JPH06343924A - Formation of ptfe layer on metallic molded product surface - Google Patents

Abstract

PURPOSE:To solidify a resin layer and thereby prevent cracking from being caused by sticking thermally fusible fluororesin powder onto a primer applied to the surface of a metal molded product, then fusing the fusible fluororesin powder to form a fluororesin layer, and forming a thick wall part at least, on one part of the fluororesin layer with the formation of a PTFE resin layer on the fluororesin layer. CONSTITUTION:The surface of a butterfly valve 2, for example, is sand-blasted to clean and roughen the surface. Next, a primer 3 consisting of a water dispersion which contains fluororesin and an organic resin is applied using a brush. After that, a thermally fusible fluororesin powder is sticked to the surface of the primer 3. Further, the powder is heated beyond the melting point thereof to form a thermally fusible fluororesin layer (resin layer) 4. Further, a resin is built up at least, on one part of the resin layer 4 to form a thick wall part 5. Finally, a PTFE resin sheet is coated on the resin layer 4 and is thermally baked beyond the melting point to form a PTFE resin layer 6.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for forming a polytetrafluoroethylene (PTFE) resin layer on a surface of a metal molded body, and more specifically, a method for forming a polytetrafluoroethylene (PTFE) resin layer on a surface of a metal molded body such as steel, copper, aluminum or platinum. A method for forming a tetrafluoroethylene resin layer.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION Fluororesin such as polytetrafluoroethylene (hereinafter sometimes referred to as PTFE) has heat resistance, weather resistance, chemical resistance, releasability, sliding property, non-adhesiveness, mechanical strength. In comparison with other synthetic resins, it has remarkably superior characteristics.By utilizing this characteristic, coating materials for valves that handle corrosive fluids or high-temperature fluids or pipelines, tanks, machinery Widely used as a corrosion resistant lining material for equipment.

However, since the PTFE resin is non-adhesive as described above, it is considerably difficult to bond it to another material such as a metal even if an adhesive is used. Therefore, many methods have been proposed for increasing the adhesiveness between the PTFE resin and the metal. As one of them, there has been proposed a method of chemically activating the surface of a PTFE resin by treating the surface with a solution of metallic sodium dissolved in liquid ammonia. However, this method has a problem in that the treatment liquid itself may cause environmental pollution and the handling thereof is dangerous. Further, a method has been proposed in which the PTFE resin surface is subjected to a physical treatment such as plasma sputtering, or the PTFE resin surface is mechanically roughened such as by blasting. However, this method requires much labor. There was a problem that it was costly or accompanied by an increase in cost.

As a solution to the above-mentioned problems of the prior art, the applicant of the present invention has previously disclosed Japanese Patent Application Laid-Open No. 62-14973.
In Japanese Patent Application Laid-Open No. 2004-242242, a metal surface is coated with an aqueous dispersion (primer), and a large particle size (10
(0 μm or more) is adhered and heated to form a heat-fusible fluororesin layer, and the whole surface of the PTFE resin powder is coated on the heat-meltable fluororesin layer. A method of forming a fluororesin layer has been proposed. According to this method, it is possible to obtain a laminate in which the metal and the fluororesin layer are firmly bonded.

By the way, the present inventor further studied the method for forming the fluororesin (PTFE) layer on the metal surface as described above, and found that such a method was used for a valve element such as a butterfly valve (disc) or a bent portion. It has been found that, when applied to a metal molded body such as a tubular body having, for example, fine cracks may occur in the PTFE resin layer at a large bend. This is due to shrinkage during molding due to the difference in linear expansion coefficient between metal and PTFE.

Therefore, the PTFE resin layer can be firmly formed on the surface of the metal molded body, and the PTFE resin layer can be formed on the surface of the metal molded body so that the PTFE resin layer can be formed without cracks. The advent of methods is desired.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, in which PTF is formed on the surface of a metal molded body.
It is possible to form a PTFE resin layer on the surface of a metal molded body such that the E resin layer can be firmly formed and a PTFE resin layer without cracks can be formed even in a metal molded body having a large bending portion. It is intended to provide a forming method.

[0008]

SUMMARY OF THE INVENTION PTF on the surface of a metal molding according to the present invention
The method for forming the E resin layer is such that PTF is formed on the surface of the metal molded body.
When forming the E resin layer, a primer is applied on the surface of the metal molded body, and the heat-meltable fluororesin powder is adhered thereon, and then heated to a temperature above the melting point of the fluororesin powder to heat-melt. Forming a fluororesin layer, then forming a thick portion of the heat-melting fluororesin on at least a part of the heat-melting fluororesin layer, and forming a PTFE resin layer on the heat-melting fluororesin layer It is characterized by that.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in more detail below. In the present invention, the fluororesin layer is formed on the surface of the metal molded body, and as the metal molded body on which the fluororesin layer is formed, metal molded bodies such as steel, iron, and copper aluminum can be widely used. Of these, the present invention is particularly useful when a PTFE resin layer is formed on a metal molded body having a large bend, and for example, the outer peripheral portion of a valve body such as a butterfly valve or a gate valve, or a T pipe or L pipe. It is useful when a PTFE resin layer is formed on a tubular body such as. That is, when the metal molded body has a flat portion and a large bent portion, PTFE having a linear expansion coefficient about 10 times larger than that of metal also shrinks in the process of cooling after heating and firing of PTFE. Since the stress is concentrated on the large bend due to the large size, the present invention is useful in such a case.

The case where the metal molded body on which the PTFE resin layer is formed is a butterfly valve will be mainly described below. FIG. 1 shows a perspective view of a disk 1 which constitutes a butterfly valve.

The disk 1 is composed of a cylindrical shaft portion 1a and a butterfly blade-shaped flat portion 1c. The flat portion 1c becomes thinner toward an outer peripheral edge portion 1b formed in an arc shape. There is.

FIG. 2 shows the II-II of the disk 1 shown in FIG.
A line cross-sectional view is shown. As shown in FIG.
The process in which the TFE resin layer is formed is shown in a schematic diagram. Figure 3
FIG. 3 is an enlarged view of the outer peripheral edge portion 1b of the disc 1 shown in FIG.

In the present invention, prior to applying the primer on the surface of the butterfly valve 2, the butterfly valve 2
The surface of the butterfly valve 2 is cleaned by removing the rust and foreign matter adhering to the surface of the butterfly valve 2 by sandblasting the surface of the butterfly valve 2 and roughening the surface of the butterfly valve 2. It is preferable for enhancing the adhesive force between the butterfly valve 2 and the PTFE resin 6.

On the surface of the butterfly valve 2, a primer such as a primer 3 made of an aqueous dispersion containing a fluororesin and an organic resin is applied by a method such as brush coating. At this time, the primer-3 is
15~50g surface 1 m ² per butterfly valve 2 is preferably 20~35g much more preferably applied in an amount of 26～28G.

Such an aqueous dispersion includes PTFE, PFA which is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, FEP which is a copolymer of tetrafluoroethylene and hexafluoropropylene, as a fluororesin, A conventionally known fluororesin such as EPE which is a copolymer of tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl vinyl ether may be used. Of these, especially PTF
E is preferred.

As the organic resin, a combination of a polyarylene sulfide resin and a polyamideimide resin, a combination of a polyarylene sulfide resin and a polyimide resin, a combination of a polyarylene sulfide resin, a polyamideimide resin and a polyimide resin, a poly Allyllen sulfide resin alone, polyether sulfone resin, epoxy resin and the like are used.

In addition to the above-mentioned fluororesin and organic resin, the primer 3 may optionally include a fluorosurfactant, a viscosity modifier, a binder, an inorganic filler, a mica-like oxide, and a coupling. Agents, wetting agents and the like may be included.

Such a primer is, for example,
JP-A-50-77,432, JP-A-53-74,53
No. 2, JP-A-56-103, 256, and JP-B-57-1.
No. 8,559, Japanese Patent Publication No. 57-29,499, etc., and such a primer can be widely used in the present invention.

Next, the heat-meltable fluororesin powder 4 is attached onto the primer 3 applied to the surface of the butterfly valve 2. Examples of the heat-meltable fluororesin include PFA which is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, FEP which is a copolymer of tetrafluoroethylene and hexafluoropropylene, or tetrafluoroethylene and hexafluoropropylene. A heat-meltable fluororesin such as EPE which is a copolymer with perfluoroalkyl vinyl ether can be widely used.

Of these, PFA is preferably used. In the present invention, the heat-meltable fluororesin is preferably particles having a particle size of 100 μm or more, preferably 100 to 500 μm, more preferably 400 to 500 μm or more, and the adhesion amount is 1 m ^{2 on} the surface of the butterfly valve ^2. 200 to 380 g, preferably 250 to 330
It is desirable to be about g.

In the present invention, the primer 3 is used in this way.
After the heat-meltable fluororesin is adhered on the upper surface, the heat-meltable fluororesin layer 4 is formed by heating and firing at a temperature higher than the melting point of the fluororesin powder.

When the heat-meltable fluororesin is PFA, it is preferable to heat and fire it at a temperature of 375 to 380 ° C. Cooling after heating and firing may be performed by, for example, natural cooling.

Next, the heat-meltable fluororesin layer 5 is formed on at least a part of the heat-meltable fluororesin layer 4 thus formed by welding or the like to form the thick portion 5. The thick portion 5 of the heat-meltable fluororesin is used for the disc 1
It is preferable that the butterfly valve is formed on a large curved portion such as the outer peripheral edge portion 1b.

The heat-meltable fluororesin 5 is coated with PFA.
It can be performed using a heat-meltable fluororesin welding rod or welding band such as. Also, regardless of welding, PFA
Arrangement can also be performed by pressing in the annular body.

Next, a PTFE resin powder or a PTFE resin sheet is adhered on the heat-meltable fluororesin layer 4 and the thick portion 5 formed as described above, and this PTFE is applied.
PTF by heating and baking at a temperature above the melting point of the resin
The E resin layer 6 is formed.

The heating and firing of the PTFE resin can be carried out, for example, by a hot coining method. The firing temperature is usually 327 ° C. or higher, preferably 360 to 380 ° C.
It is desirable that it is a degree.

When the PTFE resin layer 6 is formed in this way, the PTFE resin can be formed without pressure, and when the metal molded body is a tubular body such as a T tube, the metal molded body can be formed. When the PTFE resin is formed on the body, the PTFE resin layer can be formed under pressure.
In order to form a PTFE resin (lining) layer by applying PTFE resin powder to a tubular body such as a T-tube,
It is preferable to press the E resin powder onto the inner wall surface of the steel pipe to apply it, and in this case, for example, a diaphragm member is placed inside the steel pipe, and the PTFE resin powder is filled between the inner wall of the steel pipe and the diaphragm member. A fluid such as water or oil is pressed into the inside of the diaphragm member to press the diaphragm member against the inner wall surface of the steel pipe, thereby causing PTF.
The E powder may be compressed into the inner wall of the metal at an equal pressure. At this time, a perforated plate is fixed to the surface of the steel pipe, and the primer, the heat-melting fluororesin, and the PTFE resin that serves as a liner are provided on the perforated plate so that the gas generated during the firing of the PTFE resin layer is passed through the perforated plate. Can be removed to the outside.

When the PTFE resin thus preliminarily molded is heated and fired at a temperature above the melting point of the PTFE resin as described above, the PTFE resin layer 6 firmly bonded to the surface of the metal molded body is obtained.

PTFE on the surface of the metal molding according to the present invention
In the method for forming a resin layer, a primer layer and a heat-meltable fluororesin layer are provided between a metal molding (butterfly valve) and a PTFE resin, and a part of the butterfly valve, for example, a large bend. A thick portion of the heat-melting fluororesin is formed in the portion, and the heat-melting fluororesin having a low melt viscosity flows into the crack 7 generated at the time of contraction after heating and firing, and the butterfly valve and the PTFE
It is thought that it adheres strongly to resin.

FIG. 4 shows a sectional view of the disk 1 on which the PTFE resin layer obtained by the present invention is formed. Further, according to the method of the present invention as described above, the PTF without cracks can be obtained.
An E resin layer can be formed. In particular, when the heat-meltable fluororesin layer is provided on the large bent portion of the metal molded body, the generation of cracks due to the large stress in the bent portion can be prevented.

As described above, according to the conventional method, cracks are generated in the PTFE resin layer in the large curved portion of the metal molded body, but according to the present invention, the large curved portion of the metal molded body is cracked. Since the thick part of the heat-meltable fluororesin is formed, even if thermal stress is generated from the inside of the PTFE resin layer during heating / baking / cooling, the PTF will not eventually crack.
An E resin layer is formed.

In the above description, the metal molded body is a butterfly valve disc, but the metal molded body to which the present invention is applied is not limited to this.

[0033]

As described above, according to the present invention, it is possible to form a firmly adhered PTFE resin layer on the surface of a metal molded body. In particular, according to the present invention, even in a metal molded body having a large bending portion, PTFE without cracks
A resin layer can be formed.

The method for forming a PTFE resin layer on the surface of a metal molded body according to the present invention is particularly useful when forming a PTFE resin layer on a butterfly valve or the like. The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0035]

Example 1 A primer (TCW8109BK) which is an aqueous dispersion of a fluororesin containing polytetrafluoroethylene resin powder and polyarylene sulfide resin on the surface of a stainless butterfly valve disk.
Daikin Industry Co., Ltd.) was applied uniformly with a brush to a coating amount of 26 g / m ² .

On this primer, P with a particle size of 400 μm
After the FA powder was adhered in an amount of 300 g / m ^2, the FA powder was heated to 380 ° C., which is a temperature higher than the melting temperature of PFA, and then allowed to cool.

Further, on the outer peripheral edge of this disc, PFA
A thick portion having a thickness of about 3 mm was formed with a welding rod. Next, the whole surface was covered with PTFE powder, and this was baked at 360 ° C. by a hot coining method to form a PTFE resin layer.

When a butterfly valve (disk) coated with the PTFE resin thus obtained was subjected to a penetrant flaw detection test, no crack was confirmed. The penetrant flaw detection test was performed using a test solution [a dye penetrant flaw detector (manufactured by NOF CORPORATION)].

A heat cycle test (-50 to 10) for promoting the progress of cracks in the obtained butterfly valve was also conducted.
However, no cracks were observed.

[0040]

Comparative Example 1 A PTFE resin layer was formed on the surface of a butterfly valve (disk) in the same manner as in Example 1 except that the PFA layer was not formed on the outer peripheral edge portion.

When the butterfly valve (disk) coated with the PTFE resin thus obtained was subjected to a penetrant flaw detection test in the same manner as in Example 1, P
Cracks were observed in the TFE resin layer.

[Brief description of drawings]

FIG. 1 shows a perspective view of a disk 1 which constitutes a butterfly valve.

FIG. 2 shows a cross-sectional view of the disc 1 taken along line II-II.

3 is an enlarged view of the outer peripheral edge portion 1b of the disk 1 shown in FIG. 2, and is a schematic view showing a process in which a PTFE resin layer is formed on the surface of the disk 1. FIG.

[Fig. 4] PF was found in cracks generated in the shrinking process after heating and baking.
A state in which the A resin flows in and the cracks are filled is shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Disc 1b ... Outer peripheral edge part 4 ... Thermofusible fluororesin layer 5 ... Thick part 6 ... PTFE resin layer

Claims (2)

[Claims] 1. When forming a PTFE resin layer on the surface of a metal molded body, a primer is applied on the surface of the metal molded body, and a heat-meltable fluororesin powder is adhered onto the primer, and then this fluororesin is formed. A heat-melting fluororesin layer is formed by heating to a temperature equal to or higher than the melting point of the powder, and then a thick part of the heat-melting fluororesin is formed on at least a part of this heat-melting fluororesin layer. A method for forming a PTFE resin layer on a surface of a metal molded body, which comprises forming a PTFE resin layer on a meltable fluororesin layer. 2. The method according to claim 1, wherein the metal molded body is a butterfly valve, and the thick portion of the heat-meltable fluororesin is the outer peripheral portion of the butterfly valve.