Method of producing fluoropolymers using phosphate ester

Abstract

A FLUOROPOLYMER COMPOSITION HAVING AT LEAST ONE FLUOROPOLYMER, PREFERABLY A POLYVINYLIDENE FLUORIDE, AN AT LEAST ONE PHOSPHATE ESTER IS DISCLOSED

Description

METHOD OF PRODUCING FLUOROPOLYMERS USING PHOSPHATE ESTER

[0001] FIELD OF THE INVENTION

[0002] The invention relates to vinylidene fluoride (“VDF”) based fluoropolymers and their preparation. More particularly, as it relates to phosphate esters as surfactants for use in preparing such fluoropolymers.

[0003] BACKGROUND

[0004] Typically, VDF-based polymers are produced via aqueous polymerization (typical emulsion polymerization) processes, by reacting fluorinated monomers in the presence of a polymerization initiator and at least one surfactant (also referred to as emulsifier). Perfluorinated surfactant such as ammonium perfluorooctanoate, or highly fluorinated surfactants, such as Surfion™ and Capstone™, fluorinated surfactants have been used in vinylidene fluoride- based polymer preparation and proved to be very effective. It is generally understood in the art and commercial practice of polymerization of vinylidene fluoride (and its copolymerization) that a stabilizing additive must be used to obtain a fluid liquid of polymer particles dispersed throughout the liquid phase. Historically, fluorinated-surfactants are used because they can yield stable latex of high molecular weight fluoropolymers. Unfortunately, fluorinated- surfactants also present an environmental concern related to the bio-persistence of the surfactant. These fluorinated surfactant act to stabilize the interface of the fluoropolymer particles and the water phase, thereby reducing the strength of particle interactions and limiting premature coagulation of the solid from the liquid phase. Addition of non-fluorinated surfactants to stabilize fluoropolymer latex is known. However, these surfactants can impart undesirable effect on the kinetics of polymerization due to chaintransfer of the free-radical to the surfactant.

[0005] Due to government regulations the use of perfluorinated surfactant is being phased out. There is a need to find surfactants that can stabilize a fluoropolymer emulsion system and produce a stable fluoropolymer latex.

[0006] Processes for making fluoropolymers by an emulsion process commonly use surfactants to stabilize the fluoropolymer latex during the polymerization reaction. See, for example, US patents: US7122610, US 8080621, US8124699, US8697822, and US9068071.

[0007] US7566762B2 disclosed the use of secondary phosphate surfactants, wherein the phosphate ion is covalently bound to a secondary carbon along the alkane chain (ex: RCH(PO4)R) (R being an alkyl group).

[0008] The present invention makes use of phosphate esters and phosphodiesters, wherein the carbon bonded to the phosphate is a primary carbon.

[0009] Disclosed herein is a class of non- fluorinated surfactants that are capable of stabilizing fluoropolymer latex.

[0010] Summary of Invention

[0011] The invention provides a fluoropolymer composition comprising fluoropolymer and phosphate ester.

[0012] The invention provides a method of making a VDF based fluoropolymer. The method comprises polymerizing vinylidene fluoride, optionally in the presence of at least one further comonomer, in an aqueous emulsion in the presence of phosphate ester, as a surfactant, and a radical initiator.

[0013] The present invention also relates to a fluorinated polymer comprising recurring units derived from vinylidene fluoride, and optionally recurring units derived from at least one further comonomer, said polymer being advantageously obtained via the above-mentioned method.

[0014] In a first embodiment of the invention is disclosed a fluoropolymer composition comprising: at least one fluoropolymer and at least one phosphate ester having a phosphate group and one or two covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein each covalent grouping of atoms of the phosphate ester independently comprises from 1 to 50 carbon atoms, wherein the covalent grouping of atoms is covalently bonded to the phosphate group by a primary carbon in the covalent grouping of atoms.

[0015] Embodiment 2 is the fluoropolymer composition of embodiment 1 , wherein the fluoropolymer is a vinylidene fluoride homopolymer or a vinylidene fluoride copolymer.

[0016] Embodiment 3 is the fluoropolymer composition of any one or more of the above embodiments, wherein the fluoropolymer is a vinylidene fluoride copolymer comprising at least one fluorinated comonomer unit selected from the group consisting of tetrafluoroethylene, trifluoroethylene, hexafluoropropene, chlorotrifluoroethylene, vinyl fluoride, and combinations thereof, preferably hexafluoropropene .

[0017] Embodiment 4 is the fluoropolymer composition of any one or more of the above embodiments, wherein said fluoropolymer is a vinylidene fluoride copolymer comprising at least one non fluorinated comonomer unit.

[0018] Embodiment 5 is the fluoropolymer composition of any one or more of the above embodiments, wherein the amount of phosphate ester is from 20 ppm to 2.0 weight percent, based on the weight of the fluoropolymer.

[0019] Embodiment 6 is the fluoropolymer composition of any one or more of the above embodiments, wherein the amount of phosphate ester is from 20 ppm to 1.0 weight percent, based on the weight of the fluoropolymer.

[0020] Embodiment 7 is the fluoropolymer composition of any one or more of the above embodiments, wherein at least one phosphate ester is represented by the formula ;11(1) where: R1 is a covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein a carbon atom from the covalent grouping of atoms is covalently bonded to the oxygen of the phosphate group and is a primary carbon, R2 is selected from the group consisting of H, an alkali metal, an ammonium ion, or alkyl ammonium ion, R3 is independently selected from the group consisting of H, an alkali metal, an ammonium ion, an alkyl ammonium ion, a covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein a carbon atom from the covalent grouping of atoms is covalently bonded to the oxygen of the phosphate group and is a primary carbon.

[0021] Embodiment 8 is the fluoropolymer composition of embodiment 7, wherein R1 comprises one or more heteroatoms, and at least one hctcroatom is selected from the group consisting of oxygen, nitrogen, phosphorous, sulfur, bromine, chlorine and combinations thereof.

[0022] Embodiment 9 is the fluoropolymer composition of embodiment 7, wherein R1 comprises at least one oxygen.

[0023] Embodiment 10 is the fluoropolymer composition of any one or more of the above embodiments, wherein: R1 comprises the formula -(CFECI-EOJnX, where n is an integer from 0 to 20, and X is an alkyl or alkyl-aryl group comprising from 1 to 20 carbons, preferable X comprises from 2 to 20 carbons, more preferable X comprises from 4 to 20 carbons, more preferable X comprises from 4 to 16 carbons; R2 is selected from the group consisting of H, an alkali metal, an ammonium ion, alkyl ammonium ion, preferably R2 is an alkali metal, an ammonium ion, or alkyl ammonium ion; and R3, is selected from the group consisting of H, an alkali metal, an ammonium ion, alkyl ammonium ion, or is the same as Rl, preferably R3 is an alkali metal, an ammonium ion, or alkyl ammonium ion.

[0024] Embodiment 1 1 is the fluoropolymer composition of embodiment 10, where n is 0 and X is an alkyl group or alkene group,

[0025] Embodiment 12 is the fluoropolymer composition of embodiment 10, wherein X comprises an aryl or non-aryl cyclic group.

[0026] Embodiment 13 is the fluoropolymer composition of embodiment 10, wherein n is greater than 0.

[0027] Embodiment 14 is the fluoropolymer composition of embodiment 10, wherein n is greater than 0 and X is an alkyl group or alkene.

[0028] Embodiment 15 is the fluoropolymer composition of embodiment 10, wherein n is greater than 0 and X comprises an aryl group.

[0029] Embodiment 16 is the fluoropolymer composition of any one or more of the above embodiments 1 -14, wherein R1 comprises the formula -(CFBCFEO^X, where n is an integer from 2 to 15; X is an alkyl group; R2 and R3 are independently selected from the group H, an alkali metal, an ammonium ion, or an alkyl ammonium ion and combinations thereof.

[0030] Embodiment 17 is a method for preparing a fluoropolymer in an aqueous reaction medium comprising: (i) forming an aqueous mixture comprising at least surfactant, and at least one fluoromonomer, (ii) adding at least one radical initiator, (iii) polymerizing said fluoromonomers, thereby forming a fluoropolymer dispersion; wherein the surfactant comprises at least one phosphate ester having a phosphate group and one or two covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein each covalent grouping of atoms of the Phosphate ester independently comprises from 1 to 50 carbon atoms, wherein the covalent grouping of atoms is covalently bonded to the phosphate group by a primary carbon in the covalent grouping of atoms.

[0031] Embodiment 18 is the method of embodiment 17, wherein the fluoropolymer is a vinylidene fluoride homopolymer or a vinylidene fluoride copolymer,

[0032] Embodiment 19 is the method of embodiment 17 or 18, wherein said fluoropolymer is a vinylidene fluoride copolymer comprising at least one fluorinated comonomer unit selected from the group consisting of tetrafluoroethylene, trifluoroethylene, hexafluoropropene, chlorotrifluoroethylene, vinyl fluoride, and combinations thereof, preferably hexafluoropropene.

[0033] Embodiment 20 is the method of any one or more of embodiments 17 to 19, wherein said fluoropolymer is a vinylidene fluoride copolymer comprising at least one non fluorinated comonomer unit.

[0034] Embodiment 21 is the method of any one or more of embodiments 17 to 20, wherein the amount of phosphate ester is from 0.01 to 2.0 weight percent, based on the weight of the fluoromonomer used in the polymerization reaction.

[0035] Embodiment 22 is the method of any one or more of embodiments 17 to 20, wherein the amount of phosphate ester is from 0.01 to 1 .0 weight percent, based on the weight of fluoromonomer used in the polymerization reaction, preferably in the amount of 0,01 to 0.5 weight percent.

[0036] Embodiment 23 is the method of any one or more of embodiments 17 to 22, wherein at least one phosphate ester is represented by the formula :H(i) wherein: R1 is a covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein a carbon atom from the covalent grouping of atoms is covalently bonded to the oxygen of the phosphate group and is a primary carbon, R2 is selected from the group consisting of H, an alkali metal, an ammonium ion, or alkyl ammonium ion, R3 is independently selected from the group consisting of H, an alkali metal, an ammonium ion, an alkyl ammonium ion, a covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein a carbon atom from the covalent grouping of atoms is covalently bonded to the oxygen of the phosphate group and is a primary carbon.

[0037] Embodiment 24 is the method of embodiment 23, wherein R1 comprises one or more heteroatoms, at least one heteroatom is selected from the group consisting of oxygen, nitrogen, phosphorous, sulfur, bromine, chlorine and combinations thereof.

[0038] Embodiment 25 is the method of embodiment 23, wherein R1 comprises at least one oxygen.

[0039] Embodiment 26 is the method of any one or more of embodiments 23-25, wherein: (i) R1 comprises the formula -(CFfcCHzOJnX, where n is an integer from 0 to 20, and X is an alkyl or alkyl-aryl group comprising from 1 to 20 carbons, preferable X comprises from 2 to 20 carbons, more preferable X comprises from 4 to 20 carbons, more preferable X comprises from 4 to 16 carbons; (ii) R2 is selected from the group consisting of H, an alkali metal, an ammonium ion, alkyl ammonium ion, preferably R2 is an alkali metal, an ammonium ion, or alkyl ammonium ion; and (iii) R3, is selected from the group consisting of H, an alkali metal, an ammonium ion, alkyl ammonium ion, or is the same as Rl, preferably R3 is an alkali metal, an ammonium ion, or alkyl ammonium ion.

[0040] Embodiment 27 is the method of embodiment 26, wherein n is 0 and X is an alkyl group or alkene group.

[0041] Embodiment 28 is the method of embodiment 26, wherein X comprises an aryl or non-aryl cyclic group.

[0042] Embodiment 29 is the method of embodiment 26, wherein n is greater than 0.

[0043] Embodiment 30 is the method of embodiment 26, wherein n is greater than 0 and X is an alkyl group or alkene.

[0044] Embodiment 31 is the method of embodiment 26, wherein n is greater than 0 and X comprises an aryl group.

[0045] Embodiment 32 is the method of embodiment 26, wherein R1 comprises the formulawhere n is an integer from 2 to 15; X is an alkyl group; R2 and R3 are independently selected from the group H, an alkali metal, an ammonium ion, or an alkyl ammonium ion and combinations thereof.

[0046] Embodiment 33 is the method of any one or more of embodiments 26-32, wherein the fluoropolymer dispersion constitutes, after step (b) at least 20 wt % fluoropolymer based on total weight of the dispersion.

[0047] Embodiment 34 is the fluoropolymer composition of any one or more of embodiments 1 - 7, wherein the phosphate ester is selected form the groups consisting of butanol phosphate (mono and diester), 2-ethylhexyl phosphate (mono and diester), 2-ethylhexyl ethoxylated phosphate (mono and diester), lauryl alcohol phosphate, lauryl alcohol ethyoxylated phosphate, tridecyl alcohol phosphate, tridecyl alcohol ethoxylated phosphate, cetyl alcohol phosphate, oleyl alcohol phosphate, nonyl phenol ethoxylated phosphate and combinations thereof.

[0048] Embodiment 35 is the method of any one or more of embodiments 17 - 23, wherein the phosphate ester is selected form the groups consisting of butanol phosphate (mono and diester), 2- ethylhexyl phosphate (mono and diester), 2-ethylhexyl ethoxylated phosphate (mono and diester), lauryl alcohol phosphate, lauryl alcohol ethyoxylated phosphate, tridecyl alcohol phosphate, tridecyl alcohol ethoxylated phosphate, cetyl alcohol phosphate, oleyl alcohol phosphate, nonyl phenol ethoxylated phosphate and combinations thereof.

[0049] Detailed Description of the Invention

[0050] The references cited in this application are incorporated herein by reference.

[0051] Unless stated otherwise, all percentages, parts, ratios, etc. are by weight.

[0052] The term fluoropolymer refers to homopolymers, and copolymers (including polymers having two or more different monomers, including for example terpolymers) containing at least 50 mole percent of fluoromonomer unit. The fluorinated copolymers can be those with tw o or more fluorinated hydrocarbon monomer units and / or can be those containing functional acrylic comonomer units. The polymers formed may be homopolymers, may be random or alternating copolymers or gradient, and may be linear or branched.

[0053] “Copolymer” is used to mean a polymer having two or more different monomer units, including terpolymers and higher degree polymers. “Polymer” is used to mean both homopolymer and copolymers.

[0054] “PVDF” means polyvinylidene fluoride, this includes both homopolymer and copolymers unless otherwise noted.

[0055] Melt viscosity are according to ASTM D3835 by capillary rheometry at 232°C and 100 sec-1.

[0056] Solids means the matter that remains after drying of the fluoropolymer latex. The solids of the fluoropolymer latex were measured by means of gravimetry method in accordance with ASTM Cl 603.

[0057] The term “fluoropolymer latex” refers to the aqueous dispersion of fluoropolymer obtained from the emulsion polymerization of fluoromonomers. The terms latex and dispersion are used interchangeably.

[0058] The invention provides a suitable method to prepare fluoropolymer from fluoromonomer. The fluoropolymers are prepared in an aqueous polymerization reaction mixture that includes at least one phosphate ester as a surfactant, and an inorganic initiator, for example a persulfate, or an organic initiator such as an organic peroxide. Optionally, polymerizations to prepare the fluoropolymers may be performed in the presence of chain transfer agents to regular molecular weight, buffering agents to maintain a desired pH range during the polymerization, and antifoulants to reduce or eliminate adhesion of the polymer to the inside surfaces of the polymerization vessels.

[0059] The vinylidene fluoride-based polymers of the invention are conveniently made by aqueous polymerization, preferably emulsion polymerization. The polymerization process can be a batch, semibatch, or continuous polymerization process.

[0060] The polymerization process preferably contains no other fluorine containing compounds or molecules except for the monomers and the resulting polymerization products. No fluorinated surfactants are used.

[0061] Fluoromonomer

[0062] The term “vinylidene fluoride polymer” used herein includes both homopolymers and copolymers within its meaning.

[0063] Such copolymers include those containing at least 50 mole percent of vinylidene fluoride copolymerized with at least one comonomer. Preferably the copolymer has at least 70 mole percent of vinylidene fluoride, more preferably at least 75 mole percent VDF.

[0064] The comonomer may be selected from the group consisting of, tetrafluoroethylene (TFE), trifluoroethylene (TrFE), chlorotrifluoroethylene (C TFE), perfluorobutylethylene (PFBE), hexafluoropropene (HFP), vinyl fluoride (VF), pentafluoropropene, 2,3 ,3,3 -tetrafluoropropene, trifluoropropene, fluorinated (alkyl) vinyl ethers, such as, perfluoroethyl vinyl ether (PEVE), and perfluoro-2-propoxypropyl vinyl ether, perfluoromethyl vinyl ether (PMVE), perfluoropropyl vinyl ether (PPVE), perfluorobutylvinyl ether (PBVE), longer chain perfluorinated vinyl ethers, one or more of partlyor fully fluorinated alpha-olefins such as 3 ,3, 3 -trifluoro- 1 -propene, 2-trifluoromethyl-3,3,3- trifluoropropene, 1,2,3,3,3-pentafluoropropene, 3,3,3,4,4-pentafluoro-l -butene, hexafluoroisobutylene (HFIB), fluorinated dioxoles, such as perfluoro(l,3-dioxole) and perfluoro(2,2-dimethyl-l,3-dioxole) (PDD), partially- or per-fluorinated alpha olefins of C4 and higher, partially- or per-fluorinated cyclic alkenes of C3 and higher, partly fluorinated allylic, or fluorinated allylic monomers, and combinations thereof. Preferably the comonomer can be chosen from tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropene, vinyl fluoride, pentafluoropropcnc, pcrfluoromethylvinyl ether, perfluoropropyl vinyl ether and any other monomer that would copolymerize with vinylidene fluoride.

[0065] Monomers known to copolymerizate with vinylidene fluoride may be comonomers. Such monomers include, but are not limited to, acrylates, methacrylates, acrylic acids, methacrylic acids. Preferably such monomers have a hydrophilic group. Such monomers include those mentioned in US5415958, US8337725, and US20130273424, and WO2019199753, such monomers arc herein incorporated by reference.

[0066] Surfactant

[0067] The term "surfactant" means a type of molecule, which has both hydrophobic and hydrophilic, portions, which allows it to stabilize and disperse hydrophobic molecules and aggregates of hydrophobic molecules in aqueous systems, A preferred group of surfactants for stabilization of fluoropolymer dispersion of the present invention includes a phosphate ester. The term "phosphate ester" describes esters of phosphoric acid. The phosphate acts as the hydrophilic group while the organic group forming the ester with phosphoric acid acts as the hydrophobic group. The phosphate ester can exist as phosphoester or a phosphodieseter. The phosphate can be present in the form of an ester with a hydrocarbon preferably linear or branched and containing from 2 to 50 carbons, more preferably with 2 to 20 carbons. The hydrocarbon can have internal heteroatoms, pendant heteroatoms, side chains containing heteroatoms, or terminal heteroatoms. The term "Phosphate ester” for purposes of this invention means phosphate esters and phosphodiesters where one or two of the oxygens in the phosphate group exist as esters covalently bonded to a primary carbon. None of the oxygens of the phosphate group are bonded to a secondary' or tertiary carbon. The term phosphate ester for this invention does not include phosphotriesters.

[0068] The phosphate ester can also exist as an ester with an ethoxylated alcohol. This polyethylene oxide group can be terminated by a hydrocarbon chain that can contain aromatic units or heteroatoms.

[0069] Examples of such phosphate esters include, but are not limited to, butanol phosphate (mono and diester), 2-ethylhexyl phosphate (mono and diester), 2-ethylhexyl ethoxylated phosphate (mono and diester), lauryl alcohol phosphate, lauryl alcohol ethyoxylated phosphate, tridecyl alcohol phosphate,tridecyl alcohol ethoxylated phosphate, cetyl alcohol phosphate, oleyl alcohol phosphate, nonyl phenol ethoxylated phosphate. Mixtures of different phosphate ester may be employed.

[0070] Preferred phosphate esters are in salt form. Especially preferred phosphate ester surfactants are the ammonium, lithium, sodium, or potassium salts.

[0071] The phosphate ester demonstrated in Example 1 has FDA approval. Many ethoxylated phosphate esters are available commercially and the phosphate ester class is listed on 21.CFR.178.3400.

[0072] In accordance with an embodiment of the invention, there is provided a fluoropolymer composition comprising fluoropolymer, preferably a polyvinylidene fluoride, and phosphate ester. The phosphate ester may be represented by formula (1 )(1) where: Rl is a covalent grouping of atoms containing from 1 to 50 carbon atoms wherein a carbon atom from the covalent grouping of atoms is covalently bonded to the oxygen of the phosphate group and is a primary carbon. The carbon atom covalently bonded to the oxygen of the phosphate group must be a primary carbon. R1 can be linear or branched or can contain cyclic or aryl structures. R1 can also contain unsaturated bonds. It is understood that in the case of R1 containing 1 to 3 carbon atoms, branching cannot occur and unsaturation cannot occur. When R1 contains a cyclic group, R1 must comprise at least 6 carbons minimum. When R1 contains an aryl group, R1 must comprise at least 7 carbons. One of more heteroatoms may be present between the carbon atoms of R1 or covalently bonded to the carbon atoms of Rl . The heteroatoms may be selected from oxygen, nitrogen, phosphorous, sulfur.R2 can be an H, an alkali metal, an ammonium ion, or alkyl ammonium ion.R3 can be an H, an alkali metal, an ammonium ion, alkyl ammonium ion or a covalent grouping of atoms containing 1 to 50 carbon atoms independent of Rl . The carbon atom covalently bonded to the oxygen of the phosphate group must be a primary carbon. R3 can be linear or branched or can contain cyclic or aryl structures. R3 can also contain unsaturated bonds. In the case of R3 containing 1 to 3 carbon atoms,branching cannot occur and unsaturation cannot occur. When R3 contains a cyclic group, R3 must have at least 6 carbons minimum. When R3 contains an aryl group, R3 must have at least 7 carbons.Heteroatoms may be present between the carbon atoms of R3 or covalently bonded to the carbon atoms in R3. The heteroatoms may be selected from oxygen, nitrogen, phosphorous, sulfur or combinations thereof.

[0073] In some embodiments, R1 comprises ethylene oxide units and an alkyl group or alkene group having between 4 to 20 carbons or R1 is an alkyl or alkene group having between 4 to 20 carbons.

[0074] R1 may comprise formula 2 -(CHjCHjOjnX, where n is an integer from 0 to 20, and X is an alkyl, alkene or alkyl-aryl group consisting of Cl through C20, more preferable C2 through C20, more preferable C4 through C20, more preferable C4 through Cl 6. X can be linear or branched or can contain aryl or non-aryl cyclic structures. The carbon atom covalently bonded to the oxygen of the phosphate group must be a primary carbon. X can contain unsaturated bonds. It is understood that, in the case of n isO and X containing 1 to 3 carbon atoms, branching cannot occur and unsaturation cannot occur. When X contains a cyclic group, X must have at least 6 carbons minimum. When X contains an aryl group, X must have at least 7 carbons. Heteroatoms may be present between the carbon atoms of X or covalently bonded to the carbon atoms in X, namely oxygen, nitrogen, phosphorous, sulfur or combination thereof. R2 can be an H, an alkali metal, an ammonium ion, or alkyl ammonium ion, preferably R2 is an alkali metal, an ammonium ion, or alkyl ammonium ion. R3 can be an H, an alkali metal, an ammonium ion, or an alkyl ammonium ion or can equal Rl.

[0075] Alkyl-aryl group means a structure containing an alkyl or alkene group and an aryl moiety.

[0076] The phosphate ester used in the invention is non fluorinated.

[0077] In accordance with an embodiment of the invention, there is provided a process for preparing a fluoropolymer in an aqueous dispersion wherein the surfactant is a phosphate ester. Phosphate ester may be represented by formula (1 ) above.

[0078] The process for preparing a fluoropolymer in an emulsion polymerization, may comprise the steps of: i. forming an aqueous solution comprising a phosphate ester in a reactor; ii. raising the temperature of the reactor to a reaction temperature iii. pressurizing the reactor with fluoromonomer iv. initiating a polymerization reaction of the fluoromonomer by adding an initiator into the polymerization reactor, thereby forming a fluoropolymer dispersion.

[0079] The phosphate esters are added to the polymerization process in an amount from about 100 ppm to 5 weight percent based on total monomer fed to the reaction. Preferably, they are used in an amount from about lOOppm to about 2 weight percent based on total monomer and more preferably from about 100ppm to 1 wt%.

[0080] The final composition will have from 20 ppm to about 5 weight percent of phosphate ester based on polymer weight.

[0081] The addition of the phosphate ester can be done entirely before the addition of the initiator begins, after the addition of the initiator begins or co-fed during the addition of the initiator. The phosphate ester can be feed during the polymerization reaction. In one embodiment, the phosphate ester is also added after the termination of the polymerization to stabilize the latex (post polymerization addition).

[0082] InitiatorThe reaction is started and maintained by the addition of a radical initiator. Inorganic radical initiators include inorganic peroxides, such as persulfates. The present invention preferably uses inorganic persulfate as the initiator. Typical inorganic persulfates, including sodium, potassium or ammonium persulfate, have useful activity in the 50°C to 140°C temperature range. Organic peroxides can also be used as the radical initiator in the present invention.

[0083] Preferably, the inorganic radical initiator is selected from the group comprising, hydrogen peroxide, persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, preferably potassium persulfate in conjunction with sodium acetate or sodium acetate trihydrate.

[0084] The total amount of inorganic initiator used is from 0.005% to 4.0 wt%, preferable from 0.02%- 2.0 %, by weight based on the total monomer weight added in the polymerization. A mixture of one or more inorganic initiators as defined above, can be used to conduct the polymerization. Typically, sufficient initiator is added at the beginning to start the reaction and then additional initiator may be optionally added to maintain the polymerization at a convenient or preset rate.

[0085] CHAIN TRANSFER AGENT

[0086] A chain-transfer agent may be added to the polymerization to regulate the molecular weight of the product. They may be added to a polymerization in a single portion at the beginning of the reaction, or incrementally or continuously throughout the reaction. The amount and mode of addition of chain-transfer agent depend on the activity of the chain-transfer agent employed, and on the desired molecular weight of the polymer product. The amount of chain-transfer agent added to the polymerization reaction is from about 0 to 5 wt%, preferably 500 ppb to about 5 weight percent, more preferably from about 1000 ppb toabout 2 weight percent based on the total weight of monomer added to the reaction mixture. Examples of chain transfer agents useful in the present invention include, but are not limited to oxygenated compounds such as alcohols (preferably having 3 to 10 carbons), carbonates, ketones, esters, and ethers may serve as chain-transfer agents such as acetone, ethyl acetate, diethyl ether, methyl-ter-butyl ether, isopropyl alcohol,; bis(alkyl)carbonates wherein the alkyl has from 1 to 5 carbon atoms, such as bis(ethyl)carbonate, bi s( isobutyl)- carbonate; ethane and propane; and low molecular weight functional polymers as defined in US20180072829.

[0087] BUFFERING AGENT

[0088] The polymerization reaction mixture may optionally contain a buffering agent to maintain a controlled pH throughout the polymerization reaction. The pH is preferably controlled within the range of from about 4 to about 8, to minimize undesirable color development in the product.

[0089] Buffering agents may comprise an organic or inorganic acid or alkali metal salt thereof, or base or salt of such organic or inorganic acid, that has at least one pKavalue and / or pKi, value in the range of from about 4 to about 10, preferably from about 4.5 to about 9.5. Preferred buffering agents in the practice of the invention include, for example, phosphate buffers and acetate buffers. A “phosphate buffer” is a salt or salts of phosphoric acid. An “acetate buffer” is a salt of acetic acid.

[0090] A paraffin antifoulant may be employed, if desired, although it is not preferred, and any long- chain, saturated, hydrocarbon wax or oil may be used. Reactor loadings of the paraffin may be from 0.01% to 0.3% by weight on the total monomer weight used.

[0091] The polymer or copolymer can be isolated using standard methods such as oven drying, spray drying, shear or acid coagulation followed by drying, or kept in the aqueous media for subsequent application or use.

[0092] In a further aspect, the present invention also relates to an article made from a composition comprising the polymer composition as defined above.

[0093] In a further aspect, the present invention relates to a method for the manufacture of shaped article, said method comprising processing a composition comprising the polymer composition as defined above.

[0094] Said polymer composition can be fabricated, e.g. by molding (injection molding, extrusion molding), calendaring, or extrusion, into the desired shaped article. If necessary, the article is then subjected to vulcanization (or curing) during the processing itself and / or in a subsequent step (posttreatment or post-cure).

[0095] The following general emulsion process may be followed: to a reactor is initially added deionized water with a surfactant (also referred to as an emulsifier), followed by deoxygenation (removal of oxygen). The reactor is brought to desired preset reaction temperature. Optionally chain transfer agent, antifoulant and buffering agent may be added to the reactor, preferably before deoxygenation.Fluoromonomer, such as vinylidene fluoride and optional other comonomer(s) is added to the reactor to reach a preset reaction pressure. When the preset reaction pressure is reached, a radical initiator is added, optional with a buffering agent, to start and maintain the polymerization reaction. Additional monomer may be optionally added to replenish monomer that is consumed, and the other materials may be optionally added during the polymerization. After feeding the preset monomer amount to the reactor, the feed of the monomers can be stopped. However, the charging of initiator can be stopped or continued to consume the unreacted monomers. After the initiator charging is stopped, the reactor may be cooled, and agitation stopped. The unreacted monomers can be vented, and the prepared polymer can be collected through a drain port or by other collection means.

[0096] The reactor used in the polymerization is a pressurized polymerization reactor. The reactor usually is equipped with a stirrer and heat control means. The stirring may be constant or may be varied to optimize process conditions during the course of the polymerization. The method according to the present invention can be preferably performed in continuous, or semi-batch or batch.

[0097] The temperature of the polymerization is typically from 40°C to 140°C, preferably of 50 °C to 135 °C, more preferably from 60°C to 125 °C. The temperature can be varied during the reaction, preferably the temperature is kept constant at + / - 0.5°C.

[0098] The pressure of the polymerization may vary from 1380 to 12,500 kPa, depending on the capabilities of the reaction equipment, the initiator system chosen, and the monomer selection. The polymerization pressure is preferably from 2,000 to 9,000 kPa.

[0099] CHARACTERISTICS OF THE POLYMER

[0100] The dispersion of the invention has a solids level of from 10 to 50 weight percent, preferably from 20-50 weight percent. The fluoropolymer particles in the dispersion have a particle size in the range of 50 to 500 nm, and preferable from 100-400 nm.

[0101] The polymer is preferably not crosslinked.

[0102] The fluoropolymer comprises at least 50 mole% fluoromonomer or at least 70 mole % fluoromonomer or at least 75 mol%. The fluoropolymer can comprise up to and including 100 mole % fluoromonomer. The fluoropolymer can be a homopolymer.

[0103] The fluoropolymer can be a vinylidene fluoride polymer wherein the fluoropolymer comprises at least 50 mole% vinylidene fluoride (VDF), preferably at least 70 mole% VDF or at least 75 mole% VDF. The fluoropolymer comprises up to 100 weight percent VDF.

[0104] The melt viscosity of the inventive fluoropolymer is generally in the range of from 0.1 to 80, preferably 5 kPoise to 80 kPoise, (ASTM D3835 at 232°C and 100 sec -1)

[0105] Preferably, the dispersion of the invention has a solids level of from 20 to 45 weight percent, more preferably from 25-40 weight percent.

[0106] The fluoropolymer particles in the dispersion have a Z average particle size in the range of 50 to 500 nm, and preferable from 100-300 nm (volume average particle size).TESTING METHODS

[0107] The Z- average particle size of the dispersion was determined using a Nicomp Model 380 Sub- Micron Particle Sizer including single mode 35 mW Laser diode with wavelength of 639 nm.

[0108] Melt viscosity measurements of resin were performed with a DYNISCO LCR-7000 according to ASTM D3835 by a capillary rheometry at 232° C. and 100 sec-1 .

[0109] Latex solids content are measured in duplicate using a moisture analyzer apparatus such as Mettler-Toledo HX204, and the average is reported. Percent coagulum is determined gravimetrically by difference in mass of the mesh screen before and after collection of coagulum. Percentage coagulum is calculated as product produced that would not pass through a mesh screen (namely a cheese cloth - Cotton, Bleached Grade 90, with 44X36 threads per square inch from Idealfold Model: BIDF4436360) under gravimetric filtration divided by total monomer fed to reactor.

[0110] EXAMPLES

[0111] Example 1

[0112] A 7.5 liter volume autoclave equipped with circulating jacket and mechanical agitation was charged with 3000g deionized water and 1 .9 g neutralized laureth phosphate (14% active component neutralized to pH=7.4 with sodium hydroxide). The autoclave was deoxygenated by pressurization of the reactor to 400 kPa with ultra-pure nitrogen, holding at that pressure for 5 min with agitation, then venting to 0 kPa. This cycle is repeated an additional 2 times. The reactor was sealed and agitated at 72 rpm and heated to 83 °C. Once at 83 °C, 150 mL of 1 .0wt% potassium persulfate (KPS) and 1.0wt% sodium acetate (SAT) solution was fed to the reactor. Throughout the reaction, the feed rate of KPS / SAT was kept between 50-100mL / h. VDF was fed to maintain reactor pressure at 4480 kPa. Feeds were continued until 1577 g VDF was delivered to the reactor, then all feeds were halted. The reactor was held at 83 °C for twenty minutes. The reactor was cooled to 40 °C and vented to atmospheric pressure. Product was discharged from the reactor.

[0113] Examples 2 and 3 were run using the same general procedure as Example 1 with the differences indicated in the table.

[0114] The melt viscosities, and solids were measured and reported in Table 1 .Table 1 s'1)

Claims

Claims1. A fluoropolymer composition comprising: at least one fluoropolymer and at least one phosphate ester having a phosphate group and one or two covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein each covalent grouping of atoms of the phosphate ester independently comprises from 1 to 50 carbon atoms, wherein the covalent grouping of atoms is covalently bonded to the phosphate group by a primary carbon in the covalent grouping of atoms.

2. The fluoropolymer composition of claim 1, wherein said fluoropolymer is a vinylidene fluoride homopolymer or a vinylidene fluoride copolymer.

3. The fluoropolymer composition of claim 1 or 2, wherein said fluoropolymer is a vinylidene fluoride copolymer comprising at least one fluorinated comonomer unit selected from the group consisting of tetrafluoroethylene, trifluoroethylene, hexafluoropropene, chlorotrifluoroethylene, vinyl fluoride, and combinations thereof, preferably hexafluoropropene.

4. The fluoropolymer composition of any one or more of claims 1 to 3, wherein said fluoropolymer is a vinylidene fluoride copolymer comprising at least one non fluorinated comonomer unit.

5. The fluoropolymer composition of any one or more of claims 1-4, wherein the amount of phosphate ester is from 20 ppm to 2.0 weight percent, based on the weight of the fluoropolymer.

6. The fluoropolymer composition of any one or more of claims 1-4, wherein the amount of phosphate ester is from 20ppmto 1 .0 weight percent, based on the weight of the fluoropolymer.

7. The fluoropolymer composition of any one or more of claims 1-6, wherein at least one phosphate ester is represented by the formula :(I) wherein;R1 is a covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein a carbon atom from the covalent grouping of atoms is covalently bonded to the oxygen of the phosphate group and is a primary carbon,R2 is selected from the group consisting of H, an alkali metal, an ammonium ion, or alkyl ammonium ion,R3 is independently selected from the group consisting of H, an alkali metal, an ammonium ion, an alkyl ammonium ion, a covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein a carbon atom from the covalent grouping of atoms is covalently bonded to the oxygen of the phosphate group and is a primary carbon.

8. The fluoropolymer composition of claim 7, wherein R1 comprises one or more heteroatoms, and at least one heteroatom is selected from the group consisting of oxygen, nitrogen, phosphorous, sulfur, bromine, chlorine and combinations thereof.

9. The fluoropolymer composition of claim 7, wherein R1 comprises at least one oxygen.

10. The fluoropolymer composition of any one or more of claims 1-8, wherein: a. RI comprises the formula where n is an integer from 0 to 20, and X is analkyl or alkyl-aryl group comprising from 1 to 20 carbons, preferable X comprises from 2 to 20 carbons, more preferable X comprises from 4 to 20 carbons, more preferable X comprises from 4 to 16 carbons; b. R2 is selected from the group consisting of H, an alkali metal, an ammonium ion, alkyl ammonium ion, preferably R2 is an alkali metal, an ammonium ion, or alkyl ammonium ion; and c. R3, is selected from the group consisting of H, an alkali metal, an ammonium ion, alkyl ammonium ion, or is the same as Rl, preferably R3 is an alkali metal, an ammonium ion, or alkyl ammonium ion.

11. The fluoropolymer composition of claim 10, n is 0 and X is an alkyl group or alkene group.

12. The fluoropolymer composition of claim 10, wherein X comprises an aryl or non-aryl cyclic group.

13. The fluoropolymer composition of claim 10, wherein n is greater than 0.

14. The fluoropolymer composition of claim 10, wherein n is greater than 0 and X is an alkyl group or alkene.

15. The fluoropolymer composition of claim 10, wherein n is greater than 0 and X comprises an aryl group.

16. The fluoropolymer composition of any one or more of claims 1-14, wherein Rl comprises the formula -(CFbCTbO^X, where n is an integer from 2 to 15; X is an alkyl group; R2 and R3 are independently selected from the group H, an alkali metal, an ammonium ion, or an alkyl ammonium ion and combinations thereof.

17. A method for preparing a fluoropolymer in an aqueous reaction medium comprising: a. forming an aqueous mixture comprising at least surfactant, and at least one fluoromonomer, b. adding at least one radical initiator,c. polymerizing said fluoromonomers, thereby forming a fluoropolymer dispersion; wherein the surfactant comprises at least one phosphate ester having a phosphate group and one or two covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein each covalent grouping of atoms of the Phosphate ester independently comprises from 1 to 50 carbon atoms, wherein the covalent grouping of atoms is covalently bonded to the phosphate group by a primary carbon in the covalent grouping of atoms.

18. The method of claim 17, wherein said fluoropolymer is a vinylidene fluoride homopolymer or a vinylidene fluoride copolymer.

19. The fluoropolymer composition of claim 17 or 18, wherein said fluoropolymer is a vinylidene fluoride copolymer comprising at least one fluorinated comonomer unit selected from the group consisting of tetrafluoroethylene, trifluoroethylene, hexafluoropropene, chlorotrifluoroethylene, vinyl fluoride, and combinations thereof, preferably hexafluoropropene.

20. The method of any one or more of claims 17 to 19, wherein said fluoropolymer is a vinylidene fluoride copolymer comprising at least one non fluorinated comonomer unit.21 . The method of any one or more of claims 17-20, w’herein the amount of phosphate ester is from 0.01 to 2.0 weight percent, based on the weight of the fluoromonomer used in the polymerization reaction.

22. The method of any one or more of claims 17-20, w'herein the amount of phosphate ester is from 0.01 to 1 .0 weight percent, based on the weight of fluoromonomer used in the polymerization reaction, preferably in the amount of 0.01 to 0.5 weight percent.

23. The method of any one or more of claims 17-22, wherein at least one phosphate ester is represented by the formula :(I) wherein:R1 is a covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein a carbon atom from the covalent grouping of atoms is covalently bonded to the oxygen of the phosphate group and is a primary carbon,R2 is selected from the group consisting of H, an alkali metal, an ammonium ion, or alkyl ammonium ion.R3 is independently selected from the group consisting of H, an alkali metal, an ammonium ion, an alkyl ammonium ion, a covalent grouping of atoms containing from 1 to 50 carbon atoms, wherein a carbon atom from the covalent grouping of atoms is covalently bonded to the oxygen of the phosphate group and is a primary carbon.

24. The method of claim 23, wherein Rl comprises one or more hctcroatoms, at least one heteroatom is selected from the group consisting of oxygen, nitrogen, phosphorous, sulfur, bromine, chlorine and combinations thereof.

25. The method of claim 23, wherein Rl comprises at least one oxygen.

26. The method of any one or more of claims 23-25, wherein: a. R1 comprises the formul where n is an integer from 0 to 20, and X is an alkyl oralkyl-aryl group comprising from 1 to 20 carbons, preferable X comprises from 2 to 20 carbons, more preferable X comprises from 4 to 20 carbons, more preferable X comprises from 4 to 16 carbons; b. R2 is selected from the group consisting of H, an alkali metal, an ammonium ion, alkyl ammonium ion, preferably R2 is an alkali metal, an ammonium ion, or alkyl ammonium ion; and c. R3, is selected from the group consisting of H, an alkali metal, an ammonium ion, alkyl ammonium ion, or is the same as Rl, preferably R3 is an alkali metal, an ammonium ion, or alkyl ammonium ion.

27. The method of claim 26, wherein n is 0 and X is an alkyl group or alkene group.

28. The method of claim 26, wherein X comprises an aryl or non-aryl cyclic group.

29. The method of claim 26, wherein n is greater than 0.

30. The method of claim 26, wherein n is greater than 0 and X is an alkyl group or alkene.31 . The method of claim 26, wherein n is greater than 0 and X comprises an aryl group.

32. The method of claims 26, wherein Rl comprises the formula, where n is an integer from 2 to 15; X is an alkyl group; R2 and R3 are independently selected from the group H, an alkali metal, an ammonium ion, or an alkyl ammonium ion and combinations thereof.

33. The method of any one or more of claims 26-32, wherein the fluoropolymer dispersion constitutes, after step (b) at least 20 wt % fluoropolymer based on total weight of the dispersion.

34. The fluoropolymer composition of any one or more of claim 1 - 7 wherein the phosphate ester is selected form the groups consisting of butanol phosphate (mono and diester), 2-ethylhexyl phosphate (mono and diester), 2-ethylhexyl ethoxylated phosphate (mono and diester), lauryl alcoholphosphate, lauryl alcohol ethyoxylated phosphate, tridecyl alcohol phosphate, tridecyl alcohol ethoxylated phosphate, cetyl alcohol phosphate, oleyl alcohol phosphate, nonyl phenol ethoxylated phosphate and combinations thereof.

35. The method of any one or more of claim 17 - 23 wherein the phosphate ester is selected form the groups consisting of butanol phosphate (mono and diester), 2-ethylhexyl phosphate (mono and diester), 2-ethylhexyl ethoxylated phosphate (mono and diester), lauryl alcohol phosphate, lauryl alcohol ethyoxylated phosphate, tridccyl alcohol phosphate, tridccyl alcohol ethoxylated phosphate, cetyl alcohol phosphate, oleyl alcohol phosphate, nonyl phenol ethoxylated phosphate and combinations thereof.

Images