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The organic acid is preferably selected from the group of succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, itaconic acid, methylmalonic acid, phthalic acid, terephthalic acid, isophthalic acid. 

In a further alternative process the organic acid is a tricar› boxylic acid of the general formula le: 

<img src='content_image/941338.jpg'>

where Z is an organic radical selected from the group com› prising unsubstituted and mono- or polysubstituted, branched and straight-chain alkanetriyl radicals, cycloalkanetriyl radi› cals, alkenetriyl radicals having one or more double bonds, alkynetriyl radicals having one or more triple bonds, aryltriyl radicals, alkylaryltriyl radicals, arylalkanetriyl radicals, ary› lalkenetriyl radicals, alkyloxyalkanetriyl radicals, hydroxy› alkanetriyl radicals andalkylthioalkanetriyl radicals. The suf- fix "-triy l" indicates here that the three carboxy lie acid groups of the tricarboxylic acid are bonded to this radical. The car› boxylic acid groups may each independently be bonded to any carbon atoms of the organic radical, for example gemi› nally, vicinally or to nonadjacent carbon atoms, where the carbon atoms to which the carboxylic acid groups are bonded may either be in terminal positions or within the radical. 

Moreover, it is preferred that Z is defined as follows: unsubstituted and mono- or polysubstituted, branched and straight-chain (C 1 -C 18 )-alkanetriyl radicals, (C 3 -C 18 )-cy› cloalkanetriyl radicals, (C 2 -C 26 )-alkenetriyl radicals having one or more double bonds, (C 2 -C 26 )-alkynetriyl radicals hav› ing one or more triple bonds, (C 6 -CIO)-aryltriyl radicals, especially phenyltriyl radicals, (C 1 -C 18 )-alkyl-(CcCIO)- aryltriyl radicals, (CcCIO)-aryl-(C 1 -C 18 )-alkanetriyl radi› cals, (CcCIO)-aryl-(C 1 -C 18 )-alkenetriyl radicals, (C 1 -C 18 )› alkyloxy-(C1 -C 18 )-alkanetriyl radicals, (C 1 -C 6 )› hydroxyalkanetriyl radicals and (C 1 -C 18 )-alkylthio-(C 1 - C 18 )-alkanetriyl radicals, any substituents being selected from the group comprising OH, ORIO", NH 2 , NHRIO", NRIO"R 20 ", Cl, Br, I and F, where RIO", R 20 " are each inde› pendently selected from the group comprising H, unsubsti› tuted 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, (CcCIO)-aryl radicals, especially phenyl radicals, (C 1 -C 18 )› alkyl-(C6-CIO)-aryl radicals, (C 6 -CIO)-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. 

In a preferred embodiment, the organic acid is selected from the group of citric acid, cyclopentane-1,2,3-tricarboxy- lic acid, cyclopentane-1,2,4-tricarboxylic acid, 2-methylcy› clopentane-1,2,3-tricarboxylic acid, 3-methylcyclopentane- 1,2,4-tricarboxylic acid. 

In a further process, the organic acid corresponds to a sulphonic acid of the general formula II: 

<img src='content_image/941340.jpg'>

where R 12 is an organic radical selected from the group com› prising unsubstituted and mono- or polysubstituted, branched and straight-chain alkyl radicals, cycloalkyl radicals, alkenyl radicals having one or more double bonds, alkynyl radicals having one or more triple bonds, aryl radicals, alkylaryl radi› cals, arylalkyl radicals, arylalkenyl radicals, alkyloxyalkyl radicals, hydroxyalkyl radicals and alkylthioalkyl radicals. 

It is preferred that R 12 is defined as follows: unsubstituted and mono- or polysubstituted, branched and straight-chain (C 1 -C 18 )-alkyl radicals, (C 3 -C 18 )-cycloalkyl radicals, (C 2 - C26)-alkenyl radicals having one or more double bonds, (C 2 - C26)-alkynyl radicals having one or more triple bonds, (C 6 - C IO)-ary 1 radicals, especially pheny 1 radicals, ( C 1 -C 18 )-alkyl- (CcCIO)-aryl radicals, (CcCIO)-aryl-(C 1 -C 18 )-alkyl radicals, (C 6 -CIO)-aryl-(C 2 -C$_{18}$)-alkenyl radicals, (C 1 -C 18 )› alkyloxy-(C1 -C 18 )-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}$22, NH 2 , NHR 22 , NR 22 R 32 , Cl, Br, I and F, where R 22 and R 32 are each independently selected from the group compris› ing H, unsubstituted and mono- or polysubstituted, branched and straight-chain (C 1 -C 18 )-alkyl radicals, (C 3 -C 18 )-cy› cloalkyl radicals, (C 2 -C 26 )-alkenyl radicals having one or more double bonds, (C 6 -CIO)-aryl radicals, especially phenyl radicals, (C 1 -C 18 )-alkyl-(CcCIO)-aryl radicals, (CcCIO)› aryl-(C1 -C 18 )-alkyl radicals, especially benzyl radicals, (C 1 - C$_{18}$)-alkyloxy-(C 1 -C 18 )-alkyl radicals, (C 1 -C 18 )-hydroxy- alkyl radicals and (C 1 -C 18 )-alkylthio-(C 1 -C 18 )-alkyl radicals. 

le 10 

In a preferred process, the organic acid is selected from the group of p-toluenesulphonic acid, camphor- I 0-sulphonic acid, benzenesulphonic acid, dodecylbenzenesulphonic acid, naphthalenesulphonic acids, phenolsulphonic acids. 

In a further process according to the present invention, the organic acid is a phosphonic acid of the general formula III: 

<img src='content_image/941339.jpg'>

where R 13 is an organic radical selected from the group com› prising unsubstituted and mono- or polysubstituted, branched and straight-chain alkyl radicals, cycloalkyl radicals, alkenyl radicals having one or more double bonds, alkynyl radicals having one or more triple bonds, aryl radicals, alkylaryl radi- cals, arylalkyl radicals, arylalkenyl radicals, alkyloxyalkyl radicals, hydroxyalkyl radicals and alkylthioalkyl radicals. 

In a preferred process, R 13 is defined as follows: unsubsti- tuted 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, (CcCIO)-aryl radicals, especially phenyl radicals, $^{(C}$1 -C 18 )› alkyl-(C6-CIO)-aryl radicals, (C 6 -CIO)-aryl-(C 1 -C 18 )-alkyl radicals, (CcCIO)-aryl-(C 2 -C 18 )-alkenyl radicals, (C 1 -C 18 )› alkyloxy-(C1 -C 18 )-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 23 , NH 2 , NHR 23 , NR 23 R 33 , Cl, Br, I andF, whereR 23 and R 33 are each independently selected from the group compris- 

II 

III 

