Abstract: Water-based stains are based on an oil-in-water emulsion having a binder that includes, consists of, or consists essentially of drying oil combined with a non-aqueous polymer dispersion. The compositions can be tinted using traditional water-based pigment dispersions, yet the overall hydrophobicity results in minimal interaction with the polar cellulosic structure of wood.

Abstract: The organophilic clay comprises a smectite-type clay ion exchanged with quaternary ammonium ions, where at least 75 mol-% of said quaternary ammonium ions are bis-(2-hydroxypropyl)-dimethylammonium fatty acid esters and at least 90% of the fatty acid moieties of the bis-(2-hydroxypropyl)-dimethylammonium fatty acid esters have a structure RC(O) with group R being a linear alkyl or alkenyl group containing from 9 to 21 carbon atoms. The organophilic clay is useful for thickening oil based compositions, in particular drilling fluids for drilling oil or gas wells, comprising an oil phase.

Abstract: A flat plate frame is formed, which is flat plate-shaped, which has an opening penetrating its front and rear surfaces and groove terminal patterns formed on its front surface, and which contains a semi-cured thermosetting resin. Then, an insulating substrate is disposed on the rear surface so as to cover the opening of the flat plate frame, external connection terminals are disposed on the terminal patterns, and heating is carried out. As a result, a terminal package to which the insulating substrate and external connection terminals are firmly joined is produced using the flat plate frame. The external connection terminals included in the terminal package are reliably and firmly joined to the terminal package. Therefore, the external connection terminals are not displaced when wires are bonded to the external connection terminals.

Abstract: A process for improving a latex comprising the steps of (a) providing a latex comprising a polymer binder, wherein said polymer binder is formed by polymerization of a monomer mixture comprising one or more ethylenically unsaturated carboxylic acid functional monomer, and (b) passing said latex comprising said polymer binder over a cation exchange resin.

Abstract: A method for preparing a fluoropolymer aqueous dispersion, including: step (A) of preparing a fluoropolymer aqueous dispersion comprising a fluoropolymer having at least one selected from the group consisting of —SO2Y and —COOR (wherein Y is a halogen, and R is a C1 to C4 alkyl) by emulsion polymerization; step (B) of heating the fluoropolymer aqueous dispersion to 50° C. or higher; and step (C) of contacting the fluoropolymer aqueous dispersion with an ion exchange resin for cation exchange after step (B), thereby providing a purified fluoropolymer aqueous dispersion, the fluoropolymer aqueous dispersion being adjusted to pH 7 or lower from the end of the polymerization in step (A) to the end of step (C).

Abstract: A water color paint system which includes water, pigment, and polymeric binder.

Abstract: A process for the purification from ionic impurities of a fluoroionomer liquid composition, comprising: providing a liquid composition comprising at least one fluoroionomer (I-1) in a liquid medium, the liquid composition comprising ionic impurities; contacting the liquid composition with a solid particulate comprising at least one fluoroionomer (I-2) having ion exchange groups, wherein H+ or OH? ions are bound to at least a fraction of such ion exchange groups, and separating the liquid composition from the solid particulate.

Abstract: A silanol-group-containing-polysiloxane solution containing a silanol-group-containing polysiloxane is treated with a cation exchange resin in the presence of an alcohol solvent.

Abstract: Disclosed is a fluorine-containing polymer aqueous dispersion in which a fluorine-containing polymer is dispersed using, as an emulsifier, a polyfluoroalkylphosphonic acid salt represented by the general formula: CnF2n+1(CH2CF2)a(CF2CF2)b(CH2CH2)cP(O)(OM1)(OM2)??[I], wherein M1 is a hydrogen atom, an alkali metal, an ammonium base, or an organic amine base, M2 is an alkali metal, an ammonium base, or an organic amine base, n is an integer of 1 to 6, a is an integer of 1 to 4, b is an integer of 1 to 3, and c is an integer of 1 to 3. This fluorine-containing polymer aqueous dispersion uses a polyfluoroalkylphosphonic acid salt with a low bioaccumulation potential as an emulsifier, and has excellent mechanical stability.

Abstract: The invention provides a compound which is useful in production of a fluoropolymer and easy to be removed from the produced fluoropolymer, a method of producing the compound, and a method of producing a fluoropolymer using the compound. The invention provides a compound which is represented by Rf1—CH2O—CF2—CHF—Rf2—X, wherein Rf1 represents a fluoroalkyl group containing 1 to 5 carbon atoms, Rf2 represents a fluoroalkylene group containing 1 to 3 carbon atoms, X represents —COOM or —SO3M, and M represents one of H, K, Na, and NH4.

Abstract: An aqueous fluoropolymer dispersion comprising fluoropolymer particles having an average particle size of about 10 to about 400 nm. The dispersion has a solids content of at least about 35 to about 70 wt % and comprises about 0.03 wt % to about 10 wt % anionic polyelectrolyte dispersing agent based on the weight of fluoropolymer solids. The dispersion has a Gel Time of at least about 100 seconds.

Abstract: The invention pertain to a process for purifying a fluoropolymer dispersion, said process comprising: (i) providing an aqueous dispersion (D) of at least one fluoropolymer [polymer (F)]comprising at least one fluorinated surfactant [surfactant (FS)], having a solids content (SC) of 15% by weight or more; (ii) adding to said aqueous dispersion (D) at least one non-ionic non-fluorinated surfactant [surfactant (NS)]; (iii) adjusting said solid content (SC) to less than 10% by weight, to obtain a diluted aqueous dispersion (dD); (iv) contacting said diluted aqueous dispersion (dD) with at least one adsorbing material, so as to obtain an aqueous dispersion of polymer (F) having a content of the fluorinated surfactant (FS) of less than 1 ppm based on the total weight of solids. Still an object of the invention is an aqueous fluoropolymer dispersion comprising less than 1 ppm of fluorinated surfactant.

Abstract: The present invention relates to a process for removing volatile organic compounds (VOCs) from a liquid stream using multiple membranes that are permeable to the VOCs but impermeable to the liquid.

Abstract: A method of making a fluoropolymer dispersion by first providing a fluoropolymer dispersion comprising fluoropolymer particles and one or more fluorinated surfactants selected from fluorinated carboxylic acids or salts thereof having the general formula: [Rf—O-L-COO?]iXi+??(I) wherein L represents a linear fully fluorinated alkylene group, Rf represents a linear fully fluorinated aliphatic group or a linear fully fluorinated aliphatic group interrupted with one oxygen atom, Xi+ represents a cation having the valence i and i is 1, 2 or 3; then adding one or more non-fluorinated surfactants selected from anionic and non-ionic surfactants followed by reducing the total amount of the one or more fluorinated surfactants to an amount of not more than 500 ppm, for example not more than 250 ppm based on the total weight of the dispersion while maintaining or increasing the amount of solids in the dispersion.

Abstract: To provide an electrolyte membrane having excellent dimensional stability even upon absorption of water, a high proton conductance and high power generation performance; and a process for producing the electrolyte membrane with a high productivity. An electrolyte membrane for polymer electrolyte fuel cells, which is made mainly of an ion exchange resin and reinforced with a nonwoven fabric made of fiber of a fluororesin wherein at least some of intersecting points of the fiber are fixed, and which has, as the outermost layer on one side or each side, a layer not reinforced, made of an ion exchange resin which may be the same as or different from the above ion exchange resin, wherein the fluororesin is an ethylene/tetrafluoroethylene copolymer having a melting point of at most 240° C., and the above fixing is fixing by fusion of the fiber.

Abstract: A process for reducing fluorosurfactant content of a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion comprising contacting the stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion with an anion exchange resin comprising a polymer and quaternary ammonium functional groups to reduce fluorosurfactant content, the functional groups being resistant to degradation which releases trialkylamines. The anion exchange resin is separated from the dispersion after the fluorosurfactant content has been reduced.

Abstract: A process for reducing fluorosurfactant content of a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion comprising contacting the stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion with an anion exchange resin comprising a polymer and quaternary ammonium functional groups to reduce fluorosurfactant content, the functional groups being resistant to degradation which releases trialkylamines. The anion exchange resin is separated from the dispersion after the fluorosurfactant content has been reduced.

Abstract: A method of making a fluoropolymer dispersion by first providing a fluoropolymer dispersion comprising fluoropolymer particles and one or more fluorinated surfactants selected from fluorinated carboxylic acids or salts thereof having the general formula: [Rf—O-L-COO?]iXi+??(I) wherein L represents a linear fully fluorinated alkylene group, Rf represents a linear partially or fully fluorinated aliphatic group or a linear partially or fully fluorinated aliphatic group interrupted with one oxygen atom, Xi+ represents a cation having the valence i and i is 1, 2 or 3; then adding one or more non-fluorinated surfactants selected from anionic and non-ionic surfactants followed by reducing the total amount of the one or more fluorinated surfactants to an amount of not more than 500 ppm, for example not more than 250 ppm based on the total weight of the dispersion while maintaining or increasing the amount of solids in the dispersion.

Abstract: Waxes prepared from hydrogenated plant oils, such as castor and soybean, are formulated into aqueous ink and paper coating compositions. Ink compositions comprising these waxes and evaluated for their resistance to mar and abrasion achieved rub resistance and slip performance comparable to compositions utilizing conventional wax additives, which are generally derived from petroleum. The waxes in the inventive compositions have a low iodine value (ranging from approximately 2 to approximately 5), and a melting point between approximately 120 degrees to approximately 190 degrees F. (Mettler Drop Point). These naturally derived waxes are used as an alternative to petroleum and synthetically derived waxes in the manufacture of inks and coatings for paper and cellulosic products.

Abstract: A hydrogel having a floatability where from 40% to 90% of a solution and/or suspension to be thickened are thickened starting from the surface of the liquid and the rest of the solution and/or suspension to be thickened is thickened starting from the bottom of the container, a process for preparing the hydrogel and also its use for absorbing blood and/or body fluids, especially in hygiene articles, or for thickening aqueous solutions and/or suspensions, especially for thickening medical wastes.

Abstract: The present invention provides [1] a water dispersion for ink-jet printing containing chain-like particles each containing anionic organic pigment particles and a cationic polymer, wherein the ratio of organic pigment primary particles forming the chain-like particles to all the pigment primary particles contained in the water dispersion is 10% by number or more; [2] a water-based ink for ink-jet printing containing the water dispersion; [3] a method for producing a water dispersion for ink-jet printing as described above in [1]; and [4] a water-based ink for ink-jet printing containing a water dispersion produced through the method. The water dispersion and water-based ink for ink-jet printing of the present invention realize excellent optical density.

Abstract: A method for preparing a polymer product, the method comprising polymerizing conjugated diene monomer, optionally together with vinyl aromatic monomer, within a hydrocarbon solvent by employing a lithium-containing initiator, thereby forming a living polymer cement, where about 0.04 to about 0.

Abstract: The present invention provides a semiconductor device which comprises a substrate, a first semiconductor chip on a substrate, a second semiconductor chip on the first semiconductor chip, and an adhesive sheet between the first and second semiconductor chips. The second semiconductor chip has a mirrored back surface, and the adhesive sheet contains a metal impurity ion trapping agent.

Abstract: Novel optionally hydrogenated nitrile rubbers distinguised by a very low ruthenium content are provided as well as a process for the removal of ruthenium-containing catalyst residues from a solution of optionally hydrogenated nitrile rubber by using specific functionalized ion-exchange resins.

Abstract: The invention provides a method for recovery of a fluorinated anionic surfactant from a basic anion exchange resin having quaternary ammonium groups, the method comprising eluting the anion exchange resin with a composition comprising an ammonium salt and a water miscible organic solvent. The method according to the invention may provide one or more of the following advantages. For example, the method can be designed to allow for recovery of substantially all of the fluorinated surfactant from a basic anion exchange resin having quaternary ammonium groups. Also, the liquid used for recovering the surfactant from the anion exchange resin is a simple liquid that can be readily and cost effectively manufactured. Further the process may be carried out in a convenient and easy manner. Furthermore, the method generally does not require large amounts of the eluting composition.

Abstract: A process for reducing the fluorosurfactant content of an aqueous fluoropolymer dispersion by filling a container with fluoropolymer dispersion, inserting into the container a fabric pouch containing a fluorosurfactant sorbent so that the sorbent contacts the fluorosurfactant-containing aqueous fluoropolymer dispersion in the container and retains the fluorosurfactant to reduce fluorosurfactant content of said fluorosurfactant-containing aqueous fluoropolymer dispersion, and removing the fabric pouch from the container.

Abstract: A method for removing a fluorinated carboxylic acid or salt thereof from an aqueous liquid by contacting the aqueous liquid with adsorbent particles. The fluorinated carboxylic acid or salt thereof is selected from the group consisting of partially fluorinated carboxylic acids or salts thereof and fully fluorinated carboxylic acids or salts thereof.

Abstract: A process for reducing the fluorosurfactant content of an aqueous fluoropolymer dispersion by filling a shipping container with fluoropolymer dispersion and contacting the dispersion with a fluorosurfactant sorbent in the shipping container.

Abstract: A process for reducing fluorosurfactant content of a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion comprising contacting the stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion with an anion exchange resin comprising a polymer and quaternary ammonium functional groups to reduce fluorosurfactant content, the functional groups being resistant to degradation which releases trialkylamines. The anion exchange resin is separated from the dispersion after the fluorosurfactant content has been reduced.

Abstract: A process for reducing fluorosurfactant content of a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion comprising contacting the stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion with an anion exchange resin comprising a polymer and quaternary ammonium functional groups to reduce fluorosurfactant content, the functional groups being resistant to degradation which releases trialkylamines. The anion exchange resin is separated from the dispersion after the fluorosurfactant content has been reduced.

Abstract: A process for preparing a fluoropolymer dispersion that is substantially anionic fluorinated surfactant free includes adding to a fluoropolymer dispersion a nonionic surfactant having a cloud point (CP) between 40 and 80° C. in a concentration of 1.5% to 50% by weight of the fluoropolymer, heating the dispersion up to a temperature Tc in a range of CP±10°C., decanting the dispersion in a reactor at Tc until obtaining a lower aqueous phase containing a concentrated fluoropolymer dispersion and an upper aqueous phase substantially not containing the fluoropolymer dispersion, washing the decanted dispersion with a solution of water and nonionic surfactant having a concentration of the nonionic surfactant of 0.5% to 50% by weight of the fluoropolymer, removing the upper aqueous phase from the upper part of the reactor, and discharge and recovery of the fluoropolymer dispersion.

Abstract: A process to substantially remove fluorinated anionic surfactants from fluoropolymer dispersions comprising the following steps: a) addition to the fluoropolymer dispersion of one or more non fluorinated surfactants; b) contact of the dispersion with an anionic exchanger; c) separation of the dispersion from the anionic exchanger and recovery of the dispersion substantially fluorinated anionic surfactant free.

Abstract: A process for reducing the fluorosurfactant content of a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion by passing dispersion through a first fixed bed of anion exchange resin to reduce fluorosurfactant content. The first fixed bed has a working zone which moves though the column as the ion exchange resin is saturated. The process includes monitoring a property of the dispersion as the dispersion exits the fixed bed to determine break though of the working zone indicating saturation of the fixed bed. The property being monitored is selected from the group consisting of pH and conductivity.

Abstract: A method of making a fluoropolymer dispersion by first providing a fluoropolymer dispersion comprising fluoropolymer particles and one or more fluorinated surfactants selected from fluorinated carboxylic acids or salts thereof having the general formula: [Rf—O-L-COO?]iXi+??(I) wherein L represents a linear partially or fully fluorinated alkylene group or an aliphatic hydrocarbon group, Rf represents a linear partially or fully fluorinated aliphatic group or a linear partially or fully fluorinated aliphatic group interrupted with one or more oxygen atoms, Xi+ represents a cation having the valence i and i is 1, 2 or 3; then adding one or more non-fluorinated surfactants selected from anionic and non-ionic surfactants followed by reducing the total amount of the one or more fluorinated surfactants to an amount of not more than 500 ppm, for example not more than 250 ppm based on the total weight of the dispersion while maintaining or increasing the amount of solids in the dispersion.

Abstract: A process for reducing fluorosurfactant content of a fluorosurfactant-containing aqueous fluoropolymer dispersion stabilized with nonionic surfactant. The process includes reducing the fluorosurfactant content of the stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion to a predetermined level to provide a reduced surfactant dispersion, adding non-fluorinated anionic surfactant to the reduced fluorosurfactant dispersion, and concentrating the reduced fluorosurfactant dispersion. The non-fluorinated anionic surfactant is added in stages wherein a first portion is added to the dispersion prior to concentrating and a second portion of the non-fluorinated anionic surfactant is added to the dispersion after concentrating.

Abstract: A process for reducing fluorosurfactant content of a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion. The process includes providing a fixed bed of anion exchange resin having anion exchange groups with counter ions. The anion exchange resin is treated to replace at least some the counter ions with counter ions of non-fluorinated anionic surfactant. The stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion is passed through the treated fixed bed of anion exchange resin.

Abstract: A process for reducing fluorosurfactant content of a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion comprising contacting the stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion with an anion exchange resin comprising a polymer and quaternary ammonium functional groups to reduce fluorosurfactant content, the functional groups being resistant to degradation which releases trialkylamines. The anion exchange resin is separated from the dispersion after the fluorosurfactant content has been reduced.

Abstract: A process for reducing fluorosurfactant content of a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion comprising passing said stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion through a fixed bed of ion exchange resin beads comprising a polymer and functional groups to reduce fluorosurfactant content, the ion exchange resin beads being monodisperse.

Abstract: A process for reducing fluorosurfactant content of a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion containing ferric ions by contacting the fluoropolymer dispersion with strong base anion exchange resin to reduce fluorosurfactant content to a predetermined level, the anion exchange resin being in the hydroxide form, separating the dispersion from the anion exchange resin, and adding an effective amount of chelating agent having an equilibrium constant when complexed with iron of at least 1018 prior to the contacting with the ion exchange resin for complexing ferric ions to prevent scum formation.

Abstract: A stabilized aqueous fluoropolymer dispersion comprising: about 30 to about 70 weight % non-melt-processible fluoropolymer particles having an SSG of less than about 2.225, said fluoropolymer particles comprising a core of high molecular weight polytetrafluoroethylene and a shell of lower molecular weight polytetrafluoroethylene or modified polytetrafluoroethylene; and about 2 to about 11 weight % of aliphatic alcohol ethoxylate nonionic surfactant based on the weight of said fluoropolymer, wherein said dispersion is essentially free of surfactants containing aromatic groups and contains less than 300 ppm of fluorosurfactant based on the weight of said dispersion.

Abstract: An aqueous dispersion of polytetrafluoroethylene (PTFE) comprising from 55 to 70 mass % of PTFE fine particles having an average particle diameter of from 0.1 to 0.5 ?m, from 0.0001 to 0.02 mass %, based on PTFE, of a specific C8 fluorine-containing carboxylic acid salt (APFO) such as ammonium perfluorooctanoate, from 1 to 20 mass %, based on PTFE, of a specific nonionic surfactant and from 0.01 to 0.3 mass %, based on PTFE, of a specific C5-7 fluorine-containing carboxylic acid salt such as ammonium perfluorohexanoate. The aqueous dispersion of PTFE has excellent properties which can form crack-resistant coatings which do not undergo coloration during baking or form problematic ionic impurities by improving the friction stability of aqueous PTFE dispersions even at APFO concentrations without viscosity increase.

Abstract: To obtain a high concentration aqueous PTFE dispersion containing PTFE at a concentration of from 60 to 75 mass % by dissolving from 0.001 to 0.1 mass %, based on the mass of PTFE, of a specific carboxylic acid salt such as ammonium laurate in a low concentration aqueous dispersion of polytetrafluoroethylene (PTFE) comprising from 1 to 40 mass % of PTFE fine particles, from 0.0001 to 0.02 mass %, based on the mass of PTFE, of a specific fluorine-containing carboxylic acid type emulsifier (for example, ammonium perfluorooctanoate), and from 1 to 20 mass %, based on the mass of PTFE, of a specific nonionic surfactant, and then concentrating the low concentration aqueous dispersion of PTFE.

Abstract: The present invention provides a method of purifying an aqueous fluoropolymer emulsion by which fluorine-containing surfactants can be removed without lowering the dispersibility of the aqueous fluoropolymer dispersions. The present invention provides a method of purifying an aqueous fluoropolymer emulsion comprising; purifying an aqueous fluoropolymer emulsion by a specific technique of concentration wherein the aqueous fluoropolymer emulsion comprises a fluoropolymer and a fluorine-containing surfactant, said specific technique of concentration comprises concentration by phase separation, electric concentration and/or ion exchange concentration, and said concentration by phase separation, electric concentration and/or ion exchange concentration is carried out for removing the fluorine-containing surfactant.

Abstract: A process for producing a resin-coated pigment capable of providing an ink and a paint being superior in dispersion stability of a pigment and having rapid drying property, high gloss and density without containing those such as an organic solvent and a salt that cause the lowering of performance of pigment dispersion, characterized in that a pigment is dispersed in an aqueous solution in which an anionic group-containing resin is dissolved in the presence of a basic compound and then, the anionic group-containing resin is precipitated on the surface of the pigment by removing the basic compound in the aqueous solution, using an ion exchange means.

Abstract: A method for producing an organic solvent dispersion of an intrinsically conductive polymer which comprises a step of deionizing an aqueous colloidal dispersion of an intrinsically conductive polymer by the passing of liquid, thereby clearing the intrinsically conductive polymer of cations adhering thereto, and a subsequent step of substituting water in the aqueous colloidal dispersion by an organic solvent. This method permits easy production of an organic solvent dispersion of an intrinsically conductive polymer which can be applied to various uses as electrode materials, antistatic agents, UV light absorbers, heat ray absorbers, electromagnetic wave absorbers, sensors, electrolyte for electrolytic capacitors, and electrodes for secondary batteries.

Abstract: There is provided a method for producing colorants which can exhibit excellent color development even in a small amount and are low in thixotropy. The constituent feature of the present invention comprises: enhancing the molecular extinction coefficient of the coloring matter substance by ion exchanging method, to afford a room for increasing B (resin) of P/B; then a composition is designed and employed to enhance the effect increasing the polar group concentration which is a role of resin and the quality of the effect; it thus becomes possible to achieve the limit value of the molecular extinction coefficient as much as possible and to eliminate the factors adversely affecting the present process.

Abstract: Fluorine-containing emulsifiers can be removed from fluoropolymer dispersions by adding to the dispersion a non ionic emulsifier, removing the fluorine-containing emulsifier by contact with an anion exchanger and separating the dispersion from the anion exchanger. The resulting dispersions can be concentrated and used for coating applications.

Abstract: Anionic species are removed from aqueous dispersions of ionic fluoropolymers using anion exchange resins. In some embodiments, cationic species are also removed using cation exchange resins.

Abstract: A process for preparing fluoropolymer dispersions, substantially free from anionic fluorinated surfactants, and with a coagulum amount <0.1% by weight, comprising: a) step a1) addition of: a non ionic surfactant having cloud point (CP) between 40° and 80° C., in an amount from 1.5% to 50% by weight on the dispersion fluoropolymer; and optionally an electrolyte to bring the specific conductivity of the dispersion to values in the range 130-8,000 ?S/cm; optionally a buffer agent to have a pH between 2 and 12 to a fluoropolymer dispersion obtainable by an emulsion polymerization process; step a2): heating of the dispersion obtained in a1) up to a temperature Tc in the range CP±10° C.; decantation without stirring, at the temperature Tc, until obtaining the dispersion separation in two aqueous phases, of which the lower one containing the fluoropolymer is discharged; b) step b1): the dispersion obtained in step a2) is optionally additioned of an electrolyte and of a non ionic surfactant as in a1).

Abstract: A process for producing an aqueous dispersion of purified polytetrafluoroethylene (PTFE), comprising passing a crude aqueous dispersion of PTFE comprising from 10 to 50 mass % of PTFE fine particles having an average particle diameter of from 0.1 to 0.5 ?m, from 0.05 to 1.0 mass %, based on PTFE, of a fluorine-containing carboxylic acid salt (APFO) and from 2 to 20 mass %, based on PTFE, of a nonionic surfactant through a column packed with a weak basic AER upward at a linear velocity of 0.1 to 2 mm/sec with a contact time of 0.2 to 4 hours to reduce the APFO concentration. The process can increase the absorption of APFO by the anion exchange resin, prevents agglomeration of PTFE during passage and makes it easy to elute the absorbed APFO.