JP2016205604A - Gasket and manufacturing method of gasket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gasket that does not likely to cause leakage, and a manufacturing method of the gasket.SOLUTION: A gasket 1 includes a ring-shaped core member 3 and an outer skin member 2 made of PTFE film covering upper, lower and inner peripheral surfaces of the core member 3. In the gasket 1, the core member 3 has a configuration in which a periphery of a core member body 31 containing expanded graphite is covered with a body covering material 32 made of porous PTFE, the outer skin member 2 has a thickness of 0.3-0.8 mm and is formed into a ring shape by overlapping and bonding together the ends of the PTFE film, and further, a flatness of the outer skin member 2 covering the core member 3 is 0.25 mm or less.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a gasket and a method for manufacturing the gasket, and more particularly to a gasket and a method for manufacturing the gasket that are less likely to leak.

Various chemicals are used in production processes such as pharmaceuticals, pharmaceuticals, foods, and fine chemicals. Glass lining (GL) technique that covers the surface of metal with glass material inside the equipment used in these production processes such as tanks, heat exchangers, stirrers, and pipes so that they can withstand each chemical. Is applied to prevent the metal from corroding.
In addition, PTFE (polytetrafluoroethylene) gaskets that do not react with chemicals are used as gaskets for sealing surfaces such as manholes and flanges.
However, since it becomes expensive if the entire gasket is made of PTFE, a gasket having a structure in which the outer surface is wrapped with a PTFE film is used.

However, manholes and flange surfaces are fragile due to glass lining, and the tightening surface pressure of the gasket must be limited. However, if the surface pressure is small, the internal liquid leaks, and if the surface pressure is large, the glass surface is Since it breaks and causes failure, the users, manufacturers, and handling equipment personnel who are involved in this work are forced to struggle.
Many gasket manufacturers have also disclosed various patents such as those shown in the prior art.
Patent Document 1 discloses a gasket in which the core member includes organic fibers, inorganic fibers, inorganic powder, and a binder.
Patent Document 2 discloses a gasket in which a fluorine resin porous sheet is attached to upper and lower surfaces of a fluorine resin outer skin member.
Patent Document 3 discloses a gasket in which a core member is made of an expanded graphite sheet.
Patent Document 4 discloses a gasket in which the core member includes organic fibers, inorganic fibers, inorganic powder, and a binder, and the inorganic powder is uniformly dispersed in the core member.
However, there is still no best gasket yet.

FIG. 1 shows the structure of a conventional general gasket 11.
It consists of a ring-shaped core member 13 and a skin member 12 that covers the upper surface, the lower surface, and the inner peripheral surface of the core member 13. The core member 13 has a three-layer structure including a non-asbestos-based hard joint sheet 131 and upper and lower nonwoven felts 132. The felt 132 allows the air in the air reservoir 14 between the non-asbestos hard joint sheet 131 and the outer skin member 12 to pass therethrough.

As a defect of the conventional gasket,
(1) Although a non-asbestos-type hard joint sheet is generally used for the core member, since stress relaxation is large, even if tightened strongly, stress is relaxed and leakage is likely to occur.
(2) When creating a skin member from a PTFE sheet, if the skin member is cut into a ring shape, the number that can be taken from the PTFE sheet is small, resulting in high costs. For this purpose, the outer skin member is cut out in a rectangular shape from the PTFE sheet, and the cut-out rectangular PTFE sheet has a U-shaped cross section so as to cover the upper surface, the lower surface, and the inner peripheral surface of the ring shape of the core member. It is stretched so that both ends of the rectangular shape are overlapped and joined into a ring shape to cover the core member. However, leakage occurs due to a step generated in the overlapped portion.
In order to prevent leakage due to this level difference, the level difference portion is shaved with fine sandpaper or ironed at the site, but it takes a long time to work.
(3) As in (2) above, the cut-out rectangular PTFE sheet is stretched so that the cross-section is U-shaped, but it has a wavy shape and the flatness when the core member is covered is flat. It is bad with 0.8-3.0mm. This causes a leak.
(4) When expanded graphite is used for the core member, contamination of the expanded graphite (dust) may contaminate the inside of the container or the surroundings.

JP 2000-104832 A JP 2003-106456 A JP 2005-337401 A JP 2009-24877 A

  The present invention has been made to solve the above-described problems of the prior art, and provides a gasket and a method for manufacturing the gasket that are less likely to leak.

  The invention according to claim 1 is a gasket comprising a ring-shaped core member and a PTFE film skin member covering the upper surface, the lower surface and the inner peripheral surface of the core member, wherein the core member is expanded. The main body wrapping material made of porous PTFE wraps around the core member main body having graphite, the outer skin member has a thickness of 0.3 to 0.8 mm, and the outer skin member is made of PTFE film. The gasket is characterized in that the ends are overlapped and joined to form a ring shape, and the flatness of the outer skin member covering the core member is 0.25 mm or less.

  The flatness referred to in this specification is defined in accordance with JIS B 0182: 1993 “Machine Tool-Test and Inspection Terminology”, and all points on the surface of the outer shell member of the gasket are The distance between the two surfaces when the distance between the two planes is in the two planes parallel to the representative plane of the surface of the outer skin member and the plane is minimum.

In the invention according to claim 2, the expanded graphite has a graphite purity of 95.0 to 99.8% by mass,
2. The gasket according to claim 1, wherein the density of the expanded graphite is 0.95 to 1.46 g / cm < ³ >.

Invention of Claim 3 is a manufacturing method of the gasket of Claim 1 or Claim 2, Comprising: The joining process which piles up the ends of PTFE films and joins them, and makes it a ring-shaped outer skin member, The said joining process A covering step of covering the ring-shaped upper surface, the lower surface and the inner peripheral surface of the core member with the outer skin member whose ends are joined by each other, and the core covered with the outer skin member after the covering step From the upper surface side and the lower surface side of the member, the pressing step of pressing for 2 to 10 minutes at a temperature of 100 to 110 ° C. and a pressure of ^{3 to 5} kg / cm ² , followed by the pressing step, and covered with the outer skin member A cooling step in which the gasket is cooled to 40 ° C. or lower with a load of 0.5 to 5.0 kg / cm ² applied from the upper surface side and the lower surface side of the core member. Of gasket to Production method on.

  In the invention according to claim 4, the joining of the ends of the outer skin member in the first step sandwiches a PFA having a thickness of 0.03 to 0.15 mm between the outer skin members, and a heating temperature of 230 to 280 ° C. The method of manufacturing a gasket according to claim 3, wherein the gasket is formed by bonding at a point.

  According to the gasket of the invention of claim 1, since the core member has expanded graphite and the flatness of the outer skin member is 0.25 mm or less, there is little risk of leakage. Moreover, since the main body wrapping material wraps the periphery of the core member main body, there is no possibility that the expanded graphite contamination of the core member main body will contaminate the inside or the periphery of the container.

According to the gasket of the invention of claim 2, since the graphite purity of the expanded graphite is 95.0 to 99.8% by mass and the density of the expanded graphite is 0.95 to 1.46 g / cm ³ , Mitigation is reduced, the risk of leakage is further reduced, and cost is not increased.

  According to the gasket manufacturing method of the invention of claim 3, since the flatness of the outer skin member can be reduced, the risk of leakage is reduced.

  According to the gasket manufacturing method of the invention according to claim 4, it is possible to strengthen the joining between the ends of the outer skin member.

It is a schematic structure figure of the conventional common gasket. It is a schematic structure figure of the gasket concerning this embodiment. (A) is a schematic fragmentary sectional view of the gasket which concerns on this embodiment, (b) is a schematic fragmentary sectional view of the other form of the gasket which concerns on this embodiment. It is a general | schematic fragmentary sectional view of the other form of the gasket which concerns on this embodiment. It is a figure which shows the manufacturing method of the gasket which concerns on this embodiment. It is a figure which shows the result of the compression decompression | restoration test in a present Example. It is a figure which shows the test result of the stress relaxation characteristic in a present Example. It is the schematic of the manhole used for the test of the sealing characteristic in a present Example. It is a figure which shows the test result of the sealing characteristic in a present Example. It is a figure which shows the test result of the sealing characteristic in a present Example. It is a figure which shows the test result of the sealing characteristic in a present Example. It is a figure which shows the test result of the sealing characteristic in a conventional product.

Hereinafter, preferred embodiments of a gasket according to the present invention will be described with reference to the drawings. FIG. 2 shows a schematic external view of the gasket 1 according to the present embodiment, and FIG. 3A shows a schematic cross-sectional view of the gasket 1.
The gasket 1 includes a ring-shaped core member 3 and a PTFE film skin member 2 covering the upper surface, the lower surface, and the inner peripheral surface of the core member 3. The core member 3 is a core member having expanded graphite. A main body packaging material 32 made of porous PTFE wraps around the main body 31, the outer skin member 2 has a thickness of 0.3 to 0.8 mm, and the outer skin member 2 has the ends of the PTFE film overlapped with each other. In the shape of a ring joined. The size of the gasket 1 is not particularly limited, but the outer diameter is preferably 300 to 3000 mm.
When the thickness of the outer skin member 2 is less than 0.3 mm, the outer core member 3 is easily stretched so as to cover the core member 3, and it is difficult to leak from the step of the joint of the outer skin member 2, but the pressure resistance performance is lowered. On the other hand, if it is thicker than 0.8 mm, it will be difficult to stretch, and it will be easy to leak from the step of the joint of the outer skin member 2.
Moreover, since the main body packaging material 32 wraps the periphery of the core member main body 31, there is no possibility that the expanded graphite contamination of the core member main body 31 will contaminate the inside or the periphery of the container.

Further, the flatness of the outer skin member 2 covering the core member 3 is 0.25 mm or less. This reduces the risk of leakage.
Moreover, the graphite purity of the expanded graphite of the core member 3 is 95.0 to 99.8% by mass, and the density of the expanded graphite is 0.95 to 1.46 g / cm ³ . When the graphite purity and density are within this range, stress relaxation becomes small and leakage becomes difficult, and the cost does not increase.

As the core member main body 31, expanded graphite may be the main component, or expanded graphite and clay may be the main components. In the case where expanded graphite and clay are the main components, a configuration described in Japanese Patent Nos. 5224153 and 5514278 may be employed.
When the expanded graphite is a main component, 90% by volume or more of the core member main body 31 is preferably expanded graphite, and more preferably 95% by volume or more is expanded graphite.

  The cross-sectional shape of the outer skin member 2 is U-shaped as shown in FIG. 2A, and an air reservoir 4 is formed between the inner peripheral side of the core member 3 and the outer skin member 2. However, since the main packaging material 32 is made of porous PTFE, the air in the air reservoir 4 can be extracted to the outside.

  The outer skin member 2 overlaps with a part of the gasket 1 in the circumferential direction to form an overlapping portion 5, and there is a risk of leakage at this step. However, since the core member main body 31 of the gasket 1 of the present embodiment contains expanded graphite, stress relaxation is small. This can reduce the risk of leakage.

The shape of the outer skin member 2 may be a Y-shaped section as shown in FIG. 3B instead of a U-shaped section as shown in FIG. Further, the outer skin member 2 may also cover the outer peripheral surface of the core member 3.
Further, as shown in FIG. 4, a metal plate 6 having a corrugated cross section may be provided in the core member main body 31 and may have a layered structure with expanded graphite. It does not specifically limit as a kind of metal, For example, SUS is mentioned. By having the metal plate 6, tightening becomes uniform when the gasket 1 is tightened.

Next, the manufacturing method of the gasket 1 which concerns on this embodiment is demonstrated.
The manufacturing method includes the following steps (see FIG. 5).
<Cutting step> A PTFE film is cut into a rectangular shape, for example (see FIG. 5A).
-<Jointing step> Both ends of the rectangular PTFE film are joined together and processed into a ring shape that covers the upper surface, the lower surface, and the inner peripheral surface of the core member 3.
Specifically, for example, (1) the cut rectangular PTFE film has a U-shaped cross section so as to cover the ring-shaped upper surface, lower surface, and inner peripheral surface of the core member 3, and both ends E1 and Stretching is performed so that E2 is close (see FIG. 5B).
(2) PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) is sandwiched between both ends E1 and E2 of the ring-shaped skin member 2 and heated to bond both ends E1 and E2 (FIG. 5 ( c)). The heating temperature is preferably 230 to 280 ° C. If it is lower than this temperature range, the fusion is not sufficient, and if it is higher, the bonding position between the outer skin members 2 may be shifted. The thickness of PFA is preferably 0.03 to 0.15 mm, and more preferably 0.09 to 1.1 mm. If it is thinner than this range, the adhesive strength is not sufficient, and if it is thicker than this range, the flatness is inferior.
<Coating process> The outer skin member 2 whose both ends are joined by the joining process covers the upper, lower and inner peripheral surfaces of the ring-shaped core member 3 (see FIG. 5D) (see FIG. 5E). ).
<Pressing step> After the covering step, the pressure is 3 to 5 kg / cm ² and the temperature is 100 to 110 ° C. from the upper surface side and the lower surface side of the core member 3 covered with the outer skin member 2. Press for 10 minutes.
・ <Cooling process> Following the pressing process, the gasket is applied with a load of 0.5 to 5.0 kg / cm < ² > sandwiched between the metal plate from the upper surface side and the lower surface side of the core member covered with the outer skin member Cool until the temperature reaches 40 ° C. or lower.

By performing the pressing step and the cooling step, the outer skin member 2 becomes familiar with the core member 3, and the flatness of the outer skin member 2 becomes 0.25 mm or less.
Further, when the pressure in the pressing step is smaller than the above range, the flatness is not reduced, and when it is larger than the above range, the gasket 1 is deformed. If the temperature during pressing is lower than the above range, the flatness is not reduced, and if it is higher than the above range, the gasket 1 is deformed. When the pressing time is shorter than the above range, the flatness is not reduced, and when the pressing time is longer than the above range, the gasket 1 is deformed.
Further, when the pressure in the cooling step is smaller than the above range, the flatness is not reduced, and when it is larger than the above range, the gasket 1 is deformed. If the cooling temperature in the cooling step is higher than the above temperature, the flatness will not be reduced.

<Example>
The gasket of the Example of this invention was created as follows.
(1) Gasket dimensions Outer diameter: 400mm
Inner diameter: 300mm
Thickness: 7.8mm
(2) Core member Material of core member body: 100% expanded graphite
Purity of expanded graphite: 99.5% by mass
Expanded graphite density: 1.3 g / cm ³
Body packaging material: Porous PTFE
Body packaging material thickness: 35μm
(3) Skin member Material: PTFE film Thickness: 0.4mm
(4) Flatness 0.20mm

The manufacturing method of an Example is shown below.
<Joint process>
PFA thickness: 0.08mm
Heating temperature: 250 ° C
Crimping time: 5 minutes Pressing machine: Hot press machine manufactured by Pan Oil Pressure Industry Co., Ltd. (maximum heating temperature: 400 ° C, maximum pressure
(Force: 350 tons, pressure area: 700 x 700 mm)
<Pressing process>
Pressure: 4kg / cm ²
Temperature: 105 ° C
Time: 5 minutes Press machine: Hot press machine manufactured by Ban Oil Pressure Industry Co., Ltd. (maximum heating temperature: 400 ° C, maximum pressure
(Force: 350 tons, pressure area: 700 x 700 mm)
<Cooling process>
Pressure: 0.8 kg / cm ²
Cooling temperature: 30 ° C
The SUS304 was cooled by being sandwiched between 5 mm thick surface polishing plates.

For comparison, a conventional product having the structure shown in FIG. 1 was used.
(1) Gasket dimensions Outer diameter: 400mm
Inner diameter: 300mm
Thickness: 7.8mm
(2) Core member Three-layer structure of non-asbestos-based hard joint sheet 131 and upper and lower nonwoven felts 132 (3) Outer member Material: PTFE film Thickness: 0.4 mm
(4) Flatness 1.2mm

<Evaluation>
(1) Compression restoration test The compression restoration test of the main body packaging material of the present example and the conventional product was performed as follows.
(1-1) Test method Test standard Compliant with EN13555 Test machine used Gasket performance evaluation machine Sample dimensions JIS10K-50A RF
Sample thickness 6mm
Temperature condition 25 ° C (± 5)
Tightening surface pressure 20 [MPa]
Fastening speed 0.5 [MPa / sec]
(1-2) Test results The results are shown in FIG.
This example showed a higher compression rate than the conventional product.

(2) Stress relaxation characteristics The stress relaxation characteristics of the main body packaging material of this example and the conventional product were measured as follows.
(2-1) Test method Test standard Compliant with EN13555 Test machine used Gasket performance evaluation machine Sample dimensions JIS10K-50A RF
Sample thickness 6mm
Temperature condition 100 ° C (± 5)
Tightening surface pressure 20 [MPa]
Fastening speed 0.5 [MPa / sec]
Test time 4 hours (2-2) Test results The results are shown in FIG.
This example showed a higher surface pressure holding force than the conventional product.

(3) Seal characteristics The stress relaxation characteristics of the main body packaging material of this example and the conventional product were measured as follows.
(3-1) Test method Leaks were examined with the manhole shown in FIG. In this figure, positions 1 to 12 indicate clamp positions, and positions (1) to (12) indicate positions where leakage has been confirmed. In addition, the hinge part of a manhole is between the clamp positions of 3 and 4, and the overlap part 5 of the outer skin member 2 is located between the clamp positions of 1 and 12.
Evaluation tester: 400A glass lining manhole flange
(Maximum strain 1.6mm)
Clamp bolt: M22 x 12 bolts Lubricant: ThreeBond 1910 Molybdenum disulfide seizure prevention material Tightening torque: Initial tightening torque 150 Nm After 2 cycles 100 Nm
Temperature conditions: 100 ° C / 150 ° C / 200 ° C (exposure for 12 hours)
Temperature cycle: 5 cycles for each temperature
(Predetermined temperature (12h) → RT → Open → Retightening → Leakage confirmation →
Predetermined temperature (12h) → total 5 cycles)
Manhole opening / closing: Internal temperature for each temperature / cycle: 0.2 [MPa] / 0.5 [MPa]
Fluid: Air leakage confirmation method: Crab foam confirmation

(3-2)
The test results are shown in FIGS.
In this example, no leakage occurred in all five cycles under the conditions of the internal pressures of 0.2 MPa and 0.5 MPa and the temperatures of 100 ° C., 150 ° C., and 200 ° C.
On the other hand, in the conventional product, leakage occurred at an internal pressure of 0.2 MPa after one cycle, and occurred in the vicinity of the hinge portion of the manhole and in the vicinity of the overlapping portion 5 of the outer skin member 2, and leaked even when the tightening torque was increased to 200 Nm.
Thus, the gasket of the present invention is less likely to leak than conventional products.

  The present invention is suitably used for gaskets on sealing surfaces such as manholes and flanges constructed by, for example, a glass lining (GL) technique.

DESCRIPTION OF SYMBOLS 1, 11 Gasket 2, 12 Outer skin member 3, 13 Core member 31, 131 Core member main body 32, 132 Main body packaging material 4, 14 Pool 5 Duplicate part 6 Metal plate

Claims (4)

A gasket comprising a ring-shaped core member and a PTFE film shell member covering the upper surface, the lower surface and the inner peripheral surface of the core member,
The core member is configured so that a main body wrapping material made of porous PTFE wraps around the core member main body having expanded graphite.
The outer skin member has a thickness of 0.3 to 0.8 mm,
The outer skin member has a ring shape with the ends of the PTFE film overlapped and joined,
A gasket having a flatness of an outer skin member covering the core member of 0.25 mm or less. The expanded graphite has a graphite purity of 95.0 to 99.8% by mass,
The gasket according to claim 1, wherein the density of the expanded graphite is 0.95 to 1.46 g / cm ³ . A method for producing the gasket according to claim 1 or 2,
Bonding the ends of the PTFE film to form a ring-shaped skin member,
A covering step of covering the ring-shaped upper surface, the lower surface and the inner peripheral surface of the core member with the outer skin member whose ends are bonded by the bonding step;
Pressing step of pressing for 2 to 10 minutes at a temperature of 100 to 110 ° C. and a pressure of ^{3 to 5} kg / cm ² from the upper surface side and the lower surface side of the core member covered with the outer skin member after the covering step. When,
Subsequent to the pressing step, the gasket becomes 40 ° C. or lower with a load of 0.5 to 5.0 kg / cm ² applied from the upper surface side and the lower surface side of the core member covered with the outer skin member. And a cooling process for cooling to a temperature.   The joining of the ends of the outer skin member in the first step is performed by bonding a PFA having a thickness of 0.03 to 0.15 mm between the outer skin members and bonding at a heating temperature of 230 to 280 ° C. The method for producing a gasket according to claim 3, wherein:

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