MIXTURE OF POLYFLUOROALKENE CARBOXYLIC ACIDS OR SALTS THEREOF AND PROCESS FOR PRODUCING THE SAME

Abstract

A mixture of polyfluoroalkene carboxylic acids or salts thereof represented by the general formulas:

C.sub.nF.sub.2n+1CH═CF(CF.sub.2CF.sub.2).sub.mCF.sub.2COOM

and

C.sub.n−1F.sub.2n−1CF═CHCF.sub.2(CF.sub.2CF.sub.2).sub.mCF.sub.2COOM

wherein M is a hydrogen atom, an ammonium salt, an organic amine salt or an alkali metal, n is an integer of 1 to 6 and m is an integer of 0 to 2. The mixture of polyfluoroalkene carboxylic acids or salts thereof is produced by subjecting a polyfluoroalkane carboxylic acids represented by the general formula:

C.sub.nF.sub.2n+1(CH.sub.2CF.sub.2)(CF.sub.2CF.sub.2).sub.mCF.sub.2COOH

to a dehydrofluorination reaction in the presence of a nitrogen-containing heterocyclic compound catalyst, and has a lower critical micelle concentration and less surface tension at that time, therefore, the mixture of polyfluoroalkene carboxylic acids or salts thereof can be effectively used as a surfactant in the polymerization of fluorine-containing monomers.

Claims

1. A mixture of polyfluoroalkene carboxylic acids or salts thereof represented by the general formulas:
C.sub.nF.sub.2n+1 CH═CF(CF.sub.2CF.sub.2).sub.mCF.sub.2COOM
and
C.sub.n−1F.sub.2n−1CF═CHCF.sub.2(CF.sub.2CF.sub.2).sub.mCF.sub.2COOM wherein M is a hydrogen atom, an ammonium salt, an organic amine salt or an alkali metal, n is an integer of 1 to 6 and m is an integer of 0 to 2.

2. The mixture of polyfluoroalkene carboxylic acids or salts thereof according to claim 1, wherein the mixture is used as an emulsifying agent in an emulsion polymerization reaction of a fluorine-containing monomer, or as an emulsifying agent or a dispersing agent in a suspension polymerization reaction of a fluorine-containing monomer.

3. A process for producing a mixture of polyfluoroalkene carboxylic acids represented by the general formulas:
C.sub.nF.sub.2n+1CH═CF(CF.sub.2CF.sub.2).sub.mCF.sub.2COOH
and
C.sub.n−1F.sub.2n−1CF═CHCF.sub.2(CF.sub.2CF.sub.2).sub.mCF.sub.2COOH wherein n is an integer of 1 to 6 and m is an integer of 0 to 2, which comprises subjecting a polyfluoroalkane carboxylic acids represented by the general formula:
C.sub.nF.sub.2n+1(CH.sub.2CF.sub.2)(CF.sub.2CF.sub.2).sub.mCF.sub.2COOH wherein n is an integer of 1 to 6 and m is an integer of 0 to 2, to a dehydrofluorination reaction in the presence of a nitrogen-containing heterocyclic compound catalyst.

4. The process for producing a mixture of polyfluoroalkene carboxylic acids according to claim 3, wherein the nitrogen-containing heterocyclic compound used as a catalyst is 1,8-diazabicyclo[5.4.0]undecene-7 or 1,5-diazabicyclo[4.3.0]nonene-5.

5. A process for producing a mixture of polyfluoroalkene carboxylic acid salts, which comprises reacting a mixture of polyfluoroalkene carboxylic acids obtained by the production process according to claim 3 with an ammonia, an organic amine or an alkali metal hydroxide.

Description

EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0015] The polyfluoroalkene carboxylic acids (salts) mixture is produced by subjecting the polyfluoroalkane carboxylic acids disclosed in Patent Document 1, which is represented by the formula:

C.sub.nF.sub.2n+1(CH.sub.2CF.sub.2)(CF.sub.2CF.sub.2).sub.mCF.sub.2COOH

[0016] n: 1 to 6

[0017] m: 0 to 2

to a dehydrofluorination reaction in the presence of a nitrogen-containing heterocyclic compound catalyst, such as 1,8-diazabicyclo[5.4.0]undecene-7 [DBU] or 1,5-diazabicyclo[4.3.0]nonene-5 [DBN]. These salts are produced as an ammonium salt, an organic amine salt or an alkali metal salt by a standard method in which free carboxylic acid is reacted with an ammonia, an organic amine or an alkali metal hydroxide.

[0018] This reaction smoothly proceeds only in the presence of a nitrogen-containing heterocyclic compound catalyst. If a tertiary amine, such as triethylamine, is used in place of the nitrogen-containing heterocyclic compound catalyst, the dehydrofluorination reaction does not proceed. Moreover, if the reaction is performed using KOH, as described in Patent Document 2, as a catalyst in place of the nitrogen-containing heterocyclic compound, complicated side reactions occur in the terminal carboxylic acid moiety, and the desired dehydrofluorination product cannot be obtained. The nitrogen-containing heterocyclic compound is generally used at a ratio of 1 to 5 moles, preferably 1.5 to slightly over 2.5 moles, per mole of the raw material polyfluoroalkane carboxylic acid. The dehydrofluorination reaction is performed at room temperature.

[0019] The dehydrofluorination reaction product comprises a mixture of

C.sub.nF.sub.2n+1CH═CF(CF.sub.2CF.sub.2).sub.mCF.sub.2COOH

and

C.sub.n−1F.sub.2n−1CF═CHCF.sub.2(CF.sub.2CF.sub.2).sub.mCF.sub.2COOH

[C.sub.n−1F.sub.2n−1CF═CH(CF.sub.2CF.sub.2).sub.m+1COOH].

Here, the reason that polyfluoroalkene carboxylic acids are formed as a mixture is because in the dehydrofluorination reaction, the abstraction of the H atom of the methylene chain CH.sub.2 and the F atom of either one of the fluoromethylene groups CF.sub.2 linking back and forth to the H atom occurs equally in the anterior-posterior position. Since it is a mixture of extremely similar structural isomers, they cannot be separated from each other; however, they have equivalent reactivity, and thus, the mixture can be directly used as a raw material for the synthesis of other substances.

[0020] The mixture of polyfluoroalkene carboxylic acid salts according to the present invention can be used as a suitable emulsifying agent for the emulsion polymerization reaction of fluorine-containing monomers, or as a suitable emulsifying agent or dispersing agent for the suspension polymerization reaction thereof. The fluorine-containing monomers for the emulsion polymerization or suspension polymerization in the presence of the surfactant include, for example, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethyl ene, trifluoroethyl ene, vinyl fluoride, perfluoro(alkyl vinyl ether) having an alkyl group having 1 to 3 carbon atoms, etc. One or two or more kinds of these fluorine-containing monomers can be used in the polymerization reaction to form homopolymers or copolymers. The fluorine-containing monomers can be used to form copolymers with fluorine-free monomers, for example, propylene, ethylene, etc.

[0021] In the polymerization reaction, the surfactant can be used as an emulsifying agent for the emulsion polymerization reaction, or as an emulsifying agent or a dispersing agent for the suspension polymerization, in a proportion of about 0.05 to 5% by weight, preferably about 0.2 to 1% by weight, on the basis of water or an aqueous medium containing water-soluble alcohol, etc. The polymerization reaction can be carried out preferably in the presence of a water-soluble polymerization initiator, or a redox-based polymerization initiator formed therewith. The resulting reaction mixture can be coagulated with an aqueous solution of metal salt, followed by water washing and drying to obtain desired homopolymers or copolymers of fluorine-containing monomers.

EXAMPLES

[0022] The following describes the present invention with reference to Examples.

Reference Example 1

Synthesis Example of a Raw Material Substance

[0023] 600 g of CF.sub.3(CF.sub.2).sub.3(CH.sub.2CF.sub.2)I [C.sub.6F.sub.11H.sub.2I] (purity: 99.5%) was charged into an autoclave having a capacity of 1,200 ml, and heated to an inside temperature of 50° C. Then, 1.35 g of a peroxide-based initiator (Percadox 16, a product of Kayaku-Akuzo Co.) dissolved in 300 g of C.sub.6F.sub.11H.sub.2I was added thereto. When the inside temperature reached 55° C., tetrafluoroethylene was portionwise-added thereto, while keeping the pressure at 0.2-0.3 MPa. When the portionwise-addition amount reached to 150 g, aging was carried out at 55°-74° C. for one hour to complete the reaction. After the completion of the reaction, cooling was conducted to recover 1010 g of a product as a mixture.

[0024] Analytical results of the obtained product by gas chromatography (GC) are given in the following Table as GC % of a compound represented by the following general formula having various values of n and 1, where the remaining 1.7GC% shows impurities of unidentified structures :

C.sub.nF.sub.2n+1(CH.sub.2CF.sub.2)(CF.sub.2CF.sub.2).sub.1I

TABLE-US-00001 TABLE n 1 Raw material Product 4 0 99.5 44.7 4 1 37.1 4 2 12.0 4 3 3.5 4 4 0.8 4 5 0.2

[0025] Among the afore-mentioned reaction mixture (product), a compound (n=4 and l=2) was isolated by distillation (boiling point 85° C./3 kPa) therefrom and used as a raw material substance in Reference Example 2.

Reference Example 2

[0026] 94.4 g of CF.sub.3(CF.sub.2).sub.3(CH.sub.2CF.sub.2)(CF.sub.2CF.sub.2).sub.2I (purity: 97.0%) melted in an oven at 60° C. was charged in a glass reactor having a capacity of 500 ml, and stirred at 50° C. Then, 170.0 g of 60% fuming sulfuric acid (SO.sub.3 equivalent ratio relative to raw material compound: 8.4) was added dropwise from a dropping funnel, and the mixture was then heated to 60° C. and reacted for about 69 hours. After completion of the reaction, the reaction mixture was cooled and left to stand to separate an organic phase containing carboxylic acid fluoride as the major portion from an inorganic phase containing fuming sulfuric acid as the major portion. A carboxylic acid fluoride CF.sub.3(CF.sub.2).sub.3(CH.sub.2CF.sub.2)(CF.sub.2CF.sub.2)CF.sub.2COF phase (55.69 g (yield: 72.3%)) was obtained in the upper layer.

[0027] Carboxylic acid CF.sub.3(CF.sub.2).sub.3(CH.sub.2CF.sub.2)(CF.sub.2CF.sub.2)CF.sub.2COOH was quantitatively obtained by adding water to the carboxylic acid fluoride, followed by stirring. The surface tension of the compound was measured at each concentration at ordinary temperature using a maximum bubble pressure method. As a result, the critical micelle concentration [CMC] was 0.51 wt. %, and the surface tension at that time was 20.0 mN/m.

Example 1

[0028] 2.86 g (6.0 mmol) of CF.sub.3(CF.sub.2).sub.3(CH.sub.2CF.sub.2)(CF.sub.2CF.sub.2)CF.sub.2COOH was added and dissolved in 25 ml of diethyl ether in a screw tube in which a 50-ml stirrer was equipped. Then, 1.94 g (12.7 mmol) of 1,8-diazabicyclo[5.4.0]undecene-7 [DBU] was added thereto, and the mixture was stirred at room temperature. The reaction was tracked by .sup.1H-NMIR and .sup.19F-NMR, and it was confirmed that almost all of the raw material compounds was consumed after 88 hours. Then, the reaction was terminated.

[0029] After 1 M hydrochloric acid was added to the reaction mixture for quenching, washing with water and 1 M hydrochloric acid was performed, and the organic phase was dried over anhydrous magnesium sulfate. The drying agent was filtered off, and the solvent was removed, thereby obtaining 1.32 g (yield: 48%) of brown viscous liquid.

[0030] The results of .sup.1H-NMR and .sup.19F-NMR of the mixture revealed that the brown viscous liquid was a mixture of dehydrofluorination products of CF.sub.3(CF.sub.2).sub.3(CH.sub.2CF.sub.2)(CF.sub.2CF.sub.2)CF.sub.2COOH (n=4, m=1). CF.sub.3(CF.sub.2).sub.3CH═CF(CF.sub.2CF.sub.2)CF.sub.2COOH CF.sub.3(CF.sub.2).sub.2CF═CHCF.sub.2(CF.sub.2CF.sub.2)CF.sub.2COOH

[0031] .sup.1H-NMIR [(CD.sub.3).sub.2CO,TMS] [0032] δ(ppm): 6.88(CF.sub.3CF.sub.2CF.sub.2CF.sub.2CH═CFCF.sub.2CF.sub.2CF.sub.2COOH) (CF.sub.3CF.sub.2CF.sub.2CF═CHCF.sub.2CF.sub.2CF.sub.2CF.sub.2COOH)

[0033] .sup.19F-NMR [(CD.sub.3).sub.2CO,C.sub.6F.sub.6] [0034] δ(ppm): −126.8(CF.sub.3CF.sub.2CF.sub.2CF═CHCF.sub.2CF.sub.2CF.sub.2CF.sub.2COOH) [0035] −124.9(CF.sub.3CF.sub.2CF.sub.2CF.sub.2CH═CFCF.sub.2CF.sub.2CF.sub.2COOH) [0036] −123.3(CF.sub.3CF.sub.2CF.sub.2CF.sub.2CH═CFCF.sub.2CF.sub.2CF.sub.2COOH) [0037] −122. 6(CF.sub.3CF.sub.2CF.sub.2CF═CHCF.sub.2CF.sub.2CF.sub.2CF.sub.2COOH) [0038] −121.6(CF.sub.3CF.sub.2CF.sub.2CF═CHCF.sub.2CF.sub.2CF.sub.2CF.sub.2COOH) [0039] −118.4(CF.sub.3CF.sub.2CF.sub.2CF═CHCF.sub.2CF.sub.2CF.sub.2CF.sub.2COOH) [0040] −117.9(CF.sub.3CF.sub.2CF.sub.2CF═CHCF.sub.2CF.sub.2CF.sub.2CF.sub.2COOH) [0041] −117.7(CF.sub.3CF.sub.2CF.sub.2CF.sub.2CH═CFCF.sub.2CF.sub.2CF.sub.2COOH) [0042] −117.3(CF.sub.3CF.sub.2CF.sub.2CF.sub.2CH═CFCF.sub.2CF.sub.2CF.sub.2COOH) [0043] −111.5(CF.sub.3CF.sub.2CF.sub.2CF═CHCF.sub.2CF.sub.2CF.sub.2CF.sub.2COOH) [0044] −109.9(CF.sub.3CF.sub.2CF.sub.2CF.sub.2CH═CFCF.sub.2CF.sub.2CF.sub.2COOH) [0045] −108.4(CF.sub.3CF.sub.2CF.sub.2CF.sub.2CH═CFCF.sub.2CF.sub.2CF.sub.2COOH) (CF.sub.3CF.sub.2CF.sub.2CF═CHCF.sub.2CF.sub.2CF.sub.2CF.sub.2COOH) [0046] −80.2(CF.sub.3CF.sub.2CF.sub.2CF.sub.2CH═CFCF.sub.2CF.sub.2CF.sub.2COOH) [0047] −79. 9(CF.sub.3CF.sub.2CF.sub.2CF═CHCF.sub.2CF.sub.2CF.sub.2CF.sub.2COOH)

Example 2

[0048] 1.4 wt. % of aqueous ammonia was added to the dehydrofluorinated carboxylic acid mixture obtained in Example 1, and the resulting mixture was stirred, thereby quantitatively obtaining a carboxylic acid ammonium salts mixture.

CF.sub.3(CF.sub.2).sub.3CH═CF(CF.sub.2CF.sub.2)CF.sub.2COONH.sub.4

CF.sub.3(CF.sub.2).sub.2CF═CHCF.sub.2(CF.sub.2CF.sub.2)CF.sub.2COONH.sub.4

[0049] The surface tension of the carboxylic acid ammonium salts mixture was measured at each concentration at ordinary temperature using a maximum bubble pressure method. As a result, the critical micelle concentration [CMC] was 0.31 wt. %, and the surface tension at that time was 18.2 mN/m.

[0050] These values are better than the measurement results of perfluorooctanoic acid ammonium under the same conditions (CMC: 0.48 wt. %, surface tension: 20.0 mN/m).

Comparative Example 1

[0051] In Example 1, the reaction was performed using 0.71 g (12.7 mmol) of KOH in place of DBU, and 40 ml of methanol in place of diethyl ether. As a result, complicated side reactions occurred in the terminal carboxylic acid moiety, and the dehydrofluorination products shown in Example 1 were not obtained.

Comparative Example 2

[0052] In Example 1, the reaction was performed under reflux conditions for 96 hours using 1.21 g (4.0 mmol) of triethylamine in place of DBU; however, the reaction did not proceed, and the dehydrofluorination products shown in Example 1 were not obtained.

Example 3

[0053] The following components were charged in a stainless steel pressure reactor having a capacity of 10 L and equipped with a stirrer.

TABLE-US-00002 Carboxylic acid ammonium salts mixture obtained in 20 g Example 2 Na.sub.2HPO.sub.4•12H.sub.2O (buffer) 20 g Ethyl malonate (chain transfer agent) 2.6 g Ion exchanged water 5,100 g
Nitrogen substitution was performed to remove oxygen from the reactor. Thereafter, 120 g of hexafluoropropylene [HFP] and 351 g of a vinylidene fluoride [VdF]/tetrafluoroethylene [TFE] mixed gas (VdF/TFE molar ratio: 57.8/42.2) were introduced, and the internal temperature of the reactor was raised to 80° C. The internal pressure of the reactor when the temperature reached 80° C. was 2.14 MPa.Math.G.

[0054] After the stability of the internal temperature of the reactor was confirmed, 100 g of aqueous solution in which 0.48 g of ammonium persulfate was dissolved was introduced into the reactor as a polymerization initiator, and the polymerization reaction was initiated. When the polymerization reaction proceeded and the internal pressure of the reactor reached 1.75 MPa.Math.G, a VdF/TFE/HFP (molar ratio: 54.4/39.7/5.9) mixed gas was introduced, and the pressure was raised to 1.85 MPa.Math.G. During the polymerization reaction, the three-component mixed gas having this composition was introduced to thereby maintain the reaction pressure in a range of 1.75 to 1.85 MPa.Math.G.

[0055] When the total amount of the three-component mixed gas added in batches reached 1,680 g, the introduction of the mixed gas was stopped. When the internal pressure of the reactor reached 1.75 MPa.Math.G, the reactor was cooled to terminate the polymerization reaction. It took 240 minutes from the supply of the polymerization initiator to the termination of the polymerization reaction, and 6,400 g of fluorine-containing polymer latex was obtained.

[0056] The obtained fluorine-containing polymer latex was placed in the same amount of 1 wt. % CaCl.sub.2 aqueous solution, and the latex was coagulated by salting out. Then, filtration, washing 5 times with 5-fold amount of ion exchanged water, and vacuum drying were performed, and 1,540 g of resin-like VdF/TFE/HFP terpolymer copolymer was obtained.

[0057] The copolymerization composition (measured by .sup.19F-NMR) of the resin-like terpolymer was VdF/TFE/HFP=55.1/40.8/4.1 (molar ratio), and the weight average molecular weight Mw (measured by GPC) thereof was about 5.8×10.sup.5.

[0058] Moreover, the amount of the emulsifying agent remaining in the terpolymer was measured in the following manner.

[0059] The emulsifying agent in the terpolymer powder was soxhlet-extracted with an ethanol/water (volume ratio: 95/5) mixed solution, and the obtained extract was measured by LC-MS/MS under the following conditions. As a result, the amount of the remaining emulsifying agent was 17.0 ppm. [0060] LC-MS/MS measurement: using a system comprising the LC-20A prominence series (produced by Shimadzu Corporation) and 4000Q TRAP (produced by Applied Biosystems Japan) [0061] Column: using Mightysil RP-18(L) GP100-20 (5 μm, produced by Kanto Chemical Co., Inc.) [0062] Mobile phase: using gradient of two solutions: (A) 5 mmol/L ammonium acetate aqueous solution and (B) acetonitrile

[0063] Further, in order to evaluate the stability of the fluorine-containing polymer latex, the amount of aggregates (PHL) in the latex after the polymerization reaction was measured. The measurement was performed by filtering about 1 kg of latex through a 300-mesh filter, and measuring the filtration residue. PHL was calculated by the following formula, and a value of 0.0034 PHL was obtained.

PHL=filtration residue (g)×100/amount of filtration latex (g)