FUKUSHI TATSUO (US)
| WO2014179432A1 | 2014-11-06 |
| JP2019085475A | 2019-06-06 | |||
| EP2416488A1 | 2012-02-08 | |||
| US5225504A | 1993-07-06 |
| What is claimed is: 1. A curable, conductive fluoropolymer composition comprising: (a) partially fluorinated amorphous polymer comprising at least one of an iodine, a bromine, and a nitrile cure site; (b) an ionic liquid comprising a cationic portion and an anionic portion; (c) a peroxide; (d) a crosslinking agent; and (e) conductive particles having a surface area of less than 500 m2/g; wherein if cured to provide a cured composition, the cured composition has a volume resistivity of less than 1 x 104 Ohms*cm and a Duro A hardness of less than 80. 2. The curable, conductive fluoropolymer composition of claim 1, wherein the conductive particles comprise as least one of: elemental carbon, carbon black, acetylene black, graphite, graphene, graphitized carbon, carbon nanotubes, TKK F-type carbon, P-type carbon, graphitized Vulcan, and graphitized carbon. 3. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the cured elastomer has a Duro A hardness of at least 10. 4. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the cured elastomer has a Duro A hardness of at most 60. 5. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the cured elastomer has a volume resistivity of less than 1 x 103 Ohms*cm. 6. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the ionic liquid has a boiling point greater than 300°C. 7. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the cation portion of the ionic liquid is selected from N-ethyl-N’-methylimidazolium N -methyl-N -propylpiperidinium, N,N,N -trimethyl-N -propylammonium, N -methyl -N,N,N - tripropylammonium, N,N,N-trimethyl-N-butylammoniuim, N,N,N-trimethyl-N- methoxyethylammonium, N-methyl-N,N,N-tris(methoxyethyl)ammonium, N-methyl-N,N,N- tributylammonium, N,N,N-trimethyl-N-hexylammonium, N,N-diethyl-N-methyl-N-(2- methoxyethyl)ammonium, 1 -propyl -tetrahydrothiophenium, 1 -butyl -tetrahydrothiophenium, glycidyltrimethylammonium, N-ethyl-N-methylmorphonium, N,N,N-trioctylammonium, N- methyl-N,N,N-trioctylammonium, N-methyl-N,N,N -tributylammonium, N,N-dimethyl-N- octyl-N-(2-hydroxyethyl)ammonium, and a combination thereof. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the anion portion of the ionic liquid is selected from bis(trifluoromethanesulfonyl) imide, bis(pentafluoroethanesulfonyl)imide, bis(heptafluoropropanesulfonyl)imide, bis(nonafluorobutanesulfonyl)imide, trifluoromethanesulfonate, pentafluoroethanesulfonate, heptafluoropropane sulfonate, nonafluorobutane sulfonate , tris(trifhioromethanesulfonyl)methide, tris(pentafluoroethanesulfonyl)methide, tris(heptafluoropropanesulfonyl)methide, tris(nonafluorobutanesulfonyl)methide, and a combination thereof. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the curable, conductive fluoropolymer composition comprises at least 10 wt % and at most 80 wt % of the ionic liquid. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the ionic liquid substantially solubilizes the partially fluorinated amorphous polymer. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the curable, conductive fluoropolymer composition comprises 20-90 % by weight of the partially fluorinated amorphous polymer. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the partially fluorinated amorphous polymer comprises 0-35 wt % TFE; 25-65 wt % VDF; 16-65 wt % HFP. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the peroxide comprises at least one of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane; dicumyl peroxide; di(2-t-butylperoxyisopropyl)benzene; dialkyl peroxide; bis (dialkyl peroxide); 2,5-dimethyl-2,5-di(tertiarybutylperoxy)3-hexyne; dibenzoyl peroxide; 2,4- dichlorobenzoyl peroxide; tertiarybutyl perbenzoate; a,a’-bis(t-butylperoxy- diisopropylbenzene); t-butyl peroxy isopropylcarbonate, t-butyl peroxy 2-ethylhexyl carbonate, t-amyl peroxy 2-ethylhexyl carbonate, t-hexylperoxy isopropyl carbonate, di[ 1 ,3- dimethyl-3-(t-butylperoxy)butyl] carbonate, carbonoperoxoic acid, and O,O'-l,3-propanediyl OO, OO'-bis( 1,1 -dimethylethyl) ester. 14. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the crosslinking agent is selected from at least one of crosslinker is tri(methyl)allyl isocyanurate, triallyl isocyanurate, tri(methyl)allyl cyanurate, poly-triallyl isocyanurate, xylylene-bis(diallyl isocyanurate), N,N'-m-phenylene bismaleimide, diallyl phthalate, tris(diallylamine)-s-triazine, triallyl phosphite, 1,2-polybutadiene, ethylene glycol diacrylate, diethylene glycol diacrylate, or CH2=CH-Rfi-CH=CH2 wherein Rn is a perfluoroalkylene having from 1 to 8 carbon atoms. 15. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein composition further comprises at least one of a pigment, silica, magnesium oxide, titanium oxide, alumina, aluminum nitride, and boron nitride. 16. The curable, conductive fluoropolymer composition of any one of the previous claims, wherein the curable, conductive fluoropolymer composition is dispensable. 17. A cured composition derived from the curable, conductive fluoropolymer composition according to any one of claims 1-16. 18. A method comprising (i) combining (a) a partially fluorinated amorphous polymer comprising at least one of an iodine, a bromine, and a nitrile cure site; (b) an ionic liquid; (c) a peroxide; (d) a crosslinking agent; and (e) conductive particles having a surface area of less than 500 m2/g to form a curable composition; and -19- (ii) curing the curable composition to form the conductive fluoroelastomeric composition, wherein the conductive fluoroelastomeric composition has a volume resistivity of less than 1 x 104 Ohms*cm and a Duro A hardness of less than 80. 19. The use of an ionic liquid to reduce resistivity and hardening in a conductive fluoroelastomeric composition. -20- |
TECHNICAL FIELD
[0001] The present disclosure relates to a conductive composition comprising a partially fluorinated amorphous polymer in an ionic liquid. Methods of making an article using the composition are disclosed herein.
SUMMARY
[0002] Due to their elasticity and inertness to chemical reactivity, heat, or both, fluoropolymeric elastomers are useful in making articles such as seals, gaskets, o-rings, and hoses. However, the use of fluoroelastomers in conductive applications is limited because of the high resistivity and hardness of fluoroelastomers.
[0003] Thus, there is a desire to identify conductive fluoroelastomeric compositions, which have a lower resistivity and lower hardness to enable a broader range of applications.
[0004] In one aspect, a curable, conductive composition is disclosed. The curable, conductive fluoropolymer composition comprises:
(a) a partially fluorinated amorphous polymer comprising at least one of an iodine, a bromine, and a nitrile cure site;
(b) an ionic liquid;
(c) a peroxide;
(d) a crosslinking agent; and
(e) conductive particles having a surface area of less than 500 m 2 /g; wherein if cured to provide a cured composition, the cured composition has a volume resistivity of less than 1 x 10 4 Ohms*cm and a Duro A hardness of less than 80.
[0005] In one aspect, a method of making a conductive fluoroelastomeric composition is disclosed. The method comprising
(i) combining
(a) a partially fluorinated amorphous polymer comprising at least one of an iodine, a bromine, and a nitrile cure site;
(b) an ionic liquid;
(c) a peroxide;
(d) a crosslinking agent; and
(e) conductive particles having a surface area of less than 500 m 2 /g to form a curable composition; and (ii) curing the curable composition to form the conductive fluoroelastomeric composition, wherein the conductive fluoroelastomeric composition has a volume resistivity of less than 1 x 10 4 Ohms*cm and a Duro A hardness of less than 80.
[0006] In another aspect, the use of an ionic liquid to reduce resistivity and hardening in a conductive fluoroelastomeric composition is disclosed.
[0007] The above summary is not intended to describe each embodiment. The details of one or more embodiments of the invention are also set forth in the description below. Other features, objects, and advantages will be apparent from the description and from the claims.
DETAILED DESCRIPTION
[0008] As used herein, the term
“and/or” is used to indicate one or both stated cases may occur, for example A and/or B includes, (A and B) and (A or B);
“backbone” refers to the main continuous chain of the polymer;
“crosslink” refers to connecting two pre-formed polymer chains using chemical bonds or chemical groups;
“cure site” refers to functional groups, which may participate in crosslinking;
“interpolymerized” refers to monomers that are polymerized together to form a polymer backbone;
“monomer” is a molecule which can undergo polymerization which then form part of the essential structure of a polymer;
“perfluorinated” means a group or a compound derived from a hydrocarbon wherein all hydrogen atoms have been replaced by fluorine atoms. A perfluorinated compound may however still contain atoms other than fluorine and carbon atoms, like oxygen atoms, chlorine atoms, bromine atoms and iodine atoms; and
“polymer” refers to a macrostructure having a number average molecular weight (Mn) of at least 10,000, 30,000 dalton, 50,000, 100,000, 200,000, 500,000, or even at least 1,000,000 dalton and not such a high molecular weight as to cause premature gelling of the polymer.
[0009] Also herein, recitation of ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).
[0010] Also herein, recitation of “at least one” includes all numbers of one and greater (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).
[0011] Disclosed herein is an amorphous fluoropolymer composition. This composition comprises a partially fluorinated amorphous polymer in an ionic liquid. These curable fluoropolymer compositions can be cured with a peroxide cure reaction. The compositions of the present disclosure are conductive (e.g., electroconductive and/or thermalconductive).
[0012] Amorphous Fluoropolymer
[0013] The curable fluoropolymers of the present disclosure are amorphous, meaning that there is an absence of long-range order (i.e., in long-range order the arrangement and orientation of the macromolecules beyond their nearest neighbors is understood). The amorphous polymer has no detectable crystalline character by DSC (differential scanning calorimetry). If studied under DSC, the fluoropolymer would have no melting point or melt transitions with an enthalpy more than 0.002, 0.01, 0.1, or even 1 Joule/g from the second heat of a heat/cool/heat cycle, when tested using a DSC thermogram with a first heat cycle starting at -85°C and ramped at 10 °C/min to 350°C, cooling to -85°C at a rate of 10°C/min and a second heat cycle starting from -85°C and ramped at 10 °C/min to 350°C.
[0014] The amorphous fluoropolymers of the present disclosure are partially fluorinated. A partially fluorinated amorphous polymer comprises both C-F and C-H bonds along the carbon backbone of the polymer chain.
[0015] In one embodiment, the amorphous fluoropolymer of the present disclosure comprises at least 30, 50, 60%, 66, 68, 70, or even 71% by weight of fluorine, and no more than 72, or even 73% by weight of fluorine (based on the total weight of the amorphous fluoropolymer).
[0016] In one embodiment, the amorphous fluoropolymer is derived from at least one hydrogencontaining monomer and at least one fluorine-containing monomer. In one embodiment, the amorphous fluoropolymer is derived from a monomer comprising both an olefinic hydrogen and an olefinic fluorine, such as vinylidene fluoride. Hydrogen containing monomers include those known in the art. The hydrogen-containing monomers may or may not contain fluorine atoms. Exemplary hydrogen-containing monomers include: vinylidene fluoride, pentafluoropropylene (e.g., 2-hydropentafluoropropylene), vinyl fluoride, trifluoroethylene, propylene, ethylene, isobutylene, and combinations thereof. Fluorine-containing monomers include those known in the art. Exemplary fluorine-containing monomers include: hexafluoropropene, tetrafluoroethylene, chlorotrifluoroethylene, perfluoro(alkylvinyl ether) (such as perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, CF2=CFOCFCF2CF2OCF3, CF2=CFOCF2OCF2CF2CF3, CF2=CFOCF2OCF2CF3, and CF2=CFOCF2OCF3), and combinations thereof.
[0017] In one embodiment, the amorphous fluoropolymer comprises interpolymerized units derived from vinylidene fluoride (VDF). In one embodiment, the amorphous fluoropolymer is derived from 25-75 wt % VDF or even 35-70 wt % VDF.
[0018] In one embodiment, the amorphous fluoropolymer comprises interpolymerized units derived from (i) hexafluoropropylene (HFP), tetrafluoroethylene (TFE), and vinylidene fluoride (VDF); (ii) HFP and VDF, (iii) VDF and perfluoromethyl vinyl ether (PMVE), (iv) VDF, TFE, and PMVE, (v) VDF, TFE, and propylene, (vi) ethylene, TFE, and PMVE, (vii) TFE, VDF, PMVE, and ethylene, or (viii) TFE, VDF, and CF2=CFO(CF 2 ) 3 OCF3.
[0019] In one embodiment, the amorphous fluoropolymer comprises interpolymerized units derived from at least 25, 30, 40, 45, 50, or even 60 wt% and at most 65, 70, or even 75 wt% VDF; and at least 25, 30 or even 35 wt% and at most 50, 60, or even 70 wt% HFP. In one embodiment, the amorphous fluoropolymer comprises interpolymerized units derived from at least 45, 50, 55, or even 60 wt% and at most 65, 70, or even 75 wt% VDF; at least 10, 15, or even 20 wt% and at most 30, 35, 40, or even 45 wt% HFP; and at least 3, 5, or even 7 wt% and at most 10 or even 15 wt% TFE. In one embodiment, the amorphous fluoropolymer comprises interpolymerized units derived from at least 25, 30, or even 35 wt% and at most 40, 45, 50, 55, or even 65 wt% VDF; at least 15, 20, 25, or even 30 wt% and at most 35, 40, or even 45 wt% HFP; and at least 1, 5, 10 15, 20, or even 25 wt% and at most 30, 35, or even 40 wt% TFE. In one embodiment, the amorphous fluoropolymer comprises interpolymerized units derived from at least 30, 35, 40, or even 45 wt% and at most 55, 60, or even 65 wt% VDF; at least 25, 30, or even 35 wt% and at most 40, 45, 50, 55, 60, or even 65 wt% PMVE; and at least 3, 5, or even 7 wt% and at most 10, 15, or even 20 wt% TFE. In one embodiment, the amorphous fluoropolymer comprises interpolymerized units derived from at least 30, 35, 40, or even 45 wt% and at most 55, 60, or even 65 wt% VDF; at least 10, 15, 20, 25, or even 35 wt% and at most 40, 45, 50, 55, or even 60 wt% PMVE; and at least 10 15, or even 20 wt% and at most 25, 30, or even 35 wt% TFE. In one embodiment, the amorphous fluoropolymer comprises interpolymerized units derived from at least 5, 10, or even 15 wt% and at most 20, 25, or even 30 wt% VDF; at least 5, 10, or even 15 wt% and at most 20, 25, or even 30 wt% propylene; and at least 50, 55, 60, or even 65 wt% and at most 70, 75, 80, or even 85 wt% TFE. In one embodiment, the amorphous fluoropolymer comprises interpolymerized units derived from a perfluorinated ether monomer of the formula CF2=CF(CF2)pO(RfiO)n(Rf2O) m Rf where Rn and Rf2 are different linear or branched perfluoroalkylene groups containing 2, 3, 4, 5, or 6 carbon atoms; m and n are independently 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, p is 0 or 1, and Rfis a perfluoroalkyl group of 1, 2, 3, 4, 5, or 6 carbon atoms. Such perfluorinated ether compounds are known in the art and include for example, perfluorinated alkyl vinyl ether such as perfluorinated methyl vinyl ether (PMVE), perfluorinated alkyl allyl ether such as perfluorinated methyl allyl ether, and perfluorinated alkoxy vinyl ether and perfluorinated alkoxy allyl ether.
[0020] The amorphous fluoropolymer of the present disclosure contains cure sites which facilitate cross-linking of the fluoropolymer. These cure sites comprise at least one of I, Br, and CN. The fluoropolymer may be polymerized in the presence of a chain transfer agent and/or cure site monomers to introduce cure sites into the fluoropolymer. Such cure site monomers and chain transfer agents are known in the art. Exemplary chain transfer agents include: an iodo-chain transfer agent, a bromo-chain transfer agent, or a chloro-chain transfer agent. For example, suitable iodo-chain transfer agent in the polymerization include the formula of RI X , where (i) R is a perfluoroalkyl or chloroperfluoroalkyl group having 3 to 12 carbon atoms; and (ii) x = 1 or 2. The iodo-chain transfer agent may be a perfluorinated iodo-compound. Exemplary iodo-perfluoro- compounds include 1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane, 1, 6- diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,10-diiodoperfluorodecane, 1,12- diiodoperfluorododecane, 2-iodo- 1 ,2-dichloro-l, 1 ,2-trifluoroethane, 4-iodo- 1,2,4- trichloroperfluorobutan, and mixtures thereof. In some embodiments, the iodo-chain transfer agent is of the formula I(CF2)n-O-Rf-(CF2) m I, wherein n is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, m is is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 and Rf is a partially fluorinated or perfluorinated alkylene segment, which can be linear or branched and optionally comprises at least one catenated ether linkage. Exemplary compounds include: I-CF2-CF2-O-CF2-CF2-I, I-CF(CF 3 )-CF2-O-CF2-CF 2 -I, I-CF 2 -CF 2 -O-CF(CF 3 )- CF2-O-CF2-CF2-I, I-(CF(CF 3 )-CF 2 -O)2-CF2-CF 2 -I, I-CF 2 -CF2-O-(CF2)2-O-CF2-CF 2 -I, I-CF2-CF2- O-(CF 2 ) 3 -O-CF2-CF2-I, and I-CF 2 -CF2-O-(CF2) 4 -O-CF2-CF2-I, I-CF2-CF2-CF2-O-CF2-CF2-I, and I- CF2-CF2-CF2-O-CF(CF 3 )-CF2-O-CF2-CF2-I, In some embodiments, the bromine is derived from a brominated chain transfer agent of the formula: RBr x , where (i) R is a perfluoroalkyl or chloroperfluoroalkyl group having 3 to 12 carbon atoms; and (ii) x = 1 or 2. The chain transfer agent may be a perfluorinated bromo-compound.
[0021] Cure site monomers, if used, comprise at least one of a bromine, iodine, and/or nitrile cure moiety.
[0022] In one embodiment, the cure site monomers may be of the formula: CX2=CX(Z), wherein: (i) X each is independently H or F; and (ii) Z is I, Br, R/-U wherein U=I or Br and R/=a perfluorinated or partially perfluorinated alkylene group optionally containing ether linkages. In addition, non-fluorinated bromo-or iodo-olefins, e.g., vinyl iodide and allyl iodide, can be used. Exemplary cure site monomers include: CH2=CHI, CF2=CHI, CF2=CFI, CH2=CHCH2l, CF2CFCF2I, ICF2CF2CF2CF2I, CH2=CHCF 2 CF 2 I, CF2=CFCH 2 CH 2 I, CF2=CFCF 2 CF 2 I, CH 2 =CH(CF2)6CH 2 CH2l, CF2CFOCF2CF2I, CF2=CFOCF 2 CF2CF 2 I, CF2=CFOCF 2 CF2CH 2 I, CF2CFCF2OCH2CH2I, CF2=CFO(CF 2 ) 3 -OCF2CF 2 I, CH 2 =CHBr, CF 2 =CHBr, CF 2 =CFBr, CH 2 =CHCH 2 Br, CF 2 =CFCF 2 Br, CH2=CHCF 2 CF 2 Br, CF2=CFOCF 2 CF 2 Br, CF 2 =CFC1, 1-CF 2 - CF2CF2-O-CFCF2, 1-CF 2 -CF2CF2-O-CF 2 CF=CF2, 1-CF2-CF2-O-CF2-CFCF2, 1-CF(CF 3 )-CF 2 -O- CF=CF 2 , 1-CF(CF 3 )-CF2-O-CF 2 -CF=CF 2 , 1-CF 2 -CF2-O-CF(CF 3 )-CF2-O-CF=CF 2 , 1-CF2-CF2-O- CF(CF 3 )-CF2-O-CF2-CF=CF2, 1-CF 2 -CF2-(O-(CF(CF 3 )-CF2)2-O-CF=CF 2 , 1-CF 2 -CF 2 -(O-(CF(CF 3 )- CF2)2-O-CF2-CF=CF2, Br-CF2-CF2-O-CF2-CF=CF 2 , Br-CF(CF 3 )-CF 2 -O-CF=CF 2 , 1-CF2-CF2-CF2- O-CF(CF 3 )-CF2-O-CF=CF2, 1-CF 2 -CF2-CF2-O-CF(CF 3 )-CF2-O-CF2-CF=CF 2 , 1-CF2-CF 2 -CF 2 -(O- (CF(CF 3 )-CF 2 ) 2 -O-CF=CF 2 , I-CF 2 -CF 2 -CF 2 -O-(CF(CF 3 )-CF 2 -O) 2 -CF 2 -CF=CF 2 , Br-CF 2 -CF 2 -CF 2 - O-CF=CF 2 , Br-CF 2 -CF 2 -CF 2 -O-CF 2 -CF=CF 2 , 1-CF 2 -CF 2 -O-(CF 2 ) 2 -O-CF=CF 2 , 1-CF 2 -CF 2 -O- (CF 2 ) 3 -O-CF=CF 2 , 1-CF 2 -CF 2 -O-(CF 2 ) 4 -O-CF=CF 2 , 1-CF 2 -CF 2 -O-(CF 2 ) 2 -O-CF 2 -CF=CF 2 , I-CF 2 - CF 2 -O-(CF 2 ) 3 -O-CF 2 -CF=CF 2 , 1-CF 2 -CF 2 -O-(CF 2 ) 2 -O-CF(CF 3 )CF 2 -O-CF 2 =CF 2 , I-CF 2 -CF 2 -O- (CF 2 ) 2 -O-CF(CF 3 )CF 2 -O-CF 2 -CF 2 =CF 2 , Br-CF 2 -CF 2 -O-(CF 2 ) 2 -O-CF=CF 2 , Br-CF 2 -CF 2 -O-(CF 2 ) 3 - O-CF=CF 2 , Br-CF 2 -CF 2 -O-(CF 2 ) 4 -O-CF=CF 2 , and Br-CF 2 -CF 2 -O-(CF 2 ) 2 -O-CF 2 -CF=CF 2 [0023] In another embodiment, the cure site monomers comprise nitrile -containing cure moieties. Useful nitrile-containing cure site monomers include nitrile-containing fluorinated olefins and nitrile-containing fluorinated vinyl ethers, such as: perfluoro(8-cyano-5-methyl-3,6-dioxa-l- octene); CF 2 =CF-O-(CF 2 ) n -CN where n = 2-12, preferably 2, 3, 4, 5, or 6. Examples of a nitrile- containing cure site monomer include CF 2 =CF-O-[CF 2 -CFCF 3 -O] n -CF 2 -CF(CF 3 )-CN; where n is 0, 1, 2,3, or 4, preferably 0, 1, or 2; CF 2 =CF-[OCF 2 CF(CF 3 )] x -O-(CF 2 ) n -CN; where x is 1 or 2, and n is 1, 2, 3, or 4; and CF 2 =CF-O-(CF 2 ) n -O-CF(CF 3 )CN where n is 2, 3, or 4. Exemplary nitrile- containing cure site monomers include: CF 2 =CFO(CF 2 )5CN, CF 2 =CFOCF 2 CF(CF 3 )OCF 2 CF 2 CN, CF 2 =CFOCF 2 CF(CF 3 )OCF 2 CF(CF 3 )CN, CF 2 =CFOCF 2 CF 2 CF 2 OCF(CF 3 )CN, CF 2 =CFOCF 2 CF(CF 3 )OCF 2 CF 2 CN; and combinations thereof.
[0024] The amorphous fluoropolymer composition of the present disclose comprises iodine, bromine, and/or nitrile cure sites, which are subsequently used to crosslink the amorphous fluoropolymer. In one embodiment, the amorphous fluoropolymer composition of the present disclosure comprises at least 0.1, 0.5, 1, 2, or even 2.5 wt% of iodine, bromine, and/or nitrile groups versus the total weight of the amorphous fluoropolymer. In one embodiment, the amorphous fluoropolymer of the present disclosure comprises no more than 3, 5, or even 10 wt% of iodine, bromine, and/or nitrile groups versus the total weight of the amorphous fluoropolymer. [0025] In one embodiment, the amorphous fluoropolymer comprising cure sites is blended with a second amorphous fluoropolymer, which may or may not comprise bromine, iodine, and/or nitrile cure sites.
[0026] Conductive Particles
[0027] Fluoropolymers generally have higher resistivities. Therefore, conductive particles are added to achieve compositions with lower resistivities.
[0028] In one embodiment, the conductive particles have a surface area of less than 500, 250, 100, 50, 25, 20, 10, or even 1 m 2 /g (meters squared per gram). The surface area of the conductive particles can be determined using techniques known in the art. One common technique is the nitrogen adsorption method and application of BET theory. This method is commonly used to determine surface area and involves adsorbing a monolayer of nitrogen on the surface of the conductive particle under cryogenic conditions. The amount of adsorbed nitrogen is proportional to the surface area. If desired, information related to pore size can be obtained by allowing continued adsorption of nitrogen under cryogenic conditions, until the entire pore structure is fdled with liquid nitrogen, and applying BJH theory (or other theory) to calculate average pore diameter. This method will generally measure pores having an average diameter up to about 2000 Angstroms. For materials having larger pore sizes, mercury intrusion porosimetry may be utilized to measure average pore diameters.
[0029] In one embodiment, the conductive particles are carbon particles. The carbon particles disclosed herein are those materials that comprise predominately (e.g., greater than 90, 95, 99% mole) elemental carbon in the bulk. The carbon particles may include amorphous carbons, crystalline carbons, graphitized carbons, and combinations thereof. Exemplary carbons include, elemental carbon, carbon black, acetylene black, graphite, graphene, graphitized carbon, carbon nanotubes, multiwall carbon nanotubes (MWCNT), TKK F-type carbon, P-type carbon, graphitized Vulcan, graphitized carbon, and specialty carbon black. Exemplary conductive carbon particles include carbon fibers available under the trade designation “SG-249” from Osaka Gas Chemical Co., Ltd., Osaka, Japan, and synthetic graphite available as “4546” from Asbury Carbons, Asbury, NJ.
[0030] The scope of useful carbon particles in this disclosure is not intended to be limited to the specific examples indicated hereinabove, but is intended to include all useful physical forms of carbons, such as powders, plates, rods, foams, felts, fibers, branched fibers, cloths, etc.
[0031] The amount of conductive particles in the conductive composition (the curable composition or the elastomer) can vary depending on the type of carbon and/or the surface area of the conductive particles. In one embodiment, the conductive composition comprises at least 10, 20, 30, or even 40 wt%; and at most 50, 75, 100, 150, 200, 300, 400, or even 500 wt % of the conductive particles versus the fluoropolymer. If there are not enough conductive particles, the composition will not have the requisite conductivity. If there are too many conductive particles, then the cured composition (or fluoroelastomer) will not have the requisite hardness.
[0032] Peroxide
[0033] The curable compositions of the present disclosure comprise a peroxide. In one embodiment, the peroxide is an organic peroxide, preferably, a tertiary butyl peroxide having a tertiary carbon atom attached to peroxy oxygen.
[0034] Exemplary peroxides include: benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-di-methyl-2,5-di-tert-butylperoxyhexane, 2,4-dichlorobenzoyl peroxide, l,l-bis(tert- butylperoxy)-3,3,5-trimethylchlorohexane, tert-butyl peroxy isopropylcarbonate (TBIC), tert-butyl peroxy 2-ethylhexyl carbonate (TBEC), tert-amyl peroxy 2-ethylhexyl carbonate, tert-hexylperoxy isopropyl carbonate, carbonoperoxoic acid, O,O'-l,3-propanediyl OO, OO'-bis( 1,1 -dimethylethyl) ester, tert-butylperoxy benzoate, t-hexyl peroxy-2-ethylhexanoate, t-butyl peroxy-2- ethylhexanoate, di(4-methylbenzoyl) peroxide, laurel peroxide and cyclohexanone peroxide. Other suitable peroxide curatives are listed in U.S. Pat. No. 5,225,504 (Tatsu et al.).
[0035] The amount of peroxide used generally will be at least 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, or even 1.5; at most 2, 2.25, 2.5, 2.75, 3, 3.5, 4, 4.5, 5, or even 5.5 parts by weight per 100 parts of the amorphous fluoropolymer.
[0036] Crosslinking agent
[0037] The curable fluoropolymer composition further comprises a crosslinking agent.
[0038] In one embodiment, the crosslinking agent is a multifunctional polyunsaturated compound, which includes allyl-containing cyanurates, isocyanurates, and phthalates, homopolymers of dienes, and co-polymers of dienes and vinyl aromatics. A wide variety of these crosslinking agents are commercially available including di- and triallyl compounds, divinyl benzene, vinyl toluene, vinyl pyridine, 1,2-cis-poly butadiene and their derivatives. Exemplary Type II coagents include a diallyl ether of glycerin, triallylphosphoric acid, diallyl adipate, diallylmelamine and triallyl isocyanurate (TAIC), tri(methyl)allyl isocyanurate (TMAIC), triallyl iscocyanurate, tri(methyl)allyl cyanurate, poly-triallyl isocyanurate (poly-TAIC), and xylylene-bis(diallyl isocyanurate) (XBD) N,N'-m-phenylene bismaleimide, diallyl phthalate, tris(diallylamine)-s- triazine, triallyl phosphite, 1,2-polybutadiene, ethylene glycol diacrylate, diethylene glycol diacrylate, or CH2=CH-Rfi-CH=CH2 wherein Rn is a perfluoroalkylene having from 1 to 8 carbon atoms.
[0039] The amount of crosslinking agent used generally will be at least 0.1, 0.5, or even 1 part by weight per 100 parts of amorphous fluoropolymer; and at most 2, 2.5, 3, or even 5 parts by weight per 100 parts of amorphous fluoropolymer.
[0040] Ionic Liquid
[0041] The partially fluorinated amorphous polymers disclosed herein are dissolved and/or dispersed in the ionic liquid to form the curable compositions.
[0042] An ionic liquid is a unique salt, which is in a liquid state at about 100°C or less, has negligible vapor pressure, and high thermal stability. The ionic liquid is composed of a cation and an anion and has a melting point of generally about 100°C or less (i.e., being a liquid at about 100°C or less), about 95°C or less, or even about 80°C or less. Certain ionic liquids exist in a molten state even at ambient temperature since their melting points are less than room temperature, and therefore they are sometimes referred to as ambient temperature molten salts. The cation and/or anion of the ionic liquid are relatively sterically-bulky, and typically one and/or both of these ions are an organic ion. The ionic liquid can be synthesized by known methods, for example, by a process such as anion exchange or metathesis process, or via an acid-base or neutralization process.
[0043] The cation of the ionic liquid of the present disclosure may be an ammonium ion, a phosphonium ion, a sulfonium ion or the like, including various delocalized heteroaromatic cations, but is not limited thereto. The ammonium ion includes an ammonium ion selected from the group consisting of alkylammonium, imidazolium, pyridinium, pyrrolidinium, pyrrolinium, pyrazinium, pyrimidinium, triazonium, triazinium, quinolinium, isoquinolinium, indolinium, quinoxalinium, piperidinium, oxazolinium, thiazolinium, morpholinium, piperazinium, and a combination thereof. Examples of the phosphonium ion include a phosphonium ion selected from the group consisting of tetraalkylphosphonium, arylphosphonium, alkylarylphosphonium and a combination thereof. Examples of the sulfonium ion include a sulfonium ion selected from the group consisting of alkylsulfonium, arylsulfonium, thiophenium, tetrahydrothiophenium, and a combination thereof. The alkyl group directly bonded to nitrogen atom, phosphorus atom, or sulfur atom may be a linear, branched or cyclic alkyl group having a carbon number of at least 1, 2, or even 4 and not more than 8, 10, 12, 15, or even 20. The alkyl group may optionally contain heteroatoms such as O and N and S in the chain or at the end of the chain (e.g., a terminal -OH group). The aryl group directly bonded to nitrogen atom, phosphorus atom or sulfur atom may be a monocyclic or condensed cyclic aryl group having a carbon number of at least 5, 6, or even 8 and not more than 12, 15, or even 20. An arbitrary site in the structure constituting such a cation may be further substituted by an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, an aralkyl group, an arylalkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a carbonyl group, a carboxyl group, an ester group, an acyl group, an amino group, a dialkylamino group, an amide group, an imino group, an imide group, a nitro group, a nitrile group, a sulfide group, a sulfoxide group, a sulfone group, a halogen atom or the like, and a heteroatom such as oxygen atom, nitrogen atom, sulfur atom and silicon atom may be contained in the main chain or ring of the structure constituting the cation.
[0044] Specific examples of the cation include N-ethyl-N'-methylimidazolium, N-methyl-N- propylpiperidinium, N,N,N-trimethyl-N-propylammonium, N-methyl-N,N,N-tripropylammonium, N,N,N -trimethyl-N -butylammoniuim, N,N,N -trimethyl -N -methoxy ethylammonium, N -methyl - N,N,N-tris(methoxyethyl)ammonium, N,N-dimethyl-N-butyl-N-methoxyethylammonium, N,N- dimethyl-N,N-dibutylammonium, N-methyl-N,N-dibutyl-N-methoxyethylammonium, N-methyl- N,N,N-tributylammonium, N,N,N-trimethyl-N -hexylammonium, N,N-diethyl-N-methyl-N-(2- methoxyethyl)ammonium, 1 -propyl -tetrahydrothiophenium, 1 -butyl -tetrahydrothiophenium, 1- pentyl -tetrahydrothiophenium, 1 -hexyl -tetrahydrothiophenium, glycidyltrimethylammonium, N- ethylacryloyl-N,N,N-trimethylammonium, N-ethyl-N-methylmorphonium, N,N,N- trioctylammonium, N-methyl-N,N,N-trioctylammonium, N,N-dimethyl-N-octyl-N-(2- hydroxyethyl)ammonium, and a combination thereof.
[0045] A cation not containing a functional group or moiety exhibiting reactivity (for example, an unsaturated bond having reaction activity) is advantageous in view of heat resistance, and examples of such a cation include N-methyl-N-propyl piperidinium and N,N,N-trimethyl-N- propylammonium .
[0046] The anion of the ionic liquid of the present disclosure may be, for example, a sulfate (R- OSO3"), a sulfonate (R-SO3 ), a carboxylate (R-CO2 ), a phosphate ((RO)2P(=O)O ), a borate represented by the formula: BR 4 . such as tetrafluoroborate (BF 4 ) and tetraalkylborate, a phosphate represented by the formula: PRf, such as hexafluorophosphate (PFg ) and hexaalkylphosphate, an imide (R2N ), a methide (R3C ), nitrate ion (NO3 ), or nitrite ion (NO2 ). In the formula, each R may be independently a hydrogen atom, a halogen atom (fluorine, chlorine, bromine, iodine), a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, arylalkyl, acyl or sulfonyl group, or the like. A heteroatom such as an oxygen atom, a nitrogen atom and a sulfur atom may be contained in the main chain or ring of the group R, and a part or all of hydrogen atoms on the carbon atom of the group R may be replaced with fluorine atoms. In the case where a plurality of R's are present in the anion, these R's may be the same or different. Because of good compatibility with fluoropolymer in general, it is advantageous that a part or all of hydrogen atoms on the carbon atom of the group R in the anion be replaced by fluorine atoms and it is advantageous that the anion contains a perfluoroalkyl group.
[0047] Examples of the anion containing a perfluoroalkyl group, which can be advantageously used, include a bis(perfluoroalkylsulfonyl)imide ((RfSCh N ), a perfluoroalkylsulfonate (RfSO, ) and a tris(perfluoroalkylsulfonyl)methide ((RfSCh C ) (wherein Rf represents a perfluoroalkyl group). The carbon number of the perfluoroalkyl group may be, for example, from at least 1, 2, 3 or even 4 to at most 8, 10, 12, 15, or even 20. Specific examples of the bis(perfluoroalkylsulfonyl)imide include: bis(trifluoromethanesulfonyl)imide, bis(pentafluoroethanesulfonyl)imide, bis(heptafluoropropanesulfonyl)imide and bis(nonafluorobutanesulfonyl)imide. Specific examples of the perfluoroalkylsulfonate include: trifluoromethane sulfonate, pentafluoroethanesulfonate, heptafluoropropanesulfonate and nonafluorobutane sulfonate. Specific examples of the tris(perfluoroalkylsulfonyl)methide include: tris(trifluoromethanesulfonyl)methide, tris(pentafluoroethanesulfonyl)methide, tris(heptafluoropropanesulfonyl)methide, tris(nonafluorobutanesulfonyl)methide, and a combination thereof.
[0048] As for the ionic liquid composed of the above-described cation and anion, N-methyl-N- propylpiperidinium bis(trifluoromethanesulfonyl)imide, N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide, N-ethyl-N'-methylimidazolium bis(trifluoromethanesulfonyl)imide, N,N,N-trimethyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide and N-methyl-N,N,N-tributylammonium bis(trifluoromethanesulfonyl)imide can be advantageously used, because of excellent heat resistance and good compatibility with fluoropolymer. In the usage requiring non-coloration, N- methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide, N,N,N-trimethyl-N- hexylammonium bis(trifluoromethanesulfonyl)imide and N-methyl-N,N,N-tributylammonium bis(trifluoromethanesulfonylimide, which are free of an aromatic ring, are particularly suitable. [0049] In one embodiment, the curable composition comprises at least 10, 20, 30 or even 40 wt % of the ionic liquid. In one embodiment, the curable composition comprises at most 50, 60, 70, 75, or even 80 wt % of the ionic liquid.
[0050] In one embodiment, the ionic liquid has a boiling point greater than 275, 300, 350, or even 400°C. Ionic liquids with higher boiling points can be advantageous in the present disclosure because they can assist with the conductivity of the cured fluoropolymer. As can be seen in the example section below, the use of the ionic liquid allows the hardness of the fluoroelastomeric composition to be maintained or at least able to form sheets, even upon the addition of larger amounts of conductive particles.
[0051] Other Additives
[0052] In one embodiment, the compositions of the present disclosure comprise additional components, which facilitate the processing or final properties of the resulting article. For the purpose of, for example, enhancing the strength or imparting the functionality, conventional adjuvants, such as, for example, fillers, acid acceptors, process aids, or colorants (e.g., pigments or dyes) may be added to the curable composition. Exemplary fillers include: an organic or inorganic filler such as clay, silica (SiC>2), alumina, iron red, talc, diatomaceous earth, barium sulfate, wollastonite (CaSiCh), calcium carbonate (CaCCE), calcium fluoride, magnesium oxide, titanium oxide, iron oxide, aluminum nitride, silicon carbide, boron nitride, molybdenum sulfide, pigment, high temperature plastics, a heat-dissipating filler, and the like may be added as an optional additive to the composition. Those skilled in the art are capable of selecting specific fillers at required amounts to achieve desired physical characteristics in the vulcanized compound. The filler components may result in a compound that is capable of retaining a preferred elasticity and physical tensile, as indicated by an elongation and tensile strength value, while retaining desired properties such as retraction at lower temperature (TR-10). In one embodiment, the filler content is between 0.01 to 10 % or up to 30 % or even up to 50 % by weight based on the total weight of the composition.
[0053] Method of making [0054] The curable composition comprising the partially fluorinated amorphous polymer, the peroxide, crosslinking agent, ionic liquid, conductive filler, and optional additives can be combined together, using techniques known in the art, and cured.
[0055] In one embodiment, the curable compositions of the present disclosure are dispensable, meaning the viscosity is low enough such that the curable composition can be delivered onto a substrate. In one embodiment, the viscosity of the curable compositions at 25°C is at least 50, 100, 500, 1000, 2000, 4000, 6000 or even 10000 cP (centiPoise). In one embodiment, the curable compositions have a viscosity at 25°C of at most 2000, 4000, 6000, 8000, 10000, 15000, 20000, 50000, 100000, 200000, 500000, or even 1000000 cP.
[0056] The curable compositions disclosed herein can be dispensed and/or compounded and molded using techniques known in the art to form articles. These curable articles can then be exposed to thermal radiation to cure the fluoropolymer, generating the fluoroelastomer. For example, the curable composition is at least partially cured using thermal radiation, whereby the curable composition is exposed to temperatures greater than 120, 140, 160, 180, 200, 220, or even 250°C; and less than the decomposition temperature of the fluoropolymer or its components (e.g., less than 300, or even 275°C), causing the peroxide cure initiator to activate, resulting in the crosslinking (or curing) of the composition. Typically, curing is performed in an oven.
[0057] In one embodiment, the cured compositions have a Duro A hardness of at least 10, 20, 30 or even 40; and at most 80, 75, 70, 65, or even 60.
[0058] In one embodiment, the cured compositions have a volume resistivity of less than 1 x 10 4 Ohms*cm, or even 1 x 10 2 Ohms*cm. In one embodiment, the cured compositions have a surface resistivity of less than 1 x 10 4 Ohms per square, or even 1 x 10 2 Ohms per square of material.
[0059] In one embodiment, the cured compositions have a thermal conductivity of greater than 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, 5.0, 10.0 W/m-K, or even 12 W/m-K.
[0060] In one embodiment, the cured compositions have an electrical conductivity of greater than 10,000 1/S, or even 100 1/S.
[0061] The articles of the present disclosure are shaped and can include gaskets, ring lip seals, washer seals, O-rings, grooved seals, etc.
EXAMPLES
[0062] All materials are commercially available, for example from Sigma-Aldrich Chemical Company, Milwaukee, WI, USA, or known to those skilled in the art, unless otherwise stated or apparent. [0063] The following abbreviations are used in this section: mL=milliliters, g=grams, kg=kilograms, lb=pounds, cm=centimeters, mm=millimeters, pm=micrometers, mil=thousandths of an inch, wt%= percent by weight, min=minutes, h=hours, d=days, N=newtons, NMR=nuclear magnetic resonance, ppm=parts per million, eq=equivalent. Abbreviations for materials used in this section, as well as descriptions of the materials, are provided in Table 1.
Table 1
[0064] Characterization Methods [0065] Resistance Method 1
[0066] The volume resistivity and surface resistance were measured using a picoammeter available under the trade designation R8340A from Advantest, Tokyo, Japan, according to methods described in JIS K6911-1995. These measurements were made on press-cured sheets of compound. Measurements were not made on samples that could not be formed into sheets. The applied voltage for the measurements and the resulting measured volume and surface resistivities are presented in Table 2.
[0067] Resistance Method 2 [0068] Resistance of heat-cured samples were measured using a two contact method, with an applied voltage of 20 mV and a contact spacing of 10 mm. Measurements were not made for samples that could not be formed into sheets. The results of the measurements are presented in Table 2.
[0069] Hardness
[0070] Durometer A hardness was measured for press-cured sheets of compound according to ASTM D 2240-05 “Standard Test Method for Rubber Property-Durometer Hardness” using an ASKER Durometer Type A from Kobunshi Keiki Co., Ltd., Kyoto, Japan. Hardness was not measured for samples that could not be formed into sheets.
[0071] Cure Rheology
[0072] The cure rheology of the compounded fluoroelastomer gum sample was investigated by testing the uncured, compounded mixtures using the Alpha Technology PPA with MDR (Moving Disk Rheometer) mode and the procedure described in ASTM D 5289-95 at 120 to 177°C, no preheat, 12 minute elapsed time and a 0.5°C arc, minimum torque (ML) and maximum torque (MH), i.e., highest torque attained during specified period of time when no plateau or maximum was obtained were reported. Also reported were: Ts2 (time for torque to increase 2 units above ML), T50 (time for torque to reach ML +0.5[MH-ML]), and T90 (time for torque to reach ML +0.9[MH-ML]).
[0073] Sample preparation
[0074] An open roll mill with 6 inch (15.24 cm) diameter rolls was used for mixing of the ingredients of Comparative Examples (CE) 1 to 7 as listed in Table 2. A planetary mixer was used for mixing of the ingredients Comparative Examples (CE) 8 to 10 and Examples (EX) 1 to 3 as listed in Table 2. For all samples, a small amount of material was pressed (Pressure: 5MPa, temperature: 100 °C) for 1 minute to form a 200 micrometer thick sample.
Table 1
[0001] Foreseeable modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention. This invention should not be restricted to the embodiments that are set forth in this application for illustrative purposes. To the extent that there is any conflict or discrepancy between this specification as written and the disclosure in any document mentioned or incorporated by reference herein, this specification as written will prevail.