JP2012101398A - Cooling device of thermoplastic resin film, and method of manufacturing the thermoplastic resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a film using a cooling device, which has high productivity and is capable of producing a thick film being excellent in haze at a high speed without generating film thickness unevenness due to the unevenness formed on the film surface in the cooling device for cooling the thermoplastic resin film on an anti-cooling drum surface.SOLUTION: The cooling device, for cooling the anti-cooling drum surface film on the cooling drum by blowing air to the film from a blowing nozzle, has a means for measuring the film surface temperature on an anti-drum surface and optionally adjusting the wind velocity of air blown toward the film from a plurality of nozzle mounted on the anti-cooling drum surface. The film manufacturing method uses the cooling device for adjusting the wind velocity in accordance with the degree of the film thickness unevenness while measuring the film thickness unevenness in the film flow direction by a film thickness meter mounted in an cooling drum outlet.

Description

  The present invention relates to an optical film, a surface protective material, an electrical insulating material, a release material, and the like, in particular, a cooling device and a thermoplastic resin for a thermoplastic resin film excellent in transparency and flatness such as an optical film and a surface protective material. The present invention relates to a film manufacturing method.

  In recent years, as various display members represented by liquid crystal displays (LCDs) and plasma display panels (PDPs) have been reduced in weight and cost, the market for optical films has expanded as an important component of displays. Yes. The optical film is made of various transparent films made of thermoplastic resin such as polyester such as polyethylene terephthalate (PET), acrylic polymer, polycarbonate (PC), etc., for protection, for example, to prevent damage. It is obtained by applying various surface treatments to laminate a film (hard coat layer), AR layer (antireflection layer), light collecting / light diffusing layer, polarizing plate, etc. on the substrate. There is a strong demand for transparency. On the other hand, when it is processed by being incorporated into a large display or the like, a sufficient thickness is required, so that a thick film having a thickness of 150 μm or more is preferably used.

  The manufacturing process of such a film includes a process of extruding a molten thermoplastic resin from an extrusion die and cooling it, and in order to manufacture a film having excellent transparency, the extruded thermoplastic resin is quickly desired. It is important to cool to temperature. As a method for quickly cooling the thermoplastic resin, a method of bringing the thermoplastic resin into close contact with the cooling drum is generally used. When manufacturing a thick film having a thickness of 150 μm or more, a film surface that is not in contact with the cooling drum (anti-cooling) It is also necessary to cool from the drum surface. This is because, in a thick film, when cooling with only a cooling drum, the film temperature on the surface of the anti-cooling drum does not easily fall to a desired temperature. In particular, in the case of a film made of a crystalline resin such as polyester, if the cooling rate in the vicinity of the glass transition temperature of the thermoplastic resin is not sufficient, crystallization of the thermoplastic resin proceeds, resulting in a decrease in transparency (haze) of the film. Because it will do. As a method for quickly cooling the surface of the anti-cooling drum, a method is known in which an auxiliary cooling device is installed on the surface of the anti-cooling drum and the cooling of the molten thermoplastic resin is promoted. This auxiliary cooling device is generally constituted by a nozzle (hereinafter referred to as a spray nozzle) that blows cool air from the surface of the anti-cooling drum toward the thermoplastic resin (for example, Patent Document 1 and Patent Document). 2).

  However, the recent thick film has a high demand for haze, and the cooling with the conventional auxiliary cooling device has insufficient cooling capacity, which causes a problem in quality. It is publicly known that a film having excellent haze can be obtained by cooling the film at a cooling rate of 5 ° C./second or more in the range from 200 ° C. to 150 ° C. of the cooling crystallization temperature on the cooling drum. Yes. (For example, Patent Document 3) Since the film temperature is less likely to be lowered on the anti-cooling drum surface as the thickness is increased to 150 μm or more, the temperature-falling crystal is closer to the exit position of the cooling drum at the position where the film is cooled to 200 ° C. Since it is difficult to install the spray nozzle in the range of 200 ° C. to 150 ° C., the rotation speed of the cooling drum is slowed down, the time for the cooling drum and the film to contact is increased, or the film temperature is 200 ° C. Methods such as starting cooling with a spray nozzle from a position as close as possible to an extrusion die at a higher temperature position, increasing the spray speed of cool air, and lowering the temperature of cool air to be sprayed have been taken. However, a method of reducing the rotation speed of the cooling drum is not preferable because productivity is lowered. In addition, the method of bringing the cold air blowing position closer to the extrusion die and the method of increasing the cold air blowing speed have a large film cooling effect, but since the cold air is blown to the softened film surface near the film melting point, the film surface is uneven. This causes a problem that the film thickness unevenness increases.

JP-A-3-239525 JP 7-329153 A JP 2007-185898 A

  In order to produce a thick film excellent in haze at a high speed without causing uneven thickness of the film, which was difficult with the prior art, the present invention is cooled without deforming the film surface of the anti-cooling drum surface. An object of the present invention is to provide a thermoplastic resin film cooling device and a thermoplastic resin film manufacturing method using a spray nozzle having the highest cooling effect.

  The present invention employs the following means in order to solve such problems. That is, when a molten thermoplastic resin is cast on a cooling drum from an extrusion die and cooled and solidified on the cooling drum to produce a thermoplastic resin film, a film surface that is not in contact with the cooling drum (hereinafter referred to as an anti-cooling drum) In the apparatus which blows air toward the film from a plurality of nozzles installed on the side), it is a thermoplastic resin film cooling device having means capable of individually adjusting the wind speed of the air to be blown .

  Also, a method for producing a thermoplastic resin film in which a molten thermoplastic resin is cast from an extrusion die onto a cooling drum and is cooled and solidified on the cooling drum, the film surface not contacting the cooling drum (hereinafter referred to as anti-cooling). A method for producing a thermoplastic resin film, comprising: a step of blowing air from a plurality of nozzles installed on the side of the drum surface toward the film, and the speed of the blowing air can be adjusted individually for each nozzle.

  According to the present invention, the air blowing position of the cooling device on the anti-cooling drum surface is adjusted by measuring the film surface temperature on the anti-cooling drum surface, thereby bringing the air blowing position closer to the extrusion die than the conventional cooling device. Is possible. As a result, the film on the anti-cooling drum surface can be rapidly cooled, and a thick film excellent in haze can be produced at high speed.

  Furthermore, the film thickness measuring device installed at the outlet of the cooling drum measures the thickness unevenness in the film flow direction and feeds back the measurement data, thereby adjusting the blowing air speed of the cooling device again to produce irregularities on the film surface. The occurrence of uneven film thickness can be prevented.

  The film obtained by this invention has the characteristics of excellent haze and small film thickness unevenness, both of which have been difficult to achieve with conventional technology for manufacturing thick films having a film thickness of about 150 μm or more. It is suitable as a base material for optical functional films used for coating applications, specifically, touch panels, protective sheets, housings, and the like.

An example of the cooling device of the thermoplastic resin film of this invention is shown. (However, reference numerals 1, 2, 5, 11, and 12 are excluded because they are conventional devices.)

  First, the thermoplastic resin film obtained by the method for producing a thermoplastic resin film of the present invention is not particularly limited, but typical examples include polyethylene terephthalate, polyethylene-2, 6-naphthalate as polyester, and nylon as polyamide. -6, polyphenylene sulfide as polyarylene sulfide (hereinafter, the thermoplastic resin film may be simply expressed as a film).

  The thermoplastic resin film cooling device of the present invention is, for example, as shown in FIG. 1 (however, reference numerals 1, 2, 5, 11, and 12 are excluded for conventional devices), and an extrusion die 1 and its die As a device added to the conventional device composed of the cooling drum 2 below, the circumferential direction of the cooling drum is such that the blowing nozzle 3 blows air toward the center of the cooling drum along the rotation direction of the cooling drum. A plurality of them are arranged.

  For the blower that supplies air to the above-mentioned spray nozzle, it is necessary to select the static pressure specification according to the pressure loss of the shape of the spray nozzle, the piping used as the flow path of the spray air, and the duct. When the static pressure is low, the required wind speed (air volume) of the blowing air may not be obtained, so a turbo fan capable of obtaining a high static pressure and air volume is preferable. The pipes and ducts to be the flow paths need to be selected based on the required air volume, but are preferably selected with a cross-sectional area that is 20 m / s or less at each location in the flow path.

  The blower preferably has an air volume adjustment mechanism capable of adjusting the air volume supplied to the plurality of nozzles. For example, an air volume adjusting device 7 is attached to the blower. The blower air volume adjustment device is, for example, an inverter that changes the frequency of the blower motor if it is electric, a slidac type that changes the input current to the blower, or a blower that changes the input current to the blower. Although it is possible to use a method of installing a damper at the air outlet, it is preferable to change the blower air volume by an inverter that is highly versatile and easy to adjust the air volume. The inverter to be used is not particularly limited, but an inverter having high versatility and reliability is preferable, and examples thereof include those manufactured by Mitsubishi Electric and Toshiba. In order to prevent the inverter from being stopped due to overcurrent even at a frequency close to the lower limit, it is more preferable to use an inverter having a larger electric capacity than the blower motor to be used.

  After the supplied air is distributed to the spray nozzles, the air volume control valve 9 adjusts the spray air volume for each spray nozzle. From the spray nozzle toward the thermoplastic resin film on the anti-cooling drum surface. Be sprayed. The air volume adjustment valve is not a fully open-fully closed ON-OFF type, but can automatically adjust the valve opening steplessly by a command signal input by an electric actuator to adjust the air volume. It is preferable. It is preferable that a position meter is attached to the actuator part and the valve opening degree can be output as an electric signal. The air volume adjustment valve can be a butterfly valve (butterfly damper), ball valve, gate valve, etc., and it is desirable to have a structure that can completely shut off the air and reduce the air volume to 0, making it easy to adjust the air volume. It is preferable to use a valve (butterfly damper). The material of the valve is a flow path of air to be blown onto the product film. Therefore, stainless steel is preferably used for the inner surface of the valve, and Teflon (registered trademark) is used for the seat, in order to prevent rust and foreign matter from entering. Is preferably used.

  Although the spray nozzle in this invention becomes a shape long in the width direction of a cooling drum, it is preferable that the spray wind speed nonuniformity in the width direction is 10% or less. When the spraying wind speed unevenness in the width direction is large, even if the spraying wind speed is adjusted for each spraying nozzle, a portion where the spraying wind speed is locally high in the width direction is created, and the film thickness unevenness may occur. The spray nozzle is a cooling drum having a diameter of 1000 to 2000 mm and a width of 1000 to 2600 mm. For example, a spray nozzle having a slit-shaped tip with a gap of 2 to 10 mm is installed at a pitch of 5 to 15 ° in the circumferential direction. A configuration in which a plurality of units are installed in the unit is preferable. This is because, with conventional spray nozzles, if the number of stages is less than five, the region where the crystallization speed of the film is fast cannot be cooled, and there is a possibility that crystallization scratches may occur or the number of stages of spray nozzles is more than fifteen. In the spray nozzle portion, overcooling occurs, the film temperature from the cooling drum is lowered, and there is a possibility of inducing stretching unevenness in the next process, for example, longitudinal stretching. This is because not only the adjustment of the blowing wind speed but also the change of the spray start position and end position are possible.

  In addition, the width of the spray nozzle in the present invention is preferably 100 to 500 mm wider than the width of the thermoplastic resin film on the cooling drum. In addition, the distance between the tip surface of the spray nozzle and the surface of the thermoplastic resin film is preferably 5 to 30 mm. If the distance between the front end surface of the spray nozzle and the film is shorter than 5 mm, the sublimate generated on the film surface is deposited or dropped at the front end portion of the spray nozzle and easily adheres to the film as a foreign matter. On the other hand, if the distance is longer than 30 mm, the cooling efficiency of the blowing air is lowered, and haze may be deteriorated.

  It is preferable to have means capable of individually adjusting the air velocity of air blown from the blowing nozzle in the present invention. The wind speed of the air blown from the blowing nozzle is obtained by the blowing air volume / the opening area of the blowing nozzle, and the wind speed of the blowing air can be adjusted by adjusting the blowing air volume with the air volume adjusting valve. If the number of spray nozzles is one, the static pressure of the blower is sufficiently large, and if it is not affected by the pressure loss of the shape of the spray nozzle or the piping or duct used as the flow path of the air, The blowing air wind speed obtained by “the opening area of one stage of the nozzle” ”can be obtained, and the wind speed at this time becomes the maximum blowing air wind speed. However, the blowing air wind speed during actual use is preferably in the range of 60 m / sec or less, and more preferably in the range of 10 to 35 m / sec except when the blowing air is completely stopped.

  The spray nozzle in the present invention is preferably installed in the range of 40 ° to 180 °, assuming that the position directly above the cooling drum is 0 °, but there is no problem even in the range of 0 ° to 40 ° or a position of 180 ° or more. Can be installed. In addition, when the air speed blown from the blowing nozzle close to the extrusion die is high, the blow-up increases, and the molten thermoplastic resin is vibrated until it is extruded from the extrusion die and landed on the cooling drum. Thickness unevenness may occur. Therefore, it is preferable that the blowing air speed of the spray nozzle near the point where the thermoplastic resin lands on the cooling drum is slow, and the spraying wind speed is increased as the distance from the landing point increases. Even if the blowing nozzle wind speed at a position close to the point where the thermoplastic resin lands on the cooling drum is slow, if thickness unevenness occurs, for example, several spray nozzles near the point where the thermoplastic resin lands on the cooling drum The blowing air may be stopped to set the wind speed to 0 m / sec, and cooling may be started in the middle of the installed blowing nozzle. Conversely, if the film temperature drops too much due to the cooling device, stop the several blowing nozzles near the cooling drum outlet position to reduce the air speed to 0 m / sec, and cool down from the middle of the installed blowing nozzles. You may end.

  The temperature of the blowing air in the present invention is preferably in the range of 5 to 20 ° C., and the range of adjustment of the wind speed of the blowing air is theoretically “blower as long as air is blown evenly from each blowing nozzle. “Air volume / (opening area of each spray nozzle × total number of spray nozzles)” is the minimum value. On the other hand, in the case of spraying with the number of spray nozzles reduced, it is possible to achieve a wind speed that exceeds the wind speed when sprayed uniformly.

  When the air supplied from the blower passes through the heat exchanger 8, it exchanges heat with the refrigerant and is cooled. As the refrigerant used for heat exchange, cold water may be used when the temperature of the blowing air is high. However, when the temperature of the blowing air is low, for example, 5 ° C., for example, a Freon type refrigerator is installed and It is preferable to use cold water that is directly used as a refrigerant or heat-exchanged with Freon as the refrigerant. When using cold water heat-exchanged with chlorofluorocarbon as a refrigerant, it is preferable to mix antifreeze with the cold water in order to prevent freezing.

  In the blowing air flow path, it is preferable to install a filter at a position downstream from the heat exchanger to remove foreign matters mixed in the air. The filter to be installed is more preferably a HEPA filter because the quality of the film is lowered even if a slight amount of foreign matter is mixed in the blowing air. In addition, it is preferable to use stainless steel as a material in order to prevent rust and foreign matter in the flow path in the same way for piping, ducts, air volume control valves, nozzles, etc. downstream of the HEPA filter.

  It is desirable to provide a non-contact surface thermometer 4 for measuring the film surface temperature of the anti-cooling drum surface between the spray nozzles.

  It has a wind speed adjustment mechanism that measures the film surface temperature upstream of the part where the air from each nozzle hits the film in the film flow direction and can adjust the air speed according to the film surface temperature. Is preferred. Here, the portion of the nozzle that is exposed to air is preferably upstream of the film flow direction and immediately before it.

  The film surface temperature measurement is preferably a non-contact type surface thermometer, and the non-contact type surface thermometer is not particularly limited as long as it is a measuring instrument capable of measuring the temperature of the film surface such as an infrared radiation thermometer, but according to the measurement temperature. An infrared radiation thermometer (temperature sensor) that has a function of outputting an electrical signal, is relatively inexpensive, is small in equipment, and is easy to install is preferable. Since the infrared radiation thermometer is used in an environment where the ambient temperature is relatively high, the usable temperature range is preferably 55 ° C. or higher. For example, OMRON non-contact temperature sensor: ES1C, KEYENCE digital radiation temperature sensor: FT-H20, or the like can be used. The infrared radiation thermometer is installed at a position where the film surface temperature immediately before entering the spray nozzle of each stage can be measured, and is installed so that at least the center position in the film width direction can be measured. Further, it is more preferable if a plurality of films are installed in the film width direction and the temperature near the film edge can be measured.

  When the electrical output corresponding to the measured film surface temperature is sent to the control device 10, the control device is preset with a command signal corresponding to the type, thickness, and film surface temperature of the thermoplastic resin film. It is preferable to output a command signal corresponding to the temperature to each air volume adjustment valve to adjust the wind speed of the blowing air to an optimum wind speed.

  After the thermoplastic resin film that has passed through the cooling drum passes through the cooling guide rolls 11 and 12, the film thickness measuring device 13 measures the film thickness in the film flow direction, and the film thickness data is transmitted to the control device. . When the thickness unevenness data sent to the control device is large, a command signal is sent to the air volume adjusting valve, and the wind speed of the blowing air is readjusted.

  In the film flow direction, the film thickness measuring device installed downstream of the cooling drum measures the thickness unevenness in the film flow direction at least at one location in the film width direction. It is preferable to have a wind speed adjusting mechanism that can be adjusted.

  In the control device, the command signal value corresponding to the film thickness unevenness is set in advance, and the film thickness unevenness data is fed back and adjusted, so that the film thickness unevenness gradually decreases, and the film thickness unevenness within the specified range. It becomes. The film thickness measuring device is preferably a non-contact method using a sensor using β-rays, X-rays, infrared rays, or a light interference type in accordance with the film thickness to be measured, physical properties and the like. Moreover, as long as sufficient accuracy is obtained, the thickness may be measured using a laser displacement meter or the like. The sensor part can be moved in the width direction and preferably stopped at any position. However, when the sensor position is fixed, it should be installed at least at the center position in the film width direction, and the longitudinal (MD) direction of the film. Measure the thickness. If necessary, it is more preferable to install a plurality of units so that measurement can be performed even near the edge of the film. It is preferable that the film at the position where the film thickness is measured has less flutter, and a configuration in which guide rolls are installed at upstream and downstream positions where the film thickness measuring device is installed to reduce the flutter of the film is more preferable.

  Thereafter, the film is stretched by about 3 times in the longitudinal direction and the transverse direction by a known method, and is heat-treated and wound up as necessary to form a product film.

  The characteristic measuring method and the effect evaluating method in the present invention are as follows.

1. Unevenness of film thickness From a film having a length of 1 m and a width of 600 mm, three samples for thickness measurement having a width of 40 mm were cut out so that the position in the center in the width direction of the film and the position of 100 mm from the end were the center of the sample. Thereafter, using a contact thickness gauge (KG60 / A manufactured by Anritsu Co., Ltd.), the thickness in the longitudinal direction of each thickness measurement sample was continuously measured and output to a chart recorder. The difference between the maximum value (MAX) and the minimum value (MIN) of the thickness from the output thickness profile was defined as thickness unevenness R (= MAX−MIN) μm. Thickness unevenness R averaged the value of three places.

  In addition, about the thickness nonuniformity described in the following Examples and Comparative Examples, the film thickness measured by the film thickness measuring instrument installed after passing through the cooling guide roll is the in-line film thickness, and the apparatus of the present invention measured by this measuring method. The film thickness as a product manufactured by using the product is referred to as the product film thickness.

2. The film haze was measured using a haze meter (NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.) based on JIS-K7105 (1981). For a film having a length of 1 m and a width of 600 mm, one side in the length direction and the width direction is in the range of a square of 100 mm. However, adjacent squares do not overlap each other, and adjacent squares share one side. Measured at a total of 45 locations, 9 in the length direction and 5 in the width direction, and the average value was taken.

3. Blowing air wind speed A cup with an opening area of 120 mm x 13 mm is pressed against the tip of the nozzle,
A pitot tube connection silicon tube (φ7, length 2 m) is connected to a multi-environmental measuring instrument (testo 435, manufactured by Testo Co., Ltd.), measured at 5 locations in the width direction of each spray nozzle, and the average value is sprayed from each spray nozzle Wind speed.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
In the cooling device that cools the film on the cooling drum (diameter: 1600 mm, width: 1500 mm) on the cooling drum shown in FIG. 1 by blowing air with the blowing nozzle to cool the film, the blowing nozzle positions the extrusion die at an angle of 0 °. As a result, 14 places are installed every 10 ° in a range of 40 ° to 170 °. Hereinafter, the spray nozzle closest to the extrusion die is referred to as spray nozzle No. 1, the next spray nozzle in the rotation direction of the cooling drum is spray nozzle No. 2, and the next is spray nozzle No. 3 to No. 14. Similarly, non-contact surface thermometers installed immediately before each spray nozzle are referred to as non-contact surface thermometers No. 1, No. 2,.

  Polyethylene terephthalate having an intrinsic viscosity of 0.65 substantially free of inert particles is dried at a temperature of 180 ° C. for 5 hours under a reduced pressure of 3 torr, put into an extruder and melted at a temperature of 290 ° C., and then filtered. After filtration through a filter with an accuracy of 8 μm, the molten resin was discharged from an extrusion die and cooled and solidified as a 1.8 mm thick film on a cooling drum with a surface temperature of 20 ° C. rotating at a speed of 6 m / min. Air was blown onto the film on the surface of the anti-cooling drum at a wind speed of 30 m / sec and an air temperature of 10 ° C. through a 2 mm slit-like gap provided at the tip of all the spray nozzles. When the film surface temperature of the anti-cooling drum surface was measured with each non-contact type surface thermometer, the non-contact type surface thermometer No. 1 installed immediately before the spray nozzle No. 1 was 270 ° C. Based on the film surface temperature, only the blowing nozzle No. 1 changed the opening of the air volume adjusting valve to the wind speed: 10 m / sec. After this film passes the cooling guide roll, the film thickness measuring device measures the in-line film thickness in the film flow direction. The target thickness: 1.8 mm (1800 μm), the film thickness unevenness is within 3 μm, It was good. Moreover, the obtained product film thickness nonuniformity R value was 1 micrometer, and the haze of the obtained film was also 1.3%-1.4%, and was favorable.

(Example 2)
In the same manner as in Example 1, polyethylene terephthalate having an intrinsic viscosity of 0.65 substantially free of inert particles was dried at a temperature of 180 ° C. for 5 hours under a reduced pressure of 3 torr. After melting at ℃, after filtering through a filter with filtration accuracy of 8μm, the molten resin is discharged from an extrusion die, and on a cooling drum with a surface temperature of 20 ℃ rotating at a speed of 6 m / min, as a 2.5 mm thick film Cooled and solidified. Air was blown onto the film on the surface of the anti-cooling drum at a wind speed of 40 m / sec and an air temperature of 10 ° C. through a 2 mm slit-like gap provided at the tip of all the spray nozzles. When the film surface temperature of the anti-cooling drum surface was measured with each non-contact type surface thermometer, non-contact type surface thermometer No. 1 was 260 ° C, non-contact type surface thermometer No. 2 was 256 ° C, non-contact Formula surface thermometer No. 3 was 253 degreeC. Based on the film surface temperature, the opening degree of the air volume adjusting valve is changed, the wind speed of spray nozzle No. 1 to spray nozzle No. 3 is 0 m / sec, the speed of spray nozzle No. 4 is 5 m / sec, and the spray nozzle No. The wind speed of .5 was changed to 10 m / sec, and the wind speed of spray nozzle No. 6 was changed to 20 m / sec. After this film passed through the cooling guide roll, the film thickness in the film flow direction was measured with a film thickness meter, and the film thickness unevenness was 20 μm with respect to the target thickness: 2.5 mm (2500 μm). Based on the measured thickness unevenness, the opening of each air volume adjusting valve is changed, the blowing air speed of spray nozzle No. 1-5 is 0 m / sec, the air speed of spray nozzle No. 6 is 10 m / sec, and spray nozzle No. 7 The wind speed was changed to 20 m / sec. The thickness unevenness of the in-line film was within 8 μm with respect to the target thickness: 2.5 mm (2500 μm) with the film thickness measuring instrument after passing through the cooling guide roll, which was good. Further, the obtained product film thickness unevenness R value was 2 μm, and the haze was 1.5% to 1.6%, which was favorable.

(Comparative Example 1)
In the same manner as in Example 1, in the cooling device, 14 spray nozzles are installed, but in the device in which the non-contact type surface thermometer and the air volume adjusting valve for adjusting the wind speed of the spray nozzle are not installed, A polyethylene terephthalate having an intrinsic viscosity of 0.65 and containing no inert particles is dried at 180 ° C. for 5 hours under a reduced pressure of 3 torr, put into an extruder and melted at a temperature of 290 ° C., and a filtration accuracy of 8 μm. After filtration through a filter, the molten resin was discharged from an extrusion die, and cooled and solidified as a 1.8 mm thick film on a cooling drum with a surface temperature of 20 ° C. rotating at a speed of 6 m / min. Air was blown onto the film on the surface of the anti-cooling drum at a wind speed of 30 m / sec and an air temperature of 10 ° C. through a 2 mm slit-like gap provided at the tip of all the spray nozzles. Although the haze of the obtained film was favorable at 1.3% to 1.4%, the product film thickness unevenness R value was not satisfactory at 4.5 μm.

(Comparative Example 2)
In the same manner as in Comparative Example 1, in the cooling device, polyethylene terephthalate having an intrinsic viscosity of 0.65 substantially containing no inert particles was dried at 180 ° C. for 5 hours under a reduced pressure of 3 torr and charged into an extruder. After being melted at a temperature of 290 ° C., filtered through a filter with a filtration accuracy of 8 μm, the molten resin is discharged from an extrusion die, and the thickness is 2.5 mm on a cooling drum having a surface temperature of 20 ° C. rotating at a speed of 6 m / min. The film was cooled and solidified. Air was blown onto the film on the surface of the anti-cooling drum at a wind speed of 40 m / sec and an air temperature of 10 ° C. through a 2 mm slit-like gap provided at the tip of all the spray nozzles. At this time, when the product film thickness of the obtained film was measured, the product film thickness unevenness R value was 5.75 μm, and the wind speed of all the spray nozzles was changed to 10 m / sec. However, the haze of the obtained film was as bad as 3.5% to 3.8%, and the product film thickness unevenness R value was 4.0 μm, which was smaller than before the change, but was not satisfactory.

(Comparative Example 3)
In the same manner as in Comparative Example 1, in the cooling device, polyethylene terephthalate having an intrinsic viscosity of 0.65 substantially containing no inert particles was dried at 180 ° C. for 5 hours under a reduced pressure of 3 torr and charged into an extruder. After being melted at a temperature of 290 ° C., filtered through a filter with a filtration accuracy of 8 μm, the molten resin is discharged from an extrusion die, and the thickness is 2.5 mm on a cooling drum having a surface temperature of 20 ° C. rotating at a speed of 10 m / min. The film was cooled and solidified. Air was blown onto the film on the surface of the anti-cooling drum at a wind speed of 40 m / sec and an air temperature of 10 ° C. through a 2 mm slit-like gap provided at the tip of all the spray nozzles. When the product film thickness of the film obtained at this time was measured, the thickness unevenness R value was 7.9 μm, so the wind speed of all the spray nozzles was changed to 10 m / sec. However, the haze of the obtained film was as bad as 3.8% to 4.0%, and the product film thickness unevenness R value was 6.0 μm. Again, the wind speed of all the spray nozzles was changed to 7 m / sec. However, the haze of the obtained film was as bad as 4.1% to 4.3%, and the product film thickness unevenness R value was 5.8 μm, which was smaller than before the change, but was not satisfactory.

  As described above in detail, the present invention relates to a cooling device that cools an anti-cooling drum surface film on a cooling drum by blowing air from a spray nozzle and a film manufacturing method using the same. The invention makes it possible to rapidly cool the film on the surface of the anti-cooling drum and to produce a thick film excellent in haze at a high speed from the conventional cooling device. Moreover, by measuring the thickness unevenness in the film flow direction, the occurrence of the film thickness unevenness can be prevented, and high-quality products can be stably produced, which is useful.

1: Extrusion die 2: Cooling drum 3: Spray nozzle 4: Non-contact surface thermometer 5: Thermoplastic resin film 6: Blower 7: Blower air volume adjusting device 8: Heat exchanger 9: Air volume adjusting valve 10: Controller 11 : Cooling guide roll 12: Cooling guide roll 13: Film thickness measuring device

Claims (6)

When a molten thermoplastic resin is cast on a cooling drum from an extrusion die and cooled and solidified on the cooling drum to produce a thermoplastic resin film, a film surface that does not contact the cooling drum (hereinafter referred to as an anti-cooling drum surface) In the apparatus which blows air toward the film from the plurality of nozzles installed on the side, a cooling apparatus for a thermoplastic resin film, characterized by having means capable of individually adjusting the wind speed of the air to be blown. Claims have a wind speed adjustment mechanism that measures the film surface temperature upstream of the portion where the air from each nozzle hits the film in the film flow direction, and can adjust the air wind speed according to the film surface temperature. Item 2. The thermoplastic resin film cooling device according to Item 1. The cooling device for a thermoplastic resin film according to claim 1 or 2, further comprising an air volume adjusting mechanism capable of adjusting an air volume supplied to the plurality of nozzles. In the film flow direction, the film thickness measuring device installed downstream of the cooling drum measures the thickness unevenness in the film flow direction at least at one location in the film width direction. The cooling device for a thermoplastic resin film according to any one of claims 1 to 3, further comprising a wind speed adjusting mechanism capable of adjustment. An apparatus for blowing air from a plurality of nozzles, comprising means for individually adjusting the air velocity of the blowing air. A method for producing a thermoplastic resin film in which a molten thermoplastic resin is cast on a cooling drum from an extrusion die and is cooled and solidified on the cooling drum, wherein the film surface does not contact the cooling drum (hereinafter referred to as an anti-cooling drum surface). A method for producing a thermoplastic resin film, comprising the step of blowing air from a plurality of nozzles installed on the side toward the film, and adjusting the air velocity of the blowing air individually for each nozzle.

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