JPH11293075A - Fluororubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition with excellent resistance to carbon dioxide by adding graphite or mica to an organic hydroperoxide-curable fluororubber. SOLUTION: There is provided a composition comprising 100 pts.wt. of an organic hydroperoxide-curable fluororubber, 1-10 pts.wt. of an organic peroxide such as benzoyl peroxide or the like, 0.1-20 pts.wt. of a polyfunctional compound such as tri(meth)allyl cyanurate or the like, 5-40 pts.wt. of graphite or mica having an average particle size of 100 μm or less, not more than 50 pts.wt. of a reinforcing agent such as carbon black or the like, not more than 30 pts.wt. of an acid acceptor such as zinc oxide or the like, and further a filler, a plasticizer, a processing aid, a pigment or the like. The peroxide-curable fluororubber is obtained by polymerizing a fluorine-containing olefin such as tetrafluoroethylene or the like in the presence of a compound containing iodine and bromine such as 1-bromo-2-iodoperfluoroethane or the like thereby incorporating 0.01-5 wt.% of iodine and/or bromine into the fluoroolefin copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fluororubber composition. More specifically, the present invention relates to a fluororubber composition suitably used as a molding material for a carbon dioxide gas sealing material.

[0002]

2. Description of the Related Art Refrigerants currently used in air conditioners and the like include:
Most of them are CFC-based gases, but it goes without saying that CFC-based gases have a large effect on the global environment. Although several types of substances are currently considered as alternatives to CFC-based gas, carbon dioxide is one of the promising candidates in terms of performance and safety.

However, since carbon dioxide gas has high compatibility with almost all rubber materials, and has high swelling property and gas permeability, almost no rubber material is used as a sealing material. .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition having excellent resistance to carbon dioxide used as a refrigerant or the like.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
This is achieved by a fluororubber composition obtained by adding graphite or mica to an organic peroxide crosslinkable fluororubber.

[0006]

DETAILED DESCRIPTION OF THE INVENTION As an organic peroxide crosslinkable fluororubber, for example, a fluororubber containing iodine and / or bromine in the molecule is used. The fluorine-containing olefin constituting the main part of the fluororubber has a carbon number of
2 to 8 are preferably used, for example, vinylidene fluoride, tetrafluoroethylene, hexafluoropropene, pentafluoropropene, chlorotrifluoroethylene, methyl perfluorovinyl ether, ethyl perfluorovinyl ether, n- or iso-propyl Fluorovinyl ether, n-, iso- or tert-butyl perfluorovinyl ether, n- or iso-amyl perfluorovinyl ether, perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether),
Perfluoro (n- or iso-propyl vinyl ether), perfluoro (n-, iso- or tert-butyl vinyl ether), perfluoro (n- or iso-amyl vinyl ether), perfluoro (propoxypropyl vinyl ether) Both are mainly used, and in addition, vinyl fluoride, trifluoroethylene, perfluorocyclobutene, perfluoro (methylcyclopropene), hexafluoroisobutene, 1,2,2-trifluorostyrene, perfluorostyrene, etc. Is also used.

[0007] These fluorine-containing olefins have 2 carbon atoms.
It can also be used in the form of being copolymerized with an olefinic compound having up to 6 and / or a fluorine-containing diene having 4 to 8 carbon atoms.

Examples of the olefinic compound include those having 2 to 6 carbon atoms such as unsaturated vinyl esters such as ethylene, propylene, butene and vinyl acetate, and alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether.
Which are generally copolymerized in a proportion of about 0.1 to 50 mol%.

The fluorinated diene includes, for example, perfluoro-1,3-butadiene, perfluoro-1,4-pentadiene, 1,1,2-trifluoro-1,3-butadiene, 1,1,1 2-
Trifluoro-1,4-pentadiene, 1,1,2,3,3-pentafluoro-1,4-pentadiene, perfluoro-1,7-octadiene, perfluorodivinyl ether, perfluorovinyl perfluoroallyl ether, Examples thereof include those having 4 to 8 carbon atoms, such as vinyl perfluoroallyl ether and perfluorovinyl vinyl ether. These fluorinated dienes are preferably copolymerized so as to be present in the fluororubber at a ratio of about 1 mol% or less. If the copolymerization is carried out at a higher ratio, the gelation of the copolymer rubber becomes remarkable, and the processability (flow characteristics) and the elongation of the vulcanizate deteriorate.

Specific fluorinated olefin copolymers include hexafluoropropene-vinylidene fluoride copolymer, hexafluoropropene-vinylidene fluoride-tetrafluoroethylene terpolymer, and tetrafluoroethylene-vinylidene fluoride. -Perfluoro (methyl vinyl ether) terpolymer, tetrafluoroethylene-vinylidene fluoride-perfluoro (propyl vinyl ether) terpolymer, tetrafluoroethylene-perfluoro (propoxypropyl vinyl ether) copolymer, tetrafluoro Ethylene-perfluoro (methyl vinyl ether) copolymer, tetrafluoroethylene-propylene copolymer, tetrafluoroethylene-propylene-vinylidene fluoride terpolymer, tetrafluoroethylene-vinylidene fluoride-hexafluoropropene-pe Motor tetrafluoropropene 4 terpolymer, tetrafluoroethylene - hexafluoropropene - vinylidene fluoride - perfluoro (methyl vinyl ether) quaternary copolymer, tetrafluoroethylene -
Hexafluoropropene-hexafluoroisobutene terpolymer, tetrafluoroethylene-cyclohexylvinyl ether copolymer, hexafluoropropene-vinylidene fluoride-chlorotrifluoroethylene terpolymer, vinylidene fluoride-tetrafluoroethylene-methyl Perfluorovinyl ether terpolymer, vinylidene fluoride-tetrafluoroethyl-n-butyl perfluorovinyl ether terpolymer, vinylidene fluoride-methyl perfluorovinyl ether-perfluoro (methyl vinyl ether) terpolymer, Tetrafluoroethylene-methyl perfluorovinyl ether-perfluoro (methyl vinyl ether) terpolymer, vinylidene fluoride-hexafluoropropene-tetrafluoroethylene-methyl perfluorovinyl ether terpolymer , Tetrafluoroethylene-n-butyl perfluorovinyl ether-perfluoro (methyl vinyl ether) terpolymer, vinylidene fluoride-n-butyl perfluorovinyl ether copolymer, tetrafluoroethylene-propylene-n-butyl perfluorovinyl ether Ternary copolymers, tetrafluoroethylene-vinylidene fluoride-propylene-n-butyl perfluorovinyl ether quaternary copolymers and the like can be mentioned.

The polymerization reaction is carried out by a solution polymerization of a fluorine-containing olefin or the above-mentioned comonomer with a known method,
It is performed by suspension polymerization or emulsion polymerization.

At the time of this polymerization reaction, an iodine-containing bromine compound,
When an iodine-containing compound or a bromine-containing compound is allowed to coexist, iodine and / or bromine are introduced into the fluorinated olefin copolymer to form a crosslinking point at the time of organic peroxide crosslinking.

As the iodine-containing bromine compound, a compound represented by the general formula RBr
a saturated or unsaturated, chain or aromatic compound represented by nIm (R: fluorohydrocarbon group, chlorofluorohydrocarbon group, chlorohydrocarbon group or hydrocarbon group, n, m: 1 or 2) Preferably, n and m are each 1
Is used. Examples of the chain-containing iodine bromine compound include 1-bromo-2-iodoperfluoroethane and 1-bromo-2-iodoperfluoroethane.
Bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, 3,4-dibromo-1-iodo-1,1,2,2,4 , 4-hexafluorobutane, 3-bromo-4-iodoperfluorobutene-1, 2-bromo-4-iodoperfluorobutene-1 and the like are used, and as an aromatic iodine-containing bromine compound, for example, benzene And monoiodomonobromo-substituted, diiodomonobromo-substituted, monoiododibromo-substituted, (2-iodoethyl)-and (2-bromoethyl) -substituted compounds having various substitution positions. These iodine-containing bromine compounds generally provide a fluororubber that is bonded to molecular terminals to achieve efficient crosslinking, and for that purpose, iodine and bromine are each contained in an amount of about 0.01 to 5% by weight, preferably about 0.05 to 5% by weight.
33% by weight.

As the iodine-containing compound, an aromatic compound or a perfluoroaromatic compound poly-substituted by an iodine atom or an alkyl iodide group represented by an ethyl iodide group can be used as an iodine compound in a fluoroelastomer.
5% by weight, preferably about 0.05 to 3% by weight of the binding amount, or saturated or unsaturated aliphatic hydrocarbon, iodo-substituted fluoroaliphatic hydrocarbon or chlorofluoroaliphatic hydrocarbon And iodine in the fluororubber at a ratio of about 0.01 to 10% by weight.

As the bromine-containing compound, an aromatic compound or a perfluoroaromatic compound poly-substituted by an alkyl bromide group represented by a bromine atom or an ethyl bromide group is used in an amount of about 0.01 to 5 wt. %, Preferably in a proportion such that the binding amount is about 0.05-3% by weight,
Alternatively, the bromine-substituted saturated aliphatic hydrocarbon is in a proportion such that the amount of bromine in the fluororubber is about 0.01 to 10% by weight, and further, the bromine-containing olefin is about 0.05% by weight or more as bromine in the fluororubber, In general, they are used in such a ratio as to give a binding amount of about 0.3 to 1.5% by weight. In addition, 3- or 2-bromoperfluoropropyl perfluorovinyl ether may be used.

Fluororubber in which these iodine-containing and / or bromine compounds are bonded to the molecule (a commercially available product such as Viton manufactured by DuPont, Daikin manufactured by Daikin, and Knoxtite manufactured by Nippon Mektron can also be used)
Crosslinked by organic peroxides. Organic peroxides include benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, di-tert-butyl cumyl peroxide, 1,1-di (
(3-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (α, α-dimethylbutylperoxy) cyclohexane, 1,1-bis (α, α-dimethylbutylperoxy)
-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-
Bis (tert-butylperoxy) hexane, 2,5-dimethyl-2,
5-di (tert-butylperoxy) hexyne-3,1,3-bis (tertiary
Butylperoxydiisopropyl) benzene, α, α-bis (tert-butylperoxy-m-isopropyl) benzene, 2,
5-dimethyl-2,5-di (benzoylperoxy) hexane,
Tertiary butyl peroxybenzoate, tertiary butyl peroxyisopropyl carbonate, n-butyl-4,4-bis (tertiary
(Butyl peroxy) valerate, tertiary butyl peroxy-
3,3,5-Trimethylhexanoate or the like is generally used in a proportion of about 1 to 10 parts by weight, preferably about 2 to 8 parts by weight, per 100 parts by weight of the fluororubber. If the organic peroxide is used at a higher ratio, molding defects such as reversion and foaming will be observed.

In crosslinking the organic peroxide, it is preferable to use a polyfunctional unsaturated compound in combination. As the polyfunctional unsaturated compound, tri (meth) allyl isocyanurate,
Tri (meth) allyl cyanurate, triallyl trimellitate, N, N′-m-phenylenebismaleimide, diallyl phthalate, tris (diallylamine) -s-triazine, triallyl phosphite, (di) ethylene glycol diacrylate, A polyfunctional compound such as neopentyl glycol diacrylate that improves mechanical strength, compression set, etc. is used in an amount of about 0.1 to 20 parts by weight, preferably about 0.5 to 10 parts by weight, per 100 parts by weight of fluororubber. .

As the graphite to be added to the organic peroxide crosslinkable fluororubber, any of natural graphite and synthetic graphite can be used, and those having an average particle size of 100 μm or less, preferably 50 μm or less, About 5 to 40 parts by weight, preferably about 10 parts by weight per 100 parts by weight of fluororubber
Used in a proportion of up to 30 parts by weight. Use of graphite having an average particle size larger than this causes a problem in dispersibility. On the other hand, if the addition ratio is lower than this, the permeability of carbon dioxide gas increases, while if it is used at a higher ratio, the processability deteriorates and the kneading is hindered. The same applies to mica.

The composition is prepared by adding a reinforcing agent such as carbon black and fine silica, a filler such as talc, clay and calcium silicate, an acid acceptor, a plasticizer,
Other additives such as processing aids such as stearic acid, palmitic acid and paraffin wax, and other additives such as pigments are added as necessary.Roll mixing, kneader mixing, Banbury mixing, solution mixing, etc. This is done by mixing.

As carbon black, MT carbon black is generally used. In addition, FT carbon black, SRF carbon black, FEF carbon black, SAF
Carbon black is also used. These carbon blacks are used in an amount of about 50 parts by weight or less, preferably about 5 to 30 parts by weight, per 100 parts by weight of the fluororubber, and improve strength, compression set and the like. As the acid acceptor, an oxide or hydroxide of a metal, preferably a divalent metal, for example, calcium oxide, calcium hydroxide, magnesium oxide, zinc oxide, lead oxide, etc. is used in an amount of about 30 parts by weight per 100 parts by weight of the fluororubber. Parts by weight, preferably about 0.1 to 10 parts by weight.

The crosslinking of the composition is generally at about 150-200 ° C. for about
Primary cross-linking performed for about 3-160 minutes and at about 150-250 ° C
It is performed by secondary crosslinking performed for about 1 to 24 hours.

[0022]

The vulcanizate of a fluororubber composition obtained by adding graphite or mica to an organic peroxide crosslinkable fluororubber is completely different from a polyol crosslinkable fluororubber vulcanizate and has an excellent carbon dioxide gas barrier property. Also, when this is immersed in liquefied carbon dioxide gas, it does not foam. Therefore, the fluororubber composition according to the present invention is suitably used as a molding material for sealing materials such as O-rings and packings used in equipment using carbon dioxide as a refrigerant.

[0023]

Next, the present invention will be described by way of examples.

Example 1 Organic peroxide crosslinkable fluororubber (Daikin product G-801) 100 parts by weight MT carbon black 35 ミ ル dicumyl peroxide 2 ト リ triallyl isocyanurate 3 グ ラ graphite (average particle size 30 μm) 10 〃 Each of the above components was kneaded with a 3L kneader and an open roll, and the kneaded product was subjected to press vulcanization at 170 ° C. for 15 minutes and oven vulcanization (secondary vulcanization) at 200 ° C. for 24 hours,
The following items were measured for the obtained vulcanized rubber sheet. Normal properties: Liquefied carbon dioxide immersion test: JIS K-6301 compliant: 25 of 50 x 25 x 2 mm rubber sheet
Rate of change in volume after immersion at 70 ° C for 70 hours Presence or absence of foaming after immersion in an oven at 150 ° C for 30 minutes Carbon dioxide gas permeability test: Gas permeability coefficient at 70 ° C (ASTM D-
1413) Kneadability: ○ Wraps well around roll, △ Wraps around roll almost, × Does not wind around roll

Example 2 In Example 1, the amount of carbon black was changed to 15 parts by weight,
The amount of graphite was changed to 30 parts by weight.

Example 3 In Example 1, the same amount of mica (average particle size: 20 μm) was used instead of graphite.

Comparative Example 1 In Example 1, the amount of carbon black was changed to 45 parts by weight, and no graphite was used. Comparative Example 2 In Example 1, the amount of graphite was changed to 50 parts by weight, and no carbon black was used.

Comparative Example 3 Polyol cross-linked fluororubber (Daikin product G-701) 100 parts by weight MT carbon black 40 {magnesium oxide / calcium hydroxide 3/5}

For each of the above components, kneading, vulcanization and measurement were carried out in the same manner as in Example 1.

Comparative Example 4 NBR (Nippon Synthetic Rubber Product N220) 100 parts by weight FEF carbon black 60 亜 鉛 zinc oxide 5 ヒ ド ロ hydroquinone compound 2 〃 sulfur 1 〃 thiuram-based accelerator / thiazole-based accelerator 2/2 〃

For each of the above components, kneading, vulcanization (no oven vulcanization) and measurement were carried out in the same manner as in Example 1.

Comparative Example 5 Chloroprene Rubber (Electrochemical Product DCR-S40) 100 parts by weight FEF carbon black 70 マ グ ネ シ ウ ム magnesium oxide 6 亜 鉛 zinc oxide 5 ヒ ド ロ hydroquinone compound 2 化合物 thiuram-based accelerator / thiourea-based accelerator 1/1 〃

For each of the above components, kneading, vulcanization (no oven vulcanization) and measurement were carried out in the same manner as in Example 1.

Comparative Example 6 EPDM (Mitsui Chemicals) 100 parts by weight FEF carbon black 60 亜 鉛 zinc oxide 5 ヒ ド ロ hydroquinone compound 2 〃 dicumyl peroxide 2 〃

The above components were kneaded, vulcanized (150 ° C., 24 hours for oven vulcanization) and measured in the same manner as in Example 1.

Measurements in the above Examples and Comparative Examples
The results are shown in the following table. tableMeasurement item Real-1 Real-2 Real-3 Ratio -1 Ratio-2 Ratio -3 Ratio -4 Ratio -5 Ratio -6  [Normal physical properties] Hardness (JIS A) 85 85 86 85 86 84 82 84 83 Tensile strength (MPa) 18.4 15.4 18.6 20.2 15.0 14.7 23.1 16.1 18.0 Elongation (%) 350 280 290 320 210 210 300 180 260 [liquefied CO_TwoImmersion test] Weight change rate (%) +4.1 +3.6 +4.0 +6.0 +2.3 +10.8 +12.1 +13.6 +14.2 Foaming None Slight None None Slightly many Many Many [CO_TwoGas permeation test] (cc ・ mm / cm^Two・ Atm ・ 24hr) [Kneadability] ○ △ ○ ○ × ○ ○ ○ ○

Claims (4)

[Claims] 1. A fluororubber composition obtained by adding graphite or mica to an organic peroxide crosslinkable fluororubber. 2. The fluororubber composition according to claim 1, wherein graphite or mica having an average particle size of 100 μm or less is used. 3. The fluororubber composition according to claim 1, wherein about 5 to 40 parts by weight of graphite or mica is added per 100 parts by weight of the organic peroxide crosslinkable fluororubber. 4. The fluororubber composition according to claim 1, which is used as a molding material for a carbon dioxide gas sealing material.