JP4262622B2 - Synthetic resin film manufacturing equipment - Google Patents

Description

  The present invention relates to an apparatus for producing a synthetic resin film used, for example, as a base film for a magnetic recording medium.

  Conventionally, what was disclosed by patent document 1 as this kind of manufacturing apparatus is known. This manufacturing apparatus manufactures a synthetic resin film by discharging a molten sheet made of a heat-melted synthetic resin material from a discharge port, bringing it into close contact with the surface of a rotary cooling roll and solidifying it by cooling. This manufacturing apparatus includes a wire electrode in order to bring the molten sheet into close contact with the surface of the rotary cooling roll. The wire electrode has an elliptical cross section, and is stretched so as to extend above the rotary cooling roll and in the axial direction thereof. The wire electrode is stretched so that one end portion in the major axis direction in the cross section faces the rotating cooling roll, and an electrostatic charge is applied from the one end portion to the molten sheet to electrostatically adhere the molten sheet to the rotating cooling roll surface. .

On the other hand, Patent Document 2 discloses a blade electrode having a long rectangular thin plate shape. Since this blade electrode is polished at both corners of the end facing the rotary cooling roll, the burrs at both corners are removed and the end forms an edge. This blade electrode applies an electrostatic charge to the molten sheet from an edge portion having an edge shape.
JP 2003-127208 A Japanese Utility Model Publication No. 7-37619

  However, the wire electrode of Patent Document 1 has a short diameter of 10 μm, a long diameter of 250 μm, and a length of 2 to 3 m, for example, so that it is thin and easily twisted. Therefore, since the wire electrode is easily twisted at the time of stretching, it is difficult to make one end portion in the major axis direction face the rotating cooling roll throughout. On the other hand, in the blade electrode of Patent Document 2, when a static charge is applied to the molten sheet, a spark discharge is easily generated from an end portion having an edge shape.

  The present invention has been made paying attention to such problems existing in the prior art. An object of the invention is to provide a synthetic resin film manufacturing apparatus that can appropriately apply an electrostatic charge to a molten sheet and can easily prevent the occurrence of spark discharge.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
The invention according to claim 1 of the present application is a discharge port that discharges a molten sheet, a rotary cooling roll that is provided below the discharge port, cools the molten sheet, and is provided above the rotary cooling roll. In a synthetic resin film manufacturing apparatus including a strip-shaped blade electrode extending in an axial direction, the blade electrode has a bent portion along a lower end edge, and the bent portion bends a metal plate. The gist is that it is formed.

  In the invention according to claim 1 of the present application, since the blade electrode is formed by bending a metal plate, it is less likely to twist than the wire electrode. As a result, the blade electrode can make the bent portion face the rotating cooling roll while maintaining a proper posture, and can apply an electrostatic charge to the molten sheet appropriately. In addition, spark discharge generally occurs from protrusions such as corners and burrs formed on the outer surface of the blade electrode. On the other hand, in the blade electrode according to claim 1 of the present application, since static charges are applied from the bent portion formed by bending the metal plate, corners and burrs are hardly formed on the outer surface, and spark discharge is caused. Occurrence is easily prevented.

The invention according to claim 2 is summarized in that, in the invention according to claim 1, the lower end portion of the blade electrode is formed in a U-shaped section or a V-shaped section.
In the invention according to claim 2 of the present application, the thickness of the electrode at the lower end can be reduced by forming the lower end of the blade electrode into a U-shaped cross section or a V-shaped cross section. Here, the electrode thickness is the distance between the outer surfaces of the blade electrodes. As a result, the blade electrode can easily increase the density of the electrostatic charge applied from the bent portion to the molten sheet. For this reason, the molten sheet can enhance the adhesion to the surface of the rotating cooling roll when the electrostatic charge is applied at a high density.

The invention according to claim 3 of the present application is characterized in that, in the invention according to claim 1 or 2, an irreversible fold is formed along the bent portion in the metal plate. .
In the invention according to claim 3 of the present application, the thickness of the electrode at the lower end of the blade electrode can be further reduced by bending the metal plate until an irreversible fold is formed. As a result, since the higher density of electrostatic charge is applied to the molten sheet from the bent portion, it is possible to further improve the adhesion with the surface of the rotating cooling roll.

Hereinafter, an embodiment embodying the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1A, the synthetic resin film manufacturing apparatus 11 according to the embodiment includes a base 21 as a discharge port, a rotary cooling roll 31, and a blade electrode 41. Synthetic resin films are used as base films for magnetic recording media and adhesive tapes, and specific examples include polyester films such as polyethylene terephthalate films and polyethylene naphthalate films, polypropylene films, and nylon films.

  The base 21 is attached to a lower end portion of a melt extruder (not shown), and is configured such that a synthetic resin material heated and melted from the melt extruder is supplied to the inside. The base 21 has a long hole-like slit 22 extending along the axial direction of the rotary cooling roll 31 at the lower end portion, and is configured to discharge the molten sheet 12 downward from the slit 22. The molten sheet 12 is formed of a synthetic resin material that is heated and melted, and its thickness is usually 50 to 1000 μm.

  As shown in FIG. 1A and FIG. 2, the rotary cooling roll 31 is disposed below the slit 22. The rotary cooling roll 31 is configured so as to rotate in the direction of arrow A in FIG. 1A around the rotation shaft 32 and the molten sheet 12 discharged from the slit 22 adheres to the surface. Further, the rotary cooling roll surface 33 is cooled to the melting point of the molten sheet 12 or less, and is configured to cool and solidify the molten sheet 12 attached to the surface 33. In the following description, the rotation direction at the upper end of the rotary cooling roll 31 that is the traveling direction of the molten sheet 12 discharged from the base 21 is referred to as the front, and the rotation direction at the lower end is referred to as the rear. Behind the rotary cooling roll 31, a peeling roll 34 for peeling the cooled and solidified molten sheet 12 from the rotary cooling roll surface 33 is disposed. The peeling roll 34 rotates in the direction of arrow B in FIG.

  As shown in FIG. 1B, the blade electrode 41 is formed in a band shape by folding a metal plate 42 having a long square plate shape and folding it in the longitudinal direction. The blade electrode 41 is disposed above the rotating cooling roll 31 and is configured to apply an electrostatic charge to the molten sheet 12 on the rotating cooling roll surface 33 when energized, as indicated by an arrow C in FIG. Has been. An insulating tube 43 is coated on the outer surfaces of both end portions in the longitudinal direction of the blade electrode 41 that does not face the molten sheet 12.

  The metal plate 42 usually has a thickness of 5 to 30 μm, and examples of the material include tungsten and stainless steel. Here, the “bending of the metal plate 42” means that the metal plate 42 is bent so that the figure formed along the crease in the cross section becomes a circle or an ellipse whose major axis extends in the vertical direction. For this reason, the concept of “bending of the metal plate 42” is that the figure formed along the crease in the cross section in order to bend the metal plate 42 into an arc shape is an ellipse whose minor axis extends in the vertical direction. It does not include “curvature of plate 42”. The blade electrode 41 has a bent portion 44 along the lower edge, and the bent portion 44 has a U-shaped cross section.

  Here, the metal plate 42 is preferably folded in two so that an irreversible fold is formed along the bent portion 44. In this case, since the radius of curvature can be made smaller than when the fold is reversible, the thickness of the electrode at the lower end of the blade electrode 41 can be reduced. As a result, the blade electrode 41 can increase the density of the electrostatic charge applied from the bent portion 44 to the molten sheet 12. For this reason, the adhesiveness between the molten sheet 12 and the rotary cooling roll surface 33 is enhanced. The blade electrode 41 is constituted by the bent portion 44 and a pair of flat portions 45 having a long rectangular plate shape extending upward from both front and rear end portions of the bent portion 44. The flat portions 45 may be separated from or in contact with each other.

  As shown in FIGS. 1A and 2, the blade electrode 41 is stretched so that the bent portion 44 extends in the axial direction of the rotary cooling roll 31. Further, the blade electrode 41 is stretched slightly forward from the position where the molten sheet 12 adheres to the rotary cooling roll surface 33. The blade electrode 41 has a distance r (the shortest distance between the blade electrode 41 and the rotary cooling roll surface 33) between the lower end (the lower end of the bent portion 44) and the rotary cooling roll surface 33 facing the bent portion 44. It is preferably stretched so as to be 3 to 9 mm. In this case, by setting the distance r to 3 mm or more, an insulating layer of air between the bent portion 44 and the rotating cooling roll surface 33 facing the bent portion 44 is sufficiently thick, so that the occurrence of spark discharge is prevented. Easy to do. Further, by setting the distance r to 9 mm or less, it becomes easy to concentrate the electrostatic charge applied from the bent portion 44 on the rotary cooling roll surface 33 facing the bent portion 44, and The density of the applied electrostatic charge can be easily increased. For this reason, the adhesiveness between the molten sheet 12 and the rotary cooling roll surface 33 is enhanced.

  For example, when a polyester film is produced as a synthetic resin film, after a polyester chip is supplied to a melt extruder, the chip is heated to a temperature higher than the melting point of the polyester (for example, 270 to 310 ° C.) and melted. On the other hand, for example, a voltage of 6 to 8 V is applied to the blade electrode 41. Next, the heated and melted polyester is supplied from the melt extruder into the die 21 and continuously discharged as a molten sheet 12 from the slit 22. After the discharged molten sheet 12 adheres to the rotating cooling roll surface 33, an electrostatic charge is applied from the blade electrode 41 to electrostatically adhere to the rotating cooling roll surface 33. Further, the molten sheet 12 is cooled and solidified by the rotary cooling roll 31. Subsequently, the cooled and solidified molten sheet 12 is peeled off from the rotary cooling roll surface 33 by the peeling roll 34 and stretched as necessary to produce a polyester film.

The effects exhibited by the above embodiment will be described below.
-Since the blade electrode 41 of the embodiment is formed by bending the metal plate 42, it is less likely to twist than the wire electrode. For this reason, when the blade electrode 41 is stretched, the bent portion 44 can be opposed to the rotary cooling roll 31 while maintaining an appropriate posture throughout the blade electrode 41, and the electrostatic charge is appropriately applied to the molten sheet 12. be able to. Further, since the bent portion 44 of the blade electrode 41 is formed by folding the metal plate 42 in two, no corners or burrs are formed on the outer surface thereof. For this reason, the blade electrode 41 can easily prevent the occurrence of spark discharge.

  Here, in a conventional blade electrode having a long rectangular thin plate shape, the outer surface of the end portion is curved by polishing in order to prevent the occurrence of spark discharge from the end portion facing the rotary cooling roll 31. It is possible. However, the blade electrode is usually thin, and it is difficult to polish the end portion so that the outer surface is curved. Further, a protrusion due to polishing is formed on the outer surface of the end portion after polishing, and spark discharge is easily generated from the protrusion.

  The lower end portion of the blade electrode 41 is formed in a U-shaped cross section. For this reason, since the radius of curvature of the lower end portion of the blade electrode 41 can be easily reduced, the thickness of the electrode at the lower end portion can be reduced. For this reason, since the blade electrode 41 applies an electrostatic charge via the bent portion 44, the density of the electrostatic charge applied to the molten sheet 12 can be easily increased.

  The blade electrode 41 is easy to manufacture because it is formed in a band shape by bending a metal plate 42 having a long square plate shape and folding it in the longitudinal direction.

Next, the embodiment will be described more specifically with reference to examples and comparative examples.
(Example 1 and Comparative Examples 1 to 10)
In Example 1, a polyester film was produced according to the following measurement conditions using the production apparatus of the embodiment. On the other hand, in Comparative Examples 1 to 10, a polyester film was produced in the same manner as in Example 1 except that the blade electrode was changed to the electrode shown in Table 1. Then, the value of the applied current to the electrode and the voltage at which a spark discharge was generated from the electrode, that is, the spark discharge start voltage, were measured, and the adhesion between the molten sheet and the surface of the rotating cooling roll was evaluated. The results are shown in Table 1. In addition, about the adhesiveness of Table 1, it shows that adhesiveness is so high that the numerical value is high.

  <Measurement conditions> Distance r between the lower end of the electrode and the rotary cooling roll surface 33: 6 mm, voltage (applied voltage): 7 kV.

表１に示すように、実施例１のブレード電極４１は、火花放電開始電圧が印加電圧（７ｋV）よりも高く、かつ前記各電圧の差が比較例５〜１０のブレード電極に比べて大きかった。このため、実施例１のブレード電極４１は、比較例５〜１０のブレード電極に比べて火花放電の発生を容易に防止することができた。さらに、実施例１のブレード電極４１は、比較例１〜４のワイヤ電極に比べて溶融シート１２と回転冷却ロール表面３３との密着性を高めることができた。これは、溶融シート１２に印可する静電荷密度が高められたためと考えられる。実施例１のブレード電極４１は、その全体にわたって折曲部４４を回転冷却ロール３１に適正な姿勢を維持しつつ対向させることが容易であった。

As shown in Table 1, in the blade electrode 41 of Example 1, the spark discharge start voltage was higher than the applied voltage (7 kV), and the difference between the voltages was larger than that of the blade electrodes of Comparative Examples 5-10. . For this reason, generation | occurrence | production of the spark discharge was able to be easily prevented with the blade electrode 41 of Example 1 compared with the blade electrode of Comparative Examples 5-10. Furthermore, the blade electrode 41 of Example 1 was able to improve the adhesion between the molten sheet 12 and the rotary cooling roll surface 33 as compared with the wire electrodes of Comparative Examples 1 to 4. This is presumably because the electrostatic charge density applied to the molten sheet 12 was increased. In the blade electrode 41 of Example 1, it was easy to make the bent portion 44 face the rotary cooling roll 31 while maintaining an appropriate posture over the whole.

In addition, this embodiment can also be changed and embodied as follows.
-You may form the lower end part of the blade electrode 41 in a cross-sectional V shape. In this case, similarly to the case where the lower end portion of the blade electrode 41 has a U-shaped cross section, the radius of curvature of the lower end portion can be easily reduced, so that the thickness of the electrode at the lower end portion is reduced. be able to. Further, the lower end portion of the blade electrode 41 may be formed in a J-shaped section.

Further, the technical idea that can be grasped from the embodiment will be described below.
The synthetic resin film according to any one of claims 1 to 3, wherein a distance between a lower end of the bent portion and a surface of the rotary cooling roll facing the bent portion is set to 3 to 9 mm. Manufacturing equipment. According to this configuration, it is easier to prevent the occurrence of spark discharge, and the adhesion between the molten sheet and the surface of the rotary cooling roll can be improved.

  A blade electrode used in the synthetic resin film manufacturing apparatus according to any one of claims 1 to 3, wherein the blade electrode has a belt-like shape and has a bent portion along one end edge in a short direction. The blade electrode is formed by bending a metal plate. According to this configuration, it is possible to appropriately apply an electrostatic charge to the molten sheet and to easily prevent the occurrence of spark discharge.

  The said blade electrode is a manufacturing apparatus of the synthetic resin film as described in any one of Claims 1-3 currently formed in the strip | belt shape by bend | folding a long quadrilateral plate-shaped metal plate into a longitudinal direction. According to this configuration, it is easy to manufacture the blade electrode.

  A discharge port that discharges the molten sheet, a rotary cooling roll that is provided below the discharge port and that cools the molten sheet, and a belt-like belt that is provided above the rotary cooling roll and extends in the axial direction of the rotary cooling roll. In a synthetic resin film manufacturing apparatus comprising a blade electrode, the blade electrode is formed of a bent metal plate and has a bent portion along a lower end edge, and the bent portion is formed of the metal plate. A synthetic resin film manufacturing apparatus comprising a fold. According to this configuration, it is possible to appropriately apply an electrostatic charge to the molten sheet and to easily prevent the occurrence of spark discharge.

(A) is an end view which shows the synthetic resin film manufacturing apparatus of embodiment, (b) is a perspective view which shows a blade electrode. The perspective view which shows the manufacturing apparatus of a synthetic resin film.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Manufacturing apparatus of a synthetic resin film, 12 ... Molten sheet, 21 ... Base as a discharge outlet, 31 ... Rotary cooling roll, 41 ... Blade electrode, 42 ... Metal plate, 44 ... Bending part.

Claims (3)

A discharge port for discharging the molten sheet, a rotary cooling roll provided below the discharge port for cooling the molten sheet, and a belt-like blade provided above the rotary cooling roll and stretched in the axial direction of the rotary cooling roll In an apparatus for producing a synthetic resin film comprising an electrode,
The said blade electrode has a bending part along a lower end edge, This bending part is formed by bending a metal plate, The manufacturing apparatus of the synthetic resin film characterized by the above-mentioned. The synthetic resin film manufacturing apparatus according to claim 1, wherein a lower end portion of the blade electrode is formed in a U-shaped section or a V-shaped section. The apparatus for producing a synthetic resin film according to claim 1, wherein an irreversible fold is formed along the bent portion of the metal plate.

Images