JPH0574754B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a composite tube in which the outer circumferential surface of a plastic tube is coated with a metal tube, and more specifically, it relates to a method for manufacturing a composite tube in which the outer circumferential surface of a plastic tube is coated with a metal tube. The present invention relates to a method for manufacturing a composite pipe that can be suitably used as a piping material for an ultrapure water device for cleaning electronic components such as semiconductors.

(Prior art) Generally, plastic tubes made of vinyl chloride resin, polyethylene resin, etc. are melted through an annular resin passage provided between a die ring of the extruder, a die ring of the extruder, and a mandrel. These plastic pipes are manufactured by extruding thermoplastic resin, and these plastic pipes are used as piping materials for water, sewage, etc., as well as gas supply piping materials, etc.

In addition, although these plastic pipes have excellent corrosion resistance, they have poor impact resistance, so depending on the purpose and application, the outer circumferential surface of the plastic pipe is covered with a metal pipe. Various methods for manufacturing this composite pipe have been proposed in the past.

(Problem to be solved by the invention) In recent years, technological innovation has been remarkable in the field of electronics, and with this, high performance and high quality electronic parts are required. Cleaned with equipment.

Plastic pipes have come to be used as piping materials for ultrapure water equipment, but plastic pipes obtained by conventional manufacturing methods do not have smooth inner surfaces and have minute irregularities. Additionally, there were problems such as the accumulation of impurities in the pipes, the growth of bacteria, and the adhesion of algae.

The present invention provides a method for producing a composite tube in which the inner circumferential surface is smooth and has no irregularities, and the outer circumferential surface of the tube is coated with a metal tube to impart rigidity, impact resistance, etc. be.

(Means for Solving the Problems) The present invention consists of a process for manufacturing a plastic tube and a process for covering the outer peripheral surface of the tube with a metal tube. A plastic tube is extruded and molded while a molten thermoplastic resin is passed through an annular resin passage provided between the mandrel and the inner peripheral surface of the tube by a heating device built into the mandrel.

Next, a foaming adhesive is applied to the outer peripheral surface of the plastic tube, and the plastic tube is inserted into a metal tube to foam the adhesive.

Furthermore, another method for manufacturing a composite tube involves inserting the plastic tube obtained by the above manufacturing method into a metal tube having an inner diameter slightly larger than the outer diameter of the tube, and then reducing the diameter of the metal tube. This method involves coating the inner circumferential surface of a plastic tube by bringing it into contact with the outer circumferential surface of the tube.

EMBODIMENT OF THE INVENTION Hereinafter, the specific structure of this invention is demonstrated in detail based on an Example.

(Example) FIG. 1 is a longitudinal sectional view showing the manufacturing process of the plastic tube of the present invention, in which reference numeral 1 represents a die ring and 2 represents a mandrel.

An annular resin passage through which molten resin passes is provided between the die ring 1 and the mandrel 2, and a heating device H such as a heater or a jacket through which a heating medium circulates is installed in the mandrel 2.
is provided.

A die device consisting of a die ring 1 and a mandrel 2 is provided at the tip of the extruder, and a sizing former 3 and a cooling water tank 4 are provided in front of this die device.

In the manufacturing process of the plastic tube of the present invention, when the molten thermoplastic resin extruded from the extruder passes through the resin passage between the die ring 1 and the mandrel 2 and is formed into an annular shape, the inside of the tube is Extrusion molding is performed while the peripheral surface is heated in a heating stack H.

When the inner circumferential surface of the tube passing through the resin passage is heated by the heating device H, the flow characteristics of the resin on the inner circumferential side of the tube improve, and as a result, contact with the outer circumferential surface of the mandrel 2 is performed smoothly, and as a result, the inner circumferential surface is heated. A plastic tube P with no irregularities is extruded. The outer diameter of the plastic tube P is then regulated by a sizing former 3, and then guided to a cooling water tank 4 where it is cooled and solidified, and taken by a take-up machine (not shown).

In this way, a plastic tube P with a smooth inner circumferential surface and no unevenness is obtained.

The thermoplastic resin used in the present invention is preferably a vinyl chloride resin mixed with a tin-based stabilizer, and the molten resin is extruded at a speed lower than the extrusion speed used for forming ordinary plastic tubes. By extrusion molding, the smoothness is further improved and it is possible to reduce the unevenness of the inner circumferential surface of the tube to 1μ or less.

FIG. 2 is a longitudinal sectional view of a composite tube in which the outer peripheral surface of the plastic tube is covered with a metal tube.

This composite tube is made of a plastic tube P obtained through the above manufacturing process, and a room-temperature foaming adhesive A is applied to the outer circumferential surface of the plastic tube P.
After applying the adhesive A evenly and inserting it into the metal pipe F, the adhesive A is foamed to form a plastic pipe P.
and a metal tube F. Since the outer circumferential surface of the plastic tube P is reinforced with the metal tube F, this composite tube is particularly suitable as a piping material for parts that are susceptible to external forces such as shocks.

The foamable adhesive used in this manufacturing method is preferably a two-component adhesive in which a polyurethane resin and an isocyanate resin are bonded to each other to form a polyurethane resin.

FIG. 3 is a longitudinal sectional view showing another manufacturing process of the composite pipe of the present invention.

This composite tube is produced by inserting the plastic tube obtained through the above manufacturing process into a metal tube F having an inner diameter slightly larger than the outer diameter of the tube, passing it through a forming die 5, and squeezing the metal tube F. , reduced diameter metal tube F
This is obtained by bringing the inner circumferential surface of the plastic tube P into contact with the outer circumferential surface of the plastic tube P.

In this manufacturing process, it is important to reduce the diameter of the metal tube without deforming the plastic tube, so an appropriate thickness of adhesive is applied to the outer circumferential surface of the plastic tube in advance, and then this is applied inside the metal tube. It is preferable to insert the metal tube and reduce the diameter of the metal tube.

The composite pipe thus obtained is connected sequentially through appropriate pipe joints, but after the manufacturing process of this composite pipe is completed, a flange is provided on the outer periphery of the end of the metal pipe, and the flange surface is If the protruding inner layer plastic tube is covered with a flange process,
This is preferable because the flange connection can be easily and reliably performed.

(Operations and Effects of the Invention) When manufacturing a plastic tube by extruding molten resin from a resin passage between a die ring and a mandrel, the present invention uses a heating device built into the mandrel to heat the inner peripheral surface of the tube. Since extrusion molding is performed while heating, the flow characteristics of the molten resin on the inner circumferential side are improved and contact with the outer circumferential surface of the mandrel is made smoothly, resulting in a plastic tube with an extremely smooth inner circumferential surface and no minute irregularities. can get. In the present invention, this plastic tube is inserted into a metal tube and the plastic tube is coated without deforming the tube, so that a tube not only has a smooth inner circumferential surface but also has excellent rigidity and impact resistance.

Moreover, manufacturing this composite tube requires only a device for applying adhesive to the outer circumferential surface of the plastic tube or a forming die to reduce the diameter of the metal tube, and requires particularly large-scale equipment. Since this is not necessary, manufacturing is extremely simple and quick, and product costs can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing the manufacturing process of the plastic tube of the present invention, FIG. 2 is a vertical cross-sectional view of the composite tube obtained by the present invention, and FIG. 3 is another manufacturing process of the composite tube of the present invention. It is a longitudinal cross-sectional view showing a process. 1...Die ring, 2...Mandrel, 3...Sizing former, 4...Cooling water tank, 5...Forming die, P
...Plastic pipe, F...Metal pipe.

Claims (1)

[Claims] 1. An annular resin passage is provided between a die ring and a mandrel, and when extruding a plastic tube by passing a molten thermoplastic resin through the resin passage, a heating device is provided on the mandrel. A plastic tube is extruded while heating the inner circumferential surface of the tube formed into an annular shape using the built-in heating device. Next, a foaming adhesive is applied to the outer circumferential surface of the plastic tube, and then this plastic tube is bonded to metal. A method for manufacturing a composite tube, characterized in that the adhesive is inserted into the tube, and the adhesive is foamed to fill the space between the plastic tube and the metal tube. 2. An annular resin passage is provided between the die ring and the mandrel, and when a molten thermoplastic resin is passed through the resin passage to extrude and mold a plastic tube, a heating device is built into the mandrel to heat the thermoplastic resin. A plastic tube is extruded while heating the inner peripheral surface of the tube formed into an annular shape using a device, and then the plastic tube is inserted into a metal tube having an inner diameter slightly larger than the outer diameter of the tube. A method for manufacturing a composite tube characterized by reducing the diameter and bringing the inner circumferential surface into contact with the outer circumferential surface of a plastic tube.