JP2013199983A - Fluororesin gasket for pipe sealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluororesin gasket for pipe sealing that has a high compression rate when compressed and has an excellent restoration property, and to provide a method of manufacturing the same.SOLUTION: A fluororesin gasket for pipe sealing includes a preform of a gasket forming resin composition including a fluorocarbon resin and hollow inorganic particles as a filler, in which the hollow inorganic particles contained in the preform are crushed so that the volume of the crushed hollow inorganic particles becomes 25-60 volume% of the volume of the hollow inorganic particles prior to the crush. In a method of manufacturing the fluororesin gasket for pipe sealing, the hollow inorganic particles contained in the preform are crushed so that the volume of the crushed hollow inorganic particles becomes 25-60 volume% of the volume of the hollow inorganic particles prior to the crush by molding the gasket forming resin composition including the fluorocarbon resin and the hollow inorganic particles as filler in a sheet shape, and rolling the molded preform.

Description

  The present invention relates to a fluororesin gasket for piping sealing. More specifically, for example, the present invention relates to a fluororesin gasket for piping seal that can be suitably used as a piping sealing material or the like in a connection portion between piping.

  Generally, gaskets such as fluororesin gaskets, metal jacket gaskets, and spiral wound gaskets are used as piping sealing materials. When a gasket is attached and tightened during piping, the flange is often not smooth. In particular, since the glass-lined flange is repeatedly sintered, the waviness of the flange is large. Therefore, the waviness of the flange needs to be absorbed by the gasket. The gasket is preferably a soft sheet in order to absorb waviness of the flange, but on the other hand, the mechanical strength decreases as it becomes softer.

  Therefore, as a fluororesin sheet with a filler that achieves both high stress relaxation and high airtightness (sealing performance) even when the filling rate of the fluororesin is low and the filling rate of the filler is high, for example, graphite, carbon There has been proposed a fluororesin sheet containing a filler in which a filler such as a carbon filler such as black, an inorganic filler such as talc, a resin powder, or a fiber material such as carbon fiber is blended (for example, patent document). 1).

  The fluororesin sheet has high stress relaxation properties and high air tightness, but since the compression rate is small, a gap is formed between the flange and the gasket, and gas or liquid in the pipe may leak from the gap. .

  Therefore, in recent years, development of a fluororesin gasket for piping seals that has a high compression ratio when compressed and has excellent resilience to return to the original shape has been desired.

JP 2007-253519 A

  The present invention has been made in view of the above prior art, and has a high compression ratio when compressed, and has excellent resiliency to return to the original shape. The issue is to provide.

The present invention
(1) A gasket used for sealing a connecting portion between pipes, which is made of a preform of a resin composition for forming a gasket containing a fluororesin and a hollow inorganic particle as a filler, and crushed hollow inorganic particles A fluororesin gasket for pipe seal, in which the hollow inorganic particles contained in the preform are crushed so that the volume of the hollow inorganic particles before the crushing is 25 to 60% by volume of the volume of the hollow inorganic particles, and (2) the pipe A method for producing a gasket used for sealing a connecting portion between each other, wherein a resin composition for forming a gasket containing a fluororesin and hollow inorganic particles as a filler is formed into a sheet shape, and the preform is molded Is rolled so that the volume of the crushed hollow inorganic particles becomes 25 to 60% by volume of the volume of the hollow inorganic particles before crushing. The method for producing a fluororesin gasket pipe seal, characterized in that crushing the hollow inorganic particles.

  The fluororesin gasket for piping seal of the present invention has an excellent effect that a compression ratio is high when compressed and an excellent restoring property is exhibited. In addition, according to the method for producing a fluororesin gasket for piping seals of the present invention, an excellent effect of obtaining a fluororesin gasket for piping seals that has a high compressibility when compressed and exhibits excellent resilience can be obtained. Played.

It is an electron micrograph of the section of the preform obtained in Example 1 of the present invention. It is an electron micrograph of the section of the sheet obtained in Example 1 of the present invention. 2 is an electron micrograph of a cross section of a preform obtained in Comparative Example 1. 2 is an electron micrograph of a cross section of a sheet obtained in Comparative Example 1. 4 is an electron micrograph of a cross section of a preform obtained in Comparative Example 2. 4 is an electron micrograph of a cross section of a sheet obtained in Comparative Example 2. 4 is an electron micrograph of a cross section of a preform obtained in Comparative Example 3. 4 is an electron micrograph of a cross section of a sheet obtained in Comparative Example 3.

  As described above, the fluororesin gasket for piping seal of the present invention is a gasket used for sealing the connecting portion between piping, and the resin composition for forming a gasket containing hollow inorganic particles as a fluororesin and a filler. The hollow inorganic particles contained in the preform are crushed so that the volume of the crushed hollow inorganic particles is 25 to 60% by volume of the volume of the hollow inorganic particles before crushing. It is characterized by that.

  The fluororesin gasket for piping seal of the present invention is formed by, for example, molding a resin composition for forming a gasket containing hollow inorganic particles as a fluororesin and a filler into a sheet, and rolling the formed preform. It can manufacture by crushing the said hollow inorganic particle so that the volume of the crushed hollow inorganic particle may be 25-60 volume% of the volume of the hollow inorganic particle before crushing.

  The resin composition for forming a gasket used in the present invention contains a fluororesin and a filler.

  Examples of the fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer. Polymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), and the like are exemplified, but the present invention is limited only to such examples. It is not something. These fluororesins may be used alone or in combination of two or more. Among these fluororesins, polytetrafluoroethylene (PTFE) is preferable from the viewpoints of moldability and processability.

  The fluororesin may be in the form of a powder or may be a dispersion in which a fluororesin powder is dispersed in a solvent. The dispersion of the fluororesin powder has an advantage that the filler can be easily and uniformly dispersed.

  In the present invention, hollow inorganic particles are used as the filler. Examples of the hollow inorganic particles include hollow mineral particles such as hollow glass beads, hollow ceramic beads, and expanded pearlite, but the present invention is not limited to such examples. These hollow inorganic particles may be used alone or in combination of two or more. Among these, hollow glass beads are preferable because they are easily crushed and easily available.

  The average particle diameter of the hollow inorganic particles is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more from the viewpoint of increasing the compression ratio when the gasket is compressed, and varies depending on the thickness of the gasket. From the viewpoint of improving the smoothness of the gasket surface and improving the restoration property of the gasket, the thickness is preferably 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less.

The density of the hollow inorganic particles is preferably 0.1 g / cm ³ or more from the viewpoint of improving handleability, and varies depending on the thickness of the gasket, but improves the smoothness of the gasket surface and improves the compressibility of the gasket. From the viewpoint of increasing the thickness, it is preferably 0.3 g / cm ³ or less.

  The compressive strength of the hollow inorganic particles is such that the hollow inorganic particles are not crushed before the preform is manufactured, and the hollow inorganic particles are easily crushed when the preform is produced and when the preform is rolled. From the viewpoint of efficiently producing a gasket that has a high compression ratio when compressed and exhibits excellent restoring properties, it is preferably 0.3 to 2 MPa.

  The amount of the hollow inorganic particles per 100 parts by mass of the fluororesin is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and further preferably 2 parts by mass from the viewpoint of increasing the compressibility when the gasket is compressed. From the viewpoint of improving the resilience of the gasket, it is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 25 parts by mass or less.

  The gasket-forming resin composition used in the present invention may contain a filler other than the hollow inorganic particles as long as the purpose is not impaired. Examples of the other filler include carbon-based fillers such as graphite, carbon black, activated carbon, and carbon nanotubes, inorganic particles such as talc, mica, clay, calcium carbonate, and magnesium oxide, particles such as resin particles, and glass Examples thereof include short fibers such as fibers, carbon fibers, aramid fibers, and rock wool, but the present invention is not limited to such examples. These other fillers may be used alone or in combination of two or more.

  Further, the gasket-forming resin composition used in the present invention contains a processing aid for expanding the fluororesin when the gasket-forming resin composition is formed into a sheet and the preform is rolled. Also good.

  Examples of the processing aid include petroleum hydrocarbon compounds such as paraffinic hydrocarbon compounds, but the present invention is not limited to such examples. Processing aids are readily available commercially. As processing aids that can be easily obtained commercially, for example, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, Isopar M [above, ExxonMobil Corp., trade name] etc. Although mentioned, this invention is not limited only to this illustration.

  The amount of the processing aid per 100 parts by mass of the total amount of the fluororesin, the hollow inorganic particles and the other filler is preferably 5 to 50 mass from the viewpoint of appropriately expanding the fluororesin when rolling the preform. Parts, more preferably 10 to 30 parts by mass.

  In addition, the gasket-forming resin composition includes, for example, a terpene resin, a terpene-phenol resin, a coumarone resin, a coumarone-indene resin, a tackifier such as rosin, an ultraviolet absorber, and the like within the range in which the object of the present invention is not impaired. An appropriate amount of an agent, an antioxidant, a polymerization inhibitor, a filler, a colorant such as a pigment, and the like may be contained.

  The gasket-forming resin composition is prepared by mixing fluororesin, hollow inorganic particles, and if necessary, other fillers, processing aids, additives, etc., in an arbitrary order at once or in small portions. It can be prepared by mixing to have a uniform composition. In order to obtain a gasket-forming resin composition having a uniform composition, after adding a processing aid to the gasket-forming resin composition in an excessive amount and stirring sufficiently, It may be removed by means such as filtration, volatilization.

  As described above, the fluororesin gasket for piping seal according to the present invention is formed of a hollow inorganic particle that has been crushed by, for example, molding a gasket-forming resin composition into a sheet shape and rolling the molded preform. It can manufacture by crushing the hollow inorganic particle contained in the said preform so that it may become 25-60 volume% of the volume of the hollow inorganic particle before crushing.

  Examples of a method for producing a sheet-shaped preform from a gasket-forming resin composition include, for example, a method for producing a sheet-shaped preform by extruding a gasket-forming resin composition, and a powdery gasket-forming resin. Although the method etc. which manufacture a sheet-like preform by compression molding of a composition are mentioned, this invention is not limited only to this illustration. The thickness of the preform is preferably about 5 to 10 times the thickness of the target gasket from the viewpoint of efficiently producing a gasket that has a high compressibility when compressed and exhibits excellent resilience. .

  Next, the formed preform is rolled. The preform can be rolled using, for example, a biaxial roll. The rolling conditions when rolling the preform using a biaxial roll are preferably determined as appropriate according to, for example, the type of hollow inorganic particles and the thickness of the target gasket. As the linear pressure when rolling the preform using a biaxial roll, the pressure required for crushing the hollow inorganic particles is selected, but it is usually preferably 5 to 20 kN / m. The roll temperature of a biaxial roll is not specifically limited, Room temperature may be sufficient and it may be heated or cooled as needed.

  When rolling a preform using a biaxial roll, it is preferable to repeat the rolling a plurality of times from the viewpoint of densifying the preform. In addition, when performing rolling repeatedly, the thickness of a preform can be made thin gradually by narrowing the space | interval of a roll each time the said rolling is repeated. The roll interval when rolling the preform using a biaxial roll cannot be determined unconditionally because it varies depending on the thickness of the gasket, but is usually about 0.5 to 30 mm, and the roll speed is It is preferably about 3 to 10 m / min.

  By rolling the preform as described above, the hollow inorganic particles contained in the preform can be crushed.

  In the present invention, when a sheet-like preform is produced from the gasket-forming resin composition and the preform is rolled, the volume of the crushed hollow inorganic particles is 25-60 of the volume of the hollow inorganic particles before crushing. One of the major features of the present invention is that the hollow inorganic particles contained in the preform are crushed so as to be in volume%.

  In the present invention, since the hollow inorganic particles contained in the preform are crushed in this way, the crushed hollow inorganic particles are not dispersed in the preform, but fragments of the hollow inorganic particles are crushed. Agglomerated state, that is, the fluororesin constitutes the sea and the crushed hollow inorganic particles constitute an island, so-called “sea-island structure”, and the hollow inorganic particles are not completely crushed. Since the hollow inorganic particles contained in the preform are crushed so that the volume of the crushed hollow inorganic particles is 25 to 60% by volume of the volume of the hollow inorganic particles before crushing, the gasket of the present invention is The compression ratio when compressed is high, and an excellent effect of exhibiting excellent restoring properties is achieved. The volume of the crushed hollow inorganic particles is 25% by volume or more from the viewpoint of developing excellent restoring properties, and is 60% by volume or less from the viewpoint of increasing the compressibility. The volume of the crushed hollow inorganic particles can be easily adjusted by adjusting the linear pressure when rolling the preform when rolling the preform, the interval between the rolls, and the like.

  In the present invention, the volume of the crushed hollow inorganic particles can be determined by the following method.

  That is, for example, when the preform is composed of a fluororesin and hollow inorganic particles, the ratio (mass ratio) of the fluororesin having a density of X is X, and the ratio (mass ratio) of the hollow inorganic particles having a density of β is 1. -X. When the total amount of the fluororesin and the hollow inorganic particles is A, the mass of the fluororesin is AX and the volume is AX / α. If the ratio of the volume of the crushed hollow inorganic particles to the volume of the hollow inorganic particles before crushing is γ, the mass of the hollow inorganic particles is A (1-X), and the volume is Aγ (1-X) / β. It is. Therefore, the entire volume of the preform of the fluororesin and the hollow inorganic particles is AX / α + Aγ (1-X) / β. From this, since the preform has a total density of the fluororesin and the hollow inorganic particles of 1 / [X / α + γ (1-X) / β], the mass and volume of the preform and the mass and volume of the gasket The ratio of the volume of the crushed hollow inorganic particles to the volume of the hollow inorganic particles before crushing can be determined.

  If necessary, the sheet obtained by rolling the preform as described above can be left at room temperature or appropriately heated to volatilize and remove processing aids contained in the gasket. it can.

  Moreover, the said sheet | seat can be baked by heating at the temperature more than melting | fusing point of a fluororesin. The heating temperature varies depending on the type of fluororesin and cannot be determined unconditionally. However, from the viewpoint of uniformly firing the entire sheet and avoiding decomposition of the fluororesin, it is usually about 340 to 370 ° C. Is preferred.

  A sheet fired as described above is obtained, but the sheet may be used as it is as a gasket, or may be used as a gasket after being cut into a desired shape.

  The gasket of the present invention comprises a preform for a gasket-forming resin composition containing a fluororesin and hollow inorganic particles as a filler, and the volume of the crushed hollow inorganic particles is 25 to 25 of the volume of the hollow inorganic particles before crushing. Since the hollow inorganic particles contained in the preform are crushed so as to be 60% by volume, the compression ratio is high when compressed, and an excellent effect of exhibiting excellent restoring properties is achieved. . Therefore, the gasket of this invention can be used conveniently as a sealing material for piping etc. in the connection part of piping, for example.

  EXAMPLES Next, although this invention is demonstrated further in detail based on an Example, this invention is not limited only to this Example.

Example 1
Polytetrafluoroethylene (PTFE) fine powder [manufactured by Daikin Industries, Ltd., product number: F104] 1215 g, hollow glass beads [manufactured by Potters Barotini Co., Ltd., product number: CMC-20, average particle size: 60 μm, specific gravity: 0.25, pressure strength: 0.7 MPa] 135 g and hydrocarbon-based organic solvent [ExxonMobil Co., Ltd., trade name: Isopar G] 250 g were mixed for 5 minutes with a kneader, and the die opening size was 300 mm. A preform was produced by extruding with a 20 mm extruder.

  Next, the preform obtained above was adjusted to a linear pressure during rolling of 10 kN / m, a roll speed of 6 m / min, a roll temperature of room temperature (about 25 ° C.), and a biaxial roll (roll Diameter: 700 mm, roll interval: 20 mm), biaxial roll (roll diameter: 700 mm, roll interval: 10 mm), biaxial roll (roll diameter: 700 mm, roll interval: 5 mm) and biaxial roll ( A sheet having a thickness of 3 mm was produced by sequentially passing through a roll diameter of 700 mm and a roll interval of 3 mm.

  The sheet obtained above was allowed to stand for 24 hours in an atmosphere at room temperature (about 25 ° C.) to volatilize and remove the solvent contained in the sheet. By firing for a time, a sheet-like gasket having a thickness of 3 mm (ratio of voids in the beads: 0.45) was obtained.

  The electron micrograph of the cross section of the sheet-like gasket obtained above is shown in FIG. In FIG. 1, the photo scale (200 μm) is shown at the lower right of the photo (the same applies to the following figures). As shown in FIG. 1, it can be seen that the hollow glass beads are crushed in an aggregated state.

Next, as physical properties of the sheet-like gasket obtained above, leakage amount, compression amount (compression ratio), restoration amount and density were examined based on the following methods. As a result, the leakage amount of this sheet-like gasket was 6.0 × 10 ⁻⁵ Pa · m ³ / s, the compression amount was 0.87 mm, the restoration amount was 0.38 mm, and the density was 1710 kg / m ³ . Moreover, the compression rate calculated | required based on the said compression amount was 29%.

(1) Compression amount and restoration amount Measured according to JIS R3453.
(2) Density The density was measured according to JIS K6888.
(3) Airtightness A gasket test piece punched to an inner diameter of 48 mm and an outer diameter of 67 mm is mounted between steel flanges having a diameter of 100 mm, a height of 50 mm, and a surface roughness R _{max of} 12 μm. The load was applied so that After applying a pressure of 0.98 MPa with nitrogen gas from the pressure introduction through hole provided in the flange to the inner diameter side of the gasket test piece, the pressure introduction pipe was sealed, and the state was maintained for 1 hour. The pressure change before and after holding was read with a pressure sensor, and the amount of leakage was determined from the pressure drop.

  Next, assuming the actual use of the sheet-like gasket obtained above, the pressure was released after compression with a fastening surface pressure of 35 MPa. An electron micrograph of the cross section of the gasket after compression is shown in FIG. As shown in FIG. 2, it can be seen that the hollow glass beads, like the cross section of the sheet-like gasket shown in FIG. .

Example 2
In Example 1, a sheet-like gasket having a thickness of 3 mm (ratio of voids in beads: 0), except that the linear pressure during roll rolling was changed from 10 kN / m to 20 kN / m. .27) was obtained.

Next, as the physical properties of the sheet-like gasket obtained above, the leakage amount, compression amount (compression rate), restoration amount and density were examined in the same manner as in Example 1. As a result, the leakage amount of the sheet-like gasket is 4.0 × 10 ⁻⁵ Pa · m ³ / s, the compression amount is 0.76 mm, the compression rate is 25%, the restoration amount is 0.35 mm, and the density is 1940 kg / m. It was ³ .

Example 3
In Example 1, a sheet-like gasket having a thickness of 3 mm (ratio of voids in beads: 0), except that the linear pressure during roll rolling was changed from 10 kN / m to 5 kN / m. .58) was obtained.

Next, as the physical properties of the sheet-like gasket obtained above, the leakage amount, compression amount (compression rate), restoration amount and density were examined in the same manner as in Example 1. As a result, the leakage amount of this sheet gasket was 8.0 × 10 ⁻⁵ Pa · m ³ / s, the compression amount was 0.91 mm, the compression rate was 30%, the restoration amount was 0.43 mm, and the density was 1560 kg / m. It was ³ .

Example 4
In Example 1, the thickness of the polytetrafluoroethylene (PTFE) fine powder was changed from 1215 g to 1013 g, and the amount of the hollow glass beads was changed from 135 g to 337 g. A sheet-like gasket (ratio of voids in the beads: 0.40) was obtained.

Next, as the physical properties of the sheet-like gasket obtained above, the leakage amount, compression amount (compression rate), restoration amount and density were examined in the same manner as in Example 1. As a result, the leakage amount of the sheet-like gasket was 8.0 × 10 ⁻⁵ Pa · m ³ / s, the compression amount was 1.30 mm, the compression rate was 43%, the restoration amount was 0.55 mm, and the density was 1350 kg / m. It was ³ .

Example 5
In Example 1, the thickness of the polytetrafluoroethylene (PTFE) fine powder was 3 mm as in Example 1, except that the amount of the fine powder was changed from 1215 g to 1283 g and the amount of the hollow glass beads was changed from 135 g to 67 g. A sheet-like gasket (ratio of voids in the beads: 0.53) was obtained.

Next, as the physical properties of the sheet-like gasket obtained above, the leakage amount, compression amount (compression rate), restoration amount and density were examined in the same manner as in Example 1. As a result, the leakage amount of this sheet-like gasket is 2.0 × 10 ⁻⁵ Pa · m ³ / s, the compression amount is 0.72 mm, the compression rate is 24%, the restoration amount is 0.33 mm, and the density is 1860 kg / m. It was ³ .

Example 6
The sheet obtained in Example 1 was further adjusted to a rolling linear pressure of 10 kN / m, a roll speed of 6 m / min, a roll temperature of room temperature (about 25 ° C.), and a biaxial roll (of the roll By passing it through a diameter of 700 mm and a roll interval of 1.5 mm, a sheet-like gasket having a thickness of 1.5 mm (ratio of voids in the beads: 0.41) was obtained.

Next, as the physical properties of the sheet-like gasket obtained above, the leakage amount, compression amount (compression rate), restoration amount and density were examined in the same manner as in Example 1. As a result, the leakage amount of this sheet-like gasket is 2.0 × 10 ⁻⁵ Pa · m ³ / s, the compression amount is 0.45 mm, the compression rate is 30%, the restoration amount is 0.18 mm, and the density is 1750 kg / m. It was ³ .

Comparative Example 1
In Example 1, 135 g of hollow glass beads [Potters Ballotini Co., Ltd., product number: CMC-20, average particle size: 60 μm, specific gravity: 0.25, pressure strength: 20 MPa] Tini Co., Ltd., product number: 34P30, average particle size: 35 μm, specific gravity: 0.34] Example 1 except that 135 g was used and the linear pressure during rolling was changed from 10 kN / m to 35 kN / m. Similarly, a sheet-like gasket having a thickness of 3 mm (ratio of voids in the beads: 0.68) was obtained.

  The electron micrograph of the cross section of the sheet-like gasket obtained above is shown in FIG. As shown in FIG. 3, it can be seen that the hollow glass beads are not crushed.

  Next, assuming the actual use of the sheet-like gasket obtained above, the pressure was released after compression with a fastening surface pressure of 35 MPa. The electron micrograph of the cross section of the gasket after compression is shown in FIG. As shown in FIG. 4, it can be seen that the hollow glass beads are crushed unlike the cross section of the sheet-like gasket shown in FIG. 3, and there are almost no voids.

Next, as the physical properties of the sheet-like gasket obtained above, the leakage amount, compression amount (compression rate), restoration amount and density were examined in the same manner as in Example 1. As a result, the leakage amount of this sheet-like gasket is 4.0 × 10 ⁻⁵ Pa · m ³ / s, the compression amount is 0.94 mm, the compression rate is 31%, the restoration amount is 0.28 mm, and the density is 1470 kg / m. It was ³ .

Comparative Example 2
In Example 1, 135 g of hollow glass beads [Potters Ballotini Co., Ltd., product number: CMC-20, average particle size: 60 μm, specific gravity: 0.25, pressure strength: 55 MPa] Tini Co., Ltd., product number: 60P18, average particle size: 18 μm, specific gravity: 0.60] Example 1 except that 135 g was used and the linear pressure during rolling was changed from 10 kN / m to 35 kN / m. Similarly, a sheet-like gasket having a thickness of 3 mm (ratio of voids in the beads: 0.70) was obtained.

  The electron micrograph of the cross section of the sheet-like gasket obtained above is shown in FIG. As shown in FIG. 5, it can be seen that the hollow glass beads are not crushed.

  Next, assuming the actual use of the sheet-like gasket obtained above, the pressure was released after compression with a fastening surface pressure of 35 MPa. The electron micrograph of the cross section of the gasket after compression is shown in FIG. As shown in FIG. 6, it can be seen that the hollow glass beads are hardly crushed, like the cross section of the sheet-like gasket shown in FIG.

Next, as the physical properties of the sheet-like gasket obtained above, the leakage amount, compression amount (compression rate), restoration amount and density were examined in the same manner as in Example 1. As a result, the leakage amount of this sheet-like gasket is 4.0 × 10 ⁻⁵ Pa · m ³ / s, the compression amount is 0.47 mm, the compression rate is 16%, the restoration amount is 0.25 mm, and the density is 1450 kg / m. It was ³ .

Comparative Example 3
In Example 1, except that the linear pressure during rolling was changed from 10 kN / m to 35 kN / m, a sheet-like gasket having a thickness of 3 mm (ratio of voids in the beads: 0. 0) was the same as Example 1. 20) was obtained.

  The electron micrograph of the cross section of the sheet-like gasket obtained above is shown in FIG. As shown in FIG. 7, it can be seen that the hollow glass beads are crushed and dispersed in the fluororesin.

  Next, assuming the actual use of the sheet-like gasket obtained above, the pressure was released after compression with a fastening surface pressure of 35 MPa. An electron micrograph of the cross section of the gasket after compression is shown in FIG. As shown in FIG. 8, it can be seen that the hollow glass beads are crushed and dispersed in the fluororesin.

Next, as the physical properties of the sheet-like gasket obtained above, the leakage amount, compression amount (compression rate), restoration amount and density were examined in the same manner as in Example 1. As a result, the leakage amount of the sheet-like gasket is 2.0 × 10 ⁻⁵ Pa · m ³ / s, the compression amount is 0.50 mm, the compression rate is 17%, the restoration amount is 0.24 mm, and the density is 2050 kg / m. It was ³ .

Comparative Example 4
In Example 1, the thickness of the polytetrafluoroethylene (PTFE) fine powder was 3 mm as in Example 1, except that the amount of the fine powder was changed from 1215 g to 945 g and the amount of the hollow glass beads was changed from 135 g to 405 g. A sheet-like gasket (ratio of voids in the beads: 0.64) was obtained.

Next, as the physical properties of the sheet-like gasket obtained above, the leakage amount, compression amount (compression rate), restoration amount and density were examined in the same manner as in Example 1. As a result, the leakage amount of this sheet-like gasket is 3.0 × 10 ⁻³ Pa · m ³ / s, the compression amount is 1.47 mm, the compression rate is 49%, the restoration amount is 0.50 mm, and the density is 1200 kg / m. It was ³ .

Comparative Example 5
A preform was produced in the same manner as in Example 1. The preform was adjusted to a linear pressure during rolling of 35 kN / m, a roll speed of 6 m / min, a roll temperature of room temperature (about 25 ° C.), and a biaxial roll (roll diameter: 700 mm, Spacing: 20 mm), biaxial roll (roll diameter: 700 mm, roll spacing: 10 mm), biaxial roll (roll diameter: 700 mm, roll spacing: 5 mm), biaxial roll (roll diameter: 700 mm, roll And a biaxial roll (roll diameter: 700 mm, roll interval: 1.5 mm), and a sheet having a thickness of 1.5 mm was produced.

Next, as the physical properties of the sheet-like gasket obtained above, the leakage amount, compression amount (compression rate), restoration amount and density were examined in the same manner as in Example 1. As a result, the leakage amount of the sheet-like gasket is 2.0 × 10 ⁻⁵ Pa · m ³ / s, the compression amount is 0.13 mm, the compression rate is 4%, the restoration amount is 0.09 mm, and the density is 2045 kg / m. It was ³ .

  From the above results, all the gaskets obtained in each Example had a compression rate of 24% because the volume of the crushed hollow inorganic particles was 25-60% by volume of the volume of the hollow inorganic particles before crushing. Since the restoration rate is 40% or more, it can be seen that the restoration property is excellent.

Claims (2)

  A gasket used for sealing a connection portion between pipes, comprising a preform of a resin composition for forming a gasket containing a hollow resin as a fluororesin and a filler, and the volume of the crushed hollow inorganic particles is A gasket made of fluororesin for pipe seal, in which the hollow inorganic particles contained in the preform are crushed so as to be 25 to 60% by volume of the volume of the hollow inorganic particles before crushing.   A method for producing a gasket used for sealing a connection portion between pipes, comprising molding a resin composition for forming a gasket containing a fluororesin and hollow inorganic particles as a filler into a sheet shape, By rolling the reform, the hollow inorganic particles contained in the preform are crushed so that the volume of the crushed hollow inorganic particles is 25 to 60% by volume of the volume of the hollow inorganic particles before crushing. A method for producing a fluororesin gasket for piping seals.