JPS645525B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a synthetic resin pipe (inner pipe) suitable for water supply and drainage pipes, etc., such as a hard vinyl chloride pipe, whose outer peripheral surface is coated with a fire-resistant inorganic material (outer layer pipe) to prevent ignition in the event of a fire. The present invention relates to a fire-resistant pipe joint suitable for composite pipes, which prevents fire from spreading to adjacent rooms even if the fire ignites and travels inside the pipe, especially when used in a building.

The most technically important thing about this type of composite pipe and its pipe fittings is that the synthetic resin pipes and pipe fittings, which have a significantly large coefficient of thermal expansion, are coated with an inorganic material whose coefficient of thermal expansion is relatively small. This is to prevent harmful cracks from occurring due to the application of heat generated due to thermal expansion of the synthetic resin during flowing down, etc., which presses the coating layer of the outer pipe from the inside.

The simplest method for this is to provide a certain gap between the inner tube and the outer tube, and for this purpose, the outer tube and the inner tube are separately manufactured precisely to form a certain gap. In addition to the method of combining the above-mentioned synthetic resin foam sheet with a synthetic resin band or cushioning synthetic resin foam, there is also a method of wrapping the synthetic resin foam sheet around the outer circumference of the inner tube to form a rear outer layer tube. .

However, since the pipe joints originally have extremely diverse shapes and come in a wide variety of sizes, it is not possible to create a structure in which a void is provided or a cushion material is interposed in the void as described above. The manufacturing process is complicated, and there are many problems as an industrial manufacturing method.

Furthermore, the method of wrapping the cushion material around the outer circumference of the inner tube in advance is not suitable for uniformly fitting pipe joints with complicated shapes due to the elasticity peculiar to the cushion material.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fire-resistant pipe joint that eliminates the above-mentioned drawbacks and is free from the risk of cracking due to thermal stress. The inventors of the present invention have carried out extensive research in accordance with these objectives, and as a result, they have applied a thin layer of paper, film, cloth, etc. that swells in water only to the outer circumferential surface of the socket of a synthetic resin pipe joint. The outer peripheral surface part and the remaining outer peripheral surface part are coated and molded with a kneaded material whose main components are a hydraulic inorganic material and water, and paper,
It was discovered that if a thin layered body such as a film or cloth is swollen and gelled by the water of the above-mentioned water-kneaded product and allowed to cure and harden, it can withstand thermal stress such as when hot water of 90°C or higher is flowed down, and the present invention was completed. I came to the conclusion.

As mentioned above, unlike the conventional method in which a gap is provided throughout the inner pipe and the outer pipe, or a cushion material is used as an intervening material, the present invention is surprising in that the treatment of the swellable material only needs to be done on the outer peripheral surface of the socket. Although it is difficult at this stage to explain these results theoretically,
This can be understood in conjunction with the observation that cracks caused by thermal stress occur in most cases from the ends of the socket, and then grow toward the center and become wider.

Examples of water-swellable materials for thin layer bodies in the present invention include the following.

Starch and starch derivatives, CMC, MC, HEC,
Water-soluble cellulose derivatives such as HPC, proteins such as gelatin and casein, tannin, lignin, alginic acid, gum arabic, polyvinyl alcohol, polyethylene oxide, polypropylene oxide, polyacrylic acid, polymethacrylic acid, water-soluble polyester, polyepoxy compounds, ketones These include formaldehyde resin, polyvinylpyrrolidone, polyamide polyelectrolyte, urea formaldehyde resin, melamine formaldehyde resin, and phenol formaldehyde resin.

Of course, it will be clear from the following description that the structure of the present invention is not limited to the materials exemplified. It is also possible to partially use non-swellable materials in water to construct the shape of a thin layer such as paper, film or cloth.

In the present invention, the fire-resistant hydraulic inorganic materials include, for example, Portland cement, silica cement, blast furnace cement, fly ash cement, alumina cement, various ettringite cements, and various plasters. Asbestos, rock wool, glass fiber, wood wool, synthetic fiber, natural fiber, steel fiber, copper wire, mica, perlite, vermiculite, calcined vermiculite, volcanic limestone, silica sand for the purpose of improving properties, reducing weight, increasing weight, etc. It is also effective to add aluminum hydroxide, calcium carbonate, calcium silicate, etc.

In the present invention, the effect of interposing a water-swellable thin layer such as paper, film, or cloth is that water is absorbed from the mixture of water and the hydraulic inorganic material coated on the outer peripheral surface, and the water swells. The aim is to maintain a gel state that is thicker than the thickness of the thin layer body until the hydraulic inorganic material hardens and forms a structure. After the hydraulic inorganic material hardens, the above gel releases water and contracts during the drying process of this outer layer tube.
A certain gap will be formed between the outer tube and the inner tube. Therefore, the thickness of the thin layer of paper, film, cloth, etc. used in the present invention may be selected in accordance with the degree of swelling thereof, taking into account the necessary voids.

Examples of methods of coating the outer circumferential surface of a synthetic resin pipe joint with a thin layer of paper, film, cloth, etc. wrapped around the outer circumferential surface of the socket and bonded or fixed with a mixture of a hydraulic inorganic material and water include, for example. The above synthetic resin pipe joint is set in advance in a mold that can be divided into upper and lower parts and has an inner shape corresponding to the outer shape of the outer layer pipe, and the slurry of the hydraulic inorganic material is cast between the mold and the pipe joint. There are ways to include it. The curing method for the hydraulic inorganic material may be either room temperature curing or heating curing, and it is desirable to maintain it in a humid air condition during this time.

Pipe fittings manufactured according to the present invention not only do not have any adverse effects on the coating layer, which is the outer layer pipe, due to thermal stress when high-temperature fluid passes through the piping, but also do not damage the outer circumferential surface of the socket during manufacture. It has the advantage that only simple processing is required.

The present invention will be explained in more detail below with reference to Examples.

Example 1 A layer of polyvinyl alcohol film with a thickness of 50 μm was wrapped around the outer peripheral surface of each socket of a hard vinyl chloride pipe fitting (nominal diameter 100) having openings on three sides, and the ends were secured with small pieces of adhesive tape. Next, each end of the three sides was fixed using a holder in a mold made of chloroprene rubber that could be separated into upper and lower parts, and 60 parts by weight of Portland cement and silica powder were poured into the mold through injection holes provided at the bottom of the mold. 12 parts by weight, 3 parts by weight of expansive admixture (quicklime), 5 parts by weight of lightweight aggregate,
20 parts by weight of chrysotile asbestos and 0.1 part by weight of a thickener (methyl cellulose) were blended in advance, then an appropriate amount of water was added and kneaded.The water mixture was press-fitted and filled, then placed in a curing chamber and heated to 50℃. Raise the temperature and hold for 5 hours. After being left to cool naturally, it was removed from the mold, and after 3 weeks of air-drying, it was connected to a hard vinyl chloride straight pipe and piped to a temperature of 90°C.
Boiling water at ℃ was allowed to flow down for 20 minutes at a rate of 30/min. During and after this test, no cracking due to thermal stress was observed in the fire-resistant pipe joint of the present invention.

Example 2 A 90° elbow (nominal diameter 75) was used as a pipe joint, and a layer of paper (120 g/m ² ) made of 20% pulp and 80% CMC fiber was spread around the outer peripheral surface of the socket, and the ends were covered with adhesive tape. A fire-resistant pipe joint was manufactured using the same method and operation as in Example 1, except for fixing with small pieces.

This pipe joint was subjected to the same hot water flow test as in Example 1, but no cracking due to thermal stress was observed during or after the test.

Claims (1)

[Claims] 1. In a method for manufacturing a fire-resistant pipe joint in which the outer periphery of a synthetic resin pipe joint is coated with a fire-resistant hydraulic inorganic material, water-swellable paper, film, or cloth is coated on the outer peripheral surface of the socket of the synthetic resin pipe joint. A method for producing a fire-resistant pipe joint, comprising: wrapping a thin layer of the above-mentioned fire-resistant hydraulic inorganic material, and then coating the water-kneaded material of the above-mentioned fire-resistant hydraulic inorganic material and curing and curing and drying.