JPS6287320A - Heat-stretching device of thermoplastic polymer film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an apparatus for producing thermoplastic resin films typified by polyester, polyolefin, and polyamide. This relates to a heating/stretching device that preheats the film, then heats it with an infrared heating device, and stretches the film in this state in the machine direction (longitudinal direction).

(Yama) Prior art and its problems A heating stretching device for stretching a thermoplastic polymer film in the longitudinal direction is one that has a uniform heating density in the film width direction (sometimes referred to as the transverse direction). It is coming. In the case of an apparatus that uses a heating roller as a means for preheating the film before stretching, as a heating medium for this heating roller,
When a heating fluid is used, the entire width of the roller (that is, the entire width of the film) becomes isothermal, and the film is heated and stretched to a uniform humidity in the width direction. In this case, if the unstretched film has a uniform thickness in its width direction, ideal uniform heating and uniform stretching will be achieved. However, in reality, unstretched films rarely have a uniform thickness in the width direction. The uncoagulated film extruded from the die solidifies on the surface of the casting drum.
A neck develops and a thick portion is formed. This phenomenon occurs when the film is formed with a width slightly narrower than the width of the die (neck
(referred to as in), and the direction of the tension applied to the melt is at the side edge.
This is caused by the fact that it is not the same as the center part, the surface tension of the molten resin, etc., and is usually unavoidable.

Therefore, the thickness of the unstretched film is non-uniform in the width direction, and a more realistic solution would be to adjust the degree of softening of the stretched film to be uniform, assuming this non-uniformity.

Even when a film is preheated by an infrared heating means and then longitudinally stretched, there is no prior art that takes measures to adjust the amount of heat generated in the width direction in the infrared heating means. In the conventional technology, if the set heat value of the infrared heating means is insufficient, the heating of the thick parts at both ends of the unstretched film becomes even more insufficient, resulting in uneven stretching, and in extreme cases, A break may occur in the vicinity. Furthermore, if the set heat value of the infrared heating means becomes excessive, the central portion of the film (excluding both side edges) will be heated too much, which will not cause any other trouble.

For example, in the case of a crystalline polymer film such as polyethylene terephthalate, the amorphous state of stretched or semi-stretched rice paper tends to crystallize due to overheating, making it difficult to stretch the film in the width direction when the film is crystallized in the center. Get used to it. A film whose crystallization state differs depending on the position (portion) will have stretching unevenness during the subsequent stretching process, and in extreme cases may even break within the stenter. For example, in the case of a non-quality polymer film, overheating may cause excessive thermal deformation, leading to pinholes and non-uniform stretching throughout the film. Therefore, it is necessary to avoid such troubles, but setting the heating amount of the infrared heating means for preheating the film is not easy. Due to these circumstances, in the prior art, the amount of heat generated is not actually adjusted in the width direction of the film.

(C) Object of the Invention The object of the present invention is to provide a heating stretching device for a thermoplastic synthetic resin film, which is equipped with a heating means capable of giving a heating amount distribution corresponding to the thickness distribution in the width direction of the film when longitudinally stretching a thermoplastic synthetic resin film. This is the object of the invention.

(Small Structure of the Invention) The present invention is based on the premise that the film has a thickness distribution in its width direction, and the amount of heating in the film width direction is changed in accordance with this thickness distribution, so that the entire film (full width) is This heating stretching device is capable of uniformly stretching the film in the machine direction while keeping the plasticization state (softening level) almost uniform. , a group of high-speed rollers for running the film at a high circumferential speed, and an infrared heating device mainly installed between both roller groups.The rollers that rotate at a low circumferential speed are The roller has a built-in heating means that can heat the film.Also, it is desirable that the roller rotating at a high circumferential speed be equipped with a cooling means so that the stretched film can be cooled.Furthermore, the infrared heating device In order to supplement and adjust the preheating of the film in the group of speed rollers, it is provided above and/or below the surface of the traveling film so as not to come into contact with the surface of the film.In particular, In the apparatus of the present invention, the film has a function that allows the amount of heating to be varied in the width direction, but this is due to the infrared heating device having a different heat generation amount (heat generation density) in the width direction.

The apparatus of the present invention will be further explained with reference to the drawings. Figure 1 shows
1 is a schematic diagram of a machine for longitudinal stretching of thermoplastic polymer films.

This figure shows an apparatus for stretching or re-stretching an unstretched film, a film longitudinally stretched at a low ratio, or a film stretched in the width direction in the longitudinal direction.

The film 10 before stretching is moved to a roller group 21°2 with a low circumferential speed.
2 and 23, the infrared heating device 41 is preheated.
and roller 31 which is further heated by 42 and rotates at high speed.
．． 32 and 33 for longitudinal stretching. In the case of FIG. 1, between the rotating roller 23 with a low circumferential speed and the rotating roller 31 with a high circumferential speed, or the rotating roller 523 with a low circumferential speed.
Stretching of the film occurs on the surface of the film. Rollers 31 to 33 rotate at a high circumferential speed so that the orientation state of the stretched film is not thermally relaxed.
Something that can cool down is good. A low-speed roller (such as 21) equipped with a preheating means has a built-in appropriate heating method such as a method of circulating a heating medium or an induction heating method, so that almost the entire width of the roller can be heated at a nearly uniform temperature. The surface temperature of the roller is made almost uniform by heating the roller to a uniform temperature. When the film is thick or when the preheating temperature is to be made uniform, it is advisable to increase the number of low-speed rollers equipped with heating means. (Three low-speed rollers are illustrated in FIG. 1, but it is also possible to use a low-speed roller having 4 to 20 heating means.

) The infrared heating device is installed at the position where the film is stretched or in front of it (on the side of the low-speed roller group).

This infrared heating device includes infrared heaters 42A, 42B, which heat infrared light from one surface (upper surface) of the film surface.
42C... and a heater 41 (one heater in the case of FIG. 1, but it is also possible to install a plurality of heaters) that heats the ground surface (lower surface) of the film. This infrared heater heats the entire area or part of the film in the width direction so that the amount of heating in the film width direction can be changed as a whole. To explain this situation in detail,
The unstretched film (or the film stretched in the width direction) 10 has a thickness in the width direction that is thicker at both end portions 12 as shown in FIG. It is in. Therefore, in order to make the film thickness substantially uniform after stretching, it is necessary to plasticize the film at a slightly higher temperature than the central portion near both ends of the film so that it can be stretched well. This requirement is met by an infrared heating device as shown in FIG. In FIG. 3, the film 10 is traveling in the direction of the arrow and is preheated by a group of low-speed rollers (not shown).
This is further heated and adjusted by infrared heaters 42A, 42B and 42C. The infrared heater 42A heats only the side edge portions of the film, and has a structure such that the central portion is not irradiated with radiant heat. Similarly, the infrared heater 42B has a wider heating width than the heater 42A, but this heater also heats sections near both ends of the film. Such an infrared heater 42A.

42B etc. are arranged in parallel, the heating conditions of the film can be changed independently for each section in the width direction depending on the number and position of the infrared heaters installed. As a result, uneven thickness of the film in the width direction can be eliminated. Further, the infrared heater 42C is a conventionally known ordinary heater capable of heating the entire width of the film. By combining various infrared heaters with different heating amounts, heating conditions can be adjusted in response to thickness unevenness in the width direction of the film.

FIG. 4 is an example of an infrared heater used in the present invention, in which several nichrome wires supported by magnesium oxide are
It is sealed inside an Inconel pipe. By replacing a part of the nichrome wire 4γ with the conductive wire 4B, the amount of heat in the film width direction changes as described above (42A
, 42B) can be manufactured.

The infrared heating device of the present invention is composed of a combination of different infrared heaters as a plurality of heating means capable of heating the upper and lower surfaces of the film.

Immediately after the longitudinally stretched film 14 is stretched by a group of rollers 31, 32, 33, etc. rotating at a high circumferential speed, the film 14 is cooled to a temperature of air bubbles or a glass transition point, if necessary, to form molecules. The state of orientation is frozen (see Figure 1).

(e) Examples Example 1 An unstretched polyethylene terephthalate film having an intrinsic viscosity of 0.58 and a thickness of 250 μι shown in FIG. 1 was heated and stretched as shown in FIG. It was longitudinally stretched using a machine. This unstretched film has a thick area of about 50 mm at both ends as shown in Figure 2 (the maximum thickness is about 8 times that of the central uniform thickness area).
It had a

The infrared heating device shown in FIG. 4 was used, and an experiment was conducted to compare the case where the heat generation amount at both ends of a part of the heater was increased by 20% compared to the center part, and the case where it was the same as before. As a result, a uniaxially stretched film as shown in Table 1 was obtained, and it was confirmed that this film had a small center-edge difference in physical properties and improved uniformity.

Table 1 Furthermore, during the production time, the proportion of cutting loss time (-cutting rate) due to the above-mentioned inappropriate longitudinal stretching and heating was less than half.

Example 2 Using the same unstretched film as that used in Example 1,
It was longitudinally stretched as shown in FIG. Comparative Example 2 has an infrared heater 41. below the film surface. Three infrared heaters 42A, 42B, and 42C are placed above.

As a result of performing heating distribution using an infrared heater as shown in Table 2, it was found that in Example 2, the film could be produced stably without any film edge breakage.

Table 2 Heating distribution of infrared heater (f) Effects of the invention The heating stretching device that can locally heat thick parts such as the side edges of the film maintains a uniform heating and plasticizing state over the entire width of the film, and then As a result of being able to stretch in the machine direction, a film of excellent quality with less unevenness in film thickness can be obtained.

In addition to superior quality, the uniform plasticization state of the film has the advantage of improving the operating rate of mechanical equipment because the stretching state is stable and there are almost no abnormalities such as film breakage. .

Moreover, the effective (usable) width of the film is expanded, and the device becomes effective in improving the yield.

[Brief explanation of drawings]

FIG. 1 is a process explanatory diagram showing the arrangement of a heating stretching apparatus for a thermoplastic polymer film of the present invention. FIG. 2 is a perspective view showing a cross section of the thermoplastic film in the width direction. FIG. 3 is a perspective view showing a portion of the heating stretching apparatus of the present invention (the upper side of the film of the infrared heating apparatus). Moreover, FIG. 4 is a longitudinal sectional view showing the structure of an infrared heating device used in the present invention. In the drawings, 21, 22 and 23 are low circumferential speed rollers equipped with preheating means, 31, 32 and 33 are high circumferential speed rollers, 41 and 42 are infrared heating devices, and 10 is a film 14 before longitudinal stretching. It's a film. Patent applicant Teijin Ltd. No. 1
Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) All or some of the rollers include a group of low circumferential speed rollers, a group of high circumferential speed rollers, and a plurality of infrared heating devices, and the thermoplastic film is equipped with the heating device. This device preheats the thermoplastic film with a heated roller and heats it with an infrared heating device, and heats and stretches the thermoplastic film in the machine direction using the difference in circumferential speed. The film can be preheated across its entire width, and the plurality of infrared heating devices can vary the amount of heat generated along the width of the film, adjusting the amount of heat generated in accordance with the film thickness distribution. 1. A heating stretching apparatus for a thermoplastic polymer film, characterized in that the thickness of the stretched film can be made uniform by this. (2) The film is divided into predetermined heating sections in the width direction of the film, and the amount of heat generated by the plurality of infrared heating devices arranged at positions corresponding to the individual heating sections can be adjusted in each heating section. A heating stretching apparatus for a thermoplastic polymer film as described in 1. (3) The thermoplastic polymer film according to claim 1 or 2, in which the calorific value distribution of each heating section can be set and adjusted to match the thickness distribution of the film before stretching. Heat stretching equipment.