JP2002226615A - Corona discharge electrode, corona discharge method and sheet casting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corona discharge electrode having a multi-stylus head adjustable for a stable film production, which accommodates change of quality, molding rate and thickness of a sheet, and in which equal distance between styluses and the sheet prevents partial discharge by continuously variable curved line of arranged stylus tops in the discharge electrode. SOLUTION: The corona discharge electrode consists of the electrode having a lot of styluses which apply static charge to the back of overall width of a molten resin sheet immediately before the molten resin sheet extruded from T die in a sheet casting machine is wound on a cooling roller to improve adherence between the sheet and the roller, and of a support of an electric insulator preserving the electrode. The corona discharge electrode which is adjusted to easily fit to a curved surface by setting a large number of slits at right angle to length of the support and at rear side of the support reverse to electrode-supporting side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the adhesion between a molten resin sheet and a cooling roll before the molten resin sheet extruded from a T die of a sheet casting machine is wound around the cooling roll. The present invention relates to a configuration of a corona discharge electrode for applying an electrostatic charge to a back surface, a method for adjusting a distance between a discharge electrode and a sheet when the corona discharge electrode is used, and a sheet casting machine provided with the corona discharge electrode.

[0002]

2. Description of the Related Art When manufacturing a sheet of a thermoplastic resin material such as polyethylene, polypropylene, polyester, or polyamide, a molten resin is formed into a sheet from a T-die installed at the tip of an extruder attached to a sheet casting machine. It is extruded, wrapped around the cooling roll, and cooled and solidified on the surface of the cooling roll to form a resin sheet molded product.When the resin sheet cools, it tends to remarkably reduce its width. If the adhesiveness of the molten resin sheet is not good when doing, the width when it becomes a molded article sheet becomes irregular, and when air is trapped between the molten resin sheet and the cooling roll surface, There is a problem that bubbles and cooling spots occur on the resin sheet surface.

In order to solve such a problem, a corona discharge is applied to a surface of the molten resin sheet opposite to a side to be cooled immediately before the molten resin sheet comes into contact with a cooling roll to impart an electrostatic charge, and the ground is grounded. A known method for ensuring that the molten resin closely adheres to the surface of the cooled roll is used.

If the arrangement of the discharge point tips of the independent discharge electrodes having the multiple needle-shaped discharge points is fixed to be horizontal and straight with respect to the sheet feeding direction, the discharge object may be curved,
When the sheet-like molten resin extruded from the die cools and begins to solidify from both ends, causing unevenness in thickness, this straight-lined multi-needle discharge electrode cannot cope with it. No. 19135 proposes and discloses a corona discharge electrode having curved electrode points.

[0005]

[Problems to be Solved by the Invention]
The corona discharge electrode having a curved electrode point proposed in Japanese Patent No. 5 has a fixed curvature, but the sheet shape of the molten resin extruded from the T-die and approaching the cooling roll has a sheet material, a forming speed, and a thickness. Therefore, the curvature does not always coincide with the above-described curvature, and cannot be handled by a curve in which the arrangement lines of the electrode points of the discharge electrodes are fixed. The sheet manufacturing plant demands a multi-needle electrode that can be adjusted so that the gap between the electrode needle electrode point and the sheet is constant in any molten resin sheet shape. In response to changes in speed and thickness, the curved shape of the line at the tip of the electrode needle of the discharge electrode is steplessly variable, which makes the dimensions between the electrode needle and the sheet uniform, preventing partial discharge and stabilizing It is an object of the present invention to provide a corona discharge electrode having a multi-needle electrode that can be adjusted so that a formed film can be formed.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention aims to solve the problems by means characterized by the following constitutions and methods.

1) Immediately before the molten resin sheet extruded from the T-die of the sheet casting machine is wound around the cooling roll, an electrostatic charge is applied to the entire width of the back surface of the molten resin sheet in order to improve the adhesion between the molten resin sheet and the cooling roll. In a corona discharge electrode comprising an electrode having a large number of electrode needles to be applied and a support of an electrically insulating material holding the electrode,
A corona discharge electrode in which a plurality of slits are provided in a back portion of the support opposite to an electrode support surface at right angles to a longitudinal direction of the support so that the discharge electrode can be easily adjusted to a curved surface.

[0008] 2) In the corona discharge electrode according to 1), a corona discharge is formed by embedding a soft electric insulating material having elasticity such as silicon rubber into a number of slits provided in the support to prevent electric leakage. electrode.

3) On both sides of the T-die, the same T
Adjustment bolts capable of adjusting the average distance to the molten resin sheet immediately after being extruded from the die, a mounting table provided with nuts, and a plurality of columns fixedly arranged in a row in the longitudinal direction on the electrode support. Adjustment bolts, the same number of holes as the adjustment bolts drilled in a row in the longitudinal direction on the mounting table according to the pitch of the adjustment bolts, and an adjustment nut and a lock nut screwed into the adjustment bolts inserted into the holes. 1) and 2) corona discharge electrodes provided with an adjusting mechanism for adjusting the position of the tip of the configured electrode needle (the gap distance between the electrode point and the molten resin sheet surface) for each group.

4) In the corona discharge electrode described in 1) to 3), a heat shield plate is provided in a space between the support and the T-die, and at the same time, the support and the electrode are passed through cooling water inside the mount. A corona discharge electrode that prevents the position adjusting mechanism and the T-die from being heated.

5) The corona discharge electrode described in 3) and 4) is used, and the average reference distance between the corona discharge electrode and the cooling roll or the molten resin sheet is adjusted and fixed at the T-die mounting portion of the mounting table. The sheet casting machine is operated, and after the molten resin sheet extruded from the T-die is wound around the cooling roll, corona discharge is started, and while observing the corona discharge state, the charge application on the molten resin sheet surface is uniform. The gap distance between the tip of the electrode needle of the discharge electrode and the molten resin sheet surface is adjusted for each group by operating a plurality of adjustment bolts and adjustment nuts fixed to the support so that the molten resin sheet surface A corona discharge method for a molten resin sheet of a sheet casting machine in which the molten resin sheet is uniformly charged so that the molten resin sheet is in close contact with a cooling roll evenly. 6) A sheet casting machine having a T-die, a cooling roll around which a molten resin sheet extruded from the T-die is wound, and a corona discharge electrode mechanism for applying an electrostatic charge to the molten resin sheet, wherein the corona discharge electrode mechanism is provided. Is an electrode comprising a plurality of electrode needles, a support for supporting the electrode,
It has a mounting plate for mounting the support, and an adjusting mechanism for adjusting a distance between the support and the mounting plate, and a slit is provided on a back portion of the support opposite to the electrode support surface. A sheet casting machine, characterized in that:

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment A first embodiment of the present invention will be described with reference to the drawings. 1 is a cross-sectional view showing the corona discharge electrode mechanism and its periphery, FIG. 2 is a front view of the mounting end of the corona discharge electrode mechanism of FIG. 1 viewed from the direction of arrow A, and FIG. 3 is B of the mounting end of FIG. FIG. 4 is a rear cross-sectional view of the corona discharge electrode of FIG. 1 as viewed from the direction C (T-die side plate protrusions 2 and rotary abutment 21 are omitted).

In FIG. 1, a corona discharge electrode mechanism 10 is provided between a T-die 1 of a sheet casting machine and a cooling roll 3. Immediately before the molten resin 4 is extruded from the T-die 1 into the sheet-shaped molten resin 5 and wound around the cooling roll 3 rotating at the same peripheral speed as the feeding speed of the sheet-shaped molten resin 5, the corona discharge electrode 11 (Hereinafter, referred to as an electrode) is used to apply an electrostatic charge to the back surface of the molten resin sheet 5 and to make it adhere to the cooling roll 3. The molten resin sheet 5 is cooled and solidified to form a molded resin sheet 6.

The corona discharge electrode mechanism 10 includes a support 12 for supporting the electrode 11, an adjusting bolt 16,
A mounting plate 15a mounted via an adjustment nut 17 is integrated with the mounting base 15. Mounting base 15
The two end mounting plates 15b, 15b are attached to the rotating abutments 21, 21 by bolts 28, and the rotating abutments 21, 21
Is rotatably supported by the shaft 22 on the projections 2 and 2 which are integral with the T-die side plate supporting the T-die 1 while supporting the side surface of the resin passage of the T-die 1 (from the T-die 1 to the molten resin). In the first step of sheet casting in which the sheet 4 is extruded and wound around the cooling roll 3, it is difficult to perform the operation unless the corona discharge electrode mechanism 10 is separated, so that the sheet is rotated and placed at the position shown by the two-dot chain line in FIG. There is a need). When fixing the corona discharge electrode mechanism 10 to the operating position, T
It is fixed by a lock cam 26 that rotates about a pin 27 provided on the die side plate projection 2. The lock cam 26 has an eccentric cam.

As shown in FIG. 2 and FIG.
An adjustment bolt 23 is fixedly mounted on the
An adjusting nut 24 is screwed into the adjusting bolt 23, and a ring-shaped groove of the adjusting nut 24 is fitted into a notch long hole provided at an upper end 15 c of an end mounting plate 15 b at an end of the mounting base 15. The average distance of the entire corona discharge electrode mechanism 10 from the molten resin sheet 5 can be adjusted by adjusting the vertical position of the base 15 in the mounting surface direction. Further, a lock nut 25 is screwed into the adjustment bolt 23 so that the adjustment nut 24 can be locked when the adjustment is completed.
The mounting hole of the end mounting plate 15b is a long hole 15d. When adjusting the position of the corona discharge electrode mechanism 10, the bolt 28 is loosened, and when the position adjustment is completed, the bolt 28 is tightened and fixed.

As shown in FIG. 6, the corona discharge electrode mechanism 1
Reference numeral 0 denotes an electrode 1 having a length exceeding the entire width of the molten resin sheet 5 and having a large number of electrode needles 11a having a constant length and a constant pitch.
1, a support 12 made of an electrically insulating material (such as glass fiber reinforced thermosetting resin) for holding the electrode 11, an electric cable 14 for supplying high-voltage static electricity to the electrode 11, and an end 14a of the electric cable 14. And a current-carrying plate 13 electrically coupled to the electrodes 11 to transmit static electricity to the electrodes 11.

The corona discharge electrode mechanism 10 is easily provided with a large number of slits 12a having a constant pitch and a constant depth perpendicular to the longitudinal direction of the support 12 at the back portion of the support 12 opposite to the electrode supporting surface. A curved surface can be formed (the slit is also cut into the conductive plate 13).

[0018]

Second Embodiment A support 32 having the same shape as the support 12 shown in FIG. 6 is provided with a soft electric insulating material 33 having elasticity such as soft silicon rubber in a plurality of slits 32a provided in the support 32. This is an example of embedding to prevent leakage due to air discharge from the conductive plate 13.

In the above first and second embodiments,
The mounting base 15 integrated with the mounting plate 15a has high rigidity, and a large number of adjustment bolts 1 in which the supports 12 are arranged on the mounting plate 15a in a line in the longitudinal direction of the mounting plate 15a.
6, Adjustment nut 17, Intermediate nut 18, Lock nut 1
9 attached. The adjusting bolt 16 is attached to the support 1
2, the adjustment nut 16 is screwed into the adjustment bolt 16, and the intermediate nut 18 is engaged with a spline or a key provided in the adjustment nut 17 to restrict the rotation direction, and is relatively fixed to the adjustment nut 17. Rotation is restricted, and it is movable in the axial direction.

When the casting machine is operating and corona discharge is being performed on the molten resin sheet 5, when the discharge state is observed, it is desired to change the distance between the molten resin sheet 5 and a certain group of the electrode needles 11a. Is the electrode needle 11a
Loosen the lock nut 19 of the adjustment bolt 16 at the required position of the support 12 with respect to the group, turn the intermediate nut 18 manually or using a wrench, and turn the adjustment nut 17 to reduce the distance between the mounting plate 15a and the support 12. If adjusted, the support 12 bends and changes the position of the group of electrode needles 11a (see FIG. 5). When the adjustment is completed, the lock nut 19 is tightened to lock the adjustment nut 17 and the adjustment bolt 16 to maintain the position of the electrode needle 11a. The reason is that the electrode point (electrode needle 11
The distance between the needle tip a) and the molten resin sheet 5 is 1 to 0.5 mm.
It is.

[Third Embodiment] FIG. 7 shows an example of a corona discharge electrode mechanism 10 in which cooling water is passed through the inside of the mounting base 15 and a heat shield plate 35 is provided in the space between the support 12 and the T-die 1. Show.
The heat shield plate 35 is provided over the entire length of the corona discharge electrode mechanism 10 and is attached to the mounting plate 15a with bolts 36.
The support 12 prevents the heating from the T-die 1. Also, the cooling method of the mounting base 15 is the same as that of the mounting base 15.
A small-diameter perforated pipe 37 is concentrically and liquid-tightly fixed to the pipe constituting the pipe, and normal-temperature cooling water is supplied from the water supply pipe 38 to the outside of the double pipe, and warmed water is supplied from the inner perforated pipe 37. The structure is drained.

With the above-described structure of heat shielding and water cooling, the support 12 of the corona discharge electrode mechanism 10, the intermediate nut 18 and the lock nut 19, which are touched when adjusting the support 12 to a curved surface, are connected to the high heat of the T-die 1. , The thermal distortion of the support 12 is reduced, and the mounting base 15 is cooled, so that the mounting plate 15a, the adjusting bolt 16, the adjusting nut 17, and the intermediate nut 18 are cooled. , The adjustment position of the corona discharge electrode mechanism 10 from the molten resin sheet 5 is maintained, and the fine adjustment of the electrode needle 11a is enabled.

The working steps for performing corona discharge treatment on the surface of the molten resin sheet 5 using the corona discharge electrode mechanism 10 are as follows.

First, the lock cams 26, 26 are turned to unlock the rotary supports 21, 21, and the corona discharge electrode mechanism 10 is shown in FIG. 1 around the shafts 22, 22, which support the rotary supports 21, 21. Rotate to the position indicated by the two-dot chain line.

In this state, the extruder (not shown) of the sheet casting machine is operated to extrude the molten resin 4 from the T-die 1, and the extruded molten resin sheet 5 is wound around the cooling roll 3. After the molten resin sheet 5 is stably wound around the cooling roll 3, the corona discharge electrode mechanism 10 is returned to the original position shown by the solid line in FIG. 1, the lock cam 26 is turned back, and the rotary support 21 is moved. After the locking, when an electrostatic voltage is applied to the electrode 11, corona discharge starts between the tip of the electrode needle 11a of the electrode 11 and the molten resin sheet 5.

Observing the corona discharge state, if the entire distance of the corona discharge electrode mechanism 10 from the molten resin sheet 5 is inappropriate or inclined with respect to the surface of the molten resin sheet 5, The overall position and posture of the corona discharge electrode mechanism 10 are adjusted as described in (1). First, the mounting table 15
The two end mounting plates 15b, 15b are
1, loosen the eight bolts 28, loosen the lock nuts 25, 25 to unlock the adjustment nuts 24, 24, and turn the adjustment nuts 24, 24 to turn the end mounting plate 15.
By moving b and 15b, the average distance between the electrode 11 and the cooling roll 3 or the molten resin sheet 5 is adjusted.
After this adjustment, the lock nuts 25, 25 are tightened to fix the adjustment nuts 24, 24, and eight bolts 28 are further tightened to fix the end mounting plates 15b, 15b to the rotating abutment 21,
Fix to 21.

Next, while observing the corona discharge state, fine adjustment of the positions of the electrodes 11 requiring fine adjustment is performed for each group. A plurality of adjustment bolts 16 fixed to the support 12
, The required adjustment bolt 16 is selected, the lock nut 19 is loosened, the adjustment nut 17 is rotated via the intermediate nut 18 to deform the support 12, and the electrode needle of the electrode 11 is grouped for each group. By adjusting the gap distance between the tip of 11a and the surface of the molten resin sheet 5 to make the corona discharge state uniform, static electricity is uniformly charged on the surface of the molten resin sheet, and the molten resin sheet 5 adheres to the cooling roll 3 evenly. To do.

[0028]

The corona discharge electrode of the present invention is provided on the back surface of the molten resin sheet before the molten resin sheet extruded from the T-die is wound around the cooling roll to improve the adhesion between the molten resin sheet and the cooling roll. A corona discharge electrode having a large number of needle-like electrode points for imparting an electrostatic charge, wherein a slit is provided on a back portion of an electrode support so that the discharge electrode can be easily adjusted to a curved surface, or a leakage prevention. for,
Since the configuration is such that an electrically insulating material having elasticity is embedded in the slit, the discharge electrode points can be adjusted to a curved shape in a stepless manner, whereby the dimensions between the electrode needles and the molten resin sheet can be made uniform. As a result, partial discharge can be prevented, the sheet forming speed can be increased, the thickness can be easily changed, and a stable sheet can be manufactured.
(Claims 1, 2, 5, 6)

Since the mounting base for the discharge electrode is installed so that the relative position with respect to the T-die can be adjusted, the position and posture of the entire corona discharge electrode mechanism can be adjusted, and at the same time, the mounting of the discharge electrode mounting base can be performed. Several adjustment bolts in the longitudinal direction,
Since the adjustment nut and the lock nut are arranged in a line and provided with a discharge electrode position adjustment mechanism for each group, the discharge electrode point can be steplessly curved manually or by using a simple tool. It is possible to enhance the feasibility of the above effects. (Claims 3 and 5)

Further, a heat shield plate is provided in the space between the corona discharge electrode and the T-die, and at the same time, the electrode support and the electrode position adjusting mechanism are cooled from the high-temperature T-die by passing cooling water into the mounting base. Therefore, the thermal distortion of the electrode support is reduced, and by cooling the mounting base, the electrode adjustment bolt, the adjustment nut, etc. are cooled and kept at a low temperature, and the thermal distortion of this part is reduced. In addition, there is an effect that the adjustment position of the corona discharge electrode from the molten resin sheet surface is maintained, and the discharge electrode can be finely adjusted. (Claim 4)

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a corona discharge electrode mechanism according to a first embodiment of the present invention and the periphery thereof.

2 is a front view of the mounting end of the corona discharge electrode mechanism of FIG. 1 as viewed from the direction of arrow A.

FIG. 3 is a side cross-sectional view illustrating a cross section taken along line BB of the mounting end in FIG.

FIG. 4 is a rear view of the corona discharge electrode mechanism of FIG. 1 viewed from a direction C.

FIG. 5 is an explanatory view showing an electrode adjusting operation when corona discharge is performed by the corona discharge electrode mechanism of FIG. 1;

FIG. 6 is a back view showing a corona discharge electrode according to a second embodiment.

FIG. 7 is a cross-sectional view corresponding to FIG. 1, illustrating an example in which a heat shield plate and a cooling water passage are provided in a corona discharge electrode mechanism according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... T die 3 ... Cooling roll 5 ... Molten resin sheet 10 ... Corona discharge electrode mechanism 11 ... Electrode 11a ... Electrode needle 12 ... Support 12a ... Slit 13 ... Electric plate 15 ... Mounting base 15a ... Mounting plate 16 ... Adjustment bolt 17 ... Adjustment nut 18 ... Intermediate nut 19 ... Lock nut 21 ... Rotating support 22 ・・ ・ Shaft 23 ・ ・ ・ Adjustment bolt 24 ・ ・ ・ Adjustment nut 25 ・ ・ ・ Lock nut 32 ・ ・ ・ Support body 32a ・ ・ ・ Slit 33 ・ ・ ・ Soft electric insulation material 35 ・ ・ ・ Heat shield 37 ・ ・・ Porous tube

Claims (6)

[Claims] 1. Immediately before a molten resin sheet extruded from a T die of a sheet casting machine is wound around a cooling roll, an electrostatic charge is applied to the back of the entire width of the molten resin sheet in order to improve the adhesion between the molten resin sheet and the cooling roll. In a corona discharge electrode comprising an electrode having a large number of electrode needles to be applied and a support made of an electrically insulating material holding the electrode, a longitudinal direction of the support is provided on a back portion of the support opposite to an electrode support surface. A corona discharge electrode characterized in that a large number of slits are provided at right angles to the discharge electrode so that the discharge electrode can be easily adjusted to a curved surface. 2. The corona discharge electrode according to claim 1, wherein a plurality of slits provided in the support are filled with a soft electric insulating material having elasticity such as silicon rubber to prevent electric leakage. A corona discharge electrode. 3. A mounting table mounted on both side plates of a T-die with adjusting bolts and nuts capable of adjusting an average distance between the electrode and the molten resin sheet immediately after being extruded from the T-die; A plurality of adjustment bolts fixedly arranged in a row in the support in the longitudinal direction, and the same number of holes as the adjustment bolts drilled in the row in the longitudinal direction on the mounting table according to the pitch of the adjustment bolts; An adjustment mechanism for adjusting the position of the tip of the electrode needle (gap distance between the electrode point and the molten resin sheet surface) composed of an adjustment nut and a lock nut screwed into an adjustment bolt inserted into the hole for each group. The corona discharge electrode according to claim 1, wherein: 4. The corona discharge electrode according to claim 1, wherein a heat shield plate is provided in a space between the support and the T-die, and at the same time, cooling water is passed through the inside of the mounting base. A corona discharge electrode characterized in that a position adjusting mechanism and a high temperature T-die are protected from heat. 5. A corona discharge electrode according to claim 3, wherein an average reference distance between the corona discharge electrode and a cooling roll or a molten resin sheet is adjusted and fixed at a T-die mounting portion of the mounting base. The sheet casting machine is operated, and after the molten resin sheet extruded from the T-die is wound around the cooling roll, corona discharge is started, and while observing the corona discharge state, the charge application on the molten resin sheet surface is uniform. The gap distance between the tip of the electrode needle of the discharge electrode and the molten resin sheet surface is adjusted for each group by operating a plurality of adjustment bolts and adjustment nuts fixed to the support so that the molten resin sheet surface A corona discharge method, wherein the molten resin sheet is uniformly and uniformly charged so as to be in close contact with the cooling roll evenly. 6. A sheet casting machine comprising: a T-die; a cooling roll around which a molten resin sheet extruded from the T-die is wound; and a corona discharge electrode mechanism for applying an electrostatic charge to the molten resin sheet. The discharge electrode mechanism includes an electrode having a plurality of electrode needles, a support for supporting the electrode, a mounting plate for mounting the support, and an adjustment mechanism for adjusting a distance between the support and the mounting plate. A slit is provided in a back portion of the support opposite to the electrode support surface, and a sheet casting machine is provided.