The invention pertains to fluoropolymers derived from (i) tetrafluoroethylene (TFE), (ii) vinylidene fluoride (VF2), (iii) at least one ethylenically unsaturated monomer of the formula CF2xe2x95x90CFRf, and (iv) a perfluorovinyl ether of the formula CF2xe2x95x90CFOCF2CF(Rf)aORxe2x80x2f where a, Rf, and Rxe2x80x2f are defined below.
Polymers of tetrafluoroethylene (TFE) with other fluorinated monomers such as vinylidene fluoride (VDF) and hexafluoropropylene (HFP) are known. These polymers include both fluoroelastomers and melt processable fluoroplastics.
Fluoroelastomers with high fluorine content have been shown to have excellent permeation resistance to fuels. (U.S. Pat. No. 4,696,989). However, high-fluorine elastomer systems based on tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP) have some limitations. When the TFE-content is too high, flexibility, and the ease of processing tend to be compromised. If the HFP content, at the expense of VDF is too high, the polymerization rate is much too low.
Another class of polymers with superior permeation properties are the melt-processable fluoroplastics THV (see Modern Fluoropolymers, Wiley, 1997). The terpolymers can have melting points up to 275xc2x0 C. and show excellent permeation and low temperature properties. However, sealability and flexural properties sometimes do not meet industry requirements. The increased stiffness of those materials can lead to wrinkling when hoses are loaded onto forming mandrels. It can also lead to increased push-on force during hose installation and sealing concerns at connecting points. These fluoroplastic materials and their wide range of uses is described in more detail in xe2x80x9cModern Fluoropolymersxe2x80x9d, Wiley, 1997, p. 257. They typically are derived from monomer compositions comprising from 30-75 weight % TFE, 5-40 weight % HFP and 5-55 weight % VDF and have a melting point range of 100xc2x0 C. to 275xc2x0 C.
Because of their permeation resistance, fluoropolymers are desired in a variety of products, including hose and fuel-line designs for automotive applications such as those disclosed in U.S. Pat. No. 5,804,670 and EP 824059. Other product applications where such polymers are useful include fuel filler neck hoses, fuel vent lines, vapor return lines, chemical handling hoses and the like.
These product applications are often multilayer constructions in which the fluoropolymer layer serves as a chemically resistant or vapor impermeable barrier. The remainder of these multilayer constructions typically comprises a layer of either a less expensive non-fluorinated polymer layer or another fluoropolymer. These other polymers can be thermoplastic or they can be elastomeric in nature. The constructions can also employ a tie layer between the various layers. In any event, the layers are generally covalently bonded to each other.
These constructions generally must be highly flexible to facilitate installation, provide good sealing around connectors and to withstand the formation of bubbles and/or ripples in pieces with sharp bends. Additionally, when they are used with a non-fluorinated elastomer, the fluoropolymer must be resistant to high temperatures to minimize the temperatures encountered during the manufacture and use of constructions that employ them.
While the use of fluoropolymers in applications such as those disclosed above has increased in recent years, a need still exists to provide improved fluoropolymers. The present invention provides such improved fluoropolymers.
The present invention provides fluoropolymers that comprise TFE, VF2, at least one perfluorinated ethylenically unsaturated monomer, and a perfluorovinyl ether. The polymers of the invention demonstrate excellent physical properties over a broad range of compositions. They also demonstrate superior flexibility.
In accordance with the present invention there is provided a fluoropolymer derived from interpolymerized units of (i) TFE, (ii) VF2, (iii) at least one ethylenically unsaturated monomer of the formula CF2xe2x95x90CFRf where Rf is perfluoroalkyl of 1 to 8, preferably 1 to 3, carbon atoms, and (iv) a perfluorovinyl ether of the formula CF2xe2x95x90CFxe2x80x94(OCF2CF(Rf))aORxe2x80x2f where Rf is a perfluoroalkyl of 1 to 8, preferably 1 to 3, carbon atoms, Rxe2x80x2f is a perfluoroaliphatic, preferably perfluoroalkyl or perfluoroalkoxy, of 1 to 8, preferably 1-3, carbon atoms, and a has a value of from 0 to 3.
Also provided herein are multilayer articles comprising a first layer or strata of the polymer of the invention and a second layer or strata of the same or another polymer. The layers are preferably covalently bonded to one another either through a tie layer between them or by means of direct covalent bonding between the two layers. Other polymeric layers may also be employed in this embodiment of the invention.
Also provided in accordance with the present invention is an electrostatically dissipative (ESD) composition comprising an electrically conductive particulate material and the polymer of the invention.
Also provided herein is a method for improving the flexibility of a fluoropolymer containing interpolymerized units derived from TFE, VF2 and at least one ethylenically unsaturated monomer of the formula CF2xe2x95x90CFRf where Rf is as described above. The method comprises the steps of providing these monomers and a monomer of the formula CF2xe2x95x90CFOCF2CF(Rf)aORxe2x80x2f and polymerizing the monomers.
The polymer of the invention offers advantages, in the production of multi-layer articles by means of extrusion or coextrusion; in injection molding; and in compression molding. Fluoroplastics of the invention offer benefits in optical applications such as polymer optical fibers; and in use as an electrostatically dissipative (ESD) fluoroplastic. These advantages are especially useful in the case of complicated shapes.
Specific examples of such multilayer and/or shaped articles include fuel management components, e.g., fuel filler neck hoses, vent lines, vapor return lines, etc., where resistance to hydrocarbon fluids is important; chemical handling components (e.g., hoses containers, etc.) and polymer optical fibers. In this latter case the polymers of the invention can be used as the optical fiber itself or as a cladding around the optical fiber (typically an acrylate polymer).
The polymer of the invention is sometimes referred to herein as a quad polymer. In one preferred embodiment it is derived from 30 to 85 weight % TFE, 5 to 55 weight % VDF, and from 5 to 50 weight % of the unsaturated monomer having the formula CF2xe2x95x90CFRf and from 0.1 to 15 weight % of the vinyl ether. Included in this range of compositions are semi-crystalline and elastomeric fluoropolymers.
The molecular weight of the polymer of the invention is not critical and may vary over a wide range. Thus it may) vary from low molecular weight to ultra high molecular weight. Furthermore, the fluoropolymers may have either a generally unimodal or a multimodal molecular weight distribution.
The molecular weight of a semicrystalline fluoropolymer according to the invention may be described by its melt flow index (MFI). MFI can be determined by following the procedures described in either ISO 12086 or ASTM D-1238 at a support weight of 5 kg and a temperature of 265xc2x0 C.
The molecular weight of an elastomeric fluoropolymer according to the invention may be described by its Mooney viscosity (ML). This value can be measured according to ASTM D 1646 using a one minute pre-heat and a 10 minute test at 121xc2x0 C.
The semi-crystalline fluoropolymers of the invention typically have a peak melting temperature in the range of 100xc2x0 to 275xc2x0 C. (preferably 120 to 250xc2x0 C.) and a number average molecular weight of from 25,000 to 1,000,000. Preferably they have a hydrogen content of less than 5% by weight and a fluorine content of from 65 to 76%. Most preferably the polymers of the invention consist essentially of interpolymerized units derived from the four enumerated monomers.
The elastomeric fluoropolymers of the invention typically exhibit a glass transition temperature (Tg) and a melting point of less than 120xc2x0 C. The elastomers are essentially amorphous and are curable using known techniques. By essentially amorphous it is meant that the polymer may contain some crystallinity e.g., less than 10%. For example, they can be cured using onium cure chemistries such as are disclosed in U.S. Pat. Nos. 4,233,421; 4,882,390; and 5,262,490. Alternatively, they can be modified to include small amounts of cure-site monomers (e.g., bromine or iodine cure-site monomers or nitrile cure-site monomers) to render them peroxide curable. Such chemistries are disclosed in U.S. Pat. Nos. 4,035,565; 4,972,038; and 5,151,492.
Preferably, the thermoplastic polymers of the invention comprise interpolymerized units derived from (i) 40 to 80 weight percent (more preferably 45 to 76 weight percent) tetrafluoroethylene, (ii) 10 to 30 weight percent (more preferably 12 to 25 weight percent) vinylidene fluoride, (iii) 5 to 40 weight percent (more preferably from 10 to 30 weight percent) of a comonomer of the formula CF2xe2x95x90CFRf, and (iv) 0.1 to 15 weight percent (more preferably 1 to 10 weight percent) of the perfluorovinyl ether of the formula CF2xe2x95x90CFxe2x80x94(OCF2CF(Rf))aORxe2x80x2f.
Preferably the elastomeric polymers of the invention comprise interpolymerized units derived from (i) 20 to 50 weight percent (more preferably 30 to 46 weight percent; most preferably 33 to 46 weight percent) TFE, (ii) 10 to 35 weight percent (more preferably 15 to 30 weight percent; most preferably 17 to 28 weight percent) VDF, (iii) 20 to 50 weight percent (more preferably from 25 to 45 weight percent; most preferably from 26 to 42 weight percent) of a comonomer of the formula CF2xe2x95x90CFRf, and from 0.1 to 15 weight percent (more preferably from 0.5 to 10 weight percent; most preferably from 0.5 to 7 weight percent) of the perfluorovinyl ether of the formula CF2xe2x95x90CFxe2x80x94(OCF2CF(Rf))aORxe2x80x2t.
A preferred subclass of the perfluorovinyl ether has the formula
CF2xe2x95x90CFxe2x80x94(OCF2CF(CF3))aORxe2x80x2f. 
Examples of the perfluorovinyl ether having this formula include
CF2xe2x95x90CFOCF3xe2x80x83xe2x80x83PMVE 
CF2xe2x95x90CFOCF2CF2CF2OCF3xe2x80x83xe2x80x83MV31 
CF2xe2x95x90CFOCF2CF2CF3xe2x80x83xe2x80x83PPVE1 

Particularly preferred perfluorovinyl ethers are PPVE1 and PPVE2.
A preferred species of the quadpolymer of the invention contains interpolymerized units derived from TFE, VDF, HFP and the perfluorovinyl ether wherein the value of xe2x80x9caxe2x80x9d is 0, 1 or 2.
Fluoropolymers of this class can be prepared by methods known in the fluoropolymer art. Such methods include, for example, free-radical polymerization of the monomers. In general, the desired olefinic monomers can be copolymerized in an aqueous colloidal dispersion in the presence of water-soluble initiators which produce free radicals such as ammonium or alkali metal persulfates or alkali metal permanganates, and in the presence of emulsifiers such as the ammonium or alkali metal salts of perfluorooctanoic acid. See for example U.S. Pat. No. 4,335,238 or Canadian Pat. No. 2,147,045. They may also be prepared using a fluorinated sulfinate as a reducing agent and a water soluble oxidizing agent capable of converting the sulfinate to a sulfonyl radical. Preferred oxidizing agents are sodium, potassium, and ammonium persulfates, perphosphates, perborates, and percarbonates. Particularly preferred oxidizing agents are sodium, potassium, and ammonium persulfates.
Aqueous emulsion and suspension polymerizations can be carried out in conventional steady-state conditions in which, for example, monomers, water, surfactants, buffers and catalysts are fed continuously to a stirred reactor under optimum pressure and temperature conditions while the resulting emulsion or suspension is removed continuously. An alternative technique is batch or semibatch polymerization by feeding the ingredients into a stirred reactor and allowing them to react at a set temperature for a specified length of time or by charging ingredients into the reactor and feeding the monomer into the reactor to maintain a constant pressure until a desired amount of polymer is formed.
As previously disclosed herein, the quadpolymer may be an ESD fluoropolymer composition. In this aspect of the invention, the ESD quadpolymer composition comprises a major amount of the quadpolymer, up to 20% by weight of a conductive material, and a minor amount, up to 5% of another melt processable thermoplastic material, preferably a hydrocarbon polymer. The ESD quadpolymer composition preferably contains 2 to 10 wt % of the conductive material and 0.1 to 3 wt % of the hydrocarbon polymer. While a wide variety of conductive fillers are useful, the most commonly employed conductive materials are carbon black, graphite and fibers thereof. Likewise, a variety of hydrocarbon polymers may be used as the other melt processable thermoplastic material. Such materials are preferably fluid at the processing temperature of the quadpolymer. Additionally, the hydrocarbon polymer is preferably immiscible with the quadpolymer. Preferably, the hydrocarbon polymers are olefin polymers of the type disclosed in U.S. Pat. No. 5,549,948, col. 2, line 52 to col. 4, line 60 incorporated herein by reference.
The fluoropolymer of this invention, can be easily co-processed (for example coextruded) with a variety of thermoplastic and elastomeric polymers in the fabrication of multi-layer articles such as hoses, tubes, films, sheets, wire coatings, cable jackets, containers, pipes, etc. Examples of polymers that can be co-processed with the polymer of the invention include thermoplastic and elastomeric polymers. Examples of such polymers are polyamides, polyimides, polyurethanes, polyolefins, polystyrenes, polyesters, polycarbonates, polyketones, polyureas, polyacrylates, polymethacrylates, epichlorohydrin-containing elastomers, nitrile-butadiene elastomers, ethylene propylene diene elastomers, silicone-containing elastomers, fluoroelastomers, etc. Preferably the elastomers are curable by techniques known in the art, e.g., by peroxide curing, hydroxyl curing, polyamine curing, sulfur curing, etc. The particular polymer selected will depend upon the application or desired properties.
Polyamides that can be co-processed with the fluoropolymer and fluoropolymer compositions of the invention are generally commercially available. For example, polyamides such as any of the well-known nylons are available from a number of sources. Particularly preferred polyamides are nylon-6, nylon-6,6, nylon-l 1, nylon-12, and nylon 6-636. It should be noted that the selection of a particular polyamides material should be based upon the physical requirements of the particular application for the resulting article. For example, nylon-6 and nylon-6,6 offer higher heat resistance properties than nylon-11 or nylon-12, whereas nylon-11 and nylon-12 offer better chemical resistant properties. In addition to those polyamide materials, other nylon materials such as nylon-6,12, nylon-6,9, nylon-4, nylon-4,2, nylon-4,6, nylon-7, and nylon-8 may also be used. Ring containing polyamides, e.g., nylon-6,T and nylon-6,1, may also be used. Polyether containing polyamides, such as PEBAX polyamides (Atochem North America, Philadelphia, Pa.), may also be used.
Useful co-processable polyurethane polymers include aliphatic, cycloaliphatic, aromatic, and polycyclic polyurethanes. These polyurethanes are typically produced by reaction of a polyfunctional isocyanate with a polyol according to well-known reaction mechanisms. Useful diisocyanates for employment in the production of a polyurethane include dicyclohexylmethane-4,4xe2x80x2-diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, cyclohexyl diisocyanate, and diphenylmethane diisocyanate. Combinations of one or more polyfunctional isocyanates may also be used. Useful polyols include polypentyleneadipate glycol, polytetramethylene ether glycol, polyethylene glycol, polycaprolactone diol, poly-1,2-butylene oxide glycol, and combinations thereof. Chain extenders, such as butanediol or hexanediol, may also optionally be used in the reaction. Commercially available urethane polymer useful in the present invention include: PN-3429 from Morton International, Seabrook, N.H., and X-4107 from B. F. Goodrich Company, Cleveland, Ohio.
The polyolefin polymers that can be co-processed are generally homopolymers or copolymers of ethylene, propylene, acrylic monomers, or other ethylenically unsaturated monomers, for example, vinyl acetate and higher alpha-olefins. Such polymers and copolymers can be prepared by conventional free-radical polymerization or catalysts of such ethylenically unsaturated monomers. The degree of crystallinity of the olefin polymer or copolymer can vary. The polymer may, for example, be a semi-crystalline high density polyethylene or may be an elastomeric copolymer of ethylene and propylene. Carboxyl, anhydride, or imide functionalities may be incorporated into the hydrocarbon polymer within the present invention, by polymerizing or copolymerizing functional monomers, for example, acrylic acid or maleic anhydride, or by modifying a polymer after polymerization, for example, by grafting, by oxidation or by forming ionomers. These include, for example, acid modified ethylene vinyl acetates, acid modified ehtylene acrylates, anhydride modified ethylene acrylates, anhydride modified ethylene vinyl acetates, anhydride modified polyethylenes, and anhydride modified polypropylenes. The carboxyl, anhydride, or imide functional polymers useful as the hydrocarbon polymer are generally commercially available. For example, anhydride modified polyethylenes are commercially available from DuPont, Wilmington, Del., under the trade designation BYNEL coextrudable adhesive resins.
Polyacrylates and polymethacrylates useful that can be co-processed include, for example, polymers of acrylic acid, methyl acrylate, ethyl acrylate, acrylamide, methylacrylic acid, methyl methacrylate, and ethyl acrylate, to name a few. As mentioned above, other useful substantially non-fluorinated co-processable polymers include polyesters, polycarbonates, polyketones, and polyureas. These materials are generally commercially available, for example, SELAR polyester (DuPont, Wilmington, Del.), LEXAN polycarbonate (General Electric, Pittsfield, Mass.), KADEL polyketone (Amoco, Chicago, Ill.), and SPECTRIM polyurea (Dow Chemical, Midland, Mich.).
Examples of co-processable elastomeric polymers include acrylonitrile butadiene (NBR), butadiene rubber, chlorinated and chloro-sulfonated polyethylene, chloroprene, EPM, EPDM, epichlorohydrin (ECO), isobutylene isoprene, isoprene, polysulfide, polyurethane, silicone, PVC-NBR, styrene butadiene, and vinyl acetate ethylene. Examples of these compounds include Nipol 1052 NBR (Zeon, Louisville, Ky.), Hydrin 2000 ECO (Zeon, Louisville, Ky.), Hypalon 48 (Dupont, Wilmington, Del.), and Nordel 2760P EPDM (Dupont, Wilmington, Del.).
The co-processing of fluoropolymers is further described in U.S. Pat. Nos. 5,656,121, 5,658,670, 5,855,977, WO 98/08679, WO 99/00249, and WO 99/00454, which discloses composite articles employing a fluorine-containing polymer. The fluoropolymers and ESD polymers of the present invention may be used as the fluorine-containing polymer in such composite articles. Such articles include two, three and more than three layer composite articles. The articles may employ a tie layer to join the fluoropolymer to the other layers.
The elastomeric fluoropolymers may also be compounded with various other ingredients to modify their properties and/or usefulness. For example, they can be combined with curatives to provide composition that, upon curing, exhibits good physical properties.
Useful curatives include both peroxides or polyol/onium salt combinations. Useful peroxides include dialkyl peroxides, with di-tertiary butyl peroxides being particularly preferred. Specific examples include 2,5-dimethyl-2,5-di(tertiarybutylperoxy)-hexyne-3 and 2,5-dimethyl-2,5-di(tertiarybutylperoxy)-hexane. Additional examples of useful peroxides include dicumyl peroxide, dibenzoyl peroxide, tertiarybutyl perbenzoate, and di[1,3-dimethyl-3-(tertiarybutylperoxy)-butyl]carbonate.
One or more crosslinking co-agents may be combined with the peroxide. Examples include triallyl cyanurate; triallyl isocyanurate; tri(methallyl)-isocyanurate; tris(diallylamine)-s-triazine, triallyl phosphite; N,N-diallyl acrylamide; hexaallyl phosphoramide; N,N,Nxe2x80x2Nxe2x80x2-tetraallyl terephthalamide; N,N,Nxe2x80x2,Nxe2x80x2-teraallyl malonamide; trivinyl isocyanurate; 2,4,6-trivinyl methyltrisiloxane; and tri(5-norbornene-2-methylene) cyanurate.
Suitable onium salts are described, for example, in U.S. Pat. Nos. 4,233,421; 4,912,171; and 5,262,490, each of which is incorporated by reference. Examples include triphenylbenzyl phosphonium chloride, tributyl alkyl phosphonium chloride, tributyl benzyl ammonium chloride, tetrabutyl ammonium bromide, and triarylsulfonium chloride.
Another class of useful onium salts is represented by the following formula: 
where Q is nitrogen or phosphorus;
Z is a hydrogen atom or is a substituted or unsubstituted, cyclic or acyclic alkyl group having from 4 to about 20 carbon atoms that is terminated with a group of the formula xe2x80x94COOA where A is a hydrogen atom or is a NH4+ cation or Z is a group of the formula CY2xe2x80x94COORxe2x80x2 where Y is a hydrogen or halogen atom, or is a substituted or unsubstituted alkyl or aryl group having from 1 to about 6 carbon atoms that may optionally contain one or more catenary heteroatoms and where Rxe2x80x2 is a hydrogen atom, a NH4+ cation, an alkyl group, or is an acyclic anhydride, e.g., a group of the formula xe2x80x94COR where R is an alkyl group or is a group that itself contains organo-onium (i.e., giving a bis-organo-onium); preferably Rxe2x80x2 is hydrogen; Z may also be a substituted or unsubstituted, cyclic or acyclic alkyl group having from 4 to about 20 carbon atoms that is terminated with a group of the formula xe2x80x94COOA where A is a hydrogen atom or is a NH4+ cation;
R1, R2, and R3 are each, independently, a hydrogen atom or an alkyl, aryl, alkenyl, or any combination thereof; each R1, R2, and R3 can be substituted with chlorine, fluorine, bromine, cyano, xe2x80x94ORxe2x80x3, or xe2x80x94COORxe2x80x3 where Rxe2x80x3 is a C1 to C20 alkyl, aryl, aralkyl, or alkenyl, and any pair of the R1, R2, and R3 groups can be connected with each other and with Q to form a heterocyclic ring; one or more of the R1, R2, and R3 groups may also be a group of the formula Z where Z is as defined above;
X is an organic or inorganic anion (e.g., halide, sulfate, acetate, phosphate, phosphonate, hydroxide, alkoxide, phenoxide, or bisphenoxide); and
n is a number equal to the valence of the anion X.
Suitable polyols for use with the onium salt include polyhydroxy aromatic compounds such as 2,2-bis(4-hydroxyphenyl)propane [bisphenol A], 2,2-bis(4-hydroxyphenyl)perfluoropropane [bisphenol AF], hydroquinone, catechol, resorcinol, 4,4xe2x80x2-dihydroxydiphenyl, 4,4xe2x80x2-dihydroxydiphenylmethane, 4,4xe2x80x2-dihydroxydiphenylsulfone, and 2,2-bis(4-hydroxydiphenylbutane), their alkali metal salts, alkaline earth metal salts, and combinations thereof. Other useful polyols are described, e.g., in U.S. Pat. Nos. 4,259,463; 3,876,654; 4,912,171; 4,233,421; and 5,384,374, each of which is incorporated by reference.
The curable fluoroelastomer composition can also include fillers to improve the physical properties of both the curable and the cured composition. Examples of suitable fillers include reinforcing agents (e.g., thermal grade carbon blacks or non-black pigments), silica, graphite, clay, talc, diatomaceous earth, barium sulfate, titanium oxide, wollastonite, and combinations thereof. Other ingredients that may be added to the composition, alone or in combination with one or more fillers, include, for example, plasticizers, lubricants, retarding agents, processing aids, pigments, and combinations thereof.
The present invention is further illustrated in the following representative examples. The methods used to determine various physical properties of the polymers is first described.
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