JPS63242610A - Manufacture of polytetrafluoroethylene sealing part - Google Patents

Abstract

PURPOSE:To obtain a polytetrafluoroethylene (PTFE) sealing part, which has uniform density and smooth sealing surface and in which no filler is exposed, by a method wherein molding stock, which mainly consists of PTFE, is put in a mold under the state being heated up to a specified temperature or higher and, after that, pressed by moving a moving mold so as to form into a desired shape. CONSTITUTION:Molding stock, which mainly consists of calcined PTFE and has a simple annular shape, is heated up to 200 deg.C or higher and put in a cavity 4 formed in a mold 3. Next, without shifting mixed molds 5, 6 and 7, which constitute the mold 3, a moving mold 8 is brought close towards the fixed mold 7 so as to compress the molding stock 2 by pressurizing in order to plastically flow and deform it along the inner form of the cavity 4 into a desired form. Through the plastical flow and deformation of the molding stock 2 along the inner form of the cavity 4, the surface of the PTFE molding stock 2 is oriented and becomes be draped to the surfaces of the molds 5, 6, 7 and 8, resulting in smoothly and hardening the surface. In addition, no ununiform density of the PTFE molding stock 2 results.

Description

Detailed Description of the Invention The present invention relates to a method for manufacturing a polytetrafluoroethylene resin seal component, and more specifically, a polytetrafluoroethylene resin seal having a smooth sealing surface. Concerning a method for easily manufacturing parts.

Technical background of C and its problems 11, polytetrafluoroethylene resin (hereinafter also abbreviated as rPTFEJ)
has excellent heat resistance and chemical resistance, low coefficient of friction, and self-lubricating properties, so it is widely used as sealing parts such as gaskets, O-rings, valves, and cocks.

By the way, PTFE does not necessarily have good abrasion resistance and also does not necessarily have sufficient compressive strength.
Various fillers may be added to improve wear resistance and mechanical strength. Fillers added to such PTFE medium □ include glass fiber, carbon i! Inorganic fillers such as fiber, graphite, molybdenum disulfide, and bronze powder are known.

In order to mold such PTFE into various shapes for use as seal parts, PTFE resin, unlike other thermoplastic resins, has low fluidity when heated, so conventionally the following special molding method has been used. is used.

(b) Fill a mold with a cavity shape that is approximately the same as that of the desired 1q PTFE resin powder, pressurize and compress it to create a PTFE preform, and then process this preform. A method of obtaining a seal component of a predetermined shape by firing at a temperature higher than the melting point temperature of PTFE (327°C).

(b) PTFE resin powder is filled into a mold having a cavity shape larger than the shape to be obtained, and then compressed under pressure to create a block-shaped preformed product with a machining allowance;
Then, after firing the block at a temperature of 327°C or higher,
A method of cutting this block to obtain seal parts of a predetermined shape.

However, in the method (a) according to such a conventional example, when trying to obtain a seal part with a particularly complicated shape, PTF is used in a cavity of a predetermined shape formed in a mold.
It is difficult to uniformly and evenly fill the E-resin powder, and as a result, there is a problem in that the density of the obtained sealing part tends to be non-uniform. If there is uneven filling of PTFE resin powder in the mold, excessive pressure is applied during pressure compression in areas with high packing density, which tends to cause cracks, while in areas with low packing density, there is insufficient pressure. This results in a porous shape. In addition, if there is uneven density in the sealing part due to uneven filling, uneven expansion and contraction will occur during firing and cooling, resulting in poor dimensional stability and inconsistent mechanical strength. Ta.

On the other hand, the method (b) has relatively few drawbacks compared to the method (a), but there is a risk that the sealing surface of the seal part may become rough when cutting into a predetermined shape, resulting in a decrease in sealing performance. There was that. In addition, especially when PTFE to which a filler such as glass is added is molded as a seal part by the method (b) above, the filler such as glass may be exposed on the sealing surface by cutting and may damage the mating member. was there. Generally speaking, the method (b) involves preforming with a cutting allowance, which has the disadvantages of increasing material costs and making the cutting process complicated.

Purpose of the Invention The present invention was made in order to eliminate such inconveniences, and it is possible to produce a PTFE Wa seal component having a uniform density and a smooth sealing surface without exposing the filler without cutting it. Easy to mold at low cost
The purpose of the present invention is to provide a method for molding a TFE seal component.

In order to achieve the objective of requiring only one batch of labor, the method for manufacturing polytetrafluoroethylene resin seal parts according to the present invention involves molding into a simple shape whose main component is polytetrafluoroethylene resin that has been heated and fired in the previous step. The material is heated to about 200° C. or more and then placed in a mold, and then a movable die in the mold is moved to pressurize and plastically deform the molding material to form the molding material into a desired shape. It is characterized by

According to such a method according to the present invention, a molding material mainly composed of polytetrafluoroethylene resin (PTFE) is pressurized in a mold to cause plastic flow deformation, so that the PTFE crystals on the surface are As it becomes oriented, it conforms to the surface of the mold, and the sealing surface becomes smooth and hard. Furthermore, the density of the molded material does not become non-uniform.

The heating temperature for pressurizing the PTFE molding material to undergo plastic flow deformation may be 200°C or higher, but preferably 300°C to 350°C.

This is because if the heating temperature is low, there is a risk of shear deformation of the molding material due to pressure, and if it is heated to near the melting point of PTFE, the micro-Brownian motion of the molecules becomes active, making it easier to deform plastically. It is.

If a filler such as glass is injected into the PTFE molding material, when the molding material is plastically deformed in the mold, the PTFE oozes out to the surface and adapts to the mold surface. , fillers such as glass are not exposed on the surface that is the sealing surface, and the sealing surface is smooth in this case as well.

Hereinafter, a method for manufacturing a PTFE Iu seal component according to the present invention will be explained based on an embodiment shown in the drawings.

FIGS. 1(A) to (C) are PTFs showing one embodiment of the present invention.
FIG. 2 is a cross-sectional view of a main part showing the molding process of a seal part made by E, and FIG. 2 is a cross-sectional view of a seal part obtained by the method according to the same example.

The embodiment according to the present invention shown in FIGS. 1 and 2 shows an example in which the valve seat 1 shown in FIG. 2 is manufactured as a seal component made of PTFE.

In this example, first, a simple ring-shaped molding material mainly composed of polytetrafluoroethylene resin (PTFE) heated and baked in the previous step was heated at 200°C or higher, preferably at 30°C.
Heat at a temperature of 00°C to 350°C. Thereafter, as shown in FIG. 1 (A>), the heated molding material 2 is placed into a cavity 4 formed in a mold 3.

Next, without moving the fixed molds 5, 6.7 that constitute the mold 3, the movable mold 8 is moved toward the fixed mold 7, and the molding material 2 is moved as shown in FIGS. 1(B) and (C). Press and compress as shown. Then, the molding material 2 undergoes plastic flow deformation along the internal shape of the cavity 4, and is molded into the desired shape. By plastically deforming the molding material 2 along the internal shape of the cavity 4 in this way, the surface of the PTFE￥A molding material 2 is oriented and conforms to the surfaces of the molds 5, 6, 7.8. becomes very smooth and hard. Moreover, P.T.
The density of the FE molded material 2 does not become non-uniform. Furthermore, when a filler such as glass is injected into the PTFE molded material 2, the surface is similarly smooth, and the filler such as glass is not exposed on the sealing surface and will not damage the mating member. This is thought to be because the PTFE oozes out to the surface and adapts to the mold surface due to plastic flow deformation due to pressurization of the molding material 2.

Finally, if the valve seat 1 molded by plastic flow deformation of the molding material 2 is taken out from the mold 3, the valve seat 1 shown in FIG. 2 is obtained. The sealing surface 9 of the valve seat 1 formed in this manner is extremely smooth and hard.

Furthermore, even when molding the molding material 1 in which a filler such as glass is injected into PTFE, the filler such as glass is not exposed on the sealing surface.

According to one embodiment, PTF obtained by the method of the invention
The average surface roughness R0 of the E-manufactured seal parts was 2.2 μm. On the other hand, the average surface roughness Ra of the seal parts obtained by the conventional method (the final cutting method) was 4.0 μm, proving the effectiveness of the method of the present invention.

Note that the present invention is not limited to the embodiments described above, and can be modified in various ways.

For example, in the above-mentioned embodiment, an example was shown in which the valve seats 1 to 1 made of PTFE were manufactured, but the invention is not limited to this, and can be used in a wide range of applications such as general seal parts such as O-rings, V-packs, etc., as well as valves and cocks. The seal parts in f! The present invention can be applied when building A.

Further, in the above-described embodiment, the molding material 2 is heated and then put into the mold 3; however, the present invention is not limited to this.
After putting the molding material 2 inside, the molding material 2 may be heated and pressurized.

As explained above, according to the present invention, a simple-shaped PTFE molding material formed by heating and firing in the previous step is put into a mold in a heated state, and this molding material is placed in the mold. Since the PTFEtlJ seal parts have a uniform density and a smooth sealing surface without exposing the filler, etc., they can be molded into the desired shape without the need for cutting. It has the excellent effect of being easy to manufacture at low cost.

[Brief explanation of drawings]

FIGS. 1(A) to (C) are PTFs showing one embodiment of the present invention.
FIG. 2 is a cross-sectional view of a main part showing the molding process of a seal part made by E, and FIG. 2 is a cross-sectional view of a seal part obtained by the method according to the same example. 1... Valve seat 2... Molding material 3.
...Mold 8...Movable mold 9...Seal surface Patent applicant Nippon Valqua Industries Co., Ltd. Agent Patent attorney Shunichi Suzuki Figure 1 (A) (B)
(C) Figure 2 Procedural Amendment March 31, 1988 El. 6□1,11,11 Okaya Sea 1, Indication of the case 1988 Patent Application No. 78,347 2, Name of invention Method for manufacturing seal parts made of polytetrafluoroethylene resin Name Name Nippon Valqua Industries Co., Ltd. N.M. Building
4th floor [Telephone Tokyo (444) 3151] A. Voluntary amendment 6. Target of amendment ``Detailed description of the invention'' column teta. The phrase "Patsukin, 0 ring," should be corrected to "Patsukin, gas get, 0 ring." 2) In the second line from the bottom of page 7 of the same book, the phrase "Put it into the cavity 4." The condition is better,” he corrected. 3) In the last line of page 8 of the same book, the phrase ``The valve seat 1 shown in Figure 2 is obtained.'' was replaced with ``The valve seat 1 shown in Figure 2 is obtained. It is preferable when the temperature drops to at least 60 degrees Celsius or lower.'' I am corrected. 4) In the fourth line from the bottom of page 9 of the same book, the phrase ``0 ring, ■ packing, etc.'' is corrected to ``0 ring, V packing, gas get, etc.''

Claims (1)

[Claims] 1) A simple-shaped molding material mainly composed of polytetrafluoroethylene resin that has been heated and fired in the previous step is heated to about 200° C. or higher and placed in a mold, and then A method for manufacturing a polytetrafluoroethylene resin sealing part, which comprises moving a movable die to apply pressure to the molding material to cause plastic flow deformation and molding the molding material into a desired shape. 2) The method for manufacturing a polytetrafluoroethylene resin seal component according to claim 1, wherein the heating temperature of the molding material is 300°C to 3500°C.