DE2319078C3 - Process for the production of practically fluoride-free perfluoroalkane sulfonates - Google Patents

Description

When using calcium compounds in systems, the solubility of the sulfonate in the reactive

Form of calcium oxide or hydroxide, with the medium arbitrary within appropriate limits

naturally no foreign anions can be increased in the reaction mixture, so that the separation of the

reach is always possible by binding one mole of fluoride-calcium fluoride. This is especially true

anion as a sparingly soluble calcium fluoride each a 5 for longer-chain perfluoroalkanesulfonates, which with

Hydroxide ion equivalent for the further saponification of increasing chain length, reduced solubility in

made available. Have the equivalent ratio of water, even at higher temperatures.

The primary base to calcium hydroxide must therefore not be based on the following examples

greater than lbe. However, a method according to the invention will be explained in greater detail in the case of a precisely one method

Maintained equivalent ratio of 1 only rarely becomes an io:
optimal Entfluoridierung achieved, so that mostly a

Excess corresponding to an equivalent ratio B is ο ie 1 1
Primary base to calcium compound less than 1 necessary

is agile. The optimal ratio must be because of the potassium perfluorobutanesulfonate

different purities of the reac- 15

aunts, especially of the perfluoroalkanesulfonyl fluoride, 1201 noble water or mother liquor were in one

can be determined empirically. 2501 stirred kettle pumped and stirring

The sulfonyl fluoride is, e.g. via adjustable 12.6 kg (0.2 K-MoI 100% KOH) potassium hydroxide

DosierjMimpen, in the reaction kettle to the pre- and 6.5 kg (0.105 K-MoI 100% CaO)

added solution of appropriate bases with an ao calcium oxide. The boiler was well

dosed at such a rate that just closed and to a temperature between 85 and

there is a small reflux. The reaction 9O brought ^0C. Then perfluorobutane

speed is naturally also of the appasulfonyl fluoride with a speed of 1 to

depending on the circumstances, in particular also 1.5 kg per hour by pouring into the presented liquid

of the intensity of the mixing, so that the as speed protruding feed pipe is metered in, so that

The rate of addition of the sulfonyl fluoride resulted in as little reflux as possible. After

empirically, in accordance with the other parameters about 55 kg C ₄ F ₉ SO ₂ F (based on 100% product)

the reaction, about the reaction temperature, were added, the pH of the reaction

Is found. The optimal reaction temperature solution is continuously checked and added as long as

is preferably in the range between 20 and 100 ⁰ C, is 30 until the pH was about 7.5. The overall

but not restricted to this temperature range. Consumption of 100% sulfonyl fluoride was 58.8 kg

and can accept any value between 0 and 250 ° C (0.198 K-MoI C ₄ F ₉ SO ₂ F). The boiler content was

to take. then via a hot filter press at 90 ⁰ C of CaF ₂

The addition of the calcium compound can be filtered off and purified with mother liquor

before, during and after the hydrolysis reaction 35 stirred kettles are pumped back for crystallization. at

be added to the mixture. The Calciumverbin- 20 ⁰ C, the resulting crystal slurry was cold-filtered,

The moist cake still contains on average

Hydrolysis added to the reaction mixture. Surprisingly about 5 to 20% water, which is at 110 ⁰ C or im

calcium fluoride precipitates are formed here in a vacuum drying cabinet at a lower temperature.

that can be removed without difficulty with the help of common 40. A white powder remains

Filtration process can be filtered. high purity potassium perfluorobutane sulfonate.

The separation conditions of the in water or
Aqueous-organic systems sparingly soluble fluo- content of inorganic fluoride 0.0006% F-

rids of the respective perfluoroalkanesulfonic acid salt <~ «.t,« u., "r ^ i": "™ η ro" /

... · ν · * τ · lj τ ·. ι · 11 · Calcium content U ₁ O / / ₀

are based primarily on the Loshchkeit- 45 ^, ...

behavior of the sulfonate and may need potassium analysis

can be determined empirically. Generally found happens 11.5 / ₀

the separation simply by filtration of the calcium calculated 11.3 Λ

fluoride at the temperature at which the sulfonate

is readily soluble. The sulfonate is isolated at 5 ° yield: 64.2 kg of C ₄ F ₉ SO ₃ ^- K ⁺ , which then corresponds to 96% as a result of subsequent crystallization at lower levels of theory; Solubility product for CaF ₂ = 3.4 · temperatures or by evaporation of the solution 10 "» (18 ° C).
by means of. Since the mother liquor can be used again and again, example 2 is in the case of crystallization
for the success of the separation only the temperature 55

Temperature coefficient of the solubility of the sulfonate of potassium trifluoromethanesulfonate
dcutung, which must be sufficiently large without

here the residual solubility of the sulfonate in the one with reflux condenser, thermometer and

Crystallization temperature plays a major role. 10-1 flasks fitted with the gas inlet tube

In addition to water, the following organic 60 10 mol (56 g) potassium hydroxide and 5 mol (280 g)

Solvent - mixed with water - for the calcium oxide and 41 distilled water

Processes according to the invention are used: Me and 9.2 mol (1400 g) of trifluoromethanesulfonyl fluoride

Ethanol, ethanol, dimethylformamide or dimethyl introduced at such a rate that in

sulfoxide. the dry condenser connected to the reflux condenser

The process according to the invention yields no reflux even in an ice cooler. The

those cases where sparingly soluble sulfonates pre- reaction mixture warmed to 60 ° C and became

are satisfactory results in that they are half an hour after the end of the reaction

stirred by the transition from the aqueous to aqueous-organic 90 ⁰ C. After cooling down to room

5 6

temperature, the precipitated calcium fluoride was ^{dried at 60 °} C. in vacuo Yield 291 g of C ₈ F ₁₇ -

Filtered through a suction filter and the clear filtrate on SO ₃ K, which corresponds to 91% of theory.

Rotary evaporator concentrated and in vacuo. Analysis:

₅ 0.008%> inorganic fluoride,

Inorganic fluoride content 0.005% F '"0.01% calcium,

Calcium content 0.05% solubility product for CaF. = 3.8 x 10- «(20 ° C).

Potassium content

found 20.8% Example 4

calculated 20.8% to _._,, _ ,,

'° Ethylammonium perfluorooctanesulfonate

Αμ ^^ Λ ^ Ϊ ', μ _: corresponds to l04gC ₈ F ₁₇ SO _i F96% ig (0 ₎ 2MollOO% ig), 5.85gCaO

α Z ° J? ? r ± _ ^ ¹ ^, ES Losl'chkeitspro- _{(01 Mo} , _{100% Cll0) and 800} ml of water were

product for Cafr ₂ - 3.4 -10 "(18 C). placed in a reaction vessel and stirred

Example 3 15 20.2 (0.2 mol) of triethylamine added dropwise at 25 ° C

".. _,. the heating to 70 ⁰ C was still 1 hour after

Kahumperfluorooctansulfonat _{8srQbn md hot-filtered} . _{The filtrate} ^ fc

To a mixture consisting of 39.6 g (0.6 mol ßend concentrated to about half of its volume

100% KOH) potassium hydroxide, 18.7 g (0.3 mol and after cooling to 15 ° C from the precipitated

100% CaO) calcium oxide, 500ml ethyl alcohol ao which [C ₈ F ₁ , SO ₃ JI (CjHs) ₃ NH] ⁺ filtered off.

and 500 ml of distilled water were added at 70 ° C under weight of the filter cake after drying

Stirring 312 g (0.6 mol of 100% C ₈ F ₁₇ SOjF) perfluorine at 6O ⁰ C in a vacuum of 104 g, which corresponds to an

octanesulfonyl fluoride was added dropwise. At the end of the reac- yield of 87% of theory,

tion, the pH showed a value of 7.0. The reaction analysis:

The mixture is made _{from a 5 0> 01} ^{at 70 0} C via a glass frit. _{/ o} inorganic fluoride,

fallen CaF _t filtered off and half of the semes O 08%> calcium

Concentrated in volume by distillation. Who out in the cold ''

Any precipitate is filtered off with suction and when the solubility product for CaF ₂ = 3.4 · 10 ^-11 (18 ° C.).

Claims (1)

L nischea impurities some properties of Claim: Polycarbonates strongly negative. For the production of high-purity perfluoroalkanesulfone Process for the preparation of practically fluoric acid salts, it was also necessary, either by free perfluoroalkanesulfonates, starting from 5 extraction, a separation of the _{fluoride formed in the hydro-perfluoroalkanesulfonic acids RfSO 3} H, with Rf lysis inevitably to achieve fluoride, for a straight-chain or branched one Perfluoro or to go the detour via the free acid, alkane radical with 1 to 10 carbon atoms is, by al- whereby first the unpurified crude perfluoroalkankalic hydrolysis of the corresponding perfluorosulfonic acid salt with concentrated sulfuric acid alkanesulfonyl fluoride, thereby marked io distillative in the free sulfonic acid is converted, which shows that the inorganic base, which is formed in the hydrolysis of the inorganic base formed by neutralization with the ent-perfluoroalkanesulfonyl fluoride, is given the desired pure perfluoroalkane fluoride by adding sparingly soluble sulfonate. Apart from the inefficiency of fluoride-forming cations, whose sparingly soluble one of such a synthetic detour is the production of fluorine compounds in the solvent 15 perfluoroalkanesulfonic acids from ^{sulfonate contaminated with inorganic fluoro-a solubility product of at most ΙΟ "6} and which proves that the perfluoroalkanes are in solution The formation of strongly corrosive sulfonate is separated off at 0 to 250 ° C. and the sulfonate is isolated from the filtrate with considerable disadvantages. 20 It was completely surprising that it was according to the invention succeeds in production and defluorination in summarize in a single operation and To achieve fluoride levels in the sulfonate, at best are at a few ppm. The procedure is suitable before 25 especially for a large-scale synthesis of very The present invention relates to pure perfluoroalkanesulfonates and the previous claim is a process for the production of practiced and described methods of preparation of practically fluoride-free perfiuoralkanes and processes (cf. for example Schröder, sulfonates, starting from perfluoroalkanesulfonic acids Gä η swei η and Brauer, Z. anorg. General Chem. RfSO ₃ H, where Rf for a straight-chain or branched perfluoroalkane radical with 1 to 10 carbon atoms is clearly superior in economic terms, both in terms of technology and branching,
stands, by means of alkaline hydrolysis corresponding to the example are above all those according to the invention Perfluoroalkanesulfonic acid fluorides. established connections are called, the one Which are relatively easy to access through electrofluorination - have achieved certain technical importance, such as Perfluoroalkanesulfonyl fluorides that have been borrowed include potassium perfluorobutanesulfonate and potassium trifluoromethane Intermediate products and are already in sulfonate, potassium perfluorooctanesulfonate, triethylamine Scale made. The resulting ammonium perfluorooctane sulfonate or ammonium pertene Subsequent and end products are characterized by fluoroctanesulfonate. unusual chemical and physical properties - the cations that form sparingly soluble fluorides, create from. Fluorochemicals are therefore on the 40 can be in any form of the reaction mixture The oleophobic and hydrophobic sectors are added; one is preferred, for. B. of textiles, leather or paper in the area of surfactants use oxides, carbonates, hydroxides, chemistry and as a fire extinguishing agent of great tech- sub cations that form sparingly soluble fluorides, niche interest and constantly conquering new use- should be understood as those under the command. 45 prevailing reaction conditions with that of the In contrast to perfluorocarboxylic acid fluorides, inorganic fluorides formed by hydrolysis form a perfluoroalkanesulfonic acid fluoride that is slightly soluble in water, which is largely stable and can only be saponified as a solubility product of hydrolysis by using alkaline solvents, since an acidic hydrolysis also has a maximum of 10 ~ ^e . For this are z. B. lysis not too full even at higher temperatures. 50 Calcium, strontium, barium, magnesium, lead. Stable conversion leads (T. Gramstad and preferably calcium is used. Um das Ein-RN H aszel di ne, J, Chem. Soc. 1956, 173). To prevent dragging additional anions, accordingly, the production takes place peifluor- preferably oxides or hydroxides are used,
alkanesulfonic acid salts by alkaline hydrolysis The inventive method should now be in one the perfluoroalkanesulfonyl fluoride to the corresponding particularly preferred form using the sulfonates and inorganic fluoride. The re-calcium oxide or calcium hydroxide in more detail contains inevitably 50 mol% to be refined. The reaction can be schematically inorganic fluoride and must then be represented as follows:
Purification and isolation of the sulfonate with organic solvents, for example acetone or 60 Ethyl alcohol, can be extracted (USA patent specification Rf - SO ₂ F + M - OH + Vi CaO 2732398 and Burdon, Farazmand, Stacey - »- Vi CaF ₂ + RpSO ₃ M + Vi H ₂ O and T a 11 o w, J. Chem. Soc. 1957, 2547). The purity of perfluoroalkane is often sulfonic acid salts set high requirements, such as 65 where M is a metal, such as. B. Na, K, Li, Vi Ca, for example in the case of VsBa for the flame retardant finish or for an optionally substituted one Polycarbonates used sulfonates. This affects ammonium residue as well as strong organic nitrogen flows for example, there are already traces of inorganic bases, for example guanidine.