JPH05338060A - Production of resin-lined pipe - Google Patents

Abstract

PURPOSE:To obtain a resin-lined pipe production method in which peeling or the like hardly occurs even in a long-term use by reducing a stress generated in a bonding interface by the crystallization of a resin after production or a stress generated in the bonding interface by the expansion/shrinkage of the resin caused by heating or cooling. CONSTITUTION:An adhesive is applied to at least either an inner peripheral surface of a metallic pipe or an outer peripheral surface of a crystalline resin pipe. In this state, the resin pipe is inserted into the metallic pipe. After that, by shrinking the metallic pipe in diameter, the resin pipe is bonded to the inner peripheral surface of the metallic pipe. In this lined pipe production method, as the resin pipe, a resin pipe containing 10-50wt.% inorganic filler is used, and the resin pipe is thermally treated at a temperature for allowing the resin to crystallize to have a per cent crystallinity of 80% or more before the metallic pipe is shrunk in diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an inner resin lining pipe used for hot water supply pipes, steam pipes and the like.

[0002]

2. Description of the Related Art For the purpose of improving the corrosion resistance of a metal tube, a resin for an inner surface resin layer in a so-called inner surface resin lining tube, the inner surface of which is lined with a crystalline resin, is polyetheretherketone or polyether. Resins such as ketone, nylon (aromatic nylon, nylon 6, nylon 11, etc.), polyethylene, cross-linked polyethylene, etc., have excellent corrosion resistance and low water permeability, so that hot water etc. can be poured under such conditions. Suitable for lining tubes used in.

As a method of lining the inner peripheral surface of a metal tube with such a crystalline resin, the crystalline resin tube is inserted into the metal tube and heated to a temperature above its melting point.
A method of fusing a resin tube to a metal tube is known (Japanese Patent Laid-Open No. 52-93485).

Further, after inserting the resin pipe into the metal pipe in a state where the adhesive is applied to at least one of the inner surface of the metal pipe and the outer surface of the resin pipe, the diameter of the metal pipe is reduced to bond the both pipes to each other. There is also a method of making it (for example, Japanese Patent Publication Sho 4
8-23551).

[0005]

By the way, in the conventional lining method as described above, the resin is crystallized after being lined, which causes shrinkage stress and facilitates peeling at the adhesive interface. There are drawbacks. Further, particularly in the former method, a similar phenomenon occurs by heating for fusion. Furthermore, in any of the lining pipes obtained by any of the methods, there is a problem that the resin expands and contracts significantly due to heating / cooling, and stress is generated at the adhesive interface due to relative dimensional change with the metal pipe, causing easy peeling. ..

The object of the present invention is to reduce the stress generated at the interface due to the crystallization of the resin after the production of the lining pipe and the stress caused at the interface due to the expansion and contraction of the resin due to heating to cooling, so that it can be peeled off even after long-term use. An object of the present invention is to provide a method of manufacturing an inner resin lining tube that is difficult to do.

[0007]

In order to achieve the above object, a method for manufacturing an inner surface resin lining pipe of the present invention is to adhere to at least one of an inner peripheral surface of a metal tube and an outer peripheral surface of a crystalline resin tube. With the agent applied, insert this resin tube into the metal tube and then reduce the diameter of the metal tube.
In a method of manufacturing an inner surface resin lining pipe in which a resin pipe is adhered to an inner peripheral surface of a metal pipe, the resin pipe is
A resin tube containing 50% by weight of an inorganic filler is used, and the resin tube has a crystallinity progress rate of 80% or more at a temperature at which the resin can be crystallized before performing the above-mentioned diameter reduction. Is characterized by subjecting it to heat treatment.

The crystallinity progress rate referred to here is a value obtained by calculating the heat of fusion from the melting peak area of DSC (differential scanning calorimeter). However, the saturation crystallinity is the state when annealed at the DSC temperature falling crystallization temperature for 24 hours, and the DSC measurement condition is 2 ° C./min.
Expressing this crystallinity progress rate with an equation,

[0009]

[Equation 1]

[0010] In the present invention, as the metal tube, a copper tube, an aluminum tube or the like can be used in addition to the steel tube.

As the crystalline resin used in the present invention, polyether ether ketone (glass transition temperature 143 ° C.,
Melting point 334 ° C), polyetherketone (glass transition temperature 165 ° C, melting point 365 ° C), polyphenylene sulfide (glass transition temperature 95 ° C, melting point 280 °)
C), nylon MXD6 (glass transition temperature 102 ° C,
Melting point 243 ° C, nylon 6 (glass transition temperature 60 °
C, melting point 225 ° C.), polyethylene, cross-linked polyethylene and the like are preferable.

The crystalline resin as described above is excellent in heat resistance, water resistance and chemical resistance. When the inner peripheral surface of the metal pipe is lined with a resin pipe made of such a material, the water resistance becomes
It becomes an inner resin lining tube with excellent corrosion resistance.

Further, such a crystallization treatment of the crystalline resin tube is performed by annealing at a predetermined temperature for a certain time before adhering to the metal tube after the manufacturing step of the crystalline resin tube or after the manufacturing. Done. This crystallization treatment is carried out in advance so that the resin tube can be more completely and stably crystallized so that the dimensional change of the resin tube after the diameter reduction of the metal tube is minimized. If this crystallization is not sufficient, the resin tube will be crystallized depending on the temperature during use, causing crystallization shrinkage, which causes contraction stress in the axial and circumferential directions. The adhesive interface between the metal tube and the metal tube is likely to peel off.

Therefore, in the present invention, the rate of progress of crystallinity by this crystallization treatment is set to 80% or more. If it is less than this, the shrinkage after lining cannot be effectively suppressed, and it is preferable that it is as close to 100% as possible.

The heat treatment temperature for crystallization is a temperature between the glass transition temperature Tg and the lowered crystallization temperature, and D
A temperature close to or lower than the temperature falling crystallization temperature of SC is preferable. As a result, the crystallization speed is high, and almost complete crystallization can be achieved.

As the inorganic filler to be added into the crystalline resin pipe in the present invention, one having excellent water resistance and chemical resistance and stable at high temperature is used, for example, glass,
Carbon, ceramics, metal oxides and the like are preferably used.

Among these, examples of the metal oxide include alumina, iron oxide, titanium oxide, zirconium oxide, chromium oxide, nickel oxide and the like. Also, potassium titanate whiskers are included in this. Examples of the ceramics include silicon nitride, titanium nitride, boron carbide, silicon carbide and the like, in addition to those contained in the above metal oxides. Then, these fillers are contained in the resin as fine powder of fibrous, granular and flake shape. Such an inorganic filler increases the strength of the lining layer (resin tube), lowers the linear expansion coefficient of the resin tube, and prevents the occurrence of cracks accompanying shrinkage due to crystallization. The content of this inorganic filler in the resin is 10
-50% by weight, preferably 20-40% by weight. If it is less than 10%, the effect of reducing the linear expansion coefficient cannot be obtained,
If it exceeds 50% by weight, the resin pipe becomes brittle and the strength of the resin pipe is rather lowered, cracks may occur when the diameter is reduced, and excellent physical properties as a lining layer cannot be obtained.

Further, as the adhesive used in the present invention, a hot-melt adhesive, a reactive adhesive or the like can be used in addition to a rubber-based adhesive which is usually used.
The adhesive may be applied to at least one of the inner peripheral surface of the metal tube and the outer peripheral surface of the resin tube, but it is desirable to apply it to both. When activation such as crosslinking of the adhesive is necessary, addition of heat treatment is not hindered.

The diameter of the metal tube in the present invention can be reduced by a known method using a diameter reducing roll or the like.

[0020]

[Function] Peeling at the adhesive interface of the inner surface resin-lined pipe is caused by crystallization of the resin pipe after lining and due to the difference in linear expansion coefficient between the metal pipe and the resin pipe, which occurs during repeated heating and cooling. It is facilitated by the stress generated by the relative dimensional changes in the tube.

In the present invention, by adding an inorganic filler to the crystalline resin pipe in an appropriate amount, the substantial linear expansion coefficient is lowered, and the amount of expansion and contraction of the resin pipe during heating to cooling is reduced. Reduces the stress generated at the interface.

Further, as the lining processing method, a method of adhering the resin tube and the metal tube with each other through the adhesive layer by the diameter reduction of the metal tube is adopted instead of the fusion bonding of the resin tube. By crystallizing almost
Generation of crystallization shrinkage stress at the interface due to crystallization after lining is suppressed.

[0023]

According to the present invention, by adding an inorganic filler into the crystalline resin pipe for adhesively coating the inner peripheral surface of the metal pipe, the linear expansion coefficient thereof is lowered and the dimensional change during heating to cooling is suppressed. At the same time, the resin tube is almost crystallized and then inserted into the metal tube, and the metal tube is reduced in diameter and adhered to its inner peripheral surface, thereby suppressing the shrinkage of the resin tube due to crystallization after lining. Therefore, the obtained lining pipe has a very small dimensional change of the resin pipe after production, the stress acting on the adhesive interface is small, and even if it is used under the condition that heating-cooling is repeated, Thus, the inner surface resin lining pipe is highly durable and is unlikely to cause peeling at the adhesive interface or blockage of the pipe due to this.

[0024]

[Examples] An example of actually manufacturing an inner surface resin lining pipe by applying the present invention will be described below together with a comparative example, and finally, the performance evaluation thereof (cooling and hot water accelerated evaluation)
Describe the results.

Example 1 Cooling crystallization temperature 105 ° C., melting point 1 containing 30% by weight of milled glass fiber
A crosslinked polyethylene resin at 30 ° C was melt-extruded from a mold and immediately water-cooled to form a resin tube having a thickness of 1 mm. This resin tube was cut into a length of 5.5 m and annealed at 100 ° C. for 30 minutes for crystallization treatment. The outer diameter of this resin tube is 27.6 mm, and the progress of crystallinity is 95%.
Met.

A solvent-based adhesive consisting of a rubber / epoxy component is applied to the outer peripheral surface of the resin tube after the crystallization treatment,
It was heated and dried at ° C for 10 minutes to volatilize the solvent. on the other hand,
Carbon steel pipe for piping with nominal diameter 25A and length 5.5m (inner diameter 2
9.6 mm, thickness 3.2 mm) was subjected to inner surface treatment by grid blasting, the same adhesive was applied thereto and dried.

A resin pipe at room temperature after the above-mentioned crystallization treatment was inserted into this steel pipe. At this time, the resin tube could be inserted smoothly without any resistance. After that, the diameter of the steel pipe was reduced by a diameter reducer until the inner diameter became 27.6 mm, and the entire pipe was heated at 80 ° C. for 30 minutes to cause a cross-linking reaction of the adhesive to obtain an inner cross-linked polyethylene lined steel pipe.

The thickness accuracy of the resin lining layer of this inner surface lining steel pipe was 1.0 mm ± 0.02 mm, and no pinholes or bubbles were observed. Further, a peeling test with a knife was conducted, but the lining layer was not peeled off.

Example 2 A polyphenylene sulfide resin containing 40% by weight of milled carbon fiber and having a crystallization temperature of 240 ° C. and a melting point of 280 ° C. was melt-extruded from a mold and immediately water-cooled to obtain a thickness. A 1 mm resin tube was molded. Cut this resin tube to a length of 5.5 m and cut it into 2
Crystallization was performed by annealing at 00 ° C for 1 hour. The outer diameter of the resin tube was 27.6 mm, and the crystallinity progress rate was 98%.

A solvent-based adhesive consisting of a rubber / epoxy component was applied to the outer peripheral surface of the resin tube after the crystallization treatment in the same manner as in Example 1 and dried by heating at 80 ° C. for 10 minutes to evaporate the solvent. It was

A carbon steel pipe for pipes having a nominal diameter of 25 A and a length of 5.5 m (inner diameter 29.6 mm, thickness 3.2 mm) similar to that of the first embodiment was subjected to inner surface treatment by grid blasting, and then the inner peripheral surface thereof. A similar adhesive layer was applied to and dried.

A resin pipe at room temperature after the above-mentioned crystallization treatment was inserted into this steel pipe. Also in this example, the resin tube could be inserted smoothly. Then, in the same way, use this steel pipe to change the inner diameter to 2
After the diameter was reduced by a diameter reducer to 7.6 mm, the entire tube was heated at 80 ° C. for 30 minutes to cause a cross-linking reaction of the adhesive to obtain an inner surface polyphenylene sulfide lined steel tube.

The wall thickness accuracy of the resin lining layer of this inner surface lining steel pipe is 1.0 mm ± 0.0, which is the same as in Example 1.
It was 2 mm, and no pinholes or bubbles were observed. Further, a peeling test with a knife was conducted, but the lining layer was not peeled off.

Comparative Example 1 An inner surface cross-linked polyethylene lined steel pipe was obtained in exactly the same manner as in Example 1 except that the resin tube did not contain milled glass fiber.

Comparative Example 2 A crosslinked polyethylene tube containing milled glass fibers exactly the same as in Example 1 was molded, and this tube was not subjected to crystallization treatment by annealing at 100 ° C. An internal cross-linked polyethylene lined steel pipe was obtained in exactly the same manner as. At this time, the degree of progress of crystallinity of the crosslinked polyethylene pipe immediately before lining was 65%.

Comparative Example 3 An inner surface cross-linked polyethylene lined steel pipe was prepared in the same manner as in Example 1 except that the resin tube did not contain milled glass fiber and the resin tube was not crystallized. Obtained.

(Comparative Example 4) An inner surface polyphenylene sulfide lined steel pipe was obtained in exactly the same manner as in Example 2 except that the resin tube did not contain milled carbon fiber.

(Comparative Example 5) A polyphenylene sulfide tube containing milled carbon fiber exactly the same as in Example 2 was molded, and this tube was not subjected to crystallization treatment by annealing at 200 ° C. An inner surface polyphenylene sulfide lining steel pipe was obtained in exactly the same manner.
The crystallinity progress rate of the polyphenylene sulfide tube immediately before lining was 55%.

(Comparative Example 6) An inner surface polyphenylene sulfide lined steel pipe was prepared in exactly the same manner as in Example 2 except that the resin tube did not contain milled carbon fiber and the resin tube was not subjected to crystallization treatment. Obtained.

With respect to each of the examples of the present invention and the comparative examples described above, a test piece was cut into a tube length of 1 m, and the sample was placed in hot water of 95 ° C. for 5 minutes and then in cold water of 25 ° C. for 5 minutes. Table 1 shows the results of observing each test piece after 100 cycles of the cold and hot water accelerated evaluation test in which the test piece was repeatedly immersed for a minute.

[0041]

[Table 1]

As is clear from Table 1 above, it was confirmed that by applying the manufacturing method of the present invention, a lining tube that is difficult to peel off can be obtained even if heating and cooling are repeated.

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Claims (1)

[Claims] 1. A resin tube is inserted into the metal tube in a state where an adhesive is applied to at least one of the inner surface of the metal tube and the outer surface of the crystalline resin tube, and then the diameter of the metal tube is reduced. Thus, in the method for producing a lining pipe in which the resin pipe is bonded to the inner peripheral surface of the metal pipe, a resin pipe containing 10 to 50% by weight of an inorganic filler is used as the resin pipe, and the resin A method for producing an inner surface resin-lined pipe, characterized in that the pipe is subjected to a heat treatment before performing the above-mentioned diameter reduction so that the progress rate of crystallinity is 80% or more at a temperature at which the resin can be crystallized.