JPS5845177A - Manufacture of multi-layer tublar structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a synthetic resin pipe, such as a hard vinyl chloride pipe, which is suitable for water supply and drainage pipes installed indoors, particularly through a plurality of connected compartments, and the outer peripheral surface thereof is made of a hydraulic inorganic material. This relates to multilayer pipes that are coated to provide fire resistance and prevent the spread of fire to other compartments through hard vinyl chloride pipes in the event of a fire.

Traditionally, synthetic resin pipes such as hard vinyl chloride pipes have been widely used as water supply and drainage pipes for buildings due to their ease of construction and low cost. Because they are usually flammable, they are often unsuitable for water supply and drainage applications because in the event of a fire, the fire can spread to adjacent rooms or upper floors, and often generate toxic gases, increasing damage.

On the other hand, metal pipes are sometimes used due to their fire resistance and toughness, but they are also heavy, difficult to cut, etc., and are usually expensive, as well as the fact that rust and scale build up on the inside, resulting in poor water flow. There are drawbacks such as a decrease in the temperature and the occurrence of dew condensation on the outer circumferential surface of the tube.

Therefore, a multilayer pipe has been proposed that combines an inner pipe made of a synthetic resin pipe such as a hard vinyl chloride pipe with a fire-resistant outer pipe made of an inorganic material such as cement. It has become rapidly popular in recent years due to its excellent performance in preventing condensation.

However, the technical difficulty in manufacturing this type of multilayer tube is that the inner tube is a synthetic resin tube with significantly large thermal expansion.
Since the outer layer tube is made of an inorganic material with relatively low thermal expansion, this prevents harmful cracks from occurring in the outer layer tube due to thermal stress caused by the expansion of the synthetic resin tube, such as when hot water flows down. It is. The simplest method for this is to provide a certain gap between the inner tube and the outer tube, but one way to create and maintain this gap is to create a gap that has a precise diameter for each tube. A method is used in which the manufactured outer layer tube and inner tube are combined and two or three synthetic resin bands or cushioning synthetic resin foam sheets are interposed between the two tubes to form a composite. Another method is to wrap the synthetic resin foam sheet around the outer periphery of the inner tube and then apply and form the outer layer.

However, the manufacturing method of multilayer pipes as described above is extremely complicated and requires high precision.In addition, when using the method of wrapping the foam sheet around the inner pipe in advance as described above, it is necessary to Due to its elasticity, it is particularly difficult to wrap and fix the sheet in a uniform flat layer when the sheet has an irregular shape, such as a joint pipe with a crosspiece, and this tends to lead to non-uniformity of the outer coating layer.

SUMMARY OF THE INVENTION In view of the drawbacks of the conventional multilayer pipes, an object of the present invention is to find a method for manufacturing a multilayer pipe that improves the drawbacks of the conventional multilayer pipes. As a result of intensive research in accordance with these objectives, the present inventors have found that a thin layer of paper, film, cloth, etc. attached to or containing a material that changes in volume when water is absorbed and desorbed is attached to the outer periphery of a synthetic resin inner tube. wrapped around at least a portion of the surface;
Furthermore, if the outer peripheral surface of the synthetic resin inner tube, including at least the wrapped portion, is coated with a mixed material mainly composed of a hydraulic inorganic material and water, and then cured, hardened, and dried, The present inventors have discovered that they can withstand thermal stress caused by thermal expansion when hot water flows down, etc., and have completed the present invention.

Examples of materials that change in volume during water absorption and desorption in the present invention include the following.

Asbestos, diatomaceous earth, fly ash, various clay minerals,
engineering) IJ syngite material, starch and starch derivatives,
Water-soluble cellulose derivatives such as CMC, MC, HEC, 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 These include polyester, polyepoxy compounds, ketone formaldehyde resins, polyvinylpyrrolidone, polyamines, polyelectrolytes, urea formaldehyde resins, melamine formaldehyde resins, phenol formaldehyde resins, etc. In the present invention, of course, two or more of the above materials may be combined. May be used.

Furthermore, it will be clear from the following description that the structure of the present invention is not limited to these exemplified materials.

Various known methods can be used to attach or incorporate the above-mentioned materials into a thin layer such as paper, film or cloth. Some examples include a method of immersing the thin layer body in a liquid in which these materials are dissolved and drying it;
In addition to the method of attaching powder of these materials using a binding material such as adhesive, the method of adding and filling these materials to the raw material of the thin layer body! There are methods such as forming it into a film or fiber, and simply attaching it physically between fiber structures.

In addition, the hydraulic inorganic materials in the present invention include, for example, Portland cement, silica cement, blast furnace cement, flyash cement, alumina cement, various ettringite cements, magnesium carbonate, and various gypsums. Asbestos, rock wool, glass fiber, wood wool, synthetic fiber, natural fiber, steel fiber, copper wire, mica, perlite, vermiculite, calcined vermiculite, volcanic acid for the purpose of reinforcement, improving fire resistance, reducing weight, increasing volume, etc. It is also effective to add limestone, silica sand, aluminum hydroxide, calcium carbonate, calcium silicate, etc.

In the present invention, the effect of the thin layer body such as paper, film, or cloth to which a material that changes in volume upon absorption and desorption of water is attached or contained is that water is absorbed from the mixture of water and the hydraulic inorganic material coated on the outer peripheral surface. Until the hydraulic inorganic material absorbs, swells, and hardens to form a structure, it maintains a larger space between the outer layer tube and the inner tube in a gel state than after dehydration, and after the hydraulic inorganic material hardens. During the drying process of the multilayer tube, the gel releases water and shrinks, forming a certain gap between the outer tube and the inner tube. Therefore, the paper used in the present invention,
The amount of the above-mentioned materials to be attached to or contained in a thin layer such as a film or cloth may be selected in consideration of the shrinkage process during drying and the size of the required gap. Further, it is not necessarily necessary to wrap the entire outer circumference of the synthetic resin pipe, and the desired amount of voids and location of the voids may be selected as appropriate.

For example, as a method of wrapping and fixing paper, film, cloth, etc. treated as described above on the outer peripheral surface of a synthetic resin pipe, and then coating and molding the surface with a mixture of a hydraulic inorganic material and water, for example, the method described above is used. The wrapped synthetic resin tube is set in advance in a mold that can be divided into upper and lower parts and has a desired inner shape, and the hydraulic inorganic material is placed between the pattern mold and the synthetic resin tube around which the thin layer body is wound. A method of casting a slurry of the material, a method of extruding the material to form a coating layer around a synthetic resin tube wrapped with a thin layer similar to the above, and a method of forming a coating layer around a synthetic resin tube wrapped with a thin layer of the material, or a method of forming a coating layer of the material into a thin layer. Around the outer periphery of a synthetic resin pipe that is wrapped around and left behind.
Alternatively, a method of winding in multiple layers may be mentioned.

The curing method for the hydraulic inorganic material may be either room temperature curing or heating curing, and it is desirable to hold it in a humid air condition during this period. This interlayer is then dried.

The multilayer tubular structure manufactured by the present invention not only does not have any adverse effects on the coating layer due to thermal stress caused by thermal expansion when high-temperature fluid passes through the piping, but also can be easily installed in the case of straight pipes. Only the inner tube can be moved or extracted.゛Hereinafter, the present invention will be described as an example.
Therefore, it will be explained in more detail.

Example 1゜Hard vinyl chloride pipe (outer diameter 114 k, inner diameter 107 fi
lm, length 2100+gm) with thin paper C
A layer of MC immersed in a 9% aqueous solution and dried is wrapped around the layer one more time, and then a mixed wire of the following composition is coated on cheesecloth (material: vinylon) to a thickness of approximately β and then wrapped three times. Then, while rotating it, I compressed it in the direction of the center axis to make it close to a perfect circle. The thickness of the coating layer at that time was 9 mm. This product was left at room temperature for 30 minutes, then placed in a curing chamber at 50° C. and 804 RH for 5 hours.

After 3 weeks of air-drying, this product was connected to the multilayer tubular structure of Comparative Example 1 described below, and boiling water of 90°C was allowed to flow down at a rate of 20/min for 20 minutes, and then the lower end was closed and held for 10 minutes under full water conditions. did. No abnormalities were observed in the coating layer during or after this test, and there was no adverse effect of the stress caused by the thermal expansion of the inner tube.This is thought to be because the stress was sufficiently absorbed by the voids generated. .

After the test, the multilayer tube was cut and the inner surface was observed. The CMC attached to the thin paper swelled and gelled. During this time, the hardening reaction of the coating layer progressed to form an outer tube, and as it dried, this gelled layer re-permeated with water. A void that is thought to have been generated due to loss and shrinkage is formed between the outer tube and the inner tube, and this void provides a thermal stress absorption function to the multilayer tubular structure produced by the manufacturing method of the present invention. it is conceivable that.

Kneaded product composition (parts by weight) Ordinary Portland cement 45 Alkali-resistant glass fiber chopped strand 05 Chrysotile asbestos 45 Silica sand
9 Lightweight aggregate (perlite) 6 Thickener (methylcellulose) 01 Water 35 Comparative example 1 Completely the same as Example 1 except that the tissue paper immersed in the CMC aqueous solution in Example 1 was not used and the paper was replaced with untreated tissue paper. A multilayer tube was manufactured using the same treatment and operation.

After 3 weeks of air-drying, this product was subjected to the same heat vortex test as in Example 1, and a plurality of cracks were found in the outer tube.

Patent applicant: Showa Denko Co., Ltd. Agent: Patent attorney Sei Kikuchi

Claims (1)

[Claims] A thin layer of paper, film, cloth, etc., attached or containing a material that changes in volume during water absorption and desorption, is wrapped around at least a part of the outer circumferential surface of a synthetic resin inner tube, and the wrapped part is further included in the composition. A method for manufacturing a multilayer tubular structure, which comprises coating the outer circumferential surface of a resin inner tube with a kneaded material containing a hydraulic inorganic material and water as main components, curing, curing, and drying.