol% of terephthalic acid component
A polyester comprising 5 mol% of 2,6 naphthalenedicarboxylic acid component, 49 mol% of ethylene glycol component, 50 mol% of neopentyl glycol component, and 1 mol% of polytetramethylene glycol (molecular weight 650) component was obtained. This copolymer had an intrinsic viscosity of 0.69 dl / g.
This polyester is melt extruded at 295 ℃ and the thickness is 180μ.
An unstretched film of m was obtained. Preheat the film to 120 ° C,
It was stretched for 3 seconds and then transversely at 90 ° C. to 4.2 times. Then, heat treatment was performed at 75 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Comparative Example 3 According to the polymerization method of Example 1, 90 mol% of terephthalic acid component
A polyester comprising 10 mol% of 2,6 naphthalene dicarboxylic acid component, 65 mol% of ethylene glycol component and 35 mol% of neopentyl glycol component was obtained. This copolymer had an intrinsic viscosity of 0.72 dl / g. This polyester was melt extruded at 275 ° C. to obtain an unstretched film having a thickness of 180 μm. The film was preheated to 125 ° C. for 3 seconds and then stretched in the transverse direction at 100 ° C. to 4.0 times. Then 105 ° C
Was heat-treated for 5.5 seconds to obtain a heat-shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1.

Comparative Example 4 By the polymerization method of Example 1, 100 mol% of terephthalic acid component, 26 mol% of ethylene glycol component, 70 mol% of neopentyl glycol component, and 4 mol of polytetramethylene glycol (molecular weight 650) component. % Polyester was obtained. This copolymer had an intrinsic viscosity of 0.70 dl / g. This polyester was melt extruded at 285 ° C. to obtain an unstretched film having a thickness of 180 μm. Preheat the film
It was stretched at 70 ° C. for 3 seconds and then in the transverse direction at 55 ° C. up to 4.0 times. Then, heat treatment was performed at 52 ° C. for 5.5 seconds to obtain a heat shrinkable film having a thickness of 40 μm. Table 1 shows the physical properties of the obtained film.
Shown in

Comparative Example 5 According to the polymerization method of Example 1, 82 mol% of terephthalic acid component
18 mol% of isophthalic acid component, 95 mol% of ethylene glycol component, and polytetramethylene glycol (molecular weight
A polyester consisting of 5 mol% of component 1000) was obtained. This copolymer had an intrinsic viscosity of 0.68 dl / g. This polyester was melt extruded at 285 ° C. to obtain an unstretched film having a thickness of 180 μm. The film was preheated to 85 ° C for 3 seconds and then transversely stretched at 65 ° C to 4.0 times. Then 60 ° C
Was heat-treated for 5.5 seconds to obtain a heat-shrinkable film having a thickness of 40 μm. The physical properties of the obtained film are shown in Table 1. As is clear from Table 1, it was found that the film of the present invention had a desired finish.

[0029]

EFFECTS OF THE INVENTION A heat-shrinkable polyester film exhibiting particularly suitable heat-shrinkability in the field of packaging materials such as coating or binding and having good finish is provided.

[0030]

[Table 1]

Claims (1)

[Claims] 1. A dynamic viscoelastic property of a heat-shrinkable polyester film in at least one of the longitudinal and transverse directions.
tanδ (0.08) Temperature is 30 ℃ or more and 70 ℃ or less, tanδ
When the (maximum) temperature is 80 ° C or higher and 130 ° C or lower, the tanδ temperature range is
A heat-shrinkable polyester film having a temperature of 25 ° C or higher and 100 ° C or lower. Where tan δ (0.08) temperature is t
The temperature at which anδ is 0.08, and the tanδ (maximum) temperature is tanδ
Is the maximum temperature, tan δ temperature range is [tan δ (maximum)
Temperature−tan δ (0.08) temperature].