Shear stable aqueous fluoropolymer dispersion

Abstract

The invention relates to a shear stable aqueous fluoropolymer suspension and method of making the fluoropolymer suspension, preferably polyvinylidene fluoride (PVDF), having a particle size of less than 120 nm, solids content of greater than 25 wt%, melt viscosity of greater than 20 kP, and a shear stability of more than 20 min at 1500 rpm.

Description

Shear Stable Aqueous Fluoropolymer Dispersion

[0001] Statement Regarding Federally Sponsored Research or Development

[0002] This application was made with government suppnodrte ur DE-EE0009106 awarded by Department of Energy. The government has certgahints ri in the invention.

[0003] Field of Invention:

[0004] The invention relates to an aqueous fluoropolymisepre drsion that is shear stable and a method of making the dispersion.

[0005] Background:

[0006] Fluorocarbon polymers have been used vastly in re tche nt years. For example,polyvinylidene fluoride (PVDF) polymers as homopmoleyr or as copolymer or as alloy are melt-processable resins that are formed into polymeurct sutr es by many different processes, such asextrusion, injection molding, fiber spinning, exstrioun blow molding and blown film. Fluorocarbon polymers are also used as polymere psrsoincg aids due to their low surface energies and phase behaviors. Most of fluoroca prboolynmers are made by emulsion polymerization followed by an isolation step thsat e inergy intensive; hence, has large carbon footprint.

[0007] Fluorocarbon polymers, particularly PVDF, have a glsreoatly gained importance in the renewable energy as binder in the electrodesh oiuf m lit ion batteries due to its excellent electro- chemical resistance, superb adhesion, and fletxyi.bi PliVDF, has been found to be a useful binder for forming electrodes to be used in none-aoquus electrolytic devices. U.S. Pat. No. 5,776,637, 6,200,703, and 9,434,797 incorporateredin he by reference, describe a PVDF binder solution in organic solvents with a powdery eledcetro material for use in forming an electrode to be used in a non-aqueous-type battery. A large anmt oofu N-methyl-2-pyrrolidone (NMP) solvent is used as a dispersion media in the cotinovneanl solvent casting processes. There is an environmentally driven and safety-driven desire be to able to produce excellent, electrodes without the massive use of organic solvents.

[0008] Meanwhile, fluorocarbon polymers have greatly gdai inne importance as exterior coatings because of their excellent resistanceV t-oA U and UV-B radiation, as well as to many corrosive chemical agents. PVDF - based paints co amremonly applied having high levels of organic solvents, which are needed to dissolveli accsr aynd disperse PVDF. These organic solvents are typically present safety, health annvdiro enmental dangers that are often regulated. Organic solvents are generally toxic and flamma abnled, involve special manufacturing controls to mitigate risks and reduce environmental pollnut firoom the organic solvent. In addition, a large carbon footprint is associated with use olvfe snot-based coatings and that is not environmentally desirable.

[0009] The kinetic of polymerization of fluorinated monorm ise substantially different than non- fluorinated monomers. For that reason, fluorina etmedulsifiers were traditionally used in fluorinated emulsion processes. The fluorinatedul esimfiers, which are often referred to as“forever chemicals”, are environmental persistenndt a re band in many jurisdictions. Non-fluorinated emulsifiers are known to be used fouorr flopolymer polymerization. However, they do not provide a dispersion with the shear stayb ailsit is provided by the present invention.

[0010] The aqueous dispersions of fluoropolymers are rkeambalyr unstable and have tendency to coagulate upon shearing as well as undergo hatrlding se utpon storage. The main difference between fluoropolymer and acrylic dispersion ste frmoms the fact that fluoropolymers have high specific gravities, which varies with the amount h oefir crystallinities, for example, specific gravities of PVDF varies from 1.74 to 2.00 g / 3c amnd specific gravity of PTFE varies from 2.00 to 2.35 g / cm3. As a result, fluoropolymers dispersions are per toon quick settling due to their specific gravity. Moreover, amorphous phasesu oofr folpolymers have low glass transition temperatures (Tg); for example, Tg of PVDF and PT aFreE -40 °C and -73 °C respectively. Consequently, when fluoropolymer particles in thqeue aous dispersion are bumped into each other either due to the Brownian motion or dueh teo s thear mixing, those particles have tendency to agglomerate, ultimately causing thpee drission to coagulate and become unusable.

[0011] There is a need for more shear stable aqueousrs diiosnpse of fluoropolymers that can be used or formulated to make coatings and films fr aoqmueous-based formulations, that are more environmentally friendly and sustainable while mhaintcg excellent properties of the solution casts ones. Therefore, there is a need to imp srhoevlef-stability and shear stability of aqueous fluoropolymer dispersions so that they can be u ssuecdcessfully used in aqueous-based applications.

[0012] Summary of Invention:

[0013] The invention relates to an aqueous fluoropolymisepre drsion comprising: a. fluoropolymer have an average particle size of t lheassn 120 nm, b. Solid content of greater than 25 wt%, c. Melt viscosity of greater than 20 kP, and d. Shear stability of more than 20 min at 1500 rpm.

[0014] The invention also relates to an emulsion procoerss m faking the fluoropolymerdispersion. The use of emulsifiers, the stabil aiznedr the amount of initiator in the polymerizationprocess are important in making the stable fluolryompoer dispersion. The present invention provides a stable fluoropolymer dispersion, theen intvion also provide for a process for synthesizing the stable fluoropolymer in an aque roeuasction medium, comprising a) forming an aqueous emulsion comprising at least two non-io enmiculsifier, and at least one fluoromonomer; b) initiating polymerization of said fluoromonom uesring desired initiator; and c) afterpolymerization has started, continuously feedin lge a stt one stabilizer during the reaction orafter polymerization is concluded. The process uaste lesast two emulsifiers, a ancrylic based glycol ester and a non-ionic block copolymer connitnagi at least two blocks selected from polyethylene glycol, polypropylene glycol and poeltyrat methylene glycol. Stabilizer is also used to produce the aqueous fluoropolymer dispersion of the invention.

[0015] The aqueous fluoropolymer dispersion may be diyre ucstel d in sustainable processes without a need for isolation. The articles madeth w aiqueous fluoropolymer are moreenvironmentally friendly and sustainable then tnhaelo agous organic solvent-based processes; i.e. fabricating electrodes for use in non-aqueous-t eylpecetrochemical devices, such as batteries and electric double layer capacitors or coating ofe drieffnt substrates.

[0016] The fluoropolymer dispersion of the invention iese fr of fluorinated surfactant which are often referred to as "forever chemicals".

[0017] Embodiments of the Invention

[0018] Aspect 1 of the invention provides an aqueous o flupo lrymer dispersion comprising afluoropolymer, wherein the fluoropolymer has an average partiiczle o sf less than 120 nm, a meltviscosity of at least 20 kP or higher at 230C a0n0d s 1ec-1,wherein the dispersion has a solids content oefa astt l 25 wt%, and having a Brookfield viscosity of less than 1000 cP after shearingt fo lera ast 20 min at 1500 rpm .

[0019] Embodiment 2 is the aqueous fluoropolymer dispenrs oifo Embodiment 1, wherein the fluoropolymer comprises at least 60 wt% VDF monom uneirts, preferable at least 70 wt% VDF monomer units.

[0020] Embodiment 3 is the aqueous fluoropolymer dispenrs oifo Embodiment 1 or 2, wherein the fluoropolymer comprises at least comonomer s uenlietcted from the group consisting of HFP, CTFE, PMVE, PPVE, TFE, 2,3,3,3-tetrafluoroprope mneo,nomer units, preferably HFP.

[0021] Embodiment 4 is the aqueous fluoropolymer dispenrs oifo any one of Embodiments 1 to 3, wherein the average particle size is less th0a0n n 1m.

[0022] Embodiment 5 is the aqueous fluoropolymer dispoenrs oif any one of Embodiments 1 to 4, comprising (1) an acrylic based glycol esteer,fe prrably the acrylic based glycol ester comprises at least one of polyethylene glycol actery (lPEGA), polyethylene glycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), oorly ppropylene glycol methacrylate (PPGMA);(2) a non-ionic block copolymer emulsif cieorntaining blocks of at least two of polyethylene glycol, polypropylene glycol and / orly ptoetramethylene glycol and (3) a stabilizer.

[0023] Embodiment 6 is the aqueous fluoropolymer dispenrs oifo embodiment 5, wherein the fluoropolymer comprises polyvinylidene fluoride hinagv at least 60 wt% VDF monomer units , the acrylic based glycol ester is selected fromye ptohlylene glycol acrylate (PEGA), polyethylene glycol methacrylate (PEGMA), polypropylene glycoclry alate (PPGA), and polypropylene glycol methacrylate (PPGMA);()and the non-ionic blocko cloypmer emulsifier contains at least one block of polyethylene glycol and at least onec bklo f polypropylene glycol.

[0024] Embodiment 7 is the aqueous fluoropolymer dispenrs oifo any one of Embodiments 1 to 6, wherein the fluoropolymer comprises at least n oonne fluorinated monomer having at least one reactive double bond and an ionic moiety.

[0025] Embodiment 8 is the aqueous fluoropolymer dispenrs oifo any one of Embodiments 5 to 7, further comprising a stabilizer, wherein theb silitzaer comprises non fluorinated oligomers which contain at least one ionic moiety, prefera abnly acid moiety.

[0026] Embodiment 9 is the aqueous fluoropolymer dispenrs oifo any one of Embodiments 5 to 8, further comprising a stabilizer, wherein theb silitzaer comprises at least one of alkyl sulfate salt or alkyl sulfonate salt and wherein the al gkryolup is a C6 to C18 alkyl group.

[0027] Embodiment 10 provides a process for making ar s-shteaable aqueous fluoropolymer dispersion having a particle size of less than n 1m20 comprising: (a)providing in a reaction vessel, an aqueousi roenac mtedium, at least one fluoromonomer, at least one acrylic based glycol ester, at lenaest n oonionic emulsifier having at least two blocks selected from polyethylene glycol, polyprloepnye glycol and / or polytetramethylene glycol with repeating units of 2 to 200 per a bl,ock (b)polymerizing fluoromonomer of (a) is in presen ocfe at least one initiator wherein the amount of initiator added to the polymerization at is least 1500ppm based on weight of fluoromonomer added to the polymerization, and (c) adding at least one stabilizer to the fluoroypmoelr dispersion during or after polymerization.

[0028] Embodiment 11 is the process of Embodiment 10,e winhe thre fluoromonomer comprises vinylidene fluoride monomer.

[0029] Embodiment 12 is the process of Embodiment 10 o, r w 1h1erein the glycol-based acrylic emulsifiers comprises at least one of polyethyl gelnyecol acrylate (PEGA), polyethylene glycol methacrylate (PEGMA), polypropylene glycol acryla (PtePGA), or polypropylene glycol methacrylate (PPGMA).

[0030] Embodiment 13 is the process of any one of Embondtism 1e0 to 12, wherein the amount of the glycol-based acrylic emulsifiers added teo p tholymerization is from 0.05 to 5 wt%, preferably from 0.1 to 2 wt% based on total fluoroonmomer added in the polymerization.

[0031] Embodiment 14 is the process of any one of Embondtism 1e0 to 13, wherein the stabilizer comprises at least one alkyl sulfate al okyrl sulfonate salt.

[0032] Embodiment 15 is the process of any one of Embondtism 1e0 to 13, wherein the stabilizer is selected from the group consisting sa oltfs of C6-C18 alkyl sulfonate, C6-C18 alkyl sulfate, C6-C18 alkyl di-sulfonates, C6-C18 alkiy-ls dulfates and mixtures thereof.

[0033] Embodiment 16 is the process of Embodiment 14e winhe thre stabilizer comprising at one least one alkyl sulfate or alkyl sulfonate s isal at dded after polymerization is concluded or after at least 50wt% of the fluorinated monomer b heaesn fed to the reactor, preferable at least after 75wt % of the fluorinated monomer has beedn to fe the reactor.

[0034] Embodiment 17 is the process of Embodiment 14,e winhe thre stabilizer comprising at one least one alkyl sulfate or alkyl sulfonate sisa altdded in an amount of from 0.1 to about 5 wt % based on total weight of fluoromonomers adde tdhe to polymerization.

[0035] Embodiment 18 is the process of any one of Embondtism 1e0 to 13, wherein the stabilizer comprises oligomers containing ionic momoner units having acid groups, preferably carboxylic acid groups.

[0036] Embodiment 19 is the process of any one of Embondtism 1e0 to 13, wherein the stabilizer is selected from the group consisting ol oigfomers of polyacrylic acid, oligomers ofpoly(meth)acrylic acid, oligomers containing mcal aeicid monomer units, and co-oligomers of any of the preceding and combination thereof.

[0037] Embodiment 20 is the process of Embodiment 18,e winhe thre stabilizer is added after at least 30 wt% of the fluorinated monomer has beedn to fe the reactor, preferable at least 50wt % of the fluorinated monomer has been fed to theto rer.ac

[0038] Embodiment 21 is the process of Embodiment 18,e winhe thre stabilizer comprising oligomers containing ionic monomer units havingd a gcrioups is added in an amount of from 0.1 to about 2.5 wt% based on total fluoromonomersd ad tode the polymerization.

[0039] Embodiment 22 is the process of any one of Embondtism 1e0 to 13, wherein the stabilizer comprises non fluorinated monomers hgav aitn least one reactive carbon-carbon double bond and an ionic moiety, preferably the ionic mtyoie s an acidic moiety or its salt thereof.

[0040] Embodiment 23 is the process of any one of Embondtism 1e0 to 13, wherein the stabilizer is selected from the group consisting ac orfylic acid, methacrylic acid, salt(s) of styrenesulfonic acid, alkyl methacrylate phosphate, 2-lac mryido-2-methylpropane sulfonic acid, beta-carboxyethyl acrylate and combination thereof.

[0041] Embodiment 24 is the process of Embodiment 22,e winhe thre stabilizer comprising non fluorinated monomers having at least one reactaivrebo cn-carbon double bond and an ionic moiety is added during polymerization, preferabfltyer a at least 15 wt% of the fluorinated monomer has been fed to the reactor, preferab leleas att 30wt % of the fluorinated monomer has been fed to the reactor.

[0042] Embodiment 25 is the process of Embodiment 22,e winhe thre stabilizer comprising non fluorinated monomers having at least one reactaivrebo cn-carbon double bond and an ionic moiety is added in an amount of from 0.1 to abo.5ut w 1t % based on total monomers added to the polymerization.

[0043] In the process Embodiments, the stabilizer m coamyprise one or more of: one alkyl sulfate or alkyl sulfonate salt, oligomers contnagini onic monomer units having acid groups, non fluorinated monomers having at least one reactaivrebo cn-carbon double bond and an ionic moiety, or combinations thereof.

[0044] Another embodiment of the invention is an aqueoluuosro fpolymer dispersion comprising (1) a vinylidene fluoride polymer having at leas0t w 6t percent vinylidene fluoride monomer units (2) an acrylic based glycol ester, prefera thbely acrylic based glycol ester comprises at least one of polyethylene glycol acrylate (PEGA), polyyelethne glycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), or polyproepnyel glycol methacrylate (PPGMA);(3) a non-ionic block copolymer emulsifier containingc bklos of at least two of polyethylene glycol, polypropylene glycol and / or polytetramethylene gollyc and (4) a stablilizer,wherein the fluoropolymer has an average par stiiczle of less than 120 nm, a melt viscosity ofat least 20 kP or higher at 230C and 100 sec-1, and wherein the dispersion has a solids content oefa astt l 25 wt%, and having a Brookfield viscosity of less than 1000 cP after shearing for at leas mti 2n0 at 1500 rpm . The stabilizer may comprisenon fluorinated oligomers which contain at leaset o ionnic moiety, preferably an acid moiety orthe stabilizer may comprise at least one of alkuylfla ste salt or alkyl sulfonate salt and wherein the alkyl group is a C6 to C18 alkyl group. Theo frloupolymer may comprise at least one non fluorinated monomer having at least one reactivueb dleo bond and an ionic moiety.

[0045] Detailed Description of the Invention

[0046] The references cited in this application are inocroartped herein by reference.

[0047] Percentages, as used herein are weight percen (wtatg%e)s, unless noted otherwise,Molecular weights are weight average molecular whtesig (Mw), unless otherwise stated. Amounts in “ppm” are weight by weight based. Molleacru weight is measured by gel permeation chromatography (GPC) using PMMA (Polymethylmethalactrey) standards.

[0048] Melt viscosity are measured according to ASTM D38 b3y5 a capillary rheometry at 230°C, and at shear rate of 100-1seacnd 4 se-c1.

[0049] The term “fluoropolymer” refers to polymers ando colypmers (including polymers having two or more different monomers, including for exalem tperpolymers) containing at least 50 mole percent of fluoromonomer units. The copolymers m baey homogeneous, heterogeneous, or random, and may have a gradient distribution omf coon-omer units.

[0050] “Copolymer” is used to mean a polymer having twro m o re different monomer units,including terpolymers and higher degree polyme “Prso.lymer” is used to mean both homopolymer and copolymers.

[0051] “PVDF” means polyvinylidene fluoride, this includ beoth homopolymer and copolymers unless otherwise noted. “VDF” means vinylidener fildueo.

[0052] Dispersion means a dispersion or suspension ofm peorly particles in water. No oil phase or other organic phase is present.

[0053] Solids content means the matter that remains d arfyteinrg of the dispersion. The solids content of the aqueous dispersion was measurede bayns m of gravimetry method using a HG63 moisture analyzer from Mettler Toledo.

[0054] The present invention provides a fluoropolymer e drisp ion that is shear stable, has aparticle size of less than 120 nm, solids contefn gtre oater than 25%, and a melt viscosity of greater than 20kP. The aqueous fluoropolymer dsisiopner of this invention is suitable for direct use in applications such as coatings of differeunbts strates or casting of waterborne electrodes for lithium ion batteries, without use of any fluorineadt-surfactant. Therefore, a combination of particle size, suitable emulsifiers, and stabilsiz (ears detailed below) are used to make the fluoropolymer dispersion of this invention.

[0055] The present invention also provides for a metho mda okfing the inventive fluoropolymer dispersion. The general process for synthesizing the stabolero flpuolymer of the invention comprises a) forming an aqueous emulsion compri astin legast one non-ioni gclycol-based acrylic emulsifier, at least one non-ionic emuelsri,fi and at least one fluoromonomer; b) initiating polymerization of said fluoromonomer using pe arsulfate initiator; and c) after polymerization has started, either simultaneously feeding at loenaest stabilizer during the reaction or adding a stabilizer after polymerization is concluded.

[0056] Polymerization Process

[0057] A polymerization reaction in accordance with thes pernt invention may be carried out by charging a reactor with water (preferably deioni wzeadter), at least one non-ionic glycol-based acrylic emulsifier, at least one non-ionic emuelsrif (idifferent from the glycol-based acrylic emulsifier), at least one fluoromonomer and optliloyn,a chain-transfer agent and / or an antifoulant. Air may be purged from the reactoro prr tio the introduction of the fluoromonomer. Water generally is added to the reactor beforeg binrign the reactor to the desired starting temperature, but the other materials may be adedfeodre b or after bringing the reactor to temperature. At least one persulfate radical itnoirtia is added to start and maintain the polymerization. Additional monomer may be optiolynal dded to replenish monomer that is consumed a,nd the other materials may be optionally addedin dgu thre course of the polymerization to maintain the reaction and con tthroel final product properties. Stabilizer is generally added during the polymerization procers asft oer polymerization is completed.

[0058] Fluoromonomers

[0059] Fluoromonomers are used to have the fluoropolymf e thre o present invention. The term “fluoromonomer” as used according to the invent mioenans a fluorinated monomer having an unsaturated carbon-carbon double bond capabled oefrg uoning free radical polymerization reaction.

[0060] Preferably, the fluoropolymer of the present invioennt comprises vinylidene fluoride polymer having at least 60 wt % VDF units, prefelyra 7b0 wt% VDF units.

[0061] Vinylidene fluoride copolymers include those conitnagi at least 60 weight % of vinylidene fluoride copolymerized with at least o cnoemonomer. Fluorinated comonomer can be selected from the group consisting of, tetrafluothroyleene (TFE), trifluoroethylene (TrFE), chlorotrifluoroethylene (CTFE), perfluorobutyletheynle (PFBE), hexafluoropropene (HFP), vinyl fluoride (VF), pentafluoropropene, 2,3,3,3-tetraofrloupropene, trifluoropropene, fluorinated (alkyl) vinyl ethers, such as, perfluoroethyl vin eytlher (PEVE), and perfluoro-2-propoxypropyl vinyl ether, perfluoromethyl vinyl ether (PMVE),r pfleuoropropyl vinyl ether (PPVE), perfluorobutylvinyl ether (PBVE), longer chain pleurofrinated vinyl ethers, one or more of partly or fully fluorinated alpha-olefins such as 3,3,i3fl-utroro-1-propene, 2-trifluoromethyl-3,3,3- trifluoropropene, 1,2,3,3,3-pentafluoropropene,33,,43,4-pentafluoro-1-butene, hexafluoroisobutylene (HFIB), fluorinated dioxole ssu,ch as perfluoro(1,3-dioxole) and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD), partiya-ll or per-fluorinated alpha olefins of C4 and higher, partially- or per-fluorinated cyclic alkesn oef C3 and higher, partly fluorinated allylic, or fluorinated allylic monomers, and combinationse thoef.r

[0062] Other monomers units in these polymers may inc alundye monomer that contains a polymerizable C=C double bond that will copolymer wizith VDF monomer. Additional monomers could be 2-hydroxyethyl allyl ether, 3y-laolxlypropanediol, allylic monomers, ethane, propene, acrylic acid, methacrylic acid.

[0063] Preferred fluorinated comonomers are tetrafluoryole nthe, trifluoroethylene,chlorotrifluoroethylene, hexafluoropropene, 2,3-,t3e,t3rafluoropropene, vinyl fluoride,pentafluoropropene, perfluoromethylvinyl ether, a pnedrfluoropropyl vinyl ether. Most preferred is hexafluoropropene.

[0064] Emulsifier

[0065] Emulsifiers are used in the present invention.

[0066] Emulsifiers used in the present invention inclu bduet, are not limited to, non-ionic block copolymers containing at least two blocks selec frtoemd polyethylene glycol, polypropylene glycol and polytetramethylene glycol with repeat uinngits of 2 to 200 per a block, preferably 5 to 100. These emulsifiers do not have any carbon deo buobnld capable of undergoing free radical polymerization reaction. These emulsifiers do naovte h any acrylate or methacrylate groups. The terminal groups in these block copolymers are prarebfley selected from hydrogen, hydroxyl, carboxyl, ester, ether and / or hydrocarbon. Exam opfle thse block copolymers are poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), agrreadn in an A-B (diblock) or A-B-A triblock structure, with repeating units of 2 to 200 perlo ack b, preferably 5 to 100. Particularity preferred emulsifiers from this group comprise blocks of P aEnGd PPG, for example Poly(propyleneglycol)-block-poly(ethylene glycol) PPO-PEO, Polryo(p ylene glycol)-block-poly(ethyleneglycol)-block-poly(propylene glycol) “PPO-PEO-PPO o”r-block-poly(ethylene glycol)-block- poly(propylene glycol) - block-poly(ethylene glyc)o “Pl EO-PPO-PEO”. These non-ionic block emulsifiers do not contain any reactive double bso;n hdence, they are nor capable of undergoing free-radical polymerization.

[0067] A second group of non-fluorinated, non-ionic emfuielsrsi useful in the present invention include, but are not limited to, acrylic based golly ecsters containing an unsaturated carbon- carbon double bond capable of undergoing freea rald pioclymerization reaction, preferablyacrylate or methacrylate group and segments of e ptohly lene glycol (PEG), polypropyleneglycol (PPG), polytetramethylene glycol (PTMG) o cro ambination thereof, with repeating units between preferably between 3 to 100, and morer parbelfye 3 to 50. Example of the acrylic based glycol esters used in this invention include, bruet n aot limited to, polyethylene glycol acrylate (PEGA), polyethylene glycol methacrylate (PEG-MA po),lypropylene glycol acrylate (PPGA), polypropylene glycol acrylate (PPGA), and polyprloepnye glycol methacrylate (PPGMA).

[0068] The chemical structure of the non-ionic acrylic-ebdas glycol ester emulsifier of this invention should have the properties such as w saotleurbility and produce particle size below 120 nm fluoropolymer dispersion.

[0069] The total amount of emulsifier used is at a levfe flr o m 100 ppm to 5 wt%, preferablyfrom 100 ppm to 3 wt% and more preferably from 10 p0p0m to 1 wt %, based on the total fluoromonomer added to the polymerization.

[0070] In the polymerization process, the non-ionic emfiuelrssi of this invention could be added all upfront prior to polymerization, fed continuolyus during the polymerization, fed partly before and then during polymerization.

[0071] Initiator

[0072] The term "initiator" and the expressions "radicnaitlia itor" and "free radical initiator" refer to a chemical that is capable of providing a sou orfc feree radicals, either induced spontaneously, or by exposure to heat or light. The amount otfia intoir (in ppm based on the total weight of fluoromonomer added to the polymerization) adde tdhe to reaction mixture may be from 1500 ppm to 1.0 wt%, preferably from 2000 ppm to 1.0 % w.t The radical initiator may comprise a persulfate salt, such as sodium persulfate, poutmas psiersulfate, lithium persulfate or ammonium persulfate. The amount of persulfate salt adde thde to reaction mixture (based upon the total weight of fluoromonomer added to the polymeriza)ti monay, for example, be from about 1500 ppm to about 1.0 wt%, preferably from 2000 ppm. t0o w 1t %. The term "radical" and the expression "free radical" refer to a chemical sepsec thiat contains at least one unpaired electron. The radical initiator is added to the reaction murixet in an amount sufficient to initiate and maintain the polymerization reaction rate. The orr odfe addition may vary according to the desired process and dispersion emulsion charatcictes.ri Isn some embodiments of the invention, the initiating system does not contain a reducignegn at and most preferably does not use a reducing agent.

[0073] The radical initiator may comprise a redox syst "eRme.dox system" is understood by on having ordinary skill in the art to mean a systeomm cprising an oxidizing agent, a reducing agentand optionally, a promoter as an electron tran msfe drium. Oxidizing agents include, forexample, persulfate salts, peroxides, and oxidiz minegtal salts such as, for example, ferric sulfate. Reducing agents include, for example,u smod fiormaldehyde sulfoxylate, sodium andpotassium sulfite, ascorbic acid, bisulfite, mestaublfi te, and reduced metal salts. The promoter isa component of the redox system which, in differ oexnidtation states, is capable of reacting with both the oxidant and the reducing agent, therebceyle arcating the overall reaction. Promoters include, for example, transition metal salts susch fe arrous sulfate. In redox systems, the oxidizing agent and the reducing agent may bez uetdili in an amount from about 0.01 to about 0.5 wt% based on total fluoromonomer added to o thlyem perization. The optional promoter may be utilized in an amount from about 0.005 to ab 0o.0u2t5 wt% based on total fluoromonomer. Redox systems are described, for example, in G M.is Sr.a and U. D. N. Bajpai, Prag. Polym. Sci., 1982, 8(1-2), pp. 61-131.

[0074] Stabilizers

[0075] The term "stabilizer" means a type of moleculel oigro omers (low molecular weight water soluble polymer having molecular weight less th0a,n0010g / mol), which can provide stabilization to the particles of fluoropolymerus,ch s as PVDF, in the aqueous media and provide protection against aggregation or flocculationlu oof r fopolymers particles upon shearing or intense mixing. Surprisingly we discovered thaeta srh stability of fluoropolymer dispersionsignificantly increases when a stabilizer of thvee in tion is introduced to the fluoropolymerdispersion. The stabilizers of the invention aeresc dribed below.

[0076] The stabilizers may be used in solution such as qu ineous solution for convenient handling.

[0077] The first-class of stabilizers are type of molecsu tlheat have both hydrophobic and hydrophilic portions, which allows it to stabiliz aend disperse hydrophobic molecules and aggregates of hydrophobic molecules in aqueousa m. e Edxiamples of stabilizers include alkyl or aryl groups linked to sulphonic acid groups, suiclfu arcid groups, phosphonic acid groups,phosphoric acid groups or carboxylic acid grouphse. T acid groups are generally in salt form.

[0078] The preferred group of the first-class of stabrili fzoer fluoropolymer dispersion of the present invention includes alkyl sulfate and al skuyllfonate stabilizers. The term "alkyl sulfate stabilizers” or “alkyl sulfonate stabilizers” mea sntsabilizer having alkyl hydrocarbon groups as their hydrophobic portion, preferably alkyl hydrorbcoan groups containing C6 to C18 alkyl hydrocarbon groups and alkyl sulfate or alkyl snualftoe groups as the hydrophilic portion. Thehydrocarbon group does not contain any fluorine.fe Prr ed stabilizers of the first class are in saltform preferably having the counter ion being ana alil mk etal (i.e. lithium, sodium, or potassium),an ammonium ion, or an alkyl-substituted ammonioumn. i

[0079] Examples of alkyl sulfate stabilizers used in tnhvee intion, include, but not limited the ammonium, lithium, sodium, or potassium salts okyf l a slulfate. Examples of alkyl sulfate stabilizers include, but are not limited to, sa olfts C6 to C18 alkyl sulfates such as for example, lauryl sulfate and octyl sulfate salts. Examplecslu inde but are not limited to sodium lauryl sulfate (SLS), potassium lauryl sulfate(KLS), ammiuomn lauryl sulfate, lithium lauryl sulfate(ALS), sodium laureth sulfate, sodium oc stuyllfate, potassium octyl sulfate, ammonium octyl sulfate, lithium octyl sulfate, and mixtur tehsereof

[0080] Examples of alkyl sulfonate surfactants includet, a brue not limited to, salts of C6-C18 alkyl sulfonates, and salts of C6-C18 alkyl di-osunlaftes, and mixtures thereof. Examples of typical counter ions for alkyl sulfonate surfactsan intclude, but not limited sodium, potassium, lithium, ammonium or alkyl-substituted ammonium.r F eoxample, salts of the C8–C12 alkyl sulfonates can be used such as, octylsulfonatetysld, i osculfonates, decylsulfonates, decyldisulfonates, dodecylsulfonates, dodecyldoisnualftes and combinations thereof can be used. By example, octylsulfonate can be sodium octylsnualftoe, potassium octylsulfonate, ammonium octylsulfonate, alkyl-substituted ammonium octyflosunal te, lithium octylsulfonate. As a way of example, sodium octyl sulfonate (SOS) is a staebril tihzat is used in the invention.

[0081] The alkyl sulfate or alkyl sulfonate stabilizerse a ursed in an amount from about 0.01 to about 10 wt% based on total fluoromonomer adde thde to polymerization. Preferably, they are used in an amount from about 0.1 to about 5 wt%ed ba osn total fluoromonomer and more preferably from about 0.1 to 2.5 wt%. These sitzaebrisl are added after polymerization is concluded or after at least 50wt% of the fluorinda mteonomer has been fed to the reactor, preferable after at least 75wt % of the fluorina mteodnomer has been fed to the reactor.

[0082] The second-class of stabilizers are oligomers c tohnat ain at least one repeating monomerunit having at least one ionic moiety, preferabnly a acid moiety. Oligomers are made the same as polymers using monomer units, but their chain lehn isgt much shorter (less than 200). As aresult, they exhibit a higher water solubility th tahne analogous polymer and are easily adsorbed on the surface of the fluoropolymer particles. T ohligeomers of the present invention have a chain length of less than 200 monomeric repeatninitgs. u Examples of this group of stabilizers includes, but not limited to, oligomers of polyalcicry acid, oligomers of polymethacrylic acid, oligomers of maleic acid and their copolymers. T sehceond class of stabilizers are used in an amount from about 0.1 to about 5 wt % on total mmoenro. Preferably, they are used in an amount from about 0.2 to about 2 wt% based on wte oifg thotal fluoromonomer added to the polymerization. The second-class stabilizer isfe prraebly added after at least 30 wt% of the fluorinated monomer has been fed to the reactoerf,e prarble at least 50wt % of the fluorinated monomer has been fed to the reactor.

[0083] The third-class of stabilizers are type of non-rfilnuaoted, ionic comonomers that can be optionally co-fed with VDF during the polymerizantio after polymerization started. Theses stabilizers have at least one unsaturated carbrobno-nca double bond capable of undergoing free radical polymerization reaction and contain anc io mnioiety. The ionic moiety on the comonomer can be a carboxylic group, phosphate group, phonsicph goroup, sulfonate group, sulfonic group or –OH group.

[0084] Examples of this group of stabilizers includes n boutt limited to acrylic acid, methacrylic acid, sodium salt of styrene sulfonic acid, sodi 1u-mallyloxy-2-hydroxypropane sulfonate, alkyl methacrylate phosphate, alkyl acrylate phosphamtem,o anium allyl ether phosphate, 2- acrylamido-2-methylpropane sulfonic acid, beta-ocaxyrbethyl acrylate, ethyl methacrylate phosphate, and similar. The third-class of stzaebrisli are used in an amount from about 0.05 to about 5 wt% based on total fluoromonomer addedhe to p tolymerization. Preferably, they are used in an amount from about 0.1 to about 2 wt%ed ba osn weight on total fluoromonomer added to the polymerization. The third-class of stabeirliz is added during polymerization, preferablyafter at least 15 wt% of the fluorinated monomesr b heaen fed to the reactor, more preferably atleast 30wt % has been fed to the reactor. They b cea andded continuously or intermittency while VDF is polymerized in the presence of initiator.

[0085] Adding the stabilizers of the invention during pmoleyrization may slow down the polymerization reaction rate depending on how qluyic aknd what type is added to polymerization media. This can be compensated for by adding aodndailti initiator to the polymerization to maintain the reaction rate. Resulting Polymer Dispersion

[0086] The resultant fluoropolymers of the disclosed psrosc heave a melt viscosity of greater than 20 kPoise at 230 °C according to ASTM D383d5 r aenported at shear rates of 100-1s,e acndthe solids content of the dispersion is greatenr t 2h5a wt%.

[0087] The dispersion of the invention has a solids cotn otef n from 25 to 60 wt%.

[0088] The fluoropolymer particles in the dispersion hav pearticle size in the range of 20 to 120 nm, preferably from 50 to 120 nm, and moree prraebfly from 50-100 nm. EXAMPLES

[0089] Melt Viscosity

[0090] The melt viscosity measurements are performede on flu thoropolymer of this invention after drying in a convection oven at 110 °C ovehrnt.ig The measurements were carried out at 230 °C according to ASTM D3835 and reported atr sh raetaes of 4 se-1c and 100 se-1c.

[0091] Shear stability

[0092] Shear stability of the aqueous fluoropolymer dispioenr was measured as produced using a dispersion blade of 48 mm model A164 (by Cafra Lmabo Solution) at room temperature. A 750 ml of dispersion was placed in a 1-liter widoeu-mth jar, and dispersion blade was lowered to about 1 / 3 of the dispersion height from the bott oofm the jar and set to 1500 rpm. The stability time is recorded when the dispersion fluidity dimishines and turns into gel (Brookfield viscosity at room temperature (22C) and spindle LV-4, risbeosv ae 1000 cp). When the Brookfield viscosity is 1000 cp or greater, the dispersion o is longer fluid and behaves like a gel. To pass the shear stability a sample can be subjectede to sh thear for 20 minutes. The sample is considered shear stable if after 20 min at 1500 t rhpem Brookfield viscosity is less than 1000 cP. Brookfield viscosity is measured at room tempereat (u2r2C) with spindle LV-4.

[0093] Particle size

[0094] SEM images were acquired using a Hitachi SU 801M0 S aEnd particle size was measured directly from SEM images by averagings s oizfe over 50 particles.

[0095] PPGMA used in the examples is polypropylene gly mceotlhacrylate having a number average molecular weight (Mn) of 300 to 500. (Smaretor® SR604 from Arkema Inc.). The particle size, melt viscosities, solids cont aenndt shear stability of the Examples and counter Examples were measured and reported in Table 1.

[0096] Counter Example 1: homopolymer

[0097] To a 7.5 liter, stainless steel reactor was add0e0d04 g of water and predetermined amount of non-ionic emulsifier Pluronic® 31Rl (fro BmASF). The mixture was purged with nitrogen and agitated for 0.5 hours. The reactmorp teerature was raised to 105 °C for steam-off. The reactor was sealed, while agitation was conetdin aund the reactor temperature was set at a desired reaction temperature. The reactor wase chda wrgith vinylidene fluoride to a pressure of650 psig; an aqueous initiator solution, compri osfe 1d wt. % in potassium persulfate and 1% wt% in sodium acetate, was charged at 360 g / hr tko-s ktiacrt the reaction. The initiator solution feed rate was set at about 20 g / h to maintain g reoaocdtion rate throughout the rest of the reaction. The reaction pressure was maintained50 at p 6sig by adding, as needed, vinylidene fluoride. After total of 2000 g of VDF was added th toe reactor, the monomer feed was stopped.For a period of 10 minutes, agitation was contin,u aend the temperature was maintained. Theagitation and heating were discontinued. Afteri cnogo tlo room temperature, surplus gas was vented, and the reactor was emptied of dispershiroonug th a stainless steel mesh.

[0098] There is no acrylic based glycol ester emulsif Tiehri.s counter example shows a large particle size and low stability.

[0099] Counter Example 2: homopolymer

[0100] The following comparative example is based one thaech tings of U.S. Pat. No. 8,338,518 and 8,765,890.

[0101] To a 7.5 liter, stainless steel reactor was add2e0d04 g of water and predetermined amounts of non-ionic emulsifiers of Pluronic 31Rfrolm ( BASF) and PPGMA. The mixture waspurged with nitrogen and agitated for 0.5 hourse. T rehactor temperature was raised to 105 °C forsteam-off. The reactor sealed, while agitationc woanstinued, the temperature was set at a desired reaction temperature. The reactor wase chda wrgith vinylidene fluoride to a pressure of650 psig; an aqueous initiator solution, compri osfe 2d wt. % in potassium persulfate and 2% wt% in sodium acetate, was charged at 500 g / hr tko-s ktiacrt the reaction. The initiator solution feed rate was set at about 60 g / h to maintain g reoaocdtion rate throughout the rest of the reaction. The reaction pressure was maintained50 at p 6sig by adding as needed vinylidene fluoride. After total of 1700 g of VDF is added t thoe reactor, the monomer feed was stopped.For a period of 10 minutes, agitation was contin,u aend the temperature was maintained. Theagitation and heating were discontinued. Afteri cnogo tlo room temperature, surplus gas was vented, and the reactor was emptied of dispershiroonug th a stainless steel mesh.

[0102] This counter Example shows a particle size butta nboil sizers utilized resulting in poor stability.

[0103] Counter Example 3: Copolymer (Pilot Plant) Into an 80-gallon stainless reactor was charged lb 4s00 of de-ionized water, 270 gram of PLURONIC 31R1 (non-fluorinated non-ionic emulsif fierorm BASF), and 0.42 lbs of ethyl acetate. Following evacuation, agitation was be agtu 2n3 rpm and the reactor was heated. After the reactor temperature reached the desired snett o pfo 1i00 °C, the VDF and HFP monomers were introduced to reactor with HFP ratio of 13.t8% w to total monomers. Reactor pressure was then raised to 650 psi by charging approximately lb 3s0 total monomers into the reactor. 4.0 lbs of initiator solution made of 1.0 wt% potassiums puelfrate and 1.0 wt % sodium acetate were added to the reactor to initiate polymerization.o Unp initiation, the ratio of HFP to VDF was so adjusted to arrive at 4.3 % HFP to total monomner tshe i feed. The rate of further addition of' the initiator solution was also adjusted to obtain pmoelyrization rate of about 70 lbs per hour. The VDF and HPF copolymerization continued until appimroaxtely 150 lbs of monomers were introduced in the reaction mass. The HFP feed wtoapsp sed but VDF feed continued until approximately 172 lbs of total monomers were fed th teo reactor. The VDF feed was stopped and the batch was allowed to react-out at thei roenac tetmperature to consume residualmonomers at a decreasing pressure. After 40 msi,n tuhte initiator feed and agitation werestopped, the reactor was cooled, vented, ands thpeer dsiion recovered. The initiator to total monomer was about 555 ppm. Solution of SLS 10 w int% water (stabilizer) was then added to the resultant dispersion to reach 2500 ppm of SaLsSed b on total wt of fluoromonomers added to the polymerization. SLS= Sodium laurel sulfate.

[0104] Counter example 3 has a large particle size,l it ze udti nonionic emulsifier having at leasttwo blocks (PLURONIC) but no acrylic based glycostle er was used. This resulted in poor stability ever though there was 2500ppm of staebrili pzresent. Counter Example 4

[0105] To a 7.5 liter, stainless steel reactor was add0e0d03 g of water and predetermined amounts of PPGMA. The mixture was purged witho ngietrn and agitated for 0.5 hours. The reactor temperature was raised to 105 °C for stoefaf.m T-he reactor was sealed, while agitationwas continued and the reactor temperature wast s ae dte asired reaction temperature. The reactorwas charged with vinylidene fluoride to a press oufr 6e50 psig; an aqueous initiator solution, comprised of 2 wt. % in potassium persulfate and w 2t% % in sodium acetate, was charged at500 g / hr to kick-start the reaction. The initia stor lution feed rate was set at about 60 g / h tomaintain good reaction rate throughout the res thte of reaction. The reaction pressure was maintained at 650 psig by adding as needed vinnyelid fleuoride. After total of 1700 g of VDF was added to the reactor, the monomer feed waspe sdto.p For a period of 20 minutes, agitation was continued, and the temperature was mainta Tinheed. agitation and heating were discontinued. After cooling to room temperaturer,p sluus gas was vented, and the reactor was emptied of dispersion through a stainless steehl m. es

[0106] Example 1-4

[0107] To a 7.5 liter, stainless steel reactor was add2e0d04 g of water and predetermined amounts of non-ionic emulsifiers of Pluronic® 31 (Rfrol m BASF) and PPGMA. The mixture was purged with nitrogen and agitated for 0.5 h.o Tuhrse reactor temperature was raised to 105 °C for steam-off. The reactor sealed, while aigoitnat was continued, the temperature was set at a desired reaction temperature. The reactor wase chda wrgith vinylidene fluoride to a pressure of650 psig; an aqueous initiator solution, compri osfe 2d wt. % in potassium persulfate and 2% wt% in sodium acetate, was charged at 500 g / hr tko-s ktiacrt the reaction. The initiator solution feed rate was set at about 60 g / h to maintain g reoaocdtion rate throughout the rest of the reaction. The reaction pressure was maintained50 at p 6sig by adding as needed vinylidene fluoride. After total of 1500 g of VDF is added t thoe reactor, the monomer feed was stopped.For a period of 10 minutes, agitation was contin,u aend the temperature was maintained. Theagitation and heating were discontinued. Afteri cnogo tlo room temperature, surplus gas was vented, and the reactor was emptied of dispershiroonug th a stainless steel mesh. Solution of SLS 10 wt% in water was then added to the resu dltiasnptersion to reach 2000 ppm of SLS based on weight of fluoromonomer added to the polymerioizna.t

[0108] Example 5

[0109] To a 7.5 liter, stainless steel reactor was add2e0d04 g of water and predetermined amounts of non-ionic emulsifiers of Pluronic® 31 (Rfrol m BASF) and PPGMA. The mixture was purged with nitrogen and agitated for 0.5 h.o Tuhrse reactor temperature was raised to 105 °C for steam-off. The reactor sealed, while aigoitnat was continued, the temperature was set at a desired reaction temperature. The reactor wase chda wrgith vinylidene fluoride to a pressure of650 psig; an aqueous initiator solution, compri osfe 2d wt. % in potassium persulfate and 2% wt% in sodium acetate, was charged at 500 g / hrr tot t shtea reaction. The initiator solution feed rate was set at about 60 g / h to maintain good reactaioten t rhroughout the rest of the reaction. The reaction pressure was maintained at 650 psig biyng ad ads needed vinylidene fluoride. After total of 1500 g of VDF is added to the reactor, the VDeeFd f was stopped and 273 g of HFP monomer is added to reactor and then was topped with VD rFea toch 1500 g of total VDF. For a period of 10 minutes, agitation was continued, and the teamtupreer was maintained. The agitation andheating were discontinued. After cooling to roomp te rature, surplus gas was vented, and thereactor was emptied of dispersion through a stsasin sleteel mesh. Solution of SLS 10 wt% inwater was then added to the dispersion to reac0h p 2p0m0 of SLS based on fluoromonomeradded to the polymerization.

[0110] Example 6

[0111] To a 7.5 liter, stainless steel reactor was add0e0d03 g of water and predetermined amounts of non-ionic emulsifiers of Pluronic 31Rfrolm ( BASF) and PPGMA. The mixture waspurged with nitrogen and agitated for 0.5 hourse. T rehactor temperature was raised to 105 °C forsteam-off. The reactor sealed, while agitationc woanstinued, the temperature was set at a desired reaction temperature. The reactor wase chda wrgith vinylidene fluoride to a pressure of650 psig; an aqueous initiator solution, compri osfe 2d wt. % in potassium persulfate and 2% wt% in sodium acetate, was charged at 500 g / hr tko-s ktiacrt the reaction. The initiator solution feed rate was set at about 60 g / h to maintain g reoaocdtion rate throughout the rest of the reaction. The reaction pressure was maintained50 at p 6sig by adding as needed vinylidene fluoride. After total of 800 g of VDF was added th toe reactor, a 10% solution of (the second- class of stabilizer) such as polyacrylic acid hagv ain weight average molecular weight of ~4000in water was fed to the reactor at 200 ml / hirle w th e feeding of VDF continued. Additionof VDF and polyacrylic acid solution were stop wh thene total of fed VDF reached 1700 g. For a period of 10 minutes, agitation was continued, t ahned temperature was maintained. The agitation and heating were discontinued. Afteri cnogo tlo room temperature, surplus gas was vented, and the reactor was emptied of dispershiroonug th a stainless steel mesh. Mv means melt viscosity.

[0112] Example 7

[0113] To a 7.5 liter, stainless steel reactor was add0e0d03 g of water and predetermined amounts of non-ionic emulsifiers of Pluronic 31Rfrolm ( BASF) and PPGMA. The mixture waspurged with nitrogen and agitated for 0.5 hourse. T rehactor temperature was raised to 105 °C forsteam-off. The reactor sealed, while agitationc woanstinued, the temperature was set at a desired reaction temperature. The reactor wase chda wrgith vinylidene fluoride to a pressure of650 psig; an aqueous initiator solution, compri osfe 2d wt. % in potassium persulfate and 2% wt% in sodium acetate, was charged at 500 g / hr tko-s ktiacrt the reaction. The initiator solution feed rate was set at about 60 g / h to maintain g reoaocdtion rate throughout the rest of the reaction. The reaction pressure was maintained50 at p 6sig by adding as needed vinylidenefluoride. After total of 800 g of VDF was added th toe reactor, 1% wt / wt of solution of the third-class of stabilizer such as an alkyl methacrylahtoes p hate (Sipomer® PAM 4000 by Solvay) inwater was fed to the reactor at 100 ml / hr while f teheeding of VDF continued. Addition of VDF and PAM 4000 solution were stop when the totale odf V f DF reached 1700 g. For a period of 10 minutes, agitation was continued, and the tempreera wtuas maintained. The agitation and heating were discontinued. After cooling to room temperea,tu srurplus gas was vented, and the reactorwas emptied of dispersion through a stainless smtee slh.TABLE 1 Mv Mv Stability Stabiliz Solids Particle Temp 31R1 PPGMA Initiator (@ (@ 1500 er Content size (°C) (g) (g) * ppm 4 / s) 100 / s) rpm *ppm (%) (nm) kp kp (min) Counter Examples # 1 83 3 0 0 760 35 825 47 3.5 167 # 2 100 0.5 4 0 3900 27 280 27 14 83 # 3 100 270 0 2500 55529 34 9140 #4 100 0 3 2000 320035 285 28.5 11109Examples # 1 100 0.5 3.5 2000 3994 27 271 27 27 78 # 2 110 0.5 3.5 2000 3957 27 158 20 32 87 # 3 100 0.5 3 2000 3480 28 267 27 38 87 # 4 100 0.5 2.5 2000 3066 29 345 31 23 87 # 5 100 0.5 3 2000 2933 31 296 28 48 87 # 6 100 0.5 3 5900 2658 33 296 28 35 95 # 7 100 0.5 3 1061 3144 28 295 29 37 78 *Based on total fluoromonomer (VDF+HFP)

Claims

Claims:

1. An aqueous fluoropolymer dispersion comprisingu aor folpolymer, wherein the fluoropolymer has an average partiiczle o sf less than 120 nm, a meltviscosity of at least 20 kP or higher at 230C a0n0d s 1ec-1, and wherein the dispersion has asolids content of at least 25 wt%, and having ao Bkfrioeld viscosity of less than 1000 cP after shearing for at least 20 min at 1500 rpm.

2. The aqueous fluoropolymer dispersion of claim 1e,r wehin the fluoropolymer comprises at least 60 wt% VDF monomer units, preferable astt le 70 wt% VDF monomer units.

3. The aqueous fluoropolymer dispersion of claim 1e,r wehin the fluoropolymer comprisesat least comonomer unit selected from the groupsi csotin g of HFP, CTFE, PMVE , PPVE, TFE,2,3,3,3-tetrafluoropropene, preferably HFP.

4. The aqueous fluoropolymer dispersion of claim 1e,r wehin the average particle size is less than 100 nm.

5. The aqueous fluoropolymer dispersion of any on me o rre of claims 1 to 4, comprising(1) an acrylic based glycol ester, preferably tchreyl aic based glycol ester comprises at least one of polyethylene glycol acrylate (PEGA), polyethyele gnlycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), or polyproepnyel glycol methacrylate (PPGMA);(2) a non-ionic block copolymer emulsifier containingc bklos of at least two blocks selected from polyethylene glycol, polypropylene glycol and ptoeltyramethylene glycol; and (3) a stabilizer.

6. The aqueous fluoropolymer dispersion of claim 5e,r wehin the fluoropolymer comprises polyvinylidene fluoride having at least 60 wt% VD mFonomer units , the acrylic based glycol esteris selected from polyethylene glycol acry (laPtEeGA), polyethylene glycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), a pnodlypropylene glycol methacrylate (PPGMA);()and the non-ionic block copolymer emfuielsri contains at least one block of polyethylene glycol and at least one block of porolypylene glycol.

7. The aqueous fluoropolymer dispersion of claim 56, o wrherein the fluoropolymer comprises at least one non fluorinated monomern hga avti least one reactive double bond and an ionic moiety.

8. The aqueous fluoropolymer dispersion of claim 56, o wrherein the stabilizer comprisesnon fluorinated oligomers which contain at leaset o ionnic moiety, preferably an acid moiety.

9. The aqueous fluoropolymer dispersion of claim 56, o wrherein the stabilizer comprises at least one of alkyl sulfate salt or alkyl sulfona satelt and wherein the alkyl group is a C6 to C18 alkyl group.

10. A process for making a shear-stable aqueous fluoolyromper dispersion having a particle size of less than 120 nm comprising: a) providing in a reaction vessel, an aqueous reac mtieodnium, at least one fluoromonomer, at least one acrylic based glycotelr e,s at least one nonionic emulsifier having at least two blocks selected fr poomlyethylene glycol, polypropylene glycol and / or polytetramethylene golly wcith repeating units of 2 to 200 per a block,b) polymerizing fluoromonomer of (a) is in presence at o lfeast one initiator wherein the amount of initiator added to the polymerization at is least 1500ppm based on weight of fluoromonomer added to the polymerization, and c) adding at least one stabilizer to the fluoropolrym diespersion during or after polymerization.

11. The process of claim 10, wherein the fluoromono cmoemrprises vinylidene fluoride monomer.

12. The process of claim 10, wherein the glycol-bascerdyli ac emulsifiers comprises at least one of polyethylene glycol acrylate (PEGA), pohlyyeletne glycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), or polyproepnyel glycol methacrylate (PPGMA).

13. The process of claim 10, wherein the amount of g tlhyceol-based acrylic emulsifiers added to the polymerization is from 0.05 to 5 w pt%re,ferably from 0.1 to 2 wt% based on total fluoromonomer added in the polymerization.

14. The process of any one or more of claims 10 to w 1h3e,rein the stabilizer comprises at least one alkyl sulfate or alkyl sulfonate salt.

15. The process of any one or more of claims 10 to w 1h3e,rein the stabilizer is selected from the group consisting of salts of C6-C18 alkylo snualfte, C6-C18 alkyl sulfate, C6-C18 alkyl di- sulfonates, C6-C18 alkyl di-sulfates and mixturheesre tof.

16. The process of any one or more of claims 10 to w 1h3e,rein the stabilizer comprising at one least one alkyl sulfate or alkyl sulfonate sisa altdded after polymerization is concluded or after at least 50wt% of the fluorinated monomer b heaesn fed to the reactor, preferable after at least 75wt % of the fluorinated monomer has beedn to fe the reactor.

17. The process of any one or more of claims 10 to w 1h3e,rein the stabilizer comprising at one least one alkyl sulfate or alkyl sulfonate sisa altdded in an amount of from 0.1 to about 5 wt % based on total weight of fluoromonomers adde tdhe to polymerization.

18. The process of any one or more of claims 10 to w 1h3e,rein the stabilizer comprises oligomers containing ionic monomer units havingd a gcrioups, preferably carboxylic acid groups.

19. The process of any one or more of claims 10 to w 1h3e,rein the stabilizer is selected from the group consisting of oligomers of polyacrylcicid a, oligomers of poly(meth)acrylic acid,oligomers containing maleic acid monomer unitsd, a cno-oligomers of any of the preceding andcombination thereof.

20. The process of any one or more of claims 10 to w 1h9e,rein the stabilizer is added after at least 30 wt% of the fluorinated monomer has beedn to fe the reactor, preferable at least 50wt % of the fluorinated monomer has been fed to theto rer.ac 21. The process of any one or more of claims 10 to w 1h3e,rein the stabilizer comprising oligomers containing ionic monomer units havingd a gcrioups is added in an amount of from 0.1 to about 2.5 wt% based on total fluoromonomersd ad tode the polymerization.

22. The process of any one or more of claims 10 to w 1h3e,rein the stabilizer is added during the polymerization and comprises non fluorinatedno mmoers having at least one reactive carbon-carbon double bond and an ionic moiety, prefera thbely ionic moiety is an acidic moiety or its salt thereof.

23. The process of any one or more of claims 10 to w 1h3e,rein the stabilizer is added during the polymerization and is selected from the groounps cisting of acrylic acid, methacrylic acid, salt(s) of styrene sulfonic acid, alkyl methacreyla pthosphate, 2-acrylamido-2-methylpropane sulfonic acid, beta-carboxyethyl acrylate and conmatbioi n thereof.

24. The process of claim 22 wherein the stabilizer croisminpg non fluorinated monomers having at least one reactive carbon-carbon douobnled b and an ionic moiety is added during polymerization, preferably after at least 15 wt% th oef fluorinated monomer has been fed to the reactor, preferable at least 30wt % of the fluotreinda monomer has been fed to the reactor.

25. The process of claim 22 wherein the stabilizer croisminpg non fluorinated monomers having at least one reactive carbon-carbon douobnled b and an ionic moiety is added in an amount of from 0.1 to about 1.5 wt % based on t motoanlomers added to the polymerization.

26. An aqueous fluoropolymer dispersion comprisinga (1 v)inylidene fluoride polymer having at least 60 wt percent vinylidene fluor midoenomer units (2) an acrylic based glycol ester, preferably the acrylic based glycol estemrp croises at least one of polyethylene glycol acrylate (PEGA), polyethylene glycol methacrylaPteEG ( MA), polypropylene glycol acrylate (PPGA), or polypropylene glycol methacrylate (PPG)M;(3A) a non-ionic block copolymer emulsifier containing blocks of at least two ofy peotlhylene glycol, polypropylene glycol and / or polytetramethylene glycol and (4) a stablilizerh,e wrein the fluoropolymer has an average particle size of less than 120 nm, a melt visco osfit ayt least 20 kP or higher at 230C and 100 sec- 1, and wherein the dispersion has a solids con otfe antt least 25 wt%, and having a Brookfield viscosity of less than 1000 cP after shearingt fo lera ast 20 min at 1500 rpm .

27. The aqueous fluoropolymer dispersion of claim 2h6e,r wein the stabilizer comprises non fluorinated oligomers which contain at least onneic io moiety, preferably an acid moiety.

28. The aqueous fluoropolymer dispersion of claim 2h6e,r wein the stabilizer comprises at least one of alkyl sulfate salt or alkyl sulfona satelt and wherein the alkyl group is a C6 to C18 alkyl group.

29. The aqueous fluoropolymer dispersion of claim 2h6e,r wein the fluoropolymer comprises at least one non fluorinated monomer having att l oenaes reactive double bond and an ionic moiety.