JP4350633B2 - Cooling water circulation device for resin tube manufacturing equipment - Google Patents

Description

  The present invention relates to the manufacture of resin tubes mainly used in automobile fuel piping, and more particularly to a method of manufacturing resin tubes by extrusion molding and a cooling water circulation device of a resin tube manufacturing apparatus.

  This type of resin tube is manufactured using an extrusion molding machine using a thermoplastic resin as a material, and the manufacturing process includes an extrusion process, a cooling process, a take-up process, a cutting process, and the like. In the extrusion process, the molten resin is extruded into a tube shape from the mold, and in the cooling process, the extruded resin is rapidly cooled in a vacuum water tank or a cooling water tank in order to shape the tube into the tube.

  In the case of a resin tube used for fuel piping, if the thermoplastic resin of the material is polyamide, the resin temperature immediately after extrusion is 240 to 280 ° C. Since the shape of the thermoplastic resin does not harden when the temperature is high, the thermoplastic resin is conventionally quenched in cold water at 10 ° C. to 20 ° C. in a cooling water tank or a vacuum water tank. This is because it has been said that the rapid cooling with the cold water has the advantage that the heat exchange efficiency between the extruded resin and water is good, and the length of the water tank used in the production line is shortened to save space.

  However, in the conventional cooling process, since the resin tube is rapidly cooled by being exposed to cold water of 20 ° C. or less, there is a problem that stress and strain remain in the resin tube, and mechanical properties are significantly reduced. The efficiency of the production line was given priority, and the mechanical properties of the tube itself were improved by improving the types of materials and the multilayer structure.

  Further, the object of the present invention is to control the temperature at a predetermined temperature in order to solidify the shape of the tube with water kept at a predetermined temperature or higher, instead of cooling the resin tube immediately after extrusion with cold water. The object is to provide a cooling water circulation device for circulating water.

In order to achieve the above object, the present invention is an apparatus for circulating cooling water to a cooling water tank used in a resin tube manufacturing apparatus for extruding a molten thermoplastic resin from an extruder to form a tube. A water tank for cooling the extruded resin tube with cooling water, a preliminary water tank for storing cooling water returning from the water tank, and a water temperature adjusting device for keeping the cooling water in the preliminary water tank and supplying the water to the water tank. The water temperature adjusting device is configured to preliminarily set the temperature of the cooling water in the auxiliary water tank by controlling the heater and the heat retaining water tank for storing the cooling water overflowed from the auxiliary water tank, the heater means for heating the cooling water in the heat insulating water tank Heater control means for maintaining the temperature, and a pump for supplying cooling water kept in the preliminary water tank to the water tank.

  According to the present invention, instead of cooling the resin tube immediately after extrusion with cold water, the shape of the tube is hardened with water kept at a predetermined temperature or higher, so that stress remains in the surface layer portion of the tube. Therefore, the resin tube can be molded without deteriorating the mechanical properties.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a configuration diagram of a cooling water circulation device used for carrying out the method for producing a resin tube according to the present invention.

  In FIG. 1, reference numeral 10 indicates a vacuum water tank, 12 indicates a preliminary water tank, and 14 indicates a water temperature adjusting device. The vacuum water tank 10, the preliminary water tank 12, and the water temperature adjusting device 14 are connected by piping so that the cooling water circulates.

  The vacuum water tank 10 is a vertically long sealed container of about 3 to 4 meters. Cooling water is stored inside the container and is connected to the vacuum pump 13 to maintain a predetermined negative pressure. A take-off device (not shown) is disposed downstream of the vacuum water tank 10. When the resin extruded from the extrusion die 15 of the extruder is introduced into the drawing device (not shown), heat exchange is performed with the cooling water while passing through the inside of the vacuum water tank 10, and the tube 30 having a predetermined diameter is formed. It is shaped and picked up by the pick-up device.

  Cooling water that has overflowed from the vacuum water tank 10 is introduced into the spare water tank 12 and is temporarily stored in the spare water tank 12. A water temperature adjusting device 14 that always keeps the cooling water at a set temperature is provided between the auxiliary water tank 12 and the vacuum water tank 10, and the cooling water kept at a constant temperature is supplied from the water temperature adjusting device 14 to the vacuum water tank 10. It has become.

  The water temperature adjusting device 14 includes a heat retaining tank 16, a pump 17, an electric heater 18, a temperature detector 19, and a controller 20. A temperature detector 19 using a thermo stud or the like is provided at the inlet of the heat insulation tank 16. It is detected by the thermo stud that the temperature of the cooling water returning from the vacuum water tank 10 has fallen below the set temperature. At this time, the controller 20 operates the electric heater 18 to heat the water accumulated in the heat insulating tank 16. And if the temperature of the cooling water which returns from the vacuum water tank 10 reaches preset temperature, the electric heater 18 will stop heating. The cooling water whose temperature has been adjusted in the heat insulating tank 16 in this manner is discharged from the pump 17 and sent to the vacuum water tank 10.

Next, the manufacturing method of the resin tube implemented using the above cooling water circulation apparatuses is demonstrated.
In this embodiment, a tube for a fuel pipe of an automobile having a resin layer made of polyamide resin as an outer layer is formed.

  In the vacuum water tank 10, the pressure inside the tank is kept negative by the suction action of the vacuum pump 13, and the cooling water temperature is kept at a cooling water temperature exceeding 53 ° C. which is the glass transition point of the polyamide resin. Preferably, 60 degreeC or more is good. Then, the polyamide resin is plasticized by an extruder, extruded from the extrusion die 15, and passed through the vacuum water tank 10.

  The polyamide resin immediately after being extruded becomes a high temperature of 240 to 280 ° C. and is in a molten state. In the process of moving inside the vacuum water tank 10, heat exchange proceeds with the cooling water, and the resin temperature of the resin tube 30 gradually decreases. In the vacuum water tank 10, the cooling water whose temperature is controlled by the above-described water temperature adjusting device 14 circulates, and the water temperature is maintained so as not to drop below 53 ° C. of the glass transition point.

  During this time, the resin tube 30 moving inside the vacuum water tank 10 is solidified as the resin temperature decreases, and at the same time, the shape is determined while a force is applied in the direction of expanding the diameter from the inside by the action of negative pressure.

  As described above, since the shape of the resin tube 30 is determined without being rapidly cooled as in the prior art, the resin tube 30 is molded without causing stress to remain on the surface layer portion of the tube and without reducing the mechanical properties. Can do.

  Next, FIG. 2 shows an embodiment in which an open bath type cooling water tank 22 is used instead of the vacuum water tank 10 of FIG. 1 as a water tank for cooling the resin tube 30. Except this cooling water tank 22, it is the same as the structure of the cooling water circulation apparatus of FIG.

  The vacuum water tank 10 of FIG. 1 uses a water tank of a closed container, whereas the main body of the open bath type cooling water tank 22 is a vertically long box-shaped container whose top is open. As in FIG. 1, the cooling water tank 22 is supplied with cooling water kept at a set temperature or higher from the water temperature adjusting device 14.

  Even when such an open bath type cooling water tank 10 is used, the temperature of the resin tube 30 is lowered without rapidly cooling while adjusting the temperature of the cooling water so as not to fall below the glass transition point of the resin material of the resin tube 30. Therefore, the mechanical properties are not deteriorated.

The schematic diagram which shows one Embodiment of the cooling water circulation apparatus used for the resin tube manufacture by this invention. The schematic diagram which shows other embodiment of the cooling water circulation apparatus used for the resin tube manufacture by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Vacuum water tank 12 Preliminary water tank 13 Vacuum pump 14 Water temperature adjusting device 15 Extrusion die 16 Heat retention tank 17 Pump 18 Electric heater 19 Temperature detector 20 Controller 22 Open bath type cooling water tank 30 Resin tube

Claims (4)

An apparatus for circulating cooling water to a cooling water tank used in a resin tube manufacturing apparatus for extruding a molten thermoplastic resin from an extruder to form a tube,
A water tank for cooling the extruded resin tube with cooling water;
A preliminary water tank for storing cooling water returning from the water tank;
A water temperature adjusting device for keeping the cooling water in the preliminary water tank and then supplying it to the water tank ;
The water temperature adjusting device is
A heat retaining water tank for storing cooling water overflowed from the preliminary water tank;
Heater means for heating cooling water in the heat retaining water tank;
Heater control means for controlling the heater and maintaining the temperature of the cooling water in the preliminary water tank at a preset temperature;
A pump for supplying cooling water kept warm in the preliminary water tank to the water tank;
A cooling water circulator for a resin tube manufacturing apparatus.   In the said water tank, the temperature of cooling water is maintained by the said water temperature adjustment apparatus at the temperature which exceeds the temperature of the glass transition point of resin of material, The cooling of the manufacturing apparatus of the resin tube of Claim 1 characterized by the above-mentioned. Water circulation device.   The cooling water circulating apparatus for a resin tube manufacturing apparatus according to claim 1, wherein a vacuum water tank is used as the water tank.   The cooling water circulating apparatus for a resin tube manufacturing apparatus according to claim 1, wherein an open bath type cooling water tank is used as the water tank.

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