JP5594338B2 - Composition comprising perfluorinated saturated hydrocarbon and fluorine-containing surfactant - Google Patents

Description

The present invention relates to a composition comprising a perfluorinated saturated hydrocarbon and a fluorine-containing surfactant.

Patent Document 1 discloses a method of polymerizing a fluorine-containing monomer in an aqueous medium containing an initiator and a polymerization aid. The polymerization aid is composed of a fluoropolyether acid having a number average molecular weight of 800 g / mol or more and a fluorine-based monomer. What is a combination of surfactants is disclosed.

Patent Document 2, water, aliphatic fluoropolyoxyalkylene, good C ₁ -C ₂₀ include a halogen optionally having hydrogenated end groups and / or hydrogenated repeating units, aromatic or mixed hydrocarbons And microemulsions containing fluorinated surfactants are disclosed.

Patent Document 3 discloses a microemulsion composed of an aqueous solution, a fluorinated surfactant, and perfluoropolyether.

Patent Document 4 discloses a method for polymerizing a fluorinated monomer in the presence of a perfluoropolyether prepared in the form of an aqueous microemulsion.

US Patent Application Publication No. 2008/0269408 Japanese Patent Laid-Open No. 08-208974 U.S. Pat. No. 4,990,283 US Pat. No. 4,864,006

The present invention provides a novel composition suitable for the production of a fluoropolymer and a novel production process for producing an aqueous fluoropolymer dispersion using this composition.

The present invention is a composition comprising a perfluorinated saturated hydrocarbon having 10 to 20 carbon atoms and a fluorine-containing surfactant.

The total fluorinated saturated hydrocarbon preferably has 12 to 20 carbon atoms.

The fluorine-containing surfactant preferably has 4 to 7 carbon atoms.

Further, it preferably contains water.

The fluorine-containing surfactant is preferably 98 to 0.001% by mass of the composition.

The mass ratio of the total fluorinated saturated hydrocarbon and the fluorine-containing surfactant is preferably 100: 100 to 100: 0.01.

The present invention is also a method for producing the composition described above, wherein the composition is obtained by dissolving a perfluorinated saturated hydrocarbon in a fluorine-containing surfactant.

The present invention is also a method for producing an aqueous fluoropolymer dispersion characterized by comprising a step of polymerizing a fluoromonomer to obtain an aqueous dispersion containing fluoropolymer particles in the presence of the above-mentioned composition.

The present invention is also an aqueous fluoropolymer dispersion obtained by the above-described production method.

The present invention is also a fluoropolymer fine powder obtained from the above-mentioned aqueous fluoropolymer dispersion.

The composition of this invention can be used conveniently for manufacture of a fluoropolymer. Since the method for producing an aqueous fluoropolymer dispersion of the present invention uses the above-mentioned composition, an aqueous fluoropolymer dispersion having excellent stability can be produced.

Hereinafter, the present invention will be specifically described.

The composition of the present invention is characterized by containing a perfluorinated saturated hydrocarbon and a fluorine-containing surfactant. In the composition of the present invention, the total fluorinated saturated hydrocarbon is uniformly dispersed in the fluorine-containing surfactant or water by the fluorine-containing surfactant. For this reason, it can utilize suitably for the method of superposing | polymerizing a fluoromonomer in an aqueous medium and manufacturing a fluoropolymer, and can obtain the stable aqueous dispersion, without impairing the performance of a polymer.

The fully fluorinated saturated hydrocarbon has an appropriate thermal decomposition temperature and has a carbon number of 10 to 20, preferably 12 to 20, and more preferably 16 to 20 from the viewpoint of excellent handleability. . Two or more perfluorinated saturated hydrocarbons having different carbon numbers may be used. Both branched and straight chain perfluorinated saturated hydrocarbons can be used, but a straight chain type in which two molecules of perfluoroiodide are coupled is preferably used.

The fully fluorinated saturated hydrocarbon is a chain saturated carbon represented by C _x F _{2x + 1} (wherein X is an integer of 10 to 20, and preferably 12, 14, 16, 18 or 20). It is preferably hydrogen, and more preferably at least one selected from the group consisting of perfluorohexadecane, perfluorooctadecane, and perfluoroicosane.

The fluorine-containing surfactant is preferably a fluorine-containing surfactant that is liquid at room temperature because it is easy to uniformly disperse the fully fluorinated saturated hydrocarbon in water. The fluorine-containing surfactant is preferably a fluorine-containing anionic surfactant, and a fluorine-containing surfactant having 4 to 7 carbon atoms is preferable. Among these, a fluorine-containing anionic surfactant having 4 to 7 carbon atoms is more preferable, and it contains an oxygen atom (for example, —CF ₂ —O—CF ₂ —) located between carbon atoms. It may be a fluorine anionic surfactant. Examples include a linear or branched perfluoroalkyl group having 4 to 7 carbon atoms, a linear or branched perfluoroalkyl group having an oxygen atom inserted between carbon atoms. And perfluoroalkyl ether carboxylic acids having 4 to 7 carbon atoms. Among these, perfluorohexanoic acid or a salt thereof is more preferable, and perfluorohexanoic acid, ammonium perfluorohexanoic acid, sodium perfluorohexanoic acid, or potassium perfluorohexanoic acid is particularly preferable. Particularly preferred is ammonium perfluorohexanoate.

The fluorine-containing surfactant is preferably 98 to 0.001% by mass, preferably 98 to 0.01% by mass of the composition because it is easy to uniformly disperse the fully fluorinated saturated hydrocarbon. More preferably, it is more preferably 50 to 0.1% by mass.

The mass ratio between the perfluorinated saturated hydrocarbon and the fluorine-containing surfactant is 100: 100 to 100: 0.01 because it is easy to uniformly disperse the perfluorinated saturated hydrocarbon. Preferably, it is more preferably 100: 10 to 100: 0.1.

The composition of the present invention preferably further contains water. Further, in addition to water, 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.

A method for producing a composition, which comprises obtaining a composition by dissolving a perfluorinated saturated hydrocarbon in a fluorine-containing surfactant, is also one aspect of the present invention. The composition of the present invention can be suitably produced by this production method. Perfluorinated saturated hydrocarbons may be dissolved in an aqueous solution of a fluorinated surfactant.

A method for producing an aqueous fluoropolymer dispersion comprising the step of polymerizing a fluoromonomer in the presence of the composition of the present invention to obtain an aqueous dispersion containing fluoropolymer particles is also one aspect of the present invention. .

The composition of the present invention is preferably added so that the fluorine-containing surfactant is in an amount of 0.0001 to 2% by mass relative to water, and a more preferable lower limit is 0.001% by mass, and more preferable. The upper limit is 0.5% by mass. If the amount of the composition is too small, the dispersion force tends to be insufficient. If the amount of the composition is too large, an effect commensurate with the amount added cannot be obtained, and the polymerization rate may be lowered or the reaction may be stopped. The amount of the composition added is appropriately determined depending on the type of the fluoromonomer used, the molecular weight of the target fluoropolymer, and the like.

The fluoromonomers include fluoroolefins, preferably fluoroolefins having 2 to 10 carbon atoms; cyclic fluorinated monomers; formula CY ² = CYOR ¹ or CY ² = CYOR ² OR ³ (Y is H Or F, R ¹ and R ³ are each an alkyl group having 1 to 8 carbon atoms in which part or all of the hydrogen atoms are substituted with fluorine atoms, and R ² is a 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.

More preferably, the fluoroolefin 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, cyclohexyl allyl ether, etc .; alkyl allyl ethers such as ethyl allyl ester, propyl allyl ester, butyl allyl ester, isobutyl allyl ester, cyclohexyl allyl ester, etc. 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, the polymerization reactor is charged with the composition and the fluoromonomer, the contents of the reactor are stirred, the reactor is maintained at a predetermined polymerization temperature, and then a polymerization initiator is added. , By starting the polymerization reaction. Prior to the start of the polymerization reaction, an aqueous medium, an additive, or the like may be charged into the reactor as necessary. After the polymerization reaction is started, a fluoromonomer, a polymerization initiator, a chain transfer agent, the above composition and the like may be additionally added depending on the purpose.

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.

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.

In the production method of the present invention, when at least one fluorine-containing surfactant contained in the composition is used as the surfactant, it is possible to efficiently produce a fluoropolymer. Further, in the production method of the present invention, any surfactant other than the fluorine-containing surfactant contained in the above composition may be used as long as it may remain in a volatile or molded article made of a fluoropolymer. Other compounds having surface-active ability may be used at the same time.

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, the polymerization temperature is generally 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 fluoropolymer dispersion containing 5-45% by mass of fluoropolymer particles having an average primary particle size 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 tetrafluoroethylene polymer [PTFE] polymer such as a TFE homopolymer, or (1) TFE and (2) having 2 to 8 carbon atoms. It may be a copolymer composed of one or two or more fluoromonomers 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.

The aqueous fluoropolymer dispersion obtained by the production method of the present invention may be concentrated or dispersion-stabilized after the above-described polymerization, or may be recovered by drying after being subjected to coagulation or agglomeration and drying. It is good also as a solid substance.

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 said dispersion stabilizer, you may add the said composition and other various surfactant. 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, polyoxyethylene isotridecyl ether (Neugen TDS80C (trade name) manufactured by Daiichi Kogyo Seiyaku, Leocor TD90D (trade name) manufactured by Lion, Genapol X080 (trade name) manufactured by Clariant )), But is not limited thereto.

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.

The aqueous dispersion obtained by carrying out the polymerization can also be prepared as a fluoropolymer 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 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 tetrafluoroethylene polymer [TFE 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 polymer as TFE / propylene copolymer, TFE / propylene copolymer Copolymer / third monomer copolymer (the third monomer is VDF, HFP, CTFE, perfluoro (alkyl vinyl ether), etc.), copolymer comprising TFE and perfluoro (alkyl vinyl ether); HFP / ethylene Copolymer, HFP / ethylene / TFE copolymer; PVDF; VDF / HFP copolymer, HFP Ethylene copolymer, thermoplastic elastomer 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 ⁵ (OCFQ ¹ CF ₂ ) _k1 (OCR ⁴ Q ² CF ₂ CF ₂ ) _{k 2} (OCF ₂ ) _{k 3} OCF = CF ₂
(In the formula, Rf ⁵ 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 TFE polymer is usually carried out at a polymerization temperature of 10 to 100 ° C. and a polymerization pressure of 0.05 to 5 MPaG.
In the polymerization, pure water and the above-described composition 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 this specification, the tetrafluoroethylene polymer [TFE 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 “modified”). It is also a concept including “PTFE”).
Various modified monomers can be used in combination in the production of the TFE polymer.

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 TFE 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 TFE 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 TFE polymer, as a dispersion stabilizer in the reaction system, a saturated hydrocarbon having 12 or more carbon atoms that is substantially inert to the reaction and becomes liquid under the reaction conditions (however, all fluorine 2) to 10 parts by mass with respect to 100 parts by mass of the aqueous medium. Moreover, you may add ammonium carbonate, an ammonium phosphate, etc. as a buffering agent for adjusting pH during reaction.

When the polymerization of the TFE 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, especially 0.3 μm or less by using the above-mentioned composition An aqueous dispersion having particles made of a TFE polymer having a fine particle size of 5 μm can be obtained. The TFE 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 TFE polymer obtained by the above polymerization is also stabilized by adding a nonionic surfactant, further concentrated, and as a composition with an organic or inorganic filler 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 aqueous dispersion of the TFE polymer or the fine powder described later is also preferably used as a processing aid. When used as a processing aid, mixing the aqueous dispersion or fine powder with a host polymer or the like improves the melt strength during the melting process of the host polymer and improves the mechanical strength, electrical properties, and difficulty of the resulting polymer. It is possible to improve the flammability, the dripping prevention property, and the sliding property.

The aqueous dispersion of the TFE polymer or the fine powder described below is also preferably used as a processing aid after being combined with a resin other than the TFE polymer. Examples of the aqueous dispersion or the fine powder include JP-A-11-49912, JP-A-2003-24693, US Pat. No. 5,804,654, JP-A-11-29679, and JP-A-2003-2980. It is suitable as a raw material for PTFE described in the publication. The processing aid using the aqueous dispersion or the fine powder is not inferior to the processing aids described in the above publications.

The aqueous dispersion of the TFE polymer is also preferably co-coagulated by mixing with an aqueous dispersion of a heat-melt processable fluororesin and coagulating. The co-coagulated powder is suitable as a processing aid.

Examples of the heat-melt processable fluororesin include FEP, PFA, ETFE, and ethylene / hexafluoropropylene / tetrafluoroethylene copolymer (EFEP), among which FEP is preferable.

The fluorine-free resin to which the co-coagulated powder is added may be a powder, a pellet, or an emulsion. The addition is preferably performed while applying a shearing force by a known method such as extrusion kneading or roll kneading in that each resin is sufficiently mixed.

The aqueous TFE polymer dispersion is also preferably used as a dust control agent. A method for suppressing dust from a dust generating material by fibrillating a TFE polymer by mixing the dust suppressing treatment agent with a dust generating material and subjecting the mixture to a compression-shearing action at a temperature of 20 to 200 ° C. For example, it can be used in methods such as Japanese Patent No. 2827152 and Japanese Patent No. 2538783.

The dust suppression treatment agent is suitably used for dust suppression treatment in the fields of building materials, soil stabilization materials, solidification materials, fertilizers, landfill disposal of incinerated ash and harmful substances, explosion-proof fields, cosmetics fields, and the like.

The aqueous dispersion of the TFE polymer is also preferably used as a raw material for obtaining TFE polymer fibers by a dispersion spinning method (Dispersion Spinning method). The dispersion spinning method includes mixing an aqueous dispersion of the TFE polymer and an aqueous dispersion of a matrix polymer, and extruding the mixture to form an intermediate fiber structure. The intermediate fiber structure Is a method of decomposing the matrix polymer and sintering the TFE polymer particles to obtain TFE polymer fibers.

High molecular weight PTFE can also be produced using the composition described above. The high molecular weight PTFE powder obtained by emulsion polymerization is also useful as a raw material for the PTFE porous body (membrane). For example, after extruding and rolling high molecular weight PTFE powder, it is unfired or semi-fired and stretched in at least one direction (preferably roll-stretched in the rolling direction and then stretched in the width direction by a tenter) to obtain a porous PTFE ( Film) can be obtained. By stretching, PTFE is easily fibrillated to form a porous PTFE body (membrane) composed of nodules and fibers.

This porous body (membrane) is useful as various filters, and can be preferably used as a chemical solution filter, particularly as an air filter medium.

Low molecular weight PTFE can also be polymerized using the composition described above.

Low molecular weight PTFE (also called PTFE micropowder) with a molecular weight of 600,000 or less has excellent chemical stability, extremely low surface energy, and is less prone to fibrillation, improving slipperiness and coating surface quality The additive to be used is suitable for the production of plastics, inks, cosmetics, paints, greases and the like (for example, see JP-A-10-147617).

Further, by dispersing the above composition as a polymerization initiator and an emulsifier in an aqueous medium in the presence of a chain transfer agent and polymerizing TFE or a monomer copolymerizable with TFE and TFE, low molecular weight PTFE is obtained. You may get

When low molecular weight PTFE obtained by emulsion polymerization is used as a powder, powder particles (micro powder) can be obtained by coagulating the aqueous dispersion.

An unfired tape (raw tape) can also be obtained from the PTFE fine powder obtained using the above composition.

(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 preferable 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 = (63 to 94) :( 27 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.

(4) An electrolyte polymer precursor can also be produced using the method for producing a fluoropolymer of the present invention. In the fluoropolymer production method of the present invention, the polymerization of the electrolyte polymer precursor is preferably performed at a polymerization temperature of 20 to 100 ° C. and a polymerization pressure of 0.3 to 2.0 MPaG. The electrolyte polymer precursor is composed of a vinyl ether monomer as shown below, and can be converted into an ion-exchangeable polymer through a hydrolysis treatment.

As the vinyl ether monomer used for the electrolyte polymer precursor,
^{_{CF 2 = CF-O- (CF}} 2 CFY 1 -O) n - (CFY 2) m -A
(Wherein Y ¹ represents a fluorine atom, a chlorine atom or a perfluoroalkyl group. N represents an integer of 0 to 3. The n Y ^{1 s} may be the same or different. Y ² represents a fluorine atom or a chlorine atom, m represents an integer of 1 to 5. m Y ² may be the same or different, and A represents —SO. ₂ represents X ¹ and / or —COZ ^1. X ¹ represents a halogen atom, and Z ¹ represents an alkoxyl group having 1 to 4 carbon atoms. A preferable monomer composition (mol%) of the electrolyte polymer precursor is TFE: vinyl ether = (50 to 93) :( 50 to 7).

The electrolyte polymer precursor may be modified with the third monomer within a range of 0 to 20% by mass of the total monomers. Examples of the third monomer include polyfunctional monomers such as CTFE, vinylidene fluoride, perfluoroalkyl vinyl ether, and divinylbenzene.

The electrolyte polymer precursor thus obtained can be used in a fuel cell or the like as a polymer electrolyte membrane after being formed into a film, for example, and then subjected to hydrolysis with an alkaline solution and treatment with a mineral acid.

(III) Elastomeric Polymer In the production method of the present invention, the polymerization of the elastomeric polymer is carried out by charging pure water and the above-described composition into a pressure-resistant reaction vessel equipped with a stirrer, and after deoxygenation, charging a monomer, And the polymerization initiator can be added to initiate the reaction. 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 a thermoplastic elastomer is produced, as disclosed in WO 00/01741, pamphlet is prepared by synthesizing fluoropolymer fine particles once in the presence of a high concentration of the above-described composition. By carrying out the polymerization, it is possible to use a method that can increase the final polymerization rate as compared with normal polymerization.

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. . PAVE 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) :( 30 to 48) :( 0 to 32). 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 converted into an aqueous dispersion suitable for rubber molding by adding or concentrating a dispersion stabilizer such as a hydrocarbon surfactant as 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.

The fluoromonomer is preferably tetrafluoroethylene, or tetrafluoroethylene and a modified monomer, and the fluoropolymer is preferably a non-melt processable TFE polymer.

An aqueous fluoropolymer dispersion obtained by the above-described production method is also one aspect of the present invention.

In the aqueous fluoropolymer dispersion of the present invention, fluoropolymer particles having an average primary particle diameter of 50 to 500 nm are dispersed in water in the presence of the above composition.

In the aqueous fluoropolymer dispersion of the present invention, the concentration of fluoropolymer particles is preferably 5 to 70% by mass, and more preferably 30 to 70% by mass.

The aqueous dispersion of the present invention usually contains an aqueous medium. Examples of the aqueous medium include those described above. In the aqueous dispersion of the present invention, the content of the fluorine-containing surfactant is preferably 0.0001 to 2% by mass relative to the mass of the aqueous medium. The more preferable lower limit of the content of the compound is 0.001% by mass, and the more preferable upper limit is 0.5% by mass.

The aqueous dispersion of the fluoropolymer of the present invention is contacted with an anion exchange resin in the presence of a nonionic surfactant, and the aqueous dispersion obtained in step (I) is added to the aqueous dispersion. A fluoropolymer aqueous solution that does not contain a fluorinated surfactant and is concentrated by a production method 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 dispersion can also be obtained. The process of making it contact with the said anion exchange resin can be performed by a conventionally well-known method. Moreover, the above-mentioned thing is mentioned as said concentration method. The production method of the present invention preferably includes, after the step (I), a step of separating the anion exchange resin and recovering an aqueous dispersion of the fluoropolymer.

A fine powder of a fluoropolymer obtained from the aqueous fluoropolymer dispersion of the present invention is also one aspect of the present invention. The fine powder of the fluoropolymer of the present invention can be obtained by coagulating the fluoropolymer from the above-mentioned aqueous fluoropolymer dispersion and further drying it if 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 is 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, 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 unfavorable effect on fine powder type TFE polymers. This is because particles of this type of TFE polymer easily fibrillate even with a small shearing force and lose 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 fluorine-containing surfactant is recovered by a recovery method comprising a step of recovering the fluorine-containing surfactant from waste water and / or gas generated in the step of producing the fine powder and a step of purifying the recovered fluorine-containing surfactant. It can also be recovered. The recovery and purification can be performed by a conventionally known method.

The use of the fluoropolymer obtained from the production method of the present invention is not particularly limited, and when used as an aqueous dispersion, it is applied by coating on a substrate and drying, followed by firing as necessary; non-woven fabric, Impregnation comprising impregnating and drying a porous support such as a resin molded article, preferably firing; applying onto a substrate such as glass and drying, and then immersing in water as necessary to remove the substrate Examples thereof include cast film formation comprising peeling and obtaining a thin film. Examples of these applications include aqueous dispersion 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.

When the fluoropolymer is a fine powder, it is preferable for molding. Examples of suitable applications of such fine powders include hydraulic and fuel tubes for aircraft and automobiles, flexible hoses such as chemicals and steam, and electric wire coating applications.

Next, the present invention will be described based on examples, but the present invention is not limited to such examples.

Each numerical value of the examples was measured by the following method.

(Polymer concentration)
1 g of the aqueous dispersion was dried in an air dryer at 300 ° C. for 30 minutes, and the ratio of the mass of the heated residue to the mass of the aqueous dispersion (1 g) was expressed as a percentage.

(Polymer aggregation amount)
After completion of the polymerization reaction, the aqueous dispersion is filtered through a 200-mesh SUS net, then the aqueous dispersion aggregate remaining on the SUS net, the polymer aggregate remaining in the reaction vessel, and the polymer adhering to the stirring blade and baffle Aggregates were collected and dried in an air dryer at 300 ° C. for 1 hour, and then the weight was measured to determine the polymer agglomeration amount. If the particle stabilization effect of the emulsifier is high, the amount of polymer agglomeration decreases even in a region where the polymer concentration is high.

(Average primary particle size)
Based on a calibration curve between the transmittance of 550 nm projection light per unit length and the average primary particle diameter determined by an electron micrograph, with the solid content concentration diluted to about 0.02% by mass, the above transmittance Indirectly asked from.

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

Example 1
0.005 g (50 ppm) of powdery perfluorohexadecane was added to 100 g of a 5% aqueous solution of ammonium perfluorohexanoate, and the mixture was stirred with a stirrer at room temperature of 25 ° C. The obtained aqueous solution had a transparent and uniform appearance.

Example 2
0.005 g (50 ppm) of powdered perfluorododecane was added to 100 g of a 5% aqueous solution of ammonium perfluorohexanoate, and the mixture was stirred with a stirrer at room temperature of 25 ° C. The obtained aqueous solution had a transparent and uniform appearance.

Example 3
To 100 g of a 50% aqueous solution of ammonium perfluorohexanoate, 0.01 g (100 ppm) of powdered perfluorohexadecane was added and stirred with a stirrer at room temperature of 25 ° C. The obtained aqueous solution had a transparent and uniform appearance.

Example 4
1 g of powdery perfluorohexadecane was added to 99 g of perfluorohexanoic acid and stirred with a stirrer. A homogeneous solution was obtained. Further, when water was added to 0.5 g of this mixture and the total amount was adjusted to 100 g while adjusting the pH to 7 with 0.1N ammonia water, an aqueous solution having a transparent and uniform appearance was obtained.
When the surface tension of this aqueous solution at 25 ° C. was measured by the Wilmhelmy method (platinum plate method) using a surface tension meter manufactured by Kyowa Interface Science Co., Ltd., it was 36 mN / m. As a comparison, it can be seen that the surface tension of a 0.5% aqueous solution of ammonium perfluorohexanoate is 49 mN / m, and the surface tension of an aqueous solution containing perfluorohexadecane is reduced.

Example 5
(1) Preparation of aqueous dispersion In a glass pressure-resistant vessel equipped with a stirring blade having an internal volume of 1 L, an aqueous solution in which 2.25 g of ammonium perfluorohexanoate and 0.5 mg of perfluorohexadecane are dissolved in 500 mL of deionized water is placed. Then, 15 g of paraffin wax (melting point: 60 ° C.), nitrogen injection and depressurization were repeated three times to remove oxygen in the pressure vessel, and the inside of the vessel was further replaced with tetrafluoroethylene [TFE] monomer.
Next, at 70 ° C., TFE monomer was injected so that the internal pressure became 0.8 MPa, and 5 g of 0.05% by mass ammonium persulfate [APS] aqueous solution was charged, and the reaction was started. As the reaction progressed, the pressure in the system decreased, so TFE was continuously added to maintain the internal pressure at 0.8 MPa.
The inside of the vessel during the reaction was visually observed. Since adhesion occurred on the stirring blade after 4 hours, the stirring was stopped, the TFE monomer was depressurized, the reaction was stopped, and an aqueous PTFE dispersion was obtained.
The obtained PTFE aqueous dispersion had a polymer concentration of 21% by mass, an amount of polymer aggregation of 1.5 g, and an average primary particle size of 320 nm.

(2) Preparation of PTFE fine powder The aqueous dispersion obtained was diluted with deionized water so that the polymer concentration was 10%, and then coagulated by stirring at 20 ° C. The obtained coagulated particles were collected, washed twice with 10 times the amount of water, and further dried at 160 ° C. for 16 hours to obtain PTFE fine powder.
The obtained PTFE fine powder had an SSG of 2.158.

Claims (8)

A composition used in a step of polymerizing a fluoromonomer (excluding a liquid fluorinated monomer having a curing site) to obtain an aqueous dispersion containing fluoropolymer particles,
A composition comprising a perfluorinated saturated hydrocarbon having 10 to 20 carbon atoms and a fluorine-containing anionic surfactant having 4 to 7 carbon atoms. The composition according to claim 1, wherein the perfluorinated saturated hydrocarbon has 12 to 20 carbon atoms. Furthermore, the composition of Claim 1 or 2 containing water. The composition according to claim 1, 2 or 3, wherein the fluorine-containing surfactant is 98 to 0.001% by mass of the composition. The composition according to claim 1, 2, 3, or 4, wherein the mass ratio of the perfluorinated saturated hydrocarbon to the fluorine-containing surfactant is 100: 100 to 100: 0.01. A method for producing a composition according to claim 1, 2, 3, 4 or 5,
A production method comprising obtaining a composition by dissolving a perfluorinated saturated hydrocarbon in a fluorine-containing surfactant. 6. An aqueous dispersion comprising fluoropolymer particles obtained by polymerizing a fluoromonomer (excluding a liquid fluorinated monomer having a curing site ) in the presence of the composition according to claim 1, 2, 3, 4, or 5 . A process for producing an aqueous fluoropolymer dispersion, comprising the step of: A fluoropolymer aqueous dispersion obtained by the production method according to claim 7.