JPH05338077A - Synthetic resin-lined tube - Google Patents

Abstract

PURPOSE:To provide a synthetic resin-lined tube which cannot be penetrated with a fluid being fed, can be produced in a simple process at a low cost, hardly generates the expansion/shrinkage and peeling of a lining layer even under use conditions that hot water/cooled water are repeatedly fed, and has a superior durability for in a long period of time. CONSTITUTION:A synthetic resin tube 20 lining the inner pheripheral surface of a metal tube 10 through an adhesive layer 30 consists of an inner synthetic resin layer 21 as an innermost layer and an outer synthetic resin layer 22 provided outside the inner layer 21. The outer layer 22 has a linear expansion coefficient which is approximately intermediate between the linear expansion coefficient of the metal tube 10 and that of the inner layer 21. A thickness t1 of the inner layer 21 and a thickness t2 of the outer layer 22 have such a relation as substantially an inverse proportion to Young's moduli E1 and E2 thereof (t1:t2 E2:E1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly applied to water supply, hot water supply,
The present invention relates to a synthetic resin lining pipe used for air conditioning, drainage, etc., in which the inner peripheral surface of a metal pipe is lined with a synthetic resin pipe.

[0002]

2. Description of the Related Art For the purpose of improving the corrosion resistance of a metal pipe such as a steel pipe, a so-called synthetic resin lining pipe whose inner peripheral surface is lined with a synthetic resin pipe such as a vinyl chloride pipe is shown in FIG. As shown in a partial cross-sectional view cut in a radial direction, a structure in which a synthetic resin pipe 200 is bonded to an inner peripheral surface of a metal pipe 100 by an adhesive layer 300 is widely used.

In such a synthetic resin lining pipe, since the difference in linear expansion coefficient between the metal pipe 100 and the synthetic resin pipe 200 is large, when the high temperature fluid is intermittently flowed into the lining pipe, the synthetic resin lining pipe and the metal pipe 100 are combined. Relative expansion and contraction with the resin pipe 200 is repeated, which causes repeated stress on the adhesive layer 300, causing the synthetic resin pipe 200 to peel off or contract in the axial direction. was there.

In order to solve such a problem, conventionally, an inorganic filler is added into the synthetic resin pipe to suppress the linear expansion coefficient of the synthetic resin pipe (Japanese Patent Laid-Open No. 55-1616).
No. 39) or a synthetic resin pipe in which an inner layer made of a thermoplastic resin and an outer layer made of a thermoplastic resin containing reinforcing fibers are mutually integrated by heat fusion to form a synthetic resin pipe. The measures such as suppressing the linear expansion coefficient of the above (Japanese Patent Application No. 3-250638) have been proposed.

[0005]

Among the above-mentioned conventional measures, according to Japanese Patent Application Laid-Open No. 55-161639, the innermost layer of the lining pipe which is in contact with the fluid to be conveyed is made of an inorganic or metallic filler. Since it is made of a synthetic resin containing a large amount, there is a risk of water permeation into the lining pipe and elution of the filler, especially when used under conditions where hot water / cold water is repeatedly flowed.

On the other hand, according to Japanese Patent Application No. 3-250638, since the innermost layer of the lining tube is formed of a resin which is normally used and does not contain a filler, there is no fear as described above. There are drawbacks in that the process of molding a synthetic resin pipe in which fiber reinforcement is applied only to the outer layer is complicated and the cost is high.

The present invention has been made in view of the above circumstances, and there is no fear of permeation of a fluid to be conveyed, and it can be manufactured at a low cost by a simple process, and hot water / cold water repeatedly flows. It is an object of the present invention to provide a synthetic resin lining pipe which is not easily broken even under such a use condition and which has excellent durability and can be used for a long period of time.

[0008]

A structure for achieving the above object will be described with reference to FIG. 1 which is an embodiment drawing, and a synthetic resin lining pipe of the present invention has an inner peripheral surface of a metal pipe 10. The synthetic resin pipe 20 for lining the inner side of the metal pipe 10 and the inner synthetic resin layer 22 has an innermost synthetic resin layer 21 and an outer synthetic resin layer 22 outside thereof. which has a coefficient of linear expansion substantially intermediate linear expansion coefficient of the layer 21, the thickness t ₁ and the thickness t ₂ of the outer resin layer 22 of the inner synthetic resin layer 21 is outlined in each of the Young's modulus E ₁ and E ₂ It is characterized by an inversely proportional relationship, ie, t ₁ : t ₂ ≈E ₂ : E ₁ .

[0009]

[Function] The innermost synthetic resin layer 2 in contact with the fluid to be conveyed
By interposing the outer synthetic resin layer 22 having a linear expansion coefficient approximately in the middle of these linear expansion coefficients between the metal tube 1 and the metal tube 10, the difference in linear expansion coefficient between adjacent layers is as follows. Approximately 1 / each of the lining pipes with a normal structure without the intermediate layer (outer synthetic resin layer 22)
Relaxed to 2.

Under these circumstances, the inner synthetic resin layer 21
By making the thicknesses t ₁ and t ₂ of the outer synthetic resin layer 22 and the outer synthetic resin layer 22 inversely proportional to the Young's modulus of the respective layers, the stress generated by the difference in the linear expansion coefficient between the two layers when the temperature changes is as described above. In the lining pipe having the usual structure, the stress generated between the metal pipe and the resin layer is about 1/2, and the stress generated between the outer synthetic resin layer 22 and the metal pipe 10 is also about the same. The force generated by the difference in the linear expansion coefficient when the temperature changes is halved, and the forces are almost evenly distributed between the layers.

[0011]

1 is a view showing the structure of an embodiment of the present invention, which is a partial cross-sectional view taken along a plane along the radial direction of a pipe.

The inner synthetic resin layer 2 is formed on the inner peripheral surface of the metal tube 10.
A two-layer synthetic resin tube 20 composed of 1 and an outer synthetic resin layer 22 is bonded to each other by an adhesive layer 30. The inner synthetic resin layer 21 is a layer located at the innermost circumference of the lining pipe and is in contact with the fluid to be conveyed so as to exert the anticorrosion function of the pipe. The outer synthetic resin layer 22 is the inner synthetic resin layer 21. Is a layer located between the metal tube 10 and the metal tube 10 for the purpose of relieving the stress generated due to the difference in the linear expansion coefficients during heating or cooling. That is, the coefficient of linear expansion of the outer synthetic resin layer 22 is approximately the intermediate value between the coefficients of linear expansion of the metal tube 10 and the inner synthetic resin layer 21, and the thickness t ₂ thereof is the same as that of the outer synthetic resin layer 22. Where E ₂ is the Young's modulus and E ₁ is the Young's modulus of the inner synthetic resin layer 21, the relationship with the thickness t ₁ of the inner synthetic resin layer 21 is t ₁ : t ₂ ≈E ₂ : E ₁ It is set to satisfy.

In the lining pipe having such a structure,
A steel pipe is generally used as the metal pipe 10, but a plated steel pipe for water supply, a copper pipe, or an aluminum pipe can also be used. Further, as the material of the inner synthetic resin layer 21, a vinyl chloride pipe which is widely used for inner surface corrosion protection in a lining pipe is generally used, but chlorinated vinyl chloride, polyethylene, polybutene or the like can also be adopted.

The material of the outer synthetic resin layer 22 is a material having a linear expansion coefficient approximately in the middle of the linear expansion coefficient of the metal tube 10 and the inner synthetic resin layer 21, that is, the metal is generally linear with respect to the synthetic resin. Since the expansion coefficient is smaller by about one digit, substantially, a material different from that of the inner synthetic resin layer 21 and having a linear expansion coefficient of about 1/2 thereof is used, or the same material as the inner synthetic resin layer 21 is used. Calcium carbonate in the resin,
An inorganic filler such as talc or kaolin may be kneaded to have a linear expansion coefficient of about 1/2.

The two-layer synthetic resin tube 20 having such an inner synthetic resin layer 21 and an outer synthetic resin layer 22 may be integrally molded as shown in FIG. 1 by two-layer extrusion molding or the like. Alternatively, they may be individually molded and bonded together with an adhesive.

Further, as the material of the adhesive layer 30, in addition to a usual rubber adhesive, a hot melt adhesive or a reactive adhesive can be used. As a molding method for joining the metal tube 10 and the two-layer synthetic resin tube 20 via the adhesive layer 30, a method of applying an adhesive to at least one of the metal tube 10 and the synthetic resin tube 20, and then synthesizing Either the method of inserting the resin tube 20 into the metal tube 10 and subjecting the metal tube 10 to the diameter reduction molding or the method of heating and expanding the synthetic resin tube may be used.

Next, an example in which a synthetic resin lining pipe is actually manufactured by applying the present invention will be specifically described together with a comparative example. (Example) A rubber-based adhesive having a thickness of 30 μm was applied to the inner peripheral surface of a steel pipe having an outer diameter of 28.2 mm and a wall thickness of 2.6 mm.
Allowed to dry for hours.

A rubber adhesive is also applied to the outer peripheral surface of a vinyl chloride synthetic resin tube having a two-layer structure having an inner layer and an outer layer.
It was applied in a thickness of μm and similarly dried for 3 hours. This 2
The layered vinyl chloride pipe is made by two-layer extrusion molding, and hard vinyl chloride is used as the inner synthetic resin layer.
Resin 1 in the same rigid vinyl chloride as the outer synthetic resin layer
30 parts by weight of calcium carbonate was added as an inorganic filler to 100 parts by weight and uniformly kneaded. At this time, the coefficient of linear expansion of the outer synthetic resin layer is 4.2 × 10 ⁻⁵ /
° C, Young's modulus E ₂ is 50,000 kgf / cm ² , and the coefficient of linear expansion of the inner synthetic resin layer is 7.5 × 10 ^-5 / °
C, Young's modulus E ₁ is 30,000 kgf / cm ² .

The thickness t ₂ of the outer synthetic resin layer is 0.6.
mm, and the thickness t ₁ of the inner synthetic resin layer is 1.0 mm,
The total thickness of the two-layer synthetic resin pipe was 1.6 mm, and the outer diameter of this synthetic resin pipe was 22.2 mm.

Then, the above-mentioned two-layer synthetic resin pipe is inserted into the steel pipe after coating and drying the adhesive, and the outer diameter of the steel pipe is 27.2 mm.
The lining pipe having the structure shown in FIG. 1 was obtained by reducing the diameter of the lining pipe.

In this lining pipe, the shear adhesive strength between the steel pipe and the outer synthetic resin layer is 50 kgf / cm ^2.
Met. In addition, this lining tube 4,000mm 6
A heating-cooling cycle test was conducted in which a cycle of 10 minutes at 0 ° C. and then 10 minutes at 20 ° C. was repeated for 10,000 cycles. When the tube end portion was observed after the test was completed, as shown in a partial sectional view in the axial direction in FIG. 2, no displacement occurred between the steel pipe and the outer synthetic resin layer, and between the layers.

After the test, the shear adhesive strength between the steel pipe and the outer synthetic resin layer at the pipe end is 45 kgf.
/ Cm ² , which was almost unchanged from before the test. (Comparative Example) The same rubber-based adhesive was applied to the inner peripheral surface of the same steel pipe as in the above-described example in a thickness of 30 μm and dried for 3 hours, and a single layer having a thickness of 1.6 mm and an outer diameter of 22.2 mm was used. Use the same rubber adhesive on the outer surface of the rigid vinyl chloride pipe
The coating was applied in a thickness of μm, dried for 3 hours, inserted into a steel pipe, and subjected to the same diameter reduction molding as above to obtain a lining pipe having the structure shown in FIG.

The shear bond strength between the steel pipe and the hard vinyl chloride pipe of this lining pipe was 50 kfg / cm ² . 60 ° with respect to this lining tube of 4,000 mm
After the same heating-cooling repeated test of C × 10 minutes and 20 ° C. × 10 minutes was performed for 10,000 cycles, the tube ends were observed, and as shown in FIG. 4, the steel tube and the hard vinyl chloride tube were There was a gap of 0.5 mm between the pipe ends.

The shear bond strength between the steel pipe and the hard vinyl chloride pipe at the end of the pipe after this test is 15
It was lowered to kgf / cm ² .

[0025]

As described above, according to the present invention,
An intermediate layer (outer synthetic resin layer) having a linear expansion coefficient substantially intermediate between these is interposed between the metal pipe and its inner synthetic resin pipe (inner synthetic resin layer) for corrosion protection, Since the thickness of the resin layer is approximately inversely proportional to the Young's modulus of both of them, even if the resin layer is used under conditions in which heating and cooling are repeated, the stress acting on the adhesive layer causes such an intermediate layer to act. It is much smaller than the one without it, and it is possible to prevent the metal pipe and the synthetic resin pipe from being displaced at the pipe end portion, and at the same time, reduce the decrease in adhesive strength.

Further, unlike the conventional measures, it is not necessary to mix an inorganic filler or the like into the inner resin layer in contact with the fluid to be conveyed, and a resin having a high corrosion resistance can be selected.
There is no risk of permeation of the fluid to be conveyed such as water or hot water and elution of the filler, and the manufacturing method is simpler than that of the conventional structure in which fiber reinforcement is applied only to the outer circumference of the synthetic resin pipe. Yes, it can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view taken along the radial direction of an embodiment of the present invention.

FIG. 2 is an axial cross-sectional view showing the condition of the pipe end portion after repeated heating-cooling tests in the example of the present invention.

FIG. 3 is a partial sectional view of a conventional synthetic resin lining pipe taken along a radial direction.

FIG. 4 is an axial cross-sectional view showing a condition of a pipe end portion after a heating-cooling repeated test is given to a comparative example.

[Explanation of symbols]

 10 Metal Tube 20 Synthetic Resin Tube 21 Inner Resin Layer 22 Outer Resin Layer 30 Adhesive Layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B32B 7/02 105 9267-4F F16L 9/14 7123-3J // B29L 23:22 4F

Claims (1)

[Claims] 1. A lining pipe in which a synthetic resin pipe is bonded to an inner peripheral surface of a metal pipe via an adhesive layer, wherein the synthetic resin pipe comprises an innermost synthetic resin layer and an outer synthetic resin layer outside thereof. The outer synthetic resin layer has a resin layer, and the outer synthetic resin layer has a linear expansion coefficient approximately in the middle of the linear expansion coefficients of the metal tube and the inner synthetic resin layer, and the thickness of the inner synthetic resin layer and the outer synthetic resin layer is , A synthetic resin lining pipe having a relationship approximately inversely proportional to each Young's modulus.