JP3008343B2 - Expanded graphite sheet and gland packing using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as various sealing materials such as gaskets, V-rings and valve seats, sliding materials such as bearings, heat insulating materials for high temperature, agricultural materials and civil engineering materials. The present invention relates to an expanded graphite sheet to be used and a gland packing formed of the expanded graphite sheet as a material and used for sealing a shaft of various fluid devices and mainly used under lubrication conditions of water or steam.

[0002]

2. Description of the Related Art Expanded graphite is a tetrafluoroethylene resin (P) generally used as a constituent material for various sealing materials and the like.
TFE, PTA, etc.) and rubber have excellent heat resistance, so they are widely used as various sealing materials in recent years. By the way, the expanded graphite sheet conventionally used generally has a low water content of about 0.1 to 0.5%, and the expanded graphite sheet is formed by expanding expanded graphite particles by press molding or roll molding. Since the expanded graphite particles are self-adhered to each other by being brought into close contact between the bellows-like layers that have been expanded by pressing, the surface layer is dense and has water repellency, In the use mode, neither water nor moisture is absorbed from the surface layer. For this reason, various sealing materials composed of such an expanded graphite sheet are often used in a dry (dry) state, and as is clear from Table 1, exhibit a higher friction coefficient than PTFE or the like. . Therefore, in particular, in the case of a gland packing for shaft sealing of a fluid device using an expanded graphite sheet as a material, the sliding resistance is extremely large, which leads to a power loss and a shortened packing life. In order to avoid this, the gland packing made of expanded graphite sheet, which has been generally used in the past, is impregnated with oil or solid lubricant or coated with oil or solid lubricant on the inner peripheral surface or shaft surface. Or
Means for reducing sliding resistance have been employed.

[0003]

[Table 1]

[0004]

However, when oil or solid lubricant is impregnated or applied as described above, the friction coefficient and sliding resistance increase due to oil decomposition under high temperature conditions. There was a problem that environmental pollution due to oil spill and a decrease in the strength of the gland packing were caused.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a high water content functioning as a lubricant so that the coefficient of friction and the sliding resistance can be remarkably reduced. It is an object of the present invention to provide an expanded graphite sheet and a gland packing using the same, which can hold the sheet for a long time and can secure a very excellent sealing performance.

[0006]

In order to achieve the above object, an expanded graphite sheet according to the first aspect of the present invention is provided with an expanded graphite substrate formed by pressing expanded graphite particles and integrating them with each other. And a water content of 1 to 30% by weight with respect to a density of 1. The expanded graphite base material preferably has a moisture content of 1 to 30% by weight.
-20% by weight.

According to the first and second aspects of the present invention,
Since the expanded graphite base material itself contains a large amount of water that functions as a lubricant, a friction state close to boundary lubrication is created by the water contained therein in various usages of sealing materials and the like composed of the expanded graphite sheet. As is clear from Table 1, the coefficient of friction can be reduced by about an order of magnitude from the coefficient of friction in the conventional dry (dry) state. Problems such as characteristic degradation and oil contamination due to oil decomposition during use under high temperature conditions. Also,
The sealing surface pressure is high due to the swelling action of the expanded graphite base material due to the high water content, and excellent sealing performance can be ensured even with a low tightening pressure.

[0008] In the expanded graphite sheet according to the first or second aspect of the present invention, as described in the third aspect, the expanded graphite substrate has hydrophilicity such as a hydrophilic resin or a surfactant together with water. When the substance is contained in an amount of 10% by weight or less, the initial moisture content can be maintained even when used under high-temperature conditions, and the above-described friction coefficient reducing function can be secured for a long time. In addition, the water pressure resistance can be improved.

A gland packing according to a fourth aspect of the present invention provides an expanded graphite base material obtained by pressurizing expanded graphite particles and integrating the expanded graphite particles with each other.
It is characterized in that it is constituted by using an expanded graphite sheet containing water by weight of water as a raw material. Preferably, the expanded graphite sheet has a water content of 1 to 5 as described in claim 5. 20% by weight.

According to the fourth and fifth aspects of the present invention,
Since the base material of the expanded graphite sheet as a material itself contains a large amount of water that functions as a lubricant, a friction state close to boundary lubrication between the shaft and the shaft in a usage state of the gland packing composed of the expanded graphite sheet. Is produced, and the coefficient of sliding resistance has a coefficient of friction as a factor compared with a conventional gland packing made of an expanded graphite sheet having a low moisture content (about 0.1 to 0.5%). Is remarkably reduced, and the shaft sliding characteristics can be improved. In addition, the sealing surface pressure increases due to the swelling action of the expanded graphite sheet itself due to the high moisture content, and excellent sealing performance can be ensured even with a low tightening pressure.

In the gland packing according to the fourth or fifth aspect of the present invention, as described in the sixth aspect,
When the expanded graphite sheet contains not more than 10% by weight of a hydrophilic substance such as a hydrophilic resin and a surfactant together with water, the initial moisture content can be maintained even when used under high temperature conditions. Thus, the above-described excellent shaft sliding characteristics can be secured for a long time, and the water pressure resistance can be improved.

[0012] In the gland packing according to any one of the fourth to sixth aspects of the present invention, as in the seventh aspect, the expanded graphite sheet is formed into a tape having an appropriate width, and the tape-shaped expanded graphite sheet is formed. When spirally wound and formed into a ring-like shape, it is possible to easily produce a variety of sizes by employing a press forming means, and here, as described in claim 8, By using the above-mentioned tape-like expanded graphite sheet only for the inner peripheral portion that is a sliding portion with the shaft, and for the other outer peripheral portion, using the tape-like expanded graphite sheet having a low moisture content, the entire gland packing is improved. As a result, it is possible to reduce the sliding resistance coefficient while maintaining high strength.

Further, in the gland packing according to any one of claims 4 to 6, as set forth in claim 9, at least one of the inner and outer peripheral portions of the expanded graphite sheet has a fiber or metal wire. When the cord is reinforced or braided by braiding or twisting, in addition to the function of reducing the sliding resistance coefficient, it has hydrophilicity especially by adopting an internal reinforcement structure using fibers or metal wires. The material has an adhesive effect, improving the twisting strength and preventing the cord-like body from being unexpectedly broken even by the complex stress that acts during braiding or twisting, ensuring the predetermined braided gland packing. Can be manufactured.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partially cross-sectional perspective view of an expanded graphite sheet. As shown in FIG. 2, this expanded graphite sheet 1 has an Ho-treated graphite 2A having a thickness Ho in which flake-like graphite particles 2a are laminated. By expanding the
As shown in FIG. 3, a thickness H which is expanded in the laminating direction (the direction of arrow a) and has a gap G between the graphite particles 2a.
The expanded graphite particles 2a are integrated with each other into a sheet by self-adhesion by pressing a bellows-like structure (about 5 mm to 10 mm) by press molding or roll molding so that the expanded bellows-like layers are brought into close contact with each other. Front and back sides 1 of base material 1A
After removing the entire area of B by, for example, microblasting using an abrasive such as SiC having a particle size of 10 to 20 μm until the contact angle with water becomes 80 ° or less,
Impregnated with water or an aqueous solution of a hydrophilic resin such as polyethylene glycol or a hydrophilic inorganic substance such as sodium silicate with respect to the density of 1 to 30% by weight, preferably 1 to 20% by weight from the front and back surfaces 1B. It is made to let.

The water content of the expanded graphite sheet 1 is as follows:
It is a weight ratio of water to the entire sheet 1 and is generally represented by the following equation. Water content = (weight after impregnation of water−weight before impregnation) / weight after impregnation × 100

Next, an embodiment of a gland packing made of the expanded graphite sheet 1 manufactured as described above will be described. Example 1: As shown in FIG. 4, this gland packing 51 uses an expanded graphite sheet 1 containing 20% by weight of water and formed in a tape shape having a suitable width as two inner circumferential turns. Uses an expanded graphite sheet 4 containing 0.2% by weight of water and formed in a tape shape having the same width as that of the tape-shaped expanded graphite sheet 1. 4 is superimposed, spirally wound, and then press-molded into a ring.

Table 2 shows test results obtained by measuring the sliding resistance coefficient Kμ of the gland packing 51 of the first embodiment in comparison with a conventional product. Here, the conventional product serving as a comparative example contains water at a concentration of 0.
A gland packing formed into a ring shape as in Example 1 using an expanded graphite sheet containing 5% by weight is used as a sample. The above test conditions are as shown in Table 3, and the sliding resistance coefficient Kμ value shown in Table 2 is determined when the tightening pressure of the gland packing is 200 kgf / cm ^{2 to} 500 kgf / c.
It is the average value at m ² .

[0018]

[Table 2]

[0019]

[Table 3]

The above-mentioned sliding resistance coefficient Kμ is a value obtained by dividing the sliding resistance per unit area by the initial tightening pressure, and is the value of the gland packing's lateral pressure coefficient K (stress conversion coefficient) and friction coefficient μ. This is a unique value and is defined by the following equation. Kμ = R / (π × d × L × Pg) where R: sliding resistance per unit area (kgf) d: valve stem diameter (cm) L: contact length of gland packing (cm) Pg: gland packing Tightening pressure (kgf / cm ² )

As is clear from Table 2, the sliding resistance coefficient Kμ of the gland packing 51 of the first embodiment is reduced to about (１ ／) as compared with the conventional product.

Example 2 This gland packing comprises an expanded graphite sheet 1 formed in a tape shape having an appropriate width and containing 3% by weight of water and 2.5% by weight of polyethylene glycol as a hydrophilic resin. An expanded graphite sheet 4 formed into a tape having the same width as the tape-shaped expanded graphite sheet 1 containing 0.2% by weight of water for the other outer wraps is used. The tape-shaped expanded graphite sheets 1 and 4 are polymerized, spirally wound, and then press-formed into a ring.

Table 4 shows the test results of measuring the water pressure resistance of the gland packing of Example 2 in comparison with the conventional product. Here, the conventional product serving as a comparative example is 0.5% by weight of water.
A gland packing formed into a ring shape in the same manner as in Example 2 using an expanded graphite sheet contained below is used as a sample. The test conditions are as shown in Table 5.

[0024]

[Table 4]

[0025]

[Table 5]

As is clear from Table 4 above, the gland packing 52 of the second embodiment has a significantly higher leakage pressure (water pressure) than the conventional product in the range of the practical tightening pressure, and the shaft sealing performance is accordingly higher. It shows that it is excellent.

Embodiment 3: This gland packing 53 is
The expanded graphite sheet 1 containing 3% by weight of water and 2.5% by weight of polyethylene glycol as a hydrophilic resin is cut into a narrow width, and a plurality of the narrow-cut expanded graphite sheets 1 are bundled to form an outer periphery thereof. Is covered with a reinforcing fiber 6 such as PTFE, and is formed by braiding a string-shaped composite sealing material 7 as shown in FIG.

Embodiment 4: The gland packing 54 is
A cord-like composite sealing material 9 as shown in FIG. 6, which is obtained by folding the expanded graphite sheet 1 shown in the third embodiment into a wave shape and inserting a metal wire 8 such as a stainless wire into the folded portion to reinforce it, is braided. It was formed as follows.

Embodiment 5: This gland packing 55
A string-shaped composite sealing material 11 as shown in FIG. 7 formed by laminating two sheets of the expanded graphite sheet 1 shown in the above-mentioned Example 3 and sandwiching and inserting a reinforcing fiber 10 such as glass fiber into the bonded portion. It is formed by braiding or twisting.

As shown in the above Examples 3 to 5, at least one of the inner and outer peripheral portions of the expanded graphite sheet 1 is reinforced with the fibers 6, 10 or the metal wires 8 to form a string-shaped composite sealing material 7, 9. , 11 are braided or twisted to form a gland packing, which has a high strength in addition to the function of reducing the sliding resistance coefficient. In particular, by adopting an internal reinforcement structure using fibers or metal wires, the contained water and the contained hydrophilic substance have an adhesive effect, improving the twist strength and preventing the complex stress that acts during braiding or twisting. Also, the predetermined braided gland packing can be reliably manufactured without the string-shaped composite sealing material being unexpectedly broken.

FIGS. 8A and 8B show a density of 1.0 g / cm.
^{3. After} removing both front and back surfaces of the tape-shaped expanded graphite sheet 1 having a thickness of 0.38 mm and a width of 16 mm by blasting (a processing rate of 4.1%), each sample cut into a length of 100 mm is shown in Table 6. After being immersed in a dispersant as shown for 30 minutes, excess impregnating liquid on the surface is removed with a waste cloth to form a ring-shaped gland packing (dimensions: 19 mm inner diameter × 32 outer diameter × 6.5 mm thick). The results of a test for confirming water retention using the gland packing as a sample under the test conditions shown in Table 7 are shown.

[0032]

[Table 6]

[0033]

[Table 7]

As is clear from the test results shown in FIG. 8, the expanded graphite sheet of the present invention and the gland packing formed using the same have a high moisture content for a long time even when used under high temperature conditions. It can be seen that the ratio is maintained.

In the above embodiments and examples, 1 to 30% by weight (preferably 1 to 30% by weight) is added to the expanded graphite sheet.
As a means for imparting a water content of up to 20% by weight, the surface of the expanded graphite sheet is subjected to a removal treatment so that the contact angle with water becomes 80 ° or less, and then water or water and hydrophilicity are removed from the surface. Although a means of impregnating the substance was adopted,
In addition, the above-mentioned weight%
Of water or water and a hydrophilic substance.

[0036]

As described above, according to the first and second aspects of the present invention, since the expanded graphite base itself contains a large amount of water that functions as a lubricant, the expanded graphite sheet is constituted by the expanded graphite sheet. It is possible to create a frictional state close to boundary lubrication by using water contained in various types of sealing materials, etc., and reduce the frictional coefficient by about an order of magnitude compared to the conventional dry (dry) frictional coefficient. Can be. Therefore, it is possible to solve the problems such as characteristic deterioration and oil contamination due to oil decomposition during use under high temperature conditions, which are observed in the case of conventional oil impregnation and coating means, and to expand the graphite base due to the high moisture content. Due to the swelling action of the material itself, the sealing surface pressure is also increased, and there is an effect that excellent sealing performance can be ensured even at a low tightening pressure.

Further, in the above expanded graphite sheet, the expanded graphite base material contains not more than 10% by weight of a hydrophilic substance such as a hydrophilic resin or a surfactant together with water in the expanded graphite base material. By this, it is possible to retain the initial moisture content even when used under high temperature conditions,
The above-described friction coefficient reducing function can be ensured for a long time, and the water pressure resistance can be improved.

According to the fourth and fifth aspects of the present invention, the base material of the expanded graphite sheet used as the material of the gland packing contains a large amount of water which functions as a lubricant. In the use mode, a friction state close to boundary lubrication is created between the shaft and the shaft, and the sliding resistance coefficient, which is a factor of the friction coefficient, is significantly reduced as compared with the conventional expanded graphite gland packing, so that the shaft sliding characteristics are remarkable. Improvement can be achieved. Further, the sealing surface pressure is increased by the swelling action of the expanded graphite sheet itself due to the high moisture content, so that excellent sealing performance can be ensured even with a low tightening pressure.

In the above gland packing,
As described in claim 6, a material having hydrophilicity such as a hydrophilic resin or a surfactant together with water is added to the expanded graphite sheet.
When the content is not more than% by weight, the initial moisture content can be maintained even when used under high temperature conditions, and the above-described excellent shaft sliding characteristics can be secured for a long time. At the same time, the water pressure resistance can be improved.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional perspective view of an expanded graphite sheet according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a state before expansion of acid-treated graphite particles.

FIG. 3 is an enlarged perspective view showing expanded graphite particles.

FIG. 4 is a partially cutaway perspective view showing a gland packing of Example 1 configured using the expanded graphite sheet of the present invention.

FIG. 5 is a partially cutaway perspective view showing a gland packing according to a third embodiment configured using the expanded graphite sheet of the present invention.

FIG. 6 is a partially cutaway perspective view showing a gland packing according to a fourth embodiment configured using the expanded graphite sheet of the present invention.

FIG. 7 is a partially cutaway perspective view showing a gland packing according to a fifth embodiment configured using the expanded graphite sheet of the present invention.

FIGS. 8A and 8B are graphs showing the results of a test for confirming water retention using a gland backing formed using the expanded graphite sheet of the present invention as a sample.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Expansive graphite sheet 1A Expansive graphite base material 2a Graphite particles 6,10 Reinforcement fiber 7,9,11 String-like composite sealing material 8 Metal wire 51,53,54,55 Gland packing

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C01B 31/04 101 C04B 35/52 C09K 3/10 F16J 15/10 CA (STN)

Claims (9)

(57) [Claims] 1. An expanded graphite base material obtained by integrating expanded graphite particles by pressurizing them with each other, and having a density of 1 to 30
An expanded graphite sheet containing water by weight. 2. The expanded graphite sheet according to claim 1, wherein the moisture content of the expanded graphite base material is 1 to 20% by weight based on a density of 1. 3. The expanded graphite sheet according to claim 1, wherein the expanded graphite base material contains 10% by weight or less of a hydrophilic substance such as a hydrophilic resin and a surfactant together with water. 4. An expanded graphite base material obtained by pressing expanded graphite particles into one body by pressurizing the expanded graphite particles, and having a density of 1 to 30
A gland packing comprising an expanded graphite sheet containing water by weight as a material. 5. The gland packing according to claim 4, wherein the moisture content of the expanded graphite sheet is 1 to 20% by weight based on a density of 1. 6. The gland packing according to claim 4, wherein the expanded graphite sheet contains not more than 10% by weight of a hydrophilic substance such as a hydrophilic resin and a surfactant together with water. 7. The expanded graphite sheet is formed in a tape shape having an appropriate width, and the tape-shaped expanded graphite sheet is spirally wound and formed into a ring shape. The gland packing described in Crab. 8. The gland packing according to claim 7, wherein the expanded graphite sheet is used only for an inner peripheral portion. 9. The expanded graphite sheet according to claim 4, wherein at least one of the inner and outer peripheral portions of the expanded graphite sheet is formed by braiding or twisting a cord-like body reinforced with fibers or metal wires. The described gland packing.