JP2006029376A - Gasket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite seal material employed for a water supply apparatus, a food-processing apparatus, a pharmaceutical manufacturing apparatus or the like, which secures high heat resistance and chemical resistance, shows no possibility of aromatization, needs not to make tightening surface pressure so high, and enables repeated uses after fastening is made once. <P>SOLUTION: A composite seal material 2 which is provided with an annular and concentrical opening thereinside and formed concentrically with the annular body so as to have projections on both upper and lower surfaces of a disk, is composed of a rubber-made core member 4 which is provided with an annular and concentrical opening 8 thereinside and formed concentrically with the annular body so as to have projections 10 on both upper and lower surfaces of a disk and of a fluorocarbon resin-made outside member 6 fitted so as to cover the outer surface of the core member 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composite gasket, and more particularly to a composite gasket used for water supply equipment, food processing equipment, pharmaceutical manufacturing equipment, and the like.

  For example, in the processing plant for food and beverage products, as the size and complexity increase, the disinfection and cleaning method has recently been replaced with the conventional method of sterilizing and cleaning the entire device in a disassembled state. Then, a CIP (Cleaning in Place) system has been introduced that enables automatic internal cleaning and automatic sterilization without disassembling the apparatus and equipment.

Usually, the CIP system is an alkaline cleaning process with NaOH, HNO ₃ or NaClO
The sealing material used in such a system is exposed to a harsher environment than before.

  For this reason, the sealing materials used in such cleaning systems are not sufficient in terms of chemical resistance and heat resistance with conventional synthetic rubber that has been used so far, and even higher heat resistance and chemical resistance. Realization of a sealing material with a high degree is desired.

  Also, for example, in a beverage production line such as juice, since multiple types of products (juice etc.) are produced using the same production line, the odor of the fruit juice component etc. produced in the previous process is added to the rubber sealing material. Adhesion (hereinafter referred to as “flavoring” phenomenon) may cause the product to move to the next product through the rubber sealant, which may deteriorate the quality.

Therefore, the sealing material used in such a production line is required not to be fragrant.
On the other hand, in the pharmaceutical manufacturing field, polytetrafluoroethylene, which has excellent chemical resistance and heat resistance, has been conventionally used as a sealing material for ferrule parts for pipes in order to prevent contamination by foreign substances and impurities and to cope with severe sterilization treatment. A gasket made of (PTFE) resin is employed.

However, since PTFE is a resin and has high hardness and poor elasticity, when used as a sealing material, a high clamping surface pressure must be applied, and the sealing performance is impaired by the creep of PTFE. There was a problem of going. Furthermore, once PTFE resin is used after being tightened, it is difficult to use it again because it undergoes plastic deformation (Patent Document 1).
JP-A-5-99343

  The present invention is a composite sealing material used in, for example, water supply equipment, food processing equipment, pharmaceutical production equipment, etc., and has high heat resistance and chemical resistance, and there is no risk of flavoring. It is an object of the present invention to provide a composite sealing material that does not require a high surface pressure and that can be used repeatedly after being tightened once.

The composite sealing material according to the present invention is
An annular and concentric opening is formed inside, and further, a composite sealing material formed so as to have a convex portion on each of the upper and lower surfaces of the disk portion concentrically with the annular body,
A rubber core member formed in an annular shape with concentric openings formed therein, and further having convex portions on the upper and lower surfaces of the disk portion concentrically with the annular body,
And an outer member made of a porous fluororesin that is mounted so as to cover the outer surface of the core member.

  The composite sealing material of the present invention having such a configuration can ensure sufficient elasticity by the rubber core member, and can be sealed even when used for a strong scented piping line by the outer member made of fluororesin. There is no fear of flavoring the material.

  Further, according to the present invention, the core member is formed to have a larger diameter than the outer member so that the outer peripheral end portion is exposed from the outer member, and the outer peripheral end portion of the outer member is It is preferable to open toward the direction.

With such a configuration, it is easy to integrate the core member and the outer member.
Furthermore, in the present invention, the rubber constituting the core member is preferably EPDM (ethylene propylene rubber), silicon rubber, or the like with few impurities.

  In the present invention, the fluororesin constituting the upper and lower plate portions of the outer member is PTFE (polytetrafluoroethylene), and the upper and lower plate portions made of these fluororesins are PFA (polyethylene) on the radially inner side. It is preferable that they are integrated by welding (tetrafluoroethylene perfluoroalkyl ether copolymer).

With such a configuration, two PTFE plates can be integrated by PFA welding. Further, the outer member formed from the PTFE needs to be a porous body.

  With such a configuration, since the outer member is also provided with elasticity and flexibility, the compatibility with the mating member at the seal portion is improved. Therefore, it is possible to seal even with a low tightening surface pressure. Moreover, in addition to the elasticity of the rubber of the core member, PTFE itself can also have elasticity, so that sufficient sealing performance can be exhibited even if repeated removal and attachment from the seal portion. . This also allows repeated use.

  According to the composite sealing material of the present invention, sufficient elasticity can be ensured by the rubber of the inner core member, so that the tightening force can be set weak. Further, since the liquid contact portion is made of, for example, PTFE fluororesin, there is no risk of fragrance even if it is used for a piping line with strong odor. Therefore, for example, when used in a food production line such as a highly scented juice, the odor is not transferred to the other juice in the process of producing the other juice. Furthermore, if the outer member is a porous PTFE, the outer member becomes flexible and the compatibility with the mating member becomes good. Thereby, a clamping pressure can be made small.

  Further, in the composite sealing material according to the present invention, since the core member has sufficient elasticity and the outer member also has elasticity, it can be used repeatedly even once removed from the seal portion. .

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a composite gasket 2 according to an embodiment of the present invention.
The composite gasket 2 is composed of two members, a rubber core member 4 and a fluororesin outer member 6.

  The core member 4 has an annular, concentric circular opening 8 formed through the central portion, and convex portions 10 formed on both upper and lower surfaces of the disc portion. The convex portion 10 is formed at a vertically symmetrical position, and the top portion of the convex portion 10 is formed in a substantially arc shape. Further, the outer peripheral portion of the core member 4 is thicker on both sides than the inner peripheral portion, and step portions d and d are formed on both surfaces. Such a core member 4 is made of rubber, and specifically, is preferably formed of rubber having heat fluidity such as EDPM (ethylene propylene rubber) or silicon rubber. In this embodiment, EDPM is employed because impurities are contained or impurities are not eluted.

If the core member 4 is formed of such a material, appropriate elasticity can be obtained and molding with a mold is easy.
On the other hand, the outer member 6 is mainly made of PTFE (polytetrafluoroethylene). That is, the outer member 6 includes an upper plate portion 12, a lower plate portion 14, and a shaft portion 16 that connects the two plate portions 12 and 14 on the inner peripheral side. It is made of PTFE and is connected by PFA welding with the shaft portion 16.

  In this way, in the outer portion 6, the upper plate portion 12 and the lower plate portion 14 are connected on the radially inner side. Further, the radially outer side is not connected and is open, and the open end is bonded flush with the inner core member 4 at the step portions d and d.

  Therefore, the composite gasket 2 composed of the two members of the core member 4 and the outer member 6 is compressed and deformed because the rubber core member 4 is covered with the outer member 6 made of PTFE. In addition, an appropriate elastic deformation force is exerted by the core member 4. Moreover, even if the outer part 6 made of PTFE is used in a juice production line having a strong odor, the odor does not perfume.

  Furthermore, in this embodiment, the PTFE of the outer member 6 is formed to be porous. If the outer member 6 is formed to be porous in this manner, the outer portion 6 made of PTFE becomes flexible, so that it is easy to become familiar with the mating member and to have a sealing function with a low tightening force. .

In this embodiment, the outer member 6 made of PTFE is made porous by, for example, a method detailed in Japanese Patent No. 2780113 by the present applicant.
That is, in this patent method, a polytetrafluoroethylene powder obtained by a suspension polymerization method is compression-molded to prepare a preform, and the preform is fired at a temperature equal to or higher than the melting point to form a molded body. The molded body is then stretched uniaxially or biaxially at a temperature below the melting point, and the resulting stretched molded body is contracted by at least 3%, and then at least 1 at a temperature below the melting point of polytetrafluoroethylene. A porous body of PTFE is manufactured by a method of stretching uniaxially or biaxially more than once.

  In this example, the PTFE outer portion 6 is made porous by such a patent method, so that the porosity is increased and the thermal stability and mechanical strength are excellent. A mass is obtained. As a result, the outer member 6 has good compatibility with the mating member to be sealed, and has elasticity while being a resin.

  Further, the outer member 6 according to the present embodiment is given so-called wettability to the inner surface thereof by, for example, an inner peripheral surface treatment method disclosed in Japanese Patent Publication No. 7-68381 by the applicant.

  That is, this method improves the adhesion because PTFE is non-tacky as it is, and thus has poor adhesion to rubber. In brief, this method is a treatment method in which fluorine atoms existing on the surface of PTFE are blown to expose the carbon layer to be a rough surface, thereby improving the adhesion with the core member 4. is there.

The outer member 6 is subjected to such treatment, thereby improving flexibility and compatibility with the counterpart member.
On the other hand, in this embodiment, the core member 4 is formed by EPDM.

  In this way, when the core member 4 and the outer member 6 are prepared separately, they are set in the mold apparatus 30 as shown in FIG. And 2 members are crimped | bonded by the heating state, and the composite gasket 2 shown in FIG. 1 can be obtained.

  That is, the mold apparatus 30 includes an upper mold 32 and a lower mold 34, and a cavity 36 is defined between the upper mold 32 and the lower mold 34. Further, in the vicinity of the cavity 36 in the upper mold 32, a groove 38 for biting is formed in an annular shape. Further, a burr groove 40 for collecting liquid is formed outside the groove 38 for cutting.

  Then, the outer member 6 and the core member 4 are first set in the cavity 36 in a state where the mold device 30 thus formed is opened. Further, an appropriate adhesive is applied between the core member 4 and the outer member 6. Thereafter, unvulcanized rubber is filled into the cavity 36, and the outer member 6 and the core member 4 are vulcanized and bonded at a temperature of, for example, 170 degrees or more. A part of the filled unvulcanized EDPM protrudes from the cavity 36 and flows outward, but the discharged rubber flows into the burr groove 40. And if a mold is opened, these can be integrated. In addition, since the inner surface of the outer member 6 has been surface-treated and roughened in advance, it can be quickly integrated with the rubber. When the mold is opened, the surplus portion in the burr groove 40 is separated from the cut-off groove 38, and the composite gasket 2 that is a product material can be obtained. Moreover, if the ear | edge part etc. of the product taken out from the metal mold | die apparatus 30 are excised, a complete product part can be obtained.

Thus, the composite gasket 2 obtained in the present embodiment can obtain an appropriate elastic force because the core member 4 as a core material is made of rubber.
In addition, the part to be actually sealed is not rubber, but is contacted by the outer member 6 made of PTFE. Even if it is used in a production line such as a strong odor juice, the odor of the juice produced in the previous process may be present. There is no fragrance. Furthermore, since the seal portion is made of PTFE, it is sufficient in chemical resistance and heat resistance, and impurities are not attached.

  Even if the tightening force of the sealing member once tightened is released and reused, PTFE is porous and has an appropriate flexibility, so that there is little plastic deformation and the elasticity of the core member. Therefore, even if it is tightened again, the sealing performance can be exhibited.

Although one embodiment of the present invention has been described above, the experimental results on the sealing performance of the composite gasket of the present invention will be described below.
First, in order to investigate the effect of making the PTFE of the outer member 6 porous, the difference from the non-porous PTFE outer member was examined.

As a sample, a porous outer member and a non-porous outer member were prepared, and these were integrally bonded to a core member of the same material to prepare a sample of an example and a sample of a comparative example.
Test method: The sample of the example and the sample of the comparative example were sandwiched in order in the flange portion, and a predetermined tightening pressure was applied to examine leakage. The inspection method was to check for leaks by applying soapy water to the seal and applying internal pressure to check the soapy water.
The sealing test was performed by changing the tightening pressure stepwise to 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 MPa.
The results are shown in Table 1.

  As can be seen from Table 1, when a porous fluororesin (PTFE) is used, a sufficient sealing effect can be obtained even when the sealing pressure is low, whereas a non-porous ordinary fluororesin is used. Then, it was found that the sealing performance was not sufficient at low pressure.

From this experiment, it was confirmed that a reliable sealing can be achieved even if the sealing surface pressure is reduced by providing a large number of holes in the interior to make it porous.
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

  For example, in the above embodiment, a food production line, for example, a juice production line has been described as an example. However, the present invention can be effectively applied to a pharmaceutical production apparatus, a water supply device, and the like instead.

  Also, the method of making PTFE porous or the method of roughening the inner surface is not limited to the above-described embodiments, and other methods can be adopted.

FIG. 1 is a perspective view of a composite gasket according to an embodiment of the present invention, partially broken away. FIG. 2 is a cross-sectional view of a mold apparatus when a composite gasket according to an embodiment of the present invention is manufactured using a mold.

Explanation of symbols

2 Composite gasket 4 Core member 6 Outer member 8 Opening 10 Convex part 12 Upper plate part (PTFE)
14 Lower plate (PTFE)
16 shaft part (PFA)
30 Mold device 32 Upper mold 34 Lower mold 36 Cavity 40 Burr groove

Claims (3)

An annular and concentric opening is formed inside, and further, a composite sealing material formed so as to have a convex portion on each of the upper and lower surfaces of the disk portion concentrically with the annular body,
A rubber core member formed in an annular shape with concentric openings formed therein, and further having convex portions on the upper and lower surfaces of the disk portion concentrically with the annular body,
A composite sealing material, comprising: an outer member made of a porous fluororesin that is mounted so as to cover the outer surface of the core member.   The core member is formed to have a larger diameter than the outer member so that the outer peripheral end portion is exposed from the outer member, and the outer peripheral end portion of the outer member is opened radially outward. The composite sealing material according to claim 1, wherein:   The fluororesin constituting the upper and lower plate portions of the outer member is PTFE (polytetrafluoroethylene), and the upper and lower plate portions made of these fluororesins are PFA (polytetrafluoroethylene perfluoroalkyl) on the radially inner side. The composite sealing material according to claim 1, wherein the composite sealing material is integrated by welding of an ether copolymer).

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