JP2011153254A - Sheet forming composition, filler-containing fluororesin sheet, and method for producing the filler-containing fluororesin sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filler-containing fluororesin sheet excellent in a stress relaxation property, in particular, a stress relaxation property at a high temperature, and air-tightness, and a method for producing the same. <P>SOLUTION: This sheet forming composition contains a fluororesin (A), a filler (B), 1-20 pts.wt. of an alkoxy silane (C) expressed by formula (1): (R<SP>1</SP>)<SB>4-n</SB>Si(OR<SP>2</SP>)<SB>n</SB>per 100 pts wt. of the filler (B), and a working auxiliary (D). In the formula (1), each R<SP>1</SP>represents independently hydrogen, hydroxy group, or a 1-5C monovalent hydrocarbon group, R<SP>2</SP>represents independently a 1-5C monovalent hydrocarbon group, and n is 2, 3 or 4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sheet-forming composition, a filled fluororesin sheet, and a method for producing a filled fluororesin sheet.

  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 such a sealing material, the present applicant discloses in JP-A-2007-253519 (Patent Document 1) a method for producing a filled fluororesin sheet containing a fluororesin, a filler, and a processing aid. Yes. By this production method, a low stress relaxation property and a high airtightness are compatible, and a filled fluororesin sheet suitable for a gasket material can be obtained.

JP 2007-253519 A

However, the conventional fluororesin sheet produced by the method of Patent Document 1 has room for further improvement in stress relaxation properties, particularly stress relaxation properties at high temperatures.
The present invention has been made in view of the above situation, and provides a filled fluororesin sheet excellent in airtightness and having excellent stress relaxation properties, particularly stress relaxation properties at high temperatures, and a method for producing the same. The purpose is to do.

  The composition for sheet formation of the present invention is an alkoxysilane represented by the following formula (1) of 1 to 20 parts by weight with respect to 100 parts by weight of the fluororesin (A), the filler (B), and the filler (B). It contains (C) and a processing aid (D).

(R ¹ ) _4-n Si (OR ² ) _n (1)
[In Formula (1), R < ¹ > is respectively independently a hydrogen atom, a hydroxyl group, or a C1-C5 monovalent hydrocarbon group; R < ² > is respectively independently C1-C5. A monovalent hydrocarbon group; n is 2, 3 or 4; ]

The filler (B) is preferably at least one filler selected from silicon dioxide and silicate.
The alkoxysilane (C) is preferably tetraethoxysilane and / or tetramethoxysilane.

The weight ratio of the fluororesin (A) to the filler (B) is preferably fluororesin: filler = 1: 0.1-4.
The amount of the processing aid (D) is preferably 5 to 50 parts by weight with respect to a total of 100 parts by weight of the fluororesin (A) and the filler (B).

The filled fluororesin sheet of the present invention is characterized by being manufactured from the sheet forming composition.
The method for producing a filled fluororesin sheet according to the present invention is characterized in that the sheet-forming composition is preformed, the resulting preform is rolled, and then fired.

The filled fluororesin sheet produced from the sheet forming composition of the present invention is excellent in stress relaxation properties, particularly stress relaxation properties at high temperatures, and airtightness.
According to the method for producing a filled fluororesin sheet of the present invention, it is possible to produce a filled fluororesin sheet excellent in stress relaxation, particularly stress relaxation at high temperatures, and airtightness.

Hereinafter, the present invention will be described in more detail.
[Composition for sheet formation]
The composition for sheet formation of the present invention is an alkoxysilane represented by the following formula (1) of 1 to 20 parts by weight with respect to 100 parts by weight of the fluororesin (A), the filler (B), and the filler (B). (C) and a processing aid (D) are contained.
(R ¹ ) _4-n Si (OR ² ) _n (1)
[In Formula (1), R < ¹ > is respectively independently a hydrogen atom, a hydroxyl group, or a C1-C5 monovalent hydrocarbon group; R < ² > is respectively independently C1-C5. A monovalent hydrocarbon group; n is 2, 3 or 4; ]

<Fluororesin (A)>
Examples of the fluororesin (A) include tetrafluoroethylene resin (PTFE), modified PTFE, vinylidene fluoride resin (PVDF), tetrafluoroethylene-ethylene copolymer resin (ETFE), and trifluoroethylene chloride resin (PCTFE). ), Tetrafluoroethylene-hexafluoropropylene-ethylene copolymer resin (FEP), and tetrafluoroethylene-perfluoroalkyl copolymer resin (PFA) can be preferably used. 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 (A), the fluororesin other than the above-mentioned PTFE is contained in the fluororesin in a small amount, for example, 10% by weight (the total amount of fluororesin is 100% by weight) or less. May be included.
As the fluororesin (A), a powdery one may be used as it is, or a dispersion in which fluororesin fine particles are dispersed in water may be used.

<Filler (B)>
The filler (B) preferably has a hydroxyl group on the particle surface. As such a filler, a filler having a hydroxyl group on its particle surface and / or a filler having a hydroxyl group introduced by surface modification on the surface of a filler particle having no hydroxyl group on its particle surface is used. be able to. As the surface modification, a conventionally known method can be used. In the present invention, when the filler (B) is a filler having a hydroxyl group on the surface of the particle, the hydroxyl group on the surface of the particle of the filler reacts with an alkoxysilane (C) described later, and the filler Since it is considered that the (B) particles are bonded to each other to construct a network structure, it is possible to obtain a filled fluororesin sheet having lower stress relaxation properties, particularly lower stress relaxation properties at high temperatures. Conceivable.

  The filler (B) is preferably at least one filler selected from silicon dioxide and silicate. Many of these silicon dioxides and silicates have hydroxyl groups on the surface of the particles.

Examples of the silicon dioxide include quartz, cristobalite, phosphite, lechatellite, protein stone, and 3SiO ₂ .H ₂ O depending on the difference in crystallinity. Etc.

  Examples of the silicate include aluminum silicate (claycarionite, pyrophyllite), magnesium silicate (talc), calcium silicate (wollastonite, zonotlite), montmorillonite, bentonite, activated clay, sepiolite, imogolite, Examples thereof include sericite, glass beads, glass fiber, silica-based balun and mica. Among these, aluminum silicate (clay, karionite, pyrophyllite), magnesium silicate, calcium silicate and / or mica are preferable.

  In addition to the above, carbon-based fillers such as graphite, carbon black, expanded graphite, activated carbon, and carbon nanotubes; inorganic fillers such as calcium carbonate, magnesium oxide, silicon carbide, and alumina; or resin powders such as PPS; Those having a hydroxyl group on the surface of the filler particles are preferable.

  According to the present invention, even when the filling rate of the fluororesin (A) is high and the filling rate of the filler (B) is low, the fluorine-filled filler has high airtightness and excellent stress relaxation properties. A resin sheet can be obtained. The weight ratio of the fluororesin (A) to the filler (B) is preferably 1: 0.1 to 4, more preferably 1: 0.25 to 2.

<Alkoxysilane (C)>
The alkoxysilane (C) is represented by the following formula (1).
(R ¹ ) _4-n Si (OR ² ) _n (1)
In the above formula (1), each R ¹ is independently a hydrogen atom, a hydroxyl group or a monovalent hydrocarbon group having 1 to 5 carbon atoms, preferably a methyl group or an ethyl group.

In the above formula (1), each R ² is independently a monovalent hydrocarbon group having 1 to 5 carbon atoms, preferably a methyl group, an ethyl group, a propyl group or a butyl group, particularly preferably. Is a methyl group or an ethyl group.

In the above formula (1), n is 2, 3 or 4, preferably 4.
Examples of the alkoxysilane (C) include tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), tetrapropoxysilane (TPOS), and tetrabutoxysilane (TBOS). These alkoxysilanes may be used alone or in combination of two or more. Among these, it is preferable to use tetramethoxysilane and / or tetraethoxysilane in order to obtain a filled fluororesin sheet having lower stress relaxation properties.

  The amount of the alkoxysilane (C) in the composition for forming a sheet is 1 to 20 parts by weight, preferably 2 to 20 parts by weight, more preferably 5 to 20 parts per 100 parts by weight of the filler (B). Parts by weight. When the alkoxysilane (C) is contained in such an amount, it is possible to obtain a filled fluororesin sheet having low stress relaxation properties while maintaining high airtightness.

  When manufacturing the fluororesin sheet with a filler, when the following method (I) is used, the amount of the alkoxysilane (C) in the sheet-forming composition is 20 parts by weight with respect to 100 parts by weight of the filler (B). If it is included in an amount exceeding part by weight, the alkoxysilane (C) often remains in the rolled sheet after the rolling step, so the sheet finally obtained has many voids. There is a risk that the airtightness and stress relaxation characteristics will be inferior.

<Processing aid (D)>
The processing aid (D) is not particularly limited, and conventionally known processing aids such as petroleum hydrocarbon solvents, alcohols, and water can be used.

  Commercially available petroleum hydrocarbon solvents include, for example, Isopar C (hydrocarbon organic solvent, fractionation temperature: 97 to 104 ° C.), Isopar G (hydrocarbon organic solvent, fractionation) manufactured by ExxonMobil Co., Ltd. Temperature: 158 to 175 ° C.), Isopar M (hydrocarbon organic solvent, fractional distillation temperature: 218 to 253 ° C.), and the like.

  The amount of the processing aid (D) is preferably 5 to 50 parts by weight with respect to 100 parts by weight of the total of the fluororesin (A) and the filler (B) in the sheet-forming resin composition. Preferably it is 10-30 weight part. When the processing aid (D) is contained in such an amount, when the following method (I) is used when producing a filled fluororesin sheet, it is uniformly extruded in the preforming step. It can be molded and a good preform can be produced.

The sheet-forming resin composition essentially comprises only the above-described fluororesin (A), filler (B), alkoxysilane (C), and processing aid (D).
In order to prepare a resin composition for forming a fluororesin sheet containing these components, the above-mentioned components are added to the container at a time in an arbitrary order, or divided into a plurality of portions, and stirred, mixed, etc. do it.

The method of stirring and mixing is not particularly limited, but the fluororesin sheet with a filler to be produced is the fluororesin (A), the filler (B), the alkoxysilane (C), and the processing aid (D). It may be blended so as to correspond to the composition, and stirred and mixed in any order.
Moreover, the temperature at the time of stirring and mixing is preferably lower than the roll temperature in the rolling step so that the processing aid does not volatilize.

[Method for producing filled fluororesin sheet]
The method for producing the filled fluororesin sheet of the present invention is not particularly limited as long as the filled fluororesin sheet can be formed from the sheet forming composition, and a conventionally known method can be used. Is a method (hereinafter also referred to as method (I)) in which the sheet-forming composition is preformed, the obtained preform is rolled, and then fired.
The method (I) will be specifically described below.

≪Method (I) ≫
Method (I) includes a preforming step, a rolling step, a drying step, and a firing step in this order.

<Preliminary molding process>
In the pre-forming step, the sheet-forming composition is extruded to produce a preform (extruded product).

The shape of the 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.
In the method (I), since the processing aid is gradually volatilized in the rolling step described later, the preforming step may be performed at a temperature lower than the roll temperature in the rolling step so that the processing aid does not volatilize. preferable.

<Rolling process>
In the rolling process subsequent to the preliminary forming process, the preform is rolled and formed into a sheet shape by passing between rolling rolls represented by a biaxial roll.

In the method (I), this rolling step preferably has a roll temperature of 40 to 80 ° C.
When the roll temperature is in the above range, the hardness of the fluororesin (A) is slightly lowered, and the filled fluororesin sheet is easily densified.

  On the other hand, when the rolling step is performed at a temperature lower than 40 ° C., the processing aid (D) tends to be less volatile. Moreover, when rolling is performed at a temperature exceeding 80 ° C., the processing aid (D) may volatilize excessively. In this case, since the processing aid remaining at the initial stage of the rolling process is reduced, the fluororesin (A) is sufficiently swollen and difficult to be fiberized, and the strength of the obtained fluororesin sheet with a filler tends to be inferior. is there. Moreover, a blister phenomenon may occur when the processing aid (D) in the composition is rapidly vaporized, and the airtightness of the filled fluororesin sheet tends to be lowered.

  In the method (I), it is preferable that the method further includes a step of rolling the rolled sheet prepared by the rolling step, that is, the rolling step is repeated a plurality of times (for example, 3 to 50 times). By repeating rolling, the inside of the fluororesin sheet can be further densified. In addition, when repeating a rolling process, a roll space | interval is narrowed every time rolling is repeated.

  When forming the sheet by rolling the preform with a biaxial roll, for example, the distance between the rolls is set to 0.5 to 20 mm, and the roll surface moving speed (sheet extrusion speed) is set to 5 to 50 mm / second. Can be rolled.

<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, considering that the entire sheet needs to be uniformly fired and that a fluorine-based harmful gas is generated at an excessively high temperature. ° C is suitable.

[Filled fluororesin sheet]
Although it will not restrict | limit especially if the fluororesin sheet | seat with a filler is manufactured from the said composition for sheet formation, The sheet manufactured by the said method (I) is preferable. This filled fluororesin sheet is excellent in stress relaxation properties, particularly stress relaxation properties at high temperatures, and airtightness. Specifically, the stress relaxation rate at 200 ° C. (according to JIS R3453, heating temperature only) (Changed from 100 ° C. to 200 ° C.) is preferably 63% or less, more preferably 60% or less. The lower limit may be 45%, and the leakage amount (airtightness, φ48 × φ67 × thickness 1 The surface pressure is 19.6 MPa and the nitrogen gas internal pressure is 0.98 MPa with respect to a test piece of 0.5 mm), preferably 1.0 × 10 ⁻⁴ Pa · m ³ / s or less, more preferably 9.0 × 10 ^−5. Pa · m ³ / s or less, and the lower limit thereof may be 1.0 × 10 ⁻⁵ Pa · m ³ / s.

Such a filled fluororesin sheet of the present invention can be used for a gasket, and a gasket made of the filled fluororesin sheet of the present invention can be used for a long time at a high temperature (for example, 200 ° C. or more). .
The gasket can be easily manufactured by cutting out the filled fluororesin sheet of the present invention into a desired shape.

[Example]
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>
A test piece was prepared from a sheet having a thickness of 1.5 mm, and the stress relaxation rate and hermeticity were measured as follows.

Leakage (airtightness);
A gasket test piece punched to a size of φ48 mm × φ67 mm is mounted between steel flanges of φ100 mm × height 50 mm and surface roughness Rmax = 12 μm, and a surface pressure of 19.6 MPa (200 kgf / cm ² G) is obtained by a compression tester. The load was applied so that 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 introducing through hole provided in the flange, the pressure introducing 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 rate;
A test piece was prepared from a sheet having a thickness of 1.5 mm, and the stress relaxation rate was measured according to JIS R3453 except that the heating temperature was changed from 100 ° C. to 200 ° C. for this test piece.

[Example 1]
PTFE fine powder (CD-1, manufactured by Asahi Glass Co., Ltd.) 600 g,
NK-300 (fine powder clay, manufactured by Showa KDE Co., Ltd.) 400 g,
Isopar M (hydrocarbon organic solvent, fractional distillation temperature: 218 to 253 ° C., Exxon Mobil (existing)) 300 g, and tetraethoxysilane (TEOS) 40 g
After mixing with a kneader for 5 minutes, the mixture was aged by standing at room temperature (25 ° C.) for 16 hours to prepare a sheet-forming composition.

This composition was extruded at room temperature (25 ° C.) with a 300 mm × 20 mm die extruder to prepare a preform.
This preform was rolled by a biaxial roll under the conditions of a roll diameter of 700 mm, a roll interval of 20 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 with a roll interval of 10 mm. Furthermore, immediately after this rolling, the obtained sheet was rolled again with a roll interval of 5 mm. Finally, immediately after this rolling, the obtained sheet was rolled again with a roll interval of 1.5 mm to obtain a sheet having a thickness of 1.5 mm.

This sheet was allowed to stand at room temperature (25 ° C.) for 24 hours to remove the solvent, and then baked in an electric furnace at 350 ° C. for 3 hours to obtain a filled fluororesin sheet.
The leakage amount (airtightness) of this filled fluororesin sheet was 4.8 × 10 ⁻⁵ Pa · m ³ / s, and the stress relaxation rate was 52%.

[Example 2]
A filled fluororesin sheet was produced in the same manner as in Example 1 except that the amount of TEOS used was changed to 8 g.
The leakage amount (airtightness) of this filled fluororesin sheet was 4.2 × 10 ⁻⁵ Pa · m ³ / s, and the stress relaxation rate was 55%.

[Example 3]
A filled fluororesin sheet was produced in the same manner as in Example 1 except that the amount of TEOS used was changed to 80 g.
The leakage amount (airtightness) of this filled fluororesin sheet was 8.4 × 10 ⁻⁵ Pa · m ³ / s, and the stress relaxation rate was 53%.

[Example 4]
A filled fluororesin sheet was produced in the same manner as in Example 1 except that TEOS was changed to TMOS.
The leakage amount (airtightness) of this filled fluororesin sheet was 6.3 × 10 ⁻⁵ Pa · m ³ / s, and the stress relaxation rate was 51%.

[Example 5]
Instead of using 400 g of NK-300, a filled fluororesin sheet was produced in the same manner as in Example 1 except that 400 g of silica (Crystallite AA, manufactured by Tatsumori) was used.
The leakage amount (airtightness) of this filled fluororesin sheet was 6.7 × 10 ⁻⁵ Pa · m ³ / s, and the stress relaxation rate was 54%.

[Example 6]
Instead of using 400 g of NK-300, a filled fluororesin sheet was produced in the same manner as in Example 1 except that 400 g of alumina (A-42, Showa Denko) was used.
The leakage amount (airtightness) of this filled fluororesin sheet was 1.7 × 10 ⁻⁵ Pa · m ³ / s, and the stress relaxation rate was 57%.

[Comparative Example 1]
A filled fluororesin sheet was produced in the same manner as in Example 1 except that TEOS was not used.
The leakage amount (airtightness) of this filled fluororesin sheet was 3.4 × 10 ⁻⁵ Pa · m ³ / s, and the stress relaxation rate was 75%.

[Comparative Example 2]
A filled fluororesin sheet was produced in the same manner as in Example 1 except that the amount of TEOS used was changed to 120 g.
The leakage amount (air tightness) of this filled fluororesin sheet was 2.0 × 10 ⁻³ Pa · m ³ / s, and the stress relaxation rate was 66%.

Claims (7)

Fluororesin (A), filler (B), 1 to 20 parts by weight of alkoxysilane (C) represented by the following formula (1) with respect to 100 parts by weight of filler (B), and processing aid (D A composition for forming a sheet.
(R ¹ ) _4-n Si (OR ² ) _n (1)
[In Formula (1),
Each R ¹ is independently a hydrogen atom, a hydroxyl group or a monovalent hydrocarbon group having 1 to 5 carbon atoms;
Each R ² is independently a monovalent hydrocarbon group having 1 to 5 carbon atoms;
n is 2, 3 or 4. ]   The composition for forming a sheet according to claim 1, wherein the filler (B) is at least one filler selected from silicon dioxide and silicate.   The composition for forming a sheet according to claim 1 or 2, wherein the alkoxysilane (C) is tetraethoxysilane and / or tetramethoxysilane.   The weight ratio between the fluororesin (A) and the filler (B) is fluororesin: filler = 1: 0.1-4, according to any one of claims 1 to 3. Sheet forming composition.   The amount of the processing aid (D) is 5 to 50 parts by weight with respect to a total of 100 parts by weight of the fluororesin (A) and the filler (B). A composition for forming a sheet according to claim 1.   A filled fluororesin sheet produced from the sheet-forming composition according to claim 1.   A method for producing a filled fluororesin sheet, wherein the sheet-forming composition according to any one of claims 1 to 5 is preformed, the resulting preform is rolled, and then fired.