JPS58134271A - Packing - Google Patents

Abstract

PURPOSE:To improve performance of a packing by using aramid fiber of extremely small diameter as a fiber base material, filling the fiber with powder filling material as closing texture and a lubricant and mixing a bonding agent therein to form a deasbestos packing. CONSTITUTION:A fiber base material is aramid fiber (a general term for fibers comprising a reaction product of aromatic diacid chloride and aromatic diamine). A suitable filling material and a bonding agent are mixed with the aramid fiber having an extremely small diameter. A packing is thus constructed. This is a de-asbestos packing, which shows much better performance as compared with an asbestos packing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gasket for sealing fluid, and relates to a so-called plastic gasket.

Conventionally, for example, gaskets used to make valves for airbags are mainly made of a known fiber base material such as asbestos, and this fiber base material is filled with a powder filler such as graphite or mica (talc) to form a fluid. A packing that functions as a plugging material to prevent seepage and leakage, and has a bonding material such as rubber mixed into the sliding resistance to give the packing itself moldability, flexibility, shape retention, etc. is common.

However, using asbestos as a fiber base material
For the past few years, regulations on the use of asbestos have been promoted worldwide for environmental health reasons, and it is important to find alternatives to asbestos.
This packing technology has become an important issue even if neglected. However, as its history shows, it is extremely difficult to find a fiber base material to replace asbestos. The biggest reason for this is that the fiber diameter of asbestos is extremely fine. In other words, if the fibers are extremely thin, the mutual bonding force between the fibers increases, and the specific surface area (in the case of asbestos, lO
~40Wl/gr. ) also increases, so the cohesive force at the fiber interface increases.

This improves the strength of the packing itself, improves the retention and dispersibility of the filler and binder, and makes the packing excellent in its restorability and sealing performance. However, currently it is 1,
Among fibers other than asbestos, there are no organic or inorganic fibers with a diameter as fine as asbestos, and only fibers with a wire diameter of a few microns are being explored, and this is the reality. .

Therefore, as an alternative to asbestos, aramid fiber (of which aromatic polyamide fiber is one type) has been attracting the most attention among the fiber base materials for packaging, which has a relatively small fiber diameter and is suitable for asbestos. It is seen as promising as a fiber base material for other materials. However, even this aramid fiber has a thickness of 1 denier (.

It has a fiber diameter of approximately 9 microns or more, so it cannot be expected to be used as a fiber base material for packaging as much as asbestos. By the way, P, which is the thinnest ordinary aramid fiber,
FIG. 1 shows a scanning electron micrograph of a 500-fold magnification of the -Finishin terephthalamide fiber. As can be seen from Figure 1, the fiber diameter is approximately 12 microns, and each fiber is rod-shaped, just like glass fiber. It turns out that this cannot be expected.

The present invention has been made based on the above circumstances, and will be described in detail below.

First, the present invention began with research into whether it was possible to make the aramid fiber shown in FIG. 1 even finer. Of course, several other fiber materials were also the subject of this research, but strangely, when only aramid fibers were given the type of energy that they were, the energy in the longitudinal direction of the fibers, i.e., as shown in Figure 1. It was discovered that the rod-shaped fibers crack in the longitudinal (longitudinal) direction and branch out, resulting in fibers with a diameter of 1 micron or less. It has also been found that this energy application can be achieved by mechanical grinding. Moreover, the way this aramid fiber is destroyed by grinding is in the direction of increasing the aspect ratio, making it advantageous as a fiber base material for packing.
It is expensive. FIG. 2 is an electron micrograph of the aramid fiber shown in FIG. 1 enlarged by 500:':: after mechanically grinding. As can be seen by comparing Figure 2 and Figure 1, the condition of the fibers has completely changed, and by grinding, they become less than 0.01 denier (0.1 micron in fiber diameter), making them luxurious. , the specific surface area was as high as 10 to 16 vd/gr.

FIGS. 8 and 4 show a comparison between the ultra-fine diameter aramid fibers obtained in this way and asbestos. Figure 8 shows asbestos, and Figure 4 shows ultra-fine aramid fibers, both of which are 1
This is an optical microscope photograph magnified 00 times, and it was found that the ultra-thin diameter aramid fibers looked no different from asbestos. Regarding whether or not the ultra-fine aramid fibers obtained in this way are suitable as fiber base materials for packing,
As a result of further various studies, we found out the following.

(a) The fiber diameter is extremely fine.

It was found that the fiber diameter was sufficiently thin and comparable to asbestos in terms of sealing properties, restoring properties, filler retention properties, etc.

(b) The fibers are strong against friction, etc.

Fibers that are weak against bending and rubbing will break during the manufacture or use of the packing, lowering the aspect ratio and causing problems with the strength of the packing. On the contrary, the aspect ratio increased, resulting in a high modinilas.

(c) The coefficient of thermal expansion is not large.

For example, the coefficient of thermal expansion is larger than that of the material of the casing or shaft (valve shaft) of equipment such as valves and pumps, so there is no problem at all.

) The modulus of the fiber is sufficiently high.

This directly affects the restorability of the packing and causes stress relaxation in the packing, but since ultra-thin diameter aramid fibers are sown with high modulus, it is possible to maintain stable sealing performance.

#,) Corrosion resistant.

Since it is stable against various chemical solutions, it is not restricted by the type of fluid to be sealed.

(f) Heat resistant.

Although it is not as heat resistant as asbestos, it is used in the industrial market.
The temperature used is often 150° C. or lower, and it has been found that ultra-fine aramid fibers exhibit very little decrease in strength and modulus even at about 170 t''.

As described above, it has been confirmed that aramid fibers with ultra-fine diameters are extremely promising as fiber base materials for puff hands.

Therefore, in the present invention, ultra-thin diameter aramid fibers are used as a fiber base material, and this is filled with a powder filler as a packing and lubricant! This was mixed with a binding material to form a package. .

When we investigated the characteristics of such a seal, such as torque and leakage, we found that the results are quite good, as detailed below based on examples. , 1 The difference between the invention product M'' and 1'' and comparative product B shown in Table-1.
,,11.1 ・Installed as a seal for the valve stem of a screw-in globe valve for JI8 bronze 101- by using a kin, and the stem torque (4-an) corresponding to the number of repeated opening and closing of the valve is applied. We investigated the sliding characteristics of the packing by measuring it.

The results are shown in the graph of FIG. In FIG. 5, the horizontal axis shows the number of times N of opening and closing the valve, and the vertical axis shows the stem torque T.

Table 1 As can be seen from the results in Figure 5, product A of the present invention exhibited more stable torque than comparative product B, and moreover, the torque was lower.

Furthermore, when we observed the valve stem after measurement, we found that the surface of the valve stem of comparative product B was slightly rough due to scratches caused by friction.
No roughness was observed on the surface of the valve stem of the product of the present invention, and it had a beautiful surface.

[Example 2] With the same packing specifications shown in Table 1, the present invention product M and comparative product B were incorporated as a valve stem packing for a 10V threaded globe valve made of JI8 blue steel. The sealing characteristics of the seal were examined in detail by measuring the amount of leakage (ccz) of the seal against the tightening torque (same-em) of the valve seal retaining plate tightening bolt. Note that the test was carried out with nitrogen gas (N8) being loaded onto 101d as the fluid to be sealed.

The results are shown in the graph of FIG. The horizontal axis in FIG. 6 shows the tightening torque of the tightening bolt of the MI-valve, and the vertical axis shows the leakage amount Q of nitrogen gas.

As can be seen from the results in Figure 6, the invention product B is
Compared to , the amount of leakage is small for each tightening torque
It showed good sealing properties.

As detailed above, it has been confirmed that the packing according to the present invention is a so-called asbestos-free packing that does not use asbestos at all, and has superior performance to asbestos packing. However, there are a number of currently known fibers that can be substituted for asbestos as fiber base materials for packing materials, but inorganic fibers such as rock fibers, glass fibers, carbon fibers, and silicon carbide fibers are generally bent. Heat-transferable fibers such as polyamides, which have low strength and do not have normal one-half rings, have a large coefficient of thermal expansion, resulting in a decrease in strength, modulus, and gelatinity at high temperatures. Hard fibers are insufficiently resistant to abrasion. Furthermore, at the current technological level, all of these candidate fibers to replace asbestos have fiber diameters on the order of several microns, and none have a fiber diameter of 1 micron (1 μm) or less, making them fully satisfactory as fiber base materials for packing. There's nothing I can do.

On the other hand, the Patsukin according to the voice invention uses arami and rad fibers (a general term for fibers made of the reaction product of aromatic diazide chloride and aromatic diamine) as fiber base materials with an ultra-fine fiber diameter. The diameter of the packing is made up of a suitable filler and binder, so it is an asbestos-free packing and has even better performance than asbestos packing. Obtained.

[Brief explanation of drawings]

Fig. 1 is an electron micrograph showing normal aramid fibers, Fig. 2 is an electron micrograph showing ultra-fine aramid fibers, Fig. 8 is an optical micrograph showing asbestos, and Fig. 4 is an ultra-fine aramid fiber. Optical micrograph showing aramid/de fibers,
5 and 61 are graphs showing the characteristics of the packing according to this explanation, FIG. 5 shows the relationship between the number of valve openings and closings and the stem torque, and FIG. 6 shows the relationship between the valve tightening and stem torque. It shows the relationship between Porto's tightening torque and leakage amount. M... Invention product B... Comparative product □・” Applicant: Nippon Pillar Industries Co., Ltd., Tv (kg-cm)

Claims (1)

[Claims] (1) A packing consisting of a 111m base material, a powder filler, and a binding material, characterized in that the fiber base material is an aramid fiber with an extremely small diameter.