JP2001009359A - Production of surface-treated biaxially stretched polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a surface-treated biaxially stretched polyester film excellent in appearance free from a scratch with good operability. SOLUTION: In a method for producing a biaxially stretched polyester film by coating a film with a surface treatment agent and spraying hot air on the coated film from the nozzle arranged in a dryer to dry the same and subsequently stretching the coated film at least uniaxially, film fluttering preventing bars 3 are provided at the position separated from both end parts of the film in the dryer by 10-20 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-line coating in which film surface treatment and stretching are performed in a continuous process, wherein the film surface has excellent appearance without scratches and is suitable as a base film for vapor deposition of aluminum or silicon oxide. The present invention relates to a method for producing a surface-treated biaxially stretched polyester film.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Are excellent in mechanical properties, hot water resistance and the like, and are widely used as packaging and industrial films. Further, a film obtained by depositing aluminum, silicon oxide, or the like on PET is excellent in gas barrier properties and appearance, and is therefore used in large quantities as a film for packaging and for gold and silver threads. When various kinds of metals are deposited on PET, in order to improve the adhesion between PET and the metal, usually, PE is used.
The T film is coated with an easily adhesive layer. But,
There are scratches on the film surface of the easy-adhesive film,
For this reason, there are problems such as unevenness in vapor deposition and reduction in gas barrier properties, and it is strongly required to prevent scratches.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an in-line surface-treated biaxially stretched polyester film which does not have the above-mentioned disadvantages and has an excellent appearance without scratches on the film surface.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, after applying a surface treating agent to a polyester film, the film flapping in a step of drying in a dryer is considered. The present inventors have found that by preventing such a phenomenon, the occurrence of scratches on the film surface can be effectively prevented, and the present invention has been achieved.

That is, the gist of the present invention is to provide a biaxially stretched polyester film obtained by applying a surface treatment agent, spraying hot air from a nozzle provided in a dryer, drying the film, and stretching the film in at least one direction. The method for producing a surface-treated biaxially stretched polyester film is characterized in that a film flapping prevention bar is provided at a position of 10 to 20 mm from both ends of the film in the dryer.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, the polyester film preferably used is PET, polybutylene terephthalate (P
BT), and copolyesters thereof.

As a method for producing the in-line coated biaxially stretched polyester film of the present invention, for example, PET is melt-extruded from a T-die at a temperature of 270 to 300 ° C., and closely adhered to a cooling drum adjusted to a room temperature or lower, and cooled. An unstretched sheet having a desired thickness is obtained. Then, the obtained unstretched sheet is preliminarily stretched to about 1.2 times or less in the machine direction if necessary, and then a plurality of rolls having different rotation speeds are used to obtain a magnification of 2 times.
After stretching longitudinally at ~ 4 times, coat the surface treatment agent with a coater, and then guide it into a dryer to 50-80 ° C
After drying, the film was gripped at both ends with clips of a tenter-type transverse stretching machine, at a temperature of 50 to 150 ° C. and a magnification of 2.
It is obtained by subjecting it to a heat treatment at 150 to 250 ° C. for several seconds after transverse stretching at up to 5 times and relaxing 1 to 10% in the transverse direction.

A typical structure of the dryer used in the present invention is a staggered dryer in which hot air blowing nozzles are arranged on the upper and lower surfaces of the film. The distance between the upper and lower nozzles of the hot air blowing nozzle of the dryer is short in order to uniformly apply a stable air volume. The film that passes through the dryer has a large difference in thickness between the film's both ends and the center, so especially when produced at high speed, the film flaps in the dryer and comes into contact with the nozzles, causing film scratches. Becomes

The anti-fluttering bar must be provided at a position of 10 to 20 mm from both ends of the film.
mm, the film passing through the dryer may move to the left and right in the width direction, and the film may enter the inside of the bar. In this case, the film is prevented from fluttering by the flutter prevention bar. Cause trouble. Further, when the position of the anti-fluttering bar is inside of 20 mm from both ends of the film, the width of the film product without scratches becomes narrow, and the productivity is reduced.

FIG. 1 is an example of a vertical sectional view of the inside of a dryer according to the present invention, and FIG. 2 is a plan view thereof. In FIG. 1, an anti-fluttering bar 3 is provided above a hot-air blowing nozzle 1 having a hot-air blowing unit 2. It is appropriate that the flapping prevention bar 3 be installed at a total of four locations on the top, bottom, left, and right at positions 10 to 20 mm from both ends of the film in the dryer. Further, it is practical to use a method in which the flapping preventing bar 3 is movable in the lateral direction so as to be applied to an arbitrary film width, and is fixed in a spring type. The flapping prevention bar 3 has a diameter of 3 to 8 mm.
It is preferable that the nozzle is disposed above the hot-air blowing nozzle 1 as shown in FIG. 1 so that the portion without the nozzle does not contact the film.

The end of the film in the dryer has a large thickness, so that the film is likely to flutter, and the vicinity of the center of the film is induced by the flutter of the end. Stable without flapping of the whole film. In the present invention, both ends of the film in the dryer are restricted from moving in the vertical direction by the flutter prevention bar, and the film ends contact the flutter prevention bar, or move in the dryer at a position slightly away from the bar. Go.

The surface treating agent in the present invention is not particularly limited, and a coating agent suitable for various uses can be used. For example, isocyanates and melamines are suitable for improving the adhesiveness. .

[0013]

The present invention will be described below in more detail with reference to examples.

Example 1 PET (relative viscosity: 1.38) was heated at a temperature of 280 from an extruder.
Melt extrusion from T die at ℃, and with pinning wire
A voltage of 7 kv is applied to the molten film, and a surface temperature of 18 ° C.
Then, the unstretched film having a thickness of 120 μm and a width of 1300 mm was obtained with good operability without causing discharge or pinning bubbles, and was quenched by closely adhering to a cast roll whose temperature was controlled. The obtained unstretched film was roll-stretched 3.5 times in the machine direction at a temperature of 85 ° C. to obtain a film having a width of 1100 mm. Next, an aqueous emulsion obtained by mixing 7 parts of tri (methoxymethyl) melamine resin (curing reaction temperature: 180 ° C.) with 100 parts of the self-emulsifying polyurethane resin was applied with an air knife coater so that the thickness after stretching was 0.07 μm. After coating, each of the longitudinally stretched films was dried at 60 ° C. with a drier provided with a bar for preventing flapping 10 mm inward from both ends. Next, the clip was gripped by a clip of a flat type horizontal stretching machine controlled at a temperature of 60 ° C.
After that, the film was transversely stretched to a stretching ratio of 4.0 times, and then subjected to a heat treatment at 240 ° C. for 2 seconds at a relaxation rate in the transverse direction of 5%. This film is cooled and taken up by a winder, and has a thickness of 1 mm.
A biaxially stretched PET film having an easy adhesion of 2 μm was obtained. The film in the dryer was in a stable floating state without flapping, and in the biaxially stretched PET film, scratches were seen in the portion corresponding to the position of the bar, but that position was gripped by the clip of the horizontal stretching machine This was removed by trimming, and there was no scratch on the product film.

Examples 2 and 3 Except that the positions of the anti-flap bar in the dryer were set to 15 mm and 20 mm from both ends of the film, respectively.
In the same manner as in Example 1, a biaxially stretched PET film with an easy adhesion treatment was obtained. As in Example 1, a product film without scratches was obtained.

Comparative Example 1 A biaxially stretched PET film was obtained in the same manner as in Example 1 except that the anti-flap bar was not provided in the dryer. In the dryer, the edge of the film fluttered violently in small steps, and the center part undulated. Observation of the stretched film revealed that a linear scratch of about 4 cm was found at the end at about every 1 m in the longitudinal direction of the film.

Comparative Examples 2 and 3 An easily adhesive-treated biaxially stretched PET film was obtained in the same manner as in Example 1 except that the positions of the anti-flap bar in the dryer were 5 mm and 25 mm from both ends of the film, respectively. In the case of the position of 5 mm, the film which fluctuates delicately in the width direction in the dryer enters the inside of the bar, where the fluctuation is interrupted, and the center of the film undulates greatly.
Contacted the upper nozzle. As a result, scratches occurred at the center of the film. In the case of a position of 25 mm, after stretching,
In order to prevent the scratches from entering the product, the end trimming width had to be large.

[0018]

According to the present invention, it is possible to produce a surface-treated biaxially stretched polyester film excellent in appearance without scratches with good operability.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an example of a dryer according to the present invention.

FIG. 2 is a plan view of an example of a dryer according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot-air blowing nozzle 2 Hot-air blowing part 3 Anti-flap bar 4 Spring fixing part 5 Film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08J 7/04 CFD C08J 7/04 CFDE // B29K 67:00 B29L 9:00 C08L 67:00 F term ( Reference) 4D075 BB07X BB07Z BB24Y BB93X BB93Y BB93Z CA02 DA04 DB48 EB32 4F006 AA35 AB33 AB37 BA01 DA04 EA05 EA06 4F071 AA46 AF22 AH04 BB08 BB11 BB13 BC01 4F210 AA24 AE01 Q01G03 Q05 Q01 Q01 Q03 Q05

Claims (1)

[Claims] 1. A method for producing a biaxially stretched polyester film obtained by applying a surface treating agent to a film, spraying hot air from a nozzle installed in a dryer, drying the film, and stretching the film in at least one direction. In, 10-20m from both ends of the film in the dryer
A method for producing a surface-treated biaxially stretched polyester film, comprising: providing a film flapping prevention bar at a position m.