JPH0479714B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing water pipes made of lead pipes.

[Conventional technology and its problems]

Materials for water pipes include cast iron pipes, steel pipes, hard vinyl chloride pipes, lead pipes, etc. In addition, copper pipes are used for special purposes. This copper tube is not generally used because it is expensive.

Cast iron pipes are used for main lines, but because it is difficult to manufacture small-diameter pipes, they are not used for piping after the main line. Steel pipes are often used for trunk lines that are not very thick or where high pressure is involved. Rigid PVC pipes have become widely used as the weather resistance of the material PVC has been improved, but it is difficult to use them outdoors where they are exposed to harsh natural environments.
There are problems such as cracks, bent pipes require elbows, and connections require straight connection sleeves, branch connection sleeves, etc., which requires a lot of construction time. Since it cannot be bent or plastically changed, it is difficult to match the dimensions of the piping to the dimensions of the building, which poses a problem that requires the skill of the piping operator.

On the other hand, lead pipes are easy to plastically deform and have a low melting temperature, so they can be easily bent, connected (branched,
Multi-branching and different diameter pipe connections) can be easily performed.

As described above, lead pipes have been widely used for a long time because of the ease of construction and because the lead oxide produced on the inner surface of the pipe is chemically extremely stable.

However, even if the inner surface is coated with lead oxide, corrosion may not be completely prevented, and there are also concerns as to whether lead elution is completely prevented.

In response to these concerns, some stainless steel pipes have begun to be used in place of lead pipes, but stainless steel contains heavy metals such as chrome, albeit in small amounts, so it may not be safe to part with them. Furthermore, the construction is more difficult than that of vinyl chloride pipes, and each member such as the elbow, T-shaped sleeve, and linear connection sleeve is expensive.

In view of the above points, the inventor of the present application believes that lead pipes are superior in various respects because of their good workability, and that the above concerns can be resolved by forming a resin coating on the inner surface of the pipes.

Therefore, an object of the present invention is to provide a method for manufacturing a water pipe made of lead pipe whose inner surface is coated with resin.

[Means to solve the problem]

In order to achieve the above object, the present invention includes:
After grinding the inner surface of the lead pipe, a thermoadhesive resin is injected into the lead pipe, and after holding the lead pipe at a specified temperature for a predetermined period of time, the resin inside the lead pipe is extracted to form a resin coating layer on the inner surface of the lead pipe. I made it.

After grinding the inner surface of the lead pipe, the lead pipe may be heated to a predetermined temperature, a thermoadhesive resin may be injected into the lead pipe, held for a predetermined time, and then the resin inside the lead pipe may be extracted.

Further, the resin inside the lead pipe is preferably removed by passing a ball having a diameter smaller than the inner diameter of the lead pipe into the lead pipe using air pressure.

The predetermined temperature is appropriately determined depending on the film-forming temperature of the resin used, and the predetermined time is appropriately determined in consideration of the film-forming time and the like.

The internal surface grinding is performed using a sandblasting machine or the like using sand grains of silica sand, alumina, or the like. In this sandblasting, it is preferable that the lead pipe be in a coiled shape, since the lead pipe cannot be ground well if it is straight.

The above resin has good flexibility and can be coated without an organic solvent.

[Effect]

During the above manufacturing process, the inner surface of the lead pipe is ground, so the lead oxide layer is removed and a resin coating layer is formed on it, so there is no peeling of the resin coating layer. Therefore, corrosion of the inner surface of the tube is prevented, and elution of lead is also completely prevented.

〔Example〕

In this example, the water pipe A shown in Fig. 5 is manufactured. In the figure, 1 is a lead pipe, 2 is a resin composition a (Mitsui Petrochemical Industries, Ltd.) mainly composed of polyethylene that has good adhesion to lead. Manufactured by Co., Ltd.: Product name:
Chemipearl, manufactured by Seitetsu Kagaku Kogyo Co., Ltd.: Product name:
The outer surface coating layer 3 of Seichsen, etc.) is an inner surface coating layer made of the same resin composition a as the outer surface coating layer 2.

The lead pipe 1 is manufactured by an extrusion method, and has an outer diameter of:
It is 28.4 mm, inner diameter: 20 mm, wall thickness: 4.2 mm, and is wound around drum D. The drum D is set on the supply stand 10 shown in FIG.

Lead pipe 1 drawn out from supply stand 10
As shown in FIG. 1, the pipe passes through a guide roller 11 and a triclean cleaning tank 12, where oil and fat on the surface of the lead pipe 1 is washed away, and then passes through a drying zone 13. A suction pipe (not shown) is connected to this drying zone 13, which condenses trichlorene through a condenser, and further passes through an activated carbon adsorption tank (not shown) before releasing the outside air.

The washed and dried lead pipe 1 passes through a preheating zone 14 and then an extrusion molding machine 15, during which a plastic coating layer 2 with a thickness of 0.5 mm is applied to the outer peripheral surface of the lead pipe 1, a cooling water tank 16, and a take-off machine 17. The film is then wound onto a winding drum 18.

A sandblasting machine was connected to one end of the rolled lead pipe 1 (300m), and 1Kg of silica sand with a maximum particle size of 30 mesh was put into the machine to give sufficient rotational energy, and then the silica sand was 3Kgw/cm ² The residual silica sand is passed through the lead pipe 1 by the air pressure of , the inner surface of the lead pipe 1 is ground, and residual silica sand is completely expelled from the lead pipe 1.

Next, the entire lead pipe 1 is preheated in a preheating furnace to a temperature of about 50°C, and as shown in FIG.
Inject the liquid while pushing it up towards the pipe port 1b where the level is higher. As shown in FIG. 3, in the case of the lead pipe 1 wound around a drum, a resin tank 19 is connected to the pipe opening 1a at the beginning of the winding, and a vacuum source is connected to the pipe opening 1b at the end of the winding via a gas-liquid separation chamber 20. Following step 21, resin a is injected. The lead pipe 1 may be heated after injecting the resin a.

After injecting and keeping the condition for 5 minutes,
As shown in FIG. 4, a throttle valve 22 is installed at the pipe port 1b.
A piston ball 23 having a diameter smaller than the inner surface of the lead pipe 1 by the thickness of the coating layer 3 is moved by air pressure to the pipe port 1a with a low level or the pipe port 1 at the beginning of drum winding.
When the resin a is extracted while passing through the lead pipe 1 from the resin a, the thickness of the coating layer 3 becomes uniform. After this,
Further, by holding at 50° C. for 1 hour, a water pipe A made of a lead pipe with a plastic coat on the inside and having a coating layer 3 (average thickness 0.3 mm) is obtained.

The water-based emulsion resin a extracted above is used to coat the inner surface of the lead pipe 1.

Furthermore, the size, preheating temperature, holding time, extraction speed, composition of resin a, etc. in the above examples are merely examples and are not limited to these, and may be adjusted to suit the environmental conditions in order to obtain the desired effects of the present invention. It may be changed as appropriate.

〔Effect of the invention〕

Since the present invention manufactures a lead water pipe with the above-described structure, it is possible to obtain a lead water pipe with no internal corrosion and no lead elution.

[Brief explanation of the drawing]

1 to 4 are explanatory diagrams of each embodiment of the water pipe manufacturing method according to the present invention, and FIG. 5 is a sectional view of the manufacturing example. DESCRIPTION OF SYMBOLS 1... Lead pipe, 2... External coating layer, 3... Inner coating layer (resin coating layer), 19... Resin tank, 20... Gas-liquid separation chamber, 21... Vacuum source, 22... Throttle valve, 23... Piston ball. a...Resin.

Claims (1)

[Claims] 1. After grinding the inner surface of the lead pipe, a thermoadhesive resin is injected into the lead pipe, the lead pipe is held at a predetermined temperature for a predetermined period of time, and then the resin inside the lead pipe is extracted and the inner surface of the lead pipe is injected. A method for manufacturing a water pipe made of lead pipe, characterized by forming a resin coating layer. 2 After grinding the inner surface of the lead pipe, heat the lead pipe to a predetermined temperature, inject a thermoadhesive resin into the lead pipe and hold it for a predetermined time, then extract the resin inside the lead pipe and apply a resin coating layer to the inner surface of the lead pipe. A method for producing a water pipe made of lead pipe, characterized by forming a water pipe. 3. The manufacturing method according to claim 1 or 2, wherein the resin inside the lead pipe is removed by passing a ball having a diameter smaller than the inner diameter of the lead pipe through the lead pipe using air pressure. How to manufacture water pipes.