JPH0839687A - Production of thermoplastic resin film - Google Patents

Abstract

PURPOSE: To obtain a film having physical properties uniform in its lateral direction without lowering a product yield by stretching a thermoplastic resin sheet longitudinally and laterally and specifying the angle formed by the outlet center line of the air jet nozzle of a heat treatment device and a perpendicular line in a thermal fixing section to thermally treat and fix the stretched film. CONSTITUTION: When a biaxially stretched film is heat-treated in a lateral stretcher, the ejection angle of air ejected to the film through the nozzle 2 of a heat-treatment device is adjusted in a section fixing the film thermally after lateral stretching so that the acute angle θ formed by the center line 3 of a nozzle outlet 2a and a perpendicular line becomes 30 deg. or more, pref., 45-60 deg. to perform the heat treatment of the film F. At this time, the ejection speed is regulated so as to become 3 times or more, pref., 4-6 times the running speed of the film F. By this constitution, the shrink force acting on the film F in the direction opposite to the advance direction of the film F is set off by the shearing force generated by the relative speed of the film F and ejected air to act on the film F in the advance direction of the film F.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a thermoplastic resin film,
In particular, the present invention relates to a method for producing a thermoplastic resin film having uniform physical properties in the lateral direction. More particularly, the present invention suppresses the bowing phenomenon of the film caused by the lateral stretching and the heat setting process by the treatment on the transverse stretching machine (tenter), and the physical, chemical, or physical properties which are uniform in the lateral direction. The present invention relates to a method for producing a thermoplastic resin film having physicochemical properties.

[0002]

BACKGROUND OF THE INVENTION Thermoplastic resin films, especially polyester-based and other polypropylene, polyvinyl chloride, nylon, polyimide, polycarbonate, polystyrene, polyphenylene sulphite films, are used for packaging, recording media, industrial and various other applications. There has been an urgent need for the production of a film which is used for the above-mentioned applications and has uniform physical properties in the transverse direction. If the physical properties of the film, such as heat shrinkage, mechanical strength and density are non-uniform in the lateral direction, the final product may cause surface distortion during post-processing such as coating, vapor deposition, cutting and printing. Will deteriorate the quality of. In addition, there is a drawback in that the product yield is lowered when trying to satisfy the homogeneity of the lateral physical properties that can be tolerated during the post-processing of the film.

In the method developed to solve such a problem, since the both ends of the film are sandwiched by the cribs in the transverse stretching machine, the longitudinal stretching caused by the longitudinal stretching and the transverse stretching is caused. Although the deformation of the film is restrained by both ends of the film against the stretching stress and the contraction stress caused by the heat-setting process, the central portion of the film is less affected by the crib, so that the restraining force against the deformation is weak. Therefore, in the transverse stretching machine, the central portion is pushed in the direction opposite to the film advancing direction due to the difference in the restraining force between the both end portions and the central portion, which causes a bowing phenomenon of the film. As a problem that is unavoidable in the manufacturing process of the film accompanied by the fixing process, it causes non-uniformity of the physical properties of the film in the transverse direction. Therefore, it is extremely difficult to uniformize the physical properties of the film in the transverse direction by the above method.

Therefore, various methods have been tried in order to prevent the above-mentioned drawbacks. For example, Japan Special Public Sho3
No. 9-29214 discloses a method of heat treatment using a heating roll, but there is a drawback that both ends are not restrained by the heating roll and heat treatment causes widthwise shrinkage. In Japanese Patent Publication No. 42-9273. Heat treatment is carried out in the transverse direction of the film by using a temperature gradient, and the method is disclosed in JP-A-62-1833.
In Nos. 27 and 183328, the heat treatment process was performed by a method such as a change in wind speed or air volume and forced heating of both ends of the film. There are drawbacks such as reduced rates. Also, Japanese Patent Laid-Open No. 50-739
No. 78 discloses a method in which a film is heat-treated after the transverse stretching is completed by providing a nip roll between the transverse stretching process and the heat treatment process in the transverse stretching machine, and Japanese Patent Publication No. 63-24459 discloses a nip roll. Discloses a method of forcibly advancing the central portion of the film, but these two methods all have a problem that damage to the film due to contact with the roll at high temperature is fatal.

On the other hand, in Japanese Unexamined Patent Publication No. 3-130126, Japanese Unexamined Patent Publication No. 3-130127, Japanese Unexamined Patent Publication No. 4-142916 and Japanese Unexamined Patent Publication No. 4-142917, a heat treatment method in which a cooling step is performed after a transverse stretching step is used. Despite the cooling treatment in a long section, it has almost no effect of reducing the bowing phenomenon of the film, and there is a drawback that productivity is reduced due to increase of equipment and waste of energy. In addition, Japanese Patent Laid-Open Nos. 61-8324 and 1
No. 204723 discloses a heat treatment method in which a film is heated after a transverse stretching step in a transverse stretching machine. In this method, in order to uniformly perform the heat treatment on the entire width of the film, transverse deformation is performed. There is a problem that the variation in binding force cannot be reduced.

[0006]

Therefore, in the production of a thermoplastic resin film, it is necessary to produce a film having uniform physical properties in the transverse direction in order to improve the quality of the final product without lowering the product yield. There is an urgent need to develop new methods that can be used.

[0007]

The present inventors have conducted extensive research to solve the bowing phenomenon of a film by a conventional heat treatment method, and as a result, although a heat treatment method using a transverse stretching machine is used, Instead of the conventional method of vertically ejecting air from the nozzle of the heat treatment device to the film surface in the heat setting section, the air jet angle of the nozzle is adjusted and the air jet speed of the nozzle relative to the running speed of the film is adjusted. It has been found that an improved thermoplastic resin film can be provided in which the lateral physical properties of the film are uniform and the bowing phenomenon of the film is significantly reduced.

Accordingly, the present invention provides a method for producing a thermoplastic resin film, in which the physical properties in the transverse direction of the film are uniform and the bowing phenomenon is significantly reduced and improved.

The present invention will be described in detail below. According to the present invention, during a heat treatment process of a biaxially stretched thermoplastic resin film in a transverse stretching machine, air jetting is performed in a heat setting section with respect to an angle toward a film surface of an air jetting nozzle of a heat treatment apparatus and a traveling speed of the film. By adjusting the speed, a thermoplastic resin film having uniform lateral properties and reduced bowing phenomenon is provided.

The production of a thermoplastic resin film by a known method is carried out by drying and melt extruding polymer chips produced by a polymerization reaction to form a sheet, and then stretching and heat treating the sheet in the longitudinal and transverse directions. And a final biaxially stretched film is obtained. However, as described above, the film obtained through the above process does not have the same constraining force against deformation in the heat treatment process, so that a bowing phenomenon of the film occurs.

Therefore, in the present invention, the thermoplastic resin film is manufactured by a known method. When heat treating the biaxially stretched film in the transverse stretching machine, the nozzle of the heat treatment apparatus is used in the section where the film is heat set after the transverse stretching. As shown in FIG. 2 (enlarged view of the portion surrounded by the circle shown by the broken line in FIG. 1), the jet angle of the air jetted to the film through the film is perpendicular to the center line (3) of the nozzle outlet. The film is heat-treated by adjusting the acute angle (θ) of 30 ° or more, preferably 45 ° to 60 °. On this occasion,
The jet speed of air is adjusted to be 3 times or more, preferably 4 to 6 times, the running speed of the film. by this,
The bowing phenomenon of the film is reduced by canceling the shrinking force acting in the direction opposite to the film advancing direction by the shearing force acting in the film advancing direction caused by the difference in the relative velocity between the film and the jet air. The physical properties in the lateral direction of the film become uniform.

Examples of the thermoplastic resin used in the present invention include polyethylene terephthalate, polyethylene-2,
There are 6-naphthalate, polytetramethylene terephthalate, polytetramethylene-2,6-naphthalene carboxylate, liquid crystal polyester, polypropylene, polyvinyl chloride, nylon, polyimide, and polyphenylene sulphite. Among these, polyethylene terephthalate, polyethylene-2,6-naphthalate and polyphenylene sulphite are particularly preferable.

The thermoplastic resin film according to the present invention can be manufactured, for example, as follows. In the case of a polyester film using polyethylene terephthalate, a polyethylene terephthalate monomer is polycondensed to produce a polyethylene terephthalate chip having an intrinsic viscosity of 0.6 to 0.7 dl / g, and then the chip is treated at 290 to 300 ° C. After melt-extruding and forming into an amorphous sheet on a cooling roll, the sheet is magnified 3.5 times in the machine direction at a temperature of 100 to 110 ° C. and 4.5 times in the transverse direction at a temperature of 100 to 120 ° C. To obtain a biaxially stretched polyester film. Then, the film F is passed through the heat treatment apparatus 1 as shown in FIG. The film F introduced into the heat treatment apparatus 1 advances along the center of the apparatus, at which time the film is heated by the hot air fan 4 of the nozzle 2 and the nozzle outlet 2a.
The air ejected through (FIG. 2) is adjusted so that the acute angle (ejection angle; θ) formed by the vertical line with the outlet center line 3 is 30 ° or more, preferably 45 ° to 60 °, and the air ejection speed is The traveling speed of the film is adjusted to 3 times or more, preferably 4 to 6 times. By carrying out the heat setting treatment as described above, a biaxially stretched film having uniform physical properties in the transverse direction can be obtained.

The present invention will be described in more detail with reference to the following examples. These examples are for the purpose of illustrating the present invention and the present invention is not limited thereto.

Example 1 Dimethyl terephthalate and ethylene glycol 1: 1
After mixing in a ratio of 1 to produce a polyethylene terephthalate monomer by transesterification, the polycondensation reaction of the monomer was carried out to produce a polyethylene terephthalate chip having an intrinsic viscosity of 0.64 dl / g. After melt-extruding the chips at 290 ° C., the chips were formed into an amorphous sheet having a thickness of 200 μm on a cooling roll whose cooling water temperature was maintained at 20 ° C. A biaxially stretched polyethylene terephthalate film was obtained by stretching the film at a draw ratio of 0.5 times and then at a temperature of 110 to 120 ° C. to a draw ratio of 4.5 times in the transverse direction. Then, the film is introduced into the heat treatment apparatus of the present invention, the air jet angle (θ) of the nozzle of the heat treatment apparatus is set to 30 ° in the heat fixing section, the temperature of the jetted air is set to 220 ° C., and the running speed of the film is 4 m. / Sec, and the air jet speed was adjusted to 20 m / sec to perform heat setting treatment to obtain a biaxially stretched polyethylene terephthalate film.

The bowing amount, lateral specific gravity change rate and lateral thickness change rate of the produced film were measured as follows, and the results are shown in Table 1.

1. Amount of bowing of the film After drawing a black reference line in the width direction on the surface of the film at the entrance of the transverse stretching machine and passing the film through the transverse stretching machine, the film exiting the outlet looks like an arc as shown in Fig. 3. In this case, the bowing amount of the film was calculated using the following formula: B = b / W × 100 (%) where B is the bowing amount (%), and b is the bow shape from the reference line. Indicates the distance (mm) to the apex of the film, and W indicates the width (mm) of the film.

2. Rate of change in specific gravity of film in the lateral direction
First, the specific gravity was obtained by STM D1505, and then calculated by the following formula: Lateral specific gravity change rate = {(maximum lateral specific gravity)-(minimum lateral specific gravity)} / (average lateral specific gravity) × 100
(%) 3. Lateral thickness change rate of the film The lateral thickness change rate of the film is obtained by first measuring the film thickness with respect to the lateral direction of the film using a thickness measuring device (product of Winzen, USA). It was calculated by the following formula.

Lateral thickness change rate = {(maximum lateral thickness)-(minimum lateral thickness)} / (average lateral thickness) × 100 (%).

Example 2 A biaxially stretched polyethylene terephthalate was prepared in the same manner as in Example 1 except that the air jet angle (θ) of the nozzle with respect to the surface of the film passing through the heat treatment apparatus was 60 °. I got a film. As in Example 1, the changes in bowing amount and transverse physical properties of the produced film were measured, and the results are shown in Table 1.

Example 3 A biaxially stretched polyethylene terephthalate was prepared by the same method and conditions as in Example 1 except that the air jet angle (θ) of the nozzle with respect to the surface of the film passing through the heat treatment apparatus was 75 °. I got a film. The change in bowing amount and transverse physical properties of the resulting film was measured as in Example 1 and the results are shown in Table 1.

Comparative Example 1 The same method as in Example 1 except that the air ejection angle (θ) of the nozzle with respect to the surface of the film passing through the heat treatment apparatus was 0 °, that is, air was ejected perpendicularly to the film surface. And a condition to obtain a biaxially stretched polyethylene terephthalate film. As in Example 1,
Changes in the bowing amount and the lateral physical properties of the produced film were measured, and the results are shown in Table 1.

Comparative Example 2 A biaxially stretched polyethylene terephthalate was prepared by the same method and conditions as in Example 1 except that the air jet angle (θ) of the nozzle with respect to the surface of the film passing through the heat treatment apparatus was set to 15 °. I got a film. The change in bowing amount and transverse physical properties of the resulting film was measured as in Example 1 and the results are shown in Table 1.

[0024]

[Table 1] As can be seen from Table 1, the films of Examples 1 to 3, which satisfy the conditions of the present invention, in which the air ejection angle of the nozzle of the heat treatment apparatus is set within a specific range in the heat setting section during the heat setting process, satisfy the conditions of the present invention, The shrinkage stress generated in the direction is canceled by the shearing force acting in the moving direction of the film due to the difference in relative velocity between the film and the jet air, whereby the longitudinal shrinkage is hindered and the bowing amount is reduced. On the other hand, the film of Comparative Example 1 was processed by a conventional heat setting method in which air was jetted perpendicularly to the film surface, and not only the bowing amount but also the uniformity of the lateral physical properties of the film was extremely poor. In the film of Comparative Example 2, since the air ejection angle of the nozzle is 15 °, which is quite small,
The longitudinal shrinkage stress is not sufficiently offset by the shearing force due to the relative velocity difference between the film and the jet air, and the uniformity in the bowing amount, the specific gravity in the lateral direction of the film, and the variation in the thickness are generally poor. .

[Brief description of drawings]

FIG. 1 is a side view showing a heat fixing unit of a heat treatment apparatus for producing a thermoplastic resin film of the present invention.

FIG. 2 is an enlarged view showing an enlarged nozzle outlet of the heat treatment apparatus of FIG. 1A.

FIG. 3 is a view showing a bowing phenomenon of a film heat-treated in a transverse stretching machine.

[Explanation of symbols]

1 ... Heat treatment apparatus, 2 ... Nozzle, 2a ... Nozzle outlet, 4 ...
Hot air fan, F ... film.

Claims (3)

[Claims] 1. A method for producing a film of a thermoplastic resin by longitudinally stretching, transversely stretching and heat treating a thermoplastic resin sheet, which is perpendicular to an outlet center line of an air ejection nozzle of a heat treatment apparatus in the heat setting section during the heat treatment. A method for producing a thermoplastic resin film, comprising adjusting the acute angle (θ) formed by a line to be 30 ° or more and performing heat setting treatment. 2. The method according to claim 1, wherein the jet angle (θ) is 45 to 60 °. 3. The method according to claim 1, wherein the air ejection speed of the nozzle is at least three times the traveling speed of the film.