JPH0222376A - Soft composite gasket - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a soft composite gasket.

[Prior Art] Conventionally, asbestos joint sheet gaskets containing asbestos as a main component have been most commonly known as gasket materials used for valves, pumps, piping joints, various types of equipment, and the like. However, in recent years, the use of asbestos has been restricted due to the problem of environmental pollution. Known gasket materials that do not use asbestos include rubber sheets, vermiculite sheets using rubber as a binding material, expanded graphite sheets, glass cloth impregnated with polytetrafluoroethylene resin dispersion, and carbon cloth.

[Problems to be Solved by the Invention] Conventional gaskets have the following problems. Rubber sheets have low heat resistance, so it is difficult to use them at high temperatures. Vermiculite sheets using rubber as a binding material suffer from seizure due to thermal deterioration of the rubber, and also have poor sealing properties. Expanded graphite sheets have low strength and are difficult to handle.
It is also expensive. Glass cloth and carbon cloth impregnated with polytetrafluoroethylene resin dispersion have large stress relaxation, poor sealing properties, and are expensive.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems. In other words, we aim to provide a gasket material that can replace asbestos joint sheets, has excellent heat resistance and sealing properties, is free from environmental pollution, is inexpensive, and has excellent oil and water resistance. It contains polytetrafluoroethylene resin and inorganic filler as essential components,
The present invention provides a soft composite gasket characterized in that a sheet-like base material has a concave portion on its surface, and the concave portion is filled with a soft organic substance.

In the present invention, the polytetrafluoroethylene resin (hereinafter referred to as I'TFE) is not limited to a homopolymer of tetrafluoroethylene, but also a small amount that does not impart melt flowability (for example, 0 It also includes those modified by copolymerizing other co-In polymers (approximately .5 mol % or less). Examples of such colit-mers include hexafluoropropylene, perfluoro(alkyl vinyl ether), perfluoro(alkoxyalkyl vinyl ether) trifluoroethylene, and perfluoroalkyl ethylene. In addition, if the molecular weight is too low, it becomes liquid or gel-like, which is not preferable, and preferably contains 50% or more of solids with a molecular weight of IO'' or more calculated from standard specific gravity.In addition, PTF-E obtained by emulsion polymerization is It is preferable because it is easily fibrillated.

In the present invention, as the inorganic filler, inorganic powder, powdered inorganic fiber, or carbon powder having excellent heat resistance and chemical resistance is preferably employed. As an inorganic powder,
Those having an average particle size of about 100 μm or less are preferably employed. If the average particle size is too large, the surface and smoothness when used as a sheet-like base material are impaired, which is not preferable. In addition, inorganic powders with a large average particle size do not provide the denseness of the sheet-like base material, and the porosity and pore size become large, resulting in insufficient sealing properties, which is not preferable. Furthermore, if a hard inorganic powder with a large particle size is used, the molding device may be damaged during molding, which is not preferable. More preferably,
It is an inorganic powder with an average particle size of about 0.1 to 70μ. Further, it is preferable to use a mixture of two or more types of inorganic powders having different particle sizes, since this improves the filling efficiency. Such inorganic powders include powders of hydrated silicate minerals that are mainly composed of silicon and aluminum and also contain magnesium, iron, alkaline earth metals, alkali metals, etc., generally called clay; natural mineral powders such as wollastonite; Oxide powders such as silica, alumina, glass, titanium oxide, iron oxide, etc.
Examples include ceramic powders such as zirconium boride, aluminum nitride, silicon nitride, boron nitride, zircon carbide, silicon carbide, and tungsten carbide, and sulfide powders such as nickel sulfide, zirconium sulfate, and molybdenum disulfide. Among them, natural mineral powder is preferably employed. Particularly preferred are kaolin-type clays represented by kaolinite, halloysite, hydrated halloysite, and the like. Further, the powdered inorganic fiber has a diameter of about 0.1 to 30μ, particularly preferably about 0.5 to 15μ, and a length of 50 to 300μ.
, particularly preferably about 70 to 200 μm. Such powdered inorganic fibers include powdered carbon fiber, powdered glass fiber powder, powdered alumina fiber,
Examples include various powdered natural minerals and fibers. In addition, the carbon powder has a particle size of 0. A material having a diameter of about 0.1 μm to 0.1 μm is preferably employed.

Further, in the present invention, as the inorganic filler, an inorganic powder alone or a mixture of an inorganic powder and a small amount of powdered inorganic fiber and/or carbon powder is preferably employed. It is preferable to use an inorganic powder alone or a mixture of an inorganic powder and a carbon powder because it is easy to reduce the porosity and small pore diameter of the sheet-like base material. In addition, when powdered inorganic fibers are mixed and used, it is slightly more difficult to reduce the porosity and small pore size than when powdered inorganic fibers are not mixed, but the result is a sheet-like base material with a high compressibility. . The sealing surface has excellent conformability. In addition, if powdered inorganic fiber or carbon powder is used alone or as a mixture of powdered inorganic fiber and carbon powder as an inorganic filler, it may become difficult to form a sheet, or it may become difficult to form a sheet with a small porosity or pore size. Such a mode of use is not preferred since it may become difficult to obtain the base material. When using a mixture of inorganic powder and powdered inorganic fiber and/or carbon powder as the inorganic filler, the mixing ratio should be about 30 parts by weight or less of powdered inorganic fiber and/or carbon powder per 1 part by weight of inorganic powder. is preferred. If the proportion of powdered inorganic fibers and/or carbon powder is too large, the formability of the sheet-like base material will deteriorate, and the porosity and average pore diameter will increase, resulting in poor sealing properties and shortening the life of the sheet-like base material. It becomes small and undesirable.

The sheet-like base material in the present invention contains 5% by weight of I'TFE.
As mentioned above, it is preferable that the inorganic filler is contained in an amount of 50% by weight or more. When the amount of P1'FE is less than 5% by weight, it is difficult to form a sheet as a sheet-like base material, and
The molded sheet also has a low recovery rate against compression, making it difficult to obtain a sheet-like base material with low porosity.
This is not preferable because it becomes difficult to withstand use as a gasket. In particular, it is preferred that I'TFE be contained in an amount of 10% by weight or more. The amount of PTFE is not particularly limited, but if it is too large, it will become expensive, lose its characteristics as a general-purpose gasket material, and reduce the compressibility of the gasket material, so 50% by weight is recommended.
Hereinafter, it is particularly preferable that the amount is 40% by weight or less. Furthermore, if the amount of the inorganic filler is less than 50% by weight, the stress relaxation rate will increase, which is not preferable. Furthermore, since it is expensive, it may not be suitable for use as a general-purpose gasket. As the amount of the inorganic filler increases, the stress relaxation rate decreases, but it becomes difficult to obtain a dense sheet-like base material with small porosity and pore diameter. That is, there is a tendency for the sealing performance to deteriorate easily. The preferred content of the inorganic filler is 60 to 90% by weight: 4%.

The sheet-like base material in the present invention may contain a synthetic resin, inorganic fiber, etc. in addition to the above-mentioned PTFE and inorganic filler. Such synthetic resins are preferably ones with excellent heat resistance and oil resistance, such as fluororesins such as perfluoroalkoxy resins and perfluoroethylene propylene resins, phenol resins, polyimide resins, and polyarylsulfone resins. be done.

In addition, examples of inorganic fibers include alumina fibers, carbon fibers, and glass fibers, which are crushed during mixing or forming a sheet-like base material, but few are crushed into powder, and most are relatively It will be present in the sheet-like substrate as long fibers. When such fibers are present, the strength of the sheet-like base material is improved by -1, but it is difficult to reduce the porosity and average pore diameter, so it is preferable not to add too much fiber. do not have.

The amount of inorganic fiber added is preferably 3 iQ:111% or less.

The sheet-like base material used in the present invention preferably has a small porosity and a small pore diameter.

Although there are various methods for producing a sheet-like base material with a small porosity and pore diameter, a simple method will be exemplified below. The first method is to impregnate or add synthetic resin or liquid material. In this method, a synthetic resin such as a thermoplastic resin is added to sheet-forming 1i; 1, and the synthetic resin is applied to the pores by heating it to a temperature higher than the melting point of the synthetic resin during or after sheet-forming. By filling the material, the porosity and pore diameter can be lowered, and after forming the sheet-like material, the porosity and pore diameter can be lowered by impregnating it with a liquid material such as oil or a synthetic resin melt. I can do it. However, in such a method, since there is a synthetic resin etc. inside and on the surface of the sheet-like gasket, there is a risk of seizure etc. when using the soft composite gasket of the present invention at high temperatures. It cannot be said that this is a preferable method for manufacturing gaskets. The second method is to pressurize the sheet material again after forming it. This is a method in which pressure is applied after forming or firing the sheet-like material. This pressurization method is as follows:
A pressurizing method using a press mold or a roll is exemplified. Here, pressurization using a roll is more preferable than pressurization using a press die because continuous pressurization work is possible, and therefore it is superior in workability and is preferably employed. Further, the pressure to be applied is preferably equal to or higher than that normally used when forming a sheet-like object. This pressure is appropriately selected depending on the condition of the sheet material or the required physical properties of the sket material, but if too high a pressure is applied, the desired improvement effect will not be obtained. As for pressurizing pressure, surface pressure is +0
00kgf/cm" or less is preferable, and usually 200~
Approximately 700 kgf/cm'' is adopted. In addition, in this method of pressurizing, it is preferable to heat at the same time.

Since the plasticity of PIFH is improved by heating, the porosity and pore diameter can be easily reduced even if the applied pressure is not so great. As for the pressurizing temperature, if the temperature is too low, the effect will not be fully exhibited, and if it is too high, +1 'l' FE may be thermally decomposed, which is not preferable. Preferably 250-40
The temperature is preferably about 0°C, particularly about 300 to 380°C. The third method is to use a mixture of two or three types of inorganic fine powders with different particle sizes as an inorganic filler, or to use a mixture of two or three types of inorganic fine powders with different particle sizes and a mixture of carbon fine powder. This is a method for improving filling efficiency. This method can reduce the porosity and pore size because the gaps between the large particles of the inorganic fine powder can be filled with the medium and small particle size fine powder. Also, carbon powder is large
Middle/Small J! 1- It fills the gaps between fine wood powders, and at the same time, its low friction property makes it easy to form sheets. ! (This method has the effect of promoting sliding between the fine wood powders and increasing the filling properties of the fillers. Also, this method is easier to manufacture sheet-like base materials than the method described in 1i; 1, so it is versatile. An excellent soft composite gasket can be obtained.

In the sheet-like base material of the present invention, it is preferable that PTFE is fibrillated and an inorganic filler exists between the fibrils, r'TFE is not fibrillated, or the inorganic filler is P'TFE. l°FE
If it does not exist between the fibrils, the sheet-like base material becomes extremely brittle and may not be able to withstand actual use. II T F E is fibrillated, that is, it forms a micro three-dimensional network [1 structure, and the inorganic filler is not uniformly distributed between the three-dimensional network structures]. In other words, if the inorganic filler is firmly held by the fibrils of I'TFE, sufficient strength as a gasket material can be obtained even if the inorganic filler is very large. In addition, in a sheet-like base material having such a structure, since l'TFE is uniformly distributed over the entire base material, only one IITFE is present.
Contains right: Despite being ahead of time.

The entire soft composite gasket exhibits the excellent water and oil repellency of l'TFE. In other words, the soft composite gasket has excellent oil and water resistance. P
TFE is easily fibrillated and vines upon application of high shear forces. In addition, as a method for uniformly dispersing the inorganic filler between the fibrils of I"rFE,
This can be easily achieved by adding non-fibrillated PTFE and an inorganic filler and then fibrillating the PTFE at the same time as mixing or after uniform mixing. For example, this can be achieved by stirring and mixing a predetermined proportion of l'TFE powder and an inorganic filler under high shear force, such as by stirring at high speed with a mixer, in the presence or absence of a processing aid such as naphtha. Ru. In addition, by applying higher shear force, such as extruding this mixture using an extruder with a large ratio of the cross-sectional area of the cylinder to the cross-sectional area of the nozzle, P
TFE can also be more highly fibrillated.

The sheet-like base material in the present invention has the above-mentioned +1'r F□
A composition in which an inorganic filler is dispersed between fibrils can be produced by a known sheet forming method such as pressure forming or rolling using a press mold or a roll. Particularly from the viewpoint of manufacturing operations, a roll forming method that allows continuous forming is preferably employed.

In the sheet-like base material in the present invention, PTFE may be fired or unfired. When I'TFE is fired, it is preferable to perform the firing after forming the sheet. If PTF E is fired to form a sheet, it becomes difficult to form a sheet. In addition, l'TFE is fibrillated11
; There is a problem that fibrillation becomes difficult when calcination is performed at step 1.

In the soft composite gasket of the present invention, a recess is formed on the surface of the sheet-like base material, and the recess is filled with a soft organic substance. Therefore, the soft composite gasket of the present invention has a high compressibility and good sealing surface conformability. therefore,
High sealing performance is also exhibited on the sealing surface.

As the soft organic material in the present invention, synthetic resin, synthetic rubber, natural rubber, etc. are employed. Preferably, JIS
An organic material whose hardness is 90° or less in the Δ type K6301 spring type hardness test is preferably employed. 90° in the above test
For larger ones, the compressibility of the gasket is not small. The conformability of the sealing surface tends to deteriorate. Particularly preferably, the angle in the above test is 80° or less. Specifically, natural rubber, synthetic natural rubber, butadiene styrene rubber, butadiene acrylonitrile rubber, chloroprene rubber, butyl rubber, polysulfide rubber, urethane rubber, silicone rubber, Hypalon, acrylic rubber, ethylene brobylene rubber, and silicone. Examples include resin, urethane resin, polystyrene, and vinyl chloride resin.

Further, it is preferable that a plurality of recesses in the present invention are formed independently. The recesses are continuously formed. That is, if a groove-like recess is formed, there is a possibility that leakage may occur along the groove, which is not preferable. Further, it is preferable that the plurality of recesses are uniformly distributed on the surface of the sheet-like base material. Although the size of each independent recess is not particularly limited,
If it is too large, the flow of soft organisms will cause
This is not preferable because there is a risk that the sealing performance will deteriorate. Preferably, the width of the gasket is about 1/10 or less, but it is not limited to this, and it is desirable to select it as appropriate depending on the purpose, manufacturing method, etc. Usually, a recess of about 5 mm square or less, particularly about 2 mm square, is preferably employed. In addition, the depth of the recess is preferably about 1/3 of the thickness of the sheet-like base material or less, and the area of the surface of the sheet-like base material where the recess is formed is the sum of the areas of the openings of the recess. (hereinafter referred to as
It is preferable that the aperture ratio (referred to as an aperture ratio) is about 40% or less, particularly 25% or more. If the size, depth, and opening ratio of the recess are larger than the above ratios, the compression ratio will become too large, flow will proceed even with a general-purpose tightening force, the stress relaxation ratio will become large, and the sealing performance will deteriorate. Moreover, the strength of the composite gasket material decreases, which is not preferable.

In the present invention, the recesses may be formed on one or both sides of the sheet-like base material. In particular, it is preferable that it be formed on both sides. The formation of such recesses can be performed by pressing with an embossing die, passing between embossing rolls, or the like.

In addition, the filling of the soft organic substance described in OSj into such a recessed part is carried out by immersing the sheet-like base material in which the recessed part is formed in a solution or melt of the soft organic substance. s'! Examples of methods include applying the above solution or dissolved substance to a sheet-like base material in which recesses are formed by spraying or the like. When filling the soft organic material, it is most preferable that only the recesses are filled. In this case, try the method described above.

This method is not often adopted in practice because it becomes necessary to mask the parts other than the recessed parts, which not only makes the work complicated and unsuitable for mass production, but also increases manufacturing costs. Usually, a soft organic layer is formed in addition to the recessed portions. When the soft organic layer is formed over the entire surface of the sheet-like base material, the thickness of the portion excluding the recesses is preferably 15 μm or less. If the soft organic layer becomes thick, the stress relaxation rate will increase and the sealing performance will deteriorate, which is not preferable. In particular, it is preferable that the thickness is 10μ or less.

[Function] The soft composite gasket of the present invention uses a specific sheet-like base material6, that is, it does not contain asbestos, so there is no problem of environmental pollution. Further, since the recesses are formed on the surface of the sheet-like base material and the recesses are filled with a soft organic substance, the gasket has a high compression rate and good conformability. Furthermore, since multiple recesses are formed independently, there is no flow or protrusion of soft organisms during tightening.
The resilience of the gasket is maintained. In other words, it is considered that good sealing performance is maintained over a long period of time.

[Examples] The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples in any way.

Example 1, Comparative Example 1.2 +1TFE powder (Asahi Fluoropolymer CI)-1) 40
Iri, :, 1 part, kaolinite clay (soil 1 room Chiki-Olin Kogyo Catalbo (average particle size lOμ), ASF 17
0 ('1', average particle size 0.4μ) mixture: Catalbo:
ASF 170 = 9: I) 55QtH1Q
IS, carphone powder (Ea Kasei M^-100) 5
Weight part: 1.1. 250 parts by weight of ll-lichloroethane was added, stirred for 20 minutes with a mixer, filtered, and dried at room temperature. Add and add 1
Stirred for 0 minutes. After stirring, the mixture was aged for about 15 hours. This aged product was injected into a mold with an extrusion section having a cross-sectional dimension U of 105 mm, a conical section with an angle of 40", and a ratio of the cross-sectional area of the cylinder to the cross-sectional area of the nozzle section of 15, and the pressure was 40 kgf/cm" at room temperature and the extrusion speed was A plate-shaped product was obtained by extrusion at 120 mm/1+r. This plate-shaped object is rolled using two iron embossed rollers with an outer diameter of 200 mm and a length of 400 mm (recess specifications: height 0.5 mm).
, Polygonum x horizontal J' I mmX I mm, pitch 0
．． 5mm) at a compression ratio of 18 and a speed of 1800mm/hr, il 300mm, thickness 1.5mm.

Size of each independent recess (number 3 in the figure): lmm x 1mm
A long sheet with a depth of 0.5 mm and an aperture ratio of 25% was obtained. After drying the long sheet with hot air at 300℃,
"C" for 3 hours to obtain a sheet-like base material (symbol I in the figure).

This sheet-like base material was immersed in a solution containing a soft organic composition shown in Table 1 in a mixed solvent of toluene/n-propyl acetate = 80/20 so that the isomorphic concentration was 10% by weight and 4% for 15 hours. After soaking for 1 hour, air dry at 100℃ for 3 hours.
Heating was performed for 0 minutes to obtain a soft composite gasket. In this soft composite gasket, the recesses were filled with a soft organic material (reference numeral 2 in the figure), and the coating thickness of the soft 4181 material excluding the recesses was approximately 3 microns on average. Also, the J of this soft organism
The test result of IS 63 old spring type hardness test Δ type was 80@.

Table 2 shows the results of tests on compression ratio, recovery ratio, stress relaxation ratio, oil resistance, water resistance, and sealability using this soft composite gasket.

In addition, as Comparative Example I, a sheet material obtained in the same manner as in Example 1 except that no concave portions were formed and no coating with a soft organic material was used was subjected to one wiping test, and the results are shown in Table 2.

Table 1 Table 2 [Effects of the Invention] The soft composite gasket of the present invention has excellent oil resistance and water resistance, and has no problem of environmental pollution. In addition, because it has a special structure, it has a high compressibility, excellent conformability to the sealing surface, and good cold flow resistance. Therefore, it exhibits extremely excellent sealing performance and is extremely effective for general use. Furthermore, since the soft composite gasket of the present invention has an excellent stress relaxation rate, it has good durability and can be used continuously for a long period of time. Therefore, it is effective in significantly reducing maintenance costs.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway plan view of the soft composite gasket of Example 1, and FIG. 2 is a sectional view thereof. 1... Sheet-like base material, 2... Soft organism, 11 people () Kanji) Toshiko Hiraishi

Claims (1)

[Scope of Claims] 1. A soft composite comprising a sheet-like base material containing a polytetrafluoroethylene resin and an inorganic filler as essential components and having a recessed portion on the surface, the recessed portion being filled with a soft organic substance. gasket. 2. The soft composite gasket according to claim 1, wherein the soft organic material has a JIS K6301 spring type hardness test type A of 90° or less.