JP2013056979A - Crosslinkable fluororubber composition and fluororubber-molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crosslinkable fluororubber composition for producing a fluororubber-molded product having low frictional properties without forming a fluorine resin layer through lamination or coating on a rubber surface.SOLUTION: The crosslinkable fluororubber composition comprises a fluororubber (A) containing a vinylidene fluoride unit, the fluorine resin (B), and a crosslinking agent (C). The fluorine resin (B) consists of a copolymer comprising an ethylene unit and a tetrafluoroethylene unit and has a thermally stable group on a terminal of a main chain.

Description

The present invention relates to a crosslinkable fluororubber composition and a fluororubber molded article.

Fluororubber is widely used in various fields such as the automobile industry, semiconductor industry, chemical industry and the like because it exhibits excellent chemical resistance, solvent resistance and heat resistance. It is used as a hose, a sealing material, etc. used for peripheral devices, AT devices, fuel systems and peripheral devices.

However, since fluororubbers such as propylene [P] -tetrafluoroethylene [TFE] copolymer rubber may become brittle at low temperatures, ethylene [Et]-having a melting point of 240 to 300 ° C. is required for the improvement. A method has been proposed in which a tetrafluoroethylene copolymer resin [ETFE] is blended, melt-kneaded, and then subjected to radiation crosslinking or peroxide crosslinking (Patent Document 1).

In Patent Document 2, a fluororubber composition containing a fluororubber (vinylidene fluoride [VdF] rubber), a fluororesin [ETFE], and a fluorine-containing thermoplastic elastomer is subjected to press crosslinking (160 ° C. for 10 minutes). Subsequently, a method for producing a crosslinked rubber having improved hot strength by oven crosslinking (180 ° C. for 4 hours) is described.

Patent Document 3 describes a fluorine-containing copolymer composition comprising 75 to 98% by weight of a fluorine-containing elastomer and 25 to 2% by weight of a fluorine resin each having a reactive site that reacts with a common peroxide-based crosslinking agent. ing.

Patent Document 4 describes a rubber molded product of fluororubber and fluororesin, both of which are polyol crosslinkable.

In the field of sealing materials and the like, as a method of reducing the friction coefficient while utilizing the characteristics of rubber, for example, a method of laminating a fluororesin (or fluororesin fiber layer) on the rubber surface (Patent Documents 5 and 6), rubber A method of forming a fluororesin coating film on the surface (Patent Document 7) has been proposed.

In Patent Document 8, a crosslinkable fluororubber composition obtained by kneading a fluororubber and a fluororesin containing a vinylidene fluoride unit at a temperature of 5 ° C. lower than the melting point of the fluororesin is molded and cross-linked, It is described that, when heated to a temperature equal to or higher than the melting point of the fluororesin, a low-friction fluororubber molded product having an increased surface fluororesin ratio can be obtained.

JP 50-32244 A JP-A-6-25500 JP 2000-230096 A JP 2001-131346 A JP 7-227935 A JP 2000-313089 A JP 2006-292160 A International Publication No. 2010/029899 Pamphlet

Patent Documents 1 to 4 describe that a molded product is obtained by mixing fluororubber and fluororesin, but the obtained molded product has insufficient low friction and water repellency, and there is room for improvement. was there.

Further, as in Patent Documents 5 to 7, when a fluororesin layer is formed on the rubber surface by lamination or painting, a molded product having low friction can be obtained by the fluororesin on the surface. Increasing the adhesiveness at the interface is an important issue, and the current situation is that it is troubled by the solution.

When using a crosslinkable fluororubber composition obtained by kneading fluororubber and fluororesin at a temperature of 5 ° C. lower than the melting point of the fluororesin as in Patent Document 8, the resulting fluororubber molded article The ratio of fluororesin on the surface was not sufficiently high, and there was room for improvement in terms of low friction.

An object of the present invention is to provide a crosslinkable fluororubber composition for producing a fluororubber molded product having low friction without forming a fluororesin layer on the rubber surface by lamination or painting.

That is, the present invention includes a fluororubber (A) containing a vinylidene fluoride unit, a fluororesin (B), and a crosslinking agent (C), and the fluororesin (B) contains an ethylene unit and a tetrafluoroethylene unit. It is a crosslinkable fluororubber composition characterized by comprising a copolymer containing and having a thermally stable group at the end of the main chain.
The fluororesin (B) preferably further contains a hexafluoropropylene unit.
The mass ratio (A) / (B) of the fluororubber (A) containing the vinylidene fluoride unit and the fluororesin (B) is preferably 60/40 to 97/3.

The present invention is also a fluororubber molded product obtained by crosslinking the crosslinkable fluororubber composition described above.
In the fluororubber molded article, the area occupation ratio of the fluororesin (B) is preferably 5 to 100%.
The fluororubber molded article is preferably a sealing material.
The fluororubber molded article is preferably a sliding member.
The fluororubber molded article is preferably a non-adhesive member.
The fluororubber molded article preferably has water and oil repellency on the surface.

In the present invention, the fluororesin is segregated on the surface of the rubber molded product by adding a small amount of the fluororesin by kneading the fluororubber with a fluororesin having a thermally stable group at the main chain end, It has been found and completed that the coefficient of friction of the surface is lowered.

Since the crosslinkable fluororubber composition of the present invention contains a fluororesin having a thermally stable group at the end of the main chain, the fluororubber obtained by crosslinking the crosslinkable fluororubber composition of the present invention The molded article has rubber properties such as water repellency and is excellent in low friction properties.

The crosslinkable fluororubber composition of the present invention contains a fluororubber (A) containing a vinylidene fluoride unit, a fluororesin (B), and a crosslinker (C).
Each component and requirement are described in detail below.

(A) Fluoro rubber containing vinylidene fluoride (VdF) unit Fluoro rubber (A) containing vinylidene fluoride (VdF) unit is a fluoro rubber (hereinafter referred to as " Also referred to as “VdF fluororubber”. The VdF-based fluororubber is a fluororubber that contains at least polymerized units derived from vinylidene fluoride.

The copolymer containing VdF units is preferably a copolymer containing VdF units and copolymerized units derived from a fluorine-containing ethylenic monomer (however, VdF units are excluded). It is preferable that the copolymer containing a VdF unit further contains a copolymer unit derived from a monomer copolymerizable with VdF and a fluorine-containing ethylenic monomer.

The copolymer containing VdF units preferably contains 30 to 85 mol% of VdF units and 70 to 15 mol% of copolymerized units derived from a fluorine-containing ethylenic monomer, and 30 to 80 mol% of VdF. More preferably, it contains a unit and a copolymer unit derived from 70 to 20 mol% of a fluorine-containing ethylenic monomer. The copolymerized unit derived from the monomer copolymerizable with VdF and the fluorine-containing ethylenic monomer is 0 to 10 mol based on the total amount of the VdF unit and the copolymerized unit derived from the fluorine-containing ethylenic monomer. % Is preferred.

Examples of the fluorine-containing ethylenic monomer include TFE, CTFE, trifluoroethylene, HFP, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, perfluoro (alkyl vinyl ether) (hereinafter, And fluorine-containing monomers such as vinyl fluoride. Among these, at least one selected from the group consisting of TFE, HFP and PAVE is preferable.

As said PAVE, general formula (1):
^{_{CF 2 = CFO (CF 2 CFY}} 1 O) p - (CF 2 CF 2 CF 2 O) q -R f (1)
(Wherein, ^{Y 1} represents F or CF _{3, R f} represents an integer of .p 0-5 representing a perfluoroalkyl group having 1 to 5 carbon atoms, q is an integer of 0-5. ) And general formula (2):
CFX = CXOCF ₂ OR ¹ (2)
(In the formula, X represents H, F or CF ₃ , and R ¹ represents a linear or branched fluoroalkyl group having 1 to 6 carbon atoms or a cyclic fluoroalkyl group having 5 or 6 carbon atoms. Represents.)
It is preferably at least one selected from the group consisting of

R ¹ in the general formula (2) may be a fluoroalkyl group containing 1 to 2 atoms of at least one selected from the group consisting of H, Cl, Br and I.

The PAVE is preferably perfluoro (methyl vinyl ether) or perfluoro (propyl vinyl ether), and more preferably perfluoro (methyl vinyl ether). These can be used alone or in any combination.

Examples of the monomer copolymerizable with VdF and the fluorine-containing ethylenic monomer include ethylene, propylene, alkyl vinyl ether and the like.

Specific examples of such a copolymer containing VdF units include a VdF / HFP copolymer, a VdF / HFP / TFE copolymer, a VdF / CTFE copolymer, a VdF / CTFE / TFE copolymer, and a VdF. Preferred are one or more of / PAVE copolymer, VdF / TFE / PAVE copolymer, VdF / HFP / PAVE copolymer, VdF / HFP / TFE / PAVE copolymer, and the like. Among these copolymers containing VdF units, VdF / HFP copolymers and VdF / HFP / TFE copolymers are particularly preferred from the viewpoints of heat resistance, compression set, workability, and cost.

The VdF / HFP copolymer preferably has a VdF / HFP molar ratio of 45 to 85/55 to 15, more preferably 50 to 80/50 to 20, and still more preferably 60 to 80/40. ~ 20.

As the VdF / HFP / TFE copolymer, a VdF / HFP / TFE molar ratio of 40 to 80/10 to 35/10 to 35 is preferable.

The VdF / PAVE copolymer preferably has a VdF / PAVE molar ratio of 65 to 90/10 to 35.

As the VdF / TFE / PAVE copolymer, a VdF / TFE / PAVE molar ratio of 40 to 80/3 to 40/15 to 35 is preferable.

As the VdF / HFP / PAVE copolymer, a VdF / HFP / PAVE molar ratio of 65 to 90/3 to 25/3 to 25 is preferable.

The VdF / HFP / TFE / PAVE copolymer preferably has a VdF / HFP / TFE / PAVE molar ratio of 40 to 90/0 to 25/0 to 40/3 to 35, more preferably 40 to 80. / 3 to 25/3 to 40/3 to 25.

The VdF-based fluororubber (A) preferably has a Mooney viscosity (ML _{1 + 10} (121 ° C.)) of 5 to 140, more preferably ₁₀ to 120, and more preferably 20 to 100, from the viewpoint of good processability. More preferably.
Mooney viscosity can be measured according to ASTM-D1646 and JIS K6300.
Measuring instrument: MV2000E rotor manufactured by ALPHA TECHNOLOGIES Inc .: 2 rpm
Measurement temperature: 121 ° C

The crosslinkable fluororubber composition of the present invention preferably contains 97 to 60% by mass of the VdF fluororubber (A). If it is less than 60% by mass, rubber elasticity may be impaired. When it exceeds 97 mass%, there exists a possibility that the low friction characteristic of a composition may not express.

(B) Fluororesin The crosslinkable fluororubber composition of the present invention contains a fluororesin (B). When a specific fluororesin is added to the VdF-based fluororubber (A), the fluororesin segregates on the surface of the resulting rubber molded article, and the friction coefficient of the surface can be suitably reduced.

The fluororesin (B) is a fluororesin composed of a copolymer containing ethylene units and tetrafluoroethylene units (hereinafter also referred to as “ethylene [Et] / tetrafluoroethylene [TFE] copolymer”), It has a thermally stable group at the end.

The Et / TFE copolymer preferably has an Et / TFE molar ratio of 70 to 19/30 to 81, and more preferably 60 to 19/40 to 81.

The Et / TFE copolymer preferably further contains hexafluoropropylene [HFP] units. By using a terpolymer comprising Et units, TFE units and HFP units (hereinafter also referred to as ethylene [Et] / hexafluoropropylene [HFP] / tetrafluoroethylene [TFE] copolymer), a VdF fluorine Excellent compatibility with rubber (A).

The Et / HFP / TFE copolymer preferably contains 1 to 30 mol%, more preferably 5 to 20 mol%, of HFP units in terms of excellent compatibility with the VdF fluororubber (A). .

The fluororesin (B) may further contain a modified monomer unit.
As the modified monomer unit, the formula (I):
CH ₂ = CFR _f (I)
(In the formula, R _f is a fluoroalkyl group having 2 to 10 carbon atoms.)
The fluorovinyl compound shown by these is mentioned.
In the formula (I), when the number of carbon atoms in R _f is less than 2, the modification of the tetrafluoroethylene copolymer (for example, suppression of cracking of the molded product or molding) is not sufficiently achieved. If it exceeds 10, it becomes disadvantageous in terms of polymerization reactivity.
From the viewpoint of heat resistance of the resulting copolymer, the R _f group is most preferably a perfluoroalkyl group, an ω-hydro group or an ω-chloroperfluoroalkyl group.
Among such fluorovinyl compounds, from formula (II): from the viewpoint of copolymerizability, economics at the time of production of the monomer, and physical properties of the obtained copolymer
_{CH 2 = CF (CF 2)} n H (II)
(In the formula, n is a number of 2 to 10.)
The fluorovinyl compound represented by these is preferable. Of these, fluorovinyl compound (II) in which n is a number of 3 to 5 is particularly preferable.

The modified monomer unit is preferably 0.1 to 10 mol% in the fluororesin. If it is less than 0.1 mol%, flexibility may be lost, and if it exceeds 10 mol%, heat resistance may be reduced.

In order to improve the compatibility between the fluororesin (B) and the VdF fluororubber (A), at least one polyfunctional compound may be added. The polyfunctional compound is a compound having two or more functional groups having the same or different structures in one molecule.

The functional groups possessed by the polyfunctional compound include carbonyl groups, carboxyl groups, haloformyl groups, amide groups, olefin groups, amino groups, isocyanate groups, hydroxy groups, epoxy groups, etc., which are generally known to have reactivity. Any group can be used. The compounds having these functional groups not only have high affinity with the VdF-based fluororubber (A), but also react with functional groups known to have the reactivity possessed by the fluororesin (B), and further It is expected that the solubility will be improved.

The fluororesin (B) has a thermally stable group at the end of the main chain.
By having a thermally stable group at the end of the main chain, the area occupation ratio of the resin on the surface of the molded product can be increased.
Examples of the thermally stable group include an amide group (—CONH ₂ ), an alkyl group (including a perfluoroalkyl group, a fluoroalkyl group, and an alkyl group), an alkoxy group (—OR), and an alkoxycarbonyl group (—COOR). , An acyloxy group (—OC (═O) R), and an acyl group (—COR).
Especially, it is preferable that the fluororesin (B) has an amide group at the end of the main chain from the viewpoint that the terminal treatment is relatively easy.

The fluororesin (B) having an amide group at the end of the main chain originates from the NH bond of the terminal NH ₂ group to the height of the absorption peak at 2881 cm ⁻¹ due to the CH ₂ group of the main chain in the infrared absorption spectrum. the ratio of the height of the absorption peak at ^{3506cm -1 (3506cm -1 / 2881cm -1} ) is preferably a 0.1 or higher.
Further, the fluororesin (B) having an amide group at the end of the main chain is 3506 cm ⁻ due to the NH bond of the terminal NH ₂ group with respect to the height of the absorption peak at 2881 cm ⁻¹ due to the CH ₂ group of the main chain. more preferably the ratio of the height of the absorption peak at ^{1 (3506cm -1} / ^2881cm -1) is at least 0.15.

The fluororesin (B) having an amide group at the main chain terminal can be obtained by polymerizing using the monomer component and the polymerization initiator described above and amidating the terminal.
There is -OCOOR or the like derived from the polymerization initiator at the main chain terminal of the synthesized fluororesin before the terminal amidation treatment. For example, -OCOOR can be converted to a -CONH ₂ group by an amidation treatment.

The amidation treatment can be performed by bringing the obtained fluororesin into contact with ammonia gas or a nitrogen compound that can generate ammonia.

As a method for bringing the fluororesin before the treatment into contact with the ammonia gas, there is a method in which a copolymer before the treatment is installed in the reaction vessel and the ammonia gas is supplied into the reaction vessel. The supply of ammonia gas into the reaction vessel may be performed after mixing with a gas inert to amidation to form a mixed gas.

The gas inert to the amidation is not particularly limited, and examples thereof include nitrogen gas, argon gas, and helium gas. The ammonia gas is preferably 1% by mass or more of the mixed gas, more preferably 10% by mass or more, and may be 80% by mass or less as long as it is within the above range.

The amidation treatment is preferably performed at 0 ° C. or more and 100 ° C. or less, more preferably 5 ° C. or more, further preferably 10 ° C. or more, more preferably 90 ° C. or less, and further preferably 80 ° C. or less. It is. If the temperature is too high, the fluororesin or the like may be decomposed or fused, and if it is too low, the treatment may take a long time, which is not preferable in terms of productivity.

The time of the amidation treatment is usually about 1 minute to 24 hours, although it depends on the amount of the fluororesin.

The fluororesin (B) has a melt flow rate (MFR 265 ° C./5 kg) of preferably 5 g / 10 minutes or more, and more preferably 10 g / 10 minutes or more.
The melt flow rate is a value obtained by the method of ASTM D1238.

The fluororesin (B) preferably has a melting point equal to or higher than the crosslinking temperature of the VdF fluororubber (A). The melting point of the fluororesin (B) is appropriately determined depending on the type of the VdF-based fluororubber (A), but is usually preferably 150 ° C. or higher and more preferably 160 ° C. or higher. The upper limit is not particularly limited, but may be 200 ° C.
The melting point is a value obtained by the DSC method.

In the crosslinkable fluororubber composition of the present invention, the mass ratio (A) / (B) between the VdF fluororubber (A) and the fluororesin (B) is preferably 60/40 to 97/3.
If the proportion of the fluororesin (B) is too small, the low friction characteristics of the composition may not be exhibited, and if too large, rubber elasticity may be impaired.
The mass ratio (A) / (B) is more preferably 70/30 or more, and more preferably 85/15 or less.

(C) Cross-linking agent The cross-linking agent in the present invention is not particularly limited as long as it is generally known as a cross-linking agent applicable to fluororubbers. A peroxide type crosslinking agent can be mentioned.
Regarding the crosslinking system, a peroxide crosslinking system is preferable from the viewpoint of chemical resistance, and a polyol crosslinking system is preferable from the viewpoint of heat resistance. The crosslinking agent (C) may be appropriately selected according to the required properties.

Examples of the polyamine-based crosslinking agent include polyamine compounds such as hexamethylenediamine carbamate, N, N′-dicinnamylidene-1,6-hexamethylenediamine, and 4,4′-bis (aminocyclohexyl) methanecarbamate. Among these, N, N′-dicinnamylidene-1,6-hexamethylenediamine is preferable.

As said polyol type crosslinking agent, a polyhydroxy compound etc. can be mentioned, for example.
The polyhydroxy compound is preferably a polyhydroxy aromatic compound from the viewpoint of excellent heat resistance.

The polyhydroxy aromatic compound is not particularly limited. For example, 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A), 2,2-bis (4-hydroxyphenyl) perfluoropropane. (Hereinafter referred to as bisphenol AF), resorcin, 1,3-dihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4′-dihydroxydiphenyl, 4,4 ′ -Dihydroxystilbene, 2,6-dihydroxyanthracene, hydroquinone, catechol, 2,2-bis (4-hydroxyphenyl) butane (hereinafter referred to as bisphenol B), 4,4-bis (4-hydroxyphenyl) valeric acid, 2 , 2-Bis (4-hydroxyphenyl) Trafluorodichloropropane, 4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl ketone, tri (4-hydroxyphenyl) methane, 3,3 ′, 5,5′-tetrachlorobisphenol A, 3,3 Examples include ', 5,5'-tetrabromobisphenol A. These polyhydroxy aromatic compounds may be an alkali metal salt, an alkaline earth metal salt or the like, but when the copolymer is coagulated using an acid, it is preferable not to use the metal salt.

When the crosslinking agent (C) is a polyhydroxy compound, the crosslinkable fluororubber composition of the present invention preferably further contains a crosslinking accelerator. The crosslinking accelerator promotes the formation of an intramolecular double bond in the dehydrofluorination reaction of the polymer main chain and the addition of a polyhydroxy compound to the generated double bond.

Examples of the crosslinking accelerator include onium compounds. Among onium compounds, ammonium compounds such as quaternary ammonium salts, phosphonium compounds such as quaternary phosphonium salts, oxonium compounds, sulfonium compounds, cyclic amines, and It is preferably at least one selected from the group consisting of monofunctional amine compounds, more preferably at least one selected from the group consisting of quaternary ammonium salts and quaternary phosphonium salts.

The quaternary ammonium salt is not particularly limited. For example, 8-methyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8-methyl-1,8-diazabicyclo [5, 4,0] -7-undecenium iodide, 8-methyl-1,8-diazabicyclo [5,4,0] -7-undecenium hydroxide, 8-methyl-1,8-diazabicyclo [5 , 4,0] -7-Undecenium methyl sulfate, 8-ethyl-1,8-diazabicyclo [5,4,0] -7-undecenium bromide, 8-propyl-1,8-diazabicyclo [5 , 4,0] -7-undecenium bromide, 8-dodecyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8-dodecyl-1,8-diazabicyclo [ , 4,0] -7-undecenium hydroxide, 8-eicosyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8-tetracosyl-1,8-diazabicyclo [5]. , 4,0] -7-undecenium chloride, 8-benzyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride (hereinafter referred to as DBU-B), 8-benzyl- 1,8-diazabicyclo [5,4,0] -7-undecenium hydroxide, 8-phenethyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8- (3 -Phenylpropyl) -1,8-diazabicyclo [5,4,0] -7-undecenium chloride and the like. Among these, DBU-B is preferable because crosslinkability and physical properties of the fluororubber molded article are excellent.

The quaternary phosphonium salt is not particularly limited. For example, tetrabutylphosphonium chloride, benzyltriphenylphosphonium chloride (hereinafter referred to as BTPPC), benzyltributylphosphonium chloride, benzyltributylphosphonium chloride, tributylallylphosphonium chloride, tributyl. -2-methoxypropylphosphonium chloride, benzylphenyl (dimethylamino) phosphonium chloride, and the like. Among these, benzyltriphenylphosphonium chloride (BTPPC) is preferred because of its excellent crosslinkability and physical properties of the fluororubber molded product. preferable.

Further, as the crosslinking accelerator, a quaternary ammonium salt, a solid solution of a quaternary phosphonium salt and bisphenol AF, or a chlorine-free crosslinking accelerator disclosed in JP-A-11-147891 can be used.

It is preferable that the compounding quantity of the said crosslinking accelerator is 0.01-8 mass parts with respect to 100 mass parts of VdF type fluororubber (A), More preferably, it is 0.02-5 mass parts. When the crosslinking accelerator is less than 0.01 parts by mass, the crosslinking of the fluororubber does not proceed sufficiently, and the heat resistance and oil resistance of the resulting fluororubber molded product tend to decrease, and 8 parts by mass When it exceeds, there exists a tendency for the moldability of the said crosslinkable fluororubber composition to fall.

As said peroxide type crosslinking agent, an organic peroxide etc. can be mentioned, for example.
The organic peroxide may be an organic peroxide that can easily generate a peroxy radical in the presence of heat or a redox system. For example, 1,1-bis (t-butylperoxy)- 3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α, α-bis ( t-butylperoxy) -p-diisopropylbenzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) -Hexin-3, benzoyl peroxide, t-butyl peroxybenzene, t-butyl peroxymaleic acid, t-butyl peroxyisopropyl carbonate , T-butyl peroxybenzoate and the like. Among these, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and 2,5-dimethyl-2,5-di (t-butylperoxy) -hexyne-3 are preferable.

When the crosslinking agent is an organic peroxide, the crosslinkable fluororubber composition of the present invention preferably contains a crosslinking aid.
Examples of the crosslinking aid include triallyl cyanurate, triallyl isocyanurate (TAIC), triacryl formal, triallyl trimellitate, N, N′-m-phenylenebismaleimide, dipropargyl terephthalate, diallyl phthalate. , Tetraallyl terephthalate amide, triallyl phosphate, bismaleimide, fluorinated triallyl isocyanurate (1,3,5-tris (2,3,3-trifluoro-2-propenyl) -1,3,5-triazine- 2,4,6-trione), tris (diallylamine) -S-triazine, triallyl phosphite, N, N-diallylacrylamide, 1,6-divinyldodecafluorohexane, hexaallylphosphoramide, N, N, N ', N'-tetraallylphthalamide, N, N, ', N'- tetraallyl malonamide, trivinyl isocyanurate, 2,4,6-vinyl methyl trisiloxane, tri (5-norbornene-2-methylene) cyanurate, triallyl phosphite. Among these, triallyl isocyanurate (TAIC) is preferable from the viewpoint of excellent crosslinkability and physical properties of the fluororubber molded article.

The amount of the crosslinking aid is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the VdF fluororubber (A). . When the crosslinking aid is less than 0.01 parts by mass, the crosslinking time tends to be too long to be practically used, and when it exceeds 10 parts by mass, in addition to the crosslinking time becoming too fast, fluororubber molding The compression set of the product also tends to decrease.

In the crosslinkable fluororubber composition of the present invention, the content of the crosslinking agent (C) is preferably 0.2 to 10 parts by mass with respect to 100 parts by mass of the VdF-based fluororubber (A). If it is less than 0.2 parts by mass, the crosslinking density tends to be low and the compression set tends to be large. If it exceeds 10 parts by mass, the crosslink density becomes too high, so that it tends to break during compression.
As for content of a crosslinking agent (C), More preferably, a minimum is 0.5 mass part and an upper limit is 3 mass parts.

The crosslinkable fluororubber composition is a usual additive blended in the fluororubber as necessary, for example, a filler, a processing aid, an acid acceptor, a plasticizer, a colorant, a stabilizer, an adhesion aid, Various additives such as a release agent, a conductivity imparting agent, a thermal conductivity imparting agent, a surface non-adhesive agent, a flexibility imparting agent, a heat resistance improving agent, a flame retardant, etc. can be blended. What is necessary is just to use in the range which does not impair the effect of this invention.

Next, a method for producing a fluororubber molded product using the crosslinkable fluororubber composition of the present invention will be described.

The fluororubber molded article includes (I) a preparation step for preparing the crosslinkable fluororubber composition of the present invention, (II) a molding crosslinking step for molding and crosslinking the obtained preparation, and (III) a resulting crosslinked molded product. Can be manufactured by a manufacturing method including a heat treatment step in which a fluororubber molded article is obtained by heating to a temperature equal to or higher than the melting point of the fluororesin (B).

Hereinafter, each step will be described.

(I) Preparation Step The preparation step (I) is a mixture of the above-mentioned VdF fluororubber (A), fluororesin (B), crosslinker (C), and necessary additives to form crosslinkable fluorine. It is a step of preparing a rubber composition.
Examples of the step of preparing the crosslinkable fluororubber composition include a method of kneading and preparing the above-described components and a method of preparing by co-coagulation.

As a method of kneading and preparing each of the above components, a method of kneading the VdF-based fluororubber (A), the fluororesin (B) and the cross-linking agent (C) above the melting point of the fluororesin (B) can be mentioned. By kneading at the melting point or higher, the mechanical strength of the obtained fluororubber molded article can be improved and the friction coefficient can be lowered.
The upper limit of the kneading temperature is preferably the lower thermal decomposition temperature of the VdF fluororubber (A) or the fluororesin (B).

The kneading is preferably performed under the condition that the crosslinking agent (C) does not proceed with the crosslinking reaction of the VdF fluororubber (A). By kneading without allowing the crosslinking reaction to proceed, the mechanical strength of the fluororubber molded article can be further improved and the friction coefficient can be further reduced. In the kneading of the crosslinking agent (C), if the crosslinking reaction does not proceed, the VdF fluororubber (A), the fluororesin (B), and the crosslinking agent (C) are kneaded at the same time at a melting point of the fluororesin (B) or higher. Alternatively, the VdF-based fluororubber (A) and the fluororesin (B) are kneaded at a temperature equal to or higher than the melting point of the fluororesin (B) to obtain a premix, and then the premix and the crosslinking agent (C May be kneaded under conditions that do not allow the crosslinking reaction to proceed.

In order to knead under the condition that the crosslinking reaction does not proceed, the kneading may be performed without adding the minimum components necessary for crosslinking, or the kneading may be performed at a temperature lower than the temperature necessary for the crosslinking reaction.
Conditions under which the crosslinking reaction does not proceed are mainly determined by the type of crosslinking agent. For example, when a polyol crosslinking agent is used as the crosslinking agent (C), if a polyol crosslinking agent, a crosslinking accelerator and an acid acceptor are simultaneously kneaded at a temperature equal to or higher than the melting point of the fluororesin (B), a crosslinking reaction usually proceeds. Therefore, in the two-stage kneading step described later, the crosslinkable fluororubber after obtaining the pre-mixture without adding at least one of the polyol cross-linking agent, the cross-linking accelerator and the acid acceptor in the step of obtaining the pre-mixture. It is preferable to add in the step of obtaining the composition (full compound).
Further, when a peroxide crosslinking agent is used as the crosslinking agent (C), if a peroxide crosslinking agent is present when kneading at a temperature equal to or higher than the melting point of the fluororesin (B), a crosslinking reaction usually proceeds. In the two-stage kneading step, it is preferable to add a peroxide cross-linking agent in the step of obtaining a crosslinkable fluororubber composition (full compound) after obtaining a preliminary mixture.

As a method for kneading and preparing each of the above components, a VdF-based fluororubber (A) and a fluororesin (B) are kneaded above the melting point of the fluororesin (B) to obtain a premix (pre-compound). A two-stage kneading step of adding a crosslinking agent (C) and any other additives to the premix and kneading below the crosslinking temperature to obtain a crosslinkable fluororubber composition (full compound);
VdF-based fluororubber (A), fluororesin (B), and cross-linking agent (C) are kneaded under a condition not lower than the melting point of fluororesin (B) and the cross-linking reaction does not proceed to prepare a premix (pre-compound). After obtaining, a two-stage kneading step of adding any other additive to the premix and kneading below the crosslinking temperature to obtain a crosslinkable fluororubber composition (full compound), or
VdF-based fluororubber (A), fluororesin (B), cross-linking agent (C) and any other additives are kneaded under the melting point of the fluororesin (B) and under the condition that the cross-linking reaction does not proceed. A one-stage kneading step for obtaining a crosslinkable fluororubber composition (full compound),
It is more preferable that it is a two-stage kneading step, in particular,
After the VdF-based fluororubber (A) and the fluororesin (B) are kneaded at a melting point or higher of the fluororesin (B) to obtain a preliminary mixture, the crosslinking agent (C) and any other additives are added to the preliminary mixture. A two-stage kneading step of adding and kneading below the crosslinking temperature to obtain a crosslinkable fluororubber composition is preferred.

In the kneading for preparing the pre-mixture (pre-compound) in the two-stage kneading process, it is important to knead under conditions where the crosslinking reaction does not proceed, and the crosslinking reaction proceeds at a temperature equal to or higher than the melting point of the fluororesin (B). It is not impeded to add components that do not (for example, only a specific crosslinking agent, only a combination of a crosslinking agent and a crosslinking accelerator, etc.).

The kneading to obtain a premix (pre-compound) in the two-stage kneading step can be performed by kneading with the VdF fluororubber (A) at a melting point of the fluororesin (B), for example, 180 ° C. or more. .

For the kneading, a Banbury mixer, a pressure kneader, an extruder or the like can be used, but an extruder such as a pressure kneader or a twin screw extruder is preferably used in that a high shear force can be applied.

Kneading to obtain a crosslinkable fluororubber composition (full compound) in a two-stage kneading process is performed by using an open roll, a Banbury mixer, a pressure kneader, etc. at a temperature below the decomposition temperature of the crosslinking agent (C), for example, 100 ° C. or less. Can be used.

Here, as a process similar to the above kneading, there is a process (dynamic cross-linking) of cross-linking fluororubber in a fluororesin under the melting condition of the fluororesin. In contrast, dynamic crosslinking is a process of blending rubber in a thermoplastic resin matrix and crosslinking the rubber while kneading, whereas the above kneading is a condition that does not cause crosslinking of fluororubber (crosslinking). In the absence of necessary components, or a compound that does not cause a crosslinking reaction at that temperature).

The crosslinkable fluororubber composition obtained in the kneading step in the present invention has a structure in which the VdF fluoropolymer (A) forms a continuous phase and the fluororesin (B) forms a dispersed phase, or a VdF fluoropolymer composition. It is presumed that the fluororubber (A) and the fluororesin (B) have a structure in which a continuous phase is formed together. This is also different from dynamic crosslinking, in which a composition in which crosslinked rubber is dispersed microscopically in a matrix is obtained.

As a method of preparing by co-coagulation, a VdF-based fluororubber (A) and a fluororesin (B) are co-coagulated, and then a crosslinking agent (C) is added to prepare a crosslinkable fluororubber composition. The method of doing is mentioned.
The co-coagulation is, for example, (i) a method of coagulating after mixing an aqueous dispersion of a VdF-based fluororubber (A) and an aqueous dispersion of a fluororesin (B), (ii) a VdF-based fluororubber Method of coagulating after adding powder of (A) to fluororesin (B), (iii) Coagulation after adding powder of fluororesin (B) to aqueous dispersion of VdF fluororubber (A) The method of doing is mentioned. Especially, the method of said (i) is preferable at the point which each resin is easy to disperse | distribute uniformly.

The coagulation can be performed using a flocculant, for example. Such a flocculant is not particularly limited, and examples thereof include aluminum salts such as aluminum sulfate and alum, calcium salts such as calcium sulfate, magnesium salts such as magnesium sulfate, sodium chloride and potassium chloride. Known aggregating agents such as valent cation salts can be mentioned. When coagulating with a flocculant, the pH may be adjusted by adding an acid or an alkali in order to promote aggregation.

After co-coagulating the VdF-based fluororubber (A) and the fluororesin (B) to obtain a co-coagulated powder, a crosslinking agent (C) is added to the co-coagulated powder. The co-coagulated powder and the crosslinking agent (C) may be mixed at a temperature lower than the melting point of the fluororesin (B) by, for example, an ordinary mixing method using an open roll or the like.

(II) Molding / crosslinking step Step (II) is a step of molding the crosslinkable fluororubber composition obtained in step (I) and crosslinking to produce a crosslinked molded product. The order of molding and crosslinking is not limited, and may be crosslinked after molding, may be molded after crosslinking, or may be molded and crosslinked simultaneously.

For example, in the case of a hose, a long plate or the like, a method of crosslinking after extrusion molding is appropriate, and in the case of a deformed molded product, a method of performing a molding process such as cutting after obtaining a block-shaped crosslinked product can be adopted. . In the case of a relatively simple molded product such as a piston ring or an oil seal, it is a common practice to simultaneously perform molding and crosslinking simultaneously with a mold or the like.

Examples of the molding method include, but are not limited to, an extrusion molding method, a pressure molding method using a mold, an injection molding method, and the like.

As the crosslinking method, a steam crosslinking method, a pressure molding method, a radiation crosslinking method, or a usual method in which a crosslinking reaction is started by heating can be employed. In the present invention, from the viewpoint of efficiently increasing the occupation ratio of the fluororesin on the surface of the fluororubber molded article, a crosslinking reaction by heating is preferable.

The method and conditions for molding and crosslinking of the crosslinkable fluororubber composition may be within the range of known methods and conditions for the molding and crosslinking employed.

The temperature at which crosslinking is performed is not less than the crosslinking temperature of the VdF-based fluororubber (A) and is preferably less than the melting point of the fluororesin (B). If cross-linking is performed at a melting point or higher of the fluororesin (B), a molded product having a large number of convex portions may not be obtained.
The crosslinking time is, for example, 1 minute to 24 hours, and may be appropriately determined depending on the type of the crosslinking agent used.

By the way, in the rubber cross-linking, after the first cross-linking treatment (referred to as primary cross-linking), a post-treatment step called secondary cross-linking may be performed, as explained in the next heat treatment step (III). The conventional secondary cross-linking step is different from the forming cross-linking step (II) and the heat treatment step (III) in the present invention.

(III) Heat treatment step In this step, the crosslinked molded product obtained in the molding and crosslinking step (II) is heated to a temperature equal to or higher than the melting point of the fluororesin (B) to obtain a fluororubber molded product.

The heat treatment step (III) is a treatment step performed to increase the occupancy rate of the fluororesin on the surface of the cross-linked molded product. In accordance with this purpose, the melting point of the fluororesin (B) and the VdF fluororubber (A) And a temperature lower than the thermal decomposition temperature of the fluororesin (B) is employed as the heating temperature.

When the heating temperature is lower than the melting point of the fluororesin, a molded product having a large number of convex portions cannot be obtained. Moreover, in order to avoid thermal decomposition of fluororubber and fluororesin, the temperature must be lower than the lower thermal decomposition temperature of VdF fluoropolymer (A) or fluororesin (B). A preferable heating temperature is a temperature that is 5 ° C. or more higher than the melting point of the fluororesin (B) from the viewpoint of easily reducing friction in a short time.

The above upper limit temperature is the case of ordinary fluoro rubber, and in the case of fluoro rubber having super heat resistance, since the upper limit temperature is the decomposition temperature of fluoro rubber having super heat resistance, the above upper limit temperature is not limited to this. .

In the heat treatment step (III), the heating temperature is closely related to the heating time. When the heating temperature is relatively close to the lower limit, the heating is performed for a relatively long time, and when the heating temperature is relatively close to the upper limit, the heating is relatively short. It is preferable to employ time. As described above, the heating time may be appropriately set in relation to the heating temperature. However, if the heat treatment is performed for a long time, the fluororubber may be thermally deteriorated. It is practically up to 96 hours excluding the case where is used. Usually, the heat treatment time is preferably 1 minute to 96 hours, and more preferably 1 minute to 24 hours from the viewpoint of good productivity. However, when it is desired to sufficiently reduce the friction coefficient, it is preferably 8 to 96 hours. .

By the way, the conventional secondary cross-linking completely decomposes the cross-linking agent remaining at the end of the primary cross-linking to complete the cross-linking of the fluororubber, thereby improving the mechanical properties and compression set properties of the cross-linked molded product. This is a process to be performed.

Therefore, the conventional secondary crosslinking conditions that do not assume the coexistence of the fluororesin (B) are such that the presence of the fluororesin is determined in the secondary crosslinking even if the crosslinking conditions accidentally overlap with the heating conditions of the heat treatment step. Heating conditions within the target range of completion of cross-linking of the fluororubber (complete decomposition of the cross-linking agent) are not taken into consideration as a setting factor, and the rubber is blended with the fluororesin (B). Conditions for heat-softening or melting the fluororesin (B) in a crosslinked product (not an uncrosslinked rubber product) cannot be derived.

In addition, in the said shaping | molding bridge | crosslinking process (II), in order to complete the bridge | crosslinking of VdF type fluororubber (A) (in order to decompose | disassemble a crosslinking agent (C) completely), you may perform secondary crosslinking.

Further, in the heat treatment step (III), the remaining crosslinking agent (C) may be decomposed to complete the crosslinking of the VdF type fluororubber (A). However, the VdF type fluororubber (A) in the heat treatment step (III) may be completed. ) Is only a secondary effect.

Using the crosslinkable fluororubber composition of the present invention, according to the above production method, the fluororesin segregates on the surface, and a fluororubber molded article excellent in low friction in addition to the original rubber properties is suitably obtained. be able to.
In addition, the state which the fluororesin segregated can be observed with a laser microscope.
A fluororubber molded article obtained using such a crosslinkable fluororubber composition of the present invention is also one aspect of the present invention.

The fluororubber molded article preferably has an area occupation ratio of the fluororesin (B) of 5 to 100%. If the area occupancy is less than 5%, low friction characteristics and non-adhesive characteristics may not be exhibited.
The area occupancy is more preferably 10% or more, and still more preferably 20% or more.
The area occupancy is measured by measuring the surface of the molded product using a color 3D laser microscope (VK-9700) manufactured by Keyence Co., Ltd., and obtaining the cross-sectional area of the convex part (fluororesin part). The ratio of the total area of the measurement to the occupation ratio.

The fluororubber molded product of the present invention is useful as a sealing material, a sliding member, a non-adhesive member, etc. by utilizing its inherent rubber properties such as low friction and water repellency.

Specifically, the following molded products can be exemplified, but are not limited thereto.

Sealing material:
In semiconductor-related fields such as semiconductor manufacturing equipment, liquid crystal panel manufacturing equipment, plasma panel manufacturing equipment, plasma address liquid crystal panels, field emission display panels, solar cell substrates, etc., O (square) -rings, packings, gaskets, diaphragms, and other various types Examples thereof include a sealing material, and these can be used for a CVD apparatus, a dry etching apparatus, a wet etching apparatus, an oxidation diffusion apparatus, a sputtering apparatus, an ashing apparatus, a cleaning apparatus, an ion implantation apparatus, and an exhaust apparatus. Specifically, O-rings for gate valves, quartz-window O-rings, chamber O-rings, gate O-rings, bell jar O-rings, coupling O-rings, pump O-rings, It can be used as a diaphragm, an O-ring of a semiconductor gas control device, a resist developer, an O-ring for a stripping solution, and other various sealing materials.

In the automobile field, it can be used for gaskets, shaft seals, valve stem seals, various sealing materials used for engines and peripheral devices, and various sealing materials for AT devices. Examples of the sealing material used for the fuel system and peripheral devices include O (square) -rings, packings, diaphragms, and the like. Specifically, engine head gasket, metal gasket, oil pan gasket, crankshaft seal, camshaft seal, valve stem seal, manifold packing, oxygen sensor seal, injector O-ring, injector packing, fuel pump O-ring, Diaphragm, crankshaft seal, gearbox seal, power piston seal, cylinder liner seal, valve stem seal, automatic transmission front pump seal, rear axle pinion seal, universal joint gasket, speedometer pinion seal, foot brake Piston cup, torque transmission O-ring, oil seal, exhaust gas reburner seal, bearing seal, carburetor sensor die It can be used as Fulham like.

In the aircraft field, the rocket field, and the ship field, there are diaphragms, O (square) -rings, valves, packings, various sealing materials, and the like, and these can be used for fuel systems. Specifically, in the aircraft field, it is used for jet engine valve stem seals, gaskets and O-rings, rotating shaft seals, hydraulic equipment gaskets, firewall seals, etc., and in the ship field, screw propeller shaft stern seals, Used for intake and exhaust valve stem seals of diesel engines, valve seals of butterfly valves, shaft seals of butterfly valves, and the like.

In the chemical plant field, there are valves, packings, diaphragms, O (square) -rings, various sealing materials, and the like, and these can be used in the manufacturing process of chemical products such as pharmaceuticals, agricultural chemicals, paints, and resins. Specifically, chemical pumps, rheometers, pipe seals, heat exchanger seals, glass cooler packing for sulfuric acid production equipment, pesticide sprayers, pesticide transfer pump seals, gas pipe seals, plating solutions Seals, packing for high-temperature vacuum dryers, roller seals for papermaking belts, fuel cell seals, wind tunnel joint seals, gas chromatography, packing for pH meter tube connections, analytical instruments, physics and chemistry instrument seals, diaphragms, valve parts Etc. can be used.

In the field of photography such as a developing machine, the field of printing such as a printing machine, and the field of painting such as a painting facility, it can be used as a seal or valve part of a dry copying machine.

In the field of food plant equipment, valves, packings, diaphragms, O (square) -rings, various sealing materials, and the like can be mentioned and used in food production processes. Specifically, it can be used as a seal for a plate heat exchanger, a solenoid valve seal for a vending machine, or the like.

In the field of nuclear plant equipment, packing, O-rings, diaphragms, valves, various sealing materials, and the like can be given.

In the general industrial field, packing, O-rings, diaphragms, valves, various sealing materials and the like can be mentioned. Specifically, hydraulic, lubrication machinery seals, bearing seals, dry cleaning equipment windows, other seals, uranium hexafluoride concentrator seals, cyclotron seals (vacuum) valves, automatic packaging machine seals, air Used for diaphragms (pollution measuring devices) of sulfur dioxide and chlorine gas analysis pumps.

In the electric field, specifically, it is used as an insulating oil cap for Shinkansen, a benching seal for a liquid seal transformer, and the like.

In the fuel cell field, specifically, it is used as a sealing material between electrodes and separators, a seal for hydrogen / oxygen / product water piping, and the like.

In the field of electronic components, specifically, it is used as a heat radiating material, an electromagnetic shielding material, a hard disk drive gasket of a computer, and the like.

There are no particular limitations on what can be used for on-site molding, and examples include an engine oil pan gasket, a magnetic recording device gasket, and a clean room filter unit sealing agent.

Further, it is particularly suitably used for a seal material for clean equipment such as a gasket for a magnetic recording device (hard disk drive), a seal ring material for a semiconductor storage device or a device storage such as a wafer.

Furthermore, it is particularly preferably used for a sealing material for fuel cells such as packing used between fuel cell electrodes or surrounding piping.

Sliding member:
In automobile-related fields, piston rings, shaft seals, valve stem seals, crankshaft seals, camshaft seals, oil seals and the like can be mentioned.
In general, a fluororubber product used for a portion that slides in contact with another material is exemplified.

Non-adhesive material:
For example, hard disk crash stopper in the computer field.
In addition, roll parts and the like in the field of copying machines and printers.

Fields that utilize water and oil repellency:
Examples include automobile wiper blades and outdoor tent pulling cloths.

Next, the present invention will be described with reference to examples, but the present invention is not limited to such examples.

Various characteristics in this specification were measured by the following methods.

(1) Crosslinking (vulcanization) characteristics Clastometer type II (manufactured by JSR Corporation) measures minimum torque (ML), maximum torque (MH), induction time (T10) and optimum vulcanization time (T90). did.

(2) A —NH ₂ specific fluororesin of fluororesin was compression molded at room temperature to prepare a film having a thickness of 1.5 to 2.0 mm. The absorbance of the peak was measured by infrared absorption spectrum analysis of the film. The infrared absorption spectrum analysis was performed by scanning 40 times using a Perkin-Elmer FTIR spectrometer 1760X (manufactured by PerkinElmer). The obtained IR spectrum was analyzed using Perkin-Elmer Spectrum for Windows Ver. The baseline was automatically determined at 1.4C, and the absorbance of the peak was measured. The film thickness was measured with a micrometer.
The ratio of the height of the absorption peak at 3506 cm ⁻¹ due to the NH bond of the terminal NH ₂ group to the height of the absorption peak at 2881 cm ⁻¹ due to the CH ₂ group of the main chain in the fluororesin the ^{(3506cm -1} / 2881cm -1) was determined.

(3) Friction coefficient Measured with a friction player FPR2000 manufactured by Reska Co., with a load of 20 g, a rotation mode, a rotation speed of 60 rpm, and a rotation radius of 10 mm. The numerical value was taken as the dynamic friction coefficient.

(4) Area occupancy ratio of fluororesin Using a color 3D laser microscope (VK-9700) manufactured by Keyence Corporation, the surface of the cross-linked fluororubber sheet was measured to determine the convex cross-sectional area, and the total cross-sectional area value was The ratio occupied in the total area of the measurement was defined as the area occupation ratio.

Other materials used are as follows.
<Fluororesin a>
Ethylene / TFE / HFP / H ₂ P = 46.1 / 36.5 / 17.0 / 0.4 (mol%), melting point 161 ° C., —OC (═O) OR terminal <fluororesin b>
Ethylene / TFE / HFP / H ₂ P = 46.1 / 36.5 / 17.0 / 0.4 (mol%), melting point 161 ° C., amide terminal (—CONH ₂ ),
—NH ₂ group ratio (3506 cm ⁻¹ / 2881 cm ⁻¹ ) = 0.23
<Fluorine resin c>
Ethylene / TFE / HFP / H ₂ P = 48.8 / 37.8 / 17.5 / 0.4 (mol%), melting point 192 ° C., —OC (═O) OR terminal <fluororesin d>
Ethylene / TFE / HFP / H ₂ P = 48.8 / 37.8 / 17.5 / 0.4 (mol%), melting point 192 ° C., amide terminal (—CONH ₂ ),
—NH ₂ group ratio (3506 cm ⁻¹ / 2881 cm ⁻¹ ) = 0.20
<Fluorine resin e>
Ethylene / TFE / HFP / H ₂ P = 46.1 / 36.5 / 17.0 / 0.4 (mol%), melting point 161 ° C., carboxyl terminal (—COOH)
In all of the compositions of the fluororesin, “TFE” represents tetrafluoroethylene, “HFP” represents hexafluoropropylene, and “H ₂ P” represents H ₂ C═CF (CF ₂ ) ₃ H.

<Fluorine rubber>
Daiel G-7401 manufactured by Daikin Industries, Ltd.
(Including vinylidene fluoride (VdF) / hexafluoropropylene (HFP) copolymer, cross-linking agent (bisphenol AF))
<Filler 1>
Carbon black (MT carbon manufactured by Cancarb: N990)
<Acid acceptor 1>
Magnesium oxide (MA150 manufactured by Kyowa Chemical Industry Co., Ltd.)
<Acid acceptor 2>
Calcium hydroxide (CALDIC2000 manufactured by Omi Chemical Co., Ltd.)

Example 1
An amount of 80% filling rate of fluororubber and fluororesin b was put into a 3 L kneader and melt kneaded. After the material temperature reached 180 ° C., the mixture was further kneaded for 5 minutes, and then the material was taken out to prepare a pre-compound.
The obtained pre-compound is wound around an open roll having two 8-inch rolls, 1 part by mass of filler 1, 3 parts by mass of acid acceptor 1, and 6 parts by mass of acid acceptor 2 are added, Kneaded for minutes. The obtained composition was cooled for 24 hours, and a full compound was prepared at 30 to 80 ° C. again using an open roll equipped with two 8-inch rolls.

The obtained full compound was formed into an unvulcanized fluororubber sheet having a thickness of 3 mm by an 8-inch open roll.

This uncrosslinked fluororubber sheet was press-crosslinked with a mold at 160 ° C. for 20 minutes to obtain a crosslinked fluororubber sheet having a thickness of 2 mm.
About the obtained crosslinked fluororubber sheet, the area occupancy of the resin and the friction coefficient were measured.

Further, the obtained cross-linked fluororubber sheet was left to stand for 24 hours or 96 hours in a heating furnace maintained at 250 ° C. to perform heat treatment.
For the cross-linked fluororubber sheet after the heat treatment, the resin area occupancy and the friction coefficient were measured in the same manner. The results are shown in Table 2.

Examples 2-4, Comparative Examples 1-5
A crosslinked fluororubber sheet was prepared and evaluated in the same manner as in Example 1 except that the composition of the full compound, the kneading temperature, and the molding crosslinking conditions were as shown in Table 1.
When the fluororesin a, b, or e was used in the melt-kneading at the time of preparing the pre-compound, the material was taken out after kneading for another 5 minutes after the material temperature reached 180 ° C. When the fluororesin c or d was used, after the material temperature reached 200 ° C., the material was taken out after further kneading for 5 minutes.
Further, when the fluororesin a, b, c, or d was used at the time of forming and crosslinking the uncrosslinked rubber sheet, it was press-crosslinked at 160 ° C. for 20 minutes. When the fluororesin e was used, it was press-crosslinked at 160 ° C. for 40 minutes.

The crosslinkable fluororubber composition of the present invention can produce a fluororubber molded article excellent in low friction.

Claims (9)

A fluororubber (A) containing a vinylidene fluoride unit, a fluororesin (B), and a crosslinking agent (C);
The said fluororesin (B) consists of a copolymer containing an ethylene unit and a tetrafluoroethylene unit, and has a thermally stable group at the principal chain terminal, The crosslinkable fluororubber composition characterized by the above-mentioned. The crosslinkable fluororubber composition according to claim 1, wherein the fluororesin (B) further contains a hexafluoropropylene unit. The crosslinkable fluororubber according to claim 1 or 2, wherein a mass ratio (A) / (B) of the fluororubber (A) containing the vinylidene fluoride unit and the fluororesin (B) is 60/40 to 97/3. Composition. A fluororubber molded article obtained by crosslinking the crosslinkable fluororubber composition according to claim 1, 2 or 3. The fluororubber molded article according to claim 4, wherein the area occupation ratio of the fluororesin (B) is 5 to 100%. The fluororubber molded article according to claim 4 or 5, which is a sealing material. The fluororubber molded article according to claim 4, which is a sliding member. The fluororubber molded article according to claim 4 or 5, which is a non-adhesive member. The fluororubber molded article according to claim 4 or 5, wherein the surface has water and oil repellency.