KR970010453B1 - Process for the preparation of thermoplastic resin films - Google Patents

Abstract

A method of thermoplastic resin film effecting heat fixation treatment by controlling air injection angle to 30= or more the angle of nozzle outlet to vertical line within the heat fixation zone of the heat treatment device in heat treatment process is disclosed. Thereby, it is possible to provide method for preparing thermoplastic resin film which bending phenomenon like a bow is reduced and transverse property is uniform.

Description

Manufacturing method of thermoplastic resin film

1A of FIG. 1 is a side view showing a heat treatment apparatus for manufacturing a thermoplastic resin film of the present invention,

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

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

The present invention relates to a method for producing a thermoplastic resin film in which the physical properties of the film are uniform in the transverse direction. More particularly, the present invention suppresses the bowing of the film caused in the process of transverse stretching and heat setting through the treatment on the transverse tenter, so that the physical, chemical or physicochemical properties of the transverse direction are uniform. A method for producing a thermoplastic resin film having a composition.

Thermoplastic films, especially homopolyesters, copolyesters or mixed polyesters, polyethylene terephthalates, polyethylene-2,6-naphthalates, polytetramethylene terephthalates, polytetramethylene-2,6-naphthalenecarboxylates, liquid crystal polys Polyesters such as esters and other films such as polypropylene, polyvinylchloride, nylon, polyimide, polycarbonate, polystyrene, polyphenylenesulfite are used for packaging, recording media, industrial and many other applications. There has been a great demand for the production of films having the same physical properties in the transverse direction. If the physical properties of the film, for example, heat shrinkage, mechanical strength and density are non-uniform in the lateral direction, it may cause defects such as surface distortion during post-processing such as coating, deposition, cutting, printing, etc., thereby degrading the quality of the final product. There are not many examples. Therefore, in order to satisfy the uniformity in the transverse direction that is acceptable in the post-processing of the film, there is a disadvantage in that the yield of the product is reduced. Therefore, in order to improve the quality of the final product without lowering the product yield, it is urgent to produce a film having uniform physical properties in the transverse direction so as not to cause defects in the post-processing as described above.

However, in the conventional manufacturing method, the clips of both ends of the film are held in the transverse stretching machine, and thus the longitudinal stretching stress caused by the longitudinal and transverse stretching processes and the shrinkage stress caused by the heat setting process are caused. With respect to both ends of the film, the deformation is constrained by the clip, while the central portion of the film is less influenced by the clip and thus has less restraint against deformation. Therefore, the bowing of the film caused by the difference in the restraint force between the both ends and the center part in the transverse stretching machine in the opposite direction of the film traveling direction is a process of producing a film that involves biaxial stretching and heat setting. It is an unavoidable problem in the film because the bow-shape of the film causes a nonuniformity of the lateral physical properties of the film, it was extremely difficult to uniform the lateral physical properties of the film in the conventional film production method.

Various methods have been attempted to avoid such drawbacks. For example, Japanese Patent Publication No. 64-29214 discloses a method of heat treatment using a heating roll. However, both ends are not restrained by the heating roll and are heat treated to cause shrinkage in the width direction. No. 67-9273 performs heat treatment by using a temperature gradient in the transverse direction of the film, and Japanese Patent Laid-Open Nos. 87-183327 and 183328 disclose a heat treatment process such as a change in wind speed or air volume and forced heating at both ends of the film. However, this heat treatment method has disadvantages such as a decrease in the effective operation rate due to the complexity of the equipment and the prolongation of the condition adjustment time. In addition, Japanese Patent Laid-Open No. 75-73978 discloses a method of providing a nip roll between a lateral stretching process and a heat treatment process in a film to heat-treat the film after the lateral stretching is completed, and Japanese Patent Publication No. 88 -24459 uses a method of forcibly advancing the center portion of the film by a nip roll, but both of these methods have a problem that damage to the film due to contact with the roll at a high temperature is fatal.

On the other hand, Japanese Patent Publication Nos. 91-130126, 91-130127, 92-142916, and 92-142917 use a heat treatment method to add a cooling process after the transverse stretching process, but the cooling treatment is performed in a section longer than the full width. Nevertheless, there is almost no effect of reducing the bow-shape of the film, and there is a disadvantage in that productivity decreases due to an increase in equipment and waste of energy. Further, Japanese Patent Laid-Open Nos. 86-8324 and 89-204723 disclose a heat treatment method in which a temperature increase treatment is added to the entire width of the film after the transverse drawing process in the transverse drawing machine. Since the heat treatment is uniformly performed, there is a problem in that the piece d of the strain restraint force in the transverse direction cannot be reduced.

Thus, the present inventors have conducted extensive research to solve the bow-shape of the film according to the conventional heat treatment method, using a heat treatment method using a transverse stretching machine, but in the heat setting period perpendicular to the film surface from the nozzle in the heat setting section By adjusting the air blowing angle of the nozzle instead of the conventional method of spraying the air, the air flow rate of the nozzle is controlled with respect to the traveling speed of the film, so that the lateral physical property of the film is uniformed, thereby reducing the bow-shaped warpage of the film. It was found that the thermoplastic resin film can be provided.

Accordingly, it is an object of the present invention to provide an improved thermoplastic resin film in which the lateral physical properties of the film are uniform and the bowing warp is significantly reduced.

Another object of the present invention is to provide a method for producing such an improved thermoplastic resin film.

Hereinafter, the present invention will be described in detail.

According to the present invention, by controlling the air blowing angle toward the film surface of the nozzle and the film blowing speed in the heat setting section during the heat treatment process in the transverse stretching machine, the lateral physical properties are uniform and the bow-shaped warpage is reduced. Improved thermoplastic resin film is provided.

The production of thermoplastic resin film by a known method is carried out by drying the polymer chip produced by the polymerization reaction, followed by melt extrusion to form a sheet, and then the film obtained by biaxially stretching the sheet in the longitudinal and transverse directions. By heat treatment to obtain the final film. However, in the film obtained through the above process, as described above, the film is bowed because the restraint against deformation in the heat treatment process is not the same throughout the film.

In the present invention, in manufacturing a thermoplastic resin film, the biaxially stretched film is heat-treated in the transverse stretching machine, but when the air is blown out through the nozzle in the section for opening and setting the film after the transverse stretching process, as shown in FIG. Film and blowing air by adjusting the air blowing angle so that the acute angle θ formed between the nozzle outlet centerline and the vertical line is 30 ° or more, preferably 45 ° to 60 °, and at the same time controlling the air blowing speed with respect to the traveling speed of the film. The shear force acting in the advancing direction of the film due to the difference in relative speed of the cancels the contracting force acting in the direction opposite to the advancing direction of the film, thereby reducing the bow-shaping phenomenon and making the lateral physical properties of the film uniform.

The air blowing speed is preferably at least three times the running speed of the film, more preferably 4 to 6 times.

Examples of the thermoplastic resin used in the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, polytetramethylene terephthalate, polytetramethylene-2,6-naphthalene carboxylate, polyester such as liquid crystalline polyester, poly Propylene, polyvinylchloride, nylon, polyimide and polyphenylene sulfite. Among these, polyethylene terephthalate, polyethylene-2,6-naphthalate and polyphenylene sulfite are particularly preferable.

The thermoplastic resin film according to the invention can be produced, for example, as follows: In the case of a polyester film using polyethylene terephthalate, polycondensation of polyethylene terephthalate results in a poly having an intrinsic viscosity of 0.6 to 0.7 dl / g. An ester polymer chip was prepared and then melt-extruded at 190 to 300 ° C. and molded into an amorphous sheet on a cold roll, followed by 3.5 times longitudinally at a temperature of 100 to 110 ° C. and a temperature of 100 to 120 ° C. The biaxially stretched polyester film was obtained by stretching each at a magnification of 4.5 times in the transverse direction. The film is then passed through a heat treatment apparatus 1 as shown in 1A. The film introduced into the heat treatment apparatus 1 proceeds along the center of the apparatus, wherein the blowing angle θ of air heated by the hot air fan 4 of the nozzle 2 and ejected through the nozzle outlet 2a ) Is adjusted to 30 ° or more, preferably 45 ° to 60 °, and the air blowing speed is adjusted to be 3 times or more, preferably 4 to 6 times the running speed of the film, to perform the heat setting treatment. An improved biaxially stretched film having a uniform aromatic property is obtained.

Hereinafter, the present invention will be described in more detail based on the following examples. It should be noted that these examples are intended to illustrate the invention and are not intended to limit the invention thereto.

Example 1

Dimethyl terephthalate and ethylene glycol are mixed in a ratio of 1 to 1 to produce a polyethylene terephthalate monomer by transesterification, and then the polycondensation reaction of the monomer to polyethylene terephthalate polymer chip having an intrinsic viscosity of 0.64 dl / g. Was prepared. The polyester chip prepared as described above was melt extruded at 290 ° C., and then formed into an amorphous sheet having a thickness of 200 μm on a cooling roll at which the cooling water temperature was maintained at 20 ° C., and then the resulting sheet was 3.5 times longitudinally at 100 ° C. The film was stretched at a magnification of and then stretched at a magnification of 4.5 times in the transverse direction at a temperature of 110 to 120 ° C. to obtain a biaxially stretched polyethylene terephthalate film. Subsequently, the film is introduced into the heat treatment apparatus of the present invention, and the air blowing angle θ of the heat-opening nozzle is 30 °, the temperature of the jetted air is 220 ° C., and the traveling speed of the film is 4 m / sec and air. A biaxially stretched polyethylene terephthalate film having uniform physical properties in the transverse direction was obtained by adjusting the jetting speed of to 20 m / sec to perform a heat setting treatment.

The bow-shaped warpage, the transverse specific gravity change rate and the thickness change rate of the resulting film were measured as follows, and the results are shown in Table 1.

Since the straight line drawn transversely on the surface of the film at the inlet of the transverse stretching machine passes through the exit of the transverse stretching machine, it is deformed into a bow shape as shown in FIG. 2, so that the amount of bow bending of the film using the following equation Was calculated.

B = b / W × 100 (%)

In the above, B represents the bow deflection amount (%), b represents the distance (mm) from the reference straight line to the arcuate peak, and W represents the width (mm) of the film.

The rate of change of the specific gravity of the film in the transverse direction was first determined by the density gradient pipe method according to the conditions of ASTM D1505, and then the change rate of specific gravity was calculated by the following equation.

Next, the rate of change in the transverse thickness of the film was first measured by the film thickness in the transverse direction of the film using a thickness gauge (Winzen, Inc., USA), and then the thickness change rate was obtained from the following equation:

Example 2

A biaxially stretched polyethylene terephthalate film was obtained in the same manner and in the same manner as in Example 1 except that the air blowing angle θ of the nozzle with respect to the surface of the film passing through the heat treatment apparatus was 60 °. As shown in Table 1, the result of measuring the bow-shape amount of the film and the change in the transverse physical properties of the resulting film is shown in Table 1 below.

Example 3

A biaxially stretched polyethylene terephthalate film was obtained in the same manner and in the same manner as in Example 1 except that the air blowing angle θ of the nozzle with respect to the surface of the film passing through the heat treatment apparatus was 75 °. As shown in Table 1, the result of measuring the bow-shape amount of the film and the change in the transverse physical properties of the resulting film is shown in Table 1 below.

Comparative Example 1

The biaxially stretched polyethylene was carried out in the same manner and in the same manner as in Example 1 except that the air blowing angle (θ) of the nozzle with respect to the surface of the film passing through the heat treatment apparatus was 0 °, that is, the air was sprayed perpendicularly to the film surface. A terephthalate film was obtained. As shown in Table 1, the result of measuring the bow-shape amount of the film and the change in the transverse physical properties of the resulting film is shown in Table 1 below.

Comparative Example 2

A biaxially stretched polyethylene terephthalate film was obtained in the same manner and in the same manner as in Example 1 except that the air blowing angle θ of the nozzle with respect to the surface of the film passing through the heat treatment apparatus was 15 °. As shown in Table 1, the result of measuring the bow-shape amount of the film and the change in the transverse physical properties of the resulting film is shown in Table 1 below.

As can be seen in Table 1, the film of Examples 1 to 3 that satisfies the conditions of the present invention by inclining the air blowing angle θ of the nozzle in a specific range in the heat setting section of the heat treatment apparatus during the heat treatment process heat treatment The shrinkage stress generated in the longitudinal direction is canceled by the shear force acting in the advancing direction of the film due to the difference in relative velocity between the film and the blowing air, thereby preventing the longitudinal shrinkage and reducing the amount of bow bending.

On the other hand, the film of Comparative Example 1 was processed by a conventional heat-setting method that blows air vertically with respect to the film surface, and the uniformity of the lateral quality of the film is increased because not only the amount of bow deflection but also the change in specific gravity in the transverse direction is large. The film of Comparative Example 2 has a very small air blowing angle θ of 15 °, so that the longitudinal shrinkage stress is not sufficiently canceled by the shear force due to the difference in relative velocity between the film and the blowing air, and thus the amount of warpage is reduced. Uniformity is generally inferior in the specific gravity and thickness deviation of a film transverse direction.

As described above, the bow-shaped warpage phenomenon is reduced by adjusting the air blowing angle so that the acute angle formed by the nozzle outlet centerline and the vertical line in the heat setting section during the heat treatment process of the film is 30 ° or more, according to the present invention, and the lateral physical properties The manufacturing method of this uniform thermoplastic resin film is provided.

Those skilled in the art will be able to make various changes and modifications from the contents or examples described herein without departing from the spirit and scope of the invention as shown in the following claims, and such changes and modifications are within the scope of the present invention. Should be understood to be included in.

Claims (3)

In the method of manufacturing a thermoplastic resin film, the heat treatment process by adjusting the air blowing angle so that the acute angle formed by the nozzle exit center line and the vertical line in the heat setting section of the heat treatment apparatus is 30 ° or more during the heat treatment process . The method of claim 1 wherein said air blowing angle is between 45 and 60 degrees. The method of claim 1 wherein the air blowing speed of the nozzle is at least three times the running speed of the film.