JP4352853B2 - Method for producing polyester resin sheet - Google Patents

Description

The present invention produces a sheet having a uniform thickness and few surface defects by extruding a thermoplastic resin from an extruder into a sheet in a molten state, and bringing the molten sheet into close contact with a moving cooling body and cooling. A method for producing a polyester resin sheet is provided.

  Conventionally, in order to form a sheet having a uniform thickness and width by efficiently extruding a molten thermoplastic resin into a sheet form on a moving cooling body from a T die of an extruder, for example, Patent Document As shown in FIG. 1, by applying a high voltage to a wire-like or knife-edge-like electrode arranged along the moving cooling body, an electrostatic charge is applied to the molten sheet-like body, thereby being in close contact with the moving cooling body Has been done. When the molten sheet-like body is electrostatically brought into close contact with the moving cooling body using the wire-like or knife-edge-like electrode in this way, the moving speed of the molten sheet-like body and the moving cooling body is 25 m / min. By setting the speed relatively low, it is possible to efficiently cool the moving cooling body by properly bringing the molten sheet into close contact with the moving cooling body.

  In addition, for example, as disclosed in Patent Document 2, a needle-like, saw-shaped, saw, etc., can be efficiently cooled by properly adhering a molten sheet-like body to a moving cooling body that moves at a relatively high speed of about 40 m / min. The molten sheet-like body is electrostatically adhered to the moving cooling body by applying a streamer corona discharge to the molten sheet-like body from a blade-like, wire-like or knife-edge-like electrode and applying a large amount of charge. ing.

Furthermore, as shown in Patent Document 3, for example, the melt specific resistance of the thermoplastic resin constituting the molten sheet-like body by including at least one of an alkali metal, an alkaline earth metal, or a compound thereof in the polyester resin, etc. Is set to a low value, the moving speed of the moving cooling body is increased when the molten sheet-like body is cooled by electrostatically attaching the molten sheet-like body to the moving cooling body by applying a high voltage. It is known that it can be done.
Japanese Examined Patent Publication No. 37-6142 JP-A-56-105930 Japanese Patent Publication No.53-40231

  In the electrostatic contact method using the wire-shaped or knife-edge-shaped electrode disclosed in Patent Document 1, when the moving speed of the molten sheet-shaped body and the moving cooling body is increased to 25 m / min or more, the moving cooling body Due to the presence of the air film formed according to the accompanying flow generated on the surface, the adhesion of the molten sheet-like body to the moving cooling body becomes insufficient, and the cooling action of the molten sheet-like body by the moving cooling body is impaired. It will be. As a result, before the molten sheet is sufficiently cooled, its crystallization progresses and the transparency is lowered, and bubbles or streaks are easily generated on the surface of the sheet, and the molten sheet is There is a problem that the thickness of the sheet tends to be non-uniform due to not being uniformly cooled.

In the streamer corona discharge-type electrostatic contact method disclosed in Patent Document 2, the molten sheet-like body can be brought into close contact with the moving cooling body and efficiently cooled. For example, polyethylene terephthalate having a melt specific resistance of about 0.4 × 10 ⁸ (Ω · cm) is not limited to polyamide resin of 0 × 10 ⁶ (Ω · cm) or less. Was supposed to be unable to do. Therefore, a resin material having a high melting resistivity such as polyethylene terephthalate is not used as a raw material of a sheet that is electrostatically adhered to a moving cooling body by streamer corona discharge, and has a low melting resistivity such as a polyamide resin. Only was used.

  Furthermore, as shown in the above-mentioned Patent Document 3, by adding an additive such as an alkali metal into the thermoplastic resin that is the raw material of the sheet to lower the melting specific resistance value of the molten sheet, The moving sheet and the moving cooling body are configured to be efficiently cooled by bringing the molten sheet-like body into intimate contact with the moving cooling body by increasing the moving speed of the moving body and the moving cooling body and ensuring the adhesion between the molten sheet-like body and the moving cooling body. In such a case, there has been a problem that in order to reduce the melting specific resistance value of the molten sheet-like material, the non-foreign material property, color tone, heat resistance and the like inherent in the raw material must be sacrificed to some extent.

  Further, as disclosed in Patent Documents 2 and 3, when a thermoplastic resin having a low melting specific resistance value is used as a raw material of the sheet, the value of current flowing from the electrode to the moving cooling body becomes too large. Since the spark discharge tends to occur, the mobile cooling body is prevented from being damaged when the spark discharge occurs by installing an electrode on the upstream side of the contact point of the molten sheet-like body with respect to the mobile cooling body. There is a need. In this way, when the electrode is installed on the upstream side of the contact point of the molten sheet-like body with respect to the moving cooling body, the molten sheet-like body vibrates and is easily damaged by contact with the electrode in order to prevent this. For this, it is necessary to separate the molten sheet-like body and the electrode to some extent. When the electrodes are thus separated from the molten sheet-like body, there is a problem that the streamer corona discharge cannot be stably generated unless the voltage applied between the electrodes is set high.

  On the other hand, when a thermoplastic resin having a high melting specific resistance value is used as the raw material of the sheet, since it is relatively difficult for spark discharge to occur, theoretically, in the vicinity of the contact point of the molten sheet-like body with respect to the moving cooling body. It is possible to arrange electrodes. However, the value of current flowing from the electrode to the moving cooling body increases due to contamination of foreign materials in the raw material, improper setting of the voltage or current applied to the electrode, or improper adjustment of the electrode position, resulting in spark discharge. If this occurs, there is a possibility that an excessive current flows to the moving cooling body and the moving cooling body is damaged.

  In order to prevent damage to the moving cooling body due to the occurrence of the above spark discharge, the power supply circuit is turned off to protect the power supply circuit when it is detected that an excessive current flows in the power supply circuit to the electrode. There is a need to. However, if the streamer corona discharge to the molten sheet material is stopped when the spark discharge occurs and the streamer corona discharge is stopped, the molten sheet material cannot be electrostatically adhered to the moving cooling body. The cooling action of the solid body is impaired and the molten sheet-like body is torn off in contact with the moving cooling body, or the sheet-like body is wound around a guide roller or the like disposed on the downstream side of the moving cooling body Things happen. When such a situation occurs, a complicated operation is required to remove the sheet-like body wound around the guide roller and the like, and there is a problem that a great time loss occurs until the production line is restored. .

The present invention has been made in view of the above, polyester capable of effectively preventing the spark discharge is generated to the mobile cooling member from the electrode, to properly produce a sheet at a high speed A method for producing a resin sheet is provided.

The invention according to claim 1 is an extrusion process in which a polyester resin having a melt specific resistance value of 0.3 × 10 ⁸ (Ω · cm) or more is extruded from the extruder as a molten state, and extruded from the extruder. In the method for producing a polyester resin sheet, comprising: a cooling step in which the molten sheet-like body is closely attached to the moving cooling body and cooling; and a stretching step in which the cooled sheet-like body is drawn. A tape-shaped electrode having a thickness of 5 μm to 200 μm is installed along the vicinity of the contact point of the sheet-like body, and the gap between the tape-like electrode and the molten sheet-like body is within a range of 0.5 mm to 10 mm. A plurality of protrusions having a protrusion amount of 0.1 mm or more are arranged along the direction perpendicular to the conveying direction of the molten sheet and are adjacent to each other at the tip of the tape-like electrode. A corona in which the installation interval of the protrusions is set to be less than 5 times the gap between the tape-like electrode and the molten sheet-like body, and a limiting resistor having a resistance value of 30 kΩ to 3000 kΩ is disposed in the energization circuit for the electrode By performing streamer corona discharge on the molten sheet-like body in the cooling step from the discharge section, the molten sheet-like body is brought into close contact with the moving cooling body and cooled.

According to a second aspect of the present invention, in the polyester resin sheet manufacturing method according to the first aspect, the resistance value of the limiting resistor disposed in the energization circuit for the electrode is set to 900 kΩ or more.

According to the first aspect of the present invention, by appropriately applying streamer corona discharge that applies a predetermined voltage between the electrode and the molten sheet-like body to flow a large current through the molten sheet-like body, 0.3 × Since a large amount of electric charge can be stably and continuously applied to a molten sheet-shaped body made of a thermoplastic resin having a melting specific resistance value of 10 ⁸ (Ω · cm) or more, the movement of the molten sheet-shaped body and the moving cooling body Even when the speed is set to a high speed, the non-contaminant properties, color tone, heat resistance, and other properties inherent in the raw materials are reduced by properly cooling the molten sheet-like body in close contact with the moving cooling body. Thus, a sheet having a uniform thickness and having no surface defects can be efficiently produced at a high speed without causing the above problem, and the current-carrying circuit for the electrode has a resistance value of 30 kΩ to 3000 kΩ. Since a resistor is provided, it is possible to suppress the occurrence of spark discharge when the voltage is applied, and even if a spark discharge occurs, the value of the current flowing through the moving cooling body is suppressed to suppress the movement of the moving cooling body. There is an advantage that damage can be effectively prevented.

  According to the second aspect of the present invention, since the resistance value of the limiting resistor is set to 900 kΩ or more, when a predetermined voltage is applied between the electrode and the molten sheet to perform streamer corona discharge on the molten sheet In addition, there is an advantage that the occurrence of spark discharge due to a large current flowing from the electrode to the moving cooling body can be more effectively prevented.

FIG. 1 shows a specific example of a production apparatus used for carrying out the method for producing a polyester resin sheet according to the present invention. The manufacturing apparatus includes an extruder 3 that extrudes a thermoplastic resin material supplied from a hopper 1 into a sheet form from a die 2 made of a T die or the like in a molten state by kneading the thermoplastic resin material, and a melt extruded from the extruder 3. A moving cooling body 5 composed of a cooling roller or the like for cooling the sheet-like body 4a, and a corona discharge portion 6 for bringing the molten sheet-like body 4a into close contact with the moving cooling body 5 by performing a streamer corona discharge on the molten sheet-like body 4a. The first stretched portion 7 for stretching the sheet-like body 4b cooled by the moving cooling body 5 in the longitudinal direction, the second stretched portion 8 for stretching the sheet-like body 4b in the width direction, and the stretched sheet 4c And a winding unit 9 for winding the wire.

  As shown in FIGS. 2 and 3, the corona discharge part 6 is provided with a tape-like electrode 10 so as to extend along the vicinity of the contact point Z of the molten sheet-like body 4 a with respect to the peripheral surface of the moving cooling body 5. ing. The tape-like electrode 10 is made of a metal material such as iron or stainless steel, and rectangular cutouts are formed at regular intervals at the tip, that is, the end opposite to the surface of the molten sheet-like body 4a. Thus, a plurality of protrusions 10a having a predetermined protrusion amount H are provided at a constant interval (arrangement pitch) W in a direction orthogonal to the conveying direction of the molten sheet-like body 4a. Further, the protruding portion 10 a of the tape-like electrode 10 is installed so as to face the molten sheet-like body 4 a located on the moving cooling body 5 with a predetermined gap N therebetween.

A positive electrode of a DC high-voltage power supply 11 is connected to the tape-shaped electrode 10, a negative electrode of a DC power supply is connected to the moving cooling body 5, and between the tape-shaped electrode 10 and the DC high-voltage power supply 11, A limiting resistor 13 is provided. The limiting resistor 13 is provided in order to protect the current supply circuit for supplying current to the tape-like electrodes 10 from the DC high-voltage power supply 11, the resistance value is set in the range of 30kΩ~3000kΩ Yes. A predetermined voltage is applied between the tape-like electrode 10 and the moving cooling body 5 from the DC high-voltage power source 11, and streamer corona discharge is performed from the tape-like electrode 10 to the molten sheet-like body 4 a on the moving cooling body 5. As a result, a large amount of electric charge is continuously applied so that the molten sheet-like body 4 a is in electrostatic close contact with the moving cooling body 5.

  The streamer corona discharge refers to a state in which, for example, the tape-like electrode 10 to which a positive voltage is applied and the molten sheet-like body 4a, which is a ground body, are bridged and stable corona discharge is performed. That is, when the voltage applied between the tape-like electrode 10 and the moving cooling body 5 is increased, a dark current state (non-sustainable discharge phenomenon) first occurs, and then a glow corona discharge state occurs. The discharge from the tape-like electrode 10 results in a streamer corona discharge state in which air is ionized and a stable current continuously flows. When the voltage is further increased from this state, a spark discharge state is obtained.

  Looking at each discharge phenomenon in terms of the relationship between voltage and current, in the dark current region, the minute current region where Ohm's law is established, that is, the region where current flows in proportion to the voltage, and even if the voltage is increased, the current does not increase. There is a region, and when the voltage is further increased from this region, the current rapidly increases, and this region is a glow corona discharge region, and purple light emission covering the surface of the electrode is observed. When the voltage is further increased from this glow corona discharge region, a streamer corona discharge state is established, and at this time, light emission bridging the electrode and the earth body is observed. When the relationship between the voltage V (kV) applied to the electrode and the current value I (mA / cm) corresponding to the width dimension of the sheet-like body that is the ground body is specifically seen, I <0.025 × V A region where −0.12 is a dark current region or a goo corona discharge region, and a region where I ≧ 0.025 × V−0.12 is a streamer corona discharge region.

  A streamer corona discharge is performed from the tape-like electrode 10 of the corona discharge unit 6 to the molten sheet-like body 4a extruded from the extruder 3 onto the moving cooling body 5 as described above, and a large amount of charge is generated in the molten sheet. By being applied to the body 4a, the molten sheet body 4a is brought into electrostatic contact with the moving cooling body 5 and exchanges heat with a cooling medium such as cooling water supplied to the moving cooling body 5. The molten sheet-like body 4a is cooled.

  The thickness of the tape-like electrode 10 is set in the range of 5 μm to 200 μm, and the preferred range is 10 μm to 100 μm. When the thickness of the tape-like electrode 10 is 10 μm or less, its strength is reduced and it is easy to break. When the thickness of the tape-like electrode 10 is 100 μm or more, the concentration of the electric field is lowered and streamer corona discharge is properly performed. It is because it becomes difficult to generate in this. In order to increase the concentration of the electric field at the tip of the tape-like electrode 10 and efficiently generate streamer corona discharge, it is necessary to set the protrusion H of the protrusion 10a to 0.1 mm or more. It is preferably set to 5 mm or more, more preferably set to 1 mm or more. In addition, although it does not specifically limit about the maximum value of the said protrusion amount H, since the functional merit of raising the concentration degree of an electric field cannot be improved so much even if it exceeds 20 mm, from an economical viewpoint. The protrusion amount is preferably 20 mm or less.

When the adhesion force F [Pa] of the molten sheet-like body 4a to the moving cooling body 5 is considered as a clonal force, it is expressed as the following formula. In the following formula, q is the charge [C] on the sheet, E is the electric field [V / m] of the sheet, S is the area of the sheet defined by the length and width dimension of the sheet moving per unit time (1 s) [ cm ² ], i is a current [A] flowing through the electrostatic contact electrode, V is a voltage [V] applied to the electrode, v is a moving speed [m / s] of the moving cooling body 5, and w is electrostatic contact. The width [m] and k of the sheet to be cooled is the electric field concentration degree [1 / m] defined by the equation k = E / V. In some cases, it is obtained by numerical calculation using the finite element method.

F [Pa] = q [C] × E [V / m] / S [cm ² ]
= I · V · k / (v · w) [Pa]
From the above formula, the electrostatic adhesion force of the molten sheet 4a with respect to the moving cooling body 5 is determined according to the applied voltage V, current i, and electric field concentration k to the electrode. It can be seen that the electroadhesion force F can be increased.

  Further, if the gap N between the tape-like electrode 10 and the molten sheet-like body 4a is less than a certain value, the tip of the tape-like electrode 10 may come into contact with the molten sheet-like body 4a and the molten sheet-like body 4a may be damaged. If the gap N is equal to or greater than a certain value, it is necessary to increase the applied voltage for properly generating streamer corona discharge, and spark discharge may easily occur. For this reason, the gap N between the tape-like electrode 10 and the molten sheet-like body 4a is set within a range of 0.5 mm to 10 mm.

  When the installation interval W of the protrusions 10a arranged in the direction orthogonal to the conveying direction of the molten sheet-like body 4a becomes a certain value or more, the discharge from each protrusion 10a of the tape-like electrode 10 to the molten sheet-like body 4a There is a tendency that the interval becomes too wide and a streak-like close contact portion is likely to occur between them. In order to prevent such an adverse effect, it is necessary to set the installation interval W to be less than 5 times the gap N between the tape-like electrode 10 and the molten sheet-like body 4a. Further, if the installation interval W between adjacent protrusions 10a provided on the tape-like electrode 10 is reduced, it becomes difficult to form the protrusions 10a, and effective corona discharge is generated from all the protrusions 10a. Therefore, a preferable range of the installation interval W is within a range of 0.1 to 3 times the gap N between the tape-like electrode 10 and the molten sheet-like body 4a, and a more preferable range. Is in the range of 0.2 to 2 times the gap N.

  There is a variation in the protruding amount H between the protrusions 10a of the tape-like electrode 10 arranged in the direction orthogonal to the conveying direction of the molten sheet-like body 4a, and there is a difference between the molten sheet-like body 4a and each protrusion 10a. When the gap N formed between them is non-uniform, a discharge spot is generated, and a poor adhesion portion is easily formed. When the applied voltage is increased to prevent this, partial whitening phenomenon is likely to occur in the molten sheet-like body 4a. When this whitening phenomenon occurs, defects such as surface roughness of the sheet can be found by inspection. Because of difficulty, the variation in the protrusion amount H between the protrusions 10a provided on the tape-like electrode 10 is set to be less than 0.2 mm, preferably less than 0.1 mm, and the molten sheet-like body 4a and the tape shape It is configured to prevent the gap N with the electrode 10 from becoming uneven as much as possible.

  Specifically, when the tape-like electrode 10 is manufactured, the tip surfaces of the protrusions 10a are evenly aligned to prevent the variation in the protrusion amount H between the protrusions 10a from exceeding a predetermined amount. When the tape-like electrode 10 is bent during use, or when the tape-like electrode 10 is thermally deformed by being heated by heat generated from the die 2 of the extruder 3, the tape-like electrode 10 is attached. Is adjusted so that the variation of the gap N formed between the molten sheet-like body 4a and each protrusion 10a is within a certain range.

  Further, when the installation position of the tape-like electrode 10 is greatly shifted to the upstream side in the conveying direction of the molten sheet 4a with respect to the contact point Z of the molten sheet 4a with respect to the moving cooling body 5, the molten sheet 4a On the other hand, it is difficult to generate a stable streamer corona discharge. On the other hand, when the installation position of the tape-like electrode 10 is greatly shifted to the downstream side in the conveying direction of the molten sheet 4a with respect to the contact point Z of the molten sheet 4a with respect to the moving cooling body 5, the moving cooling body 5 On the other hand, it is difficult to properly adhere the molten sheet-like body 4a. For this reason, by setting the deviation | shift amount in the sheet conveyance direction of the contact point Z of the molten sheet-like body 4a with respect to the moving cooling body 5 and the installation position of the tape-like electrode 10 to less than 5 mm, Preferably it is set to less than 3 mm The tape-like electrode 10 is arranged in the vicinity of the contact point Z.

The thermoplastic resin that is heat-kneaded and extruded by the extruder 3 is not particularly limited as long as the melt specific resistance value R is 0.3 × 10 ⁸ (Ω · cm) or more. Resin is envisioned. The melting specific resistance value R is determined by placing the thermoplastic resin in a vacuum after drying it in a test tube having a diameter of 50 mm, melting it in a nitrogen atmosphere, and then in the thermoplastic resin in a nitrogen atmosphere at 285 ° C. A pair of copper electrodes are inserted, and the equation R = (V · S / I) according to the current value and the voltage value, the electrode area, and the distance between the electrodes measured with a voltage applied to the both electrodes from the DC high voltage generator. * Calculated based on L). In this equation, V is a voltage value, S is an electrode area, I is a current value, and L is a distance between electrodes.

  Examples of the thermoplastic resin having a high melting specific resistance value include, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, or a polyester resin composed of a copolymer mainly composed of a polymer component constituting these resins. Are preferably used.

  When the above copolymer is used, the dicarboxylic acid component includes aliphatic dicarboxylic acids such as adipic acid, sebacic acid, dodecanedioic acid; terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bis And aromatic dicarboxylic acids such as phenoxyethane-p, p′-dicarboxylic acid; and ester-forming derivatives thereof (2,5-dimethylterephthalic acid and the like). Polyfunctional carboxylic acids such as trimellitic acid and pyromellitic acid may be used.

  The glycol component of the copolymer includes ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, 1,3 propanediol, neopentyl glycol, diethylene glycol, 1,4-cyclohexanedimethanol, trimethylolpropane. , P-xylene glycol or the like, or polyethylene glycol having an average molecular weight of 150 to 2000 is used.

  In addition, you may make the composition of the said polyester-type resin contain various well-known additives which consist of an antistatic agent, UV absorber, or a stabilizer, for example.

Also, instead of the polyester resin having a high melting specific resistance value, by mixing a material having a low melting specific resistance value and various additives (for example, a resin having a high melting specific resistance value), the melting specific resistance value is obtained. May be adjusted to 0.3 × 10 ⁸ (Ω · cm) or more.

As the thermoplastic resin heated and kneaded by the extruder 3, polyethylene terephthalate having a melt specific resistance value of 0.3 × 10 ⁸ (Ω · cm) or more is used, and the sheet is formed using the manufacturing apparatus having the above configuration. The manufacturing method of the sheet to manufacture is demonstrated below. First, polyethylene terephthalate pellets blended with particles for imparting slipperiness as required are sufficiently dried in vacuum, and then supplied to the hopper 1 of the extruder 3 and heated and kneaded, whereby a die is formed. For example, a molten sheet-like body 4 a having a temperature of about 280 ° C. and a thickness of about 200 μm is extruded from 2 and brought into contact with the peripheral surface of the moving cooling body 5.

  A positive voltage is applied to the tape-like electrode 10 disposed along the vicinity of the contact point Z between the molten sheet-like body 4a extruded onto the moving cooling body 5 and the moving cooling body 5 as described above, By generating streamer corona discharge in the molten sheet-like body 4a, a large amount of electric charge is continuously given to the molten sheet-like body 4a, and the molten sheet-like body 4a is conveyed at a predetermined speed while the moving cooling body 5 It is cooled by electrostatic contact with the peripheral surface.

  That is, the tape-like electrode 10 having a thickness of 5 μm to 200 μm is provided in the corona discharge portion 6 along the vicinity of the contact point Z of the molten sheet-like body 4 a with the moving cooling body 5. A plurality of protrusions 10a having a protrusion amount H of 0.1 mm or more are arranged at the front end portion along a direction orthogonal to the conveying direction of the molten sheet-like body 4a, and the installation interval W between adjacent protrusions 10a is set. Is set to be less than 5 times the gap N between the tape-like electrode 10 and the molten sheet-like body 4a, and the gap N between the tape-like electrode 10 and the molten sheet-like body 4a is within a range of 0.5 mm to 10 mm. In the set state, a positive voltage is applied to the tape-like electrode 10 through the limiting resistor 13.

  As a result, an electric field is concentrated on each of the protrusions 10a and streamer corona discharge is performed on the molten sheet-like body 4a, so that a large amount of charge is applied to the molten sheet-like body 4 from each of the protrusions 10a. The sheet-like body 4 is charged, and the molten sheet-like body 4a is electrostatically adhered to the peripheral surface of the moving cooling body 5 to be effectively cooled. The sheet-like body 4b cooled by the moving cooling body 5 is supplied to the first extending portion 7 and extended in the longitudinal direction of the sheet-like body 4b, and then supplied to the second extending portion 8 to supply the sheet-like body 4b. The sheet 4c having a predetermined width dimension and thickness is manufactured by stretching in the width direction, and the sheet 4c is wound up in a roll shape at the winding unit 9.

Thus, an extruder 3 that extrudes a thermoplastic resin having a melting specific resistance value of 0.3 × 10 ⁸ (Ω · cm) or more into a sheet as a molten state, and a molten sheet-like body extruded from the extruder 3 A moving cooling body 5 for cooling 4a, a tape-like electrode 10 disposed along the vicinity of a contact point Z of the molten sheet-like body 4a with respect to the moving cooling body 5, and the molten sheet-like shape from the tape-like electrode 10 In the method for manufacturing a polyester resin sheet by a sheet manufacturing apparatus configured to electrostatically adhere the molten sheet body 4a to the moving cooling body 5 by performing streamer corona discharge on the body 4a, Since the limiting resistor 13 having a resistance value of 30 kΩ to 3000 kΩ is disposed in the energization circuit for the electrode 10, spark discharge is generated from the electrode 10 to the moving cooling body 5. This has the advantage that a sheet having a uniform thickness and having no surface defects can be efficiently produced at high speed.

That is, when a thermoplastic resin having a high melting specific resistance of 0.3 × 10 ⁸ (Ω · cm) or more is used as a raw material of the sheet as described above, a positive voltage is applied to the tape-like electrode 10. When the molten sheet-like body 4a on the moving cooling body 5 is subjected to streamer corona discharge, it is difficult for spark discharge to occur. Therefore, the molten sheet-like body 4a is in close contact with the moving cooling body 5 and is not easily vibrated. By disposing the tape-like electrode 10 in the vicinity of the contact point Z, while preventing the occurrence of a situation where the molten sheet-like body 4a comes into contact with the tape-like electrode 10 due to the vibration of the molten sheet-like body 4a, It is possible to cause the streamer corona discharge to the molten sheet-like body 4a to be appropriately performed at a low voltage so that the molten sheet-like body 4a is electrostatically adhered to the moving cooling body 5. Accordingly, the surface of the sheet becomes rough and becomes opaque, or air is partially trapped between the molten sheet-like body 4a and the moving cooling body 5 so that bubbles or streaks are formed on the surface of the sheet. There is an advantage that the molten sheet-like body 4a can be effectively cooled without causing adverse effects such as the formation of.

  When the tape-like electrode 10 is disposed in the vicinity of the contact point Z between the moving cooling body 5 and the molten sheet-like body 4a as described above, foreign matter is mixed into the raw material, and the applied voltage to the electrode. Alternatively, when a current value setting failure or an electrode position adjustment failure occurs, spark discharge may occur from the electrode 10 to the moving cooling body 5. However, since a limiting resistor 13 having a resistance value of 30 kΩ or more is provided in the energizing circuit of the tape-like electrode 10, even if the spark discharge occurs, an excessive current is generated with respect to the moving cooling body 5. It is possible to effectively prevent the moving cooling body 5 from being damaged due to the flow of. For this reason, when it is detected that an excessive current flows in the energization circuit of the tape-like electrode 10, the power supply is turned off, thereby the cooling action of the molten sheet-like body 4a is impaired and the moving cooling body 5 is effectively prevented from tearing while the molten sheet-like body 4a is in contact with the sheet 5, or the sheet-like body is wound around a guide roller or the like disposed on the downstream side of the moving cooling body 5. On the other hand, the molten sheet-like body 4a can be appropriately electrostatically adhered to the moving cooling body 5 by appropriately performing the streamer corona discharge on the molten sheet-like body 4a.

  In particular, when the resistance value of the limiting resistor 13 provided in the energization circuit of the tape-like electrode 10 is set to 900 kΩ or more, the tape-like electrode 10 and the molten sheet-like body 4a are interposed during the streamer corona discharge. By suppressing the time response of the current value that flows due to the contribution of the resistance R in the transient phenomenon caused by the RLC circuit of the so-called resistance R, the inductance L of the coil, and the capacitor C, a large current flows from the tape-like electrode 10 to the moving cooling body. There is an advantage that the occurrence of spark discharge due to flow can be more effectively prevented.

  When the resistance value of the limiting resistor 13 increases, it is necessary to increase the required voltage of the DC high-voltage power supply 11 more than necessary, and the amount of heat generated by the limiting resistor 13 increases when energized, resulting in a decrease in durability. There are harmful effects. For this reason, in the present invention, by setting the resistance value of the limiting resistor 13 to 3000 kΩ or less, the streamer corona discharge can be properly generated without causing the above-mentioned adverse effects.

In addition, when a sheet is manufactured using a thermoplastic resin having a melting specific resistance value of 0.3 × 10 ⁸ (Ω · cm) or more as described above as a raw material, an alkali metal or the like is included in the raw material. Since there is no need to reduce the melting specific resistance value by adding, there is an advantage that a sheet having excellent characteristics can be efficiently produced without impairing the non-foreign material property, color tone or heat resistance inherent in the raw material. .

Further, by applying a positive voltage to the tape-like electrode 10, the streamer corona is applied to the molten sheet-like body 4a made of a thermoplastic resin having a melting specific resistance value of 0.3 × 10 ⁸ (Ω · cm) or more. When configured to generate a discharge, there is a tendency that spark discharge is less likely to occur than when a negative voltage is applied to the tape-like electrode 10. Therefore, a large amount of electric charge is applied to the molten sheet 4a without causing a situation such as damage to the sheet due to the spark discharge or damage to the moving cooling body 5. The molten sheet-like body 4a can be appropriately electrostatically adhered to the peripheral surface of the moving cooling body 5 for effective cooling.

  Moreover, as shown in the said embodiment, while arrange | positioning the tape-shaped electrode 10 which has thickness of 5 micrometers-200 micrometers along the contact point Z of the molten sheet-like body 4a with respect to the moving cooling body 5, of this tape-shaped electrode 10 When a plurality of protrusions 10a having a protrusion amount H of 0.1 mm or more are provided at the tip, the streamer corona discharge can be appropriately generated by concentrating the charges on the protrusions 10a. . Therefore, by effectively ionizing the air between the tape-like electrode 10 and the molten sheet-like body 4a and continuously flowing a stable current from the tape-like electrode 10, a large amount is supplied to the molten sheet-like body 4a. Can be applied to the molten sheet-like body 4a. Accordingly, even when the moving speed of the molten sheet-like body 4a and the moving cooling body 5 is set to a high speed of, for example, 60 m / min or more, the molten sheet-like body 4a is appropriately electrostatically adhered to the moving cooling body 5. The sheet can be cooled uniformly, and the productivity of the sheet can be improved without causing adverse effects such as roughening the surface of the sheet and lowering the transparency.

  Moreover, in the said embodiment, the protrusion 10a of the tape-shaped electrode 10 is made into the molten sheet-like body 4a by setting the clearance gap N between the tape-like electrode 10 and the molten sheet-like body 4a in the range of 0.5 mm-10 mm. Therefore, the molten sheet-like body 4a can be electrostatically adhered to the moving cooling body 5 by appropriately performing streamer corona discharge on the molten sheet-like body 4a at a lower voltage. Accordingly, the surface of the sheet becomes rough and becomes opaque, or air is partially trapped between the molten sheet-like body 4a and the moving cooling body 5 so that bubbles or streaks are formed on the surface of the sheet. There is an advantage that the molten sheet-like body 4a can be effectively cooled without causing adverse effects such as the formation of.

  Furthermore, in the above embodiment, the installation interval W between the adjacent protrusions 10a provided on the tape-like electrode 10 is set to be less than 5 times the gap N between the tape-like electrode 10 and the molten sheet-like body 4a. When the streamer corona discharge is performed from each protrusion 10a of the electrode 10 to the molten sheet-like body 4a, it is possible to prevent an increase in the interval between adjacent discharge portions and to generate a uniform streamer corona discharge. . For this reason, it is possible to effectively prevent a phenomenon in which a portion having high adhesion and a portion having low adhesion to the moving cooling body 5 are alternately generated, that is, a streak-like poor adhesion portion, and the entire molten sheet-like body 4a. There is an advantage that can be cooled uniformly.

  Moreover, as shown in the said embodiment, when the variation of the protrusion amount H between each protrusion 10a provided in the tape-shaped electrode 10 is set to less than 0.2 mm, conveyance of the said molten sheet-like body 4a It is possible to effectively prevent the occurrence of discharge spots due to non-uniform gaps N between the protrusions 10a of the tape-like electrode 10 arranged in the direction orthogonal to the direction and the molten sheet-like body 4a. Therefore, the partial whitening phenomenon occurs in the molten sheet 4a by suppressing the occurrence of poor adhesion of the molten sheet 4a to the moving cooling body 5 without increasing the applied voltage so much. The molten sheet-like body 4a can be efficiently cooled by properly adhering the molten sheet-like body 4a to the moving cooling body 5 while effectively preventing the above.

  Furthermore, in the said embodiment, the deviation | shift amount in the sheet conveyance direction with the contact point Z of the molten sheet-like body 4a with respect to the moving cooling body 5 and the installation position of the tape-shaped electrode 10 is set to less than 5 mm, Preferably it is less than 3 mm Since the sheet is set, the molten sheet-like body 4a is properly brought into close contact with the moving cooling body 5 without causing adverse effects such as roughening the surface of the sheet or causing holes in the sheet. There is an advantage that the body 4a can be cooled effectively.

  That is, the installation position of the tape-like electrode 10 is prevented from shifting to the upstream side in the conveying direction of the molten sheet 4a over a predetermined value from the contact point Z of the molten sheet 4a with the moving cooling body 5. This makes it possible to generate a stable streamer corona discharge on the molten sheet-like body 4a in the vicinity of the contact point Z. For this reason, the molten sheet-like body 4a can be properly adhered to the moving cooling body 5 without setting the applied voltage to an excessively high value, and the molten sheet-like body 4a is appropriately cooled to form a sheet. It is possible to effectively suppress the surface of the sheet from being roughened and to effectively prevent the occurrence of a situation in which spark discharge occurs and the sheet is perforated.

  On the other hand, the installation position of the tape-like electrode 10 is prevented from shifting to the downstream side in the conveying direction of the molten sheet 4a over a predetermined value from the contact point Z of the molten sheet 4a with the moving cooling body 5. By doing so, it is possible to prevent the cooling and solidification from proceeding before the molten sheet-like body 4a electrostatically adheres to the moving cooling body 5. For this reason, the molten sheet-like body 4a is properly adhered to the moving cooling body 5 to suppress the partial trapping of air between the two, thereby causing defects on the surface of the sheet in the form of bubbles or streaks. There is an advantage that formation can be effectively prevented.

In addition, although the said embodiment demonstrated the manufacturing method of the polyester-type resin sheet which extends | stretches the sheet-like body 4b by the 1st extending | stretching part 7 and the 2nd extending | stretching part 8 in the longitudinal direction of a sheet | seat, and the width direction after cooling. The film may be stretched only in either one of the two directions. In the case of unidirectional stretching, a sheet having a thickness of 10 μm or more is preferably used because of its mechanical rigidity, and in the case of bi-directional stretching, a sheet of 2 μm or more is preferably used. Moreover, it is good also as a structure which provided the extending | stretching part which extends the sheet-like body 4b further to a longitudinal direction and the width direction in the downstream part of 7 and 8 of the said 1st, 2nd extending part.

  In addition, in the above-described embodiment, a plurality of protrusions 10a having a predetermined protrusion amount H and a rectangular shape are provided by forming rectangular notches at regular intervals at the tip of the tape-like electrode 10. In place of the A-type electrode 10, as shown in FIG. 4, a plurality of taper-shaped trapezoidal trapezoidal shapes are formed by forming notched portions of the tape-shaped electrode 10 at regular intervals. B-shaped electrode 10B provided with a plurality of protrusions 10b, or a plurality of protrusions formed in a tapered triangle shape by forming V-shaped notches at regular intervals as shown in FIG. A C-type electrode 10C provided with 10c, or a D-type electrode provided with a plurality of protrusions 10d formed in Mt. Fuji by forming arch-shaped notches at regular intervals as shown in FIG. 10D may be used.

  Furthermore, instead of the tape-like electrode 10, as shown in FIG. 7, a plurality of needles facing the surface of the molten sheet-like body 4a in the vicinity of the contact point of the molten sheet-like body 4a with the peripheral surface of the moving cooling body 5 The electrode 12 is arranged at a constant interval W in a direction orthogonal to the conveying direction of the molten sheet 4a, and the axis of the needle electrode 12 is installed in a direction orthogonal to the surface of the molten sheet 4a It is good. The needle-like electrode 12 is formed in a cylindrical shape with iron, brass, stainless steel, tungsten, or the like whose diameter is set to 1 mm or less, preferably 0.5 mm or less.

  When the gap N between the needle-like electrode 12 and the molten sheet-like body 4a, that is, the distance between the tip surface of the needle-like electrode 12 and the surface of the molten sheet-like body 4a located on the moving cooling body 5 is less than a certain value. The tip of the needle-like electrode 12 may come into contact with the molten sheet-like body 4a, and the molten sheet-like body 4a may be damaged. When the distance exceeds a certain value, it is applied to properly perform the streamer corona discharge. It is unavoidable that the voltage needs to be extremely high, resulting in an increase in power consumption of the apparatus and the occurrence of spark discharge. For this reason, the gap N between the needle electrode 12 and the molten sheet 4a is set within a range of 0.5 mm to 5 mm, and a preferable range thereof is 1 mm to 4 mm.

  When the installation interval W of the needle-like electrodes 12 arranged in the direction orthogonal to the conveying direction of the molten sheet-like body 4a, that is, the distance between the axial centers of the adjacent needle-like electrodes 12 becomes a certain value or more, A discharge interval from the electrode 12 to the molten sheet-like body 4a becomes too wide, and a streak-like poor adhesion portion is easily generated therebetween. In order to prevent such an adverse effect, the installation interval W is set to be less than 5 times the gap N between the needle-like electrode 12 and the molten sheet-like body 4a. Further, when the interval W between the needle-like electrodes 12 becomes equal to the diameter of the needle-like electrodes 12, as shown in FIG. Therefore, the lower limit value of the installation interval W is a value corresponding to the diameter of the needle electrode 12. A preferable range of the installation interval W is within a range of 1 to 3 times the gap N between the needle-like electrode 12 and the molten sheet-like body 4a. When the gap N with the shaped body 4a is 1 mm, the preferable range of the installation interval W is 1 mm to 3 mm.

  As shown in FIG. 9, a conical tapered portion 12 a in which a sphere Q having a predetermined radius r is inscribed in the most peripheral surface is formed at the tip of the needle electrode 12. In order to increase the concentration of charges at the tip of the needle electrode 12 and efficiently generate streamer corona discharge, the radius r of the sphere Q inscribed in the peripheral surface of the tip of the tapered portion 12a is set to 0. However, if the radius of the sphere Q is excessively small, it becomes difficult to form the tapered portion 12a, and the tip of the needle electrode 12 is easily damaged during handling. Become. Therefore, a preferable range of the radius r is 0.005 mm to 0.09 mm, and a more preferable range is 0.01 mm to 0.05 mm. The radius r of the sphere Q is obtained by drawing a circle inscribed on the peripheral surface of the most distal portion of the needle electrode 12 and measuring the radius.

In Examples 1-1 to 1-4 of the present invention, resin pellets containing CaCO _{3 in} polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g and resin pellets not containing CaCO ₃ were mixed together to form a whole. A raw material having a melt specific resistance value of 1.2 × 10 ⁸ (Ω · cm) is formed, and this is dried under reduced pressure (1.3 hPa) at a temperature of 135 ° C. for about 6 hours, and then an extruder. 3 and heated and kneaded at a temperature of 280 ° C., and extruded from the die 2 of the extruder 3 having a width of 500 mm onto the moving cooling body 5 as a molten sheet-like body 4a. Further, stainless steel (austenite manufactured by Toyo Foil Co., Ltd.) having a width dimension of 10 mm and a thickness of 50 μm so as to face the peripheral surface of the moving cooling body 5 made of a metal roll whose surface temperature is kept at 30 ° C. In a state where a tape-like electrode made of SUS316) is installed, a positive voltage is applied to the tape-like electrode to generate a streamer corona discharge, whereby the molten sheet-like body 4a is electrostatically adhered to the moving cooling body 5. While cooling, the moving speed of the moving cooling body 5 was moved at a speed of 60 m / min to form a molten sheet-like body 4a having a width dimension of 390 mm and a thickness of 140 μm.

  Then, in a state where the limiting resistors 13 having a resistance value of 30 kΩ to 950 kΩ are respectively installed in the energization circuit for the tape-shaped electrode, the voltage value and the current value applied to the tape-shaped electrode from the high-voltage power generator are changed and discharged. Whether or not a spark discharge occurs by observing the state and dropping a wire having a diameter of 1.5 mm and a length of 1.5 mm between the die 2 of the extruder 3 and the contact point Z at this time. Observed. Further, the state of the scratch formed on the surface of the moving cooling body 5 was confirmed, and the current value at the time of spark discharge was measured with an oscilloscope. As a result, data shown in Table 1 below was obtained.

  In Table 1 above, SC indicates that a streamer corona discharge phenomenon was observed, and ◯ indicates that no flaws were observed on the surface of the moving cooling body, and the energization circuit did not enter a cut-off state. Further, ◯ △ marks indicate that a colored pattern is observed on the surface of the moving cooling body 5 but no crater-like scratches are observed, and the energization circuit is not cut off. Crater-like scratches are observed on the surface, and the energization circuit is in a cut-off state.

As the tape-shaped electrodes in Examples 1-1 to 1-4, as shown in FIG. 4, a plurality of protrusions H having a protrusion amount H of 2 mm are formed by forming notches that are widened at the front end portions at regular intervals. The B-type electrode 10B provided with the protruding portion 10b is used, the installation interval W between the adjacent protruding portions 10b is set to 3 mm, and the gap N between the tape-like electrode 10B and the molten sheet-like body 4a is set. Set to 5 mm. The high-voltage power generator is a 15 kV unit, and when it is detected that a spark discharge with a current value of 200 mA has occurred over 2 msec, the voltage is temporarily applied within 2 msec. And a protective circuit that shuts off the energizing circuit when the applied voltage is restarted within 30 msec and the applied voltage is continuously stopped 5 times or more within 0.5 sec. ing.

  On the other hand, Comparative Example 2-1 was configured in the same manner as in Examples 1-1 to 1-4 except that the limiting resistor 13 was eliminated. Moreover, in Comparative Examples 3-1 to 3-4, an electrode made of a tungsten wire having a diameter of 30 μm is used instead of the tape-like electrode 10B, and the molten sheet-like body 4a with respect to the peripheral surface of the moving cooling body 5 is used. While being installed in the vicinity of the contact point Z, the gap between this electrode and the molten sheet 4a was set to 5 mm. And while setting the moving speed of the moving cooling body 5 to 30 m / min, the limiting resistance 13 having a resistance value of 30 kΩ to 2000 kΩ is respectively installed in the energizing circuit for the electrode, and the discharge state and the moving cooling body 5 The damage state was observed.

  As shown in Table 1, in Example 1-1 in which the limiting resistor 13 having a resistance value of 30 kΩ was installed, the streamer was applied when a voltage of 6.5 kV was applied and a current of 7.8 mA flowed. Corona discharge occurs and the molten sheet is in close contact with the moving cooling body 5. At this time, if the wire is dropped between the die 2 of the extruder 3 and the contact point Z, spark discharge occurs. A current value of 40 mA was measured. In Example 1-1, although a colored pattern was observed on the surface of the moving cooling body 5, no crater-like scratch was observed, and the energization circuit was not cut off.

  Further, in Example 1-2 in which the limiting resistor 13 having a resistance value of 60 kΩ is installed, when a voltage of 7.0 kV is applied and a current of 7.4 mA flows, a streamer corona discharge is generated. When the molten sheet-like body is in close contact with the moving cooling body 5 and the wire is dropped between the mouthpiece 2 of the extruder 3 and the contact point Z at this time, spark discharge occurs and a current value of 60 mA is measured. It was done. Furthermore, in Example 1-3 in which the limiting resistor 13 having a resistance value of 500 kΩ is installed, when a voltage of 7.0 kV is applied and a current of 7.4 mA flows, streamer corona discharge occurs. When the molten sheet is in close contact with the moving cooling body 5 and the wire is dropped between the base 2 of the extruder 3 and the contact point Z at this point, spark discharge occurs and a current value of 300 mA is measured. It was done. In any of Examples 1-2 and 1-3, although a colored pattern was observed on the surface of the moving cooling body 5, no crater-like scratch was observed, and the energization circuit was not cut off.

  In Example 1-4 in which the limiting resistor 13 having a resistance value of 950 kΩ is installed, a streamer corona discharge is generated when a voltage of 9.0 kV is applied and a current of 8.2 mA flows. When the molten sheet-like body is in close contact with the moving cooling body 5, no spark discharge occurs even if the wire is dropped between the base 2 of the extruder 3 and the contact point Z, and the surface of the moving cooling body 5 In addition, no flaws were observed and the energization circuit was not cut off.

  On the other hand, in Comparative Example 2-1, in which the limiting resistor 13 is eliminated, when a voltage of 3.3 kV is applied and a current of 1.5 mA flows, a streamer corona discharge occurs and the mobile cooling body 5 When the molten sheet-like body is in close contact, and the wire is dropped between the base 2 of the extruder 3 and the contact point Z at this point, spark discharge frequently occurs and the energization circuit is cut off. The current value could not be measured. Further, crater-like scratches were observed on the surface of the moving cooling body 5.

  On the other hand, in the comparative example 3-1, in which the electrode made of a tungsten wire having a diameter of 30 μm was used and the limiting resistor 13 having a resistance value of 30 kΩ was installed, the voltage of 9.1 kV was used. Is applied and 0.2 mA of current flows, the molten sheet-like body 4a comes into close contact with the moving cooling body 5, and at this point, between the die 2 of the extruder 3 and the contact point Z. When the wire was dropped, spark discharge occurred frequently and the energization circuit was cut off, so the current value could not be measured. Further, crater-like scratches were observed on the surface of the moving cooling body 5.

  Further, in Comparative Example 3-2 in which the limiting resistor 13 having a resistance value of 60 kΩ is installed, when a voltage of 9.1 kV is applied and a current of 0.3 mA flows, the molten sheet is applied to the moving cooling body 5. At this time, when the wire 4 is dropped between the base 2 of the extruder 3 and the contact point Z, a spark discharge is generated and a current value of 180 mA is measured. Although crater-like scratches were observed on the surface, the energization circuit was not interrupted.

  Furthermore, in Comparative Example 3-3 in which the limiting resistor 13 having a resistance value of 950 kΩ is installed, when a voltage of 9.6 kV is applied and a current of 0.3 mA flows, the molten sheet is applied to the moving cooling body 5. At this time, when the wire 4 is dropped between the base 2 of the extruder 3 and the contact point Z, a spark discharge is generated, and a current value of 200 mA is measured. Although a colored pattern was observed on the surface of the film, no crater-like scratches were observed, and the energization circuit was not cut off.

  In Comparative Example 3-4 in which the limiting resistor 13 having a resistance value of 2000 kΩ is installed, a molten sheet-like body is applied to the moving cooling body 5 when a voltage of 12 kV is applied and a current of 0.4 mA flows. 4a is in a close contact state, and at this time, even if the wire is dropped between the mouthpiece 2 of the extruder 3 and the contact point Z, no spark discharge occurs, and no scratches are observed on the surface of the moving cooling body 5, The energization circuit was not cut off. However, in Comparative Examples 3-3 and 4 described above, it is necessary to set the moving speed of the moving cooling body 5 to 30 m / min in order to properly adhere the molten sheet-like body 4a to the moving cooling body 5 electrostatically. It was confirmed that productivity was poor.

According to the method for producing a polyester resin sheet according to the present invention, the molten sheet-like body is appropriately electrostatically adhered to the moving cooling body made of a thermoplastic resin having a high melting specific resistance value, which has been difficult in the past, and the moving cooling is performed. Even when the moving speed of the body is increased, the molten sheet-like body can be appropriately cooled to increase the productivity of the sheet, which greatly contributes to the industry.

It is explanatory drawing which shows the whole structure of the manufacturing apparatus used for implementation of the manufacturing method of the polyester-type resin sheet which concerns on this invention. It is a side view which shows the installation state of a tape-shaped electrode. It is a front view which shows the installation state of a tape-shaped electrode. It is explanatory drawing which shows another example of a tape-shaped electrode. It is explanatory drawing which shows another example of a tape-shaped electrode. It is explanatory drawing which shows another example of a tape-shaped electrode. It is explanatory drawing which shows another example of an electrode. It is explanatory drawing which shows another example of an electrode. It is explanatory drawing which shows the structure of the front-end | tip part of a needle-like electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Extruder 4a Molten sheet-like body 5 Moving cooling body 10 Tape-like electrode 10a Protrusion part 11 DC high voltage power supply 13 Limit resistance

Claims (2)

An extrusion process in which a polyester resin having a melting specific resistance value of 0.3 × 10 ⁸ (Ω · cm) or more is melted from an extruder into a sheet shape, and the molten sheet material extruded from the extruder is moved and cooled. In a method for producing a polyester resin sheet comprising a cooling step of closely contacting the body and cooling, and a stretching step of stretching the cooled sheet-like body, in the vicinity of the contact point of the molten sheet-like body with respect to the moving cooling body A tape-like electrode having a thickness of 5 μm to 200 μm is installed along the gap between the tape-like electrode and the molten sheet-like body within a range of 0.5 mm to 10 mm. A plurality of protrusions having a protrusion amount of 0.1 mm or more are arranged along the direction orthogonal to the conveying direction of the molten sheet-like material at the tip, and the installation interval between adjacent protrusions is the above From the corona discharge part, which is set to be less than 5 times the gap between the loop-shaped electrode and the molten sheet-like body, and in which a limiting resistor having a resistance value of 30 kΩ to 3000 kΩ is disposed in the energization circuit for the electrode, the cooling A method for producing a polyester-based resin sheet, characterized in that a molten sheet-like body is cooled in close contact with a moving cooling body by performing streamer corona discharge on the molten sheet-like body in a process. The method for producing a polyester-based resin sheet according to claim 1, wherein the resistance value of the limiting resistor disposed in the energization circuit for the electrode is set to 900 kΩ or more.

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