Patent Application
20210002456
Fluoropolymers are a commercially important class of materials that include, for example, crosslinked and uncrosslinked fluorocarbon elastomers and semi-crystalline or glassy fluorocarbon plastics.
Fluorocarbon elastomers, particularly the copolymers of vinylidene fluoride with other ethylenically unsaturated halogenated and non-halogenated monomers, such as hexafluoropropene, have particular utility in high temperature applications, such as seals, gaskets, and linings. See, for example, R. A. Brullo, “Fluoroelastomer Rubber for Automotive Applications,” Automotive Elastomer & Design, June 1985, “Fluoroelastomer Seal Up Automotive Future,” Materials Engineering, October 1988, and W. M. Grootaert, et al., “Fluorocarbon Elastomers,” Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 8, pp. 990-1005 (4th ed., John Wiley & Sons, 1993).
There is a desire to identify a novel curing system for partially fluorinated amorphous fluoropolymers. In one aspect, a curable partially fluorinated polymer is disclosed comprising:
(i) a partially fluorinated amorphous fluoropolymer, wherein the partially fluorinated amorphous fluoropolymer comprises carbon-carbon double bonds or is capable of forming carbon-carbon double bonds along the partially fluorinated amorphous fluoropolymer; and
(ii) a curing agent comprising a sulfonamide compound of the formula
R2(NH—SO2R1)x, I
where
R1 is a non-fluorinated or fluorinated group,
R2 is a fluorinated or non-fluorinated group, and
subscript x is 2 to 8,
with the proviso that when R1 is fluorinated, R2 is fluorinated. It will be understood that Formula I will include the corresponding salts thereof.
In another aspect, an article comprising the cured composition described above is disclosed.
In yet another aspect a method of making a partially fluorinated elastomer is disclosed comprising curing the curable partially fluorinated polymer composition disclosed above.
As used herein, “alkyl” and “alkylene” mean the monovalent and divalent residues remaining after removal of one and two hydrogen atoms, respectively, from a linear or branched chain hydrocarbon having 1 to 20 carbon atoms. Examples of “alkyl” as used herein include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, isobutyl, t-butyl, isopropyl, n-octyl, n-heptyl, ethylhexyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, and norbornyl and the like. Unless otherwise noted, alkyl groups may be mono- or polyvalent.
As used herein, the term “heteroalkyl” includes both straight-chained, branched, and cyclic alkyl groups with one or more heteroatoms independently selected from S, O, and N both unsubstituted and substituted alkyl groups. Unless otherwise indicated, the heteroalkyl groups typically contain from 1 to 20 carbon atoms. “Heteroalkyl” is a subset of “hetero(hetero)hydrocarbyl” described below. Examples of “heteroalkyl” as used herein include, but are not limited to methoxy, ethoxy, propoxy, 3,6-dioxaheptyl, 3-(trimethylsilyl)-propyl, 4-dimethylaminobutanyl, and the like. Unless otherwise noted, heteroalkyl groups may be mono- or polyvalent.
“aryl” and “arylene” mean the monovalent and divalent residues remaining after removal of one and two hydrogen atoms, respectively, from an aromatic compound (single ring and multi- and fused-rings) having 5 to 12 ring atoms and includes substituted aromatics such as lower alkaryl and aralkyl, lower alkoxy, N,N-di(lower alkyl)amino, nitro, cyano, halo, and lower alkyl carboxylic ester, wherein “lower” means C1 to C4.
Unless otherwise noted, alkyl, aryl and heteroaryl groups may be mono- or polyvalent.
As used herein “(hetero)hydrocarbyl” is inclusive of hydrocarbyl alkyl and aryl groups, and heterohydrocarbyl heteroalkyl and heteroaryl groups. Heterohydrocarbyl may optionally contain one or more catenary (in-chain) functional groups including ester, amide, urea, urethane and carbonate functional groups. Unless otherwise indicated, the non-polymeric (hetero)hydrocarbyl groups typically contain from 1 to 60 carbon atoms. Some examples of such (hetero)hydrocarbyls as used herein include, but are not limited to methoxy, ethoxy, propoxy, 4-diphenylaminobutyl, 2-(2′-phenoxyethoxy)ethyl, 3,6-dioxaheptyl, 3,6-dioxahexyl-6-phenyl, in addition to those described for “alkyl”, “heteroalkyl”, “aryl” and “heteroaryl” supra.
In the present disclosure, it has been found that a partially fluorinated amorphous fluoropolymer can be cured with a fluorinated sulfonamide compound.
The amorphous fluoropolymers of the present disclosure are partially fluorinated polymers. As disclosed herein, an amorphous partially fluorinated polymer is a polymer comprising at least one carbon-hydrogen bond and at least one carbon-fluorine bond on the backbone of the polymer. In one embodiment, the amorphous partially fluorinated polymer is highly fluorinated, wherein at least 60, 70, 80, or even 90% of the polymer backbone comprises C—F bonds.
The amorphous fluoropolymer of the present disclosure also comprises carbon-carbon double bonds and/or is capable of forming carbon-carbon double bonds along the polymer chain. In one embodiment, the partially fluorinated amorphous fluoropolymer comprises carbon-carbon double bonds along the backbone of the partially fluorinated amorphous fluoropolymer or is capable of forming carbon-carbon double bonds along the backbone of the partially fluorinated amorphous fluoropolymer. In another embodiment, the partially fluorinated amorphous fluoropolymer comprises carbon-carbon double bonds or is capable of forming carbon-carbon double bonds in a pendent group off of the backbone of the partially fluorinated amorphous fluoropolymer.
The fluoropolymer capable of forming carbon-carbon double bonds means that the fluoropolymer contains units capable of forming double bonds. Such units include, for example, two adjacent carbons, along the polymer backbone or pendent side chain, wherein a hydrogen is attached to the first carbon and a leaving group is attached to the second carbon. During an elimination reaction (e.g., thermal reaction, and/or use of acids or bases), the leaving group and the hydrogen leave forming a double bond between the two carbon atoms. An exemplary leaving group includes: a fluoride, an alkoxide, a hydroxide, a tosylate, a mesylate, an amine, an ammonium, a sulfide, a sulfonium, a sulfoxide, a sulfone, and combinations thereof. Those fluoropolymer capable of forming carbon-carbon bonds generally have the structure ˜CH—CX˜, where X is a leaving groups such that when treated with base will provide the requisite unsaturation. In many embodiments the polymer has ˜CH—CF˜ in the backbone, which may be dehydrofluorinated.
The amorphous fluoropolymer comprises a plurality of these groups (carbon-carbon double bonds or groups capable of forming double bonds) to result in a sufficient cure. Generally, this means at least 0.1, 0.5, 1, 2, or even 5 mol %; at most 7, 10, 15, or even 20 mole % (i.e., moles of these carbon-carbon double bonds or precursors thereof per mole of polymer).
In one embodiment, the amorphous partially fluorinated polymer is derived from at least one hydrogen containing monomer such as vinylidene fluoride.
In one embodiment, the amorphous fluoropolymer comprises adjacent copolymerized units of vinylidene fluoride (VDF) and hexafluoropropylene (HFP); copolymerized units of VDF (or tetrafluoroethylene) and a fluorinated comonomer capable of delivering an acidic hydrogen atom to the polymer backbone, such as trifluoroethylene; vinyl fluoride; 3,3,3-trifluoropropene-1; pentafluoropropene (e.g., 2-hydropentafluoropropylene and 1-hydropentafluoropropylene); 2,3,3,3-tetrafluoropropene; and combinations thereof.
In some embodiments, small amounts (e.g., less than 10, 5, 2, or even 1 wt %) of additional monomers may be added so long as the amorphous fluoropolymer is able to be cured using the curing agent disclosed herein.
In one embodiment, the amorphous fluoropolymer is additionally derived from a hydrogen containing monomer including: pentafluoropropylene (e.g., 2-hydropentafluropropylene), propylene, ethylene, isobutylene, and combinations thereof. In one embodiment, the amorphous fluoropolymer is additionally derived from a perfluorinated monomer. Exemplary perfluorinated monomers include: hexafluoropropene; tetrafluoroethylene; chlorotrifluoroethylene; perfluoro(alkylvinyl ether) such as perfluoromethyl vinyl ether, CF2═CFOCFCF2CF2OCF3, CF2═CFOCF2OCF2CF2CF3, CF2═CFOCF2OCF2CF3, CF2═CFOCF2OCF3, and CF2═CFOCF2OC3F7, perfluoro(alkylallyl ether) such as perfluoromethyl allyl ether, perfluoro(alkyloxyallyl ether) such as perfluoro-4,8-dioxa-1-nonene (i.e., CF2═CFCF2O(CF2)3OCF3, and combinations thereof.
Exemplary types of polymers include those comprising interpolymerized units derived from (i) vinylidene fluoride, tetrafluoroethylene, and propylene; (ii) vinylidene fluoride, tetrafluoroethylene, ethylene, and perfluoroalkyl vinyl ether, such as perfluoro(rnethyl vinyl ether); (iii) vinylidene fluoride with hexafluoropropylene; (iv) hexafluoropropylene, tetrafluoroethylene, and vinylidene fluoride; (v) hexafluoropropylene and vinylidene fluoride, (vi) vinylidene fluoride and perfluoroalkyl vinyl ether; (vii) vinylidene fluoride, tetrafluoroethylene, and perfluoroalkyl vinyl ether, (viii) vinylidene fluoride, perfluoroalkyl vinyl ether, hydropentafluoroethylene and optionally, tetrafluoroethylene; (ix) tetrafluoroethylene, propylene, and 3,3,3-trifluoropropene; (x) tetrafluoroethylene, and propylene; (xi) ethylene, tetrafluoroethylene, and perfluoroalkyl vinyl ether, and optionally 3,3,3-trifluoropropylene; (xii) vinylidene fluoride, tetrafluoroethylene, and perfluoroalkyl allyl ether, (xiii) vinylidene fluoride and perfluoroalkyl allyl ether; (xiv) ethylene, tetrafluoroethylene, and perfluoroalkyl vinyl ether, and optionally 3,3,3-trifluoropropylere; (xv) vinylidene fluoride, tetrafluoroethylene, and perfluoroalkyl allyl ether, (xvi) vinylidene fluoride and perfluoroalkyl allyl ether; (xvii) vinylidene fluoride, tetrafluoroethylene, and perfluoroalkyloxyallyl ether, (xviii) vinylidene fluoride and perfluoroalkyloxyallyl ether; (xiv) vinylidene fluoride, tetrafluoroethylene, and perfluoroalkyloxyallyl ether, (xv) vinylidene fluoride and perfluoroalkyloxyallyl ether; and (xvi) combinations thereof.
Advantageously, by using the curing agent disclosed herein, the amorphous fluoropolymers of the present disclosure can be cured without the need for pendent bromine, iodine, or nitrile cure sites along the polymer backbone. Often, the iodine and bromine-containing cure site monomers, which are polymerized into the fluoropolymer and/or the chain ends, can be expensive among other things.
The amorphous fluoropolymer of the present disclosure is substantially free of I, Br, and nitrile groups, wherein the amorphous fluoropolymer comprises less than 0.1, 0.05, 0.01, or even 0.005 mole percent relative to the total polymer.
In one embodiment, the amorphous fluoropolymers of the present disclosure are non-grafted, meaning that they do not comprise pendant groups including vinyl, allyl, acrylate, amido, sulfonic acid salt, pyridine, carboxylic ester, carboxylic salt, hindered silanes that are aliphatic or aromatic tri-ethers or tri-esters. In one embodiment, the amorphous fluoropolymer does not comprise a monophenol graft.
The above described amorphous fluoropolymers may be blended with one or more additional crystalline fluoropolymers. With the instant curing compounds, the crystalline fluoropolymers may be cured into the matrix of the amorphous fluoropolymer.
Commercially available vinylidene difluoride-containing fluoropolymers include, for example, those fluoropolymers having the trade designation “THV” (e.g., “THV 200”, “THV 400”, “THVG”, “THV 610”, or “THV 800”) as marketed by 3M/Dyneon, St. Paul, Minn.; “KYNAR” (e.g., “KYNAR 740”) as marketed by Atofina, Philadelphia, Pa.; “HYLAR” (e.g., “HYLAR 700”) as marketed by Ausimont USA, Morristown, N.J.; and “FLUOREL” (e.g., “FLUOREL FC-2178”) as marketed by 3M/Dyneon.
Useful fluoropolymers also include copolymers of HFP, TFE, and VDF (i.e., THV). These polymers may have, for example, VDF monomeric units in a range of from at least about 2, 10, or 20 percent by weight up to 30, 40, or even 50 percent by weight, and HFP monomeric units in a range of from at least about 5, 10, or 15 percent by weight up to about 20, 25, or even 30 percent by weight, with the remainder of the weight of the polymer being TFE monomeric units. Examples of commercially available THV polymers include those marketed by 3M/Dyneon, LLC under the trade designations “3M/DYNEON THV 2030G FLUOROTHERMOPLASTIC”, “3M/DYNEON THV 220 FLUOROTHERMOPLASTIC”, “3M/DYNEON THV 340C FLUOROTHERMOPLASTIC”, “3M/DYNEON THV 415 FLUOROTHERMOPLASTIC”, “3M/DYNEON THV 500A FLUOROTHERMOPLASTIC”, “3M/DYNEON THV 610G FLUOROTHERMOPLASTIC”, or “3M/DYNEON THV 810G FLUOROTHERMOPLASTIC”.
Useful fluoropolymers also include copolymers of ethylene, TFE, and HFP. These polymers may have, for example, ethylene monomeric units in a range of from at least about 2, 10, or 20 percent by weight up to 30, 40, or even 50 percent by weight, and HFP monomeric units in a range of from at least about 5, 10, or 15 percent by weight up to about 20, 25, or even 30 percent by weight, with the remainder of the weight of the polymer being TFE monomeric units. Such polymers are marketed, for example, under the trade designation “3M/DYNEON FLUOROTHERMOPLASTIC HTE” (e.g., “3M/DYNEON FLUOROTHERMOPLASTIC HTE X 1510” or “3M/DYNEON FLUOROTHERMOPLASTIC HTE X 1705”) by 3M/Dyneon LLC.
Useful fluoropolymers also include copolymers of tetrafluoroethylene and propylene (TFE/P). These copolymers may have, for example, TFE monomeric units in a range of from at least about 20, 30 or 40 percent by weight up to about 50, 65, or even 80 percent by weight, with the remainder of the weight of the polymer being propylene monomeric units. Such polymers are commercially available, for example, under the trade designations “AFLAS” (e.g., “AFLAS TFE ELASTOMER FA 100H”, “AFLAS TFE ELASTOMER FA 150C”, “AFLAS TFE ELASTOMER FA 150L”, or “AFLAS TFE ELASTOMER FA 150P”) as marketed by 3M/Dyneon, LLC, or “VITON” (e.g., “VITON VTR-7480” or “VITON VTR-7512”) as marketed by E.I. du Pont de Nemours & Company, Wilmington, Del.
Useful fluoropolymers also include copolymers of ethylene and TFE (i.e., “ETFE”). These copolymers may have, for example, TFE monomeric units in a range of from at least about 20, 30 or 40 percent by weight up to about 50, 65, or even 80 percent by weight, with the remainder of the weight of the polymer being propylene monomeric units. Such polymers may be obtained commercially, for example, as marketed under the trade designations “3M/DYNEON FLUOROTHERMOPLASTIC ET 6210J”, “3M/DYNEON FLUOROTHERMOPLASTIC ET 6235”, or “3M/DYNEON FLUOROTHERMOPLASTIC ET 6240J” by 3M/Dyneon LLC.
VDF-containing fluoropolymers can be prepared using emulsion polymerization techniques as described, for example, in U.S. Pat. No. 4,338,237 (Sulzbach et al.) or U.S. Pat. No. 5,285,002 (Grootaert), or US 20060029812 (Jing et al.) the disclosures of which are incorporated herein by reference.
The curable composition further comprises a fluorinated sulfonamide curing agent of the formula:
R2(NH—SO2R1)x, I
where
R1 is a fluorinated or non-fluorinated group,
R2 is a fluorinated or non-fluorinated group,
subscript x is 2 to 8; and
with the proviso that when R1 is fluorinated, R2 is fluorinated.
In some embodiments R1 is a perfluorinated group (designated as Rf1), and R2 is fluorinated (designated as Rf2) or non-fluorinated (designated as Rh2. Such embodiments may be represented as:
Rh2(NH—SO2Rf1)x, II, or
Rf2(NH—SO2Rf1)x, III
In some embodiments both R1 and R2 are non-fluorinated and may be represented by the formula:
Rh2(NH—SO2Rh1)x, IV
where
Rf1 is a perfluorinated group;
Rf2 is a fluorinated group, and
Rh2 is a non-fluorinated group.
The Rf1 groups can contain straight chain, branched chain, or cyclic monovalent fluorinated groups or any combination thereof. The Rf1 groups can optionally contain one or more catenary oxygen atoms in the carbon-carbon chain so as to form a carbon-oxygen-carbon chain (i.e. a oxyalkylene group). Perfluorinated groups are generally preferred, but hydrogen or chlorine atoms can also be present as substituents, provided that no more than one atom of either is present for every two carbon atoms.
It is additionally preferred that any Rf1 group contain at least about 40% fluorine by weight, more preferably at least about 50% fluorine by weight. The terminal portion of the monovalent Rf1 group is generally perfluorinated, preferably containing at least three fluorine atoms, e.g., CF3—, CF3CF2—, CF3CF2CF2—, (CF3)2N—, (CF3)2CF—, SF5CF2—. In certain embodiments, monovalent perfluoroalkyl groups (i.e., those of the formula CnF2n+1—) are the preferred Rf1 groups, with n=3 to 5 being more preferred and with n=4 being the most preferred.
In some embodiment the Rf1 may comprise a fluoroether or fluoropolyether. Useful perfluorooxyalkyl (Rf1) correspond to the formula:
F—Rf3—O—Rf1—(Rf5)q— (V)
wherein
Rf3 represents a perfluoroalkylene group,
Rf1 represents a perfluoroalkyleneoxy group consisting of perfluoroalkyleneoxy groups having 1, 2, 3 or 4 carbon atoms or a mixture of such perfluoroalkyleneoxy groups,
Rf5 represents a perfluoroalkylene group and q is 0 or 1.
The perfluoroalkylene groups Rf3 and Rf5 in formula (IV) may be linear or branched and may comprise 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. A typical monovalent perfluoroalkyl group is CF3—CF2—CF2— and a typical divalent perfluoroalkylene is —CF2—CF2—CF2—, —CF2— or —CF(CF3)—. Examples of perfluoroalkyleneoxy groups Rf4 include: —CF2—CF2—O—, —CF(CF3)—CF2—O—, —CF2—CF(CF3)—O—, —CF2—CF2—CF2—O—, —CF2—O—, —CF(CF3)—O—, and —CF2—CF2—CF2—CF2-0, which may repeat, for example, from 3 to 30 times.
The perfluoroalkyleneoxy group Re may be comprised of the same perfluorooxyalkylene units or of a mixture of different perfluorooxyalkylene units. When the perfluorooxyalkylene group is composed of different perfluoroalkylene oxy units, they can be present in a random configuration, alternating configuration or they can be present as blocks. Typical examples of perfluorinated poly(oxyalkylene) groups include: —[CF2—CF2—O]r—; —[CF(CF3)—CF2—O]s—; —[CF2CF2—O]r—[CF2O]t—, —[CF2CF2CF2CF2—O]u and —[CF2—CF2—O]r—[CF(CF3)—CF2—O]s—; wherein each of r, s, t and u each are integers of 1 to 50, preferably 2 to 25. A preferred perfluorooxyalkyl group that corresponds to formula (V) is CF3—CF2—CF2—O—[CF(CF3)—CF2O]s—CF(CF3)CF2— wherein s is an integer of 1 to 50.
In some embodiments R1 may non-fluorinated (Rh1) and selected from monovalent (hetero)hydrocarbyl groups including aliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic having 2 to 30 carbon atoms and optionally zero to four catenary heteroatoms of oxygen, nitrogen or sulfur; i.e. a heterohydrocarbyl group.
In some embodiments R2 may non-fluorinated (Rh2) and selected from di- and polyvalent (hetero)hydrocarbyl groups including aliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic having 2 to 30 carbon atoms and optionally zero to four catenary heteroatoms of oxygen, nitrogen or sulfur; i.e. a heterohydrocarbyl group.
In some embodiments the R2 group may be fluorinated and designated as Rf2. There should be at least one non-fluorinated carbon between a fluorinated carbon and the nitrogen atom; e.g. —CF2—CH2—NH—. The Rf2 groups are di- or polyvalent and can contain straight chain, branched chain, or cyclic pendent polyvalent fluorinated groups or any combination thereof. The Rf2 groups can optionally contain one or more catenary oxygen atoms in the carbon-carbon chain so as to form a carbon-oxygen-carbon chain (i.e. a oxyalkylene group). Perfluorinated groups are generally preferred, but hydrogen or chlorine atoms can also be present as substituents, provided that no more than one atom of either is present for every two carbon atoms.
In some embodiments the Rf2 group may be a fluorinated alkylene group to produce compounds of the formula:
Rf3(Y—NH—SO2R1)x,
where
Rf3 represents a perfluoroalkylene group,
Y is a (hetero)hydrocarbyl groups, including alkylene, arylene or heteroalkylene and heteroarylene, and is preferably and alkylene of 1 to 4 carbons; and
The Rf2 group may also be a fluorinated ether or fluorinated polyether group to produce compounds of the formula:
[F—Rf3—O—Rf4—(Rf5)q]—(Y—NH—SO2R1)x, where
[F—Rf3—O—Rf4—(Rf5)q] has a valence of x from abstraction of two or more F atoms from any of the Rf3, Rf4, or Rf5 groups, and
Rf3, Rf4, Rf5, subscript q, Y and R1 are as previously defined.
The fluorinated sulfonamides of Formula I may be prepared by reaction of a sulfonyl halide compound with a di- or polyamine:
R1SO2—X+R2(NH2)x→I,
where R1 is a fluorinated or non-fluorinated group and may be designated as Rf1 supra; where R2 may be a fluorinated group or a non-fluorinated groups and is a non-polymeric organic group that has a valence of x, and x is two to eight.
In some embodiments R2 may selected from mono- and polyvalent (hetero)hydrocarbyl groups including aliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic having 1 to 30 carbon atoms and optionally zero to four catenary heteroatoms of oxygen, nitrogen or sulfur.
In some embodiments the R2 group may be fluorinated designated as Rf2 as described supra.
Useful (hetero)hydrocarbyl amines of the formula R2(NH2)x include aliphatic and aromatic polyamines. Aliphatic, aromatic, cycloaliphatic, and oligomeric di- and polyamines all are considered useful in the practice of the invention. Representative of the classes of useful di- or polyamines are 4,4′-methylene dianiline, 3,9-bis-(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, and polyoxyethylenediamine. Useful diamines include N-methyl-1,3-propanediamine; N-ethyl-1,2-ethanediamine; 2-(2-aminoethylamino)ethanol; pentaethylenehexaamine; ethylenediamine; N-methylethanolamine; and 1,3-propanediamine.
Examples of useful polyamines include polyamines having at least three amino groups, wherein at least one of the three amino groups are primary, and the remaining may be primary, secondary, or a combination thereof. Examples include H2N(CH2CH2NH)1-10H, H2N(CH2CH2CH2CH2NH)1-10H, H2N(CH2CH2CH2CH2CH2CH2NH)1-10H, H2N(CH2)3NHCH2CH═CHCH2NH(CH2)3NH2, H2N(CH2)4NH(CH2)3NH2, H2N(CH2)3NH(CH2)4NH(CH2)3NH2, H2N(CH2)3NH(CH2)2NH(CH2)3NH2, H2N(CH2)2NH(CH2)3NH(CH2)2NH2, H2N(CH2)3NH(CH2)2NH2, C6H5NH(CH2)2NH(CH2)2NH2, and N(CH2CH2NH2)3,
Other useful di- or polyamines are 4,4′-methylene dianiline, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, and polyoxyethylenediamine. Many di- and polyamines, such as those just named, are available commercially, for example, those available from Huntsman Chemical, Houston, Tex.
The curing agent should be used in quantities substantial enough to cause the amorphous fluoropolymer to cure, as indicated by a rise in torque on a moving die rheometer. For example, at least 0.5-20 parts of the crosslinking agent per 100 parts of the amorphous fluoropolymer is used. If too little curing agent is used, the amorphous fluoropolymer will not cure. For example, no more than 20, 15, 10, or even 8 millimoles of the curing agent per 100 parts of the amorphous fluoropolymer is used. If too much curing agent is used, the amorphous fluoropolymer can become brittle.
One or a blend of sulfonamide compounds with Formula I may be used, including any combination of sulfonamide compounds of Formulas II, II and IV.
In addition to the sulfonamide crosslinking agents or Formula I, the curable composition may optionally include a second, optional crosslinking agent. Examples of the optional crosslinking agent include polyol compounds, polythiol compounds, polyamine compounds, amidine compounds, bisaminophenol compounds, oxime compounds, and the like. In some embodiments, the second crosslinking agent may comprise a non-fluorinated hydrocarbyl sulfonamide analogous to Formula I.
Generally, examples are not restricted for selecting the specific combination of the sulfonamides of Formula I and secondary crosslinking agent and/or crosslinking promoter, depending on the type of polymer, but typical examples are presented below. For example, with a vinylidene fluoride system (binary system or ternary system), a polyol compound, polyamine compound, polythiophen compound is preferable. With a tetrafluoroethylene-propylene-vinylidene fluoride-based fluorine rubber (ternary) system, polyol compound, polyamine compound, polythiol compound, or the like is preferable.
Examples of preferable polyol compounds include 2,2-bis(4-hydroxyphenyl) hexafluoropropane, 4,4′-dihydroxy diphenyl sulfone, 4,4′-diisopropylidene diphenol, and the like.
Examples of preferable polythiol compounds include 2-dibutyl amino-4,6-dimercapto-s-triazine, 2,4,6-trimercapto-s-triazine, and the like.
Examples of preferable polyamine compounds include hexamethylene diamine carbamate, N,N′-dicinnamylidene-1,6-hexanediamine, 4,4′-methylene bis(cyclohexylamine) carbonate, and the like.
Examples of preferable amidine compounds include p-toluene sulfonate salts of 1,8-diazabicyclo[5.4.0]undec-7-ene, and the like.
Examples of preferable bisaminophenol compounds include 2,2-bis(3-amino-4-hydroxyphenyl))-hexafluoropropane, 2,2-bis[3-amino-4-(N-phenylamino) phenyl]hexafluoropropane, and the like.
In some embodiments, a combination of sulfonamides of Formulas I-IV may be combined with a secondary fluorinated sulfonamide of the Formula Rf[(A)zSO2NR(M1/2)]2, as described in U.S. Pat. No. 5,086,123 (Guenthner et al.), incorporated herein by reference.
In some embodiments, a combination of sulfonamides of Formulas I-IV may be combined with a secondary fluorinated compounds of the Formula Z-Q-Rf—O—(Rfo)Rf-Q-Z, as described in U.S. Pat. Nos. 5,384,374, 5,266,650, Guerra et al, each incorporated herein by reference.
If using an optional second crosslinking agent, the molar ratios of the sulfonamide crosslinking agent of Formula I to the second crosslinking agent may be from 5:1 to 1:1.
The curable composition may further comprise an acid acceptor including organic, inorganic, or blends of thereof. Examples of inorganic acceptors include magnesium oxide, lead oxide, calcium oxide, calcium hydroxide, dibasic lead phosphate, zinc oxide, barium carbonate, strontium hydroxide, calcium carbonate, hydrotalcite, etc. Organic acceptors include amines, epoxies, sodium stearate, and magnesium oxalate. Particularly suitable acid acceptors include calcium hydroxide, magnesium oxide and zinc oxide. Blends of acid acceptors may be used as well. The amount of acid acceptor will generally depend on the nature of the acid acceptor used.
If the presence of an extractable metal compound is not desirable (such as semiconductor applications), the use of inorganic acid acceptors should be minimized, and these preferably should not be used at all. For example, a hardening composition with a formula that does not use an inorganic acid acceptor is particularly useful for sealing materials and gaskets for manufacturing semiconductor elements, sealing materials that are in contact with water, hot water, or the like, and sealing materials for high temperature areas such as automotive applications.
Examples of preferred acid acceptors that are commonly used include zinc oxide, calcium hydroxide, calcium carbonate, magnesium oxide, hydrotalcite, silicon dioxide (silica), lead oxide, and the like. These compounds are generally used in order to bond with HF and other acids. These acids are possibly produced at high temperatures that can be encountered during the hardening process when molding a molded article using the fluoropolymer composition, or at temperatures that demonstrate the function of fluoropolymers and the like.
In one embodiment, at least 0.5, 1, 2, 3, or even 4 parts of the acid acceptor per 100 parts of the amorphous fluoropolymer are used. In one embodiment, no more than 10, 7, or even 5 parts of the acid acceptor per 100 parts of the amorphous fluoropolymer are used.
The curable composition may further comprise an organo onium compound added to the composition as a phase transfer catalyst to assist with the crosslinking of the amorphous fluoropolymer and/or may be used to generate the double bonds on the fluoropolymer through dehydrofluorination. Such organo onium compounds include quaternary ammonium hydroxides or salts, quaternary phosphonium hydroxides or salts, and ternary sulfonium hydroxides or salts.
Briefly, a phosphonium and ammonium salts or compounds comprise a central atom of phosphorous or nitrogen, respectively, covalently bonded to four organic moieties by means of a carbon-phosphorous (or carbon-nitrogen) covalent bonds and is ionically associated with an anion. The organic moieties can be the same or different. Briefly, a sulfonium compound is a sulfur-containing organic compound in which at least one sulfur atom is covalently bonded to three organic moieties having from 1 to 20 carbon atoms by means of carbon-sulfur covalent bonds and is ionically associated with an anion. The organic moieties can be the same or different. The sulfonium compounds may have more than one relatively positive sulfur atom, e.g. [(C6H5)2S+(CH2)4S+(C6H5)2]2Cl−, and two of the carbon-sulfur covalent bonds may be between the carbon atoms of a divalent organic moiety, i.e., the sulfur atom may be a heteroatom in a cyclic structure.
Many of the organo-onium compounds useful in this invention are described and known in the art. See, for example, U.S. Pat. No. 4,233,421 (Worm), U.S. Pat. No. 4,912,171 (Grootaert et al.), U.S. Pat. No. 5,086,123 (Guenthner et al.), and U.S. Pat. No. 5,262,490 (Kolb et al.), U.S. Pat. No. 5,929,169, all of whose descriptions are herein incorporated by reference. Another class of useful organo-onium compounds include those having one or more pendent fluorinated alkyl groups. Generally, the most useful fluorinated onium compounds are disclosed by Coggio et al. in U.S. Pat. No. 5,591,804.
Exemplary organo onium compounds include: C3-C6 symmetrical tetraalkylammonium salts, unsymmetrical tetraalkylammonium salts wherein the sum of alkyl carbons is between 8 and 24 and benzyltrialkylammonium salts wherein the sum of alkyl carbons is between 7 and 19 (for example tetrabutylammonium bromide, tetrabutylammonium chloride, benzyltributylammonium chloride, benzyltriethylammonium chloride, tetrabutylammonium hydrogen sulfate and tetrabutylnammonium hydroxide, phenyltrimethylammonium chloride, tetrapentylammonium chloride, tetrapropylammonium bromide, tetrahexylammonim chloride, and tetraheptylammonium bromidetetramethylammonium chloride); quaternary phosphoniurn salts, such as tetrabutylphosphonium salts, tetraphenylphosphonium chloride, benzyltriphenylphosphonium chloride, tributylallylphosphonium chloride, trbutylbenzyl phosphonium chloride, tributyl-2-mnethoxypropylphosphonium chloride, benzyldiphenyl(dimethylamino)phosphonium chloride, 8-benzyl-1,8-diazobicyclo[5.4.0]7-undecenium chloride, benzyltris(dimethylamino)phosphonium chloride, and bis(benzyldiphenylphosphine)iminium chloride. Other suitable organo onium compounds include 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[4.3.0]non-5-ene. Phenolate is a preferred anion for the quaternary ammonium and phosphonium salts.
In one embodiment, the organo onium compound is used between 1 and 5 millimoles per 100 parts of the amorphous fluoropolymer (mmhr).
The fluoropolymer composition can also contain various additives in addition to the aforementioned components. Examples of additives include crosslinking auxiliary agents and/or crosslinking promoting auxiliary agents that combine favorably with the crosslinking agent and/or crosslinking promoter used, fillers (such as carbon black, flowers of zinc, silica, diatomaceous earth, silicate compounds (clay, talc, wollastonite, and the like), calcium carbonate, titanium oxide, sedimentary barium sulfate, aluminum oxide, mica, iron oxide, chromium oxide, fluoropolymer filler, and the like), plasticizers, lubricants (graphite, molybdenum disulfide, and the like), release agents (fatty acid esters, fatty acid amides, fatty acid metals, low molecular weight polyethylene, and the like), colorants (cyanine green and the like), and processing aids that are commonly used when compounding fluoropolymer compositions, and the like. However, these additives are preferably sufficiently stable under the intended conditions of use.
Furthermore, the carbon black can be used to achieve a balance between fluoropolymer composition properties such as tensile stress, tensile strength, elongation, hardness, wear resistance, conductivity, processability, and the like. Preferable examples include MT blacks under the product numbers N-991, N-990, N-908, and N-907 (medium thermal black); FEF N-550; and large diameter furnace black, and the like. If carbon black is used, the amount is preferably from approximately 0.1 to approximately 70 mass parts (phr) based on 100 mass parts of the total amount of polymer containing fluorinated olefin units and the additional polymer. This range is particularly preferable for the case where large particle furnace black is used
The curable amorphous fluoropolymer compositions may be prepared by mixing the amorphous fluoropolymer, the curing agent, along with the other components (e.g., the acid acceptor, the onium compound, and/or additional additives) in conventional rubber processing equipment to provide a solid mixture, i.e. a solid polymer containing the additional ingredients, also referred to in the art as a “compound”. This process of mixing the ingredients to produce such a solid polymer composition containing other ingredients is typically called “compounding”. Such equipment includes rubber mills, internal mixers, such as Banbury mixers, and mixing extruders. The temperature of the mixture during mixing typically will not rise above about 120° C. During mixing the components and additives are distributed uniformly throughout the resulting fluorinated polymer “compound” or polymer sheets. The “compound” can then be extruded or pressed in a mold, e.g., a cavity or a transfer mold and subsequently be oven-cured. In an alternative embodiment curing can be done in an autoclave.
Curing is typically achieved by heat-treating the curable amorphous fluoropolymer composition. The heat-treatment is carried out at an effective temperature and effective time to create a cured fluoroelastomer. Optimum conditions can be tested by examining the cured fluoroelastomer for its mechanical and physical properties. Typically, curing is carried out at temperatures greater than 120° C. or greater than 150° C. Typical curing conditions include curing at temperatures between 160° C. and 210° C. or between 160° C. and 190° C. Typical curing periods include from 3 to 90 minutes. Curing is preferably carried out under pressure. For example, pressures from 10 to 100 bar may be applied. A post curing cycle may be applied to ensure the curing process is fully completed. Post curing may be carried out at a temperature between 170° C. and 250° C. for a period of 1 to 24 hours.
The partially fluorinated amorphous fluoropolymer in the curable composition has a Mooney viscosity in accordance with ASTM D1646-06 TYPE A by a MV 2000 instrument (available from Alpha Technologies, Ohio, USA) using large rotor (ML 1+10) at 121° C. Upon curing, using the curing agent disclosed herein, the amorphous fluoropolymer becomes an elastomer, becoming a non-flowing fluoropolymer, and having an infinite viscosity (and therefore no measurable Mooney viscosity).
The above curable compositions can be compounded or mixed in one or several steps, and then the mixture can be processed and shaped, for example, by extrusion (for example, in the form of a hose or hose lining) or molding (for example, in the form of an O-ring seal). The shaped article can then be heated to cure the composition and form a cured elastomer article.
In some embodiments the desired amounts of conventional additives adjuvants or ingredients are added to the uncured compositions and intimately admixed or compounded therewith by employing any of the usual rubber mixing devices such as Banbury mixers, roll mills, or any other convenient mixing device. The temperature of the mixture on the mill typically will not rise above about 120° C. During milling the components and adjuvants are distributed uniformly throughout the gum. The curing process typically comprises extrusion of the compounded mixture or pressing the compounded mixture in a mold, e.g., a cavity or a transfer mold, and subsequent oven-curing. Pressing of the compounded mixture (press cure) is usually conducted at a temperature between about 95 and about 230° C., preferably between about 150° C. and about 205° C. for a period of from 1 minute to 15 hours, typically from 5 minutes to 30 minutes. A pressure of between about 700 kPa and about 20,600 kPa is usually imposed on the compounded mixture in the mold. The molds first may be coated with a release agent, such as a silicone oil, and prebaked. The molded vulcanizate is then usually post-cured (oven-cured) at a temperature usually between about 150° C. and about 315° C. for a period of from about 2 hours to 50 hours or more depending on the cross-sectional thickness of the article.
The compositions of this invention can be used to form seals, O-rings and gaskets. The cured fluorocarbon elastomer mixture has excellent low-temperature flexibility while retaining the desired physical properties, for example tensile strength and elongation, of conventionally compounded and cured compositions. Particularly useful articles that can be fabricated from the fluorocarbon elastomer compositions of this invention are particularly useful as seals, gaskets, and molded parts in automotive, chemical processing, semiconductor, aerospace, and petroleum industry applications, among others.
All materials are commercially available, for example from Sigma-Aldrich Chemical Company, Milwaukee, Wis., USA, or known to those skilled in the art, unless otherwise stated or apparent.
The following abbreviations are used in this section: g=grams, N-m=newton meters, mm=millimeters, min=minutes, h=hours, phr=parts per hundred rubber, MPa=megapascal ° C.=degrees Celsius. Abbreviations for materials used in this section, as well as descriptions of the materials, are provided in Table 1.
To a 3-necked round-bottom flask was added 49 g (0.4517 mol) of triethyl amine, 25 g (0.2151 mol) hexamethylene diamine and 200 ml of toluene at 35° C. To this was added dropwise a solution of 114.6 g (0.4302 mol) of methane sulfonylchloride. An exotherm occurred which raised the temperature to 95° C., despite cooling the flask in an ice bath.
The contents of the flask were allowed to cool to 70° C. and heated for another hour, before 300 mL of water was added at ambient temperature. This mixture was allowed to mix for 30 min. The resulting slurry was filtered and the precipitate was washed 5 times with 200 mL water, followed by two times with 200 mL 2-propanol. The cake was then dried at 40° C. in an oven for 5-6 h.
1. Compounding
150 g batches of fluoropolymer were compounded with 0.78 phr of TPBPCl, various amounts of curing agent as indicated in Table 2, 6 phr of Ca(OH)2, 3 phr of MgO, and 20 phr of N990 carbon black, using a two-roll mill. Milling continued until a homogeneous blend formed. Ca(OH)2, 3 phr of MgO, N990 were added as a mixture. When two co-agents were used, they were added as a blend. The ratios of each component in examples and counter examples are indicated as phr in Table 2, below.
2. Cure Rheology
Cure rheology tests were carried out using uncured, compounded samples using a rheometer marketed under the trade designation RPA 200 by Alpha technologies, Akron, Ohio, in accordance with ASTM D 5289-93a at 177° C., 12 minute elapsed time, and a 0.5 degree arc. The minimum torque (ML), maximum torque (MH), the time for the torque to reach a value equal to ML+0.5(MH−ML), (t′50), and the time for the torque to reach ML+0.9(MH−ML), (t′90), the scorch time (Ts2), and Tan delta at maximum torque were measured and their values are listed in Table 3.
3. Press-Cure Molding and Physical Property Test
The compound was press-cured using a mold (size: 75 mm×150 mm×2 mm or 150 mm×150 mm X2 mm) at 6.5×103 kPa and 177° C. for 10 min. Then the elastomer sheets were removed, cooled to room temperature, and then used for physical property test and post-cure. The dumbbell specimens were cutout from the sheets with ASTM Die D and subjected to physical property testing similar to the procedure disclosed in ASTM D412-06a (2013). The typical tensile strength deviation is +/−1.4 MPa (200 psi). The typical elongation deviation is +/−25%. Hardness is +/−2
The test results are summarized in Table 4.
4. Post-Cure and Physical Property Test
The press-cured elastomer sheet was post cured at 232° C. for 16 h in a circulating air oven. The samples were then removed from the oven, cooled to room temperature, and physical properties determined. The dumbbell specimens were cutout from the sheets with ASTM Die D and subjected to physical property testing similar to the procedure disclosed in ASTM D412-06a (2013). The test results are summarized in Table 3.
5. Heat-Aging and Physical Property Test
The dumbbell specimens of post cured samples were placed in a circulating air oven for 70 h at 270° C. The samples were then removed from the oven and cooled to room temperature for measurement of physical properties according to ASTM D412-06a. The test results are summarized in Table 4.
6. O-Ring Molding and Compression Set Test
O-rings having a cross-section thickness of 0.139 inch (3.5 mm) were molded at 6.5×103 kPa and 177° C. for 10 min and then post-cured at 232° C. for 16 h. The O-rings were subjected to compression set testing similar to the procedure disclosed in ASTM 395-89 method B, with 25% initial deflection. The typical deviation is +/−2-3% Results of compression test are reported in Table 4.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2019/051151 | 2/13/2019 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62632009 | Feb 2018 | US |
