Curable fluoroelastomer compositions and low-friction cured fluoroelastomers (fkM) formed therefrom

Abstract

The curable fluoroelastomer composition comprises a curable fluoroelastomer, a dehydrohalogenating agent, an acid scavenger comprising bismuth oxide present in the curable fluoroelastomer composition in an amount of at least 3 parts per 100 parts by weight of the curable fluoroelastomer, and at least one silicon-containing chemical present in the curable fluoroelastomer composition in an amount of at least 0.05 parts per 100 parts by weight of the curable fluoroelastomer. The cured fluoroelastomer cured from the curable fluoroelastomer composition has a static coefficient of friction and a dynamic coefficient of friction of less than 1.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 415,436, filed October 12, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] FIELD OF THE INVENTION The present disclosure relates to a composition and method for curing a fluoroelastomer, and to the cured fluoroelastomer. More specifically, the present disclosure relates to a curable fluoroelastomer composition comprising a curable fluoroelastomer, a dehydrohalogenation agent, an acid scavenger comprising bismuth oxide, and at least one silicon-containing chemical. [Background technology]

[0003] Low friction fluoroelastomer materials are desirable for many applications.

[0004] In automotive shaft seals, high friction between the fluoroelastomer shaft seal and the rotating shaft causes energy loss in combustion engines, so there is a demand for reducing the surface friction of the shaft seal to improve fuel efficiency.

[0005] In electric vehicle systems, the motor shaft rotates at high speed, which generates excessive frictional heat in the sealing material. Reducing surface friction is considered important in order to minimize heat generation and enable system designs involving high-speed motor rotation.

[0006] The application of low-friction coatings is one approach to reducing friction between the surfaces of rubber components, but this requires additional processing and cost, and the durability of the coating is often an issue.

[0007] A better approach to achieving low surface friction is through material composition rather than through the application of a coating. Summary of the Invention [Means for solving the problem]

[0008] The curable fluoroelastomer compositions disclosed herein provide cured fluoroelastomers with low friction, which can significantly contribute to improved energy efficiency and cost savings compared to conventional low-friction coating processes.

[0009] In one embodiment, the curable fluoroelastomer composition comprises a curable fluoroelastomer, a dehydrohalogenating agent, an acid scavenger comprising bismuth oxide (Bi2O3) present in the curable fluoroelastomer composition in an amount of at least 3 parts per hundred parts by weight of curable fluoroelastomer (phr), and at least one silicon-containing chemical present in the curable fluoroelastomer composition in an amount of at least 0.05 parts per hundred parts by weight of curable fluoroelastomer.

[0010] In one embodiment of the composition, bismuth oxide is present in the curable fluoroelastomer composition in an amount of 5 to 15 parts per 100 parts by weight of curable fluoroelastomer.

[0011] In another embodiment of the composition, the at least one silicon-containing chemical is present in the curable fluoroelastomer composition in an amount of 0.05 to 5 parts per 100 parts by weight of curable fluoroelastomer.

[0012] In another embodiment of the composition, the at least one silicon-containing chemical is selected from the group consisting of silicon dioxide, calcium silicate (Ca2SiO4), calcium metasilicate (CaSiO3), organosilicon, gamma-aminopropyltriethoxysilane, vinylethoxysilane, and combinations thereof.

[0013] In another embodiment of the composition, the dehydrohalogenating agent is present in the curable fluoroelastomer composition in an amount of at least 1.0 part per 100 parts by weight of curable fluoroelastomer.

[0014] In another embodiment of the composition, the dehydrohalogenating agent is selected from the group consisting of 2,2-bis(4-hydroxyphenyl)hexafluoropropane, methylhydroquinone, and 2-methylresorcinol.

[0015] In another embodiment of the composition, the curable fluoroelastomer comprises a peroxide-curable fluoroelastomer curable by a peroxide cure system, and the curable fluoroelastomer composition further comprises a peroxide curative.

[0016] In another embodiment of the composition, the curable fluoroelastomer composition contains less than 0.1 parts of magnesium oxide and calcium hydroxide in combination per 100 parts by weight of curable fluoroelastomer.

[0017] In another embodiment of the composition, the curable fluoroelastomer composition is free or substantially free of magnesium oxide and calcium hydroxide.

[0018] In another embodiment of the composition, the curable fluoroelastomer is a dipolymer of hexafluoropropylene and vinylidene fluoride.

[0019] In another embodiment, the cured fluoroelastomer cured from the curable fluoroelastomer composition comprises a curable fluoroelastomer, a dehydrohalogenating agent, an acid scavenger comprising bismuth oxide (Bi2O3) present in the curable fluoroelastomer composition in an amount of at least 3 parts per 100 parts by weight of curable fluoroelastomer, and at least one silicon-containing chemical present in the curable fluoroelastomer composition in an amount of at least 0.05 parts per 100 parts by weight of curable fluoroelastomer.

[0020] In one embodiment of the cured fluoroelastomer, the bismuth oxide is present in the curable fluoroelastomer composition in an amount of 5 to 15 parts per 100 parts by weight of curable fluoroelastomer.

[0021] In another embodiment of the cured fluoroelastomer, the at least one silicon-containing chemical is present in the curable fluoroelastomer composition in an amount of 0.05 to 5 parts per 100 parts by weight of curable fluoroelastomer.

[0022] In another embodiment of the cured fluoroelastomer, the at least one silicon-containing chemical is selected from the group consisting of silicon dioxide, calcium metasilicate (CaSiO), organosilicon, gamma-aminopropyltriethoxysilane, vinylethoxysilane, and combinations thereof.

[0023] In another embodiment of the cured fluoroelastomer, the dehydrohalogenating agent is present in the curable fluoroelastomer composition in an amount of at least 1.0 part per 100 parts by weight of curable fluoroelastomer.

[0024] In another embodiment of the cured fluoroelastomer, the dehydrohalogenating agent is selected from the group consisting of 2,2-bis(4-hydroxyphenyl)hexafluoropropane, methylhydroquinone, and 2-methylresorcinol.

[0025] In another embodiment of the cured fluoroelastomer, the curable fluoroelastomer comprises a peroxide-curable fluoroelastomer curable by a peroxide cure system, and the curable fluoroelastomer composition further comprises a peroxide curative.

[0026] In another embodiment of the cured fluoroelastomer, the curable fluoroelastomer composition contains less than 0.1 parts of magnesium oxide and calcium hydroxide in combination per 100 parts by weight of curable fluoroelastomer.

[0027] In another embodiment of the cured fluoroelastomer, the cured fluoroelastomer is free or substantially free of magnesium oxide and calcium hydroxide.

[0028] In another embodiment of the cured fluoroelastomer, the cured fluoroelastomer has a static coefficient of friction of less than 0.5.

[0029] In another embodiment of the cured fluoroelastomer, the cured fluoroelastomer has a static coefficient of friction of 0.2 to 0.4.

[0030] In another embodiment of the cured fluoroelastomer, the cured fluoroelastomer has a dynamic coefficient of friction of less than 0.5.

[0031] In another embodiment of the cured fluoroelastomer, the cured fluoroelastomer has a dynamic coefficient of friction of 0.15 to 0.4.

[0032] In another embodiment of the cured fluoroelastomer, the cured fluoroelastomer has a tensile strength of 9.0 to 25 MPa.

[0033] In another embodiment of the cured fluoroelastomer, the cured fluoroelastomer has an elongation at break of 150 to 200%.

[0034] In yet another embodiment, a method for curing a curable fluoroelastomer comprises forming a curable fluoroelastomer composition and heating the curable fluoroelastomer composition to a cure temperature to cure the curable fluoroelastomer. The curable fluoroelastomer composition comprises a curable fluoroelastomer, a dehydrohalogenating agent, an acid scavenger comprising bismuth oxide (Bi2O3) present in the curable fluoroelastomer composition in an amount of at least 3 parts by weight per 100 parts by weight of the curable fluoroelastomer, and at least one silicon-containing chemical present in the curable fluoroelastomer composition in an amount of at least 0.05 parts by weight per 100 parts by weight of the curable fluoroelastomer.

[0035] In one embodiment of the method, the heating step comprises press-curing the curable fluoroelastomer composition, the cure temperature being in the range of about 160 to about 190°C, and the cure time being in the range of about 5 to about 90 minutes.

[0036] In another embodiment of the method, the method further comprises post-curing the cured fluoroelastomer at a post-cure temperature for a post-cure time.

[0037] In another embodiment of the method, the post-cure temperature is in the range of about 200 to about 260° C., and the post-cure time is about 15 minutes or longer.

[0038] In another embodiment of the method, the bismuth oxide is present in the curable fluoroelastomer composition in an amount of 5 to 15 parts per 100 parts by weight of curable fluoroelastomer.

[0039] In another embodiment of the method, the at least one silicon-containing chemical is present in the curable fluoroelastomer composition in an amount of 0.05 to 5 parts per 100 parts by weight of curable fluoroelastomer.

[0040] In another embodiment of the method, the at least one silicon-containing chemical is selected from the group consisting of silicon dioxide, calcium silicate (Ca2SiO4), calcium metasilicate (CaSiO3), organosilicon, gamma-aminopropyltriethoxysilane, vinylethoxysilane, and combinations thereof.

[0041] In another embodiment of the method, the dehydrohalogenating agent is present in the curable fluoroelastomer composition in an amount of at least 1.0 part per 100 parts by weight of curable fluoroelastomer.

[0042] In another embodiment of the method, the dehydrohalogenating agent is selected from the group consisting of 2,2-bis(4-hydroxyphenyl)hexafluoropropane, methylhydroquinone, and 2-methylresorcinol.

[0043] In another embodiment of the method, the curable fluoroelastomer comprises a peroxide-curable fluoroelastomer curable by a peroxide cure system, and the curable fluoroelastomer composition further comprises a peroxide curative.

[0044] In another embodiment of the method, the curable fluoroelastomer composition contains less than 0.1 parts of magnesium oxide and calcium hydroxide in combination per 100 parts by weight of curable fluoroelastomer.

[0045] In another embodiment of the method, the cured fluoroelastomer is free or substantially free of magnesium oxide and calcium hydroxide.

[0046] In another embodiment of the method, the cured fluoroelastomer has a static coefficient of friction of less than 0.5.

[0047] In another embodiment of the method, the cured fluoroelastomer has a static coefficient of friction of 0.2 to 0.4.

[0048] In another embodiment of the method, the cured fluoroelastomer has a dynamic coefficient of friction of less than 0.5.

[0049] In another embodiment of the method, the cured fluoroelastomer has a dynamic coefficient of friction of 0.15 to 0.4.

[0050] Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0051] Exemplary curable fluoroelastomer compositions and exemplary cured fluoroelastomers are provided that include bismuth oxide and at least one silicon-containing chemical.

[0052] In exemplary embodiments, the compositions and methods provide low-friction cured fluoroelastomers that are free or substantially free of strong acid scavengers, including, but not limited to, magnesium oxide, calcium oxide, and calcium hydroxide.

[0053] As used herein, "silicon-containing chemical" or "Si-containing chemical" refers to any compound that contains silicon.

[0054] As used herein, a "low friction cured fluoroelastomer" refers to a cured fluoroelastomer having a static coefficient of friction of less than 1 and a dynamic coefficient of friction of less than 1. In an exemplary embodiment, the low friction cured fluoroelastomer has a static coefficient of friction of about 0.5 or less and a dynamic coefficient of friction of about 0.5 or less.

[0055] As used herein, "substantially free of strong acid scavengers" refers to a curable fluoroelastomer composition or a cured fluoroelastomer formed from a curable fluoroelastomer composition having less than 1 part strong acid scavenger per 100 parts by weight of curable fluoroelastomer (phr). Suitable amounts of strong acid scavenger in the curable fluoroelastomer composition can include, but are not limited to, less than 1 phr, less than 0.5 phr, less than 0.4 phr, less than 0.3 phr, less than 0.2 phr, less than 0.1 phr, less than 0.05 phr, or any value, range, or subrange therebetween.

[0056] In an exemplary embodiment, the curable fluoroelastomer composition comprises a curable fluoroelastomer, a dehydrohalogenating agent, an acid scavenger comprising bismuth oxide (Bi2O3) present in the curable fluoroelastomer composition in an amount of at least 3 phr, and at least one silicon-containing chemical present in the curable fluoroelastomer composition in an amount of at least 0.05 phr.

[0057] Suitable amounts of bismuth oxide in the curable fluoroelastomer composition can include, but are not limited to, 1.5 phr or more, 2 phr or more, 3 phr or more, 1.5 to 25 phr, 2 to 20 phr, 3 to 18 phr, 5 to 15 phr, or any value, range, or subrange therebetween.

[0058] Suitable amounts of silicon-containing chemicals can include, but are not limited to, at least 0.05 phr, at least 0.1 phr, at least 0.2 phr, 0.05-15 phr, 0.1-15 phr, 0.2-5 phr, or any value, range, or subrange therebetween.

[0059] Suitable silicon-containing chemicals may include, but are not limited to, silicon dioxide; calcium silicate (Ca2SiO4); calcium metasilicate (CaSiO3); organosilicones; gamma-aminopropyltriethoxysilane; vinylethoxysilane; talc; diatomaceous earth; wollastonite; metal silicates, including, but not limited to, calcium silicate, sodium silicate, borosilicate, lithium disilicate, and / or potassium silicate; water glass; soda-lime glass; borosilicate glass; Z-glass; E-glass; fritted glass; silica (including, but not limited to, fumed silica, pyrogenic silica, precipitated silica, and / or silica fume); and / or metallic silicon.

[0060] Suitable amounts of dehydrohalogenating agent can include, but are not limited to, at least 1.0 phr, 1.0 to 5 phr, at least 1.2 phr, 1.2 to 5 phr, 1.0 to 4 phr, or any value, range, or subrange therebetween.

[0061] Suitable dehydrohalogenating agents include 2,2-bis(4-hydroxyphenyl)hexafluoropropane (BpAF), methylhydroquinone, 2-methylresorcinol, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)perfluoropropane, resorcinol, 1,3-dihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxystilbene, 2,6-dihydroxyphenyl, 4,4'-dihydroxystilbene, 4,4' ... These may include, but are not limited to, hydroxyanthracene, hydroquinone, catechol, 2,2-bis(4-hydroxyphenyl)butane, 4,4-bis(4-hydroxyphenyl)valeric acid, 2,2-bis(4-hydroxyphenyl)tetrafluorodichloropropane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ketone, tri(4-hydroxyphenyl)methane, 3,3',5,5'-tetrachlorobisphenol A, and / or 3,3',5,5'-tetrabromobisphenol A.

[0062] In some embodiments, the curable fluoroelastomer includes a polyhydroxy-curable fluoroelastomer that can be cured with a polyhydroxy curative. As used herein, "polyhydroxy-curable" refers to a fluoroelastomer known to crosslink with a polyhydroxy curative, such as BpAF. Such fluoroelastomers include, but are not limited to, those with multiple carbon-carbon double bonds along the elastomeric polymer backbone and those containing sites that can be readily dehydrofluorinated. The latter fluoroelastomers include, but are not limited to, those containing adjacent copolymerized units of vinylidene fluoride (VF2) and hexafluoropropylene (HFP), and those containing adjacent copolymerized units of VF2 (or tetrafluoroethylene) and a fluorinated comonomer having an acidic hydrogen atom (e.g., 2-hydropentafluoropropylene, 1-hydropentafluoropropylene, trifluoroethylene, 2,3,3,3-tetrafluoropropene, or 3,3,3-trifluoropropene). Preferred fluoroelastomers include i) copolymers of vinylidene fluoride with hexafluoropropylene and optionally tetrafluoroethylene (TFE), ii) copolymers of vinylidene fluoride with perfluoro(alkyl vinyl ethers), such as perfluoro(methyl vinyl ether), 2-hydropentafluoropropylene, and optionally tetrafluoroethylene, iii) copolymers of tetrafluoroethylene with propylene and 3,3,3-trifluoropropene, iv) copolymers of tetrafluoroethylene, perfluoro(methyl vinyl ether) and hexafluoro-2-(pentafluorophenoxy)-1-(trifluorovinyloxy)propane, and v) copolymers of ethylene with tetrafluoroethylene, perfluoro(methyl vinyl ether) and 3,3,3-trifluoropropylene. In some embodiments, the polyhydroxy-curable fluoroelastomer is a dipolymer of hexafluoropropylene and vinylidene fluoride. The polyhydroxy curable fluoroelastomer may also include an iodine-, bromine-, or chlorine-containing elastomer.For example, small amounts (0.01-1 wt%) of chlorine, bromine, or iodine can be introduced with a telogen such as CH2I2 or I(CF2)4I, or a monomer such as CH2=CHCF2CF2X (X=Br, I) or chlorotrifluoroethylene. In some embodiments, the polyhydroxy curable fluoroelastomer is, for example, a bisolefin, such as CH2=CH(CF2). n CH=CH2 (wherein n=2 to 8) or CF2=CFO(CF2) n Contains OCF=CF2 (wherein n=2 to 8).

[0063] In some embodiments, the curable fluoroelastomer is a dipolymer of hexafluoropropylene and vinylidene fluoride.

[0064] In some embodiments, the curable fluoroelastomer comprises a peroxide-curable fluoroelastomer curable by a peroxide cure system, and the curable fluoroelastomer composition further comprises a peroxide curative.

[0065] In some embodiments, the curable composition includes one or more additives. Suitable additives may include, but are not limited to, fillers, processing aids, accelerators, weak acid scavengers, peroxides, and / or colorants.

[0066] The filler may be one or more inorganic fillers, one or more polymeric fillers, or a combination thereof. Suitable inorganic fillers may include, but are not limited to, medium-temperature carbon black, silica, talc, titanium dioxide (TiO), barium sulfate (BaSO), and / or calcium carbonate (CaCO). Suitable polymeric fillers may include, but are not limited to, polytetrafluoroethylene (PTFE).

[0067] Suitable amounts of filler can include, but are not limited to, about 10 to about 40 phr, about 20 to about 40 phr, about 25 to about 35 phr, about 30 phr, or any value, range, or subrange therebetween.

[0068] Suitable amounts of processing aids can include, but are not limited to, about 0.1 to about 2 phr, about 0.2 to about 2 phr, about 0.5 to about 1.5 phr, about 1 phr, or any value, range, or subrange therebetween.

[0069] Suitable promoters include tertiary sulfonium salts, such as [(C6H5)2S + (C6H 13 )][Cl] - , and [(CH 13 )2S(C6H5)] + [CH3CO2] - , as well as quaternary ammonium salts of the formula R5R6R7R8Y + X - wherein Y is phosphorus, nitrogen, arsenic, or antimony; and R5, R6, R7, and R8 are each independently selected from the group consisting of C1-C 20 alkyl, aryl, aralkyl, alkenyl, and their chlorine, fluorine, bromine, cyano, -OR, and -COOR substituted analogs, where R is C1-C 20 alkyl, aryl, aralkyl, alkenyl, and X is halide, hydroxide, sulfate, sulfite, carbonate, pentachlorothiophenolate, tetrafluoroborate, hexafluorosilicate, hexafluorophosphate, dimethylphosphate, and C1-C 20Alkyl, aryl, aralkyl, and alkenyl carboxylates and dicarboxylates. Particularly preferred are benzyltriphenylphosphonium chloride, benzyltriphenylphosphonium bromide, tetrabutylammonium hydrogen sulfate, tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium bromide, tributylallylphosphonium chloride, tributyl-2-methoxypropylphosphonium chloride, 1,8-diazabicyclo[5.4.0]undec-7-ene, and benzyldiphenyl(dimethylamino)phosphonium chloride. Other suitable cure accelerators include methyltrioctylammonium chloride, methyltributylammonium chloride, tetrapropylammonium chloride, benzyltrioctylphosphonium bromide, benzyltrioctylphosphonium chloride, methyltrioctylphosphonium acetate, tetraoctylphosphonium bromide, methyltriphenylarsonium tetrafluoroborate, tetraphenylstibonium bromide, 4-chlorobenzyltriphenylphosphonium chloride, 8-benzyl-1 ,8-diazabicyclo(5.4.0)-7-undecenium chloride, diphenylmethyltriphenylphosphonium chloride, allyltriphenyl-phosphonium chloride, tetrabutylphosphonium bromide, m-trifluoromethyl-benzyltrioctylphosphonium chloride, and other quaternary compounds disclosed in U.S. Pat. Nos. 5,591,804, 4,912,171, 4,882,390, 4,259,463, 4,250,278, and 3,876,654.

[0070] In some embodiments, the curable fluoroelastomer is a peroxide-curable fluoroelastomer and the curable fluoroelastomer composition is a peroxide-curable fluoroelastomer composition further comprising a peroxide curative.

[0071] Suitable peroxide curing agents may include, but are not limited to, triallyl isocyanurate (TAIC), 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)-hexyne-3, benzoyl peroxide, t-butylperoxybenzene, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, and / or t-butylperoxybenzoate.

[0072] Suitable amounts of peroxide curing agent in the peroxide-curable fluoroelastomer composition can include, but are not limited to, about 3.0 to about 5.0 phr, about 3.2 to about 4.8 phr, about 3.4 to about 4.6 phr, about 3.6 to about 4.4 phr, about 3.8 to about 4.2 phr, about 4 phr, or any value, range, or subrange therebetween.

[0073] Suitable weak acid scavengers may include, but are not limited to, zinc oxide, lead oxide, and / or hydrotalcite.

[0074] Suitable amounts of weak acid scavenger can include, but are not limited to, about 1 phr or less, about 0.1 to about 1 phr, about 0.2 to about 0.8 phr, about 0.5 phr or less, about 0.2 to about 0.5 phr, or any value, range, or subrange therebetween.

[0075] In some embodiments, the curable fluoroelastomer composition contains less than 1.0 phr, for example less than 0.1 phr, of magnesium oxide and calcium hydroxide in combination, hi some embodiments, the curable fluoroelastomer composition is free or substantially free of magnesium oxide and calcium hydroxide.

[0076] In some embodiments, the cured fluoroelastomer cured from the curable fluoroelastomer composition comprises a curable fluoroelastomer, a dehydrohalogenating agent, an acid scavenger comprising bismuth oxide (Bi2O3) present in the curable fluoroelastomer composition in an amount of at least 3 parts per 100 parts by weight of curable fluoroelastomer, and at least one silicon-containing chemical present in the curable fluoroelastomer composition in an amount of at least 0.05 parts per 100 parts by weight of curable fluoroelastomer.

[0077] In some embodiments, the cured fluoroelastomer has a static coefficient of friction of less than 0.5, such as from 0.2 to 0.4.

[0078] In some embodiments, the cured fluoroelastomer has a dynamic coefficient of friction of less than 0.5, such as from 0.15 to 0.4.

[0079] In some embodiments, the cured fluoroelastomer has a tensile strength of from 9.0 to 25 MPa.

[0080] In some embodiments, the cured fluoroelastomer has an elongation at break of 150 to 200%.

[0081] In some embodiments, a method for curing a curable fluoroelastomer includes forming a curable fluoroelastomer composition and heating the curable fluoroelastomer composition to a cure temperature to cure the curable fluoroelastomer. The curable fluoroelastomer composition includes a curable fluoroelastomer, a dehydrohalogenating agent, an acid scavenger comprising bismuth oxide (Bi2O3) present in the curable fluoroelastomer composition in an amount of at least 3 parts by weight per 100 parts by weight of the curable fluoroelastomer, and at least one silicon-containing chemical present in the curable fluoroelastomer composition in an amount of at least 0.05 parts by weight per 100 parts by weight of the curable fluoroelastomer.

[0082] In some embodiments, the curable fluoroelastomer composition is cured under conventional curing conditions.

[0083] In some embodiments, the heating comprises press hardening.

[0084] Suitable curing temperatures for heating can include, but are not limited to, about 160 to about 190°C, about 165 to about 185°C, about 170 to about 180°C, about 170°C, about 180°C, or any value, range, or subrange therebetween.

[0085] Suitable curing times for heating may depend on the curing temperature, but may include, but are not limited to, about 5 minutes to about 90 minutes, about 5 minutes to about 60 minutes, about 5 minutes to about 40 minutes, about 10 minutes to about 30 minutes, about 5 minutes to about 20 minutes, or any value, range, or subrange therebetween.

[0086] In some embodiments, the method further comprises post-curing the cured fluoroelastomer at a post-cure temperature for a post-cure period.

[0087] Suitable post-cure temperatures can include, but are not limited to, about 200 to about 260°C, about 210 to about 250°C, about 220 to about 240°C, about 225 to about 235°C, about 230°C, or any value, range, or subrange therebetween.

[0088] Suitable post-cure times may depend on the post-cure temperature, but may include, but are not limited to, about 15 minutes or more, about 15 minutes to about 24 hours, about 15 minutes to about 16 hours, about 15 minutes to about 8 hours, about 15 minutes to about 4 hours, about 15 minutes to about 2 hours, about 15 minutes to about 1 hour, or any value, range, or subrange therebetween.

[0089] Without wishing to be bound by theory, it is believed that the availability of hydrogen fluoride (HF) leads to the formation of a low-friction layer on the cured fluoroelastomer of the present invention by reaction of HF with Si-containing chemicals, forming a low-friction layer of orthosilicic acid (Si(OH)4) on the surface of the cured fluoroelastomer. The curing reaction in polyhydroxyl curing systems such as BpAF produces HF, but strong acid scavengers such as magnesium oxide and calcium hydroxide scavenge the HF, thereby preventing it from reacting with Si-containing chemicals. It is believed that bismuth oxide as an acid scavenger allows the curing process to proceed while leaving some HF available to react with Si-containing chemicals.

[0090] In contrast, a pure peroxide cure system does not generate HF to react with the Si-containing chemical to produce a low friction surface layer, but it is believed that some BpAF may be included as a dehydrohalogenating agent to generate some HF for the formation of a low friction surface layer in the presence of bismuth oxide and the Si-containing chemical (and possibly in the absence of bismuth oxide).

[0091] Test Method Coefficient of static and dynamic friction The static and dynamic coefficients of friction were measured on a Shimadzu Autograph AGS-5kNX tester, and values ​​were calculated by pulling a stainless steel reference material over the test fluoroelastomer cured sheet sample at a rate of 100 mm / min.

[0092] Tensile strength and elongation at break Tensile strength (MPa) and elongation at break (%) were determined at 23°C for unaged cured fluoroelastomers according to ISO37:2011 test protocol. [Example]

[0093] Fluoroelastomer Curing Comparative Example Comparative fluoroelastomer cure compositions included a curable fluoroelastomer, 30 parts by weight per 100 parts of curable fluoroelastomer (phr) of carbon black filler, and a dehydrohalogenating agent and an acid scavenger in the amounts shown in Tables 1 through 4. Certain comparative fluoroelastomer cure compositions further included accelerators, Si-containing chemicals, and / or processing aids, as shown in phr in Tables 1 through 4.

[0094] Fluoroelastomer Curing Examples of the Invention The inventive fluoroelastomer cure compositions contained a curable fluoroelastomer, 30 phr of carbon black filler, and a dehydrohalogenating agent, a Bi2O3 acid scavenger, and a Si-containing chemical in the amounts shown in Tables 1-4, except that inventive Example 10 contained only 5 phr of carbon black filler, with some of the Si-containing chemicals listed in the tables also functioning as filler. Certain inventive fluoroelastomer cure compositions further contained accelerators, processing aids, and / or additional acid scavengers, as shown in phr in Tables 1-4.

[0095] Fluoroelastomer cure results and cure characteristics The fluoroelastomer cured compositions were press cured at a press cure temperature ranging from 170-180°C for a press cure time ranging from 7-60 minutes. The cured fluoroelastomers were then post-cured at a post-cure temperature of 230°C for a post-cure time ranging from 30 minutes to 24 hours, except for Comparative Example 7, which was not cured, and Comparative Example 8, which was not post-cured.

[0096] Effect of Acid Scavenger and Si-Containing Chemicals on Friction Properties Table 1 shows that the combined presence of bismuth oxide and silicon-containing chemicals in a curable fluoroelastomer composition produces a cured fluoroelastomer with low friction.

[0097] In inventive Examples 1-8, various types and amounts of Si-containing chemicals, in combination with bismuth oxide as the sole acid scavenger, produced cured fluoroelastomers with static coefficients ranging from 0.18 to 0.34 and dynamic coefficients ranging from 0.16 to 0.32. The Si-containing chemicals in inventive Examples 1-8 were silicon dioxide (1.1), sodium salt of silicic acid (1), silicon dioxide (2), silicon dioxide (3), silicon dioxide (4), silicon dioxide (5), γ-aminopropyltriethoxysilane (6), vinyltriethoxysilane (7), a combination of organosilicon and silicon dioxide (8), and wollastonite (9), respectively.

[0098] Inventive Example 9 demonstrates that the additional inclusion of a small amount of a weak acid scavenger (zinc oxide) does not adversely affect the frictional properties of the resulting cured fluoroelastomer.

[0099] [Table 1]

[0100] Comparative Example 1 shows that bismuth oxide as an acid scavenger does not provide a low friction cured fluoroelastomer in the absence of a Si-containing chemical.

[0101] Comparative Examples 2 and 3 show that replacing bismuth oxide with a standard acid scavenger combination of 3 phr magnesium oxide and 6 phr calcium hydroxide, both strong acid scavengers, does not provide low-friction cured fluoroelastomers, either in the absence or presence of Si-containing chemicals.

[0102] Finally, Comparative Examples 4 and 5 show that the presence of as little as 1 phr of magnesium oxide or calcium hydroxide destroys the ability of the combination of bismuth oxide and Si-containing chemicals to provide low-friction cured fluoroelastomers. Comparative Example 1.1 shows that a relatively small amount (0.01 phr) of Si-containing chemicals results in relatively poor friction properties in the resulting cured fluoroelastomers.

[0103] Effect of dehydrohalogenation agent and amount of Bi2O3 on friction properties Inventive Example 10 in Table 2 shows that even a low amount of 1.28 phr of BpAF dehydrohalogenating agent was sufficient to produce a low-friction cured fluoroelastomer, while the 0.96 phr of BpAF in Comparative Example 6 was insufficient for that purpose. As alternative dehydrohalogenating agents in place of BpAF, the compositions of Inventive Examples 11 and 12 contained methyl-hydroquinone and 2-methylresorcinol, respectively, at 1.12 phr, and both compositions were able to provide low-friction cured fluoroelastomers.

[0104] [Table 2]

[0105] Inventive Example 13 shows that as little as 5 phr of Bi2O3 was sufficient to produce a low friction cured fluoroelastomer, while 1 phr of bismuth oxide in Comparative Example 7 failed to cure.

[0106] Effect of post-curing on friction properties Table 3 shows that the composition of Comparative Example 8 without post-cure did not achieve a low friction cured fluoroelastomer.

[0107] [Table 3]

[0108] Inventive Examples 14-16 had the same composition as Comparative Example 8 but were post-cured at 230°C for the times shown in Table 3. A post-cure time of only 30 minutes at 230°C was sufficient to produce a low-friction cured fluoroelastomer, and increasing the post-cure time to 24 hours did not further decrease the coefficient of friction.

[0109] Effect of curable fluoroelastomers on friction properties Table 4 shows that peroxide (PO)-curable fluoroelastomer compositions can also be cured to low-friction cured fluoroelastomers by including appropriate amounts of bismuth oxide and Si-containing chemicals in the compositions. Examples 17, 18, and 19 of the present invention contained different PO-curable fluoroelastomers with 66% F, 68% F, and 64% F, respectively. The compositions in Table 4 also contained 1.5 phr of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and 2.5 phr of triallyl isocyanurate (TAIC) as peroxide curing agents.

[0110] [Table 4]

[0111] In contrast, Comparative Example 9 contained no bismuth oxide and Comparative Example 10 contained no Si-containing chemicals, and both compositions did not produce low-friction cured fluoroelastomers.

[0112] Tensile strength and elongation at break were measured (data not shown) for the peroxide-curable compositions of Table 4. While the inventive examples of Table 4 had advantageous, low friction properties, they also had lower tensile strength and lower elongation at break than the comparative examples of Table 4, which was not observed with the polyhydroxy-curable fluoroelastomers.

[0113] In addition to the different PO-curable fluoroelastomers in Table 4, compositions containing different BpAF-curable fluoroelastomers with Bi2O3 and Si-containing chemicals and varying F contents over the range of 66% to 70% were tested and produced low-friction cured fluoroelastomers (data not shown).

[0114] All of the above references are incorporated herein by reference.

[0115] While the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the invention. It should be understood that many modifications can be made to adapt a particular situation or material to the teachings of the invention without departing from essential scope thereof. Therefore, it is not intended that the invention be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but rather, the invention is intended to include all embodiments falling within the scope of the appended claims.

Claims

1. A curable fluoroelastomer composition, Curable fluoroelastomer and Dehalogenating agent and At least 3 parts by weight of the curable fluoroelastomer, in amounts of bismuth oxide (Bi) present in the curable fluoroelastomer composition. 2 O 3 ) containing an acid scavenger, At least 0.05 parts per 100 parts by weight of the curable fluoroelastomer, at least one silicon-containing chemical substance present in the curable fluoroelastomer composition, A curable fluoroelastomer composition containing the following:

2. The curable fluoroelastomer composition according to claim 1, wherein the bismuth oxide is present in the curable fluoroelastomer composition in an amount of 5 to 15 parts per 100 parts by weight of the curable fluoroelastomer.

3. The curable fluoroelastomer composition according to claim 1, wherein the at least one silicon-containing chemical substance is present in the curable fluoroelastomer composition in an amount of 0.05 to 5 parts per 100 parts by weight of the curable fluoroelastomer.

4. The aforementioned at least one silicon-containing chemical substance is silicon dioxide, calcium silicate (Ca 2 SiO 4 ), calcium metasilicate (CaSiO 3 A curable fluoroelastomer composition according to claim 1, selected from the group consisting of ), organosilicone, γ-aminopropyltriethoxysilane, vinylethoxysilane, and combinations thereof.

5. The curable fluoroelastomer composition according to claim 1, wherein the dehalogenating agent is present in the curable fluoroelastomer composition in an amount of at least 1.0 part per 100 parts by weight of the curable fluoroelastomer.

6. The curable fluoroelastomer composition according to claim 1, wherein the dehalogenating agent is selected from the group consisting of 2,2-bis(4-hydroxyphenyl)hexafluoropropane, methylhydroquinone, and 2-methylresorcinol.

7. The curable fluoroelastomer composition according to claim 1, wherein the curable fluoroelastomer includes a peroxide-curable fluoroelastomer that can be cured by a peroxide curing system, and the curable fluoroelastomer composition further includes a peroxide curing agent.

8. The curable fluoroelastomer composition according to claim 1, wherein the curable fluoroelastomer composition contains a combination of less than 0.1 parts by weight of magnesium oxide and calcium hydroxide per 100 parts by weight of the curable fluoroelastomer.

9. The curable fluoroelastomer composition according to claim 1, wherein the curable fluoroelastomer composition does not contain or substantially contains magnesium oxide and calcium hydroxide.

10. The curable fluoroelastomer composition according to claim 1, wherein the curable fluoroelastomer is a dipolymer of hexafluoropropylene and vinylidene fluoride.

11. A cured fluoroelastomer cured from a curable fluoroelastomer composition, wherein the curable fluoroelastomer composition Curable fluoroelastomer and Dehalogenating agent and At least 3 parts by weight of the curable fluoroelastomer, in amounts of bismuth oxide (Bi) present in the curable fluoroelastomer composition. 2 O 3 ) containing an acid scavenger, At least 0.05 parts per 100 parts by weight of the curable fluoroelastomer, at least one silicon-containing chemical substance present in the curable fluoroelastomer composition, A cured fluoroelastomer containing [a specific component].

12. The cured fluoroelastomer according to claim 11, wherein the bismuth oxide is present in the cured fluoroelastomer composition in an amount of 5 to 15 parts per 100 parts by weight of the curable fluoroelastomer.

13. The cured fluoroelastomer according to claim 11, wherein the at least one silicon-containing chemical substance is present in the cured fluoroelastomer composition in an amount of 0.05 to 5 parts per 100 parts by weight of the curable fluoroelastomer.

14. The at least one silicon-containing chemical substance is selected from the group consisting of silicon dioxide, calcium silicate (Ca 2 SiO 4 ), calcium metasilicate (CaSiO 3 ), organosilicon, γ-aminopropyltriethoxysilane, vinyl ethoxysilane, and combinations thereof, the cured fluoroelastomer according to claim 11.

15. The cured fluoroelastomer according to claim 11, wherein the dehalogenating agent is present in the cured fluoroelastomer composition in an amount of at least 1.0 part by weight per 100 parts by weight of the cured fluoroelastomer.

16. The cured fluoroelastomer according to claim 11, wherein the dehalogenating agent is selected from the group consisting of 2,2-bis(4-hydroxyphenyl)hexafluoropropane, methylhydroquinone, and 2-methylresorcinol.

17. The curable fluoroelastomer according to claim 11, wherein the curable fluoroelastomer comprises a peroxide-curable fluoroelastomer that can be cured by a peroxide curing system, and the cured fluoroelastomer further comprises a peroxide curing agent.

18. The curable fluoroelastomer according to claim 11, wherein the curable fluoroelastomer composition contains a combination of less than 0.1 parts by weight of magnesium oxide and calcium hydroxide per 100 parts by weight of the curable fluoroelastomer.

19. The cured fluoroelastomer according to claim 11, wherein the cured fluoroelastomer does not contain or substantially contains magnesium oxide and calcium hydroxide.

20. The cured fluoroelastomer according to claim 11, wherein the cured fluoroelastomer has a static friction coefficient of less than 0.

5.

21. The cured fluoroelastomer according to claim 11, wherein the cured fluoroelastomer has a static friction coefficient of 0.2 to 0.

4.

22. The cured fluoroelastomer according to claim 11, wherein the cured fluoroelastomer has a coefficient of dynamic friction of less than 0.

5.

23. The cured fluoroelastomer according to claim 11, wherein the cured fluoroelastomer has a dynamic friction coefficient of 0.15 to 0.

4.

24. The cured fluoroelastomer according to claim 11, wherein the cured fluoroelastomer has a tensile strength of 9.0 to 25 MPa.

25. The cured fluoroelastomer according to claim 11, wherein the cured fluoroelastomer has an elongation at break of 150 to 200%.

26. A method for curing a curable fluoroelastomer, A step of forming a curable fluoroelastomer composition, wherein the curable fluoroelastomer composition comprises the curable fluoroelastomer, a dehalogenating agent, and bismuth oxide (Bi) present in the curable fluoroelastomer composition in an amount of at least 3 parts per 100 parts by weight of the curable fluoroelastomer. 2 O 3 A step comprising: an acid scavenger containing ) and at least one silicon-containing chemical substance present in the curable fluoroelastomer composition in an amount of at least 0.05 parts per 100 parts by weight of the curable fluoroelastomer; The process involves heating the curable fluoroelastomer composition to a curing temperature over a curing time to form a cured fluoroelastomer, Methods that include...

27. The method according to claim 26, wherein the heating step includes a step of press-curing the curable fluoroelastomer composition, the curing temperature is in the range of about 160 to about 190°C, and the curing time is in the range of about 5 minutes to about 90 minutes.

28. The method according to claim 26, further comprising the step of post-curing the cured fluoroelastomer at a post-curing temperature for a post-curing time.

29. The method according to claim 28, wherein the post-curing temperature is in the range of approximately 200 to approximately 260°C, and the post-curing time is approximately 15 minutes or more.

30. The method according to claim 26, wherein the bismuth oxide is present in the curable fluoroelastomer composition in an amount of 5 to 15 parts per 100 parts by weight of the curable fluoroelastomer.

31. The method according to claim 26, wherein the at least one silicon-containing chemical substance is present in the curable fluoroelastomer composition in an amount of 0.05 to 5 parts per 100 parts by weight of the curable fluoroelastomer.

32. The aforementioned at least one silicon-containing chemical substance is silicon dioxide, calcium silicate (Ca 2 SiO 4 ), calcium metasilicate (CaSiO 3 The method according to claim 26, selected from the group consisting of organosilicone, γ-aminopropyltriethoxysilane, vinylethoxysilane, and combinations thereof.

33. The method according to claim 26, wherein the dehalogenating agent is present in the curable fluoroelastomer composition in an amount of at least 1.0 part per 100 parts by weight of the curable fluoroelastomer.

34. The method according to claim 26, wherein the dehalogenating agent is selected from the group consisting of 2,2-bis(4-hydroxyphenyl)hexafluoropropane, methylhydroquinone, and 2-methylresorcinol.

35. The method according to any one of claims 26 to 34, wherein the curable fluoroelastomer includes a peroxide-curable fluoroelastomer that can be cured by a peroxide curing system, and the curable fluoroelastomer composition further includes a peroxide curing agent.

36. The method according to claim 26, wherein the curable fluoroelastomer composition contains a combination of less than 0.1 parts by weight of magnesium oxide and calcium hydroxide per 100 parts by weight of the curable fluoroelastomer.

37. The method according to claim 26, wherein the cured fluoroelastomer does not contain or substantially contains magnesium oxide and calcium hydroxide.

38. The method according to claim 26, wherein the cured fluoroelastomer has a static friction coefficient of less than 0.

5.

39. The method according to claim 26, wherein the cured fluoroelastomer has a static friction coefficient of 0.2 to 0.

4.

40. The method according to claim 26, wherein the cured fluoroelastomer has a coefficient of dynamic friction of less than 0.

5.

41. The method according to claim 26, wherein the cured fluoroelastomer has a dynamic friction coefficient of 0.15 to 0.4.