JP2009029722A - Sulfonate compound, method for producing sulfonate compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sulfonate compound suitably used as a surfactant in the emulsion polymerization of a fluorine-containing polymer, and a method for producing the sulfonate compound, and to provide a surfactant containing the sulfonate compound, a method for producing a fluorine-containing polymer, an aqueous dispersion, a method for producing an aqueous dispersion, a fine powder, and a method for producing a recycled sulfonate compound. <P>SOLUTION: The sulfonate compound is represented by general formula (I): Rf<SP>1</SP>C(COOM)Rf<SP>2</SP>SO<SB>3</SB>CF<SB>2</SB>CH<SB>3</SB>(I) (wherein, M is H, NH<SB>4</SB>, Li, Na or K; Rf<SP>1</SP>and Rf<SP>2</SP>are each a 1-3C fluoroalkyl group or fluoroalkoxy group). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a sulfonic acid ester compound, a method for producing a sulfonic acid ester compound, a surfactant, a method for producing a fluoropolymer, an aqueous dispersion, a method for producing an aqueous dispersion, fine powder, and a regenerated sulfonic acid ester compound It relates to the manufacturing method.

As a method for producing a fluoropolymer, tetrafluoroethylene [TFE] is used by using, as a surfactant, a fluorine-substituted carboxylic acid having 7 to 10 carbon atoms having a linear or partially branched chain in an aqueous medium. There are many literatures describing a method for polymerizing (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

In recent years, a method of using a carboxylic acid having a fluorinated polyoxyalkylene group as a surfactant has also been disclosed as a method for producing a fluoropolymer (see Patent Document 4).

However, these surfactants are very stable thermally and chemically and are useful in that they can suppress side reactions such as chain transfer during polymerization, but they are removed from the resin obtained by polymerization. In order to do so, there has been a problem that conditions such as cleaning and heating are limited.

In view of the above problems, Patent Document 5 discloses that in an aqueous medium using a surfactant that has a small residual amount in a fluoropolymer particle after processing such as aggregation without impairing stability during polymerization. Method for producing a fluoropolymer, and fluoropolymer using a surfactant that is excellent in dispersion stability of the fluoropolymer and has a small residual amount in the fluoropolymer particles after processing such as agglomeration Aqueous dispersions are being considered.

However, 2-acyloxycarboxylic acid described in Patent Document 5 has a complicated synthesis route and a low yield. In addition, when the half ester compound described in Patent Document 5 is used as an emulsifier for emulsion polymerization of a fluorinated monomer, hydrogen atoms present in the molecule cause a chain transfer reaction, and the polymerization rate decreases. There was also a problem that a high molecular weight polymer could not be obtained.

JP 61-207413 A JP 61-228008 A Japanese Patent Laid-Open No. 10-212261 US Pat. No. 6,429,258 JP 2005-48178 A

In view of the above situation, the present invention provides a sulfonic acid ester compound that can be suitably used as a surfactant in emulsion polymerization of a fluoropolymer, and a method for producing the sulfonic acid ester compound. Provided are a surfactant containing a compound, a method for producing a fluoropolymer, an aqueous dispersion, a method for producing an aqueous dispersion, a fine powder, and a method for producing a regenerated sulfonic acid ester compound.

The present invention relates to the following general formula (I)
Rf ¹ C (COOM) Rf ² SO ₃ CF ₂ CH ₃ (I)
(Wherein M represents H, NH ₄ , Li, Na or K, and Rf ¹ and Rf ² represent a fluoroalkyl group or a fluoroalkoxy group having 1 to 3 carbon atoms). It is an acid ester compound.

The present invention also provides the following general formula (II)
Rf ¹ C (COOM) Rf ² SO ₃ H (II)
(Wherein M represents H, NH ₄ , Li, Na or K, and Rf ¹ and Rf ² represent a fluoroalkyl group or a fluoroalkoxy group having 1 to 3 carbon atoms). And a method of producing a sulfonic acid ester compound as described above, comprising a step of reacting vinylidene fluoride under acidic conditions.

The present invention is also a surfactant comprising the sulfonic acid ester compound described above.

The present invention also includes a process for polymerizing a fluorine-containing monomer in an aqueous medium, and the aqueous medium contains the sulfonic acid ester compound described above.

The present invention is also an aqueous dispersion containing the sulfonic acid ester compound described above and a fluoropolymer, wherein the fluoropolymer has an average particle size of 50 to 500 nm. It is also a dispersion.

The present invention also provides a step (I) in which the aqueous dispersion described above is contacted with an anion exchange resin in the presence of a nonionic surfactant, and the aqueous dispersion obtained in step (I) It is also a method for producing a purified aqueous dispersion characterized by comprising a step (II) of concentrating so that the solid content concentration in the body is 30 to 70% by mass with respect to 100% by mass of the aqueous dispersion.

The present invention is also a fine powder produced by coagulating the aqueous dispersion described above.

The present invention also includes at least one component selected from the wastewater generated by the coagulation, the wastewater generated by washing, and the off-gas generated in the drying step, from the following general formula (I):
Rf ¹ C (COOM) Rf ² SO ₃ CF ₂ CH ₃ (I)
(Wherein M represents H, NH ₄ , Li, Na or K, and Rf ¹ and Rf ² represent a fluoroalkyl group or a fluoroalkoxy group having 1 to 3 carbon atoms). It is also a method for producing a regenerated sulfonic acid ester compound, comprising a step of recovering and purifying the acid ester compound.
Hereinafter, the present invention will be described in detail.

The sulfonic acid ester compound of the present invention exhibits excellent performance as a surfactant, and particularly when used for the polymerization of a fluoropolymer, a high molecular weight fluoropolymer can be obtained. Since the sulfonic acid ester compound has an ester bond in the hydrophobic chain, it has an excellent performance of being excellent in degradability.

The sulfonic acid ester compound of the present invention has the following general formula (I)
Rf ¹ C (COOM) Rf ² SO ₃ CF ₂ CH ₃ (I)
It is represented by

In the above general formula (I), M represents H, NH ₄ , Li, Na or K. NH ₄ is preferable in that it can be easily removed from the produced fluoropolymer by heat treatment, and Li, Na, or K is preferable in terms of emulsification and dispersion power.

Rf ¹ and Rf ² are a fluoroalkyl group or a fluoroalkoxy group having 1 to 3 carbon atoms. Rf ¹ and Rf ² are more preferably composed of C, F, and O.

The sulfonic acid ester compound has the following general formula (II)
Rf ¹ C (COOM) Rf ² SO ₃ H (II)
(Wherein M represents H, NH ₄ , Li, Na or K, and Rf ¹ and Rf ² represent a fluoroalkyl group or a fluoroalkoxy group having 1 to 3 carbon atoms). And vinylidene fluoride is preferably produced by reacting under acidic conditions. Such a manufacturing method is also one aspect of the present invention.

It does not specifically limit as a method of performing the said reaction, A well-known method can be used. Examples thereof include a method in which a compound represented by the above formula (II) and vinylidene fluoride are mixed in the vicinity of a stoichiometric ratio and heated to 60 to 150 ° C. for reaction. In this case, an organic solvent that is amphiphilic and does not interfere with the reactivity can be used.

The production method is a sulfone represented by Rf ¹ C (COOM) Rf ² SO ₃ CF ₂ CH ₃ (wherein M, Rf ¹ and Rf ² are the same as defined above) obtained by the above reaction. A step of neutralizing the acid ester compound with ammonia, LiOH, NaOH, or KOH may be included. In the neutralization reaction, a neutralizing agent such as ammonia, LiOH, NaOH, or KOH is used as a 0.1 to 20% aqueous solution, preferably as a 1 to 5% aqueous solution, in a temperature range of 5 to 30 ° C. It is preferable that the pH is adjusted so that the pH does not exceed 8, preferably does not exceed 7, more preferably does not exceed 6, while dropping gradually under stirring.

The neutralized salt can be used in the form of an aqueous solution having a concentration of 0.1 to 30% depending on the purpose, or it can be used as a powder or a wax-like solid through a process such as freeze-drying. it can.

The sulfonic acid ester compound of the present invention can be suitably used as a surfactant. A surfactant comprising the sulfonate compound is also one aspect of the present invention. The surfactant of the present invention can be used as a surfactant as long as it contains at least one sulfonate compound represented by the above general formula (I). It may contain more than seeds.

Since the surfactant of the present invention is composed of the sulfonic acid ester, it can exhibit an appropriate surface activity in various applications. The surfactant of the present invention can be used for applications such as production of a fluoropolymer.

The present invention also includes a process for polymerizing a fluorinated monomer in an aqueous medium, wherein the aqueous medium contains the sulfonic acid ester compound.

In the method for producing a fluoropolymer of the present invention, the fluoropolymer can be produced efficiently if at least one of the sulfonic acid ester compounds is used as a surfactant. Further, in the method for producing a fluoropolymer of the present invention, two or more of the above compounds may be used simultaneously as a surfactant, or it may remain in a molded body comprising a volatile polymer or a fluoropolymer. As long as it is acceptable, other compounds having surface activity than the sulfonic acid ester compounds may be used at the same time. As the other compounds having surface activity, those described above can be used.
In addition, in the method for producing a fluoropolymer according to the present invention, in addition to the sulfonic acid ester compound and other compounds having surface active ability used as desired, additives can be used to stabilize each compound. . What was mentioned above can be used as said additive.

In the method for producing a fluoropolymer of the present invention, the polymerization is carried out by charging the polymerization reactor with an aqueous medium, the above compound, a monomer and other additives as required, stirring the contents of the reactor, and reacting. The vessel is maintained at a predetermined polymerization temperature, and then a predetermined amount of a polymerization initiator is added to start the polymerization reaction. After the polymerization reaction is started, a monomer, a polymerization initiator, a chain transfer agent, the sulfonic acid ester compound and the like may be additionally added depending on the purpose.
In the above polymerization, the polymerization temperature is usually 5 to 120 ° C., and the polymerization pressure is 0.05 to 10 MPaG. The polymerization temperature and polymerization pressure are appropriately determined depending on the type of monomer used, the molecular weight of the target fluoropolymer, and the reaction rate.

The sulfonic acid ester compound is preferably added in a total amount of 0.0001 to 2% by mass with respect to 100% by mass of the aqueous medium. A more preferable lower limit is 0.001% by mass, and a more preferable upper limit is 1% by mass. If the amount is less than 0.0001% by mass, the dispersion force may be insufficient. If the amount exceeds 2% by mass, an effect commensurate with the amount added cannot be obtained, and on the contrary, the polymerization rate may decrease or the reaction may stop. There is. The amount of the compound added is appropriately determined depending on the type of monomer used, the molecular weight of the target fluoropolymer, and the like.

The polymerization initiator is not particularly limited as long as it can generate radicals in the polymerization temperature range, and known oil-soluble and / or water-soluble polymerization initiators can be used. Furthermore, the polymerization can be started as a redox in combination with a reducing agent or the like. The concentration of the polymerization initiator is appropriately determined depending on the type of monomer, the molecular weight of the target fluoropolymer, and the reaction rate.

The aqueous medium is a reaction medium for performing polymerization and means a liquid containing water. The aqueous medium is not particularly limited as long as it contains water, and water and, for example, a fluorine-free organic solvent such as alcohol, ether, and ketone, and / or a fluorine-containing organic solvent having a boiling point of 40 ° C. or lower. May be included. For example, when carrying out suspension polymerization, a fluorine-containing organic solvent such as C318 can be used.
In the above polymerization, a known chain transfer agent and radical scavenger may be further added depending on the purpose to adjust the polymerization rate and molecular weight.

The fluorine-containing polymer is obtained by polymerizing a fluorine-containing monomer, and may be obtained by copolymerizing a fluorine-free monomer depending on the purpose.

The fluorine-containing monomer may be a fluoroolefin, preferably a fluoroolefin having 2 to 10 carbon atoms; a cyclic fluorinated monomer; a formula CY ₂ = CYOR or CY ₂ = CYOR ² OR ³ (Y is , H or F, R and R ³ are alkyl groups having 1 to 8 carbon atoms in which part or all of the hydrogen atoms are substituted with fluorine atoms, and R ² is part or all of the hydrogen atoms. And a fluorinated alkyl vinyl ether represented by a C 1-8 alkylene group substituted with a fluorine atom.

The fluoroolefin preferably has 2 to 6 carbon atoms. Examples of the fluoroolefin having 2 to 6 carbon atoms include tetrafluoroethylene [TFE], hexafluoropropylene [HFP], chlorotrifluoroethylene [CTFE], vinyl fluoride, vinylidene fluoride [VDF], Fluoroethylene, hexafluoroisobutylene, perfluorobutylethylene and the like can be mentioned. The cyclic fluorinated monomer is preferably perfluoro-2,2-dimethyl-1,3-dioxole [PDD], perfluoro-2-methylene-4-methyl-1,3-dioxolane [ PMD] and the like.
In the fluorinated alkyl vinyl ether, R and R ³ are preferably those having 1 to 4 carbon atoms, more preferably all hydrogen atoms are substituted with fluorine, and R ² Preferably has 2 to 4 carbon atoms, more preferably all of the hydrogen atoms are replaced by fluorine atoms.

Examples of the fluorine-free monomer include hydrocarbon monomers having reactivity with the fluorine-containing monomer. Examples of the hydrocarbon monomer include alkenes such as ethylene, propylene, butylene, and isobutylene; alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, and cyclohexyl vinyl ether; vinyl acetate, vinyl propionate, n -Vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl versatate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, benzoic acid Vinyl, vinyl para-t-butylbenzoate, vinyl cyclohexanecarboxylate, vinyl monochloroacetate, vinyl adipate, vinyl acrylate, vinyl methacrylate, croto Vinyl esters such as vinyl acid vinyl, vinyl sorbate, vinyl cinnamate, vinyl undecylenate, vinyl hydroxyacetate, vinyl hydroxypropioate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate and vinyl hydroxycyclohexanecarboxylate Alkyl allyl ethers such as ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether, and cyclohexyl allyl ether; alkyl allyl ethers such as ethyl allyl ester, propyl allyl ester, butyl allyl ester, isobutyl allyl ester, and cyclohexyl allyl ester Examples include esters.

The fluorine-free monomer may also be a functional group-containing hydrocarbon monomer. Examples of the functional group-containing hydrocarbon monomers include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, hydroxycyclohexyl vinyl ether; itaconic acid, succinic acid, succinic anhydride, fumaric acid Non-fluorine-containing monomers having a carboxyl group such as acid, fumaric anhydride, crotonic acid, maleic acid, maleic anhydride, perfluorobutenoic acid; non-fluorine-containing monomers having a glycidyl group such as glycidyl vinyl ether and glycidyl allyl ether; aminoalkyl Non-fluorine-containing monomers having amino groups such as vinyl ether and aminoalkyl allyl ether; (meth) acrylamide, methylol acrylic Fluorine-containing monomers having an amide group of the amide.

As the fluoropolymer suitably produced by the method for producing a fluoropolymer of the present invention, a TFE heavy monomer in which the monomer having the highest molar fraction of the polymer (hereinafter referred to as “most monomer”) is TFE. Examples thereof include a VDF polymer in which the most monomer is VDF, and a CTFE polymer in which the most monomer is CTFE.

The TFE polymer may preferably be a TFE homopolymer, or (1) TFE, (2) one or two or more fluorine-containing monomers other than TFE having 2 to 8 carbon atoms. In particular, it may be a copolymer comprising HFP or CTFE and (3) other monomers. (3) Other monomers include, for example, fluoro (alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms; fluorodioxole; perfluoroalkylethylene; And hydroperfluoroolefin.
The TFE polymer may also be a copolymer of TFE and one or more fluorine-free monomers. Examples of the fluorine-free monomer include alkenes such as ethylene and propylene; vinyl esters; vinyl ethers. The TFE polymer is also a copolymer of TFE, one or more fluorine-containing monomers having 2 to 8 carbon atoms, and one or more fluorine-free monomers. Also good.

The VDF polymer may preferably be a VDF homopolymer [PVDF], or (1) VDF, (2) other than one or two or more VDFs having 2 to 8 carbon atoms. A copolymer comprising fluoroolefin, particularly TFE, HFP or CTFE, and (3) perfluoro (alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms, etc. Also good.

The CTFE polymer may suitably be a CTFE homopolymer, (1) CTFE, (2) one or more fluoroolefins other than CTFE having 2 to 8 carbon atoms, In particular, it may be a copolymer comprising TFE or HFP and (3) perfluoro (alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms.
The CTFE polymer may also be a copolymer of CTFE and one or more fluorine-free monomers. Examples of the fluorine-free monomers include alkenes such as ethylene and propylene; vinyl Esters; vinyl ethers and the like.

The fluoropolymer produced by the method for producing a fluoropolymer of the present invention can be glassy, plastic or elastomeric. These are amorphous or partially crystalline and can be subjected to compression firing, melt processing or non-melt processing.
In the method for producing a fluoropolymer of the present invention, for example, (I) a polytetrafluoroethylene polymer [PTFE polymer] is used as a non-melt processable resin, and (II) an ethylene / TFE copolymer is used as a melt processable resin. Polymer [ETFE], TFE / HFP copolymer [FEP] and TFE / perfluoro (alkyl vinyl ether) copolymer [PFA, MFA, etc.] are used as (III) elastomeric copolymer as TFE / propylene copolymer Polymer, TFE / propylene copolymer / third monomer copolymer (the third monomer is VDF, HFP, CTFE, perfluoro (alkyl vinyl ether), etc.), TFE and perfluoro (alkyl vinyl ether) Copolymer; HFP / ethylene copolymer, HFP / ethylene / TFE copolymer; PVDF; VDF Thermoplastic elastomers such as HFP copolymers, HFP / ethylene copolymers, VDF / TFE / HFP copolymers, and fluorine-containing segmented polymers described in JP-B 61-49327 can be preferably produced. .
The perfluoro (alkyl vinyl ether) has the formula:
Rf ³ (OCFQCF ₂ ) _k1 (OCR ⁴ Q ² CF ₂ CF ₂ ) _{k 2} (OCF ₂ ) _{k 3} OCF = CF ₂
(In the formula, Rf ³ represents a perfluoroalkyl group having 1 to 6 carbon atoms. K1, k2 and k3 are the same or different integers of 0 to 5. Q, Q ² and R ⁴ are Are the same or different and are F or CF _3. )

The above-mentioned (I) non-melt processable resin, (II) melt processable resin and (III) elastomeric polymer which are preferably produced by the method for producing a fluoropolymer of the present invention are produced in the following manner. It is preferable.

(I) Non-melt processable resin In the method for producing a fluoropolymer of the present invention, the polymerization of the PTFE polymer is usually carried out at a polymerization temperature of 10 to 100C and a polymerization pressure of 0.05 to 5 MPaG. Is called.
In the polymerization, pure water and the sulfonic acid ester compound are charged into a pressure-resistant reaction vessel equipped with a stirrer, and after deoxygenation, TFE is charged to a predetermined temperature, and a polymerization initiator is added to start the reaction. Since the pressure decreases as the reaction proceeds, additional TFE is added continuously or intermittently so as to maintain the initial pressure. When a predetermined amount of TFE is supplied, the supply is stopped, the TFE in the reaction vessel is purged, the temperature is returned to room temperature, and the reaction is terminated.

In the production of the PTFE polymer, various known modifying monomers can be used in combination. In the present specification, the polytetrafluoroethylene polymer [PTFE polymer] is not only a TFE homopolymer but also a copolymer of TFE and a modified monomer, which is non-melt processable (hereinafter referred to as “ This is a concept including “modified PTFE”.
Examples of the modifying monomer include perhaloolefins such as HFP and CTFE; fluoro (alkyl vinyl ether) having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms; and a ring such as fluorodioxole. Fluorinated monomers of the formula; perhaloalkylethylenes; ω-hydroperhaloolefins and the like. Depending on the purpose and the supply of TFE, the supply of the modified monomer can be performed by initial batch addition or by continuous or intermittent addition.
The modified monomer content in the modified PTFE is usually in the range of 0.001 to 2 mol%.

In the production of the PTFE polymer, the sulfonic acid ester compound described above can be used in the range of use in the production method of the fluoropolymer of the present invention described above, but is usually 0.0001 to 2% by mass of the aqueous medium. Add the amount of. The concentration of the sulfonic acid ester compound is not particularly limited as long as it is in the above range, but it is usually added at a critical micelle concentration (CMC) or less at the start of polymerization. When the addition amount is large, acicular particles having a large aspect ratio are formed, and the aqueous dispersion becomes a gel and the stability is impaired.

In the production of the PTFE polymer, as a polymerization initiator, a persulfate (for example, ammonium persulfate) or an organic peroxide such as disuccinic acid peroxide or diglutaric acid peroxide is used alone or in the form of a mixture thereof. can do. Further, it may be used in combination with a reducing agent such as sodium sulfite to make a redox system. Furthermore, a radical scavenger such as hydroquinone or catechol can be added during polymerization, or a peroxide decomposing agent such as ammonium sulfite can be added to adjust the radical concentration in the system.

In the production of the PTFE polymer, known chain transfer agents can be used, for example, saturated hydrocarbons such as methane, ethane, propane and butane, and halogenated hydrocarbons such as chloromethane, dichloromethane and difluoroethane. In addition, alcohols such as methanol and ethanol, hydrogen and the like can be mentioned, but those in a gaseous state at normal temperature and pressure are preferable.
The amount of the chain transfer agent used is usually 1 to 1000 ppm, preferably 1 to 500 ppm, based on the total amount of TFE supplied.

In the production of the PTFE polymer, a saturated hydrocarbon having 12 or more carbon atoms, which is substantially inert to the reaction and becomes liquid under the reaction conditions, is further used as a dispersion stabilizer in the reaction system. It can also be used at 2 to 10 parts by mass with respect to parts by mass. Moreover, you may add ammonium carbonate, an ammonium phosphate, etc. as a buffering agent for adjusting pH during reaction.

When the polymerization of the PTFE polymer is completed, an aqueous dispersion having a solid content concentration of 30 to 70% by mass and an average particle size of 50 to 500 nm can be obtained. Such an aqueous dispersion containing the sulfonic acid ester compound and the fluorine-containing polymer and having an average particle diameter of 50 to 500 nm is also one aspect of the present invention. Moreover, the aqueous dispersion which has the particle | grains which consist of a PTFE polymer of a microparticle diameter of 0.3 micrometer or less can be obtained by using the said sulfonate compound. The PTFE polymer at the end of the polymerization has a number average molecular weight of 1,000 to 10,000,000.

The aqueous dispersion of the PTFE polymer can be used for various applications as a fine powder after coagulation, washing and drying. Such a fine powder produced by coagulating the aqueous dispersion is also one aspect of the present invention. When coagulating the aqueous dispersion of the PTFE polymer, the aqueous dispersion obtained by emulsion polymerization such as a polymer latex is usually diluted with water to a polymer concentration of 10 to 20% by mass. In some cases, the pH is adjusted to neutral or alkaline and then stirred more vigorously than stirring during the reaction in a vessel equipped with a stirrer. The coagulation may be performed while adding a water-soluble organic compound such as methanol or acetone, an inorganic salt such as potassium nitrate or ammonium carbonate, or an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid as a coagulant. The coagulation may be continuously performed using an in-line mixer or the like.

Before or during the coagulation, pigments for coloring and various fillers for improving the mechanical properties are added, so that the pigmented or filler-containing PTFE in which the pigment and the filler are uniformly mixed is added. A polymer fine powder can be obtained.

Drying of the wet powder obtained by coagulating the aqueous dispersion of the PTFE polymer is usually in a state where the wet powder does not flow so much, preferably in a stationary state, while maintaining a vacuum, high frequency, hot air, etc. By means. Friction between powders, particularly at high temperatures, generally has an undesirable effect on fine powder PTFE polymers. This is because particles of this type of PTFE polymer have the property of easily fibrillating even with a small shearing force and losing the original stable particle structure.
The drying is performed at a drying temperature of 10 to 250 ° C, preferably 100 to 200 ° C.

The obtained PTFE polymer fine powder is preferable for molding, and suitable applications include hydraulic and fuel tubes such as aircraft and automobiles, flexible hoses such as chemicals and steam, and wire coating applications. Can be mentioned.

The aqueous dispersion of the PTFE polymer obtained by the above polymerization is also stabilized by adding a nonionic surfactant, and further concentrated. As a composition to which an organic or inorganic filler is added depending on the purpose. It is also preferable to use it for various purposes. The above composition has a non-adhesiveness and a low coefficient of friction when coated on a base material made of metal or ceramics, and has excellent gloss, smoothness, abrasion resistance, weather resistance and heat resistance. It is suitable for coating rolls, cooking utensils, etc., impregnating glass cloth, and the like.

The method for producing a sulfonic acid ester compound of the present invention comprises the following general formula (I) from the coagulation or waste water generated by washing and / or off-gas generated in the drying step.
Rf ¹ C (COOM) Rf ² SO ₃ CF ₂ CH ₃ (I)
(Wherein M represents H, NH ₄ , Li, Na or K, and Rf ¹ and Rf ² represent a fluoroalkyl group or a fluoroalkoxy group having 1 to 3 carbon atoms). It may include a step of recovering and purifying the acid ester compound. A method for producing such a regenerated sulfonic acid ester compound is also one aspect of the present invention. Although it does not specifically limit as a method of performing the said collection | recovery and refinement | purification, It can carry out by a well-known method.

(II) Melt processable resin (1) In the method for producing a fluoropolymer of the present invention, FEP polymerization is usually carried out at a polymerization temperature of 60 to 100 ° C. and a polymerization pressure of 0.7 to 4.5 MpaG. preferable.
The preferable monomer composition (mass%) of FEP is TFE: HFP = (60-95) :( 5-40), More preferably, it is (85-90) :( 10-15). The FEP may further be modified with perfluoro (alkyl vinyl ether) s as a third component and modified within a range of 0.5 to 2% by mass of the total monomers.
In the polymerization of the FEP, the sulfonic acid ester compound can be used in the range of use in the method for producing a fluoropolymer of the present invention, but usually 0.0001 to 2% by mass with respect to 100% by mass of the aqueous medium. Add the amount of.
In the FEP polymerization, cyclohexane, methanol, ethanol, carbon tetrachloride, chloroform, methylene chloride, methyl chloride, etc. are preferably used as the chain transfer agent, and ammonium carbonate, disodium hydrogen phosphate as the pH buffering agent. Etc. are preferably used.

(2) In the method for producing a fluoropolymer of the present invention, polymerization of TFE / perfluoro (alkyl vinyl ether) copolymer such as PFA and MFA is usually performed at a polymerization temperature of 60 to 100 ° C. and a polymerization pressure of 0.7 to It is preferable to carry out at 2.5 MpaG.
A preferable monomer composition (mol%) of the TFE / perfluoro (alkyl vinyl ether) copolymer is TFE: perfluoro (alkyl vinyl ether) = (95 to 99.7) :( 0.3 to 5), more preferably. Is (98-99.5) :( 0.5-2). Examples of the perfluoro (alkyl vinyl ether), formula: CF ₂ = CFORf ⁴ (wherein, Rf ⁴ is a perfluoroalkyl group having 1 to 6 carbon atoms) preferably used those represented by.
In the polymerization of the TFE / perfluoro (alkyl vinyl ether) copolymer, the sulfonic acid ester compound described above can be used within the range of use in the method for producing a fluoropolymer of the present invention. It is preferable to add in an amount of 0.0001 to 2 mass% with respect to mass%.
In the polymerization of the TFE / perfluoro (alkyl vinyl ether) copolymer, it is preferable to use cyclohexane, methanol, ethanol, carbon tetrachloride, chloroform, methylene chloride, methyl chloride, methane, ethane or the like as a chain transfer agent. As a buffering agent, it is preferable to use ammonium carbonate, disodium hydrogen phosphate or the like.

(3) In the method for producing a fluoropolymer of the present invention, ETFE is usually preferably polymerized at a polymerization temperature of 20 to 100 ° C. and a polymerization pressure of 0.5 to 0.8 MPaG.
A preferred monomer composition (mol%) of ETFE is TFE: ethylene = (50 to 99) :( 50 to 1). As the ETFE, a third monomer may be used and modified within a range of 0 to 20% by mass of the total monomers. Preferably, TFE: ethylene: third monomer = (70 to 98) :( 30 to 2) :( 4 to 10). As the third monomer, perfluorobutylethylene, perfluorobutylethylene, 2,3,3,4,4,5,5-heptafluoro-1-pentene (CH ₂ ═CFCF ₂ CF ₂ CF ₂ H), 2-trifluoromethyl-3,3,3-trifluoropropene ((CF ₃ ) ₂ C═CH ₂ ) is preferred.
In the polymerization of ETFE, the sulfonic acid ester compound described above can be used in the range of use in the method for producing a fluoropolymer of the present invention, but is usually 0.0001 to 2 with respect to 100% by mass of the aqueous medium. Add in mass%.
In the above ETFE polymerization, it is preferable to use cyclohexane, methanol, ethanol, carbon tetrachloride, chloroform, methylene chloride, methyl chloride or the like as the chain transfer agent.

(III) Elastomeric polymer In the method for producing a fluoropolymer of the present invention, the polymerization of the elastomeric polymer is carried out by charging pure water and the sulfonate compound in a pressure-resistant reaction vessel equipped with a stirrer. After deoxygenation, the monomer is charged, the temperature is set to a predetermined temperature, a polymerization initiator is added, and the reaction is started. Since the pressure decreases as the reaction proceeds, additional monomer is added continuously or intermittently to maintain the initial pressure. When a predetermined amount of monomer is supplied, the supply is stopped, the monomer in the reaction vessel is purged, the temperature is returned to room temperature, and the reaction is terminated. When emulsion polymerization is performed, it is preferable to continuously remove the polymer latex from the reaction vessel.
In particular, when producing a thermoplastic elastomer, as disclosed in the pamphlet of WO 00/01741, once the fluorine-containing polymer fine particles are synthesized at a high concentration and then diluted, the polymerization is further performed. It is also possible to use a method that can increase the final polymerization rate compared to the polymerization.

The polymerization of the elastomeric polymer is appropriately selected from the viewpoints of physical properties of the target polymer and control of the polymerization rate. The polymerization temperature is usually -20 to 200 ° C, preferably 5 to 150 ° C, and the polymerization pressure is usually normal. It is carried out at 0.5 to 10 MPaG, preferably 1 to 7 MPaG. Moreover, it is preferable to maintain pH in a polymerization medium normally at 2.5-9 using the pH adjuster etc. which are mentioned later by a well-known method etc.

Examples of the monomer used for the polymerization of the elastomeric polymer include, in addition to vinylidene fluoride, fluorine-containing ethylenically unsaturated monomers having at least the same number of fluorine atoms as carbon atoms and capable of copolymerizing with vinylidene fluoride. Examples of the fluorine-containing ethylenically unsaturated monomer include trifluoropropene, pentafluoropropene, hexafluorobutene, and octafluorobutene. Among these, hexafluoropropene is particularly suitable because of the properties of the elastomer obtained when it blocks polymer crystal growth. Examples of the fluorine-containing ethylenically unsaturated monomer include trifluoroethylene, TFE, and CTFE. A fluorine-containing monomer having one or two or more chlorine and / or bromine substituents may be used. it can. Perfluoro (alkyl vinyl ether) such as perfluoro (methyl vinyl ether) can also be used. TFE and HFP are preferred for producing elastomeric polymers.
The preferable monomer composition (mass%) of the elastomeric polymer is vinylidene fluoride: HFP: TFE = (20 to 70) :( 20 to 60) :( 0 to 40). Elastomeric polymers of this composition exhibit good elastomeric properties, chemical resistance and thermal stability.

In the polymerization of the elastomeric polymer, the sulfonic acid ester compound described above can be used within the range of use in the method for producing a fluoropolymer of the present invention, but is usually in an amount of 0.00% with respect to 100% by mass of the aqueous medium. It is added in an amount of 0001 to 2% by mass.

In the polymerization of the elastomeric polymer, a known inorganic radical polymerization initiator can be used as the polymerization initiator. Examples of the inorganic radical polymerization initiator include conventionally known water-soluble inorganic peroxides such as sodium, potassium and ammonium persulfates, perphosphates, perborates, percarbonates and permanganates. Useful. The radical polymerization initiator further includes a reducing agent such as sodium, potassium or ammonium sulfite, bisulfite, metabisulfite, hyposulfite, thiosulfate, phosphite or hypophosphite. Or by a metal compound that is easily oxidized, such as a ferrous salt, a cuprous salt, or a silver salt. A suitable inorganic radical polymerization initiator is ammonium persulfate, and it is more preferred to use it in a redox system with ammonium persulfate and sodium bisulfite.
The concentration of the polymerization initiator added is appropriately determined depending on the molecular weight of the target fluoropolymer and the polymerization reaction rate, but is 0.0001 to 10% by mass, preferably 0. The amount is set to 01 to 5% by mass.

In the polymerization of the elastomeric polymer, a known chain transfer agent can be used, but in the polymerization of PVDF, a hydrocarbon, ester, ether, alcohol, ketone, chlorine compound, carbonate, or the like is used. In the thermoplastic elastomer, hydrocarbons, esters, ethers, alcohols, chlorine compounds, iodine compounds, and the like can be used. Among them, acetone and isopropyl alcohol are preferable for the polymerization of PVDF, and isopentane, diethyl malonate and ethyl acetate are preferable for the polymerization of the thermoplastic elastomer from the viewpoint that the reaction rate is difficult to decrease, and I (CF ₂ ) ₄ I , I (CF ₂ ) ₆ I, ICH ₂ I and the like are preferred from the viewpoint that they can be iodinated at the polymer terminal and can be used as a reactive polymer.
The amount of the chain transfer agent used is usually 0.5 × 10 ^{−3 to} 5 × 10 ⁻³ mol%, preferably 1.0 × 10 ^{−3 to} 3.5 × 10, based on the total amount of monomers supplied. ^-3 mol% is preferred.

In the polymerization of the elastomeric polymer, paraffin wax or the like can be preferably used as an emulsion stabilizer in the polymerization of PVDF, and in the polymerization of a thermoplastic elastomer, phosphate, sodium hydroxide, hydroxylation can be used as a pH regulator. Potassium etc. can be used preferably.

The elastomeric polymer obtained by the method for producing a fluoropolymer of the present invention has a solid content concentration of 10 to 40% by mass and an average particle size of 0.03 to 1 μm, preferably 0. It has a number average molecular weight of 1,000 to 2,000,000 and a thickness of 05 to 0.5 μm.

The elastomeric polymer obtained by the method for producing a fluoropolymer of the present invention is suitable for rubber molding processing by adding or concentrating a dispersion stabilizer such as a hydrocarbon surfactant, if necessary. Can be a dispersion. The dispersion is processed by adjusting pH, coagulation, heating, and the like. Each process is performed as follows.

The pH adjustment is performed by adding a mineral acid such as nitric acid, sulfuric acid, hydrochloric acid or phosphoric acid and / or a carboxylic acid having 5 or less carbon atoms and having a pK = 4.2 or less to make the pH 2 or less.
The coagulation is performed by adding an alkaline earth metal salt. Examples of the alkaline earth metal salts include nitrates, chlorates and acetates of calcium or magnesium.
Either the pH adjustment or the coagulation may be performed first, but the pH adjustment is preferably performed first.
After each operation, washing is performed with the same volume of water as the elastomer to remove a small amount of impurities such as buffer solution and salt existing in the elastomer, and drying is performed. Drying is usually performed at about 70 to 200 ° C. while circulating air at a high temperature in a drying furnace.

The fluoropolymer is usually at a concentration of 10 to 50% by mass of the aqueous dispersion obtained by performing the polymerization. In the aqueous dispersion, the preferable lower limit of the concentration of the fluoropolymer is 10% by mass, the more preferable lower limit is 15% by mass, the preferable upper limit is 40% by mass, the more preferable upper limit is 35% by mass, and the more preferable upper limit is 30% by mass. %.

The aqueous dispersion obtained by performing the above polymerization may be concentrated or dispersion-stabilized to form a dispersion, or as a powder or other solid material obtained by collecting and drying by coagulation or aggregation. Also good.

The sulfonic acid ester compound can also be suitably used as a dispersant for dispersing the fluoropolymer obtained by polymerization in an aqueous medium.

The aqueous dispersion of the present invention contains particles made of a fluoropolymer, the sulfonic acid ester compound, and an aqueous medium. The aqueous dispersion is one in which particles made of a fluoropolymer are dispersed in an aqueous medium in the presence of the sulfonic acid ester compound.

The sulfonic acid ester compound is preferably 0.0001 to 15% by mass of the aqueous dispersion of the present invention. If it is less than 0.0001% by mass, the dispersion stability may be inferior. If it exceeds 15% by mass, there is no dispersion effect commensurate with the abundance and it is not practical. A more preferable lower limit of the sulfonic acid ester compound is 0.001% by mass, a more preferable upper limit is 10% by mass, and a still more preferable upper limit is 2% by mass.

The aqueous dispersion of the present invention includes an aqueous dispersion obtained by performing the above-described polymerization, a dispersion obtained by concentrating or dispersing the aqueous dispersion, and a powder comprising a fluoropolymer. May be dispersed in an aqueous medium in the presence of the sulfonic acid ester compound.

As a method for producing the purified aqueous dispersion of the present invention, the aqueous dispersion obtained by the above polymerization is contacted with an anion exchange resin in the presence of a nonionic surfactant, and the step (I) The aqueous dispersion obtained in step (II) can be produced by the step (II) in which the solid content concentration is 30 to 70% by mass with respect to 100% by mass of the aqueous dispersion. A method for producing such a purified aqueous dispersion is also one aspect of the present invention. The nonionic surfactant is not particularly limited, and examples thereof include those described above. Although the said anion is not specifically limited, A well-known thing can be used. Moreover, a well-known method can be used for the method made to contact with the said anion exchange resin.

A known method is employed as the concentration method, and examples thereof include phase separation, electric concentration, and ultrafiltration. In the concentration, the fluorine-containing polymer concentration can be concentrated to 30 to 70% by mass depending on the application. Concentration may impair dispersion stability. In that case, a dispersion stabilizer may be further added. As the dispersion stabilizer, the sulfonic acid ester compound and other various surfactants may be added. Examples of the various dispersion stabilizers include nonionic surfactants such as polyoxyalkyl ether, particularly polyoxyethylene alkylphenyl ether (for example, Triton X-100 (trade name) manufactured by Rohm & Haas), Polyoxyethylene isotridecyl ether (for example, Neugen TDS80C (trade name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Leocor TD90D (trade name) manufactured by Lion, Genapol X080 (trade name) manufactured by Clariant), polyoxyethylene ether However, it is not limited to these.

The total amount of the dispersion stabilizer is 0.5 to 20% by mass with respect to the solid content of the dispersion. If it is less than 0.5% by mass, the dispersion stability may be inferior. If it exceeds 20% by mass, there is no dispersion effect commensurate with the abundance and this is not practical. A more preferable lower limit of the dispersion stabilizer is 2% by mass, and a more preferable upper limit is 12% by mass.

The aqueous dispersion obtained by carrying out the polymerization can also be prepared as an aqueous dispersion having a long pot life by subjecting it to a dispersion stabilization treatment without concentrating depending on the application. Examples of the dispersion stabilizer used include the same as those described above.

The use of the aqueous dispersion of the present invention is not particularly limited, and it is applied as it is as an aqueous dispersion, applied on a substrate, dried, and then fired as necessary; non-woven fabric, resin molded product After impregnating and drying a porous support such as glass, preferably by calcination; after coating and drying on a substrate such as glass, the substrate is immersed in water as necessary to peel off the substrate Examples thereof include cast film formation comprising obtaining a thin film, and examples of these applications include aqueous dispersion paints, electrode binders, electrode water repellents, and the like.

The aqueous dispersion of the present invention can be blended with known pigments, thickeners, dispersants, antifoaming agents, antifreeze agents, film forming aids, or other polymer compounds. It can be combined and used as a water-based paint for coating.

The present invention also provides the following general formula (I) from at least one component selected from the wastewater generated by the coagulation described above, the wastewater generated by washing, and the off-gas generated in the drying step.
Rf ¹ C (COOM) Rf ² SO ₃ CF ₂ CH ₃ (I)
(Wherein M represents H, NH ₄ , Li, Na or K, and Rf ¹ and Rf ² represent a fluoroalkyl group or a fluoroalkoxy group having 1 to 3 carbon atoms). It is also a method for producing a regenerated sulfonic acid ester compound, comprising a step of recovering and purifying the acid ester compound.

A method for recovering and purifying the sulfonic acid ester compound from the wastewater generated by the coagulation, the wastewater generated by washing, and the off-gas generated in the drying step is not particularly limited, but is conventionally known. The method can be adopted as it is.

Since the method for producing a fluoropolymer of the present invention comprises the above-described configuration, it is possible to efficiently produce a fluoropolymer having a very small amount of surfactant remaining in the resin, little coloration and good physical properties. . In addition, since the aqueous dispersion of the present invention has the above-described configuration, the fluoropolymer can be stably present, and a molded product and a coating film of a fluoropolymer with little coloration and good physical properties can be obtained. Can be provided.

Next, although this invention is demonstrated based on a manufacture example and an Example, this invention is not limited only to this manufacture example and an Example.

Synthesis example 1
32 g of CF ₃ CF (COOH) OCF ₂ CF ₂ SO ₃ H was put into a stainless steel autoclave with a stirring blade having an internal volume of 100 mL, and after removing oxygen in the system by nitrogen pressurization and depressurization, the internal temperature was adjusted to 100 Then, CF ₂ ═CH ₂ was introduced until the internal pressure reached 0.5 Mpa. Since decrease in pressure is observed in the stirring was continued for continuously supplying _CF 2 = CH ₂ the reaction to keep the inner pressure to 0.5Mpa. After 5 hours, the pressure was released to complete the reaction, and 38 g of a mixture of oily CF ₃ CF (COOH) OCF ₂ CF ₂ SO ₃ H and CF ₃ CF (COOH) OCF ₂ CF ₂ SO ₃ CF ₂ CH ₃ was obtained. . When 100 mL of ion exchange water was put into a 200 mL glass flask and 10 g of this mixture was further added and stirred, the pH was 1.3. When the stirring was stopped, an oil phase was seen at the bottom. Aqueous ammonia was added dropwise with stirring to raise the pH of the system to 3, and when the stirring was stopped, it was separated into two layers again. Therefore, the oil phase was recovered and washed with deionized water, and CF ₃ CF ( COOH) OCF ₂ CF ₂ SO ₃ CF ₂ CH ₃ 31 g was recovered. This was neutralized with aqueous ammonia to obtain CF ₃ CF (COONH ₄ ) OCF ₂ CF ₂ SO ₃ CF ₂ CH ₃ .

Example 1 Preparation of PTFE Latex [1]
In a stainless steel autoclave with a stirring blade with an internal volume of 3 L, deionized water 1.5 L, paraffin wax 60 g (melting point 60 ° C.), and CF ₃ CF (COONH ₄ ) OCF ₂ CF ₂ SO ₃ CF ₂ CH ₃ 5 g was charged and the system was replaced with TFE. TFE was injected so that the internal temperature was 70 ° C. and the internal pressure was 0.78 MPa, and 3.75 g of a 1% by mass ammonium persulfate [APS] aqueous solution was charged to initiate the reaction. As the polymerization proceeded, the pressure in the polymerization system decreased, so TFE was continuously added to keep the internal pressure at 0.78 MPa and the reaction was continued. The polymerization was stopped by purging TFE after the polymerization start time. The solid content concentration of this aqueous dispersion was 24.3 mass%, the standard specific gravity was 2.221, and the average primary particle size of the fluoropolymer was 264 nm.
Solid content concentration: It was determined from the decrease in mass when the obtained aqueous dispersion was dried at 150 ° C. for 1 hour.
Standard specific gravity (SSG): Measured according to ASTM D-1457-69.
Average primary particle diameter (PTFE): Based on a calibration curve of the transmittance of 550 nm projection light per unit length and the average particle diameter determined by electron micrograph, diluted to a solid content concentration of about 0.02% by mass. Thus, it was indirectly determined from the transmittance.

The sulfonic acid ester compound of the present invention can be suitably used as a surfactant in emulsion polymerization of a fluoropolymer. The present invention also provides a production method capable of suitably producing the sulfonic acid ester compound, a surfactant comprising the sulfonic acid ester compound, a method for producing a fluoropolymer, an aqueous dispersion, and an aqueous dispersion. A method for producing a body, a fine powder, and a method for producing a regenerated sulfonate compound are provided.

Claims (9)

The following general formula (I)
Rf ¹ C (COOM) Rf ² SO ₃ CF ₂ CH ₃ (I)
(Wherein M represents H, NH ₄ , Li, Na or K, and Rf ¹ and Rf ² represent a fluoroalkyl group or a fluoroalkoxy group having 1 to 3 carbon atoms). Acid ester compound. The following general formula (II)
Rf ¹ C (COOM) Rf ² SO ₃ H (II)
(Wherein M represents H, NH ₄ , Li, Na or K, and Rf ¹ and Rf ² represent a fluoroalkyl group or a fluoroalkoxy group having 1 to 3 carbon atoms). And a step of reacting vinylidene fluoride under acidic conditions. The method for producing a sulfonic acid ester compound according to claim 1. A surfactant comprising the sulfonic acid ester compound according to claim 1. Including a step of polymerizing a fluorine-containing monomer in an aqueous medium,
A method for producing a fluoropolymer, wherein the aqueous medium comprises the sulfonic acid ester compound according to claim 1. The method for producing a fluoropolymer according to claim 4, wherein the content of the sulfonic acid ester compound is 0.0001 to 2% by mass with respect to 100% by mass of the aqueous medium. An aqueous dispersion containing the sulfonic acid ester compound according to claim 1 and a fluoropolymer,
An aqueous dispersion, wherein the fluoropolymer has an average particle size of 50 to 500 nm. A step (I) of contacting the aqueous dispersion according to claim 6 with an anion exchange resin in the presence of a nonionic surfactant, and the aqueous dispersion obtained in step (I) in the aqueous dispersion A method for producing a purified aqueous dispersion comprising a step (II) of concentrating so that a solid content concentration is 30 to 70% by mass with respect to 100% by mass of an aqueous dispersion. A fine powder produced by coagulating the aqueous dispersion according to claim 6. The following general formula (I) is selected from at least one component selected from wastewater generated by coagulation according to claim 8, wastewater generated by washing, and off-gas generated in a drying step.
Rf ¹ C (COOM) Rf ² SO ₃ CF ₂ CH ₃ (I)
(In the formula, M represents H, NH ₄ , Li, Na, or K, and Rf ¹ and Rf ² represent a fluoroalkyl group or a fluoroalkoxy group having 1 to 3 carbon atoms.)
The manufacturing method of the reproduction | regeneration sulfonate compound characterized by including the process which collect | recovers and refine | purifies the sulfonate compound represented by these.