JP2005171127A - Heat-shrinkable polyester film and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester film which is excellent in the printability and shrink characteristics because the film has little occurrence of a recess of larger than 50 μm on the surface having contacted with a roll at the time of cooling and solidifying a polyester molten resin film. <P>SOLUTION: The heat-shrinkable polyester film formed by solidifying a polyester molten resin film with a cooling roll having a surface roughness (Ra) of 0.2-10 μm and then by stretching it monoaxially at least to the lengthwise direction, is characterized in that the polyester film has a shrinkage factor to the main shrink direction of 30 % or more after the treatment for 10 seconds in a 95°C-water and has a surface roughness (Ra) of 0.1 μm or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat-shrinkable polyester film and a method for producing the same. More specifically, the present invention relates to a heat-shrinkable polyester film that can be suitably used for body-wound labels such as dry batteries, tamper-proof, lid materials, etc., and is less susceptible to pattern distortion and wrinkles due to non-uniform shrinkage, and a method for producing the same. .

  Conventionally, heat-shrinkable films have been mainly made of polyvinyl chloride, polyethylene, polystyrene, etc., but for polyvinyl chloride, there is a problem of generation of chlorine-based gas when incinerated at the time of disposal, and printing is difficult for polyethylene. However, polystyrene has a problem of poor solvent resistance, and heat shrinkable polyester films are attracting attention.

  By the way, in a body-wound label such as a dry battery, a vertical shrink film is often used from the viewpoint of workability, and terephthalic acid is used as a main dicarboxylic acid, and it is composed of 99 to 95 mol% of ethylene glycol and 1 to 5 mol% of cyclohexanedimethanol. Adhesive layer on one side of a longitudinally uniaxial shrink film made of mixed glycol or heat shrinkable film made of terephthalic acid as the main dicarboxylic acid and made of mixed glycol of ethylene glycol 99-95 mol% and cyclohexanedimethanol 1-5 mol% A body-wound label for a dry cell having the above is disclosed. (For example, refer to Patent Documents 1 and 2).

However, when the heat-shrinkable polyester film is produced at a high speed (for example, when a molten resin film is cooled and solidified at a speed of 30 m / min or more using a known chromium-plated mirror roll for polyester film formation) Production of heat-shrinkable polyester film has the disadvantages that dents exceeding 50 μm are likely to occur on the surface of the film that comes into contact with it. It was not satisfied from the point of improving the performance.
JP-A-4-344222 JP-A-4-368770

  The present invention aims to eliminate the drawbacks of the prior art. That is, when a polyester molten resin film is cooled and solidified at a high speed, a dent exceeding 50 μm is hardly generated on the film surface in contact with the roll, and thus a heat-shrinkable polyester film having excellent printability and shrinkage characteristics and a method for producing the same are provided. To do.

  The first invention of the present application is a heat-shrinkable polyester film obtained by solidifying a polyester molten resin film with a cooling roll having a surface roughness (Ra) of 0.2 μm to 10 μm and then uniaxially stretching at least in the longitudinal direction, and 95 ° C. A heat-shrinkable polyester film characterized in that the shrinkage rate in the main shrinkage direction after treatment for 10 seconds in warm water is 30% or more, and the surface roughness (Ra) of the polyester film is 0.1 μm or less. In the second invention of the present application, a film is formed by uniaxially stretching at least in the longitudinal direction after solidification with a cooling roll having a surface roughness (Ra) of 0.2 μm to 10 μm. A method for producing a heat-shrinkable polyester film, characterized in that the shrinkage rate in the main shrinkage direction after the second treatment is 30% or more and the surface roughness (Ra) is 0.1 μm or less.

  The manufacturing method of the heat-shrinkable polyester film according to the present invention is not only a high-speed productivity and an economical manufacturing method, but also excellent printability, and generation of wrinkles, distortion and insufficient shrinkage after shrinkage is extremely small. It is a production method for obtaining a heat-shrinkable polyester film, and can be said to be a very useful heat-shrinkable polyester film and a method for producing a heat-shrinkable polyester film.

  In the present invention, the shrinkage rate in the main shrinkage direction of the heat-shrinkable polyester film after treatment for 10 seconds in 95 ° C. warm water needs to be 30% or more. When the shrinkage rate is less than 30%, wrinkles, distortion, and insufficient shrinkage are likely to occur after shrinkage in the heat shrinking process, which is not preferable.

  In the present invention, the dicarboxylic acid component constituting the polyester includes terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, diphenylsulfone dicarboxylic acid, 5-sodium sulfoisophthalic acid and other aromatic dicarboxylic acids, oxalic acid, succinic acid, adipine One or two of aliphatic dicarboxylic acids such as acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid and dimer acid, oxycarboxylic acids such as p-oxybenzoic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid More than seeds can be used. As glycol components, ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentylglycol and other alicyclic glycols such as cyclohexanedimethanol, bisphenol A ethylene oxide adduct, bisphenol S Aromatic glycols such as ethylene oxide adducts, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol can be used alone or in combination.

  In the present invention, neopentyl glycol and / or cyclohexane dimethanol is preferably used as the glycol component in order to obtain a heat-shrinkable polyester film having excellent shrink finish, and neopentyl glycol and / or cyclohexane dimethanol is preferably used as the glycol component. More preferably, 6 mol% or more is used.

  In the present invention, the method for producing the polyester is not particularly limited. That is, it can be used even if it is produced by either the transesterification method or the direct polymerization method. Further, it may be produced by a solid phase polymerization method in order to increase the molecular weight.

  In the present invention, antimony oxide, germanium oxide, a titanium compound or the like is used as a polymerization catalyst for polyester production.

  In the present invention, an antioxidant, a heat stabilizer, an ultraviolet absorber, a plasticizer, a pigment, an antistatic agent, a lubricant, a crystal nucleating agent, a lubricant composed of inorganic or organic particles, etc. may be added to the polyester as necessary. Good.

  In the present invention, it is necessary to solidify the molten resin film with a cooling roll having a surface roughness (Ra) of 0.2 to 10 μm. In addition, the surface shape of the cooling roll can be a spiral groove, a diamond cut groove, a satin finish, etc. Of these, the surface has a satin finish A roll is particularly preferred.

  When the roll surface roughness is less than 0.2 μm, when the molten resin film is cooled and solidified at high speed, numerous recesses exceeding 50 μm are generated on the film surface in contact with the cooling roll, and when this film is uniaxially stretched at least in the longitudinal direction The dents become large, and when printing is performed on this film, ink loss is liable to occur, and a patchy appearance defect becomes noticeable on the film in the heat shrinking process. On the other hand, when the roll surface roughness exceeds 10 μm, the satin pattern is transferred to the film, and in the heat shrinking process, a patchy appearance defect becomes remarkable on the film, and the commercial value of the shrink wrapping is lowered.

  At this time, the roll surface roughness (Ra) is more preferably 0.2 to 4.0 μm, and most preferably 0.2 to 3.5 μm.

  In the present invention, it is necessary for the surface roughness (Ra) of the heat-shrinkable polyester film to be 0.1 μm or less in order to ensure printability (particularly halftone printability) and increase the commercial value of shrink-wrap packaging. However, it is more preferable that the surface roughness (Ra) is 0.02 to 0.1 μm in order to suppress a decrease in unwinding property due to film blocking in the printing step and / or the shrinking step.

  In this invention, when making molten resin contact a cooling roll, it is preferable to employ | adopt the method of spraying air forcibly or the method of making it closely_contact | adhere with static electricity. Moreover, both the forced air spraying method and the electrostatic contact method are more preferable to carry out the method in which both end portions and the central portion of the layered resin are made independent. Further, when the molten resin contacts the cooling roll, it is more preferable to use a measure (for example, a device such as a vacuum chamber or a vacuum box) that reduces the accompanying flow by reducing the pressure on the opposite side.

  In the present invention, after cooling and solidifying, it is necessary to obtain a heat-shrinkable polyester film by uniaxially stretching at least in the longitudinal direction. As a longitudinal stretching condition, in the case of a heat-shrinkable polyester film used for a wound label such as a dry battery, it is preferably stretched 1.2 to 5.0 times in the longitudinal direction at a temperature equal to or higher than the glass transition temperature of the polyester constituting the film. . In the case of a heat-shrinkable polyester film used for tamper-proof, lid materials, etc., the glass transition temperature is 1.2 to 4.0 times longitudinally stretched in the machine direction at a temperature equal to or higher than the glass transition temperature of the polyester constituting the film. It is preferable to perform 3.0 to 5.0 times transverse stretching at the above temperature. Moreover, you may heat-treat for 1 to 20 seconds at the temperature more than extending | stretching temperature with a heating roll or a clip-type setter as needed, and may control a heat contraction rate.

  In this invention, although the thickness of a polyester film is not specifically limited, 10-150 micrometers is preferable.

  In the present invention, when the resin obtained by cutting and removing both ends is reused, the reuse rate is not particularly limited, but is preferably 5 to 50% by weight.

  Hereinafter, the present invention will be described based on examples.

[Evaluation methods]
(1) Intrinsic viscosity of polyester (IV)
It is a value (dl / g) measured at 25 ° C. in orthochlorophenol.

(2) Cooling roll surface roughness (Ra)
It measured according to JIS B0601 (1982).

(3) Surface roughness of the polyester film (Ra)
The film cut out to 10 cm × 10 cm was visually observed, and the film surface that was in contact with the cooling roll at the time of casting did not have a dent exceeding 50 μm and was evaluated by the following method as having an evaluation value. In addition, it was set as the surface roughness (Ra) with the average value of 20 times measurement.
a. Measuring device: ET-30HK manufactured by Kosaka Laboratory
b. Palpation tip radius: 0.5 μm
c. Palpation load: 5mg
d. Measurement length: 1mm
e. Cut-off value: 0.08m

(4) Heat shrinkage rate The film was cut into a 10 cm × 10 cm square, heat-shrinked in warm water at 95 ° C. ± 0.5 ° C. under no load for 10 seconds, and then stretched in the vertical and horizontal directions of the film. The dimensions were measured, and the thermal shrinkage was calculated using the following formula. The direction in which the heat shrinkage rate is large was defined as the main shrinkage rate direction.
Thermal shrinkage rate = {(length before shrinkage−length after shrinkage) / length before shrinkage} × 100 (%)

(5) Shrinkage finish Using a universal shrinker (model: K2000) manufactured by Kyowa Denki Co., Ltd., uniaxial stretching The film is wound in the circumferential direction of the dry cell, the joint is bonded with a polyester adhesive, and biaxial stretching The film is cut out on a disk and covered with an aluminum container (aluminum cup made by Kinrei Co., Ltd.), and then fixed at 4 locations (about 90 ° pitch) with polyester adhesive tape and passed through a shrinker. The finish was evaluated at a time of 9 seconds (1 zone / 2 zone temperature: 160 ° C./180° C. (n = 10).
○: No appearance defects ×: Wrinkles, insufficient shrinkage, appearance defects

    Tables (2) to (5) are shown in Table 1.

[Abbreviations and contents of polyester and olefin polymer used in Examples and Comparative Examples]
(1) PES-1: Polyethylene terephthalate (IV: 2,000 dl / g, 2000 ppm of agglomerated silica having an average particle size of 1.5 μm).
(2) PES-2: Copolyester of terephthalic acid and ethylene glycol / neopentyl glycol (70/30 mol%) (IV: 0.72).
(3) PES-3: Copolyester of terephthalic acid and ethylene glycol / cyclohexanedimethanol (70/30 mol%) (IV: 0.72).
(4) PES-4: polybutylene terephthalate (IV: 1.20 dl / g).

[Example 1]
After the polyester mixed with PES-1 / PES-2 / PES-4 = 35/65/10 (% by weight) was vacuum-dried and melted at 275 ° C. using a single screw extruder, the T die was Used, and casted in layers into a satin-like cooling roll (circumferential speed 70 m / min) with a surface roughness (Ra) of 1 μm. The distance between the T die and the cooling roll is 2 cm, and the center and both ends are separate devices. After electrostatic contact (center part: 4.5 kV, both ends: 6 kV DC power supply applied), cooled and solidified, stretched 3.0 times in the longitudinal direction at a preheating temperature of 80 ° C and a stretching temperature of 85 ° C, gripping the clip After heat-treating at 90 ° C. for 3 seconds using a method setter, both ends were cut and removed to obtain a heat-shrinkable polyester film (thickness: 25 μm).
It can be said that the method of a present Example is a manufacturing method of the heat-shrinkable polyester-type film and heat-shrinkable polyester-type film excellent in shrink finish property and surface smoothness.

[Example 2]
A heat-shrinkable polyester film (thickness: 25 μm) was obtained in the same manner as in Example 1 except that a satin-like cooling roll having a surface roughness (Ra) of 0.5 μm was used.
It can be said that the method of a present Example is a manufacturing method of the heat-shrinkable polyester-type film and heat-shrinkable polyester-type film excellent in shrink finish property and surface smoothness.

[Example 3]
A heat-shrinkable polyester film (thickness: 25 μm) was obtained in the same manner as in Example 1 except that a satin-like cooling roll having a surface roughness (Ra) of 3.3 μm was used.
It can be said that the method of a present Example is a manufacturing method of the heat-shrinkable polyester-type film and heat-shrinkable polyester-type film excellent in shrink finish property and surface smoothness.

[Example 4]
After cooling and solidifying in the same manner as in Example 1, the film was stretched 2.5 times in the longitudinal direction at a preheating temperature of 80 ° C. and a stretching temperature of 85 ° C., and then 4.0 times in the transverse direction at a preheating temperature of 100 ° C. and a stretching temperature of 85 ° C. After extending | stretching and heat-processing for 3 second at 90 degreeC using the setter of a clip holding | grip system, both ends were cut off and the heat-shrinkable polyester film (thickness: 25 micrometers) was obtained.
It can be said that the method of a present Example is a manufacturing method of the heat-shrinkable polyester-type film and heat-shrinkable polyester-type film excellent in shrink finish property and surface smoothness.

[Example 5]
A heat-shrinkable polyester film (thickness: 25 μm) was obtained in the same manner as in Example 1 except that polyester mixed with PES-1 / PES-3 / PES-4 = 35/65/10 (% by weight) was used. It was.
It can be said that the method of a present Example is a manufacturing method of the heat-shrinkable polyester-type film and heat-shrinkable polyester-type film excellent in shrink finish property and surface smoothness.

[Comparative Example 1]
A heat-shrinkable polyester film (thickness: 25 μm) was obtained in the same manner as in Example 1 except that a mirror-like cooling roll having a surface roughness (Ra) of 0.05 μm or less was used.
In this method, innumerable recesses exceeding 50 μm are generated on the surface of the heat-shrinkable polyester film, and the film has a patchy appearance in the heat-shrink process, so that the heat-shrinkable polyester film and the heat-shrinkable polyester film This is not preferable as a production method.

[Comparative Example 2]
A heat-shrinkable polyester film (thickness: 25 μm) was obtained in the same manner as in Example 1 except that a satin-like cooling roll having a surface roughness (Ra) of 11 μm was used.
In this method, the surface of the heat-shrinkable polyester film causes elephant-like spots due to the traces of the satin texture, the film-like appearance of the film becomes defective in the heat-shrinking process, and the film-like appearance appears in the heat-shrinking process. Since it becomes inferior, it is not preferable as a manufacturing method of a heat-shrinkable polyester film or a heat-shrinkable polyester film.

[Comparative Example 3]
A heat-shrinkable polyester film (thickness: 25 μm) was obtained in the same manner as in Example 1 except that the heat treatment conditions after longitudinal stretching were 120 ° C. and 3 seconds.
This method is not preferable as a method for producing a heat-shrinkable polyester film or a heat-shrinkable polyester film because wrinkles due to insufficient shrinkage occur in the heat shrinking process.

  The results are shown in Table 1.

  The manufacturing method of the heat-shrinkable polyester film according to the present invention is not only a high-speed production and economical manufacturing method, but also excellent printability and extremely low occurrence of wrinkles, distortion and insufficient shrinkage after shrinkage. It is a production method for obtaining a shrinkable polyester film, and can be said to be a very useful heat-shrinkable polyester film and a method for producing a heat-shrinkable polyester film.

Claims (2)

  A heat-shrinkable polyester film obtained by solidifying a polyester molten resin film with a cooling roll having a surface roughness (Ra) of 0.2 μm to 10 μm and then uniaxially stretching at least in the longitudinal direction, and after being treated in warm water at 95 ° C. for 10 seconds A heat-shrinkable polyester film having a shrinkage ratio in the main shrinkage direction of 30% or more and a surface roughness (Ra) of the polyester film of 0.1 μm or less.   After solidifying with a cooling roll having a surface roughness (Ra) of 0.2 μm to 10 μm, the film is formed by uniaxially stretching at least in the longitudinal direction, and the film shrinks in the main shrinkage direction after treatment for 10 seconds in 95 ° C. warm water. A method for producing a heat-shrinkable polyester film, wherein the rate is 30% or more and the surface roughness (Ra) is 0.1 μm or less.