JP2009029854A - Fluorine-containing (meth) acrylic polymer and method for producing fluoropolymer - Google Patents

Abstract

Provided are a fluorine-containing (meth) acrylic polymer useful for the production of a fluoropolymer, and a method for producing a fluoropolymer using the polymer.
SOLUTION: General formula (1)
^{CX 1 X 2 = CX 3 -COOM} (1)
(In the formula, X ¹ and X ² are the same or different and represent H or F. X ³ represents —CF ₃ or F. M represents any of H, K, Na or NH _4. .) Is a fluorine-containing (meth) acrylic polymer obtained by polymerizing a monomer composition containing at least one compound represented by formula (1) in an aqueous medium.
[Selection figure] None

Description

The present invention relates to a fluorine-containing (meth) acrylic polymer and a method for producing a fluoropolymer.

Carboxylic acid having a fluoroalkyl group such as perfluorooctane ammonium salt is thermally and chemically very stable, and is useful in that it can suppress side reactions such as chain transfer during polymerization. Although used as an emulsifier, in order to remove it from the resin obtained by polymerization, there has been a problem that conditions such as washing and heating are limited.

As a method for producing a fluoropolymer, a method is known in which tetrafluoroethylene [TFE] is polymerized by using tertiary perfluoroalkoxide as a surfactant in an aqueous medium instead of a fluorine-substituted carboxylic acid (patent) Reference 1).

In recent years, as a method for producing a fluoropolymer, a method using a carboxylic acid having a fluoroalkyl group and an alkylene group having 1 to 3 carbon atoms as a surfactant instead of a fluorine-substituted carboxylic acid (for example, Patent Document 2), A method using a carboxylic acid having an alkyl group and ether oxygen as a surfactant (for example, Patent Document 3) is also disclosed.
JP 61-207413 A Japanese Patent Laid-Open No. 10-212261 US Pat. No. 6,429,258

An object of the present invention is to provide a fluorine-containing (meth) acrylic polymer useful for the production of a fluoropolymer and a method for producing a fluoropolymer using the polymer.

The present invention relates to a general formula (1)
^{CX 1 X 2 = CX 3 -COOM} (1)
(In the formula, X ¹ and X ² are the same or different and represent H or F. X ³ represents —CF ₃ or F. M represents any of H, K, Na or NH _4. .) Is a fluorine-containing (meth) acrylic polymer obtained by polymerizing a monomer composition containing at least one compound represented by (2)) in an aqueous medium.

The present invention is an emulsifier for polymerization comprising the above-mentioned fluorine-containing (meth) acrylic polymer.

The present invention is a method for producing a fluoropolymer, characterized in that a fluoromonomer is polymerized in an aqueous medium in the presence of the polymerization emulsifier.

The present invention is an aqueous fluoropolymer dispersion obtained from the above fluoropolymer production method.

The present invention is a fine powder of a fluoropolymer obtained from the aqueous fluoropolymer dispersion.

The present invention is a fine powder of a fluoropolymer obtained by coagulating a fluoropolymer from the aqueous fluoropolymer dispersion.
Hereinafter, the present invention will be described in detail.

The fluorine-containing (meth) acrylic polymer of the present invention has the general formula (1)
^{CX 1 X 2 = CX 3 -COOM} (1)
It is obtained by polymerizing a monomer composition containing at least one compound represented by the formula (1) in an aqueous medium.

In the general formula (1), X ¹ and X ² are the same or different and represent H or F.
X ¹ and X ² are each preferably F in terms of polymer yield.

X ³ represents —CF ₃ or F.

M represents any one of H, K, Na, and NH ₄ . The above M is preferably NH _{4 from} the viewpoint of dispersibility.

As long as the monomer composition contains at least one compound represented by the above general formula (1), a fluoromonomer or a fluorine-free monomer described later is within a range in which the characteristics of the present invention are not impaired. It may be included. In the monomer composition, the compound represented by the general formula (1) may contain at least 90% by mass or more, but the fluorine-containing (meth) acrylic polymer is a single weight of the compound. It is preferably a coalescence.

Although the said monomer composition is not specifically limited, For example, solution polymerization can be performed in an aqueous medium.
In the present specification, the aqueous medium is not particularly limited as long as it contains water. For example, water and a fluorine-free organic solvent such as alcohol, ether, and ketone, and / or a boiling point of 40 ° C. or less. It may contain a certain fluorine-containing organic solvent.

As the polymerization initiator used for the polymerization of the monomer composition, conventionally known polymerization initiators can be used, and among them, a persulfate is preferable.
Examples of the persulfate include ammonium persulfate and potassium persulfate. Among them, ammonium persulfate is preferable.

In the present invention, the compound represented by the general formula (1) is preferably added in an amount of 1 to 100 parts by mass with respect to 100 parts by mass of the aqueous medium. A more preferable lower limit is 20 parts by mass and a more preferable upper limit is 50 parts by mass with respect to 100 parts by mass of the aqueous medium.

In the present invention, the polymerization initiator is preferably added in an amount of 0.001 to 5 parts by mass with respect to 100 parts by mass of the monomer composition.

In the present invention, the conditions for polymerizing the compound represented by the general formula (1) can be appropriately selected according to the type and scale of the compound, and are not particularly limited, but the polymerization temperature is 5 to 100. The polymerization pressure is preferably normal pressure.

The fluorine-containing (meth) acrylic polymer preferably has an average weight molecular weight of 1000 to 10,000. If the average weight molecular weight is in such a range, the effect of improving the dispersion stability of the fluoropolymer is particularly high. A more preferable upper limit of the average weight molecular weight is 2500.

The fluorine-containing (meth) acrylic polymer of the present invention is generally

(Wherein, X ¹ , X ² , X ³ and M are as defined above).

The fluorine-containing (meth) acrylic polymer of the present invention can stabilize dispersion of a polymer compound such as a fluoropolymer in an aqueous medium.
The reason why such a fluorine-containing (meth) acrylic polymer has such an excellent effect is not clear, but since it has the monomer unit as described above, when it is present in an aqueous medium, it contacts the periphery of the polymer compound. It is conceivable that a protective colloid is formed.

Since the fluorine-containing (meth) acrylic polymer of the present invention has a high effect of stabilizing the dispersion of the fluoropolymer and the like as described above, it can be suitably used as an emulsifier such as an emulsifier for polymerization.
The polymerization emulsifier comprising the above-mentioned fluorine-containing (meth) acrylic polymer is also one aspect of the present invention.

The fluoropolymer production method of the present invention is a method in which a fluoromonomer is polymerized in the presence of the aforementioned emulsifier for polymerization (hereinafter, this emulsifier is simply referred to as “emulsifier”).

The emulsifier is preferably added in a total addition amount of 0.0001 to 2% by mass of the aqueous medium. As for the said addition amount, a more preferable minimum is 0.001 mass%, and a more preferable upper limit is 0.5 mass%. If the amount is less than 0.0001% by mass of the aqueous medium, the dispersion force tends to be insufficient. If the amount exceeds 2% by mass of the aqueous medium, the effect corresponding to the amount added cannot be obtained, and the polymerization rate is lowered or the reaction is stopped. May happen. The amount of the emulsifier is appropriately determined depending on the type of fluoromonomer used, the molecular weight of the target fluoropolymer, and the like.

In the method for producing a fluoropolymer of the present invention, after the above monomer composition is polymerized in an aqueous medium to obtain an aqueous solution in which the fluorine-containing (meth) acrylic polymer is within the above concentration range, Polymerization of the fluoromonomer described in detail may be performed. In the present invention, the monomer composition having M = H may be used, and the polymer terminal obtained after polymerization may be neutralized with NaOH or KOH.

The fluoromonomer may be a fluoroolefin, preferably a fluoroolefin having 2 to 10 carbon atoms; a cyclic fluorinated monomer; a formula CY ² ₂ = CYOR ¹ or CY ₂ = CYOR ² OR ³ (Y is H or F, R ¹ 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. Is an alkylene group having 1 to 8 carbon atoms substituted with a fluorine atom.) And the like.

The fluoroolefin preferably has 2 to 8 carbon atoms. Examples of the fluoroolefin having 2 to 8 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 ¹ and R ³ are preferably those having 1 to 4 carbon atoms, more preferably all of the hydrogen atoms are substituted with fluorine, and the 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 that are reactive with the fluoromonomer. 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.

In the polymerization according to the present invention, an aqueous medium, the above-mentioned emulsifier, a fluoromonomer and other additives as necessary are charged into a polymerization reactor, the contents of the reactor are stirred, and the reactor is maintained at a predetermined polymerization temperature. Then, a polymerization initiator is added and the polymerization reaction is started. After the polymerization reaction is started, depending on the purpose, a fluoromonomer, a polymerization initiator, a chain transfer agent, the above emulsifier, and the like may be additionally added.

The polymerization initiator is not particularly limited as long as it can generate radicals within the above polymerization temperature range, and a known oil-soluble and / or water-soluble polymerization initiator 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 polymer, and the reaction rate.

The production method of the present invention can efficiently produce a fluoropolymer if at least one emulsifier of the present invention described above is used. In addition, in the production method of the present invention, other compounds having surface activity other than the above emulsifiers may be used at the same time as long as they can remain in a volatile or fluoropolymer molded body. Also good.

The other compounds having surface active ability are not particularly limited, and may be any of anionic, cationic, nonionic or betaine surfactants. These surfactants are hydrocarbons. It may be of the type.

In the above polymerization, generally, the polymerization temperature is 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 fluoromonomer used, the molecular weight of the target polymer, and the reaction rate.

By performing the polymerization, an aqueous dispersion containing 5 to 45% by mass of fluoropolymer particles having an average primary particle diameter of 50 to 500 nm can be obtained.

In the present specification, the average primary particle size is determined by the transmittance of 550 nm projection light with respect to the unit length of the fluoropolymer aqueous dispersion adjusted to a fluoropolymer solid content concentration of 0.22% by mass, and a transmission electron micrograph. It is a value indirectly determined from the transmittance based on a calibration curve with the determined average primary particle diameter.

The concentration of the fluoropolymer particles is as follows: 1 g of the aqueous dispersion is dried in a blow dryer at 150 ° C. for 60 minutes, and the ratio of the mass of the heating residue to the mass of the aqueous dispersion (1 g) is expressed as a percentage. It is a representation.

The above-mentioned fluoropolymer is obtained by polymerizing the above-mentioned fluoromonomer, and the above-mentioned fluorine-free monomer can also be copolymerized depending on the purpose.

As a fluoropolymer suitably produced by the production method of the present invention, a monomer having the highest molar fraction of monomers in the fluoropolymer (hereinafter, “most monomer”) is a TFE polymer having TFE, and a VDF having the most monomer being VDF. Examples thereof include a polymer and a CTFE polymer in which the most monomer is CTFE.

The TFE polymer may preferably be a polytetrafluoroethylene polymer [PTFE polymer] such as a TFE homopolymer, or (1) TFE and (2) 2 to 8 carbon atoms. It may be a copolymer composed of one or two or more fluoro monomers other than TFE, particularly HFP or CTFE, and / or (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 may also be a copolymer of TFE, one or more fluoromonomers having 2 to 8 carbon atoms, and one or more fluorine-free monomers. 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.

In the production method of the present invention, the obtained fluoropolymer may be concentrated or dispersion-stabilized after the above-mentioned polymerization to obtain an aqueous dispersion, or it may be recovered by flocculation or aggregation and dried. It may be a powder or other solid matter.

Examples of the concentration method include known methods such as phase separation, electric concentration, and ultrafiltration. By performing the concentration, the fluoropolymer concentration can be adjusted to 30 to 70% by mass. Concentration may impair the stability of the aqueous dispersion. In that case, a dispersion stabilizer may be further added. As the dispersion stabilizer, the above-described emulsifier of the present invention 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), Examples include polyoxyethylene isotridecyl ether (Neugen TDS80C (trade name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Leocor TD90D (trade name) manufactured by Lion Corporation, and Genapol X080 (trade name) manufactured by Clariant). It is not limited to only.

The total amount of the dispersion stabilizer is 0.5 to 20% by mass with respect to the solid content of the aqueous 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.

Depending on the application, the aqueous dispersion may be prepared as a fluoropolymer aqueous dispersion having a long pot life by subjecting it to a dispersion stabilization treatment without concentrating after polymerization. Examples of the dispersion stabilizer to be used include the same ones as described above.

The fluoropolymer produced by the production method 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 production method 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 [ETFE] is used as a melt processable resin. , TFE / HFP copolymer [FEP] and TFE / perfluoro (alkyl vinyl ether) copolymer [PFA, MFA, etc.] are used as (III) elastomeric copolymer: TFE / propylene copolymer, TFE / propylene Copolymer / third monomer copolymer (the third monomer is VDF, HFP, CTFE, perfluoro (alkyl vinyl ether), etc.), a copolymer comprising TFE and perfluoro (alkyl vinyl ether); HFP / Ethylene copolymer, HFP / ethylene / TFE copolymer; PVDF; VDF / HFP copolymer HFP / ethylene copolymer, a thermoplastic elastomer of VDF / TFE / HFP copolymers and the like; and, the fluorine-containing segmented polymer or the like can be suitably produced according to JP-B-61-49327.
The perfluoro (alkyl vinyl ether) has the formula:
Rf ¹ (OCFQ ¹ CF ₂ ) _k ¹ (OCR ⁴ Q ² CF ₂ CF ₂ ) _{k 2} (OCF ₂ ) _{k 3} OCF = CF ₂
(In the formula, Rf ¹ 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 ¹ , Q ² and R ^4. 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 production method of the present invention are preferably produced in the following manner.

(I) Non-melt processable resin In the production method of the present invention, the polymerization of the PTFE polymer is usually performed at a polymerization temperature of 10 to 100C and a polymerization pressure of 0.05 to 5 MPaG.
In the above polymerization, pure water and the above-described emulsifier of the present invention 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, 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, the solid content concentration is generally 10 to 50% by mass, the average particle size is 0.05 to 0.5 μm, and particularly by using the above-described emulsifier of the present invention. An aqueous dispersion having particles made of a PTFE polymer having a fine particle diameter of 3 μm or less can be obtained. 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 obtained by the above polymerization is stabilized by adding a nonionic surfactant, further concentrated, and various uses as a composition to which an organic or inorganic filler is added depending on the purpose. Can be used for 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.

(II) Melt processable resin (1) In the production method of the present invention, FEP is usually preferably polymerized at a polymerization temperature of 60 to 100 ° C. and a polymerization pressure of 0.7 to 4.5 MPaG.
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 by using a perfluoro (alkyl vinyl ether) as a third component within a range of 0.5 to 2% by mass of the total monomers.

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 production method of the present invention, polymerization of TFE / perfluoro (alkyl vinyl ether) copolymers 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 2.5 MPaG. It is preferable.
The preferable monomer composition (mol%) of the TFE / PAVE copolymer is TFE: PAVE = (95-99.7) :( 0.3-5), more preferably (98-99.5) :( 0. 5-2). As the PAVE, _formula: CF 2 = CFORf (wherein, Rf is a perfluoroalkyl group having 1 to 6 carbon atoms) preferably used those represented by.

In the polymerization of the TFE / PAVE 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, and carbonic acid as a pH buffer. It is preferable to use ammonium, disodium hydrogen phosphate, or the like.

(3) In the production method of the present invention, the polymerization of ETFE is usually preferably carried out 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 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 production method of the present invention, the polymerization of the elastomeric polymer is carried out by adding pure water and the above-described emulsifier of the present invention to a pressure-resistant reaction vessel equipped with a stirrer, and after deoxidation. The reaction can be started by charging a monomer, bringing the temperature to a predetermined temperature, and adding a polymerization initiator. 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 WO 00/01741, pamphlet is synthesized in the presence of a high concentration of the above-mentioned emulsifier, diluted and further polymerized. It is also possible to use a method that can increase the final polymerization rate as compared with normal polymerization by performing the above.

The polymerization of the elastomeric polymer is appropriately selected from the viewpoints of physical properties of the target polymer and polymerization rate control. For example, the polymerization temperature is usually -20 to 200 ° C, preferably 5 to 150 ° C, and the polymerization pressure. Can usually be 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 due to the elastomeric properties obtained when it blocks polymer crystal growth. Examples of the fluorine-containing ethylenically unsaturated monomer include trifluoroethylene, TFE, and CTFE. A fluoromonomer having one or more chlorine and / or bromine substituents can also be used. . 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 an elastomeric polymer is vinylidene fluoride: HFP: TFE = (20-70) :( 20-60) :( 0-40). Elastomeric polymers of this composition exhibit good elastomeric properties, chemical resistance and thermal stability.

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 addition concentration of the polymerization initiator is appropriately determined depending on the molecular weight of the target polymer and the polymerization reaction rate, but is 0.0001 to 10% by mass, preferably 0.01 to 5% by mass of the total amount of monomers. Set.

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%.

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 adjuster. Potassium etc. can be used preferably.

The elastomeric polymer obtained by the production method of the present invention generally has a solid content concentration of 10 to 40% by mass and an average particle size of 0.03 to 1 μm, preferably 0.05 to 0 when the polymerization is completed. 0.5 μm and a number average molecular weight of 1,000 to 2,000,000.

The elastomeric polymer obtained by the production method of the present invention can be made into an aqueous dispersion suitable for rubber molding by adding, concentrating, etc., a dispersion stabilizer such as a hydrocarbon-based surfactant, if necessary. can do. The aqueous dispersion is treated by adjusting pH, coagulating, 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.

An aqueous fluoropolymer dispersion obtained from the above-described method for producing a fluoropolymer of the present invention is also one aspect of the present invention.

The aqueous fluoropolymer dispersion of the present invention is generally one in which fluoropolymer particles are dispersed in an aqueous medium in the presence of the above-described polymerization emulsifier.
The aqueous dispersion preferably has a fluoropolymer particle concentration of 5 to 70% by mass from the viewpoint of dispersion stability and processability.

The aqueous dispersion preferably has a polymerization emulsifier concentration of 0.0001 to 2% by mass of the aqueous medium.

A fine powder of fluoropolymer obtained from the aqueous fluoropolymer dispersion is also one aspect of the present invention.

The fine powder of the fluoropolymer of the present invention is obtained by coagulating the fluoropolymer from the above-described aqueous fluoropolymer dispersion of the present invention and further drying it as necessary.

The coagulation can be performed by a conventionally known method. The coagulation conditions can be appropriately selected according to the composition and amount of the fluoropolymer based on a conventionally known method.

As such a coagulation method, for example, an aqueous fluoropolymer dispersion is diluted with water to a polymer concentration of 10 to 20% by mass, and in some cases, after adjusting the pH to neutral or alkaline, A method of stirring more vigorously than stirring during the reaction in a vessel equipped with a stirrer can be mentioned.

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, if pigments for coloring and various fillers for improving mechanical properties are added, the fine powder containing the pigment or the filler containing the pigment and the filler uniformly mixed Can be obtained.

The drying is performed using a means such as vacuum, high frequency, hot air or the like while keeping the obtained wet powder not to flow so much, preferably in a stationary state.
The drying is performed at a drying temperature of 10 to 250 ° C, preferably 100 to 200 ° C.

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 fine powder of the present invention preferably has an average particle size of 300 to 700 μm.
The average particle diameter is measured in accordance with ASTM D-1457.

The fine powder preferably has an apparent density of 0.35 to 0.65 g / ml.
The apparent density is measured according to JIS K-6891.

The use of the fluoropolymer in the present invention is not particularly limited, and when used as an aqueous dispersion, it is applied by coating on a substrate, drying and then firing as necessary; porous such as nonwoven fabric and resin molded product Impregnation comprising impregnating the conductive support, drying, and preferably firing; coating on a substrate such as glass and drying; dipping in water if necessary; peeling the substrate to obtain a thin film Examples of these applications include water-dispersed paints, electrode binders, electrode water repellents, and the like.

The above fluoropolymer is in the form of an aqueous dispersion, by blending known pigments, thickeners, dispersants, antifoaming agents, antifreezing agents, film-forming aids, etc. A polymer compound can be combined and used as an aqueous coating material for coating.

For example, when the fluoropolymer is fine powder, it is preferable for molding. Suitable applications of such fine powders include hydraulic and fuel tubes for aircraft and automobiles, flexible hoses such as chemicals and steam, and wire coating applications.

The fluorine-containing (meth) acrylic polymer of the present invention is excellent in dispersibility, and when used for production of a polymer such as a fluoropolymer, an aqueous dispersion having good dispersion stability can be obtained.

Next, the present invention will be described based on examples, but the present invention is not limited to such examples.
In addition, the measurement performed in each Example was performed with the following method.

Solid content concentration It was calculated | required from the mass reduction | decrease when the obtained aqueous dispersion was dried at 150 degreeC for 1 hour.

Standard specific gravity (SSG)
Measured according to ASTM D-1457-69.

Based on a calibration curve of the average primary particle size solid content concentration diluted to about 0.02% by mass, the transmittance of 550 nm projection light per unit length and the average particle size determined by electron micrograph, It was obtained indirectly from the transmittance.

Example 1 Preparation of fluorinated (meth) acrylic polymer A glass reactor equipped with a 100 mL stirring blade and a cooling tube was charged with 20 ml of water and 20 ml of methanol, and deaerated and purged with nitrogen to remove oxygen. While maintaining the internal temperature at 80 ° C., 0.1 g of 10% ammonium persulfate aqueous solution was added, and then 25 g of CF ₂ ═C (CF ₃ ) COOH was added dropwise over 30 minutes. After completion of the dropwise addition, the reactor internal temperature was kept at 85 ° C. and held for another 2 hours.
After the reaction was completed, a white turbid liquid was obtained by cooling. Thus, the polymer was dried at 50 ° C. and 180 mmHg to obtain 21 g of a polymer.
1.5 g of this polymer was dispersed in 13.5 g of ion-exchanged water, and aqueous ammonia was added to adjust the pH to 9 to obtain an aqueous solution of a fluorine-containing (meth) acrylic polymer.

Example 2 Preparation of polytetrafluoroethylene [PTFE] latex In a stainless steel autoclave with a stirring volume of 3 L, deionized water 1.5 L, paraffin wax 60 g (melting point 60 ° C.) and prepared in Example 1 An aqueous solution of a fluorine-containing (meth) acrylic polymer was charged, and the inside of the system was replaced with tetrafluoroethylene [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 12 hours after the start of the polymerization. The solid content concentration of this aqueous dispersion was 18.5% by mass, the standard specific gravity was 2.216, and the average primary particle size of the fluoropolymer was 273 nm.

The fluorine-containing (meth) acrylic polymer of the present invention can be suitably used for producing a polymer such as a fluoropolymer.

Claims (10)

General formula (1)
^{CX 1 X 2 = CX 3 -COOM} (1)
(In the formula, X ¹ and X ² are the same or different and represent H or F. X ³ represents —CF ₃ or F. M represents any of H, K, Na or NH _4. .) Is a fluorine-containing (meth) acrylic polymer obtained by polymerizing a monomer composition containing at least one compound represented by formula (1) in an aqueous medium. The fluorine-containing (meth) acrylic polymer according to claim 1, wherein the monomer composition is a homopolymer of a compound represented by the general formula (1). The fluorine-containing (meth) acrylic polymer according to claim 1 or 2, having an average weight molecular weight of 1,000 to 10,000. 4. The fluorine-containing (meth) acrylic polymer according to claim ¹ , wherein X ¹ and X ² are F. An emulsifier for polymerization, comprising the fluorine-containing (meth) acrylic polymer according to claim 1, 2, 3 or 4. A method for producing a fluoropolymer, comprising polymerizing a fluoromonomer in an aqueous medium in the presence of the emulsifier for polymerization according to claim 5. The method for producing a fluoropolymer according to claim 6, wherein the emulsifier for polymerization is in an amount of 0.0001 to 2% by mass relative to the mass of the aqueous medium. A fluoropolymer aqueous dispersion obtained from the method for producing a fluoropolymer according to claim 6 or 7. A fine powder of a fluoropolymer obtained from the aqueous fluoropolymer dispersion according to claim 8. A fine powder of a fluoropolymer obtained by coagulating a fluoropolymer from the aqueous fluoropolymer dispersion according to claim 8.