JPS62202719A - Manufacture of thermoplastic polymer sheet - Google Patents

Abstract

PURPOSE:To enable the titled manufacture to quicken drastically a speed of manufacturing a sheet by eliminating involving-in of air, by a method wherein vapor is made present when static electricity is applied to one side of an extruded thing in a sheetlike state of a thermoplastic polymer, the surface is grounded electrically and solidified through quenching. CONSTITUTION:A thermoplastic polymer is a copolymer or a mixture of a polyolefin such as polyethylene, or polyester or polyvinyl, or the copolymer or the mixture of them. A sheetlike extruded thing 2 obtained by extruding the quenching by a cooling roller 3 and sent to a post-treatment process continuously. On that occasion, steam controlled at a predetermined temperature by a heater 9 is blown off through a nozzle 8 and the steam is made present on the surface side of an extruded thin coming into contact with the cooling roller 3. The cooling roller 3 is grounded, positive voltage is applied to a needle electrode 6 provided between the mouthpiece 1 and cooling roller 3 from a high- voltage power source 7 and static electricity is applied to the sheetlike extrude thing 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a thermoplastic polymer sheet, and more specifically, extrudes a molten thermoplastic polymer into a sheet form from a die onto the surface of a moving cooling body, and rapidly solidifies it. The present invention relates to a method for producing a thermoplastic polymer sheet.

Prior art As a method for producing thermoplastic polymer sheets, an electrode member charged with a high voltage is provided between an electrically grounded cooling roller and an extrusion die, and the molten polymer sheet extruded from the die is A method is known in which static electricity is applied to the combined extrudate to bring the extrudate into close contact with a cooling roller. This method is usually called an electrostatic adhesion method.

However, this method also has a problem. For example, when trying to increase the speed of the cooling roller to efficiently produce a polymer sheet, air is trapped between the sheet and the cooling roller, resulting in changes in the surface condition of the polymer sheet. Deterioration occurs. This upper limit circumferential speed is 40 to 50 TrL/min.

OBJECTS OF THE INVENTION An object of the present invention is to solve the problems of the above-mentioned conventional methods and to provide a method that can stably produce a polymer sheet at high speed.

Structure and Effects of the Invention According to the present invention, the object of the present invention is to extrude a molten thermoplastic polymer into a sheet from a die, apply static electricity to one side of the sheet-shaped extrudate, and then apply static electricity to the other side. The extrudate is characterized in that when the extrudate is rapidly solidified by bringing the extrudate into close contact with an electrically grounded movable cooling body, water vapor is present in the atmosphere between the die and the movable cooling body and on the other side of the extrudate. This is accomplished by an IJ manufacturing process of thermoplastic polymer sheets.

Thermoplastic polymers in the present invention include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyamides such as nylon 6 and nylon 66, polyimides, and polystyrene. kind,
Polymers such as polyvinyl that can be molded into sheets, copolymers thereof, and mixtures thereof may also contain other additives. Furthermore, the molten sheet-like material extruded from the die may be a single layer or a multi-layered material.

In the present invention, known means for melting the thermoplastic polymer, such as nine nozzles, a moving cooling body, and a means for applying static electricity to the sheet-like extrudate, can be used.

For example, a known cap having a slit can be used as the cap. As a moving cooling body, the shape is a roller,
A belt shape or a combination thereof can be used. To illustrate these relationships in the drawings, FIG. 1 is a schematic cross-sectional view of an apparatus that can be used in the present invention.

In FIG. 1, a molten thermoplastic polymer is extruded into a sheet from a slit-shaped mouthpiece 1, and the sheet-like extrudate 2 contacts a cooling roller 3 and is rapidly cooled and solidified to become a sheet 2'. is continuously sent to a post-treatment process via a separating roller 4. At that time, the slit nozzle 8
Then, water vapor controlled to a predetermined hot water temperature is blown out by a heating heater 9, so that water vapor is present in the atmosphere between the die 1 and the cooling roller 3 and on the side of the extrudate that is in contact with the cooling roller 3. Furthermore, the cooling roller 3 is grounded to the earth by a ground wire 5, and is electrically grounded. Furthermore, a positive voltage is applied from a high-voltage power source 7 to a needle-like electrode 6 provided between the die 1 and the cooling roller 3 and on the side of the sheet-like extrudate 2 that is not in contact with the cooling roller 3. Static electricity is applied to the sheet-like extrudate 2.

In the present invention, as a method for applying static electricity to the sheet, a voltage may be applied between the cap and the moving cooling body, or a high voltage may be applied to the top surface of the moving cooling body which is electrically grounded. An electrode member may be provided to apply static electricity to the upper surface of the sheet.

In the present invention, pressurized steam or saturated steam can be used as the steam, but it is particularly preferable to use pressurized steam heated to 120 to 180°C. If the temperature is too low, condensed water droplets are likely to occur, and these water droplets adhere to the sheet-like extrudate immediately before cooling, resulting in undesirable irregularities on the sheet after cooling. On the other hand, if the temperature is too high, the cooling effect of the moving cooling body will be hindered. When water vapor is present in the atmosphere between the die and the moving cooling body and on the side of the sheet-like extrudate that is in contact with the moving cooling body, the water vapor pressure is adjusted so that the blowing speed is 20 m/min or less from the slit-shaped nozzle. It is preferable to use a method in which the liquid is finally adjusted and blown out near the boundary line where the sheet and the moving cooling body contact each other.

According to the present invention, the following advantages can be obtained.

(1) Since water vapor is present in the atmosphere near where the sheet-shaped extrudate comes into contact with the moving cooling body, air is not drawn in, and even if water vapor is drawn in, it becomes micro-edible water droplets, so the surface of the polymer sheet Does not substantially worsen the condition.

(a Furthermore, the minute water droplets form ultra-thin legs and increase the adhesion force between the polymer sheet and the moving cooling body, reducing the static electricity applied to the sheet-like extrudate. This reduces the lifespan of the electrode. Furthermore, since the electrodes are placed through the sheet, if there is a defect in the sheet, electrical discharge from the electrodes will not occur, causing damage to the surface of the cooling body.

(3) Since the sheet is moved and the cooling body is brought into close contact with the sheet, the sheet manufacturing speed can be greatly increased.

Example The present invention will be further explained below with reference to Examples.

Example 1 A sheet of polyethylene terephthalate was molded using the apparatus shown in FIG. In addition, the device conditions are nozzle width 4.
00mm, the mouthpiece slit width 1#III, the cooling roller diameter aoom, and the effective length of the electrode 300M. The water vapor was heated to 150° C. and blown out from a slit with an effective length of 250#1I11 at a blowing speed of 5 m/min. The voltage applied to the electrodes was increased each time the speed of the cooling roller was increased and poor adhesion of the sheet occurred or minute spots were generated in the sheet due to air entrainment. The potential fluctuations of the roller were monitored using an oscilloscope to check for the occurrence of minute discharges.

When a sheet was manufactured in this manner, no minute discharge occurred even when the pressure was increased to 10 KV, and no minute defects were produced on the sheet. The speed at which the sheet finally began to separate from the cooling roller was 95 TrL/min.

Comparative Example 1 A sheet was manufactured in the same manner as in Example 1, except that the blowing of steam was stopped. No micro discharge occurred even when the pressure was increased to 15 KV, but the speed of the cooling roller was changed to son.
When the speed was increased to 1/min, minute defects occurred on the sheet surface due to air entrainment, and the sheet could not be used as a high quality sheet industrially.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of one apparatus that can be used in the method of the invention. 1: Mouthpiece 2: Sheet-like extrudate 2' Double combined sheet 3: Cooling roller 4: Separating roller
5: Earth wire 6: Electrode 7: High voltage power supply 8 Nislit nozzle 9: Steam heater

Claims (1)

[Claims] Extrude the molten thermoplastic polymer into a sheet from the die,
After static electricity is applied to one side of the sheet-shaped extrudate, the other side is brought into close contact with an electrically grounded moving cooling body to rapidly solidify it. A method for producing a thermoplastic polymer sheet, characterized in that water vapor is present in the atmosphere on the other side of the extrudate.