Production of fluoropolymer latexes with dual surfactants

Abstract

A method for preparing a fluoropolymer is disclosed, the method comprising reacting a fluoromonomer in the presence of at least one acrylic glycol surfactant and at least one sulfur-containing surfactant or a mixture thereof. Also disclosed are polymers made by the method. Also disclosed are polymer compositions comprising at least one sulfur-containing surfactant, at least one acrylic glycol surfactant, and at least one fluoropolymer.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION This invention describes a fluoropolymer latex and a method for producing the fluoropolymer latex, whereby the particle size of the fluoropolymer is controlled. [Background technology]

[0002] Background of the Invention The method for producing fluoropolymers by emulsion process generally uses surfactants to stabilize the fluoropolymer latex during the polymerization reaction. For example, see US Patents US7122610, US8080621, US8124699, US8697822, and US9068071. However, none of them teach that the particle size can be controlled based on the weight ratio of surfactants by utilizing a dual surfactant system in the emulsion polymerization process.

[0003] The prior art does not disclose the use of a dual surfactant system in emulsion polymerization to control the average particle size of fluoropolymer latexes. There is no teaching of the use of the two families of surfactants used in the present invention in emulsion polymerization of fluoropolymers to control the particle size of the fluoropolymer.

[0004] This study presents the first method for controlling the particle size of fluoropolymer latex in PVDF latex during the polymerization process. The applicant discovered that by varying the weight ratio of two surfactants (a sulfur-containing surfactant and an acrylic glycol surfactant), the particle size of the fluoropolymer in the latex can be adjusted during the emulsion polymerization process. The particle size of the fluoropolymer in the latex shows a linear correlation with the ratio of surfactants used in the emulsion polymerization. This correlation can be used to target particle size in the preparation of PVDF latex. Summary of the Invention

[0005] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the linear relationship between the ratio of surfactants in the latex and the particle size of the fluoropolymer.

[0006] Summary of the Invention This invention describes a fluoropolymer latex and a method for producing the fluoropolymer latex using at least two surfactants in an emulsion polymerization process. The use of two surfactants in the emulsion polymerization process can control the average particle size of the fluoropolymer in the resulting latex. The fluoropolymer latex is prepared by emulsion polymerization using one or more fluoromonomers, two surfactants, and a persulfate initiator. Surprisingly, it has been found that the particle size of the fluoropolymer in the latex can be adjusted by changing the weight ratio of the two surfactants.

[0007] The method is: a) contacting an aqueous mixture containing a first surfactant, a second surfactant, and a monomer feed containing one or more fluoromonomers, and optional additives (e.g., chain transfer agents, buffers, etc.), with a radical initiator; b) polymerizing one or more fluoromonomers, thereby forming a fluoropolymer latex; Includes.

[0008] The first surfactant comprises a sulfur-containing surfactant and the second surfactant comprises an alkyl glycol-containing surfactant.

[0009] Embodiments of the present invention

[0010] Embodiment 1 of the present invention is a method for preparing a fluoropolymer, said method comprising: a) In a reaction vessel, an aqueous reaction medium, at least one fluoromonomer, and optionally a chain transfer agent; i) one acrylic glycol surfactant having at least one segment selected from a polyethylene glycol segment, a polypropylene glycol segment, and / or a polytetramethylene glycol segment, each having 2 to 200 repeating units in the segment; ii) a sulfur-containing surfactant, wherein the sulfur-containing surfactant is non-fluorinated and comprises one of an alkyl sulfonate, an alkyl sulfate surfactant, or a mixture thereof; and b) adding at least one radical initiator to said reaction vessel; c) initiating emulsion polymerization of said fluoromonomer; to provide a fluoropolymer latex, wherein the total amount of one or more surfactants in the process is at least 110 ppm based on the total weight of the one or more fluoromonomers fed to the polymerization reaction.

[0011] Embodiment 2: The method of embodiment 1, wherein the weight ratio of the sulfur-containing surfactant to the acrylic glycol-containing surfactant is 0.1 to 500 (weight ratio).

[0012] Embodiment 3: The method of embodiment 1, wherein the weight ratio of the sulfur-containing surfactant to the acrylic glycol-containing surfactant is 0.4 to 150 (by weight).

[0013] Embodiment 4: The method of any one of the previous embodiments, wherein the amount of sulfur-containing surfactant in the method is greater than or equal to 100 ppm and less than 5000 ppm based on the total fluoromonomer(s) fed to the emulsion polymerization reaction.

[0014] Embodiment 5: The method of any one of the preceding embodiments, wherein the amount of sulfur-containing surfactant in the method is from 200 ppm to 3500 ppm based on the total fluoromonomer(s) fed to the emulsion polymerization reaction.

[0015] Embodiment 6: The method of any one of the preceding embodiments, wherein the amount of acrylic glycol surfactant in the method is from about 10 ppm to about 1000 ppm based on the total fluoromonomer(s) fed to the emulsion polymerization reaction.

[0016] Embodiment 7: The method of any one of embodiments 1 to 5, wherein the amount of acrylic glycol surfactant in the method is from about 10 ppm to about 600 ppm based on the total fluoromonomer(s) fed to the emulsion polymerization reaction.

[0017] Embodiment 8: The method of any one of embodiments 1 to 7, wherein the volume average particle size of the fluoropolymer ranges from 110 nm to 350 nm.

[0018] Embodiment 9: The method of any one of embodiments 1 to 9, wherein the total amount of surfactant present in the method is at least 110 ppm and at most 6000 ppm, based on the total weight of the one or more fluoromonomers fed to the emulsion polymerization reaction.

[0019] Embodiment 10: The method of any one of embodiments 1 to 9, wherein the total amount of surfactant present in the method is from 200 ppm to 5000 ppm based on the total weight of the one or more fluoromonomers fed to the emulsion polymerization reaction.

[0020] Embodiment 11: The method of any one of embodiments 1 to 10, wherein the one or more acrylic glycol surfactants have 2 to 100 repeating glycol units, and are preferably ethylene glycol or propylene glycol.

[0021] Embodiment 12: The method of any one of embodiments 1-11, wherein the acrylic glycol-containing surfactant is selected from the group consisting of polyethylene glycol acrylate (PEGA), polyethylene glycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), polypropylene glycol methacrylate (PPGMA), polypropylene glycol polyethylene glycol acrylate, polypropylene glycol polyethylene glycol methacrylate, and polypropylene glycol dimethacrylate.

[0022] Embodiment 13: The method of any one of embodiments 1 to 11, wherein the one or more surfactants containing an acrylic glycol comprise polypropylene glycol methacrylate (PPGMA).

[0023] Embodiment 14: The method of any one of embodiments 1 to 13, wherein the alkyl group of the sulfur-containing surfactant comprises a C6 to C18 alkyl group.

[0024] Embodiment 15: The method of any one of embodiments 1-13, wherein the sulfur-containing surfactant comprises a non-fluorinated alkyl sulfonate selected from the group consisting of octyl sulfonate, octyl disulfonate, decyl sulfonate, decyl disulfonate, dodecyl sulfonate, dodecyl disulfonate, and combinations thereof.

[0025] Embodiment 16: The method of any one of embodiments 1-13, wherein the sulfur-containing surfactant comprises at least one of octyl sulfonate, octyl disulfonate, or decyl sulfonate.

[0026] Embodiment 18: The method of any one of embodiments 1-13, wherein the sulfur-containing surfactant comprises at least one of sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, lithium lauryl sulfate, sodium laureth sulfate, sodium octyl sulfate, potassium octyl sulfate, ammonium octyl sulfate, lithium octyl sulfate, and combinations thereof.

[0027] Embodiment 19: The method of any one of embodiments 1-10, wherein the acrylic glycol surfactant comprises polypropylene glycol methacrylate (PPGMA) and the sulfur-containing surfactant comprises octyl sulfonate.

[0028] Embodiment 20: The method of any one of embodiments 1 to 19, wherein the radical initiator comprises a persulfate.

[0029] Embodiment 21: The method of any one of embodiments 1 to 20, wherein the at least one fluoromonomer is selected from the group consisting of vinylidene fluoride, hexafluoropropene, tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, vinyl fluoride, and combinations thereof.

[0030] Embodiment 22: The method of any one of embodiments 1 to 21, wherein at least 65% by weight of the added fluoromonomers consist of vinylidene fluoride monomers.

[0031] Embodiment 23: The method of any one of embodiments 1-20, wherein the fluoromonomer comprises vinylidene fluoride monomer.

[0032] Embodiment 24: The method of any one of embodiments 1 to 22, wherein the fluoropolymer is a vinylidene fluoride copolymer comprising at least one comonomer selected from the group consisting of tetrafluoroethylene, trifluoroethylene, hexafluoropropene, chlorotrifluoroethylene, vinyl fluoride, and combinations thereof.

[0033] Embodiment 25: The method of embodiment 21, wherein said fluoromonomers comprise vinylidene fluoride and hexafluoropropene.

[0034] Embodiment 26: A fluoropolymer composition comprising: a) at least one sulfur-containing surfactant and at least one acrylic glycol surfactant, and b) at least one fluoropolymer; 1. A fluoropolymer composition comprising:

[0035] Embodiment 27: The fluoropolymer latex composition of embodiment 26, wherein the one or more acrylic glycol surfactants have from 2 to 100 repeating glycol units, and preferably is ethylene glycol or propylene glycol.

[0036] Embodiment 28: The fluoropolymer latex composition of embodiment 26, wherein the acrylic glycol-containing surfactant is selected from the group consisting of polyethylene glycol acrylate (PEGA), polyethylene glycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), polypropylene glycol methacrylate (PPGMA), polypropylene glycol polyethylene glycol acrylate, polypropylene glycol polyethylene glycol methacrylate, and polypropylene glycol dimethacrylate.

[0037] Embodiment 29: The fluoropolymer latex composition of embodiment 26, wherein the one or more surfactants containing an acrylic glycol comprise polypropylene glycol methacrylate (PPGMA).

[0038] Embodiment 30: The fluoropolymer latex composition of any one of Embodiments 26-29, wherein the sulfur-containing surfactant comprises a C6 to C18 alkyl group.

[0039] Embodiment 31: The fluoropolymer latex composition of any one of embodiments 26-29, wherein the sulfur-containing surfactant comprises a non-fluorinated alkyl sulfonate selected from the group consisting of octyl sulfonate, octyl disulfonate, decyl sulfonate, decyl disulfonate, dodecyl sulfonate, dodecyl disulfonate, and combinations thereof.

[0040] Embodiment 32: The fluoropolymer latex composition of any one of embodiments 26-29, wherein the sulfur-containing surfactant comprises at least one of octyl sulfonate, octyl disulfonate, or decyl sulfonate.

[0041] Embodiment 33: The fluoropolymer latex composition of any one of embodiments 26-29, wherein the sulfur-containing surfactant comprises at least one of sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, lithium lauryl sulfate, sodium laureth sulfate, sodium octyl sulfate, potassium octyl sulfate, ammonium octyl sulfate, lithium octyl sulfate, and combinations thereof.

[0042] Embodiment 34: The fluoropolymer latex composition of embodiment 26, wherein the acrylic glycol surfactant comprises polypropylene glycol methacrylate (PPGMA) and the sulfur-containing surfactant comprises octyl sulfonate.

[0043] Embodiment 35: The fluoropolymer latex composition of any one of embodiments 26-34, wherein the fluoropolymer comprises fluoromonomer units selected from the group consisting of vinylidene fluoride, hexafluoropropene, tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, vinyl fluoride, and combinations thereof.

[0044] Embodiment 36: The fluoropolymer latex composition of any one of embodiments 26-34, wherein the fluoropolymer is polyvinylidene fluoride comprising at least 65% by weight of vinylidene fluoride.

[0045] Embodiment 37: The fluoropolymer latex composition of any one of embodiments 26-34, wherein the fluoropolymer is a polyvinylidene fluoride homopolymer.

[0046] Embodiment 38: The fluoropolymer latex composition of any one of embodiments 26-34, wherein the fluoropolymer is a polyvinylidene fluoride copolymer comprising at least 65% by weight of vinylidene fluoride and at least one comonomer selected from the group consisting of tetrafluoroethylene, trifluoroethylene, hexafluoropropene, chlorotrifluoroethylene, vinyl fluoride, and combinations thereof.

[0047] Embodiment 39: The fluoropolymer latex composition of any one of embodiments 26-34, wherein the fluoropolymer is a polyvinylidene fluoride / hexafluoropropene copolymer comprising at least 65% by weight of vinylidene fluoride. [Brief explanation of the drawings]

[0048] [Figure 1] 1 shows a linear relationship between the ratio of surfactants in the latex and the particle size of the fluoropolymer. DETAILED DESCRIPTION OF THE INVENTION

[0049] Detailed Description of the Invention The references cited in this application are hereby incorporated by reference.

[0050] Percentages used herein are weight percentages (wt %) unless otherwise specified.

[0051] The melt viscosity is measured by capillary rheometry in accordance with ASTM D3835 at 230°C for 100 seconds. -1 is.

[0052] Solids content refers to the material remaining after drying of the fluoropolymer latex. The solids content of the fluoropolymer latex was determined gravimetrically using a HG63 moisture analyzer from Mettler Toledo.

[0053] The term "fluoropolymer" refers to polymers and copolymers (including polymers having two or more different monomers, such as terpolymers) that contain at least 50 mole percent fluoromonomer units. Polymers can be homogeneous, heterogeneous, or random, and can also have a gradient distribution of comonomer units.

[0054] The term "fluoropolymer latex" refers to an aqueous dispersion of fluoropolymer obtained from the emulsion polymerization of fluoromonomers.

[0055] "Copolymer" is used to mean a polymer having two or more different monomer units, including terpolymers and higher order polymers. "Polymer" is used to mean both homopolymers and copolymers.

[0056] "PVDF" means polyvinylidene fluoride, which includes both homopolymers and copolymers unless otherwise specified.

[0057] Ethylenic means that the monomer has a polymerizable carbon-carbon double bond.

[0058] The present invention provides a method for preparing fluoropolymers from fluoromonomers using at least two surfactants in emulsion polymerization. The fluoropolymers are prepared in an aqueous mixture containing one or more fluoromonomers, surfactant 1 (a sulfur-containing surfactant), surfactant 2 (an acrylic glycol-containing surfactant), an optional chain transfer agent, one or more optional buffers, and an initiator. The surfactants are non-fluorinated. Optionally, the polymerization of the present invention can be carried out in the presence of a chain transfer agent, a buffer to maintain a desired pH range during polymerization, and an antifouling agent to reduce or eliminate adhesion of the polymer to the interior surfaces of the polymerization vessel. The product obtained from the emulsion polymerization is a fluoropolymer latex.

[0059] The applicant has surprisingly found that the particle size of the fluoropolymer in the latex can be controlled by controlling the weight ratio of the first surfactant to the second surfactant in the emulsion polymerization of the fluoromonomer. Generally, the particle size of the fluoropolymer in the latex can be adjusted in the range of 100 nm to 400 nm.

[0060] Polymerization Process

[0061] A typical emulsion polymerization procedure can be followed: first, deionized water, surfactant 1 and surfactant 2, optional chain transfer agent, optional antifouling agent and / or optional buffer are added to a reactor, followed by deoxygenation (removal of oxygen). Generally, water is added to the reactor before bringing the reactor to the desired starting temperature, but other materials can be added before or after bringing the reactor to temperature. An oil phase, such as fluoroform, is not utilized. The reactor may be a pressurized polymerization reactor equipped with an agitator and heat control means. Agitation may be constant or adjusted to optimize process conditions during polymerization. After the reactor reaches the desired temperature, a predetermined amount of monomer and / or comonomer is added to the reactor. The ratio of monomer to comonomer can be selected. At least one radical initiator is added to initiate and maintain the polymerization. An initiator solution, optionally a buffer solution, and optionally a chain transfer agent are fed to the reactor at appropriate flow rates. Additional monomer can be optionally added to replenish consumed monomer, and other materials can be added during the polymerization to maintain the reaction and control the properties of the final product. After the desired total monomer feed is reached, the monomer feed can be stopped. Unreacted monomer can be vented, and the prepared fluoropolymer latex can be collected through a drain port or by other collection means. The fluoropolymer latex can be kept in an aqueous medium for subsequent application or use, or can be converted to a dry form.

[0062] The pressure used for polymerization can be selected from a wide range of pressures, from about 280 to about 20,000 kPa, depending on the reactor performance, the selected initiator system, and the monomer composition used. The polymerization pressure is typically from about 2,000 to about 11,000 kPa, and most typically from about 2,750 to about 9,000 kPa. The polymerization temperature can vary from about 20°C to about 160°C, typically from about 35°C to about 130°C, and most typically from about 65°C to about 100°C, depending on the selected initiator system.

[0063] Fluoropolymer

[0064] The term "fluoropolymer" as used for purposes of this invention means a polymeric material containing at least 65% by weight of vinylidene fluoride units, the remaining units being one or more fluoromonomers. The fluoropolymer may consist essentially of vinylidene fluoride and optionally other fluoromonomer units, or it may also contain other comonomer units.

[0065] Fluoropolymers can be homopolymers, copolymers, terpolymers, or higher polymers (more than three monomers). Fluoropolymers can be thermoplastic, where "thermoplastic" refers to the ability to be formed into shapes by the application of heat and (typically) pressure, as occurs in molding and extrusion processes. Exemplary polymers produced by the method of the present invention include polyvinylidene fluoride homopolymers, copolymers, terpolymers, and higher polymers having a vinylidene fluoride content of at least 65% by weight, typically at least 75% by weight. Specific fluoropolymers according to the present invention include, for example, copolymers of vinylidene fluoride with hexafluoropropylene, tetrafluoroethylene, or trifluoroethylene, and terpolymers of vinylidene fluoride with tetrafluoroethylene and hexafluoropropylene or tetrafluoroethylene and trifluoroethylene. Other copolymers and terpolymers can contain fluoromonomers other than those listed above in combination with vinylidene fluoride.

[0066] Fluoromonomer is used to obtain the fluoropolymer of the present invention.The term "fluoromonomer" used in accordance with the present invention means a fluorinated ethylenically unsaturated monomer that can participate in free radical polymerization reaction.The fluoromonomer suitable for use in accordance with the present invention contains at least one fluorine atom, and can incorporate, for example, a fluoroalkyl group, a fluoroalkoxy group, or a vinyl fluorine atom.

[0067] Exemplary fluoromonomers suitable for use in accordance with the present invention, in addition to vinylidene fluoride, include vinyl fluoride, trifluoroethylene, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), partially or fully fluorinated α-olefins such as 3,3,3-trifluoro-1-propene, 1,2,3,3,3-pentafluoropropene, 3,3,3,4,4-pentafluoro-1-butene, etc., the partially fluorinated olefin hexafluoroisobutylene, perfluorinated vinyl ethers such as It may be any one or more of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoro-n-propyl vinyl ether, and perfluoro-2-propoxypropyl vinyl ether, fluorinated dioxoles such as perfluoro(1,3-dioxole) and perfluoro(2,2-dimethyl-1,3-dioxole), and partially or fully fluorinated allyl monomers such as those based on 2-hydroxyethyl allyl ether or 3-allyloxypropanediol.

[0068] The fluoropolymer of the present invention may comprise a vinylidene fluoride polymer having at least 65% by weight of VDF monomer units.

[0069] The copolymer may be composed of at least about 65% by weight and up to 99% by weight of vinylidene fluoride, and correspondingly 1 to 35 percent of a comonomer, such as tetrafluoroethylene, hexafluoropropene, trifluoroethylene, etc. The copolymer may be a copolymer of vinylidene fluoride and hexafluoropropene.

[0070] surfactants

[0071] This invention uses at least two classes of surfactants: Surfactant 1 and Surfactant 2.

[0072] The first class of surfactants (surfactant 1) is a type of molecule that has both hydrophobic and hydrophilic moieties, allowing it to stabilize and disperse hydrophobic molecules and aggregates of hydrophobic molecules in aqueous media. Examples of surfactants include alkyl or (alk)aryl groups attached to sulfonic or sulfate groups. A preferred group of surfactants from the first class for the fluoropolymer latex of the present invention includes alkyl sulfate and alkyl sulfonate surfactants ("sulfur-containing surfactants"). The terms "alkyl sulfate surfactant" or "alkyl sulfonate surfactant" refer to surfactants having an alkyl hydrocarbon group as their hydrophobic moiety, preferably a C6-C18 alkyl group. The alkyl hydrocarbon group of these alkyl sulfate and alkyl sulfonate surfactants is functionalized with one or two sulfate and / or sulfonate groups as their hydrophilic moieties. The hydrocarbon group does not contain fluorine. The hydrocarbon group contains a C6-C18 alkyl group. The first class of preferred surfactants are in the form of salts, preferably with a counterion that is an alkali metal (eg, lithium, sodium, or potassium), an ammonium ion, or an alkyl-substituted ammonium ion.

[0073] Examples of alkyl sulfate surfactants include, but are not limited to, C6-C18 alkyl sulfates, such as lauryl sulfate and octyl sulfate, and examples include, but are not limited to, sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, lithium lauryl sulfate, sodium laureth sulfate, sodium octyl sulfate, and mixtures thereof.

[0074] Examples of alkyl sulfonate surfactants include, but are not limited to, C6-C18 alkyl sulfonates, C6-C18 alkyl disulfonates, and mixtures thereof. Typical counterions for alkyl sulfonate surfactants include, but are not limited to, sodium, potassium, lithium, ammonium, or alkyl-substituted ammonium. For example, C8-C12 alkyl sulfonates can be used, such as octyl sulfonate, octyl disulfonate, decyl sulfonate, decyl disulfonate, dodecyl sulfonate, dodecyl disulfonate, and combinations thereof. For example, octyl sulfonates can be sodium octyl sulfonate, potassium octyl sulfonate, ammonium octyl sulfonate, alkyl-substituted ammonium octyl sulfonate, or lithium octyl sulfonate.

[0075] A second class of surfactants (Surfactant 2) suitable for use in this invention are non-fluorinated nonionic acrylic glycol surfactants (also referred to as acrylic glycol surfactants) containing a vinyl double bond, preferably an acrylate or methacrylate group attached to a polyglycol segment, such as, for example, polyethylene glycol (PEG), polypropylene glycol (PPG), polytetramethylene glycol (PTMG), or any combination of these polyglycol segments, preferably having from 3 to 100 repeating units, more preferably from 3 to 50 repeating units.

[0076] Acrylic glycol surfactants for use in this invention include, but are not limited to, polyethylene glycol acrylate (PEGA), polyethylene glycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), and polypropylene glycol methacrylate (PPGMA), polypropylene glycol polyethylene glycol acrylate, polypropylene glycol polyethylene glycol methacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol dimethacrylate.

[0077] Preferably, the acrylic glycol surfactant comprises polypropylene glycol methacrylate (PPGMA) or polypropylene glycol acrylate (PPGA).

[0078] In the present invention, PPGMA and / or PPGA can be used in conjunction with octylsulfonate to control particle size.

[0079] The first class of surfactants can be used in an amount of at least 100 ppm, and can be used in an amount of about 100 ppm to less than 5000 ppm based on the total amount of one or more fluoromonomers fed to the polymerization reaction.Preferably, the first class of surfactants can be used in an amount of about 100 ppm to 4000 ppm based on the total amount of one or more fluoromonomers fed to the polymerization reaction, more preferably in an amount of 200 ppm to 3500 ppm based on the total amount of one or more fluoromonomers fed to the polymerization reaction.The second class of surfactants can be used in an amount of at least 10 ppm, and can be used in an amount of about 10 ppm to about 2000 ppm based on the total amount of one or more fluoromonomers fed to the polymerization reaction, preferably in an amount of 10 ppm to 1000 ppm based on the total amount of one or more fluoromonomers fed to the polymerization reaction, more preferably in an amount of 10 ppm to 800 ppm based on the total amount of one or more fluoromonomers fed to the polymerization reaction.

[0080] In the polymerization process, the surfactant of this invention can be added all at once before polymerization, can be fed continuously during polymerization, or can be fed partially before polymerization and then fed during polymerization.

[0081] Surfactant ratio

[0082] Smaller particle sizes are achieved by adding more acrylic glycol-containing surfactant (surfactant 2) and less sulfur-containing surfactant (surfactant 1) (the smaller the weight ratio of surfactants, the smaller the particle size of the resulting fluoropolymer). The weight ratio (weight ratio) of sulfur-containing surfactant (SCS, surfactant 1) to acrylic glycol-containing surfactant (AGS, surfactant 2) is 0.1 to 500. The present invention can be practiced with a weight ratio of 0.4 to 150.

[0083] It is envisioned that the two surfactants can be fed at different feed rates such that varying their weight ratio over the course of the polymerization results in a controlled distribution of particle sizes. Spikes of different average particle sizes can be obtained, providing a multi-modal particle size distribution that can be targeted using the weight ratio of surfactant feed amounts in the polymerization reaction.

[0084] initiator

[0085] The terms "initiator" and "radical initiator" and "free radical initiator" refer to chemicals capable of providing a source of free radicals, either spontaneously or induced by exposure to heat or light. Radical initiators may include persulfates, such as sodium persulfate, potassium persulfate (KPS), lithium persulfate, or ammonium persulfate. The amount of persulfate added to the reaction mixture may be, for example, about 0.005 to about 1.0 wt. % (based on the total weight of the monomer(s) added to the reaction mixture). The terms "radical" and "free radical" refer to chemical species containing at least one unpaired electron. The radical initiator is added to the reaction mixture in an amount sufficient to initiate and maintain the polymerization reaction rate. The order of addition may vary depending on the desired process and latex emulsion properties.

[0086] The radical initiator may include a redox system. The term "redox system" is understood by those skilled in the art to mean a system comprising an oxidizing agent, a reducing agent, and, optionally, a promoter as an electron transfer medium. Examples of oxidizing agents include persulfates, peroxides, and oxidizing metal salts, such as ferric sulfate. Examples of reducing agents include sodium formaldehyde sulfoxylate, sodium and potassium sulfite, ascorbic acid, bisulfite, metabisulfite, and reducing metal salts. The promoter is a component of the redox system that can react with both the oxidizing agent and the reducing agent in different oxidation states, thereby accelerating the overall reaction. Examples of promoters include transition metal salts, such as ferrous sulfate. In the redox system, the oxidizing agent and reducing agent can be used in an amount of about 0.01 to about 0.5 wt. % based on the total monomers added to the polymerization. The optional promoter can be used in an amount of about 0.005 to about 0.025 wt. % based on the total monomers added to the polymerization. Redox systems are described, for example, in GS Misra and UDN Bajpai, Prag. Polym. Sci., 1982, 8(1-2), pp. 61-131.

[0087] Chain transfer agent

[0088] A chain transfer agent can be used in the polymerization reaction. The chain transfer agent can be added to the aqueous reaction mixture. The chain transfer agent can be added to the polymerization in a single portion at the beginning of the reaction, or added gradually throughout the reaction, or added continuously throughout the reaction. If used, the amount and method of addition of the chain transfer agent will depend on the activity of the particular chain transfer agent used and the desired molecular weight of the polymer product. The amount of chain transfer agent added to the polymerization reaction can be up to 5% by weight, preferably 0.05 to about 3% by weight, and more preferably about 0.1 to about 2% by weight, based on the total weight of the fluoromonomer(s) added to the reaction mixture. Examples of chain transfer agents useful in the present invention include, but are not limited to, oxygen-containing compounds such as alcohols (preferably those having 3 to 10 carbon atoms), carbonates, ketones, esters, and ethers, such as acetone, ethyl acetate, diethyl ether, methyl tert-butyl ether, and isopropyl alcohol; bis(alkyl)carbonates in which the alkyl has 1 to 9 carbon atoms, such as bis(ethyl)carbonate and bis(isobutyl)carbonate; ethane, propane, and those described in US 2018 / 0072829, including, but not limited to, polyacrylic acid, polylactic acid, polyphosphonic acid, polysulfonic acid, and polymaleic acid, which may function as chain transfer agents, such as low molecular weight (less than 20,000 g / mol, preferably less than 10,000 g / mol) polymeric chain transfer agents containing one or more different functional groups.

[0089] Paraffin antifoulants are not preferred but can be used if desired, and any long-chain saturated hydrocarbon wax or oil can be used. The amount of paraffin added to the reactor can be 0.01 wt % to 0.3 wt % based on the total weight of the fluoromonomer(s) added to the polymerization.

[0090] Buffer:

[0091] The polymerization reaction mixture may optionally contain a buffer to maintain a controlled pH throughout the polymerization reaction. The pH is preferably controlled within the range of about 3 to about 8 to minimize undesirable color development in the product.

[0092] The buffer may comprise an organic or inorganic acid or an alkali metal salt thereof, or a base or salt of such an organic or inorganic acid, having at least one pKa and / or pKb value in the range of about 4 to about 10, preferably about 4.5 to about 9.5. Preferred buffers for carrying out the present invention include, for example, phosphate buffer and acetate buffer. A "phosphate buffer" is one or more salts of phosphoric acid. An "acetate buffer" is a salt of acetic acid, such as sodium acetate trihydrate (SAT).

[0093] product

[0094] Emulsion polymerization generally results in a fluoropolymer latex having a solids content of 10 to 60% by weight, preferably 20 to 50% by weight.

[0095] The product of emulsion polymerization is a fluoropolymer latex, which can be used in that form, optionally after filtering solid by-products, such as coagulated polymers from the polymerization process. For use in latex form, the fluoropolymer latex can be optionally stabilized by adding an additional surfactant, an ionic surfactant or a nonionic surfactant, which can be the same as or different from the surfactant used in emulsion polymerization. Alternatively, the fluoropolymer latex can be coagulated to isolate the solid fluoropolymer, which can then be washed and dried. Coagulation methods are well known in the art.

[0096] use

[0097] These fluoropolymer latexes can be used as components in battery separator coatings to improve adhesion.

[0098] The polymers of the present invention have applications as architectural coatings, water purification membranes, or components of high purity piping for water distribution in the semiconductor industry. [Example]

[0099] Examples are provided below: The synthesis process and properties of the fluoropolymer latex are summarized below.

[0100] Light Scattering Test Method for Latex Particle Size: Measure the particle size of latex particles using a Nicomp CW380 particle size analyzer (light scattering). Use the volume average particle size.

[0101] Examples 1-2. Preparation of Fluoropolymer Latex in a 2-Gallon Reactor

[0102] A 2-gallon autoclave was charged with 4400 g of deionized water, PPGA (poly(propylene glycol) acrylate, Mn=475, n=7—available from Arkema Inc.), and / or SOS (sodium octyl sulfonate). The autoclave was stirred at 72 rpm, heated to 83°C, and pressurized to 4475 kPa with vinylidene fluoride. An aqueous feed of 1.0 wt% KPS / 1.0 wt% SAT was started at 240 g / h. Once pressure began to drop, the KPS / SAT feed rate was adjusted to maintain pressure and the VDF feed rate at approximately 500 g / h (within a range of 5–20 g / h). Pressure was maintained by feeding additional VDF. When the VDF feed reached 900 g, 23 g of an ethyl acetate solution (8 wt% in water) was fed at 1500 ml / h. After the ethyl acetate solution feed was completed, the KPS / SAT rate was adjusted to maintain pressure and maintain a VDF feed rate of approximately 500 g / h. Feeds continued in this manner until a total of 1900 g of VDF had been fed to the reactor. The reaction temperature was maintained at 83°C for an additional 30 minutes. The pressure was then allowed to autogenously reduce for 10 minutes, at which point the reactor was vented to atmospheric pressure and cooled to room temperature. The product was discharged from the reactor.

[0103] [Table 1]

[0104] Example 3. Preparation of Fluoropolymer in an 80-Gallon Reactor

[0105] An 80-gallon autoclave was charged with 166 kg of deionized water, 135.0 g of SOS, and 4.0 g of PPGMA. The autoclave was stirred at 21 rpm, heated to 83°C, and pressurized to 4475 kPa with 3.2 kg of HFP and 15.5 kg of vinylidene fluoride. A 2.0 wt% KPS / 2.0 wt% SAT aqueous solution feed was started at 4.5 kg / h. When pressure began to drop, the KPS / SAT feed rate was reduced to 136 g / h, and pressure was maintained with additional VDF. When a total of 36.4 kg of VDF was reached, a 10.0 wt% PAA solution feed was started at 3.9 kg / h. The KPS / SAT feed rate was then increased to 1.8 kg / h. Feeds continued in this manner until a total of 72.7 kg of VDF had been fed to the reactor. The reaction temperature was maintained at 90°C for an additional 30 minutes. The pressure was then autogenously reduced for 10 minutes, at which point the reactor was vented to atmospheric pressure and cooled to room temperature. The product was discharged from the reactor.

[0106] Examples 4-6 were prepared in the same manner as Example 3, but using the amounts of SOS and PPGMA shown in Table 2. The surfactant loading (ppm) is based on the total fluoromonomer(s) added to the polymerization reaction. Figure 1 is a graph of Table 2, where the surfactant ratio is the SCS / AGS ratio.

[0107] [Table 2]

[0108] These examples demonstrate that by varying the weight ratio of the two surfactants, the particle size of the resulting polymer can be controlled. Reducing the acrylic glycol surfactant results in an increase in particle size.

Claims

1. 1. A method for preparing a fluoropolymer, said method comprising: a) providing in a reaction vessel an aqueous reaction medium, at least one fluoromonomer, and optionally a chain transfer agent; i) at least one acrylic glycol surfactant having at least one segment selected from a polyethylene glycol segment, a polypropylene glycol segment, and / or a polytetramethylene glycol segment, each having 2 to 200 repeating units in the segment; ii) at least one sulfur-containing surfactant, wherein the sulfur-containing surfactant is non-fluorinated and comprises at least one of an alkyl sulfonate, an alkyl sulfate surfactant, or a mixture thereof; and b) adding at least one radical initiator to the reaction vessel; c) initiating emulsion polymerization of said fluoromonomer; to provide a fluoropolymer latex, A process wherein the total amount of one or more surfactants in said process is at least 110 ppm based on the total weight of said fluoromonomer(s) fed to the polymerization reaction.

2. 2. The method of claim 1, wherein the weight ratio of the sulfur-containing surfactant to the acrylic glycol-containing surfactant is 0.1 to 500 (by weight).

3. 2. The method of claim 1, wherein the weight ratio of the sulfur-containing surfactant to the acrylic glycol-containing surfactant is 0.4 to 150 (by weight).

4. 10. The method of claim 1, wherein the amount of said sulfur-containing surfactant in said method is 100 ppm or more and less than 5000 ppm based on the total fluoromonomer(s) fed to the emulsion polymerization reaction.

5. 10. The method of claim 1, wherein the amount of said sulfur-containing surfactant in said method is from 200 ppm to 3500 ppm based on the total fluoromonomer(s) fed to the emulsion polymerization reaction.

6. 10. The method of claim 1, wherein the amount of said acrylic glycol surfactant in said method is from about 10 ppm to about 1000 ppm based on the total fluoromonomer(s) fed to the emulsion polymerization reaction.

7. 10. The method of claim 1, wherein the amount of said acrylic glycol surfactant in said method is from about 10 ppm to about 600 ppm based on the total fluoromonomer(s) fed to the emulsion polymerization reaction.

8. The method of claim 1, wherein the volume average particle size of the fluoropolymer ranges from 110 nm to 350 nm.

9. 2. The method of claim 1, wherein the total amount of surfactant present in the method is at least 110 ppm and at most 6000 ppm, based on the total weight of the fluoromonomer(s) fed to the emulsion polymerization reaction.

10. 10. The process of claim 1, wherein the total amount of surfactant present in the process is from 200 ppm to 5000 ppm based on the total weight of the fluoromonomer(s) fed to the emulsion polymerization reaction.

11. 2. The method of claim 1, wherein the one or more acrylic glycol surfactants have from 2 to 100 repeating glycol units, and are preferably ethylene glycol or propylene glycol.

12. 2. The method of claim 1, wherein the acrylic glycol-containing surfactant is selected from the group consisting of polyethylene glycol acrylate (PEGA), polyethylene glycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), polypropylene glycol methacrylate (PPGMA), polypropylene glycol polyethylene glycol acrylate, polypropylene glycol polyethylene glycol methacrylate, and polypropylene glycol dimethacrylate.

13. 10. The method of claim 1, wherein the one or more acrylic glycol-containing surfactants comprise polypropylene glycol methacrylate (PPGMA).

14. 2. The method of claim 1, wherein the alkyl group of the sulfur-containing surfactant comprises a C6 to C18 alkyl group.

15. 10. The method of claim 1, wherein the sulfur-containing surfactant comprises a non-fluorinated alkyl sulfonate selected from the group consisting of octyl sulfonate, octyl disulfonate, decyl sulfonate, decyl disulfonate, dodecyl sulfonate, dodecyl disulfonate, and combinations thereof.

16. 10. The method of claim 1, wherein the sulfur-containing surfactant comprises at least one of octyl sulfonate, octyl disulfonate, or decyl sulfonate.

17. 10. The method of claim 1, wherein the sulfur-containing surfactant comprises at least one of sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, lithium lauryl sulfate, sodium laureth sulfate, sodium octyl sulfate, potassium octyl sulfate, ammonium octyl sulfate, lithium octyl sulfate, and combinations thereof.

18. 2. The method of claim 1, wherein the acrylic glycol surfactant comprises polypropylene glycol methacrylate (PPGMA) and the sulfur-containing surfactant comprises octyl sulfonate.

19. The method of claim 1 , wherein the radical initiator comprises a persulfate.

20. 10. The method of claim 1, wherein the at least one fluoromonomer is selected from the group consisting of vinylidene fluoride, hexafluoropropene, tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, vinyl fluoride, and combinations thereof.

21. 10. The method of claim 1, wherein at least 65% by weight of the added fluoromonomer consists of vinylidene fluoride monomer.

22. The method of claim 1 wherein said fluoromonomer comprises vinylidene fluoride monomer.

23. 2. The method of claim 1, wherein the fluoropolymer is a vinylidene fluoride copolymer containing at least one comonomer selected from the group consisting of tetrafluoroethylene, trifluoroethylene, hexafluoropropene, chlorotrifluoroethylene, vinyl fluoride, and combinations thereof.

24. 22. The method of claim 21, wherein the fluoromonomer comprises vinylidene fluoride and hexafluoropropene.

25. 1. A fluoropolymer latex composition comprising: a) at least one sulfur-containing surfactant and at least one acrylic glycol surfactant; and b) at least one fluoropolymer, preferably a polyvinylidene fluoride fluoropolymer containing at least 65% by weight of vinylidene fluoride monomer units; 1. A fluoropolymer latex composition comprising:

26. 26. The fluoropolymer latex composition of claim 25, wherein the acrylic glycol surfactant is selected from the group consisting of polyethylene glycol acrylate (PEGA), polyethylene glycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), polypropylene glycol methacrylate (PPGMA), polypropylene glycol polyethylene glycol acrylate, polypropylene glycol polyethylene glycol methacrylate, and polypropylene glycol dimethacrylate, preferably polypropylene glycol methacrylate (PPGMA).

27. 26. The fluoropolymer latex composition of claim 25, wherein the sulfur-containing surfactant comprises a C6 to C18 alkyl group, preferably a non-fluorinated alkyl sulfonate.

28. 26. The fluoropolymer latex composition of claim 25, wherein the sulfur-containing surfactant comprises a C6 to C18 alkyl group, preferably a non-fluorinated alkyl sulfonate.

29. 26. The fluoropolymer latex composition of claim 25, wherein the acrylic glycol surfactant comprises polypropylene glycol methacrylate (PPGMA) and the sulfur-containing surfactant comprises octyl sulfonate.

30. A fluoropolymer composition made by the method of any of claims 1-24.

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