DD268685B1 - PROCESS FOR THE PREPARATION OF OMEGA-H-POLYFLUORCARBONSAEURES - Google Patents

Description

Field of application of the invention

The invention relates to a process for producing pure omega-H-polyfluorocarboxylic acids of the general formula H (CF ₂ I _n COOH (n = 1 to 20) by oxidation of corresponding omega-H polyfluoro alcohols.) The omega-H polyfluorocarboxylic acids are used as surfactants.

Characteristic of the known state of the art

For the production of highly fluorinated carboxylic acids, various methods are known, for. As electrochemical fluorination of organic halogen compounds, degradation of polymers, eg. As PTFE by ionizing radiation or oxidation of corresponding fluoroalcohols. The omega-H polyfluoro alcohols are easily accessible by telomerization of tetrafluoroethylene with methanol, so that their oxidation offers significant process engineering advantages (US Pat. No. 5,139,629). The oxidation with an HNO ₃ ZN ₂ O ₄ -GeIDiSCh requires the use of an autoclave, however, leads the oxidation with potassium permanganate to a aufarbeitenden with great effort reaction mixture.

According to a preferred variant of potassium permanganate in glacial acetic acid is dissolved to omega-H-Polyfluoralkoholen at a temperature in the range between 70 ° C and 100 ⁰ C was added portionwise. The forming MnO ₂ is then reduced with SO ₂ and then the glacial acetic acid under vacuum, finally with toluene as a tug removed. After isolation of the crude manganese salt, the omega-H-polyfluorocarboxylic acids are liberated by acidification, extracted with ether, isolated and with the aid of an organic solvent, for. B. benzene, toluene, recrystallized. The conversion of the crude manganese salt into the potassium salt is also described, from which the omega-H-polyfluorocarboxylic acids can likewise be liberated by acidification. In another variant, the reaction mixture is diluted after the oxidation with water and the MnO ₂ separated by filtration. The crude manganese salt is recovered by evaporation from the filtrate, which is converted into the omega-H-polyfluorocarboxylic acids in several process steps.

A disadvantage is the high technical and economic effort in all variants of the described manufacturing process. Due to the large number of process steps, only a moderate yield is achieved.

Object of the invention

The aim of the invention is the production of omega-H polyfluorocarboxylic acids of high purity in a technically simple and economically favorable process.

Explanation of the nature of the invention

It is an object of the present invention to develop a simple process for the preparation of pure omega-H-polyfluorocarboxylic acids of the general formula H (CF ₂ I _n COOH (n-1 to 20), in which high yields are achieved in that the corresponding omega-H-polyfluoroalcohol is oxidized with an aqueous alkaline potassium permanganate solution at room temperature, the omega-H-polyfluorocarboxylic acid formed is liberated by the addition of acid and directly from the reaction mixture with a halogen-containing solvent without prior separation or reduction of the manganese dioxide formed After distilling off the solvent, the target product is immediately obtained in high purity, the yields being greater than 70%, sulfuric acid being preferred as the acid and 1,1,2-trifluoro-1,2,2-trichloroethane as the halo-containing solvent. R 113).

The extraction is carried out when using liquid alcohols (n equal to or less than 5) directly from the reaction mixture, when using solid alcohols (n equal to or greater than 6) from the filter cake of the Soxhlets after cooling and filtration. It is surprising that the omega-H-polyfluorocarboxylic acids are selectively extracted by the halogen-containing solvents so that they are obtained immediately in high purity and in high yields. Neither reduction nor separation of the voluminous MnO _{2 formed} , nor isolation of the manganese salt of the fluorocarboxylic acid, nor additional purification process steps are required.

The extraction solutions can also directly, z. B. as Epilamisierungsmittel used. The replacement of the ether by halogen-containing solvents is particularly labor and fire protection technically important.

embodiments

In a four-necked flask with condenser, stirrer and thermometer, a mixture of water, KMnO _{4 is presented} to 'KOH. With constant stirring, the omega-H-polyfluoro alcohol is added in portions at room temperature, uabei increases

Temperature inside the piston. After completion of the reaction, which is indicated by temperature drop, is stirred

Sulfuric acid added. The omege-H-polyfluorocarboxylic acid is then extracted with 1,1,2-trifluoro-1,2,2-trichloroethane (R 113) and isolated by distilling off the K113 in high purity.

When using liquid alcohol, the extraction with R113 takes place directly from the reaction mixture.

When using solid alcohol, the reaction mixture is filtered after cooling, the filter cake air-dry into a Soxhlet transferred and extracted from this with R113.

The substances or fabric finishes used in the individual examples and the yields obtained are shown in Table 1

compiled.

Table 1

Ex. H ₂ O KMnO ₄ KOH H (CF ₂ I _n CH ₂ OH η 2 H ₂ SO ₄ H (CF ₂ J _n COOH No. (S) (G) (G) (G) 4 (G) Ausbeuie (%) 1 2000 240 85 200 10 200 70 2 1100 170 85 250 12 200 74 3 500 90 30 200 100 81 4 500 40 25 100 80 83

Claims (2)

1. A process for the preparation of omega-H-polyfluorocarboxylic acid of the general formula H (CF ₂ J _n COOH (n = 1 to 20) in high purity by oxidation of ome & a-H-polyfluoroalcohol with aqueous, alkaline potassium permanganate solution at room temperature, releasing the omega -H-polyfluorocarboxylic by addition of acid, extraction with a halogen-containing solvent and optionally isolating by distillation, characterized in that the extraction of the omega-H-polyfluorocarboxylic acid directly from the reaction mixture without prior separation or reduction of the manganese dioxide formed. 2. The method according to claim 1, characterized in that the extraction is carried out with 1,1,2-trifluoro-1,2,2-trichloroethane as a solvent.