JPS6351082B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer tubular structure suitable for use indoors, particularly for water supply and drainage pipes installed through a plurality of connected compartments. Specifically, the outer circumferential surface of a synthetic resin pipe, such as a hard vinyl chloride pipe, is coated with a hydraulic inorganic material to provide fire resistance and prevent the spread of fire to other compartments in the event of a fire. This relates to a method of manufacturing a body.

Conventionally, hard vinyl chloride pipes have been widely used as water supply and drainage pipes for buildings because they are easy to construct and are inexpensive. However, if hard vinyl chloride pipes are used as is, they are flammable and can be dangerous in the event of a fire. It was not suitable for water supply and drainage purposes because it could cause the fire to spread to neighboring rooms or upper floors, or emit toxic gases, increasing damage.

On the other hand, metal pipes are also used because they are fire-resistant and strong, but they are heavy, difficult to cut, etc., and usually expensive, and they are also susceptible to rust and limescale buildup on the inside. This has the disadvantage that water flow rate is reduced and dew condensation occurs on the outer circumferential surface of the pipe.

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 and a fire-resistant outer pipe made of an inorganic material such as cement.
It has become rapidly popular in recent years because it is easy to construct and has excellent properties such as heat insulation and prevention of dew condensation.

However, the technically difficult problem in constructing this type of multilayer pipe is that the inner pipe is a synthetic resin pipe with a significantly large thermal expansion, and the outer pipe is made of an inorganic material with a relatively small thermal expansion. This technology prevents harmful cracks from forming in the outer layer tube by thermally expanding the inner tube and compressing the outer layer tube when hot water flows down.

The simplest method for this is to provide a certain amount of space between the inner tube and the outer tube. Specifically, it is possible to combine the outer layer tube and inner tube, which are each precisely manufactured separately. Alternatively, a method has been used in which a synthetic resin foam sheet is wrapped around the outer periphery of the inner tube to form a rear outer layer tube, but these methods also have various problems. That is, as described above, the method of separately manufacturing and inserting the inner tube and the outer layer tube is not only complicated as a manufacturing process, but also practically impossible when there are branches such as a T tube or a Y tube. On the other hand, with the method of wrapping a synthetic resin foam sheet in advance, it is difficult to wrap the sheet uniformly around the inner tube due to the elasticity peculiar to the synthetic resin foam sheet, so there is a gap between the inner tube and the sheet. The hydraulic material for forming the outer layer tube flows in, making it difficult to achieve the intended purpose. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a multi-layer pipe that improves the drawbacks of the conventional multi-layer pipe manufacturing technology. As a result of extensive research in accordance with these objectives, the present inventors have developed a synthetic resin inner tube made by swelling with water a material whose volume changes during water absorption and desorption, or a powder material mainly composed of the same. The swollen granular material is dehydrated and dried by adhering it to the outer peripheral surface of the powder and drying it, and then coating it with a kneaded material mainly composed of a hydraulic inorganic material and water, and curing and drying it. Since the powder layer returns to almost its original thickness, a gap of the desired thickness is created between the inner tube and the outer tube, and the outer tube can withstand thermal stress such as when hot water of 90°C or higher flows down. , we have completed the present invention.

Examples of water-swellable materials that change volume during water absorption and desorption in the present invention are as follows.

i.e. starch, starch derivatives, CMC, MC, HEC,
Water-soluble cellulose derivatives such as HPC, tannin, lignin, alginic acid and gum arabic, proteins such as gelatin and casein, polyvinyl alcohol, polyethylene oxide, polypropylene oxide, polyacrylic acid, polymethacrylic acid, water-soluble polyester, polyepoxy compounds, and ketones. Formaldehyde resin, polyvinylpyrrolidone, polyamine, polyelectrolyte, urea formaldehyde resin, melamine formaldehyde resin, phenol formaldehyde resin, etc. Of course, it will be clear from the following description that the structure of the present invention is not limited to the materials exemplified. Further, the powder or granular material can be used by mixing the above-mentioned substances, or it is also possible to partially use a material that does not swell with water.

The hydraulic inorganic materials used in the present invention include, for example, Portland cement, silica cement, blast furnace cement, flyash cement, alumina cement, various ettringite cements, and various types of gypsum. Asbestos, rock wool, glass fiber, wood wool, synthetic fiber,
It is also effective to add natural fibers, steel fibers, copper wire, mica, perlite, vermiculite, synthetic vermiculite, volcanic rock, silica sand, aluminum hydroxide, calcium carbonate, calcium silicate, and the like.

In the present invention, the effect of attaching a swollen granular material that changes volume during water absorption and desorption to the outer surface of a synthetic resin tube and drying it is that the easily available granular material is relatively hydrophobic. , it can be easily attached to the outer surface of a synthetic resin pipe with low adhesion, once it is dried, the following processing is not subject to time constraints, and it is easy to handle. By using this method, the powder particles that absorb water from the hydraulic inorganic material, swell, and gelatinize retain their gel state until the hydraulic inorganic material hardens and forms a structure. After curing, the above-mentioned gel releases water during the drying process of the multilayer tube, and a certain gap is formed between the outer layer tube and the inner tube. Therefore, the adhesion thickness of the powder or granular material used in the present invention may be determined by selecting the number of times of application, etc., depending on the degree of swelling.

The water-swollen powder is attached to the outer peripheral surface of a synthetic resin pipe by a spraying method, and then dried and coated with a mixture of a hydraulic inorganic material and water. For example, the synthetic resin pipe after the above treatment is set in advance in a mold that can be divided into upper and lower parts, and the kneaded material of the hydraulic inorganic material is cast into the gap between the mold and the synthetic resin pipe. Alternatively, a method of extruding a kneaded product of the material to form a coating layer around the treated synthetic resin pipe, further, a method of forming a coating layer by extruding a kneaded product of the material, and further, applying one or more sheets of the kneaded product of the material to the outer periphery of the treated synthetic resin pipe. Examples include a layered method.

The curing method for the hydraulic inorganic material may be either room temperature curing or heating curing, and it is preferable to hold it in a humid air condition during this period. Next, it is dried, but air-drying is preferable.

The multilayer tubular structure produced according to the present invention includes:
Regardless of the presence or absence of branch pipes, a gap is formed between the inner pipe and the outer pipe, which not only prevents any adverse effects on the coating layer due to thermal stress when high-temperature fluid passes through the pipe, but also prevents straight pipes from forming gaps. In this case, you can easily change the position of the inner and outer pipes and remove the inner pipe during construction.

It should be noted that the formation of the voids according to the present invention does not necessarily need to be provided over the entire surface of the inner tube, but it is also effective to provide the voids partially, for example, only at the end of the outer tube body.
Therefore, even if the particles are only partially adhered, the desired effect can be produced.

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

Example 1 A water-swelled fine powder of CMC was attached to the outer peripheral surface of a hard vinyl chloride pipe (outer diameter 114 mm, inner diameter 107 mm, length 2100 mm), and on top of that, a kneaded product of the following composition was coated with cheesecloth (material: A film coated with a constant thickness was wrapped three times around vinylon), placed on two horizontally installed parallel metal rolls rotating in the same direction, and pressed while rotating to approximate a perfect circle. The thickness of the coating layer at that time was 9 mm. This stuff at room temperature
After being left for 30 minutes, it was placed in a curing room at 50°C and 80% RH for 5 hours. After 3 weeks of air-drying, this product was connected to the multilayer tubular structure of the comparative example described below using a joint, and hot water of 90°C was flowed down for 20 minutes at a rate of 20 min, and then the lower end was closed and the pipe was filled with water. Hold for 10 minutes. No abnormalities were observed in the coating layer during or after this test, and it was confirmed that the stress caused by thermal expansion of the inner tube was sufficiently absorbed.

Kneaded product composition (parts by weight) Ordinary Portland cement 45 Alkali-resistant glass fiber chopped strands
0.5 Chrysotile asbestos 4.5 Silica sand 9 Light aggregate (perlite) 6 Thickener (methylcellulose) 0.1 Water 35 When the cut surface of the multilayer pipe was continuously observed until it was air-dried, it was found that it swelled with water. The increased thickness of the polyvinyl alcohol layer remains as it is while the curing reaction of the hydraulic coating layer progresses to form the outer layer tube, and as it dries, this swollen gelled layer loses water again and shrinks, causing the inside of the outer layer tube to shrink. A phenomenon was observed in which a thinner layer than the initial one was attached to the surface and voids were formed on the outer surface of the inner tube. It is believed that the voids formed by drying the swollen layer, which has increased in volume by absorbing water, provide the multilayer tubular structure according to the present invention with a thermal stress absorbing function.

Example 2 Water was added to a powder mixture consisting of 80% polyvinyl alcohol and 20% pulp on the outer peripheral surface of a hard vinyl chloride pipe joint (the hard vinyl chloride pipe joint used in Example 1, length 104 mm). Polyvinyl alcohol was swollen and adhered to the entire surface of the joint at a solid content of 120 g/m ² and then dried. Next, this material is fixed at both ends using holders in an internal hollow form made of chloroprene rubber to match the diameter and length of the desired multilayer tubular structure, and water is poured from the injection hole at the bottom of the form. Kneaded material: 60 parts by weight of Portland cement, 12 parts by weight of silica powder, 3 parts by weight of expansive admixture (quicklime)
Part by weight, 5 parts by weight of lightweight aggregate (perlite), 20 parts by weight of chrysotile asbestos, and 0.1 part by weight of thickener (methyl cellulose) were blended in advance, and then an appropriate amount of water was added and kneaded. A water kneaded product was then press-injected. After filling, the mixture was placed in a curing chamber, heated to 50°C, and maintained for 5 hours. After natural cooling, the mold was removed, and after 3 weeks of air-drying, this product was connected to the multilayer tubular structure obtained in Example 1 and subjected to the same hot water flow test as in Example 1. During and after this test, no abnormalities were observed in the outer tube of the coating layer.

Comparative Example 1 The length of a multi-layered tubular structure was prepared using exactly the same method and operation as in Examples 1 and 2, except that the operation of spreading the film or paper on the outer peripheral surface of the hard vinyl chloride pipe in Examples 1 and 2 was omitted. Manufactured straight pipes and joints. After 3 weeks of air-drying, this product was subjected to the same hot water flow test as in Example 1, and a plurality of cracks were found in the outer layer of both the long straight pipe and the joint of the multilayer tubular structure.

Claims (1)

[Claims] 1 Add water to powder or granule of a material that changes in volume during water absorption and desorption to swell it, apply it to at least a part of the outer peripheral surface of a synthetic resin inner tube, dry it, and remove the part to which the powder or granule is attached. A multi-layered tubular structure characterized in that at least a part of the outer peripheral surface of the synthetic resin inner tube is coated with a kneaded material mainly composed of a hydraulic inorganic material and water, and then cured, hardened, and dried. How the body is manufactured.