CN117897570A - Fluororesin gasket and method for producing same - Google Patents

Fluororesin gasket and method for producing same Download PDF

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Publication number
CN117897570A
CN117897570A CN202280058667.XA CN202280058667A CN117897570A CN 117897570 A CN117897570 A CN 117897570A CN 202280058667 A CN202280058667 A CN 202280058667A CN 117897570 A CN117897570 A CN 117897570A
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CN
China
Prior art keywords
gasket
fluororesin
less
thickness
preform
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CN202280058667.XA
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Chinese (zh)
Inventor
户田清华
黑河真也
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Walka Corp
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Walka Corp
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Publication date
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Publication of CN117897570A publication Critical patent/CN117897570A/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D99/00—Subject matter not provided for in other groups of this subclass
    • B29D99/0053—Producing sealings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B11/00—Making preforms
    • B29B11/14—Making preforms characterised by structure or composition
    • B29B11/16—Making preforms characterised by structure or composition comprising fillers or reinforcement
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/005—Shaping by stretching, e.g. drawing through a die; Apparatus therefor characterised by the choice of materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/18—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets by squeezing between surfaces, e.g. rollers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J15/00—Sealings
    • F16J15/02—Sealings between relatively-stationary surfaces
    • F16J15/06—Sealings between relatively-stationary surfaces with solid packing compressed between sealing surfaces
    • F16J15/10—Sealings between relatively-stationary surfaces with solid packing compressed between sealing surfaces with non-metallic packing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2027/00—Use of polyvinylhalogenides or derivatives thereof as moulding material
    • B29K2027/12—Use of polyvinylhalogenides or derivatives thereof as moulding material containing fluorine
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/26—Sealing devices, e.g. packaging for pistons or pipe joints
    • B29L2031/265—Packings, Gaskets
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Gasket Seals (AREA)
  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)
  • Sealing Material Composition (AREA)

Abstract

A fluororesin gasket which contains a fluororesin and a filler and has a thickness of 0.8mm or less, wherein the surface roughness Ra is 2.1 [ mu ] m or less and the density is 0.920 or more, and which can ensure high air tightness (sealing property) between the gasket and a flange even when the thickness of the gasket is 0.8mm or less.

Description

Fluororesin gasket and method for producing same
Technical Field
The present invention relates to a fluororesin gasket and a method for producing the same. More specifically, the present invention relates to a fluororesin gasket which can be suitably used for applications requiring a thin gasket in equipment such as pumps and valves, and a method for manufacturing the same.
Background
The fluororesin gasket has chemical resistance, heat resistance, non-tackiness, and low abrasion resistance, and is therefore used in flanges and the like.
In recent years, as a method for producing a fluororesin sheet having high stress relaxation property and high air tightness (sealing property) even if the filling rate of the fluororesin is low and the filling rate of the filling material is high, the following method has been proposed: a process for producing a fluororesin sheet containing a filler, wherein a sheet-forming resin composition containing a fluororesin, a filler and a processing aid is subjected to a pressure-delay using a calender roll having a roll temperature of 40 to 80 ℃, and a processing aid containing 30 mass% or more of a petroleum hydrocarbon solvent having a fractionation temperature of 120 ℃ or less is used as the processing aid (for example, see patent documents 1 and 2); and a process for producing a fluororesin sheet containing a filler, wherein in the step of preparing a sheet-forming resin composition by mixing a fluororesin, a powder filler A, a powder filler B and a processing aid, the sheet-forming resin composition is subjected to a pressure-delay by a calender roll having a roll temperature of 40 to 80 ℃, and the particle diameter D is such that the cumulative number of particles in the particle size distribution of the powder filler A is 50% A (50) And particle diameter D at 50% of the cumulative number in particle size distribution of powder filler B B (50) Satisfies the relationship represented by the formula (1),
D B (50)≦0.73D A (50) (1)
volume V of powder filler material a A And volume V of powder filler B B Satisfies the relationship represented by the formula (2),
1≦V A /V B ≦3 (2)
as the processing aid, a processing aid containing 30 mass% or more of a petroleum hydrocarbon solvent having a fractionation temperature of 120 ℃ or less is used (for example, see patent document 3).
Prior art literature
Patent literature
Patent document 1: japanese patent No. 4213167
Patent document 2: japanese patent No. 4777389
Patent document 3: japanese patent No. 5226938
Disclosure of Invention
Problems to be solved by the invention
According to the above method for producing a fluororesin sheet containing a filler, a fluororesin sheet excellent in stress relaxation property and air tightness (sealing property) can be produced even if the filler is filled with a high filler.
However, in recent years, a fluororesin gasket having a thickness of 1mm or less has been used for equipment such as a pump casing. When the gasket is compressed between the flanges, the compression ratio of the gasket is lowered due to the thin thickness of the gasket. Therefore, the air tightness (sealing property) at the interface of the gasket and the flange cannot be sufficiently ensured.
The present invention provides a fluororesin gasket which can be suitably used for a purpose requiring a thin gasket in a device such as a pump casing, and which can ensure high air tightness (sealing property) between the gasket and a flange even when the thickness of the gasket is 0.8mm or less.
Means for solving the problems
The present invention relates to:
(1) A fluororesin gasket comprising a fluororesin and a filler, and having a thickness of 0.8mm or less, characterized in that the surface roughness Ra is 2.1 [ mu ] m or less and the density is 0.920 or more;
(2) A method for producing a fluororesin gasket, which is characterized by using a preform having a thickness of 20 to 200mm and containing a fluororesin and a filler, and repeatedly rolling the preform until the thickness is 0.8mm or less, the surface roughness Ra is 2.1 μm or less, and the density is 0.920 or more; and
(3) The method for producing a fluororesin gasket according to the above (2), wherein the surface temperature of the calender roll for calendering the preform is 40 to 80 ℃.
Effects of the invention
According to the present invention, there is provided a fluororesin gasket which can ensure high air tightness (sealing property) between the gasket and the flange even when the thickness of the gasket is 0.8mm or less.
Detailed Description
As described above, the fluororesin gasket of the present invention is a fluororesin gasket having a thickness of 0.8mm or less, which comprises a fluororesin and a filler, and is characterized by having a surface roughness Ra of 2.1 μm or less and a density of 0.920 or more. According to the fluororesin gasket of the present invention, even if the thickness of the gasket is 0.8mm or less, high air tightness (sealing property) can be ensured between the gasket and the flange.
When the thickness of the fluororesin gasket is 0.8mm or less, the gasket is disposed between the flanges and the flanges are fastened, and the gasket has a low compression ratio because of its thin thickness, so that the air tightness (sealing property) at the interface between the gasket and the flanges is inevitably lowered as compared with a gasket having a thickness of more than 0.8 mm.
In contrast, the fluororesin gasket according to the present invention has high air tightness (sealing property) even when the thickness of the gasket is 0.8mm or less as described above, and is mainly based on the following components: the surface roughness Ra of the gasket is 2.1 μm or less, and the compactness of the gasket is 0.920 or more.
In the fluororesin gasket of the present invention, even if the thickness of the fluororesin gasket is 0.8mm or less, high air tightness (sealing property) can be ensured, and therefore, the fluororesin gasket can be suitably used for applications requiring a thin gasket in equipment such as pumps, valves, and the like.
The fluororesin gasket of the present invention can be produced, for example, as follows: the preform having a thickness of 20 to 200mm and containing a fluororesin and a filler is repeatedly rolled until the thickness is 0.8mm or less, the surface roughness Ra is 2.1 μm or less, and the density is 0.920 or more.
As a raw material of the fluororesin gasket, a gasket-forming resin composition containing a fluororesin and a filler may be used.
Examples of the fluororesin include Polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polytrifluoroethylene (PCTFE), and chlorotrifluoroethylene-Ethylene Copolymer (ECTFE), but the present invention is not limited to the above examples. These fluororesins may be used alone or in combination of two or more. Among these fluororesins, polytetrafluoroethylene (PTFE) is preferred in terms of improving moldability and processability.
The fluororesin may be used in the form of powder, but may be used in the form of a dispersion of a fluororesin powder in which the fluororesin is dispersed in a dispersion medium. The dispersion of the fluororesin powder has an advantage that components such as the filler can be easily and uniformly dispersed in the dispersion.
Examples of the filler include carbon-based fillers such as graphite, carbon black, expanded graphite, activated carbon, and carbon nanotubes, inorganic powders such as silicon carbide, talc, mica, clay, calcium carbonate, and magnesium oxide, powders such as resin powders such as polyphenylene sulfide, and short fibers such as glass fibers, carbon fibers, aramid fibers, and rock wool, but the present invention is not limited to the above examples. These fillers may be used alone, or two or more thereof may be used in combination.
The particle size of the powdery filler is not particularly limited, but is preferably 1 μm or more, more preferably 2 μm or more, still more preferably 3 μm or more from the viewpoint of improving the mechanical strength of the fluororesin gasket, and is preferably 100 μm or less, more preferably 80 μm or less, still more preferably 30 μm or less from the viewpoint of improving the surface smoothness of the fluororesin gasket. The particle size of the powdery filler means the particle size measured by the coulter counter method. The coulter counter method is a method of measuring the particle diameter by passing an electrolyte in which a filler is suspended through a pore (aperture) and reading a change in a voltage pulse generated in proportion to the volume of the filler. The fiber length of the fibrous filler is not particularly limited, but is preferably 15 μm or less, more preferably 3 to 15 μm, and still more preferably 3 to 10 μm, from the viewpoint of improving the mechanical strength and surface smoothness of the fluororesin gasket.
The filler is preferably 10 to 200 parts by mass, more preferably 100 to 180 parts by mass, per 100 parts by mass of the fluororesin, in terms of improving the mechanical strength of the fluororesin gasket and the air tightness (sealability) at the interface between the fluororesin gasket and the gasket.
In view of expanding the fluororesin in the initial step of rolling a preform obtained by molding the resin composition for gasket formation into a strip or a tape, the resin composition for gasket formation preferably contains a processing aid.
Examples of the processing aid include petroleum hydrocarbon compounds such as paraffin hydrocarbon compounds. The fractionation temperature of the processing aid is not particularly limited, but is preferably 200 ℃ or less, more preferably 180 ℃ or less, in view of sufficiently retaining the processing aid in the fluororesin-made gasket. The petroleum hydrocarbon compound having a fractionation temperature of 200 ℃ or lower may be, for example, paraffin hydrocarbon compound having a fractionation temperature of 200 ℃ or lower, but the present invention is not limited to the above examples. Processing aids having fractionation temperatures below 200 ℃ are readily commercially available. Examples of the processing aid that can be easily obtained commercially include trade names manufactured by exxon mobil company: isopar C (fractionation temperature: 97 to 104 ℃ C.), isopar G (fractionation temperature: 158 to 175 ℃ C.), and the like.
The amount of the processing aid is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass, and even more preferably 15 to 30 parts by mass, based on 100 parts by mass of the total amount of the fluororesin and the filler, in view of properly expanding the fluororesin by pressure-delaying the preform.
The resin composition for forming a gasket may contain, for example, a terpene resin, a terpene-phenol resin, a coumarone-indene resin, a tackifier such as rosin, an ultraviolet absorber, an antioxidant, a polymerization inhibitor, a pigment, a colorant such as a dye, and the like in an appropriate amount within a range that does not hinder the object of the present invention.
The resin composition for gasket formation can be prepared as follows: the resin composition for forming a gasket is prepared by mixing a fluororesin, a filler, a processing aid, an additive, etc. in an arbitrary order at one time, or a small amount of the mixture is mixed a plurality of times at a time to have a uniform composition. In order to obtain a resin composition for forming a gasket having a uniform composition, an excessive amount of a processing aid may be added to the resin composition for forming a gasket, and after the resin composition is sufficiently stirred, the excessive processing aid may be removed by, for example, filtration, volatilization, or the like.
Next, a preform is produced from the resin composition for gasket formation. Examples of the method for producing a preform from the resin composition for gasket formation include a method for producing a preform by extrusion molding of the resin composition for gasket formation, a method for producing a preform by compression molding of the resin composition for gasket formation, and the like, but the present invention is not limited to the above examples.
The thickness of the preform is adjusted to 20 to 200mm in order to produce a fluororesin gasket which can ensure high air tightness (sealing property) between the gasket and the flange even if the thickness of the gasket is 0.8mm or less.
Next, the preform is rolled by a rolling roll. In the present invention, it is one of the features of the present invention to repeatedly calender the preform until the thickness of the fluororesin gasket is 0.8mm or less, the surface roughness Ra is 2.1 μm or less, and the density is 0.920 or more. By adopting the above-described operation, the present invention can provide a fluororesin gasket which can ensure high air tightness (sealing property) even when the thickness is 0.8mm or less.
The fluororesin gasket having a thickness of 0.8mm or less, a surface roughness Ra of 2.1 μm or less, and a density of 0.920 or more can be produced by appropriately adjusting the compression ratio and/or the number of times of compression of the fluororesin sheet when the preform is rolled.
The rolling of the fluororesin sheet may be performed using a rolling roll such as a biaxial roll. The surface temperature of the calender roll may be room temperature, a temperature higher than room temperature, or a temperature lower than room temperature, and is preferably 40 to 80 ℃ in order to obtain a fluororesin gasket which can ensure high air tightness (sealing property) even if the thickness is 0.8mm or less.
The calendering of the preform is repeated a plurality of times. When the time delay of the preform is repeated, the thickness of the preform can be gradually reduced and the compression ratio and the compactness of the fluororesin sheet can be improved by reducing the roll interval of the calender rolls each time the preform is repeatedly calendered.
The interval between the rolls of the rolling rolls at the time of rolling the preform is different depending on the thickness of the fluororesin sheet before rolling, the number of times of rolling, and the like, and thus cannot be determined in general, but is generally preferably about 40 to 60% of the thickness of the fluororesin sheet before rolling, and about 3 to 10m/min of roll speed.
The fluororesin gasket of the present invention can be obtained, for example, as follows: the fluororesin gasket is obtained by rolling the preform with a reduction ratio of 60 times or more by a rolling roller, or rolling the preform with a number of times of rolling of 7 times or more by a rolling roller, and adjusting the surface roughness Ra to 2.1 μm or less and the compactness to 0.920 or more. In the present invention, either one of the compression ratio and the number of times of rolling may be used, or both may be used.
The compression ratio of the fluororesin sheet was determined by the following formula:
[ compression ratio (multiple) ]= [ thickness of preform in initial stage (mm) ]/[ thickness of fluororesin-made gasket (mm) ].
In order to produce a fluororesin gasket that can ensure high air tightness (sealing property) between the gasket and the flange even if the thickness is 0.8mm or less, the compression ratio of the preform is preferably 60 times or more. The upper limit of the compression ratio of the preform is not particularly limited, but is preferably 500 times or less, more preferably 400 times or less, in view of efficiently producing the fluororesin gasket of the present invention. Accordingly, the compression ratio of the fluororesin sheet is preferably 60 times or more, more preferably 60 to 500 times, and still more preferably 60 to 400 times.
In the case where the compression ratio is low in order to obtain a fluororesin gasket having a predetermined surface roughness Ra and a predetermined density in the compression ratio range of the preform, the number of times of rolling the preform is increased in the range of the present invention, whereby a fluororesin gasket having a predetermined surface roughness Ra and a predetermined density can be obtained.
The number of times the preform is rolled refers to the number of times the preform is rolled. In order to produce a fluororesin gasket that can ensure high air tightness (sealing property) between the gasket and the flange even if the thickness is 0.8mm or less, the number of times of rolling the preform is preferably 6 or more. The upper limit of the number of times of rolling the preform is not particularly limited, but is preferably 20 times or less, more preferably 15 times or less, from the viewpoint of efficiently producing the fluororesin gasket of the present invention. Accordingly, the number of times of rolling the preform is preferably 6 or more, more preferably 6 to 20 times, and still more preferably 6 to 15 times.
In the case where the number of times of rolling is small in order to obtain a fluororesin gasket having a predetermined surface roughness Ra and a predetermined density in the range of the number of times of rolling of the preform, the compression ratio of the preform is increased in the range of the present invention, whereby a fluororesin gasket having a predetermined surface roughness Ra and a predetermined density can be obtained.
By repeatedly rolling the preform as described above until the thickness is 0.8mm or less, the surface roughness Ra is 2.1 μm or less, and the density is 0.920 or more, a fluororesin gasket having a surface roughness Ra of 2.1 μm or less and a density of 0.920 or more can be obtained. The thickness, surface roughness Ra, and density of the fluororesin gasket were all values at room temperature (about 25 ℃).
The surface roughness Ra of the fluororesin gasket is an arithmetic average roughness Ra defined in JIS B0601 (2013). The surface roughness Ra of the fluororesin gasket is 2.1 μm or less, preferably 2.09 μm or less, in order to obtain a fluororesin gasket that can ensure high air tightness (sealing property) between the gasket and the flange even when the thickness of the gasket is 0.8mm or less. The lower limit value of the surface roughness Ra of the fluororesin gasket is not particularly limited, but is preferably small.
The density of the fluororesin gasket was determined from the following:
density of fluororesin gasket (-)]= [ actual Density of fluororesin gasket (g/cm) 3 )][ Density of the fluororesin shim determined from the true Density of the nonvolatile components contained in the fluororesin shim ]]
The "density of the fluororesin gasket obtained from the true densities of the nonvolatile components contained in the fluororesin gasket" specifically refers to a value obtained by a calculation formula represented by the following formula based on the true densities of the nonvolatile components contained in the fluororesin gasket and the content of the nonvolatile components in the fluororesin gasket:
[ Density of the fluororesin gasket obtained from the true Density of the nonvolatile components contained in the fluororesin gasket ] =Σ (Dm×Cm)/100
[ wherein Dm represents the true density of the specific nonvolatile components constituting the fluororesin-made gasket, cm represents the content (mass%) of the specific nonvolatile components in all the nonvolatile components constituting the fluororesin-made gasket ]
The true density of the above specific nonvolatile component is, for example, 2.2g/cm in Polytetrafluoroethylene (PTFE) 3 2.6g/cm in the micro-powder clay 3 3.2g/cm in silicon carbide 3 。
The density of the fluororesin gasket is desirably the same as the density of the fluororesin gasket obtained from the true densities of the nonvolatile components contained in the fluororesin gasket. However, in practice, gaps are inevitably present between the nonvolatile components contained in the fluororesin gasket, or nonvolatile components such as a processing aid are contained in the fluororesin gasket, and therefore the density of the fluororesin gasket is usually a value smaller than the density of the fluororesin gasket obtained from the true densities of the nonvolatile components contained in the fluororesin gasket. The density of the fluororesin gasket changes according to the compression ratio and the number of times of compression of the preform, and tends to increase as the compression ratio and the number of times of compression of the preform increase.
The density of the fluororesin gasket can be obtained by measuring the mass and the volume of the fluororesin gasket. The density of the fluororesin gasket obtained from the true densities of the nonvolatile components contained in the fluororesin gasket can be obtained by separating the nonvolatile components from the fluororesin gasket, and measuring the true densities of the nonvolatile components and the content of the nonvolatile components in the fluororesin gasket.
The density of the fluororesin gasket is 0.920 or more, in terms of obtaining a fluororesin gasket that can ensure high air tightness (sealing property) between the gasket and the flange even if the thickness of the gasket is 0.8mm or less. The upper limit of the density of the fluororesin gasket is not particularly limited, but is preferably higher.
The fluororesin gasket thus obtained may be left at normal temperature or heated appropriately as needed, whereby the processing aid and the like contained in the laminated sheet are volatilized and removed.
The fluororesin gasket may be fired by heating at a temperature equal to or higher than the melting point of the fluororesin. The heating temperature is not always determined depending on the kind of the fluororesin, and is usually preferably about 340 to 370 ℃.
The fluororesin shim according to the present invention may be used in its original state or may be cut into a desired shape and size for use.
The thickness of the fluororesin gasket of the present invention varies depending on the use of the fluororesin gasket, and is preferably 0.8mm or less, in order to sufficiently exhibit the property of ensuring high air tightness (sealing property) even when the thickness of the fluororesin gasket of the present invention is small.
As described above, the fluororesin gasket of the present invention can ensure high air tightness (sealing property) even when the thickness thereof is 0.8mm or less, and therefore, can be suitably used for applications requiring a gasket having a thin thickness, for example, in equipment such as pumps and valves.
Examples
The present invention will be described in further detail with reference to examples, but the present invention is not limited to these examples.
Examples 1 to 7 and comparative examples 1 to 3
Polytetrafluoroethylene (PTFE) fine powder [ product number manufactured by dajinzhi corporation: f104]1000g of a fine powder clay [ product number manufactured by Showa KDE Co., ltd.: NK-300 [ 1450g (used in examples 1 to 6 and comparative examples 1 to 3) or silicon carbide [ product No.: #1200]1450g (used in example 7), processing aid [ manufactured by Exxon Mobil Corp., trade name: isopar C ]125g and a processing aid [ manufactured by Exxon Mobil, trade name: isopar G ]125G was mixed with a kneader for 5 minutes, and the obtained mixture was extruded with a rectangular extruder having an opening size of 300mm X20 mm in a die, whereby preforms having the thicknesses shown in Table 1 were produced.
Then, using biaxial rolls (diameter of rolls: 700mm, interval between rolls at initial stage: 20mm, surface temperature of rolls: 60 ℃) as calender rolls, the preform obtained above was passed between rolls of the biaxial rolls at a moving speed of 6m/min, and then passed between rolls of biaxial rolls having a gradually narrowed interval between rolls of biaxial rolls in order to be calendered, and finally passed between rolls of biaxial rolls having an interval corresponding to the thickness of the fluororesin gasket shown in table 1 to be calendered, thereby obtaining the fluororesin gasket. The number of times (number of times of rolling) the preform was rolled by passing the preform between the rolls of the biaxial rolls is shown in the production condition column described in table 1.
The thickness, surface roughness and density of the obtained fluororesin gasket are shown in the performance bars of the gasket shown in table 1.
Then, the air tightness (sealing property) of the fluororesin gasket obtained as described above was examined by the following method. The results are shown in the performance column of the gasket described in table 1.
[ method for measuring air tightness (sealing ]
The air tightness (sealing property) was examined in accordance with annex C of "sealing property test method of gasket for pipe flange" of JIS B2490 (2008). As a sample, a gasket punched out to have a size of 48mm in inner diameter and 67mm in outer shape was used, and the gasket was mounted between steel flanges having a diameter of 100mm, a height of 50mm and a surface roughness Rz of 3 μm, and a load was applied by a compression tester so that the surface pressure was 19.6MPa. The pressure of 0.98MPa was applied to the inner diameter side of the gasket with nitrogen gas from the pressure introduction through-hole provided in the flange, and the pressure was allowed to stand for 5 minutes, and then the leakage amount of the nitrogen gas was determined using a soap film flowmeter.
The leakage amount was 3.0X10 -4 Pa·m 3 At a value of/sec or less, the gasket satisfies a criterion for air tightness (sealing property).
As is clear from the results shown in table 1, the fluororesin gaskets obtained in the examples were excellent in air tightness (sealing property) because the surface roughness Ra was 2.1 μm or less and the density was 0.920 or more even when the thickness of the fluororesin gaskets was 0.8mm or less, regardless of the type of the filler.

Claims (3)

1. A fluororesin gasket comprising a fluororesin and a filler, and having a thickness of 0.8mm or less, characterized in that the surface roughness Ra is 2.1 [ mu ] m or less and the density is 0.920 or more.
2. A method for producing a fluororesin gasket according to claim 1, characterized in that a preform having a thickness of 20 to 200mm and containing a fluororesin and a filler is used, and the preform is repeatedly rolled until the thickness is 0.8mm or less, the surface roughness Ra is 2.1 μm or less, and the density is 0.920 or more.
3. The method for producing a fluororesin gasket according to claim 2, wherein the surface temperature of the calender roll for the time-delay of the preform is 40 to 80 ℃.
CN202280058667.XA 2021-12-24 2022-12-21 Fluororesin gasket and method for producing same Pending CN117897570A (en)

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JP5068043B2 (en) * 2006-06-28 2012-11-07 日本バルカー工業株式会社 Filled fluororesin sheet and method for producing filled fluororesin sheet
JP2011153254A (en) * 2010-01-28 2011-08-11 Nippon Valqua Ind Ltd Sheet forming composition, filler-containing fluororesin sheet, and method for producing the filler-containing fluororesin sheet
WO2018231268A1 (en) * 2017-06-15 2018-12-20 W. L. Gore & Associates, Inc. Compressible liquid seals with discontinuous adhesives
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