JP5253273B2 - Fluororesin sheet, method for producing the same, and gasket - Google Patents

Description

  The present invention relates to a fluororesin sheet, a method for producing the same, and a gasket.

  Filled fluororesin sheet is a sheet made by filling fluororesin with a filler. In addition to the chemical resistance and heat resistance of fluororesin, it has the unique functions and characteristics of the filler. By adding or improving creep resistance, which is a drawback of fluororesins, it is often used for sealing materials.

As a sealing material, there is a material in which a creep property or the like is improved by filling a fluororesin with metal, graphite, an inorganic filler or the like, and it is used for a sheet-like gasket or the like.
Regarding a fluororesin sheet with a filler, for example, in US Pat. No. 3,331,020 (Patent Document 1), a pair of rolling is performed after extruding a mixture of PTFE (polytetrafluoroethylene), a filler and a processing aid. A technique for obtaining a long sheet by rolling a roll once or a plurality of times is disclosed.

  On the other hand, Japanese Patent Laid-Open No. 11-80705 (Patent Document 2) discloses a gasket material comprising a laminated sheet in which specific biaxially stretched porous PTFE films comprising nodes and fibrils connecting the nodes are laminated. In addition, it is described that a reinforcing layer made of a material (sintered PTFE, non-porous PTFE, etc.) having higher rigidity and heat resistance equal to or higher than that of PTFE may be provided between these PTFE films. ([0026] etc.).

US Pat. No. 3,331,020 Japanese Patent Laid-Open No. 11-80705

  However, even if an attempt is made to punch a long sheet obtained by the technique disclosed in Patent Document 1 to manufacture a gasket, there is a problem that a gasket excellent in both stress relaxation and airtightness cannot be obtained.

  In addition, a gasket material composed of a specific biaxially stretched porous PTFE film and a highly rigid reinforcing layer (sintered PTFE, non-porous PTFE, etc.) described in Patent Document 2 has a PTFE film in a stretched manner. Since it is manufactured, a filler cannot be blended, so that there has been a problem that the stress relaxation rate when used at a high temperature cannot be reduced.

  The present invention made in view of the above problems is a fluororesin sheet excellent in both stress relaxation property and airtightness at high temperature and a method for producing the same, and both stress relaxation property and airtightness at high temperature are excellent. An object is to provide a gasket.

The fluororesin sheet of the present invention is
A rolled fluororesin layer comprising a fluororesin and a filler in a mass ratio of 30-50: 70-50 (however, the total of both is 100) or an inner layer made of a laminate thereof;
An outer layer made of a rolled fluororesin formed on both surfaces of the inner layer and containing a fluororesin and a filler in a mass ratio of 60 to 100: 40 to 0 (the total of both being 100). It is characterized by consisting of.

The production method of the fluororesin sheet of the present invention is:
An outer layer extrusion-molded body containing a fluororesin and a filler in a mass ratio of 60 to 100: 40 to 0 (however, the total of both is 100);
One or more extrudates for an inner layer containing a fluororesin and a filler in a mass ratio of 30 to 50:70 to 50 (the total of both being 100);
A laminate for rolling by laminating an extruded layer for outer layer containing a fluororesin and a filler in a mass ratio of 60 to 100: 40 to 0 (the sum of both being 100) in this order. Form the
The rolling laminate is rolled.

  The rolling laminate is formed by laminating the respective extruded molded bodies so that the angle formed by the extrusion directions during extrusion molding is 80 to 90 ° between the adjacent extruded molded bodies. It is preferable.

The fluororesin sheet of the present invention is preferably produced by the method for producing a fluororesin sheet of the present invention.
The gasket of the present invention comprises the fluororesin sheet of the present invention.

The fluororesin sheet of the present invention is excellent in stress relaxation and airtightness at high temperatures.
According to the method for producing a fluororesin sheet of the present invention, it is possible to produce a fluororesin sheet excellent in stress relaxation property and airtightness at high temperatures.
The gasket of the present invention is excellent in stress relaxation and airtightness at high temperatures.

FIG. 1 is a schematic cross-sectional view of one embodiment of the fluororesin sheet of the present invention. FIG. 2 is a schematic cross-sectional view of one embodiment of the fluororesin sheet of the present invention. FIG. 3 is a schematic view of one embodiment of the fluororesin sheet of the present invention.

[Fluorine resin sheet and method for producing the same]
The present invention will be described below with reference to the drawings.
1 and 2 are schematic sectional views of the fluororesin sheet of the present invention.

The fluororesin sheet 10 of the present invention includes an inner layer 1 and an outer layer 3 formed on both surfaces of the inner layer 1.
The inner layer 1 may be a single rolled fluororesin layer 2 as shown in FIG. 1, or may be a laminate composed of a plurality of rolled fluororesin layers 2 as shown in FIG. The outer layer 3 is composed of a rolled fluororesin layer 4. In the present invention, the rolled fluororesin layer 2 used for the inner layer and the rolled fluororesin layer 4 used for the outer layer are also referred to as “rolled fluororesin layer” without distinction.

<Inner layer>
The rolled fluororesin layer 2 constituting the inner layer 1 contains a fluororesin and a filler.
Examples of the fluororesin include tetrafluoroethylene resin (PTFE), modified PTFE, vinylidene fluoride resin (PVDF), tetrafluoroethylene-ethylene copolymer resin (ETFE), trifluorochloroethylene resin (PCTFE), four Examples thereof include fluorinated ethylene-hexafluoropropylene ethylene copolymer resin (FEP) and tetrafluoroethylene-perfluoroalkyl copolymer resin (PFA). Among these, tetrafluoroethylene resin (PTFE) is preferable and PTFE obtained by emulsion polymerization is particularly preferable in terms of processability when performing extrusion molding, rolling, and the like.

  When PTFE is used as the fluororesin, the fluororesin other than the above-mentioned PTFE is contained in the fluororesin in a small amount, for example, 10% by mass (the total amount of fluororesin is 100% by mass) or less. It may be.

  As the fluororesin, a powdery one may be used as it is, or a dispersion in which fluororesin fine particles are dispersed in water may be used, and after mixing this with a filler, water may be removed.

As the filler, depending on the purpose, carbon-based fillers such as graphite, carbon black, expanded graphite, activated carbon, and carbon nanotubes; inorganic fillers such as talc, mica, clay, calcium carbonate, magnesium oxide; or PPS Resin powder such as
Etc. are used. Moreover, you may use the fiber material which consists of carbon fiber, an aramid fiber, rock wool, etc. and whose fiber material length is 10 mm or less as a filler.

The mass ratio of the fluororesin to the filler (fluororesin: filler) is 30 to 50:70 to 50, preferably 35 to 50:65 to 50 (however, the total of both is 100). ). The fluororesin sheet 10 provided with the rolled fluororesin layer 2 having a mass ratio in this range or the inner layer 1 made of a laminate thereof is excellent in stress relaxation at high temperatures.

The rolled fluororesin layer 2 consists essentially of the fluororesin and filler described above.
The upper limit of the number of rolled fluororesin layers 2 is usually about 10.

<Outer layer>
The rolled fluororesin layer 4 constituting the outer layer 3 contains a fluororesin. Specific examples of the fluororesin include the fluororesin used in the above-described rolled fluororesin layer 2 for the inner layer.

  Further, the rolled fluororesin layer 4 may further contain the filler described above. In this case, the blending amount of the filler is adjusted so that the outer layer 3 is softer than the inner layer 1, The mass ratio of the fluororesin to the filler (fluororesin: filler) is 60 to 100: 40 to 0, preferably 65 to 90:35 to 10 (however, the total of both is 100). ). The fluororesin sheet 10 including the outer layer 3 having a mass ratio in this range is excellent in airtightness.

[Method for producing fluororesin sheet]
A general method for producing a filled fluororesin sheet by rolling includes a stirring process, a preforming process, a rolling process, a drying process, and a firing process in this order.

  In the method for producing the fluororesin sheet 10 of the present invention, the outer layer extruded body 14, one or a plurality of inner layer extruded bodies 12, and the outer layer extruded body 14 are laminated in this order in the preforming step. Thus, the fluororesin sheet 10 is obtained by forming the rolling laminate 15 and rolling the rolling laminate 15 in a rolling process.

<Stirring step>
In the stirring step, the fluororesin, the filler, and the processing aid are added to the container in an arbitrary order at once or in small portions, and the mixture is stirred, mixed, etc. Can be prepared. If the stirring efficiency is poor, a large amount of processing aid may be added and excess processing aid may be removed by filtration after stirring.

  The types and blending ratios of the fluororesin and the filler are appropriately determined so as to correspond to the configuration of the rolled fluororesin layer 2 for the inner layer and the configuration of the rolled fluororesin layer 4 for the outer layer, respectively, of the fluororesin sheet 10 to be manufactured. Just decide.

  Examples of the processing aid include conventionally known processing aids such as petroleum hydrocarbon solvents, alcohols, and water. Examples of petroleum hydrocarbon solvents include Isopar C, Isopar G, Isopar M (Exxon Mobil (existing)) and the like as commercial products.

<Preliminary molding process>
In the method for producing the fluororesin sheet 10 of the present invention, in the preforming step, the inner layer extruded body 12 and the outer layer extruded body 14 are respectively formed by extruding the resin composition for an extruded body. Then, these are made to correspond to a desired fluororesin sheet, that is, the outer layer extruded body 14, one or a plurality of inner layer extruded bodies 12, and the outer layer extruded body 14 Are stacked in this order to form a stretched laminate 15.

A conventionally known extruder can be used for the extrusion.
At the time of extrusion molding, if necessary, it may be heated (for example, 30 to 80 ° C.) at a temperature at which contained processing aids and the like are not volatilized so much.

The shape of the extruded product (preform) is not particularly limited, but a rod shape or a ribbon shape is desirable in consideration of efficiency of subsequent sheet formation, uniformity of sheet properties, and the like.
When forming the laminate 15 for rolling, it is preferable to laminate the respective extrusion-molded bodies so that the extrusion directions at the time of extrusion are alternately different. Specifically, it is preferable to laminate the adjacent extruded bodies so that the angle formed by the extrusion directions during extrusion (the smaller angle) is about 80 ° to 90 °.

  Such a fluororesin sheet manufactured by stretching the laminate 15 for rolling, which is formed by laminating the respective extruded molded bodies so that the extrusion directions at the time of extrusion are alternately different, Especially excellent in relaxation and airtightness.

  The angle formed by the extrusion directions is more preferably 85 to 90 °, and still more preferably a right angle (90 °). The angle formed by the extrusion directions is preferably a right angle as shown in FIG. 3 from the viewpoint of ease of manufacturing the fluororesin sheet. In addition, the arrow in FIG. 3 shows the extrusion direction (and the opposite direction) of each extrusion molded object.

  If the inner layer extruded body 12 used for forming the rolling laminate 15 is one, the formation of the rolling laminate 15 can be further simplified. On the other hand, if a plurality of inner-layer extrusion-molded bodies 12 are used, the inner-layer extrusion-molded bodies 12 can be laminated so that the extrusion directions at the time of the extrusion are alternately different. It becomes possible to further improve the stress relaxation property and air tightness of the produced fluororesin sheet.

<Rolling process>
In the rolling step subsequent to the pre-forming step, the rolling laminate 15 is rolled and formed into a sheet shape by passing between rolling rolls represented by a biaxial roll.

  By using the rolling laminate 15 as an extruded product for rolling, the fluororesin sheet 10 having excellent stress relaxation and airtightness can be produced by rolling a small number of times (about 3 to 5 times).

  When the laminated body 15 for rolling is rolled by a biaxial roll to form a sheet, for example, the distance between the rolls is set to 1.5 to 30 mm, and the roll surface moving speed (sheet extrusion speed) is set to 5 to 50 mm / second. What is necessary is just to roll the laminated body 15 for rolling. Although such a rolling process is normally performed at normal temperature, it can also be performed under about 30-200 degreeC heating.

<Drying process>
In the drying step, the processing aid is removed by leaving the rolled sheet at room temperature or heating it at a temperature below the melting point of the fluororesin.

<Baking process>
In the firing step, the dried sheet is heated and sintered at a temperature equal to or higher than the melting point of the fluororesin. The heating temperature varies slightly depending on the type of the fluororesin, for example, 340 to 370 ° C., considering that the entire sheet needs to be uniformly fired and that a fluorine-based harmful gas is generated at an excessively high temperature. Is appropriate.

  According to such a manufacturing method of the present invention, the fluororesin sheet 10 of the present invention configured as described above can manufacture the above fluororesin sheet having both high stress relaxation properties and high airtightness. .

[Fluorine resin sheet]
The fluororesin sheet 10 of the present invention comprises the inner layer 1 and the outer layer 3 formed on both surfaces of the inner layer 1, and can be manufactured by the manufacturing method described above.

The fluororesin sheet 10 of the present invention configured as described above is excellent in both stress relaxation and air tightness. Specifically, the stress relaxation rate is 200 ° C. (based on JIS R3453, heating temperature only from 100 ° C. Change to 200 ° C), and φ48mm × φ67mm × 1.5mm thickness gasket test piece made from the sheet, surface pressure 19.6MPa (200kgf / cm ² G), nitrogen gas internal pressure 0.98MPa (1.0kgf / cm ² When the airtight test is conducted as G), the leakage amount is usually 55% or less and 5 × 10 ⁻⁴ Pa · m ³ / s or less, preferably 50% or less and 1.7 × 10 ⁻⁴ Pa · m ^{3, respectively.} The lower limit value of the stress relaxation rate is about 30%, and the lower limit value of the leakage amount is about 1.7 × 10 ⁻⁵ Pa · m ³ /.

The thickness ratio (inner layer: outer layer) of the inner layer 1 and the outer layer 3 is preferably 3 to 10: 1, more preferably 4 to 8: 1.
What is necessary is just to set the thickness of the said fluororesin sheet | seat 10 suitably according to the use.

  Since the fluororesin sheet of the present invention is excellent in both stress relaxation and airtightness, it can be used for gaskets, and is particularly preferable as a gasket material used at high temperatures (for example, 200 ° C. or higher).

[gasket]
The gasket of this invention consists of the fluororesin sheet | seat of this invention mentioned above.
For this reason, the gasket of this invention is excellent in both stress relaxation property and airtightness. Moreover, the gasket of this invention can be easily manufactured by cutting out the fluororesin sheet of this invention in a desired shape.

EXAMPLES Hereinafter, although the manufacturing method of this invention is demonstrated in detail by an Example, this invention is not limited at all by these Examples.
<Test method>
Test pieces were prepared from a sheet having a thickness of 1.5 mm, and hermeticity and tensile strength were measured as follows.

Leakage (airtightness);
A gasket test piece punched into a size of φ48mm × φ67mm is mounted between steel flanges of φ100mm × height 50mm and surface roughness Rmax = 12μm, and the surface pressure is 19.6MPa (200kgf / cm ² G) by a compression tester. A load was applied. After applying a nitrogen gas internal pressure of 0.98 MPa (1.0 kgf / cm ² G) to the inner diameter of the gasket from the pressure introduction through hole provided in the flange, the pressure introduction pipe was sealed and held 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.

Stress relaxation;
A test piece was prepared from a sheet having a thickness of 1.5 mm, and the stress relaxation property of this test piece was measured according to JIS R3453 except that the heating temperature was changed from 100 ° C. to 200 ° C.

[Example 1]
<Creation of filled fluororesin layer 1>
Teflon (registered trademark) 6-J (PTFE fine powder, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) 3.3 kg,
NN kaolin clay (clay, Takehara Chemical Industry Co., Ltd.) 5.0 kg, and Isopar M (solvent, ExxonMobil Corporation) 1.7 kg
After mixing with a kneader for 5 minutes, it is aged by leaving it to stand at room temperature (25 ° C.) for 16 hours to form a filled fluororesin layer containing fluororesin and filler in a ratio of 40:60 (mass ratio). Composition 1 was prepared.

  This composition was extruded at room temperature (25 ° C.) with an extruder having a die of 300 mm × 15 mm to form two filled fluororesin layers 1 (300 mm × 300 mm × 15 mm, hereinafter also referred to as “preform 1”). did.

<Creation of filled fluororesin layer 1 '>
The composition 1 for forming a fluororesin layer with a filler is extruded at room temperature (25 ° C.) with an extruder having a base of 300 mm × 30 mm, and two fluororesin layers with a filler 1 ′ (300 mm × 300 mm × 30 mm, hereinafter “ Also called Preform 1 ′ ”.

<Creation of filled fluororesin layer 2>
Teflon (registered trademark) 6-J (PTFE fine powder, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) 5.8 kg,
NN kaolin clay (clay, manufactured by Takehara Chemical Co., Ltd.) 2.5 kg, and Isopar M (solvent, ExxonMobil Corporation) 1.7 kg
After mixing with a kneader for 5 minutes, it is aged by leaving it to stand at room temperature (25 ° C.) for 16 hours to form a filled fluororesin layer containing a fluororesin and a filler in a ratio of 70:30 (mass ratio). Composition 2 was prepared.

  This composition was extruded at room temperature (25 ° C.) with a 300 mm × 5 mm die extruder to form two filled fluororesin layers 2 (300 mm × 300 mm × 5 mm, hereinafter also referred to as “preform 2”). did.

<Manufacture of fluororesin sheet>
Preforms 1 and 2 above
Preform 2 / Preform 1 / Preform 1 / Preform 2
The laminated body 1 was prepared by stacking so that the extrusion directions at the time of extrusion molding were orthogonal to each other in this order.

  This laminate 1 was rolled with a biaxial roll under the conditions of a roll diameter of 700 mm, a roll interval of 30 mm, a roll speed of 6 m / min, and a roll temperature of 40 ° C. Immediately after this rolling, the obtained sheet was rolled again by changing the rolling direction by 90 ° and setting the roll interval to 20 mm. Immediately after this rolling, the obtained sheet was rolled again by changing the rolling direction by 90 ° and setting the roll interval to 10 mm. Furthermore, immediately after this rolling, the obtained sheet was rolled again by changing the rolling direction by 90 ° and setting the roll interval to 3 mm. Finally, immediately after this rolling, the obtained sheet was rolled again by changing the rolling direction by 90 ° and the roll interval to 1.5 mm, and a sheet having a thickness of 1.5 mm was obtained.

This sheet was allowed to stand at room temperature (25 ° C.) for 24 hours to remove the solvent, and then fired in an electric furnace at 350 ° C. for 3 hours to obtain a gasket (sheet gasket) made of a fluororesin sheet.
The stress relaxation rate (200 ° C., JIS R3453 conformity) of this sheet gasket was 44%, and the leakage amount (airtightness) was 1.3 × 10 ⁻⁴ Pa · m ³ / s (0.8 cc / 10 minutes). .

[Example 2]
In place of laminate 1,
Preform 2 / Preform 1 / Preform 1 / Preform 2
A gasket was manufactured in the same manner as in Example 1 except that a laminate formed by laminating in such a order that the extrusion directions between adjacent preforms were the same was used.
The gasket had a stress relaxation rate (200 ° C., conforming to JIS R3453) of 47% and a leakage amount (airtightness) of 2.0 × 10 ⁻⁴ Pa · m ³ / s (1.2 cc / 10 minutes).

[Example 3]
In place of laminate 1,
Preform 2 / Preform 1 '/ Preform 2
A gasket was manufactured in the same manner as in Example 1 except that a laminate formed by laminating in such a order that the extrusion directions between adjacent preforms were the same was used.
The gasket had a stress relaxation rate (200 ° C., conforming to JIS R3453) of 47% and a leakage amount (airtightness) of 2.0 × 10 ⁻⁴ Pa · m ³ / s (1.2 cc / 10 minutes).

[Comparative Example 1]
In place of laminate 1,
Preform 1 / Preform 1 / Preform 1 / Preform 1
A gasket was manufactured in the same manner as in Example 1 except that the laminate 2 formed by laminating in such an order that the extrusion directions between adjacent preforms were orthogonal to each other was used.
The gasket had a stress relaxation rate (200 ° C., in accordance with JIS R3453) of 42% and a leakage amount (airtightness) of 5.0 × 10 ⁻³ Pa · m ³ / s (30 cc / 10 minutes).

[Comparative Example 2]
In place of laminate 1,
Preform 2 / Preform 2 / Preform 2 / Preform 2
A gasket was manufactured in the same manner as in Example 1 except that the laminate 3 formed by laminating in such an order that the extrusion directions between adjacent preforms were orthogonal to each other was used.
The gasket had a stress relaxation rate (200 ° C., in accordance with JIS R3453) of 78% and a leakage amount (airtightness) of 1.2 × 10 ⁻⁴ Pa · m ³ / s (0.7 cc / 10 minutes).

DESCRIPTION OF SYMBOLS 1 ... Inner layer 2 ... Rolled fluororesin layer 3 ... Outer layer 4 ... Rolled fluororesin layer 10 ... Fluororesin sheet

Claims (5)

A rolled fluororesin layer comprising a fluororesin and a filler in a mass ratio of 30-50: 70-50 (however, the total of both is 100) or an inner layer made of a laminate thereof;
An outer layer made of a rolled fluororesin formed on both surfaces of the inner layer and containing a fluororesin and a filler in a mass ratio of 60 to 100: 40 to 0 (the total of both being 100). A fluororesin sheet characterized by comprising: An outer layer extrusion-molded body containing a fluororesin and a filler in a mass ratio of 60 to 100: 40 to 0 (however, the total of both is 100);
One or more extrudates for an inner layer containing a fluororesin and a filler in a mass ratio of 30 to 50:70 to 50 (the total of both being 100);
A laminate for rolling by laminating an extruded layer for outer layer containing a fluororesin and a filler in a mass ratio of 60 to 100: 40 to 0 (the sum of both being 100) in this order. Form the
A method for producing a fluororesin sheet, comprising rolling the laminate for rolling. Forming the rolling laminate by laminating the respective extrusion-molded bodies between adjacent extrusion-molded bodies so that the angle formed by the extrusion directions during extrusion molding is 80 to 90 °. The manufacturing method of the fluororesin sheet | seat of Claim 2 characterized by these.   A fluororesin sheet produced by the production method according to claim 3.   A gasket comprising the fluororesin sheet according to claim 1.

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