JPS61219626A - Longitudinally stretching method for thermoplastic resin film - Google Patents

Abstract

PURPOSE:To provide the longitudinally stretching of thermoplastic resin film with no adhesion of roll-like blots and at the same time with no surface blemish such as scratch, wear and the like by a method wherein a pair of chains equipped with clips is employed as a transferring means A and a pair of chains equipped with clips or rolls are employed as a transferring means B. CONSTITUTION:Stretching is done by the difference between the transferring speeds of chains equipped with clips. Chains 4 and 4' equipped with clips driven at lower speed are set in a preheating oven 1. Film is preheated in the preheating oven up to a temperature, at which the film can be stretched. A radiation heater 2 is employed for uniform stretching. Chains 5 and 5' equipped with clips driven at higher speed are set in a cool air oven 3. The film, the stretch of which has finished, is cooled at this zone or rapidly cooled by being brought into contact with cooled rolls driven at higher speed simultaneous with the finish of stretching, resulting in reducing the blemish of the film nearly to zero.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for longitudinally stretching an unstretched film or a slightly unidirectionally stretched film made of a thermoplastic resin, mainly linear polyethylene terephthalate. It is related to.

[Conventional technology]

Until now, the method of stretching a thermoplastic resin film without stretching or stretching in at least one direction in the machine direction has been carried out using heated rolls consisting of a group of low-speed rolls and a group of high-speed rolls. It has been done.

For example, FIGS. 4 and 5 illustrate this example.

FIG. 4 shows a method of stretching an unstretched sheet made of linear polyethylene terephthalate in the longitudinal direction. In the figure, rolls 7 to 11 are a group of low-speed drive rolls, rolls 12 to 15 are a group of high-speed drive rolls, and longitudinal stretching is mainly performed between rolls 11 and 12. Rolls 7-11 are.

A roll that is heated using known means such as hot water or steam.
The film is heated by contacting these rolls. Moreover, rolls 12 to 15 are.

The film is cooled by contact with the rolls, which are cooled by known means such as cooling water.

Note that a radiation heater 2 is used as an auxiliary means for heating the film between the rolls 11 and 12 in the stretching section.

FIG. 5 shows an example of a method for further stretching a biaxially stretched linear polyethylene terephthalate film in the longitudinal direction. In the figure, roll 16~i
Rolls 24 to 26 are high speed drive roll groups, and rolls 20 to 2°3 are idle roll groups. Stretching is mainly performed between rolls 19 and 24. The film is heated with hot water on rolls 16-19. Heated with steam-heated rolls 20 to 22 and cooled with water roll 23
Cooled at ~26. Further, the film is heated by a radiation heater 2.

[Problem that the invention seeks to solve]

These conventional longitudinal stretching methods have all been carried out using a difference in the circumferential speed of the rolls, so the film is stretched on the rolls,
There were problems with film scratches and roll dirt adhesion.

To resolve issues caused by this role.

Various measures have been taken, such as developing roll materials and shortening the roll interval, but none of these methods has been able to completely eliminate these problems.

An object of the present invention is to provide a method for longitudinally stretching a thermoplastic resin film without adhesion of roll-shaped dirt to the film and without surface defects such as scratches and stains.

Means to solve problem c] In the present invention, between transport means A and transport means B.

In a stretching method for longitudinally stretching a thermoplastic resin film,
This method is characterized by a longitudinal stretching method of a thermoplastic resin film, in which a pair of chains with grips is used as the transfer means A, and a pair of chains with clips or rolls are used as the transfer means B.

What is the thermoplastic resin used in the present invention?

Any known thermoplastic resin may be used. Specifically, linear polyethylene terephthalate, polypropylene, nylon-66 high-density polyethylene, etc. are used, but especially linear polyethylene terephthalate is used because of the abrasion during stretching. It is highly effective in improving scratches and roll stains and is preferred.

Transfer means A is a pair of known clip-equipped chains (including belts) provided with clips facing each other, as long as the film can be transferred while holding both ends of the film with the clips. It can be anything. The clip is not particularly limited as long as it can grip both ends of the film in the width direction, and various known clips can be used.

The transfer means B is the same as the transfer means A, or a roll. Further, the transfer means B may be any type as long as it can make the transfer speed faster than the transfer means A, and when a chain with a clip is used as the transfer means B, each of the transfer means A and B may be used. Preferably, the chains are a series of independent chains.

The longitudinal stretching is performed by giving a speed difference to the transport means A and B. In addition, when the transfer speeds of transfer means A and H are respectively V and VB, the longitudinal stretching ratio N is NM V
B, I! 4' It can be calculated as VA.

In the present invention, although not limited to l#, N is 1.2 times or more.

More preferably, it is 2.5 times or more.

The present invention will be described in detail below based on 90 drawings.

FIG. 1 is a plan view of an apparatus showing an application example of the longitudinal stretching method of the present invention. 1 is a preheating open, 2 is a radiation heater, 3 is a cold air oven, and 4.4'4;! A pair of low-speed driven chains with clips, 5.5' are a pair of high-speed driven chains with clips, and stretching is performed by a difference in conveying speed of the chains with clips, and the chain is knitted. However, the drive unit and means for supplying heat medium and coolant are not shown.

A low-speed driven clipped chain 4.4' is set in the preheating opening 1, in which the film is preheated to a temperature at which it can be stretched. The radiation heater 2 is for uniformly stretching. A high-speed drive chain with a clip 5.5' is set in a cold air oven, and the stretched film is cooled in this zone.

FIG. 2 is a plan view showing another example of the apparatus to which the stretching method of the present invention is applied, and shows a longitudinal stretching method using a low-speed driven chain with clips 4,4' and a group of high-speed driven rolls.

In the figure, reference numeral 6 denotes a group of rolls driven at high speed, and these rolls are made up of metal rolls 9 with flat surfaces through which cold water is passed.

Stretching is done by a low-speed driven chain with a clip 4.4',! :
.

This is done by the difference in transport speed between the roll groups 6 that are driven at high speed.

In Figure 2, rolls are used on the high-speed drive side, so defects due to roll stretching are expected, but most of the surface defects of the conventional roll stretching method occur on the heating roll side, and the nine-roll stretching method In this case, upon completion of stretching, the film contacts a cooled high-speed driven roll and is rapidly cooled, so film defects are greatly reduced compared to conventional films, and are almost completely eliminated.

FIG. 3 is a plan view of an apparatus showing an example of application of the stretching method of the present invention, that is, an example in which longitudinal stretching and transverse stretching are performed successively.

In the figure, the longitudinal stretching is carried out by the difference in transport speed between the low-speed driven chains with clips 4, 4' and the high-speed driven chains with clips 6, 6', and the film is stretched in the longitudinal direction. The width of the clip chain is expanded in the lateral direction without cooling, thereby performing lateral stretching heat treatment.

In addition, the high-speed drive chain with clip 6, da is.

A conventional stenter for stretching a film in the width direction can be used, and heating parts for stretching and heat treatment are not shown.

The clips used in Figures 1 to 3 are susceptible to tension in the vertical direction, so clips with self-locking properties in the vertical direction may be used, or elastomer with a high friction coefficient may be attached to the top plate. good. Here, the elastomer is a rubber-like material such as 'Pyton' EFT, acrylonitrile, urethane, silicone, etc.

〔Effect of the invention〕

The heating of the film is not done by contact on the rolls as in the conventional stretching method, but by hot air in the open, so there is no effect of film transfer due to roll contamination, and stretching does not affect the film. Since the film is gripped with a clip and heated, there are no film defects such as scratches or stains caused by roll stretching. [Examples] Hereinafter, embodiments of the present invention will be described based on Examples.

Example 1 After drying linear polyethylene terephthalate of 1V0.60 at 160°C for 5 hours at a vacuum degree of 2 to 3 mmHg,
Melt extrusion is performed at 80°C, extruded into a sheet from the lip of one die, and the sheet is heated to a thickness of 1 at 30°C on a stuttering drum.
After cooling to a 20μ film.

Using the apparatus shown in FIG. 3, the film was stretched to a longitudinal stretching ratio of 3.3 times.

At this time, the preheating open temperature of the chain with a clip driven at low speed was 92°C, the capacity of the radiation heater was 5kW, and the actual film temperature was 93.5°0.

The stretched film is placed on a fast-driven chain with clips. After being cooled to 30° C. with cold air open, it was wound up at 60 m/min. The longitudinally stretched film had no scratches or "zoo"-like surface defects, and was of excellent quality.

Example 2 A 120-inch unstretched film that had been dried, extruded, and cooled in the same manner as in Example 1 was stretched longitudinally between chains with clips using the apparatus shown in FIG. 3, and then stretched laterally. The stretching conditions were as follows.

Longitudinal stretching Stretching ratio 3.6xl Preheating open temperature 92°0 Radiation heater 5kW Preheating and stretching open temperature 95°C Heat treatment Relaxation rate 8-thickness temperature 210"0 Cooling Open temperature
30'.

The obtained biaxially stretched film was excellent, free of surface defects such as scratches and scales.

[Brief explanation of drawings]

Figures 1 and 2 are two plan views of an apparatus to which the longitudinal stretching method of the present invention is applied; Figure 3 is a plan view of an apparatus in which the longitudinal stretching and transverse stretching methods of the present invention are continuous; and Figure 4 and FIG. 5 is a side view of an apparatus to which a conventional longitudinal stretching method is applied. 6'''': High-speed drive roll group 7-11: Low-speed roll group 12-15: High-speed roll group 16-19: Low-speed roll group 20-23: Idle roll group 24-26: High-speed roll group 27; Fiber/mu

Claims (1)

[Claims] (1) In a stretching method in which a thermoplastic resin film is longitudinally stretched between transfer means A and transfer means B, a pair of chains with clips is used as transfer means A, and a pair of chains with clips or a roll is used as transfer means B. A method for longitudinally stretching a thermoplastic resin film, the method comprising: