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tuted, straight-chain and branched (C 1 -C 18 )-alkyl radicals, (C 3 -C 18 )-cycloalkyl radicals, (C 2 -C 26 )-alkenyl radicals hav› ing one or more double bonds, (CcC 10 )-aryl radicals, espe› cially phenyl radicals, (C 1 -C 18 )-alkyl-(C 6 -C 10 )-aryl radicals, (CcC 10 )-aryl-(C 1 -C 18 )-alkyl radicals, especially benzyl radicals, (C 1 -C 18 )-alkyloxy-(C 1 -C 18 )-alkyl radicals, (C 1 - C 18 )-hydroxyalkyl radicals and (C 1 -C 18 )-alkylthio-(C 1 -C 18 )› alkyl radicals. 8 

[0060] It is further preferred that R and R $^{9 }$are each inde› pendently selected from the group of unsubstituted and mono- or polysubstituted, branched and straight-chain (C 1 - C 18 )-alkyl radicals, (C 3 -C 18 )-cycloalkyl radicals, (C 2 -C 26 )› alkenyl radicals having one or more double bonds, (C 2 -C 26 )› alkynyl radicals having one or more triple bonds, (CcC 10 )› aryl radicals, especially phenyl radicals, (C 1 -C 18 )-alkyl-(Cc C 10 )-aryl radicals, (C 6 -C 10 )-aryl-(C 1 -C 18 )-alkyl radicals, (CcC 10 )-aryl-(C 2 -C 26 )-alkenyl radicals, (C 1 -C 18 )-alkyloxy› (C1-C18)-alkyl radicals, (C 1 -C 18 )-hydroxyalkyl radicals and (C 1 -C 18 )-alkylthio-(C 1 -C 18 )-alkyl radicals, any substituents being selected from the group comprising OH, OR 4 , NH 2 , NHR 4 , NR $^{4}$Rs, Cl, Br, I and F, where R 4 and Rs are each independently selected from the group comprising H, unsub› stituted and mono- or polysubstituted, branched and straight› chain (C 1 -C 18 )-alkyl radicals, (C 3 -C 18 )-cycloalkyl radicals, (C 2 -C 26 )-alkenyl radicals having one or more double bonds, (CcC 10 )-aryl radicals, especially phenyl radicals, (C 1 -C 18 )› alkyl-(CcC10)-aryl radicals, (CcC 10 )-aryl-(C 1 -C 18 )-alkyl radicals, especially benzyl radicals,(C 1 -C 18 )-alkyloxy-(C 1 - C 18 )-alkyl radicals, (C 1 -C 18 )-hydroxyalkyl radicals and (C 1 - C$_{18}$)-alkylthio-(C 1 -C 18 )-alkyl radicals. 

[0061] In a preferred process, the organic acid is selected from the group of 2-hydroxyisobutyric acid, 2-hydroxy-4- methylthiobutyric acid, lactic acid, glycolic acid, malic acid, tartaric acid, gluconic acid, glyceric acid. 

[0062] In a further preferred process, the organic acid is a beta-hydroxycarboxylic acid of the general formula lb 

<img src='content_image/928736.jpg'>

where R 10 , R 11 , R 12 and R 13 are each independently selected from the group comprising H, OH, OR 4 , NH 2 , NHR 4 , NR $^{4}$Rs, Cl, Br, I, F, unsubstituted and mono- or polysubstituted, branched and straight-chain alkyl radicals, cycloalkyl radi› cals, alkenyl radicals having one or more double bonds, alky› nyl radicals having one or more triple bonds, aryl radicals, alkylaryl radicals, arylalkyl radicals, arylalkenyl radicals, alkyloxyalkyl radicals, hydroxyalkyl radicals and alkylthio› alkyl radicals, where R 4 and Rs are each independently selected from the group comprising H, unsubstituted and mono- or polysubstituted, straight-chain and branched (C 1 - C 18 )-alkyl radicals, (C 3 -C 18 )-cycloalkyl radicals, (C 2 -C 26 )› alkenyl radicals having one or more double bonds, (CcC 10 )› aryl radicals, especially phenyl radicals, (C 1 -C 18 )-alkyl-(Cc C 10 )-aryl radicals, (CcC 10 )-aryl-(C 1 -C 18 )-alkyl radicals, especially benzyl radicals, (C 1 -C 18 )-alkyloxy-(C 1 -C 18 )-alkyl radicals, (C 1 -C 18 )-hydroxyalkyl radicals and (C 1 -C 18 )-alky› lthio-(C1 -C 18 )-alkyl radicals. 

[0063] The organic acid is preferably selected from the group of 3-hydroxypropionic acid, 3-hydroxybutyric acid, 

3-hydroxyvaleric acid, 3-hydroxyhexanoic acid, 3-hydroxy› octanoic 2 0 acid, 3-hydroxyisobutyric acid. Just like 2-hy› droxyisobutyric acid, 3-hydroxyisobutyric acid can likewise serve as a precursor for methacrylic acid and methacrylic esters. 

[0064] In a further preferred process, the stripping medium or entraining gas used is steam, air, gases, preferably natural gas, methane, oxygen, inert gas, preferably nitrogen, helium, argon, or mixtures thereof. 

[0065] With regard to the introduction of the stripping medium or entraining gas, an amount of stripping medium or entraining gas, based on the aqueous ammonium salt solution used, between 1 1/kg and 10 000 1/kg, particularly between 10 1/kg and 500 1/kg and very particularly between 20 1/kg and 100 1/kg is preferred. 

[0066] In further preferred processes, the organic extractant is selected from the group of straight-chain or branched ali› phatic ketones having 5 to 18 carbon atoms, heterocyclic ketones having 5 to 18 carbon atoms, straight-chain or branched aliphatic alcohols having 4 to 18 carbon atoms, heterocyclic alcohols having 5 to 18 carbon atoms, straight› chain or branched aliphatic alkanes having 5 to 18 carbon atoms, cycloalkanes having 5 to 14 carbon atoms, straight› chain or branched ethers having 4 to 18 carbon atoms, aro› matics substituted by halogen atoms or hydroxyl groups, straight-chain or branched alkanes which are substituted by halogen atoms and have 1 to 18 carbon atoms, cycloalkanes which are substituted by halogen atoms and have 5 to 14 carbon atoms, preferably isobutyl methyl ketone, isopropyl methyl ketone, ethyl methyl ketone, butyl methyl ketone, ethyl propyl ketone, methyl pentyl ketone, ethyl butyl ketone, dipropyl ketone, hexyl methyl ketone, ethyl pentyl ketone, heptyl methyl ketone, dibutyl ketone, 2-undecanone, 2-dode› canone, cyclohexanone, cyclopentanone, 1-butanol, 2-bu› tanol, 1-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-hep› tanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 3-octanol, 4-octanol, 1-nonanol, 2-nonanol, 3-nonanol, 5-nonanol, 1-decanol, 2-decanol, 1-undecanol, 2-undecanol, 1-dodecanol, 2-dodecanol, cyclopentanol, cyclohexanol, kerosene, petroleum benzine, pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, cyclopentane, cyclohexane, cycloheptane, methyl tert-butyl ether, petro› leum ether, dibutyl ether, diisopropyl ether, dipropyl ether, diethyl ether, ethyl tert-butyl ether, dipentyl ether, benzene, toluene, a-xylene, m-xylene, p-xylene, chlorobenzene, dichloromethane, chloroform, tetrachloromethane or mix› tures thereof. 

lb 

[0067] In further preferred processes, the free acid is obtained from the extractant laden with the extracted acid by a separation process selected from distillation, rectification, crystallization, re-extraction, chromatography, adsorption or membrane processes. 

[0068] One advantage of the process according to the invention is that of being less expensive, since the expensive workup and/or disposal of the amounts of salt obtained in equimolar amounts is eliminated, and another is that the back-integration of the ammonia released into a production process and the closed circuit of the extractant causes it to work in an environmentally friendly and resource-protective manner. 

[0069] The use of otherwise much-used assistants, for example sulphuric acid to release the free acid from the ammonium salt, is eliminated, just like additional reaction steps associated with high costs, for example the transamina- 

