JPS63130984A - Inner-surface coated tube - 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] [Field of Industrial Application] The present invention is applicable to hot water supply, water supply piping, water heaters, etc. used as building equipment piping in hotels, office buildings, hospitals, condominiums, housing complexes, etc. This invention relates to internally coated tubes used as heat exchanger tubes.

[Conventional technology and its problems]

Steel pipes, stainless steel pipes, PVC pipes, steel pipes, and internally coated steel pipes whose inner surfaces are coated with synthetic resin are generally used as building equipment piping, and each has its advantages and disadvantages.
They also have different uses.

For example, although steel pipes are inexpensive, they have drawbacks such as high corrosiveness that can cause pipe closures and red water. Stainless steel pipes have sufficient corrosion resistance, but the work of connecting the pipes is complicated. Although PVC pipes have excellent corrosion resistance and workability, they have low heat resistance, so they cannot be passed through piping for hot water such as hot water supply.

Steel pipes have excellent corrosion resistance, workability, and heat resistance, but depending on the water quality, they can cause pitting corrosion or produce blue water.

Since internally corrugated IT steel pipes maintain corrosion resistance only with a synthetic resin film as a coating material, the film needs to be thicker, which causes an increase in weight.

In addition, there are disadvantages such as poor workability due to complicated pipe connections.

An object of the present invention is to eliminate the disadvantages of the conventional examples and provide an inexpensive inner-coated tube that is excellent in corrosion resistance, workability, and heat resistance for use as architectural piping or heat exchanger tubes.

[Means for solving problems]

In order to achieve the above object, the gist of the present invention is that the inner surface of a tube containing 95 wt% or more of copper is coated with a urethane-modified epoxy resin with a film thickness of 5 to 500 μm by heating and curing. It is.

[Effect]

According to the present invention, since the resin that coats the inner surface of the tube is a urethane-modified epoxy resin, the resin itself has a three-dimensional network structure, which increases the heat resistance of the resin and reduces the amplitude of vibration of the resin structure. be able to. Unlike epoxy resins conventionally used for cladding pipes, this resin has sufficient performance for low-temperature water such as water supply, but does not have sufficient heat resistance when hot water such as hot water is passed through. When the skeleton vibrates, water molecules easily enter the membrane, and there is no problem that hydrolysis of the crosslinked portion occurs and the resin deteriorates.

Furthermore, as an incidental effect, coordination bonds are partially formed between the N atoms in the urethane and the Cu atoms at the interface between the resin and the metal, dramatically improving the adhesion of the resin. No peeling due to expansion or contraction.

Further, the present invention provides the urethane-modified epoxy resin,
A film thickness in the range of 5 to 500 μm is formed by heat curing, and heat curing has the role of starting a crosslinking reaction by modifying the urethane in the resin. And the film thickness is 5μ
m or more, even when used in applications where the water temperature inside the pipe is higher than outside the pipe, such as in hot water supply piping, water can be prevented from entering the membrane due to thermoosmotic pressure due to the temperature difference inside and outside the pipe.

Furthermore, urethane-modified epoxy resins have lower elongation than general resins, so if the film gets thicker, the film is more likely to crack due to internal stress during heating finger curing.
This is prevented by setting the upper limit of the film thickness to 500 μm.

As mentioned above, coordination bonds are formed between the N atoms in the urethane and the Cu atoms in the base, dramatically improving the adhesion between the film and the base, but the concentration of other elements other than Cu in the base metal When the temperature increases, oxides of that element are formed on the surface,
Bonding between Cu and N becomes hindered. In the present invention, the tube is made to contain 95 wt % or more of copper so that the bonding between Cu and N can be effectively performed while avoiding interference caused by this type of oxide.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

The figure is a partially cutaway front view showing one embodiment of the inner-coated tube of the present invention, and in the figure, 1 indicates a copper alloy tube containing 95 wt% copper. The inner surface of the tube 1 is coated with a urethane-modified epoxy resin 2. At this time, the resin 2 is heated to a temperature of about 150° C. or more to cure it, so that the film thickness falls within the range of 5 to 500 μm. did.

In order to test the effects of the present invention, various pipe material specimens were prepared by varying the proportion of Cu in the copper alloy as the base metal and using epoxy resin, silicone resin, and urethane-modified epoxy resin as the coating material. Water from C was passed for one year.
Corrosion of the base metal and deterioration of the coating material were investigated. The results are shown in Table 1 below. In the above investigation, corrosion and deterioration were visually determined, and the amount of Cut+ elution was analyzed by analyzing Cut't eluted from the inner surface of the tube after 24 hours of storage with water. As shown in Table 1, in the inner clad tube of the present invention, neither corrosion of the base metal nor deterioration of the coating material was observed.

Moreover, the amount of Cu melted was also <0. O was as low as 5ppm.

In comparison, in the comparison tube, deterioration of the base material and coating material was observed, and the amount of Cu eluted was also increased accordingly.

〔Effect of the invention〕

As described above, the internally coated pipe of the present invention has excellent corrosion resistance and heat resistance, and has high utility value as hot water supply, water supply piping, and heat exchanger pipe, and has improved workability without the occurrence of cranks. , it is also low cost.

[Brief explanation of the drawing]

The figure is a partially cutaway front view showing an embodiment of the inner clad tube of the present invention. 1... tube

Claims (1)

[Claims] The inner surface of the tube containing 95 wt% or more of copper is heated and cured with urethane-modified epoxy resin to a thickness of 5 to 500 μm.
An internally coated tube characterized by being coated with a film thickness of .