JPS63122735A - Valve seat material - Google Patents

Abstract

PURPOSE:To obtain an inexpensive valve seat material having excellent creep and pressure resistance in addition to original characteristics, by blending polytetrafluoroethylene with a copolymer of tetrafluoroethylene and a perfluoroalkyl vinyl ether. CONSTITUTION:A valve seat material obtained by homogeneously blending polytetrafluoroethylene with a copolymer (hereinafter referred to as PFA) of tetrafluoroethylene and a perfluoroalkyl vinyl ether at >=3-<10wt% ratio, filling the resultant blend in a mold and compression molding the blend into a sheet of desired shape while heating. The resultant sheet can be used as, e.g. a seat of a ball valve, etc., to remarkably reduce cost as compared with that of a seat material solely using PFA without causing creep to deteriorate function of the ball valve when used under high pressures with extremely small swelling by styrene monomer, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in sheet materials used in ball valves, butterfly valves, and other valves that control the opening and closing of various fluid flows. .

"Conventional technology and its technical problems" Synthetic rubber and metal were previously used as sheet materials for ball valves, etc., but in recent years, these conventional sheet materials have been replaced with materials that have low frictional resistance, Polytetrafluoroethylene (hereinafter referred to as PTFE) is widely used because of its excellent properties such as abrasion resistance, chemical resistance, and temperature resistance.

However, as a sheet material, this PTFE is not superior to conventional synthetic rubber or metal in all aspects, and its creep resistance is inferior, so it is difficult to use sheets made of P, TFE, especially under high pressure. When used, it causes creep and permanent deformation, which is a major problem that reduces the function of the ball valve, and when controlling the opening and closing of monomers such as styrene.

The styrene monomer penetrates into the sheet material and the PTFE
The sheet material swells, causing malfunction of the ball valve and, as a result, causing damage to the sheet itself.

Therefore, in view of the problems with such PTFE sheets, an improved sheet material shown in Japanese Utility Model Publication No. 51481/1983 has already been provided.

The improved sheet material is made of a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (hereinafter referred to as PFA), which has excellent properties against polymers such as styrene, and also has particularly excellent creep resistance and pressure resistance. ).

Therefore, with the advent of PFA sheets, it has become possible to eliminate the problem of PTFE sheets, but on the other hand, since the price of PFE is about 5 to 10 times that of PTFE, it has become difficult to use sheet materials. Although it has the above-mentioned advantages, it has not been put into practical use in a wide range of general situations because it has the economical problem of being extremely expensive.

"Means for Solving the Problems" Therefore, the present invention is based on the conventional PTFE1i! Alternatively, it was developed to effectively solve the problems of PFA sheets, and adopted a configuration in which a sheet material is formed from a mixture of PFA in a weight ratio of 3% to less than 10%.

"Function" Therefore, since the present invention uses a mixture of PTFE and PFA as the valve seat material, in addition to the excellent properties of PTFE,
It is now possible to simultaneously add the excellent properties of PFA to the seat material, and by mixing PFA at a weight ratio of 3% to less than 10%, a valve seat material that satisfies the requirements for a seat material is provided. Not only can this be achieved, but the manufacturing cost can be significantly reduced compared to an improved sheet material made of PFA alone.

"Example" Hereinafter, the present invention will be described in detail based on Examples.
It is not a mixture of PTFE, which has excellent abrasion resistance, chemical resistance, and temperature resistance, and PFA, which has excellent properties against monomers such as styrene, and also has excellent creep resistance and pressure resistance. Moreover, it is characterized in that the mixing ratio of PFA is 3% or more and less than 10% by weight.

In addition, the reason why the mixing ratio of PFA was limited to 3% or more and less than 10% by weight as described above is that in order to compensate for the disadvantages of PTFE and add the advantages of PFA, PFA must be at least 3% and less than 10% by weight. % is sufficient, and if the mixing ratio exceeds this, a sufficient reduction in the cost of the valve seat cannot be expected.

In addition, to give an example of manufacturing a sheet material in which PTFE and PFA are mixed, PTFE powder has a weight ratio of 3% or more.
It is sufficient to uniformly mix less than 0% PFA powder, and by filling it into a mold and heating and compressing it, it becomes possible to easily produce a sheet of a desired shape.

Next, an example in which the valve seat material of the present invention is used for the seat 1 of a ball valve will be described with reference to the drawings.

As shown in the drawing, the ball valve to be used has a valve chamber 3 defining a fluid passage, and an inlet 4 and an outlet 5 communicating with the valve chamber 3 continuously formed inside the valve body 2. At the same time, a ball 6 having a through hole 6a is rotatably arranged in the valve chamber 3, and the ball valve can be opened or closed by operating a handle 8 connected to the ball 6 via a stem 7. It is configured so that it can be rotated to any position.

Then, the sheet 1 formed of the mixed sheet material of PTFE and PFA of this embodiment is installed between the wall surface on the inflow and outflow side of the valve chamber 3 and the ball 6, and when the ball 6 is in the open state. , ensuring communication between the inlets 4 and 5 and the through hole 6a of the ball 6, and conversely ensuring a sealed state between the valve body 2 and the ball 6 when the ball 6 is in the closed state. There is.

However, in a ball valve having such a configuration, if PTFE, which has poor creep resistance and pressure resistance, is used for the sheet material of the seat 1, the ball valve is in a closed state and the inlet port 4
When high pressure is applied to the side, this pressure acts on the ball 6, which compresses the sheet on the outlet 5 side, which deforms the sheet and causes creep. When the sheet is deformed in this way, the ball 6 cannot be elastically sandwiched between the sheets on both sides, and when the sheet is opened or the pressure on the inlet 4 side is removed, the ball 6 will be slightly distorted by its own weight. When the valve falls and becomes closed, or when pressure is applied to the inlet 4 side, fluid leaks, completely reducing the sealing function of the valve.

In addition, the sheet of the inlet 4 flange may also be pressed against the ball 6 by the pressure on the inlet 4 side during the initial high pressurization, causing deformation due to creep. If it becomes impossible to hold the ball 6 and the pressure on the inlet 4 side is removed, it is highly conceivable that the ball 6 will fall due to its own weight.

However, in the case of a sheet using the sheet material of the present invention, in addition to the excellent properties of PTFE, PFA, which has excellent creep resistance and pressure resistance, is mixed, making the conventional PTFE sheet material much wider. Since this has been improved, even in the above case, there is no need to worry about creep occurring.

Furthermore, even when used in a ball valve using a monomer such as styrene as a fluid, the styrene monomer penetrates into the PTFE sheet and causes malfunction of the ball valve, as in the past.

As a result, damage to the sheet material is extremely reduced.

Therefore, the seat formed from this sheet material not only does not deteriorate the function of the ball valve due to creep as compared to the conventional PTFE seat sheet, but also has extremely little swelling due to styrene monomer, etc., so it meets the requirements for a sheet material. At the same time, the weight ratio of PFA is 3%.
Since it is less than 10%, it has become possible to significantly reduce the cost compared to a sheet material made of PFA alone, and it has become possible to greatly contribute to practical application from an economical standpoint.

Although the illustrated object is a ball valve, the seat material of the present invention is not limited to this, and it goes without saying that it can be applied to butterfly valves and other various valves that require a seat material. stomach.

"Effects of the Invention" As described above, the present invention uses PFA in a weight ratio of 3% or more as a monochrome material, so in addition to the excellent properties of PTFE, PFA
It is now possible to add the excellent properties of FA to the seat material at the same time, making it possible not only to provide a valve seat material that satisfies the requirements for a seat material, but also to significantly reduce manufacturing costs compared to sheet materials made of PFA alone. It became possible to do so.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of a ball valve using a valve seat material according to an embodiment of the present invention. 1... Seat, 2... Valve body, 3... Valve chamber,
6... Ball.

Claims (1)

[Claims] A sheet material used for valves, which is a mixture of polytetrafluoroethylene and a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, the copolymer containing 3% or more and less than 10% by weight. A valve seat material characterized by being mixed.