JP4228874B2 - Manufacturing method for internally lined steel pipe - Google Patents

Description

The present invention relates to a method for manufacturing an inner surface lining steel pipe used for piping for water supply, hot water supply, air conditioning, drainage, etc., and particularly, manufactured by an efficient method and having excellent long-term performance. The present invention relates to a method for manufacturing an inner lining steel pipe .

  Conventionally, pipes used for water supply, hot water supply, drainage, etc. are powdered in a state where the inner surface of a steel pipe that has been subjected to a surface treatment such as chemical conversion treatment or primer treatment for improving the corrosion resistance or the like. Although a method of forming an inner lining layer by body coating is used, this powder coating method is not excellent in terms of production efficiency, and pinholes etc. that lead to deterioration in anticorrosion performance occur There is a problem that it is easy to form and it is difficult to increase the film thickness.

  In addition, using a PVC resin known to have shape resilience, a pipe smaller than the inner diameter of the steel pipe, which has been given shape resilience, is produced, heated to be restored in the steel pipe, and then expanded on the inner surface of the steel pipe. Since this method is very productive and the price of the vinyl chloride resin is low, it has been the mainstream of inner surface resin-lined steel pipes for water supply. However, vinyl chloride resin has low impact resistance, especially impact resistance at low temperatures, and the lining layer may be damaged when used in cold districts as water and hot water pipes or when left outdoors during construction. In addition, in recent years, the burden of processing such as generation of harmful substances at the time of disposal of vinyl chloride resin, separation of steel pipe and vinyl chloride resin for placing on vinyl chloride resin processing route, Its use has been limited based on the recognition that it has a high environmental impact.

  In addition, there is also known a method of imparting shape restoring property to a crosslinked polyethylene pipe and expanding the diameter by lining up by heating and restoring in a steel pipe. There was a problem that it could not be secured (see, for example, Patent Document 1).

  Further, as a method free from the above problem, a method of lining the inner surface of a steel pipe by imparting a shape restoring property to a polyethylene pipe is also disclosed (for example, see Patent Document 2). It was inferior in reliability in terms of long-term durability for water supply and hot water supply.

Moreover, as a thing with high anti-corrosion performance, although various things are known as an outer surface coating material for the outer surface covering steel pipe used for a gas pipe etc., all do not have sufficient performance for this purpose. For example, fluororesins (see, for example, Patent Document 3) and polyether ether ketone resins (see, for example, Patent Document 4) are known. Use is considerably limited, such as the need for a baking process at high temperatures. Polyphenylene sulfide resins (for example, refer to Patent Document 5), polyamide resins such as nylon (for example, refer to Patent Document 6), polyphenylene ether resins (for example, refer to Patent Document 7), etc. are used for water supply, particularly for hot water supply. When steel pipe is used, there is a problem in performance. For example, polyphenylene sulfide, polyamide, and polyphenylene ether have a problem with hot water resistance that simulates the usage environment for hot water supply. In addition, flame retardants recommended in these documents are eluted to improve the hygiene of tap water. As a result, it cannot be used, and cannot be used for this purpose. Styrenic rubber and the like also reduce the resistance to chlorine water required for water use.
JP2001-9912 (2nd to 3rd pages) JP-A-2002-257265 (pages 2-4, FIG. 1) JP-A-8-300554 (2nd to 3rd pages) JP 4-50585 (pages 2-3) Japanese Patent Laid-Open No. 7-329240 (pages 2 to 5, Table 1, FIGS. 1 to 4) JP-A-8-294994 (Pages 2-4, Fig. 1) JP-A-8-238717 (7th to 8th pages, Table 1)

  The performance required for the inner lining layer of pipes used for water supply and hot water supply is completely different from the performance required for ordinary coating materials, and is resistant to chlorine, hot water, water hammer, dissolution, and low temperature impact. Sex is required.

  For example, if the chlorine water resistance is low, the chlorine added to the tap water may cause deterioration of the inner lining layer, peeling, and tsumari. Also, if the water resistance is low, the inner lining layer may be deformed or cracked due to long-term hot water flow, so that the inner surface of the steel pipe that is in direct contact with water rusts and red water is supplied from the faucet. Become.

  If the water hammer resistance is low, the negative pressure generated in the pipe at the moment when the faucet is stopped may cause the lining layer to peel off or to become thickened. Moreover, if the elution property quantified by the amount of potassium permanganate consumed is high, it means that the amount of organic matter dissolved in the tap water is large, and the hygiene is poor.

  In addition, when the low temperature impact property is poor, the inner lining layer is damaged during construction and use in a cold region, which causes tsumari and red water. Furthermore, it is also important that the inner lining is applicable to an efficient inner lining method because it is difficult to perform compared with the coating of a steel plate or the outer coating of a steel pipe.

  As described above, conventionally, there is no means that satisfies all of these, and a method that can solve them has been desired.

The present invention has been made in order to solve the above-mentioned problems, and in piping used for water supply, hot water supply, air conditioning, drainage, etc., chlorine water resistance, hot water resistance, water hammer resistance, elution, low temperature impact resistance An object of the present invention is to provide a method for producing an internally lined steel pipe having excellent diameter reduction characteristics and lining characteristics .

  As a result of earnest research on the above-mentioned characteristics required for the inner surface lining of pipes used for water supply and hot water supply, etc., the present inventors can solve the above problems by the following method and have sufficient performance for water supply and hot water supply. It has been found that an internal resin-lined steel pipe can be provided.

The method for producing an internally lined steel pipe according to the present invention provides a resin pipe made of polystyrene and polyphenylene ether resin in which the mass ratio of polystyrene and polyphenylene ether is in the range of 90:10 to 35:65, to impart shape restoration properties. The diameter of the resin pipe is reduced under heating, inserted into the steel pipe, heated again to increase the diameter, and the resin pipe is lined on the inner surface of the steel pipe.
When the mass ratio of polystyrene and polyphenylene ether is larger than 90:10, the hot water resistance becomes insufficient. On the other hand, when the mass ratio of polystyrene to polyphenylene ether is smaller than 38:65, stable lining cannot be obtained, and when it is smaller than 35:65, the warm water resistance is deteriorated.
Furthermore, the lining layer is based on 100 parts by weight of polystyrene and polyphenylene ether resin, and (ii) at least one of 100 parts by weight or less of elastomer and rubber component, (ii) 100 parts by weight or less of polystyrene graft copolymer, (Iii) It is preferable to contain an additive composed of 5 parts by weight or less of titanium oxide.
When an elastomer and a rubber component are added, the low temperature impact characteristics of the lining layer made of the resin composition are improved. However, if added in excess of 100 parts by weight, the hot water resistance and water hammer characteristics become insufficient.
When the polystyrene graft copolymer is added, the low-temperature impact characteristics of the lining layer made of the resin composition are improved. However, if it is added in an amount exceeding 100 parts by weight, the hot water resistance and water hammer characteristics become insufficient.
When titanium oxide is added, the chlorine water resistance is improved. However, if it exceeds 5 parts by weight, the hot water resistance is insufficient.

Further, an adhesive layer may be provided between the lining layer and the steel pipe. In this case, it is desirable to use one or more adhesives selected from maleic anhydride-modified polystyrene, maleic anhydride-modified polyphenylene ether, and hot-melt adhesive as the adhesive layer. By using it, the resin pipe can be firmly bonded to the inner surface of the steel pipe.
[Action]

  According to the resin composition of the present invention, as a result of sufficiently satisfying chlorine water resistance, hot water resistance, water hammer resistance, elution property, low temperature impact resistance, etc. required for the inner lining layer of water supply and hot water supply pipes, Even when used, red water due to deformation or cracking of the lining layer does not occur.

  Furthermore, since the resin composition of the present invention is excellent in shape restoration property, as a method for producing a lining steel pipe, the resin composition molded into a tubular shape is reduced in diameter by heating to give shape restoration property. By inserting and heating again, the resin pipe expands and expands in diameter, and can be lined on the inner surface of the steel pipe.

According to the method of manufacturing an inner surface lining steel pipe according to the present invention, it has sufficient performance necessary for a water supply pipe, a hot water supply pipe, or a water distribution pipe, has a high adhesive force between the lining layer and the steel pipe, and further has a heat recovery property. It can be manufactured in an efficient way.

  Various preferred embodiments of the present invention will be described below.

(Steel pipe)
The steel pipe used in the present invention may be subjected to blasting, pickling, chemical conversion, plating, primer treatment, or plastic lining on the outer surface of the steel pipe. Further, the inner surface of the steel pipe may be subjected to blasting, pickling treatment, chemical conversion treatment, plating treatment, etc., and further inside thereof may be subjected to a primer treatment. An adhesive may be interposed between the two. The steel pipe has an outer diameter of about 10 to 2000 mm, usually about 20 to 170 mm, a length of about 3 to 10 m, usually about 4 to 6 m, and a wall thickness of about 2.0 mm to 5.3 mm. Use.

(polystyrene)
Polystyrene used in the resin layer is a known general-purpose resin, and is a homopolymer or copolymer having repeating units of vinyl aromatic compounds or derivatives thereof as shown in the following general formula including most typical styrene. It is.

  In the above formula, R represents hydrogen or an alkyl group, R ′ represents a substituent of a benzene ring such as an alkyl group, a vinyl group, a halogen, or an amino group, and m represents an integer of 0 or 1 to 5. The moiety not represented by R ′ is hydrogen.

  Typical examples include polystyrene, poly α-methylstyrene, and the like, and a copolymer of such an aromatic vinyl compound and a non-aromatic compound may be used. Representative examples include styrene-acrylonitrile copolymers and styrene-maleic anhydride copolymers.

(Polyphenylene ether)
Polyphenylene ether is a polymer obtained by polymerizing one or more of phenol compounds. In the phenol compound, hydrogen in the benzene ring is alkyl, phenyl, substituted phenyl, halogen, and substituted carbon. Although it may be substituted with a hydrogen group or the like, at least one is a hydrogen atom. A preferred polyphenylene ether is a polymer having 2,6-dimethylphenol as a main monomer and having a glass transition temperature in the range of 200 to 230 ° C., but is not limited thereto.

(Composition ratio)
In these resin compositions, the mass ratio of polystyrene and polyphenylene ether needs to be in the range of 90:10 to 35:65, and when the mass ratio of polystyrene and polyphenylene ether is greater than 90:10, When the ratio becomes smaller than 38:62, stable lining cannot be obtained, and when it becomes smaller than 35:65, the hot water resistance deteriorates.

(Elastomer / Rubber)
In addition, an elastomer and / or a rubber component may be added to the resin of the present invention in order to improve low temperature impact characteristics.

  The elastomer component may be a known thermoplastic elastomer, such as a polyester elastomer in which an aliphatic polyether such as polytetramethylene glycol and an aromatic polyester such as polybutylene terephthalate are bonded, or polyamide 6, 66, 11 , 12 and other polyamide-based elastomers in which polyoxyethylene, polyoxypropylene, polytetramethylene glycol and other polyethers are combined, polyolefin resins such as polyethylene and polypropylene, ethylene propylene rubber, isobutylene isoprene rubber Copolymerized with a thermoplastic polyolefin elastomer made of olefin rubber such as the above, or polyether or polyester such as polytetramethylene glycol Urethane based or may be a elastomeric styrene such as obtained by copolymerizing a diene component such as styrene and butadiene. The rubber component may be a polymer and copolymer containing a diene component such as SBR, or acrylic rubber. However, if there is an unsaturated bond derived from the styrene component and the diene component, the chlorine-resistant water resistance is impaired. Therefore, an elastomer or a rubber component that preferably does not contain a styrene component and a diene component is excellent in terms of chlorine-resistant water resistance.

(Polystyrene graft copolymer)
In addition, a polystyrene graft copolymer may be added to the resin of the present invention in order to improve low temperature impact characteristics.

  The polystyrene graft copolymer is a polymer in which a polystyrene polymer is grafted to an olefin compound alone or a copolymer. Specific examples of the olefin compound alone or copolymer include polyethylene, ethylene ethyl acrylate. Copolymer, ethylene vinyl acetate copolymer, ethylene glycidyl methacrylate copolymer, ethylene ethyl acrylate maleic anhydride copolymer, especially the ester monomer content in these copolymers is 10 to 25% by weight, A maleic anhydride monomer content of 0 to 10% by weight is desirable. In addition, some copolymerization monomers may be mixed in the polystyrene polymer as long as the performance is not impaired.

  The addition of the elastomer, rubber or polystyrene graft copolymer is preferably 100 parts by weight or less with respect to 100 parts by weight of polystyrene and polyphenylene ether resin. If it is added excessively in excess of 100 parts by weight, the hot water resistance and water hammer characteristics become insufficient.

(Titanium oxide)
Titanium oxide may be added to the resin of the present invention in order to improve the chlorine water resistance.

  The titanium oxide may be a known one and may be a rutile type or anatase type, and the particle size is not particularly limited, but a particle size of 30 μm or less is preferable in consideration of uniform dispersion in the resin. The addition amount is preferably 5 parts by weight or less with respect to 100 parts by weight of polystyrene and polyphenylene ether resin. If it is added more than that, the hot water resistance will be insufficient.

(Mixing of resin composition)
The mixing of these resin compositions can be performed by a conventional method known as a resin kneading method, and can be carried out by kneading with a kneader or an extruder at a high temperature.

  In addition, the above resin composition may be mixed with the above resins or other resins within a range not impairing the performance of the present invention. If necessary, an antioxidant, an ultraviolet absorber, a light resistance stabilizer, a difficulty Additives such as a flame retardant, pigment, colorant, filler, lubricant, antistatic agent, and tackifier can be added.

(Adhesive layer)
Further, by providing the adhesive layer 3 between the steel pipe 2 and the lining layer 4, the adhesion between the lining layer 4 and the steel pipe 2 is improved, so that the workability on site and the reliability during use are ensured. Examples of the material for the adhesive layer include maleic anhydride-modified polystyrene, or maleic anhydride-modified polyphenylene ether, and further, for example, ethylene-maleic anhydride copolymer resin, ethylene-maleic anhydride-acrylic acid ester copolymer, Based on ethylene-methacrylic acid copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer resin, ethylene-methacrylic acid ester copolymer resin, ionomer resin, ethylene-vinyl acetate copolymer, etc. Hot melt adhesives such as polyolefin or polyester are effective, and those obtained by adding a terpene or tackifier such as rosin to these resins are also effective.

  In addition, the adhesive may be mixed with other adhesives or other resins as long as the performance of the present invention is not impaired, and an antioxidant, an ultraviolet absorber, a light stabilizer, Additives such as plasticizers, flame retardants, pigments, colorants, fillers, lubricants and antistatic agents can be added.

(process)
As a lining method, the above resin composition is kneaded and mixed by a known method, and then crushed and powdered, and then heated in a powder coating method in which the inner surface of a heated steel pipe is sprayed or in a powder flow tank A fluid dipping method for dipping a steel pipe is applicable.

  In addition, since the resin composition of the present invention has a shape restoring property, it can be applied to a shape restoring method as a method with high production efficiency. First, the resin composition of the present invention is extruded into a pipe shape from a mold by a normal method, and the outer diameter is fixed while cooling the resin to below the solidification temperature using a sizing die, a water-cooled shower, etc. Also use a resin tube with a large outer diameter. Thereafter, the resin tube was heated to a temperature higher than the glass transition temperature of the resin composition using an infrared heating furnace, a microwave heating furnace, a high-frequency heating furnace, a hot air furnace, or the like, or heated to a temperature higher than the glass transition temperature. In the state, the diameter is reduced until the outer diameter is smaller than the inner diameter of the steel pipe, and the shape is restored by cooling. This diameter reduction is achieved by adopting a line in which a heating furnace and a cooling tank are placed between the two take-up machines, and using the difference in speed between the two take-up machines to extend in the longitudinal direction of the pipe. A method of reducing the diameter by passing through a die having a taper whose outlet side diameter is smaller than the inner diameter of the steel pipe, or a method of reducing the diameter in the radial direction with a roll or the like can be applied. In addition, in order to stabilize the shape in these processes, the inside of the pipe is pressurized by a method such as sending air inside, or the outside of the pipe is decompressed to improve the follow-up of the molded product to the mold. It is also possible to apply a method such as sucking on the.

  In addition, when the resin composition is extruded from the mold into a pipe shape, the resin temperature may be equal to or higher than the glass transition temperature, and the diameter may be reduced by the above method while cooling the resin composition.

  The size of the resin pipe after the diameter reduction is usually set to an outer diameter of 12 to 158 mm and a wall thickness of 0.4 to 4.5 mm in consideration of the size of the pipe to be lined, workability, economy, etc. It is not particularly limited to this.

  Further, the glass transition temperature of the resin composition can be obtained by a commonly performed method such as differential scanning calorimetry.

  When the diameter of the resin tube is reduced below the glass transition temperature, necking or the like occurs, and the diameter cannot be stably reduced. Further, when the shape is restored, it becomes non-uniform and the inner surface of the steel tube cannot be lined cleanly.

  When covering the outer surface of the resin tube with an adhesive, either before or after imparting shape restoration, a method of coating the surface of the resin tube with a crosshead round die or T-die, or bonding in a film shape in advance A method of winding an agent around the surface of a resin tube, or a method of co-extruding a resin and an adhesive to be a lining layer in a multilayer mold can be applied. Usually, the thickness of the adhesive layer is 0.05 to 0.8 mm, but is not particularly limited thereto.

  The thus produced lining resin pipe is inserted into a steel pipe and heated in a high-frequency heating furnace, a hot air furnace or the like, and the resin pipe is preferably at a temperature higher than the [glass transition temperature −10 ° C.] of the resin composition, More preferably, by heating to a temperature equal to or higher than the glass transition temperature, the resin pipe is expanded in diameter and lined on the inner surface of the steel pipe.

  In this shape restoration process, not only heating, but also a method of further promoting heating expansion by blowing compressed air or the like into the inside of the resin tube, or a temperature rise by sealing both ends of the resin tube. There is also a method of further promoting heating expansion by increasing the volume of air in the resin tube.

  When the resin tube temperature at the time of heating is lower than [glass transition temperature −10 ° C.], there is a possibility that a portion where the gap between the steel tube and the lining layer exists due to insufficient expansion of the resin tube, The knowledge that the diameter of the resin tube can be stably expanded by heating to the glass transition temperature or higher was obtained.

Moreover, in order to make it easy to escape the air between a steel pipe and a resin pipe, it is preferable to heat from a pipe center part to both ends or from a pipe end to the other end. Furthermore, since heat is hardly transmitted to the resin pipe near the end of the steel pipe, heat treatment may be performed after lining. After the resin pipe has adhered to the inner surface of the steel pipe, it is cooled and an inner surface resin-lined steel pipe can be obtained by cutting the resin pipe portion protruding from the end of the steel pipe.
[Example]

  Hereinafter, the inner surface resin-lined steel pipe of the present invention will be described using examples. However, the present invention is not limited to the following examples.

(Examples 1-20, Comparative Examples 1-12, 14, 16-20)
Various raw materials were previously kneaded with a single screw or twin screw extruder or a kneader to obtain resin pellets having the compositions shown in Table 1. However, a numerical part shows mass ratio. In addition, in the copolymer of Table 1, content of various components is as showing below.

1) Ethylene ethyl acrylate copolymer: Ethyl acrylate content 20% by mass
2) Ethylene vinyl acetate copolymer: 15% by mass of vinyl acetate
3) Ethylene glycidyl methacrylate copolymer: glycidyl methacrylate content 15% by mass
4) Ethylene ethyl acrylate maleic anhydride copolymer: 12% by mass of ethyl acrylate / 3% by mass of maleic anhydride
The resin pipe for lining was continuously manufactured in a molding line generally arranged in the order of an extruder, a mold, a cooling tank, a take-up machine, a heating furnace, a cooling tank, a take-up machine, and a pipe cutting machine.

  First, immediately after the resin having the composition shown in Table 1 is extruded from a round die into a pipe shape having an outer diameter of 29.0 mm to 30.0 mm at a predetermined temperature, the pipe surface is cooled to 40 ° C. or less, and then the outer surface of the pipe is exposed. While heating in a heating furnace to reach the temperature shown in Fig. 1, the pipe expands and contracts so that the outer diameter of the pipe becomes 25.8mm due to the speed difference between the two take-up machines placed before and after the heating furnace. Then, it was cooled in a cooling water tank, and a resin pipe for lining having an outer diameter of 25.8 mm and a wall thickness of 0.8 to 1.2 mm was produced.

  The prepared resin pipe is 4m50cm in length and inserted into a pickled steel pipe with a nominal diameter of 25A (inner diameter 27.6mmφ, outer diameter 34mmφ × 4m), and then the resin tube reaches the temperature shown in Table 1 As described above, the steel pipe was heated by a high-frequency heating apparatus, and the resin pipe was heated and expanded to line the inner surface of the steel pipe. Further, the resin portion protruding from the end of the steel pipe was cut to obtain a lining steel pipe.

(Comparative Example 13)
This was prepared in the same manner as in Example 1, but the two types of resins listed in Table 1 were coextruded into a pipe shape with an outer diameter of 30.0 mm so that the thickness ratio of the two layers was inner layer: outer layer = 7: 3. After cooling it, while heating in the heating furnace so that the outer surface of the pipe reaches 105 ° C, the outer diameter of the pipe becomes 26.0mm due to the speed difference between the two take-up machines placed before and after the heating furnace The pipe was extended and expanded in diameter, cooled in a cooling water tank, and a lining resin tube having an outer diameter of 26.0 mm and a wall thickness of about 1.4 mm was produced.

  The produced resin pipe is 4m50cm in length, and is inserted into a pickled pipe with a nominal diameter of 25A (inner diameter 27.6mmφ, outer diameter 34mmφ × 4m), and then the resin tube is heated to 105 ° C. The steel pipe was heated with a heating device (the temperature of the steel pipe at this time was 128 ° C.), and the resin pipe was heated and expanded to line the inner surface of the steel pipe. Further, the resin portion protruding from the end of the steel pipe was cut to obtain a lining steel pipe.

(Comparative Example 15)
A resin pipe was obtained by extruding the resin shown in Table 1 into a pipe shape having an outer diameter of 30.0 mm and cooling it. The resin pipe was immersed in a hot water bath at 80 ° C. for 24 hours for crosslinking treatment. The gel fraction according to JIS K6769 of the treated resin pipe was 32%. While this pipe is heated in a heating furnace so that the outer surface of the pipe reaches 140 ° C, the pipe expands and contracts so that the outer diameter of the pipe becomes 26.0mm due to the speed difference between the two take-up machines placed before and after the heating furnace. The resin tube for lining having a diameter of 26.0 mm and a wall thickness of about 1.4 mm was prepared.

  The produced resin pipe is 4m50cm in length, and is inserted into a pickled pipe with a nominal diameter of 25A (inner diameter 27.6mmφ, outer diameter 34mmφ × 4m). The steel pipe was heated by a heating device (the temperature of the steel pipe at this time was 170 ° C.), and the resin pipe was heated and expanded to line the inner surface of the steel pipe. Further, the resin portion protruding from the end of the steel pipe was cut to obtain a lining steel pipe.

  The evaluation was made on the diameter-reducing characteristics, lining characteristics, hot water resistance, low temperature impact characteristics, dissolution properties, water hammer characteristics, and chlorine water resistance.

<Reduction characteristics>
When the diameter of the expanded tube is reduced, the resin tube is torn, or the cross-sectional shape is severely deformed and the cross-sectional shape is crushed. Measured at 10 points, “○” indicates that the variation was less than ± 5% of the target outer diameter, while the pipe diameter was good but the variation was ± 5% or more of the target outer diameter “△”.

<Lining characteristics>
After lining, cut the lining steel pipe at 10 cm pitch at 10 locations and observe the cross section. If the lining layer is at least 0.5 mm away from the inner surface of the steel pipe, the lining characteristic is “△”. When there was no gap between the gaps and the gap was less than 0.5 mm, “○”, and when there was almost no change in the outer diameter of the resin tube before lining, “×” did.

<Hot water resistance>
Cut the lining steel pipe to a length of 50 cm, pass hot water of 85 ° C on the inner surface for 5000 hours, and the red water is generated due to deformation of the lining layer such as shrinkage, expansion, peeling, or cracks on the inner surface. ”, Those that did not change were marked with“ ◯ ”.

<Low temperature impact characteristics>
The tip is a hemisphere with a diameter of 10 mm, and a weight of 3 kg is dropped on the outer surface of a lining steel pipe vertically divided at -10 ° C from a height of 2 m. “When the height was 2 m, the inner surface of the steel pipe was exposed, but when dropped from a height of 1 m, the steel pipe was not exposed,“ ◯ ”, and when the height was 1 m, the steel pipe was exposed,“ X ”.

<Elution properties>
The elution from the lining material into tap water was evaluated by the consumption of potassium permanganate. The method conforms to JIS K6769, and when the consumption is 2 mg / L or less, “○” is indicated, and when the consumption is larger than that, “×” is indicated.

<Water hammer characteristics>
Water hammer characteristics were evaluated according to JWWA (Water Supply Association) standards. The flow rate of water flowing on the inner surface of the lining steel pipe was 2.64 m / sec, the valve was opened and closed 300 times in a state where the pressure when opening and closing the valve was 1.9 kgf / cm2 or more, and the lining layer after that was deformed. “×”, and “○” was not deformed.

<Chlorine resistant water>
The chlorine water resistance of the resin composition was evaluated by the method of JIS K6762. "◎◎" indicates no change after 1000 hours, "◎" indicates no change after 500 hours, and blisters and other abnormalities were observed after 500 hours. Those with no change were marked with “◯”, and those with abnormalities such as blisters were marked with “x”.

  The evaluation results are shown in Table 2.

  Regarding the diameter-reducing characteristics and the lining characteristics, except for Examples 6 and 17 and Comparative Examples 1, 2, 3, 5 and 11 having a Δ or X evaluation, all other Examples and Comparative Examples were evaluated as “Good”. Met.

  Regarding hot water resistance, all Examples 1 to 20 were evaluated as ◯, whereas Comparative Examples 1 to 20 were all evaluated as x.

  Regarding the low temperature impact characteristics, Examples 1 to 6 and 20 were evaluated as ○ and Examples 7 to 19 were evaluated as ◎, whereas Comparative Examples 3, 14 and 19 were evaluated as ×.

  Regarding the dissolution property, all Examples 1 to 20 were evaluated as ◯, whereas Comparative Examples 1 and 15 were evaluated as ×.

  The water hammer characteristics were evaluated as “Good” in all Examples 1 to 20, whereas “Comparative Examples 6 to 10, 12, and 13” were evaluated as x.

  Regarding the chlorine-resistant aqueous solution, particularly excellent ◎◎ evaluation results were obtained in Example 20, Examples 1-9, 12, 13, 15-19 were evaluated as ◎, and Examples 10, 11, 14 were evaluated as ○. In contrast, Comparative Examples 1 and 14 were evaluated as x.

  From the above results, it was confirmed that the internally lined steel pipe according to the present invention has sufficient performance as a pipe for water supply and hot water supply as well as hot water resistance.

(Examples 21 to 50)
In addition, a resin tube for lining was produced under the conditions shown in Table 3 in the same manner as in Example 1, and then the adhesive shown in Table 3 was melt-extruded from a crosshead die on the outer surface of the pipe with a thickness of 0.1 mm. A lining resin tube with an adhesive layer was prepared by cooling immediately after coating.

  The prepared resin pipe is 4m50cm in length, and it is inserted into a pickled pipe with a nominal diameter of 25A (inner diameter 27.6mmφ, outer diameter 34mmφ × 4m), and then lining the inner surface of the steel pipe under the conditions shown in Table 3 did. Further, the resin portion protruding from the end of the steel pipe was cut to obtain a lining steel pipe.

Evaluation was made by measuring the punching shear adhesive force when cutting the lining steel pipe into 2 cm length, holding the outer steel pipe part, and pushing only the inner lining resin layer in the axial direction, 100 N / cm ² or more In the case of “◯”, the case of less than 100 N / cm ^{2 was} “Δ”. In Examples 21, 27, 33, 39, and 45 where no adhesive was used, the initial adhesive force was less than 100 N / cm ² .

Thus, it was confirmed that the adhesion between the steel pipe and the lining layer can be improved by providing an adhesive layer made of maleic anhydride-modified polystyrene, maleic anhydride-modified polyphenylene ether, or a hot melt adhesive.

In the copolymers in Table 1,
Ethylene ethyl acrylate copolymer: ethyl acrylate content 20% by mass,
Ethylene vinyl acetate copolymer: 15% by mass vinyl acetate content
Ethylene glycidyl methacrylate copolymer: glycidyl methacrylate content 15% by mass,
Ethylene ethyl acrylate maleic anhydride copolymer: 12% by mass of ethyl acrylate, 3% by mass of maleic anhydride.

It is an expanded sectional view showing a part of inner surface lining steel pipe of the present invention typically.

Explanation of symbols

1 ... Inner lining steel pipe,
2 ... Steel pipe,
3 ... adhesive layer,
4 ... Lining layer (resin composition).

Claims (4)

A resin tube made of polystyrene and polyphenylene ether resin in which the mass ratio of polystyrene and polyphenylene ether is in the range of 90:10 to 35:65 is reduced in diameter under heating in order to give shape restoration and inserted into the steel tube. And heating again to expand the diameter, and lining the resin pipe on the inner surface of the steel pipe. The resin tube has (i) at least one of 100 parts by weight or less of an elastomer and a rubber component, and (ii) 100 parts by weight or less of a polystyrene graft copolymer with respect to 100 parts by weight of the polystyrene and the polyphenylene ether resin. The manufacturing method according to claim 1, further comprising one or more additives selected from the group consisting of iii) 5 parts by weight or less of titanium oxide. Furthermore, it has an contact bonding layer between the said lining layer and a steel pipe, The manufacturing method of any one of Claim 1 or 2 characterized by the above-mentioned. 4. The adhesive layer according to claim 3, wherein one or more adhesives selected from maleic anhydride-modified polystyrene, maleic anhydride-modified polyphenylene ether, and hot melt adhesives are used. Production method.

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