JPS62288025A - Control of extruding temprature in synthetic resin extrusion molder - Google Patents

Abstract

PURPOSE:To prevent the reduction of the electrical insulation properties of a coating layer due to mixing burn marks into the coating layer, by a method wherein the temperature of extruding resin flowing through a dice head is detected by an optical fiber type infrared ray thermometer thereby the temperature of a cylinder or the dice head is controlled based on a detected temperature. CONSTITUTION:A band heater 6 is wound around a cylinder 1 and a dice head 2, and heats the cylinder 1 and the dice head 2 by heat generated by conduction. A fine hole is bored on the dice head 2 and heat resistant glass 8 is filled so as to form the inner surface of the dice head 2. An optical fiber type infrared ray thermometer 7 is inserted into the hole from the outside thereof. The thermometer 7 is connected to a temperature control mechanism and the temperature control mechanism determines a condition based on an information detected by the thermometer 7 so that the cylinder head 1 and the dice head 2 are heated to a predetermined temperature while the same mechanism is operated automatically and heats the band heater 6. The cylinder head 1 and the dice head 2 are maintained respectively at predetermined temperatures by the effect of the temperature control mechanism which copes sufficiently. With the temperature change in the atmosphere.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Application of the Invention 1 The present invention relates to a method for controlling extrusion temperature in an extrusion molding machine for synthetic resins such as thermoplastic resins, and in particular to a method for controlling extrusion temperature in an extrusion molding machine. The present invention relates to a method for measuring the temperature at an extrusion site using an optical fiber type infrared thermometer and controlling the temperature accordingly.

[Prior art] Extrusion molding of thermoplastic resins such as polyethylene and polyvinyl chloride resin involves rotating an extrusion screw placed in the cylinder of an extrusion molding machine to convey the supplied raw material resin while pressurizing it. For example, a band-shaped electric heater (band heater) wrapped around the die head is energized to generate heat, thereby heating the cylinder or the die head, which heats and softens the raw material resin in the heated cylinder, which is then heated to the die head. This is done by extruding it from a mold and molding it into a shape that corresponds to the shape of the die head. Conventionally, the temperature of this heater has been controlled by setting the temperature in advance.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, the pressure of the resin increases in the cylinder or die head of the extruder due to pressure by the extrusion screw, and the set temperature for the extruder and the melting rate of the resin are They do not necessarily match, and the resin temperature usually tends to be higher than this set temperature. Therefore, for example, when extruding polyethylene containing a crosslinking agent, if the resin is extruded at a temperature exceeding the reaction temperature of the crosslinking agent, the crosslinking reaction will proceed during extrusion, resulting in discoloration. For example, when this extrusion molded product is a coating layer of a high-voltage cable, this discoloration is mixed into the coating layer and reduces the electrical insulation properties of the coating layer. In this way, in the case of extrusion molding for a cable coating layer, it is necessary to strictly control the temperature of the raw resin in the cylinder.

[Means and operations for solving the problems] The present invention has been made to solve the problems in the prior art described above, and it is possible to achieve true extrusion of extruded resin into a synthetic resin extrusion molding machine. The purpose is to measure and control the temperature and maintain a stable extrusion temperature.

That is, the present invention is characterized in that the temperature of the extruded resin flowing through the die head section 33 of the synthetic resin extrusion molding machine is detected by an optical fiber type infrared thermometer, and the drying temperature of the cylinder or the die head is thereby controlled. This is a method for controlling extrusion temperature in a synthetic resin extrusion molding machine.

The present invention will be explained in detail below.

First, the outline of the synthetic resin extrusion molding machine used in the present invention will be explained. An extrusion molding machine basically has a cylindrical shape and a molded container, an "extrusion screw" placed inside the cylinder, a "dice head" attached to the tip of the cylinder, and a "dice head" located behind the cylinder. It is arranged in communication with the cylinder and consists of a "hopper" for supplying the resin raw material, a rotation drive mechanism for rotating the extrusion screw, a heating device for heating the cylinder, and its temperature control I1 mechanism. In an extrusion molding machine, an extrusion screw is placed inside the cylinder so as to be rotated and covered by the driving force of a rotational drive mechanism.Usually, the inside of the cylinder has a shape that tapers slightly toward its tip. Also, the pitch of the extrusion screw is formed so that it gradually becomes smaller toward the tip.As a result, the gap formed between the inner wall of the cylinder and the valley of the extrusion screw becomes smaller toward the tip, so that the pitch of the extrusion screw becomes smaller as it goes toward the tip. Then, as the extrusion screw rotates, the resin raw material is conveyed toward the tip and is pressurized as it moves toward the tip.Furthermore, the cylinder is equipped with a heating device to heat it and its temperature control III mechanism. The resin raw materials are heated to a necessary and sufficient temperature by their operation.

Furthermore, a die head is attached to the tip of the cylinder, which serves as a mold for extruding and molding the resin raw material that has been plasticized by heating.

Basically, an extrusion molding machine configured as described above first operates the extrusion screw rotation drive mechanism to rotate the extrusion screw at a predetermined speed, and also energizes the heating device attached to the cylinder. The temperature control mechanism is activated to heat the cylinder and maintain it at a temperature suitable for molding the synthetic resin. Usually, synthetic resin raw materials that have been primarily formed into pellets are continuously fed from a hopper. The raw material pellet is gradually moved (transported) inside the cylinder toward the tip as the extrusion screw rotates. As mentioned above, the cylinder is heated to an appropriate temperature for plasticizing the resin, and as the extrusion screw rotates, the raw material pellets are heated as they are conveyed, plasticize and flow at the tip of the cylinder, and then pass through the die. It is pushed out from the hole in the head. At this time, the resin is molded into a shape that corresponds to the shape of the hole in the die head.

The present invention is particularly characterized by a heating control mechanism associated with this heating device. That is, the temperature of the extruded resin flowing through the die head of the above-mentioned synthetic resin extrusion molding machine is detected by an optical fiber type infrared thermometer, and the temperature of the cylinder or the die head is thereby controlled.

[Optical fiber type infrared thermometer] consists of an optical fiber that converges and transmits the infrared energy emitted from the object to be measured (extruded resin), and an infrared detector that converts this infrared energy into an electrical signal and extracts it as a temperature signal. Become.

This optical fiber type infrared thermometer is linked to its temperature control mechanism, and while heating the cylinder or die head of the extrusion molding machine, it maintains them at a predetermined humidity by the action on the side of the temperature controller. To maintain a predetermined temperature by sufficiently faithfully and quickly responding to temperature changes. This temperature control mechanism is basically taken out by an infrared temperature controller, feeds back a temperature signal to the heating system temperature controller of the extrusion molding machine, compares it with a set temperature, and turns on and off the heating power source. By employing PID control, Zyristor control, etc. in the control system, it is possible to improve the responsiveness of the heating system.

[Example] Hereinafter, the present invention will be specifically described based on drawings showing one example thereof.

FIG. 1 is a sectional view schematically showing the tip of a cylinder of an extrusion molding machine for thermoplastic resin in which the method of the present invention is carried out. In the figure, 1 is a cylinder (tip part), 2 is a die head, 3 is an extrusion screw (tip part), 4 is a screen mesh, 5 is a breaker plate, 6 is a band heater, 7 is an optical fiber type infrared temperature A total of 8 is heat-resistant glass.

As already explained in detail, the screen mesh 4 and the breaker plate 5 that support it are stacked at the tip of the cylinder 1, and the die head 2 is stacked and attached to the cylinder 1 so as to press it. ing. An extrusion screw 3 is rotatably disposed inside the cylinder 1 and is rotated by the operation of an extrusion cylinder rotation drive mechanism (not shown). A band heater 6 is wound around the outside of the cylinder 1 and the die head 2, and when energized, generates heat to heat the cylinder 1 and the die head 2. In this figure, the die head 2 has a hole formed in a small portion thereof, and a heat-resistant glass 8 is filled so as to form the inner surface of the die head 2. An optical fiber type infrared thermometer 7, which is the most characteristic feature of the present invention, is inserted into the hole from the outside. The thermometer 7 is connected to a temperature control mechanism (not shown), and the temperature control tII mechanism heats the cylinder 1 and the die head 2 to a predetermined temperature based on the information detected by the thermometer 7. ) The conditions are determined and the band heater 6 is heated automatically.

[Effect of the invention 1 According to the present invention, the temperature of the extruded resin flowing through the die head portion of the extrusion molding machine is directly detected by an optical fiber type infrared thermometer, and the temperature of the cylinder or the die head is thereby controlled. Therefore, conventional problems can be eliminated.

An extremely excellent effect can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing the tip portion of an extrusion molding machine for thermoplastic resin according to an embodiment of the method of the present invention. In the figure, 1. Niji cylinder (tip part), 2: die head, 3: extrusion screw (tip part), 4. Nijiri mesh, 5: book cup.
G, 6: Band He -
7: Optical fiber type infrared ray 4.8: Resistance
Thermal glass.

Claims (1)

[Claims] Extrusion in a synthetic resin extrusion molding machine, characterized in that the temperature of the extruded resin flowing through a die head in the synthetic resin extrusion molding machine is detected by an optical fiber type infrared thermometer, and the temperature of the cylinder or the die head is controlled thereby. How to control temperature.