JPH06107826A - Production of fluororubber for use in vacuum - Google Patents

Abstract

PURPOSE:To obtain a fluororubber which releases little gas in a vacuum by treating a crosslinked fluororubber under a specified reduced pressure. CONSTITUTION:A crosslinked fluororubber is kept standing under a pressure of 100Torr or lower, pref. at 25-400 deg.C for 0.1hr or longer. Volatile components are thus removed from the rubber, and thus treated crosslinked fluororubber releases little gas even in a high vacuum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fluororubber, and more particularly to a method for producing fluororubber in which the amount of released gas (outgas) in vacuum is small.

[0002]

BACKGROUND OF THE INVENTION Conventionally, fluororubber (FPM) has been used as a sealing material for a vacuum device. This fluororubber sealing material is usually produced by heating a fluororubber compound by a direct pressure press or the like. It is manufactured by pressurizing, molding and then secondary vulcanization.

However, when this fluororubber sealing material is used under a vacuum condition, a large amount of released gas (outgas) is generated from the fluororubber, which causes the following problems. (A) The chamber is contaminated by the released gas from the fluororubber. (B) When a large amount of gas is released from the fluororubber, it takes a long time to reach a high vacuum, and the operating rate of the vacuum device is reduced. (C) An object to be processed such as a semiconductor is contaminated by the gas released from the fluororubber. (D) In a vacuum device such as a CVD device, the processing gas used may react with the gas released from the fluororubber to generate particles.

The inventors of the present invention have made extensive studies to solve the above problems, and have found that the above problems can be solved all at once by applying a specific treatment to fluororubber. Has been completed.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to solve the problems associated with the prior art as described above, and to provide a fluororubber capable of producing a fluororubber having a small amount of released gas in a vacuum. It is intended to provide a manufacturing method.

[0006]

SUMMARY OF THE INVENTION The method for producing a vacuum fluororubber according to the present invention is characterized in that a crosslinked fluororubber is subjected to a pressure reduction treatment at a pressure of 100 Torr or less, preferably 1 Torr or less. Such depressurization is performed at 25 to 400 ° C.
At the temperature of 0.1 hour or more.

In the present invention, the above-mentioned fluororubber is
It is preferably vinylidene fluoride rubber or tetrafluoroethylene-perfluorovinyl ether rubber.

According to the present invention, the volatile component in the crosslinked fluororubber is previously released by subjecting the fluororubber crosslinked as described above to a pressure reduction treatment under the above pressure.
Since it has been removed, it is possible to obtain a fluororubber having a small amount of released gas even when placed in a high vacuum.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The method for producing a vacuum fluororubber according to the present invention will be specifically described below.

In the present invention, the crosslinked fluororubber is subjected to a reduced pressure treatment under the conditions described below. To produce the crosslinked fluororubber, the following fluororubber compound (A
1), a fluororubber thermoplastic elastomer (A2) and the like are used.

Examples of the fluororubber compound (A1) include the following fluororubber compounds, which may optionally contain a vulcanizing agent, a vulcanization aid, an acid scavenger and a filler.

As the fluororubber, conventionally known ones are widely used, but vinylidene fluoride rubber, tetrafluoroethylene-propylene rubber, tetrafluoroethylene-perfluorovinyl ether rubber, fluorosilicone rubber, fluorophosphazene rubber. Examples include rubber.

Specific examples of the vinylidene fluoride-based rubber include, for example, a copolymerized rubber of vinylidene fluoride (VdF) and hexafluoropropylene (HFP) (eg, Daiel G 801 manufactured by Daikin Industries), vinylidene fluoride and penta. Copolymer rubber with fluoropropylene, Vinyl rubber with vinylidene fluoride and chlorotrifluoroethylene, Terpolymer rubber with vinylidene fluoride (VdF), hexafluoropropylene (HFP) and tetrafluoroethylene (TFE) (Example : Daikin Industries DAIEL G-901H, G901, G1001)
Examples of the tetrafluoroethylene-propylene rubber include tetrafluoroethylene (T
As a copolymer rubber of FE) and propylene (Pr) (eg, Aflas manufactured by Asahi Glass) and a tetrafluoroethylene-perfluorovinyl ether rubber, a copolymer of tetrafluoroethylene and perfluorovinyl ether and a small amount of a crosslinking monomer. Examples of fluorophosphazene rubbers include long-chain rubbers (PNCl) obtained by thermally decomposing a trimer of dichlorophosphonitrile.
₂ ) Examples of the rubber obtained by reacting _n with a fluorine-containing alcoholate include fluorosilicone rubbers.
A copolymer rubber of methyltrifluoropropylsiloxane and vinylmethylsiloxane may be mentioned. Among such fluororubbers, vinylidene fluoride-based rubber and tetrafluoroethylene-perfluorovinyl ether-based rubber are preferable.

As the vulcanizing agent, an amine-based vulcanizing agent (a),
Examples thereof include a polyol vulcanizing agent (b), a peroxide vulcanizing agent (c), and a triazine vulcanizing agent (d). Specific examples of the amine vulcanizing agent (a) include hexamethylenediamine carbamate. , N, N'-dicinnamylidene
-1,6-hexanediamine, hexamethylenediamine
Carbamate and the like, polyol-based vulcanizing agent (b) includes bisphenol AF, 4,4′-dihydroxyldiphenyl, and the like, and peroxide-based vulcanizing agent (c) includes α, α′- Bis (t-butylperoxy-m-isopropyl) benzene (Perbutyl P made by NOF Corporation), 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (Perhexa 25B made by NOF Corporation), dicumyl peroxide (made by NOF Corporation) Park mill D), 2,
5-Dimethyl-2,5- (t-butylperoxy) hexyne-3 (NOF Corporation Perhexin 25B), benzoyl peroxide (NOF Corporation Niper B), etc. may be mentioned, and triazine-based vulcanizing agent (d) may be triazine. Can be mentioned.

Specific examples of the vulcanization aid include, for example, triallyl isocyanurate (Taika made by Nippon Kasei), ethylene glycol dimethacrylate (Sanshin Chemical Sunester EG), trimethylolpropane trimethacrylate (Sanshin Chemical). Sunester TMP), polyfunctional methacrylate monomer (manufactured by Seiko Chemical Co., Ltd., High Cloth M), polyhydric alcohol methacrylate and acrylate, and metal salt of methacrylic acid.

Examples of the acid scavenger (acid acceptor) include divalent metal oxides, hydroxides, and mixtures of these divalent metal compounds and weak acid metal salts. Specific examples of the divalent metal include magnesium, calcium, lead and zinc. These metals are used as oxides or hydroxides, or as a mixture of these metal compounds with metal salts of weak acids such as stearic acid, benzoic acid, carbonic acid, oxalic acid and phosphorous acid.

Specific examples of such an acid scavenger include Ca (OH) ₂ and MgO. Examples of the vulcanization accelerator include quaternary phosphonium salt, quaternary ammonium salt, 8-alkyl (or aralkyl) -1,8-diaza-bicyclo [5.4.0] -7-undecene quaternary ammonium salt. Examples thereof include salts and aminophosphinic acid derivatives.

Specific examples of the filler include carbon black, barium sulfate, titanium oxide, calcium carbonate, magnesium silicate (talc) and aluminum silicate (clay).

In such a fluororubber compound, the vulcanizing agent is added in an amount of 0.5 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the fluororubber. Is
1 to 20 parts by weight, preferably 3 to 10 parts by weight, the acid scavenger in an amount of 1 to 40 parts by weight, preferably 2 to 20 parts by weight, and the vulcanization accelerator in an amount of 0.1 to 10 parts by weight. Preferably in an amount of 0.3 to 2 parts by weight, the filler being 1 to 100 parts by weight,
It is preferably used in an amount of 5 to 40 parts by weight.

In order to prepare the above-mentioned fluororubber compound, various components such as a vulcanizing agent may be compounded in the above-mentioned fluororubber and kneaded by, for example, a roll. As such a fluororubber compound, specifically, for example, (a) a fluororubber compound comprising a vinylidene fluoride-based rubber, an amine-based vulcanizing agent, an acid scavenger, a vulcanization accelerator and a filler, (B) Fluorine rubber compound consisting of vinylidene fluoride rubber, polyol vulcanizing agent, acid scavenger, vulcanization accelerator and filler, (c) vinylidene fluoride rubber, peroxide vulcanizing agent, vulcanizing agent A fluororubber compound consisting of a vulcanization aid and a filler, (D) a tetrafluoroethylene-perfluorovinylether rubber, a polyol vulcanizing agent, an acid scavenger, a fluorinated rubber compound consisting of a vulcanization accelerator and a filler, (E) Fluororubber compound comprising tetrafluoroethylene-perfluorovinyl ether rubber, triazine vulcanizing agent, acid scavenger, vulcanization accelerator and filler Etc., and the like.

Fluorine rubber type thermoplastic elastomer (A
2) exhibits rubber elasticity at room temperature and plastic flowability when heated and contains an elastomeric polymer chain segment and a non-elastomeric segment, at least one of which is a fluoropolymer. It is a chain segment.

As such a fluororubber thermoplastic elastomer, conventionally known ones are widely used. For example, the following fluororubber component (elastomer polymer chain segment) and fluororesin component (non-elastomeric polymer chain) are used. And an elastomer composed of (segment).

The elastomeric polymer chain segment is (i) vinylidene fluoride-hexafluoropropylene or pentafluoropropylene-tetrafluoroethylene terpolymer, wherein 100 mol% of the copolymer is used.
40 to 90 mol% of vinylidene fluoride units, 5 to 50 mol% of hexafluoropropylene or pentafluoropropylene units, and 0 of tetrafluoroethylene units
Contained in an amount of up to 35 mol%, or (i
i) A perfluoroalkyl vinyl ether-tetrafluoroethylene-vinylidene fluoride terpolymer, wherein the perfluoroalkyl vinyl ether unit is 15 to 75 mol% and the tetrafluoroethylene unit is 0 to 100 mol% of the copolymer. Examples thereof include those containing 85 mol% and vinylidene fluoride units in an amount of 0 to 85 mol%. These (i) and (ii) usually have a molecular weight of about 30,000 to 1,200,000.

The non-elastomeric polymer chain segment is (iii) vinylidene fluoride-tetrafluoroethylene copolymer, which is used in 100 mol% of the copolymer.
Vinylidene fluoride unit of 0 to 100 mol% and tetrafluoroethylene unit of 0 to 100 mol%, or (iv) ethylene, tetrafluoroethylene and hexafluoropropylene, 3,3,3-trifluoropropylene-
A multi-component copolymer with 1,2-trifluoromethyl-3,3,3-trifluoropropylene-1 or perfluoroalkyl vinyl ether, wherein 40 to 60 mol of ethylene units are contained in 100 mol% of the copolymer. %, Tetrafluoroethylene units are 60 to 40 mol%, and units such as hexafluoropropylene are 0 to 30 mol%.
These (iii) and (iv) usually have a molecular weight of 30.
It is about 00 to 400,000. The fluororubber thermoplastic elastomer is described in detail in JP-A-53-3,495, Japanese Patent Application No. 60-109,141 and the like.

In such a fluororubber thermoplastic elastomer, the weight ratio of the elastomeric polymer chain segment to the non-elastomeric polymer chain segment is usually about 40 to 95:60 to 5.

Further, such a copolymer of fluororubber and fluororesin, that is, a fluororubber thermoplastic elastomer is commercially available under the trade name of, for example, Daier Thermo (manufactured by Daikin Industries).

A conventional method may be used to obtain a preform from the fluororubber thermoplastic elastomer. For example, this elastomer may be filled in a mold having a desired shape, heated and cooled. At this time, it is not usually necessary to add the above-mentioned vulcanizing agent, filler, etc. to the elastomer, but a vulcanizing agent such as polyol or peroxide may be used depending on the case.

A desired crosslinked fluororubber thermoplastic elastomer is obtained by three-dimensionally crosslinking the preform obtained from such a fluororubber thermoplastic elastomer with radiation.

When the preform is cross-linked by radiation as described above, it is usually 3 to 300 KGray, preferably 7
Radiation of 0-200 KGray is irradiated. Radiation includes X-rays, gamma rays, electron rays, proton rays, deuteron rays,
Alpha rays, beta rays, etc. are used.

Release of Outgas by Reduced Pressure Treatment In the present invention, the fluororubber compound (A
The crosslinked product of 1) or the crosslinked product of the fluororubber thermoplastic elastomer (A2) is subjected to a reduced pressure treatment at a pressure of 100 Torr or less, preferably 1 Torr or less. Such depressurization treatment is usually 25 to 400 ° C., preferably 100 to 20.
It is carried out at a temperature of 0 ° C. for 0.1 hour or longer, preferably 10 hours or longer. At 100 Torr or more, the volatile components in the crosslinked fluororubber are not sufficiently released / removed, and a fluororubber with a large amount of released gas is obtained when placed in a high vacuum. The lower the pressure during the treatment, the shorter the treatment time may be and the lower the treatment temperature may be. In such a depressurized fluororubber, the amount of outgas released per unit surface area after holding for 12 hours in an atmosphere of 1 × 10 ⁻⁵ to 1 × 10 ⁻⁸ Torr at room temperature (25 ° C.) is 1 × 10 ^{5. -7} Torr · l / sec · cm ² or less, preferably 5 × 10 ⁻⁸ Torr · l / sec · cm
² or less. The outgas varies depending on the type of fluororubber used, the vulcanization method and the like and is not generally determined, but examples thereof include hydrocarbon, water, a low molecular weight component of the base polymer, and hydrogen fluoride.

Further, the pattern of the mass spectrum of the depressurized product is simplified to a hydrocarbon (H
C), hydrogen fluoride (HF), etc. are eliminated, and H ₂
Mainly H ₂ O and CO ₂ .

In the present invention, the crosslinked fluororubber may be subjected to a high temperature heat treatment for 1 hour or more at a temperature of 250 ° C. to 400 ° C. prior to or after the depressurization treatment of the fluororubber as described above. .

In the case of the fluororubber compound, the secondary vulcanization may be carried out before the high temperature heat treatment at such temperature for the above-mentioned time, or the secondary vulcanization may not be carried out. Further, in the present invention, a crosslinked fluororubber, that is, a crosslinked product of the above-mentioned fluororubber compound (A1) or a fluororubber thermoplastic elastomer (A2) is crosslinked prior to or after the above depressurization treatment. The cross-linked product may be contacted with a solvent.

To bring the crosslinked fluororubber into contact with the solvent, the crosslinked fluororubber may be dipped in the solvent. By doing this, it is possible to previously extract and remove components that would volatilize during use in a vacuum atmosphere, and to further reduce the amount of released gas (outgas) that volatilizes during use under vacuum conditions. be able to.

Examples of the solvent include organic solvents, inorganic solvents, mixed solvents and the like. As the organic solvent, acetone,
Examples thereof include polar solvents such as methyl ethyl ketone (MEK) and alcohol, and nonpolar solvents such as benzene and toluene. Of these organic solvents, polar solvents are preferably used. When such a polar solvent is used, it easily penetrates into the cross-linked fluororubber and is easily extracted.

Examples of the inorganic solvent include water.
Examples of the mixed solvent include a water-acetone mixed solvent and a water-alcohol mixed solvent. Of these solvents, water that does not pose a problem of environmental pollution is preferably used.

Of the water, pure water is preferred, especially 25 ° C.
Pure water having a specific resistance value of 10 × 10 ⁴ Ω · cm or more is preferable. The contact time between the solvent and the crosslinked fluororubber varies depending on the composition of the crosslinked fluororubber, the type of solvent used, the concentration, etc. If used, 2
Pure water heated to a temperature of 5 ° C or higher, preferably 95 to 100 ° C, and 0.1 hour or longer, preferably 0.3 to 5
The crosslinked fluororubber may be contacted for about a time.

In the present invention, it is preferable to perform the high temperature heat treatment as described above prior to the pressure reduction treatment of the crosslinked fluororubber as described above. When such a high temperature heat treatment is performed prior to depressurization of fluororubber, especially when used in a vacuum atmosphere, the release gas (eg, water, hydrogen fluoride, hydrocarbon, cross-linking such that the low molecular weight component of the base polymer is small) The obtained fluororubber is obtained.

[0039]

EFFECTS OF THE INVENTION According to the present invention, a crosslinked fluororubber that emits less gas when used in a vacuum atmosphere can be obtained.

[0040]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[0041]

Example 1 A fluororubber compound having the following component composition was prepared. Binary fluororubber consisting of vinylidene fluoride and hexafluoropropylene (in 100 mol% of fluororubber, vinylidene fluoride unit is contained in an amount of 77 mol% and hexafluoropropylene unit is contained in an amount of 23 mol%. Has an average molecular weight of 100,000.) Fluorine rubber: 100 parts by weight Magnesium oxide: 3 parts by weight Carbon black: 30 parts by weight Calcium hydroxide: 6 parts by weight Vulcanization accelerator (quaternary ammonium salt) ) 1 part by weight Vulcanizing agent (bisphenol AF): Compounded in fluororubber in an amount of 1% by weight.

The above fluororubber compound is molded in a mold.
Primary vulcanization was performed at a temperature of 170 ° C. for 10 minutes under a pressure of 30 Kgf / cm ² . Next, this primary vulcanizate was heat-treated at a temperature of 230 ° C. for 24 hours under atmospheric pressure.

The heat-treated product obtained was kept at a temperature of 150 ° C. for 16 hours under a reduced pressure of 10 ⁻² Torr. The resulting vacuum treated product, as a sample of the rubber O (O) present ring 3 of V55, at φ100 × l (el) 150 of the measuring chamber, room temperature of 1 × 10 ^over 7 to 1 × ^10-2 8 Torr 12 in the atmosphere
The amount of outgas released per O-ring surface area after 1 hour is 1.
It was 6 × 10 ⁻⁸ Torr · l / sec · cm ² .

[0044]

[Example 2] The heat-treated product obtained in Example 1 was
A reduced pressure treated product was obtained in the same manner as in Example 1 except that the temperature was kept at 200 ° C. for 16 hours under a reduced pressure of 10 ⁻² Torr.

The obtained decompressed product was V55 rubber O.
Using three (O) rings as samples, in a measuring chamber of φ100 × l (L) 150, 1 × 10 ⁻⁷ to 1 × 10 at room temperature.
^The amount of outgassing per surface area of the O-ring after 12 hours in an atmosphere of −8 Torr is 1.2 × 10 ⁻⁸ Torr · l /
It was sec · cm ² .

The mass spectrum of the released gas after 50 hours is shown in FIG.

[0047]

Comparative Example 1 A molded article of the primary vulcanizate was prepared in the same manner as in Example 1.
Obtained. The obtained molded product is a rubber of V55 O (phosphorus) phosphorus.
Measurement of φ100 × l (L) 150 using 3 samples
1x10 at room temperature in a fixed room^{ー 5}~ 1 x 10^-6The atmosphere of Torr
Outgas per O-ring surface area after 12 hours under ambient atmosphere
Release amount is 4.1 × 10 ^-6Torr · l / sec · cm²
Met.

[0048]

Comparative Example 2 In Example 1, the obtained primary vulcanizate was heat-treated at a temperature of 230 ° C. under atmospheric pressure for 24 hours to obtain a heat-treated product.

The heat-treated product obtained was tested with three rubber O (O) rings of V55 as samples, and φ100 × l (L) 1
At 50 of the measuring chamber, 1 × 10 ^over 6 to 1 × 10 ^over 7 the To at room temperature
rr outgassing amount per O-ring surface area after 12 hours in an atmosphere is 2.2 × 10 ^over 7 Torr · l / sec
・ It was cm ² . The mass spectrum of the released gas after 50 hours is shown in FIG.

The results are also shown in Table 1.

[0051]

[Table 1]

[Brief description of drawings]

FIG. 1 is a mass spectrum of released gas after 50 hours in Example 2.

FIG. 2 is a mass spectrum of released gas after 50 hours in Comparative Example 2.

Claims (2)

[Claims] 1. A cross-linked fluororubber of 100 Torr
A method for producing a fluororubber for vacuum, which comprises decompressing at the following pressure. 2. A crosslinked fluororubber is added to 100 Tor.
A method for producing a fluororubber for vacuum, which comprises decompressing under a pressure of r or less at a temperature of 25 to 400 ° C. for 0.1 hour or more.