JP4689847B2 - Corona discharge electrode, corona discharge method and sheet casting machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, 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 back surface of the molten resin sheet in order to improve the adhesion between the molten resin sheet and the cooling roll. The present invention relates to a configuration of a corona discharge electrode, a method for adjusting a gap between a discharge electrode and a sheet when the corona discharge electrode is used, and a sheet casting machine including the corona discharge electrode.
[0002]
[Prior art]
When manufacturing sheets of thermoplastic resin materials such as polyethylene, polypropylene, polyester, polyamide, etc., the molten resin is extruded into a sheet form from a T-die installed at the tip of an extruder attached to the sheet casting machine, and a cooling roll Wrapped around and cooled and solidified on the surface of the cooling roll, it becomes a molded product of the resin sheet, but when the resin sheet cools, there is a tendency to significantly reduce the width, so the molten resin comes into contact with the cooling roll If the sheet adhesion is not good, the width of the molded product sheet becomes irregular, and if air is trapped between the molten resin sheet and the surface of the cooling roll, bubbles are formed on the resin sheet surface. There are defects that cause cooling spots.
[0003]
In order to solve such a problem, a grounded cooling roll is provided by applying corona discharge to the surface opposite to the side to be cooled of the molten resin sheet immediately before the molten resin sheet comes into contact with the cooling roll, thereby providing an electrostatic charge. A well-known method is used in which the molten resin is securely adhered to the surface.
[0004]
When the alignment of the discharge point tips of the discharge electrode with independent discharge electrodes is fixed in a horizontal line with respect to the sheet feeding direction, the discharge target is curved or pushed out of the T die. When the sheet-like molten resin is cooled and solidifies from both ends, and the thickness is not uniform, the multi-needle-shaped discharge electrode fixed in this straight line cannot cope with this, so Japanese Utility Model Publication No. 63-19135 A corona discharge electrode having curved electrode points is proposed and announced.
[0005]
[Problems to be solved by the invention]
The corona discharge electrode having a curved electrode point proposed in Japanese Utility Model Publication No. 63-19135 has a fixed curvature, but the sheet shape of the molten resin extruded from the T die and approaching the cooling roll is the sheet material, Depending on the forming speed and thickness, the curvature does not necessarily match the above-described curvature, and a curve with a fixed line of electrode points of the discharge electrode cannot be used.
The sheet manufacturing factory demands a multi-needle electrode that can adjust the distance between the electrode needle electrode point and the sheet to be constant in any molten resin sheet shape. Corresponding to changes in speed and thickness, the curved shape of the line of the electrode needle tip of the discharge electrode is steplessly variable, which makes the dimension between the electrode needle and the sheet uniform, preventing partial discharge and stable It is an object of the present invention to provide a corona discharge electrode having an adjustable multi-needle electrode that can be formed into a film.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention aims to solve the problem by means characterized by the constitution and method of the following items.
[0007]
1) A large number of electrostatic charges are 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 immediately before the molten resin sheet extruded from the T die of the sheet casting machine is wound around the cooling roll. In a corona discharge electrode comprising an electrode having a plurality of electrode needles and a support made of an electrically insulating material for holding the electrode, a back portion of the support opposite to the electrode support surface is perpendicular to the longitudinal direction of the support. A corona discharge electrode provided with a large number of slits so that the discharge electrode can be easily adjusted to a curved surface.
[0008]
2) The corona discharge electrode according to 1), wherein a soft electrical insulating material having elasticity is embedded in a number of slits provided on the support to prevent leakage.
[0009]
3) A mounting base mounted with adjusting bolts and nuts that can adjust the average distance between the electrode and the molten resin sheet immediately after being extruded from the T die on both side plates of the T die, and a support for the electrode A plurality of adjustment bolts fixedly arranged in a row in the longitudinal direction, the same number of holes as the adjustment bolts opened in a row in the longitudinal direction on the mounting base in accordance with the pitch of the adjustment bolts, and the holes inserted therethrough 1) or 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) for each group, which is composed of an adjustment nut and a lock nut that are screwed into the adjustment bolt 2) Corona discharge electrode.
[0010]
4) 1) In the corona discharge electrode according to any one of the paragraphs to 3), the space between the support and the T die is cooling water inside the mount with is provided with the heat shield plate is passed through a corona discharge electrode and the support and the electrode position adjusting mechanism is characterized in that it is insulation from the hot T-die.
[0011]
5) Using the corona discharge electrode described in 3) or 4), adjusting and fixing the average reference distance between the corona discharge electrode and the cooling roll or the molten resin sheet at the T-die mounting portion of the mounting base, and sheet casting machine is running, after the molten resin sheet extruded from T-die arrived around a cooling roll to initiate corona discharge, while observing the corona discharge state, so that the charge applied in 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 body to make the molten resin sheet surface uniform. A corona discharge method for a molten resin sheet of a sheet casting machine in which charging is performed so that the molten resin sheet adheres uniformly to a cooling roll.
6) In 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 imparting an electrostatic charge to the molten resin sheet, the corona discharge electrode mechanism Has an electrode having a plurality of electrode needles, a support that supports the electrode, a mounting plate that mounts the support, and an adjustment mechanism that adjusts the distance between the support and the mounting plate, A sheet casting machine, wherein a slit is provided in a back portion of the support opposite to the electrode support surface.
[0012]
DETAILED DESCRIPTION OF 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 attachment end of the corona discharge electrode mechanism of FIG. 1 as viewed from the direction of arrow A, and FIG. 3 is B of the attachment end of FIG. 4 is a side cross-sectional view showing a cross-section B, and FIG. 4 is a back view of the corona discharge electrode of FIG.
[0013]
In FIG. 1, a corona discharge electrode mechanism 10 is installed between a T die 1 and a cooling roll 3 of a sheet casting machine. The corona discharge electrode 11 is extruded immediately before the molten resin 4 is extruded from the T die 1 into a sheet-shaped molten resin 5 and wound around the cooling roll 3 rotating at the same peripheral speed as the sheet-shaped molten resin 5 is fed. (Hereinafter referred to as an electrode) is used for imparting an electrostatic charge to the back surface of the molten resin sheet 5 to be brought into close contact with the cooling roll 3. The molten resin sheet 5 is cooled and solidified to be a molded product resin sheet 6.
[0014]
The corona discharge electrode mechanism 10 includes a support 12 that supports the electrode 11, and a mounting base 15 in which a mounting plate 15a that mounts the support 12 via an adjustment bolt 16 and an adjustment nut 17 is integrated. Yes. The mounting base 15 has end mounting plates 15b, 15b on both sides attached to the rotary supports 21, 21 by bolts 28. The rotary supports 21, 21 handle the side surfaces of the resin passage of the T die 1 and at the same time attach the T die 1. It is rotatably supported by a shaft 22 on the projecting portions 2 and 2 that are integral with the supporting T-die side plate (in the first step of sheet casting in which the molten resin 4 is extruded from the T-die 1 and wound around the cooling roll 3, Since it is difficult to work unless the corona discharge electrode mechanism 10 is placed apart, it is necessary to rotate and place it at the position indicated by the two-dot chain line in FIG. When the corona discharge electrode mechanism 10 is fixed to the operating position, the corona discharge electrode mechanism 10 is fixed by a lock cam 26 that rotates around a pin 27 provided on the T-die side plate protrusion 2. The lock cam 26 has an eccentric cam.
[0015]
As shown in FIGS. 2 and 3, an adjustment bolt 23 is fixed to the rotary abutment 21 by an interference fit, and an adjustment nut 24 is screwed into the adjustment bolt 23, and a ring-shaped groove of the adjustment nut 24 is secured. Is fitted into a notch long hole provided in the upper end 15c of the end mounting plate 15b at the end of the mounting base 15, and the vertical position of the mounting base 15 in the mounting surface direction is adjusted, whereby the corona discharge electrode mechanism 10 is adjusted. The average distance from the entire molten resin sheet 5 can be adjusted. A lock nut 25 is screwed onto the adjustment bolt 23, and the adjustment nut 24 can be locked when the adjustment is completed. The attachment hole of the end attachment 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 finished, the bolt 28 is tightened and fixed.
[0016]
As shown in FIG. 6, the corona discharge electrode mechanism 10 has a length exceeding the entire width of the molten resin sheet 5, an electrode 11 having a large number of electrode needles 11 a having a constant length and a constant pitch, and holds the electrode 11. A support 12 made of an electrically insulating material (such as a glass fiber reinforced thermosetting resin), an electric cable 14 for supplying high-voltage static electricity to the electrode 11, and an end portion 14a of the electric cable 14 and electrically coupled to the electrode 11 It is comprised with the electricity supply board 13 which conveys static electricity to.
[0017]
The corona discharge electrode mechanism 10 can be easily formed into a curved surface by providing a large number of slits 12a having a constant pitch and a constant depth perpendicular to the longitudinal direction of the support 12 on the back portion of the support 12 opposite to the electrode support surface. (The slit is also cut into the current-carrying plate 13).
[0018]
[Second Embodiment]
A support body 32 having the same shape as the support body 12 shown in FIG. 6 is formed by embedding a soft electrical insulating material 33 having elasticity such as soft silicon rubber in a large number of slits 32 a provided in the support body 32. This is an example in which leakage due to air discharge is prevented.
[0019]
In the first and second embodiments described above, the mounting base 15 integrated with the mounting plate 15a has high rigidity, and the support bodies 12 are arranged in a row in the longitudinal direction of the mounting plate 15a on the mounting plate 15a. A plurality of installed adjustment bolts 16, adjustment nuts 17, intermediate nuts 18, and lock nuts 19 are attached. The adjustment bolt 16 is fixed to the support 12, and an adjustment nut 17 is screwed onto the adjustment bolt 16, and the intermediate nut 18 is engaged with a spline or key that restricts the rotational direction provided in the adjustment nut 17 for adjustment. The relative rotation with the nut 17 is restricted, and the axial direction is movable.
[0020]
When the casting machine is in operation and corona discharge is being performed on the molten resin sheet 5, as a result of observing the discharge state, when it is desired to change the distance from the molten resin sheet 5 to a certain group of electrode needles 11a, Loosen the lock nut 19 of the adjustment bolt 16 at the required position of the support 12 with respect to the group of electrode needles 11a, turn the intermediate nut 18 manually or with a wrench, and turn the adjustment nut 17 to turn the mounting plate 15a and the support 12 If the distance is 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 hold the position of the electrode needle 11a. Incidentally, the distance between the electrode point (the needle tip of the electrode needle 11a) and the molten resin sheet 5 is 1 to 0.5 mm.
[0021]
[Third embodiment]
FIG. 7 shows an example of the corona discharge electrode mechanism 10 in which cooling water is passed through the mounting base 15 and a heat shield plate 35 is provided in the space between the support 12 and the T die 1. The heat shield plate 35 is provided over the entire length of the corona discharge electrode mechanism 10, and is attached to the attachment plate 15 a by a bolt 36 so that the support 12 prevents heating from the T die 1. In addition, a cooling method of the mounting base 15 is such that a small-diameter porous tube 37 is concentrically and liquid-tightly fixed to a pipe constituting the mounting base 15, and normal temperature cooling water is supplied to the water supply pipe 38 outside the double pipe. The heated water is drained from the inner porous tube 37.
[0022]
With the above heat shielding and water cooling configuration, the support 12 of the corona discharge electrode mechanism 10, the intermediate nut 18 and the lock nut 19 that are touched when the support 12 is adjusted to a curved surface are shielded from the high heat of the T die 1. By reducing the thermal strain of the support 12 and cooling the mounting base 15, the mounting plate 15a, the adjusting bolt 16, the adjusting nut 17, and the intermediate nut 18 are cooled to reduce the thermal strain of this portion. The adjustment position of the corona discharge electrode mechanism 10 from the molten resin sheet 5 is maintained, and the electrode needle 11a can be finely adjusted.
[0023]
The work process when the corona discharge electrode mechanism 10 is used and the surface of the molten resin sheet 5 is subjected to the corona discharge treatment is as follows.
[0024]
First, the lock cams 26 and 26 are turned to unlock the rotary abutments 21 and 21, and the corona discharge electrode mechanism 10 is centered on the shafts 22 and 22 that support the rotary abutments 21 and 21. Rotate to the position indicated by.
[0025]
In this state, an extruder (not shown) of the sheet casting machine is operated to extrude the molten resin 4 from the T die 1, and the molten resin sheet 5 that has been extruded into a sheet shape is wound around the cooling roll 3. After the molten resin sheet 5 is stably wound on 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. When a static voltage is applied to the electrode 11 after locking, corona discharge starts between the tip of the electrode needle 11 a of the electrode 11 and the molten resin sheet 5.
[0026]
When the corona discharge state is observed and the distance from the entire molten resin sheet 5 of the corona discharge electrode mechanism 10 is inappropriate or inclined with respect to the surface of the molten resin sheet 5, the following will be described. The overall position and orientation of the corona discharge electrode mechanism 10 are adjusted. First, loosen the eight bolts 28 that fasten the end mounting plates 15b, 15b at both ends of the mounting base 15 to the rotary supports 21, 21, loosen the lock nuts 25, 25, and adjust the adjustment nuts 24, 24. The average distance between the electrode 11 and the cooling roll 3 or the molten resin sheet 5 is adjusted by releasing the lock and turning the adjustment nuts 24, 24 to move the end attachment plates 15b, 15b. After this adjustment, the lock nuts 25, 25 are tightened to fix the adjustment nuts 24, 24, and further, eight bolts 28 are tightened to fix the end mounting plates 15b, 15b to the rotary abutments 21, 21.
[0027]
Next, while observing the corona discharge state, the position of the electrode 11 that needs fine adjustment is finely adjusted for each group. A required adjustment bolt 16 is selected from a plurality of adjustment bolts 16 fixed to the support body 12, the lock nut 19 is loosened, and the adjustment nut 17 is rotated via the intermediate nut 18 to support the support body. 12 is deformed, and by adjusting the gap distance between the tip of the electrode needle 11a of the electrode 11 and the surface of the molten resin sheet 5 for each group and aligning the corona discharge state, static electricity is uniformly charged on the surface of the molten resin sheet, The molten resin sheet 5 is made to adhere to the cooling roll 3 evenly.
[0028]
【The invention's effect】
The corona discharge electrode of the present invention gives an electrostatic charge to the back surface of the molten resin sheet in order to improve the adhesion between the molten resin sheet and the cooling roll before the molten resin sheet extruded from the T-die is wound around the cooling roll. A corona discharge electrode having a large number of needle-like electrode points, in which a slit is provided on the back portion of the electrode support so that the discharge electrode can be easily adjusted to a curved surface, or the slit for preventing leakage Because it has a configuration in which an electrically insulating material having elasticity is embedded, the discharge electrode point can be adjusted to a curved shape steplessly, which makes it possible to uniformly align the dimensions between the electrode needle and the molten resin sheet. Therefore, 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)
[0029]
Since the discharge electrode mounting base 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, in the longitudinal direction of the discharge electrode mounting base Is composed of a plurality of adjustment bolts, adjustment nuts and lock nuts arranged in a row, and has a discharge electrode position adjustment mechanism for each group, so the discharge electrode points can be set steplessly using manual or simple tools. A curved shape can be obtained, and the feasibility of the above effect can be enhanced. (Claims 3 and 5)
[0030]
Further, a heat shield 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 insulated from the high temperature T die by passing cooling water through the mounting base. Therefore, by reducing the thermal distortion of the electrode support, and by cooling the mounting base, the electrode adjustment bolts, adjustment nuts, etc. are cooled and kept at a low temperature. While maintaining the adjustment position of the electrode from the molten resin sheet surface, there is an effect of enabling fine adjustment of the discharge electrode. (Claim 4)
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a corona discharge electrode mechanism and its surroundings according to a first embodiment of the present invention.
2 is a front view of the attachment end portion 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 showing a BB cross section of the attachment end portion of FIG. 2;
4 is a back view of the corona discharge electrode mechanism of FIG. 1 as viewed from the C direction. FIG.
FIG. 5 is an explanatory view showing an electrode adjusting action 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 showing 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 body 12a ... Slit 13 ... Electric plate 15 ... Mount 15a ... Mount plate 16 ... Adjustment bolt 17 ... Adjust nut 18 ... Intermediate nut 19 ... Lock nut 21 ... Rotation abutment 22 .... Shaft 23 ... Adjustment bolt 24 ... Adjustment nut 25 ... Lock nut 32 ... Support 32a ... Slit 33 ... Soft electrical insulation 35 ... Heat shield plate 37 ...・ Porous pipe

Claims (6)

A number of electrodes for applying an electrostatic charge to the back surface of the entire width of the molten resin sheet in order to improve the adhesion between the molten resin sheet and the cooling roll immediately before the molten resin sheet extruded from the T die of the sheet casting machine is wound around the cooling roll. In a corona discharge electrode comprising an electrode having a needle and a support made of an electrically insulating material that holds the electrode, a number of portions perpendicular to the longitudinal direction of the support are provided on the back portion of the support opposite to the electrode support surface. A corona discharge electrode characterized in that a slit is provided so that the discharge electrode can be easily adjusted to a curved surface. In the corona discharge electrode according to claim 1, the number of slits provided on the support is corona discharge, characterized in that the soft electrically insulating material having elasticity is prevented write Marete leakage fills electrode. On both side plates of the T die, there are adjustment bolts and nuts that can be adjusted to adjust the 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 direction, the same number of holes as the adjustment bolts opened in a row in the longitudinal direction on the mounting base in accordance with the pitch of the adjustment bolts, and an adjustment inserted through the holes An adjustment mechanism is provided for adjusting the position of the tip of the electrode needle (gap distance between the electrode point and the molten resin sheet surface) for each group composed of an adjustment nut and a lock nut that are screwed into the bolt. The corona discharge electrode according to claim 1 or 2. In the corona discharge electrode according to any of claims 1 to 3, wherein the support and the water flow cooling water in the interior of the mount with the space between the T-die is provided with the heat shield plate by corona discharge electrode and the support and the electrode position adjusting mechanism is characterized in that it is insulation from the hot T-die. A sheet casting machine using the corona discharge electrode according to claim 3 or 4 and adjusting and fixing an average reference distance between the corona discharge electrode and the cooling roll or the molten resin sheet at a T-die attachment portion of the mounting base. after running, the molten resin sheet extruded from T-die arrived around a cooling roll to initiate corona discharge, while observing the corona discharge state, so that the charge applied in the molten resin sheet surface is uniform, the Operate multiple adjustment bolts and adjustment nuts fixed on the support to adjust the gap distance between the tip of the electrode needle of the discharge electrode and the molten resin sheet surface for each group to uniformly charge the molten resin sheet surface. A corona discharge method characterized in that the molten resin sheet is in intimate contact with the cooling roll. In 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 imparting an electrostatic charge to the molten resin sheet, the corona discharge electrode mechanism is: An electrode comprising a plurality of electrode needles, a support for supporting the electrode, a mounting plate for mounting the support, and an adjustment mechanism for adjusting the distance between the support and the mounting plate. A sheet casting machine, wherein a slit is provided in a back portion opposite to the electrode support surface.

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