KR0130616B1 - Method for the preparation of thermoplastic resin film - Google Patents

Abstract

The method manufactures the thermoplastic resin film with transverse regular physical properties by checking a bowing phenomenon caused in the transverse stretching or thermosetting process. The method comprises steps of performing a heat treatment on the resin film while stretching the resin fim in the transverse and longitudinal direction; reperforming the transverse stretching of the film by 1-5 % whilereperforming a heat treatment on the heating speed gradient equation, L/W is more than o.25 at least and less than 0.9 ,where L is a lengthapplied by the heating speed gradient, and W is a width of the film.

Description

Manufacturing method of thermoplastic resin film

1 is a view for explaining the bowing phenomenon that appears during heat setting with respect to the biaxially stretched film.

2 is a view for showing a method of giving a gradient of the temperature increase rate in the heat setting after lateral stretching for the biaxially stretched film.

* Explanation of symbols for the main parts of the drawings

L: Section giving a gradient of the lateral heating rate W: The full length of the film

θ: angle in which the infrared heater is inclined from both ends to the center in the direction of film travel

R: Infrared heater b: Distance from reference line to bow-shaped peak

The present invention relates to a method for manufacturing a thermoplastic resin film, and in particular, to suppress bowing of the resin film caused in the process of transverse stretching and heat setting in the transverse stretching machine, and thus uniform poly width and / or Or it relates to a method for producing a thermoplastic resin film having chemical properties.

BACKGROUND OF THE INVENTION Polyester films that are useful in many applications, such as packaging materials, insulating materials, glass substitutes, etc., are typically reacted with dimethyl terephthalate and ethylene glycol. The resulting house is melt-extruded to form a sheet, and then produced through a process of stretching and cooling in the longitudinal and transverse biaxial directions. That is, an amorphous, unscented polyester sheet or a sheet that has undergone a longitudinal stretching process is prepared by preheating, stretching, heat setting, and the like in a transverse stretching machine.

Thermoplastic films, especially homopolyesters, copolyesters or mixed polyesters, polyetherene terephthalates, polyethylene-2, 6-naphthalates, polytetramethylene terephthalates, polytetramethylene-2, 6-naphthalenecarboxylates And films made of polyesters such as liquid crystalline polyester and other polypropylenes, polyvinyl chlorides, nylons, polyimides, polycarbonates, polystyrenes, polyphenylenesulfites, and the like. Although used in these products, a film manufactured to have uniform physical properties in the transverse direction is urgently required. When the physical properties of the film, that is, the soft shrinkage rate, mechanical strength, density, etc. are nonuniform in the lateral direction, there are many cases in which various damages are caused in post-processing processes such as coating, deposition, cutting, and printing, and the quality of the product is degraded. In this case, there is a problem that the yield is lowered when the product is produced to satisfy the lateral uniformity allowed in the post-processing of the film. Thus, much effort has been made to uniformize the transverse physical properties of the film.

However, it is extremely difficult to uniformize the physical properties of the film in the conventional manufacturing method. Because, in the transverse stretching machine (or tenter), the clips are held at both ends of the film, so that both ends of the film are connected to the clip against the longitudinal stretching stress caused by the longitudinal and transverse stretching processes and the shrinkage stress caused by the heat setting process. This is because the deformation is constrained by, whereas the central portion of the film is less influenced by the clip, and the binding force to the deformation is weak.

1 is a view for explaining the bowing phenomenon that appears during heat setting with respect to the biaxially stretched film. Using the ink at the inlet of the transverse stretching machine, draw a straight line on the surface of the film in the transverse direction and perform the heat treatment process and observe it at the exit of the transverse stretching machine. As shown in the drawing, the center of the film is from the reference straight line to the arcuate peak. It can be seen that the bow is deformed as much as b, which is called a bowing phenomenon. In the figure, W indicates the width of the film and arrows indicate the advancing direction of the film.

After all, the bowing phenomenon of the film caused by the difference of the binding force between the both ends and the center part in the transverse stretching machine in the opposite direction of the film traveling direction is fundamentally inherent to the biaxial stretching and heat setting process in the film forming process. It is a problem. This bowing phenomenon causes the nonuniformity of the lateral physical properties of the film.

Various methods have been tried so far to prevent the above-mentioned bowing phenomenon. For example, Japanese Patent Laid-Open No. 39-29214 discloses a heat treatment method using a heating roll, which causes a problem that width shrinkage is caused because the both ends are heat treated without forming a heat roll.

Japanese Patent Publication No. 42-9273 discloses a method of heat treatment while giving a temperature gradient in the transverse direction of the film, and Japanese Patent Publication Nos. 62-183327 and 183328 give a change in wind speed (or air volume), There is disclosed a method of heat treatment by forcibly heating both ends of the film, which has disadvantages such as the effective operation rate is dropped as the equipment becomes complicated and the condition adjustment time is prolonged.

In addition, Japanese Patent Application Laid-open No. 50-73978 discloses a method of heat-treating a film after lateral stretching by a nip roll provided between a lateral stretching process and a heat treatment process in a transverse stretching machine. Publication No. 63-24459 discloses a method of forcibly advancing the center portion of the film by means of roll rolls, all of which point out that damage to the film due to contact with the roll at high temperatures is a fatal problem.

On the other hand, a heat treatment method for imparting a cooling process after a lateral stretching process is disclosed in Japanese Patent Laid-Open Nos. Hei 3-130126, Hei 3-130127, Hei 4-142916 and Hei 4-142917. Although cooling is performed in the section, there is little effect of reducing the bowing phenomenon of the film, and there is a disadvantage in that productivity is reduced, such as an increase in equipment and waste of energy. ·

Heat treatment methods for imparting a temperature increase rate to the full width of the film after the transverse stretching process in the transverse stretching machine are disclosed in Japanese Patent Laid-Open Nos. 61-8324 and 1-204723, which uniformly heat-treat the entire width of the film. Although it can be performed, there is a problem that the deviation of the plane restraint force cannot be reduced.

The purpose of the present invention is to use the tenter heat treatment method to solve the problem of the bowing phenomenon of the conventional heat treatment method, and to give the gradient of the temperature increase rate in the width direction of the film in a specific section of the heat-setting process, The thermoplastic resin film aimed at homogenizing the scent quality is to provide a manufacturing method.

An object of the present invention described above is a method for producing a thermoplastic resin film comprising the step of heat-treating the biaxially stretched film through the longitudinal stretching and transverse stretching process, satisfying the following formula (1) after the transverse stretching process as the heat treatment step Biaxial stretching, characterized in that 1 to 5% relateral stretching is performed while giving a gradient of the temperature rising rate in the transverse direction from both ends to the center of the film, from a high temperature rising rate to a specific heat setting temperature at a low temperature rising rate. It is achieved by a method for producing a thermoplastic resin film.

0.25 ≤ L / W ≤ 0/9 (1)

(In the above formula, L is a section giving a gradient of the temperature increase rate in the horizontal direction, and W is the full width of the film.)

According to the method of the present invention, when the film after lateral stretching is heat-treated by giving a gradient of the temperature increase rate in a specific section, the longitudinal shrinkage stress is alleviated sequentially from both ends to the center portion, so that the longitudinal shrinkage stress is reduced as a whole. Will be less. In addition to this, when re-stretching is performed, the tensile stress is applied in the transverse direction, thereby preventing the contraction in the longitudinal direction, thereby reducing the amount of bowing.

According to a known method, the chip produced by the polymerization reaction is subjected to a drying process and then melt-extruded to form a sheet, and the film biaxially stretched in the longitudinal and transverse directions is heat-treated according to the method of the present invention to produce a finished film.

2 is a view for giving a method for giving a gradient of the temperature increase rate when the heat treatment after the lateral stretching in accordance with the method of the present invention for the biaxially stretched film. That is, the infrared heater R for heat treatment of the transversely stretched biaxially stretched film is installed to have a tilt angle θ from both ends of the heat treatment portion starting point to the transverse stretching machine center to give a gradient of the temperature increase rate. In the figure, L represents a heat treatment section giving a gradient of temperature increase rate, W represents the full width of the film, and an arrow represents the advancing direction of the film.

From the drawing, the heat treatment in the present invention is performed by adjusting the inclination angle θ of the infrared heater so that the ratio of the section L and the full width W of the film satisfying the above expression 0.25≤L / W≤0.9 from the drawing. It can be done.

The thermoplastic resin used in the present invention may be homopolyester, corollaster or mixed polyester, and the like, and may include polyetherene terephthalate, polyethylene-2, 6-naphthalate, polytetramethylene terephthalate, Polyester-based and polypropylene, polyvinylchloride, nylon, polyimide, polycarbonate, polystyrene, polyphenylene sulfite, such as polytetramethylene-2, 6-naphthalene carboxylate, liquid crystalline polyester, etc. may be particularly preferably used. .

Hereinafter, the present invention will be described in detail through specific examples. However, the present invention is not limited only to the following examples.

(Example 1)

A polyethylene terephthalate chip having an intrinsic viscosity of 0.64 was melt-extruded at 290 ° C. through a narrow slit die to prepare an amorphous sheet having a thickness of 200 μm at a rate of 70 m / min on a cooling roll having a cooling water temperature of 20 ° C. The sheet was longitudinally stretched while passing through the amorphous sheet into a longitudinal stretcher with multiple rolls arranged in parallel, the rolls being all heated internally and maintained at a temperature of about 100 ° C. The edge portion of the sheet stretched at a magnification of 3.5 times in the longitudinal direction was moved to the portion where the lateral stretching started while being picked up with a clip, at which time it was preheated to about 90 to 95 ° C. The preheated sheet was stretched at a rate of 4.5 times in the transverse direction at a temperature of about 110 to 120 ° C. After the lateral stretching is completed, as shown in FIG. 2, the three-component infrared heating with a diameter of 20 mm, a power consumption of 30 kW, and a surface temperature of 700 ° C with an inclination angle θ of 30 degrees from both sides of the starting point of the ointment government to the center of the transverse stretching machine. Heat crystallization was carried out for 3 seconds with hot air of 220 ° C in the heat-entertainment unit installed on the upper surface of the giga transverse stretching machine. At the same time as crystallization, re-stretching was carried out at a magnification of 1.02 times, which was then exposed to the air and gradually cooled to prepare a 14 탆 thick biaxially stretched polyethylene terephthalate resin film.

(Example 2)

A biaxially stretched polyethylene terephthalate film was prepared in the same manner as in Example 1 with an angle θ of 45 degrees inclined from both ends to the center of the transverse stretching machine with respect to the advancing direction of the film.

(Example 3)

A biaxially stretched polyethylene terephthalate film was prepared in the same manner as in Example 1 with an angle θ of 60 degrees inclined from both ends to the center of the transverse stretching machine with respect to the advancing direction of the film.

(Comparative Example 1)

A biaxially stretched polyethylene terephthalate film was prepared in the same manner as in Example 1 but without giving an inclination angle from both ends to the center of the transverse stretching machine according to the conventional method with respect to the advancing direction of the film.

(Comparative Example 2)

A biaxially stretched polyethylene terephthalate film was prepared in the same manner as in Example 1 with an angle θ of 15 degrees inclined from both ends to the center of the transverse stretching machine with respect to the advancing direction of the film.

(Comparative Example 3)

A biaxially stretched polyethylene terephthalate film was prepared in the same manner as in Example 1 except that the angle θ inclined from the two plates to the center of the transverse stretching machine was 75 degrees with respect to the advancing direction of the film.

(Comparative Examples 4-6)

The biaxially stretched polyethylene terephthalate films were prepared in the same manner as in Examples 1 to 3, but without performing relateral stretching.

The bowing amount, the transverse specific gravity change rate, and the transverse thickness change rate of the films prepared according to the above Examples and Comparative Examples were measured, and the results are shown in Table 1.

TABLE 1

In Table 1, the amount of bowing was measured as follows.

If a straight line is drawn in the transverse direction on the surface of the film using the ink line at the inlet of the transverse stretching machine, it is deformed into a bow shape as shown in FIG. 1 after the exit of the transverse stretching machine. The bowing amount is calculated as follows.

B = b / W × 100 (%)

Where B is the amount of bowing (%), b is the distance (mm) from the reference straight line to the arcuate peak, and W is the width (mm) of the film.

The change rate of the specific gravity of the film in the lateral direction is calculated by the following formula by calculating the specific gravity according to the conditions of ASTM D1505 by the density gradient pipe method.

The lateral thickness change rate of the film was measured using a thickness gauge made by Winzen, USA.

The thickness of the film was measured in the transverse direction of and calculated according to the following equation.

By applying the inclination with respect to the advancing direction of the film, as shown in Table 1 above, the film after the lateral stretching process is increased in the transverse direction at a high temperature rate at both ends of the film at a low temperature rate at the center of the film at a specific section. The film produced according to Examples 1 to 3, which satisfies the present invention, which is adapted to give a gradient and at the same time re-stretch, has greatly reduced the amount of bowing and the change in transverse specific gravity. This is because according to the method of the present invention, the shrinkage stress is sequentially relaxed from both ends to the center portion, and at the same time, the contraction in the longitudinal direction is reduced as a whole because the tensile capacity is applied in the transverse direction.

Since the film produced according to Comparative Example 1 is a conventional heat setting method is applied, the variation in specific gravity in the lateral direction as well as the bowing amount is large, so that the quality uniformity in the lateral direction is extremely poor.

The film according to Comparative Example 2 is not preferable because the heat treatment section for giving a gradient of the temperature increase rate in the horizontal direction is too long, so that the amount of bowing is not greatly reduced and the variation in specific gravity of the film is not reduced.

The film according to Comparative Example 3 is not preferable because the amount of bowing is not small because the heat treatment section for giving the gradient of the temperature increase rate in the transverse direction is too short.

In addition, compared to the films according to Examples 1 to 3, the films according to Comparative Examples 4 to 6 were produced without accompanying transverse stretching, so that the amount of bowing and the transverse specific gravity of the films were compared with those of the films prepared according to the above Examples. And it can be seen that the lateral uniformity of the quality is generally poor in the thickness variation.

In the present invention as described above, in the production of the thermoplastic resin film, the biaxially stretched film is subjected to a heat treatment process in the transverse stretching machine, but the film after the transverse stretching process from the both ends to the center of the film in the section satisfying the above formula (1) By increasing the temperature in the transverse direction to a specific heat setting temperature at a high heating rate up to a specific heat setting temperature, the film is stretched by 1 to 5%, thereby reducing the amount of film in the film and reducing the amount of film in the transverse direction. This makes it possible to produce a more uniform resin film.

Claims (1)

In the method for producing a thermoplastic resin film comprising the step of heat-treating the biaxially stretched film through the longitudinal stretching and die-stretching process, after the lateral stretching process in the heat treatment step from both ends of the film in the section satisfying the following formula (1) A method for producing a biaxially stretched thermoplastic resin film, characterized by performing 1 to 5% relateral stretching while giving a gradient of the temperature rising rate in a mold direction from a high temperature rising rate to a specific softening temperature at a low temperature rising rate to a central portion. 0.25 ≤ L / W ≤ 0.9 (1) (In the above formula, L is a section giving a gradient of the lateral heating rate, and W is the full width of the film.)