JPS59114028A - Manufacture of thermoplastic resin film - Google Patents

Abstract

PURPOSE:To prevent the bowing phenomenon from occurring by a method wherein a film, after being stretched longitudinally, is stretched laterally until 10-90% of total percent of lateral stretch is reached and thermally set and finally stretched laterally to realize 100% of total percent of lateral stretch while running the film in the reversed direction. CONSTITUTION:A fusion-extruded thermoplastic resin film is at first longitudinally stretched. Secondly, the film is laterally stretched by holding both ends of the film until 10-90% of total percent of lateral stretch is reached and thermally set. Thirdly, the running direction of the film is reversed and the film is laterally stretched by holding both its ends until 100% of total percent of lateral stretch is realized while running in the direction opposite to that during said lateral stretching and thermal setting and finally thermally set again at a temperature higher than said thermally set temperature in order to obtain a biaxially stretched thermosetting resin film with uniform physical proterties. In addition, fusion-extrusion conditions, casting conditions, stretching conditions in the machine direction and in the width direction, all of which are well-known conditions, can be employed, as a film forming and a stretching conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a film having uniform physical properties along the width direction of the film by subjecting a biaxial Grim Reaper film made of a thermoplastic resin to heat-setting by lateral death stretching in at least two stages. More specifically, during biaxial stretching, transverse stretching and heat setting are applied at least twice to eliminate the back side effect due to the bowing phenomenon, eliminate optical fishing gear orientation, and improve temperature expansion coefficient, humidity expansion coefficient, and heat setting. The present invention relates to a method for producing a highly uniform film in which the shrinkage rate and the like are almost the same at any position along the width of the film.

Biaxially stretched films are used for various industrial applications, among them flexible liquid crystal panels.

For applications such as photography, drafting, and magnetic disks, it is desirable that the physical properties in both the vertical and horizontal directions, especially the thermal expansion coefficient, the humidity expansion coefficient, and the thermal contraction coefficient, be balanced. However, it has been extremely difficult to make the physical properties of the product film uniform in the width direction using the conventional sequential biaxial stretching method, that is, a method in which longitudinal stretching is performed followed by horizontal stretching using a tenter. The reason for this is that both ends of the film are held in the tenter, so the shrinkage stress in the longitudinal direction due to lateral dead elongation is restrained by clips, etc., but the restraining force is relatively weak in the center of the film. . As a result, the molecular orientation of the film during running progresses with the film in the central portion positionally delayed due to the shrinkage stress. If a straight line is virtually drawn in the width direction on the film surface before transverse stretching, this straight line becomes a concave curve in the direction of film travel during the transverse stretching and the subsequent tension heat treatment. This phenomenon is called bowing, and due to this bowing, the film has differences in physical properties (especially thermal expansion coefficient,
This causes non-uniformity in the coefficient of humidity expansion. When the physical properties of the central part of the film are varied in the vertical and horizontal directions, a main axis of orientation is formed at the film side edges that is further tilted in the vertical direction with respect to the bowing line, and the coefficient of thermal expansion in the direction of this main axis increases.

The humidity expansion coefficient becomes smaller, and each of the six values in the direction perpendicular to the principal axis becomes larger. Several methods have been proposed to eliminate such differences in physical properties in the width direction. However, none of them have reached a satisfactory stage. For example, Tokko Sho 37-1
Although the No. 588 publication discloses a method of transverse dead stretching→longitudinal stretching, it does not constitute an essential countermeasure. Unexamined Japanese Patent Publication 1973-1973
Although Japanese Patent No. 978 proposes a method using nip rolls between the lateral dead stretching step and the heat treatment step, another problem has arisen since there is a risk of scratches on the back surface of the film.

The present inventor has developed a film after vertical Grim Reaper in two directions, one in the forward direction and the other in the reverse direction.
The present invention was achieved based on the finding that this bowing phenomenon can be offset by performing lateral death expansion heat fixation in several stages.

That is, in the present invention, when biaxially orienting a melt-extruded thermoplastic resin film, it is first stretched in the longitudinal direction, then gripped at both ends of the film at a magnification of 10 to 90 inches of the total transverse magnification, and then ma-stretched. After heat-setting, the running direction of the film is reversed, and while running in the opposite direction to the above-mentioned transverse stretching and heat-setting, cross-dead stretching is performed while holding both ends of the film so that the integrated transverse stretching ratio becomes higher than the above-mentioned heat-setting temperature. This is a method for producing a biaxially stretched thermoplastic resin film with uniform physical properties, which includes a step of reheat-setting at a certain temperature.

The present invention will be explained. In the present invention, thermoplastic resins include those that are lacking in the production of biaxial Grim Reaper films. For example, polyesters such as polyethylene terephthalate, polytetramethylene terephthalate, and polyethylene-2,6-s7thalene dicarpoxylate, polyolefins such as polypropylene and polyethylene, and polyamides such as nylon 6 and nylon 66 can be used. In the present invention, not only a homopolymer of -F-coordinated resin, but also an inorganic substance within 15% (by weight),
Those containing organic substances (lubricants, ultraviolet absorbers, flame retardants, etc.), other polymers, etc. are also applicable.

In the present invention, as film forming conditions, known resin melt extrusion conditions and casting conditions 1, both conditions in the rock-machine direction and in the width direction, can be appropriately selected.

In the present invention, glass transition point (Tg) to melting point (Tm)
The film is subjected to coupled biaxial shinigami under stretching conditions of about -120° C., and the running direction (production direction) of the film is reversed using a tenter machine, and then the lateral deadening heat setting treatment is performed again.

The film thickness ranges from 2 to 1000μ. Can be applied to things.

The bamboo color of the present invention is achieved by running the film in the forward and reverse directions during the two-step lateral dead stretching and heat setting. This is to eliminate the problem. First stage (first stage)
The lateral stretching ratio is selected from a range of 10 to 90 inches, preferably 30 to 90 inches of the total lateral stretching ratio. During stretching and heat setting, both ends of the film are restrained with restraints (for example, tenter clips). The total lateral stretching ratio here refers to the product of the lateral stretching ratios of the first stage and the second stage. In the later stage (second stage) transverse stretching and heat treatment, the film is run in the opposite direction to the running direction of the film in the previous stage. A simple method for obtaining this reverse direction is achieved by first winding up the film after heat-setting it in the first stage, and feeding it to the tenter while unwinding it during the lateral dead stretching in the second stage. However, it is not necessary to wrap the film around the core after the pre-heat treatment, provided that the film is not damaged. In this case as well, the effects of the present invention can be achieved as long as the traveling direction 6 of the post-stage heat treatment is reversed to the direction of the transverse stretching heat-setting of the pre-stage. The stretching ratio in the lateral direction in the latter stage is a desired ratio (corresponding to the total lateral stretching ratio) by stretching the remainder of the stretching in the previous stage. There is no particular rule regarding the distribution of the stretching ratio between the front stage and the rear stage, but it is preferable to distribute more of the stretching ratio to the front stage. To obtain uniformity of physical properties in the width direction,
Particularly regarding the uniformity of linear expansion coefficient, it is important to reduce the bowing. Therefore, conditions are preferable such that a straight line drawn in the transverse direction of the film prior to the transverse stretching in the first stage bends concavely in the reverse direction, and returns to almost its original state in the transverse stretching heat treatment in the latter stage. To achieve this, it is necessary that the bowing line does not return too much in the subsequent processing, and the conditions can be selected by trial and error, but the double push ratio in the previous stage is set to be high. The reason for this is that when the first stage of heat fixation is carried out at a high temperature,
Since the stretching process in the latter stage is performed at a longer distance, the heat setting in the first stage is carried out at a relatively low temperature, but in this case, a relatively high temperature is selected for the heat setting in the latter stage. At that time, Boeing was significantly corrected. As the heating temperature in the latter stage is set high, the stretching ratio in the latter stage needs to be set low. Of course, depending on the degree of bowing correction, it is possible to further expand or relax the film in the width direction, if necessary, during the heat treatment after the post-stretching.

The film that has undergone two-stage stretching heat treatment in this way is
If necessary, the side end portions can be cut again to produce a product. A film with uniform physical properties, for example, if it has no optical anisotropy and is transparent, can be used as a flexible liquid crystal panel, and is lighter and more flexible than conventional inorganic glass-based panels. It is advantageous in that respect. Furthermore, the fact that the film has comparable physical properties in terms of mechanical and thermal properties makes it an excellent material for magnetic disk space.

Next, it will be further explained by examples.

Example 1 Polyethylene terephthalate was melted, extruded through a die slit, and formed into a film on a cold drum.The film was heated between two rollers with different circumferential speeds.
．． 5x IC! # Gradually stretch in the hand direction, then horizontally at a temperature of 105℃ (
@) The film was stretched 2.6 times in the VC direction to obtain a biaxially stretched film. The film was heat-set at a temperature of 130'C while holding the film without releasing the tenter clip used for fixing it in the width direction. Thereafter, the clip was used as a tube needle, and the side end portion of the film held by the clip was cut off with a 7-liter blade and wound up. While unraveling one layer of heat-set light film,
Grip both ends of the film with tenter clips again, stretch both sides by 1.5 times in the transverse direction at 190°C (total transverse stretching ratio: 3.9), and then reheat and fix at 230°C for about 30 seconds. I wound it up. The resulting film has a thickness of 75〃
The physical properties were as shown in Table 1.

Comparative Example 1 9-The transverse stretching heat retention conditions in Example 1 were 3.9 times, 230
Except for processing in only one stage as ℃! ! AA example 1
A 75μ film was prepared in the same manner as above. Its physical properties t4
It is shown in Table 1.

Comparative Example 2 In Example 1, the temperature of the coffin in the front stage was 3.0 times higher, the heat setting was 1.2 times higher at 200°C, and the heat setting was 190"C.
A film having a thickness of 75 μm was prepared in the same manner as in Example 1 except for the following. The physical properties are shown in Table 1.

From the results in Table 110-1, it is concluded that the method of the present invention avoids the bowing phenomenon of sequential biaxial films, produces films with uniform thermal expansion coefficients, etc., and is of great industrial value. I can say that.

Claims (1)

[Claims] When biaxially orienting a thermoplastic resin film through melt extrusion, it is first stretched in the machine direction, then dead stretched in the cross direction at a crosswise stretch ratio of 10 to 90 inches, and further heat-set.
Then, the running direction of the film was reversed, a second stage of lateral stretching was carried out to obtain the total stretching ratio, and the film was further heat-set at a higher temperature than the fixing temperature during the heat-setting described above, while gripping both ends of the film. 1. A method for producing a biaxially stretched thermoplastic resin film with uniform physical properties, the method comprising one culm being applied.